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

Abstract

The invention provides a composite current collector, a pole piece, a secondary battery and a power utilization device, the cycle performance of the secondary battery can be improved, the composite current collector comprises a supporting layer, and a bonding layer and a conductive layer which are sequentially laminated on at least one side surface of the supporting layer, and the bonding layer comprises a bonding layer main body and a convex part; the protruding part protrudes in the thickness direction of the bonding layer and is embedded in the conductive layer. According to the composite current collector provided by the invention, the bonding force between the bonding layer and the conductive layer can be improved, so that the cycle performance of the battery using the composite current collector can be improved.

Description

Technical Field

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

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

[0003] In recent years, with the increasingly wide application range of secondary batteries represented by lithium-ion batteries, secondary batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the great development of secondary batteries, higher requirements are also put forward for their energy density, cycle performance, safety performance, etc. In a secondary battery, as a component carrying the active material, the current collector has a great influence on the electrochemical performance of the battery. However, currently commonly used composite current collectors usually have the problem of poor adhesion between layers, which easily leads to problems such as a significant drop in the performance of the battery cell and poor cycle performance when used in a battery. Summary of the Invention

[0004] 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.

[0005] To achieve the above object, a first aspect of the present application provides a composite current collector, including: a support layer, and a bonding layer and a conductive layer sequentially stacked on at least one surface of the support layer, the bonding layer includes a bonding layer main body and a convex portion, and the convex portion protrudes outward along the thickness direction of the bonding layer and is embedded in the conductive layer.

[0006] In some embodiments of the present application, there are a plurality of the convex portions, and the plurality of convex portions are spaced apart.

[0007] In some embodiments of the present application, the convex portion includes a first convex portion and / or a second convex portion, the convex height of the first convex portion is less than the thickness of the conductive layer, and the convex height of the second convex portion is equal to the thickness of the conductive layer.

[0008] In some embodiments of the present application, the first convex portion includes a first sub-convex portion and / or a second sub-convex portion, the orthographic projection of the first sub-convex portion on the surface of the conductive layer includes a hole shape, and the orthographic projection of the second sub-convex portion on the surface of the conductive layer includes a stripe shape;

[0009] Optionally, the hole shape includes one or more of a circular hole, an oval hole, a fan-shaped hole, a bow-shaped hole, and a polygonal hole, and may be a circular hole and / or an oval hole;

[0010] Optionally, the stripe shape includes one or more of oval stripes, polygonal stripes, arc stripes, and wavy stripes, and may be oval stripes optionally.

[0011] In some embodiments of the present application, the angle included in the orthographic projection of the first sub-protrusion on the surface of the conductive layer is ≥45°.

[0012] In some embodiments of the present application, the first sub-protrusion satisfies at least one of the following conditions:

[0013] (1) The following is satisfied between the protrusion height h1 and the width d1 of the first sub-protrusion: 0.001% ≤ h1 / d1 ≤ 1%;

[0014] (2) The following is satisfied between the width d1 of the first sub-protrusion and the spacing Δx1 between two adjacent first sub-protrusions: 3.6% ≤ d1 / Δx1 ≤ 40%.

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

[0016] (1) The protrusion height h1 of the first sub-protrusion is 50 nm to 500 nm;

[0017] (2) The width d1 of the first sub-protrusion is 0.2 mm to 20 mm;

[0018] (3) The spacing Δx1 between two adjacent first sub-protrusions is 5 mm to 50 mm.

[0019] In some embodiments of the present application, the stripe shape includes alternately distributed stripes or intersecting stripes, and may be intersecting stripes optionally, and may further be stripes intersecting in a grid shape.

[0020] In some embodiments of the present application, at least one intersection part is included in the intersecting stripes;

[0021] Optionally, the orthographic projection of the intersection part 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 optionally;

[0022] Optionally, the angle included in the orthographic projection of the intersection part on the surface of the conductive layer is ≥45°.

[0023] In some embodiments of the present application, the second sub-protrusion satisfies at least one of the following conditions:

[0024] (1) The protrusion height h2 of the second sub-protrusion is 50 nm to 500 nm;

[0025] (2) The width d2 of the second sub-protrusion is 3 mm to 20 mm;

[0026] (3) The spacing Δx2 between two adjacent second sub-protrusions is 15 mm to 70 mm.

[0027] In some embodiments of the present application, at least one of the first protrusions is provided between two adjacent second protrusions;

[0028] Optionally, 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;

[0029] Optionally, S1 and S2 satisfy: S1 / (S1 + S2) ≥ 95%.

[0030] In some embodiments of the present application, the second protrusion satisfies at least one of the following conditions:

[0031] (1) The width d3 of the second protrusion is 30 μm to 600 μm;

[0032] (2) The spacing Δx3 between two adjacent second protrusions is 10 mm to 100 mm.

[0033] 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 oval hole, a sector hole, a bow-shaped hole, and a polygonal hole, and may be a circular hole and / or an oval hole;

[0034] Optionally, the angle included in the orthographic projection of the second protrusion on the surface of the conductive layer is ≥ 45°.

[0035] In some embodiments of the present application, the protrusion contains a binder;

[0036] Optionally, the binder includes one or more of a composition containing a polyfunctional 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;

[0037] Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0038] In some embodiments of the present application, at least one of the following conditions is satisfied:

[0039] (1) The thickness of the conductive layer is 0.5 μm to 5 μm;

[0040] (2) The thickness of the main body of the bonding layer is 0.5 μm to 3 μm;

[0041] (3) The thickness of the support layer is 2 μm to 15 μm.

[0042] In some embodiments of the present application, at least one of the following conditions is satisfied:

[0043] (1) The peeling ratio of the conductive layer ≤ 1 mm 2 / 2000 mm 2 ;

[0044] (2) The adhesion of the conductive layer ≥ 220 N / m.

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

[0046] (1) The support layer includes one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene styrene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, sulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their crosslinked products and their copolymers;

[0047] (2) The bonding layer includes one or more of a composition containing polyfunctional isocyanate and polyester polyol compounds, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea resin, modified polyolefin resin, modified polyethylene, modified polypropylene, silicone resin, ethylene-acrylic copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide.

[0048] Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane;

[0049] (3) The conductive layer includes one or more of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium and tin.

[0050] The second aspect of the present application provides a pole piece, including the composite current collector described in the first aspect of the present application.

[0051] The third aspect of the present application provides a secondary battery, including the electrode sheet described in the second aspect of the present application.

[0052] The fourth aspect of the present application provides an electrical device, including the secondary battery of the third aspect of the present application.

[0053] The electrical 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.

[0054] Details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the present application will become apparent from the specification, the drawings, and the claims.

[0055] The composite current collector provided by the present application is provided with the raised portion in the adhesive layer, which can increase the surface area of contact between the adhesive layer and the conductive layer, enhance the adhesion of the adhesive layer to the conductive layer, thereby improving the adhesion force between the adhesive layer and the conductive layer, effectively reducing the detachment of the conductive layer, and further improving the cycling performance of the battery cell using the composite current collector. At the same time, the increase in the contact surface area between the adhesive layer and the conductive layer can also reduce the probability of defects in the conductive layer, and there are fewer cracks under the same tensile extension, which is beneficial to reducing the growth rate of sheet resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] To better describe and illustrate the embodiments or examples provided by the present application, one or more drawings may be referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, and the currently understood best mode of these applications. Moreover, in all the drawings, the same reference numerals are used to denote the same components. In the drawings:

[0057] Figure 1 is a schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0058] Figure 2 is a schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0059] Figure 3 is a schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0060] Figure 4 is a schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0061] Figure 5 is a schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

[0062] Figure 6 is a schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

[0063] Figure 7 Schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

[0064] Figure 8 Schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

[0065] Figure 9 Schematic diagram of a battery cell according to an embodiment of the present application.

