钠离子电池电极复合材料的制备及电性能研究

发布时间：2018-03-17 20:19

  本文选题：钠离子电池　切入点：钛酸钠　出处：《齐鲁工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文首先对锂离子电池和钠离子电池进行了简要概述,同时对现有文献报道的钠离子电池材料进行归类整理并做了详细的介绍,并对现有材料的优点和不足进行了分析,然后提出了本论文的研究重点：利用具有优良导电性的材料对现有电极材料进行表面修饰改性,提高电极的电导率,使制备的材料具有更优异的电化学性能。主要内容包括：层状Na2Ti3O7作为钠离子电池负极材料时,存在导电性差、高温下容易形成棒状或块状结构,Na+离子扩散率低及倍率性能较差等问题。本文以介孔二氧化钛作为前驱体,热固性酚醛树脂作为碳源和保护层,制备了内部由导电碳网络分割、表面均匀包覆一层导电碳的Na2Ti3O7@C复合材料。通过X射线衍射技术、扫描电子显微镜及透射电子显微镜等测试手段对所得复合材料的结构和形貌进行了一系列表征,并以之为钠离子电池电极材料与金属钠组装成半电池进行电化学测试。测试结果表明,所得电极材料为碳层包覆的纯相Na2Ti3O7。TEM和SEM表征证明电极材料呈直径500 nm左右的球状核壳结构。这种纳米结构的存在缩短了Na+离子的传输距离,因而提高了电极材料中Na+离子的扩散速率。电极材料表面所包覆的很薄的碳壳层的存在,提高了材料的导电性能。因此,制备的Na2Ti3O7@C复合材料较纯Na2Ti3O7材料的电化学储钠性能有非常大的提高,在O.1C倍率下第2周循环的放电容量由109.2mAh/g提高到155 mAh/g,50周循环后放电容量仍保持在100 mAh/g,而Na2Ti307材料50周循环后放电容量仅保持有60.1 mAh/g。在NASICON型的Na3V2(PO4)3晶体结构中,VO6八面体和PO4四面体以顶角相连的形式组成三维框架构造,表现出可供Na+离子快速通过的通道结构,因此在理论上Na+离子具有非常高的传导率。然而电极材料的电导率相对较低,储钠的电化学活性也较差。聚苯胺是一种具有共轭π-π键结构的聚合物,在经过“掺杂”后,π电子可以沿着聚合物链方向移动,因而表现出良好的导电性。本文利用化学氧化的方法成功地制备了质子酸掺杂的聚苯胺,并将其均匀地包覆在Na3V2(PO4)3材料表面对材料进行表面修饰。相应结构表征证明了聚苯胺在电极材料表面的成功包覆；相应电化学性能测试证明,经聚苯胺包覆改性后的Na3V2(PO4)3电极材料的充放电比容量以及循环稳定性较Na3V2(PO4)3本征电极材料有显著提高。其中,在700℃C焙烧条件下获得的电极材料经导电聚合物包覆后,其电性能尤为优异。当聚苯胺的含量为Na3V2(PO4)3的万分之一时,复合材料具有最好的储钠性能,0.2C倍率下放电容量为96.5 mAh/g,20周循环后稳定在62 mAh/g。本工作扩展了导电聚合物在二次电池电极材料中的应用范围,也为钠离子二次电池电极材料的改性提供了一定的参考价值。
[Abstract]:In this paper, the lithium ion battery and sodium ion battery are briefly summarized, and the materials of sodium ion battery reported in the literature are classified and summarized in detail, and the advantages and disadvantages of the existing materials are analyzed. Then the research focus of this paper is put forward: the surface modification of the existing electrode materials is carried out by using the materials with excellent conductivity to improve the conductivity of the electrode. The main contents include: when layered Na2Ti3O7 is used as anode material of sodium ion battery, its conductivity is poor. It is easy to form rod or block structure Na ion at high temperature. In this paper, mesoporous titanium dioxide is used as precursor, thermosetting phenolic resin is used as carbon source and protective layer, and the interior is separated by conductive carbon network. The structure and morphology of Na2Ti3O7@C composites were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscope. It was used as electrode material of sodium ion battery and assembled into a half cell with sodium metal for electrochemical test. The carbon coated pure phase Na2Ti3O7.TEM and SEM showed that the electrode material was spherical core-shell structure about 500nm in diameter. The existence of the nanostructure shortened the transport distance of Na ~ (2 +). As a result, the diffusion rate of Na ions in the electrode material is increased. The existence of a thin carbon shell coated on the surface of the electrode material improves the conductivity of the electrode material. Compared with pure Na2Ti3O7 composites, the electrochemical sodium storage properties of the prepared Na2Ti3O7@C composites are greatly improved. The discharge capacity of the second cycle was increased from 109.2 mAh/ g to 155mAh/ g at the 0.1 C ratio, and the discharge capacity of the Na2Ti307 material remained at 100mAh/ g after 50 cycles, while the discharge capacity of the Na2Ti307 material remained only 60.1 mAh/ g after the 50-week cycle. In the Na3V2(PO4)3 crystal structure of NASICON type, VO6 octahedron and VO _ 6 octahedron and octahedron were obtained. The PO4 tetrahedron forms a three-dimensional frame structure in the form of a contiguous vertex. It shows that Na ion can pass through the channel structure quickly, so Na ion has very high conductivity in theory. However, the conductivity of electrode material is relatively low. The electrochemical activity of sodium storage is also poor. Polyaniline is a polymer with conjugated 蟺-蟺 bond structure. After doping, 蟺 electrons can move along the polymer chain. In this paper, the proton acid doped Polyaniline was successfully prepared by chemical oxidation. The corresponding structure characterization proved that Polyaniline was successfully coated on the surface of the electrode material, and the corresponding electrochemical performance test proved that, The charge / discharge capacity and cyclic stability of the modified Na3V2(PO4)3 electrode materials coated with Polyaniline were significantly higher than those of the Na3V2(PO4)3 intrinsic electrode materials, among which the electrode materials calcined at 700 鈩，

本文编号：1626315