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 support layer, and a bonding layer and a conductive layer which are sequentially laminated on at least one side surface of the support layer, the bonding layer comprises a bonding layer main body and a protruding part, and the protruding part protrudes from the bonding layer main body and is embedded in the support layer. The composite current collector provided by the invention has relatively high bonding layer and machinability, so that the cycle performance of the secondary battery can be improved.

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 range of secondary batteries represented by lithium-ion batteries, secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the great development of secondary batteries, higher requirements are also put forward for their energy density, cycle performance, safety performance, etc. In a secondary battery, as a component carrying active materials, the current collector has a great influence on the electrochemical performance of the battery. However, the commonly used composite current collectors at present have problems such as poor adhesion, and thus are likely to cause problems such as poor cycle performance after being used in batteries; moreover, the elastic modulus of the composite current collector is relatively low, resulting in poor 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 an adhesive layer and a conductive layer sequentially laminated on at least one surface of the support layer, the adhesive layer including an adhesive layer main body and a protrusion portion, the protrusion portion protruding from the adhesive layer main body and embedding into the support layer.

[0006] In some embodiments of the present application, there are multiple protrusion portions, and the multiple protrusion portions are arranged at intervals.

[0007] In some embodiments of the present application, the protrusion portion includes a first protrusion portion and / or a second protrusion portion, the protrusion height of the first protrusion portion is less than the thickness of the support layer, and the protrusion height of the second protrusion portion is equal to the thickness of the support 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 adhesive layer includes a hole shape, and the shape of the orthographic projection of the second sub-protrusion portion on the surface of the adhesive 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 angle included in the shape of the orthographic projection of the first sub-protrusion portion on the surface of the adhesive layer is ≥ 45°.

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

[0013] (1) The protrusion height h1 of the first sub-protrusion portion is 50 nm to 1000 nm;

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

[0015] (3) The spacing Δx1 between two adjacent first sub-protrusion portions is 10 mm to 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 adhesive 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 angle included in the shape of the orthographic projection of the intersection portion on the surface of the adhesive layer is ≥ 45°.

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

[0021] (1) The protrusion height h2 of the second sub-protrusion portion is 50 nm to 1000 nm;

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

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

[0024] 11. The composite current collector according to any one of claims 3-10, wherein the total area S1 of the orthographic projection of the first protrusion on the surface of the adhesive layer and the area S of the surface of the support layer satisfy: 2% ≤ S1 / S ≤ 50%.

[0025] In some embodiments of the present application, it is characterized in that at least one of the first protrusions is provided between two adjacent second protrusions;

[0026] Optionally, the total area S2 of the orthographic projection of the second protrusion on the surface of the adhesive layer and the total area S1 of the orthographic projection of the first protrusion on the surface of the adhesive layer satisfy: S2 < S1.

[0027] In some embodiments of the present application, the second protrusion satisfies at least one of the following conditions:

[0028] (1) The width d3 of the second protrusion is 50 μm to 500 μm;

[0029] (2) The spacing Δx3 between two adjacent second protrusions is 5 mm to 50 mm.

[0030] In some embodiments of the present application, the shape of the orthographic projection of the second protrusion on the surface of the adhesive layer includes one or more of a circular hole, an oval hole, a fan-shaped hole, a bow-shaped hole, and a polygonal hole, and may be a circular hole and / or an oval hole;

[0031] Optionally, the angle included in the shape of the orthographic projection of the second protrusion on the surface of the adhesive layer is ≥ 45°.

[0032] In some embodiments of the present application, the total area S2 of the orthographic projection of the second protrusion on the surface of the adhesive layer and the area S of the surface of the support layer satisfy: 0 ≤ S2 / S ≤ 0.8%, and may be 0.0001% ≤ S2 / S ≤ 0.8%.

[0033] In some embodiments of the present application, the protrusion contains an adhesive;

[0034] Optionally, the adhesive includes one or more of polyfunctional isocyanate, polyester polyol, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide, and may be one or more of polyfunctional isocyanate, polyester polyol, and polyurethane;

[0035] Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0036] In some embodiments of the present application, at least one of the following conditions is satisfied:

[0037] (1) The thickness of the conductive layer is 0.5 μm to 5 μm;

[0038] (2) The thickness of the main body of the adhesive layer is 0.5 μm to 3 μm;

[0039] (3) The thickness of the support layer is 2 μm to 15 μm.

[0040] In some embodiments of the present application, the adhesion between the adhesive layer and the support layer is ≥230 N / m.

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

[0042] (1) The support layer includes one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene styrene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, sulfur nitride polymer materials, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their crosslinked products and their copolymers;

[0043] (2) The adhesive layer includes one or more of a composition containing polyfunctional isocyanate and polyester polyol compounds, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, modified polyethylene, modified polypropylene, modified polyolefin, silicone resin, ethylene-acrylic copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate and polyamide;

[0044] Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane;

[0045] (3) The conductive layer includes one or more of copper, aluminum, nickel, titanium, platinum, iron, cobalt, chromium, tungsten, molybdenum, magnesium, lead, indium and tin.

[0046] The second aspect of the present application further provides a pole piece, including the composite current collector described in the first aspect of the present application.

[0047] The third aspect of the present application provides a secondary battery, including the electrode sheet described in the second aspect of the present application.

[0048] The second aspect of the present application provides an electrical device, including the secondary battery of the first aspect of the present application.

[0049] 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.

[0050] Details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the present application will become apparent from the specification, the drawings, and the claims.

[0051] The composite current collector provided by the present application is provided with the raised portion in the adhesive layer, which can increase the surface area of contact between the adhesive layer and the support layer, enhance the adhesion of the adhesive layer to the support layer, thereby improving the adhesion force between the adhesive layer and the support layer, effectively reducing the shedding of the conductive layer, and further improving the cycle performance of the battery cell using the composite current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] 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 application, the currently described embodiments or examples, and the currently understood best mode of these applications. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0053] Figure 1 is a schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0054] Figure 2 is a schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0055] Figure 3 is a schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0056] Figure 4 is a schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0057] Figure 5 is a schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

[0058] Figure 6 is a schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

[0059] Figure 7 is a schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

[0060] Figure 8 Schematic top view structure diagram of a composite current collector according to an embodiment of the present application.

