Custom-form factor batteries fabricated in non-conventional shapes can maximize the overall energy density of the systems they power, particularly when used in conjunction with energy dense materials (e.g., Li metal anodes and conversion cathodes). Additive manufacturing (AM), and specifically material extrusion (ME), have been shown as effective methods for producing custom-form cell components, particularly electrodes. However, the AM of several promising energy dense materials (conversion electrodes such as iron trifluoride) have yet to be demonstrated or optimized. Furthermore, the integration of multiple AM produced cell components, such as electrodes and separators, along with a custom package remains largely unexplored. In this work, iron trifluoride (FeF3) and ionogel (IG) separators are conformally printed using ME onto non-planar surfaces to enable the fabrication of custom-form Li-FeF3 batteries. To demonstrate printing on non-planar surfaces, cathodes and separators were deposited onto cylindrical rods using a 5-axis ME printer. ME printed FeF3 was shown to have performance commensurate with FeF3 cast using conventional means, both in coin cell and cylindrical rod formats, with capacities exceeding 700 mAh/g on the first cycle and ranging between 600 and 400 mAh/g over the next 50 cycles. Additionally, a ME process for printing polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) based IGs directly onto FeF3 is developed and enabled using an electrolyte exchange process. In coin cells, this process is shown to produce cells with similar capacity to cells built with Celgard separators out to 50 cycles, with the exception that cycling instabilities are observed during cycles 8–20. When using printed and exchanged IGs in a custom cylindrical cell package, 6 stable high-capacity cycles are achieved. Overall, this work demonstrates approaches for producing high-energy-density Li-FeF3 cells in coin and cylindrical rod formats, which are translatable to customized, arbitrary geometries compatible with ME printing and electrolyte exchange.
Glycoboehmite (GB) materials are synthesized by a solvothermal reaction to form layered aluminum oxyhydroxide (boehmite) modified by intercalated butanediol molecules. These hybrid materials offer a platform to design materials with potentially novel sorption, wetting, and catalytic properties. Several synthetic methods have been used, resulting in different structural and spectroscopic properties, but atomistic detail is needed to determine the interlayer structure to explore the synthetic control of GB materials. Here, we use classical molecular dynamics (MD) simulations to compare the structural properties of GB interlayers containing chemisorbed butanediol molecules as a function of diol loading. Accompanying quantum (density functional theory, DFT) static calculations and MD simulations are used to validate the classical model and compute the infrared spectra of various models. Classical MD results reveal the existence of two unique interlayer environments at higher butanediol loading, corresponding to smaller (cross-linked) and expanded interlayers. DFT-computed infrared spectra reveal the sensitivity of the aluminol O-H stretch frequencies to the interlayer environment, consistent with the spectrum of the synthesized material. Insight from these simulations will aid in the characterization of the newly synthesized GB materials.
This research effort examined the application of Nafion polymers in alcohol solvents as an anti-ice surface coating, as a mixture with hydrophilic polymers and freezing point depressant salt systems. Co-soluble systems of Nafion, polymer and salt were applied using dip coating methods to create smooth films for frost observation over a Peltier plate thermal system in ambient laboratory conditions. Cryo-DSC was applied to examine freezing events of the Nafion-surfactant mixtures, but the sensitivity of the measurement was insufficient to determine frost behavior. Collaborations with the Fog Chamber at Sandia-Albuquerque, and in environmental SAXS measurements with CINT-LANL were requested but were not able to be performed under the research duration. Since experimental characterization of these factors is difficult to achieve directly, computational modeling was used to guide the scientific basis for property improvement. Computational modeling was performed to improve understanding of the dynamic association between ionomer side groups and added molecules and deicing salts. The polyacrylic acid in water system was identified at the start of the project as a relevant system for exploring the effect of varying counterions on the properties of fully deprotonated polyacrylic acid (PAA) in the presence of water. Simulations were modeled with four different counterions, two monovalent counterions (K+ and Na+) and two divalent counterions (Ca2+ and Mg2+). The wt% of PAA in these systems was varied from ~10 to 80 wt% PAA for temperatures from 250K to 400K. In the second set of simulations, the interpenetration of water into a dry PAA film was studied for Na+ or Ca2+ counterions for temperatures between 300K and 400K. The result of this project is a sprayable Nafion film composite which resists ice nucleation at -20 °C for periods of greater than three hours. It is composed of Nafion polymer, hydrophilic polyethylene oxide polymer and CaCl2 anti-ice crosslinker. Durability and field performance properties remain to be determined.
