微波辅助固相法合成锂离子电池正极复合材料Li_2FeSiO_4/C

Synthesis of Li_2FeSiO_4/C Composite as Cathode Materials for Lithium Ion Battery by Microwave Assisted Solid Reaction Method

以Na2SiO3.9H2O和FeCl2.4H2O为原料,采用低热固相反应获得了分散均匀的β-FeOOH/SiO2前驱体;再以Li2CO3为锂源、聚乙烯醇和超导电炭黑为复合碳源,通过微波辅助固相法合成了Li2FeSiO4/C材料.通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和恒电流充放电测试等方法对材料的结构、微观形貌及电化学性能进行表征.650℃下微波处理12 min可获得结晶好、晶粒细小均匀的Li2FeSiO4/C材料;在选用的微波合成体系下,超导碳和聚乙烯醇热分解的无定形碳不仅利于合成反应的顺利进行,而且提高了Li2FeSiO4的整体导电性能.制备的复合正极材料在60℃下0.05C倍率首次放电容量为129.6 mAh/g,0.5C倍率下为107.5 mAh/g,0.5C下15次循环后保持为104.8 mAh/g,具有较好的放电比容量和良好的循环稳定性能.结果表明,微波辅助固相合成工艺是制备Li2FeSiO4/C复合材料的一种很有前景的方法.

The homogeneous distribution of FeOOH/SiO2 precursor material was prepared from FeCl2.4H2O and Na2SiO3.9H2O by low-heating solid-state reaction.Then Li2FeSiO4/C composites were prepared by microwave assisted solid reaction method,with prepared precursor FeOOH/SiO2 and Li2CO3 as the starting materials,PVA and super-P carbon as carbon sources.The prepared samples were characterized by X-ray diffractometry,SEM,TEM,and galvanostatic charge-discharge test.Highly pure Li2FeSiO4/C material with uniform and fine particle size was obtained at 650℃ in 12 min.Under the selective microwave synthesis system,super-P carbon powder and pyrolyzed amorphous carbon not only effectively provided the high temperature to induce the complete reaction but also formed the conductive network to enhance the electronic conductivity.The optimum Li2FeSiO4/C composite displayed discharge capacity of 129.6 mAh/g at 0.05C rate and 107.5 mAh/g at 0.5C rate at 60℃.After 15 cycles the discharge capacity maintained 104.8 mAh/g at 0.5C,indicating good electrochemical capacity and cycling stability.Consequently,the results show that microwave assisted solid synthesis process is a promising method for preparing Li2FeSiO4/C composite.