SUPPORTING INFORMATION

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1 SUPPORTING INFORMATION Inverse Vulcanization of Elemental Sulfur to Prepare Polymeric Electrode Materials for Li-S Batteries Adam G. Simmonds,**, Jared J. Griebel,**, Jungjin Park, Kwi Ryong Kim, Woo Jin Chung, Vladimir P. Oleshko, Jenny Kim, Eui Tae Kim, Richard S. Glass, Christopher L. Soles, Yung-Eun Sung, Kookheon Char, Jeffrey Pyun * Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, AZ 8721, USA, Department of Chemical and Biological Engineering, The World Class University Program of Chemical Convergence for Energy & Environment, The National CRI Center for Intelligent Hybrids, and Center for Nanoparticle Research, Institute for Basic Research, Seoul National University, Seoul , Korea, Materials Science & Engineering Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD I) EXPERIMENTAL SECTION A. Materials and Instrumentation. Sulfur (S 8, sublimed powder, reagent grade, Aldrich), 1,3- Diisopropenylbenzene (DIB, 97 %, Aldrich), anhydrous Chloroform (Aldrich), Polyethylene (Avg. M w ~4000 g/mol), Conductive carbon (Super C65, Timcal), Lithium bis(trifluoromethane)sulfonimide (Aldrich), Lithium nitrate (Aldrich), Polypropylene separator (Celgard), Lithium foil (FMC), 1,3-Dioxolane (Novolyte) and 1,2-Dimethoxy ethane (Novolyte) were commercially available and used as received without further purification. The morphology and microstructure of copolymer S-r-DIB and conventional S 8 cathodes were characterized by field-emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDXS) techniques. FESEM observations and EDXS analyses of the cycled cathodes mounted on aluminum alloy stubs were performed using a Hitachi S4700 SEM. The instrument was equipped with a cold field-emission (FE) electron gun and an 80 mm 2 active area Oxford Instruments X-Max high-speed silicon drift X-ray detector (SDD). XPS data were collected with monochromatic Al(Kα) radiation using a KRATOS 165 Ultra photoelectron spectrometer. 1. General procedure for the preparation of poly(sulfur-random-(1,3- diisopropenylbenzene)) (Poly(S-r-DIB)) copolymers. The preparation of these copolymer materials was conducted using our previously report method. 1 A general procedure is listed below along with example protocols on the synthesis of these materials. To a 24 ml glass vial equipped with a magnetic stir bar was added sulfur (S 8, masses detailed below) and heated to T = 185 C in a thermostated oil bath until a clear orange colored molten phase was formed. 1,3-Diisopropenylbenzene (DIB, masses detailed below) was then directly

2 added to the molten sulfur medium via syringe. The resulting mixture was stirred at T = 185 C for 8-10 minutes, which resulted in vitrification of the reaction media. The product was then taken directly from the vial using a metal spatula and removal of the magnetic stir bar for determination of yields after allowing the reaction mixture to cool to room temperature. a. Preparation of poly(s-r-dib) with 20-wt% DIB: The copolymerization was carried out by following the general method written above with S 8 (4.00 g, 15.6 mmol) and DIB (1.00 g, 6.32 mmol) to afford a red solid (yield: 4.98 g). b. Preparation of poly(s-r-dib) with 30-wt% DIB: The copolymerization was carried out by following the general method written above with S 8 (3.50 g, 13.7 mmol) and DIB (1.50 g, 9.48 mmol) to afford a red solid (yield: 5.0 g). c. Preparation of poly(s-r-dib) with 40-wt% DIB: The copolymerization was carried out by following the general method written above with S 8 (3.00 g, 11.7 mmol) and DIB (2.00 g, 12.6 mmol) to afford a red solid (yield: 4.97 g). d. Preparation of poly(s-r-dib) with 50-wt% DIB: The copolymerization was carried out by following the general method written above with S 8 (2.50 g, 9.69 mmol) and DIB (2.50 g, 15.8 mmol) to afford a reddish-brown solid (yield: 4.99g). 2. Fabrication and testing of Li-S Batteries Poly(S-r-DIB) of various copositions were combined with conductive carbon and polyethylene as a binder in a mass ratio of 75:20:5, respectively and ball milled into a slurry with anhydrous chloroform. The slurry was then blade cast onto carbon coated aluminum foil and air dried resulting in a sulfur loading of roughly 0.75 mg/cm 2. This cathode was assembled into CR2032 coin cells (MTI) with a polypropylene separator and a lithium foil anode in an argon filled glove box. The electrolytes used were 0.38 M lithium bis(trifluoromethane)sulfonimide and 0.32M lithium nitrate in a 1:1v/v mixture of 1,3-dioxolane and 1,2-dimethoxy ethane. Battery cycling was done on an Arbin BT2000 battery tester from 1.7 to 2.6 V. B. Battery performance for poly(s-r-dib) with 15-wt% DIB 1. Battery cycling performance of 15-wt% DIB to 290 cycles. Fig S1. Battery cycling performance of poly(s-r-dib) copolymer, 15-wt% DIB to 290 cycles.

