层状结构二硫化钼、二硒化钼复合材料的设计制备与储锂储钠性能研究

发布时间：2018-03-24 18:05

本文选题：锂离子电池　切入点：钠离子电池　出处：《浙江大学》2017年博士论文

【摘要】：本文主要针对层状结构过渡金属硫系化合物在储锂储钠领域中存在的循环寿命有限,倍率性能差等问题,以MoS2和MoSe2为研究对象,通过纳米化、表面修饰及其与碳基材料复合化的手段,构建合理可控的多层结构,改善其电化学储锂储钠性能,并结合XPS与HRTEM等分析技术,探究层状结构过渡金属硫系化合物储锂储钠反应机制,为硫系化合物的电化学储能提供理论基础与技术支持。主要研究内容与结果如下:(1)以氨水为氮源,以PEG-20000为碳源,通过两次水热反应过程构建了自支撑多孔结构碳包覆的MoS2与氮掺杂还原氧化石墨烯气凝胶(C-MoS2/N-doped rGO),碳包覆与石墨烯三维网格骨架对MoS2电极材料的双修饰效果,使C-MoS2/N-doped rGO电极具有优异的电化学储锂性能。在200mA/g电流密度下经循环500次,能保持900 mAh/g高可逆比容量,在4 A/g电流密度下循环,仍具有500mAh/g可逆比容量,远优于C-MoS2电极的电化学储锂性能。同时,通过XPS与HRTEM相结合的分析技术探究了其电化学储锂反应机制。(2)通过溶液聚合法构建了三维网格交联结构的MoS2-PPY-rGO/Cu薄膜。厚度为5-10nm的无定型导电聚合物PPY均匀包覆的MoS2纳米片,能够有效抑制MoS2与锂反应过程中中间相多硫化物溶解问题,同时连接MoS2与石墨烯骨架。而rGO三维骨架有效抑制活性物质的团聚,并提高整个薄膜的导电性。将其薄膜直接剪切为电极进行锂离子电池性能测试,该复合薄膜电极有优异的电化学储锂性能。在200mA/g电流密度下循环400次,能保持1070mAh/g比容量,在2 A/g电流密度下仍有600mAh/g的可逆比容量。同时研究了不同厚度与载量薄膜的储锂性能,表明2 mg/cm2量的MoS2-PPY-rGO薄膜具有更优异的储锂性能,说明薄膜厚度对电化学储能有重要的影响。(3)受启于大自然的生物质结构,通过水热法制备三维多孔状结构丝瓜络生物质碳与MoS2壳核结构(LSDCM/MoS2),并利用溶液聚合法与高温碳化包覆氮掺杂碳(N-C)保护层形成了三明治核壳结构LSDCM/MoS2/N-C复合材料。由于构建了独特的三元结构,该LSDCM/MoS2/N-C复合电极具有优异的电化学储锂储钠性能。在储锂方面,在200 mA/g电流密度下循环500次,能保持1058 mAh/g的可逆比容量;在4A/g大电流密度下循环,仍能保持600mAh/g可逆比容量。另外,在4 A/g大电流密度下循环,具有优异的循环稳定性,即循环320次,仍保持571 mAh/g,远高于LSDCM/MoS2,MoS2与LSDCM电极。在储钠方面,在200mA/g电流密度下循环100次,该LSDCM/MoS2/N-C复合电极能保持534 mAh/g的可逆比容量,在4 A/g高电流密度下循环保持245 mAh/g。(4)构建合理并具有高性能的电极材料,对进一步发展钠离子电池具有极其重要的作用。因此,通过以葡萄糖碳源,以氧化石墨烯为骨架,一步水热法构建了三维多孔交联网络结构C-MoSe2/rGO复合材料。在水热过程中,碳包覆MoSe2复合纳米片(C-MoSe2)均匀嵌入在三维多孔结构还原氧化石墨烯等级结构中,达到了对MoSe2电极材料的双修饰效果。直接剪切压制成电极测试,表明该C-MoSe2/rGO电极具有优异的电化学储钠性能。在200mA/g电流密度下循环350次,能保持445 mAh/g高可逆比容量,在4 A/g大电流密度下循环,仍具有225 mAh/g的可逆比容量,远优于C-MoS2电极的电化学储钠性能。同时,通过非原位的XPS与HRTEM相结合的技术探究其电化学储钠反应机制。(5)以等离子体气相沉积制备的VG为载体骨架,通过水热法制备了核壳结构VG/MoSe2垂直阵列,随后采用溶液聚合法与高温碳化包覆氮掺杂碳(N-C)保护层形成VG/MoSe2/N-C三明治核壳结构阵列。VG与N-C构建的全方位碳修饰的三维骨架,有利于电子和离子的快速转移,促进反应动力学过程。同时N-C包覆层能够有效抑制MoSe2在电化学储能过程中中间相多硒化物的溶解,而VG具有垂直片状的稳定结构与高导电性,作为载体能够抑制活性物质团聚。因此,VG/MoSe2/N-C复合阵列具有非常优异的储钠性能。在200 mA/g电流密度下循环400次,能保持545 mAh/g的可逆比容量,即使在2 A/g的电流密度下循环仍呈现出295 mAh/g的可逆比容量。更为重要的是,具有优异的高倍率循环稳定性,即在1 A/g与2 A/g循环1000次,仍能分别保持398 mAh/g与298 mAh/g的高可逆比容量。
[Abstract]:This paper focuses on the life cycle there are laminated structures of transition metal chalcogenides in lithium sodium storage in the field is limited, poor rate performance problems, using MoS2 and MoSe2 as the research object, by means of surface modification and nano technology, and carbon based composite material, multilayer structure construction reasonable and controllable, improve its electrochemical storage lithium storage performance of sodium, and the combination of XPS and HRTEM analysis techniques to explore the layered structure of transition metal chalcogenide lithium sodium storage reaction mechanism, to provide theoretical basis and technical support for the electrochemical sulfur compounds. The main research contents and results are as follows: (1) with ammonia as the nitrogen source, using PEG-20000 as carbon the source, through two times of hydrothermal reaction was constructed from MoS2 and nitrogen doped porous carbon coated support reduced graphene oxide aerogel (C-MoS2/N-doped rGO), and carbon coated graphene 3D mesh skeleton of MoS2 electrode Double modification of materials, the C-MoS2/N-doped rGO electrode has excellent electrochemical lithium storage performance. In the current density of 200mA/g after 500 cycles, can maintain a high capacity reversible cycle of 900 mAh/g at the current density of 4 A/g, 500mAh/g still has a reversible capacity, electrochemical lithium storage performance is much better than that of C-MoS2 electrode. At the same time, analysis of technology through the combination of XPS and HRTEM explore the electrochemical reaction mechanism of lithium storage. (2) to construct the MoS2-PPY-rGO/Cu film 3D mesh crosslinking structure by solution polymerization method. MoS2 nano plate shaping conductive polymer PPY uniform coating thickness is 5-10nm, can effectively inhibit MoS2 and lithium in the reaction process of mesophase multi sulfide dissolution problem, while connecting MoS2 and rGO graphene skeleton. The skeleton inhibit active substances and reunion, improve the conductivity of the whole film. The film is electric direct shear Most of the performance of lithium ion battery test, the composite film electrode has excellent electrochemical lithium storage performance. 