Application of electrolyte layers for solid oxide fuel cells by electron beam evaporation

A decrease in the operating temperature of solid oxide fuel cells below 700 °C results in a significant decrease of the output power. In this temperature regime the ionic resistance of the commonly used electrolyte yttria-stabilized zirconia becomes dominant. Therefore, it is necessary to reduce the thickness of the electrolyte layer to minimize the resistance to ionic flow — as long as no alternative electrolyte materials with higher ionic conductivity negligible electronic conductivity and sufficient stability are available.In this paper electron beam physical vapour deposition is discussed as a deposition technology for thin electrolyte layers. An electrolyte composite layer was developed with a lower specific resistance in comparison to an electrolyte layer made by vacuum slip-casting. The purpose of the composite electrolyte was to fulfil both gas tightness and electronic insulation.The performance of fully-assembled anode-supported fuel cells with an electrolyte composite manufactured by electron beam evaporation was 0.93 A/cm2 at 650 °C and 0.7 V, whereas the performance of cells with an electrolyte manufactured by vacuum slip-casting with a sintering step was 0.63 A/cm2 at 650 °C and 0.7 V. The performance improvement was interpreted in terms of a significantly different bulk ionic resistance of the electrolyte layers.