Coated mpi film for composite current collectors and preparation method thereof

Abstract

This disclosure provides a coated MPI thin film for composite current collectors and a method for preparing the same. The coated MPI thin film for composite current collectors includes a carrier film and a modified polyimide resin varnish layer formed on at least one surface of the carrier film. The carrier film has a thickness of 25 to 250 μm and a surface roughness of 0.001 to 10 μm. The modified polyimide resin varnish layer has a thickness of 1 to 150 μm and is composed of a single layer formed by one curing or multiple sub-layers formed by multiple coating and curing processes.

Description

[Technical Field]

[0001] This disclosure relates to the field of electronic circuit board technology, and in particular to black reinforcing boards with ultra-high reinforcement effect and matte finish. [Previous Technology]

[0002] Polyimide (PI) is a type of polymer with repeating propylene units, possessing advantages such as wide operating temperature, chemical resistance, and high strength. As a special engineering material, polyimide is now widely used in aerospace, microelectronics, nanotechnology, liquid crystals, separation membranes, lasers, and other fields.

[0003] Currently, the field of composite current collectors has received considerable attention due to the environmental indicators established by international conventions such as the United Nations Framework Convention on Climate Change and the Paris Agreement, as well as the booming development of the electric vehicle sector. Composite current collectors, with their lightweight, high energy density, excellent safety, and longer battery life, are expected to become an important material option for next-generation automotive lithium batteries. Currently, composite current collectors primarily use polymer films such as polyester film (PET), polypropylene film (PP), and polyimide film (PI), which are 50% to 80% lighter than pure metal current collectors. These polymer materials, especially polyimide film, possess excellent insulation, heat resistance, corrosion resistance, and mechanical strength, meeting the performance requirements of composite current collectors.

[0004] Polyimide is generally prepared by casting. It has excellent mechanical properties and heat resistance, but its thickness is 5 to 7.5 μm, which makes it difficult to stretch into a film. Its dimensional stability and mechanical properties are also average. Under the current requirements of 2.5 to 5 μm insulation film thickness for composite current collector applications, it is difficult to meet the industry's needs. [Summary of the Invention]

[0005] The main technical problem solved by this disclosure is to provide a coated MPI film for composite current collectors and its preparation method. The method involves coating at least one surface of a carrier film with a modified polyimide resin varnish layer, and then curing it at low temperature to form a modified polyimide resin film, such as polyimide (PI) film, polyamideimide (PAI) film, or modified polyimide (MPI) film. The thickness ranges from 1µm to 150µm, which is compatible with the ultra-thin thickness required by current composite current collectors. Furthermore, due to the presence of the carrier film, the modified polyimide resin film prepared by the coating method has better dimensional stability and is more rigid, which facilitates subsequent processing and reduces the limitations of equipment precision. By adjusting the surface properties and roughness design of the carrier film, and using a roller with a certain temperature (<90℃), the modified polyimide resin film can be easily peeled off in continuous roll-to-roll operations without the need for release agents on the carrier film. This is environmentally friendly, easy to recycle, and facilitates downstream operations while avoiding the problem of release agent transfer and pollution. Combined with a modified polyimide resin varnish layer containing the carrier film, this varnish layer can be multi-layered and its crosslinking agent resin ratio or doped with powders to obtain a resin layer with multiple advantages, including high heat resistance, corrosion resistance, high flame retardancy, high ionic purity, high thermal conductivity, high surface energy, and high mechanical properties.

[0006] To solve the above problems, this disclosure provides a coating-type MPI film for composite current collectors, comprising a carrier film and a modified polyimide resin varnish layer formed on at least one of two opposing surfaces of the carrier film; wherein the thickness of the carrier film is 25 to 250 μm, and the surface roughness (Rz) of the carrier film is 0.001 to 10 μm; the thickness of the modified polyimide resin varnish layer is 1 to 150 μm, and the modified polyimide resin varnish layer is composed of a single layer formed by one curing or multiple sub-layers formed by multiple coating and curing; and the modified polyimide resin varnish layer comprises 50 to 95% by weight of modified polyimide resin, 0 to 25% by weight of crosslinking agent, and 0 to 50% by weight of inorganic filler. In one specific embodiment disclosed herein, the modified polyimide resin varnish layer may be formed on both opposite surfaces of the carrier film.

