Durability of metallic interconnects and protective coatings

Abstract

Abstract To build up a useful voltage, a number of solid oxide fuel cells (SOFCs) are electrically connected in series in a stack via interconnects that are placed between adjacent cells. In addition to functioning as a bipolar electrical connector, the interconnect also acts as a separator plate that separates the fuel at the anode side of one cell from the air at the cathode side of an adjacent cell. During SOFC operation at high temperatures, the interconnects are thus simultaneously exposed to the oxidizing air at one side and a reducing fuel, which can be either hydrogen or hydrocarbon, at the other. Besides, they are in contact with adjacent components, such as electrodes or electrical contacts, seals, etc. With steady reduction in SOFC operating temperatures into the low or intermediate range of 600–850 °C, oxidation‐resistant alloys are often used to construct interconnects. However, the metallic interconnects may degrade via interactions at their interfaces with surrounding environments or adjacent components, potentially affecting the stability and performance of interconnects and the SOFC stacks. Therefore protection layers are applied to metallic interconnects, which are also intended to mitigate or prevent chromium migration into cells and the cell poisoning. This article provides a comprehensive review of materials for metallic interconnects, their degradation, and coating protection.