Synthesis and characterization of vanadium disulfide nanosheets and carbonized iron cations adsorbed onto polyaniline for high-performance supercapacitor applications

Abstract

Due to an urgent need for efficient, clean, and sustainable sources of energy, as well as new technologies associated with energy conversion and storage, the most effective and practical technologies for electrochemical energy conversion and storage are batteries, fuel cells, and electrochemical supercapacitors. In recent years, there have been a large number of research articles and technical reports on the development of electrochemical supercapacitors, motivated by their low energy density and high production cost. Consequently, research focus in supercapacitors is on improving the energy density (i.e. 5-8Wh kg?1) without compromising its high power density (i.e. 5-30 kW kg?1). In this work, the electrochemical properties of both vanadium disulfide (VS2) and carbonized iron cations adsorbed onto polyaniline (C-Fe/PANI) electrode materials were investigated for supercapacitor applications. The VS2 nanosheets electrode material was successfully synthesized by the hydrothermal method, and the C-Fe/PANI electrode material was directly synthesized on a current collector by pyrolysis of the iron-PANImixture coated on nickel foam in a tube furnace under the N2 atmosphere. The structural and morphological characterization of the as-synthesized electrode materials was carried out using X-ray diffraction (XRD), Raman spectrometer, Fourier transforminfrared (FT-IR) spectrometer, scanning electronmicroscopy (SEM), energy-dispersive X-ray spectrometer (EDS), transmission electronmicroscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical behavior of the C-Fe/PANI electrode was analyzed in both positive and negative potential window in a three-electrode cell configuration using 6 M KOH electrolyte, and thereafter, a C-Fe/PANI symmetric device was successfully fabricated. The C-Fe/PANI symmetric device was found to perform at a high cell voltage of 1.65 V in 6 M KOH. At a current density of 0.5 A g?1, this device exhibited a maximum energy and power densities of 41.3 Wh kg?1 and 231.9 W kg?1 respectively. The device further showed excellent cycling stability with capacity retention of 72% at a current density of 5 A g?1 over 10 000 galvanostatic charge-discharge cycles. To further evaluate the electrochemical performance of C-Fe/PANI with a metal disulfide material (VS2), a hybrid (asymmetric) device was successfully fabricated using VS2 nanosheets as the positive electrode and C-Fe/PANI as a negative electrode. Similarly, the electrochemical behavior of each working electrode was analyzed in a three-electrode cell configuration using 6 M KOH electrolyte, and thereafter, a hybrid (asymmetric) device was successfully fabricated using VS2 nanosheets as the positive electrode and C-Fe/PANI as a negative electrode. The fabricated VS2//C-Fe/PANI asymmetric device was found to perform at a high cell voltage of 1.7 V in 6 M KOH. At a current density of 2 A g?1, this device exhibited high energy and power densities of 27.8 Wh kg?1 and 2991.5 W kg?1 respectively. In addition, a VS2//C-Fe/PANI device showed excellent cycling stability with 95% capacity retention over 10 000 galvanostatic charge-discharge cycles at a current density of 5 A g?1.