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

ABSTRACT 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 _0.6 Ca _0.4 Fe _0.8 Ni _0.1 Co _0.1 O _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 cm ² ) 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.