Composite current collector, preparation method thereof, negative electrode sheet and battery

Abstract

The application provides a composite current collector, a preparation method thereof, a negative electrode sheet and a battery. The composite current collector comprises a substrate layer, and a conductive layer arranged on at least a first surface of the substrate layer; the conductive layer is composed of N levels of conductive parts, N is an integer greater than or equal to 2; a plurality of Nth level conductive parts are arranged on at least one side of the (N-1)th level conductive part along the length direction of the (N-1)th level conductive part; the width of the (N-1)th level conductive part is greater than the width of the Nth level conductive part, and the thickness of the (N-1)th level conductive part is greater than the thickness of the Nth level conductive part. The composite current collector can effectively reduce the weight and the surface density of the composite current collector, and improve the contact area and the adhesion between the active material, so as to finally improve the energy density, safety and stability of the lithium battery.

Description

Technical Field

[0001] This disclosure relates to the field of current collector technology, and in particular to a composite current collector and its preparation method, a negative electrode sheet, and a battery. Background Technology

[0002] Lithium-ion batteries are widely used in 3C electronic products (i.e., a general term for computers, communications, and consumer electronics), new energy vehicles, and energy storage due to their advantages such as high operating voltage, high energy density, and long cycle life. Higher energy density, safety, and stability are goals that lithium battery manufacturers have been constantly pursuing. The current collector is the component in a lithium battery responsible for electron collection and transport; improving the current collector to enhance lithium battery performance is one of the hot research topics in the lithium battery field.

[0003] Existing technical solutions include: First, as exemplified by Chinese patents CN108701817B and CN110676463B, certain technical means are used to design and add uneven structures on the surface of the current collector, thereby increasing the adhesion between the active material and the current collector and further improving the stability of the lithium battery. However, both of these patents are improvements on pure metal foil current collectors, which have a high areal density and cannot improve the battery energy density. Furthermore, pure metal foil current collectors have poor safety when punctured by hard objects. Second, polymer-metal composite current collectors are used. Although this can reduce the weight of the current collector to some extent and has better safety when punctured by hard objects than pure metal types, the contact area between the conductive layer and the active material is small, and the bonding force is poor, resulting in poor battery stability.

[0004] Therefore, reducing the weight of the current collector, lowering its areal density, providing a larger contact area for the current collector, and ultimately achieving higher energy density, safety, and stability in lithium batteries are pressing challenges that need to be addressed in this industry. Summary of the Invention

[0005] This application provides a composite current collector and its preparation method, a negative electrode sheet, and a battery, to at least solve one of the technical problems existing in the prior art.

[0006] In a first aspect, this application provides a composite current collector, comprising: basal layer; A conductive layer is provided at least on the first surface of the substrate layer; The conductive layer is composed of conductive parts of level 1 to N, where N is an integer ≥ 2; The Nth level conductive part is provided in multiple ways, and the multiple Nth level conductive parts are provided at intervals along the length direction of the (N-1)th level conductive part on at least one side of the (N-1)th level conductive part; The width of the (N-1)th level conductive part is greater than the width of the Nth level conductive part, and the thickness of the (N-1)th level conductive part is greater than the thickness of the Nth level conductive part.

[0007] This application employs a base layer and a conductive layer to form a composite current collector, which reduces the weight of the current collector and improves the energy density of the lithium battery. Compared with existing pure metal foil current collectors and existing ordinary composite current collectors, the conductive layer of this application is composed of 1 to N conductive parts. The conductive layer composed of these 1 to N conductive parts is a patterned conductive layer. Therefore, the composite current collector of this application is a patterned composite current collector. This patterned composite current collector can significantly reduce the areal density of the current collector, thereby further improving the energy density of the lithium battery.

[0008] Because the composite current collector of this application is a patterned composite current collector with a certain length, width and thickness, the patterned current collector has a three-dimensional structure, thus containing abundant lateral surface area, which can increase the contact area with the active material and increase the adhesion between the current collector and the active material, thereby improving battery stability. Specifically, since the Nth conductive part is disposed at intervals along the length direction of the (N-1)th conductive part on at least one side of the (N-1)th conductive part, these Nth conductive parts form abundant outwardly extending tentacles from the 1st conductive part. These outwardly extending tentacles not only make the patterned composite current collector contain abundant lateral surface area, thereby increasing the contact area with the active material, but also form a grass grid effect similar to "desert sand fixation", which can firmly grasp the active material on the surface and increase the adhesion.

[0009] In this application, the composite current collector consists of a base layer and a conductive layer disposed on at least a first surface of the base layer; the base layer is made of a non-conductive polymer. Compared with traditional pure metal current collectors, the composite current collector of this application relies on an insulating polymer base layer, which is less likely to generate large-sized metal burrs or form conductive paths when punctured by hard objects; the base layer has a "fuse" function, which can effectively protect and improve the overall safety performance of lithium batteries.

[0010] In one possible embodiment, the conductive layer is provided on one layer, and the conductive layer is disposed on the first surface of the substrate layer; or, The conductive layer comprises two layers, which are respectively disposed on the first surface and the second surface of the base layer, with the first surface and the second surface of the base layer facing each other.

[0011] In one possible embodiment, the Nth-level conductive portions located on the same side of the (N-1)th-level conductive portions are arranged in parallel.

[0012] In one embodiment, a plurality of Nth-level conductive portions are disposed at intervals along the length direction of the (N-1)th-level conductive portions on the first and second sides of the (N-1)th-level conductive portions, with the first and second sides of the (N-1)th-level conductive portions facing each other.

[0013] In one embodiment, one or more conductive layers are provided on the first surface of the substrate layer; wherein, one of the conductive layers is laid flat on the first surface of the substrate layer; Multiple conductive layers are laid side-by-side and spaced apart on the first surface of the substrate layer.

[0014] In one embodiment, the thickness distance between the free ends of the first to N conductive portions and the substrate layer is in the range of 0.05 to 5 μm.

[0015] In one embodiment, the width of each of the first to Nth conductive parts is in the range of 0.1 to 5 mm, and the width of the Nth conductive part is 10% to 50% of the width of the (N-1)th conductive part.

[0016] In one embodiment, the total coverage area of ​​the first to Nth conductive portions covering the first surface of the substrate layer is 30 to 70% of the area of ​​the first surface of the substrate layer.

[0017] In one embodiment, the composite current collector further includes an adhesive reinforcement layer and / or an anti-oxidation layer, wherein the adhesive reinforcement layer is stacked between the substrate layer and the conductive layer, and the anti-oxidation layer is stacked on the surface of the conductive layer facing away from the substrate layer.

[0018] Secondly, this application provides a method for preparing a composite current collector, the method comprising: A substrate is provided, and the substrate is pretreated to obtain the base layer; A conductive metal layer is magnetron sputtered onto the first surface of the substrate layer; The conductive metal layer is laser-etched according to a predetermined pattern using laser processing equipment to obtain a patterned metal layer. The patterned metal layer is cleaned and then subjected to horizontal electroplating to obtain the conductive layer; the horizontal electroplating operation speed is 0.5~3m / min.

