Composite current collector and preparation method and application thereof

Abstract

The invention relates to the field of lithium ion batteries, in particular to a composite current collector and a preparation method and application thereof. The composite current collector comprises an insulating layer, a bonding layer, a conductive layer and a substrate layer which are sequentially arranged, wherein a release layer is arranged between the conductive layer and the substrate layer; and the width of the release layer is smaller than that of the conductive layer. The composite current collector is provided with the substrate, and the current collector is uniform in thickness and convenient to roll and transport.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and more specifically, to a composite current collector, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are constructed by winding or stacking basic unit structures, which consist of a positive electrode, a separator, and a negative electrode. The positive and negative electrodes are where electrochemical reactions occur. Current collectors in the positive and negative electrodes collect and conduct the current generated by the electrochemical reactions. The separator is responsible for separating the positive and negative electrodes to prevent them from coming into contact and causing a short circuit.

[0003] The common configuration for current collectors is to use copper foil for the negative electrode and aluminum foil for the positive electrode. Due to the use of metallic materials, the current collectors account for a significant proportion (around 8%) of the total cell weight. Therefore, reducing the weight of the current collectors is an effective way to improve the energy density (kWh / kg) of lithium-ion batteries. Chinese patent applications CN106654285A and CN101071860A describe methods for preparing conductive coatings on flexible substrates to fabricate low-density current collectors. However, the drawback of these technical solutions is that to ensure current can be conducted through both metal conductor layers on both sides of the substrate, the two metal layers need to be welded together. Since the metal conductor layers are typically thin, welding is difficult.

[0004] To address these issues, engineers have made significant efforts in improving the current collector structure and welding methods. Patent application CN110165223A discloses a composite current collector with a porous structure and a conductive layer inside the pores, enabling conductivity between the metal conductor layers on both sides of the composite current collector. However, this current collector requires drilling, and the conductive layer inside the pores is difficult to fabricate, resulting in poor conductivity and hindering its widespread application. Patent CN208051145U discloses an ultrasonic welding head and welding equipment. Through the extrusion action of the welding head's conical structure during welding, the polymer layer in the welding area is penetrated, welding the metal conductor layers together and achieving simultaneous welding and conductivity between the two metal conductor layers. However, this welding process easily leads to over-welding, damaging the metal conductor layers in the welding area, resulting in low weld strength and poor conductivity.

[0005] Patent CN112234210A discloses a current collector without PET in the welding area. However, the current collector is manufactured using a chemical etching method, which is costly and polluting, making it unsuitable for widespread use. In particular, when the aluminum layer in the welding area is thickened, winding can cause deformation and damage to the product in that area.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a composite current collector with a substrate, wherein the current collector has a uniform thickness, facilitating winding and transportation.

[0008] The second objective of this invention is to provide a method for preparing the composite current collector, which is simple to operate, requires no complex preparation process, and is low in cost.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0010] One aspect of the present invention relates to a composite current collector, comprising an insulating layer, an adhesive layer, a conductive layer, and a substrate layer disposed sequentially thereon:

[0011] A release layer is disposed between the conductive layer and the substrate layer;

[0012] The width of the release layer is smaller than the width of the conductive layer.

[0013] The composite current collector has a substrate and a uniform thickness, which facilitates winding and transportation.

[0014] Another aspect of the present invention relates to a method for preparing the aforementioned composite current collector, comprising the following steps:

[0015] The insulating layer, adhesive layer, conductive layer, release layer, and substrate layer are laminated in sequence.

[0016] The method for preparing the composite current collector is simple and easy to operate. By combining the composite layers, a composite current collector with uniform thickness, easy to roll up and transport, and easy to weld can be obtained.

[0017] Another aspect of the present invention relates to a positive electrode sheet, comprising the composite current collector described above or a composite current collector prepared by the method for preparing the composite current collector described above.

