Composite current collector, pole piece, secondary battery and electric device

Abstract

The invention provides a composite current collector, a pole piece, a secondary battery and an electric device. The composite current collector comprises a base material layer, a bonding layer and a metal layer, the base material layer is provided with a first surface and a second surface which are opposite to each other; the bonding layer and the metal layer are arranged on the first surface and / or the second surface, and the bonding layer is located between the base material layer and the metal layer; the metal layer comprises a metal seed layer and a metal thickening layer, and the metal seed layer is located between the bonding layer and the metal thickening layer. According to the composite current collector, the structure of the current collector is designed, so that the metal layer and the base material layer have relatively good binding force, and meanwhile, the metal layer has relatively proper thickness.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly to a composite current collector, a pole piece, a secondary battery, and an electrical device. Background Art

[0002] The statements herein only provide background information related to the present application and do not necessarily constitute prior art.

[0003] Compared with a metal current collector, the composite current collector has the advantage of higher safety performance. In the composite current collector, since the substrate layer is usually made of an insulating material, the difference in properties between the metal layer and the insulating material restricts the improvement of the bonding force between the metal layer and the substrate layer. As a result, in the traditional composite current collector, in order to make the metal layer and the substrate layer have a good bonding force, only a metal layer with a smaller thickness can be obtained. However, a metal layer with a smaller thickness has a larger internal resistance, which may bring a larger internal resistance to the secondary battery and affect the rate performance of the battery. Therefore, in the traditional composite current collector, it is often difficult to balance the good bonding force between the metal layer and the substrate layer and the appropriate thickness of the metal layer. Summary of the Invention

[0004] To achieve the above object, a first aspect of the present application provides a composite current collector, including a substrate layer, a bonding layer, and a metal layer; the substrate layer has opposite first and second surfaces; the bonding layer and the metal layer are provided on the first surface and / or the second surface, and the bonding layer is located between the substrate layer and the metal layer; the metal layer includes a metal seed layer and a metal thickening layer, and the metal seed layer is located between the bonding layer and the metal thickening layer.

[0005] In the above composite current collector, the bonding layer can improve the bonding force between the substrate layer and the metal layer. At the same time, the metal thickening layer is provided on the metal seed layer, which can make the metal layer have an appropriate thickness. Therefore, in the above composite current collector, by designing the structure of the current collector, the bonding force between the metal layer and the substrate layer can be made better, and at the same time, the metal layer can have a more appropriate thickness.

[0006] In some embodiments, the adhesive layer comprises a polymer with a melting point ≥ 80°C. The melting point of the polymer within this range can keep the adhesive layer in good stability, reduce the risk of holes appearing on the surface of the adhesive layer when preparing the metal seed layer, and further improve the bonding strength between the metal seed layer and the adhesive layer. Optionally, the adhesive layer comprises a polymer with a melting point of 80°C to 400°C. Optionally, the adhesive layer comprises at least one of polyolefin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyurethane, epoxy resin, styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-ethylene-butene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin, and polyimide.

[0007] In some embodiments, the thickness of the adhesive layer is 200 nm to 1500 nm. The thickness of the adhesive layer within this range can keep the overall thickness of the composite current collector appropriate while achieving a good bonding effect, and reduce the risk of the composite current collector having an excessive thickness. Optionally, the thickness of the adhesive layer is 300 nm to 700 nm.

[0008] In some embodiments, the metal seed layer includes at least one of a sputtered metal seed layer, an evaporated metal seed layer, and a sprayed metal seed layer.

[0009] In some embodiments, the thickness of the metal seed layer is 1 nm to 200 nm. The metal seed layer within this thickness range is easy to prepare and can maintain a good bonding strength with the adhesive layer. Optionally, the thickness of the metal seed layer is 20 nm to 100 nm.

[0010] In some embodiments, the metal seed layer comprises at least one of copper, copper alloy, aluminum, and aluminum alloy.

[0011] In some embodiments, the metal thickening layer includes an electroplated metal thickening layer. The electroplated metal thickening layer can be a metal thickening layer formed by electroplating. The metal seed layer has good electrical conductivity, which is convenient for electroplating to form the metal thickening layer.

