發(fā)布時間：2018-03-04 11:10

  本文選題：鋰離子電池　切入點：負極　出處：《中國科學院大學(中國科學院過程工程研究所)》2017年碩士論文　論文類型：學位論文

【摘要】：當前已經(jīng)商業(yè)化的鋰電池負極材料,主流產(chǎn)品為人造石墨和改性天然石墨,還有少量產(chǎn)業(yè)化應用的鈦酸鋰,可以基本滿足一般電子產(chǎn)品、儲能電池的要求。但由于它們的理論容量均不高,不能滿足對電池儲能具有更高要求的電動汽車等領域的發(fā)展需求。因此需要開發(fā)更多的具有高容量的電極材料,來提升電池能量密度。本課題選取鍺作為研究對象,它的理論儲鋰容量高達1600mAhg-1,遠遠高于石墨(372 mAhg-1),非常有潛力提高鋰電池的性能。然而,鍺負極材料在應用到鋰電池中時,也面臨著較大的問題與挑戰(zhàn),即在充放電過程中,隨著Li+在電極材料中的嵌入與脫出,電極材料會發(fā)生不可逆的體積變化,并且膨脹率高達370%。這會直接引起材料的內(nèi)部相互擠壓,導致材料破碎并從集流體脫離下來,使鋰電池的循環(huán)穩(wěn)定性大幅度降低。本課題通過電沉積的方法,從離子液體中直接將鍺離子還原,沉積到具有特殊結構的集流體上,得到Ge鍍層/特殊結構集流體的復合電極。電化學測試表明,這種方法制備的負極可以較大程度地改善鍺的電化學性能,主要工作包括:(1)以銅網(wǎng)集流體作為沉積基底,通過離子液體電沉積的方法,實現(xiàn)了在其表面上電沉積上一層致密的鍺層。以此鍺/銅網(wǎng)復合物直接作為鋰電池的負極,研究材料結構對電池電化學性能的影響。經(jīng)沉積的鍺層由致密的納米顆粒組成,且與銅網(wǎng)之間的結合比較牢固,不易脫離。研究表明,從第2次起到第55次循環(huán),容量衰退減緩,比容量由原來的873 mAh g-1下降到了 672 mAh g-1,容量保持率為76.9%。(2)以碳布集流體作為沉積基底,同樣以離子液體電沉積的方法,制備鍺/碳布復合電極。掃描電鏡表征發(fā)現(xiàn),在碳布纖維表面沉積的鍺層具有"內(nèi)疏外密"的雙層結構。這種雙層結構的鍺鍍層材料,不僅具有較高的比容量,還有效地緩解了材料在充放電過程中的體積變化嚴重的問題,使得材料的結構穩(wěn)定性得以完善。電化學測試表明,在循環(huán)100次以后,電池的容量仍然高達989 mAh g-1,具有較高的容量保持率。
[Abstract]:At present, the commercial cathode materials for lithium batteries are made of artificial graphite and modified natural graphite, and a small amount of lithium titanate, which is used industrially, can basically meet the needs of general electronic products. However, the theoretical capacity of these batteries is not high enough to meet the development needs of electric vehicles with higher requirements for battery energy storage. Therefore, it is necessary to develop more electrode materials with high capacity. In this paper, germanium is selected as the research object. Its theoretical lithium storage capacity is as high as 1600mAhg-1, which is much higher than that of graphite (372mAhg-1g), which has great potential to improve the performance of lithium-ion batteries. However, germanium anode materials are used in lithium-ion batteries. In the process of charge and discharge, the electrode material will change irreversibly with the intercalation and release of Li in the electrode material. And the expansion rate is as high as 370. This will directly cause the internal extrusion of the material, which will cause the material to break up and separate from the collecting fluid, so that the cycle stability of the lithium battery will be greatly reduced. GE coating / special structure composite electrode was obtained by directly reducing germanium ion from ionic liquid and depositing GE ion onto the collector with special structure. The anode prepared by this method can greatly improve the electrochemical performance of germanium. A dense layer of germanium on the surface was realized. The GE / Cu net composite was used directly as the negative electrode of the lithium battery. The effect of material structure on the electrochemical performance of the battery was studied. The deposited germanium layer was composed of dense nanocrystalline particles. And the bond with the copper mesh is strong and difficult to detach. Research shows that from the second to the 55th cycle, the capacity decline slows down. The specific capacity decreased from 873 mAh g ~ (-1) to 672 mAh g ~ (-1), and the capacity retention was 76.9%. The germanium layer deposited on the surface of carbon cloth fiber has a double-layer structure of "internal and external density". This kind of bilayer structure germanium coating material not only has a high specific capacity, but also effectively alleviates the serious problem of volume change in the process of charge and discharge. The electrochemical measurements show that the capacity of the battery is as high as 989 mAh g-1 after 100th cycle, and has a high capacity retention rate.
【學位授予單位】：中國科學院大學(中國科學院過程工程研究所)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM912

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本文編號：1565390