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

Abstract

The embodiment of the present application relates to a kind of composite current collector, pole piece, secondary battery, battery module, battery pack and electric device.The composite current collector includes support layer and conductive layer.The support layer has two first surfaces opposite to each other along the thickness direction.The conductive layer is arranged on the two first surfaces, and the conductive layer includes a first part and a second part, wherein the first part includes a first subpart and a second subpart arranged on the two first surfaces respectively, the second part includes a third subpart and a fourth subpart, the third subpart and the first subpart are integrally arranged, the fourth subpart and the second subpart are integrally arranged, the third subpart and the fourth subpart are protruded from the support layer, and the third subpart and the fourth subpart are adhered to each other and integrally fused.The structure of the conductive layer of the embodiment of the present application is stable, the overcurrent capacity of the composite current collector is improved, and the composite current collector of the secondary battery is significantly improved in electrical performance, safety performance and processing performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a composite current collector, a pole piece, a secondary battery, a battery module, a battery pack and a power utilization device. BACKGROUND

[0002] Secondary batteries are widely used in electric vehicles and consumer electronics due to their high energy density, high output power, long cycle life and low environmental pollution. The composite current collector, as an important component for preparing secondary batteries, significantly affects the electrochemical performance of secondary batteries. Compared with conventional composite current collectors, the composite current collector with a "metal-insulating polymer-metal" sandwich structure can effectively improve the electrochemical performance of secondary batteries. However, the existing composite current collector has many problems, such as poor overcurrent capacity due to insufficient bonding strength between the composite current collector and the external metal foil (used for processing the pole lug), complex preparation process, and the like, which significantly affect the electrical performance, safety performance and processing performance of secondary batteries. Therefore, it is urgent to develop a new type of composite current collector. SUMMARY

[0003] The present application is made in view of the above-mentioned problems, and aims to provide a composite current collector, a pole piece, a secondary battery, a battery module, a battery pack and a power utilization device.

[0004] To achieve the above-mentioned purpose, the first aspect of the present application provides a composite current collector, which comprises a support layer and a conductive layer. The support layer has two first surfaces opposite to each other along the thickness direction. The conductive layer is arranged on the two first surfaces, and the conductive layer comprises a first part and a second part. The first part comprises a first subpart and a second subpart arranged on the two first surfaces respectively, and the second part comprises a third subpart and a fourth subpart. The third subpart and the first subpart are integrally arranged, the fourth subpart and the second subpart are integrally arranged, the third subpart and the fourth subpart protrude from the support layer, and the third subpart and the fourth subpart are integrally bonded to each other.

[0005] Thus, the first subpart and the third subpart of the embodiment of the present application are integrally arranged, the second subpart and the fourth subpart are integrally arranged, and the third subpart and the fourth subpart are integrally arranged by being attached to each other and being fused. That is, the conductive layer is an integral structure. The arrangement of the integral conductive layer avoids the disadvantages of the traditional welding process, and the external metal foil is omitted in the structure, thereby avoiding the problem of poor welding between the external metal foil and the conductive layer, significantly improving the flow capacity of the composite current collector, and improving the electrical performance of the secondary battery. The hot fusion process of the present application effectively avoids the cracking of the conductive layer and the support layer of the composite current collector during the production process, and the cracks or even the cracking of the tab root caused by the process (such as rolling), thereby significantly increasing the production yield of the composite current collector and the safety performance of the secondary battery. The processing consistency of the composite current collector is improved, the problem of misalignment of the edges of the upper and lower workpieces in the tab cutting process and burrs is avoided, the tab folding in the die cutting and winding process is prevented, and the production yield and safety performance are improved. In summary, the composite current collector of the present application can significantly improve the electrical performance, safety performance and production yield of the secondary battery.

[0006] In any embodiment, the third subpart, the end of the support layer along the first direction, and the fourth subpart are integrally arranged by being attached to each other and being fused, and the first direction is perpendicular to the thickness direction. The end can provide support and protection for the third subpart and the fourth subpart.

[0007] In subsequent rolling and other processes, the third subpart and the fourth subpart may be partially stretched, and the end will provide support for the third subpart and the fourth subpart, thereby avoiding the cracking or even the cracking of the third subpart and the fourth subpart. On the other hand, the composite current collector of this embodiment has a support layer supporting the tab root after the tab is cut, so that the rigidity of the tab root is increased, the tab folding is prevented, and the safety performance during the preparation of the secondary battery is significantly improved.

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

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

[0010] Thus, the thickness of the third subpart of the embodiment of the present application is relatively moderate, which can significantly improve the energy density of the secondary battery using the composite current collector; and can ensure the flow capacity of the secondary battery using the composite current collector, and can ensure the safety performance of the secondary battery.

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

[0012] Thus, the first sub-portion has a smaller thickness, which can improve the energy density of the secondary battery using the composite current collector to a certain extent.

[0013] In any embodiment, the thickness of the first portion is A and the thickness of the second portion is B, wherein 0.03≤A / B≤1; optionally, 0.2≤A / B≤1. The thickness ratio of the first portion and the second portion satisfies the above range, which can ensure the energy density of the secondary battery using the composite current collector and improve the overcurrent capacity of the secondary battery.

[0014] In any embodiment, the thickness of the first sub-portion is greater than or equal to the thickness of the second sub-portion. The second sub-portion can not be thinned during processing, which can reduce the cost and is beneficial to the processing and forming.

[0015] In any embodiment, the thickness of the third sub-portion is greater than or equal to the thickness of the fourth sub-portion. The fourth sub-portion can not be thinned during processing, which can reduce the cost and is beneficial to the processing and forming.

[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 lower, and the connecting layer is preferentially melted during the processing of the second portion, which is beneficial to bonding the third sub-portion and the fourth sub-portion as a whole, thereby facilitating the fusion of the third sub-portion and the fourth sub-portion as a whole.

[0018] In any embodiment, the connecting 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, polyphenyl and polyphenylacetylene. When the connecting layer uses metal, it is more beneficial to the full melting of the third sub-portion and the fourth sub-portion. When the connecting layer uses organic conductive polymer, the organic conductive polymer not only can bond the third sub-portion and the fourth sub-portion, but also can be fused and bonded with the support layer, which can further improve the connection strength between the second portion and the support layer.

[0019] In any embodiment, the thickness of the connecting layer is 1μm-5μm. When the thickness of the connecting layer is within the above range, it is beneficial to assist the full melting and bonding of the third sub-portion and the fourth sub-portion, i.e. it is beneficial to the full melting of the second portion as a whole.

[0020] In any embodiment, the support layer comprises at least two support portions arranged at intervals along a first direction, and a second portion is arranged between two adjacent support portions, and the first direction is perpendicular to the thickness direction. The composite current collector with such a structure can be used to form multiple electrode assemblies by slitting.

[0021] The second aspect of the present application provides a pole piece comprising the composite current collector according to any one of the embodiments of the first aspect of the present application and an active material layer arranged on the surface of the first portion of the composite current collector.

[0022] The third aspect of the present application provides a secondary battery comprising the pole piece according to the embodiment of the second aspect of the present application.

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

[0024] The fifth aspect of the present application provides a battery pack comprising 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] The sixth aspect of the present application provides a power consumption device comprising the secondary battery according to the embodiment of the third aspect of the present application, the battery module according to the embodiment of the fourth aspect of the present application, or the battery pack according to the fifth aspect of the present application.

[0026] The seventh aspect of the present application provides a manufacturing method of a composite current collector, comprising: providing a support layer comprising two first surfaces opposite 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 the two first surfaces respectively, wherein the first conductive sheet comprises a first sub-portion and a third sub-portion, the second conductive sheet comprises a second sub-portion and a fourth sub-portion, the first sub-portion and the second sub-portion are arranged on the two first surfaces respectively, and the third sub-portion and the fourth sub-portion protrude from the support layer; and adhering and welding the third sub-portion and the fourth sub-portion to be integrated.

[0027] Therefore, the composite current collector prepared by the manufacturing method of the embodiments of the present application can be directly laser-cut for tabs without adapter welding, greatly simplifying the process and improving the overcurrent capacity of the tabs; not only the edges are flush and free of burrs during mechanical slitting, but also the conductive layer of the second portion is well connected with the support layer, and cracking and other problems do not occur during cold pressing, and the secondary battery prepared by using the composite current collector has excellent electrochemical performance.

[0028] In any embodiment, the method further comprises: removing part of the first sub-portion along the thickness direction to reduce the thickness of the first sub-portion. The relatively lower thickness of the first sub-portion can improve the energy density of the secondary battery to a certain extent.

[0029] In any embodiment, the method further comprises: removing part of the third sub-portion in the thickness direction to thin the thickness of the third sub-portion. Thinning the thickness of the third sub-portion can improve the energy density on the basis of ensuring the overcurrent capacity. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the drawings.

[0031] Figure 1 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0032] Figure 2 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0033] Figure 3 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0034] Figure 4 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0035] Figure 5 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0036] Figure 6 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0037] Figure 7 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0038] Figure 8 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0039] Figure 9 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0040] Figure 10 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0041] Figure 11 is a structural schematic diagram of a composite current collector provided by some embodiments of the present application;

[0042] Figure 12 is another state diagram of a manufacturing process of a composite current collector provided by some embodiments of the present application;

[0043] Figure 13 is another state diagram of a manufacturing process of a composite current collector provided by some embodiments of the present application;

[0044] Figure 14 is a structural diagram of a pole piece provided by some embodiments of the present application;

[0045] Figure 15 is a cross-sectional structural diagram of the pole piece shown in FIG. 5 along the line A-A; Figure 14

[0046] Figure 16 is a structural diagram of an electrode assembly of a secondary battery provided by some embodiments of the present application;

[0047] Figure 17 is a structural diagram of an electrode assembly of a secondary battery provided by some embodiments of the present application;

[0048] Figure 18 is a structural diagram of a battery module provided by some embodiments of the present application;

[0049] Figure 19 is a structural diagram of a battery module provided by some embodiments of the present application;

[0050] Figure 20 is a structural diagram of an electrical device provided by some embodiments of the present application.

