Classical molecular dynamics (MD) simulations and M06-2X hybrid density functional theory calculations have been performed to investigate the interaction of various nonaqueous organic electrolytes with Na+ ion in rechargeable Na-ion batteries. We evaluate trends in solvation behavior of seven common electrolytes namely pure carbonate solvents (ethylene carbonate (EC), vinylene carbonate (VC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC)) and four binary mixtures of carbonates (EC:PC, EC:DMC, EC:EMC, and EC:DEC). Thermochemistry calculations for the interaction of pure and binary mixtures of carbonate solvents with Na+ ion, Na+ ion coordinated with carbonate clusters obtained from molecular dynamics simulations, show that the formation of Na-carbonate complexes is exothermic and proceeds favorably. Based on the highest binding energy (ΔEb), enthalpy of solvation (ΔH(sol)), and Gibbs free energy of solvation (ΔG(sol)) values for the interaction of Na+ ion with carbonate solvents, our results conclusively show that pure EC and binary mixture of (EC:PC) are the best electrolytes for sodium-ion based batteries. Quantum chemical analyses are performed to understand the observed trends in ion solvation. Quantum theory of atoms in molecules (QTAIM) analysis shows that the interactions in Na-carbonate complexes are classified as a closed-shell (electrostatic) interaction. The localized molecular orbital energy decomposition analysis (LMO-EDA) also indicates that the electrostatic term (ΔEele) in the interaction energy between Na+ ion and carbonate solvents has the highest value and confirms the results of QTAIM about the electrostatic nature of Na+ ion interaction. The noncovalent interaction (NCI) plots indicate that the noncovalent interactions responsible for the formation of Na-carbonate complexes are strong to weak attractive interactions. Density of state (DOS) calculations show that the HOMO−LUMO energy gap in the EC, VC, PC, BC, DMC, EMC, and DEC increases as they interact with Na+ ion, although the HOMO−LUMO energy gap decreases with the addition of EC as an electrolyte additive to PC, DMC, and EMC. Calculated trends based on these quantum chemical calculations suggest that EC and binary mixture of EC:PC emerge as the best electrolytes in sodium-ion batteries, which is in excellent agreement with previously reported in silico experimental results

In this study, two types of ionic liquids (ILs) based on 1-butyl-3-methylimidazolium [Bmim] + and butyltrimethylammonium [Btma] + cations, paired to tetrafluoroborate [BF 4 ] − , hexafluorophosphate [PF 6 ] − , dicyanamide [DCA] − , and bis(trifluoromethylsilfonyl)imide [Tf 2 N] − anions, were chosen as adsorbates to investigate the influence of cation and anion type on the adsorption of ILs on the graphene surface. The adsorption process on the graphene surface (circumcoronene) was studied using M06-2X/cc-pVDZ level of theory. Empirical dispersion correction (D3) was also added to the M06-2X functional to investigate the effects of dispersion on the binding energy values. The graphene•••IL configurations, binding energies, and thermochemistry of IL adsorption on the graphene surface were investigated. Orbital energies, charge transfer behavior, the influence of adsorption on the hydrogen bond strength between cation and anion of ILs, and the significance of noncovalent interactions on the adsorption of ILs on the graphene surface were also considered. ChelpG analysis indicated that upon adsorption of ILs on the graphene surface the overall charge on the cation, anion, and graphene surface changes, enabled by the charge transfer that occurs between ILs and graphene surface. Orbital energy and density of states calculations also show that the HOMO−LUMO energy gap of ILs decreases upon adsorption on the graphene surface. Quantum theory of atoms in molecules analysis indicates that the hydrogen-bond strength between cation and anion in ILs decreases upon adsorption on the graphene surface. Plotting the noncovalent interactions between ILs and graphene surface shows the role and significance of cooperative π•••π, C−H•••π, and X•••π (X = N, O, F atoms from anions) interactions in the adsorption of ILs on the graphene surface. The thermochemical analysis also indicates that the free energy of adsorption (ΔG ads ) of ILs on the graphene surface is negative, and thus the adsorption occurs spontaneously.

