A functional current collector and a preparation method and application thereof

Abstract

The application provides a functional current collector and a preparation method and application thereof, and the functional current collector comprises a polymer film, a transition layer, a conductive layer and a protective layer arranged on at least one side surface of the polymer film; the transition layer is located between the polymer film and the conductive layer, and the protective layer is located on the outermost side; the material of the transition layer is nickel-chromium oxide. By arranging the transition layer with the material of nickel-chromium oxide between the polymer film and the conductive layer, the nickel-chromium oxide has good bonding effects on the polymer film and the conductive layer, the problem of poor structural performance of the traditional functional current collector is effectively solved, and structural defects are not prone to being generated in the process of battery pole piece manufacturing and battery charging and discharging cycles, so that the charging and discharging cycle performance and safety performance of the battery are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, and relates to a functional current collector, and more particularly to a functional current collector and its preparation method and application. Background Technology

[0002] Currently, functional current collectors based on polymer films (i.e., composite current collectors) are receiving widespread attention and application in the new energy industry. These functional current collectors are typically prepared by depositing a metal layer on the surface of a polymer film (such as polyester or polyolefin films) using physical vapor deposition (PVD), thereby creating a functional current collector with good conductivity. Compared to traditional current collectors, functional current collectors based on polymer films offer advantages such as low cost, light weight, and good internal insulation. This allows functional current collectors to significantly reduce battery costs while improving battery energy density and safety in practical applications.

[0003] However, since this functional current collector is composed of a polymer film and a conductive layer, the surface properties of the two materials are significantly different, resulting in poor adhesion between them. This leads to poor structural stability of the functional current collector, making it prone to delamination during battery electrode fabrication and battery charge-discharge cycles, which in turn causes structural defects and ultimately results in poor charge-discharge cycle performance of the battery.

[0004] Therefore, how to provide a functional current collector and its preparation method to effectively solve the problem of poor battery charge-discharge cycle performance caused by the structural instability of functional current collectors has become the research focus of those skilled in the art. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a functional current collector and its preparation method and application, which effectively solves the problem of poor structural performance of traditional functional current collectors, and is less prone to structural defects during battery electrode fabrication and battery charge-discharge cycle, thus significantly improving the charge-discharge cycle performance and safety performance of the battery.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a functional current collector, the functional current collector comprising a polymer film and a transition layer, a conductive layer and a protective layer disposed on at least one surface of the polymer film.

[0008] The transition layer is located between the polymer film and the conductive layer, and the protective layer is located on the outermost side; the transition layer is made of nickel-chromium oxide.

[0009] This invention provides a transition layer of nickel-chromium oxide between the polymer film and the conductive layer. Since nickel-chromium oxide has a good bonding effect on both the polymer film and the conductive layer, it effectively solves the problem of poor performance of traditional functional current collector structures. Furthermore, it is less prone to structural defects during battery electrode fabrication and battery charge-discharge cycle processes, thus significantly improving the charge-discharge cycle performance and safety performance of the battery.

[0010] Preferably, the nickel content in the transition layer is 20-90 wt%.

[0011] Preferably, the chromium content in the transition layer is 9-79.95 wt%.

[0012] Preferably, the oxygen content in the transition layer is 0.05-1 wt%.

[0013] Preferably, the thickness of the transition layer is 5-100 nm, and more preferably 10-80 nm.

[0014] Preferably, the transition layer further includes yttrium, and the yttrium content is 0.05-1 wt%.

[0015] Preferably, the polymer film is made of any one or a combination of at least two of the following materials: polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (EPR), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polystyrene (PS), or polyimide (PI).

[0016] Preferably, the thickness of the polymer film is 1-10 μm.

[0017] Preferably, the conductive layer is made of any one or a combination of at least two of aluminum, copper, gold, silver, nickel, or zinc.

[0018] Preferably, the thickness of the conductive layer is 0.5-2 μm, and more preferably 0.8-1.2 μm.

[0019] Preferably, the material of the protective layer includes any one of elemental metal, metal oxide, alloy, or carbon material.

[0020] The metallic element includes nickel or chromium.

