Application of soft X-ray absorption spectroscopy and two-dimensional correlation spectroscopy to the electrochemical reaction in the Li1+xV3O8/Li cell

This paper demonstrates the use of soft X-ray absorption spectroscopy (XAS) and two-dimensional (2D) correlation spectroscopy in the investigation of the mechanism of solid electrolyte interface (SEI) formation in the Li1+xV3O8 electrode surface during the first lithium insertion–extraction cycle in a Li1+xV3O8/Li cell. The XAS spectrum of the Li1+xV3O8 electrode showed that LiF forms on the electrode surface during the lithium insertion–extraction process in the Li1+xV3O8/Li cell. For the further understanding of this process, 2D correlation spectroscopy was applied to the lithium concentration (x)-dependent F K-edge XAS spectra of the Li1+xV3O8/Li system for the first insertion–extraction process. 2D XAS correlation analysis revealed that F K-edge XAS spectra are strongly influenced by the excitation of the core electron into a bound state.