Theoretical Band Structure and X-Ray Spectroscopy Calculations for Lithium Battery Materials

X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray spectroscopy (RIXS) allow for direct measurement of an atom’s electronic environment, giving insights into the mechanisms behind lithium cyclability and ionic diffusion to improve the ionic conductivity and energy density of batteries. Advancements in lower-energy XAS and RIXS have allowed for the direct measurement of the lithium K-edge in experiments, corresponding to the 2s → 2p electron transition. However, common theoretical calculations of the lithium K-edge to produce XAS and RIXS spectra have produced inaccurate simulations of the spectra due to the low number of valence electrons in lithium affecting their response to the core hole. . Using density functional theory plus Hubbard U correction (DFT+U) calculations performed using QuantumESPRESSO and Bethe-Salpeter equation (BSE) calculations performed using OCEAN, we produce theoretical XAS spectra of common lithium compounds with increased sensitivity to core-level excitations and compare them to experimental RIXS, delineating a new protocol to model the lithium K-edge and providing important information on electronic environments of the atomic species.