First Principles Modeling of Core-Level Spectroscopy for Anionic-Redox Active Cathode Materials

X-ray core level spectroscopies, such as x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS), have emerged as powerful tools to characterize electronic structure of battery materials before and after charge. Ab initio calculations can complement experimental measurements to assist understanding of electronic and structural evolution of battery materials during cycling. Here, we present first-principles modeling of lithium cathode materials during charged and discharged state. We first discuss structural changes of the cathode materials to predict accurate ground state properties that are consistent with experimental measurements. Then, by utilizing the OCEAN code, a Bethe-Salpeter equation based method to calculate core-level spectroscopies, we were able to predict accurate XAS and RIXS spectra in the oxygen K-edge, revealing the involvement of oxygen atoms in the cycling process and the changes in chemical bonding environment during charging cycles.