[0007] In one specific embodiment of the present disclosure, the modified polyimide resin varnish layer is formed on both opposite surfaces of the carrier film.

[0008] In one specific embodiment of the present disclosure, the modified polyimide resin is synthesized from components including diamine, acid anhydride, isocyanate and tertiary amine, and the modified polyimide resin has at least one polyimide resin structure and polyamide-imide resin structure.

[0009] In one specific embodiment of this disclosure, the crosslinking agent may be an epoxy resin material. The crosslinking agent may include at least one selected from the group consisting of glycidylamine type epoxy resin, glycidyl ester type epoxy resin, epoxidized olefin compound, alicyclic epoxy resin, polyphenolic glycidyl ether epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic glycidyl ether epoxy resin, heterocyclic epoxy resin, and mixed epoxy resin. Here, the mixed epoxy resin is an epoxy resin that simultaneously contains two different types of epoxy groups in its molecule. It simultaneously possesses the characteristics of these different types of epoxy resins. Therefore, the curing performance and performance of the mixed epoxy resin may have characteristics not possessed by other single-type epoxy resins. The mixed epoxy resin may be, for example, 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester (TDE-85), but is not limited thereto.

[0010] In one specific embodiment of the present disclosure, the inorganic filler may include at least one selected from the group consisting of calcium sulfate, silicon dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, aluminum hydroxide, talc, aluminum nitride, glass powder, quartz powder and clay, or may contain at least one flame-retardant compound selected from the group consisting of halogen, phosphorus, nitrogen and boron, wherein the particle size of the powder may be 0.5 to 10 μm.

[0011] In one specific embodiment of the present disclosure, the diamine may be selected from 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2-bis(4-aminophenoxy)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]phenyl At least one of the following groups: sulfonamides, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ethyl ether, bis[4-(4-aminophenoxy)phenyl]ketone, 1,3-bis(4-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene;

[0011] The anhydride may be selected from at least one of the following groups: hexafluorodianhydride (6FDA), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic anhydride (B1317), 1,2-epoxydi[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenone tetracarboxylic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, benzoyltetracarboxylic anhydride, trimellitic anhydride (TMA), and cis-aconitine anhydride;

[0011] In the synthesis of polyamide-imide resin structures, the molar ratio of all diamines to all anhydrides can be from 1 / 2.05 to 1 / 2.20. In the synthesis of polyamide-imide resin structures, the molar ratio of all diamines to all dianhydrides can be from 1 / 0.90 to 1 / 1.10;

[0011] The isocyanate may be at least one selected from the group consisting of 4,4'-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene-1,5-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and lysine diisocyanate. In the synthesis of the polyamide-imide resin structure, the molar ratio of all diamines / isocyanates may be from 1 / 1.05 to 1 / 1.50; and

[0011] The tertiary amine may be at least one selected from the group consisting of triethylamine (Et3N), isoquinoline, pyridine, N-ethylpiperidine, and benzimidazole, and the amount of the tertiary amine added in the polyimide resin or polyamide-imide resin is 0 to 3% by weight. In the synthesis process, the reaction is carried out in the presence of a solvent, which may be at least one selected from the group consisting of N-methylpyrrolidone, γ-butyrolactone, cyclohexanone, acetone, butanone, N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, cyclohexane, dichloromethane, tetrahydrofuran, ethyl acetate, acetonitrile, 1,2-dichloroethane, trichloroethylene, triethylamine, 4-methyl-2-pentanone, toluene, and xylene.

