Dielectric film for high-temperature energy storage and preparation method and device thereofTechnical Field
The invention belongs to the technical field of energy storage material preparation, and relates to a dielectric film for high-temperature energy storage, and a preparation method and a device thereof.
Background
In recent years, dielectric capacitors have become an important component of modern power systems, with the advantage of having an intrinsically extremely fast charge-discharge capability and ultra-high power density, an all-solid structure, a high operating voltage, and at the same time low losses. However, a common problem of thin film capacitors based on various dielectric electrolyte materials is that their low energy density severely hampers the development of high power high capacity capacitor manufacturing techniques.
Therefore, in practical applications, in order to avoid occupying excessive volume in the integrated circuit, there is a need to improve the energy storage performance. In particular to the high-efficiency utilization of clean energy such as pulse power systems, hybrid electric vehicles, oil and gas energy exploration and exploitation, wind energy and the like, and further provides the requirement of higher high-temperature-resistant energy storage performance. Taking the biaxially oriented polypropylene (BOPP), a common commercial capacitor film as an example, the operating temperature is typically around 70 ℃ and typically no more than 105 ℃. For the thin film capacitor of BOPP material, the leakage current in the dielectric medium will increase exponentially under higher temperature and high electric field, resulting in a sharp decrease in charge-discharge efficiency and energy storage density, and a large amount of Joule heat is generated at the same time, which aggravates the decrease in performance. Researchers at home and abroad develop a dielectric film material which adopts a polymer with high glass transition temperature as an organic film capacitor, such as Polyimide (PI), polyetherimide (PEI) and the like, and improves the high-temperature energy storage performance. However, the thickness of the dielectric film for high-temperature energy storage is generally more than 10 μm, and the requirement of thinning the dielectric film cannot be met.
The application of various novel polymers in dielectric capacitors is often limited by film manufacturing technology, and how to manufacture large, ultrathin, continuous and uniform high-quality dielectric films is an important technical problem for developing dielectric capacitors for high-temperature energy storage. The BOPP film which is commercially used at present can be as thin as 2.2 mu m, and the technology of combining melt extrusion and biaxial stretching is adopted, so that the equipment cost is high. Heretofore, patent CN115093590a discloses a film for high-temperature electrostatic energy storage, and a preparation method and application thereof, and the film adopts an ultrasonic spraying process, has simple method and wide applicability, and is suitable for large-scale industrial production of high-quality ultrathin polymer-based dielectric films. However, the concentration of the polymer suitable for the process is 0.01-0.05g/mL, so that a large amount of organic solvent is required for dilution, and the pollution to the environment is increased. Therefore, development of a preparation process of a novel high-quality and large-area ultrathin dielectric film for high-temperature energy storage, which is more environment-friendly and low in cost, is particularly important.
Patent CN116487819a discloses a composite membrane, a preparation method and application thereof, the composite membrane porous base material and a heat-resistant coating arranged on one or both sides of the porous base material, the heat-resistant coating contains heat-resistant polymer particles, inorganic filler and auxiliary binder, the heat-resistant polymer particles contain heat-resistant resin with average particle diameter of 10-200nm and glass transition temperature of ts+40 ℃ or above. However, the composite diaphragm of the patent has uneven relative thickness, uneven distribution of filler in the diaphragm material, and defects in the performance of the diaphragm.
Patent CN116178782A discloses a preparation method of a high-filler ultra-thin polytetrafluoroethylene-based composite medium substrate, which comprises the steps of mixing and stirring 51-75% of ceramic powder, 15-25% of polytetrafluoroethylene emulsion, 1-13% of fibers and 8-19% of deionized water according to the weight ratio to obtain composite slurry, adding a flocculating agent accounting for 5-15% of the weight ratio of the composite slurry, stirring for 15-30min, filtering water to obtain a dough-shaped high-filler PTFE composite wet material, and carrying out normal-temperature calendaring, supercritical drying, atomization spraying of the impregnating agent, high-pressure calendaring technology and high-temperature drying, so as to obtain the high-filler ultra-thin PTFE-based composite medium substrate. However, the preparation process of the patent is relatively complex, the process is complicated, and the cost is high.
