Low-temperature solid oxide fuel cells (SOFCs) operated at a temperature of 500 C and below are developed by modifying the microstructures of single cells consisting of Nicermet anodes, doped ceria electrolytes and strontium-doped samaria cobaltite cathodes.
The cell microstructure is optimized by varying the starting powder firing temperature, so that the doped ceria electrolytes have a high sinterability, reducing the spin-coating cycles to decrease the electrolyte thickness to approximately 9 mm, adopting a two-step sintering process so that the electrolytes consist of small grains and have a high density; while the anodes are composed of small particles and have high porosity. In particular, the two-step sintering process depresses the co-firing temperature, thus enhancing the electrolyte conductivity and reducing the electrode polarization resistance. Outstanding performance with peak power density of 476, 319, and 189 mW cm À2 at 500, 450, and 400 C is achieved with a typical single cell comprising a 9-mm-thick Sm 0.2 Ce 0.8 O 1.9 (SDC) electrolyte, a Ni-SDC porous anode, and a Sm 0.5 Sr 0.5 CoO 3Àd -Sm 0.2 Ce 0.8 O 1.9 (SSC-SDC) composite cathode. A durability test over 110 h maintained a power density of approximately 150 mW cm À2 at 400 C, suggesting optimization of the microstructure has promise for enhancing the performance of low-temperature SOFCs.