3 C. XPS studies of cycled Li-S cathodes from S 8 and poly(s-r-dib). To probe the chemical structure of charge and discharge products formed during cycling, Li-S batteries from both elemental sulfur and poly(s-r-dib) copolymers (with 10-wt% DIB) were studied using XPS. To ensure sample fidelity for these measurements, cycled coin cells were opened in a glove box and directly placed into the XPS sample chamber under air-free conditions. To enable assignment and comparison of sulfur species in the XPS, an Li 2 S reference material was purchased from Aldrich. The S 2p XPS of Li 2 S reference material from Aldrich (Fig. S2a) revealed the presence of a number of different sulfur species of various oxidation levels as noted by peaks observed at 161 ev for Li 2 S, at 162 ev for Li 2 S 2 and from ev corresponding to substituted internal sulfides (e.g.., Li-S-S-S-Li) from Li 2 S 3 and other high order linear polysulfides (Li 2 S 4, Li 2 S 6, Li 2 S 8 ). Peaks also from ev were observed oxidized sulfide species (e.g., SO x ) which likely form upon exposure to air and moisture. Peaks in this range also corresponded to the lithium bis(trifluoromethane)sulfonamide electrolyte used in these batteries. All of these XPS assignments are consistent with literature findings on similar Li-S battery materials. 2 Figure S2: S 2p XPS spectra of: (a) Li 2 S reference material purchased from Aldrich (b) Li-S battery cathode fabricated from S 8 left in the discharged state after 100 cycles (c) Li-S battery cathode fabricated from S 8 left in the charged state after 100 cycles For XPS examination of Li-S batteries from S 8 cathodes, two coin cells were subjected to 100 charge-discharge cycles from 1.7 to 2.6 V and examined in each state. Coin cells were opened in an Ar-filled glove box and rinsed with anhydrous 1,3-dioxolane and glyme prior to XPS measurements. For the XPS of S 8 cathodes after 100 cycles left in the discharged state, two peaks at around 162 ev and from ev were observed, corresponding to insoluble discharge products of Li 2 S 2 and Li 2 S 3 (Fig. S2b). It is important to note that the fully discharged

4 product in the cathode was not Li 2 S, as was anticipated. However, similar findings by Toney et al., using in operando XRD of cycled Li-S batteries reported that the formation of Li 2 S was also not observed after analysis of cycled cathodes. 3 XPS of S 8 cathodes after 100 cycles left in the charged state, were nearly identical to the discharged cathode XPS spectrum, which was attributed to the presence of irreversibly deposited insoluble discharge products of Li 2 S 2 and Li 2 S 3 that were not in electrical contact with the charge collector and incomparable of recharging to form higher order linear polysulfides (Fig. S2c). Comparative XPS measurements of Li-S batteries fabricated from poly(s-r-dib) copolymer cathodes subjected to 1-discharge & charge cycle from 1.7 to 2.6 V were also investigated. S 2 p XPS spectrum of poly(s-r-dib) cathodes after 1-discharge cycle exhibited 2 peaks around 162 ev and from ev, corresponding to the formation of Li 2 S 2 and Li 2 S 3 insoluble discharge as similarly observed in cycled S 8 cathodes (Fig. S2b). Hence, Li 2 S discharge products were NOT formed after battery discharge as discussed for cycled S 8 cathodes. The formation of higher polysulfide species were observed after Li-S poly(s-r-dib) copolymer cathodes were subjected to 1 charge cycle, as noted by the disappearance of the Li 2 S 2 discharge product at around 162 ev and the presence of a broad peak from ev from the higher order polysulfides. The presence of oxidized sulfur species as noted by a broad peak from ev was also observed and attributed to trace electrolyte present in the sample. As an additional reference spectrum, S 2 p XPS spectrum of neat poly(s-r-dib) of both 10 and 30- wt% DIB were acquired, confirming the presence of broad interally substituted sulfur atom peaks from ev, Figure S3: S 2p XPS spectra of: (a) Li 2 S reference material purchased from Aldrich (b) Li-S battery cathode fabricated from poly(s-r-dib) with 10-wt% DIB left in the discharged state after 100 cycles (c) Li-S battery cathode fabricated from poly(s-r-dib) with 10-wt% DIB left in the charged state after 100 cycles

5 Figure S4: S 2p XPS spectra of poly(s-r-dib) copolymers (both 10 and 30-wt% DIB) Figure S5: Discharge products of free polysulfides and organosulfur DIB discharge products for high (top scheme) and low (bottom scheme) DIB content copolymers. When using high content DIB copolymers, a high concentration of organosulfur species are generated which are in equilibrium with lower sulfide (e.g., Li 2 S 3 ) to form high order polysulfides, which are more soluble in the electrolyte, do NOT re-deposite onto the cathode and result in charge capacity fading. Conversely, for low DIB content copolymers, a higher concentration of longer polysulfides are present (due to the initially lower concentration of DIB units), which favors disproportation back to insoluble Li 2 S 3 (and other lower sulfides) and organosulfur-dib discharge products. In the scheme Li + cations are omitted for clarity due to the presence of excess Li-ions in the electrolyte.

6 Figure S6: FE-SEM images in the charged state after solvent-rinsing of cathodes to remove electrolyte salts for (a) Li-S batteries using S8 cathodes at 80 cycles and (b) Li-S batteries using 10% by mass DIB sulfur copolymer cathodes at 120 cycles. Note the cathodes fabricated from sulfur copolymers remain a greater degree of structural integrity after extensive cycling in comparison to cycled S8 batteries. REFERNCES 1) Chung, W.-J.; Griebel, J.J.; Kim, E.-T.; Yoon, H. S.; Simmonds, A.G.; Ji, H.-J.; Dirlam, P.T.; Glass, R.S.; Wie, J.J.; Nguyen, N.A.; Guralnick, B.W.; Park, J.; Somogyi, A.; Theato, P.; Mackay, M.E.; Sung, Y.-E.; Char, K.-C.; Pyun, J. Nat. Chem. 2013, 5 (6),

7 2) (a) Tarascon et al., Energy Environ. Sci., 2013, 6,176. (b) Diao et al., Journal of The Electrochemical Society, 2012, 159 (11) A1816-A ) Nelson, J.; Misra, S.; Yang, Y.; Jackson, A.; Liu, Y.; Wang, H.; Dai, H.; Andrews, J. C.; Cui, Y.; Toney, M. F. J. Am. Chem. Soc. 2012, 134, 6337