A Highly Ion‐Conductive Solid Polymer Electrolyte with Good Thermal Stability and Nonflammability for All‐Solid‐State Li Metal Batteries

Lithium metal batteries (LMBs) have been recognized as one of the most promising energy storage devices due to their high energy density. The leakage, corrosion to Li metal anode, and flammability of organic liquid electrolytes bring great security problems for LMBs. Polymeric ionic liquid (PIL)‐based solid polymer electrolytes (SPE), possessing nonflammability, excellent thermal, chemical, electrochemical stability, are a kind of promising SPE for highly safe all‐solid‐state LMBs. Nevertheless, the low ambient conductivity of pristine PIL‐based SPE restricts their application in solid‐state LMBs. Herein, an ionic liquid monomer (denoted as GIM) is designed and synthesized and copolymerized with vinyl ethylene carbonate (VEC) monomer by UV‐light curing to prepare P(GIM‐VEC) SPE. The prepared P(GIM‐VEC) SPE is thermally stable and intrinsically nonflammable, possesses high ambient ionic conductivity, and can suppress lithium dendrite growth and stabilize the solid electrolyte interface. Thus, the resultant all‐solid‐state LiFePO4 (LFP)|P(GIM‐VEC)|Li battery exhibits a high initial discharge capacity of 152.7 mAh g−1 at 0.1 C along with a good stability and rate capability at room temperature. Herein, new guidance is provided for developing ambient workable SPEs with high ionic conductivity, nonflammability, and excellent thermal stability for all‐solid‐state Li metal batteries.