石墨烯改性石墨应用于锂离子电池负极材料的研究

发布时间：2018-03-13 06:06

本文选题：锂离子电池　切入点：负极材料　出处：《华中师范大学》2014年硕士论文　论文类型：学位论文

【摘要】：石墨是重要的锂离子电池负极材料,在充放电时,它会与电解液发生溶剂化反应,因而使其体积发生膨胀,甚至导致石墨层脱落。进而影响其电化学性能。石墨的理论比容量为372mAh/g,但实际比容量只有330mAh/g,循环性能也很差,大电流充放电时容量衰减很快。基于这些缺点,它已不能满足一些电子产品的快速发展需求。石墨烯具有大的比表面积、大容量且具有很好的化学和热稳定性。因此可以用石墨烯包覆石墨,这样可以防止石墨发生脱落,保持其完整性,进而提高石墨材料的电化学性能。本论文选用湖州创亚动力电池材料有限公司生产的石墨(G1620)和常州中科来方能源科技有限公司生产的石墨(G123)作为原材料,采用机械球磨、石墨烯包覆及高温热还原等改性手段制备了一系列石墨烯含量的rGO/G1620和rGO/G123材料。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、恒流充放电和循环伏安等测试方法系统地考察了石墨烯含量对rGO/G1620和rGO/G123材料的结构、形貌以及电化学性能的影响。通过XRD测试,发现石墨烯包覆后对G1620和G123材料的结构影响不大。进行SEM扫描,可以看出有石墨烯包覆在G1620和G123材料表面。循环伏安测试则说明石墨烯包覆可以提高了石墨材料的容量。在10mA/g的电流密度,0.005-2V电压范围内进行恒流充放电测试,对于石墨烯包覆G1620材料,石墨烯含量为3%的材料具有更高的容量和更好的循环性能,其首次放电和充电比容量分别为482mAh/g和388mAh/g高于G1620材料的388mAh/g和340mAh/g,其库伦效率达到80%。30次循环后,其充电比容量仍然可以达到385mAh/g而G1620材料只有79mAh/g,其容量的保留率高达99.5%. 相同的测试条件下,对于石墨烯包覆后的G123材料,石墨烯含量为4%的材料具有更高的容量和更好的循环性能,其首次放电和充电比容量为510mAh/g和393mAh/g大于G123材料的400mAh/g和357mAh/g,其库伦效率为77%。30次循环后,其充电比容量仍然可以到达387mAh/g,然而G123材料只能达到252mAh/g,其保留率高达98.5%。石墨烯包覆可以提高石墨材料的容量以及循环性能。利用本论文改性方法制备的锂离子电池G1620和G123负极材料有大容量、循环性能好等特点。
[Abstract]:Graphite is an important anode material for lithium-ion batteries. During charging and discharging, graphite reacts with the electrolyte in solvation, thus causing its volume to expand. The theoretical specific capacity of graphite is 372mAh / g, but the actual specific capacity is only 330mAh/ g, the cycle performance is very poor, and the capacity of high current charge-discharge decays rapidly. Graphene has large specific surface area, large capacity and good chemical and thermal stability. Therefore, graphene can be coated with graphene to prevent graphite from falling off. The integrity of graphite is maintained and the electrochemical properties of graphite are improved. In this paper, the graphite G1620 produced by Huzhou Chuangya Power Battery material Co., Ltd and the graphite G123 produced by Changzhou Zhongkelaifang Energy Technology Co., Ltd. A series of rGO/G1620 and rGO/G123 materials with graphene content were prepared by means of graphene coating and high temperature thermal reduction. The methods of X-ray diffraction (XRD), scanning electron microscopy (SEM), constant current charge-discharge and cyclic voltammetry were systematically investigated. The structure of rGO/G1620 and rGO/G123 materials with graphene content was studied. Effects of morphology and electrochemical properties. The results of XRD test showed that graphene coating had little effect on the structure of G1620 and G123. SEM scanning was carried out. It can be seen that graphene is coated on the surface of G1620 and G123, and cyclic voltammetry shows that graphene coating can increase the capacity of graphite. Constant current charge-discharge tests were carried out in the current density range of 0.005-2V at 10 Ma / g. For graphene coated G1620 materials, the graphene content of 3% has higher capacity and better cycling performance. The initial discharge and charging capacity of G1620 are 482mAh/ g and 388mAh/ g, respectively, which are higher than those of G1620 material (388mAh/ g and 340mAh/ g). After the Coulomb efficiency reaches 80.30 cycles, the charge specific capacity can still reach 385mAhg / g, while the G1620 material has only 79mAh/ g, and its capacity retention rate is 99.55.The ratio of the first discharge and charging capacity of G1620 is 99.5mg. Under the same test conditions, for the G123 material coated with graphene, the material with 4% graphene content has higher capacity and better cycling performance. The initial discharge and charge specific capacity of 510mAh/ g and 393mAh/ g is greater than that of G123's 400mAh/ g and 357mAh/ g, and its Coulomb efficiency is 77.30 cycles, and its charge specific capacity can still reach 387mAh-g. however, G123 material can only reach 252mAh/ g, and its retention rate is 98.5B. Graphene coating can improve the capacity and cyclic performance of graphite materials. The G1620 and G123 anode materials of Li-ion batteries prepared by the modified method in this paper have the characteristics of large capacity and good cycling performance.
【学位授予单位】：华中师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：O613.71;TM912

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