Solvation Regulation in High-Rate Aqueous Zinc–Iodine Batteries

Hydrated eutectic electrolytes offer compelling promise for aqueous Zn-iodine batteries (Zn//I2) by stabilizing Zn anodes, yet their high viscosity and poor wettability impede practical deployment. Here, we design a water-rich eutectic electrolyte by preheating eutectic Zn(CIO4)2 and DMSO and cosoluble with ZnSO4 solution, which exhibits strong water-locking capability. By optimizing the water content, the electrolyte forms a hierarchical Zn2+ solvation sheath, in which DMSO and H2O occupy the inner shell and anions the outer, respectively. High ionic conductivity in low temperature and superior wettability are realized. The polar DMSO suppresses water activity and dissolves passivating byproducts, while ClO4– confines the solvent activity to mitigate iodine shuttling. The electrolyte substantially inhibits side reactions and promotes uniform Zn deposition. As a result, the assembled Zn//I2 demonstrate exceptional stability, retaining 99.1% capacity after 6000 cycles at 80 C. This work provides a practical strategy for high-rate aqueous Zn//I2.