Stress relief in solid oxide fuel cells by leveraging on the gradient porosity design in anode layers

Abstract

Residual stresses and thermal stresses in solid oxide fuel cells (SOFCs) are the main factors to induce the reliability degradation including delamination, cracking and damage. Anode porosity is potential controller to the stresses due to the effects on the mechanical compatibility of SOFC components and electrochemical reaction rate. Herein, we establish a three-dimensional SOFC multi-physics field coupling model to explore the electrochemical and mechanical performance of SOFCs employing gradient porosity anode versus uniform porosity anode. The influence of porosity on the carrier conduction, gas flow, gas diffusion and transfer, and heat transfer in porous composite electrodes are considered. The results indicate that the gradient porosity anode significantly enhances the mechanical compatibility of SOFC components while maintaining high electrochemical performance. At room temperature, the dangerous area of residual stress occurs at the anode, and the gradient porosity anode can reduce the maximum first principal stress of the anode by 20.0 %. Under the operating condition, the dangerous area of thermal stress occurs in the electrolyte, and the gradient porosity anode can reduce the maximum first principal stress of the electrolyte by 44.9 %. Additionally, it significantly alleviates stress concentration in the SOFC. This study provides a way to optimize the reliability of SOFCs by controlling the anode porosity.