Direct molecular orbital–molecular dynamics was applied to diffusion processes of the Li+ ion on a modified graphene surface. A graphene sheet composed of carbon, fluorine and hydrogen atoms were used as a model graphene (Li+C150H3F27, denoted by FH-graphene). The edges of graphene were terminated by fluorine (F-edge region) and hydrogen atom (H-edge region). Simulation temperatures were chosen in the range of 250 to 350K. It was found that the lithium ion diffused freely on the surface, but the ion did not approach the F-edge region of the surface. This was due to the repulsive interaction with a positive charged carbon atom where C–F bond was polarized as Cδ+–Fδ-. On the other hand, the Li+ ion approached to the H-edge region and it exited from the H-edge region. The diffusion mechanism of Li+ was considered on the basis of theoretical results.

Effects of Fluorine Atom Substitution of Graphene Edge Site on the Diffusion of Lithium Ion. H.Tachikawa, T.Iyama, H.Kawabata: Japanese Journal of Applied Physics, 2010, 49, 01AH02