Life Prediction of a Solid Oxide Fuel Cell Under Thermal Cycling Conditions

Typical operating temperature of a solid oxide fuel cell (SOFC) is above 600°C, which leads to severe thermal stresses caused by the difference in coefficients of thermal expansion (CTE) during thermal cycling. Interfacial and peeling stresses are two types of thermal stress that cause the mechanical failure of the SOFC. The paper develops a mathematical model to estimate thermal stresses in a typical electrolyte-supported SOFC (NiO/8YSZ-YSZ-LSM). The proposed model is then utilized to obtain analytical expressions for interfacial and peeling stresses. This model provides insight into the distribution of interfacial and peeling stresses of SOFCs and the cause of catastrophic failure. A model for crack nucleation in multi-layered structures under thermal cycling is generalized and utilized in this study for the life prediction. It is found that the peeling and interfacial shear stresses are more concentrated near free edge areas. The relevant damage evolution rate accelerates as the crack propagates. The work also provides a foundation for future SOFC reliability and life prediction research.