Composite current collector, electrode sheet, secondary battery and electrical apparatus

Abstract

A composite current collector, an electrode sheet, a secondary battery and an electrical apparatus. The composite current collector comprises a substrate layer, a bonding layer and a metal layer; the substrate layer has a first surface and a second surface which are opposite to each other; the first surface and / or the second surface is provided with the bonding layer and the metal layer, the bonding layer being located between the substrate layer and the metal layer; the metal layer comprises a metal seed layer and a metal thickening layer, the metal seed layer being located between the bonding layer and the metal thickening layer. In the composite current collector, the structural design of the current collector allows for a good bonding force between the metal layer and the substrate layer, and allows the metal layer to have an appropriate thickness.

Description

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

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2023116012671, filed on November 27, 2023, entitled “Composite current collector, electrode, secondary battery and electrical device,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a composite current collector, a pole piece, a secondary battery, and an electrical device. Background Art

[0004] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0005] Compared with metal current collectors, composite current collectors have the advantage of higher safety performance. In composite current collectors, since the substrate layer is usually made of insulating materials, the difference in performance 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 traditional composite current collectors, in order to make the metal layer have a better bonding force with the substrate layer, 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 traditional composite current collectors, it is often difficult to give good balance between the good bonding force between the metal layer and the substrate layer and the appropriate thickness of the metal layer.

[0006] Summary of the Invention

[0007] In order to achieve the above-mentioned objectives, the first aspect of the present application provides a composite current collector, comprising a substrate layer, a bonding layer and a metal layer; the substrate layer has a first surface and a second surface relative to each other; the bonding layer and the metal layer are provided on at least one of the first surface and the second surface, and the bonding layer is located between the substrate 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.

[0008] In the composite current collector described above, the provision of the adhesive layer improves the bonding strength between the substrate layer and the metal layer. Furthermore, the provision of the metal thickening layer above the metal seed layer allows the metal layer to have an appropriate thickness. Therefore, in the composite current collector described above, by designing the current collector structure, it is possible to achieve good bonding strength between the metal layer and the substrate layer, while also ensuring that the metal layer has an appropriate thickness.

[0009] In some embodiments, the bonding layer comprises a polymer with a melting point of ≥80°C. The melting point of the polymer within this range can enable the bonding layer to maintain good stability, reduce the risk of holes appearing on the surface of the bonding layer when preparing the metal seed layer, and further improve the bonding force between the metal seed layer and the bonding layer. Optionally, the bonding layer comprises a polymer with a melting point of 80°C to 400°C. Optionally, the bonding 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-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin and polyimide.

[0010] In some embodiments, the thickness of the bonding layer is 200 nm to 1500 nm. Within this range, the bonding layer can achieve a good bonding effect while maintaining a relatively suitable overall thickness for the composite current collector, reducing the risk of excessive thickness. Alternatively, the bonding layer has a thickness of 300 nm to 700 nm.

[0011] 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.

[0012] In some embodiments, the thickness of the metal seed layer is 1 nm to 200 nm. A metal seed layer within this thickness range is easy to prepare and can maintain good bonding strength with the bonding layer. Optionally, the thickness of the metal seed layer is 20 nm to 100 nm.

[0013] In some embodiments, the metal seed layer comprises at least one of copper, a copper alloy, aluminum, and an aluminum alloy.

[0014] In some embodiments, the metal thickening layer comprises an electroplated metal thickening layer. The electroplated metal thickening layer may be a metal thickening layer formed by electroplating. The metal seed layer has good conductivity, which facilitates the formation of the metal thickening layer by electroplating.

[0015] In some embodiments, the thickness of the metal thickening layer is 0.2 μm to 2 μm. Within this range, the thickness of the metal thickening layer can provide a relatively suitable thickness for the metal layer as a whole, ensuring that the composite current collector has a relatively suitable metal layer thickness and internal resistance. Alternatively, the thickness of the metal thickening layer is 0.5 μm to 1.5 μm.

[0016] 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.

[0017] In some embodiments, the thickness of the substrate layer is 2 μm to 10 μm, optionally 3 μm to 8 μm.

[0018] The second aspect of the present application provides a method for preparing a composite current collector comprising the following steps:

[0019] providing a substrate layer having a first surface and a second surface opposite to each other;

[0020] An adhesive layer, a metal seed layer and a metal thickening layer are sequentially prepared on the first surface and / or the second surface.

[0021] In some embodiments, the metal seed layer is prepared by at least one of sputtering, evaporation, and spraying.

[0022] In some embodiments, the metal thickening layer is prepared by electroplating.

