La 0.8 Sr 0.2 Co 1 − x Mn x O 3 Cathode and Its Application to Metal-Supported Solid Oxide Fuel Cells

Abstract

Cathode properties of La0.8Sr0.2Co1−xMnxO3 (LSCM) perovskite oxides were investigated for their application to metal-supported solid oxide fuel cells (SOFCs). La0.8Sr0.2Co0.4Mn0.6O3 (LSCM-8246) had the lowest impedance on Zr0.85Y0.15O2 (YSZ) electrolyte among various compositions because the properties of the cathodic reaction kinetics, thermal expansion compatibility, and chemical reactivity were optimized. A Ce0.9Gd0.1O2 (CGO) interlayer was introduced between LSCM and YSZ to inhibit the formation of resistive phases at the interface. The cathode impedance was decreased to about 1/3 of the noninterlayer samples. The study of the partial oxygen pressure dependence and activation energy of LSCM-8246 on CGO-layered YSZ showed that the ionization of the adsorbed oxygen is the rate-determining step of the cathode reaction at the general operation condition of SOFCs. Metal-supported single cell SOFCs with LSCM-8246 cathode were fabricated and characterized. The single cell impedance was much greater than values expected from the half cell test because the cathode in the single cell was sintered in situ during the measurement. The effect of cathode sintering was observed by measuring the current-voltage (I-V) curves and impedance spectra with time.