Synthesis and characterization of core-shell F-doped LiFePO4/C composite for lithium-ion batteries

Core-shell LiFePO4/C composite was synthesized via a sol-gel method and doped by fluorine to improve its electrochemical performance. Structural characterization shows that F- ions were successfully introduced into the LiFePO4 matrix. Transmission electron microscopy verifies that F-doped LiFePO4/C composite was composed of nanosized particles with a similar to 3 nm thick carbon shell coating on the surface. As a cathode material for lithium-ion batteries, the F-doped LiFePO4/C nanocomposite delivers a discharge capacity of 162 mAh/g at 0.1 C rate. Moreover, the material also shows good high-rate capability, with discharge capacities reaching 113 and 78 mAh/g at 10 and 40 C current rates, respectively. When cycled at 20 C, the cell retains 86% of its initial discharge capacity after 400 cycles, demonstrating excellent high-rate cycling performance.