[0051] In the drawings, the drawings are not necessarily drawn according to the actual scale.

[0052] In the drawings, various reference signs are used:

[0053] X, thickness direction; Y, first direction;

[0054] 1, electrical device; 10, battery pack; 11, lower box body; 12, upper box body; 20, battery module; 30, secondary battery; 31, top cover assembly; 32, shell; 40, electrode assembly; 50, pole piece; 41, separator film;

[0055] 60, composite current collector;

[0056] 70, support layer; 71, first surface; 72, end portion; 73, support portion;

[0057] 80, conductive layer; 81, first portion; 811, first sub-portion; 8111, third surface; 812, second sub-portion;

[0058] ​82, second portion; 821, third sub-portion; 8211, second surface; 822, fourth sub-portion; 823, connecting layer;

[0059] 90, active material layer;

[0060] 100, protective layer. DETAILED DESCRIPTION

[0061] Hereinafter, embodiments of the composite current collector and the manufacturing method thereof, the electrode sheet, the secondary battery, the battery module, the battery pack, and the power-using device according to the present application will be specifically described with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0062] The ranges disclosed herein are defined by their lower and upper limits. Ranges created by the upper and lower limits are inclusive of the endpoints. Ranges created by the upper and lower limits are also inclusive of any and all sub-ranges subsumed therein. For example, a range of "60% to 120%" is inclusive of at least 60% and 120%, but also includes any and all sub-ranges between (and including) the minimum of about 60% and the maximum of about 120%, that is, all sub-ranges having a limit of less than or equal to 120% in combination with a limit of greater than or equal to 60% also fall within the range of "60% to 120%". Moreover, all statements herein reciting "a range or limits of two values and citing one of the values limits the range as including the statement range is of the other value. For example, a statement that a variable is "greater than or equal to 1" and "less than or equal to 5" defines one range; and a statement that a variable is "greater than 2" and "less than 3" defines a different range. Unless otherwise stated, the numerical values recited in this application are approximate which means that the terms "comprises" "comprising," "has" "having," "includes" "including" and the like can be read to be inclusive ever though the term "consisting" "consisting of," "consisting only of" or the like can be read to be exclusive. In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand manner of describing the entire set of ranges encompassed by each whole or partial combination of each number within the range with each number of another range described elsewhere discussed herein. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing these numerical combinations. Additionally, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0063] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, unless otherwise specified. All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, unless otherwise specified.

[0064] If not specifically stated, all steps of the present application can be performed in sequence or randomly, preferably in sequence. For example, a method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, a method can further comprise step (c) means that step (c) can be added to the method in any order. For example, a method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0065] If not specifically stated, "comprising" and "including" as used in the present application are open-ended and also include closed or blocked forms. For example, "comprising" and "including" can mean that other components not listed can also be included or comprised, or can mean that only the listed components are included or comprised.

[0066] If not specifically stated, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": 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 both A and B are true (or exist).

[0067] It should be understood that the relational terms herein, such as first, second, and the like, are used solely to distinguish one from another entity or action without necessarily requiring or implying any actual relationship or order between or among such entities or actions.

[0068] The above summary of the application is not intended to describe each disclosed embodiment or implementation of the present application. The following description more specifically illustrates example embodiments. Throughout this application, guidance is provided by a series of examples, which can be used in various combinations. In each instance, the recited list is representative only and should not be construed as exhaustive.

[0069] The inventors have found that the "sandwich" type composite current collector consisting of a support layer and conductive layers on both opposite surfaces of the support layer has many defects, resulting in secondary battery electrical performance, safety performance and processing performance that cannot meet the requirements of large-scale industrialization. Specifically:

[0070] A composite current collector in the prior art is composed of a support layer and a conductive layer on the surface of the support layer. In order to output the current collected in the main body to the outside to charge the secondary battery, the preparation process of the composite current collector needs to externally connect a metal foil to the surface of the conductive layer (the externally connected metal foil is used to process the tab), and the external connection is achieved by welding (also known as "relay welding" in the industry). However, this welding connection has many defects: 1) Because the conductive layer of the composite current collector is relatively thin, the traditional welding process makes the connection strength between the externally connected metal foil and the conductive layer insufficient, resulting in a virtual welding problem, and further limiting the overcurrent capacity of the welding area and affecting the electrical performance of the secondary battery; 2) Insufficient welding strength also makes the externally connected metal foil and the main body easily fall off in the subsequent preparation process, such as cold pressing and die cutting, significantly reducing the production yield of the composite current collector and the safety performance of the secondary battery; 3) In order to process the tab, the two conductive layers need to be externally connected to the metal foil, which makes the upper and lower metal foils need to be processed separately when cutting the tab, thereby causing the edges of the upper and lower tabs after cutting to be misaligned and burrs, reducing the production yield and safety performance; 4) After the composite current collector prepared by the traditional relay welding process is cut, the tab lacks the support of the support layer at the root of the tab, which causes the tab to easily fold, significantly reducing the safety performance in the preparation process of the secondary battery.

[0071] Based on the many defects of the existing composite current collector, the present application develops a composite current collector that can significantly improve the electrical performance, safety performance and processing performance of the secondary battery. Next, combined with Figures 1 to 20 The embodiments of the present application are described in detail.

[0072] [Composite current collector]

[0073] Figure 1 is a structural schematic diagram of the composite current collector provided by some embodiments of the present application.

[0074] As Figure 1 shown, the composite current collector 60 provided by the embodiments of the present application includes a support layer 70 and a conductive layer 80.

[0075] The support layer 70 of the embodiments of the present application supports and protects the conductive layer 80. The support layer 70 has two first surfaces 71 opposite to each other along the thickness direction X. Figure 1 The X direction shown in the figure represents the thickness direction.

[0076] The material of the support layer 70 includes one or more of a high polymer material and a high polymer-based composite material. The high polymer-based composite material includes a high polymer material and an additive, and the additive is at least one of an inorganic non-metallic material and a metallic material.

[0077] The high molecular 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, polystyrene sulfonate sodium, polyacetylene, silicone rubber, polyformaldehyde, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polyazolium, polystyrene, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, derivatives thereof, cross-linked products thereof, and copolymers thereof. Optionally, the high molecular material is at least one of polyamide, polyimide, polyethylene terephthalate, polypropylene, and polyphenylene sulfide.

[0078] The high molecular-based composite material includes the high molecular material and the additive. The additive is at least one of inorganic non-metallic material and metallic material. Optionally, the inorganic non-metallic material includes one or more of carbon-based material, aluminum oxide, silicon dioxide, silicon nitride, silicon carbide, boron nitride, silicate, and titanium oxide. The metallic material includes one or more of magnesium, calcium, strontium, lead, zinc, tin, antimony, bismuth, silver, and ruthenium.

[0079] The conductive layer 80 of the embodiment of the present application is arranged on the two first surfaces 71 of the support layer 70. The conductive layer 80 can be formed on the support layer 70 by at least one of mechanical rolling, bonding, vapor deposition, electroless plating, and electroplating. Optionally, the conductive layer 80 is a vapor deposition layer or an electroplating layer, so that the conductive layer 80 and the support layer 70 can be tightly combined, and the support layer 70 can effectively support and protect the conductive layer 80.

[0080] In some embodiments, the conductive layer 80 can be connected to the support layer 70 by an adhesive to improve the connection strength of the conductive layer 80 and the support layer 70. Optionally, the adhesive is at least one of polypropylene, carboxymethyl cellulose, polyacrylate, styrene butadiene rubber, sodium polyacrylate, polyurethane, polyethylene imine, polyvinylidene fluoride, chlorobutyl rubber, nitrile rubber, silicone rubber, polyvinyl acetate, urea-formaldehyde resin, phenol-formaldehyde resin, epoxy resin, silane coupling agent, titanate coupling agent, zirconium coupling agent, aluminate coupling agent, and borate coupling agent.

[0081] The material of the conductive layer 80 can include metal. Exemplarily, when the composite current collector 60 is a positive composite current collector, the conductive layer 80 is a positive conductive layer, and the material of the positive conductive layer is selected from aluminum or an aluminum-based alloy, which can be an aluminum-nickel alloy, an aluminum-titanium alloy, or an aluminum-silver alloy, etc. When the composite current collector 60 is a negative composite current collector, the conductive layer 80 is a negative conductive layer, and the material of the negative conductive layer is selected from copper or a copper-based alloy, which can be a copper-nickel alloy, a copper-titanium alloy, or a copper-silver alloy, etc.

[0082] Of course, in some embodiments, other substances beneficial to processing, such as a low-melting-point metal or a low-melting-point organic conductive polymer layer, etc., can also be added in the process of forming the conductive layer 80. In this context, the low-melting point is relative 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 with a melting point lower than that of aluminum metal, and the low-melting-point organic conductive polymer layer has a melting point lower than that of aluminum metal.

[0083] The conductive layer 80 includes a first part 81 and a second part 82. The first part 81 includes a first sub-part 811 and a second sub-part 812 respectively arranged on the two first surfaces 71, and the second part 82 includes a third sub-part 821 and a fourth sub-part 822, the third sub-part 821 and the first sub-part 811 are integrally arranged, the fourth sub-part 822 and the second sub-part 812 are integrally arranged, the third sub-part 821 and the fourth sub-part 822 both protrude from the support layer 70, and the third sub-part 821 and the fourth sub-part 822 are integrally adhered to each other. The third sub-part 821 and the fourth sub-part 822 are cut as an integral structure, the edges after cutting are flush and no burrs are generated, which can improve the safety performance and production rate of the secondary battery of the composite current collector 60.

