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

Abstract

The embodiments of the present application relate to a composite current collector, an electrode sheet, a secondary battery, a battery module, a battery pack, and an electric device. The composite current collector includes a support layer and a conductive layer. The support layer has two first surfaces facing each other along the thickness direction. The conductive layer is provided on the two first surfaces, the conductive layer includes a first portion and a second portion, the first portion includes a first sub-portion and a second sub-portion respectively provided on the two first surfaces, the second portion includes a third sub-portion and a fourth sub-portion, the third sub-portion and the first sub-portion are integrally provided, the fourth sub-portion and the second sub-portion are integrally provided, both the third sub-portion and the fourth sub-portion protrude from the support layer, and the third sub-portion and the fourth sub-portion are bonded to each other and welded together. The embodiments of the present application are composite current collectors in which the structural stability of the conductive layer is excellent, the overcurrent capacity is improved, and the electrical performance, safety performance, and processing performance of the secondary battery are greatly improved.

Description

[Technical field]

[0001] The present application relates to the field of battery technology, and in particular to a composite current collector, an electrode sheet, a secondary battery, a battery module, a battery pack and an electric device. [Background technology]

[0002] Secondary batteries have the advantages of high energy density, high output power, long cycle life, and less environmental pollution, and are therefore widely applied in electric vehicles and consumer electronic products. Composite current collectors, as an important component for the manufacture of secondary batteries, have a significant impact on the electrochemical performance of secondary batteries. Compared with conventional composite current collectors, composite current collectors with a "metal-insulating polymer-metal" sandwich structure can effectively improve the electrochemical performance of secondary batteries, but existing composite current collectors have many problems, such as a decrease in overcurrent capacity due to insufficient adhesive strength with the external metal foil (used for processing the tabs) and a complicated manufacturing process, which have a significant impact on the electrical performance, safety performance, and processing performance of secondary batteries, so there is an urgent need to develop new composite current collectors. Summary of the Invention [Problem to be solved by the invention]

[0003] The present application has been made in view of the above-mentioned problems, and has an object to provide a composite current collector, an electrode sheet, a secondary battery, a battery module, a battery pack, and an electric device. [Means for solving the problem]

[0004] In order to achieve the above object, an embodiment of the first aspect of the present application provides a composite current collector including a support layer and a conductive layer. The support layer has two first surfaces facing each other along a thickness direction. The conductive layer is provided on the two first surfaces, the conductive layer includes a first portion and a second portion, the first portion includes a first sub-portion and a second sub-portion respectively provided on the two first surfaces, the second portion includes a third sub-portion and a fourth sub-portion, the third sub-portion and the first sub-portion are integrally provided, the fourth sub-portion and the second sub-portion are integrally provided, both the third sub-portion and the fourth sub-portion protrude from the support layer, and the third sub-portion and the fourth sub-portion are bonded to each other to form an integral structure. Welding will be done.

[0005] Thus, in the embodiment of the present application, the first sub-portion and the third sub-portion are integrally provided, the second sub-portion and the fourth sub-portion are integrally provided, and the third sub-portion and the fourth sub-portion are integrally provided by bonding them together. Welding That is, the conductive layer is a unitary structure, and the conductive layer is integral Welding The installation method described above has the following advantages: 1) the shortcomings of the traditional welding process are avoided, and the external metal foil is omitted structurally, and the problem of poor welding between the external metal foil and the conductive layer is avoided, thereby greatly increasing the overcurrent capacity of the composite current collector and improving the electrical performance of the secondary battery; 2) the hot melt process of the present application effectively avoids the cracks of the conductive layer and the support layer of the composite current collector during the manufacturing process, and the cracks and even cracks at the base of the tab caused by the process (such as rolling), greatly improving the production yield of the composite current collector and the safety performance of the secondary battery; 3) the processing consistency of the composite current collector is improved, and the problems of edge misalignment and burrs of the upper and lower two workpieces during the tab cutting process are avoided, and the folding of the tab during the die cutting and winding process is prevented, improving the production yield and safety performance. In short, the composite current collector of the present application can greatly improve the electrical performance, safety performance and production yield of the secondary battery.

[0006] In any embodiment, the third sub-portion, the end portion along the first direction of the support layer, and the fourth sub-portion are bonded together to form an integral structure. WeldingThe first direction is perpendicular to the thickness direction, and the end portion can play a role of supporting and protecting the third sub-portion and the fourth sub-portion.

[0007] In subsequent processes such as rolling, the third and fourth sub-portions may be partially stretched, and the ends provide support for the third and fourth sub-portions, thereby preventing the third and fourth sub-portions from breaking or cracking. Meanwhile, in the composite current collector of this embodiment, after the tab is cut, the base of the tab is supported by the support layer, which increases the rigidity of the base of the tab and prevents the tab from folding, thereby greatly improving safety in the manufacturing process of the secondary battery.

[0008] In any embodiment, the width of the end portion along the first direction is 1 mm to 10 mm, optionally 5 mm to 8 mm. When the end portion is within the above width range, the connection strength between the end portion and the third and fourth sub-portions can be further improved, and the support strength for the third and fourth sub-portions can be further improved.

[0009] In any embodiment, the third sub-portion includes two second surfaces facing each other along the thickness direction, and the first sub-portion protrudes relative to the second surfaces along the thickness direction.

[0010] As a result, since the thickness of the third sub-portion in the embodiment of the present application is relatively moderate, the energy density of a secondary battery using the composite current collector can be greatly increased, and the overcurrent capability of a secondary battery using the composite current collector can be ensured, and the safety performance of the secondary battery can be ensured.

[0011] In any embodiment, the third sub-portion includes two second surfaces that are opposite each other along the thickness direction, and the first sub-portion includes two third surfaces that are opposite each other along the thickness direction, one of the two third surfaces being flush with the second surface.

[0012] As a result, since the thickness of the first sub-portion in the embodiment of the present application is small, the energy density of a secondary battery using the composite current collector can be increased to a certain extent.

[0013] In any embodiment, the first portion has a thickness A and the second portion has a thickness B, where 0.03≦A / B≦1, and optionally 0.2≦A / B≦1. When the thickness ratio of the first portion to the second portion satisfies the above range, the energy density of a secondary battery using the composite current collector can be ensured and the overcurrent capability of the secondary battery can be improved.

[0014] In any embodiment, the thickness of the first sub-portion is equal to or greater than the thickness of the second sub-portion, which may not need to be thinned during fabrication, reducing costs and aiding in fabrication and shaping.

[0015] In any embodiment, the thickness of the third sub-portion is equal to or greater than the thickness of the fourth sub-portion, and the fourth sub-portion does not need to be thinned during the fabrication process, which can reduce costs and aid in fabrication and shaping.

[0016] In any embodiment, the second portion further includes a connecting layer between the third sub-portion and the fourth sub-portion, and the melting point of the connecting layer is lower than the melting point of the third sub-portion.

[0017] Thus, the melting point of the connecting layer is relatively low, and the connecting layer melts preferentially during processing of the second portion, which helps to bond and attach the third sub-portion and the fourth sub-portion together, so that the third sub-portion and the fourth sub-portion are integrated. Welding will be done.

[0018] In any embodiment, the connection layer includes at least one of a metal layer and an organic conductive polymer layer. Optionally, the metal includes at least one of tin, indium, bismuth, and cadmium. Optionally, the organic conductive polymer includes at least one of polypyrrole, polythiophene, polyaniline, polyacetylene, polyphenylene, and polyphenylenevinylene. When a metal is used for the connection layer, it is more conducive to sufficient melting between the third sub-part and the fourth sub-part. When an organic conductive polymer is used for the connection layer, the organic conductive polymer can not only bond the third sub-part and the fourth sub-part, but also fuse with the support layer, which can further improve the connection strength between the second part and the support layer.

[0019] In any embodiment, the thickness of the connecting layer is 1 μm to 5 μm. When the thickness of the connecting layer is within the above range, it helps to support sufficient melting and bonding of the third sub-portion and the fourth sub-portion, i.e., helps the second portion to melt sufficiently together.

[0020] In any embodiment, the support layer includes at least two support portions spaced apart along a first direction, and a second portion is provided between two adjacent support portions, and the first direction is perpendicular to the thickness direction. A composite current collector having such a structure can be cut to form a plurality of electrode assembly components.

[0021] A second aspect of the present application provides an electrode sheet comprising a composite current collector according to any one of the embodiments of the first aspect of the present application, and an active material layer provided on a surface of a first portion of the composite current collector.

[0022] A third aspect of the present application provides a secondary battery including the electrode sheet according to the embodiment of the second aspect of the present application.

[0023] A fourth aspect of the present application provides a battery module including the secondary battery according to the embodiment of the third aspect of the present application.

[0024] A fifth aspect of the present application provides a battery pack including the secondary battery according to the embodiment of the third aspect of the present application or the battery module according to the embodiment of the fourth aspect of the present application.

[0025] A sixth aspect of the present application provides an electric device including the secondary battery according to an embodiment of the third aspect of the present application, the battery module according to an embodiment of the fourth aspect of the present application, or the battery pack provided in the fifth aspect of the present application.

[0026] A seventh aspect of the present application includes the steps of providing a support layer including two first surfaces facing each other along a thickness direction; providing a first conductive sheet and a second conductive sheet, and connecting the first conductive sheet and the second conductive sheet to the two first surfaces, respectively, where the first conductive sheet includes a first sub-portion and a third sub-portion, and the second conductive sheet includes a second sub-portion and a fourth sub-portion, the first sub-portion and the second sub-portion are provided on the two first surfaces, respectively, and both the third sub-portion and the fourth portion protrude from the support layer; and bonding the third sub-portion and the fourth sub-portion to each other to form an integral body. Welding and b. a step of forming a composite current collector.

