Synthesis and characterization of LiNixCo1-2xMnxO2 (1/3 <= x <= 1/2) electrode powders prepared by a sol-gel method were investigated. The synthesized LiNixCo1-2xMnxO2 materials with single phase and R (3) over barm layered structure were confirmed from X-ray diffraction analysis. The particle size distribution of the materials synthesized by the sol-gel process is quite uniform. Increasing the x value in the synthesized LiNixCo1-2xMnxO2 powder leads to decrease its particle size and increase its cation mixing. The average particle size for the LiNi0.375Co0.25Mn0.375O2 powder was found to be an order of 0.3-0.4 mu m. The best specific capacity of 192 mAh g(-1) was obtained for the LiNi0.375Co0.25Mn0.375O2 electrode with good capacity retention among the synthesized materials cycled at 0.1C in the potential between 3.0 and 4.5 V at room temperature. Although structural parameters of the LiNi0.375Co0.25Mn0.375O2 powder are similar to those of the LiNi1/3Co1/3Mn1/3O2 powder, its specific capacity is higher due to the increase of the stoichiometry of active site Ni. The increase of Ni and Mn content could reduce cost of the materials. It was found that the cell performance of the LiNixCo1-2xMnxO2 electrode drops dramatically and its cation mixing increases while the x value is higher than 0.4. (c) 2005 Elsevier B.V. All rights reserved.