阅读说明：本技术 一种具有双梯度结构的聚醚酰亚胺基复合介质及其制备方法与应用 (Polyetherimide composite medium with double-gradient structure and preparation method and application thereof ) 是由 迟庆国 薛金鹏 冯宇 张天栋 张月 张昌海 王暄 于 2020-05-26 设计创作，主要内容包括：本发明涉及一种具有双梯度结构的聚醚酰亚胺基复合介质及其制备方法与应用,属于储能电介质技术领域。为解决填料掺杂量过高导致复合介质击穿性能下降的问题,本发明提供了一种具有双梯度结构的聚醚酰亚胺基复合介质,由含有BNNS的填料层与含有BZCT@SiO<Sub>2</Sub> NFs的填料层逐层交替纺丝并经热压和淬火工艺获得,其中两种填料在介质中的含量分别呈梯度分布和反向梯度分布。本发明实现了更高体积分数的高介电常数填料在不影响击穿强度的情况下,增强了复合介质的能量密度,同时使复合介质保持了极高的储能效率,最高储能密度为9.1J/cm<Sup>3</Sup>,最高储能效率为94.6％,可用于制造优良储能特性的电介质储能器件。(The invention relates to a polyetherimide composite medium with a double-gradient structure, and a preparation method and application thereof, and belongs to the technical field of energy storage dielectrics. In order to solve the problem that the breakdown performance of the composite medium is reduced due to overhigh filler doping amount, the invention provides a polyetherimide composite medium with a double-gradient structure, which comprises a filler layer containing BNNS and a filler layer containing BZCT @ SiO 2 NFs the filler layers are alternatively spun layer by layer and are hot pressed and quenchedThe process is carried out by gradient distributing and reverse gradient distributing two kinds of filler content in medium. The invention realizes that the high-dielectric constant filler with higher volume fraction enhances the energy density of the composite medium under the condition of not influencing the breakdown strength, simultaneously ensures that the composite medium keeps extremely high energy storage efficiency, and the highest energy storage density is 9.1J/cm 3 The highest energy storage efficiency is 94.6%, and the method can be used for manufacturing a dielectric energy storage device with excellent energy storage characteristics.)

1. The polyetherimide composite medium with a double-gradient structure is characterized in that polyetherimide is used as a substrate, and the polyetherimide composite medium comprises a filler layer containing BNNS and a filler layer containing BZCT @ SiO₂NFs the packing layers are alternately spun layer by layer and are obtained by hot pressing and quenching processes, wherein the volume fraction of BNNS in each layer of BNNS packing layer is in gradient change of decreasing and increasing, and each layer of BZCT @ SiO₂NFs BZCT @ SiO in filler layer₂NFs has a gradient of increasing volume fraction followed by decreasing volume fraction.

2. The polyetherimide composite medium with the dual-gradient structure as claimed in claim 1, wherein the composite medium comprises 6 filler layers containing BNNS and 5 filler layers containing BZCT @ SiO₂NFs, wherein the filler layers are alternately formed layer by layer, and the filler and the volume content thereof in each filler layer are as follows in sequence:

1.5vol.％BNNS、0.5vol.％[email protected]₂NFs、1.0vol.％BNNS、1.0vol.％[email protected]₂NFs、0.5vol.％BNNS、1.5vol.％[email protected]₂NFs、0.5vol.％BNNS、1.0vol.％[email protected]₂NFs、1.0vol.％BNNS、0.5vol.％[email protected]₂NFs、1.5vol.％BNNS；

or 1.5 vol%BNNS、3.0vol.％[email protected]₂NFs、1.0vol.％BNNS、6.0vol.％[email protected]₂NFs、0.5vol.％BNNS、9.0vol.％[email protected]₂NFs、0.5vol.％BNNS、6.0vol.％[email protected]₂NFs、1.0vol.％BNNS、3.0vol.％[email protected]₂NFs、1.5vol.％BNNS；

Or 9.0 vol.% BNNS, 0.5 vol.% BZCT @ SiO₂NFs、6.0vol.％BNNS、1.0vol.％[email protected]₂NFs、3.0vol.％BNNS、1.5vol.％[email protected]₂NFs、3.0vol.％BNNS、1.0vol.％[email protected]₂NFs、6.0vol.％BNNS、0.5vol.％[email protected]₂NFs、9.0vol.％BNNS。