[0021] Preferably, the metal oxide includes any one of aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, or copper-chromium oxide.

[0022] Preferably, the alloy comprises a nickel-based alloy or a copper-based alloy.

[0023] Preferably, the carbon material includes any one of graphite, carbon black, carbon nanotubes, carbon nanofibers, graphene, or graphene oxide.

[0024] Preferably, the thickness of the protective layer is 5-100 nm, and more preferably 10-80 nm.

[0025] In a second aspect, the present invention provides a method for preparing a functional current collector as described in the first aspect, the method comprising the following steps:

[0026] (1) Obtaining a polymer film;

[0027] (2) A transition layer is deposited on at least one side of the polymer film using magnetron sputtering;

[0028] (3) A conductive layer and a protective layer are deposited sequentially on the surface of the transition layer to obtain a functional current collector.

[0029] This invention effectively solves the problem of structural instability in functional current collectors by sequentially depositing a transition layer, a conductive layer, and a protective layer on a polymer film. Specifically, the polymer film serves as the substrate, and a transition layer is deposited on its surface using magnetron sputtering to enhance the adhesion between the transition layer and the conductive layer. Subsequently, the conductive layer and the protective layer are deposited sequentially, giving the entire functional current collector good conductivity and safety, ultimately improving the charge-discharge cycle performance of the battery.

[0030] Preferably, the method for preparing the polymer film in step (1) includes sequential melting, extrusion and biaxial stretching.

[0031] Preferably, the deposition method of the conductive layer in step (3) includes any one of physical vapor deposition, chemical plating, or electroplating.

[0032] Preferably, the deposition method of the protective layer in step (3) includes any one of physical vapor deposition, chemical vapor deposition, in-situ molding, or coating.

[0033] Thirdly, the present invention provides a battery comprising a functional current collector as described in the first aspect.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This invention provides a transition layer of nickel-chromium oxide between the polymer film and the conductive layer. Since nickel-chromium oxide has a good bonding effect on both the polymer film and the conductive layer, it effectively solves the problem of poor performance of traditional functional current collector structures. Furthermore, it is less prone to structural defects during battery electrode fabrication and battery charge-discharge cycle processes, thus significantly improving the charge-discharge cycle performance and safety performance of the battery. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the functional current collector structure provided by the present invention.

[0037] Wherein: 1-polymer film; 2-transition layer; 3-conductive layer; 4-protective layer. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0039] One embodiment of the present invention provides a functional current collector, the functional current collector comprising a polymer film and a transition layer, a conductive layer and a protective layer disposed on at least one surface of the polymer film.

[0040] The transition layer is located between the polymer film and the conductive layer, and the protective layer is located on the outermost side; the transition layer is made of nickel-chromium oxide.

[0041] This invention provides a transition layer of nickel-chromium oxide between the polymer film and the conductive layer. Since nickel-chromium oxide has a good bonding effect on both the polymer film and the conductive layer, it effectively solves the problem of poor performance of traditional functional current collector structures. Furthermore, it is less prone to structural defects during battery electrode fabrication and battery charge-discharge cycle processes, thus significantly improving the charge-discharge cycle performance and safety performance of the battery.

[0042] Specifically, the functional current collector provided by this invention features a multi-layer structure, comprising four main parts: a polymer film, a transition layer, a conductive layer, and a protective layer. The polymer film serves as the substrate material, providing the basic structure of the functional current collector. The transition layer, made of nickel-chromium oxide, is positioned between the polymer film and the conductive layer, enhancing the adhesion between them and preventing battery delamination. The conductive layer provides excellent conductivity, while the protective layer, located on the outermost layer, protects the internal structure from external environmental influences. Through the synergy of these technical features, the problem of poor charge-discharge cycle performance caused by structural instability in functional current collectors is effectively solved.

[0043] In some embodiments, the nickel content in the transition layer is 20-90 wt%, for example, it can be 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, or 90 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0044] In some embodiments, the chromium content in the transition layer is 9-79.95 wt%, for example, it can be 9 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, or 79.95 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0045] In some embodiments, the oxygen content in the transition layer is 0.05-1 wt%, for example, it can be 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0046] This invention further enhances the adhesion of the transition layer to the polymer film and conductive layer by strictly limiting the content range of each element in the transition layer, i.e. optimizing the material composition of the transition layer, thereby significantly improving the structural stability of the functional current collector and improving the charge-discharge cycle performance of the battery.

