Estimation of Diffusion Coefficient of Lithium in Carbon Using AC Impedance Technique

A characterization of the ionic conduction of the active layer of a polymer electrolyte membrane fuel cell (PEMFC) cathode by ac impedance measurement at open-circuit potential conditions was conducted. Porous electrode theory was used to derive a compact equation, ∂2normalΦ̑2/∂y2+∂lnffalse(yfalse)/∂y×∂normalΦ̑2/∂y−R/ffalse(yfalse)false(1+jnormalΩfalse)normalΦ̑2=0, to solve for the impedance response of a cathode at open-circuit potential conditions. This equation includes a parameter R, the ratio of an ionic resistance (evaluated at the active layer/membrane interface), to the total charge-transfer resistance of the active layer. The influence of an assumed ionic conductivity distribution profile ffalse(yfalse) on the error in the estimation of total double-layer capacitance of the active layer from the −1/false(ZnormalImωfalse) vs. ZnormalRe plot was also investigated in this work. The increase of ionic conductivity in the active layer of an air cathode with an increase in the ionomer loading was revealed from both impedance data and surface area measurements. A nonlinear parameter estimation method was used to extract the ionic resistance from the high-frequency region of the impedance data at open-circuit potential conditions. The assumed ionic conductivity distribution profile in the active layer was found to vary with ionomer loadings. © 2003 The Electrochemical Society. All rights reserved.

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“…10. To determine the accuracy of values obtained for this parameter, a 95% confidence interval 10,[13][14][15][16] for (l/ 0 ) was found by using…”

Section: Resultsmentioning

confidence: 99%

Study of Ionic Conductivity Profiles of the Air Cathode of a PEMFC by AC Impedance Spectroscopy

Guo

Cayetano²,

Tsou³

et al. 2003

J. Electrochem. Soc.

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“…On the other side, ion intercalation in the graphite atomic layers produces and extra increase of electrode capacitance. The combination of these two contributions has been known for a long time and has been used to build supercapacitors and battery electrodes [13][14][15][16]. In our specific case, microporosity provides a large area accessible for the growth of an electrochemically active biofilm, which is needed to obtain large currents.…”

Section: Analysis Of Bioanode Performance At Different Anode Potentialsmentioning

confidence: 99%

Analysis of bio-anode performance through electrochemical impedance spectroscopy

Heijne

Schaetzle²,

Giménez

et al. 2015

Bioelectrochemistry

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In this paper we studied the performance of bioanodes under different experimental conditions using polarization curves and impedance spectroscopy. We have identified that the large capacitances of up to 1 mF·cm −2 for graphite anodes have their origin in the nature of the carbonaceous electrode, rather than the microbial culture. In some cases, the separate contributions of charge transfer and diffusion resistance were clearly visible, while in other cases their contribution was masked by the high capacitance of 1 mF·cm −2 . The impedance data were analyzed using the basic Randles model to analyze ohmic, charge transfer and diffusion resistances. Increasing buffer concentration from 0 to 50 mM and increasing pH from 6 to 8 resulted in decreased charge transfer and diffusion resistances; lowest values being 144 Ω·cm 2 and 34 Ω·cm 2 , respectively. At acetate concentrations below 1 mM, current generation was limited by acetate. We show a linear relationship between inverse charge transfer resistance at potentials close to open circuit and saturation (maximum) current, associated to the ButlerVolmer relationship that needs further exploration.

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“…Numerous experimental methods were developed to determine them, e.g., potentiostatic intermittent titration technique (PITT), [6][7][8][9][10] galvanostatic intermittent titration technique (GITT), [11][12][13] cyclic voltammetry (CV), 14 and electrochemical impedance spectroscopy (EIS). 15,16 Depending on the method, a wide range of solid diffusion coefficients is reported in the literature for a similar AM. 17 For each technique, a physical model (with either a numerical or an analytic solution) is used to fit the system response to an out-of-equilibrium perturbation and to adjust the parameters.…”

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confidence: 99%

Guidelines for the Analysis of Data from the Potentiostatic Intermittent Titration Technique on Battery Electrodes

Malifarge

Delobel

Delacourt

2017

J. Electrochem. Soc.

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The Li-ion battery (LIB) modeling community needs to rely on a vast bank of measured Li-ion cell parameters. Most of them are determined by routine experiments but some can solely be estimated by fitting a model to a well-designed experiment. For instance, the determination of the lithium chemical diffusion coefficient has been the focus of numerous studies. Specific techniques have been proposed for its estimation, e.g., the potentiostatic intermittent titration technique (PITT), the galvanostatic intermittent titration technique (GITT), the cyclic voltammetry (CV), and the electrochemical impedance spectroscopy (EIS). Our study focuses on the PITT so as to provide guidelines for experimental measurements and corresponding data analysis. The validity of underlying assumptions of published analytic solutions used to fit PITT data is assessed using a pseudo-2D (P2D) model. Among the tested assumptions are the drop of the porous-electrode effect, of the particle size distribution and of the finite kinetics of Li insertion/de-insertion. Tests are also conducted to assess the error made on the chemical diffusion coefficient and reaction-rate constant determination by fitting 2-electrode simulated data with a 3-electrode P2D model. Lithium-ion battery (LIB) cell energy density has been greatly enhanced over the years owing to research in new materials and electrode engineering.1 Further improvement of LIB energy density is possible by packing more active material within the electrodes. However, doing this usually trades off with a power decrease as lithium-ion transport in the liquid phase becomes a major issue in thick and/or dense porous electrodes.2 Nonetheless, a compromise is still achievable through engineering of the electrode fabrication process, i.e., by tuning the electrode microstructure to optimize the ion and electron transport paths. This would decrease electrode nonuniformities that appear during cell operation, e.g., in terms of state of charge, liquidphase salt concentration, and solid/liquid-phase potentials.3 On this matter, LIB physical models prove an efficient tool to shed light on phenomena such as the development of concentration/potential gradients across the cell. Moreover, LIB models are tunable to the studied physics and cost effective compared to an experimental trial-and-error process, which makes them well-suited to determine parameters that optimize the porous-electrode design depending on the application. It also helps to assess the possible occurrence of unwanted phenomena such as Li metal plating. Among these models, the pseudo-2D (P2D) one introduced by Newman group in the early nineties is a widely used continuum model. 4,5 It relies on porous-electrode and concentrated-solution theories. In this model, the porous electrode is described as the superposition of the liquid and solid phases that are defined by their respective volume fractions and the interfacial surface area. Electrode properties are averaged over volume elements that are small compared to the overall dimension of t...

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Estimation of Diffusion Coefficient of Lithium in Carbon Using AC Impedance Technique

Cited by 37 publications

References 17 publications

Study of Ionic Conductivity Profiles of the Air Cathode of a PEMFC by AC Impedance Spectroscopy

Study of Ionic Conductivity Profiles of the Air Cathode of a PEMFC by AC Impedance Spectroscopy

Analysis of bio-anode performance through electrochemical impedance spectroscopy

Guidelines for the Analysis of Data from the Potentiostatic Intermittent Titration Technique on Battery Electrodes

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