3. A method for preparing the polyetherimide based composite media with the dual-gradient structure as claimed in claim 1 or 2, wherein BNNS and BZCT @ SiO are mixed₂NFs are respectively and uniformly dispersed in N-methyl pyrrolidone solution, PEI particles are respectively added to prepare PEI-BNNS spinning precursor solution with various required BNNS volume fractions and various BZCT @ SiO₂NFs volume fraction PEI-BZCT @ SiO₂NFs spinning the precursor liquid; mixing the obtained PEI-BNNS spinning precursor solution and PEI-BZCT @ SiO₂NFs the spinning precursor liquid is sequentially subjected to high-speed electrostatic spinning layer by layer according to the sequence of the filler of each filler layer and the volume content requirement thereof to obtain a polyetherimide composite wet film with a double-gradient structure, and the wet film is sequentially subjected to drying treatment, stepped hot pressing treatment and quenching treatment to obtain the dense polyetherimide composite medium with the filling phase volume content distributed in the double-gradient structure.

4. The method for preparing the polyetherimide-based composite medium with the dual-gradient structure as claimed in claim 3, wherein the BNNS is prepared by: the method comprises the steps of putting a BN raw material into a sodium hydroxide solution with the mass concentration of 5-10%, sequentially carrying out stirring, ball milling treatment for 10-48 hours at the rotation speed of 450-600 r/min, ultrasonic dispersion treatment for 24-48 hours at the ultrasonic power of 50-90W, alternately cleaning with deionized water and absolute ethyl alcohol, drying and grinding to obtain the stripped BNNS.

5. The method for preparing the polyetherimide-based composite medium with the dual-gradient structure as claimed in claim 3 or 4, wherein the BZCT @ SiO is used as the material of the composite medium₂NFs the preparation method comprises: dissolving barium hydroxide octahydrate, calcium hydroxide, zirconium acetylacetonate and tetrabutyl titanate in a mixed solution of acetic acid and acetylacetone according to a molar ratio of 0.04-1.20: 0.04-0.35: 0.01-0.25: 0.40-2.20, stirring at room temperature until the mixed solution is clear, adding polyvinylpyrrolidone, continuously stirring until the polyvinylpyrrolidone is completely dissolved, ensuring that the concentration of the polyvinylpyrrolidone in the mixed solution is 0.1-1.0 g/10ml, aging to obtain a BZCT spinning precursor solution, sequentially performing low-speed electrostatic spinning, calcining and grinding on the obtained BZCT spinning precursor solution to obtain BZCT NFs, adding the obtained BZCT NFs into deionized water, adding hexadecyl trimethyl ammonium bromide and ammonia water into the BZCT spinning precursor solution, stirring at a certain temperature to obtain a dispersion liquid, mixing ethyl orthosilicate and absolute ethyl alcohol dropwise, adding the mixture into the obtained dispersion liquid, stirring at a certain temperature, centrifugally collecting precipitate, washing, drying and grinding to obtain BZCT @ SiO₂NFs。

6. The method for preparing the polyetherimide composite medium with the dual-gradient structure according to claim 5, wherein the low-speed electrostatic spinning process comprises the steps that the advancing speed of an injector is 0.1-0.5 mm/min, the rotating speed of a receiver is 50-150 r/min, the receiving distance is 10-20 cm, a spinning needle is 23G in size, the voltage applied to the needle of the injector is + 8- +15kV, the voltage applied to a receiving end is-8-15 kV, the spinning environment temperature is 10-35 ℃, and the relative air humidity is 5-30%; the calcination process comprises the steps of placing the BZCT NFs after spinning is finished in a muffle furnace, setting the temperature in the muffle furnace to gradually rise to 300-400 ℃ from room temperature at the rising rate of 1-2 ℃/min, keeping the temperature for 2-4 h, then continuing to gradually rise to 800-1000 ℃ at the rising rate of 1-2 ℃/min, and calcining for 2-4 h; the mass-volume ratio of the BZCT NFs, the hexadecyl trimethyl ammonium bromide, the ammonia water, the deionized water, the ethyl orthosilicate and the absolute ethyl alcohol is 1.50-3.50 g, 0.05-0.10 g, 3.00-5.00 ml, 400-600 ml, 4.00-6.00 ml, and 15.00-30.00 ml; the stirring temperature is 60-80 ℃, and the stirring time is 10-16 h.

