Battery casing welding method, battery casing and battery cell

Abstract

The present application belongs to the technical field of battery manufacturing. Disclosed are a battery casing welding method, a battery casing and a battery cell. The battery casing comprises a cover plate and a casing body, wherein the cover plate comprises a body and an lapping protrusion, and a welding laser beam travels a full circle on the top of the lapping protrusion, such that the lapping protrusion is fused and welded to the top of the body. Using a top-welding method can also realize better welding between the lapping protrusion and the casing body, retains the advantage of top welding having a high welding speed and also has the advantage of side welding preventing laser leakage into a battery.

Description

Battery casing welding method, battery casing and battery cell

[0001] This application claims priority to Chinese patent applications filed with the Chinese Patent Office on December 31, 2024, with application numbers 202411987086.1 and 202423305567.8, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to a battery casing welding method, a battery casing, and a battery cell. Background Technology

[0003] In the welding process of square lithium battery casings, the current main welding methods are top welding and side welding. Top welding has the weld seam on the top, and its main advantage is speed. However, the laser beam can leak into the battery through the weld seam, which may burn the core pack and cause a short circuit. Side welding has the weld seam on the side, and the battery casing structure is designed with a light shield to avoid the risk of the laser leaking into the battery. Invention Overview

[0004] During the side welding process, the battery needs to be flipped and welded in four sections. This welding method is inefficient. To improve efficiency, a laser needs to be added for simultaneous welding, which increases costs. In addition, during the side welding process, after the light shield melts, there is a risk that the laser beam will hit the plastic on the electrode post, causing insulation failure.

[0005] This application provides a battery casing welding method. The battery casing includes a cover plate and a housing. The cover plate includes a body and an overlapping protrusion. The overlapping protrusion protrudes from the top of the peripheral side of the body. The housing forms a receiving cavity with an opening. The cover plate blocks the opening, and the overlapping protrusion abuts against the top of the housing. The outer edge of the overlapping protrusion is offset inwardly by a predetermined distance H relative to the outer edge of the housing sidewall. The battery casing welding method includes: a welding laser circling around the top of the overlapping protrusion to melt and weld the overlapping protrusion to the top of the body.

[0006] This application also provides a battery casing manufactured using the above-described battery casing welding method, wherein the welding position of the battery casing forms a vertical molten pool, and the protrusion height H2 of the molten pool at the top of the cover plate is 0mm; and / or the protrusion height of the molten pool on the side is 0mm≤H1≤0.2mm.

[0007] This application also provides a battery cell, including the aforementioned battery casing. Beneficial effects

[0008] This application discloses a battery casing welding method. For cover plates with overlapping protrusions, the prior art uses side welding for welding. For square batteries, welding needs to be done in four sections. However, by offsetting the outer edge of the overlapping protrusion inward by a preset distance H relative to the outer edge of the casing sidewall, the top welding method can also achieve good welding of the overlapping protrusion and the casing. This method retains the advantage of the high welding speed of top welding and the advantage of side welding in avoiding light leakage into the battery.

[0009] This application also provides a battery casing. By using the above-described battery casing welding method, the size of the battery casing is more easily guaranteed, which facilitates subsequent PACK assembly.

[0010] This application also provides a battery cell, including the aforementioned battery casing. By using the aforementioned battery casing, the battery cell achieves a higher dimensional yield rate, facilitating subsequent assembly. Attached Figure Description

[0011] Figure 1 is a partial cross-sectional view of the battery casing before welding, provided in an embodiment of this application.

[0012] Figure 2 is a partial cross-sectional view of the battery casing after welding, provided in an embodiment of this application.

[0013] Figure 3 is a partial cross-sectional view of the battery casing before welding, provided in an embodiment of this application.

[0014] Figure 4 is a partial cross-sectional view of the battery casing after welding, provided in an embodiment of this application.

