Li-ion diffusivity and electrochemical performance of Ni-rich cathode material doped with fluoride ions

Ni-rich cathode materials with high specific capacity of ~200 mAh g−1 are suitable for use in Li-ion batteries; however, the stability and cycling properties of these materials in batteries need to be improved. Herein, a solid-state reaction method is used to prepare the Ni-rich ternary cathode (NCM) materials doped with various amounts of F dopant. The F-doping and chemical states of the prepared cathode samples are characterized using X-ray photoelectron spectroscopy. Specifically, the diffusivity of Li+ ions in the cathode samples is measured by various characterization methods. Compared to the undoped NCM sample, the F-doped cathode materials exhibit improved cycle performance owing to the strong bond of the transition metals and F and the improved Li+ ion transport behavior. However, the F-doped NCM cathode with more than an optimal amount of F shows the deteriorated LIB performance owing to the deteriorated Li+ ion transport caused by the Li/Ni antisite defects.