Effect of different solvents on the synthesis of δ-vanadyl phosphate and its performance as cathode for li-ion battery

In the present work δ-vanadyl phosphate (VOPO₄) was synthesized in the presence of different solvents like water, ethanol, diethyl ketone and 2-propanol. Role of these solvents on the Li-intercalation behaviour of synthesized δ-VOPO₄ has been studied. The solvents affected significantly the size of the crystallites and the level of impurities in the synthesized material. δ-VOPO₄ synthesized using water as solvent, possessed a significant Li-intercalation capacity ca., 124 mAh.g⁻¹ at 3.7 V corresponding to 75% of its theoretical capacity. Among the organic solvents used, sample prepared using ethanol exhibited the highest Li intercalation capacity. Small amount of β-phase was observed in the synthesized δ-VOPO₄ (with phosphate/vanadium ratio of 2) using ethanol and Li-intercalation capacity of this phase was about 137 mAh.g¹, corresponding to 85% of the theoretical capacity. The capacity was found to be almost stable at 110 mAh.g⁻¹ over 100 cycles.