Layered LiNi0.5-xCr2xMn0.5-xO2 materials with various Cr contents have been successfully prepared by a coprecipitation method. X-ray diffraction, scanning electron microscopy (SEM), Brunauer-Emmett-Teller method, and charge-discharge tests have been adopted to study the physical and electrochemical performance of LiNi0.5-xCr2xMn0.5-xO2. A single- phase product was obtained in the range of 0 <= 2x <= 0.1 in LiNi0.5-xCr2xMn0.5-xO2, although some impurity phases were found for 2x >= 0.2. SEM observation shows that Cr doping in LiNi0.5-xCr2xMn0.5-xO2 has obviously changed the morphologies of its particles and the agglomeration of primary particles becomes tighter with the increasing of Cr contents. The specific surface area of LiNi0.5-xCr2xMn0.5-xO2 decreases linearly from 5.8 m(3)/g (2x = 0) to 0.34 m(3)/g (2x = 0.2) with the addition of Cr. Moreover, we have found that the presence of Cr can greatly improve the density of LiNi0.5-xCr2xMn0.5-xO2 powder. The electric conductivity of LiNi0.5-xCr2xMn0.5-xO2 abruptly increases with the addition of a small amount of Cr (2x <= 0.1) and decreases with the further increase of Cr contents (2x >= 0.2). An electrochemical test indicates that the addition of a small amount of Cr can improve the cycling performance of LiNi0.5-xCr2xMn0.5-xO2, although it has no significant effects on the reversible capacity of the sample. However, the electrochemical performance of LiNi0.5-xCr2xMn0.5-xO2 becomes worse when the content of Cr further increases (2x >= 0.2). (c) 2005 The Electrochemical Society.