基于金属有机框架化合物合成多孔碳基纳米材料及其在锂电池负极材料中的应用
发布时间：2018-09-06 17:56
【摘要】：金属有机框架化合物是由有机配体把金属或金属簇连接在一起所形成的一类新型材料。由于它可控的孔道结构和功能的多样性,已经广泛应用于催化、生物成像、气体分离和储存等领域,从而引起了科研工作者的广泛关注。此外,金属有机框架化合物具有较大的比表面积、多孔结构以及大量含碳有机配体,从而已被认为有望成为模板或者前驱物制备多孔纳米材料。本论文主要研究了以不同的金属有机框架化合物纳米粒子作为前驱物制备结构独特的碳基纳米粒子、金属氧化物纳米粒子及它们的复合结构的方法,并对所制备的纳米粒子进行了储锂性能的研究。具体内容如下： 1.理论和实验结果表明,氮掺杂石墨烯的储锂性能很大程度上依赖于氮的掺杂量。然而,目前报道应用于锂离子电池负极材料的氮掺杂碳材料的含氮量大约为10wt%,并且,大量的氮原子掺杂到晶格里会降低其结构稳定性,故电池容量等电化学性能的进一步提高和改善受到限制。通过湿化学方法得到的石墨烯材料表面和边缘含有很多羟基、羧基、环氧基等官能团,从而严重阻碍了氮原子在石墨烯边缘掺杂。本章节建立了一种利用高含氮配合物ZIF-8为前驱物在氮气气氛中焙烧一步法制备高氮掺杂的类石墨烯粒子,如800℃制备的样品其氮含量达17.72wt%。制备的氮掺杂类石墨烯作为锂离子电池负极材料时,在电流密度为100mAg-1测试条件下,循环50次后,放电容量保持在2132mA hg-1,高于文献报道的碳基材料的储锂性能。在电流密度为5A g-1测试条件下,充放电循环1000次后,放电容量依然保持在785mAhg-1,表明所制备负极材料具有多次充放电循环稳定性。优异的储锂性能归因于类石墨烯粒子聚集体内含大量孔洞,其边缘富含吡啶、吡咯型氮掺杂原子。 2.Fe203因具有较大的理论比容量被广泛研究应用于锂离子电池负极材料。然而,Fe203电极材料在充放电过程中容易遭受体积膨胀,从而导致负极极化和电极材料导电性变差。因此,Fe203在应用于锂离子电池负极材料时,容量易衰减,作为实际应用需进一步提高它的循环稳定性。本章通过在空气中直接煅烧铁基沸石型咪唑框架化合物(Fe-ZIF),制备了超细Fe203纳米粒子均匀分布在氮掺杂碳球壳层里(Fe2O3@N-C)。这种材料作为锂离子电池负极材料应用时,在电流密度0.1C(1C=1000mAg-1)测试条件下循环50次后,容量依然保持在1573mAh g-1。值得一提的是,电极材料在经受了两次高倍率测试后,继续在大电流密度1C测试条件下循环100次后,容量还能达1142mAh g-1。所表现出优异的电化学性能可以归因于超细Fe203纳米粒子均匀分布在所制备的氮掺杂碳球壳层里。这种复合结构在充放电过程中可以减小电极的极化,有利于电子和锂离子的传输,以及有效地避免Fe203超细纳米粒子的团聚。由于金属有机框架化合物中含有多种多样的有机配体和金属中心离子,这种新颖的制备方法可以扩展应用到制备其它功能纳米复合材料。 3.MnO具有较高的理论容量(755mAhg-1)、相对较低的滞后电压(0.8V)、成本低以及环境污染小等特点,因而有望应用于锂离子电池负极材料。然而,MnO在充放电循环过程中会遇到体积膨胀和容量急剧衰减等问题,从而严重阻碍了其广泛应用。本章报道了通过煅烧金属有机框架化合物制备超细的MnO纳米晶均匀分布在多孔碳基底里(MnO@C)。这种多孔碳基底不但可以储存锂离子,而且电解质中的离子可以有效地扩散到碳基底内部与MnO纳米晶反应。作为锂离子电池负极材料时,这种MnO@C复合材料在电流密度为100mA g。测试条件下循环100次后,容量依然保持在1221mAh g-1,且具有良好的循环稳定性。这种优异的电化学性能可以归功于MnO纳米晶均匀分布在多孔碳基底这种独特的结构。多孔碳基底在充放电过程中很大程度上改善了电极的导电性,有效地避免了MnO纳米晶的团聚,以及缓解电极材料的体积膨胀。这种合成路线可以扩大到通过煅烧不同金属有机框架化合物制备其它功能材料,应用于不同研究领域。 4.以室温下制备的金属有机框架化合物Mn3[Fe(CN)6]2·nH2O为前驱物,在空气中热分解,成功地制备了Mn1.8Fe1.2O4立方块。所制备的Mn1.8Fe1.2O4多孔立方块保持了Mn3[Fe(CN)6]2·nH2O前驱物的形貌。在空气中煅烧过程中,放出大量的气体分子,如C02和N02,从而所制备的Mn1.8Fe1.2O4立方块具有多孔结构,比表面积为124m2g-。在应用于锂离子电池负极材料时,Mn1.8Fe1.2O4多孔立方块表现出了优异的储锂性能。在电流密度为200mA g。测试条件下充放电循环60次后,容量为827mAhg-1。Mn1.8Fe1.2O4多孔立方块优异的储锂性能可以归为其内部联通的孔道结构以及含有大量的介孔。以合成的NixCo1-xOH为前驱物,在空气中加热450。C焙烧两小时,得到二维NixCo3-xO4多孔纳米片。NixCo3-xO4纳米片作为锂离子电池负极材料时,表现出良好的充放电性能。在电流密度为100mAgJ测试条件下,经过50次循环以后,放电容量保持在1330mAhg-1。当电流密度进一步提高到500mA g-1时,经过200次循环以后,放电容量依然可以保留在844mAhg-1。与传统的C0304锂离子电池负极材料相比,由于Co元素的价格昂贵以及有毒性,NixCo3-xO4中Co含量的降低是十分有意义的。以上两种特殊结构纳米粒子在充放电过程中有效地提高了结构稳定性,减小了锂离子和电子的扩散距离,以及缓解了体积膨胀效应。
[Abstract]:Metallo-organic frameworks (MOFs) are a new class of materials formed by organic ligands linking metals or clusters of metals together. Due to their controllable pore structure and functional diversity, MOFs have been widely used in catalysis, bioimaging, gas separation and storage, and have attracted wide attention of researchers. Macromolecular frameworks have been considered as templates or precursors for the preparation of porous nanomaterials because of their large specific surface area, porous structure and a large number of carbon-containing organic ligands. Metal oxide nanoparticles and their composite structures were prepared, and the lithium storage properties of the prepared nanoparticles were studied.
