A method for matte finish treatment of flexible connection on battery cover

Abstract

This invention belongs to the technical field of secondary battery structure, specifically relating to a method for matte finishing of a flexible connector on a battery cover. When performing a matte finishing process on the flexible connector of the battery cover, mold A is used to press the flexible connector, followed by mold B. Mold A and mold B include pressing surfaces directly opposite the flexible connector during pressing; both pressing surfaces include protrusions extending beyond the pressing surfaces. When molds A and B form opposing pressing recesses on the flexible connector, at least some of the recesses overlap. Furthermore, the flexible connector comprises two surfaces; mold A is first used to press one surface of the flexible connector, followed by mold B to press the other surface. The flexible connector obtained using this method can effectively improve the laser welding strength.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery structure technology. More specifically, it relates to a method for matte finishing of a battery cover plate's soft connection. Background Technology

[0002] With the widespread adoption of lithium batteries, their related components have also developed rapidly. Among the structural components of lithium batteries, one of the most critical components is the battery cover. Its main function is to form a sealed environment after welding with the battery casing to encapsulate the battery cells and electrolyte inside. Of course, as a battery cover, another very important function is to electrically connect with the tabs of the battery cells, thereby enabling current exchange between the external and internal battery cells.

[0003] However, due to limitations such as the lead-out method of the electrode tabs, it is difficult to achieve direct electrical connection between the electrode tabs of the battery cell and the terminals on the battery cover structure. Therefore, an adapter piece is often used for the connection. Considering the ultimate utilization of the internal space of the battery, after the adapter piece is electrically connected to the electrode tabs of the battery cell, it is necessary to fold the adapter piece appropriately. Therefore, it is desirable for the adapter piece to be flexible and foldable. Currently, the selection of adapter piece materials is basically aluminum for the positive electrode and copper for the negative electrode, which corresponds to the current collector foil of the positive or negative electrode sheet while meeting the conductivity requirements.

[0004] However, during their actual research, the inventors discovered that in the process of welding the flexible connector and the electrode body, the commonly used laser welding method, in order to achieve a reliable electrical connection, is prone to laser reflection due to the smooth surface of the metal, especially for the copper material of the negative electrode. This has the most significant impact, thus affecting the laser welding effect between the negative electrode flexible connector and the electrode. Therefore, it is necessary to perform a matte finish on the surface of the flexible connector. Currently, it is common to use a mold with a grid to directly stamp the flexible connector. Although this treatment can improve the surface roughness and reduce reflection, it is still prone to slight reflection, which can still have an adverse effect on laser welding, especially high-power laser welding processes. Therefore, in order to further improve the welding effect between the negative electrode flexible connector and the electrode, it is necessary to develop a matte finish treatment method more suitable for copper surfaces. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing method of directly pressing copper cover plate flexible connection with mold to obtain a rough surface. However, although the roughness is improved, it is still easy to produce slight reflection, which affects the quality of laser welding. The present invention provides a method for matte treatment of battery cover plate flexible connection.

[0006] The purpose of this invention is to provide a method for matte treatment of flexible connections on battery cover plates.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A method for matte finishing of a flexible connection on a battery cover, comprising the following steps:

[0009] After pressing the cover plate flexible connection with mold A, the cover plate flexible connection is then pressed with mold B.

[0010] Wherein, mold A and mold B include pressing surfaces that are directly opposite to the cover plate flexible connection during pressing, and both the pressing surfaces of mold A and mold B include protrusions that protrude from the pressing surfaces.

[0011] When mold A and mold B form opposing pressing recesses on the flexible connection, at least part of the recesses overlap.

[0012] The above solution still uses the mainstream mold pressing method to quickly form a rough surface on the flexible connector. However, the inventors discovered that by using two sets of molds to press the same flexible connector sequentially, and by making the marks formed by molds A and B overlap, mold B can be used in the second pressing process to form a secondary pressing at the overlap, thereby forming three surface structures on the flexible connector: the surface formed by mold A alone, the surface formed by mold B alone, and the surface formed by the overlap of molds A and B. By forming multiple surface structures, and with some overlap, a rougher surface structure with significantly reduced reflectivity is formed, thereby effectively improving the laser welding effect.

[0013] Furthermore, the protrusion is a hemispherical protrusion.

