Composite current collector, electrode sheet, secondary battery, and electric device

Abstract

A composite current collector, an electrode sheet, a secondary battery, and an electric device. The composite current collector comprises a first metal layer, a bonding layer and a second metal layer. The bonding layer comprises a first surface and a second surface which are oppositely arranged, the first metal layer is located on the first surface, and the second metal layer is located on the second surface. In the composite current collector, by providing the bonding layer between the first metal layer and the second metal layer, the peeling strength of the first metal layer and the second metal layer can be improved, thereby reducing the risk of the metal layers falling off during processing.

Description

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

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2023115973722, filed on November 24, 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 to pure metal current collectors, composite current collectors often offer advantages such as thinner metal layers, lighter weight, and higher safety. However, the metal layer in traditional composite current collectors suffers from poor peel strength, making it prone to metal layer shedding during processing.

[0006] Summary of the Invention

[0007] To achieve the above objectives, the first aspect of the present application provides a composite current collector. The composite current collector includes a first metal layer, a bonding layer, and a second metal layer. The bonding layer has a first surface and a second surface disposed opposite each other, the first metal layer is located on the first surface, and the second metal layer is located on the second surface.

[0008] In the composite current collector, by providing an adhesive layer between the first metal layer and the second metal layer, the peeling strength of the first metal layer and the second metal layer can be improved, and the risk of the metal layer falling off during processing can be reduced.

[0009] In some embodiments, a portion of the adhesive layer is embedded in the first metal layer. The embedding of the adhesive layer can enhance the bonding force between the first metal layer and the adhesive layer, thereby further improving the peel strength of the first metal layer.

[0010] In some embodiments, a portion of the adhesive layer is embedded in the second metal layer. The embedding of the adhesive layer can enhance the bonding force between the second metal layer and the adhesive layer, thereby further improving the peel strength of the second metal layer.

[0011] In some embodiments, the roughness of the surface of the first metal layer near the bonding layer satisfies the following conditions: 0.1 μm ≤ Ra1 ≤ 0.5 μm and / or 0.5 μm ≤ Rz1 ≤ 1 μm, where Ra1 represents the arithmetic mean roughness of the surface of the first metal layer near the bonding layer, and Rz1 represents the maximum height roughness of the surface of the first metal layer near the bonding layer. Having an appropriate roughness of the surface of the first metal layer near the bonding layer helps improve the bonding strength between the first metal layer and the bonding layer.

[0012] In some embodiments, the roughness of the surface of the second metal layer near the bonding layer satisfies the following conditions: 0.1 μm ≤ Ra2 ≤ 0.5 μm and / or 0.5 μm ≤ Rz2 ≤ 1 μm, where Ra2 represents the arithmetic mean roughness of the surface of the second metal layer near the bonding layer, and Rz2 represents the maximum height roughness of the surface of the second metal layer near the bonding layer. Having an appropriate roughness of the surface of the second metal layer near the bonding layer helps improve the bonding strength between the second metal layer and the bonding layer.

[0013] In some embodiments, the thickness of the first metal layer is 1 μm to 10 μm. The thickness of the first metal layer within this range can make the first metal layer have a relatively suitable volume and weight. Optionally, the thickness of the first metal layer is 1 μm to 6 μm.

[0014] In some embodiments, the first metal layer comprises at least one of aluminum, aluminum alloys, copper, copper alloys, silver, silver alloys, nickel, nickel alloys, gold, gold alloys, chromium, and chromium alloys.

[0015] In some embodiments, the thickness of the second metal layer is 1 μm to 10 μm. The thickness of the second metal layer within this range can make the second metal layer have a relatively suitable volume and weight. Optionally, the thickness of the second metal layer is 1 μm to 6 μm.

[0016] In some embodiments, the second metal layer comprises at least one of aluminum, aluminum alloys, copper, copper alloys, silver, silver alloys, nickel, nickel alloys, gold, gold alloys, chromium, and chromium alloys.

[0017] In some embodiments, the composite current collector further includes a flame retardant layer, which is located inside the adhesive layer. The flame retardant layer can improve the flame retardant effect of the composite current collector and reduce the risk of combustion of the composite current collector.

[0018] In some embodiments, the thickness of the flame retardant layer is 300 nm to 700 nm. The thickness of the flame retardant layer within this range can better exert the flame retardant effect while making the composite current collector have better tensile strength.

[0019] In some embodiments, the flame-retardant layer comprises flame-retardant particles; the flame-retardant particles include at least one of sodium aluminum fluoride, calcium fluoride, aluminum fluoride, sodium fluorosilicate, magnesium fluoride, lithium fluoride, zinc borate, phosphate esters, phosphites, phosphates, phosphites, polyphosphoramide flame retardants, phenolic resins, flame-retardant silicone rubber, and flame-retardant epoxy resins. Optionally, the flame-retardant particles have a Dv50 of 100 nm to 300 nm.

