微纳米结构钒氧化物可控制备及锂电性能研究

发布时间：2018-05-27 12:26

本文选题：钒氧化物 + 微纳米结构　；参考：《大连理工大学》2016年博士论文

【摘要】：微纳米钒氧化物因其多变的价态、可调的微观结构及特殊的电学性质在电极材料、气敏及开关材料等方面展现出潜在应用价值,已成为国内外研究热点。本文针对当前广泛关注的钒氧化物微纳米结构调控方法学及结构与性能关系开展研究,旨在获得可批量化定向制备不同微纳米结构钒氧化物的新方法,研究解决其结构对锂电等性能控制关系问题,为将微纳米钒氧化物推向应用提供技术和理论支撑。基于这一指导思想,本文跳出前人水热法等调控钒氧化物微纳米结构的传统方式,提出一种基于直接沉淀和前驱体结构调控获得相应微纳米结构钒氧化物的新思路：首先用简单的直接沉淀法获得结构可控的钒氧化物前驱体-钒酸铵,再利用在不同条件下热处理时材料微结构的演化得到与前驱体骨架结构相同的钒氧化物,并详细研究所获得产物作为锂电池材料的正极性能,同时探讨了微纳米结构与性能之间相互关系规律。具体研究内容如下：(1)直接沉淀法控制合成不同微纳米结构钒酸铵前驱体。论文研究了V205与熔融尿素固液反应,并以此反应产物为原料,基于钒酸盐结构多变的特点,选择醇水混合溶剂体系,以氨水作为沉淀剂控制合成了微球与花状结构钒酸铵前驱体。研究醇水比例和陈化时间等因素对钒酸铵前驱体形貌及结构的影响。结果表明：随着醇水比的增加会导致制得钒酸铵微球的粒径逐渐减小；醇水比提高能阻止组成花状(NH4)2V3O8的纳米片进-步长厚；因而在高醇水比时,陈化时间的增加会促使形成花瓣密集堆积的花状结构,而醇水比低时,则会随着晶体生长形成较厚的块状结构。(2)钒酸铵盐前驱体对其相应钒氧化物微纳米结构的影响与控制关系。以直接沉淀法制得的不同微纳米结构钒酸铵前驱体为研究对象,基于氧化还原及热分解反应的热力学定律,研究了热处理气氛和温度等因素对前驱物形成钒氧化物的价态和微纳米结构的影响：结果发现,在氨气气氛下热处理钒酸铵微球以及花状结构(NH4)2V3O8能分别制得V203空心微球和花状多级结构的V203；氮气气氛下热处理钒酸铵微球和花状(NH4) 2V3O8则能分别得到V02多孔微球以及花状的V02；空气气氛下煅烧这些低价态钒氧化物可以获得相应微纳米结构V205。(3)微纳米结构V02及W掺杂V02对相变性质以及锂电池性能影响关系研究。研究了多孔微球和花状VO2与掺杂VO2的相变性质以及作为锂电池正极材料的性能。结果表明其中多孔微球V02(B)具有较高的充放电比容量(140mAh·g-1),且同时具有最稳定循环性能,充放电循环100次后的容量保持率为87%；而W掺杂或Na、W共掺杂V02虽能降低相变温和内阻,一定程度上改善了VO2(M/R)锂离子可逆插入能力,但是相比于V02(B)和V205的性能还有一定差距。实验探讨分析了相关机理,认为V02(B)转变为金红石相(R)和单斜相(M),导致可逆储存锂离子能力大幅降低。研究不同热处理温度对于掺杂VO2相变性质的影响,结果表明经过适当高温热处理后,可以提高掺杂VO2在室温或更低温度时相变的温敏性,使其在热敏电阻开关方面展现潜在应用。(4)不同微纳米结构V2O5锂电池性能研究。研究了上述获得的不同微纳米结构V2O5(包括纳米棒、空心微球、多孔微球、花状以及花状多级结构等)作为锂电池正极材料时的锂电池性能。结果表明,这些微纳米结构的V2O5均表现出了比上述VO2或商业V2O5更高的充放电比容量等锂电池性能；其中花状多级结构V2O5展现出了最高的充放电比容量286 mAh·g-1(接近理论值294 mAh·g-1),而空心微球则具有最稳定循环性能,充放电循环100次后的可逆放电比容量仍可达210 mAh·g-1,容量保持率为78%。
[Abstract]:Micro nano vanadium oxide has been a research hotspot at home and abroad because of its changeable valence state, adjustable microstructure and special electrical properties in electrode materials, gas sensing and switching materials. This paper has been concerned with the relationship between structure and properties of vanadium oxide micro nanostructures. The aim of this study is to obtain a new method for batch oriented preparation of vanadium oxides with different micro nanostructures, to study the relationship between the structure and control of lithium, so as to provide technical and theoretical support for the application of micro nano vanadium oxide to the application. Based on this guiding ideology, this paper leapt out of the previous hydrothermal method and other regulation of vanadium oxide micro nanorips. A new way of obtaining the corresponding micro nanostructure vanadium oxide based on the direct precipitation and precursor structure regulation is proposed in the traditional way. First, a simple direct precipitation method is used to obtain the structure controlled vanadium oxide precursor, ammonium vanadate, and then the microstructure evolution of the material is obtained with the precursor bone during the heat treatment under different conditions. The vanadium oxide with the same structure was studied, and the positive properties of the products were studied in detail. The relationship between the microstructure and properties of the micro nanostructures was discussed. The specific contents were as follows: (1) the direct precipitation method was used to control the synthesis of the precursor of ammonium vanadate with different micro and nanoscale structures. The solid liquid of V205 and molten urea was studied in this paper. The reaction product was used as the raw material. Based on the characteristics of the vanadate structure, the mixture of alcohol and water was selected and the ammonia water was used as the precipitator to control the synthesis of the microspheres and the flower like structure of ammonium vanadate precursor. The effects of the proportion