Cell pack assembly, battery and battery tab welding method

Abstract

Disclosed are a cell pack assembly, a battery and a battery tab welding method, the cell pack assembly comprising cells (1) and a connecting plate (4), wherein the cell (1) comprises a tab cluster (2) having a plurality of tab bodies (210) which are stacked; a pre-weld area (201) and a non-pre-weld area (203) are provided on the tab cluster (2), the connection strength of the pre-weld area (201) being greater than the connection strength of the non-pre-weld area (203), and the absolute value of the height difference between a weld bump (2011) and a first weld dip (2012) in the pre-weld area (210) being X1; and a final weld area (202) is further provided in the pre-weld area (201), the final weld area (202) being welded to the connecting plate (4), and the absolute value of the height difference between a second weld dip (2021) in the final weld area (202) and a surface of the final weld area (201) being X2, where X1＜X2.

Description

Core package assembly, battery and battery tab welding method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 27, 2023 with application number 202322650776.5, and the Chinese patent application filed with the China Patent Office on September 27, 2023 with application number 202311279036.3. The entire contents of the above applications are incorporated by reference into this application.

[0002] Technical Field

[0003] The present application relates to the technical field of energy storage equipment, for example, to a core pack assembly, a battery, and a battery tab welding method.

[0004] Background Art

[0005] A battery cell contains pole pieces. For laminated cells, the pole pieces are arranged in multiple layers, each with a tab. The tabs are stacked to form a tab cluster. Currently, the battery cell and pole connection method in the industry is: tab cluster - connecting piece - pole. Ultrasonic welding is used to weld the tab cluster to the tab, that is, to weld the tab to the tab cluster. However, during the welding process, the tab closest to the welding head is easily damaged by the welding head. Therefore, the industry generally uses a protective sheet to protect this tab to prevent damage from ultrasonic vibration.

[0006] Technical issues

[0007] The following situations exist when auxiliary welding is performed on the protective sheet:

[0008] During ultrasonic vibration, the edge of the protective sheet can easily cut the tab, causing damage to the tab.

[0009] The protective sheet is difficult to position, easily deviates during welding, and easily inserts into the battery cell during the core assembly process, causing a short circuit.

[0010] Technical Solutions

[0011] In a first aspect, a core package assembly is provided, including a battery cell and a connecting piece, the battery cell including a tab cluster, the tab cluster including a plurality of stacked tab bodies, a pre-welding area and a non-pre-welding area being provided on the tab cluster, the connection strength of the pre-welding area being greater than the connection strength of the non-pre-welding area, a welding protrusion and a first welding recess being provided in the pre-welding area, the absolute value of the height difference between the welding protrusion and the first welding recess being X1, a final welding area being further provided in the pre-welding area, the final welding area being welded to the connecting piece, a second welding recess being provided on the surface of the final welding area, the absolute value of the height difference between the second welding recess and the surface of the final welding area being X2, and X1<X2.

[0012] In a second aspect, a battery is provided, comprising a shell, on which a pole is provided, and the core package assembly mentioned above is provided in the shell, wherein the tab clusters of the battery cells of the core package assembly are connected to the pole via connecting sheets.

[0013] In a third aspect, a battery tab welding method is provided, which is applied to a core package assembly, wherein the core package assembly includes a battery cell and a connecting piece, the battery cell has a tab cluster, and the tab cluster includes multiple stacked tab bodies, including:

[0014] Pre-welding the tab clusters by ultrasonic toothless welding process and forming pre-welding areas on the tab clusters;

[0015] The connecting piece is aligned with the pre-welding area, and the tab cluster and the connecting piece are finally welded by an ultrasonic tooth welding process, and a final welding area is formed on the tab cluster.

[0016] Beneficial effects

[0017] The core package assembly provided by the present application pre-welds the tab clusters before welding the tab clusters and the connecting pieces, thereby forming a pre-welding area. The connection strength between the tab bodies in the pre-welding area is greater than the connection strength between the tab bodies in the non-pre-welding area, that is, the tab bodies in the pre-welding area are tightly connected, forming a connection strength in the pre-welding area greater than that in the non-pre-welding area. During the final welding, even if the connecting piece needs to be moved, the tab bodies located on the surface of the tab cluster will not move with the connecting piece, thereby facilitating the welding positioning between the tab cluster and the connecting piece. Since the tab cluster has a lifting connection The pre-welding area has a strong bonding strength. Therefore, no additional protective sheet is needed between the tab cluster and the connecting piece. In the final welding stage, the original positioning of the protective sheet, the tab cluster and the connecting piece is simplified to the positioning of the two between the tab cluster and the connecting piece. This not only avoids the protective sheet from scratching the tab, but also reduces the difficulty of the welding process. The final welding area is set in the pre-welding area. During the final welding process, the connecting piece is contacted and positioned with the tab cluster in the pre-welding area. This can avoid the connecting piece from moving to the non-pre-welding area of ​​the tab cluster, and avoid the tab body in the non-pre-welding area from being scratched by the connecting piece.

[0018] The battery provided in the present application utilizes the core package assembly described above, so that the connection between the tab and the connecting piece is stable, of good quality, and has low processing difficulty.

