CN108638616B - Layered dielectric material and preparation method thereof - Google Patents

Layered dielectric material and preparation method thereof Download PDF

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CN108638616B
CN108638616B CN201810440998.5A CN201810440998A CN108638616B CN 108638616 B CN108638616 B CN 108638616B CN 201810440998 A CN201810440998 A CN 201810440998A CN 108638616 B CN108638616 B CN 108638616B
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layer
woven fabric
fiber non
fabric layer
dielectric material
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CN108638616A (en
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沈洋
江建勇
南策文
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Shenzhen Research Institute Tsinghua University
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Shenzhen Research Institute Tsinghua University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B32B5/24—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
    • B32B5/26—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer another layer next to it also being fibrous or filamentary
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/06—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the heating method
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/10—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the pressing technique, e.g. using action of vacuum or fluid pressure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G13/00—Apparatus specially adapted for manufacturing capacitors; Processes specially adapted for manufacturing capacitors not provided for in groups H01G4/00 - H01G11/00
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G4/00—Fixed capacitors; Processes of their manufacture
    • H01G4/002—Details
    • H01G4/018—Dielectrics
    • H01G4/06—Solid dielectrics
    • H01G4/14—Organic dielectrics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G4/00—Fixed capacitors; Processes of their manufacture
    • H01G4/002—Details
    • H01G4/018—Dielectrics
    • H01G4/06—Solid dielectrics
    • H01G4/14—Organic dielectrics
    • H01G4/16—Organic dielectrics of fibrous material, e.g. paper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/40—Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/42—Alternating layers, e.g. ABAB(C), AABBAABB(C)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/02—Synthetic macromolecular fibres
    • B32B2262/0223—Vinyl resin fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/16—Capacitors

Abstract

The invention relates to a laminated dielectric material and a preparation method thereof, and the laminated dielectric material comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are arranged in a laminated manner, wherein the first fiber non-woven fabric layer is a vinylidene fluoride-hexafluoropropylene copolymer layer, the second fiber non-woven fabric layer is a vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer, and the total number of layers of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer is 2-30. The vinylidene fluoride-hexafluoropropylene copolymer layer has high breakdown performance, the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer has high polarization performance and high energy storage efficiency, and the vinylidene fluoride-hexafluoropropylene copolymer layer and the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer are mutually laminated to control the internal mesoscopic structure of the laminated dielectric material, so that the conductive loss and the ferroelectric loss in the laminated dielectric material are favorably inhibited, and the laminated dielectric material has high energy storage density and energy storage efficiency at the same time.

Description

Layered dielectric material and preparation method thereof
Technical Field
The invention relates to the technical field of dielectric material preparation, in particular to a layered dielectric material and a preparation method thereof.
Background
With the development of modern technologies, capacitors are widely used as important basic electronic components and high-power energy storage devices in consumer electronics, communication products, automation control, high-speed railways, new energy vehicles, aviation and military equipment. Among them, the film capacitor has received much attention from researchers and markets due to its advantages such as high dielectric strength and high power density. However, the commercial dielectric film BOPP (biaxially oriented polypropylene) has a low dielectric constant (2-3), resulting in a low energy storage density (2J/cm 3), which limits its wider application. For example, an orbital electromagnetic gun requires approximately 100MJ of energy input per shot, while the volume of the capacitor providing the energy is typically on the order of 10 cubic meters, which is extremely limited by the excessive volume and weight. In order to improve the dielectric constant and energy storage density of dielectric films, researchers have turned their attention to PVDF-based polymers with high polarization capabilities. In 2006, professor of state university, bingo, usa proposed P (VDF-CTFE) as a dielectric energy storage film in journal Science, resulting in a dielectric constant higher than 10 and an energy storage density higher than 10J/cm3, much higher than that of conventional BOPP. Thereafter, researchers have employed various ways to further increase the energy storage density of PVDF-based polymers, such as preparing polymer nanocomposites, constructing composites with multilayer structures, and preparing polymer-modified materials such as blending and grafting. Through decades of efforts, the energy storage density of the PVDF-based polymer material can reach 5-15J/cm 3, but the energy storage efficiency is only 50-70%, which means that a large amount of energy is dissipated. Most of this dissipated energy is converted into useless and harmful thermal energy, and due to the intrinsically low thermal conductivity of the polymer material, heat is accumulated inside the polymer, resulting in internal temperature rise and ultimately deterioration of the material. Therefore, how to improve the energy storage efficiency of PVDF-based polymers while ensuring high energy storage density becomes a research hotspot and difficulty.
The low energy storage efficiency of PVDF-based polymers is mainly due to two losses: 1) ferroelectric loss: PVDF is a nonlinear ferroelectric material, an internal dipole cannot follow the change of an external electric field, and a hysteresis phenomenon exists, and the hysteresis process can bring energy loss, so that ferroelectric loss is generated. 2) Conductivity loss: electrons and ions which move freely exist in the PVDF, and can move directionally under the action of an external electric field to form leakage current, so that the conduction loss is generated. In order to inhibit the loss of the PVDF-based polymer and improve the energy storage efficiency of the material, researchers also carry out a great deal of research work. In 2013, the professor of chapter enlightenment adds large-size CFE or CTFE monomer to P (VDF-TrFE) to prepare a P (VDF-TrFE-CFE) or P (VDF-TrFE-CTFE) terpolymer, and reduces the large-size ferroelectric domain in the original P (VDF-TrFE) polymer into a nano-size ferroelectric domain through a nano-restriction effect, so that the limit of domain wall to dipole turnover is reduced, dipoles in the polymer can rapidly respond to the change of an applied electric field, the ferroelectric loss is reduced, and the efficiency is improved. Meanwhile, the professor congratulatively deposits and grafts Polystyrene (PS) on the basis of P (VDF-TrFE-CTFE) to prepare a P (VDF-TrFE-CTFE) -g-PS block copolymer, thereby further inhibiting the loss of the polymer. In 2010, professor xuzhu, west ann university of transportation, by preparing PVDF with a different phase structure, we found that α -PVDF and γ -PVDF are less lossy and more efficient than β -PVDF. The above research work has been mainly performed from the viewpoint of suppressing ferroelectric loss, and some have been performed from the direction of suppressing conduction loss. In 2012, the professor congratulates about the preparation of PVDF/PC (polypropylene) multilayer polymer materials by using a microlayer coextrusion method, and better controls the conductance loss inside the polymer by layer structure design and interface charge transfer inhibition. In 2015, journal Energy & Environmental Science of professor wang celebration at state university of bingzhou, usa proposed that BNNS (boron nitride nanosheet) was used as filler to prepare P (VDF-TrFE-CFE)/BNNS nanocomposite, and experimental results showed that the composite exhibited lower leakage current and higher breakdown performance due to the large aspect ratio structure and high insulation of the BNNS two-dimensional sheet layer, and the prepared composite had higher Energy storage density and efficiency.
