A Review on Recent Advances and Perspectives in Hydrogel Polymer Electrolytes for Aqueous Zinc‐Ion Batteries

In comparison with solid polymer electrolytes, hydrogel polymer electrolytes are now a potentially suitable candidate for aqueous zinc‐ion batteries (ZIBs). Generally, a hydrogel is mainly composed of a hydrophilic polymer network with a high water absorption propensity and the distinctive properties of being soft and wet, becoming a gel and solid polymer electrolyte in terms of ionic conductivity and mechanical properties. All these unique characteristics of electrolytes combine with an appropriate anode and cathode materials to deliver high safety, low cost, environmental friendliness, and excellent electrochemical performance in ZIB. Nevertheless, there is no comprehensive overview on the development of hydrogel electrolytes for ZIBs available. Therefore, this study focuses on the most recent breakthroughs in hydrogel‐based polymer electrolytes for ZIBs. Further, a brief explanation of various types of hydrogel electrolytes as well as the electrochemical performance of different polymer‐based electrolytes arediscussed. Finally, the challenges of hydrogel electrolytes for currently established Zn‐ion batteries and the future research directions towards the high‐performance flexibile ZIBs are explored.