Synthesis of LiFePO4/C cathode materials through an ultrasonic-assisted rheological phase method

LiFePO4/C active material was synthesized using an ultrasonic-assisted rheological phase method. In addition, polyvinyl butyral (PVB) was added in various concentrations to provide carbon coating on the surface of the LiFePO4 particles for enhanced electrical conductivity. The crystal structure, morphology, and carbon coating layer of the synthesized LiFePO4/C was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The electrochemical performance of LiFePO4/C, such as initial capacity, rate capability, cycling performance and EIS, were also evaluated. The synthesized particle had a size range of 100-150nm and a carbon layer of about 8 nm. The LiFePO4/C (5 wt% PVB) delivered an initial discharge capacity of 167.5 mAh/g at a 0.1 C rate. It also showed an excellent capacity retention ratio of 100% after the 50th charging/discharging. EIS results demonstrate that the charge transfer resistance of the sample decreases greatly by coating with 5 wt% PVB. (C) 2011 Elsevier B.V. All rights reserved.