Lithium Intercalation in Graphene/MoS2 Composites: First-Principles Insights

As a storage material for Li-ion batteries, graphene/molybdenum disulfide (Gr/MoS2) composite has been intensively studied experimentally. However, the relevant theoretical works from first principles are lacking. In the current work, van-der-Waals-corrected density functional theory calculations are performed to investigate the intercalation of Li in Gr/MoS2 composites. Several interesting features have been revealed for the intercalated Gr/Li(n)/MoS2 composites (n = 1-9). First, the reason for the large Li storage capacity of Gr/MoS2 is found to be due to the increase of the binding energy per Li atom with the increasing number of intercalated Li atoms besides the large space in Gr/MoS2 for Li-atom intercalation. Second, the band-gap opening of Gr is found. The band gap is enlarged with the increasing number of intercalated Li atoms, up to 160 meV with nine Li, suggesting an efficient way to tune the band gap of graphene. Third, the Dirac cone of Gr is always preserved for different numbers of ionically bonded Li atoms