General Trend of Negative Transference Number in Li Salt/Ionic Liquid Mixtures

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Transference Number ◽  
Liquid Mixtures ◽  
Single Linkage ◽  
Self Diffusion ◽  
Wide Range ◽  
Single Linkage Cluster ◽  
Concentrated Solution ◽  
The One ◽  
Dynamics Simulations

We show that strong cation-anion interactions in a wide range of lithium-salt/ionic liquid mixtures result in a negative lithium transference number, using molecular dynamics simulations and rigorous concentrated solution theory. This behavior fundamentally deviates from the one obtained using self-diffusion coefficient analysis and agrees well with experimental electrophoretic NMR measurements, which accounts for ion correlations. We extend these findings to several ionic liquid compositions. We investigate the degree of spatial ionic coordination employing single-linkage cluster analysis, unveiling asymmetrical anion-cation clusters. Additionally, we formulate a way to compute the effective lithium charge that corresponds to and agrees well with electrophoretic measurements and show that lithium effectively carries a negative charge in a remarkably wide range of chemistries and concentrations. The generality of our observation has significant implications for the energy storage community, emphasizing the need to reconsider the potential of these systems as next generation battery electrolytes.<br>

General Trend of Negative Transference Number in Li Salt/Ionic Liquid Mixtures

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Transference Number ◽  
Liquid Mixtures ◽  
Single Linkage ◽  
Self Diffusion ◽  
Wide Range ◽  
Single Linkage Cluster ◽  
Concentrated Solution ◽  
The One ◽  
Dynamics Simulations

We show that strong cation-anion interactions in a wide range of lithium-salt/ionic liquid mixtures result in a negative lithium transference number, using molecular dynamics simulations and rigorous concentrated solution theory. This behavior fundamentally deviates from the one obtained using self-diffusion coefficient analysis and agrees well with experimental electrophoretic NMR measurements, which accounts for ion correlations. We extend these findings to several ionic liquid compositions. We investigate the degree of spatial ionic coordination employing single-linkage cluster analysis, unveiling asymmetrical anion-cation clusters. Additionally, we formulate a way to compute the effective lithium charge that corresponds to and agrees well with electrophoretic measurements and show that lithium effectively carries a negative charge in a remarkably wide range of chemistries and concentrations. The generality of our observation has significant implications for the energy storage community, emphasizing the need to reconsider the potential of these systems as next generation battery electrolytes.<br>

Transport Anomalies Emerging from Strong Correlation in Ionic Liquid Electrolytes

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Nathan Craig ◽  
Jake Christensen ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Species Interactions ◽  
Clustering Algorithm ◽  
Experimental Studies ◽  
Transference Number ◽  
Liquid Electrolyte ◽  
Total Conductivity ◽  
Single Linkage ◽  
Ionic Liquid Electrolyte ◽  
Dynamics Simulations

<div>Recent works on ionic liquid electrolyte systems motivate the present study of transport regimes where strong species interactions result in significant correlations and deviations from ideal solution behaviour. In order to obtain a complete description of transport in these systems we use rigorous concentrated solution theory coupled with molecular dynamics simulations, beyond the commonly used uncorrelated Nernst-Einstein equation. As a case study, we investigate the NaFSI - Pyr<sub>13</sub>\FSI room temperature ionic liquid electrolyte. When fully accounting for intra- and inter-species correlation, an anomalously low and even negative transference number emerges for NaFSI molar fractions lower than 0.2, emphasising that strong ion-ion coupling in the electrolyte can significantly impact the rate performance of the cell. With increasing concentration the transference number monotonically increases, approaching unity, while the total conductivity decreases as the system transitions to a state resembling a single-ion solid-state electrolyte. The degree of spatial ionic association is explored further by employing a variant of unsupervised single-linkage clustering algorithm. Using this combination of numerical techniques we examine the microscopic mechanisms responsible for the trade-off between key electrolyte transport properties, previously overlooked in both computational and experimental studies.</div>

Transport Anomalies Emerging from Strong Correlation in Ionic Liquid Electrolytes

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Nathan Craig ◽  
Jake Christensen ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Species Interactions ◽  
Clustering Algorithm ◽  
Experimental Studies ◽  
Transference Number ◽  
Liquid Electrolyte ◽  
Total Conductivity ◽  
Single Linkage ◽  
Ionic Liquid Electrolyte ◽  
Dynamics Simulations

<div>Recent works on ionic liquid electrolyte systems motivate the present study of transport regimes where strong species interactions result in significant correlations and deviations from ideal solution behaviour. In order to obtain a complete description of transport in these systems we use rigorous concentrated solution theory coupled with molecular dynamics simulations, beyond the commonly used uncorrelated Nernst-Einstein equation. As a case study, we investigate the NaFSI - Pyr<sub>13</sub>\FSI room temperature ionic liquid electrolyte. When fully accounting for intra- and inter-species correlation, an anomalously low and even negative transference number emerges for NaFSI molar fractions lower than 0.2, emphasising that strong ion-ion coupling in the electrolyte can significantly impact the rate performance of the cell. With increasing concentration the transference number monotonically increases, approaching unity, while the total conductivity decreases as the system transitions to a state resembling a single-ion solid-state electrolyte. The degree of spatial ionic association is explored further by employing a variant of unsupervised single-linkage clustering algorithm. Using this combination of numerical techniques we examine the microscopic mechanisms responsible for the trade-off between key electrolyte transport properties, previously overlooked in both computational and experimental studies.</div>

