Abstract:

A cellulose-based highly conductive film (RGO/CNF/RGO(RCR)) was prepared using graphene oxide (GO) and cellulose nanofiber (CNF). Graphene oxide@polypyrrole (GO@PPy) active material was deposited on both sides of the film, then an integrated flexible film with conductive anisotropy and good flexibility was acquired. Furthermore, the liquid electrolyte was infiltrated into the composite film, and the copper foil was used as the current collector to prepare the integrated sandwich structure supercapacitor(SC). The morphology and surface elements of the film were analyzed by scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Afterwards, the electrochemical performance of integrated capacitor was compared with stacked capacitor and gel capacitor. The results showed that PPy was wrapped on the surface of GO and deposited on the surface of RCR film in the form of GO@PPy, and a pseudo-capacitive layer of about 400 nm was formed. When the scanning rate was 5 mV/s, the area specific capacitances of integrated, stacked and gel capacitor reached the maximum, which were 28.5, 28.1 and 33.8 mF/cm², respectively. When the scanning rate increased to 200 mV/s, the area specific capacitances decreased to 4.6, 3.2 and 1.1 mF/cm², respectively. It could be seen that the integrated capacitor has higher stability. The tight and seamless connection of the integrated capacitor could effectively avoid the relative displacement and shedding between the adjacent components, and effectively reduce the resistance of electron/ion transfer. At the same time, the integrated capacitor also showed better flexibility, and its electrical performance remained stable after bending test. When the current density was 0.2 mA/cm², the area and volume specific capacitance of the integrated capacitor could reach 64.8 mF/cm² and 31.0 F/cm³, respectively, showing excellent electrochemical performance. The preparation of the integrated supercapacitor provides a new method for development of wearable electronic devices.

Key words: sandwich structure, graphene oxide, integrated supercapacitor, polypyrrole, nanocellulose