In Situ intercalating expandable graphite for mesoporous carbon/graphite nanosheet composites as high-performance supercapacitor electrodes.

Mesoporous-carbon-coated graphite nanosheet (GNS@MC) composites have been synthesized by the intercalation of resol prepolymer into the interlayers of expandable graphite (EG) under vacuum-assisted conditions, followed by the exfoliation of EG through in situ polymerization, the growth of resol under hydrothermal conditions, and carbonization under Ar. The GNS@MC composites exhibit enhanced capacitive performance compared to mesoporous carbon (MC), microwaved EG after thermal treatment (T-EG), and the physical mixture of MC and T-EG (MC+T-EG). In particular, the GNS@MC-35-800 composite carbonized at 800 °C, which has a graphite-nanosheet content of 35 % and a Brunauer-Emmett-Teller surface area (S(BET) ) of 432.3 m(2)  g(-1) , exhibits the highest capacitance of 203 F g(-1) at 1 A g(-1) in 6 M KOH electrolyte. Furthermore, the GNS@MC-35-800 composite exhibits a good cyclic stability with 95 % capacitance retention and a high columbic efficiency of 99 % after 5000 cycles. The energy density of the symmetric supercapacitor GNS@MC-35-800/GNS@MC-35-800 achieved was as high as 11.5 Wh kg(-1) at a high power density of 10 kW kg(-1) . This good performance is attributable to the GNSs in the GNS@MC composite facilitating electron transport owing to its excellent conductivity; moreover, the MC in GNS@MC favors the rapid diffusion of ions by providing low-resistance pathways. The GNS@MC composite may find application in high-performance energy storage and conversion devices.