[0066] Figure 10 is Figure 9 Exploded view of the battery cell shown in an embodiment of the present application.

[0067] Figure 11 Schematic diagram of a battery module according to an embodiment of the present application.

[0068] Figure 12 Schematic diagram of a battery pack according to an embodiment of the present application.

[0069] Figure 13 is Figure 12 Exploded view of the battery pack shown in an embodiment of the present application.

[0070] Figure 14 Schematic diagram of an electrical device powered by a secondary battery according to an embodiment of the present application.

[0071] Explanation of reference numerals:

[0072] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device; 11 Support layer; 12 Adhesive layer; 13 Conductive layer; 121, Adhesive layer main body; 122 Protrusion; 1221 First protrusion; 1222 Second protrusion; 12211 First sub-protrusion; 12212 Second sub-protrusion. Detailed description of specific embodiments

[0073] Hereinafter, some embodiments of the composite current collector, secondary battery, and electrical device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying 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 recited in the claims.

[0074] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or exclude the end values. Any end value can be independently included or excluded, and any combination can be made, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4, and 5 are also listed, the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when a certain parameter is expressed as an integer ≥2, it is equivalent to listing the parameter as integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a certain parameter is expressed as an integer selected from "2 - 10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0075] In this application, when it comes to "a plurality of", "a variety of", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0076] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0077] Referring to "embodiment" in this text means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment or implementation manner of this application. The occurrence of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. The understanding of "implementation manner" mentioned in this text is similar.

[0078] Those skilled in the art can understand that in the methods of various embodiments or examples, the written order of each step does not mean a strict execution order that constitutes any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Without special instructions, all steps of this application can be carried out in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out in sequence, or may also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may also include steps (a), (c), and (b), or may also include steps (c), (a), and (b), etc.

[0079] In this application, in an open technical feature or technical solution described by words such as "containing", "comprising", "including", etc., without other instructions, additional members other than the listed members are not excluded, and it can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that also includes additional members outside the listed members. For example, A includes a1, a2, and a3. Without other instructions, it may also include other members or may not include additional members, and it can be regarded as providing both a feature or solution of "A is composed of a1, a2, and a3" and a feature or solution of "A not only includes a1, a2, and a3, but also includes other members". In this application, without other instructions, A (such as B) means that B is a non-limiting example in A, and it can be understood that A is not limited to B.

[0080] In this application, "optionally", "optional", "option" mean that it can be either present or absent, that is, it refers to either of the two parallel options of "present" or "absent". If "optional" appears multiple times in a technical solution, without special instructions and without contradictions or mutual constraints, each "optional" is independent of each other.

[0081] Currently, a metal is used as a conductive layer and is combined with a polymer material layer to form a composite current collector with a "metal / polymer material / metal" sandwich structure. When it is used in a battery, it can improve the battery energy density, reduce costs, and make the battery lighter. During the preparation process of this composite current collector, a binder is usually introduced to bond the conductive layer and the polymer material layer. However, during the process of introducing the binder and combining the conductive layer and the polymer material layer, the binder layer formed by the binder is extremely likely to form bubbles or pores with the conductive layer, resulting in poor adhesion of the binder layer, and thus leading to problems such as the shedding of the conductive layer during the processing of the battery cell and during the cyclic use of the battery cell, resulting in a significant drop in the performance of the battery cell.

[0082] To solve the above technical problems, the present application proposes a composite current collector. By providing a raised portion on the surface of the adhesive layer adjacent to the conductive layer, the surface area of contact between the adhesive layer and the conductive layer can be increased, thereby enhancing the adhesion between the adhesive layer and the conductive layer, and further improving the cycling performance of the battery cell using this composite current collector. The following will provide a more detailed description of this composite current collector.

[0083] In a 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 sequentially laminated on at least one surface of the support layer 11. The adhesive layer 12 includes an adhesive layer main body 121 and a raised portion 122, and the raised portion 122 protrudes outward along the thickness direction of the adhesive layer 12 and is embedded in the conductive layer 13.

[0084] It can be understood that the raised portion protrudes in a direction away from the adhesive layer main body along the thickness direction of the adhesive layer.

[0085] It should be noted that the "surface of the conductive layer" or "the surface of the conductive layer" referred to in the present application refers to the surface perpendicular to the thickness direction of the current collector of the conductive layer, that is, the surface adjacent (or in contact) to the adhesive layer of the conductive layer. The "area of the surface of the conductive layer" refers to the area of the surface adjacent (or in contact) to the adhesive layer of the conductive layer.

[0086] In the composite current collector provided by the present application, the above-mentioned raised portion is provided in the adhesive layer, which can increase the surface area of contact between the adhesive layer and the conductive layer, enhance the adhesion of the adhesive layer to the conductive layer, thereby improving the adhesion between the adhesive layer and the conductive layer, effectively reducing the peeling off of the conductive layer, and further improving the cycling performance of the battery cell using this composite current collector. At the same time, the increase in the 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 extension, there are fewer cracks, which is conducive to reducing the growth rate of sheet resistance.

[0087] In some embodiments, there are multiple raised portions, and the multiple raised portions are arranged at intervals.

[0088] It can be understood that the multiple raised portions are arranged at intervals, which means that there is a gap (spacing) between any two adjacent raised portions.

[0089] The multiple raised portions arranged at intervals can, while improving the adhesion between the adhesive layer and the conductive layer, enable the conductive layer and the composite current collector to have sufficient mechanical strength, thereby enhancing the structural stability of the composite current collector.

[0090] In some embodiments, the total area S' of the orthographic projection of the raised portion 122 on the surface of the conductive layer 13 and the area S of the surface of the conductive layer 13 satisfy: S' < S.

[0091] The total area S' of the orthographic projection of the convex portion on the surface of the conductive layer is smaller than the area S of the surface of the conductive layer, which can improve the adhesion between the adhesive layer and the conductive layer while enabling the conductive layer and the composite current collector to have sufficient mechanical strength, thereby enhancing the structural stability of the composite current collector.

[0092] In some embodiments, the convex portion includes a first convex portion and / or a second convex portion. The height of the first convex portion is less than the thickness of the conductive layer, and the height of the second convex portion is equal to the thickness of the conductive layer.

[0093] The height of the first convex portion being less than the thickness of the conductive layer can improve the adhesion between the adhesive layer and the conductive layer while enabling the conductive layer and the composite current collector to have sufficient mechanical strength.

[0094] The height of the second convex portion is equal to the thickness of the conductive layer, that is, the second convex portion penetrates the conductive layer along the thickness direction of the composite current collector. At this time, the second convex portion can play a role in exhausting air and reducing bubbles in the adhesive layer. For example, if there are bubbles between the conductive layer and the adhesive layer, it is likely to cause a decrease in the adhesion between the conductive layer and the adhesive layer, and the conductive layer is likely to peel off. If there are bubbles between the adhesive layer and the support layer, it is likely to cause a decrease in the adhesion between the adhesive layer and the support layer, and the whole composed of the conductive layer and the adhesive layer is likely to peel off from the support layer. And setting the second convex portion that penetrates the conductive layer is beneficial to exhausting the bubbles between the adhesive layer and the support layer and between the adhesive layer and the conductive layer, thereby further improving the adhesion between the adhesive layer and the support layer and between the adhesive layer and the conductive layer.

