A nanocomposite dielectric thin film of a laminated structure and a method for preparing the same

Abstract

The application discloses a kind of nanocomposite dielectric thin film of laminated structure and preparation method thereof, characterized by pressure-bearing layer and polarization layer are alternately stacked to form 2-8 layers of nanocomposite dielectric thin film with total thickness of 10-14 microns, its preparation method includes the steps of coating organic PDI on the surface of Ni (OH) 2 nanosheet to obtain the core-shell structure of Ni (OH) 2@PDI nanosheet;The steps of electrospinning the volume ratio of P (VDF-HFP) and Ni (OH) 2@PDI nanosheet 50% pressure-bearing layer solution and P (VDF-HFP) and Ni (OH) 2 nanosheet 50% polarization layer solution, and controlling the thickness ratio of pressure-bearing layer and polarization layer is 6-3:2-5 to obtain the step of preliminary nanocomposite dielectric thin film, and finally the step of hot-pressing film to obtain the nanocomposite dielectric thin film of laminated structure, the advantage is to realize the synchronous improvement of breakdown field strength and dielectric constant, and improve energy storage density.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of dielectric capacitor, in particular to a nanocomposite dielectric film with a laminated structure and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for energy storage, dielectric capacitors have been widely used in electronic circuits, microwave communication and power systems due to their high power density and ultrafast charging and discharging speed, and play an important role. However, the energy storage density and charging and discharging efficiency of dielectric capacitors are relatively low, which leads to an increase in volume and weight, and part of the energy is lost in the form of heat. This is not in line with the trend of future energy storage devices pursuing efficient, stable storage and release of energy. Therefore, improving the energy storage density and efficiency of dielectric capacitors has become the focus of researchers. From the definition of the energy storage density of dielectric capacitors, it can be known that the square of the dielectric constant ε r and the breakdown field strength E b is proportional to the energy storage density U d , so it is more effective to improve the energy storage density by improving the breakdown field strength. Among the materials used as dielectrics, organic polymers often have a high breakdown field strength, while inorganic ceramics have a high dielectric constant. At present, the method to improve the energy storage density by improving the breakdown field strength is to composite inorganic ceramics with organic polymers to combine the high breakdown field strength of organic polymers and the high dielectric constant of inorganic ceramics.

[0003] In the initial design, researchers found that inorganic ceramics can be divided into zero-dimensional (0D), one-dimensional (1D) and two-dimensional (2D) fillers according to the shape. Many studies have shown that 2D fillers have a larger aspect ratio than the other two, which can act as electron scattering centers to extend the electrical tree path, but there are still problems such as electric field distortion at the interface and poor compatibility of the composite film, so researchers generally use materials with similar dielectric constants and core-shell structures to solve these problems. In addition, researchers will also increase the compatibility between the filler and the substrate through the organic shell layer to reduce the defects brought by the filling of the filler. However, there is a difficult challenge in balancing the performance of the composite film. At a low filling content of inorganic ceramics, although the breakdown field strength of the film is high, the dielectric constant cannot be significantly improved; while when the filling content of inorganic ceramics increases, the dielectric constant is improved, but the breakdown field strength is sharply decreased. This mutual restriction makes it extremely difficult to further improve the energy storage density of the composite film, and brings a new bottleneck to the development and application of composite dielectric materials. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a nanocomposite dielectric film with a laminated structure and a preparation method thereof, which can simultaneously improve the breakdown field strength and the dielectric constant and improve the energy storage density.

[0005] The technical scheme adopted by the present application to solve the above technical problems is: a nanocomposite dielectric film of a laminated structure, which is formed by alternately stacking pressure-bearing layers and polarization layers to form a nanocomposite dielectric film with a total thickness of 10-14 microns and 2-8 layers, wherein the pressure-bearing layer is polyvinylidene fluoride-hexafluoropropylene copolymer P(VDF-HFP) filled with Ni(OH)2@PDI nanosheets, and the polarization layer is P(VDF-HFP) filled with Ni(OH)2 nanosheets.

