A stacked high energy storage composite dielectric coupling an enhanced insulating layer and a horizontally oriented polarization layer and a method of making the same

Abstract

This invention discloses a stacked high-energy-storage composite medium consisting of a coupling-enhanced insulating layer and a horizontally oriented polarization layer, and a method for preparing the same. The stacked high-energy-storage composite medium comprises, from top to bottom, a first insulating layer, a polarization intermediate layer, and a second insulating layer. Both the first and second insulating layers are linear thin film layers with a multi-point bonding network structure. The polarization intermediate layer is a horizontally oriented nonlinear thin film layer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite dielectric, and particularly relates to a stacked high-energy storage composite dielectric coupled with an enhanced insulation layer and a horizontal orientation polarization layer and a preparation method thereof. BACKGROUND

[0002] With the rapid development of renewable energy systems, electric vehicles and flexible electronic devices, there is an increasing demand for high-performance thin film capacitors and other energy storage devices. These devices need to have high energy density, high energy storage efficiency and excellent operating stability under extreme conditions such as high temperature (e.g. 120°C) and high electric field.

[0003] Currently, the main polymer dielectric materials are mainly divided into two categories: linear polymers (such as polyetherimide PEI) and nonlinear polymers (such as polyvinylidene fluoride-hexafluoropropylene copolymer P(VDF-HFP)). Linear polymers usually have high breakdown strength (> 400 kV / mm) and low dielectric loss (tanδ < 5×10⁻³), excellent insulation performance, but their relative dielectric constant is relatively low (εᵣ < 4), which limits their energy storage density (usually U d < 5 J / cm³). On the contrary, although the nonlinear ferroelectric polymer has a relatively high dielectric constant (10-15) and polarization capacity, its breakdown strength is relatively low (usually < 400 kV / mm), and the dielectric loss increases significantly at high temperature, and the energy storage efficiency decreases sharply.

[0004] In order to balance the insulation and polarization performance, the multi-layer structure design has become a promising strategy, aiming to combine the advantages of linear insulation layer and nonlinear polarization layer. However, the existing multi-layer thin films generally have a key defect: the band structure matching between the layers is not good. This mismatch promotes the migration of charge carriers between the layers, aggravates the leakage current, and ultimately damages the overall insulation performance and reliability of the device.

[0005] In terms of filler modification, inorganic nano-fillers such as barium titanate (BaTiO3) and titanium dioxide (TiO2) are often added to improve the dielectric constant of the polymer. However, this method usually faces two major challenges: first, the fillers tend to randomly agglomerate in the matrix, forming defects and reducing the breakdown strength; second, the interface between the fillers and the polymer matrix is weak, which is easy to become the starting point of charge traps and breakdown channels, making it difficult to achieve a synergistic improvement in dielectric constant and breakdown strength.

[0006] Metal-organic frameworks (MOFs), particularly zeolite imidazole ester frameworks (ZIF-8), offer a unique platform for optimizing polymer-filler interfaces due to their high specific surface area, tunable pore structure, and abundant Zn²⁺ unsaturated coordination sites. However, current techniques for modifying polymers with ZIF-8 primarily employ simple physical blending methods. This approach fails to fully activate the Zn²⁺ active sites on the ZIF-8 surface, preventing them from forming strong chemical interactions with the polymer matrix. Consequently, it offers limited improvement to the overall properties of the composite material, particularly its breakdown strength.

[0007] On the other hand, high aspect ratio nanofillers (such as titanium dioxide nanotubes, TNTs) have been shown to effectively enhance the polarization intensity of nonlinear polymers. However, TNTs are also prone to random orientation and aggregation in the polymer matrix, forming conductive pathways that severely impair the breakdown strength of the material, making it extremely difficult to simultaneously achieve high polarization and high insulation. Summary of the Invention

[0008] Purpose of the invention: To address the problems existing in the prior art, this invention proposes a stacked high-energy-storage composite dielectric consisting of a coupling-enhanced insulating layer and a horizontally oriented polarization layer, and its preparation method.

