Enhanced electrochemical performance of LiFePO4 cathode with synergistic modification of Na3V2(PO4)3 and carbon network

Abstract

A high performance 9LiFePO4–Na3V2(PO4)3/C composite is successfully prepared by a sol–gel technique followed by subsequent carbonthermal reduction process. The structure and performance of 9LiFePO4–Na3V2(PO4)3/C composite have been investigated by XRD, SEM, TEM, EDS, CV and EIS. The result shows that the Na3V2(PO4)3 acting as ionic conductor improves the lithium ion transmission rate, while a thin amorphous carbon layer on the surface of nanoparticles and interfacial structure between the two phase enhances the electronic transmission rate of the composite. The synergistic effect of continual conductive carbon network and Na3V2(PO4)3 phase facilitates the diffusion of lithium ion and electron, ensures the stability of the LiFePO4 nanoparticles by limiting the direct contact of LiFePO4 particle with the electrolyte and ultimately improve the rate capability and long-cycling life of the material. The 9LiFePO4–Na3V2(PO4)3/C composite delivers discharge capacities of 151.2, 144.9 and 118.1mAhg−1 at 1.0, 2.0, 5.0 C, respectively, with high capacity retention up to 88.2% after 2000cycles at 2.0 C, exhibiting good electrochemical performance compared with that of the pristine one.