[0027] As a result, the composite current collector manufactured by the manufacturing method of the embodiment of the present application does not require transfer welding, and can directly laser die cut the tab, which greatly simplifies the process and increases the overcurrent capacity of the tab. Not only does the mechanical cutting process produce flat edges and no burrs, but the conductive layer of the second part is firmly connected to the support layer, and no problems such as cracks occur in the cold pressing process. The electrochemical performance of a secondary battery manufactured using the composite current collector is excellent.

[0028] In an optional embodiment, the method further includes removing a portion of the first sub-portion along a thickness direction to reduce a thickness of the first sub-portion, whereby the energy density of the secondary battery can be increased to a certain extent because the thickness of the first sub-portion is relatively small.

[0029] In an optional embodiment, the method further includes removing a portion of the third sub-portion along a thickness direction to reduce a thickness of the third sub-portion, whereby reducing the thickness of the third sub-portion can increase energy density in ensuring overcurrent capability. [Brief description of the drawings]

[0030] In order to more clearly explain the technical solutions in the embodiments of the present application, the following briefly introduces drawings necessary for the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without requiring creative efforts.

[0031] [Figure 1] FIG. 2 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application. [Diagram 2] FIG. 2 is a structural schematic diagram of a composite current collector provided by another embodiment of the present application. [Diagram 3] FIG. 2 is a structural schematic diagram of a composite current collector provided by another embodiment of the present application. [Figure 4] FIG. 2 is a structural schematic diagram of a composite current collector provided by another embodiment of the present application. [Diagram 5] FIG. 2 is a schematic diagram of a manufacturing process for a composite current collector provided by some embodiments of the present application. [Figure 6] FIG. 2 is a state schematic diagram of a manufacturing process for a composite current collector provided by some embodiments of the present application. [Figure 7] FIG. 2 is a schematic diagram of another state of the manufacturing process of the composite current collector provided by some embodiments of the present application. [Figure 8] 4 is a flowchart of a method for manufacturing a composite current collector provided by some other embodiments of the present application. [Figure 9] FIG. 2 is a schematic diagram of another state of the manufacturing process of the composite current collector provided by some embodiments of the present application. [Figure 10]FIG. 2 is a schematic diagram of another state of the manufacturing process of the composite current collector provided by some embodiments of the present application. [Figure 11] 4 is a flowchart of a method for manufacturing a composite current collector provided by some other embodiments of the present application. [Figure 12] FIG. 2 is a schematic diagram of another state of the manufacturing process of the composite current collector provided by some embodiments of the present application. [Figure 13] FIG. 2 is a schematic diagram of another state of the manufacturing process of the composite current collector provided by some embodiments of the present application. [Figure 14] 1 is a structural schematic diagram of an electrode sheet provided by some embodiments of the present application. [Figure 15] 15 is a schematic diagram of the cross-sectional structure of the electrode sheet shown in FIG. 14 taken along line AA. [Figure 16] FIG. 2 is a structural schematic diagram of an electrode assembly of a secondary battery provided by some embodiments of the present application. [Figure 17] FIG. 1 is an exploded schematic view of a secondary battery provided by some embodiments of the present application. [Figure 18] 1 is a schematic diagram of a partial structure of a battery module provided by some embodiments of the present application. [Figure 19] 1 is an exploded schematic diagram of a battery pack provided by some embodiments of the present application. [Figure 20] 1 is a structural schematic diagram of an electrical device provided by some embodiments of the present application.

[0032] In the drawings, the drawings are not necessarily drawn to scale.

[0033] Wherein, the respective reference numbers in each of the drawings are as follows: X, thickness direction; Y, first direction; 1, electrical device; 10, battery pack; 11, lower housing; 12, upper housing; 20, battery module; 30, secondary battery; 31, top cover assembly; 32, case; 40, electrode assembly; 50, electrode sheet; 41, separator; 60, composite current collector; 70, support layer; 71, first surface; 72, end; 73, support portion; 80, conductive layer; 81, first portion; 811, first sub-portion; 8111, third surface; 812, second sub-portion; 82, second portion; 821, third sub-portion; 8211, second surface; 822, fourth sub-portion; 823, connection layer; 90, active material layer; 100, protective layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, with appropriate reference to the attached drawings, embodiments specifically disclosing the composite current collector and its manufacturing method, electrode sheet, secondary battery, battery module, battery pack, and electric device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of the same actual structure may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0035] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by the selection of one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may or may not include the endpoint values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Also, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are listed, then ranges of 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 can all be contemplated. In this application, unless otherwise specified, the numerical range "a-b" represents a shorthand notation for any combination of real numbers between a and b, where both a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed herein, and "0-5" is just a shorthand representation of combinations of these numbers. Also, when a parameter is expressed as an integer ≧2, this is equivalent to disclosing that the parameter is an integer, e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0036] Unless otherwise specified, all the embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.Unless otherwise specified, all the technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0037] Unless otherwise stated, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method can include steps (a) and (b) performed sequentially, and can also include steps (b) and (a) performed sequentially. For example, a method is mentioned that the method can further include step (c), which indicates that step (c) can be added to the method in any order, for example, the method can include steps (a), (b) and (c), can also include steps (a), (c) and (b), and can also include steps (c), (a) and (b), etc.

[0038] Unless otherwise specified, the terms "inclusive" and "including" referred to in this application may be open ended or closed ended. For example, "inclusive" and "including" may indicate that other elements not listed may be included or included, or that only the elements listed may be included or included.

[0039] In this application, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" stands for "A, B, or both A and B." More specifically, any one of the following conditions: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or A and B are both true (or exist) satisfies the condition "A or B."

[0040] It should be understood that relational terms such as "first," "second," and the like are merely intended to distinguish one entity or operation from another, but do not necessarily require or imply that any actual relationship or order exists between those entities or operations.

[0041] The above summary of the invention of this application is not intended to describe each disclosed embodiment or every implementation in this application. In the following description, exemplary embodiments are described in more detail. In various places throughout this application, guidance is provided through a series of examples that can be used in various combinations. In each instance, the enumeration is only a representative group and should not be construed as exhaustive.

[0042] The inventors have found that the "sandwich" type composite current collector, which is composed of a support layer and conductive layers located on two opposite sides of the support layer, has many defects, which makes the electrical performance, safety performance and processing performance of the secondary battery unable to meet the large-scale industrialization requirements. Specifically,

[0043] The composite current collector of the prior art has a body composed of a support layer and a conductive layer located on the surface of the support layer. In order to allow the body to output the collected current to the outside or to charge the secondary battery with an external current, the manufacturing process of the composite current collector requires an external metal foil to be connected to the surface of the conductive layer (the external metal foil is used to process the tab), and the external connection method is a welding connection (also known as "transfer welding" in the industry). However, such a welding connection method has many disadvantages: 1) Due to the thin conductive layer of the composite current collector, the conventional welding process results in insufficient connection strength between the external metal foil and the conductive layer, which leads to virtual welding problems, and further limits the overcurrent capacity of the welding area, affecting the electrical performance of the secondary battery. 2) Due to the insufficient welding strength, the external metal foil and the body are very easily detached in subsequent manufacturing processes such as cold pressing and die cutting processes, which greatly reduces the production yield of the composite current collector and the safety performance of the secondary battery. 3) Because two conductive layers need to be connected to the external metal foil to process the tab, the upper and lower metal foils are processed separately when cutting the tab from the external metal foil, which results in edge misalignment and burrs on the upper and lower tabs after cutting, reducing production yield and safety performance. 4) In the composite current collector manufactured by the conventional transfer welding process, the base of the tab is not supported by the support layer after the tab is cut, so the tab is easily folded, which significantly reduces safety performance during the manufacturing of secondary batteries.

[0044] Based on the above-mentioned many shortcomings of the existing composite current collector, the present application has developed a composite current collector that can greatly improve the electrical performance, safety performance and processing performance of secondary batteries. Next, the embodiments of the present application will be described in detail with reference to Figs. 1 to 20.

[0045] [Composite current collector]

[0046] FIG. 1 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application.

[0047] As shown in FIG. 1, a composite current collector 60 provided by an embodiment of the present application includes a support layer 70 and a conductive layer 80 .

[0048] The support layer 70 in the embodiment of the present application serves to support and protect the conductive layer 80. The support layer 70 has two first surfaces 71 facing each other along the thickness direction X. The X direction shown in Fig. 1 indicates the thickness direction.

[0049] The material of the support layer 70 includes one or more of a polymeric material and a polymeric matrix composite material. The polymeric matrix composite material includes a polymeric material and an additive, the additive being at least one of an inorganic non-metallic material and a metallic material.

[0050] The polymeric material includes at least one of polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene ethylene, 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, polysulfur nitride, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, derivatives thereof, crosslinked products thereof, and copolymers thereof. Optionally, the polymeric material is at least one of polyamide, polyimide, polyethylene terephthalate, polypropylene, and polyphenylene sulfide.

[0051] The polymer matrix composite material includes a polymeric material and an additive, the additive being at least one of an inorganic non-metallic material and a metallic material. Optionally, the inorganic non-metallic material includes one or more of a carbon-based material, alumina, silicon dioxide, silicon nitride, silicon carbide, boron nitride, silicates, and titanium oxide. The metallic material includes one or more of magnesium, calcium, strontium, lead, zinc, tin, antimony, bismuth, silver, and ruthenium.

[0052] In the embodiment of the present application, the conductive layer 80 is provided on the two first surfaces 71 of the support layer 70 . The conductive layer 80 may be formed on the support layer 70 by at least one of mechanical rolling, adhesion, vapor deposition, electroless plating, and electroplating, and the vapor deposition or electroplating method can be selected, that is, the conductive layer 80 can be selectively a vapor deposition layer or an electroplating layer, thus better realizing a tight bond between the conductive layer 80 and the support layer 70 and effectively playing the role of supporting and protecting the support layer 70 against the conductive layer 80.

