Effect of carbon coating on low temperature electrochemical performance of LiFePO4/C by using polystyrene sphere as carbon source

Carbon perfectly coated LiFePO4 cathode materials are synthesized by carbon-thermal reduction method using polystyrene (PS) spheres as carbon source. The PS spheres with diameters of 150-300 nm used for the pyrolysis reaction not only inhibit the particle growth but also lead to uniform distribution of carbon coating on the surface of LiFePO4 particles. Rate capability and cycling stability of LiFePO4/C with the carbon contents ranging from 1.4 wt% to 3.7 wt% are investigated at -20 degrees C. The LiFePO4/C with 3.0 wt% C exhibits excellent electrochemical capability at low temperature, which delivers 147 mAh g(-1) at 0.1 C. After 100 cycles at a charge-discharge rate of 1 C, there is still 100% of initial capacity retained for the LiFePO4/C electrode at -20 degrees C. According to the transmission electron microscope analysis and cyclic voltammetry measurement, this can be attributed to the good carbon coating morphology and optimal carbon coating thickness. (C) 2011 Elsevier Ltd. All rights reserved.