[0012] In some embodiments, the thickness of the metal thickening layer is 0.2 μm to 2 μm. The thickness of the metal thickening layer within this range can make the overall thickness of the metal layer appropriate, enabling the composite current collector to have a more suitable metal layer thickness and internal resistance. Optionally, the thickness of the metal thickening layer is 0.5 μm to 1.5 μm.

[0013] In some embodiments, the substrate layer comprises at least one of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polyethylene, polypropylene, polypropylene styrene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyoxymethylene, epoxy resin, phenolic resin, silicone rubber, and polycarbonate.

[0014] In some embodiments, the thickness of the substrate layer is 2 μm to 10 μm, optionally 3 μm to 8 μm.

[0015] The second aspect of the present application provides a method for preparing a composite current collector, comprising the following steps:

[0016] Providing a substrate layer having opposite first and second surfaces;

[0017] Successively preparing an adhesive layer, a metal seed layer, and a metal thickening layer on the first surface and / or the second surface.

[0018] In some embodiments, the metal seed layer is prepared by at least one of sputtering, evaporation plating, and spraying.

[0019] In some embodiments, the metal thickening layer is prepared by electroplating.

[0020] The third aspect of the present application provides an electrode sheet, comprising at least one of the composite current collector and the composite current collector prepared by the preparation method.

[0021] The fourth aspect of the present application provides a secondary battery, comprising the electrode sheet.

[0022] The fifth aspect of the present application provides an electrical device, comprising at least one of the composite current collector, the composite current collector prepared by the preparation method, the electrode sheet, and the secondary battery. Description of the Drawings

[0023] To better describe and illustrate the embodiments or examples provided in the present application, one or more drawings may be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, and the currently understood best mode of these applications. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0024] Figure 1 It is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0025] Figure 2 For Figure 1Exploded view of a secondary battery according to an embodiment of the present application as shown

[0026] Figure 3 Schematic diagram of an electrical device using the secondary battery according to an embodiment of the present application as a power source

[0027] Figure 4 Schematic diagram of the structure of a composite current collector according to an embodiment of the present application

[0028] Figure 5 Schematic diagram of the structure of a composite current collector according to another embodiment of the present application

[0029] Description of reference numerals:

[0030] 1. Secondary battery; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device; 3. Composite current collector; 31. Substrate layer; 32. Adhesive layer; 33. Metal seed layer; 34. Metal thickening layer Detailed embodiments

[0031] For ease of understanding the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present application more thorough and comprehensive

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items

[0033] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or exclude the end values. Any end value can be independently included or excluded, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, ranges of 60 to 110 and 80 to 120 are understood to be contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4, and 5 are also listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to listing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when stating that a certain parameter is an integer selected from "2 to 10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0034] In this application, when it comes to "multiple", "a variety of", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0035] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0036] Referring to "embodiment" in this text means that the specific features, structures, or characteristics described in combination with the embodiment can be included in at least one embodiment or implementation manner of this application. The occurrence of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. The understanding of "implementation manner" mentioned in this text is similar.

[0037] Those skilled in the art can understand that in the methods of various embodiments or examples, the written order of each step does not mean a strict execution order and does not impose any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. If there is no special indication, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0038] In this application, in an open technical feature or technical solution described by words such as "containing", "comprising", "including", etc., without other instructions, additional members other than the listed members are not excluded, and it can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that further includes additional members outside the listed members. For example, A includes a1, a2 and a3. Without other instructions, it may also include other members or may not include additional members, and it can be regarded as providing both a feature or solution of "A is composed of a1, a2 and a3" and a feature or solution of "A not only includes a1, a2 and a3, but also includes other members".

[0039] In this application, without other instructions, A (such as B) means that B is a non-limiting example in A, and it can be understood that A is not limited to B.

[0040] In this application, "optionally", "optional", "option" mean that it can be either present or absent, that is, it refers to any one of two alternative options of "present" or "absent". If "optional" appears multiple times in a technical solution, without special instructions and without contradiction or mutual restriction, each "optional" is independent of each other.

[0041] One embodiment of this application provides a composite current collector. The composite current collector includes a substrate layer, an adhesive layer and a metal layer. The substrate layer has opposite first and second surfaces. The adhesive layer and the metal layer are provided on the first surface and / or the second surface, and the adhesive layer is located between the substrate layer and the metal layer. The metal layer includes a metal seed layer and a metal thickening layer, and the metal seed layer is located between the adhesive layer and the metal thickening layer.

