Improved thermal expansion and electrochemical performance of La0.4Sr0.6Co0.9Sb0.1O3-δ-Ce0.8Sm0.2O1.9 composite cathode for IT-SOFCs

Abstract

La0.4Sr0.6Co0.9Sb0.1O3-δ (LSCSb)-xCe0.8Sm0.2O1.9 (LSCSb-xSDC, x = 0, 20, 30, 40 and 50 wt%) composite materials have been studied systemically as cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). XRD result shows an excellent chemical compatibility between LSCSb cathode and SDC/LSGM electrolytes. Although electrical conductivity is reduced with the introduction of SDC content, the electrical conductivities of all the composite cathodes are still above 100 S cm−1 at 300–850 °C. Thermal expansion result shows that the increase in SDC content greatly reduces thermal expansion coefficients (TECs) and the TEC for the LSCSb-50SDC cathode attains as low as 13.1 × 10−6 K−1 at 30–900 °C. Polarization resistance (Rp) decreases monotonously with increasing SDC content, and the LSCSb-50SDC cathode shows the lowest polarization with the Rp of 0.086 Ω cm2 at 700 °C. For a 300 μm thick La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte-supported single cell, the maximum power density (Pmax) of the cell with LSCSb-50SDC cathode achieves 432 mW cm−2 at 700 °C. Moreover, the single cell with the LSCSb-50SDC cathode also shows a good cell stability at operating temperature. Above results indicate that LSCSb-50SDC composite material is a potential cathode for IT-SOFCs.