Enhancing the cycling stability of spinel LiMn2O4 via Ni-Co surface gradient Doping: Mechanisms of structural stabilization and Mn dissolution mitigation

To address the rapid capacity degradation of spinel LiMn 2 O 4 caused by Mn dissolution and Jahn-Teller distortion, this work develops a surface-engineered LiMn 2 O 4 material (LMO@NCM) through a urea-assisted homogeneous precipitation and gradient sintering strategy. The resultant gradient Ni-Co co-doped LiNi x Co y Mn 2-x-y O 4 coating synergistically combines bulk-phase doping and surface modification benefits. Systematic investigations reveal that LMO@NCM1 % delivers enhanced cycling stability with an initial discharge capacity of 119.74 mA h g −1 and 92.25 % capacity retention after 200 cycles at 1C (148 mA h g −1 ) under 25 °C, significantly outperforming pristine LMO (116.48 mA h g −1 , 84.47 % retention).Characterization results revealed that the Ni-Co gradient co-doping improved the electrode's interfacial kinetics, suppressed manganese dissolution, and mitigated side reactions between the electrolyte and the electrode, thereby significantly enhancing the battery's rate capability and cycling stability.