Reducing degradation effects in SOFC stacks manufactured at Forschungszentrum Jülich - Approaches and results

Solid Oxide Fuel Cell (SOFC) stacks as developed by Forschungszentrum Jülich (FZJ) are based on nickel-cermet anode supported cells. The planar anode supported design offers high performance at lower temperatures thanks to an extremely thin electrolyte YSZ layer. Fabrication techniques involving hot-pressing and/or tape-casting of the anode side substrate, vacuum slip casting of the electrolyte and the screen-printing of cathodes have been developed to a high standard wherein cells can be manufactured that produce consistent, reliable and high electro-chemical performance during long-term operation. Cells are made in sizes 5×5, 10×10 and 20 × 20 cm² and assembled in stacks with a maximum of 60 cells. More than 250 stacks have been tested, some of them also in external laboratories. Recent investigations rationalize the differences between optimum single cell performance and the limitations resulting from stack operation. Work also concentrates on the understanding and modeling of degradation phenomena. The paper gives an overview over the performance improvements in FZJ SOFC stacks and the various approaches to analyze and quantify degradation of cells and stacks.