Temperature-Adaptive Fluorine in Electrolyte for Lithium-Metal Batteries at Low Temperatures

Li-metal batteries (LMBs) are heavily constrained at low temperatures due to increased ion desolvation and transportation barriers. Here, we report a weakly solvating sulfonamide-based electrolyte that features a temperature-sensitive local chemical environment of the fluorine atoms in the sulfonamide molecules at low temperatures. The reactivity of the sulfonamide with Li-metal is further tailored by the adaptive fluorine chemistry at low temperatures, promoting the formation of more conductive LiF_x components in the solid-electrolyte interphase. Benefiting from these characteristics, our electrolyte enables high Li-metal reversibility and delivers a high discharge capacity of 164.4 mAh g^-1 at −30 °C (197.9 mAh g^-1 at 25 °C) with a high capacity retention of 83.0% after 180 cycles at −30 °C in a 4.6-V-class Li||NMC622 battery, significantly outperforming the carbonate-based electrolyte. These results highlight the critical role of electrolyte design in practical LMBs under extreme conditions.