A high molecular polymer composite film for a composite current collector and a method for preparing the same

Abstract

This application discloses a polymer composite membrane for composite current collectors and its preparation method, relating to the field of composite current collector technology for lithium-ion batteries. The polymer composite membrane includes a polymer base membrane and a coating layer disposed on at least one surface of the polymer base membrane. By mass percentage, the coating slurry of the coating layer consists of the following components: 85-94% nanofibers, 5-10% binder, and 0.5-5% curing agent. The curing agent undergoes a polymerization reaction with the nanofibers and binder, guiding the nanofibers and binder to form a three-dimensional cross-linked network, reducing the porosity of the polymer membrane, effectively preventing electrolyte penetration and corrosion, and improving heat resistance. Simultaneously, it eliminates the weak interface layer of the base membrane, and the polar groups of the cross-linked network strengthen the intermolecular forces with the substrate, improving peel strength and effectively preventing coating layer detachment, ensuring reliable interlayer bonding.

Description

Technical Field

[0001] This application relates to the field of composite current collector technology for lithium-ion batteries, and more specifically, to a polymer composite film for composite current collectors and its preparation method. Background Technology

[0002] As a core component in battery cells that carries current and fixes active materials, the performance of the battery current collector directly determines the battery's safety, cycle life, and cost, making it one of the key components for the development of the battery industry. Currently, the traditional current collectors widely used in the industry are mostly pure metal foils, but they have inherent defects such as poor heat resistance and insufficient mechanical toughness, which seriously restrict the improvement of battery safety performance, especially posing significant risks in abuse scenarios.

[0003] Under abusive conditions such as battery puncture, compression, and overheating, pure metal foil is prone to breakage and the formation of metal burrs. These burrs can easily puncture the battery separator, causing internal short circuits within the cell. When a battery experiences thermal runaway, the pure metal foil cannot actively cut off the current path; instead, it acts as an excellent heat conductor, accelerating heat dissipation and ultimately leading to serious safety accidents such as battery fires and explosions. Furthermore, during high-rate charging and discharging, the growth of lithium dendrites can easily penetrate the pure metal foil, further exacerbating the risk of internal short circuits. This problem is even more pronounced in high-performance cells such as silicon-based anodes and high-nickel ternary batteries, severely limiting the industrial application of high-performance batteries.

[0004] To address the shortcomings of traditional pure metal foil current collectors, metal-polymer-metal (MPM) composite current collectors have emerged. This novel current collector employs a sandwich structure of "metal layer-polymer layer-metal layer," offering significant advantages over traditional pure metal foil current collectors: safety is greatly improved; in the event of thermal runaway, the intermediate polymer layer melts and fractures, creating a current interruption and effectively suppressing internal short circuits and heat dissipation; the metal burrs generated during puncture are smaller, and the intermediate insulating layer can block the conduction of large currents; the amount of precious metals such as copper and aluminum used is significantly reduced, resulting in a substantial decrease in material costs compared to traditional copper foil; and the flexible polymer layer can also disperse the stress generated by lithium dendrite growth, reducing the risk of electrode interface failure.

[0005] However, there are still technical bottlenecks to be solved in MPM composite current collectors. The polymer film, its core component, has poor heat resistance and corrosion resistance. Moreover, the polymer film itself has a porous structure, which makes it susceptible to erosion by the electrolyte during long-term charging and discharging of the battery. This leads to a decrease in the structural stability of the composite current collector, which in turn affects its service life and the overall performance of the battery, thus limiting its large-scale industrial application. Summary of the Invention

[0006] The purpose of this application is to provide a polymer composite membrane for composite current collectors, which has the advantages of good heat resistance, excellent resistance to electrolyte corrosion and high structural stability.

[0007] Another objective of this application is to provide a method for preparing a polymer composite membrane for composite current collectors, which is simple, convenient, and suitable for large-scale mass production.

[0008] To solve the above-mentioned technical problems, the technical solution adopted in this application is as follows: On the one hand, this application provides a polymer composite membrane for composite current collectors, including a polymer base membrane and a coating layer disposed on at least one surface of the polymer base membrane; The coating slurry of the coating layer, by weight percentage, consists of the following components: 85-94% nanofibers, 5-10% binder, and 0.5-5% curing agent.

