題目:Lithium Ion Diffusion in a Metal–Organic Framework Mediated by an Ionic Liquid
作者:Kazuyuki Fujie*†‡, Ryuichi Ikeda‡§, Kazuya Otsubo‡, Teppei Yamada‡, and Hiroshi Kitagawa*‡∥¶#
† R&D Center Kagoshima, Kyocera Corporation, 1-4 Kokubuyamashita-cho, Kirishima, Kagoshima 899-4312, Japan
‡ Division of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
§ Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305, Japan
∥ Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), 5 Sanban-cho, Chiyoda-ku,
Tokyo 102-0075, Japan
¶ Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
# INAMORI Frontier Research Center, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-3095, Japan
摘要:Metal–organic frameworks (MOFs) are desirable host materials to study and control the dynamics of molecules and ions such as lithium ions. We show the first study of a lithium ion-doped ionic liquid (IL) incorporated into a MOF and investigate its phase behavior and ionic conductivity. Moreover, for the first time, we have studied the dynamics of lithium ions in the micropores of the MOF in terms of the self-diffusion coefficient of the lithium ions. The IL was a mixture of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) with LiTFSA (lithium bis(trifluoromethylsulfonyl)amide), and the MOF was ZIF-8 (Zn(MeIM)2; H(MeIM) = 2-methylimidazole). The TFSA– anions showed a gradual decrease of mobility in the micropores at low temperatures, which indicates the absence of the apparent freezing transition. The mobility of the Li+ cations showed a slightly steeper decrease than that of the TFSA– anions at low temperature. The ionic conductivity of the (EMI0.8Li0.2)TFSA in the micropores was 2 orders of magnitude lower than that of the bulk (EMI0.8Li0.2)TFSA. However, the activation energy for the diffusion of lithium ions in the micropores of ZIF-8 was comparable with the bulk (EMI0.8Li0.2)TFSA. These results suggest that the Li+ cations diffuse through the micropores via the exchange of the solvating TFSA– anions, similar to the Grotthuss mechanism in proton conductivity.![大牛Teppei Yamada最新鋰電力作(Chemistry of Materials,2015年10月29日)]()
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