【作者】 黄建兵；

【导师】 毛宗强；

【作者基本信息】 清华大学 ， 化学工程与技术， 2007， 博士

【摘要】 低温(400-600oC)陶瓷燃料电池(CFC)是近年来燃料电池领域的研究热点,具有很好的商业化前景。发展实用的低温CFC的关键在于开发高性能、低成本的材料和工艺。本文基于新型复合电解质材料,开发了与之相匹配的电极材料,探索了合适的电池制备工艺,初步设计了电池堆的结构,建立了新型复合电解质燃料电池的理论电化学模型,为进一步研究开发低温CFC打下了基础。本文从Ce0.8Sm0.2O1.9(SDC)-碳酸盐复合电解质着手,制备了不同组成的材料体系,研究了材料的结构与电性能。结果表明,SDC与碳酸盐形成了两相复合体系,而且其导电行为具有两个显著特征:电导跃迁温度和电导率增强效应。电导跃迁温度主要与碳酸盐类型有关,通常比碳酸盐的共熔点低20-40oC。在电导跃迁温度附近,其电导率比SDC的电导率高几倍到数十倍,电导率增强效应与不同方法制备的SDC粉体、碳酸盐含量、碳酸盐摩尔比及碳酸盐类型有关。采用冷压工艺制备了SDC-碳酸盐复合电解质单电池,考察了上述材料因素和电池结构及操作条件等对电池性能的影响。结果表明,所有SDC-碳酸盐复合电解质低温CFC均表现出良好的性能。其中,采用SDC-LiNaCO3复合电解质的氢-空燃料电池在500oC时获得的最高性能为690mWcm-2,400oC时最高输出超过300mWcm-2。首次发现,该复合电解质在燃料电池气氛中的离子导电性质随LiNaCO3的含量而改变。发展了一体化热压新工艺制备较大尺寸的单电池。该电池在500-600oC能稳定工作,500oC时以约500mWcm-2的输出稳定放电超过12h,但在475oC以下性能不稳定。设计并组装了2-3个单电池的短堆,其中三片堆在550oC时的最大输出功率为1.55W,改进气体歧管密封有望提高其输出性能。制备了新型Ce0.8Zn0.2O1.9(ZDC)-碳酸盐复合电解质、类钙钛矿结构La2NiO4+δ(LNO)基阴极和NiO基双组分阳极,研究表明,采用这些新材料的复合电解质燃料电池适合在低温范围内工作,而且材料的匹配性良好。在离子-电子混合传导体系的基础上,结合缺陷化学理论,建立了共离子传导复合电解质燃料电池的一维电化学模型,并比较了SDC基复合电解质CFC与SDC电解质CFC的操作特性,表明新型共离子传导复合电解质CFC更有优势。更多还原

【Abstract】 Low-temperature (400-600oC) ceramic fuel cell (CFC) has received much attention in recent years due to its promising prospect for commercialization. The key to develop practical low-temperature CFC is to develop materials and techniques with high performance and low cost. In this thesis, based on the innovative composite electrolyte materials, compatible electrode materials were developed, and suitable techniques were explored to fabricate single cell, furthermore, the structure of the fuel cell stack was designed. In addition, a theoretical electrochemical model was proposed to describe the fuel cell with a co-ionic conducting composite electrolyte. All these have laid a foundation for further R & D in low temperature CFC.Beginning from Ce0.8Sm0.2O1.9(SDC)-carbonate composite electrolytes, the material systems with various compositions were prepared, and the structure and electrical properties of these materials were studied. The results show that SDC and carbonates have formed a composite, and its conductivity behavior has two typical features: conductivity transition temperature and conductivity enhancement effect. The conductivity transition temperature is mainly dependent of the type of carbonates, and it is normally 20-40oC lower than the eutectic melting point of the carbonates. Around the conductivity transition temperature, the conductivities of these composite electrolytes are several to several ten times to that of SDC. The conductivity enhancement effect is related to the SDC powder prepared by different methods, the content of the carbonates, the mole ratio of the carbonates and the type of the carbonates.Single cells with SDC-carbonate composite electrolytes were fabricated by a cold-pressing technique, and the effects of the above factors, cell structure and operating conditions on the cell performances were investigated. The results show that all cells with SDC-carbonate composite electrolytes have exhibited excellent performances. Among them, the best performances of 690 mWcm-2 at 500oC and more than 300 mWcm-2 at 400oC were achieved by the hydrogen-air fuel cells with SDC-LiNaCO3 composite electrolytes. It has found for the first time that the ionic conduction properties of such composite electrolytes varied with the content of the carbonates. A new integrated hot-pressing technique has been developed to fabricate single cell with larger size. The cell was operated steadily at 500-600oC, and it discharged at 500oC for more than 12h with an output of about 500 mWcm-2. However, it became unsteady below 475oC. Short stacks with 2 or 3 cells were constructed with designed structure. A maximum output power of 1.55W was achieved at 550oC for a three-cell stack. The stack performances are expected to be improved by solving the sealing on the gas manifold.Novel Ce0.8Zn0.2O1.9(ZDC)-carbonate composite electrolytes, pervoskite-like structured La2NiO4+δ(LNO) based cathodes, and NiO based binary anodes were prepared and tested in fuel cells. It shows that the composite electrolyte fuel cells using these new materials are suitable to be operated at low temperatures, and they are compatible with existing material systems.Based on the ionic-electronic conducting system, a one-dimension electrochemical model was set up to describe the fuel cell with a co-ionic conducting composite electrolyte in combination with the theory of defect chemistry. The operating characteristics of the fuel cell with a SDC based composite electrolyte and the fuel cell with a SDC electrolyte were compared, which showed that the former is superior to the later.更多还原