Laminated battery tab welding method and full-tab laminated battery

Abstract

The invention relates to the technical field of laminated battery tab welding, in particular to a laminated battery tab welding method and a full-tab laminated battery. The invention aims to solve the problems of interlayer bubbles, pseudo soldering, surface cracking, welding faults and the like existing in lamination full-tab ultrasonic welding. Specifically, by introducing a composite welding technology combining laser welding and ultrasonic welding, the welding quality and stability of the tabs are improved, and the overall performance of the laminated full-tab battery cell is further improved.

Description

Technical Field

[0001] This invention relates to the field of electrode tab welding technology for laminated batteries, specifically to a method for welding electrode tabs of laminated batteries and a laminated battery with all tabs. Background Technology

[0002] In the production of lithium-ion batteries, the stacked full-tab structure is widely used because it can reduce internal resistance and improve rate performance, but the welding process of this structure has always been a challenge for the industry.

[0003] Traditional stacked battery tabs, especially those in full-tab stacked batteries, suffer from numerous problems when relying solely on ultrasonic welding. First, the substantial thickness of the stacked tabs in stacked batteries makes it difficult for ultrasonic energy to be evenly distributed across layers, leading to defects such as bubbles and incomplete welds between tab layers. This significantly impacts weld strength. Second, the tab surface is prone to cracking due to excessive compression during welding, reducing battery safety. Furthermore, the sharp edges of the weld marks created by ultrasonic welding can easily cause delamination when welding to the terminal blocks, affecting the battery's dielectric properties. These issues severely limit the full potential of the cells in stacked batteries, reducing production yield and product reliability.

[0004] Therefore, there is an urgent need to design a tab welding method for stacked batteries to improve the production yield and product reliability of stacked batteries. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for welding tabs of stacked batteries to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for welding tabs of a stacked battery includes the following steps: Step S1: The positive and negative electrodes of the laminated battery cell are pressed and welded together using an ultrasonic welding head to form the positive electrode welding part and the negative electrode welding part. Step S2: Perform laser weld mark treatment on the positive electrode tab welding part and the negative electrode tab welding part respectively; Step S3: Shape the positive electrode tab welding part processed in step S2 and attach it to the positive electrode post of the battery cover plate; shape the negative electrode tab welding part processed in step S2 and attach it to the negative electrode post of the battery cover plate. Step S4: Weld the positive electrode tab welded part after step S3 to the positive electrode post by laser welding, and weld the negative electrode tab welded part after step S3 to the negative electrode post.

[0007] Compared with the prior art, the beneficial effects of the present invention are: This application introduces a composite welding technology combining laser welding and ultrasonic welding in the above-mentioned technical solution to improve the quality and stability of tab welding, thereby enhancing the overall performance of the laminated all-tab laminated battery cell.

[0008] As a further improvement to the electrode tab welding method of the stacked battery of this application, in step S1, one or both sides of the positive electrode tab welding part and the negative electrode tab welding part are formed by pressure welding to form an ultrasonic weld mark.

[0009] As a further improvement to the electrode tab welding method of the stacked battery of this application, in step S2, during the laser weld mark treatment process, the laser welding head is adjusted to perform tilted scanning on the ultrasonic weld mark, so that the surface of the ultrasonic weld mark is treated as a non-flat surface.

[0010] As a further improvement to the electrode tab welding method of the stacked battery of this application, the laser weld mark treatment process includes ultrasonic welding treatment of both sides and the other side of the ultrasonic weld mark respectively. Specifically, one arm of the ultrasonic soldering is scanned at a first preset angle, and the other arm of the ultrasonic soldering is scanned at a second preset angle.

[0011] As a further improvement to the electrode tab welding method of the stacked battery of this application, the laser welding head moves forward along an S-shaped trajectory and covers the area where the ultrasonic weld mark is located during the laser weld mark treatment process.

[0012] As a further improvement to the electrode tab welding method of the stacked battery of this application, the depth value of the ultrasonic solder mark meets the requirement of 0.15mm-0.25mm.