[0012] In one specific embodiment of this disclosure, a method for preparing a coated MPI thin film for a composite current collector is further provided, comprising:

[0012] A modified polyimide resin varnish layer is coated on one surface of the carrier film; the coated modified polyimide resin varnish layer is cured at 50 to 180°C to form a modified polyimide resin layer; another modified polyimide resin varnish layer is coated on the other surface of the carrier film; and the other modified polyimide resin varnish layer coated on the other surface is cured at 50 to 180°C to form another modified polyimide resin layer.

[0013] In one specific embodiment of the present disclosure, the method further includes the steps of repeatedly applying a modified polyimide resin varnish layer to the surface of the carrier film and curing the applied modified polyimide resin varnish layer before applying the other modified polyimide resin varnish layer to the other surface of the carrier film.

[0014] In one specific embodiment of the present disclosure, the method further includes, after curing the other modified polyimide resin varnish layer coated on the other surface, repeating the steps of coating the modified polyimide resin varnish layer on the other surface of the carrier film and curing the modified polyimide resin varnish layer coated on the other surface.

[0015] In one specific embodiment of the present disclosure, the method further includes the steps of repeatedly coating the modified polyimide resin varnish layer on the surface of the carrier film and then curing the coated modified polyimide resin varnish layer.

[0016] In one specific embodiment of the present disclosure, the method further includes the steps of repeatedly coating the other modified polyimide resin varnish layer on the other surface of the carrier film, and then curing the other modified polyimide resin varnish layer coated on the other surface.

[0017] In a specific embodiment of this disclosure, the present disclosure further provides a method for preparing a composite current collector, which includes: forming a metallized layer on each of the two opposing surfaces of a coated MPI film on which the modified polyimide resin varnish layer is formed on both opposing surfaces of the carrier film described in the present disclosure; removing the carrier film of the coated MPI film for the composite current collector to obtain two single-sided metallized composite films to expose the surface of the modified polyimide resin varnish layer; and forming a metallized layer on each of the exposed surfaces of the modified polyimide resin varnish layer of the two single-sided metallized composite films to obtain the composite current collector.

[0018] The coated MPI thin film for composite current collectors disclosed herein and its preparation method have at least the following advantages:

[0018] This disclosure utilizes a carrier film to produce a thin film. The surface properties and roughness of the carrier film are designed to match those of the resin layer, eliminating the need for a release agent on the carrier film. The carrier film does not contain a release agent and can be recycled or reshaped after the modified polyimide film is peeled off from the carrier film, making it more environmentally friendly and reducing production costs. Furthermore, the high surface properties of the resin layer make it easy to use in steps such as lamination, coating, and electroplating without the need for additional surface treatment technologies such as corona treatment.

[0018] This disclosure enables multi-layer coating, easily takes into account various properties and meets the requirements of subsequent processing;

[0018] This invention discloses a carrier film coated with a varnish layer, which is cheaper than films produced by casting. The release force of the film surface can be adjusted by adjusting the crosslinking agent, powder type and addition ratio in the formula to make the release force stable, which is convenient for subsequent processing. The ultra-thin resin layer does not require additional film preparation in subsequent processes, thus avoiding tearing, and is easier to handle. The strength provided by the carrier film can also greatly reduce the requirements for low operating tension and precision of processing equipment, and is easy to handle with existing general equipment in the industry.

[0018] Compared with films produced by casting, the varnish-type resin layer disclosed herein has better dimensional stability due to the absence of residual tensile stress during the process.

[0018] The thin design disclosed herein makes it easy to produce films of various thicknesses and can replace high-priced thin PI (<10um) and low heat and chemical resistance BOPP, BOPET and PEN films on the market;

[0018] This disclosure describes the application of MPI coating in conjunction with a carrier film. The product width depends on the carrier film and can be quite flexible. The production width of PET, PEN and other film materials used as carrier films is much larger than that of the most advanced biaxially stretched polyimide (1500 to 2000 mm) film currently in the industry, enabling production with diverse widths while still maintaining high utilization.

[0018] The formula disclosed herein improves and designs the powder content ratio and particle size to obtain a resin layer with multiple advantages such as high flame retardancy, high ionic purity, and high thermal conductivity. [Simplified Explanation of the Diagram]

[0019] Figure 1 is a schematic diagram of the structure of the coating-type modified polyimide resin film for composite current collectors disclosed herein.

