Potential Application of Metal Dichalcogenides Double-Layered

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The Potential Application of Metal Dichalcogenides DoubleLayered Heterostructures as Anode Materials for Li-Ion Batteries Da Wang, Li-Min Liu, Shi-Jin Zhao, Ziyu Hu, and Hao Liu J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.5b11677 • Publication Date (Web): 05 Feb 2016 Downloaded from http://pubs.acs.org on February 5, 2016

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The Journal of Physical Chemistry

The Potential Application of Metal Dichalcogenides Double-Layered Heterostructures as Anode Materials for Li-Ion Batteries Da Wang,†,⊥ Li-Min Liu,*,‡ Shi-Jin Zhao,*,† Zi-Yu Hu‡ and Hao Liu§ †

Key Laboratory of Microstructures and Institute of Materials Science, Shanghai

University, Shanghai 200072, China ‡

Beijing Computational Science Research Center, Beijing 100084, China

§

Chengdu Green Energy and Green Manufacturing Technology R&D Center,

Chengdu, Sichuan 610207, China

Abstract It is great desire to develop the high-efficient anode materials for Li batteries, which not only require the large capacity, but also the high stability and mobility. In this work, the MX2 (M = Mo, W; X = S, Se) single-layer and double-layered heterostructures were carefully explored by the first principles calculations. We show that the lattice-matched MoS2/WS2 heterostructure can effectively reduce the band gap, which leads to the enhancement of the electrical conductivity in heterostructure. Moreover, considering the relatively weak binding energy (1.4-1.8 eV) of Li on the monolayer MoX2, the MoS2/WS2 and MoS2/MoSe2 heterostructures can improve the binding energy (to about 2.1 eV) but without affecting the high mobility of Li within the layers. Besides, although Li atoms could conveniently diffuse in both MoS2/WS2 ⊥

Da Wang,†,‡ (†Key Laboratory of Microstructures and Institute of Materials Science,

Shanghai University, Shanghai 200072, China; ‡Beijing Computational Science Research Center, Beijing 100084, China) 1

ACS Paragon Plus Environment


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and MoS2/MoSe2 heterostructures, they do not tend to cluster during the charge-discharge cycling. The results presented here provide valuable insights into exploring high-capacity MX2 double-layered heterostructures for potential battery applications.

2


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1.

Introduction Lithium ion batteries have now become the main power sources for portable

electronic devices. In order to meet the requirements for the high power tools and electric vehicles, electrode materials with high Li reversible storage capacity and fast Li and electron transport are needed for lithium ion batteries.1-3 After graphene became experimentally accessible in 2004,4 the layered materials like graphite have attracted great attention mainly due to their unique physical properties and capability to fulfill the demands of future nano-electronic industry on adaptability, flexibility, and multi-functionality.5-6 Transition metal dichalcogenides (TMD) also have layered structure with strong in-plane covalent bonding and weak van der Waals (vdW) coupling between layers.7-8 The quasi-two dimensional structural characteristic of TMD facilitates foreign atoms or alkali metals into their structure between the layers,9-11 while these atoms within layers are bound by strong covalent bonds. As a result of its pronounced redox variability and structural peculiarities, TMD is considered to be an interesting/promising anode material for Li based batteries.12-14 Many reports have demonstrated that MX2 (M is a transition metal and X is a chalcogen), such as MoS2, WS2 and SnS2 deliver a higher theoretical capacity (600-1200 mAh/g) than that of graphite/graphene (372-900 mAh/g), indicating they are the excellent candidate for high capacity and rechargeable lithium ion batteries (LIBs).14-19 A good electrode material should have a high Li mobility and intercalation voltage.20 Nano-structural materials could significantly shorten the Li diffusion path, 3



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which could facilitate Li intercalation. Novel two-dimensional single layered materials, such as graphene,6,

21

transition-metal carbides,22-23 and silicene,24 have

been widely studied and show better performance as LIBs electrode materials. More recently, TMD nanostructures, such as MoS214, 25, WS226-27, MoSe228-29 and WSe217 have also been reported to be used as efficient electrode materials for the advanced rechargeable batteries. Liang et al.30 demonstrated experimentally that highly exfoliated graphene-like MoS2 monolayer is a good electrode material for magnesium batteries. Cheon et al.31 found that the electrochemical lithiated capacity of nano-layered WS2 had been significantly improved compared to bulk WS2, however, its capacity was fade to 63% after 30 cycles, thus the cycling stability should be improved. The major issues faced in the use of intrinsic layered TMD in LIBs are lack of cycling stability and rate capability limitations. The main reason comes from their proneness to aggregation after repetitive cycles, as well as the formation of gel-like polymeric layers due to electrochemically driven electrolyte degradation.15,

32

In

addition, most of the monolayer MX2 is semiconducting with a considerable band gap of 1.60-2.00 eV,33 and the relatively large band gap would essentially limit its electrochemical performances.34 To further expand the range of electrochemical properties achieved by TMD materials, the pristine systems may be modified through doping35-38 or alloying,37, 39 and also by the layer stacking37, 40-43. The monolayer TMD stacking with other TMD has captured much attention for their super properties. Recent computational studies suggested that the electronic properties may be engineered by constructing TMD/TMD heterostructures.44-46 4


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Terrones et al.46 confirmed that the well-conductive bi-layers TMD with the direct band gap ranging from 0.79 eV to 1.157 eV can be achieved by alternating individual layers of different TMDs with particular stacking. Further, many research groups have devoted to enhance the electrochemical performance of MoS2-based anodes by constructing hetero-layered composites.25,

32, 47

Zhou et al.32 synthesized the

MoS2-graphene layered materials that exhibit excellent cycling stability and rate capability as anode materials for LIBs. Xiao et al.47 prepared MoS2/polyethylene oxide (MoS2/PEO) nanocomposites by exfoliated MoS2 and PEO. They found that their lithiated capacity and cycling behavior were greatly improved. It is naturally to wonder whether the TMD/TMD double-layered heterostructures have the potential to be used as anode materials in LIBs. In this work, we systematically investigated the Li adsorption and diffusion properties of the monolayer MX2 (M = Mo, W; X = S, Se) and double-layered heterostructures by means of density functional theory (DFT) calculations. Contrary to previous works, the heterostructures were first constructed in the way that both MX2 (M = Mo, W; X = S, Se) layers retain their unstrained lattices. The results show that both the Li binding strength can be effectively enhanced in MoS2/WS2 and MoS2/MoSe2 systems. However, no reduction of the Li mobility are found in these heterostructures, comparing with that in the separated MX2 single-layers. On the other side, although it convenient for Li atoms to diffuse in the double-layered heterostructures, Li atoms would not tend to cluster in both double-layered heterostructures. Our studies suggest that the great improvement of the 5



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electrochemical properties in double-layered heterostructures comparing with that in the single-layer, which are interesting to the development of Li-ion batteries based on MX2 heterostructures.

