MoS2 Nanosheet Superstructures Based Polymer Composites for

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MoS Nanosheet Superstructures Based Polymer Composites for High Dielectric and Electrical Energy Storage Applications Qingchao Jia, Xingyi Huang, Guanyao Wang, Jinchao Diao, and Pingkai Jiang J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.6b02968 • Publication Date (Web): 02 May 2016 Downloaded from http://pubs.acs.org on May 7, 2016

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The Journal of Physical Chemistry

MoS2 Nanosheet Superstructures Based Polymer Composites for High Dielectric and Electrical Energy Storage Applications Qingchao Jia, Xingyi Huang,* Guanyao Wang, Jinchao Diao and Pingkai Jiang Department of Polymer Science and Engineering, Shanghai Key Laboratory of Electrical Insulation and Thermal Ageing, Shanghai Jiao Tong University, Shanghai 200240, China

ABSTRACT: This work reports the advances of utilizing molybdenum disulfide (MoS2) nanosheet superstructures to enhance dielectric property and electrical energy storage capability of flexible ferroelectric polymer composites. Hydrangea-like flowers or clusters comprising MoS2 nanosheets were synthesized by hydrothermal methods and used as filler of ferroelectric polymer composites. Both MoS2 superstructure based composites show percolation-like electrical behavior. The composites with high loading of MoS2 superstructures exhibit significantly enhanced dielectric constant, whereas those with low loading of MoS2 superstructures can withstand high electric field and exhibit significantly enhanced electric polarization, resulting in significant improvement of electrical energy storage capability. The MoS2 flowers show strong potential to enhance the dielectric constant and electrical energy storage capability of the composites.

Introduction High-dielectric-constant (high-κ) materials have attracted ever-increasing attention because of their wide range of applications in electronic and electrical industry and military field, such as electrostatic capacitors, weapons and field-effect transistors. Taking the electrostatic capacitors as an example, the utilization of high-κ dielectrics can overcome the disadvantage of low energy density while maintaining the advantage of high power density.1-3 Polymeric materials are good candidates as dielectrics because of their flexibility and ease of processing.4,5 However, most of dielectric polymers are low-κ materials and thus efforts should be made to enhance their dielectric constant while maintaining other desirable properties. Apart from the synthesis of intrinsic high-κ polymers, hybrid strategies have been widely used to achieve high-κ materials. Two strategies have been widely utilized so far. One is the addition of high-κ dielectric filler (e.g., ferroelectric ceramics) into a polymer matrix,6-12 and the other is incorporating conductive fillers such as carbon nanotubes and graphene nanosheets into a polymer matrix to form percolating systems.13-19

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The dielectric enhancement in percolating composites comprising conductive filler and insulating polymers follows the percolation theory. In this case, the dielectric constant of the composites exhibits an exponential increase when the filler is near but lower than the percolation threshold. Huge dielectric constant of up to several hundreds or thousands can be technologically achieved at a low loading when large-aspect-ratio particles were used as filler. However, the percolating composites can’t withstand high electric field because of the large electrical mismatch between polymer and filler. The enhancement of dielectric constant in high-κ ceramic filler based polymer composites obeys the effective medium theory. Utilizing this strategy, however, we usually achieve a dielectric enhancement lower than ten times. Apart from conductive filler and high-κ ceramic filler, semiconductive filler such as zinc oxide (ZnO)20 and silicon carbide (SiC)21 have also been used to enhance the dielectric constant of polymers. More importantly, the semiconducting filler based composites have unique nonlinear electrical behavior, which makes them promising for high voltage applications. For instance, it has been found in previous report that the ZnO superstructure based polyvinylidene fluoride (PVDF) composites not only show significantly enhanced dielectric constant but also can withstand high electric field20. Recently, molybdenum disulfide (MoS2) nanosheets received a lot of attention because of their semiconducting nature, appreciable band gap,22-27 and electric field tunable dielectric constant.28 These features make MoS2 nanosheets exhibit high potential to tune the dielectric properties of polymer composites. However, so far the role of MoS2 nanostructure in dielectric properties of polymer composites hasn’t been documented in detail. In this study, two kinds of MoS2 nanosheet superstructures (i.e, hydrangea-like flowers29 and nanosheet clusters30) were synthesized by hydrothermal methods. Ferroelectric polymer composites were prepared by introducing the MoS2 superstructures into a ferroelectric polymer (i.e., PVDF). Nanosheet superstructures rather than individual nanosheets were used as filler because of their facile large scale production and excellent repeatability of the products. It was shown for the first time that the MoS2 superstructures based composites can exhibit significantly enhanced dielectric properties. More interestingly, the composites exhibit significantly improved electrical energy storage capability when the loading of MoS2 superstructures was low. This may open a new route to fabricate flexible high-κ polymer composites for high dielectric and electrical energy storage applications. Experimental section Materials. Sodium molybdate dihydrate, hydroxylamine hydrochloride, thiocarbamide, hexaammonium heptamolybdate tetrahydrate, cetyl trimethyl ammonium bromide (CTAB), hydrochloric acid, absolute ethanol, N, N-dimethyform amide (DMF), methanol were all analytical grade and purchased by Sinopharm Chemical Reagent Co., Ltd., China. polyvinylidene fluoride (PVDF, 6010) powder was ACS Paragon Plus Environment

