Detection of Cells State-of-Health in PEM Fuel Cell Stack Using EIS Measurements Coupled with Multiphysics Modeling

This paper presents a pseudo 2D multiphysics A.C. and D.C. model that has been successfully used with Electrochemical impedance spectroscopy (EIS) measurements to detect cells state-of-health in a PEMFC stack. The model is able to reproduce the gas concentration oscillations that develop along the cell channel while doing EIS measurements. This feature makes it possible to explicitly take into account the air stoichiometry effects on cells state-of health. The model being both static and harmonic, the identification of model parameters is based on static cell data (current and voltage) and on measured cells impedance spectra. The cells state-of-health is presented in terms of repartition of losses due to four limiting phenomena: the membrane ionic resistance, the mass and charge transport limitations in the electrode, the mass transport limitations through GDLs and along the cell channels and the kinetic irreversibilities. When coupled with pressure drop measurements across the stack, it has been possible to prove that flooding conditions for the stack leads to inhomogeneous cells state-of-health: on one hand, most of the cells get flooded while, on the other hand, some of them remain in the nominal conditions.