Li1+0.5xCo1-xVx(PO4)(1+0.5x)/C (x=0, 0.05, 0.10) composites with ordered olivine structure have been synthesized for use as cathode material in lithium ion batteries. The morphology and microstructure are characterized by scanning electron microscope, transmission electron microscopy and X-ray diffraction. The electrochemical test results show that addition of vanadium into LiCoPO4 remarkably improves its charge and discharge behavior. Li1.025Co0.95V0.05(PO4)(1.025)/C electrode gives its initial discharge capacity of 134.8 mAh g(-1) at 0.1 C current rate, against 112.2 mAh g(-1) for the pristine LiCoPO4/C, and exhibits much better cyclic stability than the latter. In particular, vanadium doping leads to an enhancement of the discharge voltage plateau for about 70 mV. (C) 2010 Elsevier BM. All rights reserved.