Tab welding structure for soft package battery cell and soft package battery cell

Abstract

The application relates to a tab welding structure of a soft package battery cell and the soft package battery cell, and belongs to the technical field of soft package batteries. The tab welding structure is characterized in that a pole group accommodating cavity is formed through pit punching of an encapsulation film, an inner tab and an outer tab are welded to form a welding mark, the relationship among the area A of the welding mark, the tensile force value F of the tensile property of the welding mark and the tensile force coefficient delta of the welding is defined, the welding area is ensured to be sufficient to disperse stress, and fatigue failure caused by stress concentration is avoided; meanwhile, the parameter relationship and the synergistic effect of material matching are used to improve the reliability and durability of the soft package battery cell.

Description

Technical Field

[0001] This application relates to the field of pouch battery technology, and in particular to tab welding structures for pouch cells and pouch cells themselves. Background Technology

[0002] With the development of pouch battery technology, a pouch cell tab welding process has emerged. This process directly affects the structural stability and energy transmission efficiency of the battery module and is a key link in ensuring the safe operation of the battery system.

[0003] In related technologies, welding is commonly used to achieve metal-to-metal bonding; however, the above welding process still has defects: continuous vibration and thermal cycling under vehicle conditions will accelerate material fatigue at the welding site, leading to a decrease in welding strength. In particular, stress concentration is prone to occur in the connection area between the electrode root and the current collector. Under a certain tensile force, it may eventually cause a short circuit in the battery cell or failure of the module structure. In addition, welding defects such as incomplete welding often occur during the electrode welding process, which will lead to insufficient welding strength. Summary of the Invention

[0004] Therefore, it is necessary to provide a tab welding structure for pouch cells and a pouch cell in order to address the above problems, thereby protecting the welding structure of the internal and external tabs of the pouch cell and ensuring high welding reliability.

[0005] A tab welding structure for pouch cells, comprising:

[0006] The inner cavity formed by the perforation of the encapsulation film is used to accommodate the electrode assembly;

[0007] The inner pole ear extends from the inner cavity to the outside of the septum;

[0008] The outer electrode tab is welded to the inner electrode tab;

[0009] Wherein, a weld mark is formed at the welding connection between the inner electrode and the outer electrode;

[0010] The area of ​​the weld mark at the welding connection between the inner and outer electrodes is A;

[0011] When the inner and outer tabs are made of aluminum, the tensile strength of the solder mark is F1, and the welding tensile coefficient is δ1.

[0012] When the inner and outer tabs are made of copper, the tensile strength of the solder is F2, and the welding tensile coefficient is δ2.

[0013] The tensile strength value F1 satisfies: F1 = 1.1 * A * δ1;

[0014] The tensile strength value F2 satisfies: F2 = 1.3 * A * δ2.

[0015] In one embodiment, the tensile strength value F1 satisfies: F1≥160N; the tensile strength value F2 satisfies: F2≥220N.

[0016] In one embodiment, the welding tensile strength coefficient δ1 satisfies: 2 N / mm 2 ≤δ1≤10N / mm 2 ;

[0017] The welding tensile strength coefficient δ2 satisfies: 2.5 N / mm 2 ≤δ2≤12N / mm 2 .

[0018] In one embodiment, the area A of the weld mark at the weld joint between the inner and outer electrodes satisfies: 25 mm. 2 ≤A≤200mm 2 .

[0019] In one embodiment, the thickness of the outer electrode tab satisfies:

[0020] When the material of the outer electrode is aluminum, the thickness of the outer electrode is H1, and 0.3mm≤H1≤0.5mm;

[0021] When the material of the outer electrode is copper, the thickness of the outer electrode is H2, and 0.25mm≤H2≤0.45mm.

[0022] In one embodiment, the outer electrode includes a positive outer electrode and a negative outer electrode;

[0023] The positive electrode outer tab is made of Al 1060 or Al 1N30; the negative electrode outer tab is made of Cu 1020.

[0024] In one embodiment, a plating layer is added to the surface of the negative electrode tab; preferably, the plating layer is made of nickel, and the thickness of the nickel plating layer is 0.001μm~0.005μm.

[0025] In one embodiment, when the number of inner tabs is less than 60, ultrasonic welding is used; when the number of inner tabs exceeds 60, laser welding is used to avoid incomplete welds.