[0019] This application employs a combination of laser etching and horizontal electroplating, utilizing the technical characteristic that different linewidths result in different current densities and deposition rates. Specifically, within the same electroplating time, the conductive portion deposited at wider linewidths is thicker, while the conductive portion deposited at narrower linewidths is thinner. Compared to first thickening the composite copper foil and then patterning it, the patterning process in this application is faster and saves raw materials. This method efficiently yields a composite current collector with a three-dimensional structure and good microstructural consistency.

[0020] In one embodiment, the method further includes: before preparing the conductive metal layer, first magnetron sputtering a bonding reinforcement layer on a first surface of the substrate layer, and then magnetron sputtering a conductive metal layer on the surface of the bonding reinforcement layer opposite to the substrate layer; and / or, After washing the conductive layer with water, an anti-oxidation treatment is performed on the surface of the conductive layer facing away from the substrate layer to obtain an anti-oxidation layer.

[0021] Thirdly, this application provides a negative electrode sheet, including a composite current collector.

[0022] Fourthly, this application provides a lithium battery, including a composite current collector or a negative electrode.

[0023] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0024] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0025] Figure 1 A schematic diagram of the planar structure of the conductive layer of the composite current collector of this disclosure is shown; Figure 2 A schematic diagram showing the orientation of the first to N conductive portions of the composite current collector of this disclosure is provided. Figure 3 A partial cross-sectional view of the composite current collector of this disclosure is shown; Figure 4 A photograph of the composite current collector disclosed herein is shown; Figure 5 A schematic diagram of a composite current collector according to an embodiment of the present disclosure is shown; Figure 6 A schematic diagram of another structure of the composite current collector according to an embodiment of the present disclosure is shown; Figure 7 A schematic diagram of another structure of the composite current collector according to an embodiment of the present disclosure is shown; Figure 8 A schematic diagram of yet another structure of the composite current collector according to an embodiment of the present disclosure is shown; Figure 9 A schematic diagram of the layer structure of the composite current collector according to an embodiment of the present disclosure is shown. Detailed Implementation

[0026] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0027] Firstly, such as Figure 1-7 As shown, this application provides a composite current collector, comprising: Basal layer 1; The conductive layer 2 is disposed at least on the first surface of the base layer 1; The conductive layer 2 is composed of conductive parts of level 1 to level N, where N is an integer ≥ 2; The Nth level conductive part is provided in multiple ways, and the multiple Nth level conductive parts are provided at intervals along the length direction of the (N-1)th level conductive part on at least one side of the (N-1)th level conductive part; The width of the (N-1)th level conductive part is greater than the width of the Nth level conductive part, and the thickness of the (N-1)th level conductive part is greater than the thickness of the Nth level conductive part.

[0028] The composite current collector of this application can be used in batteries, including but not limited to lithium batteries. The following description uses a lithium battery as an example.

[0029] In this application, a composite current collector is composed of a base layer 1 and a conductive layer 2. This composite current collector reduces the weight of the current collector and improves the energy density of the lithium battery. Compared with existing pure metal foil current collectors and existing ordinary polymer-metal composite current collectors, the conductive layer 2 of this application is composed of first to N conductive parts. The conductive layer formed by connecting these first to N conductive parts is a patterned conductive layer. Therefore, the composite current collector of this application is a patterned composite current collector. This patterned composite current collector can significantly reduce the areal density of the current collector, thereby further improving the energy density of the lithium battery. In addition, in this application, the base layer 1 can be made of polymer materials, and compared with a pure metal foil current collector of the same thickness, the weight of the composite current collector of this application is reduced.

[0030] Furthermore, in this application, the composite current collector consists of a substrate layer 1 and a conductive layer 2 disposed at least on a first surface of the substrate layer; the substrate layer 1 is made of a non-conductive polymer (such as an insulating thin film material). Compared with traditional pure metal current collectors, the composite current collector of this application relies on an insulating polymer substrate layer, which is less likely to generate large-sized metal burrs or form conductive paths when punctured by hard objects. The substrate layer 1 has a "fuse" function, which can effectively protect and improve the overall safety performance of the lithium battery.

[0031] Furthermore, since the composite current collector of this application is a patterned composite current collector with a certain length, width, and thickness, the patterned composite current collector has a three-dimensional structure with abundant lateral surface area, which can increase the contact area with the active material and increase the adhesion strength with the active material, thereby improving battery stability. Specifically, since the Nth conductive part is disposed at intervals along the length direction of the (N-1)th conductive part on at least one side of the (N-1)th conductive part, these 2nd to Nth conductive parts form abundant outwardly extending tentacles from the 1st conductive part. These outwardly extending tentacles not only make the patterned composite current collector have abundant lateral surface area, thereby increasing the contact area with the active material, but also form a grass grid effect similar to "desert sand fixation", which can firmly grasp the active material on the surface and increase the adhesion strength.

[0032] For example, in this application, the first-level conductive portion 21 is at least provided on the first surface of the substrate layer 1. The first-level conductive portion 21 can be arranged along the length direction of the substrate layer 1 or along the width direction of the substrate layer 1, depending on the specific battery type. When the composite current collector of this application is applied to a lithium battery, the lithium battery includes, but is not limited to, pouch batteries and cylindrical batteries. Taking a pouch battery as an example, its external shape can be cuboid or cubic, so the corresponding substrate layer can be cuboid or cubic. For a cuboid pouch battery, the optimal implementation is to set the first-level conductive layer 21 along the length direction of the substrate layer 1. For a cubic pouch battery, the first-level conductive layer 21 can be arranged along the length direction or the width direction of the substrate layer 1. In the preparation of cylindrical batteries, after the current collector is made into an electrode sheet, it needs to be laminated with the separator and then made into a cylindrical core through a winding process. Therefore, when the composite current collector of this application is applied to a cylindrical battery, the length direction of the substrate layer 1 can be set as the winding film movement direction. In this case, the first conductive part 21 is arranged along the length direction of the substrate layer 1 as the optimal implementation method.

[0033] Regardless of whether it is a pouch cell, a cylindrical cell, or another type of battery, the end of the first-level conductive portion 21 in the composite current collector of this application needs to be welded to the tab. For example, taking the first-level conductive portion 21 as being perpendicular to the tab, that is, the length direction of the first-level conductive portion 21 is perpendicular to the direction of the tab. Using this as a reference, the length direction of the first-level conductive portion 21 is determined, such that the second-level conductive portions 22 are spaced apart along the length direction of the first-level conductive portion 21 on at least one side of the first-level conductive portion, the third-level conductive portions are spaced apart along the length direction of the second-level conductive portion on at least one side of the second-level conductive portion, and so on.

