Unlocking High-Performance Four-Electron Zinc-Iodine Batteries through Halogen Bonding Inversion and Non-Identical-Frequency Molecular Vibrations

The activation of four-electron transfer behavior through I^-/I⁰/I⁺ conversion reactions is crucial for the development of high-energy-density zinc-iodine batteries (ZIBs) but is hindered by the rapid hydrolysis of I⁺ in protic solvents. Theoretically, the directionality and modifiability of halogen bonds (XBs) can be used to regulate the hydrolytic disproportionation of I⁺. Given that the conventional coordination configuration is not applicable because of the locking of the XB donor (I⁺), the inversion of the coordination configuration to establish a charge distribution preanisotropy (σ-holes) and thus realize XB-stabilizing electron-scale coordination is vital for breaking down the barriers existing in protic solvents. To counteract external environmental disturbances, the cohesive energy differentiation based on the Hansen parameter creates the non-identical-frequency molecular vibrations of additives with water. Herein, an electrolyte additive (chloroacetonitrile, ClAN) with these advantages enabled the redox coupling of I^-/I⁰/I⁺ at a very low salt concentration (4 molar kg^-1). The corresponding ZIB exhibited a specific discharge capacity of 175.7 mA h g^-1 after 4000 cycles at 2 A g^-1 and showed an extremely high specific capacity at high rates (133.1 mA h g-1 at 50 A g^-1). This work establishes a generalized framework and new horizons for halogen batteries with multiple electron transfers. © 2025 Wiley-VCH GmbH.