Comprehensive Insights into Gel Polymer Electrolytes and Electrode/Electrolyte Interfaces for Aqueous Zinc Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) have been considered as promising candidates for large-scale energy storage due to environmental friendliness, abundant resources, and high safety. However, aqueous electrolytes suffer from inevitable problems including water splitting, evaporation, and liquid leakage. Gel polymer electrolytes (GPEs), acting as electrolyte and separator simultaneously, can effectively alleviate the challenges of aqueous electrolytes due to hydrogen bonds between hydrophilic polymers and free water molecules. However, GPEs still face serious challenges on the electrode/electrolyte interfaces. Therefore, it is imperative to provide comprehensive insights into recent advances of design principles to optimize electrode/electrolyte interfaces. This review systematically summarizes recent progress of GPEs in AZIBs from the aspects of fundamentals, optimization strategies on electrode/electrolyte interfaces, and applications in detail. First, the fundamentals of GPEs including elaborate classification, synthesis methods, and crucial properties are discussed. Then, the current challenges on the interfaces along with multiple strategies to modulate the interfaces and the practical applications of assembled AZIBs under different conditions are discussed. Finally, this review outlines the opportunities and challenges for obtaining advanced GPEs. This review provides an in-depth understanding of the relationship between properties of electrode/electrolyte interfaces and performances for GPEs, and it is expected to facilitate the development of AZIBs.