Efficient Aluminium Chloride Natural Graphite Battery

Transcription

1 Supporting Information for Efficient Aluminium Chloride Natural Graphite Battery Kostiantyn V. Kravchyk,,# Shutao Wang,,# Laura Piveteau, and Maksym V. Kovalenko *,, Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, CH-8093 Zürich, Switzerland Laboratory for Thin Films and Photovoltaics, Empa Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland * mvkovalenko@ethz.ch # Equal contributions

2 Figure S1. Galvanostatic charge-discharge curves for processed graphite flakes measured using CCCV protocol (100 mah g -1 ) at various AlCl 3 :EMIMCl molar ratios ( ). Figure S2. Plastic cell used for electrochemical measurements. S2

3 Figure S3. Cycling stability measurements for pristine, processed smaller flakes and both potato-shaped specimens with respect to AlCl - 4 ion storage. Figure S4. Schematics of various intercalation stages and their notation. S3

4 Figure S5. XRD patterns of graphite flakes before and after charge at 50 ma g -1 ; the latter is measure with and without washing with CCl 4. Figure S6. XRD patterns showing the effect of solvent rinse of the charged graphite flakes on the retention of the charged state. The results point to partial or complete discharge (reduction) in most solvents, except CCl 4. S4

5 Figure S7. 13 C solid-state NMR spectra of charged graphite flakes, washed with CCl 4. The absence of any signal indicates complete removal of the electrolyte and evaporation of the residual CCl 4. Figure S8. 13 C solution NMR spectra of AlCl 3 :EMIMCl solutions of variable acidity in C 6 D 6. The assignment of the peaks from the EMIM + cation is indicated with numbers. No variation in linewidth is observed with varying acidity of the solution, which indicates that the linewidth changes observed in 27 Al solution spectra are not due to sample properties such as viscosity (which has been reduced by diluting with C 6 D 6 and heating to 315 K). S5

6 Figure S9. 27 Al solution NMR spectra of of AlCl 3 :EMIMCl solutions of variable acidity in C 6 D 6. All peak maxima are at 103 ppm but the peak width differs with the AlCl 3 :EMIMCl molar ratio. The narrowest peak is observed at a 1:1 ratio (FWHM=6 Hz, black), while some broadening is observed when increasing the concentration of EMIMCl (FWHM = 45 Hz, green). The maximal FWHM (1740 Hz) was found for an excess of aluminium chloride. The changes in peak width can be explained by the difference in speed of the dynamic equilibrium between AlCl 4 - (103 ppm) and Al 2 Cl 7 - (96 ppm). 1, 2 The large number of monomers is dominating the chemical shift. An excess of either AlCl 3 or EMIMCl reduces the exchange rate, causing the broadening of the signal. In the case of acidic melts (excess of AlCl 3 ) this effect is most pronounced, wherein the point of coalescence is crossed and a shoulder appears at approximately 97 ppm. The ionic solutions were diluted with C 6 D 6 and heated to 315 K in order to reduce the viscosity during the solution NMR measurements. Table S1. Characteristics of pristine graphite flakes, their processed particles (sphere and flake) and commercial spherical graphite. BET (m 2 g -1 ) Size (µm) I D /I G d 002 (Å) Pristine Flake Sphere Sphere (C) S6

7 Table S2. Acquisition parameters for 27 Al ssnmr spectra Magnetic field Temperature 16.4 T Room temperature Rotor diameter (mm) 2.5 Pulse Sequence Hahnecho Number of scans 1024 Recycle delay (s) 2 Spectral width (khz) 909 Spinning frequency (Hz) 0 Acquisition length (number of points) Al 90 pulse width [π/2] (µs) 3.4 Echo delay (ms) 0.2 Table S3. Acquisition parameters for 13 C ssnmr spectra Magnetic field Temperature 16.4 T Room temperature Rotor diameter (mm) 2.5 Pulse Sequence zg30 Number of scans Recycle delay (s) 2 Spectral width (khz) 78 Spinning frequency (Hz) 0 Acquisition length (number of points) Cd 30 pulse width [π/6] (µs) 1.1 S7

8 Table S4. Acquisition parameters for 27 Al solution NMR spectra. Magnetic field Temperature 11.7 T 315 K NMR tube diameter (mm) 5 Pulse Sequence zgpg Number of scans 1,4 or 16 Recycle delay (s) 2 Spectral width (khz) 66 Spinning frequency (Hz) 0 Acquisition length (number of points) Al 90 pulse width [π/2] (µs) 9.8 Decoupling sequence waltz16 1H 90 pulse for decoupling sequence (µs) 80 Table S5. Acquisition parameters for 13 C solution NMR spectra. Magnetic field Temperature 11.7 T 315 K NMR tube diameter (mm) 5 Pulse Sequence zgpg Number of scans 64 or 128 Recycle delay (s) 2 Spectral width (khz) 31 Spinning frequency (Hz) 0 Acquisition length (number of points) Al 90 pulse width [π/2] (µs) 9.5 Decoupling sequence waltz16 1H 90 pulse for decoupling sequence (µs) 80 S8

9 References (1) Taulelle, F.; Popov, A. I. Journal of Solution Chemistry 1986, 15, (6), (2) Nakayama, Y.; Senda, Y.; Kawasaki, H.; Koshitani, N.; Hosoi, S.; Kudo, Y.; Morioka, H.; Nagamine, M. Physical Chemistry Chemical Physics 2015, 17, (8), S9