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, which can improve the cycle performance of the secondary battery. The composite current collector comprises a support layer, and a bonding layer and an electrically conductive layer, which are sequentially stacked on at least one side surface of the support layer, wherein the bonding layer comprises a bonding-layer main body and a protruding portion, the protruding portion protruding in the thickness direction of the bonding layer and being embedded in the electrically conductive layer.

Description

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

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202311621396.7, filed on November 28, 2023, entitled “Composite current collector, electrode, secondary battery and electrical device,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the field of battery technology, 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] In recent years, the application range of secondary batteries, represented by lithium-ion batteries, has become increasingly broad. They are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As secondary batteries have achieved significant development, higher requirements have been placed on their energy density, cycle performance, and safety performance. In secondary batteries, the current collector, as the component that carries the active material, has a significant impact on the electrochemical performance of the battery. However, currently commonly used composite current collectors often suffer from poor inter-layer adhesion, which can easily lead to problems such as poor cell performance and poor cycle performance when used in batteries.

[0006] Summary of the Invention

[0007] The present application provides a composite current collector, a pole piece, a secondary battery and an electrical device, which can improve the cycle performance of the secondary battery.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a composite current collector, comprising: a supporting layer and a bonding layer and a conductive layer stacked in sequence on the surface of at least one side of the supporting layer, the bonding layer comprising a bonding layer body and a protrusion, the protrusion protruding outward along the thickness direction of the bonding layer and embedded in the conductive layer.

[0009] In some embodiments of the present application, there are multiple raised portions, and the multiple raised portions are arranged at intervals.

[0010] In some embodiments of the present application, the raised portion includes a first raised portion and / or a second raised portion, the raised height of the first raised portion is less than the thickness of the conductive layer, and the raised height of the second raised portion is equal to the thickness of the conductive layer.

[0011] In some embodiments of the present application, the first protrusion includes a first sub-protrusion and / or a second sub-protrusion, the orthographic projection of the first sub-protrusion on the surface of the conductive layer includes a hole shape, and the orthographic projection of the second sub-protrusion on the surface of the conductive layer includes a stripe shape;

[0012] Optionally, the hole shape includes one or more of a circular hole, an elliptical hole, a fan-shaped hole, an arcuate hole and a polygonal hole, and can be a circular hole and / or an elliptical hole;

[0013] Optionally, the stripe shape includes one or more of elliptical stripes, polygonal stripes, arc stripes and wavy stripes, and the elliptical stripes can be selected.

[0014] In some embodiments of the present application, an angle included in an orthographic projection of the first sub-protrusion on the surface of the conductive layer is ≥45°.

[0015] In some embodiments of the present application, the first sub-protrusion satisfies at least one of the following conditions:

[0016] (1) The height h1 of the first sub-protrusion and the width d1 of the first sub-protrusion satisfy the following: 0.001% ≤ h1 / d1 ≤ 1%;

[0017] (2) The width d1 of the first sub-protrusion and the distance Δx1 between two adjacent first sub-protrusions satisfy the following relationship: 3.6%≤d1 / Δx1≤40%.

[0018] In some embodiments of the present application, the first sub-protrusion satisfies at least one of the following conditions:

[0019] (1) The protrusion height h1 of the first sub-protrusion is 50 nm to 500 nm;

[0020] (2) The width d1 of the first sub-protrusion is 0.2 mm to 20 mm;

[0021] (3) The distance Δx1 between two adjacent first sub-protrusions is 5 mm to 50 mm.

[0022] In some embodiments of the present application, the striped shape includes alternately distributed stripes or mutually intersecting stripes, and can be selected as mutually intersecting stripes, and further can be selected as grid-like intersecting stripes.

[0023] In some embodiments of the present application, the mutually intersecting stripes contain at least one intersection;

[0024] Optionally, the orthographic projection of the intersection on the surface of the conductive layer includes one or more of a circle, an ellipse and a polygon, and may be a circle and / or an ellipse;

[0025] Optionally, an angle included in an orthographic projection of the intersection portion on the surface of the conductive layer is ≥45°.

[0026] In some embodiments of the present application, the second sub-protrusion satisfies at least one of the following conditions:

[0027] (1) The protrusion height h2 of the second sub-protrusion is 50 nm to 500 nm;

[0028] (2) The width d2 of the second sub-protrusion is 3 mm to 20 mm;

[0029] (3) The distance Δx2 between two adjacent second sub-protrusions is 15 mm to 70 mm.

[0030] In some embodiments of the present application, at least one first protrusion is provided between two adjacent second protrusions;

[0031] Optionally, the total area S2 of the orthographic projections of the second protrusions on the surface of the conductive layer and the total area S1 of the orthographic projections of the first protrusions on the surface of the conductive layer satisfy the following: S2 <S1;

[0032] Optionally, the relationship between S1 and S2 satisfies: S1 / (S1+S2)≥95%.

[0033] In some embodiments of the present application, the second protrusion satisfies at least one of the following conditions:

[0034] (1) The width d3 of the second protrusion is 30 μm to 600 μm;

[0035] (2) The distance Δx3 between two adjacent second protrusions is 10 mm to 100 mm.

[0036] In some embodiments of the present application, the orthographic projection of the second protrusion on the surface of the conductive layer includes one or more of a circular hole, an elliptical hole, a fan-shaped hole, an arcuate hole and a polygonal hole, and can be a circular hole and / or an elliptical hole;

[0037] Optionally, an angle included in an orthographic projection of the second protrusion on the surface of the conductive layer is ≥45°.

[0038] In some embodiments of the present application, the raised portion comprises an adhesive;

[0039] Optionally, the binder includes one or more of a composition containing a multifunctional isocyanate and a polyester polyol compound, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide;

[0040] Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0041] In some embodiments of the present application, at least one of the following conditions is met:

[0042] (1) The thickness of the conductive layer is 0.5 μm to 5 μm;

[0043] (2) The thickness of the adhesive layer body is 0.5 μm to 3 μm;

[0044] (3) The thickness of the support layer is 2 μm to 15 μm.

[0045] In some embodiments of the present application, at least one of the following conditions is met:

[0046] (1) The peeling ratio of the conductive layer is ≤1 square millimeter (mm 2 ) / 2000mm 2 ;

[0047] (2) The adhesive force of the conductive layer is ≥220 Newtons / meter (N / m).

[0048] In some embodiments of the present application, at least one of the following conditions is met:

[0049] (1) The support layer comprises one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyformaldehyde, polyphenylene oxide, polyphenylene sulfide, polyethylene glycol, polysulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their cross-linked products and their copolymers;

[0050] (2) the adhesive layer comprises one or more of a composition containing a multifunctional isocyanate and a polyester polyol compound, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, modified polyethylene, modified polypropylene, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide;

[0051] Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane;

[0052] (3) The conductive layer comprises one or more of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium and tin.

[0053] The second aspect of the present application provides a pole piece, comprising the composite current collector described in the first aspect of the present application.

[0054] The third aspect of the present application provides a secondary battery, comprising the electrode described in the second aspect of the present application.

[0055] A fourth aspect of the present application provides an electrical device comprising the secondary battery according to the third aspect of the present application.

[0056] The electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0057] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims.

