Effect of the particle size on the electrochemical performance of nano-Li2FeSiO4/C composites

Nano-Li2FeSiO4/C composites were prepared from three kinds of nano-SiO2 (their particle sizes are 15 +/- 5, 30 +/- 5, and 50 +/- 5 nm, respectively) by a traditional solid-state reaction method. The as-prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elementary analyzer, Brunauer-Emmett-Teller (BET) analysis, galvanostatic charge-discharge test, and electrochemical impedance spectroscopy. XRD results reveal that nano-Li2FeSiO4 composites fabricated from nano-SiO2 (smaller than 30 nm) have less impurity. SEM results indicate that the particle size of nano-Li2FeSiO4 composites is nearly accord with the particle size of nano-SiO2. BET analysis indicates that the specific surface areas of LFS15, LFS30, and LFS50 are 35.10, 35.27, and 26.68 m(2) g, respectively, and the main pore size distribution of LFS15, LFS30, and LFS50 are 1.5, 5.5, and 10 nm, respectively. Electrochemical measurements indicate that nano-Li2FeSiO4 composites prepared from nano-SiO2 of 30 +/- 5 nm have the best electrochemical performance among the three samples.