HIGH PERFORMANCE INTERMEDIATE TEMPERATURE SOLID OXIDE FUEL CELI WITH DOPED LANTHANUM GALLATE ELECTROLYTE, Ni-SDC CERMET ANODE, AND Sm(Sr)CoO_3 CATHODE

摘要

The operation of the solid oxide fuel cells (SOFCs) at intermediate temperatures between 600℃ and 800℃ gives some advantages (i.e. wider choices of low-cost and high Performance component materials, reduced amount of degradation and increased freedom for structural desigr etc.). To develop a practical intermediate temperature SOFC, two approaches are under active consideration. One is to use an extremely thin YSZ membrane to make the ohmic loss due to the electrolyte as small as possible. Another is to use a new electrolyte material that shows an excellent oxide ion conductivity at temperatures below 800℃, comparable to that of YSZ a 1000℃. It has been reported that doped lanthanum gallate compounds, La(Sr)Ga(Mg)O_(3-δ) (LSGM) possess oxide ion conductivity high enough to be used as an electrolyte at intermediate temperatures over a broad range of oxygen partial pressures(1). Furthermore, double doping by a transient metal, e.g. Co, was proved to be the most appropriate in further improving the oxide ion conduction in La(Sr)Ga(Mg,Co)O_(3-δ)(2,3). Since lowering the operation temperature increases no only the ohmic loss but also the polarization loss at the anode and the cathode, it is necessary to develop highly active electrodes that show sufficiently low polarization at intermediate temperatures. We have already developed the highly active Ni-(CeO_2)]_(1-x)(SmO_(1.5))_x cermet anodes which were prepared using highly dispersed composite particles synthesized by spray pyrolysis technique(4). On the other hand, Samarium cobaltite compounds, Sm(Sr)CoO_(3-δ) have beer demonstrated to show very small polarization as the cathode material(5). In this study, we repor the high performance intermediate temperature SOFC, composed of Lao.gSr_(0.2)Ga_(0.8)Mg_(0.15)Co_(0.05)O_(3-) (LSGMC) electrolyte, Ni-(CeO_2)_(0.8)(SmO_(1.5))_(0.2) (Ni-SDC) cermet anode, and Sm_(0.5)Sr_(0.5)CoO_(3-) (SSC) cathode.