铁的氧、硫化合物的制备及其电化学性能研究

发布时间：2018-04-30 09:12

本文选题：磁赤铁矿 + 多孔材料　；参考：《青岛科技大学》2017年硕士论文

【摘要】：锂离子电池具有高的能量密度,高充放电效率,寿命长以及无记忆效应等优点,已成为满足未来经济社会可持续发展的高能电池之一,电极材料是其发挥这一效能的关键。然而前商业上普遍使用的石墨负极材料,理论容量较低,无法满足高能量应用的要求,如汽车动力电源、智能电网等。因此,人们致力于研究新的电池材料来满足未来锂离子电池的发展需求。就这一点而言,过渡金属氧化物及过渡金属硫化物具有高的理论比容量,成为近年来负极材料的研究热点。其中,由于铁氧化物及硫化物具有成本低廉,生态友好,储量丰富以及容量高等优点,得到广泛的关注。本研究主要在于研究铁的氧化物和硫化物用做锂离子电池负极材料的电化学性能。主要研究内容如下:(1)由多孔纳米带组装成的磁赤铁矿微米结构用于锂离子电池负极材料通过一种简单有效、自下而上的方法合成金属有机物前驱体模板,后对其进行热处理得到具有由纳米晶组成的多孔纳米带进而组装成多级微米结构。这种合成方法简单易行,成本低,适于大规模生产。在锂离子电池中作为负极材料,具有高的可逆容量,当电流密度为0.1 A·g-1时,放电比容量达到1344 mAh·g-1,在5 A·g-1时,放电容量达到408 mAh·g-1,以及良好的循环稳定性,1 A·g-1下,进行100次充放电后,容量仍可保持700 mAh·g-1。这种多级多孔结构提高了离子的运输效率,缓解在充放电过程中的体积变化而造成的结构破坏。(2)采用固相硫化法制备FeS/C,并用于锂离子电池负极材料通过原位硫化MOF-Fe的方法,制备出梭形FeS/C微纳米结构材料,在电流密度为0.1 A·g-1时,进行500次充放电,放电容量仍可保持744 mAh·g-1,具有较好的循环稳定性能,在10 A·g-1时,放电容量可达到322.2 mAh·g-1,良好的倍率性能,这主要是由于碳的掺杂以及多级多孔的微纳米结构不仅缩短离子运输路径提高离子传输速度,而且有利于结构保持稳定,从而使材料表现出优异的电化学性能。(3)Fe_3O_4@C材料的制备,并用于锂离子电池负极材料的电化学性能研究。为改善铁基氧化物的缺点,将铁基氧化物的结构进行设计,制备出Fe_3O_4@C具有核壳结构的材料,碳的包覆结构既可以提高材料的导电性能有可以保证充放电过程中结构的稳定性。实验结果显示:Fe_3O_4@C的电化学性能相比Fe_3O_4得到很大改善,因此Fe_3O_4@C具有更好的电化学性能。当电流密度为0.1 A·g-1时,可逆容量为788.2 mAh·g-1,在10 A·g-1时,可逆容量达到358.8mAh·g-1,具有良好的倍率性能。在0.1 A·g-1经过500次循环容量仍可以保持良好,具有优异的循环稳定性。
[Abstract]:Li-ion batteries have many advantages, such as high energy density, high charge-discharge efficiency, long life and no memory effect. They have become one of the high energy batteries to meet the sustainable development of economy and society in the future. Electrode materials are the key to play this role. However, the theoretical capacity of graphite anode materials, which are widely used in the former commercial field, is low and can not meet the requirements of high-energy applications, such as automobile power supply, smart grid, etc. Therefore, people devote themselves to the research of new battery materials to meet the development needs of lithium ion batteries in the future. In this respect, transition metal oxides and transition metal sulfides have high theoretical specific capacity and have become a hot research topic of anode materials in recent years. Among them, iron oxides and sulfides have attracted wide attention due to their advantages of low cost, ecological friendliness, rich reserves and high capacity. The main purpose of this study is to study the electrochemical performance of iron oxides and sulfides as anode materials for lithium ion batteries. The main research contents are as follows: (1) Magneto-hematite microstructures assembled from porous nanobelts are used as cathode materials for lithium ion batteries through a simple and effective bottom-up method to synthesize metal organic precursor templates. After heat treatment, porous nanoribbons with nanocrystalline structure were obtained and assembled into multilevel micron structures. This synthetic method is simple and feasible, low cost and suitable for mass production. When the current density is 0. 1 A g ~ (-1), the discharge specific capacity is 1344 mAh g ~ (-1), the discharge capacity is 408 mAh g ~ (-1) at 5 A g ~ (-1), and the good cycle stability is 1 A g ~ (-1). After 100 times of charge and discharge, the capacity can still be maintained at 700 mAh g ~ (-1). This multilevel porous structure can improve the transport efficiency of ions and alleviate the structural damage caused by volume change during charge and discharge. FES / C is prepared by solid phase vulcanization method, and used for lithium ion battery anode material through in-situ vulcanization of MOF-Fe. The fusiform FeS/C microstructures were prepared. When the current density was 0.1A g ~ (-1), the discharge capacity could be maintained at 744 mAh g ~ (-1), and the discharge capacity could reach 322.2 mAh g ~ (-1) at 10 Ag ~ (-1). This is mainly due to the fact that carbon doping and multilevel porous microstructures not only shorten the ion transport path and improve the ion transport speed, but also help to keep the structure stable, thus making the materials exhibit excellent electrochemical properties. It is also used to study the electrochemical performance of cathode materials for lithium ion batteries. In order to improve the defects of iron based oxides, the structure of iron based oxides was designed, and the core-shell structure of Fe_3O_4@C was prepared. The coating structure of carbon can not only improve the conductivity of the materials, but also guarantee the stability of the structure during charging and discharging. The results show that the electrochemical performance of Fe_3O_4@C is better than that of Fe_3O_4. When the current density is 0. 1 A g ~ (-1), the reversible capacity is 788.2 mAh g ~ (-1), and the reversible capacity is up to 358.8mAh g ~ (-1) when the current density is 10 A g ~ (-1). After 500 cycles at 0.1 A g ~ (-1), the capacity can be maintained well and has excellent cycle stability.
【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】：TM912

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