[0013] As a further improvement to the method for welding tabs of a stacked battery according to this application, in step S3, during the shaping process of the positive tab welding portion, the positive tab welding portion is bent so that the positive tab welding portion contacts the positive electrode post; during the shaping process of the negative tab welding portion, the negative tab welding portion is bent so that the negative tab welding portion contacts the negative electrode post.

[0014] As a further improvement to the method for welding tabs of a stacked battery according to this application, during the shaping process of the positive tab welding portion, the portion of the positive tab welding portion that is not in contact with the positive electrode post is removed; during the shaping process of the negative tab welding portion, the portion of the negative tab welding portion that is not in contact with the negative electrode post is removed.

[0015] The second objective of this invention is to apply the above-mentioned method for welding the tabs of stacked batteries to the production process of all-tab stacked batteries, thereby producing an all-tab stacked battery with high yield and reliability.

[0016] To achieve the above-mentioned objectives, this application implements the following technical solution: A multi-tab stacked battery includes one or two multi-tab stacked cells, a cover plate fixedly connected to the cells, and a casing for assembling the multi-tab stacked battery. The cover plate is provided with a positive terminal and a negative terminal. The positive terminal of the full-tab laminated cell is welded to the positive terminal using any of the above-mentioned laminated battery terminal welding methods; the negative terminal of the full-tab laminated cell is welded to the negative terminal using any of the above-mentioned laminated battery terminal welding methods.

[0017] The above technical solution produces the following technical effects: By applying a composite welding technology combining laser welding and ultrasonic welding to the welding process of tabs and terminals in all-tab laminated batteries, the robustness of the tab welds is significantly enhanced. This strong weld connection ensures more stable current transmission during charging and discharging, reducing problems such as increased resistance and overheating caused by poor welding, thereby effectively improving the battery's charging and discharging efficiency. Simultaneously, the improved welding quality leads to a more stable internal battery structure, reducing the risk of loosening or detachment of the tabs and terminals during use, significantly improving the reliability and lifespan of all-tab laminated batteries.

[0018] As a further improvement to the all-tab stacked battery of this application, the separator in the all-tab stacked cell is folded according to the Z-shaped folding process, and the positive electrode and negative electrode in the all-tab stacked cell are alternately inserted into the grooves of the separator; wherein, the tabs of the positive electrode and the negative electrode are all all-tabs. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for welding tabs of a stacked battery according to the present invention; Figure 2 This is a schematic diagram illustrating the workflow of a method for welding tabs of a stacked battery according to the present invention. Figure 3 This is a schematic diagram of the welding of the positive electrode tab of the stacked battery in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the welding of the negative electrode tab of the stacked battery in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the welding of the positive electrode tab of the stacked battery in Comparative Example 1; Figure 6 This is a schematic diagram of the structure of the multi-tab stacked battery of the present invention; Figure 7 This is a side view of the cell structure on the positive electrode tab side of the multi-tab stacked battery of the present invention; Figure 8 This is a side view of the cell structure on the negative electrode tab side of the multi-tab stacked battery of the present invention; Figure 9The graphs show the discharge temperature rise test data for Example 1 and Comparative Example 1. Tag name: 1 - Cover plate; 11 – Positive terminal post; 12 - Negative electrode post; 2 - Shell; 3-All-tab laminated cell; 31-Positive electrode sheet; 311 - Positive electrode tab; 32-Negative electrode sheet; 321 – Negative electrode tab; 33 - Diaphragm. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It is worth noting that this application has discovered technical defects in the shaping and welding of the tabs of traditional stacked batteries, as well as in the welding of the tabs to the terminals in the battery cover plate 1. Therefore, this application proposes an approach to improve the welding process of existing stacked batteries. While this application focuses on the experimental and comparative analysis of all-tab stacked batteries, the proposed process improvement technology is applicable to all stacked batteries.

