Core-shell Nanostructures Design in Polymer Nanocomposites

Dec 28, 2018 - Four types of BaTiO3@PTFMPCS nanostructures are prepared and incorporated into polymer matrix for capacitor application...
0 downloads 0 Views 7MB Size
Download PDF
Research Article pubs.acs.org/journal/ascecg

Cite This: ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Core−Shell Nanostructure Design in Polymer Nanocomposite Capacitors for Energy Storage Applications Hang Luo,†,∥ Sheng Chen,‡,∥ Lihong Liu,*,†,§ Xuefan Zhou,† Chao Ma,† Weiwei Liu,† and Dou Zhang*,† †

State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, Hunan Province, China Key Laboratory of Polymeric Materials and Application Technology of Hunan Province, College of Chemistry, Xiangtan University, Xiangtan 411105, Hunan Province, China § Department of Orthopedics, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan Province, China ACS Sustainable Chem. Eng. Downloaded from pubs.acs.org by UNIV OF EDINBURGH on 01/23/19. For personal use only.

‡

S Supporting Information *

ABSTRACT: The ability to tune the interfacial layer in nanocomposites is attracting increasing interest due to its wide application in the field of nanoscale energy storage materials. However, most of the current interfacial modifiers are flexible coils collapsing on the surface of fillers. The interfacial layer thickness cannot be readily tailored. This work demonstrates an inspiring approach to design the interfacial layer of BaTiO3 nanowires and nanoparticles with poly{5-bis[(4-trifluoromethoxyphenyl)oxycarbonyl]styrene} (PTFMPCS). The PTFMPCS is a kind of fluoric-liquid-crystalline polymer (LCPs) that possesses polymer-chain rigidity and an orientated structure, which is useful to design the interfacial layer thicknesses of fillers. Four types of BaTiO3@PTFMPCS nanostructures are prepared and incorporated into a polymer matrix for capacitor applications. The experimental results show that the PTFMPCS interfacial layer thicknesses are precisely controlled and in good agreement with the theoretically predicted thicknesses. In addition, the performance of the nanocomposites are obviously affected by the PTFMPCS interfacial layer thickness, e.g., the discharge energy density of the nanocomposites with a 14.8 nm thickness of the PTFMPCS layer increased by 8.5% than with 9.2 nm, which reaches to 14.64 J/cm3. The findings provide an innovative way to design the interfacial layer thickness in various nanostructured materials for applications related to energy storage. KEYWORDS: Core−shell structures, Liquid crystalline polymers, Polymer nanocomposites, BaTiO3 nanowires, Energy storage

■

INTRODUCTION Interfacial polarization is a topic with intense interest in many fields of material science, such as photovoltaic, photocatalytic, ferro-/piezoelectric, and dielectric materials, etc.1−5 Recently, polymer based capacitors have been extensively explored due to their advantages of ultrahigh power density compared to other renewable energy systems.6−11 Ferroelectric ceramic nanofillers are being employed by incorporating them into polymer matrixes to create polymer nanocomposites due to their potential to achieve a high energy density through combination of the advantages from the hybrids.12−16 Nanosized ceramic fillers embedded in a polymer matrix leads to the formation of a large interfacial region, which becomes a key factor to affect the energy storage properties of the nanocomposites.17−23 One challenge is to understand the mechanism of interfacial regions determining the dielectric properties and energy storage capability of the dielectric nanocomposites.24−28 Researchers revealed the effect inorganic buffer layer thickness on the performance of polymer nanocomposite. Huang et al. prepared BaTiO3 nanowires with variable TiO2 shell thicknesses and TiO2 nanowires with © XXXX American Chemical Society

variable BaTiO3 shell thicknesses, respectively. It was found that compared with nanocomposites with bare ceramic nanowires, significantly enhanced energy density was achieved for nanocomposites with ceramic nanowires encapsulated by an inorganic buffer layer, and the shell thickness of the buffer layer shows a significant role in tailoring the performance of the dielectric nanocomposite.29,30 However, there is little research on the organic layer thickness. Therefore, it is of interest to control the thicknesses of the interfacial layers in the polymer nanocomposites.31−35 Despite this interest, the recent interfacial modifier is limited to organic small molecules or flexible molecules which always exhibit random polymer coils coated on the surfaces of the fillers.36−38 Therefore, the thickness interfacial layer cannot be precisely designed. Rigid polymer poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrenes} (PMPCS) was proposed for the first time to design the interfacial layer using its feature of rigidity Received: September 27, 2018 Revised: December 1, 2018 Published: December 28, 2018 A

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

ACS Sustainable Chemistry & Engineering and orientation in our previous work.39 However, PMPCS exhibited poor compatibility with the polymer matrix, resulting in that the effect of interfacial layer thicknesses on the energy storage properties was still unclear. Fluoric-polymers were demonstrated as candidate modifiers because they can obviously improve the dispersibility and compatibility problems in the nanocomposites.40−43 Therefore, a fluoropolymer, poly{5-bis[(4-trifluoro-methoxyphenyl)oxycarbonyl]styrene} (PTFMPCS), was designed in this work, of which each structural unit had six fluorine atoms to effectively decrease the surface energy mismatch between PTFMPCS and the polymer matrix. PTFMPCS is a kind of rigid polymer due to the strong spatial effects, originating from the bulky side groups. The molecular chain is able to self-assemble into a columnar phase by taking on an extended conformation. Therefore, the thicknesses of the PTFMPCS can be precisely controlled by design of its molecular weight according to eq 1, which has been confirmed by our previous work.39,44

Figure 1. Process of PTFMPCS interfacial layer thickness modulation.

