Supporting layer suitable for composite current collector, corresponding composite current collector and battery

Abstract

The invention discloses a supporting layer suitable for a composite current collector, a corresponding composite current collector and a battery. Wherein the supporting layer is formed by curing insulating adhesive liquid; the insulating adhesive liquid comprises a component A and a component B which are mixed, wherein the component A is at least one of polyurethane resin, acrylic resin, epoxy resin, polyester resin, polyimide, an organosilicon polymer and a modified compound thereof; the liquid B is at least one of amino resin, isocyanate, an aziridine cross-linking agent, carbodiimide, a silane coupling agent and an organic silicon tackifier; wherein the ratio of the component A to the component B is (90-99): (1-5). Compared with an existing supporting layer and an existing composite current collector, the viscous insulating layer structure can replace common PET, PP, PI and other types of base film middle supporting layer structures, the adhesive strength of the metal layer and the supporting layer is improved, and meanwhile additional hierarchical structures are avoided. And the production process is simplified, so that mass production is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and more specifically, to a support layer suitable for a composite current collector and a corresponding 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 increase the total thickness of the composite copper foil, etc., which weakens the advantages of the composite current collector over 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 present invention aims to overcome at least one of the shortcomings of the above-mentioned prior art and provide a support layer suitable for a composite current collector and a corresponding composite current collector and a battery. Based on the support layer of the present application, while maintaining the hierarchical structure and function of the basic support layer and the metal layer, no additional layer structure is required, so that the metal layer can be tightly attached to the corresponding support structure.

[0006] The technical solution adopted by the present invention is a support layer suitable for a composite current collector, the composite current collector includes a support layer and a metal layer located on at least one side of the support layer; the support layer is formed by curing an insulating adhesive liquid; the insulating adhesive liquid includes a mixed component A and a component B, the component A is at least one of a polyurethane resin, an acrylic resin, an epoxy resin, a polyester resin, a polyimide, a silicone polymer and a modified compound thereof; the liquid B is at least one of an amino resin, an isocyanate, an aziridine crosslinking agent, a carbodiimide, a silane coupling agent and a silicone tackifier; wherein the ratio of component A to component B is: (90-99): (1~5). The support layer has insulation, viscosity, tensile strength and elongation. The support layer of the present application can replace traditional base film support structures such as PET, PP, PI, etc., to ensure the basic support structure and corresponding functions, and at the same time can make full use of the bonding properties to make the metal layer closely attached to the support structure. No additional hierarchical structure is required to solve the matching 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 smaller 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, is simple in production process, and is convenient for mass production.

[0007] Further, the insulating adhesive liquid also includes a C filler component, wherein the ratio of the A component, the B component and the C filler component is: (90-99): (1-5): (1-5); the C filler component includes at least one of silicon dioxide, aluminum hydroxide, aluminum oxide, 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 particles, rubber particles, polyamide particles, organosilicon particles, graphene, nanotube structures and antimony trioxide. Through the C filler component, it is beneficial to improve the performance of the support layer without affecting the thickness.

[0008] Furthermore, the tensile strength of the support layer is ≥250 Mpa; the elongation at break of the support layer is ≥80%. Further, the tensile strength of the support layer is 280 Mpa - 400 Mpa; more preferably, the tensile strength of the support layer is 280 - 350 Mpa. Further, the bonding force between the support layer and the metal layer ranges from 3 N / 25 mm to 30 N / 25 mm; more preferably, the bonding force between the support layer and the metal layer ranges from 3 N / 25 mm to 20 N / 25 mm; even more preferably, the bonding force between the support layer and the metal layer ranges from 3 N / 25 mm to 15 N / 25 mm. The support layer has physical properties equivalent to those of conventional support structures such as PET-based films, including tensile strength and elongation at break, effectively ensuring the insulation, toughness, and safety of the corresponding composite current collector.

[0009] Further, the thickness of the support layer is 1 - 8 μm; more preferably, the thickness of the support layer is 1.9 - 8 μm. Even more preferably, the thickness of the support layer is 1.9 - 6 μm.

