First-principles investigation on extraction of lithium ion from monoclinic LiMnO2

Changes with Li extraction in the crystal structure and electronic structure of monoclinic LiMnO2 have been investigated by first-principle calculations using spin-polarized generalized gradient approximation method. It is found that the Li extraction has changed the oxidation state of Mn ion from 3+ to 4+ and thereby induced a phase transition from the monoclinic structure to rhombohedral symmetry, which opens channels for the migration of Mn ions from their own octahedral sites to the interlayer Li vacancies. It is the migration of Mn ions that responds for the phase transition to a spinel-like structure and the severe capacity loss during the electrochemical cycles of monoclinic LiMnO2.

Band structures of monoclinic LiMnO2 (a) and its Li-extracted form (b), which reveals the phase transition mechanism in this material with Li extraction.Figure optionsDownload as PowerPoint slide