Lrod = 0.154 (nm) × 2Nrod × sin 52° ≈ 0.24Nrod (nm)

polymerization method. To achieve this, the RAFT agent (4cyanopentanoic acid dithiobenzoate, CPDB) was grafted onto the surfaces of BaTiO3 nanowires and activated by Nhydroxysuccinimide (NHS). Subsequently, PTFMPCS with specifically designed molecular weights is readily coated on the surface of BaTiO3 nanowire. As shown in Figure 1, the blue region is BaTiO3 nanowire, and the pink region is the PTFMPCS layer. The thickness of PTFMPCS layer can be precisely determined by the designed molecular weight of PTFMPCS. The BaTiO3 nanowires (BT NWs) were synthesized according to eq 2 based on previous reports.53,54

(1)

where Nrod is the degree of polymerization, and Lrod is the shell thickness.45−48 In this regard, the rigid polymer PTFMPCS is utilized to design the interfacial layers on the surface of BaTiO 3 nanowires and nanoparticles, respectively. Four kinds of BaTiO3@PTFMPCS nanostructures with a shell thickness varying from 4.7 to 14.8 nm were manufactured, which were close to the theoretically predicted (i.e., designed) values. The core−shell structured BaTiO3@PTFMPCS nanofillers were incorporated into poly(vinylidene fluoride-trifluoroethylenechlorotrifluoroethylene) (P(VDF-TrFE-CTFE)), which was a relaxor ferroelectric polymer with a high relative permittivity.49,50 The fluoro-polymer shells were robustly grafted onto the surface of the BaTiO3 nanofillers and provided interchain forces with a P(VDF-TrFE-CTFE) matrix. A strong polarization was generated in the nanocomposites due to the cumulative free charges on the surfaces of the PTFMPCS layer. A high discharge energy density of 14.64 J/cm3 was achieved due to the combination of a high polarization with high breakdown strength of the nanocomposites. Using a rigid polymer to design the interfacial layer thickness, such as PTFMPCS employed in this work, allows adaptation to various nanoparticles and provides a potential strategy to fabricate high-capacity capacitor materials.

■

Na 2Ti3O7 + 3Ba 2 + + 4OH− → 3BaTiO3 + 2Na + + 2H 2O

(2)

As can be seen from Figure 2, the Na2Ti3O7 nanowires were prepared as the first step, which are subsequently converted to BaTiO3. Figure 2a,c displays the morphologies of the synthesized Na2Ti3O7 and BaTiO3 nanowires, respectively. As can be seen, the smooth surface and high aspect ratio were possessed by the Na2Ti3O7 nanowires, and the BaTiO3 nanowires had a high aspect ratio of approximately 21 using ImageJ software. Figure 2b,d shows the X-ray diffraction pattern of Na2Ti3O7 and BaTiO3 nanowires, which showed that Na2Ti3O7 nanowires were indexed to the monoclinic phase (31-1329) and BaTiO3 nanowire was indexed to the tetragonal phase (no. 31-0174). Figure 2e show the transmission electron microscopy (TEM) results of the BaTiO3 nanowires. Figure 2f presents a high-resolution-transmission electron microscopy (HR-TEM) image of a BaTiO3 nanowire. It was found that the parallel lattice spacings were approximately 0.406 and 0.286 nm, corresponding to the (001) and (101) planes of the tetragonal phase, respectively. In Figure 3a,d, the polymer and the polymer coated BaTiO3 nanowires exhibited birefringence phenomenon, indicating that PTFMPCS formed the liquid crystalline phase. The phase behavior and structure of PTFMPCS was further confirmed by DSC and 1D/2D WAXD. As shown in Figure S2, the only and obvious glass transiton (112 °C) was detected in heating or cooling cycle curves, which was often observed in the rigid mesogen-jacketed liquid-crystalline polymer systems.55 From the 1D WAXD result (Figure 3b), a sharp diffraction peak at 4.98° and an amorphous peak at approximately 18° were seen.

EXPERIMENTAL SECTION

The activated RAFT agent CPDB was synthesized according to the reported literature.51,52 Polymer matrix P(VDF-TrFE-CTFE) (powder, PolyK Technologies, LLC), H2O2 (30 wt %), dichloromethane (99.9%, Acros), N-hydroxysuccinimide (NHS), N,N′-dicyclohexylcarbodiimide (99%, Alfa), 4-dimethylaminopyridine (99%, Alfa), γaminopropyl triethoxysilane (99%, Acros), and AIBN (98%, TCI) were used for the experiments. All other chemicals were used “as received”, unless otherwise stated. The experimental details of the synthesis of BaTiO3 nanowires, PTFMPCS@BaTiO3, and nanocomposites and characterization details are described in the Supporting Information.

■

RESULTS AND DISCUSSION Figure 1 depicts the process of PTFMPCS self-assembly on the surface of BaTiO3 nanostructures where a BaTiO3 nanowire was used as an example to show the details. PTFMPCS was grafted onto the BaTiO3 nanowires surface by the RAFT B

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

ACS Sustainable Chemistry & Engineering

Figure 2. SEM images of (a) Na2Ti3O7 nanowires and (c) BaTiO3 nanowires; XRD patterns of (b) Na2Ti3O7 nanowires and (d) BaTiO3 nanowires; and (e) TEM image and (f) HR-TEM image of BaTiO3 nanowires.

Figure 3. (a) Polarized optical microscopy (POM), (b) XRD, and (c) 2D WAXD patterns of the PTFMPCS and (d) POM, (e) FT-IR, and (f) TGA of PTFMPCS functionalized BaTiO3 nanowires.

