Effect of magnesium substitution in lithium nickel oxide -: An ab initio study

The total energy of lithiated and delithiated Mg-substituted lithium nickel oxide LiMgxNi1-xO2 has been calculated using the ab initio projector-augmented wave method implemented in the density functional theory code VASP. The lattice parameters and cell volumes obtained from the calculations are in general agreement with the experimental results (<2% error). By calculating the average cell voltage using the Nernst equation, it is observed that the Mg-substituted lithium nickel oxide possesses a higher average voltage during the deintercalation process, which also agrees with the observed experimental results. Further calculations on the charges of Li, Ni, Mg, and O in lithiated and delithiated LiMgxNi1-xO2 indicate that the substitution of Mg has more influence on the O charge. Because oxygen is oxidized more than Ni during the process of Li removal (oxidation process) and the substitution of Ni with Mg causes oxygen to be further oxidized, it can be concluded that the increase in the average cell voltage is more related to this further oxidation of oxygen resulting from the substitution of Mg. (C) 2004 The Electrochemical Society.