Anion‐Anchored Polymer‐in‐Salt Solid Electrolyte for High‐Performance Zinc Batteries

Abstract Solid polymer electrolytes hold promise for addressing key challenges in rechargeable zinc batteries (ZBs) utilizing aqueous electrolytes. However, achieving simultaneous high ionic conductivity, excellent mechanical strength, and a high cation transference number while effectively suppressing Zn dendrites remains challenging. Herein, we design a novel polymer‐in‐salt solid electrolyte (PISSE) composed of polyacrylonitrile (PAN), zinc chloride (ZnCl 2 ), and niobium pentoxide with oxygen vacancies (Nb 2 O 5‐x ) with high ionic conductivity. PAN polymer matrix provides the electrolyte good mechanical properties and solubility of Zn salt. The high concentration of ZnCl 2 effectively decouples the Zn 2+ from polymer chain segments and provides more ionic conduction amorphous region. Moreover, incorporating Nb 2 O 5‐x filler accelerates Zn 2+ desolvation by anchoring (Zn x Cl y ) 2x–y clusters and enhances the system's mechanical properties, achieving a superior Zn 2+ transference number (~0.93) and interfacial stability. Consequently, the optimized PISSE demonstrates exceptional stability during prolonged cycling periods, wide temperature range operation (−40 °C to 60 °C), remarkable flexibility, and compatibility with diverse electrode materials. This study provides valuable insights into the design of solid‐state electrolytes based on ZBs and elucidates their multifunctional prospects.