[0058] The composite current collector provided in this application has the aforementioned raised portion in the adhesive layer, which can increase the surface area of ​​contact between the adhesive layer and the conductive layer, strengthen the adhesion of the adhesive layer to the conductive layer, thereby improving the bonding force between the adhesive layer and the conductive layer, effectively reducing the shedding of the conductive layer, and thus improving the cycle performance of the battery cell using the composite current collector. At the same time, the increased contact surface area between the adhesive layer and the conductive layer can also reduce the probability of defects in the conductive layer. Under the same tensile elongation, there are fewer cracks, which is conducive to reducing the square resistance growth rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive work. In the drawings:

[0060] FIG1 is a schematic diagram of the cross-sectional structure of a composite current collector according to one embodiment of the present application.

[0061] FIG2 is a schematic diagram of the cross-sectional structure of a composite current collector according to one embodiment of the present application.

[0062] FIG3 is a schematic diagram of the cross-sectional structure of a composite current collector according to one embodiment of the present application.

[0063] FIG4 is a schematic diagram of the cross-sectional structure of a composite current collector according to one embodiment of the present application.

[0064] FIG5 is a schematic diagram of a top view of a composite current collector according to an embodiment of the present application.

[0065] FIG6 is a schematic diagram of a top view of a composite current collector according to an embodiment of the present application.

[0066] FIG7 is a schematic diagram of a top view of a composite current collector according to an embodiment of the present application.

[0067] FIG8 is a schematic diagram of a top view of a composite current collector according to an embodiment of the present application.

[0068] FIG9 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0069] FIG. 10 is an exploded view of the battery cell shown in FIG. 9 according to an embodiment of the present application.

[0070] FIG11 is a schematic diagram of a battery module according to an embodiment of the present application.

[0071] FIG12 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0072] FIG13 is an exploded view of the battery pack shown in FIG12 according to one embodiment of the present application.

[0073] FIG14 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0074] Explanation of the reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 cover plate; 6 electrical device; 11 supporting layer; 12 adhesive layer; 13 conductive layer; 121, adhesive layer body; 122 raised portion; 1221 first raised portion; 1222 second raised portion; 12211 first sub-raised portion; 12212 second sub-raised portion. DETAILED DESCRIPTION

[0075] Below, some embodiments of the composite current collector, secondary battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0076] " range " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be including end value or excluding end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that the scope of 60 to 110 and 80 to 120 is 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, then the following range can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range " a to b " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" are listed herein, and "0 to 5" is merely an abbreviation for a combination of these values. 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 to 10," this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0077] 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.

[0078] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0079] 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.

[0080] 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.

[0081] In this application, in the open technical features or technical solutions described with words such as "contain", "include", and "include", unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that also include additional members in addition to the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or may not include additional members. It 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". 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.

[0082] 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.

[0083] Currently, metal is used as a conductive layer and composited with a polymer material layer to form a composite current collector with a "metal / polymer material / metal" sandwich structure. When used in batteries, this can increase battery energy density, reduce costs, and make the battery lightweight. During the preparation of this composite current collector, it is usually necessary to introduce a binder to bond the conductive layer to the polymer material layer. However, during the process of introducing the binder and composite the conductive layer with the polymer material layer, bubbles or pores are easily formed between the binder layer formed by the binder and the conductive layer, resulting in a weak adhesion of the binder layer. This can lead to the conductive layer easily falling off during the battery cell processing and during the battery cell recycling process, resulting in problems such as a drop in battery cell performance.

[0084] To address the above technical issues, this application proposes a composite current collector. By providing raised portions on the surface adjacent to the adhesive layer and the conductive layer, the composite current collector increases the surface area of ​​contact between the adhesive layer and the conductive layer, thereby enhancing the bonding force between the adhesive layer and the conductive layer, and thereby improving the cycling performance of a battery cell using the composite current collector. This composite current collector is described in more detail below.

[0085] In the first aspect, the present application provides a composite current collector, as shown in Figure 1, which includes a support layer 11 and an adhesive layer 12 and a conductive layer 13 stacked in sequence on at least one side surface of the support layer 11, the adhesive layer 12 includes an adhesive layer body 121 and a protrusion 122, and the protrusion 122 protrudes outward along the thickness direction of the adhesive layer 12 and is embedded in the conductive layer 13.

[0086] It can be understood that the raised portion protrudes along the thickness direction of the adhesive layer in a direction away from the adhesive layer body.

[0087] It should be noted that the term "conductive layer surface" or "conductive layer surface" as used herein refers to the surface of the conductive layer perpendicular to the thickness of the current collector, i.e., the surface of the conductive layer adjacent to (or in contact with) the adhesive layer. The term "conductive layer surface area" refers to the area of ​​the surface of the conductive layer adjacent to (or in contact with) the adhesive layer.

[0088] The composite current collector provided in this application has the aforementioned raised portion in the adhesive layer, which can increase the surface area of ​​contact between the adhesive layer and the conductive layer, strengthen the adhesion of the adhesive layer to the conductive layer, thereby improving the bonding force between the adhesive layer and the conductive layer, effectively reducing the shedding of the conductive layer, and thus improving the cycle performance of the battery cell using the composite current collector. At the same time, the increased contact surface area between the adhesive layer and the conductive layer can also reduce the probability of defects in the conductive layer. Under the same tensile elongation, there are fewer cracks, which is conducive to reducing the square resistance growth rate.

[0089] In some embodiments, there are multiple protrusions, and the multiple protrusions are arranged at intervals.

[0090] It can be understood that the multiple protrusions are arranged at intervals, which means that there is a gap (spacing) between any two adjacent protrusions.

[0091] The multiple protrusions are arranged at intervals to improve the bonding force between the bonding layer and the conductive layer while providing the conductive layer and the composite current collector with sufficient mechanical strength, thereby improving the structural stability of the composite current collector.

[0092] In some embodiments, the total area S' of the orthographic projections of the protrusions 122 on the surface of the conductive layer 13 and the area S of the surface of the conductive layer 13 satisfy the following relationship: <S。

[0093] The total area S' of the orthographic projection of the protrusions on the surface of the conductive layer is smaller than the area S of the surface of the conductive layer, which can improve the bonding force between the adhesive layer and the conductive layer while providing the conductive layer and the composite current collector with sufficient mechanical strength, thereby improving the structural stability of the composite current collector.

[0094] In some embodiments, the protrusion includes a first protrusion and / or a second protrusion, the protrusion height of the first protrusion is less than the thickness of the conductive layer, and the protrusion height of the second protrusion is equal to the thickness of the conductive layer.

[0095] The height of the first protrusion is smaller than the thickness of the conductive layer, which can improve the bonding force between the adhesive layer and the conductive layer while ensuring that the conductive layer and the composite current collector have sufficient mechanical strength.

[0096] The height of the second raised portion is equal to the thickness of the conductive layer, that is, the second raised portion penetrates the conductive layer along the thickness direction of the composite current collector. At this time, the second raised portion can play a role in exhausting and reducing bubbles in the bonding layer. For example, if there are bubbles between the conductive layer and the bonding layer, it is easy to cause the bonding force between the conductive layer and the bonding layer to decrease, and the conductive layer is easy to peel off. If there are bubbles between the bonding layer and the supporting layer, it is easy to cause the bonding force between the bonding layer and the supporting layer to decrease, and the conductive layer and the bonding layer as a whole are easy to peel off from the supporting layer. The second raised portion that penetrates the conductive layer is conducive to exhausting bubbles between the bonding layer and the supporting layer, and between the bonding layer and the conductive layer, thereby further improving the bonding force between the bonding layer and the supporting layer, and between the bonding layer and the conductive layer.

