Few-Atomic-Layered Hollow Nanospheres

Constructed from Alternate Intercalation of

Carbon and MoS2 Monolayers for Sodium and

Lithium Storage

Laiying Jing,†,⊥ Gang Lian,*,†,⊥ Feier Niu,‡ Jian Yang,‡ Qilong Wang,‡ Deliang

Cui,*,† Ching-Ping Wong,*,§ and Xizheng Liu∥

†State Key Lab of Crystal Materials, Shandong University, Jinan 250100, P.R. China

‡Key Laboratory for Special Functional Aggregated Materials of Education Ministry,

School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100,

P.R. China

§School of Materials Science and Enigneering, Georgia Institute of Technology,

Atlanta, Georgia 30332, United States

∥Tianjin Key Laboratory of Advanced Functional Porous Materials, Institute for New

Energy Materials and Low-Carbon Technologies, School of Materials Science and

Engineering, Tianjin University of Technology, Tianjin 300384, P.R. China

*Corresponding author:

E-mail: liangang@sdu.edu.cn; cuidl@sdu.edu.cn; cpwong@cuhk.edu.hk

Figure S1 FTIR spectra of the pristine MoS2, CTAB/MoS2 and m-C/MoS2. The peak

located at 1150 cm-1 can be indexed to be the C-N bond. These peaks marked with

circles correspond to adsorption peaks of CTAB molecule.

Figure S2 Thermogravimetric analysis curves of m-C/MoS2 measured under air

atmosphere. Carbon content in the m-C/MoS2 was determined by thermogravimetric

analysis. There are three parts of weight loss can be seen in the diagram. The weight

loss of 10.5% between room temperature and 200 oC should be attributed to the loss

of adsorbed water. The weight loss between 280 oC and 360 oC, which can be ascribed

to the oxidation of MoS2. After that, a distinct weight loss at 380-450 oC is owing to

the oxidation of MoS2 and carbon.

Figure S3 TEM images of m-C/MoS2 synthesized at different temperature: (a) 230

oC; (b) 240 oC; (c) 250 oC; (d) 260 oC.

TEM images of CTAB/MoS2 samples synthesized at different temperature have

been exhibited in Figure S3. Dense aggregates of CTAB/MoS2 hybrid were obtained

at 230 oC. When the temperature was improved to 240 oC, non-uniform CTAB/MoS2

hollow spheres were prepared. Then uniformly dispersed CTAB/MoS2 hollow

nanospheres were obtained at 250 oC. It is pity that the temperature of 260 oC resulted

in serious agglomeration of hollow nanospheres.

Figure S4 Typical HRTEM images of m-C/MoS2 hollow nanospheres. Monolayer

carbon and MoS2 monolayers are labelled with green and red lines on the ultrathin

shells, respectively.

Figure S5 TEM images of m-C/MoS2 hollow spheres with thick shell obtained

through a traditional hydrothermal method.

Figure S6 Pore size distribution of m-C/MoS2 hollow nanospheres with few atomic

layers.

Figure S7 (a) Nitrogen adsorption-desorption isotherms and (b) XRD pattern of the

m-C/MoS2 sample prepared via a traditional hydrothermal condition. The inset is the

corresponding pore-size distribution curve; (c) electrochemical impedance spectra of

m-C/MoS2 hollow spheres obtained by high-pressure and traditional hydrothermal

methods; (d) cycling performance of m-C/MoS2 hollow spheres obtained by

traditional hydrothermal method at 200 mA g-1 of SIBs.

The BET specific surface area (SSA) is ca. 23 m2 g-1 with a pore volume of 0.16

cm3 g-1 (Figure S7a). The XRD test indicates that the m-C/MoS2 hollow spheres

obtained via a traditional hydrothermal condition also present expended interlayer

spacing (Figure S7b). As shown in Figure S7c, the EIS curve (red) of ultrathin-

layered m-C/MoS2 hollow nanospheres exhibits sharper slope at low frequency than

that of hollow spheres prepared by traditional hydrothermal method. The sharper

slope determines fast diffusion ability of ions, indicating reduced Li+/Na+ diffusion

barrier in the ultrathin nanostructure. As shown in Figure S7d, the discharge capacity

of hollow spheres with thick shell obviously fades and the capacity for the 150 th cycle

is only 176 mAh g-1.