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kindly provided from Solvay Shanghai Co. Ltd., China. All chemicals were used as received without further purification. Preparation of hydrangea-like MoS2. Sodium molybdate dehydrate (1.03 g), hydroxylamine hydrochloride (0.725 g) and thiocarbamide (1.4 g) were dissolved in 50 ml deionized water at room temperature. The above solutions were stirred slightly and then cetyl trimethyl ammonium bromide (0.18 g) were added into the solution. The resulting mixture was stirred for several minutes. Hydrochloric acid (2 mol/L) was used to adjust the pH value of the mixture to 6 before the solution was transferred to a 100 mL Teflon-lined stainless steel autoclave. The autoclave was sealed and the mixed hydrothermal reaction was conducted at 180 °C for 24 h. After naturally cooling down to room temperature, black precipitates was harvested by centrifugation and washed with distilled water and absolute ethanol several times, and finally dried in a vacuum oven at 60 °C for 12 h. Preparation of MoS2 nanosheet cluster. Hexaammonium heptamolybdate tetrahydrate (1.236 g) and thiocarbamide (2.28 g) were dissolved in 35 ml deionized water at room temperature. The resulting mixture was stirred for 15 minutes. Then the solution was transferred into a 100 mL Teflon-lined stainless steel autoclave and maintained at 220 °C for 24 h. After naturally cooling down to room temperature, black precipitates was harvested by centrifugation and washed with distilled water and absolute ethanol several times, and finally dried in a vacuum oven at 60 °C for 12 h. Preparation of composite samples. Both two types of MoS2 composites were fabricated by a combination of solution blend, sequential precipitation, and hot-press processes. The procedures were carried out as follows: a certain amount of MoS2 was first ultra-sonicated in DMF for 1 h at room temperature, and then a certain amount of PVDF powder was added while agitating. The mixture was then stirred vigorously at 60 °C for another 2 h. The suspension was then added into a methanol bath drop by drop, at the same time, the methanol bath was stirred constantly. The resulting precipitates were filtered off from a colorless filter paper. Finally, the obtained precipitates were dried in a vacuum oven at 60 °C for 24 h in order to remove the remaining trace of the solvent. And then, the composite films for testing were prepared by hot compression molding at 180 °C. Characterization. A field emission scanning electron microscope (SEM, Nova NanoSEM, NPE218, FEI, USA) was used to observe the morphology of MoS2 superstructures. The dispersion of MoS2 superstructures were investigated by TEM (JEM-2010, JEOL, Japan). The elemental composition of the synthesized materials was investigated by energy-dispersive X-ray spectroscopy (EDX) (Link-Inca, model 622, U.K.). Wide-angle X-ray diffraction(XRD) patterns were recorded on a Rigaku D/MAX2200/PC automatic diffractometer (Rigaku Corporation, Tokyo, Japan), and all measurements were performed at atmospheric pressure and room temperature with nickel-filtered Cu target Kα radiation at 40 ACS Paragon Plus Environment


