Structure and electrochemical behaviour of LiNi0.4Mn0.4Co0.2O2 as cathode material for lithium ion batteries

• A small amount of cation disordered in LiNi0.4Mn0.4Co0.2O2 can be achieved using conventional solid state synthesis by preparing at 950 °C in O2.
• Combined X-ray diffraction data with Rietveld analysis were used to quantify the amount of cation disorder.
• The galvanostatic cycling studies of LiNi0.4Mn0.4Co0.2O2 showed the initial charge–discharge capacity value of ~ 180 mAh g− 1 and ~ 145 mAh g− 1, respectively, at a constant current density of 15 mA g− 1.

The layered rock-salt LiNi0.4Mn0.4Co0.2O2 that formed the α-NaFeO2 structure were synthesised using conventional solid state method between 800 and 950 °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 °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 ~ 180 mAh g− 1 and ~ 145 mAh g− 1, respectively, while the initial charge and discharge capacity for sample prepared at 950 °C in air was ~ 140 mAh g− 1 and ~ 105 mAh g− 1, respectively.