[0006] Preferably, the volume percentage of the Ni(OH)2@PDI nanosheets in the P(VDF-HFP) is 1.3%, and the volume percentage of the Ni(OH)2 in the P(VDF-HFP) is 2%. The density of the prepared material is measured by the drainage method, and then the volume size of the added material is calculated to convert the corresponding volume fraction content. The volume fraction can intuitively express the spatial proportion of the doped material in the composite medium.

[0007] Preferably, the pressure-bearing layer and the polarization layer are alternately stacked to form a nanocomposite dielectric film with a total thickness of 10-14 microns and 4 layers, and the thickness ratio of the pressure-bearing layer to the polarization layer is (6-3):(2-5).

[0008] Preferably, the pressure-bearing layer and the polarization layer are alternately stacked to form a nanocomposite dielectric film with a total thickness of 12 microns and 4 layers, and the thickness ratio of the pressure-bearing layer to the polarization layer is 5:3.

[0009] The present application also provides a preparation method of the nanocomposite dielectric film of the above-mentioned laminated structure, comprising the following steps:

[0010] Step 1: preparing Ni(OH)2 nanosheets by a hydrothermal method:

[0011] Step 2: coating the surface of the Ni(OH)2 nanosheets with organic matter perylene-3,4,8,10-tetracarboxylic dianhydride (PDI) to obtain Ni(OH)2@PDI nanosheets with a core-shell structure;

[0012] Step 3: electrospinning to form a film:

[0013] (1) Dissolve the Ni(OH)2@PDI nanosheets in N,N-dimethylformamide (DMF), disperse by ultrasonic, and then stir by magnetic force until mixed uniformly to obtain a Ni(OH)2@PDI nanosheet solution with a volume fraction of 1.3%;

[0014] (2) Dissolve the Ni(OH)2nanosheet in N, N-dimethylformamide (DMF), and then mix uniformly by ultrasonic dispersion and magnetic stirring to obtain a Ni(OH)2nanosheet solution with a volume fraction of 2.0%;

[0015] (3) Add P(VDF-HFP) to the Ni(OH)2@PDI nanosheet solution, stir at 600 r / min by magnetic force at 60°C for 2 h, and then stir at room temperature for 4 h to obtain a pressure-bearing layer solution with a volume ratio of P(VDF-HFP) to Ni(OH)2@PDI nanosheet of 50%;

[0016] (4) Add P(VDF-HFP) to the Ni(OH)2nanosheet solution, stir at 600 r / min by magnetic force at 60°C for 2 h, and then stir at room temperature for 4 h to obtain a polarization layer solution with a volume ratio of P(VDF-HFP) to Ni(OH)2nanosheet of 50%;

[0017] (5) Remove bubbles from the pressure-bearing layer solution and the polarization layer solution by vacuum treatment, form a composite film structure by alternately stacking the pressure-bearing layer and the polarization layer on top of each other, electrospun at a rate of 1 mm / min in an environment with a temperature of 40°C and a humidity of 30%, and control the thickness ratio of the pressure-bearing layer to the polarization layer to be (6-3):(2-5) by the spinning time, collect on an aluminum foil, and then place in an oven at 60°C for 2 h to remove residual solvents to obtain a preliminary nanocomposite dielectric film;

[0018] Step 4, hot-press the preliminary nanocomposite dielectric film obtained in step 3 to form a film to obtain a nanocomposite dielectric film with a laminated structure.

[0019] Further, step 1 is as follows: dissolve 6.5 g of NiCl2 and 4 g of NaOH in 25 ml of deionized water respectively, stir at 600 r / min by magnetic force for 30 minutes until completely dissolved, then slowly drop the NiCl2 solution into the NaOH solution and add 80 ml of deionized water, mix, and then stir at 600 r / min for 30 min, pour into a high-pressure reaction kettle, react fully at 200°C for 24 h, centrifuge the reaction product with deionized water several times, then vacuum dry at 60°C for 24 h, and then grind to obtain light green Ni(OH)2nanosheets.