A theoretical study on mixtures of amino acid-based ionic liquids

2018 ◽  
Vol 20 (15) ◽  
pp. 10213-10223 ◽  
Author(s):  
Cesar Herrera ◽  
Mert Atilhan ◽  
Santiago Aparicio
Keyword(s):  
Molecular Dynamics ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Amino Acid ◽  
Molecular Dynamics Simulations ◽  
Theoretical Study ◽  
Liquid Mixtures ◽  
Microscopic Level ◽  
Dynamics Simulations

Ionic liquid mixtures containing amino acid anions are studied at the microscopic level using molecular dynamics simulations.

scholarly journals Determining the composition of the vacuum–liquid interface in ionic-liquid mixtures

2018 ◽  
Vol 206 ◽  
pp. 497-522 ◽  
Author(s):  
E. J. Smoll ◽  
M. A. Tesa-Serrate ◽  
S. M. Purcell ◽  
L. D’Andrea ◽  
D. W. Bruce ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Ionic Liquid ◽  
Molecular Dynamics Simulations ◽  
Liquid Mixtures ◽  
Liquid Interface ◽  
Liquid Interfaces ◽  
Dynamics Simulations

The vacuum–liquid interfaces of a number of ionic-liquid mixtures have been investigated using a combination of RAS-LIF, selected surface tension measurements, and molecular dynamics simulations.

scholarly journals On the Transport Properties of Li-TFSI Water-in-Salt Electrolytes

2019 ◽  
Author(s):  
Zhujie Li ◽  
Roza Bouchal ◽  
Trinidad Mendez-Morales ◽  
Anne-Laure Rollet ◽  
Cecile Rizzi ◽  
...  
Keyword(s):  
Force Field ◽  
Transport Properties ◽  
Transport Number ◽  
Lithium Ion ◽  
Ionic Species ◽  
Self Diffusion ◽  
New Family ◽  
The One ◽  
Dynamics Simulations ◽  
Percolating Network

Water-in-salts are a new family of electrolytes that may allow the development of aqueous Li-ion batteries. They have a structure which is reminiscent of the one of ionic liquids, and they are characterized by a large concentration of ionic species. In this work we study their transport properties and how they evolve with concentration by using molecular dynamics simulations. We first focus on the choice of the force field. By comparing the simulated viscosities and self diffusion coefficients with experimental measurements, we select a set of parameters that reproduces well the transport properties. We then use the selected force field to study in detail the variations of the self and collective diffusivities of all the species as well as the transport number of the lithium ion. We show that correlation between ions and water play an important role over the whole concentration range. In the water-in-salt regime, the anions form a percolating network which reduces the cation-anion correlations and leads to rather large values for the transport number compared to other standard electrolytes.

scholarly journals Exploring the bulk-phase structure of ionic liquid mixtures using small-angle neutron scattering

2018 ◽  
Vol 206 ◽  
pp. 265-289 ◽  
Author(s):  
Christopher P. Cabry ◽  
Lucía D’Andrea ◽  
Karina Shimizu ◽  
Isabelle Grillo ◽  
Peixun Li ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ionic Liquid ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Liquid Mixture ◽  
Liquid Mixtures ◽  
System P ◽  
Dynamics Simulations ◽  
Mixture System

Small-angle neutron scattering experiments, supported by molecular dynamics simulations, have been performed on a range of compositions of the [C2mim]1−x[C12mim]x[Tf2N] ionic liquid mixture system.

scholarly journals Short-time diffusion of charge-stabilized colloidal particles: generic features

2010 ◽  
Vol 43 (5) ◽  
pp. 970-980 ◽  
Author(s):  
Marco Heinen ◽  
Peter Holmqvist ◽  
Adolfo J. Banchio ◽  
Gerhard Nägele
Keyword(s):  
Experimental Data ◽  
Colloidal Particles ◽  
Stokesian Dynamics ◽  
Self Diffusion ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Dynamics Simulations ◽  
Short Time ◽  
Hydrodynamic Function

Analytical theory and Stokesian dynamics simulations are used in conjunction with dynamic light scattering to investigate the role of hydrodynamic interactions in short-time diffusion in suspensions of charge-stabilized colloidal particles. The particles are modeled as solvent-impermeable charged spheres, repelling each otherviaa screened Coulomb potential. Numerical results for self-diffusion and sedimentation coefficients, as well as hydrodynamic and short-time diffusion functions, are compared with experimental data for a wide range of volume fractions. The theoretical predictions for the generic behavior of short-time properties obtained from this model are shown to be in full accord with experimental data. In addition, the effects of microion kinetics, nonzero particle porosity and residual attractive forces on the form of the hydrodynamic function are estimated. This serves to rule out possible causes for the strikingly small hydrodynamic function values determined in certain synchrotron radiation experiments.

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