Synthesis of Nanocrystalline VO 2 and Its Electrochemical Behavior in Lithium Batteries

Nanocrystalline having a metastable shear structure, designated as (B), has been synthesized by a simple chemical method. The procedure involves a reduction of aqueous potassium vanadate solution with potassium borohydride around pH 4. The sample has been characterized by x‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and transmission electron microscopy. The metastable (B) begins to transform irreversibly to the more stable monoclinic rutile around 350°C and the transformation is complete around 500°C. (B) exhibits a maximum reversible capacity of about 320 mAh/g in the range 4 to 1 V in lithium cells. A good capacity retention on cycling makes it an attractive cathode for rechargeable lithium cells. In addition, the excellent cyclability without any capacity decline around an intermediate 2.5 V range may become particularly useful for the recently suggested aqueous lithium‐ion cells consisting of (B) anode and cathode.