Composite current collector and preparation method therefor, and electrode and manufacturing method therefor and use thereof

Abstract

A composite current collector and a preparation method therefor, and an electrode and a manufacturing method therefor and the use thereof. The composite current collector comprises a substrate (1), a first metal layer (2) and a second metal layer (3). The first metal layer (2) and the second metal layer (3) are respectively provided on surfaces of two opposite sides of the substrate (1). The composite current collector is divided into a blank area (4) and an electrode area (5) in the width direction thereof, wherein the blank area (4) is configured to form tabs; the electrode area (5) is configured to be an area coated with active material slurry; a plurality of through holes (6) are distributed in the blank area (4); the through holes (6) penetrate the first metal layer (2), the substrate (1) and the second metal layer (3) in sequence; an electrically conductive layer (7) is provided inside each through hole (6); and two ends of the electrically conductive layer (7) are respectively connected to the first metal layer (2) and the second metal layer (3).

Description

Composite current collector and preparation method thereof, electrode and preparation method thereof and application thereof

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 16, 2023, with application number 202310718941.8, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the field of new energy battery preparation technology, and relates to a composite current collector and its preparation method, an electrode and its manufacturing method and application. Background Art

[0003] New energy power battery structures typically include cylindrical, prismatic, or soft-pack types. Large cylindrical batteries, due to their superior safety and structural stability, have seen their market share increase year by year. Taking the 4680 large cylindrical battery as an example, the typical manufacturing process involves: active material preparation - current collector coating - rolling - drying - slitting - tab cross-cutting - winding - flattening - welding the current collector plate to the positive electrode column - casing - grooving - drying - liquid injection - coiling and spot welding - cleaning - film coating - activation - opening and formation - exhaust - laser welding and capping - sorting.

[0004] Conventional new energy batteries use metal foil as the current collector, typically aluminum foil for the positive electrode and copper foil for the negative electrode. With the increasing popularity of electric vehicles and consumer electronics, demand for products with high energy density and long lifespan is increasing, leading to the emergence of composite current collectors. Composite current collectors, consisting of a multilayer composite material consisting of two metal layers and a central substrate, offer advantages such as high safety, high energy density, lightweight, resource conservation, and ease of processing.

[0005] The application of composite current collectors in soft-pack batteries is relatively mature, mainly using traditional foil for transfer welding and then welding with the tabs. However, the cell structure of cylindrical batteries is different from that of soft-pack batteries, and composite current collectors are less used in large cylindrical batteries. There are two main application methods: the first is to directly weld the composite current collector to the positive and negative current collector plates after coating, rolling, cross-cutting and flattening the composite current collector. However, since the current collector is only in contact with the current collector plate on one side, the internal resistance of the battery increases seriously, which is about three times more than that of traditional batteries, and the battery heats up seriously. The second is to learn from the application of soft-pack batteries. After the current collector is coated and rolled, the composite current collector is transferred to the ear side by welding two pieces of traditional metal foil to the two sides of the composite current collector, and then the ear is cross-cut and kneaded. However, since one layer of composite current collector corresponds to two layers of traditional foil, after the large cylindrical ear is flattened, the thickness of the overlapping part is twice or even higher than the original, resulting in insufficient space above and below the shell. In addition, during the flattening process, the ear is bent at different angles, which can easily cause the welding wire to fall off and break, reducing the production yield of the battery.

[0006] Summary of the Invention

[0007] The present application provides a composite current collector and its preparation method, an electrode and its manufacturing method and application, which provides a feasible way for the application of composite current collector in large cylindrical full-electrode batteries, thereby reducing the internal resistance of the battery cell and solving the problem of low-impedance welding between the composite current collector and the current collecting plate.

[0008] In the first aspect, the present application provides a composite current collector, which includes a substrate, a first metal layer and a second metal layer, and the first metal layer and the second metal layer are respectively provided on the opposite side surfaces of the substrate, and the composite current collector is divided into a blank area and an electrode area along the width direction of the composite current collector, the blank area is configured to form a pole ear, and the electrode area is configured to coat an active material slurry. A plurality of through holes are distributed in the blank area, and the through holes sequentially penetrate the first metal layer, the substrate and the second metal layer, and a conductive layer is provided inside the through hole, and the two ends of the conductive layer are respectively connected to the first metal layer and the second metal layer.

[0009] In the present application, the conductive layer can be a thin layer structure bonded along the hole wall of the through hole, that is, covering part of the hole cavity area of ​​the through hole; it can also be a structure that fills the through hole along the height direction of the through hole, that is, completely covers the hole cavity area of ​​the through hole. Those skilled in the art can make adjustments according to actual conditions. As long as other types of conductive layer setting structures can be used in the present application as long as they can achieve conductive connection between the first metal layer and the second metal layer.