[0019] The battery tab welding method provided in the present application performs pre-welding on the tab cluster, thereby achieving effective fusion connection between the tab bodies and improving the connection strength between each other. Therefore, in the final welding stage, there is no need for a protective sheet to assist in welding the tab cluster, so as to avoid resonance of the protective sheet and scratching the tab body during welding; pre-welding is to improve the local connection strength of the tab cluster, and pre-welding does not play a role in final fixation. Using ultrasonic toothless welding for pre-welding can reduce the damage to the tab body caused by the pre-welding process, avoid breakage and other damage to the tab body during final welding, and ensure the connection stability between the tab and the connecting piece in the battery cell; using ultrasonic toothed welding for final welding can allow the ultrasonic energy of the welding to penetrate the tab cluster, so that each layer of the tab body can be welded and fixed to the connecting piece, ensuring that the battery cell can transmit electrical energy through the connecting piece.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic diagram of a battery cell and tab cluster (before pre-welding) provided in a possible embodiment of the present application;

[0022] FIG2 is a schematic diagram of a battery cell and tab cluster (after pre-welding and before cutting) provided in a possible embodiment of the present application;

[0023] FIG3 is a schematic diagram of a battery cell and tab cluster provided in a possible embodiment of the present application (after cutting);

[0024] FIG4 is a schematic top view of a tab cluster provided in a possible embodiment of the present application;

[0025] FIG5 is a schematic cross-sectional view of a pre-welding area provided in a possible embodiment of the present application;

[0026] FIG6 is a schematic cross-sectional view of a final welding area provided in a possible embodiment of the present application.

[0027] In the picture:

[0028] 1. Battery cell; 2. Tab cluster; 21. Tab body; 201. Pre-welding area; 2011. Welding protrusion; 2012. First welding depression; 202. Final welding area; 2021. Second welding depression; 203. Non-pre-welding area; 3. Substrate.

[0029] Modes for Carrying Out the Invention

[0030] In the description of this application, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0031] As shown in Figures 1 to 6, a core package assembly provided in the present application includes a battery cell 1 and a connecting piece, the battery cell 1 includes a tab cluster 2, the tab cluster 2 includes a plurality of stacked tab bodies 21, a pre-welding area 201 is provided on the tab cluster 2, the connection strength between the tab bodies 21 in the pre-welding area 201 is greater than the connection strength between the tab bodies 21 in the non-pre-welding area 203, a welding protrusion 2011 and a first welding recess 2012 are provided in the pre-welding area 201, and the absolute value of the height difference between the welding protrusion 2011 and the first welding recess 2012 is X1, and a final welding area 202 is also provided in the pre-welding area 201, the final welding area 202 is welded to the connecting piece, and a second welding recess 2021 is provided on the surface of the final welding area 202, and the absolute value of the height difference between the second welding recess 2021 and the surface of the final welding area 202 is X2, X1<X2. In this embodiment, before the tab cluster 2 and the connecting piece are welded, the tab cluster 2 is pre-welded to form a pre-welding area 201. The connection strength between the tab bodies 21 in the pre-welding area 201 is greater than the connection strength between the tab bodies 21 in the non-pre-welding area 203, that is, the tab bodies 21 in the pre-welding area 201 are tightly connected, and the connection strength between the tab bodies 21 in the pre-welding area 201 is greater than the connection strength between the tab bodies 21 in the non-pre-welding area 203; by adopting the pre-welding method, the connection strength between the tab bodies 21 is changed, so that the tab bodies 21 in the pre-welding area 201 are no longer in a loose state, and they maintain as close a connection as possible with each other. For example, the tab body 21 on the outermost surface of the tab cluster 2 can be tightly fused and connected with the adjacent tab body 21. In this way, when performing the final welding, even if the connecting piece needs to be moved, the tab body 21 located on the surface of the tab cluster 2 will not move with the connecting piece, which facilitates the welding positioning between the tab cluster 2 and the connecting piece.

[0032] Since the tab cluster 2 has a pre-welding area 201 for improving the connection strength, the tab bodies 21 are effectively fused and connected, and the connection strength between them is improved. Therefore, in the final welding stage, no additional protective sheet is required between the tab cluster 2 and the connecting piece. The original three-way positioning welding process of the protective sheet, the tab cluster 2 and the connecting piece is simplified to a two-way positioning welding process between the tab cluster 2 and the connecting piece. Compared with the related art, the protective sheet is no longer needed, and there is no situation where the protective sheet scratches the tab body 21. At the same time, the process difficulty of the two-way positioning welding process is also effectively reduced compared to the three-way positioning welding process.

[0033] The final welding area 202 is set in the pre-welding area 201. During the final welding process, the connecting piece is in contact and positioned with the tab cluster 2 in the pre-welding area 201. This can prevent the connecting piece from moving to the non-pre-welding area 203 of the tab cluster 2, and prevent the tab body 21 in the non-pre-welding area 203 from being scratched by the connecting piece.

[0034] Using a pre-welding process to form a pre-welding area 201 on the tab cluster 2 can gather the originally loose tab bodies 21, connect the tab bodies 21 together as much as possible, increase the connection strength between the tab bodies 21, and support each other between adjacent tab bodies 21, so that the connection strength between the tab bodies 21 in the pre-welding area 201 is greater than the connection strength between the tab bodies 21 in the non-pre-welding area 203, which is beneficial to the subsequent final welding with the connecting piece.

[0035] A pre-welding process is used to form a pre-welding area 201 on the tab cluster 2. The pre-welding area 201 can also be formed on the tab cluster 2, which changes the original structure and shape of the tab cluster 2. The connection between the tab bodies 21 in the tab cluster 2 is tighter, which can facilitate the positioning between the tab cluster 2 and the connecting piece before and during the final welding process. In other words, the pre-welding area 201 can also play a role in pre-positioning the final welding of the connecting piece; since pre-welding is only a processing method to assist the final welding, the connection strength between the tab bodies 21 in the pre-welding area 201 does not need to be too high, and it is sufficient to ensure that the tab bodies 21 are no longer in a loose state.

