Electrochemical performance of the carbon coated Li3V2(PO4)3 cathode material synthesized by a sol-gel method

A carbon coated Li3V2(PO4)(3) cathode material for lithium ion batteries was synthesized by a sol-gel method using V2O5, H2O2, NH4H2PO4, LiOH and citric acid as starting materials, and its physicochemical properties were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscope (TEM), and electrochemical methods. The sample prepared displays a monoclinic structure with a space group of P2(1)/n, and its surface is covered with a rough and porous carbon layer. In the voltage range of 3.0-4.3 V, the Li3V2(PO4)(3) electrode displays a large reversible capacity, good rate capability and excellent cyclic stability at both 25 and 55 degrees C. The largest reversible capacity of 130 mAh g(-1) was obtained at 0.1C and 55 degrees C, nearly equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)(3) formula unit (133 mAh g(-1)). It was found that the increase in total carbon content can improve the discharge performance of the Li3V2-(PO4)(3) electrode. In the voltage range of 3.0-4.8 V, the extraction and reinsertion of the third lithium ion in the carbon coated Li3V2(PO4)(3) host are almost reversible, exhibiting a reversible capacity of 177 mAh g(-1) and good cyclic performance. The reasons for the excellent electrochemical performance of the carbon coated Li3V2(PO4)(3) cathode material were also discussed. (c) 2007 Elsevier Ltd. All rights reserved.