[0020] In some embodiments, there are multiple flame-retardant layers, each spaced apart within the adhesive layer. Multiple, spaced-apart flame-retardant layers can further improve the flame retardancy of the composite current collector and enhance its tensile strength. Optionally, the multiple flame-retardant layers are disposed in parallel.

[0021] In some embodiments, the distance between adjacent flame retardant layers is 300 nm to 700 nm. The distance between adjacent flame retardant layers within this range can make the bonding layer between adjacent flame retardant layers have a suitable thickness, which is conducive to maintaining good bonding strength between the flame retardant layer and the bonding layer.

[0022] In some embodiments, a distance between the flame retardant layer closest to the first metal layer and the first metal layer is 300 nm to 700 nm.

[0023] In some embodiments, a distance between the flame retardant layer closest to the second metal layer and the second metal layer is 300 nm to 700 nm.

[0024] In some embodiments, the thickness of the bonding layer is 1 μm to 8 μm. Within this range, the bonding layer maintains good adhesion between the first and second metal layers, ensuring strong peel strength between the first and second metal layers while also ensuring the composite current collector has an appropriate thickness. Alternatively, the bonding layer has a thickness of 1 μm to 4 μm.

[0025] In some embodiments, the adhesive layer comprises at least one of polyolefin, 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, polyimide, polyamide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyoxymethylene, and polycarbonate.

[0026] In some embodiments, the composite current collector further includes a passivation layer; the passivation layer is located on a surface of the first metal layer and / or the second metal layer that is distal from the bonding layer. The provision of the passivation layer can improve the corrosion resistance of the first metal layer and / or the second metal layer, thereby promoting a stable structure of the composite current collector. Furthermore, the provision of the passivation layer can also improve the tensile strength of the composite current collector.

[0027] In some embodiments, the thickness of the passivation layer is 10 nm to 2000 nm. The thickness of the passivation layer within this range can provide a good passivation effect while maintaining a relatively suitable thickness of the composite current collector. Optionally, the thickness of the passivation layer is 20 nm to 200 nm.

[0028] A second aspect of the present application provides a pole piece comprising the composite current collector.

[0029] A third aspect of the present application provides a secondary battery, comprising the pole piece.

[0030] A fourth aspect of the present application provides an electrical device comprising at least one of the composite current collector, the pole piece, and the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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:

[0032] 1 to 4 are schematic structural diagrams of composite current collectors in different embodiments of the present application.

[0033] FIG5 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0034] FIG. 6 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .

[0035] FIG. 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0036] Explanation of the accompanying symbols: 1. Secondary battery; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Electrical device; 3. Composite current collector; 31. First metal layer; 32. Adhesive layer; 33. Second metal layer; 34. Flame retardant layer; 35. Passivation layer. DETAILED DESCRIPTION

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0042] 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.

[0043] Those skilled in the art will appreciate that, in the methods of each embodiment or example, 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 internal logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also 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 may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] In this application, open technical features or technical solutions described with words such as "contain," "include," and "includes" do not exclude additional members beyond the listed members unless otherwise specified, and can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" and the feature or solution of "A includes not only a1, a2, and a3, but also other members."

[0045] 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.

[0046] 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.

[0047] Referring to FIG. 1 , one embodiment of the present application provides a composite current collector 3. The composite current collector 3 includes a first metal layer 31, an adhesive layer 32, and a second metal layer 33. The adhesive layer 32 has a first surface and a second surface disposed opposite each other, with the first metal layer 31 located on the first surface and the second metal layer 33 located on the second surface. In the composite current collector 3 of this embodiment, by providing the adhesive layer 32 between the first metal layer 31 and the second metal layer 33, the peel strength between the first metal layer 31 and the second metal layer 33 can be improved, thereby reducing the risk of the metal layers falling off during processing.

[0048] In some embodiments, a portion of the bonding layer is embedded in the first metal layer. In this case, by embedding the bonding layer, the bonding force between the first metal layer and the bonding layer can be improved, thereby further improving the peel strength of the first metal layer. It is understandable that the embedding of the bonding layer in the first metal layer means that a portion of the bonding layer is located within the first metal layer at the position where the bonding layer and the first metal layer contact. For example, the surface of the first metal layer close to the bonding layer has an uneven structure, or the surface of the first metal layer close to the bonding layer has pores, etc. In this case, the bonding layer is partially embedded in the uneven structure of the surface of the first metal layer close to the bonding layer, or is embedded in the pores of the surface of the first metal layer close to the bonding layer, and the bonding layer and the first metal layer can be better combined by a mechanism such as a mechanical interlocking mechanism, thereby improving the peel strength of the first metal layer.