[0009] On the other hand, this application provides a method for preparing a polymer composite film for composite current collectors, comprising the following steps: S1. Mix nanofibers, binder and curing agent evenly in solvent to obtain coating slurry; S2. Apply the coating slurry to at least one side of the polymer base film and cure it to form a coating layer.

[0010] Compared with the prior art, the embodiments of this application have at least the following advantages or beneficial effects: 1. The coating layer of this application uses nanofibers, binders and curing agents as raw materials. The curing agent undergoes a polymerization reaction with the nanofibers and binders, guiding the nanofibers and binders to form a three-dimensional cross-linked network, which significantly reduces the porosity of the polymer membrane, effectively prevents electrolyte penetration and corrosion, and improves the mechanical properties and thermal stability of the membrane. At the same time, it eliminates the weak interface layer of the base film, and the polar groups of the cross-linked network strengthen the intermolecular forces with the substrate, improves the peel strength, effectively prevents the coating layer from falling off, and ensures the reliability of interlayer bonding.

[0011] 2. The heat resistance temperature of the composite membrane in this application is increased from the existing 50-100℃ to 180-250℃, which can effectively melt the polymer layer and block the short circuit current in the event of battery thermal runaway, thus greatly improving battery safety. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 These are photographs of the diaphragm in Example 1 of this application before (a) and after (b) the test at 150°C / h; Figure 2 These are photographs of the diaphragm in Example 10 of this application before (a) and after (b) the test at 200°C / h; Figure 3 These are photographs of the diaphragm in Example 14 of this application before (a) and after (b) the test at 250°C / h; Figure 4 The diagram shows the peel strength test method of this application (a) and the comparative examples (c, e) before and after the test (b, d). Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to specific embodiments.

[0016] A polymer composite membrane for composite current collectors includes a polymer base membrane and a coating layer disposed on at least one surface of the polymer base membrane; The coating slurry of the coating layer, by weight percentage, consists of the following components: 85-94% nanofibers, 5-10% binder, and 0.5-5% curing agent.

[0017] In some embodiments of this application, the aforementioned nanofibers are MFC (microfibrillated cellulose), CNC (cellulose nanofibers), lignin nanofibers, CNF (cellulose nanowhiskers), BC (bacterial cellulose), PI (polyimide nanofibers), ANF (aramid nanofibers), and nanofibers modified by one or more composite methods including carboxylation, sulfonation, esterification, etherification, graft polymerization, oxidation, acetylation, phosphorylation, isocyanate modification, and silane coupling agent modification.

[0018] In some embodiments of this application, the polymer base film is one or more of PET (polyethylene terephthalate) film, PP (polypropylene) film, PE (polyethylene) film, PA (polyamide) film, PEN (polyethylene naphthalate) film, PI (polyimide) film, aramid film, PC (polycarbonate) film, PEEK (polyether ether ketone) film, and cellulose-based porous film, wherein the polypropylene film includes BOPP, CPP, OPP, mPP, MOPP, and PPTF.

[0019] In some embodiments of this application, the adhesive is one or more of PAA (polyacrylic acid), PAE (polyacrylate), CAR (carboxyl-modified acrylic resin), SA (acrylic acid-styrene copolymer), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer, CMC (sodium carboxymethyl cellulose), HEC (hydroxyethyl cellulose), MC (methyl cellulose), PVA (polyvinyl alcohol), epoxy resin, phenolic resin, PI (polyimide) resin, SBR (styrene-butadiene rubber), NBR (nitrile rubber), and PEG (polyethylene glycol).

[0020] In some embodiments of this application, the curing agent is one or more of the following: diethyltoluenediamine, dimethylthiotoluenediamine, diaminodiphenylmethane, aminodiphenyl sulfone, m-phenylenediamine, isophoronediamine, 1,3-cyclohexanedimethylamine, diaminodicyclohexylmethane, diethylenetriamine, triethylenetetramine, polyetheramine, phenolic amine, polyamideamine, low-formaldehyde melamine-formaldehyde resin, benzoated melamine-formaldehyde resin, carbodiimide, toluene diisocyanate, diphenylmethane diisocyanate, polyphenyl polymethylene polyisocyanate, hexamethylene diisocyanate, 1,12-dodecylmethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, 1,3-cyclohexane diisocyanate, 4,4-dicyclohexylmethane diisocyanate, phenyldimethylmethylene diisocyanate, and modified polymeric isocyanates.

