Method for connecting pole piece and tab and ultrasonic welding joint

Abstract

The application belongs to the technical field of battery welding formation, and discloses a method for connecting a pole piece and a pole lug and an ultrasonic welding joint. The method for connecting the pole piece and the pole lug comprises the following steps: S1, splicing the pole lug on at least one side surface of the pole piece; S2, welding a welding mark at the splicing position of the pole piece and the pole lug, so that the welding mark connects the pole piece and the pole lug; and S3, filling and coating conductive glue in the welding mark, so that the conductive glue electrically connects the two metal layers of the pole piece. The welding mark is formed at the splicing position of the pole piece and the pole lug, and penetrates the pole piece and the pole lug, so that the two metal layers of the pole piece are electrically connected. The conductive glue is filled and coated in the welding mark, so as to further supplement and strengthen the electronic connection between the two metal layers of the pole piece, and make the electronic connection more stable. In addition, metal dust is generated when the welding mark is formed by welding. The filling and coating of the conductive glue can reduce the free movement of the metal dust in the battery cell, reduce the self-discharge phenomenon of the battery cell, and help to improve the service life of the battery cell.

Description

Technical Field

[0001] This invention relates to the field of battery welding technology, and more particularly to a method for connecting electrode sheets and tabs and an ultrasonic welding head. Background Technology

[0002] Traditional current collectors are typically made of aluminum or copper foil, which are quite hard and prone to puncturing the diaphragm and causing a short circuit if burrs are formed. Composite foil is now commonly used as a current collector. The composite foil has a sandwich structure with a polymer layer in the middle and metal layers on either side.

[0003] The polymer layer in composite foil has advantages such as high tensile strength, soft texture, and thin coating, making it less prone to burrs. Even if burrs do appear, the soft texture and thin coating reduce the likelihood of them puncturing the separator, thus effectively preventing internal short circuits and improving battery safety. Furthermore, the polymer material itself has a low coefficient of thermal expansion and exhibits thermal contraction, further preventing problems such as overheating, combustion, and explosion.

[0004] However, the two sides of the composite foil are not conductive. When connecting the electrode sheet made of composite foil to the tabs, if the tabs are directly connected to both sides of the electrode sheet, the two metal layers of the electrode sheet cannot be made conductive. The traditional process uses ultrasonic welding to make the upper and lower metal layers conductive at the weld teeth, and the current is conducted out by the pure foil. The electronic conductivity at the weld teeth is greatly affected by the welding process fluctuations, resulting in a large and fluctuating internal resistance of the formed cell.

[0005] Therefore, there is an urgent need for a method to connect the electrode plate and the electrode tab to solve the above problems. Summary of the Invention

[0006] The first objective of this invention is to provide a method for connecting an electrode sheet and a tab, which can improve the conductivity stability of the upper and lower metal layers of the electrode sheet made of composite foil, thereby improving the stability of the electrical connection between the electrode sheet and the tab, and reducing the internal resistance and internal resistance fluctuation of the battery cell after molding.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] Methods for connecting the electrode plate and the electrode tab include:

[0009] S1: An electrode tab is spliced ​​onto at least one side of the electrode sheet;

[0010] S2: Welding a solder mark to form a solder mark at the joint between the electrode and the tab, so that the solder mark connects the electrode and the tab;

[0011] S3: Fill the solder stamp with conductive adhesive to make the conductive adhesive electrically connect the two metal layers of the electrode.

[0012] The solder mark electrically connects the two metal layers of the electrode.

[0013] As an alternative to the above-mentioned method of connecting the electrode and the tab, the electrode and the tab are connected by ultrasonic welding, and the ultrasonic welding teeth form the welding mark on the electrode and the tab.

[0014] As an alternative to the above-mentioned method of connecting the electrode and the tab, multiple weld marks are formed at the joint between the electrode and the tab.

[0015] As an alternative to the above-mentioned method of connecting the electrode sheet and the tab, the plurality of solder marks are arranged in a matrix.

[0016] As an alternative to the above-mentioned method of connecting the electrode plate and the electrode tab, the ultrasonic welding teeth form multiple weld marks arranged in a matrix in one welding operation.

[0017] As an alternative to the above-mentioned method of connecting the electrode and the tab, in step S3, the conductive adhesive is applied to both sides of the joint between the electrode and the tab, so that the conductive adhesive fills the solder mark.

[0018] As an alternative to the above-mentioned method of connecting the electrode sheet and the tab, the conductive adhesive can cover all areas where the solder marks are located.

