Strong Solvent and Dual Lithium Salts Enable Fast-Charging Lithium-Ion Batteries Operating from -78 to 60 °C.

Current lithium-ion batteries degrade under high rates and low temperatures due to the use of carbonate electrolytes with restricted Li conduction and sluggish Li desolvation. Herein, a strong solvent with dual lithium salts surmounts the thermodynamic limitations by regulating interactions among Li ions, anions, and solvents at the molecular level. Highly dissociated lithium bis(fluorosulfonyl)imide (LiFSI) in dimethyl sulfite (DMS) solvent with a favorable dielectric constant and melting point ensures rapid Li conduction while the high affinity between difluoro(oxalato)borate anions (DFOB) and Li ions guarantees smooth Li desolvation within a wide temperature range. In the meantime, the ultrathin self-limited electrode/electrolyte interface and the electric double layer induced by DFOB result in enhanced electrode compatibility. The as-formulated electrolyte enables stable cycles at high currents (41.3 mA cm) and a wide temperature range from -78 to 60 °C. The 1 Ah graphite||LiCoO (2 mAh cm) pouch cell achieves 80% reversible capacity at 2 C rate under -20 °C and 86% reversible capacity at 0.1 C rate under -50 °C. This work sheds new light on the electrolyte design with strong solvent and dual lithium salts and further facilitates the development of high-performance lithium-ion batteries operating under extreme conditions.