Microwave-assisted hydrothermal synthesis of vanadium oxides for Li-ion supercapacitors: The influences of Li-ion doping and crystallinity on the capacitive performances

Abstract

Vanadium oxides (VOx·nH2O) with long cycle-life for Li-ion supercapacitors have been successfully synthesized by means of the microwave-assisted hydrothermal synthesis (MAHS) method, a faster and more energy-saving method than the conventional hydrothermal synthesis. Such oxides show capacitor-like, lithium-ion intercalation/de-intercalation responses in aqueous media. Although electrochemical activation is required to reveal the capacitor-like behavior of VOx·nH2O, doping Li ions by adding LiCl into the precursor solution not only effectively shortens the activation time but also enhances the specific capacitance of VOx·nH2O. This kind of materials shows the promising application potential in the aqueous-based Li-ion supercapacitors. X-ray diffraction (XRD), Raman spectroscopic, and X-ray photoelectron spectroscopic (XPS) analyses are employed to identify the fine tune-up in microstructures of various VOx·nH2O.