【作者】 沙雪清；

【导师】 苏文辉； 吕喆；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2007， 博士

【摘要】 固体氧化物燃料电池（SOFCs,Solid Oxide Fuel Cells）是一种高效率、低污染的新型能源装置,被认为是二十一世纪的绿色能源。传统的以氧化钇稳定的氧化锆（8YSZ）做电解质的SOFC需要高温工作,由于高温而带来的电极-电解质界面反应、阳极烧结,金属连接材料的腐蚀等问题的存在限制了SOFC的实际应用。目前,SOFC的研制正向中温化发展,降低SOFC的工作温度主要有两种途径,一是开发在中温具有高离子电导率的固体电解质材料;另外的办法是YSZ电解质的薄膜化。本文主要集中于中温固体电解质材料的研发,对稀土氧化物双掺杂的CeO₂基电解质进行了系统的研究;并对Sr、Mg双掺杂的LaGaO₃基电解质与新型阴极材料的化学相容性问题进行研究,以进一步提高中温固体氧化物燃料电池的各项性能指标。目前,对掺杂CeO₂基电解质的研究主要集中于掺杂剂的研究上,并且已经从单掺杂体系转移到了双掺杂体系的研究。本文采用硝酸盐-柠檬酸法成功制备了Ce_0.8La_0.2-xY_xO_1.9和Ce_0.8Sm_0.2-xY_xO_1.9两个系列的电解质材料,对其进行多种测试和性能研究,考察了稀土元素及掺杂量对CeO₂基电解质性能的影响,并进一步对优选出的高电导率的电解质材料进行烧结温度对电解质性能影响的研究。结果发现,掺杂后的CeO₂电解质电导率明显提高,单掺杂已经大幅度提高了电解质的电导率;对于稀土双掺杂的Ce_0.8La_0.2-xY_xO_1.9系列电解质,在700～850℃之间,当Y掺杂浓度x=0.06和x=0.10时,电解质的电导率达到最高,La、Y双掺杂在单掺杂的基础上进一步改善了CeO₂基电解质的离子导电性。对于Ce_0.8Sm_0.2-xY_xO_1.9系列电解质,在中温区间（550～700℃）,当Y的掺杂浓度x=0.05和x=0.1时的双掺杂电解质相对于单掺杂电解质有更高的电导率;并且这两种电解质在中低温区间（250～700℃）均具有较单掺杂电解质更低的活化能。在相同工作温度下,这两种电解质的单电池最大功率密度和最大短路电流密度都比其他电池高,在相同空位浓度的情况下,这两种双掺杂电解质都比单掺杂的电解质有更好的导电性能,表明CeO₂基电解质的离子导电性可以通过Sm、Y双掺杂在单掺杂基础上可以进一步提高。该双掺杂系列CeO₂基电解质单电池的性能指标为同条件下的YSZ电解质电池的几倍。烧结温度对电解质导电性能有很大的影响,经过800℃预烧,1300、1400℃烧结的Ce_0.8Sm_0.1Y_0.1O_1.9电解质电性能对比其他条件处理后的电解质,有更高的总电导率和晶粒、晶界电导率以及更低的活化能,表现出更好的电性能。这是因为1300℃和1400℃烧结的电解质片比较致密的,各组成元素在电解质中分布更为均匀,而1500℃和1600℃烧结后的电解质片,因高温处理造成了电解质的过烧结,同时造成了Y元素在电解质中的偏析,导致1500、1600℃烧结后电解质的电性能比1300、1400℃烧结后的电解质的电性能要弱很多。本文还成功制备了纯相的La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85（LSGM1020）电解质材料,并对该电解质为支撑体的多种阴极材料的单电池性能和化学相容性等问题进行研究。研究发现,LSGM1020电解质为支撑体的单电池的输出功率密度和短路电流密度都较大;尤其以La_0.6Sr_0.4Fe_0.8Co_0.2O_3-δ材料为阴极的单电池表现出较好的性能:以La_0.6Sr_0.4Fe_0.8Co_0.2O_3-δ为阴极、以500μm厚LSGM1020为电解质的单电池的最大输出功率超过500 mW/cm²,最大短路电流密度超过1.5 A/cm2,单电池的性能指标有望通过改进厚膜工艺进一步提高。Ba_0.5Sr_0.5Co_0.6Fe_0.4O_3-δ和Sm0.5Sr0.5CoO3两种阴极材料均与LSGM1020发生反应生成了杂相物质,而La_0.6Sr_0.4Fe_0.8Co_0.2O_3-δ未与其生成杂相,因此La_0.6Sr_0.4Fe_0.8Co_0.2O_3-δ阴极与LSGM1020电解质间导电过程不受影响,阴极和电解质间的界面电阻小,从而以该材料为阴极的单电池性能最佳。从以上研究可以看出,稀土双掺杂的CeO₂电解质和Sr、Mg双掺杂的LaGaO₃基电解质是二种良好的中温电解质材料,有望成为中温SOFC适宜的电解质材料。更多还原