[0061] Figure 9 Schematic cross-sectional structure diagram of a composite current collector according to an embodiment of the present application.

[0062] Figure 10 Schematic diagram of a battery cell according to an embodiment of the present application.

[0063] Figure 11 is Figure 10 Exploded view of the battery cell shown in an embodiment of the present application.

[0064] Figure 12 Schematic diagram of a battery module according to an embodiment of the present application.

[0065] Figure 13 Schematic diagram of a battery pack according to an embodiment of the present application.

[0066] Figure 14 is Figure 13 Exploded view of the battery pack shown in an embodiment of the present application.

[0067] Figure 15 Schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0068] Explanation of reference numerals:

[0069] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device; 11 Support layer; 12 Adhesive layer; 13 Conductive layer; 121 Adhesive layer main body; 122 Protrusion; 1221 First protrusion; 1222 Second protrusion; 12211 First sub-protrusion; 12212 Second sub-protrusion. Detailed description of specific embodiments

[0070] Hereinafter, some embodiments of the composite current collector, the electrode sheet, the secondary battery, and the electrical device of the present application will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters are omitted 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 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.

[0071] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can include or not include the end values, and 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 understood to be anticipated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4, and 5 are also listed, the following ranges are all anticipated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to listing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when it is stated that a certain parameter is an integer selected from "2 - 10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0072] In this application, when it comes to "multiple", "a variety of", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0073] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0074] Referring to "embodiment" in this text means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment or implementation manner of this application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. The same understanding applies to "implementation manner" mentioned in this text.

[0075] Those skilled in the art can understand that in the methods of each embodiment or example, the written order of each step does not mean a strict execution order that constitutes any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Without special instructions, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means 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), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0076] In this application, in an open technical feature or technical solution described by words such as "containing", "comprising", "including", etc., without other instructions, additional members other than the listed members are not excluded, and it can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution that further includes additional members outside the listed members. For example, A comprises a1, a2 and a3. Without other instructions, it may further include other members or may not include additional members, and it can be regarded as providing both a feature or solution that "A consists of a1, a2 and a3" and a feature or solution that "A not only includes a1, a2 and a3, but also includes other members". In this application, without other instructions, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0077] In this application, "optionally", "optional", "option" mean that it is optional, that is, it refers to any one of two alternative options of "having" or "not having". If "optional" appears multiple times in a technical solution, without special instructions and without contradictions or mutual restrictions, each "optional" is independent of each other.

[0078] 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 usually not very high. During the cell processing and the cell recycling process, the conductive layer and the polymer material layer in the composite current collector are prone to peeling off, resulting in problems such as a significant drop in cell performance. 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, which may cause problems such as wrinkling during the processing of the composite current collector, making its mechanical properties unable to meet the processing requirements.

[0079] To solve the above technical problems, the present application proposes a composite current collector. By providing a protrusion on the surface of the adhesive layer adjacent to the support layer, the surface area of contact between the adhesive layer and the support layer can be increased, thereby enhancing the adhesion between the adhesive layer and the support layer, and further improving the cycling performance of the cell using this composite current collector. The following will describe this composite current collector in more detail.

[0080] In a first aspect, the present application provides a composite current collector, which can be referred to Figure 1 , including a support layer 11 and an adhesive layer 12 and a conductive layer 13 sequentially stacked on at least one surface of the support layer 11. The adhesive layer 12 includes an adhesive layer main body 121 and a protrusion 122. The protrusion 122 protrudes from the adhesive layer main body 121 and embeds into the support layer 11.

[0081] It should be noted that the "surface of the adhesive layer" or "the surface of the adhesive layer" in the present application refers to the surface of the adhesive layer that is perpendicular to the thickness direction of the current collector and adjacent (or in contact) to the support layer. The "area of the surface of the adhesive layer" refers to the area of the surface of the adhesive layer that is adjacent (or in contact) to the support layer and perpendicular to the thickness direction of the current collector. The "surface of the support layer" or "the surface of the support layer" in the present application refers to the surface of the support layer that is perpendicular to the thickness direction of the current collector and adjacent (or in contact) to the adhesive layer. The "area of the surface of the support layer" refers to the area of the surface of the support layer that is adjacent (or in contact) to the adhesive layer and perpendicular to the thickness direction of the current collector.

[0082] The above composite current collector provided by the present application is provided with the protrusion in the adhesive layer, which can increase the surface area of contact between the adhesive layer and the support layer, enhance the adhesion of the adhesive layer to the support layer, thereby enhancing the adhesion between the adhesive layer and the support layer, effectively reducing the peeling off of the conductive layer, and further improving the cycling performance of the cell using this composite current collector.

[0083] In some embodiments, there are multiple raised portions, and the multiple raised portions are spaced apart.

[0084] It can be understood that the multiple raised portions being spaced apart means that there is a gap (spacing) between any two adjacent raised portions.

[0085] The multiple raised portions being spaced apart can, while enhancing the adhesion between the adhesive layer and the support layer, endow the support layer and the composite current collector with sufficient mechanical strength, thereby enhancing the structural stability of the composite current collector. In addition, when there are multiple raised portions, the support layer will be embedded in the gaps between adjacent raised portions. At this time, the support layer embedded in the gaps between adjacent raised portions can play a role in supporting the adhesive layer; the adhesive layer is embedded in the support layer, and the contact area between the adhesive layer and the support layer increases, making the adhesive layer and the support layer combine more tightly, enabling the adhesive layer to better obtain support from the support layer; enabling the elastic modulus of the adhesive layer to be increased, thereby increasing the overall elastic modulus of the composite current collector, reducing the occurrence of problems such as wrinkling during the processing process, and enhancing its processability.

[0086] In some embodiments, the total area S' of the orthographic projection of the raised portion on the surface of the adhesive layer and the area S of the surface of the support layer satisfy: S' < S.

[0087] The total area S' of the orthographic projection of the raised portion on the surface of the adhesive layer being less than the area S of the surface of the support layer can, while enhancing the adhesion between the adhesive layer and the support layer, endow the support layer and the composite current collector with sufficient mechanical strength, thereby enhancing the structural stability of the composite current collector.