1. Theoretical and experimental results show that the performance of nitrogen-doped graphene for lithium storage depends largely on nitrogen doping. However, the nitrogen content of nitrogen-doped carbon materials used as anode materials for lithium-ion batteries is about 10wt%. Moreover, a large number of nitrogen atoms doped into the lattice will reduce its structural stability, so the battery capacity is isoelectric. The surface and edge of graphene materials obtained by wet chemical methods contain many functional groups, such as hydroxyl, carboxyl and epoxy groups, which seriously hinder the doping of nitrogen atoms on the edge of graphene. In this chapter, a new type of graphene material, ZIF-8, with high nitrogen content as the precursor, was established. The nitrogen content of high nitrogen doped graphene-like particles prepared by one-step calcination method was 17.72 wt% for the samples prepared at 800 C. The discharge capacity of the nitrogen-doped graphene-like particles as anode materials for lithium-ion batteries remained at 2132 mA HG-1 after 50 cycles at 100 mAg-1 current density, which was higher than that of carbon-based materials reported in the literature. The lithium storage performance of the anode material is attributed to the large number of holes in the aggregates of graphene-like particles with pyridine-rich edges and pyrrole-type nitrogen-doped atoms.
2. Fe203 is widely used as anode materials for lithium-ion batteries because of its large theoretical specific capacity. However, Fe203 electrode materials are subject to volume expansion during charging and discharging, resulting in negative polarization and poor conductivity of electrode materials. Therefore, Fe203 is easy to decay when used as anode materials for lithium-ion batteries. In this chapter, ultrafine Fe203 nanoparticles were synthesized by calcining iron-based zeolite imidazole framework compounds (Fe-ZIF) directly in air and uniformly distributed in nitrogen-doped carbon spherical shell (Fe2O3@N-C). This material was used as anode material for lithium ion batteries with current density of 0.1C (1C = 1000mAg-C). 1) After 50 cycles under test conditions, the capacitance of the electrode material remains at 1 573 mAh g-1. It is worth mentioning that the excellent electrochemical performance of the electrode material can be attributed to the uniformity of ultrafine Fe203 nanoparticles after two high rate tests and 100 cycles under high current density 1C test conditions. This composite structure can reduce the polarization of the electrode, facilitate the transport of electrons and lithium ions, and effectively avoid the agglomeration of Fe203 ultrafine nanoparticles during charge and discharge. A novel preparation method can be extended to the preparation of other functional nanocomposites.
