Abstract
This study demonstrates the method of preparing a flexible supercapacitor with high areal capacitance by integrating tailored graphene with electrospun polyamide 6,6 nanofibers. Graphene oxide was assembled on polyamide 6,6 nanofibers by hydrogen bonding, which avoids the use of surfactant and prevents the aggregation of graphene. The GNS with three different dimensions(<200nm S, 200~450nm M, >450nm L) can be fabricated by ultrasonication, centrifugation, and filtration method. GNS was integrated into Polyamide 6,6 by a simple dipping process. Field emission scanning electron microscopy (FE-SEM) was utilized to investigate the nanostructures of GNS-Polyamide 6,6. From the observations of FE-SEM images, SGNS-Polyamide 6,6 shows more porous morphology than that of MGNS-Polyamide 6,6 and LGNS-Polyamide 6,6. Moreover, SGNS were adsorbed onto the whole framework of the 3D porous polyamide 6,6 nanofibers uniformly and a great conductive path with textile were constructed. From the electrochemical analysis, the SGNS-Polyamide 6,6 flexible electrodes exhibited the highest specific capacitance (302 F/g at 5mVs-1) at all scan rates than that of MGNS-Polyamide 6,6(120 F/g at 5mVs-1) and LGNS-Polyamide 6,6(125 F/g at 5mVs-1) flexible electrodes. The capacitance retention of SGNS-Polyamide 6,6 electrodes can still maintain at 90.6% after 2000 charge/discharge cycles. From the Ragone plot, it can be seen that the power density and energy density of the SGNS-Polyamide 6,6 electrode can achieve as high as 3.4 kW/kg and 41.9 Wh/kg, respectively. In summary, such SGNS-Polyamide 6,6 with outstanding performances can be realized by an environment-friendly approach, which is a promising electrode material for the next generation of ECs. In order to enhance the loading amount of SGNS composite, the filtration process was adopted and compared with dipping process, the loading of SGNS by filtration process(0.16 mg/mg) is higher than that by dipping process(0.1 mg/mg). From FE-SEM, the morphologies of SGNS-Polyamide 6,6 electrodes fabricated by filtration process and dipping process are almost similar. The results of electrochemical impedance spectroscopy (EIS) reveal that the SGNS-Polyamide 6,6 electrodes by filtration process exhibit not only low internal resistance but also high speed of electrons transfer. From cyclic voltammetry (CV) study with different bending angles, the CV results demonstrate that the decay of electrochemical performance of the SGNS-Polyamide 6,6 electrodes is acceptable under different bending angles. According to galvanostatic charging /discharging test, the specific capacitance of flexible supercapacitor is 75F/g and 33F/g at fixed current density of 1A/g and 10A/g, respectively. Consequently, a flexible supercapacitor based on a SGNS-Polyamide 6,6 hybrid structure through a simple filtration process can be fabricated with high specific capacitance(75F/g at 1A/g).