Adaptive biasing force molecular dynamics simulations and density functional theory calculations were performed to understand the interaction of Li(+) with pure carbonates and ethylene carbonate (EC)-based binary mixtures. The most favorable Li carbonate cluster configurations obtained from molecular dynamics simulations were subjected to detailed structural and thermochemistry calculations on the basis of the M06-2X/6-311++G(d,p) level of theory. We report the ranking of these electrolytes on the basis of the free energies of Li-ion solvation in carbonates and EC-based mixtures. A strong local tetrahedral order involving four carbonates around the Li(+) was seen in the first solvation shell. Thermochemistry calculations revealed that the enthalpy of solvation and the Gibbs free energy of solvation of the Li(+) ion with carbonates are negative and suggested the ion-carbonate complexation process to be exothermic and spontaneous. Natural bond orbital analysis indicated that Li(+) interacts with the lone pairs of electrons on the carbonyl oxygen atom in the primary solvation sphere. These interactions lead to an increase in the carbonyl (C=O) bond lengths, as evidenced by a redshift in the vibrational frequencies [ν(C=O)] and a decrease in the electron density values at the C=O bond critical points in the primary solvation sphere. Quantum theory of atoms in molecules, localized molecular orbital energy decomposition analysis (LMO-EDA), and noncovalent interaction plots revealed the electrostatic nature of the Li(+) ion interactions with the carbonyl oxygen atoms in these complexes. On the basis of LMO-EDA, the strongest attractive interaction in these complexes was found to be the electrostatic interaction followed by polarization, dispersion, and exchange interactions. Overall, our calculations predicted EC and a binary mixture of EC/dimethyl carbonate to be appropriate electrolytes for Li-ion batteries, which complies with experiments and other theoretical results.

The adsorption of ionic liquids (ILs) on the hexagonal boron-nitride (h-BN) surface was studied at the M06-2X/ cc-pVDZ level of theory. Three types of ionic liquids based on 1-butyl-3-methylimidazolium [Bmim] + , 1-butylpyridinium [Bpy] + , and butyltrimethylammonium [Btma] + cations, paired with tetrafluoroborate [BF 4 ] − , hexafluorophosphate [PF 6 ] − , and bis(trifluoromethylsilfonyl)imide [Tf 2 N] − anions were chosen as the adsorbates to better understand the trends in adsorption behavior of ILs on the h-BN surface. We have identified the various stable configurations of the h-BN-ionic liquid (h-BN···IL) complexes based on their binding energies and investigated the effect of charge transfer behavior and noncovalent interactions on the adsorption of ILs. ChelpG analysis indicated that, upon adsorption of ionic liquids on the h-BN surface, the overall charge on the cation, anion, and h-BN surface changes and the transfer (CT) between ILs and h-BN surface occurs. The order for the magnitude of charge transfer between different ILs and the h-BN surface is as follows: [Bmim][Tf 2 N] (−0.059e) > [Btma][PF 6 ] (0.036e) > [Bpy][Tf 2 N] (0.028e) > [Btma][Tf 2 N] (0.021e) > [Bmim][PF 6 ] (0.009e) > [Bpy][BF 4 ] (0.007e) > [Bpy][PF 6 ] (−0.006e) > [Btma][BF 4 ] (−0.003e) > [Bmim][BF 4 ] (−0.001e), respectively. Orbital energy and density of states (DOSs) calculations also show that the HOMO−LUMO energy gap of ILs decreases upon adsorption on the h-BN surface. The order of the HOMO−LUMO gap energy changes of ILs upon adsorption on the h-BN surface is as follows: [Btma][PF 6 ] (3.25 eV) > [Btma][BF 4 ] (2.84 eV) > [Bpy][PF 6 ] (2.41 eV) > [Bpy][BF 4 ] (2.29 eV) > [Bmim][BF 4 ] (1.76 eV) > [Bmim][PF 6 ] (1.54 eV) > [Btma][Tf 2 N] (1.26 eV) > [Bmim][Tf 2 N] (1.19 eV) > [Bpy][Tf 2 N] (0.86 eV), respectively. The binding energies based on QTAIM analysis indicate that the [BF 4 ] − , [PF 6 ] − , and [Tf 2 N] − anions in the ILs have a stronger interaction with the h-BN surface than [Bmim] + , [Bpy] + , and [Btma] + cations. The role of cooperative π···π, C−H···π, and X···π (X = N, O, F atoms from anions) interactions on the adsorption of ILs on the h-BN surface was elucidated by analyzing the noncovalent interactions between ILs and the h-BN surface. Energy decomposition analysis (EDA) carried out for the h-BN···IL complexes indicates that the contribution of the ΔE disp component in each complex is also more than electrostatic (ΔE elect ) and orbital (ΔE orb ) components (ΔE disp > ΔE elect > ΔE orb ), with the exception of the h-BN[Btma][BF 4 ] complex whose ΔE disp and ΔE elect components are almost equal. For the complexes with the same cations, dispersion interaction increases by increasing size of anion from [BF 4 ] − to [PF 6 ] − and [Tf 2 N] − . This is confirmed by more favorable enthalpy of adsorption for ILs on the h-BN surface. The thermochemical analysis also indicates that the free energy of adsorption (ΔG ads ) of ILs on the h-BN surface is negative, and thus, the adsorption occurs spontaneously. Our first-p...

