金属氧化物纳米结构的合成及电化学储锂性能研究

发布时间：2018-01-06 15:16

本文关键词：金属氧化物纳米结构的合成及电化学储锂性能研究　出处：《青岛科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着工业经济的迅速发展和环境治理的日益紧迫,人们希望得到越来越多的清洁能源。化石燃料因其污染严重且不可再生已经无法满足社会的需求,开发清洁高效的新型能源是大势所趋,早已成为人们关注的热点。锂离子电池作为一种新型的能量储存和转化装置,已经广泛应用于各种小型电子设备,并且在电动车电源和太阳能、风能等可再生能源的储存方面有广阔的应用前景。锂离子电池的电极材料是影响其性能的关键,目前商业化的石墨类材料理论容量低且有安全性问题,因此亟需开发其他高能量、高稳定性的新型锂离子电池负极材料。过渡金属氧化物具有高容量、优异的循环性能和安全性能等优点,是替代石墨的理想电池负极材料,然而其导电性差、不可逆容量大以及充放电前后体积变化大等问题在很大程度上制约了其实际应用。研究发现,通过纳米化、形貌控制、碳包覆可以有效地提高材料的导电性,缓解充放电时的体积膨胀,改善材料的电化学性能。另外,氢能作为另外一种清洁能源也受到了人们的广泛关注,如何高效地从水中制取氢气是目前的研究热点之一。而电催化析氢反应被认为是一种高效产氢的方式,但是作为电催化析氢反应催化剂的贵金属价格昂贵、储量贫乏,因此急需寻找一种高效、经济的催化剂。过渡金属硫化物可以作为一种高效的析氢催化剂替代以往的贵金属催化剂,但是如何进一步提高过渡金属硫化物的催化活性依然是一个限制因素。研究发现合成特殊形貌的过渡金属硫化物纳米结构或者与其他材料掺杂都可以有效的改善催化活性。本论文采用水热法制备过渡金属氧化物和硫化物材料,应用X-射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)等技术分析材料的形貌和结构等物理特征,运用恒电流充放电、循环伏安(CV)和交流阻抗谱(EIS)等技术测试材料的电化学性能,并分析了材料的结构和形貌与电化学性能之间的关系。主要研究内容和结果如下:(1)在前驱体FeOOH表面构造二氧化硅包覆层,在二氧化硅包覆层的保护作用下,氧化铁材料能够保持前驱体的一维纳米结构。煅烧过程中,前驱体FeOOH转变成氧化铁,同时发生脱水在材料表面形成多孔的结构。这种独特的多孔一维纳米结构有利于锂离子的嵌入-脱出和电子的快速迁移,同时表面的微孔又可以有效的缓解电极在充放电过程中的体积变化,提高循环稳定性。(2)利用一种简易方式在二氧化硅表面构筑超薄CoMoO_4纳米片,同时腐蚀掉位于中心的二氧化硅模板,制备出CoMoO_4纳米片组装的中空纳米结构。放射状的直立片层结构可以为锂离子的嵌入提供更多的位置,内部的中空结构可以有效的缓解材料的体积效应,因此材料具有良好的储锂性能。在500 mA·g-1的电流密度下循环200圈,放电容量依然可以达到1066 mAh·g-1,容量保持率为93%,库伦效率为98%。由于材料特定的中空结构和大的表面积使其实际容量要高于CoMoO_4的理论容量。在10 A·g-1的电流密度下,CoMoO_4中空纳米结构依然可以保留较高的可逆容量为470 mAh·g-1,数值仍然高于石墨的理论容量372 mAh·g-1。结果表明材料具有良好的倍率性能和循环稳定性。(3)通过在四氧化三铁纳米球模板的表面包覆二硫化钼纳米片,合成Fe3O_4@MoS_2异质结构材料,作为电催化析氢反应的催化剂。经过测试证明这种特殊结构的Fe3O_4@MoS_2材料具有比空心二硫化钼更好的析氢催化性能。计算结果显示,材料的电催化活性面积为空心二硫化钼的两倍;四氧化三铁的加入也提高了材料单位面积上活性位点的催化活性。
[Abstract]:With the rapid development of industrial economy and environment is increasingly urgent, people hope to get more and more clean energy. Because of the serious pollution of fossil fuels and non renewable has been unable to meet the needs of society, the new development of clean and efficient energy is already represent the general trend, as the focus of attention. The lithium ion battery as an energy storage and conversion device, has been widely used in a variety of small electronic devices, and the electric power and solar energy, has wide application prospect in storage, wind and other renewable energy. The electrode materials of lithium ion battery is the key to affect the performance of the current commercial graphite materials have low theoretical specific capacity and security issues therefore, it is necessary to develop other high energy, new anode material for lithium ion battery with high stability. The transition metal oxide has the advantages of high capacity, excellent cycle Energy and safety performance and other advantages, is the ideal battery cathode materials to replace graphite, but its poor conductivity, the irreversible capacity and charge discharge before and after volume change and restricts its practical application to a great extent. The study found that the morphology control of nano carbon coating, and can effectively improve the conductivity of the material the ease, charge and discharge volume expansion, improve the electrochemical properties of the material. In addition, hydrogen as another clean energy has attracted people's attention, how to efficiently produce hydrogen from water is one of the research hotspots. The electrocatalytic hydrogen evolution reaction is considered to be an efficient way to produce hydrogen. But as the price of the precious metal catalytic hydrogen