Composite current collector foil tab with conductive functional coating and method of making and use thereof

Abstract

The application discloses a composite current collector foil tab with a conductive functional coating and a preparation method and application thereof, and relates to the technical field of lithium ion batteries. The tab is coated with a conductive functional coating containing metal nanowires and a polymer on the surface of a composite current collector foil. The preparation method comprises the following steps: preparing a metal nanowire conductive glue solution, and coating the solution on the surface of the foil and drying and curing. The welding method comprises the following steps: punching the tab laminates, coating the conductive glue solution on the hole walls and curing, and then pressing and melting after penetrating the conductive connecting piece. The application realizes the conductive connection of the tab through the conductive coating, avoids the traditional tab transfer printing and welding process, reduces the equipment investment and process time, solves the problems of edge curling and internal resistance rising caused by welding, improves the flatness and conductive performance of the tab of the battery, and is suitable for the manufacture of lithium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and in particular relates to a composite current collector foil tab with a conductive functional coating, its preparation method and application. Background Technology

[0002] Lithium-ion batteries have been widely used in various electronic devices, and the rapid updates and iterations of electronic products have led to increasingly higher requirements for energy density and safety performance.

[0003] When lithium-ion batteries are abused under extreme or abnormal environmental conditions, internal short circuits may occur, leading to battery failure. The battery may release a large amount of heat in a short period, potentially causing thermal runaway and posing a safety hazard. Therefore, technologies to prevent and suppress short circuits between the positive and negative electrodes of lithium-ion batteries are crucial.

[0004] CN121601982A describes a composite current collector with a locally enhanced welding area and its preparation method. The composite current collector has a metal foil attached to a predetermined welding area for welding with an electrode tab. By increasing the effective conductive thickness of the predetermined welding area, the sheet resistance and contact resistance of the area are significantly reduced.

[0005] CN121394411A discloses a composite current collector welding structure and its welding method. The composite current collector welding structure includes a first connector and a second connector, which are respectively disposed on the upper and lower surfaces of the composite current collector welding end. Welding is performed in a molten groove. The molten current collector flows along the gap between the first connector and the second connector and does not aggregate into a sphere under the action of surface tension, thereby ensuring welding strength and good contact of the metal layer.

[0006] CN223858148U discloses a composite current collector, electrode sheet, and battery that are easy to weld. The composite current collector stack unit forms a battery current collector assembly structure. The composite current collector stack unit has cavities, and the inclined side of the cavity channel is exposed in a stepped manner. The cavities effectively dissipate heat at the connection of the composite current collector, thereby improving the safety of the lithium-ion battery.

[0007] The aforementioned patented technologies have a clear but limited function. When the foil tabs are heated unevenly or have poor contact, incomplete polymer vaporization can lead to issues such as incomplete soldering and detachment, severely impacting the welding reliability of the composite current collector foil tabs. In short, the aforementioned technologies or inventions cannot achieve further improvements in the safety performance of lithium-ion batteries and have significant shortcomings.

[0008] Composite current collectors, with their short-circuit self-healing capability, represent an important direction in the development of lithium-ion batteries. Currently, efficient welding of composite current collector foil tabs remains a critical challenge. The welding mechanism involves the heat generated during the foil tab welding process vaporizing the polymer layer in the middle of the composite current collector foil tab, causing the metal layers to melt and bond together. When the foil tabs are heated unevenly or have poor contact, incomplete polymer vaporization can lead to incomplete welding, detachment, and other issues, severely impacting the welding reliability of the composite current collector foil tabs. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a composite current collector foil tab with a conductive functional coating, its preparation method, and its application, solving problems such as insufficient conductivity and welding difficulties of the composite current collector foil tab.

