title: Li(+) Local Structure in Hydrofluoroether Diluted Li-Glyme Solvate Ionic Liquid.
abstract: Hydrofluoroethers have recently been used as the diluent to a lithium battery electrolyte solution to increase and decrease the ionic conductivity and the solution viscosity, respectively. In order to clarify the Li(+) local structure in the 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE) diluted [Li(G4)][TFSA] (G4, tetraglyme; TFSA, bis(trifluoromethanesulfonyl)amide) solvate ionic liquid, Raman spectroscopic study has been done with the DFT calculations. It has turned out that the HFE never coordinates to the Li(+) directly, and that the solvent (G4) shared ion pair of Li(+) with TFSA anion (SSIP) and the contact ion pair between Li(+) and TFSA anion (CIP) are found in the neat and HFE diluted [Li(G4)][TFSA] solvate ionic liquid. It is also revealed that the two kinds of the CIP in which TFSA anion coordinates to the Li(+) in monodentate and bidentate manners (hereafter, we call them the monodentate CIP and the bidentate CIP, respectively) exist with the SSIP of predominant [Li(G4)](+) ion-pair species in the neat [Li(G4)][TFSA] solvate ionic liquid, and that the monodentate CIP decreases as diluting with the HFE. To obtain further insight, X-ray total scattering experiments (HEXTS) were carried out with the aid of MD simulations, where the intermolecular force field parameters, mainly partial atomic charges, have been newly proposed for the HFE and glymes. A new peak appeared at around 0.6-0.7 Å(-1) in X-ray structure factors, which was ascribed to the correlation between the [Li(G4)][TFSA] ion pairs. Furthermore, MD simulations were in good agreement with the experiments, from which it is suggested that the terminal oxygen atoms of the G4 in [Li(G4)](+) solvated cation frequently repeat coordinating/uncoordinating to the Li(+), although almost all of the G4 coordinates to the Li(+) to form [Li(G4)](+) solvated cation in the neat and HFE diluted [Li(G4)][TFSA] solvate ionic liquid.
authors.affiliation: Graduate School of Science and Technology, Niigata University , 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City, 950-2181, Japan.
authors.forename: Soshi
authors.initials: S
authors.lastname: Saito
authors.affiliation: Graduate School of Science and Technology, Niigata University , 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City, 950-2181, Japan.
authors.forename: Hikari
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Graduate School of Medicine, Yamaguchi University , 2-16-1 Tokiwadai, Ube City, Yamaguchi 755-8611, Japan.
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Ueno
authors.affiliation: Department of Chemistry and Biotechnology, Yokohama National University , 79-5 Tokiwadai, Hodogaya-ku, Yokohama City, Kanagawa 240-8501, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Mandai
authors.affiliation: Materials Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI) , 2-6-1 Nagasaka, Yokosuka City, Kanagawa 240-0196, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Seki
authors.affiliation: Research Center for Computational Design of Advanced Functional Materials (CD-FMat), National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba, Ibaraki 305-8568, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Tsuzuki
authors.affiliation: Department of Material and Biological Chemistry, Faculty of Science, Yamagata University , 1-4-12, Kojirakawa-machi, Yamagata City, Yamagata 990-8560, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kameda
authors.affiliation: Department of Chemistry and Biotechnology, Yokohama National University , 79-5 Tokiwadai, Hodogaya-ku, Yokohama City, Kanagawa 240-8501, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Dokko
authors.affiliation: Department of Chemistry and Biotechnology, Yokohama National University , 79-5 Tokiwadai, Hodogaya-ku, Yokohama City, Kanagawa 240-8501, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Graduate School of Science and Technology, Niigata University , 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City, 950-2181, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Umebayashi