Optimization of functionally graded electrode for anode supported planar solid oxide fuel cells by multi-physics modeling

Functional-graded electrodes significantly impact solid oxide fuel cell (SOFC) performances, yet existing studies rarely systematically explore the synergistic effects of multiple gradient parameters on multi-physics fields. In this study, a three-dimensional model of anode-supported planar SOFC is constructed to comprehensively investigate the effects of electrodes with gradient porosity, gradient particle size, and gradient solid phase volume fraction on electrochemical performance, gas transport, triple-phase boundary (TPB), and thermal stress. It is found that for the anode, the simultaneous reduction of porosity, particle size, and YSZ solid phase volume fraction along the thickness direction can significantly enhance electrochemical performance by increasing the TPB length and effectively mitigate thermal stress through improved matching of the thermal expansion coefficient. For the cathode, increasing porosity on the under-rib side enhances oxygen transport capacity, but single gradient designs have little effect on electrode-electrolyte thermal stress. Further, implementing a particle size gradient in the anode and coupling all gradients in the cathode effectively reduces thermal stress, while coupling all three gradients in both anode and cathode achieves the optimal comprehensive performance, reducing the stress in the electrolyte layer by 24.2% while maintaining high electrochemical output. This research provides a systematic reference for optimizing SOFC comprehensive performance through integrated gradient electrode design, highlighting the necessity of balancing multiple parameters to improve both performance and structural stability.