[0036] In this embodiment, both the pre-welding and final welding are ultrasonic welding, with the pre-welding being ultrasonic toothless welding and the final welding being ultrasonic toothed welding. Ultrasonic toothless welding does not mean that the contact surface is smooth, but rather that the weld mark on the welding head's weld surface is a combination of corrosion patterns and reticulation, with uneven, uneven, and misaligned welds. Ultrasonic toothed welding refers to a weld surface with distinct weld teeth, which come in a variety of shapes, including prismatic, hemispherical, and pyramidal. Simply put, a significant difference between ultrasonic toothless welding and ultrasonic toothed welding is that the surface of an ultrasonic toothless welded product is smoother than that of an ultrasonic toothed welded product.

[0037] In this embodiment, the weld mark of the pre-weld area 201 is a combination of corrosion marks and reticulation. The weld mark formed by ultrasonic toothless pre-weld welding in the pre-weld area 201 includes a weld protrusion 2011 and a first weld depression 2012. Referring to FIG5 , the absolute value of the height difference between the highest point of the weld protrusion 2011 and the lowest point of the first weld depression 2012 is X1, where X1 = 50 μm. In another embodiment, 20 μm ≤ X1 ≤ 100 μm. The value of X1 can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm. Of course, the value of X1 can also be any number within the range of 20 μm-100 μm, and this embodiment is not limited thereto. It can be understood that the larger the X1 is, the tighter the connection between the tab bodies 21 is, but the more difficult it is to align the welding protrusion 2011 in the pre-welding area 201 with the final welding head, and the more difficult it is to position the tab cluster 2 and the connecting piece. In other words, the larger the value of X1 is, the more difficult the final welding operation is. Therefore, X1 should be taken within the example range as much as possible. In another embodiment, 40μm≤X1≤60μm, and the value of X1 can be 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, 51μm, 52μm, 53μm, 54μm, 55μm, 56μm, 57μm, 58μm, 59μm, 60μm. Of course, the value of X1 can also be any number in the range of 40μm-60μm, which is not limited in this embodiment.

[0038] 6 , X2 is the absolute value of the height difference between the surface of the final welding area 202 and the lowest point of the second welding recess 2021, and X2>500μm. In this embodiment, the final welding process is used to fix the tab cluster 2 and the connecting piece. That is, the final welding area 202 of the tab cluster 2 and the connecting piece need to have a high connection strength. The weld mark height on the surface of the final welding area 202 is set to be greater than 500μm. The connection between the tab bodies 21 in the tab cluster 2 is relatively tight, and the fitting between the connecting piece and the tab cluster 2 is relatively tight, which can improve the connection stability between the two.

[0039] The absolute value X1 of the height difference between the welding protrusion 2011 and the first welding recess 2012 in the pre-welding area 201 is smaller than the absolute value X2 of the height difference between the second welding recess 2021 in the final welding area 202 and the surface of the final welding area 202. That is to say, the connection strength between the tab bodies 21 in the pre-welding area 201 will be lower than the connection strength between the tab bodies 21 in the final welding area 202.

[0040] X1 is the absolute value of the height difference between the welding protrusion 2011 and the first welding depression 2012 in the pre-welding area 201. In the design of the related art, both the pre-welding and the final welding are ultrasonic toothed welding, and the tab cluster 2 is pre-welded using a toothed welding head so that the entire tab cluster 2 is completely and stably connected together. During the final welding, it is also necessary to try to ensure that the tooth mark formed by the final welding head matches the tooth mark formed by the pre-welding, which significantly increases the difficulty of the process. In order to reduce the difficulty, the related art uses a protective sheet during the final welding, and places the protective sheet between the final welding head and the weld mark formed by the pre-welding on the surface of the tab cluster 2, and then performs the final welding. In this way, even if the weld mark produced by the final welding is slightly misaligned with the weld mark formed by the pre-welding, the quality of the finished welding product can be guaranteed under the protection of the protective sheet to avoid the tab body 21 from breaking, but the protective sheet There is a situation where the protective sheet may scratch the tab body 21. This solution changes the pre-welding method and adopts ultrasonic toothless welding to form the pre-welding area 201, thereby reducing the height of the weld mark in the pre-welding area 201 and reducing the use of protective sheets. Ultrasonic toothless pre-welding can gather the originally loose tab bodies 21 and connect the tab bodies 21 as much as possible. The connection strength between the tab bodies 21 is increased, and adjacent tab bodies 21 support each other, so that the connection strength between the tab bodies 21 in the pre-welding area 201 is greater than the connection strength between the tab bodies 21 in the non-pre-welding area 203, which is conducive to the subsequent final welding with the connecting sheet to achieve the connection between the tab bodies 21.

[0041] It is understood that ultrasonic welding is divided into toothed welding and toothless welding according to the weld mark height. In this embodiment, the pre-welding process of the tab cluster 2 adopts ultrasonic toothless welding, and the final welding process adopts ultrasonic toothed welding. The welding time, temperature rise, and welding power of the pre-welding process of the tab cluster 2 are all lower than those of the final welding process between the tab cluster 2 and the connecting piece. In one embodiment, the welding time of the pre-welding process is less than 0.3 seconds, the temperature rise is less than 50°C, and the welding power is less than 3000W. The welding time of the final welding process is less than 0.5 seconds, the temperature rise is less than 80°C, and the welding power is less than 5000W.

