Enhancing the structural stability and alleviating voltage decay of Li1.2Mn0.6Ni0.2O2 through ZnO coating and gradient Zn doping

Cobalt–free lithium–rich manganese–based cathode materials Li 1.2 Mn 0.6 Ni 0.2 O 2 (LMNO) are regarded as a promising candidate for next generation high–energy–density lithium–ion batteries due to its high specific capacity, low cost and environmental friendliness. However, its practical application is constrained by voltage decay and capacity decay. To address these issues, a synchronous ZnO–coated and gradient Zn–doped Li 1.2 Mn 0.6 Ni 0.2 O 2 is designed and prepared via wet chemical and thermally driven diffusion methods. The ZnO coating acts as an interfacial buffer that reduces direct cathode–electrolyte contact and associated interfacial side reactions. Meanwhile, gradient Zn doping on the surface of LMNO stabilizes the surface crystal structure, thereby alleviating irreversible phase transitions and reducing the dissolution of transition metal ions (TM 2+ ). DFT calculations suggest that Zn doping promotes a more uniform electron density distribution around oxygen, which could contribute to the stabilization of lattice oxygen. Research results show that at 1 C, the discharge specific capacity of LMNO@ZnO is 239.1 mAh g −1 with a capacity retention of 89.7% after 100 cycles, compared to 209.1 mAh g −1 and 64.9% for LMNO. At 5 C, LMNO@ZnO maintains a discharge specific capacity of 129.4 mAh g −1 . These results indicate that the combined surface coating and gradient doping strategy offers a viable route toward improving the electrochemical performance of LMNO.