金属有机框架（MOF）制备、改性及其在锂硫电池中的应用

发布时间：2018-01-22 19:22

本文关键词： 锂硫电池硫正极多孔材料金属有机框架　出处：《中南大学》2014年硕士论文　论文类型：学位论文

【摘要】：摘要：锂硫电池是一种极具发展前景的高能量密度电池体系。比容量高和循环性能好的多孔骨架／硫复合电极材料是锂硫电池的研究重点和热点。探寻具有良好导电网络、高比表面积、合适孔结构和大小的多孔骨架材料,提高硫正极的电化学活性、吸附性能和结构稳定性,实现高载硫量与高利用率的协同,对于高能量密度锂硫电池的发展具有重要理论基础和学术价值。本文以金属有机框架作为多孔骨架研究对象,成功制备了两种比表面积大,孔径适合的多孔金属有机框架Cr3F(H2O)2O(BDC)3·nH2O(MIL-101)和Zn4O(BDC)3(MOF-5)(BDC=对苯二甲酸),通过原位包覆或碳化进行改性,制备了三种电化学性能优异的复合多孔骨架；通过低温液相和熔融热处理,分别合成了硫-介孔金属有机框架／石墨烯复合材料,硫-介孔炭／多壁碳纳米管复合材料和硫-介孔炭／氧化石墨烯复合材料三种含硫正极材料,研究其理化性质和电化学性能。获得的主要结果如下： 1.硫-介孔金属有机框架／石墨烯复合材料：采用水热法成功合成了微孔结构丰富、比表面积大的介孔金属有机框架(MIL-101),采用“石墨烯与介孔金属有机框架原位复合+硫的液相渗透”二步工艺制备了电化学性能优异的硫-介孔金属有机框架／石墨烯／复合正极材料。电化学测试结果显示,与常规的单质硫正极材料相比,MIL-101(Cr)@rGO/S硫正极半电池首次放电比容量为980mAh g-1,50次循环后仍保持650mAh g-1,容量保持率为66.7%,循环性能表现得到明显的改善,保持较高的正极材料活性物质利用率,并显著提高硫基正极循环稳定性。 2.硫-介孔炭／多壁碳纳米管复合材料：采用溶剂热法成功合成了具有丰富介孔结构的介孔金属有机框架／多壁碳纳米管(MWCNT@MOF-5),以此材料为模板和前驱体,采用高温碳化法制备具有良好导电网络、高比表面积、合适孔结构的介孔炭／多壁碳纳米管复合材料,通过热处理的方法,将熔融的硫渗入多孔碳骨架中得到硫-介孔炭／多壁碳纳米管复合材料(MWCNT@Meso-C/S)。实验测试结果显示,0.5C电流密度下,MWCNT@Meso-C/S半电池首次放电比容量为1384mAh g-1,50次循环后放电比容量仍然保持在874mAh g-1.这种复合结构可有效降低充放电极化,减小电池内阻,电池的循环和大倍率性能良好。 3.硫-介孔炭／氧化石墨复合材料：采用溶剂热法成功合成了具有丰富介孔结构的介孔金属有机框架／氧化石墨烯(GO@MOF-5),以其为模板和前驱体,采用高温碳化的方法制备具有良好导电网络、高比表面积、合适孔径的介孔炭／氧化石墨烯复合材料,通过热处理的方法,将熔融的硫渗入到多孔骨架中制得硫-介孔炭／氧化石墨烯复合材料(GO@Meso-C/S).电化学结果显示,在0.2C电流密度下GO@Meso-C/S半电池首次放电比容量为1122mAh g-1,100次循环后放电比容量仍然保持在820mAh g-1,显示了硫-介孔炭／氧化石墨烯复复合材料较高的活性物质利用率和优异的循环性能。
[Abstract]:Abstract: lithium sulfur battery is a battery system high energy density is a very promising. High specific capacity and good cycle performance of the porous / sulfur composite electrode material is the research focus of lithium sulfur battery. To find a good conductive network, high surface area, porous materials suitable pore structure and size, improve the electrochemical activity of sulfur cathode, the stability of structure and properties of adsorption, high load and high utilization rate of sulfur coordination, has important theoretical basis and academic value to the development of high energy density of lithium sulfur battery.
In this paper, metal organic frameworks as the research object of porous skeleton, successfully prepared two kinds of large specific surface area, porous metal organic frameworks (H2O) for the diameter of Cr3F (BDC 2O) 3 - nH2O (MIL-101) and Zn4O (BDC) 3 (MOF-5) (BDC=, terephthalic acid) was modified by in situ coating or carbonation, composite porous skeleton three excellent electrochemical properties were prepared by low temperature liquid phase; melting heat treatment, were synthesized with sulfur - mesoporous metal organic frameworks / graphene composite materials, mesoporous carbon / sulfur - multi walled carbon nanotubes composites and sulfur oxide mesoporous carbon / graphene composite materials three kinds of sulfur cathode materials, study its physicochemical properties and electrochemical properties. The main results are as follows:
1. sulfur - mesoporous metal organic frameworks / graphene composite materials: synthesis of microporous structure rich by hydrothermal method. The specific surface area of mesoporous metal organic framework (MIL-101), the use of graphene and in situ organic framework of mesoporous metal composite + sulfur liquid infiltration "two step process preparation the excellent electrochemical performance of sulfur - mesoporous metal organic frameworks / Shi Moxi / composite cathode material. The electrochemical test results showed that, compared with conventional sulfur cathode materials, MIL-101 (Cr) @rGO/S sulfur cathode half cell initial discharge capacity was 980mAh after g-1,50 cycles remain 650mAh g-1, the capacity retention rate was 66.7%, cycle the performance has been significantly improved, the utilization rate of cathode active material remained high, and significantly improve the cycle stability of sulfur based cathode.
2. sulfur - mesoporous carbon / multi walled carbon nanotubes composites by solvothermal method successfully synthesized mesoporous metal organic frameworks / multi walled carbon nanotube rich mesoporous structure (MWCNT@MOF-5), this material as template and precursor by high temperature carbonization with good conductive network, high specific surface area mesoporous carbon / multi walled carbon nanotubes composites suitable pore structure, by heat treatment, the sulfur melt into porous carbon skeleton in mesoporous carbon / sulfur composite of multi walled carbon nanotubes (MWCNT@Meso-C/S). The experimental results show that the current density of 0.5C, the MWCNT@Meso-C/S half cell discharge capacity of 1384mAh after g-1,50 cycles the discharge capacity remains at 874mAh g-1. this composite structure can effectively reduce the polarization charge and discharge, reduce the internal resistance of the battery cycle performance and high rate battery is good.
3. sulfur oxide mesoporous carbon / graphite composite materials by solvothermal method successfully synthesized mesoporous metal organic frameworks / graphene oxide rich mesoporous structure (GO@MOF-5), with the template and precursor made by high temperature carbonization preparation has good conductive network, high surface area, mesoporous oxide mesoporous carbon / graphene composite materials with suitable pore size, by heat treatment, the molten sulfur into the porous scaffold made of sulfur oxide mesoporous carbon / graphene composite materials (GO@Meso-C/S). The electrochemical results show that in the current density of 0.2C GO@Meso-C/S half cell initial discharge capacity was 1122mAh g-1100 cycles after the discharge capacity remains at 820mAh g-1, shows the active substance sulfur oxidation of mesoporous carbon / graphene composite composite high utilization and excellent cycle performance.

【学位授予单位】：中南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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