[0014] Furthermore, after pressing the cover plate flexible connection with mold A to form a corresponding circular recess 1, mold B is then used to press the cover plate flexible connection to form a recess 2 on the basis of recess 1. The coverage area of ​​recess 2 is larger than that of recess 1, and recess 2 completely covers recess 1.

[0015] Specifically, when forming overlapping pits, the flexible connection is first pressed using mold A with a relatively small protrusion, and then pressed using mold B with a relatively large protrusion. The pit formed by mold B completely covers the pit formed by mold A. In this way, the edge formed by mold A can directly become the transition boundary between pit 1 and pit 2, thereby forming a circumferential transition surface, further reducing the surface reflectivity and improving the welding effect.

[0016] Furthermore, the flexible connection includes two surfaces. First, mold A is used to press one surface of the cover plate flexible connection, and then mold B is used to press the other surface of the cover plate flexible connection.

[0017] Specifically, by pressing the two surfaces of the flexible connector one after the other using two different molds, the pits formed by the two pressings are recessed towards the two surfaces respectively. This results in a lower reflectivity at the junction between the two pits, making it easier to achieve a good welding effect during laser welding.

[0018] Furthermore, the surface pressed by mold A is used as the welding surface, and the surface pressed by mold B is in contact with the terminal surface of the battery cover.

[0019] Furthermore, the diameter of the hemispherical protrusion on the surface of mold B is 0.8-1.2 mm; the diameter of the hemispherical protrusion on the surface of mold A is 0.4-0.7 mm.

[0020] Furthermore, when pressing the cover plate flexible connection sequentially using mold A and mold B, the central axis of the hemispherical protrusion on the surface of mold A is kept in a one-to-one correspondence with the central axis of the hemispherical protrusion on the surface of mold B.

[0021] Furthermore, the cover plate flexible connection is a battery negative electrode flexible connection, and the battery negative electrode flexible connection is made of copper. Detailed Implementation

[0022] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0023] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0024] Example 1

[0025] A copper plate with a thickness of 0.8 mm is used as the flexible connector substrate for the battery cover. Specifically, it is used as the flexible connector for the negative electrode. After laser cutting, the surface oxide layer is removed by acid pickling, and the surface oil is removed by acetone. Then, it is cleaned twice with deionized water. After drying, the substrate is fixedly placed. First, mold A is used to press the flexible connector substrate for the battery cover, and the pressing pressure is controlled at 5.2 MPa. After holding the pressure for 10 seconds, mold B is used to press the fixed flexible connector substrate for the battery cover, and the pressing pressure is controlled at 5.2 MPa. After holding the pressure for 10 seconds, the pressing positions of mold B and mold A are adjusted to ensure that when mold A and mold B form relative pressing pits on the flexible connector, only part of the pits overlap.

[0026] Mold A and mold B include pressing surfaces that are directly opposite the cover plate flexible connection during pressing, and both the pressing surfaces of mold A and mold B include protrusions that protrude from the pressing surfaces.

[0027] The protrusion is a hemispherical protrusion, and the diameter of the hemispherical protrusion on the surface of mold B is 0.8 mm; the diameter of the hemispherical protrusion on the surface of mold A is 0.4 mm.

[0028] In this embodiment, when mold A and mold B are used to press the flexible connection substrate of the battery cover plate one after the other, the same surface of the substrate is pressed sequentially; and the partial overlap of the pits specifically refers to the two circles forming a partially overlapping area and a partially non-overlapping area; the surface pressed by the mold is used as the laser welding surface, and the opposite side directly abuts against the battery cover plate pole.

[0029] Example 2

[0030] A copper plate with a thickness of 0.8 mm is used as the flexible connector substrate for the battery cover. Specifically, it is used as the flexible connector for the negative electrode. After laser cutting, the surface oxide layer is removed by acid pickling, and the surface oil is removed by acetone. Then, it is cleaned twice with deionized water. After drying, the substrate is fixedly placed. First, mold A is used to press the flexible connector substrate for the battery cover, and the pressing pressure is controlled at 5.2 MPa. After holding the pressure for 10 seconds, mold B is used to press the fixed flexible connector substrate for the battery cover, and the pressing pressure is controlled at 5.2 MPa. After holding the pressure for 10 seconds, the pressing positions of mold B and mold A are adjusted to ensure that when mold A and mold B form relative pressing pits on the flexible connector, only part of the pits overlap.

