Research On The Materials For Electrochemical Supercapacitors

Electrochemical 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 fieids 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 carbon material, metal oxide and conducting polymer.A series of experiments were conducred to research on electrode material with the aids of the measure methods such as cyclic voltammetric measurements (CV), constant charge/discharge measurements, impedance spectrum, transmission electronic microscope measurements(TEM), and so on. As for carbon material, its activation in nitrate acid; In addition, we also studied the effect on capacitance of nitrate acid concentration and activation time in ammonia. The conclusion were obtained that electrode capacitance enhance with the increase of nitrate acid concentration, and decreased with the activation time in ammonia. The paper also found that the positive carbon electrode was much smaller than that of negative one, so it urged to develop new positive material to make up hybrid capacitor. Abstract The Ag2O was synthesized by solid-phase reaction as electrode material for electrochemical supercapacitor that was tested by cyclic voltammetry(CV) and constant charge-discharge curves. The results of experiment show that Ag2O electrode has good performance of faradic pseudocapacitance in 7molL-1'KOH between 0.15 and 0.35V(vs Hg/HgO). The electrode can provide a specific capacitance of 427.3 to 554.9 Fg-1 and the Ag2O/active carbon electrodes can provide a specific capacitance of 42.5 to 61.65 F-g-1 at different current densities. The effect of Ag2O content in the cathode and conductive substance on Ag2O/active carbon electrodes performance was also studied. The -PbO, -PbO, PbO2 and MnO2 were synthesized by solid-phase reaction. We use MnO2as the positive electrode material and add different lead oxide to the positive material.The results of experiment show that MnO2 electrode of adding P -PbO has good performance of faradic pseudocapacitance in TmolL"1 KOH between -0.3 and 0.4V(vs Hg/HgO). MnO2 electrode of adding 2% 3 -PbO can provide a specific capacitance of 165.7 to 260Fg"' that inhance by 65% than that of no additive. It appeared that the ratio of P -PbO in samples had greater effect on the electrochemical capacity. The better discharge capacity could be obtained when the ratio of P -PbO was 2%. After 2000 cycles of constant charge-discharge the electrode was stable and the capacitance reduces no more than 10% at current density of 50mAcm"2. Successfully we made kilifarads hybrid capacitor ,the anode is active carbon electrode and the cathode is MnO2 electrode.Its capacitance is 2000F. Its specific energy is 5Wh/kg. Its cyclic life was over 20000 cycles.