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In this study, we presented a theoretical investigation focused on the free energy barriers associated with Na + intercalation in various negative electrode morphologies based on graphite immersed in the [Pyr 14 ][Tf 2 N] ionic liquid. Additionally, we explored the influence of triglyme on the co-intercalation process. Our findings reveal that larger interlayer distances effectively reduce the energy barrier for sodiation. However, this also promotes the intercalation of [Pyr 14 ] + ions and decreases the population of sodium-ions within the electrode. We observed the co-intercalation mechanism in all electrode morphologies, but the interlayer distance significantly impacts this behavior. Therefore, using electrode materials with interlayer distances slightly larger than those of graphite shows promise for enhancing Na + intercalation. Nevertheless, when designing the electrolyte, careful consideration should be given to the size and shape of the cation in the ionic liquid to prevent unintended intercalation events. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluoroalkoxyaluminate anion size and charge distribution weaken Na+[anion] pair. • The weak Na+[anion] pair decreases its lifetime improving Na+ transport. • Fluoroalkoxyaluminate anion-based electrolytes present a wide electrochemical window. Ionic liquids (ILs) are a promising class of materials because of their unique properties such as high electrochemical stability window and intrinsic conductive nature, which are desirable in the development of high-performance electrolytes for energy storage applications. However, the strong Coulombic interactions between cation and anion, which contributes to the high viscosity of the ILs, are the main bottleneck in their applications as electrolytes. Weakly coordinated anions-based ILs are a class of electrolytes with high degree of charge delocalization, which leads to weak ionic interactions and improves the ionic transport. Here, we have performed molecular dynamics simulations and density functional theory calculations of imidazolium and ammonium-based ionic liquids in different Na+ mole fractions comprising the weakly coordinated fluoroalkoxyaluminate anion ([Al(Ohfip) 4 ]−). The results have shown that the 0.8-scaled OPLS-AA based force field predicted the transport properties of neat systems with good accuracy. The Na+-[anion] pair structural and lifetime analysis suggest that the fluoroalkoxyaluminate promotes lower lifetimes and facilitates the mobility of Na+ in these systems. Although the cations provided similar transport and structural results for Na+, the theoretical electrochemical stability windows of the ammonium-derived ILs exhibited values above 5.0 eV, which indicates good performance for energy storage applications. [ABSTRACT FROM AUTHOR]

• Development of a coarse-grained force field for an ionic liquid-based electrolyte. • Simulations capture the concentration dependence sizes of [Nax[Anion]y]x−y aggregates. • Vehicular and hoping mechanisms of sodium-ion transport reproduced by the modeling. Sodium-ion batteries have a great potential for energy storage applications, however, its realization depends strongly on a deep atomistic understanding of the sodium-ion transport mechanisms, which is a key step to optimize its performance. A complete characterization of sodium-ion transport mechanism requires large time-scale calculations, which is a challenge even for classical atomistic force-field molecular dynamics simulations. Thus, in this work, we performed a calibration of a coarse-grained force-field to describe the thermodynamic and transport properties of sodium-ion for the particular case of cyanoborate-based ionic liquid using different molar fractions of sodium tetracyanoborate salt dissolved in 1-ethyl-3-methyl-imidazolium tetracyanoborate. The results from coarse-grained modeling were found to be in fair agreement with atomistic simulations and experimental data, and they captured concentration dependence of [Na x [Anion] y ] x − y aggregate sizes. In particular, two distinct populations of sodium-ions were identified inside the [Na x [Anion] y ] x − y aggregates: 1) a slow one in vehicular diffusion and 2) a fast one in hoping diffusion. Both of them contribute to sodium ion transport and occur preferentially at different sodium-ion concentrations. The present findings were obtained for a cyanoborate-based ionic liquid, however, we expect that our insights can be used to understand similar ionic liquids. [ABSTRACT FROM AUTHOR]