[0095] In some embodiments, reference may be made to Figure 2 , the convex portion 122 includes a first convex portion 1221.

[0096] In some embodiments, reference may be made to Figure 3 , the shown convex portion 122 includes a second convex portion 1222.

[0097] In some embodiments, reference may be made to Figure 4 , the convex portion 122 includes a first convex portion 1221 and a second convex portion 1222.

[0098] In some embodiments, the convex portion contains an adhesive.

[0099] It should be noted that when the convex portion includes a first convex portion and a second convex portion, the adhesives in the first convex portion and the second convex portion may be the same or different.

[0100] The raised portion includes a first raised portion and / or a second raised portion. Among them, the first raised portion can increase the wettability of the conductive layer to the binder, and the filling of the binder in the raised portion can increase the surface area of contact between the conductive layer and the adjacent bonding layer, thereby enhancing the bonding force between the bonding layer and the conductive layer.

[0101] In addition to increasing the surface area of contact between the conductive layer and the adjacent bonding layer, the second raised portion also helps to discharge the bubbles or pores formed between the bonding layer and the conductive layer during the process of introducing the binder to form the bonding layer, enabling the bonding layer to better adhere to the conductive layer, thereby enhancing the bonding force between the bonding layer and the conductive layer, effectively reducing the shedding of the conductive layer, and further improving the cycle performance of the battery cell using the composite current collector.

[0102] When the raised portion includes both the first raised portion and the second raised portion, the interfacial contact between the conductive layer and the bonding layer can be made closer, which helps to further enhance the bonding force.

[0103] In some embodiments, the binder includes one or more of a composition containing polyfunctional 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.

[0104] In some embodiments, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0105] In some embodiments, the first raised portion 1221 includes a first sub-raised portion 12211 and / or a second sub-raised portion 12212.

[0106] It can be understood that when the raised portion 122 includes the first raised portion 1221, the bonding layer 12 can be provided with only the first sub-raised portion 12211 (see Figure 5 and Figure 6 ), or only the second sub-raised portion 12212 can be provided (see Figure 7 and Figure 8 ), or a combination of the first sub-raised portion 12211 and the second sub-raised portion 12212 can also be provided.

[0107] When the first sub-raised portion and the second sub-raised portion are combined, it can achieve a better effect of enhancing the bonding force, and at the same time, the composite current collector can have sufficient mechanical strength.

[0108] In some embodiments, the orthographic projection of the first sub-raised portion 12211 on the surface of the conductive layer 13 includes a hole shape (see Figure 5 and Figure 6)。

[0109] It can be understood that the "hole shape" or "hole" described in this application refers to a shape with a regular or irregular bounded shape or a closed planar geometric figure in the orthographic projection on the surface of the conductive layer. For example, a "circular hole" refers to a circular shape in the orthographic projection, and a "sector hole" refers to a sector shape in the orthographic projection.

[0110] In some embodiments, the hole shape includes, but is not limited to, one or more of a circular hole, an oval hole (see Figure 6 ), a sector hole, a bow-shaped hole, and a polygonal hole (see Figure 5 ), and may be optionally a circular hole and / or an oval hole.

[0111] It can be understood that the orthographic projection of the first sub-protrusion on the surface of the conductive layer includes a hole shape. At this time, the first sub-protrusions are in a discrete distribution (or alternating distribution) pattern, and there is no intersection and there is a gap between any two first sub-protrusions.

[0112] It can be understood that the "bow shape" described in this application refers to a figure enclosed by an arc and the chord it faces.

[0113] When the hole shape includes a circular hole and / or an oval hole, the first sub-protrusion does not include an acute tip. At this time, the binder 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 detachment of the conductive layer.

[0114] In some embodiments, the angle included in the orthographic projection of the first sub-protrusion on the surface of the conductive layer ≥ 45°.

[0115] It can be understood that the angle included in the orthographic 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 ≥ 45°; when the hole shape is a sector or a bow shape, the central angle corresponding to the sector or the bow shape ≥ 45°.

[0116] The angle included in the orthographic projection of the first sub-protrusion on the surface of the conductive layer ≥ 45° helps to more completely infiltrate and fill the protrusion with the binder, reduce the problem that the tip of the protrusion is not easily infiltrated by the binder, improve the adhesion of the adhesive layer to the conductive layer, and reduce the detachment of the conductive layer.

[0117] In some embodiments, the protrusion height h1 of the first sub-protrusion (see Figure 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 within the range composed of any of the above values.

[0118] 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.

[0119] When the protrusion height of the first sub-protrusion is within the above range, on the one hand, the binder can better infiltrate and fill the protrusion, thereby further improving the adhesion of the adhesive layer to the conductive layer and further enhancing the adhesion force between the two. On the other hand, it can also reduce the impact on the conductivity of the conductive layer.

[0120] In some embodiments, the width d1 of the first sub-protrusion (see Figure 5 and Figure 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 within the range composed of any of the above values.

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

[0122] 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 sector hole or a bow-shaped hole), or the maximum side length of the contour (when the orthographic projection is a polygonal hole).

[0123] In some embodiments, the spacing Δx1 between two adjacent first sub-protrusions (see Figure 2 ) is 5 mm to 50 mm. For example, the spacing 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 within the range composed of any of the above values.

[0124] It should be noted that the "spacing between two adjacent first sub-protrusions" refers to the horizontal distance between the center points of two adjacent first sub-protrusions. It can be understood that the "horizontal" here refers to the direction perpendicular to the thickness of the current collector and parallel to the surface of the conductive layer.

[0125] The distance between two adjacent first sub-protrusions is within the above range. On the one hand, it can enable the adhesive to better infiltrate and fill the protrusions, thereby further enhancing the adhesion of the adhesive layer to the conductive layer and further improving the adhesion force between the two. On the other hand, it can also reduce the impact on the conductivity of the conductive layer.

[0126] In some embodiments, the following relationship is satisfied between the protrusion height h1 and the width d1 of the first sub-protrusion: 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 within the range composed of any of the above values.

[0127] When the relationship between the protrusion height and width of the first sub-protrusion is satisfied as above, the wettability of the adhesive in the protrusion can be enhanced, avoiding dead corners that are difficult to infiltrate, enabling the adhesive to infiltrate to the top of the protrusion, and achieving as much as possible the complete infiltration and filling of the protrusion by the adhesive; in this way, the gap between the top of the protrusion and the adjacent conductive layer can be reduced, and the adhesion force between the adhesive layer and the conductive layer can be improved.

[0128] In some embodiments, the following relationship is satisfied between the width d1 of the first sub-protrusion and the distance Δx1 between two adjacent first sub-protrusions: 3.6% ≤ d / Δx ≤ 40%. For example, d1 / Δx1 can be 3.6%, 7%, 9%, 10%, 20%, 25%, 30%, 35%, 40% or within the range composed of any of the above values.

[0129] When the relationship between the width of the first sub-protrusion and the distance between two adjacent first sub-protrusions is satisfied as above, the wettability of the adhesive in the protrusion can be enhanced, avoiding dead corners that are difficult to infiltrate, and achieving as much as possible the complete infiltration and filling of the protrusion by the adhesive; in this way, the gap at the bottom of the protrusion can be reduced, and the adhesion force between the adhesive layer and the conductive layer can be improved. If the distance between two adjacent first sub-protrusions is relatively large, the effect of enhancing the surface energy of the conductive layer is relatively low, which will reduce the infiltration effect of the adhesive in the protrusion; if the distance between two adjacent first sub-protrusions is relatively small, the distance between the protrusions is relatively narrow, which is likely to form narrow protrusions and lead to a relatively low effect of enhancing the surface energy of the conductive layer, thereby reducing the infiltration effect of the adhesive in the protrusion.

