Blended crosslinked polymer films for capacitor energy storage and methods of making the same

Abstract

Disclosed are a blended crosslinked polymer film for capacitor energy storage and a preparation method thereof, and a preparation solution, wherein a predetermined proportion of polyvinylidene fluoride solution and polymethyl methacrylate solution are weighed and placed into a reaction container, 3 wt% of 1,6-hexanediamine crosslinking agent based on the total weight of the polyvinylidene fluoride solution and the polymethyl methacrylate solution is added into the reaction container, the reaction container is placed in a room temperature environment and stirred to obtain a homogeneous pre-crosslinked solution; low-temperature film forming, after the pre-crosslinked solution is placed in a vacuum oven and vacuumized at room temperature to remove bubbles in the pre-crosslinked solution, the pre-crosslinked solution is heated in the vacuum oven by a flow casting method to prepare a blended polymer film; high-temperature crosslinking, the blended polymer film is placed in an oven to perform a crosslinking reaction of polyvinylidene fluoride and polymethyl methacrylate, and a blended crosslinked polymer film is obtained after the reaction. The glass transition temperature and the maximum electric field strength at high temperature are improved to achieve higher energy storage density and better charging and discharging efficiency at a higher temperature.

Description

Technical Field

[0001] This invention relates to the field of polymer energy storage medium technology, and in particular to a blended crosslinked polymer film for capacitor energy storage and its preparation method. Background Technology

[0002] Dielectric capacitors are widely used in high-voltage direct current (HVDC) transmission systems, electric vehicles, and pulsed power systems due to their fast charging and discharging speeds, low manufacturing costs, high reliability, and good operational safety. The performance of a dielectric capacitor depends on the properties of its dielectric material. Many materials, including ceramics, mica, paper, electrolytes, and synthetic polymers, have been used to manufacture dielectric capacitors. Among these, polymer materials are the most widely used due to their good electrical properties, low cost, excellent processability, and high flexibility. However, traditional polymers such as polypropylene have low dielectric constants and low thermal distortion temperatures, resulting in low energy storage density and low operating temperatures, making them unsuitable for smart grids and electric vehicles. With societal development, the demand for high-temperature energy storage capacitors is increasing. Therefore, current research on polymer energy storage materials mainly focuses on improving the energy storage density and temperature stability of the materials. If the energy storage density of the capacitor is too low, it will occupy too much space and significantly increase costs; if the energy storage density is increased, since energy storage density is mainly determined by the dielectric constant and breakdown strength of the material, improving the energy storage performance of polymers will lead to a decrease in efficiency and a reduction in temperature stability, seriously affecting the use of polymer energy storage materials at high temperatures. Therefore, balancing the energy storage performance and temperature stability of materials has become a major research direction.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a blended crosslinked polymer film for capacitor energy storage and its preparation method. By blending and crosslinking, a blended crosslinked material of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA) with high glass transition temperature is obtained, thereby achieving high energy storage performance temperature stability and high efficiency temperature stability of the all-organic energy storage polymer.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The present invention provides a method for preparing a blended crosslinked polymer film for capacitor energy storage, comprising,

[0007] To prepare a solution, weigh and mix polyvinylidene fluoride powder and dimethylformamide solution, and stir to obtain a polyvinylidene fluoride solution with a mass fraction of 10 wt%. Weigh and mix polymethyl methacrylate powder and dimethylformamide solution, and stir to obtain a polymethyl methacrylate solution with a mass fraction of 10 wt%. Weigh a predetermined proportion of polyvinylidene fluoride solution and polymethyl methacrylate solution and place them into a reaction vessel. Add 3 wt% of the total weight of the polyvinylidene fluoride solution and polymethyl methacrylate solution as a 1,6-hexanediamine crosslinking agent to the reaction vessel. Place the reaction vessel at room temperature and stir to obtain a homogeneous pre-crosslinked solution.

[0008] Low-temperature film formation: After the pre-crosslinked solution is placed in a vacuum oven and vacuumed at room temperature to remove air bubbles, the pre-crosslinked solution is heated at 60°C for 1 hour in a vacuum oven by casting to prepare a blended polymer film.

