锂硫电池正极材料的制备及结构设计
发布时间：2018-11-15 10:33
【摘要】：近年来,随着能源危机的日益加重,以及电子电动设备的迅猛发展,研究清洁的可持续能源已逐渐成为一个研究热点。锂硫电池因其具有高理论比容量(1675 m Ah/g)和能量密度(2600 Wh/kg),被公认为是最具有发展前景的能源存储体系之一。同时,锂硫电池还具有单质硫资源地壳含量丰富,成本低廉和对环境友好等优点。然而硫及其放电产物硫化锂的电子绝缘性,硫放电过程中的产生的中间产物多硫化物易溶于电解液中并向负极迁移,从而造成的“穿梭效应”以及硫电极在充放电循环中的体积膨胀都严重的影响锂硫电池的电化学性能。针对以上问题,本文主要通过采用将单质硫与碳进行复合的方法进行改善,主要的实验有以下三个方面:1.我们选用生物质废弃物稻壳为原材料经过简单的煅烧和氢氧化钾活化,制备了一种SiO_2修饰的多孔碳。采用熔融浸渍法制备了碳硫复合材料,并表征其作为锂硫电池正极材料的性能。含有SiO_2吸附质的多孔碳可兼具微孔固硫及化学吸附双重固硫作用,表现出优良的电化学性能。2.我们以生物质废弃物玉米芯为来源经过简单的煅烧和氢氧化钾活化制度,制备了纳米片微孔碳。通过熔融浸渍法制备了碳硫复合材料,并表征其作为锂硫电池正极材料时的性能。纳米片层的玉米芯微孔碳能够增加电子的电导率并能缩短离子的传输路径,增大材料与电解液的接触面积,在合适的粘结剂海藻酸钠存在下表现出了优越的循环稳定性及倍率性能。3.我们选取廉价易得的天然高分子材料海藻酸盐,经过简单的活化,制备了一系列的比表面积、孔容和孔隙度可调的富含含氧官能团的碳材料。并探讨了不同物理结构的碳材料同电性能间的关系。在碳材料同时具备合适的孔容及孔结构分布时,能够容纳活性物质体因而获得了优异的电化学循环性能及倍率性能。这些对材料微观结构、表面化学与电化学性能之间关系的研究可以很好的指导我们以后对碳基体材料的合理设计。4.我们选取聚丙烯腈为原料,利用可批量化生产的静电纺丝技术,制备了一种氮掺杂的碳纤维膜。该碳纤维膜可用作锂硫电池正极集流体,与硫复合后可获得无导电剂无粘结剂的高能量密度的一体化正极。该正极良好的电化学性能归因于可调的电极孔隙度及杂原子掺杂导致的化学键合多硫化物作用。
[Abstract]:In recent years, with the aggravation of energy crisis and the rapid development of electronic electric equipment, the research of clean and sustainable energy has become a research hotspot. Because of its high theoretical specific capacity (1675 m Ah/g) and energy density (2600 Wh/kg), lithium-sulfur battery is recognized as one of the most promising energy storage systems. At the same time, lithium-sulfur batteries have the advantages of rich crustal content of simple sulfur resources, low cost and environmental friendliness. However, the electronic insulation of sulfur and its discharge product lithium sulphide, the intermediate product polysulfide produced during the discharge of sulfur, is easily dissolved in the electrolyte and migrated to the negative electrode. As a result, the "shuttle effect" and the volume expansion of the sulfur electrode in the charge / discharge cycle seriously affect the electrochemical performance of the lithium sulfur battery. In view of the above problems, this paper mainly adopts the method of compounding simple sulfur and carbon to improve, the main experiment has the following three aspects: 1. A kind of porous carbon modified by SiO_2 was prepared by simple calcination and activation of potassium hydroxide with biomass waste rice husk as raw material. Carbon and sulfur composites were prepared by melt impregnation and their properties as cathode materials for lithium sulfur batteries were characterized. The porous carbon containing SiO_2 adsorbate has both microporous sulfur fixation and chemisorption double sulfur fixation, showing excellent electrochemical performance. 2. Nanoscale microporous carbon was prepared from biomass waste corncob by simple calcination and potassium hydroxide activation system. Carbon and sulfur composites were prepared by melt impregnation and their properties as cathode materials for lithium-sulfur batteries were characterized. The nanoscale corncob micropore carbon can increase the electron conductivity, shorten the ion transport path, and increase the contact area between the material and the electrolyte. In the presence of suitable binder sodium alginate, it showed excellent cycling stability and rate performance. 3. A series of oxygen rich carbon materials with adjustable specific surface area, pore volume and porosity were prepared by simple activation of alginate, a cheap and easily available natural polymer material. The relationship between electrical properties and carbon materials with different physical structures is also discussed. When the carbon material has a suitable pore volume and pore structure distribution, it can accommodate the active materials and thus obtain excellent electrochemical cycling performance and rate performance. These studies on the relationship between the microstructure, surface chemistry and electrochemical properties of the materials can be used to guide the reasonable design of carbon matrix materials in the future. 4. Using polyacrylonitrile (pan) as raw material, a nitrogen-doped carbon fiber film was prepared by batch electrospinning technique. The carbon fiber film can be used as the positive collector of lithium-sulfur battery, and the integrated positive electrode with high energy density without conductive agent can be obtained when the carbon fiber film is combined with sulfur. The excellent electrochemical performance is attributed to the adjustable porosity of the electrode and the chemically bonded polysulfide due to the doping of hetero atoms.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912
