Correlation of the electrochemistry of poly(acrylonitrile)–sulfur composite cathodes with their molecular structure

Differences in Electrochemistry between Fibrous SPAN and Fibrous S/C Cathodes Relevant to Cycle Stability and Capacity

“…6,[23][24][25] Elemental analysis (Table S1) revealed S-contents between 38 and 44 wt.-%. S/ACF-based cathode material was synthesized using Kynol ACF-1603-20 (2000 m 2 g −1 ; pores < 20 Å).…”

“…This z E-mail: michael.buchmeiser@ipoc.uni-stuttgart.de high cycle stability is related to the very unique structure of SPAN, which has been elucidated earlier by our group (Figure 1). 6,[23][24][25] One of the most important structural features of SPAN is the presence of covalently bound sulfur in form of (vinylogous) thioamides, which exist in their enolate form, thereby allowing for the formation of intra-and intermolecular oligosulfide chains. In turn, during charging, the enolic thioamides in their anionic form have been proposed to serve as "docking sites" for sulfur during recharge, which allow for the reversible reformation of the above-outlined oligosulfides.…”

Understanding of Sulfurized Polyacrylonitrile for Superior Performance Lithium/Sulfur Battery

“…Many spectroscopic characterizations have consistently identified that sulfurs in the SPAN are present in the form of short -S x -chains covalently bonded to the cyclized and dehydrogenated PAN backbones through C-S bonds [8][9][10]16,17]. The group peaks at 1600-1200 cm −1 and characteristic peak at 802 cm −1 in the Fourier Transform Infrared Spectroscopy (FTIR) spectra are good indications of the dehydrogenated six-membered ring structure containing unsaturated carbon double bonds and heteroatoms [16].…”

“…In general, the signal intensity ratios of the S-C to S-S and of G mode to D mode are increased with the reaction temperature and the reaction time, reflecting the fact that the length of -S x -chains decreases and the degree of graphitization increases with the reaction temperature and reaction time. The covalent bonding of sulfur to the polymer backbones has been also indirectly verified by two experiments of (1) the solvent (toluene) extraction showing that the sulfur in the SPAN is unextractable [9] and (2) the thermogravimetric analysis (TGA) showing that the sulfur in the SPAN cannot be completely removed even at above 800 °C [10,12]. Based on the results above, two structures as shown by Structure-a and Structure-b in Scheme 1 were proposed by Yu et al [16] and Fanous et al [9], respectively.…”

“…Among numerous potential candidates, sulfurized polyacrylonitrile (SPAN) has been most intensively studied due to its excellent electrochemical performance and low process cost. The synthesis of SPAN was first reported in 2002 by Wang et al who heated a 5:1 (wt) S/PAN mixture at 280-300 °C under argon for 6 h [2,3], and since intensive investigations have been followed, especially by the groups OPEN ACCESS led by He [4][5][6][7][8], Buchmeiser [9][10][11], and Chen [12][13][14][15]. Most of previous works were focused on the structural characterization, the optimization of synthesis conditions in variations of reaction temperature, reaction time and S/PAN ratio, as well as the applications with different electrolyte systems [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”