[0042] In the composite current collector of the present embodiment, the bonding layer can improve the bonding force between the base material layer and the metal layer. At the same time, the metal thickening layer is disposed on the metal seed layer, so that the metal layer has a suitable thickness. Therefore, in the composite current collector of the present embodiment, by designing the structure of the current collector, a good bonding force can be achieved between the metal layer and the base material layer, and at the same time, the metal layer has a relatively suitable thickness.

[0043] Please refer to Figure 4 , which shows the structure of the composite current collector 3 in an embodiment of the present application. The composite current collector 3 includes a base material layer 31, a bonding layer 32, and a metal layer. The base material layer 31 has opposite first and second surfaces. The bonding layer 32 and the metal layer are provided on the first surface or the second surface, and the bonding layer 32 is located between the base material layer 31 and the metal layer. The metal layer includes a metal seed layer 33 and a metal thickening layer 34, and the metal seed layer 33 is located between the bonding layer 32 and the metal thickening layer 34.

[0044] Please refer to Figure 5 , which shows the structure of the composite current collector 3 in another embodiment of the present application. The composite current collector 3 includes a base material layer 31, a bonding layer 32, and a metal layer. The base material layer 31 has opposite first and second surfaces. The bonding layer 32 and the metal layer are provided on both the first surface and the second surface, and the bonding layer 32 is located between the base material layer 31 and the metal layer. The metal layer includes a metal seed layer 33 and a metal thickening layer 34, and the metal seed layer 33 is located between the bonding layer 32 and the metal thickening layer 34.

[0045] It can be understood that in the composite current collector, reducing the thickness of the metal layer can, to a certain extent, reduce the overall thickness and manufacturing cost of the composite current collector. However, a metal layer with a smaller thickness may bring a larger internal resistance. Therefore, it is necessary to keep the thickness of the metal layer within a relatively suitable range. At the same time, due to the difference between the base material layer and the metal layer, it is difficult to form a relatively stable bonding force between the integrally thick metal layer and the base material layer. In the present embodiment, by providing the bonding layer, the metal seed layer, and the metal thickening layer, the metal layer can have a relatively suitable thickness, and at the same time, a good bonding force can be achieved between the base material layer and the metal layer.

[0046] In some embodiments, the adhesive layer comprises a polymer with a melting point ≥ 80°C. Optionally, the adhesive layer comprises a polymer with a melting point of 80°C to 400°C. The melting point of the polymer within this range can keep the adhesive layer in good stability, reduce the risk of holes appearing on the surface of the adhesive layer when preparing the metal seed layer, and further improve the bonding strength between the metal seed layer and the adhesive layer. Additionally, the reduction of holes can also reduce the risk of lithium plating in the electrode sheet. Further optionally, the adhesive layer comprises at least one of polyolefin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyurethane, epoxy resin, styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-ethylene-butene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin, and polyimide. Further optionally, the melting point of the polymer comprised in the adhesive layer can be 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 250°C, 280°C, 300°C, 320°C, 350°C, 380°C, 400°C, etc.

[0047] In some embodiments, the melting point of the adhesive layer is greater than that of the substrate layer. At this time, it is not easy to form holes on the surface of the adhesive layer when preparing the metal seed layer, which is beneficial to further improving the bonding strength between the metal seed layer and the adhesive layer.

[0048] In some embodiments, the thickness of the adhesive layer is 200 nm to 1500 nm. The thickness of the adhesive layer within this range can keep the overall thickness of the composite current collector appropriate while achieving a good bonding effect, and reduce the risk of the composite current collector having an excessive thickness. Optionally, the thickness of the adhesive layer can be 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, etc. Further optionally, the thickness of the adhesive layer is 300 nm to 700 nm.

[0049] In some embodiments, the metal seed layer includes at least one of a sputtered metal seed layer, an evaporated metal seed layer, and a sprayed metal seed layer. It can be understood that the sputtered metal seed layer can be a metal seed layer formed by sputtering methods such as magnetron sputtering. The evaporated metal seed layer can be a metal seed layer formed by evaporation. The sprayed metal seed layer can be a metal seed layer formed by spraying. The sputtered metal seed layer, the evaporated metal seed layer, and the sprayed metal seed layer can maintain good adhesion to the adhesive layer, which is beneficial to improving the overall stability of the composite current collector structure. Optionally, the metal seed layer includes a sprayed metal seed layer. The sprayed metal seed layer has a relatively low temperature during formation, which can reduce the impact on the adhesive layer when preparing the metal seed layer and reduce the risk of holes in the adhesive layer due to high temperature.

