Cascade In Situ Cross-Linking–Quenching Enables High Ionic Conductivity and Interfacial Stability for Polyether Electrolytes

Poly(ethylene oxide) (PEO)-based polymer electrolytes hold great promise for all-solid-state lithium metal batteries (ASSLMBs), but their practical use is severely limited by crystalline domains that cause sluggish room-temperature ion-transport kinetics and inferior mechanical robustness. Herein, we propose a cascade in situ cross-linking–quenching strategy to regulate polymer network topology and suppress crystallization, yielding a networked polyether electrolyte with dominant amorphous domains. Specifically, Li + -conductive poly(propylene oxide- co -ethylene oxide- co -propylene oxide) oligomers are in situ cross-linked within the linear PEO matrix, forming a homogeneous polyether network. Subsequent rapid quenching further locks the system in a predominantly amorphous state, minimizing crystalline regions that restrict ion migration. The as-designed electrolyte achieves a remarkable room-temperature ionic conductivity of 8.5 × 10 –5 S cm –1 and reaches 1.3 × 10 –3 S cm –1 at 60 °C. Meanwhile, the covalently cross-linked network endows the electrolyte with significantly reinforced mechanical strength and excellent interfacial stability. Li/Li symmetric cells deliver stable cycling over 800 h at 0.1 mA cm –2, demonstrating superior dendrite-suppression capability. Impressively, the assembled ASSLMBs maintain 96.2% capacity retention after 300 cycles at 0.1 C at room temperature, overcoming the ambient-temperature limitation of conventional polymer electrolytes. This strategy provides a feasible route for developing advanced polymer electrolytes for high-performance ASSLMBs.