[0010] As a technical solution of the present application, the substrate includes a polymer layer.

[0011] As a technical solution of the present application, the materials of the first metal layer and the second metal layer independently include any one of copper, aluminum, gold, tungsten, platinum, cobalt, magnesium, zinc or titanium.

[0012] As a technical solution of the present invention, the average pore diameter of the through hole is 0.5 to 3 mm, for example, it can be 0.5 mm, 0.6 mm, 0.7 mm, 1.0 mm, 1.2 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2.0 mm, 2.3 mm, 2.5 mm, 2.8 mm or 3.0 mm, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] As a technical solution of the present application, the through hole is a polygonal hole.

[0014] As a technical solution of the present application, the through hole is in the shape of a polygonal star, including a triangle, a quadrangle, a pentagram, a hexagon, a heptagon, an octagon or a nine-pointed star.

[0015] As a technical solution of the present application, the number of sides of the polygonal hole is 3 to 20, for example, it can be 3, 4, 5, 6, 8, 10, 12, 14, 16, 18 or 20.

[0016] As a technical solution of the present application, the hole coverage of the through holes in the blank area is 30% to 80%, for example, it can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] As a technical solution of the present application, the blank area is located at one side edge of the composite current collector, and the width of the blank area is smaller than the width of the electrode area.

[0018] In a second aspect, the present application provides a method for preparing the composite current collector according to the first aspect, the preparation method comprising:

[0019] Providing a substrate, and forming a first metal layer and a second metal layer on two opposite surfaces of the substrate respectively;

[0020] Dividing a blank area and an electrode area along the width direction of the substrate, and drilling holes in the blank area to form through holes that sequentially penetrate the first metal layer, the substrate, and the second metal layer;

[0021] A conductive paste is filled in the through hole to form a conductive layer, so that the first metal layer and the second metal layer are connected to each other.

[0022] As a technical solution of the present application, the punching is performed by laser punching.

[0023] As a technical solution of the present application, the laser includes picosecond ultraviolet light.

[0024] As a technical solution of the present application, the wavelength of the laser is 350 to 455 nm, for example, it can be 350 nm, 355 nm, 360 nm, 380 nm, 390 nm, 395 nm, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm or 455 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] As a technical solution of the present application, the power of the laser drilling is 3 to 35 W, for example, it can be 3W, 5W, 10W, 12W, 15W, 18W, 20W, 22W, 25W, 28W, 30W or 35W, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] The laser of the present application is picosecond ultraviolet light, and its working principle is: after absorbing energy, the electrons in the atoms transition from a low energy level to a high energy level, and then fall back from a high energy level to a low energy level. In the above-mentioned energy level transition process, the energy released by the electrons is released in the form of photons to form a laser. After the initially generated laser is filtered through layers, ultraviolet light with a short wavelength is left. The laser in this band is sharp. When the laser is working, it generates ultrashort pulses. Since the time of a single pulse is only a few picoseconds, its thermal effect is very small, and the workpiece can be "cold" processed to avoid excessive processing temperature, which will cause deformation and carbonization of the polymer layer of the composite current collector.

[0027] As a technical solution of the present application, the conductive paste includes any one of silver paste, nickel paste, copper paste or aluminum paste.

[0028] As a technical solution of the present application, the coating amount of the conductive paste is 0.1 to 1 g / m2, for example, it can be 0.1 g / m2, 0.2 g / m2, 0.3 g / m2, 0.4 g / m2, 0.5 g / m2, 0.6 g / m2, 0.7 g / m2, 0.8 g / m2, 0.9 g / m2 or 1 g / m2, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In a third aspect, the present application provides an electrode, comprising the composite current collector described in the first aspect, and an active material layer arranged in the electrode area of ​​the composite current collector, wherein the blank area is wound and bent to form an electrode ear portion.

[0030] In a fourth aspect, the present application provides a method for manufacturing the electrode according to the third aspect, the method comprising:

[0031] Providing a substrate, forming a first metal layer and a second metal layer on two opposite surfaces of the substrate, respectively, and dividing a blank area and an electrode area along the width direction of the substrate;

[0032] Punching holes in the blank area to form through holes that sequentially penetrate the first metal layer, the substrate, and the second metal layer, and filling the through holes with a conductive paste to form a conductive layer, so that the first metal layer and the second metal layer are interconnected to obtain a composite current collector;

[0033] coating an active material slurry in the electrode region of the composite current collector to form an active material layer;

[0034] The blank area is cut to form a plurality of tabs, and the tabs are wound and flattened to obtain the electrode.

