Structure and Characteristic of LiFePO₄ Cathode Material Synthesized in the Mixed Solvent Environment

In this paper, LiFePO₄ samples were synthesized in the water/ethanol mixture solvent environment with different volume ratio of water/ethanol, and the effects of different solvent environment (different water/ethanol ratio) on the morphology, the crystal structure and the cell performances were studied in detail. The prepared samples were investigated comparatively by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and various electrochemical testing techniques. The results showed that the water/ethanol ratio seriously affected the crystal structure, the micro-morphologies and the electrochemical properties of the resulting LiFePO₄-based electro-active material. And the growth of [010] direction of LiFePO₄ crystal was limited with the increase of alcohol proportion in the mixed solvent, while the size of obtained particles became small in the same process. In addition, LiFePO₄ samples obtained at high alcohol content presented the improved specific capacity and rate performances. Specially, the LFP-D electrode displayed the discharge capacity of 153.2 mAh · g⁻¹ at the rate of 0.1 C and the improved rate performance of 150.6, 143.6, 133.8, 121.4, 99.5 and 78.2 mAh · g⁻¹ at 0.2 C, 0.5 C, 1 C, 2 C, 5 C and 10 C, respectively.