Rational design and microwave-assisted synthesis of a novel terthiophene derivative for facile preparation of binder-free polymer/metal oxide-based binary composite electrodes with high electrochemical performance

In this study, a simple and effective method was presented for the preparation of binder-free conducting polymer/metal oxide binary composite electrode materials. The novel electropolymerizable thiophene monomer, 3-[(2,2′:5′,2′′-terthiophen-3′-yl)]-2-cyanoacrylic acid) (SDOGA), was specifically designed to fabricate homogeneous and chemically stable redox-active composite electrodes for pseudocapacitor applications. Poly(3-[(2,2′:5′,2′′-terthiophen-3′-yl)]-2-cyanoacrylic acid) (PSDOGA) was electrochemically deposited on stainless steel substrates and modified with TiO and VO particles via a simple, efficient and low-cost process without any polymeric binder. Cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques were used to study the pseudocapacitive properties of PSDOGA/TiO and PSDOGA/VO binder-free binary composites in both three-electrode and two-electrode cell configurations. PSDOGA/TiO and PSDOGA/VO composites delivered high specific capacitances of 396.4 Fg and 444.5 Fg, respectively, at 2.5 mA cm current density in single electrode measurements. Symmetrical supercapacitor devices assembled by using PSDOGA/TiO and PSDOGA/VO binder-free binary composite electrodes exhibited satisfactory energy (78 W h kg and 94.8 W h kg) and power (700 W kg and 736 W kg) densities with good charge/discharge characteristics at a large operating voltage of 1.85 V. Furthermore, symmetric type supercapacitor cells achieved an excellent capacitance retention of 87% and 90% for 12 500 consecutive galvanic charge/discharge cycles at a constant current density of 2.5 mA cm. The experimental results revealed that the cooperation between conducting polymer film and metal oxide particles not only greatly enhanced the capacitive performances, but also improved the long-term charge/discharge stability of the redox-active electrode materials.