三维石墨烯基氧化锡多元复合材料的锂电性能研究

发布时间：2019-04-21 16:29

【摘要】：由石墨烯构筑形成的多孔材料相对于其他的多孔碳材料有很多优异之处。首先,石墨烯组成的多孔结构有很强的机械强度,有助于增强多孔结构以及缓解多孔结构的拉伸压缩性能。然后,石墨烯优异的热稳定和化学稳定性能增强多孔材料的受恶劣环境的冲击。再者,多孔材料的通道能加速电解液浸润,石墨烯多孔骨架优异的导电性更有利于电荷的传输转移。石墨烯包含含氧官能团等的衍生物如氧化石墨烯以及还原的氧化石墨烯能作为负载多种有机无机材料的活性基体,有利于构筑多种石墨烯基多孔结构。这些优异的多孔石墨烯材料被用于锂离子电池,超级电容器和燃料电池等高性能电化学存储和转化设备。二氧化锡具有较高的理论容量、在自然界中含量丰富、制备简便以及环境无害被认为是优异的锂离子电池负极材料。但是,二氧化锡因为导电性差、高的体积膨胀效应直接影响了其大规模的应用。本论文采用原位生长的方法在石墨烯表面构筑氧化锡纳米颗粒,再通过水热的方法构筑成三维多孔结构,改善氧化锡的锂电性能。具体方案如下：(1)采用一种简便的方法在氧化石墨烯表面原位生长二氧化锡纳米颗粒,再通过水热自组装形成三维多孔结构的骨架,构成三维多孔石墨烯骨架负载二氧化锡纳米颗粒的复合材料。复合材料用作锂离子电池的负极进行相应的锂电测试,得出三维多孔结构相对于二维石墨烯负载的二氧化锡材料的锂电性能有明显的改善。由于三维石墨烯骨架的缓冲作用,以及多级孔道的结构,三维石墨烯复合材料用作锂离子电池度及材料时其稳定性有明显的增加。(2)通过研究发现SnO2/GAs用作锂离子电池负极材料,经过大电流充放电循环测试时,材料的容量衰减比较显著,为了进一步改善二氧化锡材料的锂电性能,我们采用二氧化钛和二氧化锡的纳米颗粒通过水热自主装的方法共同生长在石墨烯三维骨架上,得到大孔和介孔共存的多级孔结构,能对二氧化锡进行储锂的过程中所产生的体积膨胀起到有效的缓冲。同时二氧化锡与二氧化钛之间形成的异质结结构能提高二氧化锡储锂效率,有效提高二氧化锡材料的容量。
[Abstract]:Porous materials made of graphene have many advantages over other porous carbon materials. Firstly, the porous structure composed of graphene has strong mechanical strength, which helps to strengthen the porous structure and alleviate the tensile and compressive properties of the porous structure. Then, the excellent thermal stability and chemical stability of graphene enhance the impact of porous materials under harsh environment. Furthermore, the channel of porous materials can accelerate the electrolyte infiltration, and the excellent conductivity of graphene porous framework is more conducive to the transfer of charge. Graphene contains derivatives of oxygen-containing functional groups such as graphene oxide and reduced graphene oxide, which can be used as active substrates to support a variety of organic and inorganic materials, which is conducive to the construction of a variety of graphene-based porous structures. These excellent porous graphene materials are used in high performance electrochemical storage and conversion equipment such as lithium ion batteries, supercapacitors and fuel cells. Tin dioxide is considered to be an excellent anode material for lithium-ion batteries with high theoretical capacity, rich content in nature, simple preparation and environmentally sound. However, due to its poor conductivity, the large-scale application of tin dioxide is directly affected by the high volume expansion effect. In this paper, tin oxide nanoparticles were fabricated on graphene surface by in-situ growth method, and then three-dimensional porous structure was constructed by hydrothermal method to improve the lithium electrical properties of tin oxide. The specific plans are as follows: (1) the tin dioxide nanoparticles were in situ grown on the surface of graphene oxide by a simple method, and then three-dimensional porous framework was formed by hydrothermal self-assembly. Three-dimensional porous graphene framework loaded tin dioxide nanoparticles composite materials were formed. The results show that the three-dimensional porous structure is better than the two-dimensional graphene-loaded tin dioxide material in lithium-ion battery negative electrode. 3-D porous structure is better than the two-dimensional graphene-loaded tin dioxide material in lithium-ion battery. As a result of the cushioning effect of the three-dimensional graphene skeleton, and the structure of the multi-channel, The stability of three-dimensional graphene composites used as lithium-ion batteries has been significantly increased. (2) it was found that SnO2/GAs was used as anode materials for lithium-ion batteries after high-current charge-discharge cycle test, and that the three-dimensional graphene composites were used as cathode materials for lithium-ion batteries. In order to further improve the lithium electrical properties of tin dioxide materials, the nano-particles of titanium dioxide and tin dioxide were co-grown on the three-dimensional framework of graphene by hydrothermal self-loading method. The coexistence of macroporous and mesoporous multi-stage pore structure can effectively buffer the volume expansion of Sn _ 2O _ 2 in the process of lithium storage. At the same time, the heterojunction structure formed between tin dioxide and titanium dioxide can improve the efficiency of lithium storage and the capacity of tin dioxide materials.
【学位授予单位】：上海应用技术学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332

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