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KV and 20 mA with a scintillation counter system. Tests were performed at a scanning rate of 6°/min in a range of 2θ=3-70° for MoS2 superstructures and at a scanning rate of 2°/min in a range of 2θ=2-30° for PVDF/MoS2 superstructures composites. Differential scanning calorimetry (DSC) characterization of the nanocomposites was conducted under nitrogen atmosphere at a heating/cooling rate of 10 °C/min by using a NETZSCH 200 F3 instrument. Fourier-transform infrared spectroscopy (FT-IR) was conducted with a Perkin-Elmer Paragon 1000 instrument. Dielectric properties of the composite samples were measured by a Novocontrol Alpha-N high resolution dielectric analyzer (Concept 40, GmbH, Germany) in the frequency range 10-1 to 106 Hz and an Agilent HP4991 impedance analyzer in the frequency range 106 to 109 Hz at room temperature. A layer of gold was evaporated on both sides of the samples to serve as electrodes. Electric displacementelectric field (D - E) loops and current-voltage (I - V) measurements were conducted by a Precision Multiferroic Material Analyzer equipped with Precision 10 kV HVI-SC and Terk MODEL 609B (Radiant Inc.). Samples were sputtered by gold with diameter of 3 mm on both sides as electrodes. Results and discussion Characterization of MoS2 superstructures. Fig. 1 shows typical SEM images of as synthesized MoS2 superstructures. One looks like hydrangea-like flowers with a diameter of 1 to 2 µm, which were fabricated by a combination of nucleation, oriented aggregation and self-assembly processes. The other looks like clusters composed of randomly assembled nanosheets. The XRD patterns of both superstructures were provided in Fig. S1 (see Supporting Information) to confirm the structure of MoS2. One can see that all diffraction peaks can be indexed to the hexagonal phase of MoS2, which are in agreement with the standard card (JCPDS No.37-1492). The intense peaks indicate high degree of crystallinity and high phase purity of both MoS2 superstructures. The results of elemental analysis through EDX were shown in Fig. S1.

Fig. 1 SEM images of MoS2 superstructures: (a) hydrangea-like flowers, (b) nanosheet clusters. ACS Paragon Plus Environment

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Fig. 2 TEM images showing the dispersion of MoS2 superstructures in the composites. Composites with 1.9 % (a) and 19.8 % (b) MoS2 flower; Composites with 1.9 % (c) and 19.8 % (d) nanosheet clusters. Characterization of composites. The dispersion state of the MoS2 superstructures in matrix is an important factor in determining the dielectric proper-ties of the composites. In order to obtain the detailed dispersion information of the MoS2 superstructure in the polymer matrix, TEM was used to observe the ultra-microtome composite slices. Fig. 2 shows the typical TEM images of MoS2 composites. When the volume fraction of superstructure is low (e.g., 1.9 %, volume fraction used throughout of the study), both MoS2 flowers and nanosheet clusters show a random dispersion and the original morphology of both MoS2 superstructures are retained in the composites. In addition, a small amount of individual MoS2 nanosheets can be observed, which should be those exfoliated from the superstructures during the preparation process of the composites. In the case of highly filled composites, both MoS2 flowers and nanosheet clusters are still randomly dispersed and most of the superstructures exist in their original morphology in the composites. Unlike the composites with low loading of MoS2 superstructures, the highly filled flower composites contain a large amount of individual nanosheets. In addition, the cluster composites display a lower density of individual nanosheets, indicating that the clusters are more stable



