Crack Growth Rate at Oxygen Electrode/Electrolyte Interface in Solid Oxide Electrolysis Cells Predicted by Experiment Coupled Multiphysics Modeling

Abstract

An electro-chemo-mechanical model and experiment coupled approach is established and employed to predict the delamination failure at oxygen electrode and electrolyte interface. Two groups of oxygen electrode (OE) configurations are studied and compared: baseline LSCF (La1-xSrxCo1-yFeyO3-) single layer design and SCT (SrCo0.9Ta0.1O3-) - LSCF bilayer designs with different SCT loadings. The experimental overpotential data under different current densities and time are obtained from long-term tests of OE symmetric cells. Initial observation reveals that SCT coating on LSCF enhances oxygen evolution reaction kinetics over electrode surface, which reduces chemical stress due to lattice oxygen non-stoichiometry. Through modeling and experiment coupling, we successfully correlated crack growth rate with the experimental overpotential profiles under a fixed current density during long-term testing. Results show that the bilayer with 20wt% SCT loading delivers the best electrochemical performance and has the slowest long-term degradation performance while compared to the other OE configurations. As the operating current density decreases, it takes longer for the cell to reach complete delamination with the same critical crack length of 6.5 µm (93% of the electrode/electrolyte interface length).

Unveiling the high-temperature degradation mechanism of solid oxide electrolysis cells through direct imaging of nanoscale interfacial phenomena

“…72,73 Enhancing the oxygen evolution reaction was found to be effective in mitigating this delamination. 74 The physical and chemical state of the electrode–electrolyte interface is more complex for MIEC electrodes compared to LSM electrodes, primarily due to the involvement of more elements and increased interdiffusion. This work lays the groundwork for a clearer understanding of the delamination phenomena in state-of-the-art MIEC electrodes.…”