Abstract: The cathode material for lithium batteries Li_1.15-xN_i0.₃₃Co_0.33Mn_0.33O_2+δwith good electrochemical properties was synthesized by the sol-gel method. The synthesis mechanism was examined via X-ray diffraction, X-ray photoelectron spectra, scanning electron microscopy, thermogravimetric analysis and difference thermal analysis and cyclic voltammetry. Li_1.15-xN_i0.₃₃Co_0.33Mn_0.33O_2+δexhibited initial specific discharge capacity of 190mAh/g and tenth of 180mAh/g at 2.5～4.5V by current density of 0.1 mA/cm². That Li_1.15-xN_i0.₃₃Co_0.33Mn_0.33O_2+δmain phase can be obtained as low as 400℃ is attributed to the short distance among lithium, manganese, cobalt and nickel formed in precursor prepared by the citric acid gel process. The crystallinty and layered structure were improved by sintering at high temperature. The solid solution formation could be a three-step process: (1) formation of small particle Li-Ni-Co-Mn-O solid solution main phase at lower temperature; (2) decomposition of residual lithium carbonate; (3) bulk diffusion of lithium oxide from exterior into the bulk of Li-Ni-Co-Mn-O solid solution.

Key words: Li1.15-xNi0.33Co0.33Mn0.33O2+δ, sol-gel method, reaction mechanism