Asymmetric composition of ionic aggregates and the origin of high correlated transference number in water-in-salt electrolytes

Zhou Yu, Larry A. Curtiss, Randall E. Winans, Yang Zhang, Tao Li, Lei Cheng

Research output: Contribution to journalArticlepeer-review

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 languageEnglish (US)
Pages (from-to)1276-1281
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume11
Issue number4
Early online dateJan 17 2020
DOIs
StatePublished - Feb 20 2020

ASJC Scopus subject areas

  • General Materials Science
  • Physical and Theoretical Chemistry

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