Composite current collector with local enhanced welding area and preparation method of composite current collector

Abstract

The invention relates to the technical field of lithium battery materials, in particular to a composite current collector with a local enhanced welding area and a preparation method thereof.The composite current collector with the local enhanced welding area comprises a composite current collector body, and a through hole is formed in a preset welding area of the composite current collector body; a metal foil is attached to a preset welding area of the composite current collector body and is used for being welded with a tab, and the metal foil covers the through hole. According to the technical scheme provided by the invention, the through holes are formed in the tab preset welding area of the composite current collector to form a microscopic exhaust channel, so that an escape path is provided for gas generated in the welding process, and the compactness and firmness of a welding interface are ensured; by increasing the effective conductive thickness of the predetermined welding area, the sheet resistance and contact resistance of the area are significantly reduced.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, specifically to a composite current collector with a locally reinforced welding zone and its preparation method. Background Technology

[0002] In lithium-ion batteries, with the development of composite current collector technology, sandwich-structured composite current collectors are becoming an important development direction for current collectors due to their advantages of lightweight, high safety and potential low cost.

[0003] However, when composite current collectors are adapted to advanced all-tab battery structures, they face severe welding challenges. The heat generated during the welding process can cause the intermediate polymer substrate to vaporize locally and produce gas. Due to the metal layer, the gas cannot be discharged in time, which can easily form bubbles at the welding interface, leading to poor welding and desoldering, which seriously restricts the manufacturing yield and safety reliability of the battery. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of difficult welding of composite current collectors when adapting to advanced all-tab battery structures. It provides a composite current collector with a locally enhanced welding zone and its preparation method. Without increasing the overall weight and thickness, it achieves performance enhancement only at the key welding points, perfectly balancing multiple goals such as low resistance, high welding reliability, lightweight, and high safety.

[0005] To achieve the above objectives, the present invention provides a composite current collector with a locally enhanced welding area, comprising a composite current collector body, wherein a predetermined welding area of ​​the composite current collector body is provided with a through hole, and a metal foil is attached to the predetermined welding area of ​​the composite current collector body for welding with an electrode tab, wherein the metal foil covers the through hole.

[0006] Preferably, the thickness of the metal foil is no greater than 1 μm.

[0007] Preferably, the metal foil is attached to the predetermined welding area of ​​the composite current collector body through a conductive adhesive layer.

[0008] In another aspect, the present invention provides a method for preparing the above-mentioned composite current collector with locally reinforced welding area, comprising the following steps: S1. The metal foil is deposited on one side of a polymer carrier with weak adhesion to the metal foil; S2. A conductive adhesive is applied to the entire side of the metal foil near the composite current collector body. After drying and curing, the conductive adhesive forms an adhesive layer that is firmly bonded to the metal foil. S3. The metal foil is attached to the predetermined welding area of ​​the composite current collector body and covers the through hole of the predetermined welding area of ​​the composite current collector body, so that the metal foil is separated from the polymer carrier, and a composite current collector with a locally enhanced welding area is obtained.

[0009] Preferably, the polymer carrier is configured as a release film.

[0010] Preferably, the thickness of the adhesive layer formed after the conductive adhesive has dried and cured is set to 0.5-1 μm.

[0011] Preferably, the separation of the metal foil from the polymer carrier is performed by a rewinding and laminating machine, wherein the metal foil is mounted on the upper shaft of the rewinding and laminating machine, and the composite current collector body is mounted on the lower shaft of the rewinding and laminating machine.

[0012] Preferably, the temperature of the attaching roller is set to 95-105°C when the metal foil is attached to the predetermined welding area of ​​the composite current collector body.

[0013] Preferably, the composite current collector body includes a substrate, a through hole is formed by drilling a hole in a predetermined welding area of ​​the substrate, an underlayer and a metal layer are respectively plated on at least one side of the substrate, and an underlayer and a metal layer of the same thickness are plated on the inner wall of the through hole.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: In the technical solution provided by this invention, by setting through holes in the predetermined welding area of ​​the tab of the composite current collector, a microscopic exhaust channel is formed, providing an escape path for the gas generated during the welding process, ensuring that the welding interface is dense and firm. In addition, by setting metal foil in the predetermined welding area of ​​the tab of the composite current collector, the effective conductive thickness of the predetermined welding area is increased, and the sheet resistance and contact resistance of the area are significantly reduced. The advantages of the composite current collector are successfully combined with the requirements of the full tab structure, providing an ideal solution for high-performance and high-safety lithium batteries. Attached Figure Description

[0015] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts. Wherein: Figure 1 This is a schematic diagram of a composite current collector with a locally reinforced welding zone.

