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 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, the conductive layer comprises a conductive layer main body and a first convex part, and the first convex part protrudes along the thickness direction of the conductive layer and is embedded into the bonding layer. The composite current collector provided by the invention can improve the cycle performance of the secondary battery.

Description

Technical Field

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

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

[0003] In recent years, with the increasingly wide application scope of secondary batteries represented by lithium-ion batteries, secondary batteries are widely used in energy storage power systems such as hydroelectric power plants, thermal power plants, wind power plants, and solar power plants, 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 for carrying active materials, the current collector will have a greater impact on the electrochemical performance of the battery. However, the commonly used composite current collectors currently usually have problems of poor adhesion between layers, which easily lead to problems such as a decline in the performance of the battery cell and poor cycle performance after being used in the battery; moreover, the elastic modulus of the composite current collector is relatively low, resulting in relatively low processability. 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 adhesion and processability of the composite current collector, and further 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 conductive layer including a conductive layer main body and a first protrusion portion, the first protrusion portion protruding along the thickness direction of the conductive layer and embedding into the bonding layer.

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

[0007] In some embodiments of the present application, the protrusion height of the first protrusion portion is less than the thickness of the bonding layer.

[0008] In some embodiments of the present application, the first protrusion portion includes a first sub-protrusion portion and / or a second sub-protrusion portion, the shape of the orthographic projection of the first sub-protrusion portion on the surface of the conductive layer includes a hole shape, and the shape of the orthographic projection of the second sub-protrusion 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 an oval stripe, a polygonal stripe, an arc stripe, and a wavy stripe, and may be an oval stripe.

[0011] In some embodiments of the present application, the included angle and its supplementary angle of the shape of the orthographic projection of the first sub-protrusion on the surface of the conductive layer are ≥ 45°.

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

[0013] (1) The protrusion height h1 of the first sub-protrusion is 15% - 85% of the thickness of the adhesive layer;

[0014] (2) The width d1 of the first sub-protrusion is 5 mm - 50 mm;

[0015] (3) The spacing Δx1 between two adjacent first sub-protrusions is 10 mm - 100 mm.

[0016] In some embodiments of the present application, the stripe shape includes alternately distributed stripes or intersecting stripes, and may be intersecting stripes, and further may be stripes intersecting in a grid shape.

[0017] In some embodiments of the present application, at least one intersection portion is included in the intersecting stripes;

[0018] Optionally, the shape of the orthographic projection of the intersection portion on the surface of the conductive layer includes one or more of a circle, an oval, and a polygon, and may be a circle and / or an oval;

[0019] Optionally, the included angle and its supplementary angle of the shape of the orthographic projection of the intersection portion on the surface of the conductive layer are ≥ 45°.

[0020] In some embodiments of the present application, the second sub-protrusion satisfies at least one of the following conditions:

[0021] (1) The protrusion height h2 of the second sub-protrusion is 15% - 85% of the thickness of the adhesive layer;

[0022] (2) The width d2 of the second sub-protrusion is 5 mm - 40 mm;

[0023] (3) The spacing Δx2 between two adjacent second sub-protrusions is 20 mm - 150 mm.

[0024] In some embodiments of the present application, 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: 1% ≤ S1 / S ≤ 50%.

[0025] In some embodiments of the present application, the adhesive layer includes an adhesive layer main body and a second protrusion, and the second protrusion protrudes along the thickness direction of the adhesive layer and is embedded in the conductive layer.

[0026] In some embodiments of the present application, the protrusion height of the second protrusion is equal to the thickness of the conductive layer.

[0027] In some embodiments of the present application, there are a plurality of the second protrusions, and the plurality of second protrusions are arranged at intervals;

[0028] Optionally, the distance Δx3 between two adjacent second protrusions is 5 mm to 100 mm.

[0029] In some embodiments of the present application, the second protrusion is arranged at intervals from the first protrusion; and / or,

[0030] At least one of the first protrusions is provided between two adjacent second protrusions.

[0031] In some embodiments of the present application, 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.

[0032] In some embodiments of the present application, the width d3 of the second protrusion is 50 μm to 500 μm.

[0033] In some embodiments of the present application, the shape of 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 shape of 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 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: 0.001% ≤ S2 / S ≤ 0.8%.

[0036] In some embodiments of the present application, the second protrusion contains an adhesive;

[0037] Optionally, the binder includes one or more of a composition containing polyfunctional isocyanate and polyester polyol compound, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, modified polyethylene, modified polypropylene, modified polyolefin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide;

[0038] Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0039] In some embodiments of the present application, at least one of the following conditions is satisfied:

[0040] (1) The thickness of the main body of the adhesive layer is 0.5 μm to 3 μm;

[0041] (2) The adhesive force of the conductive layer is ≥ 230 N / m.

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

[0043] (1) The thickness of the main body of the conductive layer is 0.5 μm to 5 μm;

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

[0045] In some embodiments of the present application, at least one of the following conditions is 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, polyazotized sulfur-based 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 adhesive layer includes one or more of a composition containing polyfunctional isocyanate and polyester polyol compound, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, modified polyethylene, modified polypropylene, modified polyolefin, silicone resin, ethylene-acrylic acid 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 also provides an electrode sheet, including the composite current collector described in the first aspect of the present application.

[0051] The third aspect of the present application also 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 in 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 following drawings and description. Other features, objects, and advantages of the present application will become apparent from the specification, drawings, and claims.

[0055] The composite current collector provided by the present application is provided with the first protrusion on the conductive layer, which can increase the surface area of contact between the conductive layer and the adhesive 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 cycle performance of the battery cell using the composite current collector. 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, or the currently understood best mode of these applications. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[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 4Schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

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

[0062] Figure 6 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 cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0065] Figure 9 Schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0066] Figure 10 Schematic diagram of a battery cell according to an embodiment of the present application.

[0067] Figure 11 is Figure 10 Exploded view of the battery cell shown in an embodiment of the present application.

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

[0069] Figure 13 Schematic diagram of a battery pack according to an embodiment of the present application.

[0070] Figure 14 is Figure 13 Exploded view of the battery pack shown in an embodiment of the present application.

[0071] Figure 15 Schematic diagram of an electrical device powered by a secondary battery according to an embodiment of the present application.

[0072] Explanation of reference numerals:

[0073] 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; 121 Adhesive layer main body; 122 Second protrusion; 13 Conductive layer; 131, Conductive layer main body; 132 First protrusion; 1321 First sub-protrusion; 1322 Second sub-protrusion. Detailed implementation manners

[0074] Hereinafter, some embodiments of the composite current collector, the electrode sheet, the secondary battery, and the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there 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.