[0020] Further, step 2 is as follows: add 0.3 g of Ni(OH)2nanosheets and 0.02 g of PDI to 30 ml of deionized water in sequence, stir at 60°C for 12 hours, and then dry at 60°C for 12 hours to obtain Ni(OH)2@PDI nanosheets with a core-shell structure.

[0021] Further, step 4 is specifically as follows: the preliminary nanocomposite dielectric film prepared in step 3 is pasted on the conductive surface of the conductive glass, and is hot-pressed in a vacuum vulcanizing machine at 150 DEG C and a pressure of 15 MPa for 30 min; after the hot-pressing is completed, the composite dielectric film is placed in an oven at 200 DEG C for heat preservation for 10 min, and then is quickly placed in an ice-water mixture to complete quenching operation; after cleaning and drying, the nanocomposite dielectric film with a laminated structure is obtained.

[0022] Compared with the prior art, the advantages of the nanocomposite dielectric film with a laminated structure and the preparation method thereof are as follows: by adjusting the number of layers and the thickness of each layer of the multi-layer structure, the electric field can be reasonably distributed, and the electron transmission is hindered at the interface, so that the electric tree branches grow horizontally along the interface, which helps to improve the insulation capacity of the multi-layer film. The NPP can capture electrons multiple times in the four-layer structure, hinders the carrier transmission, and enhances the breakdown field strength. By keeping the total thickness unchanged and adjusting the thickness of the NP layer, the NP can provide a high enough polarization while the NPP can bear as much electric field as possible within a bearable range, which helps to further enhance the breakdown field strength. The 37.5 vol.% NP / NPP composite film is optimized and prepared. The suitable number of layers and thickness make it maintain a high breakdown field strength and dielectric constant, and finally obtain the highest energy storage performance, that is, an excellent energy storage density of 32.1 J / cm 3 and an energy storage efficiency of 80.8% under a high breakdown field strength of 705.7 MV / m.

[0023] In summary, the nanocomposite dielectric film with a laminated structure and the preparation method thereof can greatly improve the overall energy storage performance of the composite material by adjusting the number of layers and the thickness of each layer, so that the composite material has excellent breakdown resistance and dielectric performance. Moreover, the preparation process is green and environmentally friendly, the process is simple, and the method can be widely used. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a schematic diagram of four-layer different thickness structures of the nanocomposite dielectric film;

[0025] Figure 2 It is a scanning electron microscope micro-morphology diagram of the nanocomposite dielectric film;

[0026] Figure 3 It is a P-E curve diagram of the nanocomposite dielectric film with different numbers of layers;

[0027] Figure 4 It is an energy storage density and efficiency diagram of the nanocomposite dielectric film with different numbers of layers;

[0028] Figure 5 It is an electric breakdown simulation diagram of the nanocomposite dielectric film with different numbers of layers;

[0029] Figure 6 P-E curves of different thicknesses of the nanocomposite dielectric thin film;

[0030] Figure 7 Energy storage density and efficiency diagrams of different thicknesses of the nanocomposite dielectric thin film;

[0031] Figure 8 Electric breakdown simulation diagrams of different thicknesses of the nanocomposite dielectric thin film. DETAILED DESCRIPTION

[0032] The application will be further described in detail below with reference to the embodiments of the drawings.

[0033] Polyvinylidene fluoride-hexafluoropropylene copolymer P(VDF-HFP) and polymethyl methacrylate PMMA were purchased from Shanghai Sanaifu New Materials Co., Ltd, DMF N, N-dimethylformamide (AR, 99.5%), NaOH sodium hydroxide (AR, 99.5%), nickel chloride NiCl2·6H2O (AR, 99.5%), and perylene-3, 4, 8, 10-tetracarboxylic dianhydride (PDI) were purchased from Aladdin. I. Embodiments