in solution under the effect of ultrasonication. It should be noted that the highly filled composites are still capable of being easily rolled up, exhibiting excellent flexibility (see Fig. S2). PVDF is a highly nonreactive thermoplastic polymer, which have different crystalline forms. The addition of filler can modify the crystalline forms and crystallization dynamics of PVDF. The XRD patterns of PVDF and the superstructures composites are presented in Fig. 3 to investigate the effect of MoS2 superstructures on crystalline forms of PVDF. As shown in Fig. 3, the pure PVDF exhibit four major α phase reflections, which correspond to α(100), α(020), α(110) and α(021) diffractions.31-33 β phase characteristic peaks were not observed in the XRD pattern of the pure PVDF. After introducing the MoS2 flower superstructures, the density of α phase decreases with the increase of MoS2 loading. In addition, the β phase (2θ = 20.26°) appears regardless of the MoS2 loading level. In the case of MoS2 nanosheet cluster based composites, the density of α phase characteristic peak also generally exhibit a decrease with the increase of MoS2 loading, but the intensity of β phase characteristic peak was not strong until the MoS2 loading is higher than 1.9 %. The existence of β phases in the MoS2 superstructures based composites can further approved by FTIR spectra. Fig. S3 shows the FTIR spectra of pure PVDF and the MoS2 superstructure composites. One can see that the characteristic band of β phase at 840 cm-1 becomes much stronger in the composites.34 The mechanism for the formation of β phases in the MoS2 superstructures based composites is not clear. It is expected that the interaction between the charges of the MoS2 surface and the PVDF dipole should be main factor. MoS2 is negatively charged because that the S atoms are rich on the surface of MoS2 sheets.35 In this case, the interaction between negatively charged MoS2 and the positive rich CH2 groups can favor the formation of β phases. (a)

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Fig. 3 XRD patterns of the MoS2 superstructure composites: flower (a) and nanosheet cluster (b). XRD analysis indicates that the addition of MoS2 superstructures results in apparent influence on the crystallization of PVDF. In order to achieve more details, DSC measurement was carried out and the ACS Paragon Plus Environment

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melting and cooling curves were shown in Fig. 4. One can see from the melting curves that each type composites have the similar main melting temperature regardless of the MoS2 loading. At high loading of MoS2 superstructures, a secondary melting peak appears at high temperatures, which should be another indicator of the existence of β phase in the composites. It should be noted that the MoS2 nanosheet cluster based composites show higher secondary melting temperatures and slightly higher main melting temperatures in comparison with the MoS2 flower based composites. Such a phenomenon can be understood by the crystalline behavior of the composites. As can be seen from cooling curves, the addition of high loading of MoS2 nanosheet cluster can favor the nucleation of α and β phase crystals, resulting higher crystallization temperatures and more perfect crystal. In the case of MoS2 flower based composites, however, all the composites show decreased crystallization temperatures. This results shows that the MoS2 flowers retard the nucleation of PVDF. In this case, crystallization can only be carried out low temperatures and thus the crystals are not perfect. (a) MoS Flower Composites 2

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Fig. 4 DSC curves of PVDF and PVDF/MoS2 superstructures: melting process (a, b), cooling process (c, d). ACS Paragon Plus Environment


