Coupled Electrochemical–Mechanical Degradation Mechanisms of Solid Oxide Fuel Cells under Redox Conditions

The instability of anode-supported solid oxide fuel cells (ASOFCs) during high-temperature reduction–oxidation (RedOx) cycling is a critical factor limiting long-term operation. In this study, the evolution of electrochemical and mechanical properties of ASOFCs under RedOx cycling was examined by electrochemical impedance spectroscopy, small-punch testing, and nanoindentation. Microstructural analysis was further employed to elucidate the degradation mechanisms. Results showed that the peak power density decreased by nearly 70% after five cycles. Quantification of degradation contributions indicated that ohmic resistance accounted for 70% of total performance loss, followed by hindered H2 transport in the anode. Mechanically, flexural strength declined by nearly half, with the largest reduction during early cycles, while the elastic modulus and hardness decreased by 25.6% and 50.69%, respectively. SEM and EDS revealed that Ni particle migration and agglomeration led to a nearly 4-fold increase in large particle-sized Ni clusters. Based on the driving role of Ni particle degradation in coupled electrochemical–mechanical processes, a theoretical model was developed to describe performance evolution. This work provides theoretical and experimental insights for extending ASOFC service life and improving engineering applicability.