[0047] In some embodiments, the thickness of the transition layer is 5-100 nm, for example, it can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm or 100 nm, more preferably 10-80 nm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0048] By strictly limiting the thickness range of the transition layer, this invention not only avoids the problem of insufficient interlayer adhesion due to an excessively thin transition layer, but also avoids the problem of unnecessary increase in material costs due to an excessively thick transition layer, thus balancing product performance and production costs.

[0049] In some embodiments, the transition layer also includes yttrium, and the yttrium content is 0.05-1 wt%, for example, it can be 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0050] This invention further enhances the density and adhesion of the transition layer by adding yttrium.

[0051] In some embodiments, the polymer film is made of any one or a combination of at least two of polyethylene terephthalate, polypropylene, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, or polyimide. Typical but non-limiting combinations include combinations of polyethylene terephthalate and polypropylene, polypropylene and polybutylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyethylene naphthalate and polyethylene, polyethylene and polypropylene, polypropylene and polyvinyl chloride, polyvinyl chloride and polyvinylidene fluoride, polyvinylidene fluoride and polytetrafluoroethylene, polytetrafluoroethylene and polyphenylene sulfide, polyphenylene sulfide and polyphenylene ether, polyphenylene ether and polystyrene, or polystyrene and polyimide.

[0052] In some embodiments, the thickness of the polymer film is 1-10 μm, for example, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0053] This invention improves the mechanical properties and chemical stability of polymer films by strictly limiting the selection of polymer film materials and the thickness range, while also taking into account material costs.

[0054] In some embodiments, the conductive layer is made of any one or a combination of at least two of aluminum, copper, gold, silver, nickel, or zinc. Typical but non-limiting combinations include combinations of aluminum and copper, copper and gold, gold and silver, silver and nickel, nickel and zinc, aluminum, copper and gold, copper, gold and silver, gold, silver and nickel, or silver, nickel and zinc.

[0055] In some embodiments, the thickness of the conductive layer is 0.5-2 μm, for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm or 2 μm, more preferably 0.8-1.2 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0056] In this invention, the thickness of the conductive layer has a significant impact on conductivity and energy density. When the conductive layer is too thin, the conductivity is poor; when the conductive layer is too thick, the resulting functional current collector is too heavy, which is not conducive to improving the energy density of the battery. Therefore, in order to balance conductivity and energy density, this invention specifically limits the thickness of the conductive layer to 0.5-2 μm.

[0057] In some embodiments, the protective layer is made of any one of elemental metals, metal oxides, alloys, or carbon materials.

[0058] In some embodiments, the metallic element includes nickel or chromium.

[0059] In some embodiments, the metal oxide includes any one of aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, or copper-chromium oxide.

[0060] In some embodiments, the alloy comprises a nickel-based alloy or a copper-based alloy.

[0061] In some embodiments, the carbon material includes any one of graphite, carbon black, carbon nanotubes, carbon nanofibers, graphene, or graphene oxide.

[0062] This invention effectively prevents chemical corrosion or physical damage to the conductive layer during battery use by specifically defining the material of the protective layer, thereby further improving the safety performance of the battery.

[0063] In some embodiments, the thickness of the protective layer is 5-100 nm, for example, it can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm or 100 nm, more preferably 10-80 nm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0064] One embodiment of the present invention provides a method for preparing the above-mentioned functional current collector, the method comprising the following steps:

[0065] (1) Obtaining a polymer film;

[0066] (2) A transition layer is deposited on at least one side of the polymer film using magnetron sputtering;

[0067] (3) A conductive layer and a protective layer are deposited sequentially on the surface of the transition layer to obtain a functional current collector.

