Electrochemical performance of a Ni0.8Co0.15Al0.05LiO2 cathode for a low temperature solid oxide fuel cell

The electrochemical performance of the Ni_0.8Co_0.15Al_0.05LiO₂ (NCAL) cathode was investigated by comparing it with the traditional La_0.4Sr_0.6Co_0.2Fe_0.8O_3-δ (LSCF) and LSCF/Ce_0.9Gd_0.1O_2-δ (GDC) cathodes with a GDC electrolyte-supported solid oxide fuel cell (SOFC). It is found that the electrochemical performance of the cells with the NCAL and NCAL/GDC cathode is better than that of the cells with the LSCF and LSCF/GDC cathode at 550 °C. The results of the electrochemical performance tests of the cells with different NCAL/GDC mass ratios (10/0, 9/1, 8/2, 7/3 and 6/4) show that the NCAL/GDC composite cathode with the mass ratio of 8/2 has the best electrochemical performance. XRD results show that when the sintering temperature is higher than 700 °C, the NCAL/GDC composite will undergo chemical reactions and generate new phases, reducing the performance of the composite cathode. XPS results show that a small amount of Li₂CO₃ was formed on the surface of NCAL during cathode preparation, forming a special interface between NCAL, Li₂CO₃ and GDC. At the NCAL-Li₂CO₃/GDC interfaces, due to the migration and aggregation of Li⁺ to the interface, a space charge region may be formed in which the Li⁺ enrichment may lead to the formation of the region with a high oxygen vacancy concentration. A very high oxygen vacancy concentration at the NCAL-Li₂CO₃/GDC interfaces will provide sufficient oxygen ion conductivity for oxygen reduction reaction (ORR) and reduce the activation energy of the reaction. NCAL will be a potential cathode material that can reduce the operating temperature of the traditional SOFC to 550 °C or lower.