Select Page

Journal Articles and Books






Sandia National Laboratories (SNL) Journal Articles and Books

SNL | PNNL | ORNL

Date Title Authors Publisher
2017-10-18 Maintaining Balance: The Increasing Role of Energy Storage for Renewable Integration

Abstract: For nearly a century, global power systems have focused on three key functions: generating, transmitting, and distributing electricity as a real-time commodity. Physics requires that electricity generation always be in real-time balance with load—despite variability in load on time scales ranging from subsecond disturbances to multiyear trends. With the increasing role of variable generation from wind and solar, the retirement of fossil-fuel-based generation, and a changing consumer demand profile, grid operators are using new methods to maintain this balance.

Derek Stenclik,
Paul Denholm,


Babu Chalamala,
,

IEEE Power & Energy Magazine
2017-9-17Maximizing the Cost-savings for Time-of-use and Net-metering Customers Using Behind-the-meter Energy Storage Systems

Abstract: The transformation of today’s grid toward smart grid has given the energy storage systems (ESSs) the opportunity to provide more services to the electric grid as well as the end customers. On the grid’s side, ESSs can generate revenue streams participating in electricity markets by providing services such as energy arbitrage, frequency regulation or spinning reserves. On the customers’ side, ESSs can provide a wide range of applications from on-site back-up power, storage for offgrid renewable systems to solutions for load shifting and peak shaving for commercial/industrial businesses. In this work, we provide an economic analysis of behind-the-meter (BTM) ESSs. A nonlinear optimization problem is formulated to find the optimal operating scheme for ESSs to minimize the energy and demand charges of time-of-use (TOU) customers, or to minimize the energy charge of net-metering (NEM) customers. The problem is then transformed to Linear Programming (LP) problems and formulated using Pyomo optimization modeling language. Case studies are conducted for PG&E’s residential and commercial customers in San Francisco.

Tu A. Nguyen, Raymond H. Byrne,2017 North American Power Symposium (NAPS)
Sunday, September 17 – Tuesday, September 19, 2017
www.naps2017.org
2017-08-31Next Generation Molten NaI Batteries for Grid Scale Energy Storage

Abstract: Robust, safe, and reliable grid-scale energy storage continues to be a priority for improved energy surety, expanded integration of renewable energy, and greater system agility required to meet modern dynamic and evolving electrical energy demands. We describe here a new sodium-based battery based on a molten sodium anode, a sodium iodide/aluminum chloride (NaI/AlCl3) cathode, and a high conductivity NaSICON (Na1+xZr2SixP3−xO12) ceramic separator. This NaI battery operates at intermediate temperatures (120–180 °C) and boasts an energy density of >150 Wh kg−1. The energy-dense NaI-AlCl3 ionic liquid catholyte avoids lifetime-limiting plating and intercalation reactions, and the use of earth-abundant elements minimizes materials costs and eliminates economic uncertainties associated with lithium metal. Moreover, the inherent safety of this system under internal mechanical failure is characterized by negligible heat or gas production and benign reaction products (Al, NaCl). Scalability in design is exemplified through evolution from 0.85 to 10 Ah (28 Wh) form factors, displaying lifetime average Coulombic efficiencies of 99.45% and energy efficiencies of 81.96% over dynamic testing lasting >3000 h. This demonstration promises a safe, cost-effective, and long-lifetime technology as an attractive candidate for grid scale storage.

L.J. Small,
A. Eccleston,


J. Lamb,
A.C. Read,
M. Robins,
T. Meaders, D. Ingersoll,
P.G. Clem,
S. Bhavaraju,
E.D. Spoerke,,

Journal of Power Sources, 360 (2017) 569-574.
https://doi.org/10.1016/j.jpowsour.2017.06.038
2017-07-26MetILs³: A Strategy for High Density Energy Storage Using Redox-Active Ionic Liquids

Abstract: A systematic approach is presented for increasing the concentration of redox-active species in electrolytes for nonaqueous redox flow batteries (RFBs). Starting with an ionic liquid consisting of a metal coordination cation (MetIL), ferrocene-containing ligands and iodide anions are substituted incrementally into the structure. While chemical structures can be drawn for molecules with 10 m redox-active electrons (RAE), practical limitations such as melting point and phase stability constrain the structures to 4.2 m RAE, a 2.3x improvement over the original MetIL. Dubbed “MetILs3,” these ionic liquids possess redox activity in the cation core, ligands, and anions. Throughout all compositions, infrared spectroscopy shows the ethanolamine-based ligands primarily coordinate to the Fe2+ core via hydroxyl groups. Calorimetry conveys a profound change in thermophysical properties, not only in melting temperature but also in suppression of a cold crystallization only observed in the original MetIL. Square wave voltammetry reveals redox processes characteristic of each molecular location. Testing a laboratory-scale RFB demonstrates Coulombic efficiencies >95% and increased voltage efficiencies due to more facile redox kinetics, effectively increasing capacity 4x. Application of this strategy to other chemistries, optimizing melting point and conductivity, can yield >10 m RAE, making nonaqueous RFB a viable technology for grid scale storage.

L.J. Small,
H.D. Pratt,

C.L. Staiger,
T.M. Anderson,

Advanced Sustainable Systems, 2017. doi: 10.1002/adsu.201700066.
2017-03-23Deposition of Tungsten Metal by an Immersion Process

Abstract: A new multi-step, solution-phase method for the spontaneous deposition of tungsten from a room temperature ethereal solution is reported. This immersion process relies on the deposition of a sacrificial zinc coating which is galvanically displaced by the ether-mediated reduction of oxophilic WCl6. Subsequent thermal treatment renders a crystalline, metallic tungsten film. The chemical evolution of the surface and formation of a complex intermediate tungsten species is characterized by X-ray diffraction, infrared spectroscopy, and X-ray photoelectron spectroscopy. Efficient metallic tungsten deposition is first characterized on a graphite substrate and then demonstrated on a functional carbon foam electrode. The resulting electrochemical performance of the modified electrode is interrogated with the canonical aqueous ferricyanide system. A tungsten-coated carbon foam electrode showed that both electrode resistance and overall electrochemical cell resistance were reduced by 50%, resulting in a concomitant decrease in redox peak separation from 1.902 V to 0.783 V. This process promises voltage efficiency gains in electrodes for energy storage technologies and demonstrates the viability of a new route to tungsten coating for technologies and industries where high conductivity and chemical stability are paramount

Fu L.J. Small,
M.T. Brumbach,


P.G. Clem,
E.D. Spoerke,

Journal of the Electrochemical Society,
164 (2017) D269-D274 doi: 10.1149/2.0131706jes Deposition of Tungsten Metal by an Immersion Process
2017-02-21Screening for High Conductivity/Low Viscosity Ionic Liquids Using Product Descriptors

Abstract: We seek to optimize Ionic liquids (ILs) for application to redox flow batteries. As part of this effort, we have developed a computational method for suggesting ILs with high conductivity and low viscosity. Since ILs consist of cation-anion pairs, we consider a method for treating ILs as pairs using product descriptors for QSPRs, a concept borrowed from the prediction of protein-protein interactions in bioinformatics. We demonstrate the method by predicting electrical conductivity, viscosity, and melting point on a dataset taken from the ILThermo database on June 18th, 2014. The dataset consists of 4,329 measurements taken from 165 ILs made up of 72 cations and 34 anions. We benchmark our QSPRs on the known values in the dataset then extend our predictions to screen all 2,448 possible cation-anion pairs in the dataset.

Martin, S.,


Pratt, H.,
Anderson, T.,

Molecular Informatics,
DOI: 10.1002/minf.201600125
2016-04-18Monitoring of CoS2 reactions using high-temperature XRD coupled with gas chromatography (GC)

Abstract: High-temperature X-ray diffraction with concurrent gas chromatography (GC) was used to study cobalt disulfide cathode pellets disassembled from thermal batteries. When CoS2 cathode materials were analyzed in an air environment, oxidation of the K(Br, Cl) salt phase in the cathode led to the formation of K2SO4 that subsequently reacted with the pyrite-type CoS2 phase leading to cathode decomposition between ~260 and 450 °C. Independent thermal analysis experiments, i.e. simultaneous thermogravimetric analysis/differential scanning calorimetry/mass spectrometry (MS), augmented the diffraction results and support the overall picture of CoS2 decomposition. Both gas analysis measurements (i.e. GC and MS) from the independent experiments confirmed the formation of SO2 off-gas species during breakdown of the CoS2. In contrast, characterization of the same cathode material under inert conditions showed the presence of CoS2 throughout the entire temperature range of analysis.

Rodriguez, M.,


Coker, E.,
Griego, J.,
Mowry,C.,
Pimentel. A.,
and Anderson, T.,

Powder Diffraction,
Volume 31,
Issue 2,
DOI: https://doi.org/10.1017/S0885715616000166
2017The Value Proposition for Energy Storage at the Sterling Municipal Light Department

Abstract: The Sterling Municipal Light Department (SMLD) is a progressive public power utility located 10 miles NNE of Worcester, Massachusetts in the Town of Sterling. SMLD has a long history of investment in renewable generation, with approximately 35% of generation coming from renewable sources. The goal of this report is to identify potential benefits and value streams from electrical energy storage. Benefits considered in this analysis include: energy arbitrage, frequency regulation, reduction in monthly network load, reduction in capacity payments to ISO New England, and grid resiliency.

Byrne, R.,


Hamilton, S.,
Borneo, D.,
Olinsky-Paul, T.,
Gyuk, I.,

2017 IEEE PES
General Meeting
2017Maximizing Revenue from Electrical Energy Storage in MISO Energy & Frequency Regulation Markets

Abstract: FERC Order 755 requires RTO/ISOs to compensate the frequency regulation resources based on the actual regulation service provided. Based on this rule, a resource is compensated by a performance-based payment including a capacity payment which accounts for its provided regulation capacity and a performance payment which reflects the quantity and accuracy of its regulation service. The RTO/ISOs have been implementing different market rules to comply with FERC Order 755. This paper focuses on the MISO's implementation and presents the calculations to maximize the potential revenue of electrical energy storage (EES) from participation in arbitrage and frequency regulation in the day-ahead market using linear programming. A case study was conducted for the Indianapolis Power & Light's 20MW/20MWh EES at Harding Street Generation Station based on MISO historical data from 2014 and 2015. The results showed the maximum revenue was primarily produced by frequency regulation.

Nguyen, T.,


Byrne, R.,
Concepcion, R.,
Gyuk, I.,

2017 IEEE PES
General Meeting
2016-11-01Photovoltaic Frequency-Watt Curve Design for Frequency Regulation and Fast Contingency Reserves

Abstract: When renewable energy resources are installed in electricity grids, they typically increase generation variability and displace thermal generator control action and inertia. Grid operators combat these emerging challenges with advanced distributed energy resource (DER) functions to support frequency and provide voltage regulation and protection mechanisms. This paper focuses on providing frequency reserves using autonomous IEC TR 61850-90-7 pointwise frequency-watt (FW) functions that adjust DER active power as a function of measured grid frequency. The importance of incorporating FW functions into a fleet of photovoltaic (PV) systems is demonstrated in simulation. Effects of FW curve design, including curtailment, deadband, and droop, were analyzed against performance metrics using Latin hypercube sampling for 20%, 70%, and 120% PV penetration scenarios on the Hawaiian island of Lanai. Finally, to understand the financial implications of FW functions to utilities, a performance function was defined based on monetary costs attributable to curtailed PV production, load shedding, and generator wear. An optimization wrapper was then created to find the best FW function curve for each penetration level. It was found that in all cases, the utility would save money by implementing appropriate FW functions.

Johnson, J.,


Neely, J.,
Delhotal, J.,
Lave, M.,

IEEE Journal of Photovoltaics
vol. 6, issue 6,
pp. 1611 - 1618
2016-08DOE Global Energy Storage Database - A Platform for Large Scale Data Analytics and System Performance Metrics

Abstract: The U.S. Department of Energy (U.S. DOE) Global Energy Storage Database (GESDB) is an openly accessible archive of electrical energy storage projects across the electric grid infrastructure and a global repository of relevant policies. The data included in the archive has been fully validated. The GESDB represents a dynamic catalogue with a continuously updated dataset. This is essentially a global industry platform for dissemination of project and performance metrics on the growing fleet of energy storage installations. Over the last four years, the database has been utilized to help shape the development of new projects, improve existing systems and to help develop policy and regulatory framework.

Hernández, J.,


Gyuk, I.,
Christensen, C.,

POWERCON 2016
Submission 339
2016-02-17Estimating Potential Revenue from Electrical Energy Storage in PJM

Abstract: FERC order 755 and FERC order 784 provide pay-for-performance requirements and direct utilities and independent system operators to consider speed and accuracy when purchasing frequency regulation. Independent System Operators (ISOs) have differing implementations of pay-for-performance. This paper focuses on the PJM implementation. PJM is a regional transmission organization in the northeastern United States that serves 13 states and the District of Columbia. PJM's implementation employs a two part payment based on the Regulation Market Capability Clearing price (RMCCP) and the Regulation Market Performance Clearing Price (RMPCP). The performance credit includes a mileage ratio. Both the RMCCP and RMPCP employ an actual performance score. Using the PJM remuneration model, this paper outlines the calculations required to estimate the maximum potential revenue from participation in arbitrage and regulation in day-ahead markets using linear programming. Historical PJM data from 2014 and 2015 was then used to evaluate the maximum potential revenue from a 5 MWh, 20 MW system based on the Beacon Power Hazle Township flywheel plant. Finally, a heuristic trading algorithm that does not require perfect foresight was evaluated against the results of the optimization algorithm.

Byrne, R.,


Concepcion, R.,
Silva-Monroy, C.,

2016 IEEE PES
General Meeting
2016-04-01Synthesis of water-soluble mono- and ditopic imidazoliums for carbene ligands

Abstract:

Antsey, M.,


Murtagh, D.,
Cordaro, J.,
Stavila, V.,
Feng, P.,
Mengesha, M.,

Organic Letters
2016-03-21Voltage Clustering in Redox-Active Ligand Complexes: Mitigating Electronic Communication through Choice of Metal Ion

Abstract: The redox-active bis(imino)acenapthene (BIAN) ligand was used to synthesize homoleptic aluminum, chromium, and gallium complexes of the general formula (BIAN)3M. The resulting compounds were characterized using X-ray crystallography, NMR, EPR, magnetic susceptibility and cyclic voltammetry measurements and modeled using both DFT and ab initio wavefunction calculations to compare the orbital contributions of main group elements and transition metals in ligand-based redox events. Complexes of this type have the potential to improve the energy density and electrolyte stability of grid-scale energy storage technologies, such as redox flow batteries, through thermodynamically-clustered redox events.

Zarkesh,R.,


Ichimura, A.,
Monson, T.,
Tomson, N.,
Anstey, M.,

RSC Dalton Transactions,
DOI: 10.1039/C6DT00422A
2016-02-16Ensuring Profitability of Energy Storage

Abstract: Energy storage (ES) is a pivotal technology for dealing with the challenges caused by the integration of renewable energy sources. It is expected that a decrease in the capital cost of storage will eventually spur the deployment of large amounts of ES. These devices will provide transmission services, such as spatiotemporal energy arbitrage, i.e., storing surplus energy from intermittent renewable sources for later use by loads while reducing the congestion in the transmission network.
This paper proposes a bilevel program that determines the optimal location and size of storage devices to perform this spatiotemporal energy arbitrage. This method aims to simultaneously reduce the system-wide operating cost and the cost of investments in ES while ensuring that merchant storage devices collect sufficient profits to fully recover their investment cost. The usefulness of the proposed method is illustrated using a representative case study of the ISO New England system with a prospective wind generation portfolio.

Dvorkin, Y.,


Fernandez-Blanco, R.,
Kirschen, D.,
Pandzic, H.,
Watson, J.,
Silva-Monroy, C.,

IEEE Transactions
2016-02-16A Comparison of Policies on the Participation of Storage in U.S. Frequency Regulation Markets

Abstract: Because energy storage systems have better ramping characteristics than traditional generators, their participation in frequency regulation should facilitate the balancing of load and generation. However, they cannot sustain their output indefinitely. System operators have therefore implemented new frequency regulation policies to take advantage of the fast ramps that energy storage systems can deliver while alleviating the problems associated with their limited energy capacity. This paper contrasts several U.S. policies that directly affect the participation of energy storage systems in frequency regulation and compares the revenues that the owners of such systems might achieve under each policy.

Xu, B.,


Dvorkin, Y.,
Kirschen, D.,
Silva-Monroy, C.,
Watson, J.,

IEEE Transactions
2016-02-16Nanoporous polysulfone membranes via a degradable block copolymer precursor for redox flow batteries

Abstract: Nanoporous polysulfone (PSU) membranes were fabricated via post-hydrolysis of polylactide (PLA) from PLA-PSU-PLA triblock copolymer membranes. The PSU scaffold was thermally crosslinked before sacrificing PLA blocks. The resulting nanopore surface was chemically modified with sulfonic acid moieties. The membranes were analyzed and evaluated as separators for vanadium redox flow batteries. Nanoporous PSU membranes prepared by this new method and further chemically modified to a slight degree exhibited unique behavior with respect to their ionic conductivity when exposed to solutions of increasing acid concentration.

Gindt, B.,


Abebe, D.,
Tang, Z.,
Lindsey, M.,
Chen, J.,
Elgammal, R.,
Zawodzinski, T.,
Fujiwara, T.,

J. Mater. Chem,
A, vol. 4, pp. 4288-4295,
DOI: 10.1039/C6TA00698A
2016Creating Orbiting Vorticity Vectors in Magnetic Particle Suspensions Through Field Symmetry Transitions - A Route to Multi-axis Mixing

Abstract:

Martin, J.,


...Solis, K.,

Soft Matter,
vol. 12, pp. 1021-1031,
DOI: 10.1039/C5SM01975C
2015-12-10In situ XANES and EXAFS Analysis of Redox Active Fe Center Ionic Liquids

Abstract: In situ X-Ray Absorption Near Edge Spectroscopy (XANES) and Extended X-Ray Absorption Fine Structure (EXAFS) techniques are applied to a metal center ionic liquid undergoing oxidation and reduction in a three electrode spectroscopic cell. Determination of the extent of reduction under negative bias on the working electrode and the extent of oxidation are determined after pulse voltammetry to quiescence. While the ionic liquid undergoes full oxidation, it undergoes only partial reduction, likely due to transport issues on the timescale of the experiment. Nearest neighbor Fe-O distances in the fully oxidized state match well to expected values for similarly coordinated solids, but reduction does not result in an extension of the Fe-O bond length, as would be expected from comparisons to the solid phase. Instead, little change in bond length is observed. We suggest that this may be due to a more complex interaction between the monodentate ligands of the metal center anion and the surrounding charge cloud, rather than straightforward electrostatics between the metal center and the nearest neighbor grouping.

Apblett, C.,


Stewart, D.,
Fryer, R.,
Sell, J.,
Pratt III, H.,
Anderson, T.,
Meulenberg, R.,

Electrochimica Acta,
vol. 185, pp. 156-161,
doi:10.1016/j.electacta.2015.09.093
2015-11-28Characterization of Vanadium Ion Uptake in Sulfonated Diels Alder Poly(phenylene) Membranes

Abstract: Sulfonated diels alder poly(phenylene) (SDAPP), alternative aromatic hydrocarbon membranes for vanadium redox flow batteries (VRFBs) are characterized using electron paramagnetic resonance (EPR). Membranes soaked in sulfuric acid and vanadyl sulfate are analyzed to determine the membrane environment in which the vanadyl ion (VO2+) diffuses in the membranes. These results are compared to Nafion 117 membranes. In contrast to Nafion, the VO2+ in SDAPP membranes exists in two different environments. The results of analysis of rotational diffusion determined from fits the EPR spectral lineshapes in comparison with previously reported permeation studies and measurements of partitioning functions reported here suggest that the diffusion pathways in SDAPP are considerably different than in Nafion.

Lawton, J.,


Jones, A.,
Tang, Z.,
Lindsey, M.,
Fujimoto, C.,
Zawodzinski, T.,

J. Electrochem. Soc.,
vol. 163, no. 1,
pp. A5229-A5235,
doi: 10.1149/2.0291601jes
2015-11-14 Full Cell Study of Diels Alder Poly(phenylene) Anion and Cation Exchange Membranes in Vanadium Redox Flow Batteries

Abstract: In this work, we report on the performance of Diels Alder poly(phenylene) membranes in vanadium redox flow batteries. The membranes were functionalized with quaternary ammonium groups to form an anion exchange membrane (QDAPP) and with sulfonic acid groups to form a cation exchange membrane (SDAPP). Both membrane classes showed similar conductivities in the battery environment, suggesting that the ion conduction mechanism in the material is not strongly affected by the moieties along the polymer backbone. The resistance to vanadium permeation in QDAPP was not improved relative to SDAPP, further suggesting that the polarity of the functional groups do not play a significant role in the membrane materials tested. Both QDAPP and SDAPP outperformed Nafion membranes in cycling tests, with both achieving voltage efficiencies above 85% while maintaining 95% coulombic efficiency while at a current density of 200 mA/cm2.

A. M. Pezeshki,
Z. J. Tang,


C. Fujimoto,
C.-N. Sun,
M. M. Mench,
T. A. Zawodzinski,

J. Electrochem. Soc.,
vol. 163, no. 1,
pp. A5154-A5162,
2015-10-23Diels Alder Polyphenylene Anion Exchange Membrane for Nonaqueous Redox Flow Batteries

Abstract: Here highly conductive, solvent-resistant anionic Diels Alder polyphenylene (DAPP) membranes were synthesized with three different ionic contents and tested in an ionic liquid-based nonaqueous redox flow battery (RFB). These membranes display 3-10x increase in conductivity in propylene carbonate compared to some commercially available (aqueous) anion exchange membranes. The membrane with an ion content of 1.5 meq/g (DAPP1.5) proved too brittle for operation in a RFB, while the membrane with an ion content of 2.5 meq/g (DAPP2.5) allowed excessive movement of solvent and poor electrochemical yields (capacity fade). Despite having lower voltage efficiencies compared to DAPP2.5, the membrane with an intermediate ion content of 2.0 meq/g (DAPP2.0) exhibited higher coulombic efficiencies (96.4% vs. 89.1%) and electrochemical yields (21.6% vs. 10.9%) after 50 cycles. Crossover of the electroactive species was the primary reason for decreased electrochemical yields. Analysis of the anolyte and catholyte revealed degradation of the electroactive species and formation of a film at the membrane-solution interface. Increases in membrane resistance were attributed to mechanical and thermal aging of the membrane; no chemical change was observed. Improvements in the ionic selectivity and ionic conductivity of the membrane will increase the electrochemical yield and voltage efficiency of future nonaqueous redox flow batteries.

Small, L.,


Pratt III, H.,
Fujimoto, C.,
Anderson, T.,

J. Electrochem. Soc.,
vol. 163, no. 1,
pp. A5106-A5111,
doi: 10.1149/2.0141601jes
2015-09-09Spectroscopic investigations of band offsets of MgO| AlxGa1-xN epitaxial heterostructures with varying AlN content

Abstract: Epitaxial (111) MgO films were prepared on (0001) AlxGa1-xN via molecular-beam epitaxy for x=0 to x=0.67. Valence band offsets of MgO to AlxGa1-xN were measured using X-ray photoelectron spectroscopy as 1.65±0.07 eV, 1.36±0.05 eV, and 1.05±0.09 eV for x = 0, 0.28, and 0.67, respectively. This yielded conduction band offsets of 2.75 eV, 2.39 eV, and 1.63 eV for x = 0, 0.28, and 0.67, respectively. All band offsets measured between MgO and AlxGa1-xN provide a > 1 eV barrier height to the semiconductor.

Paisley, E.,


Brumbach, M.,
Allerman, A.,
Atcitty, S.,
Baca, A.,
Armstrong, A.,
Kaplar, R.,
Ihlefeld, J.,

Applied Physics Letters,
vol. 107, no. 10,
pp. 102101-102103,
doi: 0.1063/1.4930309
2015-09Analyzing system safety in lithium-ion grid energy storage

Abstract: As grid energy storage systems become more complex, it grows more difficult to design them for safe operation. This paper first reviews the properties of lithium-ion batteries that can produce hazards in grid scale systems. Then the conventional safety engineering technique Probabilistic Risk Assessment (PRA) is reviewed to identify its limitations in complex systems. To address this gap, new research is presented on the application of Systems-Theoretic Process Analysis (STPA) to a lithium-ion battery based grid energy storage system. STPA is anticipated to fill the gaps recognized in PRA for designing complex systems and hence be more effective or less costly to use during safety engineering. It was observed that STPA is able to capture causal scenarios for accidents not identified using PRA. Additionally, STPA enabled a more rational assessment of uncertainty (all that is not known) thereby promoting a healthy skepticism of design assumptions. We conclude that STPA may indeed be more cost effective than PRA for safety engineering in lithium-ion battery systems. However, further research is needed to determine if this approach actually reduces safety engineering costs in development, or improves industry safety standards.

Rosewater, D.,


Williams, A.,

Journal of Power Sources
300 (2015): 460-471
2015-09International Development of Energy Storage Interoperability Test Protocols for Photovoltaic Integration

Abstract: As variable, non-dispatchable photovoltaic power continues to displace traditional generation assets, additional resources are needed to control bulk and local power systems. One highly versatile option for providing frequency and voltage stability is to incorporate Energy Storage Systems (ESSs) at the distribution-level. Deployment of these technologies is expected to increase rapidly as time-of-use pricing and self-consumption requirements become wide-spread and provide greater financial incentives. Japanese, European and American stakeholders are working on the standardization of interoperability certification protocols for many grid support functions to validate the Distributed Energy Resource (DER) operations and communications within the power system. Specifically, in this project, Smart Grid International Research Facility Network (SIRFN) laboratories--Sandia National Laboratories (SNL), Austrian Institute of Technology (AIT), Ricerca sul Sistema Energetico (RSE), and National Institute of Advanced Industrial Science and Technology (AIST) Fukushima Renewable Energy Institute (FREA)--are collaborating to create a concise set of test protocols for evaluating the ESS interoperability and functionality. First, a survey of grid-support standards and use cases from several countries was completed. Then the grid support functions were condensed to the unique set of ESS capabilities and organized by function, control signal requirements, and response requirements. From this list, draft certification protocols were written to enable advanced interoperable ESSs covering this range of capabilities to better support photovoltaic and renewable energy integration. An overview of the protocol development process along with preliminary ESS test results for four initial functions (active power, fixed power factor, volt-var, and frequency-watt) is presented. This work is expected to provide the basis of an international testing standard for ESS grid-support functions in the future.

Rosewater, D.,


Johnson, J.,
Verga, M.,
Lazzari, R.,
Messner, C.,
Bründlinger, R.,
Johannes, K.,
Hashimoto, J.,
Otani, K.,

Proceedings of the 2015 European Photovoltaic Solar Energy Conference (EU PVSEC)
2015-08-13Through-Plane Conductivities of Membranes for Nonaqueous Redox Flow Batteries

Abstract: Nonaqueous redox flow batteries (RFB) leverage nonaqueous solvents to enable higher operating voltages compared to their aqueous counterparts. Most commercial components for flow batteries, however, are designed for aqueous use. One critical component, the ion-selective membrane, provides ionic conductance between electrodes while preventing crossover of electroactive species. Here we evaluate the area-specific conductances and through-plane conductivities of commercially available microporous separators (Celgard 2400, 2500) and anion exchange membranes (Neosepta AFX, Neosepta AHA, Fumasep FAP-450, Fumasep FAP-PK) soaked in acetonitrile, propylene carbonate, or two imidazolium-based ionic liquids. Fumasep membranes combined with acetonitrile-based electrolyte solutions provided the highest conductance values and conductivities by far. When tested in ionic liquids, all anion exchange membranes displayed conductivities greater than those of the Celgard microporous separators, though the separators' decreased thickness-enabled conductances on par with the most conductive anion exchange membranes. Ionic conductivity is not the only consideration when choosing an anion exchange membrane; testing of FAP-450 and FAP-PK membranes in a nonaqueous RFB demonstrated that the increased mechanical stability of PEEK-supported FAP-PK minimized swelling, in turn decreasing solvent mediated crossover and enabling greater electrochemical yields (40% vs. 4%) and Coulombic efficiencies (94% vs. 90%) compared to the unsupported, higher conductance FAP-450.