[0034] For example, in this application, multiple Nth-level conductive parts are spaced apart along the length direction of the (N-1)th-level conductive parts on at least one side of the (N-1)th-level conductive parts. The phrase "spaced apart" should be interpreted broadly, meaning that two conductive parts of the same level are not directly connected, but have a certain gap between them. Conductive parts of the same level can only be indirectly connected through their preceding conductive parts. For example, ... Figure 1As shown, multiple second-level conductive parts 22 are provided, and these multiple second-level conductive parts 22 are disposed along the length direction of the first-level conductive part 21 on at least one side of the first-level conductive part 21, with adjacent second-level conductive parts 22 spaced apart. The second-level conductive parts 22 are indirectly connected to each other through the first-level conductive parts 21. Multiple third-level conductive parts 23 are provided. Multiple spaced-apart third-level conductive parts 23 can be provided on at least one side of the second-level conductive part 22; or one third-level conductive part 23 can be provided on each of the at least one side of adjacent second-level conductive parts 22, in which case the third-level conductive parts 23 on adjacent second-level conductive parts 22 are also spaced apart. The third-level conductive parts 23 are indirectly connected to each other through the second-level conductive parts 22.

[0035] For example, in this application, when N is an integer ≥ 3, the Nth-level conductive parts on adjacent (N-1)th-level conductive parts are not connected to each other (i.e., the Nth-level conductive parts on adjacent (N-1)th-level conductive parts are spaced apart); the Nth-level conductive parts on the (N-1)th-level conductive parts are not connected to adjacent (N-1)th-level conductive parts (i.e., the Nth-level conductive parts on the (N-1)th-level conductive parts are spaced apart). For example, as... Figure 1 As shown, N=3, and the third-level conductive parts 23 on adjacent second-level conductive parts 22 are not connected. Figure 1 As can be seen, the third conductive parts 23 on adjacent second conductive parts 22 are spaced apart. The third conductive parts on the second conductive parts are not connected to the adjacent second conductive parts, that is, the third conductive parts 23 on the second conductive parts are spaced apart from the adjacent second conductive parts 22.

[0036] For example, in this application, the Nth-level conductive part is directly connected only to the (N-1)th-level conductive part and the (N+1)th-level conductive part, while the (N-1)th-level conductive part and the (N+1)th-level conductive part are not directly connected to each other. For example, as... Figure 1 As shown, one end of the second-level conductive part 22 is connected to the first-level conductive part 21, and one end of the second-level conductive part 22 and the third-level conductive part 23 are connected. The third-level conductive part is directly connected to the second-level conductive part and the fourth-level conductive part. However, the first-level conductive part 21 is not directly connected to the third-level conductive part 23, and the second-level conductive part is not directly connected to the fourth-level conductive part.

[0037] Since the core function of the current collector in a battery is to collect and transport electrons, when the composite current collector of this application is used to collect and transport electrons, the electrons are collected to the first-level conductive part 21 through the Nth-level conductive part and the (N-1)th-level conductive part, and then led out through the tab connected to the end of the first-level conductive part. For example, as... Figure 1 As shown, electrons flow through the third-level conductive section 23 to the second-level conductive section 22, and then converge to the first-level conductive section 21 connected to the second-level conductive section 22.

[0038] Therefore, in the composite current collector of this application, the Nth-level conductive part is configured to be directly connected only to the (N-1)th and (N+1)th-level conductive parts, while the (N-1)th-level conductive part and the (N+1)th-level conductive part are not directly connected. This allows electrons to be collected from their respective independent Nth-level, 3rd-level, and 2nd-level conductive parts onto the 1st-level conductive part. If some of the 1st to Nth-level conductive parts are damaged, it will not affect the normal operation of the composite current collector.

[0039] For example, in this application, the first to Nth conductive portions are in the shape of a strip. Exemplarily, the strip can be straight, curved, or any arbitrarily curved shape.

[0040] For example, in this application, "multiple" refers to two or more.

[0041] For example, in this application, preferably, N=3, that is, the conductive layer 2 is composed of a first-level conductive part 21, a second-level conductive part 22, and a third-level conductive part 23.

[0042] For example, in this application, such as Figure 5 As shown, when N is 2, the conductive layer 2 is composed of a first-level conductive part 21 and a second-level conductive part 22; a plurality of second-level conductive parts 22 are provided, and the plurality of second-level conductive parts 22 are disposed at intervals along the length direction of the first-level conductive part 21 on at least one side of the first-level conductive part 21.

[0043] For example, in this application, when N is an integer greater than 2 (i.e., N≥3), the conductive layer 2 includes, but is not limited to, any of the following methods: The first type: such as Figure 6-7 As shown, the conductive layer 2 is composed of a first-level conductive part 21, a second-level conductive part 22, a third-level conductive part 23, and an Nth-level conductive part; The second-level conductive part 22 is provided in multiple ways, and the multiple second-level conductive parts 22 are provided at intervals along the length direction of the first-level conductive part 21 on at least one side of the first-level conductive part 21. The third-level conductive part 23 is provided in multiple ways, and the multiple third-level conductive parts 23 are provided at intervals along the length direction of the second-level conductive part 22 on at least one side of the second-level conductive part 22; Multiple N-level conductive parts are provided, and multiple N-level conductive parts are provided at intervals on at least one side of each (N-1)-level conductive part and along the length direction of the (N-1)-level conductive part.

[0044] The second type: The conductive layer is composed of a first-level conductive part 21, a second-level conductive part 22, and an Nth-level conductive part; The second-level conductive part 22 is provided in multiple ways, and the multiple second-level conductive parts 22 are provided at intervals along the length direction of the first-level conductive part 21 on at least one side of the first-level conductive part 21. The third-level conductive part 23 is provided in multiple ways. The multiple third-level conductive parts 23 are only provided on a portion of the second-level conductive parts 22, and are provided at intervals on at least one side of the second-level conductive parts 22 along the length direction of the second-level conductive parts 22. Multiple N-level conductive parts are provided, and multiple N-level conductive parts are provided only on a portion of the (N-1)-level conductive parts, and are provided at intervals along the length direction of the (N-1)-level conductive parts on at least one side of the (N-1)-level conductive parts.

[0045] Preferably, in this application, when N≥3, the first method is adopted.

[0046] For example, in this application, the conductive layer 2 is an integrally formed structure composed of conductive parts of levels 1 to N. For instance, the integral forming of the conductive layer can be achieved through magnetron sputtering combined with laser etching.

[0047] For example, in this application, the material of the substrate layer 1 is an insulating film material. This insulating film material includes, but is not limited to, one or more of the following: polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, polyvinyl alcohol, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, sodium polystyrene sulfonate, polyacetylene, silicone rubber, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, polyethylene glycol, polysulfide, polyphenylene, polypyrrole, polyaniline, polythiophene, polypyridine, cellulose, starch, protein, epoxy resin, phenolic resin, derivatives of these materials, crosslinks, and copolymers.

