Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a composite dielectric material with a multilayer gradient structure and a preparation method thereof.
The design and preparation of the multilayer gradient structure polymer/ceramic composite material are expected to solve the problems. Through the design of a multilayer structure in the composite material and the optimization of filler distribution, the breakdown voltage and the dielectric property of the composite dielectric material can be synchronously improved, and further the dielectric energy storage property of the composite dielectric material is greatly improved, so that the composite dielectric material plays an important role in a related electronic power system.
In order to solve the technical problems, the invention adopts the following technical scheme:
the composite dielectric material with the multilayer gradient structure comprises pure ferroelectric polymer layers and ferroelectric polymer/dielectric ceramic filler composite layers which are arranged at intervals, the total number of the layers of the dielectric material is odd, the outer layer of the dielectric material is the ferroelectric polymer/dielectric ceramic filler composite layer, and the content of the dielectric ceramic filler in the ferroelectric polymer/dielectric ceramic filler composite layer is changed according to the rule of increasing gradient from the outer layer to the inner layer.
Preferably, the pure ferroelectric polymer layer is the same thickness as the ferroelectric polymer/dielectric ceramic filler composite layer.
Preferably, the total number of layers of the dielectric material is 5 or 7 or 9.
Preferably, the pure ferroelectric polymer layer is made of any one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polyvinylidene fluoride-trifluoroethylene.
Preferably, the dielectric ceramic filler is any one of barium titanate, barium strontium titanate and titanium dioxide.
Preferably, the content of the dielectric ceramic filler in the ferroelectric polymer/dielectric ceramic filler composite layer is 1 wt% to 20 wt%.
The invention also provides a preparation method of the composite dielectric material with the multilayer gradient structure, which comprises the following steps:
preparing a pure ferroelectric polymer solution;
preparing ferroelectric polymer/dielectric ceramic filler mixed solutions with different dielectric ceramic filler contents;
sequentially spinning the pure ferroelectric polymer solution and the ferroelectric polymer/dielectric ceramic filler mixed solution layer by adopting an electrostatic spinning technology to obtain pure ferroelectric polymer layers which are arranged at intervals and ferroelectric polymer/dielectric ceramic filler composite layers with different dielectric ceramic filler contents;
and collecting the prepared electrostatic spinning film by adopting a roller collector, and carrying out hot pressing treatment to obtain the dielectric material.
Preferably, the diameter of the roller collector is 10 cm-15 cm, and the rotating speed is 1500 rpm-2500 rpm.
Preferably, the hot-pressing treatment temperature is 150-200 ℃, and the pressure is 10-20 Mpa.
Preferably, the pure ferroelectric polymer solution and the ferroelectric polymer/dielectric ceramic filler mixed solution use N, N-dimethylformamide as a solvent.
Compared with the prior art, the invention has the beneficial effects that:
(1) the content of the dielectric ceramic filler in the ferroelectric polymer/dielectric ceramic filler composite layer is sequentially increased from outside to inside according to a certain gradient, and the ferroelectric polymer/dielectric ceramic filler composite layer with lower content of the dielectric ceramic filler at the outer layer can effectively avoid current carriers injected from an electrode under the condition of a high-voltage electric field, so that the high-voltage resistance is improved; the ferroelectric polymer/dielectric ceramic filler composite layer with high content of the dielectric ceramic filler of the inner layer can ensure the improvement of the overall dielectric property of the composite material.
(2) The ferroelectric polymer/dielectric ceramic filler composite layers are separated by pure ferroelectric polymer layers, the pure ferroelectric polymer has relatively high resistivity and the interfaces among the layers can effectively limit the development of carrier migration and electric breakdown branches, and further the composite material film is protected from being broken down under high application voltage.
(3) The composite dielectric material with the multilayer gradient structure is prepared by adopting an electrostatic spinning layer-by-layer construction method, and the method can accurately control the thickness of the multilayer structure and the distribution proportion of the filler content. By combining the characteristics of the multilayer structure of the composite material and the gradient distribution of the dielectric ceramic filler, the composite dielectric material with the multilayer gradient structure can obtain comprehensive, efficient and stable energy storage performance, including breakdown performance, energy storage efficiency, energy storage density and cycle performance.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present invention are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present invention will be more clearly understood from the detailed description that follows.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
It is to be understood that the processing equipment or apparatus not specifically identified in the following examples is conventional in the art.
Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.
