Ion Association Constants for Lithium Ion Battery Electrolytes from First-Principles Quantum Chemistry

Self, Julian; Fong, Kara D.; Logan, Eric; Persson, Kristin A.

doi:10.1149/2.1061914jes

Cited by 6 publications

(4 citation statements)

References 65 publications

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“…In addition to these effects, electrolyte performance depends on interactions between the non-coordinated ion and the solvent, and cation-anion interactions. 17,18 At the continuum level, ion transport in binary electrolytes, which are composed of a solvent and two ions, is governed by three Stefan-Maxwell diffusion coefficients that quantify inverse frictional interactions between the cation and the solvent, , 0 D + the anion and the solvent, , 0 Dand the cation and the anion, , D +-as well as a thermodynamic factor. 19 Methods to measure these quantities have been established in the literature and have been applied to several systems.…”

Section: List Of Symbols Amentioning

confidence: 99%

Impact of Frictional Interactions on Conductivity, Diffusion, and Transference Number in Ether- and Perfluoroether-Based Electrolytes

Grundy

Shah

Nguyen

et al. 2020

J. Electrochem. Soc.

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There is growing interest in fluorinated electrolytes due to their high-voltage stability. We use full electrochemical characterization based on concentrated solution theory to investigate the underpinnings of conductivity and transference number in tetraglyme/ LiTFSI mixtures (H4) and a fluorinated analog, C8-DMC, mixed with LiFSI (F4). Conductivity is significantly lower in F4 than in H4, and F4 exhibits negative cation transference numbers, while that of H4 is positive at most salt concentrations. By relating Stefan-Maxwell diffusion coefficients, which quantify ion-solvent and cation-anion frictional interactions, to conductivity and transference number, we determine that at high salt concentrations, the origin of differences in transference number is differences in anion-solvent interactions. We also define new Nernst-Einstein-like equations relating conductivity to Stefan-Maxwell diffusion coefficients. In H4 at moderate to high salt concentrations, we find that all molecular interactions must be included. However, we demonstrate another regime, in which conductivity is controlled by cation-anion interactions. The applicability of this assumption is quantified by a pre-factor, , b +-which is similar to the "ionicity" pre-factor that is often included in the Nernst-Einstein equation. In F4, b +-is unity at all salt concentrations, indicating that ionic conductivity is entirely controlled by the Stefan-Maxwell diffusion coefficient quantifying cation-anion frictional interactions.

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Section: List Of Symbols Amentioning

confidence: 99%

Impact of Frictional Interactions on Conductivity, Diffusion, and Transference Number in Ether- and Perfluoroether-Based Electrolytes

Grundy

Shah

Nguyen

et al. 2020

J. Electrochem. Soc.

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“…The improvements in predictions of structural and transport properties of such electrolytes were achieved with many-body polarizable force fields − or the ion charge renormalization method based on the semiempirical “charge titration” . The predictions of equilibrium population of ionic species and the dissociation constants were recently improved using rescaling of dielectric constants of solvents caused by formation of solute dipolar aggregates (“redissociation”). ,, However, these relatively cheap computational recipes suffer from the lack of consistency caused by problems of finding a self-consistent solution for coupled ε s = ε s (ρ i ) and ρ i = ρ i (ε s ), where ε s and ρ i are the dielectric permittivity of a solution and the ion–ion distribution function, respectively. Moreover, because the main focus of QM-PCM protocol based methods is on finding the energy difference Δ G dis between bound and dissociated states, the discussion of equilibrium population of ion pairs remains incomplete as the stability of that population implies kinetic barriers (Figure S6) that separate these states whose evaluation is beyond the scope of these methods.…”

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confidence: 99%

Ion Solvation Engineering: How to Manipulate the Multiplicity of the Coordination Environment of Multivalent Ions

Baskin

2020

J. Phys. Chem. Lett.

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Free energy analysis of solvation structures of free divalent cations, their ion-pairs and neutral aggregates in low dielectric solvents reveals the multiplicity of thermodynamically stable cation solvation configurations and identifies the micro-and macroscopic factors responsible for this phenomenon. Specifically, we show the role of ion-solvent interactions and solvent mixtures in determining the cation solvation free energy landscapes. We show that it is the entropic contribution of solvent degrees of freedom that is responsible for the solvation multiplicity, and the mutual balance between enthalpic and entropic forces or their concerted contributions is what ultimately defines the most stable ion solvation configuration and creates new ones. We show general consequences of ion solvation multiplicity on thermodynamics of complex electrolytes, specifically in the context of homogeneous or interfacial charge transfer. Identified factors and their interplay provide a pathway to formulation of solvation design rules that can be used to control bulk solvation, interfacial chemistry and charge transfer. Our findings also suggest experimentally testable predictions.

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“…The anions's radii were calculated in a similar fashion, in this case without an explicit first solvation shell as anion-solvent short range interactions are approximated here as negligible. 42,52 We note that preferential solvation of cations over anions is an active research topic. 53 As expected, the values for − PF 6 found were very close to the "bare" ionic radii.…”

Section: Various Radii Are Shown In Tablementioning

confidence: 99%

A Theoretical Model for Computing Freezing Point Depression of Lithium-Ion Battery Electrolytes

Self

Bergstrom

Fong

et al. 2021

J. Electrochem. Soc.

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Reliable prediction of freezing point depression in liquid electrolytes will accelerate the development of improved Li-ion batteries which can operate in low temperature environments. In this work we establish a computational methodology to calculate activity coefficients and liquidus lines for battery-relevant liquid electrolytes. Electronic structure methods are used in conjunction with classical molecular dynamics simulations and theoretical expressions for Born solvation energy, ion-atmosphere effects from Debye-Hückel theory and solvent entropic effects. The framework uses no a priori knowledge beyond neat solvent properties and the concentration of salt. LiPF 6 in propylene carbonate (PC), LiPF 6 in dimethyl carbonate (DMC) and LiClO4 in DMC are investigated up to 1 molal with accuracy better than 3◦C when compared to experimental freezing point measurements. We find that the difference in freezing point depression between the propylene carbonate-based electrolyte and the dimethyl cabonate electrolytes originates from the difference in the solvent dielectric constant.

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Ion Association Constants for Lithium Ion Battery Electrolytes from First-Principles Quantum Chemistry

Cited by 6 publications

References 65 publications

Impact of Frictional Interactions on Conductivity, Diffusion, and Transference Number in Ether- and Perfluoroether-Based Electrolytes

Impact of Frictional Interactions on Conductivity, Diffusion, and Transference Number in Ether- and Perfluoroether-Based Electrolytes

Ion Solvation Engineering: How to Manipulate the Multiplicity of the Coordination Environment of Multivalent Ions

A Theoretical Model for Computing Freezing Point Depression of Lithium-Ion Battery Electrolytes

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