Double role of silicon in improving the rate performance of LiFePO4 cathode materials

LiFeP1-xSixO4/(C + yLi(2)SiO(3)), (0 <= x <= 0.04, 0 <= y <= 2%) composites with a particle size of about 200 nm were synthesized via a simple solid state route. In this work, silicon plays double roles-silicon doping in lattice to enhance the electronic conductance of LiFePO4, meanwhile Li2SiO3 with high Li-ion conductivity and carbon hybrid coating can decrease the interface resistance between LiFePO4 grain and electrolyte. In this work, starch and TEOS were used as carbon source and the silicon source respectively. XRD, SEM, TEM, EIS and galvanostatic charge-discharge test are used to characterize these samples. The effects of the modification on the microstructure and electrochemical performances of LiFePO4 cathodes at 25 degrees C are systematically investigated. The results show the sample with x = 0.03 and y = 1.0 wt % exhibits excellent rate capacity and cycle performance among the investigated materials. Based on half cell testing, the best sample achieves a high special discharge capacity of 119 mAh g(-1) at 5C rate and a capacity of 94 mAh g(-1) at the 10C rate with an excellent cycle life in the usual cycling voltage range 2.5-4.2 V. EIS result demonstrates that the R-ct of the samples decrease greatly due to the modification of LiFePO4 via doping and coating. (C) 2017 Elsevier B.V. All rights reserved.