本文選題：鋰離子電池 + 負極材料　； 參考：《大連海事大學》2017年碩士論文

【摘要】：鋰離子電池作為可以反復使用的二次電池,具有高工作電壓、高能量密度、環(huán)境友好等優(yōu)點,被廣泛應用在運載工具的動力、電子、儲能等領(lǐng)域,特別是能作為汽車動力電源改善城市霧霾及環(huán)境污染。為獲得更好的使用性能,高能量密度的鋰離子電池成為科研工作者追求的目標之一。開發(fā)新型高性能負極材料成為提高鋰離子電池能量密度的重要方法。來源廣泛的硅材料因其高達4200mAh/g的理論比容量,具有巨大的應用潛力,但是反應過程中嚴重的體積變化嚴重限制了其作為負極材料的循環(huán)性能,而碳與硅材料復合是有效的改性方法之一。本文選取微米硅作為硅源,利用機械球磨法、高溫熱解法等手段制備了四種類型多種不同質(zhì)量配比的硅碳復合物。利用SEM、EDS、XRD等測試手段對材料表面形貌,成分和結(jié)構(gòu)進行表征。通過對其進行充放電、循環(huán)伏安以及交流阻抗測試研究其脫嵌鋰性能。首先,相比于純硅粉電極,以石墨為基體制得的不同質(zhì)量比的硅/石墨復合材料的電化學性能均有不同程度的提高。復合材料首次嵌鋰量隨硅含量的增加而增加。當硅含量過高時,循環(huán)穩(wěn)定性的提高不再明顯。石墨與硅質(zhì)量比為8:2時,復合電極材料獲得了最優(yōu)的電化學性能;其次,在硅含量為復合材料總質(zhì)量20%的前提下制備的硅/石墨/無定形碳復合材料循環(huán)穩(wěn)定性隨無定形碳含量的增加而下降,質(zhì)量比為2:7:1的硅/石墨/無定形碳復合物表現(xiàn)出更優(yōu)的電化學性能;最后,以蔗糖為碳源,采用高溫熱解法制備的包覆型硅碳復合材料,其電化學性能與碳包覆情況密切相關(guān),蔗糖與硅質(zhì)量比為70:30的復合材料中硅顆粒被碳包覆的情況相對最好,同時也表現(xiàn)出最優(yōu)的電化學性能,以100mA/g的電流密度恒流充放電,首次放電比容量約為1400mAh/g,循環(huán)至五十次時放電比容量可以保持在340mAh/g左右。
[Abstract]:Lithium ion battery, as a reusable secondary battery, has the advantages of high working voltage, high energy density and environmental friendliness. It is widely used in the fields of power, electronics, energy storage and so on. Especially, it can be used as power supply to improve city haze and environmental pollution. In order to obtain better performance, lithium ion battery with high energy density has become one of the goals pursued by researchers. The development of new high performance anode materials has become an important method to improve the energy density of lithium ion batteries. Silicon materials from a wide range of sources have great potential for application due to their theoretical specific capacity as high as 4200mAh/g, but the serious volume changes in the reaction process seriously limit their cyclic properties as anode materials. Carbon and silicon composite is one of the effective modification methods. In this paper, four kinds of silicon / carbon composites with different mass ratios were prepared by mechanical ball milling and high temperature pyrolysis with micron silicon as silicon source. The surface morphology, composition and structure of the materials were characterized by means of SEM EDS- XRD. The performance of lithium deintercalation was investigated by charge-discharge, cyclic voltammetry and AC impedance measurements. Firstly, compared with pure silicon powder electrode, the electrochemical properties of silicon / graphite composites with different mass ratios were improved in different degrees. The content of lithium intercalation increases with the increase of silicon content for the first time. When the silicon content is too high, the improvement of cycle stability is not obvious. When the mass ratio of graphite to silicon is 8:2, the composite electrode material has the best electrochemical performance. The cyclic stability of silicon / graphite / amorphous carbon composites prepared with silicon content of 20% of the total mass of composites decreases with the increase of amorphous carbon content. The silicon / graphite / amorphous carbon composites with a mass ratio of 2:7:1 showed better electrochemical performance. Finally, the electrochemical properties of the coated silica / carbon composites prepared by high temperature pyrolysis with sucrose as carbon source were closely related to the carbon coating. When the mass ratio of sucrose to silicon is 70:30, the carbon coating of silicon particles is the best, and the optimal electrochemical performance is also shown. The current density of 100mA/g is constant current charge and discharge. The first discharge specific capacity is about 1400mAh/ g, and the discharge specific capacity can be kept at about 340mAh/g at 50 cycles.
【學位授予單位】：大連海事大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM912

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