Insights into degradation mechanisms and engineering strategies of layered manganese-based oxide cathodes for sodium-ion battery

Manganese-based oxides are widely regarded as highly promising cathode materials for sodium-ion batteries due to their abundant resources, low cost and high specific capacity. Especially in the P2 and O3-type structures, excellent electrochemical performance and structural stability are expected to be achieved by modulating the ratio of Mn to other transition metals. However, these materials are susceptible to phase transitions, Jahn-Teller distortions and manganese dissolution during cycling, which limits their structural stability and electrochemical performance. To solve these critical issues, researchers have proposed various material design and modulation strategies and achieved remarkable progress. This review provides a systematic summary of the current state of research on manganese-based oxides in sodium-ion batteries and offers a detailed analysis of the root causes of performance degradation in terms of material structural features, defect types and formation mechanisms. Meanwhile, the current research progress in ion doping, high entropy strategy, surface modification, and interfacial engineering is reviewed in order to explore the synergistic regulation on structural stability and electrochemical behavior. The unique advantages of these materials in terms of phase stability, rate capability and cycle life are demonstrated. Finally, this paper looks forward to the future research directions and development trends for manganese-based oxides, providing a theoretical foundation and technical support for the construction of high-performance and scalable cathode materials for sodium-ion batteries.