Extremely large, non-oxidized graphene flakes based on spontaneous solvent insertion into graphite intercalation compounds

Demand for an effective strategy for exfoliating layered materials into flakes without perturbing their intrinsic structure is growing. Herein, we introduce an effective fabrication method of large-sized non-oxidized graphene flakes (NOGFs) as a representative example of a general strategy using spontaneous insertion of exfoliating medium into a layered material. We fabricated a ternary graphite intercalation compound (t-GIC) with stoichiometry of KC24(THF)2, and analyzed its morphology and electronic structure through experimental and computational approach. Interactions between the t-GIC and aprotic organic solvents with different polarities were investigated, where a unique swelling behavior was observed with dimethyl sulfoxide (DMSO). Based on the analysis of the phenomena, we demonstrate facile exfoliation of the t-GIC in polyvinyl pyrrolidone (PVP)-DMSO solution for fabrication of highly crystalline and large-sized NOGFs. The lateral size of the NOGFs ranges over 30 μm, while the 98% having thickness below 10 layers. The NOGF film exhibits supreme electrical conductivity of 3.36 × 105 S/m, which is, to our best knowledge, the highest value for a thin conductive film made of graphene flakes.