Topologically protected oxygen redox in a layered manganese oxide cathode for sustainable batteries

Manganese could be the element of choice for cathode materials used in large-scale energy storage systems owing to its abundance and low toxicity levels. However, both lithium- and sodium-ion batteries adopting this electrode chemistry suffer from rapid performance fading, suggesting a major technical barrier that must be overcome. Here we report a P3-type layered manganese oxide cathode Na0.6Li0.2Mn0.8O2 (NLMO) that delivers a high capacity of 240 mAh g−1 with outstanding cycling stability in a lithium half-cell. Combined experimental and theoretical characterizations reveal a characteristic topological feature that enables the good electrochemical performance. Specifically, the -α-γ- layer stack provides topological protection for lattice oxygen redox, whereas reversibility is absent in P2-structured NLMO, which takes an -α-β- configuration. The identified new order parameter opens an avenue towards the rational design of reversible Mn-rich cathode materials for sustainable batteries. Favoured cathodes for batteries should include abundant and redox-active elements, such as manganese. Here the authors report a Na0.6Li0.2Mn0.8O2 cathode design featuring a unique layer stacking sequence that provides topological protection to oxygen redox to overcome the performance fading.