First-principles study of native point defects in LiNi1/3Co1/3Mn1/3O2 and Li2MnO3

Abstract

We have studied native point defects in the layered oxides of LiNi_1/3Co_1/3Mn_1/3O₂ and Li₂MnO₃, the promising cathode materials for rechargeable Li-ion batteries for the application of high lithium capacity, by performing first-principles calculations. Through the calculations of formation energies for native point defects in LiNi_1/3Co_1/3Mn_1/3O₂, it was found that the Ni vacancy and the Li_Ni antisite are the most dominant defects, which shows a good agreement with previous experiments. Contrary to the previous experimental analysis, however, the Ni_Li antisite defect is not dominant, even though both Ni and Li ions have a similar ionic radius. In Li₂MnO₃, the Li_Mn antisite defect is dominant under the O-rich and Mn-poor condition. In contrast, the Mn_Li antisite, the Li vacancy in the Li layer, and the oxygen vacancy are dominant at the chemical potential of the boundary in equilibrium with Li₂O. To enhance the migration of Li ions for achieving high power, the experimental syntheses of LiNi_1/3Co_1/3Mn_1/3O₂ under the Ni-rich condition and Li₂MnO₃ under O-rich and Mn-poor condition were suggested. For Li₂MnO₃ suffering from poor electronic conductivity, it was found that the electronic conductivity can be increased by p- and n-type extrinsic doping under the O-rich and Mn-poor condition and the chemical potential of the boundary coexisting with Li₂O, respectively, without losing the Li ion conductivity.