真实空气环境中锂空气电池正极催化剂研究

发布时间：2018-04-23 09:02

本文选题：锂空气电池 + 环境空气　；参考：《天津理工大学》2017年硕士论文

【摘要】：锂空气电池在现有储能器件中具有最高的理论比能量,成为下一代储能器件的研究重点。但是目前大部分的研究集中在纯氧条件下,无法实际应用。锂空气电池从纯氧走向真实空气,还面临诸多问题:1.正极:放电产物与空气中的水蒸气、二氧化碳等反应,生成氢氧化锂、碳酸锂等更难分解的副产物,极大降低了电池的充放电效率,并且损失了电池寿命;2.电解液:电解液面临更为严重的挥发与分解等问题;3.负极:空气与金属锂负极反应,发生负极腐蚀、粉化等问题,影响电池的寿命。基于以上问题,针对真实空气环境中锂空气电池正极催化剂的设计与制备,以此来降低电池充电电压,并提高电池的循环性能。第一:系统研究了三种商业化碳材料(乙炔黑、科琴黑和碳纳米管)作正极催化剂在环境空气中的锂空气电池性能。当容量限定500 mAh g-1充放电电流密度200 mA g-1时,三种碳材料都能循环100圈,其中科琴黑在空气中循环最稳定。100圈循环结束后,扫描电镜和红外光谱表明电极表面存在碳酸锂。对锂片直接观察发现负极金属锂片有一定程度的粉化,两方面的共同作用导致了电池性能的衰减。第二:为进一步提高电池的充放电效率和循环性能,我们设计了一种氧化亚锰微米片作正极催化剂并应用于环境空气中的锂空气电池。当容量限定500 mAh g-1充放电电流密度200 m A g-1时,电池能够稳定循环100圈。即使到第100圈时,放电终止电压还能维持在2.65 V左右,充电终止电压为4.0 V。相比于单纯科琴黑的放电终止电压下降到2.36 V,充电终止电压为4.44 V。氧化亚锰的加入有效减小了充电极化,提高了电池的循环稳定性。扫描电镜和X射线光电子能谱研究了氧化亚锰催化的锂空气电池不同放电深度的电极,以此探究在环境空气中放电产物的生成过程和深度分布。发现放电产物表层的碳酸锂来源于空气中的二氧化碳,而电极表面附近的碳酸锂则可能是二氧化碳的反应以及碳材料的腐蚀造成的。本工作研究了廉价的碳材料和氧化亚锰作催化剂的锂空气电池在真实空气环境中的应用。对未来锂空气电池的的实际应用及降低电池成本进行了有益探索。
[Abstract]:Lithium air battery has the highest theoretical specific energy among the existing energy storage devices, so it has become the focus of the next generation energy storage devices. However, most of the current studies focus on pure oxygen conditions, and can not be applied in practice. Lithium air batteries from pure oxygen to real air, but also face a number of problems: 1. Positive electrode: the discharge product reacts with water vapor and carbon dioxide in the air to produce lithium hydroxide, lithium carbonate and other by-products that are more difficult to decompose, which greatly reduces the charge and discharge efficiency of the battery and loses the battery life. Electrolyte: electrolyte is faced with more serious problems such as volatilization and decomposition. Negative electrode: air reacts with metal lithium negative electrode, occurs negative electrode corrosion, powdering and so on, affecting battery life. Based on the above problems, the design and preparation of cathode catalyst for lithium-air battery in real air environment is proposed to reduce the charging voltage and improve the cycle performance of the battery. First, the performance of three commercial carbon materials (acetylene black, Cochan black and carbon nanotube) as cathode catalysts for lithium-air batteries in ambient air was studied. When the charge / discharge current density of 500mAg-1 is limited to 500mAg-1, the three kinds of carbon materials can cycle around 100mAg ~ (-1). After the cycle is most stable in air, scanning electron microscope (SEM) and infrared spectroscopy show that lithium carbonate exists on the electrode surface. The direct observation of the lithium plate shows that the cathode metal lithium sheet has a certain degree of pulverization, and the joint action of the two aspects leads to the attenuation of the battery performance. Second, in order to further improve the charge / discharge efficiency and cycle performance of the battery, we have designed a kind of manganese oxide microchip as cathode catalyst and applied it to the lithium-air battery in ambient air. When the capacity is limited to 500 mAh g ~ (-1), the current density is 200mAg ~ (-1). Even at the 100th cycle, the discharge termination voltage can be maintained at about 2.65 V and the charge termination voltage is 4.0 V. Compared with the pure Cochan black, the discharge termination voltage decreased to 2.36 V, and the charging termination voltage was 4.44 V. The addition of manganese oxide can effectively reduce the charge polarization and improve the cycle stability of the battery. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the formation process and depth distribution of discharge products in lithium air batteries catalyzed by manganese oxide at different discharge depths. It is found that the lithium carbonate in the surface layer of the discharge product originates from the carbon dioxide in the air, while the lithium carbonate near the electrode surface may be caused by the reaction of carbon dioxide and the corrosion of the carbon material. In this paper, the application of cheap carbon materials and manganese oxide as catalyst for lithium air batteries in real air environment has been studied. The practical application and cost reduction of lithium-air battery in the future are discussed.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ426;TM911.41

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