“Tennis racket” hydrogel electrolytes to synchronously regulate cathode and anode of zinc-iodine batteries

Aqueous zinc-iodine (Zn-I₂) batteries show great potential as energy storage candidates due to their high-safety and low-cost, but confronts hydrogen evolution reaction (HER) and dendrite growth at anode side and polyiodide shuttling at cathode side. Herein, “tennis racket” (TR) hydrogel electrolytes were prepared by the co-polymerization and co-blending of polyacrylamide (PAM), sodium lignosulfonate (SL), and sodium alginate (SA) to synchronously regulate cathode and anode of Zn-I₂ batteries. “Gridline structure” of TR can induce the uniform transportation of Zn²⁺ ions through the coordination effect to hinder HER and dendrite growth at anode side, as well as hit I₃⁻ ions as “tennis” via the strong repulsion force to avoid shuttle effect at cathode side. The synergistic effect of TR electrolyte endows Zn-Zn symmetric battery with high cycling stability over 4500 h and Zn-I₂ cell with the stably cycling life of 15000 cycles at 5 A g⁻¹, outperforming the reported works. The practicability of TR electrolyte is verified by flexible Zn-I₂ pouch battery. This work opens a route to synchronously regulate cathode and anode to enhance the electrochemical performance of Zn-I₂ batteries.