▎ 摘　　要

Physical flexibility of supercapacitors is a crucial advantage for solid state devices. This investigation demonstrates 4 V flexible supercapacitor with graphene as the active material and trihexyl(tetradecyl) phosphonium bis(trifluoromethanesulfonyl) imide [PC6C6C6C14] [Tf2N] as the electrolyte. The methods of electrode fabrication are discussed in detail. Furthermore, the morphology is examined using scanning electron microscopy, atomic force microscopy, x-ray diffraction, Fourier transform infrared spectroscopy and a zeta particle size analyser. To assess the electrochemical performance, cyclic voltammetry, impedance spectroscopy and charge-discharge investigations are conducted. A very high specific capacitance of 495 F g(-1) with high rate scalability (up to 3500 cycles), high energy density and an increased operation voltage of 4 V are achieved, supporting the use of this electrode electrolyte combination as a potential candidate for future ionic liquid-based flexible supercapacitors, for applications in wearable and/or portable electronics.