of alcohol and water and the aging time on the shape and structure of the precursor of ammonium vanadate were studied. The results showed that with alcohol, with alcohol The increase of water ratio will lead to a gradual decrease in the size of the prepared ammonium vanadate microspheres, and the increase in the ratio of alcohol and water to the thickness of the nanoscale nanoscale (NH4) 2V3O8, and the increase of the aging time in the high alcohol water ratio will lead to the formation of a flower like structure with densely stacked petals, and the thicker blocks will be formed with the crystal growth when the ratio of alcohol and water is low. (2) the influence of ammonium vanadate precursor on its corresponding vanadium oxide micro nanostructure and its control relationship. The precursor of ammonium vanadate, a different micro nano structure obtained by direct precipitation method, was studied. Based on the thermodynamic law of redox and thermal decomposition reaction, the heat treatment atmosphere and temperature were studied to form vanadium in the precursor. The valence state of oxide and the influence of micro and nano structure: the results show that the V203 hollow microspheres and the flower like multistage structure V203 can be obtained by heat treatment of ammonium vanadate microspheres and flower like structure (NH4) in ammonia atmosphere. In nitrogen atmosphere heat treated ammonium vanadate microspheres and flower like (NH4) 2V3O8 can get V02 porous microspheres and flower shape respectively. The effect of V205. (3) micro nanostructure V02 and W doped V02 on the phase transition properties and the performance of lithium battery can be obtained by calcining these low valence vanadium oxides in air atmosphere. The phase transition properties of porous microspheres and flower like VO2 and doped VO2 are studied. The results show that the properties of the doped VO2 are as the cathode material for lithium batteries. The porous microsphere V02 (B) has a high charge discharge ratio (140mAh. G-1), and has the most stable cycle performance at the same time, and the capacity retention rate is 87% after 100 times of charge discharge cycle. While W doping or Na, W Co doped V02 can reduce the phase transition mild resistance and improve the reversible insertion ability of VO2 (M/R) lithium ion to a certain extent, but compared to V02 (B). There is still a gap between the performance of V205 and the performance of V02 (B). It is considered that the conversion of V02 (B) to rutile phase (R) and Dan Xiexiang (M) leads to a significant reduction in the ability of reversible storage of lithium ion. The temperature sensitivity of phase transition at room temperature or lower temperature makes it potential applications in the field of thermistor switch. (4) study on the performance of different micro nano structure V2O5 lithium batteries. The different micro nano structure V2O5 (including nanorods, hollow microspheres, porous microspheres, flower like, multistage structure, etc.) as cathode material for lithium battery is studied. The results show that the V2O5 of these micro and nanoscale structures show higher charge discharge ratio than the above VO2 or commercial V2O5, and the flower like multistage structure V2O5 shows the highest charge discharge ratio of 286 mAh. G-1 (close to the theoretical value of 294 mAh. G-1), and the hollow microspheres have the most stable cycle. The reversible discharge specific capacity of the charge and discharge cycle after 100 cycles can still reach 210 mAh? G-1, and the capacity retention rate is 78%.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ135.11;TM912

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