Cylindrical battery shell bottom welding mark structure and cylindrical secondary battery

Abstract

The utility model provides a cylindrical battery shell bottom welding mark structure and a cylindrical secondary battery. The cylindrical battery shell bottom welding mark structure comprises a shell bottom and a welding mark positioned on the shell bottom, the welding track of the shell bottom and the negative collector plate is the welding mark; the welding mark is in a vortex line shape, the center point of the welding mark is a point O, the vertex angle, away from the point O, of the outer end of the welding mark is a point A, the vertex angle, close to the point O, of the inner end of the welding mark is a point B, the area of a circle which takes the point O as the circle center and passes through the point A is S11, the area of a circle which takes the point O as the circle center and passes through the point B is S12, the area of a radiation surface of the welding mark is S10, the area of the shell bottom is S0, and S10 = S11-S12. And S10 is not less than 1.5% S0 and not more than 8.5% S0. According to the utility model, the welding print is arranged to be in the vortex line shape, so that the length of the welding print can be guaranteed, the area of the radiation surface of the welding print can be reduced, and the welding effect can be effectively improved, the safety performance of the battery can be guaranteed and the processing cost of the battery can be reduced by limiting the area of the radiation surface of the welding print.

Description

Technical Field

[0001] This utility model relates to the technical field of cylindrical battery negative electrode structure, and in particular to a cylindrical battery casing bottom welding structure and a cylindrical secondary battery. Background Technology

[0002] With the continuous development of new energy technologies, batteries, as high-efficiency energy storage devices, are widely used in various portable electronic products, electric vehicles, and large-scale energy storage systems. Among them, cylindrical batteries have gradually become one of the mainstream products in the market due to their excellent performance and high energy density.

[0003] Welding, as a reliable connection method, can provide strong mechanical strength and enable the two welded components to conduct electricity. In the assembly process of cylindrical batteries, laser welding or ultrasonic welding is used to fix the negative electrode current collector to the bottom of the casing, which can ensure that the current is conducted between the core and the casing.

[0004] For example, the invention patent with publication number CN112736372A discloses a cylindrical lithium battery negative terminal connection structure and its manufacturing method. It sets multiple solder points on the negative terminal of the battery casing to connect the solder points to the negative terminal connector of the cell. However, when the number of solder points is small, the welding area of ​​the negative terminal is reduced, resulting in a reduction in the current flow area at the welding point and an increase in temperature, which will affect the safety performance of the battery. When the number of solder points is large, the welding area of ​​the negative terminal is too large, which is prone to burn-through, increases the battery processing cost, and increases the risk of battery leakage. Utility Model Content

[0005] In view of this, this utility model proposes a cylindrical battery casing bottom welding structure and a cylindrical secondary battery, which can balance the proportion of the welding radiation surface on the bottom of the casing and ensure the safe operation of the battery.

[0006] The technical solution of this utility model is achieved as follows: On the one hand, this utility model provides a cylindrical battery casing bottom soldering structure, including a casing bottom and soldering located on the casing bottom;

[0007] The solder mark is used for welding and fixing the bottom of the shell to the negative electrode current collector, and the welding trajectory between the bottom of the shell and the negative electrode current collector is the solder mark;

[0008] The solder mark is swirling in shape. The center point of the solder mark is point O. The apex of the outer end of the solder mark furthest from point O is point A. The apex of the inner end of the solder mark closest to point O is point B. The area of ​​the circle centered at point O and passing through point A is S. 11 Let S be the area of ​​the circle centered at point O and passing through point B. 12 The area of ​​the solder radiating surface is S. 10 The area of ​​the bottom of the shell is S0, where S 10 =S11 -S 12 And 1.5%S0≤S 10 ≤8.5%S0.

[0009] Based on the above technical solutions, the preferred option is 0.05%S0≤S 12 ≤0.15%S0.

[0010] Based on the above technical solutions, preferably, the perimeter of the shell bottom is C0, and the length of the solder mark is L, wherein 20%C0≤L≤40%C0.

[0011] Based on the above technical solutions, preferably, the included angles formed by line segment OA and line segment OB are α and β, respectively, and the inner and outer ends of the solder mark are both located within α, wherein 145°≤β≤200°.

[0012] More preferably, the distance from point B to point O is R2, where R2 = 0.1mm - 0.5mm.

[0013] More preferably, the distance from point A to point O is R1, where R1 = 1mm - 3mm.

[0014] More preferably, the width of the solder mark is W1, where W1 = 0.2mm-0.6mm.

