Abstract
Both microstructural evolution and crack nucleation occur in Solid Oxide Fuel Cells (SOFCs) at elevated operation temperature (above 600°C), which cause severe performance degradation in electrochemical activity as well as structural integrity during their lifetime application. Nickel (Ni) coarsening of Ni-yttria stabilized zirconia (YSZ) in the anode of SOFCs is believed to lead to the microstructural evolution. In the meanwhile, severe thermal stress due to high operation temperature is one of the main factors responsible for crack propagation in the microstructure. Both microstructural evolution and crack nucleation have a significant impact on both electrochemical activity and structural integrity of SOFCs during operation. Based on theories of diffuse-interface and linear elastic fracture mechanics (LEFM), an integrated phase field model is established to couple electrode microstructural evolution and crack nucleation in SOFCs. Then, the model is applied to SOFCs with nonlinearly graded microstructures, which is proposed in our previous work (1), to explore the couple effects on SOFCs performance degradation. The preliminary results show that particle size and ratio, which dictates the triple phase boundaries (TPBs) contact angle, are ones of the most influential microstructural parameters in the microstructural evolution that affects SOFCs’ electrochemical activity. Different crack shapes are considered to reveal the effect of crack nucleation on SOFCs’ structural integrity. With combining the analysis of coupling effect of microstructural evolution and crack propagation on SOFCs’ performance degradation, it is expected the understanding of SOFCs’ performance degradation could be advanced. This work will provide one comprehensive evaluation computational tool for SOFC’s long-term degradation analysis and novel electrode design. 1. L. Liu, R. Flesner, G. Y. Kim and A. Chandra, Fuel Cells, 12, 97 (2012).
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