[0053] In some embodiments, the conductive layer 80 may be connected to the support layer 70 by an adhesive to improve the connection strength between the conductive layer 80 and the support layer 70. Exemplarily, the adhesive is at least one selected from polypropylene, carboxymethyl cellulose, polyacrylate, styrene butadiene rubber, sodium polyacrylate, polyurethane, polyethyleneimine, polyvinylidene fluoride, chloroprene rubber, nitrile rubber, silicone rubber, polyvinyl acetate, urea formaldehyde resin, phenolic resin, epoxy resin, silane coupling agent, titanate coupling agent, zirconium coupling agent, aluminate coupling agent, and borate coupling agent.

[0054] The material of the conductive layer 80 may include a metal. For example, when the composite current collector 60 is a positive electrode composite current collector, the conductive layer 80 is a positive electrode conductive layer, and the material of the positive electrode conductive layer is selected from aluminum or an aluminum-based alloy, which may be an aluminum-nickel alloy, an aluminum-titanium alloy, an aluminum-silver alloy, or the like. When the composite current collector 60 is a negative electrode composite current collector, the conductive layer 80 is a negative electrode conductive layer, and the material of the negative electrode conductive layer is selected from copper or a copper-based alloy, which may be a copper-nickel alloy, a copper-titanium alloy, a copper-silver alloy, or the like.

[0055] Of course, in some embodiments, other materials that are advantageous for processing, such as low melting point metals or low melting point organic conductive polymer layers, can be added in the process of forming the conductive layer 80. In this specification, the low melting point refers to the main material of the conductive layer 80. Exemplarily, the main material of the conductive layer 80 is aluminum, and the low melting point metal refers to a metal whose melting point is lower than that of aluminum metal, and the melting point of the low melting point organic conductive polymer layer is lower than that of aluminum metal.

[0056] The conductive layer 80 includes a first portion 81 and a second portion 82. The first portion 81 includes a first sub-portion 811 and a second sub-portion 812 provided on the two first surfaces 71, respectively, and the second portion 82 includes a third sub-portion 821 and a fourth sub-portion 822, the third sub-portion 821 and the first sub-portion 811 being provided integrally, the fourth sub-portion 822 and the second sub-portion 812 being provided integrally, both the third sub-portion 821 and the fourth sub-portion 822 protruding from the support layer 70, and the third sub-portion 821 and the fourth sub-portion 822 being bonded to each other to form an integral structure. Welding The third sub-portion 821 and the fourth sub-portion 822 are cut as an integral structure, and the edges after cutting are flush and burr-free, which can improve the safety performance and production yield of the secondary battery including the composite current collector 60.

[0057] Both the first sub-portion 811 and the second sub-portion 812 of the first portion 81 are provided on the first surface 71 and are used for applying an active material layer. The third sub-portion 821 and the fourth sub-portion 822 of the second portion 82 are used as tabs.

[0058] The first sub-portion 811 includes two third surfaces 8111 facing each other along the thickness direction X. The third sub-portion 821 includes two second surfaces 8211 facing each other along the thickness direction X. The first sub-portion 811 and the third sub-portion 821 are integrally provided, and one of the two third surfaces 8111 of the first sub-portion 811 may be flush with one of the two second surfaces 8211, or the first sub-portion 811 may protrude from the second surfaces 8211 or may be recessed relative to the second surfaces 8211.

[0059] The second sub-portion 812 includes two fourth surfaces facing each other along the thickness direction X. The fourth sub-portion 822 includes two fifth surfaces facing each other along the thickness direction X. The second sub-portion 812 and the fourth sub-portion 822 are integrally provided, and one of the two fourth surfaces of the second sub-portion 812 may be flush with one of the two fifth surfaces, or the second sub-portion 812 may protrude from or be recessed relative to the fifth surfaces.

[0060] The first sub-portion 811 and the third sub-portion 821 are integrally formed, and the second sub-portion 812 and the fourth sub-portion 822 are integrally formed. When the first sub-portion 811, the third sub-portion 821, the second sub-portion 812 and the fourth sub-portion 822 form the conductive layer 80, the first sub-portion 811 and the second sub-portion 812 can have the same thickness, and of course, the first sub-portion 811 and the second sub-portion 812 can have different thicknesses. The third sub-portion 821 and the fourth sub-portion 822 can have the same thickness, and the third sub-portion 821 and the fourth sub-portion 822 can have different thicknesses.

[0061] In the embodiment of the present application, the first sub-portion 811 and the third sub-portion 821 are integrally formed, the second sub-portion 812 and the fourth sub-portion 822 are integrally formed, and the third sub-portion 821 and the fourth sub-portion 822 are integrally formed by bonding together. Welding That is, the conductive layer 80 is a unitary structure. WeldingThe installation method described above has the following advantages: 1) the shortcomings of the traditional welding process are avoided, and the external metal foil is omitted structurally, and the problem of poor welding between the external metal foil and the conductive layer is avoided, thereby greatly increasing the overcurrent capacity of the composite current collector 60 and improving the electrical performance of the secondary battery; 2) the hot melt process of the present application effectively avoids the cracks of the conductive layer 80 and the support layer 70 of the composite current collector 60 in the manufacturing process, and the cracks and even cracks at the base of the tab caused by the process (such as rolling), greatly improving the production yield of the composite current collector 60 and the safety performance of the secondary battery; and 3) the processing consistency of the composite current collector 60 is improved, and the problems of edge misalignment and burrs of the upper and lower two workpieces in the tab cutting process are avoided, and the folding of the tab in the die cutting and winding process is prevented, improving the production yield and safety performance. In short, the composite current collector of the present application can greatly improve the electrical performance, safety performance and production yield of the secondary battery.

[0062] Continuing to refer to FIG. 1, in some embodiments, the third sub-portion 821, the end portion 72 of the support layer 70 along the first direction Y, and the fourth sub-portion 822 are bonded together to form an integral structure. Welding will be done. The Y direction shown in FIG. 1 represents a first direction, and the first direction Y is perpendicular to the thickness direction X.

[0063] The third sub-portion 821, the end portion 72 and the fourth sub-portion 822 are integrally Welding Rephrased: R For example, the three are connected to each other, and the end 72 can play a supporting and protective role for the third sub-portion 821 and the fourth sub-portion 822. In a subsequent rolling process, the third sub-portion 821 and the fourth sub-portion 822 may be partially stretched, and the end 72 provides a supporting force for the third sub-portion 821 and the fourth sub-portion 822, thereby preventing the third sub-portion 821 and the fourth sub-portion 822 from being broken or cracked. In the composite current collector 60 of this embodiment, after the tab 60 is cut, the base of the tab is supported by the support layer 70, so that the rigidity of the base of the tab is increased, and the tab is prevented from being folded, and the safety in the manufacturing process of the secondary battery is greatly improved.

[0064] Optionally, the width of the end 72 along the first direction Y is 1 mm to 10 mm. For example, it may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm, or the width range may be any two of the above values, optionally 5 mm to 8 mm. When the end 72 is within the above width range, the connection strength between the end 72, the third sub-portion 821, and the fourth sub-portion 822 can be further improved, and the support strength for the third sub-portion 821 and the fourth sub-portion 822 can be further improved. In the width measurement method, the thickness of the end 72 is first measured with a micrometer, and the limit position near the first portion 81 and the limit position near the second portion 82 of the end 72 can be roughly determined, and then the end face of the composite current collector 60 is cut near the limit position using a JEOL IB-19500 and observed with a Zeiss Sigma 300 scanning electron microscope to further measure the thickness of the support layer 70 and the conductive layer 80, and the limit end face position is confirmed. After the end face position is determined, the width of the end 72 portion is measured with a scale. The dimension C in FIG. 1 roughly represents the width dimension of the end 72 along the first direction Y.

[0065] 1, in some embodiments, the first sub-portion 811 protrudes toward the second surface 8211 of the third sub-portion 821 along the thickness direction X. Since the third sub-portion 821 has a relatively moderate thickness, the energy density of the secondary battery using the composite current collector 60 can be significantly increased, and the overcurrent capability of the secondary battery using the composite current collector 60 can be ensured, thereby ensuring the safety performance of the secondary battery.

[0066] FIG. 2 is a structural schematic diagram of a composite current body provided according to some other embodiments of the present application.

[0067] 2, in some other embodiments, one of the two third surfaces 8111 of the first sub-portion 811 is flush with the second surface 8211 of the third sub-portion 821. Since the thickness of the first sub-portion 811 is small, the energy density of a secondary battery using the composite current collector 60 can be increased to some extent.

[0068] In some embodiments, the second sub-portion 812 protrudes toward the fifth surface of the fourth sub-portion 822 along the thickness direction X. Since the thickness of the fourth sub-portion 822 is relatively moderate, the energy density of the secondary battery using the composite current collector 60 can be significantly increased, and the overcurrent capability of the secondary battery using the composite current collector 60 can be ensured.

[0069] In some other embodiments, one of the two fourth surfaces of the second sub-portion 812 is flush with the fifth surface of the fourth sub-portion 822. Since the thickness of the second sub-portion 812 is small, the energy density of a secondary battery using the composite current collector 60 can be increased to some extent.

[0070] In some embodiments, the first portion 81 has a thickness A and the second portion 82 has a thickness B, and A and B satisfy 0.03≦A / B≦1, for example, A / B is 0.03, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, or the A / B ratio may be in the range of any two of the above values, optionally 0.2≦A / B≦1. When the thickness ratio of the first portion 81 to the second portion 82 satisfies the above range, the energy density of a secondary battery using the composite current collector 60 can be ensured and the overcurrent capability of the secondary battery can be increased.