[0035] In a fifth aspect, the present application provides a method for manufacturing the electrode according to the third aspect, the manufacturing method comprising:

[0036] Providing a substrate, forming a first metal layer and a second metal layer on opposite sides of the substrate, dividing a blank area and an electrode area along the width direction of the substrate, and coating an active material slurry on the surface of the electrode area to form an active material layer;

[0037] Punching holes in the blank area to form through holes that sequentially penetrate the first metal layer, the substrate, and the second metal layer, and filling the through holes with a conductive paste to form a conductive layer, so that the first metal layer and the second metal layer are interconnected, thereby obtaining a composite current collector with an active material layer provided on the surface;

[0038] The blank area is cut to form a plurality of tabs, and the tabs are wound and flattened to obtain the electrode.

[0039] In a sixth aspect, the present application provides an application of the electrode described in the third aspect, wherein the electrode is used for a cylindrical full-tab battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG1 is a schematic cross-sectional view of a composite current collector provided in an embodiment of the present application;

[0041] FIG2 is a front view of a composite current collector provided in an embodiment of the present application;

[0042] FIG3 is a schematic diagram of a through-hole structure provided in an embodiment of the present application.

[0043] Among them, 1-substrate; 2-first metal layer; 3-second metal layer; 4-blank area; 5-electrode area; 6-through hole; 7-conductive layer; 8-active material layer. DETAILED DESCRIPTION

[0044] In the description of the present application, the terms "center", "up", "down", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., which indicate orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, "multiple" means two or more.

[0045] In the description of this application, unless otherwise specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. A person of ordinary skill in the art will be able to understand the meanings of the above terms in this application based on the specific circumstances.

[0046] The technical solution of this application is described below with reference to the accompanying drawings and through specific implementation methods.

[0047] In a specific embodiment, the present application provides a composite current collector, as shown in Figures 1 and 2, comprising a substrate 1, a first metal layer 2 and a second metal layer 3, wherein the first metal layer 2 and the second metal layer 3 are respectively provided on the opposite side surfaces of the substrate 1, and the composite current collector is divided into a blank area 4 and an electrode area 5 along its width direction, wherein the blank area 4 is configured to form a pole ear, and the electrode area 5 is an area configured to coat an active material slurry, and a plurality of through holes 6 are distributed in the blank area 4, wherein the through holes 6 sequentially penetrate the first metal layer 2, the substrate 1 and the second metal layer 3, and a conductive layer 7 is provided inside the through hole 6, wherein the two ends of the conductive layer 7 are respectively connected to the first metal layer 2 and the second metal layer 3.

[0048] The blank area 4 is located at one side edge of the composite current collector, and the width of the blank area 4 is smaller than the width of the electrode area 5. In this application, the electrode area 5 of the composite current collector is configured to be coated with active material, while the blank area 4 is provided at one side edge of the composite current collector to be flattened during battery assembly to form a tab and welded to the current collecting plate. The blank area 4 is not coated with active material, which helps to reduce the thickness, reduce the battery weight, and increase the battery energy density. When the width of the composite current collector is 30-80 mm, the width of the blank area 4 is 5-10 mm.

[0049] In this embodiment, FIG. 1 is a partial cross-sectional schematic diagram along the thickness direction of the composite current collector, which only shows a portion of the conductive layer 7 disposed in the through hole 6 .

[0050] The composite current collector of the present application adopts a multi-layer composite structure of an intermediate substrate + metal layers on both sides, which has a high energy density and is conducive to reducing the weight of the battery. A plurality of densely distributed through holes are formed in the blank area of ​​the composite current collector, and a conductive layer is arranged in the through holes, so that the first metal layer and the second metal layer of the upper and lower layers are conductive, thereby reducing the internal resistance of the battery and improving the electrical performance.

