石墨烯纳米带及其复合材料的制备与电化学储锂性能的研究

发布时间：2018-05-17 05:34

本文选题：锂离子电池 + 石墨烯纳米带　；参考：《重庆大学》2015年硕士论文

【摘要】：锂离子电池具有能耗低、能量密度大、工作电压高、自放电小、环境友好、循环性能好等显著优点,被广泛应用于笔记本电脑、移动电话、照相机、矿灯等便携式电子设备。目前,材料对锂离子电池性能有着至关重要的影响。碳材料具有价格低、环境友好、结构多样、制备简单、易于改性以及安全性高等诸多优点,本文从石墨烯纳米带的制备、金属氧化物的复合以及含锂过渡金属磷酸盐的复合等方面系统研究了石墨烯纳米带在锂离子电池正极/负极材料中的使用效能和作用机理。本文采用溶剂氧化法制备出的石墨烯纳米带相互缠绕,自组装成三维多孔网络结构,相对于原料碳纳米管具有更大比表面积及孔结构,不仅提供了更多的锂离子存储位点,同时为锂离子反应提供了更多的锂离子反应界面,缩短了锂离子及电解液的传输扩散路径,能够很好的提升其作为锂离子电池负极材料的嵌锂容量和倍率性能。通过循环伏安测试及恒电流充放电测试,结果表明,在0.6 A g-1和1 A g-1的电流密度下充放电循环200次以后,脱锂比容量分别保持在716 m Ah g-1和519 m Ah g-1。石墨烯纳米带展现出了优异的循环倍率性能。本文采用两步水热法制备出了石墨烯纳米带/Sn O2@碳纳米管复合物。研究发现,直径为5 nm左右的Sn O2纳米颗粒均匀的生长在碳纳米管上,而石墨烯纳米带紧紧的包覆在Sn O2@碳纳米管之上。电化学测试表明,石墨烯纳米带/Sn O2@碳纳米管复合物表现出优异的电化学性能。在电流密度为0.1 A g-1条件下,比容量高达1038 m Ah g-1,而比容量在电流密度为1 A g-1条件下循环1000次后仍能保持502m Ah g-1。这种优越的电化学性能主要是由于墨烯纳米带/Sn O2@碳纳米管复合物特殊的结构造成的。本文采用简单的溶液扩散法,利用磷酸铁锂和石墨烯纳米带之间的静电引力作用,成功制得了石墨烯纳米带均匀包覆磷酸铁锂颗粒的复合正极材料。研究结果表明,石墨烯纳米带的静电粘附作用比碳纳米管的掺杂更能有效提高磷酸铁锂的电化学性能。通过对石墨烯纳米带和碳纳米管与磷酸铁锂复合的对比研究发现,石墨烯纳米带有望成为高功率锂离子电池的导电剂。
[Abstract]:Li-ion battery has many advantages such as low energy consumption, high energy density, high working voltage, low self-discharge, friendly environment and good cycling performance. It is widely used in portable electronic devices such as notebook computer, mobile phone, camera, mine lamp and so on. At present, the material has a vital effect on the performance of lithium ion battery. Carbon materials have many advantages, such as low price, friendly environment, diverse structure, simple preparation, easy modification and high safety. The application efficiency and mechanism of graphene nanobelts in cathode / anode materials of lithium ion batteries were systematically studied in the aspects of metal oxide and lithium transition metal phosphate. In this paper, graphene nanobelts prepared by solvent oxidation method are wound together and self-assembled into a three-dimensional porous network structure, which has a larger specific surface area and pore structure than the raw carbon nanotubes, which not only provides more lithium-ion storage sites. At the same time, it provides more lithium ion reaction interface for lithium ion reaction, shortens the transfer and diffusion path of lithium ion and electrolyte, and can improve its lithium intercalation capacity and rate performance as anode material for lithium ion battery. The results of cyclic voltammetry and constant current charge-discharge tests showed that the specific capacity of lithium removal was kept at 716 mAh g-1 and 519 mAh g-1 after 200 cycles at current density of 0.6 Ag ~ (-1) and 1 A g ~ (-1), respectively. Graphene nanobelts exhibit excellent cyclic rate performance. In this paper, graphene nanoribbons / Sno _ 2 @ carbon nanotube composites were prepared by two-step hydrothermal method. It was found that Sno _ 2 nanoparticles with a diameter of about 5 nm were uniformly grown on carbon nanotubes, while graphene nanobelts were tightly coated on Sno _ 2 @ carbon nanotubes. Electrochemical measurements show that graphene nanobelts / Sn O 2 @ carbon nanotube composites exhibit excellent electrochemical properties. When the current density is 0.1 A g ~ (-1), the specific capacity can reach 1038 mAh g ~ (-1), but the specific capacity can maintain 502m Ah g ~ (-1) after 1000 cycles at the current density of 1 A g ~ (-1). This superior electrochemical performance is mainly due to the special structure of the / Sn-O _ 2 @ carbon nanotube composite. In this paper, a simple solution diffusion method was used to prepare the composite cathode material which was uniformly coated with lithium iron phosphate particles by using the electrostatic force between lithium iron phosphate and graphene nanoribbons. The results show that the electrostatic adhesion of graphene nanobelts is more effective than the doping of carbon nanotubes in improving the electrochemical performance of lithium iron phosphate. Through the comparative study of graphene nanobelts and carbon nanotubes with lithium iron phosphate, it is found that graphene nanobelts are expected to be the conductive agents for high-power lithium ion batteries.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM912;TB383.1

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