[0071] In this specification, the thickness of the first portion 81 refers to the entire thickness of the first portion 81 along the thickness direction X. Exemplarily, the first portion 81 includes a first sub-portion 811 and a second sub-portion 812, and the sum of the thicknesses of the first sub-portion 811 and the second sub-portion 812 along the thickness direction X is A.

[0072] In this specification, the thickness of the second portion 82 refers to the entire thickness of the second portion 82 along the thickness direction X. Exemplarily, the second portion 82 includes a third sub-portion 821 and a fourth sub-portion 822, and the sum of the thicknesses of the third sub-portion 821 and the fourth sub-portion 822 along the thickness direction X is B. Or, the second portion 82 further includes another member, for example a connecting layer, and the sum of the thicknesses of the third sub-portion 821, the connecting layer, and the fourth sub-portion 822 along the thickness direction X is B.

[0073] Optionally, the thickness A of the first portion 81 is 1 μm≦A≦26 μm, for example 1 μm, 3 μm, 6 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 26 μm, or the thickness range may consist of any two of the above values.

[0074] Optionally, the thickness B of the second portion 82 is 5 μm≦B≦26 μm, for example, 5 μm, 6 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 26 μm, or the thickness range may consist of any two of the above values.

[0075] In some embodiments, the thickness of first sub-portion 811 is greater than or equal to the thickness of second sub-portion 812. Second sub-portion 812 does not have to be thinned during processing, which can reduce costs and aid in processing and shaping.

[0076] In some embodiments, the thickness of the third sub-portion 821 is greater than or equal to the thickness of the fourth sub-portion 822. The fourth sub-portion 822 does not have to be thinned during processing, which can reduce costs and aid in processing and molding.

[0077] FIG. 3 is a structural schematic diagram of a composite current body provided according to some other embodiments of the present application.

[0078] 3, in some embodiments, the second portion 82 further includes a connecting layer 823 between the third sub-portion 821 and the fourth sub-portion 822, and the melting point of the connecting layer 823 is lower than that of the third sub-portion 821. The melting point of the connecting layer 823 is relatively low, so that the connecting layer 823 melts preferentially during processing of the second portion 82, which helps to adhere and bond the third sub-portion 821 and the fourth sub-portion 822 together, thereby allowing the third sub-portion 821 and the fourth sub-portion 822 to be bonded together. Welding This will encourage people to

[0079] Optionally, the melting point of the connecting layer 823 is lower than the melting point of the fourth sub-portion 822, and the melting point of the connecting layer 823 is lower than the melting points of the third sub-portion 821 and the fourth sub-portion 822, which helps the third sub-portion 821 and the fourth sub-portion 822 to be bonded and attached together when the second sub-portion 821 is processed.

[0080] Optionally, the connection layer 823 includes at least one of a metal layer and an organic conductive polymer layer, in other words, the connection layer 823 is a metal layer, an organic conductive polymer layer, or a composite layer of a metal layer and an organic conductive polymer layer.

[0081] As an example of the material of the metal layer, the metal includes at least one of tin, indium, bismuth and cadmium, in other words, the metal may be, for example, tin, indium, bismuth or cadmium, or may be a tin-indium alloy, a tin-bismuth alloy, a tin-cadmium alloy, an indium-bismuth alloy, a bismuth-cadmium alloy, a tin-indium-bismuth alloy, a tin-bismuth-cadmium alloy, etc. When a metal is used for the connection layer 823, it is more conducive to sufficient melting between the third sub-portion 821 and the fourth sub-portion 822.

[0082] When the connection layer 823 includes a metal layer, the metal layer may include one or more first sub-layers, for example, multiple first sub-layers may be used, and the first sub-layers of each layer may use the same metal material or different materials.

[0083] Examples of materials for the organic conductive polymer layer include at least one of polypyrrole, polythiophene, polyaniline, polyacetylene, polyphenylene, and polyphenylenevinylene. When an organic conductive polymer is used for the connection layer 823, the organic conductive polymer can not only bond the third sub-portion 821 and the fourth sub-portion 822, but also fuse with the support layer 70, thereby further improving the connection strength between the second sub-portion 82 and the support layer 70.

[0084] When the connecting layer 823 includes an organic conductive polymer layer, the organic conductive polymer layer can include one or more second sub-layers, for example, multiple second sub-layers can be used, and each second sub-layer can use the same organic conductive polymer material or can use a different organic conductive polymer material.

[0085] In some embodiments, the thickness of the connecting layer 823 is 1 μm to 5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm, or the thickness range may be any two of the above values. When the thickness of the connecting layer 823 is in the above range, it helps to support sufficient melting and bonding of the third sub-portion 821 and the fourth sub-portion 822, i.e., helps the second portion 82 to melt sufficiently together.

[0086] FIG. 4 is a structural schematic diagram of a composite current body provided according to some other embodiments of the present application.

[0087] 4, in some embodiments, the support layer 70 includes at least two support portions 73 spaced apart along the first direction Y, and a second portion 82 is provided between two adjacent support portions 73. The composite current collector 60 having such a structure can be cut to form components of multiple electrode assemblies.

[0088] In some other embodiments, the support layer 70 includes one support portion 73, and the second portion 82 protrudes from at least one end portion 72 of the support portion 73 along the first direction Y. Illustratively, the second portion 82 protrudes from one end portion 72 of the support portion 73 along the first direction Y, or from two ends 72 of the support portion 73 along the first direction Y.

[0089] [Manufacturing method of composite current collector]

[0090] The embodiments of the present application further provide a method for making the composite current collector.

[0091] Figure 5 is a schematic diagram of a manufacturing process for a composite current collector provided by some embodiments of the present application. Figure 6 is a schematic diagram of a state of a manufacturing process for a composite current collector provided by some embodiments of the present application. Figure 7 is another schematic diagram of a state of a manufacturing process for a composite current collector provided by some embodiments of the present application.

[0092] As shown in FIG. 5 to FIG. 7, the manufacturing method includes the following steps:

[0093] In S100, a support layer is provided that includes two first surfaces opposed to each other along a thickness direction.

[0094] In S200, a first conductive sheet and a second conductive sheet are provided, and the first conductive sheet and the second conductive sheet are respectively connected to two first surfaces via an adhesive layer, the first conductive sheet includes a first sub-portion and a third sub-portion, and the second conductive sheet includes a second sub-portion and a fourth sub-portion, the first sub-portion and the second sub-portion are respectively provided on the two first surfaces, and both the third sub-portion and the fourth sub-portion protrude from the supporting layer.

[0095] In S300, the third sub-section and the fourth sub-section are bonded together to form a single unit. Welding The composite current collector manufactured by the manufacturing method of the embodiment of the present application has flush edges during the cutting process, and the electrochemical performance of a secondary battery manufactured using the composite current collector is excellent.

[0096] Figure 8 is a flow chart of a method for manufacturing a composite current collector provided by some embodiments of the present application. Figure 9 is a schematic diagram of another state of the manufacturing process of a composite current collector provided by some embodiments of the present application. Figure 10 is a schematic diagram of another state of the manufacturing process of a composite current collector provided by some embodiments of the present application. The arrows in Figure 9 indicate the thinning direction.

[0097] As shown in FIGS. 8 to 10, in some embodiments, after step S300, the method further includes the following steps:

[0098] In S400, a portion of the first sub-portion is removed along the thickness direction to reduce the thickness of the first sub-portion.

[0099] By reducing the thickness of the first sub-portion, the thickness of the first sub-portion becomes relatively thin, and the energy density of the secondary battery can be increased to some extent.

[0100] One of the two third surfaces 8111 of the first sub-portion 811 after thinning may be flush with the second surface 8211 of the third sub-portion 821, and of course, the first sub-portion 811 after thinning may protrude relative to the second surface 8211 along the thickness direction X.

[0101] In step S400, in order to prevent the thinning process of the first sub-portion 811 from interfering with the third sub-portion 821, a protective layer 100 can be provided on the second surface 8211 of the third sub-portion 821, and in addition to the third sub-portion 821 including the protective layer 100, the first sub-portion 811 is thinned, and then the protective layer 100 is removed after the first sub-portion 811 is thinned, which basically does not affect the thickness of the third sub-portion 821.

[0102] The material of the protective layer 100 is one or more of polymethyl methacrylate (PMMA), polymethacrylamide, polymethylisopropenylketone, polyisobutylene, and polyalphamethylstyrene. Such a protective layer 100 can be dissolved and removed after the first sub-portion 811 is thinned.

[0103] In some embodiments, after step S300, the method further includes the steps of:

[0104] A portion of the second sub-portion is removed along the thickness direction to reduce the thickness of the second sub-portion.

[0105] The thinning process of the second sub-portion is the same as that described in step S400, and is not described here. Here, the thinned thicknesses of the first sub-portion and the second sub-portion may be the same or different.

[0106] Figure 11 is a flow chart of a method for manufacturing a composite current collector provided by some embodiments of the present application. Figure 12 is a schematic diagram of another state of the manufacturing process of a composite current collector provided by some embodiments of the present application. Figure 13 is a schematic diagram of another state of the manufacturing process of a composite current collector provided by some embodiments of the present application. The arrows in Figure 12 indicate the thinning direction.

[0107] As shown in FIGS. 11 to 13, in some embodiments, after step S300, the method further includes the following steps:

[0108] In step S500, a portion of the third sub-portion is removed along the thickness direction to reduce the thickness of the third sub-portion.

[0109] By reducing the thickness of the third sub-portion 821, it is possible to increase the energy density while ensuring the overcurrent capability.

[0110] In the composite current collector after being thinned, the first sub-portion 811 can protrude toward the second surface 8211 along the thickness direction X.