[0050] In some embodiments, the thickness of the metal seed layer is 1 nm to 200 nm. The metal seed layer within this thickness range is easy to prepare and can maintain good bonding force with the adhesive layer. Optionally, the metal seed layer can be prepared by at least one of sputtering, evaporation, and spraying. Optionally, the thickness of the metal seed layer can be 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, etc. Further optionally, the thickness of the metal seed layer is 20 nm to 100 nm.

[0051] In some embodiments, the metal seed layer contains at least one of copper, copper alloy, aluminum, and aluminum alloy.

[0052] In some embodiments, the metal thickening layer includes an electroplated metal thickening layer. It can be understood that the electroplated metal thickening layer can be a metal thickening layer formed by electroplating. The metal seed layer has good electrical conductivity, which is convenient for electroplating to form the metal thickening layer.

[0053] In some embodiments, the thickness of the metal thickening layer is 0.2 μm to 2 μm. The thickness of the metal thickening layer within this range can make the overall metal layer have a more appropriate thickness, enabling the composite current collector to balance a more appropriate metal layer thickness and internal resistance. Optionally, the thickness of the metal thickening layer can be 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.5 μm, 1.8 μm, 2 μm, etc. Further optionally, the thickness of the metal thickening layer is 0.5 μm to 1.5 μm.

[0054] In some embodiments, the substrate layer comprises at least one of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polyethylene, polypropylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyoxymethylene, epoxy resin, phenolic resin, silicone rubber and polycarbonate. Optionally, the thickness of the substrate layer is 2 μm to 10 μm. For example, the thickness of the substrate layer can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. Further optionally, the thickness of the substrate layer is 3 μm to 8 μm.

[0055] Another embodiment of the present application provides a method for preparing a composite current collector. The method for preparing a composite current collector comprises the following steps: providing a substrate layer, the substrate layer having a first surface and a second surface opposite to each other; sequentially preparing a bonding layer, a metal seed layer and a metal thickening layer on the first surface and / or the second surface;

[0056] Optionally, the metal seed layer is prepared by at least one of sputtering, evaporation and spraying, and the metal thickening layer is prepared by electroplating.

[0057] In some embodiments, the method for preparing the bonding layer includes: coating a slurry containing raw materials for the bonding layer on a surface of the substrate layer, and then aging to form the bonding layer.

[0058] Optionally, the slurry can be coated by gravure coating. Optionally, a metal seed layer is prepared on the surface of the slurry and then matured. This can improve the surface hardness of the bonding layer on the one hand, and further improve the bonding force between the metal seed layer and the bonding layer on the other hand. Optionally, the maturation temperature is 80°C to 90°C, and the maturation time is 4s to 8s.

[0059] Further optionally, the cured product is rolled to ensure that the metal seed layer and the bonding layer are fully adhered to each other and to improve the uniformity of the thickness of the bonding layer.

[0060] In some embodiments, the preparation method of the composite current collector includes the following steps: coating a slurry containing raw materials for a bonding layer on at least one surface of a substrate layer; preparing a metal seed layer on the surface of the slurry; maturing the slurry; rolling the matured product; maturing again after rolling; and preparing a metal thickening layer on the surface of the metal seed layer of the matured product.

[0061] It can be understood that when the bonding layer and the metal seed layer are prepared on two surfaces of the substrate respectively, the two surfaces of the substrate layer can be operated separately or simultaneously.

[0062] Another embodiment of the present application provides a current collector plate. The current collector plate includes at least one of the above-mentioned composite current collector and the composite current collector prepared by the above-mentioned preparation method.

[0063] Another embodiment of the present application provides a secondary battery. The secondary battery includes the above-mentioned current collector plate.

[0064] Another embodiment of the present application provides an electrical device. The electrical device includes at least one of the above-mentioned composite current collector, the composite current collector prepared by the above-mentioned preparation method, the above-mentioned current collector plate, and the above-mentioned secondary battery.

[0065] The secondary battery and the electrical device of the present application will be described below with appropriate reference to the accompanying drawings.

