Method—Multi-Cell Testing with Active Driven Gas Layer Concept: Advantages and Limitations

This study validates a novel method for simultaneous durability testing of multiple symmetrical cells with Ni/ceria fuel electrodes. The investigation demonstrates that gas diffusion losses in the multi-cell test setup utilizing the active driven gas layer concept have a smaller impact on cell performance compared to the single-cell setup. This method proves effective for testing multiple identical cells, offering a time and cost-efficient approach. However, testing symmetrical cells with different fuel electrodes reveals an unexpected pseudo-inductive loop in the impedance spectra, observable only in the multi-cell setup. Analysis of impedance spectra and relaxation times indicates that differences in electrode polarization resistance result in varying gas compositions at the two electrodes of a cell, disrupting symmetry and superimposing an additional Nernst voltage term. To understand this, an electrical equivalent circuit model with the Nernst voltage term was developed to reproduce the observed behavior. Comparison of experimental and simulation results substantiates the model and elucidates the mechanisms. The findings indicate that testing multiple cells with the active driven gas layer concept is applicable only for identical cells and not for those with different electrodes.