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Dielectric properties of composites. The frequency dependent dielectric properties of the MoS2 composites were measured by broadband dielectric spectroscopy at room temperature. In general, as is shown in Fig. 5, both types of composites exhibit percolation-like electrical characteristics. The dielectric constant (Fig. 5) and dielectric loss tangent (see Fig. S4) of both composites increase slowly with either flower or cluster loading when the loading is low. Starting from a critical concentration (i.e., percolation threshold), significantly increase of dielectric constant starts to be observed and the dielectric constant exhibits a strong frequency dependence. To further investigate the effects of MoS2 superstructures on the dielectric constant of the composites, the MoS2 loading dependent dielectric constant at 1000 Hz is shown in Fig. 5. One can see that both types of composites exhibit similar values of dielectric constant when the MoS2 loading is low (≤ 8.5 %). Starting from 11 %, however, the flower filled composites have higher dielectric constant and the difference becomes larger as the MoS2 loading increases to 23.3 %. For example, the dielectric constant of the composites with 23.3 % flower is 373 at 1000 Hz, which is 38.8 times higher than that of the polymer. In contrast, the dielectric constant of the composites with 23.3 % cluster is about 163 at 1000Hz, which is only 18 times of that of the polymer. This result shows that the MoS2 flowers have the merit to enhance the dielectric constant of the composites. The electrical conductivity of both types of composites shows strong frequency dependence and increases slowly with the increase of either MoS2 flower or cluster when the loading is low, indicating that the composites with low MoS2 loading are insulating materials. Starting from a critical concentration, the electrical conductivity at low frequencies shows a significant increase because of the onset of the percolating network formation. For the composites with MoS2 loading slightly higher than the critical concentration, the electrical conductivity is independent of the frequency at low frequencies. Above a critical frequency, the electrical conductivity starts to increase with the increase of frequency. Finally, the composites with MoS2 loading much higher than the critical concentration exhibit frequency independent electrical conductivity over the whole frequency range, indicating that a percolating MoS2 network throughout the whole composites has been formed. The critical concentration (percolation threshold) of the composites can be predicted by the percolation theory: σ = σ 0 (ρc - ρ

-s

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, ρc > ρ ,

t

σ = σ 0 (ρ - ρ c ) , ρ c < ρ

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where σ and σ0 is the DC electri-cal conductivity of the composites and the poly-

mer matrix, respectively. ρ is the volume fraction of MoS2 in the composites and t and s are critical exponents.18 Taking the frequency-independent plateau conductivity or the conductivity at 0.1 Hz as the DC electrical conductivity, the percolation threshold of each composites can be calculated by fitting the MoS2 loading dependent electrical conductivity shown in Fig. 5f. The experimental results fit well with the percolation laws and the calculated ρc values are 8.6 % and 11.1 % for the flower filled composites ACS Paragon Plus Environment

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and cluster filled composites, respectively. This result indicates that the percolating structure is easily developed in the MoS2 flower composites. Apart from the lower percolation threshold, it also should be noted that the DC electrical conductivity of the flower composites is much higher than that of the corresponding cluster composites. The radio frequency dielectric properties of the MoS2 superstructure composites were also characterized in Fig. S5. A brief summary of the results shows that the highly filled composites still exhibit significantly enhanced dielectric constant even at radio frequency range. On the other hand, the composites also show enhanced dielectric loss tangent because of their high electrical conductivity, making the composites be promising candidates for microwave absorption and electromagnetic interference shielding applications.

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Fig. 5 Frequency dependent dielectric constant and electrical conductivity of flower (a, b) and (c, d) cluster filled composites; Dielectric constant of composites versus MoS2 loading at 1 kHz (e); Electrical conductivity of composites versus MoS2 loading at 0.1 Hz (f). The electrical conductivities of 1000 Hz for composites with MoS2 flower loading higher than 13.7 % were used as DC conductivities since the composites show frequency independent electrical conductivity. Dielectric spectra versus temperature and frequency of the composite samples with 4% MoS2 superstructure were provided in Fig. S6. Temperature dependent dielectric parameters of the composites at selected frequencies were shown in Fig. 6. Once can see from Fig. S6 and Fig. 6 that: (i) both composites exhibit enhanced dielectric constants as the temperature increases; (ii) both composites exhibit the αa dielectric relaxation of PVDF and the relaxation peak move to high temperatures with increasing frequency; (iii) the MoS2 flower composite always shows higher real and imaginary dielectric constant. Although both composites show similar temperature and frequency dependent dielectric behavior, the MoS2 flower composite exhibit much higher dielectric enhancement at low frequency and high temperature range. A possible reason is that there exist stronger interfacial polarization in the MoS2 flower composites. The aforementioned dielectric phenomena indicate that the large difference of electrical property between the two types of composites does’not mainly originate from the dielectric relaxation, but can only be understood in terms of the microstructure of composites.20,36-38 As shown in Fig. 2, the highly filled MoS2 flower composites have much higher concentration of individual nanosheets exfoliated from the MoS2 superstructures. These individual nanosheets facilitate the formation of percolating network in the composites. On the other hand, the interfacial area increases with increasing individual nanosheet concentration. Both factors result in much higher dielectric constant and electrical conductivity in the MoS2 flower composite, particularly at high loading levels.