[0035] Example 1

[0036] A nanocomposite dielectric thin film of a laminated structure, formed by alternately stacking pressure-bearing layers and polarization layers, has a total thickness of 12 microns, wherein the pressure-bearing layers are P(VDF-HFP) filled with Ni(OH)2@PDI nanosheets, and the polarization layers are P(VDF-HFP) filled with Ni(OH)2 nanosheets. The preparation method comprises the following specific steps:

[0037] Step 1, preparing Ni(OH)2nanosheets by a hydrothermal method: 6.5g of NiCl2and 4g of NaOH were respectively dissolved in 25ml of deionized water, and stirred at 600r / min for 30 minutes until completely dissolved. Then, the NiCl2solution was slowly dropped into the NaOH solution and mixed with 80ml of deionized water, and stirred at 600r / min for 30 minutes. After that, the mixture was poured into a high-pressure reaction kettle and reacted at 200℃ for 24 hours. The reaction product was centrifuged with deionized water for several times, and then vacuum dried at 60℃ for 24 hours. Finally, the light green Ni(OH)2nanosheets were obtained by grinding.

[0038] Step 2, coating the surface of Ni(OH)2nanosheet with organic matter perylene-3,4,8,10-tetracarboxylic dianhydride (PDI), as follows: 0.3 g of Ni(OH)2nanosheet and 0.02 g of PDI were sequentially added to 30 ml of deionized water, stirred at 60°C for 12 hours, and then dried at 60°C for 12 hours to obtain Ni(OH)2@PDI nanosheet with core-shell structure, abbreviated as N@P.

[0039] Step 3, electrospinning into a film:

[0040] (1) 0.247 g of Ni(OH)2@PDI nanosheet was dissolved in 11 mL of N,N-dimethylformamide (DMF), ultrasonically dispersed, and then magnetically stirred at 600 r / min for 30 min to obtain a Ni(OH)2@PDI nanosheet solution with a volume fraction of 1.3%;

[0041] (2) 0.247 g of Ni(OH)2nanosheet was dissolved in 11 mL of N,N-dimethylformamide (DMF), ultrasonically dispersed, and then magnetically stirred at 600 r / min for 30 min to obtain a Ni(OH)2nanosheet solution with a volume fraction of 2.0%;

[0042] (3) 0.8 g of P(VDF-HFP) was added to the Ni(OH)2@PDI nanosheet solution, magnetically stirred at 600 r / min at 60°C for 2 h, and then stirred at room temperature for 4 h to obtain a pressure-bearing layer solution with a volume ratio of P(VDF-HFP) to Ni(OH)2@PDI nanosheet of 50%, and the pressure-bearing layer was abbreviated as NPP;

[0043] (4) 0.8 g of P(VDF-HFP) was added to the Ni(OH)2nanosheet solution, magnetically stirred at 600 r / min at 60°C for 2 h, and then stirred at room temperature for 4 h to obtain a polarization layer solution with a volume ratio of P(VDF-HFP) to Ni(OH)2nanosheet of 50%, and the polarization layer was abbreviated as NP;

[0044] (5) The pressure-bearing layer solution and the polarization layer solution were vacuum treated to remove bubbles, and were stacked in an alternating manner to form a 4-layer film with a total thickness of 12 microns, electrospun at a rate of 1 mm / min in an environment with a temperature of 40°C and a humidity of 30%, and the thickness ratio of the polarization layer NP to the pressure-bearing layer NPP was controlled by the spinning time to be 3:5, collected on aluminum foil paper, and then placed in an oven at 60°C for 2 h to remove residual solvent, to obtain a preliminary nanocomposite dielectric film.

[0045] Step 4, hot-pressing into film: the preliminary nano-composite dielectric film prepared in step 3 is pasted on the conductive surface of the conductive glass, and is hot-pressed in a vacuum vulcanizing machine at 150°C and 15Mpa for 30min; after the hot-pressing is completed, the composite dielectric film is placed in an oven at 200°C for 10min, and then is quickly placed in an ice-water mixture to complete the quenching operation; after cleaning and drying, the nano-composite dielectric film with a laminated structure (denoted as 37.5%NP / NPP composite dielectric film) is obtained.

