Low‐Concentration Eutectic Electrolyte Enables Four‐Electron Zinc‐Iodine Batteries

ABSTRACT Four‐electron iodine cathodes () promise high‐capacity zinc‐iodine batteries, yet stabilizing the high‐valence couple has so far remained a challenge. Here, we propose a low‐concentration eutectic electrolyte that, for the first time, enables fully reversible redox chemistry at only 1 M ZnCl 2 concentration in ethylene glycol by constructing a water‐free eutectic solvation environment. At the molecular level, the eutectic electrolyte realizes dual regulation of iodine chemistry that ethylene glycol coordinates with high‐valence iodine species to suppress hydrolysis and stabilize reactive intermediates, and meanwhile, its hydroxyl groups hydrogen‐bond with I − / to inhibit polyiodide diffusion. Furthermore, ethylene glycol participates in Zn 2+ solvation and promotes the formation of an O/Cl‐rich hybrid interphase on Zn, enabling uniform deposition. The battery delivers 386 mAh g −1 at 1 A g −1 with over 5000 stable cycles, a 2.15 V stability window, and operation from −20 to 40°C. This work establishes a low‐threshold eutectic solvation strategy to unlock high‐valence iodine chemistry, offering a new electrolyte paradigm for high‐capacity zinc‐iodine batteries.