Determination of Mass Transfer Parameters and Ionic Association of LiPF<sub>6</sub>: Organic Carbonates Solutions

Krachkovskiy, Sergey A.; Bazak, J. David; Fraser, Sean; Halalay, Ion C.; Goward, Gillian R.

doi:10.1149/2.1531704jes

Cited by 55 publications

(119 citation statements)

References 27 publications

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“…Applying the IM technique to the data obtained from this experiment leads to negative values of the transference number t + (c) < 0 at large concentrations. For binary electrolytes based on lithium salts and neutral organic carbonates, such as the one used in our study, negative transference numbers are not possible [3,4]. However, negative values of lithium transference numbers can occur for lithium salt/ionic liquid ternary mixtures with two cations and common anion, as reported in [5].…”

Section: Introductionmentioning

confidence: 56%

The Effect of Ionic Aggregates on the Transport of Charged Species in Lithium Electrolyte Solutions

Richardson

Foster

Sethurajan

et al. 2018

J. Electrochem. Soc.

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In this investigation we focus on the problem of modelling the transport of the charged species (lithium ions) in electrolyte solutions with moderate and high salt concentrations (0.1M to >2M), and consider the Nernst-Planck equation as a model of such processes. First, using a combination of magnetic resonance imaging (MRI) and inverse modelling (IM) we demonstrate that at higher concentrations the Nernst-Planck equation requires negative transference numbers in order to accurately describe the concentration profiles obtained from experiments. The need for such a physically inconsistent constitutive relation indicates the loss of validity of the Nernst-Planck equation as a model for this process. Next we consider the formation of ion pairs and clusters as a possible effect responsible for the appearance of negative transference numbers and derive an extended version of the Nernst-Planck system which accounts for these additional species. However, a careful analysis of this model reveals that incorporation of ion-pairing effects into the modelling will not change the transference

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Section: Introductionmentioning

confidence: 56%

The Effect of Ionic Aggregates on the Transport of Charged Species in Lithium Electrolyte Solutions

Richardson

Foster

Sethurajan

et al. 2018

J. Electrochem. Soc.

Self Cite

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“…where H R =Haven ratio=1.72=1/0.58; R =ideal gas constant; T =temperature;

c_{L i P F_{6}}

=concentration of lithium salt.…”

Section: Resultsmentioning

confidence: 99%

Influence of the Formation Current Density on the Transport Properties of Galvanostatically Formed Model‐Type Solid Electrolyte Interphases

Kranz

Graubner

et al. 2019

Batteries & Supercaps

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During the production of commercial lithium-ion batteries, the solid electrolyte interphase (SEI) on the graphite particles of the negative electrode is typically formed through galvanostatic protocols with low current densities. Consequently, SEI formation is a time-consuming and rather expensive production step. In order to better understand the influence of the formation current density on the transport of ions and molecules across the SEI, we formed model-type SEIs on planar glassy carbon electrodes under galvanostatic control. In accordance with the expectations from electrochemical nucleation and growth theory, we find that the transport of both ions and molecule becomes slower with increasing formation current density. However, it is remarkable that the ion transport is slowed down more strongly than the molecule transport. We show that at high formation current densities of about À 71 μA cm À 2 , our model-type SEIs clearly exceed the area-specific resistance tolerable in commercial lithium-ion cells.

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“…The ratio of measured conductivity and the conductivity calculated from the Nernst-Einstein equation, known as the Haven ratio 10 , is frequently used as an estimate of the degree of dissociation. 11 Another approach, 12,13 again using the Nernst-Einstein equation, decomposes diffusivities into those of ions and ion pairs, the relative quantities of which yield the degree of dissociation in the dilute limit. The modified method described in the Theory section involves a similar approach, distinguishing ions from ion pairs, but incorporates concentrated solution theory and so is not limited to dilute conditions.…”

Section: Resultsmentioning

confidence: 99%

Evaluating Transport Properties and Ionic Dissociation of LiPF₆in Concentrated Electrolyte

Feng

Higa

Han

et al. 2017

J. Electrochem. Soc.

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The presence of lithium hexafluorophosphate (LiPF 6) ion pairs in carbonate-based electrolyte solutions is widely accepted in the field of battery electrolyte research and is expected to affect solution transport properties. No existing techniques are capable of directly quantifying salt dissociation in these solutions. Previous publications by others have provided estimates of dissociation degrees using dilute solution theory and pulsed field gradient nuclear magnetic resonance spectroscopy (PFG-NMR) measurements of self-diffusivity. However, the behavior of a concentrated electrolyte solution can deviate significantly from dilute solution theory predictions. This work, for the first time, instead uses Onsager-Stefan-Maxwell concentrated solution theory and the generalized Darken relation with PFG-NMR measurements to quantify the degrees of dissociation in electrolyte solutions (LiPF 6 in ethylene carbonate/diethyl carbonate, 1:1 by weight). At LiPF 6 concentrations ranging from 0.1M to 1.5M, the salt dissociation degree is found to range from 61% to 37%. Transport properties are then calculated through concentrated solution theory with corrections for these significant levels of ion pairing.

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Determination of Mass Transfer Parameters and Ionic Association of LiPF₆: Organic Carbonates Solutions

Cited by 55 publications

References 27 publications

The Effect of Ionic Aggregates on the Transport of Charged Species in Lithium Electrolyte Solutions

The Effect of Ionic Aggregates on the Transport of Charged Species in Lithium Electrolyte Solutions

Influence of the Formation Current Density on the Transport Properties of Galvanostatically Formed Model‐Type Solid Electrolyte Interphases

Evaluating Transport Properties and Ionic Dissociation of LiPF₆in Concentrated Electrolyte

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Determination of Mass Transfer Parameters and Ionic Association of LiPF6: Organic Carbonates Solutions

Cited by 55 publications

References 27 publications

The Effect of Ionic Aggregates on the Transport of Charged Species in Lithium Electrolyte Solutions

The Effect of Ionic Aggregates on the Transport of Charged Species in Lithium Electrolyte Solutions

Influence of the Formation Current Density on the Transport Properties of Galvanostatically Formed Model‐Type Solid Electrolyte Interphases

Evaluating Transport Properties and Ionic Dissociation of LiPF6in Concentrated Electrolyte

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Determination of Mass Transfer Parameters and Ionic Association of LiPF₆: Organic Carbonates Solutions

Evaluating Transport Properties and Ionic Dissociation of LiPF₆in Concentrated Electrolyte