Interface engineering by atomically thin layer tungsten disulfide catalyst for high performance Li–S battery

https://doi.org/10.1016/j.mtener.2019.100380Get rights and content

Highlights

  • A highly crystalline and atomically thin tungsten disulfides on carbon cloth (WS2@CC) was developed.

  • Atomically thin WS2 with high crystal quality and abundant edges sites can effectively accelerates the redox kinetics.

  • The hierarchical flower-stacked WS2 shows extremely strong polysulfide adsorption for Li–S batteries.

Abstract

Owing to high aspect ratio of edge sites and superior catalytic activity, atomically thin transition metal dichalcogenides (TMDCs) show great promise to tailor the electrolyte/electrode interface properties for high performance lithium-sulfur battery (Li–S battery). However, the TMDCs that engineer the electrode/electrolyte interface are usually produced through chemical hydrothermal methods, which show low crystallinity and thick multilayer structure. Herein, a highly crystalline and atomically thin tungsten disulfides on carbon cloth (WS2@CC) was developed via chemical vapor deposition (CVD) and served as an effective electrode/electrolyte interface for Li–S battery. Our results demonstrate that the atomically thin WS2 with high crystal quality and abundant edges sites can effectively accelerates the redox kinetics of sulfur/lithium polysulfides and regulates the precipitation/decomposition of insoluble Li2S. More importantly, it was revealed that the hierarchical flower-stacked WS2 with excessive exposed catalytic edges shows extremely strong polysulfide adsorption, which causes the sulfur species aggregation and passivation on the WS2@CC surface, thus resulting in deformed rate performance and poor cycling stability as compared to the few-layer WS2@CC. Our work provides a new insight into the structural engineering of TMDCs by CVD for Li–S battery, and suggests the importance of rational chemisorption and catalysis of the interface to realize the high-performance Li–S battery.

Introduction

Advances in rechargeable batteries technology for sustainable and clean energy applications such as electric vehicles, portable electronic devices and smart grid storage remain challenging due to the limited theoretical energy density and high cost of the current lithium ion batteries (LIBs) technology [[1], [2], [3]]. Lithium-sulfur (Li–S) batteries have emerged as a promising alternative to resolve the issue of renewable energy intermittency due to their low cost, high energy density (2600 Wh kg−1), and environmental friendless [1,[4], [5], [6]]. However, the implementation of Li–S battery for practical applications has been impeded by the following intrinsic issues: (a) the poor electronic conductivity of sulfur and its discharge products (Li2S/Li2S2) that results in sluggish redox kinetics and low sulfur utilization [[7], [8], [9]], (b) the diffusion of intermediate lithium polysulfide species during cycling causes shuttle effect and parasitic reaction to lithium anode, resulting in a rapid capacity decay and short cycle life [2,9,10], and (c) the large volumetric changes of the electrode, which leads to the cathode electrode pulverization that significantly affects its cycling stability [11].

Considerable efforts have been made to solve the abovementioned issues, such as cathode host material design, electrolyte modifications, and etc [[12], [13], [14]]. Although great progress has been made, however, in some cases, these strategies cannot realize high sulfur loading, stable cycling, fast redox transformation simultaneously. Recently, engineering the interface between electrolyte and separator by inserting a functional interlayer such as carbon cloth, carbon nanotube coated separator [15,16], has been developed for the absorption of soluble polysulfide and reuse of the absorbed active material. However, the diffusion of polysulfides is prone to the precipitation of polysulfides on electrode/separator interfaces, resulting in the passivation of active surface, aggregation of solid polysulfide on the interlayer [17,18]. Notably, the precipitation of insoluble polysulfides is highly relied on the surface chemistry where sulfur redox reactions occur. Designing an effective collaborative sulfur/polysulfide physicochemical transformation interface between electrolyte and electrode with high electrical conductivity, strong sulfur/sulfides chemisorption, superior electrocatalysis and intense catalytic reactive sites simultaneously is essential for improving the sulfur utilization, and realizing stable and high-rate Li–S batteries. In searching for an efficient collaborative sulfur/polysulfide physicochemical transformation interface to suppress the polysulfide shuttle effect and regulate the solid sulfur species deposition, two-dimensional (2D) transition metal dichalcogenides (TMDCs) are attractive owing to their high catalytic reactive surface, superior chemical stability, and low cost [[19], [20], [21], [22], [23]]. The catalytic activity of this type of materials highly depends on the number of exposed edge sites that exhibits unique chemical and electronic structure compared to their basal planes [5,24]. It has been proven that atomically thin layered structures with high aspect ratio of edge sites and high effective catalytic surface is an effective catalytic interfacial candidate for sulfur redox reaction [5]. So far, intensive efforts have been done to improve the aspect ratio of active catalytic sites in TMDCs through nanostructure engineering [5,[25], [26], [27], [28]]. However, these TMDCs are usually obtained through chemical hydrothermal method, which show unsatisfactory catalytic effect due to their low crystallinity and stacked multilayer structure [29,30]. Besides, the intrinsic defects in the crystal structure such as sulfur vacancy induce poor structural stability to restrain the lamella pulverization and active site invalidation, thus resulting in poor electrochemical performance. Chemical vapor deposition (CVD) is a promising, highly controllable method to synthesize high crystallinity and atomically thin layer 2D materials. Up to date, several types of TMDCs have been prepared via CVD to construct the catalytic active sites and accelerate the sulfur redox conversion, however, the large-scale production of ultrathin TMDCs as well as the potential application of TMDCs as catalytic interface are rarely reported.