[0088] 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. However, in the process of introducing the adhesive and compounding the conductive layer and the polymer material layer, the adhesive layer formed by the adhesive is extremely likely to form bubbles or pores with the polymer material layer, resulting in poor adhesion of the adhesive layer, and thus easily causing the detachment of the adhesive layer together with the conductive layer during the processing of the battery cell and during the cyclic use of the battery cell, leading to problems such as a significant drop in the performance of the battery cell.

[0089] In some embodiments, the raised portion includes a first raised portion and / or a second raised portion, the height of the first raised portion is less than the thickness of the support layer, and the height of the second raised portion is equal to the thickness of the support layer.

[0090] The raised portion includes a first raised portion, and the height of the first raised portion is less than the thickness of the support layer. This can, while enhancing the adhesion between the adhesive layer and the support layer, also reduce the impact on the main structural strength of the support layer, endowing the support layer and the composite current collector with sufficient mechanical strength.

[0091] The raised portion includes a second raised portion, and the height of the second raised portion is equal to the thickness of the support layer, that is, the second raised portion penetrates the support layer along the thickness direction of the composite current collector, which helps to promote the discharge of air bubbles or pores formed between the adhesive layer and the support layer during the formation of the adhesive layer, thereby further improving the adhesion between the adhesive layer and the support layer.

[0092] In some embodiments, refer to Figure 2 , the raised portion 122 includes a first raised portion 1221.

[0093] In some embodiments, refer to Figure 3 , the shown raised portion 122 includes a second raised portion 1222.

[0094] In some embodiments, refer to Figure 4 , the raised portion 122 includes a first raised portion 1221 and a second raised portion 1222.

[0095] In some embodiments, the raised portion contains an adhesive.

[0096] It should be noted that when the raised portion includes a first raised portion and a second raised portion, the adhesives in the first raised portion and the second raised portion may be the same or different.

[0097] The raised portion includes a first raised portion and / or a second raised portion. Among them, the first raised portion can increase the wettability of the support layer to the adhesive, and the filling of the adhesive in the raised portion can increase the surface area of contact between the support layer and the adjacent adhesive layer, thereby improving the adhesion between the adhesive layer and the support layer.

[0098] In addition to increasing the surface area of contact between the support layer and the adjacent adhesive layer, the second raised portion also helps to discharge air bubbles or pores formed between the adhesive layer and the support layer during the introduction of the adhesive to form the adhesive layer, enabling the adhesive layer to better adhere to the support layer, thereby improving the adhesion between the adhesive layer and the support 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.

[0099] When the raised portion includes both a first raised portion and a second raised portion at the same time, the interfacial contact between the adhesive layer and the support layer can be made closer, which helps to further improve the adhesion.

[0100] In some embodiments, the binder includes one or more of polyfunctional isocyanate, polyester polyol, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide, and may be one or more of polyfunctional isocyanate, polyester polyol, and polyurethane.

[0101] In some embodiments, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

[0102] In some embodiments, the first protrusion 1221 includes a first sub-protrusion 12211 and / or a second sub-protrusion 12212.

[0103] It can be understood that when the protrusion 122 includes the first protrusion 1221, the adhesive layer 12 may be provided with only the first sub-protrusion 12211 (see Figure 5 and Figure 6 ), or may be provided with only the second sub-protrusion 12212 (see Figure 7 and Figure 8 ), or may also be provided with a combination of the first sub-protrusion 12211 and the second sub-protrusion 12212.

[0104] When the first sub-protrusion and the second sub-protrusion are combined, it can achieve a better effect of improving the adhesive force, and at the same time enable the composite current collector to have sufficient mechanical strength.

[0105] In some embodiments, the shape of the orthographic projection of the first sub-protrusion on the surface of the adhesive layer includes a hole shape (see Figure 5 and Figure 6 ).

[0106] In some embodiments, the hole shape includes, but is not limited to, a circular hole, an oval hole (see Figure 6 ), a fan-shaped hole, a bow-shaped hole, and a polygonal hole (see Figure 5 ) and the like, and may be a circular hole and / or an oval hole.

[0107] It can be understood that the "hole shape" or "hole" described in this application refers to a regular or irregular bounded shape or a closed planar geometric figure of the orthographic projection on the surface of the adhesive layer. For example, a "circular hole" means that the orthographic projection shape is circular, and a "fan-shaped hole" means that the orthographic projection shape is fan-shaped.

[0108] It can be understood that the orthographic projection of the first sub-protrusion on the surface of the adhesive layer includes a hole shape. At this time, the first sub-protrusions are in a discrete distribution (or alternating distribution) pattern, and any two first sub-protrusions do not intersect and there is a gap between them.

[0109] It can be understood that the "bow shape" described in this application refers to the figure enclosed by an arc and the chord it subtends.

[0110] When the hole shape includes a circular hole and / or an oval hole, the first sub-protrusion does not include an acute tip, which is beneficial for the adhesive to more completely infiltrate and fill the entire protrusion, helps to improve the adhesion between the adhesive layer and the support layer, and reduces the detachment of the adhesive layer and the conductive layer. At the same time, the circular hole shape and / or the oval shape can provide support for the adhesive layer in 360 degrees, making the elastic modulus of the adhesive layer higher, and thus making the elastic modulus of the composite current collector higher.

[0111] In some embodiments, the angle included in the shape of the orthographic projection of the first sub-protrusion on the surface of the adhesive layer is ≥45°.

[0112] It can be understood that the angle included in the shape of the orthographic projection of the first sub-protrusion on the surface of the adhesive layer, that is, the angle included in the hole shape, means that when the hole shape is a polygon, each angle of the polygon is ≥45°; when the hole shape is a sector or a bow shape, the central angle corresponding to the sector or the bow shape is ≥45°.

[0113] The angle included in the shape of the orthographic projection of the first sub-protrusion on the surface of the adhesive layer is ≥45°, which helps the adhesive to more completely infiltrate and fill the protrusion, reduces the problem that the tip of the protrusion is not easily infiltrated by the adhesive, improves the adhesion of the adhesive layer to the support layer, and reduces the detachment of the support layer.

[0114] In some embodiments, the protrusion height h1 of the first sub-protrusion (see Figure 2 ) is 50 nm to 1000 nm.

[0115] For example, the protrusion height of the first sub-protrusion can be 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or within the range composed of any of the above values.

[0116] 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 adhesive layer provided with the first sub-protrusion.

