Multi-Functional Liquefied Gas Electrolytes for Lithium-Metal Batteries

High-energy density, improved safety, temperature resilience, and sustainability are desirable properties for lithium battery electrolytes, yet these metrics are rarely achieved simultaneously. Inspired by the compositions of clean fire extinguishing agents, we demonstrate inherently safe liquefied gas electrolytes based on 1,1,1,2-tetrafluoroethane and pentafluoroethane that maintain > 3 mS cm^-1ionic conductivity from –78 to +80 ^oC. As a result of beneficial solvation chemistry and a fluorine-rich environment, Li cycling at > 99% Coulombic efficiency for over 200 cycles at 3 mA cm^-2 and 3 mAh cm^-2 was demonstrated in addition to stable cycling of Li/NMC622 full batteries from –60 to +55 ^oC. Additionally, we demonstrate a one-step solvent recycling process based on the vapor pressure difference at different temperatures of LGE, which promises sustainable operation at scale. This work provides a route to sustainable, temperature-resilient lithium metal batteries with fire-extinguishing properties that maintain state-of-the-art electrochemical performance.