Investigation of local sensitivity for vehicle-oriented fuel cell stacks based on electrochemical impedance spectroscopy

Abstract

The lifetime of fuel cells is a severe constraint on fuel cell industrialization, which is significantly influenced by the consistency of the fuel cell stack. This paper is the first to measure the impedance of a whole high-power fuel cell stack throughout its ten equal areas based on a multi-channel impedance test system. Based on the equivalent circuit model combined with the relaxation time distribution, the differences in the local polarization dynamics processes of the stack and its sensitivity to working condition variations are analyzed in detail. Additionally, the Pearson correlation between the local voltage and internal state parameters is quantified. The results show that the distribution characteristics of the local polarization dynamics losses are inherent to the stack structure and assembly errors, but are less influenced by the working conditions without extreme conditions. Furthermore, the robust correlations between the local voltage and the internal ohmic resistance and oxygen diffusion resistances in the stack are revealed. More importantly, this study would support the variance assessment of the internal state based on the local voltage, which will have comprehensive applications in controlling fuel cell systems.