[0049] In some embodiments, a portion of the bonding layer is embedded in the second metal layer. In this case, by embedding the bonding layer, the bonding force between the second metal layer and the bonding layer can be improved, thereby further improving the peel strength of the second metal layer. It is understandable that the embedding of the bonding layer in the second metal layer means that a portion of the bonding layer is located within the second metal layer at the position where the bonding layer and the second metal layer contact. For example, the surface of the second metal layer close to the bonding layer has an uneven structure, or the surface of the second metal layer close to the bonding layer has pores, etc. In this case, the bonding layer is embedded in the uneven structure of the surface of the second metal layer close to the bonding layer, or is embedded in the pores of the surface of the second metal layer close to the bonding layer. The bonding layer and the second metal layer can be better combined by a mechanism such as a mechanical interlocking mechanism, thereby improving the peel strength of the second metal layer.

[0050] In some embodiments, the roughness of the surface of the first metal layer close to the bonding layer satisfies: 0.1 micrometer (μm) ≤ Ra1 ≤ 0.5 μm and / or 0.5 μm ≤ Rz1 ≤ 1 μm, where Ra1 represents the arithmetic average roughness of the surface of the first metal layer close to the bonding layer, and Rz1 represents the maximum height roughness of the surface of the first metal layer close to the bonding layer. At this time, the surface of the first metal layer close to the bonding layer has a suitable roughness, which is beneficial to improve the bonding force between the first metal layer and the bonding layer. Optionally, the surface of the first metal layer close to the bonding layer can be treated by methods such as plasma spraying, spraying, mechanical friction, etc. to adjust the roughness of the surface of the first metal layer close to the bonding layer, so that the roughness of the surface satisfies 0.1 μm ≤ Ra1 ≤ 0.5 μm and / or 0.5 μm ≤ Rz1 ≤ 1 μm. Further optionally, Ra1 may be 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, etc. Further optionally, Rz1 may be 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, etc.

[0051] In some embodiments, the roughness of the surface of the second metal layer close to the bonding layer satisfies: 0.1 μm ≤ Ra2 ≤ 0.5 μm and / or 0.5 μm ≤ Rz2 ≤ 1 μm, where Ra2 represents the arithmetic average roughness of the surface of the second metal layer close to the bonding layer, and Rz2 represents the maximum height roughness of the surface of the second metal layer close to the bonding layer. At this time, the surface of the second metal layer close to the bonding layer has a suitable roughness, which is beneficial to improve the bonding force between the second metal layer and the bonding layer. Optionally, the surface of the second metal layer close to the bonding layer can be treated by methods such as plasma spraying, spraying, mechanical friction, etc. to adjust the roughness of the surface of the second metal layer close to the bonding layer, so that the roughness of the surface satisfies 0.1 μm ≤ Ra2 ≤ 0.5 μm and / or 0.5 μm ≤ Rz2 ≤ 1 μm. Further optionally, Ra2 may be 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, etc. Further optionally, Rz2 may be 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, etc.

[0052] In some embodiments, the thickness of the first metal layer is 1 μm to 10 μm. The thickness of the first metal layer within this range can make the first metal layer have a more suitable volume and weight. Applying the composite current collector to the secondary battery can enable the battery to maintain a more suitable energy density. Optionally, the thickness of the first metal layer can be 1 μm, 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 first metal layer can be 1 μm to 6 μm.

[0053] Further, as some examples of material selection for the first metal layer, the first metal layer includes at least one of aluminum, aluminum alloy, copper, copper alloy, silver, silver alloy, nickel, nickel alloy, gold, gold alloy, chromium and chromium alloy.

[0054] In some embodiments, the thickness of the second metal layer is 1 μm to 10 μm. The thickness of the second metal layer within this range can make the second metal layer have a more suitable volume and weight. Applying the composite current collector to the secondary battery can make the battery maintain a more suitable energy density. Optionally, the thickness of the second metal layer can be 1 μm, 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 second metal layer can be 1 μm to 6 μm.

[0055] Further, as some examples of material selection for the second metal layer, the second metal layer includes at least one of aluminum, aluminum alloy, copper, copper alloy, silver, silver alloy, nickel, nickel alloy, gold, gold alloy, chromium and chromium alloy.

[0056] Referring to Figure 2 , the composite current collector 3 also includes a flame-retardant layer 34, which is located within the adhesive layer 32. The flame-retardant layer improves the flame-retardant effect of the composite current collector and reduces the risk of combustion. When the composite current collector is used in a secondary battery, the flame-retardant layer can reduce the risk of combustion during thermal runaway. Furthermore, the flame-retardant layer and the adhesive layer provide mutual support, which helps to improve the tensile strength of the composite current collector.

