Functional current collector without transfer welding

Abstract

The invention relates to the technical field of lithium batteries, in particular to a functional current collector without transfer welding. Comprising the following steps that 1, laser drilling is conducted on a base film, round holes are formed, and a base film A is obtained; 2, filling a round hole of the base film A with a medium-temperature curing conductive adhesive, and drying to obtain a base film B; 3, the surface of the base film B is subjected to film coating treatment; therefore, the functional current collector without transfer welding is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of lithium batteries, in particular to a functional current collector that does not require transfer welding. Background Art

[0002] Functional current collectors have attracted extensive attention in the lithium battery industry because they can improve the energy density and safety of batteries. Since the middle layer is a non-conductive polymer layer, it needs to be transferred to conduction. Transfer welding is to weld a layer of conventional metal foil on each of the metal layers on both sides. The welded metal foil draws out the current, and then conduction is completed through pre-welding.

[0003] Since the metal layer must be conductive before it can be used in the battery, and the application of the transfer welding process is not yet mature, this has hindered the promotion of functional current collectors to a certain extent. In addition, most of the existing transfer welding equipment is still in the development stage and the equipment cost is high. In the welding process, a large amount of copper / aluminum foil is also required, and most of these foils will be removed in the subsequent process, which causes a certain waste of materials.

[0004] In summary, it is of great significance to obtain a functional current collector that does not require transfer welding. Summary of the invention

[0005] The object of the present invention is to provide a functional current collector that does not require transfer welding, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A functional current collector without transfer welding comprises the following steps:

[0008] Step 1: punch holes in the basement membrane by laser to form circular holes, thereby obtaining basement membrane A;

[0009] Step 2: Fill the medium temperature curing conductive adhesive into the circular holes of the base film A and dry it to obtain the base film B;

[0010] Step 3: The surface of the base film B is subjected to coating treatment to obtain a functional current collector.

[0011] In a further embodiment, the drying temperature is 90-110° C. and the drying time is 20-40 minutes, so as to prevent the base film from being damaged by the baking temperature being too high.

[0012] Preferably, the base film has a thickness of 1 to 10 μm; the base film includes one of polyethylene terephthalate (PET) and polypropylene (PP), serving as an intermediate layer of the functional current collector.

[0013] In a further embodiment, the width of the base film is 250 to 350 mm.

[0014] More optimally, in step 1, the process is: reserve 20 to 30 mm on both sides of the base film, perform laser drilling in the middle of the base film at a laser speed of 750 to 850 mm / s, a laser power of 25 to 35% and a frequency of 1400 to 1600 kHz to form regular circular holes to obtain base film A.

[0015] In a further solution, the circular hole is produced by laser drilling, and the laser processing has high precision.

[0016] More optimally, the diameter of the circular holes is 0.5-1 mm, and the spacing between the holes is 4-6 mm.

[0017] In a further solution, a medium-temperature curing conductive adhesive is coated on the circular hole area so that the circular hole is filled with the medium-temperature curing conductive adhesive, and excess medium-temperature curing conductive adhesive is scraped off to keep the film surface flat.

[0018] More optimally, the functional current collector includes one of a composite copper current collector and a composite aluminum current collector; and the thickness of the deposited metal layer on both sides of the base film B is 0.5 to 2 μm.

[0019] More optimally, when the functional current collector is a composite aluminum current collector, the coating process is an evaporation process; when the functional current collector is a composite copper current collector, the coating process is a magnetron sputtering process or an electroplating process.

[0020] Preferably, the preparation method of the medium temperature curing conductive adhesive is:

[0021] S1-1: Preparation of modified conductive filler: Grind graphene oxide and carbon nanotubes, blend and add into deionized water, ultrasonically treat for 2-3 hours, add ethylenediamine and ammonia water, the mass ratio of graphene oxide, carbon nanotubes, ethylenediamine and ammonia water is 0.5-1:0.2-0.5:8-10:2-3, react at 90-100°C for 12-14 hours, filter and dry to obtain modified conductive filler;

[0022] S1-2: Preparation of medium-temperature curing conductive adhesive: Add modified conductive filler and polyurethane with amide bonds to N-methylpyrrolidone, react at 70-90°C for 2-4 hours to obtain modified polyurethane; ultrasonically mix the modified polyurethane and epoxy resin to obtain medium-temperature curing conductive adhesive.

