锡基纳米复合材料的制备及储锂性能研究

发布时间：2018-04-30 06:28

本文选题：锡基纳米复合材料 + 介孔碳　；参考：《鲁东大学》2017年硕士论文

【摘要】：当前,耐热性好、化学性质稳定的石墨作为锂离子电池的负极材料,具有热膨胀系数小,放电损失小等优点,但是它的理论比容量较低,仅为372 mAh/g,难以在电动汽车等领域得到广泛应用。锡基复合材料作为一种新型清洁的锂离子电池负极材料,具有较高的充放电容量、较低的嵌锂电势等优点而受到了广泛关注。但是锡基材料在充放电过程中体积变化过大,导致材料严重损坏,不可逆容量损失较大,循环稳定性差。纳米化和合金化是解决这一问题的有效途径。本文研究了一系列锡基纳米复合材料,特别是锡或二氧化锡纳米线、纳米颗粒与无定形碳复合材料的制备,考察了其在锂离子电池负极材料中的应用。主要研究内容如下:1.通过溶剂挥发诱导自组装制备了介孔碳,并以其为模板,在其纳米孔道中生长二氧化锡,除去部分碳得到了二氧化锡纳米线/碳复合材料。通过透射电镜(TEM)、扫描电镜(SEM)、X-射线粉末衍射(XRD)等手段对所得产品进行了表征。结果表明,纳米线的直径为5 nm,纳米线间平行排列呈阵列分布,材料的比表面积较大,合成的二氧化锡为四方金红石结构,二氧化锡在复合材料中的质量分数为92%。对复合材料进行电化学性能测试,结果表明在160 mA/g的电流密度下,100次充放电循环以后,可逆比容量仍高达539 mAh/g,约为纯二氧化锡纳米线的1.4倍。二氧化锡纳米线/碳复合材料具有较好的循环性能和较高的可逆容量,主要归因于碳材料可以充当缓冲层缓解体积变化引起的内应力,保护二氧化锡纳米结构,防止因锂离子的嵌入与脱出过程引起的结构损坏。2.以二氧化锡溶胶和聚丙烯腈为原料,通过静电纺丝工艺合成了锡/碳纳米纤维。锡纳米颗粒均匀地分散在碳纤维材料中,二氧化锡溶胶作为锡的前驱体可提高锡碳间的相容性,阻止锡纳米颗粒间由于热处理引起的团聚现象。合成的金属锡为四方晶系结构,纳米纤维直径约为300 nm,锡占总含量的61.3%。通过恒流充放电、循环伏安曲线(CV)、电化学阻抗谱(EIS)测试了复合材料的电化学性能,结果表明在200 mA/g的电流密度下,复合材料具有较高的可逆容量和库伦效率。100次充放电循环以后,可逆容量仍高达583 mAh/g,库伦效率保持在99%左右。这主要归因于锡纳米颗粒均匀地嵌入在碳纤维中,碳的缓冲作用缓解了锡的体积效应,进而增加材料的循环稳定性和可逆容量。3.以三嵌段共聚化合物(F-127)为表面活性剂,通过水热合成法制备了介孔酚醛树脂。以其为碳源,二氧化锡溶胶为锡源,通过共沉淀法合成二氧化锡/介孔碳复合材料。合成的二氧化锡为四方金红石结构,纳米颗粒直径约为3.5 nm,二氧化锡在复合材料中的质量分数为43%。电化学性能测试表明复合材料在200mA/g的电流密度下,100次充放电循环以后,可逆容量相对较低,为328 mAh/g。原因可能是共沉淀法制备的复合材料中,部分二氧化锡沉积在介孔碳表面,不能有效缓冲体积变化,且二氧化锡沉积量较低,因而可逆容量较低。
[Abstract]:At present, graphite with good heat resistance and stable chemical properties is a negative material for lithium ion batteries. It has the advantages of small thermal expansion coefficient and small discharge loss, but its theory is lower than the capacity of 372 mAh/g. It is difficult to be widely used in electric vehicle and other fields. Tin based composites are used as a new clean lithium ion battery negative electrode Materials, with the advantages of high charge discharge capacity and lower lithium EMF, are widely concerned. However, the volume change of tin based materials in the process of charging and discharging is too large, resulting in serious damage of materials, large loss of irreversible capacity and poor circulation stability. The effective way to solve this problem is nanoscale and alloying. A series of tin based nanocomposites, especially tin or two tin oxide nanowires, and the preparation of nano particles and amorphous carbon composites, were prepared and applied to the negative electrode materials of lithium ion batteries. The main contents are as follows: 1. the mesoporous carbon was prepared by solvent evaporation induced self assembly, and it was used as a template to grow in the nanoscale channel. Two tin oxide was obtained by removing some carbon. The products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X- ray powder diffraction (XRD). The results showed that the diameter of the nanowires was 5 nm, the parallel arrangement of nanowires was array, the surface area of the material was larger and synthetic. Two tin oxide is a tetragonal rutile structure, and the mass fraction of two tin oxide in the composite is 92%. for electrochemical performance test. The results show that the reversible specific capacity is still up to 539 mAh/g after 100 charge discharge cycles at 160 mA/g current density, about 1.4 times that of pure two tin oxide nanowires. Two tin oxide nanowires / Carbon composites have good cycling performance and high reversible capacity, mainly due to carbon materials can act as buffer layers to alleviate the internal stress caused by volume change, protect the two tin oxide nanostructures, prevent structural damage caused by the insertion and removal of lithium ion, and use two tin oxide sol and polyacrylonitrile as raw materials, through.2.. Tin / carbon nanofibers are synthesized by the electrospinning process. The tin nanoparticles are evenly dispersed in the carbon fiber materials. The two tin oxide sol as a precursor of tin can improve the compatibility of tin carbon and prevent the agglomeration between the tin nanoparticles due to heat treatment. The synthetic metal tin is a tetragonal crystal structure with a diameter of about 300 n. M, tin accounted for the total content of 61.3%. by constant current charge discharge, cyclic voltammetry curve (CV) and electrochemical impedance spectroscopy (EIS) to test the electrochemical performance of the composite. The results show that under the current density of 200 mA/g, the composite has high reversible capacity and Kulun efficiency.100 secondary charge discharge cycle, and the reversible capacity is still up to 583 mAh/g, and the efficiency of the composite is up to 583 mAh/g. The rate remains about 99%. This is mainly attributed to the uniform embedding of tin nanoparticles in carbon fibers. The buffer effect of carbon reduces the volume effect of tin, and then increases the cyclic stability and reversible capacity of the material.3. with three block copolymers (F-127) as the surface active agent. Carbon source, two tin oxide sols as tin sources, two tin oxide / mesoporous carbon composites are synthesized by coprecipitation. The synthesized two tin oxide is tetragonal rutile structure, the diameter of nano particles is about 3.5 nm, and the mass fraction of two tin oxide in the composite is 43%. electrochemical properties test sheet under the current density of 200mA/g, 100 times After charging and discharging cycle, the reversible capacity is relatively low, which may be 328 mAh/g. in the composite prepared by coprecipitation. Some two tin oxide deposited on the mesoporous carbon surface, which can not effectively buffer volume change, and the deposition of two tin oxide is low, thus the reversible capacity is low.

【学位授予单位】：鲁东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;TM912

【相似文献】