[0026] On the other hand, this application also provides a pouch cell, including the above-mentioned tab welding structure for pouch cells, and a cell housing connected to the tab welding structure; the cell housing is made of an encapsulation film, and the pit depth of the encapsulation film matches the thickness of the electrode assembly to ensure the stability of the electrode assembly in the inner cavity.

[0027] The above-mentioned tab welding structure for pouch cells and pouch cells define the relationship between the tensile strength value F of the solder stamp, the area A of the solder stamp, and the tensile coefficient δ of the welding through a formula. This ensures that the welding area is sufficiently distributed to disperse stress and avoid fatigue failure caused by stress concentration. This ensures both reliability and avoids material waste caused by over-design.

[0028] This application also has the following advantages:

[0029] (1) The material of the positive electrode outer tab of this application is Al 1060 or Al 1N30, and the material of the negative electrode outer tab is Cu 1020 to ensure conductivity, processing performance and strength; in addition, a nickel plating layer of 0.001μm~0.005μm is added to the surface of the negative electrode outer tab to effectively prevent copper oxidation, reduce interface resistance, and enhance the corrosion resistance and long-term stability of the welding interface.

[0030] (2) The welding process is determined based on the number of inner tab layers in this application, which can avoid false welding, significantly improve the durability of the welded parts under vehicle vibration and thermal cycling conditions, and reduce the risk of short circuit or structural failure. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the opposite-side output tab state in one embodiment of this application.

[0032] Figure 2 This is a schematic diagram of the same-side output tab state in one embodiment of this application.

[0033] Figure 3 This is a schematic diagram of the final welding tensile test of the flexible package in this application.

[0034] Among them: 100, inner electrode tab; 200, outer electrode tab; 300, solder mark; 400, first tensile testing machine; 500, second tensile testing machine; 600, diaphragm;

[0035] 110. Positive inner electrode ear; 120. Negative inner electrode ear;

[0036] 210. Positive outer electrode ear; 220. Negative outer electrode ear;

[0037] 310. Positive electrode solder mark; 320. Negative electrode solder mark. Detailed Implementation

[0038] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0039] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0040] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0042] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0043] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0044] See Figure 1 , Figure 1 A schematic diagram of a tab welding structure for a pouch cell according to an embodiment of this application is shown, with the figure showing a tab structure on opposite sides.

[0045] A tab welding structure for pouch cells, wherein an inner cavity is formed on the encapsulation film by a stamping process, the depth of the inner cavity matching the thickness of the electrode assembly; an inner tab 100 extends from the inner cavity to the outside of the separator 600; and an outer tab 200 is welded to the inner tab 100.

[0046] Among them, a weld mark 300 is formed at the welding connection between the inner electrode 100 and the outer electrode 200;

[0047] The area of ​​the weld mark 300 at the welded connection between the inner electrode 100 and the outer electrode 200 is A;

[0048] When the inner tab 100 and the outer tab 200 are made of aluminum, the tensile strength of the corresponding positive electrode solder mark 310 is F1, and the welding tensile strength coefficient is δ1.

[0049] When the inner electrode 100 and the outer electrode 200 are made of copper, the tensile strength of the corresponding negative electrode solder mark 320 is F2, and the welding tensile strength coefficient is δ2.

[0050] The tensile strength value F1 satisfies: F1 = 1.1 * A * δ1;

[0051] The tensile strength value F2 satisfies: F2 = 1.3 * A * δ2.

[0052] In some embodiments, the tensile strength value F1 satisfies: F1≥160N; the tensile strength value F2 satisfies: F2≥220N.

[0053] In some embodiments, the welding tensile strength coefficient δ1 satisfies: 2 N / mm 2 ≤δ1≤10N / mm 2 The welding tensile strength coefficient δ2 satisfies: 2.5 N / mm. 2 ≤δ2≤12N / mm 2 .

[0054] In some embodiments, the area A of the weld mark 300 at the welded connection between the inner electrode 100 and the outer electrode 200 satisfies: 25 mm. 2 ≤A≤200mm 2 .

[0055] In some embodiments, the outer electrode 200 includes a positive outer electrode 210 and a negative outer electrode 220;

[0056] Among them, the positive electrode outer tab 210 is made of Al 1060 or Al 1N30; the negative electrode outer tab 220 is made of Cu 1020, and a nickel plating layer is added to the surface of the negative electrode outer tab 220.

[0057] Furthermore, the thickness of the nickel plating layer is 0.001μm~0.005μm.

