Effect of symbiotic compound Fe2P2O7 on electrochemical performance of LiFePO4/C cathode materials

Abstract In order to study the effect of symbiotic compound Fe 2 P 2 O 7 on electrochemical performance of LiFePO 4 /C cathode materials, the LiFePO 4 /Fe 2 P 2 O 7 /C cathode materials were synthesized by in-situ synthesis method. The phase compositions and microstructures of the products were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscope (FESEM). Results indicate that the existence of Fe 2 P 2 O 7 does not alter LiFePO 4 crystal structure and the existence of Fe 2 P 2 O 7 decreases the particles size of LiFePO 4 . The electrochemical behavior of cathode materials was analyzed using galvanostatic measurement and cyclic voltammetry (CV). The results show that the existence of Fe 2 P 2 O 7 improves electrochemical performance of LiFePO 4 cathode materials in specific capability and lithium ion diffusion rate. The charge–discharge specific capacity and apparent lithium ion diffusion coefficient increase with Fe 2 P 2 O 7 content and maximizes around the Fe 2 P 2 O 7 content is 5 wt%. It has been had further proved that the Fe 2 P 2 O 7 adding enhances the lithium ion transport to improve the electrochemical performance of LiFePO 4 cathode materials. However, excessive Fe 2 P 2 O 7 will block the electron transfer pathway and affect the electrochemical performances of LiFePO 4 directly.