Composite current collector and battery

Abstract

A composite current collector comprises an insulating bonding layer and a metal layer bonded on at least one side of the insulating bonding layer. Compared with an existing composite current collector, the composite current collector has the advantages that the viscous insulating layer structure is adopted to replace common PET, PP, PI and other types of base film supporting layer structures, so that the adhesive strength of the metal layer and the supporting structure is improved, and meanwhile, the additional hierarchical structure is avoided. In the composite current collector formed based on the matching of the insulating bonding layer and the metal layer, the metal layer and the supporting structure are matched more tightly, so that the use performance and the service life are effectively guaranteed; compared with an existing composite current collector which utilizes a bonding force enhancing layer to improve the adhesive force, the composite current collector has the advantages that on the premise that similar adhesive strength is needed, the number of needed hierarchical structures is smaller, and the overall thickness is smaller; the weight of the battery formed based on the composite current collector is obviously reduced, and the energy density is higher. And the supporting layer with the bonding characteristic is directly compounded with the metal layer, so that the production process can be obviously simplified, and the realization of mass production is facilitated.

Description

Technical Field

[0001] The utility model relates to the technical field of battery materials, and more specifically, to a composite current collector and a battery. Background Art

[0002] The composite current collector for lithium batteries is a new type of current collector material with a "sandwich" structure. The supporting layer usually uses polymer insulating resins such as PET (polyethylene terephthalate), PP (polypropylene), PI (polyimide), etc. as the film substrate, and then magnetron sputtering, vacuum evaporation, water electroplating or a combination of multiple processes are used to make a metal layer, such as a copper foil layer, on the surface of the film substrate to form a composite current collector sandwich structure. Compared with the metal current collector formed by traditional all-metal materials, the composite current collector has the advantages of high energy density and low metal consumption. Therefore, the replacement of traditional metal current collectors by composite current collectors has become the current development trend of batteries.

[0003] Although the composite current collector has certain advantages over the traditional all-metal current collector, there are still some shortcomings; specifically, in the coordination between the metal layer and the support layer of the composite current collector, the poor adhesion of the metal layer on the base film support layer often affects the performance and life of the composite current collector. Therefore, there is still a need for improvement in how to enhance the coordination between the support layer and the metal layer. To this end, the prior art also proposes a method for enhancing the bonding force between the support layer and the metal layer, such as setting an adhesion enhancement layer between the base film support layer and the metal layer, and enhancing the bonding force between the base film support layer and the metal layer by adding a copper alloy layer, an aluminum alloy layer and other types of adhesion enhancement layers. However, it is worth noting that the process corresponding to the structure is relatively complicated, and the required equipment is large and expensive, which is not conducive to the large-scale production of the composite current collector; and because of the additional adhesion enhancement layer, under the premise of achieving the same performance, it is easy to cause the total thickness of the composite copper foil to increase, etc., which weakens the advantages of the composite current collector compared to the traditional all-metal current collector.

[0004] Therefore, the prior art urgently needs a composite current collector or a support layer thereof, so as to solve the coordination problem between the support layer and the metal layer while avoiding increasing the layers and thickness of the composite current collector as much as possible. Summary of the invention

[0005] The utility model aims to overcome at least one of the deficiencies of the above-mentioned prior art and provide a composite current collector and a battery, which do not require an additional layer structure while maintaining the hierarchical structure and function of the base support layer and the metal layer, so that the metal layer can be tightly attached to the corresponding support structure.

[0006] The technical solution adopted by the utility model is a composite current collector, including an insulating adhesive layer and a metal layer bonded to at least one side of the insulating adhesive layer. Further, it includes an insulating adhesive layer and a metal layer bonded to both sides of the insulating adhesive layer. The insulating adhesive layer has insulation, viscosity, tensile strength, and elongation, and is formed by a material that has insulation, viscosity, tensile strength, and elongation after curing. In the present application, the insulating adhesive layer replaces the traditional base film support structure such as PET, PP, PI, etc., ensures the basic support structure and corresponding functions, and at the same time can make full use of the bonding characteristics to make the metal layer tightly attached to the support structure. No additional hierarchical structure is required to solve the coordination problem between the support structure and the metal layer, so that when the same composite current collector conductivity is required, it can be achieved with a less hierarchical structure, and the thickness of the composite current collector is avoided as much as possible, which is conducive to enhancing the energy density. And because the insulating adhesive layer has corresponding adhesive properties, there are more options for forming the metal layer on the support structure. In addition to complex methods such as magnetron sputtering and electroplating on the support structure, the support layer can also be directly bonded to the metal foil layer, which significantly simplifies the production process, simplifies the production process, and facilitates mass production.

