Synergistic doping chemistry enable the cycling properties of single-crystal Ni-rich cathode for lithium-ion batteries

Nickel-rich cobalt-low layered oxides have attracted much attention as positive electrode materials for high-energy lithium-ion batteries due to their high capacity and low cost, but their inherent stress accumulation and severe cationic mixed reactions will deteriorate the cycling performance. Herein, the nickel-rich single-crystalline LiNi_0.90Co_0.06Mn_0.04O₂ cathode material doped with W and Mg (NCM-WM) has been fabricated to overcome its structure degradation issues. It can be found that the Li/Ni cation mixture can be suppressed by the introduction of Mg²⁺ into Li⁺ situs and the replacement of transition metal ions by W⁶⁺. Meanwhile, the co-doing strategy synergistically depresses the irreversible H2-H3 phase transition to weaken the internal stress, and employs the heteroatoms as the pillar ions to prevent layer structure collapse. In addition, the reduced particle size induced by the W⁶⁺ and increased free electron resulted by Mg²⁺ can cooperatively improve the migration kinetics of ions and electrons in the process of cycling. As expected, the above advanced effects result in the prominent cycling properties (capacity retention of 86.7 %, 150 cycles, 2C) of the designed Ni-rich electrode materials. These results demonstrate that the co-doped design is a greatly effective strategy to reinforce the cycling performance of Ni-rich single-crystalline materials.