Binder-free all-carbon composite supercapacitors

Abstract

Carbon-based electrode materials have widely been used in supercapacitors. Unfortunately, the fabrication of the supercapacitors includes a polymeric binding material that leads to an undesirable addition of weight along with an increased charge transfer resistance. Herein, binder-free and lightweight electrodes were fabricated using a powder processing of carbon nanofibers (CNFs) and graphene nanoplatelets (GNPs) resulting in hybrid all-carbon composite material. The structural, morphological, and electrochemical properties of the composite electrodes were studied at different concentrations of GNPs. The specific capacitance (Cs) of the CNFs was improved by increasing the concentration of GNPs in the composite. A maximum Cs of around 120 F g−1 was achieved at 90 wt.% GNPs which is around 5-fold higher in value than the pristine CNFs in 1 M KOH, which then further increased to 189 F g−1 in 6 M KOH electrolyte. The energy density of around 20 Wh kg−1 with the corresponding power density of 340 W kg−1 was achieved in the supercapacitor containing 90 wt.% GNPs. The enhanced electrochemical performance of the composite is related to the presence of a synergistic effect and the CNFs establishing conductive/percolating networks. Such binder-free all-carbon electrodes can be a potential candidate for next-generation energy applications.