2.

Methods TMDs generally have two types of sandwich structures, 1T- and 2H-MX2,

depending on coordination of the transition metal atom by the chalcogen. Among them, the 2H type, which has trigonal prismatic coordination around M and two X-M-X units per elemental cell, is the most stable modification at normal conditions.9 Therefore, our investigations are based on the H-phase structure. Our calculations are performed using the Vienna ab initio simulation package (VASP).48 The general gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE) is adopted for the exchange-correlation functional.49 Also the Heyd-Scuseria-Ernzerhof (HSE) hybrid functionals50 was used in our study. Hybrid functionals (which include a portion of Hartree-Fock exchange) have been successfully applied in the calculation of thermochemical properties of solids., in addition to yielding good structural properties.51 We treat both the transition metal orbitals 4p6 4d5 5s1 for Mo and 5d4 6s2 for W together with the sulfur orbitals 3s2 3p4 for S and 4s2 4p4 for Se as valence states, and the rest are considered as core. The energy cutoff for plane-wave expansion is set to 500 eV. All the structures were relaxed, including the cells, until the forces became smaller than 0.01 eV/Å, and the energy tolerances were less than 10-5 eV/atom. A vacuum of 15 Å between the layers was considered. Brillouin zone of 6


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lithiated monolayer MX2 (M = Mo, W; X = S, Se), MoS2/WS2 and MoS2/MoSe2 double-layered heterostructures with the cell contained Mo9X18, Mo9W9S36 and Mo25S26Se24 are sampled with 4 × 4 × 4, 4 ×4 × 1 and 2 × 2 × 1 k points, respectively. The interlayer interaction in MX2 heterostructures are van der Waals (VDW) interactions in nature, which are overestimated in the simple GGA method. Thus, we employed the vdW-DF scheme52 so as to better describe their interlayer interactions. The diffusion barrier values are calculated by the “nudge elastic band” method.53 This method allows one to determine an energy optimized pathway (reaction path) between the two nearest energy minima. The atom charge was analyzed by the grid-based bader analysis algorithm54, in which the grid is obtained by decomposition of the charge density by the static self-consistent calculation for the optimized structures. The binding energy (Eb) per atom for the adsorption of n Li atoms is defined as

E b = [ E ( MX 2 + nLi ) − E ( MX 2 ) − nE Li ] / n

(1)

where E ( MX 2 + nLi ) is the total energy of n Li-adsorption MX2 structures,

E ( MX 2 ) is the total energy of the pristine MX2 structures, and ELi represent the energy of an isolated Li atom. In this scheme, the larger the negative value of Eb, the stronger the binding of Li to TMD. In addition, the stacking stability (Es) of MoS2/WS2 and MoS2/MoSe2 heterostructures were calculated by the following equation

Es = [E(M A X 2A ) + E(M B X 2B ) − E(M A X 2A / M B X 2B )]/ S 2

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(2)


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where E(MAX2A ), E(MBX2B ) and E(MAX2A /MBX2B ) indicate the total energies of the separated monolayer and heterostructure MX2, respectively. S indicates the area of the interface.

3.

Results

3.1 Adsorption and diffusion of Li in monolayer MX2 (M = Mo, W; X = S, Se) We first consider the electrochemical properties of monolayer MX2 (M = Mo, W; X = S, Se). As seen from Figure 1, each molecular sheet consists of a chalcogen-metal-chalcogen sandwich structure, with trigonal prismatic coordination of the metal atoms.7,

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Basic lattice parameters and physical properties of MX2

calculated by PBE and HSE functionals are listed in Table S1. It can be seen that the lattice parameters obtained by PBE are slightly overestimated, while the band gap values are significantly underestimated. Despite this discrepancy, we note that these two methods provide similar physical trends, as discussed in Supplementary Information. Moreover, it is well-known that the spin-orbit coupling (SOC) effect has great effect on the calculated band gap of systems including heavy metals, such as Mo and W, we further check the impact of SOC on the band structures of MX2 (Figure S1 and Table S3). The spin-orbit splitting predicted by PBE+SOC methods are comparable in different MX2 systems. Thus, all results on the electrochemical properties of MX2 single-layer and double-layered heterostructures are based on the PBE functional in our study. To examine the energetic stability of Li atoms on the monolayer MX2, the binding energies (Eb) of Li atoms on Top-on-M (TM), Top-on-M 8


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(TS) and hollow (H) sites were calculated by HSE and PBE functionals (Figure 1). It is noted that as Li adsorbed on TS site, it would spontaneously move to the H site, as the red circle illustrated in Figure 1b. Thus, only TS and H sites were discussed, as the results are shown in Table 1. Both the HSE and PBE results show that the LiT configurations are more stable than LiH in all cases.

Figure 1. (a) Illustration for atomic structure of monolayer MX2 (M = Mo, W; X = S, Se) that are used as anode materials for LIBs. (b) Top (above) and side (bottom) views of three representative sites (H, TMo and TS) for Li adsorbed on monolayers MX2.

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Table 1. Binding energies (Eb, eV), average bond length (lbond, Å), equilibrium vertical distances (h, Å) and the charge transfer (eLi) of Li atom on the T and H sites of MX2-based structures calculated by PBE and HSE functionals.

MoS2

EbT

hT

lbond T

eLiT

EbH

hH

lbond H

eLiH

PBE

-1.856

1.456

2.390

0.867

-1.712

1.541

2.415

0.878

HSE

-1.917

1.491

2.399

0.878

-1.781

1.551

2.427

0.885

PBE

-1.465

1.469

2.391

0.864

-1.293

1.586

2.439

0.878

HSE

-1.527

1.501

2.395

0.871

-1.348

1.592

2.454

0.889

PBE

-1.560

1.496

2.492

0.857

-1.388

1.621

2.542

0.873

HSE

-1.627

1.537

2.506

0.861

-1.449

1.623

2.551

0.878

PBE

-1.232

1.510

2.495

0.853

-1.048

1.649

2.559

0.861

HSE

-1.301

1.542

2.501

0.862

-1.112

1.652

2.574

0.872

1.377/

2.345/

PBE

-1.723

0.826

-1.876

1.698

2.526

0.866

2.252

2.252

1.384/

2.350/ 0.832

-1.931

1.684

2.518

0.870

2.266

2.266

1.381/

2.434/ 0.830

-2.023

1.758

2.631

0.862

2.359

2.359

WS2 MoSe2

WSe2

MoS2/Li/MoS2

WS2/Li/WS2

MoSe2/Li/MoSe2

PBE

PBE

-1.784

-1.828

When Li adsorbed on MX2 surface, as the partial density of states (PDOS) of the lithiated structure shown in Figure S2. It shows that the Li-sp orbital hybrid with MoS2, suggesting an obviously bonding characteristics between them. Through the Bader charge analysis, we find 0.867 and 0.878 electrons transferred from Li atom to MoS2 at T and H sites, respectively. In this case, the existence of states crossed the Fermi surface can be observed in Li adsorption system, as shown in Figure S2b. We further study the diffusion properties of Li on monolayer MX2 by calculating the 10


