Soft‐Hard Synergistic Solid All‐Polymer Electrolyte Inspired by Musculoskeletal Structure for High‐Temperature Lithium Metal Batteries

Abstract Robust structures are essential for extending the application of shapeless soft polymer electrolytes and maintaining the self‐supporting of solid‐state all‐polymer electrolytes (SPEs) at elevated temperatures. Common strategies of introducing additional separators or cross‐linking can significantly increase the manufacturing complexity of SPEs, thus limiting their commercialization. Herein, inspired by the musculoskeletal structure, a “soft‐hard synergy” enhanced SPE (named PPH‐SPE) is successfully designed and manufactured by a simple one‐step in situ microphase separation strategy for high‐temperature lithium–metal batteries. In the bicontinuous PPH‐SPE, the “soft” polyphosphazene liquid polymer electrolyte (PPZ‐LPE) phase provides excellent electrochemical properties, interfacial compatibility, and high‐temperature stable Li 3 N/Li 3 PO 4 ‐rich hybrid interfaces. PVDF‐HFP crystals are skillfully used to build a 3D continuous, high‐strength (0.32 ± 0.02 MPa at 90 °C), thermotolerant “hard” skeleton. In the synergy of two phases, Li//Li cell can maintain continuous electrodeposition over 4500 h of the plating/stripping process at 0.25 mA cm −2 and 0.25 mAh cm −2 . Furthermore, LiFePO 4 //Li coin and pouch cells achieve an ultra‐long lifetime of over 1000 (1 C) and 1800 (0.5 C) cycles at 90 °C, respectively. This strategy provides new ideas for large‐scale fabrication and enhancement of solid all‐polymer electrolytes.