Synthesis of Li3V2(PO4)3/C with enhanced rate performance by a two-step technique

The nano-particles, Li3V2(PO4)(3) embedded in carbon matrix, are synthesized by a novel two-step procedure based on a sol-gel method. In the two-step process, the carbon-encapsulated trivalent vanadium phosphorus precursors are obtained without adding lithium compound in the first step. Because of carbon matrix, small particle size of Li3V2(PO4)(3)/C composite is obtained in the second step, which involves lithiation and heating to 800 A degrees C in argon. The electronic conductivity of Li3V2(PO4)(3)/C composite is 2.88 x 10(-3) S cm(-1), increased by five orders of magnitude compared with the pristine Li3V2(PO4)(3) (2.3 x 10(-8) S cm(-1)). The prepared Li3V2(PO4)(3)/C shows high discharge capacity 132 mAh g(-1) (3.0-4.3 V), which is up to 99.2 % of the theoretical value, and good high-rate specific discharge capacity, which is greater than 100 mAh g(-1) at a rate of 10 C. Even after cycling at 15 C, the charge-discharge performance of the prepared Li3V2(PO4)(3)/C cathode hardly deteriorates at 1 C indicating that the structure of Li3V2(PO4)(3) is not destroyed irreversibly at high rate. The improved electrochemical properties of the Li3V2(PO4)(3)/C cathode electrodes are also verified by electrochemical impedance spectroscopy.