[0057] In some embodiments, the thickness of the flame retardant layer is 300 nanometers (nm) to 700 nm. Within this range, the flame retardant layer can effectively exert its flame retardant effect while also providing the composite current collector with good tensile strength. Alternatively, the thickness of the flame retardant layer can be 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, etc.

[0058] In some embodiments, the flame-retardant layer comprises flame-retardant particles; the flame-retardant particles include at least one of sodium aluminum fluoride, calcium fluoride, aluminum fluoride, sodium fluorosilicate, magnesium fluoride, lithium fluoride, zinc borate, phosphate esters, phosphites, phosphates, phosphites, polyphosphoramide flame retardants, phenolic resins, flame-retardant silicone rubber, and flame-retardant epoxy resins. Optionally, the flame-retardant particles have a Dv50 value of ≤ the designed thickness of the flame-retardant layer.

[0059] It is understood that in this application, Dv50 refers to the particle size corresponding to the 50% cumulative particle size distribution in the volume cumulative distribution curve. Its physical meaning is that particles with a smaller (or larger) size account for 50%. As an example, Dv50 can be obtained by referring to the GB / T 19077-2016 test method and using a laser diffraction particle size distribution analyzer Mastersizer3000 to obtain a particle size distribution curve.

[0060] In some embodiments, the flame retardant layer can be prepared by spraying a material containing flame retardant particles.

[0061] In some embodiments, there are multiple flame-retardant layers. These multiple flame-retardant layers are spaced apart and distributed within the adhesive layer. The multiple flame-retardant layers spaced apart can further improve the flame-retardant effect of the composite current collector and further enhance the tensile strength of the composite current collector. Optionally, the multiple flame-retardant layers are disposed in parallel.

[0062] Please refer to Figure 3. In some embodiments, there are two flame retardant layers 34. Both flame retardant layers 34 are located inside the adhesive layer 32, and the two flame retardant layers 34 are arranged in parallel.

[0063] Please refer to Figure 4. In some other embodiments, there are three flame retardant layers 34. The three flame retardant layers 34 are all located inside the adhesive layer 32, and the three flame retardant layers 34 are arranged in parallel.

[0064] It is understandable that there may be four, five, six, etc. flame retardant layers. In the structure of the composite current collector, a corresponding number of flame retardant layers may be provided according to design requirements.

[0065] In some embodiments, the distance between adjacent flame retardant layers is 300nm to 700nm. Please refer to Figure 3 again, which shows the distance between adjacent flame retardant layers 34. The distance between adjacent flame retardant layers 34 is L1, and L1 is 300nm to 700nm. The distance between adjacent flame retardant layers in this range can make the bonding layer between adjacent flame retardant layers have a suitable thickness, which is conducive to maintaining good bonding between the flame retardant layer and the bonding layer. Optionally, the distance between adjacent flame retardant layers can be 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, etc.

[0066] In some embodiments, the distance between the flame retardant layer closest to the first metal layer and the first metal layer is 300nm to 700nm. Please refer to Figure 3 again, which shows the distance between the flame retardant layer 34 closest to the first metal layer 31 and the first metal layer 31. The distance between the flame retardant layer 34 closest to the first metal layer 31 and the first metal layer is L2, and L2 is 300nm to 700nm. L2 within this range can maintain good bonding between the first metal layer and the flame retardant layer and the adhesive layer. Optionally, the distance between the flame retardant layer closest to the first metal layer and the first metal layer can be 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, etc.

[0067] In some embodiments, the distance between the flame retardant layer closest to the second metal layer and the second metal layer is 300nm to 700nm. Please refer to Figure 3 again, which shows the distance between the flame retardant layer 34 closest to the second metal layer 33 and the second metal layer 33. The distance between the flame retardant layer 34 closest to the second metal layer 33 and the second metal layer 33 is L3, and L3 is 300nm to 700nm. L3 within this range can maintain good bonding between the second metal layer and the flame retardant layer and the adhesive layer. Optionally, the distance between the flame retardant layer closest to the second metal layer and the second metal layer can be 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, etc.

[0068] In some embodiments, the thickness of the bonding layer is 1 μm to 8 μm. The thickness of the bonding layer within this range can maintain good bonding between the first metal layer, the second metal layer and the bonding layer, while making the first metal layer and the second metal layer have strong peel strength, so that the composite current collector has a suitable thickness. Optionally, the thickness of the bonding layer can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, etc. Further optionally, the thickness of the bonding layer is 1 μm to 4 μm. It will be understood that when the composite current collector includes a flame retardant layer, the flame retardant layer is located inside the bonding layer, and the thickness of the bonding layer includes the thickness of the flame retardant layer.

[0069] In some embodiments, the adhesive layer comprises at least one of polyolefin, 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, polyimide, polyamide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyoxymethylene, and polycarbonate. Alternatively, the polyolefin comprises at least one of ethylene-propylene copolymer, polyethylene, polypropylene, and polypropylene.

