Pulse-potential electrochemical fabrication of coaxial-nanostructured polypyrrole/multiwall carbon nanotubes networks on cotton fabrics as stable flexible supercapacitor electrodes with high areal capacitance

Abstract

Flexible supercapacitors (FSCs) with a high areal capacitance are essential for future wearable energy-storage devices due to the limitation of available area on the surface of the human body (< 2 m2). To achieve the performance with high areal capacitance, the surface structure of electrodes should be designed carefully. In this paper, a hierarchical composite electrode based on coaxial-nanostructured polypyrrole (PPy) and multiwall carbon nanotube (MWCNT) was electrochemical co-deposited on the surface of the MWCNT-coated cotton fabric (MCF) by a facile pulse potential method. The pulse potential co-deposition conditions-lower potential (EL), the number of cycles (NC) and EL duration time (tL)-played crucial roles in the uniform distribution of MWCNT within PPy/MWCNT composites, thickness of PPy shell and porous morphology. The three-dimension porous networks of PPy/MWCNT/MCF electrodes not only enhanced the efficiency of faradaic redox reactions but also facilitated the accessibility of the electrolyte to electrode surface, accordingly presenting an ultrahigh areal specific capacitance of 5.05 F cm−2 (0.001 V s−1) and unexceptionable cycling stability of 129.20% specific capacitance retention (1000 cycles, 0.02 V s−1). This work provides a new route to develop FSCs electrodes and shows a promising application in wearable energy-storage technology.