Design and processing parameters of La₂NiO_4+δ-based cathode for anode-supported planar solid oxide fuel cells (SOFCs)

The Ruddlesden-Popper phase lanthanum nickelate, La₂NiO_4+δ (LNO), is successfully implemented as a strontium- and cobalt-free cathode in anode-supported planar solid oxide fuel cells (SOFCs) through systematic optimization of materials, processing and structural parameters. Chemical interaction between LNO and gadolinia-doped ceria (GDC), which leads to phase decomposition of composite cathode and significant deterioration of the electrochemical performance, is prevented by lowering the processing temperature below 1000 °C. For low-temperature fabrication process, the thermo-mechanical stability at the interface is secured by modifying the powder characteristics and inserting the adhesive interlayer. The issues associated with the electrical contact and current distribution are resolved by incorporating the perovskite La_0.6Sr_0.4CoO_3-δ (LSC) as a current collecting layer, and the thermal stresses at the interface are relieved by constructing a gradient electrode structure. Consequently, the optimized anode-supported planar cell with an LNO-based cathode exhibits superior performance compared to the reference cell with a conventional cathode in the intermediate-temperature range, which is attributed to the enhanced interfacial process and surface reaction kinetics based on impedance analysis.