[0066] Generally, a secondary battery includes a positive electrode current collector plate, a negative electrode current collector plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode current collector plate and the negative electrode current collector plate. The electrolyte plays a role in conducting ions between the positive electrode current collector plate and the negative electrode current collector plate. The separator is disposed between the positive electrode current collector plate and the negative electrode current collector plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0067] Positive electrode current collector plate

[0068] The positive electrode current collector plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0069] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0070] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0071] In some of these embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 )), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds, etc. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, etc. Non-limiting examples of lithium cobalt oxide may include LiCoO 2 ; non-limiting examples of lithium nickel oxide may include LiNiO 2 ; non-limiting examples of lithium manganese oxide may include LiMnO 2 , LiMn 2 O 4 , etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ), etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.8 Co 0.15Al 0.05 O 2 。

[0072] In some embodiments, the positive electrode active material layer may further optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0073] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0074] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate, such as positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one surface of the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained. The type of the solvent can be selected from, but not limited to, any one of the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector on which the positive electrode slurry is coated can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The surface of the positive electrode current collector on which the positive electrode slurry is coated can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 - 25000 mPa·s. When coating the positive electrode slurry, the coating unit surface density in terms of dry weight (deducting the solvent) can be 15 - 35 mg / cm 2 。The compaction density of the positive electrode plate can be 3.0 - 3.6 g / cm 3 ,optionally 3.3 - 3.5 g / cm 3 。

[0075] Negative electrode plate

[0076] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0077] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on either or both of the two opposite surfaces of the negative electrode current collector.

[0078] In some of these embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on the polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0079] In some of these embodiments, the negative electrode active material may be a negative electrode active material for a battery well-known in the art. As non-limiting examples, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone, or two or more of them may be used in combination.

[0080] In some of these embodiments, the negative electrode active material layer may also optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0081] In some of these embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some of these embodiments, the negative electrode active material layer may also optionally include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0083] In some of these embodiments, the negative electrode sheet can be prepared in the following manner: dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (non-limiting examples of the solvent include deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% - 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 - 10000 mPa·s. When coating the negative electrode slurry, the coating unit surface density based on dry weight (deducting the solvent) can be 75 - 220 g / m 2 . The tap density of the negative electrode sheet can be 1.0 g / cm 3 ~1.8 g / cm 3 .

[0084] Electrolyte

[0085] The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. There is no particular limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0086] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0087] In some of these embodiments, the electrolyte salt can include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate) borate (LiBOB), lithium difluoro bis(oxalate) phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP), or one or more of them.

[0088] In some of these embodiments, the solvent can include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate One or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0089] In some embodiments, the electrolyte may optionally further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, and the like.

[0090] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), and the like.

[0091] Separator

[0092] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0093] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0094] In some embodiments, the thickness of the separator is 6 to 40 μm, and may be optionally 12 to 20 μm.

[0095] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be made into an electrode assembly by a winding process or a stacking process.

[0096] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0097] In some embodiments, the outer package of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery may also be a soft package, such as a pouch-type soft package. The material of the soft package may be plastic. Further, non-limiting examples of the plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0098] The secondary battery includes at least one battery cell. The secondary battery may include 1 or more battery cells.

[0099] In this application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy into each other. Further, generally, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0100] This application places no particular restrictions on the shape of the battery cell, which can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 is a battery cell 1 with a square structure as an example.

[0101] In some of the embodiments, referring to Figure 2 , the outer package may include a housing 11 and a cover plate 13. Among them, the housing 11 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be disposed on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator may form an electrode assembly 12 through a winding process or a stacking process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 included in the battery cell 1 can be one or more, and those skilled in the art can select according to actual needs.

[0102] The secondary battery can be a battery module or a battery pack.

[0103] The battery module includes at least one battery cell. The number of battery cells included in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0104] In the battery module, multiple battery cells can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other arbitrary manner. Further, the multiple battery cells can be fixed by fasteners.

[0105] Optionally, the battery module can further include a housing having a receiving space, and multiple battery cells are received in the receiving space.

[0106] In some of the embodiments, the above-mentioned battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0107] A battery pack may include a battery box and a plurality of battery modules disposed in the battery box. The battery box includes an upper box body and a lower box body. The upper box body can cover the lower box body and form a closed space for accommodating the battery modules. The plurality of battery modules can be arranged in the battery box in any manner.

