过钼酸铵辅助合成自支撑石墨烯材料及其电化学储能性质研究

发布时间：2018-05-07 17:33

本文选题：石墨烯 + 纳米石墨片阵列　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：锂空气电池因其超高的能量密度在储能领域有良好的应用前景,然而还存在诸多问题如电池充放电过电位过高导致的低库伦效率,循环寿命低,功率密度小等。上述问题大都取决于正极催化剂的催化能力,研究表明电极材料的微观结构(比表面积、孔容、孔径)对电化学性能有重要的影响。运用有效的手段设计高活性、低成本、高稳定性的电极材料对锂空气电池或锂离子电池十分重要,许多课题组在利用电沉积或水热的合成方法构造理想的电极结构如自支撑、或者混合结构做了大量的工作。因此研究低成本、高效的合成方法制备自支撑电极对锂空气电池十分必要。垂直石墨烯阵列(Vertically aligned graphitic carbon nanosheets,VAGN)在各领域都有广阔的应用前景,但是其合成过程比较复杂。本文中,我们利用一种新的、制备简单的(NH4)2Mo2O11-剪裁辅助自组装方法在泡沫镍表面合成VAGN,该方法可用于组装孔尺寸和片层厚度可控的VAGN。制备的阵列不仅作为锂空气电池正极催化剂表现出高容量,作为超级电容器也表现出高比容量和长循环寿命。作为锂空气电池正极催化剂,限压2.0-4.2 V,电流密度为0.1 A·g 1下VAGN薄膜的首次放电容量高达6500 m Ah·g 1;限容500 m Ah·g 1,充放电电流为0.5A·g 1时电池在放/充电电压低于1.5 V和超过4.5 V之前,循环100次后容量仍能保持不变。VAGN作为电容器也表现出优异的电容性能。电流密度为20 A·g 1时,VAGN比容量达到了634 F·g 1;在电流密度高达200 A·g 1下,比容量仍然达到了240 F·g 1,充放电循环超过1000次容量不衰减。此外利用水热合成,将过钼酸铵作为氧化石墨的剪裁剂和尺寸调节剂,成功制备出孔尺寸可调的泡沫石墨烯。以此作为自支撑电极应用在锂空气电池和锂离子电池中,取得了优异的电化学性能。作为锂空气电池正极,电流密度为0.2 A·g 1时,首次放电容量为5523m Ah·g 1,而充电容量为5510 m Ah·g 1;限容500 m Ah·g 1,充放电电流为0.5 A·g 1时,电池在放/充电电压低于2.0 V或超过4.5 V之前,循环60次后容量仍保持不变。作为锂离子电池负极,充放电电流密度为0.1 A·g 1时嵌锂容量达到1300 m Ah·g 1;放电电流密度为100 A·g 1时,嵌锂比容量仍达到100 m Ah·g 1。在电流为50 A·g 1时电池循环超过250圈容量保持在240 m Ah·g 1左右,库伦效率一直保持接近100%。
[Abstract]:Lithium air battery has a good application prospect in the field of energy storage due to its super high energy density. However, there are still many problems such as low Coulomb efficiency, low cycle life and low power density caused by the over-potential of charge and discharge of the battery. Most of the above problems depend on the catalytic ability of the cathode catalyst. It is shown that the microstructure (specific surface area, pore volume, pore size) of the electrode material has an important influence on the electrochemical performance. The design of high active, low cost and high stability electrode materials is very important for lithium-air batteries or lithium-ion batteries by effective means. Many research groups are using electrodeposition or hydrothermal synthesis methods to construct ideal electrode structures such as self-supporting. Or mixed structures do a lot of work. Therefore, it is necessary for lithium air battery to prepare self-supporting electrode by low cost and high efficiency synthesis method. Vertically aligned graphitic carbon nanosheetsVAGNN has a wide application prospect in various fields, but its synthesis process is complex. In this paper, we synthesized VAGNN on the surface of nickel foam by a new, simple self-assembly method of NH _ 4N _ 2Mo _ 2O _ 11-Cutting-assisted self-assembly, which can be used to fabricate VAGN with controllable pore size and lamellar thickness. The prepared arrays not only exhibit high capacity as cathode catalysts for lithium-air batteries, but also show high specific capacity and long cycle life as supercapacitors. As a cathode catalyst for lithium-air batteries, The initial discharge capacity of VAGN thin film is as high as 6500 m Ah g ~ (-1) at current density of 0.1A g ~ (-1) with voltage limit of 2.0-4.2 V, and the initial discharge capacity of VAGN film is as high as 6500 m Ah g ~ (-1) with a charge / discharge current of 0.5 A g ~ (-1) before discharge / charge voltage is below 1.5V and over 4.5V. After 100 cycles, the capacity can remain unchanged. VAGN as capacitor also shows excellent capacitive performance. The specific capacity of VAGN reaches 634F g / g ~ (-1) when the current density is 20A / g ~ (-1), and when the current density is as high as 200A / g ~ (-1), the specific capacity is still up to 240F / g ~ (-1), and the capacity of charge / discharge cycle exceeds 1000 times without attenuation. In addition, using ammonium permolybdate as the cutting agent and size regulator of graphite oxide, the foam graphene with adjustable pore size was successfully prepared by hydrothermal synthesis. The self-supporting electrode has been applied to lithium air battery and lithium ion battery, and excellent electrochemical performance has been obtained. As the positive electrode of lithium air battery, the initial discharge capacity is 5523mAh / g / g and the charge capacity is 5510 m Ah g / 1, the current density is 0.2A / g / 1, and the limited capacity is 5510 m Ah g / 1, and the charge / discharge current is 0.5A / g / 1. Before the discharge / charge voltage is below 2.0 V or over 4.5 V, the capacity of the battery remains unchanged after 60 cycles. As a negative electrode of lithium ion battery, the current density of charge and discharge is 0. 1 A g / L, the capacity of intercalation lithium is 1300 m Ah g / 1, and the specific capacity of lithium intercalation is still 100 m Ah g / 1 when the current density of discharge is 100A g / m ~ (-1). The Coulomb efficiency has been kept close to 100 when the current is 50 A g / 1 and the cycle capacity is about 240 mAh g / g ~ (-1) over 250 cycles.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.11;TM911.41

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