锂离子电池硅基高分子导电复合负极材料的制备和改性研究

发布时间：2018-06-16 21:26

  本文选题：Si + 高分子导电材料　； 参考：《北京理工大学》2015年硕士论文

【摘要】：作为元素周期表上第三周期,IVA族的类金属元素,硅原子的最外层有四个电子,使硅具有一定的导电性,且化学性质比较稳定。硅约占地壳总质量的25.7%,仅次于氧。硅的理论处理容量高达4200 mAh/g、放电电压低、安全性能好,以上这些优点都是使硅成为锂离子电池负极材料的研究热点的原因。但是,硅在重放电的嵌脱锂时体积效应大,造成从导电介质集流体上剥离,并导致循环性能差、首次库伦效率低等问题。且硅材料本身比金属材料低的导电率限制了硅在锂离子电池中商业化应用中发展的步伐。针对上述问题,如何缓冲硅在循环过程中体积膨胀、导电率低等问题,成为对硅进行改善的重要研究方向。本文主要以聚丙烯晴(PAN)、4-(2-吡啶偶氮)-1,3-苯二酚(PAR)和聚吡咯(PPy)为主,与纳米硅材料进行复合。运用各类设备,包括:X射线电子能谱(XPS)、扫描电子显微镜(SEM)、拉曼光谱(Raman)、X射线衍射测试(XRD)、傅里叶红外变换光谱(FT-IR)等观察复合材料的结构与形貌特征,并以此分析和探讨对材料改性的研究。将制备好的复合材料装配电池,运用交流阻抗、循环伏安、恒电流充放电等测试,对材料的电化学性能进行检测。先制备石墨烯,采用的方法为Hummer法。再添加PAN与纳米硅进行包覆(质量比比:PAN:Si=3:7),在氩气气氛下煅烧不同温度后制得PAN@Si复合材料。热处理温度为300℃时,得到的PAN@Si复测材料的性能最佳,首次放电容量达到3249.2 mAh/g,经过50周循环后仍保留1063.1 mAh g-1的可逆容量,相对于硅纳米颗粒用聚偏氟乙烯(PVDF)粘结剂制备的电极在首周可逆容量及随后的循环稳定性上均有很大提升。通过添加PAR,并采用类溶胶-凝胶法与纳米硅单质进行复合,将粘度适中的材料直接涂抹在铜箔上,在氩气气氛下高温煅烧,使复合材料很好的与铜箔粘结,最终得到PAR@Si复合材料,研究了不同配比、不同煅烧温度对复合材料性能的影响。热处理温度为300℃时,复合材料均表现了很好的循环稳定性。首次放电容量为3015.9mAh/g,首次库伦效率为80.5%,经过50周循环后仍保留944.8 mAh/g的可逆容量。进行预锂化改性实验,将制备好的复合电极与废弃的锂片组装电池,循环一周后,拆解出极片再重新装电池。通过此方法,提前在材料表面形成一层固体电解质界面膜(SEI),有效阻止溶剂分子的通过,保护活性材料在铜箔上的稳定性。采用原位聚合法制备聚吡咯(PPy),并分别采取同步添加纳米硅方法和聚合后再添加纳米硅的方法制备PPy@Si复合材料。同步添加法,主要是将纳米硅单质与吡咯单体及表面活性剂均匀混合后,在低温下缓慢添加氧化剂,聚合过程不断搅拌,使硅单质被聚合的吡咯均匀包覆,再通过添加导电剂及粘结剂制备负极极片;后添加法,主要是在制备PPy后,按照不同配比,采用添加粘结剂和导电剂将材料混匀后制备成电极。
[Abstract]:As a metal-like element of the third cycle IVA family on the periodic table, the outermost layer of silicon atom has four electrons, which makes silicon have certain electrical conductivity and relatively stable chemical properties. Silicon accounts for about 25.7% of the total mass of the crust, second only to oxygen. The theoretical treatment capacity of silicon is as high as 4200 mAh/ g, the discharge voltage is low and the safety performance is good. These advantages are the reasons why silicon has become a hot topic in the research of lithium ion battery anode materials. However, the volume effect of silicon in the heavy discharge intercalation of lithium removal is large, which results in the stripping from the conductive medium, and leads to poor cycling performance and low Coulomb efficiency for the first time. The lower conductivity of silicon than that of metallic materials limits the development of commercial applications of silicon in lithium-ion batteries. In view of the above problems, how to buffer silicon in the cycle process, such as volume expansion and low conductivity, has become an important research direction for silicon improvement. In this paper, polypropylene (PAN) and polypyrrole (Pyrrolidine) are the main materials, which are mainly composed of polypropylene (PAN) and poly (pyrrolidine) (PPyrx), which are mainly composed with nanocrystalline silicon. The structure and morphology of the composites were observed by means of various kinds of equipment, including: X ray electron spectroscopy (XPS), scanning electron microscopy (SEM), Raman spectroscopy (Raman spectrum), Ramanghy X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), etc. Based on this, the study on the modification of materials is analyzed and discussed. The electrochemical properties of the composite materials were tested by AC impedance, cyclic voltammetry and constant current charge-discharge test. Graphene was prepared by Hummer method. Pan was added to nanocrystalline silicon for coating (mass ratio: pan: Si 3: 7), and then calcined in argon atmosphere at different temperatures to obtain pan / Si composite. When the heat treatment temperature is 300 鈩，

本文编号：2028164