[0130] In some embodiments, the orthographic projection of the second sub-protrusion 12212 on the surface of the conductive layer includes a stripe shape (see Figure 7 and Figure 8 ).

[0131] The stripe shape can further increase the contact area between the conductive layer and the adhesive layer, and further enhance the wettability of the convex surface, which helps the adhesive achieve better wetting and filling effects in the convexities, thereby further improving the adhesion between the adhesive layer and the conductive layer.

[0132] In some embodiments, the stripe shape includes, but is not limited to, one or more of oval stripes, polygonal stripes, arc stripes, and wavy stripes, and oval stripes are optional.

[0133] The oval stripes can better connect the inside of the second sub-convex part, further enhance the wettability of the convex surface, improve the wetting and filling effects of the adhesive in the convexities, and thereby further improve the adhesion between the adhesive layer and the conductive layer.

[0134] In some embodiments, the stripe shape includes stripes distributed at intervals (see Figure 7 ) or intersecting stripes (see Figure 8 ), and intersecting stripes are optional, and further optionally stripes intersecting in a grid shape.

[0135] It can be understood that the "stripes distributed at intervals" described in this application means that there is no intersection and there is a gap between any two stripes; the "intersecting stripes" means that there is an intersection between the stripes. For example, there is an intersection between horizontally distributed stripes at intervals and vertically distributed stripes at intervals.

[0136] In some embodiments, at least one intersection part is included in the intersecting stripes.

[0137] The intersecting stripes can make the convexities on the whole surface present a connected state, enable the adhesive to flow better inside the convexities, improve the wetting and filling effects of the adhesive in the convexities, and thus improve the adhesion of the adhesive layer to the conductive layer.

[0138] In some embodiments, the orthographic projection of the intersection part 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 a circle and / or an ellipse are optional.

[0139] When the orthographic projection of the intersection part on the surface of the conductive layer includes a circle and / or an ellipse, the intersection part does not include an acute tip. At this time, the adhesive can be more completely wetted and filled in the intersection part, which helps to improve the adhesion of the adhesive layer to the conductive layer and reduce the detachment of the conductive layer.

[0140] In some embodiments, the angle included in the orthographic projection of the intersection part on the surface of the conductive layer ≥ 45°.

[0141] It can be understood that the angle included in the positive projection of the intersection on the surface of the conductive layer ≥ 45°, which means that when the positive projection is a polygon, each angle of the polygon ≥ 45°.

[0142] The angle included in the positive projection of the intersection on the surface of the conductive layer ≥ 45° helps the binder to more completely infiltrate and fill the intersection, reduces the problem that the tip of the intersection is not easily infiltrated by the binder, improves the adhesion of the adhesive layer to the conductive layer, and reduces the detachment of the conductive layer.

[0143] In some embodiments, the protrusion height h2 of the second sub-protrusion (see Figure 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 within the range composed of any of the above values.

[0144] 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.

[0145] In some embodiments, the width d2 of the second sub-protrusion (see Figure 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 within the range composed of any of the above values.

[0146] It should be noted that the "width of the second sub-protrusion" refers to the stripe width. If the stripe is rectangular, it refers to the distance between the two long sides of the rectangle; if the stripe is an irregular shape (such as arc, wavy, etc.), it refers to the maximum value of the width of the irregular shape.

[0147] In some embodiments, the spacing Δx2 between two adjacent second sub-protrusions (see Figure 2 ) is 15 mm to 70 mm. For example, the spacing 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 within the range composed of any of the above values.

[0148] It should be noted that the "spacing between two adjacent second sub-protrusions" refers to the horizontal distance between the centers of two adjacent second sub-protrusions. It can be understood that the "horizontal" here refers to the direction perpendicular to the thickness of the current collector and parallel to the surface of the conductive layer.

[0149] When the height, width of the second sub-protrusion and the distance between two adjacent second sub-protrusions are within the above ranges, on the one hand, it can enable the binder to better infiltrate and fill the protrusions, thereby further improving the adhesion of the adhesive layer to the conductive layer and further enhancing the adhesion force between the two. On the other hand, it can also reduce the impact on the conductivity of the conductive layer.

[0150] In some embodiments, the height h2 of the second sub-protrusion and the width d2 of the second sub-protrusion satisfy: 0.0015% ≤ h2 / d2 ≤ 0.01%. For example, h2 / d2 can be 0.0015%, 0.003%, 0.005%, 0.008%, 0.01% or within the range composed of any of the above values.

[0151] When the height and width of the second sub-protrusion satisfy the above relationship, it can enhance the wettability of the binder in the protrusion, avoid dead corners that are difficult to infiltrate, enable the binder to infiltrate to the bottom of the protrusion, and try to achieve complete infiltration and filling of the protrusion by the binder; in this way, the voids at the bottom of the protrusion can be reduced, and the adhesion force between the adhesive layer and the conductive layer can be improved.

[0152] In some embodiments, the width d2 of the second sub-protrusion and the distance Δx2 between two adjacent second sub-protrusions satisfy: 7.5% ≤ d2 / Δx2 ≤ 28.6%. For example, d2 / Δx2 can be 7.5%, 10%, 20%, 25%, 28.6% or within the range composed of any of the above values.

[0153] When the width of the second sub-protrusion and the distance between two adjacent second sub-protrusions satisfy the above relationship, it can enhance the wettability of the binder in the protrusion, avoid dead corners that are difficult to infiltrate, and try to achieve complete infiltration and filling of the protrusion by the binder; in this way, the voids at the bottom of the protrusion can be reduced, and the adhesion force between the adhesive layer and the conductive layer can be improved.

[0154] In some embodiments, 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: 0.1% ≤ S1 / S ≤ 50%. For example, S1 / S can be 0.1% 1%, 3%, 5%, 7%, 10%, 20%, 30%, 40%, 50% or within the range composed of any of the above values.

[0155] When 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 adhesion force, it can also enable the composite current collector to have sufficient mechanical strength, improve the structural stability of the composite current collector, and improve the safety of the battery cell.

[0156] In some embodiments, at least one of the first protrusions is provided between two adjacent second protrusions.

[0157] The second protrusions and the first protrusions are arranged in an interspersed manner, which can reduce the problem of uneven exhaust during the composite process of the adhesive layer and the conductive layer, or reduce the problem of weakened local conductivity of the conductive layer, so that the composite current collector has better comprehensive performance.

[0158] In some embodiments, the total area S2 of the orthographic projection of the second protrusions on the surface of the conductive layer and the total area S1 of the orthographic projection of the first protrusions on the surface of the conductive layer satisfy: S2 < S1.

[0159] The total area S2 of the orthographic projection of the second protrusions on the surface of the conductive layer and the total area S1 of the orthographic projection of the first protrusions 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 adhesion, but also ensure the performance of the battery cell and improve the safety.

[0160] In some embodiments, S1 and S2 satisfy: S1 / (S1 + S2) ≥ 95%. For example, S1 / (S1 + S2) can be 95%, 97%, 100% or within the range composed of any of the above values.

