Effect of electrolyte composite on the performance of SmBa_0.5Sr_0.25Ca_0.25CoFeO_5+δ cathode for IT-SOFCs

In the present work, in order to further improve the electrochemical performance and reduce the thermal expansion coefficient (TEC) of the SmBa_0.5Sr_0.25Ca_0.25CoFeO_{5 + δ} (SBSCCFO) cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs), Gd_0.1Ce_0.9O_1.95 (GDC) electrolyte composite for the SBSCCFO (SBSCCFO–xGDC, x = 0, 20, 30, 40, 50 wt%) cathode is systematically studied to obtain the optimal performance. The effect of sintering temperature on the microstructure and area-specific resistance (ASR) of the cathode is also examined. Results show that the electrical conductivity and TEC decrease as the GDC content increases. TEC decreases from 19.61 × 10⁻⁶ K⁻¹ for SBSCCFO to 13.46 × 10⁻⁶ K⁻¹ for SBSCCFO–50GDC. Furthermore, the composite cathode SBSCCFO–40GDC exhibits the best electrochemical performance among the SBSCCFO–xGDC cathodes. The ASR of SBSCCFO–40GDC is 0.1638, 0.0692, and 0.0342 Ω cm² at 700, 750, and 800 °C, respectively. An anode-supported single cell with the SBSCCFO–40GDC cathode obtains a maximum power density of 561 mW cm⁻² at 800 °C, and this value is higher than that of the cell with SBSCCFO cathode (320 mW cm⁻²).