[0018] Another aspect of the present invention relates to a lithium-ion battery, including the aforementioned positive electrode.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) The composite current collector provided by this invention has a substrate, and the current collector has a uniform thickness, which facilitates winding and transportation. A release layer is provided between the conductive layer and the substrate layer. The substrate layer near the release layer can be easily peeled off and breaks at the point where no release agent is applied. The folding marks facilitate the breakage of the substrate layer, thereby forming a composite current collector with a thicker substrate layer on the other side. The side with the substrate layer is the current collector tab, which is the current collector welding area. The conductive layer plus the remaining substrate thickens the conductive layer, which facilitates welding and makes the two sides conductive. The peeled substrate material can be recycled to reduce costs.

[0021] (2) The method for preparing the composite current collector provided by the present invention is simple and easy to operate. After the composite layers are combined, a composite current collector with uniform thickness, easy to roll up and transport, and easy to weld can be obtained. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a single-sided composite current collector structure provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of a double-sided composite current collector structure provided in an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of a composite current collector structure with vapor deposition on the other side, provided in an embodiment of the present invention.

[0026] Figure 4 A schematic diagram of a composite current collector structure with one side of the insulating layer hollowed out, provided in an embodiment of the present invention;

[0027] Figure 5 A schematic diagram of a composite current collector structure with folded marks in the pre-fractured area provided in an embodiment of the present invention;

[0028] Figure 6 A schematic diagram of an aluminum composite current collector structure with a thickened aluminum layer in the welding area of ​​the unpeeled substrate aluminum foil provided in an embodiment of the present invention;

[0029] Figure 7 This is a schematic diagram of an aluminum composite current collector structure with a thickened aluminum layer in the welding area after peeling off the aluminum foil of the substrate, provided in an embodiment of the present invention.

[0030] Figure 8 A schematic diagram of an aluminum composite current collector structure with thickened aluminum layer in the welding area of ​​the unpeeled substrate aluminum foil, without PET, provided in an embodiment of the present invention;

[0031] Figure 9 A schematic diagram of an aluminum composite current collector structure with thickened aluminum layer in the welding area after peeling off the substrate aluminum foil, without PET, provided in an embodiment of the present invention;

[0032] Figure 10 This is a schematic diagram of the positive electrode structure provided in an embodiment of the present invention;

[0033] Figure 11 This is a schematic diagram of the positive electrode structure provided in another embodiment of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not 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 skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0035] One aspect of the present invention relates to a composite current collector, such as Figure 1 As shown, it includes an insulating layer, an adhesive layer, a conductive layer, and a substrate layer arranged sequentially:

[0036] A release layer is disposed between the conductive layer and the substrate layer;

[0037] The width of the release layer is smaller than the width of the conductive layer.

[0038] The composite current collector has a substrate and uniform thickness, facilitating winding and transportation. A release layer is provided between the conductive layer and the substrate layer. The substrate layer near the release layer can be easily peeled off, breaking at the point where no release agent is applied. A crease is provided to facilitate the breakage of the substrate layer, thus forming a thicker composite current collector with a substrate layer on the other side. The side with the substrate layer is the current collector tab, which is the current collector welding area. The conductive layer, plus the remaining substrate, thickens the conductive layer, facilitating welding and enabling conductivity on both sides. The peeled substrate material can be recycled to reduce costs.

[0039] Thickening the tabs can prevent the current collector from being wound up, and wrinkles or breakage can occur at the junction of the thickened and unthickened areas. The composite current collector has a substrate, and the current collector thickness is uniform, facilitating winding and transportation.

[0040] Furthermore, the width of the release layer is 50% to 99% of the width of the conductive layer (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99%). If the width of the release layer exceeds 99% of the width of the conductive layer, the substrate bonding area is too small, making subsequent bonding difficult; if the width of the release layer is less than 50% of the width of the conductive layer, the substrate bonding area is too large, affecting the battery energy density.

[0041] Further, the thickness of the release layer after drying is 0.05 to 2 μm (e.g., 0.05 μm, 0.1 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm).

