锂离子电池硅基负极用关键材料的研究
发布时间：2018-09-13 16:32
【摘要】：锂离子电池结构主要由电极、隔膜、电解液三部分组成,其中电极作为锂离子电池的核心部分,对锂离子电池的性能起决定性作用。电极主要由活性材料、导电剂、粘结剂组成。之前的研究中,活性物质作为锂离子电池的核心材料备受研究人员关注,而导电剂与粘结剂作为锂离子电池中使用量最少的材料,所受关注相对较少。导电剂与粘结剂在电极中用量虽少,但起到的作用却不容忽视,这一点在高容量负极中尤其明显。对于高容量负极,活性材料在锂离子电池充放电过程中的较大的体积变化会造成电极中导电通道断开、活性层与集流体分离等问题,造成锂离子电池容量大幅衰减。采用新型导电剂与粘结剂可以在对电池成本影响较小的前提下缓解或解决这些问题。因此,本论文希望通过对导电剂和粘结剂的开发和改善,来提升高容量负极的电性能。论文首先确定了一个适合高容量负极的基本电池装配工艺。结合之前的研究,高容量负极在充放电循环中变化与传统的碳基材料不同,传统的电池工艺无法发挥出高容量负极的性能。因此我们通过多次尝试找到了比较适合高容量负极的电池工艺,并选用了纳米硅作为负极的活性材料,以此为基础来研究导电剂与粘结剂。导电剂方面我们开发出了二维纳米材料与三维纳米材料复合的导电剂,以适应高容量负极材料。二维纳米材料我们选用了酸化(羧基功能化)多壁碳纳米管。制备了酸化多壁碳纳米管,在表面引入缺陷与接枝羧基、羟基等基团的同时,因多壁碳纳米管的多通道传输特性,保证了碳纳米管的导电性。羧基引入的作用有两点,一是极大的改善了碳纳米管的分散性,保证了极片长程导电网络的畅通;二是增强了碳纳米管与粘结剂之间的结合力。三维纳米材料我们选用了SP,SP的比表面积较大,增大了导电剂与活性材料的接触面积。与传统的SP导电剂相比,0.1 C放电倍率下,混合导电剂将锂离子电池的首次放电比容量从1938 m Ah g-1提升为2927 m Ah g-1,首次库伦效率从79.2%提升到81.9%,100次循环后的容量保持率由59%提升到74.3%。粘结剂方面我们首次使用阴离子聚丙烯酰胺(APAM)作为锂离子电池粘结剂。APAM作为粘结剂有以下优点。一是水溶性好,环境友好。二是含有羧酸及羧酸盐基团,能够与金属活性材料和金属集流体具有更强的结合力。三是分子量较大,可以较好的缓冲活性材料的体积膨胀。四是分子中含有大量的酰胺基,可形成大量的分子间和分子内氢键,增强了APAM的自修复能力。本论文对比了不同分子量的APAM与不同刷片配比对纳米硅负极电池性能的影响。结果显示当使用1600万分子量的APAM(APAM16)作为粘结剂时,相比传统的海藻酸钠,锂离子电池的首次放电比容量从2005.8 m Ah g-1提升为3485 m Ah g-1,首次库伦效率从78.6%提升到85.9%。
[Abstract]:The structure of lithium-ion battery is mainly composed of three parts: electrode, diaphragm and electrolyte. As the core part of lithium-ion battery, electrode plays a decisive role in the performance of lithium-ion battery. The electrode is mainly composed of active material, conductive agent and binder. In previous studies, active substances as the core materials for lithium-ion batteries have attracted much attention, while conductive agents and binders have received relatively little attention as the least used materials in lithium-ion batteries. Although the amount of conductive agent and binder in the electrode is small, the effect can not be ignored, especially in the high capacity negative electrode. For the high capacity negative electrode, the large volume change of the active material in the charge and discharge process of the lithium ion battery will lead to the disconnection of the conductive channel in the electrode and the separation of the active layer from the collector, which will lead to the large attenuation of the lithium-ion battery capacity. These problems can be alleviated or solved by using new conductive agent and binder with little effect on battery cost. Therefore, this paper hopes to improve the electrical properties of high capacity anode by developing and improving the conductive agent and binder. Firstly, a basic battery assembly process suitable for high capacity negative electrode is determined. In combination with previous studies, the change of high capacity anode in charge-discharge cycle is different from that of traditional carbon based materials, and the traditional battery technology can not play the role of high capacity negative electrode. Therefore, we have found a battery process suitable for high capacity negative electrode through many attempts, and selected nano-silicon as the active material of negative electrode, based on which we studied the conductive agent and binder. In order to adapt to high capacity anode materials, we have developed two-dimensional nano-materials and three-dimensional nano-materials composite conductive agents. Two-dimensional nanomaterials we selected acidified (carboxyl functionalized) multi-wall carbon nanotubes. Acidified multiwalled carbon nanotubes were prepared. Defects and groups such as carboxyl groups and hydroxyl groups were introduced into the surface, and the conductivity of multi-walled carbon nanotubes was ensured because of the multi-channel transport characteristics of multi-walled carbon nanotubes. The introduction of carboxyl groups can greatly improve the dispersion of carbon nanotubes and ensure the smooth flow of the polar long range conductive network. The other is to enhance the binding force between carbon nanotubes and binders. The specific surface area of SP,SP is larger and the contact area between conductive agent and active material is increased. Compared with the conventional SP conductive agent, the initial discharge specific capacity of lithium-ion battery was increased from 1938 m Ah g ~ (-1) to 2927 m Ah g ~ (-1), and the first Coulomb efficiency was increased from 79.2% to 81.9%. The capacity retention rate was increased from 59% to 74.3%. Anionic polyacrylamide (APAM) as binder for lithium ion battery has the following advantages for the first time. First, water-soluble, environmental friendly. Second, it contains carboxylic acid and carboxylate groups, which can bind to metal active material and metal collector more strongly. The third is the bigger molecular weight, which can better buffer the volume expansion of active materials. Fourth, there are a large number of amide groups in the molecule, which can form a large number of intermolecular and intramolecular hydrogen bonds, enhancing the self-repair ability of APAM. In this paper, the effects of different molecular weight of APAM and different ratio of brushes on the performance of nanocrystalline silicon anode batteries were compared. The results show that when APAM (APAM16) with 16 million molecular weight is used as binder, the initial discharge specific capacity of lithium-ion battery is increased from 2005.8 m Ah g ~ (-1) to 3485 m Ah g ~ (-1), and the first Coulomb efficiency is increased from 78.6% to 85.9% compared with conventional sodium alginate.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM912