[0075] The "range" disclosed in the present 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 boundary of a specific range. The range defined in this way can include or not include the end values. Any end value can be independently included or not included, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 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 1 and 2 are listed, and if the maximum range values 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 the present 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" have been 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, for example, integers 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 integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0076] In the present application, the terms "a plurality of", "a variety of", etc., unless otherwise specified, mean greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0077] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0078] References to "embodiments" in this document mean that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment or implementation of the present application. The phrase appearing 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 will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. Similar understanding applies to "implementations" mentioned in this document.

[0079] Those skilled in the art can understand that in the methods of each implementation or embodiment, 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. If there is no special description, all steps of the present application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), indicating 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.

[0080] In the present application, in open technical features or technical solutions described with words such as "containing", "comprising", "including", etc., without other explanations, additional members other than the listed members are not excluded, and it can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that further includes additional members outside the listed members. For example, A includes a1, a2, and a3. Without other explanations, it may or may not include other members, and it can be regarded as providing both the feature or solution that "A is composed of a1, a2, and a3" and the feature or solution that "A not only includes a1, a2, and a3, but also includes other members". In the present application, without other explanations, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0081] In the present application, "optionally", "optional", "option" mean that it can be either present or absent, that is, it refers to any one of two alternative options of "present" or "absent". If "optional" appears in multiple places in a technical solution, without special explanations and without contradictions or mutual restrictions, each "optional" is independent of each other.

[0082] At present, when a metal is used as a conductive layer and combined with a polymer material layer, a traditional composite current collector with a "metal / polymer material / metal" sandwich structure can be formed. When 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, and a binder layer is formed. However, in this composite current collector, the adhesion between layers is relatively low. Therefore, during the processing of the battery cell and during the cyclic use of the battery cell, the conductive layer in the composite current collector is likely to fall off, resulting in problems such as a significant decline in the performance of the battery cell. At the same time, due to the relatively low elastic modulus of the binder layer, the overall elastic modulus of the composite current collector is relatively low. This will cause problems such as wrinkling in the composite current collector during the processing, making its mechanical properties unable to meet the processing requirements.

[0083] To solve the above technical problems, the present application proposes a composite current collector. By providing a protrusion on the surface of the conductive layer adjacent to the binder layer, the surface area of contact between the conductive layer and the binder layer can be increased, thereby enhancing the adhesion between the binder layer and the conductive layer, and further enhancing the cyclic performance of the battery cell using this composite current collector. At the same time, the protrusion is embedded in the binder layer, which can also play a supporting role for the binder layer, increasing the elastic modulus of the binder layer, and thus enhancing the overall elastic modulus of the composite current collector. The following will describe this composite current collector in more detail.

[0084] In a first aspect, the present application provides a composite current collector, which can be referred to Figure 1 , and it includes a support layer 11 and a binder layer 12 and a conductive layer 13 that are sequentially stacked on at least one surface of the support layer 11. The conductive layer 13 includes a conductive layer main body 131 and a first protrusion 132. The first protrusion 132 protrudes along the thickness direction of the conductive layer 13 and is embedded in the binder layer 12.

[0085] It can be understood that the first protrusion protrudes along the thickness direction of the conductive layer towards the binder layer.

[0086] It should be noted that the "surface of the conductive layer" or "the surface of the conductive layer" 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 binder 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 binder layer of the conductive layer.

[0087] The above-mentioned composite current collector provided by the present application is provided with the first raised portion on the conductive layer, which can increase the surface area of contact between the conductive layer and the adhesive 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 peeling off 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. Under the same tensile extension, there are fewer cracks, which is beneficial to reducing the growth rate of sheet resistance. In addition, the first raised portion is embedded in the adhesive layer, which can also play a supporting role in the interior of the adhesive layer, improve the elastic modulus of the adhesive layer, thereby improving the overall elastic modulus and mechanical properties of the composite current collector, reducing the occurrence of problems such as wrinkling during the processing, and improving its processability.

[0088] In some embodiments, there are multiple first raised portions, and the multiple first raised portions are arranged at intervals.

[0089] It can be understood that the multiple first raised portions are arranged at intervals, which means that there is an interval (spacing) between any two adjacent first raised portions.

[0090] The multiple first raised portions can increase the wettability of the adhesive contained in the adhesive layer to the conductive layer, and can increase the surface area of contact between the conductive layer and the adjacent adhesive layer, thereby further improving the adhesion force between the adhesive layer and the conductive layer. In addition, it can further enhance the supporting effect on the interior of the adhesive layer, and further improve the elastic modulus of the adhesive layer and the composite current collector. The multiple first raised portions are arranged at intervals, which can improve the adhesion force between the adhesive layer and the conductive layer while enabling the conductive layer, the adhesive layer, and the composite current collector to have sufficient mechanical strength, and improving the structural stability of the composite current collector.

[0091] In some embodiments, the raised height of the first raised portion is less than the thickness of the adhesive layer.

[0092] The raised height of the first raised portion being less than the thickness of the adhesive layer can enable the conductive layer, the adhesive layer, and the composite current collector to have sufficient mechanical strength while improving the adhesion force between the adhesive layer and the conductive layer.

[0093] In some embodiments, the first raised portion 132 includes a first sub-raised portion 1321 and / or a second sub-raised portion 1322.

[0094] It can be understood that only the first sub-raised portion 1321 can be provided on the conductive layer 13 (see Figure 2 ), or only the second sub-raised portion 1322 can be provided (see Figure 3 ), or a combination of the first sub-raised portion 1321 and the second sub-raised portion 1322 can also be provided.

[0095] When the first sub-protrusion and the second sub-protrusion are combined, it can achieve a better effect of improving the bonding force, and at the same time enable the composite current collector to have sufficient mechanical strength.

[0096] The shape of the orthographic projection of the first sub-protrusion 1321 on the surface of the conductive layer includes a hole shape (see Figure 4 and Figure 5 ).

[0097] In some embodiments, the hole shape includes, but is not limited to, 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.

[0098] 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 shape with a circular orthographic projection, and a "fan-shaped hole" refers to a shape with a fan-shaped orthographic projection.

[0099] It can be understood that the shape of 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 distributed discretely (or alternately), and no two first sub-protrusions intersect and there are intervals between them.

