Abstract
This paper discusses the relationship between the elongation and compression behavior and microstructural changes under redox cycles of porous Ni(O)–YSZ cermets for solid oxide fuel cells (SOFC). Mechanical damage in SOFC and SOEC is one of the most important degradation factors governing the electrical performance of cells. Therefore, it is necessary to know the mechanical properties of each component material, such as elastic and deformation properties, in the operating environment. Particularly, of the Ni(O)–YSZ cermets which currently makes up 90% of the volume of the cell, with present mainstream anode supported SOFC and SOEC. Therefore, understanding the properties of the Ni(O)–YSZ cermets plays an important role in ensuring the performance of the entire SOFC and SOEC. In this study, the microstructural changes of Ni(O)–YSZ cermet by reduction, re-oxidation and re-reduction were observed in detail using microstructural observations and systematically compared with the dimensional change behavior. For the dimensional change behavior, a simple model considering the initial porosity and Ni content is proposed, which successfully predicts the dimensional change due to re-oxidation. Furthermore, Ni(O)–YSZ cermets with high Ni content show large initial dimensional changes, but the dimensional reversibility improves with increase of the number of redox cycles.
Highlights
One kind of next-generation high-performance energy conversion systems, solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC) are made exclusively of solid components, including the electrolytes and electrodes
Jiao et al [12]succeeded in developing a method for quantitative comparison of anode microstructure changes after long-time operation by increasing the reconstruction size as large as possible, using 3D reconstruction based on focused ion beam scanning electron microscope (FIB-SEM) technology
In this study, based on the results of these many previous studies, we evaluated the microstructural changes and deformation behaviors caused by redox cycling with Ni content and porosity as parameters
Summary
One kind of next-generation high-performance energy conversion systems, solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC) are made exclusively of solid components, including the electrolytes and electrodes. Faes et al [10, 11] investigated the change behavior of the elongation volume with one re-oxidation using the Ni content, porosity and Ni/YSZ grain size as parameters. Jiao et al [12]succeeded in developing a method for quantitative comparison of anode microstructure changes after long-time operation by increasing the reconstruction size as large as possible, using 3D reconstruction based on FIB-SEM technology. In this study, based on the results of these many previous studies, we evaluated the microstructural changes and deformation behaviors caused by redox cycling with Ni content and porosity as parameters. By using multivariate analysis, a prediction equation for re-oxidation elongation considering Ni content and porosity was developed, and we succeeded in relating the microstructural change to macroscopic deformation
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