C Hierarchical Tubular Heterostructures for High

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Construction of MoS2/C Hierarchical Tubular Heterostructures for High Performance Sodium Ion Batteries Qichang Pan, Qiaobao Zhang, Fenghua Zheng, Yanzhen Liu, Youpeng Li, Xing Ou, Xunhui Xiong, Chenghao Yang, and Meilin Liu ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.8b07172 • Publication Date (Web): 19 Nov 2018 Downloaded from http://pubs.acs.org on November 20, 2018

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Construction of MoS2/C Hierarchical Tubular Heterostructures for High Performance Sodium Ion Batteries Qichang Pan,† Qiaobao Zhang,§ Fenghua Zheng,† Yanzhen Liu,† Youpeng Li,† Xing Ou,† Xunhui Xiong,† Chenghao Yang,*,† Meilin Liu†,‡ †Guangzhou

Key Laboratory of Surface Chemistry of Energy Materials, New Energy Research

Institute, School of Environment and Energy, South China University of Technology, Guangzhou 510006, China ‡School

of Materials Science & Engineering, Georgia Institute of Technology, Atlanta, GA

30332-0245, USA §Department

of Materials Science and Engineering, Xiamen University, Xiamen, Fujian

361005, China ∗Corresponding

author, E-mail: [email protected] (C. Yang)

KEYWORDS: sodium ion batteries, MoS2, conversion reaction, in-situ TEM, in-situ XRD

ACS Paragon Plus Environment

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ABSTRACT

Molybdenum disulfide (MoS2) has been considered as a promising anode material for SIBs due to its high capacity and graphene-like layered structure. However, irreversible conversion reaction during the sodiation/desodiaion process is the major problem that needs to be overcome before its practical applications. In this work, MoS2/amorphous carbon (C) microtubes (MTs) composed of heterostructured MoS2/C nanosheets have been developed via a simple template method. The existence of MoS2/C heterointerface plays a key role in achieving high and stable performance by stabilizing the reaction products Mo and sulfide phases, providing fast electronic and Na+ ions diffusion mobility, and alleviating the volume change. MoS2/C MTs exhibit a high reversible specific capacity of 563.5 mA h g-1 at 0.2 A g-1, good rate performance (520.5, 489.4, 452.9, 425.1 and 401.3 mA h g-1 at 0.5, 1.0, 2.0, 5.0 and 10.0 A g-1, respectively), and excellent cycling stability (484.9 mA h g-1 at 2.0 A g-1 after 1500 cycles).

Lithium ion batteries (LIBs) have been widely applied as the power sources in portable electronic devices, electric vehicles (EVs) and hybrid electric vehicles (HEVs) because of its high energy density and long cycle life.1,2 However, the applications of LIBs in renewable energy storage and power grid are restricted by the limited and uneven distribution lithium sources. Recently, sodium ion batteries (SIBs) have been considered as one of the promising state-of-the-art battery systems and attracted extensive attentions for large-scale energy storage, due to the abundance nature of sodium resources in the earth crust (23,000 ppm compared with a mere 20 ppm for lithium).3,4 Therefore, the price of Na2CO3 is 50 times lower than that of Li2CO3 and this gap is continuously widening due to the Na sources such abundance. The cost of Na2CO3 is lower than Li2CO3, and it results in the cost of cathode materials for SIBs are lower


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than that of the LIBs. Furthermore, unlike the expensive Cu current collector for LIBs anode, a cheap Al current collector can be used for SIBs anode, because Al does not alloy with Na. Assuming they deliver the same energy density, SIBs are considered to be at least 10 % cheaper than the commercialized LIBs. For practical applications, the lower cost of SIBs is very important for large-scale energy storage systems. More importantly, the abundance of Na in Earth’s crust is critical to applying SIBs in large scale energy storage, which can ensure the sustainability.5-8 Unfortunately, commercial graphite anode is not suitable for SIBs owing to the larger Na+ ion diameter (Na+ for 1.02 Å vs. Li+ for 0.76 Å), resulting in poor electrochemical performance, e.g. low reversible specific capacity, poor cycle and rate performance. Therefore, developing high performance anode materials with high capacity as well as excellent rate capability for SIBs are urgently desired.9-11 Recently, a wide range of functional materials including carbonaceous materials,12 metals and alloys,9,13 and metal oxides/sulfides et al.14-16 have been studied as the anode materials of SIBs. Among them, MoS2 has attracted significant interests and been extensively studied, because its structural similarity to graphite but much larger interlayer distance (0.615 nm), which allows Na+ ions to be insert reversibly with acceptable mobility.17 However, the practical utilization of MoS2 has been mainly hindered by the severe specific capacity fading and poor capacity retention due to the large volume change and pulverization of the electrode during the charge/discharge cycling. Synthesizing nanostructured MoS2 with expended interlayer spacing along c-axis (e.g. nanoflowers,18 nanosheets,19 and nanotubes20) is a promising strategy that has been extensively studied, as it allows effective strain relaxation. Meanwhile, incorporating MoS2 with carbonaceous materials (e.g. porous carbon/fibers/nanotubes21-23 and graphene24,