[0100] It can be understood that the "bow shape" described in this application refers to a figure formed by an arc and the chord it faces.

[0101] 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 infiltrate the entire protrusion more completely, which helps to improve the bonding force of the bonding layer to the conductive layer and reduce the detachment of the conductive layer. At the same time, the circular hole shape and / or the oval shape can provide support for the bonding layer at 360 degrees, making the elastic modulus of the bonding layer higher, and thus making the elastic modulus of the composite current collector higher.

[0102] In some embodiments, the angles and their supplementary angles included in the shape of the orthographic projection of the first sub-protrusion on the surface of the conductive layer are ≥ 45°.

[0103] It can be understood that the angles included in the shape of the orthographic projection of the first sub-protrusion on the surface of the conductive layer, that is, the angles included in the hole shape, refer to when the hole shape is a polygon, the angles of the polygon and their supplementary angles are ≥ 45°; when the hole shape is a fan shape or a bow shape, the central angles of the fan shape or the bow shape and their supplementary angles are ≥ 45°.

[0104] The angles and their supplementary angles included in the shape of the orthographic projection of the first sub-protrusion on the surface of the conductive layer are ≥ 45°, which helps the binder to wet the protrusion more completely, reduces the problem that the binder is not easily wetted when there are tips on the protrusion, improves the adhesion of the adhesive layer to the conductive layer, and reduces the detachment of the conductive layer. At the same time, it is also beneficial to further improve the supporting effect of the protrusion on the adhesive layer, thereby further improving the elastic modulus of the adhesive layer and the composite current collector.

[0105] In some embodiments, the protrusion height h1 of the first sub-protrusion (see Figure 2 ) is 15% - 85% of the thickness of the adhesive layer. For example, the protrusion height of the first sub-protrusion can be 15%, 30%, 45%, 60%, 75%, 85% of the thickness of the adhesive layer or within the range composed of any of the above values.

[0106] 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 provided with the first sub-protrusion.

[0107] When the protrusion height of the first sub-protrusion is within the above range, on the one hand, the binder can wet the protrusion better, 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 influence on the conductivity of the conductive layer and further improve the supporting effect on the adhesive layer, thereby improving the elastic modulus of the adhesive layer and the composite current collector.

[0108] In some embodiments, the width d1 of the first sub-protrusion (see Figure 4 and Figure 5 ) is 5 mm - 50 mm. For example, the width of the first sub-protrusion can be 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm or within the range composed of any of the above values.

[0109] When the width of the first sub-protrusion is within the above range, on the one hand, the binder can wet the protrusion better, 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 will not affect the conductivity of the conductive layer as much as possible.

[0110] 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 of the orthographic projection of the first sub-protrusion on the surface of the conductive layer (when the shape of 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 shape of the orthographic projection is a polygonal hole).

[0111] In some embodiments, the spacing Δx1 between two adjacent first sub-protrusions (see Figure 2) is 10 mm to 100 mm. For example, the distance between two adjacent first sub-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.

[0112] It should be noted that the "distance 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.

[0113] When the distance between two adjacent first sub-protrusions is within the above range, on the one hand, it can enable the binder to better infiltrate 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.

[0114] The shape of the orthographic projection of the second sub-protrusion 1322 on the surface of the conductive layer includes a stripe shape (see Figure 6 and Figure 7 ).

[0115] The stripe shape can further increase the contact area between the conductive layer and the adhesive layer, and further enhance the wettability of the protrusion surface, which is helpful for the binder to better infiltrate the protrusion, thereby further improving the adhesion force between the adhesive layer and the conductive layer. At the same time, the stripe shape can also better improve the elastic modulus of the adhesive layer, and then improve the elastic modulus of the entire composite current collector.

[0116] In some embodiments, the stripe shape includes, but is not limited to, one or more of oval stripes, polygon stripes, arc stripes, and wavy stripes, and can be oval stripes.

[0117] The oval stripes can better connect the inside of the second sub-protrusion, further enhance the wettability of the protrusion surface, improve the infiltration effect of the binder on the protrusion, and further increase the contact area between the conductive layer and the adhesive layer, thereby further improving the adhesion force between the adhesive layer and the conductive layer.

[0118] In some embodiments, the stripe shape includes stripes distributed alternately (see Figure 6 ) or stripes intersecting each other (see Figure 7 ), and can be stripes intersecting each other, and further can be stripes intersecting in a grid shape.

[0119] It can be understood that the "stripes distributed alternately" described in this application refer to that there is no intersection and there is a gap between any two stripes; the "stripes intersecting each other" refer to the situation where the stripes intersect each other. For example, there is an intersection between the horizontally alternately distributed stripes and the vertically alternately distributed stripes.

[0120] In some embodiments, at least one intersection part is included in the intersecting stripes.

[0121] The intersecting stripes can make the protrusions on the whole surface present a connected state, enable the binder to flow better inside the protrusions, improve the wetting effect of the binder on the protrusions, and thus improve the adhesion of the adhesive layer to the conductive layer.

[0122] In some embodiments, the shape of 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 can be a circle and / or an ellipse.

[0123] When the shape of 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 binder can wet the intersection part more completely, which helps to improve the adhesion of the adhesive layer to the conductive layer and reduce the detachment of the conductive layer.

[0124] In some embodiments, the angles and their supplementary angles included in the shape of the orthographic projection of the intersection part on the surface of the conductive layer are ≥ 45°.

[0125] It can be understood that the angles and their supplementary angles included in the shape of the orthographic projection of the intersection part on the surface of the conductive layer are ≥ 45°, which means that when the shape of the orthographic projection is a polygon, each angle of the polygon and its supplementary angle are ≥ 45°.

[0126] The angles included in the shape of the orthographic projection of the intersection part on the surface of the conductive layer are ≥ 45°, which helps to make the binder wet the intersection part more completely, reduce the problem that the intersection part is not easily wetted by the binder when there is a tip, improve the adhesion of the adhesive layer to the conductive layer, and reduce the detachment of the conductive layer.

[0127] In some embodiments, the protrusion height h2 of the second sub-protrusion part (see Figure 3 ) is 15% - 85% of the thickness of the adhesive layer. For example, the protrusion height of the second sub-protrusion part can be 15%, 30%, 45%, 60%, 75%, 85% of the thickness of the adhesive layer or within the range composed of any of the above values.

[0128] It should be noted that the "protrusion height of the second sub-protrusion part" refers to the distance between the highest point of the top of the second sub-protrusion part and the surface of the conductive layer provided with the second sub-protrusion part.

