Water-Ion Interaction Determines the Mobility of Ions in Highly Concentrated Aqueous Electrolytes

Jungyu Kim, Bonhyeop Koo, Anahita Khammari, Kwanghee Park, Hochun Lee, Kyungwon Kwak, Minhaeng Cho

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Solvation engineering plays a critical role in tailoring the performance of batteries, particularly through the use of highly concentrated electrolytes, which offer heterogeneous solvation structures of mobile ions with distinct electrochemical properties. In this study, we employed spectroscopic techniques and molecular dynamics simulations to investigate mixed-cation (Li+/K+) acetate aqueous electrolytes. Our research unravels the pivotal role of water in facilitating ion transport within a highly viscous medium. Notably, Li+ cations primarily form ion aggregates, predominantly interacting with acetate anions, while K+ cations emerge as the principal charge carriers, which is attributed to their strong interaction with water molecules. Intriguingly, even at a concentration as high as 40 m, a substantial amount of water molecules persistently engages in hydrogen bonding with one another, creating mobile regions rich in K+ ions. Our observations of a redshift of the OH stretching band of water suggest that the strength of the hydrogen bond alone cannot account for the expansion of the electrochemical stability window. These findings offer valuable insights into the cation transfer mechanism, shedding light on the contribution of water-bound cations to both the ion conductivity and the electrochemical stability window of aqueous electrolytes for rechargeable batteries. Our comprehensive molecular-level understanding of the interplay between cations and water provides a foundation for future advances in solvation engineering, leading to the development of high-performance batteries with improved energy storage and safety profiles.

Original languageEnglish
Pages (from-to)10033-10041
Number of pages9
JournalACS Applied Materials and Interfaces
Volume16
Issue number8
DOIs
Publication statusPublished - 2024 Feb 28

Bibliographical note

Publisher Copyright:
© 2024 American Chemical Society.

Keywords

  • aqueous electrolyte
  • dielectric relaxation
  • dynamics
  • ion mobility
  • IR
  • spectroscopy

ASJC Scopus subject areas

  • General Materials Science

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