On the molecular scale, it resembles a traditional black-and-white soccer ball, but that molecule holds the promise of being a big player in the nation’s energy storage efforts.
CHEMICAL TECHNOLOGIST Harry Pratt (2546) synthesizes a copper-based ionic liquid. (Photo by Randy Montoya)
Sandia researchers have discovered a new family of liquid salt electrolytes, which could lead to batteries packed with three times the energy density of other available storage technologies. The findings, featured on the Nov. 21 cover of Dalton Transactions, offer a possible new solution to the vexing challenge of incorporating intermittent renewable energy sources into the nation’s electric grid.
Energy demand is at an all-time high; as of Oct. 31, the UN Population Fund estimates that there are more than 7 billion of us roaming the planet, and exploring every energy option has become the only option to meet the energy demands of all these people. Renewable energy sources are a likely part of the solution, but incorporating them into the current electrical grid on a large scale is problematic. The world’s grids were built to accommodate steady power sources and aren’t equipped to deal with the peaks and valleys produced by intermittent power sources.
A long-term, high-capacity option
Energy storage technologies are one way to even out the flow of electricity from intermittent renewable sources of energy. Sandia is researching new storage technologies and materials that will help in the design of a more flexible and reliable electric grid with higher storage capacity. For the past 20 years, lithium-ion batteries have been at the forefront of energy storage research. The compact, lightweight, and affordable design is ideal for cell phones and laptop computers, but there’s a nagging problem. No matter how new your cell phone is, during every charge and discharge, lithium physically moves from the cathode to the anode and back again. All this motion degrades the battery, and over time, it will just give out.
Such an option might be adequate for electronics that come and go, but the nation’s electric grid needs a long-term, high-capacity option.
Sandian Travis Anderson (2546), an inorganic chemist with nine years of experience, is leading a team that’s developing the next generation of flow batteries. A flow battery pumps a solution of charged metals dissolved in an electrolyte from an external tank through an electrochemical cell to convert chemical energy into electricity. Flow batteries are rapidly charged and discharged by changing the charge state of the electrolyte, and the electroactive material can be easily re-used many times.
“The system is simple, it performs very well, lasts a long time, and has a high cycle efficiency. In a lab, it can do well over 14,000 cycles, which is equivalent to about 20-plus years. That’s unheard of in a lithium-ion battery,” says Travis. “But these batteries are huge — about the size of a building — so they’re expensive. The goal is to make them smaller and cheaper, and we do that by increasing the energy density.”
Flow batteries are not easy to find — only one has been built in the US — but they are more common in Japan and Australia, where the first patented flow battery originated. Of the existing flow batteries, the highest performers use vanadium, which is moderately toxic and fluctuates in price. Furthermore, temperature impacts the performance of aqueous flow batteries. Finally, water limits how much material can be dissolved, which ultimately limits how much energy can be stored.
Non-aqueous flow battery research is largely unchartered territory, and Sandia is leading the way.
“We’re not trying to reinvent the wheel. We want a liquid that flows from storage tank to cell, just like vanadium,” Travis says. “But we’re trying to generate a new fuel.”
Tripling energy density
Travis pulled together a multidisciplinary team of experts from around the Labs to find that fuel, including electrochemist David Ingersoll (2546), organic chemist Chad Staiger (6124), and chemical technologists Harry Pratt and Jonathan Leonard (both 2546). What they’ve built is a new family of electrochemically reversible, metal-based ionic liquids (MetILs), and it’s generating a lot of attention from the energy storage community.
“So instead of dissolving the salt into a solvent, our salt is a solvent,” Travis says. “We’re able to get a much higher concentration of the active metal because we’re not limited by saturation. It’s actually in the formula. So we can triple our energy density just by the nature of the material we have.”
The ionic liquids the team prepared use readily available, inexpensive, nontoxic materials that can be found in the US, such as iron, copper, and manganese.
A common problem when mixing positively and negatively charged species is that these species will want to start aggregating together, eventually causing the solution to turn gummy, crash out, and clog the battery components such as the membrane and electrode surfaces.
The team addressed that challenge by developing asymmetric cations, or positively charged ions, that resemble a soccer ball. In this analogy, the black pentagons represent negatively charged areas and the white hexagons represent positively charged regions. Such an arrangement keeps the melting point low enough to prevent the ionic liquid from bonding to itself and becoming a solid, while the partial charge still allows electrons to flow freely through the cell to generate a current.
Exceeding the ferrocene standard
Another desirable property is high electrochemical efficiency, or reversibility of the charge.
“The ease at which you can change the charge state of MetILs is by far better than anything that’s ever been published,” says Travis. The gold standard for determining reversibility is to measure it against ferrocene. If the compound has better reversibility, it’s considered a top performer.
“We’ve prepared nearly 200 combinations of cations, anions, and ligands, and of those, there are five that exceed the ferrocene standard,” Chad says.
The family of compounds the team discovered with reasonably desirable properties is growing; last year, there were 11, this year, there are more than 30.