[0129] The protrusion height of the second sub-protrusion is within the above range, which can further improve the adhesion of the adhesive layer to the conductive layer while further enhancing its supporting effect on the adhesive layer, thereby improving the elastic modulus of the adhesive layer and the composite current collector.

[0130] In some embodiments, the width d2 of the second sub-protrusion (see Figure 6 and Figure 7 ) is 5 mm to 40 mm. For example, the width of the second sub-protrusion can be 5 mm, 10 mm, 20 mm, 30 mm, 40 mm or within the range composed of any of the above values.

[0131] It should be noted that the "width of the second sub-protrusion" refers to the distance between the two relatively longer long sides in the stripe.

[0132] In some embodiments, the spacing Δx2 between two adjacent second sub-protrusions (see Figure 3 ) is 20 mm to 150 mm. For example, the spacing between two adjacent second sub-protrusions can be 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150 mm or within the range composed of any of the above values.

[0133] It should be noted that the "spacing between two adjacent second sub-protrusions" refers to the horizontal distance between the center points 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.

[0134] When the protrusion height, width of the second sub-protrusion, and the spacing between two adjacent second sub-protrusions are within the above ranges, on the one hand, it can enable the binder to better infiltrate 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.

[0135] 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: 1% ≤ S1 / S ≤ 50%. For example, S1 / S can be 1%, 3%, 5%, 7%, 10%, 20%, 30%, 40%, 50% or within the range composed of any of the above values.

[0136] 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.

[0137] In some embodiments, reference may be made to Figure 8 , the adhesive 12 includes an adhesive layer main body 121 and a second convex portion 122, and the second convex portion 122 protrudes along the thickness direction of the adhesive layer 12 and is embedded in the conductive layer 13.

[0138] Currently, in the process of preparing a composite current collector with a traditional sandwich structure, it is usually necessary to introduce an adhesive to bond the conductive layer and the polymer material layer. During the process of introducing the adhesive and compounding the conductive layer and the polymer material layer, air bubbles or pores are likely to form between the adhesive layer formed by the adhesive and the conductive layer, resulting in poor adhesion of the adhesive layer, and thus during the process of cell processing and during the cyclic use of the cell, the conductive layer is likely to fall off, leading to problems such as a decline in cell performance.

[0139] Accordingly, by providing a second convex portion on the adhesive layer, on the one hand, the surface area of contact between the adhesive layer and the adjacent conductive layer can be increased, improving the adhesion between the adhesive layer and the conductive layer; on the other hand, during the process of introducing the adhesive to form the adhesive layer, it also helps to discharge the air bubbles or pores formed between the adhesive layer and the conductive layer, enabling the adhesive layer to better adhere to the conductive layer, thereby improving the adhesion between the adhesive layer and the conductive layer, effectively reducing the detachment of the conductive layer, and further improving the cyclic performance of the cell using the composite current collector. In addition, the second convex portion can also provide a certain degree of support for the adhesive layer and improve the elastic modulus of the adhesive layer to a certain extent.

[0140] In some embodiments, the protruding height of the second convex portion is equal to the thickness of the conductive layer.

[0141] The protruding height of the second convex portion being 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, helps to further promote the discharge of air bubbles or pores formed between the adhesive layer and the conductive layer during the formation of the adhesive layer (i.e., the air exhaust property), thereby further improving the adhesion between the adhesive layer and the conductive layer. In addition, the protruding height of the second convex portion being equal to the thickness of the conductive layer also helps to cause the fracture of the conductive layer during thermal runaway, improving the safety of the composite current collector.

[0142] In some embodiments, there are a plurality of the second convex portions, and the plurality of second convex portions are arranged at intervals.

[0143] The plurality of second convex portions are arranged at intervals. While further improving the air exhaust property, it can also enable the composite current collector to have sufficient mechanical strength and improve the structural stability of the composite current collector.

[0144] In some embodiments, there is a spacing between the second convex portion and the adjacent first convex portion.

[0145] The first raised portion and the second raised portion are provided simultaneously, and there is a spacing between the first raised portion and the adjacent second raised portion, which can make the interface contact between the conductive layer and the adhesive layer closer, contributing to the further improvement of the adhesive force. At the same time, it is also beneficial to further enhance the supporting effect on the adhesive layer, thereby further enhancing the elastic modulus of the adhesive layer and the composite current collector. In addition, it can also endow the composite current collector with sufficient mechanical strength and improve the structural stability of the composite current collector.

[0146] In some embodiments, at least one of the first raised portions is provided between two adjacent second raised portions.

[0147] The second raised portion and the first raised portion are arranged in an interlaced manner, which can reduce the problem of uneven exhaust during the compounding process of the adhesive layer and the conductive layer, or reduce the problem of weakened local conductivity of the conductive layer, enabling the composite current collector to obtain better comprehensive performance.

[0148] In some embodiments, the total area S2 of the orthographic projection of the second raised portion on the surface of the conductive layer and the total area S1 of the orthographic projection of the first raised portion on the surface of the conductive layer satisfy: S2 < S1.

[0149] The total area S2 of the orthographic projection of the second raised portion on the surface of the conductive layer and the total area S1 of the orthographic projection of the first raised portion on the surface of the conductive layer satisfying the above relationship can not only reduce the generation of bubbles during the compounding process of the adhesive layer and the conductive layer and improve the adhesive force, but also ensure the performance of the battery cell and improve the safety.

[0150] In some embodiments, the width d3 of the second raised portion is 50 μm to 500 μm. For example, the width of the second raised portion can be 50 μm, 60 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm or within the range composed of any of the above values.

[0151] It should be noted that similar to the width of the first sub-raised portion, the "width of the second raised portion" in this application refers to the maximum value of the distance between any two points on the contour of the shape of the orthographic projection of the second raised portion on the surface of the conductive layer (when the shape of the orthographic projection is a circular hole, an elliptical hole, a fan-shaped hole or a bow-shaped hole), or the maximum side length of the contour (when the shape of the orthographic projection is a polygonal hole).

[0152] In some embodiments, the spacing Δx3 between two adjacent second raised portions (see Figure 9 ) is 5 mm to 100 mm. For example, the spacing between two adjacent second raised portions can be 5 mm, 7 mm, 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.

[0153] It should be noted that the "spacing 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.

[0154] When the width of the second protrusion and the distance between two adjacent second protrusions are within the above range, it is beneficial to enhance the exhaust function of the second protrusion, and it helps the binder to more completely infiltrate the protrusion. At the same time, it can also reduce the cracking problem that is prone to occur 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.