3. MnO has the advantages of high theoretical capacity (755mAhg-1), relatively low hysteresis voltage (0.8V), low cost and low environmental pollution, so it is expected to be used as anode materials for lithium-ion batteries. However, MnO will encounter problems such as volume expansion and rapid capacity degradation during charge-discharge cycles, which seriously hinder its wide application. The preparation of ultrafine MnO nanocrystals by calcining organometallic frameworks is reported. The porous carbon substrate can store lithium ions and the ions in the electrolyte can effectively diffuse into the carbon substrate to react with MnO nanocrystals. As the anode material of lithium ion batteries, the MnO nanocrystals can be well distributed in the porous carbon substrate (MnO@C). After 100 cycles at current density of 100 mA g, the capacity of @C composite remains at 1212 mAh g-1 and has good cycling stability. This excellent electrochemical performance can be attributed to the unique structure of MnO nanocrystals uniformly distributed on porous carbon substrates. It can improve the conductivity of the electrode, avoid the agglomeration of MnO nanocrystals and alleviate the volume expansion of the electrode materials. This synthetic route can be extended to prepare other functional materials by calcining different metal-organic frameworks and be applied in different research fields.
4. Mn1.8Fe1.2O4 cubic block was successfully prepared by thermal decomposition of Mn3[Fe(CN)6]2.nH2O as precursor in air. The prepared Mn1.8Fe1.2O4 porous cubic block retained the morphology of Mn3[Fe(CN)6]2.nH2O precursor. During calcination in air, a large number of gas molecules, such as C02 and N02, were released. The Mn1.8Fe1.2O4 cubic block has a porous structure with a specific surface area of 124m2g -. The Mn1.8Fe1.2O4 porous cubic block has excellent lithium storage performance when used as anode material for lithium ion batteries. Different lithium storage properties can be attributed to the interconnected pore structure and the large amount of mesopores. Two-dimensional NixCo3-xO4 porous nanosheets were prepared by calcining NixCo1-xOH in air for two hours. NixCo3-xO4 nanosheets exhibited good charge-discharge performance when used as anode materials for lithium-ion batteries. When the current density is further increased to 500 mAhg-1, the discharge capacity can still be retained at 844 mAhg-1 after 200 cycles. Compared with the traditional anode materials of C0304 lithium ion batteries, the discharge capacity of N 0304 lithium ion batteries can be kept at 1 330 mAhg-1 after 50 cycles. The decrease of Co content in ixCo3-xO4 is significant. The above two special nanoparticles can effectively improve the structural stability, reduce the diffusion distance of lithium ions and electrons, and alleviate the volume expansion effect.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ127.11;TM912
本文编号：2227092
[Abstract]:Metallo-organic frameworks (MOFs) are a new class of materials formed by organic ligands linking metals or clusters of metals together. Due to their controllable pore structure and functional diversity, MOFs have been widely used in catalysis, bioimaging, gas separation and storage, and have attracted wide attention of researchers. Macromolecular frameworks have been considered as templates or precursors for the preparation of porous nanomaterials because of their large specific surface area, porous structure and a large number of carbon-containing organic ligands. Metal oxide nanoparticles and their composite structures were prepared, and the lithium storage properties of the prepared nanoparticles were studied.
1. Theoretical and experimental results show that the performance of nitrogen-doped graphene for lithium storage depends largely on nitrogen doping. However, the nitrogen content of nitrogen-doped carbon materials used as anode materials for lithium-ion batteries is about 10wt%. Moreover, a large number of nitrogen atoms doped into the lattice will reduce its structural stability, so the battery capacity is isoelectric. The surface and edge of graphene materials obtained by wet chemical methods contain many functional groups, such as hydroxyl, carboxyl and epoxy groups, which seriously hinder the doping of nitrogen atoms on the edge of graphene. In this chapter, a new type of graphene material, ZIF-8, with high nitrogen content as the precursor, was established. The nitrogen content of high nitrogen doped graphene-like particles prepared by one-step calcination method was 17.72 wt% for the samples prepared at 800 C. The discharge capacity of the nitrogen-doped graphene-like particles as anode materials for lithium-ion batteries remained at 2132 mA HG-1 after 50 cycles at 100 mAg-1 current density, which was higher than that of carbon-based materials reported in the literature. The lithium storage performance of the anode material is attributed to the large number of holes in the aggregates of graphene-like particles with pyridine-rich edges and pyrrole-type nitrogen-doped atoms.