[0084] The first sub-part 811 and the second sub-part 812 of the first part 81 are both arranged on the first surface 71 for coating the active material layer. The third sub-part 821 and the fourth sub-part 822 of the second part 82 are used as the tab.

[0085] The first sub-part 811 includes two third surfaces 8111 opposite to each other along the thickness direction X. The third sub-part 821 includes two second surfaces 8211 opposite to each other along the thickness direction X. The first sub-part 811 and the third sub-part 821 are integrally arranged, one of the two third surfaces 8111 of the first sub-part 811 can be flush with one of the two second surfaces 8211, or the first sub-part 811 can protrude from the second surface 8211, or be recessed relative to the second surface 8211.

[0086] The second sub-portion 812 includes two fourth surfaces opposite to each other along the thickness direction X. The fourth sub-portion 822 includes two fifth surfaces opposite to each other along the thickness direction X. The second sub-portion 812 and the fourth sub-portion 822 are integrally arranged, one of the two fourth surfaces of the second sub-portion 812 can be flush with one of the two fifth surfaces, or the second sub-portion 812 can protrude from the fifth surface, or be recessed relative to the fifth surface.

[0087] The first sub-portion 811 and the third sub-portion 821 are integrally arranged, and the second sub-portion 812 and the fourth sub-portion 822 are integrally arranged. When the conductive layer 80 is formed by the first sub-portion 811, the third sub-portion 821, the second sub-portion 812 and the fourth sub-portion 822, the first sub-portion 811 and the second sub-portion 812 can have the same thickness, or 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, or the third sub-portion 821 and the fourth sub-portion 822 can have different thicknesses.

[0088] In the embodiments of the present application, the first sub-portion 811 and the third sub-portion 821 are integrally arranged, and the second sub-portion 812 and the fourth sub-portion 822 are integrally arranged. The third sub-portion 821 and the fourth sub-portion 822 are attached to each other and integrally fused, that is, the conductive layer 80 is an integral structure. This arrangement of integrally fusing the conductive layer 80 has the following advantages: 1) avoids the disadvantages of traditional welding processes, and the structure does not need to be externally connected to a metal foil, thereby avoiding the problem of poor welding between the externally connected metal foil and the conductive layer, thereby significantly improving the current-carrying capacity of the composite current collector 60 and the electrical performance of the secondary battery; 2) the hot fusion process of the present application effectively avoids the cracking of the conductive layer 80 and the support layer 70 during the process, and the cracking of the tab root caused by the process (such as rolling), thereby significantly increasing the production yield of the composite current collector 60 and the safety performance of the secondary battery; 3) improves the processing consistency of the composite current collector 60, avoids the misalignment of the edges of the upper and lower workpieces in the tab cutting process and the burr problem, prevents the tab from being folded during the die cutting and winding process, and improves the production yield and safety performance. In summary, the composite current collector of the present application can significantly improve the electrical performance, safety performance and production yield of the secondary battery.

[0089] Please continue to refer to Figure 1 In some embodiments, the third sub-portion 821, the end 72 of the support layer 70 along the first direction Y and the fourth sub-portion 822 are integrally attached and fused. Figure 1 The Y direction shown in the figure represents the first direction, and the first direction Y is perpendicular to the thickness direction X.

[0090] The third sub-portion 821 and the fourth sub-portion 822 are integrally fused with the end portion 72, in other words, the three are connected with each other, and the end portion 72 can provide support and protection to the third sub-portion 821 and the fourth sub-portion 822. In subsequent rolling and other processes, the third sub-portion 821 and the fourth sub-portion 822 can be partially stretched, and the end portion 72 will provide support to the third sub-portion 821 and the fourth sub-portion 822, thereby avoiding the third sub-portion 821 and the fourth sub-portion 822 from cracking or even breaking. The composite current collector 60 of this embodiment has a support layer 70 supporting the tab root after the tab is cut, so that the rigidity of the tab root is increased, the tab folding is prevented, and the safety performance in the secondary battery preparation process is significantly improved.

[0091] Optionally, the width of the end portion 72 along the first direction Y is 1 mm to 10 mm. For example, it can 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 can be composed of any two of the foregoing values; or it can be 5 mm to 8 mm. Within the above width range, the end portion 72 can further improve the connection strength between the end portion 72 and the third sub-portion 821 and the fourth sub-portion 822, and further improve the support strength of the third sub-portion 821 and the fourth sub-portion 822. The measurement method of the width is as follows: first, the thickness of the end portion 72 is measured by using a micrometer, so that the critical position of the end portion 72 near the first portion 81 and the critical position of the end portion 72 near the second portion 82 can be roughly determined; then, the cross section of the composite current collector 60 is cut near the critical positions by using a Japanese electronic IB-19500; then, the thickness of the support layer 70 and the conductive layer 80 is measured and the critical end surface position is confirmed by using a Zeiss Sigma 300 scanning electron microscope; after the end surface position is determined, the width of the end portion 72 is measured by using a scale. Figure 1 The size of C in the above formula approximately represents the width of the end portion 72 along the first direction Y.

[0092] Please continue to refer to Figure 1 In some embodiments, the first sub-portion 811 protrudes relative to the second surface 8211 of the third sub-portion 821 along the thickness direction X. The thickness of the third sub-portion 821 is relatively moderate, which can greatly improve the energy density of the secondary battery using the composite current collector 60; and can ensure the overcurrent capacity of the secondary battery using the composite current collector 60, and can ensure the safety performance of the secondary battery.

[0093] Figure 2 is a structural schematic diagram of a composite current collector provided by another embodiment of the present application.

[0094] As Figure 2In some embodiments, the first sub-portion 811 is in contact with the second surface 8211 of the third sub-portion 821. The thickness of the first sub-portion 811 is relatively small, which can improve the energy density of the secondary battery employing the composite current collector 60 to a certain extent.

[0095] In some embodiments, the second sub-portion 812 protrudes relative to the fifth surface of the fourth sub-portion 822 along the thickness direction X. The thickness of the fourth sub-portion 822 is relatively moderate, which can improve the energy density of the secondary battery employing the composite current collector 60 to a large extent; and can ensure the overcurrent capacity of the secondary battery employing the composite current collector 60.

[0096] In some embodiments, the second sub-portion 812 is in contact with the fifth surface of the fourth sub-portion 822. The thickness of the second sub-portion 812 is relatively small, which can improve the energy density of the secondary battery employing the composite current collector 60 to a certain extent.

[0097] In some embodiments, the thickness of the first portion 81 is A, the thickness of the second portion 82 is B, and the ratio A / B satisfies: 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 ratio A / B ranges from any two of the foregoing values; optionally, 0.2≤A / B≤1. The thickness ratio of the first portion 81 and the second portion 82 satisfies the above range, which can ensure the energy density of the secondary battery employing the composite current collector 60, and improve the overcurrent capacity of the secondary battery.

[0098] In this document, the thickness of the first portion 81 refers to the overall thickness of the first portion 81 along the thickness direction X. For example, the first portion 81 comprises the first sub-portion 811 and the second sub-portion 812, and the thicknesses of the first sub-portion 811 and the second sub-portion 812 along the thickness direction X add up to A.

[0099] In this document, the thickness of the second portion 82 refers to the overall thickness of the second portion 82 along the thickness direction X. For example, the second portion 82 comprises the third sub-portion 821 and the fourth sub-portion 822, and the thicknesses of the third sub-portion 821 and the fourth sub-portion 822 along the thickness direction X add up to B. Or the second portion 82 further comprises other components such as a connecting layer, and the thicknesses of the third sub-portion 821, the connecting layer and the fourth sub-portion 822 along the thickness direction X add up to B.

[0100] 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 can be composed of any two of the aforementioned values.

[0101] 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 can be composed of any two of the aforementioned values.

[0102] In some embodiments, the thickness of the first sub-portion 811 is greater than or equal to the thickness of the second sub-portion 812. The second sub-portion 812 can not be thinned during processing, which can reduce costs and facilitate processing.

[0103] 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 can not be thinned during processing, which can reduce costs and facilitate processing.

[0104] Figure 3 is a structural schematic diagram of a composite current collector provided by another embodiment of the present application.

[0105] As shown in Figure 3 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 less than the melting point of the third sub-portion 821. The melting point of the connecting layer 823 is relatively lower, and the connecting layer 823 is preferentially melted during processing of the second portion 82, which facilitates bonding of the third sub-portion 821 and the fourth sub-portion 822 into a whole, thereby facilitating fusion bonding of the third sub-portion 821 and the fourth sub-portion 822 into a whole.

[0106] Optionally, the melting point of the connecting layer 823 is less than the melting point of the fourth sub-portion 822, and the melting point of the connecting layer 823 is relatively lower than the melting points of the third sub-portion 821 and the fourth sub-portion 822, which facilitates bonding of the third sub-portion 821 and the fourth sub-portion 822 into a whole during processing of the second portion 82.

[0107] Optionally, the connecting layer 823 includes at least one of a metal layer and an organic conductive polymer layer. In other words, the connecting 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.

[0108] 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 is a single metal such as tin, indium, bismuth, or cadmium; or can 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, or a tin-bismuth-cadmium alloy, etc. When the connecting layer 823 is of metal, it is more conducive to the full melting of the third sub-portion 821 and the fourth sub-portion 822.

[0109] When the connecting layer 823 includes a metal layer, the metal layer can include one or more first sub-layers. When the metal layer includes multiple first sub-layers, the first sub-layers can be of the same metal material or of different metal materials.

[0110] As an example of the material of the organic conductive polymer layer, the organic conductive polymer includes at least one of polypyrrole, polythiophene, polyaniline polyacetylene, polyphenyl, and polyphenylacetylene. When the connecting layer 823 is of organic conductive polymer, the organic conductive polymer not only can bond the third sub-portion 821 and the fourth sub-portion 822, but also can be melt-bonded with the support layer 70, and can further improve the connection strength between the second portion 82 and the support layer 70.

