Synthesis of Surface-Functionalized WS₂ Nanosheets and Performance as Li-Ion Battery Anodes

Abstract

Separation of bulk tungsten disulfide (or WS2) into few-layer two-dimensional (2-D) crystals is of interest because of their high surface area for certain chemical processes and size-dependent optical and electronic characteristics. Herein, we demonstrate a process that involves the physical separation of weakly bonded WS2 layers by use of a strong acid treatment (chlorosulfonic acid) at 2 mg/mL, followed by quenching in deionized (DI) water. X-ray photoelectron spectroscopy of the superacid-treated WS2 suggests the formation of W-O type bonds, signifying oxidation of tungsten and reduction of the sulfur phase. Thermogravimetric analysis showed a three-phase weight-loss pattern, suggesting acid functionalization of WS2 surfaces. We also studied the electrochemical behavior of an acid-treated WS2 anode in a lithium half-cell configuration that showed a three-step charge-discharge behavior, characteristic of a conversion reaction. The electrochemical capacity was 118 mAh/g after 50 cycles.

Two-dimensional inorganic analogues of graphene: transition metal dichalcogenides

“…Electrodes prepared from hydrothermally synthesized MoS 2 nanoflakes and nanoplates exhibited capacities of as high as 1000 mAh −1 g −1 [140] and 1062 mAh −1 g −1 [141], respectively. WS 2 nanosheets and nanoflakes also show good reversible capacity [142][143][144]. Julien et al [145] have shown that 0.6 mol of Li ions intercalates per mole of WS 2 .…”

Thermal decomposition of ammonium tetrathiotungstate

“…Tetraalkylammonium thiotungstates are precursors for WS 2 catalysts [7,[15][16][17]. WS 2 can be also used as gas sensor [6,[19][20], dry lubricant [21,22] and in lithium batteries [23][24][25].…”

Synthesis of layered platelets by self-assembly of rhenium-based clusters directed by long-chain amines

“…4a. Deposition of the clusters on top of graphene A stock dispersion of graphene was prepared by sonication of graphite (1 g) in 100 cm 3 of IPA with a Fisher Scientific sonic tip (nominal power 500 W, working at 40% amplitude, with pulses of 5 s length for 8 h). 9 The mixture was distributed in 50-cm 3 centrifuge tubes, and centrifuged in a Heraeus Multifuge centrifuge at 3500 rpm for 90 min.…”

“…Two-dimensional (2D) materials have emerged as promising candidates for a broad range of applications, which include energy storage, [1][2][3][4] catalyst supports, 5,6 transistors 1,4,7,8 or drug delivery agents. 9,10 There has been intense research to define suitable routes for the production of ultrathin nanosheets of layered materials, based either on the exfoliation of the bulk compounds by different techniques 4,[11][12][13][14][15][16][17] or on the growth of the 2D materials from molecular precursors via chemical vapour deposition 18,19 and wet chemistry methods.…”

“…3a), which is probably due to the overlapping of low intensity peaks, arising from the interatomic distances in the clusters. The ability of rhenium to form chalcohalide compounds which contains rhenium-rhenium single or multiple bonds has led to the report of a variety of structures, which includes triangular-shaped clusters of the type [Re 3 [45][46][47][48] In the rhenium chalcohalide clusters, the rhenium-rhenium distances are in the range of 2.60 to 3.40 Å, while the rhenium-selenium distances are around 2.5 Å. 41,44,47,49 In the clusters reported in this work, the rhenium-rhenium The main features of the XRD pattern, a series of peaks of decreasing intensity observed in the region between 6 and 18 Å, are due to the harmonics of the 00l reflection resulting from the spacing between the clusters layers.…”