【Abstract】 Solid oxide fuel cells （SOFCs） are novel energy conversion devices with high efficiency and low emission, which have been recognized as a green energy at 21century. However, the high operating temperature of conventional electrolyte-supported cells can lead to not only a high fabrication cost for SOFCs systems, but also complex materials problems including electrode sintering, interfacial diffusion between electrolytes and electrodes. These problems have limited the commercial development of SOFCs. Recently, the development of SOFCs has changed to intermediate temperatures. There are two approaches to lower SOFCs operating temperatures: one is the development of high ionically conducting solid electrolyte materials at the intermediate temperatures; the other is reducing the YSZ electrolyte thickness. This investigation is concentrated on the research and development of intermediate temperatures solid electrolyte materials. The systematic investigation was done about the rare-earth double-doped CeO₂-based electrolyte; the chemical compatibility of the different cathodes materials and Sr and Mg double-doped LaGaO₃ based electrolyte was investigated. The aims are to improve the performance of intermediate temperatures solid oxide fuel cells （ITSOFCs）.Now most investigations about doped ceria electrolytes are focused on dopants and more attentions have been paid on double doping systems rather than single ones. Two series of samples with the general compositions of Ce_0.8La_0.2-xY_xO_1.9 and Ce_0.8Sm_0.2-xY_xO_1.9 were successfully synthesized by the sol-gel method and characterized. Influence of rare-earth elements and their different doped quantity on the ceria-based electrolyte performance was studied, from which the electrolyte materials with the highest conductivity were selected, and the effect of sintering temperatures on electrical property was investigated, too.Results indicated that the conductivity of the ceria-based electrolyte was pronounced improved after doped with other oxides. The performances of ceria-based electrolytes have been improved greatly by single doped. To the serial rare earth double-doped Ce_0.8La_0.2-xY_xO_1.9 electrolytes, the highest conductivity was obtained with the x values of 0.06 and 0.10. Therefore, the doping of La and Y could further improve the ion conductivity of the single-doped ceria-based electrolytes.To the electrolyte Ce_0.8Sm_0.2-xY_xO_1.9, when the x value is 0.05 and 0.1, the double-doped samples showed higher conductivity than their corresponding single doped samples from 550 to 700℃. The two kinds of electrolytes indicated lower activation energy than their corresponding single doped samples from 250 to 700℃. The maximum power density and the maximum current density of the SOFCs based on the two electrolytes at 700℃were higher than single doped sample with the same vacancy concentration. Results reveal that co-doping of samarium and yttrium can further improve the electrical performance of the single-doped ceria-based electrolytes. The performance of single cell with the series double-doped ceria electrolytes was far higher than that with the YSZ electrolytes on the same conditions.The electrical performance of the electrolyte was subject greatly of the sintering temperatures. The samples Ce_0.8Sm_0.1Y_0.1O_1.9 sintered at 1300 and 1400℃appear to be higher total, bulk and grain-boundary electrical conductivities and lower activation energies than at 1500 and 1600℃in all operating temperatures. This is because the pellets were dense and the compositions were homogeneous when sintered at 1300 and 1400℃. After the samples were sintered at 1500 and 1600℃, the over-sintering occurred and Y element became badly unhomogeneous simultaneously leading to a poorer electrical property of the samples sintered at 1500 and 1600℃than 1300 and 1400℃.Moreover, pure phase of La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 （LSGM1020） electrolyte material was successfully prepared. Electrolyte-supported SOFCs were fabricated. The influence of the different cathodes materials on the single cell performance and chemical compatibility was investigated. Results showed that the high maximum power density and the maximum current density were obtained of the LSGM1020 electrolyte-supported single cell. Especially, La_0.6Sr_0.4Fe_0.8Co_0.2O_3-δ as a cathode material indicated the best performance. With 500μm electrolyte thickness and with La_0.6Sr_0.4Fe_0.8Co_0.2O_3-δ as a cathode, the LSGM1020 electrolyte-supported single cell showed good performance of the maximum power density of 500 mW/cm² and the maximum current density of 1.5 A/cm². The performances of single cells expect to further enhance by progressing the technics of the thick film. The cathodes materials of Ba_0.5Sr_0.5Co_0.6Fe_0.4O_3-δ and Sm_0.5Sr_0.5CoO₃ could react with LSGM1020 electrolyte and the impurity phases were observed. However, no impurity was observed on the interface between La_0.6Sr_0.4Fe_0.8Co_0.2O_3-δ cathode and LSGM1020 electrolyte, and small interface resistance was obtained, leading to the resulting good cell performance.Results from above demonstrate that Sr, Mg double-doped LaGaO₃ electrolyte and rare eath double-doped CeO₂ based electrolyte materials are excellent intermediate temperature electrolyte materials, which are promising for ITSOFCs application.更多还原