Preparation and properties of LiCoyMnxNi1−x−yO2 as a cathode for lithium ion batteries

The preparation of LiCoyMnxNi1−x−yO2 from LiOH·H2O, Ni(OH)2 and γ-MnOOH in air was studied in detail. Single-phase LiCoyMnxNi1−x−yO2 (0less-than over equal toyless-than over equal to0.3 and x=0.2) is obtained by heating at 830–900°C. The optimum heating temperatures are 850°C for y=0–0.1 and 900°C for y=0.2–0.3. Excess lithium (1less-than over equal tozless-than over equal to1.11 for y=0.2) and the Co doping level (0.05less-than over equal toyless-than over equal to0.2) do not significantly affect the discharge capacity of LizCoyMn0.2Ni0.8−yO2. The doping of Co into LiMn0.2Ni0.8O2 accelerates the oxidation of the transition metal ion, and suppresses partial cation mixing. Since the valence of the manganese ion in LiMn0.2Ni0.8O2 is determined to be 4, the formation of a solid solution between LiCoyNi1−yO2 and Li2MnO3 is confirmed.