[0010] This invention is achieved as follows: a composite current collector foil tab with a conductive functional coating includes a composite current collector foil material, which comprises a middle polymer material layer and metal layers disposed on both sides of the polymer material layer. The surface of the composite current collector foil material is coated with a conductive functional coating, which includes metal nanowires and a polymer. The thickness of the conductive functional coating is 500 nm to 2 µm. In the conductive functional coating, the metal nanowires have a diameter of 10 nm to 200 nm and a length of 500 nm to 50 µm. The metal nanowires are silver nanowires or copper nanowires. The polymer used as a binder is at least one of polymethyl methacrylate, polymethyl cyanoacrylate, and ethyl cyanoacrylate. The mass content of the metal nanowires is 50% to 80%.

[0011] Furthermore, the conductive functional coating is applied to one or both sides of the composite current collector foil.

[0012] Furthermore, the metal layer is copper, aluminum, nickel, or an alloy thereof, and the polymer material layer is PET, PP, PI, or PA.

[0013] The method for preparing the composite current collector foil tab with the conductive functional coating described above includes the following steps: (1) Prepare a conductive adhesive solution for metal nanowires by adding metal nanowires and organic polymers or organic polymer monomers to anhydrous acetone as solvent and mixing them evenly. In the conductive adhesive solution, the metal nanowires are 4% to 20% by mass percentage, and the organic polymers or polymer monomers are 1% to 10%. (2) Apply the prepared metal nanowire conductive adhesive to one or both sides of the composite current collector foil, and dry and cure it.

[0014] Furthermore, the organic polymer is polymethyl methacrylate; the organic polymer monomer is methyl cyanoacrylate or ethyl cyanoacrylate.

[0015] Furthermore, in step (2), the drying and curing temperature is 20℃~80℃, and the drying time is ≥1min.

[0016] A method for welding electrode tabs, comprising the following steps: S1. A composite current collector stack unit is formed by stacking several of the above-mentioned composite current collector foil tabs with conductive functional coatings in the form of a stack; S2. Drill through holes in the composite current collector stack unit, with the through holes connecting each composite current collector foil tab in the composite current collector stack unit. Apply the prepared metal nanowire conductive adhesive to the hole wall, and dry and cure it. S3. After connecting the conductive connecting piece through the through hole of the composite current collector stack unit and the battery cell tab, the tab is welded using a pressure welding method.

[0017] Furthermore, in S2, the drying and curing temperature is 20℃~60℃, and the drying time is ≥1min.

[0018] A lithium-ion battery includes a cell, a casing, and a cover plate assembly. The cell includes a positive electrode and a negative electrode, and at least one of the positive electrode and / or negative electrode is a tab obtained by welding the electrode tabs as described above.

[0019] The advantages and technical effects of this invention are as follows: (1) The surface of the composite current collector foil tab is coated with a conductive functional coating. Among them, silver nanowires have a high melting point and good thermal stability, which can ensure the connection between the metal layers of the foil tab during welding, thereby ensuring the conductivity of the tab after welding.

[0020] (2) In the welding method, methyl cyanoacrylate and ethyl cyanoacrylate in the silver nanowire conductive adhesive solution can be used for in-situ rapid curing of the silver nanowire conductive adhesive solution, which improves the welding reliability and welding efficiency.

[0021] (3) The foil tab bundle is perforated and wetted to increase the conductive channel between the composite current collector metal conductive layer and the conductive connecting piece, thereby improving the conductivity of the tab after welding and the welding consistency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the composite current collector foil tab structure with a conductive functional coating of the present invention.

[0023] Figure 2 This is a schematic diagram of the microstructure of the conductive functional coating of the present invention.

[0024] Figure 3 This is a schematic diagram of the electrode tab structure prepared using the welding method of the present invention.

[0025] In the figure, 1-composite current collector foil; 2-conductive functional coating; 3-conductive connecting piece; 4-cell electrode tab. Detailed Implementation

[0026] The present invention will be further described below with reference to embodiments and accompanying drawings. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments and comparative examples only, and are not intended to limit the scope of protection of the present invention. It should be specifically noted that the same organic structure may have multiple names, and any structure that falls within the scope of the present invention is protected by the present invention.