“There are so many parameters we can try, and you hit more bad ones than you can hit good ones, so when you find one that’s better than ferrocene, the data get very exciting,” Harry says. “This is new research. We aren’t following on anyone else’s coattails.”
The current research will apply to new flow battery cathode materials; the next step is to find similar materials for flow battery anodes.
The team is in its last year of a Sandia Laboratory Directed Research and Development project, but has also received funding from the DOE’s Office of Electricity Deliverability and Energy Reliability. Imre Gyuk, an energy storage systems program manager for that office, has been a champion of Sandia’s efforts and provided the necessary funding.
“There are three things you’re juggling at the same time, and they aren’t always related: viscosity, electrical conductivity, and the fundamental electrochemistry efficiency,” Travis says. “The excitement
of having all three things go right at the same time, it’s like finding the treasure, but without the map. We’re creating that map, and we’re very excited by the possibilities." - Stephanie Hobby
By Iris Aboytes
The fall issue of Hispanic Engineer & Information Technology highlights Bernadette Hernandez-Sanchez (1815) as one of the Forty Under Forty rising stars in science, technology, engineering, and mathematics, or STEM.
BERNADETTE HERNANDEZ-SANCHEZ, at home in her lab, is one of Hispanic Engineer and Information/Technology magazine’s “Forty Under Forty” rising stars. (Photo by Randy Montoya)
The publication is devoted to promoting engineering, information technology, science, and technology to Hispanic Americans.
Bernadette works on luminescent materials for radiation detectors along with biofouling- and corrosion-proof coatings for devices that harness the ocean’s kinetic and thermal energy. In the seven years Bernadette has been at Sandia, she has been published in 23 journals and has three patent applications.
Bernadette’s journey in becoming a scientist began at Sandia. As a high school intern, she worked under Timothy Boyle (1815).
“I just had fun,” says Bernadette. “I liked chemistry because you got to work with your hands. I liked mixing solutions, seeing colors change, and growing crystals.”
This experience fueled her desire to become a chemist. She attended New Mexico Institute of Mining and Technology for her undergraduate degree and Colorado State University, where she earned her PhD in chemistry in 2004.
Bernadette’s love of the Labs and strong work ethic shaped her early career.
“From an early age my parents taught me about work ethics,” says Bernadette. “That was later reinforced by my mentors and teachers. I attribute my work ethic, along with my passion for working in the lab, as the catalyst for my success. The lab is where I still feel most comfortable because I enjoy learning about how things work.”
Outside the lab, Bernadette’s love is educational outreach. She leads
Sandia’s MANOS ChemisTRY program, is an Explora Portal to the Public (PoP) scientist, and also mentors students (K–12 to graduate students) in her lab. As a postdoc, she helped design the CSI Dognapping Workshop, which she helps coordinate. The two-hour workshop, held at Sandia every year since 2006, introduces elementary school children to science, engineering, and nanotechnology.
“By engaging them as ‘junior scientists’ and guiding them to pore over evidence at various stations, students help solve the mystery of a missing dog,” says Bernadette.
Giving back to Sandia
She is dedicated to encouraging young scientists-in-training to follow their dreams and to giving back to Sandia through her outreach.
“I am grateful to Sandia and my scientific family in Center 1800 for supporting student programs,” says Bernadette. “They made my and other new staff members’ early research experiences memorable. It encouraged us to return to Sandia and begin our professional careers.
“I felt excited and honored to hear I was selected for my early career contributions to science. It made me reflect on my own personal struggles, my experimental triumphs and failures, and what I have learned through those processes. I know this sounds silly, but this reflection helped reinforce my self-perception of who I am. Yes, I am a scientist through and through and am living my dream! However, I am not done yet, and am on my way to new scientific adventures.” -- Iris Aboytes
The Combustion Research Facility has launched its new WordPress-based website at crf.sandia.gov. The dramatically redesigned site, sponsored by the Energy, Climate and Infrastructure Security Strategic Management Unit (SMU), embodies the CRF’s forward–thinking vision and commitment to the growing needs of the combustion community.
“We launched the refreshed, engaging CRF website to easily deliver information about the collaborative research facility to our customers, sponsors, employees, the media, and many others. Our goal is to place relevant and timely communications at the fingertips of the combustion research community,” says Bob Carling, director of Transportation Energy Center 8300.
The site’s homepage welcomes visitors with bold new colors, a clean uncluttered design, and moving images with featured content centered on CRF as a premier research facility for developing and applying new scientific understanding, advanced detection methods, and quantitative predictive models to advance the clean, efficient use of energy sources, reduce oil dependence, and enhance national security.
The new site offers:
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The goal of the redesigned website is to create greater awareness and understanding of the CRF and its capabilities, increased collaboration, and partnerships.
“I encourage our customers and partners to get connected through the website — join the CRF Blog for the latest news and watch for the new interactive tour, coming in the New Year,” says Bob. “Our anticipation is that this will allow for valuable exchanges of ideas and even greater engagement with the combustion community. This site will continue to evolve; we plan to expand crf.sandia.gov with new features and continued improvements. We look forward to feedback from our users and exciting new developments to come.”