Structural Modification of Segmented-in-series Tubular SOFCs Using Performance Simulation and the Effect of (Sm, Ce)O2 Cathode Interlayer on the Generation Characteristics under Pressurization

To improve the segmented-in-series tubular SOFC performance operating at 1173 K, we studied cathode interlayer (CIL) and a structural modification of the cell stack using a performance simulation. As the result of changing CIL into (Ce0.8Sm0.2)O-2 (SDC20) (type 2) from La0.7Sr0.3MnO3-YSZ (type 1), ohmic polarization (eta(IR)) and activation/concentration polarizations (eta(A) + eta(c)) of type 2 decreased 16% and 47% than those of type 1, respectively. Next, based on the simulation results of eta(IR), a tubular SOFC (type 4) with structural modification in the length ratio of the effective generation part (EGP) and interconnector part (ICP) was fabricated by applying SDC20 to CIL. Ohmic polarization of type 4 decreased 52% than that of type 2, while eta(A) + eta(c) increased 63%. However, the generation performance of type 4 improved than that of type 2, since eta(IR) decreased more than the increase Of eta(A) + eta(c). In a pressurized test of type 4, an increase of pressure resulted in a decrease of the area specific resistance calculated from the inclination of I-V characteristics including EGP and ICP resistances. In a durability test of type 4 conducted for 7000 h in atmospheric pressure, a degradation rate of 0.73% 1000 h(-1) was obtained.