Hudak, N.,


Small, L.,
Pratt, H.,
Anderson, T.,

J. Electrochem. Soc.,
vol. 162, np. 10,
pp. A2188-A2194,
doi: 10.1149/2.0901510jes
2015-08Mesmerizing Magnetic Fields

Abstract:

Martin, J.,


...James, K.,

Physics Today,
vol. 68, no. pp. 66-67,
DOI: 10.1063/PT.3.2892
2015-07-24Improving the ionic conductivity of NASICON through aliovalent cation substitution of Na3Zr2Si2PO12

Abstract: Doping the zirconium site in NASICON (Na3Zr2Si2PO12) with lower valent cations enhanced the ionic transport of the material. Both Na3.2Zr1.8M0.2Si2PO12 (M=Al3+, Fe3+, Y3+) and Na3.4Zr1.8M0.2Si2PO12 (M=Co2+, Ni2+, Zn2+) exhibited a higher bulk conductivity than undoped Na3Zr2Si2PO12 at room temperature. A decrease in the low temperature activation energy for all doped NASICON was observed, which helped contribute to the higher room temperature conductivity. The lower activation energy and enhanced conductivity of doped materials were a result of alterations in the NASICON structure. The charge imbalance created by aliovalent substitution increased the sodium in the lattice resulting in more charge carriers with better mobility. Furthermore, the conductivity was optimized by the ionic radius of the species in the zirconium site. Ultimately, NASICON doped with a +2 oxidation state cation having an ionic radius of approximately 0.73 Å (Zn and Co) attained a maximum in conductivity. Zn-doped NASICON displayed the greatest room temperature bulk conductivity of 3.75x10-3 S/cm, while Co-doped NASICON demonstrated the greatest total conductivity of 1.55x10-3 S/cm.

Jolley, A.,


Cohn, G.,
Hitz, G.,
Wachsman, E.,

Ionics 21,
3031-3038,
DOI 10.1007/s11581-015-1498-8
2015-07Potential Revenue from Electrical Energy Storage in ERCOT: The Impact of Location and Recent Trends

Abstract: This paper outlines the calculations required to estimate the maximum potential revenue from participation in arbitrage and regulation in day-ahead markets using linear programming. Then, we use historical Electricity Reliability Council of Texas (ERCOT) data from 2011-2013 to evaluate the maximum potential revenue from a hypothetical 32 MWh, 8 MW system. We investigate the maximum potential revenue from two different scenarios: arbitrage only and arbitrage combined with regulation. This analysis was performed for each load zone over the same period to show the impact of location and to identify trends in the opportunities for energy storage. Our analysis shows that, with perfect foresight, participation in the regulation market would have produced more than twice the revenue compared to arbitrage in the ERCOT market in 2011-2013. Over the last three years, there has been a significant decrease in the potential revenue for an energy storage system. We also quantify the impact of location on potential revenue.

Byrne, R. ,


Silva-Monroy, C.,

Proceedings of the 2015 Power and Energy Society General Meeting
2015-06-18Structural Investigation of Monoclinic-Rhombohedral Phase Transition in Na3Zr2Si2PO12and Doped NASICON

Abstract: Aliovalent doping of the zirconium site in Na3Zr2Si2PO12 (NASICON) was performed with a range of +3 (Al, Y, Fe) and +2 (Co, Ni, Zn) valent cations. The monoclinic-rhombohedral phase transition was analyzed with high-temperature in situ X-ray diffraction, and differential scanning calorimetry (DSC). From the lattice parameters extracted at room temperature up to 300°C it was determined that the high-temperature rhombohedral phase distorts to the low-temperature monoclinic phase through a shear deformation of the unit cell. DSC confirmed the phase transition and demonstrated that the phase transition temperature was lowered by doping the NASICON structure. Furthermore, the distortion of the lattice was less severe for all doped samples. Ultimately aliovalent substitution for zirconium stabilized the higher symmetry rhombohedral phase of NASICON, with yttrium doping providing the lowest phase transition temperature and the smallest distortion of the lattice through the phase change.

Jolley, A.,


Taylor, D.,
Schreiber, N.,
Wachsman, E.,

J. Am. Ceram. Soc.,
98(9), 2902-2907
2015-06-15Characterization of fast interface states in nitrogen- and phosphorus-treated 4H-SiC MOS capacitors

Abstract: We investigate 'fast interface states' at semiconductor-dielectric interfaces in SiC MOS capacitors that underwent three different interface passivation processes: two nitrogen-based annealing techniques (NO and nitrogen-plasma) and phosphosilicate glass (PSG). 'Fast interface' states in this case refer to interface states with response times <1 us typically used in standard admittance based MOS characterization methods. In order to appropriately characterize the density of interface states (Dit) taking into account these fast states, conductance and high-low frequency C-V methods were used from room temperature down to 100 K. Measuring at lower temperature shifts the response of the fast interface states into the accessible measurement frequency range. The key finding of this work is that while fast interface states were detected in the nitrided samples, such states were not observed in PSG-passivated samples. On the other hand, conventional interface states with time constants similar to those found in silicon samples were detected at room temperature in the PSG samples. The capture cross-section of fast interface states is larger than that of conventional interface states and demonstrates a different energy dependence. These results strongly indicate that the significantly lower density of fast states at the PSG-SiC interface is one of the main reasons for higher channel mobility in PSG MOSFETs.

Kao, W.,


Goryll, M.,
Marinella, M.,
Kaplar, R.,
Jiao, C.,
Dhar S.,
Cooper, J.,
Schroder, D.,

Semiconductor Science and Technology,
vol. 30, p. 075011,
doi:10.1088/0268-1242/30/7/075011
2015-06-01Exploring the Role of Phosphate Structural Distortions on the Sodium Jump Dynamics in NASICON Phases

Abstract: High temperature solid state sodium (23Na) magic angle spinning (MAS) NMR spin lattice relaxation times (T1) were evaluated for a series of NASICON (Na3Zr2PSi2O12) materials to directly determine Na jump rates. Simulations of the T1 temperature variations that incorporated distributions in Na jump activation energies, or distribution of jump rates, improved the agreement with experiment. The 23Na NMR T1 relaxation results revealed that distributions in the Na dynamics were present for all of the NASICON materials investigated here. The 23Na relaxation experiments also showed that small differences in material composition and/or changes in the processing conditions impacted the distributions in the Na dynamics. The extent of the distribution was related to the presence of a disordered or glassy phosphate phase present in these different sol-gel processed materials. The 23Na NMR T1 relaxation experiments are a powerful tool to directly probing Na jump dynamics and provide additional molecular level details that could impact transport phenomena.

Alam, T.,


Nelson, B.,
Wheeler,J.,
Spoerke, E.,
Cygan, R.,
Ingersoll, D.,

MRS Proceedings,
vol. 1773,
DOI: 10.1557/opl.2015.522
2015-04-30Amine-Assisted Delamination of Nb2C MXene for Li-Ion Energy Storage Devices

Abstract: 2D Nb2CTx MXene flakes are produced using an amine-assisted delamination process. Upon mixing with carbon nanotubes and filtration, freestanding, flexible paper is produced. The latter exhibits high capacity and excellent stability when used as the electrode for Li-ion batteries and capacitors.

Mashtalir, O.,


Lukatskaya, M.,
Zhao, M.,
Barsoum, M.,
Gogotsi, Y.,

Advanced Materials,
vol. 27,
pp. 3501-3506
2015-04-17Ionic Liquid Redox Catholyte for High Energy Efficiency, Low-Cost Energy Storage

Abstract: An approach to energy storage using ionic liquids as joint ion-conducting medium and redox active catholyte material is described. The earth-abundant ferric ion is incorporated as an oxidizing agent in the form of the low-melting NaFeCl4 in a 1:1 mixture with ethylmethylimidazolium tetrachloraluminate, an ambient temperature ionic liquid. Different possible anode types are considered, and the most obvious one involving liquid sodium (with special wetting of a sodium ion-conducting ceramic separator) is tested. The high voltage >3.2 V predicted for this cell is verified, and its cyclability is confirmed. Operating at 180 °C, an unexpectedly high energy efficiency >96%, is recorded. This establishes this type of cell as an attractive candidate for energy storage. For optimum energy storage, high energy efficiency is mandated for thermal management, as well as economic reasons. The theoretical capacity of the cell is 288 Wh kg-1 (418 Wh L-1) of which 73% is realized. The cell is shown to be fail-safe against internal shorts. As there are many degrees of freedom for developing this type of cell, it is suggested as a promising area of future research effort in the energy storage area.

Xue, L.,


Tucker, T.,
Angell, C.,

Advanced Energy Materials,
Volume 5, Issue 12,
DOI: 10.1002/aenm.201500271
2015-03-24Current Density Scaling in Electrochemical Flow Capacitors

Abstract: Electrochemical flow capacitors (EFCs) are a recently developed energy storage technology. One of the principal performance metrics of an EFC is the steady-state electrical current density that it can accept or deliver. Numerical models exist to predict this performance for specific cases, but here we present a study of how the current varies with respect to the applied cell voltage, flow rate, cell dimensions, and slurry properties using scaling laws. The scaling relationships are confirmed by numerical simulations and then subsequently by comparison to results from symmetric cell EFC experiments. This modeling approach permits the delimitation of three distinct operational regimes dependent on the values of two nondimensional combinations of the pertinent variables (specifically, a capacitive Graetz number and a conductivity ratio). Lastly, the models and nondimensional numbers are used to provide design guidance in terms of criteria for proper EFC operation.

Hoyt, N.,


Wianright, J.,
Savinell, R.,

J. Electrochem. Soc.,
162(6), A1102-11
2015-01-17Structured optimization for parameter selection of frequency-watt grid support functions for wide area damping

Abstract: Deployment of distributed renewable energy resources is increasing rapidly, which is leading to growing concerns over the impact of distributed power electronics energy converters on grid stability. In general, power electronic coupled systems do not provide frequency or voltage support through feedback compensation. This is leading to changes in utility interconnection requirements for distributed generation systems to provide voltage and frequency regulation ability through the use of newly developed advanced grid functions (AGFs). In this paper, the types of grid stability problems which can be mitigated by AGFs is expanded; in particular, it is demonstrated that the energy storage function which adjusts active power injection as a function of grid frequency, i.e., P(f) or freq-watt, can provide damping control using local frequency information. Specifically, a structured optimization scheme is presented that is scalable to multi-node distributed damping applications. An algorithm computes optimal damping controller gains for distributed resources that use only local frequency feedback. The local control may be implemented using the freq-watt AGF recently defined by the International Electrotechnical Commission (IEC). The proposed approach is applicable to local and inter-area oscillation damping and could be valuable for utility operations centers to identify appropriate gains for installed systems that implement AGFs.

Neely, J.,


Johnson, J.,
Byrne, R.,

International Journal of Distributed Energy Resources and Smart Grids,
vol. 11, no. 1,
pp. 69-94
2015-01-15Synthesis and electrochemical properties of niobium pentoxide deposited on layered carbide-derived carbon

Abstract: Herein we report on the hydrothermal synthesis of niobium pentoxide on carbide-derived carbon (Nb2O5/CDC) with a layered structure. The presence of phenylphosphonic acid guides the deposition during preparation, leading to the formation of amorphous Nb2O5 particles which are 4-10 nm in diameter and homogeneously distributed on the CDC framework. Electrochemical testing of the Nb2O5/CDC electrode indicated that the highest capacitance and Coulombic efficiency occurred using an electrolyte comprised of 1 M lithium perchlorate in ethylene carbonate/dimethyl carbonate. Subsequent heat treatment of Nb2O5/CDC in CO2 environment led to crystallization of the Nb2O5, allowing reversible Li+ intercalation/de-intercalation. For sweep rates corresponding to charging and discharging in under 3 min, a volumetric charge of 180 C cm-3 and Coulombic efficiency of 99.2% were attained.

Zhang, C.,


Maloney, R.,
Lukatskaya, M.,
Meidaghi, M.,
Dyatkin, B.,
Perre, E.,
Long, D.,
Qiao, W.,
Dunn, B.,
Gogotsi, Y.,

Journal of Power Sources,
vol. 274, pp. 121-129,
doi:10.1016/j.jpowsour.2014.10.018
2015Fully Alternating, Triaxial Electric or Magnetic Fields Offer New Routes to Fluid Vorticity

Abstract:

Martin, J.,


...Solis, K.,

Soft Matter,
vol. 11, pp. 241-254,
DOI: 10.1039/C4SM01936A
2015Quantifying Vorticity in Magnetic Particle Suspensions Driven by Symmetric and Asymmetric Multiaxial Fields

Abstract:

Martin, J.,


...Solis, K.,

Soft Matter,
vol. 11, pp. 7130-7142,
DOI: 10.1039/C5SM00966A
2014-12-24Cathode materials for magnesium and magnesium-ion based batteries

Abstract: Rechargeable magnesium-ion batteries are a promising candidate technology to address future electrical energy storage needs of large scale mobile and stationary devices, due to the high environmental abundance of magnesium metal and divalent character of magnesium ion. With the recent increase in reports discussing cathode materials for magnesium-ion batteries, it is instructive to assess recent research in order to provide inspiration for future research. This review is a summary of the different chemistries and structures of the materials developed for magnesium ion cathodes. The particular strategies which may lead to future research initiatives are amplified.

Huie, M.,


Bock, D.,
Takeuchi, E.,
Marshilok, A.,
Takeuchi, K.,

Coordination Chemistry Reviews,
vol. 287, pp. 15-27,
doi:10.1016/j.ccr.2014.11.005
2014-12-10Maximizing plating density and efficiency for a negative deposition reaction in a flow battery

Abstract: Flow batteries utilizing a plating reaction as the negative reaction are limited in energy capacity by the available void area in the cell stack. Large scale energy storage applications necessitate maximizing the plating density within the flow battery. Six porous negative electrode configurations using conductive and non-conductive materials are considered for use in a hybrid flow battery. Plating results using a Cu-Fe sulfate chemistry demonstrated a plating density in a carbon felt electrode (145 mAh cm-2 at 40 mA cm-2). Two layered electrode configurations were able to achieve 150 mAh cm-2 of plating density: carbon felt with non-conductive felt, and carbon felt-Daramic-carbon felt. Both electrode designs were tested with the all-iron chemistry using shallow charge/discharge cycles. The carbon felt with non-conducting felt electrode configuration maintained a voltaic efficiency of 81% over six cycles.

Hawthorne, K.,


Wainright, J.,
Savinell, R.,

J. Power Sources,
vol. 269, pp. 216-224,
doi:10.1016/j.jpowsour.2014.06.12
2014-12Maximizing plating density and efficiency for a negative deposition reaction in a flow battery

Abstract: Flow batteries utilizing a plating reaction as the negative reaction are limited in energy capacity by the available void area in the cell stack. Large scale energy storage applications necessitate maximizing the plating density within the flow battery. Six porous negative electrode configurations using conductive and non-conductive materials are considered for use in a hybrid flow battery. Plating results using a Cu Fe sulfate chemistry demonstrated a plating density in a carbon felt electrode (145 mAh cm-2 at 40 mA cm-2). Two layered electrode configurations were able to achieve 150 mAh cm-2 of plating density: carbon felt with non-conductive felt, and carbon felt-Daramic-carbon felt. Both electrode designs were tested with the all-iron chemistry using shallow charge/discharge cycles. The carbon felt with non-conducting felt electrode configuration maintained a voltaic efficiency of 81% over six cycles.

Hawthorne, K.,


Wainright, J.,
Savinell, R.,

Journal of Power Sources
269(10):216-224
2014-12The Role of Excess Sodium in Sol-Gel NaSICON Synthesis and Stability

Abstract: Controlling the materials chemistry of the solid-state ion conductor NaSICON is key to realizing its potential utility in emerging sodium-based battery technologies. We describe here the influence of excess sodium on phase evolution of sol-gel synthesized NaSICON. Alkoxide-based sol-gel processing was used to produce powders of Na3Zr2PSi2O12 NaSICON with 0-2 atomic % excess sodium. Phase formation and component volatility were studied as a function of temperature. NaSICON synthesis at temperatures between 900-1100°C with up to 2% excess sodium significantly reduced the presence of zirconia, sodium phosphate, and sodium silicate secondary phases in fired NaSICON powders. Insights into the role of sodium on the phase chemistry of sol-gel processed NaSICON may inform key improvements in NaSICON development.

Bell, N.,


Edney, C.,
Wheeler, J.,
Ingersoll, D.,
Spoerke, E.,

J. Amer. Ceram. Soc.
DOI: 10.1111/jace.13167
2014-11-18An Investigation into Factors Affecting the Iron Plating Reaction for an All-Iron Flow Battery

Abstract: The all-Iron flow battery utilizes the iron II/III redox couple at the positive electrode and the iron II/0 reaction at the negative electrode. The standard reduction potential of the iron II/0 reaction is at -0.44 V vs. NHE, suggesting that hydrogen evolution could be a significant factor in coulombic losses on the negative electrode. Methods of increasing the coulombic efficiency of iron plating are considered, such as anion concentration and electrolyte additives. The use of a chloride anion containing electrolyte showed less hydrogen evolution rates and faster plating kinetics than an electrolyte containing the same concentration of sulfate anions. Increasing the chloride concentration significantly reduced the hydrogen evolution observed on an iron electrode, and plating efficiencies of 97% were demonstrated on a rotating rod electrode. The effect of complexing ligands on plating and hydrogen evolution was also investigated.

Hawthorne, K.,


Petek, T.,
Miller, M.,

J. Electrochemical Society,
vol. 162, no. 1,
pp. A108-A113,
doi: 10.1149/2.0591501jes
2014-11-12Composite Anodes for Secondary Magnesium Ion Batteries Prepared via Electrodeposition of Nanostructured Bismuth on Carbon Nanotube Substrates

Abstract: Magnesium-ion batteries are attractive in part due to the high environmental abundance and low cost of magnesium metal. Anode materials other than Mg metal can provide access to new electrochemistries in non-corrosive Mg2+ electrolytes. A cyclic voltammetric method for the preparation of bismuth (Bi) based anodes was developed by systematically exploring electrodeposition using a quartz crystal microbalance. Controlled deposition of Bi on carbon nanotubes substrates could be achieved, enabling the first electrochemical investigation of bismuth-carbon nanotube (Bi-CNT) composite electrodes. Quasi-reversible Mg electrochemistry of Bi-CNT composite electrodes in non-corrosive magnesium-based electrolyte was demonstrated, with an initial delivered capacity exceeding 180 mAh/g. While the initial capacities were high, significant capacity decreases were observed with repeated cycling, indicating that additional development is warranted to further optimize this system.

DiLeo, R.,


Zhang, Q.,
Marschilok, A.,
Takeuchi, K.,
Takeuchi, E.,

ECS Electrochemistry Letters,
vol. 4, no. 1,
pp. A10-A14,
doi: 10.1149/2.0081501eel
2014-10Characterization of Reliability in SiC Power Devices

Abstract: Power devices based on the wide-bandgap semiconductors SiC and GaN have many potential advantages compared to conventional Si-based switching devices, especially for renewable energy and smart grid applications. However, while these emerging devices have developed rapidly in recent years, many factors affecting their performance and reliability remain unknown. In this paper, we discuss some of the key results that have been obtained for both SiC- and GaN-based devices under Sandia National Lab's “post-Silicon” power electronics reliability program. State-of-the-art, commercially available 4H-SiC MOSFETs are evaluated for stability under high-temperature over-voltage and pulsed over-current conditions. The devices show maximum vulnerability under high-temperature off-state operation at high temperature. The room-temperature pulsed over-current operation results in degradation similar to that observed under high-temperature on-state DC conditions, presumably due to overheating of the device beyond its specified junction temperature. Prototype AlGaN/GaN HEMTs with ~1800 V breakdown are evaluated for stability under different bias conditions. Current collapse is observed and analyzed, and trapping components with very different time constants are found to be involved. The specific nature of degradation and recovery depends strongly upon the particular stress bias (gate vs. drain) condition applied.

Marinella, M.,


Hughart, D.
Flicker, J.
Atcitty, S.
Kaplar, R.,

Proceedings of the 226th meeting of the Electrochemical Society
2014-10Switching frequency optimization of a high-frequency link based energy storage system

Abstract: There is currently a big thrust for integrating renewable resources to the electric grid. With increasing variable generation the need for energy storage devices has escalated. Traditional storage devices have bulky 60 Hz transformer to provide the electrical isolation from the grid. But, with the advent of advanced magnetic materials, power electronic topologies with high frequency link transformers are being researched. These systems have high power density and can be quickly dispatched for remote installations. This paper presents the design of the energy storage system consisting of the three phase rectifier and bi-directional dual active bride converter. It presents a methodology to optimize the switching frequency of the dual active bridge converter by minimizing the volume of the transformer and the total losses in the system. Frequency dependent and independent terms are aggregated and minimized over the range of switching frequency.

Kulasekaran, S.,


Ayyanar, R.,
Atcitty, S.,

Proceedings of the Annual Conference of the IEEE Industrial Electronics Society (IECON)
2014-09-04Approaches to, and Problems with, Ionic Liquid Electrolytes for Alkali Metal Electrochemical Devices: The Case of Low-Melting Chloroaluminate Binary Solutions

Abstract: Despite many attempts to use ionic liquid media with dissolved lithium salts as the electrolyte component of electrochemical cells, there has been only limited success. Despite its small size, Li+ seems to be the slowest species in the electrolyte, so the cells polarize. As sodium batteries gain attention, the needed Na+-containing ionic liquid electrolytes are likely to encounter similar, but more serious, kinetic problems. Here we first review past attempts to use, as an alternative, inorganic salts and quasi-salts of high conductivity, where conductivity increases with alkali content. Then we provide a detailed study of one organic cation system which confirms and extends earlier work by the Wilkes laboratory that showed how the opposite trend applied for mixtures of NaAlCl4 with the ionic liquid ethylmethylimidazolium tetrachloroaluminate [EMI][AlCl4]. In the present work the depression of conductivity for the Na+ case is fully characterized and is discussed in terms of a 1983 coulomb field alkali trapping concept for low-melting mixtures. This itself is an adaptation of earlier molten salt electrostatic and ionic polarizability models. The apparent exceptionalism of lithium salts in inorganic quasi-ionic liquid solutions is reviewed and possible ways of sidestepping the identified problems for sodium ion conductors are considered.

Tucker, T.,


Angell, C.,

J. Electrochem. Soc.,
vol. 161, no. 12,
pp. H796-H801,
doi: 10.1149/2.0471412jes
2014-08-11The Influences of Excess Sodium on Low-Temperature NaSICON Synthesis

Abstract: Controlling the materials chemistry of the solid-state ion conductor NaSICON is key to realizing its potential utility in emerging sodium-based battery technologies. We describe here the influence of excess sodium on phase evolution of sol-gel synthesized NaSICON. Alkoxide-based sol-gel processing was used to produce powders of Na3Zr2PSi2O12 NaSICON with 0-2 atomic % excess sodium. Phase formation and component volatility were studied as a function of temperature. NaSICON synthesis at temperatures between 900-1100°C with up to 2% excess sodium significantly reduced the presence of zirconia, sodium phosphate, and sodium silicate secondary phases in fired NaSICON powders. Insights into the role of sodium on the phase chemistry of sol-gel processed NaSICON may inform key improvements in NaSICON development.

Nelson, B.,


Edney, C.,
Wheeler, J.,
Ingersoll, D.,
Spoerke, E.,

Journal of The American Ceramic Society,
vol. 97, no. 12,
pp. 3744-3748
2014-07Optimal Locations for Energy Storage Damping Systems in the Western North American Interconnect

Abstract: Electromechanical oscillations often limit transmission capacity in the western North American Power System (termed the wNAPS). Recent research and development has focused on employing large-scale damping controls via wide area feedback. Such an approach is made possible by the recent installation of a wide-area real-time measurement system based upon Phasor Measurement Unit (PMU) technology. One potential large-scale damping approach is based on energy storage devices. Such an approach has considerable promise for damping oscillations. This paper considers the placement of such devices within the wNAPS system. We explore combining energy storage devices with HVDC modulation of the Pacific DC Intertie (PDCI). We include eigenanalysis of a reduced-order wNAPS system, detailed analysis of a basic two-area dynamic system, and full order transient simulations. We conclude that the optimal energy storage location is in the area with the lower inertia.

Byrne, R.,


Trudnowski, D.,
Neely, J.,
Elliott, R.,
Schoenwald, D.,
Donnelly, M.,

Proceedings of the 2014 Power and Energy Society General Meeting
2014-07Maximizing Revenue from Electrical Energy Storage in the Electricity Reliability Council of Texas (ERCOT)

Abstract: This paper outlines the calculations required to estimate the maximum potential revenue from participation in arbitrage and regulation in day-ahead markets using linear programming. Then, we use historical Electricity Reliability Council of Texas (ERCOT) data from 2011-2012 to evaluate the maximum potential revenue from a hypothetical 32 MWh, 8 MW system. We investigate the maximum potential revenue from two different scenarios: arbitrage only and arbitrage combined with regulation. Our analysis shows that, with perfect foresight, participation in the regulation market would have produced more than twice the revenue compared to arbitrage in the ERCOT market in 2011 and 2012. Three simple trading strategies that do not rely on perfect knowledge are then compared to the optimization results.

Byrne, R.,


Silva-Monroy, C.,

Proceedings of the 2014 Power and Energy Society General Meeting
2014-07Integrating Energy Storage Devices Into Market Management Systems

Abstract: Intuitively, the integration of energy storage technologies such as pumped hydro and batteries into vertically integrated utility and independent system operator/regional transmission operator (ISO/RTO)-scale systems should confer significant benefits to operations, ranging from mitigation of renewables generation variability to peak shaving. However, the realized benefits of such integration are highly dependent upon the environment in which the integration occurs. Further, integration of storage requires careful modeling extensions of existing market management systems (MMSs), which are currently responsible for market and reliability operations in the grid. In this paper, we outline the core issues that arise when integrating storage devices into an MMS system, ranging from high-level modeling of storage devices for purposes of unit comment and economic dispatch to the potential need for new mechanisms to more efficiently allow for storage to participate in market environments. We observe that the outcomes of cost-benefit analyses of storage integration are sensitive to system-specific details, e.g., wind penetration levels. Finally, we provide an illustrative case study showing significant positive impacts of storage integration.

Silva-Monroy, C.,


Watson, J.,

Proceedings of the IEEE
(102):1084-1093
2014-07Studies of Iron-Ligand Complexes for an All-Iron Flow Battery Application

Abstract: Seven organic ligands were investigated for use to coordinate reactive ions in the positive electrolyte of an all-iron flow battery. Exchange current densities, diffusion coefficients, and open circuit potentials of the ligand complexed ferric/ferrous redox couple are presented on a glassy carbon electrode. Results in a flow cell configuration suggest an ohmically controlled cell voltage and a highly distributed current distribution; the contributions from charge transfer and mass transfer are minor. The open circuit potential becomes a major factor in the selection of the complexed redox couple for determining which ligand to use in a flow battery. The iron-glycine complex was further investigated as a function of the ratio of glycine to ferric/ferrous ions and the pH of the solution. Results suggest a 1:1 glycine to iron ion electrolyte will be soluble up to 0.5 M ferric ion at a pH of 2 with a reaction potential of 468 mV vs. Ag/AgCl (0.690 vs SHE), suitable for use as a positive redox couple in the all-iron flow battery.

Hawthorne, K.,


Wainright, J.,
Savinell, R.,

Journal of The Electrochemical Society
161(10):A1662-A1671
2014-06-01Sensitivity Analysis of a Technique for the Extraction of Interface Trap Density in SiC MOSFETs from Subthreshold Characteristics

Abstract: A method for extracting interface trap density (DIT) from subthreshold I-V characteristics is used to analyze data on a SiC MOSFET stressed for thirty minutes at 175°C with a gate bias of -20 V. Without knowing the channel doping, the change in DIT can be calculated when referenced to an energy level correlated with the threshold voltage.

Hughart, D.,


Flicker, J.,
Atcitty, S.,
Marinella, M.,
Kaplar, R.,

Proc. IEEE IRPS,
pp. 2C.2.1-2C.2.6 (2014)
DOI 10.1109/IRPS.2014.6860589
2014-06Mixed-Metal, Structural, and Substitution Effects of Polyoxometalates on Electrochemical Behavior in a Redox Flow Battery

Abstract: A pair of redox flow batteries containing polyoxometalates was tested as part of an ongoing program in stationary energy storage. The iron-containing dimer, (SiFe3W9(OH)3 O34)2(OH)311−, cycled between (SiFe3W9(OH)3 O34)2(OH)311− /(SiFe3W9(OH)3 O34)2(OH)314− and (SiFe3W9(OH)3O34)2(OH)317−/ (SiFe3W9(OH)3 O34)2(OH)314− for the positive and negative electrode, respectively. This compound demonstrated a coulombic efficiency of 83% after 20 cycles with an electrochemical yield (measured discharge capacity as a percentage of theoretical capacity) of 55%. Cyclic voltammetry on the Lindqvist ion, cis-V2W4O194−, showed quasi-reversible vanadium electrochemistry, but tungsten reduction was mostly irreversible. In a flow cell configuration, cis-V2W4O194− had a coulombic efficiency of 45% (for a two-electron process) and an electrochemical yield of 16% after 20 cycles. The poor performance of cis-V2W4O194- was attributed primarily to its higher charge density. Collectively, the results showed that both polyoxometalate size and charge density are both important parameters to consider in battery material performance.