[0042] Furthermore, the material of the release layer includes at least one of the following: acrylic resin, silicone oil, silane coupling agent, graphite oxide, graphite, triazole nitrogen-containing compound, or tungsten-nickel alloy.

[0043] Furthermore, a pre-fracture region is provided on the substrate layer, the pre-fracture region is located below the release layer, and the horizontal distance between the pre-fracture region and the edge of the release layer is 0 to 10 mm (e.g., 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm).

[0044] Furthermore, the pre-fractured area undergoes bending, scoring, stamping, and laser drilling to create creases. The creases should be positioned as close as possible to the uncoated blank area, allowing for easy breakage. Figure 5 As shown. The pre-fractured region must not damage the conductive layer deposited on it.

[0045] Furthermore, the width of the conductive layer is greater than the width of the insulating layer; the width of the insulating layer is greater than the width of the adhesive layer, such as... Figure 4 As shown. At this point, the insulation layer is in a perforated state, which facilitates welding.

[0046] A battery has a multi-layered, repeating structure of positive electrode / separator / negative electrode / separator. During battery manufacturing, the positive electrode current collector of each layer needs to be welded to allow current to be drawn out. Current battery welding typically uses ultrasonic welding. Ultrasonic welding uses ultrasonic vibration to cause the materials at the welding interface to melt, diffuse, and connect at a microscopic level. However, in batteries where the insulating layer is a polymer and the conductive and substrate layers are metals, ultrasonic welding is difficult to apply to the polymer and metal. A hollowed-out insulating layer, consisting only of the metallic conductive and substrate layers, facilitates welding.

[0047] Furthermore, the width ratio of the conductive layer, the insulating layer, and the adhesive layer is 101–120:100:80–99 (e.g., 101:100:99, 105:100:95, 110:100:90, 115:100:85, or 120:100:80).

[0048] Furthermore, the thickness of the insulating layer is 1.5 to 15 μm (e.g., 1.5 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm or 15 μm).

[0049] Furthermore, the thickness of the adhesive layer after drying is 0.2–3 μm (e.g., 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, 2.5 μm, 2.8 μm or 3 μm).

[0050] Furthermore, the thickness of the conductive layer is 0.3 to 3 μm (e.g., 0.3 μm, 0.7 μm, 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3 μm).

[0051] Furthermore, the thickness of the substrate layer is 2 to 20 μm (e.g., 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm).

[0052] Furthermore, the material of the insulating layer includes at least one of polyethylene terephthalate, polypropylene, or polyethylene.

[0053] Furthermore, the adhesive layer is made of at least one of maleic anhydride-modified polypropylene, polyurethane, or acrylic-acrylate copolymer.

[0054] Furthermore, the conductive layer is made of at least one of aluminum, iron, nickel, silver, chromium, cobalt, or cobalt.

[0055] Furthermore, the substrate layer is made of at least one of aluminum, iron, nickel, chromium, or cobalt.

[0056] In some specific embodiments, the composite current collector has a double-sided structure, such as... Figure 2 As shown, the insulating layer has a symmetrical structure on both sides.

[0057] In some specific embodiments, the composite current collector is deposited or sputtered with a conductive layer on the other side of the insulating layer, such as... Figure 3 As shown.

[0058] Another aspect of the present invention relates to a method for preparing the aforementioned composite current collector, comprising the following steps:

[0059] The insulating layer, adhesive layer, conductive layer, release layer, and substrate layer are laminated in sequence.

[0060] The method for preparing the composite current collector is simple and easy to operate. It does not require complex processes or equipment. After the composite layers are combined, a composite current collector with uniform thickness, easy to roll up and transport, and easy to weld can be obtained.

[0061] Furthermore, the composite specifically includes:

[0062] (a) After coating the substrate with a release agent, perform a first drying, leaving a blank area on one side of the substrate without coating the release agent, and forming the conductive layer on the surface of the side of the substrate coated with the release agent.

