钒基材料的合成、表征及其电化学性能研究

发布时间：2018-04-19 04:00

本文选题：锂离子电池 + 五氧化二钒　；参考：《华南理工大学》2015年硕士论文

【摘要】：二次电池是能量储存和转化的重要方式。锂离子电池因优异的电化学性能得到广泛的关注和应用。正极材料和负极材料是锂离子电池的重要组成部分,寻找容量高、循环性能优越、成本低、环境友好的正负极材料是目前锂离子电池领域的研究热点。本论文从合成方法和结构形貌设计入手,以钒基材料为研究重点,探讨了锂离子电池的正极材料多孔V2O5纳米管、负极材料VN/石墨烯纳米复合材料的合成、表征及其在电化学性能方面的研究。利用X射线衍射、扫描电镜、透射电镜等表征手段对制备样品的微观结构和形貌进行了分析,并采用恒流充放电测试、循环伏安法测试和交流阻抗测试等技术手段研究其电化学性能。在论文第一章中,作者简要介绍了锂离子电池的工作原理、结构组成等,并对常见的锂离子电池电池正极材料和负极材料做了简单介绍。在论文第二章中,作者简单介绍了论文中所用到的主要实验药品、实验仪器、表征手段和分析方法,阐述了电极的制备和电池的组装,以及电池的电化学性能测试的手段和方法。在论文第三章中,我们采用低成本的钒源作前驱体,使用静电纺丝的方法合成了多孔V2O5纳米管。静电纺丝是一种可以用来合成一维纳米材料的简单的可调节的方法。通过控制静电纺丝的相关参数,可以获得直径大小均匀的纳米纤维。多孔V2O5纳米管是多孔一维纳米结构。多孔纳米结构有利于电解液的浸润和锂离子的扩散距离的缩短。一维纳米管具有很大的纵横比,这可以有效避免纳米材料的团聚,而且一维纳米管可以沿着一维方向提供一个有效的电子通道,从而有利于电子的传导。这些优点有益于提高五氧化二钒的电化学性能。电化学性能测试结果表明,在400 oC热处理15 min获得的多孔五氧化二钒纳米管,在2.5-4.0 V电压范围,放电比容量在5C、10C、20C、30C、40C、50C时分别为124.8 m Ah g-1、114.9 m Ah g-1、99.7 m Ah g-1、93.1 m Ah g-1、84.9 m Ah g-1和79.6 m Ah g-1。在50C时,经过200次循环,容量保持率是97.4%,表现出优异的倍率性能和循环性能。在论文第四章中,用简单的水热法结合热还原,得到VN/石墨烯纳米复合材料,石墨烯的存在提高了VN的导电性且在一定程度上缓解了VN的聚集,VN纳米颗粒的存在也阻止了石墨烯的可能堆积,两者之间具有协同效应。将VN/石墨烯纳米复合材料作为负极材料应用于锂离子电池中,其表现出良好的倍率性能。在电压窗口为0.01-3.0 V内,电流密度为1000 m A g-1、2000 m A g-1、3000 m A g-1时,可逆比容量为188.7 m Ah g-1、161.9 m Ah g-1和148.7 m Ah g-1。
[Abstract]:Secondary battery is an important way of energy storage and conversion.Lithium ion battery has been widely concerned and applied because of its excellent electrochemical performance.Cathode materials and anode materials are important components of lithium ion batteries. Looking for positive and negative materials with high capacity, excellent cycling performance, low cost and friendly environment is a hot research topic in the field of lithium-ion batteries.In this paper, the synthesis of porous V2O5 nanotubes and VN/ graphene nanocomposites for lithium ion batteries was studied, starting with the synthesis method and structural morphology design, and taking vanadium based materials as the focus of the research, in this paper, the synthesis of porous V2O5 nanotubes and VN/ graphene nanocomposites as anode materials for lithium ion batteries was discussed.Characterization and electrochemical properties.The microstructure and morphology of the prepared samples were analyzed by means of X-ray diffraction, scanning electron microscope and transmission electron microscope, and the constant current charge-discharge test was used.The electrochemical performance was studied by cyclic voltammetry and AC impedance measurement.In the first chapter, the author briefly introduces the working principle, structure and composition of lithium ion battery, and gives a brief introduction to the common cathode and negative materials of lithium ion battery.In the second chapter, the author briefly introduces the main experimental drugs, experimental instruments, characterization methods and analytical methods used in the paper, and describes the preparation of electrodes and the assembly of batteries.And the electrochemical performance of the battery means and methods.In chapter 3, we synthesized porous V2O5 nanotubes by electrospinning using low-cost vanadium as precursor.Electrostatic spinning is a simple and adjustable method for synthesizing one-dimensional nanomaterials.The nanofibers with uniform diameter can be obtained by controlling the parameters of electrostatic spinning.Porous V2O5 nanotubes are one-dimensional porous nanostructures.The porous nanostructure is beneficial to the infiltration of electrolyte and the shortening of the diffusion distance of lithium ion.One-dimensional nanotubes have a large aspect ratio, which can effectively avoid the agglomeration of nanomaterials, and one-dimensional nanotubes can provide an effective electron channel along the one-dimensional direction, which is conducive to the conduction of electrons.These advantages are beneficial to improve the electrochemical performance of vanadium pentoxide.The electrochemical properties of porous vanadium pentoxide nanotubes obtained by heat treatment at 400oC for 15 min were 124.8 mAh g-1114.9 mAh g-199. 7 mAh g-199. 7 mAh g-1 84.9 mAh g-1 and 79.6 mg-1Ah at the voltage range of 2.5-4.0 V, and the specific discharge capacity was 124.8 mAh g-1114.9 mAh g-1C and 79.6 mg-1 at 50C, respectively.At 50 C, after 200 cycles, the capacity retention rate is 97.4, showing excellent performance of rate and cycle.In chapter 4, VN/ graphene nanocomposites were prepared by a simple hydrothermal method combined with thermal reduction.The existence of graphene improves the electrical conductivity of VN and to some extent alleviates the existence of VN aggregating VN nanoparticles and prevents the possible accumulation of graphene. There is a synergistic effect between the two.When VN/ graphene nanocomposites were used as anode materials in lithium ion batteries, they showed good rate performance.The reversible specific capacity of 188.7 mAh g-1161.9 mAh g-1 and 148.7 mAh g-1 were obtained when the voltage window was 0.01-3.0 V and the current density was 1000 mg / g ~ (-1) 2 000 mg ~ (-1).
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ135.11;O646

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