[0046] Example 2

[0047] The same as example 1 above, except that in step 3(5), the thickness ratio of NP to NPP is controlled to be 2:6 by the spinning time, and the 4-layer 25%NP / NPP composite dielectric film is collected on aluminum foil paper, and then is placed in an oven at 60°C for 2h to remove residual solvent.

[0048] Example 3

[0049] The same as example 1 above, except that in step 3(5), the thickness ratio of NP to NPP is controlled to be 4:4 (i.e. 50%NP / NPP composite dielectric film) by the spinning time, and the 4-layer 50%NP / NPP composite dielectric film is collected on aluminum foil paper, and then is placed in an oven at 60°C for 2h to remove residual solvent.

[0050] Example 4

[0051] The same as example 1 above, except that in step 3(5), the thickness ratio of NP to NPP is controlled to be 5:3 by the spinning time, and the 4-layer 62.5%NP / NPP composite dielectric film is collected on aluminum foil paper, and then is placed in an oven at 60°C for 2h to remove residual solvent.

[0052] Example 5

[0053] The same as example 1 above, except that the composite dielectric film is designed to be formed by the pressure-bearing layer NPP and the polarization layer NP alternately stacked in an upper-lower manner to form a 2-layer nano-composite dielectric film with a total thickness of 12 microns, and the thickness of NP is controlled to be the same as that of NPP by the spinning time.

[0054] Example 6

[0055] The same as example 1 above, except that the composite dielectric film is designed to be formed by the pressure-bearing layer NPP and the polarization layer NP alternately stacked in an upper-lower manner to form an 8-layer nano-composite dielectric film with a total thickness of 12 microns, and the thickness of NP is controlled to be the same as that of NPP by the spinning time.

[0056] Control group

[0057] 0.3 g Ni(OH)2 nanosheets and 0.02 g PDI were added to 30 ml deionized water in sequence, stirred at 60 °C for 12 hours, and dried at 60 °C for 12 hours to obtain core-shell structured Ni(OH)2@PDI nanosheets, abbreviated as N@P.

[0058] 0.247 g of Ni(OH)2@PDI nanosheets were dissolved in 11 mL of N,N-dimethylformamide (DMF), dispersed by ultrasonication, and then magnetically stirred at 600 rpm for 30 min until uniformly mixed to obtain a Ni(OH)2@PDI nanosheet solution with a volume fraction of 1.3%.

[0059] 0.8 g of P(VDF-HFP) was added to the Ni(OH)2@PDI nanosheet solution, stirred at 60°C for 2 h at a magnetic force of 600 r / min, and then stirred at room temperature for 4 h to obtain a pressure-bearing layer solution with a volume ratio of P(VDF-HFP) to Ni(OH)2@PDI nanosheets of 50%.

[0060] The pressure-bearing layer solution was vacuum treated to remove bubbles, and electrospun at a rate of 1 mm / min in an environment of temperature 40°C and humidity 30, and the thickness was controlled to 12 microns by the spinning time. The film was collected on aluminum foil and then placed in a 60°C oven for 2 hours to remove residual solvent. The film was then pasted on the conductive surface of the conductive glass and hot-pressed in a vacuum vulcanizer at 150°C and a pressure of 15 MPa for 30 minutes. After the hot pressing was completed, the composite dielectric film was placed in a 200°C oven for 10 minutes and then quickly placed in an ice-water mixture to complete the quenching operation. After cleaning and drying, a single-layer nanocomposite dielectric film was obtained, which was recorded as 1.3 vol.% N@P / PVH (abbreviated as NPP). 1.3 vol.% N@P / PVH (NPP) obtained 21.7 J / cm at 569.0 MV / m. 3 energy storage density.

[0061] 2. Experimental Results Analysis

[0062] Figure 1 The schematic diagram of the structure of four layers of nanocomposite dielectric film with different thicknesses is shown in Figure 2. Figure 1 As shown, the volume fraction ratio of NP to NPP layers in the four-layer composite dielectric films (reflected in thickness) is 2:6, 3:5, 4:4, and 5:3, corresponding to 25 vol.% NP / NPP, 37.5 vol.% NP / NPP, 50 vol.% NP / NPP, and 62.5 vol.% NP / NPP composite dielectric films.