[0042] It should be noted that the toothless pre-welding and toothed pre-welding have an impact on the foil. The toothless pre-welding can effectively integrate and fix the tab body 21, and the damage to the tab body 21 is relatively small. The consistency of the tab body 21 in the weld mark area is relatively high. If toothed welding is used to pre-weld the tab cluster 2, then during the toothed pre-welding integration process, the tab body 21 will be pierced downward, causing greater damage to the tab body 21. The height change in the weld mark area is relatively large. During the final welding process, the final welding mark and the pre-welding mark are very easy to be misaligned, causing damage to the tab body 21.

[0043] In one embodiment, within the pre-welding area 201, the connection strength between the tab bodies 21 gradually increases along the direction from the center of the tab cluster 2 to the surface of the tab cluster 2. In this embodiment, pre-welding can gather the originally loose tab bodies 21, connect the tab bodies 21 together as much as possible, and facilitate the positioning between the tab cluster 2 and the connecting piece. Since the connecting piece is provided on the surface of the tab cluster 2, it can only be limited to improving the connection strength between the tab bodies 21 on the surface of the tab cluster 2. That is, along the direction from the center of the tab cluster 2 to the surface of the tab cluster 2, the connection strength between the tab bodies 21 gradually increases. In other words, the closer the tab bodies 21 are to the surface, the stronger the connection strength is, and the closer the tab bodies 21 are to the center, the weaker the connection strength is. This can avoid the pre-welding process from taking too long, and avoid excessive temperature rise resulting in excessive weld mark height in the pre-welding area 201, which affects the subsequent final welding process.

[0044] In this embodiment, the welding time of the pre-welding process is less than 0.3 seconds, the temperature rise is less than 50°C, the welding power is less than 3000W, 20μm≤X1≤100μm, and when the welding head acts on the upper surface of the tab cluster 2 for high-frequency vibration, the upper tab body 21 gradually merges; at the same time, the ultrasonic welding base also acts on the lower surface of the tab cluster 2, and the lower tab body 21 gradually aggregates, and the center of the tab cluster 2 points to the direction of the surface of the tab cluster 2, and the connection strength between the tab bodies 21 gradually increases.

[0045] In one embodiment, within the pre-welding area 201, the tab bodies 21 located at the center of the tab cluster 2 are surface-contacted with each other, that is, within the pre-welding area 201, the tab bodies 21 located at the center of the tab cluster 2 may not be fused with each other, and there is no excessive bonding force between the tab bodies 21 located at the center of the tab cluster 2. This makes it convenient to control multiple parameters of the pre-welding process and avoid the pre-welding process from forming an excessively deep weld mark on the surface of the tab cluster 2.

[0046] In one embodiment, the distance between the edge of the final welding area 202 and the edge of the pre-welding area 201 is L, and L is ≥ 2 mm. In this embodiment, the pre-welding area 201 is larger than the final welding area 202, and the distance between the edge of the final welding area 202 and the edge of the pre-welding area 201 is set to be greater than 2 mm. During the welding process, even if there is a slight positional offset between the connecting piece and the tab cluster 2, the final welding area 202 can still be ensured to be within the range of the pre-welding area 201, thereby ensuring the welding quality between the tab cluster 2 and the connecting piece; the shape and size of the pre-welding area 201 and the final welding area 202 can be selected according to actual needs, and this embodiment is not limited here. The shapes of the pre-welding area 201 and the final welding area 202 in this embodiment are both rectangular, and the distances between multiple edges of the final welding area 202 and multiple edges of the pre-welding area 201 are not required to be equal, that is, the center of the final welding area 202 is not required to coincide with the center of the final welding area 202. It is only necessary to ensure that the final welding area 202 is within the pre-welding area 201 and that the final welding area 202 is 2 mm away from the edge of the pre-welding area 201.

[0047] In one embodiment, the final welding region 202 is located at the center of the pre-welding region 201 .

[0048] In one embodiment, the edges of all the tab bodies 21 on the tab cluster 2 are flush. Referring to Figure 1, it can be understood that before the pre-welding process, the edges between the tab bodies 21 are basically flush, that is, in Figure 1, the right edge of the tab body 21 in the length direction is basically flush. Referring to Figure 2, after the pre-welding process, after the multiple layers of tab bodies 21 are stacked and aggregated, the edges of the tab bodies 21 are stepped in the thickness direction, that is, in the thickness direction, the tab bodies 21 on both sides of the tab cluster 2 are shorter than the tab body 21 in the center of the tab cluster 2, which will affect the connection between the tab cluster 2 and the connecting piece. In addition, the tab body 21 with an overly long edge is also prone to contact with the battery shell, causing an internal short circuit in the battery, affecting the safety of the battery. In this embodiment, referring to FIG3 , the pre-welded tab cluster 2 is cut (i.e., the stepped right edge of the tab body 21 located on the right side of the pre-welding area 210 in FIG2 is cut). The tab cluster 2 can be placed on a substrate 3, and then a cutter is used to cut and integrate the tab cluster 2 so that the edges of all the tab bodies 21 on the tab cluster 2 are flush. On the one hand, this can facilitate the welding positioning between the tab cluster 2 and the connecting piece, and on the other hand, it can also prevent the tab body 21 with too long edges from being short-circuited with the shell. Because within the pre-welding area 201, in the thickness direction, along the direction from the center of the tab cluster 2 to the upper surface or lower surface of the tab cluster 2, the connection strength between the tab bodies 21 gradually increases. After cutting, the connection strength between the tab bodies 21 at the center of the tab cluster 2 is weak, and the tab cluster 2 may be delaminated.

