Recent advances for medium- and high-entropy based layered cathodes for sodium ion batteries

Sodium ion batteries (SIBs) are a promising alternative to lithium-ion batteries for large-scale energy storage due to their cost-effectiveness and enhanced safety. Layered transition metal oxides (LTMOs) represent one of the most fascinating electrode materials owing to their superior specific capacity, environmental benignity, and facile synthesis. However, they are confronted with challenges, such as irreversible phase transition, structural instability, and insufficient battery performance. Notably, entropy engineering emerges as an effective strategy to mitigate the above issues in energy storage research. This strategy aims to achieve precise composition control and optimized structure–property relationships, thereby enabling LTMOs to overcome the aforementioned limitations. This review focuses on medium- and high-entropy oxides (MEOs and HEOs), highlighting their design principles, growth mechanisms, and applications in layered oxide cathodes for SIBs. Through an in-depth analysis of electrochemical performance, phase transition behavior, and disorder structure regulation, we provide comprehensive insights into the application prospects and optimization pathways of MEO/HEO materials in advanced SIBs. Current challenges are also discussed, offering valuable insights and perspectives to overcome the performance bottlenecks of SIBs and facilitate their large-scale deployment.