Sn基复合纳米碳纤维制备及其储能功能研究

发布时间：2018-11-10 19:00

【摘要】：新型功能纤维的开发及推广应用,开拓出染整功能研究领域的新空间,使染整工艺技术不再局限于日常服用功能。随着消费类锂离子电池的不断推陈出新,染整功能整理技术应用于储能功能纤维的制备设计正迎合了市场需求。据此,本文以染整工艺技术拓展新思路为引导,以纺织纤维能量转化与储存应用为切入点,结合锡(Sn)基材料的储能特性和纳米碳纤维(CNFs)的高导电性,赋予Sn基复合纳米碳纤维储能功能。针对Sn基材料体积效应,通过内部改性及外部保护两种方式,分别对Sn基复合纳米碳纤维的成分、形貌和结构进行设计,以提高循环性能。通过分析不同方法制备的Sn基复合纳米碳纤维成分、结构和储能功能之间的关系,探讨其储能机理。第一章首先介绍了锂离子电池的研究背景及工作原理,而后简要阐述了负极材料类型及特点,随后着重论述了Sn基负极材料的研究现状和存在的问题,据此提出了本文的研究意义及工作内容。在第二章工作中,利用Sn盐作为单质Sn前驱体,与PAN共混纺丝-碳化,制得Sn基复合多孔纳米碳纤维(Sn-PCNFs)。金属Sn以无定形态超均匀分散于CNFs中,部分溢出团聚成Sn基大颗粒裸露于CNFs表面。结果表明,Sn-PCNFs在0.8 A g~(-1)大电流密度下循环200次,能保持774 mA h g~(-1)的高比容量;由于裸露的Sn基大颗粒易在充放电过程中破碎脱落而失去活性,因此Sn-PCNFs的循环寿命及稳定性有待提高。在第三章工作中,以利用第二章裸露的Sn基大颗粒为出发点,利用Sn和Cu的前驱体与PAN发生络合反应高度分散Sn-Cu前驱体,采用碳化-合金化一步法制得Sn-Cu合金与CNFs基体(Sn-Cu-CNFs),控制温度为700oC可使惰性Cu3Sn和活性Cu6Sn5共存于Sn基大颗粒中,显著提升Sn基复合纳米碳纤维的循环性能。结果表明,Sn-Cu-CNFs在1.0 A g~(-1)大电流密度下,可循环1200次,比容量保持400 mA h g~(-1),库伦效率为99%;对比Sn-PCNFs,循环寿命大幅提升。在第四章工作中,以保护第二章裸露的Sn基大颗粒为思路,以廉价的蔗糖为碳源,采用低温水热法进行碳包覆保护,制得碳包覆Sn基复合纳米碳纤维(Sn-SnO_2-CNF@C),控制蔗糖浓度可获得均匀包覆的碳层结构。电化学测试结果表明,Sn-SnO_2-CNF@C2在电流密度为0.8 A g~(-1)下循环200次,容量保持712.2 mA h g~(-1);对比Sn-PCNFs,Sn-SnO_2-CNF@C2具有更好的循环稳定性和倍率性能。在第五章工作中,首次利用准分子紫外光辐照技术微氧化改性纳米碳纤维(UV20-CNFs)和Sn基纳米碳纤维(UV20-Sn-CNFs),使纤维表面产生含氧官能团,不仅有利于提高反应动力学,而且使循环过程中形成的固体电解质界面(SEI)膜稳定锚固在纤维上,提高循环稳定性;同时在纤维表面形成多孔结构,增加物理储锂量。结果表明,UV20-Sn-CNFs在0.5 A g~(-1)的电流密度下循环200次,放电比容量为733 mA h g~(-1),库伦效率达99%;UV20-CNFs在2.0 A g~(-1)的大电流密度下,循环次数可达1000次,且比容量保持300 mA h g~(-1),库伦效率为98%;准分子紫外光微氧化技术简单易行,具有潜在商业前景。最后,在第六章中,系统总结了本论文的研究结果,指出研究工作中存在的不足,并提出未来的发展方向及建议。
[Abstract]:The new functional fiber is developed and applied, and the new space in the research field of dyeing and finishing function is developed, so that the dyeing and finishing technology is no longer limited to the daily administration function. With the continuous development of the consumer Li-ion battery, the technology of dyeing and finishing function finishing technology is applied to the preparation and design of the energy-storage functional fiber, and the market demand is being met. In this paper, based on the development of the new thought of dyeing and finishing technology, the energy storage of Sn-based composite nano-carbon fiber is given by combining the energy storage characteristics of the tin (Sn)-based material and the high electrical conductivity of the nano-carbon fiber (CNFs). The composition, morphology and structure of the Sn-based composite nano-carbon fiber were designed by internal modification and external protection for the volume effect of the Sn-based material, so as to improve the cycle performance. The relationship between the composition, structure and energy storage function of Sn-based composite nano-carbon fiber prepared by different methods was analyzed, and its energy storage mechanism was discussed. In the first chapter, the research background and working principle of the Li-ion battery are introduced in the first chapter, then the types and characteristics of the negative materials are briefly described, and then the research status and the existing problems of the Sn-based negative material are emphatically discussed, and the research significance and the working contents of this paper are put forward. In the second chapter, Sn-based composite porous nano-carbon fiber (Sn-PCNFs) was prepared by using Sn salt as the precursor