Pratt III, H.,


Pratt, W.,
Fang, X.,
Hudak, N.,
Anderson, T.,

Electrochimica Acta
138 (2014) 210-214
2014-06Performance and Reliability Characterization of 1200 V Silicon Carbide Power JFETs at High Temperatures

Abstract: We have characterized 1200 V SiC MOSFETs as well as Junction FETs (JFETs), which do not utilize a gate oxide, at high temperatures under both static and dynamic gate bias stress conditions. SiC JFET devices demonstrate more stable VT than SiC MOSFET devices for both types of gate bias stresses at high temperatures (Fig. 1b). For static gate bias stresses, packaged JFET devices exhibited a negligible VT shift (ΔVT < 2 mV) for temperatures up to 250oC. At higher temperatures, bare JFET die demonstrated ΔVT < 10 mV up to 525oC. Further, in contrast to the SiC MOSFETs, the VT of the SiC JFETs was unaffected by dynamic gate bias stress over the test period, although the sub-threshold leakage current increased with time. In addition to monitoring VT shifts, we have calculated the change in density of SiC/SiO2 interface traps (ΔDIT) due to the application of gate stress to MOSFETs. These profiles can be extracted from I-V curves for SiC MOSFETs based on the changes in sub-threshold slope. This technique can either be used to determine ΔDIT (if body doping and gate capacitance are unknown) or absolute DIT at specific energies within the bandgap (if doping and capacitance are known).

Flicker, J.,


Hughart, D.,
Marinella, M.,
Atcitty, S.,
Kaplar, R.,

Proceedings of the High Temperature Electronics Conference
2014-06Trap-Related Parametric Shifts under DC Bias and Switched Operation Life Stress in Power AlGaN/GaN HEMTs

Abstract: This paper reports on trap-related shifts of the transfer curve and threshold voltage of power AlGaN/GaN HEMTs under switched bias operating life and reverse and forward DC bias stress. Opposite polarity threshold voltage shifts at room temperature under operating life and reverse bias stress conditions can be explained by means of drain current transient measurements under reverse bias stress conditions. A proposed model to explain the trapping/de-trapping behavior under different stress conditions is described and highlights the critical role of the electric field. Experimental evidence of the importance of the role of the electric field is seen in reduced parametric shift by improving the field plate design.

Khalil, S.,


Ray, L.,
Chen, M.,
Chu, R.,
Zehnder, D.,
Garrido, A.,
Munsi, M.,
Hughes, B.,
Boutros, K.,
Kaplar, R.,
Dickerson, J.,
DasGupta, S.,
Atcitty, S.,
Marinella, M.,

Proceedings of the International Reliability Physics Symposium
2014-06-15Impact of Gate Stack on the Stability of Normally-Off AlGaN/GaN Power Switching HEMTs

Abstract: We have examined the response of AlGaN/GaN power switching HEMTs to electrical bias stress. Three different gate stack structures were studied. In devices containing a ~ 5 nm thick AlGaN layer in the gate stack, both positive and negative shifts in the threshold voltage were observed following high blocking voltage stress, consistent with a short initial period of electron trapping followed by a longer period of de-trapping. Correlated changes in reverse bias leakage current were also observed, although this also occurred in devices containing only residual AlGaN in the gate stack. The data have been explained by a field-enhanced emission model in which an electron trapping to de-trapping transition occurs. The exact nature of the transition is found to be sensitive to a variety of parameters including trap energy, geometry, and initial and boundary conditions.

Kaplar, R.,


Dickerson, J.,
DasGupta, S.,
Atcitty, S.,
Marinella, M.,
Khalil, S.,
Zehnder, D.,
Garrido, A.,

Proc. IEEE ISPSD,
pp. 209-212 (2014)
2014-06Static and Switching characteristics of 1200 V SiC Junction Transistors with on-chip integrated Schottky rectifiers

Abstract: A comprehensive evaluation of high-temperature (up to 200°C) on-state, blocking voltage and switching operation of 1200 V-class SiC Junction Transistors (SJTs) with on-chip integrated Schottky rectifiers is presented in this paper. The SJTs feature current gains of 69 and on-resistance of 6.3 mΩ-cm2 at room-temperature. The integrated free-wheeling Schottky rectifier displays a 0.9 V knee voltage and low on-resistance of 3.3 mΩ-cm2 at 25°C. Both the SJT and integrated Schottky rectifier show purely majority carrier characteristics with a desirable positive temperature co-efficient of on-state voltage drop. The integrated devices display robust 1200 V blocking voltages with low-leakage currents and a positive temperature co-efficient of breakdown - a clear signature of avalanche multiplication. Sub-50 ns switching waveforms are observed during hard-switching with an inductive load, due to the lower parasitic inherent to the integrated devices. Promising long-term current gain stability is obtained for the latest generation of SiC SJTs.

Sundaresan, S.,


Jeliazkov, S.,
Issa, H.,
Grummel, B.,
Singh, R.,

IEEE 26th International Symposium on Power Semiconductor Devices and ICs (ISPSD)
p. 249-252
2014-06Evaluation of Diels Alder poly(phenylene) anion exchange membranes in all-vanadium redox flow batteries

Abstract: Quaternary ammonium functionalized Diels-Alder poly(phenylene)s (QDAPPs) with different ion exchange capacities (IECs) are examined as membranes in all-vanadium redox flow batteries. QDAPP membrane behavior is compared to a standard, Nafion 212, in measurements of cycling efficiencies, areal specific resistance (ASR), vanadium permeation and durability. The IEC of the QDAPPs clearly shows an impact on the cell ASR and vanadium crossover. The results imply a trade-off between performance, indicated by cell voltage loss at a given current density, and rate of cross-over driven capacity loss in the system. Among the membranes studied, QDAPP with moderate IEC represents the best trade-off of these factors and exhibits higher performance and lower capacity loss compared to Nafion 212. All QDAPP membranes are found to be more durable than the analogous cation exchange membrane, sulfonated DAPP (SDAPP), in V5+ solution.

Sun, C.,


Tang, Z.,
Belcher, C.,
Zawodzinski, T.,
Fujimoto, C.,

Electrochem. Comm.
43:63-66
2014-05-29Sol Gel Based Synthesis and Electrochemistry of Mangesium Vanadium Oxide: A Promising Cathode Material for Secondary Magnesium Ion Batteries

Abstract: Magnesium-ion batteries are desirable due to the high environmental abundance and low cost of magnesium metal. Preparation, characterization, and an initial electrochemical study of Mg0.1V2O5 prepared by a novel sol gel method with no high temperature post processing is presented. Cyclic voltammetry showed the material to be quasi-reversible, with improved kinetics in an acetonitrile relative to a carbonate based electrolyte. Galvanostatic test data under a C/10 discharge showed a delivered capacity >250 mAh/g over several cycles. Projecting these results to a magnesium anode battery would yield an average operating voltage ~3.2 V with an energy density ~800 mWh/g for the cathode material, suggesting promise of our synthesized material as a viable cathode material for secondary magnesium batteries.

Lee, S.,


DiLeo, R.,
Marschilok, A.,
Takeuchi, K.,
Takeuchi, E.,

ECS Electrochemistry Letters,
vol. 3, no. 8,
pp. A87-A90,
doi: 10.1149/2.0021408eel
2014-05-16Redox Flow Batteries: An Engineering Perspective

Abstract: Redox flow batteries are well suited to provide modular and scalable energy storage systems for a wide range of energy storage applications. In this paper, we review the development of redox-flow-battery technology including recent advances in new redox active materials, cell designs, and systems, all from the perspective of engineers interested in applying this technology. We discuss cost, performance, and reliability metrics that are critical for deployment of large flow-battery systems. The technology, while relatively young, has the potential for significant improvement through reduced materials costs, improved energy efficiency, and significant reduction in the overall system costs.

Chalamala, B.,


Soundappan, T.,
Fisher, G.,
Anstey, M.,
Viswanathan, V.,
Perry, M.,

Proceedings of the IEEE,
vol. 102, no. 6,
pp. 976-999,
doi: 10.1109/JPROC.2014.232031
2014-05Sol Gel Based Synthesis and Electrochemistry of Magnesium Vanadium Oxide: A Promising Cathode Material for Secondary Magnesium Ion Batteries

Abstract: Magnesium-ion batteries are desirable due to the high environmental abundance and low cost of magnesium metal. Preparation,characterization, and an initial electrochemical study of Mg0.1V2O5 prepared by a novel sol gel method with no high temperature post processing is presented. Cyclic voltammetry showed the material to be quasi-reversible, with improved kinetics in an acetonitrile relative to a carbonate based electrolyte. Galvanostatic test data under a C/10 discharge showed a delivered capacity >250 mAh/g over several cycles. Projecting these results to a magnesium anode battery would yield an average operating voltage ∼3.2 V with an energy density ∼800 mWh/g for the cathode material, suggesting promise of our synthesized material as a viable cathode material for secondary magnesium batteries.

Lee, S.,


DiLeo, R.,
Marschilok, A.,
Takeuchi, K.,
Takeuchi, E.,

ECS Electrochemistry Letters
3(8):A87-A90
2014-04-14Chemical Expansion: Implications for Electrochemical Energy Storage and Conversion Devices

Abstract: Many energy-related materials rely on the uptake and release of large quantities of ions, for example, Li+ in batteries, H+ in hydrogen storage materials, and O2- in solid-oxide fuel cell and related materials. These compositional changes often result in large volumetric dilation of the material, commonly referred to as chemical expansion. This article reviews the current knowledge of chemical expansion and aspires to facilitate and promote future research in this field by providing a taxonomy for its sources, along with recent atomistic insights of its origin, aided by recent computational modeling and an overview of factors impacting chemical expansion. We discuss the implications of chemical expansion for mechanical stability and functionality in the energy applications above, as well as in other oxide-based systems. The use of chemical expansion as a new means to probe other materials properties, as well as its contribution to recently investigated electromechanical coupling, is also highlighted.

Bishop, S.,


Marrocchelli, D.,
Chatzichristodoulou, C.,
Perry, N.,
Moegensen, M.,
Tuller, H.,
Wachsman, E.,

Annual Review of Materials Research,
vol. 44, pp. 205-23,
DOI: 10.1146/annurev-matsci-070813-11332
2014-01Optical measurements of impurities in room-temperature ionic liquids

Abstract: The absorption spectra of 1-methylimidazole and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI], mixtures from 0% to 20% mole fraction are reported at ultraviolet to infrared wavelengths. Quantitative measurement of 1-methylimidazole in [EMIM][TFSI] is reported using an isolated 1-methylimidazole absorption feature at 1520 cm-1. UV measurements reveal a 1-methylimidazole absorption feature at 270 nm and a 260 nm feature for [EMIM][TFSI]. Absorption at 280 nm is demonstrated to scale with 1-methylimidazole mole fraction in [EMIM][TFSI] and is used to measure 1-methylimidazole mole fractions. Absorption is shown to increase around 240 nm upon addition of 1-methylimidazole to [EMIM][TFSI], which preliminary time-dependent density functional theory (DFT) calculations identify as an intermolecular excitation between [EMIM][TFSI] and 1-methylimidazole. We report recommendations for UV and infrared detection schemes for the quantitative detection of 1-methylimidazole in [EMIM][TFSI].

Porter, J.,


Dreyer, C.,
Bicknase, D.,
Vyas, S.,
Maupin, M.,
Poshusta, J.,
Martin, J.,

Quant. Spectr. Rad. Trans.
133:300-310
2014-01Optical Measurements of Impurities in Room Temperature Ionic Liquids

Abstract: The absorption spectra of 1-methylimidazole and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMIM][TFSI], mixtures from 0% to 20% mole fraction are reported at ultraviolet to infrared wavelengths. Quantitative measurement of 1-methylimidazole in [EMIM][TFSI] is reported using an isolated 1-methylimidazole absorption feature at 1520 cm(-1). UV measurements reveal a 1-methylimidazole absorption feature at 270 nm and a 260 nm feature for [EMIM][TFSI]. Absorption at 280 nm is demonstrated to scale with 1-methylimidazole mole fraction in [EMIM][TFSI] and is used to measure 1-methylimidazole mole fractions. Absorption is shown to increase around 240 nm upon addition of 1-methylimidazole to [EMIM][TFSI], which preliminary time-dependent density functional theory (DFT) calculations identify as an intermolecular excitation between [EMIM][TFSI] and 1-methylimidazole. We report recommendations for UV and infrared detection schemes for the quantitative detection of 1-methylimidazole in [EMIM][TFSI].

Porter, J. ,


Dreyer, C.,
Bicknase, D.,
Vyas, S.,
Maupin, C.,
Poshusta, J.,
Martin, J.,

J. of Quantitative Spectroscopy and Radiative Transfer
133:300-310
2014-01Preparation and Processing Temperature Effects on Ion Conductivity in Solution Derived Sodium Zirconium Phosphate (NaZr2P3O12) Thin Films

Abstract: Sodium zirconium phosphate, NaZr2P3O12, thin films have been prepared via a chemical solution approach on platinized silicon substrates. The films are observed to crystallize at temperatures in excess of 725°C and are highly 012-textured. Film grain size scales with processing temperature with grain sizes of 96 to 142 nm measured for films processed at 750°C to 800°C, respectively. Room temperature sodium-ion conductivity also scales with processing temperature with values of 3.5 × 10−7 to 5.1 × 10−7 S/cm measured. Activation energies for sodium-ion conduction measured from room temperature to 150°C were invariant with processing condition and are approximately 0.49 eV. The ionic conductivity and activation energy values agree well with bulk ceramic reference data and thus demonstrate that sodium super ionic conducting thin films with bulk-like properties are possible in thin film embodiments.

Meier, W.,


Apblett, C.,
Ingersoll, D.,
McDaniel, A.,
Ihlefeld, J.,

Journal of The Electrochemical Society
161(3), A364-367, (2014)
2014Silicon Carbide Junction Transistors and Schottky Rectifiers optimized for 250°C operation

Abstract: Electrical performance and reliability of SiC Junction Transistors (SJTs) and Schottky rectifiers are presented. The 650 V/50 A-rated SiC SJTs feature current gains (β) up to 110 at room-temperature, 70 at 250°C, and stable breakdown characteristics. Single current pulse measurements indicate an almost invariant β up to 800 A/cm2 at 175°C - a measure of the SOA boundary for pulsed current SJT operation. Lower than 5 mA/cm2 leakage currents are measured on the SJTs at the rated blocking voltage and at 250°C. 1200 V Schottky rectifiers designed for high-temperature operation display < 3 mA/cm2 leakage currents up to 250°C. A 10x reduction in leakage current and 23% reduction in junction capacitance are observed when compared to the nearest competitor. The high-temperature Schottky rectifiers and SJTs display stable breakdown voltages and on-state characteristics after long-term HTRB stressing. A significant improvement in current gain stability is achieved by fine-tuning the fabrication process.

Sundaresan, S.,


Grummel, B.,
Singh, R.,

MRS Proceedings
1693 mrss14-1693-dd03-08
doi:10.1557/opl.2014.531
2014Rapidly Maturing SiC Junction Transistors featuring current gain > 130, blocking voltages up to 2700 V and stable long-term operation

Abstract: SiC npn Junction Transistors (SJTs) with current gains as high as 132, low on-resistance of 4 mΩ-cm2, and minimal emitter-size effect are demonstrated with blocking voltages > 600 V. 2400 V-class SJTs feature blocking voltages as high as 2700 V combined with on-resistance as low as 5.5 mΩ-cm2. A significant improvement in the current gain stability under long-term high current stress is achieved for the SJTs fabricated by the high gain process.

Sundaresan, S.,


Jeliazkov, S.,
Grummel, B.,
Singh, R.,

Materials Science Forum
778-780:1001-1004
2014Phase formation of BaTiO3 - Bi(Zn1/2Ti1/2)O3 perovskite ceramics

Abstract: Materials based on BiMO3-modified BaTiO3 have been shown to exhibit a number of attractive electrical and electromechanical properties. In addition, many of the materials in this broad family exhibit reduced sintering temperatures for densification as compared to pure BaTiO3. We report here a study of the phase evolution and sintering behavior of Bi(Zn1/2Ti1/2)O3-modified BaTiO3 materials from low-cost mixed oxide/carbonate precursor powders. By accelerating the reaction of the BaCO3 species and increasing the diffusion kinetics associated with densification, Bi(Zn1/2Ti1/2)O3 additions reduce the calcination and sintering temperatures by ~200°C compared to unmodified BaTiO3. This system provides an example of the important and often overlooked role of additives in the calcination, phase evolution, and densification processes, and provides insight into mechanisms that may be further exploited in this and other important materials systems. We are quite honored to have the opportunity to publish in a special issue dedicated to the life and work of our dear late colleague Prof. Marija Kosec. The topic of this paper is fitting as well, since the work was in large part directly inspired by her work on the importance of reactions and intermediate phases in the alkali niobate systems and heavily informed by her work on the Pb-based perovskites. Marija appreciated better than most the importance of careful processing in the formation of fine ceramics, and the global ceramics community is grateful to her for all of the lessons that she taught us—and through her papers and her students, continues to teach us.

Triamnak, N.,


Brennecka, G.,
Brown-Shaklee, H.,
Rodriguez, M.,
Cann, D.,

J. Cer. Soc. Jpn.
122:260-266
2014The Design and Development of a 15 kV SiC Half-Bridge Multi-Chip Power Module for Medium Voltage Applications

Abstract: In this work, the packaging design and development of a high voltage (> 15 kV), high current (120 A) silicon carbide (SiC) multi-chip power module (MCPM) will be presented. The module implements a MCPM packaging strategy which itself uses subassemblies to reduce manufacturing cost through reworkability. The use of solderless internal connections aids in reducing cost both by simplifying the assembly process as well as enabling a high level of flexibility in the manufacturing process in order to drive down costs by increasing yield. A wire bondless flip-chip die interconnection scheme has been developed in this work in parallel with a more traditional wire bonded method. Both presented approaches utilize a common set of parts with minimal differences due to the divergent portions of each interconnection scheme. Device neutrality in this design ensures that a variety of die types from any manufacturer may be housed in a number of arrangements depending on the requirements of the end-use application without requiring significant redesign effort for each new application or improvement in device technology. The SiC MCPM is constructed using high temperature capable materials, enabling operation at high junction temperatures. This leads to the ability to design a small, low profile module with low parasitic inductances and a small junction to case thermal resistance. A low module thermal resistance makes it possible to significantly reduce the size and complexity of the cooling systems, ultimately, reducing the size of the system. Thus, the novel high voltage SiC MCPM represents a significant step forward in high voltage switching applications. This paper discusses the overall mechanical design of the SiC high voltage MCPM; the three-dimensional finite-element modeling and analysis of the thermal and electrical characteristics of the high voltage power module are also presented.

Cole, Z.,


Stabach, J.,
Falling, G.,
Killeen, P.,
McNutt, T.,
Passmore, B.,

Proceedings of the IMAPS 47th International Symposium on Microelectronics
2014AlGaN composition dependence of the band offsets for epitaxial Gd2O3/ AlxGa1-xN (0≤x≤0.67) heterostructures

Abstract: In this work we investigated the dependence of AlGaN composition on the valence band offsets at a Gd2O3/AlGaN interface. We found that as the AlN content in the AlGaN semiconductor layer increases, the valence band offset with the gate oxide, Gd2O3, decreases. An AlGaN composition with ~67% AlN possessed virtually no valence band offset with the gate oxide and therefore shows that this is an important design criteria for the development of next generation nominally-off power electronic devices.

Ihlefeld, J.,


Brumbach, M.,
Allerman, A.,
Wheeler, D.,
Atcitty, S.,

Applied Physics Letters
105:012102
2013-12-31An Ambient Temperature Molten Sodium-Vanadium Battery with Aqueous Flowing Catholyte

Abstract: In this study, we have investigated the key factors dictating the cyclic performance of a new type of hybrid sodium-based flow batteries (HNFBs) that can operate at room temperature with high cell voltages (>3 V), multiple electron transfer redox reactions per active ion, and decoupled design of power and energy. HNFBs are composed of a molten Na-Cs alloy anode, flowing aqueous catholyte, and a Na-ß"-Al2O3 solid electrolyte as the separator. The surface functionalization of graphite felt electrodes for the flowing aqueous catholyte has been studied for its effectiveness in enhancing V2+/V3+, V3+/V4+, and V4+/V5+ redox couples. The V4+/V5+ redox reaction has been further investigated at different cell operation temperatures for its cyclic stability and how the properties of the solid electrolyte membrane play a role in cycling. These fundamental understandings provide guidelines for improving the cyclic performance and stability of HNFBs with aqueous catholytes. We show that the HNFB with aqueous V-ion catholyte can reach high storage capacity (~70% of the theoretical capacity) with good Coulombic efficiency (90% ± 1% in 2-30 cycles) and cyclic performance (>99% capacity retention for 30 cycles). It demonstrates, for the first time, the potential of high capacity HNFBs with aqueous catholytes, good capacity retention and long cycling life. This is also the first demonstration that Na-ß"-Al2O3 solid electrolyte can be used with aqueous electrolyte at near room temperature for more than 30 cycles.

Liu, C.,


Shamie, J.,
Shaw, L.,
Sprenkle, V.,

ACS Appl. Mater. Interfaces,
vol. 8, pp. 1545-1552,
DOI: 10.1021/acsami.5b11503
2013-12Computational model of a sodium-copper-iodide rechargeable battery

Abstract: This paper first derives a model to describe a class of Na-metal-halide secondary batteries, using molten sodium as the anode, NASICON as the sodium-ion-conducting separator, and copper-iodide chemistry in an aqueous electrolyte for the cathode. The model is based upon solving transient conservation equations using a Nernst-Planck-Poisson (NPP) formulation. The broad objective is to develop a predictive model that can assist the design and development of large-scale grid-storage batteries. However, the model-predicted results and discussion are focused on a laboratory-scale battery. Several examples are discussed, considering the effects of current density and catholyte molar concentrations on battery performance.

Zhu, H.,


Bhavaraju, S.,
Kee, R.,

Electrochim. Acta
112:629-639
2013-12Computational model of a sodium-copper-iodide rechargeable battery

Abstract: This paper first derives a model to describe a class of Na-metal-halide secondary batteries, using molten sodium as the anode, NASICON as the sodium-ion-conducting separator, and copper-iodide chemistry in an aqueous electrolyte for the cathode. The model is based upon solving transient conservation equations using a Nernst-Planck-Poisson (NPP) formulation. The broad objective is to develop a predictive model that can assist the design and development of large-scale grid-storage batteries. However, the model-predicted results and discussion are focused on a laboratory-scale battery. Several examples are discussed, considering the effects of current density and catholyte molar concentrations on battery performance.

Zhu, H.,


Bhavaraju, S.,
Kee, R.,

Electrochmica Acta
112:629-639
2013-10Progress in SiC MOSFET Reliability

Abstract: Bias-temperature stress experiments performed on two generations of SiC power MOSFETs from the same manufacturer show reductions in threshold voltage (VT) shift at elevated temperatures from first- to second-generation. The negative VT shift is reduced from a range of -1 V to -1.6 V to a range of -100 mV to -300 mV for temperatures from 125°C to 175°C. Plastic-packaged parts show a gate-bias-independent junction leakage current at temperatures above the rated temperature, suggesting that the plastic packaging introduces an extrinsic leakage path. Junction leakage in metal-packaged parts can be significantly reduced by applying a small negative gate bias at elevated temperatures. Switching gate bias temperature stresses show VT shifts dependent on duty cycle, with a higher duty cycle resulting in a higher rate of VT shift. Cumulative damage effects may be observed between switching gate bias stresses.

Marinella, M.,


Hughart, D.,
Flicker, J.,
DasGupta, S.,
Atcitty, S.,
Kaplar, R.,

Proceedings of the 224th Meeting of the Electrochemical Society
2013-09Application of Redox Non-Innocent Ligand to Non-Aqueous Flow Battery Electrolytes

Abstract: Demonstrate that electrolytes comprising redox “non-innocent” ligands, which store equivalents of charge separate from the metal center, are a new avenue for electrical energy storage.

Cappillino, P.,


Pratt III, H.,
Hudak, N.,
Tomson, N.,
Anderson, T.,
Anstey, M.,

Adv. Energy Mater.
(4):1-4
2013-09Application of Redox Non-Innocent Ligands to Non-Aqueous Flow Battery Electrolytes

Abstract: High energy-density, redox flow batteries (RFB) can provide cost-effective, grid-scale energy storage, facilitating the use of intermittent sources such as solar and wind power. A new electrolyte based on vanadium and redox-active ligands that stores equivalents of charge separately from the metal center is presented. Electrolytes composed of non-innocent ligands greatly enhance both the energy density and stability of non-aqueous RFBs.

Cappillino, P.,


Pratt III, H.,
Hudak, N.,
Tomson, N.,
Anderson, T.,
Anstey, M.,

Advanced Energy Materials
2013-09Copper Ionic Liquids: Tunable ligand and anion chemistries to control electrochemistry and deposition morphology

Abstract: A multi-technique investigation was performed on three copper-based ionic liquids to elucidate the influence of coordinating ligands and charge-balancing anions on the electrochemical properties of the materials. Galvanostatic cycling of Cu(OHCH2CH2NH2)6(BF4)2 (Cu1) in 1-butyl-3-methyl-imidazolium hexafluorophosphate gave partially reversible plating of copper that was consistent with cyclic voltammetry data (collected using an ionic liquid-based reference electrode verified with measurements of ferrocene, cobaltocene, and lithium). Scanning electron microscopy also showed pitting in the copper-coated surface of the electrode that was consistent with the stripping wave observed by cyclic voltammetry. Potentiostatic deposition in neat Cu1 showed significant dendrite formation. The substitution of the OHCH2CH2NH2 ligands of Cu1 with stronger coordinating NH(CH2CH2OH)2 in Cu(NH(CH2CH2OH)2)6(BF4)2 (Cu2) resulted in the complete suppression of both copper stripping and dendrite formation. Substitution of the BF4- anions of Cu2 with CF3SO3- in Cu(NH(CH2CH2OH)2)6(CF3SO3)2 (Cu3) shifted the copper deposition 0.1 V more negative and produced slightly larger spherical particles (1.5 μm versus 5 μm). The results suggested that while the anion composition influenced particle size, and the metal-ligand bond strength helped control particle morphology, both factors affected the electrochemical properties including the plating and stripping of copper.

Pratt III, H.,


Ingersoll, D.,
Hudak, N.,
McKenzie, B.,
Anderson, T.,

J. Electroanal. Chem.
704:153-158
2013-08-07Progress in SiC MOSFET Reliability

Abstract: Bias-temperature stress experiments performed on two generations of SiC power MOSFETs from the same manufacturer show reductions in threshold voltage (VT) shift at elevated temperatures from first- to second-generation. The negative VT shift is reduced from a range of -1 V to -1.6 V to a range of -100 mV to -300 mV for temperatures from 125°C to 175°C. Plastic-packaged parts show a gate-bias-independent junction leakage current at temperatures above the rated temperature, suggesting that the plastic packaging introduces an extrinsic leakage path. Junction leakage in metal-packaged parts can be significantly reduced by applying a small negative gate bias at elevated temperatures. Switching gate bias temperature stresses show VT shifts dependent on duty cycle, with a higher duty cycle resulting in a higher rate of VT shift. Cumulative damage effects may be observed between switching gate bias stresses.

