Two-Dimensional Tungsten Oxide/Selenium Nanocomposite Fabricated for Flexible Supercapacitors with Higher Operational Voltage and Their Charge Storage Mechanism

The present work elaborates the high-energy-density, stable, and flexible supercapacitor devices (full-cell configuration with asymmetric setup) based on a two-dimensional tungsten oxide/selenium (2D WO3/Se) nanocomposite. For this, the 2D WO3/Se nanocomposite synthesized by a hydrothermal method followed by air annealing was coated on a flexible carbon cloth current collector and combined separately with both 0.1 M H2SO4 and 1-butyl-3-methyl imidazolium tetrafluoroborate room temperature ionic liquid (BmimBF(4) RTIL) as electrolyte. Different physicochemical characterization techniques, viz., transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, are utilized for phase confirmation and morphology identification of the obtained samples. The electrochemical analysis was used to evaluate charge storage mechanism. The half-cell configuration (three electrode system) in 0.1 M H2SO4 shows a specific capacitance of 564 F g(-1) at 6 A g-1 current density, whereas with ionic liquid as electrolyte, a higher specific capacitance of 1650 F g(-1) was obtained at a higher current of 40 mA and working potential of 4 V. Importantly, the asymmetric flexible supercapacitor device with PVA-H2SO4 electrolyte shows a working voltage of 1.7 V. A specific capacitance of 858 mF g(-1) is obtained for the asymmetric electrode system with an energy density of 47 mWh kg-1 and a power density of 345 mW kg(-1) at a current density of 0.2 A g(-1).

Automated summary

This study focuses on the development of high-energy-density, stable, and flexible supercapacitors based on a two-dimensional tungsten oxide/selenium (2D WO3/Se) nanocomposite with an asymmetric setup. Results showed that using ionic liquid as electrolyte can achieve higher specific capacitance and energy density, while the asymmetric flexible supercapacitor device with PVA-H2SO4 electrolyte demonstrates a good working voltage.