[0063] (b) After applying an adhesive to the insulating layer, a second drying process is performed; the adhesive-coated area completely covers the width of the insulating layer;

[0064] (c) After bonding one side surface of the insulating layer coated with the adhesive to the side surface of the conductive layer away from the substrate layer, hot pressing and curing are performed.

[0065] Furthermore, the hot pressing temperature is 45–90°C (e.g., 45°C, 50°C, 60°C, 70°C, 80°C, or 90°C).

[0066] Further, the pressure of the hot pressing is 0.1 to 2 MPa (e.g., 0.1 MPa, 0.3 MPa, 0.5 MPa, 0.8 MPa, 1.0 MPa, 1.4 MPa, 1.6 MPa, 1.8 MPa or 2 MPa).

[0067] Furthermore, the ripening temperature is 75–85°C (e.g., 75°C, 77°C, 79°C, 81°C, 83°C, or 85°C).

[0068] Furthermore, the curing time is 6 to 72 hours (e.g., 6 hours, 10 hours, 14 hours, 18 hours, 22 hours, 26 hours, 30 hours, 34 hours, 38 hours, 42 hours, 46 hours, 50 hours, 54 hours, 58 hours, 62 hours, 66 hours, 70 hours, or 72 hours).

[0069] Furthermore, the temperature of the first drying process is 40–150°C.

[0070] Furthermore, the temperature for the second drying is 40–150°C.

[0071] The width mentioned in this invention refers to the length of the shorter side of the rectangular plane containing the material layer.

[0072] Another aspect of the present invention relates to a positive electrode sheet, comprising the composite current collector described above or a composite current collector prepared by the method for preparing the composite current collector described above.

[0073] Another aspect of the present invention relates to a lithium-ion battery, including the aforementioned positive electrode.

[0074] The embodiments of the present invention will now be described in detail with reference to specific examples and comparative examples.

[0075] Example 1

[0076] Fabricating a thickened aluminum composite current collector in the tab welding area includes the following steps:

[0077] (1) A release agent is coated on the substrate aluminum foil. The substrate aluminum foil is 7μm thick and 200mm wide. The release agent coating width is 150mm. A 50mm blank area is left on one side without the release agent. The release agent used is WDL806 water-based release agent produced by Changfeng Chemical. The thickness of the release agent after drying is 0.3μm.

[0078] (2) An aluminum layer is deposited on the substrate aluminum foil to form a conductive layer. The width of the conductive layer is 200 mm and the thickness of the deposited aluminum layer is 1 μm.

[0079] (3) Apply adhesive to PET and dry at 80°C; the PET width is 200mm, the PET thickness is 4μm, the adhesive thickness after drying is 1μm, and the adhesive coating area completely covers the width of the PET; the adhesive is Yantai MX-8347 adhesive;

[0080] (4) The PET-coated adhesive surface and the vapor-deposited aluminum surface are hot-pressed and cured. The hot-pressing pressure is 0.3 MPa, the hot-pressing temperature is 75℃, the curing temperature is 80℃, and the curing time is 72 h. The resulting aluminum composite current collector structure with a thickened aluminum layer in the welding area of ​​the unpeeled substrate aluminum foil is as follows: Figure 6 As shown;

[0081] (5) The area of ​​the aluminum foil substrate coated with the release agent layer is peeled off and cut to obtain an aluminum composite current collector with a thickened welding area; the cut position is at the release agent layer, 55 mm from the edge of the aluminum foil substrate and 5 mm beyond the release agent blank area; the aluminum layer thickness in the welding area is 8 μm, and the resulting aluminum composite current collector structure with a thickened aluminum layer in the welding area after peeling off the aluminum foil substrate is as follows. Figure 7 As shown.

