title: Li(+) Local Structure in Li-Tetraglyme Solvate Ionic Liquid Revealed by Neutron Total Scattering Experiments with the (6/7)Li Isotopic Substitution Technique.
abstract: Equimolar mixtures of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and tetraglyme (G4: CH3O-(CH2CH2O)4-CH3) yield the solvate (or chelate) ionic liquid [Li(G4)][TFSA], which is a homogeneous transparent solution at room temperature. Solvate ionic liquids (SILs) are currently attracting increasing research interest, especially as new electrolytes for Li-sulfur batteries. Here, we performed neutron total scattering experiments with (6/7)Li isotopic substitution to reveal the Li(+) solvation/local structure in [Li(G4)][TFSA] SILs. The experimental interference function and radial distribution function around Li(+) agree well with predictions from ab initio calculations and MD simulations. The model solvation/local structure was optimized with nonlinear least-squares analysis to yield structural parameters. The refined Li(+) solvation/local structure in the [Li(G4)][TFSA] SIL shows that lithium cations are not coordinated to all five oxygen atoms of the G4 molecule (deficient five-coordination) but only to four of them (actual four-coordination). The solvate cation is thus considerably distorted, which can be ascribed to the limited phase space of the ethylene oxide chain and competition for coordination sites from the TFSA anion.
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 Science and Technology, Niigata University , 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City 950-2181, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hayashi
authors.affiliation: Faculty of Liberal Studies, National Institute of Technology, Kumamoto College , 2659-2 Suya, Koshi, Kumamoto 861-1102, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Matsugami
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: 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: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa , 1049 001 Lisboa, Portugal.|Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa , 2780 157 Oeiras, Portugal.
authors.forename: José N
authors.initials: JN
authors.lastname: Canongia Lopes
authors.affiliation: Priority Research Center for Advanced Fluids and Interfaces, The University of Newcastle , Callaghan, New South Wales 2308, Australia.
authors.forename: Rob
authors.initials: R
authors.lastname: Atkin
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: 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: 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: 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