Factors Affecting the Exfoliation of Graphite Intercalation\nCompounds for Graphene Synthesis

Abstract

We investigate the mechanism of the\nintercalation-aided exfoliation\nof graphite using van der Waals force-corrected density functional\ntheory (DFT) calculations. From a comparative study on various intercalation\nsystems, we find that, depending on the intercalant species, the exfoliation\nenergies vary significantly, not only due to the size of intercalants\nbut also due to interactions with the host graphite. While it is generally\nperceived that an expanded interlayer distance with intercalants weakens\nthe binding between graphene layers, as the van der Waals forces decrease,\nthe calculations reveal that the intercalation of electronegative\nor electropositive intercalants (e.g., Li, K, F, Cl, and Br) result\nin a 1.5–5-fold higher exfoliation energy than pristine graphite\ndue to additional binding forces from charge transfer between intercalants\nand graphene layers. Furthermore, we demonstrate that this additional\nbinding force could be manipulated with cointercalation or neutral\nintercalants, which hints at effective exfoliation strategies with\ngraphite intercalation compounds. This theoretical study broadens\nour understanding of the mechanism underlying graphite exfoliation\nand will facilitate development of more effective exfoliation strategies\nfor other related layered materials.