[0019] As an optional solution for the above-mentioned method of connecting the electrode sheet and the electrode tab, the coating thickness of the conductive adhesive on the surface of the electrode tab or the surface of the electrode sheet is 1μm-5μm.

[0020] As an optional solution to the above-mentioned method of connecting the electrode plate and the electrode tab, before step S1, step S01 is further included, which includes:

[0021] The electrode is formed by welding, a metal layer is laminated on both surfaces of the polymer layer, a composite foil is formed by welding, and an electrode paste is coated on the surface of the composite foil to weld the electrode.

[0022] The second objective of this invention is to provide an ultrasonic welding head for ultrasonic welding of electrode plates and electrode tabs.

[0023] To achieve this objective, the present invention adopts the following technical solution:

[0024] An ultrasonic welding head is used in the electrode and tab connection method described above. The ultrasonic welding head includes an upper welding head and a lower welding head, and at least one of the upper welding head and the lower welding head is provided with a plurality of welding teeth arranged in a matrix.

[0025] Beneficial effects:

[0026] The electrode and tab connection method proposed in this invention achieves electrical conductivity between the two metal layers of the electrode and the tab by welding a solder mark at the joint. This is accomplished by filling the solder mark with conductive adhesive, which further supplements and strengthens the electronic conductivity between the two metal layers, making the conductivity more stable. Additionally, the welding process generates metal dust; filling with conductive adhesive reduces the ionization of this dust within the battery cell, decreasing self-discharge and thus extending the battery cell's lifespan. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the composite foil provided in Embodiment 1 of the present invention;

[0028] Figure 2 This is the flowchart of the electrode and tab connection method provided in Embodiment 1 of the present invention. Figure 1 ;

[0029] Figure 3 This is a schematic diagram of the connection between the electrode plate and the electrode tab provided in Embodiment 1 of the present invention;

[0030] Figure 4 This is a schematic diagram of the structure of the electrode sheet and the electrode tab with solder marks provided in Embodiment 1 of the present invention;

[0031] Figure 5 This is a schematic diagram of the structure in which conductive adhesive is disposed within the solder joint of the electrode sheet and the electrode tab according to Embodiment 1 of the present invention;

[0032] Figure 6 This is the flowchart of the electrode and tab connection method provided in Embodiment 1 of the present invention. Figure 2 ;

[0033] Figure 7 This is a schematic diagram of the structure of the ultrasonic welding head provided in Embodiment 2 of the present invention.

[0034] In the picture:

[0035] 1. Composite foil; 11. Polymer layer; 12. First metal layer; 13. Second metal layer;

[0036] 10. Electrode; 101. Welding mark; 20. Electrode tab; 30. Conductive adhesive; 40. Ultrasonic welding head; 401. Welding tooth. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0038] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0040] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0041] Example 1

[0042] To improve battery safety, the use of composite foil for battery current collectors has become common practice in the battery industry. Composite foil has a sandwich-like structure, with the middle polymer layer primarily composed of high-molecular insulating resin and other materials. Metal layers are deposited on both sides of the middle polymer layer using electroplating, chemical plating, or other methods. In actual use, when the battery has a potential risk of thermal runaway, the middle polymer layer melts and cuts off the current, thereby improving battery safety and effectively enhancing its thermal runaway resistance. Furthermore, when the battery is subjected to a needle penetration or other impact, the metal layers on both sides of the polymer layer fracture. The middle polymer layer, due to its own ductility, prevents the fractured surface from piercing the separator and contacting other areas, thus preventing short circuits and solving the internal short circuit problem in battery needle penetration tests.

[0043] Specifically, such as Figure 1As shown, the composite foil 1 includes a polymer layer 11, a first metal layer 12 disposed on the upper surface of the polymer layer 11, and a second metal layer 13 disposed on the lower surface of the polymer layer 11. The polymer layer 11 can be made of high molecular polymers such as PP and PET, and the polymer layer 11 may also include other functional fillers, such as active substances or necessary binders.

[0044] Furthermore, the overall melting point of the polymer layer 11 should be lower than that of the metal layer, so that the polymer layer 11 can melt first when the battery has a potential risk of thermal runaway.

[0045] This embodiment does not have any special requirements for the forming method and material of the first metal layer 12 and the second metal layer 13. The first metal layer 12 and the second metal layer 13 can be obtained by rolling, chemical deposition, electroplating deposition, physical vapor deposition, magnetron sputtering deposition, etc.

[0046] Optionally, the first metal layer 12 and the second metal layer 13 may be made of the same or different materials, and no specific material is restricted here.

