Research On Planar Intermediate Temperature Solid Oxide Fuel Cell Prepared By Tape Casting And Laminating

Due to the zero emission, high efficiency, good fuel flexibility and being a clean energy conversion device, the Solid Oxide Fuel Cell (SOFC) has now got a lot of attention in the world. To provide commercial and practical applications, some problems should be resolved. Among them, one is that the operating temperature of SOFC is too high, which leads to some technical and materials problems. The main method of reducing operating temperature of SOFC is decreasing the resistance of electrolyte, increasing the catalytic activity and mechanical properties of electrodes. Developing electrolyte materials with high ionic conductivity at intermediate temperature, and using the anode-supported film electrolyte with good matching and mechanical properties have become hotspots in recent years.Using the environment-friendly acetate as raw materials, Sm2O3 doped CeO2 (SDC) powder was prepared by spray paralysis. The effect of composition and processing technics of spray paralysis on the properties of SDC powder was investigated. The formation mechanics of SDC was studied by TG-TDA analysis and thermodynamics.This paper focuses systematically on the preparation of aqueous tape casting SDC slurry, dispersant and dispersing mechanism, the film forming mechanism and the rheological behaviors of suspensions. Results showed that the pseudoplastic behavior was appeared when the solid content was above 50 wt.%. The dispersing mechanism of triethanolamine was electrostatic stabilization. After dried at 20～25℃for 16～24 h, SDC, NiO-SDC and NiO-YSZ green tapes with smooth face, good microstructure and high strength were obtained. The thickness of green tapes was 1/2.5～1/3 of the gap height of the second doctor blade.The effect of binder burnout and sintering process on the properties of SDC electrolyte prepared by tape casting was investigated. Results showed that the phase structure of SDC was not changed besides grain sized was increased. The relative density of SDC reached 97% of the theory density after sintered at 1400℃for 2 h. The dynamics model indicated that increasing the sintering temperature and reducing the particle size could improve the sintering process. The ionic conductivity of SDC showed itself an Arrhenius behavior. The activation energy for conduction of SDC electrolyte sintered at 1300℃,1400℃and 1500℃for 2 h was 1.24 eV,0.90 eV and 1.08 eV, respectively. The ionic conductivity of SDC electrolyte sintered at 1400℃ for 2 h reached a maximum value of 9.5×10-3 S·cm-1 (tested at 600℃).The effect of electrolyte thickness, laminating number of sheets, laminating temperature amd press, and co-sintering process on the properties of NiO-SDC anode, NiO-YSZ anode, NiO-SDC anode-supported or NiO-YSZ anode-supported SDC film electrolytes prepared by tape casting were studied. Results showed that the laminated green tapes with smooth face were prepared at low temperature and pressure. NiO-YSZ anode reached good mechanical properties and practical utility after co-sintered at 1400℃for 2 h. The half cell with NiO-YSZ anode-supported SDC film electrolyte and with a diameter of 25 mm and a thickness of 1.2 mm was successfully prepared by laminating process.The relationships between electromotive force and temperature, current and hydrogen consumption were deduced theoretically. The threshold value of hydrogen consumption was firstly demonstrated. The effect of temperature and hydrogen consumption on the electrical properties of Ni-YSZ//SDC//LSCF-SDC single cell was studied. Results showed that the maximum power density of single cell reached 26.60 mW/cm2,42.30 mW/cm2,66.78 mW/cm2,93.03 mW/cm2 at 500℃,600℃,700℃, 800℃, respectively. And the open circuit voltage was 0.978 V,0.921 V,0.861 V, 0.803 V, respectively. The concentration polarization kept high at various temperatures, and the ohmic polarization was high only at relatively lower temperature. A boundary layer with low conductivity was formed between Ni-YSZ anode and SDC electrolyte. Before reaching the threshold value, the current (I) of single cell and hydrogen consumption (v) had a relationship of v=1.25×10-7I. After reaching the threshold value, the current did not change with the increasing of hydrogen consumption.Lastly, the developing perspective of anode-supported planar ITSOFC prepared by tape casting and laminating was described. It was pointed out that the Ni-SDC//SDC//LSCF-SDC single cell with good match, no interface reaction and better performance could be prepared by double layer tape casting.