Does capillary evaporation limit the accessibility of nonaqueous electrolytes to the ultrasmall pores of carbon electrodes?

Liu, Kun; Zhang, Pengfei; Wu, Jianzhong

doi:10.1063/1.5064360

Cited by 15 publications

(12 citation statements)

References 61 publications

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“…The critical pore width is shown dependent with the properties of the electrolyte [36], thus the capillary evaporation of ionic liquids with larger dispersion force may happen in the given silt pore. It should be noted that the ions density discontinuously jumps to a larger value at 1.16 V in the case of ε ij = 2 k B T, indicating a first-order phase transition [36]. The phase transition can be understood as the balance between the electrostatic correlations and the volume exclusion interaction.…”

Section: Resultsmentioning

confidence: 96%

“…From MD simulations, scientists also found that there exists a critical pore widthin wetting the neutral pore [35]. The critical pore width is shown dependent with the properties of the electrolyte [36], thus the capillary evaporation of ionic liquids with larger dispersion force may happen in the given silt pore. It should be noted that the ions density discontinuously jumps to a larger value at 1.16 V in the case of ε ij = 2 k B T, indicating a first-order phase transition [36].…”

Section: Resultsmentioning

confidence: 99%

“…A simple coarse-grained model based on Lennard-Jones monomers showed that the dispersion force plays a critical role in the "camel-shaped" differential capacitance behavior observed experimentally [32][33][34]. Moreover, an extraordinary increase in capacitance was found derived from the thermodynamic response in both RTILs [35,36] and RTILs plus solvent mixtures [37][38][39]. Owing to the significance of dispersion force on EDLC performance, more effort should be devoted to investigate the phase behavior and charging mechanism of RTILs with different dispersion force in nanoconfinement, which will benefit the design of RTILs electrolytes.…”

Section: Introductionmentioning

confidence: 89%

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Theoretical Insights into the Structures and Capacitive Performances of Confined Ionic Liquids

et al. 2020

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Room-temperature ionic liquids (RTILs) together with nano-porous electrodes are the most promising materials for supercapacitors and batteries. Many theoretical works have addressed the structures and performances of RTILs inside nanopores. However, only limited attention has been given to how the dispersion forces of RTILs influence the behavior of ions inside the slit pores. Toward this aim, we investigate the effects of various dispersion forces between ions on the macroscopic structures in nanoconfinement and the capacitance performance of supercapacitors by the classical density functional theory (CDFT). The results show that the dispersion force can significantly change the mechanism of the charging process and even the shape of differential capacitance curves. In addition, the voltage-dependent structures of RTILs with appropriate dispersion force appears in a given silt pore, which leads to extremely high capacitance and enhances the energy storage density. We hope that this work could further offer guidance for the optimizing of electrolytes for electrical double layer capacitors, like tuning the dispersion force between ions by adding/removing certain chemical groups on the cations and anions of RTILs.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 89%

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Theoretical Insights into the Structures and Capacitive Performances of Confined Ionic Liquids

et al. 2020

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“…The same mechanisms studied here enter into the partitioning of nonaqueous electrolytes (ionic liquids) into nanopores [10][11][12][13], a topic of great current scientific and industrial interest, although the physical system parameters will take on different values compared to aqueous electrolytes. The theoretical approach we develop is general enough to be employed for both types of systems.…”

Section: Introductionmentioning

confidence: 86%

“…We recall that this previous work predicts that the confinement of a common mineral salt to a nanopore can lead to an ionic liquid-vapor phase transition at room temperature, in contrast to what occurs in the bulk (for which the theoretical transition temperature is predicted to be far below freezing and therefore unphysical). In contrast to most studies of nonaqueous electrolytes (ionic liquids), where the shift in vapor-liquid coexistence induced by confinement is studied in the density-temperature plane [10], we work at room temperature and investigate how ionic vapor-liquid coexistence is modified by the nanopore radius and bulk reservoir concentration.…”

Section: Introductionmentioning

confidence: 99%

Competition between Born solvation, dielectric exclusion, and Coulomb attraction in spherical nanopores

2021

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The recent measurement of a very low dielectric constant, , of water confined in nanometric slit pores leads us to reconsider the physical basis of ion partitioning into nanopores. For confined ions in chemical equilibrium with a bulk of dielectric constant b > , three physical mechanisms, at the origin of ion exclusion in nanopores, are expected to be modified due to this dielectric mismatch: dielectric exclusion at the water-pore interface (with membrane dielectric constant, m < ), the solvation energy related to the difference in Debye-Hückel screening parameters in the pore, κ, and in the bulk κ b , and the classical Born solvation self-energy proportional to −1 − −1 b . Our goal is to clarify the interplay between these three mechanisms and investigate the role played by the Born contribution in ionic liquid-vapor (LV) phase separation in confined geometries. We first compute analytically the potential of mean force (PMF) of an ion of radius R i located at the center of a nanometric spherical pore of radius R. Computing the variational grand potential for a solution of confined ions, we then deduce the partition coefficients of ions in the pore versus R and the bulk electrolyte concentration ρ b . We show how the ionic LV transition, directly induced by the abrupt change of the dielectric contribution of the PMF with κ, is favored by the Born self-energy and explore the decrease of the concentration in the pore with both in the vapor and liquid states. Phase diagrams are established for various parameter values and we show that a signature of this phase transition can be detected by monitoring the total osmotic pressure as a function of R. For charged nanopores, these exclusion effects compete with the electrostatic attraction that imposes the entry of counterions into the pore to enforce electroneutrality. This study will therefore help in deciphering the respective roles of the Born self-energy and dielectric mismatch in experiments and simulations of ionic transport through nanopores.

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Phase behavior of ionic fluid in charged confinement: An associating polymer density functional theory study

Cheng,

Xu,

Wang

et al. 2024

AIChE Journal

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With the rapid advancement of the new energy industry, porous electrode materials and complex electrolytes have gained widespread usage. Electrolytes exhibit distinctive phase behavior when subjected to the combined influence of confined space and electric fields. However, the measurement and prediction of such phase behavior encounter significant challenges. Consequently, numerous theoretical tools have been employed to establish models for phase equilibrium calculations. Nevertheless, current research in this field has notable limitations and fails to address the confinement of space or complex polymer electrolytes. Considering these shortcomings, an associating polymer density functional theory (PDFT) was developed by modifying excess free energy. This study examines the phase behavior of electrolytes with various chain lengths within diverse confined slits, revealing that the confinement effect and fluid tail chains can narrow the phase diagram. Additionally, a linear correlation between the electric field strength and the phase equilibrium offset has been identified, and a quantitative relationship is derived. The results of this investigation contribute to a deeper comprehension of complex fluid phase behavior and guide the design of electrochemical devices.

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Does capillary evaporation limit the accessibility of nonaqueous electrolytes to the ultrasmall pores of carbon electrodes?

Cited by 15 publications

References 61 publications

Theoretical Insights into the Structures and Capacitive Performances of Confined Ionic Liquids

Theoretical Insights into the Structures and Capacitive Performances of Confined Ionic Liquids

Competition between Born solvation, dielectric exclusion, and Coulomb attraction in spherical nanopores

Phase behavior of ionic fluid in charged confinement: An associating polymer density functional theory study

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