Achieving Balanced Performance and Safety for Manufacturing All‐Solid‐State Lithium Metal Batteries by Polymer Base Adjustment

Abstract Organic–inorganic composite solid electrolytes (CSEs) have aroused intensive attention due to their balanced performance and environmental adaptability. However, their high performance, e.g., the high ionic conductivity, wide electrochemical window, and excellent interfacial compatibility, is achieved by sacrificing their mechanical strength, which increases the possibility of short circuits and thus poses serious safety hazards. Herein, a high‐performance and rigid‐flexible PM polymer matrix is synthesized by a simple process of polymerization addition reaction between polyethylene oxide (PEO) and methylene diphenyl diisocyanate (MDI), where PM‐based CSEs (denoted as PMPS@LATP‐NF) is also prepared through a porous non‐woven fabric (NF) dense filling process. The effect of PM polymer on the mechanical properties, ionic transport, and interactions of CSEs is elucidated by the combined experimental and theoretical methods, where functional groups (─C─O─C, ─NCO, ─NH) contribute to the dissociation of lithium salts, self‐healing, and interfacial compatibility. Besides, PMPS@LATP‐NF can further mechanically regulate lithium dendrites and demonstrates ultra‐high thermal stability. Moreover, PMPS@LATP‐NF exhibits significantly enhanced cycling performance and rate capability in all‐solid‐state Li/LiFePO₄ cells. This work emphasizes the pivotal role of the mechanical properties of CSEs in electrolyte modification, cycling stability, and lifespan of all‐solid‐state lithium metal batteries, and provides inspiration for the development of practical solid electrolytes.