[0007] Furthermore, the tensile strength of the insulating adhesive layer is ≥250Mpa; the elongation at break of the insulating adhesive layer is ≥80%. Furthermore, the tensile strength of the insulating adhesive layer is 280Mpa~400Mpa; further, the tensile strength of the insulating adhesive layer is 280~350Mpa. Furthermore, the bonding force between the insulating adhesive layer and the metal layer is in the range of 3N / 25mm~30N / 25mm; further, the bonding force between the insulating adhesive layer and the metal layer is in the range of 3N / 25mm~20N / 25mm; further, the bonding force between the insulating adhesive layer and the metal layer is in the range of 3N / 25mm~15N / 25mm. The insulating adhesive layer has physical properties comparable to those of conventional PET base film and other types of support structures, including tensile strength and elongation at break, which effectively ensures the insulation, toughness and safety of the corresponding composite current collector.

[0008] Furthermore, the thickness of the insulating adhesive layer is 1-8 μm; the thickness of the metal layer is 0.5-3 μm. The thickness of the insulating adhesive layer is 1.9-8 μm; the thickness of the metal layer is 1-2 μm. Further, the thickness of the insulating adhesive layer is 1.9-6 μm. Within this thickness range, it meets the requirements of common lithium battery negative current collectors; when the thickness is relatively thin, it is beneficial to reduce the material cost of the corresponding battery, and improve the battery energy density by thinning and weight reduction. The thickness range of the metal layer can ensure a certain degree of toughness and rigidity, meet the overall elongation at break of the composite current collector, make the composite current collector have a high tensile strength, and meet the expansion problem of the positive and negative electrode materials of the battery during charge and discharge. It can also ensure the current transmission of the battery and the stable welding of the electrode tabs.

[0009] Furthermore, both sides of the insulating adhesive layer are directly bonded to the corresponding side metal layer to form a composite current collector; that is, the two side surfaces of the insulating adhesive layer are directly bonded to the corresponding side metal layer. Compared with methods such as magnetron sputtering to form a metal layer on a support structure, in this application, by utilizing the self-bonding property of the insulating adhesive layer, the metal layer can be directly compounded on the insulating adhesive layer, thereby forming the corresponding composite current collector. The process of forming the composite current collector is simpler and faster, does not require complex production equipment, is convenient for mass production, and overcomes the problem of difficult mass production in the prior art. The insulating adhesive layer can be a pre-formed layer structure, which is combined with a metal foil layer for direct compounding.

[0010] Furthermore, cavities for accommodating functional solid fillers are left in the insulating adhesive layer. The insulating adhesive layer can be filled with functional solid fillers to further improve the performance of the insulating adhesive layer without affecting the thickness. Further, the functional solid fillers include at least one of silicon dioxide, aluminum hydroxide, aluminum oxide, talcum powder, aluminum nitride, boron nitride, silicon carbide, barium sulfate, barium titanate, strontium titanate, boehmite, calcium carbonate, calcium silicate, mica, graphite, magnesium oxide, magnesium hydroxide, kaolin, starch, montmorillonite, titanium dioxide, zinc sulfide, calcium bicarbonate, calcium phosphate, calcium hydrogen phosphate, calcium sulfate, carbon black, graphite, multi-walled and single-walled carbon nanotubes, carbon nanofibers, polytetrafluoroethylene particles, polyurethane microparticles, rubber particles, polyamide microparticles, silicone particles, graphene, nanotube structures, and antimony trioxide.