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variation in energy as Li moves between T site and H site, as shown in Figure 2. The diffusion barrier of Li in monolayer MX2 have almost the same values, which are around 0.22 eV, indicating that Li can readily diffuse in MX2. As discussed above, the monolayer MX2 (M = Mo, W; X = S, Se) with large Li embedding strength and high Li mobility have great potential to be used as the anode materials for LIBs. However, the considerable band gaps of these monolayer MX2, as well as their proneness to aggregate or restack during repetitive cycling essentially limit their electrochemical performances.15, 32-34 We next turn to study the structural and electronic characteristics of double-layered heterostructure MX2, as well as their improvement on the electrochemical properties.

Figure 2. Energy barriers for Li atom diffusion along T to H site on monolayer MX2 (M = Mo, W; X = S, Se).

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3.2 Electrochemical properties of MoS2/WS2 double-layered heterostructure For MoS2/WS2 system, the lattice constants of MoS2 and WS2 are close to each other. Thus, the double-layered heterostructure can be constructed simply from the primitive cells of MoS2 and WS2 with negligible strain. Two types of stackings were selected to overlap the monolayers, as shown in Figure 3a. It shows that the total energy/cell (one cell contain one unit of MoS2 and WS2, respectively) favors the Type A stacking with a different of 0.054 eV/cell. Therefore, our investigations are based on this stacked structure, unless the otherwise specified.

Figure 3. (a) Type A and Type B stacking of MoS2/WS2 heterostructures, respectively, (b) Side (above) and top (bottom) views of three representative sites for Li adsorbed in MoS2/WS2 heterostructure, and (c) The pathway and energy barriers for Li atoms diffused between two neighboring H sites by pass through the TW and TMo sites, respectively. 12


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Table 2. The binding energies (Eb, eV), average bond length (lbond, Å), equilibrium vertical distances (h, Å) and the charge transfer (e) of Li atom on the T and H sites of MoS2/WS2 heterostructure calculated by PBE and HSE (in parenthesis) functionals. MoS2/Li/WS2 MoS2-side

Li/MoS2/WS2

MoS2/WS2/Li

-1.829 (-1.882)

-1.493 (-1.541)

1.443 (1.485)

1.457 (1.489)

WS2-side

TMo

-1.935 (-1.990)

Tw

-1.815 (-1.859)

EbT TMo

1.360 (1.372)

2.266 (2.193)

Tw

2.239 (2.237)

1.387 (1.432)

TMo

2.340 (2.343)

2.267 (2.274)

2.381 (2.389)

-

Tw

2.239 (2.237)

2.392 (2.364)

-

2.387 (2.393)

0.868 (0.872)

0.862 (0.865)

-1.693 (-1.737)

-1.341 (-1.389)

hT

lbond T TMo

0.832 (0.841)

Tw

0.830 (0.834)

eT EbH

-2.047 (-2.096)

hH

1.633 (1.629)

1.734 (1.766)

1.475

1.506

lbond H

2.486 (2.482)

2.550 (2.571)

2.392

2.410

0.873 (0.875)

0.869 (0.873)

eH

0.862 (0.871)

We firstly investigate Li incorporation in MoS2/WS2 heterostructure. Two cases were considered in our study: (1) Li atom lying on MoS2 (Li/MoS2/WS2) and WS2 surface (MoS2/WS2/Li), and (2) Li embedded in MoS2/WS2 interface (MoS2/Li/WS2) (Figure 3b). Comparing the binding energies and diffusion barriers of Li on Li/MoS2/WS2 (or MoS2/WS2/Li) with that on the monolayer MoS2 (or WS2), as the results shown in Table 2 and Figure S3. It is shown that the forming of the

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heterostructure have almost no influence on the adsorption and diffusion of Li atoms at both MoS2 and WS2 side. This is somewhat expected, since the MoS2-WS2 interaction is weak. However, the MoS2/Li/WS2 system exhibits a very different picture, in which the Li atoms feel the presence of both two layers. We investigate the MoS2/Li/WS2 system by both PBE and HSE functionals. Three representative sites for Li lithiation are available in MoS2/WS2 heterostructure: (1) Top on Mo (TMo), (2) Top on W (Tw), and (3) Hollow (H) sites, as shown in Figure 3b. It can be seen that the MoS2/Li/WS2 system is energetically more stable than Li/MoS2 and Li/WS2 monolayers by 0.191 (0.179) eV and 0.582 (0.569) eV by PBE (HSE) calculations, respectively, indicating that Li atoms are more likely to intercalate at the MoS2/ WS2 interface than adsorption on MoS2 or WS2 surface. Moreover, the binding energy of LiH with Li bonded with six S atoms are calculated to be -2.047 eV, which are 0.112 and 0.232 eV more stable than LiT (Mo) and LiT (W) where only 4 Li-S bonds formed in structures. This suggested that the Li binding strength of different adsorption sites is strongly dependent on the Li coordination number. As we further investigate the Li adsorption in the parent MoS2/MoS2 and WS2/WS2 bilayers, the Li binding energies calculated by PBE was 1.876 eV and 1.931 eV, respectively, which was 0.171 eV and 0.116 eV smaller than that in MoS2/WS2 structure. We propose that the Li binding energy in MX2 bilayers was mainly determined by two factors: One is the bonding length of Li atoms, which was closely affected by the interlayer distance of bilayers. The other is the electronegativity difference between the host and Li. Considering the same Li-S bonds formed in MoS2/WS2 and their parent MoS2/MoS2 and WS2/WS2 14


