Ball-Milled Graphite as an Electrode Material for High Voltage Supercapacitor in Neutral Aqueous Electrolyte

Amorphous carbonaceous material with specific surface area of 422 m 2 g −1 has been prepared from natural flake graphite by high-energy ball-milling under air atmosphere. Milling treatment introduces abundant oxygen functional groups (carboxyl and alkoxy) to the graphite surface, and oxygen content reaches as high as 11.5 atom% after 75 h milling. The ball-milled graphite exhibits a three electrode stable potential window of 1.8 V in 1 mol L −1 Na 2 SO 4 aqueous electrolyte. Symmetric supercapacitor based on ball-milled graphite shows a stable charge/discharge cycle behavior when cell voltage is set as high as 1.6 V with a specific capacitance of 81 F g −1 . The high utilization ratio (89%) of potential window for this system is attributed to the more negative value of E 0V (electrodes potential when the cell voltage is set to 0 V).