[0051] In some embodiments, the substrate 1 includes a polymer layer. The material of the polymer layer in the present application can be any one of polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate, polypropylene, polyamide, polyimide, polyethylene, polyethylene oxide, polyvinyl chloride, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, polyvinyl alcohol, styrene-butadiene rubber, fluorinated rubber, etc., or a combination of at least two. The materials of the first metal layer 2 and the second metal layer 3 independently include any one of copper, aluminum, gold, tungsten, platinum, cobalt, magnesium, zinc or titanium. The composite current collector of the present application can be a positive electrode current collector or a negative electrode current collector. Those skilled in the art can adjust the materials of the substrate 1, the first metal layer 2 and the second metal layer 3 according to actual conditions. For example, the positive electrode current collector can be a composite aluminum foil, and the negative electrode current collector can be a composite copper foil. In the present application, the substrate 1 adopts a polymer layer with insulating properties, so that the first metal layer 2 and the second metal layer 3 arranged opposite to each other cannot be directly conductive. Therefore, by forming a through hole 6 in the blank area 4 and filling the through hole 6 with a conductive layer 7, the first metal layer 2 and the second metal layer 3 on both sides of the composite current collector are electrically connected, thereby reducing the weight of the battery and the internal resistance of the battery cell.

[0052] In some embodiments, as shown in FIG3 , the average pore size of the through hole 6 is 0.5 to 3 mm. The through hole 6 is a polygonal hole, and the number of sides of the polygonal hole is 3 to 20. The polygonal hole can be, for example, a triangular hole, a quadrilateral hole, a pentagonal hole, a hexagonal hole, a heptagonal hole, an octagonal hole, a nonagonal hole or a decagonal hole. The through hole 6 can be in the shape of a polygonal star, including a triangle, a quadrilateral, a pentagonal star, a hexagonal star, a heptagonal star, an octagonal star or a nonagonal star. In this application, the number of sides of the polygonal hole is limited to 3 to 20, which not only increases the conduction cross-section and helps to reduce the internal resistance of the battery, but also ensures the tensile strength of the composite current collector and avoids the problem of welding wire falling off and disconnecting during the electrode flattening process.

[0053] The hole coverage of the plurality of through holes 6 within the blank area 4 is 30% to 80%. The hole coverage refers to the ratio of the total hole area of ​​the plurality of through holes 6 to the area of ​​the blank area 4. Furthermore, the shapes and sizes of the different through holes 6 within the blank area 4 can be the same or different. For ease of processing, multiple through holes 6 of the same shape and size can be used.

[0054] In another specific embodiment, the present application provides a method for preparing the composite current collector described in the above specific embodiment, the preparation method comprising:

[0055] (I) A substrate 1 is provided, and a first metal layer 2 and a second metal layer 3 are formed on two opposite surfaces of the substrate 1 .

[0056] (II) A blank area 4 and an electrode area 5 are divided along the width direction of the substrate 1, and laser drilling is performed in the blank area 4 to form a through hole 6 that sequentially penetrates the first metal layer 2, the substrate 1 and the second metal layer 3. The laser uses picosecond ultraviolet light with a wavelength of 350 to 455 nm, and the power of the laser drilling is 3 to 35 W.

[0057] (III) Filling the through hole 6 with a conductive paste to form a conductive layer 7, so that the first metal layer 2 and the second metal layer 3 are connected to each other, wherein the conductive paste includes any one of silver paste, nickel paste, copper paste or aluminum paste, and the coating amount of the conductive paste is 0.1 to 1 g / m 2 .

[0058] The present application divides the composite current collector into a blank area and an electrode area, and punches holes in the blank area. A conductive slurry is applied on the cross section of the hole so that the first metal layer and the second metal layer are interconnected, which is beneficial to reducing the internal resistance of the battery cell and improving the electrical performance of the battery.

[0059] This application does not limit or impose special requirements on the coating process of the conductive paste. Any method known to those skilled in the art for coating the conductive paste may be used. For example, a glue needle may be used, and the amount of conductive paste coated may be controlled by a precision feed pump configured at the rear of the needle.

[0060] In another specific embodiment, the present application provides an electrode, comprising the composite current collector described in the above specific embodiment, and an active material layer 8 disposed within the electrode region 5 of the composite current collector, wherein the blank region 4 is wound and bent to form a pole ear portion. In the present application, the electrode region 5 and the active material layer 8 of the composite current collector form the body of the electrode, and the blank region 4 of the composite current collector is wound and bent to form the pole ear portion of the electrode. Depending on the composite current collector, the electrode can be either a positive electrode or a negative electrode.

[0061] In another specific embodiment, the present application provides a method for manufacturing the electrode in the above specific embodiment, the manufacturing method comprising:

[0062] S1 provides a substrate 1 , forms a first metal layer 2 and a second metal layer 3 on two opposite sides of the substrate 1 , and divides a blank area 4 and an electrode area 5 along the width direction of the substrate 1 .