[0097] In some embodiments, referring to FIG. 2 , the protrusion 122 includes a first protrusion 1221 .

[0098] In some embodiments, referring to FIG. 3 , the protrusion 122 includes a second protrusion 1222 .

[0099] In some embodiments, referring to FIG. 4 , the protrusion 122 includes a first protrusion 1221 and a second protrusion 1222 .

[0100] In some embodiments, the raised portion comprises an adhesive.

[0101] It should be noted that when the protrusion includes a first protrusion and a second protrusion, the adhesives in the first protrusion and the second protrusion may be the same or different.

[0102] The raised portion includes a first raised portion and / or a second raised portion, wherein the first raised portion can increase the wettability of the conductive layer to the adhesive, and the adhesive filled in the raised portion can increase the surface area of ​​contact between the conductive layer and the adjacent adhesive layer, thereby enhancing the bonding force between the adhesive layer and the conductive layer.

[0103] In addition to increasing the surface area of ​​contact between the conductive layer and the adjacent adhesive layer, the second protrusion also helps to expel bubbles or pores formed between the adhesive layer and the conductive layer during the process of introducing the adhesive to form the adhesive layer, so that the adhesive layer can better adhere to the conductive layer, thereby improving the bonding force between the adhesive layer and the conductive layer, effectively reducing the shedding of the conductive layer, and thus improving the cycle performance of the battery cell using the composite current collector.

[0104] When the protrusion includes both the first protrusion and the second protrusion, the interface contact between the conductive layer and the adhesive layer can be made closer, which helps to further improve the adhesive force.

[0105] In some embodiments, the binder includes one or more of a composition containing a multifunctional isocyanate and a polyester polyol compound, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide.

[0106] In some embodiments, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0107] In some embodiments, the first protrusion 1221 includes a first sub-protrusion 12211 and / or a second sub-protrusion 12212 .

[0108] It can be understood that when the raised portion 122 includes the first raised portion 1221, the adhesive layer 12 can be provided with only the first sub-raised portion 12211 (see Figures 5 and 6), or only the second sub-raised portion 12212 (see Figures 7 and 8), or a combination of the first sub-raised portion 12211 and the second sub-raised portion 12212 can be provided.

[0109] When the first sub-protrusion and the second sub-protrusion are arranged in combination, the bonding force can be better improved, and at the same time, the composite current collector can have sufficient mechanical strength.

[0110] In some embodiments, the orthographic projection of the first sub-protrusion 12211 on the surface of the conductive layer 13 includes a hole shape (see FIG. 5 and FIG. 6 ).

[0111] It is understood that the "hole shape" or "hole" described in this application refers to a shape whose orthographic projection on the surface of the conductive layer is a regular or irregular bounded shape, or a closed planar geometric figure. For example, a "circular hole" means that the orthographic projection is a circle, and a "sector-shaped hole" means that the orthographic projection is a sector.

[0112] In some embodiments, the hole shape includes but is not limited to one or more of a circular hole, an elliptical hole (see FIG6 ), a fan-shaped hole, an arcuate hole, and a polygonal hole (see FIG5 ), and can be a circular hole and / or an elliptical hole.

[0113] It can be understood that the orthographic projection of the first sub-protrusions on the surface of the conductive layer includes a hole shape. At this time, the first sub-protrusions are discretely distributed (or alternately distributed), and any two first sub-protrusions do not intersect and there is a gap between them.

[0114] It can be understood that the "bow shape" mentioned in this application refers to a figure formed by an arc and its corresponding chord.

[0115] When the hole shape includes a circular hole and / or an elliptical hole, the first sub-protrusion does not include an acute-angled tip. At this time, the adhesive can more completely infiltrate and fill the entire protrusion, which helps to improve the adhesion of the adhesive layer to the conductive layer and reduce the shedding of the conductive layer.

[0116] In some embodiments, an angle included by an orthographic projection of the first sub-protrusion on the surface of the conductive layer is ≥45°.

[0117] It can be understood that the angle included in the positive projection of the first sub-protrusion on the surface of the conductive layer, that is, the angle included in the hole shape, means that when the hole shape is a polygon, each angle of the polygon is ≥45°; when the hole shape is a fan shape or an arc shape, the central angle corresponding to the fan shape or the arc shape is ≥45°.

[0118] The angle included in the orthographic projection of the first sub-protrusion on the surface of the conductive layer is ≥45°, which helps the adhesive to more completely infiltrate and fill the protrusion, reduces the problem of the protrusion being difficult to be infiltrated by the adhesive when it has a pointed end, improves the bonding force of the adhesive layer to the conductive layer, and reduces the shedding of the conductive layer.

[0119] In some embodiments, the protrusion height h1 of the first sub-protrusion (see FIG. 2 ) is 50 nm to 500 nm. For example, the protrusion height of the first sub-protrusion can be 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or any range thereof.

[0120] It should be noted that the “protrusion height of the first sub-protrusion” refers to the distance between the highest point of the top of the first sub-protrusion and the surface of the conductive layer embedded in the first sub-protrusion.

[0121] The protrusion height of the first sub-protrusion is within the above range. On the one hand, it can enable the adhesive to better infiltrate and fill the protrusion, thereby further improving the adhesion of the adhesive layer to the conductive layer and further enhancing the bonding force between the two. On the other hand, it can also reduce the impact on the conductivity of the conductive layer.

[0122] In some embodiments, the width d1 of the first sub-protrusion (see Figures 5 and 6) is 0.2 mm to 20 mm. For example, the width of the protrusion can be 0.2 mm, 1 mm, 5 mm, 7 mm, 9 mm, 11 mm, 13 mm, 15 mm, 17 mm, 19 mm, 20 mm, or any range thereof.

[0123] The width of the first sub-protrusion is within the above range. On the one hand, it can enable the adhesive to better infiltrate and fill the protrusion, thereby further improving the adhesion of the adhesive layer to the conductive layer and further enhancing the bonding force between the two. On the other hand, it will minimize the impact on the conductivity of the conductive layer.

[0124] It should be noted that the "width of the first sub-protrusion" refers to the maximum value of the distance between any two points on the contour of the shape formed by the orthographic projection of the first sub-protrusion on the surface of the conductive layer (when the orthographic projection is a circular hole, an elliptical hole, a fan-shaped hole or an arcuate hole), or the maximum side length of the contour (when the orthographic projection is a polygonal hole).

[0125] In some embodiments, the distance Δx1 between two adjacent first sub-protrusions (see FIG. 2 ) is 5 mm to 50 mm. For example, the distance between two adjacent first sub-protrusions can be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, or any range thereof.

[0126] It should be noted that the "distance between two adjacent first sub-protrusions" refers to the horizontal distance between the center points of the two adjacent first sub-protrusions. It is understood that "horizontal" here refers to the direction perpendicular to the thickness of the current collector and parallel to the surface of the conductive layer.

