Characterization and Optimization of La0.97Ni0.5Co0.5O3-δ-Based Air-Electrodes for Solid Oxide Cells

On the basis of previous studies of perovskites in the quasi ternary system LaFeO3-LaCoO3-LaNiO3, LaNi0.5Co0.5O3 (LNC) is chosen as the most promising air-electrode material in the series for solid oxide cells (SOCs). In the present study, A-site deficiency of LNC is discussed and La0.97Ni0.5Co0.5O3 (LNC97) is selected as the optimal composition. Compatibility of LNC97 with 8 mol % Y2O3 stabilized ZrO2 (8YSZ) is analyzed and compared with that of the state-of-the-art air-electrode La0.58Sr0.4Co0.2Fe0.8O3-delta (LSCF) and 8YSZ. Targeting to the requirements of high-performance SOC air-electrodes (high electronic and ionic conductivity and high catalytic activity for the oxygen reduction reaction), LNC97-based air electrodes are tailored, characterized and optimized by symmetric-cell tests. Principles of air-electrode design for SOCs are revealed accordingly. Long-term measurement of the symmetric cells over a period of 1000 h is performed and possible degradation mechanisms are discussed. Full cells based on optimized LNC97 air-electrodes are also tested. Lower reactivity with 8YSZ in comparison to LSCF and a similar performance render LNC97 a very competitive candidate to substitute LSCF as air-electrode material of choice for SOCs.