Supercapacitor\nElectrodes Based on High-Purity Electrospun Polyaniline and Polyaniline–Carbon\nNanotube Nanofibers

Abstract

Freestanding, binder-free\nsupercapacitor electrodes based on high-purity polyaniline (PANI)\nnanofibers were fabricated via a single step electrospinning process.\nThe successful electrospinning of nanofibers with an unprecedentedly\nhigh composition of PANI (93 wt %) was made possible due to blending\nultrahigh molecular weight poly­(ethylene oxide) (PEO) with PANI in\nsolution to impart adequate chain entanglements, a critical requirement\nfor electrospinning. To further enhance the conductivity and stability\nof the electrodes, a small concentration of carbon nanotubes (CNTs)\nwas added to the PANI/PEO solution prior to electrospinning to generate\nPANI/CNT/PEO nanofibers (12 wt % CNTs). Scanning electron microscopy\n(SEM) and Brunauer–Emmett–Teller (BET) porosimetry were\nconducted to characterize the external morphology of the nanofibers.\nThe electrospun nanofibers were further probed by transmission electron\nmicroscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared\nspectroscopy (FT-IR). The electroactivity of the freestanding PANI\nand PANI/CNT nanofiber electrodes was examined using cyclic voltammetry,\ngalvanostatic charge–discharge, and electrochemical impedance\nspectroscopy. Competitive specific capacitances of 308 and 385 F g^–1 were achieved for PANI and PANI-CNT based electrodes,\nrespectively, at a current density of 0.5 A g^–1.\nMoreover, specific capacitance retentions of 70 and 81.4% were observed\nfor PANI and PANI-CNT based electrodes, respectively, after 1000 cycles.\nThe promising electrochemical performance of the fabricated electrodes,\nwe believe, stems from the porous 3-D electrode structure characteristic\nof the nonwoven interconnected nanostructures. The interconnected\nnanofiber network facilitates efficient electron conduction while\nthe inter- and intrafiber porosity enable excellent electrolyte penetration\nwithin the polymer matrix, allowing fast ion transport to the active\nsites.