Preparaion Of SDC Electrolytes And Their Application Research On Anode Support SOFCs

Operating temperatures of traditional SOFC are higher then1000℃that caused manyproblems in practice, such as shorter available lifetime of fuel cell, limited selection inconnecting materials and sealing materials, high manufacturing cost, and low thermal cyclingreliability. Using new materials and new technologies would fundamentally solve theseproblems. For meeting the commercial requirements, making the single cell size larger couldimprove the stack output power and reduce costs.In this paper, using Ce_0.8Sm_0.2O_1.9（SDC） which has cubic fluorite structure as theelectrolyte material of low temperature solid oxide fuel cell, and have discussed itselectrolchemical properties in detail. Three different methods fabricated three kinds of SDCpowders with different microstructure. SDC powders which were synthesized by oxalateco-precipitation method, have the claviform structure with the average length5μm and sectiondiameter less than1μm. When using Na2CO3as the precipitator, SDC powders have the globestructure with the diameter100²00nm. Synthesized the SDC powders with glycinecombustion method, could make them having the mesh sponge microstructure. These threekinds of SDC powders have similar conductivity and their activation energies are0.69eV,0.58eV and0.59eV, respectively. Based on these different micro-structures, they could beused into anode, electrolyte and cathode layers respectively, for meeting differentrequirements of different layers.Tape casting method is the best choose to produce the anode support in large-scale withlow cost. Anode powders compose with50wt.%NiO and50wt.%SDC powders which weresynthesized by oxalate co-precipitation method. The reason of using this kind of SDC is thatits claviform microstructure is good for fabricating the porous anode and offer much highersupport strength than the other two kinds of SDC powders. After making a number of ratiotests which were about solvent, dispersant, binder and plasticizer, fabricated tow kinds of tapecasting slurry successfully. Both of them own the well dispersion, stability and after dryingprocess green tapes are smooth and defect-free with suitable plastic quality. After calcinations,the green tapes turned to flat and defect-free pieces with1～1.5mm thickness and themaximum support strength is91.71MPa. All of materials using in these processes have thelow cost and the whole process has characteristic of environmental friendly.One of the effective ways of increase the SOFC conductivity is reduced the electrolyte layer thickness. In this paper, using screen print method to fabricate the electrolyte layer withSDC powders which were synthesized by Na2CO3co-precipitation method at one side ofpre-anode support. This kind of structure is good for making close packing in slurry andthrough the calcine process electrolyte layer became denser than using the SDC powderswhich were synthesized by other two methods. SDC powders mixed with5wt.%ethylic-cellulose and moderate terpineol as the slurry. After co-sintered this bilayer structureat1350℃for10h in air, gotten the uniform flat and crack free bilayer sample, includingporous anode support and the dense well electrolyte film with12μm thickness.Using the same methods made the cathode slurry which was mixed La_0.5Sr_0.5Co_0.2Fe_0.8O₃powders with40wt.%SDC and the content of ethylic-cellulose is10wt.%, printed this slurryonto the electrolyte side of the bilayer sample then calcined at900℃for4h in air. So afterthese processes, it got the planar anode support solid oxide fuel cell with70mm diameter.Open-circuit voltage （OCV） of0.94V and the maximum power density of797mW·cm^-2achieved with dry hydrogen as fuel gas and air as oxidant gas at600℃.In order to develop the properties of low-temperature solid oxide fuel cells, new solidoxide electrolytes with high ionic conductivities are being extensively studied. In this paper,discussed the two-phase materials electrolyte SDC/25wt.%K₂CO₃, which consisting of adoped ceria matrix phase and a small amount of a second carbonate phase K₂CO₃. Single cellsbased on this kind of electrolyte were fabricated by a simple dry-pressing technique.Open-circuit voltage （OCV） of1.05V and the maximum power density of602mW·cm^-2achieved with dry hydrogen as fuel gas and air as oxidant gas at700℃.