[0020] Figure 2 is a schematic diagram of the processing of the coating-type modified polyimide resin film for composite current collectors disclosed herein.

[0021] Figure 3 is a schematic diagram of the structure of the composite current collector containing a coated MPI thin film disclosed herein.

[0022] Figure 4 is a schematic diagram of the structure of the single-sided coated MPI film disclosed herein.

Implementation Method

[0023] The following describes the implementation of this disclosure by way of specific embodiments and / or in conjunction with the drawings. Those skilled in the art can easily understand the advantages and effects of this disclosure from the content disclosed in this specification.

[0024] It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which this disclosure can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and purposes that this disclosure can produce, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "first," "second," "above," "below," and "one" used in this specification are only for clarity of description and are not intended to limit the scope of implementation of this disclosure. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of implementation of this disclosure. In addition, all ranges and values ​​herein are inclusive and can be combined. Any numerical value or point falling within the ranges described herein, such as any integer or decimal, can be used as a minimum or maximum value to derive a lower range, etc.

[0025] As shown in FIG4, the present invention discloses a specific embodiment of a coated MPI film for a composite current collector, including a carrier film 101 and a modified polyimide resin varnish layer 102 formed on at least one of two opposing surfaces of the carrier film 101, wherein the modified polyimide resin varnish layer is coated on one side only.

[0025] The thickness of the carrier film 101 can be from 25 to 250 μm, for example, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240 or 250 μm. The surface roughness (Rz) of the carrier film 101 can be from 0.001 to... The morphology is 10 μm, preferably 2.0 to 10.0 μm, for example 0.001, 0.005, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 μm. This morphology control makes it easier to separate the modified polyimide resin layer from the carrier membrane, thereby improving the operability of downstream terminals.

[0025] The thickness of the modified polyimide resin varnish layer 102 can be from 1 to 150 μm, for example, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140 or 150 μm. The modified polyimide resin varnish layer 102 can be a single layer formed by curing once or multiple sub-layers formed by coating and curing multiple times. By coating and curing multiple varnish-type resin sub-layers, the micropores existing in the coating process can be solved, the micropore problem on the surface can be solved, and the mechanical properties and processing operability can be improved.

[0025] The modified polyimide resin varnish layer 102 may be composed of the following components:

[0025] (1) 50 to 95% by weight of modified polyimide resin;

[0025] (2) Crosslinking agent, 0 to 25% by weight;

[0025] (3) Inorganic filler with a weight percentage of 0 to 50%.

[0026] In one specific embodiment of this disclosure, the modified polyimide resin content in the modified polyimide resin varnish layer is 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94 or 95% by weight. In one specific embodiment of this disclosure, the crosslinking agent content in the modified polyimide resin varnish layer is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25% by weight. In one specific embodiment of this disclosure, the inorganic filler content in the modified polyimide resin varnish layer is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50% by weight.

[0027] In another specific embodiment of this disclosure, as shown in FIG1, the coated modified polyimide resin film 100 may have a modified polyimide resin varnish layer 102 formed on both opposite surfaces of the carrier film 101. The film includes a carrier film and a modified polyimide resin varnish layer. The modified polyimide resin varnish layer before curing into resin may be one or more varnish-type resin sublayers. After curing, removing the carrier film can form a coated MPI film for subsequent applications. When the modified polyimide resin varnish layer 102 is formed on both opposite surfaces, the thickness of the modified polyimide resin varnish layer 102 on either surface is independently 1 to 150 μm.

[0028] The modified polyimide resin is synthesized from components including diamine, acid anhydride, isocyanate and tertiary amine in the presence of a solvent, and the modified polyimide resin has at least one polyimide resin structure and polyamide-imide resin structure.