25)

or

PEO/Li4Ti5O1226,27 to buffer the volume changes during sodiation/desodiation process and


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enhance the structural integrity. Up to now, a number of nanostructured MoS2 and MoS2-based composites have been exploited as the anode materials for SIBs, demonstrating improved specific capacity and cycling stability.28 Typically, the sodiation process of MoS2 is proceed in two steps, an intercalation process (MoS2 + xNa → NaxMoS2) and conversion reaction (NaxMoS2 + (4-x)Na → Mo + 2Na2S). Especially, in the conversion reaction, Na+ ions react with MoS2 and bare MoS2 will be fully converted to Mo metal and Na2S.29 However, the cyclic stress and recrystallization during the sodiation/desodiation process often induce the coarsening of Mo nanoparticles in Mo0/Na2S mixture.30,31 It will further result in the limited conversion reaction of Mo0/Na2S back to MoS2 during Na extraction, collapse of MoS2 crystal structure and fast degrade of Na+ accommodation capacity.32,33 Therefore, maintaining the stability of nanostructured Mo0/Na2S conversion reaction interface and high activity for inter-diffusion between Mo and Na2S are critical challenges for achieving a high capacity retention in MoS2-based electrodes. Herein, we describe the preparation of hierarchical MoS2/amorphous carbon (MoS2/C) microtubes (MTs) constructed by heterostructured MoS2/C nanosheets (NSs) through a facile template method. Figure 1A illustrates the overall synthesis processes of the hollow tubular heterostructres. First, Sb2S3 microrods were prepared via a simple hydrothermal method.9 Then, individual layers of MoS2/C NSs are grown on the out surface of Sb2S3 microrods. The electrocatalytic functions of MoS2 and C are integrated into 2D hetero-junction NSs and 1D microtubes, which can well adapt the volume expansion/contraction upon cycling, fix the reaction product Mo nanoparticles (NPs) and prevent it from coarsening, and eventually enhance the conversion reactions reversibility of MoS2 electrode.34 Accordingly, the optimal MoS2/C


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MTs display outstanding performance of Na+ storage with excellent rate capability and high stability.

Figure 1. Schematic illustration of the synthesis process of MoS2/C MTs (A), and schematic illustration showing paths for sodium-ion diffusion/electron conduction in the MoS2/C MTs electrode and structural models of the MoS2/C MTs with expanded interlayer spacing (B). RESULTS AND DISCUSSION XRD pattern of MoS2/C MTs is shown in Figure S7. Two broaden diffraction peaks at 33.3o and 56.9o have been observed in the samples, which are ascribed to (100) and (110) planes of hexagonal 2H-MoS2 (JCPDF 37-1492), respectively. While, two broaden diffraction peaks at 8.96o and 17.90o corresponding to (002) and (004) planes of 2H-MoS2 have also been detected in the sample, compared with pure MoS2 MFs and bulk MoS2, the MoS2/C MTs exhibit obvious shift of (002) peak to lower 2θ degree, indicating that the significantly expanded interlayer distance along c-axis.35,36 SEM images of MoS2/C MTs are shown in Figure 2A-C. As indicated