[0009] High-temperature crosslinking: The blended polymer film is placed in an oven and subjected to a crosslinking reaction of polyvinylidene fluoride and polymethyl methacrylate at 180°C for 1 hour, resulting in a blended crosslinked polymer film.

[0010] In the method for preparing a blended crosslinked polymer film for capacitor energy storage, the predetermined ratio is 4:6.

[0011] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, 3 wt% of 1,6-hexanediamine crosslinking agent (total weight of polyvinylidene fluoride solution and polymethyl methacrylate solution) is added to the reaction vessel and stirred evenly at room temperature.

[0012] In the method for preparing a blended crosslinked polymer film for capacitor energy storage, the pre-crosslinked solution is placed in a vacuum oven and vacuumed at room temperature for 1 hour to remove air bubbles from the pre-crosslinked solution.

[0013] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, the pre-crosslinked solution, which is uniformly mixed and degassed in the reactor, is uniformly spread on a quartz glass substrate by casting, and then treated in a vacuum oven at 60°C for 1 hour to remove the solvent and obtain the blended film.

[0014] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, the blended film sample obtained at 60°C in a vacuum oven is transferred to an oven at 180°C for high-temperature crosslinking for 1 hour to obtain the blended crosslinked polymer film.

[0015] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, the blended crosslinked polymer film is heated at 200°C for 15 minutes and then placed in ice water for quenching treatment.

[0016] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, the blended crosslinked polymer film is peeled off from the substrate in deionized water and then dried in an oven at 60°C for 24 hours.

[0017] A blended crosslinked polymer film for capacitor energy storage is prepared by the method described above.

[0018] In the blended crosslinked polymer film, the energy storage density of the blended crosslinked polymer film is 10.4 J / cm² in the temperature range of 30℃-90℃. 3 -11.9J / cm 3 The charge / discharge efficiency is 78.3%-88.5%.

[0019] In the above technical solution, the present invention provides a method for preparing a blended crosslinked polymer film for capacitor energy storage, which has the following beneficial effects: The present invention uses a blended crosslinking method to improve the temperature stability of the material. First, PVDF and PMMA, which has good compatibility with PVDF, are selected as two blended materials. In addition, since the crosslinking method can form a crosslinked network structure between polymers, thereby significantly improving the temperature stability of the material, the crosslinked network structure can also be used to improve the compatibility of the two substances. 1,6-hexanediamine, a crosslinking agent that can crosslink both PVDF and PMMA, is selected to achieve blended crosslinking between PVDF and PMMA. Since the breakdown performance of the material is related to the impurity content in the material, the effect of different crosslinking agent contents on the breakdown performance of the blended crosslinked material is tested to obtain the optimal crosslinking agent content. At the same time, the optimal ratio and process for achieving good temperature stability are explored by measuring the temperature-dependent energy storage performance of samples obtained with different blended crosslinking ratios. When the PMMA content is 60%, the energy storage density of the PVDF / PMMA blended crosslinked material is stable at 10.4 J / cm² in the range of 30℃-90℃. 3 -11.9J / cm 3 The charge / discharge efficiency remained stable at 78.3%-88.5%; although the electric field strength decreased to 400kV / mm when the temperature rose to 110℃, the energy storage density still reached 8.5J / cm³. 3 Its charge-discharge efficiency can reach 71.1%, which is far superior to pure PVDF and higher than most similar ferroelectric polymer dielectrics. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0021] Figure 1 This is a schematic diagram illustrating the principle of the crosslinking reaction between PVDF and PMMA using 1,6-hexanediamine, as an embodiment of a method for preparing a blended crosslinked polymer film for capacitor energy storage.

[0022] Figure 2 This is a schematic SEM-EDX image of a blended crosslinked polymer film, one embodiment of a method for preparing a blended crosslinked polymer film for capacitor energy storage.

[0023] Figure 3 This is a DSC curve of materials with different blending and crosslinking ratios in one embodiment of a method for preparing a blended crosslinked polymer film for capacitor energy storage;

[0024] Figure 4 This is an example of a method for preparing a cross-linked polymer film for capacitor energy storage, showing the energy storage density versus efficiency curves of a cross-linked PVDF / PMMA (40 / 60) film at varying temperatures.