[0058] Furthermore, the outer electrode 200 is manufactured using a stamping process, and the thickness of the outer electrode 200 satisfies the following requirements: the thickness of the positive electrode outer electrode 210 is 0.3mm≤H1≤0.5mm, and the thickness of the negative electrode outer electrode 220 is 0.25mm≤H2≤0.45mm.

[0059] In some embodiments, the inner electrode 100 includes a positive inner electrode 110 and a negative inner electrode 120;

[0060] Among them, the positive electrode inner tab 110 is made of aluminum, and the negative electrode inner tab 120 is made of copper, both extending from the end of the electrode assembly to the outside of the diaphragm 600.

[0061] Furthermore, the number of layers of the inner tab 100 is adjusted according to the cell capacity;

[0062] Furthermore, when the number of layers of the inner tab 100 is less than 60, ultrasonic welding is preferred; when the number of layers of the inner tab 100 exceeds 60, laser welding is preferred. This is because when the number of layers of the inner tab 100 is too large, ultrasonic welding is prone to producing incomplete welds, which affects the welding strength.

[0063] See Figure 2In other embodiments, the positive and negative electrodes adopt a same-side output tab structure.

[0064] In addition, this application also includes a soft-pack battery cell, including the above-mentioned tab welding structure and a battery cell housing connected to the tab welding structure;

[0065] Furthermore, the battery cell housing is made of an encapsulation film, and the depth of the perforation in the encapsulation film matches the thickness of the electrode assembly to ensure the stability of the electrode assembly in the inner cavity; wherein, the encapsulation film is preferably an aluminum-plastic film.

[0066] Example 1:

[0067] In this embodiment, the inner electrode 100 and the outer electrode 200 are limited to aluminum materials for the experiment. The inner electrode 100 and the outer electrode 200 are welded together, and the tensile strength of the weld 300 is tested. The comparison results are divided into experimental group and control group.

[0068] For the solder joint pull test method, please refer to [link / reference]. Figure 3 This includes the following processes:

[0069] S1, cut the electrode tabs after final welding;

[0070] S2, clamp one side of the outer tab 200 onto the fixture of the first tensile testing machine 400, and clamp one side of the inner tab 100 onto the fixture of the second tensile testing machine 500. The length dimension L1 of the fixture is greater than or equal to the length dimension L2 of the solder mark.

[0071] S3, the first tensile testing machine 400 and the second tensile testing machine 500 pull outwards to both sides to perform tensile testing.

[0072] Please refer to Table 1 for the experimental comparison results of this embodiment.

[0073] Table 1

[0074]

[0075] As shown in Table 1 above, when 2N / mm 2 ≤δ1≤10N / mm 2 At that time, the area A of the weld mark 300 at the welded connection between the inner electrode 100 and the outer electrode 200 satisfies: 25mm² 2 ≤A≤200mm 2 In this case, the calculated tensile strength value F1 is greater than 160N. At this time, after actual measurement, there is no tearing phenomenon even when the measured tensile force is greater than 160N, which meets the requirements.

[0076] However, when the area A of the weld mark 300 at the welded connection between the inner tab 100 and the outer tab 200 is less than 25 mm 2At that time, both the calculated tensile strength value F1 and the measured tensile strength were lower than 160N;

[0077] When the area A of the weld mark 300 at the welding connection between the inner tab 100 and the outer tab 200 is greater than 200 mm 2 Although the calculated tensile strength value F1 and the measured tensile strength are both greater than 160N, the large area of ​​the solder 300 will cause problems such as misaligned soldering and poor soldering due to the insufficient distribution of the electrode tabs.

[0078] Example 2:

[0079] In this embodiment, the inner electrode 100 and the outer electrode 200 are made of copper for the experiment. The inner electrode 100 and the outer electrode 200 are welded together, and the tensile strength of the weld 300 is tested. The comparison results are divided into an experimental group and a control group.

[0080] For the solder joint pull test method, please refer to [link / reference]. Figure 3 This includes the following processes:

[0081] S1, cut the electrode tabs after final welding;

[0082] S2, clamp one side of the outer tab 200 onto the fixture of the first tensile testing machine 400, and clamp one side of the inner tab 100 onto the fixture of the second tensile testing machine 500. The length dimension L1 of the fixture is greater than or equal to the length dimension L2 of the solder mark.

[0083] S3, the first tensile testing machine 400 and the second tensile testing machine 500 pull outwards to both sides to perform tensile testing.