The embodiment of the invention provides a composite dielectric material with a multilayer gradient structure, which consists of pure ferroelectric polymer layers and ferroelectric polymer/dielectric ceramic filler composite layers which are arranged at intervals, wherein the total number of the layers of the dielectric material is odd, the outer layer of the dielectric material is the ferroelectric polymer/dielectric ceramic filler composite layer, and the content of the dielectric ceramic filler in the ferroelectric polymer/dielectric ceramic filler composite layer is changed according to the rule of increasing the gradient from the outer layer to the inner layer. The "inner" direction referred to herein means the direction in which the intermediate layer of dielectric material is located, and the "outer" direction means the direction on both sides of the intermediate layer.
The content of the dielectric ceramic filler in the ferroelectric polymer/dielectric ceramic filler composite layer of the composite dielectric material with the multilayer gradient structure prepared by the invention is sequentially increased from outside to inside according to a certain gradient, and the ferroelectric polymer/dielectric ceramic filler composite layer with lower content of the dielectric ceramic filler at the outer layer can effectively avoid current carriers injected from an electrode under the condition of a high-voltage electric field, thereby improving the high-voltage resistance; the ferroelectric polymer/dielectric ceramic filler composite layer with high content of the dielectric ceramic filler of the inner layer can ensure the improvement of the overall dielectric property of the composite material.
In addition, the ferroelectric polymer/dielectric ceramic filler composite layers are separated by pure ferroelectric polymer layers, the relatively high resistivity of the pure ferroelectric polymer and the interfaces among the layers can effectively limit the development of carrier migration and electric breakdown branches, and further the composite material film is protected from being broken down under high application voltage.
On the other hand, the composite dielectric material with the multilayer gradient structure is prepared by adopting an electrostatic spinning layer-by-layer construction method, and the method can accurately control the thickness of the multilayer structure and the distribution proportion of the filler content. By combining the characteristics of the multilayer structure of the composite material and the gradient distribution of the dielectric ceramic filler, the composite dielectric material with the multilayer gradient structure can obtain comprehensive, efficient and stable energy storage performance, including breakdown performance, energy storage efficiency, energy storage density and cycle performance.
Preferably, the pure ferroelectric polymer layer is the same thickness as the ferroelectric polymer/dielectric ceramic filler composite layer. In the preferred embodiment of the invention, the overall thickness of the finally prepared composite dielectric material with a multilayer gradient structure is kept between 10 and 18 μm, and the thickness of each layer is ensured to be 2 μm. The thicknesses of all layers are kept the same, so that the overall performance of the prepared composite dielectric material with the multilayer gradient structure is improved.
Preferably, the total number of layers of the dielectric material is 5 or 7 or 9, and when the number of layers is less than 5, the layer interface is less and the gradient structure cannot be designed. When the number of layers is more than 9, the thickness of the film material is thick, so that the use of the film material in the field of dielectric energy storage is limited. The specific structural layer number is adjusted according to the application condition of the material. 5 layers of structure A1BA2BA1Wherein the layer B is a pure ferroelectric polymer layer, A1And A2The layer is a ferroelectric polymer/dielectric ceramic filler composite layer. A. the1And A2The content of the dielectric ceramic filler in the layer is changed in an increasing way according to a certain gradient. The structural layer of the dielectric material is designed in a symmetrical structure to be positioned at A of the middle layer2The position is the inner layer, and is located at A2A on both sides1Is the outer layer. Similarly, the 7-layer structure is A1BA2BA2BA1Wherein the layer B is a pure ferroelectric polymer layer, A1And A2The layer is a ferroelectric polymer/dielectric ceramic filler composite layer. A. the1And A2The content of the dielectric ceramic filler in the layer is changed in an increasing way according to a certain gradient. 9 layers of A1BA2BA3BA2BA1Wherein the layer B is a pure ferroelectric polymer layer, A1、A2And A3The layer is a ferroelectric polymer/dielectric ceramic filler composite layer. A. the1、A2And A3The content of the dielectric ceramic filler in the layer is changed in an increasing way according to a certain gradient.
Preferably, the material of the pure ferroelectric polymer layer is any one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (P (VDF-HFP)), and polyvinylidene fluoride-trifluoroethylene (P (VDF-TrFE)).
Preferably, the dielectric ceramic filler is barium titanate (BaTiO)3) Barium strontium titanate (BaTi)xO1-x) Titanium dioxide (TiO)2) Any one of them.
