Redox Mediators for Aqueous Electrolytic Zinc‐Manganese Batteries: Fundamentals and Design Criteria

Abstract

Although aqueous electrolytic zinc‐manganese batteries (AZMBs) have attracted significant attention due to their high theoretical energy density, their practical application has been hindered by the insufficient reversibility of the cathodic Mn2+/MnO2 conversion reaction. Introducing redox mediators (RMs) as electron transfer catalysts enables the conversion of electrochemically inert “dead MnO2” into active Mn2+ ions during discharging, effectively enhancing cathodic reversibility. However, the practical application of RM‐assisted AZMB systems is severely hindered by a limited understanding of the relationship between the fundamental properties of RMs and their reaction kinetics with MnO2. By applying classical Marcus theory, the correlation between the fundamental structures of RMs and their reaction kinetics is elucidated, offering a coherent explanation for the conflict between the thermodynamic and kinetic behaviors of the RM‐assisted MnO2 electroreduction process. Emphases are placed on establishing a theoretical foundation and design paradigms, including the design of organic RM molecules, construction of efficient RM‐based reaction systems, and formulation of shuttle‐free approaches, thereby designing and advancing high‐performance RM‐assisted AZMBs.