高性能SNO2基锂离子电池负极材料的制备与电化学性能研究

发布时间：2018-03-26 10:39

本文选题：锂离子电池　切入点：负极材料　出处：《天津工业大学》2017年硕士论文

【摘要】：近年来,二氧化锡被视为最具有发展潜力的新型锂离子电池负极材料之一,但由于二氧化锡在首次充放电过程中体积膨胀高达50%以上,循环期间锂离子的反复嵌入与脱嵌易出现粉化和团聚现象,以至于二氧化锡电化学性能迅速下降,从而限制了它在锂离子电池中的广泛应用,成为其应用推广的瓶颈。如何有效缓解二氧化锡在充放电过程中的体积效应和粉化现象,提高电极的循环稳定性已成为当前研究二氧化锡负极材料的关键。目前,研究者们主要通过以下方式克服二氧化锡负极材料的局限性,并取得了很大的进步。一是制备纳米结构的二氧化锡,如SnO_2纳米薄片、SnO_2纳米线、SnO_2纳米阵列等,通过改变材料的形貌和减小材料颗粒尺寸来增加材料中的空隙率,从而在一定程度上能舒缓材料在充放电过程中带来的体积效应。二是构建二氧化锡复合材料,如碳包覆、SnO_2-碳纳米管复合、SnO_2-石墨烯复合等,通过在材料表面包覆无机或有机物质来限制充放电过程中体积效应对材料结构和性能的破坏。本文采用水热法合成SnO_2材料,通过研究表明,SnO_2纳米片的电化学性能最佳。在此基础上,本文从以下三个方面对SnO_2纳米片进行了改性研究。1.对SnO_2纳米片与氧化石墨烯进行了复合,制备了不同氧化石墨烯含量的SnO_2/石墨烯纳米复合材料。研究结果表明:氧化石墨烯含量为50%的SnO_2/石墨烯纳米复合材料的循环性能最佳,在160mA/g的电流密度下,经过100次循环后,放电比容量维持在636.2mAh/g。2.对SnO_2纳米片与多壁碳纳米管进行了复合,制备了不同碳纳米管含量的SnO_2/MCNTs复合材料。研究结果表明:多壁碳纳米管含量为50%的SnO_2/MCNTs复合材料的循环性能最佳,在160mA/g的电流密度下,经过50次循环后,放电比容量维持在480.6mAh/g。3.在MCNTs50-SnO_2复合材料表面包覆PPy,制得了不同PPy含量的PPy-MCNTs/SnO_2复合材料。研究结果表明:聚吡咯含量为11%时,PPy-MCNTs/SnO_2复合材料的循环性能最好,在160mA/g的电流密度下,循环100次后,可逆容量维持在525.8mAh/g。且相对于MCNTs/SnO_2复合材料,包覆PPy后的循环性能更好,更稳定。
[Abstract]:In recent years, tin dioxide has been regarded as one of the most promising anode materials for lithium ion batteries. However, the volume expansion of tin dioxide in the first charge / discharge process is more than 50%. During the cycle, the repeated intercalation and deintercalation of lithium ions are prone to powder and agglomeration, so that the electrochemical performance of tin dioxide drops rapidly, which limits its wide application in lithium ion batteries. It has become the bottleneck of its application and popularization. How to effectively alleviate the volume effect and powdering phenomenon of tin dioxide in charge and discharge process and improve the cycle stability of the electrode has become the key to study the tin dioxide negative electrode material. The researchers have made great progress in overcoming the limitations of tin dioxide negative electrode materials in the following ways. One is the preparation of nanostructured tin dioxide, such as SnO_2 nanowires, SnO2 nanowires, SnO2 nanoarrays, and so on. By changing the morphology of the material and reducing the particle size of the material to increase the porosity of the material, the volume effect of the material during charge and discharge can be alleviated to a certain extent. For example, carbon coated SnO2- carbon nanotube composite Sno _ 2-graphene composite, by coating inorganic or organic substances on the surface of the material to limit the damage of the volume effect on the structure and properties of the material during charge and discharge. In this paper, the hydrothermal method is used to synthesize the SnO_2 material. The results show that SnO-2 nanocrystalline has the best electrochemical performance. On the basis of this, the modification of SnO_2 nanoparticles was carried out in the following three aspects. 1. The composite of SnO_2 nanoparticles and graphene oxide was carried out. SnO_2/ graphene nanocomposites with different graphene oxide contents were prepared. The results showed that the SnO_2/ graphene nanocomposites with 50% graphene oxide content had the best cycling performance. Under the current density of 160mA/g, after 100 cycles, The specific discharge capacity was maintained at 636.2mAh路 g.2.The composite of SnO_2 nanoparticles and multi-walled carbon nanotubes (MCNTs) was prepared, and the SnO_2/MCNTs composites with different carbon nanotubes contents were prepared. The results showed that the SnO_2/MCNTs composites with 50% MwCNT content had the best cycling performance. At the current density of 160mA/g, after 50 cycles, The specific discharge capacity was maintained at 480.6 mg 路路g. 3. The PPy-MCNTs/SnO_2 composites with different PPy content were prepared by coating PPy on the surface of MCNTs50-SnO_2 composites. The results showed that PPy-MCNTs / SnO2 composites had the best cycling performance when the PPY-MCNTs / SnO2 content was 11, and at the current density of 160mA/g, the composites had the best cycling performance. After 100 cycles, the reversible capacity is maintained at 525.8 mg 路h / g, and the cyclic performance of PPy coated with PPy is better and more stable than that of MCNTs/SnO_2 composite.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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