of simple substance Sn and blending with PAN. The metal Sn is superuniformly dispersed in CNFs in a non-constant form, and the partial overflow is agglomerated into Sn-based large particles and exposed on the surface of the CNFs. The results show that the cycle life and stability of Sn-PCNFs need to be improved because the Sn-PCNFs are cycled 200 times under a large current density of 0.8 A g ~ (-1), and the high specific capacity of 774 mA h g ~ (-1) can be maintained. In the third chapter, the Sn-Cu precursor and the CNFs matrix (Sn-Cu-CNFs) were prepared by a step of carbonization-alloying by using the second exposed Sn-based large particles as the starting point, using the precursor of Sn and Cu and the complex reaction of the PAN to disperse the Sn-Cu precursor. The control temperature is 700oC, so that the inert Cu3Sn and the active Cu6Sn5 can coexist in the Sn-based large particles, and the cycle performance of the Sn-based composite nano carbon fiber is remarkably improved. The results show that Sn-Cu-CNFs can be cycled for 1200 times at a large current density of 1. 0 A g ~ (-1), with a specific capacity of 400 mA h g ~ (-1), and the coulomb efficiency is 99%. Compared with Sn-PCNFs, the cycle life of Sn-Cu-CNFs is greatly improved. In chapter 4, in order to protect the exposed Sn-based large particles of the second chapter, the carbon-coated Sn-based composite nano-carbon fiber (Sn-SnO_2-CNF@C) was prepared by using the low-temperature water heat method as the carbon source, and the carbon-coated carbon layer structure can be obtained by controlling the concentration of the sucrose. The results of the electrochemical test show that the Sn-SnO_2-CNF@C2 is 200 times under the current density of 0.8 A g ~ (-1), the capacity is 71.2 mA h g ~ (-1), and compared with the Sn-PCNFs, the Sn-SnO_2-CNF@C2 has better cycle stability and multiplying power performance. In the fifth chapter, the nano-carbon fiber (UV20-CNFs) and the Sn-based nano-carbon fiber (UV20-Sn-CNFs) were micro-oxidized by excimer UV irradiation, so that the oxygen-containing functional group was generated on the surface of the fiber, which not only is beneficial to the improvement of the reaction kinetics, and the solid electrolyte interface (SEI) film formed in the circulation process is stably anchored on the fiber, and the cycle stability is improved; meanwhile, the porous structure is formed on the surface of the fiber, and the physical lithium storage amount is increased. The results show that the discharge ratio of UV20-Sn-CNFs is 200 times under the current density of 0.5 A g ~ (-1), the discharge specific capacity is 733 mA h g ~ (-1), the coulomb efficiency is 99%, the number of cycles can be up to 1000 times under the large current density of 2.0 A g ~ (-1), and the capacity of the UV20-CNFs is 300 mA h g ~ (-1), and the coulomb efficiency is 98%. The excimer ultraviolet micro-oxidation technology is simple and feasible, and has potential commercial prospect. Finally, in the sixth chapter, the system summarizes the research results of this paper, points out the deficiency in the research work, and puts forward the future development direction and suggestion.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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