Manganese could be the element of choice for cathode materials used in large-scale energy storage systems owning 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 Na 0.6 Li 0.2 Mn 0.8 O 2 (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 stacking provides topological protection for lattice oxygen redox, whereas the reversibility is absent in P2-structured NLMO which takes a -α-β-configuration. The identified new order parameter opens an avenue towards the rational design of reversible Mn-rich cathode materials for sustainable batteries. / 32Sustainable energy applications in today's society, especially transportation and grid, require safe high-energy density lithium (Li) and sodium (Na) ion batteries with low-cost and/or abundant natural resources 1, 2 . Compared to cobalt (Co) and nickel (Ni) as the major component of commercial cathode materials, redox active manganese is the element of choice for cathode materials used in large-scale energy storage systems owning to its abundance and low toxicity levels 3 . In particular, Li/Na-rich Mn-based cathodes exhibit the excellent capacity and high potential (> 4 V vs. Li + /Li or Na + /Na), resulting from the extra lattice oxygen redox (LOR) [4][5][6][7] . However, the poor cycling stability of LOR-related processes, including voltage hysteresis and voltage fade, hampers its practical use because of the irreversible local structural transformation or the lattice oxygen loss [8][9][10] . The stability and/or reversibility of LOR is correlated significantly with the atomic structure or the local oxygen coordination environment, as elaborated by various theories, including the oxygen lone-pair states [11][12][13] , reductive coupling mechanism [14][15][16][17] , O−O dimer 18,19 , ligand-to-metal charge transfer (LMCT) 13 , and critical oxygen hole 20 theories, as well as a number of other theories [21][22][23][24][25][26] . Thus, exploring crystal structures compatible with reversible LOR in Mn-rich oxides is desirable to meet the demand for sustainable energy storage.At present, the correlation between the specific atomic structures with reversible LOR in the electrode materials has not been well established. Kang et al. 27 found that transition metal (TM) layer stacking can control the voltage decay of LOR process by comparing O2-and O3-type Li x (Li 0.2 Ni 0.2 Mn 0.6 )O 2 . Li-excess disordered (rock salt) TM oxides, such as

Loss of active materials is a critical problem of layered oxide cathodes for lithium‐ion batteries and undermines their long‐term electrochemical performance. However, the atomic‐scale outward migration mechanism of transition metals and oxygen remains elusive due to a highly localized environment at surface. Here, the robust surface reconstruction of LiNi0.8Mn0.1Co0.1O2 (NMC811) induced by artificially introduced Ni/Li antisites is reported. Using scanning transmission electron microscopy, the outward co‐migration process of nickel and oxygen ions is directly revealed at the atomic scale, finally resulting in a stable surface structure. The robust nature of this surface structure originates from the strong linear superexchange interaction between subsurface NiLi and surface Ni as supported by first‐principles calculations. An idealized subsurface structure with 13 NiLi is designed to suppress the outward migration of transition metal and oxygen ions and provide a universal lattice‐coherent surface protection strategy for layered lithium transition metal oxide cathodes.