Although researchers have made many efforts, it is still difficult to combine high energy storage density and energy storage efficiency with the PVDF-based polymer prepared.
Disclosure of Invention
In view of the above, there is a need to provide a layered dielectric material and a method for preparing the same, which can solve the problem that PVDF-based polymers still have difficulty in achieving both high energy storage density and high energy storage efficiency.
A laminated dielectric material comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are arranged in a stacked mode, wherein the first fiber non-woven fabric layer is a vinylidene fluoride-hexafluoropropylene copolymer layer, the second fiber non-woven fabric layer is a vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer, and the total number of layers of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer is 2-30.
In one embodiment, the total number of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer is 3, and the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer are alternately stacked;
or, the laminated dielectric material is laminated in an ABA mode, wherein B represents one of the first fiber nonwoven fabric layer and the second fiber nonwoven fabric layer, and a represents the other of the first fiber nonwoven fabric layer and the second fiber nonwoven fabric layer.
In one embodiment, the total number of layers of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer is an odd number, and the layered dielectric material comprises an intermediate layer and a first alternating layer group and a second alternating layer group which are respectively arranged on two side surfaces of the intermediate layer; the middle layer is a first fiber non-woven fabric layer or a second fiber non-woven fabric layer, the first alternating layer group comprises first fiber non-woven fabric layers and second fiber non-woven fabric layers which are alternately stacked, the second alternating layer group comprises first fiber non-woven fabric layers and second fiber non-woven fabric layers which are alternately stacked, and the number of layers of the first alternating layer group and the second alternating layer group is the same; the first alternating layer group has a layer adjacent to the intermediate layer of a different material than the intermediate layer, and the second alternating layer group has a layer adjacent to the intermediate layer of a different material than the intermediate layer;
or, the laminated dielectric material is laminated in the form of (AB)nA(BA)nOr B (AB)nA(BA)nB, wherein A represents one of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer, and B represents the other of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer; and n is more than or equal to 1 and less than or equal to 7.
In one embodiment, the total number of layers of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer is an even number, the layered dielectric material includes a first alternating layer group and a second alternating layer group stacked on the first alternating layer group, the first alternating layer group includes the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer which are stacked alternately, the second alternating layer group includes the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer which are stacked alternately, and the number of layers of the first alternating layer group and the second alternating layer group is the same; a layer of the first alternating group of layers that is adjacent to the second alternating group of layers is the same material as a layer of the second alternating group of layers that is adjacent to the first alternating group of layers;
or, the laminated dielectric material is laminated in the form of (AB)m(BA)mOr B (AB)m(BA)mB, wherein A represents one of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer, and B represents the other of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer; and m is more than or equal to 1 and less than or equal to 7.
The preparation method of the layered dielectric material comprises the following steps:
dissolving a vinylidene fluoride-hexafluoropropylene copolymer in a first solvent to obtain a first solution;
dissolving the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer in a second solvent to obtain a second solution;
forming the first solution and the second solution in an electrostatic spinning mode to obtain an intermediate, wherein the intermediate comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are mutually laminated; forming the first solution to obtain a first fiber non-woven fabric layer, and forming the second solution to obtain a second fiber non-woven fabric layer; the total number of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer is 2-30;
carrying out hot pressing treatment on the intermediate; and
and carrying out cold quenching treatment on the intermediate.
In one embodiment, the first solvent is selected from a mixed solution of N, N-dimethylformamide and acetone, wherein the volume ratio of the N, N-dimethylformamide to the acetone is 3: 2-5: 1;
and/or the second solvent is selected from a mixed solution of N, N-dimethylformamide and acetone, wherein the volume ratio of the N, N-dimethylformamide to the acetone is 3: 2-5: 1.
In one embodiment, the mass percentage of the vinylidene fluoride-hexafluoropropylene copolymer in the first solution is 15% -30%;
and/or the mass percentage of the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer in the second solution is 15-30%.
In one embodiment, in the step of respectively forming the first solution and the second solution by electrostatic spinning to obtain the intermediate, the voltage is 4 kV-15 kV, the bolus speed of the injection pump is 0.1 mL/h-2 mL/h, the spinning distance is 5 cm-50 cm, the drum rotation speed is 100 rpm-1000 rpm, and the spinning time is 10 min-10 h.
In one embodiment, the hot pressing temperature is 150-220 ℃, the hot pressing pressure is 2-20 MPa, and the hot pressing time is 15-120 min.
In one embodiment, the step of cold quenching specifically includes:
heating the intermediate at 180-240 ℃ for 5-30 min; and
and cooling the intermediate, wherein the cooling temperature of the cooling treatment is 0-100 ℃, and the time of the cooling treatment is 2-15 min.
