Tailoring High‐Elasticity Cross‐Linked Polymer Electrolytes to Harmonize Flexible Solid‐State Lithium–Oxygen Batteries

Abstract Solid‐state lithium‐oxygen (Li‐O 2 ) batteries (SSLOBs) are promising for next‐generation energy storage due to their high theoretical energy density. However, their development is hindered by the lack of competent solid‐state electrolytes (SSEs). This study develops cross‐linked SSEs with controlled ultraviolet crosslinking polymerization. This advanced molecular architecture provides high ionic conductivity (8.35 × 10 −4 S cm −1 at 25 °C), an extended electrochemical window (0–5.4 V vs Li/Li + ), and a high lithium‐ion transference number (0.76). The engineered elastomer exhibits exceptional mechanical resilience with an elongation rate of 1824.7%, minimal energy dissipation, and efficient strain recovery. This enables over 4000 h of stable lithium plating/stripping at 0.1 mA cm −2 . Additionally, SSLOBs show excellent cycling performance (106 cycles), and the electrolyte's geometric adaptability supports pouch‐type flexible batteries, with enhanced safety. This work offers insights into stress‐mitigation strategies in electrolyte matrices and sets a framework for designing next‐generation flexible lithium‐air batteries.