Integration Framework for Multifunctional Hydrogel Electrolyte Modification Strategies in Aqueous Zinc‐Ion Batteries from Molecular Design to Device Application

Aqueous zinc‐ion batteries (AZIBs) have emerged as candidates for large‐scale and flexible energy storage owing to abundant zinc resources, low cost, high theoretical capacity, and intrinsic safety. Conventional liquid electrolytes remain limited by a narrow electrochemical stability window, hydrogen evolution, corrosion‐induced parasitic reactions, zinc dendrite growth, and electrolyte leakage, hindering practical deployment. Hydrogel electrolytes have evolved beyond quasi‐solid media into structurally programmable platforms that integrate polymer networks, bound water, and ionic species to regulate water activity, Zn 2+ solvation environments, ion transport, and interfacial reactions. This review presents a cross‐scale design framework for multifunctional hydrogel electrolytes in AZIBs, encompassing structural foundations, multiscale regulation strategies, and device‐level applications. The structural classification, electrochemical advantages, and fundamental design principles of hydrogel electrolytes are summarized. Nine representative regulation strategies are discussed, from molecular interactions to network architectures and interfacial engineering, including solvation regulation, hydrogen‐bond reconstruction, hierarchical crosslinking, ordered transport channels, spatially heterogeneous structures, and dynamic dual‐network designs. The emerging applications of hydrogel electrolytes in wearable electronics, multifunctional integrated devices, and physiological‐environment‐compatible bioelectronics are further highlighted. The mechanistic and engineering challenges are analyzed, and a cross‐scale synergistic design pathway is proposed to accelerate the transition of hydrogel electrolytes from empirical optimization toward predictable and engineering‐reliable systems.