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bilayer, the smaller layer distance in MoS2/WS2 structure eventually leads to the larger Li binding energy, as the equilibrium vertical distances shown in Table S2. We next studied Li atom diffusion between two neighboring H sites pass through TMo and Tw site in MoS2/WS2 interface, as shown in Figure 3c. It is shown that Li can more readily diffuse through the TMo site with the barrier of 0.221 eV, and it increases to 0.303 eV when Li atoms diffuse through the TW site. We note that Du et al.55 experimentally confirmed that the mobility of Li atoms in MoS2 bulk could be improved by increasing the stacking distance between MoS2 layers. Such statement was also supported by the computational study performed by Li et al.56 They suggest that the diffusion barrier decreases from 0.49 eV in MoS2 bulk to 0.21 eV in MoS2 surface. In our scenario, MoS2/WS2 reveals a very interesting characteristic for LIBs. The Li atoms at MoS2/WS2 interface are energetically more stable than that on the monolayer MS2 (M = Mo, W). Nevertheless, due to the larger layer distance in MoS2/WS2, as well as the weak interaction between Li atoms and MS2, there is no appreciable increase on the Li diffusion barrier, as compared with Li/MS2, e.g., by summing the maximum distances of Li on MoS2 (1.541 Å) and WS2 (1.586 Å) surfaces, which is shorter than the equilibrium vertical distance in MoS2/WS2 heterostructure, 3.626 Å at T site and 3.367 Å at H site.

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Figure 4. (a) Band structures of MoS2 and WS2 monolayers and their heterostructure. Crosses (blue) and circles (green) denote the band structures of MoS2 and WS2 monolayer, respectively, while band structures of heterostructure was represented by solid red lines. The partial charge densities of G1, G2, G3, K1, K2 states are also shown on the right side. (b) Schematic of the band alignment between MoS2 and WS2 and the coupling effect in MoS2/WS2 heterostructure. The band energies are obtained by aligning the MoS2 and WS2 monolayer with respect to the vacuum level.

Generally, electrical conductivity is an essential factor for the electrochemical properties of an electrode. However, most of monolayer MX2 are semiconductors with wide band gaps (Table S1), implying their poor electrical conductivity as 16


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electrode materials. The van der Waals interlayer coupling of MoS2/WS2 heterostructure would lead to the observed orbital interaction between two layers, which was consistent with that in previous studies46, 57. As shown in Figure 4a, the interlayer coupling is negligible at K points, while K1 is only contributed by dx2-y2+dxy orbitals of WS2 layer and K2 is contributed by dz2 orbitals of MoS2 layer. However, the G1 point is jointly contributed by dz2 + pz hybrid orbitals from both MoS2 and WS2 layers, the interaction of the antibonding dz2 (Mo or W) + pz (S) orbitals between layers leads the rising of valence-band state at Г-point, which eventually reduce the bandgap from 1.90-2.00 eV (HSE) in monolayer MS2 (M = Mo, W) to 1.451 eV. (see Supplementary Information for more details) As Li atoms embedded in MoS2/WS2 system, the electron are feasible to fill in the conduction band minimum (CBM), as shown in Figure S2. Moreover, the band gap of parent MoS2/MoS2 and WS2/WS2 bilayers is calculated to be 1.537 eV (HSE) and 1.574 eV (HSE), respectively, which is larger than that in MoS2/WS2 system. This is mainly due to that in the homojunction MoS2/MoS2 and WS2/WS2 bilayers, the interlayer coupling at the K point is negligible and the bilayer bands are just a superposition of their MoS2 or WS2 monolayer states. This eventually resulted in a quite similar electronic structure in homogeneous bilayers to that in monolayer MoX2.

3.3 Electrochemical properties of MoS2/MoSe2 double-layered heterostructure We next shift our attention to the electrochemical properties of MoS2/MoSe2 double-layered heterostructure. Many theoretical researches on the electronic 17



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properties of MoS2/MoSe2 heterostructure have been reported recently.45, 58 In these studies, the lattice misfit between MoSe2 and MoS2 was neglected, while the two layers were manually stretched or compressed to form a common lattice. However, it is confirmed by Kang et al.59 that the van der Waals binding energy between MoSe2 and MoS2 layers is not strong enough to achieve the formation of the common lattice, thus a nanometer-scale Moiré pattern is usually formed. Similar observation was also found in the (MoS2)/Cu (111) system. It is found that the (4 × 4) MoS2 overlayer on a (5 × 5) Cu (111) substrate Moiré pattern with the lowest stress in surface60 agrees well with the size of Moiré unit cell observed in the STM experiment.61 In this study, the rotated Moiré pattern MoS2/MoSe2 was constructed with the lattice deformations of both layers are minimized, as illustrated in Figure 5a. We denote the primitive cell basis vectors of MoS2, MoSe2 and MoS2/MoSe2 as (aS, bS), (aSe, bSe) and (aH, bH), while b is always oriented at a 120 angle with a. We then look for a set of coefficients (n, m, x, y) match: (naSe ) 2 + (mbSe ) 2 + 2nmaSe bSe cos 60° ≈ ( xaS ) 2 + ( ybS ) 2 + 2xyaS bS cos 60° = a H = bH (3)

Here, we chose the minimum cell for which the lattice misfit is less than 1%. The resulting structure include 75 atoms (Mo25S26Se24), while n, m, x, y were eventually defined as 4, 2, 4, 1, respectively, and the angle between the lattices θ is 17.1. Furthermore, both MoS2/WS2 and MoS2/MoSe2 are found to be energy stable with the stacking stability Es (Eq. 2) calculated to be 20.2 meV/Å2 and 21.4 meV/Å2 (Table S2), respectively.

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Figure 5. (a) Illustration of the MoS2/MoSe2 commensuration cell for the case of a mis-orientation angle θ = 17.1°. Shown also are the 4×4 supercells of the un-rotated MoS2 layer (vectors as, bs) and MoSe2 layer (vectors aSe, bSe). (b) The partial density of states (PDOS) of MoS2 and MoSe2 separated from the TDOS of MoS2/MoSe2 heterostructure. The Fermi level is shifted to zero.

We further studied the electronic structure of MoS2/MoSe2 heterostructure, similar to MoS2/WS2 system, the CBM shows the same contributions from the d (Mo) orbitals of MoS2 layer. However, due to the rotation between MoS2 and MoSe2 lattices, the split strength of dz2 + pz hybrid orbitals between layers at Г point (Figure 4b) is significantly reduced, so that the valence band maximum (VBM) changes to the K point, which is consisted with dx2-y2+dxy (Mo) of MoSe2 layer. In this case, the band gap of MoS2/MoSe2 heterostructure was calculated to be 1.446 eV (HSE). The localization of CBM and VBM can be also seen from the partial density of states (PDOS) of MoS2 and MoSe2 which are separated from the TDOS of MoS2/MoSe2 heterostructure, as shown in Figure 5b.