[0009] Technical solution: A stacked high-energy-storage composite dielectric consisting of a coupled reinforced insulating layer and a horizontally oriented polarization layer, comprising, from top to bottom, a first insulating layer, a polarization intermediate layer, and a second insulating layer;

[0010] Both the first insulating layer and the second insulating layer are linear thin film layers with a multi-point bonding network structure;

[0011] The polarization intermediate layer is a horizontally oriented nonlinear thin film layer.

[0012] Furthermore, the linear thin film with a multi-point bonded network structure is obtained based on 2-methylimidazolium zinc salt nanoparticles.

[0013] Furthermore, the 2-methylimidazolium zinc salt nanoparticles are obtained by adding the surfactant cetyltrimethylammonium bromide as a coating agent to an aqueous system to regulate the morphology and size of the 2-methylimidazolium zinc salt crystals.

[0014] Furthermore, the horizontally oriented nonlinear film is obtained by spinning a PT suspension; the PT suspension is based on titanium dioxide nanotubes, N,N-dimethylformamide and polyvinylidene fluoride-hexafluoropropylene particles.

[0015] This invention proposes a method for preparing a multilayer high-energy-storage composite medium, comprising the following steps:

[0016] By adding the surfactant cetyltrimethylammonium bromide as a coating agent to an aqueous system, the morphology and size of 2-methylimidazolium zinc salt crystals were controlled to obtain 2-methylimidazolium zinc salt nanoparticles.

[0017] Based on the 2-methylimidazolium zinc salt nanoparticles, a linear thin film with a multi-point bonded network structure was prepared.

[0018] A PT suspension was obtained based on titanium dioxide nanotubes, N,N-dimethylformamide, and polyvinylidene fluoride-hexafluoropropylene particles; the PT suspension was then spun to obtain a horizontally oriented nonlinear film.

[0019] By placing linear thin films on the top and bottom layers and using horizontally oriented nonlinear thin films as the middle layer, a stacked high-energy-storage composite medium is obtained through hot pressing.

[0020] Furthermore, step 1 specifically includes:

[0021] S100: Dissolve 600-620 mg of zinc acetate dihydrate in 10-15 mL of deionized water to obtain a zinc acetate dihydrate solution. Dissolve 2.70-2.74 mol / L of 2-methylimidazole and 0.52-0.56 mmol / L of hexadecyltrimethylammonium bromide in 10-15 mL of deionized water to obtain a mixture. Add the zinc acetate dihydrate solution to the mixture and stir until the mixture changes from transparent to white to obtain a white mixture.

[0022] S110: Let the white mixture stand at room temperature for 2-3 hours to obtain 2-methylimidazolium zinc salt nanoparticles;

[0023] S120: 2-methylimidazolium zinc salt nanoparticles were washed with deionized water to obtain wet 2-methylimidazolium zinc salt particles;

[0024] S130: The wet 2-methylimidazolium zinc salt particles are dried to obtain the final 2-methylimidazolium zinc salt nanoparticles.

[0025] Furthermore, step 2 specifically includes:

[0026] S200: Dissolve 0.5wt%~5wt% of 2-methylimidazolium zinc salt nanoparticles in 40~50 mL of N,N-dimethylacetamide solution;

[0027] S210: Powdered 4,4'-diaminodiphenyl ether is added to the N,N-dimethylacetamide solution and mixed thoroughly. Then, 4,4'-isopropyldiphenoxydiphthalic anhydride is added in batches to the above mixture and mixed thoroughly to obtain a polyamic acid / 2-methylimidazolium zinc salt precursor. The molar ratio of 4,4'-isopropyldiphenoxydiphthalic anhydride to 4,4'-diaminodiphenyl ether is 1.01:1.

[0028] S220: Curing the polyamic acid / 2-methylimidazolium zinc salt precursor, gradually heating the cured polyamic acid / 2-methylimidazolium zinc salt precursor to 100, 150, 200 and 250 ℃, holding at each temperature for 1~2 hours to complete the imidization reaction, and finally obtaining a horizontally oriented nonlinear thin film layer.

