Insights on lean-water hydrogel electrolyte designs for next-generation zinc batteries

Owing to their intrinsic safety and low cost, aqueous zinc-ion batteries (AZIBs) have emerged as promising large-scale energy storage devices. Hydrogel electrolytes have been extensively studied because of their superior electrochemical performance their ability to endow AZIBs with excellent flexibility. However, traditional hydrogel electrolytes typically suffer from a narrow electrochemical stability potential window (ESPW) and poor cycling stability, primarily due to their high water content. In recent years, lean-water hydrogel electrolytes (L-WHEs) have been developed to address these issues. By confining free water molecules and regulating ion transport within the hydrogel network, L-WHEs can efficiently suppress side reactions, widen the ESPW, and enhance interfacial stability. This review systematically discusses the fundamental principles of L-WHEs, current strategies for developing practical L-WHEs, and recent research progress. Finally, future prospect and challenges in the development of high-performance L-WHEs are outlined.