WSe2 Flakelets on N‐Doped Graphene for Accelerating Polysulfide Redox and Regulating Li Plating
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The practical application of lithium-sulfur batteries is still limited by the lithium polysulfides (LiPSs) shuttling effect on the S cathode and uncontrollable Li-dendrite growth on the Li anode. Herein, elaborately designed WSe2 flakelets immobilized on N-doped graphene (WSe2 /NG) with abundant active sites are employed to be a dual-functional host for satisfying both the S cathode and Li anode synchronously. On the S cathode, the WSe2 /NG with a strong interaction towards LiPSs can act as a redox accelerator to promote the bidirectional conversion of LiPSs. On the Li anode, the WSe2 /NG with excellent lithiophilic features can regulate the uniform Li plating/stripping to mitigate the growth of Li dendrite. Taking advantage of these merits, the assembled Li-S full batteries exhibit remarkable rate performance and stable cycling stability even at a higher sulfur loading of 10.5 mg cm-2 with a negative to positive electrode capacity (N/P) ratio of 1.4 : 1.Keywords:
Polysulfide
Plating (geology)
Dendrite (mathematics)
Stripping (fiber)
Abstract Lithium–sulfur batteries are regarded as one of the most promising candidates for next‐generation rechargeable batteries. However, the practical application of lithium–sulfur (Li–S) batteries is seriously impeded by the notorious shuttling of soluble polysulfide intermediates, inducing a low utilization of active materials, severe self‐discharge, and thus a poor cycling life, which is particularly severe in high‐sulfur‐loading cathodes. Herein, a polysulfide‐immobilizing polymer is reported to address the shuttling issues. A natural polymer of Gum Arabic (GA) with precise oxygen‐containing functional groups that can induce a strong binding interaction toward lithium polysulfides is deposited onto a conductive support of a carbon nanofiber (CNF) film as a polysulfide shielding interlayer. The as‐obtained CNF–GA composite interlayer can achieve an outstanding performance of a high specific capacity of 880 mA h g −1 and a maintained specific capacity of 827 mA h g −1 after 250 cycles under a sulfur loading of 1.1 mg cm −2 . More importantly, high reversible areal capacities of 4.77 and 10.8 mA h cm −2 can be obtained at high sulfur loadings of 6 and even 12 mg cm −2 , respectively. The results offer a facile and promising approach to develop viable lithium–sulfur batteries with high sulfur loading and high reversible capacities.
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Abstract BACKGROUND A large amount of research has improved electrochemical performance by strengthening the chemical affinity by using polar materials in lithium–sulfur batteries. However, only some of this research has focused on the relationship between structure and polysulfide adsorption ability. RESULTS In this work, a Ti 3 C 2 nanosheet structure has been applied as sulfur host matrix to improve electrochemical performance. Due to the nanosheet structure, the polysulfide was able to diffuse between the Ti 3 C 2 layers, therefore improving the catalytic effect of the polysulfide. Moreover, the space between the Ti 3 C 2 layers can store the soluble polysulfide as an effective reservoir. As a result, the traditional shuttle effect of the polysulfide could be efficiently inhibited. CONCLUSION Therefore, the as‐prepared Ti 3 C 2 /S composites exhibited high specific capacity, high rate performance, and stable cycle performance. All these superior electrochemical performances are attributed to the presence of the Ti 3 C 2 nanosheet. © 2022 Society of Chemical Industry (SCI).
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Literature data for the redox potential of the aqueous sulfur‐polysulfide redox couple have been correlated by accounting for the complex equilibration of various sulfur‐bearing species in alkaline electrolyte. For electrolytes wherein the ratio of zero‐valent sulfur to total sulfide ranges from 0.1 to 3.0, the pH ranges from 10.6 to 13.8, and the temperature ranges from 25 to 90°C, the redox potential is correlated by the expression
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Abstract A certain portion of the sulfur used appears as polysulfide sulfur in all vulcanization processes. The polysulfide concentration passes through a maximum with time, so that it must be considered to be an intermediate product which disappears to form final products. It is shown that the dependence of polysulfide sulfur concentration on time may be described by an empirical equation with three constants, of which one is related to the system, the other two depending in a characteristic way on concentration or temperature. The application of this equation permits recognition of a close relation between the kinetics of sulfur decrease and that of polysulfide formation. This leads to a kinetic theory of formation and decrease of polysulfide sulfur which is developed in detail. Applying the experimentally determined first order velocity constants of sulfur decrease and conditions obtaining for polysulfide maximum, velocity constants for polysulfide decrease can be calculated. With these, equations for the functional relation between polysulfide sulfur and time as well as for the increase of final products may be set up. Good correspondence between theory and experiment is found for the dependence of polysulfide sulfur in the vulcanizate on time. Comparisons were examined which indicate the validity and applicability of the kinetics developed.
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Polysulfides have received increased interest in redox biology due to their role as the precursors of H2S and persulfides. However, the compounds that are suitable for biological investigations are limited to cysteine- and glutathione-derived polysulfides. In this work, we report the preparation and evaluation of a novel polysulfide derived from thioglucose, which represents the first carbohydrate-based polysulfide. This compound, thioglucose tetrasulfide (TGS4), showed excellent stability and water solubility. H2S and persulfide production from TGS4, as well as its associated antioxidative property were also demonstrated. Additionally, TGS4 was demonstrated to significantly induce cellular sulfane sulfur level increase, in particular for the formation of hydropersulfides/trisulfides. These results suggest that TGS4 is a useful tool for polysulfide research.
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Abstract Added sulfur in polysulfide aircraft sealants can become chemically bound to the polymer backbone. The chemical processes involved, and their effect on thermal performance of the resulting sealants, have been examined. Reactions of aliphatic thiols with sulfur and amine catalysts have been reinterpreted to include possible involvement of hydropolysulfide intermediates. When the procedure was applied to polysulfide liquid polymers, products with substantial levels of tri‐ and tetra‐sulfide links were formed. 13 C–NMR spectroscopy of model compounds enabled the assignment of chemical shifts associated with S 3 to S 5 links in the sulfur enriched polymers. Spectroscopic examination afforded no evidence for the presence of such species in commercial polysulfide liquid polymers. No obvious detrimental effects on elevated temperature performance of polysulfide sealants resulted from the incorporation of up to 1% sulfur into the polymer backbone. A higher degree of cure is achieved and this is associated with increased hardness and modulus, together with reduced extension as compared with untreated sealants. © 1994 John Wiley & Sons, Inc.
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