Environmentally adaptable hydrogel electrolyte with the triple interpenetrating network in the flexible zinc-ion battery with ultralong stability

With the increasing development of wearable electronic devices, the stabilities of the flexible battery are in great demand. However, the rapid capacity degradation and the limits of the traditional aqueous electrolyte in cold environmental condition still retards the practical application of the aqueous zinc ion batteries (ZIBs). Herein, a polyacrylamide/carboxymethyl cellulose/gelatin (PCG) hydrogel electrolyte with triple interpenetrating network was fabricated by an integrated physical crosslinking and free-radical polymerization process. Benefitting from its hierarchical porous structure, the PCG hydrogel electrolyte exhibits the stable mechanical compression deformation. The integrated cross-linked networks with abundant hydrogen bonds and high electrolyte salt prevent the crystallization of water, contributing to broadening its operating temperature (from −20 °C to room temperature). Therefore, the PCG electrolyte cannot only promise the highly reversible Zn2+ insertion/extraction, but also accelerate ion transfer in electrochemical process. As a result, the PCG-based ZIBs with magnesium vanadium oxide deliver a high capacity of 382.7 mAh g−1 and good cycling stability (10000 cycles at 0 °C). Besides, the assembled flexible ZIBs also exhibit a good capacity retention under various bending states. This unique strategy of hydrogel electrolyte provides new insights for flexible ZIBs with superior cycling stability.