[0117] When the protrusion height of the first sub-protrusion is within the above range, on the one hand, it can enable the binder to better infiltrate the protrusion, thereby further enhancing the adhesion of the adhesive layer to the support layer and further increasing the adhesive force between the two. On the other hand, it can further enhance the supporting effect of the support layer embedded in the gap between adjacent protrusions on the adhesive layer, thereby increasing the elastic modulus of the adhesive layer and the composite current collector.

[0118] In some embodiments, the width d1 of the first sub-protrusion (see Figure 5 and Figure 6 ) is 5 mm to 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.

[0119] When the width of the first sub-protrusion is within the above range, on the one hand, it can enable the binder to better infiltrate the protrusion, thereby further enhancing the adhesion of the adhesive layer to the support layer and further increasing the adhesive force between the two. On the other hand, it can also enable the support layer embedded in the gap between adjacent protrusions to better support the adhesive layer, so that the elastic modulus of the current collector is further increased.

[0120] 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 positive projection of the first sub-protrusion on the surface of the adhesive layer (when the shape of the positive projection is a circular hole, an oval hole, a fan-shaped hole or a bow-shaped hole), or the maximum side length of the contour (when the shape of the positive projection is a polygonal hole).

[0121] In some embodiments, the spacing Δx1 between two adjacent first sub-protrusions (see Figure 2 ) is 10 mm to 100 mm. For example, the spacing 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.

[0122] It should be noted that the "spacing between two adjacent first sub-protrusions" refers to the horizontal distance between the centers 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 adhesive layer.

[0123] When the spacing between two adjacent first sub-protrusions is within the above range, on the one hand, it can enable the binder to better infiltrate the protrusion, thereby further enhancing the adhesion of the adhesive layer to the support layer and further increasing the adhesive force between the two. On the other hand, it can also enable the support layer embedded in the gap between adjacent protrusions to better support the adhesive layer, so that the elastic modulus of the current collector is further increased.

[0124] In some embodiments, the shape of the orthographic projection of the second sub-protrusion on the surface of the adhesive layer includes a stripe shape (see Figure 7 and Figure 8 ).

[0125] The stripe shape can further increase the contact area between the support layer and the adhesive layer, and further enhance the wettability of the protrusion surface, which helps the adhesive to better wet the protrusion, thereby further improving the adhesion between the adhesive layer and the support 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 and mechanical strength of the entire composite current collector.

[0126] In some embodiments, the stripe shape includes one or more of oval stripes, polygonal stripes, arc stripes, and wavy stripes, and may be an oval stripe.

[0127] The oval stripe can better connect the inside of the second sub-protrusion, further enhance the wettability of the protrusion surface, improve the wetting effect of the adhesive on the protrusion, and further increase the contact area between the support layer and the adhesive layer, thereby further improving the adhesion between the adhesive layer and the support layer.

[0128] In some embodiments, the stripe shape includes stripes distributed at intervals (see Figure 7 ) or intersecting stripes (see Figure 8 ), and may be intersecting stripes, and further may be stripes intersecting in a grid shape.

[0129] It can be understood that the "stripes distributed at intervals" described in this application means that there is no intersection and there is an interval between any two stripes; the "intersecting stripes" means that there is an intersection between the stripes. For example, there is an intersection between horizontally distributed stripes and vertically distributed stripes.

[0130] In some embodiments, at least one intersection part is included in the intersecting stripes.

[0131] The intersecting stripes can make the protrusions on the whole surface in a connected state, enable the adhesive to flow better inside the protrusions, improve the wetting effect of the adhesive on the protrusions, and thus improve the adhesion of the adhesive layer to the support layer.

[0132] In some embodiments, the shape of the orthographic projection of the intersection part on the surface of the adhesive layer includes one or more of a circle, an ellipse, and a polygon, and may be a circle and / or an ellipse.

[0133] When the shape of the orthographic projection of the intersection on the surface of the adhesive layer includes a circle and / or an ellipse, the intersection does not include an acute-angled tip. At this time, the adhesive can more completely infiltrate the intersection, which helps to improve the adhesion of the adhesive layer to the support layer and reduce the detachment of the support layer.

[0134] In some embodiments, the angles included in the shape of the orthographic projection of the intersection on the surface of the adhesive layer are ≥45°.

[0135] It can be understood that the angles included in the shape of the orthographic projection of the intersection on the surface of the adhesive layer being ≥45° means that when the shape of the orthographic projection is a polygon, each angle of the polygon is ≥45°.

[0136] The angles included in the shape of the orthographic projection of the intersection on the surface of the adhesive layer being ≥45° helps to make the adhesive more completely infiltrate the intersection, reduce the problem that the tip of the intersection is not easily infiltrated by the adhesive, improve the adhesion of the adhesive layer to the support layer, and reduce the detachment of the support layer.

[0137] In some embodiments, the height h2 of the second sub-protrusion (see Figure 9 ) is 50 nm to 1000 nm. For example, the height of the second sub-protrusion can be 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm or within the range composed of any of the above values.

[0138] It should be noted that the "height of the second sub-protrusion" refers to the distance between the highest point of the top of the second sub-protrusion and the surface of the adhesive layer provided with the second sub-protrusion.

[0139] When the height of the second sub-protrusion is within the above range, while further improving the adhesion of the adhesive layer to the support layer, it can also further improve the support effect of the support layer embedded in the gap between adjacent protrusions on the adhesive layer, thereby improving the elastic modulus of the adhesive layer and the composite current collector.

[0140] In some embodiments, the width d2 of the second sub-protrusion (see 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.

[0141] 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.

[0142] In some embodiments, the spacing Δx2 between two adjacent second sub-protrusions (seeFigure 9 ) is from 20 mm to 150 mm. For example, the distance 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, 120 mm, 140 mm, 150 mm or within the range composed of any of the above values.

[0143] It should be noted that the "distance 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 adhesive layer.

[0144] When the protrusion height, width of the second sub-protrusion and the distance between two adjacent second sub-protrusions are within the above ranges, on the one hand, it can enable the adhesive to better infiltrate the protrusions, thereby further improving the adhesion of the adhesive layer to the support layer and further enhancing the adhesive force between the two. On the other hand, it can reduce the impact on the strength of the main support layer, and at the same time enable the support layer embedded in the gap between adjacent protrusions to play a better supporting role for the adhesive layer, further enhancing the elastic modulus of the composite current collector.

