碳基材料的制备及其在锂硫电池中的应用

发布时间：2018-06-06 12:56

本文选题：锂硫电池 + 碳基材料　；参考：《济南大学》2017年硕士论文

【摘要】：锂硫电池得益于高达1675 m Ah g~(-1)的理论比容量和2600 Wh kg~(-1)的能量密度,已成为当今较有前景的研究热点。除此以外,天然的硫的含量丰富、无毒性环境友好并且价格低廉等优势,使Li-S电池具有超广阔的应用前景,成为当今电化学储能方面的研究热点。但是自身差的导电性以及穿梭效应严重影响了Li-S电池发展。碳基材料得益于自身高的导电性和纳米结构的多样性使得其在锂硫电池的应用上备受关注。本文以发展高稳定性硫正极为目的,设计制备了廉价绿色且具有杂原子掺杂的衍生碳材料作为硫的载体,有效地抑制了穿梭效应,改善锂硫电池的电化学性能。主要的研究内容和结果如下:设计制备了一种类珊瑚状、氮氧共掺杂的高比表面的多级孔碳材料,作为硫的载体,提高硫正极的循环稳定性能。该类多级孔碳材料采用浒苔作为原料,通过水热碳化,再用氢氧化钾辅助活化制得。该原料属于海洋废弃污染物,来源广泛,制备方法简单,变废为宝,经济环保。其中,CNHPC700G在电流密度为0.1 C的条件下,初始的放电比容量为1555 m Ah g~(-1)(占理论比容量的93%),在电流密度为0.5 C时,循环500个周期后,库伦效率一直稳定在100%左右,平均每圈容量衰减率是0.05%。在该碳硫复合材料中,因碳自身独特的孔结构,对活性物质硫有物理限域,再有其自身丰富的氮氧共掺杂,不但提高了碳基体材料的电子电导,而且对多硫离子有一定的吸附能力,有效抑制了穿梭效应,从而获得了稳定的电化学活性。设计制备了一种类银耳状、高氮氧氟共掺杂的高比表面的微孔碳材料,作为硫的载体,增强硫正极的循环稳定性。该类微孔碳材料选用四害之一苍蝇的幼虫作为原料,通过碳化、活化制得,为优化实验过程,对样品活化、酸洗过程进行改良,简化了实验流程,提高了样品纯度。该原料丰富、合成路线绿色合理。其中,TNMC300/40%S在经过100圈循环后,其放电比容量依然可达851.2 m Ah g~(-1)。且所有TNMCs在不同电流密度下,都得到接近100%的库伦效率,平均每圈容量衰减率都低于0.25%。其优异的电化学性能归因于微孔良好地限域多硫离子,以及材料自身固有的丰富的氮物种、氧物种以及氟物种,提升了复合材料的电导率,抑制了多硫离子的迁移、扩散,减少活性组分的流失,因此得到了稳定的循环性能以及较高的放电比容量。
[Abstract]:The theoretical specific capacity and energy density of 2600 Wh 路kg ~ (-1) of lithium-sulfur batteries have become a promising research topic. In addition, the advantages of rich sulfur content, non-toxic environment and low price make Li-S batteries have a broad application prospect and become the research hotspot of electrochemical energy storage. However, the poor conductivity and shuttle effect seriously affect the development of Li-S cells. Carbon based materials are widely used in lithium-sulfur batteries due to their high conductivity and diversity of nanostructures. In order to develop the high stability sulfur positive electrode, a cheap green and hetero-doped derivative carbon material was designed and prepared as the carrier of sulfur, which effectively inhibited the shuttle effect and improved the electrochemical performance of lithium-sulfur battery. The main research contents and results are as follows: a kind of coral-like, nitrogen-oxygen co-doped multilevel porous carbon material with high specific surface is designed and prepared, which can be used as the carrier of sulfur to improve the cyclic stability of sulfur positive electrode. This kind of multiporous carbon material was prepared by hydrothermal carbonization and then activated by potassium hydroxide using Enteromorpha enteromorpha as raw material. The raw material is a marine waste pollutant with wide source, simple preparation method, economic and environmental protection. The initial discharge specific capacity of CNHPC700G is 1555 mAh / g ~ (-1) at the current density of 0.1C (933C). When the current density is 0.5C, the Coulomb efficiency is about 100% after 500 cycles. The average capacity attenuation rate per cycle is 0. 05. Due to the unique pore structure of carbon and sulfur, there is a physical limit to the active material sulfur, and its rich nitrogen and oxygen co-doping can not only improve the electronic conductivity of carbon matrix material, but also improve the electronic conductivity of carbon matrix material. In addition, it has a certain adsorption capacity for polysulfide ions, which effectively inhibits the shuttle effect and thus obtains a stable electrochemical activity. A kind of Tremella and high nitroxy-fluorine co-doped microporous carbon material with high specific surface was designed and prepared as the carrier of sulfur to enhance the cyclic stability of sulfur positive electrode. This kind of microporous carbon material was made from the larvae of one of the four harmful flies by carbonization and activation. In order to optimize the experimental process, the sample activation and pickling process were improved, the experimental process was simplified and the purity of the sample was improved. The raw material is abundant and the synthetic route is green and reasonable. After 100 cycles, the discharge specific capacity of TNMC300 / 40S is still up to 851.2 mAh / g ~ (-1). At different current densities, all TNMCs have a Coulomb efficiency of nearly 100%, and the average capacity attenuation rate per cycle is lower than 0.25. Its excellent electrochemical performance is attributed to the micropore well confined polysulfide ions, as well as the rich nitrogen species, oxygen species and fluorine species inherent in the material itself, which enhance the conductivity of the composite materials and inhibit the migration and diffusion of polysulfide ions. By reducing the loss of active components, stable cycle performance and high discharge specific capacity are obtained.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.4;TM912

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