Lithium-ion Energy Storage at Very Low Temperatures

Li-ion batteries with specific energy >180 Wh/kg, calendar life (>15years), and a wide operating temperature range (-60oC to 60oC) are crucial for the deployment of exploration vehicles such as rovers, landers, and penetraters as well as for low temperature burst power communication. The sub-ambient conductivity and liquid range of present rechargeable Li-ion battery electrolytes severely limit low temperature use. Co-solvents freezing as low as -132oC and Li salts with highly delocalized anions, enabling high degree of ionic dissociation in low dielectric environments provide us with a unique opportunity to develop non aqueous electrolytes for the low temperature with ionic conductivities well above 10-4 Scm-1. Our aim is to use these novel electrolytes as a direct substitute for the present electrolytes without affecting Li-ion battery performance or life during normal operation and access as least half the rated capacity at -60oC and 1/2C discharge rate. Working in collaboration with a leading developer of Li-ion batteries in Phase I, our low temperature electrolyte formulations will be evaluated in Li test cells containing anodes and cathodes used in commercial scale battery manufacture. In Phase II, electrolyte composition will be further optimized and prototype batteries will be fabricated and tested for performance.