[0011] Further, it further includes a protective layer, and the protective layer is provided on the surface of the metal layer away from the insulating adhesive layer; the protective layer is formed of at least one material among chromium, tungsten, molybdenum, nickel, iron, titanium, niobium, zirconium, gold, silver, platinum, carbon, chromate compounds, silane compounds, and benzotriazole and its modified compounds. On the basis of the basic composite current collector structure, a protective layer structure can be added. The protective layer can prevent the conductive layer of the current collector from being chemically corroded or oxidized, and can also enhance the mechanical strength of the current collector, and can improve the current-carrying capacity of the current collector and the electrode. Further, the thickness of the protective layer is 0.01~0.15μm; it is convenient to provide the function of the protective layer while hardly affecting the overall thickness of the current collector.

[0012] Further, the metal layer is at least one of copper, aluminum, titanium, nickel, cadmium, iron, and silver. Further, the metal layer is a copper layer. The metal layer is a copper foil layer; and the number of pinholes on the copper foil layer is ≤5 per square meter, and the diameter of the pinholes is ≤0.1mm.

[0013] Further, the surface roughness Ra of the metal layer is ≤0.3μm. However, the metal layer also has a certain surface roughness. In addition to directly improving the electrical conductivity, it can promote the formation of a mechanical bite interface between the metal layer and the insulating adhesive layer, and enhance the bonding between the metal layer and the insulating adhesive layer.

[0014] Further, the surface dyne value of the metal layer is ≥46; wherein, the surface dyne value parameter is measured by a dyne pen. In the composite current collector of the present application, the surface dyne value of the metal layer is beneficial to the stable adhesion of the metal layer to the insulating adhesive layer, and is also beneficial to the coating of other layers or active substances on the metal layer.

[0015] Further, the thermal shrinkage rate of the insulating adhesive layer after being treated at 150°C for 30 minutes is ≤3%; further, the elongation rate of the composite current collector is ≥3%. Further, the thermal shrinkage rate of the insulating adhesive layer after being treated at 150°C for 30 minutes is 0.9~2.5%. Further, the surface sheet resistance of the composite current collector is ≤23mΩ. In the present application, different from traditional PET, PP, and PI films, the insulating adhesive layer is not stretched and produced on a certain length production line, but is directly coated and then cured. Therefore, its mechanical properties in the transverse and longitudinal directions are similar; although the test process is carried out based on the longitudinal length, in fact, its thermal shrinkage rate, tensile strength, and elongation at break are almost equal in the longitudinal and transverse directions, and the error does not exceed 3%. The thermal shrinkage rate, elongation at break, and tensile strength of the insulating adhesive layer in the present application should be understood as values that do not distinguish between the longitudinal and transverse directions, or can also be considered to represent the longitudinal and transverse values at the same time. The thermal shrinkage rate of the insulating adhesive layer in the present application is tested according to the JISC2151 standard. The thermal shrinkage rate of the insulating adhesive layer in the present application is ≤3%, which has excellent heat resistance and thermal stability, and is beneficial to improving the safety of application on batteries.

[0016] Another object of the present utility model is to provide a battery, including the aforementioned composite current collector. Based on the composite current collector of the present application, it is conducive to mass production, and is also conducive to forming a battery with high energy density and stable performance, promoting the development of corresponding products applying the composite current collector.

