Molecular Dynamics Simulation of Li⁺BF₄^- in Ethylene Carbonate, Propylene Carbonate, and Dimethyl Carbonate Solvents

Abstract

Molecular dynamics simulations of Li + BF 4 - in liquid ethylene carbonate, propylene carbonate, and dimethyl carbonate at low concentration are reported. Structural, thermodynamical, and dynamical properties have been obtained at 323 and 348 K in ethylene carbonate, 298 and 323 K in propylene carbonate, and 298 K in dimethyl carbonate. The diffusion coefficient of the lithium cation is found to be very similar in the three solvents ((0.3−0.6) × 10 -9 m 2 s -1 in this temperature range). This behavior is linked to the structure of the first solvation shell, which contains four strongly bound solvent molecules in a tetrahedral arrangement in all three cases. No exchange of solvent molecules between the first and the second solvation shells of the lithium ion have been observed during the 100-ps simulations. In the three carbonates, the fluoroborate ion is bound to 19 or 20 solvent molecules in the first solvation shell, the coordination shell being much less structured than in the case of the lithium ion, and the diffusion coefficient exhibits a more significant solvent and temperature dependence.