▎ 摘　　要

CO2-expanded organic solvents are considered to be the most promising candidates for the liquid-phase exfoliation (LPE) of graphene. Understanding the effect of the initial graphite size on LPE efficiency is important for the production of higher-quality few-layer graphene. The mechanisms involved in the exfoliation process were studied in three different sizes of expanded graphene flakes (with areas of 1.05, 3.78, and 17.92nm(2)) in the CO2-expanded solvent by means of molecular dynamics simulations. The simulation results verified at a molecular level that the graphene sheets obtained from small-size expanded graphene have fewer layers than those obtained from large-size expanded graphene. Faster solvent intercalation during the exfoliation process was observed with smaller-sized expanded graphene. Furthermore, an intact solvent monolayer between the graphene sheets and a larger desorption energy barrier with a small expanded graphene size ultimately leads to the rapid formation of a stable and less defective super-burger-like conformation. This enables exfoliation with a considerable yield of mono- or few-layered graphene sheets. We believe that the results reported in this work provide the guidelines for obtaining a high yield of mono- or few-layered graphene by exfoliation with a large sheet area in the CO2-expanded solvent and provide theoretical clues for controlling the size of the graphene sheets produced by exfoliation.