Skeleton/skin structured (RGO/CNTs)@PANI composite fiber electrodes with excellent mechanical and electrochemical performance for all-solid-state symmetric supercapacitors

Polyaniline coated reduced graphene oxide/carbon nanotube composite fibers ((RGO/CNTs)@PANI, RCP) with skeleton/skin structure are designed as fiber-shaped electrodes for high performance all-solid-state symmetric supercapacitor. The one-dimensional reduced graphene oxide/carbon nanotube composite fibers (RGO/CNTs, RC) are prepared via a simple in-situ reduction of graphene oxide in presence of carbon nanotubes in quartz glass pipes, which exhibit excellent mechanical performance of >193.4 MPa of tensile strength. Then polyaniline is coated onto the RC fibers by electrodepositing technique. The electrochemical properties of the RCP fiber-shaped electrodes are optimized by adjusting the feeding ratio of carbon nanotubes. The optimized one exhibits good electrochemical characteristic such as highest volumetric specific capacitance of 193.1 F cm^-3 at 1 A cm^-3, as well as excellent cyclic retention of 92.60% after 2000 cyclic voltammetry cycles. Furthermore, the all-solid-state symmetric supercapacitor, fabricated by using the final composite fiber as both positive and negative electrodes pre-coated with the poly(vinyl alcohol)/H₂SO₄ gel polyelectrolyte, possesses volumetric capacitance of 36.7 F cm^-3 at 0.2 A cm^-3 and could light up a red light-emitting diode easily. The excellent mechanical and electrochemical performances make the designed supercapacitor as promising high performance wearable energy storage device.