[0027] like Figure 1 As shown, the composite current collector foil tab with conductive functional coating of the present invention includes a composite current collector foil 1, which includes a middle polymer material layer and metal layers disposed on both sides of the polymer material layer. The surface of the composite current collector foil is coated with a conductive functional coating 2, which includes metal nanowires and polymers, and the thickness of the conductive functional coating is 500nm~2µm.

[0028] like Figure 2 As shown, in the conductive functional coating, the metal nanowires have a diameter of 10nm~200nm and a length of 500nm~50µm. The metal nanowires are silver nanowires or copper nanowires, and the polymer is at least one of polymethyl methacrylate, polymethyl cyanoacrylate, and polyethyl cyanoacrylate. The mass content of the metal nanowires is 50%~80%.

[0029] Furthermore, the conductive functional coating is applied to one or both sides of the composite current collector foil.

[0030] Furthermore, the metal layer is copper, aluminum, nickel, or an alloy thereof, and the polymer material layer is PET, PP, PI, or PA.

[0031] The method for preparing the composite current collector foil tab with the conductive functional coating described above includes the following steps: (1) Prepare a conductive adhesive solution for metal nanowires by adding metal nanowires and organic polymers or organic polymer monomers to anhydrous acetone as solvent and mixing them evenly. In the conductive adhesive solution, the metal nanowires are 4% to 20% by mass percentage, and the organic polymers or polymer monomers are 1% to 10%. (2) Apply the prepared metal nanowire conductive adhesive to one or both sides of the composite current collector foil, and dry and cure it.

[0032] Furthermore, the organic polymer is polymethyl methacrylate; the organic polymer monomer is methyl cyanoacrylate or ethyl cyanoacrylate.

[0033] Furthermore, in step (2), the drying and curing temperature is 20℃~80℃, and the drying time is ≥1min.

[0034] like Figure 3 As shown, a method for welding electrode tabs includes the following steps: S1. A composite current collector stack unit is formed by stacking several of the above-mentioned composite current collector foil tabs with conductive functional coatings in the form of a stack; S2. Drill through holes in the composite current collector stack unit, with the through holes connecting each composite current collector foil tab in the composite current collector stack unit. Apply the prepared metal nanowire conductive adhesive to the hole wall, and dry and cure it. S3. After the conductive connecting piece 3 passes through the through hole of the composite current collector stack unit and connects to the battery cell tab 4, the tab is welded by pressure welding.

[0035] Furthermore, in S2, the drying and curing temperature is 20℃~60℃, and the drying time is ≥1min.

[0036] A lithium-ion battery includes a cell, a casing, and a cover plate assembly. The cell includes a positive electrode and a negative electrode, and at least one of the positive electrode and / or negative electrode is a tab obtained by welding the electrode tabs as described above.

[0037] The following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, the raw materials, reagents, etc. used in the following embodiments and comparative examples can be obtained commercially or prepared according to reported methods.

[0038] Example 1 Step 1: Prepare a positive electrode sheet using an 8μm thick composite aluminum foil as the positive electrode foil and NCM622 as the positive electrode material, with a coating amount of 48mg / cm². 2 A negative electrode sheet was prepared using a 6μm thick composite copper foil as the negative electrode foil and a graphite / silicon composite material as the negative electrode, with a coating amount of 14 mg / cm². 2 ,stand-by.

[0039] Step 2: Prepare the silver nanowire conductive adhesive. Anhydrous acetone is used as the solvent; the silver nanowires have a diameter of 10nm~30nm and a length of 0.5μm~10µm; the binder is methyl cyanoacrylate; the conductive adhesive contains 4% silver nanowires and 1% methyl cyanoacrylate by mass.

[0040] Step 3: Prepare the copper nanowire conductive adhesive. Anhydrous acetone is used as the solvent; the copper nanowires have a diameter of 100nm~200nm and a length of 1μm~5µm; other organic components include polymethyl methacrylate and ethyl cyanoacrylate (mass ratio 1:1); the conductive adhesive contains 4% copper nanowires and 1% methyl cyanoacrylate by mass.

