Theoretical calculation of electronic structure and X-ray absorption near-edge structure of cathode materials for Li ion batteries

First principles calculations were performed on the electronic structure, chemical bonding and X-ray absorption near edge structure (XANES) of various lithium transition metal oxides. In the electronic structure using the discrete variational Xα method (DV-Xα), chemical bonding is changed by Li deintercalation. Li is found to be nearly ionized in LiMO2 and strong covalent bonding between M and O is noted. The larger the difference of covalency between cation and nearest neighbor anion when Li intercalated/deintercalated is, the lower the voltage calculated by Vienna Ab Initio Simulation Package (VASP) is. By calculations of transition state, we reproduce the characteristics of the spectra as well as the chemical shifts and the origin of peaks appearing in the experimental XANES spectra is interpreted in terms of orbital interactions using bond overlap population diagrams.