Calcium-ion batteries show promise as high-density, next-generation replacements for current lithium-ion batteries. The precise chemical structure of the carbonate electrolyte solvent has a large impact on calcium battery efficacy. In this computational study, we have investigated the solvation behavior of calcium tetrafluoroborate in both neat carbonates and carbonate mixtures using combined molecular dynamics simulations and quantum mechanical calculations. Our results indicate that both neat ethyl methyl carbonate and a mixture of ethylene carbonate and diethyl carbonate show the highest free energy of solvation for the Ca2+ ion, making them likely candidates for further focus. The cation’s interaction with the carbonyls of the coordinating solvents, rather than those with the tetrafluoroborate counterions, plays the primary role in delocalizing the charge on Ca2+. Detailed calculations indicate that the HOMO–LUMO energy gap (E g), electronic chemical potential (μ), and chemical hardness (η) of the calcium–carbonate complexes are directly proportional to the free energy of solvation of the complex. Comparison of these observed trends with our previous results from Li+, Na+, and Mg2+ ions shows that this correlation is also observed in solvated magnesium ions but not in lithium or sodium salts. This observation should assist in the rational design of next-generation battery materials in the rational selection of additives, counterions, or electrolyte solvents.

A computational framework to rank the solvation behavior of Mg(2+) in carbonates by using molecular dynamics simulations and density functional theory is reported. Based on the binding energies and enthalpies of solvation calculated at the M06-2X/6-311++G(d,p) level of theory and the free energies of solvation from ABF-MD simulations, we find that ethylene carbonate (EC) and the ethylene carbonate:propylene carbonate (EC:PC) binary mixture are the best carbonate solvents for interacting with Mg(2+) . Natural bond orbital and quantum theory of atoms in molecules analyses support the thermochemistry calculations with the highest values of charge transfer, perturbative stabilization energies, electron densities, and Wiberg bond indices being observed in the Mg(2+) (EC) and Mg(2+) (EC:PC) complexes. The plots of the noncovalent interactions indicate that those responsible for the formation of Mg(2+) carbonate complexes are strong-to-weak attractive interactions, depending on the regions that are interacting. Finally, density of state calculations indicate that the interactions between Mg(2+) and the carbonate solvents affects the HOMO and LUMO states of all carbonate solvents and moves them to more negative energy values.

The oxidant-free dehydrogenation of alcohols to corresponding carbonyl compounds has been performed by using silver (0) nanoparticles supported on silica-coated ferrite as an efficient and recyclable heterogeneous catalyst.

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