[0111] When the connecting layer 823 includes an organic conductive polymer layer, the organic conductive polymer layer can include one or more second sub-layers. When the organic conductive polymer layer includes multiple second sub-layers, the second sub-layers can be of the same organic conductive polymer material or of different organic conductive polymer materials.

[0112] 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 can be composed of any two of the foregoing values. When the thickness of the connecting layer 823 is within the above range, it is conducive to assisting the full melting and bonding of the third sub-portion 821 and the fourth sub-portion 822, that is, it is conducive to the full melting of the second portion 82 into one body.

[0113] Figure 4 is a structural schematic diagram of a composite current collector provided by another embodiment of the present application.

[0114] As shown in Figure 4 In some embodiments, the support layer 70 includes at least two support portions 73 spaced apart along the first direction Y, and the second portion 82 is arranged between the two adjacent support portions 73. The composite current collector 60 of this structure can constitute a component of a plurality of electrode assemblies by slitting.

[0115] In another embodiment, 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. Exemplarily, the second portion 82 protrudes from one end portion 72 of the support portion 73 along the first direction Y, or protrudes from both end portions 72 of the support portion 73 along the first direction Y.

[0116] [Manufacturing method of composite current collector]

[0117] The application also provides a manufacturing method of a composite current collector.

[0118] Figure 5 is a schematic diagram of a manufacturing process of a composite current collector provided by some embodiments of the application; Figure 6 is a schematic diagram of a manufacturing process of a composite current collector provided by some embodiments of the application; Figure 7 is another schematic diagram of a manufacturing process of a composite current collector provided by some embodiments of the application.

[0119] As shown in Figures 5 to 7 , the manufacturing method comprises the following steps:

[0120] S100, providing a support layer, the support layer comprising two first surfaces opposite to each other along a thickness direction.

[0121] S200, 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 through an adhesive layer respectively, wherein the first conductive sheet comprises a first sub-portion and a third sub-portion, the second conductive sheet comprises a second sub-portion and a fourth sub-portion, the first sub-portion and the second sub-portion are arranged on the two first surfaces respectively, and the third sub-portion and the fourth sub-portion are protruded from the support layer.

[0122] S300, adhering and welding the third sub-portion and the fourth sub-portion to be integral with each other. The composite current collector prepared by the manufacturing method provided by the embodiments of the application has flush edges in the slitting process, and the secondary battery prepared by using the composite current collector has excellent electrochemical performance.

[0123] Figure 8 is a schematic diagram of a manufacturing process of a composite current collector provided by some embodiments of the application; Figure 9 is a schematic diagram of a manufacturing process of a composite current collector provided by some embodiments of the application; Figure 10 is another schematic diagram of a manufacturing process of a composite current collector provided by some embodiments of the application. Figure 9 The arrow in indicates the thinning direction.

[0124] As shown in Figures 8 to 10 , in some embodiments, after step S300, the manufacturing method further comprises:

[0125] S400, removing part of the first sub-portion along the thickness direction to thin the thickness of the first sub-portion.

[0126] By thinning the thickness of the first sub-portion, the relatively lower thickness of the first sub-portion can improve the energy density of the secondary battery to a certain extent.

[0127] One of the two third surfaces 8111 of the thinned first sub-section 811 can be flush with the second surface 8211 of the third sub-section 821, of course, the thinned first sub-section 811 can also protrude relative to the second surface 8211 along the thickness direction X.

[0128] In step S400, in order to prevent the process of thinning the first sub-section 811 from interfering with the third sub-section 821, a protective layer 100 can be provided on the second surface 8211 of the third sub-section 821, and then the first sub-section 811 is thinned based on the third sub-section 821 containing the protective layer 100, and then the protective layer 100 is removed after the first sub-section 811 is thinned, which basically does not affect the thickness of the third sub-section 821.

[0129] The material of the protective layer 100 is one or more of polymethyl methacrylate (PMMA), polymethyl methacrylamide, polymethyl isopropyl ketone, polyisobutylene, and poly-α-methyl styrene. Such a protective layer 100 can be dissolved and removed after the first sub-section 811 is thinned.

[0130] In some embodiments, after step S300, further comprising:

[0131] Removing part of the second sub-section along the thickness direction to thin the thickness of the second sub-section.

[0132] The thinning process of the second sub-section is as described in step S400, which will not be repeated here. The thicknesses of the first sub-section and the second sub-section after thinning can be the same or different.

[0133] Figure 11 is a flowchart of a manufacturing method of a composite current collector provided by another embodiment of the present application; Figure 12 is another state diagram of the manufacturing process of the composite current collector provided by some embodiments of the present application; Figure 13 is another state diagram of the manufacturing process of the composite current collector provided by some embodiments of the present application. Figure 12 The arrow in indicates the thinning direction.

[0134] As shown in Figures 11 to 13 some embodiments, after step S300, further comprising:

[0135] S500, removing part of the third sub-section along the thickness direction to thin the thickness of the third sub-section.

[0136] Thinning the thickness of the third sub-section 821 can improve the energy density on the basis of ensuring the flow capacity.

[0137] After the thinning, the first sub-portion 811 can protrude relative to the second surface 8211 along the thickness direction X.

[0138] In step S500, to prevent the process of thinning 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. The third sub-portion 821 is thinned based on the first sub-portion 811 including the protective layer 100. Then, the protective layer 100 is removed after the third sub-portion 821 is thinned, and the thickness of the first sub-portion 811 is not substantially affected.

[0139] In some embodiments, after step S300, the method further includes:

[0140] A portion of the fourth sub-portion is removed along the thickness direction to thin the fourth sub-portion.

[0141] The thinning process of the fourth sub-portion is as described in step S500, which is not repeated here. The thicknesses of the third sub-portion and the fourth sub-portion can be the same or different.

[0142] The above-described steps of thinning can be used in combination or individually. For example, after step S300, the method further includes steps S400 and S500. Alternatively, after step S300, the method includes step S400. Alternatively, after step S300, the method includes step S500.

[0143] [Tab]

[0144] Embodiments of the present application also provide a tab.

[0145] Figure 14 is a structural schematic diagram of a tab provided by some embodiments of the present application; Figure 15 is Figure 14 is a cross-sectional structural schematic diagram of the tab shown in

[0146] As shown in Figure 14 and Figure 15 The tab 50 of the embodiments of the present application includes the composite current collector 60 of any of the above-described embodiments of the present application and the active material layer 90, and the active material layer 90 is disposed on the surface of the first portion 81 of the composite current collector 60. The secondary battery using the tab 50 with such a structure has excellent electrochemical performance, especially excellent overcurrent capacity and energy density. The tab 50 and the separator are wound to form an electrode assembly.

[0147] [Positive electrode tab]

[0148] The positive electrode tab includes a positive electrode composite current collector and a positive electrode active material layer.

[0149] The main material of the conductive layer of the positive electrode composite current collector includes aluminum or aluminum-based alloy, and the structural form adopts the composite current collector of any one of the above embodiments of the present application.

[0150] The positive electrode active material layer adopts a positive electrode active material, which can be a positive electrode active material for a secondary battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material can also be used. These positive electrode active materials can be used alone only or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi0.8Co0.1Mn0.1O2, which can also be referred to as NCM811), LiNi0.6Co0.2Mn0.2O2 (which can also be referred to as NCM622), LiNi0.5Co0.2Mn0.3O2 (which can also be referred to as NCM532), LiNi0.4Co0.3Mn0.3O2 (which can also be referred to as NCM431), LiNi0.3Co0.3Mn0.4O2 (which can also be referred to as NCM333), LiNi0.2Co0.3Mn0.5O2 (which can also be referred to as NCM223), lithium nickel cobalt aluminum oxide (such as LiNi0.8Co0.1Al0.1O2), a modified compound thereof, and the like. Examples of the lithium-containing phosphate with an olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (which can also be referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which can also be referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be referred to as NCM 523 ), LiNi0 .5 Co 0.25 Mn 0.25 O2 (which can also be referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2), a modified compound thereof, and the like.

[0151] In some embodiments, the positive active material layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0152] In some embodiments, the positive active material layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0153] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the second binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, coating the positive electrode slurry on a positive electrode composite current collector, and drying, cold-pressing, or the like to obtain the positive electrode sheet.

[0154] [Negative electrode sheet]

[0155] The negative electrode sheet includes a negative electrode composite current collector and a negative active material layer.

[0156] The main material of the conductive layer of the negative electrode composite current collector includes copper or a copper-based alloy, and the structure thereof is the composite current collector according to any one of the above-mentioned embodiments.

[0157] The negative active material in the negative active material layer can be a negative active material for a secondary battery known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, lithium titanate, and the like. The silicon-based material can be selected from at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can be selected from at least one of elemental tin, a tin oxide compound, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative active material can also be used. The negative active material can be used alone or in combination of two or more.

[0158] In some embodiments, the negative active material layer can further optionally include a binder. The binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0159] In some embodiments, the negative active material layer can also optionally include a conductive agent. The conductive agent can be selected from at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0160] In some embodiments, the negative active material layer can also optionally include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0161] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative composite current collector, and after processes such as drying, cold pressing, etc., the negative electrode sheet can be obtained.

[0162] [Electrolyte]

[0163] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not specifically limited in the embodiments of the present application, and can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid-state.

[0164] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0165] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0166] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl 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, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0167] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive for improving the overcharge performance of the battery, an additive for improving the high-temperature or low-temperature performance of the battery, etc.

[0168] [Separator]

[0169] In some embodiments, the secondary battery further comprises a separator. The type of the separator is not particularly limited in the embodiments of the present application, and any known porous separator having good chemical stability and mechanical stability can be used.