Usually, the polymer layer formed on the surface of the BaTiO3 nanostructures can be directly observed by TEM images. Figure 4a is a bright field image, revealing that dense polymer layers are coated on BaTiO3 nanowire. Mapping pattern images in Figure S3 (Supporting Information) confirmed that the shells on BaTiO3 nanowires and nanoparticles are PTFMPCS. HR-TEM images of BaTiO3@ PTFMPCS nanowire are given in Figure 4b,c. Due to the different lattice fringe between BaTiO3 nanowire and polymer shell, the coated polymer layer can be readily observed. Two different thicknesses of PTFMPCS were specifically designed, and thicknesses of 9.2 ± 1.2 nm and 14.8 ± 1.0 nm were obtained, which agreed well with the theoretically predicted/ designed thicknesses based on eq 1. A similar method was used to synthesize BaTiO3@PTFMPCS nanoparticles, and two different thicknesses of PTFMPCS were specifically designed with thicknesses of 4.7 ± 0.8 nm and 7.8 ± 0.9 nm as shown in

Meantime, a strong diffraction arc was found on the equator when the beam of the X-ray incident was perpendicular to the fiber (Figure 3c). Considering the similar X-ray results reported previously, the PTFMPCS was a kind of typical mesogen-jacketed liquid crystalline polymer and presented columnar nematic phase. Infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) were used to prove that the PTFMPCS was coated on BaTiO3 nanostructures. As we take the BaTiO3 nanowires as the example, new absorption bands were found in the spectrum of BaTiO3@PTFMPCS compared with the FT-IR curve of pure BaTiO3 nanowire, which agreed well with the results of pure PTFMPCS, as shown in Figure 3e. TGA curves in Figure 3f was used to calculate the amount of the PTFMPCS shell in the core−shell structure. The weight loss of the BaTiO3 nanowires with different PTFMPCS shell thicknesses are 6.5 and 9.8 wt %, respectively. C

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

ACS Sustainable Chemistry & Engineering

Figure 4. (a) Bright field TEM images and (b,c) HRTEM image of BaTiO3@PTFMPCS nanowire with different PTFMPCS layer thicknesses; (d) bright field TEM images and (e,f) HRTEM image of BaTiO3@PTFMPCS nanoparticles with different PTFMPCS layer thicknesses

in Figure 5b. In addition, increasing the PTFMPCS layer thickness can also further decrease the dielectric loss of the nanocomposite. In Figure 5d, the dielectric loss of the sample with 14.8 nm thickness PTFMPCS was lower than that with a 9.2 nm thickness PTFMPCS at the same condition, e.g., the dielectric loss was decreased from 0.075 to 0.071 when the PTFMPCS layer thickness was increased from 9.2 to 14.8 nm for the samples with 5.0 vol % BaTiO3@PTFMPCS, which was due to the low dielectric loss of the pure PTFMPCS itself, shown in Figure S4 in the Supporting Information. To further investigate the dielectric properties of the nanocomposites, frequency dependent electric conductivity of the nanocomposites with various BaTiO3 nanowire loadings and PTFMPCS thicknesses are provided in Figure S5. It is found that polymer matrix P(VDF-TrFE-CTFE) shows relatively high electric conductivity due to the high polarization of itself. The electric conductivity of the nanocomposites was decreased with the introduction of BaTiO3@PTFMPCS nanowires due to the PTFMPCS layer can prevent the space charge from free moving, which will produce enhanced interfacial polarization to contribute to the permittivity. As is known that breakdown strength is one of the key parameters to achieve a high discharge energy density, since it is a squared factor in the equation.56,57 The breakdown strengths of the samples analyzed by a two-parameter Weibull distribution function with various BaTiO3@PTFMPCS nanowires loadings are shown in Figure 6a,b. The function is as below (eq 3):

Figure 4d−f, implying that the interfacial layer can be accurately tailored by using the rigid liquid-crystalline polymer. Table 1 summarized the data of PTFMPCS from the BaTiO3@PTFMPCS nanoparticles and nanowires. Table 1. Characteristics of BaTiO3@PTFMPCS Nanoparticles and Nanowires a

sample

Mn

1 2 3 4

6704 12712 20340 27120

Mn

b

7600 14400

b

PDI

1.22 1.24

theoretical thicknessc (nm)

actual thicknessd (nm)

3.56 6.75 10.8 14.4

4.7 ± 0.8 7.8 ± 0.9 9.2 ± 1.2 14.8 ± 1.0

a

Average number molecular weight (Mn) is the theoretical designed value. bMn and polydispersity (PDI) were tested by GPC. c Theoretical thicknesses were calculated by eq 1: Lrod = 0.154 (nm) × 2Nrod × sin 52° ≈ 0.24Nrod (nm). dActual thickness was detected by TEM.

The frequency dependent permittivity and dielectric loss of the nanocomposite with different PTFMPCS shell layers are shown in Figure 5a,b, respectively, This enables an examination of the effects of the PTFMPCS layer thickness on the dielectric properties. Polymer matrix P(VDF-TrFECTFE) possess a high relative permittivity of 35.7 at 1 kHz due to the response of dipoles in the randomly distributed polar nanoregion in the terpolymer.56 The permittivity was enhanced by adding BaTiO3 nanowires, and the maximum permittivity reached to 62.0 (1 kHz) due to the high permittivity of BaTiO3 filler. It is worth noting that the thickness of PTFMPCS layer also significantly affects the permittivity of the nanocomposites. For Figure 5c, the permittivity of the nanocomposites with 14.8 nm thickness PTFMPCS is higher than that with 9.2 nm thickness PTFMPCS at the same conditions. For example, the relative permittivity of the nanocomposite with 5.0 vol % BaTiO3@ PTFMPCS was increased by 8.7% (from 47.2 to 51.3) when the PTFMPCS layer thickness was increased from 9.2 to 14.8 nm. Although the terpolymer endows a high relative permittivity, the dielectric loss is relatively high at 0.10 (1 kHz). It is amazing that the dielectric loss was clearly decreased when the BaTiO3 nanowires were added, as shown

ÄÅ É ÅÅ ij E yz β ÑÑÑ Å j z Å P(E) = 1 − expÅÅ−jj zz ÑÑÑÑ ÅÅÇ jk E0 z{ ÑÑÖ

(3)

where E0 and β are the characteristic breakdown strength and the shape parameter, respectively.58 As can be seen from Figure 6a,b, the breakdown strength was monotonously decreased with the BaTiO3 nanowire loadings, while the samples possessed an excellent insulating property even when the loading of the nanowires was increased to 7.5 vol %, e.g., the value of breakdown strength was as high as 435.9 MV/m. As can be seen from Figure 6c, the sample with 2.5 vol % BaTiO3@PFTMPCS nanowires possessed the highest breakdown strength of 531.0 kV/mm, which is even higher than the unfilled P(VDF-TrFE-TFE) polymer (470.3 kV/mm). PreD

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

ACS Sustainable Chemistry & Engineering

Figure 5. Frequency dependent (a) relative permittivity and (b) dielectric loss of the samples with different PTFMPCS shell layers. Comparison of (c) permittivity and (d) dielectric loss of the samples with various fillers loadings and PTFMPCS layer thicknesses at 1 kHz.

