Nanopores created by carbon onion conductive agent providing enhanced capacitance in supercapacitors

In order to enhance the performance of supercapacitors, electrode materials and electrolytes have drawn a great deal of attention, however, there is limited research on conductive agents. Carbon onions were reported as a promising conductive agent for supercapacitor. In this paper, highly graphitized carbon onions were prepared by chemical vapor deposition using methane as carbon source and then purified with pickling - calcination - pickling method. The purified carbon onions and commercial super-P were employed as conductive agents of supercapacitors with the same proportion and dosage. Electrochemical tests reveal that carbon onion conductive agent provides an excellent electrochemical performance for supercapacitor, including high specific capacity (142.3 F/g) and relatively stable cycle stability (86.9% capacity retention after 5000 cycles). We believe that the nanopores among packing carbon onions are responsible for the enhanced performance of supercapacitor.