[0025] Figure 5 This is a comparison chart of the energy storage density of cross-linked polymer blends with different proportions at an electric field strength of approximately 340-350 kV / mm, used for capacitor energy storage.

[0026] Figure 6 This is a comparison graph showing the efficiency of cross-linked polymer blends with different proportions as a function of temperature, based on an electric field strength of approximately 340-350 kV / mm. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the appendices of the embodiments of the present invention will be described below. Figures 1 to 6 The technical solutions in the embodiments of this invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0032] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0035] like Figures 1 to 6 As shown, a method for preparing a blended crosslinked polymer film for capacitor energy storage includes:

[0036] In the method for preparing a blended crosslinked polymer film for capacitor energy storage, the predetermined ratio is 4:6.

[0037] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, 3 wt% of 1,6-hexanediamine crosslinking agent (total weight of polyvinylidene fluoride solution and polymethyl methacrylate solution) is added to the reaction vessel and stirred evenly at room temperature.

[0038] In the method for preparing a blended crosslinked polymer film for capacitor energy storage, the pre-crosslinked solution is placed in a vacuum oven and vacuumed at room temperature for 1 hour to remove air bubbles from the pre-crosslinked solution.

[0039] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, the pre-crosslinked solution, which is uniformly mixed and degassed in the reactor, is uniformly spread on a quartz glass substrate by casting, and then treated in a vacuum oven at 60°C for 1 hour to remove the solvent and obtain the blended film.

[0040] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, the blended film sample obtained at 60°C in a vacuum oven is transferred to an oven at 180°C for high-temperature crosslinking for 1 hour to obtain the blended crosslinked polymer film.

[0041] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, the blended crosslinked polymer film is heated at 200°C for 15 minutes and then placed in ice water for quenching treatment.

[0042] In the preparation method of the blended crosslinked polymer film for capacitor energy storage, the blended crosslinked polymer film is peeled off from the substrate in deionized water and then dried in an oven at 60°C for 24 hours.

[0043] In one embodiment, PVDF and PMMA are mixed in solution and then crosslinked using the crosslinking agent 1,6-hexanediamine to form a uniformly distributed blended crosslinked material, improving the temperature stability of energy storage density and efficiency. The preparation method includes solution blending, low-temperature casting, and high-temperature crosslinking, resulting in a blended crosslinked polymer medium with both high energy storage density and high temperature stability. The energy storage density remains stable at 10.4 J / cm² within the temperature range of 30°C to 90°C. 3 -11.9J / cm 3 The charge / discharge efficiency remained stable at 78.3%-88.5%; although the maximum electric field strength decreased to 400 kV / mm when the temperature rose to 110℃, the energy storage density could still reach 8.5 J / cm³. 3 The charge / discharge efficiency can reach 71.1%. The main feature of this invention is that it improves the glass transition temperature of PVDF and PMMA and the maximum electric field strength at high temperatures through a blending and crosslinking method, thereby achieving higher energy storage density and better charge / discharge efficiency at higher temperatures. It is mainly applied in fields such as capacitor energy storage.

[0044] In one embodiment, the preparation method of the blended crosslinked polymer film for capacitor energy storage includes the following steps:

[0045] Solution preparation: Weigh appropriate amounts of polyvinylidene fluoride (PVDF) powder and dimethylformamide (DMF) solution, each with a PVDF mass fraction of 10 wt%, and mix them at 50°C for 12 h to obtain a clear 10 wt% PVDF solution; Weigh appropriate amounts of PMMA powder and DMF solution, each with a PMMA mass fraction of 10 wt%, and mix them at 50°C for 12 h to obtain a clear 10 wt% PMMA solution.

[0046] Weighing: Weigh appropriate amounts of 10wt% PVDF solution (g) : 10wt% PMMA solution = 40 : 60, filter to remove impurities, and place them into the reaction vessel. Weigh 3wt% of the total weight of PVDF and PMMA as 1,6-hexanediamine crosslinking agent and add them into the reaction vessel.