Preferably, the content of the dielectric ceramic filler in the ferroelectric polymer/dielectric ceramic filler composite layer is 1 wt% to 20 wt%. The concentration of the dielectric ceramic filler is increased progressively according to the gradient rule that the outer layer is low and the inner layer is high, and the increasing amplitude of the concentration of the dielectric ceramic filler in the adjacent composite layers is not more than 10 wt%; to ensure overall performance, the overall proportion of dielectric ceramic filler in the composite dielectric material is preferably not more than 6 wt%.
The embodiment of the invention also provides a preparation method of the composite dielectric material with the multilayer gradient structure, which comprises the following steps:
(1) preparing a pure ferroelectric polymer solution;
(2) preparing ferroelectric polymer/dielectric ceramic filler mixed solutions with different dielectric ceramic filler contents;
(3) sequentially spinning the pure ferroelectric polymer solution and the ferroelectric polymer/dielectric ceramic filler mixed solution layer by adopting an electrostatic spinning technology to obtain pure ferroelectric polymer layers which are arranged at intervals and ferroelectric polymer/dielectric ceramic filler composite layers with different dielectric ceramic filler contents;
(4) and collecting the prepared electrostatic spinning film by adopting a roller collector, and carrying out hot pressing treatment to obtain the dielectric material.
According to the preparation method, the composite dielectric material with the multilayer gradient structure is prepared by utilizing a method of electrostatic spinning layer-by-layer construction, namely according to a structural design scheme, the ferroelectric polymer and the dielectric ceramic powder which are proportioned are respectively dissolved in N, N-Dimethylformamide (DMF) to prepare spinning solution; and then, carrying out layer-by-layer spinning by utilizing an electrostatic spinning technology, wherein the content of the dielectric ceramic powder filler in the laminated structure is controlled by the proportion of the spinning solution, and the thickness of the laminated structure is determined by the spinning time. The final composite dielectric material with the multilayer gradient structure can be obtained after the prepared electrostatic spinning film is subjected to hot pressing treatment, and preferably, the hot pressing treatment temperature is 150-200 ℃, and the pressure is 10-20 Mpa. Naturally cooling after the hot pressing treatment. In the preferred embodiment of the invention, the overall thickness of the finally prepared composite dielectric material with the multilayer gradient structure is kept between 10 and 18 mu m, and the thickness of each layer is kept consistent.
The composite dielectric material with the multilayer gradient structure is prepared by adopting an electrostatic spinning layer-by-layer construction method, and the method can accurately control the thickness of the multilayer structure and the distribution proportion of the filler content. By combining the characteristics of the multilayer structure of the composite material and the gradient distribution of the dielectric ceramic filler, the composite dielectric material with the multilayer gradient structure can obtain comprehensive, efficient and stable energy storage performance, including breakdown performance, energy storage efficiency, energy storage density and cycle performance.
Preferably, the diameter of the roller collector is 10 cm-15 cm, and the rotating speed is 1500 rpm-2500 rpm. Thus, the oriented arrangement structure of the nano-fibers after spinning can be ensured, and the uniform dispersion of the nano-dielectric ceramic filler is further promoted.
The following is a further description with reference to specific examples.
Example 1
The embodiment 1 of the invention provides a composite dielectric material with a multilayer gradient structure and a preparation method thereof. The structure of the composite dielectric material with the multilayer gradient structure is A1BA2BA2BA1As shown in fig. 1. Wherein A is1The content of barium titanate in the layer is 5 wt%. A2The barium titanate content of the layer was 15 wt%. Before spinning, 0.5 g of P (VDF-HFP) powder is dissolved in 10 mL of DMF solution, stirred overnight until the powder is completely dissolved to prepare a pure ferroelectric polymer solution, and BaTiO with different contents is added into the pure ferroelectric polymer solution3Preparing different BaTiO respectively from nano particles (5 wt% and 15 wt%)3The ferroelectric polymer/dielectric ceramic filler mixed solution with the content is continuously stirredAfter 24h, carrying out ultrasonic treatment for 30 min until BaTiO3And (4) completely dispersing the nano particles to prepare the spinning solution. Spinning the prepared spinning solution layer by using an electrostatic spinning method according to a preset multilayer structure, wherein in order to ensure the uniformity and stability of the structure, a spinning film is collected by a roller, the diameter of the roller is 10cm, the rotating speed is 1800 rpm, the spinning voltage is 15 kV, the spinning speed is 1.0 mL/h, and the spinning time of each layer is 1 h. After the film is prepared, the composite dielectric material with a multilayer gradient structure is obtained after the composite dielectric material is hot-pressed for 10min under the conditions of 10 Mpa and 170 ℃, the section scanning picture of the material is shown in figure 2, the thickness of each layer is 2 microns, and the overall thickness of the film is 14 microns.