[0070] It is understood that the bonding layer can be prepared by coating. For example, a slurry including bonding layer raw materials can be coated on the first metal layer and then subjected to a aging treatment to prepare the bonding layer.

[0071] It is also understood that when the composite current collector includes a flame retardant layer, the bonding layer is divided into multiple sub-layers. In this case, the bonding layer can be prepared by coating the flame retardant layer with a slurry to obtain each sub-layer.

[0072] Please refer to Figures 2 to 4 again. In some embodiments, the composite current collector 3 further includes a passivation layer 35. The passivation layer 35 is located on the surface of the first metal layer 31 and / or the second metal layer 33 away from the bonding layer 32. The provision of the passivation layer can improve the corrosion resistance of the first metal layer and / or the second metal layer, which is conducive to promoting the composite current collector to maintain a stable structure. In addition, the provision of the passivation layer can also improve the tensile strength of the composite current collector. At the same time, the provision of the passivation layer can reduce the risk of adhesion of the composite current collector during the laser cutting process, thereby increasing the cutting speed of the laser cutting.

[0073] It is understood that in the embodiments shown in Figures 2 to 4, the surface of the first metal layer 31 away from the bonding layer 32 and the surface of the second metal layer 33 away from the bonding layer 32 are both provided with a passivation layer 35. As other examples of the disposition of the passivation layer 35, the surface of the first metal layer 31 away from the bonding layer 32 can also be provided with a passivation layer 35, while the surface of the second metal layer 33 away from the bonding layer 32 is not provided with a passivation layer 35. Alternatively, the surface of the first metal layer 31 away from the bonding layer 32 is not provided with a passivation layer 35, while the surface of the second metal layer 33 away from the bonding layer 32 is provided with a passivation layer 35.

[0074] In some embodiments, the thickness of the passivation layer is 10 nm to 2000 nm. Within this range, the thickness of the passivation layer can provide a good passivation effect while maintaining a relatively suitable thickness for the composite current collector. For example, the thickness of the passivation layer can be 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 800 nm, 1000 nm, 1500 nm, 2000 nm, etc. Optionally, the thickness of the passivation layer is 20 nm to 200 nm.

[0075] In some embodiments, the passivation layer may be an oxide layer. Further, the passivation layer may be an oxidized coloring layer. By providing the oxidized coloring layer, the composite current collector may have a corresponding color.

[0076] Optionally, the passivation layer includes an oxide film layer of one or more of aluminum hydrate oxide, chromium-containing oxide, molybdenum-containing oxide, silicon-containing oxide, or phosphorus-containing oxide.

[0077] In some embodiments, the passivation layer can be obtained by chemical oxidation, for example, by placing the product in an oxidizing solution for oxidation treatment to obtain the passivation layer.

[0078] Optionally, the composition of the oxidizing solution, the temperature of the chemical oxidation, the time of the chemical oxidation, and the color of the resulting passivation layer are shown in Table 1. When performing the chemical oxidation treatment, the oxidizing solution, the temperature and time of the chemical oxidation, and other conditions can be selected accordingly in Table 1. In Table 1, the unit of the content is grams per liter (g / L), the unit of the temperature is degrees Celsius (°C), the unit of the time is minutes (min), and the unit of the passivation layer thickness is nanometers (nm).

[0079] Table 1

[0080] Another embodiment of the present application provides a method for preparing a composite current collector. The preparation method comprises the following steps:

[0081] The slurry is applied between the first metal layer and the second metal layer to obtain a composite current collector preform. The composite current collector preform is then subjected to an aging treatment to form a bonding layer between the first metal layer and the second metal layer. Optionally, the aging treatment temperature is 85° C. and the aging treatment time is 72 hours.

[0082] Optionally, before the aging treatment, the process further includes: performing a roller pressing treatment on the composite current collector preformed product. The roller pressing treatment can discharge gas inside the composite current collector.

[0083] Another embodiment of the present application provides a pole piece. The pole piece includes the above-mentioned composite current collector. It is understood that the pole piece can be a positive pole piece or a negative pole piece.

[0084] Another embodiment of the present application provides a secondary battery. The secondary battery includes the above-mentioned electrode.

[0085] Another embodiment of the present application provides an electrical device, which includes at least one of the composite current collector, the electrode, and the secondary battery.

[0086] The secondary battery and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0087] 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.

[0088] Positive electrode

[0089] 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.

[0090] 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.

[0091] 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.

[0092] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery that is well known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional 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.

[0093] 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.

[0094] 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.

[0095] 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 .

[0096] Negative electrode

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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).

[0102] 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.

[0103] 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)).

[0104] 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 on both 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 surface density on a dry weight basis (excluding the solvent) can be 75g / m 2 ~220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~1.8g / cm 3 .

[0105] electrolytes

[0106] 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.