[0023] More optimally, in the raw materials of the modified polyurethane, the mass ratio of the modified conductive filler to the polyurethane with amide bonds is 3-10:100-120;

[0024] In the raw materials of the medium-temperature curing conductive adhesive, the mass ratio of modified polyurethane to epoxy resin is 1.2-1.5:0.5-0.8.

[0025] More optimally, the preparation method of the polyurethane with amide bonds is:

[0026] S1-2: adding hexamethylenediamine in a molar ratio of 2:2:2 to 2.2 to a 20 wt% to 40 wt% sodium hydroxide aqueous solution, and then adding to a xylene solution of 1H-pyrazole-1-yl chloride, stirring with ultrasound at 20 to 30° C. for 30 to 60 min, washing, and drying to obtain a product A with an amide bond;

[0027] S2-2: Add trifluoromethoxyphenyl isocyanate and ethylene glycol to N,N-dimethylacetamide, react at 60-70°C for 1-3 hours, then add product A with an amide bond and stir evenly at 70-90°C. The molar ratio of trifluoromethoxyphenyl isocyanate, ethylene glycol and product A with an amide bond is 5-6:1:1 to obtain a polyurethane with an amide bond.

[0028] In the scheme, polyurethane is selected as the bonding polymer of the medium-temperature curing conductive adhesive, which has good bonding properties and high temperature resistance. The introduction of amide bonds further enhances the medium-temperature curing performance of polyurethane. Graphene oxide and carbon nanotubes are used as conductive fillers and compounded with polyurethane to improve the interface performance while producing synergistic properties, thereby preparing a medium-temperature curing conductive adhesive with high bonding properties and high conductivity.

[0029] Among them, in order to improve the medium-temperature curing performance of polyurethane, the polyurethane is modified and amide bonds are introduced to further improve the performance. In addition, during the modification process, pyrazole groups and fluorine elements are introduced to improve the conductivity and chemical stability.

[0030] Among them, graphene oxide and carbon nanotubes have high conductivity, but there are problems with their interfacial composite ability with polyurethane. In order to improve the interfacial performance between the conductive filler and polyurethane, the conductive filler is amino-modified in the scheme to react with the isocyanate group in the polyurethane, so that the polyurethane and the conductive filler are successfully composited. Subsequently, epoxy resin is added for further composite, and epoxy groups are introduced to improve the reaction with the active groups in the base film, further improving the conductivity and bonding ability.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The scheme punches holes in the polymer base film and fills it with medium-temperature curing conductive glue, so that the metal layers on both sides of the functional current collector can be connected through the medium-temperature curing conductive glue in the hole, omitting the transfer welding process, improving application efficiency, and avoiding the large amount of copper / aluminum foil waste generated during the transfer welding process.

[0033] (2) The medium-temperature curing conductive adhesive prepared in this scheme is used in the preparation of functional current collectors and has good interface properties, medium-temperature curing ability, and bonding properties. At the same time, it can further improve the conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0035] Figure 1 This is a schematic diagram of the basement membrane after laser drilling;

[0036] Figure 2 This is a diagram of the resistance test method. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] It should be noted that there are no special restrictions on the manufacturers of all raw materials involved in the present invention, and exemplarily include: in the following embodiments, the model of the medium-temperature curing conductive adhesive in Example 1 is ALTEXE, which is purchased from Qieke New Material Technology (Shanghai) Co., Ltd.