[0047] Solution blending: The reaction vessel containing the two-phase solution was placed on a magnetic stirrer and stirred at 500 rpm / s for 4-6 hours at room temperature to obtain a homogeneous light brown pre-crosslinked solution;

[0048] Low-temperature film formation: A homogeneous light brown pre-crosslinked solution was placed in a vacuum oven and vacuumed at room temperature for 1 hour to remove air bubbles from the solution; the solution was then cast in a vacuum oven under vacuum conditions and heated at 60°C for 1 hour to prepare a blended polymer film.

[0049] High-temperature crosslinking: The polymer film prepared at low temperature was placed in an oven at 180℃ for 1 hour to achieve the crosslinking reaction between PVDF and PMMA. The crosslinking principle is as follows: Figure 1 As shown, the cross-linked polymer film obtained after the reaction is light yellow. The film is heated at 200°C for 15 minutes and then placed in ice water for quenching treatment to obtain the desired film.

[0050] Drying of the film: The film prepared in step (7) is peeled off from the substrate in deionized water and dried in an oven at 60°C for 24 hours to obtain a dry film with a thickness of about 15 μm; the film is tested for energy storage density and efficiency at 30-110°C.

[0051] Example:

[0052] In a specific implementation example, the optimal PMMA content of the PVDF / PMMA blend crosslinked material obtained by blending and crosslinking is 60%, and the optimal ratio of crosslinking agent is 3wt% of the total mass of PVDF and PMMA. Among them, the ratio of 10wt% PVDF solution (g) to 10wt% PMMA solution is 40:60, and the mass of 1,6-hexanediamine is 3wt% of the total weight of PVDF and PMMA. Figure 2 This is a SEM-EDX image of the energy storage material obtained by in-situ polymerization in an embodiment of the present invention. As can be seen from the image, the polymer film obtained by this method has a smooth surface without obvious defects, and through… Figure 1 It is known that only cross-linking bonds contain nitrogen (N), only PVDF contains sulfur (F), and only PMMA contains oxygen (O). Therefore, the distribution uniformity of cross-linking bonds can be characterized by the distribution of nitrogen, and the distribution uniformity of PVDF and PMMA can be characterized by the distribution of sulfur (F) and oxygen (O). Figure 2 The EDX images show that F, O, and N elements are relatively uniformly dispersed, indicating that the polymer film PVDF, PMMA, and crosslinking bonds obtained by this method are uniformly distributed on the entire film.

[0053] Figure 3This is the DSC secondary temperature rise curve of the embodiments of the present invention and other energy storage materials with different PMMA contents in the temperature range of -50℃ to 250℃. The curves show that the glass transition temperature of various blended polymers crosslinked with 1,6-hexanediamine is correspondingly increased. Taking the crosslinked PVDF / PMMA (40 / 60) in this example as an example, its glass transition temperature is 76.8℃, which is much higher than the glass transition temperature of PVDF / PMMA (40 / 60) under normal conditions, which is close to 60℃. This proves that crosslinking effectively increases the glass transition temperature of the polymer. Meanwhile, from... Figure 3 The crystallinity and melting temperature of crosslinked polymers with different proportions can be obtained, indicating that the addition of a small amount of crosslinking agent has little effect on the melting temperature and crystallinity of the polymer. After crosslinking, the overall temperature stability of the material is mainly affected by influencing the structural properties of the amorphous regions.

[0054] Figure 4 The graph shows the temperature-dependent energy storage density versus charge / discharge efficiency of this invention within the temperature range of 30℃-110℃. As can be seen from the graph, when the temperature is between 30℃ and 90℃, the maximum electric field strength of this blended crosslinked material remains above 500 kV / mm, and the energy storage density remains at 10.4 J / cm². 3 -11.9J / cm 3 Between 78.3% and 88.5%, the charge-discharge efficiency remained between 78.3% and 88.5%, exhibiting good temperature stability. When the temperature further increased to 110℃, the maximum electric field strength of the material in this example decreased due to the increased temperature, but it still remained at around 400kV / mm, and the energy storage density still reached 8.5J / cm². 3 Its charge-discharge efficiency can reach 71.1%, which is much higher than that of pure PVDF and most similar ferroelectric polymer materials, and it has high application value.