[0049] In one embodiment, the edge of the pre-welding area 201 away from the battery cell 1 is flush with the edge of the tab cluster 2, that is, the pre-welding area 201 is connected to the end face of the tab cluster 2, and along the width direction of the tab body 21, the size of the connecting piece is smaller than the size of the tab body 21, and the size of the connecting piece is larger than the size of the pre-welding area 201. By setting the size of the connecting piece smaller than the size of the tab body 21 along the width direction of the tab body 21, and the size of the connecting piece larger than the size of the pre-welding area 201, the difficulty of positioning the connecting piece and the tab cluster 2 can be reduced, while also reducing the difficulty of positioning the welding head and reducing the difficulty of the final welding process.

[0050] In this embodiment, the overall thickness of the tab cluster 2 is about 5 mm to 35 mm. The tab cluster 2 includes multiple layers of tab bodies 21. The number of tab bodies 21 can be 30 layers, 40 layers, 50 layers, 60 layers, etc. The pre-welding process standards of this embodiment are as follows:

[0051] a. After pre-welding, the loose multi-layered tab bodies 21 are integrated into a whole to form a tab cluster 2. However, due to the weak connection between the tab bodies 21 at the center of the tab cluster 21, after cutting, the entire tab cluster 2 may delaminate and split into two or more layers. For example, when split into two layers, the cluster includes an upper layer (including the upper weld surface near the welding head) and a lower layer (including the lower weld surface near the welding base); when split into three layers, the cluster includes an upper layer, a middle layer, and a lower layer; another example is when split into four layers, the cluster includes an upper layer, two middle layers, and a lower layer; when split into five layers, the cluster includes an upper layer, three middle layers, and a lower layer. The more layers a cluster has, the more middle layers it has.

[0052] b. After cutting, the tab cluster 2 includes at least an upper layer and a lower layer after being split. Therefore, for the upper layer, at least the first 10 tab bodies 21 closest to the welding head are guaranteed to be highly fused. For the lower layer, at least the first 10 tab bodies 21 closest to the welding base are guaranteed to be highly fused. There is an inspection standard for high fusion, that is, the tab cluster 2 after pre-welding is torn open. When the tab body A of the upper or lower layer (at least the first 10 pieces) is broken, it will stick to the other adjacent tab body B. At this time, there is a residue of tab body A on the tab body B, and it can be considered that the tab body A and the tab body B are highly fused; if the tab body A and the tab body B can be easily separated, and the two are not adhered and there is no residue, they are not considered to be highly fused (it can be equivalent to the middle layer).

[0053] c. The tab body 21 at the pre-welding edge (ie, the non-pre-welding area 203 ) is not damaged.

[0054] This embodiment further provides a battery, comprising a housing, on which a pole is disposed, and a core pack assembly according to any embodiment disposed within the housing, wherein the tab cluster 2 of the battery cell 1 of the core pack assembly is connected to the pole via a connecting piece. Because the core pack assembly in the embodiment eliminates the protective sheet and provides a hardened pre-weld area 201 on the tab body 21, the three-position positioning is changed to a two-position positioning, which reduces the difficulty of the welding process. Therefore, the battery including this core pack assembly has a low process difficulty, which is conducive to improving production efficiency. Because the connection between the tab cluster 2 and the connecting piece of the core pack assembly in the embodiment is stable, the battery including this core pack assembly is of high quality.

[0055] This embodiment also provides a battery tab welding method, which is applied to a core package assembly, wherein the core package assembly includes a battery cell and a connecting piece, the battery cell has a tab cluster, and the tab cluster includes multiple stacked tab bodies, and the method includes the following steps:

[0056] Step 100: pre-weld the tab cluster 2 using an ultrasonic toothless welding process to form a pre-weld area 201 on the tab cluster 2;

[0057] Step 200 , aligning the connecting piece with the pre-welding area 201 , and performing final welding on the tab cluster 2 and the connecting piece using an ultrasonic tooth welding process, forming a final welding area 202 on the tab cluster 2 .

[0058] It should be noted that ultrasonic serrationless welding does not mean a smooth surface. Instead, the weld mark on the welding head is a combination of corrosion and mesh patterns, with uneven, uneven, and misaligned welds. Ultrasonic serration welding, on the other hand, has distinct serrations on the weld surface. These serrations come in a variety of shapes, including prisms, hemispheres, and pyramids. Simply put, a significant difference between ultrasonic serrationless welding and ultrasonic serrationless welding is that the surface of the finished product is smoother than that of the finished product.

[0059] It should be noted that the toothless pre-welding and toothed pre-welding have an impact on the foil. The toothless pre-welding can effectively integrate and fix the tab body 21, and the damage to the tab body 21 is relatively small. The consistency of the tab body 21 in the weld mark area is relatively high. If toothed welding is used to pre-weld the tab cluster 2, then during the toothed pre-welding integration process, the tab body 21 will be pierced downward, causing greater damage to the tab body 21. The height change in the weld mark area is relatively large. During the final welding process, the final welding mark and the pre-welding mark are very easy to be misaligned, causing damage to the tab body 21.

[0060] An ultrasonic toothless pre-welding process is used to form a pre-welding area 201 on the tab cluster 2. The function of pre-welding has been described above and will not be repeated here.

[0061] In this embodiment, pre-welding is performed to improve the local connection strength of the tab cluster 2. Pre-welding does not play a role in final fixation. Using ultrasonic toothless welding for pre-welding can reduce the damage to the tab body 21 caused by the pre-welding process, avoid the tab body 21 from being broken or damaged during final welding, and ensure the connection stability between the pole piece and the connecting piece in the battery cell 1.