[0063] Figure 2 The scanning electron microscope microscopic morphology of the nanocomposite dielectric film is shown in Figure 2. Figure 2As shown, the cross-sectional morphology of the composite film prepared in Example 1 is free of obvious defects, with no significant differences between layers. Furthermore, the filler in the film is uniformly distributed perpendicular to the electric field. This demonstrates that the method for preparing the nanocomposite dielectric film of the present invention can reduce voids and defects in the composite film, significantly improving film quality. This preparation method essentially achieves mechanized operation, reducing the impact of human error on the finished film and facilitating practical production applications.

[0064] Figure 3 The PE curve of different layers of nanocomposite dielectric film is shown in Figure 2. Figure 3 As shown, the 2-, 4-, and 8-layer composite films prepared in Examples 5, 3, and 6 have greater E b , and the dielectric constant corresponding to the slope is also improved. The 50 vol.% NP / NPP composite film prepared in Example 3 has a larger E than the 2-layer composite film prepared in Example 5 and the 8-layer composite film prepared in Example 6. b , which also helps to obtain higher energy storage performance at the same slope.

[0065] Figure 4 The energy storage density and efficiency diagram of different layers of nanocomposite dielectric films are shown in Figure 2. Figure 4 As shown in the figure, the 2-, 4-, and 8-layer composite films prepared in Examples 5, 3, and 6 have a higher energy storage density (21.7 J / cm 3 ) has a preliminary improvement. The 50 vol.% NP / NPP composite film prepared in Example 3 has an E of 652.8 MV / m. b Compared with the composite films of Examples 5 and 6, a higher 27.8 J / cm 3 The energy storage density shows that 4 layers of composite film are the layers with the best energy storage performance.

[0066] Figure 5 The electrical breakdown simulation diagram of different layers of nanocomposite dielectric films is shown in Figure 2. Figure 5As shown, the electrical trees in the first layer of NPP are coarser, and at the interface between NPP and NP, the trees clearly grow horizontally, increasing the number of paths. This is because NPP can capture electrons and reduce their kinetic energy, helping to hinder electron injection and transport. Under the same NP content and applied electric field, the 50 vol.% NP / NPP prepared in Example 3 did not break down, and the electrical trees only grew to the fourth NP layer. This is because the third layer of NPP further reduces the electron kinetic energy on top of the first layer and causes the electrical trees to branch, increasing the number of paths. Under the influence of the NPP layer and the interface, the electrical trees eventually deplete at the NP layer and fail to form a conductive path. Interestingly, the 8-layer 50 vol.% NP / NPP prepared in Example 6 did not have better insulation performance due to its additional NPP layer. This is mainly because the NPP layer is too thin, and the electrical trees pass through before they can effectively hinder carrier transport. It can be seen that the effect of the NPP layer and the interface is significantly less than that of the 2-layer and 4-layer composite films, and the electrical trees grow downward faster and form a conductive path. The simulation results well illustrate the effect of layer number on the breakdown field strength of 50 vol.% NP / NPP and are consistent with the experimental results.

[0067] Figure 6 The PE curves of different thickness of nanocomposite dielectric films are shown in Figure 2. Figure 6 As shown in the figure, as the volume percentage x% increases, the slope of the PE curve gradually increases, while the breakdown field strength decreases with increasing x. However, the breakdown field strength of the 37.5 vol.% NP / NPP composite film prepared in Example 1 does not decrease significantly. This means that the 37.5 vol.% NP / NPP composite film can achieve the best energy storage performance among the four-layer composite film designs.

