High Lithium Transference Number Electrolytes. Containing Lithium Tetratriflylpropene Salt

Transcription

1 Supporting Information for Publication High Lithium Transference Number Electrolytes Containing Lithium Tetratriflylpropene Salt J. Popovic *, D. Höfler *, J. P. Melchior $, A. Münchinger, B. List, J. Maier Max Planck Institute for Solid State Research, Stuttgart, Germany Max Planck Institute for Coal Research, Mülheim an der Ruhr, Germany $ Current address: Oak Ridge National Laboratory, Neutron Scattering Division, Oak Ridge, TN, USA Corresponding authors: Jelena Popovic, popovic@fkf.mpg.de; Denis Höfler, hoefler@mpimuelheim.mpg.de 1. Synthesis and characterization of LiTTP General information The solvents (CH2Cl2, CHCl3, Et2O, THF, toluene) were dried by distillation with an appropriate drying agent in the technical department of the Max-Planck-Institut für Kohlenforschung and used in Schlenk flasks under argon. Additional solvents were purchased from commercial suppliers and dried over molecular sieves. All non-aqueous reactions were performed in oven-dried (85 C) or flame dried glassware under argon. Upon synthesis, solvents were removed under reduced pressure at 40 C using a rotary evaporator and/or under high vacuum if appropriate (10 2 to 10 3 S1

2 mbar). Diglyme (diethylenglycoldimethylether) was distilled over CaH2 to remove residual water. Bis(trifluoromethylsulfonyl)methane was purchased from Sigma Aldrich and sublimated before usage. All NMR spectra were recorded on Bruker Avance III 500 MHz spectrometer in deuterated solvents. Proton chemical shifts are reported in ppm (δ) relative to tetramethylsilane (TMS) with the solvent resonance employed as the internal standard. The solvent employed and respective measuring frequency are indicated for each experiment (Acetone-D6 δ = 2.05 ppm, CD2Cl2, δ = 5.32 ppm; CDCl3 δ = 7.26 ppm, DMSO δ = 2.50 ppm). 13 C, 19 F, 7 Li NMR spectra were referenced according to Ξ-values (IUPAC recommendations 2008) relative to the internal references set in 1 H NMR spectra (e.g. 19 F: CCl3F, 31 P: H3PO4, 15 N: MeNO2 each 0.00 ppm). All spectra were recorded at 298 K unless otherwise noted, processed with Bruker TOPSPIN 2.1 or MestReNova suits of programs. Coupling constants (J) are reported as observed. Data are reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, b = broad), coupling constants (Hz) and integration. 13 C chemical shifts are reported in ppm (δ) from tetramethylsilane (TMS) with the solvent resonance as the internal standard (CD2Cl2, δ = ppm; CDCl3, δ = ppm, DMSO δ = ppm). Electron impact (EI) mass spectrometry (MS) was performed on a Finnigan MAT 8200 (70 ev) or MAT 8400 (70 ev) spectrometer. Electrospray ionization (ESI) mass spectrometry was conducted on a Bruker ESQ 3000 spectrometer. High resolution mass spectrometry (HRMS) was performed on a Finnigan MAT 95 (EI) or Bruker APEX III FTMS (7T magnet, ESI). S2

3 The ionization method and mode of detection employed is indicated for the respective experiment and all masses are reported in atomic units per elementary charge (m/z) with an intensity normalized to the most intense peak. High-resolution mass spectra were aquired on a Bruker APEX III FTMS (7 T magnet). Elemental analysis (EA) was provided by Mikroanalytisches Laboratorium Kolbe. Micropore filters (CHROMAFIL Xtra, Macherey-Nagel, 0.45 μm, 13 mm diameter) were employed for filtration. Synthesis of LiTTP Firstly, 1,1,3,3-tetrakis((trifluoromethyl)sulfonyl)prop-1-ene (TTP) was made in accordance to our previously reported route. S1 For the preparation of lithium 1,1,3,3- tetrakis((trifluoromethyl)sulfonyl)prop-1-ene (LiTTP), a colourless, clear solution of TTP (2.70 g, 4.73 mmol) in 20 ml dry CH2Cl2 was treated with solid, colourless Li2CO3 (0.18 g, 2.37 mmol; 0.50 equiv) under argon. The reaction was stirred at room temperature over night. The supernatant was removed and the colourless suspension was triturated with CH2Cl2 (2X20 ml). The obtained, colourless solid was fully dissolved in 40 ml dry acetone and a clear, colourless solution was obtained. This solution was filtered into a flame dried Schlenk flask under argon. All volatiles were removed under reduced pressure and dry CHCl3 was used to remove residual acetone. LiTTP was obtained as a colourless, hygroscopic powder (2.58 g, 4.48 mmol, 95% yield). 1 H NMR (500 MHz, Acetone-D6): δ = 8.32 (s, 1H). 13 C NMR (126 MHz, Acetone-D6): δ = , (q, J = 327 Hz), (m). 19 F NMR (470 MHz, Acetone-D6): δ = -69 to -80 (br). 7 Li NMR (194 MHz, Acetone-D6): δ = MS (ESIneg) m/z: (TTP ). S3

4 HRMS (ESIneg) m/z: calculated (TTP = C7HF12O8S4 - ) , found Elemental Analysis: C7HF12LiO8S4 ( g/mol) Calcd: C, 14.59; H, 0.17; S, 22.25; F, 39.56; Li, 1.20 Found: C, 14.65; H, 0.18; S, 22.14; F, 39.43; Li, 1.19 Copies of NMR spectra Lithium 1,1,3,3-tetrakis((trifluoromethyl)sulfonyl)propene: S4

