Degradations of the electrochemical performance of solid oxide fuel cell induced by material microstructure evolutions

Long-term performance stability is essential for the commercialization of solid oxide fuel cell (SOFC) technology. The performance degradations of SOFCs induced by the microstructure evolutions of cell component materials are examined by multi-physics numerical simulations. Explicit considerations are given to the typical material set: nickel (Ni) - Yttria-stabilized zirconia (YSZ) anode, YSZ electrolyte, and SS430 interconnect. Degradation of the Ni-YSZ anode is attributed to the agglomeration of Ni particles that results in a reduced three-phase-boundary length and a reduced electrical conductivity of the anode. Degradation of the SS430 interconnect is considered based on the growth of its oxide scale. The decreased conductivity of YSZ due to its phase transformation from cubic to tetragonal is the cause of degradation associated with the electrolyte. The simulations provide quantitatively the effects of the microstructure evolutions of the cell components on the cell performance. It is concluded that the long-term stability required for the SOFC commercialization can be achieved through an anti-oxidation coating of SS430 and a proper choice of the initial anode compositions.