Eco-friendly synthesis of VO₂ with stripped pentavalent vanadium solution extracted from vanadium-bearing shale by...

VO₂(B) has shown excellent cathode performance in lithium batteries and become a hot research topic in recent years. A stripped vanadium solution extracted from vanadium-bearing shale containing a high concentration of vanadium and certain amounts of impurities was used as a vanadium source to synthesize VO₂(B) by hydrothermal process. The VO₂ conversion rate can reach as high as 99.47% in a reaction time of 8 h, and this is the highest result reported. The crystalline structure and morphology of the synthesized products were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Furthermore, the electrochemical properties of VO₂(B) in lithium-ion batteries were investigated. The results indicated that the VO₂(B) has the initial specific discharge capacity of 192.0 mAh g^-1. Stripped vanadium solution is a raw material for producing V₂O₅ and NH₄VO₃, which are indispensable vanadium sources in VO₂ synthesis. Therefore, synthesis of VO₂ via hydrothermal reduction by oxalic acid using stripped vanadium solution extracted from vanadium-bearing shale as a direct vanadium source is an eco-friendly, innovative and efficient method, and will have a great impact on VO₂ synthesis.