[0155] In some embodiments, the shape of 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 fan-shaped hole, a bow-shaped hole, and a polygonal hole, and can be a circular hole and / or an oval hole.

[0156] When the shape of 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 the protrusion, which helps to enhance the bonding force of the bonding layer to the conductive layer and reduce the detachment of the conductive layer.

[0157] In some embodiments, the angle included in the shape of the orthographic projection of the second protrusion on the surface of the conductive layer ≥ 45°.

[0158] It can be understood that the angle included in the shape of the orthographic projection of the second protrusion on the surface of the conductive layer means that when the shape of the orthographic projection is a polygon, each angle of the polygon ≥ 45°; when the shape of the orthographic projection is a fan shape or a bow shape, the central angle corresponding to the fan shape or the bow shape ≥ 45°.

[0159] The angle included in the shape of the orthographic projection of the second protrusion on the surface of the conductive layer ≥ 45° helps the binder to more completely infiltrate 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.

[0160] 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 surface of the conductive layer satisfy: 0.001% ≤ S2 / S ≤ 0.8%. For example, S2 / S can be 0.001%, 0.003%, 0.005%, 0.007%, 0.01%, 0.03%, 0.05%, 0.07%, 0.1%, 0.3%, 0.5%, 0.8% or within the range composed of any of the above values.

[0161] The total area S2 of the orthographic projection of the second raised portion 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, enhance the structural stability of the composite current collector, and improve the safety of the battery cell.

[0162] In some embodiments, the second raised portion contains a binder.

[0163] 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, modified polyethylene, modified polypropylene, modified polyolefin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide.

[0164] In some embodiments, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0165] In some embodiments, the thickness of the main body of the conductive layer is 0.5 μm to 5 μm. For example, the thickness of the main body 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.

[0166] 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.

[0167] 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.

[0168] When the thicknesses of the support layer, the main body of the adhesive layer, and the main body of the conductive layer are each within the above ranges, while improving the adhesion, the conductivity and strength (mechanical) properties of the current collector can be taken into account.

[0169] In some embodiments, the adhesion of the conductive layer ≥ 230 N / m.

[0170] 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 performing an adhesion test on the composite current collector, and can be tested by the test method described later.

[0171] When the adhesion of the conductive layer is within the above range, it can not only ensure 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.

[0172] In some embodiments, 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-based polymers, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their crosslinked products, and their copolymers.

[0173] In some embodiments, 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, modified polyolefin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide.

[0174] In some embodiments, the polyurethane comprises one or more of thermoplastic polyurethane and reactive polyurethane.

[0175] In some embodiments, the conductive layer comprises one or more of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium, and tin.

[0176] 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:

[0177] S1. Prepare grooves on at least one surface of the metal foil to form a conductive layer.

[0178] S2. Coat a slurry containing an adhesive on the surface of the conductive layer where the grooves are provided to prepare an adhesive layer, and form a composite layer containing the adhesive layer and the conductive layer after drying.

[0179] S3. Composite the composite layer containing the adhesive layer and the conductive layer with the support layer to prepare a composite current collector.

[0180] In some embodiments, in step S1, grooves may be prepared on at least one surface of the metal foil by etching.

[0181] It can be understood that after the metal foil is etched to form grooves, a first raised portion and a conductive layer main body are prepared on the surface of the metal foil, and a conductive layer is formed.

[0182] In some embodiments, the etching depth of the grooves is less than or equal to the thickness of the metal foil. Optionally, the etching depth of the grooves is less than the thickness of the metal foil.

[0183] It can be understood that when the etching depth of the grooves is less than the thickness of the metal foil, a conductive layer including a first raised portion can be prepared. When the etching depth of the grooves is equal to the thickness of the metal foil, an adhesive layer including a second raised portion can be prepared.

[0184] In some embodiments, the conductive layer includes a conductive layer main body and a first raised portion, and the first raised portion protrudes along the thickness direction of the conductive layer and is embedded in the adhesive layer.

[0185] In some embodiments, the adhesive layer includes an adhesive layer main body and a second raised portion, and the second raised portion protrudes along the thickness direction of the adhesive layer and is embedded in the conductive layer.

[0186] It can be understood that in step S2, after a slurry containing an adhesive is coated on the surface of the conductive layer where the grooves are provided, the slurry will penetrate into the grooves and fill the grooves. After the grooves are completely filled, the slurry can continue to be coated on the surface of the conductive layer to form a slurry layer, and after drying, the slurry layer forms the adhesive layer main body, and the grooves filled with the slurry (when the etching depth of the grooves is equal to the thickness of the metal foil) form the second raised portion, and the adhesive layer main body and the second raised portion become an integral body to form the adhesive layer, thereby realizing the composite of the adhesive layer and the conductive layer and embedding the second raised portion into the conductive layer.

[0187] In some embodiments, the composite treatment in step S3 includes: thermally pressing and laminating the composite layer including the adhesive layer and the conductive layer with the support layer, wherein the adhesive layer in the composite layer is in contact with the support layer.

[0188] The temperature of the thermocompression lamination is close to the melting point of the adhesive, so that the adhesive is in a fully softened or molten state. The fully softened or molten adhesive can be better laminated with the adhesive layer in the composite layer.

[0189] It should be noted that when the bonding layer includes the second convex portion, on the one hand, the presence of the second convex portion can play a role in removing air bubbles when applying the slurry containing the binder, reducing the air bubbles and pores between the conductive layer and the bonding layer, and enhancing the bonding force between the two. On the other hand, during thermocompression lamination, the air bubbles can be discharged from the second convex portion. Thus, the presence of the second convex portion can further remove air bubbles and further improve the bonding force.

[0190] In some embodiments, the process of passivating the conductive layer is further included in step S1.

[0191] In some embodiments, the passivating agent for passivation treatment includes one or more of chromate, organic phosphate, Al 2 O 3 , SiO 2 and Si 3 N 4 .

[0192] It can be understood that in the above steps, the materials of the metal foil, the binder, and the support layer can respectively correspond to the materials included in the conductive layer, the binder, and the support layer in the first aspect of the present application, and will not be elaborated herein.

[0193] In a third aspect, the present application provides a pole piece, 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.

[0194] In some embodiments, the pole piece includes a positive pole piece and / or a negative pole piece.

[0195] 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 pole piece and / or the negative pole piece.

