  We discuss how x-ray Compton scattering spectra can be used for investigating
the evolution of electronic states in cathode materials of Li batteries under
the lithiation/delithiation process. In particular, our analysis of the Compton
spectra taken from polycrystalline LixCoO2 samples shows that the spectra are
dominated by the contribution of the O-2p redox orbital. We identify a distinct
signature of d-orbital delocalization, which is tied directly to the
conductivity of the material, providing a descriptor based on Compton spectra
for monitoring the lithiation range with improved conductivity and kinetics for
electrochemical operation. Our study demonstrates that Compton scattering
spectroscopy can provide a window for probing complex electronic mechanisms
underlying the charging and discharging processes in Li-battery materials.