[0127] The spacing between two adjacent first sub-protrusions within the above range, on the one hand, enables the adhesive to better wet and fill the protrusions, thereby further improving the adhesion of the adhesive layer to the conductive layer and further enhancing the bonding force between the two. On the other hand, it can also reduce the impact on the conductivity of the conductive layer.

[0128] In some embodiments, the height h1 of the first sub-protrusion and the width d1 of the first sub-protrusion satisfy the following relationship: 0.001%≤h1 / d1≤1%. For example, h1 / d1 can be 0.001%, 0.005%, 0.008%, 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, or any range thereof.

[0129] The height and width of the first sub-protrusion satisfy the above-mentioned relationship, which can enhance the wettability of the adhesive in the protrusion, avoid dead corners that are difficult to wet, and allow the adhesive to penetrate into the top of the protrusion, trying to achieve complete wetting and filling of the protrusion with the adhesive; in this way, the gap between the top of the protrusion and the adjacent conductive layer can be reduced, and the bonding force between the adhesive layer and the conductive layer can be improved.

[0130] In some embodiments, the width d1 of the first sub-protrusion and the spacing Δx1 between two adjacent first sub-protrusions satisfy the following relationship: 3.6% ≤ d / Δx ≤ 40%. For example, d1 / Δx1 can be 3.6%, 7%, 9%, 10%, 20%, 25%, 30%, 35%, 40%, or any range thereof.

[0131] The relationship between the width of the first sub-protrusion and the spacing between two adjacent first sub-protrusions satisfies the aforementioned relationship, which can enhance the adhesive's wettability within the protrusions, avoid dead corners that are difficult to wet, and maximize complete wetting and filling of the protrusions with the adhesive. This can reduce the gaps at the bottom of the protrusions and enhance the bonding strength between the adhesive layer and the conductive layer. If the spacing between two adjacent first sub-protrusions is relatively large, the effect of increasing the surface energy of the conductive layer is relatively low, which will reduce the adhesive's wetting effect within the protrusions. If the spacing between two adjacent first sub-protrusions is relatively small, the spacing between the protrusions is relatively narrow, which can easily form narrow protrusions, resulting in a relatively low effect of increasing the surface energy of the conductive layer, thereby reducing the adhesive's wetting effect within the protrusions.

[0132] In some embodiments, the orthographic projection of the second sub-protrusion 12212 on the surface of the conductive layer includes a stripe shape (see FIG. 7 and FIG. 8 ).

[0133] The striped shape can further increase the contact area between the conductive layer and the adhesive layer, and further enhance the wettability of the protrusion surface, which helps the adhesive to achieve better wetting and filling effects in the protrusion, thereby further improving the bonding force between the adhesive layer and the conductive layer.

[0134] In some embodiments, the stripe shape includes but is not limited to one or more of elliptical stripes, polygonal stripes, arc stripes and wavy stripes, and can be elliptical stripes.

[0135] The elliptical stripes can make the interior of the second sub-protrusion better connected, so that the wettability of the protrusion surface is further enhanced, and the wetting and filling effect of the adhesive in the protrusion is improved, thereby further improving the bonding force between the adhesive layer and the conductive layer.

[0136] In some embodiments, the stripes include alternately distributed stripes (see FIG. 7 ) or mutually intersecting stripes (see FIG. 8 ), and may be mutually intersecting stripes, or further may be grid-like intersecting stripes.

[0137] It can be understood that the "alternating stripes" mentioned in this application mean that any two stripes do not intersect and there is a gap between them; the "mutually intersecting stripes" mentioned herein refer to the situation where the stripes intersect with each other, for example, there is an intersection between the stripes alternately distributed horizontally and the stripes alternately distributed vertically.

[0138] In some embodiments, the intersecting stripes contain at least one intersection.

[0139] The intersecting stripes can make the protrusions on the entire surface appear to be connected, allowing the adhesive to flow better inside the protrusions, improving the wetting and filling effect of the adhesive in the protrusions, and thus improving the adhesion of the adhesive layer to the conductive layer.

[0140] In some embodiments, the orthographic projection of the intersection on the surface of the conductive layer includes, but is not limited to, one or more of a circle, an ellipse, and a polygon, and can be optionally a circle and / or an ellipse.

[0141] When the orthographic projection of the intersection on the surface of the conductive layer includes a circle and / or an ellipse, the intersection does not contain an acute-angled tip. At this time, the adhesive can more completely infiltrate and fill the intersection, which helps to improve the adhesion of the adhesive layer to the conductive layer and reduce the shedding of the conductive layer.

[0142] In some embodiments, an angle included by an orthographic projection of the intersection on the surface of the conductive layer is ≥ 45°.

[0143] It can be understood that the angle included in the orthographic projection of the intersection on the surface of the conductive layer is ≥45°, which means that when the orthographic projection is a polygon, each angle of the polygon is ≥45°.

[0144] The angle included in the orthographic projection of the intersection on the surface of the conductive layer is ≥45°, which helps the adhesive to more completely infiltrate and fill the intersection, reduces the problem of the intersection being difficult to be infiltrated by the adhesive when there is a sharp point, improves the bonding force of the adhesive layer to the conductive layer, and reduces the shedding of the conductive layer.

[0145] In some embodiments, the protrusion height h2 of the second sub-protrusion (see FIG. 2 ) is 50 nm to 500 nm. For example, the protrusion height of the second sub-protrusion can be 50 nm, 70 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, or any range thereof.

[0146] It should be noted that the “protrusion height of the second sub-protrusion” refers to the distance between the highest point of the top of the second sub-protrusion and the surface of the conductive layer embedded in the second sub-protrusion.

[0147] In some embodiments, the width d2 of the second sub-protrusion (see FIG. 7 ) is 3 mm to 20 mm. For example, the width of the second sub-protrusion can be 3 mm, 5 mm, 7 mm, 9 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, or any range thereof.

[0148] It should be noted that the "width of the second sub-protrusion" refers to the width of the stripe. If the stripe is a rectangle, it refers to the distance between the two long sides of the rectangle; if the stripe is an irregular shape (such as an arc, wave, etc.), it refers to the maximum width of the irregular shape.

[0149] In some embodiments, the distance Δx2 between two adjacent second sub-protrusions (see FIG. 2 ) is 15 mm to 70 mm. For example, the distance between two adjacent second sub-protrusions can be 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 70 mm, or any range thereof.

[0150] It should be noted that the "distance between two adjacent second sub-protrusions" refers to the horizontal distance between the center points of the two adjacent second sub-protrusions. It is understood that "horizontal" here refers to the direction perpendicular to the thickness of the current collector and parallel to the surface of the conductive layer.

[0151] The height and width of the second sub-protrusions, as well as the spacing between two adjacent second sub-protrusions, are within the aforementioned ranges. This, on the one hand, allows the adhesive to better wet and fill the protrusions, thereby further improving the adhesion of the adhesive layer to the conductive layer and the bonding strength therebetween. On the other hand, it also reduces the impact on the conductivity of the conductive layer.

[0152] In some embodiments, the height h2 of the second sub-protrusion and the width d2 of the second sub-protrusion satisfy the following relationship: 0.0015%≤h2 / d2≤0.01%. For example, h2 / d2 can be 0.0015%, 0.003%, 0.005%, 0.008%, 0.01%, or any range thereof.

