Understanding the function of cetyltrimethyl ammonium bromide in Lithium/Sulfur Cells

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1 Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 2017 Supporting Information Understanding the function of cetyltrimethyl ammonium bromide in Lithium/Sulfur Cells Ayako Kawase a and Elton J. Cairns a,b a. Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA b. Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA Contents Fig. S1 Graphical explanation of the method to calculate the contents in -CTA. Fig. S2 TGA results of references. Fig. S3 MS spectrum of S-CTA model compound with the theoretical isotope pattern. Fig. S4 1H NMR spectra of -CTA composite. Fig. S5. 13C NMR spectra of -CTA composite. Fig. S6 1H NMR spectra of -CTA composite. Fig. S7 XRD patterns of composite. Fig. S8 MS spectra of S-CDMA model compound with the theoretical isotope pattern. Fig. S9 XAS spectra of composite. Fig. S10 Raman spectra of references. Fig. S11 Theoretically calculated Raman spectra of amine compounds. Fig. S12 SEM images of -CTA composite. Fig. S13 Cyclic voltammetry of -CTA composites. Fig. S14 Voltage profiles of -CTA composites. Fig. S15 Voltage profiles of -CTA composites for the first 5 cycles. Fig. S16 Voltage profiles of -CTA composites after 100 cycles.

2 Abbreviations used in this Supporting Information -CTA: composite of sulfur, graphene oxide and cetyltrimetylammonium bromide (CTAB), TGA: Thermogravimetric analysis, Me2Sx: Dimethyl polysulfide, CA: cetylamine, CMA: etylmethylamine, CDMA: cetyldimethylamine, MS: mass spectrometry, S-CTA: model composite of sulfur and CTAB, NMR: nuclear magnetic resonance spectrometry, H2Sx: Hydrogen polysulfides, XRD: X-ray diffraction, S-CDMA: model composite of sulfur and CDMA.

3 Fig. S1 Graphical explanation of the method to calculate the contents in -CTA. Before the heat treatment After the heat treatment Evaporated (measured by weighing the samples) 100 Sulfur Weight % Sulfur Weight % GO Temperature [ C] TGA result before the heat treatment Phase X GO Temperature [ C] TGA result after the heat treatment Fig. S1 Graphical explanation of the method to calculate the contents of sulfur and Phase X produced during the heat treatment in -CTA using the TGA results and the measurement of the weight of the samples before and after the heat treatment. Fig. S2 TGA results of references. Weight% Sulfur Me2Sx 2 S x CA CMA CDMA Temperature [ C] Fig. S2 TGA results of sulfur, Me 2 S x, CA, CMA and CDMA as references.

4 Fig. S3 MS spectrum of S-CTA model compound with the theoretical isotope pattern. Fig. S3 ESI-MS spectrum of S-CTA model composite after the heat treatment with the theoretical isotope pattern to identify CMA.

5 Fig. S4 1H NMR spectra of -CTA composite. Fig. S4 Enlarged NMR spectra of S-CTA, -CTA2 and Me 2 S x as reference to identify Me 2 S x produced in S-CTA and -CTA after the heat treatment.

6 Fig. S5. 13C NMR spectra of -CTA composite. C AB -GO-C A2 ynthesized Me 2 x Fig. S5 13C NMR spectrum of -CTA after the heat treatment, and the spectra of CTAB and Me 2 S x as references.

7 Fig. S6 1H NMR spectra of -CTA composite. -GO-C A2 CDMA Intensity([a.u.]( CMA CA 6< H 2 x in reference (9) ynthesized H 2 x 2 1 Water Acetone 4.5" 4" 3" 2.5" 2" 1.5" 1" 0.5" Chemical(Shi4 ([ppm]( Fig. S6 1H NMR spectra of -CTA2 with reference spectra of synthesized H 2 S x, water, acetone and three types of amines, CDMA, CMA and CA.