evolution reaction catalyst is expensive, poor reserves, it is urgent to find an efficient and economical catalyst. Transition metal sulfides can be used as an efficient hydrogen evolution Catalysts instead of noble metal catalysts in the past, but how to further improve the catalytic activity of transition metal sulfides is still a limiting factor. The study found that transition metal sulfide nanostructures with special morphology or with other materials doped can improve the catalytic activity effectively. This paper adopts the hydrothermal synthesis of transition metal oxides and sulfides, application X- ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) technique. The morphology and structure of materials and other physical characteristics, using constant current charge discharge, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques such as electrochemical performance test materials, and analyzes the relationship between material the structure and morphology and electrochemical performance. The main research contents and results are as follows: (1) in the precursor FeOOH surface structure of silica coated layer protection in two oxygen silicon coating Under the influence of iron oxide material can keep the one-dimensional nano structure of precursor. The calcination process, the precursor FeOOH into iron oxide, simultaneous dehydration to form a porous structure on the surface of the material. This unique porous nanostructures have rapid migration for lithium ions and electron - intercalation, while the surface pores can alleviate again the volume change of electrode during the charge discharge process effectively, improve the cycle stability. (2) using a simple way to construct ultrathin CoMoO_4 nanosheets on silica surface and etching is located in the center of the two silica template prepared CoMoO_4 nanosheets assembled hollow nanostructures. Vertical lamellar structure of radial for lithium ion insertion to provide more position inside the hollow structure can reduce the volume effect of the material effectively, so the material has good lithium storage performance in 500. The current density of mA and g-1 under 200 cycles, the discharge capacity can reach 1066 mAh - g-1, the capacity retention rate was 93%, the efficiency of Kulun for 98%. with a theoretical capacity of hollow structure specific materials and large surface area to the actual capacity is higher than that of CoMoO_4. In the current 10 A - g-1 density. CoMoO_4 hollow nanostructures can still retain the higher reversible capacity of 470 mAh - g-1, the value is still higher than the theoretical capacity of graphite is 372 mAh - g-1. results show that the material has good cycling performance and rate capability. (3) on the surface of Fe3O4 nanospheres by template coated with molybdenum disulfide, synthesis of Fe3O_4@MoS_2 heterostructure materials as catalyst electrocatalytic hydrogen evolution reaction. After testing the special structure of the Fe3O_4@MoS_2 material has better catalytic performance than MoS2 hollow hydrogen. The calculation results show that the material The active area of the electrocatalytic activity is two times of that of the hollow molybdenum disulfide, and the addition of iron oxide also improves the catalytic activity of the active site on the unit area of the material.

【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1;TM912

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