Hughart, D.,


Flicker, J.,
DasGupta, S.,
Atcitty, S.,
Kaplar, R.,
Marinella, M.,

ECS Transactions,
v. 58(8), pp. 211-220 (2013)
2013-08Synthesis and characterization of a family of solvated sodium aryloxide compounds

Abstract: A family of crystallographically characterized solvated sodium alkoxides ([(solv)xNa(OR)]n) was synthesized from the reaction of sodium bis(trimethylsilyl)amide with a series of sterically varied aryl alcohols (H-OAr): 2-alkyl phenol [alkyl = methyl (oMP), iso-propyl (oPP), and tert-butyl (oBP)] or 2,6-di-alkyl phenol [alkyl = methyl (DMP), iso-propyl (DIP), and tert-butyl (DBP)]. Single crystal X-ray experiments revealed the structure of the products to be highly dependent on the ligand set employed and the solvent used (THF or py). The [(solv)xNa(OAr)]n products were identified as: [(THF)Na(μ3-oMP)]6 (1), [(THF)4Na6(μ3-oPP)4(μ4-oPP)2] (2), [(THF)Na(μ3-oBP)]4 (3)·THF, [(THF)Na(μ3-DMP)]4 (4), [(THF)2Na(μ-DIP)]2 (5), [(THF)2Na(μ-DBP)]2 (6), {[Na(μ-DPhP-ηx)]2}n (7), [(py)5Na6(μ3-oMP)4(μ4-oMP)2]2[(py)4Na6(μ3-oMP)4(μ4-oMP)2] (8), [(py)6Na4(μ3-oPP)4] (9)·py, [(py)Na(μ3-DMP)]4 (11), [(py)2Na(μ-DIP)]2 (12), [(py)4Na(DBP)] (13). Crystals could not be isolated for the Na/oBP/py (10) system but the powder was assigned the '[(py)Na(oBP)]4' structure based on the available analytical data. In addition, under similar conditions, the neo-pentoxide (ONep) derivatives were isolated and characterized as [(solv)4Na6(μ3-ONep)4(μ4-ONep)2] (solv = THF, 14; py 15). A number of complex structures (monomers, squares, cubes, fused-cubes, hexagons) were observed for this family of [(solv)xNa(OAr)]n compounds. The solution behaviors of these compounds were studied using heteronuclear 23Na NMR. A comparison of these [(solv)xA(OR)]n A = Li, Na, K, Rb, Cs structural motifs is also presented.

Boyle, T.,


Velazquez, A.,
Yonemoto, D.,
Alam, T.,
Moore, C.,
Rheingold, A.,

Inorganica Chimica Acta
405:374-386
2013-08A Photocapacitance Decay Technique for Interface Trap Characterization near Inversion Band in Wide Bandgap MOS Capacitors

Abstract: A technique to characterize interface traps near the minority carrier band for wide bandgap metal-oxide-semiconductor (MOS) capacitors at room temperature is presented. The method uses photogeneration of minority carriers and transient analysis of the subsequent photocapacitance decay to evaluate trap response times. The technique is demonstrated using n-type substrate 6H-SiC/SiO2 MOS capacitors to extract interface trap density (Dit) ranging in energy from 0.2 to 0.8 eV above the valence band edge (Ev) and trap cross sections from 0.4 to 0.7 eV above Ev. For the given material system, traps near Ev exhibit significant differences between n-and p-type substrate MOS capacitors.

DasGupta, S.,


Kaplar, R.,
Atcitty, S.,
Marinella, M.,

IEEE Transactions on Electron Devices
60(8):2619
2013-07Battery Energy Storage System

Abstract: This chapter discusses the various technical components of battery energy storage systems for utility-scale energy storage and how these technical components are interrelated. The introduction lists the basic types of large-scale storage and how storage can be used to mitigate the variability associated with renewable generation. It also provides an overview of how to define storage applications as primarily “power” or “energy” based. A basic description of how battery energy storage works is provided with several examples to illustrate how battery energy storage can be used in large-scale applications. A brief discussion of the various battery chemistries that are suited to large-scale applications is provided, as well as guidance on what factors to look for when trying to select an appropriate chemistry for a given application. An overview of how the storage system’s power electronics work is followed by a more detailed description of possible power electronic topologies and power electronic controls that are used to ensure that the system can be properly integrated with the generation source and, if necessary, the load. Battery management and battery monitoring via the power electronic controls is discussed briefly. This chapter concludes with a detailed example of battery energy storage system integration that is summarized with data obtained in the field.

Atcitty, S.,


Neely, J.,
Ingersoll, D.,
Akhil, A.,
Waldrip, K.,

Springer-Verlag London.
2013-07Damping of Inter-area Oscillations using Energy Storage

Abstract: Low frequency inter-area oscillations have been identified as a significant problem in utility systems due to the potential for system damage and the resulting restrictions on power transmission over select lines. Previous research has identified real power injection by energy storage based damping control nodes as a promising approach to mitigate inter-area oscillations. In this paper, a candidate energy storage system based on UltraCapacitor technology is evaluated for damping control applications in theWestern Electric Coordinating Council (WECC), and an analytical method for ensuring proper stability margins is also presented for inclusion in a future supervisory control algorithm. Dynamic simulations of the WECC were performed to validate the expected system performance. Finally, the Nyquist stability criteria was employed to derive safe operating regions in the gain, time delay space for a simple two-area system to provide guaranteed margins of stability.

Neely, J.,


Byrne, R.,
Elliott, R.,
Silva-Monroy, C.,
Schoenwald, D.,
Trudnowski, D.,
Donnelly, M.,

IEEE Power & Energy Society
2013-07Performance and Reliability Characterization of 1200 V Silicon Carbide Power MOSFETs at High Temperatures

Abstract: Commercially available, 1200 V SiC power MOSFETs have been characterized under bias-temperature stress conditions. Two generations of devices from a single manufacturer were tested. For the first-generation MOSFETs, both plastic- and metal-packaged devices were evaluated, whereas for the second-generation MOSFETs, only plastic-packaged devices were tested. Threshold voltage was observed to decrease with increasing temperature in the absence of gate bias stress, as expected. Drain leakage current increased with increasing temperature above the rated temperature of 125˚C for first-generation plastic-packaged parts, with the leakage ~10× higher for the plastic-packaged parts compared to the metal-packaged parts. A negative gate voltage was shown to reduce drain leakage current for the metal-packaged parts only, suggesting a parasitic leakage path associated with the plastic packaging. The threshold voltage shift DVT was minimal for T < 125˚C. DVT increased with increasing temperature above 125˚C, and was larger for negative gate voltage bias stress, suggesting that the oxide is more sensitive to trapping of holes than trapping of electrons. DVT was insensitive to the type of package. The second-generation SiC MOSFET showed significantly less susceptibility to bias temperature stress, especially for negative gate voltage, indicating improvement in device design and/or processing in the second-generation MOSFET. Switching gate stress showed complex behavior, with a rapid initial shift in VT followed by a much slower shift. Initial testing indicates a strong dependence on duty cycle and possible influence of self-heating. More detailed study of reliability under switching conditions is needed.

Kaplar, R.,


Hughart, D.,
Atcitty, S.,
Flicker, J.,
DasGupta, S.,
Marinella, M.,

High Temperature Electronics Network,
Oxford, UK
2013-05Highly Li-Stuffed Garnet-Type Structured Li7+xLa3Zr2-xYxO12

Abstract: We report the synthesis, microstructure and Li ion conductivity of Li-stuffed garnet-type metal oxides, with nominal chemical formulae Li7.06La3Zr1.94Y0.06O12 and Li7.16La3Zr1.84Y0.16O12. Powder X-ray diffraction (PXRD) shows the formation of cubic garnet-type structure at 950°C (12 h in air) with cell constant of 12.974(3) Å and 12.995(2) Å for Li7.06La3Zr1.94Y0.06O12 and Li7.16La3Zr1.84Y0.16O12, respectively. The slight increase in cubic cell constant is consistent with Y-substitution for Zr in Li7La3Zr2O12. For samples sintered at 1100-1150°C, PXRD displays multi-phase mixtures, but the garnet-type structure remained the major phase. Scanning electron microscopy (SEM) studies show an average crystallite size in the range of 2-5 μm, and particle size increases with increasing sintering temperature, as anticipated. Energy dispersive spectroscopy (EDS) elemental mapping show single homogenous distribution of elements, for samples prepared at 950°C. Electrochemical AC impedance spectra exhibit mainly bulk contribution at temperatures higher than 150°C, and at low temperature, we see contributions from bulk and grain-boundary resistance. The bulk electrical conductivity of the sample was found to be comparable to those of the high temperature tetragonal Li7La3Zr2O12 phase. The electrical conductivity of Y-doped samples investigated in the present work was ~10-6 Scm-1 at 23°C with an activation energy of 0.47 eV. The lower conductivity of this Y-doped garnet was explained based on Raman spectroscopy and SEM analysis.

Hitz, G.,


Wachsman, E.,
Thangadurai, V.,

Electrochem. Soc.
160:A1248-A1255
2013-05Characterization and Reliability of SiC- and GaN-Based Power Transistors for Renewable Energy Applications

Abstract: Power devices based on the wide-bandgap semiconductors SiC and GaN have many potential advantages compared to conventional Si-based switching devices, especially for renewable energy and smart grid applications. However, while these emerging devices have developed rapidly in recent years, many factors affecting their performance and reliability remain unknown. In this paper, we discuss some of the key results that have been obtained for both SiC- and GaN-based devices under Sandia National Lab's “post-Silicon” power electronics reliability program. State-of-the-art, commercially available 4H-SiC MOSFETs are evaluated for stability under high-temperature over-voltage and pulsed over-current conditions. The devices show maximum vulnerability under high-temperature off-state operation at high temperature. The room-temperature pulsed over-current operation results in degradation similar to that observed under high-temperature on-state DC conditions, presumably due to overheating of the device beyond its specified junction temperature. Prototype AlGaN/GaN HEMTs with ~1800 V breakdown are evaluated for stability under different bias conditions. Current collapse is observed and analyzed, and trapping components with very different time constants are found to be involved. The specific nature of degradation and recovery depends strongly upon the particular stress bias (gate vs. drain) condition applied.

Kaplar, R.,


Marinella, M.,
DasGupta, S.,
Smith, M.,
Atcitty, S.,
Sun, M.,
Palacios, T.,

IEEE Energy Tech,
Cleveland, OH
2013-04Reliability Analysis and Prediction of Commercial 1200 V, 33A, 4H-SiC MOSFETs under DC and Pulsed Stress

Abstract: State-of-the-art, commercially available, 4H-SiC MOSFETs are evaluated for stability under high-temperature over-voltage and pulsed over-current conditions. The devices show maximum vulnerability under high-temperature accumulation stress, demonstrating that the gate oxide is more prone to hole trapping than to electron trapping. The power MOSFET architecture coupled with a high interface trap density enables us to predict the stability of the device through a simple evaluation of the free-wheeling diode ideality factor (h) of the unstressed device. The pulsed over-current operation results in degradation similar to electron trapping at high temperature, presumably due to overheating of the device beyond its specified junction temperature. Over-current degradation is more severe at high switching frequency.

DasGupta, S.,


Kaplar, R.,
Marinella, M.,
Smith, M.,
Atcitty, S.,

International Reliability Physics Symposium,
Anaheim, CA
2013-03A Polyoxometalate Flow Battery

Abstract: A redox flow battery utilizing two, three-electron polyoxometalate redox couples was investigated for use in stationary storage in either aqueous or non-aqueous conditions. The aqueous battery had coulombic efficiencies greater than 95% with relatively low capacity fading over 100 cycles. Infrared studies showed there was no decomposition of the compound under these conditions. The non-aqueous analog had a higher operating voltage but at the expense of coulombic efficiency. The spontaneous formation of these clusters by self-assembly facilitates recovery of the battery after being subjected to reversed polarity. Polyoxometalates offer a new approach to stationary storage materials because they are capable of undergoing multielectron reactions and are stable over a wide range of pH values and temperatures.

Pratt III, H.,


Hudak, N.,
Fang, X.,
Anderson, T.,

Journal of Power Sources
2013-02Copper ionic liquids: examining the role of the anion in determining physical and electrochemical properties

Abstract: Five new copper(II)-based ionic liquids and three crystalline compounds have been synthesized in order to further understand the role of the anion in determining their physicochemical properties. Materials were prepared with combinations of three different anions (2-ethylhexanoate (EHN), tetrafluoroborate (BF4), and triflate (OTf)) and six-coordinate Cu(II) cations. The complexes that contain at least one BF4 anion consistently displayed both the highest specific conductivity and electrochemical reversibility. The presence of one OTf anion (in combination with one EHN or BF4) facilitates the formation of crystalline materials. Single crystal X-ray diffraction studies were completed on two of the mixed anion compounds. The results show that both ethanolamine (EA) and diethanolamine (DEA) chelate to the Cu(II) centers in a highly distorted tetragonal geometry. The properties of the ionic liquid with the overall lowest viscosity and highest conductivity and electrochemical reversibility (Cu{NH2CH2CH2OH}6(BF4)2, 4) were studied as a function of temperature. The viscosity decreases with increasing temperature, but at 45 °C (over three hours) there is a loss of two EA ligands to form a more viscous four-coordinate complex. Cyclic voltammetry of 4 reveals a quasi-reversible Cu(II)/Cu(I) reduction wave that shifts to more positive potentials with increasing temperature.

Pratt III, H.,


Leonard, J.,
Steele, L.,
Staiger, C.,
Anderson, T.,

Inorg. Chim. Acta
396:78-83
2013Mixed addenda polyoxometalate 'solutions' for stationary energy storage

Abstract: A series of redox flow batteries utilizing mixed addenda (vanadium and tungsten), phosphorus-based polyoxometalates (A-α-PV3W9O406-, B-α-PV3W9O406−, and P2V3W15O629−) were prepared and tested.

Pratt III, H.,


Anderson, T.,

Dalton Trans.
42:15650-15655
2013Band offsets of La2O3 on (0001) GaN grown by reactive molecular-beam epitaxy

Abstract: In this work we studied how a candidate gate oxide material, La2O3, grows on (0001) GaN and investigated the band offsets at the oxide/semiconductor interface. We found that the oxide grows in a hexagonal symmetry (same as GaN) for the first several nanometers and transitions to a cubic symmetry as the thickness increases. This transition in symmetry is accompanied by increased oxide roughness, which leads to increased threading defect densities. The band offsets, measured for the hexagonal phase, were less than 1eV for the valence band and therefore show that while this material has many desirable properties for a gate oxide (high permittivity, lattice matching with GaN), there may be low high temperature performance owing to the limited band offset and electrical leakage.

Ihlefeld, J.,


Brumbach, M.,
Atcitty, S.,

Applied Physics Letters
102:162903
2012-11Dielectric Properties of BaTiO3 - Bi(Zn1/2Ti1/2)O3 - NaNbO3 Solid Solutions

Abstract: In order to develop dielectric ceramics with temperature-stable permittivity characteristics, perovskite BaTiO3-Bi(Zn1/2Ti1/2)O3-NaNbO3 ceramic solid solutions were investigated with a particular focus on effects of BaTiO3 and NaNbO3 contents on the dielectric properties of ternary compounds. Keeping the ratios of the other two constituents constant, decreasing the BaTiO3 content leads to a broadening of the temperature-dependent permittivity maximum and a decrease in the overall permittivity. For compositions of constant BaTiO3 content, replacing Bi(Zn1/2Ti1/2)O3 with NaNbO3 shifts the temperature of the maximum permittivity to lower temperatures (e.g., to −103 °C for a composition of 70BT-5BZT-25NN) while maintaining a broad permittivity peak with temperature, which for the 50BT-25BZT-25NN composition also satisfies the X9R standard. Thus, the investigation of BT-BZT-NN compounds resulted in promising dielectric properties with broad temperature ranges of high permittivity, which is of interest for advanced capacitor applications.

Raengthon, N.,


Brown-Shaklee, H.,
Brennecka, G.,
Cann, D.,

J. Mater. Sci.
48:031401
2012-10Secondary Battery Science: At the Confluence of Electrochemistry and Materials Engineering

Abstract: Considerations of energy density, power, and calendar life are critical to effectively develop advanced secondary systems. For next generation battery applications requiring multiple features including long life, large cycle count, high energy density and high power, new strategies are needed for the rational design of electroactive materials and electrodes. This article discusses several conceptual approaches under exploration with examples from our research group. The first approach is the systematic synthesis of materials with structures facilitating ion insertion and deinsertion at high voltage and energy density, where we control materials properties such as surface area, particle size and in particular crystallite size. A second approach is the investigation of novel electrode structures and substrates to increase energy density and capacity retention under cycling, where we have developed strategies for minimizing passive components. A third approach is investigation of catalysts for metal air batteries where the cathode active material is drawn from the air rather than carried in the battery.

Takeuchi, E.,


Marschilok, A.,
Takeuchi, K.,

Electrochemistry
80(10):700-705
2012-07Vanadium redox flow battery efficiency and durability studies of sulfonated Diels Alder poly(phenylene)s

Abstract: Sulfonated Diels Alder poly(phenylene) (SDAPP) was examined for vanadium redox flow battery (VRFB) use. The ion exchange capacity (IEC) was varied from 1.4, 1.6 and 2.0 meq/g in order to tune the proton conductivity and vanadium permeability. Coulombic efficiencies between 92 to 99% were observed, depending on IEC (lower IEC, higher coulombic efficiencies). In all cases the SDAPP displayed comparable energy efficiencies (88-90%) to Nafion 117 (88%) at 50 mA/cm2. Membrane durability also was dependent on IEC; SDAPP with the highest IEC lasted slightly over 50 cycles while SDAPP with the lowest IEC lasted over 400 cycles and testing was discontinued only due to time constraints. Durability screening tests were initialed with SDAPP, by soaking films in a 0.1 M V5+ and 5.0 M total SO4− 2 solution. The rate of degradation was also proportional with IEC; the 2 meq/g sample dissolved within 376 h, the 1.6 meq/g sample dissolved after 860 h, while the 1.4 meq/g sample broke apart after 1527 h.

Fujimoto, C.,


Soowhan, K.,
Stanis, R.,
Wei, X.,
Li, L.,
Zhenguo, Y,

Electrochem. Comm.
20:48-51
2012Linear single phase inverter model for Battery Energy Storage System evaluation and controller design

Abstract: A method for deriving a set of linear transfer functions for a single phase grid tied system is presented, which can be used to determine how small signal perturbations and transients on the utility side are translated through the inverter to the dc link, as well as assist in controller design. These transfer functions can be used by a Battery Energy Storage System (BESS) designer to predict what harmonics the battery will see in the field, without the need for expensive simulation software. With this information, battery designers will be able to design a more robust battery specifically tailored for single phase inverter applications.

Watson, L.,


Kimball, J.,
Atcitty, S.,

Proc. Applied Power Electronics Conference and Exposition (APEC)
2012 Twenty-Seventh Annual
IEEE 10(1109):1861-1867, /apec.2012.6166075
2012Carbide-Derived Carbon Monoliths with Hierarchical Pore Architectures

Abstract: Porous carbon materials are crucial components in catalysis, gas storage, electronics, and biochemistry. A hierarchical pore architecture in these materials is essential to achieve high surface areas combined with advanced mass transport kinetics. Widely used approaches for the generation of micro- or mesopores are activation and nanocasting. In contrast, macroporous carbon materials are primarily obtained by carbonization of polymeric precursor gels or replication of larger templates. A relatively new class of micro- and mesoporous carbon material with tunable porosity are carbide-derived carbon materials (CDCs). High-temperature chlorination of carbides leads to selective removal of metal- or semi-metal atoms and allows control over the pore size of the resulting CDCs in a sub-Angstrom range by changing synthesis conditions or the carbide precursor. These materials have been studied for applications in gas storage and as electrode materials in supercapacitors because of their high specific surface areas.

Oschatz, M.,


Borchardt, L.,
Thommes, M.,
Cychosz, K.,
Senkovska, I.,
Klein, N.,
Frind, R.,
Leistner, M.,
Presser, V.,
Gogotsi, Y.,
Kaskel, S.,

Angewandte Chemie
51:7577-7580
2012Tunable Young's Modulus in Carbon MEMS using Graphene-based Stiffeners

Abstract: Carbon composite micro-electromechanical systems (C-MEMS) incorporating 2 wt.% graphene stiffeners show a 65% increase in Young's modulus and 11% increase in conductivity. An improved reduced graphene oxide (iRGO), is blended into pyrolytic carbon beams prepared for resonant frequency testing. Designed around a 10:1 (length: width) aspect ratio, the linearity of wt.% iRGO in the cantilevers as a function of resonant frequencies is evaluated. The collection of the 1st through 3rd bending modes using laser Doppler velocimetery (LDV) of the graphene filled cantilevers shows an increase in frequency response with nanomaterial loading (wt.%). A model was developed using the 3-bending modes and correlated with cross sectional geometry and density to extract a Young's modulus.

Washburn, C.,


Lambert, T.,
Blecke, J.,
Davis, D.,
Finnegan, P.,
Hance, B.,
Strong, J.,

J. Electrochem. Soc. Trans.
50(12):423-434
2012Defect Mechanisms in High Resistivity BaTiO3 - Bi(Zn0.5Ti0.5)O3 Ceramics

Abstract: The defect mechanisms that underpin the high energy density dielectric 0.8BaTiO3-0.2Bi(Zn1/2Ti1/2)O3 were investigated. Characterization of the nominally stoichiometric composition revealed the presence of a Ti3+-related defect center, which is correlated with lower resistivities and an electrically heterogeneous microstructure. In compositions with 2 mol. % Ba-deficiency, a barium vacancy-oxygen vacancy pair Active content removed , acted as an electron-trapping site. This defect was responsible for a significant change in the transport behavior with a high resistivity and an electrically homogeneous microstructure.

Raengthon, N.,


DeRose, V.,
Brennecka, G.,
Cann, D.,

Appl. Phys. Lett.
101:112904






Pacific Northwest National Laboratory (PNNL) Journal Articles and Books

SNL | PNNL | ORNL

Date Title Authors Publisher
2017-04A high-voltage rechargeable magnesium-sodium hybrid battery

Abstract: Growing global demand of safe and low-cost energy storage technology triggers strong interests in novel battery concepts beyond state-of-art Li-ion batteries. Here we report a high-voltage rechargeable Mg–Na hybrid battery featuring dendrite-free deposition of Mg anode and Na-intercalation cathode as a low-cost and safe alternative to Li-ion batteries for large-scale energy storage. A prototype device using a Na3V2(PO4)3 cathode, a Mg anode, and a Mg–Na dual salt electrolyte exhibits the highest voltage (2.60 V vs. Mg) and best rate performance (86% capacity retention at 10C rate) among reported hybrid batteries. Synchrotron radiation-based X-ray absorption near edge structure (XANES), atomic-pair distribution function (PDF), and high-resolution X-ray diffraction (HRXRD) studies reveal the chemical environment and structural change of Na3V2(PO4)3 cathode during the Na ion insertion/deinsertion process. XANES study shows a clear reversible shift of vanadium K-edge and HRXRD and PDF studies reveal a reversible two-phase transformation and V–O bond length change during cycling. The energy density of the hybrid cell could be further improved by developing electrolytes with a higher salt concentration and wider electrochemical window. This work represents a significant step forward for practical safe and low-cost hybrid batteries.

Yifei Li,
Qinyou An,


Yingwen Cheng,
Yanliang Liang,
Yang Ren,
Cheng-Jun Sunc,
Hui Dong,
Zhongjia Tang,
Guosheng Li,
Yan Yao,

Nano Energy,
34: 188-194
2017-03Advanced Na-NiCl2 Battery Using Nickel-Coated Graphite with Core–Shell Microarchitecture

Abstract: Stationary electric energy storage devices (rechargeable batteries) have gained increasing prominence due to great market needs, such as smoothing the fluctuation of renewable energy resources and supporting the reliability of the electric grid. With regard to raw materials availability, sodium-based batteries are better positioned than lithium batteries due to the abundant resource of sodium in Earth’s crust. However, the sodium–nickel chloride (Na-NiCl2) battery, one of the most attractive stationary battery technologies, is hindered from further market penetration by its high material cost (Ni cost) and fast material degradation at its high operating temperature. Here, we demonstrate the design of a core–shell microarchitecture, nickel-coated graphite, with a graphite core to maintain electrochemically active surface area and structural integrity of the electron percolation pathway while using 40% less Ni than conventional Na-NiCl2 batteries. An initial energy density of 133 Wh/kg (at ∼C/4) and energy efficiency of 94% are achieved at an intermediate temperature of 190 °C.

HJ Chang,
NL Canfield,


K Jung,
VL Sprenkle,
and G Li,

ACS Appl. Mater. Interfaces, 2017,
9 (13), pp 11609–11614, March 16, 2017. DOI: 10.1021/acsami.7b00271
2017-03Tuning the Solid Electrolyte Interphase for Selective Li- and Na-Ion Storage in Hard Carbon

Abstract: Solid-electrolyte interphase (SEI) films with controllable properties are highly desirable for improving battery performance. In this paper, a combined experimental and theoretical approach is used to study SEI films formed on hard carbon in Li- and Na-ion batteries. It is shown that a stable SEI layer can be designed by precycling an electrode in a desired Li- or Na-based electrolyte, and that ionic transport can be kinetically controlled. Selective Li- and Na-based SEI membranes are produced using Li- or Na-based electrolytes, respectively. The Na-based SEI allows easy transport of Li ions, while the Li-based SEI shuts off Na-ion transport. Na-ion storage can be manipulated by tuning the SEI layer with film-forming electrolyte additives, or by preforming an SEI layer on the electrode surface. The Na specific capacity can be controlled to < 25 mAh g−1; ≈ 1/10 of the normal capacity (250 mAh g−1). Unusual selective/preferential transport of Li ions is demonstrated by preforming an SEI layer on the electrode surface and corroborated with a mixed electrolyte. This work may provide new guidance for preparing

F. A. Soto,
P. Yan,


M. H. Engelhard,
A. Marzouk,
C. Wang,
G. Xu,
Z. Chen,
K. Amine,
J. Liu,
V. L. Sprenkle,
F. El-Mellouhi,
P. B. Balbuena,
X. Li,

Adv. Mater., 29, 1606860, 2017.
DOI: 10.1002/adma.201606860
2016-12New Mechanism for the Reduction of Vanadyl Acetylacetonate to Vanadium Acetylacetonate for Room Temperature Flow Batteries

Abstract: In this study, a new mechanism for the reduction of vanadyl acetylacetonate, VO(acac)2, to vanadium acetylacetonate, V(acac)3, is introduced. V(acac)3 has been studied for use in redox flow batteries (RFBs) for some time; however, contamination by moisture leads to the formation of VO(acac)2. In previous work, once this transformation occurs, it is no longer reversible because there is a requirement for extreme low potentials for the reduction to occur. Here, we propose that, in the presence of excess acetylacetone (Hacac) and free protons (H+), the reduction can take place between 2.25 and 1.5 V versus Na/Na+ via a one-electron-transfer reduction. This reduction can take place in situ during discharge in a novel hybrid Na-based flow battery (HNFB) with a molten Na–Cs alloy as the anode. The in situ recovery of V(acac)3 during discharge is shown to allow the Coulombic efficiency of the HNFB to be ≈100 % with little or no capacity decay over cycles. In addition, utilizing two-electron-transfer redox reactions (i.e., V3+/V4+ and V2+/V3+ redox couples) per V ion to increase the energy density of RFBs becomes possible owing to the in situ recovery of V(acac)3 during discharge. The concept of in situ recovery of material can lead to more advances in maintaining the cycle life of RFBs in the future.

JS Shamie,
C. Liu,


LL Shaw,
VL Sprenkle,

ChemSusChem,
vol. 10, no. 3, pp. 533-540, 2017.
DOI: //dx.doi.org/10.1002/cssc.201601126
2016-12Template-directed synthesis of nitrogen- and sulfur-codoped carbon nanowire aerogels with enhanced electrocatalytic performance for oxygen reduction

Abstract: Heteroatom doping, precise composition control, and rational morphology design are efficient strategies for producing novel nanocatalysts for the oxygen reduction reaction (ORR) in fuel cells. Herein, a cost-effective approach to synthesize nitrogen- and sulfur-codoped carbon nanowire aerogels using a hard templating method is proposed. The aerogels prepared using a combination of hydrothermal treatment and carbonization exhibit good catalytic activity for the ORR in alkaline solution. At the optimal annealing temperature and mass ratio between the nitrogen and sulfur precursors, the resultant aerogels show comparable electrocatalytic activity to that of a commercial Pt/C catalyst for the ORR. Importantly, the optimized catalyst shows much better long-term stability and satisfactory tolerance for the methanol crossover effect. These codoped aerogels are expected to have potential applications in fuel cells.

