B-Site Fe-Co-Ni Triple Doping for High-Performance Oxygen Electrodes in Industrial-sized Reversible Solid Oxide Cells

The development of oxygen electrodes for reversible solid oxide cells (RSOCs) is hindered by insufficient catalytic activity, limited stability, and a mismatch in the thermal expansion coefficients (TEC) with electrolytes. Herein, we design and synthesize a novel perovskite oxide, La_0.6Ca_0.4Fe_0.8Ni_0.1Co_0.1O_3-δ (LCFNC), using a multi-element B-site synergistic doping strategy. Systematic investigations reveal that the incorporation of Fe stabilizes the perovskite lattice, while the addition of Ni and Ca effectively suppresses the TEC (to 12.7 × 10^-6 K^-1 after GDC compositing), ensuring excellent electrolyte compatibility. Furthermore, the cooperative interplay between Ni, Co, and Fe establishes ternary active centers, significantly increasing the concentration of surface oxygen vacancies. Full-cell measurements demonstrate a peak power density of 1.60 W·cm^-2 at 800°C and a high electrolysis current density of 1.82 A·cm^-2 at 1.3 V. Stability tests, including 100 h of constant-current electrolysis at 750°C and 24 reversible operation cycles, highlight exceptional interfacial and structural stability. More importantly, the assembled industrial-sized RSOCs (15 × 15 cm²) achieve an output power of 64 W in fuel cell mode and a maximum current of 105 A in electrolyzer mode at 800°C, demonstrating its potential for practical applications. This work elucidates the mechanistic role of multi-element B-site regulation and provides an effective design principle for oxygen electrode materials that enhance activity, stability, and compatibility simultaneously, thus advancing the practical deployment of high-performance RSOCs.