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

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 Li₄Mn₅O₁₂ 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.