Abstract
With the growing demand of the portable and wearable energy storage systems, the flexible supercapacitors have been received great attention. This study demonstrates that the flexible graphene nanosheets/carbon nanotube hybrid film (GS-SWCNT, GS-MWCNT) as electrode for supercapacitors and discusses the substrates (e.g. cellulose fibers and PTFE membrane) and preparation method (e.g. vacuum filtration and dip-drying) of hybrid film. The nanoarchitecture of carbon as active materials is important for energy storage. 8GS-2SWCNT exhibits much higher porosity and improves the electrical conductivities by using SWCNT as both the spacers and conductive linkers between individual graphene sheets, compared with bare graphene. Using cellulose fibers and vacuum filtration to support 8GS-2SWCNT (8GS-2SWCNT-cel(F)) which possesses 3D porous nanostructure due to the backbones of cellulose fibers and porous of carbon materials. The GS and SWCNT are strongly bound to cellulose fibers and fill the pores. This structure significantly enhances the specific surface area, improving both ionic and electronic transport kinetics. 8GS-2SWCNT-cel(F) exhibits the capacitive performance with a high specific capacitance of 127.2 F/g at 5 mV/s. Upon further decoration with MnO2 by chemical co-deposition, the MnO2/GS/SWCNT hybrid film (MnO2-8GS-2SWCNT-cel(F)) reaches a specific capacitance as high as 318.6 F/g at 5 mV/s, demonstrating the introduction of MnO2 is feasible to improve the capacitance performance. MnO2-8GS-2SWCNT-cel(F) also shows good flexibility and cycle stability (83.7 % after 5000 cycles) causes them as a promising electrode material for supercapacitor applications. The symmetric flexible supercapacitor prepared with MnO2-8GS-2SWCNT-cel(F) exhibits high energe density of 4.28 Wh/kg at a power density of 500 W/kg. Consequently, it is found that as-prepared hybrid film shows high specific capacitance, excellent rate capability, and good stability which is a promising potential application as an effective electrode material for supercapacitors.