[0023] A third aspect of the present application provides a pole piece, comprising at least one of the composite current collector and the composite current collector prepared by the preparation method.

[0024] A fourth aspect of the present application provides a secondary battery comprising the pole piece.

[0025] In a fifth aspect, 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 pole piece, and the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0027] FIG1 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0028] FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .

[0029] FIG3 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0030] FIG4 is a schematic structural diagram of a composite current collector in one embodiment of the present application.

[0031] FIG5 is a schematic structural diagram of a composite current collector in another embodiment of the present application.

[0032] Explanation of the accompanying symbols: 1. Secondary battery; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Electric device; 3. Composite current collector; 31. Base material layer; 32. Adhesive layer; 33. Metal seed layer; 34. Metal thickening layer. DETAILED DESCRIPTION

[0033] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] The "ranges" disclosed in this application can be defined in the form of lower limits and upper limits. 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 the particular range. Ranges defined in this way can be inclusive or exclusive of the end values, any end value can be included or excluded independently, and can be arbitrarily combined, 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 particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4, and 5 are also listed, the following ranges are all expected: 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" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10," this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0036] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0037] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0038] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0039] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0040] In this application, open-ended technical features or technical solutions described with terms such as "contain," "include," and "includes" do not exclude additional members beyond the listed members, unless otherwise specified. These technical features or solutions may be considered to provide both closed-ended features or solutions consisting of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, and unless otherwise specified, it may or may not include additional members, this may be considered to provide both closed-ended features or solutions consisting of a1, a2, and a3 and open-ended features or solutions that include additional members beyond the listed members.

[0041] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0042] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0043] One embodiment of the present 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 a first surface and a second surface facing each other. The adhesive layer and the metal layer are provided on at least one of the first surface and the second surface, with the adhesive layer being located between the substrate layer and the metal layer. The metal layer includes a metal seed layer and a metal thickening layer, with the metal seed layer being located between the adhesive layer and the metal thickening layer.

[0044] In the composite current collector of this embodiment, the provision of the adhesive layer improves the bonding strength between the substrate layer and the metal layer. Furthermore, the provision of the metal thickening layer above the metal seed layer allows the metal layer to have an appropriate thickness. Therefore, in the composite current collector of this embodiment, the design of the current collector structure allows for a good bonding strength between the metal layer and the substrate layer, while also allowing the metal layer to have an appropriate thickness.

[0045] Please refer to Figure 4, which shows the structure of a composite current collector 3 in one embodiment of the present application. The composite current collector 3 includes a substrate layer 31, an adhesive layer 32, and a metal layer. The substrate layer 31 has a first surface and a second surface facing each other. An adhesive layer 32 and a metal layer are provided on the first surface or the second surface, with the adhesive layer 32 located between the substrate layer 31 and the metal layer. The metal layer includes a metal seed layer 33 and a metal thickening layer 34, with the metal seed layer 33 located between the adhesive layer 32 and the metal thickening layer 34.

[0046] Please refer to Figure 5, which shows the structure of a composite current collector 3 in another embodiment of the present application. The composite current collector 3 includes a substrate layer 31, a bonding layer 32, and a metal layer. The substrate layer 31 has a first surface and a second surface facing each other. The bonding layer 32 and the metal layer are provided on both the first surface and the second surface, with the bonding layer 32 located between the substrate layer 31 and the metal layer. The metal layer includes a metal seed layer 33 and a metal thickening layer 34, with the metal seed layer 33 located between the bonding layer 32 and the metal thickening layer 34.

[0047] It is understandable that in the composite current collector, reducing the thickness of the metal layer can reduce the overall thickness and manufacturing cost of the composite current collector to a certain extent. However, a metal layer with a smaller thickness may bring about a larger internal resistance, so it is necessary to keep the thickness of the metal layer within a more appropriate range. At the same time, due to the difference between the substrate layer and the metal layer, it is difficult for the integrated metal layer with a larger thickness to form a more stable bonding force with the substrate layer. In this embodiment, by providing a bonding layer, a metal seed layer, and a metal thickening layer, the metal layer can have a more appropriate thickness, and at the same time, the substrate layer and the metal layer have a better bonding force.

[0048] In some embodiments, the bonding layer comprises a polymer having a melting point ≥ 80 degrees Celsius (°C). Optionally, the bonding layer comprises a polymer having a melting point of 80°C to 400°C. The melting point of the polymer within this range can enable the bonding layer to maintain good stability, reduce the risk of holes appearing on the surface of the bonding layer when preparing the metal seed layer, and further improve the bonding force between the metal seed layer and the bonding layer. In addition, the reduction of holes can also reduce the risk of lithium precipitation in the pole piece. Further optionally, the bonding 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-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin and polyimide. Further optionally, the melting point of the polymer contained 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.