[0062] The pre-welding method of the ultrasonic toothless welding process changes the connection strength between the tab bodies 21, so that the tab bodies 21 in the pre-welding area 201 are no longer in a loose state, and they maintain as close a connection as possible with each other. For example, the tab body 21 on the outermost surface of the tab cluster 2 can be tightly fused with the adjacent tab body 21. In this way, when performing the final welding, even if the connecting piece needs to be moved, the tab body 21 located on the surface of the tab cluster 2 will not move with the connecting piece, which facilitates the welding positioning between the tab cluster 2 and the connecting piece.

[0063] Pre-welding is performed on the tab cluster 2, and a pre-welding area 201 and a non-pre-welding area 203 can be formed in the tab cluster 2. The connection strength between the tab bodies 21 in the pre-welding area 201 is greater than the connection strength between the tab bodies 21 in the non-pre-welding area 203 around the pre-welding area 201. Since the tab cluster 2 has a pre-welding area 201 for improving the connection strength, the tab bodies 21 are effectively fused and connected, and the connection strength between each other is improved. Therefore, in the final welding stage, the protective sheet is no longer needed to assist in welding the tab cluster 2. The original three-position welding process of the protective sheet, the tab cluster 2 and the connecting sheet is simplified to a two-position welding process between the tab cluster 2 and the connecting sheet. Compared with the related art, the protective sheet is no longer needed, and there is no situation where the protective sheet scratches the tab body 21. At the same time, the process difficulty of the two-position welding process is also effectively reduced compared to the three-position welding process.

[0064] 2 , in one embodiment, in step 100 , during pre-welding, the welding head is spaced from the edge of the tab cluster 2. It is understood that, before pre-welding, the edges of the laminated tab bodies 21 are aligned. During pre-welding, the tab bodies 21 on both sides of the tab cluster 2 converge toward the center of the tab cluster 2. That is, the tab bodies 21 on both sides of the tab cluster 2 bend, resulting in stepped edges and height differences. During pre-welding, the welding head is spaced from the edge of the tab cluster 2 to prevent the edge of the tab body 21 from being within the pre-welding area 201, thereby ensuring pre-welding quality.

[0065] In one embodiment, between step 100 and step 200, the following steps are further included:

[0066] The tab cluster 2 is placed on a substrate 3 , and the ends of the tab cluster 2 are cut with a cutting knife so that the ends of the tab cluster 2 are flush.

[0067] Referring to Figure 1, before the pre-welding process, the edges between the tab bodies 21 are basically flush. Referring to Figure 2, after the pre-welding process, after the multiple layers of tab bodies 21 are stacked and gathered, the tab bodies 21 are stepped, that is, the tab bodies 21 on both sides of the tab cluster 2 are shorter than the tab body 21 in the center of the tab cluster 2, which will affect the connection between the tab cluster 2 and the connecting piece. In addition, the tab body 21 that is too long is also easy to contact with the battery shell, causing an internal short circuit in the battery, affecting the safety of the battery. In this embodiment, referring to Figure 3, the pre-welded tab cluster 2 is cut. The tab cluster 2 can be placed on a substrate 3, and then a cutter is used to cut and integrate the tab cluster 2 so that the edges of all the tab bodies 21 on the tab cluster 2 are flush. On the one hand, it can facilitate the welding positioning between the tab cluster 2 and the connecting piece, and on the other hand, it can also avoid the short circuit between the tab body 21 that is too long and the shell.

[0068] In this embodiment, within the pre-welding area 201, the connection strength between the tab bodies 21 gradually increases along the direction from the center of the tab cluster 2 to the surface of the tab cluster 2. Pre-welding can gather the originally loose tab bodies 21, connect the tab bodies 21 together as much as possible, and facilitate the positioning between the tab cluster 2 and the connecting piece. Since the connecting piece is set on the surface of the tab cluster 2, it can only be limited to improving the connection strength between the tab bodies 21 on the surface of the tab cluster 2. That is, along the direction from the center of the tab cluster 2 to the surface of the tab cluster 2, the connection strength between the tab bodies 21 gradually increases. In other words, the closer the tab bodies 21 are to the surface, the stronger the connection strength is, and the closer the tab bodies 21 are to the center, the weaker the connection strength is. Therefore, after cutting, the connection strength between the tab bodies 21 at the center of the tab cluster 2 is weaker, and the tab cluster 2 may be delaminated.

[0069] In one embodiment, the cutting line is flush with the edge of the pre-welding area 201 so that the pre-welding area 201 is connected to the end face of the tab cluster 2. In other words, the pre-welding area 201 is connected to the end face of the tab cluster 2, which can reduce the difficulty of positioning the connecting piece and the tab cluster 2. In one embodiment, along the width direction of the tab body 21, the size of the connecting piece is smaller than the size of the tab body 21, and the size of the connecting piece is larger than the size of the pre-welding area 201. By setting the size of the connecting piece smaller than the size of the tab body 21 along the width direction of the tab body 21, and the size of the connecting piece larger than the size of the pre-welding area 201, it is possible to avoid the connecting piece completely blocking the pre-welding area 201. This can reduce the difficulty of positioning the connecting piece and the tab cluster 2, while also reducing the difficulty of positioning the welding head and reducing the difficulty of the final welding process.

[0070] In this embodiment, ultrasonic serrated welding is used for final welding. Ultrasonic serrated welding refers to the welding surface having obvious weld teeth. During the serrated pre-welding integration process, the ultrasonic energy of the welding penetrates the tab cluster 2 and pierces each layer of the tab body 21, so that each layer of the tab body 21 can be welded and fixed to the connecting piece, ensuring that the battery cell 1 can transmit electrical energy through the connecting piece.

