Abstract
"Water-in-salt" electrolytes open up exciting new avenues for expanding the electrochemical window of aqueous electrolytes. We investigated the solvation structure and dynamics of highly concentrated lithium bis(trifluoromethane)sulfonimide aqueous electrolyte using experimentally corroborated molecular dynamics simulations. The simulations revealed that the heterogeneous structure of the electrolyte comprises percolating networks of ion and water domains/aggregates. Interestingly, the ionic regions are composed of more TFSI- ions than Li+ ions. The Li+-ion transport mechanism was further explored. Li+ ions can hop along the coordinated TFSI- ions in the ionic aggregates. The calculated correlated transference number of the 20 m electrolyte is â 0.32, which is reasonably high for the high concentration due to a weak negative correlation between the motion of cations and anions within the heterogeneous microscopic domains. These molecular dynamics results connect the heterogeneous structure of the electrolyte to the correlated dynamics of the Li+ ion and provide a new understanding of the Li+-ion transport mechanism in this novel electrolyte.
| Original language | English |
|---|---|
| Pages (from-to) | 1276-1281 |
| Number of pages | 6 |
| Journal | Journal of Physical Chemistry Letters |
| Volume | 11 |
| Issue number | 4 |
| DOIs | |
| State | Published - Feb 20 2020 |
| Externally published | Yes |
Funding
This research was supported by the Joint Center for Energy Storage Research (JCESR), a U.S. Department of Energy, Energy Innovation Hub. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under contract no. DE-AC02-06CH11357. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. We acknowledge Dr. Oleg Borodin, Dr. Yong Zhang, Dr. Edward J. Maginn, Dr. Karina Shimizu, and Dr. Mingfei Zhao for helpful discussions. We thank the Laboratory Computing Resource Center at Argonne National Laboratory for the generous allocation of computing time on the Bebop cluster.