Novel synthesis of LiVPO4F cathode material by chemical lithiation and postannealing

Here, we report a chemical process for the preparation of nano-carbon coated LiVPO4F cathode material for lithium ion batteries. V2O5 powders are first lithiated in the mixture of LiF, NH4H2PO4 and oxalic acid at room temperature and then form an amorphous Li-V-P-O-F precursor by ball milling, which is subsequently converted to LiVPO4F by a short postannealing. X-ray photoelectron spectroscopy (XPS) results reveal that the V5+ in the Li-V-P-O-F precursor is reduced to V3+ by oxalic acid at room temperature. X-ray diffraction results show that the LiVPO4F sample is triclinic structure. TEM image indicates the LiVPO4F particles are about 100 nm in diameter and wrapped by nano-carbon webs. The LiVPO4F/C composites synthesized at 500 degrees C for 2 h deliver a discharge capacity of 143 mAh g(-1) at 0.5 C in the range of 3.0-4.4V at the first cycle, and possess a favorable capacity cycling maintenance at the 0.5C, 1C and 3C rates. (C) 2011 Elsevier B.V. All rights reserved.