Lithium diffusion in graphene and graphite: Effect of edge morphology

By means of density functional theory calculation that includes van der Waals (vdW) interactions, we study adsorption and diffusion of lithium in graphene, graphite and the corresponding lower-dimensional structures with different edge morphology. Because of the presence of unique edge states, the edge modified systems exhibit remarkably enhanced lithium binding energies with significantly better Li mobility. Irrespective of where the Li atom is adsorbed, for H and O-terminated graphitic systems, Li prefers to migrate towards the edge by crossing the diffusion barriers that gradually decrease toward the edge. Because of charge transfer and local environments on the edge C atoms, Li diffusion to the edge is significantly influenced in the OH-terminated systems. Our results indicate that O-terminated systems have facilitated Li diffusion compared to H and OH-terminated graphitic materials. Therefore, such systems can be considered as promising candidates for high-performance anode materials for rechargeable lithium-ion batteries with fast charge/discharge rates and high power density.