Structural stability and lithium storage property of Sn_x clusters (x? 6) deposited on graphene based on first-principles calculation

First-principles calculation based on the density functional theory are performed to investigate the structural stability and lithium (Li) storage property of tin (Sn) clusters (i.e., Snx; where x is the number of Sn atoms) deposited on a graphene substrate, i.e., Snx/Gr (x <= 6). The latter is a promising candidate for anode material in a lithium-ion battery (LIB). The geometry and electronic properties of Snx clusters on graphene are systematically studied. Our results confirm that Snx clusters (x <= 4) tend to be deposited on graphene in a two-dimensional configuration parallel to the graphene plane, while Snx clusters (x >= 5) are usually deposited on graphene in a three-dimensional configuration. With the increase of the number of Sn atoms x, the charge transfer between Snx clusters and graphene decreases, and the interface binding between them weakens, resulting in a decrease in the structural stability of the Snx/Gr compound system. Furthermore, the adsorption energy of Li atoms on the Snx/Gr system are further calculated to examine the lithium storage property of Snx/Gr composites. Li atoms are preferentially stored on graphene and then adsorbed around Snx clusters. The complex synergistic effect of Snx clusters and graphene enhances the structural stability of Li adsorption. However, the structural stability of yLi-Snx/Gr system decreases with the increase of the number of Li atoms.