Spherical morphology layered Li[Ni0.5Mn0.5](1-x)CoxO2 (0less than or equal toxless than or equal to0.33) powders have been synthesized by ultrasonic spray pyrolysis method. Single phase of Li[Ni(0.5)Nn(0.5)](1-x)CoxO2 could be prepared in 0less than or equal toxless than or equal to0.33 region. Structural and electrochemical properties of the Li[Ni0.5Mn0.5](1-x)CoxO2 materials were characterized by means of powder X-ray diffraction (XRD), Rietveld refinements, and galvanostatic charge/discharge test. The discharge capacity increased linearly with the increase of Co-substituted contents. Li[Ni0.4Mn0.4Co0.2]O-2 electrode delivered a high discharge capacity over 175 mA h g(-1) between 2.8 and 4.4 V with a good capacity retention. (C) 2004 Elsevier B.V. All rights reserved.