Enhancing the efficiency of asymmetric supercapacitors using high-performance Fe-doped CoWO4 electrodes

Abstract

Herein, the synthesis of iron-doped cobalt tungstate (Fe–CoWO₄) nanostructures using a cost-effective hydrothermal method for application as electrodes in high-performance supercapacitors is reported. Comprehensive characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were performed, and the results confirmed the wolframite-type monoclinic crystal structure while providing detailed insights into the material's morphology and electronic structure. Electrochemical measurements performed with a three-electrode system revealed that the Fe–CoWO₄ electrode achieved a specific capacitance of 336 F g⁻¹ at a current density of 1 A g⁻¹, surpassing the performance of undoped CoWO₄ (284 F g⁻¹). Furthermore, an asymmetric supercapacitor (ASC) device was constructed with Fe–CoWO₄ as the positive electrode and activated carbon as the negative electrode. This ASC device demonstrated a specific capacitance of 82.6 F g⁻¹ at 1 A g⁻¹, along with a remarkable retention of 77.3% after 10 000 charge–discharge cycles. Additionally, the Fe–CoWO₄//AC device delivered an energy density of 25.8 W h kg⁻¹ at a power density of 750 W kg⁻¹ at 1 A g⁻¹. This study introduces Fe–CoWO₄ nanostructures that are synthesized via a cost-effective hydrothermal method, which exhibited significantly improved electrochemical performances, including a higher capacitance and excellent cycling stability, suggesting they are promising candidates for advanced supercapacitor applications.