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in the pictures, the fabricated sample displays a tubular morphology with a diameter of 300-400 nanometers (nm). The well-defined MoS2/C MTs possess a rough surface and are assembled by MoS2/C NSs. For comparison, MoS2 microflowers (MFs) have been fabricated, and their XRD pattern and SEM images are exhibited in Figure S8 and Figure S12, respectively. TEM and HRTEM images of MoS2/C MTs are exhibited in Figure 2D and E, they confirm that the MoS2/C MTs are composed of NSs. HRTEM study shown in Figure 2E suggests that NSs in MoS2/C MTs possess amorphous carbon and 7-8 layers stacked MoS2 NSs with an enlarged interlayer distance of 1.1 nm, which is much larger than 0.67 nm of MoS2 MFs (Figure S13), and the HRTEM image further demonstrate that the carbon monolayer was sandwiched between two adjacent MoS2 monolayers (Fig. S14). TEM image and corresponding EDS elemental mapping results are shown in Figure S15. It reveals that C, Mo and S are uniformly distributed throughout MoS2/C MTs.


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Figure 2. SEM (A, B, C), TEM (D), HRTEM (E) images and corresponding intensity profile for the line scan across the lattice fringes (F) of MoS2/C microtubes (MTs). High-resolution Mo 3d (G), S 2p (H) and C 1s spectra (I) of MoS2/C MTs, MoS2 MFs and pure C, respectively. To investigate how the C interact with MoS2 in MoS2/C MTs, XPS has been conducted on pure C, MoS2 MFs and MoS2/C MTs samples. The Mo 3d, S 2p and C 1s spectra of MoS2/C MTs, MoS2 MFs are shown in Figure 2G-I. Two peaks centered at 232.1 and 229.4 eV have been observed in the Mo 3d spectrum of MoS2 MFs, which are attributed to Mo 3d3/2 and Mo 3d5/2, respectively (Figure 2G). While, two peaks at around 161.8 and 162.8 eV are obtained in the S 2s spectrum of MoS2 MFs, which are assigned to S 2P1/2 and S 2P3/2, respectively (Figure 2H). It indicates the existence of Mo4+ and S2- in the MoS2 MFs. For comparison, the XPS spectrum of pure C NSs has been studied, the two peaks located at 284.6 and 285.7 eV are attributed to the


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sp2-C and sp3-C, respectively (Figure 2I). As exhibited in Figure 2G, compared to pure MoS2 MFs, the characteristic peaks of Mo 3d and S 2p for MoS2/C MTs shift towards to the lower binding energy, demonstrating an increased electron clouds density around MoS2.32,37 While, compared to pure C NSs, the characteristic peaks of C in MoS2/C MTs shift toward high binding energy, indicating the oxidation state of C in MoS2/C MTs increases by sharing the electron clouds with MoS2. The observed electron clouds bias from C to MoS2 arises from the enhanced interaction between different valence-band potentials and larger Pauling electronegativity of Mo and C, thus resulting a strong coupling and forming an intimate heterojunction between MoS2 and C layers.38 Cyclic voltammograms (CVs) for the first three cycles of MoS2/C MTs and MoS2 MFs at the scan rate of 0.1 mV s-1 in the voltage range of 0.01-3.0 V are shown in Figure S16. During the first discharge process, the reduction peaks range from at around 0.82 and 0.50 V have been observed, which are attributed to the insertion of Na+ ions into the 2H-MoS2 crystals and conversion reaction between Na+ ions and 2H-NaxMoS2, respectively. A broad peak located at 0.08 V has also been observed, but it disappears in the following cycles, indicating the formation of solid electrolyte interphase (SEI) layer on 2H-MoS2 during the initial discharge process. While, a broad oxidation peak located at 1.79 V has been detected in the first charging process, it is related to the reverse conversion reaction between metallic Mo and Na2S matrix.39-41 The reduction and oxidation peaks are almost overlapped in the subsequent cycles, indicating high reversibility and cycling stability of Na+ storage in the MoS2/C MTs electrode. The electrochemical performance of MoS2/C MTs and MoS2 MFs are shown in Figure 3. As exhibited in Figure 3A, MoS2/C MTs deliver a discharge capacities of 791.8 mA h g-1 at the current density of 0.2 A g-1, with a high initial Coulombic efficiency of 86.6%. The irreversible


