TEES researcher leads project for Department of Energy

September 4, 2014
| By: Aubrey Bloom

Dr. Perla Balbuena, a researcher with the Texas A&M Engineering Experiment Station (TEES), holder of the GPSA Professorship and a professor in the Artie McFerrin Department of Chemical Engineering, has been awarded $990,000 from the Department of Energy. Balbuena will lead a project to research design improvements and optimization of lithium-sulfur batteries in their application as plug-in electric vehicles (PEV) batteries. Her research will explore a phenomenon called the “internal shuttle effect” within the Li/S battery and evaluate a multitude of other impacts to the battery’s chemistry.

Balbuena’s research project is one of 19 sponsored by President Obama’s EV Everywhere Grand Challenge that seeks to equalize affordability and convenience in PEVs for consumers, in comparison to current gasoline-powered vehicles.

 “Our faculty members are consistently at the forefront of emerging technologies and cutting-edge research,” said John Sharp, chancellor of The Texas A&M University System. “Dr. Balbuena’s research is an important step in developing more efficient methods to power electric vehicles, which can in turn lower the cost so that more people can afford to drive these environmentally friendly vehicles.”

Balbuena offered more background information on the complexities of Li/S batteries and an analysis of why such a study is helpful economically and environmentally during a recent question and answer session.

Q: How do Li/S batteries differ from batteries in electric vehicles?

Balbuena: Currently electric vehicles are mostly powered by Li-ion batteries, which are very expensive and provide a limited driving range (approximately 100 miles based on a single charge). Li/S batteries are attractive due to their low cost and high theoretical specific energy density, which would significantly extend the driving range and make the cost of the vehicle affordable compared with that of gasoline. 

Q: Are Li/S batteries better for the environment?

Balbuena: Li/S batteries hold a significant promise due to their high theoretical specific energy density. In addition, [sulfur] is an attractive option because it is inexpensive and has low toxicity. It also has low weight and is relatively abundant in the Earth’s crust, meaning that Li/S batteries would be neither prohibitively expensive nor take a large toll on the environment.

Q: Describe the “internal shuttle effect” you indicate will be at the center of your research. How does this effect support Li/S batteries?

A battery is composed of three parts with very different chemistries: two solid electrodes each in contact with a liquid (electrolyte) phase and the liquid electrolyte phase. At the interface between each of the solid electrodes and the liquid electrolyte there is an electrochemical reaction taking place that ultimately releases electricity. On the other hand, the liquid electrolyte is the medium where lithium ions (charged particles) travel from one electrode to the other during charge and discharge of the battery. In the lithium-sulfur battery, in addition to lithium ions, other products of the reactions “shuttle” from one electrode to the other when the battery is working. This effect is characteristic of the Li/S electrode/electrolyte interfacial chemistries, and needs to be understood and controlled in order to ensure efficient and long-lasting battery performance.

Q: The goal of the EV Everywhere Grand Challenge is to "make the U.S. automotive industry the first to produce PEVs that are as affordable and convenient as today’s gasoline-powered vehicles by 2022.” How will your research impact this end goal?

Balbuena: Development of the Li/S couple into a commercially viable battery has been hampered by poor reversibility during discharge/recharge. This means that the electrode materials and their storage capacity suffer a degradation effect. This is in part due to low electronic conductivity in the sulfur electrode. Another problem is the shuttle effect of the reaction subproducts that modifies the chemistries in both electrodes. Our research will tackle these problems in two ways: first, a detailed theoretical analysis at the atomistic and mesoscopic levels will provide a detailed understanding of the reactions and the effect of the microstructure of the materials on the battery performance; second, this knowledge will allow us to guide our synthesis experiments to develop improved electrode and electrolyte materials and a much more efficient battery. This is a team effort where the theoretical computational components investigated by my group and that of Dr. Partha Mukherjee (assistant professor in Texas A&M’s Department of Mechanical Engineering) will be integrated with the experimental studies and tests from the group of Dr. Vilas Pol (associate professor in Purdue University’s Department of Chemical Engineering).

Q: What are other ways Li/S batteries can be utilized? 

Balbuena: If successful, these batteries may be utilized in other applications, thus substituting the current Li-ion technology.

Q: What are you most looking forward to in this project?

Balbuena: It is very exciting to contribute with theoretical/computational analysis to the development of practical technologies that may help society in many ways.
Q:  Do you have any other thoughts to add?

Balbuena: It is important also to emphasize the educational aspects of the project: a formation of new generations of scientists and engineers [that are] able to use theoretical/computational tools as the basis of design of materials that provide effective solutions to crucial areas such as energy, water, medicine and environment.


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