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Extraction of the parameters of a fractional order equivalent circuit from time-domain data

Heim, Christopher and Strunz, Werner and Wagner, Norbert and Friedrich, Kaspar Andreas (2017) Extraction of the parameters of a fractional order equivalent circuit from time-domain data. Conference on Electrochemical Impedance Analysis, 06.-10. Nov. 2017, Genua, Italien.

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The derivation of impedance spectra and impedance parameters from time-domain data has been an interesting topic of investigations for some years now. Currently applied techniques usually consist of transforming the time-domain data into the frequency-domain by means of Fourier or Laplace-transformations[1]. Different approaches fit the time-domain data with a series of exponential functions that translate into a series of parallel resistor-capacitor elements, to achieve an accurate description of the resulting impedance spectra[2]. In this work we apply concepts from fractional calculus to achieve a time-domain description of parallel resistor-constant-phase-elements for the accurate fitting of time-domain current-step responses. To achieve an accurate description of the fractional equivalent circuit in the time domain we formulate an equation based on the Mittag-Leffler function from fractional mathematics. Advantages of this approach allow a direct evaluation of impedance parameters for the assumed equivalent circuit model function without any further transformation to the frequency domain. To this end we explore the ability of fractional order models to fit the time-domain response of a system and if the real impedance spectrum could be reproduced by comparisons to actually measured impedance spectra of 18650 cells. Preliminary results show that the time domain data fits have high accuracy. Comparing the resulting impedance spectra to actually measured impedance spectra show the dependence of applied current-step magnitude, relaxation time and sampling rate. A meaningful fitting result can easily be transformed to achieve a distribution of relaxation times by means of the method proposed by Boukamp[3]. Future endeavors will also explore the ability of fractional order models to accurately model arbitrary load response of electrochemical systems as is oftentimes applied in industrial applications. References [1] K.Takano, K. Nozaki, Y. Saito, K. Kato, A. Negishi, J. Electrochem. Soc. 147 (2000) 922-929. [2] J. P. Schmidt, E.Ivers-Tiffeé, J.Power Sources. 315 (2016) 316-323. [3] B. A. Boukamp, Electrochim. Acta. 154 (2015) 35-46.

Item URL in elib:https://elib.dlr.de/116480/
Document Type:Conference or Workshop Item (Speech)
Additional Information:Gefördert durch das BMBF-Projekt Li-EcoSafe
Title:Extraction of the parameters of a fractional order equivalent circuit from time-domain data
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Heim, ChristopherChristopher.Heim (at) dlr.dehttps://orcid.org/0000-0001-7204-6065
Strunz, Wernerzahner-elektrikUNSPECIFIED
Wagner, NorbertNorbert.Wagner (at) dlr.dehttps://orcid.org/0000-0002-2596-8689
Friedrich, Kaspar AndreasAndreas.Friedrich (at) dlr.deUNSPECIFIED
Date:7 November 2017
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:Lithium-Ion, Battery, Impedance, Electrochemical Impedance Spectroscopy, Distribution of Relaxation Times
Event Title:Conference on Electrochemical Impedance Analysis
Event Location:Genua, Italien
Event Type:international Conference
Event Dates:06.-10. Nov. 2017
Organizer:Universität Genua
HGF - Research field:Energy
HGF - Program:Storage and Cross-linked Infrastructures
HGF - Program Themes:Electrochemical Energy Storage
DLR - Research area:Energy
DLR - Program:E SP - Energy Storage
DLR - Research theme (Project):E - Electrochemical Prcesses (Batteries)
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Electrochemical Energy Technology
Deposited By: Heim, Christopher
Deposited On:01 Dec 2017 13:50
Last Modified:07 Feb 2020 13:42

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