锂空气电池氧化钌复合电极的制备及其性能研究

发布时间：2018-05-11 19:01

本文选题：锂空气电池 + RuO2/MWNTs催化剂　；参考：《电子科技大学》2015年硕士论文

【摘要】：锂空气电池因具有非常高的理论比容量引起了研究学者的广泛关注,是一种新型的环保电池。但是其过大的过电位、较差的倍率性能、较低的循环寿命等缺点严重阻碍了锂空气电池的商业化进程。如今锂空气电池的的开发和研究面临着许多困难,如:充放电反应机理、负极锂片的保护、电解液的分解、空气电极的结构设计和催化剂的选择等关键技术。本论文以探索可以同时催化锂空气电池的氧还原反应(ORR)和析氧反应(OER)的双效催化剂为目标,以RuO2为锂空气电池空气电极的主要催化剂为主要研究对象,分别采用液相共沉积法和水热反应法制备了不同形貌的RuO2/MWNTs复合材料,选出具有制备催化性能较好的催化剂的方法,进一步利用这种方法在MWNTs表面上同时负载纳米级的MnO2和RuO2颗粒,我们利用XRD、SEM、TEM等方法对复合材料的物化性能进行表征。最后对由这些复合材料组装成的锂空气电池进行电化学性能测试。我们得到如下结论:1.由水热反应法制备出了RuO2/MWNTs复合材料中的RuO2结晶程度比液相共沉积法制备的好,并且具有较小的颗粒粒径。此外,由水热反应法制备出了RuO2/MWNTs复合材料表现出较好的电化学性能,在电流密度为0.1 mA/cm2时,截止电压为2.3~4.0 V,放电容量高达2033 mAh/g;电流密度为0.2 m A/cm2时,放电容量为1534 mAh/g,当电流密度增加到0.4 mA/cm2时,放电容量衰减到896mAh/g,随着充放电电流密度的增大,充放电容量明显减少,过电位缓慢的增加,电极极化增大;电流密度为0.1 mA/cm2时,锂空气电池在循环三周后的放电容量为1808 mAh/g,且具有88.9%的容量保留率,此后在较大的电流密度下进行循环测试,电流密度为0.3 mA/cm2,截止容量为400 mAh/g,可以循环50次充放电比容量不发生衰减且过电压较小。2.由水热法进一步合成了MnO2-RuO2/MWNTs复合纳米材料,由MnO2-RuO2/MWNTs复合材料组成的锂空气电池在电流密度为0.1 mA/cm2时,具有较大的放电平台2.88 V和较小的充电平台3.32 V,过电位为0.44 V,该电池的放电比容量值高达5736 mAh/gcarbon。由MnO2-RuO2/MWNTs复合材料组成的锂空气电池的放电平台比RuO2/MWNTs的高0.06 V,且具有较好的放电比容量。此外,由MnO2-RuO2/MWNTs复合材料组成的锂空气电池还具有较好的循环特性,在电流密度为0.3 mA/cm2,截止容量为1000 mAh/gcarbon(380 mAh/g)时,电池的循环周期高达65次,这就表明了MnO2-RuO2/MWNTs复合材料具有较好的ORR催化活性。3.锂空气电池的电化学性能与催化剂的形貌和纳米颗粒的大小密切相关,较小颗粒的催化剂表现出较大的放电容量。纳米MnO2的加入可以提高锂空气电池的放电电位并提高锂空气电池的放电容量和循环寿命。但较多催化剂的加入会减少电极的孔容和增加锂空气电池的电化学阻抗。
[Abstract]:Lithium air battery is a new type of environmental protection battery because of its high theoretical specific capacity. However, its shortcomings such as excessive overpotential, poor rate performance and low cycle life seriously hinder the commercialization of lithium-air batteries. Nowadays, the development and research of lithium air battery are facing many difficulties, such as the mechanism of charge and discharge reaction, the protection of cathode lithium, the decomposition of electrolyte, the structure design of air electrode and the selection of catalyst. The aim of this thesis is to explore a dual catalyst that can catalyze the oxygen reduction reaction of lithium-air battery (ORR) and oxygen evolution reaction (ORR) at the same time, and take RuO2 as the main catalyst for the air electrode of lithium-air battery as the main research object. RuO2/MWNTs composites with different morphologies were prepared by liquid phase co-deposition and hydrothermal reaction respectively. Furthermore, the nano-scale MnO2 and RuO2 particles were loaded on the surface of MWNTs by this method, and the physical and chemical properties of the composites were characterized by XRD-SEMT-TEM. Finally, the electrochemical performance of the lithium-air battery assembled from these composite materials was tested. We get the following conclusion: 1. The crystallization degree of RuO2 in RuO2/MWNTs composites prepared by hydrothermal reaction method was better than that by liquid phase co-deposition method, and the particle size was smaller than that prepared by liquid phase co-deposition method. In addition, the RuO2/MWNTs composites prepared by hydrothermal reaction showed good electrochemical properties. When the current density was 0.1 mA/cm2, the cutoff voltage was 2.3N 4.0 V, the discharge capacity was up to 2033 mg / g, and the current density was 0.2 m A/cm2. The discharge capacity is 1534 mg / g. When the current density increases to 0.4 mA/cm2, the discharge capacity attenuates to 896 mg / g. With the increase of charge / discharge current density, the charge-discharge capacity decreases obviously, the overpotential increases slowly and the electrode polarization increases, and when the current density is 0.1 mA/cm2, The discharge capacity of the lithium-air battery is 1808 mg / g after three weeks of cycle and has a retention rate of 88.9%. The current density is 0.3 Ma / cm ~ 2, the cutoff capacity is 400 mg 路h / g, the specific capacity of charging and discharging can be recirculated 50 times without attenuation and the overvoltage is smaller. 2. MnO2-RuO2/MWNTs composite nanomaterials were further synthesized by hydrothermal method. The lithium-air batteries composed of MnO2-RuO2/MWNTs composites were prepared at a current density of 0.1 mA/cm2. The battery has a large discharge platform of 2.88 V and a smaller charging platform of 3.32 V and an overpotential of 0.44 V. the specific discharge capacity of the battery is as high as 5736 mAh/ g carbon. The discharge platform of lithium-air battery composed of MnO2-RuO2/MWNTs composite is 0.06 V higher than that of RuO2/MWNTs, and has good discharge capacity. In addition, the lithium air battery made of MnO2-RuO2/MWNTs composite material also has good cycling characteristics. When the current density is 0.3 Ma / cm ~ 2 and the cutoff capacity is 1000 mAh/gcarbon(380 路h / g, the cycle period of the battery is up to 65 times. This shows that the MnO2-RuO2/MWNTs composite has good ORR catalytic activity. 3. The electrochemical performance of lithium-air batteries is closely related to the morphology of the catalyst and the size of the nanoparticles. The catalyst with smaller particles exhibits a larger discharge capacity. The addition of nanometer MnO2 can increase the discharge potential of lithium air battery and improve the discharge capacity and cycle life of lithium air battery. However, the addition of more catalysts can reduce the pore volume of the electrode and increase the electrochemical impedance of the lithium air battery.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O646.54;TM911.41

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