Fu S,
Zhu C,


Song J,
Engelhard M H,Li X,
Zhang P,
Xia H,
Du D,
Lin Y,

Nano Research
10 (6): 1888-1895 (Dec. 2016)
DOI: 10.1007/s12274-016-1371-8
2016-11-23Tuning the Perfluorosulfonic Acid Membrane Morphology for Vanadium Redox-Flow Batteries

Abstract: The microstructure of perfluorinated sulfonic acid proton-exchange membranes such as Nafion significantly affects their transport properties and performance in a vanadium redox-flow battery (VRB). In this work, Nafion membranes with various equivalent weights ranging from 1000 to 1500 are prepared and the morphology-property-performance relationship is investigated. NMR and small-angle X-ray scattering studies revealed their composition and morphology variances, which lead to major differences in key transport properties related to proton conduction and vanadium-ion permeation. Their performances are further characterized as VRB membranes. On the basis of this understanding, a new perfluorosulfonic acid membrane is designed with optimal pore geometry and thickness, leading to higher ion selectivity and lower cost compared with the widely used Nafion 115. Excellent VRB single-cell performance (89.3% energy efficiency at 50 mA·cm-2) was achieved along with a stable cyclical capacity over prolonged cycling.

Murugesan, V.,


Luo, Q.,
Lloyd, R.,
Nie, Z.,
Wei, X.,
Li, B.,
Sprenkle, V.,
Londono, J.,
Unlu, M.,
Wang, W.,

ACS Applied Materials and Interfaces,
8 (50): 34327-34334
2016-11-08Material design and engineering of next-generation flow-battery technologies

Abstract: Spatial separation of the electrolyte and electrode is the main characteristic of flow-battery technologies, which liberates them from the constraints of overall energy content and the energy/power ratio. The concept of a flowing electrolyte not only presents a cost-effective approach for large-scale energy storage, but has also recently been used to develop a wide range of new hybrid energy storage and conversion systems. The advent of flow-based lithium-ion, organic redox-active materials, metal–air cells and photoelectrochemical batteries promises new opportunities for advanced electrical energy-storage technologies. In this Review, we present a critical overview of recent progress in conventional aqueous redox-flow batteries and next-generation flow batteries, highlighting the latest innovative alternative materials. We outline their technical feasibility for use in long-term and large-scale electrical energy-storage devices, as well as the limitations that need to be overcome, providing our view of promising future research directions in the field of redox-flow batteries.

Park, M.,


Ryu, J.,
Wang, W.,
Cho, J.,

Nature Review Materials,
2: 16080
2016-10-23Rechargeable Mg-Li hybrid batteries: status and challenges

Abstract: A magnesium–lithium (Mg–Li) hybrid battery consists of an Mg metal anode, a Li+ intercalation cathode, and a dual-salt electrolyte with both Mg2+ and Li+ ions. The demonstration of this technology has appeared in literature for few years and great advances have been achieved in terms of electrolytes, various Li cathodes, and cell architectures. Despite excellent battery performances including long cycle life, fast charge/discharge rate, and high Coulombic efficiency, the overall research of Mg–Li hybrid battery technology is still in its early stage, and also raised some debates on its practical applications. In this regard, we focus on a comprehensive overview of Mg–Li hybrid battery technologies developed in recent years. Detailed discussion of Mg–Li hybrid operating mechanism based on experimental results from literature helps to identify the current status and technical challenges for further improving the performance of Mg–Li hybrid batteries. Finally, a perspective for Mg–Li hybrid battery technologies is presented to address strategic approaches for existing technical barriers that need to be overcome in future research direction.

Cheng, Y.,


Chang, H.,
Dong, H.,
Choi, D.,
Sprenkle, V.,
Liu, J.,
Yao, Y.,
Li, G.,

Journal of Materials Research,
31 (20): 3125-3141
2016-10-15Effect of Al2O3 on the sintering of garnet-type Li6.5La3Zr1.5Ta0.5O12

Abstract: It is widely recognized that Al plays a dual role in the fabrication of garnet-type solid electrolytes, i.e., as a dopant that stabilizes the cubic structure and a sintering aid that facilitates the densification. However, the sintering effect of Al2O3 has not been well understood so far because Al is typically "unintentionally" introduced into the sample from the crucible during the fabrication process. In this study, we have investigated the sintering effect of Al on the phase composition, microstructure, and ionic conductivity of Li6.5La3Zr1.5Ta0.5O12 by using an Al-free crucible and intentionally adding various amounts of y-Al2O3. It was found that the densification of Li6.5La3Zr1.5Ta0.5O12 occurred via liquid-phase sintering, with evidence of morphology change among different compositions. Among all of the compositions, samples with 0.05mol Al per unit formula of garnet oxide (i.e., 0.3wt% Al2O3) exhibited the optimal microstructure and the highest total ionic conductivity of 5x10-4Scm-1 at room temperature.

Wang, Y.,


Yan, P.,
Xiao, J.,
Lu, X.,
Zhang, J.,
Sprenkel, V.,

Solid State Ionics,
294: 108-115
2016-09-15Highly Ordered Mesoporous Bimetallic Phosphides as Efficient Oxygen Evolution Electrocatalysts

Abstract: Oxygen evolution from water using earth-abundant transition-metal-based catalysts is of importance for the commercialization of water electrolyzers. Herein, we report a hard templating method to synthesize transition metal phosphides with uniform shape and size. By virtue of the structural feature, synergistic effects among metals, and the in situ formed active species, the as-prepared phosphides with optimized composition present enhanced electrocatalytic performance toward the oxygen evolution reaction in alkaline solution. In detail, the catalyst with optimized composition reaches a current density of 10 mA/cm2 at a potential of 1.511 V vs a reversible hydrogen electrode, which is much lower than that of a commercial RuO2 catalyst. Our work offers a new strategy to optimize the catalysts for water splitting by controlling the morphology and composition.

Fu, S.,


Zhu, C.,
Song, J.,
Engelhard, M.,
Li, X.,
Du, D.,
Lin, Y.,

ACS Energy Letters,
1 (4): 792-796
2016-09-05A High-Current, Stable Nonaqueous Organic Redox Flow Battery

Abstract: Nonaqueous redox flow batteries are promising in pursuit of high energy density storage systems owing to the broad voltage windows (>2 V) but currently are facing key challenges such as limited cyclability and rate performance. To address these technical hurdles, here we report the nonaqueous organic flow battery chemistry based on N-methylphthalimide anolyte and 2,5-di-tert-butyl-1-methoxy-4-[2'-methoxyethoxy]benzene catholyte, which harvests a theoretical cell voltage of 2.30 V. The redox flow chemistry exhibits excellent cycling stability under both cyclic voltammetry and flow cell tests upon repeated cycling. A series of Daramic and Celgard porous separators are evaluated in this organic flow battery, which enable the cells to be operated at greatly improved current densities as high as 50 mA cm-2 compared to those of other nonaqueous flow systems. The stable cyclability and high-current operations of the organic flow battery system represent significant progress in the development of promising nonaqueous flow batteries.

Wei, X.,


Duan, W.,
Huang, J.,
Zhang, L.,
Li, B.,
Reed, D.,
Xu, W.,
Sprenkle, V.,

ACS Energy Letters
1: 705-711
2016-09Rechargeable Mg–Li hybrid batteries: status and challenges

Abstract: A magnesium–lithium (Mg–Li) hybrid battery consists of an Mg metal anode, a Li+ intercalation cathode, and a dual-salt electrolyte with both Mg2+ and Li+ ions. The demonstration of this technology has appeared in literature for few years and great advances have been achieved in terms of electrolytes, various Li cathodes, and cell architectures. Despite excellent battery performances including long cycle life, fast charge/discharge rate, and high Coulombic efficiency, the overall research of Mg–Li hybrid battery technology is still in its early stage, and also raised some debates on its practical applications. In this regard, we focus on a comprehensive overview of Mg–Li hybrid battery technologies developed in recent years. Detailed discussion of Mg–Li hybrid operating mechanism based on experimental results from literature helps to identify the current status and technical challenges for further improving the performance of Mg–Li hybrid batteries. Finally, a perspective for Mg–Li hybrid battery technologies is presented to address strategic approaches for existing technical barriers that need to be overcome in future research direction.

Yingwen Cheng,
Hee Jung Chang,


Hui Dong,
Daiwon Choi,
Vincent L. Sprenkle,
Jun Liu,
Yan Yao and Guosheng Li,

Journal of Materials Research
31 (20) :3125-3141
2016-09The importance of solid electrolyte interphase formation for long cycle stability full-cell Na-ion batteries

Abstract: Na-ion battery, as an alternative high-efficiency and low-cost energy storage device to Li-ion battery, has attracted wide interest for electrical grid and vehicle applications. However, demonstration of a full-cell battery with high energy and long cycle life remains a significant challenge. Here, we investigated the role of solid electrolyte interphase (SEI) formation on both cathodes and anodes and revealed a potential way to achieve long-term stability for Na-ion battery full-cells. Pre-cycling of cathodes and anodes leads to preformation of SEI, and hence mitigates the consumption of Na ions in full-cells. The example full-cell of Na0.44MnO2-hard carbon with pre-cycled and capacity-matched electrodes can deliver a specific capacity of ~116 mAh/g based on Na0.44MnO2 at 1 C rate (1 C=120 mA/g). The corresponding specific energy is ~313 Wh/kg based on the cathode. Excellent cycling stability with ~77% capacity retention over 2000 cycles was demonstrated at 2 C rate. Our work represents a leap forward in Na-ion battery development.

Li, X.,


Yan, P.,
Engelhard, M.,
Crawford, A.,
Viswanathan, V.,
Wang, C.,
Liu, J.,
Sprenkle, V.,

Nano Energy,
27: 664-672
2016-06-07Metal-Organic Frameworks as Highly Active Electrocatalysts for High-Energy Density, Aqueous Zinc-Polyiodide Redox Flow Batteries

Abstract: The new aqueous zinc-polyiodide redox flow battery (RFB) system with highly soluble active materials as well as ambipolar and bifunctional designs demonstrated significantly enhanced energy density, which shows great potential to reduce RFB cost. However, the poor kinetic reversibility and electrochemical activity of the redox reaction of I3-/I- couples on graphite felts (GFs) electrode can result in low energy efficiency. Two nanoporous metal-organic frameworks (MOFs), MIL-125-NH2 and UiO-66-CH3, that have high surface areas when introduced to GF surfaces accelerated the I3-/I- redox reaction. The flow cell with MOF-modified GFs serving as a positive electrode showed higher energy efficiency than the pristine GFs; increases of about 6.4% and 2.7% occurred at the current density of 30 mA/cm2 for MIL-125-NH2 and UiO-66-CH3, respectively. Moreover, UiO-66-CH3 is more promising due to its excellent chemical stability in the weakly acidic electrolyte. This letter highlights a way for MOFs to be used in the field of RFBs.

Li, B.,


Liu, J.,
Nie, Z.,
Wang, W.,
Reed, D.,
Liu, J.,
McGrail, P.,
Sprenkle, V.,

Nano Letters
16 (7): 4335-4340
2016-05-23Ultra-Thick, Low-Tortuosity, and Mesoporous Wood Carbon Anode for High-Performance Sodium-Ion Batteries

Abstract: Pyrolysis of earth-abundant wood yields to ultra-thick, low-tortuosity, and mesoporous carbon anodes for sodium-ion batteries. Such a low-tortuosity and porous structure promotes electrolyte diffusion and provides fast transport channels for Na ions, which enables a high areal capacity.

Shen, F.,


Luo, W.,
Dai, J.,
Yao, Y.,
Zhu, M.,
Hitz, E.,
Tang, Y.,
Chen, Y.,
Sprenkle, V.,
Li, X.,
Hu, L.,

Advanced Energy Materials,
6 (14): 1600377
2016-05-17Tunable oxygen functional groups as electrocatalysts on graphite felt surfaces for all-vanadium flow batteries

Abstract: A dual oxidative approach using O2 plasma followed by treatment with H2O2 to impart oxygen functional groups onto the surface of a graphite felt electrode. When used as electrodes for an all-vanadium redox flow battery (VRB) system, the energy efficiency of the cell is enhanced by 8.2 % at a current density of 150 mA cm-2 compared with one oxidized by thermal treatment in air. More importantly, by varying the oxidative techniques, the amount and type of oxygen groups was tailored and their effects were elucidated. It was found that O-C=O groups improve the cells performance whereas the C-O and C=O groups degrade it. The reason for the increased performance was found to be a reduction in the cell overpotential after functionalization of the graphite felt electrode. This work reveals a route for functionalizing carbon electrodes to improve the performance of VRB cells. This approach can lower the cost of VRB cells and pave the way for more commercially viable stationary energy storage systems that can be used for intermittent renewable energy storage.

Estevez, L.,


Reed, D.,
Nie, Z.,
Schwarz, A.,
Nandasiri, M.,
Kizewski, J.,
Wang, W.,
Thomsen, E.,
Liu, J.,
Zhang, J.,
Sprenkle, V.,
Li, B.,

ChemSusChem
9 (12): 1455-1461
2016-05-16Highly Reversible Zinc-Ion Intercalation into Chevrel Phase Mo6S8 Nanocubes and Applications for Advanced Zinc-Ion Batteries

Abstract: This work describes the synthesis of Chevrel phase Mo6S8 nanocubes and its application as the anode material for rechargeable Zn-ion batteries. Mo6S8 can host Zn(2+) ions reversibly in both aqueous and nonaqueous electrolytes with specific capacities around 90 mAh/g, and exhibited remarkable intercalation kinetics and cyclic stability. In addition, we assembled full cells by integrating Mo6S8 anodes with zinc-polyiodide (I-/I3-)-based catholytes, and demonstrated that such full cells were also able to deliver outstanding rate performance and cyclic stability. This first demonstration of a zinc-intercalating anode could inspire the design of advanced Zn-ion batteries.

Cheng, Y.,


Luo, L.,
Zhong, L.,
Chen, J.,
Li, B.,
Wang, W.,
Mao, S.,
Wang, C.,
Sprenkle, V.,
Li, G.,
Liu, J.,

ACS Applied Materials and Interfaces
8 (22):13673-13677
2016-04-13A magnesium-sodium hybrid battery with high operating voltage

Abstract: We report a high performance magnesium-sodium hybrid battery utilizing a magnesium-sodium dual-salt electrolyte, a magnesium anode, and a Berlin green cathode. The cell delivers an average discharge voltage of 2.2 V and a reversible capacity of 143 mA h g-1. We also demonstrate the cell with an energy density of 135 W h kg-1 and a high power density of up to 1.67 kW kg-1.

Dong, H.,


Li, Y.,
Liang, Y.,
Li, G.,
Sun, C.,
Ren, Y.,
Lu, Y.,
Yao, Y.,

Chemical Communications
52: 8263-8266
2016-04Development of intermediate temperature sodium nickel chloride rechargeable batteries using conventional polymer sealing technologies

Abstract: Developing advanced and reliable electrical energy storage systems is critical to fulfill global energy demands and stimulate the growth of renewable energy resources. Sodium metal halide batteries have been under serious consideration as a low cost alternative energy storage device for stationary energy storage systems. Yet, there are number of challenges to overcome for the successful market penetration, such as high operating temperature and hermetic sealing of batteries that trigger an expensive manufacturing process. Here we demonstrate simple, economical and practical sealing technologies for Na-NiCl2 batteries operated at an intermediate temperature of 190 °C. Conventional polymers are implemented in planar Na-NiCl2 batteries after a prescreening test, and their excellent compatibilities and durability are demonstrated by a stable performance of Na-NiCl2 battery for more than 300 cycles. The sealing methods developed in this work will be highly beneficial and feasible for prolonging battery cycle life and reducing manufacturing cost for Na-based batteries at elevated temperatures (<200 °C).

HJ Chang,
X. Lu,


JF Bonnett,
NL Canfield,
S Son,
Y-C Park,
K Jung,
VL Sprenkle,
G Li,

J, Power Sources,
vol. 348, pp. 150–157, 30 April 2017
DOI: 10.1016/j.jpowsour.2017.02.059
2016-02-19Energy Storage: Redox Flow Batteries Go Organic

Abstract: The use of renewable resources as providers to the electrical grid is hampered by the intermittent and irregular nature in which they generate energy. Electrical energy storage technology could provide a solution and now, by using an iterative design process, a promising anolyte for use in redox flow batteries has been developed.

Wang, W,


Sprenkle, V.,

Nature Chemistry,
8, 204–206,
doi:10.1038/nchem.2466
2016-02-11Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density

Abstract: Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium–nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg-1, higher than that of conventional tubular sodium–nickel chloride batteries (280 °C), is obtained for planar sodium–nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium–nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.

Li, G.,


Lu, X.,
Kim, J.,
Meinhardt, K.,
Chang, H.,
Canfield, N.,
Sprenkle, V.,

Nature Communications,
7, Article 10683
2016-02LiCoPO4 cathode from a CoHPO4·xH2O nanoplate precursor for high voltage Li-ion batteries

Abstract: A highly crystalline LiCoPO4/C cathode material has been synthesized without noticeable impurities via a single step solid-state reaction using CoHPO4·xH2O nanoplate as a precursor obtained by a simple precipitation route. The LiCoPO4/C cathode delivered a specific capacity of 125 mAhg-1 at a charge/discharge rate of C/10. The nanoplate precursor and final LiCoPO4/C cathode have been characterized using X-ray diffraction, thermogravimetric analysis - differential scanning calorimetry (TGA-DSC), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) and the electrochemical cycling stability has been investigated using different electrolytes, additives and separators.

Choi, D.,


Li, X.,
Henderson, W.,
Huang, Q.,
Nune, S.,
Lemmon, J.,
Sprenkle, V.,

Heliyon
2 (2)
2016-02Performance of a low cost interdigitated flow design on a 1 kW class all vanadium mixed acid redox flow battery

Abstract: Three flow designs were operated in a 3-cell 1 kW class all vanadium mixed acid redox flow battery. The influence of electrode surface area and flow rate on the coulombic, voltage, and energy efficiency and the pressure drop in the flow circuit will be discussed and correlated to the flow design. Material cost associated with each flow design will also be discussed.

Reed, D.,


Thomsen, E.,
Li, B.,
Wang, W.,
Nie, Z.,
Koeppel, B.,
Sprenkle, V.,

Journal of Power Sources,
306: 24-31
2016-01-31Toward the design of high voltage magnesium-lithium hybrid batteries using dual-salt electrolytes

Abstract: We report a design of high voltage magnesium-lithium (Mg-Li) hybrid batteries through rational control of the electrolyte chemistry, electrode materials and cell architecture. Prototype devices with a structure of Mg-Li/LiFePO4 (LFP) and Mg-Li/LiMn2O4 (LMO) have been investigated. A Mg-Li/LFP cell using a dual-salt electrolyte 0.2 M [Mg2Cl2(DME)4][AlCl4]2 and 1.0 M LiTFSI exhibits voltages higher than 2.5 V (vs. Mg) and a high specific energy density of 246 W h kg-1 under conditions that are amenable for practical applications. The successful demonstrations reported here could be a significant step forward for practical hybrid batteries.

Cheng, Y.,


Choi, D.,
Han, K.,
Mueller, K.,
Zhang, J.,
Sprenkle, V.,
Liu, J.,
Li, G.,

Chemical Communications
52: 5379-5382
2015-12-01A Total Organic Aqueous Redox Flow Battery Employing a Low Cost and Sustainable Methyl Viologen Anolyte and 4-HO-TEMPO Catholyte

Abstract: Increasing worldwide energy demands and rising CO2 emissions have motivated a search for new technologies to take advantage of renewables such as solar and wind energies. Redox flow batteries (RFBs) with their high power density, high energy efficiency, scalability (up to MW and MWh), and safety features are one suitable option for integrating such energy sources and overcoming their intermittency. However, resource limitation and high system costs of current RFB technologies impede wide implementation. Here, a total organic aqueous redox flow battery (OARFB) is reported, using low-cost and sustainable methyl viologen (MV, anolyte) and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-HO-TEMPO, catholyte), and benign NaCl supporting electrolyte. The electrochemical properties of the organic redox active materials are studied using cyclic voltammetry and rotating disk electrode voltammetry. The MV/4-HO-TEMPO ARFB has an exceptionally high cell voltage, 1.25 V. Prototypes of the organic ARFB can be operated at high current densities ranging from 20 to 100 mA cm2, and deliver stable capacity for 100 cycles with nearly 100% Coulombic efficiency. The MV/4-HO-TEMPO ARFB displays attractive technical merits and thus represents a major advance in ARFBs.

Liu, T.,


Wei, X.,
Nie, Z.,
Sprenkle, V.,
Wang, W.,

Adv. Energy Mater.,
6:1501449,
doi: 10.1002/aenm.201501449
2015-11Enhanced sintering of ß"-Al2/O3/YSZ with the sintering aids of TiO2 and MnO2

Abstract: ß"-Al2O3 has been the dominateChoi, D.ce for the electrolyte materials of sodium batteries because of its high ionic conductivity, excellent stability with the electrode materials, satisfactory mechanical strength, and low material cost. To achieve adequate electrical and mechanical performance, sintering of ß"-Al2O3 is typically carried out at temperatures above 1600°C with deliberate efforts on controlling the phase, composition, and microstructure. Here, we reported a simple method to fabricate ß"-Al2O3/YSZ electrolyte at relatively lower temperatures. With the starting material of boehmite, single phase of ß"-Al2O3 can be achieved at as low as 1200°C. It was found that TiO2 was extremely effective as a sintering aid for the densification of ß"-Al2O3 and similar behavior was observed with MnO2 for YSZ. With the addition of 2 mol% TiO2 and 5 mol% MnO2, the ß"-Al2O3/YSZ composite was able to be densified at as low as 1400°C with a fine microstructure and good electrical/mechanical performance. This study demonstrated a new approach of synthesis and sintering of ß"-Al2O3/YSZ composite, which represented a simple and low-cost method for fabrication of high-performance ß"-Al2O3/YSZ electrolyte.

Lu, X.,


Li, G.,
Kim, J.,
Meinhardt, K.,
Sprenkle, V.,

Journal of Power Sources,
295:167-174
2015-11An Aqueous Redox Flow Battery Based on Neutral Alkali Metal Ferri/ferrocyanide and Polysulfide Electrolytes

Abstract: We have demonstrated a new ferri/ferrocyanide - polysulfide (Fe/S) flow battery, which employs less corrosive, relatively environmentally benign neutral alkali metal ferri/ferrocyanide and alkali metal polysulfides as the active redox couples. A cobalt nanoparticle - decorated graphite felt was used at the polysulfide side as the catalyst. Excellent electrochemical performance was successfully acquired in the Fe/S flow cells with high cell efficiencies (99% coulombic efficiency and ~74% energy efficiency) and good cycling stability over extended charge/discharge operations. The positive half-cell appears to be the performance - limiting side in the Fe/S flow battery determined by using a carbon cloth probe. The inexpensive redox materials and possibly cell part materials can lead to reduced capital cost, making the Fe/S flow battery a promising cost-effective energy storage technology candidate.

Wei, X.,


Xia, G.,
Kirby, B.,
Thomsen, E.,
Li, B.,
Nie, Z.,
Graff, G.,
Liu, J.,
Sprenkle, V.,
Wang, W.,

Journal of The Electrochemical Society,
163(1):A5150-A5153
2015-11Stack Developments in a kW Class All Vanadium Mixed Acid Redox Flow Battery at the Pacific Northwest National Laboratory

Abstract: Over the past several years, efforts have been focused on improving the performance of kW class all vanadium mixed acid redox flow battery stacks with increasing current density. The influence of the Nafion membrane resistance, an interdigitated design to reduce the pressure drop in the electrolyte circuit, the temperature of the electrolyte, and the electrode structure will be discussed and correlated to the electrical performance. Improvements to the stack energy efficiency and how those improvements translate to the overall system efficiency will also be discussed.

Reed, D.,


Thomsen, E.,
Li, B.,
Wang, W.,
Nie, Z.,
Koeppel, B.,
Kizewski, J.,
Sprenkle, V.,

Journal of the Electrochemical Society,
163 (1):A5211-A5219
2015-10Comparative analysis for various redox flow batteries chemistries using a cost performance model

Abstract: The total energy storage system cost is determined by means of a robust performance-based cost model for multiple flow battery chemistries. Systems aspects such as shunt current losses, pumping losses and various flow patterns through electrodes are accounted for. The system cost minimizing objective function determines stack design by optimizing the state of charge operating range, along with current density and current-normalized flow. The model cost estimates are validated using 2-kW stack performance data for the same size electrodes and operating conditions. Using our validated tool, it has been demonstrated that an optimized all-vanadium system has an estimated system cost of < $350 kWh-1 for 4-h application. With an anticipated decrease in component costs facilitated by economies of scale from larger production volumes, coupled with performance improvements enabled by technology development, the system cost is expected to decrease to 160 kWh-1 for a 4-h application, and to $100 kWh-1 for a 10-h application. This tool has been shared with the redox flow battery community to enable cost estimation using their stack data and guide future direction.

Crawford, A.,


Viswanathan, V.,
Stephenson, D.,
Wang, W.,
Thomsen, E.,
Reed, D.,
Li, B.,
Balducci, P.,
Kinter-Meyer, M.,
Sprenkle, V.,

Journal of Power Sources,
293: 388-399
2015-09Anion-Tunable Properties and Electrochemical Performance of Functionalized Ferrocene Compounds

Abstract: We report a series of ionically modified ferrocene compounds for hybrid lithium-organic non-aqueous redox flow batteries, based on the ferrocene/ferrocenium redox couple as the active catholyte material. Tetraalkylammonium ionic moieties were incorporated into the ferrocene structure, in order to enhance the solubility of the otherwise relatively insoluble ferrocene. The effect of various counter anions of the tetraalkylammonium ionized species appended to the ferrocene, such as bis(trifluoromethanesulfonyl)imide, hexafluorophosphate, perchlorate, tetrafluoroborate, and dicyanamide on the solubility of the ferrocene was investigated. The solution chemistry of the ferrocene species was studied, in order to understand the mechanism of solubility enhancement. Finally, the electrochemical performance of these ionized ferrocene species was evaluated and shown to have excellent cell efficiency and superior cycling stability.

Cosimbescu, L.,


Wei, X.,
Vijayakumar, M.,
Xu, W.,
Helm, M.,
Burton, S.,
Sorensen, C.,
Liu, J.,
Sprenkle, V.,
Wang, W.,

Scientific Reports,
5:14117
2015-08A Low Cost, High Energy Density, and Long Cycle Life Potassium-Sulfur Battery for Grid-Scale Energy Storage

Abstract: A potassium-sulfur battery using K+-conducting beta-alumina as the electrolyte to separate a molten potassium metal anode and a sulfur cathode is presented. The results indicate that the battery can operate at as low as 150°C with excellent performance. This study demonstrates a new type of high-performance metal-sulfur battery that is ideal for grid-scale energy-storage applications.

Lu, X.,


Bowden, M.,
Sprenkle, V.,
Liu, J.,

Advanced Materials,
27(39):5915-5922
2015-07Radical Compatibility with Nonaqueous Electrolytes and Its Impact on an All-Organic Redox Flow Battery

Abstract: Nonaqueous redox flow batteries hold the promise of achieving higher energy density because of the broader voltage window than aqueous systems, but their current performance is limited by low redox material concentration, cell efficiency, cycling stability, and current density. We report a new nonaqueous all-organic flow battery based on high concentrations of redox materials, which shows significant, comprehensive improvement in flow battery performance. A mechanistic electron spin resonance study reveals that the choice of supporting electrolytes greatly affects the chemical stability of the charged radical species especially the negative side radical anion, which dominates the cycling stability of these flow cells. This finding not only increases our fundamental understanding of performance degradation in flow batteries using radical-based redox species, but also offers insights toward rational electrolyte optimization for improving the cycling stability of these flow batteries.

Wei, X.,


Xu, W.,
Huang, J.,
Zhang, L.,
Walter, E.,
Lawrence, C.,
Vijayakumar, M.,
Henderson, W.,
Liu, T.,
Cosimbescu, L.,
Li, B.,
Sprenkle, V.,
Wang, W.,

Angewandte Chemie,
54 (30):8684-8687
2015-07Performance of Nafion® N115, Nafion® NR-212, and Nafion® NR-211 in a 1 kW class all vanadium mixed acid redox flow battery

Abstract: Three Nafion® membranes of similar composition but different thicknesses were operated in a 3-cell 1 kW class all vanadium mixed acid redox flow battery. The influence of current density on the charge/discharge characteristics, coulombic and energy efficiency, capacity fade, operating temperature and pressure drop in the flow circuit will be discussed and correlated to the Nafion® membrane thickness. Material costs associated with the Nafion® membranes, ease of handling the membranes, and performance impacts will also be discussed.