[0039] Embodiment 1: A functional current collector without transfer welding, comprising the following steps:

[0040] Step 1: Select a PET base film with a thickness of 6 μm and a width of 300 mm as the middle layer of the functional current collector, reserve 25 mm on both sides of the base film, and perform laser drilling in the middle of the base film at a laser speed of 800 mm / s, a laser power of 30%, and a frequency of 1500 kHz to form circular holes with a hole diameter of 0.75 mm and a hole spacing of 5 mm, such as Figure 1 As shown, basement membrane A is obtained;

[0041] Step 2: Fill the circular hole area of ​​the base film A with the medium temperature curing conductive adhesive, fill the circular hole with the medium temperature curing conductive adhesive, scrape off the excess medium temperature curing conductive adhesive, keep the film surface flat, and then dry at 100° C. for 30 minutes to obtain the base film B;

[0042] Step 3: A 1 μm metal aluminum layer is deposited on both sides of the dried base film B through an evaporation process to obtain a functional current collector.

[0043] Embodiment 2: A functional current collector without transfer welding, comprising the following steps:

[0044] Step 1: Preparation of medium-temperature curing conductive adhesive: S1: Add hexamethylenediamine in a molar ratio of 2:2:2.1 to a 30wt% sodium hydroxide aqueous solution, then add it to a xylene solution of 1H-pyrazole-1-yl chloride, ultrasonically stir for 45 minutes at 25°C, wash, and dry to obtain a product A with an amide bond; S2: Add trifluoromethoxyphenylisocyanate and ethylene glycol to N,N-dimethylacetamide, react at 65°C for 2 hours, then add the product A with an amide bond and stir evenly at 80°C. The molar ratio of trifluoromethoxyphenylisocyanate, ethylene glycol, and the product A with an amide bond is 5.5:1:1 to obtain a product with an amide bond. bonded polyurethane; S3: Grind graphene oxide and carbon nanotubes, blend and add to deionized water, ultrasonically treat for 2.5 hours, add ethylenediamine and ammonia water, the mass ratio of graphene oxide, carbon nanotubes, ethylenediamine and ammonia water is 0.8:0.3:9:2.5, react at 95°C for 13 hours, filter and dry to obtain a modified conductive filler; S4: Add the modified conductive filler and polyurethane with amide bonds to N-methylpyrrolidone at a mass ratio of 7:110, react at 80°C for 3 hours to obtain a modified polyurethane; Ultrasonically mix the modified polyurethane and epoxy resin at a mass ratio of 1.3:0.6 to obtain a medium-temperature curing conductive adhesive;

[0045] Step 2: Select a PET base film with a thickness of 6 μm and a width of 300 mm as the middle layer of the functional current collector, reserve 25 mm on both sides of the base film, and perform laser drilling in the middle of the base film at a laser speed of 800 mm / s, a laser power of 30%, and a frequency of 1500 kHz to form circular holes with a hole diameter of 0.75 mm and a hole spacing of 5 mm, such as Figure 1 As shown, basement membrane A is obtained;

[0046] Step 3: Fill the circular hole area of ​​the base film A with the medium temperature curing conductive adhesive, fill the circular hole with the medium temperature curing conductive adhesive, scrape off the excess medium temperature curing conductive adhesive, keep the film surface flat, and then dry at 100° C. for 30 minutes to obtain the base film B;

[0047] Step 4: A 1 μm metal aluminum layer is deposited on both sides of the dried base film B through an evaporation process to obtain a functional current collector.

[0048] Embodiment 3: A functional current collector without transfer welding, comprising the following steps:

[0049] Step 1: Preparation of medium-temperature curing conductive adhesive: S1: Add hexamethylenediamine in a molar ratio of 1:1:1 to a 20wt% sodium hydroxide aqueous solution, then add it to a xylene solution of 1H-pyrazole-1-yl chloride, ultrasonically stir for 45 minutes at 25°C, wash, and dry to obtain a product A with an amide bond; S2: Add trifluoromethoxyphenylisocyanate and ethylene glycol to N,N-dimethylacetamide, react at 65°C for 2 hours, then add the product A with an amide bond and stir evenly at 80°C. The molar ratio of trifluoromethoxyphenylisocyanate, ethylene glycol, and the product A with an amide bond is 5.5:1:1 to obtain a product with an amide bond. bonded polyurethane; S3: Grind graphene oxide and carbon nanotubes, blend and add to deionized water, ultrasonically treat for 2.5 hours, add ethylenediamine and ammonia water, the mass ratio of graphene oxide, carbon nanotubes, ethylenediamine and ammonia water is 0.5:0.2:8:2, react at 95°C for 13 hours, filter and dry to obtain a modified conductive filler; S4: Add the modified conductive filler and polyurethane with amide bonds to N-methylpyrrolidone at a mass ratio of 3:100, react at 80°C for 3 hours to obtain a modified polyurethane; Ultrasonically mix the modified polyurethane and epoxy resin at a mass ratio of 1.2:0.5 to obtain a medium-temperature curing conductive adhesive;

