多孔过渡金属氧化物、碳材料的设计合成及其在锂离子电池中的应用

发布时间：2018-01-12 14:28

本文关键词：多孔过渡金属氧化物、碳材料的设计合成及其在锂离子电池中的应用　出处：《聊城大学》2017年硕士论文　论文类型：学位论文

【摘要】：过渡金属氧化物材料具有理论容量高、储量丰富、环境友好等优点,是代替商业石墨类负极材料的新一代负极材料,但导电性差、首次充放电效率低和锂离子嵌入和脱嵌过程中体积变化明显等问题制约了其在现实中的应用。天然碳材料储量丰富、无污染等优点,也被认为是替代石墨的理想负极材料,但其导电性差,理论容量低等缺点同样制约其实际应用。本论文从提高电极材料的导电性和优化结构出发,采用盐焙法、配合物热分解法、生物模板法、溶剂热和天然产物功能化等方法制备了一系列纳米负极材料并研究其电化学性能。主要研究内容和结果如下:(1)通过新颖盐焙法合成Mn_3O_4@C、MoO_3@C多孔纳米复合材料。以氯化钠作为保护层和硬模板,利用氯化钠高的比热容量和热稳定性的优点,在空气中直接热分解乙酰丙酮锰,实现了Mn_3O_4@C多孔复合纳米结构的制备。所制备的Mn_3O_4@C多孔纳米复合材料表现出优异的电化学性能,在电流密度为1 Ag~(-1)下,循环950圈后,仍然具有754.4 m A hg~(-1)的比容量。利用该方法还实现了MoO_3@C多孔纳米复合材料的合成,该电极材料在4 Ag~(-1)的大电流密度下,循环500圈后,仍能保持411.1 m A hg~(-1)的比容量;在10 Ag~(-1)的倍率下,仍然具有291.8 m A hg~(-1)的比容量。(2)通过生物模板法制备氧缺陷型α-Fe_2O_3-δ多孔纳米结构。针对α-Fe_2O_3自身导电性和循环性能较差的缺点,从改善α-Fe_2O_3自身结构出发,设计合成了氧缺陷型α-Fe_2O_3-δ。实验中以天然椰子壳为模板,通过物理吸附的方法将Fe(OH)3胶体吸附至椰壳表面。进而在空气中煅烧分解上述复合物,利用原位碳热反应实现氧缺陷型α-Fe_2O_3-δ多孔纳米结构的合成。氧缺陷的引入有效提升了α-Fe_2O_3的导电性,使其电化学性能显著增强,在1 Ag~(-1)的电流密度下,循环900圈,仍能保持1062.6m A hg~(-1)的比容量。(3)针对尖晶石型NiCo_2O_4充放电过程中容量衰减快等问题,从增加材料的结构稳定性出发,设计合成了具有花状形貌的NiCo_2O_4纳米结构。采用溶剂热的方法,通过控制反应时间,实现了花状结构Ni-Co前驱体的形貌控制性合成,热分解得到多孔花状NiCo_2O_4纳米材料。制备的NiCo_2O_4在1 Ag~(-1)的电流密度下,循环330圈,仍然具有1128 m A hg~(-1)的比容量。在5 Ag~(-1)的倍率下,仍然具有948.1 m A hg-1的比容量。(4)通过热分解十一烷胺锰金属配合物制备片状Mn_3O_4@C多孔纳米材料。以十一烷胺作为配体,以Mn Cl2·4H2O作为锰源制备了十一烷胺锰金属配合物,通过热分解得到片层Mn_3O_4@C多孔纳米材料。所制备的Mn_3O_4@C表现出优异的电化学性能,在2 Ag~(-1)的电流密度下,循环2000圈后,仍然具有934.1 m A hg~(-1)的比容量。(5)通过天然产物功能化修饰制备N/S共掺杂的C多孔纳米片。以天然杨絮为原料,通过硫脲辅助原位水热碳化法,设计合成了具有多孔片状结构的N/S双掺杂型C。该合成方法有效利用了天然杨絮本身的片层结构,通过N/S双掺杂进一步提升了材料本身的导电性,极大的促进了碳材料电化学性能。该材料表现出优异的循环稳定性,在0.5 Ag~(-1)的电流密度下,循环700圈后,仍然具有502 m A hg~(-1)的比容量。
[Abstract]:The transition metal oxide materials has high theoretical capacity, abundant reserves, environment friendly and other advantages, is a new generation of anode materials instead of commercial graphite anode materials, but the conductivity difference, the first charge discharge efficiency is low and the lithium ion intercalation and deintercalation process of volume change obvious problems restricting its application in reality carbon materials. Natural reserves, no pollution, is also considered an ideal cathode material to replace graphite, but its poor conductivity, low capacity theory also restricts its practical application. This paper focuses on improving the conductivity of electrode materials and optimizing the structure of the salt baking method, thermal decomposition method. Biological template method, solvent and natural products such as a series of preparation methods of nano anode materials and their electrochemical performances were studied. The main research contents and results are as follows: (1) through the synthesis of novel Mn_3O_4@C salt baking method, Mo O_3@C porous nanometer composite material. With sodium chloride as a protective layer and hard template, using the advantages of sodium chloride high specific heat capacity and thermal stability in air, the direct thermal decomposition of manganese acetylacetonate, the porous Mn_3O_4@C composite nanostructures were prepared. The preparation of porous Mn_3O_4@C nanocomposites exhibit electrochemical properties excellent, at a current density of 1 Ag~ (-1), after 950 cycles, still