The compounds Li(4-x)/3Mn2(1-x)/3CoxO2 (0 < x < 0.5) were prepared by the sol-gel technique. X-ray diffraction patterns of these compounds were identified as alpha-NaFeO2 type layered structure, though some super-structure lines, related to the ordered array of Li and transition metal ions in the transition metal layer, were observed. The magnetic susceptibility exhibited an antiferromagnetic transition around 40 K for x < 0.2, however the specimens with x > 0.3 had no magnetic transition. The magnetic percolation may explain these magnetic variations. The electrochemical performances were evaluated for the compound of x=0.5, and it was seen that the electrochemical properties were sensitive to the potential window. Additionally, it was also found that the discharge capacity strongly depended on the preparation temperature; it took a maximum value at the preparation temperature of 900 degrees C. The discharge capacity is sensitive not only to the cation mixing degree but also to the particle size. (c) 2006 Elsevier B.V. All rights reserved.