Density functional theory investigations showed that the Li + ion was stabilized at the center of hexagonal carbon ring with the distance of 1.84 from graphene surface. The potential barrier of Li+ ion diffusion on the graphene surface, about 0.32eV, was much lower than that of Li+ ion penetrating the carbon ring which was 10.68eV. When a vacancy of graphene existed, potential barrier about 10.25eV for Li+ ion penetrating the defect was still high, and the ability of the vacancy to sizing the Li+ ion was also observed. Electronic densities of states showed that the formation of a localized bond between Li atom and edge carbon of vacancy was the main reason for high potential barrier when Li + ion penetrate a vacancy. While Coulomb repulsion was the control factor for high potential barrier in case of Li+ ion penetrating a carbon ring

Diffusion of Li+ Ion on Graphene: a DFT Study. Zheng, J., Ren, Z., Guo, P., Fang, L., Fan, J.: Applied Surface Science, 2011, 258[5], 1651-5