[0041] Step 4: Using microgravure coating, the silver nanowire conductive adhesive is coated onto the positive electrode foil tab. The coating is applied to one side only, dried and cured at 60℃ for 1 min, with a coating thickness of 0.5µm and a coating width of 5mm. The electrode is ready for use. Copper nanowire conductive adhesive was applied to the negative electrode foil tab using a micro-gravure coating method. The coating was applied to one side only and dried and cured at 60°C for 1 minute. The coating thickness was 0.5µm and the coating width was 5mm. The electrode was then ready for use. After the positive and negative electrode sheets are die-cut, 30 layers of positive electrode sheets and 31 layers of negative electrode sheets are stacked to prepare a lithium-ion battery electrode assembly.

[0042] Step 5: Drill holes in the positive electrode foil tab bundle of the lithium-ion battery electrode assembly prepared in Step 4, with the holes penetrating the tab bundle. The holes have a diameter of 1 mm and the number of holes is 20. Perform a wetting treatment, that is, apply 20 μL of the silver nanowire conductive adhesive prepared in Step 1 to the hole wall, and dry and cure at 60°C for 2 min.

[0043] The negative electrode foil tab bundle is perforated, with the holes being 1 mm in diameter and numbering 20. It is then wetted by applying 20 μL of the copper nanowire conductive adhesive prepared in the first step onto the hole wall, and then dried and cured at 60°C for 2 min.

[0044] Step 6: Connect the positive conductive connecting piece to the positive foil tab bundle and the adhesive positive tab of the battery cell in order from top to bottom, and then weld the tabs using pressure welding. The pressure welding pressure is 50 kg and the current is 7000 A.

[0045] After connecting the negative electrode conductive connecting piece to the negative electrode foil tab bundle and the battery cell adhesive negative electrode tab in a top-to-bottom order, the tabs are welded using a pressure welding method with a pressure of 50 kg and a current of 5000 A.

[0046] Step 7: The welded electrode assembly is then subjected to assembly, formation, and other processes that complete the lithium-ion battery production process to obtain the high-safety lithium-ion battery.

[0047] Example 2 Step 1: Prepare a positive electrode sheet using an 8μm thick composite aluminum foil as the positive electrode foil and NCM622 as the positive electrode material, with a coating amount of 48mg / cm². 2 A negative electrode sheet was prepared using a 6μm thick composite copper foil as the negative electrode foil and a graphite / silicon composite material as the negative electrode, with a coating amount of 14 mg / cm². 2 ,stand-by.

[0048] Step 2: Prepare the silver nanowire conductive adhesive. Anhydrous acetone is used as the solvent; the silver nanowires have a diameter of 10nm~30nm and a length of 0.5μm~10µm; the binder is methyl cyanoacrylate; the conductive adhesive contains 4% silver nanowires and 1% methyl cyanoacrylate by mass.

[0049] Step 3: Prepare the copper nanowire conductive adhesive. Anhydrous acetone is used as the solvent; the copper nanowires have a diameter of 100nm~200nm and a length of 1μm~5µm; other organic components include polymethyl methacrylate and ethyl cyanoacrylate (mass ratio 1:1); the conductive adhesive contains 4% copper nanowires and 1% methyl cyanoacrylate by mass.

[0050] Step 4: Using microgravure coating, the silver nanowire conductive adhesive is coated onto the positive electrode foil tab, dried and cured at 60℃ for 1 min, with a single-sided coating thickness of 0.5µm and a coating width of 5mm. Then, double-sided coating is performed using the same coating thickness and width. The electrode is ready for use. Copper nanowire conductive adhesive was applied to the negative electrode foil tab using a micro-gravure coating process. The coating was applied to one side only and dried and cured at 60°C for 1 minute. The coating thickness on one side was 0.5µm and the coating width was 5mm. Then, the same coating thickness and width were applied to both sides. The electrode was then ready for use. After the positive and negative electrode sheets are die-cut, 30 layers of positive electrode sheets and 31 layers of negative electrode sheets are stacked to prepare a lithium-ion battery electrode assembly.

