关键词: 锂离子电池, 正极材料, LiFePO4/C, 核-壳结构

Abstract: The LiFePO₄/C composite electrode material was synthesized by a moderate in situ carbothermal reduction method at 600 °C using FeCl₃.6H₂O, LiOH.H₂O, and NH₄H₂PO₄ as starting materials, soluble starch sol as a carbon source and a reducing agent. This method is readily reproducible and possibly feasible to carry out large-scale synthesis. The structure and morphology of the LiFePO₄/C samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesized LiFePO₄/C composite was in pure phase of olivine-type, shows highly crystalline and spherical morphology with the particle sizes in the range of 60 ~ 100 nm. The thickness of the carbon film could be as thin as about 2 nm for the isolated LiFePO₄/C particles, and the amount of carbon introduced into the composite was about 5% (by mass). The measured tap density of LiFePO₄/C composite was as high as 1.3 g.cm^-3 and the initial discharge capacities of LiFePO₄/C composite reached 162, 143, 135, 127, 116 and 105 mAh?g-1 at 0.2C, 0.5C, 1C, 2C, 5C and 10C rates, respectively. Remarkably, even after 500 cycles at 10C, the capacity of 81 mAh.g^-1 could be obtained.

Key words: Li ion battery, cathode materials, LiFePO4/C, core-shell structure