Abstract
A symmetric supercapacitor with porous activated carbon as the active material and trihexyl (tetradecyl) phosphonium bis (trifluoromethanesulfonyl) imide [PC6C6C6C14][Tf2N] as the electrolyte was fabricated. Scanning electron microscopy, atomic force microscopy, x-ray diffraction, Fourier transform infrared spectroscopy and a zeta particle size analysis were conducted to examine the surface morphology and other physical properties. Differential scanning calorimetry and a thermal gravimetric analysis were performed to study the thermal stability of the ionic liquid based electrolyte. The binary mixture route was taken with acetonitrile and ionic liquid for reducing the viscosity to enhance the ionic mobility. Cyclic voltammetry, impedance spectroscopy and charge-discharge investigations were conducted to assess the performance of the supercapacitor. A very high specific capacitance of 300 F g(-1), an ultra high energy density of 110 Wh kg(-1), a high rate scalability (up to 1000 cycles) and an increased operation voltage of 3.5 V were achieved to propose this electrode electrolyte combination as a potential candidate for future ionic liquid based supercapacitor.