Surface Li ⁺ /H ⁺ Exchange Engineering for Enhancing Structural Stability and Electrochemical Performance of Lithium‐Rich Manganese‐Based Layered Oxides

Abstract Lithium‐rich manganese‐based layered oxides (LRO) are promising ultra‐high‐capacity cathode materials for next‐generation lithium‐ion batteries but suffer from structural instability, capacity/voltage decay, and poor rate capability. Herein, a novel surface spinel coating strategy is proposed to address these challenges through a citric acid solution treatment followed by thermal annealing. A Li ₄ Mn ₅ O ₁₂ spinel coating layer is formed on the cathode material surface via Li ⁺ /H ⁺ exchange and structural rearrangement, while preserving the bulk‐layered structure. The spinel phase not only suppresses interfacial side reactions and lattice oxygen loss but also establishes 3D Li ⁺ diffusion channels, enhancing kinetics and surface stability. The modified cathode material exhibits remarkable electrochemical improvements with a high‐rate capacity of 205.29 mAh g ⁻¹ at 5 C, and 86.3% capacity retention after 150 cycles at 1 C, outperforming the untreated LRO. This work provides a scalable surface engineering approach to reconcile the trade‐off between high energy density and long‐cycle stability in the LRO, advancing their practical viability for high‐energy‐density batteries.