7. The method for preparing the polyetherimide-based composite medium with the double-gradient structure as claimed in claim 6, wherein the high-speed electrospinning process of each filler layer is as follows: PEI-BNNS spinning precursor solution or PEI-BZCT @ SiO used for each layer of packing layer₂NFs the volume of the spinning precursor liquid is 0.2ml, the rotation speed of the receiver is 2000r/min, the positive voltage is +14kV, the negative voltage is-14 kV, and the distance from the injector needle to the receiver is 15 cm.

8. The preparation method of the polyetherimide composite medium with the dual-gradient structure as claimed in claim 7, wherein the drying treatment process of the wet film is to dry the composite medium in a vacuum oven at 60-80 ℃ for 10-20 h; the step-type hot pressing treatment process and the quenching treatment process comprise the following steps: the first stage hot pressing temperature is 100-180 ℃, and the pressure is maintained for 5-25 min under 5-10 MPa; in the second stage, pressure relief and exhaust treatment are carried out, the pressure is completely relieved firstly, then the pressure is increased to 5-15 MPa, the temperature is 170-200 ℃, the temperature is kept for 10-30 min, and the second stage is repeated for three times; and in the third stage, the hot pressing temperature is 220-250 ℃, the pressure is 10-20 MPa, the hot pressing time is kept for 10-30 min, and then the temperature is cooled to 0-25 ℃ by a water cooling device to complete quenching treatment.

9. The method for preparing the polyetherimide-based composite medium with the dual-gradient structure as claimed in claim 8, wherein the thickness of the polyetherimide-based composite medium is 13-17 μm.

10. Use of a polyetherimide-based composite dielectric having a dual gradient structure as defined in claim 1 or 2 for high performance dielectric capacitors.

Technical Field

The invention belongs to the technical field of energy storage dielectrics, and particularly relates to a polyetherimide composite medium with a double-gradient structure, and a preparation method and application thereof.

Background

The dielectric capacitor has the unique advantage of high power density, and is widely applied to the fields of rapid charging and discharging of high-power pulse power supplies, hybrid electric vehicles, electromagnetic weapons and the like. However, the current energy storage dielectric material still cannot meet the requirements of the contemporary society due to the low energy storage density. As biaxially oriented polypropylene has been used as a commercial energy storage dielectric material, the energy storage density is only 2J/cm³. The Polyetherimide (PEI) has excellent electrical insulation performance, mechanical performance and high and low temperature resistance, and is a good energy storage dielectric material. However, its low energy storage density due to its low dielectric constant limits its applications. Doping of fillers with high dielectric constants is a common practice to improve the energy storage characteristics of polymers, however, when the doping content of the filler is too high, the breakdown performance of the polymer is severely reduced.

Disclosure of Invention

In order to solve the problem that the breakdown performance of a polymer is seriously reduced due to overhigh doping amount of a high-dielectric-constant filler, the invention provides a polyetherimide composite medium with a double-gradient structure, and a preparation method and application thereof.

The technical scheme of the invention is as follows:

the polyetherimide composite medium with double gradient structure is prepared with polyetherimide as base body, and through filling layer containing BNNS nanometer boron nitride sheet and BZCT @ SiO₂NFs (silica-coated barium calcium zirconate titanate nanofiber) filler layer-by-layer alternate spinning and hot pressing and quenching process, wherein the volume fraction of BNNS in each BNNS filler layer is in gradient change of decreasing and increasing, and each BZCT @ SiO is₂NFs BZCT @ SiO in filler layer₂NFs has a gradient of increasing volume fraction followed by decreasing volume fraction.

Further, the composite medium consists of 6 layers of filler layers containing BNNS and 5 layers of filler layers containing BZCT @ SiO₂NFs, wherein the filler layers are alternately formed layer by layer, and the filler and the volume content thereof in each filler layer are as follows in sequence:

1.5vol.％BNNS、0.5vol.％[email protected]₂NFs、1.0vol.％BNNS、1.0vol.％[email protected]₂NFs、0.5vol.％BNNS、1.5vol.％[email protected]₂NFs、0.5vol.％BNNS、1.0vol.％[email protected]₂NFs、1.0vol.％BNNS、0.5vol.％[email protected]₂NFs、1.5vol.％BNNS；

or 1.5 vol.% BNNS, 3.0 vol.% BZCT @ SiO₂NFs、1.0vol.％BNNS、6.0vol.％[email protected]₂NFs、0.5vol.％BNNS、9.0vol.％[email protected]₂NFs、0.5vol.％BNNS、6.0vol.％[email protected]₂NFs、1.0vol.％BNNS、3.0vol.％[email protected]₂NFs、1.5vol.％BNNS；