[0015] More preferably, the width of the interval between two adjacent rings of solder marks is W2, where W2 = 0.15mm-0.35mm.

[0016] More preferably, the minimum distance from point A to the periphery of the shell bottom is W3, where W3 = 7mm - 10mm.

[0017] Secondly, this utility model provides a cylindrical secondary battery, including the aforementioned cylindrical battery casing bottom soldering structure.

[0018] The cylindrical battery casing bottom welding structure and cylindrical secondary battery of this utility model have the following advantages over the prior art:

[0019] (1) By setting the solder mark to a spiral shape, not only can the length of the solder mark be guaranteed, but the area of ​​the solder mark radiation surface can also be reduced. By limiting the area of ​​the solder mark radiation surface, the welding effect can be effectively improved, the safety performance of the battery can be guaranteed, and the processing cost of the battery can be reduced.

[0020] (2) By restricting the specifications and location of the solder marks, the safety performance of the battery can be further improved, the problem of the bottom of the casing being burned through can be avoided, and the risk of battery leakage can be reduced. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a top view of the bottom of a cylindrical battery casing according to the present invention.

[0023] Figure 2 This is a top view of the soldering in the bottom soldering structure of a cylindrical battery casing according to this utility model;

[0024] Figure 3 This is a partial top view of the soldering in the bottom soldering structure of a cylindrical battery casing according to this utility model;

[0025] Figure 4 This is a schematic diagram of the unfolded state of the soldering in the bottom soldering structure of a cylindrical battery casing according to this utility model.

[0026] Figure 5 This is a partial cross-sectional view of a cylindrical secondary battery according to the present invention.

[0027] Among them: 1. Shell bottom; 11. Solder mark; 2. Negative electrode current collector. Detailed Implementation

[0028] The technical solutions of this utility model will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0029] Cylindrical batteries are divided into cylindrical primary batteries and cylindrical secondary batteries. Due to their advantages such as good consistency, high energy density and good heat dissipation, they have been widely used in electronic equipment, industrial equipment, energy storage and transportation.

[0030] like Figure 5 As shown, the present invention discloses a cylindrical battery casing bottom welding structure, including a casing bottom 1 and welding marks 11 located on the casing bottom 1. The casing bottom 1 is the bottom cover of the battery casing. During the battery assembly process, the core and the negative electrode current collector 2 fixed and electrically connected to the negative electrode tab of the core are first placed into the casing. Then, the negative electrode current collector 2 is fixed to the casing bottom 1 by laser welding, thereby realizing the conduction between the casing bottom 1 and the negative electrode of the core.

[0031] The shell bottom 1 and the negative current collector 2 are fixed by laser penetration welding. During the welding process, the negative current collector 2 is placed against the inner side of the shell bottom 1, and welding is performed from the outer side of the shell bottom 1 to the inner side of the shell bottom 1 to weld the shell bottom 1 and the negative current collector 2 together and realize the transmission of current.

[0032] The welding mark 11 is used to weld and fix the shell bottom 1 and the negative electrode current collector 2. During the laser welding process, the laser welding head moves along the welding mark 11 as the welding trajectory. After the welding is completed, the position on the shell bottom 1 located at the welding mark 11 is fused together with the negative electrode current collector 2. Compared with the spot welding method in the prior art, it can effectively increase the fixing firmness between the shell bottom 1 and the negative electrode current collector 2 and improve the current carrying capacity of the shell bottom 1 and the negative electrode current collector 2.

[0033] like Figure 1 As shown, the solder mark 11 is in the shape of a vortex. This shape of the solder mark 11 can not only ensure the length of the solder mark 11 and effectively guarantee the flow area between the bottom shell 1 and the negative electrode current collector 2, but also reduce the overall area of ​​the welding area where the solder mark 11 is located, so as to prevent the welding position between the bottom shell 1 and the negative electrode current collector 2 from exceeding the weldable area of ​​the negative electrode current collector 2.

[0034] To ensure the welding stability between the bottom shell 1 and the negative electrode current collector 2, it is preferable to position the solder mark 11 in the middle of the bottom shell 1, that is, to make the center point of the solder mark 11 coincide with the center point of the bottom shell 1. Figures 1-3 As shown, the center point of the weld 11 and the center point of the shell bottom 1 are both point O. The apex of the outer end of the weld 11 away from point O is point A. The distance from point A to point O is R1. The circle with point O as its center and passing through point A is the welding area, and the area of ​​the welding area is S. 11 Point B is the apex of the inner end of solder mark 11 closest to point O. The distance from point B to point O is R2. The area of ​​the central blank area is a circle centered at point O and passing through point B. 12 The radiating area of ​​weld mark 11 is the area occupied by welding minus the central blank area, i.e. Figure 2 The area of ​​the radiating surface of solder mark 11 in the dashed annular region is S. 10 And S 10 =S 11 -S 12 The area of ​​the bottom of the shell is S0, and the radius of the bottom of the shell is R0.

