Chemiacl Potential and Degradation of Solid Electrolyte for SOFCs

The stability of a solid oxide fuel cell (SOFC) stack is strongly dependent on the magnitude and profile of the internal chemical potential of the solid electrolyte. If the internal partial pressure is too high, the electrolyte can be delaminated from the electrodes. The formation of high internal pressure is attributed to a negative cell voltage, and this phenomenon can occur in a bad cell (with higher resistance) in a stack. This fact implies that the internal chemical potential plays an important role in determining the lifetime of a stack. In the present work, we fabricate two kinds of electrolyte, oxygen ion conductor (YSZ) and proton conductor (BCY), for solid oxide fuel cells and conduct degradation tests under a negative voltage condition, as a function of electrolyte structure and composition. Results indicate that the addition of electronic conduction in the electrolyte with bi-layer structure can effectively enhance the cell stability, especially under severe operating conditions.