Study of Stable Cathodes and Electrolytes for High Specific Density Lithium-Air Battery

Future NASA missions require high specific energy battery technologies, > 400 Wh/kg. Current NASA missions are using “state-of-the-art” (SOA) Li-ion batteries (LIB), which consist of a metal oxide cathode, a graphite anode and an organic electrolyte.   The design and chemistry of these cells have safety issues and relatively low specific energy.  Among all the advanced energy storage systems, metal-air batteries, especially lithium-air batteries comprise a new system that has the potential to significantly enhance the energy density (10,000 Wh/kg). It has been shown theoretically work that their energy density is comparable with that of gasoline. The most challenge is that the lithium-air batteries undergo severe degradation upon cycling which limit the cycle life. An intriguing possible solution can be found in pairing a pure sp²carbon cathode with a non-traditional electrolyte such as ionic liquids.

NASA Glenn Research Center is currently studying the physical and electrochemical properties of the anode-electrolyte interface for ionic liquid based Li-air batteries. The voltage-time profiles for Pyr13FSI and Pyr14TFSI ionic liquids electrolytes studies on symmetric cells show low overpontentials and no dendritic lithium morphology. Cyclic voltammetry measurements indicate that these ionic liquids have a wide electrochemical window. As a continuation of this work, sp² carbon cathode and these low flamability electrolytes were paired and the physical and electrochemical properties were studied in a Li-air battery system under an oxygen environment.