8 Fig. S7 XRD patterns of composite. -CTA3-BH -CTA3 Sulfur Relative Intensity [u. a.] θ Fig. S7 XRD patterns of -CTA with and without CTAB and before and after the heat treatment with reference of sulfur. Fig. S8 MS spectra of S-CDMA model compound with the theoretical isotope pattern. Fig. S8 MS spectra of S-CDMA model composite after the heat treatment with the theoretical isotope pattern corresponding to the part to identify (a) Cetylmethylaminomethanethiol (S-CDMA-1) and (b) N-cethyl-1- cetylsulfanylmethanamine (S-CDMA-2).

9 Fig. S9 XAS spectra of composite. (a) S-S -BH -CTA1-BH (b) S-S S-C -CTA1 -CTA2-BH -CTA2 -CTA3-BH -CTA3 Intensity [a. u.] Intensity [a. u.] Photon Energy [ev] Photon Energy [ev] Fig. S9 XAS spectra of -CTA composite having different amount of CTAB before the heat treatment (a) and after the heat treatment (b). Fig. S10 Raman spectra of references. CTAB Intensity [a. u.] CA CMA CDMA Raman Shift [cm-1] Fig. S10 Raman spectra of CTAB, CA, CMA and CDMA as references.

10 Fig. S11 Theoretically calculated Raman spectra of amine compounds. (CN) amine (CH) end of chain (CN) amine (CC) (CN) (CC) amine (CH) (CH) CTA+ Intensity [a. u.] (CH3) amine (CH3) amine CA CMA (CH3) amine CDMA Raman shift [cm-1] Fig. S11 Theoretically calculated Raman spectra of CTA +, CA, CMA and CDMA with their vibration modes by using optimized models.

11 Fig. S12 SEM images of -CTA composite. (a) (b) (c) 2 m 2 m -BH (d) 2 m -CTA0.625-BH 2 m -CTA0.625 (e) (f) (g) 2 m 2 m -CTA1.25-BH (h) -CTA m -CTA2.5-BH 2 m -CTA2.5 Fig. S12 SEM images of -CTA composites having different amount of CTAB before and after the heat treatment.

12 Fig. S13 Cyclic voltammetry of -CTA composites. -CTA2.5 -CTA25 Me2Sx 2 S x Current Voltage [V vs Li] Fig. S13 Cyclic voltammetry of -CTA composites having CTAB and no CTAB and dimethylpolysulfide.

13 Fig. S14 Voltage profiles of -CTA composites. (a) -CTA1.25 (b) -CTA0.625 (c) Fig. S14 Voltage profiles of (a) -CTA1.25, (b) -CTA0.625 and (c) at different C rates. C rate in discharge and charge are indicated on left side and right side of the slash respectively.

14 Fig. S15 Voltage profiles of -CTA composites for the first 5 cycles. (a) CTA2.5 Voltage [V] cycle 2 cycles 3 cycles 4 cycles 5 cycles (b) (c) Voltage [V] Capacity [mah/g (Sulfur)] CTA cycle cycles 3 cycles cycles cycles Capacity [mah/g (Sulfur)] CTA0.625 Voltage [V] cycle 2 cycles 3 cycles 4 cycles 5 cycles (d) Capacity [mah/g (Sulfur)] Voltage [V] cycle 2 cycles 3 cycles 4 cycles 5 cycles Capacity [mah/g (Sulfur)] Fig. S15 Voltage profiles of (a) -CTA2.5, (b) -CTA1.25, (c) -CTA0.625 and (d) for the first 5 cycles.

15 Fig. S16 Voltage profiles of -CTA composites after 100 cycles cycle Voltage [V] CTA06 -CTA CTA12 -CTA1.25 -CTA25 -CTA Capacity [mah/g (Sulfur)] Fig. S16 Voltage profiles of -CTA2.5, -CTA1.25, -CTA0.625 and after 100 cycles.