[0021] In some embodiments of this application, the thickness of the polymer base film is 2-10 μm; the thickness of the coating layer is 0.5-5 μm.

[0022] A method for preparing a polymer composite film for composite current collectors includes the following steps: S1. Mix nanofibers, binder and curing agent evenly in solvent to obtain coating slurry; S2. Apply the coating slurry to at least one side of the polymer base film and cure it to form a coating layer.

[0023] In some embodiments of this application, the mixing in step S1 above specifically involves: mixing nanofibers with a solvent to form a dispersion, then adding a binder and a curing agent to the dispersion, and stirring to obtain the coating slurry. The solid content of the dispersion is 5-30%, and the solvent is water or ethanol.

[0024] In some embodiments of this application, the coating is a wet coating, selected from one or more of the following: gravure coating, slot coating, doctor blade coating, roller coating, curtain coating, spraying, dip coating, spin coating, and bar coating.

[0025] In some embodiments of this application, the curing temperature is 50-120°C and the curing time is 2-24 hours.

[0026] The features and performance of this application will be further described in detail below with reference to the embodiments. Example 1

[0027] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: CNC 92%, PVDF 7%, diethyltoluene diamine 1%.

[0028] Preparation steps: CNC is mixed with solvent water to form a dispersion, then PVDF and diethyltoluene diamine are added to the dispersion and stirred to obtain a coating slurry; the coating slurry is coated on one side of a PP porous base membrane (base membrane thickness 4.5μm) with a coating thickness of 1μm, and cured in an oven at 60℃ for 4h to form a coating layer on the base membrane surface, thus finally obtaining the polymer composite membrane. Example 2

[0029] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: BC 92%, PVDF 7%, diethyltoluene diamine 1%.

[0030] Preparation steps: BC is mixed with solvent to form a dispersion, then PVDF and diethyltoluene diamine are added to the dispersion and stirred to obtain the coating slurry; the coating slurry is coated on both sides of the PP porous base membrane (base membrane thickness 4.5μm) with a coating thickness of 1μm, and cured in an oven at 60℃ for 6h to form a coating layer on the base membrane surface, thus finally obtaining the polymer composite membrane. Example 3

[0031] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: CNF 91%, PVDF 7%, diethyltoluene diamine 2%.

[0032] Preparation steps: CNF is mixed with a solvent to form a dispersion, then PVDF and diethyltoluene diamine are added to the dispersion and stirred to obtain the coating slurry; the coating slurry is coated on both sides of the PP porous base membrane (base membrane thickness 4.5μm) with a coating thickness of 1μm, and cured in an oven at 60℃ for 6h to form a coating layer on the base membrane surface, thus obtaining the polymer composite membrane. Example 4

[0033] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: 93% carboxyl-modified BC, 6% PVDF, and 1% diethyltoluene diamine.

[0034] Preparation steps: Carboxyl-modified BC is mixed with a solvent to form a dispersion. Then, PVDF and diethyltoluene diamine are added to the dispersion and stirred to obtain a coating slurry. The coating slurry is coated on one side of a porous PE base membrane (base membrane thickness 4.5 μm) with a coating thickness of 1 μm. The membrane is cured in an oven at 60°C for 8 hours to form a coating layer on the base membrane surface, thus obtaining the polymer composite membrane. Example 5

[0035] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: Carboxylated CNC 92%, PVDF 6%, dimethylthiotoluene diamine 2%.

[0036] Preparation steps: Carboxylated CNC is mixed with a solvent to form a dispersion. Then, PVDF and dimethylthiotoluene diamine are added to the dispersion and stirred to obtain a coating slurry. The coating slurry is coated on one side of a porous PET base film (base film thickness 4μm) with a coating thickness of 1μm. The film is cured in an oven at 80℃ for 8h to form a coating layer on the base film surface, thus obtaining the polymer composite film. Example 6

[0037] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: Carboxylated CNC 92%, PI 7%, diethyltoluene diamine 1%.

