| Description |
Molecular dynamics (MD) simulations of various room temperature ionic liquids (RTILs), RTIL/lithium salt mixtures, and RTIL/lithium salt/organic solvents mixtures have been conducted using a well-established polarizable force field which demonstrated unprecedented accuracy and transferability in simulations of liquids, electrolytes, and polymers. The influence of inclusion atom polarizability on the accuracy of properties predicted from MD simulations of RTILs has been systematically investigated. Simulations of RTILs in which the atom-based polarizability was set to zero for all atoms (nonpolarizable model) resulted in changes in thermodynamic and dynamic properties from those predicted by the polarizable force field (polarizable model). Investigation of structural and dynamical correlations using both the polarizalbe and nonpolarizable model allowed us to obtain a mechanistic understanding of the influence of polarization on dynamics in the RTILs investigated. MD simulations of N-methyl-N-propylpyrrolidinium(pyr13) bis(trifluoromethanesulfonyl)imide(Ntf2) ionic liquid [pyr13][Ntf2] mixed with [Li][Ntf2] salt have been conducted at 363 K and 423 K. Mixture simulations with lithium salt mole fractions between 0% and 33% at 363 K and 423 K yield densities, ion self-diffusion coefficients, and ionic conductivities in very good agreement with available experimental data. The concentration dependence of Li+ solvation structure, conductivity, and diffusion mechanism has been successfully investigated. The organic solvents acetonitrile (ACN) and ethylene carbonate (EC) were iv added into the [pyr13][Ntf2]/[Li][Ntf2] mixtures at two concentrations (20 mol% and 40 mol%). Ion mobility was found to be improved in the diluted electrolytes. In addition, EC and ACN molecules were found to be able to influence the coordination structure and diffusion mechanism of Li+ cations. The interfacial structures of the mixtures near charged and uncharged graphite electrode have been exposed as well, using an electroactive interface molecular dynamics simulation methodology. Multilayer structures were observed near the atomically flat graphite electrodes. The orientations of the components in the mixtures near the charged and uncharged surface were discussed thoroughly. |