[0010] Another object of the present invention is to provide a composite current collector, including the aforementioned support layer and metal layers bonded to both surfaces of the support layer. The metal layers are directly adhered to both sides of the support layer to form a composite current collector; that is, both surfaces of the support layer are directly bonded to the corresponding side metal layers. Compared with methods such as magnetron sputtering to form a metal layer on a support structure, in this application, the support layer itself has adhesive properties, and the metal layer can be directly compounded on the support layer to form 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 support layer can be a pre-formed layer structure, which is directly compounded with a metal foil layer.

[0011] Further, the thickness of the support layer is 1 - 8 μm; the thickness of the metal layer is 0.5 - 3 μm. The thickness of the support layer is 1.9 - 8 μm; the thickness of the metal layer is 1 - 2 μm. Even more preferably, the thickness of the support layer is 1.9 - 6 μm. In this thickness range, it meets the requirements of common lithium battery negative current collectors; when the thickness is thinner, it is beneficial to reduce the material cost of the corresponding battery, and improve the battery energy density by reducing the thickness and weight. 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 battery positive and negative electrode materials during charge and discharge. It can also ensure the current transmission of the battery and the stable welding of the electrode tabs.

[0012] Further, it further includes a protective layer, and the protective layer is disposed on the surface of the metal layer away from the support 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, 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 sheet. 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.

[0013] 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 there are ≤5 pinholes per square meter on the copper foil layer, and the diameter of the pinholes is ≤0.1mm.

[0014] 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.

[0015] Further, the surface dyne value of the metal layer is ≥46; wherein, the surface dyne value parameter is measured by a dyne pen. The surface dyne value of the metal layer in the composite current collector of the present application is beneficial to the stable adhesion of the metal layer to the support layer, and is also beneficial to the coating of other layers or active substances on the metal layer.

[0016] 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, 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 longitudinal and transverse directions, or can also be considered to represent 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.

[0017] Another object of the present invention is to provide a battery, comprising the aforementioned support layer or the aforementioned composite current collector. Based on the support layer or composite current collector of the present application, mass production is facilitated, and it is also conducive to forming a battery with high energy density and stable performance, promoting the development of corresponding composite current collector application products.

[0018] Compared with the prior art, the beneficial effects of the present application are as follows: The sticky support structure of the present application can replace common base film support layer structures such as PET, PP, and PI. While improving the adhesion strength between the metal layer and the support layer, it avoids adding additional hierarchical structures. Compared with the composite current collector 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 support layer and the metal layer of the present application, the metal layer and the support layer are more closely matched and are not easily separated from each other during actual use, effectively ensuring the service performance and service life; compared with the existing composite current collectors that use an adhesion-enhancing layer to improve adhesion, on the premise of requiring similar adhesion strength, support layer thickness, and metal layer thickness, the present application requires fewer hierarchical structures, and the overall thickness of the composite current collector is smaller; 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 and other methods. In this process, due to high process requirements, it is often difficult to achieve mass production; 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 properties can be directly compounded with the metal layer, thereby significantly simplifying the production process and being able to be controlled within a certain thickness, which is conducive to realizing mass production. Especially when using a support 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 properties. In addition, the support 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the hierarchical structure of the composite current collector of the present application.

[0020] Figure 2 It is a schematic diagram of the hierarchical structure of the composite current collector with a protective layer of the present application.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS: Composite current collector 100, support layer 110, metal layer 120, protective layer 130. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The accompanying drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. 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.

[0023] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase. Example 1

[0024] This example discloses a support layer 110 suitable for the composite current collector 100, that is, the aforementioned insulating adhesive support structure. The support layer 110 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 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 example, 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.

