Welding method for battery shell

Abstract

The invention discloses a welding method for a battery shell, the battery shell comprises a shell body and a cover body, one side of the shell body along a first direction is provided with a shell opening, the cover body is arranged at the shell opening of the shell body, the welding method comprises the following steps: placing the cover body at the shell opening of the shell body, and welding the shell body and the cover body through a first laser beam; identifying a sharp bulge on the outer surface of the welding position of the cover body and the shell body, wherein the sharp bulge is a bulge with a sharp end; the sharp protrusions are irradiated through a second laser beam so that the sharp protrusions can be melted. According to the welding method for the battery shell disclosed by the embodiment of the invention, the sharp bulge is irradiated by the second laser beam to melt the sharp bulge, so that the sharp bulge on the outer surface of the welding position of the cover body and the shell body can be eliminated, namely, the sharp bulge on the outer surface of the battery shell is eliminated; therefore, the sharp protrusions on the outer surface of the battery shell can be prevented from puncturing an insulating film and other structures on the outer surface of the battery shell, and the welding quality of the battery shell is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a welding method for battery casings. Background Technology

[0002] In a battery structure, the battery cells are placed inside the battery casing. To facilitate the installation of the cells, the battery casing typically consists of two parts: a shell with an opening and a cover. After the cells are installed inside the casing, the opening is closed by the cover and then welded together to achieve encapsulation. Poor welding quality between the cover and the shell directly affects the overall performance of the battery. Summary of the Invention

[0003] This invention proposes a welding method for battery casings, which can eliminate sharp protrusions on the outer surface of the welding position between the cover and the casing body, thereby improving the welding quality of the battery casing.

[0004] According to an embodiment of the present invention, a welding method for a battery casing includes a casing body and a cover body. The casing body has a casing opening on one side along a first direction, and the cover body is disposed at the casing opening of the casing body. The welding method includes: placing the cover body at the casing opening of the casing body and welding the casing body and the cover body with a first laser beam; identifying a sharp protrusion on the outer surface of the welding position of the cover body and the casing body, the sharp protrusion being a protrusion with a pointed tip; and irradiating the sharp protrusion with a second laser beam to melt the sharp protrusion.

[0005] According to the welding method for battery casing of the present invention, the sharp protrusion is irradiated by a second laser beam to melt the sharp protrusion, thereby eliminating the sharp protrusion on the outer surface of the welding position between the cover and the casing body, that is, eliminating the sharp protrusion on the outer surface of the battery casing. This can prevent the sharp protrusion on the outer surface of the battery casing from piercing the insulating film and other structures on the outer surface of the battery casing, thereby improving the welding quality of the battery casing.

[0006] According to some embodiments of the present invention, the step of melting the sharp protrusion by irradiating it with a second laser beam includes: the moving trajectory of the second laser beam extends circumferentially along the cover body, and along the circumferential direction of the cover body, the moving trajectory of the second laser beam has an elimination start point and an elimination end point located on opposite sides of the sharp protrusion, and the distance between the elimination start point and the elimination end point and the sharp protrusion is not less than 2 mm.

[0007] According to some embodiments of the present invention, the cross-section of the battery casing is a rounded rectangle. When a sharp protrusion is detected at the rounded corner where the casing body and the cover body are welded, the sharp protrusion located at the rounded corner is irradiated by the second laser beam to melt the sharp protrusion. This includes: the second laser beam moves along a first moving trajectory along the circumference of the cover body. The first moving trajectory has a first elimination start point and a first elimination end point located on both sides of the rounded corner in the circumferential direction. The distance between the first elimination start point and the first elimination end point and the rounded corner is in the range of 10~20mm.

[0008] According to some embodiments of the present invention, when a sharp protrusion is detected on the straight side of the welding position between the shell body and the cover body, the sharp protrusion located on the straight side is irradiated by the second laser beam to melt the sharp protrusion. This includes: the second laser beam moves along a second moving trajectory, the second moving trajectory having a second elimination start point and a second elimination end point located on opposite sides of the sharp protrusion, and the distance between the second elimination start point and the second elimination end point and the sharp protrusion along the circumference of the cover body is in the range of 2~5mm.

[0009] According to some embodiments of the present invention, identifying sharp protrusions on the outer surface of the welding position between the cover and the shell body includes: scanning the outer surface of the welding position between the cover and the shell body using a 3D profilometer as a detection profile, setting multiple detection points on the detection profile, and marking the area between the two detection points as the sharp protrusion when the included angle between the tangents corresponding to two adjacent detection points is less than a preset angle.

