Assessing performance degradation induced by thermal cycling in solid oxide cells

Abstract

Commercialization of solid oxide cells (SOCs) is hindered by their poor durability. In particular, electrode–electrolyte delamination due to the mismatch in thermal expansion coefficients under thermal cycling is one of the main sources of performance degradation during the long-term SOCs operation. We establish a macroscopic mathematical model describing the delamination propagation inside SOCs under thermal cycling. The extent to which excessive stresses at different sides affect delamination is assessed. Then the change in delamination length with different thermal cycles and the influence factors on delamination is quantified by using a cohesion zone model. Accordingly, control strategies that can effectively inhibit delamination are further proposed. In addition, a separate computational fluid dynamics model based on the results of the cohesion zone model is developed to evaluate the mechanism and extent of delamination on the electrochemical performance degradation. Based on the results of the above model, after 10 thermal cycles, the electrode–electrolyte delamination can reach 40.7%, resulting in a 37.3% loss of electrochemical performance. Furthermore, electrochemical analysis demonstrates that, regardless of which side the delamination occurs on, it affects the electrochemical reaction within the electrode at the same location on the opposite side by hindering the electron and ion transport paths.