scholarly journals Generalized Distribution of Relaxation Times Analysis for the Characterization of Impedance Spectra

Batteries ◽  
2019 ◽  
Vol 5 (3) ◽  
pp. 53 ◽  
Author(s):  
Michael A. Danzer
Keyword(s):  
Impedance Spectroscopy ◽  
Relaxation Times ◽  
Complex Impedance ◽  
Lithium Ion ◽  
Vanadium Redox Flow Battery ◽  
Impedance Spectra ◽  
Model Free ◽  
Single Polarization ◽  
Generalized Distribution

Impedance spectroscopy is a universal nondestructive tool for the analysis of the polarization behavior of electrochemical systems in frequency domain. As an extension and enhancement of the standard impedance spectroscopy, the distribution of relaxation times (DRT) analysis was established, where the spectra are transferred from frequency into time domain. The DRT helps to analyze complex impedance spectra by identifying the number of polarization processes involved without prior assumptions and by separating and quantifying their single polarization contributions. The DRT analysis, as introduced in literature, claims to be a model-free approach for the characterization of resistive-capacitive systems. However, a data preprocessing step based on impedance models is often required to exclude non-resistive-capacitive components off the measured impedance spectra. The generalized distribution of relaxation times (GDRT) analysis presented in this work is dedicated to complex superposed impedance spectra that include ohmic, inductive, capacitive, resistive-capacitive, and resistive-inductive effects. The simplified work flow without preprocessing steps leads to a reliable and reproducible DRT analysis that fulfills the assumption of being model-free. The GDRT is applicable for the analysis of electrochemical, electrical, and even for non-electrical systems. Results are shown for a lithium-ion battery, a vanadium redox flow battery, and for a double-layer capacitor.

scholarly journals Optimized Process Parameters for a Reproducible Distribution of Relaxation Times Analysis of Electrochemical Systems

Batteries ◽  
2019 ◽  
Vol 5 (2) ◽  
pp. 43 ◽  
Author(s):  
Markus Hahn ◽  
Stefan Schindler ◽  
Lisa-Charlotte Triebs ◽  
Michael A. Danzer
Keyword(s):  
Distribution Function ◽  
Electrochemical Impedance ◽  
Regularization Parameter ◽  
Relaxation Times ◽  
Measurement Data ◽  
Complex Impedance ◽  
Lithium Ion ◽  
Parameter Study ◽  
Model Free ◽  
The Impact

The distribution of relaxation times (DRT) analysis offers a model-free approach for a detailed investigation of electrochemical impedance spectra. Typically, the calculation of the distribution function is an ill-posed problem requiring regularization methods which are strongly parameter-dependent. Before statements on measurement data can be made, a process parameter study is crucial for analyzing the impact of the individual parameters on the distribution function. The optimal regularization parameter is determined together with the number of discrete time constants. Furthermore, the regularization term is investigated with respect to its mathematical background. It is revealed that the algorithm and its handling of constraints and the optimization function significantly determine the result of the DRT calculation. With optimized parameters, detailed information on the investigated system can be obtained. As an example of a complex impedance spectrum, a commercial Nickel–Manganese–Cobalt–Oxide (NMC) lithium-ion pouch cell is investigated. The DRT allows the investigation of the SOC dependency of the charge transfer reactions, solid electrolyte interphase (SEI) and the solid state diffusion of both anode and cathode. For the quantification of the single polarization contributions, a peak analysis algorithm based on Gaussian distribution curves is presented and applied.

Electrochemical Characterization of Phosphosilicate-modified Nafion Membranes

2004 ◽  
Vol 847 ◽  
Author(s):  
L. C. Klein ◽  
M. Aparicio
Keyword(s):  
Impedance Spectroscopy ◽  
Relative Humidity ◽  
Complex Impedance ◽  
Electrochemical Characterization ◽  
Hybrid Membranes ◽  
Impedance Spectra ◽  
Nafion Membranes ◽  
Electrode Interface ◽  
Interface Effects

ABSTRACTHybrid membranes containing Nafion and phosphosilicate gels were prepared using infiltration and recasting methods. The hybrid membranes were investigated using complex impedance spectroscopy. Conductivities were determined as a function of relative humidity. Infiltrated membranes, which contained gel in more or less discrete particles, were compared with recast membranes where the gel was more evenly distributed. Both of the modified membranes were compared to unmodified Nafion. The impedance spectra were analyzed to distinguish electrode interface effects from bulk transport phenomena.

