Breaking the Thermal Limits: Solvation Chemistry of Hydrogel Electrolytes for Extreme‐Temperature Stable Zinc‐Ion Batteries

Aqueous zinc metal batteries (AZMBs) are promising candidates for safe and cost‐effective energy storage, yet their practical deployment across a wide temperature range is severely constrained by temperature‐dependent ion‐transport limitations and electrode–electrolyte interfacial instability. At low temperatures, sluggish Zn 2+ transport and desolvation promote concentration polarization and nonuniform Zn deposition, while elevated temperatures accelerate water‐induced parasitic reactions, corrosion, and interfacial degradation. Hydrogel electrolytes offer opportunities to address these challenges by regulating water activity, Zn 2+ solvation, ion transport, and interfacial mechanics within an integrated polymer network. This review systematically elucidates five representative design strategies: high‐entropy environments, water‐deficient hydrogels, deep eutectic solvent‐mediated regulation, zwitterionic networks, and nanofiller reinforcement, with particular emphasis on their effects on Zn 2+ coordination, water organization, transport kinetics, and interfacial stability. Quantitative solvation and kinetic descriptors, including coordination numbers, ion‐pair populations, diffusion coefficients, transference numbers, interaction energies, and activation energies, are compared to clarify how electrolyte structure influences performance at different temperatures. The advantages and limitations of the five strategies are further compared in relation to their applicable temperature‐dependent challenges. Finally, key priorities are discussed for temperature‐resolved solvation characterization, operando analysis, practical cell evaluation, and standardized thermal testing, providing guidance for the development of hydrogel electrolytes toward reliable wide‐temperature AZMBs.