Characterization and Synthesis Reaction Mechanism of Li_(1.15-x)Ni_(0.33)Co_(0.33)Mn_(0.33)O_(2+δ) Cathode for Li-ion Battery

The cathode material for lithium batteries Li1.15-xNi0.33Co0.33Mn0.33O2+δ with 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. Li1.15-xNi0.33Co0.33-Mn0.33O2+δ exhibited 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 Li1.15-xNi0.33Co0.33Mn0.33O2+δ main 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.