Enhancing the performance and stability of Sm0.2Ce0.8O1.9 decorated La0.6Sr0.4CoO3-δ composite cathode in flat tube solid oxide fuel cell

The commercialization of solid oxide fuel cell hinges on the cathode possessing both high catalytic activity and a thermal expansion coefficient that aligns with the electrolyte. While the cobalt based cathode, La0.6Sr0.4CoO3 (LSC), has excellent catalytic performance, its thermal expansion coefficient (TEC) is too large to match the electrolyte. Herein, we mechanically mixed Sm0.2Ce0.8O2-δ (SDC) with LSC to create a composite cathode. With the addition of 50 wt.% SDC, the TEC dramatically decreased from 18.29×10-6 K-1 to 13.90×10-6 K-1. Under thermal shock conditions ranging from room temperature to 800 °C, the growth rate of polarization resistance was just 0.658%/cycle, only 49% of that of pure LSC. The button cell with the LSC-SDC composite cathode operated stably for over 900 h without Sr segregation, with a voltage growth rate of 1.11%/kh. The commercial flat-tube cell (70 cm2 active area) with the LSC-SDC composite cathode delivered 54.8 W at 750 °C. The distribution of relaxation time analysis revealed that the non-electrode part became the main rate-limiting step. This work demonstrates that the LSC-SDC mixture strategy effectively improves the compatibility with electrolyte, while maintaining high output, making it a promising commercial cathode material.