Impedance analysis of porous electrode structures in batteries and fuel cells

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
André Weber
Keyword(s):  
Fuel Cells ◽  
Porous Electrode ◽  
Relaxation Times ◽  
Lithium Ion ◽  
Impedance Analysis ◽  
Wide Frequency Range ◽  
Impedance Spectra ◽  
Transmission Line Model ◽  
Error Sources ◽  
Lithium Ion Cells

AbstractToday technical electrodes in batteries and fuel cells rely on complex multiphase microstructures that facilitate electronic, ionic and, in case of fuel cells, diffusive gas transport to the active reaction sites distributed in the electrode volume. The impedance of such electrodes can be described by the well-established transmission line model (TLM) approach. In a TLM, transport, charge transfer phenomena and capacitive effects are coupled considering microstructural features of the electrode. Its application for impedance data analysis of technical cells is challenging as the TLM impedance extends over a wide frequency range and quite often a strong overlapping with other contributions takes place.In this paper the application of the distribution of relaxation times (DRT) to the analysis of technical electrodes in batteries and fuel cells is elucidated. Different examples how to apply the DRT to analyze impedance spectra of solid oxide-, polymer electrolyte- and lithium ion-cells will be discussed. It will be shown that the TLM is usually represented by multiple peaks in the DRT, which might be strongly affected if contributions of different electrode layers overlap in the spectra. Related error sources and countermeasures are illustrated. Approaches how the DRT can be applied for the analysis of measured spectra and how it is able to support CNLS-fitting are presented.

Characterization, Optical and Impedance Study of ZnSe Nanostructure

2013 ◽  
Vol 699 ◽  
pp. 490-495
Author(s):  
Ramna Tripathi ◽  
Akhilesh Kumar
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Impedance Spectroscopy ◽  
Zinc Selenide ◽  
Relaxation Times ◽  
Complex Impedance ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Stability

Zinc selenide nanoparticle has been synthesized using soft chemical routes. The particles were capped using 2-mercaptoethanol to achieve the stability and avoid the coalescence. The as-obtained particles were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV–VIS absorption and photoluminescence (PL) spectra. The impedance studies were carried out as a function of frequency (100 Hz–1 MHz) and temperature (298–373 K) by impedance spectroscopy. An analysis of the complex impedance (z' and z") with frequency is performed assuming a distribution of relaxation times.

Characterization of ZnO nanolayers by complex impedance spectroscopy

2017 ◽  
Author(s):  
Yordan Marinov ◽  
Todor Vlakhov ◽  
Blagoy Blagoev ◽  
Grzegorz Luka ◽  
Tomasz Krajewski ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Complex Impedance ◽  
Complex Impedance Spectroscopy

Application of AC Impedance Spectroscopy for Characterization of BiNbO4 Ceramics

2012 ◽  
Vol 512-515 ◽  
pp. 1193-1197 ◽  
Author(s):  
Agata Lisińska-Czekaj ◽  
Beata Wodecka-Duś ◽  
Dionizy Czekaj
Keyword(s):  
Impedance Spectroscopy ◽  
Least Squares Method ◽  
Complex Impedance ◽  
Impedance Measurement ◽  
Simulated Data ◽  
Electrode Processes ◽  
Usual Representation ◽  
Ac Response ◽  
Input Perturbation

Impedance spectroscopy is known as an important technique used for describing the electrical processes occurring in a system on applying an ac signal as input perturbation. In the present paper results of a study of BiNbO4 ceramics fabricated by mixed oxide method and sintered by free sintering are reported. Results on the ac response of the electroceramic samples by impedance spectroscopy at temperature T= 100 – 400 °C are given. The usual representation (i.e. Z” vs. Z’ where Z’ and Z” are the real and imaginary parts of the complex impedance, respectively) as well as the alternative representations of the impedance measurement (electrical modulus representation) was used to interpret the impedance spectra of BiNbO4 ceramics in order to obtain separate contributions of the bulk, grain boundary and electrode processes. The Kramers-Kronig data validation test was employed in the impedance data analysis. Experimental data of impedance spectroscopy were fitted to the corresponding equivalent circuit using the complex non-linear least squares method. Agreement between experimental and simulated data was established.

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