Sandwich‐Like Ultrathin TiS₂ Nanosheets Confined within N, S Codoped Porous Carbon as an Effective Polysulfide Promoter in Lithium‐Sulfur Batteries

Abstract

lithium-sulfur, sodium-, magnesium-, and aluminum-based batteries. [2] Among these competitors, lithium-sulfur battery (LSB) is a promising candidate since the earth-abundant sulfur has a high theoretical capacity of 1675 mAh g −1 and LSB provides a high theoretical energy density of 2600 Wh kg −1 or 2800 Wh l −1 . [3] Nevertheless, the practical application of LSB is still limited by the poor electric/ionic conductivity of sulfur and the "shuttle effect" caused by the dissolution and diffusion of lithium polysulfides (LiPSs), resulting in an uncompetitive capacity, rate performance, and cycling life. [4] To address these issues, intensive studies have been done, such as cathode design, separator modification, electrolyte optimization, and anode protection. [5] LiPSs immobilization and LiPSs ↔ Li 2 S 2 /Li 2 S conversion acceleration are two major considerations for LSB cathode design. [6] The anchoring and catalyzing effect of various candidates (such as metal oxides/sulfide/nitride) have been investigated by first principle calculations [7] or quantitative adsorption experiments. [8] Although some species show strong chemical interactions with LiPSs or effective catalysis on the conversion reaction, battery performances have been largely restrained by the poor electronic/ionic conductivity As the lightest member of transition metal dichalcogenides, 2D titanium disulfide (2D TiS 2 ) nanosheets are attractive for energy storage and conversion. However, reliable and controllable synthesis of single-to few-layered TiS 2 nanosheets is challenging due to the strong tendency of stacking and oxidation of ultrathin TiS 2 nanosheets. This study reports for the first time the successful conversion of Ti 3 C 2 T x MXene to sandwich-like ultrathin TiS 2 nanosheets confined by N, S co-doped porous carbon (TiS 2 @NSC) via an in situ polydopamine-assisted sulfuration process. When used as a sulfur host in lithium-sulfur batteries, TiS 2 @NSC shows both high trapping capability for lithium polysulfides (LiPSs), and remarkable electrocatalytic activity for LiPSs reduction and lithium sulfide oxidation. A freestanding sulfur cathode integrating TiS 2 @NSC with cotton-derived carbon fibers delivers a high areal capacity of 5.9 mAh cm −2 after 100 cycles at 0.1 C with a low electrolyte/sulfur ratio and a high sulfur loading of 7.7 mg cm −2 , placing TiS 2 @NSC one of the best LiPSs adsorbents and sulfur conversion catalysts reported to date. The developed nanospace-confined strategy will shed light on the rational design and structural engineering of metal sulfides based nanoarchitectures for diverse applications.

Molecular‐Level Design of Pyrrhotite Electrocatalyst Decorated Hierarchical Porous Carbon Spheres as Nanoreactors for Lithium–Sulfur Batteries

“…[ 15 ] However, metal sulfides generally have poor electrical conductivity and high gravimetric density. To address these issues, recently nanostructural metal sulfides combined with carbon materials such as ultrathin TiS 2 nanosheets layered with N, S codoped carbon, [ 35 ] interlaced carbon nanotubes threaded hollow Co 3 S 4 nanoboxes, [ 36 ] polypyrrole on CoS nanoboxes, [ 37 ] and CoS 2 nanoparticles embedded in porous carbon [ 38 ] have been reported.…”

Efficient Na‐Ion Storage in 2D TiS2 Formed by a Vapor Phase Anion‐Exchange Process

“…Last but not least, the hierarchical porous nanohoneycomb together with the downsized TiS 2 nanolayers could work as a physical confinement and provide many chemical binding sites, respectively, to suppress the dissolution of polysulfide intermediates. [21,22,[25][26][27][28] As a result, when the current density returns back to 1.0 A g −1 from 100 A g −1 , the discharge capacity is recovered to 526 mAh g −1 immediately, demonstrating the superior rate capability of TiS 2 @C nano-honeycomb (Figure 3d). Besides rate performance, the long-term cycling stability is another key character for the practical application of the as-prepared electrode material.…”

“…[23,24] With regards to TMDs, 2D layered titanium disulfide (TiS 2 ) with a strong binding energy toward polysulfide has demonstrated its effectiveness in Li-S batteries, which make it a competent candidate for NIBs with limited polysulfide-shuttle. [25][26][27] As a typical 2D TMD, TiS 2 also offers many other advantages towards Na + storage, such as light…”

Highly Stable Lithium−Sulfur Batteries Promised by Siloxene: An Effective Cathode Material to Regulate the Adsorption and Conversion of Polysulfides

“…Besides, many 2D materials have been demonstrated to have unique sulfur species catalytic property, thus ameliorating the sluggish kinetics. Common polar 2D materials employed as sulfur host are molybdenum compounds (MoS 2 ,25,26 Sn 0.063 MoO 3 27), MXenes28 and their ramification,29 phosphorene,1 borophene,30 graphitic carbon nitride (C 3 N 4 , C 4 N 4 ),31,32 etc. Although these 2D materials are considered as ideal candidates for Li‐S cathodes, there are still some defects needed to be improved.…”