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capacity loss during the first charge/discharge process are mainly ascribed to the formation of a SEI layer and side reactions. While, MoS2 MFs exhibit a discharge capacity of 607.8 mA h g-1 at 0.2 A g-1 with an initial Coulombic efficiency of 79.3%, as indicated in Figure 3B. In the subsequent cycles, the charge/discharge profiles of MoS2/C MTs do not change significantly, the MoS2/C MTs still deliver a high reversible discharge capacity of 493.6 mA h g-1 at 1.0 A g-1 after 500 cycles (Figure 3E). But the discharge capacity of MoS2 MFs drops quickly after 50 cycles, a discharge capacity of 87 mA h g-1 at 1.0 A g-1 can be only obtained after 500 cycles. Moreover, the area capacity and volumetric capacity of MoS2/C MTs have been provided in Figure S17. Subsequently, the rate performance of MoS2 MFs and MoS2/C MTs were further studied. MoS2 MFs can deliver a reversible capacity of 326.4, 314, 290.8, 256.5, 194.2 and 137.8 mA h g-1 at 0.2, 0.5, 1.0, 2.0, 5.0 and 10.0 A g-1, respectively. After incorporated with C, MoS2/C MTs also show an enhanced rate performance. As demonstrated in Figure 3D, high rate capacities of 563.5, 520.5, 489.4, 452.9, 425.1 and 401.3 mA h g-1 have been obtained for MoS2/C MTs at 0.2, 0.5, 1.0, 2.0, 5.0 and 10.0 A g-1, respectively. More importantly, the MoS2/C MTs can retain a high discharge capacity of 484.9 mA h g-1 at 2.0 A g-1 even after 1500 cycles (Figure S18). Compared with the other MoS2-based SIB anode materials, MoS2/C MTs fabricated in this work exhibit a better rate capability and long-term cycling stability (Table S1).


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Figure 3. Charge/discharge profiles of the MoS2/C MTs (A) and MoS2 MFs (B) for the initial three cycles at 0.2 A g-1; rate capability (D) and cycling performance at 0.2 (C) and 1.0 A g-1 (E) of the MoS2/C MTs and MoS2 MFs, respectively. The above results indicate that MoS2/C MTs composed of heterostructured MoS2/C NSs can achieve a high and stable electrochemical performance in SIBs. Such a design has multiple advantages: First, an intimate heterointerface formed between MoS2 and C can mitigate the restacking and aggregation of MoS2, and more active sites are available for Na+ ions interaction.


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While, the heterointerface can dramatically enhance the electronic and Na+ ions diffusion mobility, resulting a high specific capacity and rate performance.42-44 More importantly, the MoS2 and reaction product Mo can be effectively stabilized on the MoS2/C heterointerface, the transportation/diffusion of Mo from one grain to another caused by the recrystallization and driving force from repeated electrochemical stress are greatly restricted.45 The coarsening of nanosized Mo phase are greatly prevented, resulting a good conversion reaction of Mo0/Na2S during Na extraction as well as excellent cycling stability.31,46,47 This theory has been further verified by in situ TEM and HRTEM measurements of individual MoS2/C MT during the sodiation and desodiation processes. In situ TEM measurements taken during the initial sodiation and desodiation of individual MoS2/C MT with the bias of -3 V against Na counter electrode are provided in Figure 4 and Supplementary Movie 1. During the sodiation process, it shows a progressive sodiation of MoS2/C MT proceeds both along the axial and radial directions. The MoS2/C MT has an original diameter of about 230 nm (Figure 4A). The diameter increase slightly to 320 nm at 100 s of sodiation (Figure 4B), as the Na intercalation happened in MoS2/C MT is rather rapid. Further sodiation to 300 s only leads to a slight increase in the MT diameter to 360 nm (Figure 4C), indicating the conversion reaction happened in MoS2/C MT and Na storage is close to it theoretical capacity. While, the MoS2/C MT exhibits volume shrunk during the subsequently desodiation process at 400 and 500 s (Figure 4D, E). After the fully desodiation at 560 s, the diameter of MoS2/C MT shrinks to 340 nm and its tubular structure is well-maintained (Figure 4F). It indicates that the MoS2/C MT exhibits an excellent structure stability during the sodiation/desodiation process.