[0010] According to some embodiments of the present invention, the preset angle is no greater than 160°.

[0011] According to some embodiments of the present invention, the power of the second laser beam is greater than 500W; and / or, the moving speed of the second laser beam is not less than 50mm / s.

[0012] According to some embodiments of the present invention, the power of the second laser beam is less than the power of the first laser beam.

[0013] According to some embodiments of the present invention, the moving speed of the second laser beam is less than the moving speed of the first laser beam.

[0014] According to some embodiments of the present invention, the angle between the emission angle of the first laser beam and the emission angle of the second laser beam is in the range of 70°~110°.

[0015] According to some embodiments of the present invention, when the sharp protrusion is irradiated by the second laser beam to melt the sharp protrusion, an inert gas is delivered to the location of the sharp protrusion.

[0016] According to some embodiments of the present invention, welding the shell body and the cover body by the first laser beam includes: the first laser beam being emitted from the outer peripheral side of the cover body toward the connection position of the cover body and the shell body; Irradiating the sharp protrusion with a second laser beam includes: the second laser beam being emitted from one side of the cover along the first direction toward the sharp protrusion.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] Figure 1 This is a flowchart of a welding method for a battery casing according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the treatment of sharp protrusions on rounded corners and straight sides in a welding method for a battery casing according to an embodiment of the present invention. Figure 3 This is a schematic diagram showing the positional relationship between the second laser beam and the battery casing in a welding method for a battery casing according to an embodiment of the present invention. Figure 4 This is a schematic diagram showing the positional relationship between the first laser beam and the battery casing in a welding method for a battery casing according to an embodiment of the present invention.

[0019] Figure label: 10. Battery casing; 1. Shell body; 2. Cover body; 21. Straight side; 22. Rounded corner; 10a. Sharp protrusion; 20a, First laser beam; 20b, Second laser beam; 30a, First moving trajectory; a1, First elimination start point; a2, First elimination end point; 30b, Second moving trajectory; b1, Second elimination start point; b2, Second elimination end point. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Additionally, examples of various specific processes and materials are provided in this invention; however, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0023] In the description of this invention, "first feature" and "second feature" may include one or more of the features.

[0024] In the description of this invention, "a plurality of" means two or more.

[0025] In the description of this invention, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or it may include the first and second features not being in direct contact but being in contact through another feature between them.

[0026] In the description of this invention, the terms "above," "over," and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is at a higher horizontal level than the second feature.

[0027] The following describes a welding method for a battery casing 10 according to an embodiment of the present invention with reference to the accompanying drawings.

[0028] like Figure 1 , Figure 3 and Figure 4As shown, according to an embodiment of the present invention, the welding method for a battery housing 10 includes a housing body 1 and a cover 2. The housing body 1 has a housing opening on one side along a first direction, and the cover 2 is disposed at the housing opening of the housing body 1. Therefore, after the battery cell is placed inside the housing body 1, the housing opening of the housing body 1 can be closed by the cover 2 to ensure the sealing of the battery housing 10.

[0029] The welding method includes placing the cover 2 at the opening of the shell body 1 and welding the shell body 1 and the cover 2 together using a first laser beam 20a. In other words, the shell body 1 and the cover 2 are connected by laser welding. Laser welding has advantages such as high efficiency, high precision, and a small heat-affected zone, thus improving the welding efficiency and quality of the shell body 1 and the cover 2, and also significantly enhancing the sealing performance of the battery casing 10.

[0030] Furthermore, after the shell body 1 and the cover 2 are welded, sharp protrusions 10a on the outer surface of the welded position of the cover 2 and the shell body 1 are identified. Here, sharp protrusions 10a refer to pointed protrusions on the outer surface of the welded position of the cover 2 and the shell body 1, such as conical or needle-shaped protrusions. Identifying sharp protrusions 10a facilitates the inspection of the welding quality between the cover 2 and the shell body 1. For example, in some embodiments, a 3D profilometer can be used to scan the outer surface of the welded position of the cover 2 and the shell body 1 to identify sharp protrusions 10a. Of course, sharp protrusions 10a can also be identified by acquiring an image of the outer surface of the welded position of the cover 2 and the shell body 1, etc., without specific limitations.

