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Development and manufacturing of electrolyte-supported cells with high power density and durability

Entwicklung und Fertigung elektrolyt-gestützter Zellen mit hoher Leistungsdichte und Beständigkeit
: Kellner, M.; Betz, T.; Kusnezoff, M.; Trofimenko, N.; Mosch, S.

European Fuel Cell Forum -EFCF-:
8th European SOFC Forum. CD-ROM : European Solid Oxide Fuel Cell Forum, held at Lucerne Fuel Cell Forum 2008, international fuel cell conference with exhibition. 30 June - 4 July 2008, Kultur- und Kongresszentrum Luzern, Lucerne/Switzerland
Oberrohrdorf, 2008
9 pp.
European Solid Oxide Fuel Cell Forum (SOFC) <8, 2008, Lucerne>
Lucerne Fuel Cell Forum <2008, Lucerne>
Conference Paper
Fraunhofer IKTS ()
Festoxidbrennstoffzelle; Festelektrolyt; Ionenleitfähigkeit; Langzeitverhalten; Temperaturwechselbeständigkeit; Oxidationsbeständigkeit; stabilisiertes Zirkoniumoxid; Scandiumzusatz; Keramikbrennen; Leistungsdichte; elektrochemische Polarisation

Since the 1990s KERAFOL - Keramische Folien GmbH is developing zirconia based ceramic tapes and sintered substrates for Electrolyte Supported Cells (ESC). Together with Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) in Dresden investigations and developments had taken place to improve the properties of the ESC. The result of this cooperation is the possibility to produce ESCs at KERAFOL which meet all requirements for an application in stacks and systems like mechanical strength, long-term stability during operation at temperatures of 750 deg C to 950 deg C, thermal cycling, very low degradation during repeated anode reduction/oxidation cycles and an enhanced power density that is comparable to ASCs (Anode Supported Cells). The cells are based on scandia doped zirconia electrolytes (ScSZ) and are completely manufactured at KERAFOL including electrolyte production, paste preparation, screen printing, firing and quality assurance. With improving the electrolytes at KERAFOL and the electrodes at IKTS and combining both technologies it was possible to make high performance ESCs commercially available. The ESCs show an excellent long term operation at high power densities (>400 mW/cm(exp 2)). The values for the degradation of the ionic conductivity and the activation energy measured on 10 mol% stabilized ScSZ electrolytes during 1000 h were significantly lower than those of 8 mol% stabilized YSZ electrolytes. Even though KERAFOL uses hard conditions for reduction/oxidation cycles, the degradation rate is very low. By optimizing the functional layers low polarization resistances <0.25 Wcm(exp 2) could be realized as well as low electrolyte resistances (0.06 Ohm cm(exp 2)) due to the facts of using highly ionic conducting materials and decreasing the electrolyte thicknesses. The electrolyte part of the total cell resistance at 850 deg C is only 27 %. So there is potential to increase power density by improving the electrodes especially for intermediate temperatures. The possibilities at KERAFOL and the results of the measurements are shown in the paper. With showing a high power density, long-term and redox stability the decision was made at KERAFOL to install a fuel cell production line to extend its product portfolio of SOFC kiln furniture, different electrolytes, tape development and production with inhouse manufactured electrolyte supported cells.