Development of Flexible Energy Storage Device by Using Polymer Electrolyte Based on Ionic Liquid

A flexible supercapacitor composed of the reduced graphene oxide / acid-treated single-wall carbon nanotubes (rGO/ASWCNTs) composite (weight ratio of 1:9) electrode with the polymer based gel electrolyte was fabricated via spray coating technique. The ionic liquid based polymer electrolyte (IL-b-PE) was prepared by using polyvinyl alcohol (PVA) and 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), which was able to fabricate full device as flexible supercapacitor. The electrochemical performances evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge / discharge (GCD) measurements. The flexible supercapacitor with the ionic liquid based polymer electrolyte (IL-b-PE) exhibited enhanced electrochemical performances compared to the flexible supercapacitor with PVA-H3PO4 gel electrolyte. The electrochemical properties of the flexible supercapacitor assembled by IL-b-PE were investigated as a function of bending cycles. The cycling stability of the flexible supercapacitor was analysed as the function of bending test (0 approximate to 300) and GCD cycles (0 approximate to 4000). The specific capacitance value of the flexible supercapacitor (unbent) was 62.4 F g(-1), which decreased to 55.7 F g(-1) (89.3% retention after 1000 GCD cycles. The flexible supercapacitor was retained 64.6% (40.3 F g(-1)) of its initial capacitance value (62.4 F g(-1)) after 300 bending with application 4000(th) GCD cycles.