Design of a dual-layer ceramic interconnect based on perovskite oxides for segmented-in-series solid oxide fuel cells

A segmented-in series (SIS) SOFC consists of segmented unit cells connected in electrical series and shows improved stack efficiency over conventional SOFCs. In this design, a thin interconnect film provides both electrical contact and sealing between the anode of one cell and the cathode of the next; thus, it should have high conductivity and chemical/structural stability in both reducing and oxidizing atmospheres as well as impermeability to gases. Here, we report a dual-layer interconnect film for SIS–SOFCs comprising perovskite-type oxides, Sr 0.7 La 0.2 TiO 3 (exposed to a reducing atmosphere) and La 0.8 Sr 0.2 FeO 3 (exposed to an oxidizing atmosphere). The interconnect film is not only very dense but also highly conductive and stable under SOFC operating conditions; in particular, it shows an area-specific resistance of 19.6 mΩ cm 2 at 800 °C, which is much lower than the generally accepted limit for SOFCs. A flat-tubular SIS–SOFC fabricated using these interconnect films exhibits a power density as high as 340 mW cm −2 , which proves the feasibility of the dual-layer interconnect design.