本文選題：Si + 高分子導電材料　； 參考：《北京理工大學》2015年碩士論文

【摘要】：作為元素周期表上第三周期,IVA族的類金屬元素,硅原子的最外層有四個電子,使硅具有一定的導電性,且化學性質(zhì)比較穩(wěn)定。硅約占地殼總質(zhì)量的25.7%,僅次于氧。硅的理論處理容量高達4200 mAh/g、放電電壓低、安全性能好,以上這些優(yōu)點都是使硅成為鋰離子電池負極材料的研究熱點的原因。但是,硅在重放電的嵌脫鋰時體積效應(yīng)大,造成從導電介質(zhì)集流體上剝離,并導致循環(huán)性能差、首次庫倫效率低等問題。且硅材料本身比金屬材料低的導電率限制了硅在鋰離子電池中商業(yè)化應(yīng)用中發(fā)展的步伐。針對上述問題,如何緩沖硅在循環(huán)過程中體積膨脹、導電率低等問題,成為對硅進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)為主,與納米硅材料進行復(fù)合。運用各類設(shè)備,包括:X射線電子能譜(XPS)、掃描電子顯微鏡(SEM)、拉曼光譜(Raman)、X射線衍射測試(XRD)、傅里葉紅外變換光譜(FT-IR)等觀察復(fù)合材料的結(jié)構(gòu)與形貌特征,并以此分析和探討對材料改性的研究。將制備好的復(fù)合材料裝配電池,運用交流阻抗、循環(huán)伏安、恒電流充放電等測試,對材料的電化學性能進行檢測。先制備石墨烯,采用的方法為Hummer法。再添加PAN與納米硅進行包覆(質(zhì)量比比:PAN:Si=3:7),在氬氣氣氛下煅燒不同溫度后制得PAN@Si復(fù)合材料。熱處理溫度為300℃時,得到的PAN@Si復(fù)測材料的性能最佳,首次放電容量達到3249.2 mAh/g,經(jīng)過50周循環(huán)后仍保留1063.1 mAh g-1的可逆容量,相對于硅納米顆粒用聚偏氟乙烯(PVDF)粘結(jié)劑制備的電極在首周可逆容量及隨后的循環(huán)穩(wěn)定性上均有很大提升。通過添加PAR,并采用類溶膠-凝膠法與納米硅單質(zhì)進行復(fù)合,將粘度適中的材料直接涂抹在銅箔上,在氬氣氣氛下高溫煅燒,使復(fù)合材料很好的與銅箔粘結(jié),最終得到PAR@Si復(fù)合材料,研究了不同配比、不同煅燒溫度對復(fù)合材料性能的影響。熱處理溫度為300℃時,復(fù)合材料均表現(xiàn)了很好的循環(huán)穩(wěn)定性。首次放電容量為3015.9mAh/g,首次庫倫效率為80.5%,經(jīng)過50周循環(huán)后仍保留944.8 mAh/g的可逆容量。進行預(yù)鋰化改性實驗,將制備好的復(fù)合電極與廢棄的鋰片組裝電池,循環(huán)一周后,拆解出極片再重新裝電池。通過此方法,提前在材料表面形成一層固體電解質(zhì)界面膜(SEI),有效阻止溶劑分子的通過,保護活性材料在銅箔上的穩(wěn)定性。采用原位聚合法制備聚吡咯(PPy),并分別采取同步添加納米硅方法和聚合后再添加納米硅的方法制備PPy@Si復(fù)合材料。同步添加法,主要是將納米硅單質(zhì)與吡咯單體及表面活性劑均勻混合后,在低溫下緩慢添加氧化劑,聚合過程不斷攪拌,使硅單質(zhì)被聚合的吡咯均勻包覆,再通過添加導電劑及粘結(jié)劑制備負極極片;后添加法,主要是在制備PPy后,按照不同配比,采用添加粘結(jié)劑和導電劑將材料混勻后制備成電極。
[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，

本文編號：2028164