Novel materials based on the aluminum oxyhydroxide boehmite phase were prepared using a glycothermal reaction in 1,4-butanediol. Under the synthesis conditions, the atomic structure of the boehmite phase is altered by the glycol solvent in place of the interlayer hydroxyl groups, creating glycoboehmite. The structure of glycoboehmite was examined in detail to determine that glycol molecules are intercalated in a bilayer structure, which would suggest that there is twice the expansion identified previously in the literature. This precursor phase enables synthesis of two new phases that incorporate either polyvinylpyrrolidone or hydroxylpropyl cellulose nonionic polymers. These new materials exhibit changes in morphology, thermal properties, and surface chemistry. All the intercalated phases were investigated using PXRD, HRSTEM, SEM, FT-IR, TGA/DSC, zeta potential titrations, and specific surface area measurement. These intercalation polymers are non-ionic and interact through wetting interactions and hydrogen bonding, rather than by chemisorption or chelation with the aluminum ions in the structure.
This report describes research and development (R&D) activities conducted during fiscal year 2021 (FY21) specifically related to the Engineered Barrier System (EBS) R&D Work Package in the Spent Fuel and Waste Science and Technology (SFWST) Campaign supported by the United States (U.S.) Department of Energy (DOE). The R&D activities focus on understanding EBS component evolution and interactions within the EBS, as well as interactions between the host media and the EBS. A primary goal is to advance the development of process models that can be implemented directly within the Generic Disposal System Analysis (GDSA) platform or that can contribute to the safety case in some manner such as building confidence, providing further insight into the processes being modeled, establishing better constraints on barrier performance, etc.
Stereolithography (SL) is a process that uses photosensitive polymer solutions to create 3D parts in a layer by layer approach. Sandia National Labs is interested in using SL for the printing of ceramic loaded resins, namely alumina, that we are formulating here at the labs. One of the most important aspects for SL printing of ceramics is the properties of the slurry itself. The work presented here will focus on the use of a novel commercially available low viscosity resin provided by Colorado Photopolymer Solutions, CPS 2030, and a Hypermer KD1 dispersant from Croda. Two types of a commercially available alumina powder, Almatis A16 SG and Almatis A15 SG, are compared to determine the effects that the size and the distribution of the powder have on the loading of the solution using rheology. The choice of a low viscosity resin allows for a high particle loading, which is necessary for the printing of high density parts using a commercial SL printer. The Krieger-Dougherty equation was used to evaluate the maximum particle loading for the system. This study found that a bimodal distribution of micron sized powder (A15 SG) reduced the shear thickening effects caused by hydroclusters, and allows for the highest alumina powder loading. A final sintered density of 90% of the theoretical density of alumina was achieved based on the optimized formulation and printing conditions.
The impact on the morphology nanoceramic materials generated from group 4 metal alkoxides ([M(OR)4]) and the same precursors modified by 6,6′-(((2-hydroxyethyl)azanediyl)bis(methylene))bis(2,4-di-tert-butylphenol) (referred to as H3-AM-DBP2 (1)) was explored. The products isolated from the 1:1 stoichiometric reaction of a series of [M(OR)4] where M = Ti, Zr, or Hf; OR = OCH(CH3)2(OPri); OC(CH3)3(OBut); OCH2C(CH3)3(ONep) with H3-AM-DBP2 proved, by single crystal X-ray diffraction, to be [(ONep)Ti(k4(O,O′,O′′,N)-AM-DBP2)] (2), [(OR)M(μ(O)-k3(O′,O′′,N)-AM-DBP2)]2 [M = Zr: OR = OPri, 3·tol; OBut, 4·tol; ONep, 5·tol; M = Hf: OR = OBut, 6·tol; ONep, 7·tol]. The product from each system led to a tetradentate AM-DBP2 ligand and retention of a parent alkoxide ligand. For the monomeric Ti derivative (2), the metal was solved in a trigonal bipyramidal geometry, whereas for the Zr (3-5) and Hf (6, 7) derivatives a symmetric dinuclear complex was formed where the ethoxide moiety of the AM-DBP2 ligand bridges to the other metal center, generating an octahedral geometry. High quality density functional theory level gas-phase electronic structure calculations on compounds 2-7 using Gaussian 09 were used for meaningful time dependent density functional theory calculations in the interpretation of the UV-vis absorbance spectral data on 2-7. Nanoparticles generated from the solvothermal treatment of the ONep/AM-DBP2 modified compounds (2, 5, 7) in comparison to their parent [M(ONep)4] were larger and had improved regularity and dispersion of the final ceramic nanomaterials.