[0161] The total area S2 of the orthographic projection of the second protrusions on the surface of the conductive layer and the total area S1 of the orthographic projection of the first protrusions on the surface of the conductive layer satisfy the above relationship, which is beneficial to taking into account the exhaust function of the second protrusions and the mechanical properties of the composite current collector. Thus, while improving the adhesion, the composite current collector can also have sufficient mechanical strength, improve the structural stability of the composite current collector, and improve the safety of the battery cell.

[0162] In some embodiments, the width d3 of the second protrusions is 30 μm to 600 μm. For example, the width of the second protrusions can be 30 μm, 60 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm or within the range composed of any of the above values.

[0163] It should be noted that, similar to the width of the first sub-protrusions, the "width of the second protrusions" 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 protrusions on the surface of the conductive layer (when the orthographic projection is a circular hole, an oval hole, a fan-shaped hole or a bow-shaped hole), or the maximum side length of the contour (when the orthographic projection is a polygonal hole).

[0164] In some embodiments, the spacing Δx3 between two adjacent second protrusions (see Figure 3) is from 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 within the range composed of any of the above values.

[0165] It should be noted that the "distance between two adjacent second protrusions" described in this application refers to the horizontal distance between the center points of two adjacent second protrusions. It can be understood that the "horizontal" here refers to the direction perpendicular to the thickness of the current collector and parallel to the surface of the conductive layer.

[0166] The width of the second protrusion and the distance between two adjacent second protrusions being within the above range is beneficial to enhancing the exhaust function of the second protrusion, and helps the binder to more completely infiltrate and fill the protrusion. At the same time, it can also reduce the cracking problem that easily occurs at the position of the second protrusion during the processing of the composite current collector. Thus, while enhancing the bonding force, the conductivity and strength (mechanical) properties of the current collector can be taken into account.

[0167] 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 oval hole, a sector hole, a bow-shaped hole, and a polygonal hole, and can be a circular hole and / or an oval hole.

[0168] When the orthographic projection of the second protrusion on the surface of the conductive layer includes a circular hole and / or an oval hole, the second protrusion does not include an acute-angle tip. At this time, the binder can more completely infiltrate and fill the entire second protrusion, which helps to enhance the bonding force of the bonding layer to the conductive layer and reduce the detachment of the conductive layer.

[0169] In some embodiments, the angle included in the orthographic projection of the second protrusion on the surface of the conductive layer ≥ 45°.

[0170] It can be understood that the angle included in the orthographic projection of the second protrusion on the surface of the conductive layer refers to that when the orthographic projection is a polygon, each angle of the polygon ≥ 45°; when the orthographic projection is a sector or a bow-shaped hole, the central angle corresponding to the sector or the bow-shaped hole ≥ 45°.

[0171] The angle included in the orthographic projection of the second protrusion on the surface of the conductive layer ≥ 45° helps the binder to more completely infiltrate and fill the protrusion, reduces the problem that the tip of the second protrusion is not easily infiltrated by the binder, enhances the bonding force of the bonding layer to the conductive layer, and reduces the detachment of the conductive layer.

[0172] In some embodiments, 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 conductive layer on the surface of the conductive layer satisfy: 0.0003% ≤ S2 / S ≤ 0.29%.

[0173] 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 adhesion, it can also endow the composite current collector with sufficient mechanical strength, improve the structural stability of the composite current collector, and enhance the safety of the battery cell.

[0174] 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 within the range composed of any of the above values.

[0175] In some embodiments, the thickness of the main body of the adhesive layer is 0.5 μm to 3 μm. For example, the thickness of the main body of the adhesive layer can be 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or within the range composed of any of the above values.

[0176] 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 within the range composed of any of the above values.

[0177] When the thicknesses of the support layer, the main body of the adhesive layer, and the conductive layer are respectively within the above ranges, while improving the adhesion, the conductivity and strength (mechanical) properties of the current collector can be taken into account.

[0178] In some embodiments, the peeling ratio of the conductive layer of the composite current collector is ≤ 1 mm 2 / 2000 mm 2 .

[0179] It should be noted that the "peeling ratio of the conductive layer" described in this application refers to the peeling ratio of the conductive layer when the adhesion of the composite current collector is tested, and can be tested by the test method described later.

[0180] When the peeling ratio of the conductive layer is within the above range, the film peeling problem of the composite current collector during electrolyte immersion can be reduced, the long-term stability of the composite current collector can be improved, and finally the long-term stability of the battery can be improved.

[0181] In some embodiments, the adhesion of the conductive layer is ≥ 220 N / m.

[0182] It should be noted that the above "adhesion of the conductive layer" refers to the pulling force required to detach the conductive layer from the composite current collector when the adhesion of the composite current collector is tested, and can be tested by the test method described later.

[0183] When the adhesion of the conductive layer is within the above range, it can not only result in a relatively high adhesion between the adhesive layer and the conductive layer, but also endow the composite current collector with sufficient mechanical properties, reducing the processing defects caused by the decline in mechanical properties during subsequent processing.

[0184] In some embodiments, the support layer includes, but is not limited to, one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene styrene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, sulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their crosslinked products, and their copolymers.

[0185] In some embodiments, the adhesive layer includes one or more of a composition containing polyfunctional isocyanate and polyester polyol compounds, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide.

[0186] In some embodiments, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0187] 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.

[0188] 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 may include the following steps:

[0189] S1. Prepare grooves and / or through holes on at least one surface of the metal foil to form a conductive layer.

[0190] S2. Coat a slurry containing an adhesive on the surface of the conductive layer where the grooves and / or through holes are provided to prepare an adhesive layer, and after drying, form a composite layer containing the adhesive layer and the conductive layer.

[0191] S3. Compose the composite layer containing the adhesive layer and the conductive layer with the support layer to prepare a composite current collector.

[0192] In some embodiments, in step S1, grooves and / or vias can be prepared on at least one surface of the metal foil by etching.

[0193] It can be understood that when the etching depth is less than the thickness of the metal foil, grooves can be prepared; and when the etching depth is equal to the thickness of the metal foil, vias can be prepared.

[0194] In some embodiments, the bonding layer includes a bonding layer main body and a protruding portion, and the protruding portion protrudes along the thickness direction of the bonding layer and is embedded in the conductive layer.

[0195] It can be understood that in step S2, after a slurry containing a binder is coated on the surface of the conductive layer where the grooves and / or vias are provided, the slurry will penetrate into the grooves and / or vias and fill the grooves and / or vias. After the grooves and / or vias are completely filled, a slurry layer can be continuously coated and formed on the surface of the conductive layer, and after drying, the slurry layer forms the bonding layer main body, while the grooves and / or vias filled with the slurry form the protruding portion, and the bonding layer main body and the protruding portion become an integral body to form the bonding layer. Thus, the bonding layer and the conductive layer can be compounded, and the protruding portion is embedded in the conductive layer.

[0196] In some embodiments, the protruding portion includes a first protruding portion and / or a second protruding portion.

[0197] It can be understood that the first protruding portion can correspond to the groove in step S1, while the second protruding portion can correspond to the via in step S1.

[0198] In some embodiments, the composite treatment in step S3 includes: thermally pressing and compounding the composite layer including the bonding layer and the conductive layer with the support layer, wherein the bonding layer in the composite layer is in contact with the support layer.

[0199] The temperature of the thermal pressing and compounding is close to the melting point of the binder, so that the binder is in a fully softened or molten state. The fully softened or molten binder can be better compounded with the support layer and the conductive layer in the composite layer.