[0017] Compared with the prior art, the beneficial effects of the present utility model are as follows: Compared with the existing composite current collectors, the present application uses an insulating layer structure with adhesiveness to replace the common base film support layer structures such as PET, PP, and PI. While improving the adhesion strength between the metal layer and the support structure, it avoids adding additional hierarchical structures. Compared with the composite current collectors with the same support layer thickness and metal layer thickness in the prior art, in the composite current collector formed by the cooperation of the insulating adhesive layer and the metal layer in the present application, the metal layer and the support structure are more closely matched and are not easily separated from each other during actual use, effectively ensuring the use performance and service life; compared with the existing composite current collectors that use an adhesion enhancement layer to improve adhesion, on the premise of requiring similar adhesion strength, support layer thickness, and metal layer thickness, the present application has fewer necessary hierarchical structures and a smaller overall thickness of the composite current collector; and when applied to large-area batteries, its weight is significantly reduced and the energy density is higher. It should be noted that in the prior art, in order to reduce the thickness while providing a certain degree of bonding stability, it is common to form a composite current collector by means of magnetron sputtering, etc. In this process, due to high process requirements, it is often difficult to achieve mass production; while based on the present application, the insulating adhesive support layer and the metal layer can be formed separately in advance, and then the support layer with adhesive characteristics is directly compounded with the metal layer, thereby significantly simplifying the production process and being able to control within a certain thickness, which is conducive to realizing mass production. Especially when using an insulating adhesive layer with mechanical properties and insulating properties equivalent to those of common base film materials, it can fully retain the advantages of existing base film structures such as PET, PP, and PI, while realizing the advantages brought by the aforementioned adhesive characteristics. In addition, the insulating adhesive layer of the present application can further improve its mechanical properties by adding functional fillers, thereby optimizing the performance of the composite current collector formed thereon. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the hierarchical structure of the composite current collector of the present application.

[0019] Figure 2 It is a schematic diagram of the hierarchical structure of the composite current collector with a protective layer of the present application.

[0020] Description of the Drawings: Composite current collector 100, insulating adhesive layer 110, metal layer 120, protective layer 130. Detailed Embodiments

[0021] The attached drawings of the present utility model are only for illustrative purposes and should not be construed as a limitation to the present utility model. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0022] The technical solutions of the present utility model will be clearly and completely described below in conjunction with the attached drawings and specific implementation manners. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present utility model, rather than all embodiments, and are only used to illustrate the present utility model and should not be regarded as a limitation to the scope of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present utility model. For those conditions not specified in the embodiments, they shall be carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase. Embodiment 1

[0023] This embodiment discloses a support layer applicable to a composite current collector, that is, the aforementioned insulating adhesive layer. The support layer is formed by coating and curing an insulating adhesive liquid; the insulating adhesive liquid includes a mixed component A and component B. Component A is at least one of polyurethane resin, acrylic resin, epoxy resin, polyester resin, polyimide, silicone polymer and its modified compounds; component B liquid is at least one of amino resin, isocyanate, aziridine crosslinking agent, carbodiimide, silane coupling agent and silicone-based tackifier; wherein, the weight ratio of component A to component B is: (90 - 99):(1 - 5). In this embodiment, component A uses polyurethane resin, component B uses amino resin, the ratio of component A to component B is: 92:3, and component A and component B are mixed to form an insulating adhesive liquid.

[0024] In the component A of this embodiment, the polyurethane resin has a polyester backbone part and a polyether backbone part, and the mass ratio range of the polyester backbone part to the polyether backbone part in the polyurethane resin is (1:9) to (5:5); the polyester backbone can be formed by a polyester polyol compound, and the polyester polyol compound is obtained by reacting low-molecular-weight polyols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 3-methylpentanediol, 1,6-hexanediol, hydrogenated bisphenol A, trimethylolpropane, and glycerol with polyacids such as succinic acid, glutaric acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, tetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, and hexahydrophthalic acid. It is a compound with an ester structure and terminal hydroxyl groups. The polyether backbone can be formed by a polyether polyol. Preferably, the polyether polyol is a compound obtained by adding an alkylene oxide having 2 to 4 carbon atoms (such as ethylene oxide, propylene oxide, butylene oxide) to a diol containing a bisphenol backbone. The diols containing a bisphenol backbone are, for example, methylene bisphenol, ethylidene bisphenol, butylidene bisphenol, isopropylidene bisphenol, etc. The addition molar number of the alkylene oxide is preferably 1 to 10. The amino resin in the component B can be selected from at least one of commercially available Cytec 216, Cytec 301, Cytec 303, Cytec 327, Cytec 325, Cytec 370, Cytec 385, Cytec 659, Cytec 683, Cytec 1156, Cytec 1123, Cytec MM-100, Ineos 717, Ineos 718, Ineos R747, Ineos R757, Ineos 917, Ineos MF927, Ineos MF984, Ineos MF985, Ineos MF986, Ineos MF988, Ineos M195, Ineos MR921, Ineos CE7103, Ineos CE8824, Ausi OS 303-98, Ausi OS 325-80, methylated amino resin 5717W, fully methylated amino resin MR603, MELCROSS-83, Changxing ETERMINO9411, ETERMINO9412; other amino resins can also be used. In this embodiment, according to actual requirements, the polyester backbone part, the polyether backbone part and their mass ratio in the polyurethane resin of component A are selected, and the specific amino resin in component B is selected, so that after the mixing of component A and component B, an insulating adhesive liquid with a cured tensile strength ≥ 250 Mpa and a fracture elongation rate ≥ 80% is formed.

