磷酸铁锂的低成本合成技术和性能探究

发布时间：2018-03-31 02:30

  本文选题：水热法　切入点：喷雾干燥法　出处：《上海应用技术学院》2015年硕士论文

【摘要】：在锂离子电池被广泛应用的形势下,磷酸铁锂因具备生产原料来源广泛、价格便宜、材料本身热稳定性好、循环性能好等优点已成为锂离子电池中最具发展潜力的正极材料。目前,磷酸铁锂制备工艺日渐成熟,但依旧存在原料成本高、制备过程污染环境、制备工艺复杂、产品性能不足等缺点。针对这些缺点,本文以开发磷酸铁锂的绿色低成本合成技术为主要目的,同时探究了影响磷酸铁锂电化学性能的因素。1、水热法可控合成沿(010)晶面和(001)晶面生长的片状磷酸铁锂采用水热法通过改变原料比例制备了具有(010)晶面取向(即)和(001)晶面取向(即c轴取向)的LiFePO4/C材料。XRD, SEM和HRTEM测试结果阐述了两种样品的晶体生长过程。电化学性能测试结果表明,具备(010)晶面取向的磷酸铁锂的锂离子扩散速率和比容量均高于具备(001)晶面取向的磷酸铁锂,且稳定性更高。2、纳米球磨制备球形磷酸铁锂/C复合材料及其电化学性能研究以LiOH·H2O, H3PO4,铁粉和蔗糖为原料,结合球磨工艺和喷雾干燥技术制备多孔球形的磷酸铁锂前驱体,原料在720℃煅烧时间3h,得到多孔球形的纳米LiFePO4/C材料。电化学结果表明,在0.2C,0.5C,1C倍率下的放电比容量达到166.2 mAh/g,160.8 mAh/g,155.2 mAh/g,经过10次循环后的容量保持率均达到97%以上,具备优异的高倍率充放电性能。该材料制备工艺符合绿色低成本的要求,具备工业化潜力。3、水热法直接转化磷酸铁制备高纯度的磷酸铁锂以LiOH·H2O, FePO4·2H2O为原料(Li:Fe:P=1.35:1:1),蔗糖作为还原剂和碳源,采用水热法在180℃下保温4h获得高纯度的LiFePO4/C.该材料具备优异的电化学性能。采用喷雾干燥技术将水热产品制备成多孔球形材料,该材料在0.1C,0.2C,0.5C倍率下的首次放电比容量为164.5 mAh/g,161 mAh/g,151.1 mAh/g,经过20次循环后容量几乎没衰减,具备优异的高倍率电化学性能。4、水热法将磷酸铁转化成为LiFePO4OH合成磷酸铁锂的工艺探究以LiOH·H2O, FePO4·2H2O作为原料,通过水热法在140℃的温度下制备LiFePO4OH,然后加入12%的蔗糖,将所得溶液进行喷雾干燥,将得到的粉末于700℃下煅烧6h,得到样品(A)。作为对比,另一组实验不经过水热反应,直接进行喷雾干燥,于800℃煅烧得样品(B)。结果表明,以LiFePO4OH中间相最终经煅烧合成的LiFePO4/C在0.1C,0.2C,0.5C倍率下,首次充放电比容量为168 mAh/g,157 mAh/g,145 mAh/g,样品(B)比样品(A)具备更优异的电化学性能。
[Abstract]:Under the situation that lithium ion battery is widely used, lithium iron phosphate has a wide range of raw materials, low price and good thermal stability. The advantages of good cycling performance have become the most potential cathode materials in lithium ion batteries. At present, the preparation process of lithium iron phosphate is becoming more and more mature, but the raw material cost is high, the preparation process pollutes the environment, and the preparation process is complex. The main purpose of this paper is to develop the green and low cost synthesis technology of lithium iron phosphate. At the same time, the factors affecting the electrochemical performance of lithium ferric phosphate were investigated. The flake lithium ferric phosphate, which grew along the crystal plane of 010) and along the crystal plane, was synthesized by hydrothermal method, and the orientation of the crystal plane was prepared by changing the ratio of raw materials. The crystal growth process of LiFePO4/C material. XRD, SEM and HRTEM with crystal plane orientation (c axis orientation) was described. The electrochemical properties of the two samples were measured. The lithium ion diffusion rate and specific capacity of lithium ferric phosphate with crystal plane orientation are higher than that of lithium iron phosphate with crystal plane orientation, and the diffusion rate and specific capacity of lithium iron phosphate with crystal plane orientation are higher than that of lithium iron phosphate with crystal plane orientation. The spherical lithium ferric phosphate / C composites were prepared by nano-ball milling and their electrochemical properties were studied. Using LiOH _ 2O, H _ 3PO _ 4, iron powder and sucrose as raw materials, the porous spherical lithium iron phosphate precursor was prepared by ball milling and spray drying technology. After calcined at 720 鈩，

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