[0145] In some embodiments, the total area S1 of the orthographic projection of the first protrusion on the surface of the adhesive layer and the area S of the surface of the support layer satisfy: 0 ≤ S1 / S ≤ 30%. For example, S1 / S can be 2%, 5%, 7%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or within the range composed of any of the above values.

[0146] When the total area S1 of the orthographic projection of the first protrusion on the surface of the adhesive layer and the area S of the surface of the support layer satisfy the above relationship, while improving the adhesive force, it can also reduce the impact on the strength of the support layer, enable the composite current collector to have sufficient mechanical strength, improve the structural stability of the composite current collector, and enhance the safety of the battery cell.

[0147] In some embodiments, at least one first protrusion is provided between two adjacent second protrusions.

[0148] The second protrusions and the first protrusions are arranged alternately, which can not only reduce the problem of uneven exhaust during the compounding process of the adhesive layer and the support layer, but also enable the composite current collector to have sufficient mechanical strength and structural stability.

[0149] In some embodiments, the total area S2 of the orthographic projection of the second protrusion on the surface of the adhesive layer and the total area S1 of the orthographic projection of the first protrusion on the surface of the adhesive layer satisfy: S2 < S1.

[0150] The total area S2 of the orthographic projection of the second convex portion on the surface of the adhesive layer and the total area S1 of the orthographic projection of the first convex portion on the surface of the adhesive layer satisfy the above relationship, which can not only reduce the generation of air bubbles during the compounding process of the adhesive layer and the support layer, improve the adhesive force, but also ensure the performance of the battery cell and enhance the safety.

[0151] In some embodiments, the width d3 of the second convex portion is 50 μm to 500 μm. For example, the width of the second convex portion can be 50 μm, 60 μm, 100 μm, 300 μm, 500 μm or within the range composed of any of the above values.

[0152] It should be noted that, similar to the width of the first sub-convex portion, the "width of the second convex portion" in this application refers to the maximum value of the distance between any two points on the shape contour of the orthographic projection of the second convex portion on the surface of the adhesive 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).

[0153] In some embodiments, the spacing Δx3 between two adjacent second convex portions (see Figure 9 ) is 5 mm to 50 mm. For example, the spacing between two adjacent second convex portions can be 5 mm, 7 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm or within the range composed of any of the above values.

[0154] It should be noted that the "spacing between two adjacent second convex portions" in this application refers to the horizontal distance between the centers of two adjacent second convex portions. 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 adhesive layer.

[0155] When the width of the second convex portion and the distance between two adjacent second convex portions are within the above ranges, it is beneficial to enhance the exhaust function of the second convex portion, and helps the adhesive to more completely infiltrate the convex portion. At the same time, it can also reduce the cracking problem that is likely to occur at the position of the second convex portion during the processing of the composite current collector. Thus, while improving the adhesive force, the conductivity and strength (mechanical) performance of the current collector can also be taken into account.

[0156] In some embodiments, the shape of the orthographic projection of the second convex portion on the surface of the adhesive layer includes one or more of a circular hole, an elliptical hole, a sector hole, a bow-shaped hole and a polygonal hole, and can be selected as a circular hole and / or an elliptical hole.

[0157] When the shape of the orthographic projection of the second convex portion on the surface of the adhesive layer includes a circular hole and / or an elliptical hole, the second convex portion does not include an acute-angle tip. At this time, the adhesive can more completely infiltrate the convex portion, which helps to improve the adhesive force of the adhesive layer to the support layer and reduce the detachment of the support layer.

[0158] In some embodiments, the angles included in the shape of the orthographic projection of the second protrusion on the surface of the adhesive layer are ≥45°.

[0159] It can be understood that the angles included in the shape of the orthographic projection of the second protrusion on the surface of the adhesive layer refer to that when the shape of the orthographic projection is a polygon, each angle of the polygon is ≥45°; when the shape of the orthographic projection is a sector or a segment of a circle, the central angle corresponding to the sector or the segment of a circle is ≥45°.

[0160] The angles included in the shape of the orthographic projection of the second protrusion on the surface of the adhesive layer being ≥45° helps the adhesive to more completely wet the protrusion, reduces the problem that the tip of the second protrusion is not easily wetted by the adhesive, improves the adhesive force of the adhesive layer to the support layer, and reduces the detachment of the support layer.

[0161] In some embodiments, the total area S2 of the orthographic projection of the second protrusion on the surface of the adhesive layer and the area S of the surface of the support layer satisfy: 0 ≤ S2 / S ≤ 0.8%. For example, S2 / S can be 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or within the range composed of any of the above values. Optionally, S2 / S satisfies: 0.0001% ≤ S2 / S ≤ 0.8%.

[0162] The total area S2 of the orthographic projection of the second protrusion on the surface of the adhesive layer and the area S of the surface of the support layer satisfying the above relationship can, while improving the adhesive force, 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.

[0163] In some embodiments, the thickness of the conductive layer is 0.5 μm to 5 μm. For example, the thickness of the conductive layer can be 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or within the range composed of any of the above values.

[0164] 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.

[0165] 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.

[0166] The thicknesses of the support layer, the main body of the adhesive layer, and the conductive layer are each within the above ranges. While improving the adhesion, the conductivity and strength (mechanical) properties of the current collector can also be taken into account.

[0167] In some embodiments, the adhesion between the adhesive layer and the support layer is ≥230 N / m.

[0168] When the adhesion between the adhesive layer and the support layer is within the above range, there can be a relatively high adhesion between the adhesive layer and the support layer, reducing the film peeling problem of the composite current collector when immersed in the electrolyte, improving the long-term stability of the composite current collector, and ultimately enhancing the long-term stability of the battery; and it can also endow the composite current collector with sufficient mechanical properties, reducing the processing defects caused by the decline in mechanical properties during subsequent processing.

[0169] In some embodiments, the surface dyne value of the support layer is ≥50 mN / m.

[0170] When the surface dyne value of the support layer reaches the above range, the surface energy of the support layer can be increased, making it easier for the binder to be coated on the surface of the support layer, improving the wettability of the support layer to the binder, and thus being beneficial to enhancing the adhesion between the adhesive layer and the support layer.