[0196] In addition, the secondary battery and the electrical device of the present application will be described below with appropriate reference to the drawings.

[0197] Generally, a secondary battery includes a positive pole piece, a negative pole piece, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The separator is disposed between the positive pole piece and the negative pole piece, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0198] Positive pole piece

[0199] The positive pole piece includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The positive active material layer includes a positive active material.

[0200] 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 either one or both of the two opposite surfaces of the positive electrode current collector.

[0201] In some of these embodiments, the positive electrode current collector may employ the composite current collector of the first aspect of the present application.

[0202] In some of these embodiments, the positive electrode current collector may be a metal foil or other composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0203] In some of these embodiments, the negative electrode may employ a positive electrode active material for a battery known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: 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. 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. 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 Co1 / 3 Mn 1 / 3 O 2 (which can also be abbreviated as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide can include LiNi 0.85 Co 0.15 Al 0.05 O 2 .

[0204] Regarding the change in the Li content in the cathode material, how to define the subscript of Li in the general formula:

[0205] Regarding the ternary material:

[0206] Li x (Ni a Co b Mn c ) 1-d M d O 2-y A y , where x is 0.2 - 1.2;

[0207] 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.

[0208] Regarding the lithium iron manganese phosphate material:

[0209] Li a Mn 1-y By P 1-z C z O 4-n D n where a ranges from 0 to 1.1;

[0210] Li a A x Mn 1-y B y P 1-z C z O 4-n D n where a + x ranges from 0 to 1.1.

[0211] The above limitation on x includes the molar content of Li under different charge - discharge states of the battery (usually the battery voltage is between 2 - 5V).

[0212] It can be understood that during the charge - 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 of the battery is different when the battery is discharged to different states. In the list of 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 - 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 on the basis of the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non - restrictive examples include coating modification.

[0213] In the list of positive electrode materials in this application, the content of oxygen (O) is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual content of O will fluctuate. Among them, the content of O can be measured by molar content, but is not limited thereto.

[0214] 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 - type compounds. However, this application is not limited to these materials, and other conventionally well - known materials that can be used as positive electrode active materials for sodium - ion batteries can also be used.

[0215] As an optional 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 - restrictive example of the sodium transition metal oxide can be Na x MO 2, where M may include one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1.

[0216] As an alternative technical solution of the present application, the polyanionic compound may be a type of compound having sodium ions, transition metal ions, and tetrahedral (YO 4 ) n- anion units. The transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si; n represents the valence state of (YO 4 ) n- .

[0217] The polyanionic compound may also be a type of compound having sodium ions, transition metal ions, tetrahedral (YO 4 ) n- anion units and halogen anions. The transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si, n represents the valence state of (YO 4 ) n- ; the halogen may be one or more of F, Cl, and Br.

[0218] The polyanionic compound may also be a type of compound having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) m+ and optionally halogen anions. Y may be one or more of P, S, and Si, n represents the valence state of (YO 4 ) n- ; Z represents a transition metal, which may 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 may be one or more of F, Cl, and Br.

[0219] The polyanionic compound may 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, M’ in NaM’PO 4 F can include one or more of V, Fe, Mn and Ni.

[0220] Prussian blue compounds can be a class of compounds having sodium ions, transition metal ions and cyanide ions (CN - ). Transition metals can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Non-limiting examples of Prussian blue compounds can be Na a Me b Me’ c (CN) 6 , where Me and Me’ can each independently be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0221] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder can 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.

[0222] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent. As non-limiting examples, the conductive agent can include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0223] In some of these embodiments, the positive electrode sheet can be prepared in the following manner: dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the 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 sheet 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 40wt% to 80wt%. 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 calculated by dry weight (deducting the solvent) can be 15 - 35 mg / cm 2 . The tap density of the positive electrode sheet can be 3.0 - 3.6 g / cm 3 , and can be optionally 3.3 - 3.5 g / cm 3 .

[0224] Negative electrode sheet

[0225] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0226] 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.

[0227] In some of these embodiments, the negative electrode current collector can adopt the composite current collector of the first aspect of the present application.

[0228] In some of these embodiments, the negative electrode current collector can also adopt a metal foil or other composite current collectors. For example, as the metal foil, copper foil can be adopted. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base. The composite current collector can be obtained by forming a metal material on the polymer material base. 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 base can include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE), etc.

[0229] In some of these embodiments, the negative electrode active material may be the negative electrode active material for batteries known in the art. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone, or two or more of them may be used in combination.

[0230] In some of these embodiments, the negative electrode active material layer may also optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0231] 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.

[0232] In some of these embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0233] In some of these embodiments, the negative electrode sheet may be prepared in the following manner: dispersing the above components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the 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 sheet can be obtained. The surface of the negative electrode current collector on which the negative electrode slurry is coated may be a single surface of the negative electrode current collector, or may be two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry may be 40wt% to 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 in terms of dry weight (deducting the solvent) may be 75 - 220 g / m 2 The tap density of the negative electrode sheet may be 1.0 g / cm 3 ~1.8 g / cm 3 。

[0234] Electrolyte

[0235] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. There is no particular limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0236] In some of these embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0237] In some of these embodiments, the electrolyte salt can include lithium hexafluorophosphate (LiPF 6 )、lithium tetrafluoroborate (LiBF 4 )、lithium perchlorate (LiClO 4 )、lithium hexafluoroarsenate (LiAsF 6 )、lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO 2 F 2 )、lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro(dioxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP), or one or more of them.

[0238] In some of these embodiments, the solvent can include ethylene carbonate (EC, )、propylene carbonate (PC, )、ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate 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, or one or more of them.

[0239] In some of these embodiments, the electrolytic solution may also optionally include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0240] In some embodiments, the additives in the electrolytic solution can include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl carbonate (TFPC), etc.

[0241] Separator

[0242] In some of these embodiments, a separator is further included in the secondary battery. The present application places no particular limitation on the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0243] In some of these 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.

[0244] In some embodiments, the thickness of the separator is 6 - 40 μm, and may be optionally 12 - 20 μm.

[0245] In some of these embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be made into an electrode assembly through a winding process or a stacking process.

[0246] In some of these embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0247] In some of these embodiments, the outer package of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery may also be a soft package, such as a pouch soft package. The material of the soft package may be plastic. Further, non-limiting examples of the plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0248] The secondary battery includes at least one battery cell. The secondary battery may include 1 or more battery cells.