[0050] Step 2: Select a PET base film with a thickness of 6 μm and a width of 300 mm as the middle layer of the functional current collector, reserve 25 mm on both sides of the base film, and perform laser drilling in the middle of the base film at a laser speed of 800 mm / s, a laser power of 30%, and a frequency of 1500 kHz to form circular holes with a hole diameter of 0.75 mm and a hole spacing of 5 mm, such as Figure 1 As shown, basement membrane A is obtained;

[0051] Step 3: Fill the circular hole area of ​​the base film A with the medium temperature curing conductive adhesive, fill the circular hole with the medium temperature curing conductive adhesive, scrape off the excess medium temperature curing conductive adhesive, keep the film surface flat, and then dry at 100° C. for 30 minutes to obtain the base film B;

[0052] Step 4: A 1 μm metal aluminum layer is deposited on both sides of the dried base film B through an evaporation process to obtain a functional current collector.

[0053] Embodiment 4: A functional current collector without transfer welding, comprising the following steps:

[0054] Step 1: Preparation of medium-temperature curing conductive adhesive: S1: Add hexamethylenediamine in a molar ratio of 2:2:2.2 to a 40wt% sodium hydroxide aqueous solution, then add it to a xylene solution of 1H-pyrazole-1-yl chloride, ultrasonically stir for 45 minutes at 25°C, wash, and dry to obtain a product A with an amide bond; S2: Add trifluoromethoxyphenylisocyanate and ethylene glycol to N,N-dimethylacetamide, react at 65°C for 2 hours, then add the product A with an amide bond and stir evenly at 80°C. The molar ratio of trifluoromethoxyphenylisocyanate, ethylene glycol, and the product A with an amide bond is 6:1:1 to obtain a product with an amide bond. bonded polyurethane; S3: Grind graphene oxide and carbon nanotubes, blend and add to deionized water, ultrasonically treat for 2.5 hours, add ethylenediamine and ammonia water, the mass ratio of graphene oxide, carbon nanotubes, ethylenediamine and ammonia water is 1:0.5:10:3, react at 95°C for 13 hours, filter and dry to obtain a modified conductive filler; S4: Add the modified conductive filler and polyurethane with amide bonds to N-methylpyrrolidone at a mass ratio of 10:120, react at 80°C for 3 hours to obtain a modified polyurethane; Ultrasonically mix the modified polyurethane and epoxy resin at a mass ratio of 1.5:0.8 to obtain a medium-temperature curing conductive adhesive;

[0055] Step 2: Select a PET base film with a thickness of 6 μm and a width of 300 mm as the middle layer of the functional current collector, reserve 25 mm on both sides of the base film, and perform laser drilling in the middle of the base film at a laser speed of 800 mm / s, a laser power of 30%, and a frequency of 1500 kHz to form circular holes with a hole diameter of 0.75 mm and a hole spacing of 5 mm, such as Figure 1 As shown, basement membrane A is obtained;

[0056] Step 3: Fill the circular hole area of ​​the base film A with the medium temperature curing conductive adhesive, fill the circular hole with the medium temperature curing conductive adhesive, scrape off the excess medium temperature curing conductive adhesive, keep the film surface flat, and then dry at 100° C. for 30 minutes to obtain the base film B;

[0057] Step 4: A 1 μm metal aluminum layer is deposited on both sides of the dried base film B through an evaporation process to obtain a functional current collector.

[0058] Comparative Example 1: The composite aluminum current collector that needs to be welded in the prior art is specifically:

[0059] Step 1: Clean the aluminum metal layer with sodium hydroxide solution, then place it on the predetermined welding position of the metal layers on both sides of the functional current collector, fix it, and weld it for 0.3s at a set current of 2000A and an electrode pressure of 10N to obtain a functional current collector.

