Bottlenecks‐Breaking in Zinc‐Iodine Batteries Toward Practical Implementation: A Review and Perspective

Aqueous zinc–iodine batteries (Zn–I 2 Bs) emerge as promising candidates for grid‐scale energy storage due to their inherent safety, low cost, and environmental benignity. However, their practical deployment is hindered by critical challenges, including severe self‐discharge driven by coupled polyiodide shutting and hydrogen evolution reaction (HER), limited practical energy density constrained by low voltage plateaus and predominantly two‐electron iodine redox, sluggish reaction kinetics from complex iodine species interconversion, and zinc anode instability (dendrites, corrosion, passivation). This work provides a comprehensive analysis of Zn–I 2 B mechanisms, debating the interplay between iodine's layered structure favoring intercalation and its multivalency enabling conversion reactions, particularly pathways for electron redox beyond I − /I 2 . Strategies to mitigate these challenges are critically reviewed: anchoring iodine species within tailored host materials (e.g., functionalized carbons, COFs, perovskites) to suppress shuttling; electrolyte engineering (e.g., DES, additives) to sequester free I − and modulate solvation; functional separators/membranes for ion sieving; catalytic materials (transition metal/nonmetal‐based) to accelerate kinetics; and anode protection/modification (interfacial layers, hydrogel electrolytes, nonmetallic anodes) to enhance reversibility. The review synthesizes recent advances, identifies persistent bottlenecks, and outlines future research directions essential for realizing the commercial potential of high‐performance Zn–I 2 Bs.