锂离子电池硅碳负极材料的制备及其脱嵌锂性能研究

发布时间：2018-04-24 11:39

本文选题：锂离子电池 + 负极材料　；参考：《大连海事大学》2017年硕士论文

【摘要】：锂离子电池作为可以反复使用的二次电池,具有高工作电压、高能量密度、环境友好等优点,被广泛应用在运载工具的动力、电子、储能等领域,特别是能作为汽车动力电源改善城市雾霾及环境污染。为获得更好的使用性能,高能量密度的锂离子电池成为科研工作者追求的目标之一。开发新型高性能负极材料成为提高锂离子电池能量密度的重要方法。来源广泛的硅材料因其高达4200mAh/g的理论比容量,具有巨大的应用潜力,但是反应过程中严重的体积变化严重限制了其作为负极材料的循环性能,而碳与硅材料复合是有效的改性方法之一。本文选取微米硅作为硅源,利用机械球磨法、高温热解法等手段制备了四种类型多种不同质量配比的硅碳复合物。利用SEM、EDS、XRD等测试手段对材料表面形貌,成分和结构进行表征。通过对其进行充放电、循环伏安以及交流阻抗测试研究其脱嵌锂性能。首先,相比于纯硅粉电极,以石墨为基体制得的不同质量比的硅/石墨复合材料的电化学性能均有不同程度的提高。复合材料首次嵌锂量随硅含量的增加而增加。当硅含量过高时,循环稳定性的提高不再明显。石墨与硅质量比为8:2时,复合电极材料获得了最优的电化学性能;其次,在硅含量为复合材料总质量20%的前提下制备的硅/石墨/无定形碳复合材料循环稳定性随无定形碳含量的增加而下降,质量比为2:7:1的硅/石墨/无定形碳复合物表现出更优的电化学性能;最后,以蔗糖为碳源,采用高温热解法制备的包覆型硅碳复合材料,其电化学性能与碳包覆情况密切相关,蔗糖与硅质量比为70:30的复合材料中硅颗粒被碳包覆的情况相对最好,同时也表现出最优的电化学性能,以100mA/g的电流密度恒流充放电,首次放电比容量约为1400mAh/g,循环至五十次时放电比容量可以保持在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.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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