[0048] For example, in this application, the conductive layer 2 is made of a metallic material. Preferably, the metallic material is copper or a copper alloy.

[0049] In one embodiment, a conductive layer 2 is provided, and the conductive layer 2 is disposed on the first surface of the substrate layer 1; or, The conductive layer 2 has two layers, which are respectively disposed on the first surface and the second surface of the substrate layer 1, with the first surface and the second surface of the substrate layer 1 facing each other. The conductive layer 2 can be disposed on one side or both sides of the substrate layer 1. The specific placement can be determined according to the requirements of the composite current collector and the lithium battery.

[0050] In one embodiment, the Nth-level conductive parts located on the same side of the (N-1)th-level conductive parts are arranged in parallel.

[0051] For example, whether multiple Nth-level conductive parts are spaced apart along the length direction of the (N-1)th-level conductive parts on one side of the (N-1)th-level conductive part, or multiple Nth-level conductive parts are spaced apart along the length direction of the (N-1)th-level conductive part on two opposite sides of the (N-1)th-level conductive part, then the Nth-level conductive parts on the same side of the (N-1)th-level conductive part are arranged in parallel.

[0052] For example, such as Figure 1 , Figure 6-7 As shown, when N is 3, the second-level conductive parts 22 located on the same side of the first-level conductive part 21 are arranged in parallel, and the third-level conductive parts 23 located on the same side of the second-level conductive part 22 are arranged in parallel. However, the third-level conductive parts on two opposite sides of the same second-level conductive part 22 can be arranged in parallel, as shown below. Figure 1 , Figure 6 As shown, they can also be set in a non-parallel manner, such as... Figure 7 As shown.

[0053] In this application, the Nth-level conductive parts located on the same side of the (N-1)th-level conductive parts are arranged in parallel, so that more Nth-level conductive parts can be arranged on the same side of the (N-1)th-level conductive parts, which makes it easier for electrons to collect and transmit, and is also easier to process during manufacturing.

[0054] In one embodiment, a plurality of Nth-level conductive portions are disposed at intervals along the length direction of the (N-1)th-level conductive portions on the first and second sides of the (N-1)th-level conductive portions, with the first and second sides of the (N-1)th-level conductive portions facing each other.

[0055] For example, such as Figure 1 , Figure 6-7 As shown, a plurality of second-level conductive portions 22 are provided at intervals along the length direction of the first-level conductive portion 21 on the first side and the second side of the first-level conductive portion 21, with the first side and the second side of the first-level conductive portion 21 facing each other.

[0056] Multiple third-level conductive portions 23 are disposed at intervals along the length direction of the second-level conductive portion 22 on the first and second sides of the second-level conductive portion 22, with the first and second sides of the second-level conductive portion 22 facing each other.

[0057] Taking the first-level conductive portion 21 as an example where its length direction is the same as the length direction of the substrate layer 1, the second-level conductive portion 22 is perpendicular to the length direction of the first-level conductive portion 21. That is, the length direction of the second-level conductive portion 22 is the same as the width direction of the substrate layer 1.

[0058] For example, in this application, when multiple Nth-level conductive portions are spaced apart along the length direction of the (N-1)th-level conductive portions on the first and second sides of the (N-1)th-level conductive portions, two arrangement methods are included: The first type involves Nth-level conductive portions on the first and second sides of the (N-1)th level conductive portion not being aligned; wherein, this non-alignment arrangement includes staggered and intersecting arrangements. For example, as... Figure 1 The second-level conductive portions 22 on the first and second sides of the first-level conductive portion 21 are alternately arranged, and the third-level conductive portions 23 on the first and second sides of the second-level conductive portion 22 are alternately arranged. For example... Figure 7 The third conductive part 23 on the first side of the second conductive part 22 intersects with the third conductive part 23 on the second side.

[0059] The second type involves aligning the Nth-level conductive portions on the first and second sides of the (N-1)th-level conductive portion. For example... Figure 6 As shown, the second-level conductive portions 22 on the first and second sides of the first-level conductive portion 21 are aligned with each other, and the third-level conductive portions 23 on the first and second sides of the second-level conductive portion 22 are aligned with each other. Figure 7 As shown, the second-level conductive parts 22 on the first and second sides of the first-level conductive part 21 are aligned with each other.

[0060] Therefore, in this application, the arrangement of the Nth-level conductive parts on the first and second opposite sides of the N-1th-level conductive part is not specifically limited, as long as the Nth-level conductive parts on the same side of the N-1th-level conductive part are spaced apart.

[0061] In one embodiment, one or more conductive layers 2 are provided on the first surface of the substrate 1; wherein, when there is one conductive layer on the first surface of the substrate 1, one conductive layer 2 is laid flat on the first surface of the substrate 1; or, when there are multiple conductive layers on the first surface of the substrate 1, multiple conductive layers 2 are laid flat side by side and spaced apart on the first surface of the substrate 1. Figure 8 As shown, there are three conductive layers 2 on the first surface of the substrate 1. These three conductive layers 2 are laid side by side and spaced apart on the first surface of the substrate 1. When the composite current collector with this arrangement is used in a lithium battery after the electrode sheet is prepared, electrons are transferred between the spaced conductive layers 2 through the positive / negative electrode active materials coated on the surface, so that the electrons are collected on the first-level conductive part 21 of each conductive layer and led out from the tab connected to the first-level conductive part 21.

[0062] When conductive layers 2 are provided on both the first and second surfaces of the substrate layer 1, the patterns of conductive layers 2 on the two opposing surfaces may be the same or different.

[0063] In one embodiment, the thickness distance between the free ends of the first to Nth conductive portions and the substrate layer 1 is all in the range of 0.05 to 5 μm. Preferably, the thickness of the first conductive portion 21 is in the range of 2 to 5 μm, the thickness of the second conductive portion 22 is in the range of 1 to 2 μm, and the thickness of the third conductive portion 23 is in the range of 0.05 to 1 μm. Figure 3 As shown, the thickness of the first-level conductive part 21 is greater than the thickness of the second-level conductive part 22, and the thickness of the second-level conductive part 22 is greater than the thickness of the third-level conductive part 23.

[0064] In one embodiment, the width of each of the first to Nth conductive portions is in the range of 0.1 to 5 mm, and the width of the Nth conductive portion is 10% to 50% of the width of the (N-1)th conductive portion. Preferably, the width of the first conductive portion 21 is in the range of 2 to 5 mm. Exemplarily, the width of the Nth conductive portion is 10%, 20%, 30%, 40%, 50% of the width of the (N-1)th conductive portion, or any value between two adjacent values.