The laminated dielectric material and the preparation method thereof adopt the lamination of the vinylidene fluoride-hexafluoropropylene copolymer layer and the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer, the vinylidene fluoride-hexafluoropropylene copolymer layer has high breakdown performance, the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer has high polarization performance and high energy storage efficiency, and the vinylidene fluoride-hexafluoropropylene copolymer layer and the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer are mutually laminated to control the internal mesoscopic structure of the laminated dielectric material, thereby being beneficial to inhibiting the conduction loss and the ferroelectric loss in the laminated dielectric material, and leading the laminated dielectric material to have high energy storage density and energy storage efficiency at the same time.
Drawings
FIG. 1 is a process flow diagram of one embodiment of a method for forming a layered dielectric material;
FIG. 2 is a scanning electron micrograph of a first fibrous nonwoven fabric layer (a) obtained by electrospinning P (VDF-HFP), a second fibrous nonwoven fabric layer (b) obtained by electrospinning P (VDF-TrFE-CFE), a surface morphology (c) of a layered dielectric material, and a cross-sectional morphology (d) of the layered dielectric material in example 1;
FIG. 3 is a spectrum of relative dielectric constant of the layered dielectric materials prepared in examples 1 to 5;
FIG. 4 is a potentiometer-electric field curve of the layered dielectric materials prepared in examples 1 to 5.
Detailed Description
The layered dielectric material and the method for manufacturing the same will be described in further detail with reference to the following embodiments and accompanying drawings.
The layered dielectric material of one embodiment includes a first fibrous nonwoven fabric layer and a second fibrous nonwoven fabric layer that are stacked.
Furthermore, the first fiber non-woven fabric layer is a vinylidene fluoride-hexafluoropropylene copolymer layer, and the second fiber non-woven fabric layer is a vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer. Further, the thickness of the first fiber nonwoven fabric layer and the second fiber nonwoven fabric layer can be adjusted as required.
Further, the thickness of the first fibrous nonwoven fabric layer is the same as the thickness of the second fibrous nonwoven fabric layer, but in other embodiments, the thicknesses of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer may be different and may be adjusted according to the properties of the resulting layered dielectric material.
In one embodiment, the total number of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer is 2 to 30.
Further, the first fiber nonwoven fabric layer and the second fiber nonwoven fabric layer are alternately laminated, and the internal structure of the layered dielectric material is preferably centrosymmetric.
In one embodiment, when the total number of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer is 2, the laminated dielectric material is laminated in the form of AB, where a is the first fibrous nonwoven fabric layer and B is the second fibrous nonwoven fabric layer.
In one embodiment, when the total number of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer is 3, the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer are alternately laminated. For example, the layered dielectric material is of an ABA type in which B represents one of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer, and a represents the other of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer.
In one embodiment, the total number of the first fibrous nonwoven layer and the second fibrous nonwoven layer is an odd number of layers. Furthermore, the layered dielectric material comprises an intermediate layer, and a first alternating layer group and a second alternating layer group which are respectively arranged on two side surfaces of the intermediate layer. Wherein the middle layer is a first fiber non-woven fabric layer or a second fiber non-woven fabric layer; the first alternate layer group comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are sequentially and alternately stacked, the second alternate layer group comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are sequentially and alternately stacked, and the number of layers of the first alternate layer group and the second alternate layer group is the same. Furthermore, the material of the layer of the first alternating layer group close to the middle layer is different from that of the middle layer, and the material of the layer of the second alternating layer group close to the middle layer is different from that of the middle layer, that is, when the middle layer is a first fiber non-woven fabric layer, the layer of the first alternating layer group close to the middle layer and the layer of the second alternating layer group close to the middle layer are both second fiber non-woven fabric layers; when the middle layer is the second fiber non-woven fabric layer, the layer of the first alternating layer group close to the middle layer and the layer of the second alternating layer group close to the middle layer are both the first fiber non-woven fabric layers. For example, the layered dielectric material is laminated in the form of (AB)nA(BA)nOr B (AB)nA(BA)nB, wherein A is a first fiber non-woven fabric layer or a second fiber non-woven fabric layer; when A is a first fiber non-woven fabric layer, B is a second fiber non-woven fabric layer; when A is a second fiber non-woven fabric layer, B is a first fiber non-woven fabric layer; and n is more than or equal to 1 and less than or equal to 7.
In one embodiment, the first fibers are free ofThe total number of the layers of the woven fabric layer and the second fiber non-woven fabric layer is even. The layered dielectric material includes a first alternating group of layers and a second alternating group of layers stacked on the first alternating group of layers. Furthermore, the first alternating layer group comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are sequentially and alternately stacked, the second alternating layer group comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are sequentially and alternately stacked, and the number of layers of the first alternating layer group and the second alternating layer group is the same. Furthermore, a layer of the first alternating layer group close to the second alternating layer group is made of the same material as a layer of the second alternating layer group close to the first alternating layer group, that is, when a layer of the first alternating layer group close to the second alternating layer group is a first fiber non-woven fabric layer, a layer of the second alternating layer group close to the first alternating layer group is also a first fiber non-woven fabric layer; when the layer of the first alternate layer group adjacent to the second alternate layer group is the second fiber non-woven fabric layer, the layer of the second alternate layer group adjacent to the first alternate layer group is also the second fiber non-woven fabric layer. For example, the layered dielectric material is laminated in the form of (AB)m(BA)mOr B (AB)m(BA)mB, wherein A is a first fiber non-woven fabric layer or a second fiber non-woven fabric layer; when A is a first fiber non-woven fabric layer, B is a second fiber non-woven fabric layer; when A is a second fiber non-woven fabric layer, B is a first fiber non-woven fabric layer; and m is more than or equal to 1 and less than or equal to 7.
Furthermore, the total number of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer is even, and the thicknesses of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer are equivalent, so that the structural symmetry of the layered dielectric material can be obtained, and the volume ratio of the vinylidene fluoride-hexafluoropropylene copolymer component to the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer component in the layered dielectric material is 50: 50.
