Potential and Current Distribution in Electrochemical Cells: Interpretation of the Half‐Cell Voltage Measurements as a Function of Reference‐Electrode Location

Existing analytical solutions for the long-time chronoamperometric current response at an inlaid disk electrode are restricted to diffusion-limited currents due to extreme polarisation or reversible kinetics at the electrode surface. In this article, we derive an approximate analytical solution for the long-time-dependent current when the kinetics of the redox reaction at the electrode surface are quasi-reversible and the diffusion coefficients of the oxidant and reductant are different. We also detail a novel method for calculating the steady-state current. We show that our new method encapsulates and extends the existing solutions, and agrees with numerically simulated currents.

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“…Using a Green's function, the solution for C ss O can be expressed in terms of the flux, q(β; r), defined in (19c), as [14,38]:…”

Section: Steady-state Problemmentioning

confidence: 99%

The long-time chronoamperometric current at an inlaid disk electrode

Bell

Howell

Stone

et al. 2012

Journal of Electroanalytical Chemistry

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“…The difference between the governing equations for charge and those for discharge is that the signs in front of J c in (1) and (2) are opposite according to the previous studies [22]. The current density c J is a function of the potential difference between positive and negative electrodes and is expressed as [23,24]:…”

Section: Battery Electric Model and Problem Formulationmentioning

confidence: 99%

“…However, it requires exhaustive enumeration to search the optimal value of x . Therefore, it The current density J c is a function of the potential difference between positive and negative electrodes and is expressed as [23,24]:…”

Section: Battery Electric Model and Problem Formulationmentioning

confidence: 99%

Multi-Scale Parameter Identification of Lithium-Ion Battery Electric Models Using a PSO-LM Algorithm

Shen

2017

Energies

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This paper proposes a multi-scale parameter identification algorithm for the lithium-ion battery (LIB) electric model by using a combination of particle swarm optimization (PSO) and Levenberg-Marquardt (LM) algorithms. Two-dimensional Poisson equations with unknown parameters are used to describe the potential and current density distribution (PDD) of the positive and negative electrodes in the LIB electric model. The model parameters are difficult to determine in the simulation due to the nonlinear complexity of the model. In the proposed identification algorithm, PSO is used for the coarse-scale parameter identification and the LM algorithm is applied for the fine-scale parameter identification. The experiment results show that the multi-scale identification not only improves the convergence rate and effectively escapes from the stagnation of PSO, but also overcomes the local minimum entrapment drawback of the LM algorithm. The terminal voltage curves from the PDD model with the identified parameter values are in good agreement with those from the experiments at different discharge/charge rates.

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“…As recommended from a modeling study by Newman and Tiedemann, the best RE location for reliable measurements is between the WE and the CE and reasonably close to the tabs. 3 Accordingly, Dollé et al inserted a microRE made up of a small piece of a plastic Li 4 Ti 5 O 12 electrode adhered to an isolated copper wire and inserted between the main electrodes and then performed reliable EIS measurements on a plastic MCMB/LiCoO 2 pouch cell. 4 A similar design was used in other studies throughout the literature.…”

Section: Electrochemical Impedance Spectroscopy (Eis) Proves a Powerfulmentioning

confidence: 99%

Measurements and Simulations of Electrochemical Impedance Spectroscopy of a Three-Electrode Coin Cell Design for Li-Ion Cell Testing

Delacourt

Ridgway

Srinivasan

et al. 2014

J. Electrochem. Soc.

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A 2-D mathematical model of the secondary current distribution in a three-electrode cell is used in order to understand distortion of impedance spectra influenced by the position of the reference electrode (RE) in a cell when one electrode extends past the other. The cell setup consists of a modified coin cell, i.e., working and counter electrodes face each other, and a RE is positioned behind the counter electrode (CE) that has a small hole in it to allow for electrolyte access. This configuration shows large distortion of WE and CE impedance data when taken against the RE. The WE/RE impedance is underestimated and contains a negative impedance contribution from the CE whereas the CE/RE impedance is overestimated and contains a positive impedance contribution from the WE. As supported by simulations, the distortions arise from a radial ionic current flowing from the WE toward the edge of the CE hole, and are minimized through an increase of the electrolyte conductivity, an increase of the separator thickness, or a decrease of the hole size in the CE. The distortions nearly disappear when an additional hole is included in the WE that is perfectly aligned with the hole in the CE. These results should be considered whenever designing a 3-electrode cell where the RE is not sandwiched between the two other electrodes. Electrochemical impedance spectroscopy (EIS) proves a powerfultechnique to analyze limiting phenomena in Li-ion batteries. Analysis of EIS spectra allows in principle to separate out and quantify the various contributions to the overall cell impedance, such as charge transfer at the solid/electrolyte interfaces, diffusion, electrolyte resistance, etc. In order to separate out the effects at anode and cathode, a reference electrode (RE) is introduced in the cell, and impedance is measured between the working electrode (WE) and the RE and between the counter electrode (CE) and the RE. Positioning of the reference electrode turns out to be non-trivial, because for particular three-electrode cell configurations, EIS spectra exhibit distortions and meaningful analysis of the data is not straightforward.This problem has long been pointed out and investigated in the fuelcell community. In fuel cells, the electrolyte membrane layer usually extends past that of the electrodes to limit gas mixing, and the RE is positioned at one side of the electrolyte layer, in an area which is not covered with the electrodes. Distortion of the EIS signal was shown to arise whenever the WE and CE are misaligned or are of different surface area, but it is observed as well in the absence of geometrical mismatch, whenever the time constants of the two electrodes differ substantially from each other. Readers are invited to refer to Refs. 1 and 2 for an extensive modeling and experimental study on this type of cell. Other modeling works are detailed as well in the introduction of those references.To our knowledge, there have been many less studies for the case of batteries. As recommended from a modeling study by Newman and Tiedema...

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Potential and Current Distribution in Electrochemical Cells: Interpretation of the Half‐Cell Voltage Measurements as a Function of Reference‐Electrode Location

Cited by 143 publications

References 2 publications

The long-time chronoamperometric current at an inlaid disk electrode

The long-time chronoamperometric current at an inlaid disk electrode

Multi-Scale Parameter Identification of Lithium-Ion Battery Electric Models Using a PSO-LM Algorithm

Measurements and Simulations of Electrochemical Impedance Spectroscopy of a Three-Electrode Coin Cell Design for Li-Ion Cell Testing

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