[0068] This invention effectively solves the problem of structural instability in functional current collectors by sequentially depositing a transition layer, a conductive layer, and a protective layer on a polymer film. Specifically, the polymer film serves as the substrate, and a transition layer is deposited on its surface using magnetron sputtering to enhance the adhesion between the transition layer and the conductive layer. Subsequently, the conductive layer and the protective layer are deposited sequentially, giving the entire functional current collector good conductivity and safety, ultimately improving the charge-discharge cycle performance of the battery.

[0069] In some embodiments, the magnetron sputtering method uses a nickel-chromium-oxygen target as the sputtering target material, controls the target power to be 5-6 kW, the argon flow rate to be 55-65 mL / min, the coating vacuum degree to be 0.06-0.08 Pa, the coating time to be 1-20 s, and the spindle temperature during the coating process to be -4°C to -6°C. However, the parameters are not limited to the above ranges, as long as the deposition of the transition layer can be achieved, so they are not specifically limited here.

[0070] In some embodiments, the preparation method of the polymer film in step (1) includes sequential melting, extrusion and biaxial stretching, and the resulting polymer film has good mechanical properties and surface characteristics, thereby improving the structural stability of the functional current collector.

[0071] Specifically, this invention first heats the polymer raw material to a molten state, then extrudes the molten polymer into a crude film using an extrusion process. Subsequently, it undergoes biaxial stretching to fully stretch the film in both the longitudinal and transverse directions, thereby improving its mechanical properties. The combination of these steps results in excellent structural stability of the polymer film in functional current collectors.

[0072] In this invention, melting, extrusion, and biaxial stretching are all conventional steps in the polymer film preparation process. As long as the preparation of the polymer film can be achieved, no specific process parameters for each step are particularly limited.

[0073] For example, the melting step can be carried out using conventional heating devices; the extrusion step can be carried out using a single-screw or twin-screw extruder; and biaxial stretching can be carried out using stretching equipment at specific temperatures and stretch ratios.

[0074] In this invention, the polymer film can also be obtained by direct purchase.

[0075] In some embodiments, the deposition method of the conductive layer in step (3) includes any one of physical vapor deposition, electroless plating, or electroplating.

[0076] Specifically, physical vapor deposition (such as evaporation or magnetron sputtering) can be performed in a high vacuum environment, resulting in a conductive layer with good purity and density; chemical plating can be performed at room temperature and pressure, with simple processes and low costs; electroplating can be performed at lower voltages, with fast deposition rates, making it suitable for large-scale production.

[0077] In some embodiments, the deposition method of the protective layer in step (3) includes any one of physical vapor deposition, chemical vapor deposition, in-situ molding, or coating.

[0078] Specifically, chemical vapor deposition can be carried out at lower temperatures, and the resulting protective layer has good uniformity; in-situ molding can achieve rapid molding of the protective layer during the deposition process, resulting in high process efficiency; coating can achieve uniform coating of the protective layer through mechanical means, which is suitable for functional current collectors with complex shapes.

[0079] One embodiment of the present invention provides a battery that includes the above-described functional current collector.

[0080] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0081] Example 1

[0082] This embodiment provides a functional current collector and its preparation method, such as... Figure 1 As shown, the functional current collector includes a polymer film 1 and a transition layer 2, a conductive layer 3, and a protective layer 4 disposed on both sides of the polymer film 1. The transition layer 2 is located between the polymer film 1 and the conductive layer 3, and the protective layer 4 is located on the outermost side; the transition layer 2 is made of nickel-chromium oxide.

[0083] Specifically, in the transition layer 2, the content of nickel is 90wt%, the content of chromium is 9.95wt%, the content of oxygen is 0.05wt%, and the thickness is 40nm; the polymer film 1 is a biaxially oriented PET film (manufacturer: Yihua Dongli, model: 4.5D08) with a thickness of 4.5μm; the conductive layer 3 is made of copper with a thickness of 1μm; and the protective layer 4 is made of nickel with a thickness of 10nm.

[0084] The preparation method provided in this embodiment includes the following steps:

[0085] (1) The polymer film 1 is placed in a magnetron sputtering machine. A nickel-chromium-oxygen target (Ni 90wt%, Cr 9.95wt%, O 0.05wt%) is used as the sputtering target material. The target power is controlled at 5.2kW, the argon flow rate is 60mL / min, the coating vacuum degree is 0.07Pa, the coating time is 8s, and the spindle temperature during the coating process is -5℃. That is, a transition layer 2 is deposited on both sides of the polymer film 1.