[0015] Explanation of reference numerals in the attached figures:

[0016] 10. Cover plate; 11. Body; 12. Overlapping protrusion;

[0017] 20. Shell; 21. Receiving cavity;

[0018] 30. Molten pool; 31. Trough area; 32. Flat area;

[0019] 40. Welding laser. Embodiments of the present invention

[0020] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" 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. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, where the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, where the first feature is at a lower horizontal level than the second feature.

[0022] In the description of some embodiments of this application, the terms "upper," "lower," "left," "right," "front," and "rear," etc., refer to the orientation or positional relationship shown in the accompanying drawings. These terms are used for ease of description and simplification of operation, 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. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive distinction and have no special meaning.

[0023] Some embodiments of this application provide a battery casing welding method that combines the advantages of high efficiency of top welding with the advantages of preventing light leakage into the battery interior through side welding. Specifically, as shown in Figures 1 and 3, the battery casing includes a cover plate 10 and a housing 20. The cover plate 10 includes a body 11 and an overlapping protrusion 12, which protrudes from the top of the peripheral side of the body 11. The housing 20 forms a receiving cavity 21 with an opening. The cover plate 10 seals the opening, and the overlapping protrusion 12 abuts against the top of the housing 20. The outer edge of the overlapping protrusion 12 is offset inwardly by a predetermined distance H relative to the outer edge of the sidewall of the housing 20. The battery casing welding method includes:

[0024] S10: The welding laser 40 circles around the top of the overlapping protrusion 12 to melt and weld the overlapping protrusion 12 to the top of the body 11.

[0025] It is understandable that for the cover plate 10 with the overlapping protrusion 12, the existing technology uses side welding for welding. For square batteries, it is necessary to weld in four sections. However, after setting a preset distance H to offset the outer edge of the overlapping protrusion 12 from the outer edge of the side wall of the housing 20, the top welding method can also achieve the welding of the overlapping protrusion 12 and the housing 20 well. It retains the advantage of the wide welding speed of top welding and the advantage of side welding in avoiding light leakage into the battery.

[0026] Optionally, during welding, the welding laser 40 is offset inward by L1 relative to the outer edge of the overlapping protrusion 12, where 0.1mm ≤ L1 ≤ 0.2mm. This results in a portion of the overlapping protrusion 12 being melted on both the inner and outer sides of the welding laser 40, allowing for more thorough melting of the overlapping protrusion 12 and the top of the body 11. Optionally, the value of L1 can be 0.1mm, 0.12mm, 0.15mm, 0.18mm, 0.2mm, etc.

[0027] Optionally, as shown in Figure 1, the thickness of the sidewall of the housing 20 is defined as T3, where 0.25mm ≤ T3 ≤ 0.8mm. For example, the thickness of the housing 20 can be 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, etc. A thinner housing 20 results in poorer structural strength, making it difficult to support the cover plate 10. Furthermore, during laser welding, there may be insufficient remaining material, allowing the laser to penetrate the battery and cause a short circuit. Conversely, a thicker housing 20 results in excessive battery weight. This design provides a moderate thickness and good structural strength.

[0028] Optionally, as shown in Figure 1, the thickness of the overlapping protrusion 12 is T1, where 0.2mm ≤ T1 ≤ 0.8mm. When T1 < 0.2mm, since the overlapping protrusion 12 serves as part of the load-bearing cover plate 10, its strength at the connection between the shell 20 and the overlapping protrusion 12 is insufficient, making it prone to bending and deformation. Furthermore, since the overlapping protrusion 12 is the main part of the fusion, designing it to be too thin results in insufficient fusion and unstable welding. When T1 > 0.8mm, it wastes raw materials, and during welding, the overlapping protrusion 12 is not easily penetrated, affecting the welding effect.

