Abstract: The work reported in this paper is on LiNi_0.8Co_0.2O₂ cathode material for lithium-ion batteries applications. A high-density precursor, Ni_0.8Co_0.2(OH)₂, was prepared first by concurrent co-precipitation using nickel sulfate, cobalt sulfate and sodium hydroxide as raw materials. The cathode material was made by high temperature solid state reaction in an air environment. The s as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and constant current electrochemical test (ECT), and the impact of sintering time on the structure, surface morphology and electrochemical properties was investigated. The LiNi_0.8Co_0.2O₂ sample made with n(Li)∶n(Ni+Co)=1.13∶1 and sintered in the air at 700 ℃ for 9 h and then 750 ℃ for 12 h shows optimal electrochemical performance, giving an initial discharge capacity of 153.0 mA·h/g, a capacity of 150.7 mA·h/g at 20th discharge and a capacity retention so high as 98.5% at the rate of 0.5 C from 2.7 V to 4.3 V. These results demonstrate excellent cyclic stability of the material and good potential for use as the cathode material of high power density power batteries.

Key words: lithium-ion batteries, cathode material, LiNi0.8Co0.2O2, air atmosphere, co-precipitation method, solid state synthesis, electrochemical properties