[0068] Figure 7 The energy storage density and efficiency diagram of nanocomposite dielectric films of different thicknesses are shown in Figure 2. By calculating the PE curves of x vol.% NP / NPP under different electric fields, the energy storage density and energy storage efficiency of x vol.% NP / NPP are obtained, as shown in Figure 2. Figure 7 As shown. With the increase of electric field strength, the energy storage density gradually increases, while the energy storage efficiency first decreases and then increases. This is because with the increase of electric field strength, the dipole orientation gradually moves toward the direction of the electric field. Since the 37.5 vol.% NP / NPP composite film prepared in Example 1 has a suitable thickness of each layer, it has a large dielectric constant while maintaining a high breakdown field strength. Finally, the 37.5 vol.% NP / NPP composite film achieved the highest breakdown field strength of 32.1 J / cm at a high breakdown field strength of 705.7 MV / m. 3 energy storage density and 80.8% energy storage efficiency.

[0069] Figure 8The figure shows the electrical breakdown simulation of nanocomposite dielectric films of different thicknesses. As the volume percentage x% increases, the electrical tree branches get closer to the lower plate and a conductive path is generated. This is because the proportion of NPs with poor insulation performance is increasing, and the NPP layer begins to be unable to withstand the gradually increasing electric field. Figure 8 As shown, electrons are accelerated by the thicker NP layer, and the insufficient NPP layer is no longer able to effectively hinder electron transport, causing electrical treeing to propagate directly from top to bottom throughout the composite film. The 25 vol.% NP / NPP and 37.5 vol.% NP / NPP composite films prepared in Examples 2 and 1 exhibit similar insulation properties, and outperform the 50 vol.% NP / NPP and 62.5 vol.% NP / NPP composite films prepared in Examples 3 and 4. The simulation results are consistent with the experimental results.

[0070] In summary, the present invention will have a high breakdown field strength E b NPP is placed on the upper layer as the pressure-bearing layer, and 2.0 vol.% Ni(OH)2 / PVH(NP) with a high dielectric constant is placed on the lower layer as the polarization layer. In this order, 2-layer, 4-layer and 8-layer composite films NP / NPP are constructed, and the volume fractions of the two are the same. By comparison, it is found that the 4-layer 50 vol.% NP / NPP obtains a breakdown field strength of 652.8 MV / m when the polarization is not much different, which is higher than the 2-layer 50 vol.% NP / NPP and 8-layer 50 vol.% NP / NPP. Then, four 4-layer x vol.% NP / NPP composite films are obtained by adjusting the thickness of NP. 37.5 vol.% NP / NPP has the most suitable ratio. Each layer can be allocated to the appropriate electric field and bring higher polarization, while not making the electron kinetic energy too large to cause the NPP layer to be unblocked. The 4-layer 37.5 vol.% NP / NPP composite film achieved an excellent 32.1 J / cm at the highest breakdown field strength of 705.7 MV / m. 3 The energy storage density is improved, and the high energy storage efficiency is still maintained at 80.8%.

[0071] The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by persons of ordinary skill in the art within the spirit and scope of the present invention shall also fall within the scope of protection of the present invention.

Claims

1. A nanocomposite dielectric film with a laminated structure, characterized in that: A nanocomposite dielectric film with a total thickness of 10 to 14 microns is formed by alternating pressure-bearing layers and polarization layers, wherein the pressure-bearing layer is P(VDF-HFP) filled with Ni(OH)2@PDI nanosheets, and the polarization layer is P(VDF-HFP) filled with Ni(OH)2 nanosheets.

2. The nanocomposite dielectric film with a laminated structure according to claim 1, characterized in that: The added volume percentage of the Ni(OH)2@PDI nanosheets in P(VDF-HFP) is 1.3%, and the added volume percentage of the Ni(OH)2 in P(VDF-HFP) is 2%.

3. The nanocomposite dielectric film with a laminated structure according to claim 2, characterized in that: The pressure-bearing layer and the polarization layer are alternately stacked up and down to form four layers of nanocomposite dielectric films with a total thickness of 10 to 14 microns. The thickness ratio of the pressure-bearing layer to the polarization layer is (6 to 3): (2 to 5).

