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

Abstract

In order to study the effect of symbiotic compound Fe2P2O7 on electrochemical performance of LiFePO4/C cathode materials, the LiFePO4/Fe2P2O7/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 Fe2P2O7 does not alter LiFePO4 crystal structure and the existence of Fe2P2O7 decreases the particles size of LiFePO4. The electrochemical behavior of cathode materials was analyzed using galvanostatic measurement and cyclic voltammetry (CV). The results show that the existence of Fe2P2O7 improves electrochemical performance of LiFePO4 cathode materials in specific capability and lithium ion diffusion rate. The charge–discharge specific capacity and apparent lithium ion diffusion coefficient increase with Fe2P2O7 content and maximizes around the Fe2P2O7 content is 5 wt%. It has been had further proved that the Fe2P2O7 adding enhances the lithium ion transport to improve the electrochemical performance of LiFePO4 cathode materials. However, excessive Fe2P2O7 will block the electron transfer pathway and affect the electrochemical performances of LiFePO4 directly.