LiNi0.74Co0.26-xMgxO2 cathode material for a Li-ion cell

The effects of a partial substitution of Co with Mg in LiNi0.74Co0.26-xMgxO2 material on its X-ray structure, electrochemical properties, and thermal stability in the charged (delithiated) state have been studied. Results showed that the lattice parameters a and c as well as the cia ratio increased as the x-value increased. The DSC exothermic peak of the charged electrode LiNi0.74Co0.26-xMgxO2 (when x = 0.04 or higher) was significantly smaller than that of LiNi0.74Co0.26O2, indicating that the Mg substitution improved its thermal stability. The improvements of both the electrochemical and thermal stability are possibly due to the reduced cation mixing and improvement of layer structure by the expansion of the c-axis.