Thermo-mechanical response and failure-probability assessment of solid oxide electrolysis cells during thermal cycling

In this study, a multiphysics simulation framework for the long-term reliability assessment of solid oxide electrolysis cells (SOECs) was developed by integrating creep deformation and Weibull-based failure probability models into an existing three-dimensional electrochemical–thermal–fluid coupled model. The framework combines an electrochemical–thermal–fluid model with finite element structural analysis to investigate the coupled effects of temperature gradients, thermal expansion mismatch, and time-dependent deformation throughout representative operating cycles, including stack assembly, start-up, steady operation, cool-down, and maintenance. The electrochemical model was validated against available experimental polarization data, and the coupled framework was subsequently applied to a real-scale SOEC cell to assess thermo-mechanical responses and failure-probability trends. The coupled simulations revealed that thermo-mechanical responses vary significantly depending on the operating stage. During low-temperature processes such as heat-up and cool-down, tensile stress concentrations led to increased failure probabilities, whereas during high-temperature operation, creep deformation progressively accumulated, resulting in long-term stress relaxation accompanied by material degradation. These results indicate that SOEC durability is strongly influenced by both low- and high-temperature operating conditions. Therefore, stable operation near the thermoneutral voltage and structural designs that minimize thermal expansion coefficient mismatches over the entire temperature range are essential for ensuring performance stability and long-term reliability of SOEC systems.