According to the laminated dielectric material and the preparation method thereof, the vinylidene fluoride-hexafluoropropylene copolymer layer has high breakdown performance, the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer has high polarization performance and high energy storage efficiency, and the vinylidene fluoride-hexafluoropropylene copolymer layer and the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer are mutually laminated to control the internal mesoscopic structure of the laminated dielectric material, so that the conductive loss and the ferroelectric loss in the laminated dielectric material are favorably inhibited, and the laminated dielectric material has high energy storage density and energy storage efficiency at the same time.
The reason for the symmetrical structural design is: dielectric capacitors typically operate under an alternating electric field and a symmetrical structural design ensures that the capacitors have the same dielectric response when operated at positive and negative reverse voltages.
Referring to fig. 1, the method for preparing the layered dielectric material includes the following steps:
s110, dissolving the vinylidene fluoride-hexafluoropropylene copolymer in a first solvent to obtain a first solution.
In one embodiment, the vinylidene fluoride-hexafluoropropylene copolymer (P (VDF-HFP)) is in a powder state, and the molecular weight of P (VDF-HFP) is 10 to 100 ten thousand, and further, the molecular weight of P (VDF-HFP) may be 20, 35, 47, 60, or 75 ten thousand.
In one embodiment, P (VDF-HFP) is obtained from 2800-01 brand powder of Arkema, France.
In one embodiment, the first solvent is a mixed solution of N, N-dimethylformamide and acetone, and the volume ratio of N, N-dimethylformamide to acetone is 3:2 to 5:1, and further, the volume ratio of N, N-dimethylformamide to acetone may be 2:1, 3:1, or 4: 1.
Compared with the traditional method that only single N, N dimethylformamide is used, the acetone added into the mixed solvent is beneficial to increasing the volatility of the solvent on one hand and improving the viscosity of the solution on the other hand, and the method is beneficial to increasing the spinnability of P (VDF-HFP) and P (VDF-TrFE-CFE) polymer fibers.
In one embodiment, the mass percentage of P (VDF-HFP) in the first solution is 15% to 30%. Further, the mass percentage of P (VDF-HFP) in the first solution may be 17%, 20%, 25% or 27%, and preferably, the mass percentage of P (VDF-HFP) in the first solution is 25%.
In one embodiment, the vinylidene fluoride-hexafluoropropylene copolymer is fully dissolved in the first solvent by adopting a stirring mode, the stirring speed during stirring is 200 rpm-500 rpm, and the stirring time is 2 h-10 h.
S120, dissolving the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer in a second solvent to obtain a second solution.
In one embodiment, the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer (P (VDF-TrFE-CFE)) is in a powder state, and the molecular weight of P (VDF-TrFE-CFE) is from 10 to 100 ten thousand, and further, the molecular weight of P (VDF-TrFE-CFE) may be from 20 to 35, 45, 65 or 85 ten thousand.
In one embodiment, P (VDF-TrFE-CFE) is obtained from powder of PiezotechRT FS (VDF-TrFE-CFE) from Arkema, France.
In one embodiment, the second solvent is a mixed solution of N, N-dimethylformamide and acetone, and the volume ratio of N, N-dimethylformamide to acetone is 3:2 to 5:1, and further, the volume ratio of N, N-dimethylformamide to acetone may be 2:1, 3:1, or 4: 1.
In one embodiment, the mass percentage of P (VDF-TrFE-CFE) in the second solution is 15% to 30%. Further, the mass percentage of P (VDF-TrFE-CFE) in the second solution may be 18%, 20%, 25% or 27%, and preferably, the mass percentage of P (VDF-TrFE-CFE) in the second solution is 18%.
In one embodiment, the P (VDF-TrFE-CFE) is sufficiently dissolved in the second solvent by stirring, wherein the stirring speed is 200rpm to 500rpm, and the stirring time is 2h to 10 h.
And S130, forming the first solution and the second solution in an electrostatic spinning mode to obtain an intermediate, wherein the intermediate comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are mutually laminated.
In one embodiment, the first solvent is electrospun to form a first fibrous nonwoven layer, and the second solvent is electrospun to form a second fibrous nonwoven layer.
Further, the sum of the first fiber non-woven fabric layer and the second fiber non-woven fabric layerThe number of layers is 2-30; when the intermediate is produced by electrospinning, the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer may be laminated in an AB type, ABA type or (AB)nA(BA)nType, B (AB)nA(BA)nB type, (AB)m(BA)mType or B (AB)m(BA)mAnd (B) type. The details are described above and will not be described herein.
Further, when the intermediate is obtained by electrostatic spinning, the voltage of electrostatic spinning is 4 kV-15 kV, the injection speed of an injection pump is 0.1 mL/h-2 mL/h, the spinning distance is 5 cm-50 cm, the rotating speed of a roller is 100 rpm-1000 rpm, and the spinning time is 10 min-10 h. Further, the spinning distance of the electrospinning is preferably 15cm, and the drum rotation speed is preferably 300 rpm. The time for spinning is generally adjusted depending on the number of layers and the thicknesses of the first fibrous nonwoven fabric layer and the second fibrous nonwoven fabric layer.
And S140, carrying out hot pressing treatment on the intermediate.
In one embodiment, the hot pressing temperature is 150 ℃ to 220 ℃ when the hot pressing is performed, and further, the hot pressing temperature may be 180 ℃ or 200 ℃, and preferably, the hot pressing temperature is 200 ℃.
In one embodiment, the hot-pressing pressure is 2 to 20MPa, and further, 6, 10, or 15 MPa.
In one embodiment, the hot pressing is performed for 15min to 120min, and further, the hot pressing time may be 30min or 60 min.
S150, performing cold quenching treatment on the intermediate.