2. Fe203 is widely used as anode materials for lithium-ion batteries because of its large theoretical specific capacity. However, Fe203 electrode materials are subject to volume expansion during charging and discharging, resulting in negative polarization and poor conductivity of electrode materials. Therefore, Fe203 is easy to decay when used as anode materials for lithium-ion batteries. In this chapter, ultrafine Fe203 nanoparticles were synthesized by calcining iron-based zeolite imidazole framework compounds (Fe-ZIF) directly in air and uniformly distributed in nitrogen-doped carbon spherical shell (Fe2O3@N-C). This material was used as anode material for lithium ion batteries with current density of 0.1C (1C = 1000mAg-C). 1) After 50 cycles under test conditions, the capacitance of the electrode material remains at 1 573 mAh g-1. It is worth mentioning that the excellent electrochemical performance of the electrode material can be attributed to the uniformity of ultrafine Fe203 nanoparticles after two high rate tests and 100 cycles under high current density 1C test conditions. This composite structure can reduce the polarization of the electrode, facilitate the transport of electrons and lithium ions, and effectively avoid the agglomeration of Fe203 ultrafine nanoparticles during charge and discharge. A novel preparation method can be extended to the preparation of other functional nanocomposites.
3. MnO has the advantages of high theoretical capacity (755mAhg-1), relatively low hysteresis voltage (0.8V), low cost and low environmental pollution, so it is expected to be used as anode materials for lithium-ion batteries. However, MnO will encounter problems such as volume expansion and rapid capacity degradation during charge-discharge cycles, which seriously hinder its wide application. The preparation of ultrafine MnO nanocrystals by calcining organometallic frameworks is reported. The porous carbon substrate can store lithium ions and the ions in the electrolyte can effectively diffuse into the carbon substrate to react with MnO nanocrystals. As the anode material of lithium ion batteries, the MnO nanocrystals can be well distributed in the porous carbon substrate (MnO@C). After 100 cycles at current density of 100 mA g, the capacity of @C composite remains at 1212 mAh g-1 and has good cycling stability. This excellent electrochemical performance can be attributed to the unique structure of MnO nanocrystals uniformly distributed on porous carbon substrates. It can improve the conductivity of the electrode, avoid the agglomeration of MnO nanocrystals and alleviate the volume expansion of the electrode materials. This synthetic route can be extended to prepare other functional materials by calcining different metal-organic frameworks and be applied in different research fields.
4. Mn1.8Fe1.2O4 cubic block was successfully prepared by thermal decomposition of Mn3[Fe(CN)6]2.nH2O as precursor in air. The prepared Mn1.8Fe1.2O4 porous cubic block retained the morphology of Mn3[Fe(CN)6]2.nH2O precursor. During calcination in air, a large number of gas molecules, such as C02 and N02, were released. The Mn1.8Fe1.2O4 cubic block has a porous structure with a specific surface area of 124m2g -. The Mn1.8Fe1.2O4 porous cubic block has excellent lithium storage performance when used as anode material for lithium ion batteries. Different lithium storage properties can be attributed to the interconnected pore structure and the large amount of mesopores. Two-dimensional NixCo3-xO4 porous nanosheets were prepared by calcining NixCo1-xOH in air for two hours. NixCo3-xO4 nanosheets exhibited good charge-discharge performance when used as anode materials for lithium-ion batteries. When the current density is further increased to 500 mAhg-1, the discharge capacity can still be retained at 844 mAhg-1 after 200 cycles. Compared with the traditional anode materials of C0304 lithium ion batteries, the discharge capacity of N 0304 lithium ion batteries can be kept at 1 330 mAhg-1 after 50 cycles. The decrease of Co content in ixCo3-xO4 is significant. The above two special nanoparticles can effectively improve the structural stability, reduce the diffusion distance of lithium ions and electrons, and alleviate the volume expansion effect.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ127.11;TM912
【参考文献】
相关期刊论文 前1条
1 孙颢;何向明;任建国;李建军;姜长印;万春荣;;锂离子电池锑基负极材料研究进展[J];稀有金属材料与工程;2007年07期
，本文编号：2227092
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