[0170] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0171] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to make an electrode assembly by a winding process or a stacking process.

[0172] In some embodiments, the secondary battery can comprise an outer package. The outer package can be used to package the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte described above.

[0173] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be listed.

[0174] [Secondary battery]

[0175] The embodiments of the present application also provide a secondary battery.

[0176] Figure 16 is a structural schematic diagram of an electrode assembly of a secondary battery provided by some embodiments of the present application; Figure 17 is a schematic diagram of the decomposition of a secondary battery provided by some embodiments of the present application.

[0177] As shown in Figure 16 and Figure 17 , the secondary battery 30 comprises a top cover assembly 31 and a shell 32, and an electrode assembly 40 and an electrolyte contained in the shell 32. The electrode assembly 40 comprises an electrode sheet 50 and a separator 41. The electrode sheet 50 comprises a positive electrode sheet and a negative electrode sheet. During the charging and discharging of the secondary battery 30, active ions are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator 41 is arranged between the positive electrode sheet and the negative electrode sheet, and mainly plays a role in preventing the short circuit of the positive and negative electrodes, while allowing ions to pass through. Specifically, the secondary battery can be a winding-type or a stacking-type battery, such as one of a lithium-ion secondary battery, a lithium primary battery, a sodium-ion battery, and a magnesium-ion battery, but is not limited thereto. Figure 14 A winding-type electrode assembly is shown.

[0178] In some embodiments, the positive electrode plate comprises the positive electrode plate of the embodiment of the second aspect of the present application. Because the secondary battery 30 of the embodiment of the present application adopts the plate of the second aspect of the present application, it has better electrochemical performance than traditional secondary batteries. Accordingly, the negative electrode plate can adopt a conventional negative electrode plate in the art, or the negative electrode plate of the embodiment of the second aspect of the present application.

[0179] In some embodiments, the negative electrode plate includes the negative electrode plate of the embodiment of the second aspect of the present application. Because the secondary battery 30 of the embodiment of the present application uses the plate of the second aspect of the present application, it has better electrochemical performance than traditional secondary batteries. Accordingly, the positive electrode plate can be a conventional negative electrode plate in the art.

[0180] 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. Because the secondary battery 30 of the embodiment of the present application adopts the electrode sheet of the second aspect of the present application, it has better electrochemical performance than traditional secondary batteries.

[0181] The present application has no particular limitation on the shape of the secondary battery 30, which may be cylindrical, square, or any other shape. Figure 17 This is a secondary battery with a square structure as an example.

[0182] In some embodiments, the outer packaging of the secondary battery 30 may include a shell 32 and a top cover assembly 31. The shell 32 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 32 has an opening connected to the receiving cavity, and the top cover assembly 31 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film 41 can form an electrode assembly 40 through a winding process or a lamination process. The electrode assembly 40 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 40. The number of electrode assemblies 40 contained in the secondary battery 30 can be one or more, and those skilled in the art can select according to specific actual needs.

[0183] In some embodiments, the secondary batteries 30 can be assembled into a battery module. The battery module can contain one or more secondary batteries. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0184] Figure 18 It is a schematic diagram of the partial structure of the battery module provided in some embodiments of the present application.

[0185] like Figure 18As shown, in the battery module 20, the plurality of secondary batteries 30 can be arranged in sequence along the length direction of the battery module 20. Of course, they can also be arranged in any other manner. Further, the plurality of secondary batteries 20 can be fixed by fasteners.

[0186] Optionally, the battery module 20 may further include a housing having an accommodation space, and the plurality of secondary batteries 30 may be accommodated in the accommodation space.

[0187] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0188] Figure 19 This is a schematic diagram of an exploded view of a battery pack provided in some embodiments of the present application.

[0189] like Figure 19 As shown, the battery pack 10 may include a battery box and multiple battery modules 20 disposed in the battery box. The battery box includes an upper box body 12 and a lower box body 11. The upper box body 12 can cover the lower box body 11 and form an enclosed space for accommodating the battery modules 20. The multiple battery modules 20 can be arranged in the battery box in any manner.

[0190] In addition, the present application also provides an electrical device.

[0191] Figure 20 It is a schematic diagram of the structure of the electrical device provided in some embodiments of the present application.

[0192] like Figure 20 As shown, the electrical device 1 includes at least one of the secondary battery 10, battery module, or battery pack provided in this application. The secondary battery 10, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device 1 may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but is not limited thereto.

[0193] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0194] The electric device 1 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the electric device 1's requirements for high power and high energy density of the secondary battery 30 , a battery pack or a battery module may be used.

[0195] As another example, the device can be a mobile phone, a tablet, a notebook computer, etc. The device generally requires thinness, and a secondary battery can be used as a power source.

[0196] Embodiments

[0197] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are for the purpose of explanation of the present application and should not be understood as a limitation of the present application. In the embodiments, unless a specific technique or condition is mentioned, the technique or condition described in the literature in the art or according to the product manual is used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained commercially.

[0198] Embodiment 1

[0199] 1. Preparation of positive electrode composite current collector

[0200] A PET support layer (melting point: 251°C) having a thickness of 4.5 μm was selected, and the support layer was subjected to surface cleaning treatment;

[0201] A polyurethane adhesive was applied to one surface of the support layer to form a coating layer for forming an adhesive layer (thickness: about 2 μm);

[0202] The coating layer was pre-baked;

[0203] An aluminum layer was provided on the pre-baked coating layer as a first conductive sheet, the first conductive sheet including a first sub-portion and a third sub-portion, so that the first conductive sheet and the support layer formed a first laminate of the composite current collector;

[0204] The first laminate was subjected to high-temperature pressing, and was then cured;

[0205] A polyurethane adhesive was applied to the other surface of the support layer to form a coating layer for forming an adhesive layer (thickness: about 2 μm);

[0206] An aluminum layer was provided on the pre-baked coating layer as a second conductive sheet, the second conductive sheet including a second sub-portion and a fourth sub-portion, so that the second conductive sheet and the support layer formed a second laminate of the composite current collector;

[0207] The second laminate was subjected to high-temperature pressing, and was then cured; a composite current collector containing an adhesive layer between the PET and the aluminum layer was formed; and the two aluminum layers formed a first conductive sheet and a second conductive sheet, respectively;

[0208] 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 arranged on the two first surfaces respectively, and the third sub-portion and the fourth sub-portion protrude from the support layer. 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 A of the first portion is 10 μm, the thickness B of the second portion is 10 μm, and A / B = 1.

[0209] The third sub-portion and the fourth sub-portion are adhered to each other and fused into one body: a customized heating roller is used, the surface temperature is heated to 675 ℃, and the third sub-portion and the fourth sub-portion are hot-pressed and fused at a pressure of 60T.

[0210] 2. Preparation of the positive electrode sheet

[0211] The positive electrode 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 binder polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 82:14:2:2 in an appropriate amount of N-methyl pyrrolidone (NMP) solvent, and are fully stirred to form a uniform positive electrode slurry; the positive electrode slurry is coated on the surface of the positive electrode composite current collector, and after processes such as drying, cold pressing, and tab cutting, a positive electrode sheet is obtained.

[0212] 3. Negative electrode composite current collector

[0213] A copper foil with a thickness of 6 μm is used.

[0214] 4. Preparation of the negative electrode sheet

[0215] The negative electrode active material graphite, conductive carbon black, thickening agent carboxymethyl cellulose sodium (CMC), and binder styrene-butadiene rubber emulsion (SBR) are mixed in a weight ratio of 96.5:1.0:1.0:1.5 in an appropriate amount of deionized water, and are fully stirred to form a uniform negative electrode slurry; the negative electrode slurry is coated on the negative electrode composite current collector, and after processes such as drying, a negative electrode sheet is obtained.

[0216] 5. Isolation film

[0217] A PP film is used.

[0218] 6. Preparation of the electrolyte

[0219] Ethylene carbonate (EC) and methyl ethyl carbonate (EMC) in a volume ratio of 3:7 are mixed uniformly to obtain an organic solvent, and then 1 mol / L of LiPF6 is uniformly dissolved in the organic solvent.

[0220] 7. Preparation of the secondary battery

[0221] The positive electrode sheet, the separator, and the negative electrode sheet are sequentially stacked, then wound into a core and put into a packaging case, the above electrolyte is injected into the core, and then the secondary battery is obtained through the processes of sealing, standing, hot and cold pressing, formation, etc.

[0222] Example 2

[0223] Different from Example 1, the following steps are added after the hot-pressing fusion step:

[0224] PMMA protective layers are respectively arranged on the outer surfaces of the third subpart and the fourth subpart: a PMMA-benzyl ether solution is purchased as the initial coating, iron-fluorine rubber gaskets are pasted on the back roller of the coating machine at positions corresponding to the third subpart and the fourth subpart, and the gasket size is designed to exactly correspond to the third subpart and the fourth subpart, the PMMA protective layers are coated only at positions of the third subpart and the fourth subpart, the oven temperature is set to 80-100℃, the coating speed is 8 m / min, and the final protective layer thickness is about 30 μm;

[0225] The thicknesses of the first subpart and the second subpart are thinned by chemical etching, the composite current collector with the specific area coated with the protective layer is passed through an etching tank containing a NaOH solution, the solution temperature is 60℃, the running speed is 11 m / min, the thickness of the conductive layer without the PMMA protective layer is thinned, and after water washing and drying, the thickness of the first subpart is 3 μm and the thickness of the second subpart is 3 μm;

[0226] The PMMA protective layer is removed, the etched composite current collector is passed through a dissolving tank containing acetone, the acetone temperature is 50℃, and the running speed is 10 m / min, so that the surface PMMA layer can be removed;

[0227] The thickness of the first subpart of this example is 3 μm, the thickness of the second subpart is 3 μm, the thickness of the third subpart is 5 μm, and the thickness of the fourth subpart is 5 μm. The thickness A of the first part is 6 μm, the thickness B of the second part is 10 μm, and A / B = 0.6.