[0200] It should be noted that when the protruding portion includes a second protruding portion, on the one hand, the second protruding portion can play a role in removing bubbles when coating the slurry containing the binder, reducing the bubbles and pores between the conductive layer and the bonding layer, and improving the bonding force between the two; on the other hand, during the thermal pressing and compounding, the bubbles can be discharged from the second protruding portion. Therefore, the presence of the second protruding portion can further remove the bubbles and further improve the bonding force.

[0201] In some embodiments, step S1 further includes a process of passivating the conductive layer.

[0202] In some embodiments, the passivating agent for passivation treatment includes one or more of chromate, organic phosphate, aluminum oxide (Al 2 O 3 ), silicon oxide (SiO 2 ), and silicon nitride (Si 3 N 4 ).

[0203] It can be understood that in the above steps, the material of the metal foil, the material of the binder, and the material of the support layer can respectively correspond to the materials included in the conductive layer, the binder material, and the support layer in the first aspect of the present application, which will not be elaborated here.

[0204] In a third aspect, the present application provides an electrode sheet, including 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.

[0205] In some embodiments, the electrode sheet includes a positive electrode sheet and / or a negative electrode sheet.

[0206] 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.

[0207] In addition, the secondary battery and the electrical device of the present application will be described below with appropriate reference to the drawings.

[0208] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0209] Positive electrode sheet

[0210] 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. The positive electrode active material layer includes a positive electrode active material.

[0211] As a non-limiting example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0212] In some of these embodiments, the positive electrode current collector can adopt the composite current collector of the first aspect of the present application.

[0213] In some of these embodiments, the positive current collector introduction may employ a metal foil or other composite current collector. For example, as the metal foil, aluminum foil may be used. 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 current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the positive 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.

[0214] In some of these embodiments, the negative electrode may employ a positive electrode active material for a battery known in the art. As non-limiting examples, the positive electrode active material may include one or more of the following materials: lithium phosphate with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds, etc. Non-limiting examples of the lithium phosphate with an olivine structure may include, but are not limited to, lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon, etc. Non-limiting examples of the lithium cobalt oxide may include LiCoO 2 ; non-limiting examples of the lithium nickel oxide may include LiNiO 2 ; non-limiting examples of the lithium manganese oxide may include LiMnO 2 , LiMn 2 O 4 , etc.; non-limiting examples of the lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which may also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which may also be abbreviated as NCM 523 ), LiNi0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxides can include LiNi 0.85 Co 0.15 Al 0.05 O 2 .

[0215] Regarding the change in the Li content in the cathode material, how to define the subscript of Li in the general formula:

[0216] Regarding the ternary material:

[0217] Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y , where x is 0.2 - 1.2;

[0218] Li x A a (Ni a Co b Mn c ) 1-d M d O 2-y A y , where x + a is 0.2 - 1.2.

[0219] Regarding the lithium iron manganese phosphate material:

[0220] Li a Mn 1-y B y P 1-z C z O 4-n D n , where a is 0 - 1.1;

[0221] Li a A x Mn 1-y B yP 1-z C z O 4-n D n where a + x ranges from 0 to 1.1.

[0222] The above limitation on x includes the molar content of Li under different charge and discharge states of the battery (usually the battery voltage is between 2 - 5V).

[0223] It can be understood that during the charge and discharge process of the battery, the insertion and extraction and consumption of lithium (Li) will occur, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the listing of the positive electrode materials in this application, unless otherwise specified, the content of Li is the initial state of the material. When the positive electrode material is applied to the positive electrode plate in the battery system, after charge and discharge cycling, the content of Li in the positive electrode material contained in the plate usually changes. Among them, the content of Li can be measured by molar content, but is not limited thereto. Regarding "the content of Li is the initial state of the material", the initial state of the material refers to the state before being fed into the positive electrode slurry. It can be understood that new materials obtained by appropriate modification based on the listed positive electrode materials are also within the scope of the positive electrode materials. The aforementioned appropriate modification refers to the acceptable modification methods for the positive electrode materials, and non-limiting examples include coating modification.

[0224] In the listing of the positive electrode materials in this application, the content of oxygen (O) is only the theoretical state value. The release of oxygen from the crystal lattice will cause the molar content of oxygen to change, and the actual content of O will show fluctuations. Among them, the content of O can be measured by molar content, but is not limited thereto.

[0225] In some embodiments, the positive electrode active material may also include at least one of the following materials: sodium transition metal oxides, polyanion-type compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as the positive electrode active material of the sodium ion battery can also be used.

[0226] As an alternative technical solution of this 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. A non-limiting example of the sodium transition metal oxide can be Na x MO 2 , where M may include one or several of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1.

[0227] As an alternative technical solution of this application, the polyanion-type compound may be a compound having sodium ions, transition metal ions, and a tetrahedral shape (YO 4 ) n-A class of compounds with anionic units. The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si; n represents the valence state of (YO 4 ) n- .

[0228] The polyanionic compound can also be a class of compounds with sodium ions, transition metal ions, tetrahedral (YO 4 ) n- anionic units, and halogen anions. The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si, n represents the valence state of (YO 4 ) n- ; the halogen can be one or more of F, Cl, and Br.

[0229] The polyanionic compound can also be a class of compounds with sodium ions, tetrahedral (YO 4 ) n- anionic units, polyhedral units (ZO y ) m+ , and optional halogen anions. Y can be one or more of P, S, and Si, n represents the valence state of (YO 4 ) n- ; Z represents a transition metal, which can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, m represents the valence state of (ZO y ) m+ ; the halogen can be one or more of F, Cl, and Br.

[0230] The polyanionic compound can include NaFePO 4 , Na 3 V 2 (PO 4 ) 3 (sodium vanadium phosphate, abbreviated as NVP), Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), NaM’PO 4 F, and Na 3 (VO y ) 2 (PO 4 ) 2 F 3-2y (0 ≤ y ≤ 1), one or more of them. Among them, NaM’PO4 M' in F may include one or more of V, Fe, Mn, and Ni.

[0231] The Prussian blue compound may be a compound having 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 the Prussian blue compound may be Na a Me b Me' c (CN) 6 , where Me and Me' may each independently be one or more of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0232] 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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0233] In some embodiments, the positive electrode active material layer may further optionally 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.

[0234] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the positive electrode binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one surface of the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained. The type of the solvent can be selected from but not limited to any one of the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector on which the positive electrode slurry is coated can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 - 25000 mPa·s. When coating the positive electrode slurry, the coating unit surface density in terms of dry weight (deducting the solvent) can be 15 - 35 mg / cm 2 . The tap density of the positive electrode plate can be 3.0 - 3.6 g / cm 3 , and can be optionally 3.3 - 3.5 g / cm 3 .

[0235] Negative electrode plate

[0236] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. The negative electrode active material layer includes negative electrode active material.

[0237] As a non-limiting example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0238] In some embodiments, the negative electrode current collector can adopt the composite current collector of the first aspect of the present application.

[0239] In some embodiments, the negative electrode current collector can also adopt a metal foil or other composite current collector. For example, as the metal foil, copper foil can be adopted. Other composite current collectors can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc. In the negative electrode current collector, non-limiting examples of the polymer material substrate can include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0240] In some embodiments, the negative electrode active material can adopt the negative electrode active material for batteries well-known in the art. As a non-limiting example, the negative electrode active material can include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials can include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0241] In some embodiments, the negative electrode active material layer may also optionally include a negative electrode binder. The negative electrode binder can 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).