[0031] After identifying the sharp protrusion 10a, the second laser beam 20b irradiates the sharp protrusion 10a to melt it. The second laser beam 20b raises the temperature of the sharp protrusion 10a. When the temperature reaches its melting point, the sharp protrusion 10a melts. The molten sharp protrusion 10a has a certain fluidity, allowing the smoothing effect to eliminate the sharp corner structure on the original sharp protrusion 10a. This eliminates the sharp protrusion 10a on the outer surface of the welding position between the cover 2 and the shell body 1, i.e., eliminates the sharp protrusion 10a on the outer surface of the battery casing 10. Therefore, it prevents the sharp protrusion 10a from piercing the insulating film and other structures on the outer surface of the battery casing 10, thus improving the welding quality of the battery casing 10.

[0032] According to the welding method for battery casing 10 of the present invention, the sharp protrusion 10a is irradiated by the second laser beam 20b to melt the sharp protrusion 10a, thereby eliminating the sharp protrusion 10a on the outer surface of the welding position between the cover 2 and the casing body 1, that is, eliminating the sharp protrusion 10a on the outer surface of the battery casing 10. This avoids the sharp protrusion 10a on the outer surface of the battery casing 10 from piercing the insulating film and other structures on the outer surface of the battery casing 10, thereby improving the welding quality of the battery casing 10.

[0033] In some embodiments, after the sharp protrusions 10a are irradiated and eliminated by the second laser beam 20b, the outer surface of the welding position between the cover 2 and the shell body 1 is re-inspected. For example, the outer surface of the welding position between the cover 2 and the shell body 1 can be scanned again by a 3D profilometer to confirm that the sharp protrusions 10a have been eliminated. If there are any missed or uneliminated sharp protrusions 10a, the elimination steps are repeated until there are no sharp protrusions 10a on the outer surface of the welding position between the cover 2 and the shell body 1.

[0034] According to some embodiments of the present invention, such as Figure 3 and Figure 4 As shown, melting the sharp protrusion 10a by irradiating it with a second laser beam 20b includes: the movement trajectory of the second laser beam 20b extending circumferentially along the cover 2; the movement trajectory of the second laser beam 20b having a starting point and an ending point of elimination located on opposite sides of the sharp protrusion 10a; and the distance between the starting point and the ending point of elimination and the sharp protrusion 10a being not less than 2 mm. The welding position between the cover 2 and the shell body 1 is located at the outer peripheral edge of the top cover. The movement trajectory of the second laser beam 20b extending circumferentially along the cover 2 allows the second laser beam 20b to reliably eliminate the sharp protrusion 10a located at the outer peripheral edge of the top cover.

[0035] Specifically, after identifying the sharp protrusion 10a on the outer surface of the welding position between the cover 2 and the shell body 1, the second laser beam 20b is planned to move along the trajectory of the sharp protrusion 10a. The trajectory covers the sharp protrusion 10a, that is, the sharp protrusion 10a is located on the trajectory of the second laser beam 20b. The second laser beam 20b moves continuously along the circumference of the cover 2 from the elimination starting point located on one side of the sharp protrusion 10a to the sharp protrusion 10a, and finally moves to the elimination ending point located on the other side of the sharp protrusion 10a.

[0036] The distance between the removal start point and the removal end point and the sharp protrusion 10a is set to be no less than 2mm. That is, the second laser beam 20b covers an area of ​​at least 2mm on both sides of the sharp protrusion 10a in its moving trajectory, ensuring that the area where the sharp protrusion 10a is located can be melted under the irradiation of the second laser beam 20b, which is more conducive to the smoothing of the sharp protrusion 10a after melting, thereby improving the effect of removing the sharp protrusion 10a by the second laser beam 20b. The distance between the removal start point and the removal end point and the sharp protrusion 10a along the circumference of the cover 2 can be 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 13mm, 16mm, 20mm, etc.

[0037] According to some embodiments of the present invention, such as Figure 3 and Figure 4 As shown, the cross-section of the battery casing 10 is a rounded rectangle. When a sharp protrusion 10a is detected at the rounded corner 22 where the casing body 1 and the cover body 2 are welded, the sharp protrusion 10a at the rounded corner 22 is irradiated by a second laser beam 20b to melt the sharp protrusion 10a. This includes: the second laser beam 20b moves along a first moving trajectory 30a along the circumference of the cover body 2. The first moving trajectory 30a has a first elimination starting point a1 and a first elimination ending point a2 located on both sides of the rounded corner 22 in the circumferential direction. The distance between the first elimination starting point a1 and the first elimination ending point a2 and the rounded corner 22 is in the range of 10~20mm. It should be noted that the rounded corner 22 refers to the arc-shaped connection corner between two adjacent straight side edges 21 of the cover body 2, such as the four corners of the cover body 2 being treated with R-angle.

