Density functional theory guidance on rare earth doping-inhibition of lattice oxygen evolution in lithium-rich layered manganese oxide materials

Lithium-rich manganese layered oxide (LLMO) materials are one of the key materials for high energy density lithium ion batteries, but the loss of lattice oxygen during cycling leads to the increase of lithium ion transport resistance and the deterioration of material properties. In this study, density functional theory is used to calculate the formation energies and doping sites of 13 rare earth-doped LLMOs. Rare earth elements tend to occupy the Co site in the LiMO2 phase and screen out Yb, Lu, etc. as the higher-order dopant. The theoretical screening is verified by synthesizing Li1.2Ni0.133Co0.123Mn0.533RE0.01O2 (RE=La, Ce, Nd, Eu, Tm, Yb and Lu) cathode materials. Compared with undoped materials, the doping effect of heavy rare earth elements is better than that of light rare earth elements, which is consistent with the calculation results. Among them, Yb doping has the lowest formation energy, which enhances the TM-O hybridization. The evolution of lattice oxygen is significantly reduced and the material exhibits excellent electrochemical performance (the first discharge capacity is as high as 342.5 mAh g(-1)). These results provide a reference for the preparation of rare earth doped lithium-rich layered cathode materials with high capacity and stability. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study utilized density functional theory to investigate the formation energies and doping sites of 13 rare earth-doped LLMOs. It was found that heavy rare earth elements exhibit better doping effects compared to light rare earth elements. Yb doping, with the lowest formation energy, enhances TM-O hybridization and significantly reduces the evolution of lattice oxygen, leading to excellent electrochemical performance.