Low-Cost Fabrication and Improved Performance of SOFC Stack Components

摘要

The project LOCO-SOFC (Low-cost fabrication and improved performance of SOFC stack components), partly funded by the European Commission, has dealt with the fabrication of SOFC stack components using low-cost ceramic manufacture methods and state-of-the-art materials (zirconia, NiO, lanthanum-manganates and lanthanum-chromites). SOFC components with improved performances at temperatures down to 800°C and lower have been developed. The fabrication methods were tape casting, screen printing, viscous processing and spray deposition. Thin (5-40 μm) zirconia electrolytes have been developed, both anode-supported and as free-standing electrolytes. The cathode has been improved by the grading of composition as well as microstructure, yielding an about 50 fold improvement at 750°C. Different anodes have been used (Ni/YSZ cermets, doped ceria, and lanthanum-chromite based anodes). Most significantly in this area has been the improvement of the ceria based anodes by the use of Ni as a catalyst for bond breaking. Both metallic and ceramic interconnect materials have been investigated. A lanthanum-chromite based interconnect material with a sufficiently small dimensional change upon reduction has been identified. Also, a previously identified metallic Fe-Cr ferritic steel has been tested with respect to contact resistance to the electrode current collectors. The contact resistance has been lowered to about 10% of the total stack resistance. Various full cells have been fabricated. Cells based on a thin zirconia electrolyte on a NiO/YSZ support and a graded cathode have been made routinely. The cell area was chosen to be 25 cm~2, but larger cells can be made using the same methods. Stack performances of 0.6 Wcm~(-2) at 800°C has been obtained using these cells together with the Fe-Cr interconnector.