Eco-friendly synthesis of VO 2 with stripped pentavalent vanadium solution extracted from vanadium-bearing shale by hydrothermal process in high conversion rate

VO 2 (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 VO 2 (B) by hydrothermal process. The VO 2 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 VO 2 (B) in lithium-ion batteries were investigated. The results indicated that the VO 2 (B) has the initial specific discharge capacity of 192.0 mAh g −1 . Stripped vanadium solution is a raw material for producing V 2 O 5 and NH 4 VO 3 , which are indispensable vanadium sources in VO 2 synthesis. Therefore, synthesis of VO 2 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 VO 2 synthesis.