[0086] (2) The polymer film 1 with the above-mentioned transition layer 2 is placed in the vacuum evaporation chamber, and the high-purity copper wire (purity ≥99.99%) in the metal evaporation chamber is melted and evaporated at a high temperature of 1600°C. After evaporation, the metal atoms are deposited on both sides of the current collector through the cooling system in the vacuum coating chamber, that is, a conductive layer 3 is formed on the surface of the transition layer 2.

[0087] (3) The polymer film 1 with the conductive layer 3 deposited above is placed in a magnetron sputtering machine. A nickel target is used as the sputtering target material. The target power is controlled at 4.5kW, the argon flow rate is 60mL / min, the coating vacuum degree is 0.07Pa, the coating time is 2s, and the spindle temperature during the coating process is -5℃. That is, protective layers 4 are deposited on both sides of the current collector to obtain a functional current collector.

[0088] Example 2

[0089] This embodiment provides a functional current collector and its preparation method. Except that the composition of the nickel-chromium-oxygen target in step (1) is changed to Ni 90wt%, Cr 9.5wt%, O 0.5wt%, and the target power is changed to 5.4kW, the content of nickel in the resulting transition layer 2 is 90wt%, the content of chromium is 9.5wt%, and the content of oxygen is 0.5wt%, the remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0090] Example 3

[0091] This embodiment provides a functional current collector and its preparation method. Except that the composition of the nickel-chromium-oxygen target in step (1) is changed to Ni 90wt%, Cr 9wt%, O 1wt%, and the target power is changed to 5.8kW, the content of nickel in the resulting transition layer 2 is 90wt%, the content of chromium is 9wt%, and the content of oxygen is 1wt%. The remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0092] Example 4

[0093] This embodiment provides a functional current collector and its preparation method. Except that the composition of the nickel-chromium-oxygen target in step (1) is changed to Ni 50wt%, Cr 49.95wt%, O 0.05wt%, and the target power is changed to 5.8kW, the content of nickel in the resulting transition layer 2 is 50wt%, the content of chromium is 49.95wt%, and the content of oxygen is 0.05wt%, the remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0094] Example 5

[0095] This embodiment provides a functional current collector and its preparation method. Except that the composition of the nickel-chromium-oxygen target in step (1) is changed to Ni 20wt%, Cr 79.95wt%, O 0.05wt%, and the target power is changed to 6.0kW, the content of nickel in the resulting transition layer 2 is 20wt%, the content of chromium is 79.95wt%, and the content of oxygen is 0.05wt%, the remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0096] Example 6

[0097] This embodiment provides a functional current collector and its preparation method. Except that the coating time in step (1) is changed to 1s, the thickness of the resulting transition layer 2 is 10nm. The other steps and conditions are the same as in embodiment 1, so they will not be described in detail here.

[0098] Example 7

[0099] This embodiment provides a functional current collector and its preparation method. Except that the coating time in step (1) is changed to 16s, the thickness of the resulting transition layer 2 is 80nm. The other steps and conditions are the same as in embodiment 1, so they will not be described in detail here.

[0100] Example 8

[0101] This embodiment provides a functional current collector and its preparation method. Except that the coating time in step (1) is changed to 20s, the thickness of the resulting transition layer 2 is 100nm. The other steps and conditions are the same as in embodiment 1, so they will not be described in detail here.

[0102] Example 9

[0103] This embodiment provides a functional current collector and its preparation method. Except that the coating time in step (1) is changed to 22s, the thickness of the resulting transition layer 2 is 110nm. The other steps and conditions are the same as in embodiment 1, so they will not be described in detail here.

