Improvement on durability and thermal cycle performance for solid oxide fuel cell stack with external manifold structure

Two 5-cell solid oxide fuel cell (SOFC) stacks with an external manifold structure are constructed and their degradation and thermal cycle performance are investigated at 750 °C. The cell consists of anode-supported cells with a size of 11 × 11 cm. In Stack A, the voltage degradation rate during 140 h tests at a current density of 400 mA/cm2 is about 50%/1000 h. The factors influencing the performance of stack are investigated by post-test analysis. We found partial decomposition of the cathode contact materials LaCo0.6Ni0.4O3-δ and higher oxidation rate of metallic interconnect, resulting in an increase of the electrical resistance of the stack. Owning to the improvement of suitable sealing materials and interconnect, the resulting Stack B exhibited reasonable degradation rate of about 5%/1000 h during 140 h at a current density of 500 mA/cm2 together with a good thermal cycle stability. The applicability of stacks with an external manifold structure can be demonstrated in planar intermediate temperature SOFC.