With first-principles DFT calculations, the interaction between Li and carbon in graphene-based nanostructures was investigated as Li was adsorbed on graphene. It was found that the Li/C ratio of less than 1/6 for the single-layer graphene was favorable energetically, which could explain what was observed in Raman spectrum reported recently. In addition, it was also found that the pristine graphene could not enhance the diffusion energetics of Li ion. However, the presence of vacancy defects could increase the ratio of Li/C largely. With double-vacancy and higher-order defects, Li ion could diffuse freely in the direction perpendicular to the graphene sheets and hence boost the diffusion energetics to some extent.

Adsorption and Diffusion of Li on Pristine and Defective Graphene. Fan, X., Zheng, W.T., Kuo, J.L.: ACS Applied Materials and Interfaces, 2012, 4[5], 2432-8