[0104] Example 10

[0105] This embodiment provides a functional current collector and its preparation method. Except for replacing the polymer membrane 1 with a PP membrane (manufacturer: Jiadeli, model: 6014H), the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0106] Example 11

[0107] This embodiment provides a functional current collector and its preparation method. Except for replacing the polymer membrane 1 with a PPS membrane (manufacturer: Toray, model: 4-1X00), the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0108] Example 12

[0109] This embodiment provides a functional current collector and its preparation method. Except that the composition of the nickel-chromium-oxygen target in step (1) is changed to Ni 90wt%, Cr 9.98wt%, O 0.02wt%, and the target power is changed to 5.1kW, the content of nickel in the resulting transition layer 2 is 90wt%, the content of chromium is 9.98wt%, and the content of oxygen is 0.02wt%. The remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0110] Example 13

[0111] This embodiment provides a functional current collector and its preparation method. Except that the composition of the nickel-chromium-oxygen target in step (1) is changed to Ni 90wt%, Cr 8.8wt%, O 1.2wt%, and the target power is changed to 6.0kW, the content of nickel in the resulting transition layer 2 is 90wt%, the content of chromium is 8.8wt%, and the content of oxygen is 1.2wt%, the rest of the steps and conditions are the same as in Example 1, so they will not be repeated here.

[0112] Example 14

[0113] This embodiment provides a functional current collector and its preparation method. Except that the composition of the nickel-chromium-oxygen target in step (1) is changed to Ni 92wt%, Cr 7.95wt%, O 0.05wt%, and the target power is changed to 5.1kW, the content of nickel in the resulting transition layer 2 is 92wt%, the content of chromium is 7.95wt%, and the content of oxygen is 0.05wt%. The remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0114] Example 15

[0115] This embodiment provides a functional current collector and its preparation method. Except that the composition of the nickel-chromium-oxygen target in step (1) is changed to Ni 18wt%, Cr 81.95wt%, O 0.05wt%, and the target power is changed to 6.6kW, the content of nickel in the resulting transition layer 2 is 18wt%, the content of chromium is 81.95wt%, and the content of oxygen is 0.05wt%, the remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0116] Example 16

[0117] This embodiment provides a functional current collector and its preparation method. Except that the nickel-chromium-oxygen target in step (1) is replaced with a nickel-chromium-oxygen-yttrium target with the composition of Ni 90wt%, Cr 9.45wt%, O 0.05wt%, Y 0.5wt%, and the target power is changed to 5.9kW. The material of the resulting transition layer 2 is nickel-chromium-oxygen-yttrium, and the content of nickel is 90wt%, the content of chromium is 9.45wt%, the content of oxygen is 0.05wt%, and the content of yttrium is 0.5wt%. The remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0118] Example 17

[0119] This embodiment provides a functional current collector and its preparation method. Except that the nickel-chromium-oxygen target in step (1) is replaced with a nickel-chromium-oxygen-yttrium target with the composition of Ni 88wt%, Cr 9.95wt%, O 0.05wt%, Y 2wt%, and the target power is changed to 6.8kW. The material of the resulting transition layer 2 is nickel-chromium-oxygen-yttrium, and the content of nickel is 88wt%, the content of chromium is 9.95wt%, the content of oxygen is 0.05wt%, and the content of yttrium is 2wt%. The remaining steps and conditions are the same as in Example 1, so they will not be repeated here.

[0120] Comparative Example 1

[0121] This comparative example provides a functional current collector and its preparation method. Except that a transition layer 2 is not provided between the polymer film 1 and the conductive layer 3, but the conductive layer 3 is directly deposited on both sides of the polymer film 1, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0122] Comparative Example 2

[0123] This comparative example provides a functional current collector and its preparation method. Except that the nickel-chromium-oxygen target in step (1) is replaced with a nickel-chromium target, the composition is 90wt% Ni and 10wt% Cr, the material of the resulting transition layer 2 is nickel-chromium, and the content of nickel element is 90wt% and the content of chromium element is 10wt%. The other steps and conditions are the same as in Example 1, so they will not be repeated here.

[0124] Comparative Example 3

[0125] This comparative example provides a functional current collector and its preparation method. Except that the nickel-chromium-oxygen-yttrium target in step (1) is replaced with a nickel-chromium-yttrium target with a composition of 90wt% Ni, 9.5wt% Cr, and 0.5wt% Y, and the target power is changed to 5.6kW, the material of the resulting transition layer 2 is nickel-chromium-yttrium, and the content of nickel is 90wt%, the content of chromium is 9.5wt%, and the content of yttrium is 0.5wt%. The remaining steps and conditions are the same as in Example 16, so they will not be repeated here.