[0063] S2 punches a hole in the blank area 4 to form a through hole 6 that sequentially passes through the first metal layer 2, the substrate 1 and the second metal layer 3, and fills the hole of the through hole 6 with a conductive paste to form a conductive layer 7, so that the first metal layer 2 and the second metal layer 3 are interconnected to obtain a composite current collector.

[0064] S3: coating the active material slurry in the electrode region 5 of the composite current collector to form an active material layer 8.

[0065] S4 cuts the blank area 4 to form a plurality of tabs, and then rolls and flattens the tabs to obtain the electrode.

[0066] In another specific embodiment, the present application provides another method for manufacturing the electrode described in the above specific embodiment, the manufacturing method comprising:

[0067] S01 provides a substrate 1, forms a first metal layer 2 and a second metal layer 3 on the opposite sides of the substrate 1, divides a blank area 4 and an electrode area 5 along the width direction of the substrate 1, and coats an active material slurry on the surface of the electrode area 5 to form an active material layer 8.

[0068] S02 punches a hole in the blank area 4 to form a through hole 6 that sequentially passes through the first metal layer 2, the substrate 1 and the second metal layer 3, and fills the hole of the through hole 6 with a conductive paste to form a conductive layer 7, so that the first metal layer 2 and the second metal layer 3 are interconnected to obtain a composite current collector with an active material layer 8 provided on the surface.

[0069] S03: cutting the blank area 4 to form a plurality of tabs, and then rolling and flattening the tabs to obtain the electrode.

[0070] This application does not impose any restrictions or special requirements on the coating process of the active material slurry in the above two manufacturing processes. Any method for coating the active material slurry known to those skilled in the art can be used. For example, the pre-prepared active material slurry can be coated on the electrode area 5 of the composite current collector by narrow slit extrusion. In addition, during the cutting process of the above two manufacturing processes, the blank area 4 is cut at an angle of 30 to 60 degrees. The tabs formed after cutting are conducive to the flattening operation, and the punching area is smaller than the cutting area of ​​the tabs to avoid wrinkles or breaks.

[0071] The composite current collector in the electrode of the present application is perforated in the blank area 4 to form densely distributed through holes 6, and a conductive material is coated on the cross section produced by the perforation to make the upper and lower metal layers conductive, providing a feasible method for the application of composite current collectors in cylindrical full-pole tab batteries, reducing the internal resistance of the battery cell and solving the problem of low-impedance welding between the composite current collector and the current collecting plate. In order to help those skilled in the art understand the overall technical solution and working process of the present application, the present application exemplarily provides the following method for manufacturing a cylindrical full-pole tab battery, including the following steps:

[0072] Option 1:

[0073] (1) A substrate 1 is provided for use as a positive electrode and a negative electrode, respectively. A first metal layer 2 and a second metal layer 3 are formed on opposite sides of the substrate 1, respectively. A blank area 4 and an electrode area 5 are divided along the width direction of the substrate 1.

[0074] (2) Laser drilling is performed in the blank area 4 to form a through hole 6 that sequentially penetrates the first metal layer 2, the substrate 1, and the second metal layer 3, and a conductive paste is filled in the hole of the through hole 6 to form a conductive layer 7, so that the first metal layer 2 and the second metal layer 3 are interconnected to obtain a positive composite current collector and a negative composite current collector, respectively.

[0075] (3) Prepare the required positive electrode active material slurry and negative electrode active material slurry, and use a narrow slit extrusion method to coat the positive electrode active material slurry on the electrode area 5 of the positive electrode composite current collector to form a positive electrode active material layer 8, thereby obtaining a positive electrode sheet. Simultaneously, use a narrow slit extrusion method to coat the negative electrode active material slurry on the electrode area 5 of the negative electrode composite current collector to form a negative electrode active material layer 8, thereby obtaining a negative electrode sheet.

[0076] (4) Roll-press the positive and negative electrodes to reduce the thickness of the electrodes and increase the volume energy density of the battery.

[0077] (5) The blank area 4 of the positive electrode sheet is cut at an angle of 30 to 60 degrees to form a plurality of positive electrode tabs, and the blank area 4 of the negative electrode sheet is cut at an angle of 30 to 60 degrees to form a plurality of negative electrode tabs.

[0078] (6) Provide a diaphragm and a shell, and prepare an electrolyte. Stack the positive electrode sheet, diaphragm, and negative electrode sheet in sequence, wind them into a cylindrical shape, and place them in the shell. Flatten the positive and negative electrode ears, and laser weld the current collecting plates separately. After injecting the electrolyte into the shell, seal and fix the open end of the shell.