[0025] The formed insulating adhesive layer has a tensile strength of ≥250 Mpa and an elongation at break of ≥80%. To improve the mechanical properties of the formed composite current collector, the tensile strength of the insulating adhesive layer can also be 280 Mpa - 400 Mpa, or a more specific tensile strength, such as 280 - 350 Mpa. The bonding force between the insulating adhesive layer and the metal layer ranges from 3 N / 25 mm - 30 N / 25 mm, and can also be 3 N / 25 mm - 20 N / 25 mm; further, the bonding force between the insulating adhesive layer and the metal layer can range from 3 N / 25 mm - 15 N / 25 mm.

[0026] The thickness of the insulating adhesive layer is 1 - 8 μm; considering the comprehensive performance and the thickness suitable for the composite current collector, the thickness of the insulating adhesive layer can be 1.9 - 8 μm. More preferably, the thickness of the insulating adhesive layer is 1.9 - 6 μm.

[0027] The specific process for manufacturing the insulating adhesive layer includes: after the insulating adhesive liquid is coated on the plane of the peelable carrier, it is dried and cured to form the insulating adhesive layer; further, the peelable carrier is a release film. After the insulating adhesive liquid is coated and cured to form the insulating adhesive layer, a release film is covered on the side not covered by the insulating adhesive layer. The formed insulating adhesive layer is between the release films. When the insulating adhesive layer is covered with release films on both sides; during the composite process of the insulating adhesive layer and the metal layer, the corresponding side release film is synchronously peeled off before the insulating adhesive layer is bonded to the metal layer to bond with the metal layer. That is, in this embodiment, the current collector includes the following manufacturing process: A1. Coat the insulating adhesive liquid on the plane of the first peelable carrier, cure it, and then cover the second peelable carrier above to obtain a packaged insulating adhesive layer for standby; A2. Use a raw foil machine to produce the metal layer and unwind it; the packaged insulating adhesive layer is unwound in the same direction as the unwinding of the metal layer. At the same time, the first peelable carrier on the side close to the unwound metal layer is peeled off, and the surface of the insulating adhesive layer exposed on the first peelable carrier side is bonded to the corresponding side metal layer to obtain a semi-composite material; A3. Unwind the semi-composite material after adjusting the direction so that the second peelable carrier side of the semi-composite material is close to the metal layer, and peel off the second peelable carrier to bond the surface of the corresponding side insulating adhesive layer to the metal layer; both sides of the insulating adhesive layer are bonded to the metal layer.

[0028] Further, it also includes step A4, placing the composite material obtained in step A3 at 50 - 90 °C for 24 - 48 h for curing to obtain the current collector. The curing process can fully exert the performance of the insulating adhesive layer and improve the composite effect.

[0029] Further, after curing in step A1, it can be in a state where the insulating adhesive liquid is cured to form but not completely cured. Further, the curing temperature range is 80 - 90 °C.

[0030] In this embodiment, after the insulating adhesive liquid is coated on the release film, it is dried and cured to form an insulating adhesive layer with the required thickness. Then, the side of the insulating adhesive layer that is not covered is covered with the release film. Both sides of the insulating adhesive layer are covered with the release film, which facilitates the placement, storage of the insulating adhesive layer, and the subsequent process of laminating the metal layer. When one side of the insulating adhesive layer needs to be laminated with the metal layer, the corresponding side of the release film is peeled off and then laminated with the metal layer.

