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

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 (ZnCl₂), and niobium pentoxide with oxygen vacancies (Nb₂O_5-x) with high ionic conductivity. PAN polymer matrix provides the electrolyte good mechanical properties and solubility of Zn salt. The high concentration of ZnCl₂ effectively decouples the Zn²⁺ from polymer chain segments and provides more ionic conduction amorphous region. Moreover, incorporating Nb₂O_5-x filler accelerates Zn²⁺ desolvation by anchoring (Zn_xCl_y)^2x–y clusters and enhances the system's mechanical properties, achieving a superior Zn²⁺ 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.