Synthesis and electrochemical evaluation of high capacity nanostructured VO2 cathodes

A metastable form of vanadium dioxide—designated as VO2(B)—has been synthesized by an ambient temperature reduction of aqueous vanadate ions with potassium borohydride and sodium dithionite followed by heating in vacuum at 230 °C. The samples have been characterized by X-ray diffraction, thermogravimetric analysis (TGA), infrared spectroscopy, scanning electron microscopy (SEM), and electrochemical discharge–charge cycling in lithium cells. These oxides exhibit a high reversible capacity of >300 mAh/g at 3.5–1 V and a moderate reversible capacity of close to 200 mAh/g at 3.5–2 V with good cyclability in a wide temperature range of −30 to 60 °C. Also, the VO2(B) cathodes exhibit excellent safety characteristics as indicated by the absence of exothermic peaks below 350 °C in differential scanning calorimetry (DSC).