Single-atom-doped zeolite electrolyte for quasi-solid-state zinc-iodine batteries

Quasi-solid electrolytes can mitigate polyiodide shuttling and suppress parasitic reactions at zinc negative electrode in zinc-iodine batteries by reducing free water, but their limited liquid content often results in sluggish interfacial charge transfer. Here we show liquid-electrolyte-wetted quasi-solid electrolytes by combining single-atom-modified zeolites (single-atom = iron, cobalt, nickel, and copper) with zinc sulfate aqueous solution for high-rate zinc-iodine batteries. Theoretical calculations, in situ spectroscopy, and laser confocal microscopy reveal that the single-atom metal sites enhance iodine conversion kinetics and suppress polyiodide shuttling through a synergistic catalytic-adsorption effect, with iron-doped zeolite exhibiting the strongest performance. Iron-doped zeolite further stabilizes water molecules, suppresses side reactions, and promotes uniform zinc deposition. The iron-doped zeolite-assembled zinc-iodine batteries maintain a discharge capacity of 81.2 mAh g−1 (based on iodine mass) after 6,800 cycles at 4 A g−1, while proof-of-concept pouch cells exhibit a capacity of 147.6 mAh g−1 (based on iodine mass) or 52 mAh g−1 (based on total positive electrode mass) after 200 cycles at 0.5 A g−1. Lastly, iron-doped zeolite also demonstrates compatibility with other positive electrode materials for rechargeable zinc batteries. Quasi-solid zinc iodine batteries face sluggish kinetics due to low liquid content. Here, authors report single-atom metal-doped zeolite electrolytes that simultaneously catalyze iodine conversion, suppress polyiodide shuttling, and stabilize zinc deposition, achieving 6,800 stable cycles at high rates and demonstrating proof-of-concept pouch-cell performance.