[0051] Step 5: Drill holes in the positive electrode foil tab bundle of the lithium-ion battery electrode assembly prepared in Step 4, with the holes penetrating the tab bundle. The holes have a diameter of 1 mm and the number of holes is 20. Perform a wetting treatment, that is, apply 20 μL of the silver nanowire conductive adhesive prepared in Step 1 to the hole wall, and dry and cure at 60°C for 2 min.

[0052] The negative electrode foil tab bundle is perforated, with the holes being 1 mm in diameter and numbering 20. It is then wetted by applying 20 μL of the copper nanowire conductive adhesive prepared in the first step onto the hole wall, and then dried and cured at 60°C for 2 min.

[0053] Step 6: Connect the positive electrode conductive connecting piece to the positive electrode foil tab bundle and the battery cell adhesive positive electrode tab in order from top to bottom, and then weld the tabs using pressure welding. The pressure welding pressure is 50 kg and the current is 7500 A.

[0054] After connecting the negative electrode conductive connecting piece to the negative electrode foil tab bundle and the battery cell adhesive negative electrode tab in a top-to-bottom order, the tabs are welded using a pressure welding method with a pressure of 50 kg and a current of 5500 A.

[0055] Step 7: The welded electrode assembly is then subjected to assembly, formation, and other processes that complete the lithium-ion battery production process to obtain the high-safety lithium-ion battery.

[0056] Example 3 Step 1: Prepare a positive electrode sheet using an 8μm thick composite aluminum foil as the positive electrode foil and NCM622 as the positive electrode material, with a coating amount of 48mg / cm². 2 A negative electrode sheet was prepared using a 6μm thick composite copper foil as the negative electrode foil and a graphite / silicon composite material as the negative electrode, with a coating amount of 14 mg / cm². 2 ,stand-by.

[0057] Step 2: Prepare the silver nanowire conductive adhesive. Anhydrous acetone is used as the solvent; the silver nanowires have a diameter of 25nm~50nm and a length of 20μm~50µm; the binder is methyl cyanoacrylate; the conductive adhesive contains 20% silver nanowires and 10% methyl cyanoacrylate by mass.

[0058] Step 3: Prepare the copper nanowire conductive adhesive. Anhydrous acetone is used as the solvent; the copper nanowires have a diameter of 100nm~200nm and a length of 10μm~20µm; other organic components include polymethyl methacrylate and ethyl cyanoacrylate (mass ratio 1:1); the conductive adhesive contains 20% copper nanowires and 10% methyl cyanoacrylate by mass.

[0059] Step 4: Using microgravure coating, the silver nanowire conductive adhesive is coated onto the positive electrode foil tab. The coating is applied to one side only, dried and cured at 60℃ for 2 min, with a coating thickness of 2µm and a coating width of 5mm. The electrode is ready for use. Copper nanowire conductive adhesive was applied to the negative electrode foil tab using a micro-gravure coating method. The coating was applied to one side only, dried and cured at 60°C for 2 min, with a coating thickness of 2µm and a coating width of 5mm. The electrode was then ready for use. After the positive and negative electrode sheets are die-cut, 30 layers of positive electrode sheets and 31 layers of negative electrode sheets are stacked to prepare a lithium-ion battery electrode assembly.

[0060] Step 5: Drill holes in the positive electrode foil tab bundle of the lithium-ion battery electrode assembly prepared in Step 4, with the holes penetrating the tab bundle. The holes have a diameter of 1 mm and the number of holes is 20. Perform a wetting treatment, that is, apply 20 μL of the silver nanowire conductive adhesive prepared in Step 1 to the hole wall, and dry and cure at 60°C for 2 min.

[0061] The negative electrode foil tab bundle is perforated, with the holes being 1 mm in diameter and numbering 20. It is then wetted by applying 20 μL of the copper nanowire conductive adhesive prepared in the first step onto the hole wall, and then dried and cured at 60°C for 2 min.

