Basal-Plane-Activated Molybdenum Sulfide Nanosheets with Suitable Orbital Orientation as Efficient Electrocatalysts for Lithium–Sulfur Batteries

Abstract

Lithium−sulfur (Li−S) batteries are one of the most promising candidates for next-generation energy storage systems because of their high theoretical energy density. However, the shuttling behavior and sluggish conversion kinetics of lithium polysulfides (LiPSs) limit their practical application. Herein, Bdoped MoS 2 nanosheets are synthesized on carbon nanotubes (denoted as CNT@MoS 2 -B) to function as catalysts to boost the performance of Li−S batteries. The poor catalytic performance of the pristine MoS 2 is revealed to be the result of unsuitable orbital orientation of the basal plane, which hinders the orbital overlap with sulfur species. B in CNT@MoS 2 -B is sp 3 hybridized, and it has a vacant σ orbital perpendicular to the basal plane, which can maximize the head-on orbital overlap with S. The incorporation of B significantly increases the reactivity of MoS 2 basal plane, which can facilitate the kinetics of Li 2 S formation and dissolution. With these merits, the S/CNT@MoS 2 -B cathodes deliver high rate capability and outstanding cycling stability, holding great promise for both scientific research and practical application. This work affords fresh insights for developing effective catalysts to accelerate LiPS conversion.

Mo‐O‐C Between MoS2 and Graphene Toward Accelerated Polysulfide Catalytic Conversion for Advanced Lithium‐Sulfur Batteries

“…On the one hand, the construction of MoS 2 , to increase the exposure of active edge sites, combined with carbon materials is designed to boost the trapping and conversion of LiPSs in Li–S batteries. [ 21 , 22 ] On the other hand, researcher has focused on the micro/nanostructures of MoS 2 /C composites via van der Waals forces and utilize their synergistic effect to enhance the electrochemical performance of Li–S batteries. [ 23 , 24 , 25 ] Although these MoS 2 /C composites can effectively suppress the shuttle effect of LiPSs, they are mainly bound through van der Waals bonds, and it is difficult to effectively exert the synergistic effect of the two components owing to the weak electronic pathway of the heterogeneous interface.…”

Computational screening of functionalized MXenes to catalyze the solid and non-solid conversion reactions in cathodes of lithium–sulfur batteries

“…The modified CNT@MoS 2 -B samples can achieve a discharge capacity of 711 mAh g À1 at 5C, and a slow capacity decay rate of 0.02% per cycle in 1300 cycles. 44 A capacity of 904 mAh g À1 at 0.5C, and with 894 mAh g À1 retention after 200 cycles was reported for the Mo 2 C/CHS composites. 46 The effects of electrocatalysts have also been demonstrated by introducing electrocatalytic cobalt atoms into nitrogen-doped graphene, which can obviously reduce the reaction barriers from Li 2 S 2 to Li 2 S as confirmed by density functional theory (DFT) calculations and experimental results.…”

“…Therefore, a more progressive criterion requires that the additives should not only adsorb polysulfides and inhibit their shuttling effect, but also should facilitate the conversion reactions of Li 2 S. 43 Many researchers have tried to introduce electrocatalysts into lithium-sulfur batteries. Some electrocatalysts, including transition-metal sulfides and carbides, [44][45][46][47] such as B-doped MoS 2 nanosheets/carbon nanotubes (CNT@MoS 2 -B) and Mo 2 C nanocluster/carbon nanosheets hybrid based hollow spherical materials (Mo 2 C/CHS), have been synthesized as sulfur-bearing materials to catalyze the redox processes of sulfur. These active components are bonded to conductive substrates in the form of covalent bonds or chemisorption, which can transfer electrons and activate the substrates.…”

Electrocatalyst Modulation toward Bidirectional Sulfur Redox in Li–S Batteries: From Strategic Probing to Mechanistic Understanding

“…To this end, Tian et al developed a B-doped MoS 2 nanosheets decorated carbon nanotubes (denoted as CNT@MoS 2 -B), which alters the electronic structure of MoS 2 and enhances the affinity with various sulfur species (Figure 5a). [133] It is uncovered that the electrocatalytic effect of pristine MoS 2 is restricted by inappropriate orbital orientation of the basal plane, which leads to sluggish adsorptioncatalysis-conversion for PSs. Encouragingly, this defect manipulating strategy of B-doping greatly activates the basal planes of MoS 2 , thereby readily elevating the electrocatalytic activity to expedite bidirectional sulfur redox kinetics (Figure 5b).…”