SOFC Stack Operation: Effects of Electrode-Interconnect Contacts

Planar SOFC multicell stacks incorporating metallic interconnects generally exhibit average cell performance lower than that observed for out-of-stack cells under similar conditions. It has been suggested that electrode/interconnect, especially cathode/interconnect, contacts (and their ohmic resistances) are the main cause for this observed difference. In addition, cathode/interconnect contacts can evolve in long-term operation, resulting in stack performance reduction/degradation with time. Experiments using current interruption, AC electrochemical impedance and other characterization techniques have been conducted on one-cell stacks and button cells in contact with various types of interconnect materials. The data obtained to date confirmed the hypothesis that contact ohmic resistance significantly contributes to stack performance losses. Thsi paper summarizes and discusses experimental results on the effects of cathode/interconnect contacts on stack performance.