LiFePO4正极材料的合成及电化学性能研究
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