Fig. 3 is a schematic view of carrier injection of the structural composite material under a high-voltage electric field condition, and fig. 4 is a schematic view of the development of electric tree inside the material under the high-voltage electric field condition. FIG. 5 is the hysteresis loop of the composite material under the highest withstand voltage electric field, and it can be seen that the material loss is low, and under the electric field strength of 610 MV/m, the energy storage efficiency is 70%, and the energy storage density is 17.55J/cm3。
Example 2
Embodiment 2 of the invention provides a composite dielectric material with a multilayer gradient structure and a preparation method thereof. The structure of the multilayer gradient composite material is A1BA2BA1. Wherein A is1Layer of TiO2Content 1 wt%, A2Layer of TiO2The content was 10 wt%. Before spinning, 0.5 g of P (VDF-TrFE) powder is dissolved in 10 mL of DMF solution, stirred overnight until the powder is completely dissolved to prepare a pure ferroelectric polymer solution, TiO with different contents is added into the pure ferroelectric polymer solution2Preparing different TiO respectively from nano particles (1 wt% and 10 wt%)2Continuously stirring the ferroelectric polymer/dielectric ceramic filler mixed solution with the content for 24 hours, and then carrying out ultrasonic treatment for 30 min until TiO is formed2And (4) completely dispersing the nano particles to prepare the spinning solution. Spinning the prepared spinning solution layer by using an electrostatic spinning method according to a preset multilayer structure, wherein in order to ensure the uniformity and stability of the structure, a spinning film is collected by a roller, the diameter of the roller is 12 cm, the rotating speed is 1500 rpm, the spinning voltage is 15 kV, the spinning speed is 1.0 mL/h, and the spinning time of each layer is 1 h. After the film is prepared, it isAnd hot pressing at 10 MPa and 170 ℃ for 10min to obtain the composite dielectric material with a multilayer gradient structure, wherein the thickness of each layer is 2 microns, and the overall thickness of the film is 10 microns. Fig. 6 is a hysteresis loop of the composite material under the highest withstand voltage electric field. Under the electric field strength of 570 MV/m, the energy storage efficiency is 70 percent, and the energy storage density is 13.9J/cm3。
Example 3
Embodiment 3 of the invention provides a composite dielectric material with a multilayer gradient structure and a preparation method thereof, wherein the structure of the multilayer gradient composite material is A1BA2BA3BA2BA1. Wherein A is1The content of barium strontium titanate layer is 1 wt%, A2The content of barium strontium titanate of the layer is 5 wt%. A. the3The content of barium strontium titanate of the layer is 10 wt%. Before spinning, 0.5 g of PVDF powder is dissolved in 10 mL of DMF solution, the mixture is stirred overnight until the PVDF powder is completely dissolved to prepare a pure ferroelectric polymer solution, ferroelectric polymer/dielectric ceramic filler mixed solutions with different barium strontium titanate contents are respectively prepared by adding barium strontium titanate nanoparticles (1 wt%, 5 wt% and 10 wt%) with different contents into the pure ferroelectric polymer solution, the mixture is continuously stirred for 24 hours and then is subjected to ultrasonic treatment for 30 minutes until the barium strontium titanate nanoparticles are completely dispersed, and a spinning solution is prepared. Spinning the prepared spinning solution layer by using an electrostatic spinning method according to a preset multilayer structure, wherein in order to ensure the uniformity and stability of the structure, a spinning film is collected by a roller, the diameter of the roller is 15cm, the rotating speed is 1500 rpm, the spinning voltage is 15 kV, the spinning speed is 1.0 mL/h, and the spinning time of each layer is 1 h. After the film is prepared, the composite dielectric material with a multilayer gradient structure is obtained after the film is hot-pressed for 10min under the conditions of 10 Mpa and 170 ℃, wherein the thickness of each layer is 2 microns, and the overall thickness of the film is 18 microns. Fig. 7 is a hysteresis loop of the composite material under the highest withstand voltage electric field. Under the electric field strength of 580 MV/m, the energy storage efficiency is 68 percent, and the energy storage density is 14.3J/cm3。
The protective scope of the present invention is not limited to the above-described embodiments, and it is apparent that various modifications and variations can be made to the present invention by those skilled in the art without departing from the scope and spirit of the present invention. It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.