The layered rock-salt LiNi0.4Mn0.4Co0.2O2 that formed the alpha-NaFeO2 structure were synthesised using conventional solid state method between 800 and 950 degrees C. The samples were prepared in oxygen and in air to compare the effects of different atmospheres on the amount of cation disorder (also known as interlayer mixing). A combined X-ray diffraction and Rietveld refinement showed that temperature and atmospheres significantly influenced the amount of cation disorder. The amount of cation disorder decreased as temperature increased disregarding the atmospheres in which the samples were prepared. In addition, the cation ordering of the samples correlates with the electrochemical properties. The sample that was prepared at 950 degrees C in oxygen possessed the lowest amount of cation disorder (3.8%) and better cycling performance compared to the sample that was prepared in air with higher cation disorder (4.2%). The initial charge-discharge capacity delivered was similar to 180 mAh g(-1) and similar to 145 mAh g(-1), respectively, while the initial charge and discharge capacity for sample prepared at 950 degrees C in air was similar to 140 mAh g(-1) and similar to 105 mAh g(-1), respectively. (C) 2015 Elsevier B.V. All rights reserved.