Development and Characterization of Porous Composites for Solid Oxide Fuel Cell Anode Conduction Layers Using Ceramic‐Filled Highly Porous Ni Foam

Abstract

Porous Ni‐yttria stabilized zirconia (YSZ) composites are the most common materials used for solid oxide fuel cell anodes. In conventional anodes, percolation of the Ni phase for acceptable conductivity requires relatively high Ni contents (i.e., >35 vol% of solids) which can reduce cell reliability due to increased coefficient of thermal expansion (CTE) mismatch with the YSZ electrolyte and damage produced by redox cycling. In this study, the incorporation of highly porous Ni foam into an anode structure was investigated in order to produce an anode conduction layer with high conductivity values at lower Ni volumes. This was done by developing techniques for pasting various YSZ based slurries into a Ni foam structure followed by sintering. The electrical conductivity, dimensional stability, and CTE of these structures were measured as a function of Ni, YSZ, and porous volume. Sintered anodes made with Ni‐foam exhibited a superior combination of conductivity and CTE compared with conventional anode structures. For example, a Ni foam–YSZ composite with a nickel loading of 13 vol% has a CTE of 10.7 × 10−6 K−1, but with a similar electrical conductivity to a conventional anode (∼3000 S/cm) which requires at least 30 vol% Ni resulting in a CTE >13 × 10−6 K−1. Alteration of the paste composition produced a porous composite with engineered porosity and good dimensional stability.