Development of Electrolyte Supported Cells Based on a Thin 3YSZ Substrate: Through Optimized Contact Layer to High Power Density

The 3YSZ substrates with thickness between 90-200 μm are excellent from mechanical and economical points of view, but its main disadvantage is rather low ionic conductivity when compared with scandia-doped zirconia or fully stabilized 8YSZ. With decreasing electrolyte thickness between 40-60 μm, it is possible to significantly improve the electrochemical performance of the 3YSZ based electrolyte-supported cell (ESC) thereby fully utilizing the available mechanical stability. Development and progress in manufacturing of high power density electrolyte supported cell based on a thin (50 µm) 3YSZ substrate is presented. The cells with improved cathode based on LSMM’/ScSZ and the multilayer anode based on Ni/GDC cermet show very good electrochemical performance. The maximum power density increases up to 750 mW/cm² for developed cell without additional contact layer at 0.7V@860 °C and is greater than one of the commercial cells based on partially scandia stabilized zirconia electrolytes as well as 95 µm 3YSZ. The changes in polarization resistance of tested cells under different operating conditions as well as during redox-cycling and durability tests are discussed on basis of analysis of impedance spectra. The developed cells show a good long-term stability (proved for >1300 h) under high current density (500 mA/cm²@850 °C, N₂:H₂:H₂O=55:40:5, air). The estimated power degradation rate is lower than 0.5%/1300 h. By using Ni/GDC anode the redox cycle ability of cell under real operating conditions is considerably improved. To reduce the contacting losses in stack different contacting layers have been tested and optimized in test bench. The influence of different parameters on electrochemical performance of the cell as well as first results for cells integration in stack are presented and discussed.