Synthesis of Functionalized CNT Film-Supported Poly(2, 5-dihydroxy-1, 4-benzoquinonyl sulfide) Flexible Electrode and Its Application in Flexible Asymmetric Supercapacitors

p-Chloroaniline modified carbon nanotube film (pca-CNT) was prepared by diazotization reaction of carbon nanotube (CNT) film. Poly(2, 5-dihydroxy-1, 4-benzoquinonyl sulfide) (PDBS) was grown uniformly on the the surface of pca-CNT by in situ polycondensation method. The obtained pca-CNT@PDBS composite was used as flexible electrode later. The morphology and structure of composite was characterized by field scanning electron microscope (FE-SEM), field transmission electron microscope (TEM), energy dispersive spectrum (EDS), Fourier infrared spectrum (FI-IR) and photoelectron spectroscopy (XPS). The results indicated that PDBS was coated on the pca-CNT film successfully. The electrochemical testing showed that the pca-CNT@PDBS flexible electrode exhibited an area specific capacitance (C_A) of 108 mF/cm² at the current density of 1 mA/cm², higher than pure PDBS (65.6 mF/cm²) and CNT-supported PDBS (CNT@PDBS, 83.2 mF/cm²). With the pca-CNT@PDBS and CNT@PDBS as flexible positive electrode respectively, CNT-supported poly(1, 5-diamino-anthraquinone) (CNT@PDDA) as flexible negative electrode, and crylic rubber cross-linked memberane/tetraethyl tetrafluorate acetonitrile electrolyte (ACM/Et₄NBF₄-AN) as the quasi-solid-state electrolyte, organic asymmetric supercapacitor were assembled at the same time. The electrochemical results showed that area specific capacitance of the as-assembled flexible organic asymmetric supercapacitor was 79.6 mF/cm² at the current density of 2 mA/cm² and its volumetric energy density was 1.63 mW·h/cm³ at the power density of 63.5 mW/cm³. The capacitance retention of CNT@PDBS//ACM/Et₄NBF₄-AN//CNT@PDAA organic asymmetric supercapacitor was about 30.5% after only 7 500 cycles, exhibiting bad cycle performance. After 8 000 charging-discharging cycles, specific capacitance retention of pca-CNT@PDBS//ACM/Et₄NBF₄-AN//CNT@PDAA was 80.5%, presenting much better cycle performance.