Book/Dissertation / PhD Thesis

FZJ-2019-01699

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Degradation Study of SOC Stacks with Impedance Spectroscopy

Yan, Y. (Corresponding author)FZJ*

2018
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-367-9

Please use a persistent id in citations: http://hdl.handle.net/2128/22005  urn:nbn:de:0001-2019040105

Abstract: The Solid Oxide Fuel Cell (SOFC) is a high temperature fuel cell operated at 600 °C ~900 °C. The SOC stack can switch between fuel cell mode (SOFC) and electrolysis mode(SOEC). The performance degradation mechanisms are different under these two modes. The Electrochemical Impedance Spectroscopy (EIS) is an in-situ characterization method and its resolution can be improved by the DRT (Distribution of Relaxation Times)technique. The aim of this thesis is the investigation of SOC stack characterization in large testrigs with EIS and DRT. The EIS and DRT analysis can be influenced by 1) the inductance, 2) electrical noises and 3) noisy signal from the test rig. The test rig inductance and the electrical noises can affect the EIS data quality at high frequencies, while the influence of noisy signals is at low frequencies. The inductance error can be corrected by subtracting the test rig inductance from the stack impedance. The electrical noises can be excluded by physically cutting the built-in electric load and power supply off from the EIS circuit. By data processing with the HIT (Hilbert transform) correction, the noisy signal at low frequencies can be removed. The DRT peaks identification was performed with an SOC stack through the parameter study. Up to five DRT peaks can be identified and related to corresponding electrode processes according to the experimental results and previous results obtained with single cells by KIT (Karlsruhe Institute of Technology). A four-cell stack was assembled with JÜLICH’s F10 design. The durability of the stack was investigated by a long-term stationary electrolysis operation with a constant current density of -0.5 Acm$^{-2}$ at 800 °C. EIS and DRT were used to study the performance of the stack. The results helped give prediction to the degradation mechanisms of each cell during operation, which was supported by the post-mortem analysis results.

Note: RWTH Aachen, Diss., 2018

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Contributing Institute(s):

1. Elektrochemische Verfahrenstechnik (IEK-3)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

Appears in the scientific report 2019

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