Er/Ce Co-doped bismuth oxide ((Er_0.20Ce_0.05Bi_0.75)₂O_3-δ)–La_0.8Sr_0.2MnO_3-δ composite cathode for SOFC electrochemical performance regulation: Interfacial diffusion effects

This study investigates the use of highly conductive Er/Ce co-doped bismuth oxide ((Er_0.20Ce_0.05Bi_0.75)₂O_3-δ, ECSB) combined with strontium-doped lanthanum manganite (La_0.8Sr_0.2MnO_3-δ, LSM) to examine the cathode-electrolyte diffusion effect in solid oxide fuel cells (SOFCs). The impact of composite ratio and sintering temperature on bonding strength and electrochemical performance is evaluated. The results indicate that the ECSB phase diffuses into the YSZ electrolyte during the sintering process, thereby increasing the oxygen vacancy concentration. As the sintering temperature increases from 750 °C to 900 °C, the symmetrical cell's ohmic resistance decreases from 2.82 to 2.48 Ω cm² at 700 °C, and the grain conductivity of the cell improves by 12.2 % between 550 °C and 700 °C. The full cell employing the M3B7 composite cathode (cell 1) exhibits twice the power density of the LSM-YSZ cathode (cell 2) and higher open-circuit voltage (OCV) values. Furthermore, the ohmic impedance of cell 1 (1.59 Ω cm²) is approximately 52.6 % of that of cell 2 (3.02 Ω cm²) at 700 °C, owing to the diffusion effect. These findings suggest that adjusting the sintering temperature accelerates the diffusion of the ECSB phase into the electrolyte, enhancing ionic conductivity and overall SOFC performance.