[0031] In this embodiment, insulating adhesive layers with thicknesses of 3 μm, 4.5 μm, and 8 μm were respectively coated and fabricated, and corresponding tests were conducted. The test results are as follows (where the peel strength was tested after laminating the metal layer on one side).

[0032] Test Items Unit Test Result 1 Test Result 2 Test Result 3 Test Method Average Thickness μm 3.1 4.55 7.98 ASTM E-252 Tensile Strength Mpa 261 303 360 JISC2151 Elongation at Break % 89% 97% 105% JISC2151 Peel Strength / Adhesion N / 25mm 3.6 5.575 9.825 180° Peel Test Heat Shrinkage Rate (150°C × 30 min) % 1.8% 2.1% 1.5% JISC2151

[0033] In this embodiment, the insulating adhesive liquid may further include a C filler component. The ratio of the A component, B component, and C filler component is: (90 - 99):(1 - 5):(1 - 5). Mixing them gives the insulating adhesive liquid. The C filler component includes at least one of silica, aluminum hydroxide, alumina, talc, aluminum nitride, boron nitride, silicon carbide, barium sulfate, barium titanate, strontium titanate, boehmite, calcium carbonate, calcium silicate, mica, graphite, magnesium oxide, magnesium hydroxide, kaolin, starch, montmorillonite, titanium dioxide, zinc sulfide, calcium bicarbonate, calcium phosphate, calcium hydrogen phosphate, calcium sulfate, carbon black, graphite, multi-walled and single-walled carbon nanotubes, carbon nanofibers, polytetrafluoroethylene particles, polyurethane microparticles, rubber particles, polyamide microparticles, silicone particles, graphene, nanotube structures, and antimony trioxide. In this embodiment, aluminum hydroxide may be used as the C filler component, and the ratio of the A component, B component, and C filler component is: 92:3:3. Based on the insulating adhesive liquid containing the A component, B component, and C component, the above performance tests were conducted, and the test results were similar to the previous results. The tensile strength of the insulating adhesive layer is ≥250 Mpa, the elongation at break is ≥80%, and the adhesive force is ≥3 N / 25 mm. Moreover, compared with the insulating adhesive layer containing the A component and B component, the performance test results of the insulating adhesive layer containing the C component are better, and it has obvious flame retardant properties. Example 2

[0034] This embodiment uses the same manufacturing process as in Example 1 to fabricate an insulating adhesive layer with a thickness of 4 μm. Five groups of insulating adhesive layers were fabricated with different weight ratios of the A component, B component, and C component. The performance test results are shown in the following table (where the peel strength was tested after laminating the metal layer on one side).

[0035] Performance Test Unit ① Test Result (A∶B ∶C = 91∶1∶1) ② Test Result (A∶B ∶C = 93∶3∶3) ③ Test Result (A∶B ∶C = 96∶5∶5) ④ Test Result (A∶B ∶C = 90∶5∶5) ⑤ Test Result (A∶B ∶C = 100∶0∶2.5) Average Thickness μm 3.98 4.05 4.12 4.06 3.95 Tensile Strength Mpa 278 298 313 254 220 Elongation at Break % 95 97 110 84 75 Peel Strength / Adhesion N / 25mm 5.075 5.375 5.475 4.925 1.575 Heat Shrinkage Rate (150°C × 30 min) % 1.82 1.11 0.98 1.03 1.12

[0036] The results show that groups ① to ④ all have good performance test results and meet the requirements as the support layer of the composite current collector. Compared with groups ① to ③, group ④ shows a decrease in tensile strength and elongation at break, and the adhesion also decreases. Group ⑤ shows weak adhesion to the metal layer and unstable attachment of the metal layer; moreover, its mechanical properties, tensile strength, etc. are also significantly weaker than those of groups ① to ④. Example 3

[0037] This example discloses a composite current collector, including an insulating adhesive layer and metal layers adhered to both side surfaces of the insulating adhesive layer, as Figure 1 shown. In this example, the tensile strength of the insulating adhesive layer is ≥250 Mpa; the elongation at break of the insulating adhesive layer is ≥80%. In this example, in addition to being formed in the manner of Example 1, the insulating adhesive layer can also be formed of materials that have insulation, adhesiveness, tensile property, and extensibility after curing in the prior art.