Reed, D.,


Thomsen, E.,
Wang, W.,
Nie, Z.,
Li, B.,
Wei, X.,
Koeppel, B.,
Sprenkle, V.,

Journal of Power Sources,
285:425-430
2015-07Effects of fabrication conditions on mechanical properties and microstructure of duplex ß"-Al2O3 solid electrolyte

Abstract: Na-beta batteries are an attractive technology as a large-scale electrical energy storage for grid applications. However, additional improvements in performance and cost are needed for wide market penetration. To improve cell performance by minimizing polarizations, reduction of electrolyte thickness was attempted using a duplex structure consisting of a thin dense electrolyte layer and a porous support layer. In this paper, the effects of sintering conditions, dense electrolyte thickness, and cell orientation on the flexural strength of duplex BASEs fabricated using a vapor phase approach were investigated. It is shown that sintering at temperatures between 1500 and 1550°C results in fine grained microstructures and the highest flexural strength after conversion. Increasing thickness of the dense electrolyte has a small impact on flexural strength, while the orientation of load such that the dense electrolyte is in tension instead of compression has major effects on strength for samples with a well-sintered dense electrolyte.

Canfield, N.,


Kim, J.,
Bonnett, J.,
Pearson III, R.,
Sprenkle, V.,
Kung, J.,

Materials Science and Engineering: B,
197: 43-50
2015-06A Duplex ß"-Al2O3 Solid Electrolyte Consisting of A Thin Dense Layer and A Porous Substrate

Abstract: To improve the performance of Na-beta batteries at intermediate temperatures (≤200°C) where much improved cyclability and reduced degradation can be achieved, there is a need to lower the resistance/polarization coming from BASEs while maintaining good strength. In this paper, the concept of a duplex BASE consisting of a thin dense electrolyte and a porous support was proposed as a solution to achieve low area-specific resistance while maintaining good mechanical strength. The effects of various factors including porosity, composition, and the homogeneity of ingredients on the flexural strength of duplex BASEs were examined. In summary, lower porosity, higher YSZ content in the structure, and the attrition milling of powders resulted in improved strength. The area-specific resistance measurement exhibited that the resistance of duplex BASEs was mainly originated from a dense layer. Overall, the maximum strength of 260 MPa and the ASR value of 0.31 cm2 (at 350°C) was achieved from a duplex BASE consisting of a 50 µm thick dense layer (Al2O3: YSZ = 7:3 in volume) and a 500 µm thick porous support (Al2O3: YSZ = 4:6 in volume with 19% open porosity). The effects of various factors on the properties of duplex BASEs will be explained in details.

Kim, J.,


Canfield, N.,
Bonnett, J.,
Sprenkle, V.,
Jung, K.,
Hong, I.,

Solid State Ionics,
278: 192-197
2015-06An Advanced Na-FeCl2 ZEBRA Battery for Stationary Energy Storage Application

Abstract: In article 1500357, Guoshen Li, Jin Y. Kim, and co-workers report a remarkably reliable Na-FeCl2 ZEBRA battery for stationary energy storage applications. The removal of surface oxide passivation layers on iron particles is critical and it is attributed to polysulfide species generated from sulfur-based additives through polysulfide reactions. The Na-FeCl2 cells presented can be assembled at the discharge state (NaCl + Fe powder) without handling highly hazardous materials such as anhydrous FeCl2 and metallic sodium.

Li, G.,


Lu, X.,
Kim, J.,
Viswanathan, V.,
Meinhardt, K.,
Engelhard, M.,
Sprenkle, V.,

Advanced Energy Materials,
5(12)
2015-06Room Temperature, Hybrid Sodium-Based Flow Batteries with Multi-Electron Transfer Redox Reactions

Abstract: We introduce a new concept of hybrid Na-based flow batteries (HNFBs) with a molten Na alloy anode in conjunction with a flowing catholyte separated by a solid Na-ion exchange membrane for grid-scale energy storage. Such HNFBs can operate at ambient temperature, allow catholytes to have multiple electron transfer redox reactions per active ion, offer wide selection of catholyte chemistries with multiple active ions to couple with the highly negative Na alloy anode, and enable the use of both aqueous and non-aqueous catholytes. Further, the molten Na alloy anode permits the decoupled design of power and energy since a large volume of the molten Na alloy can be used with a limited ion-exchange membrane size. In this proof-of-concept study, the feasibility of multi-electron transfer redox reactions per active ion and multiple active ions for catholytes has been demonstrated. The critical barriers to mature this new HNFBs have also been explored.

Shamie, J.,


Liu, C.,
Shaw, L.,
Sprenkle, V.,

Scientific Reports,
5, article 11215
2015-05Porous Polymeric Composite Separators for Redox Flow Batteries

Abstract: Currently, the most commonly used membranes in redox flow batteries (RFB) are ion-exchange membranes. In particular, in all vanadium flow battery systems (VRB), perfluorinated polymers such as Nafion® are widely used, owing to their high proton conductivity and chemical stability; however, the extremely high cost of currently available membranes has limited the commercialization of VRB technology. Recently, low-cost porous polymeric composite separators (e.g.,
polytetrafluoroethylene [PTFE]/silica), as an alternative to traditional ion-exchange membranes, have attracted a great deal of interest because of their significantly lower cost. Porous separators prepared from various polymer materials and inorganic fillers have demonstrated comparable electrochemical performances to that of Nafion® in flow battery tests with different redox chemistries. This paper provides a review of porous separators for flow battery applications. In addition to discussions of separator material selection and preparation methods, we also emphasize the electrochemical performance of various flow battery systems, especially the capacity fade mechanism that is closely related to ion-transport across porous separator.

Wei, X.,


Li, B.,
Wang, W.,

Polymer Reviews,
55(2):247-272
2015-04Highly Active Electrolytes for Rechargeable Mg Batteries Based on [Mg2(μ-Cl)2]2+ Cation Complex in Dimethoxyethane

Abstract: A novel [Mg2(μ-Cl)2]2+ cation complex, which is highly active for reversible Mg electrodeposition, was identified for the first time in this work. This complex was found to be present in electrolytes formulated in dimethoxyethane (DME) through dehalodimerization of non-nucleophilic MgCl2 by reacting with either Mg salts (such as Mg(TFSI)2, TFSI = bis(trifluoromethane)sulfonylimide) or Lewis acid salts (such as AlEtCl2 or AlCl3). The molecular structure of the cation complex was characterized by single crystal X-ray diffraction, Raman spectroscopy and NMR. The electrolyte synthesis process was studied and rational approaches for formulating highly active electrolytes were proposed. Through control of the anions, electrolytes with an efficiency close to 100%, a wide electrochemical window (up to 3.5 V) and a high ionic conductivity (>6 mS cm-1) were obtained. The understanding of electrolyte synthesis in DME developed in this work could bring significant opportunities for the rational formulation of electrolytes of the general formula [Mg2(μ-Cl)2][anion]x for practical Mg batteries.

Cheng, Y.,


Stolley, R.,
Han, K.,
Shao, Y.,
Arey, B.,
Washton, N.,
Mueller, K.,
Helm, M.,
Sprenkle, V.,
Liu, J.,
Li, G.,

Physical Chemistry Chemical Physics,
17: 13307-13314
2015-03Aqua-vanadyl ion interaction with Nafion® membranes

Abstract: Lack of comprehensive understanding about the interactions between Nafion® membrane and battery electrolytes prevents the straightforward tailoring of optimal materials for redox flow battery applications. In this work, we analyzed the interaction between aqua-vanadyl cation and sulfonic sites within the pores of Nafion® membranes using combined theoretical and experimental X-ray spectroscopic methods. Molecular level interactions, namely, solvent share and contact pair mechanisms are discussed based on vanadium and sulfur K-edge spectroscopic analysis.

Vijayakumar, M.,


Govind, N.,
Li, B.,
Wei, X.,
Nie, Z.,
Thevuthasan, S.,
Sprenkle, V.,
Wang, W.,

Frontiers in Energy Research,
3, article 10
2015-02Ambipolar zinc-polyiodide electrolyte for a high-energy density aqueous redox flow battery

Abstract: Redox flow batteries are receiving wide attention for electrochemical energy storage due to their unique architecture and advantages, but progress has so far been limited by their low energy density (~25Whl-1). Here we report a high-energy density aqueous zinc-polyiodide flow battery. Using the highly soluble iodide/triiodide redox couple, a discharge energy density of 167Whl-1 is demonstrated with a near-neutral 5.0 M Znl2 electrolyte. Nuclear magnetic resonance study and density functional theory-based simulation along with flow test data indicate that the addition of an alcohol (ethanol) induces ligand formation between oxygen on the hydroxyl group and the zinc ions, which expands the stable electrolyte temperature window to from -20 to 50°C, while ameliorating the zinc dendrite. With the high-energy density and its benign nature free from strong acids and corrosive components, zinc-polyiodide flow battery is a promising candidate for various energy storage applications.

Li, B.,


Nie, Z.,
Vijayakumar, M.,
Li, G.,
Liu, J.,
Sprenkle, V.,
Wang, W.,

Nature Communications,
6, article 6303
2014-12TEMPO-based Catholyte for High Energy Density Nonaqueous Redox Flow Batteries

Abstract: A TEMPO-based non-aqueous electrolyte with the TEMPO concentration as high as 2.0 M is demonstrated as a high-energy-density catholyte for redox flow battery applications. With a hybrid anode, Li|TEMPO flow cells using this electrolyte deliver an energy efficiency of ca. 70% and an impressively high energy density of 126 W h L-1.

Wei, X.,


Xu, W.,
Vijayakumar, M.,
Cosimbescu, L.,
Liu, T.,
Sprenkle, V.,
Wang, W.,

Advanced Materials,
26(45):7649-7653
2014-12The Role of FeS in Initial Activation and Performance Degradation of Na-NiCl2 Batteries

Abstract: The role of iron sulfide (FeS) in initial cell activation and degradation in the Na-NiCl2 battery was investigated in this work. The research focused on identifying the effects of the FeS level on the electrochemical performance and morphological changes in the cathode. The x-ray photoelectron spectroscopy study along with battery tests revealed that FeS plays a critical role in initial battery activation by removing passivation layers on Ni particles. It was also found that the optimum level of FeS in the cathode resulted in minimum Ni particle growth and improved battery cycling performance. The results of electrochemical characterization indicated that sulfur species generated in situ during initial charging, such as polysulfide and sulfur, are responsible for removing the passivation layer. Consequently, the cells containing elemental sulfur in the cathode exhibited similar electrochemical behavior during initial charging compared to that of the cells containing FeS.

Li, G.,


Lu, X.,
Kim, J.,
Engelhard, M.,
Lemmon, J.,
Sprenkle, V.,

Journal of Power Sources,
272:398-403
2014-09Understanding Aqueous Electrolyte Stability through Combined Computational and Magnetic Resonance Spectroscopy: A Case Study on Vanadium Redox Flow Battery Electrolytes

Abstract: Commercial sodium-sulphur or sodium-metal halide batteries typically need an operating temperature of 300-350°C, and one of the reasons is poor wettability of liquid sodium on the surface of beta alumina. Here we report an alloying strategy that can markedly improve the wetting, which allows the batteries to be operated at much lower temperatures. Our combined experimental and computational studies suggest that addition of caesium to sodium can markedly enhance the wettability. Single cells with Na-Cs alloy anodes exhibit great improvement in cyclinLi, G.fe over those with pure sodium anodes at 175 and 150°C. The cells show good performance even at as low as 95°C. These results demonstrate that sodium-beta alumina batteries can be operated at much lower temperatures with successfully solving the wetting issue. This work also suggests a strategy to use liquid metals in advanced batteries that can avoid the intrinsic safety issues associated with dendrite formation.

Vijayakumar, M.,


Nie, Z.,
Walter, E.,
Hu, J.,
Liu, J.,
Sprenkle, V.,
Wang, W.,

ChemPlusChem,
doi: 10.1002/cplu.201402139
2014-08Liquid-metal electrode to enable ultra-low temperature sodium-beta alumina batteries for renewable energy storage

Abstract: Commercial sodium-sulphur or sodium-metal halide batteries typically need an operating temperature of 300-350 °C, and one of the reasons is poor wettability of liquid ​sodium on the surface of beta alumina. Here we report an alloying strategy that can markedly improve the wetting, which allows the batteries to be operated at much lower temperatures. Our combined experimental and computational studies suggest that addition of ​caesium to ​sodium can markedly enhance the wettability. Single cells with Na-Cs alloy anodes exhibit great improvement in cycling life over those with pure ​sodiumanodes at 175 and 150 °C. The cells show good performance even at as low as 95 °C. These results demonstrate that sodium-beta alumina batteries can be operated at much lower temperatures with successfully solving the wetting issue. This work also suggests a strategy to use liquid metals in advanced batteries that can avoid the intrinsic safety issues associated with dendrite formation.

Lu, X.,


Li, G.,
Kim, J.,
Mei, D.,
Lemmon, J.,
Sprenkle, V.,

Nat. Commun.
5:4578 doi: 10.1038/ncomms5578
2014-08Facile Synthesis of Chevrel Phase Nanocubes and their Applications for Multivalent Energy Storage

Abstract: The Chevrel phases (CPs, MxMo6T8, M=metal, T=S or Se) are capable of rapid and reversible intercalation of multivalent ions and are the most practical cathode materials for rechargeable magnesium batteries. For the first time, we report a facile method for synthesizing Mo6S8 nanoparticles and demonstrate that these nanoparticles have significantly better Mg2+ intercalation kinetics compared with microparticles. The results described in this work could inspire the synthesis of nanoscale CPs, which could substantially impact their application.

Cheng, Y.,


Parent, L.,
Shao, Y.,
Wang, C.,
Sprenkle, V.,
Li, G.,
Liu, J.,

Chemistry of Materials,
26(17):4904-4907,
doi:10.1021/cm502306c
2014-06Redox Flow Batteries: An Engineering Perspective

Abstract: Redox flow batteries are well suited to provide modular and scalable energy storage systems for a wide range of energy storage applications. In this paper, we review the development of redox-flow-battery technology including recent advances in new redox active materials, cell designs, and systems, all from the perspective of engineers interested in applying this technology. We discuss cost, performance, and reliability metrics that are critical for deployment of large flow-battery systems. The technology, while relatively young, has the potential for significant improvement through reduced materials costs, improved energy efficiency, and significant reduction in the overall system costs.

Chalamala, B.,


Soundappan, T.,
Fisher, G.,
Anstey, M.,
Viswanathan, V.,
Perry, M.,

Proceedings of the IEEE,
102 (6): 976-999
2014-06High performance batteries based on hybrid magnesium and lithium chemistry

Abstract: This work studied hybrid batteries assembled with a Mg metal anode, a Li+ ion intercalation cathode and a dual-salt electrolyte containing Mg2+ and Li+ ions. We show that such hybrid batteries were able to combine the advantages of Li and Mg electrochemistry. They delivered outstanding rate performance (83% capacity retention at 15 C) with superior safety and stability (~5% fade for 3000 cycles).

Cheng, Y.,


Shao, Y.,
Zhang, J.,
Sprenkle, V.,
Liu, J.,
Li, G.,

Chem. Commun.,
2014, 50, 9644-9646
2014-04Towards High Performance Nonaqueous Redox Flow Electrolyte Via Ionic Modification of Active Species

Abstract: Nonaqueous redox flow batteries are emerging flow-based energy storage technologies that have the potential for higher energy densities than their aqueous counterparts because of their wider voltage windows. However, their performance has lagged far behind their inherent capability due to one major limitation of low solubility of the redox species. Here, a molecular structure engineering strategy towards high performance nonaqueous electrolyte is reported with significantly increased solubility. Its performance outweighs that of the state-of-the-art nonaqueous redox flow batteries. In particular, an ionic-derivatized ferrocene compound is designed and synthesized that has more than 20 times increased solubility in the supporting electrolyte. The solvation chemistry of the modified ferrocene compound. Electrochemical cycling testing in a hybrid lithium-organic redox flow battery using the as-synthesized ionic-derivatized ferrocene as the catholyte active material demonstrates that the incorporation of the ionic-charged pendant significantly improves the system energy density. When coupled with a lithium-graphite hybrid anode, the hybrid flow battery exhibits a cell voltage of 3.49 V, energy density about 50 Wh L-1, and energy efficiency over 75%. These results reveal a generic design route towards high performance nonaqueous electrolyte by rational functionalization of the organic redox species with selective ligand.

Wei, X.,


Cosimbescu, L.,
Xu, W.,
Hu, J.,
Vijayakumar, M.,
Feng, J.,
Hu, M.,
Deng, X.,
Xiao, J.,
Liu, J.,
Sprenkle, V.,
Wang, W.,

Advanced Energy Materials,
(1400678),
doi:DOI: 10.1002/aenm.201400678
2014-02Cost and Performance Model for Redox Flow Batteries

Abstract: A cost model is developed for all vanadium and iron-vanadium redox flow batteries. Electrochemical performance modeling is done to estimate stack performance at various power densities as a function of state of charge and operating conditions. This is supplemented with a shunt current model and a pumping loss model to estimate actual system efficiency. The operating parameters such as power density, flow rates and design parameters such as electrode aspect ratio and flow frame channel dimensions are adjusted to maximize efficiency and minimize capital costs. Detailed cost estimates are obtained from various vendors to calculate cost estimates for present, near-term and optimistic scenarios. The most cost-effective chemistries with optimum operating conditions for power or energy intensive applications are determined, providing a roadmap for battery management systems development for redox flow batteries. The main drivers for cost reduction for various chemistries are identified as a function of the energy to power ratio of the storage system.

Viswanathan, V.,


Crawford, A.,
Stephenson, D.,
Kim, S.,
Wang, W.,
Li, B.,
Coffey, G.,
Thomsen, E.,
Graff, G.,
Balducci, P.,
Kintner-Meyer, M.,
Sprenkle, V.,

Journal of Power Sources,
247:1040-1051,
doi:10.1016/j.jpowsour.2012.12.023
2014-02GeOx/Reduced Graphene Oxide Composite as an Anode for Li-ion Batteries: Enhanced Capacity via Reversible Utilization of Li2O along with Improved Rate Performance

Abstract: A self-assembled GeOx/reduced graphene oxide (GeOx/RGO) composite, where GeOx nanoparticles are grown directly on reduced graphene oxide sheets, is synthesized via a facile one-step reduction approach and studied by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy loss spectroscopy elemental mapping, and other techniques. Electrochemical evaluation indicates that incorporation of reduced graphene oxide enhances both the rate capability and reversible capacity of GeOx, with the latter being due to the RGO enabling reversible utilization of Li2O. The composite delivers a high reversible capacity of 1600 mAh g-1 at a current density of 100 mA g-1, and still maintains a capacity of 410 mAh g-1 at a high current density of 20 A g-1. Owing to the flexible reduced graphene oxide sheets enwrapping the GeOx particles, the cycling stability of the composite is also improved significantly. To further demonstrate its feasibility in practical applications, the synthesized GeOx/RGO composite anode is successfully paired with a high voltage LiNi0.5Mn1.5O4 cathode to form a full cell, which shows good cycling and rate performance.

Yi, R.,


Feng, J.,
Lu, D.,
Gordin, M.,
Chen, S.,
Choi, D.,
Wang, D.,

Advanced Functional Materials,
24, 1059-1066
2014-01Improved cycling behavior of ZEBRA battery operated at intermediate temperature of 175°C

Abstract: Operation of the sodium-nickel chloride battery at temperatures below 200°C reduces cell degradation and improves cyclability. One of the main technical issues with operating this battery at intermediate temperatures such as 175°C is the poor wettability of molten sodium on ß"-alumina solid electrolyte (BASE), which causes reduced active area and limits charging. In order to overcome the poor wettability of molten sodium on BASE at 175°C, a Pt grid was applied on the anode side of the BASE using a screen printing technique. Cells with their active area increased by metallized BASEs exhibited deeper charging and stable cycling behavior.

Li, G.,


Lu, X.,
Kim, J.,
Lemmon, J.,
Sprenkle, V.,

Journal of Power Sources,
249(2014):414-417
2013-12Nanorod Niobium Oxide as Powerful Catalysts for an All Vanadium Redox Flow Battery

Abstract: A powerful low-cost electrocatalyst, nanorod Nb2O5, is synthesized using hydrothermal method with monoclinic phases and simultaneously deposited on the surface of graphite felt (GF) electrode in an all vanadium flow battery (VRB). Cyclic voltammetry (CV) study confirmed that Nb2O5 has catalytic effects towards redox couples of V(II)/V(III) at the negative side and V(IV)/V(V) at the positive side to facilitate the electrochemical kinetics of the vanadium redox reactions. Because of poor conductivity of Nb2O5, the performance of the Nb2O5 loaded electrodes is strongly dependent on the nanosize and uniform distribution of catalysts on GFs surfaces. Accordingly, optimal amounts of W-doped Nb2O5 nanorods with minimum agglomeration and improved distribution on GFs surfaces are established by adding water-soluble compounds containing tungsten (W) into the precursor solutions. The corresponding energy efficiency is enhanced by ~10.7% at high current density (150 mA.cm-2) as compared with one without catalysts. Flow battery cyclic performance also demonstrates the excellent stability of the as prepared Nb2O5 catalyst enhanced electrode. These results suggest that Nb2O5-based nanorods, replacing expensive noble metals, uniformly decorating GFs holds great promise as high-performance electrodes for VRB applications.

Li, B.,


Gu, M.,
Nie, Z.,
Wei, X.,
Wang, C.,
Sprenkle, V.,
Wang, W.,

Nano Letters,
2014, 14, 158-165
2013-11Cell Degradation of a Na-NiCl2 (ZEBRA) Battery

Abstract: In this work, the parameters influencing the degradation of a Na-NiCl2 (ZEBRA) battery were investigated. Planar Na-NiCl2 cells using β"”-alumina solid electrolyte (BASE) were tested with different C-rates, Ni/NaCl ratios, and capacity windows, in order to identify the key parameters for the degradation of Na-NiCl2 battery. The morphology of NaCl and Ni particles were extensively investigated after 60 cycles under various test conditions using a scanning electron microscope. A strong correlation between the particle size (NaCl and Ni) and battery degradation was observed in this work. Even though the growth of both Ni and NaCl can influence the cell degradation, our results indicate that the growth of NaCl is a dominant factor in cell degradation. The use of excess Ni seems to play a role in tolerating the negative effects of particle growth on degradation since the available active surface area of Ni particles can be still sufficient even after particle growth. For NaCl, a large cycling window was the most significant factor, of which effects were amplified with decrease in Ni/NaCl ratio.

Li, G.,


Lu, X.,
Kim, J.,
Lemmon, J.,
Sprenkle, V.,

Journal of Materials Chemistry A,
47 (2013) 14935 - 14942
2013-10On-Line Investigation of the Capacity-Decay Mechanism of Micro-porous Separator-Based All-Vanadium Redox Flow Batteries and Its Recovery

Abstract: In this paper, we report the results of our investigation of the capacity decay mechanism of vanadium redox flow batteries with micro-porous separators as membranes. Our investigation focused on the relationship of electrochemical performance and electrolyte compositions at both the positive and negative half-cells. Although the concentration of total vanadium ions remains nearly constant at both sides over cycling, the net transfer of solutions from one side to the other and thus the asymmetrical valance of vanadium ions due to the subsequent disproportionate self-discharge reactions at both sides lead to capacity fading. Through in situ monitoring of the hydraulic pressure of the electrolyte during cycling at both sides, we found that convection arising from differential hydraulic pressures at both sides of separators plays a dominant role in capacity decay. We developed a capacity stabilizing method, and successfully demonstrated it through the regulation of gas pressures in both electrolyte tanks.

Li, B.,


Luo, Q.,
Wei, X.,
Nie, Z.,
Thomsen, E.,
Chen, B.,
Sprenkle, V.,
Wang, W.,

ChemSusChem
2014(7):577 - 584
2013-09Performance Evaluation of Microporous Separator in Fe/V Redox Flow Battery

Abstract: The newly developed Fe/V redox flow battery has demonstrated attractive cell performance. However, the deliverable energy density is relatively low due to the reduced cell voltage. To compensate this disadvantage and compete with other redox flow battery systems, cost reduction of the Fe/V system is necessary. This paper describes evaluation of hydrocarbon-based Daramic® microporous separators for use in the Fe/V system. These separators are very inexpensive and have exceptional mechanical properties. Separator B having ion exchange capacity demonstrated excellent capacity retention capability, and exhibited energy efficiency above 65% over a broad temperature range of 5-50°C and at current densities up to 80mA/cm2. Therefore, this separator shows great potential to replace the expensive Nafion® membrane. This will drive down the capital cost and make the Fe/V system a promising low-cost energy storage technology.

Wei, X.,


Luo, Q.,
Li, B.,
Nie, Z.,
E. Miller, J. Chambers, Sprenkle, V.,
Wang, W.,

ECS Transactions,
45 (26):17-24
2013-091 kW/1 kWh advanced vanadium redox flow battery utilizing mixed acid electrolytes

Abstract: This paper reports on the recent demonstration of an advanced vanadium redox flow battery (VRFB) using a newly developed mixed acid (sulfuric and hydrochloric acid) supporting electrolyte at a kW scale. The developed prototype VRFB system is capable of delivering more than 1.1 kW in the operation range of 15~85% state of charge (SOC) at 80 mA cm-2 with an energy efficiency of 82% and energy content of 1.4 kWh. The system operated stably without any precipitation at electrolyte temperatures >45°C. At similar electrolyte temperatures, tests with a conventional sulfuric acid electrolyte suffered from precipitation after 80 cycles. By operating stably at elevated temperatures (>40°C), the mixed acid system enables significant advantages over the conventional sulfate system, namely; 1) high stack energy efficiency due to better kinetics and lower electrolyte resistance, 2) lower viscosity resulting in reduced pumping losses, 3) lower capital cost by elimination of heat exchanger, 4) higher system efficiency and 5) simplified system design and operation. Demonstration of the prototype stack with the mixed acid electrolyte has been shown to lower the cost of conventional VRFB systems for large-scale energy storage applications.

Kim, S.,


Thomsen, E.,
Xia, G.,
Nie, Z.,
Bao, J.,
Recknagle, K.,
Wang, W.,
Viswanathan, V.,
Luo, Q.,
Wei, X.,
Crawford, A.,
Coffey, G.,
Maupin, G.,
Sprenkle, V.,

Journal of Power Sources,
237 (2013) 300-309
2013-08Simply AlF3-treated Li4Ti5O12 composite anode materials for stable and ultrahigh power lithium-ion batteries

Abstract: The commercial Li4Ti5O12 (LTO) is successfully modified by AlF3 via a low temperature process. After being calcined at 400°C for 5 h, AlF3 reacts with LTO to form a composite material, which mainly consists of Al3+ and F- co-doped LTO with small amounts of anatase TiO2. Al3+ and F- co-doped LTO demonstrates ultrahigh rate capability comparing to the pristine LTO. Since the amount of the byproduct TiO2 is relatively small, the modified LTO electrodes retain the main voltage characteristics of LTO with a minor feature similar to those of anatase TiO2. The doped LTO anodes deliver slightly higher discharge capacity and maintain the excellent long-term cycling stability when compared to the pristine LTO anode. Therefore, Al3+ and F- co-doped LTO composite material synthesized at low temperature is an excellent stable and ultra-high power lithium-ion batteries.

Xu, W.,


Chen, X.,
Wang, W.,
Choi, D.,
Ding, F.,
Zheng, J.,
Nie, Z.,
Choi, Y.,
Zhang, J.,
Yang, Z.,

Journal of Power Sources
236(2013):169-174
2013-07High performance batteries based on hybrid magnesium and lithium chemistry

Abstract: This work studied hybrid batteries assembled with a Mg metal anode, a Li+ ion intercalation cathode and a dual-salt electrolyte containing Mg2+ and Li+ ions. We show that such hybrid batteries were able to combine the advantages of Li and Mg electrochemistry. They delivered outstanding rate performance (83% capacity retention at 15 C) with superior safety and stability (B5% fade for 3000 cycles).

