Review of ion doping and intercalation strategies for advancing manganese-based oxide cathodes in aqueous zinc-ion batteries

Among various energy storage systems, aqueous zinc-ion batteries (AZIBs) are widely regarded as a promising option due to their high theoretical capacity, cost-effectiveness, and environmental friendliness. Similarly, manganese-based oxides (MBO), with their desirable specific capacity and eco-friendly nature, have gained popularity as a suitable cathode material for AZIBs. Nonetheless, these materials also face various challenges like poor electrical conductivity, low ion diffusion kinetics, manganese dissolution, inferior structural stability, and irreversible inert phase formation. Strategies like defect engineering, surface coating, electrolyte optimization, morphology control and compositing have been explored. Notably, ion doping and intercalation strategy has been widely applied for their easy fabrication process and effective modification effect. This review delves into the working mechanism of MBO cathodes in AZIBs, comprehensively discusses the existing challenges, and elucidates the modification mechanisms aimed at enhancing electrochemical performance through ion doping and intercalation. Some recommendations and outlooks are also provided for future research at the end.