Biopolymer-Based Gel Electrolytes for Advanced Zinc Ion Batteries: Progress and Perspectives

In recent years, aqueous zinc ion batteries (ZIBs) with ultra-high safety and environmental friendliness have emerged as a promising candidates for energy storage and energy conversion devices. However, the severe side reactions and dendrites issues discourage the practical application of ZIBs. Recently, biopolymer-based gel electrolytes have disclosed large potential in tackling these challenges of ZIBs, with numerous advancements reported. Their advantages lie in suppressing side reactions including hydrogen evolution and Zn metal anode corrosion, as well as inhibiting the growth of Zn dendrites. This review comprehensively examines the classification, structures and properties of biopolymer-based gel electrolytes, with a focus on hydrogel electrolytes derived from various natural macromolecular biopolymers, along with a brief discussion on non-hydrogel electrolytes using ionic liquids or organic solutions as solvents. Subsequently, the preparation of biopolymer-based gel electrolytes with physical and chemical methods are summarized. Furthermore, the practical applications of biopolymer-based gel electrolytes in ZIBs with diverse cathodes materials are introduced. Finally, it highlights the environmental benefits and excellent electrochemical performance of biopolymer-based gel electrolytes, outlining their prospects for the next generation of ZIBs and proposing future perspectives.