[0029] The crosslinking agent can be an epoxy resin material, which may include at least one selected from the group consisting of glycidylamine type epoxy resin, glycidyl ester type epoxy resin, epoxidized olefin compound, alicyclic epoxy resin, polyphenol type glycidyl ether epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, aliphatic glycidyl ether epoxy resin, heterocyclic epoxy resin, and mixed epoxy resin. Here, the mixed epoxy resin is an epoxy resin that simultaneously contains two different types of epoxy groups in its molecule, and it simultaneously possesses the characteristics of these different types of epoxy resins. Therefore, the curing performance and performance of the mixed epoxy resin may have characteristics not possessed by other single-type epoxy resins. The mixed epoxy resin may be, for example, 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester (TDE-85), but is not limited thereto.

[0030] The inorganic filler may include at least one selected from the group consisting of calcium sulfate, silicon dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, aluminum hydroxide, talc, aluminum nitride, glass powder, quartz powder and clay, or may contain at least one flame-retardant compound selected from the group consisting of halogen, phosphorus, nitrogen and boron, wherein the particle size of the glass powder and the quartz powder may be 0.5 to 10 μm, for example 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 μm.

[0031] The flame retardancy varies with the increase of different proportions of powder. The higher the proportion of powder composed of one or more inorganic powders such as silicon dioxide, alumina, aluminum hydroxide, and calcium carbonate, the higher the flame retardancy. When higher flame retardancy is required, it is recommended to use one or more inorganic powders such as aluminum hydroxide, alumina, and calcium carbonate. However, to further improve the flame retardancy, a mixture of one or more of these inorganic powders with one or more flame-retardant compounds such as halogens, phosphorus, nitrogen, or boron can be used.

[0032] The diamine may be at least one selected from the group consisting of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]sulfonamide, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ethyl ether, bis[4-(4-aminophenoxy)phenyl]ketone, 1,3-bis(4-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene;

[0032] The anhydride may be at least one selected from the group consisting of hexafluorodianhydride (6FDA), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic anhydride (B1317), 1,2-epenyl bis[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenone tetracarboxylic anhydride, 3,3',4,4'-biphenyltetracarboxylic anhydride, benzoyl tetracarboxylic anhydride, trimellitic anhydride (TMA), and cis aconitine anhydride;

[0032] In the synthesis of polyamide-imide resin structures, the molar ratio of all diamines to all anhydrides can be from 1 / 2.05 to 2.20. In the synthesis of polyamide-imide resin structures, the molar ratio of all diamines to all dianhydrides can be from 1 / 0.90 to 1.10;

[0032] The isocyanate may be at least one selected from the group consisting of 4,4'-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene-1,5-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and lysine diisocyanate. In the synthesis of the polyamide-imide resin structure, the molar ratio of all diamines / isocyanates may be from 1 / 1.05 to 1.50;

[0032] The tertiary amine may be at least one selected from the group consisting of triethylamine (Et3N), isoquinoline, pyridine, N-ethylpiperidine, and benzimidazole. In the polyimide resin or polyamide-imide resin, the amount of the tertiary amine added is 0 to 3% by weight, for example, 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1, 2, or 3% by weight.

[0032] The solvent may be at least one selected from the group consisting of N-methylpyrrolidone, γ-butyrolactone, cyclohexanone, acetone, butanone, N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, cyclohexane, dichloromethane, tetrahydrofuran, ethyl acetate, acetonitrile, 1,2-dichloroethane, trichloroethylene, triethylamine, 4-methyl-2-pentanone, toluene, and xylene.

[0033] This disclosure further provides a method for preparing a coated MPI thin film for composite current collectors, which may include:

[0033] A modified polyimide resin varnish layer is coated on one surface of a carrier film and cured at 50 to 180°C to form a modified polyimide resin layer. If multiple curing is required, the modified polyimide resin layer can be formed in the same manner.

[0033] A modified polyimide resin varnish layer is coated on another surface of the carrier film and cured at 50 to 180°C to form another modified polyimide resin layer; and

[0033] A carrier film having another modified polyimide resin layer is wound to obtain a coated modified polyimide resin film 100 as shown in Figure 1.

