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

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_1.5V_1.5NB) 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_1.5V_1.5NB‖Na₃V₂(PO₄)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).