[0071] In one embodiment, the area of ​​the pre-welding area 201 is larger than the area of ​​the final welding area 202, and the final welding area 202 is located within the pre-welding area 201. By setting the area of ​​the pre-welding area 201 to be larger than the area of ​​the final welding area 202, during the welding process, even if there is a slight positional offset between the connecting piece and the tab cluster 2, it can still be ensured that the final welding area 202 is located within the range of the pre-welding area 201, thereby ensuring the welding quality between the tab cluster 2 and the connecting piece; the shape and size of the pre-welding area 201 and the final welding area 202 can be selected according to actual needs, and this embodiment is not limited thereto. The shapes of the pre-welding area 201 and the final welding area 202 in this embodiment are both rectangular, and the distances between the multiple edges of the final welding area 202 and the multiple edges of the pre-welding area 201 are not required to be equal, that is, the center of the final welding area 202 is not required to coincide with the center of the final welding area 202.

[0072] In one embodiment, during final welding, the center of the welding head is aligned with the center of the pre-welding area 201. By aligning the center of the welding head with the center of the pre-welding area 201 during final welding, the center of the final welding area 202 can be aligned with the center of the pre-welding area 201 as much as possible, which helps to improve the welding quality of the connecting piece and the tab cluster 2.

[0073] In this embodiment, the distance between the edge of the final welding area 202 and the edge of the pre-welding area 201 is L, and L is ≥ 2 mm. In this embodiment, the area of ​​the pre-welding area 201 is larger than the area of ​​the final welding area 202, and the distance between the edge of the final welding area 202 and the edge of the pre-welding area 201 is set to be greater than 2 mm. During the welding process, even if there is a slight positional offset between the connecting piece and the tab cluster 2, the final welding area 202 can still be ensured to be located within the range of the pre-welding area 201, thereby ensuring the welding quality between the tab cluster 2 and the connecting piece; the shape and size of the pre-welding area 201 and the final welding area 202 can be selected according to actual needs, and this embodiment is not limited here. The shapes of the pre-welding area 201 and the final welding area 202 in this embodiment are both rectangular, and the distances between multiple edges of the final welding area 202 and multiple edges of the pre-welding area 201 are not required to be equal, that is, the center of the final welding area 202 is not required to coincide with the center of the final welding area 202. It is only necessary to ensure that the final welding area 202 is located within the pre-welding area 201 and that the final welding area 202 is 2 mm away from the edge of the pre-welding area 201.

[0074] In one embodiment, the welding time of pre-welding is T1, the welding time of final welding is T2, T1<T2; the temperature rise of pre-welding is S1, the temperature rise of final welding is S2, S1<S2; the welding power of pre-welding is P1, the welding power of final welding is P2, P1<P2. In this embodiment, the pre-welding process can gather the originally loose tab bodies 21 and connect the tab bodies 21 together as much as possible, thereby increasing the connection strength between the tab bodies 21. Adjacent tab bodies 21 support each other, so that the connection strength between the tab bodies 21 in the pre-welding area 201 is greater than the connection strength between the tab bodies 21 in the non-pre-welding area 203, which is beneficial to the subsequent final welding with the connecting piece. Since pre-welding is only a processing method to assist final welding, the connection strength between the tab bodies 21 in the pre-welding area 201 does not need to be too high, as long as the tab body is no longer in a loose state. It is understandable that multiple welding will easily damage the tab body 21. In order to reduce the damage to the tab body 21 foil by the pre-welding process, it is necessary to control the welding time, temperature rise and power of the pre-welding. Since the connection strength between the tab bodies 21 after pre-welding does not need to be higher than the connection strength between the tab bodies 21 after final welding, then, on the basis of the final welding parameter standard, the welding time, temperature rise and power standard of the pre-welding can be reduced, thereby reducing the damage to the tab body 21 foil.

[0075] The welding time T1 of the pre-welding is less than 0.3 seconds, and the welding time T2 of the final welding is less than 0.5 seconds. It is understandable that the welding time affects the total energy of the welding and also affects the transfer depth of the welding heat. By controlling the welding time of the pre-welding within 0.3 seconds, the heat transferred to the center of the tab cluster 2 can be reduced, and the damage to the tab body 21 can be reduced; because the tab bodies 21 located on the surface of the tab cluster 2 have already reached a certain degree of bonding during the pre-welding, controlling the welding time of the final welding within 0.5 seconds can reduce the damage to the tab body 21 caused by the secondary welding, which is conducive to improving the welding quality.

[0076] The temperature rise S1 of the pre-welding is less than 50°C, and the temperature rise S2 of the final welding is less than 80°C. It can be understood that in a very short period of time, the temperature rise of welding mainly affects the degree of fusion of the surface welding object. Since the pre-welding is to gather the loose tab bodies 21 and facilitate the positioning between the tab cluster 2 and the connecting piece, the connection strength between the tab bodies 21 in the pre-welding area 201 does not need to be too high, and it is sufficient to ensure that the tab bodies are no longer in a loose state. Therefore, controlling the temperature rise of the pre-welding to no more than 50°C can, on the one hand, meet the forming requirements of the pre-welding area 201, and on the other hand, avoid the excessive melting of the tab bodies 21 on the surface of the tab cluster 2, which may cause defects such as cracks in subsequent welding.

[0077] The pre-welding power P1 is less than 3000W, and the final welding power P2 is less than 5000W. It is understood that the welding power affects the quality of welding. Excessively high power in the laser welding machine burns alloy elements in the weld zone, reducing the strength and mechanical properties of the weld. High welding power also worsens weld formation and increases surface holes. Therefore, setting the pre-welding power within 3000W and the final welding power within 5000W can reduce the probability of defects occurring in the pre-welding zone 201 of the tab cluster 2, between the tab cluster 2, and the connecting piece during welding.

