Improvement in stability of La_0.4Ba_0.6CoO₃ cathode by combination with La_0.6Sr_0.4Co _0.2Fe_0.8O₃ for intermediate temperature-solid oxide fuel cells

Improvement in long-term stability and cathodic activity of La _0.4Ba_0.6CoO₃ (BLC) was studied by mixing with La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF). LSCF exhibits good long-term stability; however, surface activity is not high like Co-based perovskite. On the other hand, the cathodic activity of BLC is high; however, long-term stability was not so good and large degradation at initial period is observed. Combination of the two oxides shows small overpotential as well as improved long-term stability. Effects of BLC/LSCF ratio on stability and overpotential were studied and it was found that BLC-LSCF (7:3) showed the most stable and small cathodic overpotential among the examined compositions. Although the power density was still slightly decreased over 24 h at 0.5 V terminal voltage, the maximum powder density of the cell using BLC-LSCF composite oxides for cathode shows 2.5 times larger than that of the cell using LSCF cathode and 1.06 times larger than that of BLC. Degradation rate is smaller than 4 % from 5 to 24 h on this BLC-LSCF cathode at current density as high as 682 mA/cm² after 24 h operation.