[0047] Preferably, the first metal layer 12 and the second metal layer 13 are made of at least one of aluminum, copper, nickel, cobalt, tungsten, tin, lead, iron, silver, or gold. For example, when the composite foil 1 is used as a positive electrode material, the first metal layer 12 and the second metal layer 13 are made of aluminum; when the composite foil 1 is used as a negative electrode material, the first metal layer 12 and the second metal layer 13 are made of copper.

[0048] Regarding the thickness of the polymer layer 11 and the metal layer, if the thickness of the polymer layer 11 is too small, the supporting strength of the current collector formed by welding the composite foil 1 will be insufficient. If the thickness of the polymer layer 11 is too large, it will be detrimental to the improvement of battery energy density and does not conform to the development trend of battery portability. In this embodiment, the thickness of the polymer layer 11 is set to 3μm-8μm, and the thickness of the first metal layer 12 and the second metal layer 13 is 0.5μm-5μm. In actual working conditions, the composite foil 1 of appropriate thickness can be selected according to the design requirements of the battery cell to be produced.

[0049] In one embodiment, the thicknesses of the first metal layer 12 and the second metal layer 13 are equal or unequal. The thickness design of the first metal layer 12 and the second metal layer 13 is reasonably selected within the range of 0.5-5 micrometers according to the actual production requirements of the battery cell.

[0050] Electrode paste is coated onto the surface of composite foil 1, forming a planar surface on the metal layer. After drying, rolling, and die-cutting, electrode sheets are obtained. For composite foil 1 intended to be welded to form a positive electrode sheet, a positive electrode paste is coated onto its surface to form the positive electrode sheet; for composite foil 1 intended to be welded to form a negative electrode sheet, a negative electrode paste is coated onto its surface to form the negative electrode sheet. The composition and coating method of the electrode paste are mature technologies in the prior art and will not be described in detail here.

[0051] The presence of the polymer layer 11 in the composite foil 1 prevents the electrode 10 from being welded to the tab 20. A first metal foil and a second metal foil are needed for welding. The first and second metal foils can serve as tabs 20, or be welded separately to tabs 20. This results in high production costs and complex processes, hindering large-scale production. An adapter welding method is used to make the upper and lower metal layers conductive at the weld teeth, with the pure foil conducting the current. However, the electronic conductivity at the weld teeth is significantly affected by fluctuations in the welding process, resulting in a high and fluctuating internal resistance of the formed cell.

[0052] To solve the above problems, such as Figures 2-5 As shown, this embodiment provides a method for connecting an electrode plate and an electrode tab, including:

[0053] S1: At least one side of the electrode 10 is spliced ​​with an electrode tab 20;

[0054] S2: Weld a solder mark 101 at the joint of the electrode 10 and the tab 20 to connect the electrode 10 and the tab 20.

[0055] S3: Fill the solder mark 101 with conductive adhesive 30 so that the conductive adhesive 30 is electrically conductive to the two metal layers of the electrode 10; the solder mark 101 is electrically conductive to the two metal layers of the electrode 10.

[0056] By welding the electrode 10 and the tab 20 together to form a solder mark 101 connecting the electrode 10 and the tab 20, the two metal layers of the electrode 10 are made conductive. Furthermore, by filling the solder mark 101 with conductive adhesive 30, the electronic conductivity between the two metal layers of the electrode 10 is further supplemented and strengthened, making the electronic conductivity more stable. In addition, metal dust is generated during the welding process of forming the solder mark 101. Filling the solder mark with conductive adhesive 30 reduces the ionization of metal dust within the cell, reduces self-discharge, and helps to improve the cell's lifespan.

[0057] In this embodiment, as Figure 3 and Figure 4 As shown, tabs 20 are provided on both sides of the electrode 10. The two tabs 20 clamp the electrode 10, and the solder mark 101 connects the upper and lower tabs 20 and the electrode 10.

[0058] Furthermore, the electrode 10 and the tab 20 are connected by ultrasonic welding. After ultrasonic roll welding, the ultrasonic welding teeth form a weld mark 101 on the electrode 10 and the tab 20. By means of ultrasonic welding, the tab 20 and the electrode 10 can be connected, and the weld mark 101 is formed at the same time, which prepares for the next step of filling conductive adhesive 30.

[0059] Optionally, multiple solder marks 101 are welded at the joint between the electrode 10 and the tab 20 to form multiple electrical conductive points between the first metal layer 12 and the second metal layer 13 of the electrode 10.

[0060] Preferably, the multiple solder marks 101 are arranged in a matrix, for example, in a rectangular matrix of four rows and five columns. In practice, the solder marks 101 are arranged reasonably according to the width of the tab 20 and the length of the joint with the electrode 10.

