SUBSTRATE-PROTECTED ELECTRODE-ELECTROLYTE UNIT

The different expansion coefficients between a solid electrolyte layer and an electrode substrate can cause permanent curvatures in the finished substrate-electrode-solid electrolyte layer unit, especially during the production of the solid electrolyte layer, or cause curvatures in the entire electrode-electrolyte unit during the reduction process. The invention provides a means of preventing unwanted curvatures. The electrode-electrolyte unit (2) has a stress relief layer (8)on the side of the substrate (5) facing away from the solid electrolyte layer (7), this stress relief layer having the same heat-related expansion and contraction characteristics as the solid electrolyte layer (7). The stress relief layer (8) can consist of the same material as the solid electrolyte layer (7) and can have holes (9) to allow the passage of fuel. The invention also relates to fuel cells.