400 cycles at the current density of 200mA/g, to maintain the 1070mAh/g capacity, under the current density of 2 A/g 600mAh/g still reversible capacity of lithium storage properties were also studied. Different thickness and load the film, show MoS2-PPY-rGO film 2 mg/cm2 amount has more excellent lithium storage performance, which shows that the film thickness has an important influence on the electrochemical energy storage. (3) by the biomass structure and on the nature, through the hydrothermal synthesis of 3D porous structure of Luffa raw material of carbon and MoS2 core-shell structure (LSDCM/MoS2), and by solution polymerization high temperature carbonization method and coated nitrogen doped carbon protective layer (N-C) formed a sandwich LSDCM/MoS2/N-C core-shell structure composite materials. Because of the unique structure of the construction of three yuan, the LSDCM/MoS2/N-C composite electrode has excellent electrochemical The lithium storage performance of sodium. In lithium storage, 500 cycles at the current density of 200 mA/g, 1058 mAh/g can maintain a reversible capacity; cycle in 4A/g under high current density, 600mAh/g can still maintain a reversible capacity. In addition, circulation at 4 A/g under high current density, excellent cycling stability, i.e. 320 cycles, still maintain 571 mAh/g, much higher than that of LSDCM/MoS2, MoS2 and LSDCM electrodes. In sodium storage, 100 cycles at the current density of 200mA/g, the LSDCM/MoS2/N-C composite electrode can keep 534 mAh/g reversible capacity, on environmental protection to 245 mAh/g. at 4 A/g under the condition of high current density (4) to construct reasonable electrode materials with high performance, to the further development of sodium ion battery plays a very important role. Therefore, by using glucose as carbon source, graphene oxide skeleton, one-step hydrothermal method to construct the three-dimensional porous crosslinked network structure of C-MoSe2/rGO composite material in the water. In the process of heat, carbon coated MoSe2 nano composite film (C-MoSe2) embedded in a uniform three-dimensional porous structure of graphene grade structure, achieves the double effect of MoSe2 modified electrode material. The direct shear test show that the pressed electrode, C-MoSe2/rGO electrode has excellent electrochemical performance of sodium. 350 cycles at a current density 200mA/g next, can maintain a high capacity reversible cycle in 445 mAh/g, 4 A/g high current density is 225 mAh/g, the reversible capacity, the electrochemical behavior of sodium is much better than that of C-MoS2 electrode. At the same time, to explore through the combination of XPS and HRTEM non in situ phase of the electrochemical reaction mechanism of sodium storage technology. (5) to plasma chemical vapor deposition preparation of VG vector backbone, were prepared by hydrothermal method with core-shell structure of VG/MoSe2 vertical array, followed by solution polymerization and carbonization of coated nitrogen doped carbon (N-C) protective layer formation VG/MoSe The full range of carbon skeleton 2/N-C array sandwich core-shell structure of.VG and N-C to build the modified, fast transfer to electron and ion dynamics. At the same time, promote the N-C coating layer can effectively inhibit MoSe2 in electrochemical energy storage solution of mesophase selenide multi process, and stable structure with vertical sheet VG with high conductivity, as a carrier of active substances can inhibit agglomeration. Therefore, VG/MoSe2/N-C composite sodium storage array has very excellent performance. 400 cycles at the current density of 200 mA/g, 545 mAh/g can maintain a reversible capacity, even at the current density of 2 A/g cycle is still showing a reversible specific capacity of 295 mAh/g. More importantly, with excellent high rate cycling stability, i.e. 1000 cycles at 1 A/g and 2 A/g respectively, can still maintain a high reversible 398 mAh/g and 298 mAh/g capacity.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB33;O646

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