Figure 6. (a,b) Weibull distribution of the breakdown strength of samples with various BaTiO3@PTFPMCS nanowires loadings, (c) characteristic breakdown strength for the samples; (d) D−E loops of the samples with different PTFMPCS shell layers; discharge energy densities of the nanocomposites with various BaTiO3@PTFPMCS nanowires loadings and PTFPMCS thicknesses (e) 9.2 nm and (f) 14.8 nm; (g) discharge energy densities of the nanocomposites with 5.0 vol % BaTiO3@PTFPMCS nanowires with different PTFPMCS thicknesses, (h) discharge energy density of the samples with different thicknesses PTFMPCS layer engineered BaTiO3 nanoparticles; and (i) energy efficiency of the samples with different thicknesses of the PTFMPCS layer engineered BaTiO3 nanowires

the P(VDF-TrFE-CTFE) matrix, shown in Figure 5b, which is beneficial to obtain a higher breakdown strength. The nanocomposites with uniformly dispersed BaTiO 3 @

vious work also reported that a low concentration of nanowires can improve the value of the breakdown strength.59 The dielectric loss of the nanocomposites is decreased compared to E

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

ACS Sustainable Chemistry & Engineering Table 2. Comparsion of the Performance between This Work and Reported Works filler (nanowire)

polymer matrix

modifers

breakdown strength (MV/m)

discharge energy density (J/cm3)

ref

BaTiO3 BaTiO3 BaTiO3 BaTiO3 BaTiO3 BaTiO3 BaTiO3 BaTiO3

P(VDF-TrFE-CFE) PVDF P(VDF-HFP) PVDF PVDF PVDF P(VDF-TrFE-CTFE) P(VDF-TrFE-CTFE)

polydopamine Al2O3 fluoro-polydopamine TiO2

300 400 480 360 320 420 454 466

10.48 12.18 12.87 10.94 11.82 10.58 13.49 14.64

54 61 62 63 64 65 this work this work

Al2O3 PTFMPCS-1 PTFMPCS-2

with 5.0 vol % BaTiO3@PTFMPCS obtained a high η of 52.5% at 466 MV/m, and the energy discharge density reached to 14.64 J/cm3. The large interfacial region would be formed in the ceramic/ polymer nanocomposites, and charges will be generated at the interfaces due to the chemical potential or Fermi levels mismatch between the ceramic filler and polymer matrix.66 According to the multicore model, the interfacial region includes three layers, which are the bonded layer, bound layer, and loose layer. When the nanoparticles are positively charged, a diffuse electrical double layer and a stern layer are formed and overlap the three layers described above.50 A surface modification treatment is usually carried out to improve the dispersibility and compatibility of the nanoparticles in the polymer matrix, and therefore, an organic shell layer of several nanometers is formed. In this regard, an improved model is proposed based on the multicore model, as shown in Figure 7.

PFTMPCS nanowires can also lead to high breakdown strength due to the good compatibility between these two kinds of fluoro-polymers, which could be clearly exhibited by the sectional SEM image of the nanocomposites in Figure S6 (Supporting Information). The discharge energy density of the samples can be calculated from the electric displacement (D)−electric field (E) loops. Typical D−E loops of the samples were obtained at 10 Hz at room temperature with BaTiO3 nanowires loadings and electric field values, as shown in Figure S7 in the Supporting Information. The D−E loops of the samples with various PTFMPCS thickness at the highest electric field are summarized in Figure 6d. The nanocomposite with a thicker PTFMPCS layer possesses larger saturation electric displacement due to the higher permittivity and interfacial polarization, which is favorable for energy storage.60 A high discharge energy density of the BaTiO3@PTFMPCS/P(VDF-TrFECTFE) nanocomposite was achieved due to the high saturated electric displacement and breakdown strength (Figure 6e,f). In addition, it can be seen that the energy density of all of the samples increased with increasing the loadings of BaTiO3@ PTFMPCS nanowires and applied electric field. The maximum discharge energy density of 14.64 J/cm3 was achieved with 5.0 vol % BaTiO3@PTFMPCS in the nanocomposites, which was 68.3% higher than that of the neat polymer matrix. It is interesting that the nanocomposites with a thicker PTFMPCS layer achieved the highest discharge energy density shown in Figure 6g. The larger polarization due to the thicker PTFMPCS layer induced a higher electric displacement, and the thicker PTFMPCS layer achieved lower dielectric loss and higher breakdown strength, which is beneficial for achieving higher energy density and agrees well with the results from Figure 5. Similar results are achieved in the BaTiO3@ PTFMPCS nanoparticles system, as can be seen in Figure 6h. Table 2 summarizes previously reported works on dielectric capacitors.54,61−65 It is found that the discharge energy density obtained in our work is larger than many of the dielectric capacitors with other ceramic fillers and interfacial modifiers, which demonstrates that PTFMPCS is a kind of effective modifier for high-energy density capacitors. In addition, energy efficiency (η) is calculated by eq 4:

η = Udis/Usto

Figure 7. Interface model in the polymer based nanocomposites with core−shell structured ceramic fillers.