[0079] Option 2:

[0080] (1) A substrate 1 is provided for use as a positive electrode and a negative electrode, respectively. A first metal layer 2 and a second metal layer 3 are formed on opposite sides of the substrate 1, respectively. A blank area 4 and an electrode area 5 are divided along the width direction of the substrate 1.

[0081] (2) Prepare the required positive electrode active material slurry and negative electrode active material slurry, and use a narrow slit extrusion method to coat the positive electrode active material slurry on the surface of the electrode area 5 used as the positive electrode to form a positive electrode active material layer 8. At the same time, use a narrow slit extrusion method to coat the negative electrode active material slurry on the surface of the electrode area 5 used as the negative electrode to form a negative electrode active material layer 8. Then, roll press them separately to reduce the thickness of the electrode sheet and improve the volume energy density of the battery.

[0082] (3) Laser drilling is performed in the blank area 4 to form a through hole 6 that passes through the first metal layer 2, the substrate 1 and the second metal layer 3 in sequence, and a conductive paste is filled in the hole of the through hole 6 to form a conductive layer 7, so that the first metal layer 2 and the second metal layer 3 are connected to each other to obtain a positive electrode sheet and a negative electrode sheet.

[0083] (4) The blank area 4 of the positive electrode sheet is cut at an angle of 30 to 60 degrees to form a plurality of positive electrode tabs, and the blank area 4 of the negative electrode sheet is cut at an angle of 30 to 60 degrees to form a plurality of negative electrode tabs.

[0084] (5) Provide a diaphragm and a shell, and prepare an electrolyte. Stack the positive electrode sheet, diaphragm, and negative electrode sheet in sequence, wind them into a cylindrical shape, and place them in the shell. Flatten the positive and negative electrode ears, and laser weld the current collecting plates separately. After injecting the electrolyte into the shell, seal and fix the open end of the shell.

[0085] Example 1

[0086] This embodiment provides a composite current collector, comprising a substrate 1, a first metal layer 2 and a second metal layer 3. The first metal layer 2 and the second metal layer 3 are respectively provided on the opposite side surfaces of the substrate 1. The width of the composite current collector is 50 mm, and it is divided into a blank area 4 and an electrode area 5 along its width direction. The blank area 4 is located at one edge of the composite current collector and has a width of 5 mm. The electrode area 5 is from the edge of the blank area 4 to the other edge of the composite current collector. A plurality of triangular through holes 6 with an average aperture of 1.5 mm are densely distributed in the blank area 4. The through holes 6 pass through the first metal layer 2, the substrate 1 and the second metal layer 3 in sequence. The hole coverage rate of the plurality of through holes 6 in the blank area 4 is 70%, and a conductive layer 7 is provided on the hole wall surface of the through hole 6. The two ends of the conductive layer 7 are respectively connected to the first metal layer 2 and the second metal layer 3. The substrate 1 is made of polyethylene, and the materials of the first metal layer 2 and the second metal layer 3 are both aluminum foil.

[0087] Example 2

[0088] This embodiment provides a composite current collector, which differs from the first embodiment in that the through holes 6 in the blank area 4 are quadrilateral holes, and the other structural parameters are the same as those of the first embodiment.

[0089] Example 3

[0090] This embodiment provides a composite current collector, which differs from the first embodiment in that the through hole 6 in the blank area 4 is in the shape of a five-pointed star, and the other structural parameters are the same as those of the first embodiment.

[0091] Example 4

[0092] This embodiment provides a composite current collector, which differs from the first embodiment in that the through hole 6 in the blank area 4 is in the shape of a hexagonal star, and the other structural parameters are the same as those of the first embodiment.

[0093] Example 5

[0094] This embodiment provides a composite current collector, which differs from the first embodiment in that the through hole 6 in the blank area 4 is in the shape of a seven-pointed star, and the other structural parameters are the same as those of the first embodiment.

[0095] Example 6

[0096] This embodiment provides a composite current collector, which differs from the first embodiment in that the through hole 6 in the blank area 4 is in the shape of an octagonal star, and the other structural parameters are the same as those of the first embodiment.

[0097] Example 7

[0098] This embodiment provides a composite current collector, which differs from the first embodiment in that the through hole 6 in the blank area 4 is in the shape of a nine-pointed star, and the other structural parameters are the same as those of the first embodiment.

[0099] Example 8

[0100] This embodiment provides a composite current collector, which differs from the embodiment 4 in that the hole coverage of the plurality of through holes 6 in the blank area 4 is 20%, and the other structural parameters are the same as those of the embodiment 4.

