Correlations from Ion Pairing and the Nernst-Einstein Equation

France‐Lanord, Arthur; Grossman, Jeffrey C.

doi:10.1103/physrevlett.122.136001

Cited by 133 publications

(197 citation statements)

References 32 publications

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“…If the dissociated cation is slower than the cluster, perhaps due to coordination between the cation and the polymer, then the net velocity of the cation will also be negative. [61,64,65]…”

Section: Ion Migrationmentioning

confidence: 99%

Diffusion and migration in polymer electrolytes

Choo

Halat

Villaluenga

et al. 2020

Progress in Polymer Science

118

113

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Mixtures of neutral polymers and lithium salts have the potential to serve as electrolytes in next-generation rechargeable Li-ion batteries. The purpose of this review is to expose the delicate interplay between polymer-salt interactions at the segmental level and macroscopic ion transport at the battery level. Since complete characterization of this interplay has only been completed in one system: mixtures of poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI), we focus on data obtained from this system. We begin with a discussion of the activity coefficient, followed by a discussion of six different diffusion coefficients: the Rouse motion of polymer segments is quantified by Dseg, the self-diffusion of cations and anions is quantified by Dself,+ and Dself,-, and the build-up of concentration gradients in electrolytes under an applied potential is quantified by Stefan-Maxwell diffusion coefficients, 0+ , 0− , and +−. The Stefan-Maxwell diffusion coefficients can be used to predict the velocities of the ions at very early times after an electric field is applied across the electrolyte. The surprising result is that 0− is negative in certain concentration windows. A consequence of this finding is that at these concentrations, both cations and anions are predicted to migrate toward the positive electrode at early times. We describe the controversies that surround this result. Knowledge of the Stefan-Maxwell diffusion coefficients enable prediction of the limiting current. We argue that the limiting current is the most important characteristic of an electrolyte. Excellent agreement between theoretical and experimental limiting current is seen in PEO/LiTFSI mixtures. What sequence of monomers that, when polymerized, will lead to the highest limiting current remains an important unanswered question. It is our hope that the approach presented in this review will guide the development of such polymers.

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“…If the dissociated cation is slower than the cluster, perhaps due to coordination between the cation and the polymer, then the net velocity of the cation will also be negative. [61,64,65]…”

Section: Ion Migrationmentioning

confidence: 99%

Diffusion and migration in polymer electrolytes

Choo

Halat

Villaluenga

et al. 2020

Progress in Polymer Science

118

113

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“…Unfortunately, computational approaches to probe such dynamical correlations require long simulations and are less statistically reliable. 72 In the absence of results characterizing the true conductivity, we base our discussion on the NE values and note that quantitative equivalence with experiments cannot be expected. The diffusivity is computed from the time-average meansquared displacement (MSD),…”

Section: Ion Mobilities and Conductivitiesmentioning

confidence: 99%

“…In system such as the ones considered in this study, we expect that the correlated motions involving the pairs Li + ‐TFSI − , Li + ‐ZI − , and TFSI − ‐ZI + to likely play an important role in determining the conductivity. Unfortunately, computational approaches to probe such dynamical correlations require long simulations and are less statistically reliable . In the absence of results characterizing the true conductivity, we base our discussion on the NE values and note that quantitative equivalence with experiments cannot be expected.…”

Section: Introductionmentioning

confidence: 99%

Ion transport mechanisms in salt‐doped polymerized zwitterionic electrolytes

Keith

Ganesan

2020

Journal of Polymer Science

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Polyzwitterions (polyZIs), macromolecules with repeating ampholytic monomers, are a novel class of materials with attractive properties for battery electrolytes. In this study, we probe the ion transport characteristics and underlying mechanisms in two salt‐doped (Li+‐TFSI−) polyZIs of similar composition with contrasting zwitterion (ZI) ionic organization: pendant monomers organized via backbone‐anion‐cation (B‐ZI−‐ZI+, Motif B) and backbone‐cation‐anion (B‐ZI+‐ZI−, Motif C). Within both Motifs B and C, the counterion of the pendant‐end ZI moiety shows higher mobility. Similarly, when comparing Li+ or TFSI− across motifs, it is seen that the respective pendant‐end counterion possesses higher mobility than its backbone‐adjacent counterpart. Furthermore, when comparing counterions to same‐position ZI moieties, TFSI− is seen to possess higher mobility than Li+ in each case, a result rationalized by invoking the lower interaction strength between the TFSI− and ZI+. Analysis of ion‐transport mechanisms demonstrate that the mobility of countercharges to the pendant‐end ZI moiety correlates with the ion‐association relaxation timescale, similar to ideas noted in polymerized ionic liquids in past studies. However, the mobility of countercharges to the backbone‐adjacent ZI moiety is shown to be correlated with a cage relaxation time, which incorporates the combined effects of frustrated motion due to the presence of the polymer backbone and pendant‐end ZI moiety and the higher mobility in a population of lightly ZI‐coordinated ions. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 578–588

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“…First, the NE relation severely underestimates the conductivity in SI water, as already observed in other SI systems 53 . At variance with these findings, when charge carriers of opposite signs coexist in an electrolyte, the short-range correlations among them may screen the amount of transported charge, thus determining a decrease of the electric conductivity with respect to the predictions of the NE approximation 54 . In the second place, the electrical conductivity in the FCC-SI phase is sensitively larger than in the BCC one, in contrast to the opposite trend displayed by hydrogen diffusivity, which are instead slightly smaller in the FCC phase, thus resulting in comparable predictions for the two phases of the NE approximation ( σ N E ).…”

Section: Discussionmentioning

confidence: 97%

Heat and charge transport in H2O at ice-giant conditions from ab initio molecular dynamics simulations

2020

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The impact of the inner structure and thermal history of planets on their observable features, such as luminosity or magnetic field, crucially depends on the poorly known heat and charge transport properties of their internal layers. The thermal and electric conductivities of different phases of water (liquid, solid, and super-ionic) occurring in the interior of ice giant planets, such as Uranus or Neptune, are evaluated from equilibrium ab initio molecular dynamics, leveraging recent progresses in the theory and data analysis of transport in extended systems. The implications of our findings on the evolution models of the ice giants are briefly discussed.

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Correlations from Ion Pairing and the Nernst-Einstein Equation

Cited by 133 publications

References 32 publications

Diffusion and migration in polymer electrolytes

Diffusion and migration in polymer electrolytes

Ion transport mechanisms in salt‐doped polymerized zwitterionic electrolytes

Heat and charge transport in H2O at ice-giant conditions from ab initio molecular dynamics simulations

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