The nanocomposites predominantly include ceramic nanoparticles, a polymer matrix, and interfacial regions. Increasing the thickness of the interfacial layer will lead to an increase of the interfacial volume.67 Thus, the interfacial region can dominate the electric properties and the dielectric response.68,69 Compared with the multicore model, the new model includes an organics shell layer by the interfacial modification on the surface of nanowires. The shell layer, i.e., PFTMPCS layer between the BaTiO3 nanowires and P(VDFTrFE-CTFE) matrix, acts as insulation layer, which can block the transmission of free electrons in the extra electric field. The capability of holding cumulative free electrons at the interfacial region becomes stronger and stronger with an increase of the PTFMPCS layer thickness, which will generate a stronger

(4)

where Udis and Usto are discharge energy density and energy storage density of the samples, respectively. The η with the applied electric field is exhibited in Figure 6i. P(VDF-TrFECTFE) without any fillers showed higher η compared to the nanocomposites with BaTiO3@PTFMPCS, which was decreased with the addition of BaTiO3@PTFMPCS loading and the applied electric field. The nanocomposites produced a relatively high η, even at high electric fields, e.g., the sample F

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

ACS Sustainable Chemistry & Engineering

Storage of Sandwich-Structured PVDF-Based Composite at Low Electric Field by Introduction of the Hybrid CoFe2O4 @BZT−BCT Nanofibers. ACS Sustainable Chem. Eng. 2018, 6 (1), 403−412. (4) Fredin, L. A.; Li, Z.; Ratner, M. A.; Lanagan, M. T.; Marks, T. J. Enhanced Energy Storage and Suppressed Dielectric Loss in Oxide Core-Shell-Polyolefin Nanocomposites by Moderating Internal Surface Area and Increasing Shell Thickness. Adv. Mater. 2012, 24 (44), 5946−5953. (5) Zhang, D.; Liu, W. W.; Guo, R.; Zhou, K. C.; Luo, H. High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array. Adv. Sci. 2018, 5, 1700512. (6) Zhang, G.; Brannum, D.; Dong, D.; Tang, L.; Allahyarov, E.; Tang, S.; Kodweis, K.; Lee, J.-K.; Zhu, L. Interfacial PolarizationInduced Loss Mechanisms in Polypropylene/BaTiO3 Nanocomposite Dielectrics. Chem. Mater. 2016, 28 (13), 4646−4660. (7) Luo, S.; Shen, Y.; Yu, S.; Wan, Y.; Liao, W.-H.; Sun, R.; Wong, C.-P. Construction of a 3D-BaTiO3 Network Leading to Significantly Enhanced Dielectric Permittivity and Energy Storage Density of Polymer Composites. Energy Environ. Sci. 2017, 10 (1), 137−144. (8) Liu, F.; Li, Q.; Cui, J.; Li, Z.; Yang, G.; Liu, Y.; Dong, L.; Xiong, C.; Wang, H.; Wang, Q. Nanocomposites: High-Energy-Density Dielectric Polymer Nanocomposites with Trilayered Architecture. Adv. Funct. Mater. 2017, 27 (20), 1606292. (9) Yao, Z.; Song, Z.; Xu, B.; Hao, H.; Yu, Z.; Cao, M.; Zhang, S.; Lanagan, M.; Liu, H. Homogeneous/Inhomogeneous-Structured Dielectrics and their Energy-Storage Performances. Adv. Mater. 2017, 29 (20), 1601727. (10) Wang, Y.; Hou, Y.; Deng, Y. Effects of Interfaces Between Adjacent Layers on Breakdown Strength and Energy Density in Sandwich-Structured Polymer Composites. Compos. Sci. Technol. 2017, 145, 71−77. (11) Pan, Z.; Yao, L.; Zhai, J.; Yang, K.; Shen, B.; Wang, H. T. Ultrafast Discharge and High-Energy-Density of Polymer Nanocomposites Achieved via Optimizing the Structure Design of Barium Titanates. ACS Sustainable Chem. Eng. 2017, 5, 4707−4717. (12) Fredin, L. A.; Li, Z.; Lanagan, M. T.; Ratner, M. A.; Marks, T. J. Substantial Recoverable Energy Storage in Percolative Metallic Aluminum-Polypropylene Nanocomposites. Adv. Funct. Mater. 2013, 23 (28), 3560−3569. (13) Zhang, D.; Liu, W.; Tang, L.; Zhou, K.; Luo, H. High Performance Capacitors via Aligned TiO2 Nanowire Array. Appl. Phys. Lett. 2017, 110 (13), 133902. (14) Li, Q.; Zhang, G.; Zhang, X.; Jiang, S.; Zeng, Y.; Wang, Q. Relaxor Ferroelectric-Based Electrocaloric Polymer Nanocomposites with a Broad Operating Temperature Range and High Cooling Energy. Adv. Mater. 2015, 27, 2236−2241. (15) 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 (4), 660−723. (16) Lu, Y.; Wang, W.; Xue, F.; Yang, J.; Qi, X.; Zhou, Z.; Wang, Y. Bio-inspired Polydopamine-Assisted Graphene Oxide Coating on Tetra-Pod Zinc Oxide Whisker for Dielectric Composites. Chem. Eng. J. 2018, 345, 353−363. (17) Huang, X.; Jiang, P. Core-Shell Structured High-k Polymer Nanocomposites for Energy Storage and Dielectric Applications. Adv. Mater. 2015, 27 (3), 546−554. (18) Luo, H.; Zhang, D.; Wang, L.; Chen, C.; Zhou, J.; Zhou, K. Highly Enhanced Dielectric Strength and Energy Storage Density in Hydantoin@BaTiO3−P (VDF-HFP) Composites with a SandwichStructure. RSC Adv. 2015, 5 (65), 52809−52816. (19) Khanchaitit, P.; Han, K.; Gadinski, M. R.; Li, Q.; Wang, Q. Ferroelectric Polymer Networks with High Energy Density and Improved Discharged Efficiency for Dielectric Energy Storage. Nat. Commun. 2013, 4, 2845. (20) Niu, Y.; Bai, Y.; Yu, K.; Wang, Y.; Xiang, F.; Wang, H. Effect of the Modifier Structure on the Performance of Barium Titanate/ Poly(vinylidene fluoride) Nanocomposites for Energy Storage Applications. ACS Appl. Mater. Interfaces 2015, 7, 24168−24176.