[0022] In the specific implementation process, such as Figure 1-2 As shown, the method for welding the tabs of a laminated battery in this application includes the following steps: Step S1: The positive electrode tab 311 and the negative electrode tab 321 of the laminated battery cell are pressed and welded together using an ultrasonic welding head to form the positive electrode tab 311 welding part and the negative electrode tab 321 welding part. In the aforementioned ultrasonic welding and pressing process, an ultrasonic welding head is specifically used to press-weld multiple layers of tabs, fusing the multiple tabs into a single unit to form a tab welding portion, and forming an ultrasonic weld mark on at least one side surface of the tab welding portion. Specifically, this application sets the depth of the ultrasonic weld mark to be greater than or equal to 0.15 mm and less than or equal to 0.25 mm. Within this range, the gap between the tab layers can be compressed, reducing or avoiding the occurrence of air bubbles between the tab layers, and initially solving the problem of incomplete welding that easily occurs in ultrasonic welding on tabs.

[0023] Step S2: Perform laser weld mark treatment on the welding parts of the positive electrode tab 311 and the negative electrode tab 321 respectively; The introduction of laser welding for weld scar treatment is a key step in resolving defects in the ultrasonic welding of laminated electrode tabs. A laser welding head is used to sweep the ultrasonic weld marks at an angle, creating a non-flat surface and adjusting the weld depth to less than 0.12mm. This laser sweeping selectively melts the edges of the weld marks, locally smoothing them and reducing unevenness. This effectively mitigates the risk of delamination caused by welding the ultrasonically welded tabs to the electrode terminal, while also reducing the possibility of surface cracking of the tabs.

[0024] Furthermore, during operation, the laser welding head can be controlled to scan the two sides of the weld mark at a suitable angle. The laser welding head moves sequentially along an "S"-shaped trajectory and covers the entire weld mark area, improving the scanning effect.

[0025] Specifically, in the above-mentioned laser weld mark treatment process, the ultrasonically welded battery cell is transferred to the laser weld mark treatment equipment. The position and angle of the laser welding head are adjusted to align it with the ultrasonic weld mark. The laser welding head is controlled to irradiate one side wall of the weld mark at a first preset angle (such as 45° or set between 30° and 40° depending on the actual situation) for one sweep.

[0026] During the laser scanning process described above, the laser power and the moving speed of the laser welding head are controlled to ensure that the laser can effectively melt the edges of the weldment. After one scan, the laser welding head is controlled to irradiate the other sidewall of the ultrasonic weldment at a second preset angle (such as 45° or set between 50° and 60° depending on the actual situation) to perform a second scan. During the scan, the laser welding head moves sequentially along an "S"-shaped trajectory and covers the entire weldment area, thereby treating the surface of the weldment to be a non-flat surface and adjusting the depth of the weldment to less than 0.12mm.

[0027] Step S3, as follows Figure 3-4 As shown, the positive electrode tab 311 welding part processed in step S2 is shaped and attached to the positive electrode post 11 of the battery cover plate 1, and the negative electrode tab 321 welding part processed in step S2 is shaped and attached to the negative electrode post 12 of the battery cover plate 1. During the above shaping process, the shaping force must be strictly controlled to avoid damaging the tabs due to excessive force, while also ensuring a good shaping effect. After shaping, the surface flatness and fit of the tab welding part are checked. If there are any unevenness or poor fit, fine adjustments are made in time. The shaped positive tab 311 welding part is carefully attached to the positive terminal post 11 of the battery cover plate 1.

[0028] Similarly, the negative electrode tab 321 is attached to the negative electrode post 12 of the battery cover plate 1 in the same manner. During the attachment process, care must be taken to avoid gaps or misalignment between the tab and the post to ensure the quality of subsequent welding and the performance stability of the battery. After attachment, the attachment of the tab and post is checked again to ensure that the entire attachment process is accurate.

