Graded‐Interface Dual‐Environment Hydrogel‐Polymer Electrolyte for Stabilized Anode and Sustained Cathode Kinetics in Aqueous Zinc‐Ion Batteries

ABSTRACT

Aqueous zinc‐ion batteries (AZIBs) face conflicting electrolyte needs: the zinc anode requires minimal water to suppress corrosion, dendrite growth, and hydrogen evolution reaction (HER), while cathodes demand a water‐rich environment for efficient Zn ^{2 +} /H ⁺ insertion/extraction and high capacity. To resolve this, we developed a graded‐interface dual‐environment hydrogel‐polymer electrolyte (GIDE‐HE/SPE). It integrates a water‐limited solid polymer electrolyte (SPE) layer at the anode for highly reversible Zn plating/stripping and a hydrogel electrolyte (HE) layer at the cathode for optimal ion transport. A graded interface forms a dynamic de‐solvation layer, enabling Zn ²⁺ to shed H ₂ O ligands and coordinate with acetamide/BF ₄ ⁻ , significantly lowering de‐solvation energy compared to sharp bilayers. Consequently, Zn||Zn symmetric cells achieve 1600 h stability, and Zn||Cu cells reach 1000 cycles with >99.6% Coulombic efficiency. Zn||MnO ₂ and Zn||V ₂ O ₅ full cells retain 82.3% capacity after 1000 cycles and 78.9% after 5000 cycles, respectively, far outperforming pure SPE or HE. The graded‐interface dual‐environment hydrogel‐polymer electrolyte (GIDE‐HE/SPE) design represents a significant step forward in reconciling the opposing demands of ZIBs by offering distinct microenvironments optimized for each electrode while also minimizing desolvation energy losses compared to sharp physical bilayers.