[0060] Comparative Example 2: Based on Example 2, only carbon nanotubes are introduced as conductive fillers, and the rest of the process remains unchanged, specifically:

[0061] Step 1: Preparation of medium temperature curing conductive adhesive: S1: Add hexamethylenediamine with a molar ratio of 2:2:2.1 to a 30wt% sodium hydroxide aqueous solution, then add it to a xylene solution of 1H-pyrazole-1-yl chloride, ultrasonically stir for 45 minutes at 25°C, wash, and dry to obtain a product A with an amide bond; S2: Add trifluoromethoxyphenylisocyanate and ethylene glycol to N,N-dimethylacetamide, react at 65°C for 2 hours, then add the product A with an amide bond and stir evenly at 80°C. The molar ratio of trifluoromethoxyphenylisocyanate, ethylene glycol, and the product A with an amide bond is 5.5 : 1:1, to obtain a polyurethane with an amide bond; S3: Add carbon nanotubes to deionized water, ultrasonically treat for 2.5 hours, add ethylenediamine and ammonia water, the mass ratio of carbon nanotubes, ethylenediamine and ammonia water is 1:9:2.5, react at 95°C for 13 hours, filter and dry to obtain a modified conductive filler; S4: Add the modified conductive filler and the polyurethane with an amide bond to N-methylpyrrolidone at a mass ratio of 7:110, react at 80°C for 3 hours to obtain a modified polyurethane; Ultrasonically mix the modified polyurethane and epoxy resin at a mass ratio of 1.3:0.6 to obtain a medium-temperature curing conductive adhesive;

[0062] Step 2: Select a PET base film with a thickness of 6 μm and a width of 300 mm as the middle layer of the functional current collector, reserve 25 mm on both sides of the base film, and perform laser drilling in the middle of the base film at a laser speed of 800 mm / s, a laser power of 30%, and a frequency of 1500 kHz to form circular holes with a hole diameter of 0.75 mm and a hole spacing of 5 mm, such as Figure 1 As shown, basement membrane A is obtained;

[0063] Step 3: Fill the circular hole area of ​​the base film A with the medium temperature curing conductive adhesive, fill the circular hole with the medium temperature curing conductive adhesive, scrape off the excess medium temperature curing conductive adhesive, keep the film surface flat, and then dry at 100° C. for 30 minutes to obtain the base film B;

[0064] Step 4: A 1 μm metal aluminum layer is deposited on both sides of the dried base film B through an evaporation process to obtain a functional current collector.

[0065] Comparative Example 3, based on Example 2, 9-anthracenecarbonyl chloride was replaced by 1H-pyrazole-1-yl chloride, and the rest of the process remained unchanged, specifically:

[0066] Step 1: Preparation of medium-temperature curing conductive adhesive: S1: Add hexamethylenediamine in a molar ratio of 2:2:2.1 to a 30wt% sodium hydroxide aqueous solution, then add it to a xylene solution of 9-anthracenecarbonyl chloride, ultrasonically stir for 45 minutes at 25°C, wash, and dry to obtain a product A with an amide bond; S2: Add trifluoromethoxyphenylisocyanate and ethylene glycol to N,N-dimethylacetamide, react at 65°C for 2 hours, then add the product A with an amide bond and stir evenly at 80°C. The molar ratio of trifluoromethoxyphenylisocyanate, ethylene glycol, and product A with an amide bond is 5.5:1:1 to obtain a product with an amide bond. Polyurethane; S3: Grind graphene oxide and carbon nanotubes, blend and add into deionized water, ultrasonically treat for 2.5 hours, add ethylenediamine and ammonia water, the mass ratio of graphene oxide, carbon nanotubes, ethylenediamine and ammonia water is 0.8:0.3:9:2.5, react at 95°C for 13 hours, filter and dry to obtain a modified conductive filler; S4: Add the modified conductive filler and polyurethane with amide bonds into N-methylpyrrolidone at a mass ratio of 7:110, react at 80°C for 3 hours to obtain a modified polyurethane; Ultrasonically mix the modified polyurethane and epoxy resin at a mass ratio of 1.3:0.6 to obtain a medium-temperature curing conductive adhesive;