[0038] More preferably, the tensile strength of the insulating adhesive layer can be 280 - 350 Mpa. The range of the adhesion between the insulating adhesive layer and the metal layer is 3 N / 25 mm - 30 N / 25 mm; further, the range of the adhesion between the insulating adhesive layer and the metal layer is 3 N / 25 mm - 20 N / 25 mm; further, the range of the adhesion between the insulating adhesive layer and the metal layer is 3 N / 25 mm - 15 N / 25 mm.

[0039] The thickness of the insulating adhesive layer is 1 - 8 μm; the thickness of the metal layer is 0.5 - 3 μm. Further, the thickness of the insulating adhesive layer is 1.9 - 8 μm; the thickness of the metal layer is 1 - 2 μm. To meet the common thickness requirements of the support layer of the composite current collector and considering the comprehensive performance, the thickness of the insulating adhesive layer can be 1.9 - 6 μm.

[0040] In this embodiment, the two side surfaces of the insulating adhesive layer are directly attached to the corresponding side metal layers to form a composite current collector. To improve the performance of the insulating adhesive layer, in addition to the method of adding Component C filler into the insulating adhesive liquid in Embodiment 1, cavities for accommodating functional solid fillers can also be provided in the insulating adhesive layer, so as to facilitate the subsequent addition of functional solid fillers such as Component C to improve the performance of the insulating adhesive layer. The functional solid fillers include at least one of silicon dioxide, aluminum hydroxide, aluminum oxide, talcum powder, aluminum nitride, boron nitride, silicon carbide, barium sulfate, barium titanate, strontium titanate, boehmite, calcium carbonate, calcium silicate, mica, graphite, magnesium oxide, magnesium hydroxide, kaolin, starch, montmorillonite, titanium dioxide, zinc sulfide, calcium bicarbonate, calcium phosphate, calcium hydrogen phosphate, calcium sulfate, carbon black, graphite, multi-walled and single-walled carbon nanotubes, carbon nanofibers, polytetrafluoroethylene particles, polyurethane microparticles, rubber particles, polyamide microparticles, silicone particles, graphene, nanotube structures, and antimony trioxide.

[0041] In addition to the basic composite current collector structure, in this embodiment, a protective layer can also be provided on the surface of the metal layer away from the support layer (i.e., the insulating adhesive layer), such as Figure 2 shown, the protective layer is provided on the surface of the metal layer away from the insulating adhesive layer; the protective layer is formed of at least one material selected from chromium, tungsten, molybdenum, nickel, iron, titanium, niobium, zirconium, gold, silver, platinum, carbon, chromate compounds, silane compounds, and benzotriazole and its modified compounds. The thickness of the protective layer is 0.01 - 0.15 μm.

[0042] The metal layer is at least one of copper, aluminum, titanium, nickel, cadmium, iron, and silver. In this embodiment, the metal layer is a copper foil layer; and there are ≤5 pinholes per square meter on the copper foil layer, and the diameter of the pinholes is ≤0.1 mm. The surface roughness Ra of the metal layer is ≤0.3 μm.

[0043] In the formed composite current collector, the surface dyne value of the metal layer is ≥46; the thermal shrinkage rate of the adhesive layer after being treated at 150 °C for 30 min is ≤3%; the elongation rate of the composite current collector is ≥3%. Further, the thermal shrinkage rate of the adhesive layer after being treated at 150 °C for 30 min is 0.9 - 2.5%. The surface sheet resistance of the composite current collector is ≤23 mΩ. Embodiment 4