[0107] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0108] 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).

[0109] 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.

[0110] 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.

[0111] 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.

[0112] Isolation film

[0113] 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.

[0114] 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.

[0115] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may optionally be 12 μm to 20 μm.

[0116] 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.

[0117] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0118] 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.

[0119] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0120] 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.

[0121] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG5 shows a battery cell 1 with a square structure as an example.

[0122] In some embodiments, referring to Figure 6, 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.

[0123] The secondary battery may be a battery module or a battery pack.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0131] Figure 7 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] Example 1

[0136] The preparation method of the composite current collector in this embodiment includes:

[0137] S101: gravure coating a bonding slurry on one surface of the first aluminum foil. The bonding slurry is polyurethane.

[0138] S102: attaching a second aluminum foil on the adhesive slurry.

[0139] S103: Roll-press the product obtained in S102.

[0140] S104: The product obtained in S103 is subjected to aging treatment in an oven at a temperature of 85° C. for 72 hours.

[0141] S105: Using a corrosive liquid to thin the first aluminum foil and the second aluminum foil in the product obtained in S104.

[0142] Example 2

[0143] The preparation method of the composite current collector in this embodiment includes:

[0144] S101: gravure coating a bonding slurry on one surface of a first aluminum foil.

[0145] S102: Spraying flame-retardant granular cryolite on the bonding slurry.

[0146] S103: gravure coating the bonding slurry on the flame retardant particles.

[0147] S104: attaching a second aluminum foil on the bonding slurry.

[0148] S105: Roll-press the product obtained in S104.

[0149] S106: The product obtained in S105 is subjected to aging treatment in an oven at a temperature of 85° C. for 72 hours.

[0150] S107: Using a corrosive liquid to thin the first aluminum foil and the second aluminum foil in the product obtained in S106.

[0151] Example 3

[0152] The preparation method of the composite current collector in this embodiment includes:

[0153] S101: gravure coating a bonding slurry on one surface of a first aluminum foil.

[0154] S102: Spraying flame-retardant granular cryolite on the bonding slurry.

[0155] S103: gravure coating the bonding slurry on the flame retardant particles.

[0156] S104: attaching a second aluminum foil on the bonding slurry.

[0157] S105: Roll-press the product obtained in S104.

[0158] S106: The product obtained in S105 is subjected to aging treatment in an oven at a temperature of 85° C. for 72 hours.

[0159] S107: Using a corrosive liquid to thin the first aluminum foil and the second aluminum foil in the product obtained in S106.

[0160] S108: The product obtained in S107 is subjected to chemical oxidation treatment using the oxidation solution and chemical oxidation conditions listed in sequence number 6 in Table 1 to obtain a passivation layer.

[0161] Example 4

[0162] The preparation method of the composite current collector in this embodiment includes:

[0163] S101: gravure coating a bonding slurry on one surface of a first aluminum foil.

[0164] S102: Spraying flame-retardant granular cryolite on the bonding slurry.

[0165] S103: gravure coating the bonding slurry on the flame retardant particles.

[0166] S104: Spraying flame-retardant granular cryolite on the bonding slurry.

[0167] S105: gravure coating the bonding slurry on the flame retardant particles.

[0168] S106: attaching a second aluminum foil on the bonding slurry.

[0169] S107: Roll-press the product obtained in S106.

[0170] S108: The product obtained in S107 is subjected to aging treatment in an oven at a temperature of 85° C. for 72 hours.

[0171] S109: Using a corrosive liquid to thin the first aluminum foil and the second aluminum foil in the product obtained in S108.

[0172] S110: The product obtained in S109 is subjected to chemical oxidation treatment using the oxidation solution and chemical oxidation conditions listed in sequence number 6 in Table 1 to obtain a passivation layer.

[0173] Example 5-Example 6

[0174] Compared with Example 1, Examples 5 to 6 are different in that Ra1 of the first metal layer, Rz1 of the first metal layer, Ra2 of the second metal layer, and Rz2 of the second metal layer are different.

[0175] Example 7

[0176] Compared with Example 3, the difference of this embodiment is that the first metal layer and the second metal layer are both copper layers. The oxidizing solution and chemical oxidation conditions are the oxidizing solution and chemical oxidation conditions corresponding to No. 10 in Table 1.

[0177] Example 8

[0178] Compared with Example 4, the difference of this embodiment is that the first metal layer and the second metal layer are both copper layers. The oxidizing solution and chemical oxidation conditions are the oxidizing solution and chemical oxidation conditions corresponding to No. 10 in Table 1.

[0179] Example 9

[0180] Compared with Example 7, the difference of this embodiment is that the adhesive layer does not contain a flame retardant layer.

[0181] The parameters of the first metal layer, the second metal layer, the adhesive layer, the flame retardant layer, the passivation layer, etc. in Examples 1 to 9 are shown in Table 2.

