High-performance lanthanum-ferrite-based cathode for SOFC

(La0.6Sr0.4)1-xCo0.2Fe0.8O3/Ce0.9Gd0.1O3 (LSCF/CGO) composite cathodes were investigated for SOFC application at intermediate temperature, i.e., 500-700 °C. The LSCF/CGO cathodes have been studied on three types of tape-casted electrolyte substrates including CGO electrolyte, Yttrium-stabilized Zirconia (YSZ) electrolyte coated with a thin layer of CGO, and YSZ electrolyte. Impedance spectra were measured to determine the polarization resistance (Rp) and series resistance (Rs) on cells in a symmetric configuration. Rp of 0.19 Ω cm2 at 600 °C and 0.026 Ω cm2 at 700 °C were obtained using LSCF/CGO cathode on CGO electrolyte. On the YSZ electrolyte with thin layer CGO coating, Rp of 0.6 Ω cm2 at 600 °C and 0.12 Ω cm2 at 700 °C were obtained. On the YSZ electrolyte directly, Rp of 1.0 Ω cm2 at 600 °C and 0.13 Ω cm2 at 700 °C were achieved. These results are roughly six times better than our typical LSM cathodes. Slightly higher Rs was observed in the samples with LSCF/CGO cathode on the YSZ electrolyte with CGO coating due to extra contribution from the thin CGO layer and the CGO/YSZ interface. For the samples with LSCF/CGO on YSZ, the Rs was the same as that of our best LSM samples, which indicates good adhesion between LSCF/CGO cathode and YSZ electrolyte. Aging experiment at 800 °C for the cathode of LSCF/CGO on YSZ electrolyte shows a degradation rate of 5×10−4 Ω cm2/h in Rp, while the Rs has no obvious change.