4. The nanocomposite dielectric film with a laminated structure according to claim 3, characterized in that: The pressure-bearing layers and the polarization layers are alternately stacked up and down to form four layers of nanocomposite dielectric films with a total thickness of 12 microns. The thickness ratio of the pressure-bearing layers to the polarization layers is 5:

3.

5. A method for preparing a nanocomposite dielectric film having a laminated structure according to any one of claims 1 to 4, characterized in that The following steps are involved: Step 1: Prepare Ni(OH)2 nanosheets using a hydrothermal method: Step 2: coating the surface of Ni(OH)2 nanosheets with organic perylene-3,4,8,10-tetracarboxylic dianhydride PDI to obtain core-shell structured Ni(OH)2@PDI nanosheets; Step 3: Electrospinning film formation: (1) Dissolving Ni(OH)2@PDI nanosheets in N,N-dimethylformamide, dispersing by ultrasonication, and then stirring by magnetic force until the mixture is uniform, thereby obtaining a Ni(OH)2@PDI nanosheet solution; (2) dissolving Ni(OH)2 nanosheets in N,N-dimethylformamide, dispersing by ultrasonication, and then stirring by magnetic force until the mixture is uniformly mixed to obtain a Ni(OH)2 nanosheet solution; (3) P(VDF-HFP) was added to the Ni(OH)2@PDI nanosheet solution, stirred at 60°C for 2 h at a magnetic force of 600 r / min, and then stirred at room temperature for 4 h to obtain a pressure-bearing layer solution; (4) P(VDF-HFP) was added to the Ni(OH)2 nanosheet solution, stirred at 600 r / min magnetic force and 60°C for 2 h, and then stirred at room temperature for 4 h to obtain a polarization layer solution; (5) The pressure-bearing layer solution and the polarization layer solution were vacuum treated to remove bubbles, and the pressure-bearing layer and the polarization layer were alternately stacked to form a composite film structure. The film was electrospun at a rate of 1 mm / min in an environment with a temperature of 40 °C and a humidity of 30, and the thickness ratio of the pressure-bearing layer to the polarization layer was controlled by the spinning time. The film was collected on aluminum foil and then placed in an oven at 60 °C for 2 h to remove the residual solvent, thereby obtaining a preliminary nanocomposite dielectric film. Step 4: hot-pressing the preliminary nanocomposite dielectric film prepared in step 3 to obtain a nanocomposite dielectric film with a laminated structure.

6. The method for preparing a laminated nanocomposite dielectric film according to claim 5, characterized in that Step 1 is as follows: 6.5 g NiCl2 and 4 g NaOH are dissolved in 25 ml deionized water respectively, and magnetically stirred at 600 r / min for 30 minutes until completely dissolved. Then, the NiCl2 solution is slowly dripped into the NaOH solution and 80 ml deionized water is added and mixed. After magnetic stirring at 600 r / min for 30 minutes, the mixture is poured into a high-pressure reactor and fully reacted at 200°C for 24 hours. The reaction product is centrifuged and washed several times with deionized water, and then vacuum dried at 60°C for 24 hours, and then ground to obtain light green Ni(OH)2 nanosheets.

7. The method for preparing a laminated nanocomposite dielectric film according to claim 5, characterized in that Step 2 is as follows: 0.3 g Ni(OH)2 nanosheets and 0.02 g PDI were added to 30 ml deionized water in sequence, stirred at 60°C for 12 hours, and dried at 60°C for 12 hours to obtain core-shell structured Ni(OH)2@PDI nanosheets.

8. The method for preparing a laminated nanocomposite dielectric film according to claim 5, characterized in that Step 4 is as follows: the preliminary nanocomposite dielectric film prepared in step 3 is pasted on the conductive surface of the conductive glass, and is hot-pressed in a vacuum vulcanizer at 150°C and a pressure of 15 MPa for 30 minutes. After the hot pressing is completed, the composite dielectric film is placed in an oven at 200°C and kept warm for 10 minutes, and then quickly placed in an ice-water mixture to complete the quenching operation. After cleaning and drying, a nanocomposite dielectric film with a laminated structure is obtained.

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