Abnormal adsorption of lithium on the graphene surface of graphene/dT(H)-MoS2 heterostructures

Abstract

The graphene/MoS2 heterostructures (Gr/MoS2) exhibit excellent performance for ion batteries, such as superior stability and cyclicity for ion battery storage, and have great potentials for other applications. Lithium (Li) adsorption on/in Gr/MoS2 heterostructures exhibits advanced properties and interesting phenomena, as well as the phase engineering of MoS2. However, unified understanding for the different adsorption behaviors remains lacking, although fully understanding to the adsorption behaviors is of vital importance for their applications. In the current work, the Li adsorptions on the Gr surface of Gr/dT(H)-MoS2 heterostructures are systematically analyzed based on density functional theory calculations, and highlight the differences between Gr/H-MoS2 and Gr/dT-MoS2 for Li adsorption. To fully understand the adsorption behaviors, we perform detailed analyses from four interrelated aspects: 1) Electrostatic interactions from detailed Bader charge analysis, 2) charge density difference Δρ(z), 3) energy-level alignment between Li and the band edges of Gr, dT-, and H-MoS2, and 4) the resulted interface dipoles. We find that partial electrons in Li can pass through Gr to H-MoS2 and the origin is attributed to the weak electronic-shielding of Gr (even weaker than H-MoS2). All of the above extended analysis not only enables us to understand the abnormal adsorption of Li on the Gr surface of Gr/dT(H)-MoS2 heterostructures, but also helps guide the selection of ion battery materials. Moreover, we extend the discussion of Li adsorption to other alkali metal atoms with smaller work functions (such as: Na and K). Our work not only provides understanding to the abnormal adsorption of Li on the Gr surface of Gr/dT(H)-MoS2 heterostructures, but also helps guide the selection of ion battery materials. So, the insights from this study are important for their related applications. This paper reveals and explains an interesting abnormal adsorption phenomenon of lithium on van der Waals heterostructures of graphene and different phases of MoS2.The conclusion and insights from this work is not limited to Li (applicable at least to Na and K, also), and hence our work is helpful for establishing the surface-adsorption mechanisms of ion batteries.