[0153] The height and width of the second sub-protrusion satisfy the above-mentioned relationship, which can enhance the wettability of the adhesive in the protrusion, avoid dead corners that are difficult to wet, and allow the adhesive to penetrate into the bottom of the protrusion, so as to achieve complete wetting and filling of the protrusion with the adhesive as much as possible; in this way, the gap at the bottom of the protrusion can be reduced and the bonding force between the adhesive layer and the conductive layer can be improved.

[0154] In some embodiments, the width d2 of the second sub-protrusion and the spacing Δx2 between two adjacent second sub-protrusions satisfy the following relationship: 7.5% ≤ d2 / Δx2 ≤ 28.6%. For example, d2 / Δx2 can be 7.5%, 10%, 20%, 25%, 28.6%, or any range thereof.

[0155] The width of the second sub-protrusion and the spacing between two adjacent second sub-protrusions satisfy the above-mentioned relationship, thereby enhancing the wettability of the adhesive in the protrusion, avoiding dead corners that are difficult to wet, and achieving complete wetting and filling of the protrusion with the adhesive as much as possible; this can reduce the gap at the bottom of the protrusion and enhance the bonding force between the adhesive layer and the conductive layer.

[0156] In some embodiments, the total area S1 of the orthographic projections of the first protrusions on the surface of the conductive layer and the area S of the conductive layer surface satisfy the following ratio: 0.1% ≤ S1 / S ≤ 50%. For example, S1 / S can be 0.1%, 1%, 3%, 5%, 7%, 10%, 20%, 30%, 40%, 50%, or any range thereof.

[0157] The total area S1 of the orthographic projection of the first protrusion on the surface of the conductive layer and the area S of the surface of the conductive layer satisfy the above relationship. While improving the bonding force, it can also make the composite current collector have sufficient mechanical strength, improve the structural stability of the composite current collector, and improve the safety of the battery cell.

[0158] In some embodiments, at least one first protrusion is provided between two adjacent second protrusions.

[0159] The second protrusions and the first protrusions are interlaced to reduce the problem of uneven exhaust during the composite process of the adhesive layer and the conductive layer, or reduce the problem of local conductivity weakening of the conductive layer, so that the composite current collector has better comprehensive performance.

[0160] In some embodiments, the total area S2 of the orthographic projections of the second protrusions on the surface of the conductive layer and the total area S1 of the orthographic projections of the first protrusions on the surface of the conductive layer satisfy: S2 <S1。

[0161] The total area S2 of the orthographic projection of the second protrusion on the surface of the conductive layer and the total area S1 of the orthographic projection of the first protrusion on the surface of the conductive layer satisfy the above relationship, which can not only reduce the generation of bubbles during the composite process of the adhesive layer and the conductive layer and improve the bonding force, but also ensure the performance of the battery cell and improve safety.

[0162] In some embodiments, the relationship between S1 and S2 satisfies: S1 / (S1+S2)≥95%. For example, S1 / (S1+S2) may be 95%, 97%, 100%, or any range thereof.

[0163] The total area S2 of the orthographic projection of the second protrusion on the surface of the conductive layer and the total area S1 of the orthographic projection of the first protrusion on the surface of the conductive layer satisfy the above-mentioned relationship, which is conducive to taking into account both the exhaust function of the second protrusion and the mechanical properties of the composite current collector. Thus, while improving the bonding force, the composite current collector can also have sufficient mechanical strength, thereby improving the structural stability of the composite current collector and improving the safety of the battery cell.

[0164] In some embodiments, the width d3 of the second protrusion is 30 μm to 600 μm. For example, the width of the second protrusion can be 30 μm, 60 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, or any range thereof.

[0165] It should be noted that, similar to the width of the first sub-protrusion, the "width of the second protrusion" mentioned in this application refers to the maximum value of the distance between any two points on the shape contour of the orthographic projection of the second protrusion on the surface of the conductive layer (when the orthographic projection is a circular hole, an elliptical hole, a fan-shaped hole or an arcuate hole), or the maximum side length of the contour (when the orthographic projection is a polygonal hole).

[0166] In some embodiments, the distance Δx3 between two adjacent second protrusions (see FIG. 3 ) is 10 mm to 100 mm. For example, the distance between two adjacent second protrusions can be 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, or any range thereof.

[0167] It should be noted that the "distance between two adjacent second protrusions" mentioned in this application refers to the horizontal distance between the center points of the two adjacent second protrusions. It is understood that "horizontal" here refers to the direction perpendicular to the thickness of the current collector and parallel to the surface of the conductive layer.

[0168] The width of the second protrusion and the distance between two adjacent second protrusions are within the above range, which is beneficial to improving the exhaust effect of the second protrusion and helping the adhesive to more completely infiltrate and fill the protrusion. At the same time, it can also reduce the cracking problem that is easy to occur at the position of the second protrusion during the processing of the composite current collector. Therefore, while improving the bonding force, it can also take into account the conductivity and strength (mechanical) properties of the current collector.

[0169] In some embodiments, the orthographic projection of the second protrusion on the surface of the conductive layer includes but is not limited to one or more of a circular hole, an elliptical hole, a fan-shaped hole, an arcuate hole and a polygonal hole, and can be a circular hole and / or an elliptical hole.

[0170] When the orthographic projection of the second protrusion on the surface of the conductive layer includes a circular hole and / or an elliptical hole, the second protrusion does not include an acute-angled tip. At this time, the adhesive can more completely infiltrate and fill the entire second protrusion, which helps to improve the adhesion of the adhesive layer to the conductive layer and reduce the shedding of the conductive layer.

[0171] In some embodiments, an angle included by an orthographic projection of the second protrusion on the surface of the conductive layer is ≥45°.

[0172] It can be understood that the angle included in the orthographic projection of the second protrusion on the surface of the conductive layer means that when the orthographic projection is a polygon, each angle of the polygon is ≥45°; when the orthographic projection is a fan or an arc, the central angle corresponding to the fan or arc is ≥45°.

[0173] The angle included in the orthographic projection of the second protrusion on the surface of the conductive layer is ≥45°, which helps the adhesive to more completely infiltrate and fill the protrusion, reduces the problem of the second protrusion being difficult to be infiltrated by the adhesive when it has a pointed end, improves the bonding force of the adhesive layer to the conductive layer, and reduces the shedding of the conductive layer.

[0174] In some embodiments, the total area S2 of the orthographic projections of the second protrusions on the surface of the conductive layer and the area S of the conductive layer on the surface of the conductive layer satisfy the following relationship: 0.0003%≤S2 / S≤0.29%.

[0175] The total area S2 of the orthographic projection of the second protrusion on the surface of the conductive layer and the area S of the surface of the conductive layer satisfy the above relationship. While improving the bonding force, it can also make the composite current collector have sufficient mechanical strength, improve the structural stability of the composite current collector, and improve the safety of the battery cell.

[0176] In some embodiments, the thickness of the conductive layer is 0.5 μm to 5 μm. For example, the thickness of the conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any range thereof.

[0177] In some embodiments, the thickness of the adhesive layer body is 0.5 μm to 3 μm. For example, the thickness of the adhesive layer body can be 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or any range thereof.

