The mechanism of thermal decomposition of lithium-ion battery electrolytes and the related reactions of the electrolyte with the electrode materials will be investigated. The thermal decomposition of electrolytes at 60 - 100 oC can be inhibited by the addition of Lewis basic or donor solvent additives or the presence of electrode materials. While the decomposition of bulk electrolyte is slow in lithium-ion batteries, due to the thermal stabilizing properties of the electrode materials, the reaction of the electrolyte with the electrode materials at elevated temperature (> 60 oC) results in decreased charge capacity and increased internal resistance. Electrolytes containing thermal stabilizing additives impede the formation of surface films on cathode materials. A thorough investigation of thermal stabilizing additives including the effect of the additive on the stability of pure electrolyte, surface film formation on cathode particles, and stability of solid electrolyte interface (SEI) on the anode will be conducted. The development of thermally stable electrolytes that do not react with electrode materials at elevated temperature (> 60 oC) will lead to lithium-ion batteries with improved high temperature performance and better calendar and cycle life.
Lithium-ion batteries have the potential for power and cycle life required for many electric vehicle (EV), military, aircraft, and intelligence community (IC) applications. However, for several of these applications the high temperature stability, cycle life, and calendar life need to be improved. The investigation of novel electrolytes with improved thermal stability will lead to the development of lithium-ion batteries with improved calendar and cycle life. The Approaches to Combat Terrorism Program in the Directorate for Mathematics and Physical Sciences supports new concepts in basic research and workforce development with the potential to contribute to national security.
