First-principles study on lithium absorption in carbon nanotubes

The Li absorption energy in carbon nanotubes and local Li–C and C–C chemical bondings have been investigated using the first-principles molecular orbital methods. It is found that the Li absorption energy is larger in the Li absorption outside the nanotube than inside the nanotube as far as the nanotube diameter is small. However, the Li outside-absorption energy decreases, whereas the Li inside-absorption energy increases with the nanotube diameter. When the nanotube diameter increases more than about 0.824 nm, the Li outside-absorption energy tends to reach a value similar to the Li inside-absorption energy. It is also shown that the distinctive chemical interactions are operating between Li and C atoms and between C atoms due to the curvature of carbon sheet in the Li absorbed carbon nanotubes. Such interactions are somewhat different from those in the Li absorbed graphite with flat carbon sheet.