[0025] In the A component 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, etc., 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, etc. It is a compound with an ester structure and terminal hydroxyl groups. The polyether backbone can be formed by a polyether polyol, and preferably a compound obtained by adding an alkylene oxide with 2 - 4 carbon atoms (such as ethylene oxide, propylene oxide, butylene oxide) to a diol containing a bisphenol backbone is used. The diol containing a bisphenol backbone is, for example, methylene bisphenol, ethylidene bisphenol, butylidene bisphenol, isopropylidene bisphenol, etc. The addition molar number of the alkylene oxide is preferably 1 - 10. The amino resin in the B component 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 A - component polyurethane resin are selected, and the specific amino resin in the B component is selected, so that after the A component and the B component are mixed, an insulating adhesive liquid with a cured tensile strength ≥ 250 Mpa and an elongation at break ≥ 80% is formed.

[0026] The formed support layer 110 has a tensile strength ≥ 250 Mpa and an elongation at break ≥ 80%. To improve the mechanical properties of the formed composite current collector 100, the tensile strength of the support layer 110 can also be 280 Mpa - 400 Mpa, or more specifically, a tensile strength such as 280 Mpa - 350 Mpa. The adhesion between the support layer 110 and the metal layer 120 ranges from 3 N / 25 mm - 30 N / 25 mm, and can also be 3 N / 25 mm - 20 N / 25 mm; further, the adhesion between the support layer 110 and the metal layer 120 can range from 3 N / 25 mm - 15 N / 25 mm.

[0027] The thickness of the support layer 110 is 1 - 8 μm; considering the comprehensive performance and the thickness suitable for the composite current collector 100, the thickness of the support layer 110 can be 1.9 - 8 μm. More preferably, the thickness of the support layer 110 is 1.9 - 6 μm.

[0028] The specific process for manufacturing the support layer 110 includes: after the insulating adhesive liquid is coated on the plane of the peelable carrier, it is dried and cured to form the support layer 110; further, the peelable carrier is a release film. After the insulating adhesive liquid is coated and cured to form the support layer 110, a release film is covered on the side not covered by the support layer 110. Between the release films is the formed support layer 110. When the support layer 110 is covered with release films on both sides; during the composite process of the support layer 110 and the metal layer 120, the corresponding side release film is synchronously peeled off before the support layer 110 is bonded to the metal layer 120 to bond with the metal layer 120. 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 120 and unwind it; the packaged insulating adhesive layer is unwound in the same direction as the unwinding of the metal layer 120. At the same time, the first peelable carrier on the side close to the unwinding metal layer 120 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 120 to obtain a semi-composite material; A3. Adjust the direction of the semi-composite material to unwind, so that the second peelable carrier side of the semi-composite material is close to the metal layer 120, and peel off the second peelable carrier to bond the surface of the corresponding side insulating adhesive layer to the metal layer 120; both sides of the insulating adhesive layer are bonded with the metal layer 120.

[0029] Further, it also includes step A4 of 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.

[0030] 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.

[0031] In this embodiment, after the insulating adhesive liquid is coated on the release film, it is dried and cured to form a support layer 110 with a required thickness. Then, the side of the support layer 110 that is not covered is covered with the release film. Both sides of the support layer 110 are covered with the release film, which facilitates the placement, storage of the support layer 110 and the subsequent process of laminating the metal layer 120. When one side of the support layer 110 needs to be laminated with the metal layer 120, the corresponding side release film is peeled off and then laminated with the metal layer 120.

[0032] In this embodiment, support layers 110 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 is based on the test after laminating the metal layer 120 on one side).

[0033] 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℃ × 30min) % 1.8% 2.1% 1.5% JISC2151

[0034] In this embodiment, the insulating adhesive liquid may further include a C filler component. Among them, the ratio of the A component, B component, and C filler component is: (90 - 99):(1 - 5):(1 - 5). The insulating adhesive liquid is obtained by mixing; the C filler component includes at least one of silica, aluminum hydroxide, alumina, talc 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. 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. And on the premise of this 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 support layer 110 ≥ 250 Mpa, the elongation at break ≥ 80%, and the adhesion ≥ 3 N / 25 mm; and compared with the support layer 110 containing the A component and B component, the performance test results of the support layer 110 containing the C component are better, and it has obvious flame retardant properties. Example 2

[0035] In this embodiment, the same manufacturing process as in Example 1 is adopted to fabricate an insulating adhesive support layer 110 with a thickness of 4 μm. Five insulating adhesive layers are fabricated with different weight ratio proportions of the A component, B component, and C component. The performance test results are shown in the following table (where the peel strength is based on the test after laminating the metal layer 120 on one side).