[0031] Mold A and mold B include pressing surfaces that are directly opposite the cover plate flexible connection during pressing, and both the pressing surfaces of mold A and mold B include protrusions that protrude from the pressing surfaces.

[0032] The protrusion is a hemispherical protrusion. The diameter of the hemispherical protrusion on the surface of mold B is 0.8 mm; the diameter of the hemispherical protrusion on the surface of mold A is 0.4 mm. When the cover plate soft connection is pressed sequentially using mold A and mold B, the central axis of the hemispherical protrusion on the surface of mold A is kept in a one-to-one correspondence with the central axis of the hemispherical protrusion on the surface of mold B.

[0033] In this embodiment, when mold A and mold B are used to press the flexible connection substrate of the battery cover plate sequentially, the same surface of the substrate is pressed sequentially. Furthermore, the overlapping of the recesses specifically refers to the process where, after mold A presses the flexible connection of the cover plate to form a corresponding circular recess 1, mold B is then used to press the flexible connection of the cover plate to form a recess 2 on top of recess 1. The coverage area of ​​recess 2 is larger than that of recess 1, and recess 2 completely covers recess 1. Specifically, when the central axis of the hemispherical protrusion on the surface of mold A corresponds one-to-one with the central axis of the hemispherical protrusion on the surface of mold B, recess 1 and recess 2 form concentric circles. The surface pressed by mold A serves as the laser welding surface, and the surface pressed by mold B contacts the terminal surface of the battery cover plate.

[0034] Example 3

[0035] A copper plate with a thickness of 0.8 mm is used as the flexible connector substrate for the battery cover. Specifically, it is used as the flexible connector for the negative electrode. After laser cutting, the surface oxide layer is removed by acid pickling, and the surface oil is removed by acetone. Then, it is cleaned twice with deionized water. After drying, the substrate is fixedly placed. First, mold A is used to press the flexible connector substrate for the battery cover, and the pressing pressure is controlled at 5.2 MPa. After holding the pressure for 10 seconds, mold B is used to press the fixed flexible connector substrate for the battery cover, and the pressing pressure is controlled at 5.2 MPa. After holding the pressure for 10 seconds, the pressing positions of mold B and mold A are adjusted to ensure that when mold A and mold B form relative pressing pits on the flexible connector, only part of the pits overlap.

[0036] Mold A and mold B include pressing surfaces that are directly opposite the cover plate flexible connection during pressing, and both the pressing surfaces of mold A and mold B include protrusions that protrude from the pressing surfaces.

[0037] The protrusion is a hemispherical protrusion, and the diameter of the hemispherical protrusion on the surface of mold B is 0.8 mm; the diameter of the hemispherical protrusion on the surface of mold A is 0.4 mm.

[0038] In this embodiment, when mold A and mold B are used to press the flexible connection substrate of the battery cover plate in sequence, the two surfaces of the substrate are pressed in sequence; and the partial overlap of the pits specifically refers to the two circles forming a partially overlapping area and a partially non-overlapping area; the surface pressed by the mold is used as the laser welding surface, and the opposite side directly abuts against the battery cover plate pole.

[0039] Example 4

[0040] A copper plate with a thickness of 0.8 mm is used as the flexible connector substrate for the battery cover. Specifically, it is used as the flexible connector for the negative electrode. After laser cutting, the surface oxide layer is removed by acid pickling, and the surface oil is removed by acetone. Then, it is cleaned twice with deionized water. After drying, the substrate is fixedly placed. First, mold A is used to press the flexible connector substrate for the battery cover, and the pressing pressure is controlled at 5.2 MPa. After holding the pressure for 10 seconds, mold B is used to press the fixed flexible connector substrate for the battery cover, and the pressing pressure is controlled at 5.2 MPa. After holding the pressure for 10 seconds, the pressing positions of mold B and mold A are adjusted to ensure that when mold A and mold B form relative pressing pits on the flexible connector, only part of the pits overlap.

[0041] Mold A and mold B include pressing surfaces that are directly opposite the cover plate flexible connection during pressing, and both the pressing surfaces of mold A and mold B include protrusions that protrude from the pressing surfaces.