[0034] This disclosure further provides a method for preparing a coated MPI thin film for composite current collectors, which may include:

[0034] A modified polyimide resin varnish layer is coated on the surface of the carrier film, and multiple coatings are applied as needed;

[0034] After all the modified polyimide resin varnish layers are applied, they are cured at 50 to 180°C to form a modified polyimide resin layer;

[0034] A modified polyimide resin varnish layer is coated on another surface of the carrier film, and multiple coatings are applied as needed, cured at 50 to 180°C to form another modified polyimide resin layer; and

[0034] A carrier film having another modified polyimide resin layer formed on it is wound to obtain a coated modified polyimide resin film 100 as shown in Figure 1.

[0035] This disclosure further provides a method for preparing a composite current collector, which involves preparing the composite current collector from a coating-type MPI thin film for composite current collectors. The preparation method includes:

[0035] Metalize (sputtering, water plating or a combination of both) the roll material of the double-sided coated MPI film to form a metallized layer 200, as shown in Figure 2;

[0035] The metallized roll material is passed through a wheel with a certain temperature (<90°C) to peel off the modified polyimide resin varnish layer from the two opposing surfaces of the carrier film, and the carrier film is recovered and wound into another roll of MPI composite film with a single-sided metallized layer.

[0035] The MPI composite film is metallized again (sputtering, water plating or a combination of both) so that both opposite surfaces are metallized, and then wound to obtain a composite current collector containing a modified polyimide resin film.

[0036] The modified polyimide resin is synthesized according to the following method, and the quantity is scaled up or reduced proportionally according to the required output, but the composition, formulation and operating conditions are not limited thereto.

[0037] Example 1

[0037] Preparation of MPI. The following formulation was synthesized and coated onto 75 μm PET. The resulting MPI was then tested after peeling.

[0038] 41.1 g of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was dissolved in 330 g of N-methylpyrrolidone (NMP), followed by the addition of 40.3 g of trimellitic anhydride (TMA), and the reaction was carried out at 80 °C for 1 hour. After adding 50 ml of toluene, the temperature was raised to 170 °C for dehydration, and then raised to 190 °C to evaporate the toluene. After cooling back to room temperature, 30 g of 4,4'-diphenylmethane diisocyanate (MDI) and 1.3 g of triethylamine (Et3N) were added, and the reaction was carried out at 120 °C for 3 hours to obtain a modified polyimide resin varnish, which includes a polyimide resin structure and a polyamide-imide resin structure.

[0039] Example 2

[0039] Preparation of MPI. The following formulation was synthesized and coated onto 75 μm PET. The resulting modified polyimide was then tested after peeling.

[0040] 32.02 g of 2,2'-di(trifluoromethyl)diaminobiphenyl (TFMB), 21.99 g of hexafluorodianhydride (6FDA), and 12.41 g of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride (B1317) were added to 349 g of N-methylpyrrolidone (NMP) at 80°C. The temperature was raised to 150°C, and 0.80 g of N-ethylpiperidine was added. The temperature was then raised to 190°C and reacted for 4 hours to obtain a modified polyimide resin varnish, which includes a polyimide resin structure.

[0041] Table 1

[0041] (D Company PI: DuPont, 20EN; R Company PI: Ruihuatai, HV; P Company PI: PIAM, GF030; T Company PET: Yihua Dongli D08)

[0042] As can be seen from the results in Table 1, the mechanical properties and coefficient of thermal expansion (CTE) of the coated MPI and other industry insulating films of Examples 1 and 2 disclosed herein are more suitable for processing with a carrier film due to their lower strength. When used in composite current collector applications (Figure 3, including a modified polyimide resin varnish layer 102 and metallized layers 200 on opposite surfaces), the processing steps, such as forming Figure 2 (including a carrier film 101, a modified polyimide resin varnish layer 102, and a metallized layer 200, where the metallized layer is generally obtained by sputtering, water plating, etc., of copper foil, aluminum foil, nickel foil, copper-nickel composite coating, aluminum-nickel composite coating, copper-aluminum-nickel composite coating, copper-aluminum composite coating, copper-aluminum composite coating, etc.), since the attached metallized layer (taking 2μm copper plating as an example, tensile strength: 200 to 300 MPa, elastic modulus: 110 to 130 GPa, elongation: 1 to 3%), can retain excellent mechanical properties after peeling off the MPI film (removing the carrier film) for subsequent processing.

