TY - JOUR
T1 - Local Structure of Li+ in Concentrated Ethylene Carbonate Solutions Studied by Low-Frequency Raman Scattering and Neutron Diffraction with 6Li/7Li Isotopic Substitution Methods
AU - Maeda, Shunya
AU - Kameda, Yasuo
AU - Amo, Yuko
AU - Usuki, Takeshi
AU - Ikeda, Kazutaka
AU - Otomo, Toshiya
AU - Yanagisawa, Maho
AU - Seki, Shiro
AU - Arai, Nana
AU - Watanabe, Hikari
AU - Umebayashi, Yasuhiro
N1 - Funding Information:
The authors thank members of the NOVA group for their help during neutron diffraction measurements. Neutron scattering experiments were approved by the Neutron Scattering Program Advisory Committee of IMSS, KEK (Proposal No. 2014S09 and No. 2015A0121). All calculations were carried out at Yamagata University Networking and Computing Service Center. This work was partially supported by Grant-in-Aid Scientific Research (C) (Nos. 2639110 and 16K05508), from the Ministry of Education, Culture, Sports, and Technology, Japan. This study was supported in part by the Advanced Low Carbon Technology Research and Development Program (ALCA-SPRING) of the Japan Science and Technology Agency (JST).
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/12/7
Y1 - 2017/12/7
N2 - Isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for concentrated LiTFSA-EC solutions to obtain structural insight on solvated Li+ as well as the structure of contact ion pair, Li+⋯TFSA-, formed in highly concentrated EC solutions. Symmetrical stretching vibrational mode of solvated Li+ and solvated Li+⋯TFSA- ion pair were observed at ν = 168-177 and 202-224 cm-1, respectively. Detailed structural properties of solvated Li+ and Li+⋯TFSA- contact ion pair were derived from the least-squares fitting analysis of first-order difference function, ΔLi(Q), between neutron scattering cross sections observed for 6Li/7Li isotopically substituted 10 and 25 mol %∗LiTFSA-ECd4 solutions. It has been revealed that Li+ in the 10 mol % LiTFSA solution is fully solvated by ca. 4 EC molecules. The nearest neighbor Li+⋯O(EC) distance and Li+⋯O(EC)=C(EC) bond angle are determined to be 1.90 ± 0.01 Å and 141 ± 1°, respectively. In highly concentrated 25 mol % LiTFSA-EC solution, the average solvation number of Li+ decreases to ca. 3 and ca. 1.5. TFSA- are directly contacted to Li+. These results agree well with the results of band decomposition analyses of isotropic Raman spectra for intramolecular vibrational modes of both EC and TFSA-.
AB - Isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for concentrated LiTFSA-EC solutions to obtain structural insight on solvated Li+ as well as the structure of contact ion pair, Li+⋯TFSA-, formed in highly concentrated EC solutions. Symmetrical stretching vibrational mode of solvated Li+ and solvated Li+⋯TFSA- ion pair were observed at ν = 168-177 and 202-224 cm-1, respectively. Detailed structural properties of solvated Li+ and Li+⋯TFSA- contact ion pair were derived from the least-squares fitting analysis of first-order difference function, ΔLi(Q), between neutron scattering cross sections observed for 6Li/7Li isotopically substituted 10 and 25 mol %∗LiTFSA-ECd4 solutions. It has been revealed that Li+ in the 10 mol % LiTFSA solution is fully solvated by ca. 4 EC molecules. The nearest neighbor Li+⋯O(EC) distance and Li+⋯O(EC)=C(EC) bond angle are determined to be 1.90 ± 0.01 Å and 141 ± 1°, respectively. In highly concentrated 25 mol % LiTFSA-EC solution, the average solvation number of Li+ decreases to ca. 3 and ca. 1.5. TFSA- are directly contacted to Li+. These results agree well with the results of band decomposition analyses of isotropic Raman spectra for intramolecular vibrational modes of both EC and TFSA-.
UR - https://www.scopus.com/pages/publications/85037725020
U2 - 10.1021/acs.jpcb.7b10933
DO - 10.1021/acs.jpcb.7b10933
M3 - Article
C2 - 29135254
AN - SCOPUS:85037725020
SN - 1520-6106
VL - 121
SP - 10979
EP - 10987
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 48
ER -