[0029] Furthermore, step 3 specifically includes:

[0030] S300: Add 1wt%~10wt% of titanium dioxide nanotubes to 10~12mL of N,N-dimethylformamide and disperse by ultrasonication to obtain a uniform titanium dioxide nanotube / N,N-dimethylformamide solution.

[0031] S310: Add 1.0~1.2g of polyvinylidene fluoride-hexafluoropropylene particles to a uniform titanium dioxide nanotube / N,N-dimethylformamide solution, and stir until the polyvinylidene fluoride-hexafluoropropylene particles are completely dissolved to obtain a PT suspension;

[0032] S320: Use PT suspension as a precursor for electrospinning, then completely dry the PT wet film obtained by electrospinning to obtain a PT film; then subject the PT film to hot pressing and cooling in sequence to obtain a horizontally oriented PT composite film.

[0033] Beneficial Effects: Compared with existing technologies, the composite medium proposed in this invention features a linear composite film with a metal-organic framework (MOF)-induced internal bonding network as the insulating (L) layer, while a horizontally oriented nonlinear (PT) composite film prepared by electrospinning serves as the polarization (N) intermediate layer. The resulting EZ-PT-EZ LNL film exhibits excellent overall performance, particularly in energy storage. For example, at room temperature, when the voltage is 620 kV mm... -1 At that time, the EZ1-PT1-EZ1 thin film achieved a high J / cm² intensity of 13.67 J / cm². -3 Discharge energy density (U dThe energy storage efficiency (η) is approximately 85%. The multi-site bonding network in the EZ layer effectively restricts the mobility of polyethyleneimine (PEI) molecular chains under high temperature and electric field, thereby widening the band gap of the insulating layer and improving its intrinsic breakdown strength. This, in turn, increases the energy barrier for charge injection at the electrodes and enhances the overall breakdown strength of the EZ-PT-EZ film. Furthermore, the horizontally oriented PT composite layer provides high polarization capability while mitigating breakdown strength degradation. The band gap alignment difference between the L and N layers forms a heterojunction-like interface where the built-in electric field is opposite to the applied electric field, further suppressing charge carrier transport. These synergistic effects enable the EZ-PT-EZ LNL dielectric film to simultaneously achieve high breakdown strength and high polarization capability, fundamentally explaining its excellent energy storage properties. This invention provides valuable insights into the interfacial interactions between MOFs and polymer matrices and offers an effective pathway for designing high-performance energy storage materials. Attached Figure Description

[0034] Figure 1 A schematic diagram of the preparation process of 2-methylimidazolium zinc salt (ZIF-8) nanoparticles;

[0035] Figure 2 A schematic diagram for preparing an EZ insulating layer film with a multi-point bonding network structure;

[0036] Figure 3 Schematic diagram of the preparation of horizontally oriented PT polarized layer thin films by electrospinning;

[0037] Figure 4 This is a flowchart illustrating the fabrication of EZ-PT-EZLNL structured energy storage dielectric films using hot pressing technology;

[0038] Figure 5 EZ-PT-EZ LNL structural model and cross-sectional morphology;

[0039] Figure 6 XRD spectra of pure PEI, pure P (VDF-HFP), and EZ1-PT-EZ1;

[0040] Figure 7 Schematic diagram of dielectric properties of pure PEI, pure P (VDF-HFP), and EZ1-PT-EZ1;

[0041] Figure 8 This is a schematic diagram of the breakdown field strength Weibull distribution of pure PEI, pure P (VDF-HFP), and EZ1-PT-EZ1 sandwich composite films of each component;

[0042] Figure 9 This is a schematic diagram of the room temperature energy storage performance of pure PEI, P(VDF-HFP) and EZ1-PT-EZ1. Detailed Implementation

[0043] The technical solution of the present invention will now be further described in conjunction with the accompanying drawings and embodiments.