[0043] Examples 1-1 to 1-5

[0043] Using the resin from Example 1 as the modified polyimide resin varnish, inorganic powder and a crosslinking agent were added in proportion to their weight. The crosslinking agent was dicyclopentadiene phenolic epoxy resin (DCPD), and the added inorganic powder was SiO2 (particle size distribution D50 = 2.89 μm). The coated carrier film was a 50 μm PET film (Kunshan Yasen Electronics, CA9047) without release agent, resulting in the structure shown in Figure 4 (this film, compared to Figure 1, only has a single-sided coating of modified polyimide resin varnish layer 102 and is cured into a modified polyimide resin layer). The release force was measured by a peel test with the carrier film. The fast-press release force is the release force measured by peeling it from the carrier film after pressing with TPX protective films as separators on both sides, according to fast-press parameters (10s pre-press, pressing parameters: 180℃, 120s, 100kgf gauge pressure). The heating platform release force is the release force measured by peeling it from the carrier film after pressing with fast-press parameters and heating at a temperature of 70 to 80℃.

[0044] Table 2

[0045] As can be seen from the above, by adding crosslinking agent and inorganic powder, the operability of this disclosure can be further improved. The results of the heating platform confirm that even if the material is difficult to peel off the carrier film during continuous processing, it can be applied to peel off by setting high-temperature wheels on the running path.

[0046] This disclosure adopts continuous production with a long length and has good carrier operability during coating. The modified polyimide resin film has better dimensional stability, which can greatly improve the yield and efficiency of manufacturing and subsequent processing. Compared with the general film casting process technology, it significantly reduces costs and improves product competitiveness.

[0047] The above-described example of the synthesis of modified polyimide resin varnish is merely illustrative. Anyone skilled in the art can freely substitute conventional polyimide resin or polyamide-imide resin synthesis formulas and methods as needed. In other words, using other conventional polyimide resin or polyamide-imide resin synthesis formulas and methods does not exceed the scope of this invention.

[0048] The above embodiments are used to illustrate the principles and effects of the present invention, and are not intended to limit the present invention. Any person skilled in the art can modify the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be as set forth in the following claims.

Claims

1. A coated MPI film for composite current collectors, comprising a carrier film and a modified polyimide resin varnish layer formed on at least one of two opposing surfaces of the carrier film; wherein, The thickness of the carrier film is 25 to 250 μm, and the surface roughness of the carrier film is 0.001 to 10 μm; the thickness of the modified polyimide resin varnish layer is 1 to 150 μm, and the modified polyimide resin varnish layer is composed of a single layer formed by one curing or multiple sub-layers formed by multiple coatings and curings; and the modified polyimide resin varnish layer contains 50 to 95% by weight of modified polyimide resin, 1 to 25% by weight of crosslinking agent and 1 to 50% by weight of inorganic filler.

2. The coated MPI thin film for the composite current collector as described in claim 1, wherein, The modified polyimide resin varnish layer is formed on both opposite surfaces of the carrier membrane.

3. The coated MPI thin film for the composite current collector as described in claim 1, wherein, The modified polyimide resin is synthesized from components including diamine, acid anhydride, isocyanate and tertiary amine, and the modified polyimide resin has at least one polyimide resin structure and polyamide-imide resin structure.

4. The coated MPI thin film for the composite current collector as described in claim 1, wherein, The crosslinking agent is an epoxy resin material.

5. The coated MPI thin film for the composite current collector as described in claim 4, wherein, The crosslinking agent includes at least one selected from the group consisting of glycidylamine epoxy resin, glycidyl ester epoxy resin, epoxidized olefin compound, alicyclic epoxy resin, polyphenol glycidyl ether epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, aliphatic glycidyl ether epoxy resin, heterocyclic epoxy resin and mixed epoxy resin.

