First-Principles Calculation Study on the Structure and Electrochemical Properties of Nb- and V-Doped Ni-Rich Ternary (NCM911) Cathode Materials

Nickel-rich ternary layered cathodes for lithium-ion batteries are promising and widely used materials, with high energy density and discharge capacity. However, nickel-rich cathodes present serious mixing and structural instability. At present, doping is one of the most effective modification methods. We studied the modification of high-valence elements Nb5+ and V5+ doped in LiNi0.89Co0.055Mn0.055O2 (NCM911) through first-principles calculation and analyzed the structure and electrochemical mechanism of the material at the atomic level. It was found that the electrochemical performance of the doped material was improved. The dopants effectively shortened the bandgap of the material and inhibited the formation of oxygen vacancies. In addition, through the calculation of Li+ diffusion paths, V doping more efficiently reduced the diffusion barrier of Li+ [similar to 15% decrease in oxygen dumbbell hop (ODH) path and similar to 40% decrease in tetrahedral site hop (TSH) path], which is conducive to the diffusion of Li+. This theoretical study provides insights into the dopants of high-valence transition metals and is a necessary complement to experimental research.