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Figure 6. (a) Binding energies of Li atom intercalated in 22 different positions. The average binding energies of 7 different types of lithiated structures are presented by the red color, and the blue dash line indicates the total average binding energy of MoS2/Li/MoSe2 system. (b) Top view of the typical TMo-TMo site (label 1), TMo-TSe site (label 2) and H-H site (label 3) for Li adsorbed in MoS2/MoSe2 interface. (c) Isosurface of the charge density difference for Li located at three representative sites. Yellow surfaces correspond to charge gains and blue surfaces correspond to an equivalent charge lost. To make the plot clear, the isovalues are defined as 0.0015 in all cases. eLi Indicate the charge transfer of Li to the heterostructures.

We then investigate the adsorption properties of Li atom in MoS2/MoSe2 heterostructure, a total of 50 different Li-embedded configurations were considered. After the identification of repetitive structures by the structural relaxation process, 22 different lithiated structures were finally obtained, which can be divided into seven types, as illustrated in Figure 6a. Here, we denote the locations of Li atom corresponding to MoS2 and MoSe2 layers as P(MoS2)-P(MoSe2), where P(MoS2) include the Top-on-Mo (or S) sites, TMo (or TS) and Hollow sites, H, and P(MoSe2) 20


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contain TMo (or TSe) and H sites. The total average binding energy of Li atom in MoS2/MoSe2 (-2.153 eV) is larger than Li in the most stable sites of MoS2/WS2 system (-2.047 eV). Moreover, it is clearly shown in Figure 6a that Li locates at the TMo or H sites of both MoS2 and MoSe2 layers are energetically more stable than that the one at the Tx (x = Se, S) sites. To clarify this difference, three representative lithiated structures were selected (Figure 6b): (1) TMo-TMo, (2) H-TSe, and (3) H-H. Two important trends were revealed here. Firstly, the Li binding strength in system is strongly dependent on the Li coordination number of different adsorption sites. For example, in TMo-TMo equilibrium geometry, Li atom lies directly above the Mo atom of both MoS2 and MoSe2 sides, being three-fold coordinated with the nearest neighbor S and Se atoms, respectively. In this case, the Li binding energy is 2.207 eV (Figure 6a). However, in H-TSe structure, three Li-S bonds were formed at the hollow sites of MoS2 side, while Li lies directly on Se atom on MoSe2 side with only one Li-Se bond between them. The H-TSe lithiated structures eventually exhibits the lower Li binding energy (1.993 eV). Accordingly, both the Bader charge results by HSE and PBE calculations (Figure 6c) show that the Li charge transfer on H-TSe site is less than that on TMo-TMo. From these results, we suggest that the number of Li-x bonds (x = Se, S) at the interlayer plays a critical role in determining the binding energy. Besides, although Li atom in H-H configurations lies in the hollow sites of both sides with six Li-x bonds formed, low binding energy were found in them, as shown in Figure 6a. Because S atoms in H-H lithiated structures are all located directly above Se atoms, the strong coulomb repulsion between these positive ions in two layers would reduce 21



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the structural stability, which eventually decreases the Li binding strength in H-H sites. When in their parent MoS2/MoS2 and MoSe2/MoSe2 bilayers, the Li binding energy are calculated to be 1.876 eV and 2.023 eV, respectively. In spite of the large interface distance (3.523 Å, Table S2) in MoSe2/MoSe2, the large electronegativity difference between Li and Se eventually leads the strong Li binding strength. One important point should be noted here is that the theoretical capacity of electrode material (mAh/g) is directly related to their atomic mass. Even with the suitable Li adsorption properties in homogeneous MoSe2/MoSe2 bilayers, the larger atomic mass and wider band gap strong limit its using as electrode material in LIBs. Since the Li binding strength has great effect on the diffusion properties, we next turn our attention to the mobility of Li atoms in MoS2/MoSe2 heterostructure. Causing by the lattice mismatch between MoS2 and MoSe2 layers, more diversification of the Li-adsorption sites can be found in MoS2/MoSe2. It is rather expensive to consider all the possible diffusion pathways. Thus, in our work, a typical diffusion circuit is selected, which contains 10 Li-adsorbed sites to identify the Li diffusion characteristics in MoS2/MoSe2 heterostructure, as demonstrated in Figure 7a, and their diffusion barriers are also shown in Figure 7b and 7c. It is suggested that for some particularly stable positions in the lattice misfit MoS2/MoSe2 system, such as position 1 and position 7, Li atoms can diffuse easily into such sites from the adjacent position. However, it is difficult to diffuse out due to the high barriers. These positions like the “traps” to capture the early embedded lithium atoms, so that they don’t participate in the subsequent diffusion process. In the following stage, the diversified Li adsorption 22


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sites with moderate diffusion barrier would make Li atoms easy to completely fill the remaining positions, e.g., although the occupation of Li atom in the position 7, those surrounding positions that could avoid the electrostatic repulsive between Li atoms are convenient for Li to diffuse or occupy. Moreover, as we further consider the deintercalation of Li atoms away from the “trap” in the delithiation process, the calculated maximum barriers is 0.22 eV (from position 7 to position 8), similar to the case of MoS2/WS2 structure. In this regard, we suggest that the MoS2/MoSe2 heterostructure with the diversified Li diffusion paths and moderate diffusion barriers (0.04-0.22 eV) are suitable for the anode materials for LIBs.

Figure 7. (a) The selected Li diffusion paths in MoS2/MoSe2 system. (b) Calculated energy barriers for Li atom diffuse along the paths shown in part a. (c) Diagrams illustrating the energy barriers with respect to the diffusion paths in MoS2/MoSe2 heterostructure. The red line indicate the average barrier.

