The Multifunctional Role of Ionic Liquids in Aqueous Zinc–Iodine Batteries

Aqueous zinc–iodine batteries (ZIBs) are promising candidates for next‐generation energy storage because of their inherent safety, high theoretical energy density, and low cost. However, their practical application is hindered by polyiodide shuttling at the cathode, dendrite growth at the zinc anode, and water‐induced side reactions such as corrosion and hydrogen evolution. Conventional electrolytes fail to address these issues simultaneously. Ionic liquids (ILs) offer a versatile and designable electrolyte platform that can mitigate all three challenges. At the anode, ILs regulate the Zn 2+ solvation structure, construct a water–poor interfacial layer, and guide uniform (002)‐oriented deposition. At the cathode, IL cations immobilize polyiodides through strong coordination, suppressing the shuttle effect and enhancing redox kinetics. In this review, we systematically discuss the fundamental properties of ILs and their specific effects on both electrodes in ZIBs. We also summarize recent progress in advanced characterization techniques and molecular simulations that provide insights into interfacial processes and solvation structures. Finally, we outline remaining challenges and future directions, including cost‐effective IL synthesis, low‐temperature operation, and practical device integration. This review aims to offer theoretical guidance and design principles for developing high‐performance, long‐life ZIBs through ILs electrolyte engineering.