Lithium Intercalation in Graphene-MoS₂ Heterobilayers

Using first-principles calculations, we investigate the structural and electronic properties of lithium-intercalated graphene/MoS₂ bilayers. Three distinct phases for MoS₂ have been considered, namely 2H, 1T, and 1T’. We vary the number of Li atoms between the layers, and establish a potential energy surface which predicts the stable low-energy sites for Li binding and indicates that diffusion barriers between the sites will enable forward and reverse intercalation. Increasing the number of Li atoms, up to the maximum of 1 Li per Mo atom, decreases the energy difference between the 2H and 1T' phases. Our study shows that electron carrier doping of graphene (MoS₂) up to a maximum level of n_C = 3.6 × 10¹⁴ cm⁻² (n_MoS2 = 6.0 × 10¹⁴ cm⁻²) is energetically allowed. This carrier doping pushes the Fermi level into the conduction band of the semiconducting 2H phase. We also find evidence for interesting electronic interactions between graphene and metallic 1T’-MoS₂. This points the way for tailoring device heterostructures through varying intercalant concentration and layer polymorphs.