Intercalation stage dependence of core electronic excitations in Li-intercalated graphite from inelastic X-ray scattering

Abstract

Li and C 1s core-electron excitation spectra of electrochemically prepared stage-II and stage-I lithiated graphite were investigated by means of inelastic X-ray scattering spectroscopy. The near-edge structure is discussed, and the spectral features are interpreted using ab initio calculations. Our results confirm the invariance of the excitation threshold for transitions from C 1s core-states to empty π∗ states upon Li intercalation for stage-I and show this invariance also occurs for the second stage of intercalation. A systematic shift of the σ∗ excitation threshold to lower energies with the Li content was observed. The Li core spectra reveal an ionic character of the intercalated Li in stage-I and in stage-II. The present results provide further valuable information for forthcoming in situ studies of lithiation/delithiation processes in graphite anodes by inelastic X-ray scattering spectroscopy.