Parametrization with Explicit Water of Solvents Used in Lithium-Ion Batteries: Cyclic Carbonates and Linear Ethers.

Abstract

Molecular dynamics simulations are performed to study carbonates and ethers that are widely used as electrolytes in energy storage devices. The first type contains in their molecular geometry a hydrocarbon tail of ethylene, propylene, and butylene whereas in the second type, the tail comprises 1,2-dimethoxyethane and 1,2-diethoxyethane. The evaluation of optimized potential for liquid simulations (OPLS), CHARMM, and GROMOS force fields for some of the solvents shows poor agreement with experimental thermodynamic and transport properties leading us to parameterize those solvents using the OPLS parameters as the starting point. A systematic procedure that uses the solubility of the solvents as the target property in simulations with explicit water is applied. The transferability of the parameters of the smallest cyclic or linear molecules was used to simulate systems with longer hydrocarbon chains. The optimized parameter reproduce the experimental solubility of butylene carbonate and 1,2-diethoxyethane in water. The interaction parameters were used to obtain the self-diffusion coefficients of ions of the salt LiPF6 at 1 M concentration in mixtures with ethylene carbonate or propylene carbonate. The simulation results for pure components and mixtures with the new parameters are in excellent agreement with the experimental data.