[0065] For example, in this application, the direction of the connecting segment between the Nth-level conductive part and the (N-1)th-level conductive part is the width direction of the Nth-level conductive part, and the direction perpendicular to the direction of the connecting segment is the length direction of the Nth-level conductive part. The thickness directions of the 1st to Nth-level conductive parts are all set in the same direction, which is the stacking direction of the composite current collector. Specifically, as shown... Figure 2As shown, taking the first-level conductive portion 21 with its length direction aligned with the length direction of the substrate layer 1 as an example, the direction indicated by L1 is the length direction of the first-level conductive portion 21, and the direction indicated by W1 is the width direction of the first-level conductive portion 21. Therefore, the length of the first-level conductive portion 21 is much greater than its width. The second-level conductive portions 22 are spaced apart along the length direction of the first-level conductive portion 21, and the width of the second-level conductive portion 22 is 10-50% of the width of the first-level conductive portion 21. Therefore, the length of the second-level conductive portion 22 is much greater than its width. Furthermore, the second-level conductive portions 22 are spaced apart from the sides of the first-level conductive portion 21. Therefore, when manufacturing these first to Nth level conductive parts, the width of each conductive part must first be determined. For example, when manufacturing the first level conductive part 21, the width of the first level conductive part 21 is determined first, and then the length of the first level conductive part 21 is determined according to the structural requirements for use in lithium batteries. Then, when manufacturing the second level conductive part 22, based on the ratio that the width of the Nth level conductive part is 10% to 50% of the width of the (N-1)th level conductive part, the width of the second level conductive part 22 is determined first (that is, the width of the connecting segment between the first level conductive part and each second level conductive part is determined; the direction of the width of this connecting segment is the width direction of the second level conductive part 22, and the direction perpendicular to it is the length direction of the second level conductive part 22, such as...). Figure 2 As shown, W2 represents the width direction of the second-level conductive part 22, and L2 represents the length direction of the second-level conductive part 22. Then, the length of the second-level conductive part 22 is determined according to the requirements of its application in lithium battery structures. Further, when manufacturing the third-level conductive part 23, based on the aforementioned proportional relationship, the width value of the third-level conductive part is first determined (i.e., the width of the connecting segment between the second-level conductive part and each third-level conductive part is determined; this connecting segment width is the width direction of the third-level conductive part, and the direction perpendicular to it is the length direction of the third-level conductive part 23, such as...). Figure 2 As shown, W3 indicates the width direction of the third-level conductive part 23, and L3 indicates the length direction of the third-level conductive part 23. These third-level conductive parts are spaced along the length direction (L2 direction) of the second-level conductive part 22. The length of the third-level conductive part 23 is not particularly limited; it only needs to be spaced apart from adjacent second-level conductive parts 22. The fourth-level conductive part follows the same method. Therefore, in this application, the direction of the connecting segment between the Nth-level conductive part and the (N-1)th-level conductive part is the width direction of the Nth-level conductive part. Then, based on the width and width direction of the Nth-level conductive part, its length direction is determined, thereby determining the width, width direction, and length direction of the (N+1)th-level conductive part.

[0066] For example, the width of the first-level conductive portion 21 is the largest and ranges from 0.1 to 5 mm, while the width of the second-level conductive portion 22 is 10% to 50% of the width of the first-level conductive portion 21. As the value of N increases, the width of the conductive portion gradually decreases and cannot be less than 0.1 mm. The smaller the width, the more difficult the required processing technology. Therefore, preferably, when the conductive layer 2 of this application is composed of the first to third-level conductive portions, it can not only reduce the weight of the composite current collector, reduce the surface density of the composite current collector, increase the energy density of the lithium battery, and increase the contact area and adhesion strength with the active material, but also reduce the processing difficulty and facilitate large-scale production.

[0067] In one embodiment, the total coverage area of ​​the first to Nth conductive portions covering the first surface of the substrate 1 is 30% to 70% of the area of ​​the first surface of the substrate 1. Exemplarily, the total coverage area of ​​the first to Nth conductive portions covering the first surface of the substrate 1 is 30%, 40%, 50%, 60%, 70% of the area of ​​the first surface of the substrate 1, and any value between two adjacent values.

[0068] In one possible implementation, such as Figure 9 As shown in the present application, the composite current collector further includes an adhesive reinforcement layer 3 and / or an anti-oxidation layer 4. The adhesive reinforcement layer 3 is stacked between the base layer 1 and the conductive layer 2, and the anti-oxidation layer 4 is stacked on the surface of the conductive layer 2 facing away from the base layer 1. Figure 8 In the diagram, T represents the stacking direction of the composite current collector, which is also the thickness direction.

[0069] For example, the material of the bonding reinforcement layer 3 includes, but is not limited to, Ni-Cr alloy. The material of the anti-oxidation layer 4 includes, but is not limited to, chromium oxide or chromium hydroxide.

[0070] For example, the thickness of the bonding reinforcement layer 3 is 10~30nm. The thickness of the anti-oxidation layer 4 is 5~15nm.

[0071] Secondly, this application also provides a method for preparing the above-mentioned composite current collector, the method comprising: Step 1), provide a substrate, pre-treat the substrate to obtain base layer 1; Step 2), a conductive metal layer is magnetron sputtered on the first surface of the substrate 1; Step 3) Using laser processing equipment, the conductive metal layer is laser etched according to the predetermined processing pattern to obtain a patterned metal layer; Step 4), after cleaning the patterned metal layer, perform horizontal electroplating to obtain conductive layer 2; the horizontal electroplating speed is 0.5~3m / min.

[0072] This application employs a combination of laser etching and horizontal electroplating, utilizing the technical characteristic that different linewidths result in different current densities and deposition rates. Specifically, within the same electroplating time, the conductive portion deposited at wider linewidths is thicker, while the conductive portion deposited at narrower linewidths is thinner. Compared to first thickening the composite copper foil and then patterning it, the patterning process in this application is faster and saves raw materials. This method efficiently obtains a composite current collector with a three-dimensional structure and good microstructural consistency. Furthermore, the method is simple and allows for the mass production of this composite current collector.

[0073] For example, in step 1), the substrate pretreatment methods include, but are not limited to, at least one of: plasma treatment, corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, and ozone treatment. Substrate pretreatment can enhance the adhesion between the conductive layer and the substrate layer. For example, the plasma treatment process conditions are: ion source power of 0.1~1KW.

[0074] For example, in step 2), the substrate layer 1 is placed in the vacuum chamber of a roll-to-roll vacuum sputtering coating machine, and a conductive metal layer is magnetron sputtered onto the first surface of the substrate layer 1. The thickness of the conductive metal layer is 30 nm to 300 nm. Exemplarily, the magnetron sputtering coating process parameters are: a base vacuum of 4 × 10⁻⁶. -4 Pa ~ 1×10 -3 Pa, the working gas atmosphere is argon, and the working gas pressure is 1×10 Pa. -1 pa~3×10 -1 The power of the target material used for the conductive metal layer is 2~8KW, and the transmission speed of the substrate 1 is >0 and ≤15m / min. For example, the material of the conductive metal layer is copper or copper alloy, and the power of the copper target or copper alloy target used is 2~8KW.

