Preparation Of Micro Tubular SOFCs Based On The Highly Asymmetric Electrolyte Hollow Fibre Membranes

Micro tubular solid oxide fuel cells (MT-SOFCs) are referred to those with about 1 mm in outer diameter. They exhibit a lot of advantages over the planar and tubular configurations such as large electrode areas, high volumetric power density, high resistance to thermal shock and quick start-up and shut-down operations, and thus are to find extensive potential applications in portable and mobile power supplications. In this study, a kind of hollow fiber ceramics with a support layer with special pore structure and a gas-tight skin layer were prepared in a single-step via a phase inversion-sintering process. Then a thin Ni layer was deposited on the inner of the YSZ hollow fiber by electroless plating as anode layer and LSCF slurry was coated on the outer of the hollow fibers as cathode after sintering. The new technology of preparation of MT-SOFC was systematically studied in this paper.First of all, YSZ hollow fiber ceramic membranes with asymmetric structure were prepared by the phase inversion-sintering, which was made up of special pore structure in the support electrolyte layer and dense skin layer. The composition of phase inversion solution, non-solvent addition and the composition of the pore fluid were studied. The results show that while a solution contented PESf:NMP:non-solvent addition:YSZ (1:4:1.8:5.4) and a 9.4% non-solvent addition-90.6% pore fluid, a ceramic hollow fiber membrane was obtained, the effective separation layer is 4.68μm, the pore density on the inner surface is 5000-8000·mm-2 and the interspace reaches 35.39%, the bending strength is up to 222 MPa. It is complete suitable for the requirement of the anode of micro tubular SOFC.Secondly, a thin Ni layer was prepared by depositing the Ni catalyst into the special pore structure in the support electrolyte layer of the YSZ hollow fiber by electroless plating after sintering of oxidation-reduction as SOFC anode layer. And the influence of the composition of the chemical bath and the operating conditions on Ni coating layer were studied. The results showe that a layer with 40.32% surface porosity,1.3 microns thickness and 6 m2·g-1 surface area is obtained by a time of 30min electroless plating at temperature of 70℃using a solution, which is composed of 26.3 g·L-1 NiSO4,26 g·L-1 NaH2PO2,30 g·L-1 H3BO3,30 g·L-1 NaCl,30 g·L-1 TEA 1.2 g·L-1 NaF and 9 ml·L-1 lactic acid. Finally, a micro tubular SOFC was prepared by coating LSCF cathode materials on the outer surface of the prepared YSZ hollow fibers after sintering. To test the electrical property of the cell at different work temperatures, a flow rate of humidified hydrogen, 30ml·min-1, was put into the inside of micro tubular and a flow rate of air,50ml·min-1, was accessed to the outside of the single cell. The experiments have showed that the prepared single cell has a good open circuit voltage up to 1.15 V, which is very close to the theoretical electromotive force. It indicates the good sealing of the electrolyte layer. Only 8 mW·cm-2 output power is obtained at the operating temperature of 600℃, but a 133 mW·cm-2 output power density is measured at operating temperature 800℃, and the corresponding current density of 0.24 A·cm-2 and voltage of 0.55 V.