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Fig. 6 Dielectric spectra versus temperature at selected frequencies for the composite with 4.0 % MoS2 flower and the composite with 4.0 % MoS2 nanosheet cluster. Energy storage and leakage current density of composites. When the concentration of MoS2 superstructures is low, the dielectric constant of composites exhibits a slight enhancement whereas the dielectric loss tangent is as low as that of the polymer matrix. For example, when the MoS2 loading is 0.4 %, the flower filled composite and the cluster filled composite exhibit dielectric constants of 11.3 and 10.5 at 100 Hz, respectively, which are 16.5 % and 8.5 % higher than that of pure polymer, respectively. On the other hand, the flower filled composite and the cluster filled composites exhibit a dielectric loss tangent of 0.05 and 0.07 at 100 Hz, respectively, which are still at the same low level with the pure polymer. In this case, the MoS2 superstructures based composites should be promising for electrical energy storage applications.



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Fig. 7 (a) Electric displacement−electric field (D−E) loops, (b) Stored energy density, (c) discharged energy densities, (d) leakage current density of the MoS2 composites. In order to evaluate energy storage capability of the MoS2 superstructures based composites, unipolar D-E loops of composites with low MoS2 loading were measured under various electric fields.39-44 We can see from Fig. 7(a) that the electric displacement of the composites is greatly increased with the introduction of MoS2. For example, the maximum polarization of the composite with 0.4 % MoS2 flower is about 3.37 µC/cm2 at 200 MV/m, which is 1.65 times of that of the pure polymer (2.04 µC/cm2). On the other hand, the maximum polarization of the composite with 0.4 % MoS2 nanosheet cluster is 2.64 µC/cm2 at 200 MV/m, which is still 30 % higher than that of the pure polymer. The total stored and discharged energy densities of the composites were calculated according to the D-E loops and the results are given in Fig. 7(b, c). One can see that the energy storage densities of the composites show a significant enhancement when compared with the pure polymer. For instance, at the electric field of 200 MV/m, the total stored energy density of the composites with 0.4 % MoS2 flower and MoS2 cluster are 4.1 and 3.1 J/cm3, respectively, which are 86 % and 41 % higher than that of the ACS Paragon Plus Environment

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pure polymer (i.e., 2.2 J/cm3). On the other hand, the discharged energy densities of the composites with 0.4 % MoS2 flower and cluster are 2.3 J/cm3 and 1.9 J/cm3, respectively, which are 44 % and 19 % higher than that of the pure polymer (i.e., 1.6 J/cm3) at the electric field of 200 MV/m. The energy storage efficiency was defined as the ratio of discharged energy density to the total stored energy density. Although the composites with MoS2 flower exhibit apparent enhancement in energy storage density, the two types of composites exhibit similar energy storage efficiency (see Fig. S7). For example, the energy storage efficiencies under the electric field of 140 MV/m for the composites with 0.4 % MoS2 flower and MoS2 cluster are 71.9 % and 72.7 %, respectively, which are slightly lower than that of the pure polymer (i.e., 78.6 %). This is because both composite samples have comparable dielectric loss tangent (Fig. S3) and comparable leakage current density of the composites. As shown in Fig. 7(d), both composite samples with 0.4 % MoS2 show slightly higher leakage current density in comparison with the pure polymer, while no apparent difference was observed between the two composite samples. The enhanced energy density of the composites should be mainly ascribed to the increase of dielectric constant of the composites, which was induced by the introduction of MoS2 superstructures. The introduction of MoS2 flower results in higher enhancement of dielectric constant in the composites when compared with the cluster, which in turn results in higher electric displacement of the composites and thus the composites with MoS2 flower exhibit higher energy storage capability. Conclusions In summary, we are the first to report that MoS2 superstructures can significantly enhance the dielectric property and electrical energy storage capability of flexible ferroelectric polymer composites. Both MoS2 superstructures based composites exhibit percolation-like electrical behavior, showing significantly enhanced dielectric constant when the loading of MoS2 superstructures is near the percolation threshold. Compared with the nanosheet clusters, the hydrangea-like flower exhibits a lower percolation threshold and stronger potential to enhance the dielectric constant of the composites. When the loading of MoS2 superstructures is low, the electrical energy storage capability of the composites can be significantly enhanced and the flower has stronger enhancement potential. This research opens the door toward constructing MoS2 based flexible polymer composites for high dielectric and electrical energy storage applications. Surface functionalization of MoS2 superstructures may be an effective way to further improve the dielectric properties of their composites. ASSOCIATED CONTENT Supporting Information.