[0078] In general, the welding time of the pre-welding process is less than 0.3 seconds, the temperature rise is less than 50°C, the welding power is less than 3000W, 20μm≤X1≤100μm, and when the welding head acts on the upper surface of the tab cluster 2 for high-frequency vibration, the upper tab body 21 gradually merges; at the same time, the ultrasonic welding base also acts on the lower surface of the tab cluster 2, and the lower tab body 21 gradually aggregates, and the center of the tab cluster 2 points to the direction of the surface of the tab cluster 2, and the connection strength between the tab bodies 21 gradually increases; the welding time of the final welding process is less than 0.5 seconds, the temperature rise is less than 80°C, and the welding power is less than 5000W.

[0079] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and do not have any special meaning.

[0080] In the description of this specification, reference to the terms "one embodiment" or "example" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of terms does not necessarily refer to the same embodiment or example.

[0081] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in multiple embodiments can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A core package assembly, comprising a battery cell and a connecting sheet, the battery cell comprising a tab cluster, the tab cluster comprising a plurality of tab bodies arranged in a stacked manner, a pre-welding area and a non-pre-welding area being arranged on the tab cluster, the connection strength of the pre-welding area being greater than the connection strength of the non-pre-welding area, a welding protrusion and a first welding depression being arranged in the pre-welding area, the absolute value of the height difference between the welding protrusion and the first welding depression being X1, a final welding area being further arranged in the pre-welding area, the final welding area being welded to the connecting sheet, a second welding depression being arranged on the surface of the final welding area, the absolute value of the height difference between the second welding depression and the surface of the final welding area being X2, and X1<X2.

2. The core package assembly according to claim 1, wherein: 20μm≤X1≤100μm.

3. The core package assembly according to claim 2, wherein: 40μm≤X1≤60μm.

4. The core package assembly according to claim 1, wherein: X2>500μm.

5. The core package assembly according to claim 1, wherein: The distance between the edge of the final welding area and the edge of the pre-welding area is L, and L is ≥ 2 mm.

6. The core package assembly according to any one of claims 1 to 5, wherein: In the pre-welding area, in the thickness direction, along the direction from the center of the tab cluster to the upper surface or the lower surface of the tab cluster, the connection strength between the tab bodies gradually increases.

7. The core package assembly according to claim 6, wherein: In the pre-welding area, in the thickness direction, the tab bodies located at the center of the tab cluster are in surface contact with each other.

8. The core package assembly according to any one of claims 1 to 5, wherein: The edges of all the tab bodies on the tab cluster are flush.

9. The core package assembly according to claim 8, wherein: Along the width direction of the tab body, the size of the connecting piece is smaller than the size of the tab body, and the size of the connecting piece is larger than the size of the pre-welding area.

10. A battery, comprising a shell, on which a pole is arranged, and in which a core package assembly according to any one of claims 1 to 9 is arranged, wherein a pole lug cluster of a cell of the core package assembly is connected to the pole via a connecting sheet.

11. A battery tab welding method, applied to a core package assembly, the core package assembly comprising a battery cell and a connecting sheet, the battery cell having a tab cluster, the tab cluster comprising a plurality of tab bodies stacked together, the method comprising: Pre-welding the tab clusters by ultrasonic toothless welding process, and forming pre-welding areas on the tab clusters; The connecting piece is aligned with the pre-welding area, and the tab cluster and the connecting piece are finally welded by an ultrasonic toothed welding process, and a final welding area is formed on the tab cluster.

12. The battery tab welding method according to claim 11, wherein: When the tab cluster is pre-welded by the ultrasonic toothless welding process, the welding head is spaced from the edge of the tab cluster.

13. The battery tab welding method according to claim 12, wherein after the tab cluster is pre-welded by ultrasonic toothless welding and a pre-welding area is formed on the tab cluster, the connecting piece is aligned with the pre-welding area, the tab cluster and the connecting piece are final-welded by ultrasonic toothed welding, and before a final welding area is formed on the tab cluster, the method further comprises: The ends of the tab clusters are cut to make the ends of the tab clusters flush.

14. The battery tab welding method according to claim 13, wherein: When the end of the tab cluster is cut, the cutting line is flush with the edge of the pre-welding area, so that the pre-welding area is connected to the end surface of the tab cluster.

15. The battery tab welding method according to claim 11, wherein: The area of ​​the pre-welding area is larger than that of the final welding area, and the final welding area is located within the pre-welding area.

16. The battery tab welding method according to claim 11, wherein: When the terminal lug cluster and the connecting sheet are finally welded by the ultrasonic toothed welding process, the center of the welding head is aligned with the center of the pre-welding area.

17. The battery tab welding method according to any one of claims 11 to 16, wherein: The method satisfies at least one of the following: The welding time of pre-welding is T1, and the welding time of final welding is T2, T1<T2; The temperature rise of pre-welding is S1, the temperature rise of final welding is S2, S1<S2; and The welding power for pre-welding is P1, and the welding power for final welding is P2, P1<P2.

18. The battery tab welding method according to claim 17, wherein: In response to determining that the welding time of the pre-welding is T1 and the welding time of the final welding is T2, T1<T2, it is determined that T1<0.3 seconds and T2<0.5 seconds.

19. The battery tab welding method according to claim 17, wherein: In response to determining that the temperature rise of the pre-welding is S1, the temperature rise of the final welding is S2, S1<S2, it is determined that S1<50℃, S2<80℃.

20. The battery tab welding method according to claim 17, wherein: In response to determining that the welding power of the pre-welding is P1 and the welding power of the final welding is P2, P1<P2, it is determined that P1<3000W and P2<5000W.

Images