[0061] Specifically, the ultrasonic welding teeth 401 form multiple weld marks 101 arranged in a matrix in one welding process, which is relatively quick and convenient.

[0062] Further, in step S3, as Figure 5 As shown, conductive adhesive 30 is applied to both sides of the joint between the electrode 10 and the tab 20, filling the solder joint 101 and enabling the conductive adhesive 30 to electrically conduct electricity between the two sides of the joint between the electrode 10 and the tab 20. In this embodiment, two tabs 20 are sandwiched between the two sides of the electrode 10, and conductive adhesive 30 is applied to the outer surfaces of the two tabs 20, thus achieving electrical connection between the two tabs 20.

[0063] Preferably, the conductive adhesive 30 can cover all areas where the solder marks 101 are located, so that each solder mark 101 can be filled with conductive adhesive 30. In one embodiment, the conductive adhesive 30 is applied to the edge of the tab 20, so that the applied area is the same width as the tab 20.

[0064] Optionally, the coating thickness of conductive adhesive 30 on the surface of tab 20 or electrode 10 is 1μm-5μm, and preferably 3μm.

[0065] Furthermore, such as Figure 6 As shown, before step S1, there is also step S01, which includes welding to form an electrode 10, bonding metal layers to the two surfaces of the polymer layer 11, welding to form a composite foil 1, rolling the composite foil 1 to make the two metal layers electrically conductive, and coating the surface of the composite foil 1 with electrode paste to weld and form the electrode 10. The specific processing method is as described above and will not be repeated in detail here.

[0066] Example 2

[0067] like Figure 7 As shown, this embodiment provides an ultrasonic welding head 40, which is used in the electrode and tab connection method in Embodiment 1 to connect the electrode 10 and the tab 20.

[0068] Specifically, the ultrasonic welding head 40 includes an upper welding head and a lower welding head. At least one of the upper welding head and the lower welding head is provided with a plurality of welding teeth 401 arranged in a matrix. When the ultrasonic welding head 40 performs ultrasonic welding on the electrode 10 and the electrode tab 20, the welding teeth 401 can pierce the electrode 10 and the electrode tab 20, thereby forming the weld mark 101 required in Embodiment 1 on the electrode 10 and the electrode tab 20.

[0069] For the other structures in the ultrasonic welding device, except for the ultrasonic welding head 40, conventional structures in the existing technology can be used, and will not be described in detail here.

[0070] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for connecting an electrode plate and an electrode tab, characterized in that, include: S1: At least one side of the electrode sheet (10) is spliced ​​with an electrode tab (20). S2: Weld a solder mark (101) to form at the joint between the electrode (10) and the electrode tab (20), so that the solder mark (101) connects the electrode (10) and the electrode tab (20). S3: Fill the solder mark (101) with conductive adhesive (30) so that the conductive adhesive (30) electrically connects the two metal layers of the electrode (10). The solder mark (101) electrically connects the two metal layers of the electrode (10); In step S3, the conductive adhesive (30) is applied to both sides of the joint between the electrode (10) and the tab (20) so that the conductive adhesive (30) fills the solder mark (101); The conductive adhesive (30) can cover all areas where the solder marks (101) are located.

2. The method for connecting the electrode plate and the electrode tab according to claim 1, characterized in that, The electrode (10) and the tab (20) are connected by ultrasonic welding, and the ultrasonic welding teeth (401) form the welding mark (101) on the electrode (10) and the tab (20).

3. The method for connecting the electrode plate and the electrode tab according to claim 2, characterized in that, Multiple weld marks (101) are formed at the joint between the electrode (10) and the tab (20).

4. The method for connecting the electrode plate and the electrode tab according to claim 3, characterized in that, The multiple solder marks (101) are arranged in a matrix.

5. The method for connecting the electrode plate and the electrode tab according to claim 1, characterized in that, The conductive adhesive (30) is coated on the surface of the tab (20) or the electrode (10) with a thickness of 1 μm-5 μm.

6. The method for connecting the electrode plate and the electrode tab according to any one of claims 1-5, characterized in that, Before step S1, there is also step S01, which includes: The electrode (10) is formed by welding, and a composite metal layer is formed on both surfaces of the polymer layer (11). A composite foil (1) is formed by welding, and an electrode paste is applied to the surface of the composite foil (1) to form the electrode (10).

7. The method for connecting the electrode plate and the electrode tab according to claim 2, characterized in that, The ultrasonic welding is performed by an ultrasonic welding head, which includes an upper welding head and a lower welding head. At least one of the upper welding head and the lower welding head is provided with a plurality of welding teeth (401) arranged in a matrix.

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