(462i) Electrical Conductivities of Binary and Ternary Deep Eutectic Solvents Via Molecular Simulation

Authors: 
Federle, B., South Dakota School of Mines & Technology
Benjamin, K. M., South Dakota School of Mines and Technology
Solvent properties, such as electrical conductivity, are crucial to the successful design and operation of batteries. In several instances, the types of conventional solvents used in batteries are both potentially toxic to an individual, as well as to the environment. As an alternative, deep eutectic solvents (DES) are biologically based ionic liquid eutectic mixtures which possess tunable properties according to the selected cation, anion, and hydrogen bond donating co-solvent partner. These tunable properties include density, dielectric constant, and solvating power. DES possess extremely low vapor pressures, and therefore do not volatilize as easily as some conventional solvents used in the battery industry. Moreover, because DES are comprised of biologically based ions (i.e. choline) rather than synthetic ions (i.e. 1-ethyl-3-methyl-imidazolium), they are less toxic to organisms and the environment, and less expensive.

This work seeks to characterize environmentally benign, non-toxic, tunable DES through molecular simulation. In particular, molecular dynamics (MD) simulations are used to compute electrical conductivities for various binary and ternary DES, comprised of mixtures of choline chloride, urea, and glycerol. Electrical conductivities are calculated by two approaches: 1.) via post-processing of mean-squared displacement data from conventional MD simulations and 2.) on-the-fly during the course of an MD simulation. This latter on-the-fly approach involves the development of a new computational method within the popular open-source MD code, LAMMPS, developed by Sandia National Laboratories. Comparisons of computed electrical conductivities between the two approaches for NaCl/H2O mixtures are presented for benchmarking against experimental data, along with new predictions for various binary and ternary DES. Comparison against electrical conductivities of conventional battery solvents are made, too.