[0182] Comparative Example 1

[0183] The preparation method of the composite current collector of this comparative example includes: evaporating an aluminum layer on the surface of a PET substrate layer.

[0184] Comparative Example 2

[0185] The preparation method of the composite current collector of this comparative example includes:

[0186] A copper seed layer is magnetically controlled on the surface of the PET substrate layer, and a copper layer is electroplated on the surface of the copper seed layer. Then, a chemical oxidation treatment is performed using the oxidizing solution and chemical oxidation conditions listed in sequence number 10 in Table 1 to obtain a passivation layer.

[0187] Test Case

[0188] (1) Metal-laminated glass strength difference test: Cut the sample into 30mm wide samples, apply 3M double-sided tape to a steel plate, and evenly attach the sample to the double-sided tape. Then, use special yellow tape (24mm wide) to evenly attach the sample. Use a tensile testing machine to test the adhesion strength at 50mm / min (180° peeling). The requirement is ≥150 Newtons per meter (N / m). Adhesion strength = the sum of the adhesion strengths of 10 test samples / 10.

[0189] (2) Transmittance Test: The transmittance of the composite current collector was tested using an LS117 transmittance meter according to GB2410-80. First, the instrument was turned on for self-calibration. The interface displayed T = 100%, indicating a successful calibration. The composite current collector was then placed between the probe and the receiver. The interface automatically displayed the transmittance value of the composite current collector. The test results are shown in Table 2.

[0190] (3) Tensile Strength Test: The tensile strength of the composite current collector was tested using a tensile strength tester in accordance with DIN 53455-6-5. A Japanese ALGOL (1 kg) tensile test head was used, with the composite current collector mounted between two test heads. The maximum tensile stress experienced by the composite current collector when it broke along its length was measured. The ratio of the maximum tensile stress experienced by the composite current collector when it broke to its cross-sectional area was the tensile strength of the composite current collector. The test results are shown in Table 2.

[0191] (4) Cutting performance test: Using an IPG fiber laser model YLP-V2-1-100-100-100, set the power to 100 watts (W) and the frequency to 150 kilohertz (kHz). The composite current collector is mounted on the laser cutting equipment and cut to test the maximum cutting speed of the current collector. The maximum cutting speed of the composite current collector refers to the maximum cutting speed that can be achieved when the laser cuts the composite current collector without causing adhesion.

[0192] (5) Thickness test: Use liquid nitrogen quenching or argon ion etching to prepare the cross-section sample of the composite current collector. Use a scanning electron microscope to magnify (1000-30000 times) to observe the secondary electron phase morphology of the cross-section of the composite current collector and measure the thickness of each layer. The minimum resolution can reach the nanometer level.

[0193] (6) Square resistance test:

[0194] 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 in (mΩ / □).

[0195] Table 2

[0196] In Table 2, the thickness of the first and second metal layers is in μm. The unit for Ra1, Rz1, Ra2, and Rz2 is in μm. The unit for the thickness of a single flame retardant layer is in nm. The unit for the thickness of the adhesive layer is in μm. The unit for the thickness of the passivation layer is in nm. The unit for peel strength is in N / m. The unit for light transmittance is in %. The unit for tensile strength is in MPa. The unit for maximum cutting speed is in meters per minute (m / min). The unit for square resistance is in milliohms per square (mΩ / □).

[0197] It can be seen from Examples 1 to 6 and Comparative Example 1 that when the metal layer is an aluminum layer, the introduction of the adhesive layer can improve the peeling strength between the first metal layer and the second metal layer.

[0198] It can be seen from Examples 7 to 9 and Comparative Example 2 that when the metal layer is a copper layer, the introduction of the adhesive layer can improve the peeling strength between the first metal layer and the second metal layer.

[0199] It can be seen from Examples 2 to 4 and Example 1 that when the adhesive layer contains a flame retardant layer, the tensile strength of the composite current collector can be improved.

[0200] It can be seen from Example 1 and Example 5 that when the surface roughness of the first metal layer and the second metal layer is relatively small, the peeling strength of the first metal layer and the second metal layer may be reduced.

[0201] It can be seen from Examples 1 and 6 that when the surface roughness of the first metal layer and the second metal layer is large, the glass strength of the first metal layer and the second metal layer may be improved, but the tensile strength of the composite current collector may be reduced and the square resistance may be increased.

[0202] 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.

[0203] 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 first metal layer, a bonding layer and a second metal layer; the bonding layer has a first surface and a second surface arranged opposite to each other, the first metal layer is located on the first surface, and the second metal layer is located on the second surface.

2. The composite current collector according to claim 1, wherein: A portion of the bonding layer is embedded in the first metal layer.

3. The composite current collector according to any one of claims 1 to 2, wherein: A portion of the bonding layer is embedded in the second metal layer.

