【作者】 王鹏；

【导师】 文利雄；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2012， 硕士

【摘要】 LiFePO₄/C复合材料具有安全性高、绿色环保、原材料来源广泛、循环寿命高等特点。采用水热法能使原料在分子级别上进行混合并发生反应，另外，相对于固相法而言水热法只需要在相对较低的温度下就能完成固相法需要在1000℃左右才能完成的反应，这大大减低了能量的耗费。本文采用水热均匀沉淀法合成了纯相的LiFePO₄，并采用水热法对制备得到的纯相LiFePO₄进行了碳包覆，获得了具有均匀可控碳覆层的LiFePO₄/C，最后对固相工艺中用到的一种原料FePO₄提出了一种新的制备工艺，并制备出满足工业要求的FePO₄。主要工作如下:1、采用以尿素做均匀沉淀剂控制溶液的酸度值、以LiAc做锂源、以FeSO₄做铁源、以NH4H2PO₄做磷源的水热方法，合成出不含杂相的LiFePO₄目标产物；研究了水热反应温度、尿素用量、磷源用量、产量等对LiFePO₄制备的影响。2、采用一步水热覆碳法合成出LiFePO₄/C。一步水热覆碳法制备的LiFePO₄/C复合材料中的碳并不是以碳层的形式存在于LiFePO₄颗粒表面，应该主要是与LiFePO₄相互混合胶连在一起形成了颗粒，在这种颗粒表面有一定量的碳层存在。研究了葡萄糖用量、反应温度、尿素用量等因素对于LiFePO₄/C制备的影响。3、采用两步水热覆碳法合成出LiFePO₄/C。通过控制葡萄糖的用量、氨水用量以及反应温度，能有效控制碳覆层的厚度；葡萄糖的用量和反应温度对于碳覆层的厚度及总体碳含量呈正相关关系，氨水的加入量对碳覆层的厚度及总体碳含量呈负相关关系。4、提出了一种更为廉价的制备FePO₄的新工艺。以廉价的化工副产物FeSO₄做铁源，采用空气做氧化剂将亚铁氧化，制备得到了纯净的FePO₄产物。系统研究了原料铁磷比、反应温度、溶液的酸度值等因素对于制备FePO₄的影响。更多还原

【Abstract】 LiFePO₄/C composite material is an ideal anode material for lithium ionbatteries which has fine properties of high safety, green initiative, high circlelife, and abundant raw materials. The hydrothermal method allows rawmaterials mixed and reacted at the molecular level at a relative low reactiontemperature as compared to the solid phase method which reacts in atemperature higher than600℃, hence reducing energy comsumption greatly.In this work, pure LiFePO₄was synthesized by the hydrothermalhomogeneous precipitation method, and a controllable compound material ofLiFePO₄/C with uniform carbon coating layer was prepared by using thehydrothermal method. A new preparation technology for FePO₄wasdeveloped as well. The main achievements are as follows:1. Hydrothermal homogeneous precipitation method was adopted firstlyto prepare pure LiFePO₄with urea as the precipitation agent to control the pHof the solution, LiAc as the lithium source, FeSO₄as the iron source, andNH4H2PO₄as the phosphorus source. The systematic study on the effects ofthe hydrothermal temperature, urea consumption, phosphorus source dosageon LiFePO₄preparation has been conducted. 2. One step hydrothermal carbon coating method was proposed to preparecomposite material of LiFePO₄/C. The form of the carbon prepared by thismethod is not a carbon layer on the particle’s surface, but forming a grainmixed with LiFePO₄. The influences of the usage of glucose and urea, and thereaction temperature on the preparation of the LiFePO₄/C were studied.3. Two steps hydrothermal carbon coating method was adopted as well toprepare composite material of LiFePO₄/C. The thickness of coated carbonlayer on the particle surface of LiFePO₄could be effectively controlled by theamount of glucose, ammonia water dosage and reaction temperature. Theamount of glucose and reaction temperature had positive relation with thethickness of coated carbon layer, while the amount of mmonia water wasinversely related with he thickness of coated carbon layer.4. A new cheapper technology for the preparation of FePO₄wasdeveloped. FeSO₄, a cheap chemical by-product, was working as the ironsourceto prepare the pure FePO₄. Systematic experiments on the effects of theproportion between the iron and phosphate, the reaction temperature, thereaction pH value on the preparation process were conducted.更多还原