[0029] Optionally, during the shaping process of the positive electrode tab 311 welding section, the portion of the positive electrode tab 311 welding section that does not contact the positive electrode post 11 is removed; similarly, during the shaping process of the negative electrode tab 321 welding section, the portion of the negative electrode tab 321 welding section that does not contact the negative electrode post 12 is removed. This further reduces the space occupied by excess tabs within the battery, improving the overall space utilization of the battery. Simultaneously, removing excess portions also helps reduce the probability of short circuits and other safety hazards during battery use. Cleaning away these excess tab portions also ensures a tighter and more stable fit between the tab and the post, reducing potential contact problems caused by movement of excess portions.

[0030] Step S4: The positive electrode tab 311, processed in step S3, is welded to the positive electrode post 11 using laser welding, and the negative electrode tab 321, processed in step S3, is welded to the negative electrode post 12. In practice, a high-power laser beam is used to perform penetration welding on the area where the laser weld mark is located after weld treatment to the electrode post connection terminal. The high-power laser beam ensures that the energy penetrates the relatively thick full-tab welding portion and melts the contact surface between the electrode post connection terminal and the tab welding portion, further improving welding strength and stability, reducing welding defects, and fully utilizing the performance of the laminated full-tab. Simultaneously, an air blowing device and a dust extraction device are added during the welding process to ensure welding quality.

[0031] The above specific implementation methods can effectively solve the problems existing in ultrasonic welding of stacked full-tab cells, complete high-quality tab welding, give full play to the performance advantages of stacked full-tab cells 3, and improve the overall performance and production efficiency of the battery.

[0032] Preferably, this application applies the above-mentioned technical solution to the manufacturing process of multi-tab stacked batteries. For example, Figure 6-8As shown, the all-tab laminated battery of this application includes one or two all-tab laminated cells 3, a cover plate 1 fixedly connected to the cells, and a housing 2 for assembling the all-tab laminated cells. The cover plate 1 is provided with a positive terminal 11 and a negative terminal 12. The positive terminal 311 of the all-tab laminated cell 3 is welded to the positive terminal 11 by any of the above-mentioned laminated battery terminal welding methods. The negative terminal 321 of the all-tab laminated cell 3 is welded to the negative terminal 12 by any of the above-mentioned laminated battery terminal welding methods. When there are two cells, the two all-tab laminated cells 3 are connected in parallel. After the positive electrode tabs 311 of the two battery cells are processed by the welding process described above in this application, the welding part of the positive electrode tab 311 of one battery cell is welded to the positive electrode post 11 on one side, and the welding part of the positive electrode tab 311 of the other battery cell is welded to the positive electrode post 11 on the other side; the welding part of the negative electrode tab 321 of one battery cell is welded to the negative electrode post 12 on one side, and the welding part of the negative electrode tab 321 of the other battery cell is welded to the negative electrode post 12 on the other side. This connection method can increase the battery capacity.

[0033] It is worth noting that the separator 33 in the all-tab laminated cell 3 of this application is folded using a Z-shaped folding process. The positive electrode 31 and negative electrode 32 in the all-tab laminated cell 3 are alternately inserted into the folded grooves of the separator 33; wherein the tabs of both the positive electrode 31 and the negative electrode 32 are all all-tabs. The Z-shaped folded structure of the separator 33 can effectively increase the wetting area of ​​the electrolyte and improve the ion transport efficiency.

[0034] Furthermore, multiple sets of positive and negative electrode plates are provided. These multiple sets of positive and negative electrode plates are alternately inserted into the grooves of the separator 33 from both sides and wrapped by the separator 33 to form a stacked structure. Each set of positive and negative electrode plates features a full tab design, meaning the tabs are continuously distributed along the edges of the electrode plates. Each set of positive electrode plates includes multiple positive electrode plates arranged in layers, and each set of negative electrode plates includes multiple negative electrode plates arranged in layers. This makes the electrode arrangement inside the cell more compact and regular, reduces the gaps between the electrode plates, and improves the space utilization and energy density of the cell.

[0035] Furthermore, in the aforementioned battery cell, each group of positive electrode sheets and each group of negative electrode sheets are arranged in a bent, stacked strip structure. This arrangement increases the effective area of ​​the electrode sheets, thereby improving battery capacity; it also buffers the expansion and contraction of the electrode sheets during charging and discharging, reducing electrode deformation and improving cycle life.