[0228] Example 3

[0229] Different from Example 1, the following steps are added after the hot-pressing fusion step:

[0230] PMMA protective layer is arranged on the third subpart and the fourth subpart respectively: PMMA-benzyl ether solution is purchased as initial coating, iron fluoride rubber gasket is pasted on the back roller of coating machine corresponding to the positions of the third subpart and the fourth subpart, the gasket size is designed to correspond to the third subpart and the fourth subpart, only the third subpart and the fourth subpart positions are coated when the PMMA protective layer is coated, the oven temperature is set to 80-100℃, the coating speed is 8m / min, and the final protective layer thickness is about 30μm;

[0231] The thicknesses of the first subpart and the second subpart are etched and thinned by chemical etching, the composite current collector with the specific area coated with the protective layer is passed through the etching tank containing NaOH solution, the solution temperature is 60℃, the running speed is 9m / min, the thickness of the conductive layer without the PMMA protective layer is thinned, after water washing and drying, the thickness of the first subpart is 1μm, and the thickness of the second subpart is 1μm;

[0232] The PMMA protective layer is removed, the etched composite current collector is passed through the dissolving tank containing acetone, the acetone temperature is 50℃, and the running speed is 10m / min, so that the PMMA layer on the surface can be removed.

[0233] The thickness of the first subpart is 1μm, the thickness of the second subpart is 1μm, the thickness of the third subpart is 5μm, and the thickness of the fourth subpart is 5μm. The thickness A of the first part is 2μm, the thickness B of the second part is 10μm, and A / B=0.2.

[0234] Example 4

[0235] Different from example 1, the following steps are added after the hot-pressing fusion step:

[0236] PMMA protective layer is arranged on the third subpart and the fourth subpart respectively: PMMA-benzyl ether solution is purchased as initial coating, iron fluoride rubber gasket is pasted on the back roller of coating machine corresponding to the positions of the third subpart and the fourth subpart, the gasket size is designed to correspond to the third subpart and the fourth subpart, only the third subpart and the fourth subpart positions are coated when the PMMA protective layer is coated, the oven temperature is set to 80-100℃, the coating speed is 8m / min, and the final protective layer thickness is about 30μm;

[0237] The thicknesses of the first subpart and the second subpart are etched and thinned by chemical etching, the composite current collector with the specific area coated with the protective layer is passed through the etching tank containing NaOH solution, the solution temperature is 63℃, the running speed is 9m / min, the thickness of the conductive layer without the PMMA protective layer is thinned, after water washing and drying, the thickness of the first subpart is 0.75μm, and the thickness of the second subpart is 0.75μm;

[0238] Remove the PMMA protective layer, the etched composite current collector, through the dissolution tank containing acetone, the temperature of acetone is 50℃, the walking speed is 10m / min, the surface PMMA layer can be removed;

[0239] The thickness of the first subpart is 0.75μm, the thickness of the second subpart is 0.75μm, the thickness of the third subpart is 10μm, and the thickness of the fourth subpart is 5μm. The thickness A of the first part is 5μm, the thickness B of the second part is 10μm, and A / B=0.15.

[0240] Example 5

[0241] Different from example 1, the following steps are added after the hot-pressing fusion step:

[0242] PMMA protective layers are respectively arranged on the third subpart and the fourth subpart, PMMA-benzyl ether solution is purchased as the initial coating, iron fluoride rubber pads are attached to the back roller of the coating machine corresponding to the positions of the third subpart and the fourth subpart, the size of the pads is designed to correspond to the third subpart and the fourth subpart, only the positions of the third subpart and the fourth subpart are coated when the PMMA protective glue layer is coated, the oven temperature is set to 80-100℃, the coating speed is 8m / min, and the final protective layer thickness is about 30μm.

[0243] The thicknesses of the first subpart and the second subpart are thinned by chemical etching, the composite current collector with the composite current collector with the specific area coated with the protective layer is passed through the etching tank containing NaOH solution, the solution temperature is 65℃, the walking speed is 8m / min, the thickness of the conductive layer without the PMMA protective layer is thinned, after water washing and drying, the thickness of the first subpart is 0.5μm, and the thickness of the second subpart is 0.5μm.

[0244] Remove the PMMA protective layer, the etched composite current collector, through the dissolution tank containing acetone, the temperature of acetone is 50℃, the walking speed is 10m / min, the surface PMMA layer can be removed;

[0245] The thickness of the first subpart is 0.5μm, the thickness of the second subpart is 0.5μm, the thickness of the third subpart is 5μm, and the thickness of the fourth subpart is 5μm. The thickness A of the first part is 1μm, the thickness B of the second part is 10μm, and A / B=0.1.

[0246] Example 6

[0247] Different from example 1, the following steps are added after the hot-pressing fusion step:

[0248] Setting PMMA protective layer on the third and fourth sub-parts: PMMA-benzyl ether solution is purchased as the initial coating, and iron-fluorine rubber pads are pasted on the back roller of the coating machine corresponding to the positions of the third and fourth sub-parts. The size of the pads is designed to correspond to the third and fourth sub-parts. When coating the PMMA protective layer, only the third and fourth sub-parts are coated. The oven temperature is set to 80-100°C. After baking in the oven, the coating speed is 8 m / min, and the final protective layer thickness is about 30 μm.

[0249] The thickness of the first sub-part is thinned by chemical etching. The composite current collector with the specific area coated with the protective layer is passed through the etching tank containing NaOH solution. The solution temperature is 60°C, and the running speed is 11 m / min. The thickness of the conductive layer without the PMMA protective layer is thinned. After water washing and drying, the thickness of the first sub-part is 3 μm.

[0250] The PMMA protective layer is removed. The etched composite current collector is passed through the dissolving tank containing acetone. The temperature of the acetone is 50°C, and the running speed is 10 m / min. The surface PMMA layer can be removed.

[0251] The thickness of the first sub-part of the embodiment is 3 μm, the thickness of the second sub-part is 5 μm, the thickness of the third sub-part is 5 μm, and the thickness of the fourth sub-part is 5 μm. The thickness A of the first part is 8 μm, the thickness B of the second part is 10 μm, and A / B=0.8.

[0252] Example 7

[0253] Different from Example 1, the following steps are added after the hot-pressing fusion step:

[0254] The PMMA protective layer is set on the second and fourth sub-parts. PMMA-benzyl ether solution is purchased as the initial coating. The second and fourth sub-parts are coated using a coating machine. The oven temperature is set to 80-100°C. The coating speed is 8 m / min. The final protective layer thickness is about 30 μm.

[0255] The thicknesses of the first and third sub-parts are thinned by chemical etching. The composite current collector with the specific area coated with the protective layer is passed through the etching tank containing NaOH solution. The solution temperature is 60°C, and the running speed is 11 m / min. The thickness of the conductive layer without the PMMA protective layer is thinned. After water washing and drying, the thicknesses of the first and third sub-parts are 3 μm.

[0256] The PMMA protective layer is removed. The etched composite current collector is passed through the dissolving tank containing acetone. The temperature of the acetone is 50°C, and the running speed is 10 m / min. The surface PMMA layer can be removed.

[0257] The thickness of the first subpart is 3 μm, the thickness of the second subpart is 5 μm, the thickness of the third subpart is 3 μm, and the thickness of the fourth subpart is 5 μm. The thickness A of the first part is 8 μm, the thickness B of the second part is 8 μm, and A / B = 1.

[0258] Example 8

[0259] Different from Example 1, the following steps are added after the hot-pressing fusion step:

[0260] The thickness of the first subpart, the second subpart, the third subpart and the fourth subpart is thinned by directly using chemical etching. The composite current collector with the protective layer on the specific area is passed through an etching tank containing NaOH solution, the solution temperature is 60 ℃, the running speed is 11 m / min, the thickness of the conductive layer in the unprotected area is thinned, and then water washing and drying are performed, so that the thickness of the first subpart is 3 μm, the thickness of the second subpart is 3 μm, the thickness of the third subpart is 3 μm, and the thickness of the fourth subpart is 3 μm.

[0261] The PMMA protective layer is removed, and the etched composite current collector is passed through a dissolving tank containing acetone, the temperature of the acetone is 50 ℃, the running speed is 10 m / min, and the surface PMMA layer is removed.

[0262] The thickness of the first subpart is 3 μm, the thickness of the second subpart is 3 μm, the thickness of the third subpart is 3 μm, and the thickness of the fourth subpart is 3 μm. The thickness A of the first part is 6 μm, the thickness B of the second part is 6 μm, and A / B = 1.

[0263] Example 9

[0264] Different from Example 1, the following steps are added after the hot-pressing fusion step:

[0265] The PMMA protective layer is arranged on the first subpart, the second subpart and the fourth subpart, respectively.

[0266] The thickness of the third subpart is thinned by using chemical etching. The composite current collector with the protective layer on the specific area is passed through an etching tank containing NaOH solution, the solution temperature is 60 ℃, the running speed is 11 m / min, the thickness of the conductive layer in the unprotected area is thinned, and then water washing and drying are performed, so that the thickness of the third subpart is 3 μm.

[0267] The PMMA protective layer is removed, and the etched composite current collector is passed through a dissolving tank containing acetone, the temperature of the acetone is 50 ℃, the running speed is 10 m / min, and the surface PMMA layer is removed.

[0268] The thickness of the first subpart is 5 μm, the thickness of the second subpart is 5 μm, the thickness of the third subpart is 3 μm, and the thickness of the fourth subpart is 5 μm. The thickness A of the first part is 10 μm, the thickness B of the second part is 8 μm, and A / B = 1.1.

