Spin-coating derived solid oxide fuel cells operated at temperatures of 500 °C and below

Abstract

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 Ni-cermet 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 μm, 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 −2 at 500, 450, and 400 °C is achieved with a typical single cell comprising a 9-μm-thick Sm 0.2Ce 0.8O 1.9 (SDC) electrolyte, a Ni-SDC porous anode, and a Sm 0.5Sr 0.5CoO 3− δ -Sm 0.2Ce 0.8O 1.9 (SSC-SDC) composite cathode. A durability test over 110 h maintained a power density of approximately 150 mW cm −2 at 400 °C, suggesting optimization of the microstructure has promise for enhancing the performance of low-temperature SOFCs.