A competitive candidate material for aqueous supercapacitors: High surface-area graphite

The specific surface area of flake natural graphite can be definitely increased from 7 m2 g−1 to 580 m2 g−1 by high-energy ball-milling. The obtained high surface-area graphite (HSG) was first investigated in detail as a new kind of electrode material for aqueous supercapacitors. HSG sample obtained by long-time ball-milling showed quite large capacitance, e.g. 205 F g−1 for 70 h milling. The high capacitance of HSG might profit from the high open surface area contributed by the nanoparticle exterior, the large quantity of lattice defects, as well as the high density of oxygen functional groups in HSG produced by high-energy ball-milling. The capacitance of HSG maintained well during 5000 cycles of charge/discharge process. Moreover, compared to the commercial activated carbon which has a fully developed porous structure, HSG promised a high electrode density due to its low porosity thus it exhibited a much higher volumetric capacitance than commercial activated carbon.