[0038] Preparation steps: Carboxylated CNC is mixed with a solvent to form a dispersion. Then, PI and diethyltoluene diamine are added to the dispersion and stirred to obtain a coating slurry. The coating slurry is coated on one side of a porous PET base film (base film thickness 4μm) with a coating thickness of 1μm. The film is cured in an oven at 100℃ for 4h to form a coating layer on the base film surface, thus obtaining the polymer composite film. Example 7

[0039] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: Carboxylated CNC 90%, PAA 9%, dimethylthiotoluene diamine 1%.

[0040] Preparation steps: Carboxylated CNC is mixed with a solvent to form a dispersion. Then, PAA and dimethylthiotoluene diamine are added to the dispersion and stirred to obtain a coating slurry. The coating slurry is coated on one side of a PE porous base membrane (base membrane thickness 4.5 μm) with a coating thickness of 1 μm. The membrane is cured in an oven at 60°C for 8 hours to form a coating layer on the base membrane surface, thus obtaining the polymer composite membrane. Example 8

[0041] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: Carboxylated CNC 91%, PVA 8%, diaminodiphenylmethane 1%.

[0042] Preparation steps: Carboxylated CNC is mixed with a solvent to form a dispersion. Then, PVA and diaminodiphenylmethane are added to the dispersion and stirred to obtain a coating slurry. The coating slurry is coated on one side of a porous PET base film (base film thickness 4μm) with a coating thickness of 1μm. The film is cured in an oven at 100℃ for 6h to form a coating layer on the base film surface, thus obtaining the polymer composite film. Example 9

[0043] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: sulfonated CNC 92%, SBR 7%, diethyltoluene diamine 1%.

[0044] Preparation steps: Sulfonated CNC is mixed with solvent to form a dispersion, then SBR and diethyltoluenediamine are added to the dispersion and stirred to obtain a coating slurry; the coating slurry is coated on one side of a PET porous base film (base film thickness 4μm) with a coating thickness of 1μm, and cured in an oven at 80℃ for 12h to form a coating layer on the base film surface, thus obtaining the polymer composite film. Example 10

[0045] This embodiment prepares a polymer composite membrane for composite current collectors using the following method: Coating slurry formulation: Carboxylated CNC 93%, PI 6%, diethyltoluene diamine 1%.

[0046] Preparation steps: Carboxylated CNC is mixed with a solvent to form a dispersion. Then, PI and diethyltoluenediamine are added to the dispersion and stirred to obtain a coating slurry. The coating slurry is coated on one side of a porous PET base film (base film thickness 4μm) with a coating thickness of 1μm. The film is cured in an oven at 100℃ for 10h to form a coating layer on the base film surface, thus obtaining the polymer composite film. Example 11

[0047] This embodiment prepares a polymer composite membrane for composite current collectors. The coating slurry formulation and preparation method are the same as in Example 1. The only difference is that the coating thickness is 1 μm on both sides. Example 12

[0048] This embodiment prepares a polymer composite membrane for composite current collectors. The coating slurry formulation and preparation method are the same as in Example 4. The only difference is that the coating thickness is 1 μm on both sides. Example 13

[0049] This embodiment prepares a polymer composite membrane for composite current collectors. The coating slurry formulation and preparation method are the same as in Example 5. The only difference is that the coating thickness is 1 μm on both sides. Example 14

[0050] This embodiment prepares a polymer composite membrane for composite current collectors. The coating slurry formulation and preparation method are the same as those in Example 10. The only difference is that the coating thickness is 1 μm on both sides.

[0051] Comparative Example 1 This comparative example maintains the same preparation steps as Example 1, except that the binder is omitted from the raw materials. Specifically: Coating slurry formulation: CNC 98%, diethyltoluene diamine 2%.

[0052] Comparative Example 2 This comparative example maintains the same preparation steps as Example 1, but the curing agent is omitted. Specifically: Coating slurry formulation: CNC 93%, PVDF 7%.

[0053] Comparative Example 3 This comparative example maintains the same preparation steps as Example 1, except that PVDF is used instead of CNC. Specifically: Coating slurry formulation: PVDF 99%, diethyltoluene diamine 1%.