[0036] To further verify the effectiveness of the electrode tab welding method for stacked batteries in improving the yield and reliability of stacked batteries, especially full-tab stacked batteries, this application provides a set of embodiments and a set of comparative examples.

[0037] Example 1 The fabrication process of the all-tab stacked battery in this embodiment is as follows: First, the electrode sheets are prepared by thoroughly mixing the positive electrode active material, conductive agent, binder, etc., according to the formula to form a positive electrode slurry, and mixing the negative electrode active material, additives, etc., to form a negative electrode slurry. Then, the positive and negative electrode slurries are uniformly coated on the positive and negative current collectors, respectively. After drying, rolling and other processes, the desired positive and negative electrode sheets are obtained. The electrode sheets adopt a full tab design to ensure that the tabs are continuously distributed at the edge of the electrode sheet.

[0038] Next, the separator 33 is prepared. A separator 33 material with good ion permeability and chemical stability is selected and processed into a structure with folds. Multiple sets of prepared positive and negative electrode sheets are alternately inserted into the folds of the separator 33 from both sides, so that the separator 33 wraps the electrode sheets to form a stacked structure. Each set of positive and negative electrode sheets consists of multiple bent and stacked strip-shaped electrode sheets to increase the effective area of ​​the electrode sheets and buffer the expansion and contraction of the electrode sheets during charging and discharging.

[0039] Next, the tabs are welded using the stacked battery tab welding method of this application. The positive tab 311 and the negative tab 321 are welded separately to ensure a strong weld and low contact resistance, thereby improving the conductivity and reliability of the battery.

[0040] After welding, the stacked structure is placed into the battery casing 2 for encapsulation to ensure the battery's airtightness and prevent electrolyte leakage. Finally, electrolyte is injected, and after formation and capacity testing, the battery reaches a usable state, completing the fabrication of the all-tab stacked battery.

[0041] Specifically, in this embodiment, the positive electrode tab 311 welding part and the negative electrode tab 321 welding part of the cell of the multi-tab stacked battery are as follows: Figure 3 , 4 As shown.

[0042] Comparative Example 1 Unlike Example 1, in this example, the cells of the multi-tab stacked battery are all welded to the positive electrode tab 311 and the negative electrode tab 321 respectively by ultrasonic welding.

[0043] Specifically, in this embodiment, the welding of the positive electrode tab 311 and the negative electrode tab 321 of the cell in the multi-tab laminated battery is as follows: Figure 5 As shown.

[0044] Furthermore, this application conducted battery discharge temperature rise performance tests on the stacked batteries prepared in Example 1 and Comparative Example 1, respectively. The battery discharge temperature rise test method involved placing the battery under test in a temperature-controlled environmental chamber, setting the ambient temperature to 25°C, to allow the battery to reach thermal equilibrium. Then, the battery was discharged at a constant current of 1C, while a high-precision temperature sensor was used to monitor the temperature changes on the battery surface in real time. The temperature sensors were evenly distributed across various key parts of the battery, including near the tabs and at the center of the cell surface, to ensure accurate capture of temperature changes at different locations. During the discharge process, temperature data at each monitoring point was recorded every minute until the battery discharged to its cutoff voltage.

[0045] The parameters involved in the test are SOC, temperature, and temperature rise. SOC represents the battery's state of charge, reflecting the proportion of remaining charge in the battery and is an important indicator of its usable energy. Accurately recording the SOC value at different times in this test helps analyze the discharge temperature rise characteristics of the battery under different charge states.

[0046] Temperature refers to the actual temperature value measured in real time at various monitoring points on the battery surface. This data can intuitively show the heat generation of the battery during the discharge process.

[0047] Temperature rise refers to the increase in battery temperature relative to the initial temperature during discharge. It more clearly reflects the degree of heat generated by the battery during discharge and is a key parameter for evaluating battery thermal stability.