[0084] Please refer to Table 2 for the experimental comparison results of this embodiment.

[0085] Table 2

[0086]

[0087] As shown in Table 2 above, when 2.5 N / mm 2 ≤δ2≤12N / mm 2 At that time, the area A of the weld mark 300 at the welded connection between the inner electrode 100 and the outer electrode 200 satisfies: 25mm² 2 ≤A≤200mm 2 In this case, the calculated tensile strength values ​​F1 are all greater than 220N. At this time, after actual measurement, there is no tearing phenomenon even when the measured tensile strength is greater than 220N, which meets the requirements.

[0088] However, when the area A of the weld mark 300 at the welded connection between the inner tab 100 and the outer tab 200 is less than 25 mm 2At that time, both the calculated tensile strength value F1 and the measured tensile strength were lower than 220N, which did not meet the requirements;

[0089] When the area A of the weld mark 300 at the welding connection between the inner tab 100 and the outer tab 200 is greater than 200 mm 2 Although the calculated tensile strength value F1 and the measured tensile strength are both greater than 220N, the large area of ​​the solder 300 will cause problems such as misaligned soldering and poor soldering due to the insufficient distribution of the electrode tabs.

[0090] In summary, this application utilizes the synergistic effect of the relationship between the weld area A, the tensile strength F of the weld, and the tensile coefficient δ of the weld to ensure that the weld area sufficiently disperses stress and avoids fatigue failure caused by stress concentration.

[0091] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0092] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A tab welding structure for a jelly-roll cell, characterized by, The application relates to a welding structure of a tab of a soft package battery cell. The welding structure comprises: an inner cavity formed by punching of a packaging film, used for accommodating a pole group; an inner tab extending from the inner cavity to the outside of a diaphragm; an outer tab welded to the inner tab; a welding mark formed at the welded connection between the inner tab and the outer tab; an area of the welding mark at the welded connection between the inner tab and the outer tab is A; when the material of the inner tab and the outer tab is aluminum, the tensile strength of the welding mark is F1, and the welding tensile coefficient is delta 1; when the material of the inner tab and the outer tab is copper, the tensile strength of the welding mark is F2, and the welding tensile coefficient is delta 2; the tensile strength F1 satisfies F1=1.1*A*delta 1; The welding tension coefficient δ1 satisfies: 2 N / mm 2 ≤ δ1 ≤ 10 N / mm 2 ; The welding tension coefficient δ2 satisfies: 2.5 N / mm 2 ≤ δ2 ≤ 12 N / mm 2 ; The area A of the weld print of the inner and outer lug weld joint satisfies: 25mm 2 ≤ A ≤ 200mm 2 .

2. The tab welding structure for a jelly-roll cell according to claim 1, characterized by, the tensile strength F2 satisfies F2=1.3*A*delta 2; 3. The tab welding structure for a jelly-roll cell according to claim 1, characterized by, the tensile strength F1 satisfies F1>=160N, and the tensile strength F2 satisfies F2>=220N. The thickness of the outer tab satisfies: when the material of the outer tab is aluminum, the thickness of the outer tab is H1, and 0.3mm<=H1<=0.5mm; 4. The tab welding structure for a pouch battery cell according to claim 1, characterized by, when the material of the outer tab is copper, the thickness of the outer tab is H2, and 0.25mm<=H2<=0.45mm. The outer tab comprises a positive outer tab and a negative outer tab; 5. The tab welding structure for a pouch battery cell according to claim 4, characterized by, the material of the positive outer tab is Al 1060 or Al 1N30, and the material of the negative outer tab is Cu1020.

6. The tab welding structure for a pouch battery cell according to claim 5, characterized by, A plating layer is additionally arranged on the surface of the negative outer tab.

7. The tab welding structure for a pouch battery cell according to claim 1, characterized by, The material of the plating layer is nickel, and the thickness of the nickel plating layer is 0.001um-0.005um.

8. A pouch cell, characterized by, When the number of layers of the inner tab is less than 60, ultrasonic welding is adopted; when the number of layers of the inner tab exceeds 60, laser welding is adopted to avoid false welding. The application further relates to a battery cell shell connected to the welding structure of the tab of the soft package battery cell. The battery cell shell is made of a packaging film, and the punching depth of the packaging film matches the thickness of the pole group to ensure the stability of the pole group in the inner cavity.

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