[0111] In step S500, in order to prevent the thinning process of the third sub-portion 821 from interfering with the first sub-portion 811, a protective layer 100 can be provided on the third surface 8111 of the first sub-portion 811, in addition to the first sub-portion 811 including the protective layer 100, the third sub-portion 821 is thinned, and then the protective layer 100 is removed after the thinning of the third sub-portion 821, which basically does not affect the thickness of the first sub-portion 811.

[0112] In some embodiments, after step S300, the method further includes the steps of:

[0113] A portion of the fourth sub-portion is removed along the thickness direction to reduce the thickness of the fourth sub-portion.

[0114] The thinning process of the fourth sub-portion is the same as that described in step S500, and will not be described here. Here, the thinned thicknesses of the third sub-portion and the fourth sub-portion may be the same or different.

[0115] The above thinning steps may be used in combination or alone. For example, after step S300, steps S400 and S500 may be included at the same time. Or, after step S300, step S400 may be included. Or, after step S300, step S500 may be included.

[0116] [Electrode sheet]

[0117] The embodiments of the present application further provide an electrode sheet.

[0118] Fig. 14 is a structural schematic diagram of an electrode sheet provided by some embodiments of the present application. Fig. 15 is a cross-sectional structural schematic diagram of the electrode sheet shown in Fig. 14 taken along line AA.

[0119] 14 and 15, the electrode sheet 50 in the embodiment of the present application includes a composite current collector 60 and an active material layer 90 in any of the above embodiments of the present application, and the active material layer 90 is provided on a surface of a first portion 81 of the composite current collector 60. A secondary battery using the electrode sheet 50 of this structure has excellent electrochemical performance, particularly excellent overcurrent capability and energy density. The electrode sheet 50 and a separator are wound to form an electrode assembly.

[0120] [Positive electrode sheet]

[0121] The positive electrode sheet includes a positive electrode composite current collector and a positive electrode active material layer.

[0122] The main body material of the conductive layer of the positive electrode composite current collector includes aluminum or an aluminum-based alloy, and the structural form thereof adopts the composite current collector of any of the above-mentioned embodiments of the present application.

[0123] The positive electrode active material used in the positive electrode active material layer may be a positive electrode active material used in a secondary battery known in the art. For example, the positive electrode active material may include at least one of lithium-containing phosphates having 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 positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of the lithium transition metal oxide include lithium cobalt oxide (LiCoO2, etc.), lithium nickel oxide (LiNiO2, etc.), lithium manganese oxide (LiMnO2, LiMn2O4, etc.), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (also abbreviated as LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523(also abbreviated as LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (also abbreviated as LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (also abbreviated as LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 Lithium nickel cobalt aluminum oxide (LiNi 0.85 Co 0.15 Al 0.05 Examples of lithium-containing phosphates having an olivine structure include, but are not limited to, at least one of lithium iron phosphate (LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0124] In some embodiments, the positive electrode active material layer optionally includes an adhesive. For example, the adhesive can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0125] In some embodiments, the positive electrode active material layer optionally includes a conductive agent. For example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the positive electrode sheet can be manufactured in the following manner: the above-mentioned components for manufacturing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the second adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, and the positive electrode slurry is applied to a positive electrode composite current collector. After processes such as drying and cold pressing, the positive electrode sheet can be obtained.

[0127] [Negative electrode sheet]

[0128] The negative electrode sheet includes a negative electrode composite current collector and a negative electrode active material layer.

[0129] The main body material of the conductive layer of the negative electrode composite current collector includes copper or a copper-based alloy, and its structure adopts the composite current collector of any of the above-mentioned embodiments of the present application.

[0130] The negative electrode active material in the negative electrode active material layer may be a negative electrode active material used in a secondary battery known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material may be at least one selected from silicon alone, silicon oxygen compound, silicon carbon composite, silicon nitrogen composite, and silicon alloy. The tin-based material may be at least one selected from tin alone, tin oxygen compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative electrode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

[0131] In some embodiments, the negative electrode active material layer optionally includes an adhesive, which may be at least one selected from styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and chitosan methyl carboxylate (CMCS).

[0132] In some embodiments, the negative electrode active material layer optionally contains a conductive agent, which may be at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In some embodiments, the negative electrode active material layer optionally includes other additives, such as a thickener (such as sodium carboxymethylcellulose (CMC-Na)).

[0134] In some embodiments, the negative electrode sheet can be manufactured by the following method: the above-mentioned components for manufacturing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, and the negative electrode slurry is applied to a negative electrode composite current collector. After processes such as drying and cold pressing, the negative electrode sheet can be obtained.

[0135] [Electrolyte]

[0136] The electrolyte plays a role in ion conduction between the positive electrode sheet and the negative electrode sheet. The type of electrolyte in the embodiment of the present application is not specifically limited and can be selected as needed. For example, the electrolyte may be liquid, gel, or all solid.

[0137] In some embodiments, the electrolyte employs an electrolyte solution, which includes an electrolyte salt and a solvent.

[0138] In some embodiments, the electrolyte salt may be at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0139] In some embodiments, the solvent may be at least one selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propionic acid, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0140] In some embodiments, the electrolyte solution optionally further includes additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives that can improve certain performance of the battery, such as an additive that improves the overcharge performance of the battery, or an additive that improves the high temperature or low temperature performance of the battery.

[0141] [Separator]

[0142] In some embodiments, the secondary battery further includes a separator. In the embodiments of the present application, the type of the separator is not particularly limited, and any known separator with a porous structure having good chemical stability and mechanical stability can be selected.

[0143] In some embodiments, the separator may be made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single layer membrane or a multi-layer composite membrane, and is not particularly limited. When the separator is a multi-layer composite membrane, the materials of each layer may be the same or different, and is not particularly limited.

[0144] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be fabricated into an electrode assembly by a winding or lamination process.

[0145] In some embodiments, the secondary battery may include an exterior case used to package the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte.

[0146] In some embodiments, the exterior of the secondary battery may be a hard case such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a soft package such as a pouch-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0147] [Secondary battery]

[0148] An embodiment of the present application further provides a secondary battery.

[0149] Fig. 16 is a structural schematic diagram of an electrode assembly of a secondary battery provided by some embodiments of the present application. Fig. 17 is an exploded schematic diagram of a secondary battery provided by some embodiments of the present application.

[0150] As shown in FIG. 16 and FIG. 17, the secondary battery 30 includes a top cover assembly 31, a case 32, an electrode assembly 40 housed in the case 32, and an electrolyte. The electrode assembly 40 includes an electrode sheet 50 and a separator 41. The electrode sheet 50 includes a positive electrode sheet and a negative electrode sheet. In the charge / discharge process of the secondary battery 30, active ions are embedded and escaped by going back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role of ion conduction between the positive electrode sheet and the negative electrode sheet. The separator 41 is provided between the positive electrode sheet and the negative electrode sheet, and mainly plays a role of preventing short circuit between the positive electrode and the negative electrode, and allows ions to pass through. Specifically, the secondary battery may be a wound or stacked battery such as a lithium ion secondary battery, a lithium primary battery, a sodium ion battery, a magnesium ion battery, etc., but is not limited thereto. FIG. 14 shows a wound electrode assembly.

[0151] In some embodiments, the positive electrode sheet includes the positive electrode sheet of the embodiment of the second aspect of the present application. The secondary battery 30 of the embodiment of the present application has superior electrochemical performance compared to conventional secondary batteries because it uses the electrode sheet of the second aspect of the present application. Accordingly, the negative electrode sheet can be a conventional negative electrode sheet in the field or a negative electrode sheet of the embodiment of the second aspect of the present application.

[0152] In some embodiments, the negative electrode sheet includes the negative electrode sheet of the embodiment of the second aspect of the present application. The secondary battery 30 of the embodiment of the present application has superior electrochemical performance compared to conventional secondary batteries because it uses the electrode sheet of the second aspect of the present application. Accordingly, the positive electrode sheet can use a conventional positive electrode sheet in the field.

[0153] In some embodiments, the positive electrode sheet includes the positive electrode sheet of the embodiment of the second aspect of the present application. The negative electrode sheet includes the negative electrode sheet of the embodiment of the second aspect of the present application. The secondary battery 30 of the embodiment of the present application has superior electrochemical performance compared to conventional secondary batteries because it uses the electrode sheet of the second aspect of the present application.

[0154] In the present application, the shape of the secondary battery 30 is not particularly limited, and may be cylindrical, rectangular, or other shapes. For example, FIG. 17 shows a secondary battery with a rectangular structure as an example.

[0155] In some embodiments, the exterior of the secondary battery 30 may include a case 32 and a top cover assembly 31. Here, the case 32 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are surrounded to form a receiving cavity. The case 32 has an opening communicating with the receiving cavity, and the top cover assembly 31 may cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the separator 41 may form an electrode assembly 40 by a winding process or a stacking process. The electrode assembly 40 is packaged in the receiving cavity. The electrolyte is infiltrated into the electrode assembly 40. The number of electrode assemblies 40 included in the secondary battery 30 may be one or more, and may be selected by those skilled in the art according to specific practical needs.

[0156] In some embodiments, the secondary battery 30 may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number may be selected by a person skilled in the art according to the application and capacity of the battery module.

[0157] FIG. 18 is a schematic diagram of a partial structure of a battery module provided by some embodiments of the present application.

[0158] 18, in the battery module 20, the multiple secondary batteries 30 may be arranged in sequence along the length direction of the battery module 20. Of course, they may be arranged in any other manner. Furthermore, the multiple secondary batteries 30 may be fixed with a fastener.

[0159] Optionally, the battery module 20 may further include a housing having an accommodation space for accommodating a plurality of secondary batteries 30 .

[0160] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery pack.

[0161] FIG. 19 is an exploded schematic view of a battery pack provided according to some embodiments of the present application.

