A Nontoxic, High-Voltage Zinc-Bromine Battery Utilizing Multi-Oxidation-State Bromine (Br-/BrO-/BrO3-) Redox Chemistry

Abstract

Zinc-bromine batteries suffer from significant bromine gas leakage, posing serious safety hazards. This work introduces a novel Br-/BrO-/BrO3- triple redox system within alkaline zinc-bromide batteries. This system facilitates the electrochemical conversion of Br-/BrO3- to the mediator species BrO- via murexide organic chelation under alkaline conditions. The coordinated three-phase redox transition enables a multi-electron transfer mechanism, achieving a discharge plateau of 2.0 V while effectively suppressing Br2 release. Through a synergistic electrolyte design incorporating acidic substances (oxalic acid) and urea-based complexes (murexide), bromine is confined to non-volatile ionic states, effectively mitigating persistent bromine leakage. The optimized system delivers an area capacity of 2.2 mAh/cm2 and maintains 83% capacity retention over 800 cycles, demonstrating the practical viability of complete bromine containment in aqueous alkaline batteries. This system-level approach advances fundamental principles for designing multi-electron redox pairs in aqueous batteries and provides key insights into halogen-mediated reaction mechanisms relevant to electrocatalysis and environmental remediation.