Hydrothermal synthesis of vanadium dioxides/carbon composites and their transformation to surface-uneven V2O5 nanoparticles with high electrochemical properties

Abstract

Vanadium dioxides/carbon composites composed of vanadium dioxides@carbon core–shell structures and amorphous carbon spheres were successfully synthesized using glucose as the carbon sources by a facile one-step hydrothermal route. Then vanadium dioxides/carbon composites were converted to surface-uneven V₂O₅ nanoparticles by the calcination in air atmospheres. The amorphous carbon reacting with O₂ in the air to release gas results in remaining V₂O₅ nanoparticles possessing broken, rough and poral structures. The electrochemical properties of surface-uneven V₂O₅ nanoparticles as supercapacitor electrodes were measured by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) both in the aqueous and organic electrolyte. Surface-uneven V₂O₅ nanoparticles exhibit the specific capacitance of 406 F g⁻¹ at the current density of 0.2 A g⁻¹ and retain 246 F g⁻¹ even at high current density of 10 A g⁻¹. The influence of the calcined temperature and time on the specific capacitance, phase and morphology of the products were discussed in detail. The results revealed that the calcination at 400 °C for 4 h with comparatively low ratio of V⁵⁺/V⁴⁺ are favorable for surface-uneven V₂O₅ nanoparticles with the high electrochemical property. During the cycle performance, the specific capacitances of V₂O₅ nanoparticles after 100 cycles are 13.8% and 98.5% of the initial discharge capacity in the aqueous and organic electrolyte, respectively, indicating the cycle performance is significantly improved in organic electrolyte. It turns out that surface-uneven V₂O₅ nanoparticles are an ideal material for supercapacitor electrode in the present work.