[0171] In some embodiments, the surface dyne value of the support layer can reach the above range by corona treating the support layer.

[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 polymer materials, 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 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.

[0174] In some embodiments, the polyurethane includes 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 and / or through-holes on at least one surface of the support layer;

[0178] S2. Coat a slurry containing a binder on the surface of the support layer provided with grooves and / or through-holes to prepare a bonding layer, and after drying, form a composite layer containing the support layer and the bonding layer;

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

[0180] In some embodiments, in step S1, grooves can be prepared on at least one surface of the support layer by a hot embossing method.

[0181] In some embodiments, in step S1, through-holes can be prepared on at least one surface of the support layer by an etching method.

[0182] It can be understood that when the embossing depth of hot embossing is less than the thickness of the support layer, grooves can be prepared; and when the etching depth of etching is equal to the thickness of the support layer, through-holes can be prepared.

[0183] In some embodiments, the bonding layer includes a bonding layer main body and a protruding portion, and the protruding portion protrudes along the thickness direction of the bonding layer and is embedded in the support layer.

[0184] It can be understood that in step S2, after coating the slurry containing the binder on the surface of the support layer provided with grooves and / or through-holes, the slurry will penetrate into the grooves and / or through-holes and fill the grooves and / or through-holes. After completely filling the grooves and / or through-holes, a slurry layer can be continuously coated on the surface of the support layer and formed. After drying, the slurry layer forms the bonding layer main body, and the grooves and / or through-holes filled with the slurry form the protruding portion, and the bonding layer main body and the protruding portion become an integral body to obtain the bonding layer. Thus, the bonding layer can be composite with the conductive layer, and the protruding portion is embedded in the conductive layer.

[0185] In some embodiments, the protruding portion includes a first protruding portion and / or a second protruding portion.

[0186] It can be understood that the first convex portion can correspond to the groove in step S1, and the second convex portion can correspond to the through hole in step S1.

[0187] In some embodiments, the composite treatment in step S3 includes: thermocompression bonding a composite layer including a bonding layer and a support layer with a conductive layer. During thermocompression bonding, the bonding layer in the composite layer is brought into contact with the conductive layer.

[0188] The temperature of thermocompression bonding is close to the melting point of the binder, so that the binder in the bonding layer is in a molten state. The molten binder can be better bonded with the conductive layer.

[0189] It should be noted that when the convex portion includes the second convex portion, on the one hand, the presence of the second convex portion can play a role in removing bubbles when applying the slurry containing the binder, reducing the bubbles and pores between the support layer and the bonding layer, and improving the bonding force therebetween; on the other hand, during thermocompression bonding, the bubbles can be discharged from the second convex portion. Therefore, the presence of the second convex portion can further remove bubbles and further improve the bonding force.

[0190] In some embodiments, step S3 further includes a process of passivating the conductive layer.

[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 conductive layer, 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 electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions are intercalated and deintercalated back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, mainly functioning to prevent short circuit between the positive and negative electrodes and allowing ions to pass through at the same time.

[0198] Positive electrode sheet

[0199] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode 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 provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0201] In some embodiments, the positive electrode current collector can adopt the composite current collector of the first aspect of the present application.

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

[0203] In some embodiments, the positive electrode can adopt the positive electrode active material for a battery well-known in the art. As a non-limiting example, the positive electrode active material can 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 battery positive electrode active materials can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (such as LiCoO 2) one or more of lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their modified compounds, etc. Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, composite materials of lithium iron phosphate and carbon, lithium manganese phosphate, composite materials of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and composite materials of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide may include LiCoO 2 ; non-limiting examples of lithium nickel oxide may include LiNiO 2 ; non-limiting examples of lithium manganese oxide may include LiMnO 2 , LiMn 2 O 4 etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 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 may 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 Mnc ) 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 B y P 1-z C z O 4-n D n where a is 0 - 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 is 0 - 1.1.

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

[0212] It can be understood that during the charge and discharge process of the battery, the insertion and extraction and consumption of lithium (Li) will occur, and the content of Li in the positive electrode plate of the battery is different when the battery is discharged to different states. In the listing of the positive electrode materials in this application, unless otherwise specified, the content of Li is the initial state of the material. When the positive electrode material is applied to the positive electrode plate in the battery system, after charge and discharge cycling, the content of Li in the positive electrode material contained in the plate usually changes. Among them, the content of Li can be measured by molar content, but is not limited to this. 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 the positive electrode materials. The aforementioned appropriate modification refers to the acceptable modification methods for the positive electrode materials, and non-limiting examples include coating modification.

[0213] In the enumeration of the cathode material in this application, the content of oxygen (O) is only the theoretical value. 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 it is not limited to this.

[0214] In some embodiments, the cathode active material may also include at least one of the following materials: sodium transition metal oxides, polyanion-type compounds, and one or more of Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as the cathode active material of sodium ion batteries can also be used.

[0215] As an alternative technical solution of this application, in the sodium transition metal oxide, the transition metal may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of the sodium transition metal oxide may be Na x MO 2 , where M may include one or several of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1.

[0216] As an alternative technical solution of this application, the polyanion-type compound may be a class of compounds 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 polyanion-type compound may also be a class of compounds 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, and n represents the valence state of (YO 4 ) n- ; the halogen may be one or more of F, Cl, and Br.

[0218] The polyanion-type compound may also be a class of compounds having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) m+A class of compounds including Y and optional halogen anions. Y can be one or more of P, S, and Si, and n represents the valence state of (YO 4 ) n- ; Z represents a transition metal, which can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents the valence state of (ZO y ) m+ ; The halogen can be one or more of F, Cl, and Br.

[0219] The polyanion-type compound can include NaFePO 4 , Na 3 V 2 (PO 4 ) 3 (sodium vanadium phosphate, abbreviated as NVP), Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), NaM’PO 4 F, and Na 3 (VO y ) 2 (PO 4 ) 2 F 3-2y (0 ≤ y ≤ 1), one or more of which. Among them, M’ in NaM’PO 4 F can include one or more of V, Fe, Mn, and Ni.

[0220] The Prussian blue-type compound can be a class of compounds having sodium ions, transition metal ions, and cyanide ions (CN - ). The transition metal can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Non-limiting examples of the Prussian blue-type compound 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 of these embodiments, the positive electrode active material layer may further optionally include a conductive agent. As a non-limiting example, 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.