[0162] 19, a battery pack 10 may include a battery housing and a plurality of battery modules 20 provided in the battery housing. The battery housing includes an upper housing 12 and a lower housing 11, and the upper housing 12 covers the lower housing 11 to form an enclosed space for accommodating the battery modules 20. The plurality of battery modules 20 may be arranged in the battery housing according to any manner.

[0163] Additionally, the present application further provides an electrical device.

[0164] FIG. 20 is a structural schematic diagram of an electrical device provided according to some embodiments of the present application.

[0165] As shown in Fig. 20, the electric device 1 includes at least one of the secondary batteries 30, battery modules, or battery packs provided in the present application. The secondary battery 30, battery modules, or battery packs may be used as a power source for the electric device, or may be used as an energy storage unit for the electric device. The electric device 1 may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0166] As the electric device, a secondary battery, a battery module or a battery pack can be selected according to the usage needs.

[0167] The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the need for high power and high energy density of the secondary battery 30 of the electric device 1, a battery pack or a battery module can be used.

[0168] Another example of the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such devices are usually required to be thin and can use a secondary battery as a power source. EXAMPLES

[0169] The following describes the examples of the present application. The examples described below are illustrative and are only for interpreting the present application, and should not be understood as limiting the present application. If no specific techniques or conditions are shown in the examples, they will be carried out according to the techniques or conditions or product specifications described in the literature in this field. Reagents or equipment without manufacturer's markings are all conventional products available on the market. In addition, when the "connection layer" is defined as an invention-specific feature, Examples 1 to 9 are reference examples.

[0170] Example 1

[0171] 1. Manufacturing of positive electrode composite current collector A PET support layer (melting point 251° C.) having a thickness of 4.5 μm was selected, and the surface of the support layer was cleaned. A polyurethane adhesive was applied to one surface of the support layer to form a coating layer (thickness: about 2 μm) for forming an adhesive layer. The coating layer was prebaked. An aluminum layer was provided on the prebaked coating layer as a first conductive sheet including a first sub-portion and a third sub-portion, and the first conductive sheet was formed into a first laminate of a support layer and a composite current collector. The first laminate was pressed at high temperature and cured after pressing. A polyurethane adhesive was applied to the other surface of the support layer to form a coating layer (thickness: about 2 μm) for forming an adhesive layer. An aluminum layer was provided on the prebaked coating layer as a second conductive sheet including a second sub-portion and a fourth sub-portion, and the second conductive sheet was formed into a second laminate of a support layer and a composite current collector. The second laminate was pressed at high temperature and cured after pressing to form a composite current collector including an adhesive layer between the PET and the aluminum layer, and the two aluminum layers formed a first conductive sheet and a second conductive sheet, respectively. The first conductive sheet included a first sub-portion and a third sub-portion, and the second conductive sheet included a second sub-portion and a fourth sub-portion, the first sub-portion and the second sub-portion were provided on two first surfaces respectively, and both the third sub-portion and the fourth sub-portion protruded from the support layer, where the thicknesses of the first sub-portion, the second sub-portion, the third sub-portion and the fourth sub-portion were all 5 μm, the thickness A of the first portion was 10 μm, the thickness B of the second portion was 10 μm, and A / B=1. The third sub-part and the fourth sub-part are bonded together to form a single unit. Welding That is, a customized heated roller is used to heat the surface temperature to 675°C, and the third and fourth sub-parts are hot-pressed with a pressure of 60T. Welding was carried out.

[0172] 2. Manufacturing of positive electrode sheets Cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), conductive carbon black, and adhesive polyvinylidene fluoride (PVDF) were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent in a weight ratio of 82:14:2:2 to form a uniform positive electrode slurry, which was then applied to the surface of the positive electrode composite current collector, and after drying, cold pressing, tab cutting, and other processes, a positive electrode sheet was obtained.

[0173] 3. Negative electrode composite current collector A copper foil with a thickness of 6 μm was used.

[0174] 4. Manufacturing of negative electrode sheets The negative electrode active material graphite, conductive carbon black, thickener sodium carboxymethylcellulose (CMC), and adhesive styrene butadiene rubber emulsion (SBR) were thoroughly mixed in a weight ratio of 96.5:1.0:1.0:1.5 with an appropriate amount of deionized water and stirred to form a uniform negative electrode slurry. The negative electrode slurry was then applied to a negative electrode composite current collector, and after drying and other processes, a negative electrode sheet was obtained.

[0175] 5. Separator A PP membrane was used.

[0176] 6. Preparation of electrolyte Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7 were uniformly mixed to obtain an organic solvent, and then 1 mol / L LiPF6 was uniformly dissolved in the organic solvent.

[0177] 7. Manufacturing of secondary batteries A positive electrode sheet, a separator, and a negative electrode sheet were laminated in this order, then wound around a battery core and placed in a packaging housing. The above-mentioned electrolyte was injected into the battery core, and a secondary battery was obtained through processes such as sealing, standing, hot pressing, cold pressing, and chemical formation.

[0178] Example 2 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: The PMMA protective layer was applied to the outer surface of the third and fourth sub-parts, respectively. That is, PMMA-anisole solution was purchased as the initial coating material, and Teflon pads were attached to the positions of the back roller of the coating machine corresponding to the third and fourth sub-parts, and the dimensions of the pads were designed to exactly correspond to the third and fourth sub-parts. When applying the PMMA protective layer, only the positions of the third and fourth sub-parts were coated, and the oven temperature was set to 80-100°C. After baking in the oven, the coating speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the first sub-portion and the second sub-portion were thinned by chemical etching, and the composite current collector coated with the protective layer in certain areas was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 11 m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the first sub-portion was 3 μm and the thickness of the second sub-portion was 3 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 3 μm, the thickness of the second sub-portion was 3 μm, the thickness of the third sub-portion was 5 μm, and the thickness of the fourth sub-portion was 5 μm. The thickness A of the first portion was 6 μm, the thickness B of the second portion was 10 μm, and A / B=0.6.

[0179] Example 3 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: The third and fourth sub-parts were coated with PMMA protective layers, that is, PMMA-anisole solution was purchased as the initial coating material, Teflon pads were attached to the back roller of the coating machine at positions corresponding to the third and fourth sub-parts, the dimensions of the pads were designed to exactly correspond to the third and fourth sub-parts, and only the positions of the third and fourth sub-parts were coated when the PMMA protective layer was coated, the oven temperature was set to 80-100°C, and after baking in the oven, the coating speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the first sub-portion and the second sub-portion were thinned by chemical etching, and the composite current collector coated with the protective layer in certain areas was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 9m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the first sub-portion was 1 μm and the thickness of the second sub-portion was 1 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the first sub-portion had a thickness of 1 μm, the second sub-portion had a thickness of 1 μm, the third sub-portion had a thickness of 5 μm, and the fourth sub-portion had a thickness of 5 μm. The thickness A of the first portion was 2 μm, the thickness B of the second portion was 10 μm, and A / B=0.2.

[0180] Example 4 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: The third and fourth sub-parts were coated with PMMA protective layers, that is, PMMA-anisole solution was purchased as the initial coating material, Teflon pads were attached to the back roller of the coating machine at positions corresponding to the third and fourth sub-parts, the dimensions of the pads were designed to exactly correspond to the third and fourth sub-parts, and only the positions of the third and fourth sub-parts were coated when the PMMA protective layer was coated, the oven temperature was set to 80-100°C, and after baking in the oven, the coating speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the first sub-portion and the second sub-portion were thinned by chemical etching, and the composite current collector coated with the protective layer in certain areas was passed through an etching tank containing NaOH solution, the solution temperature was 63°C, and the moving speed was 9m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the first sub-portion was 0.75μm and the thickness of the second sub-portion was 0.75μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 0.75 μm, the thickness of the second sub-portion was 0.75 μm, the thickness of the third sub-portion was 10 μm, and the thickness of the fourth sub-portion was 5 μm. The thickness A of the first portion was 5 μm, the thickness B of the second portion was 10 μm, and A / B=0.15.

[0181] Example 5 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: The third and fourth sub-parts were coated with PMMA protective layers, that is, PMMA-anisole solution was purchased as the initial coating material, Teflon pads were attached to the back roller of the coating machine at positions corresponding to the third and fourth sub-parts, the dimensions of the pads were designed to exactly correspond to the third and fourth sub-parts, and only the positions of the third and fourth sub-parts were coated when the PMMA protective layer was coated, the oven temperature was set to 80-100°C, and after baking in the oven, the coating speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the first sub-portion and the second sub-portion were thinned by chemical etching, and the composite current collector with the protective layer applied in certain areas was passed through an etching tank containing NaOH solution, the solution temperature was 65°C, and the moving speed was 8m / min, the thickness of the conductive layer without the PMMA protective layer was thinned, and after washing and drying, the thickness of the first sub-portion was 0.5 μm and the thickness of the second sub-portion was 0.5 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 0.5 μm, the thickness of the second sub-portion was 0.5 μm, the thickness of the third sub-portion was 5 μm, and the thickness of the fourth sub-portion was 5 μm. The thickness A of the first portion was 1 μm, the thickness B of the second portion was 10 μm, and A / B=0.1.

[0182] Example 6 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: The third and fourth sub-parts were coated with PMMA protective layers, that is, PMMA-anisole solution was purchased as the initial coating material, Teflon pads were attached to the positions of the back roller of the coating machine corresponding to the third and fourth sub-parts, the dimensions of the pads were designed to exactly correspond to the third and fourth sub-parts, and only the positions of the third and fourth sub-parts were coated when the PMMA protective layer was coated, the oven temperature was set to 80-100°C, and after baking in the oven, the coating speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the first sub-portion was thinned by chemical etching. The composite current collector coated with the protective layer in a specific area was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 11 m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the first sub-portion was 3 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 3 μm, the thickness of the second sub-portion was 5 μm, the thickness of the third sub-portion was 5 μm, and the thickness of the fourth sub-portion was 5 μm. The thickness A of the first portion was 8 μm, the thickness B of the second portion was 10 μm, and A / B=0.8.