[0178] In some embodiments, the thickness of the support layer is 2 μm to 15 μm. For example, the thickness of the support layer can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, or any range thereof.

[0179] The thicknesses of the support layer, the main adhesive layer, and the conductive layer are each within the above ranges, which can improve the adhesive force while also taking into account the conductivity and strength (mechanical) properties of the current collector.

[0180] In some embodiments, the conductive layer peeling ratio of the composite current collector is ≤1 mm 2 / 2000mm 2 .

[0181] It should be noted that the "peeling ratio of the conductive layer" mentioned in the present application refers to the peeling ratio of the conductive layer when the composite current collector is subjected to an adhesion test, which can be tested by the test method described below.

[0182] The stripping ratio of the conductive layer is within the above range, which can reduce the demolding problem of the composite current collector when immersed in the electrolyte, improve the long-term stability of the composite current collector, and ultimately improve the long-term stability of the battery.

[0183] In some embodiments, the adhesive force of the conductive layer is ≥220 N / m.

[0184] It should be noted that the above-mentioned “adhesion of the conductive layer” refers to the tensile force required to cause the conductive layer to fall off the composite current collector when performing an adhesion test on the composite current collector, which can be tested by the test method described below.

[0185] The adhesive force of the conductive layer is within the above range, which can not only ensure a relatively high adhesive force between the adhesive layer and the conductive layer, but also enable the composite current collector to have sufficient mechanical properties, thereby reducing processing defects caused by the decline of mechanical properties in subsequent processing.

[0186] In some embodiments, the support layer includes but is not limited to polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyformaldehyde, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their cross-linked products and their copolymers. One or more.

[0187] In some embodiments, the bonding layer includes one or more of a composition containing a multifunctional isocyanate and a polyester polyol compound, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide.

[0188] In some embodiments, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0189] In some embodiments, the conductive layer includes, but is not limited to, one or more of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium, and tin.

[0190] In a second aspect, the present application provides a method for preparing a composite current collector, which can be used to prepare the composite current collector of the first aspect of the present application, and can include the following steps:

[0191] S1. preparing grooves and / or through holes on at least one side of the metal foil to form a conductive layer;

[0192] S2. Coating a slurry containing an adhesive on the surface of the conductive layer having the grooves and / or through holes to prepare an adhesive layer, and drying the slurry to form a composite layer containing the adhesive layer and the conductive layer;

[0193] S3. Compounding the composite layer containing the bonding layer and the conductive layer with the support layer to prepare a composite current collector.

[0194] In some embodiments, in step S1 , grooves and / or through holes may be prepared on at least one surface of the metal foil by etching.

[0195] It can be understood that when the etching depth is less than the thickness of the metal foil, a groove can be formed; and when the etching depth is equal to the thickness of the metal foil, a through hole can be formed.

[0196] In some embodiments, the adhesive layer includes an adhesive layer body and a protrusion, wherein the protrusion protrudes along a thickness direction of the adhesive layer and is embedded in the conductive layer.

[0197] It is understood that in step S2, after the slurry containing the adhesive is applied to the surface of the conductive layer on the side where the grooves and / or through-holes are provided, the slurry will penetrate into the grooves and / or through-holes and fill the grooves and / or through-holes. After the grooves and / or through-holes are completely filled, a slurry layer can be applied to the surface of the conductive layer to form a layer. After drying, the slurry layer forms the main body of the adhesive layer, and the grooves and / or through-holes filled with the slurry form the protrusions. The main body of the adhesive layer and the protrusions become a whole and form an adhesive layer, thereby achieving the composite of the adhesive layer and the conductive layer, so that the protrusions are embedded in the conductive layer.

[0198] In some embodiments, the protrusion includes a first protrusion and / or a second protrusion.

[0199] It can be understood that the first protrusion may correspond to the groove in step S1, and the second protrusion may correspond to the through hole in step S1.

[0200] In some embodiments, the composite treatment in step S3 includes: hot-pressing the composite layer including the adhesive layer and the conductive layer with the support layer, wherein the adhesive layer in the composite layer contacts the support layer.

[0201] The temperature of the hot pressing lamination is close to the melting point of the adhesive, so that the adhesive is in a fully softened or molten state. The fully softened or molten adhesive can be better laminated with the support layer and the conductive layer in the composite layer.

[0202] It should be noted that when the raised portion includes a second raised portion, the presence of the second raised portion can, on the one hand, play a role in removing bubbles when coating the slurry containing the adhesive, reducing bubbles and pores between the conductive layer and the adhesive layer, and improving the bonding strength between the two; on the other hand, during hot pressing and compounding, bubbles can be discharged from the second raised portion, so that the presence of the second raised portion can further remove bubbles and further improve the bonding strength.

[0203] In some embodiments, step S1 further includes a process of passivating the conductive layer.

[0204] In some embodiments, the passivation agent of the passivation treatment includes one or more of chromate, organic phosphate, aluminum oxide (Al2O3), silicon oxide (SiO2), and silicon nitride (Si3N4).

[0205] It can be understood that in the above steps, the material of the metal foil, the material of the adhesive and the material of the support layer can respectively correspond to the material contained in the conductive layer, the material of the adhesive and the material contained in the support layer in the first aspect of the present application, and will not be elaborated here.

[0206] In a third aspect, the present application provides a pole piece, comprising the composite current collector of the first aspect of the present application or the composite current collector prepared by the preparation method of the second aspect of the present application.

[0207] In some embodiments, the electrode sheet includes a positive electrode sheet and / or a negative electrode sheet.

[0208] It can be understood that the composite current collector of the first aspect of the present application or the composite current collector prepared by the preparation method of the second aspect of the present application can be used in the positive electrode sheet and / or the negative electrode sheet.

[0209] In addition, the secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0210] 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.

[0211] Positive electrode

[0212] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0213] 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.

[0214] In some embodiments, the positive electrode current collector may be the composite current collector of the first aspect of the present application.

[0215] In some embodiments, the positive electrode current collector may be introduced using a metal foil or other composite current collector. For example, aluminum foil may be used as the metal foil. Other composite current collectors may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may 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.

[0216] In some embodiments, the negative electrode may adopt a positive electrode active material for a battery known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: a lithium-containing phosphate with an olivine structure, 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 positive electrode active materials for batteries 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 lithium-containing phosphate with an olivine structure 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 Mn0.2 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.

[0217] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the Li content in the positive electrode material contained in the plate will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0218] In the examples of positive electrode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by molar content, but is not limited to this.

[0219] In some embodiments, the positive electrode active material may also include at least one of the following materials: one or more of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0220] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of sodium transition metal oxides may be Na x MO2, wherein M may include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0221] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n-A class of compounds with anionic units. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si; n represents (YO4) n- valence.

[0222] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si, and n represents (YO4) n- valence state; the halogen can be one or more of F, Cl and Br.

[0223] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen can be one or more of F, Cl and Br.

[0224] Polyanionic compounds may include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y (0≤y≤1) wherein M′ in NaM′PO4F may include one or more of V, Fe, Mn and Ni.

[0225] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of Prussian blue compounds may include Na a Me b Me' c(CN)6, wherein Me and Me' can each independently be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0226] In some embodiments, the positive electrode active material layer may further optionally include a positive electrode binder. As non-limiting examples, the positive electrode 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.

