Effects of bi-layer La0.6Sr0.4Co0.2Fe0.8O3−δ-based cathodes on characteristics of intermediate temperature solid oxide fuel cells

In this study, anode-supported planar IT-SOFCs, with a thin Sm0.2Ce0.8O2−δ (SDC) electrolyte film and a bi-layer cathode, are fabricated using tape-casting and screen-printing processes. The bi-layer cathode consists of a current collector La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) layer and a functional LSCF–SDC composite layer in various thicknesses. Microstructure studies reveal that the interfaces among various layers show good adhesion, except for Cell A equipped with a cathode of pure LSCF. Cell A reports the lowest ohmic (R0) and polarization (RP) resistances. RP, which increases with the thickness of the LSCF–SDC composite layer in the cathode, rises rapidly as the temperature drops, particularly at temperatures ≤550 °C. This indicates the high electrical conductivity of the cathode as a major contribution to the decrease of RP at 500 °C. The best cell performances are observed at 650 °C for all cases, in which Cell A shows a maximum power density of 1.51 W cm−2 and an open circuit voltage of 0.80 V. Considering both of the electrical and the mechanical integrity of the single cell, insertion of the composite layer is required to guarantee a good adhesion of cathode layer to electrolyte layer. However, the thickness of the composite layer should be retained as thin as possible to minimize the R0 and RP and maximize the cell performance.