polarization because of the construction of multiple interfaces.58,70

■

CONCLUSIONS Fluoric-liquid-crystalline polymer PFTMPCS was designed and synthesized to tailor the surface of BaTiO3 nanowires and nanoparticles via the RAFT polymerization method. Four kinds of BaTiO3@PFTMPCS core−shell nanostructures were prepared with designed PFTMPCS layer thicknesses. The nanocomposites with different PFTMPCS layer thicknesses showed large effects on the performance, such as the permittivity, and discharge energy density of the nanocomposites. A high energy discharge density of 14.64 J/cm3 was obtained due to the modification of the PTFMPCS layer thickness. This novel approach will provide an inspiring path for various nanostructured materials, particularly in which the interfacial effects play the critical roles.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.8b04943. Synthesis of BaTiO 3 nanowires and monomer TFMPCS; 1H NMR spectrum of PTFMPCS; mapping pattern images of BaTiO3@PTFMPCS nanowires and nanoparticles; dielectric spectrum of the pure PTFMPCS; SEM images of the nanocomposites; and P−E loops of the nanocomposites (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Hang Luo: 0000-0003-3351-4238 Dou Zhang: 0000-0001-8555-2784 Author Contributions ∥

Hang Luo and Sheng Chen contributed equally to this work.

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors give special thanks to Prof. Chris Bowen from the University of Bath for polishing the language of this manuscript. This work was financially supported by Special Funding for the Postdoctoral Science Fund of China (Grant 2018T110840) and supported by the State Key Laboratory of Powder Metallurgy, Central South University, Changsha, China.

■

REFERENCES

(1) Shen, Z.; Wang, J.; Lin, Y.; Nan, C.; Chen, L.; Shen, Y. HighThroughput Phase-Field Design of High-Energy-Density Polymer Nanocomposites. Adv. Mater. 2018, 30 (2), 1704380. (2) Li, Z.; Fredin, L. A.; Tewari, P.; DiBenedetto, S. A.; Lanagan, M. T.; Ratner, M. A.; Marks, T. J. In Situ Catalytic Encapsulation of Core-Shell Nanoparticles Having Variable Shell Thickness: Dielectric and Energy Storage Properties of High-Permittivity Metal Oxide Nanocomposites. Chem. Mater. 2010, 22 (18), 5154−5164. (3) Chi, Q. G.; Ma, T.; Zhang, Y.; Chen, Q. G.; Zhang, C. H.; Cui, Y.; Zhang, T. D.; Lin, J. Q.; Wang, X.; Lei, Q. Q. Excellent Energy G

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

ACS Sustainable Chemistry & Engineering (21) Li, Q.; Han, K.; Gadinski, M. R.; Zhang, G.; Wang, Q. High Energy and Power Density Capacitors from Solution-Processed Ternary Ferroelectric Polymer Nanocomposites. Adv. Mater. 2014, 26 (36), 6244−6249. (22) Yu, D.; Xu, N. X.; Hu, L.; Zhang, Q. L.; Yang, H. Nanocomposites with BaTiO3-SrTiO3 Hybrid Fillers Exhibiting Enhanced Dielectric Behaviours and Energy-Storage Densities. J. Mater. Chem. C 2015, 3 (16), 4016−4022. (23) Wang, J.; Shi, Z.; Mao, F.; Chen, S.; Wang, X. Bilayer Polymer Metacomposites Containing Negative Permittivity Layer for New High-k Materials. ACS Appl. Mater. Interfaces 2017, 9 (2), 1793− 1800. (24) Cho, S.; Lee, J. S.; Jang, J. Poly (vinylidene fluoride)/NH2Treated Graphene Nanodot/Reduced Graphene Oxide Nanocomposites with Enhanced Dielectric Performance for Ultrahigh Energy Density Capacitor. ACS Appl. Mater. Interfaces 2015, 7, 22301− 22314. (25) Huang, Q.; Luo, H.; Chen, C.; Zhou, X.; Zhou, K.; Zhang, D. Enhanced Energy Density in P(VDF-HFP) Nanocomposites with Gradient Dielectric Fillers and Interfacial Polarization. J. Alloys Compd. 2017, 696, 1220−1227. (26) Li, J.; Claude, J.; Norena-Franco, L. E.; Il Seok, S.; Wang, Q. Electrical Energy Storage in Ferroelectric Polymer Nanocomposites Containing Surface-Functionalized BaTiO3 Nanoparticles. Chem. Mater. 2008, 20 (20), 6304−6306. (27) Luo, H.; Zhou, K.; Bowen, C.; Zhang, F.; Wei, A.; Wu, Z.; Chen, C.; Zhang, D. Building Hierarchical Interfaces Using BaSrTiO3 Nanocuboid Dotted Graphene Sheets in an Optimized Percolative Nanocomposite with Outstanding Dielectric Properties. Adv. Mater. Interfaces 2016, 3 (15), 1600157. (28) Hao, Y.; Wang, X.; Bi, K.; Zhang, J.; Huang, Y.; Wu, L.; Zhao, P.; Xu, K.; Lei, M.; Li, L. Significantly Enhanced Energy Storage Performance Promoted by Ultimate Sized Ferroelectric BaTiO3 Fillers in Nanocomposite Films. Nano Energy 2017, 31, 49−56. (29) Kang, D.; Wang, G. Y.; Huang, Y. H.; Jiang, P. K.; Huang, X. Y. Decorating TiO2 Nanowires with BaTiO3 Nanoparticles: A New Approach Leading to Substantially Enhanced Energy Storage Capability of High-k Polymer Nanocomposites. ACS Appl. Mater. Interfaces 2018, 10, 4077−4085. (30) Wang, G. Y.; Huang, Y. H.; Wang, Y. X.; Jiang, P. K.; Huang, X. Y. Substantial Enhancement of Energy Storage Capability in Polymer Nanocomposites by Encapsulation of BaTiO3 NWs with Variable Shell Thickness. Phys. Chem. Chem. Phys. 2017, 19, 21058−21068. (31) Wang, G.; Huang, X.; Jiang, P. Tailoring Dielectric Properties and Energy Density of Ferroelectric Polymer Nanocomposites by High-k Nanowires. ACS Appl. Mater. Interfaces 2015, 7 (32), 18017− 18027. (32) Yang, M.; Hu, C.; Zhao, H.; Haghi-Ashtiani, P.; He, D.; Yang, Y.; Yuan, J.; Bai, J. Core@Double-Shells Nanowires Strategy for Simultaneously Improving Dielectric Constants and Suppressing Losses of Poly(vinylidene fluoride) Nanocomposites. Carbon 2018, 132, 152−156. (33) Yang, K.; Huang, X.; Zhu, M.; Xie, L.; Tanaka, T.; Jiang, P. Combining RAFT Polymerization and Thiol-Ene Click Reaction for Core-Shell Structured Polymer@BaTiO3 Nanodielectrics with High Dielectric Constant, Low Dielectric Loss, and High Energy Storage Capability. ACS Appl. Mater. Interfaces 2014, 6 (3), 1812−1822. (34) Wang, S.; Huang, X.; Wang, G.; Wang, Y.; He, J.; Jiang, P. Increasing the Energy Efficiency and Breakdown Strength of HighEnergy-Density Polymer Nanocomposites by Engineering the Ba0.7Sr0.3TiO3 Nanowire Surface via Reversible Addition−Fragmentation Chain Transfer Polymerization. J. Phys. Chem. C 2015, 119 (45), 25307−25318. (35) Du, H.; Lin, X.; Zheng, H.; Qu, B.; Huang, Y.; Chu, D. Colossal permittivity in percolative ceramic/metal dielectric composites. J. Alloys Compd. 2016, 663, 848−861. (36) Caruso, F. Nanoengineering of Particle Surfaces. Adv. Mater. 2001, 13 (1), 11−22.

