Cu- and Ni-doped Mn1.5Co1.5O4 spinel coatings on metallic interconnects for solid oxide fuel cells

An interconnect in solid oxide fuel cells electrically connects unit cells and separates fuel from oxidant in the adjoining cells. Metallic interconnects are usually coated with conductive oxides to improve their surface stability and to mitigate chromium poisoning of a cathode. In this study, Mn_1.5Co_1.5O₄ (MCO) spinel oxides doped with Cu and Ni are synthesized and applied as protective coatings on a metallic interconnect (Crofer 22 APU). Doping of Cu and Ni into MCO improves sintering characteristics as well as electrical conductivity and thermal expansion match with the Crofer interconnect. The dense layers of Cu- and Ni-doped MCOs are fabricated on the interconnects by a slurry coating process and subsequent heat-treatment. The coated interconnects exhibit area-specific resistances as low as 13.9–17.6 mΩ cm² at 800 °C. The Cu-doped MCO coating acts as an effective barrier to evaporation and migration of Cr-containing species from the interconnect, thereby reducing Cr poisoning of a cathode.