[0126] Performance testing

[0127] The functional current collectors obtained in Examples 1-17 and Comparative Examples 1-3 were tested for adhesion strength, tensile strength, elongation at break, and battery cycle performance, respectively. The specific test methods are as follows:

[0128] (I) Adhesion between the polymer film and the conductive layer: A layer of Permacel P-94 double-sided adhesive was bonded to a 1 mm thick aluminum foil. The functional current collector prepared above was bonded on top of the double-sided adhesive. A layer of ethylene-acrylic acid copolymer film (DuPont Nurcel 0903, 50 μm thick) was then covered on top of the functional current collector. Then, a 1.3 × 10⁵ N / m... 2 Hot-press at 120℃ for 10s, cool to room temperature (25℃), and cut into strips of 150mm×15mm. Finally, fix the ethylene-acrylic acid copolymer film of the sample strips to the upper clamp of the tensile testing machine, and fix the rest to the lower clamp. After fixing, peel the two at an angle of 180° and a speed of 100mm / min to test the peel force, that is, the adhesion force between the polymer film and the conductive layer.

[0129] (ii) Tensile strength and elongation at break: The tensile strength of the functional current collector was tested in accordance with the standard GB / T 1040.3-2006.

[0130] (III) Battery cycle performance: Characterized by the battery capacity retention rate after 800 high-temperature charge-discharge cycles, specifically:

[0131] ① Battery assembly: For the positive electrode, the positive electrode current collector uses 13μm thick aluminum foil (1060 alloy), and the positive electrode material is LiNi. 0.6 Mn 0.2 Co 0.2 O2 (NCM622); for the negative electrode, the current collector is the functional current collector prepared above, and the negative electrode material is artificial graphite; for the separator, an alumina ceramic-coated polyethylene separator (25 μm thick) is used; for the electrolyte, a 1 mol·L⁻¹ electrolyte is used. -1A carbonate solution of LiPF6, wherein the carbonate is a mixture of ethylene carbonate and methyl ethyl carbonate in a mass ratio of 1:1; using the above materials, lithium-ion batteries are assembled according to standard procedures.

[0132] ② Cyclic performance test: At 45℃, the battery was cycled 800 times at a charge-discharge rate of 1C within a voltage range of 3.0V to 4.2V, and the battery capacity retention rate after the cycle was recorded.

[0133] The relevant test results of the functional current collectors obtained in Examples 1-17 and Comparative Examples 1-3 are shown in Table 1 below.

[0134] Table 1

[0135]

[0136]

[0137] Based on Table 1 above, the following conclusions can be drawn:

[0138] (1) As can be seen from Examples 1-17 and Comparative Example 1, compared with the traditional functional current collector (i.e., Comparative Example 1), the functional current collectors obtained in Examples 1-17 show enhanced adhesion between the polymer film and the conductive layer, indicating good structural stability. The tensile strength and elongation at break of the functional current collector are significantly improved. The increased adhesion between the polymer film and the conductive layer, as well as the improved tensile strength and elongation at break, collectively contribute to the improved cycle performance of the battery based on the functional current collector.

[0139] (2) As can be seen from Examples 1-3 and Examples 12-13, increasing the oxygen content in the transition layer first increases and then decreases the adhesion between the polymer film and the conductive layer of the functional current collector, while the tensile strength and elongation at break of the functional current collector first increase and then decrease. The trend of the adhesion between the polymer film and the conductive layer, the tensile strength and elongation at break first increasing and then decreasing together contributes to the first increase and then decrease of the cycle performance of the battery based on the functional current collector.

[0140] (3) As can be seen from Examples 1, 4-5 and Examples 14-15, increasing the nickel content in the transition layer first increases and then decreases the adhesion between the polymer film and the conductive layer of the resulting functional current collector, while the tensile strength and elongation at break of the functional current collector first increase and then decrease. The trend of the adhesion between the polymer film and the conductive layer, the tensile strength and elongation at break first increasing and then decreasing together contributes to the first increase and then decrease of the cycle performance of the battery based on the functional current collector.