[0036] 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℃ × 30min) % 1.82 1.11 0.98 1.03 1.12

[0037] The results show that groups ① to ④ all have good performance test results and meet the requirements for the support layer 110 of the composite current collector 100. Compared with groups ① to ③, group ④ shows a decrease in tensile strength and elongation at break, and the adhesion force also decreases. For group ⑤, it shows weak adhesion to the metal layer 120, and the attachment of the metal layer 120 is unstable; moreover, the mechanical properties, tensile strength, etc. are also significantly weaker than those of groups ① to ④. Example 3

[0038] This example discloses a composite current collector 100, including a support layer 110 and metal layers 120 bonded to both side surfaces of the support layer 110, as Figure 1 shown. In this example, the tensile strength of the insulating adhesive support layer 110 ≥ 250 Mpa; the elongation at break of the insulating adhesive support layer 110 ≥ 80%. The insulating adhesive support layer 110 in this example can be formed in the manner of Example 1.

[0039] More preferably, the tensile strength of the insulating adhesive support layer 110 can be 280 - 350 Mpa. The range of the adhesion force between the insulating adhesive support layer 110 and the metal layer 120 is 3 N / 25 mm - 30 N / 25 mm; further, the range of the adhesion force between the insulating adhesive support layer 110 and the metal layer 120 is 3 N / 25 mm - 20 N / 25 mm; further, the range of the adhesion force between the insulating adhesive support layer 110 and the metal layer 120 is 3 N / 25 mm - 15 N / 25 mm.

[0040] The thickness of the insulating adhesive support layer 110 is 1 - 8 μm; the thickness of the metal layer 120 is 0.5 - 3 μm. Further, the thickness of the insulating adhesive support layer 110 is 1.9 - 8 μm; the thickness of the metal layer 120 is 1 - 2 μm. To meet the common intermediate layer thickness requirements of the composite current collector 100 and considering the comprehensive performance, the thickness of the insulating adhesive support layer 110 can further be 1.9 - 6 μm.

[0041] In this embodiment, the two side surfaces of the support layer 110 are directly attached to the corresponding side metal layers 120 to form the composite current collector 100. To improve the performance of the support layer 110, in addition to the method of incorporating component C filler into the insulating adhesive liquid in Embodiment 1, cavities for accommodating functional solid fillers can also be left in the insulating adhesive layer, thereby facilitating 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 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, alumina, 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.

[0042] In addition to the basic structure of the composite current collector 100, in this embodiment, a protective layer 130 can also be provided on the surface of the metal layer 120 away from the support layer 110 (i.e., the insulating adhesive layer), such as Figure 2 shown, the protective layer 130 is provided on the surface of the metal layer 120 away from the insulating adhesive layer; the protective layer 130 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 130 is 0.01 - 0.15 μm.

[0043] The metal layer 120 is at least one of copper, aluminum, titanium, nickel, cadmium, iron, and silver. In this embodiment, the metal layer 120 is a copper foil layer; and there are ≤ 5 pinholes per square meter on the copper foil layer, and the diameter of the pinholes ≤ 0.1 mm. The surface roughness Ra of the metal layer 120 ≤ 0.3 μm.

[0044] In the formed composite current collector 100, the surface dyne value of the metal layer 120 ≥ 46; the thermal shrinkage rate of the support layer 110 after being treated at 150 °C for 30 min ≤ 3%; the elongation rate of the composite current collector 100 ≥ 3%. Further, the thermal shrinkage rate of the support layer 110 after being treated at 150 °C for 30 min is 0.9 - 2.5%. The surface sheet resistance of the composite current collector 100 ≤ 23 mΩ. Embodiment 4

