First-principles calculations for Li adatom diffusion on a graphene surface through a V6 defect partly terminated by hydrogen atoms

Abstract

Using first-principles electronic state calculations we investigated the adsorption of a Li atom on graphene with a V6 defect terminated by H atoms at the edge. We found that a Li atom is more stably adsorbed on a defect site with fewer H atoms since the energy gain depends on the electrostatic interaction between C atoms with a dangling bond and the Li ion. We further estimated the diffusion of a Li atom through a V6 defect. We found that more than half of the H termination configurations allow a Li atom to go through them. On the other hand, Li atoms are easily trapped and aggregated on the defect sites. Even though it is difficult for a Li atom trapped in a defect to escape from the trap site by itself, it can diffuse via exchange diffusion with a reasonable activation barrier of less than 1 eV. We expect that the mechanism of diffusion would be applicable to larger vacancy defects/holes on graphene, and they will affect the diffusion of Li atoms.