Evaluation of La_0.6Sr_0.4CoO₃-δ-Ce_0.85Sm_0.075Nd_0.075O_2-δ composite cathodes for intermediate temperature solid oxide fuel cells

Aiming to lower the operating temperature of solid oxide fuel cells down to 500–700 °C, a Co-containing composite cathode La_0.6Sr_0.4CoO_3-δ-Ce_0.85Sm_0.075Nd_0.075O_2-δ (LSC-SNDC) is prepared by the solid-liquid method. The crystallinity, grain size and microstructure of LSC powders are analyzed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The LSC-SNDC cathodes with different mass ratios (LSC: SNDC = 100:0, 90:10, 70:30, 60:40 and 50:50) are implemented into symmetrical cells and full cells using screen printing. The effect of cathode sintering temperatures (900, 950, 1000, 1050 °C) is investigated at the symmetrical cell level. The lowest cathode polarization resistance (R_p) is obtained with the 50:50 sample sintered at 950 °C, demonstrating a R_p (symmetrical cell) of 0.0248, 0.0319, 0.0597, 0.1107 and 0.2304 Ω cm² and a maximum power density (full cell) of 1963, 1535, 1013, 585, and 302mW cm⁻² at 800, 750, 700, 650 and 600 °C, respectively. The LSC-SNDC (50:50) cathode exhibits a low thermal expansion coefficient of 12.3×10⁻⁶ K⁻¹ and good compatibility with other cell components, as confirmed from SEM observations. The current work demonstrates that LSC-SNDC is a promising cathode material for intermediate temperature solid oxide fuel cells.