• Adding 50 wt% SDC to LSC reduces the thermal expansion coefficient from 18.29 × 10−6 to 13.90 × 10−6 K−1, improving compatibility with YSZ electrolyte.
• The LSC-SDC composite cathode exhibits exceptional thermal-shock stability, with polarization resistance growth rate of only 0.658% per cycle, 49% lower than pure LSC.
• Button cells with LSC-SDC operate stably for over 900 hours without Sr segregation, showing a voltage degradation rate of 1.11%/kh.
• A commercial flat-tube cell with LSC-SDC delivers 54.8 W at 750°C, demonstrating practical viability for SOFC commercialization.