[0183] Example 7 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: The second and fourth sub-parts were provided with a PMMA protective layer. PMMA-anisole solution was purchased as the initial coating, and the second and fourth sub-parts were coated with a coating machine, respectively. The oven temperature was set at 80-100°C, the coating speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the first and third sub-parts was thinned by chemical etching, and the composite current collector coated with the protective layer in certain areas was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 11 m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the first and third sub-parts was 3 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 3 μm, the thickness of the second sub-portion was 5 μm, the thickness of the third sub-portion was 3 μm, and the thickness of the fourth sub-portion was 5 μm. The thickness A of the first portion was 8 μm, the thickness B of the second portion was 8 μm, and A / B=1.

[0184] Example 8 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: The thickness of the first sub-portion, the second sub-portion, the third sub-portion and the fourth sub-portion were directly thinned by chemical etching, and the composite current collector coated with the protective layer in certain areas was passed through an etching tank containing NaOH solution, the solution temperature was 60° C., and the moving speed was 11 m / min, the thickness of the conductive layer in the non-protected areas was thinned, and then washing and drying were performed, and the thickness of the first sub-portion was 3 μm, the thickness of the second sub-portion was 3 μm, the thickness of the third sub-portion was 3 μm, and the thickness of the fourth sub-portion was 3 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 3 μm, the thickness of the second sub-portion was 3 μm, the thickness of the third sub-portion was 3 μm, and the thickness of the fourth sub-portion was 3 μm. The thickness A of the first portion was 6 μm, the thickness B of the second portion was 6 μm, and A / B=1.

[0185] Example 9 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: The first, second and fourth sub-parts were each provided with a PMMA protective layer. The thickness of the third sub-portion was thinned by chemical etching, and the composite current collector coated with the protective layer in certain areas was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 11 m / min, the thickness of the conductive layer in the non-protected areas was thinned, and then it was washed and dried, and the thickness of the third sub-portion was reduced to 3 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 5 μm, the thickness of the second sub-portion was 5 μm, the thickness of the third sub-portion was 3 μm, and the thickness of the fourth sub-portion was 5 μm. The thickness A of the first portion was 10 μm, the thickness B of the second portion was 8 μm, and A / B=1.1.

[0186] Example 10 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: A connection layer (tin layer) was formed between the first conductive sheet and the second conductive sheet. That is, tin powder was purchased, sieved through a 1 μm sieve to remove powder with a particle size exceeding 1 μm, and added to NMP in a weight ratio of tin powder to PVDF of 98:2 and stirred uniformly. Next, a slurry containing tin particles was applied to the surface of the third sub-part facing the fourth sub-part, and dried at an oven temperature of 80 to 100°C to make the tin layer 1 μm thick. The third sub-portion, the tin layer and the fourth sub-portion are bonded together to form an integral structure. Welding And, Welding The temperature was 300°C and the pressure was 30T. A PMMA protective layer was applied to the first sub-part, PMMA-anisole solution was purchased as the initial coating, a Teflon pad was attached to the position corresponding to the first sub-part on the back roller of the coating machine, and the dimensions of the pad were designed to exactly correspond to the first sub-part. When applying the PMMA protective layer, only the position of the first sub-part was applied, the oven temperature was set to 80-100°C, and after baking in the oven, the coating speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the third sub-part was thinned by chemical etching, where the composite current collector coated with the protective layer in a specific area was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 12 m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the third sub-part was 4 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 5 μm, the thickness of the second sub-portion was 5 μm, the thickness of the third sub-portion was 4 μm, the thickness of the fourth sub-portion was 5 μm, and the thickness of the tin layer was 1 μm. The thickness A of the first portion was 10 μm, the thickness B of the second portion was 10 μm, and A / B=1.

[0187] Example 11 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: A connection layer (tin layer) was formed between the first conductive sheet and the second conductive sheet. That is, tin powder was purchased, sieved through a 2 μm sieve, added to NMP in a weight ratio of tin powder to PVDF of 98:2 and stirred uniformly, and then a slurry containing tin particles was applied to the surface of the third sub-part facing the fourth sub-part, and dried at an oven temperature of 80 to 100°C to make the tin layer 2 μm thick. The third sub-portion, the tin layer and the fourth sub-portion are bonded together to form an integral structure. Welding And, Welding The temperature was 300°C and the pressure was 30T. A PMMA protective layer is applied to the first sub-part. PMMA-anisole solution is purchased as the initial coating material. A Teflon pad is attached to the back roller of the applicator at the position corresponding to the first sub-part. The dimensions of the pad are designed to exactly correspond to the first sub-part. When applying the PMMA protective layer, only the position of the first sub-part is applied. The oven temperature is set to 80-100°C. After baking in the oven, the application speed is 8m / min, and the final thickness of the protective layer is about 30μm. The thickness of the third sub-part was thinned by chemical etching, where the composite current collector coated with the protective layer in a specific area was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 11 m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the third sub-part was 3 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 5 μm, the thickness of the second sub-portion was 5 μm, the thickness of the third sub-portion was 3 μm, the thickness of the fourth sub-portion was 5 μm, and the thickness of the tin layer was 2 μm. The thickness A of the first portion was 10 μm, the thickness B of the second portion was 10 μm, and A / B=1.

[0188] Example 12 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: A connection layer (tin layer) was formed between the first conductive sheet and the second conductive sheet. That is, tin powder was purchased, sieved through a 5 μm sieve to remove powder with a particle size exceeding 5 μm, and added to NMP in a weight ratio of tin powder to PVDF of 98:2 and stirred uniformly. Next, a slurry containing tin particles was applied to the surface of the third sub-part facing the fourth sub-part, and dried at an oven temperature of 80 to 100°C to make the tin layer 5 μm thick. The third sub-portion, the tin layer and the fourth sub-portion are bonded together to form an integral structure. Welding And, WeldingThe temperature was 310° C. and the pressure was 35T. A PMMA protective layer was applied to the first and second sub-parts. PMMA-anisole solution was purchased as the initial paint. The dimensions of the pad were designed to exactly correspond to the first and second sub-parts. When applying the PMMA protective layer, only the positions of the first and second sub-parts were applied. The oven temperature was set at 80-100°C. After baking in the oven, the application speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the third and fourth sub-parts was thinned by chemical etching, and the composite current collector coated with the protective layer in certain areas was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 10 m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the third sub-part was 2.5 μm and the thickness of the fourth sub-part was 2.5 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 5 μm, the thickness of the second sub-portion was 5 μm, the thickness of the third sub-portion was 2.5 μm, the thickness of the fourth sub-portion was 2.5 μm, and the thickness of the tin layer was 5 μm. The thickness A of the first portion was 10 μm, the thickness B of the second portion was 10 μm, and A / B=1.

[0189] Example 13 The difference from Example 1 is that the following steps were added after the heat and pressure fusion step: A connection layer (polyaniline layer) was formed between the first conductive sheet and the second conductive sheet. That is, conductive polyaniline powder was purchased, polished to refine the particles, sieved through a 2 μm sieve to remove powder with a particle size exceeding 2 μm, added to NMP at a weight ratio of polyaniline particles to PVDF of 99:1, heated to 100°C in the NMP solution, and stirred uniformly in a vacuum, and then the polyaniline-containing slurry was applied to the surface facing the fourth sub-part of the third part, and dried in an oven at a temperature of 80 to 100°C, resulting in a polyaniline layer with a thickness of 2 μm. The third sub-portion, the polyaniline layer and the fourth sub-portion are bonded together to form an integral structure. Welding And, Welding The temperature was 370° C. and the pressure was 35T. A PMMA protective layer was applied to the first sub-part, PMMA-anisole solution was purchased as the initial paint, the dimensions of the pad were designed to exactly correspond to the first sub-part, and when applying the PMMA protective layer, only the position of the first sub-part was applied. The oven temperature was set to 80-100°C, and after baking in the oven, the application speed was 8m / min, and the final thickness of the protective layer was about 30μm. The thickness of the third sub-part was thinned by chemical etching, where the composite current collector coated with the protective layer in a specific area was passed through an etching tank containing NaOH solution, the solution temperature was 60°C, and the moving speed was 11 m / min, the thickness of the conductive layer not provided with the PMMA protective layer was thinned, and after washing and drying, the thickness of the third sub-part was 3 μm. After removing the PMMA protective layer, the etched composite current collector was passed through a dissolving tank containing acetone, where the temperature of the acetone was 50° C. and the moving speed was 10 m / min, so that the surface PMMA layer could be removed. In this example, the thickness of the first sub-portion was 5 μm, the thickness of the second sub-portion was 5 μm, the thickness of the third sub-portion was 3 μm, the thickness of the fourth sub-portion was 5 μm, and the thickness of the polyaniline layer was 2 μm. The thickness A of the first portion was 10 μm, the thickness B of the second portion was 10 μm, and A / B=1.

[0190] Example 14

[0191] 1. Manufacturing of negative electrode composite current collector A PP support layer (melting point 189° C.) having a thickness of 4.5 μm was selected, and the surface of the support layer was cleaned. A polyurethane adhesive was applied to one surface of the support layer to form a coating layer (thickness: 2 um) for forming an adhesive layer. The coating layer was prebaked. A copper layer is provided on the pre-baked coating layer as a first conductive sheet including a first sub-portion and a third sub-portion, a tin layer is applied to the third sub-portion, the tin layer has a thickness of 2 μm, and the third sub-portion and the fourth sub-portion are bonded together to form an integral structure. Welding Then, a customized heated roller was used to perform heat-compression fusion on only the third and fourth sub-portions at a pressure of 35 T and a temperature of 300° C. to form a first laminate for forming a composite current collector. The above first laminate was pressed at high temperature and cured after pressing to form a composite current collector including an adhesive layer between the PET and the copper layer, and the two copper layers formed a first conductive sheet and a second conductive sheet, respectively. The first conductive sheet includes a first sub-portion and a third sub-portion, and the second conductive sheet includes a second sub-portion and a fourth sub-portion, the first sub-portion and the second sub-portion are respectively provided on two first surfaces, and both the third sub-portion and the fourth sub-portion protrude from the support layer, where the thicknesses of the first sub-portion, the second sub-portion, the third sub-portion and the fourth sub-portion are all 5 μm, the thickness of the Sn connection layer is 2 μm, the thickness A of the first portion is 10 μm, the thickness B of the second portion is 12 μm, and A / B=0.83.