[0042] The protrusion is a hemispherical protrusion. The diameter of the hemispherical protrusion on the surface of mold B is 0.8 mm; the diameter of the hemispherical protrusion on the surface of mold A is 0.4 mm. When the cover plate soft connection is pressed sequentially using mold A and mold B, the central axis of the hemispherical protrusion on the surface of mold A is kept in a one-to-one correspondence with the central axis of the hemispherical protrusion on the surface of mold B.

[0043] In this embodiment, when mold A and mold B are used to press the flexible connection substrate of the battery cover plate sequentially, the two surfaces of the substrate are pressed sequentially. Specifically, the overlapping of the recesses refers to the process where, after mold A presses the flexible connection of the cover plate to form a corresponding circular recess 1, mold B is then used to press the flexible connection of the cover plate to form a recess 2 on top of recess 1. The coverage area of ​​recess 2 is larger than that of recess 1, and recess 2 completely covers recess 1. In particular, when the central axis of the hemispherical protrusion on the surface of mold A corresponds one-to-one with the central axis of the hemispherical protrusion on the surface of mold B, recess 1 and recess 2 form concentric circles. The surface pressed by mold A serves as the laser welding surface, and the surface pressed by mold B contacts the terminal surface of the battery cover plate.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that only mold A is used to press the flexible connection substrate of the battery cover plate once, while the other conditions remain unchanged.

[0046] Comparative Example 2

[0047] The difference between this comparative example and Example 1 is that only mold B is used to press the battery cover plate with a flexible connection substrate in a single operation, while the other conditions remain unchanged.

[0048] The flexible connectors obtained in the above embodiments and comparative examples were laser welded to copper battery negative electrode posts. The welding area was controlled to be 2 square centimeters. After the welding was completed and the welded metal cooled to room temperature, the electrode post was fixed in a tooling fixture. A vertical pull-out test was conducted by clamping the flexible connector with a tension gauge. The reading of the tension gauge when the weld scar at the weld between the flexible connector and the electrode post broke was taken as the maximum pull-out force. The flexible connector obtained in the same embodiment was subjected to 10 repeated pull-out tests. The average value of the tension gauge readings obtained in the 10 tests was calculated to obtain the final tensile strength. The specific test results are shown in Table 1.

[0049] Table 1: Product Performance Test Results

[0050] Tensile strength Example 1 325.5N Example 2 362.3N Example 3 342.6N Example 4 377.5N Comparative Example 1 223.2N Comparative Example 2 215.5N

[0051] As can be seen from the test results in Table 1, the product obtained by the present invention can effectively solve the drawback that the welding effect cannot be further improved due to single mold pressing, and effectively improve the laser welding strength.

[0052] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for matte finishing of a flexible connection on a battery cover, characterized in that, The specific processing steps include: After pressing the cover plate flexible connection with mold A, the cover plate flexible connection is then pressed with mold B. Wherein, mold A and mold B include pressing surfaces that are directly opposite to the cover plate flexible connection during pressing. The pressing surfaces of mold A and mold B both include protrusions that protrude from the pressing surfaces, and the protrusions are hemispherical protrusions. When mold A and mold B form opposing pressing recesses on the flexible connection, only part of the recesses overlap. The partial overlap of the recesses means that the two circles form a partially overlapping area and a partially non-overlapping area. The cover plate flexible connection includes two surfaces. First, mold A is used to press one surface of the cover plate flexible connection, and then mold B is used to press the other surface of the cover plate flexible connection.

2. The method for matte finishing of a flexible connection for a battery cover plate according to claim 1, characterized in that, The surface pressed by mold A is used as the welding surface, and the surface pressed by mold B is in contact with the terminal surface of the battery cover.

3. The method for matte finishing of a flexible connection for a battery cover plate according to claim 1, characterized in that, The diameter of the hemispherical protrusion on the surface of mold B is 0.8-1.2 mm; the diameter of the hemispherical protrusion on the surface of mold A is 0.4-0.7 mm.

4. A method for matte finishing of a battery cover plate with a flexible connection according to any one of claims 1-3, characterized in that, The cover plate flexible connection is a battery negative terminal flexible connection, and the battery negative terminal flexible connection is made of copper.