[0054] Comparative Example 4 This comparative example maintains the same preparation steps as Example 1, but uses... (Alumina) replaces nanocellulose crystals, specifically: Coating paste formulation: 92%, PVDF 7%, diethyltoluene diamine 1%.

[0055] Performance tests were conducted on the products of each embodiment, the comparative example, and the PP, PE, and PET base films. The thickness of the battery separator was measured using a thickness gauge, with measurements taken at five random points on the separator, and the average value calculated. The heat shrinkage rate was tested according to the method in GB / T12027-2004, and the test results are shown in Table 1. The peel strength test was conducted according to the test method in GB / T2792-1998, and the test photos are shown below. Figures 1-4 As shown, where Figure 1 The images are of the diaphragm before and after testing at 150°C / h in Example 1 of this application (where a is before the test and b is after the test). Figure 2 These are photographs of the diaphragm in Example 10 before and after the test at 200℃ / h (where a is before the test and b is after the test). Figure 3 The images show the diaphragm before and after testing at 250°C / h in Example 14 (where a is before the test and b is after the test). Figure 4 This is a schematic diagram of the peel strength test method of this application (a) and a comparison diagram of Example 1 and Comparative Example 4 before and after the test (where b is before the test of Example 1, d is after the test of Example 2, c is before the test of Comparative Example 3, and e is after the test of Comparative Example 4).

[0056] Table 1 Note: The thickness in each embodiment is the base film thickness + coating thickness. The lower the areal density, the better, as it is more conducive to the lightweighting of the battery. MD represents the longitudinal direction, TD represents the transverse direction, and the smaller the heat shrinkage, the better the heat resistance.

[0057] As shown in Table 1, the PP / PET / PE base films have extremely high thermal shrinkage rates. For example, the MD / TD thermal shrinkage rates of PP base films reach 67% and 70% at 150℃, while those of PET base films are 15% and 20% at 250℃. After introducing CNC, the thermal shrinkage rate of Example 1 (CNC+PVDF+diethyltoluenediamine) at 150℃ is reduced to 3% and 4%. After modifying CNC (such as carboxylated CNC) with PI, diethyltoluenediamine and other components, the thermal shrinkage rates of Examples 6 and 10 at 250℃ are only 1.9%-4%. The double-sided coated Examples 13 and 14 further reduce the thermal shrinkage rate at 250℃ to 1.8%-2.8%, which is far superior to the comparative examples (comparative examples 3 and 4, after replacing CNC, have thermal shrinkage rates as high as 58%-67% at 150℃ and 82%-85% at 200℃), effectively ensuring the dimensional stability of the battery under high-temperature conditions and in the early stages of thermal runaway. The single-sided areal density is controlled at 0.8-1.2 g / m², which effectively reduces the overall weight of the battery while achieving high performance, which is beneficial to the lightweight design of the battery.

[0058] from Figure 4 As can be seen, the coating layer and the base film in the embodiment have good adhesion. After the tape is peeled off, the interface between the coating layer and the base film remains intact, with no obvious peeling, flaking, or damage. This indicates that the three-dimensional cross-linked network constructed by CNC has stronger interfacial adhesion and can effectively resist external tearing. In contrast, after the tape is peeled off in the comparative example, the red box shows that the coating layer has a large area of ​​peeling and damage, and even the base film is exposed. This indicates that without CNC or curing agent, the interfacial adhesion is relatively weak and cannot meet the requirements of practical applications. This further verifies the core role of CNC in improving interfacial adhesion. The polar groups of the three-dimensional cross-linked network formed by nanofibers and adhesive strengthen the intermolecular forces with the substrate, greatly enhancing the adhesion between the coating layer and the base film and preventing peeling and failure.

[0059] In summary, the polymer composite membrane for composite current collectors and its preparation method according to the embodiments of this application have the following advantages: 1. The coating layer of this application uses nanocellulose whiskers, binders and curing agents as raw materials. The curing agent undergoes a polymerization reaction with the nanofibers and binders, guiding the nanofibers and binders to form a three-dimensional cross-linked network, which significantly reduces the porosity of the polymer membrane, effectively prevents electrolyte penetration and corrosion, and improves the mechanical properties and thermal stability of the membrane. At the same time, it eliminates the weak interface layer of the base film, and the polar groups of the cross-linked network strengthen the intermolecular forces with the substrate, improves the peel strength, effectively prevents the coating layer from falling off, and ensures the reliability of interlayer bonding.

