Graphene-Templated Growth of WS₂ Nanoclusters for Catalytic Conversion of Polysulfides in Lithium–Sulfur Batteries

Abstract

The practical application of lithium−sulfur (Li−S) batteries is hindered by poor cycling stability mainly derived from the shuttling of lithium polysulfides (LiPSs). Catalysis, which can promote the fast conversion of LiPSs, is a promising solution to the abovementioned problem. In this work, ultrasmall WS 2 nanoclusters with the size around 2 nm are synthesized, with graphene as the growth template. The ultrasmall WS 2 nanoclusters have abundant exposed edges and numerous unsaturated sulfur sites, which significantly enhance the adsorption ability toward LiPSs and render a high catalytic activity for their fast conversion. In addition, the three-dimensional structure assembled with graphene also provides a highly conductive network and large surface area for the fast conversion of LiPSs. As a result, the Li−S battery using the abovementioned hybrid as a catalytic sulfur host shows a low capacity fading of 0.067% per cycle within 250 cycles at 1 C. With the sulfur loading of 2.7 mg cm −2 , a high capacity retention of 74.7% after 500 cycles is achieved. Overall, this work proposes a promising catalyst design to improve the performance of Li−S batteries.

Unravel the Catalytic Effect of Two-Dimensional Metal Sulfides on Polysulfide Conversions for Lithium–Sulfur Batteries

“…As shown in Figure d, after processing ∼6000 s, the integral areas by the current and time related to the deposition of Li 2 S varied significantly. , To prove the positivity of promoting Li 2 S oxidation during the charge process, similar kinetic investigations were conducted by employing a potentiostatic charge process at 2.4 V after galvanostatic discharge (Figure e). The surface areas on Cr 3 S 4 /C and WS 2 /C are clearly larger than MoS 2 /C and NCs, indicating more electrodeposition and the dissolution capacity on the reactive interfaces, suggesting excellent electrocatalysis in regulating kinetics of redox reactions of polysulfides. − CV measurements were also conducted to estimate the Li ion diffusivity property at a scan rate of 0.1 mV s –1 (Figure f). All the appeared peaks belong to the regular redox peaks.…”

3D Tungsten Disulfide/Carbon Nanotube Networks as Separator Coatings and Cathode Additives for Stable and Fast Lithium–Sulfur Batteries

“…The interaction of WS 2 with LiPS was determined from the W 4f and S 2p analysis. Before Li 2 S 6 adsorption, a pair of doublet peaks at 32.9 and 35.1 eV in the W 4f 7/2‑5/2 spectrum is assigned to W 4+ in WS 2 (Figure b), and the other pair of doublet at 36.0 and 38.7 eV is derived from the W 6+ in WO 3 formed by surface oxidation of WS 2 during preparation and transportation. , After the interaction of WS2/CNTs with Li 2 S 6 , the doublet peaks of W 4+ shift toward lower binding energies of 32.2 and 34.3 eV, indicating the charge transfer between Li 2 S 6 and WS 2 . It is noteworthy that extra doublet peaks located at 33.2 and 35.3 eV are attributed to the newly formed W–S bond between the W atoms exposed at sulfur-defective or/and edge sites of WS 2 with surrounding LiPS (Figure c) .…”

“…In contrast, after Li 2 S 6 adsorption, the S 2p 3/2–1/2 spectrum can be fitted to five pairs of doublets (Figure e): one pair for S 2– in WS 2 , two pairs for the bridging sulfur (SB 0 ) and terminal sulfur (S T –1 ) of adsorbed Li 2 S 6 molecules, and two pairs for thiosulfate and polythionate formed by surface redox of Li 2 S 6 with WS 2 and further reaction of thiosulfate with polysulfides. , The conversion of Li 2 S 6 to thiosulfate/polythionate is accompanied with a decrease in the W valence state. Studies show that the formation of polythionate is reversible, and the polythionate could serve as an intermediate for anchoring and transport of LiPS, , thus suppressing LiPS dissolution and shuttling. Furthermore, discrete Fourier transform (DFT) calculations were performed to compare the adsorption configuration and adsorption energy of Li 2 S 6 on the surface of WS 2 and carbon.…”

Sodium Sulfate Template-Directed Methodology of Rolling Up a Two-Dimensional Graphene Nanosheet into a One-Dimensional Nanoscroll and Its Anode Performance in a Lithium-Ion Battery

“…The XPS spectra of graphite oxide and 1D-GNS show two major peaks at 282 and 534 eV for the C 1s and O 1s, respectively (Figure S2). Parts C and D of Figure compare the C 1s high-resolution XPS spectra of graphite oxide and 1D-GNS, in which the deconvoluted C 1s spectra of graphite oxide (Figure C) can be resolved into four components centered at 283.8, 285.5, 287.9, and 290.5 eV, representing C–C/CC, C–O–C/C–O, CO, and OC–O, respectively. − In contrast, from the C 1s spectra of 1D-GNS (Figure D), the shrinking or even concealment of the peak area of the oxygen-containing groups can be seen, which can be attributed to the reduction of most of the oxygen-containing groups caused during the high-temperature treatment process in the Ar/H 2 atmosphere. Raman spectra can be used to judge the degree of disorder and graphitization, as shown in Figure E.…”