二维层状复合薄膜电极材料的制备及其电化学性能研究

发布时间：2018-05-14 10:20

本文选题：二维层状材料 + 锂离子电池　；参考：《浙江大学》2015年博士论文

【摘要】：近年来,随着各种中小型便携式电子产品的普及以及电动交通工具的推广开发具有高功率和高能量密度以及循环性能好的储能装置已是当今的研究热点。其中,锂离子电池和超级电容器具有高的可逆容量、循环性能稳定以及高能量密度等优点,倍受青睐。在2011年,加拿大皇后大学发布了一款名为“纸手机”的概念设备,随后,在2013年三星和LG公司推出了柔性智能手机。柔性电子通讯设备是未来电子产品的发展趋势之一,这就需要柔性电池及电容器与其匹配。二维层状薄膜电极材料由于其独特的结构,在柔性小型电子器件中有很大的应用潜力。但是如何解决二维层状薄膜电极材料的自堆积及其与活性物质的均匀组装是进一步提高其电化学性能的关键。本论文主要的研究内容是基于溶液真空抽滤组装法,实现了多种二维层状复合薄膜电极材料的组装并较好的克服了二维层状材料之间的自堆积团聚,改善了其电化学储能性能,为其在柔性储能器件中的应用提供一定的指导。主要研究内容及成果如下：1、采用静电自组装及真空抽滤法制备了CuO/还原氧化石墨烯(rGO)复合薄膜。CuO纳米片均匀地分布在石墨烯片层中并形成了无序的多孔网络结构。无需添加粘结剂和导电剂。该复合薄膜可以直接用作电极材料。其中的孔洞结构能有效阻止石墨烯层的团聚,进而提高了石墨烯的可利用面积,促进电解液的传输；同时石墨烯也有利于提高CuO的导电性,促进可逆反应的顺利进行。因此,复合薄膜具有比单一的CuO和rGO高的锂离子电池特性、超级电容器性能,和优越的循环稳定性。2、采用真空抽滤和后续水热处理法制备了具有三维孔状结构及良好机械性能的Mn3O4/rGO柔性复合薄膜。Mn304纳米棒均匀穿插在石墨烯片层中间,形成的三维孔洞结构增加了石墨烯的层间距并形成了导电通道,提高了其与电解液的有效接触面积,用作锂离子电池和超级电容器电极材料时可有效促进电解液的扩散。通过系统研究发现Mn304和rGO配比为1：1时,电化学性能最好。用作锂离子电池负极时,在100 mA/g电流密度下,循环100次以后,放电比容量还可以保持669.6 mA h g-1。用作超级电容器电极时,在2 mV/s扫描速率下,容量可达到204.2 F g-13、采用过滤组装和水热处理制备了WS2/rGO复合薄膜。水热还原之后,作为无粘结剂的锂离子电池负极材料,在100 mA/g电流密度下循环100次以后,其容量还可保持在697.7 mA h g-1。进一步研究表明,在这种交替叠加的复合薄膜中,rGO能有效阻止WS2纳米片的团聚并提高其导电性,并降低了rGO片层之间的团聚,有效缓解充放电过程中带来的体积膨胀,保持结构的完整性,并显著提高了复合薄膜的电化学性能。4、为提高WS2纳米片的导电性和降低它们之间的自团聚,采用抽滤自组装的方法将单壁碳管(SWCNT)均匀地穿插在WS2纳米片中,制得WS2/SWCNT复合薄膜。这种杂化的复合薄膜可用作锂离子电池和超级电容器电极材料。用作超级电容器电极时,将WS2纳米片容量从67.8 Fg-1提高到240.0 F g-1；作为锂离子电池负极时,在循环50次后,放电比容量还保持为861.6 mA h g-1。是纯的WS2纳米片的3倍。电化学性能的提高主要是由于SWCNT均匀地穿插在WS2片中间,提高了层间距还阻止了WS2纳米片的自堆积团聚,为电解液的扩散以及电子传输提供导电通道。在用作锂电材料时,这种复合网络结构能有效缓冲脱嵌锂时的体积膨胀,保持良好的循环稳定性。5、为了进一步提高WS2/SWCNT的容量,我们采用静电自组装和真空抽滤的方法制备了WS2/CuO/SWCNT三元复合薄膜。作为锂离子电池负极,在循环100次后,放电容量仍保持962.4 mA h g-1。这主要是由于CuO纳米片的厚度约为10 nm,跟SWCNT相比能进一步加大WS2的层间距,促进电解液的扩散。这种多孔的网络结构还有利于提高整体的导电性,以及缓冲脱嵌锂过程中的体积膨胀。此外,CuO的理论容量比WS2和SWCNT高,能有效提高整体的容量。6、为探寻以上过滤组装法的普适性,我们用该方法制备了Ti3C2/SWCNT复合薄膜。Ti3C2是近年来发展起来的一种新型二维层状材料,但由于其表面带有F-和OH-,导致其高的扩散势垒和差的导电性能。因此,在Ti3C2片层中穿插导电性良好的碳管,能有效提高整体的导电性,进而促进电子的快速传递,并形成了独特的层状网络结构,能缓冲锂离子在脱嵌过程中的体积膨胀。在0.5 C电流密度下循环300次以后,放电比容量还可以保持428.1 mA h g-1，而纯的Ti3C2仅可以达到96.2 mA h g-1。复合薄膜还具有良好的倍率性能。
[Abstract]:In recent years, with the popularization of various small and medium portable electronic products and the promotion and development of electric traffic tools, the energy storage devices with high power and high energy density and good cycling performance have become the hot spots of the present research. In 2011, the Queen's University released a concept device called "paper cell phone". Then, in 2013, Samsung and LG launched flexible smartphones. Flexible electronic communications equipment is one of the trends in future electronic products, which requires a flexible battery and capacitor to match it. Due to its unique structure, thin film electrode materials have great potential in the application of small flexible electronic devices. But how to solve the self accumulation of two-dimensional layered thin film electrode materials and the uniform assembly of active materials is the key to improve their electrochemical performance. The main research content of this paper is based on the vacuum pumping. The filter assembly method has realized the assembly of a variety of two-dimensional layered composite film electrode materials and better overcome the self accumulation and agglomeration between the two-dimensional layered materials, and improved the electrochemical energy storage performance. It provides some guidance for its application in the flexible energy storage devices. The main research contents and results are as follows: 1, electrostatic self assembly and true. The CuO/ reduced graphene oxide (rGO) composite film.CuO nanometers are distributed uniformly in the graphene layer and formed a disordered porous network structure. The composite film can be directly used as an electrode material. The pore structure of the composite film can effectively prevent the agglomeration of the graphene layer. The available area of graphene is higher to promote the transmission of the electrolyte. At the same time, graphene is also beneficial to improving the conductivity of CuO and promoting the smooth reversible reaction. Therefore, the composite films have the characteristics of lithium ion batteries higher than the single CuO and rGO, supercapacitor performance, and superior cyclic stability.2, vacuum pumping and follow up. Mn3O4/rGO flexible composite