钴基钒酸盐电极材料的制备及电化学性能研究

发布时间：2018-05-26 08:22

本文选题：超级电容器 + 锂离子电池　；参考：《新疆大学》2017年硕士论文

【摘要】：能源危机和温室气体效应严重制约了整个社会的全面可持续发展,通过超级电容器和锂离子电池等储能器件将可再生能源以电能的形式储存起来,此举被视作是解决以上难题的有效途径之一。电极材料的研究发展在一定程度上决定了超级电容器和锂离子电池的商业价值和实际应用,所以最核心的问题就是开发新型高活性电化学电极材料或者改善提高已有电极材料的电化学活性。近年来,三元过渡金属氧化物因其理论比容量高、导电性好以及双金属之间的协同效应等优点使之成为了一个研究热点,并且在储能领域展现出了巨大的应用潜力。然而,其中关于钴基钒酸盐电极材料的文献报道却不够丰富,究其原因是由于钒的价态多变导致缺乏适合的制备方法、反应过程中的电化学机理尚不够明确、循环稳定性不够优异等。我国钒和钴资源非常丰富,但综合开发利用尚不足够,因此研究如何将丰富的钒和钴资源转变为功能化材料是一项有意义的工作。基于以上分析,本论文针对钴基钒酸盐材料开展了以下工作:(1)以偏钒酸铵和六水硝酸钴为原料,蒸馏水为反应溶剂,利用微波辅助法结合高温煅烧处理成功合成了准立方块结构的CoV_2O_6。将准立方块结构的CoV_2O_6作为超级电容器的电极材料,经电容性能测试表明其比电容为223 F g-1(电流密度为1 A g-1),且倍率性能也较好,当经过15000圈循环后(电流密度为5 A g-1),比电容未出现衰减,表现出良好的循环稳定性。本工作拓宽了超级电容器材料的种类,同时也推动了钴基钒酸盐材料在超级电容器领域内的进一步研究。(2)钴基钒酸盐因其理想的电化学性能已经在锂离子电池领域内引起了关注,但是其制备方法仍面临着诸多问题。本章经实验探索,提出通过室温共沉淀的方法控制合成球形前驱体,而后通过煅烧得到由纳米小颗粒组成的分级介孔Co_3V_2O_8微米球。当将Co_3V_2O_8微米球作为锂电负极材料时,初始放电容量可达1099.0 mA h g-1(电流密度为500 mA g-1),循环200圈后放电容量相比第二圈的容量未出现衰减,电流密度提高至2000 mA g-1时,平均放电容量仍然可达545.5mA h g-1,表现出良好的倍率性能。这种合成方法相较于文献所报道的方法更为节能、温和和简单,同时可实现对材料结构的有效调控。(3)采用液相合成方法,以常见且廉价的尿素作为形貌调控剂,通过控制反应过程参数,制备出三维花状形貌结构的Co_2V_2O_7·nH_2O。将三维花状形貌结构的Co_2V_2O_7·nH_2O作为超级电容器的电极材料时,通过电容测试结果发现:当电流密度为1 A g-1时,其比电容为326.9 F g-1;当电流密度扩大10倍时,其比电容为247.3 F g-1,展现出较好的倍率性;在5 A g-1的电流密度下循环15000圈后的比电容未出现衰减,体现出良好的循环稳定性。
[Abstract]:The energy crisis and the greenhouse gas effect seriously restrict the overall sustainable development of the whole society. It is considered as one of the effective ways to solve the above problems by storing the renewable energy in the form of electric energy through the energy storage devices such as supercapacitors and lithium ion batteries. The research and development of electric electrode materials is determined to a certain extent. With the commercial value and practical application of supercapacitors and lithium ion batteries, the most important problem is to develop new highly active electrochemical electrode materials or improve the electrochemical activity of existing electrode materials. In recent years, three meta transition metal oxides have high theoretical specific volume, good conductivity and synergy between bimetal. Effect and other advantages make it a hot research focus and show great potential in the field of energy storage. However, the literature on cobalt based vanadate electrode materials is not rich enough. The reason is that the valence state of vanadium leads to the lack of suitable preparation methods, and the electrochemical mechanism in the reaction process is not clear enough. It is true that the circulation stability is not excellent. The resources of vanadium and cobalt are very rich in our country, but the comprehensive development and utilization are not enough. Therefore, it is a meaningful work to study how to transform the rich vanadium and cobalt resources into functional materials. Based on the above analysis, the following work has been carried out on the cobalt base vanadium acid materials: (1) ammonium vanadate and ammonium vanadate are used in this paper. Six water cobalt nitrate is used as the raw material and distilled water is a reaction solvent. The quasi vertical block structure of CoV_2O_6. is successfully synthesized by microwave assisted method and high temperature calcination. The CoV_2O_6 of the quasi vertical block structure is used as the electrode material of the supercapacitor. The capacitance performance test shows that the specific capacitance is 223 F g-1 (the current density is 1 A g-1). It can also be better, when after 15000 cycles (the current density is 5 A g-1), the capacitance is not attenuated and shows good cyclic stability. This work widens the types of supercapacitor materials and also promotes the further study of cobalt based vanadate materials in the supercapacitor field. (2) cobalt based vanadate is ideal for its electrochemistry. The performance has attracted a lot of attention in the field of lithium ion batteries, but the preparation method still faces many problems. In this chapter, the synthetic spherical precursor is controlled by the method of room temperature coprecipitation, and then the mesoporous Co_3V_2O_8 microspheres composed of small nanoparticles are obtained by calcining. When the Co_3V_2O_8 microsphere is made, the microsphere is made by calcining. The initial discharge capacity can reach 1099 mA h g-1 (the current density is 500 mA g-1). The capacity of the discharge capacity is not attenuated and the current density increases to 2000 mA g-1 after 200 cycles, and the average discharge capacity is still 545.5mA h g-1, showing a good multiplier performance. The methods reported in the literature are more energy-saving, mild and simple, and can effectively control the structure of materials. (3) using liquid phase synthesis method, the common and cheap urea is used as a morpho regulator. By controlling the parameters of the reaction process, the three-dimensional flower like structure of Co_2V_2O_7. NH_2O. is prepared by the control of the parameters of the reaction process. When _7 nH_2O is a supercapacitor electrode material, it is found that the specific capacitance is 326.9 F g-1 when the current density is 1 A g-1, and when the current density expands 10 times, its specific capacitance is 247.3 F g-1, showing a better multiplier, and the specific capacitance is not attenuated after the circulation of 15000 cycles at the current density of 5 A g-1. There is a good cycle stability.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ138.12;O646

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