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Figure 4. In-situ TEM sodiation and desodiation of individual MoS2/C MT during the sodiation (A, B and C) and desodiation (D, E and F) processes. To unravel the phase transformation behavior and reversible sodiation kinetics, in situ HRTEM measurements of an individual MoS2/C MT have been taken during the sodiation/desodiation process, the results are shown in Figure 5 and Supplementary Movie 2. As indicated in Figure 5A, during the sodiation process, the d-spacing corresponding to (002) plane grew rapidly to 1.25 nm, which is much larger than that of raw H-MoS2 (1.1 nm) as shown in Figure 2H, suggesting the occurrence of Na+ intercalation into 2H-MoS2.31,48 During the


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Figure 5. In situ HRTEM images of MoS2/C individual MT (A, B, C) sodiation and (D, E, F) and desodiation process; (G) Proposed schematic atomistic models of illustrated reaction mechanism of MoS2 anode during the sodiation and desodiation processes. sodiation to 400 s, the crystal structure of layered 2H-MoS2 weakened gradually, and the observation of Na2S and Mo nanoparticles indicates a partial concurrent conversion reaction taking place. When it is sodiated to 600 s, no noticeable layered structure 2H-MoS2 can be


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observed, only Mo and Na2S nanoparticles can be detected in the final products, implying that the accomplishment of conversion reaction. As the MT is continued desodiated to 700 s, the layered structure 1T-NaMoS2 appeared, demonstrating dissociation of the conversion reaction products. After 900 s, the conversion reaction products (Mo and Na2S nanoparticles) are completely converted back to 1T-NaMoS2, indicating a good stability of the nanostructured Mo0/Na2S conversion reaction interface and excellent reversibility of Mo0/Na2S conversion reaction. When it is desodiated to 1000 s, a new crystal structure of the layered 1-T MoS2 appeared. To recap, the four-stage reaction mechanism for MoS2/C MT anode operated at different sodiation/desodiation states can be described as follows (Figure 5G) 31,49-51: Stage I (intercalation)

2H-MoS2 + xNa+ → 2H-NaxMoS2

(1)

Stage II (conversion)

2H-NaxMoS2 → xNa2S + Mo

(2)

Na2S + Mo → 1T NaMoS2

(3)

Stage III (de-conversion)

Stage IV (de-intercalation) 1T NaMoS2 → 1T-MoS2 + Na+

(4)

The high reversibility of conversion reaction for MoS2 in MoS2/C MTs during the sodiation/desodiation process can be further confirmed by in situ XRD measurement, the results are shown in Figure S19. It is noticed that the peak located at 26.5o is derived from carbon paper. As indicated in Figure S19B, when it is discharged from OCV to 0.4 V, the rapid decrease in the potential corresponds well with the left shift of (110) plane for 2H-MoS2. It indicates the intercalation of Na+ into MoS2 forming 2H-NaxMoS2 as expressed in reaction (1), which has led to an expansion of the lattice. When it is discharge from 0.4 to 0.01 V, a gradually weakened in intensity of (110) plane for 2H-MoS2 has been observed (Figure S17B). While, a new peak appears at 24.7o, it is ascribed to the (042) plane of Na2S.52,53 These observations are well consistence with the in situ TEM and HRTEM testing results. After recharging back to 0.5 V, the


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peak of Na2S as demonstrated in Figure S19B gradually disappears, and the electrode becomes 1T-NaMoS2, implying the completion of de-conversion reaction. At fully charged state of 3.0 V, the in situ XRD patterns as shown in Figure S19 A and B can be indexed into 1T-MoS2.54 The in situ XRD testing results agree well with the electrode reaction mechanism as described above in Equation 1-4, confirming the reversible of MoS2/C MTs anode for Na+ storage. Furthermore, SEM, TEM and corresponding EDX elemental mapping images of MoS2/C MTs after 500 cycling were also studied, and the results are shown in Figure S21 and S22. As exhibited in the figures, the morphology of the MoS2/C MTs are well maintained after 500 cycles at 1.0 A g-1. However, as the separation of metal and sulfide phases is almost irreversible for MoS2 MFs, it leads to irreversible of de-conversion reaction Mo/Na2S and the collapse of the MoS2 MFs crystal structure (Figure S23). CONCLUSIONS In summary, hierarchical MoS2/C MTs composed of heterostructured MoS2/C NSs has been prepared via a facile template method. The MoS2/C MTs exhibit a high specific capacity of 563.5 mA h g-1 at 0.2 A g-1, good rate performance of 520.5, 489.4, 452.9, 425.1 and 401.3 mA h g-1 at 0.5, 1.0, 2.0, 5.0 and 10.0 A g-1, respectively, and excellent stability for 1500 cycles. In situ TEM and in situ XRD study indicate that the high reversible capacity of MoS2/C MTs is mainly ascribed to the MoS2/C heterointerface formed in the MoS2/C NSs. MoS2 and reaction product Mo can be effectively stabilized on the MoS2/C heterointerface, coarsening of Mo nanoparticles is greatly prevented, resulting in a good reversible conversion reaction of Mo0/Na2S during Na extraction and excellent cycling stability. Moreover, the heterointerface formed between MoS2 and C is an enabler for high and stable performance by fast electronic and Na+ ions diffusion