[0269] Example 10

[0270] Different from Example 1, the following steps are added after the hot-pressing fusion step:

[0271] A connecting layer (tin layer) is formed between the first conductive sheet and the second conductive sheet: the powder of tin is sieved through a 1 μm sieve to remove the powder with a particle size greater than 1 μm, and then the tin powder is added to NMP according to a weight ratio of 98:2 of tin powder to PVDF for uniform stirring, and then the slurry containing tin particles is coated on the surface of the third subpart facing the fourth subpart, and the oven temperature is 80-100 ℃ for drying, and the thickness of the tin layer is 1 μm;

[0272] The third subpart, the tin layer and the fourth subpart are adhered to each other and fused into one body, the fusion temperature is 300 ℃, and the pressure is 30T;

[0273] A PMMA protective layer is arranged on the first subpart, a PMMA-benzyl ether solution is purchased as the initial coating, and a Teflon pad is placed on the back roll of the coating machine corresponding to the positions of the third subpart and the fourth subpart, the size of the pad is designed to correspond to the third subpart and the fourth subpart, and only the positions of the third subpart and the fourth subpart are coated when the PMMA protective glue layer is coated, the oven temperature is set to 80-100 ℃, the coating speed is 8 m / min, and the final protective layer has a thickness of about 30 μm;

[0274] The thickness of the third subpart is reduced by chemical etching, and the composite current collector with a specific area coated with a protective layer is passed through an etching tank containing NaOH solution, the solution temperature is 60 ℃, the running speed is 12 m / min, the thickness of the conductive layer without the PMMA protective layer is reduced, and after water washing and drying, the thickness of the third subpart is 4 μm;

[0275] The PMMA protective layer is removed, and the etched composite current collector is passed through a dissolving tank containing acetone, the temperature of the acetone is 50 ℃, and the running speed is 10 m / min, so that the PMMA layer on the surface can be removed;

[0276] The thickness of the first subpart is 5 μm, the thickness of the second subpart is 5 μm, the thickness of the third subpart is 4 μm, the thickness of the fourth subpart is 5 μm, and the thickness of the tin layer is 1 μm. The thickness A of the first part is 10 μm, the thickness B of the second part is 10 μm, and A / B = 1.

[0277] Example 11

[0278] Different from example 1, the following steps are added after the hot-pressing fusion step:

[0279] A connecting layer (tin layer) is formed between the first conductive sheet and the second conductive sheet: the powder of tin is sieved through a 2 μm sieve, added to NMP according to a weight ratio of tin powder to PVDF of 98:2, and uniformly stirred, and then the slurry containing tin particles is coated on the surface of the third sub-portion facing the fourth sub-portion, and dried in an oven at a temperature of 80-100°C, and the thickness of the tin layer is 2 μm;

[0280] The third sub-portion, the tin layer and the fourth sub-portion are adhered to each other and fused into one body, and the fusion temperature is 300°C and the pressure is 30T;

[0281] A PMMA protective layer is provided on the first sub-portion, and a PMMA-benzyl ether solution is purchased as the initial coating, and a Teflon pad is placed on the back roller of the coating machine corresponding to the positions of the third sub-portion and the fourth sub-portion, and the size of the pad is designed to correspond to the third sub-portion and the fourth sub-portion, and only the positions of the third sub-portion and the fourth sub-portion are coated when the PMMA protective glue layer is coated, and the oven temperature is set to 80-100°C, and after baking in the oven, the coating speed is 8 m / min, and the final protective layer thickness is about 30 μm;

[0282] The thickness of the third sub-portion is thinned by chemical etching, and the composite current collector with the specific area coated with the protective layer is passed through an etching tank containing NaOH solution, the solution temperature is 60°C, and the running speed is 11 m / min, thereby thinning the thickness of the conductive layer without the PMMA protective layer, and after water washing and drying, the thickness of the third sub-portion is 3 μm;

[0283] The PMMA protective layer is removed, and the etched composite current collector is passed through a dissolving tank containing acetone, the temperature of the acetone is 50°C, and the running speed is 10 m / min, thereby removing the PMMA layer on the surface;

[0284] The thickness of the first sub-portion of this embodiment is 5 μm, the thickness of the second sub-portion is 5 μm, the thickness of the third sub-portion is 3 μm, the thickness of the fourth sub-portion is 5 μm, and the thickness of the tin layer is 2 μm. The thickness A of the first portion is 10 μm, the thickness B of the second portion is 10 μm, and A / B=1.

[0285] Example 12

[0286] Different from example 1, the following steps are added after the hot-pressing fusion step:

[0287] Forming a connecting layer (tin layer) between the first conductive sheet and the second conductive sheet: purchasing a tin powder, sieving through a 5 μm sieve, removing the powder with a particle size greater than 5 μm, adding the tin powder and PVDF in a weight ratio of 98:2 into NMP for uniform stirring, and then coating the slurry containing tin particles on the surface of the third sub-portion facing the fourth sub-portion, drying in an oven at a temperature of 80-100°C, and the thickness of the tin layer is 5 μm,

[0288] Laminating and welding the third sub-portion, the tin layer and the fourth sub-portion into one body, the welding temperature is 310°C, and the pressure is 35T;

[0289] Setting a PMMA protective layer on the first sub-portion and the second sub-portion, purchasing a PMMA-benzyl ether solution as the initial coating, and the gasket size is designed to correspond to the first sub-portion and the second sub-portion, and only the third sub-portion and the fourth sub-portion are coated when coating the PMMA protective layer, the oven temperature is set to 80-100°C, the coating speed is 8 m / min, and the final protective layer thickness is about 30 μm;

[0290] Thinning the thickness of the third sub-portion and the fourth sub-portion by chemical etching, and the composite current collector with a specific area coated with a protective layer is passed through an etching tank containing NaOH solution, the solution temperature is 60°C, the running speed is about 10 m / min, and the thickness of the conductive layer without PMMA protective layer is thinned, after water washing and drying, the thickness of the third sub-portion is 2.5 μm, and the thickness of the fourth sub-portion is 2.5 μm;

[0291] Removing the PMMA protective layer, and the etched composite current collector is passed through a dissolving tank containing acetone, the temperature of the acetone is 50°C, and the running speed is 10 m / min, so that the PMMA layer on the surface can be removed;

[0292] The thickness of the first sub-portion of the embodiment is 5 μm, the thickness of the second sub-portion is 5 μm, the thickness of the third sub-portion is 2.5 μm, the thickness of the fourth sub-portion is 2.5 μm, and the thickness of the tin layer is 5 μm. The thickness A of the first portion is 10 μm, the thickness B of the second portion is 10 μm, and A / B=1.

[0293] Example 13

[0294] Different from example 1, the following steps are added after the hot-pressing and welding step:

[0295] A connecting layer (polyaniline layer) is formed between the first conductive sheet and the second conductive sheet: a powder of conductive polyaniline is purchased, ground, and the particles are refined and sieved through a 2 μm sieve to remove powder with a particle size greater than 2 μm, and the polyaniline particles are added to NMP at a weight ratio of 99:1 to PVDF, heated to 100°C in the NMP solution and stirred uniformly under vacuum, and then the polyaniline-containing slurry is coated on the surface of the third sub-portion facing the fourth sub-portion, and dried in an oven at a temperature of 80-100°C, and the thickness of the polyaniline layer is 2 μm;

[0296] The third sub-portion, the polyaniline layer and the fourth sub-portion are adhered to and fused together, the fusion temperature is 370°C, and the pressure is 35T;

[0297] A PMMA protective layer is provided on the first sub-portion, a PMMA-benzyl ether solution is purchased as the initial coating, and the gasket size is designed to correspond to the first sub-portion, and only the third sub-portion and the fourth sub-portion are coated when the PMMA protective layer is coated, and the oven temperature is set to 80-100°C, and after baking in the oven, the coating speed is 8 m / min, and the final protective layer thickness is about 30 μm;

[0298] The thickness of the third sub-portion is thinned by chemical etching, and the composite current collector with a specific area coated with a protective layer is passed through an etching tank containing a NaOH solution, the solution temperature is 60°C, and the running speed is 11 m / min, thereby thinning the thickness of the conductive layer without the PMMA protective layer, and after water washing and drying, the thickness of the third sub-portion is 3 μm;

[0299] The PMMA protective layer is removed, and the etched composite current collector is passed through a dissolving tank containing acetone, the temperature of the acetone is 50°C, and the running speed is 10 m / min, thereby removing the PMMA layer on the surface;

[0300] The thickness of the first sub-portion of the embodiment is 5 μm, the thickness of the second sub-portion is 5 μm, the thickness of the third sub-portion is 3 μm, the thickness of the fourth sub-portion is 5 μm, and the thickness of the polypyrrole layer is 2 μm. The thickness A of the first portion is 10 μm, the thickness B of the second portion is 10 μm, and A / B = 1.

[0301] Example 14

[0302] 1. Preparation of a negative electrode composite current collector

[0303] A PP support layer with a thickness of 4.5 μm (melting point of 189°C) is selected, and the support layer is subjected to surface cleaning treatment;

[0304] A polyurethane adhesive is applied to one surface of the support layer to form a coating layer (thickness of 2 um) for forming an adhesive layer;

[0305] The coating layer is pre-baked;

[0306] A copper layer is provided on the pre-baked coating as a first conductive tab, the first conductive tab includes a first sub-part and a third sub-part, a tin layer is coated on the third sub-part, the thickness of the tin layer is 2 pm, the third sub-part and the fourth sub-part are adhered to each other and fused into one, and a first laminated body for forming a composite current collector is formed by a customized hot press roller, only the third sub-part and the fourth sub-part are hot-pressed and fused, the pressure is 35T, and the temperature is 300°C.

[0307] The second laminated body is high-temperature pressed, and then solidified; a composite current collector containing an adhesive layer between the PET and the copper layer is formed; and two copper layers form a first conductive tab and a second conductive tab, respectively.

