中孔纳米碳纤维的制备及其在插层型超级电容器中的应用

发布时间：2018-03-17 05:39

本文选题：超级电容器　切入点：中孔纳米碳纤维　出处：《华东理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：超级电容器是一种介于电池和传统电容器间的新型储能设备,具有功率密度高、使用寿命长、温度特性好、绿色环保等突出优点。但超级电容器较低的能量密度是限制其应用的瓶颈,提高其能量密度成为该领域的研究重点。本论文以化学气相沉积法所制备的纳米碳纤维为原料,经氧化-热处理得到中孔纳米碳纤维,并以此为电极材料,组装得到了高能量密度的插层型超级电容器。主要研究结果如下： (1)采用Hummers法将纳米碳纤维氧化成类氧化石墨烯结构,进一步通过热处理得到弹簧状中孔纳米碳纤维。经过氧化-热膨胀处理后,纳米碳纤维的比表面积明显增大,并呈现中孔结构；石墨层间距增大,且可通过改变氧化值或热处理温度调节。 (2)中孔纳米碳纤维可发生插层电化学活化过程。该过程中,电解液离子在电压的驱动下插入到石墨层间,导致层间距不可逆扩大,可用于离子吸／脱附的表面积增大,容量得以提升；且随截止电压的增大,离子插层过程深化,电容量进一步提高。插层活化后的电极以双电层原理工作。由于中孔纳米碳纤维的弹簧状结构和松散的空间三维结构,能够在插层过程中起到缓冲应力作用,所制材料具有优异的插层电化学性能。经电化学活化后,整体电容器容量由2.8F/g增大到31.5F/g,正负极电容分别增至115.2F/g和138.1F/g。 (3)系统考察了电化学插层活化过程的因素影响。结果发现：板状纳米碳纤维比鱼骨状纳米碳纤维插层电位更低,更易于发生电化学活化；氧化程度越大,层间距越大,导致初始活化电压降低,插层过程越容易发生,且活化后获得电容量也越高；插层活化过程还要求电解液对高电压保持性质稳定,四氟硼酸螺环季铵盐(SBPBF4)的螯合结构使其稳定性更强,相比四氟硼酸四乙基铵(Et4NBF4)更有利于高工作电压下的插层活化。 (4)以板状膨胀纳米碳纤维为正极材料,原始纳米碳纤维作为负极材料,构造新型纳米碳纤维基锂离子超级电容器。该锂离子电容器的功率密度和能量密度分别可以达到11.7kW//kg和18.8Wh/kg,且具有良好的倍率性能。
[Abstract]:Supercapacitor is a new type of energy storage equipment between battery and traditional capacitor. It has high power density, long service life and good temperature characteristic. However, the low energy density of supercapacitors is the bottleneck to limit their application, and increasing their energy density has become the research focus in this field. In this paper, carbon nanofibers prepared by chemical vapor deposition were used as raw materials, and mesoporous carbon fibers were prepared by oxidation-heat treatment. The intercalated supercapacitors with high energy density have been assembled. The main results are as follows:. 1) carbon nanofibers were oxidized into graphene oxide structure by Hummers method, and the spring mesoporous carbon fibers were obtained by heat treatment. The specific surface area of carbon nanofibers increased obviously after oxidation and thermal expansion treatment. The graphite layer spacing increases and can be adjusted by changing the oxidation value or heat treatment temperature. (2) Intercalation electrochemical activation can occur in mesoporous carbon nanofibers. In this process, electrolyte ions are inserted into graphite layer driven by voltage, which results in irreversible expansion of interlayer spacing, which can be used to increase the surface area of ion adsorption / desorption. The capacity is increased, and the ion intercalation process deepens with the increase of cutoff voltage. The electrode after intercalation can work on the principle of double electric layer. Because of the spring-like structure of mesoporous carbon nanofibers and the loose three-dimensional structure of space, it can play a role of buffer stress in the intercalation process. After electrochemical activation, the capacitor capacity increased from 2.8 F / g to 31.5 F / g, and the positive and negative capacitance increased to 115.2 F / g and 138.1 F / g, respectively. The results show that the intercalation potential of plate carbon nanofibers is lower than that of fishbone carbon nanofibers, and electrochemical activation is more likely to occur, and the greater the degree of oxidation, the greater the interlayer spacing. The lower the initial activation voltage, the easier the intercalation process is, and the higher the capacitance is, the more stable the electrolyte is to the high voltage. The chelating structure of SBPBF4) is more stable than tetraethyl ammonium tetrafluoroborate (et _ 4NBF _ 4), which is more favorable for intercalation activation at high working voltage than tetraethyl ammonium tetrafluoroborate (et _ 4NBF _ 4). (4) sheet expanded carbon nanofibers are used as cathode materials, and raw carbon nanofibers are used as negative electrode materials. A new type of carbon fiber based lithium ion supercapacitor was constructed. The power density and energy density of the lithium ion capacitor can reach 11.7kW / r / kg and 18.8W / kg, respectively, and have good rate performance.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM53;TQ127.11

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