title: Characteristics of Lithium Ions and Superoxide Anions in EMI-TFSI and Dimethyl Sulfoxide.
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.
authors.affiliation: Advanced Institute for Materials Research, Tohoku University , Katahira, Sendai, Japan.
authors.forename: Sun-ho
authors.initials: SH
authors.lastname: Jung
authors.affiliation: Aalto Science Institute, Aalto University , PO Box 15500, FI-00076 Aalto, Finland.
authors.forename: Filippo
authors.initials: F
authors.lastname: Federici Canova
authors.affiliation: Advanced Institute for Materials Research, Tohoku University , Katahira, Sendai, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Akagi