[0049] In some embodiments, the melting point of the bonding layer is greater than that of the substrate layer. In this case, it is difficult to form holes on the surface of the bonding layer when preparing the metal seed layer, which is conducive to further improving the bonding strength between the metal seed layer and the bonding layer.

[0050] In some embodiments, the thickness of the bonding layer is 200 nanometers (nm) to 1500 nm. The thickness of the bonding layer within this range can maintain a relatively suitable overall thickness of the composite current collector on the basis of exerting a good bonding effect, thereby reducing the risk of the composite current collector being too thick. Alternatively, the thickness of the bonding 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 bonding layer is 300 nm to 700 nm.

[0051] 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 is understandable that the sputtered metal seed layer may be a metal seed layer formed by a sputtering method such as magnetron sputtering. The evaporated metal seed layer may be a metal seed layer formed by evaporation. The sprayed metal seed layer may 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 with the bonding 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 temperature of the sprayed metal seed layer is relatively low during the formation process, which can reduce the impact on the bonding layer when preparing the metal seed layer and reduce the risk of holes in the bonding layer due to high temperature.

[0052] 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 with the bonding 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.

[0053] In some embodiments, the metal seed layer includes at least one of copper, a copper alloy, aluminum, and an aluminum alloy.

[0054] In some embodiments, the metal thickening layer includes an electroplated metal thickening layer. It is understood that the electroplated metal thickening layer can be a metal thickening layer formed by electroplating. The metal seed layer has good conductivity, which facilitates the formation of the metal thickening layer by electroplating.

[0055] In some embodiments, the thickness of the metal thickening layer is 0.2 micrometers (μm) to 2 μm. The thickness of the metal thickening layer within this range can make the metal layer have a more appropriate thickness as a whole, so that the composite current collector takes into account 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.

[0056] 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 substrate layer has a thickness of 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.

[0057] Another embodiment of the present application provides a method for preparing a composite current collector. The method comprises the following steps: providing a substrate layer having a first surface and a second surface opposite to each other; and sequentially preparing a bonding layer, a metal seed layer, and a metal thickening layer on the first surface and / or the second surface.

[0058] 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.

[0059] 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.

[0060] Alternatively, the slurry can be applied using gravure coating. Alternatively, a metal seed layer can be prepared on the surface of the slurry and then aged. This can increase the surface hardness of the bonding layer and further enhance the bonding strength between the metal seed layer and the bonding layer. Alternatively, the aging temperature can be 80°C to 90°C, and the aging time can be 4 to 8 seconds.

[0061] 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.

[0062] 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; aging the slurry; rolling the aging product; aging again after rolling; and preparing a metal thickening layer on the surface of the metal seed layer of the aging product.

[0063] It is understandable that when the bonding layer and the metal seed layer are prepared on the two surfaces of the substrate respectively, the two surfaces of the substrate layer can be operated separately or simultaneously.

[0064] Another embodiment of the present application provides a pole piece, which includes at least one of the composite current collector and the composite current collector prepared by the above preparation method.

[0065] Another embodiment of the present application provides a secondary battery, which includes the above-mentioned electrode.

[0066] Another embodiment of the present application provides an electrical device, which includes at least one of the composite current collector, the composite current collector prepared by the preparation method, the electrode sheet, and the secondary battery.

[0067] The secondary battery and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0068] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0069] Positive electrode

[0070] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0071] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0072] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may be the above-mentioned composite current collector. The composite current collector may also 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. 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), polyethylene (PE), etc.

[0073] In some embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art. As non-limiting examples, the positive electrode active material may include one or more of the following materials: olivine-structured lithium-containing phosphates, 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 battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), 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. Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of 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 iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0074] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0075] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, 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.

[0076] In some embodiments, the positive electrode sheet can be prepared by dispersing the components for preparing the positive electrode sheet, such as the 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 side of the positive electrode current collector, and performing drying, cold pressing, and other processes to obtain the positive electrode sheet. The type of solvent can be selected from, but is not limited to, any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40% by weight (wt%) to 80% by weight. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 millipascals·seconds (mPa·s) to 25000 mPa·s. When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15 mg / cm2 (mg / cm 2 )~35mg / cm 2 The compacted density of the positive electrode can be 3.0 g / cm3 (g / cm 3 )~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0077] Negative electrode

[0078] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0079] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0080] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may be the above-mentioned composite current collector. The composite current collector may also include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on a 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. 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.

