微乳液法合成LiFePO_4/C正极材料及其电化学性能

Microemulsion Synthesis and Electrochemical Properties of LiFePO_4/C Cathode Materials

本文采用微乳液方法合成了纳米LiFePO4/C正极材料。制备样品分别用XRD和SEM进行表征,充放电测试其电化学性能。600℃制备样品为单一物相,平均粒径90nm,在室温2.0￣4.0V(vsLi)放电电压范围和15mA·g-1放电速率下,首次放电容量达到159mAh·g-1。制备样品同样展现良好的循环性能。在15mA·g-1速率下40次循环后,制备样品放电容量仍保持首次放电容量的98.9%。优异的电化学性能得益于样品颗粒的纳米尺寸、均匀分布以及表面碳层包覆提高了活性材料的电子电导率。

The electroactive LiFePO4/C cathode materials have been synthesized by a microemulsion method. The materials were characterized by X-ray powder diffraction, scanning electron microscopy and the electrochemical properties were investigated by charge-discharge tests. The X-ray diffraction shows that the LiFePO4 prepared at 600℃ is single-phase, which has the average particle size of 90 nm, the first discharge capacity of 159 mAh·g^-1 and the composite also displays a stable cycle-life at 15 mA· g^-1 between 2.0 and 4.0 V （vs Li） under room temperature. After 40 cycles, the as-prepared sample still keeps about 98.9% of its first discharge capacities. The improved electrode performance can be mainly attributed to the fine particle of nanometric dimension and the uniform size distribution as well as the increase in electronic conductivity by the carbon coating.