Or 9.0 vol.% BNNS, 0.5 vol.% BZCT @ SiO₂NFs、6.0vol.％BNNS、1.0vol.％[email protected]₂NFs、3.0vol.％BNNS、1.5vol.％[email protected]₂NFs、3.0vol.％BNNS、1.0vol.％[email protected]₂NFs、6.0vol.％BNNS、0.5vol.％[email protected]₂NFs、9.0vol.％BNNS。

The preparation method of the polyetherimide composite medium with the double-gradient structure comprises the steps of mixing BNNS and BZCT @ SiO₂NFs are respectively and uniformly dispersed in N-methyl pyrrolidone solution, PEI (polyetherimide) particles are respectively added to prepare PEI-BNNS spinning precursor solution with various gradient BNNS volume fractions and BZCT @ SiO with various gradients₂NFs volume fraction [email protected]₂NFs spinning the precursor liquid; mixing the obtained PEI-BNNS spinning precursor solution and PEI-BZCT @ SiO₂NFs the spinning precursor liquid is sequentially subjected to high-speed electrostatic spinning layer by layer according to the sequence of the filler of each filler layer and the volume content requirement thereof to obtain a polyetherimide composite wet film with a double-gradient structure, and the wet film is sequentially subjected to drying treatment, stepped hot pressing treatment and quenching treatment to obtain the dense polyetherimide composite medium with the filling phase volume content distributed in the double-gradient structure.

Further, the preparation method of the BNNS comprises the following steps: the method comprises the steps of putting a BN raw material into a sodium hydroxide solution with the mass concentration of 5-10%, stirring for 8-12 hours at 30 ℃, performing ball milling treatment for 10-48 hours at the rotation speed of 450-600 r/min, performing ultrasonic dispersion treatment for 24-48 hours at the ultrasonic power of 50-90W, alternately cleaning with deionized water and absolute ethyl alcohol for 3-5 times respectively, drying for 8-20 hours at 50-90 ℃, and grinding to obtain the stripped BNNS.

Further, the BZCT @ SiO₂NFs the preparation method comprises: dissolving barium hydroxide octahydrate, calcium hydroxide, zirconium acetylacetonate and tetrabutyl titanate in a mixed solution of acetic acid and acetylacetone according to a molar ratio of 0.04-1.20: 0.04-0.35: 0.01-0.25: 0.40-2.20, stirring at room temperature until the mixed solution is clear, adding polyvinylpyrrolidone, continuously stirring until the polyvinylpyrrolidone is completely dissolved, enabling the concentration of the polyvinylpyrrolidone in the mixed solution to be 0.1-1.0 g/10ml, aging to obtain a BZCT spinning precursor solution, sequentially performing low-speed electrostatic spinning, calcining and grinding on the BZCT spinning precursor solution to obtain BZCTNFs, adding the BZCT NFs into deionized water, adding hexadecyl trimethyl ammonium bromide and ammonia water into the deionized water, stirring at a certain temperature to obtain a dispersion liquid, mixing ethyl orthosilicate and absolute ethyl alcohol, dropwise adding the dispersion liquid, stirring at a certain temperature, centrifugally collecting precipitates, washing, drying, Grinding to obtain BZCT @ SiO₂NFs。

Further, the low-speed electrostatic spinning process comprises the steps that the advancing speed of an injector is 0.1-0.5 mm/min, the rotating speed of a receiver is 50-150 r/min, the receiving distance is 10-20 cm, a spinning needle head is 23G in type, the voltage applied to the injector needle head is + 8-15 kV, the voltage applied to a receiving end is-8-15 kV, the spinning environment temperature is 10-35 ℃, and the relative air humidity is 5-30%; the calcination process comprises the steps of placing the BZCT NFs after spinning is finished in a muffle furnace, setting the temperature in the muffle furnace to gradually rise to 300-400 ℃ from room temperature at the rising rate of 1-2 ℃/min, keeping the temperature for 2-4 h, then continuing to gradually rise to 800-1000 ℃ at the rising rate of 1-2 ℃/min, and calcining for 2-4 h; the mass-volume ratio of the BZCT NFs, the hexadecyl trimethyl ammonium bromide, the ammonia water, the deionized water, the ethyl orthosilicate and the absolute ethyl alcohol is 1.50-3.50 g, 0.05-0.10 g, 3.00-5.00 ml, 400-600 ml, 4.00-6.00 ml, and 15.00-30.00 ml; the stirring temperature is 60-80 ℃, and the stirring time is 10-16 h.