[0223] In some of these embodiments, the positive electrode sheet can be prepared by the following method: dispersing the components for preparing the positive electrode sheet described above, 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 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 - 25000 mPa·s. When coating the positive electrode slurry, the coating unit surface density 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 may also be a metal foil or other composite current collector. For example, as the metal foil, copper 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 substrate. The composite current collector may be obtained by forming a metal material on the polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc. In the negative electrode current collector, non-limiting examples of the polymer material substrate may 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 a negative electrode active material for a battery well-known in the art. As non-limiting examples, 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 in combination of two or more.

[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 can be prepared in the following manner: dispersing the above components for preparing the negative electrode sheet, such as the negative electrode active material, conductive agent, 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 coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% - 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) can be 75 - 220 g / m 2 . The tap density of the negative electrode sheet can be 1.0 g / cm 3 ~1.8 g / cm 3 .

[0234] Electrolyte

[0235] The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. The present application does not have any special restrictions on the type of electrolyte, 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 One or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

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

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

[0241] Separator

[0242] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0243] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator can 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 can be the same or different, without particular limitation.

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

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

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

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

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

[0249] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can convert chemical energy and electrical energy into each other. Further, generally, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0250] This application places no particular restrictions on the shape of the battery cell, and it can 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 form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 contained 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 contained 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 a battery module 4 as an example. Referring to Figure 12 , in the battery module 4, multiple 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 arbitrary manner. Further, the multiple battery cells 5 can be fixed by fasteners.

[0255] Optionally, the battery module 4 can further include a housing with a receiving space, and multiple battery cells 5 are accommodated in the receiving space.

[0256] In some of these embodiments, the above-mentioned battery module can also be assembled into a battery pack. The number of battery modules contained 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 14The battery pack 1 is taken as an example. Refer to Figure 13 and Figure 14 In the battery pack 1, a battery box and a plurality of battery modules 4 arranged in the battery box can be included. 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 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0258] In addition, the present application also provides an electrical device, and the electrical device includes the secondary battery provided by the present application. The secondary battery can be used as the power source of the electrical device or can be used 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 The electrical device 6 is taken 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 thin and light, and a secondary battery can be used as the power source.

[0262] Embodiment

[0263] Hereinafter, the 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 in terms of technology or conditions, they shall be carried out according to the technology or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial procurement.

[0264] Embodiment 1

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

[0266] ① Grooves are hot embossed on both surfaces of a support layer (PET) with a thickness of 8 μm at the bottom to obtain the support layer.

[0267] ②Coat a polyurethane-containing slurry on one side surface of the support layer to form a slurry layer with a coating thickness of 1.5 μm, and after drying, form a bonding layer to obtain a composite layer.

[0268] ③Thermocompression laminate the composite layer with a 5-μm passivated aluminum foil, and make the bonding layer contact with the support layer. Then, carry out curing treatment (passivation at 85 °C for 72 hours) to obtain a current collector with a single-sided composite aluminum foil.

[0269] ④Repeat steps ② to ③ on the other side of the support layer to obtain a current collector with a double-sided composite aluminum layer, and then reduce the thickness of the aluminum layer by chemical method to obtain the final composite current collector.

[0270] (2) Preparation of the positive electrode sheet

[0271] Mix LiNi 0.8 Co 0.1 Mn 0.1 O 2 and LiNi 0.5 Co 0.2 Mn 0.3 O 2 as the positive electrode active material in a ratio of 17:3. 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 a positive electrode slurry; uniformly coat the positive electrode slurry on both side surfaces of the composite current collector prepared in step (1), and after drying and cold pressing, obtain the positive electrode sheet.

[0272] (3) Preparation of the negative electrode sheet

[0273] 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 a negative electrode slurry under the action of a vacuum mixer; uniformly coat the negative electrode slurry on both side surfaces of the copper foil; dry the copper foil at room temperature and then transfer it to an oven at 120 °C for 1 h, and then obtain the negative electrode sheet through cold pressing and slitting.

[0274] (4) Separator

[0275] Select a 12-μm thick polypropylene separator.

[0276] (5) Preparation of the electrolyte

[0277] The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), and the volume ratio of EC, EMC, and DEC is 20:20:60. In a glove box under an argon atmosphere with a water content of <10 ppm, add the fully dried lithium salt LiPF 6Dissolve it in an organic solvent and mix evenly to obtain an electrolyte. Among them, the concentration of the lithium salt is 1 mol / L.

[0278] (6) Preparation of the battery

[0279] 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 a role in isolation. Then wind it into a square bare battery cell, install it in an aluminum shell, bake it at 80 °C to remove water, inject the corresponding non-aqueous electrolyte, and after standing, forming, secondary injection, sealing, capacity measurement, wrapping with blue film and other processes, the battery is obtained.

[0280] Examples 2 - 31

[0281] Similar to the preparation process of Example 1, the difference lies in: adjusting the parameters of the composite current collector, as shown in Table 1 below for details.

[0282] Comparative Example 1

[0283] Similar to the preparation process of Example 1, the difference lies in: in step ①, no grooves are formed on both surfaces of the support layer (PET), that is, no protrusions are provided on the adhesive layer.

[0284] Table 1

[0285]

[0286]

[0287] Test section

[0288] (1) Measurement of the protrusion height and size of the first protrusion and the second protrusion

[0289] Perform ion beam polishing cross-section sample preparation (CP) on the current collector, and then conduct SEM observation. Use the SEM equipment to measure the height of the first protrusion and the second protrusion; the sizes of the first protrusion and the second protrusion are observed and measured directly under the SEM through the metal foil.

[0290] (2) Adhesion force test

[0291] After the sample is attached to the non-corona surface of the ethylene-acrylic copolymer (EAA) film, a 12-μm-thick PET is then covered on the EAA film, and the assembly is placed on a heat sealer and attached at a temperature of 120 °C and a pressure of 0.2 MPa. The attached sample is cut into samples with a length of 100 mm and a width of 20 mm, and the non-attached 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 °C peel test. The peel force is read and converted to the unit of N / m. Five parallel samples are taken, and finally the average peel force is taken; average peel force = sum of peel forces of 5 test samples / 5, and this is the adhesion force.