Cheng, Y.,


Shao, Y.,
Zhang, J.,
Sprenkle, V.,
Liu, J.,
Li, G.,

Chem. Commun.,
2014(50):9644-9646
2013-06A novel low-cost sodium-zinc chloride battery

Abstract: The sodium-metal halide (ZEBRA) battery has been considered as one of the most attractive energy storage systems for stationary and transportation applications. Even though Na-NiCl2 battery has been widely investigated, there is still a need to develop a more economical system to make this technology more attractive for commercialization. In the present work, a novel low-cost Na-ZnCl2 battery with a planar β"-Al2O3 solid electrolyte (BASE) was proposed, and its electrochemical reactions and battery performance were investigated. Compared to the Na-NiCl2 chemistry, the ZnCl2-based chemistry was more complicated, in which multiple electrochemical reactions includinLi, G.quid-phase formation occurred at temperatures above 253°C. During the first stage of charge, NaCl reacted with Zn to form Na in the anode and Na2ZnCl4 in the cathode. Once all the residual NaCl was consumed, further charging led to the formation of a NaCl-ZnCl2 liquid phase. At the end of charge, the liquid phase reacted with Zn to produce solid ZnCl2. To identify the effects of liquid-phase formation on electrochemical performance, button cells were assembled and tested at 280°C and 240°C. At 280°C where the liquid phase formed during cycling, cells revealed quite stable cyclability. On the other hand, more rapid increase in polarization was observed at 240°C where only solid-state electrochemical reactions occurred. SEM analysis indicated that the stable performance at 280°C was due to the suppressed growth of Zn and NaCl particles, which were generated from the liquid phase during discharge of each cycle.

Lu, X.,


Li, G.,
Kim, J.,
Lemmon, J.,
Sprenkle, V.,
Yang, Z.,

Energy & Environmental Science, 6(6): 1837-1843
2013-06Composite blend polymer membranes with increased proton selectivity and lifetime for vanadium redox flow batteries

Abstract: Composite membranes based on blends of sulfonated fluorinated poly(arylene ether) (SFPAE) and poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-co-HFP)) were prepared with varying P(VDF-co-HFP) content for vanadium redox flow battery (VRFB) applications. The properties of the SFPAE-P(VDF-co-HFP) blends were characterized by atomic force microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. The water uptake, mechanical properties, thermal properties, proton conductivity, VO2+ permeability and VRFB cell performance of the composite membranes were investigated in detail and compared to the pristine SFPAE membrane. It was found that SFPAE had good compatibility with P(VDF-co-HFP) and the incorporation of P(VDF-co-HFP) increased the mechanical properties, thermal properties, and proton selectivity of the materials effectively. An SFPAE composite membrane with 10 wt.% P(VDF-co-HFP) exhibited a 44% increase in VRFB cell lifetime as compared to a cell with a pure SFPAE membrane. Therefore, the P(VDF-co-HFP) blending approach is a facile method for producing low-cost, high-performance VRFB membranes.

Chen, D.,


Kim, S.,
Sprenkle, V.,
Hickner, M.,

Journal of Power Sources
231(2013):301-306
2013-05Elucidating the Higher Stability of Vanadium (V) Cations in Mixed Acid Based Redox Flow Battery Electrolytes

Abstract: The Vanadium (V) cation structures in mixed acid based electrolyte solution were analysed by density functional theory (DFT) based computational modelling and 51V and 35Cl Nuclear Magnetic Resonance (NMR) spectroscopy. The Vanadium (V) cation exists as di-nuclear [V2O3Cl2.6H2O]2+ compound at higher vanadium concentrations (=1.75M). In particular, at high temperatures (>295K) this di-nuclear compound undergoes ligand exchange process with nearby solvent chlorine molecule and forms chlorine bonded [V2O3Cl2.6H2O]2+ compound. This chlorine bonded [V2O3Cl2.6H2O]2+ compound might be resistant to the de-protonation reaction which is the initial step in the precipitation reaction in Vanadium based electrolyte solutions. The combined theoretical and experimental approach reveals that formation of chlorine bonded [V2O3Cl2.6H2O]2+ compound might be central to the observed higher thermal stability of mixed acid based Vanadium (V) electrolyte solutions.

Vijayakumar, M.,


Wang, W.,
Nie, Z.,
Sprenkle, V.,
Hu, J.,

Journal of Power Sources,
236 (2013), 169-174
2013-05Polyvinyl Chloride/Silica Nanoporous Composite Separator for All-Vanadium Redox Flow Battery Applications

Abstract: We demonstrate application of a commercial nanoporous polyvinyl chloride (PVC)/silica separator in an all-vanadium redox flow battery (VRB) as a low-cost alternative to expensive Nafion® membranes. This hydrophilic separator is composed of silica particles enmeshed in a PVC matrix that creates unique porous structures. These nano-scale pores with an average pore size of 45nm and a porosity of 65% serve as ion transport channels that are critically important for flow battery operation. The VRB flow cell using the PVC/silica separator produces excellent electrochemical performance in a mixed-acid VRB system with average energy efficiency (EE) of 79% at the current density of 50 mA cm-2. This separator affords the VRB flow cell with excellent rate capability with its EE higher than that of Nafion® membrane at current densities above 100 mA cm-2. With this separator, the EE of the VRB flow cell exhibits great tolerance to temperature fluctuations in the typical operational temperature range of the mixed-acid VRB system. More importantly, the flow cell using the separator demonstrates an excellent capacity retention over cycling, which enables the VRB system to operate in the long term with minimal electrolyte maintenance.

Wei, X.,


Nie, Z.,
Luo, Q.,
Li, B.,
Sprenkle, V.,
Wang, W.,

Journal of the Electrochemical Society,
160 (8):A1215-A1218
2013-05Fe/V Redox Flow Battery Electrolyte Investigation and Optimization

Abstract: The recently invented iron (Fe)/vanadium (V) redox flow battery (IVB) system has attracted increasing attention because of its long-term cycling stability and low-cost membrane/separator. In this paper, we describe our extensive matrix study of factors such as electrolyte composition; state of charge (SOC), and temperature that influence the stability of electrolytes in both positive and negative half-cells. During the study, an optimized electrolyte that can be operated in a temperature range from -5°C to 50°C without precipitation is identified. Fe/V flow cells using the optimized electrolyte and low-cost separator exhibit satisfactory cycling performance at different temperatures. Efficiencies, capacities, and energy densities of flow batteries at various temperatures are studied.

Li, B.,


Li, L.,
Wang, W.,
Nie, Z.,
Chen, B.,
Wei, X.,
Luo, Q.,
Yang, Z.,
Sprenkle, V.,

Journal of Power Sources,
229 (2013), 1-5
2013-04Nanoporous Polytetrafluoroethylene/Silica Composite Separator as a High-Performance All-Vanadium Redox Flow Battery Membrane

Abstract: A novel low-cost nanoporous polytetrafluoroethylene (PTFE)/silica composite separator has been prepared and evaluated for its use in an all-vanadium redox flow battery (VRB). The separator consists of silica particles enmeshed in a PTFE fibril matrix. It possesses unique nanoporous structures with an average pore size of 38 nm and a porosity of 48%. These pores function as the ion transport channels during redox flow battery operation. This separator provides excellent electrochemical performance in the mixed-acid VRB system. The VRB using this separator delivers impressive energy efficiency, rate capability, and temperature tolerance. In additon, the flow cell using the novel separator also demonstrates an exceptional capacity retention capability over extended cycling, thus offering excellent stability for long-term operation. The characteristics of low cost, excellent electrochemical performance and proven chemical stability afford the PTFE/silica nanoporous separator great potential as a substitute for the Nafion membrane used in VRB applications.

Wei, X.,


Nie, Z.,
Luo, Q.,
Li, B.,
Chen, B.,
Simmons, K.,
Sprenkle, V.,
Wang, W.,

Advanced Energy Materials
3:1215-1220
2013-02High Energy Density Na-S/NiCl2 Hybrid Battery

Abstract: High temperature (250-350°C) sodium-beta alumina batteries (NBBs) are attractive energy storage devices for renewable energy integration and other grid related applications. Currently, two technologies are commercially available in NBBs, e.g., sodium-sulfur (Na-S) battery and sodium-metal halide (ZEBRA) batteries. In this study, we investigated the combination of these two chemistries with a mixed cathode. In particular, the cathode of the cell consisted of molten NaAlCl4 as a catholyte and a mixture of Ni, NaCl and Na2S as active materials. During cycling, two reversible plateaus were observed in cell voltage profiles, which matched electrochemical reactions for Na-S and Na-NiCl2 redox couples. An irreversible reaction between sulfur species and Ni was identified during initial charge at 280°C, which caused a decrease in cell capacity. The final products on discharge included Na2Sn with 1 < n < 3, which differed from Na2S3 found in traditiona l Na-S battery. Reduction of sulfur in the mixed cathode led to an increase in overall energy density over ZEBRA batteries. Despite of the initial drop in cell capacity, the mixed cathode demonstrated relatively stable cycling with more than 95% of capacity retained over 60 cycles under 10mA/cm2. Optimization of the cathode may lead to further improvements in battery performance.

Lu, X.,


Lemmon, J.,
Kim, J.,
Sprenkle, V.,
Yang, Z.,

Journal of Power Sources,
224 (2013) 312-316
2013-02Bismuth Nanoparticle Decorating Graphite Felt as a High-Performance Electrode for an All-Vanadium Redox Flow Battery

Abstract: Employing electrolytes containing Bi3+, bismuth nanoparticles are synchronously electrodeposited onto the surface of a graphite-felt electrode during operation of an all-vanadium redox flow battery (VRFB). The influence of the Bi nanoparticles on the electrochemical performance of the VRFB is thoroughly investigated. It is confirmed that Bi is only present at the negative electrode and facilitates the redox reaction between V(II) and V(III). However, the Bi nanoparticles significantly improve the electrochemical performance of VRFB cells by enhancing the kinetics of the sluggish V(II)/V(III) redox reaction, especially under high power operation. The energy efficiency is increased by 11% at high current density (150 mA.cm-2) owing to faster charge transfer as compared with one without Bi. The results suggest that using Bi nanoparticles in place of noble metals offers great promise as high-performance electrodes for VRFB application.

Li, B.,


Gu, M.,
Nie, Z.,
Shao, Y.,
Luo, Q.,
Wei, X.,
Li, X.,
Xiao, J.,
Wang, C.,
Sprenkle, V.,
Wang, W.,

Nano Letters,
13, 1330-1335
2013-02Capacity Decay and Remediation of Nafion®-based All-Vanadium Redox Flow Batteries

Abstract: The relationship between the electrochemical performance of vanadium redox flow batteries (VRB) and electrolyte compositions has been investigated, and the reasons for capacity decay over charge-discharge cycling have been analyzed and are discussed in this paper. The results show that the reasons for capacity fading over real charge-discharge cycling include not only the imbalanced vanadium active species, but also the asymmetrical valence of vanadium ions in positive and negative electrolytes. The asymmetrical valence of vanadium ions leads to the SOC range to decrease in positive electrolyte and increase in negative electrolyte, respectively. As a result, the higher SOC range in negative half-cells further aggravate the capacity fading by creating a higher over-potential and possible hydrogen evolution. Based on this finding, we developed two methods for restoring the lost capacity; thereby enabling long-term operation of VRBs to be achieved without the substantial loss of energy resulting from periodic remixing of electrolytes.

Luo, Q.,


Li, L.,
Wang, W.,
Nie, Z.,
Wei, X.,
Li, B.,
Chen, B.,
Yang, Z.,
Sprenkle, V.,

ChemSusChem,
6(2), 268-274
2013-02Recent Progress in Redox Flow Battery Research and Development

Abstract: With the increasing need to seamlessly integrate renewable energy with the current electricity grid, which itself is evolving into a more intelligent, efficient, and capable electrical power system, it is envisioned that energy-storage systems will play a more prominent role in bridging the gap between current technology and a clean sustainable future in grid reliability and utilization. Redox flow battery technology is a leading approach in providing a well-balanced approach for current challenges. In this paper, we review recent progress in the research and development of redox flow battery technology, including cell-level components of electrolytes, electrodes, and membranes. Our review focuses on new redox chemistries for both aqueous and non-aqueous systems.

Wang, W.,


Luo, Q.,
Li, B.,
Wei, X.,
Li, L.,
Yang, Z.,

Advanced Functional Materials
23(8): 970-986
2013-01Li-Ion Battery with LiFePO4 Cathode and Li4Ti5O12 Anode for Stationary Energy Storage

Abstract: Li-ion batteries based on commercially available LiFePO4 cathode and Li4Ti5O12 anode were investigated for potential stationary energy storage applications. The full cell that operated at flat 1.85 V demonstrated stable cycling up to 200 cycles followed by a rapid fade. A Li-ion full cell with Ketjen black modified LiFePO4 cathode and an unmodified Li4Ti5O12 anode exhibited negligible fade after more than 1200 cycles with a capacity of ~130 mAh/g at C/2. The improved stability, along with its cost-effectiveness, environmental benignity, and safety, make the LiFePO4/Li4Ti5O12 combination Li-ion battery a promising option for storing renewable energy.

Wang, W.,


Choi, D.,
Yang, Z.,

Metallurgical and Materials Transactions A,
Physical Metallurgy and Materials Science,
44A(1 Supplement): 21-25
2013-01Advanced Intermediate-Temperature Na-S Battery

Abstract: In this study, we reported an intermediate-temperature (~150°C) sodium-sulfur (Na-S) battery. With a reduced operating temperature, this novel battery can potentially reduce the cost and safety issues associated with the conventional high-temperatures (300~350°C) Na-S battery. A dense β"-Al2O3 solid membrane and tetraglyme were utilized as the electrolyte separator and catholyte solvent in this battery. Solubility tests indicated that cathode mixture of Na2S4 and S exhibited extremely high solubility in tetraglyme (e.g., > 4.1 M for Na2S4 + 4 S). CV scans of Na2S4 in tetraglyme revealed two pairs of redox couples with peaks at around 2.22 and 1.75 V, corresponding to the redox reactions of polysulfide species. The discharge/charge profiles of the Na-S battery showed a slope region and a plateau, indicating multiple steps and cell reactions. In-situ Raman spectra during battery operation suggested that polysulfide species were formed in the sequence of Na2S5 + S → Na2S5 + Na2S4 → Na2S4 + Na2S2 during discharge and in a reverse order during charge. This battery showed dramatic improvement in rate capacity and cycling stability over room-temperature Na-S batteries, which makes it extremely attractive for renewable energy integration and other grid related applications.

Lu, X.,


Kirby, B.,
Xu, W.,
Li, G.,
Kim, J.,
Lemmon, J.,
Sprenkle, V.,
Yang, Z.,

Energy & Environmental Science,
6(1) (2013), 299-306
2012-12Novel ternary molten salt electrolytes for intermediate-temperature sodium/nickel chloride batteries

Abstract: The sodium-nickel chloride (ZEBRA) battery is typically operated at relatively high temperature (250~350°C) to achieve adequate electrochemical performance. Reducing the operating temperature in the range of 150 to 200°C can lead to enhanced cycle life by suppressing temperature related degradation mechanisms. The operation at these intermediate temperatures also allows for lower cost materials of construction such as elastomeric sealants and gaskets. To achieve adequate electrochemical performance at lower operating temperatures requires an overall reduction in ohmic losses associated with temperature. This includes reduction in the ohmic resistance of β"-alumina solid electrolyte (BASE) and the incorporation of low melting point molten salt as the secondary electrolyte. In present work, planar-type Na/NiCl2 cells with a thin flat BASE (600 μm) and low melting point secondary electrolyte were evaluated at reduced temperatures. Molten salts used as secondary electrolytes were fabricated by the partial replacement of NaCl in the standard secondary electrolyte (NaAlCl4) with other lower melting point alkali metal salts such as NaBr, LiCl, and LiBr. Electrochemical characterization of these ternary molten salts demonstrated improved ionic conductivity and sufficient electrochemical window at reduced temperatures. Furthermore, Na/NiCl2 cells with 50 mol% NaBr-containing secondary electrolyte exhibited reduced polarizations at 175°C compared to the cell with the standard NaAlCl4 catholyte. The cells also exhibited stable cycling performance even at 150°C.

Li, G.,


Lu, X.,
Coyle, C.,
Kim, J.,
Lemmon, J.,
Sprenkle, V.,
Yang, Z.,

Journal of Power Sources,
220, 193-198
2012-11In-situ investigation of vanadium ion transport in redox flow battery

Abstract: Flow batteries with vanadium and iron redox couples as the electroactive species were employed to investigate the transport behavior of vanadium ions in the presence of an electric field. It was shown that the electric field accelerated the positive-to-negative and reduced the negative-to-positive transport of vanadium ions in the charging process and affected the vanadium ion transport in the opposite way during discharge. In addition, a method was designed to differentiate the concentration-gradient–driven vanadium ion diffusion and electric-field–driven vanadium ion migration. A simplified mathematical model was established to simulate the vanadium ion transport in real charge-discharge operation of the flow battery. The concentration gradient diffusion coefficients and electric-migration coefficients of V2+, V3+, VO2+, and VO2+ across a NAFION® membrane were obtained by fitting the experimental data.

Luo, Q.,


Li, L. Nie, Z.,
Wang, W.,
Wei, X.,
Li, B.,
Chen, B.,
Yang, Z.,

Journal of Power Sources,
218 (2012), 15-30
2012-11Microporous separators for Fe/V redox flow batteries

Abstract: The Fe/V redox flow battery has demonstrated promising performance with distinct advantages over other redox flow battery systems. Due to the less oxidative nature of the Fe(III) species, hydrocarbon-based ion exchange membranes or separators can be used. Daramic® microporous polyethylene separators were tested on Fe/V flow cells using sulfuric/chloric mixed acid-supporting electrolytes. Among them, separator C exhibited good flow cell cycling performance with satisfactory repeatability over a broad temperature range of 5-50°C. Energy efficiency (EE) of C remains around 70% at current densities of 50-80 mA.cm-2 in temperatures ranging from room temperature to 50°C. The capacity decay problem could be circumvented through hydraulic pressure balancing by means of applying different pump rates to the positive and negative electrolytes. Stable capacity and energy were obtained over 20 cycles at room temperature and 40°C. These results show that extremely low-cost separators ($1-20/m2) are applicable in the Fe/V flow battery system with acceptable energy efficiency. This represents a remarkable breakthrough: a significant reduction of the capital cost of the Fe/V flow battery system, which could further its market penetration in grid stabilization and renewable integration.

Wei, X.,


Li, L.,
Luo, Q.,
Nie, Z.,
Wang, W.,
Li, B.,
Xia, G.,
Millar, E.,
Chambers, J.,
Yang, Z.,

Journal of Power Sources,
218 (2012), 39-45
2012-10A new hybrid redox flow battery with multiple redox couples

Abstract: A redox flow battery using V4+/V5+ vs. V2+/V3+ and Fe2+/Fe3+ vs. V2+/V3+ redox couples in chloric/sulfuric mixed acid supporting electrolyte was investigated for potential stationary energy storage applications. The Fe/V hybrid redox flow cell using mixed reactant solutions and operated within a voltage window of 0.5~1.7 V demonstrated stable cycling over 100 cycles with energy efficiency ~80% and negligible capacity fading at room temperature. A 66% improvement in the energy density of the Fe/V hybrid cell was achieved compared with the previously reported Fe/V cell using only Fe2+/Fe3+ vs. V2+/V3+ redox couples.

Wang, W.,


Li, L.,
Nie, Z.,
Chen, B.,
Luo, Q.,
Shao, Y.,
Wei, X.,
Chen, F.,
Xia, G.,
Yang, Z.,

Journal of Power Sources,
216 (2012), 99-103
2012-10The effects of temperature on the electrochemical performance of sodium-nickel chloride batteries

Abstract: The sodium-nickel chloride (ZEBRA) battery is typically operated at relatively high temperatures (≥ 300°C) to achieve adequate electrochemical performance. In the present study, the effects of operating temperature on the electrochemical performance of planar-type sodium-nickel chloride batteries were investigated in order to evaluate the feasibility of the battery operation at low temperatures (≥ 200°C). Electrochemical test results revealed that the battery was able to be cycled at C/3 rate at as low as 175°C despite the higher cell polarization at the reduced temperature. Overall, low operating temperature resulted in a considerable improvement in the stability of cell performance. Cell degradation was negligible at 175°C, while 55% increase in end-of-charge polarization was observed at 280°C after 60 cycles. SEM analysis indicated that the performance degradation at higher temperatures was related to the particle growth of both nickel and sodium chloride in the cathode. The cells tested at lower temperatures (e.g., 175 and 200°C), however, exhibited a sharp drop in cell voltage at the end of discharge due to the diffusion limitation, possibly caused by the limited ionic conductivity of NaAlCl4 melt or the poor wettability of sodium on the β"-Al2O3 solid electrolyte (BASE). Therefore, improvements in the ionic conductivity of a secondary electrolyte and sodium wetting as well as reduction in the ohmic resistance of BASE are required to further enhance the battery performance at low temperatures.

Lu, X.,


Li, G.,
Kim, J.,
Lemmon, J.,
Sprenkle, V.,
Yang, Z.,

Journal of Power Sources,
215 (2012), 288-295
2012-05Anthraquinone with Tailored Structure for Nonaqueous Metal-Organic Redox Flow Battery

Abstract: A nonaqueous, hybrid metal-organic redox flow battery based on tailored anthraquinone structure is demonstrated to have an energy efficiency of ~82% and a specific discharge energy density similar to these of aqueous redox flow batteries, which is due to the significantly improved solubility of anthraquinone in supporting electrolytes.

Wang, W.,


Xu, W.,
Cosimbescu, L.,
Choi, D.,
Li, L.,
Yang, Z.,

Chemical Communications
48(53):6669-6671
2012-03Advanced Redox Flow Batteries for Stationary Electrical Energy Storage (PNNL-21174)

Abstract: This report describes the status of advanced redox flow battery research being performed at Pacific Northwest National Laboratory for the U.S. Department of Energy's Energy Storage Systems Program. The FY12, Quarter 1 milestone was completed on time. The milestone entails completing evaluation and optimization of single cell components for the advanced all vanadium (V/V) mixed acid redox flow battery electrolyte chemistries recently developed at the Laboratory. All the single cell components to be used in future kW-scale stacks have been identified and optimized in this quarter, which include solution electrolyte, membrane; carbon felt electrode and bi-polar plate. Varied electrochemical, chemical and physical evaluations were performed to assist the component screening and optimization. The mechanisms of the battery capacity fading behavior for the all (V/V) redox flow were discovered, which allowed us to optimize the related cell operation parameters and continuously operate the system for more than 3 months without any capacity decay.

Li, L.,


Kim, S.,
Xia, G.,
Wang, W.,
Z Yang,

Pacific Northwest National Laboratory
Richland, WA
2012-02A New Fe/V Redox Flow Battery Using Sulfuric/Chloric Mixed Acid Supporting Electrolyte

Abstract: A redox flow battery using Fe2+/Fe3+ and V2+/V3+ redox couples in chloric/sulfuric mixed-acid supporting electrolyte was investigated for potential stationary energy storage applications. The Fe/V redox flow cell using mixed reactant solutions operated within a voltage window of 0.5~1.35 V with a nearly 100% utilization ratio and demonstrated stable cycling over 100 cycles with energy efficiency > 80% and no capacity fading at room temperature. A 25% improvement in the discharge energy density of the Fe/V cell was achieved compared with the previous reported Fe/V cell using pure chloride-acid supporting electrolyte. Stable performance was achieved in the temperature range between 0°C and 50°C as well as using a microporous separator as the membrane. The improved electrochemical performance makes the Fe/V redox flow battery a promising option as a stationary energy storage device to enable renewable integration and stabilization of the electric grid.

Wang, W.,


Nie, Z.,
Chen, B.,
Chen, F.,
Luo, Q.,
Wei, X.,
Xia, G.,
Skyllas-Kazacos, M.,
Li, L.,
Yang, Z.,

Advanced Energy Materials,
2(4): 487-493
2011-06A New Redox Flow Battery Using Fe/V Redox Couples in Chloride Supporting Electrolyte

Abstract: A new redox flow battery using Fe2+/Fe3+ and V2+/V3+ redox couples in chloride-supporting electrolyte was proposed and investigated for potential stationary energy storage applications. The Fe/V redox flow cell using mixed reactant solutions operated within a voltage window of 0.5~1.35 V with a nearly 100% utilization ratio and demonstrated stable cycling with energy efficiency around 80% at room temperature. Stable performance was also achieved in the temperature range between 0°C and 50°C. The improved stability and electrochemical activity over a broader temperature range over the current technologies (such as Fe/Cr redox chemistry) potentially eliminate the necessity of external heat management and use of catalysts, making the Fe/V redox flow battery a promising option as a stationary energy storage device to enable renewable integration and stabilization of the electrical grid.

Wang, W.,


Kim, S.,
Chen, B.,
Nie, Z.,
Zhang, J.,
Xia, G.,
Li, L.,
Yang, Z.,

Energy & Environmental Science,
4(10):4068-4073
2011-04Effects of additives on the stability of electrolytes for all-vanadium redox flow batteries

Abstract: The stability of the electrolytes for all-vanadium redox flow battery was investigated with ex-situ heating/cooling treatment and in situ flow-battery testing methods. The effects of inorganic and organic additives have been studied. The additives containing the ions of potassium, phosphate, and polyphosphate are not suitable stabilizing agents because of their reactions with V(V) ions, forming precipitates of KVSO6 or VOPO4. Of the chemicals studied, polyacrylic acid and its mixture with CH3SO3H are the most promising stabilizing candidates, which can stabilize all the four vanadium ions (V2+, V3+, VO2+, and VO2+) in electrolyte solutions up to 1.8 M. However, further effort is needed to obtain a stable electrolyte solution with >1.8 M V5+ at temperatures higher than 40°C.

Zhang, J.,


Li, L.,
Nie, Z.,
Chen, B.,
Vijayakumar, M.,
Kim, S.,
Wang, W.,
Schwenzer, B.,
Liu, J.,
Yang, Z.,

Journal of Applied Electrochemistry,
41(10 - Special Issue S1):1215-1221
2011-03A Stable Vanadium Redox-Flow Battery with High Energy Density for Large-scale Energy Storage

Abstract: The all-vanadium redox flow battery is a promising technology for large-scale renewable and grid energy storage, but is limited by the low energy density and poor stability of the vanadium electrolyte solutions. A new vanadium redox flow battery with a significant improvement over the current technology is reported in this paper. This battery uses sulfate-chloride mixed electrolytes, which are capable of dissolving 2.5 M vanadium, representing about a 70% increase in energy capacity over the current sulfate system. More importantly, the new electrolyte remains stable over a wide temperature range of -5 to 50 °C, potentially eliminating the need for electrolyte temperature control in practical applications. This development would lead to a significant reduction in the cost of energy storage, thus accelerating its market penetration.

Li, L.,


Kim, S.,
Wang, W.,
Vijayakumar, M.,
Nie, Z.,
Chen, B.,
Zhang, J.,
Xia, G.,
Hu, J.,
Graff, G.,
Liu, J.,
Yang, Z.,

Advanced Energy Materials
1(3):394-400
2011-03Electrochemical Energy Storage for Green Grid

Abstract: Electrochemical Energy Storage (EES) is an established, valuable approach for improving the reliability and overall use of the entire power system (generation, transmission, and distribution [T&D]). Sited at various T&D stages, EES can be employed for providing many grid services, including a set of ancillary services such as (1) frequency regulation and load following (aggregated term often used is balancing services), (2) cold start services, (3) contingency reserves, and (4) energy services that shift generation from peak to off -peak periods. In addition, it can provide services to solve more localized power quality issues and reactive power support.

Yang, Z.,


Zhang, J.,
Kintner-Meyer, M.,
Lu, X.,
Choi, D.,
Lemmon, J.,
Liu, J.,

Chemical Reviews
111(5):3577-3613






Oak Ridge National Laboratory (ORNL) Journal Articles and Books

SNL | PNNL | ORNL

Date Title Authors Publisher
In preparationStable Electrolytes for High Energy (4 V) Electrochemical Capacitors

Abstract:

Ruther, R.,

Sun, C., Delnick, F., Nanda, J.,

2014-06Evaluation of Diels-Alder poly (phenylene) anion exchange membranes in all-vanadium redox flow batteries

Abstract: Quaternary ammonium functionalized Diels–Alder poly(phenylene)s (QDAPPs) with different ion exchange capacities (IECs) are examined as membranes in all-vanadium redox flow batteries. QDAPP membrane behavior is compared to a standard, Nafion 212, in measurements of cycling efficiencies, areal specific resistance (ASR), vanadium permeation and durability. The IEC of the QDAPPs clearly shows an impact on the cell ASR and vanadium crossover. The results imply a trade-off between performance, indicated by cell voltage loss at a given current density, and rate of cross-over driven capacity loss in the system. Among the membranes studied, QDAPP with moderate IEC represents the best trade-off of these factors and exhibits higher performance and lower capacity loss compared to Nafion 212. All QDAPP membranes are found to be more durable than the analogous cation exchange membrane, sulfonated DAPP (SDAPP), in V5+ solution.

