LSM-YSZ cathodes for medium-temperature solid oxide fuel cells

The effect of cathode composition, processing, and structure on the performance of medium-temperature (600-800 degrees C) solid oxide fuel cells (SOFCs) is described. The SOFC cathodes were two-phase mixtures of (La1-xSrx)(1-y)MnO3 (LSM) and Yttria-stabilized Zirconia (YSZ). The electrolytes were < 10 mu m thick YSZ, and the anodes were Ni-YSZ with Y-doped CeO2 interfacial layers. The cathode overpotential was the primary factor limiting cell power densities. Increasing the YSZ volume fraction in LSM-YSZ cathodes from 0 to 60% reduced the low-current area-specific resistance of the cells (in air and humidified hydrogen) from similar to 3.3 to 0.7 Omega cm(2) at 750 degrees C. The use of LSM with y=0.1 suppressed the formation of zirconate phases during cathode sintering. Optimal cathode porosity was approximate to 40%. The maximum power densities measured in humidified H-2 and air ranged from similar to 110 mW/cm(2) at 600 to 470 mW/cm(2) at 800 degrees C.