In this contribution, a conductive and catalytic interface constructed by atomically thin layer WS2 catalysts on conductive support matrix is proposed to effectively inhibit the polysulfides shuttle effect, facilitate the polysulfides redox transformation and regulate the Li2S deposition. A low-pressure CVD method was employed to synthesize the atomically thin WS2 on carbon cloth (WS2@CC) on a large scale to imitate the electrocatalysis-driven process for achieving the commercial demand of the battery application. By tuning the precursor quantity, growth period, and growth times, different morphologies of the WS2 nanostructures such as few-layer planar flakes or layer-by-layer grown hierarchical flower-stacked structure were obtained. In addition, this strategy also demonstrates the substrate-independent growth mechanism, suggesting a versatile growth route for WS2 nanostructures with diverse substrate. Compared with the multilayer flower-stacked WS2, the atomically thin layer WS2@CC provides a more effective interface with strong chemisorption, high reactive catalytic sites and high electrical conductivity for promoting the redox conversion kinetics of sulfur intermediates and eliminating the polysulfide shuttle effects. Therefore, the cell with atomically thin layer WS2@CC interlayer delivers a high initial specific capacity of 1198 mAh g−1 at 0.2 C, excellent rate capability (830 mAh g−1 at 2 C) and long cycle life at 0.5 C (0.07% capacity decay per cycle). Our works inspire the exploration of large-scale production of atomically thin layer TMDCs by CVD method, which opens a new avenue for developing efficient energy storage applications.

Section snippets

Results and discussions

Chemical vapor deposition (CVD) is a widely used technique for controllable synthesis of atomically thin layer transition metal dichalcogenides (TMDCs). In our CVD synthesis, atomically thin WS2 grows onto carbon cloth (WS2@CC), which serves as a multifunctional interface among electrolyte/electrode for high-performance lithium-sulfur (Li–S) battery. In order to synthesize atomically thin WS2@CC, a modified low-pressure CVD approach was applied. Prior to the growth process, the carbon cloth

Conclusion

In summary, we have developed a novel strategy for controllable synthesis of large-area and atomically thin WS2 nanosheets on carbon cloth via a low-pressure CVD method, which can be used as a multifunctional interlayer for Li–S battery. The formation mechanism of atomically thin WS2 nanosheet on carbon cloth is investigated. Benefiting from the layer-by-layer growth mechanism by our growth process, the obtained few-layer WS2@CC with abundant atomically thin fresh edges shows strong anchoring

Author contribution

Mei Er Pam: Conceptualization, Methodology, Experiment; Shaozhuan Huang: Data analyzing, Writing- Original draft preparation; Shuang Fan: Visualization, Investigation. Dechao Geng: Writing- Reviewing and Analysing; Dezhi Kong: Experiments; Meng Ding: Experiments, Investigation. Lu Guo: Experiments, Investigation; Lay Kee Ang: Computation, Validation.: Hui Ying Yang: Supervision, Writing- Reviewing and Editing.

Declaration of competing interest

The authors declare no competing financial interest.

Acknowledgement

This work is funded by Singapore Ministry of Education Academic Research Fund Tier 2 (MOE2018-T2-2-178) and Singapore University of Technology and Design International Design Center (IDC) grant.

References (35)

  • J. Zhang et al.

    A conductive molecular framework derived Li2S/N, P-Co doped carbon cathode for advanced lithium–sulfur batteries

    Adv. Energy Mater.

    (2017)
  • H. Yamin et al.

    Lithium sulfur battery: oxidation/reduction mechanisms of polysulfides in THF solutions

    J. Electrochem. Soc.

    (1988)
  • W. Xu et al.

    Lithium metal anodes for rechargeable batteries

    Energy Environ. Sci.

    (2014)
  • Z.W. Seh et al.

    Sulphur–TiO2 yolk–shell nanoarchitecture with internal void space for long-cycle lithium–sulphur batteries

    Nat. Commun.

    (2013)
  • G. Li et al.

    Three-dimensional porous carbon composites containing high sulfur nanoparticle content for high-performance lithium–sulfur batteries

    Nat. Commun.

    (2016)
  • G. Zheng et al.

    Hollow carbon nanofiber-encapsulated sulfur cathodes for high specific capacity rechargeable lithium batteries

    Nano Lett.

    (2011)
  • R. Elazari et al.

    Sulfur-impregnated activated carbon fiber cloth as a binder-free cathode for rechargeable Li-S batteries

    Adv. Mater.

    (2011)
  • Cited by (0)

    1

    These authors contributed equally.

    View full text