二维分级纳米碳材料的制备及其在锂电池中的应用

发布时间：2018-02-10 04:11

  本文关键词： 二维纳米碳 分级结构 氮掺杂 多孔结构 储锂性能　出处：《中国科学技术大学》2017年硕士论文　论文类型：学位论文

【摘要】：二维纳米碳材料在新一代能量存储与转换体系中被广泛地应用和研究。当被用作锂离子电池负极材料时,其超高的比表面积可以提供丰富的电化学活性位点,从而保证了材料的高比容量。其二维纳米结构可以缩短Li+离子的扩散路径、提升材料的倍率性能。其优异的机械性能保证电极具有良好的结构稳定性,从而使材料获得优异的循环性能。然而由于范德瓦尔斯力的存在,二维纳米碳材料通常会面临严重的团聚和堆叠效应,这造成了有效比表面积的损失,阻碍了 Li+离子的扩散。构建二维分级结构可以有效地缓解这种团聚与堆叠,促进二维纳米碳材料高比表面积的充分利用。此外,优化孔径分布、杂元素功能化均对提升二维纳米碳材料的储锂性能有重要的意义。传统制备分级纳米碳材料的方法耗时耗能、价格昂贵且产率低,远不能满足需求。因此,用环境友好型方法制备二维分级纳米碳材料是一个有前景的研究方向。本文中的研究内容主要集中于以下几点:(1)以镁铝双金属氢氧化物为模板,吸收工业污水中的常见有机染料橙黄Ⅱ作为碳源,制备了一种二维分级纳米碳材料(2D-HCA),并用一系列的表征手段研究了这种分级碳材料的微观结构、探究了它的制备机理。实验结果表明,2D-HCA由二维纳米亚单元组成;同时,这种碳材料具有分级孔结构和N、S杂元素共掺杂的特性。(2)基于2D-HCA的制备方法,进一步以三聚氰胺为氮源,用"一步掺杂法"成功制备了富氮二维纳米碳(N-2D-HCA),并表征了 N-2D-HCA的结构,分析了 N元素的含量和种类。实验结果表明,N-2D-HCA也具有由二维纳米亚单元组成的分级结构;N-2D-HCA含N量为15.5%,其中电化学活性高的吡啶氮和吡咯氮占所有N原子的84%。(3)测试了两种分级纳米碳的储锂性能,包括循环伏安曲线、循环性能、倍率性能等。电化学数据表明,2D-HCA表现出了极高的储锂比容量、N-2D-HCA表现出了优异的循环稳定性。本文的实验结果表明,通过构建二维分级结构的纳米碳材料,能够有效地缓解纳米碳单元片层间的团聚与堆叠,有效提高二维纳米碳材料表面积利用率,实现其优异的储锂性能。本论文以有机染料橙黄Ⅱ为碳源,制备出具有优异储锂性能的二维分级结构纳米碳材料,实现了污染物的绿色利用。
[Abstract]:Two-dimensional nano-carbon materials have been widely used and studied in the new generation of energy storage and conversion systems. When used as anode materials for lithium ion batteries, their ultra-high specific surface areas can provide abundant electrochemical active sites. Thus, the high specific capacity of the material is ensured. The two-dimensional nanostructure can shorten the diffusion path of Li ion and improve the performance of the material. Its excellent mechanical properties ensure the electrode has good structural stability. However, due to the existence of van der Waals force, two-dimensional nano-carbon materials usually face serious agglomeration and stacking effect, which results in the loss of effective specific surface area. The structure of two-dimensional hierarchical structure can effectively alleviate the agglomeration and stacking, and promote the full utilization of high specific surface area of two-dimensional carbon nanomaterials. In addition, the pore size distribution can be optimized. The functionalization of heterogenous elements is of great significance in improving the lithium-storage properties of two-dimensional nano-carbon materials. Traditional methods for preparing graded nano-carbon materials are time-consuming, energy consuming, expensive and low yield, and can not meet the demand. It is a promising research direction to prepare two-dimensional graded nano-carbon materials by environment-friendly method. The research contents in this paper are mainly focused on the following points: 1) Mg-Al bimetallic hydroxides are used as templates. A 2-D graded nano-carbon material was prepared by absorbing orange 鈪，

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