| This work explores the use of polyacrylonitrile (PAN) and isotropic pitch precursor (IPP) as composite electrospun carbon fibers for use as supercapacitor electrode material in aqueous, organic and ionic liquid electrolytes. The polyacrylonitrile is soluble in N,N-dimethylformamide while IPP is soluble in THF. As the solvent evaporates, this results in phase-separation where the IPP occupies the outer shell of the fiber while is at the core. The effect of phase separation is evident in the electrochemical performance of the devices fabricated using the carbon fibers as electrode. The highest specific capacitance was obtained using KOH with from devices using steam activated 1/1 PAN/Pitch fibers as electrode, while the highest specific capacitance obtained in EMITFSI, an ionic liquid is 56 F/g using carbonized PAN/Pitch. With the use of ionic liquids as electrolyte, the voltage window for a single cell device can be expanded to >1 V. Using EMIIm with a working voltage of 4.1 V, the energy density was as high as 10.8 Wh/kg at 5.3 kW/kg power density using 1/1 PAN/Anshan pitch or 7.7 Wh/kg at 15 kW/kg using 7/3 PAN/Hahnwa pitch. |