[0067] Step 2: Select a PET base film with a thickness of 6 μm and a width of 300 mm as the middle layer of the functional current collector, reserve 25 mm on both sides of the base film, and perform laser drilling in the middle of the base film at a laser speed of 800 mm / s, a laser power of 30%, and a frequency of 1500 kHz to form circular holes with a hole diameter of 0.75 mm and a hole spacing of 5 mm, such as Figure 1 As shown, basement membrane A is obtained;

[0068] Step 3: Fill the circular hole area of ​​the base film A with the medium temperature curing conductive adhesive, fill the circular hole with the medium temperature curing conductive adhesive, scrape off the excess medium temperature curing conductive adhesive, keep the film surface flat, and then dry at 100° C. for 30 minutes to obtain the base film B;

[0069] Step 4: A 1 μm metal aluminum layer is deposited on both sides of the dried base film B through an evaporation process to obtain a functional current collector.

[0070] Comparative Example 4: Based on Example 2, the polyurethane is replaced by a polyurethane with an amide bond, and the other processes remain unchanged, specifically:

[0071] Step 1: Preparation of medium-temperature curing conductive adhesive: S1: Grind graphene oxide and carbon nanotubes, blend and add to deionized water, ultrasonically treat for 2.5 hours, add ethylenediamine and ammonia water, the mass ratio of graphene oxide, carbon nanotubes, ethylenediamine and ammonia water is 0.8:0.3:9:2.5, react at 95°C for 13 hours, filter and dry to obtain modified conductive filler; S2: Add modified conductive filler and polyurethane to N-methylpyrrolidone at a mass ratio of 7:110, react at 80°C for 3 hours to obtain modified polyurethane; ultrasonically mix the modified polyurethane and epoxy resin at a mass ratio of 1.3:0.6 to obtain medium-temperature curing conductive adhesive;

[0072] Step 2: Select a PET base film with a thickness of 6 μm and a width of 300 mm as the middle layer of the functional current collector, reserve 25 mm on both sides of the base film, and perform laser drilling in the middle of the base film at a laser speed of 800 mm / s, a laser power of 30%, and a frequency of 1500 kHz to form circular holes with a hole diameter of 0.75 mm and a hole spacing of 5 mm, such as Figure 1 As shown, basement membrane A is obtained;

[0073] Step 3: Fill the circular hole area of ​​the base film A with the medium temperature curing conductive adhesive, fill the circular hole with the medium temperature curing conductive adhesive, scrape off the excess medium temperature curing conductive adhesive, keep the film surface flat, and then dry at 100° C. for 30 minutes to obtain the base film B;

[0074] Step 4: A 1 μm metal aluminum layer is deposited on both sides of the dried base film B through an evaporation process to obtain a functional current collector.

[0075] Test experiment: The functional current collector without transfer welding prepared in Examples 1 to 4 and Comparative Examples 1 to 4 was tested for its performance: (1) Overcurrent resistance test: The test results of the functional current collector without transfer welding prepared in Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1. The test method is as follows: Figure 2 As shown; (2) Square resistance test: The functional current collector without transfer welding prepared in Examples 1 to 2 and Comparative Example 1 was tested for square resistance of the functional current collector using a four-probe square resistance tester. The test results are shown in Table 2; (3) The functional current collector without transfer welding prepared in Examples 1 to 2 and Comparative Example 1 was made into an 18650 battery cell (NCM+graphite system) to further test its internal resistance. The results are shown in Table 3;

[0076]

[0077] Table 1

[0078]

[0079]

[0080] Table 2

[0081]

[0082] Table 3

[0083] Result analysis: According to the data analysis of Table 1, Table 2 and Table 3, it can be seen that the scheme makes holes on the polymer base film and fills them with medium-temperature curing conductive glue, so that the metal layers on both sides of the functional current collector can be connected through the medium-temperature curing conductive glue in the holes, omitting the transfer welding process, improving the application efficiency, and avoiding the large amount of copper / aluminum foil waste generated during the transfer welding process; the medium-temperature curing conductive glue prepared by this scheme is used in the preparation of functional current collectors, and has good interface properties, medium-temperature curing ability, and bonding properties. At the same time, it can further improve the conductivity.

