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 Li₃N/Li₃PO₄-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, LiFePO₄//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.