[0308] The first conductive tab includes a first sub-part and a third sub-part, and the second conductive tab includes a second sub-part and a fourth sub-part, the first sub-part and the second sub-part are arranged on the two first surfaces, respectively, and the third sub-part and the fourth sub-part are protruded from the support layer, wherein the thicknesses of the first sub-part, the second sub-part, the third sub-part and the fourth sub-part are all 5 pm, the thickness of the Sn connecting layer is 2 pm, the thickness A of the first part is 10 pm, the thickness B of the second part is 12 pm, and A / B=0.83.

[0309] 2. Preparation of negative electrode tab

[0310] The negative active material graphite, conductive carbon black, thickening agent carboxymethyl cellulose sodium (CMC), and binder styrene-butadiene rubber emulsion (SBR) are mixed in a weight ratio of 96.5:1.0:1.0:1.5 in a proper amount of deionized water to form a uniform negative electrode slurry; the negative electrode slurry is coated on the negative electrode composite current collector, and after drying and other processes, the negative electrode tab is obtained.

[0311] 3. Positive electrode composite current collector

[0312] An aluminum foil with a thickness of 13 pm is used.

[0313] 4. Preparation of positive electrode tab

[0314] The positive active materials 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 binder polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 82:14:2:2 in a proper amount of N-methyl pyrrolidone (NMP) solvent to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode composite current collector, and after drying and other processes, the positive electrode tab is obtained.

[0315] 5. Isolation film

[0316] PP film is used.

[0317] 6. Preparation of electrolyte

[0318] Ethylene carbonate (EC) and methyl ethyl carbonate (EMC) in a volume ratio of 3:7 were mixed uniformly to obtain an organic solvent, and then 1 mol / L LiPF6 was uniformly dissolved in the organic solvent.

[0319] 7. Preparation of secondary battery

[0320] The positive electrode sheet, the isolation film, and the negative electrode sheet were sequentially stacked and set, and then wound into an electrode core and loaded into a packaging shell, the electrolyte was injected into the electrode core, and then the secondary battery was obtained after the processes of sealing, standing, hot and cold pressing, and formation.

[0321] Comparative Example 1

[0322] A PP film material with a thickness of 4.5 μm was selected as a support layer, and an aluminum foil with a thickness of 0.5 μm was arranged on the upper and lower surfaces as a conductive layer, and an external aluminum foil was welded on the edge of the conductive layer by a transfer welding process for cutting the tab.

[0323] Performance test method

[0324] 1. Volume energy density test of secondary battery

[0325] At room temperature, the secondary battery was charged at a current of 1C rate for the first time, and the charging was constant current and constant voltage charging, the terminal voltage was 4.2V, and the current was 0.05C; discharged at a current of 1C rate, the discharge terminal voltage was 2.8V, and the discharge capacity Cb and discharge platform voltage U of the secondary battery were recorded when the secondary battery was cycled for the first time.

[0326] The length (L), width (W), and height (H) of the battery were measured using a soft ruler or a steel ruler with a minimum graduation value of 1 mm, and the volume energy density of the secondary battery was calculated by the following formula:

[0327] Volume energy density = Cb*U / (L*W*H).

[0328] 2. Direct current discharge resistance DCR detection:

[0329] The test condition is under room temperature condition, the secondary battery is discharged at 50% SOC at 4C rate (constant current I) for 30s, the voltage drop before and after discharge is ΔV, and DCR = ΔV / I.

[0330] Table 1

[0331]

[0332]

[0333] As can be seen from Table 1, the edge of the conductive layer of Comparative Example 1 is welded with the external aluminum foil by using the transition welding process, and there are two independent aluminum foils in the upper and lower welding areas, and there is welding in the welding area. This welding method will limit the welding strength to some extent, and will increase the thickness of the tab in the welding area, although it can improve the overcurrent capacity, but the overcurrent capacity and energy density of the secondary battery are relatively low. Compared with Comparative Example 1, Example 5 uses hot melt connection, and the overcurrent capacity and energy density of the secondary battery are significantly improved.

[0334] In Examples 1-5, as the thickness of the first part decreases, the A / B value gradually decreases, and the energy density of the secondary battery gradually increases, but at the same time the direct current discharge resistance also gradually increases. As can be seen from Table 1, when A / B is 0.2-1, the energy density and DCR of the secondary battery are excellent. When A / B < 0.2, the DCR increases significantly.

[0335] In Examples 6-9, by differentiating the thickness of different regions of the second part, the energy density and overcurrent capacity of the secondary battery can be adjusted, and the secondary battery can adapt to different application scenarios.

[0336] In Examples 10-13, by increasing the metal connecting layer or the conductive polymer connecting layer between the third subpart and the fourth subpart, the temperature of the hot-pressing fusion can be reduced, the processing difficulty can be reduced, and the temperature of the hot-pressing fusion can be reduced to below 400°C, for example; and the secondary batteries of Examples 10-12 can maintain an energy density and overcurrent capacity similar to that of Example 1 directly hot-pressing fusion. As can be seen, the metal connecting layer is beneficial to the processing of the composite current collector, and basically does not adversely affect the energy density and overcurrent capacity of the secondary battery.

[0337] The energy density and overcurrent capacity of the secondary battery of Example 14 are relatively excellent, and as can be seen, the composite current collector of the present application is not only suitable for preparing a positive composite current collector, but also suitable for a negative composite current collector, and has universality.

[0338] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the present application, and equivalent components can be substituted therefor. In particular, the technical features mentioned in each embodiment can be combined in any way as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A composite current collector, comprising: a support layer having two first surfaces opposite to each other along a thickness direction; and, a conductive layer disposed on the two first surfaces, the conductive layer comprising a first portion and a second portion, wherein, the first portion comprises a first sub-portion and a second sub-portion disposed on the two first surfaces respectively, the second portion comprises a third sub-portion and a fourth sub-portion, the third sub-portion and the first sub-portion are integrally disposed, the fourth sub-portion and the second sub-portion are integrally disposed, the third sub-portion and the fourth sub-portion each protrude from the support layer along a first direction, and the third sub-portion and the fourth sub-portion are integrally bonded to each other; wherein the second portion further comprises a connecting layer between the third sub-portion and the fourth sub-portion, and a melting point of the connecting layer is lower than a melting point of the third sub-portion; the third sub-portion, an end portion of the support layer along the first direction, and the fourth sub-portion are integrally bonded to each other. 2.The composite current collector of claim 1, wherein, a width of the end portion along the first direction is 1 mm to 10 mm. 3.The composite current collector of claim 1, wherein, a width of the end portion along the first direction is 5 mm to 8 mm. 4.The composite current collector of any one of claims 1 to 3, wherein, the third sub-portion comprises two second surfaces opposite to each other along the thickness direction, and the first sub-portion protrudes from the second surfaces along the thickness direction. 5.The composite current collector of any one of claims 1 to 3, wherein, the third sub-portion comprises two second surfaces opposite to each other along the thickness direction; the first sub-portion comprises two third surfaces opposite to each other along the thickness direction, and one of the two third surfaces is flush with the second surfaces. 6.The composite current collector of any one of claims 1 to 3, wherein, a thickness of the first portion is A, and a thickness of the second portion is B, wherein 0.03≤A / B≤1. 7.The composite current collector of any one of claims 1 to 3, wherein, a thickness of the first portion is A, and a thickness of the second portion is B, wherein 0.2≤A / B≤1. 8.The composite current collector of any one of claims 1 to 3, wherein, a thickness of the first sub-portion is greater than or equal to a thickness of the second sub-portion; and / or a thickness of the third sub-portion is greater than or equal to a thickness of the fourth sub-portion. 9.The composite current collector of claim 1, wherein, the connecting layer comprises at least one of a metal layer and an organic conductive polymer layer. 10.The composite current collector of claim 9, wherein, a material of the metal layer comprises at least one of tin, indium, bismuth, and cadmium. 11.The composite current collector of claim 9, wherein, a material of the organic conductive polymer layer comprises at least one of polypyrrole, polythiophene, polyaniline, polyacetylene, polyphenyl, and polyphenylacetylene. 12.The composite current collector of claim 1 or 9, wherein, a thickness of the connecting layer is 1 μm to 5 μm. 13.A method for manufacturing a composite current collector, comprising: providing a support layer including two first surfaces opposite to each other in 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, wherein the first conductive sheet includes a first sub-portion and a third sub-portion, the second conductive sheet includes a second sub-portion and a fourth sub-portion, the first sub-portion and the second sub-portion are disposed on the two first surfaces, respectively, and the third sub-portion and the fourth sub-portion are protruded from the support layer; adhering and welding the third sub-portion and the fourth sub-portion to each other to form an integrated structure, wherein the third sub-portion and the fourth sub-portion have a connecting layer therebetween, and the connecting layer has a melting point lower than that of the third sub-portion; adhering and welding the third sub-portion, an end portion of the support layer in a first direction, and the fourth sub-portion to each other to form an integrated structure.

14. The method of claim 13, further comprising: removing a portion of the first sub-portion in the thickness direction to thin the thickness of the first sub-portion.

15. The method of claim 13 or 14, further comprising: removing a portion of the third sub-portion in the thickness direction to thin the thickness of the third sub-portion.

16. A pole piece, comprising: a composite current collector active material, and a composite current collector as claimed in any one of claims 1 to 12 or prepared according to the method of any one of claims 13 to 15, the active material layer being disposed on a surface of the first portion of the composite current collector.

17. A secondary battery comprising the pole piece of claim 16.

18. A battery module comprising the secondary battery of claim 17.

19. A battery pack comprising the secondary battery of claim 17 or the battery module of claim 18.

20. An electric device comprising one of the secondary battery of claim 17, the battery module of claim 18, or the battery pack of claim 19.

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