[0029] Optionally, the total thickness of the cover plate 10 is defined as T2, where 0.4 ≤ T1 / T2 ≤ 0.6. With this design, on the one hand, if this ratio is set too low, the overlapping protrusion 12, as part supporting the cover plate 10, is prone to bending and deformation at the connection point between the housing 20 and the overlapping protrusion 12. On the other hand, if this ratio is set too high, it wastes raw materials, and during welding, the overlapping protrusion 12 is not easily penetrated, affecting the welding effect. For example, T1 / T2 = 0.4, 0.45, 0.5, 0.55, 0.6, etc.

[0030] Optionally, 1.0mm≤T2≤3.0mm. For example, the thickness of the cover plate 10 is 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, etc. If the cover plate 10 is too thin, the structural strength is poor, making it difficult to support other structures on the cover plate 10, thereby reducing the bending strength of the cover plate 10, making it difficult to guarantee the flatness of the cover plate 10, and there is a possibility that during laser welding, there is less remaining material, and the laser penetrates into the battery, causing a short circuit, etc. If the cover plate 10 is too thick, the battery weight will be too large. This design has a moderate thickness of cover plate 10, a lighter structure, good structural strength, is not easy to deform, and the flatness is guaranteed.

[0031] Understandably, after the sidewalls of the housing 20 and the overlapping protrusions 12 are welded, a molten pool 30 is formed as shown in Figure 2. The shape of the molten pool 30 determines the final external dimensions of the battery casing. The protrusions of the molten pool 30 on the top surface of the cover plate 10 and the side surface of the housing 20 determine the external dimensions of the battery casing.

[0032] Optionally, 0.1mm ≤ H ≤ 0.25mm. When the offset distance exceeds 0.25mm, the contact area between the overlapping protrusion 12 and the housing 20 is insufficient, which will reduce the strength of the weld. When the offset distance is less than 0.1mm, the effect on reducing the protrusion is not significant. For example, H = 0.1mm, 0.13mm, 0.15mm, 0.18mm, 0.2mm, 0.22mm, 0.25mm, etc. Combined with the inward offset distance of the welding laser 40, the protrusion height of the molten pool 30 on the side wall of the housing 20 is further reduced.

[0033] Some embodiments of this application also provide a battery casing manufactured using the aforementioned battery casing welding method. As shown in Figure 2, the molten pool 30 has a protrusion height H2 = 0 mm at the top of the cover plate 10. For ease of understanding, in Figure 2, the height of the flat area 32 protruding from the cover plate 10 is defined as H2. In the prior art, this value is positive. The protrusion at this position disappears after a top welding test, with the overlapping protrusion 12 and the outer edge of the housing 20 offset by a distance H, ensuring the flatness and dimensional accuracy of the top of the cover plate 10. In other words, in some actual embodiments of this application, the H2 indicated in the figure does not exist.

[0034] Optionally, the height of the molten pool 30 protruding from the side is 0mm ≤ H1 ≤ 0.2mm. This means that, after testing, the height of the molten pool 30 protruding from the side of the battery casing has also been reduced. In the prior art, the protrusion on this side is approximately 0.3mm. Through the design of some embodiments of this application, after top welding, a better effect can be achieved by eliminating the protrusion, with most protrusions within 0.1mm and a small portion around 0.2mm, all within the tolerance range of the battery casing dimensions. For example, the value of H1 can be 0.02mm, 0.05mm, 0.07mm, 0.1mm, 0.2mm, etc. Since the dimensions of the battery casing are within the tolerance range, the battery casing is easier to assemble during subsequent PACK assembly.

[0035] Optionally, as shown in Figure 2, the depth of the molten pool 30 is L2, where 1.1mm ≤ L2 ≤ 2.0mm. By setting the depth as described above, the depth of the deepest part of the molten pool 30 is guaranteed to be within this range. At this time, the depth is approximately ten times that of H, ensuring that the material at the welding position is fully melted. For example, the value of L2 can be 1.0mm, 1.2mm, 1.5mm, 1.7mm, 1.9mm, 2.0mm, etc.