[0035] In some embodiments, 1.5%S0≤S 10 ≤8.5%S0, meaning the area of ​​the radiating surface of solder mark 11 is 1.5%, 3.5%, 5.5%, or 8.5% of the area of ​​the shell bottom 1, etc. If S 10If S < 1.5%, the area of ​​the radiating surface of the solder mark 11 is too small, reducing the area of ​​the solder mark 11 and thus decreasing the effective welding area between the bottom of the casing 1 and the negative current collector 2. This reduces the current flow area at the weld between the bottom of the casing 1 and the negative current collector 2, leading to increased temperature rise at this welding point during battery operation and reduced battery safety performance. If S 10 If the area of ​​the radiating surface of the solder mark 11 is too large, the actual welding position may exceed the weldable area on the bottom of the shell 1 and the negative electrode current collector 2 due to the influence of the welding offset. This may lead to defects such as weld penetration during the welding operation, increase the risk of battery leakage, and increase welding costs.

[0036] In some embodiments, 0.05%S0≤S 12 ≤0.15%S0, meaning the area of ​​the central blank area is 0.05%, 0.1%, or 0.15% of the area of ​​the shell bottom 1, etc. Since the solder mark 11 has a certain width, the inner end of the solder mark 11 is the starting position of the laser welding head. If S 12 If S < 0.05%, then point B is too close to point O, and the starting position of solder joint 11 is particularly close to other positions of solder joint 11. This not only results in an unsightly solder joint 11 but also leads to concentrated heat, causing problems such as solder blasts and abnormal solder color. Simultaneously, there is a certain amount of deviation in the welding process. Because point B is too close to point O, it also makes it difficult to position the welding joint, increasing the difficulty of welding and reducing welding efficiency. If S 12 If the value is greater than 0.15%S0, the welding area occupied by the solder mark 11 will increase. Due to the influence of the welding offset, the actual welding position is likely to exceed the weldable area on the bottom of the shell 1 and the negative electrode current collector 2, which will easily lead to defects such as weld penetration during the welding operation, increase the risk of battery leakage, and increase the welding cost.

[0037] In some embodiments, R2 = 0.1mm-0.5mm, meaning the minimum distance from the inner end of the solder mark 11 to the center point of the bottom of the casing 1 is 0.1mm, 0.3mm, or 0.5mm, etc. Since the solder mark 11 has a certain width, and the inner end of the solder mark 11 is the starting position of the laser welding head, if R2 < 0.1mm, point B is too close to point O, and the starting position of the solder mark 11 is very close to other positions of the solder mark 11. This not only results in an unsightly solder mark 11 but also leads to concentrated heat, causing problems such as welding spalls and abnormal welding color. Simultaneously, there is a certain amount of welding deviation. Because point B is too close to point O, it also makes positioning the welding head difficult, increasing the difficulty of welding and reducing welding efficiency. If R2 > 0.5mm, point B is too far from point O, increasing the welding area occupied by the solder mark 11. Due to the welding offset, the actual welding position is prone to exceeding the weldable area on the bottom of the casing 1 and the negative electrode current collector 2, leading to defects such as weld burn-through during welding operations, increasing the risk of battery leakage, and increasing welding costs.

[0038] In some embodiments, R1 = 1mm-3mm, that is, the maximum distance from the outer end of the solder mark 11 to the center point of the bottom of the casing 1 is 1mm, 2mm or 3mm, etc. If R1 < 1mm, point A is too close to point O, and the spacing between two adjacent solder marks 11 will be reduced, resulting in more concentrated heat and causing problems such as soldering explosion and abnormal soldering color; if R1 > 3mm, point A is too far from point O, and the soldering area occupied by the solder mark 11 will increase. Affected by the soldering offset, the actual soldering position is likely to exceed the solderable area on the bottom of the casing 1 and the negative electrode current collector 2, which makes the soldering operation prone to defects such as solder burn-through, increases the risk of battery leakage and increases the soldering cost.

