Quantitative contribution of cells and interfaces to SOEC stack performance

Abstract

This study employs the method of embedding voltage leads within three cells of an electrolysis stack to investigate the quantitative impact of the electrolysis cells and their interfaces on overall stack performance. A 900-h stability test was conducted at a constant temperature of 750 °C with a current density of 500 mA/cm² and 60 vol.% (volume fraction) water steam content. The results indicate the electrolysis voltage of the stack increased by 0.213 V, while the voltage across the three cells increased by 0.268 V. Post-mortem analysis reveals changes in the three-phase boundary (TPB) and porosity of the Ni-YSZ electrodes across different cells. These structural changes explain the variations in both ohmic resistance and polarization resistance. In contrast, the voltage drop across the current-collecting interface between the interconnect and the cell decreases by 0.055 V, accounting for 25.82% of the total stack degradation. Improved interface contact helps inhibit stack degradation. Future work will further investigate the stability of stack components and their interfaces, aiming to optimize stack design.

Graphical abstract

Keywords

solid oxide electrolysis cell (SOEC) stack / flat-tube solid oxide fuel cell / interface / metal interconnect / water electrolysis / degradation

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