Comprehensive study of tantalum doping on morphology, structure, and electrochemical performance of Ni-rich cathode materials

Due to their high specific capacity, nickel (Ni)-rich layered oxide cathode materials are considered to be promising for use as cathode materials in lithium (Li)-ion batteries. However, such materials exhibit poor cycling performance, which hinders their commercial applications. Herein, Ta bulk doping in Ni-rich layered oxide cathode materials is comprehensively analysed using experimental results and density functional theory calculations. It is observed that Ta5+ uniformly distributes in the bulk of the cathode materials. Further studies reveal that Ta prefers to enter both Li and TM sites, and when the doping amount increases Ta doped at TM site dominates. After Ta doping, the energy of the (001) facets is lowered, which thus affects the primary particle morphology, resulting in a preferential growth mode that produce elongated and radially oriented primary particles. A Ni-rich cathode material doped with 1 wt% of Ta shows the best cycling and rate performance, which indicates that a certain level of Ta doping is beneficial towards improving the structural stability and electrochemical performance of Ni-rich cathode materials.