[0044] This invention provides a method for preparing a stacked high-energy-storage composite dielectric consisting of a coupling-enhanced insulating layer and a horizontally oriented polarization layer, mainly comprising the following steps:

[0045] Step 1: Add cetyltrimethylammonium bromide (CTAB) as a coating agent to an aqueous system to precisely control the morphology and size of 2-methylimidazolium zinc salt (ZIF-8) crystals, thereby obtaining 2-methylimidazolium zinc salt (ZIF-8) nanoparticles with uniform morphology and size. Figure 1 The preparation process of 2-methylimidazolium zinc salt (ZIF-8) nanoparticles is shown. Figure 1 In this context, CTAB represents hexadecyltrimethylammonium bromide; 2-MiM represents 2-methylimidazole; Zn 2+ solution represents Zn 2+ Solution; Let stand for 2-3 hours; Evaporation of the solvent; ZIF-8 nanoparticles. See also: 2-methylimidazolium zinc salt nanoparticles. Figure 1 The specific preparation steps include:

[0046] S100: Add zinc acetate dihydrate (600-620 mg) dissolved in 10-15 mL of deionized water (DI) to a mixed solution of 2-methylimidazole (2-MiM) (2.70-2.74 mol / L) and hexadecyltrimethylammonium bromide (CTAB) (0.52-0.56 mmol / L) dissolved in 10-15 mL of deionized water (DI), and stir gently for 30-35 seconds until the mixture changes from transparent to white.

[0047] S110: The resulting white mixture was left to stand at room temperature for 2-3 hours to obtain 2-methylimidazolium zinc salt (ZIF-8) nanoparticles;

[0048] S120: The obtained 2-methylimidazolium zinc salt (ZIF-8) nanoparticles were transferred to a 100 mL centrifuge tube and washed with deionized water (DI) 2-3 times at a speed of 9000 rpm to obtain wet 2-methylimidazolium zinc salt (ZIF-8) particles.

[0049] S130: Collect wet 2-methylimidazolium zinc salt (ZIF-8) particles and dry them in a vacuum drying oven at 60 ℃ for 8~10 hours for later use.

[0050] Step 2: Based on 2-methylimidazolium zinc salt (ZIF-8) nanoparticles, prepare an EZ insulating layer film with a multi-point bonded network structure. For example... Figure 2 As shown, ODA represents 4,4'-diaminodiphenyl ether; ZIF-8 represents 2-methylimidazolium zinc salt; BPADA represents 4,4'-isopropyldiphenoxydiphthalic anhydride; Precursor PAA represents precursor polyamic acid; and EZ linearinsulating layer represents EZ linear insulating layer. The specific preparation steps include:

[0051] S200: Dissolve the corresponding mass fractions (0.5wt%, 1wt%, 3wt%, 5wt%) of 2-methylimidazolium zinc salt (ZIF-8) in 40-50 mL of N,N-dimethylacetamide (DMAc) solution.

[0052] S210: Add 2.8~3.2 g of 4,4'-diaminodiphenyl ether (ODA) ground into powder to the N,N-dimethylacetamide (DMAc) solution obtained in S200, and sonicate for 1~2 hours; then divide 7.6~8.0 g of 4,4'-isopropyldiphenoxydiphthalic anhydride (BPADA) into 4 portions, add them in batches to the N,N-dimethylacetamide (DMAc) suspension, and stir continuously for 4~5 hours until fully mixed. The molar ratio of 4,4'-isopropyldiphenoxydiphthalic anhydride (BPADA) to 4,4'-diaminodiphenyl ether (ODA) is 1.01:1 to obtain the polyamic acid / 2-methylimidazolium zinc salt (PAA / ZIF-8) precursor;

[0053] S220: The polyamic acid / 2-methylimidazolium zinc salt (PAA / ZIF-8) precursor is coated onto a glass substrate using an adjustable coating tool and heated at 80 °C overnight to obtain the cured polyamic acid / 2-methylimidazolium zinc salt (PAA / ZIF-8) precursor;

[0054] S230: The cured polyamic acid / 2-methylimidazolium zinc salt (PAA / ZIF-8) precursor is gradually heated to 100, 150, 200 and 250 °C, and held at each temperature for 1 to 2 hours to complete the imidization reaction, finally obtaining an EZ composite film with a thickness of about 5 to 6 μm.

[0055] Step 3: Prepare PT composite electrospinning precursors with different mass fractions by melt blending. Specific preparation steps include:

[0056] S300: Weigh 1wt%~10wt% of titanium dioxide nanotubes and add them to 10~12mL of N,N-dimethylformamide. Disperse the mixture by ultrasonication for 30~35 minutes.