[0060] 2. The heat resistance temperature of the composite membrane in this application is increased from the existing 50-100℃ to 180-250℃, which can effectively melt the polymer layer and block the short circuit current in the event of battery thermal runaway, thus greatly improving battery safety.

[0061] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A polymer composite membrane for composite current collectors, characterized in that, It includes a polymer base film and a coating layer disposed on at least one surface of the polymer base film; The coating slurry of the coating layer, by weight percentage, consists of the following components: 85-94% nanofibers, 5-10% binder, and 0.5-5% curing agent.

2. The polymer composite film for a composite current collector according to claim 1, characterized by The polymer base film is one or more of the following: polyethylene terephthalate film, polypropylene film, polyethylene film, polyamide film, polyethylene naphthalate film, polyimide film, aramid film, polycarbonate film, polyetheretherketone film, and cellulose-based porous film; the polypropylene film includes BOPP, CPP, OPP, mPP, MOPP, and PPTF.

3. The polymer composite film for a composite current collector according to claim 1, wherein The nanofibers include one or more of the following: microfibrillated cellulose, cellulose nanofibers, lignin nanofibers, cellulose nanowhiskers, bacterial cellulose, polyimide nanofibers, aramid nanofibers, and modified nanofibers; the modified nanofibers are nanofibers modified by one or more composite methods including carboxylation, sulfonation, esterification, etherification, graft polymerization, oxidation, acetylation, phosphorylation, isocyanate modification, and silane coupling agent modification.

4. The polymer composite film for a composite current collector according to claim 1, wherein The adhesive is one or more of the following: polyacrylic acid, polyacrylate, carboxyl-modified acrylic resin, acrylic-styrene copolymer, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol, epoxy resin, phenolic resin, polyimide resin, styrene-butadiene rubber, nitrile rubber, and polyethylene glycol.

5. The polymer composite film for a composite current collector according to claim 1, wherein The curing agent is one or more of the following: diethyltoluenediamine, dimethylthiotoluenediamine, diaminodiphenylmethane, aminodiphenyl sulfone, m-phenylenediamine, isophoronediamine, 1,3-cyclohexanedimethylamine, diaminodicyclohexylmethane, diethylenetriamine, triethylenetetramine, polyetheramine, phenolic amine, polyamideamine, low-formaldehyde melamine-formaldehyde resin, phenyl melamine-formaldehyde resin, carbodiimide, toluene diisocyanate, diphenylmethane diisocyanate, polyphenyl polymethylene polyisocyanate, hexamethylene diisocyanate, 1,12-dodecylmethylene diisocyanate, pentamethylene diisocyanate, isophorone diisocyanate, 1,3-cyclohexane diisocyanate, 4,4-dicyclohexylmethane diisocyanate, phenyldimethylmethylene diisocyanate, and modified or polymeric isocyanates.

6. The polymer composite membrane for composite current collectors according to claim 1, characterized in that, The thickness of the polymer base film is 2-10 μm; the thickness of the coating layer is 0.5-5 μm.

7. A method for preparing a polymer composite film for composite current collectors as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix nanofibers, binder and curing agent evenly in solvent to obtain coating slurry; S2. Apply the coating slurry to at least one side of the polymer base film and cure it to form a coating layer.

8. The method for preparing a polymer composite membrane for composite current collectors according to claim 7, characterized in that, The mixing process in step S1 specifically involves: mixing nanofibers with a solvent to form a dispersion, then adding a binder and a curing agent to the dispersion and stirring to obtain the coating slurry. The solid content of the dispersion is 5-30%, and the solvent is water or ethanol.

9. The method for preparing a polymer composite membrane for composite current collectors according to claim 7, characterized in that, The coating is a wet coating process, selected from one or more of the following: gravure coating, slot coating, doctor blade coating, roller coating, curtain coating, spraying, dip coating, spin coating, and bar coating.

10. The method for preparing a polymer composite membrane for composite current collectors according to claim 7, characterized in that, The curing temperature is 50-120℃, and the curing time is 2-24h.

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