[0082] Example 2

[0083] Fabrication of an aluminum composite current collector with a thickened electrode tab welding area and no PET layer:

[0084] The difference from Example 1 is that the adhesive coating width on the PET is 170 mm, and the resulting aluminum composite current collector structure with a thickened aluminum layer in the welding area of ​​the unpeeled substrate aluminum foil and no PET is as follows. Figure 8 As shown:

[0085] The aluminum foil substrate is peeled and cut, and then the PET is cut to a width of 175 mm, extending 5 mm beyond the adhesive coating area. At this point, the welding area is 25 mm wide, the aluminum layer thickness in the welding area is 8 micrometers, and there is no PET layer in the welding area. The resulting aluminum composite current collector structure with a thickened aluminum layer in the welding area after peeling off the aluminum foil substrate and without PET is shown below. Figure 9 As shown.

[0086] Example 3

[0087] Fabricating a thickened aluminum composite current collector in the tab welding area includes the following steps:

[0088] (1) Coating a release agent on the substrate aluminum foil. The substrate aluminum foil is 2μm thick and 200mm wide. The release agent coating width is 100mm, leaving a 100mm blank area on one side without coating the release agent. The release agent used is WDL806 water-based release agent produced by Changfeng Chemical. The thickness of the release agent after drying is 0.05μm.

[0089] (2) An aluminum layer is deposited on the substrate aluminum foil to form a conductive layer. The width of the conductive layer is 200 mm and the thickness of the deposited aluminum layer is 0.3 μm.

[0090] (3) Coat the PET with adhesive and dry at 80°C; the PET width is 200mm, the PET thickness is 15μm, the adhesive thickness after drying is 0.2μm, and the adhesive coating area completely covers the width of the PET; the adhesive is Yantai MX-8347 adhesive;

[0091] (4) The PET coated adhesive surface and the vapor-deposited aluminum surface are hot-pressed and cured. The hot-pressing pressure is 2MPa, the hot-pressing temperature is 100℃, the curing temperature is 85℃, and the curing time is 6h.

[0092] (5) Peel off and cut the area of ​​the aluminum foil substrate coated with release agent layer to obtain an aluminum composite current collector with thickened welding area; the cut position is the release agent layer, 100mm away from the edge of the aluminum foil substrate; the aluminum layer thickness of the welding area is 2.2μm.

[0093] Example 4

[0094] Fabricating a thickened aluminum composite current collector in the tab welding area includes the following steps:

[0095] (1) Coating a release agent on the substrate aluminum foil. The substrate aluminum foil is 20μm thick and 200mm wide. The release agent coating width is 198mm. Leave a 2mm blank area on one side without coating the release agent. The release agent used is WDL806 water-based release agent produced by Changfeng Chemical. The thickness of the release agent after drying is 2μm.

[0096] (2) An aluminum layer is deposited on the substrate aluminum foil to form a conductive layer. The width of the conductive layer is 200 mm and the thickness of the deposited aluminum layer is 3 μm.

[0097] (3) Coat the PET with adhesive and dry at 80°C; the PET width is 200mm, the PET thickness is 1.5μm, the adhesive thickness after drying is 3μm, and the adhesive coating area completely covers the width of the PET; the adhesive is Yantai MX-8347 adhesive;

[0098] (4) The PET coated adhesive surface and the vapor-deposited aluminum surface are hot-pressed and cured. The hot-pressing pressure is 0.1 MPa, the hot-pressing temperature is 50℃, the curing temperature is 75℃, and the curing time is 32h.

[0099] (5) Peel off and cut the area of ​​the aluminum foil substrate coated with release agent layer to obtain an aluminum composite current collector with thickened welding area; the cut position is the release agent layer, 12mm away from the edge of the aluminum foil substrate and 10mm beyond the release agent blank area; the aluminum layer thickness of the welding area is 23μm.

[0100] Example 5

[0101] The positive electrode sheet is fabricated using the aluminum composite current collector prepared in Example 1, including the following steps:

[0102] 1) The aluminum composite current collector with thickened aluminum layer in the welding area of ​​the unpeeled substrate aluminum foil prepared in step 4) of Example 1 is wound up. At this time, since the current collector has a uniform thickness, it will not cause damage during winding.

