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-delta (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-delta (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 (R-O) and polarization (R-P) resistances. R-P, which increases with the thickness of the LSCF-SDC composite layer in the cathode, rises rapidly as the temperature drops, particularly at temperatures <= 550 degrees C. This indicates the high electrical conductivity of the cathode as a major contribution to the decrease of R-P at 500 degrees C. The best cell performances are observed at 650 degrees 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 0.80V. 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 R-O and R-P and maximize the cell performance. (C) 2010 Elsevier B.V. All rights reserved.