[0062] Step 6: Connect the positive electrode conductive connecting piece to the positive electrode foil tab bundle and the battery cell adhesive positive electrode tab in order from top to bottom, and then weld the tabs using pressure welding. The pressure welding pressure is 50 kg and the current is 7500 A.

[0063] After connecting the negative electrode conductive connecting piece to the negative electrode foil tab bundle and the battery cell adhesive negative electrode tab in a top-to-bottom order, the tabs are welded using a pressure welding method with a pressure of 50 kg and a current of 5500 A.

[0064] Step 7: The welded electrode assembly is then subjected to assembly, formation, and other processes that complete the lithium-ion battery production process to obtain the high-safety lithium-ion battery.

[0065] Example 4 (Blank Experiment) Step 1: Prepare a positive electrode sheet using an 8μm thick composite aluminum foil as the positive electrode foil and NCM622 as the positive electrode material, with a coating amount of 48mg / cm². 2 A negative electrode sheet was prepared using a 6μm thick composite copper foil as the negative electrode foil and a graphite / silicon composite material as the negative electrode, with a coating amount of 14 mg / cm². 2 ,stand-by.

[0066] After the positive and negative electrode sheets are die-cut, 30 layers of positive electrode sheets and 31 layers of negative electrode sheets are stacked to prepare a lithium-ion battery electrode assembly.

[0067] Step 2: Drill holes in the positive electrode foil tab bundle of the lithium-ion battery electrode assembly prepared in Step 1. The holes should be 1 mm in diameter and 20 in number.

[0068] The negative electrode foil tab bundle is perforated, with the holes being 1mm in diameter and numbering 20.

[0069] Step 3: Connect the positive conductive connecting piece to the positive foil tab bundle and the battery cell adhesive positive tab in order from top to bottom, and then weld the tabs using pressure welding. The pressure welding pressure is 50 kg and the current is 6500 A.

[0070] After connecting the negative electrode conductive connecting piece to the negative electrode foil tab bundle and the battery cell adhesive negative electrode tab in a top-to-bottom order, the tabs are welded using a pressure welding method with a pressure of 50 kg and a current of 4500 A.

[0071] Step 7: The welded electrode assembly is then subjected to assembly, formation, and other processes that complete the lithium-ion battery production process to obtain the high-safety lithium-ion battery.

[0072] Test (1) The electrode resistance is tested using a multimeter to measure the contact resistance between the battery tab with adhesive and the electrode. Test method: The red probe tip is positioned 5mm above the adhesive on the tab of the electrode assembly and in the center of the horizontal direction. The black probe tip is positioned 5mm directly below the center of the tab of the electrode foil. The resistance value is measured (the contact resistance between the adhesive tab of the battery positive electrode and the positive electrode is referred to as Rpositive, and the contact resistance between the adhesive tab of the battery negative electrode and the negative electrode is referred to as Rnegative).

[0073] (2) Battery internal resistance: The internal resistance at 1KHz was tested using an AC internal resistance tester. Test method: The red probe tip was positioned 5mm above the adhesive tab of the positive electrode of the battery and centered horizontally. The black probe tip was positioned 5mm above the adhesive tab of the negative electrode of the battery and centered horizontally. The battery internal resistance was tested.

[0074] (3) 2C discharge temperature rise: Test the change of the highest temperature of the battery after 2C discharge of a fully charged battery; Test method: attach the thermocouple to the center of the battery body, test the temperature of the battery from 100% SOC state to 0% SOC state when the 2C rate is discharged, take the maximum value, and the difference between the maximum temperature and the temperature before the start of discharge is the battery temperature rise.

[0075] The test results are shown in Table 1.

[0076] Table 1 Comparison of Basic Data in Examples

[0077] As can be seen from Table 1: (1) The contact resistance (Rpositive) between the positive electrode tab and the positive electrode sheet of the batteries in Examples 1, 2 and 3 is smaller than that of the blank experiment. The Rpositive values ​​of the batteries in Examples 1, 2 and 3 vary less than those of the blank experiment.

