Defect transport and thermal mismatch induced fracture in planar solid oxide fuel cell
Sen Yang, Yongjun Lü, Kejie Wang, Xiang Zhao, Fenghui Wang
Abstract
During the manufacturing process of planar solid oxide fuel cells (SOFCs), it produces various defects and microcracks. Multiphysics field coupling drives crack propagation in SOFCs under normal operation, ultimately resulting in degradation or even failure of the cell's electrochemical performance. In this study, an electro-chemo-thermo-mechanical coupling model was proposed to describe the stress distribution in planar SOFCs based on the defect transport of the cathode and electrolyte, and the fracture behavior of the cathode and elastic energy under multi-stress conditions is also evaluated. The modeling results indicate that an increase in the thermal expansion coefficient of the cathode and the sintering temperature significantly increases the tensile stress in the cathode. While the high chemical expansion alleviates the stress at the electrolyte-cathode interface, it increases the stress gradient in the cathode. Furthermore, under low sintering temperature, when the pre-existing edge crack is less than 10 µm, and the pre-existing central crack is less than 12 µm, the cracks do not propagate further during operation. This study provides theoretical support for enhancing the stability of planar SOFCs and optimizing electrode material parameters.