Oxygen Vacancies of WO3-x Enhance the Performance of Asymmetric Supercapacitors

Abstract

The study about the relationship between micro-nano structure and performance in supercapacitors is important. Oxygen vacancies are prevalent in tungsten oxide. The effect of oxygen vacancies in WO_3-x on supercapacitors is currently unclear. In this study, we synthesized WO_3-x, an electrode material with rich oxygen vacancies, using a solvothermal-calcination method. The micro-nano structures of WO_3-x was characterized using SEM, EDS, XRD, FTIR, XPS, and UV–vis absorption spectrum, WO₃ serving as a comparative control. The above structural characterization demonstrated that there are more oxygen vacancies in WO_3-x than WO₃. The electrochemical performance of the WO_3-x electrode was assessed through both three-electrode and asymmetric supercapacitors (ASCs). The results of CV and EIS indicate that better capacitance performance comes from more electron transport (larger current in CV) and faster electron transport (smaller R_ct in EIS). The GCD tests show that WO_3-x has a greater specific capacitance (35.03 F g⁻¹) than WO₃ (19.76 F g⁻¹) at a current density of 0.1 A g⁻¹ across a potential range of 0.0 to 3.5 V. Additionally, WO_3-x ASC displays superior cycling stability, maintaining 69.07% of its initial specific capacitance over 10,000 cycles at 0.5 A g⁻¹. These results imply that oxygen vacancies in WO_3-x make it a promising candidate for supercapacitor applications.