[0057] S310: Preheat a uniform titanium dioxide nanotube / N,N-dimethylformamide solution at 70 °C for 30-35 minutes, add 1.0-1.2g of polyvinylidene fluoride-hexafluoropropylene particles, and stir at 70 °C for 4-5 hours until the polyvinylidene fluoride-hexafluoropropylene particles are completely dissolved.

[0058] S320: The resulting uniform PT suspensions with different mass fractions (1, 3, 5 and 10 wt%) (denoted as PT1, PT3, PT5 and PT10, respectively) were used as electrospinning precursors.

[0059] Step 4: Spin the PT suspension to obtain a horizontally oriented PT polarization layer film. For example... Figure 3 As shown, P(VDF-HFP)TNTs in dmf indicates the addition of polyvinylidene fluoride-hexafluoropropylene particles / titanium oxide nanotubes to N,N-dimethylformamide; Gigh-speed electrospinning indicates high-speed electrospinning; and PT nonlinear polarization layer indicates a PT nonlinear polarization layer. Specific operations include:

[0060] S400: The PT precursor is drawn into the syringe and fixed on the push rod. The ±6 kV voltage source is turned on for spinning. The electrospinning electric field strength is 1.5 kV / cm, and the push rod advance speed is 0.08 mm / min. The set thickness is achieved by controlling the spinning time.

[0061] S410: The PT wet film obtained by electrospinning is transferred to an 80℃ oven and dried for 10-12 hours, and then transferred to a 120℃ vacuum oven and dried for 2-3 hours; the completely dried PT film is hot-pressed at 15MPa pressure and 180℃ for 12-15 minutes, and then cooled by a water cooling device to obtain a horizontally oriented PT composite film.

[0062] Step 5: To obtain a stable and dense EZ-PT-EZ energy storage film, the corresponding functional layers need to be stacked and hot-pressed. For example... Figure 4 As shown, "Hot pressing" indicates hot pressing, and "EZ-PT-EZ energy storage dielectric film" indicates an EZ-PT-EZ energy storage dielectric film; High E b Indicates high breakdown strength (E) b High Polarization D m -D r Indicates high polarization intensity D m -D rSpecifically, the EZ linear composite film is placed in the upper and lower layers. As an insulating and heat-resistant layer, the middle layer uses a PT nonlinear composite film to provide high polarization intensity, while a reinforced linear-nonlinear-linear (LNL) structure is adopted. The EZ-PT-EZ energy storage film was prepared by hot pressing at 200℃ and 15MPa for 15 minutes.

[0063] Zinc acetate dihydrate (Zn(CH3COO)2·2H2O), 2-methylimidazole (2-MiM, C4H6N2), hexadecyltrimethylammonium bromide (CTAB, C19H42BrN), 4,4'-(4,4'-isopropylidenediphenoxy)phthalic anhydride (BPADA), and P(VDF-HFP) particles used in the above steps were purchased from Sigma-Aldrich. 4,4'-Diphenylamine oxide (ODA) was provided by Sinopharm Chemical Reagent Co., Ltd. Titanium oxide nanotubes (TNTs) were purchased from Beijing Decode Aojin Technology Co., Ltd., and prepared using a hydrothermal method. N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and anhydrous ethanol were provided by Tianjin Fuyu Fine Chemical Co., Ltd. All chemical reagents were of analytical grade and used directly without further purification.

[0064] Figure 5 The structural model and cross-sectional morphology of EZ-PT-EZ LNL are shown, where Linear insulating layer represents linear insulating layer; Nonlinear insulating layer represents nonlinear insulating layer. Figure 5 Image (a) shows a conceptual model of the EZ-PT-EZ composite film and a cross-sectional SEM image of the corresponding functional layer. The cross-section of the EZ-PT-EZ composite film is flat and dense, with a clear layer structure, good interlayer structure, and no obvious defects. The overall thickness of the film is approximately 20 μm. Furthermore, some exposed, oriented TNTs can be seen in the middle PT layer. Figure 5 (b) shows the element mapping image, which shows that the Zn element in the EZ insulating layer is uniformly distributed in the top and bottom layers, and the Ti element in the PT polarization layer is uniformly distributed in the middle layer.