[0108] In addition, the present application also provides an electrical device, which includes the secondary battery provided by the present application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include a mobile device, an electric vehicle, an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0109] As the electrical device, the secondary battery can be selected according to its usage requirements.

[0110] Figure 3 This is the electrical device 2 as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device for the high power and high energy density of the secondary battery, a battery pack or a battery module can be adopted.

[0111] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires to be thin and light, and a secondary battery can be used as the power source.

[0112] Embodiment

[0113] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the present application will be further described in detail below in conjunction with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way constitutes a limitation to the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0114] For those not specified in the embodiments in terms of specific techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments not specified in the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0115] Embodiment 1

[0116] The preparation method of the composite current collector in this embodiment includes the following steps:

[0117] S101: Apply the slurry containing the raw materials of the adhesive layer on one surface of the substrate layer by gravure coating.

[0118] S102: Prepare a metal seed layer on the surface of the slurry by magnetron sputtering.

[0119] S103: Bake the product obtained in S102 at 80°C - 90°C for 4s - 8s to cure the slurry to form the adhesive layer.

[0120] S104: Perform a rolling process on the product obtained in S103.

[0121] S105: Re-cure the product after the rolling process, with a curing temperature of 85°C and a curing time of 72h.

[0122] S106: Electroplate on the surface of the metal seed layer of the product obtained in S105 to prepare a metal thickening layer. The electroplating speed is 4m / min - 8m / min. After electroplating, the composite current collector in this embodiment is obtained.

[0123] Example 2

[0124] The preparation method of the composite current collector in this embodiment includes the following steps:

[0125] S101: Apply the slurry containing the raw materials of the adhesive layer on one surface of the substrate layer by gravure coating.

[0126] S102: Prepare a metal seed layer on the surface of the slurry by magnetron sputtering.

[0127] S103: Bake the product obtained in S102 at 80°C - 90°C for 4s - 8s to cure the slurry to form the adhesive layer.

[0128] S104: Perform a rolling process on the product obtained in S103.

[0129] S105: Apply the slurry containing the raw materials of the adhesive layer on the other surface of the substrate layer by gravure coating.

[0130] S106: Prepare a metal seed layer on the surface of the slurry by magnetron sputtering.

[0131] S107: Bake the product obtained in S106 at 80°C - 90°C for 4s - 8s to cure the slurry to form the adhesive layer.

[0132] S108: Perform a rolling process on the product obtained in S107.

[0133] S109: Re-cure the product after the rolling process, with a curing temperature of 85°C and a curing time of 72h.

[0134] S110: Simultaneously electroplate a metal thickening layer on the surfaces of the two metal seed layers of the product obtained in S109. The electroplating speed is 4 m / min to 8 m / min. After electroplating, the composite current collector in this embodiment is obtained.

[0135] Examples 3 to 18

[0136] Compared with Example 2, the differences in Examples 3 to 18 lie in the material of the substrate layer, the thickness of the substrate layer, the material of the adhesive layer, the thickness of the adhesive layer, the material of the metal seed layer, the preparation method of the metal seed layer, the thickness of the metal seed layer, the thickness of the metal thickening layer, etc. Specifically, as shown in Table 1.

[0137] Comparative Examples 1 to 3

[0138] Compared with Example 2, the differences in Comparative Examples 1 to 3 are that the composite current collector does not include an adhesive layer and the material of the substrate layer is different.

[0139] Test Examples

[0140] (1) Metal layer peel strength test: After the sample is attached to the non-corona surface of the EAA film, then cover a 12-um PET on the EAA film, and place it on a heat sealer at a temperature of 120 °C and a pressure of 0.2 Mpa for lamination. Cut the laminated sample into a sample with a length of 100 mm and a width of 20 mm, and use 3M double-sided tape to attach the non-attached surface of the metal layer to the steel plate; clamp the sample on the fixture of the tensile machine, with a spacing of 50 mm, and perform a 180 °C peel test at a speed of 300 mm / min, read the peel force value and convert it into the unit of N / m, with 5 parallel samples, and finally take the average value of the peel force.

[0141] (2) Composite current collector hole test: Use an online CCD high-speed camera to test the number of holes in a 1000-m length of the composite current collector, and then divide it by the area of the current collector in the test section to calculate the number of holes per square meter.

