Characteristics and electrochemical performance of cathode material Co-coated LiNiO2 for Li-ion batteries

Spherical Ni(OH)2 powder coated with Co(OH)2 as raw material was mixed with LiOH to synthesize cathode material for lithium ion battery by using solid-state reaction. After sintered at temperature above 600 °C, a solid solution with layer structure was formed. The result of XPS shows that it is a concentration gradient material with higher cobalt content at the surface, and the gradient decreases with increasing sintering temperature from 650 to 750 °C. This new gradient material, called as Co-coated LiNiO2, exhibits excellent electrochemical performances for the cathode of Li-ion batteries in comparison with LiNiO2 and Co-doping LiNiO2. The discharge capacity of Co-coated LiNiO2 is over 180 mA · h/g and capacity decay per cycle is less than 0.07% when Co-coated LiNiO2 consisting of 92% nickel and 8% cobalt was sintered at the temperatures between 650–670 °C. Though initial discharge capacity could be increased with higher sintering temperature, the cycle life would be reduced.