[0039] like Figure 4 As shown, the unfolded length of the solder mark 11 is L, and the circumference of the bottom shell 1 is C0. In some embodiments, 20%C0≤L≤40%C0, that is, the unfolded length of the solder mark 11 is 20%, 30%, or 40% of the circumference of the bottom shell 1, etc. If L<20%C0, the length of the solder mark 11 is too small, resulting in a reduction in the effective welding area between the bottom shell 1 and the negative electrode current collector 2, which reduces the current flow area at the weld between the bottom shell 1 and the negative electrode current collector 2. During battery operation, the temperature rise at this welding position increases, reducing the battery's safety performance. If L>40%C0, the length of the solder mark 11 is too large. Under the condition of meeting the current flow capacity, an excessively long solder mark 11 will not have more beneficial effects on the current flow, but will instead reduce the reliability of the welding quality and increase the risk of welding cracks, explosions, and leakage.

[0040] like Figure 3 As shown, line segments OA and OB share a common endpoint, and the included angles formed by line segments OA and OB are α and β, respectively. The inner and outer ends of the solder mark 11 are both located within α, not within β. In some embodiments, 145°≤β≤200°, that is, β can be 145°, 175°, or 200°, etc. If β<145°, the length of the solder mark 11 will increase. Under the condition of meeting the current carrying capacity, an excessively long solder mark 11 will not have more beneficial effects on the current carrying capacity, but will instead reduce the reliability of the welding quality and increase the risk of welding cracks, explosions, and leakage. If β>200°, the length of the solder mark 11 is too small, resulting in a reduction in the effective welding area between the bottom of the casing 1 and the negative electrode current collector 2, which reduces the current carrying area at the welding point between the bottom of the casing 1 and the negative electrode current collector 2. During battery operation, the temperature rise at this welding point increases, reducing the battery's safety performance.

[0041] like Figure 1 , Figure 2 and Figure 4 As shown, the width of solder mark 11 is W1, the width between two adjacent solder marks 11 is W2, and the minimum distance from point A to the bottom of the shell is W3.

[0042] In some embodiments, W1 = 0.2mm-0.6mm, that is, the width of the solder mark 11 is 0.2mm, 0.4mm, or 0.6mm, etc. If W1 < 0.2mm, the width of the solder mark 11 is too small, resulting in a reduction in the effective welding area between the bottom of the casing 1 and the negative current collector 2, which reduces the current flow area at the weld between the bottom of the casing 1 and the negative current collector 2. During battery operation, the temperature rise at this welding position increases, reducing the battery's safety performance. If W1 > 0.6mm, the width of the solder mark 11 is too large. Due to the influence of welding offset, the actual welding position is likely to exceed the weldable area on the bottom of the casing 1 and the negative current collector 2, which makes the welding operation prone to defects such as burn-through, increasing the risk of battery leakage and increasing welding costs.

[0043] In some embodiments, W2 = 0.15mm-0.35mm, that is, the width of the interval between two adjacent rings of solder 11 is 0.15mm, 0.25mm, or 0.35mm, etc. If W2 < 0.15mm, the width of the interval between two adjacent rings of solder 11 is too small. Due to the influence of the welding offset, the two adjacent rings of solder 11 are very close together, which increases the welding difficulty. At the same time, the close proximity of the two adjacent rings of solder 11 will also cause heat concentration, resulting in problems such as welding explosions and abnormal welding color, reducing welding reliability. If W2 > 0.35mm, the width of the interval between two adjacent rings of solder 11 is too large. Due to the influence of the welding offset, the actual welding position is likely to exceed the weldable area on the bottom of the shell 1 and the negative electrode current collector 2, which makes the welding operation prone to defects such as weld penetration, increasing the risk of battery leakage and increasing welding costs.

[0044] In some embodiments, W3 = 7mm-10mm, that is, the minimum distance from point A to the perimeter of the bottom of the casing is 7mm, 8mm, 9mm or 10mm, etc. If W3 < 7mm, the welding area occupied by the solder mark 11 will increase. Due to the influence of the welding offset, the actual welding position is likely to exceed the weldable area on the bottom of the casing 1 and the negative electrode current collector 2, which will easily lead to defects such as weld penetration during welding operation, increase the risk of battery leakage and increase welding cost. If W3 > 10mm, the solder mark 11 will move closer to the center point of the bottom of the casing 1. Due to the influence of the welding offset, the two adjacent solder marks 11 are very close, which increases the welding difficulty. At the same time, the two adjacent solder marks 11 being very close will also cause heat concentration, resulting in problems such as welding explosion and abnormal welding color, reducing welding reliability.

