The degradation of solid oxide cell (SOC) stacks needs to be alleviated to accelerate its commercialization. Therefore, a time-dependent model is proposed for a SOC stack designed by Forschungszentrum Jülich GmbH for the fuel cell and the steam electrolysis modes. The model employs a macroscale modeling approach, computational fluid dynamics. The duration of the simulation is up to ~ 100 kh. The model can be used to attribute the causes of severe degradation and serve as guidance for future stack design. The modeling framework includes well-known degradation processes, such as metal interconnect oxidation, chromium poisoning, nickel agglomeration and migration, and manganese poisoning. The simulated degradation is supported by experimental data, such as voltage-time plots and electrochemical impedance spectroscopy. Simulations reveal that for the state-of-the-art SOC stack under the fuel cell operation, degradation is primarily attributed to nickel agglomeration and migration, and manganese poisoning. Additionally, a good protective coating is crucial for maintaining a low degradation rate. For the steam electrolysis mode, nickel migration reduces the thickness of the reactive fuel electrode by forming an unreactive layer, resulting in a high degradation rate. Based on these findings, an optimization of the stack design is carried out to reduce the degradation with the help of the model. Major modifications include using a different ionic conductor in the fuel electrode, increasing the thickness of the fuel electrode, and applying a metal interconnect with a low content of manganese. According to simulations, under the same operation conditions, the optimization helps decrease degradation rates by two-thirds and by seven-eighths for the fuel cell operation and the steam electrolysis operation respectively.
Shangzhe Yu (Thu,) studied this question.