[0036] Optionally, as shown in Figure 2, the effective penetration depth of the molten pool 30 is L3, where 0.8mm≤L3≤1.3mm. The effective penetration depth refers to the portion where the cover plate 10 and the shell 20 are fused together, that is, the portion of the molten pool 30 that is fused to the shell 20 on one side is removed. Through the above setting, it is ensured that the cover plate 10 and the shell 20 are fully fused during welding. In other words, the effective penetration depth L3 is definitely greater than the value of T1. For example, the value of L3 can be 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, etc.

[0037] Optionally, as shown in Figure 4, the weld width of the molten pool 30 is L4, where 1.0mm ≤ L4 ≤ 2.0mm. Under this premise, L4 must be greater than T3 and also greater than the distance by which the overlapping protrusion 12 protrudes from the body 11. Through the above settings, sufficient melting of the cover plate 10 and the shell 20 is ensured, improving the stability of the welded connection. For example, the value of L4 can be 1.0mm, 1.2mm, 1.5mm, 1.8mm, 1.9mm, etc.

[0038] The direction perpendicular to the height of the battery casing (Z direction in the figure) is defined as the first direction (X direction in the figure, which is perpendicular to the Z direction). The first direction is the direction of the molten pool 30 generated by side welding. The molten pool 30 includes connected trough areas 31 and a straight section. The trough area 31 is located below the straight section 32. In the first direction, the bottom of the trough area 31 is trough-shaped, and the bottom of the straight section 32 is gently sloping and extends to the top of the cover plate 10. The cladding depth of the straight section 32 is defined as L5, where L5 ≥ 0.6 mm. It can be understood that during the side welding process, by adjusting the cladding depth of the straight section 32 corresponding to the welded molten pool 30, the vertical cladding depth can be made to be greater than 0.6 mm, ensuring that the volume of the molten material of the cover plate 10 and the casing 20 is sufficient to weld the casing 20 and the cover plate 10 firmly.

[0039] Optionally, the cover plate 10 is made of a smooth aluminum sheet, which has good thermal conductivity and can quickly dissipate the heat inside the battery.

[0040] It should be noted that the shape of the molten pool 30 of the side weld is roughly as shown in Figure 2. The bottom of the straight area 32 is roughly flat and smoothly transitions to the top surface of the cover plate 10.

[0041] Optionally, as shown in Figure 4, the dimension of the straight section 32 in the height direction is defined as L6, where L6 ≤ L5. It can be understood that during side welding, the depth of L5 should be sufficiently ensured to guarantee the melting depth of the straight section. The larger L6 is, the more unmelted material is inside the molten pool 30. Therefore, L6 should be set to a smaller value to ensure the melting effect inside the molten pool 30.

[0042] Optionally, in the first direction, the depth of the deepest position of the trough region 31 is defined as H3, where 1.0mm ≤ H3 ≤ 2.0mm. This setting ensures that the depth of the deepest position of the trough region 31 is within this range. In this case, the depth is approximately ten times H, ensuring sufficient melting of the material at the welding location. For example, the value of H3 can be 1.0mm, 1.2mm, 1.5mm, 1.7mm, 1.9mm, 2.0mm, etc.

[0043] Optionally, as shown in Figure 4, the top height of the flat area 32 is flush with or lower than the surface of the cover plate 10. For ease of understanding, in Figure 3, the height of the flat area 32 protruding from the cover plate 10 is defined as H2. In the prior art, this value is positive. After the overlapping protrusion 12 and the outer edge of the housing 20 are offset by a distance H, the protrusion at this position disappears after a side welding test, ensuring the flatness and dimensional accuracy of the top of the cover plate 10. That is to say, in some embodiments of this application, the H2 indicated in the figure does not exist.