[0101] Example 9

[0102] This embodiment provides a composite current collector, which differs from the fourth embodiment in that the hole coverage of the plurality of through holes 6 in the blank area 4 is 90%, and the other structural parameters are the same as those of the fourth embodiment.

[0103] Comparative Example 1

[0104] This comparative example provides a composite current collector, which differs from Example 1 in that no through hole 6 is provided in the blank area 4 .

[0105] In this application, the materials of the first metal layer and the second metal layer of the composite current collector in Examples 1 to 9 and Comparative Example 1 are used to prepare a positive electrode (the first metal layer 2 and the second metal layer 3 are both aluminum foil) and a negative electrode (the first metal layer 2 and the second metal layer 3 are both copper foil), respectively. The prepared positive and negative electrodes are then used to make cylindrical batteries, and the internal resistance of the cylindrical batteries and the laser welding tensile force are measured respectively. The results are shown in Table 1.

[0106] (1) The test method for the internal resistance of the battery in this application is:

[0107] A constant DC current (50A) is forced through the cylindrical battery for a short period of time (2 to 3 seconds). The voltage across the battery is measured at this time, and the current internal resistance of the battery is calculated based on the physical formula R=U / I.

[0108] (2) The test method for the laser welding tensile strength of the battery in this application is:

[0109] The test is carried out using a tensile gauge. The tensile gauge fixture clamps the two ends of the cylindrical battery at a test speed of 20mm / min until it breaks. The value displayed on the tensile gauge is the welding tension.

[0110] Table 1

[0111] As can be seen from Table 1, the internal resistance of batteries prepared using the composite current collectors of Examples 1-9 is relatively low, no higher than 40 mΩ, while the internal resistance of batteries prepared using the composite current collector of Comparative Example 1 is very high, reaching 120 mΩ, much higher than that of Examples 1-9. This is primarily because the composite current collectors of Examples 1-9, by providing through-holes 6 and disposing conductive layers 7 within the holes, connect the upper and lower metal layers, significantly reducing the battery resistance and achieving a significant improvement.

[0112] As can be seen from Table 1, in Examples 1 to 7, as the number of sides of the through hole 6 increases, the internal resistance of the battery decreases, and at the same time, the welding tension decreases. This is because the number of sides of the through hole 6 increases, which can increase the length of the wire for conduction between the upper and lower layers, but also reduces the welding wire area and the tensile strength of the blank area 4, resulting in a decrease in tension. Since the battery requires a welding tension greater than 10N, the hexagonal star-shaped through hole 6 has the best effect.

[0113] Compared to Example 4, when the hole coverage of through-holes 6 in the blank area 4 in Example 8 was less than 30%, the internal resistance of the resulting battery increased. This is because the smaller number of through-holes 6 in the blank area 4 reduces the connection area between the first metal layer 2 and the second metal layer 3 on the upper and lower layers of the substrate 1, reducing the conductivity and resulting in an increase in battery resistance. In Example 9, when the hole coverage of through-holes 6 in the blank area 4 was greater than 80%, the welding tension decreased. This is because the excessive number of through-holes 6 reduced the strength of the composite current collector, and the perforated area exceeded the cutting area, which was prone to wrinkling or breakage.

[0114] The present application provides a composite current collector and its preparation method, an electrode and its manufacturing method and application. The composite current collector adopts a multi-layer composite structure of an intermediate substrate + metal layers on both sides, has a high energy density, and is conducive to reducing the weight of the battery. A plurality of densely distributed through holes are formed in the blank area of ​​the composite current collector, and a conductive layer is arranged in the through holes, so that the first metal layer and the second metal layer of the upper and lower layers are conductive, reducing the internal resistance of the battery. The internal resistance of the prepared battery is not higher than 40mΩ, which improves the electrical performance of the battery, provides a feasible way for the application of composite current collectors in cylindrical full-ear batteries, effectively improves the welding strength between the composite current collector and the current collecting plate, and solves the problem of low-impedance welding between the composite current collector and the current collecting plate.

Claims

1. A composite current collector, comprising a substrate (1), a first metal layer (2) and a second metal layer (3), wherein the first metal layer (2) and the second metal layer (3) are respectively arranged on opposite side surfaces of the substrate (1), and the composite current collector is divided into a blank area (4) and an electrode area (5) along the width direction of the composite current collector, wherein the blank area (4) is arranged to form a pole ear, and the electrode area (5) is an area arranged to coat an active material slurry, wherein a plurality of through holes (6) are distributed in the blank area (4), wherein the through holes (6) sequentially penetrate the first metal layer (2), the substrate (1) and the second metal layer (3), and wherein a conductive layer (7) is arranged inside the through hole (6), and the two ends of the conductive layer (7) are respectively connected to the first metal layer (2) and the second metal layer (3).

