Mapping Structural Changes in Electrode Materials: Application of the Hybrid Eigenvector-Following Density Functional Theory (DFT) Method to Layered Li_0.5MnO₂

Abstract

The migration mechanism associated with the initial layered-to-spinel transformation of partially delithiated layered LiMnO₂ was studied using hybrid eigenvector-following coupled with density functional theory. The initial part of the transformation mechanism of Li_0.5MnO₂ involves the migration of Li into both octahedral and tetrahedral local minima within the layered structure. The next stage of the transformation process involves the migration of Mn and was found to occur through several local minima, including an intermediate square pyramidal MnO₅ configuration and an independent Mn³⁺ to Mn²⁺ charge-transfer process. The migration pathways were found to be significantly affected by the size of the supercell used and the inclusion of a Hubbard U parameter in the DFT functional. The transition state searching methodology described should be useful for studying the structural rearrangements that can occur in electrode materials during battery cycling, and more generally, ionic and electronic transport phenomena in a wide range of energy materials