Supporting Information

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1 Supporting Information Ionic Liquid-Based Electrolytes Containing Surface-Functionalized Inorganic Nanofibers for Quasisolid Lithium Battery Takahiro Yuuki, Yuichi Konosu, Minoru Ashizawa, Takashi Iwahashi, Yukio Ouchi, Yoichi Tominaga, Rie Ooyabu, Hajime Matsumoto, and Hidetoshi Matsumoto,* Department of Materials Science and Engineering, Tokyo Institute of Technology, Mail Box S8-27, Ookayama, Meguro-ku, Tokyo , Japan Graduate School of Bio-Applications and Systems Engineering, Tokyo Univeristy of Agriculture and Technology, Naka-cho, Koganei, Tokyo, , Japan Department of Energy and Environment, Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), Midorigaoka, Ikeda, Osaka , Japan *Address correspondence to S1

2 Electrokinetic Characterization. The streaming potential measurements were done using an electrokinetic analyzer (SurPASS, Anton Paar GmbH, Austria) equipped with an adjustable gap cell. 1 A pair of f-sio2nf nonwoven webs having an area of mm 2 were placed in the measuring cell. The streaming potential was detected by the Ag/AgCl electrodes with an average gap height of 100 μm. A background electrolyte of 1 mm KCl solution was used and the ph was adjusted in the range of 2 11 with 0.1 M HCl and 0.1 M KOH. All measurements were performed at approximately 25 C. The apparent surface charge density was calculated from streaming potential via zeta potential. 2 To estimate the density of surface amino groups of NFs, the obtained apparent surface charge density at ph 2-11 was analyzed by site dissociation model as described previously. 3 The dissociation constant of surface basic group, Kb and the site density of surface basic group Nb, which were determined by implementing the nonlinear parameter estimation program UNCIMIN, 4 are summarized in Table S1. Table S1. Characteristic parameters for f-sio2nfs from the site dissociation model pkb 10 3 Nb (nm -2 ) f-sio 2NF (D = 400) f-sio 2NF (D = 1000) S2

3 Internal Structure of the IL-NF composites. Figure S1 A confocal laser image of the solid-state composite electrolyte (IL-NF composite (0.5 M) D = 1000). S3

4 FT-IR measurements. To examine an interaction between amino groups and IL, we carried out FT- IR measurements of the mixture of IL (EMITFSA) and hexylamine (HA). Herein, we used HA as model amino groups, because we cannot directly detect the interaction in the prepared IL-NF composite with a small fraction of f-sio2nf. The mixture of IL and chloroform (CHCl3) is used as a reference for confirmation of the dissolution effect of IL. FT-IR spectra were recorded using FT/IR spectrometer (JASCO, Japan) equipped with attenuated total reflectance (ATR) attachment ATR PRO450-S (JASCO, Japan). Figures S2 shows the FT-IR spectra. The peaks at 1052, 1132, 1167 (1178), 1230, and 1328 (1349) cm -1 are assigned to SNS, SO2-symmetric stretching mode (ss), CF3- asymmetric stretching mode (as), CF3-ss, and SO2-as, respectively. The peak of CF3-ss does not shift, but the peaks of SNS, SO2-ss, and SO2-as are slightly blue-shifted and the widths broadened. In particular, the SO2-ss peak position is relatively highly blue-shifted with a decrease in the IL mole fraction (i.e., blue-shifted with an increase in the HA mole fraction) (Figure S3). At the point of IL mole fraction of 0.17, the peak shift in IL/HA mixture is larger than that in IL/CHCl3 one. This clearly indicates the presence of relatively strong intermolecular interaction between SO2 groups of TFSA anion and amino groups of HA (i.e., hydrogen bonding). 5 S4

5 Figure S2 FT-IR spectra of the mixtures of IL and HA. The legends stand for IL mole fraction. Figure S3 Change of SO2-ss peak position of the mixtures of IL and HA as a function of IL mole fraction. S5

6 Rheological Properties. Figures S4-S8 show viscoelastic properties of the prepared IL-NF composites with various compositions. These support that all the prepared solid-state composites are gel state. Figure S4 Viscoelastic properties for the solid-state composite electrolyte (IL-NF composite (0 M) D = 400). S6

7 Figure S5 Viscoelastic properties for the solid-state composite electrolyte (IL-NF composite (0.5 M) D = 1000). Figure S6 Viscoelastic properties for the solid-state composite electrolyte (IL-NF composite (1.32 M) D = 400). S7

8 Figure S7 Viscoelastic properties for the solid-state composite electrolyte (IL-NF composite (1.32 M) D = 1000). Figure S8 Additive effect of f-sio2nfs (D = 400) with various fractions on complex viscosities and storage modulus of the composite electrolytes at 40 C in 0.01 Hz. S8

9 Thermogravimetric Behavior. Figure S9 Thermogravimetric curves of IL-NF composite electrolytes (D = 400). S9

10 REFERENCES (1) Matsumoto, H.; Yako, H.; Minagawa, M.; Tanioka, A. Characterization of Chitosan Nanofiber Fabric by Electrospray Deposition: Electrokinetic and Adsorption Behavior, J. Colloid Interface Sci. 2007, 310, (2) Healy, T. W.; White, L. R. Ionizable Surface Group Models of Aqueous Interfaces. Adv. Colloid Interface Sci. 1978, 9, (3) Matsumoto, H.; Koyama, Y.; Tanioka, A. Characterization of Novel Weak Amphoteric Charged Membranes Using -Potential Measurements: Effect of Dipolar Ion Structure. Langmuir 2001, 17, (4) Kahaner, D.; Moler, C.; Nash, S. Numerical Methods and Software; Prentice Hall: Englewood Cliffs, NJ, (5) Iwahashi, T.; Sakai, Y.; Kim, D.; Ishiyama, T.; Morita, A.; Ouchi, Y. Nonlinear Vibrational Spectroscopic Studies on Water/ionic liquid([cnmim]tfsa: N = 4, 8) Interfaces. Faraday Discuss. 2012, 154, S10