Sulfur‐Assisted Surface Modification of Lithium‐Rich Manganese‐Based Oxide toward High Anionic Redox Reversibility

Abstract Energy storage via anionic redox provides extra capacity for lithium‐rich manganese‐based oxide cathodes at high voltage but causes gradual structural collapse and irreversible capacity loss with generation of Oⁿ⁻ (0 ≤ n < 2) species upon deep oxidation. Herein, the stability and reversibility of anionic redox reactions are enhanced by a simple sulfur‐assisted surface modification method, which not only modulates the material's energy band allowing feasible electron release from both bonding and antibonding bands, but also traps the escaping Oⁿ⁻ via an as‐constructed SnS_2−x−σO_y coating layer and return them to the host lattice upon discharge. The regulation of anionic redox inhibits the irreversible structural transformation and parasitic reactions, maintaining the specific capacity retention of as‐modified cathode up to 94% after 200 cycles at 100 mA g⁻¹, along with outstanding voltage stability. The reported strategy incorporating energy band modulation and oxygen trapping is promising for the design and advancement of other cathodes storing energy through anion redox.