2. [Corrected 07.09.2023 according to Rule 26] A composite current collector according to claim 1, wherein: The substrate (1) comprises a polymer layer.

3. The composite current collector according to claim 2, wherein: The materials of the first metal layer (2) and the second metal layer (3) independently include one of copper, aluminum, gold, tungsten, platinum, cobalt, magnesium, zinc or titanium.

4. [Corrected 07.09.2023 according to Rule 26] A composite current collector according to any one of claims 1 to 3, wherein: The average pore diameter of the through hole (6) is 0.5 to 3 mm.

5. [Corrected 07.09.2023 according to Rule 26] A composite current collector according to claim 4, wherein: The through hole (6) is a polygonal hole.

6. [Corrected 07.09.2023 according to Rule 26] A composite current collector according to claim 5, wherein: The through hole (6) is in the shape of a polygonal star.

7. [Corrected 07.09.2023 according to Rule 26] A composite current collector according to claim 5, wherein: The polygonal hole has 3 to 20 sides.

8. [Corrected 07.09.2023 according to Rule 26] A composite current collector according to claim 4, wherein: The hole coverage rate of the plurality of through holes (6) in the blank area (4) is 30 to 80%.

9. The composite current collector according to claim 4, wherein: The blank area (4) is located at one side edge of the composite current collector, and the width of the blank area (4) is smaller than the width of the electrode area.

10. A preparation method for preparing the composite current collector according to any one of claims 1 to 9, the preparation method comprising: Providing a substrate, and forming a first metal layer and a second metal layer on two opposite side surfaces of the substrate respectively; Dividing a blank area and an electrode area along the width direction of the substrate, and drilling holes in the blank area to form through holes that sequentially penetrate the first metal layer, the substrate, and the second metal layer; A conductive paste is filled in the hole of the through hole to form a conductive layer, so that the first metal layer and the second metal layer are connected to each other.

11. [Corrected 07.09.2023 in accordance with Rule 26] A process according to claim 10, wherein: The punching is performed by laser punching.

12. [Corrected 07.09.2023 in accordance with Rule 26] A process according to claim 11, wherein: The laser includes picosecond ultraviolet light.

13. [Corrected 07.09.2023 in accordance with Rule 26] A process according to claim 12, wherein: The wavelength of the laser is 350-455 nm.

14. The preparation method according to claim 13, wherein: The power of the laser drilling is 3-35W.

15. [Corrected 07.09.2023 in accordance with Rule 26] A process according to any one of claims 10 to 14, wherein: The conductive paste includes one of silver paste, nickel paste, copper paste or aluminum paste.

16. The preparation method according to claim 15, wherein: The coating amount of the conductive paste is 0.1 to 1 g / m2.

17. An electrode, comprising the composite current collector according to any one of claims 1 to 9, and an active material layer (8) arranged in an electrode region (5) of the composite current collector, wherein the blank region (4) of the composite current collector is bent after winding to form an electrode ear portion.

18. A method for preparing the electrode according to claim 17, the method comprising: Providing a substrate, forming a first metal layer and a second metal layer on two opposite side surfaces of the substrate, respectively, and dividing a blank area and an electrode area along a width direction of the substrate; Punching holes in the blank area to form through holes that sequentially penetrate the first metal layer, the substrate, and the second metal layer, and filling the holes of the through holes with a conductive paste to form a conductive layer, so that the first metal layer and the second metal layer are connected to each other to obtain a composite current collector; Coating active material slurry in the electrode region of the composite current collector to form an active material layer; The blank area is cut to form a plurality of pole tabs, and the pole tabs are rolled up and flattened to obtain the electrode.

19. A method for preparing the electrode according to claim 17, the method comprising: Providing a substrate, forming a first metal layer and a second metal layer on two opposite sides of the substrate, dividing a blank area and an electrode area along the width direction of the substrate, and coating an active material slurry on the surface of the electrode area to form an active material layer; Punching holes in the blank area to form through holes that sequentially penetrate the first metal layer, the substrate, and the second metal layer, and filling the holes of the through holes with a conductive paste to form a conductive layer, so that the first metal layer and the second metal layer are connected to each other, so as to obtain a composite current collector with the active material layer disposed on the surface; The blank area is cut to form a plurality of pole tabs, and the pole tabs are rolled up and flattened to obtain the electrode.

20. Use of the electrode according to claim 17, wherein: The electrode is configured as a cylindrical full-tab battery.

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