(37) Luo, H.; Wu, Z.; Zhou, X.; Yan, Z.; Zhou, K.; Zhang, D. Enhanced Performance of P(VDF-HFP) Composites Using TwoDimensional BaTiO3 Platelets and Graphene Hybrids. Compos. Sci. Technol. 2018, 160, 237−244. (38) Tang, H.; Sodano, H. A. Ultra High Energy Density Nanocomposite Capacitors with Fast Discharge Using Ba0.2Sr0.8TiO3 Nanowires. Nano Lett. 2013, 13 (4), 1373−1379. (39) Luo, H.; Ma, C.; Zhou, X.; Chen, S.; Zhang, D. Interfacial Design in Dielectric Nanocomposite Using Liquid-Crystalline Polymers. Macromolecules 2017, 50 (13), 5132−5137. (40) Yang, K.; Huang, X.; Fang, L.; He, J.; Jiang, P. Fluoro-Polymer Functionalized Graphene for Flexible Ferroelectric Polymer-based High-k Nanocomposites with Suppressed Dielectric Loss and Low Percolation Threshold. Nanoscale 2014, 6 (24), 14740−14753. (41) Kim, P.; Doss, N. M.; Tillotson, J. P.; Hotchkiss, P. J.; Pan, M.J.; Marder, S. R.; Li, J.; Calame, J. P.; Perry, J. W. High Energy Density Nanocomposites Based on Surface-Modified BaTiO3 and a Ferroelectric Polymer. ACS Nano 2009, 3 (9), 2581−2592. (42) Hu, X.; Yi, K. C.; Liu, Jie.; Chu, B. High Energy Density Dielectrics Based on PVDF-based Polymers. Energy Technology 2018, 6 (5), 849−864. (43) Yang, K.; Huang, X.; Huang, Y.; Xie, L.; Jiang, P. FluoroPolymer@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 (11), 2327−2338. (44) Zhang, D.; Ma, C.; Zhou, X. F.; Chen, S.; Luo, H.; Bowen, C.; Zhou, K. C. High Performance Capacitors Using BaTiO3 Nanowires Engineered by Rigid Liquid-crystalline Polymers. J. Phys. Chem. C 2017, 121, 20075−20083. (45) Zhang, D.; Liu, Y. X.; Wan, X. H.; Zhou, Q. F. Synthesis and Characterization of a New Series of ″Mesogen-Jacketed Liquid Crystal Polymers″ Based on the Newly Synthesized Vinylterephthalic Acid. Macromolecules 1999, 32 (16), 5183−5185. (46) Peng, C.; Turiv, T.; Guo, Y.; Shiyanovskii, S. V.; Wei, Q.-H.; Lavrentovich, O. D. Control of Colloidal Placement by Modulated Molecular Orientation in Nematic Cells. Sci. Adv. 2016, 2, 1600932. (47) Shi, L. Y.; Zhou, Y.; Fan, X. H.; Shen, Z. Remarkably Rich Variety of Nanostructures and Order−Order Transitions in a Rod− Coil Diblock Copolymer. Macromolecules 2013, 46 (46), 5308−5316. (48) Li, P.; Chen, S.; Luo, H.; Zhang, D.; Zhang, H. Influence of Main Chain on the Phase Behaviors of Side-Chain Liquid-Crystalline Polymers with Triphenylene Mesogens of Long Alkyl Tail Substituents. J. Polym. Sci., Part A: Polym. Chem. 2017, 55 (4), 754−766. (49) Zhang, X.; Shen, Y.; Shen, Z.; Jiang, J.; Chen, L.; Nan, C.-W. Achieving High Energy Density in PVDF-Based Polymer Blends: Suppression of Early Polarization Saturation and Enhancement of Breakdown Strength. ACS Appl. Mater. Interfaces 2016, 8 (40), 27236−27242. (50) Chen, Q.; Shen, Y.; Zhang, S.; Zhang, Q. M. Polymer-Based Dielectrics with High Energy Storage Density. Annu. Rev. Mater. Res. 2015, 45, 433−458. (51) Chen, S.; Lv, X. G.; Han, X. H.; Luo, H.; Bowen, C.; Zhang, D. Significantly Improved Energy Density of BaTiO3 Nanocomposites by Accurate Interfacial Tailoring Using a Novel Rigid-Fluoro-Ppolymer. Polym. Chem. 2018, 9, 548−557. (52) Zhao, Y.; Perrier, S. Synthesis of Well-defined Homopolymer and Diblock Copolymer Grafted Onto Silica Particles by Z-Supported RAFT Polymerization. Macromolecules 2006, 39 (25), 8603−8608. (53) Zhang, D.; Zhou, X.; Roscow, J.; Zhou, K.; Wang, L.; Luo, H.; Bowen, C. R. Significantly Enhanced Energy Storage Density by Modulating the Aspect Ratio of BaTiO3 Nanofibers. Sci. Rep. 2017, 7, 45179. (54) Tang, H.; Lin, Y.; Sodano, H. A. Synthesis of High Aspect Ratio BaTiO3 Nanowires for High Energy Density Nanocomposite Capacitors. Adv. Energy Mater. 2013, 3, 451−456. H

