多孔碳球、碳纤维制备和电化学性能研究

发布时间：2018-03-04 14:29

本文选题：锂离子电池　切入点：PVP　出处：《湘潭大学》2014年硕士论文　论文类型：学位论文

【摘要】：多孔碳材料因具有更加有效的充放电路径，比较好的导电性和大量的锂存储的活性部位等优点，将其用作锂离子电池的负极材料具有较优异的的电化学性能。传统的制备多孔碳纤维/球的方法需要对材料进行活化处理，其中包括复杂的物理和化学处理工艺。而静电纺丝/静电喷雾是一种相对而言更为简单、经济有效的新型制备方法。我们用经济环保的聚乙烯吡咯烷酮(PVP)取代聚丙烯腈原料(PAN)作为碳的前驱体，以聚甲基丙烯酸甲酯(PMMA)作为造孔剂，通过三步热处理工艺制备多孔碳纤维/球。这此过程中，需要综合考虑两种原料的热处理温度与时间，克服PVP在热处理过程中容易发生热收缩导致很难维持纤维/球的初始形貌的困难，最终得到多孔的结构。本文主要以多孔碳微纳纤维为研究对象，以分子量为130万的PVP和分子量为9万的PMMA为原材料，采用静电纺丝法结合三步热处理工艺，成功地制备出多孔碳微纳纤维。经过大量的热处理对比实验和相关TGA、SEM测试，，最终确定了三步热处理的温度和时间。具体热处理条件为：首先在150°C干燥24h，然后在280°C预氧化6h，最终在氮气的保护下1000°C碳化4h。采用X射线衍射、扫描电镜、透射电镜和比表面积分析仪等测试手段系统分析了不同PVP/PMMA质量比对多孔碳微纳纤维的形貌和微观结构的影响。实验测试结果表明当PVP:PMMA质量比为3:2时得到的多孔碳微纳纤维其孔的尺寸属于介孔范围，并且它的比表面积的值最大，在没有进行活化的情况下可达到545.4m2·g 1。以制备的多孔碳微纳纤维作为负极材料，组装成CR2025型扣式电池，采用电化学工作站和电池充放电测试仪系统研究了不同PVP/PMMA质量比得到的多孔碳微纳纤维对电化学性能的影响。结果表明：在0.1C充放电速率下，所有多孔碳微纳纤维的可逆比容量比没有加PMMA的碳微纳纤维高，其中PVP/PMMA质量比为3:2的多孔碳纤维的可逆比容量最高，50次循环之后比容量约为220mAh·g 1。本文制备的所有碳纤维样品都有较好的循环稳定性。我们也尝试采用分子量为3万的PVP和分子量为9万的PMMA为原材料，采用静电喷雾法结合三步热处理尝试制备多孔碳球，由于碳纤维和碳球的形貌差别，相同的热处理工艺不能成功制备出多孔碳微纳球，但是通过改进工艺条件并进行相关的实验摸索，已经得到了其热处理的初步工艺参数。
[Abstract]:Porous carbon materials have many advantages, such as more effective charge-discharge path, better electrical conductivity and a large number of lithium-storage active sites. The anode material used for lithium ion battery has excellent electrochemical performance. The traditional method of preparing porous carbon fiber / ball requires activation of the material. These include complex physical and chemical processes, and electrostatic spinning / electrostatic spraying is a relatively simple, A new economical and effective preparation method. We used the economical and environmentally friendly polyvinylpyrrolidone (PVP) instead of polyacrylonitrile (pan) as the precursor of carbon, and the polymethyl methacrylate (PMMA) as the pore-making agent. Porous carbon fiber / ball was prepared by three-step heat treatment. In this process, the heat treatment temperature and time of two kinds of raw materials should be considered comprehensively. It is difficult to maintain the initial morphology of fiber / ball due to the thermal shrinkage of PVP during heat treatment, and the porous structure is finally obtained. In this paper, the porous carbon micro-nano fiber was used as the research object, PVP with molecular weight of 1.3 million and PMMA with molecular weight of 90,000 were used as raw materials, and the electrostatic spinning method combined with three-step heat treatment process was adopted. The porous carbon micronanofibers were successfully prepared. A large number of heat treatment contrast experiments and related TGA SEM measurements were carried out. The temperature and time of three-step heat treatment were determined as follows: drying at 150 掳C for 24 h, preoxidation at 280 掳C for 6 h and carbonization at 1000 掳C for 4 h under the protection of nitrogen. X-ray diffraction, scanning electron microscopy, The effects of different mass ratios of PVP/PMMA on the morphology and microstructure of porous carbon nanofibers were systematically analyzed by means of transmission electron microscope and surface area analyzer. The experimental results showed that the porous carbon was obtained when the mass ratio of PVP:PMMA was 3: 2. The pore size of the micro-nano fiber belongs to the mesoporous range, Moreover, its specific surface area is the largest, which can reach 545.4 m2 路g ~ (-1) without activation. The porous carbon micro-nano fiber was used as the negative electrode material to assemble the CR2025 button battery. The effect of porous carbon micro-nano fibers with different mass ratios of PVP/PMMA on electrochemical performance was studied by electrochemical workstation and battery charge-discharge tester. The results showed that: at the charge / discharge rate of 0.1C, the effect of porous carbon microfibers on electrochemical performance was studied. The reversible specific capacity of all porous carbon nanofibers is higher than that of carbon nanofibers without PMMA. The reversible specific capacity of porous carbon fiber with a mass ratio of 3: 2 is about 220 mAh 路g ~ (-1) after 50 cycles. All the carbon fiber samples prepared in this paper have good cyclic stability. We also try to use PVP with molecular weight of 30,000 and PMMA with molecular weight of 90,000 as raw materials. We also try to prepare porous carbon spheres by electrostatic spray and three-step heat treatment. Due to the different morphology of carbon fiber and carbon ball, The porous carbon microspheres could not be successfully prepared by the same heat treatment process, but the initial technological parameters of the microspheres were obtained by improving the process conditions and groping through related experiments.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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