Characteristics of Lithium Ions and Superoxide Anions in EMI-TFSI and Dimethyl Sulfoxide

Sun Ho Jung*, Filippo Federici Canova, Kazuto Akagi

*Corresponding author for this work

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

To clarify the microscopic effects of solvents on the formation of the Li+-O2 process of a Li-O2 battery, we studied the kinetics and thermodynamics of these ions in dimethyl sulfoxide (DMSO) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI) using classical molecular dynamics simulation. The force field for ions-solvents interactions was parametrized by force matching first-principles calculations. Despite the solvation energies of the ions are similar in both solvents, their mobility is much higher in DMSO. The free-energy profiles also confirm that the formation and decomposition rates of Li+-O2 pairs are greater in DMSO than in EMI-TFSI. Our atomistic simulations point out that the strong structuring of EMI-TFSI around the ions is responsible for these differences, and it explains why the LiO2 clusters formed in DMSO during the battery discharge are larger than those in EMI-TFSI. Understanding the origin of such properties is crucial to aid the optimization of electrolytes for Li-O2 batteries.

Original languageEnglish
Pages (from-to)364-371
Number of pages8
JournalJournal of Physical Chemistry A
Volume120
Issue number3
DOIs
Publication statusPublished - 28 Jan 2016
MoE publication typeA1 Journal article-refereed

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