In one embodiment, the step of performing cold quenching on the intermediate specifically comprises:
and S151, heating the intermediate.
In one embodiment, the temperature of the intermediate is 180 to 240 ℃ and the time of the heat treatment is 5 to 30 min.
And S152, cooling the intermediate.
In one embodiment, the step of subjecting the intermediate to temperature reduction treatment is to put the intermediate into a cooling liquid for cold quenching. Further, the cooling liquid is water.
In one embodiment, the cooling temperature for the temperature reduction treatment of the intermediate body is 0 to 100 ℃, and it is understood that the cooling temperature is 0 to 100 ℃ which is the temperature of the cooling liquid. Further, the cooling temperature of the cooling treatment can also be 35 ℃, 45 ℃, 60 ℃ or 85 ℃.
The temperature of the cooling liquid is controlled to carry out cold quenching during the cooling treatment, and the phase structure composition of the layered dielectric material can be adjusted, so that the high polarization capability of the layered dielectric material is ensured while the low loss is obtained. The composition of the nonpolar alpha phase in P (VDF-HFP) and P (VDF-TrFE-CFE) gradually increases with increasing cooling temperature. For example, when the alloy is subjected to cold quenching at 0 ℃, the phase structures of P (VDF-HFP) and P (VDF-TrFE-CFE) are that a polar beta phase and a non-polar alpha phase coexist; when the alloy is quenched at 60 ℃, the P (VDF-HFP) and P (VDF-TrFE-CFE) phase structures are mainly nonpolar alpha phases. Since the ferroelectric loss is lower in the nonpolar alpha phase relative to the polar beta phase, the cold quenching temperature is increased, the content of the nonpolar phase is increased, and the ferroelectric loss is reduced. In contrast to P (VDF-HFP), which has a reduced polarizability due to an increased content of nonpolar phases, P (VDF-TrFE-CFE) has an increased polarizability due to an increased content of nonpolar phases. Therefore, two effects are combined, and the cooling temperature is set to be 0-100 ℃ during cold quenching treatment, so that the polarization capability of the layered dielectric material can be kept at a higher level.
And S153, drying the intermediate.
In one embodiment, the intermediate is removed from the cooling fluid and dried to a surface with water to obtain the layered dielectric material.
In one embodiment, the drying is carried out at a temperature of 30 ℃ to 60 ℃. Further, the temperature for the drying treatment may be 45 ℃.
The preparation method of the laminated dielectric material adopts the lamination of the vinylidene fluoride-hexafluoropropylene copolymer layer and the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer, the vinylidene fluoride-hexafluoropropylene copolymer layer has high breakdown performance, the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer has high polarization performance and high energy storage efficiency, and the vinylidene fluoride-hexafluoropropylene copolymer layer and the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer are mutually laminated to control the internal mesoscopic structure of the laminated dielectric material, so that the inhibition of the conduction loss and the ferroelectric loss in the laminated dielectric material is facilitated, and the laminated dielectric material has high energy storage density and energy storage efficiency at the same time. And the preparation method of the layered dielectric material is simple and easy to realize industrial production.
In other embodiments, step S153 may be omitted.
The following are descriptions of specific examples, and unless otherwise specified, the following examples contain no other components not specifically mentioned except for inevitable impurities.
Example 1
Dissolving 1g P (VDF-HFP) powder in a mixed solvent of 2.4mL DMF and 1.6mL acetone to obtain a first solution, and dissolving 1g P (VDF-TrFE-CFE) powder in a mixed solvent of 3.3mL DMF and 2.2mL acetone to obtain a second solution, wherein the molecular weight of P (VDF-HFP) powder is 47 ten thousand, and the molecular weight of P (VDF-TrFE-CFE) powder is 85 ten thousand. Firstly, carrying out electrostatic spinning by using a first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time was 40 min. And then spinning by using a second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.67 mL/h; the drum speed was 300rpm and the spinning time was 40 min. Thereafter, spinning was carried out in the order of ABBA (including the above-described AB process had been carried out) to obtain a fibrous nonwoven fabric intermediate having a 4-layer structure. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 deg.C for 15min on a heating platform, adding into 60 deg.C water, cold quenching for 5min, and oven drying at 45 deg.C until the water on the surface is completely dried to obtain the final 4-layer layered dielectric material.
Example 2
Dissolving 1g P (VDF-HFP) powder in a mixed solvent of 2.4mL DMF and 1.6mL acetone to obtain a first solution, and dissolving 1g P (VDF-TrFE-CFE) powder in a mixed solvent of 3.3mL DMF and 2.2mL acetone to obtain a second solution, wherein the molecular weight of P (VDF-HFP) powder is 47 ten thousand, and the molecular weight of P (VDF-TrFE-CFE) powder is 85 ten thousand. Firstly, carrying out electrostatic spinning by using a first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time was 20 min. And then spinning by using a second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.67 mL/h; the drum speed was 300rpm and the spinning time was 20 min. Thereafter, spinning was carried out in the order of ABABBABA (including the above-described AB process having been carried out) to obtain a fibrous nonwoven fabric intermediate having an 8-layer structure. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 deg.C for 15min on a heating platform, adding into 60 deg.C water, cold quenching for 5min, and oven drying at 45 deg.C until the water on the surface is completely dried to obtain the final laminated dielectric material with 8-layer structure.
Example 3
Dissolving 1g P (VDF-HFP) powder in a mixed solvent of 2.4mL DMF and 1.6mL acetone to obtain a first solution, and dissolving 1g P (VDF-TrFE-CFE) powder in a mixed solvent of 3.3mL DMF and 2.2mL acetone to obtain a second solution, wherein the molecular weight of P (VDF-HFP) powder is 47 ten thousand, and the molecular weight of P (VDF-TrFE-CFE) powder is 85 ten thousand. Firstly, carrying out electrostatic spinning by using a first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time was 10 min. And then spinning by using a second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.67 mL/h; the drum speed was 300rpm and the spinning time was 10 min. Thereafter, spinning was carried out using the sequence of ABABABABABBABABABABA (including the above-described AB process having been carried out) to obtain a fibrous nonwoven fabric intermediate having a 16-layer structure. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 deg.C for 15min on a heating platform, adding into 60 deg.C water, cold quenching for 5min, and oven drying at 45 deg.C until the water on the surface is completely dried to obtain the final laminated dielectric material with 16-layer structure.