[0081] In some of these embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As a non-limiting example, 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, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0082] In some embodiments, the negative electrode active material layer may further 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).

[0083] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0084] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0085] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, 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% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s to 10000mPa·s. When coating the negative electrode slurry, the coating unit area density based on dry weight (excluding the solvent) can be 75 grams per square meter (g / m 2 )~220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~1.8g / cm 3 .

[0086] electrolytes

[0087] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0088] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0089] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0090] In some embodiments, the solvent may 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), butylene 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.

[0091] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0092] 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), trifluoromethylethylene carbonate (TFPC), and the like.

[0093] Isolation film

[0094] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0095] 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.

[0096] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0097] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0098] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0099] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0100] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0101] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0102] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 1 having a square structure as an example.

[0103] In some embodiments, referring to Figure 2, the outer packaging may include a shell 11 and a cover plate 13. The shell 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 shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to actual needs.

[0104] The secondary battery may be a battery module or a battery pack.

[0105] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0106] In a battery module, multiple battery cells can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Further, the multiple battery cells can be fixed by fasteners.

[0107] Optionally, the battery module may further include a housing having an accommodation space, wherein the plurality of battery cells are accommodated in the accommodation space.

[0108] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0109] A battery pack may include a battery box and multiple battery modules disposed within the box. The battery box comprises an upper case and a lower case. The upper case can be placed over the lower case to form an enclosed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0110] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0111] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0112] Figure 3 shows an example of an electric device 2. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0113] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0114] Example

[0115] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0116] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0117] Example 1

[0118] The preparation method of the composite current collector in this embodiment includes the following steps:

[0119] S101: gravure coating a slurry containing a raw material for an adhesive layer on one surface of the substrate layer.

[0120] S102: preparing a metal seed layer on the surface of the slurry by magnetron sputtering.

[0121] S103: baking the product obtained in S102 at 80° C. to 90° C. for 4 to 8 seconds to mature the slurry to form a bonding layer.

[0122] S104: Roll-press the product obtained in S103.

[0123] S105: The product after the roller pressing process is re-cured at a curing temperature of 85° C. and a curing time of 72 hours (h).

[0124] S106: Electroplating the surface of the metal seed layer of the product obtained in S105 to prepare a metal thickening layer. The electroplating speed is 4 meters per minute (m / min) to 8 m / min. After electroplating, the composite current collector of this embodiment is obtained.

[0125] Example 2

[0126] The preparation method of the composite current collector in this embodiment includes the following steps:

[0127] S101: gravure coating a slurry containing a raw material for an adhesive layer on one surface of the substrate layer.

[0128] S102: preparing a metal seed layer on the surface of the slurry by magnetron sputtering.

[0129] S103: baking the product obtained in S102 at 80° C. to 90° C. for 4 to 8 seconds to mature the slurry to form a bonding layer.

[0130] S104: Roll-press the product obtained in S103.

[0131] S105: Gravure coating the other surface of the substrate layer with a slurry containing the raw materials of the adhesive layer.

[0132] S106: preparing a metal seed layer on the surface of the slurry by magnetron sputtering.

[0133] S107: Bake the product obtained in S106 at 80° C. to 90° C. for 4 to 8 seconds to mature the slurry to form a bonding layer.

[0134] S108: Roll-press the product obtained in S107.

[0135] S109: The product after the roller pressing process is re-cured at a curing temperature of 85° C. and a curing time of 72 hours.

[0136] S110: Electroplating is performed simultaneously on the surfaces of the two metal seed layers of the product obtained in S109 to form a metal thickening layer. The electroplating speed is 4 m / min to 8 m / min. After electroplating, the composite current collector of this embodiment is obtained.

[0137] Example 3 to Example 18

[0138] Compared with Example 2, Examples 3 to 18 differ in the material of the substrate layer, the thickness of the substrate layer, the material of the bonding layer, the thickness of the bonding layer, the material of the metal seed layer, the preparation method of the metal seed layer, the thickness of the metal seed layer, and the thickness of the metal thickening layer. The details are shown in Table 1.

[0139] Comparative Example 1 to Comparative Example 3

[0140] Compared with Example 2, the differences between Comparative Examples 1 to 3 are that the composite current collector does not include a bonding layer, and the materials of the substrate layer are different.

