Fabrication of MoS2 Nanoflakes Supported on Carbon Nanotubes

for High Performance Anode in Lithium Ion Batteries (LIBs)

T. Minh Nguyet Nguyen1, Vinh-Dat Vuong1, 2, Mai Thanh Phong3, Thang Van Le1, 2, *

1 VNU-HCM Key Laboratory for Material Technologies, HCMUT, VNU-HCM, Ho Chi Minh City, 740128, Viet Nam.2 Department of Energy Materials, Faculty of Materials Technology, HCMUT, VNU-HCM, Ho Chi Minh City, 740128, Viet Nam.3 Ho Chi Minh City University of Technology, VNU-HCM, Ho Chi Minh City, 740128, Viet Nam.

Supplementary Materials

S1. Materials

Synthesis and purification of multi-walled carbon nanotubes (MWNTs)

The following synthesis and purification process of MWNTs were published by group of

authors [1]. MMWNTs are produced by thermal chemical vapor deposition (T-CVD) method,

using a reactor, which was built by VNU-HCM Key Laboratory for Material Technologies

(MTLab), HCMUT, VNU-HCM (Supported figure 1). MWNTs was purified in three steps. The

detailed processes are as follows.

Air oxidation treatment: Raw MWNTs were annealed at 460 for 24 hours to remove℃

carbonaceous impurities, such as amorphous carbon and graphite. The annealing step can

exposed metal or metal oxide catalysts enclosed in raw materials for acid treatment in next

steps.

Nitric acid treatment: Annealed MWNTs was immersed in 6M HNO3 at 60 for 24 hours℃

to metallic catalysts and oxidized amorphous carbon and graphite, which still remained

after air oxidation step. Products were filtered and washed in DI water several times to

remove residual nitric acid completely.

Hydrochloric acid treatment: The second acid treatment step with HCl was used to shorten

nitric acid treatment process, which can make damage effect on MWNTs. After first acid

treatment, MWNTs was refluxed in 6M HCl at 60 for 24 hours, then it was filtered and℃

washed in DI water several times.

Supported figure 1. Thermal-chemical vapor deposition (T-CVD) system built by VNU-HCM Key Laboratory for Material Technologies (MTLab), HCMUT, VNU-HCM.

Surface treatment of MWNTs

The following surface treatment process of MWNTs were published by group of authors [2].

65 mg of MWNTs were refluxed in mixture of C6H7NSO3 and NaNO2 (with mole ratio of carbon

in MWNTs and precursors is n(C) : n(C6H7NSO3) : n(NaNO2) = 12: 1: 1.03). The functionalized

reaction was carried out at 69 for 30 mins. The products were filtered and washed in DI water℃

several times.

S2. Cyclic voltammograms of MoS2/CNTs

The detailed cyclic voltammograms of MoS2/CNTs were showed in Supported figure 2.

0.0 1.0 2.0 3.0 4.0-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

2.32.11.10.4

Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5

Cur

rent

den

sity

(A.g

-1)

Voltage (vs. Li/Li+)

Supported figure 2. The cyclic voltammograms for MoS2/CNTs as anode materials.

Due to differences of raw materials (precursors and treated MWNTs) and reaction process

provided in our manuscript, the cyclic voltammograms of MoS2/CNTs showed and obvious peak

at wide potential window of 0.4 ÷ 1.1 V. The center of peak is set at 0.6 ÷ 0.7 V, which

attributed to lithiation into MWNTs and the formation of Li2S to release Mo. This peak

overlapped the peak should appear at about 0.5 V, which is attributed to decomposition of MoSx

to Mo. Therefore, direct decomposition of MoS2 in our nanocomposite have low rate. Otherwise,

the oxidation peak of Mo to MoS2, which should appear at about 2.3 V, were overlapped by wide

peak at 2.1 ÷ 3 V (peak center at 2.7 V) showed officious delithiation step is the conversion of

Li2S to S82-. In subsequent scans, the lithiation and delithiation peaks still appeared to show the

reversible performance of MoS2/CNTs. The offset value of delithiation peaks were shifted from

0.4 V (in first scan) to 0.5 V (in 5 th scan) and potential windows is narrowed, meaning

disappearance of MoS2 decomposition. The potential windows of delithiation peaks were also

shifted from 2.1 ÷ 3 V to 2.3 ÷ 3 V, meaning disappearance of Mo oxidation to MoS2. Such

information of wide cathodic peak at 0.4 ÷ 1.1 V and wide anode peak at 2.1 ÷ 3 V demonstate

durable of MoS2 layers on surface of MWNTs and reversible of their lithiation and delithiation

performance.

Supported references

[1] T. M. N. Nguyen, T. V. Le, V. D. Nguyen et al., “A facile and effective purification method

for multi-walled carbon nanotubes (MWNTS)”, Journal of Science and Technology (ISSN:

0866 708X), vol. 49, no. 6C, pp.279-286, 2011.

[2] V. D. Nguyen, H. T. Vu, T. M. N. Nguyen, H. T. Nguyen, and T. V. Le, “Diazonium

functionalization of multiwall carbon nanotubes (MWCNTS) for carrying MoS2

nanoparticles”, Journal of Science and Technology (ISSN: 0866 708X), vol. 51, no. 5C,

pp.215-222, 2013.