Example 4
Dissolving 1g P (VDF-HFP) powder in a mixed solvent of 2.4mL DMF and 1.6mL acetone to obtain a first solution, and dissolving 1g P (VDF-TrFE-CFE) powder in a mixed solvent of 3.3mL DMF and 2.2mL acetone to obtain a second solution, wherein the molecular weight of P (VDF-HFP) powder is 47 ten thousand, and the molecular weight of P (VDF-TrFE-CFE) powder is 85 ten thousand. Firstly, carrying out electrostatic spinning by using a first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time was 10 min. And then spinning by using a second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.67 mL/h; the drum speed was 300rpm and the spinning time was 10 min. Thereafter, spinning was carried out using the sequence of ABABABABABBABABABABA (including the above-described AB process having been carried out) to obtain a fibrous nonwoven fabric intermediate having a 16-layer structure. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 ℃ for 15min on a heating platform, then putting into 45 ℃ water, performing cold quenching for 5min, and then putting into a 45 ℃ oven until the water on the surface of the film is completely dried, thereby obtaining the final laminated dielectric material with a 16-layer structure.
Example 5
Dissolving 1g P (VDF-HFP) powder in a mixed solvent of 2.4mL DMF and 1.6mL acetone to obtain a first solution, and dissolving 1g P (VDF-TrFE-CFE) powder in a mixed solvent of 3.3mL DMF and 2.2mL acetone to obtain a second solution, wherein the molecular weight of P (VDF-HFP) powder is 47 ten thousand, and the molecular weight of P (VDF-TrFE-CFE) powder is 85 ten thousand. Firstly, carrying out electrostatic spinning by using a first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time was 10 min. And then spinning by using a second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.67 mL/h; the drum speed was 300rpm and the spinning time was 10 min. Thereafter, spinning was carried out using the sequence of ABABABABABBABABABABA (including the above-described AB process having been carried out) to obtain a fibrous nonwoven fabric intermediate having a 16-layer structure. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 ℃ for 15min on a heating platform, then putting into water at 0 ℃, after cold quenching for 5min, putting into a baking oven at 45 ℃ until the water on the surface of the film is thoroughly dried, and finally obtaining the layered dielectric material with 16-layer structure.
Example 6
Dissolving 1g P (VDF-HFP) powder in a mixed solvent of 6.4mL of DMF and 1.6mL of acetone to obtain a first solution, and dissolving 1g P (VDF-TrFE-CFE) powder in a mixed solvent of 8.8mL of DMF and 2.2mL of acetone to obtain a second solution, wherein the molecular weight of P (VDF-HFP) powder is 60 ten thousand, and the molecular weight of P (VDF-TrFE-CFE) powder is 65 ten thousand. Firstly, carrying out electrostatic spinning by using a first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 1.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time was 10 min. And then spinning by using a second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 1.67 mL/h; the drum speed was 300rpm and the spinning time was 10 min. Thereafter, spinning was carried out using the sequence of ABABABABABBABABABABA (including the above-described AB process having been carried out) to obtain a fibrous nonwoven fabric intermediate having a 16-layer structure. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 ℃ for 15min on a heating platform, then putting into 45 ℃ water, performing cold quenching for 5min, and then putting into a 45 ℃ oven until the water on the surface of the film is completely dried, thereby obtaining the final laminated dielectric material with a 16-layer structure.
Example 7
Dissolving 1g P (VDF-HFP) powder in a mixed solvent of 2.4mL DMF and 1.6mL acetone to obtain a first solution, and dissolving 1g P (VDF-TrFE-CFE) powder in a mixed solvent of 3.3mL DMF and 2.2mL acetone to obtain a second solution, wherein the molecular weight of P (VDF-HFP) powder is 47 ten thousand, and the molecular weight of P (VDF-TrFE-CFE) powder is 85 ten thousand. Firstly, carrying out electrostatic spinning by using a first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time was 9.5 min. And then spinning by using a second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.67 mL/h; the drum speed was 300rpm and the spinning time was 9.5 min. Then, the fiber nonwoven fabric intermediate having a 17-layer structure was obtained by spinning in the sequence of abababababa (including the AB process performed above), where a is a P (VDF-HFP) fiber nonwoven fabric layer and B is a P (VDF-TrFE-CFE) fiber nonwoven fabric layer. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 deg.C for 15min on a heating platform, adding into 60 deg.C water, cold quenching for 5min, and oven drying at 45 deg.C until the water on the surface is completely dried to obtain the final 17-layer layered dielectric material.
Example 8
Dissolving 1g P (VDF-HFP) powder in a mixed solvent of 2.4mL DMF and 1.6mL acetone to obtain a first solution, and dissolving 1g P (VDF-TrFE-CFE) powder in a mixed solvent of 3.3mL DMF and 2.2mL acetone to obtain a second solution, wherein the molecular weight of P (VDF-HFP) powder is 47 ten thousand, and the molecular weight of P (VDF-TrFE-CFE) powder is 85 ten thousand. Firstly, carrying out electrostatic spinning by using a second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time was 9.5 min. Then spinning by using the first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.67 mL/h; the drum speed was 300rpm and the spinning time was 9.5 min. Then, the fiber nonwoven fabric intermediate having a 17-layer structure was obtained by spinning in the sequence of abababababa (including the above-described AB process), where a is a P (VDF-TrFE-CFE) fiber nonwoven fabric layer and B is a P (VDF-HFP) fiber nonwoven fabric layer. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 deg.C for 15min on a heating platform, adding into 60 deg.C water, cold quenching for 5min, and oven drying at 45 deg.C until the water on the surface is completely dried to obtain the final 17-layer layered dielectric material.
