Application and Prospects of Ni–Mn-Based Layered Oxide Cathodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have garnered considerable research attention due to their cost-effectiveness and abundant raw materials. Among the numerous cathode materials under investigation, Ni–Mn-based layered oxides have been widely studied in recent years owing to their advantages, including high energy density and convenient sodium-ion diffusion pathways. Nonetheless, the challenges associated with these materials must be addressed, specifically, their irreversible phase transition at high voltage, which leads to rapid capacity deterioration and diminished cycling performance. Herein, we provide a comprehensive overview of the current state and progress of research on Ni–Mn-based layered oxides. Research strategies combining high capacity and long cycle life are discussed in detail. Furthermore, we offer practical insight for optimizing their components, implementing interface control, and refining their structural design. Advancements in low-temperature performance and thermal safety are also evaluated. Finally, we outline the future prospects and potential applications of Ni–Mn-based layered oxides in the context of SIBs.