Unveiling the characteristic EIS fingerprint of the ion-transfer process in air electrodes for solid oxide cells

The development of high-performing electrodes for the new generation of solid oxide cells requires in-depth understanding of the physical processes that lie behind their resistive contributions. The performance limitation provided by the ion-transfer step scales with the properties of the electrode-electrolyte heterointerface and must be optimized to increase the cells durability. During long-term testing, the electrode dynamic response can be affected by the increased limitation of the ion-transfer step due to the delamination of the electrode from the electrolyte or the generation of secondary phases. In this study, a 1-D physics-based model is used to unravel the characteristic fingerprint of the ion-transfer process in impedance spectra. The model reproduces the qualitative dynamic behavior of LSCF and LSCF-CGO air electrodes and perform sensitivity analyses to elucidate the role played by the electrode-electrolyte adherence and the governing kinetic regime. The effect provided by a parallel reaction pathway and its identifiability in experimental data were also investigated. The obtained simulations highlight that the ion-transfer resistive peak can emerge in the 10⁴–10⁶ Hz range, depending on the electrode kinetics and surface properties. Furthermore, in experimental data, its characteristic contribution can be masked by the wires inductance and result as a higher ohmic resistance.