[0249] In the present 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 sheet, a negative electrode sheet, 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 sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0250] The present application places no particular limitation on the shape of the battery cell, and it may be cylindrical, square, or any other arbitrary shape. For example, Figure 10 is a battery cell 5 with a square structure as an example.

[0251] In some of these embodiments, referring to Figure 11, 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 by 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.

[0252] The secondary battery can be a battery module 4 or a battery pack 1.

[0253] 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.

[0254] Figure 12 is the battery module 4 as an example. Refer to Figure 12 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0255] Optionally, the battery module 4 can further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0256] In some embodiments, the above battery module can also be assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery pack.

[0257] Figure 13 and Figure 14 is the battery pack 1 as an example. Refer to Figure 13 and Figure 14 , in the battery pack 1, it can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 and form a closed space for receiving the battery module 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0258] In addition, the present application also provides an electrical device, which includes the secondary battery provided by the present application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can include mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto. Among them, the mobile device can be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle can 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.

[0259] As the electrical device, the secondary battery can be selected according to its usage requirements.

[0260] Figure 15 Shown is an 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 can be adopted.

[0261] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a secondary battery can be used as the power source.

[0262] Embodiment

[0263] Hereinafter, embodiments of the present application will be described. 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 not specified in the embodiments regarding techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments not specified regarding the manufacturers, they are all conventional products that can be obtained through commercial purchase.

[0264] Embodiment 1

[0265] (1) Preparation of the composite current collector

[0266] ① Grooves are etched on one side surface of an aluminum foil with a thickness of 10 μm, and then the aluminum foil is passivated with sodium chromate to obtain a conductive layer.

[0267] ② A slurry containing polyurethane is coated on the surface of the conductive layer on the side where the grooves are etched to form a slurry layer with a coating thickness of 1 μm, and after drying, a bonding layer is formed to obtain a composite layer.

[0268] ③ The composite layer is thermally pressed and compounded with a support layer with a thickness of 8 μm, and the bonding layer is made to contact the support layer.

[0269] ④ After the thermal pressing and compounding, it is cured at 85 °C for 72 hours.

[0270] ⑤Repeat steps ① to ④ to laminate the other side of the support layer with the aluminum foil.

[0271] ⑥Thin the metal layer with a NaOH solution to obtain the composite current collector.

[0272] (2) Preparation of the positive electrode sheet

[0273] Mix LiNi 0.8 Co 0.1 Mn 0.1 O 2 and LiNi 0.5 Co 0.2 Mn 0.3 O 2 in a ratio of 17:3 as the positive electrode active material. Disperse the positive electrode active material, super conductive carbon black SP as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder in N-methylpyrrolidone (NMP) as the solvent in a mass ratio of 95:3:2 and mix evenly to obtain the positive electrode slurry; uniformly coat the positive electrode slurry on both surfaces of the composite current collector prepared in step (1), and after drying and cold pressing, obtain the positive electrode sheet.

[0274] (3) Preparation of the negative electrode sheet

[0275] Mix the negative electrode active material graphite, thickening agent sodium carboxymethyl cellulose, binder styrene-butadiene rubber, and conductive agent acetylene black in a mass ratio of 97:1:1:1, add deionized water, and obtain the negative electrode slurry under the action of a vacuum mixer; uniformly coat the negative electrode slurry on both surfaces of the copper foil; after air-drying the copper foil at room temperature, transfer it to a 120 °C oven for drying for 1 h, and then obtain the negative electrode sheet through cold pressing and slitting.

[0276] (4) Separator

[0277] Select a 12-μm-thick polypropylene separator.

[0278] (5) Preparation of the electrolyte

[0279] The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), where the volume ratio of EC, EMC, and DEC is 20:20:60. In a glove box filled with argon with a water content of <10 ppm, dissolve the fully dried lithium salt LiPF 6 in the organic solvent and mix evenly to obtain the electrolyte. Among them, the concentration of the lithium salt is 1 mol / L.

[0280] (6) Preparation of the battery

[0281] Stack the positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed between the positive and negative electrode sheets to play an insulating role. After winding them into a square bare battery cell, place it in an aluminum shell. Then, bake it at 80°C to remove moisture, inject the corresponding non-aqueous electrolyte, and after processes such as standing, formation, secondary injection, sealing, capacity measurement, and wrapping with blue film, a battery is obtained.

[0282] Examples 2 to 32

[0283] 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.

[0284] Comparative Example 1

[0285] 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 conductive layer does not have the first raised portion, and the adhesive layer does not have the second raised portion.

[0286] Table 1

[0287]

[0288]

[0289] In addition, the composite current collectors and batteries obtained in the above Examples 1 to 32 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 2 below.

[0290] Test section

[0291] (1) Measurement of the raised height and size of the first raised portion and the second raised portion

[0292] Prepare a sample of the composite current collector by ion milling (CP), and then observe it with a scanning electron microscope (SEM). Measure the height of the first raised portion and the second raised portion with the SEM equipment; the sizes of the first raised portion and the second raised portion are observed and measured directly under the SEM with a metal foil.

[0293] (2) Adhesion force test of the conductive layer

[0294] After the sample is non-corona surface bonded with an ethylene-acrylic acid copolymer (EAA) film, a 12-μm-thick PET is then covered on the EAA film. The covered film is placed on a heat sealer and bonded at a temperature of 120 °C and a pressure of 0.2 MPa. The bonded sample is cut into samples with a length of 100 mm and a width of 20 mm. The non-bonded surface of the conductive layer is attached to a steel plate with 3M double-sided tape. The sample is clamped on the fixture of a tensile testing machine with a spacing of 50 mm and a speed of 300 mm / min for a 180° peel test. The peel force is read and converted into the unit of N / m. Five parallel samples are tested, and finally the average peel force is taken. The average peel force = the sum of the peel forces of the 5 test samples / 5, which is used as the adhesion force of the conductive layer.

[0295] (3) Elastic modulus test

[0296] The composite current collector is cut into strips with a size of 15 mm * 150 mm. A universal tensile testing machine is used for tensile testing with a gauge length of 50 mm and a tensile speed of 50 mm / min until the test breaks. The chord slope method is adopted, and the chord slope corresponding to the strain from 0.05% to 0.5% is calculated. E = (σ2 - σ1) / (ε2 - ε1), where E is the elastic modulus, σ1 is the stress measured when the strain value ε1 = 0.001 (0.1%), with the unit of MPa; σ2 is the stress measured when the strain value ε2 = 0.01 (1%), with the unit of MPa.