4. The composite current collector according to any one of claims 1 to 3, wherein The roughness of the surface of the first metal layer close to the bonding layer satisfies: 0.1 μm≤Ra1≤0.5 μm, where Ra1 represents the arithmetic mean roughness of the surface of the first metal layer close to the bonding layer.

5. The composite current collector according to any one of claims 1 to 4, wherein The roughness of the surface of the first metal layer close to the bonding layer satisfies: 0.5 μm≤Rz1≤1 μm, where Rz1 represents the maximum height roughness of the surface of the first metal layer close to the bonding layer.

6. The composite current collector according to any one of claims 1 to 5, wherein: The roughness of the surface of the second metal layer close to the bonding layer satisfies: 0.1 μm≤Ra2≤0.5 μm, where Ra2 represents the arithmetic mean roughness of the surface of the second metal layer close to the bonding layer.

7. The composite current collector according to any one of claims 1 to 6, wherein: The roughness of the surface of the second metal layer close to the bonding layer satisfies: 0.5 μm≤Rz2≤1 μm, where Rz2 represents the maximum height roughness of the surface of the second metal layer close to the bonding layer.

8. The composite current collector according to any one of claims 1 to 7, wherein The thickness of the first metal layer is 1 μm to 10 μm.

9. The composite current collector according to any one of claims 1 to 8, wherein The thickness of the first metal layer is 1 μm to 6 μm.

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

11. The composite current collector according to any one of claims 1 to 10, wherein: The thickness of the second metal layer is 1 μm to 10 μm.

12. The composite current collector according to any one of claims 1 to 11, wherein: The thickness of the second metal layer is 1 μm to 6 μm.

13. The composite current collector according to any one of claims 1 to 12, wherein: The second metal layer includes at least one of aluminum, aluminum alloy, copper, copper alloy, silver, silver alloy, nickel, nickel alloy, gold, gold alloy, chromium and chromium alloy.

14. The composite current collector according to any one of claims 1 to 13, wherein: The composite current collector further includes a flame retardant layer, and the flame retardant layer is located inside the bonding layer.

15. The composite current collector according to claim 14, wherein: The thickness of the flame retardant layer is 300nm-700nm.

16. The composite current collector according to any one of claims 14 to 15, wherein: The flame retardant layer contains flame retardant particles; the flame retardant particles include at least one of sodium aluminum fluoride, calcium fluoride, aluminum fluoride, sodium fluorosilicate, magnesium fluoride, lithium fluoride, zinc borate, phosphate ester, phosphite ester, phosphate, phosphite, polyphosphoramide flame retardant, phenolic resin, flame retardant silicone rubber and flame retardant epoxy resin.

17. The composite current collector according to claim 16, wherein: The Dv50 of the flame retardant particles is 100nm to 300nm.

18. The composite current collector according to any one of claims 14 to 17, wherein: There are multiple flame retardant layers; the multiple flame retardant layers are distributed inside the bonding layer at intervals.

19. The composite current collector according to claim 18, wherein: A plurality of the flame retardant layers are arranged in parallel.

20. The composite current collector according to claim 19, wherein: The distance between adjacent flame retardant layers is 300nm to 700nm.

21. The composite current collector according to any one of claims 19 to 20, wherein: The distance between the flame retardant layer closest to the first metal layer and the first metal layer is 300 nm to 700 nm.

22. The composite current collector according to any one of claims 19 to 21, wherein: The distance between the flame retardant layer closest to the second metal layer and the second metal layer is 300 nm to 700 nm.

23. The composite current collector according to any one of claims 1 to 22, wherein: The thickness of the bonding layer is 1 μm to 8 μm.

24. The composite current collector according to any one of claims 1 to 23, wherein: The thickness of the bonding layer is 1 μm to 4 μm.

25. The composite current collector according to any one of claims 1 to 24, wherein: The bonding layer comprises at least one of polyolefin, 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, polyimide, polyamide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), polytetrafluoroethylene, polyvinylidene fluoride, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polyoxymethylene and polycarbonate.

26. The composite current collector according to any one of claims 1 to 25, wherein: The composite current collector further includes a passivation layer; the passivation layer is located on a surface of the first metal layer and / or the second metal layer away from the bonding layer.

27. The composite current collector according to claim 26, wherein: The thickness of the passivation layer is 10nm-2000nm.

28. The composite current collector according to any one of claims 26 to 27, wherein: The thickness of the passivation layer is 20nm-200nm.

29. A pole piece comprising the composite current collector according to any one of claims 1 to 28.

30. A secondary battery comprising the electrode sheet according to claim 29.

31. An electrical device comprising at least one of the composite current collector according to any one of claims 1 to 28, the pole piece according to claim 29, and the secondary battery according to claim 30.

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