[0016] The diagram shows the following labels: 1. Substrate; 2. Underlayer; 3. Metal layer; 4. Metal foil; 5. Adhesive layer; 6. Through-hole. Detailed Implementation

[0017] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0018] This invention provides a specific embodiment of a composite current collector with a locally reinforced welding zone, such as... Figure 1 As shown, the substrate 1 is made of a non-polar or low surface energy polymer material, such as PP, PE, PS, PTFE, PMMA, PET, PA, PI, etc. The thickness of the substrate 1 is 2.5-8μm. The predetermined welding area of ​​the substrate 1 is provided with a number of through holes 6. The pore diameter of the through holes 6 is 10-150μm, and the density of the through holes 6 is 20-200 holes / square centimeter. The substrate 1 is coated with a base layer 2 and a metal layer 3 on both sides. It should be noted that the base layer 2 and the metal layer 3 can also be coated only on one side of the substrate 1. This embodiment is described with the base layer 2 and the metal layer 3 coated on both sides of the substrate 1. The inner wall of the through holes 6 is coated with a base layer 2 and a metal layer 3 of the same thickness. The through holes 6 form a microscopic exhaust channel, providing an escape path for the gas generated during the welding process, ensuring that the welding interface is dense and strong.

[0019] A metal foil 4 is attached to the predetermined welding area of ​​the metal layer 3 on one side of the substrate 1 via an adhesive layer 5. The metal foil 4 is used to weld with the electrode tab. The adhesive layer 5 is a dry film formed by curing conductive adhesive. The thickness of the adhesive layer 5 is set to 0.5-1μm to ensure conductivity. The metal foil 4 covers the through hole 6. The thickness of the metal foil 4 is no more than 1μm to ensure that it does not significantly increase the overall weight and cost. The entire surface of the metal foil 4 on the side close to the composite current collector body is attached to the adhesive layer 5 to ensure stable attachment. By attaching the metal foil 4 to the predetermined welding area, the effective conductive thickness of the welding area is increased, and the sheet resistance and contact resistance of the area are significantly reduced.

[0020] In another aspect, the present invention provides a method for preparing the above-mentioned composite current collector having a locally reinforced welding area, comprising depositing a metal foil 4 on one side of a polymer carrier with weak adhesion to the metal foil 4.

[0021] Conductive adhesive is coated onto the entire surface of the metal foil 4 near the composite current collector body. This is achieved using either slit extrusion coating or microgravure roller coating processes. Both methods enable high-precision, large-area uniform coating. A high-precision metering pump delivers the conductive adhesive to the coating head. The pressure of the coating head, the conveyor speed of the base film, and the supply speed of the adhesive are controlled to ensure a uniform and continuous wet film is formed on the entire surface of the metal foil 4. An online thickness gauge, such as a beta-ray or infrared thickness gauge, is used to monitor the wet film thickness in real time. A closed-loop control system dynamically adjusts the coating parameters to maintain the wet film thickness at 3-4 μm. Slit extrusion coating and microgravure roller coating processes are existing technologies and will not be elaborated upon here.

[0022] After the conductive adhesive is dried and cured, it forms an adhesive layer 5 that is firmly bonded to the metal foil 4. The coated metal foil 4 is then guided through a multi-temperature drying oven, such as a 5-10 meter long tunnel oven, and dried and cured under a specific temperature profile, for example, by stepwise heating from 80℃ to 120℃ to 150℃. This allows the solvent to fully evaporate, and the conductive adhesive is completely cured to form the adhesive layer 5, which is firmly bonded to the metal foil 4. After the solvent evaporates and the wet film is cured, the dry film thickness will be significantly reduced from 3-4μm to 0.5-1μm. The cured metal foil 4 and adhesive layer 5 are cooled by cooling rollers. An online defect detection system is used to check the uniformity of the coating surface and for defects such as pinholes and scratches. Finally, the qualified products are rolled up.

[0023] Next, the metal foil 4 is attached to the predetermined welding area of ​​the composite current collector body and covers the through hole 6 of the predetermined welding area of ​​the composite current collector body, so that the metal foil 4 is separated from the polymer carrier, and a composite current collector with a locally reinforced welding area is obtained after separation.

[0024] In lithium-ion batteries, copper current collectors are typically used for the negative electrode, while aluminum current collectors are used for the positive electrode. Therefore, this application provides the following two embodiments for preparing composite copper foil with locally reinforced welding areas and composite aluminum foil with locally reinforced welding areas, respectively.