Figure S8 (a) TEM and (b) high-magnified TEM images of bulk MoS2; (c) XRD

pattern of bulk MoS2; (d) cycling performance of bulk MoS2 at 200 mA g-1 of SIBs.

Bulk MoS2 was prepared under the same condition of MoS2 hollow spheres except

for without CTAB. As a result, aggregated MoS2 flakes were obtained (Figure S8a-b).

XRD test indicates the MoS2 flakes present a typical interlayer spacing of 0.62 nm

(Figure S8c). Cycling test of the bulk MoS2 electrode shows seriously faded discharge

capacity. The capacity for the 150th cycles is only 116 mAh g-1.

Figure S9 (a) TEM and (b) high-magnified TEM images of graphene/MoS2

composite; (c) XRD pattern of graphene/MoS2 composite; (d) cycling performance of

graphene/MoS2 composite at 200 mA g-1 of SIBs.

The graphene/MoS2 composite was prepared under the same condition of bulk

MoS2 except for with graphene oxide nanosheets. It is clear that MoS2 nanoflakes

vertically grow on the surfaces of reduced graphene oxide nanosheets (Figure S9a-b).

XRD test shows a typical interlayer spacing of 0.62 nm (Figure S9c). Similar to that

of bulk MoS2, the discharge capacity severely degrades. The capacity for the 150th

cycles is 226 mAh g-1, which is much lower than that of ultrathin-layered m-C/MoS2

hollow nanospheres.

Figure S10 (a-b) The possible adsorption position of Li+ in double MoS2 layers with

different interlayer spacing; (c-d) the corresponding energy profiles of Li+.

The first-principles calculations within the density functional theory (DFT) in

conjunction with the projector augmented wave (PAW) method, utilizing the Vienna

ab initio simulation package (VASP), have been demonstrated to calculate the

insertion /extraction behaviors of Li+ on MoS2 with different interlayer spacing.

Firstly, we examined the adsorption and diffusion behaviors of standard double-layer

MoS2 with an interlayer spacing of 0.62 nm (Figure S10a). In this situation, the site of

H has the maximum binding energy (Eb), which is set to 0. The site of T2 has the

second maximum Eb in table S2. So the diffusion path of Li+ is H-T2-H and the

diffusion barrier is 0.47 eV (Figure S10c). While when the interlayer spacing was

expanded to 0.96 nm (Figure S10b), the diffusion path of Li+ is T2-H-T2. The diffusion

barrier is only 0.20 eV (Figure S10d), indicating a much lower diffusion barrier of Li+

in the expanded interlayer spacing of MoS2.

Figure S11 Cycling performance of m-C/MoS2 hollow nanospheres with few atomic

layers at 1000 mA g-1 of LIBs.

The long-life cycling of m-C/MoS2 hollow nanospheres with few atomic layers has

been exhibited in Figure S11. The reversible discharge capacity maintains ~900 mAh

g-1 over 220 cycles at 1000 mA g-1 without obvious capacity fading, indicating

excellent cycling stability.

Table S1 Comparison of the electrochemical performance of ultrathin-layered m-C/MoS2 hollow nanospheres with other MoS2-based materials for SIBs.

Materials Current density

(mA g-1)

Cycle number

Capacity

(mA h g-1)

Ref.

MoS2 nanosheets 40 100 386 1

Micro-MoS2 50 20 420 2

MoS2/carbon nanofibers 100 600 283.9 3

MoS2/graphene 25 20 218 4

MoS2/graphene 320 300 227 5

MoS2-C composite 100 100 400 6

MoS2/N-doped carbon 1000 1000 265 7

MoS2/S-doped graphene 1000 1000 309 8

m-C/MoS2 hollow nanospheres with few atomic layers

200

1000

2000

150

350

600

401

320

262

This work

Table S2 The binding energy of Li+ on MoS2 with different interlayer spacing.

T1 T2 H

Normal double

MoS2 layers2.3745eV 2.3754eV 2.7574eV

Expanded double

MoS2 layers1.6755eV 2.3176eV 2.1754eV

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