Diffusion and condensation of lithium atoms in single-walled carbon nanotubes

Abstract

We have carried out theoretical investigations to explore the diffusion of lithium on the exteriors and the interiors of single-walled carbon nanotubes (SWNTs). We found that lithium can adsorb on both interior and exterior surfaces with adsorption energy around $\ensuremath{-}2.44\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. Lithium has a higher mobility with the diffusion barriers less than $0.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ on both the exteriors and interiors of SWNTs. The diffusion barriers (exo- and endohedral) of lithium depend on the radius and chirality of SWNTs. The lithium capacity trapped inside SWNTs increases with the increasing tube diameter and can be as high as $\mathrm{Li}{\mathrm{C}}_{2.6}$ in a (10,10) SWNT. These lithium atoms tend to form single- or multishelled coaxis nanotubes, together with a linear atomic chain in the axis at low temperature depending on the diameter of SWNTs, suggesting a potential way to synthesize small metal nanotubes and metal nanowires.