Anisotropic Ion-Guiding Hydrogel Electrolyte with High-Water Affinity for Zn Ion Battery

Aqueous zinc-ion batteries (AZIBs) are a promising alternative to lithium-ion batteries, boasting superior safety, eco-friendliness, and cost-effectiveness. Despite these advantages, performance issues such as irregular Zn deposition and cathode material dissolution remain challenging. This study introduces an intrinsically anisotropic ion-guiding hydrogel electrolyte (APHE) fabricated via a double-stabilization anisotropic freezing strategy. The synergistic effect of anisotropic structure and high water affinity of APHE effectively suppress water-induced parasitic reactions. In brief, the anisotropic structure promotes rapid Zn²⁺ ion diffusion, leading to the uniform Zn²⁺ ion flux. Additionally, abundant hydroxyl groups in APHE facilitate Zn²⁺ ion dissociation and adjust the solvation structure, setting it apart from an isotropic matrix. Furthermore, the improvement of ion diffusion tortuosity enhances the electrode/electrolyte kinetics, thereby improving the rate-capability and reversibility of Zn²⁺ ion (de)-intercalation. Thus, APHE demonstrates a thin and dense Zn deposition layer of 31.7 µm, which is less than half the thickness of IPHE (67.5 µm) after 500 cycles. This research addresses fundamental challenges in the performance of AZIBs and provides valuable insights into the design of advanced electrolytes for future energy storage systems.