Enhanced electrochemical performance of Na_0.9Li_0.1Mn_0.9O₂ by MgO coating for sodium-ion batteries

O3-Na_0.9Li_0.1Mn_0.9O₂/MgO compounds were synthesized as cathode materials for sodium-ion batteries by high-temperature solid-state and wet chemical methods. The effects of different MgO coating amounts on the crystal structure, surface morphology, and electrochemical properties of O3-Na_0.9Li_0.1Mn_0.9O₂ materials were investigated. The results showed that the appropriate amount of MgO coating had a positive effect on the cyclic and rate performance. This is attributed to the fact that the MgO layer inhibits harmful side reactions of the electrode material with the electrolyte, which improves structural stability and reduces interfacial transport resistance. Meanwhile, the doped Mg²⁺ can effectively inhibit the irreversible phase transition. Particularly, the sample of Na_0.9Li_0.1Mn_0.9O₂ coated with 2 wt% MgO exhibits high initial discharge specific capacity of 164.9 mAh/g at 0.1C and maintains 83.7% capacity retention after 100 cycles at 0.1C, suggesting enhanced electrochemical performance. Therefore, the surface modification of the material by MgO provides a new strategy for designing high-rate cathode materials for SIBs.