[0025] Example 1 This embodiment is used to prepare composite copper foil with locally enhanced welding areas. First, the metal foil 4 is prepared: the release film is fed into a roll-to-roll magnetron sputtering machine for magnetron copper plating with a thickness of 70nm. The material after the magnetron copper plating is completed is then fed into a water plating line for water plating, allowing the single-sided copper layer to thicken rapidly to 1μm, resulting in a pure copper foil with a thickness of 1μm as the metal foil 4. Then, conductive adhesive is coated on the entire surface of the pure copper foil to obtain the adhesive layer 5. Through the pure copper foil, without changing the overall thickness and weight of the current collector, the sheet resistance of the welding area is selectively and precisely reduced by about 40%. This effectively reduces the overall internal resistance of the battery and the heat generation at the welding point, giving the battery better fast charging and discharging capabilities and reducing performance degradation during cycling.

[0026] Next, the composite copper foil body is prepared: a 4.5μm thick substrate 1 is perforated in the predetermined welding area on a roll-to-roll laser machine to obtain several through holes 6 with a diameter of 0.1mm. The perforated substrate 1 is then placed in a roll-to-roll magnetron sputtering machine for magnetron copper plating as the underlayer 2. After double-sided magnetron copper plating, the inner walls of the through holes 6 are also plated with an underlayer 2 of the same thickness as the plane, with a thickness of 70nm. The material with the completed magnetron copper plating underlayer is then placed on a water plating line for water plating copper plating, allowing the copper layer to be quickly deposited. The copper layer 3 is rapidly thickened, and the inner wall of the through hole 6 is also thickened, with the thickness being consistent with that of the planar copper layer. The total thickness of the bottom layer 2 and the metal layer 3 is 1000nm. The through hole 6 provides an effective escape channel for the gas generated during the welding process, fundamentally eliminating bubbling and incomplete soldering. This allows the metal-to-metal interface to be in direct contact, resulting in a strong bond and a welding tensile strength that can be increased by more than 30%. The welding yield is significantly improved, greatly enhancing the process window and consistency of battery manufacturing.

[0027] Finally, the pure copper foil and the composite copper foil body are bonded together, and the pure copper foil and the release film are separated: The release film and pure copper foil are fed to a roll-to-roll slitting machine, which cuts them into the required width for bonding. The pure copper foil is then transferred using a rewinding and bonding machine. The slit release film and pure copper foil are mounted on the upper shaft of the rewinding and bonding machine, while the composite copper foil body is mounted on the lower shaft. After alignment, the pure copper foil is bonded to the predetermined welding area of ​​the composite copper foil body. The temperature of the bonding roller is 100°C. Because the release film has a low surface energy, the copper layer can be easily transferred from the release film and bonded to the predetermined welding area of ​​the composite copper foil body, providing local reinforcement. This yields a roll of composite copper foil with a locally reinforced welding area. This method cleverly utilizes the poor adhesion between the release film and copper, transforming it into an advantage that allows for the perfect transfer of ultra-thin copper foil. This process is highly mature and cost-controllable, providing a reliable and scalable manufacturing path for achieving the aforementioned locally reinforced structure.

[0028] In this embodiment, the pure copper foil provides a better ultrasonic energy conduction path, which promotes welding, while the through hole 6 ensures a perfect bond at the welding interface under the better energy path. Together, they fundamentally overcome the last obstacle for composite current collectors to move towards all-tab applications.

[0029] Example 2 This embodiment is used to prepare composite aluminum foil with locally reinforced welding areas. First, metal foil 4 is prepared: release film is fed into a roll-to-roll evaporation coating machine for single-sided aluminum evaporation coating with a thickness of 1μm, resulting in a pure aluminum foil with a thickness of 1μm as metal foil 4. Then, conductive adhesive is coated on the entire surface of the pure aluminum foil to obtain adhesive layer 5. By increasing the effective conductive thickness of the predetermined welding area of ​​the composite aluminum foil body with pure aluminum foil, the sheet resistance and contact resistance of the area are significantly reduced. This selectively and precisely compensates for the conductivity disadvantage of aluminum, reducing the overall sheet resistance of the welding area. This directly leads to a decrease in battery internal resistance, an improvement in rate performance, and a reduction in heat generation during cycling.