has 754.4 m A hg~ (-1) than the capacity. The advantage of this method is to achieve a synthesis of porous MoO_3@C nanometer composite material, the electrode material in 4 Ag~ (-1) high current density of 500 cycles. After 411.1 m A hg~ can still maintain the specific capacity; (-1) at 10 Ag~ (-1) the rate is still 291.8, m A hg~ (-1) than capacity. (2) preparation of oxygen deficient -Fe_2O_3- alpha delta porous nanostructures by biological template method. For its conductive alpha -Fe_2O_3 and cycle The performance is poor, starting from the improvement of alpha -Fe_2O_3 structure itself, oxygen deficient alpha Delta -Fe_2O_3- were designed and synthesized. Using natural coconut shell as a template in the experiment, through physical adsorption of Fe (OH) 3 colloid adsorption to the coconut shell surface. And then calcined in air the decomposition of the complexes, synthesis of the oxygen defect type -Fe_2O_3- alpha delta porous nano structure by in-situ carbothermal reaction. The introduction of oxygen defects effectively enhance the conductivity of alpha -Fe_2O_3, the electrochemical performance was significantly enhanced in 1 Ag~ (-1) of the current density, 900 cycles, can still maintain 1062.6m A hg~ (-1) specific capacity (3. According to the capacity of spinel type NiCo_2O_4) during charge and discharge attenuation problem, starting from the increased structural stability of the material, with flower like NiCo_2O_4 nanostructures were synthesized by solvothermal method. The design, by controlling the reaction time, the flower. Morphology control synthesis structure of Ni-Co precursor, thermal decomposition to obtain porous flower like NiCo_2O_4 nano material. The preparation of NiCo_2O_4 in 1 Ag~ (-1) of the current density, 330 cycles, still has 1128 m A hg~ (-1) than the capacity. In 5 Ag~ (-1) rate, still has 948.1 m A HG-1 capacity. (4) preparation of flake porous Mn_3O_4@C nano materials complexes produced by thermal decomposition of eleven manganese metal. With eleven alkyl amine alkyl amine as ligand, manganese source prepared eleven alkyl amine manganese metal complexes with Mn Cl2 4H2O as obtained lamellar porous Mn_3O_4@C nanometer materials by heat decomposition. The prepared Mn_3O_4@C exhibited excellent electrochemical performance, at 2 Ag~ (-1) of the current density, after 2000 cycles, still has 934.1 m A hg~ (-1) than capacity. (5) preparation of C porous nano N/S doped by natural product modification to system. Natural Yangxu as raw materials by sulfur Urea assisted in situ hydrothermal carbonization method, porous sheet structure of N/S double doped C. the synthesis method of the effective use of the lamellar structure of natural Yangxu itself designed and synthesized by double doped N/S to further enhance the conductivity of the material itself, greatly promote the electrochemical performance of carbon materials. The material exhibits excellent the cycle stability at 0.5 Ag~ (-1) of the current density, after 700 cycles, still has 502 m A hg~ (-1) than the capacity.

【学位授予单位】：聊城大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383;TM912

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