[0038] Specifically, during the process of welding the cover 2 to the shell body 1, the first laser beam 20a is emitted from the outer periphery of the cover 2 toward the connection position between the cover 2 and the shell body 1. The moving trajectory of the first laser beam 20a moves along the length or width direction of the battery shell 10. Since the cover 2 has rounded corners 22, the position of the rounded corners 22 is more likely to have sharp protrusions 10a due to the change in defocusing amount and the overlap of the welding trajectories of adjacent sides.

[0039] In other words, after identifying a sharp protrusion 10a at the rounded corner 22, the second laser beam 20b is set to move along the first moving trajectory 30a. Along the circumference of the cover 2, the two ends of the first moving trajectory 30a are located on opposite sides of the rounded corner 22, meaning the first moving trajectory 30a covers the rounded corner 22. This allows the second laser beam 20b to continuously move from the first elimination starting point a1 along the first moving trajectory 30a to the first elimination ending point a2, illuminating all the sharp protrusions 10a at the rounded corner 22. Thus, the second laser beam 20b can eliminate all the sharp protrusions 10a at the rounded corner 22 after moving along the first moving trajectory 30a. This reduces the difficulty of planning the moving trajectory of the second laser beam 20b to eliminate the sharp protrusions 10a at the rounded corner 22 and improves the efficiency of eliminating the sharp protrusions 10a at the rounded corner 22.

[0040] Specifically, by setting the distances between the first elimination starting point a1 and the first elimination ending point a2 and the rounded corner 22 within the range of 10mm to 20mm—that is, setting the distance between the first elimination starting point a1 and the rounded corner 22 (as shown by L3 in the figure) within the range of 10mm to 20mm, and setting the distance between the first elimination ending point a2 and the rounded corner 22 (as shown by L4 in the figure) within the range of 10mm to 20mm—it can be ensured that the first moving trajectory 30a can completely cover the area of ​​the rounded corner 22. Specifically, the first moving trajectory 30a covers at least 10mm on each side of the rounded corner 22. Simultaneously, it avoids the first moving trajectory 30a being too long, which would increase the efficiency and cost of eliminating the sharp protrusion 10a. Therefore, it is possible to ensure that the second laser beam 20b, after moving along the first moving trajectory 30a, eliminates the sharp protrusion 10a at the rounded corner 22, while simultaneously improving the elimination efficiency of the sharp protrusion 10a and reducing the cost of eliminating the sharp protrusion 10a. For example, the distance between the first elimination starting point a1 and the first elimination ending point a2 and the rounded corner 22 can be 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, etc.

[0041] In some embodiments, after eliminating the sharp protrusion 10a, the included angle of the initial tangent in the rounded corner area should be no greater than 160°, that is, the included angle between the tangents of any two points at the rounded corner position should be no greater than 160°, so as to ensure the elimination effect of the sharp protrusion 10a.

[0042] According to some embodiments of the present invention, when a sharp protrusion 10a is detected on the straight side 21 where the shell body 1 and the cover body 2 are welded, the sharp protrusion 10a located on the straight side 21 is irradiated by a second laser beam 20b to melt the sharp protrusion 10a. This includes: the second laser beam 20b moves along a second moving trajectory 30b, the second moving trajectory 30b having a second elimination starting point b1 and a second elimination ending point b2 located on opposite sides of the sharp protrusion 10a, and the distance between the second elimination starting point b1 and the second elimination ending point b2 and the sharp protrusion 10a along the circumference of the cover body 2 is in the range of 2~5mm. In other words, when a sharp protrusion 10a is identified at the straight side 21, the second laser beam 20b is set to move along the second moving trajectory 30b. Along the circumference of the cover 2, the two ends of the second moving trajectory 30b are located on opposite sides of the sharp protrusion 10a. That is, the second moving trajectory 30b covers the sharp protrusion 10a located on the straight side 21. During the process of the second laser beam 20b moving from the second elimination starting point b1 along the second moving trajectory 30b to the second elimination ending point b2, the sharp protrusion 10a on the straight side 21 can be eliminated by irradiating it.