[0065] The XRD pattern of the EZ1-PT-EZ1 sandwich composite film is as follows: Figure 6 As shown in the figure, amorphous diffuse scattering represents amorphous diffuse scattering. For example... Figure 6 As shown, the diffuse scattering peak at 2θ = 20° originates from the disordered arrangement of the amorphous polymer PEI molecular chains and the amorphous region of the semi-crystalline polymer P(VDF-HFP). The diffraction peaks near 2θ = 18°, 19°, and 26° correspond to the α, β, and γ phases in P(VDF-HFP), respectively.

[0066] Similar to the PI.ZIF-8 composite film, no characteristic diffraction peaks of ZIF-8 were observed in the EZ1-PT-EZ1 composite film. No obvious characteristic diffraction peaks of the (101) and (200) crystal planes of TNTs were found in the XRD patterns of all components of the EZ1-PT-EZ1 composite film. The reasons are as follows: First, the TNTs prepared by the hydrothermal method have weak crystallinity, resulting in a small mass fraction doped into the PEI matrix, leading to insignificant crystallization in the matrix; second, the positions of the characteristic diffraction peaks of TNTs overlap with those of P(VDF-HFP), potentially being masked by the latter; finally, TNTs form a large number of pendant groups in the P(VDF-HFP) matrix, further reducing its crystallinity and causing the crystallization peaks to disappear.

[0067] The dielectric properties of EZ1-PT-EZ1 thin films are shown in [reference needed]. Figure 7 As shown. Frequency represents frequency, dielectric constant represents dielectric constant, dielectric loss tangent represents dielectric loss tangent, and AC conductivity represents alternating current conductivity. Figure 7 In Figure (a), the dielectric constant and dielectric loss of EZ1-PT-EZ1 depend on frequency. It can be seen that the EZ1-PT-EZ1 composite film has a higher dielectric constant (i.e., higher polarization intensity) compared with the linear polymer PEI. As the TNT content in the PT polarization layer increases from 0 wt% to 5 wt%, the dielectric constant of EZ1-PT-EZ1 increases from 3.30 to 8.58.

[0068] Compared to the nonlinear polymer P(VDF-HFP), the EZ1-PT-EZ1 composite film exhibits higher dielectric stability. The dielectric loss of the EZ1-PT-EZ1 composite film remains at a low level, almost an order of magnitude lower than that of P(VDF-HFP) in the low-frequency range, and even slightly lower than that of PEI. Similarly, in the low-frequency range, the AC conductivity of the EZ1-PT-EZ1 film is significantly lower than that of P(VDF-HFP), and the conductivity of some samples is even lower than that of linear PEI (e.g., ...). Figure 7 As shown in (b)). At 102 Hz, the dielectric constant, dielectric loss, and conductivity of each sample were statistically analyzed. Figure 7 In (c), it is evident that the EZ1-PT-EZ1 LNL film combines the advantages of linear and nonlinear polymers, possessing a higher dielectric constant (compared to PEI) and lower dielectric loss and conductivity (compared to P(VDF-HFP)).

[0069] Figure 8 The Weibull distributions of breakdown field strengths are shown for pure PEI, pure P (VDF-HFP), and EZ1-PT-EZ1 sandwich composite films of various components. Probability of breakdown represents the failure probability, and breakdown strength represents the breakdown intensity. Figure 8 As shown, with the increase of TNT content, the ET of the ET of the ET film increases. b The value gradually decreases. At TNT loads of 1% and 3% (weight percentage), the Eb values ​​of EZ1-PT1-EZ1 and EZ1-PT3-EZ1 reach 631.93 kV mm, respectively. -1 and 601.93kV mm -1 Compared to PEI (446.62 kV mm) -1 ), respectively compared to the value of P(VDF - HFP) (346.16 kV mm) -1 The E2 content of the EZ1-PT-EZ1 film is 82.6% and 73.9% higher than that of the others. b The value is attributed to the following factors: (1) ZIF-induced multi-site bonding network significantly enhances the electrical boundary (EZ) of the EZ insulating layer. b (1) It suppresses carrier injection at the electrode; (2) The mesoscopic interface in the LNL structure effectively hinders charge propagation; (3) The low content of horizontally oriented TNT helps to delay the expansion of the breakdown channel. However, when the TNT content increases to 5 wt%, the high aspect ratio nanotubes inevitably form aggregates, leading to structural defects, thereby reducing the E of EZ1-PT5-EZ1. b value.