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XRD patterns, EDX of MoS2 superstructures, digital photos, FTIR spectra, frequency dependent dielectric loss tangent, the radio frequency dielectric properties and the energy efficiency of the composites. This material is available free of charge via the Internet at http://www.acs.org. AUTHOR INFORMATION Corresponding Author * (X.Y.H.). E-mail: [email protected]. Tel: +862154740787 Notes The authors declare no competing financial interest. ACKNOWLEDGMENT The current work was supported by National Natural Science Foundation of China (nos. 51522703, 51277117, 51477096) and the Special Fund of the National Priority Basic Research of China under Grant 2014CB239503. REFERENCES (1) Li, Q.; Chen, L.; Gadinski, M. R.; Zhang, S.; Zhang, G.; Li, H.; Haque, A.; Chen, L. Q.; Jackson, T.; Wang, Q. Flexible High-Temperature Dielectric Materials from Polymer Nanocomposites. Nature 2015, 523, 576-9. (2) Chu, B.; Zhou, X.; Ren, K.; Neese, B.; Lin, M.; Wang, Q.; Bauer, F.; Zhang, Q. A Dielectric Polymer with High Electric Energy Density and Fast Discharge Speed. Science 2006, 313, 334-336. (3) Huang, X.; Jiang, P. Core-Shell Structured High-K Polymer Nanocomposites for Energy Storage and Dielectric Applications. Adv. Mater. 2015, 27, 546-54. (4) Dang, Z.-M.; Yuan, J.-K.; Zha, J.-W.; Zhou, T.; Li, S.-T.; Hu, G.-H. Fundamentals, Processes and Applications of High-Permittivity Polymer–Matrix Composites. Prog. Mater. Sci. 2012, 57, 660-723. (5) Zhu, L.; Wang, Q. Novel Ferroelectric Polymers for High Energy Density and Low Loss Dielectrics. Macromolecules 2012, 45, 2937-2954. (6) Dang, Z.-M.; Zhou, T.; Yao, S.-H.; Yuan, J.-K.; Zha, J.-W.; Song, H.-T.; Li, J.-Y.; Chen, Q.; Yang, W.-T.; Bai, J. Advanced Calcium Copper Titanate/Polyimide Functional Hybrid Films with High Dielectric Permittivity. Adv. Mater. 2009, 21, 2077-2082. (7) Yang, K.; Huang, X.; Huang, Y.; Xie, L.; Jiang, P. Fluoro-Polymer@ BaTiO3 Hybrid Nanoparticles Prepared Via Raft Polymerization: Toward Ferroelectric Polymer Nanocomposites with High Dielectric Constant and Low Dielectric Loss for Energy Storage Application. Chem. Mater. 2013, 25, 2327-2338. (8) Zhang, X.; Shen, Y.; Zhang, Q.; Gu, L.; Hu, Y.; Du, J.; Lin, Y.; Nan, C. W. Ultrahigh Energy


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Ferroelectric Polymer Nanocomposites by High-K Nanowires. ACS Appl. Mater. Interfaces 2015, 7, 18017-27.


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MoS2 Nanosheet Superstructures Based Polymer Composites for

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