Nanocellulose incorporated graphene/polypyrrole film with a sandwich-like architecture for preparing flexible supercapacitor electrodes

Abstract

Abstract A novel and well-designed film was prepared from cellulose nanofibers (CNF), reduced graphene oxide (RGO) and polypyrrole (PPy). It was fabricated through an altering vacuum filtration by combining the chemical reduction process. The obtained film displayed a sandwich-like structure and the bulk PPy was wrapped in RGO/CNF framework, resulting a free-standing and highly flexible supercapacitor electrode. The incorporation of hydrophilic CNF into film enhanced the diffusion paths for ions and electrons, and the excellent interactions between these three constituents achieved a synergistic effect on the structural integrity and electrochemical performance of the resultant film electrode. The specific capacitance of the sandwich-like film electrode was as high as 304\u202fF\u202fg−1 and 81.8% capacitance was retained after 1000 charge/discharge cycles. This capacitance value was higher than those of individual RGO or PPy films and randomly mixed film with identical constituents. Besides, a solid state symmetric supercapacitor was assembled by two pieces of the resultant film electrodes and 1\u202fM\u202fH2SO4-saturated CNF membrane as a polymer electrolyte separator. The device exhibited a high specific capacitance of 625.6\u202fF\u202fg−1 at 0.22\u202fA\u202fg−1, the capacitance retention of 75.4% after 5000 cycles, and a high energy density of 21.7\u202fWh kg−1 at the power density of 0.11\u202fkW\u202fkg−1. These above results demonstrated that the presented sandwich-like film electrode was promising and alternative approach for the development of further portable energy storage devices with lightweight and flexible characteristics.