A reusable biomass electrolyte with dual-interface regulation towards flexible and durable zinc-iodine batteries

Hydrogel electrolytes have been widely explored to achieve flexible zinc-iodine (Zn-I₂) batteries for wearable electronics and relieve the challenges of Zn dendrites, hydrogen evolution reaction (HER), and shuttle effect. However, natural biomass hydrogel electrolyte is largely overlooked, as well as its dual-interface regulation on cathode and anode remains quite elusive. Herein, gelatinous fungus with excellent flexibility and outstanding workability is developed as hydrogel electrolyte for flexible Zn-I₂ batteries, and its abundant ion-transport channels afford high Zn²⁺ transfer number of 0.72 and fast desolvation kinetics. The polysaccharide and protein components of hydrogel electrolytes induce water-poor solvation structure and in-situ formation of C, N, and S-rich solid electrolyte interface for suppressing HER and dendrite of Zn anode, while the electrostatic repulsion towards I₃^- ions effectively restrains the shuttle effect of I₃^- at cathode interface. Encouragingly, Zn anodes deliver ultra-long cycle-life of 6000 h and good stability at high current density of 100 mA cm^-2, and Zn-I₂ pouch battery displays durable cycle-life over 4000 cycles. Moreover, flexible Zn-I₂ battery maintains initial state under bending and cutting conditions and successfully powers wearable electronics. More encouragingly, the cycled APHE can be reused to afford good battery performance of 2000 cycles after resoaking in aqueous electrolyte.