Structural stability and ion migration of Li2MnO3 cathode material under high pressures

Abstract

Some special fields, such as deep-sea exploration, require batteries and their electrode materials to withstand extremely high pressure. As the cathode material has the highest energy density, Li-excess Mn-based materials are also likely to be utilized in such an environment. However, the effect of pressure on the crystal structure and migration barrier of this kind of material is still not clear at present. Therefore, in this study, we investigate the properties of the matrix material of Li-excess Mn-based material, Li2MnO3, under high pressure. The equation of state, bulk modulus, and steady-state volume of Li2MnO3 are predicted by the method of first principles calculation. The calculations of unit cells at different pressures reveal that the cell parameters suffer anisotropic compression under high pressure. During compression, Li–O bond is more easily compressed than Mn–O bond. The results from the climbing image nudged elastic band (CINEB) method show that the energy barrier of Li+ migration in the lithium layer increases with pressure increasing. Our study can provide useful information for utilizing Li-excess Mn-based materials under high pressure.