Electrode of electric double layer capacitor prepared from densified activated carbon fiber

A coal tar based isotropic pitch was spun into fibers by using melt spinner and stabilized under air condition. The stabilized fibers was chopped and densified at 5-15 MPa and 400 degreesC with no addition of binder to be bulk densities of 0.3 similar to1.2 g/cc. The component fibers were effectively densified sustaining the original fiber shape. The densified disc was carbonized and followed by steam activation. The activated carbon disc (DACF) showed high enough electrical conductivity of 2.3 x 10 S/cm. to be used as an electrode. The pore size distribution and BET surface area of the DACFs prepared at various activation conditions were 15-19 Angstrom and 2,023 m(2)/g at 82% burn-off, respectively. The BET surface area of the coal tar based ACF is normally higher than that of the ACF from petroleum based one. A unit cell of electric double layer capacitor (EDLC) was prepared with the DACFs in 7.5 mol dm(-3) KOH aqueous solution. The charge/discharge capacitances of the unit cell showed relatively high specific capacitances of 45 similar to 75 F/g and 22 similar to 29 F/cm(3). The AC impedance measurements of the unit cells showed a decrease in internal/interfacial resistance with an increase in burn-off and a decrease in thickness, indicating the enhanced ionic conductivity caused by both widening of pore size and an increase in surface area.