Wide‐Temperature and High‐Rate Operation of Lithium Metal Batteries Enabled by an Ionic Liquid Functionalized Quasi‐Solid‐State Electrolyte

Abstract The development of high‐energy‐density solid‐state lithium metal battery has been hindered by the unstable cycling of Ni‐rich cathodes at high rate and limited wide‐temperatures adoptability. In this study, an ionic liquid functionalized quasi‐solid‐state electrolyte (FQSE) is prepared to address these challenges. The FQSE features a semi‐immobilized ionic liquid capable of anchoring solvent molecules through electrostatic interactions, which facilitates Li + desolvation and reduces deleterious solvent‐cathode reactions. The FQSE exhibits impressive electrochemical characteristics, including high ionic conductivity (1.9 mS cm −1 at 30 °C and 0.2 mS cm −1 at ‐30 °C) and a Li + transfer number of 0.7. Consequently, Li/NCM811 cells incorporating FQSE demonstrate exceptional stability during high‐rate cycling, enduring 700 cycles at 1 C. Notably, the Li/LFP cells with FQSE maintain high capacity across a wide temperature range, from ‐30 to 60 °C. This research provides a new way to promote the practical application of high‐energy lithium metal batteries.