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mobility, and easy adaption to volume change. Overall, MoS2/C MTs have been demonstrated as promising anode materials for SIBs.

EXPERIMENTAL SECTION

Synthesis of Sb2S3 microrods. The Sb2S3 microrods were obtained via a simple hydrothermal method. 0.912 g of SbCl3, 0.968 g of L-cysteine, and 1.92 g of Na2S·9H2O were orderly dissolved in 60 mL of distilled water (DIW) to form a homogeneous suspension under continuously stirring for 3 h. Afterwards, the above solution was transferred into an 80 mL Teflon-lined stainless steel autoclave and then kept at 180 °C for 12 h. Finally, the dark-brown product was obtained by filtration, and washed with DIW for several time before drying at 60 °C overnight . Synthesis of MoS2/C microtubes. 0.1 g of the as-prepared Sb2S3 smicrorods (MTs) were dispersed in 30 ml of distilled water under sonication and stirring. Then, 0.1 g of sodium molybdate dehydrate (Na2MoO4·2H2O), 0.2 g of thiourea (N2H4CS) and 0.125 g of glucose (C6H12O6) were added to the solution, which was continuous stirred for 30 min until the reagents dissolved completely. Subsequently, the mixture solution was transferred to a Teflon-lined stainless steel autoclave and kept at 200 °C for 24 h. And the black precipitate of Sb2S3@MoS2/C was collected, and dried in an oven at 60 °C. Finally, the Sb2S3@MoS2/C was further annealed in Ar (95%)/H2 (5%) at 700 oC for 3 h to remove the Sb2S3 microrods and obtain the MoS2/C MTs. For comparison, MoS2 microflowers (MFs) have been prepared with the similar hydrothermal method without added Sb2S3 microrods and glucose.


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Materials characterization. The morphology of the samples were characterized by SEM (JEOL JSM07600F) and TEM (JEOL JEM-2100F). X-Ray Diffractometer with Cu Kα radiation was conducted to determine the composition and phase of the samples. Thermogravimetric analysis (TGA) and Raman measurement were performed at Mettler-Toledo TGA/DSC1 and a laser Raman spectrometer (Jobin Yvon, T6400), respectively. The nitrogen adsorption and desorption measurements using a Micromeritics ASAP 2020 analyzer. The chemical state of elements was confirmed via XPS (AXIS ULTRA DLD). In-situ TEM test. A tungsten tip covered with MoS2/C microtubes was loaded on the TEMSTM holder as an electrode. Sodium metal with a grown Na2O layer was mounted on a piezodriven biasing probe to serve as the Na source, and a thin Na2O layer served as the solid electrolyte. The samples were brought into contact with the Na2O/Na particles, and an appropriate bias voltage was applied by means of a potentiostat to drive the sodiation/desodiation reaction.

In-situ XRD test. For in situ XRD test, using carbon paper as a current collector. And the electrode is composed of MoS2/C microtubes, acetylene black and polyvinylidene fluoride (PVDF) with a weight ratio of 75:15:15. The XRD chamber was equipped with a Be window to allow X-ray passage. Each scan was performed in 0.02o step incremental between 2θ=15° and 40. And the charge/discharge test was conducted at 0.1 A g-1. Electrochemical measurements. To prepare working electrode, the MoS2/C MTs mixed with carboxymethyl cellulose (CMC) and acetylene black with a weight ratio of 70:15:15 and added deionized water to form a slurry. CR2032-type coin cells were assembled for electrochemical test, sodium metal as counter and reference electrode, and electrolyte composed