[0070] Figure 9 The room-temperature energy storage performance of pure PEI, P(VDF-HFP), and EZ1-PT-EZ1 is shown. DE loop under critical electric field represents the DE loop under the critical electric field, Electric field represents the electric field, Electric displacement represents the electric displacement, Nonlinear represents nonlinearity, High polarization represents high polarization, LNL structure represents the LNL structure, and Linear represents linear high E b Indicates high E b . Figure 9(a) summarizes the DE loops of PEI, EZ1-PT-EZ1 LNL composite films and P(VDF-HFP) at the critical breakdown field. The DE loop distribution of the EZ1-PT-EZ1 LNL composite film is between linear PEI and nonlinear P(VDF-HFP), balancing high polarization and high E. b The charging energy density (U / μm) of pure PEI, EZ1-PT-EZ1 LNL sandwich composite films and pure P(VDF-HFP) films. s Discharge energy density (U) d The energy storage efficiency (η) and the energy storage efficiency (η) are obtained analytically from the DE hysteresis loop and are presented respectively in Figure 9 (b) Figure 9 (c) and Figure 9 (d) is shown in the figure. Under a low electric field (≤ 320 kV / mm), the U of P(VDF-HFP) s and U d The highest values ​​were 11.97 and 6.18 J / cm³, respectively. 3 This is due to the high polarization intensity of nonlinear polymers. However, it is limited by the low E0 of nonlinear polymers. b P(VDF-HFP) cannot operate at higher electric fields. Conversely, while PEI can operate at higher electric fields, its low polarization due to its linear polymer structure leads to a decrease in U0. s and U d The lowest, at only 5.23 and 4.79 J / cm. 3 Protected by the EZ insulating layer, the EZ1-PT-EZ1 composite film can be charged and discharged under an electric field of approximately 600 kV / mm, and the horizontally oriented PT polarization layer improves polarization without significantly degrading the EZ1. b For example, at room temperature and 620 kV / mm, the UT of the EZ1-PT1-EZ1 composite film... s and U d Up to 16.25 and 13.67 J / cm 3 The EZ1-PT3-EZ1 composite film exhibited the best energy storage density among all samples; with a slight increase in TNT content, the U0 of the EZ1-PT3-EZ1 composite film at 580 kV / mm at room temperature was [missing information]. s and U d Up to 15.37 and 13.15 J / cm 3 .

Claims

1. A stacked high-energy-storage composite dielectric consisting of a coupling-enhanced insulating layer and a horizontally oriented polarization layer, characterized in that: From top to bottom, it includes a first insulating layer, a polarization intermediate layer, and a second insulating layer; Both the first insulating layer and the second insulating layer are linear thin film layers with a multi-point bonding network structure; The polarization intermediate layer is a horizontally oriented nonlinear thin film layer.

2. The stacked high-energy-storage composite dielectric of a coupling-enhanced insulating layer and a horizontally oriented polarization layer according to claim 1, characterized in that: The linear thin film with a multi-point bonded network structure is obtained based on 2-methylimidazolium zinc salt nanoparticles.

3. The stacked high-energy-storage composite dielectric of a coupling-enhanced insulating layer and a horizontally oriented polarization layer according to claim 2, characterized in that: The 2-methylimidazolium zinc salt nanoparticles were obtained by adding the surfactant cetyltrimethylammonium bromide as a coating agent to an aqueous system to regulate the morphology and size of the 2-methylimidazolium zinc salt crystals.

