摘要:采用定向凝固的方法制备了一种新型的不含粘合剂的石墨烯-碳纳米管-二氧化锡(GCNT-SnO2)炭气凝胶,其中的孔隙由于冰晶的诱导作用而表现为垂直取向结构。{ 221 }高能面暴露的八面体SnO2可以紧紧地帖在片层状石墨烯/碳纳米管上,并实现均匀分布。垂直排列的孔能有效地防止那些无法负载活性SnO2纳米颗粒的“闭合型”孔隙结构的出现。进一步确保电解液在整个气凝胶中的快速浸润,并且在很大程度上缩短锂离子的传输距离,并充分利用SnO2的活性位点。特别地,由于石墨烯和碳纳米管良好的网络结构,实现了GCNT-SnO2气凝胶的优异的导电性能。此外,取向排列的孔隙结构中附带的中孔和大孔结构可以为锂离子和电子的传输提供极大的便利,并且为SnO2体积膨胀提供足够的空间。由于GCNT-SnO2气凝胶的多层次结构,实现了极高的比容量(1332 mAh/g),并且具有良好的长循环稳定性(1000次)。这项工作可以为制备独立自支撑锂离子电池和其他储能装置的电极材料提供有益的指导。49307
毕业论文关键词:二氧化锡八面体,石墨烯/碳纳米管杂化材料,气凝胶,锂离子电池
Octahedral Tin Dioxide Nanocrystals-Carbonic Aerogels as High Capacity Anode Materials for Lithium-Ion Batteries
Abstract: A novel binder-free graphene - carbon nanotubes - SnO2 (GCNT-SnO2) aerogel with vertically aligned pores was prepared according to a simple yet efficient method of directional freezing. SnO2 octahedrons exposed of {221} high energy facets were uniformly distributed and tightly anchored on multidimensional carbon nanomaterials of giant graphene /carbon nanotubes (GCNT). Vertically aligned pores can effectively prevent the emersion of “closed” pores which cannot load the active SnO2 nanoparticles, further ensure quickly immersion of electrolyte throughout the aerogel, and can largely shorten the transportation distance between lithium ions and active sits of SnO2. Especially, excellent electrical conductivity of GCNT-SnO2 aerogel was achieved as a result of good inter-connected networks of graphene and CNTs. Furthermore, meso- and macroporous structures with large surface area created by the vertically aligned pores can provide great benefit to the favorable transport kinetics for both lithium ion and electrons and afford sufficient space for volume expansion of SnO2. Due to the well-designed architecture of GCNT-SnO2 aerogel, a high specific capacity of 1332 mAh/g with good long-term cycling stability up to 1000 times was achieved. Moreover, this work can provide promising strategy for preparing free-standing and binder-free active electrode materials with high performance for lithium ion batteries and other energy storage devices.
Keywords: SnO2 octahedrons, graphene /carbon nanotube hybrids, aerogel, lithium-ion batteries
前言锂离子电池(lithium ion batteries, LIBs),作为最重要的能量储存装置之一,由于它们的高能密度、低自放电和环境友好在科学和生产领域吸引了许多研究者的关注[1-7]。超高的比容量和良好的循环稳定性的新型电极材料,是开发锂离子电池设备至关重要的一步,更可以促进能源存储元件的大规模应用[8-10]。直到现在,研究者通过制备具有纳米结构和形貌的高性能电极材料来有效地推进新型的锂离子电池的发展。其中,在负极材料中经常用到的包括金属、金属氧化物、共轭聚合物等等[11-14]。其中,氧化锡(SnO2)由于它们的高理论比容量、大量的锂离子嵌入能力、无毒、经济廉价等特点,是目前研究最广泛的阳极材料之一[15,16]。特别地,与不规则的SnO2纳米颗粒相比,高能面暴露的SnO2材料表现出了明显增强的锂离子存储能力[17-20]。在锂离子电池中八面体SnO2的纳米晶体电化学性能的显著提高可以归因于高能面有一个开放的表面结构、具有高密度的原子截面和边缘、锂离子嵌入/脱出的大量活性位点[21,22]。