The LiNi0.5-xMn0.5-xCo2xO2 (0 < x < 0.1) series was first prepared at 800 degreesC by the spray dry method. The structural and electrochemical characteristics of these compounds were also studied. The Co substitution seems to promote the formation of LiNi0.5-xMn0.5-xCo2xO2. In addition, the Co introduction in LiNi0.5Mn0.5O2 can not only reduce the cell polarization, but increase the reversible capacity. The LiNi0.5-xMn0.5-xCo2xO2 series shows an excellent cyclability and rate ability. After 50 cycles, LiNi0.425Mn0.425Co0.15O2 shows a reversible capacity of about 110 mAh g(-1) at the rate of 1 mA cm(-2) (100mA g(-1)) in 3-4.6V at room temperature and more than 140mAh g(-1) at the rate of 2 mA cm(-2) (200 mA g(-1)) at 55 degreesC. (C) 2004 Elsevier Ltd. All rights reserved.