[0045] In this embodiment, composite current collectors 100 were obtained by laminating metal layers 120 and support layers 110 (i.e., intermediate layers / insulating adhesive layers) with different thicknesses, and corresponding performance tests were conducted. The test results are shown in the following table. They include a. 1-μm metal layer + 4-μm insulating adhesive support layer + 1-μm metal layer; b. 2-μm metal layer + 8-μm insulating adhesive support layer + 2-μm metal layer; c. 2-μm metal layer + 3-μm insulating adhesive support layer + 2-μm metal layer; d. 0.5-μm metal layer + 6-μm insulating adhesive support layer + 0.5-μm metal layer; e. 2-μm metal layer + 0.5-μm insulating adhesive support layer + 2-μm metal layer. In this embodiment, the metal layer 120 is a copper foil layer; the insulating adhesive support layer 110 can be formed from the insulating adhesive liquid with the ratio of A∶B∶C = 93∶3∶3 in the aforementioned embodiment 2.

[0046] 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

[0047] The results show that overall, the current collector 100 containing the insulating adhesive support layer 110 based on this application has excellent mechanical properties. In terms of performance, the insulating adhesive support layer 110 can significantly improve the tensile strength, elongation, and adhesion in multiple aspects. The metal layer 120 also has an obvious influence at least on factors such as tensile strength. It should be noted that the cooperation between the insulating adhesive support layer 110 and the metal layer 120 can synergistically ensure the comprehensive excellent performance of the corresponding current collector. Example 5

[0048] This embodiment discloses a battery, including the support layer 110 in the aforementioned embodiment 1; or, including the composite current collector 100 in the aforementioned embodiment 3, which is used as the negative current collector of the battery. Example 6

[0049] This embodiment discloses the application of the support layer 110 in embodiment 1, the composite current collector 100 in embodiment 3, or the battery in embodiment 5 in a power vehicle.

[0050] 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 support layer suitable for a composite current collector, the composite current collector comprising a support layer and a metal layer located on at least one side of the support layer, characterized in that, The support layer is formed by curing an insulating adhesive liquid; the insulating adhesive liquid includes a mixed component A and a component B. The component A is at least one of polyurethane resin, acrylic resin, epoxy resin, polyester resin, polyimide, silicone polymer and its modified compounds; the component B liquid is at least one of amino resin, isocyanate, aziridine crosslinking agent, carbodiimide, silane coupling agent and silicone-based tackifier; wherein, the ratio of component A to component B is: (90-99):(1-5).

2. The support layer according to claim 1, characterized in that, The insulating adhesive liquid further includes a C filler component, wherein the ratio of component A, component B and the C filler component is: (90-99):(1-5):(1-5); the C filler component includes at least one of silica, aluminum hydroxide, alumina, talc 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.

3. The support layer according to claim 1, wherein, The tensile strength of the support layer is ≥250 Mpa; the elongation at break of the support layer is ≥80%.

4. A composite current collector, characterized in that, It includes the support layer according to any one of claims 1 to 3 and metal layers adhered to both side surfaces of the support layer.

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

6. The composite current collector according to claim 4, wherein It further includes a protective layer, and the protective layer is provided on the side of the metal layer away from the support layer; further, the protective layer is formed by at least one material of chromium, tungsten, molybdenum, nickel, iron, titanium, niobium, zirconium, gold, silver, platinum, carbon, chromate compounds, silane compounds and benzotriazole and its modified compounds.

7. The composite current collector according to any one of claims 4 to 6, characterized in that, The metal layer is at least one of copper, aluminum, titanium, nickel, cadmium, iron and silver.

8. The composite current collector according to any one of claims 4 to 6, wherein The surface roughness Ra of the metal layer is ≤0.3 μm; and / or, the surface dyne value of the metal layer is ≥46; and / or, the thermal shrinkage rate of the support layer after being treated at 150°C for 30 minutes is ≤3%; and / or, the elongation rate of the composite current collector is ≥3%.

9. A battery, characterized in that, It includes the support layer according to any one of claims 1 to 3 or the composite current collector according to any one of claims 4 to 8.

10. Application of the support layer according to any one of claims 1 to 3, the composite current collector according to any one of claims 4 to 8 or the battery according to claim 9 in a power vehicle.

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