[0044] In this embodiment, composite current collectors were obtained by laminating metal layers and support layers (i.e., support layer / insulating adhesive layer) with different thicknesses, and corresponding performance tests were carried out. The test results are shown in the following table. They include: a. 1 μm metal layer + 4 μm insulating adhesive layer + 1 μm metal layer; b. 2 μm metal layer + 8 μm insulating adhesive layer + 2 μm metal layer; c. 2 μm metal layer + 3 μm insulating adhesive layer + 2 μm metal layer; d. 0.5 μm metal layer + 6 μm insulating adhesive layer + 0.5 μm metal layer; e. 2 μm metal layer + 0.5 μm insulating adhesive layer + 2 μm metal layer. In this embodiment, the metal layer is a copper foil layer; the insulating adhesive layer can be formed from the insulating adhesive liquid with the ratio of A∶B∶C = 93∶3∶3 in the aforementioned Embodiment 2, or can be formed from other existing insulating adhesive materials (e.g., formed by interweaving and mixing polyester fibers and sticky fibers).

[0045] Performance Test Unit a b c d e Average Total Thickness μm 6 12 7 7 4.5 Tensile Strength Mpa 275 353 287 157 135 Elongation % 5.6 7.5 4.5 1.6 1.1 Peel Strength / Adhesion N / 25mm 6.625 10.075 3.85 7.825 2.575

[0046] The results show that overall, the current collector containing an insulating adhesive layer based on this application has excellent mechanical properties. In terms of performance, the insulating adhesive layer can significantly improve the tensile strength, elongation, and adhesion. The metal layer also has an obvious impact on factors such as tensile strength. It should be noted that the cooperation between the insulating adhesive layer and the metal layer can synergistically ensure the comprehensive excellent performance of the corresponding current collector. Example 5

[0047] This embodiment discloses a battery, including the composite current collector of the aforementioned Embodiment 3, which is used as the negative current collector of the battery. Example 6

[0048] This embodiment discloses the application of the composite current collector described in Embodiment 3 or the battery described in Embodiment 5 in a power vehicle.

[0049] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solutions of the present invention, rather than limitations on the specific implementation manners of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the claims of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A composite current collector, characterized in that, It includes an insulating adhesive layer and a metal layer adhered to at least one side of the insulating adhesive layer; the tensile strength of the insulating adhesive layer ≥ 250 Mpa; the elongation at break of the insulating adhesive layer ≥ 80%.

2. The composite current collector according to claim 1, wherein It includes an insulating adhesive layer and metal layers adhered to both sides of the insulating adhesive layer.

3. The composite current collector according to claim 1, wherein The tensile strength of the insulating adhesive layer is 280 Mpa to 400 Mpa.

4. The composite current collector according to claim 1, wherein The thickness of the insulating adhesive layer is 1 to 8 μm; the thickness of the metal layer is 0.5 to 3 μm.

5. The composite current collector according to claim 1, wherein, The insulating adhesive layer and the metal layer are directly adhered to form a composite current collector.

6. The composite current collector according to claim 1, wherein, The adhesive force between the insulating adhesive layer and the metal layer is 3 N / 25 mm to 30 N / 25 mm.

7. The composite current collector according to claim 1, wherein The insulating adhesive layer has cavities for accommodating functional solid fillers.

8. The composite current collector according to any one of claims 1 to 7, characterized in that, It further includes a protective layer, and the protective layer is provided on the side of the metal layer away from the insulating adhesive layer; further, the protective layer is formed of at least one material among chromium, tungsten, molybdenum, nickel, iron, titanium, niobium, zirconium, gold, silver, platinum, carbon, chromate compounds, silane compounds, and benzotriazole and its modified compounds.

9. The composite current collector according to any one of claims 1 to 7, characterized in that The metal layer is at least one of copper, aluminum, titanium, nickel, cadmium, iron, and silver.

10. The composite current collector according to any one of claims 1 to 7, characterized in that The surface roughness Ra of the metal layer ≤ 0.3 μm; and / or, the surface dyne value of the metal layer ≥ 46; and / or, the thermal shrinkage rate of the insulating adhesive layer after being treated at 150 °C for 30 min ≤ 3%; and / or, the elongation rate of the composite current collector ≥ 3%.

11. A battery, characterized in that, It includes the composite current collector according to any one of claims 1 to 10.

12. Application of the composite current collector according to any one of claims 1 to 10 or the battery according to claim 11 in a power vehicle.

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