Disclosure of Invention
The invention aims to overcome at least one defect in the prior art and provide a dielectric film for high-temperature energy storage, a preparation method and a device thereof.
The aim of the invention can be achieved by the following technical scheme:
The invention provides a dielectric film for high-temperature energy storage, which is prepared by supercritical spray film forming and heat treatment and comprises the following components in parts by weight:
5-30 parts of high-temperature resistant polymer, 0.1-5 parts of additive and 60-95 parts of solvent;
The high-temperature resistant polymer is selected from one or more of polyimide polymers and polyamide acid which is a precursor of the polyimide polymers;
the additive is one or more inorganic fillers selected from aluminum oxide, boehmite and silicon carbide.
Further, the polyimide polymer is selected from one or more of polyimide, fluorine-containing polyimide and polyetherimide.
As a preferable technical scheme, the high-temperature resistant polymer is selected from one or more polyimide polymer precursors polyamide acid in polyimide, fluorine-containing polyimide and polyetherimide.
The glass transition temperature of the high temperature resistant polymer is not less than 150 ℃, and the band gap of the high temperature resistant polymer is not less than 3eV.
Further, the solvent is selected from one or more of N, N '-dimethylacetamide, N-methylpyrrolidone and N, N' -dimethylformamide.
One of the technical schemes of the invention is to provide a preparation method of the dielectric film for high-temperature energy storage, which comprises the following steps:
S1, prefabricating slurry, and mixing a high-temperature resistant polymer and a solvent to obtain spraying slurry;
S2, supercritical spraying, namely adding spraying slurry and additives, introducing carbon dioxide as a diluent, mixing the spraying slurry in a supercritical state, and spraying the polymer slurry with a gas-liquid mixture in the supercritical state to the surface of the substrate to form a wet film;
S3, post-treatment, namely performing gradient heating treatment on the wet film, removing the solvent as much as possible, and completing thermal imidization to obtain the dielectric film for high-temperature energy storage.
Further, the substrate in step S2 includes an aluminum foil, a copper foil, a glass sheet, or a polymer film.
Further, the temperature of the mixture in the step S1 is 20-40 ℃ and the time is 0.5-2h.
Further, the temperature of the mixture in the step S2 is 32-40 ℃, the pressure is 7.4-8.4MPa, and the time is 2-5h.
Further, the minimum temperature of the gradient heating treatment in the step S3 is 50-80 ℃, the maximum temperature is 200-350 ℃, the gradient temperature difference is 20-80 ℃, and each time is 0.5-2h.
Further, when the multilayer wet film is prepared in the step S3, the wet film sprayed on the front layer is subjected to heating treatment at 50-80 ℃ for 0.5-2 hours, then the wet film sprayed on the rear layer is subjected to gradient heating treatment, and finally the wet film sprayed on the rear layer is subjected to gradient heating treatment.