[0141] Test Case

[0142] (1) Metal layer peel strength test: After laminating the sample to the non-corona surface of the EAA film, cover the EAA film with 12μm PET and place it on a heat sealer at a temperature of 120°C and a pressure of 0.2 MPa for lamination. Cut the sample after lamination into 100mm long and 20mm wide samples, and use 3M double-sided tape to stick the non-laminated surface of the metal layer to the steel plate; clamp the sample on the fixture of the tensile testing machine with a spacing of 50mm and a speed of 300 mm / min to perform a 180°C peel test. Read the peel force and convert it into Newton / meter (N / m) units. 5 parallel samples are tested and the average peel force is finally taken.

[0143] (2) Composite current collector hole test: Use an online CCD high-speed camera to test the number of holes in a composite current collector with a length of 1000 meters (m), and then divide it by the area of ​​the current collector in the test section to calculate the number of holes per square meter.

[0144] (3) Composite current collector square resistance test: Use a four-probe square resistance tester to test the square resistance of the large surface of the sample metal layer, randomly test 30 points, and take the average square resistance of the 30 points.

[0145] Table 1

[0146] In Table 1, the unit of substrate layer thickness is μm. Melting point indicates the melting point of the polymer contained in the adhesive layer, and the unit is °C. The unit of adhesive layer thickness is nm. The unit of metal seed layer thickness is nm. The unit of metal thickening layer thickness is μm. The unit of metal layer peel strength is N / m. The unit of hole number is pieces / m2 (pieces / m2). 2 The unit of square resistance is milliohm per square (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 the metal seed layer is prepared by spraying, the number of pores in the composite current collector can be reduced, especially the number of pores with a diameter of ≤100 μm.

[0149] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0150] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A composite current collector, comprising a substrate layer, a bonding layer and a metal layer; the substrate layer has a first surface and a second surface relative to each other; the bonding layer and the metal layer are provided on at least one of the first surface and the second surface, and the bonding layer is located between the substrate 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.

2. The composite current collector according to claim 1, wherein: The bonding layer comprises a polymer having a melting point ≥ 80°C.

3. The composite current collector according to claim 1 or 2, wherein: The adhesive layer comprises a polymer having a melting point of 80°C to 400°C.

4. The composite current collector according to any one of claims 1 to 3, wherein The bonding 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-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, silicone rubber, phenolic resin, urea-formaldehyde resin and polyimide.

5. The composite current collector according to any one of claims 1 to 4, wherein The thickness of the bonding layer is 200nm to 1500nm.

6. The composite current collector according to any one of claims 1 to 5, wherein: The thickness of the bonding layer is 300nm-700nm.

7. The composite current collector according to any one of claims 1 to 6, wherein: 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.

8. The composite current collector according to any one of claims 1 to 7, wherein The thickness of the metal seed layer is 1 nm to 200 nm.

9. The composite current collector according to any one of claims 1 to 8, wherein The thickness of the metal seed layer is 20nm-100nm.

10. The composite current collector according to any one of claims 1 to 9, wherein: The metal seed layer includes at least one of copper, copper alloy, aluminum and aluminum alloy.

11. The composite current collector according to any one of claims 1 to 10, wherein: The metal thickening layer comprises an electroplated metal thickening layer.

12. The composite current collector according to any one of claims 1 to 11, wherein: The thickness of the metal thickening layer is 0.2 μm to 2 μm.

13. The composite current collector according to any one of claims 1 to 12, wherein: The thickness of the metal thickening layer is 0.5 μm to 1.5 μm.

14. The composite current collector according to any one of claims 1 to 13, wherein: 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.

15. The composite current collector according to any one of claims 1 to 14, wherein: The thickness of the substrate layer is 2 μm to 10 μm.

16. The composite current collector according to any one of claims 1 to 15, wherein: The thickness of the substrate layer is 3 μm to 8 μm.

17. A method for preparing a composite current collector, comprising the following steps: Providing a substrate layer having a first surface and a second surface opposite to each other; An adhesive layer, a metal seed layer and a metal thickening layer are sequentially prepared on the first surface and / or the second surface.

18. The preparation method according to claim 17, wherein: The metal seed layer is prepared by at least one of sputtering, evaporation and spraying.

19. The preparation method according to claim 17 or 18, wherein: The metal thickening layer is prepared by electroplating.

20. A pole piece, wherein: The invention comprises at least one of the composite current collector according to any one of claims 1 to 16 and the composite current collector prepared by the preparation method according to any one of claims 17 to 19.

21. A secondary battery comprising the electrode sheet according to claim 20.

22. An electrical device comprising at least one of the composite current collector according to any one of claims 1 to 16, the composite current collector prepared by the preparation method according to any one of claims 17 to 19, the pole piece according to claim 20, and the secondary battery according to claim 21.

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