[0045] In some embodiments, the solder mark 11 is preferably configured as a regular and uniform vortex-shaped structure, that is, the width of the solder mark 11 remains unchanged and the spacing between two adjacent solder marks 11 remains unchanged, thereby further improving the welding stability between the bottom shell 1 and the negative electrode current collector 2 and ensuring the performance of the battery.

[0046] In some embodiments, R0 = 10.5 mm, R1 = 2 mm, R2 = 0.3 mm, L = 20 mm, β = 180°, W1 = 0.4 mm, W2 = 0.25 mm, W3 = 8.5 mm, then S0 = 346.36 mm 2 S 11 =12.57mm 2 S 12 =0.28mm 2 S 10 =12.29mm 2 S 10 =3.5%S0,S 12 =0.08%S0, C0=65.97mm, L=30%C0. At this point, the welding quality between the shell bottom 1 and the negative electrode current collector 2 can be guaranteed, avoiding problems such as welding explosion, abnormal welding color, weld penetration and leakage. At the same time, the welding difficulty between the shell bottom 1 and the negative electrode current collector 2 can be reduced, the welding efficiency between the shell bottom 1 and the negative electrode current collector 2 can be improved, and the welding cost can be reduced.

[0047] The welding method for the bottom soldering structure of a cylindrical battery casing according to this utility model is as follows:

[0048] First, the negative current collector 2 is installed inside the battery casing. Then, the negative current collector 2 is brought into contact with the inner side of the casing bottom 1. Finally, the laser welding head is used to perform laser welding on the outer side of the casing bottom 1 along the welding mark 11, thereby fixing and electrically connecting the casing bottom 1 and the negative current collector 2.

[0049] The present invention relates to a cylindrical secondary battery, comprising the aforementioned cylindrical battery casing bottom soldering structure.

[0050] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A bottom soldering structure for a cylindrical battery casing, characterized in that: Includes a shell bottom (1) and solder marks (11) located on the shell bottom (1); The welding mark (11) is used for welding and fixing the bottom shell (1) and the negative electrode current collector (2), and the welding trajectory of the bottom shell (1) and the negative electrode current collector (2) is the welding mark (11); The solder mark (11) is in the shape of a spiral. The center point of the solder mark (11) is point O. The apex of the outer end of the solder mark (11) away from point O is point A. The apex of the inner end of the solder mark (11) close to point O is point B. The area of ​​the circle with point O as the center and passing through point A is S. 11 Let S be the area of ​​the circle centered at point O and passing through point B. 12 The area of ​​the radiating surface of the solder mark (11) is S. 10 The area of ​​the shell bottom (1) is S0, where S 10 =S 11 -S 12 And 1.5%S0≤S 10 ≤8.5%S0.

2. The cylindrical battery casing bottom soldering structure as described in claim 1, characterized in that: 0.05%S0≤S 12 ≤0.15%S0。 3. The cylindrical battery casing bottom soldering structure as described in claim 1, characterized in that: The perimeter of the shell bottom (1) is C0, and the length of the solder mark (11) is L, wherein 20%C0≤L≤40%C0.

4. The cylindrical battery casing bottom soldering structure as described in claim 1, characterized in that: The included angles formed by line segment OA and line segment OB are α and β, respectively. The inner and outer ends of the solder mark (11) are both located within α, where 145°≤β≤200°.

5. The cylindrical battery casing bottom soldering structure as described in any one of claims 1-4, characterized in that: The distance from point B to point O is R2, where R2 = 0.1mm - 0.5mm.

6. The cylindrical battery casing bottom soldering structure as described in claim 5, characterized in that: The distance from point A to point O is R1, where R1 = 1mm - 3mm.

7. The cylindrical battery casing bottom soldering structure as described in any one of claims 1-4, characterized in that: The width of the solder mark (11) is W1, where W1 = 0.2mm-0.6mm.

8. The cylindrical battery casing bottom soldering structure as described in claim 7, characterized in that: The width of the interval between two adjacent rings of the solder mark (11) is W2, where W2 = 0.15mm-0.35mm.

9. The cylindrical battery casing bottom soldering structure as described in claim 6, characterized in that: The minimum distance from point A to the periphery of the shell bottom (1) is W3, where W3 = 7mm - 10mm.

10. A cylindrical secondary battery, characterized in that: Includes the cylindrical battery case bottom soldering structure as described in any one of claims 1-9.

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