The effect of Cr-doping on the structural, physical and electrochemical properties of Li2MnO3 and LiNi0.5Mn0.5O2 is reported. The formation of the solid solution and local distortion of the structure with the increase in Cr doping (0.7Li(2)MnO(3)- 0.3LiNi(0.5)Mn(0.5)O(2)) was confirmed respectively, by X-Ray diffraction and Raman spectroscopy. Morphological investigations and elemental mapping showed the formation of primary particles in the range 0.5-1.0 mu m and homogeneity, respectively. Electrochemical measurements on the materials were carried out in different voltage ranges and temperatures. Structural transformation of the material from layered to spinel symmetry has been observed with cycling in case of the samples with low Li2MnO3 content (0.3Li(2)MnO(3)-0.7LiNi(0.5)Mn(0.5)O(2)). Cr acted as a catalyst to enhance the activation of the material with high Li2MnO3 content. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.059204jes] All rights reserved.