On the benefits of structured composite electrodes in solid oxide cells

Abstract

Functional composites of electronic and ionic conductors are the backbone of oxygen and fuel electrodes in solid oxide cells. A typical oxygen electrode is fabricated from a lanthanum strontium manganite and yttria-stabilized zirconia (LSM-YSZ) composite, while the fuel electrode is based on a Ni-YSZ cermet. While the composite materials exhibit enhanced kinetic capabilities, the electron-conductive phases, i.e., LSM and Ni, exhibit high electrical conductivity. The goal of this study was to develop an electrode layout with enhanced performance by tailoring the benefits of both, the composites and the single-phase electron conductors, within individual electrodes. The electrodes were fabricated in a two-layer layout with different thicknesses by screen-printing: composite material layer, electron-conductive material. The results suggested that the presence of YSZ is essential in the entire electrode body of a fuel electrode for enhanced performance as it increases the triple phase boundary length, as well as mechanical stability by forming a scaffold for the Ni network. Hence, for the optimal performance a thick layer of Ni-YSZ composite is required. On the contrary, the optimal oxygen electrode requires only very thin layer of the composite, otherwise the presence of YSZ is retarding the electrode’s performance.Graphical abstract