[0075] Preferably, in step 2), the substrate layer 1 is placed in the vacuum chamber of a roll-to-roll vacuum sputtering coating machine. A bonding reinforcement layer 3 is first magnetron sputtered onto the first surface of the substrate layer 1, and then a conductive metal layer is magnetron sputtered onto the surface of the bonding reinforcement layer 3 facing away from the substrate layer 1. The thickness of the conductive metal layer is 30 nm to 300 nm. For example, the magnetron sputtering coating process parameters are: a base vacuum of 4 × 10⁻⁶. -4 Pa ~ 1×10 -3 Pa, the working gas atmosphere is argon, and the working gas pressure is 1×10 Pa. -1 pa~3×10 -1The target power used for the bonding reinforcement layer 3 is 0.3~3KW, and the target power used for the conductive metal layer is 2~8KW. The transmission speed of the substrate layer 1 is >0 and ≤15m / min. For example, the bonding reinforcement layer is made of Ni-Cr alloy, therefore the corresponding Ni-Cr alloy target power is 0.3~3KW. The conductive metal layer is made of copper or a copper alloy, therefore the corresponding copper target power or copper alloy target power is 2~8KW.

[0076] For example, in step 3), the pattern to be processed is pre-designed using software and imported into the laser processing equipment. Then, the laser processing equipment performs laser etching on the conductive metal layer according to the predetermined pattern. For example, the laser etching conditions are: the laser repetition frequency is controlled at 200~400Hz, and the laser etching speed is controlled at 70~130mm / s.

[0077] For example, in step 4), the horizontal electroplating conditions also include: the pH value of the electroplating solution is 1~2, the current density is 0.8~5ASD (amperes per square decimeter), the sulfuric acid concentration in the immersion tank is controlled at 50~150g / L, the copper sulfate concentration is controlled at 80~200g / L, the hydrochloric acid concentration is controlled at 20~80ppm, the temperature is controlled at 20~30℃, and the electroplating time is 1~4min.

[0078] For example, in this application, the method further includes: step 5), after washing the conductive layer with water, performing an anti-oxidation treatment on the surface of the conductive layer facing away from the substrate layer 1 to obtain an anti-oxidation layer 4. Further, the anti-oxidation layer 4 is dried at a temperature of 50~70°C.

[0079] For example, step 5) includes: step 5-1), pretreatment: cleaning and degreasing the conductive layer 2 to remove surface impurities and oxides, ensuring the effect of subsequent treatment; Step 5-2), passivation treatment: Immerse the conductive layer 2 after the treatment in step 5-1) into a solution containing chromates (such as potassium chromate, sodium chromate, etc.) to form a passivation film on the surface of the conductive layer. This passivation film is the anti-oxidation layer 4. Alternatively, passivation treatment: under specific conditions, chromate is reacted on the surface of the conductive layer by an electrochemical method to form a passivation film on the surface of the conductive layer, which is the anti-oxidation layer 4.

[0080] Step 5-3), post-processing: After passivation, the conductive layer and the anti-oxidation layer 4 formed on its surface are cleaned and dried to remove residual chemical substances and ensure that the conductive layer 2 and the anti-oxidation layer 4 are clean.

[0081] Secondly, this application also provides a negative electrode sheet, which includes the aforementioned composite current collector and an active material. The active material is coated on the surface of the conductive layer 2 of the composite current collector facing away from the substrate layer 1, or the active material is coated on the surface of the anti-oxidation layer 4 of the composite current collector facing away from the substrate layer 1. The negative electrode sheet with the composite current collector of this application can also increase the contact area between the composite current collector and the active material, and increase the adhesion strength between them, thereby improving battery stability.

[0082] Thirdly, this application also provides a battery, including the composite current collector in any of the above-described embodiments or the composite current collector or negative electrode prepared by the above-described preparation method. This battery includes, but is not limited to, a lithium battery.

[0083] The composite current collector of this application can further reduce the weight of the current collector while providing a larger contact area, and ultimately improve the energy density, safety and stability of lithium batteries.

[0084] For example, the lithium batteries in this application include, but are not limited to, cylindrical lithium batteries and pouch lithium batteries.

[0085] The present application will be further described in detail below with reference to specific embodiments.

[0086] Example 1 like Figure 1 , Figure 9 As shown, a composite current collector includes: a base layer 1; An adhesive reinforcement layer 3 is disposed on the first surface of the base layer 1; The conductive layer 2 is disposed on the surface of the adhesive reinforcement layer 3 facing away from the base layer 1; The conductive layer 2 is composed of a first-level conductive part 21, a second-level conductive part 22, and a third-level conductive part 23; The second-level conductive part 22 is provided in multiple ways. The multiple second-level conductive parts 22 are provided at intervals along the length direction of the first-level conductive part 21 on the first side and the second side of the first-level conductive part 21, and the first side and the second side of the first-level conductive part 21 are opposite to each other. The third-level conductive part 23 is provided in multiple ways. The multiple third-level conductive parts 23 are arranged at intervals along the length direction of the second-level conductive part 22 on the first side and the second side of the second-level conductive part 22, and the first side and the second side of the second-level conductive part 22 are opposite to each other. The width of the first-level conductive part 21 is 2 mm and the thickness of the first-level conductive part 21 is 2 μm; the width of the second-level conductive part 22 is 1 mm and the thickness of the second-level conductive part 22 is 1~1.5 μm; the width of the third-level conductive part 23 is 0.5 mm and the thickness of the third-level conductive part 23 is 0.5~0.8 μm. Anti-oxidation layer 4 is disposed on the surface of conductive layer 2 facing away from substrate layer 1.

[0087] The preparation method of the composite current collector in Example 1 includes: Step 1): A 4.5 μm PET film is selected as the substrate, and plasma treatment is used to pretreat the substrate to obtain substrate layer 1. The plasma treatment process conditions are as follows: ion source power is 0.2 kW.

[0088] Step 2): The substrate 1 is placed in the vacuum chamber of a roll-to-roll magnetron sputtering machine. A bonding reinforcement layer 3 is deposited on the first surface of the substrate 1 by magnetron sputtering, and a copper seed layer (i.e., a conductive Cu layer) is magnetron sputtered on the surface of the bonding reinforcement layer 3 facing away from the substrate 1. The bonding reinforcement layer 3 is made of Ni-Cr alloy and has a thickness of 10 nm, while the conductive Cu layer has a thickness of 60 nm. The magnetron sputtering process parameters are: a base vacuum of 8 × 10⁻⁶. -4 Pa, the working gas atmosphere is argon, and the working gas pressure is controlled at 2×10 Pa. -1 The power of the Pa, Ni-Cr alloy target is 0.7 kW, the power of the Cu target is 5 kW, and the transmission speed of the substrate 1 is 3 m / min.