Example 9
Dissolving 2g P (VDF-HFP) powder in a mixed solvent of 4.8mL of DMF and 3.2mL of acetone to obtain a first solution, wherein the molecular weight of the P (VDF-HFP) powder is 47 ten thousand. Carrying out electrostatic spinning by using the first solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.5 mL/h; the rotating speed of the roller is 300 rpm; the spinning time is 160min, and a fiber non-woven fabric intermediate is obtained. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 deg.C for 15min on a heating platform, adding into 45 deg.C water, cold quenching for 5min, and oven drying at 45 deg.C until the water on the surface is completely dried to obtain the final dielectric material.
Example 10
And (3) dissolving 2g P (VDF-TrFE-CFE) powder in a mixed solvent of 6.6mL of DMF and 4.4mL of acetone to obtain a second solution, wherein the molecular weight of the P (VDF-TrFE-CFE) powder is 85 ten thousand. Spinning with the second solution, wherein the spinning conditions are as follows: the voltage is 10 kV; the distance is 15 cm; the bolus injection speed is 0.67 mL/h; the rotating speed of the roller is 300rpm, and the spinning time is 160min, so that the fiber non-woven fabric intermediate is obtained. Hot pressing at 200 deg.C under 10MPa for 30 min. Taking out, heating at 200 deg.C for 15min on a heating platform, adding into 45 deg.C water, cold quenching for 5min, and oven drying at 45 deg.C until the water on the surface is thoroughly dried to obtain the final dielectric material.
Scanning electron microscope tests were performed on the first fibrous nonwoven fabric layer (a) obtained by electrospinning P (VDF-HFP), the second fibrous nonwoven fabric layer (b) obtained by electrospinning P (VDF-TrFE-CFE), the surface morphology (c) of the layered dielectric material, and the cross-sectional morphology (d) of the layered dielectric material in example 1, and the results are shown in fig. 2, in which the scanning electron microscope test was performed using a scanning electron microscope instrument of MWRLIN compact of zeiss corporation.
A copper electrode with the diameter of 3mm is evaporated on the layered dielectric material or the dielectric material prepared in the embodiments 1 to 10, and then the dielectric property test is carried out.
The relative dielectric constant of the layered dielectric material prepared in examples 1 to 5 was measured by an HP4294A precision impedance analyzer from agilent corporation, and the obtained relative dielectric constant spectrum is shown in fig. 3, where the specific parameters of the measurement are: bias voltage 1V, frequency range 102～107Hz；
The results of testing the electromigration-electric field curves of the layered dielectric materials prepared in examples 1 to 5 using a Premier II ferroelectric tester from Radiant Technologies corporation are shown in fig. 4, and the specific parameters of the test are: the test frequency is 10 Hz;
the energy storage efficiency and the energy storage density of the layered dielectric material or the dielectric material prepared in the embodiments 1 to 10 were measured by using a Premier II ferroelectric tester of Radiant Technologies, and the results are shown in table 1, where the specific parameters of the measurement are: the test frequency was 10 Hz.
TABLE 1
Figure BDA0001655937990000161
Figure BDA0001655937990000171
As can be seen from the energy storage density of example 10, the energy storage density of pure P (VDF-TrFE-CFE) itself is only 7.53J/cm3This is because P (VDF-TrFE-CFE) breakdown is low, whereas the energy storage efficiency of example 9 shows that pure P (VDF-HFP) has an energy storage efficiency of only 77.48%, less than 80%. And a large number of mesoscopic interfaces can be introduced by adopting a mutual stacking mode, and the interfaces can block the migration of current carriers and the growth of electric branches, so that the leakage current can be inhibited, and the breakdown field intensity can be improved. The breakdown field strength is obviously improved relative to P (VDF-TrFE-CFE), and the energy storage density is also improved. And leakage current is restrained, so that leakage conduction loss can be reduced remarkably, and in addition, the ferroelectric loss of a system can be restrained by adjusting a system phase structure through cold quenching at different water temperatures, and compared with pure P (VDF-HFP), the energy storage efficiency of a laminated sample is improved to more than 80%.
As can be seen from FIGS. 2a and b, the nanofibers of P (VDF-HFP) (FIG. 2a) and P (VDF-TrFE-CFE) (FIG. 2b) obtained by electrospinning with proper ratio of mixed solvent have smooth surfaces and no beading phenomenon. After hot pressing, heat treatment and cold quenching, the obtained multilayer composite film has a flat and compact surface (figure 2c), uniform section thickness and compact and non-porous structure (figure 2c), which shows that the high-quality polymer film is prepared.
FIG. 3 is a graph showing the variation of the relative dielectric constant with frequency of the samples of examples 1 to 5. The samples in examples 1 to 3 adopt the same heat treatment process, and only the number of internal layers is different, and the test results show that the relative dielectric constant of the samples is continuously increased with the increase of the number of internal layers, because the increase of the number of internal layers increases the mesoscopic interface area of the system, thereby increasing the interface polarization of the system and improving the overall dielectric constant. In comparison with the samples of examples 3-5, the number of internal layers is the same, and different cold quenching processes are adopted, so that the relative dielectric constant of the system is reduced along with the reduction of the water temperature of cold quenching. This is because when the temperature of the quenching water drops, the phase structure of one phase P (VDF-TrFE-CFE) in the system changes from a nonpolar phase to a nonpolar phase and a polar phase coexists, and for P (VDF-TrFE-CFE), dipoles in the nonpolar phase are more likely to be inverted by the external field, and thus the dielectric constant is larger.