[0242] In some of these embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0243] In some of these embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0244] In some of these embodiments, the negative electrode plate can be prepared in the following manner: dispersing the above components for preparing the negative electrode plate, such as the negative electrode active material, conductive agent, negative electrode binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one surface of the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained. The surface of the negative electrode current collector on which the negative electrode slurry is coated can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% - 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 - 10000 mPa·s. When coating the negative electrode slurry, the coating unit surface density based on dry weight (after deducting the solvent) can be 75 - 220 g / m 2 . The tap density of the negative electrode plate can be 1.0 g / cm 3 ~1.8 g / cm 3 .

[0245] Electrolyte

[0246] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. There are no particular limitations on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0247] In some of these embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0248] In some of these embodiments, the electrolyte salt may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO 2 F 2) one or more of lithium difluorooxalate borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro diphosphate oxalate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0249] 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), butenyl carbonate one or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0250] In some embodiments, the electrolyte may also optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, etc.

[0251] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl carbonate ethylene (TFPC), etc.

[0252] Separator

[0253] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of the separator, and any well-known multi-perforated structure separator with good chemical stability and mechanical stability can be selected.

[0254] 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.

[0255] In some embodiments, the thickness of the separator is 6-40 μm, and may be optionally 12-20 μm.

[0256] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be made into an electrode assembly by a winding process or a stacking process.

[0257] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0258] In some embodiments, the outer package of the secondary battery can be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. Further, non-limiting examples of the plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0259] The secondary battery includes at least one battery cell. The secondary battery can include one or more battery cells.

[0260] In this application, unless otherwise specified, a "battery cell" refers to a basic unit capable of converting chemical energy and electrical energy into each other. Further, generally, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0261] This application does not particularly limit the shape of the battery cell, and it can be cylindrical, square, or any other shape. For example, Figure 9 is a battery cell 5 with a square structure as an example.

[0262] In some embodiments, referring to Figure 10 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly 52 through a winding process or a stacking 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 included in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0263] The secondary battery can be a battery module 4 or a battery pack 1.

[0264] The battery module includes at least one battery cell. The number of battery cells included in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.

[0265] Figure 11 is a battery module 4 as an example. Referring to Figure 11, in the battery module 4, a plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other arbitrary manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0266] 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.

[0267] In some embodiments, the above battery modules may also be assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and those skilled in the art may select a suitable number according to the application and capacity of the battery pack.

[0268] Figure 12 and Figure 13 is the battery pack 1 as an example. Refer to Figure 12 and Figure 13 , in the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box may be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0269] In addition, the present application also provides an electrical device. The electrical device includes the secondary battery provided by the present application. The secondary battery may be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0270] As the electrical device, the secondary battery may be selected according to its usage requirements.

[0271] Figure 14 is the electrical device 6 as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or a battery module may be adopted.

[0272] As another example of the device, it may be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinness and lightness, and a secondary battery may be used as the power source.

[0273] Embodiment

[0274] The embodiments of the present application will be described below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those without specified techniques or conditions in the embodiments, the techniques or conditions described in the literature in this field or according to the product specifications are followed. For reagents or instruments without specified manufacturers, they are all conventional products that can be obtained through commercial purchases.

[0275] Example 1

[0276] (1) Preparation of the composite current collector

[0277] ① Grooves were etched on both surfaces 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.

[0278] ② A slurry containing polyurethane was coated on the surface of the conductive layer with grooves to form a slurry layer with a coating thickness of 1.5 μm, and after drying, a bonding layer was formed to obtain a composite layer.

[0279] ③ The composite layer was thermocompression bonded with a support layer with a thickness of 8 μm, and the bonding layer was made to contact the support layer, and cured at 85 °C for 72 hours to obtain a composite current collector with a single-sided composite conductive layer.

[0280] ④ Steps ② to ③ were repeated. The other side of the 8-μm support layer was thermocompression bonded with the composite layer, and cured at 85 °C for 72 hours, and then the thickness of the aluminum layer was chemically thinned to obtain the final composite current collector.

[0281] (2) Preparation of the positive electrode sheet

[0282] LiNi 0.8 Co 0.1 Mn 0.1 O 2 and LiNi 0.5 Co 0.2 Mn 0.3 O 2 were mixed in a ratio of 17:3 as the positive electrode active material. The positive electrode active material, super conductive carbon black SP as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder were dispersed in N-methylpyrrolidone (NMP) as the solvent in a mass ratio of 95:3:2 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on both surfaces of the composite current collector prepared in step (1), and after drying and cold pressing, a positive electrode sheet was obtained.

[0283] (3) Preparation of the negative electrode sheet

[0284] The graphite as the negative electrode active material, sodium carboxymethyl cellulose as the thickener, styrene-butadiene rubber as the binder, and acetylene black as the conductive agent are mixed in a mass ratio of 97:1:1:1, and deionized water is added. The negative electrode paste is obtained under the action of a vacuum mixer; the negative electrode paste is evenly coated on both surfaces of the copper foil; the copper foil is air-dried at room temperature and then transferred to an oven at 120 °C for drying for 1 h, and then cold-pressed and slit to obtain the negative electrode sheet.

[0285] (4) Separator

[0286] A 12-μm-thick polypropylene separator is selected.

[0287] (5) Preparation of the electrolyte

[0288] The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). Among them, the volume ratio of EC, EMC, and DEC is 20:20:60. In a glove box under an argon atmosphere with a water content < 10 ppm, the fully dried lithium salt LiPF 6 is dissolved in the organic solvent and mixed evenly to obtain the electrolyte. Among them, the concentration of the lithium salt is 1 mol / L.

[0289] (6) Preparation of the battery

[0290] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, and the separator is placed between the positive and negative electrode sheets to play a role in isolation. After being wound into a square bare battery core, it is installed in an aluminum shell, and then baked at 80 °C to remove water, and then the corresponding non-aqueous electrolyte is injected. After standing, forming, secondary liquid injection, sealing, capacity measurement, wrapping with blue film and other processes, the battery is obtained.

[0291] Examples 2 to 31

[0292] Similar to the preparation process of Example 1, the difference is that the parameters of the composite current collector are adjusted, as shown in Table 1 below for details.

[0293] Comparative Example 1

[0294] Similar to the preparation process of Example 1, the difference is that in step ①, grooves are not etched on both surfaces of the aluminum foil, that is, the bonding layer does not have raised parts.

[0295] Table 1

[0296]

[0297]

[0298]

[0299] In addition, the composite current collectors and batteries obtained in the above Examples 1 to 31 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 2 below.

[0300] Test section

[0301] (1) Testing the protrusion height and size of the first protrusion and the second protrusion

[0302] The composite current collector was prepared 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 directly observed and measured under SEM with a metal foil.

[0303] (2) Testing the adhesion of the conductive layer

[0304] After the sample was adhered to the non-corona side of an ethylene-acrylic copolymer (EAA) film, a 12-μm-thick PET was covered on the EAA film, and it was placed on a heat sealer and adhered at a temperature of 120°C and a pressure of 0.2 MPa. The adhered sample was cut into a sample with a length of 100 mm and a width of 20 mm, and the non-adhered surface of the conductive layer was adhered to a steel plate with 3M double-sided tape; the sample was clamped on the fixture of a tensile machine, with a spacing of 50 mm, and a 180° peel test was carried out at a speed of 300 mm / min. The peel force was read and converted into the unit of N / m. Five parallel samples were taken, and finally the average peel force was taken; the average peel force = the sum of the peel forces of 5 test samples / 5, and this is the adhesion force.