[0297] (4) Coating wrinkling situation

[0298] A coating design of one-out-four (i.e., after the pole piece coating is slit, it becomes 4 pole pieces) is adopted. Observe the coating process to check whether the tab has wrinkles and whether the tab bulges during winding. If the bulge exceeds 1 mm, it is determined that there are wrinkles.

[0299] (5) Cycling test

[0300] The fresh battery cell is cycled at a 1C charge rate and a 1C discharge rate under the condition of 60 °C until the capacity decays to 80% of the initial capacity. Record the corresponding number of cycles at this time, which is the cycling performance of the corresponding battery.

[0301] (6) DC resistance (DCR) test

[0302] The battery cell is adjusted to a state of 50% SOC and discharged at a rate of 4C (the corresponding discharge current is I) for 30 s. Record the voltage difference ΔV before and after the 30-s discharge. Calculate the DCR corresponding to 50% SOC according to the following formula: DCR = ΔV / I to obtain the DCR data of each battery cell.

[0303] Table 2

[0304]

[0305]

[0306] Comparing the examples with Comparative Example 1, it can be seen that compared with the conventional composite current collector, the composite current collector provided by the present application and the battery using the composite current collector have higher adhesion and cycling performance respectively.

[0307] The descriptions of the above embodiments tend to emphasize the differences between the embodiments. Their similarities or similarities can be referred to each other. For the sake of brevity, they will not be elaborated herein.

[0308] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same structure and the same effect as the technical idea within the technical solution scope of the present application are included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

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

2. The composite current collector according to claim 1, characterized in that, there are a plurality of the first protrusion portions, and the plurality of first protrusion portions are spaced apart.

3. The composite current collector according to claim 1 or 2, characterized in that, the protrusion height of the first protrusion portion is less than the thickness of the bonding layer.

4. The composite current collector according to any one of claims 1-3, characterized in that, the first protrusion portion includes a first sub-protrusion portion and / or a second sub-protrusion portion. The shape of the positive projection of the first sub-protrusion portion on the surface of the conductive layer includes a hole shape, and the shape of the positive 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 and its supplementary angle included in the shape of the positive 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) The protrusion height h1 of the first sub-protrusion portion is 15% - 85% of the thickness of the bonding layer; (2) The width d1 of the first sub-protrusion portion is 5 mm - 50 mm; (3) The distance Δx1 between two adjacent first sub-protrusion portions is 10 mm - 100 mm.

7. The composite current collector according to any one of claims 4-6, characterized in that, the stripe shape includes alternately distributed stripes or intersecting stripes, and may be intersecting stripes, and further may be stripes intersecting in a grid shape.

8. The composite current collector according to claim 7, characterized in that, at least one intersection portion is included in the intersecting stripes; Optionally, the shape of the positive projection of the intersection portion on the surface of the conductive layer includes one or more of a circle, an oval, and a polygon, and may be a circle and / or an oval; Optionally, the angle and its supplementary angle included in the shape of the positive projection of the intersection portion on the surface of the conductive layer ≥ 45°.

9. The composite current collector according to any one of claims 4-8, 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 15% - 85% of the thickness of the bonding layer; (2) The width d2 of the second sub-protrusion portion is 5 mm - 40 mm; (3) The distance Δx2 between two adjacent second sub-protrusion portions is 20 mm - 150 mm.

10. The composite current collector according to any one of claims 1-9, characterized in that, the total area S1 of the positive projection of the first raised portion on the surface of the conductive layer and the area S of the surface of the conductive layer satisfy: 1% ≤ S1 / S ≤ 50%.

11. The composite current collector according to any one of claims 1-10, characterized in that, the adhesive layer includes an adhesive layer main body and a second raised portion, and the second raised portion protrudes along the thickness direction of the adhesive layer and is embedded in the conductive layer.

12. The composite current collector according to claim 11, characterized in that, the raised height of the second raised portion is equal to the thickness of the conductive layer.

13. The composite current collector according to claim 11 or 12, characterized in that, there are a plurality of the second raised portions, and the plurality of second raised portions are arranged at intervals; optionally, the distance Δx3 between two adjacent second raised portions is 5 mm to 100 mm.

14. The composite current collector according to any one of claims 11-13, characterized in that, the second raised portion and the first raised portion are arranged at intervals; and / or, at least one of the first raised portions is provided between two adjacent second raised portions.

15. The composite current collector according to any one of claims 11-14, characterized in that, the total area S2 of the positive projection of the second raised portion on the surface of the conductive layer and the total area S1 of the positive projection of the first raised portion on the surface of the conductive layer satisfy: S2 < S1.

16. The composite current collector according to any one of claims 11-15, characterized in that, the width d3 of the second raised portion is 50 μm to 500 μm.

17. The composite current collector according to any one of claims 11-16, characterized in that, the shape of the positive projection of the second raised portion 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; optionally, the angle included in the shape of the positive projection of the second raised portion on the surface of the conductive layer is ≥ 45°.

18. The composite current collector according to any one of claims 11-17, characterized in that, the total area S2 of the positive projection of the second raised portion on the surface of the conductive layer and the area S of the surface of the conductive layer satisfy: 0.001% ≤ S2 / S ≤ 0.8%.

19. The composite current collector according to any one of claims 11-18, characterized in that, the second raised portion contains an adhesive; optionally, the adhesive 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, modified polyethylene, modified polypropylene, modified polyolefin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide; Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

20. The composite current collector according to any one of claims 11-19, characterized in that at least one of the following conditions is satisfied: (1) The thickness of the main body of the adhesive layer is 0.5 μm to 3 μm; (2) The adhesion of the conductive layer is ≥ 230 N / m.

21. The composite current collector according to any one of claims 1-20, characterized in that at least one of the following conditions is satisfied: (1) The thickness of the main body of the conductive layer is 0.5 μm to 5 μm; (2) The thickness of the support layer is 2 μm to 15 μm.

22. The composite current collector according to any one of claims 1-21, characterized in that at least one of the following conditions is satisfied: (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, polyazotized sulfur-based polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their crosslinked products and their copolymers; (2) The adhesive layer includes 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, modified polyolefin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide; Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane; (3) The conductive layer includes one or more of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium and tin.

23. An electrode sheet, characterized in that it includes the composite current collector according to any one of claims 1-22.

24. A secondary battery, characterized in that it includes the electrode sheet according to claim 23.

25. An electrical device, characterized in that it includes the secondary battery according to claim 24.

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