中温固体氧化物燃料电池LSCF阴极性能衰减机理研究

Solid oxide fuel cells (SOFCs) have attracted much attention due to their high energy efficiency, modularity, and excellent fuel capability. To study and develop intermediate temperature solid oxide fuel cells (IT-SOFCs), which operate at 600-800℃, is the direction of SOFCs. (La, Sr)(Co, Fe)O3-δ（LSCF）perovskite oxide has been extensively investigated and utilized as a cathode material for IT-SOFCs due to its excellent electrode performance at lower temperatures. However, inadequate long-term stability of LSCF is a primary factor impeding the widely practical commercial application. In this study, the LSCF and LSCF-GDC cathodes with repeatability are fabricated by tape casting technique, respectively. The effects of elemental composition, microstructure and interface characteristics on electrochemical performances of the above two cathodes before and after long stability test (>500h) are investigated. Further, we will discuss the migration, routes and chemical reactions of the related elements of the LSCF and LSCF-GDC cathodes under operational conditions and reveal the changes of microstructure and interface characteristics in this progress. On the basis of these conclusions, the degradation mechanism of LSCF cathodes for SOFCs will be supposed. The achievement of the project will contribute to the development of cathode material with high stability and good performance for IT-SOFC, which is significant for the cross and fusion of different subjects, such as materials, chemistry and energy.

固体氧化物燃料电池(SOFCs)是近年来燃料电池领域研究的热点，中低温化则目前SOFCs的发展方向。钙钛矿型(La, Sr)(Co, Fe)O3-δ（LSCF）复合氧化物是一种综合性能优异的中低温固体氧化物燃料电池阴极材料，然而限制LSCF阴极广泛应用的主要问题是其稳定性较差，在长期放电过程中有明显的性能衰减现象。本项目拟采用流延成型工艺制备结构和性能稳定的LSCF以及LSCF-GDC阴极，分别研究两种阴极在长期放电前后(>500h)元素构成、微观形貌以及界面特征对电化学性能的影响，探讨相关元素在放电过程中的迁移方式、路径以及反应过程，揭示不同阴极在放电过程中界面特征及微观结构的演变规律，从而确立LSCF阴极的性能衰减机制。本项目的完成将有助于稳定性和电化学性能良好的中低温固体氧化物燃料电池阴极材料的开发和应用，对于促进材料、化学和能源学科的交叉融合具有重要的学术意义。

(La, Sr)(Co, Fe)O3-δ(LSCF)是一种得到广泛研究的的中温SOFC阴极材料，在600-800℃具有良好的离子-电子混合导电性和电化学催化性能。然而，在工作温度下，LSCF的阴极的长期稳定性会出现衰减，这也成为限制其作为SOFC阴极材料得到广泛应用的关键因素。本项目设计并制备LSCF薄膜电池，并对其长期放电前后电化学性能、微观形貌、元素构成进行了研究分析，结果表明薄膜电池在长期放电后欧姆阻抗和界面阻抗增加，LSCF晶粒出现团聚，裂纹增加，Sr和Co元素由晶格内析出，在LSCF薄膜电极表面以不连续氧化物的形式存在；在对多孔LSCF阴极长期放电后的研究也出现相同结论，而多孔阴极中Sr和Co元素出现由电解质/阴极界面向阴极/空气界面迁移的趋势。采用浸渗工艺优化制备LSCF-GDC、LSCF-LSM复合阴极：LSCF-GDC复合阴极在190h测试时间内的衰减率为3.7%，低于纯LSCF阴极在前190h测试时间内4.3%的衰减率，通过DGC浸渗可以在一定程度上提高LSCF阴极的稳定性；LSCF-LSM复合阴极在550h测试时间内的衰减率为0.9%，远低于纯LSCF阴极在500h测试时间内12.7%的衰减率，通过优化LSM浸渗工艺能明显改善LSCF阴极的长期稳定性。