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

The preparation of LiCoyMnxN1-x-yN1-x-yO2 from LiOH . H2O, Ni(OH)(2) and ga mma-MnOOH in air was studied in detail. Single-phase LiCoyMnxN1-x-yO2 (0 le ss than or equal to y less than or equal to 0.3 and x = 0.2) is obtained by heating at X30-900 degrees C. The optimum heating temperatures are 850 deg rees C for y = 0-0.1 and 900 degrees C for y = 0.2-0.3. Excess Lithium (1 l ess than or equal to z less than or equal to 1.11 for y = 0.2) and the Co d oping level (0.05 less than or equal to y less than or equal to 0.2) do not significantly affect the discharge capacity of LizCoyMn0.2Ni0.8-yO2. The d oping 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 s olid solution between LiCoyNit-yO2 and Li2MnO3 is confirmed. (C) 2000 Elsev ier Science S.A. All rights