Cathodic performance of VOPO₄ with various crystal phases for Li ion rechargeable battery

Cathodic performance of six different VOPO₄ phases for Li ion rechargeable battery was investigated. It was found that VOPO₄ exhibits a high flat discharge potential of 3.7 V for Li ion electrochemical intercalation and de-intercalation excepting for β- and -types. On the other hand, slightly higher flat discharge potential of 3.9 and 3.8 V was observed for β- and -types. Capacity for Li intercalation is strongly related with the crystal structure of VOPO₄. In particular, δ-phase exhibits the largest reversible capacity of ca. 130 mAh/g among the examined VOPO₄. High capacity for Li intercalation in δ-phase VOPO₄ hardly decreased over 30 times of charge and discharge cycles. Although the reversible capacity decreased with increasing the current density for charge and discharge, large capacity of 80 mAh/g was still sustained at 0.4 mA/cm² for δ-type VOPO₄.