Chemo-Thermo-Mechanical Coupling in Protonic Ceramic Fuel Cells from Fabrication to Operation

Abstract

This paper develops and discusses a two-dimensional, axisymmetric, computational model that predicts the coupled chemo-thermo-induced stresses associated with a protonic-ceramic fuel cell (PCFC) in a button-cell configuration. The cell is structurally supported on a porous composite Ni-BZY20 anode, with a 20-μm dense BZY20 electrolyte membrane, and a 20-μm porous composite cathode. BZY20 (BaZr0.8Y0.2O3 − δ) is a doped perovskite that is dominantly a proton conductor, but supports three mobile charged defects (protons, oxygen vacancies, and small polarons). Lattice-scale strain associated with defect concentrations and temperature manifests itself as a macroscopic stress. The model first evaluates thermally induced stresses that result from large temperature differences during membrane-electrode-assembly fabrication. The model is also applied to evaluate the coupled effects of chemo-thermo-mechanical stresses in the operating fuel cell. Sensitivity analysis is used to characterize the effects of electrochemical and mechanical properties, as well as cell architecture.