Synthesis and characterization of LiFePO4/(Ag + C) composite cathodes with nano-carbon webs

LiFePO4/(Ag + C) composite cathodes with a new type of nano-sized carbon webs were synthesized by two methods of an aqueous co-precipitation and a sol–gel process, respectively. Simultaneous thermogravimetric-differential thermal analysis indicates that the crystallization temperature of LiFePO4 is about 455–466 °C, which is close to the pyrolysis temperature of polypropylene, 460 °C. The silver and carbon co-modifying does not affect the olivine structure of LiFePO4 but improves its kinetics in terms of discharge capacity and rate capability. Discharge capacities were improved from 153.4 mA h g− 1 of LiFePO4/C to 160.5 mA h g− 1and 162.1 mA h g− 1 for LiFePO4/(Ag + C) cathodes synthesized by the co-precipitation and sol–gel methods, respectively. The possible reasons for the small difference in discharge capacity of two LiFePO4/(Ag + C) cathodes were discussed. AC impedance measurements show that the Ag + C co-modification decreases the charge transfer resistance of LiFePO4/(Ag + C) cathodes.