本文编号：2333058
[Abstract]:In recent years, with the aggravation of energy crisis and the rapid development of electronic electric equipment, the research of clean and sustainable energy has become a research hotspot. Because of its high theoretical specific capacity (1675 m Ah/g) and energy density (2600 Wh/kg), lithium-sulfur battery is recognized as one of the most promising energy storage systems. At the same time, lithium-sulfur batteries have the advantages of rich crustal content of simple sulfur resources, low cost and environmental friendliness. However, the electronic insulation of sulfur and its discharge product lithium sulphide, the intermediate product polysulfide produced during the discharge of sulfur, is easily dissolved in the electrolyte and migrated to the negative electrode. As a result, the "shuttle effect" and the volume expansion of the sulfur electrode in the charge / discharge cycle seriously affect the electrochemical performance of the lithium sulfur battery. In view of the above problems, this paper mainly adopts the method of compounding simple sulfur and carbon to improve, the main experiment has the following three aspects: 1. A kind of porous carbon modified by SiO_2 was prepared by simple calcination and activation of potassium hydroxide with biomass waste rice husk as raw material. Carbon and sulfur composites were prepared by melt impregnation and their properties as cathode materials for lithium sulfur batteries were characterized. The porous carbon containing SiO_2 adsorbate has both microporous sulfur fixation and chemisorption double sulfur fixation, showing excellent electrochemical performance. 2. Nanoscale microporous carbon was prepared from biomass waste corncob by simple calcination and potassium hydroxide activation system. Carbon and sulfur composites were prepared by melt impregnation and their properties as cathode materials for lithium-sulfur batteries were characterized. The nanoscale corncob micropore carbon can increase the electron conductivity, shorten the ion transport path, and increase the contact area between the material and the electrolyte. In the presence of suitable binder sodium alginate, it showed excellent cycling stability and rate performance. 3. A series of oxygen rich carbon materials with adjustable specific surface area, pore volume and porosity were prepared by simple activation of alginate, a cheap and easily available natural polymer material. The relationship between electrical properties and carbon materials with different physical structures is also discussed. When the carbon material has a suitable pore volume and pore structure distribution, it can accommodate the active materials and thus obtain excellent electrochemical cycling performance and rate performance. These studies on the relationship between the microstructure, surface chemistry and electrochemical properties of the materials can be used to guide the reasonable design of carbon matrix materials in the future. 4. Using polyacrylonitrile (pan) as raw material, a nitrogen-doped carbon fiber film was prepared by batch electrospinning technique. The carbon fiber film can be used as the positive collector of lithium-sulfur battery, and the integrated positive electrode with high energy density without conductive agent can be obtained when the carbon fiber film is combined with sulfur. The excellent electrochemical performance is attributed to the adjustable porosity of the electrode and the chemically bonded polysulfide due to the doping of hetero atoms.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912
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