高性能LiFePO_4材料的研究

The study of the LiFePO_4 materials with excellent electrochemical performance

为了提高LiFePO4的电化学性能,采用球磨辅助分段焙烧高温固相法,在前躯体中掺入不同的碳源(蔗糖、煤焦油沥青、改性后的煤焦油沥青-标记为M),合成了锂离子蓄电池LiFePO4/C正极材料。用X射线衍射(XRD)、扫描电镜(SEM)、循环伏安(CV)和恒流充放电测试等方法对其物相结构、表观形貌和电化学性能进行表征和分析。结果表明,合成的LiFePO4/C材料具有单一的橄榄石晶体结构,是粒径为纳米级的球形颗粒;材料具有较高的放电容量和良好的循环性能。其中,以M为碳源合成的LiFePO4/C材料的电化学性能最优异,在以0.1C倍率充放电时,掺入8.5%M的样其容量高达168mAh/g且经过30个循环后容量没有衰减。

To improve the electrochemical performance of LiFePO4, the high temperature solid-state reaction method with two-stage sintering assistant by milling was used to synthesize the LiFePO4/C composite cathode materials by doping different carbon sources（Sucrose, Coal tar asphaltum and Coal tar asphaltum after improving identifier＂M＂）. The crystalline structure, morphology of composite particles and the charge-discharge performances of the samples were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and galvanostatic charging-discharge experiments. The results showed that the LiFePO4/C samples, which possessed good reversibility and cycle performance, were pure olive-type structure and spherical particles whose diameter was nm level. The materials synthesized by doping M owned the most excellent electrochemical performance. The specific capacitiy for the composites synthesized by doping 8. 5 percent M was 168mAh/g at the rate of 0.1C and wasn＇t reduced after 30 cycles.