5 S5

6 2. Details on preparation of electrolytes, pulse field gradient NMR and impedance spectroscopy measurements Electrolyte preparation Di(ethylene glycol) dimethyl ether (Mw = g mol -1, Sigma Aldrich, diglyme) was used as received (water content below 150 ppm, as confirmed by Karl Fischer titration). Lithium trifluoromethanesulfonate (LiF3CSO3, Sigma Aldrich, %, LiOTf) was used as received. All electrolytes were prepared in a glovebox (< 0.1 ppm H2O, 0.1 ppm O2) under Ar atmosphere. Salt concentration of the final electrolyte solutions was determined by flame atomic absorption spectroscopy using an Analytik Jena contraa 300 spectrometer. S6

7 NMR spectra of 1:1 LiTTP/diglyme product of salting out Pulse field gradient NMR measurements The tracer diffusion coefficients of species containing Li, D Li,NMR, species containing F, D TTP,NMR, D OTf,NMR and H, D H,NMR, were measured by pulsed field gradient NMR (PFG-NMR). As the experiment s diffusion times are on the millisecond scale and the respective species exchange faster, the measured diffusion coefficients are weighted averages of the diffusion coefficients of all species containing the specific nucleus. S2 The measurements were performed at room temperature with a Bruker Avance III 400 spectrometer equipped with a diff60 gradient probe with specialized RF inserts for the nuclei 1 H, 7 Li and 19 F. A stimulated echo sequence with spoiler gradients has been used resulting in an attenuation of the echo intensity as function of gyromagnetic ratio γ, gradient strength g, gradient duration δ, and diffusion time Δ by the Steyskal-Tanner equation for sine shaped gradient pulses as described in Ref. S3: S7

8 I π = e γ2 δ 2 g 2 (Δ 8 δ)d Eq. S1 I 0 Using Eq. S1, the diffusion coefficients have been obtained through fit to echo intensities at incrementing gradient strength. All diffusion coefficients were recorded for constant Δ = 20 ms (no dependence on the diffusion time noticed), and for an effective gradient duration δ = 1 ms. Remagnetization times were chosen to be 4 to 5 times higher than the spin-lattice relaxation time, T 1. Due to the short spin-spin relaxation time T2 of the 19 F nucleus in the LiTTP solutions at room temperature, PFG-NMR measurements for the 0.45 M LiTTP solution can only be conducted at higher temperatures. Extrapolated diffusion coefficients were recorded at 343 K, 353 K, and 363 K, using a pulse sequence for suppression of convection artifacts S4, resulting in the same values as obtained by a 1 H PFG-NMR experiment using the 1 H signal of TTP at δ = 8.32 ppm at room temperature. Diffusion coefficients of TTP species were measured just by 1 H PFG-NMR at room temperature. Fig. S1 Diffusion coefficients from 19 F and 1 H PFG-NMR in 0.45 M LiTTP/diglyme electrolyte. S8

9 Impedance spectroscopy The ionic conductivities of various electrolyte solutions were measured in a self-made gold plated cell through ac-impedance spectroscopy in the frequency range from 1 to 10 7 Hz (0.1 V amplitude) using a Solartron 1260 frequency analyzer as previously descibed. S5 A RC6CP Lauda thermostat controlled the temperature externally. Low frequency impedance spectroscopy of LiTTP/diglyme electrolytes was measured in a selfmade Li / electrolyte / Li cell. Electrolytes were firstly infiltrated in a typical battery separator material (Whatman borosilicate glass microfiber filters, Grade GF/A), sandwiched between two lithium electrodes and placed in a glass compartment inside an Ar-filled glovebox. Impedance spectroscopy was measured in a frequency range from 10 MHz to 1 mhz using a Solartron 1260 frequency analyzer. Fig. S2 Room temperature low frequency impedance spectroscopy of Li / (0.2 M LiTTP/diglyme) / Li cell. S9

10 Fig. S3 Calculated LiOTf salt concentration dependent: (a) transport coefficients of cations, σ+, anions, σ-, ion pairs, s, and indirect transport of lithium, σpol, (b) effective lithium transference numbers that take into account either lithium transport through ion pairs and solvated free lithium, tpol,+, or only the transport through solvated lithium, t+. References S1. Höfler, D.; van Gemmeren, M.; Wedemann, P.; Kaupmees, K.; Leito, I.; Leutzsch, M.; Lingnau, J. B.; List., B. 1,1,3,3-Tetratriflylpropene (TTP): A Strong, Allylic C H Acid for Brønsted and Lewis Acid Catalysis, Angew. Chem. Int. Ed. 2016, 56(5), S2. Aihara, Y.; Bando, T.; Nakagawa, H.; Yoshida, H.; Hayamizu, K.; Akiba, E.; Price, W. S. The characteristic properties of ions for six lithium salts including lithium bis-(oxorateborate) dissolved in g-butyrolactone, J. Electrochem. Soc. 2004, 151. A119. S3. Price, W. S.; Kuchel, P. W. Effect of Nonrectangular Field Gradient Pulses in the Stejskal and Tanner (Diffusion) Pulse Sequence, J. Magn. Reson. 1991, 94, 133. S4. Jerschow, A.; Müller, N. Suppression of Convection Artifacts in Stimulated-Echo Diffusion Experiments. Double-Stimulated-Echo Experiments, J. Magn. Reson. 1997, 125(2), 372. S5. Pfaffenhuber, C; Hoffmann, F.; Fröba, M.; Popovic, J.; Maier, J. Soggy sand effects in liquid composite electrolytes with mesoporous materials as fillers, Journal of Mat. Chem. A 2013, 1(40), S10