The intercalation and diffusion of lithium ions in a bundle of carbon nanotubes were investigated using an ab initio molecular dynamics simulation method that was based upon density functional theory. It was found that lithium ions quickly penetrated into the nanotubes, and the space between neighboring nanotubes. At a low Li ion density, the Li ions tended to stay close to the nanotube ends. The Li ions were able to penetrate through the carbon nanotubes and move from one end to the other. It was also discovered that Li ions could remain between two neighboring nanotubes; offering a new approach to Li ion intercalation and storage. The Li ions located among three neighboring nanotubes had very strong adsorption potentials that were a factor of four larger than those of Li ions located along the central axis of a single-walled nanotube. This indicated that Li ions located among three neighboring nanotubes would be very difficult to remove from a nanotube bundle, suggesting that the Li storage capacity in this case was perhaps irreversible. Keeping the nanotubes apart by an appropriate distance would hinder or promote the formation of irreversible intercalation.

Intercalation and Diffusion of Lithium Ions in a Carbon Nanotube Bundle by ab initio Molecular Dynamics Simulations. B.Song, J.Yang, J.Zhao, H.Fang: Energy and Environmental Science, 2011, 4[4], 1379-84