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From the above discussion, it is suggested that Li atoms are conveniently diffuse in MoS2/MoSe2 heterostructure, in this case, we would like to know whether the low Li diffusion barriers would lead to the clustering of the Li atoms in these systems. To answer this question, the Li-Li cluster formation energies, Ec, were calculated, and a 2×1 supercell containing 150 atoms (Mo50Se52S48) was used to avoid the interaction of Li atoms. ∆Ec = E ( Li2 Mo50 Se52 S 48 ) + E (Mo50 Se52 S 48 ) − E1 ( LiMo50 Se52 S 48 ) − E2 ( LiMo50 Se52 S 48 ) (4)

where E(Mo50Se52S48), En(LiMo50Se52S48) and E(Li2Mo50Se52S48) denote the total energies of the MoS2/MoSe2 heterostructure and their single and double Li-adsorbed structures, respectively. In this scheme, the larger the positive value of ∆Ec, the stronger the Li atoms do not tend to cluster. For comparison, the Li cluster behavior in MoS2/WS2 containing 216 atoms (Mo36W36S72) is also calculated. The results are shown in Figure 8. It is clear that the Li atoms are more favorable to separate to each other in both systems. As the Li-Li distance is larger than 6.5 Å, there have almost no interaction between Li atoms. Moreover, due to the lattice mismatch in MoS2/MoSe2 heterostructure, the large environment difference for Li adsorption eventually led to the obviously oscillation of the cluster formation energies, as the blue line shown in Figure 8. Moreover, by further investigated the distribution characteristics of Li atoms with high concentrations in MoS2/WS2 and MoS2/MoSe2 heterostructures, as shown in Figure S4 and Figure S5. It is shown that the Li atoms are prefer to evenly distributed in the interlayer space in the initial stage. This fact reflects that the interlayer region 24


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provides a unique space for the accommodation of Li atoms, which is beneficial for the improvement of Li capacities. In the next stage, the Li atoms were broadly adsorbed on both interface and two external surfaces with the Li binding energy changes steadily, e.g., in the fully lithiated structure, the changing of the Li binding energy in MoS2/WS2 and MoS2/MoSe2 heterostructures is 0.159 eV (1.994-1.835 eV) and 0.225 eV (2.197-1.972 eV), respectively. From the above discussions, we can safely infer that although Li atoms were found to easily diffuse in both MoS2/MoSe2 and MoS2/WS2 heterostructures, they do not tend to cluster during the charge-discharge cycling. Thus, the MoS2/MoSe2 and MoS2/WS2 double-layered heterostructures with high stability for lithiation and high Li mobility should have great potential to be applied as anode materials for LIBs.

Figure 8. The cluster formation energies as functions of Li-Li distance in MoS2/MoSe2 (blue line) and MoS2/WS2 (orange line) heterostructures, respectively. The inserts show the illustration with Li-Li distance of 5.723 Å in MoS2/WS2 heterostructure (left) and 5.617 Å in MoS2/MoSe2 heterostructure (right).

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4.

Conclusion In this work, we explored the possibility of using MX2 (M = Mo, W; X = S, Se)

double-layered heterostructures as LIB anode materials by means of first-principles calculations. We systematically examined structures, adsorption and diffusion properties of Li atoms into MoS2/WS2 and MoS2/MoSe2 heterostructures in comparison with their single layers. The band gap of monolayer MX2 would be reduced by constructing TMD/TMD double-layered heterostructures, which would have an effect on the electrochemical properties of heterostructures, such as the Li adsorption or diffusion characteristic. In addition, the strong interaction of Li atoms with two layers in both MoS2/MoW2 and MoS2/MoSe2 heterostructures lead to the obviously increase of Li binding energies. Meanwhile, the interbedded Li atoms remain the high mobility in comparison with Li atoms on the surface. Notably, because of the large lattice misfit of about 4% between MoS2 and MoSe2, more diversified Li adsorption sites were found in MoS2/MoSe2 heterostructure, which make Li atoms diffuse more flexibility in the system. Although Li atoms were found to easily diffuse in both MoS2/MoSe2 and MoS2/WS2 heterostructures, they do not tend to cluster during the charge-discharge cycling. With all these extraordinary characteristics, including the high stability for lithiation and high Li mobility, the MoS2/MoSe2 and MoS2/WS2 double-layered heterostructures should have great potential to be applied as anode materials for LIBs. Considering that MX2-based heterostructures have been realized experimentally, our results should be important for the development of Li-ion batteries. 26


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Supporting Information Available Methods and Descriptions of simulation results. This information is available free of charge via the Internet at http://pubs.acs.org

Corresponding Authors *Li-Min Liu. E-mail: [email protected]. *Shi-Jin Zhao. E-mail: [email protected].

Notes The authors declare no competing financial interests.

Acknowledgments This work was supported by the National Natural Science Foundation of China (Grant Nos. 51222212, 51572016 and 11574193) and The Program for Professor of Special Appointment (Eastern Scholar). The computations supports from Tianhe-2JK computing time award at the Beijing Computational Science Research Center (CSRC).

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References (1) Goodenough, J. B.; Park, K.-S. The Li-Ion Rechargeable Battery: A Perspective. J. Am. Chem. Soc. 2013, 135, 1167-1176. (2) Islam, M. S.; Fisher, C. A. J. Lithium and Sodium Battery Cathode Materials: Computational Insights into Voltage, Diffusion and Nanostructural Properties. Chem. Soc. Rev. 2014, 43, 185-204. (3) Noorden, R. V. The Rechargeable Revolution: A Better Battery. Nature 2014, 507, 26-28. (4) Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric Field Effect in Atomically Thin Carbon Films. Science 2004, 306, 666-669. (5) Britnell, L., et al. Field-Effect Tunneling Transistor Based on Vertical Graphene Heterostructures. Science 2012, 335, 947-950. (6) Du, A.; Sanvito, S.; Li, Z.; Wang, D.; Jiao, Y.; Liao, T.; Sun, Q.; Ng, Y. H.; Zhu, Z.; Amal, R. Hybrid Graphene and Graphitic Carbon Nitride Nanocomposite: Gap Opening, Electron–Hole Puddle, Interfacial Charge Transfer, and Enhanced Visible Light Response. J. Am. Chem. Soc. 2012, 134, 4393-4397. (7) Huang, C.; Wu, S.; Sanchez, A. M.; Peters, J. J. P.; Beanland, R.; Ross, J. S.; Rivera, P.; Yao, W.; Cobden, D. H.; Xu, X. Lateral Heterojunctions within Monolayer MoSe2–WSe2 Semiconductors. Nat. Mater. 2014, 13, 1096-1101. (8) Mak, K. F.; He, K.; Lee, C.; Lee, G. H.; Hone, J.; Heinz, T. F.; Shan, J. Tightly Bound Trions in Monolayer MoS2. Nat. Mater. 2013, 12, 207-211. (9) Benavente, E.; Santa Ana, M. A.; Mendizábal, F.; González, G. Intercalation Chemistry of Molybdenum Disulfide. Coordin. Chem. Rev. 2002, 224, 87-109. (10) Miki, Y.; Nakazato, D.; Ikuta, H.; Uchida, T.; Wakihara, M. Amorphous MoS2 as the Cathode of Lithium Secondary Batteries. J. Power Sources 1995, 54, 508-510. (11) Mortazavi, M.; Wang, C.; Deng, J.; Shenoy, V. B.; Medhekar, N. V. Ab Initio Characterization of Layered MoS2 as Anode for Sodium-Ion Batteries. J. Power Sources 2014, 268, 279-286. 28


