Effect of CeO2 interlayer on ZrO2 electrolyte/La(Sr)CoO3 cathode for low-temperature SOFCs

Porous Ce0.9Gd0.1O2−δ (GDC) and dense Ce0.8Sm0.2O2−δ (SDC) protection interlayer were introduced between Scandia-stabilized zirconia (SSZ) electrolyte and La0.6Sr0.4CoO3−δ (LSC) cathode of low-temperature SOFCs which operate at 600–800 °C. The reactivity of the interlayer and the area-specific resistance (ASR) were investigated. EPMA analysis clearly showed that the reaction between LSC cathode and SSZ electrolyte did not occur even though GDC interlayer (3–6 μm) was porous. Moreover, the reaction between GDC interlayer and SSZ electrolyte which were fired at 1320 °C was not observed. The ASR of LSC/GDC/SSZ measured by an AC impedance method was reduced 40% or more at each temperature compared to LSC cathode on a GDC pellet and showed a low value in 600–800 °C. Thin and relatively dense SDC interlayer (<1 μm) was fabricated between LSC cathode and SSZ electrolyte by using 2-ethylhexanoic acid salts of Sm and Ce, and also in the system using this SDC thin interlayer, low ASR equivalent to LSC/GDC/SSZ was shown, and it became clear that the interlayer in this experiment is very effective in the reduction of ASR.