Preparation Key Materials Of Solid Oxide Fuel Cells By Tape Casting Method

Solid Oxide Fuel Cell (SOFC) was a new energy conversion device. For its high efficiency and low greenhouse gas emission, governments of different countries and companies paid great attention to SOFCs. Among various fuel cells, efficiency of Solid Oxide Fuel Cells was the highest, which was more than twice efficiency of internal combustion engine. Not only Hydrogen, but also CH4, CO et.al can be used as fuel for SOFCs. In order to introduce SOFC technology commercially and industrially, some problems still have to be resolved. One of these issues is to decrease the thickness of electrolyte in order to decrease the operation temperature of SOFCs. The preparation of low-cost, large area anode supported electrolyte film is the key issue to commercilize the intermediate temperature SOFC.In this thesis, the researches aim was to develop key materials for SOFC of high performance, large area and low cost. Tape casting technology was developed to prepare SOFC anode. Spray-tape casting, multi-layer tape casting was used for preparation of gradient anode. Magnetron sputtering and double-layer tape casting was developed to preparation electrolyte.An overview of the work principle of SOFC was given in Chapter 1. SOFC components such as electrolyte, cathode, anode and connector were discussed. In addition, the research status of SOFC was also briefly reviewed.Tape casting technology was widely used to prepare planar SOFC components. In Chapter 2, the preparation and characterization of Ni/YSZ anode substrates by organic tape casting technique were presented. The tape casting system, the doctor blade height and the green tapes thickness were optimized. The selection of initial ceramic powders were also investigated.For the purpose of optimizing microstructure of anode and forming a graded multilayer anode, different microstructures of anode created by different pore formers were investigated; spray-tape casting and dual layer tape casting were used to perpare anode and anode functional layer. In Chapter 3, different pore former, such as starch and carbon were added to anode slurry, Different microstructures of anode created by different pore formers were also investigated, which showed the diameter of the hollows was about 50 microns by the addition of starch as pore former, while narrow channels can be seen when the graphite was applied. Graded anode structure was fabricated by spray—tape casting and dual tape casting. The thickness of anode functional layer were about 10μm and 30μm that fabricated by spray-tape casting and dual tape casting respectively. The microstructure of the modified anode was characterized by scanning electron microscopy (SEM). It was found that each method improved the performance and structure of anode.In chapter 4, single cells composed of Ni-YSZ anode and YSZ electrolyte were prepared by dual-layer tape casting and Tape casting-Magnetron sputtering method. The cathode material of La0.8Sr0.2MnO3 powders were synthesized by glycine nitrate process (GNP). On the anode substrates, different thickness of YSZ electrolytes range from 5μm to 40μm were prepared by dual tape casting method. The thickness of electrolyte which was perpared by Magnetron sputtering was about 10μm. The cathode was coated on the electrolyte by screen-printed process. The performance of single cells were all above 600 mW cm-2.In chapter 5, Dense protonic electrolyte membrane and porous anode substrate of BaCe0.5Zr0.3Y0.16Zn0.04O3-δ(BCZYZ)/BCZYZ-NiO and Ba3Ca1.18Nb1.82O9-δ(BCN18) /BCN18-NiO were prepared by a simple and effective method of in-situ tape casting/co-sintering, the thickness of BCZYZ electrolyte was about 25μm. With LSCF as cathode, single cell was assembled and tested at different temperature. The open circuit voltage and maximum power density of the cell were 1.03V,1.02V,1.00V, 0.95V and 56 mW cm-2,175 mW cm-2,250 mW cm-2, and 275 mW cm-2 at 550℃, 600℃,650℃,700℃, respectively. To sum up, this novel method can be considered as a quite promising membrane fabrication technique for the future commercialization of proton-conducting solid oxide fuel cells.In chapter 6, Dense Sm0.2Ce0.8O2-δ(SDC) electrolyte membrane and porous cathode substrate of SDC/La0.3Sr0.7FeO3-δ(LSF)/CeO2 were prepared by a simple and effective method of multi-layer tape casting/co-sintering, the thickness of SDC electrolyte was about 20μm. With NiO/SDC as anode, single cell was assembled and tested at different temperature. The Open Current Voltage (OCV) and power densities were 0.72V,0.69V,0.65V,0.61V,0.55V and 55mW/cm2,105 mW/cm2,164 mW/cm2, 233mW/cm2,245mW/cm2 at 600℃,650℃,700℃,750℃,800℃. respectively. To sum up, this method can be considered as a quite promising membrane fabrication technique for the future commercialization of solid oxide fuel cells.In chapter 7, tubular SOFCs were prepared by Gel-casting method. The diameter and length of the prepared single cell was 0.56cm and 3cm, respectively. As prepared single cell have porous anode and dense electrolyte. The open current voltage and power density was 1V,0.99V,0.96V and 126mW/cm2,154mW/cm2,155mW/cm2 at 700℃,750℃and 800℃。...