[0227] 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.

[0228] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the positive electrode binder and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any one 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 two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 to 25000 milliPascal seconds (mPa s). When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15 to 35 mg / cm 2 The compaction density of the positive electrode sheet can be 3.0 to 3.6 g / cm 3 , can be selected as 3.3~3.5g / cm 3 .

[0229] Negative electrode

[0230] 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.

[0231] 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.

[0232] In some embodiments, the negative electrode current collector may be the composite current collector of the first aspect of the present application.

[0233] In some embodiments, the negative electrode current collector may also be a metal foil or other composite current collector. For example, copper foil may be used as the metal foil. Other composite current collectors may 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 may 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.

[0234] 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.

[0235] In some embodiments, the negative electrode active material layer may further include a negative electrode binder. The negative electrode 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).

[0236] 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.

[0237] 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)).

[0238] 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 negative electrode 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 2000 to 10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75 to 220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~1.8g / cm 3 .

[0239] electrolytes

[0240] 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.

[0241] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0242] 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).

[0243] 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.

[0244] 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.

[0245] 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.

[0246] Isolation film

[0247] 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 separator with a multi-perforated structure having good chemical and mechanical stability can be selected.

[0248] 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.

[0249] In some embodiments, the isolation film has a thickness of 6 to 40 μm, and may optionally be 12 to 20 μm.

[0250] 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.

[0251] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0252] 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.

[0253] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0254] 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.

[0255] 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, FIG9 shows a battery cell 5 with a square structure as an example.

[0256] In some embodiments, referring to Figure 10, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 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 51 has an opening connected to the receiving cavity, and the cover plate 53 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 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0257] The secondary battery may be a battery module 4 or a battery pack 1 .

[0258] 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.

[0259] Figure 11 shows an example battery module 4. Referring to Figure 11 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0260] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0261] 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.

[0262] Figures 12 and 13 illustrate an example battery pack 1. Referring to Figures 12 and 13 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0263] 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.

[0264] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0265] Figure 14 shows an example of an electric device 6. 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.

[0266] 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.

[0267] Example

[0268] Below, the embodiment of the present application is described. The embodiment described below is exemplary, is only used to explain the present application, and is not to be construed as limiting the present application. Where the technology or conditions are not specified in the embodiment, the technology or conditions described in the literature in this area or the product instructions are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0269] Example 1

[0270] (1) Preparation of composite current collector

[0271] ① Grooves were etched on both sides of an aluminum foil with a thickness of 10 μm, and then the aluminum foil was passivated with sodium chromate to obtain a conductive layer.

[0272] ② A polyurethane-containing slurry is coated on the groove-containing side surface of the conductive layer to form a slurry layer with a coating thickness of 1.5 μm, and a bonding layer is formed after drying to obtain a composite layer.

[0273] ③ The composite layer was hot-pressed with a support layer having a thickness of 8 μm, and the adhesive layer was brought into contact with the support layer. The composite layer was aged at 85° C. for 72 hours to obtain a composite current collector having a single-sided composite conductive layer.

[0274] ④ Repeat ② to ③, hot-press the other side of the 8μm support layer and the composite layer, and age them at 85°C for 72 hours, and then chemically thin the aluminum layer to obtain the final composite current collector.

[0275] (2) Preparation of positive electrode sheet

[0276] LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiNi 0.5 Co 0.2 Mn 0.3 O2 is mixed in a ratio of 17:3 as a positive electrode active material. The positive electrode active material, superconductive carbon black SP as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder are dispersed in a mass ratio of 95:3:2 in N-methylpyrrolidone (NMP) as a solvent and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on both sides of the composite current collector prepared in step (1), and after drying and cold pressing, a positive electrode sheet is obtained.

[0277] (3) Preparation of negative electrode sheet

[0278] The negative electrode active material graphite, thickener sodium carboxymethyl cellulose, binder styrene-butadiene rubber, and conductive agent acetylene black were mixed in a mass ratio of 97:1:1:1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on both sides of the copper foil; the copper foil was dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then super-cold pressed and cut to obtain a negative electrode sheet.

[0279] (4) Isolation film

[0280] A 12μm thick polypropylene isolation film was selected.

[0281] (5) Preparation of electrolyte

[0282] The organic solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with the volume ratio of EC, EMC, and DEC being 20:20:60. In an argon atmosphere glove box with a water content of <10 parts per million (ppm), fully dried lithium salt LiPF6 is dissolved in the organic solvent and mixed thoroughly to obtain an electrolyte solution. The concentration of the lithium salt is 1 mol / L.

[0283] (6) Preparation of batteries

[0284] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation. The cells are then wound into square bare cells and placed in an aluminum shell. After being baked at 80°C to remove water, the corresponding non-aqueous electrolyte is injected. After standing, forming, secondary liquid injection, sealing, capacity measurement, and blue film wrapping, a battery is obtained.

[0285] Examples 2 to 31

[0286] The preparation process is similar to that of Example 1, except that the parameters of the composite current collector are adjusted. See Table 1 below for details.

[0287] Comparative Example 1

[0288] The preparation process is similar to that of Example 1, except that in step ①, grooves are not etched on the double-side surfaces of the aluminum foil, that is, no protrusions are provided on the bonding layer.

[0289] Table 1

[0290] In addition, the composite current collectors and batteries obtained in Examples 1 to 31 and Comparative Example 1 were subjected to performance tests. The test results are shown in Table 2 below.

[0291] Test section

[0292] (1) Test of the height and size of the first and second raised parts

[0293] The composite current collector was sampled by ion milling (CP) and then observed by scanning electron microscopy (SEM) to measure the heights of the first protrusion and the second protrusion; the sizes of the first protrusion and the second protrusion were measured by directly observing the metal foil under the SEM.

[0294] (2) Adhesion test of conductive layer

[0295] After laminating the sample to the non-corona surface of an ethylene-acrylic acid copolymer (EAA) film, a 12μm-thick PET film was then placed on the EAA film. The film was then placed on a heat sealer and laminated at a temperature of 120 degrees Celsius (°C) and a pressure of 0.2 MPa. The laminated sample was cut into 100mm long and 20mm wide samples, and the non-laminated surface of the conductive layer was attached to a steel plate using 3M double-sided tape. The sample was clamped in the fixture of a tensile testing machine with a spacing of 50mm and a speed of 300 millimeters / minute (mm / min) for a 180°C peel test. The peel force was read and converted into N / m. Five parallel samples were tested, and the average peel force was finally taken. The average peel force = the sum of the peel forces of the five test samples / 5, which is the bonding strength.

[0296] (3) Conductive layer peeling ratio test

[0297] Cut the sample into a width of ≥20mm and a length greater than 100mm, secure it to a steel plate with double-sided tape, and apply a 20mm wide tape (adhesive force ~200N / m) to the sample surface. Perform a peel test at a speed of 500mm / min through 180°. Simultaneously, observe the metal shavings remaining on the tape under a microscope and read the area of ​​the metal shavings. Sum the areas of all fallen metal shavings to obtain the area of ​​conductive layer detachment for each current collector. Divide the conductive layer detachment area by the total tape stripping area to obtain the conductive layer detachment ratio.