The invention provides a preparation device of a dielectric film for high-temperature energy storage, which adopts the method to perform slurry prefabrication and supercritical spraying, and comprises a diluent pressure container, a spraying slurry mixing container, an additive storage container, a supercritical dilution mixing container, a buffer container, a regulating valve and a spray gun,
The diluent pressure container stores diluent liquid, the spraying slurry mixing container mixes the high-temperature resistant polymer and the solvent to obtain spraying slurry, the additive storage container stores additive,
The supercritical dilution mixing container is communicated with a diluent pressure container, a spraying slurry mixing container and an additive storage container, the spraying slurry, the additive and the diluent are mixed to obtain polymer slurry,
The supercritical dilution mixing container is communicated with the buffer container, the buffer container is communicated with the regulating valve, the regulating valve is communicated with the spray gun, under the specified saturation pressure, according to the program set in the device, the polymer slurry is conveyed outwards in a supercritical state under a certain pressure and temperature by controlling the opening size of the regulating valve, and the polymer slurry is diffused at a certain angle and radian through the diffusion nozzle of the spray gun to be scattered on the substrate to form a wet film.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention adopts the soluble high-temperature resistant polymer with high glass transition temperature or the soluble precursor thereof, which has great application potential in the field of high-temperature energy storage, and the wide band gap of the polymer and the addition of the additive filler can provide higher breakdown strength;
(2) The invention adopts the supercritical spraying process, utilizes the diffusivity of similar gas, the density and the dissolution capacity of similar liquid under the supercritical state, and has the characteristics of low viscosity and low surface tension;
(3) The invention uses supercritical carbon dioxide with stable property, safety and innocuity as the diluent, controls the viscosity and the mixing uniformity of the slurry to improve the film forming performance, reduces the defects, simultaneously reduces the baking after a large amount of organic solvents are diluted, saves the energy for removing the solvents at high temperature and reduces the pollution of a large amount of diluents;
(4) The invention has the advantages of convenient implementation, simple operation, good applicability and high efficiency, is suitable for large-scale and low-cost industrial production of high-quality ultrathin polymer-based dielectric films, greatly reduces the equipment cost compared with a complete set of biaxial stretching equipment, and has the advantages of uniform film thickness, strong breakdown resistance, high dielectric strength, excellent high-temperature energy storage performance and good reliability.
Drawings
Fig. 1 is a schematic structural diagram of a device for preparing a dielectric thin film for high-temperature energy storage according to an embodiment of the present invention.
The figure indicates:
1-diluent pressure vessel, 2-spraying slurry mixing vessel, 3-additive storage vessel, 4-supercritical dilution mixing vessel, 5-buffer vessel, 6-regulating valve, 7-diffusion nozzle, 8-substrate, 9-wet film.
Detailed Description
The present invention will be described in detail with reference to specific examples. The present embodiment is implemented on the premise of the technical scheme of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following examples.
The apparatus used in the examples below represent conventional apparatus in the art unless otherwise specified, and the reagents used, unless otherwise specified, represent commercially available products or are prepared by conventional methods in the art, and are not specifically described in the examples below.
The preparation device of the dielectric film for high-temperature energy storage comprises a diluent pressure container 1, a spraying slurry mixing container 2, an additive storage container 3, a supercritical dilution mixing container 4, a buffer container 5, a regulating valve 6 and a spray gun 7 as shown in figure 1,
The diluent pressure container 1 stores diluent liquid, the spraying slurry mixing container 2 adopts a magnetic stirring tank, the high temperature resistant polymer and the solvent are mixed to obtain spraying slurry, the additive storage container 3 stores additive,
The supercritical diluting and mixing container 4 is a high-pressure magnetic stirring tank which is communicated with the diluent pressure container 1, the spraying slurry mixing container 2 and the additive storage container 3, the spraying slurry, the additive and the diluent are mixed to obtain polymer slurry,
The supercritical diluting and mixing container 4 is communicated with the buffer container 5, the buffer container 5 is communicated with the regulating valve 6, the regulating valve 6 is communicated with the spray gun 7, under the specified saturation pressure, according to the program set in the device, the polymer slurry is conveyed outwards in a supercritical state under a certain pressure and temperature by controlling the opening size of the regulating valve 6, and the polymer slurry is diffused in a certain angle and radian through the diffusion nozzle of the spray gun 7 to be scattered on the substrate 8 to form the wet film 9.
Example 1:
A dielectric film for high-temperature energy storage and a preparation method thereof adopt the device to perform slurry prefabrication and supercritical spraying, and the preparation method comprises the following specific steps:
S1, prefabricating slurry, namely mixing Polyimide (PI) precursor polyamide acid and N-methylpyrrolidone in a spraying slurry mixing container 2 at the normal temperature of 25 ℃ for 1h to obtain a polyamide acid solution with uniform solid content of 20% as spraying slurry;
S2, supercritical spraying, namely adding the spraying slurry and alumina powder from an additive storage container 3 into a supercritical dilution mixing container 4 according to the mass ratio of 99:1, introducing carbon dioxide serving as a diluent from a diluent pressure container 1, controlling the temperature to be 36 ℃ and the pressure to be 7.6MPa, mixing the mixture with the spraying slurry in a supercritical state for 3 hours, and spraying the polymer slurry with a gas-liquid mixture mixed into the supercritical state to the surface of an aluminum foil of 15cm multiplied by 20cm to form a wet film 9 by operating a regulating valve 6 and a spray gun 7;
S3, post-treatment, namely performing gradient heating treatment on the wet film 9 at 60 ℃, 1h,100 ℃, 1h,150 ℃, 1h,210 ℃, 1h,260 ℃ and 1h to remove the solvent as much as possible and complete thermal imidization so as to obtain the PI dielectric film for high-temperature energy storage.
