钽氧化物的水热合成及其在锂-空气电池中的应用

发布时间：2018-04-10 05:24

本文选题：五氧化二钽　切入点：还原氧化石墨烯　出处：《吉林大学》2017年硕士论文

【摘要】：近阶段,金属-空气电池的研究掀起了学术界的新浪潮,与大多数电池相比,金属-空气电池的阴极活性材料为氧气,主要来源于空气中,不存储在电池内部,在充、放电过程中被阴极表面的催化剂材料催化参与电池的相关反应。大多数金属-空气电池使用的是水系电解液,如浓的氢氧化钾溶液,但锂-空气电池使用的电解液更多的是非水系溶液,在电池的工作过程中不参与反应。由于它具有最高的理论能量密度(11700 Wh/kg),锂-空气电池在众多电池体系中脱颖而出,但要将其应用到现实生活中还有很多挑战需要我们去面对,比如阴极反应的机理、在半开放体系中电池各组分的稳定、容量的衰减以及循环寿命短等等。为了得到更好的电池性能,学者们不断对研究体系进行调整和完善,其中阴极催化剂材料的设计备受学者们的青睐。目前,主要的阴极催化剂材料有多孔碳材料(碳纳米管、石墨烯等)、过渡金属氧化物(Fe_2O_3、MnO_2、Co_3O_4等)、合金(Au-Pt/XC-72、Pt-GNS等)等。在本工作中,我们利用水热法制备了Ta_2O_5、rGO/Ta(MeO)_5、rGO/Ta_2O_5纳米催化剂材料。通过XRD、SEM和TEM等测试手段对样品的形貌及结构进行了表征和分析,数据显示,该方法制得的Ta_2O_5为正交晶系P21212(18)空间群,晶胞参数a=6.198?,b=40.29?,c=3.888?,α=β=γ=90°;样品rGO/Ta_2O_5具有最大的比表面积和最高的还原程度,作为锂-空气电池的阴极催化剂可得到较好的电池性能,该样品首次放电比容量为8300 mAh/g,相比其他几种催化剂过电势降低了0.4 V,循环稳定性提高了近4倍。结合文献分析,电极材料具有较大的比表面积、较高的还原程度,在电池充、放电的过程中可提供更多的反应活性位点,有利于提高放电产物的沉积量及层间Li_2O_2的生成量,从而提高电池的放电容量及降低反应的过电势,得到较好的电池循环性能。这项研究表明,五氧化二钽/还原氧化石墨烯复合催化剂材料将成为非常有前景的锂-空气电池阴极催化剂之一。此外,我们还制备了具有石墨烯骨架结构的五氧化二钽纳米材料。通过XRD、SEM和TEM等测试手段对样品进行了表征和分析;有关锂-空气电池的性能测试显示,当电流密度为100 mA/g时,首次放电比容量为2843 mAh/g,相比于普通无定形Ta_2O_5纳米材料,其性能提升了30%,且具有更好的倍率性能和循环稳定性。本论文通过探究钽氧化物在锂-空气电池中的催化性能,为金属-空气电池的研究提供了新的研究思路与实验方法。
[Abstract]:In recent years, the research of metal-air battery has set off a new wave in academia. Compared with most batteries, the cathode active material of metal-air battery is oxygen, which is mainly derived from the air, not stored in the battery, but filled.In the discharge process, the catalyst materials on the cathode surface catalyze to participate in the battery reaction.Most metal-air batteries use aqueous electrolytes, such as concentrated potassium hydroxide solutions, but lithium-air batteries use more non-aqueous solutions and do not take part in the reaction.Because it has the highest theoretical energy density of 11, 700 what / kg / kg, lithium-air batteries stand out in many battery systems, but there are still many challenges to face in real life, such as the mechanism of cathodic reaction.In the semi-open system, the stability of each component, the attenuation of capacity and the short cycle life, etc.In order to obtain better battery performance, the research system has been continuously adjusted and improved, among which the design of cathode catalyst materials is favored by scholars.At present, the main cathode catalyst materials are porous carbon materials (carbon nanotubes, graphene, etc., transition metal oxides, Fe2O3MnO2CO3O4, Au-Pt / XC-72Pt-GNS and so on).In this work, we have prepared the Ta2O5R / TaMeOG / Tas / Tas / T / T _ 2O _ 5 nano-catalyst materials by hydrothermal method.The morphology and structure of the samples were characterized and analyzed by means of TEM and SEM. The data show that the Ta_2O_5 prepared by this method is an orthogonal crystal system P21212O18) space group, the unit cell parameter a6.19880.290.29cncncncncncncncncnchrc88-8, 伪 = 尾 = 纬 90 掳, the sample rGO/Ta_2O_5 has the largest specific surface area and the highest degree of reduction, and the results show that the sample rGO/Ta_2O_5 has the highest specific surface area and the highest reduction degree, and the crystal cell parameters of the sample are as follows: P2121212) space group.As a cathode catalyst for lithium-air battery, the performance of the cathode catalyst is better. The initial discharge specific capacity of the sample is 8300 mg / g, which is 0.4 V lower than that of other catalysts, and the cyclic stability is improved nearly 4 times.Combined with literature analysis, the electrode material has a large specific surface area, a higher reduction degree, and can provide more reactive sites in the process of battery charge and discharge, which is helpful to increase the deposition amount of discharge products and the production of interlaminar Li_2O_2.Thus, the discharge capacity of the battery is increased and the overpotential of the reaction is reduced, and the better cycle performance of the battery is obtained.This study shows that tantalum pentoxide / reduced graphene oxide composite catalyst materials will become one of the most promising cathode catalysts for lithium-air batteries.In addition, tantalum pentoxide nanomaterials with graphene skeleton structure were prepared.The samples were characterized and analyzed by means of XRD-SEM and TEM. The performance tests of lithium-air batteries show that the first discharge specific capacity of the lithium-air battery is 2843 mg / g when the current density is 100 mA/g, which is higher than that of the ordinary amorphous Ta_2O_5 nanomaterials.Its performance improves 30%, and has better rate performance and cycle stability.In this paper, the catalytic performance of tantalum oxide in lithium-air battery is studied, which provides a new research idea and experimental method for metal-air battery.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TM911.41

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