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@PHDTHESIS{Fitzek:905044,
      author       = {Fitzek, Katharina},
      title        = {{D}istribution of {R}elaxation {T}imes for {A}nalysis of
                      {S}olid {O}xide {F}uel {C}ell {S}tacks},
      volume       = {559},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2022-00343},
      isbn         = {978-3-95806-599-4},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {237},
      year         = {2021},
      note         = {Dissertation, RWTH Aachen University, 2021},
      abstract     = {Electrochemical Impedance Spectroscopy (EIS) is a
                      frequently used measurement technique toinvestigate the
                      electrical and structural properties of electrochemical
                      energy converters such as fuelcells and electrolyzers.
                      Recently the Distribution of Relaxation Times (DRT) analysis
                      became apromising method to increase the resolution of
                      electrochemical processes on the relaxation timescale and to
                      support the Equivalent Circuit Modelling (ECM) approach by
                      an a priori estimation ofthe number of processes
                      contributing to the total polarization loss. Among the
                      possibilities tocalculate the DRT function, the Tikhonov
                      approach of regularized regression is a promising way
                      todetermine the DRT numerically. However, a main drawback of
                      this method is the fact that a suitableregularization
                      parameter has to be chosen that has a big impact on the
                      shape of the DRT.The aim of this thesis is to investigate
                      the influence of constant phase element (CPE)
                      behavior,inductive effects and EIS data structure on the
                      accuracy and repeatability of the DRT with DRTtools.CPE
                      behavior is observed in EIS measurements of fuel cells and
                      leads to depressed semicircular arcsin the complex plane and
                      a broadening of the relaxation time distribution. Inductive
                      effects andmeasurement errors can originate from parasitic
                      inductances in the test rig or the cables and leadto a
                      disturbance of the impedance measurement especially in the
                      high-frequency regime. For thesimulation study conducted in
                      this thesis, a theoretical impedance is calculated with an
                      equivalentcircuit model consisting of an ohmic resistor, an
                      inductor and three parallel connections of an idealresistor
                      and a CPE (called RQ elements) in series to simulate three
                      electrochemical processes in anSOFC which exhibit frequency
                      dispersion behavior in different extents depending on the
                      magnitudeof the CPE exponent n. Additionally, simulation
                      sets with different error structures and data pointdensities
                      are simulated in varying frequency ranges to investigate
                      their impact on the DRTcalculated with DRTtools, as well as
                      co-effects of the above mentioned parameters such ascombined
                      effects of parasitic inductances and high degrees of
                      frequency dispersion. Subsequently,the results of the
                      simulation study are verified on EIS measurements performed
                      on a two-layer SOFCstack in F10 design of Forschungszentrum
                      Jülich, highlighting the practical relevance of
                      thesimulation results. Furthermore, the numerical origin of
                      the observed calculation artefacts isinvestigated and a
                      method to remove the artefacts is proposed.},
      cin          = {IEK-14},
      cid          = {I:(DE-Juel1)IEK-14-20191129},
      pnm          = {1231 - Electrochemistry for Hydrogen (POF4-123)},
      pid          = {G:(DE-HGF)POF4-1231},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2022020823},
      url          = {https://juser.fz-juelich.de/record/905044},
}