Page 28 of 34

Page 29 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(12) Wang, H.; Lan, X.; Jiang, D.; Zhang, Y.; Zhong, H.; Zhang, Z.; Jiang, Y. Sodium Storage and Transport Properties in Pyrolysis Synthesized MoSe2 Nanoplates for High Performance Sodium-Ion Batteries. J. Power Sources 2015, 283, 187-194. (13) Youn, D. H.; Jo, C.; Kim, J. Y.; Lee, J.; Lee, J. S. Ultrafast Synthesis of MoS2 or WS2-Reduced Graphene Oxide Composites Via Hybrid Microwave Annealing for Anode Materials of Lithium Ion Batteries. J. Power Sources 2015, 295, 228-234. (14) Zhu, C.; Mu, X.; van Aken, P. A.; Yu, Y.; Maier, J. Single-Layered Ultrasmall Nanoplates of MoS2 Embedded in Carbon Nanofibers with Excellent Electrochemical Performance for Lithium and Sodium Storage. Angew. Chem. Int. Edit. 2014, 126, 2184-2188. (15) Balendhran, S.; Walia, S.; Nili, H.; Ou, J. Z.; Zhuiykov, S.; Kaner, R. B.; Sriram, S.; Bhaskaran, M.; Kalantar-zadeh, K. Two-Dimensional Molybdenum Trioxide and Dichalcogenides. Adv. Funct. Mater. 2013, 23, 3952-3970. (16) Geim, A. K.; Novoselov, K. S. The Rise of Graphene. Nat. Mater. 2007, 6, 183-191. (17) Liu, B.; Luo, T.; Mu, G.; Wang, X.; Chen, D.; Shen, G. Rechargeable Mg-Ion Batteries Based on WSe2 Nanowire Cathodes. ACS Nano 2013, 7, 8051-8058. (18) Sun, C.; Searles, D. J. Lithium Storage on Graphdiyne Predicted by Dft Calculations. J. Phys. Chem. C 2012, 116, 26222-26226. (19) Winter, M.; Brodd, R. J. What Are Batteries, Fuel Cells, and Supercapacitors? Chem. Rev. 2004, 104, 4245-4270. (20) Whittingham, M. S. Lithium Batteries and Cathode Materials. Chem. Rev. 2004, 104, 4271-4302. (21) Yao, F.; Güneş, F.; Ta, H. Q.; Lee, S. M.; Chae, S. J.; Sheem, K. Y.; Cojocaru, C. S.; Xie, S. S.; Lee, Y. H. Diffusion Mechanism of Lithium Ion through Basal Plane of Layered Graphene. J. Am. Chem. Soc. 2012, 134, 8646-8654. (22) Eames, C.; Islam, M. S. Ion Intercalation into Two-Dimensional Transition-Metal Carbides: Global Screening for New High-Capacity Battery Materials. J. Am. Chem. Soc. 2014, 136, 16270-16276. 29



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(23) Mashtalir, O.; Naguib, M.; Mochalin, V. N.; Dall’Agnese, Y.; Heon, M.; Barsoum, M. W.; Gogotsi, Y. Intercalation and Delamination of Layered Carbides and Carbonitrides. Nat. Commun. 2013, 4, 1716. (24) Tritsaris, G. A.; Kaxiras, E.; Meng, S.; Wang, E. Adsorption and Diffusion of Lithium on Layered Silicon for Li-Ion Storage. Nano Lett. 2013, 13, 2258-2263. (25) Chang, K.; Chen, W. L-Cysteine-Assisted Synthesis of Layered MoS2/Graphene Composites with Excellent Electrochemical Performances for Lithium Ion Batteries. ACS Nano 2011, 5, 4720-4728. (26) Shiva, K.; Ramakrishna Matte, H. S. S.; Rajendra, H. B.; Bhattacharyya, A. J.; Rao, C. N. R. Employing Synergistic Interactions between Few-Layer WS2 and Reduced Graphene Oxide to Improve Lithium Storage, Cyclability and Rate Capability of Li-Ion Batteries. Nano Energy 2013, 2, 787-793. (27) Liu, Y.; Wang, W.; Huang, H.; Gu, L.; Wang, Y.; Peng, X. The Highly Enhanced Performance of Lamellar WS2 Nanosheet Electrodes Upon Intercalation of Single-Walled Carbon Nanotubes for Supercapacitors and Lithium Ions Batteries. Chem. Commun. 2014, 50, 4485-4488. (28) Kim, S.-W.; Seo, D.-H.; Ma, X.; Ceder, G.; Kang, K. Electrode Materials for Rechargeable Sodium-Ion Batteries: Potential Alternatives to Current Lithium-Ion Batteries. Adv. Energy Mater. 2012, 2, 710-721. (29) Shi, Y., et al. Highly Ordered Mesoporous Crystalline MoSe2 Material with Efficient Visible-Light-Driven Photocatalytic Activity and Enhanced Lithium Storage Performance. Adv. Funct. Mater. 2013, 23, 1832-1838. (30) Liang, Y.; Feng, R.; Yang, S.; Ma, H.; Liang, J.; Chen, J. Rechargeable Mg Batteries with Graphene-Like MoS2 Cathode and Ultrasmall Mg Nanoparticle Anode. Adv. Mater. 2011, 23, 640-643. (31) Seo, J.-w.; Jun, Y.-w.; Park, S.-w.; Nah, H.; Moon, T.; Park, B.; Kim, J.-G.; Kim, Y. J.; Cheon, J. Two-Dimensional Nanosheet Crystals. Angew. Chem. Int. Edit. 2007, 46, 8828-8831. (32) Zhou, X.; Wan, L.-J.; Guo, Y.-G. Synthesis of MoS2 Nanosheet-Graphene 30


