Fabrication of a flexible free-standing film electrode composed of polypyrrole coated cellulose nanofibers/multi-walled carbon nanotubes composite for supercapacitors

Today, flexible energy storage systems have become attractive alternatives for applications in portable electronic devices. This account reports a simple and low-cost dipping and polymerization method for preparing flexible and free-standing supercapacitor film electrodes. The process consisted of depositing polypyrrole (PPy) coating on the surface and inside the network of an entangled cellulose nanofibers (CNFs)/multi-walled carbon nanotubes (MWCNTs) film. The electrochemical performance of the resulting CNFs/MWCNTs/PPy hybrid electrode was evaluated and compared with that of CNFs/MWCNTs film electrodes. The CNFs/MWCNTs/PPy nanocomposite electrode exhibited a particular entangled 3D network structure with an elevated specific capacitance of 288 F g(-1), obtained at a scan rate of 5 mV s(-1). This value is higher than that of the CNFs/MWCNTs electrode, calculated to be 32.2 F g(-1). Furthermore, the CNFs/MWCNTs/PPy electrode exhibited excellent redox reversibility and cycle stability. This novel procedure could provide an effective method for achieving flexible, free-standing, high-performance, low-cost, and environmentally friendly materials for use in supercapacitor electrodes.