Sun, C.,


Tang, Z.,
Belcher, C.,
et al.,

Electrochemistry Communications
vol. 43, pp. 63-66
2014-09Characterization of Sulfonated Diels-Alder Poly(phenylene) Membranes for Electrolyte Separators in Vanadium Redox Flow Batteries

Abstract: Sulfonated Diels-Alder poly(phenylene) (SDAPP) membranes were synthesized and characterized as potential electrolyte separators for vanadium redox flow batteries. The SDAPP membranes studied had ion exchange capacities of 1.4, 1.8 and 2.3 meq/g. Transmission electron microscopy imaging shows that the ionic domains in SDAPP are roughly 0.5 nm in dimension, while Nafion has a hydrophilic phase width of around 5 nm. The sulfuric acid uptake by SDAPP was higher than that for Nafion, but the materials had similar water uptake from solutions of various sulfuric acid concentrations. In equilibration with sulfuric acid concentrations ranging from 0–17.4 mol·kg−1, SDAPP with a IEC of 2.3 meq/g had the highest conductivity, ranging from 0.21 to 0.05 S·cm−1, while SDAPP with a IEC of 1.8 had conductivity close to Nafion 117, ranging from 0.11 to 0.02 S·cm−1. With varying sulfuric acid concentration and temperature, vanadium permeability in SDAPP is positively correlated to the membrane's IEC. The vanadium permeability of SDAPP 2.3 is similar to that of Nafion, but permeability values for SDAPP 1.8 and SDAPP 1.4 are substantially lower. The vanadium permeation decreases with increasing electrolyte sulfuric acid concentration. Vanadium diffusion activation energy is about 20 kJ·mol−1 in both SDAPP and Nafion. The vanadium redox flow battery (VRFB) has shown technical potential for large scale electrical energy storage.13 One possible role of VRFBs is their integration with the electrical grid to “level off” supply and demand mismatches and to improve overall reliability and efficiency of the grid.1 Another scenario for VRFB use is buffering stochastic energy sources, such as solar or wind, which will improve the stability of electricity output from these renewable resources.1,4 A VRFB is essentially a regenerative fuel cell, with a flowing operation pattern similar to proton exchange membrane fuel cells.5,6 In a VRFB the energy is carried by vanadium redox couples V5+/V4+ and V2+/V3+ in electrolyte solutions. The energy is interconverted between electrical and electrochemical forms by the battery cell or stack, where the functional core is the membrane electrode assembly. The function of the membrane is to separate positive and negative electrolyte solutions and conduct ionic current, while vanadium redox reactions take place on the electrode surface in each half-cell. During battery operation, electrolyte solutions are constantly fed through the battery to support electrochemical reactions and to generate steady current output or recharge the electrolyte solution. In the VRFB cell, the electrolyte separator is a primary limiting factor in the battery's performance.3 As has been demonstrated, resistance from the separator is the most important source of the battery's internal resistance, impeding battery performance during high current density operation.3,7 Ideally, the electrolyte separator should have high conductivity to minimize battery efficiency losses caused by internal resistance and also high ion selectivity to suppress vanadium crossover to maintain battery efficiency and capacity. A commonly used separator for VRFB research is Nafion,8,9 a perfluorosulfonic acid copolymer cation exchange membrane from DuPont. Unfortunately, due to the high acidity and vanadium concentration in the electrolyte solution, Nafion's conductivity decreases as a result of the electrolyte diffusing into the membrane.7,10 Capacity loss can also be caused by the rapid vanadium transport across Nafion, which effectively chemically short circuits the cell.11 The high cost of Nafion is another issue hindering VRFB commercial competiveness, since a low cost electrical storage solution is the only path toward both grid and alternative energy storage commercial success.12 Hydrocarbon, aromatic cation exchange membranes are attracting attention from VRFB researchers because their performance is comparable to Nafion in electrochemical devices.13,14 Aromatic cation exchange membranes are generally developed from thermoplastics by sulfonation which results in high chemical/thermal stability, good mechanical properties and low cost.1517 Several hydrocarbon cation exchange membranes have been synthesized and tested in flow batteries; these include sulfonated poly(ether ether ketone) (SPEEK),16,18 sulfonated poly(phenylsulfone) (S-Radel),1921 sulfonated poly(thioether ketone) series (SPTK or SPTKK)22 and sulfonated Diels-Alder poly(phenylene) (SDAPP).23 Sulfonated Diels-Alder poly(phenylene) (SDAPP) was initially synthesized as a proton exchange membrane for PEM fuel cells.24 SDAPP membranes have been studied as polymer electrolytes for proton exchange membrane fuel cells via investigations of conductivity, permeability and water uptake properties.25 A preliminary investigation has also been reported on SDAPP as an electrolyte separator in VRFBs.23 SDAPP membranes can achieve very high ionic selectivity to provide comparable conductivity to Nafion, and also lower VO2+ permeability. Membranes with higher IEC had higher ionic conductivity, but lower durability in both long-term battery testing and V+5 solutions. We note in passing that that some membranes of this class are not completely stable over the long-term (longer that our typical experiment time!). However, there is an important as yet unmet need to define the physical chemistry of membranes in the context of the environment of a device. Thus, we need to understand membrane behavior for the widest possible range of material types. In this work, acid and water uptake were examined to determine its impact on the membrane's ionic transport properties relevant to VRFBs. As a reference, Nafion 117 was tested in parallel. The molecular formulas of SDAPP and Nafion are displayed in Figure 1. The sulfuric acid and water uptake properties of SDAPP were quantitatively measured after equilibration in sulfuric acid solutions with concentration ranges between 0 to 17.4 mol·kg−1. After equilibration, the membrane's conductivity was also measured to investigate the influence of the electrolyte-polymer equilibrium on the membrane's ion transport. Vanadium permeation in SDAPP was measured under different conditions (varying acid concentration or temperature) to study the influence of electrolyte conditions and membrane pore fluid composition on vanadium transport. Transmission electron microscopy work was carried out to study the morphology of SDAPP and ionic domain distribution and size. This work forms the foundation for more detailed studies of ion motion and other chemical details of the interacting membrane and solution.

Tang, Z.,


Lawton, J.,
Sun, C.,
et al,

Journal of the Electrochemical Society
Vol. 161, Issue 12
Pages A1860-A1868
2014Resolving Losses at the Negative Electrode in All-Vanadium Redox Flow Batteries Using Electrochemical Impedance Spectroscopy

Abstract: We present an in situ electrochemical technique for the quantitative measurement and resolution of the ohmic, charge transfer and diffusion overvoltages at the negative electrode of an all-vanadium redox flow battery (VRFB) using electrochemical impedance spectroscopy (EIS). The mathematics describing the complex impedance of the V+2/V+3 redox reaction is derived and matches the experimental data. The voltage losses contributed by each process have been resolved and quantified at various flow rates and electrode thicknesses as a function of current density during anodic and cathodic polarization. The diffusion overvoltage was affected strongly by flow rate while the charge transfer and ohmic losses were invariant. On the other hand, adopting a thicker electrode significantly changed both the charge transfer and diffusion losses due to increased surface area. Furthermore, the Tafel plot obtained from the impedance resolved charge transfer overvoltage yielded the geometric exchange current density, anodic and cathodic Tafel slopes (135 ± 5 and 121 ± 5 mV/decade respectively) and corresponding transfer coefficients α = 0.45 ± 0.02 and β = 0.50 ± 0.02 in an operating cell.

Sun, C.,


Delnick, F.,
Aaron, D.,
et al.,

Journal of the Electrochemical Society
Vol. 161, Issue 6
Pages A981-A988
2014Hydrogen Evolution at the Negative Electrode of the All-Vanadium Redox Flow Batteries

Abstract: This work demonstrates a quantitative method to determine the hydrogen evolution rate occurring at the negative carbon electrode of the all vanadium redox flow battery (VRFB). Two carbon papers examined by buoyancy measurements yield distinct hydrogen formation rates (0.170 and 0.005 μmol min−1 g−1). The carbon papers have been characterized using electron microscopy, nitrogen gas adsorption, capacitance measurement by electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). We find that the specific electrochemical surface area (ECSA) of the carbon material has a strong influence on the hydrogen generation rate. This is discussed in light of the use of high surface area material to obtain high reaction rates in the VRFB.

Sun, C.,


Delnick, F.,
Baggetto, L.,
Veith, G.,
Zawodzinski, T.,

J. Power Sources,
248, 560-564
2014Community Energy Storage with Secondary Use EV/PHEV Batteries

Abstract: This study presents the testing of a community energy storage system composed of repurposed used electric or plug-in hybrid electric vehicle (EV/PHEV) battery packs. The expectation is that the vehicular batteries will be replaced with a fresh battery pack by the original equipment manufacturers (OEMs) once their performance (storage capacity and peak power capability) decrease to its 80% of the initial performance. Community energy storage (CES) systems can be a feasible application of these after vehicle batteries due to economic and environmental reasons. These batteries, if their power electronic interfaces are controlled properly, can perform many grid support applications or provide grid ancillary services as will be detailed in this study. The testing configuration along with results of testing will be discussed.

Starke, M.,


Irminger, P.,
Ollis, B.,
Andrews, G.,
Onar, O.,
Karlson, P.,
Valencia, P.,
Massin, S.,
Goodson, A.,
Rosenfeld, P.,

TechConnect
2014Factors Enabling High Mobility of Protons and Water in Perfluorosulfonate Membranes Under Low Hydration Conditions

Abstract: This work describes new features describing the mechanism of proton and water transport in ion conducting membranes used in Proton Exchange Membrane Fuel Cells. A combination of NMR diffusion measurements and AC conductivity measurements as a function of water content reveal enhanced mobility of protons and water in low equivalent weight 3M perfluorosulfonic acid membranes at low water content. It is proposed that this is a result of the close proximity of adjacent acid-bearing sidechains in the lower equivalent weight ionomers. This proximity allows more facile exchange of species from group to group.

Maalouf, M.,

Sun, C., Pyle, B., Emery, M., Haugen, G., Hamrock, S., Zawodzinski Jr., T.,

International Journal of Hydrogen Energy, vol. 39, pages 2795-2800
2014Electrochemistry and Morphology Studies of Aluminum Plating/Stripping in a Chloroaluminate Ionic Liquid on Porous Carbon Materials

Abstract: Aluminum electrodeposition and electrodissolution in mixtures of AlCl3 and 1-ethyl-3-methylimidazolium chloride on carbon paper electrodes consisting of graphitized fibers were investigated. Porous electrodes, such as carbon paper electrodes, often offer possible advantages such as higher nominal current densities and less dendrite formation, over solid planar electrodes. Cyclic voltammetry, chronoamperometry and pulse current deposition were used to investigate Al plating and stripping on this porous structure. The Al morphology on the carbon paper was probed using SEM. Composition and temperature affect the Al electrode performance through their influence on the diffusivity of ions. Therefore, control of the diffusion process during Al plating/stripping is essential.

Zhang, M.,

Watson, J., Counce, R., Trulove, P., Zawodzinski Jr., T.,

J. Electrochem. Soc., vol. 161, pages D163-D167
2013-07-03In Situ Formation of Micron-Scale Li-Metal Anodes with High Cyclability

Abstract: Scanning probe microscopy methods have been used to electrodeposit and cycle micron-scale Li anodes deposited electrochemically under nanofabricated Au current collectors. An average Li volume of 5 x 108 nm3 was deposited and cycled with 100% coulombic efficiency for ∼160 cycles. Integrated charge/discharge values agree with before/after topography, as well as in situ dilatometry, suggesting this is a reliable method to study solid-state electrochemical processes. In this work we illustrate the possibility to deposit highly cyclable nanometer thick Li electrodes by mature SPM and nanofab techniques which can pave the way for inexpensive nanoscale battery arrays.

Arruda, T.,


Lawton, J.,
Kumar, A.,
Unocic, R.,
Kravchenco, I.,
Zawodzinski, T.,
Jesse, S.,
Kalinin,S.,
Balke, N.,

Electrochemistry Letters, vol. 3, pages A4-A7
2013Probing Electrode Losses in All-Vanadium Redox Flow Batteries with Impedance Spectroscopy

Abstract: We report on single-electrode electrochemical impedance spectroscopy studies of an all-vanadium redox battery using a dynamic hydrogen reference electrode. The negative electrode, comprising the V2+/V3+ couple, contributes approximately 80% of the total cell overpotential during discharge. The impedance spectra measured at the negative electrode exhibit high-frequency, semicircular arcs which correspond to the double layer capacitance in parallel with a faradaic resistance. The faradaic resistance decreases in magnitude with increasing polarization. Integration of the current-dependent faradaic resistance quantifies the fraction of the overvoltage that is attributed to the kinetic limitations of the charge transfer reaction.

Sun, C.,


Delnick, F.,
Aaron, D.,
Papandrew, A.,
Mench, M.,
Zawodzinski, Jr., T.,

ECS Electrochemistry Letters,
2, A43-A45
2013-04-08Nanometer-scale Mapping of Irreversible Electrochemical Nucleation Processes on Solid Li-ion Electrolytes

Abstract: Electrochemical processes associated with changes in structure, connectivity or composition typically proceed via new phase nucleation with subsequent growth of nuclei. Understanding and controlling reactions requires the elucidation and control of nucleation mechanisms. However, factors controlling nucleation kinetics, including the interplay between local mechanical conditions, microstructure and local ionic profile remain inaccessible. Furthermore, the tendency of current probing techniques to interfere with the original microstructure prevents a systematic evaluation of the correlation between the microstructure and local electrochemical reactivity. In this work, the spatial variability of irreversible nucleation processes of Li on a Li-ion conductive glass-ceramics surface is studied with ~30 nm resolution. An increased nucleation rate at the boundaries between the crystalline AlPO4 phase and amorphous matrix is observed and attributed to Li segregation. This study opens a pathway for probing mechanisms at the level of single structural defects and elucidation of electrochemical activities in nanoscale volumes.

Kumar, A.,


Arruda, T.,
Tselev, A.,
Ivanov, I.,
Lawton, J.,
Zawodzinski, T.,
Butyaev, O.,
Zayats, S.,
Jesse, S.,
Kalinin, S.,

Scientific Reports, vol. 3, page 1621
2013-02-01Qualitative Behavior of Vanadium Ions in Nafion Membranes Using Electron Spin Resonance

Abstract: Nafion 117 membranes for applications in Vanadium Redox Flow Batteries (VRFBs) are characterized using electron paramagnetic resonance (EPR). EPR can directly detect the V(II) and VO2+ ions, but in the battery environment the membrane is directly exposed to V(II–V). The use of nitroxide spin probes such as 2,2,6,6-tetramethyl-4-piperidone N-oxide (TEMPONE) allows observations of changes in the fluid channels of the membrane as it is exposed to all possible ionic species. These observations can give a clearer picture of the effect of the ions on the ion exchange membrane and serve as a basis of comparison in developing membranes with lower vanadium crossover.

Lawton, J.,


Aaron, D.,
Tang, Z.,
Zawodzinski, T.,

Journal of Membrane Science, vol. 428, pages 38-45
2013-06-28Composition Dependence of the Pore Structure and Water Transport of Composite Catalyst Layers for Polymer Electrolyte Fuel Cells

Abstract: The material distribution, porous features, and ionomer behavior in the catalyst layer (20wt% platinum on Vulcan carbon impregnated with Nafion) of polymer electrolyte fuel cells were investigated by microscopy, nitrogen adsorption, and water uptake as a function of ionomer loading or relative humidity. As revealed by microscopy, thin ionomer coverage along the carbon surface is observed when ionomer loading is low, while for higher loading, the pore spaces among the carbon agglomerates were mostly flooded. Even at a low ionomer to carbon ratio, the micro-porosity is closed off and the BET surface area decreases by more than 50%. At 100% relative humidity, the water content in the ionomer within the I/C = 0.5 catalyst layer reaches only 4 water molecules per sulfonate, presumably due to the inhibition of swelling by the carbon filler. The resulting structures and properties in the catalyst layer induce a tortuous pathway for water or proton transport in the ionomer phase, particularly at low water content. A distinct feature is observed in the catalyst layers using differential scanning calorimetry (DSC). DSC measurements on the sub-components lead us to conclude that the feature reflects interactions between the ionomer and the carbon or the Pt particles.

Sun, C.,


More, K.,
Veith, G.,
Zawodzinski, T.,

J. Electrochem. Soc., vol. 60, pages F1000-F1005
2013Composition and Conductivity of Membranes Equilibrated with Solutions of Sulfuric Acid and Vanadyl Sulfate

Abstract: The sulfuric acid, vanadyl (VO2+) and water equilibrium in Nafion membranes contacted by solutions containing these species is described. Of particular interest is the influence of composition on ionic transport behavior inmembrane separators for an all-vanadium redox flow battery (VRFB). Ex-situ membrane conductivity measurements were conducted on Nafion 117 membranes equilibrated in electrolyte solutions of varying sulfuric acid and vanadyl ion concentrations. Electrolyte species imbibed in the membrane were analyzed by an experimental protocol including titration, ICP-OES and weight analysis. Sulfuric acid in the membrane can increase proton concentration but reduce proton mobility by reducing water content. In a mixed vanadyl/proton form Nafion, vanadyl has a mobility of 6.28 x 10−5 cm2 ·V−1 · s−1, much lower than proton mobility of 8.79 x 10−4 cm2 ·V−1 · s−1 in H+-form Nafion. The presence of vanadyl in Nafion can also decrease the proton mobility: uH+ = (8.79 − 8.04 x xVO2+) x 10−4cm2V−1s−1. With equilibration in a practical electrolyte containing 5 mol · dm−3 total sulfate, Nafion’s conductivity is decreased due to uptake of vanadyl ions.

Tang, Z.,

Svoboda, R., Lawton, J., Aaron, D., Papandrew, A., Zawodzinski, T.,

J. Electrochem. Soc., vol. 160, pages F1040-F1047
2013-05-24Intrinsic Thermodynamic and Kinetic Properties of Sb Electrodes for Li-ion and Na-ion Batteries: Experiment and Theory

Abstract: A detailed comparative study between the electrochemical lithiation and sodiation of pure antimony (Sb), relating changes in structural, thermodynamic, kinetic and electrochemical properties has been carried out. For this purpose, a wide range of measurements using electrochemical (galvanostatic cycling, GITT, PITT), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) methods as well as density functional theory (DFT) based investigations have been undertaken. Assessment of the thermodynamics reveals that the reaction proceeds identically during the first and second cycles for Li whereas it differs between the first and subsequent cycles for Na as the reaction with Na proceeds through a different pathway associated with the formation of amorphous NaxSb phases. For the first time we rationalize the amorphization of NaxSb phases by the long ranged strain propagation due to Na-vacancy compared to Li–Sb. At full discharge, our XRD results show for the first time that a minor fraction of hexagonal Li3Sb forms concomitantly with cubic Li3Sb. The XRD results confirm that Sb crystallizes into hexagonal Na3Sb at full sodiation. The kinetics of the reaction is assessed by rate performance tests which highlight that both Li and Na can diffuse rapidly throughout micron thick films at room temperature. However, it is found that the (de)insertion of Li provides lower overpotentials and larger storage capacities compared to Na. The difference in rate performance is complemented by diffusion coefficient determinations near the 0 V region where both materials are crystallized into M3Sb (M = Li, Na). Interestingly, calculations show that the energy barrier for near-neighbor vacancy migration, predominant in these close-packed phases, is about twice for Na than for Li. Our analysis tries to relate the lower intrinsic diffusivity of Na compared to Li with the long-range strain propagation induced by the former, thereby leading to an intrinsic origin of differences in rates, mechanical properties and amorphization. Finally, the surface chemistry of Sb electrodes cycled in NaClO4 dissolved in pure PC with(out) the addition of 5 wt% EC or FEC shows presence of ethers and NaF for the EC- and FEC-based electrolytes, respectively, and SEI films rich in Na-based carbonates.

Baggetto, L.,


Ganesh, P.,
Sun, C.,
Meisner, R.,
Zawodzinski, T.,
Veith, G.,

Journal of Materials Chemistry A, vol. 1, pages 7985-7994
2013-03-22In Situ Potential Distribution Measurement in an All-Vanadium Flow Battery

Abstract: An experimental method for measurement of local redox potential within multilayer electrodes was developed and applied to all-vanadium redox flow batteries (VRFBs). Through-plane measurement at the positive side reveals several important phenomena including potential distribution, concentration distribution of active species and the predominant reaction location within the porous carbon electrodes.

Liu, Q.,


Turhan, A.,
Zawodzinski, T.,
Mench, M.,

Chemical Communications, vol. 49, pages 6292-6294
2013In Situ Kinetics Studies in All-Vanadium Redox Flow Batteries

Abstract: We report results of polarization measurements resolved for the negative and positive electrodes of vanadium redox batteries (VRBs) using a dynamic hydrogen electrode in an operating battery cell. Electrochemical experiments with symmetric electrolyte feeds were also performed. Greater kinetic polarization is observed at the negative (V3/2+) electrode compared to the positive electrode (V5/4+), in contrast with previously reported ex situ measurements. For the positive electrode, the polarization in the low-current regime was modest and was not kinetically controlled. The relative rates of reaction are a surprise since it might be expected that the V3/2+ redox reaction is a simple outer-sphere electron transfer.

Aaron, D.,

Sun, C., Bright, M., Papandrew, A., Mench, M., Zawodzinski, T.,

ECS Electrochemistry Letters, vol. 2, pages A29-A31
2013Concentration Dependence of VO2+ Crossover of Nafion for Vanadium Redox Flow Batteries

Abstract: The VO2+ crossover, or permeability, through Nafion in a vanadium redox flow battery (VRFB) was monitored as a function of sulfuric acid concentration and VO2+ concentration. A vanadium rich solution was flowed on one side of the membrane through a flow field while symmetrically on the other side a blank or vanadium deficit solution was flowed. The blank solution was flowed through an electron paramagnetic resonance (EPR) cavity and the VO2+ concentration was determined from the intensity of the EPR signal. Concentration values were fit using a solution of Fick’s law that allows for the effect of concentration change on the vanadium rich side. The fits resulted in permeability values of VO2+ ions across the membrane. Viscosity measurements of many VO2+ and H2SO4 solutions were made at 30–60&186;C. These viscosity values were then used to determine the effect of the viscosity of the flowing solution on the permeability of the ion.

Lawton, J.,

Jones, A., Zawodzinski, T.,

J. Electrochem. Soc., vol. 160, pages A697-A702
2012-06Modeling, Controls, and Applications of Community Energy Storage Systems with Used EV/PHEV Batteries

Abstract: This study presents the modeling and controls of a community energy storage system composed of repurposed used electric or plug-in hybrid electric vehicle (EV/PHEV) battery packs. The expectation is that the vehicular batteries will be replaced with a fresh battery pack by the original equipment manufacturers (OEMs) once their performance (storage capacity and peak power capability) decrease to its 80% of the initial performance. Community energy storage (CES) systems can be a feasible application of these after vehicle batteries due to economic and environmental reasons. These batteries, if their power electronic interfaces are controlled properly, can perform many grid support applications or provide grid ancillary services as will be detailed in this study.

Onar, O.,


Starke, M.,
Andrews, G.,
Jackson, R.,

IEEE Transportation Electrification Conference and Expo
2012-07-20High Performance Vanadium Redox Flow Batteries with Optimized Electrode Configuration and Membrane Selection

Abstract: The performance of a vanadium flow battery with no-gap architecture was significantly improved via several techniques. Specifically, gains arising from variation of the overall electrode thickness, membrane thickness, and electrode thermal treatment were studied. There is a trade-off between apparent kinetic losses, mass transfer losses, and ionic resistance as the electrode thickness is varied at the anode and cathode. Oxidative thermal pretreatment of the carbon paper electrode increased the peak power density by 16%. Results of the pretreatment in air showed greater improvement in peak power density compared to that obtained with pretreatment in an argon environment. The highest peak power density in a VRB yet published to the author's knowledge was achieved at a value of 767 mW cm−2 with optimized membrane and electrode engineering.

Liu, Q.,


Grim, G.,
Papandrew, A.,
Turhan, A.,
Zawodzinski, T.,
Mench, M.,

J. Electrochem. Soc, vol. 159, pages A1246-A1252
2012-07-20Capital Cost Sensitivity Analysis of an All-Vanadium Redox-Flow Battery

Abstract: Interest in the development of redox-flow batteries (RFBs) for large-scale grid storage is growing, and considerable investments have been made into the research and development of RFBs over the past few decades. Unfortunately, practical implementation has been hampered by various cost and performance issues typical of an immature state of development. One critical factor for the competitiveness of this technology is the installed cost. In this work, we incorporate recent developments in all-vanadium RFBs research and present an analysis of the associated cost factors. The major components of a RFB that affect installed cost are identified and used as variables to create a capital cost function. The function is then used to calculate the rate of change of the capital costs with respect to the major components. The capital costs are also calculated for a range of component values and plotted. Key findings include a high sensitivity of system capital cost to purity of vanadium and substantial fractions of the cost associated with perflurorosulfonic acid membranes currently used for proton transport.

Moore, M.,


Watson, J.,
Zawodzinski, T.,
Zhang, M.,
Counce, R.,

J. Electrochem. Soc, vol. 159, pages A1183-A1188
2012-05-15Dramatic Performance Gains in Vanadium Redox Flow Batteries through Modified Cell Architecture

Abstract: We demonstrate a vanadium redox flow battery with a peak power density of 557 mW cm−2 at a state of charge of 60%. This power density, the highest reported to date, was obtained with a zero-gap flow field cell architecture and non-wetproofed carbon paper electrodes. The electrodes were comprised of stacked sheets of carbon paper and optimized through systematic variation of the total electrode thickness. We anticipate significant reductions in the ultimate system cost of redox flow battery systems based on this design.

Aaron, D.,


Liu, Q.,
Tang, Z.,
Grim, G.,
Papandrew, A.,
Turhan, A.,
Zawodzinski, T.,
Mench, M.,

J. Power Sources, vol. 206, pages 450-453
2011-08-18Polarization Curve Analysis of All-Vanadium Redox Flow Batteries

Abstract:  We outline the analysis of performance of redox flow batteries (RFBs) using polarization curves. This method allows the researcher immediate access to sources of performance losses in flow batteries operating at steady state. We provide guidance on 'best practices' for use of this tool, illustrated using examples from single cells operating as vanadium redox batteries.

Aaron, D.,


Tang, Z.,
Papandrew, A.,
Zawodzinski, T.,

Journal Of Applied Electrochemistry, vol. 41, pages 1175-1182
--Community Energy Storage Utilizing Secondary Use EV/PHEV Batteries

Abstract: An important aspect to wide-scale energy storage acceptance for the utility industry is verification of the performance and life of energy storage systems. In support of this objective, a testing platform has been developed at Oak Ridge National Laboratory (ORNL) to test energy storage units in real-world applications and analyze key performance metrics. Various hardware and software systems have been interlinked to represent actual grid conditions, while maintaining a high level of safety and robust operation. Currently, ORNL is performing grid application testing on a stationary energy storage system consisting of secondary-use electric vehicle batteries provided by General Motors.

Starke, M.,

Irminger, P., Ollis, B., Andrews, G., Karlson, P., Thambiappah, S., Valencia, P., Labaza, C., Massin, S., Parn, K.,

--
2015Sodium-Ion Conducting Membranes for Non-Aqueous Redox Flow Batteries

Abstract: Recently we proposed a new concept for high energy density redox flow batteries that utilize two highly soluble polyaromatic hydrocarbons to mediate reversible redox reactions on the surface of high capacity solid anode materials located in flow reactor reservoirs. Among other things, the success of this technology depends on the development of a membrane separator that has high Na+ or Li+ ion conductivity with minimal cross-over. In addition the membrane should be chemically stable with respect to highly reactive anion radicals such as biphenyl·-. In an attempt towards achieving such goals, we first improved the ionic conductivity of poly(ethylene oxide) (PEO) membranes by using tetraethylene glycol dimethyl ether (TEGDME) as a plasticizer with sodium triflate (NaTFS) and sodium bis(trifluoromethanesulnonyl)imide (NaTFSI) as salts. Our results show at least 3 orders of magnitude higher conductivity compared to NaTFS-PEO films. In general films with more plasticizer showed less trans-granular impedance at low temperature, and higher amorphous conduction at higher temperatures. In this study we report Raman and FT-IR spectroscopy to characterize the changes in ion coordination when the salt is dissolved in the plasticizer and PEO blend. Efforts are underway to correlate changes in conductivity with results from Raman and infrared spectroscopy.

Nanda, J.,

Ruther, R., Delnick, F.,

--