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摘要本次实验以磷酸铁锂的制备方法和其电化学性能研究为目的，用不同温度水热法合成磷酸铁锂。实验采用七水硫酸亚铁、氢氧化锂，磷酸，硫酸镁原料，蔗糖作为还原剂，在140℃，160℃和180℃温度下水热合成抽滤干燥得到锂离子正极材料LiFePO4，高温700℃真空煅烧得到LiFePO4/C粉体。通过XRD、SEM等表征材料结构和形貌对比。利用电化学分析技术考察LiFePO4正极材料的充放电性能和循环稳定性及寿命，通过电化学阻抗技术分析其水热温度对其性能的影响。通过实验对比表明：在160℃的温度条件下进行水热反应直接制备的材料性能最好。在0.2C倍率下160℃水热反应制备的磷酸铁锂材料放电比容量在152mAh/g，充电比容量为160mA•h/g并且充放电电压平台稳定，放电平台约为3.4伏，充电平台约为3.5伏，容量保持率高，循环伏安曲线表明材料具有优异的充放电可逆性。22129
- 上一篇：纳米非晶材料的热学性能表征差示扫描量热法
- 下一篇：铜萃取有机物对酸性溶液中磁黄铁矿生物溶解的影响
本次实验还研究了一种新的合成线路制备磷酸铁锂的方法，以水热反应为前提，制备前驱体，抽滤干燥，将溶液放入球磨机球磨，再喷雾干燥，水热反应后进行球磨，喷雾干燥法得到磷酸铁锂正极材料，再通过XRD、SEM等表征材料结构和形貌对比，充放电性能、循环稳定性和电化学阻抗对比只通过水热法制备的样品.实验表明：在0.2C倍率下球磨后喷雾干燥的样品首次充电比容量为136mA•h/g、128mA•h/g，放电平台为3.3伏，充电平台为3.5伏。水热后球磨喷雾后片状结构被破坏了，导致材料的扩散通道在一定程度了发生了变化，同时材料致密度也发生了变化，这两个原因导致了球磨后喷雾所得的原料比容量降低了。
毕业论文关键词：磷酸铁锂；水热合成；球磨；喷雾；高温真空煅烧；材料表征；XRD；交流阻抗
Abstract
This experiment for the purpose of preparation method of lithium iron phosphate and its electrochemical performance study.Using different temperature hydrothermal synthesis of lithium iron phosphate. The experiment adopts seven water ferrous sulfate, lithium hydroxide, phosphate, Magnesium sulfate raw material, sucrose as the reducing agent, at 140℃, 160℃ and 180℃ temperature hydrothermal synthesis filtering and drying to obtain the cathode materials for lithium ion LiFePO4, temperature 700℃ degrees high temperature vacuum calcination of the obtained LiFePO4/C powder. Through the XRD, SEM characterization of materials structure and topography. Analysis of LiFePO4 cathode material charging and discharging performance and cycle stability and lifetime using electrochemical, by electrochemical impedance technique and analyzing the influence of water temperature on the performance of. The contrast experiment shows: the direct material properties were best hydrothermal reaction at a temperature of 160℃.In the lithium iron phosphate material discharge system at 160℃ hydrothermal reaction at 0.2C than at 152mAh/g production capacity, the charge capacity was 160mA • h/g and the charge and discharge voltage platform stability, discharge plateau of approximately 3.4 volts, charging platform is about 3.5 volts, high capacity retention ratio, cyclic voltammetry showed that the charge discharge reversibility excellent material.
This experiment also studied a method for the synthesis of new lines of lithium iron phosphate preparation, the hydrothermal reaction as the premise, the preparation of the precursor, filtration, drying, the solution into the milling, and then spray drying, water thermal reaction ball milling, lithium iron phosphate cathode materials by spray drying method, and then the same XRD, SEM characterization of materials structure and morphology, charge discharge performance, cycle stability and electrochemical impedance contrast only through the samples prepared by hydrothermal method. Experiment show that: Spray dried at 0.2C magnification milled samples the first charge capacity is 136mA • h/g, 128mA • h/g, discharge platform for 3.3V, 3.5V charging platform. Hydrothermal sheet structure after ball milling spray was destroyed, resulting in diffusion channel materials in a certain degree of change, but the material density change. These two reasons lead to the ball mill spray income material specific capacity decrease
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