[0048] Specifically, the battery temperature rise test results of Example 1 and Comparative Example 1 are as follows: Figure 9 As shown, the following are the data for Example 1 and Example 2.

[0049] In summary, a comparison of the data from Example 1 and Comparative Example 1 shows that the battery cell prepared by the technical solution of this application exhibits a significantly lower temperature rise under the same SOC conditions compared to the battery cell prepared by the technical solution of Comparative Example 1. In particular, when the SOC reaches 100%, the temperature rise rate of the battery cell prepared by Comparative Example 1 increases sharply, while the temperature rise of the battery cell prepared by Example 1 shows no significant change. This indicates that the technical solution of this application has a significant advantage in battery thermal stability. Under high SOC conditions, the rapid temperature rise of the battery cell prepared by Comparative Example 1 may lead to a series of safety hazards, such as accelerated battery aging, reduced battery lifespan, and even serious problems such as thermal runaway. In contrast, the temperature rise of the battery cell prepared by the technical solution of this application is relatively gradual, better maintaining battery performance and safety.

[0050] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of welding a tab of a laminated battery cell, characterized by, The method comprises the following steps: Step S1, the positive and negative tab of the laminated cell is pressed and welded by ultrasonic welding head to form the positive and negative tab welding part; Step S2, the positive and negative tab welding part is respectively processed by laser welding mark; Step S3, the positive and negative tab welding part processed by step S2 is shaped and adhered to the positive and negative pole of the battery cover plate; Step S4, the positive and negative tab welding part processed by step S3 is welded to the positive and negative pole by laser welding.

2. The method of claim 1, wherein the method further comprises: In step S1, the surface of one side or both sides of the positive and negative tab welding part is formed by pressure welding to form the ultrasonic welding mark.

3. The method of claim 2, wherein the welding is performed by a laser beam. In step S2, the laser welding mark processing process, the laser welding head is adjusted to obliquely scan the ultrasonic welding mark, and the surface of the ultrasonic welding mark is processed into a non-flat surface.

4. The method of claim 3, wherein the welding is performed by a laser beam. The laser welding mark processing process comprises ultrasonic welding processing of one side wall and the other side wall of the ultrasonic welding mark; Wherein, the one side arm of the ultrasonic welding mark is scanned by a first preset angle, and the other side arm of the ultrasonic welding mark is scanned by a second preset angle.

5. The method of claim 3, wherein the welding is performed by a laser beam. The laser welding head moves along the S-shaped trajectory in the laser welding mark processing process and covers the area where the ultrasonic welding mark is located.

6. The method of claim 2, wherein the welding is performed by a laser beam. The depth value of the ultrasonic welding mark satisfies 0.15mm-0.25mm.

7. The method of claim 1, wherein the method further comprises: In step S3, in the shaping process of the positive tab welding part, the positive tab welding part is bent to make the positive tab welding part contact with the positive pole; in the shaping process of the negative tab welding part, the negative tab welding part is bent to make the negative tab welding part contact with the negative pole.

8. The method of claim 7, wherein the welding is performed by a laser beam. In the shaping process of the positive tab welding part, the part of the positive tab welding part not in contact with the positive pole is removed; in the shaping process of the negative tab welding part, the part of the negative tab welding part not in contact with the negative pole is removed.

9. A full tabbed stack battery, characterized by, It comprises one or two full tab laminated cells, a cover plate fixedly connected with the cell, and a shell assembled with the full tab laminated cell; The cover plate is provided with a positive pole and a negative pole, the positive tab of the full tab laminated cell is welded to the positive pole by the laminated battery tab welding method according to any one of claims 1-8, and the negative tab of the full tab laminated cell is welded to the negative pole by the laminated battery tab welding method according to any one of claims 1-8.

10. A full tabbed jelly-roll battery according to claim 9, wherein, The separator in the full tab laminated cell is folded according to the Z-shaped folding process, and the positive and negative pole pieces in the full tab laminated cell are alternately inserted into the folding groove of the separator; The tabs of the positive and negative pole pieces are full tabs.

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