[0030] Next, the composite aluminum foil body is prepared: a 6μm thick substrate 1 is perforated in the predetermined welding area on a roll-to-roll laser machine to obtain several through holes 6 with a diameter of 0.1mm. The perforated substrate 1 is placed in a roll-to-roll magnetron sputtering machine to perform magnetron sputtering alumina coating as the base layer 2. After double-sided magnetron sputtering, the inner wall of the through holes 6 is also coated with the base layer 2 of the same thickness as the plane, with a thickness of 30nm. The material with completed magnetron sputtering is fed to an evaporation aluminum plating machine, and an aluminum layer is coated on the side of the base layer 2 as the metal layer 3. The base layer 2 on the inner wall of the through holes 6 is also coated with the metal layer 3, with the same thickness as the aluminum layer on the plane. The total thickness of the base layer 2 and the metal layer 3 is 1000nm. The through holes 6 form a microscopic exhaust channel, providing an escape path for the gas generated during the welding process, ensuring the smooth discharge of gas, preventing bubbling, and ensuring a dense and firm welding interface.

[0031] Finally, the pure aluminum foil and the composite aluminum foil body are bonded together, and the pure aluminum foil and the release film are separated: The release film and pure aluminum foil are fed to a roll-to-roll slitting machine, which cuts them into the required widths for bonding. The pure aluminum foil is then transferred through a rewinding and laminating machine. The cut release film and pure aluminum foil are mounted on the upper shaft of the rewinding and laminating machine, and the composite aluminum foil body is mounted on the lower shaft. After alignment, the pure aluminum foil is bonded to the predetermined welding area of ​​the composite aluminum foil body. The temperature of the bonding roller is 100℃. Because the surface energy of the release film is low, the aluminum layer can be easily transferred from the release film and bonded to the predetermined welding area of ​​the composite aluminum foil body, playing a local reinforcement role. Thus, a roll of composite aluminum foil with locally reinforced welding area is obtained. This process ingeniously achieves the non-destructive and stable transfer of ultra-thin pure aluminum foil, solving the industry problem of its difficulty in independent production and application. This method has a high degree of maturity and provides a reliable and scalable technical guarantee for realizing local reinforcement of the welding area.

[0032] In this embodiment, the through hole 6 ensures the smooth discharge of gas and prevents bubbling, while the attached ultra-thin pure aluminum layer provides a highly active fresh aluminum surface for welding. The synergistic effect of these two elements fundamentally ensures the robustness and low resistance of the welding interface, thereby improving the welding yield and strength. This successfully combines the advantages of composite current collectors with the requirements of the all-tab structure, providing an ideal positive electrode current collector solution for high-performance, high-safety lithium batteries. Without increasing the overall weight and thickness, performance enhancement is achieved only at key welding points, perfectly balancing multiple objectives such as low resistance, high welding reliability, lightweight, and high safety. This makes the application of composite aluminum foil in positive electrode all-tab batteries possible.

[0033] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A composite current collector with a locally reinforced welding zone, characterized in that: The composite current collector body includes a predetermined welding area with a through hole (6), and a metal foil (4) is attached to the predetermined welding area of ​​the composite current collector body for welding with the electrode tab, the metal foil (4) covering the through hole (6).

2. The composite current collector with a locally reinforced welding zone according to claim 1, characterized in that: The thickness of the metal foil (4) is no greater than 1 μm.

3. The composite current collector with a locally reinforced welding zone according to claim 1, characterized in that: The metal foil (4) is attached to the predetermined welding area of ​​the composite current collector body through a conductive adhesive layer (5).

4. The composite current collector with a locally reinforced welding zone according to claim 3, characterized in that: The thickness of the adhesive layer (5) is set to 0.5-1 μm.

5. A method for preparing a composite current collector with a locally reinforced weld zone as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Coating a metal foil onto a polymer carrier (4). S2. A conductive adhesive is applied to the side of the metal foil (4) away from the polymer carrier to obtain an adhesive layer (5). S3. The metal foil (4) is bonded to the predetermined welding area of ​​the composite current collector body through the adhesive layer (5); S4. Separate the metal foil (4) from the polymer carrier to obtain a composite current collector with a locally reinforced welding area.

6. The method according to claim 5, characterized in that: The polymer carrier is a release membrane.

7. The method according to claim 5, characterized in that: The metal foil (4) and the polymer carrier are separated by a rewinding and laminating machine. The metal foil (4) is installed on the upper shaft of the rewinding and laminating machine, and the composite current collector body is installed on the lower shaft of the rewinding and laminating machine.

8. The method according to claim 7, characterized in that: The temperature of the attachment roller is 95-105°C when the metal foil (4) is attached to the predetermined welding area of ​​the composite current collector body.

9. The method according to claim 5, characterized in that: The composite current collector body includes a substrate (1), through holes (6) are drilled in a predetermined welding area of ​​the substrate (1), and a base layer (2) and a metal layer (3) are plated on at least one side of the substrate (1), and the inner wall of the through hole (6) is plated with a base layer (2) and a metal layer (3) of the same thickness.

Images