[0089] Step 3): Design the pattern to be processed using software and import it into the laser processing equipment. Place the substrate layer with the conductive Cu layer deposited on the surface obtained in Step 2) into the laser processing equipment. Perform laser etching on the conductive Cu layer according to the preset processing pattern to obtain a patterned Cu layer. Then, a patterned composite film composed of a patterned Cu layer, a bonding reinforcement layer and a substrate layer is obtained. In the patterned Cu layer, the width of the first conductive part 21 is 2 mm, the width of the second conductive part 22 is 1 mm, and the width of the third conductive part 23 is 0.5 mm. The laser etching conditions are: laser repetition frequency 300 Hz and etching speed 100 mm / s.

[0090] Step 4): After cleaning the patterned composite film obtained in Step 3), the patterned Cu layer is electroplated with an acidic copper plating solution to thicken it, resulting in conductive layer 2. The electroplating process is as follows: horizontal electroplating is used, with the concentrations of sulfuric acid, copper sulfate, and hydrochloric acid in the immersion tank controlled at 100 g / L, 100 g / L, and 50 ppm. The pH value of the electroplating solution is 1.5, the current density is 1.5 ASD, the film rotation speed is 2 m / min, the temperature is 25℃, and the electroplating time is 3 minutes. The width and thickness of each conductive layer in conductive layer 2 are as follows: the width of the first-level conductive layer 21 is 2 mm, and the thickness is 2 μm; the line width of the second-level conductive layer 22 is 1 mm, and the thickness is 1~1.5 μm; the line width of the third-level conductive layer 23 is 0.5 mm, and the thickness is 0.5~0.8 μm.

[0091] Step 5) Wash the substrate layer with the conductive layer formed on the surface obtained in Step 4) with water, and then perform an anti-oxidation treatment on the surface of the conductive layer 2 facing away from the substrate layer 1 to form an anti-oxidation layer 4 on the surface of the conductive layer 2 facing away from the substrate layer 1. The material of the anti-oxidation layer 4 is chromium oxide; finally, dry the substrate layer at a drying temperature of 70°C.

[0092] In Example 1, a composite current collector (i.e., a patterned composite current collector) was prepared.

[0093] Example 2 like Figure 5 , Figure 9 As shown, a composite current collector includes: a base layer 1; An adhesive reinforcement layer 3 is disposed on the first surface of the base layer 1; The conductive layer 2 is disposed on the surface of the adhesive reinforcement layer 3 facing away from the base layer 1; The conductive layer 2 is composed of a first-level conductive part 21 and a second-level conductive part 22; The second-level conductive part 22 is provided in multiple ways. The multiple second-level conductive parts 22 are provided at intervals along the length direction of the first-level conductive part 21 on the first side and the second side of the first-level conductive part 21, and the first side and the second side of the first-level conductive part 21 are opposite to each other. The width of the first-level conductive part 21 is 5 mm and the thickness of the first-level conductive part 21 is 5 μm; the width of the second-level conductive part 22 is 0.5 mm and the thickness of the second-level conductive part 22 is 0.6~1 μm. Anti-oxidation layer 4 is disposed on the surface of conductive layer 2 facing away from substrate layer 1.

[0094] The preparation method of the composite current collector in Example 2 includes: Step 1): A 4.5 μm PET film is selected as the substrate, and plasma treatment is used to pretreat the substrate to obtain substrate layer 1. The plasma treatment process conditions are as follows: ion source power is 0.2 kW.

[0095] Step 2): The substrate 1 is placed in the vacuum chamber of a roll-to-roll magnetron sputtering machine. A bonding reinforcement layer 3 is deposited on the first surface of the substrate 1 by magnetron sputtering, and a copper seed layer (i.e., a conductive Cu layer) is magnetron sputtered on the surface of the bonding reinforcement layer 3 facing away from the substrate 1. The bonding reinforcement layer 3 is made of Ni-Cr alloy and has a thickness of 30 nm, while the conductive Cu layer has a thickness of 60 nm. The magnetron sputtering process parameters are: a base vacuum of 8 × 10⁻⁶. -4 Pa, the working gas atmosphere is argon, and the working gas pressure is controlled at 2×10 Pa. -1 The power of the Pa, Ni-Cr alloy target is 0.7 kW, the power of the Cu target is 5 kW, and the transmission speed of the substrate 1 is 1 m / min.

[0096] Step 3): Design the pattern to be processed using software and import it into the laser processing equipment. Place the substrate layer with the conductive Cu layer deposited on the surface obtained in Step 2) into the laser processing equipment. Perform laser etching on the conductive Cu layer according to the preset processing pattern to obtain a patterned Cu layer. Then, a patterned composite film composed of a patterned Cu layer, a bonding reinforcement layer and a substrate layer is obtained. In the patterned Cu layer, the width of the first conductive part 21 is 5 mm and the width of the second conductive part 22 is 0.5 mm. The laser etching conditions are: laser repetition frequency 300 Hz and etching speed 100 mm / s.

[0097] Step 4): After cleaning the patterned composite film obtained in Step 3), the patterned Cu layer is electroplated with an acidic copper plating solution to thicken it, resulting in conductive layer 2. The electroplating conditions are as follows: horizontal electroplating; sulfuric acid concentration in the immersion tank is controlled at 100 g / L, copper sulfate concentration at 100 g / L, hydrochloric acid concentration at 50 ppm, pH of the electroplating solution at 1.5, current density at 1.5 ASD, film rotation speed at 0.7 m / min, temperature at 25℃, and electroplating time at 3 minutes. The width and thickness of each conductive layer 2 are as follows: the width of the first-level conductive layer 21 is 5 mm, and the thickness is 5 μm; the line width of the second-level conductive layer is 0.5 mm, and the thickness is 0.6~1 μm.

[0098] Step 5) Wash the substrate layer with conductive layer formed on the surface obtained in step 4) with water, and then perform anti-oxidation treatment on the surface of conductive layer 2 facing away from substrate layer 1 to form anti-oxidation layer 4 on the surface of conductive layer 2 facing away from substrate layer 1. The material of anti-oxidation layer 4 is chromium oxide; finally, dry treatment: drying temperature 70℃.

[0099] In Example 2, a composite current collector (i.e., a patterned composite current collector) was prepared.

[0100] Comparative Example 1 Comparative Example 1 uses commercially available pure copper foil as the current collector. The thickness of this commercially available pure copper foil current collector is 6 μm.

[0101] Performance test (a) The surface density of the composite current collectors of Examples 1-2 and the current collector of Comparative Example 1 was tested. The results are shown in Table 1 below.

[0102] Table 1. Surface density of the composite current collectors in Examples 1-2 and the current collector in Comparative Example 1.

[0103] The areal density of the current collector (mass per unit area, usually expressed in g / m²) is negatively correlated with the energy density of the battery (Wh / kg or Wh / L): the lower the areal density of the current collector, the higher the energy density of the battery.

