Recent progress in interfacial engineering strategies for Mn-based oxide cathodes in aqueous zinc-ion batteries: Mechanisms, modifications, and performance enhancement

Aqueous zinc-ion batteries (ZIBs) are competitive candidates for stable and efficient commercial energy storage systems. As one of the most studied cathode materials for ZIBs, manganese oxides have illustrated remarkable merits, such as high theoretical capacity, attractive cost efficiency, and non-toxicity. Much research has focused on the cathode–electrolyte interfacial reaction mechanisms and the cathode performance improvement through different interfacial modifications. Here, we review the recent progress in the understanding of Mn-based electrode interfaces and discuss relevant interfacial engineering strategies. First, various structures of manganese oxides (i.e., different polymorphs of MnO2, Mn3O4, MnO, Mn2O3, and Mn5O8) and mechanisms (i.e., ion insertion mechanisms, chemical reaction mechanisms, deposition-dissolution mechanisms) which extensively impact the battery's energy storage performance are presented. Subsequently, strategies for interfacial modifications, such as electrolyte design, defect engineering, coating procedures, and morphology optimization, are comprehensively discussed, with a detailed evaluation of their mechanisms and effects. Finally, this review concludes with a critical outlook on current and future interfacial studies of Mn-based cathodes, with the aim of providing practical ZIBs implementation ideas.