MOF基碳复合材料的设计、制备及其储锂性能研究
发布时间：2018-11-07 13:50
【摘要】：随着能源和环境问题的日益突出,开发环境友好、能量密度高、循环寿命长、安全系数高的储能电子器件成为各国学者研究的热点。与传统的商业石墨相比,碳基复合材料作为电池的电极材料时具有较好导电能力、良好的机械性能以及较高的理论比容量和能量密度,目前,已经被广泛的应用在储能领域中。本文以金属有机结构框架(MOFs)作为模板,制备多孔碳基复合材料,研究其作为电极材料在锂离子电池和锂硫电池中的储锂性能。研究发现,氮掺杂多孔碳材料具有较好的电化学性能,如较稳定的循环性能,良好的倍率性能等。本文主要工作归纳为以下三个部分:(1)以正十二面体核壳结构的ZIF8@ZIF67为前驱体,在氩气气氛中800℃碳化3 h后得到双金属嵌入的氮掺杂多面体碳纳米笼,并表现出良好的电化学性质。在电流密度为200 mA g~(-1)时,其首圈放电比容量可达到809 mA h g~(-1),充放电循环400圈之后,其放电比容量仍能保持在702 mA h g~(-1)。此外,当电流密度高达2 A g~(-1),放电比容量仍能保持在444 mA h g~(-1)。如此优异的电化学性质主要归因于双金属的嵌入提高了结构的完整性;氮原子的掺杂带来了更多的活性位点以及空心结构可以缓冲充放电过程中的体积膨胀。(2)以传统的ZIF8为前驱体,在氩气气氛下通过改变碳化温度,制备出不同含氮量和比表面积的多孔氮掺杂碳复合材料并以此作为单质硫的载体。当碳/硫复合物作为锂硫电池的正极材料时,经研究表明,在800℃的条件下高温碳化后所制备的碳材料作为载体时,表现出最为优异的电化学性能。当复合物中单质硫的含量为55%,电流密度为800 mA g~(-1)时,其首圈的放电比容量可高达1646 mA h g~(-1),已经接近了单质硫的理论放电比容量,充放电循环400圈后,充放电比容量仍能够保持在600 mA h g~(-1)而库伦效率仍能接近100%。该复合材料较为突出的电化学性能主要归因于合适的氮含量以及比表面积相互协同。(3)以ZIF8@ZIF67为前驱体,室温下将前驱体与磷酸二氢铵按不同比例混合并研磨,在适当的比例下核壳结构的前驱体逐渐变换为Yolk-shell结构复合材料,在合适的温度下碳化制备卵黄结构的多孔氮掺杂碳复合材料,并在锂硫电池中表现出了较为优异的电化学性质。电化学测试结果表明,复合物中单质硫含量为60%,电流密度为800 mA g~(-1)时,其首圈充放电比容量可以达到921 mA h g~(-1),充放电循环200圈之后,其放电比容量仍能达到600 mA h g~(-1)。该复合材料展现出优异的循环性能和倍率性能等储锂性能。
[Abstract]:With the increasingly prominent energy and environmental problems, the development of environment-friendly, high energy density, long cycle life, high safety factor energy storage electronic devices have become a hot spot in the world. Compared with traditional commercial graphite, carbon matrix composites have good conductivity, good mechanical properties and high theoretical specific capacity and energy density when used as electrode materials of batteries. At present, carbon matrix composites have been widely used in the field of energy storage. In this paper, porous carbon matrix composites were prepared by using organometallic framework (MOFs) as template, and their lithium storage properties in lithium-ion batteries and lithium-sulfur batteries were investigated as electrode materials. It is found that nitrogen doped porous carbon materials have good electrochemical performance, such as stable cycling performance and good rate performance. The main work of this paper is summarized as follows: (1) with the ZIF8@ZIF67 structure of dodecahedral core-shell structure as the precursor, after carbonization at 800 鈩，
本文编号：2316557
[Abstract]:With the increasingly prominent energy and environmental problems, the development of environment-friendly, high energy density, long cycle life, high safety factor energy storage electronic devices have become a hot spot in the world. Compared with traditional commercial graphite, carbon matrix composites have good conductivity, good mechanical properties and high theoretical specific capacity and energy density when used as electrode materials of batteries. At present, carbon matrix composites have been widely used in the field of energy storage. In this paper, porous carbon matrix composites were prepared by using organometallic framework (MOFs) as template, and their lithium storage properties in lithium-ion batteries and lithium-sulfur batteries were investigated as electrode materials. It is found that nitrogen doped porous carbon materials have good electrochemical performance, such as stable cycling performance and good rate performance. The main work of this paper is summarized as follows: (1) with the ZIF8@ZIF67 structure of dodecahedral core-shell structure as the precursor, after carbonization at 800 鈩，
本文编号：2316557
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