Abstract
We present the complex microscopic dynamics of 1-butyl-3-methyl-imidazolium bis(trifluromethylsulfonyl)imide, [Bmim+][TFSI-], ionic liquid mixed with organic solvents to improve its properties for energy storage applications. To probe the microscopic dynamics on different length and time scales, we have used different neutron scattering spectrometers for quasielastic neutron scattering measurements to compare the effects of solvation in several organic solvents with nearly the same dipole moment but broadly varying bulk diffusivity. The ionic liquid-solvent mixtures show a nanoscopic phase separation into an ionic liquid-rich and a solvent-rich phase, as revealed by the model-free dynamic susceptibility data and further corroborated by the cluster histogram analysis of molecular dynamics (MD) simulation. In both phases, we observe a long-range translational mobility of the [Bmim+] cation, which scales with the bulk diffusivities of the organic solvents; this correlation becomes stronger in the solvent-rich phase. Additionally, various localized motion modes of the [Bmim+] cation are observed. A combination of neutron scattering and MD simulations reveals the parameters governing solvent-controlled diffusivity in an ionic liquid, which helps formulate new electrolytes optimized for efficient energy storage devices.
| Original language | English |
|---|---|
| Pages (from-to) | 19354-19361 |
| Number of pages | 8 |
| Journal | Journal of Physical Chemistry C |
| Volume | 123 |
| Issue number | 32 |
| DOIs | |
| State | Published - Aug 15 2019 |
Funding
This work was supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Work at ORNL’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division Office of Basic Energy Sciences, U.S. Department of Energy. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for U.S. DOE under contract no. DEAC05-00OR22725. Certain commercial material suppliers are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose. This work was supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Work at ORNL’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for U.S. DOE under contract no. DEAC05-00OR22725. Certain commercial material suppliers are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.
| Funders | Funder number |
|---|---|
| Scientific User Facilities Division | |
| Scientific User Facilities Division Office of Basic Energy Sciences | |
| U.S. Department of Energy | DEAC05-00OR22725 |
| National Institute of Standards and Technology | |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory |