Organo-interhalogen chemistry enables high-voltage bromine redox for stable zinc batteries

Abstract

High-voltage Br₃⁻/Br⁺ redox offers promise for energetic aqueous Zn batteries, yet its reliance on Cl⁻-concentration usually causes severe Zn pitting and battery decay. Herein, we initiate an organo–interhalogen pathway to fast and stable Br₃⁻/Br⁺ redox, eliminating the Cl⁻-concentration reliance. Chloroacetone (CA), as an organic interhalogen bonding receptor, efficiently binds the activated Br⁺ intermediate, forming a stable organo–interhalogen adduct. Compared with the conventional Cl⁻-mediated pathway, this new pathway simultaneously lowers the Br₃⁻/Br⁺ redox barrier and reduces the axial σ-site activity of interhalogens. Additionally, CA raises the Cl₂ evolution reaction (CER) potential of the electrolyte and averts Zn pitting. Consequently, a Zn‖TBABr₃ battery leveraging cascaded Br⁻/Br₃⁻/Br⁺ conversion exhibits a high specific capacity (508 mAh g⁻¹) and dual plateaus (Br₃⁻/Br⁺: 2.0 V; Br⁻/Br₃⁻: 1.7 V). With PEG 200 as an electrolyte co-solvent, a lifespan of over 1000 cycles, a high-rate capability of up to 10 A g⁻¹ and high energy/power densities (848 Wh kg⁻¹/19.7 kW kg⁻¹) are further achieved. This work establishes a feasible organo–interhalogen pathway to unlock multi-electron halogen redox for high-energy aqueous batteries.