沉淀法制备磷酸铁锂的研究

发布时间：2018-06-27 06:12

  本文选题：磷酸铁锂 + 磷酸铁　； 参考：《长沙理工大学》2011年硕士论文

【摘要】：磷酸铁锂晶体结构稳定、比容量高、放电平台平稳和循环寿命长,是锂离子动力电池的首选正极材料之一。作为动力电池关键材料其存在三个缺陷:一是电导率低,导致材料的比容量和倍率性能都难以发挥;二是振实密度较低,这在很大程度上面影响了其能量密度上面的发挥;三是生产过程中单位能耗高,废气排放量大。本文针对上述缺陷,设计了磷酸铁锂的改性方案。以三价铁盐取代二价铁盐为原料,制备前驱体磷酸铁,重点研究控制前驱体的粒度和形貌的方法与碳热还原制备磷酸铁锂的工艺参数。在上述基础上对磷酸铁锂进行二氧化钛的掺杂改性,以提高其导电率。本文工作可以分为下面四个部分: (1)沉淀法制备球形磷酸铁。通过研究不同铁源、水浴温度和PH对制备过程的影响,选择氯化铁和磷酸体系作为反应试剂,在高于90℃的条件下,在PH=0.9时可以制备出粒度大小在1~2μm,形貌类球形的磷酸铁。 (2)表面活性剂辅助形貌控制生长磷酸铁。以zeta电位为研究依据,分别引入小分子表面活性剂和高聚物表面活性剂。研究表明,小分子SDS(十二烷基硫磺钠)表面活性剂改性以后,颗粒表面光滑,颗粒呈类球形,有利于提高磷酸铁锂的振实密度;高聚物表面活性剂PVP(聚乙烯基吡咯烷)改性磷酸体,颗粒呈片层状,并存在团聚现象。 (3)碳热还原法制备磷酸铁锂。研究了组成、分散剂、还原剂和烧成制度等主要参数对磷酸铁锂结构和性能影响。锂铁比为1.02:1,酒精介作分散为质,葡萄糖为还原剂,在750℃温度下烧结12小时为最优工艺条件。研究表明,乙炔黑作为碳源,磷酸铁锂在0.1C的初始容量可达到152 mAh/g,但在0.2C时的乙炔黑样品比容量降至125 mAh/g左右,而葡萄糖样品却依然保持130 mAh/g。 (4)二氧化钛掺杂磷酸铁锂复合材料。在葡萄糖碳热还原法制备磷酸铁锂的基础上,本文引入二氧化钛作为掺杂物,研究了不同钛含量对磷酸铁锂晶体结构的影响,优化了掺杂二氧化钛以后的磷酸铁锂产物,最终提高了磷酸铁锂的初始容量和倍率容量。经过优化的样品首次充电容量和放电容量分别达到了157.9 mAh/g和155.2 mAh/g。1C倍率循环100次以后,比容量依然达到130 mAh/g。CV(循环伏安)和EIS(交流阻抗)测试表明,二氧化钛掺杂磷酸铁锂复合材料极化和电阻均明显降低。
[Abstract]:Lithium iron phosphate is one of the preferred cathode materials for lithium-ion power batteries due to its stable structure, high specific capacity, stable discharge platform and long cycle life. As the key material of power battery, there are three defects: one is the low conductivity, the other is that the specific capacity and rate performance of the material are difficult to play, the second is the low vibrational density, which affects the exertion of the energy density to a great extent. Third, the unit energy consumption in the production process is high, the exhaust gas emission is big. In view of the above defects, the modification scheme of lithium iron phosphate was designed in this paper. The precursor ferric phosphate was prepared by replacing divalent ferric salt with trivalent iron salt. The methods of controlling the particle size and morphology of the precursor and the technological parameters of preparing lithium iron phosphate by carbothermal reduction were studied. On the basis of above mentioned above, lithium iron phosphate was doped with titanium dioxide to improve its conductivity. This work can be divided into the following four parts: (1) preparation of spherical iron phosphate by precipitation method. By studying the effects of different Tie Yuan, water bath temperature and PH on the preparation process, ferric chloride and phosphoric acid system were selected as reaction reagents under conditions above 90 鈩，

本文编号：2072947