Improved Electrochemical Performance in Li3V2(PO4)3 Promoted by Niobium-Incorporation

Niobium-incorporated Li 3 V 2 (PO 4 ) 3 (LVP) with nominal formula Li 3 V 2− x Nb x (PO 4 ) 3 cathode materials for lithium ion batteries are synthesized via two-step solid-state reaction. Significant improvement in capacity, rate capability and cyclability are achieved in the Nb-incorporated LVP/C composites compared with pristine LVP/C. The Nb-incorporated LVP/C composite with x = 0.03 delivers an initial discharge capacity as high as 182 mAh g −1 at 0.1 C and an excellent rate-capability with about 160 mAh g −1 at 1 C and 125 mAh g −1 at 5 C. Transmission electron microscopy and X-ray photoelectron spectroscopy clearly show the existence of β-NbOPO 4 , demonstrating that Nb has not doped into the crystal lattice. Our experiments further indicate that the particle size is reduced and the electrical conductivity is enhanced for LVP with Nb-incorporation. The improvement in electrochemical performance can be contributed to the formation of β-NbOPO 4 and reduced particle size of LVP.