The Preparation Of V₂O₅ As Electrode Material And Its Application In Electrochemical Capacitors

Electrochemical capacitors are becoming attractive energy storage devices and will fill the gap between batteries and conventional capacitors because they have higher energy density than conventional dielectric capacitors and have higher power density and a longer cycling life than batteries. In this study, V2O5 has been synthesized by chemical precipitation method and its physical properties was characterized by X-ray diffraction, SEM, and BET analysis. Active carbon and as-prepared V2O5 were investigated as electrode materials for electrochemical capacitors using CV and discharge-charge curves.It was confirmed that active carbon had good reversibility in working potential range. There is no Faraday redox reaction containing mass transferring indicating that carbon capacitors are"dielectric", which is helpful to high-power discharge; the material has good circle performance confirmed by capacitance-decline experiment; Three different electrolytes were investigated during the experiment aimed to find out the influence of electrolytes on the carbon capacitor's performance. The results showed that the capacitors had good circle performance and discharge-charge characteristics using LiClO4/EC+DMC(1:1)as electrolyte.V2O5 powder was prepared using chemical precipitation method and its physical properties was characterized by X-ray diffraction, SEM, and BET analysis. The results showed that the V2O5 powder particle is spherical and the average size is about 440nm. The specific surface area was 43m2/g measured by BET and calculated using multi-point method. Electrode was made using as-prepared V2O5 powder and the capacitor was tested in the water solution electrolytes and organic electrolytes, respectively. The results showed that among the water solution electrolytes, the specific capacitance using KCl solution is best, and the specific capacitance is 142F/g under the scan rate of 5mV/s. The material in all of three kinds of organic electrolytes exhibits some pseudocapacitance. But compared to the other two electrolytes, the circle performance and capacitance characteristics are best when using 1.0mol/L LiClO4/(EC+DMC) as electrolyte, which reaches the capacitance of 8.4Wh/kg under the current density of 500mA/g and the charge-discharge efficiency reaches 98%.Ni and carbon were doped into as-prepared V2O5 and the influence of different ratio on the capacitance performance is studied. The results show that when doped with Ni at low and middle ratio, the specific capacitance increased as the ratio increasing, however, when doped at higher ratio, the specific capacitance decreased. The specific capacitances are 10.2Wh/kg, 11.4Wh/kg and 5.6Wh/kg, respectively. When doped with carbon, the capacitance increased as the ration increasing. The specific capacitances are 11.3Wh/kg,12.4Wh/kg and 13.1Wh/kg, respectively.