Further, the high-speed electrostatic spinning process of each filler layer comprises the following steps: PEI-BNNS spinning precursor solution or PEI-BZCT @ SiO used for each layer of packing layer₂NFs the volume of the spinning precursor liquid is 0.2ml, the rotation speed of the receiver is 2000r/min, the positive voltage is +14kV, the negative voltage is-14 kV, and the distance from the injector needle to the receiver is 15 cm.

Further, the drying treatment process of the wet film is drying for 10-20 hours in a vacuum oven at the temperature of 60-80 ℃; the step-type hot pressing treatment process and the quenching treatment process comprise the following steps: the first stage hot pressing temperature is 100-180 ℃, and the pressure is maintained for 5-25 min under 5-10 MPa; in the second stage, pressure relief and exhaust treatment are carried out, the pressure is completely relieved firstly, then the pressure is increased to 5-15 MPa, the temperature is 170-200 ℃, the temperature is kept for 10-30 min, and the second stage is repeated for three times; and in the third stage, the hot pressing temperature is 220-250 ℃, the pressure is 10-20 MPa, the hot pressing time is kept for 10-30 min, and then the temperature is cooled to 0-25 ℃ by a water cooling device to complete quenching treatment.

Furthermore, the thickness of the polyetherimide composite medium is 13-17 mu m.

The invention relates to application of a polyetherimide composite medium with a double-gradient structure in a high-performance dielectric capacitor, in particular to the application fields of high-power pulse power supplies, hybrid electric vehicles, electromagnetic weapons and the like, and the polyetherimide composite medium can be used for storing extremely high energy density in the working process, simultaneously keeping extremely high charge-discharge efficiency, greatly saving charge time and reducing energy waste, and is a candidate of a novel clean energy material.

The invention has the beneficial effects that:

the invention fills barium calcium zirconate titanate nano-fiber coated by two-dimensional filler boron nitride nano-sheet with high insulativity and one-dimensional filler silicon dioxide with high dielectric property into polyetherimide matrix with high breakdown and high energy storage efficiency to prepare the composite medium, wherein the volume fraction of the barium calcium zirconate titanate nano-fiber is BZCT @ SiO with gradient change₂NFs the defect of low dielectric loss and low polarization of polyetherimide is solved by doping NFs into polyetherimide, and the volume fraction is changed in gradient and is in gradient with BZCT @ SiO₂NFs BNNS packing layer with opposite gradient change can prevent BZCT @ SiO₂NFs when the doping amount is larger, the breakdown performance of the composite dielectric is reduced.

The invention greatly improves the polarization and breakdown field strength of the medium through the interaction of double filling phases and structural optimization, realizes that the high-dielectric-constant nano filler with higher volume fraction enhances the energy density and the charge-discharge efficiency under the condition of hardly influencing the breakdown strength by balancing the breakdown strength and the polarization characteristic of the nano composite medium, ensures that the composite medium keeps extremely high energy storage efficiency, and solves the problem that the breakdown strength and the polarization strength of the conventional nano composite medium cannot be obtained at the same time.

The invention provides a new mode for greatly improving the energy density and the charge-discharge efficiency of the polyetherimide polymer-based nano composite medium, and the highest energy storage density of the polyetherimide composite medium prepared by the invention is 9.1J/cm³The highest energy storage efficiency is 94.6%, and the method can be used for manufacturing dielectric energy storage devices with excellent energy storage characteristics and has wide application prospects in the field of dielectric capacitors.

Drawings

FIG. 1 is an XRD contrast diagram of the four media provided in examples 1, 3, 5 and comparative example 1;

fig. 2 is an SEM photograph of exfoliated two-dimensional boron nitride nanoplates prepared in example 2;

FIG. 3 is an SEM photograph of silica-coated barium calcium zirconate titanate nanofibers prepared in example 2;

FIG. 4 is the BZCT NFs and BZCT @ SiO prepared in example 2₂NFs comparison infrared spectra;

FIG. 5 is a graph showing the variation of dielectric constant with frequency for four media provided in examples 1, 3, 5 and comparative example 1;

FIG. 6 is a Weibull plot of breakdown field strengths for four media provided in examples 1, 3, 5 and comparative example 1;

fig. 7 is a graph comparing the energy storage characteristics of the four media provided in examples 1, 3, 5 and comparative example 1.

Detailed Description

The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.