Amidoxime-functionalized hydrogel electrolyte enables dendrite-free and shuttle-free zinc-iodine batteries

Zinc-iodine batteries have received significant attention due to their high theoretical capacity and environmental friendliness, but their performance is restricted by the growth of zinc dendrites, the hydrogen evolution reaction, and the shuttling effect of polyiodide ions (I3−/I5−). In this study, an amidoxime-functionalized hydrogel electrolyte, created by amidoximated porous polymer of intrinsic microporosity (AO-PIM-1) and sodium alginate (Alg), is designed to address the aforementioned problems through synergistically optimizing the interfaces of the zinc anode and iodine cathode. The rigid microporous framework and amidoxime groups of AO-PIM-1 can repel polyiodides and inhibit their shuttle effect. Meanwhile, the polyanionic properties of Alg guide the uniform deposition of Zn2+ along the (0 0 2) crystal plane through the “egg-box” structure, thus suppressing the formation of dendrites. The AO-PIM-1/Alg electrolyte has a high ionic conductivity (18.6 mS cm−1). The assembled symmetric battery can achieve highly reversible dendrite-free zinc plating/stripping (stably cycling for 2550 h at 1 mA cm−2). The Zn-I2 full battery with the AO-PIM-1/Alg electrolyte has a long lifespan of 8700 cycles at 0.5 A g−1. The working mechanism of the electrolyte was elucidated through density functional theoretical calculations and molecular dynamics simulations. This study provides a new strategy for the hydrogel electrolyte of Zn-I2 batteries.