基于石墨烯纳米片改性的钠离子电池负极材料的研究

发布时间：2018-02-22 19:00

  本文关键词： 钠离子电池 负极材料 溶胶凝胶 石墨烯纳米片 硫化钴 电化学性能　出处：《南京理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：锂离子电池由于高电压、高能量密度,以及循环稳定性等特点,被认为是优异的储能系统。然而,锂资源在地壳中的储量十分有限,这成为制约大规模储能系统发展的瓶颈。而钠资源储量丰富、成本低廉,又具有与锂元素相似的物理、化学特性及储能机制,被视为有望替代锂离子电池的下一代电池。但是,由于钠的相对原子质量和离子半径较大,使钠离子在材料中嵌入脱出更难。因此,研究高性能的储钠电极材料具有重要意义。本论文旨在制备高性能的钠离子电池负极材料,改善材料的容量、循环性能、倍率性能,使其具有一定的应用价值。主要研究内容包括以下几个方面:一,采用溶胶凝胶法制备掺氮功能石墨烯纳米片,通过改变烧结温度,获得合适氮含量且形貌优异的石墨烯纳米片(750℃),该方法大大简化了石墨烯的制备过程。750℃下的样品在0.1Ag~(-1)下能够提供225mAhg~(-1)的可逆容量;在1Ag~(-1)下循环2000周,还有约150mAhg~(-1)的可逆容量;不足之处在于比容量较低,由于二维材料易于团聚堆叠的特性,限制了比表面积的发挥,使石墨烯在储能过程中性能远不及理论计算。二,(1)为了抑制石墨烯纳米片的堆叠,提高掺氮功能石墨烯纳米片的容量,通过改进的溶胶凝胶法,使硫化钴颗粒(Co_(1-x)S)原位生长在功能石墨烯纳米片(FGNs)上,获得Co_(1-x)S/FGNs纳米复合材料。容量远大于掺氮功能石墨烯纳米片(466mAhg~(-1)在1001mAg~(-1),211mAhg~(-1)在10Ag~(-1));并且具有较好的循环稳定性,在1Ag~(-1)下循环200周后,还保留了 251mAhg~(-1)的容量。(2)通过对比Co_(1-x)S/FGNs与Co_(1-x)S和FGNs在电化学性能上的差异,以突出Co_(1-x)S/FGNs在结构设计上的优势。如FGNs在0.1Ag~(-1)下只有275mAhg~(-1)的比容量,Co_(1-x)S在1Ag~(-1)下循环130周后,容量已降至约50mAhg~(-1)。因此,Co_(1-x)S/FGNs的优势可以归因于FGNs的纳米薄片和Co_(1-x)S的小颗粒缩小了钠离子的扩散距离;FGNs的掺杂元素(氮、硫)提供更多的储钠位点;原位的复合方法有效提高材料的稳定性,进而提高了电极的倍率性能和循环性能。
[Abstract]:Lithium ion batteries are considered to be excellent energy storage systems due to their high voltage, high energy density and cycle stability. However, the reserves of lithium in the earth's crust are very limited. This has become a bottleneck restricting the development of large-scale energy storage systems. Sodium is abundant in reserves, low in cost, and has physical, chemical and energy storage mechanisms similar to that of lithium, which is considered to be the next generation battery to replace lithium ion batteries. Because the relative atomic mass and ionic radius of sodium are larger, it is more difficult to intercalate sodium ions into the materials. Therefore, it is of great significance to study the high performance sodium storage electrode materials. In this paper, the purpose of this paper is to prepare high performance negative electrode materials for sodium ion batteries. The main research contents are as follows: firstly, nitrogen-doped graphene nanocrystals were prepared by sol-gel method, and the sintering temperature was changed. The method greatly simplifies the preparation process of graphene. The method can provide the reversible capacity of 225mAhgcn-1) at 0.1AgGG ~ (-1), and the reversible capacity of about 150mAhg-1) for 2000 weeks under the cyclic condition of 1AgGG ~ (-1), and the reversion capacity of graphene nanocrystalline is about 150mAhg-1) by using the method of preparing graphene nanocrystalline at 750 鈩，

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