Effect of complexing agents on the electrochemical performance of LiFePO(4)/C prepared by sol-gel method

LiFePO(4)/C is synthesized via sol-gel method using Fe(3+ )as iron sources and different complexing agents, followed by sintering at high temperature for crystallization. The amount of carbon in these composites is less than 6.8 wt.%, and the X-ray diffraction experiment confirms that all samples are pure single phase indexed with the orthorhombic Pnma space group. The particle size of the LiFePO(4)/C synthesized by acetic acid as a complexing agent is very fine with a size of 200 nm. The electrochemical performance of this material, including reversible capacity, cycle number, and charge-discharge characteristics, is better than those of LiFePO(4)/C synthesized by other complexing agents. The cell of this sample can deliver a discharge capacity of 161.1 mAh g(-1 )at the first cycle. After 30 cycles, the capacity decreases to 157.5 mAh g(-1), and the capacity fading rate is 2.2%. The mechanism is studied to explain the effect of a complexing agent on the synthesis of LiFePO(4)/C by sol-gel method. The results show that the complexing agent with a low stability constant may be proper for the synthetic process of LiFePO(4)/C via sol-gel method.