Influences Of Surface Area And Pore Structure On Electrochemical Performance Of Electric Double-layer Capacitance

The supercapacitor is a newly energy storage component whose electric performance is shown in between batteries and electrostatic capacitors, for example, it displays much higher power density than that of batteries and higher energy density than that of electrostatic capacitors. Now the study on supercapacitors has become a leading area in development of energy storage devices. The performance of supercapacitor is highly depended on the electrode materials. Because carbon materials have several advantages such as relative low cost, very high specific surface area and chemical stability, they have been received great attention for preparing electrodes of supercapacitors.The labmade activated carbon with specific surface area from 548 to 1932 m²Â·g^-1 was used as the electrode material. The wet characteristic of these activated carbon were measured by contact angle apparatus, and the electrochemical performance, such as specific capacitance, energy density, inner resistance and leakage current, of capacitors was tested by cyclic voltammetry and constant charge-discharge in 1 mol·L^-1 H₂SO₄ electrolytic solution.In order to ensure the chemical stability and reproducible of capacitors, a stainless steel mould for comprising supercapacitors was used showing advantages of assembly with ease, good reproducibility and so on.It has been shown that the wetting time of electrode B7, B11, B12 is in 10 seconds, while it is from 2 to 1900 minutes for other electrodes. The B14 showed a good stability and reversibility in cyclic voltammograms test at the scan speed of 10 mV·s^-1 which displayed a near rectangle in shape behaving a typical double layer capacitance. The specific capacitance of these samples made from the activated carbons with specific surface area of 548～1932 m²Â·g^-1 was from 42 to 167 F·g^-1with the energy density from 4.73 to 18.79 Wh·kg^-1 at the discharge current of 17 mA. The specific capacitance, energy density, inner resistance and leakage current of C14 were 167 F·g^-1, 18.79 Wh·kg^-1, 0.91Ωand 0.48 mA, respectively, and the cycling life of C4 is over 8000 times, showing that the labmade activated carbons were good enough as electrode material. It has been also shown that the specific capacitance of capacitors increased with an increase of BET specific surface area and pore volume, and decreased with an increase of ash content.The specifie surface area of AS11 increased as additional washed by acid solution. The specific capacitance of CS11 increased from 67 to 110 F·g^-1, as high as 64%, after acid washing was performed. In addition, the inner resistance obviously decreased from 2.43 to 1.93Ω. The specific surface area of A13 and the specific capacitance of C13 decreased lightly after heat treatment at 850℃and 950℃, while the charge-discharge curve and cyclic voltammograms displayed more typical double layer capacitance in sharp.