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX

Research Article

ACS Sustainable Chemistry & Engineering (55) Chen, X. F.; Shen, Z. H.; Wan, X. H.; Fan, X. H.; Chen, E. Q.; Ma, Y. G.; Zhou, Q. F. Mesogen-jacketed liquid crystalline polymers. Chem. Soc. Rev. 2010, 39, 3072−3101. (56) Klein, R. J.; Runt, J.; Zhang, Q. Influence of Crystallization Conditions on the Microstructure and Electromechanical Properties of Poly (vinylidene fluoride−trifluoroethylene−chlorofluoroethylene) Terpolymers. Macromolecules 2003, 36 (19), 7220−7226. (57) Hu, P.; Song, Y.; Liu, H.; Shen, Y.; Lin, Y.; Nan, C.-W. Largely Enhanced Energy Density in Flexible P(VDF-TrFE) Nanocomposites by Surface-Modified Electrospun BaSrTiO3 Fibers. J. Mater. Chem. A 2013, 1 (5), 1688−1693. (58) Luo, H.; Roscow, J.; Zhou, X.; Chen, S.; Han, X.; Zhou, K.; Zhang, D.; Bowen, C. R. Ultra-high Discharged Energy Density Capacitor Using High Aspect Ratio Na0.5Bi0.5TiO3 Nanofibers. J. Mater. Chem. A 2017, 5 (15), 7091−7102. (59) Liu, S.; Zhai, J.; Wang, J.; Xue, S.; Zhang, W. Enhanced Energy Storage Density in Poly(Vinylidene Fluoride) Nanocomposites by a Small Loading of Suface-Hydroxylated Ba0.6Sr0.4TiO3 Nanofibers. ACS Appl. Mater. Interfaces 2014, 6 (3), 1533−1540. (60) Wu, J. Y.; Mahajan, A.; Riekehr, L.; Zhang, H. F.; Yang, B.; Meng, N.; Zhang, Z.; Yan, H. X. Perovskite Srx(Bi1−xNa0.97−xLi0.03)0.5TiO3 Ceramics with Polar Nano Regions for High Power Energy Storage. Nano Energy 2018, 50, 723−732. (61) Pan, Z.; Yao, L.; Zhai, J.; Shen, B.; Liu, S.; Wang, H.; Liu, J. Excellent Energy Density of Polymer Nanocomposites Containing BaTiO3@Al2O3 Nanofibers Induced by Moderate Interfacial Area. J. Mater. Chem. A 2016, 4 (34), 13259−13264. (62) Wang, G.; Huang, X.; Jiang, P. Bio-Inspired Fluoro-polydopamine Meets Barium Titanate Nanowires: A Perfect Combination to Enhance Energy Storage Capability of Polymer Nanocomposites. ACS Appl. Mater. Interfaces 2017, 9 (8), 7547−7555. (63) Lin, X.; Hu, P. H.; Jia, Z. Y.; Gao, S. M. Enhanced Electric Displacement Induces Large Energy Density in Polymer Nanocomposites Containing Core−Shell Structured BaTiO3@TiO2 Nanofibers. J. Mater. Chem. A 2016, 4, 2314−2320. (64) Yao, L.; Pan, Z.; Zhai, J.; Chen, H. H. Novel Design of Highly [110]-oriented Barium Titanate Nanorod Array and its Application in Nanocomposite Capacitors. Nanoscale 2017, 9 (12), 4255−4264. (65) Pan, Z.; Yao, L.; Zhai, J.; Fu, D.; Shen, B.; Wang, H. HighEnergy-Density Polymer Nanocomposites Composed of Newly Structured One-Dimensional BaTiO3@Al2O3 Nanofibers. ACS Appl. Mater. Interfaces 2017, 9 (4), 4024−4033. (66) Cai, Z.; Wang, X.; Luo, B.; Hong, W.; Wu, L.; Li, L. Dielectric Response and Breakdown Behavior of Polymer-Ceramic Nanocomposites: The Effect of Nanoparticle Distribution. Compos. Sci. Technol. 2017, 145, 105−113. (67) Dang, Z. M.; Yuan, J. K.; Yao, S. H.; Liao, R. J. Flexible Nanodielectric Materials with High Permittivity for Power Energy Storage. Adv. Mater. 2013, 25 (44), 6334−6365. (68) Lewis, T. J. Interfaces: Nanometric Dielectrics. J. Phys. D: Appl. Phys. 2005, 38 (2), 202−212. (69) Luo, H.; Zhang, D.; Jiang, C.; Yuan, X.; Chen, C.; Zhou, K. Improved Dielectric Properties and Energy Storage Density of Poly (vinylidene fluoride-co-hexafluoropropylene) Nanocomposite with Hydantoin Epoxy Resin Coated BaTiO3. ACS Appl. Mater. Interfaces 2015, 7 (15), 8061−8069. (70) Hu, P.; Jia, Z.; Shen, Z.; Wang, P.; Liu, X. High Dielectric Constant and Energy Density Induced by the Tunable TiO2 Interfacial Buffer Layer in PVDF Nanocomposite Contained with Core−Shell Structured TiO2@BaTiO3 Nanoparticles. Appl. Surf. Sci. 2018, 441, 824−831.

I

DOI: 10.1021/acssuschemeng.8b04943 ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX