Composite current collector and processing method thereof, battery

Abstract

This invention provides a composite current collector, comprising a composite current collector body and a tab region, wherein the tab region of the composite current collector used to fabricate a negative electrode sheet has a pure copper layer. The composite current collector manufacturing process of this invention includes the following steps: First, a metal layer is sputtered onto the surface of a polymer material using physical vapor deposition; second, the surface metal layer is thickened using ion replacement or electroplating; third, the metal layer undergoes washing, anti-oxidation treatment, and drying; fourth, copper foil is electrolyzed at the edge of the composite current collector, surface treated, and slit; fifth, the current collector is packaged and shipped. This invention also provides a battery using the aforementioned composite current collector. This invention, with only simple processing of the composite current collector, can effectively improve the welding conductivity of the tab region in battery applications and reduce the resistance, allowing the battery to better utilize its energy.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and in particular to a composite current collector and its processing method, and a battery. Background Technology

[0002] Composite current collectors offer superior flexibility and mechanical strength, reducing the likelihood of electrode breakage during rolling and use. Their high ductility allows them to effectively contain the fractured metal layers when lithium-ion batteries are subjected to external physical impacts, especially from sharp or heavy objects. This prevents the fractured metal layers from puncturing the separator and causing short circuits, thus mitigating the risk of internal short circuits and thermal runaway in lithium-ion batteries after impact. The polymer film, used as a substrate, has a lower mass density, reducing overall battery weight and increasing energy density. However, welding between current collector tabs or between current collector tabs and external electrodes can be challenging. Using composite current collectors directly in batteries without proper treatment results in poor conductivity, high resistance, and reduced energy efficiency.

[0003] Chinese invention patent application CN111900413A discloses a method for welding composite current collector tabs in lithium batteries. This method involves pre-welding the composite current collector tabs by clamping them together with two metal tabs, then stacking them with conventional tabs at intervals, and finally welding multiple layers of tabs together to improve conductivity. While this patented method can solve the problem of poor conductivity during the welding process of composite current collectors, the operation is complex, requiring equipment upgrades, specialized personnel training, and the increased complexity can also compromise battery consistency. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a composite current collector and its processing method, which can solve the problems of poor conductivity, high resistance and poor energy utilization of composite current collectors at the electrode tab in battery applications in a simple and effective way.

[0005] To achieve the above and other related objectives, the present invention provides a composite current collector, comprising a composite current collector body and a tab region, wherein the tab region of the composite current collector for fabricating a negative electrode sheet has a pure copper layer.

[0006] In one embodiment of the present invention,

[0007] The insulating layer in the middle of the composite current collector body is a high molecular polymer;

[0008] The metal layers on both sides of the composite current collector body are copper or aluminum.

[0009] In one embodiment of the present invention, the tab region of the negative electrode sheet is formed by electroplating pure copper at the edge of the negative electrode composite current collector.

[0010] In one embodiment of the present invention, the composite current collector is rolled and slit to obtain an electrode sheet, and the tab region is disposed on the electrode sheet.

[0011] In one embodiment of the invention, the composite flow collector is prepared before the slurry is applied.

[0012] In one embodiment of the present invention, the composite current collector is prepared after the slurry is coated.

[0013] The present invention also provides a method for processing a composite current collector, wherein the composite current collector described in any of the above-mentioned embodiments is obtained, and a pure copper layer is plated on the edge of the negative electrode composite current collector as the tab region.

[0014] In one embodiment of the present invention, the following process steps are included:

[0015] The first step is to sputter a layer of metal onto the surface of the polymer material using physical vapor deposition.

[0016] The second step is to thicken the surface metal layer using ion replacement or electroplating methods.

[0017] The third step involves washing the metal layer with water, treating it against oxidation, and drying it.

[0018] The fourth step involves electrolyzing copper foil at the edge of the composite current collector, surface treatment, and slitting.

[0019] Step 5: Pack and ship.

[0020] In one embodiment of the present invention, the tab region is formed by a pure copper plating extending from the edge of the negative electrode composite current collector, or the tab region is formed by a pure copper plating covering the edge of the negative electrode composite current collector.

[0021] The present invention also provides a battery employing the composite current collector described in any of the above claims.

[0022] As described above, the composite current collector and its processing method of the present invention have the following beneficial effects: by simply processing the composite current collector, the welding conductivity of the tab part of the composite current collector in battery applications can be effectively improved and the resistance value can be reduced, so that the energy of the battery can be better utilized. Attached Figure Description

[0023] Figure 1 The diagram shown is a structural schematic of an embodiment of the composite current collector of the present invention.

[0024] Figure 2The diagram shown is a structural schematic of another embodiment of the composite current collector of the present invention.

[0025] Figure 3 The diagram shows the steps of the composite current collector and its processing method according to the present invention.

[0026] Component designation explanation

[0027] Metal layer 1; Insulating layer 2; Tab region 3. Detailed Implementation

[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. It should also be understood that the terminology used in the embodiments of the present invention is for describing specific implementation schemes and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0029] Please see Figures 1 to 3 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness or purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0030] Please see Figure 1 The present invention provides a composite current collector, comprising a composite current collector body and a tab region, wherein the tab region of the composite current collector used to make a negative electrode sheet has an additional pure copper plating layer.

[0031] Composite current collectors are composite materials made by depositing copper / aluminum molecules on both sides of a polymer film such as PET (polyethylene terephthalate) as a base film through processes such as vacuum coating, forming a "sandwich" type composite structure. For example... Figure 1As shown, the middle isolation layer 2 is a polymer layer, and the two sides are stacked metal layers 1.

[0032] Typically, the metal layer of the positive current collector is aluminum, and the metal layer of the negative current collector is copper. Based on the properties of copper, this invention uses a common copper plating process to plate an additional layer of pure copper onto the tab area of ​​the composite current collector (i.e., the negative current collector) used to make the negative electrode sheet, in order to enhance the weldability and conductivity of the negative current collector tab.

[0033] Furthermore, on top of the metal layer 1 (i.e., copper film) of the negative electrode current collector, a layer of pure copper with a purity of 99% is electroplated onto the composite current collector on a conventional copper foil electroplating roller to form the tab area 3. This process can be performed before or after the composite current collector is coated with slurry. This ensures both the high safety and high flexibility of the composite current collector and leverages the excellent conductivity of the pure copper tab, enabling the rapid application of the composite current collector.

[0034] The manufacturing processes for composite copper foil for negative electrode current collectors mainly include one-step, two-step, and three-step methods. The one-step method involves direct chemical deposition or magnetron sputtering to form a copper metal layer on the surface of a polymer film. The two-step method combines magnetron sputtering with electroplating. The three-step method combines magnetron sputtering with vapor deposition and electroplating. Considering both cost and efficiency, the mainstream process for composite copper foil is currently the two-step method. First, a 20–70 nm copper metal layer is formed on the surface of the polymer film using magnetron sputtering, and then electroplating is used to thicken it to approximately 1 μm.

[0035] Common vacuum coating technologies include evaporation coating, magnetron sputtering, and ion plating. Ion plating is an organic combination of the first two technologies.

[0036] The working principle of evaporation coating is to first heat the film material, so that the surface components are evaporated in the form of atomic or molecular clusters and deposited on the surface of the substrate.

[0037] Magnetron sputtering uses high-energy plasma to bombard a target, sputtering surface components as atomic clusters or ions, which then deposit on the substrate surface. Electrons, accelerated towards the substrate under the influence of an electric field, collide with argon atoms, ionizing into a large number of argon ions and electrons. The electrons then fly towards the substrate. The argon ions, accelerated by the electric field, bombard the target, sputtering out a large number of target atoms, resulting in neutral target atoms (or molecules) deposited on the substrate to form a film.

[0038] Electroplating: After magnetron sputtering, the film material has formed a copper layer with a thickness of nanometers and a certain degree of conductivity. In a horizontal continuous electroplating device, under the action of an electric field, copper ions are further deposited on the surface of the film material to form a copper layer with a thickness of about 1 micrometer.

[0039] As a specific embodiment, see [reference] Figure 1The pure copper plating extends from the edge of the composite current collector. Most of the tab region 3 is a pure copper plating, with a small portion covering the metal layer 1 of the composite current collector to connect with it.

[0040] As a specific embodiment, see [reference] Figure 2 The pure copper plating completely covers the metal layer 1 of the composite current collector, serving as the tab region 3.

[0041] As an example, the current collector is a negative electrode current collector. A negative electrode slurry containing a negative electrode active material is coated onto the non-welding area of ​​the first and second metal layers of the negative electrode current collector, and the solvent is evaporated. After rolling and slitting, a negative electrode sheet is obtained. During application, the current collector can be cut according to actual needs to obtain a current collector that meets the requirements. Then, pure copper is plated onto the current collector. The negative electrode active material can be graphite negative electrode material, or a mixture of silicon suboxide negative electrode material and graphite negative electrode material in any proportion. The negative electrode slurry is coated onto the negative electrode current collector, then dried at 110°C, and rolled under 40 tons of pressure. It is then cut according to the required electrode size for the battery, resulting in negative electrode sheets. The final negative electrode sheet has a welding area as the tab area 3.

[0042] As a specific example, the pure copper plating process can also be performed after the composite current collector electrode sheet has been cut.

[0043] The present invention also proposes a battery that uses the composite current collector proposed in the present invention.

[0044] Furthermore, an experiment was designed to test the performance of the composite current collector of this invention. A total of six lithium batteries were used: three lithium batteries used ordinary composite current collectors, and the other three lithium batteries used the composite current collector of this invention, i.e., composite current collector + electroplated copper tabs. The remaining battery characteristics were: lithium iron phosphate positive electrode, artificial graphite negative electrode, soft-pack system, 15-20 Ah. The charge-discharge test was performed for 500 cycles. As can be seen from the experimental data in Table 1, the combination of "composite current collector + electroplated copper tabs" significantly improves both DC impedance and battery degradation, meaning that the conductivity of the lithium battery using the composite current collector of this invention is significantly improved.

[0045] Table 1 Experimental Data

[0046]

[0047]

[0048] This invention also proposes a method for processing composite current collectors to obtain the aforementioned composite current collector. The core of this method lies in plating a pure copper layer onto the edge of a standard negative electrode composite current collector to form the tab region. The specific process steps are as follows:

[0049] S1, a layer of metal is sputtered onto the surface of a polymer material using a physical vapor deposition method;

[0050] S2, the surface metal layer is thickened by ion replacement or electroplating.

[0051] S3, the metal layer then undergoes water washing, anti-oxidation treatment, and drying;

[0052] S4, copper foil is generated by electrolysis at the edge of the composite current collector, followed by surface treatment and slitting;

[0053] S5, packaged and shipped.

[0054] In summary, this invention uses a pure copper layer plated on the edge of a conventional negative electrode composite current collector to form the tab area. This improves the conductivity and reduces the impedance of the welds between the composite current collector tabs or between the composite current collector tab and the external tab. Consequently, the battery composed of the composite current collector exhibits significant improvements in battery degradation rate and conductivity. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0055] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A composite current collector, comprising a composite current collector body and a tab region, characterized in that, The tab region of the composite current collector used to make the negative electrode sheet has a pure copper layer; The insulating layer in the middle of the composite current collector body is a polymer; the metal layers on both sides of the composite current collector body are copper or aluminum. The pure copper layer extends from the edge of the composite current collector, and most of the tab area is a pure copper plating layer, with a small portion covering the metal layer of the composite current collector to connect with it. Alternatively, the pure copper layer can completely cover the metal layer of the composite current collector, serving as the tab region; The insulating layer in the middle of the composite current collector body extends to the tab region.

2. The composite current collector according to claim 1, characterized in that, The composite current collector is rolled and slit to obtain an electrode sheet, and the tab area is disposed on the electrode sheet.

3. The composite current collector according to claim 1, characterized in that, The composite current collector is prepared before the slurry is applied.

4. The composite current collector according to claim 1, characterized in that, The composite current collector is prepared after the slurry is applied.

5. A method for processing a composite current collector, obtaining the composite current collector according to any one of claims 1 to 4, characterized in that, A pure copper layer is plated again at the edge of the negative electrode composite current collector to serve as the tab area.

6. The composite current collector treatment method according to claim 5, characterized in that, The process includes the following steps: The first step is to sputter a layer of metal onto the surface of the polymer material using physical vapor deposition. The second step is to thicken the surface metal layer using ion replacement or electroplating methods. The third step involves washing the metal layer with water, treating it against oxidation, and drying it. The fourth step involves electrolyzing copper foil at the edge of the composite current collector, surface treatment, and slitting. Step 5: Pack and ship.

7. The composite current collector treatment method according to claim 5, characterized in that, The tab area is formed by extending a pure copper plating layer from the edge of the negative electrode composite current collector, or the tab area is formed by covering the edge of the negative electrode composite current collector with a pure copper plating layer.

8. A battery, characterized in that, The composite current collector described in any one of claims 1 to 4 is used.

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