Selenium as Extra Binding Site for Sulfur Species in Sulfurized Polyacrylonitrile Cathodes for High Capacity Lithium‐Sulfur Batteries

Abstract

Due to their high theoretical energy density, lithium sulfur (LiÀ S) batteries are promising candidates for next generation energy storage systems. Unfortunately, polysulfide dissolution in ether-based electrolytes is still a major problem of LiÀ S batteries. Sulfurized polyacrylonitrile (SPAN) can be used as electrode material in carbonate-based electrolytes to avoid large-scale dissolution of polysulfides. But SPAN composites usually suffer from low sulfur content (< 50 wt %) and low capacity, limiting their practical application. Here, we synthesize a novel Se doped SPAN (SeSPAN) composite by one-step thermal treatment. Se atoms are uniformly distributed in the SeSPAN composite and serve as binding sites for S species, increasing the sulfur content up to about 60 wt %, higher than previously reported results. In addition, the Se doping itself is contributing to an increased capacity. The discharge/charge mechanism of the SeSPAN composite is investigate by Raman and X-ray photoelectron spectroscopy, indicating the existence of SeÀ S bonds and good electrochemical reversibility. Thus, the SeSPAN cathode delivers an excellent initial specific capacity of 1044 mA h g À 1 (calculated for the mass of the whole composite) and a high coulombic efficiency of almost 100 %. Compared with conventional SPAN composites, our SeSPAN material shows a great improvement on the capacity and cycle life and provides a new way to build high capacity SPAN composites.

Graphene Foam Current Collector for High-Areal-Capacity Lithium–Sulfur Batteries

“…This set of peaks correspond to the transformation from short-chain sulfur to Li 2 S (SPAN-S x – + 2Li + + 2e – ↔ SPAN-S x –1 – + Li 2 S; 2 ≤ x ≤ 7). It should be mentioned that recently in Se 0.06 SPAN similar reduction peaks were observed but the transformation of short-chain sulfur was suggested to be mediated through to the fast reduction of soluble Li 2 S n ( n ≤ 4) to insoluble Li 2 S 2 /Li 2 S. , …”

“…). It should be mentioned that recently in Se 0.06 SPAN similar reduction peaks were observed but the transformation of short-chain sulfur was suggested to be mediated through to the fast reduction of soluble Li 2 S n (n ≤ 4) to insoluble Li 2 S 2 /Li 2 S. 44,45 Figure 3a,b shows cyclic voltammograms for GF0, GF1, GF2, and Al/C1 normalized by the weight of S and the weight of the cathode, respectively. As seen in Figure 3a, Al/C1 appears to be superior to GF0 when normalized by the mass of S. This observation is attributed to lower thickness of SPAN coating on Al/C1 compared to GF0.…”

Structure Engineering of BiSbSx Nanocrystals Embedded within Sulfurized Polyacrylonitrile Fibers for High Performance of Potassium‐Ion Batteries

“…The peaks at approximately 1351 and 1570 cm −1 area assigned to the D and G bands of carbon, respectively, belonging to the bond stretching of sp 3 carbon atoms associated with the disordered carbon, and sp 2 carbon atoms representing the ordered carbon, respectively [44] . By using the integral area values for the D and G peaks (Figure S3), the I D / I G ratios for the BiSbS x @SPAN‐450 and BiSbS x @SPAN‐550 samples are 1.2 and 2.02, respectively, confirming that the ordered carbon in SPAN was destroyed with the increase of reaction temperature [45] . In addition, the C−S modes for SPAN can be observed at 180 cm −1 and approximately 307 and 366 cm −1 , and the peaks at 474 and 934 cm −1 are associated with the S−S stretching mode [37,46] .…”

“…[44] By using the integral area values for the D and G peaks (Figure S3), the I D /I G ratios for the BiSbS x @SPAN-450 and BiSbS x @SPAN-550 samples are 1.2 and 2.02, respectively, confirming that the ordered carbon in SPAN was destroyed with the increase of reaction temperature. [45] In addition, the CÀ S modes for SPAN can be observed at 180 cm À 1 and approximately 307 and 366 cm À 1 , and the peaks at 474 and 934 cm À 1 are associated Chemistry-A European Journal with the S À S stretching mode. [37,46] Remarkably, the increase in reaction temperature leads to the peaks corresponding to the CÀ S bonds to disappear in BiSbS x @SPAN-550, demonstrating the structural destruction of SPAN with increased temperature.…”

Capturing polysulfides by sulfurized‐polyacrylonitrile in lithium‐sulfur batteries and the sulfur‐chain effects through Density Functional Theory

“…[34][35][36][37][38] Nevertheless, when combining SPAN with other materials or doping S with homologous elements, an improved life cycle could be achieved. [39][40][41][42][43][44][45][46][47] During the vulcanization of polyacrylonitrile (PAN) into SPAN, H atoms are usually removed from the PAN, forming H 2 S gas during the synthesis and leaving behind a π-conjugated system at the cyclized-polyacrylonitrile (cPAN) backbone, where sulfur can chemically bind to carbon in the π-conjugated units, forming SPAN. [35,40,[48][49][50][51][52][53][54][55] A C uc may appear in the cPAN backbone during the final stages of syntheses, [56] or due to C-S bond cleavage during the LiSB cycles.…”