[0055] Figure 5 and Figure 6 This is a comparison graph showing the energy storage density and efficiency of the present invention's embodiment with other blended crosslinked materials of different proportions as a function of temperature (where the maximum achievable electric field strength is taken when the electric field strength cannot reach 340-350 kV / mm at higher temperatures). As can be seen from the graph, compared to other blended crosslinked ratios, the film material in this example exhibits a relatively stable energy storage density (changing by 1.8 J / cm²) under the same electric field strength despite a large range of ambient temperature changes (30℃ to 110℃). 3 The change in energy density and efficiency (which changed by 0.12) is good, and it also has relatively high energy density.

[0056] A blended crosslinked polymer film for capacitor energy storage is prepared by the method described above.

[0057] In the blended crosslinked polymer film, the energy storage density of the blended crosslinked polymer film is 10.4 J / cm² in the temperature range of 30℃-90℃. 3 -11.9J / cm 3 The charge / discharge efficiency is 78.3%-88.5%.

[0058] Blended crosslinked polymer films have a blended crosslinked polymer network structure.

[0059] Finally, it should be noted that the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0060] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a blended crosslinked polymer film for capacitor energy storage, characterized in that, It includes: To prepare a solution, weigh and mix polyvinylidene fluoride powder and dimethylformamide, and stir to obtain a polyvinylidene fluoride solution with a mass fraction of 10 wt%. Weigh and mix polymethyl methacrylate powder and dimethylformamide, and stir to obtain a polymethyl methacrylate solution with a mass fraction of 10 wt%. Weigh a predetermined proportion of polyvinylidene fluoride solution and polymethyl methacrylate solution and place them into a reaction vessel. Add 3 wt% of the total weight of the polyvinylidene fluoride solution and polymethyl methacrylate solution as a 1,6-hexanediamine crosslinking agent to the reaction vessel. Place the reaction vessel at room temperature and stir to obtain a homogeneous pre-crosslinked solution. Low-temperature film formation: After the pre-crosslinked solution is placed in a vacuum oven and vacuumed at room temperature to remove air bubbles, the pre-crosslinked solution is heated at 60°C for 1 hour in a vacuum oven by casting to prepare a blended polymer film. High-temperature crosslinking: The blended polymer film is placed in an oven and subjected to a crosslinking reaction of polyvinylidene fluoride and polymethyl methacrylate at 180°C for 1 hour, resulting in a blended crosslinked polymer film.

2. The method for preparing a blended crosslinked polymer film for capacitor energy storage according to claim 1, characterized in that, The planned ratio is 4:

6.

3. The method for preparing a blended crosslinked polymer film for capacitor energy storage according to claim 1, characterized in that, The pre-crosslinked solution was placed in a vacuum oven and vacuumed at room temperature for 1 hour to remove air bubbles.

4. The method for preparing a blended crosslinked polymer film for capacitor energy storage according to claim 1, characterized in that, The pre-crosslinked solution, which was mixed evenly and degassed in the reaction vessel, was uniformly spread on a quartz glass substrate using a casting method. The substrate was then treated in a vacuum oven at 60°C for 1 hour to remove the solvent and obtain a blended film.

5. The method for preparing a blended crosslinked polymer film for capacitor energy storage according to claim 1, characterized in that, The blended crosslinked polymer film was heated at 200°C for 15 minutes, and then quenched in ice water.

6. The method for preparing a blended crosslinked polymer film for capacitor energy storage according to claim 4, characterized in that, The blended crosslinked polymer film was peeled off from the substrate in deionized water and then dried in an oven at 60°C for 24 hours.

7. A blended crosslinked polymer film for capacitor energy storage, formed by the method for preparing a blended crosslinked polymer film for capacitor energy storage according to any one of claims 1-6.

8. The blended crosslinked polymer film according to claim 7, characterized in that, The energy storage density of the blended crosslinked polymer film is 10.4 J / cm³ in the temperature range of 30℃-90℃. 3 -11.9J / cm 3 The charge / discharge efficiency is 78.3%-88.5%.

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