4. The stacked high-energy-storage composite dielectric of a coupling-enhanced insulating layer and a horizontally oriented polarization layer according to claim 1, characterized in that: The horizontally oriented nonlinear film is obtained by spinning a PT suspension; the PT suspension is based on titanium dioxide nanotubes, N,N-dimethylformamide and polyvinylidene fluoride-hexafluoropropylene particles.

5. A method for preparing a multilayer high-energy-storage composite medium, characterized in that: Includes the following steps: By adding the surfactant cetyltrimethylammonium bromide as a coating agent to an aqueous system, the morphology and size of 2-methylimidazolium zinc salt crystals were controlled to obtain 2-methylimidazolium zinc salt nanoparticles. Based on the 2-methylimidazolium zinc salt nanoparticles, a linear thin film with a multi-point bonded network structure was prepared. A PT suspension was obtained based on titanium dioxide nanotubes, N,N-dimethylformamide and polyvinylidene fluoride-hexafluoropropylene particles; The PT suspension is spun to obtain a horizontally oriented nonlinear thin film; By placing linear thin films on the top and bottom layers and using horizontally oriented nonlinear thin films as the middle layer, a stacked high-energy-storage composite medium is obtained through hot pressing.

6. The method for preparing a multilayer high-energy-storage composite medium according to claim 5, characterized in that: Step 1 specifically includes: S100: Dissolve 600-620 mg of zinc acetate dihydrate in 10-15 mL of deionized water to obtain a zinc acetate dihydrate solution. Dissolve 2.70-2.74 mol / L of 2-methylimidazole and 0.52-0.56 mmol / L of hexadecyltrimethylammonium bromide in 10-15 mL of deionized water to obtain a mixture. Add the zinc acetate dihydrate solution to the mixture and stir until the mixture changes from transparent to white to obtain a white mixture. S110: Let the white mixture stand at room temperature for 2-3 hours to obtain 2-methylimidazolium zinc salt nanoparticles; S120: 2-methylimidazolium zinc salt nanoparticles were washed with deionized water to obtain wet 2-methylimidazolium zinc salt particles; S130: The wet 2-methylimidazolium zinc salt particles are dried to obtain the final 2-methylimidazolium zinc salt nanoparticles.

7. The method for preparing a multilayer high-energy-storage composite medium according to claim 5, characterized in that: Step 2 specifically includes: S200: Dissolve 0.5wt%~5wt% of 2-methylimidazolium zinc salt nanoparticles in 40~50 mL of N,N-dimethylacetamide solution; S210: Powdered 4,4'-diaminodiphenyl ether is added to the N,N-dimethylacetamide solution and mixed thoroughly. Then, 4,4'-isopropyldiphenoxydiphthalic anhydride is added in batches to the above mixture and mixed thoroughly to obtain a polyamic acid / 2-methylimidazolium zinc salt precursor. The molar ratio of 4,4'-isopropyldiphenoxydiphthalic anhydride to 4,4'-diaminodiphenyl ether is 1.01:

1. S220: Curing the polyamic acid / 2-methylimidazolium zinc salt precursor, gradually heating the cured polyamic acid / 2-methylimidazolium zinc salt precursor to 100, 150, 200 and 250 ℃, holding at each temperature for 1~2 hours to complete the imidization reaction, and finally obtaining a horizontally oriented nonlinear thin film layer.

8. The method for preparing a multilayer high-energy-storage composite medium according to claim 5, characterized in that: Step 3 specifically includes: S300: Add 1wt%~10wt% of titanium dioxide nanotubes to 10~12mL of N,N-dimethylformamide and disperse by ultrasonication to obtain a uniform titanium dioxide nanotube / N,N-dimethylformamide solution. S310: Add 1.0~1.2g of polyvinylidene fluoride-hexafluoropropylene particles to a uniform titanium dioxide nanotube / N,N-dimethylformamide solution, and stir until the polyvinylidene fluoride-hexafluoropropylene particles are completely dissolved to obtain a PT suspension; S320: Use PT suspension as a precursor for electrospinning, then completely dry the PT wet film obtained by electrospinning to obtain a PT film; then subject the PT film to hot pressing and cooling in sequence to obtain a horizontally oriented PT composite film.

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