[0298] (4) Cycle test

[0299] A fresh battery cell is cycled at a 1C rate of charge and discharge at a high temperature of 60°C until the capacity decays to 80% of the initial capacity. The corresponding number of cycles is recorded, which is the corresponding cycle performance of the battery.

[0300] (5) DC resistance (DCR) test

[0301] Adjust the battery cells to 50% SOC and discharge them at a rate of 4C (corresponding to a discharge current of I) for 30 seconds. Record the voltage difference ΔV before and after the 30-second discharge. Calculate the DCR corresponding to 50% SOC using the following formula: DCR = ΔV / I, and obtain the DCR data for each battery cell.

[0302] Table 2

[0303] Comparing the embodiment with comparative example 1, it can be seen that the adhesion and peeling ratio of the conductive layer of the composite current collector in the embodiment are better than those in comparative example 1. At the same time, the number of cycles and DCR impedance of the battery at 60°C are also better than those in comparative example 1, indicating that compared with conventional composite current collectors, the composite current collector of the present application is beneficial to improving the adhesion and cycle performance of the battery.

[0304] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0305] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite current collector comprising: Support layer; and An adhesive layer and a conductive layer are sequentially stacked on at least one side surface of the support layer. The adhesive layer includes an adhesive layer body and a protruding portion. The protruding portion protrudes outward along the thickness direction of the adhesive layer and is embedded in the conductive layer.

2. The composite current collector according to claim 1, wherein: There are a plurality of protrusions, and the plurality of protrusions are arranged at intervals.

3. The composite current collector according to claim 1 or 2, wherein: The protrusions include a first protrusion and / or a second protrusion. The protrusion height of the first protrusion is less than the thickness of the conductive layer. The protrusion height of the second protrusion is equal to the thickness of the conductive layer.

4. The composite current collector according to claim 3, wherein: The first protrusion includes a first sub-protrusion and / or a second sub-protrusion, the orthographic projection of the first sub-protrusion on the surface of the conductive layer includes a hole shape, and the orthographic projection of the second sub-protrusion on the surface of the conductive layer includes a stripe shape.

5. The composite current collector according to claim 4, wherein: Satisfy at least one of the following conditions: (1) The hole shape includes one or more of a circular hole, an elliptical hole, a fan-shaped hole, an arcuate hole and a polygonal hole; (2) The stripe shape includes one or more of elliptical stripes, polygonal stripes, arc stripes and wavy stripes.

6. The composite current collector according to claim 4 or 5, wherein: An angle included by an orthographic projection of the first sub-protrusion on the surface of the conductive layer is ≥45°.

7. The composite current collector according to any one of claims 4 to 6, wherein: The first sub-protrusion satisfies at least one of the following conditions: (1) The height h1 of the first sub-protrusion and the width d1 of the first sub-protrusion satisfy the following: 0.001%≤h1 / d1≤1%; (2) The width d1 of the first sub-protrusion and the interval Δx1 between two adjacent first sub-protrusions satisfy the following relationship: 3.6%≤d1 / Δx1≤40%.

8. The composite current collector according to any one of claims 4 to 7, wherein: The first sub-protrusion satisfies at least one of the following conditions: (1) The protrusion height h1 of the first sub-protrusion is 50 nm to 500 nm; (2) The width d1 of the first sub-protrusion is 0.2 mm to 20 mm; (3) The distance Δx1 between two adjacent first sub-protrusions is 5 mm to 50 mm.

9. The composite current collector according to any one of claims 4 to 8, wherein: The stripe shape includes alternately distributed stripes or mutually intersecting stripes, and can be selected as mutually intersecting stripes, and further can be selected as grid-shaped intersecting stripes.

10. The composite current collector according to claim 9, wherein: The mutually intersecting stripes contain at least one intersection.

11. The composite current collector according to claim 10, wherein: The intersection satisfies at least one of the following conditions: (1) The orthographic projection of the intersection on the surface of the conductive layer includes one or more of a circle, an ellipse and a polygon; (2) The angle included by the orthographic projection of the intersection on the surface of the conductive layer is ≥ 45°.

12. The composite current collector according to any one of claims 4 to 11, wherein: The second sub-protrusion satisfies at least one of the following conditions: (1) The protrusion height h2 of the second sub-protrusion is 50 nm to 500 nm; (2) The width d2 of the second sub-protrusion is 3 mm to 20 mm; (3) The distance Δx2 between two adjacent second sub-protrusions is 15 mm to 70 mm.

13. The composite current collector according to any one of claims 3 to 12, wherein: At least one first protrusion is disposed between two adjacent second protrusions.

14. The composite current collector according to claim 13, wherein: The total area S2 of the orthographic projection of the second protrusion on the surface of the conductive layer and the total area S1 of the orthographic projection of the first protrusion on the surface of the conductive layer satisfy: S2 <S1。 15. The composite current collector according to claim 13 or 14, wherein: The total area S2 of the orthographic projections of the second protrusions on the surface of the conductive layer and the total area S1 of the orthographic projections of the first protrusions on the surface of the conductive layer satisfy the following: S1 / (S1+S2)≥95%.

16. The composite current collector according to any one of claims 3 to 15, wherein: The second protrusion satisfies at least one of the following conditions: (1) The width d3 of the second protrusion is 30 μm to 600 μm; (2) The distance Δx3 between two adjacent second protrusions is 10 mm to 100 mm.

17. The composite current collector according to any one of claims 3 to 16, wherein: Satisfy at least one of the following conditions: (1) the orthographic projection of the second protrusion on the surface of the conductive layer includes one or more of a circular hole, an elliptical hole, a fan-shaped hole, an arcuate hole and a polygonal hole; (2) An angle included by an orthographic projection of the second protrusion on the surface of the conductive layer is ≥ 45°.

18. The composite current collector according to any one of claims 1 to 17, wherein: The raised portion contains an adhesive.

19. The composite current collector according to claim 18, wherein: The binder includes one or more of a composition containing multifunctional isocyanate and polyester polyol compounds, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide.

20. The composite current collector according to any one of claims 1 to 19, wherein: Satisfy at least one of the following conditions: (1) The thickness of the conductive layer is 0.5 μm to 5 μm; (2) The thickness of the adhesive layer body is 0.5 μm to 3 μm; (3) The thickness of the support layer is 2 μm to 15 μm.

21. The composite current collector according to any one of claims 1 to 20, wherein: Satisfy at least one of the following conditions: (1) The peeling ratio of the conductive layer is ≤1 mm 2 / 2000mm 2 ; (2) The adhesive force of the conductive layer is ≥220 N / m.

22. The composite current collector according to any one of claims 1 to 21, wherein: Satisfy at least one of the following conditions: (1) The support layer comprises one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyformaldehyde, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their cross-linked products and their copolymers; (2) The adhesive layer comprises one or more of a composition containing a multifunctional isocyanate and a polyester polyol compound, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, modified polyethylene, modified polypropylene, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide; (3) The conductive layer comprises one or more of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium and tin.

23. A pole piece, comprising the composite current collector according to any one of claims 1 to 22.

24. A secondary battery comprising the electrode sheet according to claim 23.

25. An electrical device comprising the secondary battery according to claim 24.

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