All‐Round Ionic Liquids for Shuttle‐Free Zinc‐Iodine Battery

Abstract The practical implementation of aqueous zinc‐iodine batteries (ZIBs) is hindered by the rampant Zn dendrites growth, parasite corrosion, and polyiodide shuttling. In this work, ionic liquid EMIM[OAc] is employed as an all‐round solution to mitigate challenges on both the Zn anode and the iodine cathode side. First, the EMIM + embedded lean‐water inner Helmholtz plane (IHP) and inert solvation sheath modulated by OAc − effectively repels H 2 O molecules away from the Zn anode surface. The preferential adsorption of EMIM + on Zn metal facilitates uniform Zn nucleation via a steric hindrance effect. Second, EMIM + can reduce the polyiodide shuttling by hindering the iodine dissolution and forming an EMIM + ‐I 3 − dominated phase. These effects holistically enhance the cycle life, which is manifested by both Zn || Zn symmetric cells and Zn‐I 2 full cells. ZIBs with EAc deliver a capacity decay rate of merely 0.01 ‰ per cycle after over 18,000 cycles at 4 A g −1 , and lower self‐discharge and better calendar life than the ZIBs without ionic liquid EAc additive.