Controllable Crosslinking Enables High‐Ionic‐Conductivity Polymer Electrolyte for Solid‐State Sodium Metal Batteries

ABSTRACT Ultraviolet (UV) photo‐crosslinking technology is a research focus in the fabrication of solid‐state polymer electrolytes (SPEs) due to its efficiency, low energy consumption, and eco‐friendliness. However, its inherent uncontrollability elevates polymer network crystallinity, severely compromising ionic conductivity. This study fabricates SPEs with high ionic conductivity through controllable photo‐crosslinking. By strategically incorporating mono‐functional vinyl ethylene carbonate (VEC) into poly (ethylene glycol) diacrylate (PEGDA) to consume crosslinking sites and form “dead‐end” structures, thereby achieving synergistic regulation of crystallinity and crosslinking density. The optimized electrolyte (P _1.5 V _1.5 NB) exhibited a high ionic conductivity of 1.39 × 10 ^{– 3} S cm ⁻¹ at 30°C and a wide electrochemical stability window of 4.8 V (vs. Na ⁺ /Na). Na‖P _1.5 V _1.5 NB‖Na ₃ V ₂ (PO ₄ ) ₃ (NVP) cell delivering 92.62 mAh g ⁻¹ at 2C with 89.26% capacity retention after 1000 cycles. This strategy delivers a novel strategy for developing SPEs with high ionic conductivity via controllable photo‐crosslinking, substantially enhancing the electrochemical performance of solid‐state sodium metal batteries (SSMBs).