Ultra-flexible fibrous supercapacitors with carbon nanotube/polypyrrole brush-like electrodes

Ultra-flexible fibrous supercapacitors have been fabricated with oxidized carbon nanotubes grown on carbon fiber (OCNTF)/polypyrrole (PPY) brush-like electrodes, for the first time. Hierarchically mesoporous OCNTF serves as a large surface area-bearing electrically conductive substrate for the electropolymerization of PPY during the synthesis of OCNTF/PPY nanocomposites. Here, carbon fiber serves as a mechanical support for the OCNTF/PPY nanocomposite architecture and current collector for the supercapacitor. X-ray photoelectron spectroscopic analysis has revealed the presence of various oxygen-containing functional groups on the surface of OCNTF. The OCNTF/PPY supercapacitor exhibits a maximum gravimetric capacitance of 305 F g(-1) with a gravimetric energy density of 42 W h kg(-1) and a maximum volume specific capacitance of 14 950 mF cm(-3) at a current density of 2.5 mA cm(-2). The enhanced supercapacitive performance of the ultra-flexible OCNTF/PPY supercapacitor is due to the superior pseudocapacitive charge storage exhibited by the oxygen-containing surface functional groups and the redox-active PPY. The supercapacitor is highly bendable and twistable. The ultra-flexible supercapacitor exhibits an excellent cyclic stability of more than 5000 cycles. The all-solid-state flexible OCNTF/PPY supercapacitor module is a promising candidate for application in flexible and wearable electronic devices.