Gas leak diffusion induced polarization in submicro/nanoscale non-tight electrolytes of solid oxide fuel cells

Abstract

Solid oxide fuel cells with submicro/nanoscale electrolytes (μSOFCs) are attracting increasing attention since the ohmic energy loss arising from an ion-resistive electrolyte decreases significantly with decreasing thickness of the electrolyte interlayers. However, gas leak diffusion can be induced due to increasing microstructural flaws such as cracks and pinholes in thin electrolytes. Evaluation of the effects of gas leak diffusion through electrolyte on cell performance is thus an urgent demand. In this work, the effect of gas leak diffusion on concentration polarizations (CPs) is investigated quantitatively for both anodes and cathodes of SOFCs under various operating conditions. The results show that gas leak diffusion through electrolyte typically induces dominant cathode CP. The direct reaction of leaked H₂ and O₂ correlates has a large impact on both anode and cathode CP induced by gas leak diffusion. Lowering the operating temperature decreases CP induced by gas leak diffusion. Our work provides a quantitative model to evaluate the impact of gas leak diffusion in electrolytes on SOFC performance and facilitates the rational design of high performance μSOFCs.