固体氧化物燃料电池纳米复合电极有效性质理论及模拟计算

发布时间：2019-06-14 19:02

【摘要】：世界范围内对煤、石油、天然气等化石燃料高效、无污染利用的需求,使得能够直接使用碳氢燃料发电的清洁高效发电装置——固体氧化物燃料电池(简称SOFC)越来越受到人们的重视。多孔电极是固体氧化物燃料电池中非常重要的组成部分,其性能的优劣对固体氧化物燃料电池性能的提高起着关键作用。纳米复合电极作为一种新兴的多孔电极,由于具有跟电解质之间的力学匹配性高,极化损耗小等优点而倍受关注。尽管纳米复合电极实验方面的研究很多,理论研究却相对贫乏,这影响着人们对纳米复合电极内部反应机理的理解及对其微结构和材料组成的优化设计。科学合理的建立和发展纳米复合电极的有效性质理论,进而建立多物理场模型对纳米复合电极的相关性能进行对比和优化,对实验研究有非常重要的指导意义。本论文基于纳米复合电极的实际物理图像,在传统电极的有效性质理论的基础上,使用理论推导和多物理场模拟等方法,对具有纳米复合电极结构的固体氧化物燃料电池进行了有效性质理论研究和性能模拟优化工作,主要内容包括如下几个部分：在第一章中,我们首先介绍了燃料电池的发展概况,其次概述了多物理场模拟相关理论,对建模过程中需要用到的控制方程进行了简单介绍,进而简要介绍了纳米复合电极这种新兴多孔电极的发展背景,制作工艺,国内外研究现状以及优势所在,最后我们对理论模拟过程中常见的模拟技术和方法做了简要介绍。第二章从纳米复合电极的几何结构特殊性出发,引入了多孔电极是由匀质导电的等效球随机排布而成的假设,在已有的由硬球堆积传统电极电导率理论的基础上,提出和发展了纳米复合电极的有效电导率理论,给出了二元纳米复合电极电导率的解析表达式,同时基于三元纳米复合电极中核心骨架的离子传输和纳米小颗粒之间的离子传输形成两条并联的离子传输通路的物理图像,给出了三元纳米电极的等效离子电导率表达式,并跟相关的实验数据进行了比较验证。第三章利用有限厚度逾渗阈值的维度理论,对第二章电导率公式中的球壳层电导率进行修正,并用修正后的理论对纳米复合电极的一些特有的实验现象进行解释,还进一步讨论了层数因子对球壳层电导率的修正。该电导率理论的计算结果跟不同Ni的组分,不同温度和不同电极结构导致的电导率变化的实验数据符合的很好,进一步证明了我们理论的正确性。该理论的提出为纳米复合电极的优化设计奠定了基础。第四章发展了纳米复合电极中的电化学有效性质理论和气体传输有效性质理论,分别给出了有效三相线和有效气孔直径的解析表达式,并跟实验数据对比,验证了有效性质理论的准确性,我们还进一步建立了三元纳米电极的多物理场模型,对三元纳米电极的微结构参数和电极组分配比做了一系列的讨论和优化。第五章基于前面已经验证过的纳米复合电极有效性质理论,耦合电子传输,离子传输,电化学反应,气体传输等过程建立了不同结构电极对应的固体氧化物燃料单电池多物理场模型,该多物理场模型给出的Ⅰ-Ⅴ曲线跟实验符合的很好,验证了我们有效性质理论的准确性。对传统电极,单相浸渍纳米电极,双相浸渍纳米电极等不同结构电极的相关性质的比较,使我们对不同结构的多孔电极的优缺点有了进一步了解。第六章对本论文研究内容进行简单的总结。
[Abstract]:The demand of high efficiency and pollution-free utilization of fossil fuels such as coal, oil and natural gas in the world has made it more and more important to use the clean and high-efficiency power generation device _ solid oxide fuel cell (SOFC) that can directly use hydrocarbon fuel to generate electricity. The porous electrode is a very important component in the solid oxide fuel cell, and the performance of the porous electrode plays a key role in the improvement of the performance of the solid oxide fuel cell. As an emerging porous electrode, the nano-composite electrode is of great concern due to the advantages of high mechanical matching and low polarization loss. In spite of many researches on the experimental aspects of the nano-composite electrode, the theoretical research is relatively poor, which influences the understanding of the internal reaction mechanism of the nano-composite electrode and the optimization design of the microstructure and the material. It is very important to establish and develop the effective property theory of the nano-composite electrode in a scientific and reasonable way, and then to establish the multi-physical field model to compare and optimize the relative performance of the nano-composite electrode. In this paper, based on the actual physical image of the nano-composite electrode, on the basis of the effective property theory of the traditional electrode, the theoretical derivation and the multi-physical field simulation are used. The solid oxide fuel cell with nano-composite electrode structure was studied and the performance of the solid oxide fuel cell was studied. The main contents include the following parts: in chap. I, we first introduce that development of the fuel cell In this paper, the paper briefly introduces the theory of multi-physical field simulation, and briefly introduces the control equation that needs to be used in the modeling process, and then briefly introduces the development background, the manufacturing process, the present situation and the excellent of the new porous electrode of the nano-composite electrode. In the end, we have made a brief introduction to the simulation techniques and methods that are common in the theoretical simulation process In the second chapter, based on the particularity of the geometrical structure of the nano-composite electrode, the assumption that the porous electrode is made from the equivalent ball of homogeneous conduction is introduced. On the basis of the theory of effective conductivity of the nano-composite electrode, the conductivity of the binary nano-composite electrode is given. The expression is analyzed, and meanwhile, the physical image of the two parallel ion transmission paths is formed on the basis of the ion transmission of the core framework in the ternary nano composite electrode and the ion transmission between the nano small particles, and the equivalent ion power of the three-way nano electrode is provided. Expression, and follow the relevant experimental data In the third chapter, the conductivity of the spherical shell in the second conductivity formula is modified by the dimension theory of the percolation threshold of the finite thickness, and some specific examples of the nano-composite electrode are given by the modified theory. The interpretation of the phenomenon is also discussed, and the number of layers of the spherical shell is further discussed. The results of the conductivity theory are in good agreement with the experimental data of the change of conductivity caused by different Ni components, different temperatures and different electrode structures. The theory is based on the optimization of the nano-composite electrode. The paper lays the foundation for the design. The fourth chapter has developed the theory of the electrochemical and effective properties of the nano-composite electrode and the theory of the effective property of the gas transmission. The analytical expression of the effective three-phase line and the diameter of the effective air hole is given, and compared with the experimental data, it is verified that The accuracy of the effect property theory, we have further established the multi-physical field model of the three-way nano-electrode, and the micro-structure parameter and the electrode group distribution ratio of the ternary nano-electrode are compared. A series of discussions and optimization are carried out. The fifth chapter is based on the theory of the effective properties of the nano-composite electrodes that have been verified in the foregoing, and the corresponding solid oxides of different structure electrodes are established in the process of coupling electron transport, ion transport, electrochemical reaction, gas transmission and the like. The multi-physical field model of the fuel cell, the I-V curve given by the multi-physical field model is in good agreement with the experiment, and it is verified that I The accuracy of the theory of effective property is the comparison of the related properties of different structure electrodes, such as the traditional electrode, the single-phase impregnated nano-electrode, the two-phase impregnated nano-electrode, and the like, so that the porous electrode with different structure The advantages and disadvantages of this paper are further understood.
【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】：2014
【分类号】：TM911.4

【共引文献】