Capacitive properties of novel N-alkyl substituted poly(3,6-dithienyl-9H-carbazole)s as redox electrode materials and their symmetric micro-supercapacitor applications

Abstract

Herein, we present a comparative study about charge storage performances of novel N-alkyl substituted poly(3,6-dithienylcarbazole)-based electrodes for supercapacitor applications. The poly(3,6-dithienylcarbazole) derivatives, poly(9-butyl-3,6-di(thien-2-yl)-9H-carbazole) (PTCB), poly(9-hexyl-3,6-di(thien-2-yl)-9H-carbazole) (PTCH) and poly(9-octyl-3,6-di(thien-2-yl)-9H-carbazole) (PTCO), were electrochemically synthesized for the first time on a metal substrate and directly used as electrode materials in supercapacitor applications. The capacitive performances of PTCB, PTCH and PTCO polymeric films were studied by using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques in both three-electrode and real two-electrode micro-supercapacitor device configurations. PTCB, PTCH and PTCO redox-active materials achieved high gravimetric specific capacitances of 147.7, 218.7 and 509.8 F g−1, respectively, at a current density of 2.5 mA cm−2 in three-electrode cell configurations. Assembled symmetric devices reached maximum specific capacitances of 70.4 (for PTCB), 96 (for PTCH) and 185.5 F g−1 (for PTCO). Devices also delivered energy densities of 20.3, 26 and 55 W h kg-1 and power densities of 750, 755 and 760 W kg−1 with good rate capabilities. Moreover, micro-supercapacitor devices exhibited good long-term cycling stability performances and retained 83.7%, 86.5% and 89.4% of their initial capacitances after 10 000 charge/discharge cycles. The electrochemical performance tests reveal that PTCB, PTCH and PTCO redox-active materials have promising potential to meet requirements of a practical electrochemical energy storage applications. © 2018 Elsevier Ltd