Classical, polarizable molecular dynamics simulations have been performed for a series of Mg­(N­(SO2CF3)2)2–dimethoxyethane electrolytes with salt concentration varying in the range c = 0.1–1.2 M. It has been found that in dimethoxyethane solutions, magnesium salt exists as free ions, with metal cations coordinated to solvent molecules. Cation–solvent interactions favor TTT, TGT, and TGG′ conformations of dimethoxyethane, modifying the population of conformers in the electrolyte. Mg2+ ions form stable solvates with about three dimethoxyethane molecules. Two sets of solvent molecules with different mobility have been detected in simulations: fast diffusing free solvent molecules and dimethoxyethane molecules bound in the solvates, diffusing slowly with magnesium ions. All these findings are in good agreement with the recent experimental data.

Classical molecular dynamics simulations have been performed in polarizable and nonpolarizable force fields for series of electrolytes based on MeTFSI (Me = Li, Na) salts dissolved in EMIM−TFSI ionic liquid. Structure and dynamics of the solvation shell of Me + ions have been investigated. Contributions to the total conductivity of the electrolyte arising from motions of different ions and cross-correlations between them have been analyzed. The analysis has indicated that regardless of the type of Me + cation, motions of Me + ions and ionic liquid anions are positively correlated, contributing toward conductivity decrease and leading to negative transference numbers of metal ions. The results have confirmed experimental findings of negative transference numbers of Li + and have suggested that the effect of Me-anion correlations in certain concentration range is a general feature of Me + solutions in ionic liquids.

Classical and ab initio molecular dynamics (MD) simulations have been performed for electrolytes based on LiTFSI and NaTFSI solutions in ethylene carbonate and its mono- and difluoro derivatives. Differences between electrolytes with Li+ or Na+ ions and the effect of fluorination on the structure and transport properties have been analyzed. The observed differences are related to the strength of Me+–carbonate binding, which is weaker for the Na+ cation and/or fluorinated solvents. Infrared spectra have been computed from ab initio MD and density functional tight binding (DFTB) MD trajectories. The changes of vibrational frequencies have been related to the local structure of the electrolyte and to interactions between salt cations and solvent molecules. The frequency shifts obtained from the AIMD simulations agree with experimental data, whereas DFTB underestimates Na+–carbonate interactions.

Although the electrical conductivity of an electrolyte can be estimated from the molecular dynamics trajectory, it is often a challenging task because of the need to obtain a substantial amount of data to ensure sufficient averaging. Here, we present an analysis on the convergence of results with the number of simulated trajectories. A series of molecular dynamics simulations have been performed for a model electrolyte (NaCl in water) and the Einstein relation has been used to calculate the electrical conductivity. The standard deviation of the conductivity estimates is relatively large compared to the mean value, and it has been shown that the off-diagonal contributions to the collective displacement of ions are responsible for large deviations between systems. It has been found that about 40 independent MD simulations may be required to reduce the errors. A procedure to improve the final estimate of the conductivity has been proposed.

Classical molecular dynamics simulations were performed for Na conducting electrolytes based on EMIM-TFSI ionic liquid and NaTFSI salt. Several parametrizations of force fields have been tested, including polarizable fields with dipole polarizabilities or Drude-type polarization. Trajectories up to 1 μs long have been used to estimate viscosities, diffusion coefficients, and conductivities of electrolytes with increasing amount of sodium salt. Results have been compared to available experimental data. In most cases the best agreement to measured values has been obtained in nonpolarizable simulations. Nevertheless, results have indicated the need for further development of polarizable parametrizations, preferably based on the Drude polarization model.