thin film.Mn304 nanorods with three-dimensional pore structure and good mechanical properties were evenly interspersed in the middle of graphene lamellae. The three-dimensional pore structure formed the interlayer spacing of graphene and formed a conductive channel, which improved the effective contact area with the electrosolution and used as the lithium ion electricity. The cell and supercapacitor electrode materials can effectively promote the diffusion of the electrolyte. It is found that the electrochemical performance is best when the ratio of Mn304 and rGO is 1:1. When the anode of lithium ion battery is used as negative electrode of lithium ion battery, the discharge specific capacity can also hold 669.6 mA h g-1. when it is used as the supercapacitor electrode at 100 mA/g current density. At 2 mV/s scanning rate, the capacity can reach 204.2 F g-13, and WS2/rGO composite thin film is prepared by filter assembly and hydrothermal treatment. After hydrothermal reduction, as a anode material for lithium ion battery without adhesive, after 100 cycles at 100 mA/g current density, its capacity can be maintained at 697.7 mA h g-1. further research shows that this type of lithium ion battery can be further studied in this way. In the alternatively superimposed composite films, rGO can effectively prevent the agglomeration of WS2 nanoscale and improve its electrical conductivity, and reduce the agglomeration between the rGO layers, effectively alleviate the volume expansion of the charge and discharge process, maintain the integrity of the structure, and significantly improve the electrochemical properties of the composite film,.4, in order to improve the conductivity and decrease of the WS2 nanoscale. Self reunion between them, the single wall carbon tube (SWCNT) is uniformly inserted in the WS2 nanoscale to produce a WS2/SWCNT composite film. The hybrid composite film can be used as a lithium ion battery and a supercapacitor electrode material. As the electric pole of the supercapacitor, the capacity of the WS2 nanoscale is increased from 67.8 Fg-1 to 240. F g-1, as the anode of a lithium ion battery, after 50 cycles, the discharge specific capacity remains 861.6 mA h g-1. is 3 times that of pure WS2 nanoscale. The improvement of the electrochemical performance is mainly due to the uniformity of SWCNT interspersed in the middle of the WS2 slices, the increase of the interval between the layers and the self accumulation and reunion of the WS2 nanoscale, the diffusion of the electrolyte and the electron. The composite network structure can effectively buffer the volume expansion of lithium and maintain good cyclic stability.5. In order to further improve the capacity of WS2/SWCNT, the WS2/CuO/SWCNT three element composite film is prepared by electrostatic self assembly and vacuum pumping. Battery negative electrode, after 100 cycles, the discharge capacity remains 962.4 mA h g-1., which is mainly due to the thickness of CuO nanoscale about 10 nm, which can further increase the spacing of the WS2 and promote the diffusion of the electrolyte compared with SWCNT. This porous network structure is also beneficial to the improvement of the overall conductivity and the volume expansion in the buffer stripping process. In addition, the theoretical capacity of CuO is higher than that of WS2 and SWCNT, which can effectively improve the overall capacity.6. In order to explore the universality of the above filtering assembly method, the Ti3C2/SWCNT composite film.Ti3C2 is a new two-dimensional layered material developed in recent years, but the surface with F- and OH- on its surface leads to its high diffusion barrier. Therefore, the conductive properties of the carbon tube inserted in the Ti3C2 layer can effectively improve the electrical conductivity of the whole and promote the rapid transmission of the electrons, and form a unique layered network structure, which can buffer the volume expansion of the lithium ion in the process of inlaying. After 300 cycles under the current density of 0.5 C, the discharge ratio is also available. It can maintain 428.1 mA h g-1, while pure Ti3C2 can only reach 96.2 mA h g-1. composite film with good rate performance.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.2

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