A study on the synthesis from Li2CO3, NiO and Co3O4 and the electrochemical properties of cathode materials LiNi1−yCoyO2 for lithium secondary battery

LiNi1−yCoyO2 was synthesized by the solid-state reaction method using Li2Co3, NiO and Co3O4 as starting materials, and their electrochemical properties are investigated. LiNi1−yCoyO2 (y = 0.1, 0.3 and 0.5) calcined at 750, 800 and 850 °C had the α-NaFeO2 structure of the rhombohedral system (space group; R3¯m). The particles become larger, on the whole, as the synthesizing temperature and the value of y in LiNi1−yCoyO2 increase. LiNi0.7Co0.3O2 calcined at 800 °C has the highest first discharge capacity (154 mA h/g) and LiNi0.7Co0.3O2 calcined at 750 °C exhibits the best cycling performance (the discharge capacity at n = 10 is 97.7% of the first discharge capacity). The better the crystallinity of the samples is, the higher the discharge capacity fading rate becomes.