Study On Carbon-based Supercapacitor

Supercapacitor is a new energy storage equipment and component between batteries and electrostatic capacitors, which has higher energy density than that of electrostatic capacitor and higher power density than that of batteries. When working with batteries, they can meet the high power out-put need of electric vehicles when starting-up or accelerating. It can also be applied into many field such as hybrid electric vehicle, fuel cell mobile telephone and microcomputer. According to the principle of energy-storage there are two types of capacitors: electric double-layer capacitor and faradaic pseudocapacitor. Electrode material mainly includes carban material, metal oxide and conducting polymei.In this thesis, BP2000 carbon owning large specific surface area is chosen as original material, then three experimental techniques are carried on including vacuumizing, nitric acid activation and ball-milling. The simulative capacitor has been fabricated by prepared carbon with one method as eletrode materials. The performance of the capacitor was studied by cyclic voltammograms, constant current charge/discharge methods and impedance test. These results show that the capacitor has the typical character of capacitance.The best time of vacuumizing is 30min, the specific capacitance of carbon electrode is 260.1 F/g, more than that of original carbon electrode 200%; the specific capacitance of capacitor is 84.01 F/g that inhance by 85.17% than that of no-vacuumizing; also the specific capacitance of 1000 times decline 34.9% under current density of 3A/g. The best conditions of nitric acid oxidation are:concentration of nitric acid is 65%, oxidation time is 60min and oxidation temperature is 60℃; the specific capacitance of carbon electrode is 307.9 F/g, more than that of original carbon electrode 206%; the specific capacitance of capacitor is 95.19 F/g that inhance by 109.81% than that of no-activation; also the specific capacitance of 1000 times decline 36.38% under current density of 3A/g. The best time of ball-milling is 2h, the specific capacitance of carbon electrode is 185.1 F/g, more than that of original carbon electrode 110%; the specific capacitance of capacitor is 57.71 F/g that inhance by 27.19% than that of no ball-milling; also the specific capacitance of 1000 times decline 48.8% under current density of 3A/g.