[0192] 2. Manufacturing of negative electrode sheets The negative electrode active material graphite, conductive carbon black, thickener sodium carboxymethylcellulose (CMC), and adhesive styrene butadiene rubber emulsion (SBR) were thoroughly mixed with an appropriate amount of deionized water in a weight ratio of 96.5:1.0:1.0:1.5 to form a uniform negative electrode slurry. The negative electrode slurry was applied to a negative electrode composite current collector, and after processes such as drying, a negative electrode sheet was obtained.

[0193] 3. Positive electrode composite current collector Aluminum foil with a thickness of 13 μm was used.

[0194] 4. Manufacturing of positive electrode sheets Cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), conductive carbon black, and adhesive polyvinylidene fluoride (PVDF) were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent in a weight ratio of 82:14:2:2 to form a uniform positive electrode slurry, which was then applied to a positive electrode composite current collector and, after drying and other processes, a positive electrode sheet was obtained.

[0195] 5. Separator A PP membrane was used.

[0196] 6. Preparation of electrolyte Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7 were uniformly mixed to obtain an organic solvent, and then 1 mol / L LiPF6 was uniformly dissolved in the organic solvent.

[0197] 7. Manufacturing of secondary batteries A positive electrode sheet, a separator, and a negative electrode sheet were laminated in this order, then wound around a battery core and placed in a packaging housing. The above-mentioned electrolyte was injected into the battery core, and a secondary battery was obtained through processes such as sealing, standing, hot pressing, cold pressing, and chemical formation.

[0198] Comparative Example 1 A PP film with a thickness of 4.5 μm was selected as the supporting layer, and aluminum foil with a thickness of 0.5 μm was provided as the conductive layer on the top and bottom surfaces, and the outer aluminum foil was welded to the edge of the conductive layer by a transfer welding process so as to cut the tab.

[0199] Performance Test Methodology

[0200] 1. Volumetric energy density test of secondary batteries At room temperature, the fabricated secondary battery was initially charged at a current of 1C, the charging was constant current and constant voltage charging, the final voltage was 4.2V, the cut-off current was 0.05C, and the secondary battery was discharged at a current of 1C, the final discharge voltage was 2.8V, and the discharge capacity Cb and discharge platform voltage U when the secondary battery was subjected to the first cycle were recorded. The length (L), width (W) and height (H) of the battery were measured with a soft ruler or a steel ruler with a minimum scale of 1 mm, and the volumetric energy density of the secondary battery was calculated by the following formula: Volumetric energy density=Cb*U / (L*W*H).

[0201] 2. DC current discharge internal resistance (DCR) detection: The test conditions were as follows: at room temperature, the secondary battery was discharged at SOC 50% and 4C (constant current is written as I) for 30 seconds, the voltage before and after discharge was reduced to ΔV, and DCR = ΔV / I.

[0202] [Table 1]

[0203] As can be seen from Table 1, in Comparative Example 1, the edge of the conductive layer and the outer aluminum foil are welded by a transfer welding process, and there are two independent aluminum foils in the welding area, and there is welding in the welding area, and this welding method limits the welding strength to a certain extent, and the thickness of the tab in the welding area is increased, which can increase the overcurrent capacity, but the overcurrent capacity and energy density of the secondary battery are relatively low. Compared with Comparative Example 1, in Example 5, hot melt connection is adopted, and the overcurrent capacity and energy density of the secondary battery are greatly improved.

[0204] In Examples 1 to 5, as the thickness of the first portion became thinner, the A / B value gradually decreased and the energy density of the secondary battery gradually increased, but at the same time, the DC discharge internal resistance also gradually increased. As can be seen from Table 1, the energy density and DCR of the secondary battery were excellent when A / B was 0.2 to 1. When A / B<0.2, the DCR increased significantly.

[0205] In Examples 6 to 9, by differentiating and designing the thicknesses of different regions of the second portion, the energy density and overcurrent capability of the secondary battery can be adjusted, and the secondary battery can adapt to different application scenarios.

[0206] In Examples 10 to 13, a metal connection layer or a conductive polymer connection layer is added between the third sub-portion and the fourth sub-portion, so that the hot pressing can be performed. Welding It can reduce the temperature and reduce the processing difficulty, especially hot pressing. Welding The temperature can be reduced to, for example, 400° C. or less, and the secondary batteries of Examples 10 to 12 can be manufactured by directly hot pressing the secondary batteries of Example 1. Welding This shows that the metal connection layer is advantageous for processing the composite current collector and does not substantially affect the energy density and overcurrent capacity of the secondary battery.

[0207] The secondary battery of Example 14 has excellent energy density and overcurrent capability. This indicates that the composite current collector of the examples of the present application is not only applicable to the manufacture of positive electrode composite current collectors, but also applicable to negative electrode composite current collectors, and has universal applicability.

[0208] Although the present application has been described with reference to the preferred embodiments, various modifications can be made and parts can be replaced with equivalents without departing from the scope of the present application. In particular, the technical features described in each embodiment can be combined in any manner as long as there is no structural contradiction. The present application is not limited to the specific embodiments disclosed in this specification, but includes all solutions within the scope of the claims.

Claims

1. A composite current collector, A support layer having two first surfaces facing each other along a thickness direction; a conductive layer disposed on the two first surfaces, the conductive layer including a first portion and a second portion, wherein: a conductive layer, the first portion including a first sub-portion and a second sub-portion provided on each of the two first surfaces, the second portion including a third sub-portion and a fourth sub-portion, the third sub-portion and the first sub-portion being integrally provided, the fourth sub-portion and the second sub-portion being integrally provided, both the third sub-portion and the fourth sub-portion protruding from the support layer along a first direction, and the third sub-portion and the fourth sub-portion being bonded to each other and welded together; Including, the second portion further includes a connection layer between the third sub-portion and the fourth sub-portion, and the melting point of the connection layer is lower than the melting point of the third sub-portion; A composite current collector, in which the third sub-portion, the end portion of the support layer along the first direction, and the fourth sub-portion are attached to each other and welded together.

2. The composite current collector according to claim 1 , wherein the end portion has a width in the first direction of 1 mm to 10 mm.

3. 3. The composite current collector according to claim 1, wherein the third sub-portion includes two second surfaces facing each other along a thickness direction, and the first sub-portion protrudes relative to the second surfaces along the thickness direction.

4. The third sub-portion includes two second surfaces opposed to each other along the thickness direction, 3. The composite current collector according to claim 1, wherein the first sub-portion includes two third surfaces that face each other along the thickness direction, and one of the two third surfaces is flush with the second surface.

5. 5. The composite current collector of claim 1, wherein the first portion has a thickness A and the second portion has a thickness B, where 0.03≦A / B≦1.

6. the thickness of the first sub-portion is greater than or equal to the thickness of the second sub-portion; and / or The composite current collector according to any one of claims 1 to 5, wherein the third sub-portion has a thickness equal to or greater than a thickness of the fourth sub-portion.

7. the connection layer includes at least one of a metal layer and an organic conductive polymer layer; the metal material includes at least one of tin, indium, bismuth, and cadmium; 2. The composite current collector according to claim 1, wherein the material of the organic conductive polymer layer includes at least one of polypyrrole, polythiophene, polyaniline, polyacetylene, polyphenylene, and polyphenylenevinylene.

8. The composite current collector according to claim 1 or 7, wherein the thickness of the connection layer is from 1 μm to 5 μm.

9. A method for producing a composite current collector, comprising the steps of: providing a support layer, the support layer including two first surfaces opposed to each other along a thickness direction; providing a first conductive sheet and a second conductive sheet, and connecting the first conductive sheet and the second conductive sheet to two of the first surfaces, respectively, the first conductive sheet including a first sub-portion and a third sub-portion, the second conductive sheet including a second sub-portion and a fourth sub-portion, the first sub-portion and the second sub-portion being provided on the two first surfaces, respectively, and both the third sub-portion and the fourth sub-portion protruding from the support layer; laminating the third sub-portion and the fourth sub-portion together and welding them together by hot press welding; Including, a connecting layer between the third sub-portion and the fourth sub-portion, the melting point of the connecting layer being lower than the melting point of the third sub-portion; The third sub-portion, the end portion of the support layer along the first direction, and the fourth sub-portion are attached to one another and welded together.

10. The method of claim 9 , further comprising removing a portion of the first sub-portion along the thickness direction to reduce a thickness of the first sub-portion.

11. 11. The method of claim 9 or 10, further comprising removing a portion of the third sub-portion along the thickness direction to reduce a thickness of the third sub-portion.

12. 9. An electrode sheet comprising: an active material layer; and the composite current collector according to claim 1, wherein the active material layer is provided on a surface of the first portion of the composite current collector.

13. A secondary battery comprising the electrode sheet according to claim 12.

14. A battery module comprising the secondary battery according to claim 13.

15. A battery pack comprising the secondary battery according to claim 13 or the battery module according to claim 14.

16. An electric device comprising the secondary battery according to claim 13, the battery module according to claim 14, or the battery pack according to claim 15.

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