Page 30 of 34

Page 31 of 34

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Nanosheet Hybrid Materials for Stable Lithium Storage. Chem. Commun. 2013, 49, 1838-1840. (33) Mak, K. F.; Lee, C.; Hone, J.; Shan, J.; Heinz, T. F. Atomically Thin MoS2: A New Direct-Gap Semiconductor. Phys. Rev. Lett. 2010, 105, 136805. (34) Peng, X.; Peng, L.; Wu, C.; Xie, Y. Two Dimensional Nanomaterials for Flexible Supercapacitors. Chem. Soc. Rev. 2014, 43, 3303-3323. (35) Komsa, H.-P.; Kotakoski, J.; Kurasch, S.; Lehtinen, O.; Kaiser, U.; Krasheninnikov, A. V. Two-Dimensional Transition Metal Dichalcogenides under Electron Irradiation: Defect Production and Doping. Phys. Rev. Lett. 2012, 109, 035503. (36) Yadgarov, L., et al. Controlled Doping of Ms2 (M=W, Mo) Nanotubes and Fullerene-Like Nanoparticles. Angew. Chem. Int. Edit. 2012, 51, 1148-1151. (37) Hong, X.; Kim, J.; Shi, S.-F.; Zhang, Y.; Jin, C.; Sun, Y.; Tongay, S.; Wu, J.; Zhang, Y.; Wang, F. Ultrafast Charge Transfer in Atomically Thin MoS2/WS2 Heterostructures. Nat. Nano. 2014, 9, 682-686. (38) Gao, J.; Zhang, J.; Liu, H.; Zhang, Q.; Zhao, J. Structures, Mobilities, Electronic and Magnetic Properties of Point Defects in Silicene. Nanoscale 2013, 5, 9785-9792. (39) Dumcenco, D. O.; Kobayashi, H.; Liu, Z.; Huang, Y.-S.; Suenaga, K. Visualization and Quantification of Transition Metal Atomic Mixing in Mo1−Xwxs2 Single Layers. Nat. Commun. 2013, 4, 1351. (40) Ceballos, F.; Bellus, M. Z.; Chiu, H.-Y.; Zhao, H. Ultrafast Charge Separation and Indirect Exciton Formation in a MoS2-MoSe2 Van Der Waals Heterostructure. ACS Nano 2014, 8, 12717-12724. (41) Zhou, K.-G.; Withers, F.; Cao, Y.; Hu, S.; Yu, G.; Casiraghi, C. Raman Modes of MoS2 Used as Fingerprint of Van Der Waals Interactions in 2-D Crystal-Based Heterostructures. ACS Nano 2014, 8, 9914-9924. (42) Song, B.; Yang, J.; Zhao, J.; Fang, H. Intercalation and Diffusion of Lithium Ions in a Carbon Nanotube Bundle by Ab Initio Molecular Dynamics Simulations. 31



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energ. Environ. Sci. 2011, 4, 1379-1384. (43) Zhou, X.; Wang, Z.; Chen, W.; Ma, L.; Chen, D.; Lee, J. Y. Facile Synthesis and Electrochemical Properties of Two Dimensional Layered MoS2/Graphene Composite for Reversible Lithium Storage. J. Power Sources 2014, 251, 264-268. (44) Bernardi, M.; Palummo, M.; Grossman, J. C. Extraordinary Sunlight Absorption and One Nanometer Thick Photovoltaics Using Two-Dimensional Monolayer Materials. Nano Lett. 2013, 13, 3664-3670. (45) Kou, L.; Frauenheim, T.; Chen, C. Nanoscale Multilayer Transition-Metal Dichalcogenide Heterostructures: Band Gap Modulation by Interfacial Strain and Spontaneous Polarization. J. Phys. Chem. Lett. 2013, 4, 1730-1736. (46) Terrones, H.; López-Urías, F.; Terrones, M. Novel Hetero-Layered Materials with Tunable Direct Band Gaps by Sandwiching Different Metal Disulfides and Diselenides. Sci. Rep. 2013, 3, 1549. (47) Xiao, J.; Choi, D.; Cosimbescu, L.; Koech, P.; Liu, J.; Lemmon, J. P. Exfoliated MoS2 Nanocomposite as an Anode Material for Lithium Ion Batteries. Chem. Mater. 2010, 22, 4522-4524. (48) Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set. Phys. Rev. B 1996, 54, 11169-11186. (49) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865-3868. (50) Heyd, J.; Scuseria, G. E.; Ernzerhof, M. Hybrid Functionals Based on a Screened Coulomb Potential. J. Chem. Phys. 2003, 118, 8207-8215. (51) Becke, A. D. Density‐Functional Thermochemistry. III. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648-5652. (52) Klimeš, J.; Bowler, D. R.; Michaelides, A. Van Der Waals Density Functionals Applied to Solids. Phys. Rev. B 2011, 83, 195131. (53) Henkelman, G.; Jónsson, H. Improved Tangent Estimate in the Nudged Elastic Band Method for Finding Minimum Energy Paths and Saddle Points. J. Chem. Phys. 32


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2000, 113, 9978-9985. (54) Sanville, E.; Kenny, S. D.; Smith, R.; Henkelman, G. Improved Grid-Based Algorithm for Bader Charge Allocation. J. Comput. Chem. 2007, 28, 899-908. (55) Du, G.; Guo, Z.; Wang, S.; Zeng, R.; Chen, Z.; Liu, H. Superior Stability and High Capacity of Restacked Molybdenum Disulfide as Anode Material for Lithium Ion Batteries. Chem. Commun. 2010, 46, 1106-1108. (56) Li, Y.; Wu, D.; Zhou, Z.; Cabrera, C. R.; Chen, Z. Enhanced Li Adsorption and Diffusion on MoS2 Zigzag Nanoribbons by Edge Effects: A Computational Study. J. Phys. Chem. Lett. 2012, 3, 2221-2227. (57) Kośmider, K.; Fernández-Rossier, J. Electronic Properties of the MoS2-WS2 Heterojunction. Phys. Rev. B 2013, 87, 075451. (58) Ataca, C.; Şahin, H.; Ciraci, S. Stable, Single-Layer MX2 Transition-Metal Oxides and Dichalcogenides in a Honeycomb-Like Structure. J. Phys. Chem. C 2012, 116, 8983-8999. (59) Kang, J.; Li, J.; Li, S.-S.; Xia, J.-B.; Wang, L.-W. Electronic Structural Moiré Pattern Effects on MoS2/MoSe2 2D Heterostructures. Nano Lett. 2013, 13, 5485-5490. (60) Le, D.; Sun, D.; Lu, W.; Bartels, L.; Rahman, T. S. Single Layer MoS2 on the Cu(111) Surface: First-Principles Electronic Structure Calculations. Phys. Rev. B 2012, 85, 075429. (61) Kim, D.; Sun, D.; Lu, W.; Cheng, Z.; Zhu, Y.; Le, D.; Rahman, T. S.; Bartels, L. Toward the Growth of an Aligned Single-Layer MoS2 Film. Langmuir 2011, 27, 11650-11653.

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Potential Application of Metal Dichalcogenides Double-Layered

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