Bilateral Nitrogen Interface Chemistry for Dendrite-Free Zinc–Iodine Batteries with Enhanced Four-Electron Redox Activity

Aqueous zinc–iodine (Zn–I2) batteries, owing to their compelling combination of environmental friendliness, cost-effectiveness, and enhanced safety features, are regarded as promising candidates for large-scale energy storage systems. Nevertheless, the limited I2/2I– two-electron redox chemistry and nonuniform Zn deposition critically impair the energy density and cycling stability of aqueous Zn–I2 batteries, hindering their practical deployment. Herein, multifunctional cyclohexylamine hydrochloride (CHAH) additive is introduced into the ZnSO4 electrolyte, which synergistically enables a dendrite-free Zn anode for extended cyclability and simultaneously activates a stable four-electron 2I+/I2/2I– redox chemistry at the I2 cathode. Combined experimental characterization and theoretical calculations reveal that the cyclohexylamine (CHA) reconstructs the Zn2+ solvation structure by displacing active H2O, while fostering a nitrogen-rich solid electrolyte interphase on the Zn anode at the same time. It suppresses parasitic reactions and enables excellent Zn plating/stripping cycling for 2150 h at 1 mA cm–2/1 mAh cm–2. Furthermore, nucleophilic amine groups in CHA act synergistically with Cl– to coordinate I+ by forming (2CHA)ICl, which improves four-electron 2I+/I2/2I– redox kinetics and achieves exceptional Zn–I2 battery performances (256.3 mAh g–1 at 10 A g–1). This bilateral nitrogen interface chemistry mechanism offers key insights into the development of high-performance Zn–I2 batteries.