[0103] 2) Using NCM523 material of model S7LC from Ronbay Technology as the positive electrode material, the positive electrode slurry is prepared by mixing NCM523:PVDF:conductive carbon black with NMP at a mass ratio of 90:7:3.

[0104] 3) Unwind the aluminum composite current collector with thickened aluminum layer in the welding area of ​​the unpeeled substrate aluminum foil, peel and cut the substrate aluminum foil, coat the positive electrode paste onto the evaporated aluminum layer and dry to form the positive electrode layer, with a coating surface density of 180 g / m². 2 .

[0105] 4) The dried electrode sheets are rolled to obtain positive electrode sheets, and the compaction density of the positive electrode layer reaches 3.4 g / m³. 3 The positive electrode structure is as follows: Figure 10 As shown.

[0106] Example 6

[0107] The difference from Example 5 is that a PET-free aluminum composite current collector with a thickened aluminum layer in the solder area of ​​the unpeeled substrate aluminum foil prepared in Example 2 is used for winding. The positive electrode structure is as follows: Figure 11 As shown.

[0108] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A composite current collector, characterized in that, It includes an insulating layer, an adhesive layer, a conductive layer, and a substrate layer arranged sequentially: A release layer is provided between the conductive layer and the substrate layer; The width of the release layer is smaller than the width of the conductive layer.

2. The composite current collector according to claim 1, characterized in that, The width of the release layer is 50% to 99% of the width of the conductive layer; Preferably, the thickness of the release layer is 0.05–2 μm; Preferably, the material of the release layer includes at least one of the following: acrylic resin, silicone oil, silane coupling agent, graphite oxide, graphite, triazole nitrogen-containing compound, or tungsten-nickel alloy.

3. The composite current collector according to claim 1, characterized in that, A pre-fracture region is provided on the substrate layer, the pre-fracture region is located below the release layer, and the horizontal distance between the pre-fracture region and the edge of the release layer is 0-10 mm.

4. The composite current collector according to claim 1, characterized in that, The width of the conductive layer is greater than the width of the insulating layer; the width of the insulating layer is greater than the width of the adhesive layer; Preferably, the width ratio of the conductive layer, the insulating layer and the adhesive layer is 101-120:100:80-99.

5. The composite current collector according to any one of claims 1 to 4, characterized in that, Includes at least one of the following technical features (1) to (6): (1) The thickness of the insulating layer is 1.5 to 15 μm; (2) The thickness of the adhesive layer is 0.2–3 μm; (3) The thickness of the conductive layer is 0.3–3 μm; (4) The material of the conductive layer includes at least one of aluminum, iron, nickel, silver, chromium or cobalt; (5) The thickness of the substrate layer is 2 to 20 μm; (6) The substrate layer is made of at least one of aluminum, iron, nickel, chromium or cobalt.

6. The method for preparing the composite current collector according to any one of claims 1 to 5, characterized in that, Includes the following steps: The insulating layer, adhesive layer, conductive layer, release layer, and substrate layer are laminated in sequence.

7. The method for preparing the composite current collector according to claim 6, characterized in that, The composite specifically includes: (a) After coating the substrate with a release agent, a first drying is performed to form the conductive layer on the side surface of the substrate coated with the release agent; (b) After applying an adhesive to the insulating layer, a second drying process is performed; (c) After bonding one side surface of the insulating layer coated with the adhesive to the side surface of the conductive layer away from the substrate layer, hot pressing and curing are performed.

8. The method for preparing the composite current collector according to claim 7, characterized in that, The hot pressing temperature is 50–100°C; Preferably, the pressure of the hot pressing is 0.1–2 MPa; Preferably, the ripening temperature is 45–90°C; Preferably, the ripening time is 6 to 72 hours.

9. A positive electrode sheet, characterized in that, The composite current collector includes the composite current collector prepared by the preparation method of the composite current collector according to any one of claims 1 to 5 or the composite current collector according to any one of claims 6 to 8.

10. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 9.

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