6. The coated MPI thin film for the composite current collector as described in claim 1, wherein, The inorganic filler includes at least one selected from the group consisting of calcium sulfate, silicon dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, aluminum hydroxide, talc, aluminum nitride, glass powder, quartz powder, and clay, or contains at least one flame-retardant compound selected from the group consisting of halogens, phosphorus, nitrogen, and boron, wherein the particle size of the powder of such inorganic filler or flame-retardant compound is 0.5 to 10 μm.

7. The coated MPI thin film for the composite current collector as described in claim 3, wherein, The diamine is selected from at least one of the following groups: 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 2,2-bis(4-aminophenoxy)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]sulfonamide, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ethyl ether, bis[4-(4-aminophenoxy)phenyl]ketone, 1,3-bis(4-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene. The anhydride is selected from at least one of the following groups: hexafluorodianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 1,2-epenyl bis[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylic acid ester], 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, phenyltetracarboxylic acid dianhydride, trimellitic anhydride, and cis aconitine anhydride; In the synthesis of this polyamide-imide resin structure, the molar ratio of all diamines to all anhydrides is from 1 / 2.05 to 1 / 2.20; In the synthesis of the polyamide-imide resin structure, the molar ratio of all diamines to all anhydrides is from 1 / 0.90 to 1 / 1.

10. The isocyanate is at least one selected from the group consisting of 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene-1,5-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and lysine diisocyanate. In the synthesis of the polyamide-imide resin structure, the molar ratio of all diamines / isocyanates is from 1 / 1.05 to 1 / 1.

50. The tertiary amine is at least one selected from the group consisting of triethylamine, isoquinoline, pyridine, N-ethylpiperidine, and benzimidazole. In the polyamide-imide resin or polyamide-imide resin, the amount of the tertiary amine added is from 0% to 3% by weight.

8. A method for preparing a coated MPI thin film for a composite current collector as described in claim 1, comprising: A modified polyimide resin varnish layer is coated on one surface of the carrier membrane; The modified polyimide resin varnish layer is cured at 50 to 180°C to form a modified polyimide resin layer; another modified polyimide resin varnish layer is coated on another surface of the carrier film; and the other modified polyimide resin varnish layer coated on the other surface is cured at 50 to 180°C to form another modified polyimide resin layer.

9. The method for preparing the coated MPI film for the composite current collector as described in claim 8 further includes, before coating the other modified polyimide resin varnish layer on the other surface of the carrier film, repeating the steps of coating the modified polyimide resin varnish layer on the surface of the carrier film and curing the coated modified polyimide resin varnish layer.

10. The method for preparing the coating-type MPI film for the composite current collector as described in claim 8 further includes, after curing the other modified polyimide resin varnish layer coated on the other surface, repeating the steps of coating the modified polyimide resin varnish layer on the other surface of the carrier film and curing the modified polyimide resin varnish layer coated on the other surface.

11. The method for preparing the coated MPI film for the composite current collector as described in claim 8 further includes the step of repeatedly coating the modified polyimide resin varnish layer on the surface of the carrier film and then curing the coated modified polyimide resin varnish layer.

12. The method for preparing the coating-type MPI film for the composite current collector as described in claim 8 further includes the step of repeatedly coating the other modified polyimide resin varnish layer on the other surface of the carrier film, and then curing the other modified polyimide resin varnish layer coated on the other surface.

13. A method for preparing a composite current collector, comprising: A metallized layer is formed on each of the two opposing surfaces of the coated MPI thin film for the composite current collector as described in claim 2. The carrier film of the coated MPI film used in the composite current collector is removed to obtain a composite film with two single-sided metallizations, so that the surface of the modified polyimide resin varnish layer is exposed; and a metallized layer is formed on the surface of the modified polyimide resin varnish layer exposed on the two single-sided metallized composite films to obtain the composite current collector.

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