Optimized Catalytic WS₂–WO₃ Heterostructure Design for Accelerated Polysulfide Conversion in Lithium–Sulfur Batteries

Abstract

lems by the physical confinement with nanostructured carbon materials [4][5][6][7][8] and the chemical adsorption with various noncarbon oxides/sulfides/nitrides. [9][10][11][12][13][14][15][16] However, the weak affinity of carbonbased materials and the limited adsorption capacity of noncarbon materials toward polar LiPSs make these strategies fail to meet the high sulfur loading electrode and the long cycling process. The basic reason should be ascribed to the slow conversion of high concentrated LiPSs, where their accumulation in the electrolyte causes severe shuttling between electrodes.Recently, the catalysis in Li-S batteries has received much attention because the introduction of catalyst accelerates the LiPS conversion and then, fundamentally suppresses their shuttling even with high sulfur loading. [17] To accelerate the conversion of LiPSs, the catalytic materials should not only have strong adsorption ability toward LiPSs, but also the good conductivity and activity for their conversion. Besides, the relatively high surface area for the Li 2 S deposition is also required. Nevertheless, all these characters are hard to be integrated into one material. Our group previously proposed a TiO 2 -TiN heterostructure that combines the advantages of TiO 2 with the strong adsorption ability and TiN with excellent conductivity, and more importantly, forms abundant active interface to realize the smooth trapping-diffusion-conversion of LiPSs. [18] UntilThe lithium-sulfur (Li-S) battery is a next generation high energy density battery, but its practical application is hindered by the poor cycling stability derived from the severe shuttling of lithium polysulfides (LiPSs). Catalysis is a promising way to solve this problem, but the rational design of relevant catalysts is still hard to achieve. This paper reports the WS 2 -WO 3 heterostructures prepared by in situ sulfurization of WO 3 , and by controlling the sulfurization degree, the structure is controlled, which balances the trapping ability (by WO 3 ) and catalytic activity (by WS 2 ) toward LiPSs. As a result, the WS 2 -WO 3 heterostructures effectively accelerate LiPS conversion and improve sulfur utilization. The Li-S battery with 5 wt% WS 2 -WO 3 heterostructures as additives in the cathode shows an excellent rate performance and good cycling stability, revealing a 0.06% capacity decay each cycle over 500 cycles at 0.5 C. By building an interlayer with such heterostructure-added graphenes, the battery with a high sulfur loading of 5 mg cm −2 still shows a high capacity retention of 86.1% after 300 cycles at 0.5 C. This work provides a rational way to prepare the metal oxide-sulfide heterostructures with an optimized structure to enhance the performance of Li-S batteries.

Boosting Dual‐Directional Polysulfide Electrocatalysis via Bimetallic Alloying for Printable Li–S Batteries

“…[ 13 ] Decorating electrocatalysts in favor of robust polysulfide regulation capability within the framework of mesoporous carbon is expected to synergistically address a multitude of problems at the cathode side. Various types of electrocatalysts, such as metal oxides/nitrides/sulfides/phosphides [ 14 – 17 ] and their heterostructures, [ 18 – 21 ] have been developed in due course. Of note, metals (e.g., Fe, Co, Ni) supported on carbons have demonstrated high effectiveness toward polysulfide conversion due to their high surface free energy and abundant active sites.…”

Emerging Catalysts to Promote Kinetics of Lithium–Sulfur Batteries

“…Thus far, key efforts have been devoted to designing reasonable heterostructure system to realize the synergy of catalysis and adsorption, such as TiO 2 –TiN, VO 2 –VN, MoN–VN, VTe 2 @MgO, WS 2 –WO 3 , TiO 2 –TiN, V 2 O 3 /V 8 C 7 , NiO–NiCo 2 O 4 , SnS 2 /SnO 2 , and ZnS–FeS, etc. [ 29,62,168–174 ] In this section, we focus on the effective construction strategies for heterostructure with respect to simultaneously improved adsorption and catalysis throughout catalytic materials design.…”

“…e) Cycle performance of the LSBs based on WO 3 , WS 2 –WO 3 , and WS 2 at 0.5 C. Panel (e) reproduced with permission. [ 170 ] Copyright 2020, Wiley‐VCH.…”

“…Yang and co‐workers balanced the adsorption ability of WO 3 toward LiPSs and the catalytic activity of WS 2 through the WS 2 –WO 3 heterostructure prepared by in situ vulcanization of WO 3 . [ 170 ] The analytical results demonstrated that the addition of only 5 wt% of WS 2 –WO 3 heterostructure in the cathodes can effectively accelerate the LiPS transformation and improve the utilization of S, delivering a capacity attenuation of 0.06% each cycle over 500 cycles at 0.5 C (Figure 18e).…”

Function and Application of Defect Chemistry in High‐Capacity Electrode Materials for Li‐Based Batteries

“…Once a vacancy is generated, an interstitial defect is generated at the new location or the disappearance of the oppositely charged ions. [7] In particular, the anionic O and S vacancies have been widely reported as the functional sites in various materials (such as TiO 2 , [8] WO, [9] and MoS 2 [10] ) for improving their electrochemical performance. Our group has introduced the cathodic Li vacancies by a solid-state method and verified their functional sites in LRMC cathode materials.…”