Mass production of robust hydrogel electrolytes for high-performance zinc-ion batteries

Hydrogel electrolytes are crucial for solving the problems of random zinc dendrite growth, hydrogen evolution reactions, and uncontrollable passivation. However, their complex fabrication processes pose challenges to achieving large-scale production with excellent mechanical properties required to withstand multiple cycles of mechanical loads while maintaining high electrochemical performance needed for the new-generation flexible zinc-ion batteries. Herein, we present a superspreading-based strategy to produce robust hydrogel electrolytes consisting of polyvinyl alcohol, sodium alginate and sodium acetate. The hydrogel electrolytes have a tensile strength of 54.1 ± 2.5 MPa, a fracture strain of up to 1113 ± 37%, and a fracture toughness of 374.1 ± 6.1 MJ m^-3, showcasing endurance of 2500 cycles at 80% strain without damage. Besides, the hydrogel electrolytes feature a high ionic conductivity of 14 mS cm^-1 and a Zn²⁺ transference number of 0.62, as interfacial regulation enables the symmetric cell to achieve 1300 hours of highly stable and reversible zinc plating/stripping. As a preliminary attempt toward mass production, soft-pack batteries assembled using modified hydrogel electrolytes demonstrate robust machinability, with minimal voltage change after being bent and deformed 100 times. This work is expected to pave the way for developing a convenient hydrogel electrolyte for effective and stable zinc-ion batteries.