Synthesis and electrochemical properties of Li3V2(PO4)3/C cathode material with an improved sol–gel method by changing pH value

Abstract

Abstract An improved sol–gel method by changing pH value is developed to synthesize high performance Li3V2(PO4)3/C cathode material. Li3V2(PO4)3/C powders are prepared by a conventional sol–gel process without special controlling pH value and the improved sol–gel process, respectively. They are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), galvanostatic charge/discharge test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and potential step chronoamperometry (PSCA). Not only the cycle performance for the samples prepared by the improved sol–gel method shows obvious enhancement compared with that for the sample prepared via a conventional sol–gel process, but also initial specific capacities have been improved markedly. In the voltage range of 3.0–4.8 V, the sample prepared at pH value of 4 exhibits an optimum capability at low-rate. The sample prepared at pH value of 9 possesses a good performance at high-rate. The enhanced electrochemical performance can be attributed to the microstructure of the powders, which can make the lithium ion diffusion and electron transfer easier across the Li3V2(PO4)3/C interfaces, thus resulting in enhanced electrode reaction kinetics and improved electrochemical performance.