Charge polarization in partially lithiated single-walled carbon nanotubes.

Investigation of carbon/lithium interfaces is of great importance for elaboration of energy storage devices. Here, the effect of vacuum thermal deposition of lithium on single-walled carbon nanotubes (SWCNTs) is investigated by in situ X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy. From the XPS data, the composition of lithiated sample is LiC24. That corresponds to the presence of two types of carbon atoms on the SWCNT surface, namely, those located closely and far away from the adsorbed lithium. Quantum-chemical modeling of XPS valence-band spectra and calculation of atomic charges and molecular electrostatic potential map found that the former type of carbon atoms is in strong positive electric field created by lithium, whereas the Li-free SWCNT areas are charged negatively. An alternation of areas of positive potential and negative potential on the surface of partially lithiated SWCNTs can significantly affect processes in an electrochemical cell.