三维结构碳材料的制备及其在储能器件中的性能研究

发布时间：2018-03-05 17:05

本文选题：锂硫电池　切入点：锂离子电池　出处：《合肥工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：近年来,随着能源需求的持续增加以及人们对环境问题的关注,研究者们开始致力于研究清洁的可持续能源来替代传统化石燃料。其中,电化学储能受到越来越多的重视。锂硫电池被认为是最有吸引力的下一代电化学储能系统之一。并且,研究者们认为将正极材料硫“束缚”在一定纳米结构碳材料从而抑制穿梭效应是解决锂硫电池走向商用的有效途径之一。此外,作为商用锂离子电池首选的负极材料,碳基材料由于容量低和倍率性能差越来越无法满足商业需求。本文通过制备多种三维结构碳材料并运用到锂硫电池和锂离子电池中,提高电池容量和循环性能。主要完成工作如下：首先,本文使用生物质树皮作为碳源,通过简单的碳化过程制备出具有三维复合结构多孔碳,并且该碳材料还具有528 m2/g的比表面积。在不使用集流体、导电剂和粘合剂的情况下,我们制备了高载硫量的正极片并组装成锂硫电池。结果表明,该结构碳/硫电极在0.2 A/g电密度流下首次放电容量能达到1159 mAh/g。即使循环60次后,容量依然能达到608 mAh/g,并且库伦效率高于98%,优于大孔被破坏后的电极达到的容量410 mAh/g。其次,本文使用三聚氰胺作为碳源,乙酸钴作为固相模板,一步法固相合成原位氮掺杂中空碳纳米微球(N-PHC),并且该中空球同时拥有微孔和介孔结构。我们将该材料通过热熔法与硫复合制备电极组装成锂硫电池,并进行表征与测试。结果表明该结构碳材料能很好吸附硫及其中间产物,从而有效提高锂硫电池的容量和循环性能。N-PHC/S复合材料在0.5放电倍率下首次容量能达到1164 mAh/g,150周循环后容量仍然保持在615 mAh/g,容量每周衰减仅为0.35%。最后,我们使用钛酸四丁酯作为交联剂,三聚氰胺为碳源,固相合成富氮碳钛混合物。该复合碳材料具有三维孔结构,提供稳定的锂离子快速传输通道。电化学测试表明,富氮碳钛复合材料即使在大电流2 A/g充放电条件下,首次容量能依然能达到523.3 mAh/g,超过商用石墨的理论容量。同时该材料还表现出优异的高倍率性能和循环性能。
[Abstract]:In recent years, with the increasing demand for energy and environmental concerns, researchers have been working on clean and sustainable energy to replace traditional fossil fuels. Electrochemical energy storage has attracted more and more attention. Lithium-sulfur batteries are considered to be one of the most attractive next-generation electrochemical energy storage systems. The researchers believe that "binding" the positive material sulfur to a certain nanostructured carbon material to suppress the shuttle effect is one of the effective ways to solve the commercial lithium-sulfur battery. In addition, as the preferred anode material for commercial lithium-ion batteries, Because of its low capacity and poor performance, carbon based materials can not meet the commercial needs. In this paper, a variety of three-dimensional carbon materials were prepared and applied to lithium sulfur batteries and lithium ion batteries. The main work is as follows: firstly, using biomass bark as carbon source, porous carbon with three-dimensional composite structure was prepared by simple carbonization process. And the carbon material also has a specific surface area of 528 m2 / g. Without the use of fluids, conductors and binders, we have prepared positive plates with high sulfur loading and assembled them into lithium sulfur batteries. The initial discharge capacity of the structure carbon / sulfur electrode can reach 1159 mAh/ g at 0.2 A / g electric density. Even after 60 cycles, the discharge capacity can reach 608 mAh-g. and the Coulomb efficiency is higher than 98%, which is superior to the capacity of 410 mAhg. after the macroporous electrode has been destroyed. Melamine was used as carbon source and cobalt acetate as solid template. In situ nitrogen-doped hollow carbon nanospheres N-PHCO were synthesized by a one-step solid-phase method, and the hollow spheres have both microporous and mesoporous structures. The results show that the structure carbon material can adsorb sulfur and its intermediate products well. Thus effectively improving the capacity and cycling performance of the lithium-sulfur battery. The first capacity of the N-PHC-S composite at 0.5 discharge rate can reach 1164 mAhs / g after 150 cycles, and the capacity remains at 615 mg / g, and the capacity attenuation is only 0.35% per week. We used tetrabutyl titanate as crosslinking agent and melamine as carbon source to synthesize nitrogen-rich carbon titanium mixture in solid phase. The composite carbon material has a three-dimensional pore structure and provides a stable lithium ion fast transport channel. The initial capacity energy of nitrogen-rich carbon titanium composite is 523.3 mg / g, which is higher than the theoretical capacity of commercial graphite, even under the condition of high current 2 A / g charge / discharge, and the material also shows excellent performance of high rate and cycle.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM912

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