A comparative study of equivalent circuit model and distribution of relaxation times for fuel cell impedance diagnosis

Abstract

Summary Electrochemical impedance spectroscopy (EIS) is an important diagnostic tool for fuel cells. Accurate extraction of physical parameters from impedance spectra remains a significant challenge for vehicle fuel cells. The reliability analysis results obtained herein revealed that precise identification of middle and low‐frequency impedance by a traditional equivalent circuit model (ECM) was difficult. However, it was determined that the distribution of relaxation times (DRT) could be used to extract three characteristic peaks from the EIS data, which corresponded to the main polarization processes, including gas diffusion, oxygen reduction reaction, and proton transfer. The present work involved the development of a DRT‐based EIS reconstruction method for fuel cells. The sensitivity analysis results demonstrated that the designed method enabled the characterization of the gas diffusion impedance and proton transfer impedance at low and high current density, respectively. Notably, these properties could not be accurately determined by a traditional ECM method. The developed approach considerably improved the interpretability of impedance spectra; thus making it applicable for fuel cell fault diagnosis and durability analysis.

A Kernel for Calculating PEM Fuel Cell Distribution of Relaxation Times

“…One therefore could expect four corresponding peaks in the DRT spectra. However, in Heinzmann et al (2018), Avioz Cohen et al (2021), and Wang et al (2021), a single oxygen transport peak has been reported. There are two options to explain this result: either some of the oxygen transport peaks overlap with each other (or with the ORR peak) and DRT is not able to separate them, or the codes used were unable to resolve all the transport processes.…”

“…Since 2002, a lot of works from the group of Ivers-Tiffée have been devoted to deciphering of solid oxide fuel cell spectra by means of DRT [see a review (Ivers-Tiffee and Weber, 2017)]. Analysis of PEMFC impedance spectra using DRT is a relatively new field (Heinzmann et al, 2018;Avioz Cohen et al, 2021;Reshetenko and Kulikovsky, 2021;Wang et al, 2021). Heinzmann et al (2018) measured impedance spectra of a small (1 cm 2 ) laboratory PEMFC and studied DRT peak behavior depending on cell temperature, relative humidity (RH), oxygen concentration, and current density.…”

“…Note that Heinzmann et al and Cohen et al used different codes for DRT calculation. Wang et al (2021) measured impedance spectra of application-relevant 25-cm 2 PEMFC and obtained a three-peak DRT; the lowest frequency peak was attributed to oxygen diffusion processes in the cell. In our recent work (Reshetenko and Kulikovsky, 2021), DRT spectra of a low-Pt PEMFC have been reported; we attributed the low-frequency peak to oxygen transport in the GDL and, possibly, in the channel.…”

“…There are two options to explain this result: either some of the oxygen transport peaks overlap with each other (or with the ORR peak) and DRT is not able to separate them, or the codes used were unable to resolve all the transport processes. It is important to note that the code for DRT calculation of Wan et al (2015) used in Heinzmann et al (2018) and Wang et al (2021), the ISGP code (Hershkovitz et al, 2011) used in Avioz Cohen et al (2021), and our code using Tikhonov regularization (Tikhonov, 1995) in combination with NNLS solver (Kulikovsky, 2020a;Kulikovsky, 2021a) are based on the RC kernel, Eq. 5.…”

A kernel for PEM fuel cell distribution of relaxation times

“…Since 2002, a lot of works from the group of Ivers-Tiffée have been devoted to deciphering of solid oxide fuel cell spectra by means of DRT (see a review 6 ). Analysis of PEMFC impedance spectra using DRT is a relatively new field [7][8][9][10] . Heinzmann, Weber and Ivers-Tiffée 7 measured impedance spectra of a small (1 cm 2 ) laboratory PEMFC and studied DRT peaks behavior depending on cell temperature, relative humidity (RH), oxygen concentration and current density.…”