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of NaClO4 (1 M), ethylene carbonate (EC), propylene (PC) (EC : PC = 1 : 1 wt.%) with 5 wt.% fluoroethylene carbonate additive. Cycling and rate performance were tested on a LANDBT2013A measurement system. CV measurements and EIS analysis were carried out at CHI 660E workstation with a voltage range of 0.01-3.0 V and in the frequency range from 100000 Hz to 0.01 Hz, respectively. ASSOCIATED CONTENT Supporting Information. The following files are available free of charge on the ACS Publications website: In-situ TEM observation of first sodiation/desodiation of a single MoS2/C MT. In-situ HRTEM observation of first sodiation/desodiation of a single MoS2/C MT. Schematic configuration of in-situ TEM measurements; XRD, SEM images of Sb2S3 microtubes and Sb2S3@MoS2/C microtubes; Raman spectra of Sb2S3@MoS2/C microrods, MoS2 MFs and MoS2/C MTs; TEM images and corresponding EDX elemental mapping images

of

Sb2S3@MoS2/C microrods and MoS2/C MTs; XRD, BET, XPS and TGA curves for MoS2/C MTs; SEM and TEM images of MoS2 MFs; HRTEM image of MoS2/C MTs; CV curves of MoS2/C MTs and MoS2 MFs; Area capacity and Volumetric capacity of MoS2/C MTs; Cycling performance, In situ XRD patterns, and capacitive contribution measurements of MoS2/C MTs; SEM and TEM images of MoS2/C MTs and MoS2 MFs after cycling; EIS of MoS2/C MTs and MoS2 MFs before and after cycling. AUTHOR INFORMATION Corresponding Author


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*E-mail (C. Yang): [email protected]. Author Contributions Q. Pan and Q. Zhang contributed equally. ACKNOWLEDGMENT We gratefully acknowledge the financial support from the Science and Technology Planning Project of Guangdong Province, China (No. 2017B090916002), National Natural Science Foundation of China (51872098), Guangdong Natural Science Funds for Distinguished Young Scholar (2016A030306010), Guangdong Innovative and Entrepreneurial Research Team Program

(2014ZT05N200),

Natural

Science

Foundation

of

Guangdong

Province

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(48) Li, P.; Jeong, J. Y.; Jin, B. J.; Zhang, K.; Park, J. H. Vertically Oriented MoS2 with Spatially Controlled Geometry on Nitrogenous Graphene Sheets for High-Performance Sodium-Ion Batteries. Adv. Energy Mater. 2018, 8, 1703300. (49) Xu, X.; Zhao, R. S.; Ai, W.; Chen, B.; Du, H. F.; Wu, L. S.; Zhang, H.; Huang, W.; Yu T. Controllable Design of MoS2 Nanosheets Anchored on Nitrogen-Doped Graphene: Toward Fast Sodium Storage by Tunable Pseudocapacitance. Adv. Mater. 2018, 30, 1800658. (50) Wang, X. F.; Shen, X.; Wang, Z. X.; Yu, R. C.; Chen, L. Q. Atomic-Scale Clarification of Structural Transition of MoS2 upon Sodium Intercalation. ACS Nano 2014, 8, 11394-11400. (51) Gao, P.; Wang, L. P.; Zhang, Y. Y.; Huang, Y.; Liu, K. H.; Atomic-Scale Probing of the Dynamics of Sodium Transport and Intercalation-Induced Phase Transformations in MoS2. ACS Nano 2015, 9, 11296-11301. (52) David, L.; Bhandavat, R.; Singh, G. MoS2/Graphene Composite Paper for Sodium-Ion Battery Electrodes. ACS Nano 2014, 8, 1759-1770. (53) Zhang, S.; Yu, X. B.; Yu, H. L.; Chen, Y. J.; Gao, P.; Li, C. Y.; Zhu, C. L. Growth of Ultrathin MoS2 Nanosheets with Expanded Spacing of (002) Plane on Carbon Nanotubes for High-Performance Sodium-Ion Battery Anodes. ACS Appl. Mater. Interfaces 2014, 6, 21880-21885. (54) Wang, J.; Luo, C.; Gao, T.; Langrock, A.; Mignerey, A. C.; Wang, C. An Advanced MoS2/Carbon Anode for High-Performance Sodium-Ion Batteries. Small 2015, 11, 473-481.


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TOC Figure


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C Hierarchical Tubular Heterostructures for High

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