[0141] (4) As can be seen from Examples 1 and 6-9, increasing the thickness of the transition layer increases the adhesion between the polymer film and the conductive layer of the functional current collector, and consequently increases the tensile strength and elongation at break of the functional current collector. The increasing adhesion between the polymer film and the conductive layer, as well as the increasing tensile strength and elongation at break, collectively contribute to the improved cycle performance of the battery based on the functional current collector. When the thickness of the transition layer exceeds 100 nm, further increasing the thickness does not significantly improve the battery performance. Therefore, the thickness of the transition layer is preferably 5-100 nm, and more preferably 10-80 nm.

[0142] (5) As can be seen from Example 1 and Comparative Example 2, and Example 16 and Comparative Example 3, the transition layer contains oxygen, which can significantly improve the performance of the functional current collector and the performance of the assembled battery.

[0143] Therefore, this invention provides a transition layer of nickel-chromium oxide material between the polymer film and the conductive layer. Since nickel-chromium oxide has a good bonding effect on both the polymer film and the conductive layer, it effectively solves the problem of poor performance of traditional functional current collector structures. Furthermore, it is less prone to structural defects during battery electrode fabrication and battery charge-discharge cycle processes, thus significantly improving the charge-discharge cycle performance and safety performance of the battery.

[0144] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A functional current collector, characterized in that, The functional current collector includes a polymer film and a transition layer, a conductive layer, and a protective layer disposed on at least one surface of the polymer film; The transition layer is located between the polymer film and the conductive layer, and the protective layer is located on the outermost side; the transition layer is made of nickel-chromium oxide.

2. The functional current collector according to claim 1, characterized in that, The nickel content in the transition layer is 20-90 wt%. And / or, the chromium content in the transition layer is 9-79.95 wt%; And / or, the oxygen content in the transition layer is 0.05-1 wt%.

3. The functional current collector according to claim 1 or 2, characterized in that, The thickness of the transition layer is 5-100 nm, more preferably 10-80 nm; And / or, the transition layer also includes yttrium, and the yttrium content is 0.05-1 wt%.

4. The functional current collector according to claim 1 or 2, characterized in that, The polymer film is made of any one or a combination of at least two of the following materials: polyethylene terephthalate, polypropylene, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, or polyimide. And / or, the thickness of the polymer film is 1-10 μm.

5. The functional current collector according to claim 1 or 2, characterized in that, The conductive layer is made of any one or a combination of at least two of the following materials: aluminum, copper, gold, silver, nickel, or zinc. And / or, the thickness of the conductive layer is 0.5-2 μm, more preferably 0.8-1.2 μm.

6. The functional current collector according to claim 1 or 2, characterized in that, The material of the protective layer includes any one of elemental metals, metal oxides, alloys, or carbon materials; The metallic element includes nickel or chromium; And / or, the metal oxide includes any one of aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, or copper-chromium oxide; And / or, the alloy comprises a nickel-based alloy or a copper-based alloy; And / or, the carbon material includes any one of graphite, carbon black, carbon nanotubes, carbon nanofibers, graphene, or graphene oxide; And / or, the thickness of the protective layer is 5-100 nm, more preferably 10-80 nm.

7. A method for preparing a functional current collector as described in any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Obtaining a polymer film; (2) A transition layer is deposited on at least one side of the polymer film using magnetron sputtering; (3) A conductive layer and a protective layer are deposited sequentially on the surface of the transition layer to obtain a functional current collector.

8. The preparation method according to claim 7, characterized in that, The method for preparing the polymer film in step (1) includes sequential melting, extrusion and biaxial stretching.

9. The preparation method according to claim 7, characterized in that, The deposition method of the conductive layer in step (3) includes any one of physical vapor deposition, electroless plating, or electroplating; And / or, the deposition method of the protective layer in step (3) includes any one of physical vapor deposition, chemical vapor deposition, in-situ molding, or coating.

10. A battery, characterized in that, The battery contains a current collector as described in any one of claims 1-6.

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