[0084] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A functional current collector without transfer welding, characterized in that: The following steps are involved: Step 1: punch holes in the basement membrane by laser to form circular holes, thereby obtaining basement membrane A; Step 2: Fill the circular holes of base film A with medium-temperature curing conductive adhesive and dry to obtain base film B; Step 3: The surface of the base film B is subjected to coating treatment to obtain a functional current collector.

2. A functional current collector without transfer welding according to claim 1, characterized in that: The thickness of the base film is 1-10 μm; the base film comprises one of polyethylene terephthalate and polypropylene.

3. A functional current collector without transfer welding according to claim 1, characterized in that: In step 1, the process is as follows: 20 to 30 mm is reserved on both sides of the base film, and laser drilling is performed in the middle of the base film at a laser speed of 750 to 850 mm / s, a laser power of 25 to 35%, and a frequency of 1400 to 1600 kHz to form regular circular holes to obtain base film A.

4. A functional current collector without transfer welding according to claim 3, characterized in that: The diameter of the circular holes is 0.5-1 mm, and the spacing between the holes is 4-6 mm.

5. The functional current collector without transfer welding according to claim 1, characterized in that: The functional current collector includes one of a composite copper current collector and a composite aluminum current collector; the thickness of the deposited metal layer on both sides of the base film B is 0.5-2 μm.

6. A functional current collector without transfer welding according to claim 5, characterized in that: When the functional current collector is a composite aluminum current collector, the coating process is an evaporation process; when the functional current collector is a composite copper current collector, the coating process is a magnetron sputtering process or an electroplating process.

7. The functional current collector without transfer welding according to claim 1, characterized in that: The preparation method of the medium temperature curing conductive adhesive is as follows: S1-1: Preparation of modified conductive filler: Grind graphene oxide and carbon nanotubes, blend and add into deionized water, ultrasonically treat for 2-3 hours, add ethylenediamine and ammonia water, the mass ratio of graphene oxide, carbon nanotubes, ethylenediamine and ammonia water is 0.5-1:0.2-0.5:8-10:2-3, react at 90-100°C for 12-14 hours, filter and dry to obtain modified conductive filler; S1-2: Preparation of medium-temperature curing conductive adhesive: Add modified conductive filler and polyurethane with amide bonds to N-methylpyrrolidone, react at 70-90°C for 2-4 hours to obtain modified polyurethane; ultrasonically mix the modified polyurethane and epoxy resin to obtain medium-temperature curing conductive adhesive.

8. The functional current collector without transfer welding according to claim 7, characterized in that: In the raw materials of the modified polyurethane, the mass ratio of the modified conductive filler to the polyurethane with amide bonds is 3-10:100-120; In the raw materials of the medium-temperature curing conductive adhesive, the mass ratio of modified polyurethane to epoxy resin is 1.2-1.5:0.5-0.

8.

9. A functional current collector without transfer welding according to claim 8, characterized in that: The preparation method of the polyurethane with amide bonds is: S1-2: adding hexamethylenediamine in a molar ratio of 2:2:2 to 2.2 to a 20 wt% to 40 wt% sodium hydroxide aqueous solution, and then adding to a xylene solution of 1H-pyrazole-1-yl chloride, stirring with ultrasound at 20 to 30° C. for 30 to 60 min, washing, and drying to obtain a product A with an amide bond; S2-2: Add trifluoromethoxyphenyl isocyanate and ethylene glycol to N,N-dimethylacetamide, react at 60-70°C for 1-3 hours, then add product A with an amide bond and stir evenly at 70-90°C. The molar ratio of trifluoromethoxyphenyl isocyanate, ethylene glycol and product A with an amide bond is 5-6:1:1 to obtain a polyurethane with an amide bond.

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