Example 2:
A dielectric film for high-temperature energy storage and a preparation method thereof are basically the same as those in the embodiment 1, except that in the step S3, single-layer spraying is replaced by double-layer spraying, the wet film 9 sprayed on the single layer is subjected to heating treatment at 60 ℃ for 1h, then the step S2 is repeated, the previous wet film 9 is used as a substrate to carry out second-layer spraying, and gradient heating treatment is carried out, so that the PI dielectric film for double-layer high-temperature energy storage is obtained.
Example 3:
A dielectric film for high-temperature energy storage and a preparation method thereof are basically the same as those in the embodiment 2, except that in the step S3, the double-layer spraying is replaced by three-layer spraying, the wet film 9 of the double-layer spraying is subjected to heating treatment at 60 ℃ for 1h, then the step S2 is repeated, the wet film 9 of the previous layer is used as a substrate to carry out third-layer spraying, and then gradient heating treatment is carried out, so that the three-layer PI dielectric film for high-temperature energy storage is obtained.
Example 4:
A dielectric film for high temperature energy storage and a method for manufacturing the same are basically the same as in example 1, except that a polyamic acid solution having a solid content of 15% is used as a spray coating slurry in step S1 instead of 20%.
Example 5:
A dielectric thin film for high temperature energy storage and a method for preparing the same are basically the same as in example 1, except that a Polyetherimide (PEI) precursor polyamic acid solution having a solid content of 20% is used as a spray coating slurry in step S1 instead of the PI precursor polyamic acid solution.
Example 6:
A dielectric thin film for high temperature energy storage and a method for manufacturing the same are substantially the same as in example 1, except that the mass ratio of the spray slurry and the alumina powder in step S2 is 99.5:0.5 instead of 99:1.
Example 7:
A dielectric thin film for high temperature energy storage and a method for manufacturing the same are substantially the same as in example 1, except that boehmite powder is used instead of alumina powder in step S2.
Comparative examples 1 to 7:
A dielectric thin film for high temperature energy storage and a method for preparing the same are substantially the same as those of examples 1 to 7, except that no additive powder is added in step S2.
Comparative examples 8 to 14:
a dielectric thin film for high temperature energy storage and a method for manufacturing the same are basically the same as those of examples 1 to 7, except that carbon dioxide is not introduced for direct injection in step S2.
Between examples 1 to 3, the breakdown field strength is increased by 5-10% at 9,150 ℃ for each layer of wet film added, and the dielectric loss is reduced by 10-20%;
Examples 1 to 7 have 5-8% higher breakdown field strength at 150 ℃ and 10-15% lower dielectric loss than comparative examples 1 to 7;
Examples 1 to 7 were reduced by 10-15% in thickness as compared with comparative examples 8 to 14, and the surfaces of examples were leveled at the same time for the post-treatment time, while the surfaces of comparative examples had black impurities, and even if the time per gradient heat treatment was increased to 3 hours, the surfaces of comparative examples 8,9, 11, 13 and 14 were wrinkled and did not reach a leveled state.
Through testing, the embodiment of the invention has the advantages of convenient implementation, simple operation, good applicability and high efficiency, is suitable for large-scale and low-cost industrial production of high-quality ultrathin polymer-based dielectric films, greatly reduces the equipment cost compared with a set of biaxial stretching equipment, and has the advantages of uniform film thickness, strong breakdown resistance, high dielectric strength, excellent high-temperature energy storage performance and good reliability.
The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.