[0305] (3) Testing the peeling ratio of the conductive layer

[0306] The sample was cut into a width of ≥20 mm and a length greater than 100 mm, fixed on a steel plate with double-sided tape, and a 20-mm-wide tape (adhesive force ~200 N / m) was adhered to the surface of the sample for a peel test. A 180° peel test was carried out at a speed of 500 mm / min. At the same time, the metal chips remaining on the tape were observed under a microscope, and the area of the metal chips was read. The areas of all the dropped metal chips were summed up to obtain the area where the conductive layer of each current collector peeled off. The peeling ratio of the conductive layer was obtained by dividing the peeled-off area of the conductive layer by the total peeled-off area of the tape.

[0307] (4) Cycling test

[0308] The fresh battery cells were cycled at a 1C charge rate and a 1C discharge rate under the condition of 60°C until the capacity decayed to 80% of the initial capacity, and the corresponding number of cycles was recorded, which is the cycling performance of the corresponding battery.

[0309] (5) Direct current resistance (DCR) test

[0310] The battery cell is adjusted to 50% SOC, discharged at a rate of 4C (corresponding to discharge current I) for 30s, and the voltage difference ΔV before and after 30s discharge is recorded. The DCR corresponding to 50% SOC is calculated according to the following formula: DCR = ΔV / I, and the DCR data of each battery cell is obtained.

[0311] Table 2

[0312]

[0313]

[0314] By 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.

[0315] The above description of various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other, and for the sake of brevity, they will not be repeated herein.

[0316] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite current collector, characterized in that, it comprises: a support layer; and a bonding layer and a conductive layer which are sequentially laminated on at least one surface of the support layer, the bonding layer includes a bonding layer main body and a protrusion portion, and the protrusion portion protrudes outward along the thickness direction of the bonding layer and is embedded in the conductive layer.

2. The composite current collector according to claim 1, characterized in that, there are a plurality of the protrusion portions, and the plurality of protrusion portions are arranged at intervals.

3. The composite current collector according to claim 2, characterized in that, the protrusion portion includes a first protrusion portion and / or a second protrusion portion, the protrusion height of the first protrusion portion is less than the thickness of the conductive layer, and the protrusion height of the second protrusion portion is equal to the thickness of the conductive layer.

4. The composite current collector according to claim 3, characterized in that, the first protrusion portion includes a first sub-protrusion portion and / or a second sub-protrusion portion, the orthographic projection of the first sub-protrusion portion on the surface of the conductive layer includes a hole shape, and the orthographic projection of the second sub-protrusion portion on the surface of the conductive layer includes a stripe shape; Optionally, the hole shape includes one or more of a circular hole, an oval hole, a fan-shaped hole, a bow-shaped hole, and a polygonal hole, and may be a circular hole and / or an oval hole; Optionally, the stripe shape includes one or more of an oval stripe, a polygonal stripe, an arc stripe, and a wavy stripe, and may be an oval stripe.

5. The composite current collector according to claim 4, characterized in that, the angle included in the orthographic projection of the first sub-protrusion portion on the surface of the conductive layer ≥ 45°.

6. The composite current collector according to claim 4 or 5, characterized in that, the first sub-protrusion portion satisfies at least one of the following conditions: (1) Between the protrusion height h1 of the first sub-protrusion portion and the width d1 of the first sub-protrusion portion: 0.001% ≤ h1 / d1 ≤ 1%; (2) Between the width d1 of the first sub-protrusion portion and the spacing Δx1 between two adjacent first sub-protrusion portions: 3.6% ≤ d1 / Δx1 ≤ 40%.

7. The composite current collector according to claim 4 or 5, characterized in that, the first sub-protrusion portion satisfies at least one of the following conditions: (1) The protrusion height h1 of the first sub-protrusion portion is 50 nm to 500 nm; (2) The width d1 of the first sub-protrusion portion is 0.2 mm to 20 mm; (3) The spacing Δx1 between two adjacent first sub-protrusion portions is 5 mm to 50 mm.

8. The composite current collector according to any one of claims 4-7, characterized in that, the stripe shape includes stripes distributed alternately or stripes intersecting each other, and may be stripes intersecting each other, and further may be stripes intersecting in a grid shape.

9. The composite current collector according to claim 8, characterized in that, at least one intersection portion is included in the intersecting stripes; Optionally, the orthographic projection of the intersection portion 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; Optionally, the angle included in the orthographic projection of the intersection portion on the surface of the conductive layer ≥ 45°.

10. The composite current collector according to any one of claims 4-9, characterized in that the second sub-protrusion portion satisfies at least one of the following conditions: (1) The protrusion height h2 of the second sub-protrusion portion is 50 nm to 500 nm; (2) The width d2 of the second sub-protrusion portion is 3 mm to 20 mm; (3) The spacing Δx2 between two adjacent second sub-protrusion portions is 15 mm to 70 mm.

11. The composite current collector according to any one of claims 2-10, characterized in that at least one of the first protrusion portions is provided between two adjacent second protrusion portions; Optionally, the total area S2 of the orthographic projection of the second protrusion portion on the surface of the conductive layer and the total area S1 of the orthographic projection of the first protrusion portion on the surface of the conductive layer satisfy: S2 < S1; Optionally, the following is satisfied between S1 and S2: S1 / (S1 + S2) ≥ 95%.

12. The composite current collector according to any one of claims 2-11, characterized in that the second protrusion portion satisfies at least one of the following conditions: (1) The width d3 of the second protrusion portion is 30 μm to 600 μm; (2) The spacing Δx3 between two adjacent second protrusion portions is 10 mm to 100 mm.

13. The composite current collector according to any one of claims 2-12, characterized in that the orthographic projection of the second protrusion portion on the surface of the conductive layer includes one or more of a circular hole, an oval hole, a fan-shaped hole, a bow-shaped hole, and a polygonal hole, and may be a circular hole and / or an oval hole; Optionally, the angle included in the orthographic projection of the second protrusion portion on the surface of the conductive layer ≥ 45°.

14. The composite current collector according to any one of claims 1-13, characterized in that the protrusion portion contains a binder; Optionally, the binder includes a composition containing a polyfunctional 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, etc. One or more; Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

15. The composite current collector according to any one of claims 1-14, characterized in that at least one of the following conditions is satisfied: (1) The thickness of the conductive layer is 0.5 μm to 5 μm; (2) The thickness of the main body of the adhesive layer is 0.5 μm to 3 μm; (3) The thickness of the support layer is 2 μm to 15 μm.

16. The composite current collector according to any one of claims 1-15, characterized in that at least one of the following conditions is satisfied: (1) The peeling ratio of the conductive layer ≤ 1 mm 2 / 2000 mm 2 ; (2) The adhesive force of the conductive layer ≥ 220 N / m.

17. The composite current collector according to any one of claims 1-16, characterized in that at least one of the following conditions is satisfied: (1) The support layer comprises one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene styrene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, sulfur nitride polymers, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their crosslinked products and their copolymers; (2) The adhesive layer comprises one or more of a composition containing a polyfunctional 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. Further optionally, the polyurethane comprises one or more of thermoplastic polyurethane and reactive polyurethane; (3) The conductive layer comprises one or more of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium and tin.

18. A pole piece, characterized in that, it comprises the composite current collector according to any one of claims 1-17.

19. A secondary battery, characterized in that, it comprises the pole piece according to claim 18.

20. An electrical device, characterized in that, it comprises the secondary battery according to claim 19.

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