Bifunctional Additive Enabled Thermoresponsive Electrolytes With Dual‐Mode Manipulation Toward Safe Lithium Metal Batteries

ABSTRACT Thermal safety issues arising from electrolyte instability at elevated temperatures pose a critical challenge for lithium (Li) metal batteries (LMBs). Thermoresponsive electrolytes offer a promising solution, yet battery systems with high‐rate capability and reliable thermal protection have not been realized. Herein, we introduce a bifunctional LiNO 3 additive into a high‐volume‐fraction vinylene carbonate‐based thermoresponsive electrolyte (HVCE‐N) to enhance the performance of LMBs at room and elevated temperatures. Notably, the introduction of the LiNO 3 additive modifies the solvation structure of Li + and forms a Li 3 N/LiN x O y solid electrolyte interface with high ionic conductivity. Under thermal shock, HVCE‐N undergoes a rapid liquid‐to‐solid phase transition upon free radical polymerization to form a polymer network. More importantly, LiNO 3 can regulate the free radical concentration to control the degree of polymerization, thereby preserving high ion transport capability even after phase transition. As a result, a Li||NCM811 cell based on HVCE‐N exhibits high‐rate performance from 1C to 10C, and stable cycling at 100°C. When subjected to a thermal shock of 200°C, HVCE‐N suppresses thermal runaway for Li||NCM811 pouch cell. This electrolyte design offers a new strategy to develop highly safe LMBs with high‐rate performance.