FIG. 4 is a polarization curve diagram of examples 1 to 5. Comparing examples 1-3, it can be seen that, under the same heat treatment process, the more the number of layers inside the system, the higher the breakdown field strength of the system, and the higher the electric polarization value, so the higher the obtained discharge energy density. The reason is that the mesoscopic interface is a weak electric field area, which can inhibit the growth of the electrical tree, the more the number of layers in the system, the more the mesoscopic interface, the stronger the inhibition effect on the electrical tree, and the higher the breakdown field strength of the system. Comparing examples 3-5, it can be seen that, under the condition that the number of layers in the system is the same, the polarization curve of the system gradually becomes thicker with the decrease of the water temperature of the cold quenching, which means that the dielectric loss of the system gradually increases and the efficiency gradually decreases. This is because the phase structure of the system changes from a state in which a nonpolar phase is mainly used to a state in which nonpolar and polar phases coexist with each other as the cold quenching temperature decreases, and the ferroelectric loss of the polar phase increases, and the increase in the phase increases the dielectric loss of the system.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. The laminated dielectric material is characterized by comprising a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are stacked, wherein the first fiber non-woven fabric layer is a vinylidene fluoride-hexafluoropropylene copolymer layer, the second fiber non-woven fabric layer is a vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer layer, and the total number of layers of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer is 16-30.
2. The layered dielectric material of claim 1, wherein the total number of layers of the first fibrous nonwoven layer and the second fibrous nonwoven layer is an odd number, and the layered dielectric material comprises an intermediate layer and a first alternating layer group and a second alternating layer group respectively disposed on two side surfaces of the intermediate layer; the middle layer is a first fiber non-woven fabric layer or a second fiber non-woven fabric layer, the first alternating layer group comprises first fiber non-woven fabric layers and second fiber non-woven fabric layers which are alternately stacked, the second alternating layer group comprises first fiber non-woven fabric layers and second fiber non-woven fabric layers which are alternately stacked, and the number of layers of the first alternating layer group and the second alternating layer group is the same; the first alternating layer group has a layer adjacent to the intermediate layer of a different material than the intermediate layer, and the second alternating layer group has a layer adjacent to the intermediate layer of a different material than the intermediate layer.
3. The layered dielectric material of claim 1 wherein the layered dielectric material is laminated in a manner (AB)nA(BA)nOr B (AB)nA(BA)nB, wherein A represents one of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer, and B represents the other of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer; and n is more than or equal to 4 and less than 7.
4. The layered dielectric material of claim 1, wherein the total number of layers of the first fibrous nonwoven layer and the second fibrous nonwoven layer is an even number, the layered dielectric material comprises a first alternating layer group and a second alternating layer group stacked on the first alternating layer group, the first alternating layer group comprises a first fibrous nonwoven layer and a second fibrous nonwoven layer which are stacked alternately, the second alternating layer group comprises a first fibrous nonwoven layer and a second fibrous nonwoven layer which are stacked alternately, and the number of layers of the first alternating layer group and the second alternating layer group is the same; a layer of the first alternating group of layers that is adjacent to the second alternating group of layers is the same material as a layer of the second alternating group of layers that is adjacent to the first alternating group of layers;
or, the laminated dielectric material is laminated in the form of (AB)m(BA)mOr B (AB)m(BA)mB, wherein A represents one of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer, and B represents the other of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer; and m is more than or equal to 4 and less than or equal to 7.
5. The method of preparing the layered dielectric material of any of claims 1 to 4, comprising the steps of:
dissolving a vinylidene fluoride-hexafluoropropylene copolymer in a first solvent to obtain a first solution;
dissolving the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer in a second solvent to obtain a second solution;
forming the first solution and the second solution in an electrostatic spinning mode to obtain an intermediate, wherein the intermediate comprises a first fiber non-woven fabric layer and a second fiber non-woven fabric layer which are mutually laminated; forming the first solution to obtain a first fiber non-woven fabric layer, and forming the second solution to obtain a second fiber non-woven fabric layer; the total number of the first fiber non-woven fabric layer and the second fiber non-woven fabric layer is 16-30;
carrying out hot pressing treatment on the intermediate; and
and carrying out cold quenching treatment on the intermediate.
6. The method for preparing the layered dielectric material according to claim 5, wherein the first solvent is selected from a mixed solution of N, N-dimethylformamide and acetone, wherein the volume ratio of N, N-dimethylformamide to acetone is 3:2 to 5: 1;
and/or the second solvent is selected from a mixed solution of N, N-dimethylformamide and acetone, wherein the volume ratio of the N, N-dimethylformamide to the acetone is 3: 2-5: 1.
7. The method for preparing the layered dielectric material as claimed in claim 5, wherein the mass percentage of the vinylidene fluoride-hexafluoropropylene copolymer in the first solution is 15% -30%;
and/or the mass percentage of the vinylidene fluoride-trifluoroethylene-chlorofluoroethylene copolymer in the second solution is 15-30%.
8. The method for preparing the layered dielectric material according to claim 5, wherein the voltage in the step of forming the intermediate by electrospinning the first solution and the second solution is 4kV to 15kV, the injection speed of an injection pump is 0.1mL/h to 2mL/h, the spinning distance is 5cm to 50cm, the drum rotation speed is 100rpm to 1000rpm, and the spinning time is 10min to 10 h.
9. The method for preparing a layered dielectric material according to claim 5, wherein the hot pressing temperature is 150 ℃ to 220 ℃, the pressure is 2MPa to 20MPa, and the time is 15min to 120 min.
10. The method for preparing the layered dielectric material according to claim 5, wherein the step of cold quenching specifically comprises:
heating the intermediate at 180-240 ℃ for 5-30 min; and
and cooling the intermediate, wherein the cooling temperature of the cooling treatment is 0-100 ℃, and the time of the cooling treatment is 2-15 min.
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