[0078] (2) The contact resistance (Rnegative) between the negative electrode tab and the negative electrode sheet of the batteries in Examples 1, 2, and 3 is smaller than that of the blank experiment. The Rnegative values ​​of the batteries in Examples 1, 2, and 3 have a smaller range of variation than those of the blank experiment.

[0079] (3) The internal resistance values ​​of batteries in Examples 1, 2, and 3 are smaller than those in the blank experiment. The range of variation of the internal resistance of batteries in Examples 1, 2, and 3 is smaller than that in the blank experiment. The internal resistance of batteries in Examples 1, 2, and 3 is more stable than that in the blank experiment.

[0080] (4) The high-rate (2C) discharge of the batteries in Examples 1, 2, and 3 generated less heat than the blank experimental battery. Specifically, the temperature rise of the batteries in Examples 1, 2, and 3 was smaller than that of the blank experimental battery.

[0081] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite current collector foil tab with a conductive functional coating, comprising a composite current collector foil material, the composite current collector foil material comprising a middle polymer material layer and metal layers disposed on both sides of the polymer material layer, characterized in that, The surface of the composite current collector foil is coated with a conductive functional coating, which includes metal nanowires and polymers. The thickness of the conductive functional coating is 500 nm to 2 µm. In the conductive functional coating, the metal nanowires have a diameter of 10 nm to 200 nm and a length of 500 nm to 50 µm. The metal nanowires are silver nanowires or copper nanowires. The polymer used as a binder is at least one of polymethyl methacrylate, polymethyl cyanoacrylate, and ethyl cyanoacrylate. The mass content of the metal nanowires is 50% to 80%.

2. The composite current collector foil tab with a conductive functional coating according to claim 1, characterized in that, The conductive functional coating is applied to one or both sides of the composite current collector foil.

3. The composite current collector foil tab with a conductive functional coating according to claim 1, characterized in that, The metal layer is copper, aluminum, nickel or their alloys, and the polymer material layer is PET, PP, PI or PA.

4. The method for preparing the composite current collector foil tab with a conductive functional coating as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Prepare a conductive adhesive solution for metal nanowires by adding metal nanowires and organic polymers or organic polymer monomers to anhydrous acetone as solvent and mixing them evenly. In the conductive adhesive solution, the metal nanowires are 4% to 20% by mass percentage, and the organic polymers or polymer monomers are 1% to 10%. (2) Apply the prepared metal nanowire conductive adhesive to one or both sides of the composite current collector foil, and dry and cure it.

5. The method for preparing the composite current collector foil tab with a conductive functional coating according to claim 4, characterized in that, The organic polymer is polymethyl methacrylate; the organic polymer monomer is methyl cyanoacrylate or ethyl cyanoacrylate.

6. The method for preparing the composite current collector foil tab with a conductive functional coating according to claim 4, characterized in that, In step (2), the drying and curing temperature is 20℃~80℃, and the drying time is ≥1min.

7. A method for welding electrode tabs, characterized in that the steps include... include: S1. The composite current collector foil tabs with conductive functional coatings as described in any one of claims 1-3 are stacked to form a composite current collector stack unit; S2. Drill through holes in the composite current collector stack unit, the through holes connecting each composite current collector foil tab in the composite current collector stack unit, apply the metal nanowire conductive adhesive prepared in claim 4 to the hole wall, and dry and cure. S3. After connecting the conductive connecting piece through the through hole of the composite current collector stack unit and the battery cell tab, the tab is welded using a pressure welding method.

8. The welding method for electrode tabs according to claim 7, characterized in that, In S2, the drying and curing temperature is 20℃~60℃, and the drying time is ≥1min.

9. A lithium-ion battery, comprising a cell, a casing, and a cover assembly, wherein the cell comprises a positive electrode and a negative electrode, characterized in that, At least one of the positive electrode and / or negative electrode is a tab obtained by welding the electrode tab as described in claim 7.

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