Exploring the Electronic Structure of Graphene and Graphene Ultrathin Films with Adsorbed Lithium

Our research investigates the electronic structure of graphene and ultrathin graphene films, a topic that is gaining increasing attention. We present a novel approach to understanding the unique features of these 2D materials, not only in single layers but also in the superposition of graphene layers. We calculated and compared the geometric and electronic features of graphene and ultrathin graphene films (two and three layers) and evaluated the impact of the second and third layers on the lithium adsorption. All calculations were performed employing the density functional theory (DFT) method. Our systematic analysis of many DFT functionals revealed the most suitable for accurately describing these systems. In the electronic structure context, the films’ density of states (DOS) exhibits a noticeable feature within the valence band due to an increased contribution from 2p and 2s orbitals. This effect could be attributed to a primitive covalent interaction involving a sp2–sp3 hybridization exchange. Furthermore, lithium adsorption displayed distinct energetics on both graphene and the ultrathin film. Our findings revealed significant differences in the behaviors of ultrathin graphene films compared to monolayer graphene.