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

Abstract

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.