[0104] As can be seen from the areal density test results in Table 1, the areal density of the patterned composite current collectors in Examples 1-2 of this application is significantly lower than that of existing commercial pure copper foil current collectors, resulting in a significant weight reduction effect. Therefore, the reduced areal density of the composite current collectors in this application can improve the energy density of lithium batteries when applied to them.

[0105] Furthermore, the substrate layer of the composite current collector used in this application is an insulating thin film material, which significantly reduces the weight compared to copper foil of the same thickness, thereby significantly reducing the weight of the composite current collector in this application.

[0106] (II) Preparation and peel strength test of negative electrode sheet (i.e., patterned negative electrode sheet): Example 1: Preparation of patterned negative electrode sheet: The negative electrode active material artificial graphite, conductive agent Super-P, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were thoroughly mixed in a deionized water solvent system at a weight ratio of 96:1:2:1 to obtain a negative electrode active slurry. The negative electrode active slurry was coated on the surface of the anti-oxidation layer 4 of the composite current collector of Example 1 facing away from the substrate layer 1. After drying, cold pressing, slitting, and cutting, the patterned negative electrode sheet of Example 1 was obtained.

[0107] Example 2: Patterned negative electrode sheets were prepared using the same method.

[0108] The pure copper foil current collector of Comparative Example 1 was also prepared using the same method to obtain a pure copper foil negative electrode sheet.

[0109] Peel strength test: The peel strength of the above-mentioned negative electrode sheet was tested using a mechanical testing machine. Specifically, a certain length of double-sided tape was first fixed along the length of the steel plate; then the prepared negative electrode sheet was pasted onto the double-sided tape. One end of the mechanical testing machine was used to fix the steel plate, and the negative electrode sheet was folded 180° and fixed to the other end of the machine before the tensile test began. The test results are shown in Table 2 below.

[0110] Table 2. Peel strength results of patterned negative electrode sheets in Examples 1-2 and pure copper foil negative electrode sheets in Comparative Example 1.

[0111] As can be seen from the peel strength test results in Table 2, the patterned negative electrode sheet prepared using the patterned composite current collector of this application has a high bonding strength between the active material and the current collector. This indicates that the composite current collector structure of this application can increase the contact area and adhesion strength between the active material and the current collector, thereby improving the stability and safety of lithium batteries.

[0112] In summary, as mentioned above, the composite current collector of this application consists of a base layer 1 and a conductive layer 2; the base layer 1 is made of an insulating thin film material. Compared with traditional pure metal current collectors, the composite current collector of this application, relying on an insulating polymer base layer, is less prone to generating large metal burrs and forming conductive paths when punctured by hard objects; the base layer 1 also functions as a "fuse". Therefore, the composite current collector of this application not only effectively ensures its own safety but also effectively reduces its weight and areal density, and increases the contact area and adhesion strength with the active material, thereby ultimately improving the energy density, safety, and stability of lithium batteries.

[0113] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this disclosure can be achieved, and this is not limited herein.

[0114] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0115] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A composite current collector, characterized in that, include: basal layer; A conductive layer is provided at least on the first surface of the substrate layer; The conductive layer is composed of conductive parts of level 1 to N, where N is an integer ≥ 2; The Nth level conductive part is provided in multiple ways, and the multiple Nth level conductive parts are provided at intervals along the length direction of the (N-1)th level conductive part on at least one side of the (N-1)th level conductive part; The width of the (N-1)th level conductive part is greater than the width of the Nth level conductive part, and the thickness of the (N-1)th level conductive part is greater than the thickness of the Nth level conductive part.

2. The composite current collector according to claim 1, characterized in that, The conductive layer is provided in one layer, and the conductive layer is disposed on the first surface of the substrate layer; or, The conductive layer comprises two layers, which are respectively disposed on the first surface and the second surface of the base layer, with the first surface and the second surface of the base layer facing each other.

3. The composite current collector according to claim 1, characterized in that, The Nth-level conductive parts located on the same side of the (N-1)th-level conductive parts are arranged in parallel.

4. The composite current collector according to claim 1, characterized in that, Multiple Nth-level conductive portions are disposed at intervals along the length direction of the (N-1)th-level conductive portions on the first and second sides of the (N-1)th-level conductive portions, with the first and second sides of the (N-1)th-level conductive portions facing each other.

5. The composite current collector according to claim 1, characterized in that, One or more conductive layers are provided on the first surface of the substrate layer; wherein, one conductive layer is laid flat on the first surface of the substrate layer; or... Multiple conductive layers are laid side-by-side and spaced apart on the first surface of the substrate layer.

6. The composite current collector according to any one of claims 1-5, characterized in that, The thickness distance between the free ends of the first to Nth conductive parts and the substrate layer is in the range of 0.05 to 5 μm.

7. The composite current collector according to any one of claims 1-5, characterized in that, The width of each of the first to Nth conductive parts is in the range of 0.1 to 5 mm, and the width of the Nth conductive part is 10% to 50% of the width of the (N-1)th conductive part.

8. The composite current collector according to claim 6 or 7, characterized in that, The total coverage area of ​​the first to Nth conductive portions covering the first surface of the substrate is 30 to 70% of the area of ​​the first surface of the substrate.

9. The composite current collector according to any one of claims 1-8, characterized in that, The composite current collector further includes an adhesive reinforcement layer and / or an anti-oxidation layer, wherein the adhesive reinforcement layer is stacked between the substrate layer and the conductive layer, and the anti-oxidation layer is stacked on the surface of the conductive layer facing away from the substrate layer.

10. A method for preparing a composite current collector as described in any one of claims 1-9, characterized in that, The method includes: A substrate is provided, and the substrate is pretreated to obtain the base layer; A conductive metal layer is magnetron sputtered onto the first surface of the substrate layer. The conductive metal layer is laser-etched according to a predetermined pattern using laser processing equipment to obtain a patterned metal layer. The patterned metal layer is cleaned and then subjected to horizontal electroplating to obtain the conductive layer; the horizontal electroplating operation speed is 0.5~3m / min.

11. The preparation method according to claim 10, characterized in that, The method further includes: Before the conductive metal layer is prepared, a bonding reinforcement layer is first magnetron sputtered onto the first surface of the substrate layer, and then the conductive metal layer is magnetron sputtered onto the surface of the bonding reinforcement layer facing away from the substrate layer; and / or, After washing the conductive layer with water, an anti-oxidation treatment is performed on the surface of the conductive layer facing away from the substrate layer to obtain an anti-oxidation layer.

12. A negative electrode sheet, characterized in that, The composite current collector includes the composite current collector according to any one of claims 1-9 or the composite current collector prepared by the preparation method according to claim 10 or 11.

13. A battery, characterized in that, Includes the composite current collector as described in any one of claims 1-9, or the composite current collector prepared by the preparation method described in claim 10 or 11, or the negative electrode sheet as described in claim 12.

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