Tunnel‐Type Sodium Manganese Oxide Cathodes for Sodium‐Ion Batteries

Abstract Tunnel‐type sodium manganese oxide is attracting attention as a cheap and earth‐abundant cathode material for sodium‐ion batteries, offering more stable cycling performance than other layered materials due to its special structural ordering. Developments and applications in aqueous and nonaqueous electrolyte solutions are reviewed, and problems and possible solutions are discussed in detail.