A Focused Review on Zinc-Anode Protection for Durable Aqueous Zinc-Iodine Soft-Gel Electrode Batteries

Aqueous zinc-iodine batteries offer a safe and low-cost storage option, but their durability is limited by coupled zinc-anode degradation and iodine-species crossover. Soft-gel iodine cathodes can improve iodine retention through confinement and molecular interactions, yet mobile iodine/polyiodide intermediates may still reach zinc. The anode is concurrently vulnerable to heterogeneous plating/stripping, hydrogen evolution, corrosion, passivation, and dead-zinc formation; these processes are further intensified by iodine-derived oxidants, causing self-discharge and active-material loss. This review examines zinc-anode protection in aqueous zinc-iodine soft-gel electrode batteries. It discusses interfacial failure modes, fundamental protection principles, and strategies based on substrate engineering, artificial interphases, structural designs, separator-assisted regulation, and electrolyte modification. Emphasis is placed on iodine/polyiodide compatibility and coordinated design of the zinc anode, electrolyte, separator, and soft-gel cathode. Durable operation requires simultaneous control of zinc reversibility, water activity, polyiodide crossover, and redox-state-compatible iodine retention.