Understanding the iodine electrochemical behaviors in aqueous zinc batteries

Iodine is widely used in aqueous zinc batteries (ZBs) due to its abundant resources, low cost, and active redox reactions. In addition to the active material in zinc-iodine batteries, iodine also plays an important role in other ZBs, such as regulating the electrochemical behavior of zinc ions, promoting the reaction kinetic and reversibility of other redox pairs, catalytic behaviors related to iodine reactions, coupling with other halogen ions, shuttle behaviors of polyiodides, etc. However, there is currently a lack of comprehensive discussion on these aspects. Here, this review provides a comprehensive overview of the electrochemical behaviors of iodide in the aqueous ZBs. The effect of iodine ions on the Zn²⁺ desolvation behaviors and the interfacial behaviors of Zn anode was summarized. Iodine redox pairs boosting other redox pairs, such as MnO₂/Mn²⁺ redox pair and vanadium redox pair to obtain high reversibility and capacity was also discussed. Moreover, the catalytic behaviors related to iodine reactions in aqueous ZBs, synergistic reaction with other halogen ions and suppression of shuttle behaviors for high performance zinc-iodine batteries were systematically analyzed. Finally, future prospects for designing effective iodine electrochemical behaviors with practicability are proposed, which will provide scientific guidance for the practical application of iodine-related aqueous ZBs.