锂电池纳米负极材料的制备与电化学性能研究

发布时间：2018-11-07 20:53

【摘要】：锂离子电池具有很高的质量比能量和体积比能量，循环寿命长，可充且无污染，无记忆效应等优点，因而得到了现在许多便携式电子设备和电池电源高效混合动力汽车或电动汽车的普遍应用。为了满足日益增长的对高性能锂离子电池的需求，有效的解决方案之一是利用纳米材料具有反应活性高，以及独特的结构优势有利于电荷传导和物质输送，有效的提高锂电池的性能。因此，本文主要研究了棒状CoMn2O4,球状Li4Ti5O12和Fe2O3@TiO2中空纳米管的制备及电化学性能。具体工作如下；（1）利用水热法合成出二氧化锰，并以二氧化锰为模板合成直径约100nm长度约几十微米的单晶状的锰酸钴，电化学性能测试表明锰酸钴产物在电流密度为100mA/g时，循环100圈后容量达到512mAh/g,库伦效率达到近98%。当电流密度高达1000mA/g时容量保持在400mAh/g.表现出高电容量以及良好的循环可逆性。表明了锰酸钴纳米棒作为负极材料在锂离子电池应用方面具有极大的潜力。（2）以锐钛矿型二氧化钛作为模板，通过水热法合成出尖晶石型的钛酸锂并以聚乙烯吡咯烷酮（PVP）为碳源对样品进行碳包覆。利用XRD、SEM、XPS和电化学测试系统对样品进行了表征及测试。电化学性能测试表明，，包碳后的钛酸锂在电流密度为1C循环100圈后容量达到160mAh/g，相比在电流密度在2C时循环100圈后，其循环稳定性减少的非常小。更优异于未进行碳包覆的钛酸锂。与此同时，我们也对复合材料的温度湿度影响进行了研究，当湿度从50%增加到90%容量基本保持在175mAh/g,当温度从室温增至50°C时，容量达到220mAh/g。实验结果表明，碳包覆可以提高电极材料的导电性，有利于锂离子的嵌入脱出。（3）以钛酸异丙脂和氯化铁为原料，采用同轴静电纺丝法制备了Fe2O3@TiO2空心结构纳米纤维。对其结构进行了表征,制备的纳米管直径约240nm，将Fe2O3@TiO2纳米纤维作电极材料组装成模拟电池测试电化学性能，该材料在电流密度为200mA/g下，循环150圈后电容量保持在780mAh/g且库伦效率一直维持在约99%,同时Fe2O3@TiO2纳米纤维表现出良好的倍率性能，当电流密度增至800mA/g时，循环150圈后电容量保持在740mAh/g,衰减很小。这主要是由于具有中空结构的Fe2O3@TiO2纳米纤维缩短了锂离子的扩散路径，有利于锂离子的快速嵌入和脱出，能明显提高材料的动力学性能。
[Abstract]:Li-ion batteries have the advantages of high mass specific energy and volume specific energy, long cycle life, recharge and no pollution, no memory effect, etc. As a result, many portable electronic devices and battery power efficient hybrid vehicles or electric vehicles are widely used. In order to meet the increasing demand for high performance lithium-ion batteries, one of the effective solutions is to utilize nanomaterials with high reactive activity and unique structural advantages to facilitate charge conduction and material transportation. Effectively improve the performance of lithium batteries. Therefore, the preparation and electrochemical properties of rod-shaped CoMn2O4, spherical Li4Ti5O12 and Fe2O3@TiO2 hollow nanotubes were studied. The specific work is as follows: The main results are as follows: (1) Manganese dioxide was synthesized by hydrothermal method, and the single crystal cobalt manganate about tens of microns in diameter of 100nm was synthesized by using manganese dioxide as template. The electrochemical performance test showed that the product of cobalt manganate was of 100mA/g at current density. After 100 laps, the capacity reached 512 mg / g, and the efficiency of Coulomb reached nearly 98%. When the current density is as high as 1000mA/g, the capacity remains at 400mAh / g. High capacity and good cycle reversibility. The results show that cobalt manganese nanorods have great potential in lithium ion batteries as anode materials. (2) Spinel lithium titanate was synthesized by hydrothermal method using anatase titanium dioxide as template and polyvinylpyrrolidone (PVP) as carbon source. The samples were characterized and tested by XRD,SEM,XPS and electrochemical measurement system. The electrochemical performance test shows that the capacity of lithium titanate after the current density is 100 cycles is 1 C, and the capacity of lithium titanate is 160 mg 路h / g, which is very small compared with that of 100 cycles when the current density is at 2C. It is superior to lithium titanate without carbon coating. At the same time, the effect of temperature and humidity on the temperature and humidity of the composites is studied. When the humidity increases from 50% to 90%, the capacity is maintained at 175 mg / g, and when the temperature increases from room temperature to 50 掳C, the capacity reaches 220 mg / g. The experimental results show that the carbon coating can improve the conductivity of the electrode material and is beneficial to the intercalation and removal of lithium ions. (3) Fe2O3@TiO2 hollow nanofibers were prepared by coaxial electrospinning with isopropyl titanate and ferric chloride as raw materials. The structure of the nanotubes was characterized, and the diameter of the nanotubes was about 240 nm. The Fe2O3@TiO2 nanofibers were assembled as electrode materials to test the electrochemical performance of the simulated batteries. The material was tested at current density of 200mA/g. After 150 cycles, the capacitance remains at 780mAh/g and the Coulomb efficiency remains at about 99g, while the Fe2O3@TiO2 nanofibers exhibit good rate performance. When the current density is increased to 800mA/g, the capacitance remains at 740mAh/ g after the 150th cycle. The attenuation is very small. This is mainly due to the fact that the hollow Fe2O3@TiO2 nanofibers shorten the diffusion path of lithium ions, which is beneficial to the rapid intercalation and removal of lithium ions, and can obviously improve the kinetic properties of the materials.
【学位授予单位】：哈尔滨师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912;TQ131.11

【相似文献】