Li insertion into V6O13 battery cathodes studied by soft x-ray spectroscopies

Changes in the electronic structure of ${\mathrm{V}}_6{\mathrm{O}}_{13}$ on lithium-ion insertion into battery cathodes were studied by soft x-ray absorption (SXA) spectroscopy and resonant soft x-ray emission (SXE) spectroscopy. SXA and resonant SXE spectra were recorded ex situ for cycled battery cathodes discharged to different potentials corresponding closely to distinct lithiated stages $({\mathrm{Li}}_x{\mathrm{V}}_6{\mathrm{O}}_{13}\text{,x=0,1,…,6).}$ Large systematic changes were observed in the vanadium and oxygen x-ray spectra, reflecting the effects of electrochemical reduction associated with the Li-ion insertion. Spectral shape analysis indicates that a large fraction of the vanadium ions have been reduced to ${\mathrm{V}}^{\text{3+}}$ ions for the highest degree of lithiation, $\text{x=6.}$ Nevertheless, further lithiation may be possible, in view of the linear development of the vanadium and oxygen bands on charge uptake.