[0142] (3) Composite current collector sheet resistance test: Use a four-probe sheet resistance tester to test the sheet resistance of the large surface of the metal layer of the sample, randomly test 30 points, and take the average value of the sheet resistance of the 30 points.

[0143] Table 1

[0144]

[0145]

[0146] In Table 1, the unit of the substrate layer thickness is μm. The melting point represents the melting point of the polymer contained in the adhesive layer, and the unit is °C. The unit of the adhesive layer thickness is nm. The unit of the metal seed layer thickness is nm. The unit of the metal thickening layer thickness is μm. The unit of the metal layer peel strength is N / m. The unit of the number of holes is pieces / m 2 . The unit of the sheet resistance is mΩ / □.

[0147] It can be seen from Examples 1 to 18 and Comparative Examples 1 to 3 that introducing an adhesive layer between the substrate layer and the metal layer can improve the peel strength of the metal layer.

[0148] It can be seen from Examples 11 to 16 that when spraying to prepare the metal seed layer, the number of holes in the composite current collector can be reduced, especially the number of holes with a diameter ≤ 100 μm can be reduced.

[0149] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0150] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A composite current collector, characterized in that, it comprises a substrate layer, an adhesive layer and a metal layer; the substrate layer has opposite first and second surfaces; the adhesive layer and the metal layer are provided on the first surface and / or the second surface, and the adhesive layer is located between the substrate layer and the metal layer; the metal layer includes a metal seed layer and a metal thickening layer, and the metal seed layer is located between the adhesive layer and the metal thickening layer.

2. The composite current collector according to claim 1, characterized in that, the adhesive layer contains a polymer with a melting point ≥ 80°C; optionally, the adhesive layer contains a polymer with a melting point of 80°C to 400°C; optionally, the adhesive layer contains at least one of polyolefin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyurethane, epoxy resin, styrene-isoprene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-ethylene-butene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin and polyimide.

3. The composite current collector according to any one of claims 1 to 2, characterized in that, the thickness of the adhesive layer is 200 nm to 1500 nm, optionally 300 nm to 700 nm.

4. The composite current collector according to any one of claims 1 to 3, characterized in that, the metal seed layer includes at least one of a sputtered metal seed layer, an evaporated metal seed layer and a sprayed metal seed layer.

5. The composite current collector according to any one of claims 1 to 4, characterized in that, the thickness of the metal seed layer is 1 nm to 200 nm, optionally 20 nm to 100 nm.

6. The composite current collector according to any one of claims 1 to 5, characterized in that, the metal seed layer contains at least one of copper, copper alloy, aluminum and aluminum alloy.

7. The composite current collector according to any one of claims 1 to 6, characterized in that, the metal thickening layer includes an electroplated metal thickening layer.

8. The composite current collector according to any one of claims 1 to 7, characterized in that, the thickness of the metal thickening layer is 0.2 μm to 2 μm, optionally 0.5 μm to 1.5 μm.

9. The composite current collector according to any one of claims 1 to 8, characterized in that, the substrate layer contains at least one of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polyethylene, polypropylene, polypropylene styrene, polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyoxymethylene, epoxy resin, phenolic resin, silicone rubber and polycarbonate.

10. The composite current collector according to any one of claims 1 to 9, characterized in that, the thickness of the substrate layer is 2 μm to 10 μm, optionally 3 μm to 8 μm.

11. A method for preparing a composite current collector, characterized in that, it includes the following steps: Provide a substrate layer having opposite first and second surfaces; Successively prepare an adhesive layer, a metal seed layer, and a metal thickening layer on the first surface and / or the second surface.

12. The preparation method according to claim 11, characterized in that, the metal seed layer is prepared by at least one of sputtering, evaporation plating, and spraying; and / or, the metal thickening layer is prepared by electroplating.

13. An electrode sheet, characterized in that, comprises at least one of the composite current collectors described in any one of claims 1 to 10 and the composite current collectors prepared by the preparation method described in any one of claims 11 to 12.

14. A secondary battery, characterized in that, comprises the electrode sheet described in claim 13.

15. An electrical device, characterized in that, comprises at least one of the composite current collectors described in any one of claims 1 to 10, the composite current collectors prepared by the preparation method described in any one of claims 11 to 12, the electrode sheet described in claim 13, and the secondary battery described in claim 14.

Images