本文编号：2241720
[Abstract]:The structure of lithium-ion battery is mainly composed of three parts: electrode, diaphragm and electrolyte. As the core part of lithium-ion battery, electrode plays a decisive role in the performance of lithium-ion battery. The electrode is mainly composed of active material, conductive agent and binder. In previous studies, active substances as the core materials for lithium-ion batteries have attracted much attention, while conductive agents and binders have received relatively little attention as the least used materials in lithium-ion batteries. Although the amount of conductive agent and binder in the electrode is small, the effect can not be ignored, especially in the high capacity negative electrode. For the high capacity negative electrode, the large volume change of the active material in the charge and discharge process of the lithium ion battery will lead to the disconnection of the conductive channel in the electrode and the separation of the active layer from the collector, which will lead to the large attenuation of the lithium-ion battery capacity. These problems can be alleviated or solved by using new conductive agent and binder with little effect on battery cost. Therefore, this paper hopes to improve the electrical properties of high capacity anode by developing and improving the conductive agent and binder. Firstly, a basic battery assembly process suitable for high capacity negative electrode is determined. In combination with previous studies, the change of high capacity anode in charge-discharge cycle is different from that of traditional carbon based materials, and the traditional battery technology can not play the role of high capacity negative electrode. Therefore, we have found a battery process suitable for high capacity negative electrode through many attempts, and selected nano-silicon as the active material of negative electrode, based on which we studied the conductive agent and binder. In order to adapt to high capacity anode materials, we have developed two-dimensional nano-materials and three-dimensional nano-materials composite conductive agents. Two-dimensional nanomaterials we selected acidified (carboxyl functionalized) multi-wall carbon nanotubes. Acidified multiwalled carbon nanotubes were prepared. Defects and groups such as carboxyl groups and hydroxyl groups were introduced into the surface, and the conductivity of multi-walled carbon nanotubes was ensured because of the multi-channel transport characteristics of multi-walled carbon nanotubes. The introduction of carboxyl groups can greatly improve the dispersion of carbon nanotubes and ensure the smooth flow of the polar long range conductive network. The other is to enhance the binding force between carbon nanotubes and binders. The specific surface area of SP,SP is larger and the contact area between conductive agent and active material is increased. Compared with the conventional SP conductive agent, the initial discharge specific capacity of lithium-ion battery was increased from 1938 m Ah g ~ (-1) to 2927 m Ah g ~ (-1), and the first Coulomb efficiency was increased from 79.2% to 81.9%. The capacity retention rate was increased from 59% to 74.3%. Anionic polyacrylamide (APAM) as binder for lithium ion battery has the following advantages for the first time. First, water-soluble, environmental friendly. Second, it contains carboxylic acid and carboxylate groups, which can bind to metal active material and metal collector more strongly. The third is the bigger molecular weight, which can better buffer the volume expansion of active materials. Fourth, there are a large number of amide groups in the molecule, which can form a large number of intermolecular and intramolecular hydrogen bonds, enhancing the self-repair ability of APAM. In this paper, the effects of different molecular weight of APAM and different ratio of brushes on the performance of nanocrystalline silicon anode batteries were compared. The results show that when APAM (APAM16) with 16 million molecular weight is used as binder, the initial discharge specific capacity of lithium-ion battery is increased from 2005.8 m Ah g ~ (-1) to 3485 m Ah g ~ (-1), and the first Coulomb efficiency is increased from 78.6% to 85.9% compared with conventional sodium alginate.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM912
【参考文献】
相关期刊论文 前1条
1 顾长志;吕文刚;李海钧;李俊杰;白雪冬;;多壁碳纳米管中的多通道弹道输运特性[J];物理;2005年12期
，本文编号：2241720
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