[0292] (3) Elastic modulus test

[0293] The current collector is cut into strips of 15 mm * 150 mm and subjected to a tensile test using a universal tensile testing machine with a gauge length of 50 mm and a tensile speed of 50 mm / min until the test fails. The chord slope method is used to calculate with the chord slope corresponding to a strain from 0.05% to 0.5%. 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%), in MPa; σ2 is the stress measured when the strain value ε2 = 0.01 (1%), in MPa.

[0294] (4) Coating wrinkling situation

[0295] A coating design of one-out-four (i.e., after the electrode coating is slit, it becomes 4 electrodes) is adopted. Observe the coating process to check if the tab wrinkles and if the tab position bulges during winding. If the bulge exceeds 1 mm, it is determined that wrinkling exists. (5) Cycling test

[0296] The fresh battery cell is cycled at a 1C charge rate and a 1C discharge rate under a high temperature condition of 60 °C until the capacity decays to 80% of the initial capacity, and the corresponding number of cycles is recorded, which is the cycling performance of the corresponding battery.

[0297] (6) DC resistance (DCR) test

[0298] The battery cell is adjusted to a state of 50% SOC and discharged at a rate of 4C (corresponding discharge current is I) for 30 s, and the voltage difference ΔV before and after the 30-s discharge is recorded. The DCR corresponding to 50% SOC is calculated according to the following formula: DCR = ΔV / I, and the DCR data of each battery cell are obtained.

[0299] Table 2

[0300]

[0301] Comparing the examples with Comparative Example 1, it can be seen that the adhesion and elastic modulus of the composite current collector in the examples are superior to those in Comparative Example 1. At the same time, the cycle life and DCR impedance of the battery at 60°C are also better than those in Comparative Example 1, indicating that compared with the conventional composite current collector, the composite current collector of the present application is beneficial to improving the adhesion and the cycle performance of the battery.

[0302] The descriptions of the various embodiments above tend to emphasize the differences between the embodiments. Their similarities or commonalities can be referred to each other. For the sake of brevity, they will not be elaborated herein.

[0303] 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 of the 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 stacked on at least one surface of the support layer, the bonding layer includes a bonding layer main body and a protrusion, and the protrusion protrudes from the bonding layer main body and is embedded in the support layer.

2. The composite current collector according to claim 1, characterized in that, there are multiple protrusions, and the multiple protrusions are arranged at intervals.

3. The composite current collector according to claim 1 or 2, characterized in that, the protrusion includes a first protrusion and / or a second protrusion, the protrusion height of the first protrusion is less than the thickness of the support layer, and the protrusion height of the second protrusion is equal to the thickness of the support layer.

4. The composite current collector according to claim 3, characterized in that, the first protrusion includes a first sub-protrusion and / or a second sub-protrusion, the shape of the positive projection of the first sub-protrusion on the surface of the bonding layer includes a hole shape, and the shape of the positive projection of the second sub-protrusion on the surface of the bonding 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 can 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 can be an oval stripe.

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

6. The composite current collector according to any one of claims 3-5, characterized in that, the first sub-protrusion satisfies at least one of the following conditions: (1) The protrusion height h1 of the first sub-protrusion is 50 nm to 1000 nm; (2) The width d1 of the first sub-protrusion is 5 mm to 50 mm; (3) The spacing Δx1 between two adjacent first sub-protrusions is 10 mm to 100 mm.

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

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

9. The composite current collector according to any one of claims 4-8, characterized in that, the second sub-protrusion satisfies at least one of the following conditions: (1) The protrusion height h2 of the second sub-protrusion is 50 nm to 1000 nm; (2) The width d2 of the second sub-protrusion is 5 mm to 40 mm; (3) The spacing Δx2 between two adjacent second sub-protrusions is 20 mm to 150 mm.

10. The composite current collector according to any one of claims 3-9, characterized in that the total area S1 of the positive projection of the first convex portion on the surface of the adhesive layer and the area S of the surface of the support layer satisfy: 2% ≤ S1 / S ≤ 50%.

11. The composite current collector according to any one of claims 3-10, characterized in that at least one of the first convex portions is provided between two adjacent second convex portions; Optionally, the total area S2 of the positive projection of the second convex portion on the surface of the adhesive layer and the total area S1 of the positive projection of the first convex portion on the surface of the adhesive layer satisfy: S2 < S1.

12. The composite current collector according to any one of claims 3-11, characterized in that the second convex portion satisfies at least one of the following conditions: (1) The width d3 of the second convex portion is 50 μm to 500 μm; (2) The spacing Δx3 between two adjacent second convex portions is 5 mm to 50 mm.

13. The composite current collector according to any one of claims 3-12, characterized in that the shape of the positive projection of the second convex portion on the surface of the adhesive layer includes one or more of a circular hole, an oval hole, a fan-shaped hole, a bow-shaped hole, and a polygonal hole, and may be a circular hole and / or an oval hole; Optionally, the angle included in the shape of the positive projection of the second convex portion on the surface of the adhesive layer is ≥ 45°.

14. The composite current collector according to any one of claims 3-13, characterized in that the total area S2 of the positive projection of the second convex portion on the surface of the adhesive layer and the area S of the surface of the support layer satisfy: 0 ≤ S2 / S ≤ 0.8%, and may be 0.0001% ≤ S2 / S ≤ 0.8%.

15. The composite current collector according to any one of claims 1-14, characterized in that the convex portion contains a binder; Optionally, the binder includes one or more of polyfunctional isocyanate, polyester polyol, polyurethane, epoxy resin, polyacrylate, polyvinyl acetate, unsaturated polyester, phenolic resin, urea-formaldehyde resin, modified polyolefin resin, silicone resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, acrylic resin, polycarbonate, and polyamide, and may be one or more of polyfunctional isocyanate, polyester polyol, and polyurethane; Further optionally, the polyurethane includes one or more of thermoplastic polyurethane and reactive polyurethane.

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

17. The composite current collector according to any one of claims 1-16, characterized in that the adhesion between the adhesive layer and the support layer is ≥ 230 N / m.

18. The composite current collector according to any one of claims 1-17, characterized in that Meet at least one of the following conditions: (1) The support layer includes one or more of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene styrene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, sulfur nitride polymers, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, their derivatives, their crosslinked products and their copolymers; (2) The adhesive layer 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; 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.

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

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

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

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