[0044] Optionally, as shown in Figure 4, the protrusion on the side of the molten pool 30 is located on the side of the molten pool 30 near the shell 20. Compared with the prior art, where the protrusion on the side of the molten pool 30 is located at the center of the molten pool 30, the protrusion on the side is located at the center of the molten pool 30. In essence, due to the setting of H, the molten pool 30 moves to the right side as shown in Figure 4, causing the protrusion on the side to be traction-deformed, changing the height and position of the protrusion on the side.

[0045] Some embodiments of this application also provide a battery cell, including the aforementioned battery casing. By using the aforementioned battery casing, the battery cell achieves a higher dimensional compliance rate, facilitating subsequent assembly.

Claims

1. A battery casing welding method, wherein the battery casing includes a cover plate (10) and a housing (20), the cover plate (10) includes a body (11) and an overlapping protrusion (12), the overlapping protrusion (12) protruding from the top of the peripheral side of the body (11); the housing (20) forms a receiving cavity (21) with an opening, the cover plate (10) blocks the opening, and the overlapping protrusion (12) abuts against the top of the housing (20), the outer edge of the overlapping protrusion (12) is offset inwardly by a predetermined distance H relative to the outer edge of the side wall of the housing (20), the battery casing welding method includes: S10: The welding laser (40) goes around the top of the overlapping protrusion (12) to melt and weld the overlapping protrusion (12) to the top of the body (11).

2. According to the battery casing welding method of claim 1, the welding laser (40) is offset inward by L1 relative to the outer edge of the overlapping protrusion (12) during welding, where 0.1mm≤L1≤0.2mm.

3. In the battery casing welding method according to claim 1, the thickness of the overlapping protrusion (12) is T1, 0.2mm≤T1≤0.8mm.

4. According to the battery casing welding method of claim 3, the total thickness of the cover plate (10) is defined as T2, 0.4mm≤T1 / T2≤0.6mm.

5. The battery casing welding method according to claim 4, where 1.0mm ≤ T2 ≤ 3.0mm.

6. The battery casing welding method according to any one of claims 1-5, wherein 0.1mm ≤ H ≤ 0.25mm.

7. The battery casing welding method according to any one of claims 1-5, wherein the thickness of the sidewall of the casing (20) is T3, 0.25mm≤T3≤0.8mm.

8. A battery casing, manufactured using the battery casing welding method as described in any one of claims 1-7, wherein the welding position of the battery casing forms a vertical molten pool (30), and the height H2 of the molten pool (30) protruding from the top of the cover plate (10) is 0 mm; and / or The height of the convexity on the side of the molten pool (30) is 0mm≤H1≤0.2mm.

9. The battery casing according to claim 8, wherein the melting depth of the molten pool (30) is L2, 1.1mm≤L2≤2.0mm.

10. The battery casing according to claim 9, wherein the effective melting depth of the molten pool (30) is L3, 0.8mm≤L3≤1.3mm.

11. The battery casing according to claim 8, wherein the weld width of the molten pool (30) is L4, 1.0mm≤L4≤2.0mm.

12. The battery casing according to claim 8, wherein the direction perpendicular to the height of the battery casing is defined as the first direction, the first direction being the direction of the molten pool (30) generated by the side welding, the molten pool (30) including connected trough areas (31) and flat areas (32), the trough areas (31) being located below the flat areas (32), in the first direction, the bottom of the trough areas (31) being trough-shaped, the bottom of the flat areas (32) being gently set and extending to the top of the cover plate (10), and the cladding depth of the flat areas (32) being defined as L5, L5 ≥ 0.6 mm.

13. The battery casing according to claim 12, wherein the dimension of the flat area (32) in the height direction is defined as L6, where L6 ≤ L5.

14. The battery casing according to claim 12, in the first direction, the depth of the deepest position of the trough region (31) is defined as H3, 1.0mm≤H3≤2.0mm.

15. The battery casing according to claim 12, wherein the top height of the flat area (32) is flush with or lower than the surface of the cover plate (10).

16. A battery cell, comprising a battery casing as described in any one of claims 8-15.

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