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

Abstract

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 TiO₂ and V₂O₅ 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/TiO₂ and PSDOGA/V₂O₅ binder-free binary composites in both three-electrode and two-electrode cell configurations. PSDOGA/TiO₂ and PSDOGA/V₂O₅ composites delivered high specific capacitances of 396.4 Fg⁻¹ and 444.5 Fg⁻¹, respectively, at 2.5 mA cm⁻² current density in single electrode measurements. Symmetrical supercapacitor devices assembled by using PSDOGA/TiO₂ and PSDOGA/V₂O₅ binder-free binary composite electrodes exhibited satisfactory energy (78 W h kg⁻¹ and 94.8 W h kg⁻¹) and power (700 W kg⁻¹ and 736 W kg⁻¹) 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⁻². 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.