Molten salt in-situ exfoliation of graphite to graphene nanoplatelets applied for energy storage

Abstract

The in-situ exfoliation of graphite in molten NaCl–KCl salt at 750 °C yielded a homogeneous composite, from which graphene nanoplatelets (GnP) could be easily and completely separated. The GnP product displayed relatively large-size particles (12 μm, TEM, SEM, laser diffraction) and low defect density (Raman, XPS), indicating the superiority of the molten salt exfoliation approach over the conventional liquid-phase approach for producing GnP. The mechanism of GnP production involves the formation of cavities in the molten salt, such that impregnation of the graphite by the molten material facilitated gentle exfoliation of the graphite to GnP. The methodology for the in-situ production of GnP in molten salt is highly applicable in the field of thermal energy storage, where molten inorganic salts are one of the most widely used heat-transfer fluids, such as phase-change materials. In graphite-GnP-salt composite, the thermal conductivity is enhanced by more than one order of magnitude compared to the neat salt matrix, which is essential for efficient thermal energy storage applications.