The differences in material properties of different components of solid oxide fuel cells cause high stresses during sintering and operation, and functional gradient material electrodes are expected to alleviate this problem. In this study, electrodes with three different material compositions are compared with electrodes using conventional materials, and the residual and thermal stresses are calculated by applying functional gradient materials to single-sided and double-sided electrodes, respectively, and the results are analyzed with the optimization goal of minimizing the stresses to find the optimal functional gradient material composition distribution. The study shows that the functional gradient material electrode can significantly reduce the interfacial stress and alleviate the local stress concentration. When using functional gradient materials for one side of the electrode, a specific material component distribution can reduce the residual stress and thermal stress on the other side, but the stresses may increase on the local side of the electrode. The interfacial stress between layers can be reduced to a maximum of 0.1 MPa when a functional gradient material with a quadratic linear distribution of components is used for both sides of the electrodes. This study has implications for the fabrication of functional gradient materials for SOFC electrodes.

The performance degradation of solid oxide fuel cells (SOFC) is directly related to the damage and fracture of electrode microstructures. In this study, the phase field fracture method is used to simulate the fracture of anode microstructures, and the effects of boundary constraints, thermal load, and Ni phase on the fracture of Ni–YSZ anode microstructures are investigated. Results show that tensile stresses occur in the Ni and YSZ phases whether above or below the reference temperature. The cracks propagate along the direction perpendicular to the first principal stress, showing a brittle fracture characteristic. When the microstructure is cooled, all cracks appear in YSZ phase, and almost all cracks initiate at the lowest point of YSZ–pore concave interface. When the microstructure is heated, the tensile first principal stress induces few cracks at local positions but will not make the cracks propagate continuously. The thermal mismatch between Ni and YSZ is not enough to induce cracks, and the fracture of electrode microstructure is more likely to be caused by external tensile load or the thermal mismatch between anode and electrolyte layers. The presence of Ni increases the stiffness of the microstructure, and solid phase’s disconnection reduces the strength of the microstructure.