锂离子电池硅基复合负极材料的制备及电化学性能研究

发布时间：2018-01-03 00:43

本文关键词：锂离子电池硅基复合负极材料的制备及电化学性能研究　出处：《重庆大学》2016年硕士论文　论文类型：学位论文

【摘要】：在目前众多的已被研究的锂离子电池负极材料当中,硅材料有着最高的理论容量(4200mAh/g)。和商业上常用的石墨类材料(372mAh/g)相比,硅材料高出了十倍,所以说以硅作为锂离子电池负极材料具有非常大的前景。但是硅材料的导电性很低,此外硅材料在充放电过程中会发生严重的体积膨胀,导致材料结构遭到破坏,循环性能随之降低。因此硅材料在商业化应用上受到了极大的限制。所以对硅材料进行改性研究以缓解或限制它的体积效应,是现在对硅材料研究的主要方向。在本文中,以苯胺为单体,以球形纳米硅为硅源,利用原位聚合法制备具有核壳结构的硅/聚苯胺复合材料,制备过程中硅/苯胺的质量比为1:0.3,1:0.5,1:1,1:2,1:3;采用原位聚合和高温炭化两步法,制备硅/聚苯胺基炭复合材料,制备过程中硅/苯胺的质量比为1:1,1:2,1:3,1:4,炭化温度为950℃。利用SiO的歧化反应和氢氟酸洗两步法,制备多孔硅材料;采用甲苯作炭源,利用化学气相沉积法制备多孔硅/炭复合材料。采用红外光谱和扫描电镜等方法对所制备硅/聚苯胺复合材料以及硅/聚苯胺基炭复合材料的结构进行表征,采用恒流充放电法测试两种复合材料的电化学性能。结果表明:当硅:苯胺的比例为1:0.5时所制备的复合材料,测试条件为充放电时间限制在77h,充放电电流密度在20mAh/g时,经19次循环后其可逆容量保持在1464 mAh/g。当硅:苯胺比例为1:3时所制备硅/炭复合材料表现出最优的电化学性能。充放电时间限制在77h,充放电电流密度为20mAh/g时,经19次循环后其可逆容量保持在1484mAh/g。当充放电电流密度分别为50,100,200mAh/g时,其可逆容量分别为1141mAh/g、930mAh/g、625 mAh/g,这表明炭包覆量对复合材料的电化学性能具有一定的影响。通过X-射线衍射和比表面积及孔径测试等方法对所制备多孔硅进行结构表征,采用恒流充放电法对多孔硅及多孔硅/炭复合材料的电化学性能进行测试。结果表明:多孔硅材料的BET比表面积为7.73m2/g,BJH总孔容为0.0144cm3/g,平均孔径为74.8nm。当充放电电流密度为20mAh/g时,经18次循环后多孔硅和多孔硅/炭复合材料的可逆容量分别保持在485 mAg/h,727mAg/h,这表明炭包覆有利于多孔硅材料电化学性能的提高。
[Abstract]:At present many have been studied as anode materials for lithium ion batteries, silicon material has a maximum theoretical capacity (4200mAh/g). And the most frequently used commercial graphite materials (372mAh/g) compared to silicon material ten times higher, so using silicon as anode materials for lithium ion batteries has great prospects. But the conductivity of the silicon material is very low, in addition of silicon materials will result in serious volume expansion in the process of charge and discharge, resulting in the destruction of the structure material, the cycle performance decreases. Therefore silicon materials are restricted in commercial application. So the silicon material was modified to alleviate or limit the volume effect of it now, is the main direction of the silicon material research. In this paper, using aniline as monomer, with spherical nano silica as silicon source, prepared with core-shell structure prepared by in situ polymerization of silicon / polyaniline composite material, preparation process The silicon / aniline mass ratio is 1:0.3,1:0.5,1:1,1:2,1:3; by in situ polymerization and carbonization and two step method for preparing silicon based carbon / polyaniline composite material, preparation process of Si / aniline mass ratio 1:1,1:2,1:3,1:4, carbonization temperature is 950 DEG C. By disproportionation reaction and hydrofluoric acid SiO to wash the two step, the preparation of porous silicon materials; using toluene as carbon source, porous silicon / carbon composites prepared by chemical vapor deposition. By infrared spectroscopy and scanning electron microscopy of the prepared silicon / polyaniline composites and structure of Polyaniline / silicon based carbon composites were characterized, using constant current charge discharge test of two kinds of electrochemical performance of composite materials the results indicate that when the ratio of aniline: silicon composite material prepared by 1:0.5, test conditions to limit the charge and discharge time at 77h, charge discharge current density at 20mAh/g, after 19 cycles, the reversible capacity. When a silicon at 1464 mAh/g.: the ratio of aniline prepared silicon / carbon composite exhibits the best electrochemical performance of 1:3. The charge and discharge time at 77h, the charge discharge current density of 20mAh/g, after 19 cycles, the reversible capacity is maintained at 1484mAh/g. when the charge discharge current density respectively 50100200mAh/g. The reversible capacity was 1141mAh/g, 930mAh/g, mAh/g 625, which indicates that the amount of carbon coating has certain effect on electrochemical properties of composite materials. By means of X- ray diffraction and specific surface area and pore size testing method for the preparation of porous silicon structures were characterized by galvanostatic charge discharge, the porous silicon the electrochemical performance / carbon composites were tested. The results show that the porous silicon BET surface area of 7.73m2/g, BJH and total pore volume is 0.0144cm3/g, average pore size is 74.8nm. when the charge discharge current density is 20mAh/g, after 18 times After cycling, the reversible capacity of porous silicon and porous silicon / carbon composites is kept at 485 mAg/h, 727mAg/h, which indicates that carbon coating is favorable for improving the electrochemical performance of porous silicon materials.

【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB33;TM912

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