Beyond the 3rd Generation of Planar SOFC: Development of Metal Foam Supported Cells with Thin Film Electrolyte

Abstract

The manufacturing of thin and gas tight electrolyte in solid oxide fuel cells (SOFCs) remains challenging especially when alloys are used for the substrate. In this work, we present a porosity graded multi-layer structure supporting thin film electrolyte, as a further evolution of the metal supported planar cell architecture. The substrate is made of NiCrAl metal foam impregnated with La0.1Sr0.9TiO3-α (LST) ceramic. Furthermore, a 20 μm thick composite anode functional layer with LST and Gd0.1Ce0.9O2-α (GDC) was deposited onto the substrate. The surface of the anode functional layer is later engineered with a suspension of nanoparticles with 40 nm average particle size of yttria-stabilized zirconia (YSZ). This results in a mesoporous layer with a smooth surface. Finally, a gas-tight GDC electrolyte was deposited by EBPVD method. The thickness of the thin-film YSZ layer and the gas-tight CGO layer was approximately 1 μm and 2 μm, respectively. Button half cells with size up to 25cm² were successfully produced showing an air leakage rate down to 0.7 Pa·m·s-1 satisfying the gas-tightness quality control threshold of the state of the art metal supported SOFCs at DLR. Full cells with La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathodes showed an OCV of 0.97 V at 750°C and power density of about 80mW/cm² was obtained at 0.7 V.