[0043] Specifically, by setting the distances between the second elimination starting point b1 and the second elimination ending point b2 and the sharp protrusion 10a within the range of 2mm to 5mm, that is, setting the distance between the second elimination starting point b1 and the sharp protrusion 10a (as shown by L1 in the figure) within the range of 2mm to 5mm, and setting the distance between the second elimination ending point b2 and the sharp protrusion 10a (as shown by L2 in the figure) within the range of 2mm to 5mm, it can be ensured that the second moving trajectory 30b can completely cover the sharp protrusion 10a on the straight side 21. That is, the second moving trajectory 30b covers at least 2mm of the sharp protrusion 10a on each side of the straight side 21. At the same time, it can avoid the second moving trajectory 30b being too long, which would increase the efficiency and cost of eliminating the sharp protrusion 10a. Therefore, the effect and efficiency of the second laser beam 20b in eliminating the sharp protrusion 10a can be improved, and the cost of eliminating the sharp protrusion 10a can be reduced. For example, the distance between the second elimination starting point b1 and the second elimination ending point b2 and the sharp protrusion 10a located on the straight side 21 can be 2mm, 2.2mm, 2.5mm, 2.7mm, 3mm, 3.3mm, 3.5mm, 3.8mm, 4mm, 4.5mm, 5mm, etc.

[0044] According to some embodiments of the present invention, identifying sharp protrusions 10a on the outer surface of the welding position between the cover 2 and the shell body 1 includes: scanning the contour of the outer surface of the welding position between the cover 2 and the shell body 1 using a 3D profilometer as a detection contour, setting multiple detection points on the detection contour, and marking the area between the two detection points as sharp protrusions 10a when the included angle between the tangents corresponding to two adjacent detection points is less than a preset angle. In this process, the distance between two adjacent detection points is no more than 0.1m. In the area where there is no sharp protrusion 10a in the detection contour, the transition of the detection contour is relatively smooth, and the tangents corresponding to two adjacent detection points are nearly parallel. However, since the sharp protrusion 10a protrudes from the outer wall of the battery casing, there is an obvious undulation between the sharp protrusion 10a and other areas of the detection contour (specifically, areas where there is no sharp protrusion 10a in the detection contour). Therefore, by judging the angle between the tangents corresponding to two adjacent detection points, the undulation of two closely spaced adjacent detection points can be judged, thereby judging whether there is a sharp protrusion 10a on the outer surface of the welding position between the cover 2 and the shell body 1, which can improve the accuracy of identifying the sharp protrusion 10a.

[0045] According to some embodiments of the present invention, the preset angle is no greater than 160°. The preset angle can be 160°, 158°, 155°, 152°, 150°, 147°, 145°, 143°, 140°, etc., and no specific limitation is made here.

[0046] According to some embodiments of the present invention, the power of the second laser beam 20b is greater than 500W. The power of the second laser beam 20b is directly proportional to its efficiency in melting the sharp protrusion 10a; in other words, the higher the power of the second laser beam 20b, the higher the efficiency with which it melts the sharp protrusion 10a, thereby improving the efficiency of eliminating the sharp protrusion 10a. Therefore, by controlling the power of the second laser beam 20b to be greater than 500W, the efficiency of eliminating the sharp protrusion 10a by the second laser beam 20b can be improved. The efficiency of the second laser beam 20b can be 500W, 520W, 550W, 570W, 600W, 630W, 650W, 680W, 700W, etc.

[0047] According to some embodiments of the present invention, the moving speed of the second laser beam 20b is not less than 50 mm / s. The faster the moving speed of the second laser beam 20b, the more sharp protrusions 10a can be irradiated per unit time. Therefore, by controlling the moving speed of the second laser beam 20b to a range of not less than 50 mm / s, the efficiency of eliminating sharp protrusions 10a by the second laser beam 20b can be significantly improved. The moving speed of the second laser beam 20b can be 50 mm / s, 55 mm / s, 60 mm / s, 65 mm / s, 70 mm / s, 75 mm / s, 80 mm / s, 85 mm / s, etc.

[0048] In some embodiments, the power of the second laser beam 20b is greater than 500W, and the moving speed of the second laser beam 20b is not less than 50mm / s. This improves the efficiency of eliminating sharp protrusions 10a using the second laser beam 20b.

[0049] According to some embodiments of the present invention, the power of the second laser beam 20b is less than the power of the first laser beam 20a. The sharp protrusion 10a is typically relatively small in size compared to the welding depth between the shell body 1 and the cover 2, and since the sharp protrusion 10a is located on the outer surface of the welding position between the cover 2 and the shell body 1, the second laser beam 20b can act more directly on the sharp protrusion 10a. Therefore, by setting the power of the second laser beam 20b to be less than the power of the first laser beam 20a, while ensuring that the second laser beam 20b can stably eliminate the sharp protrusion 10a, the power consumption during elimination of the sharp protrusion 10a can be reduced, thereby reducing the cost of eliminating the sharp protrusion 10a.

[0050] According to some embodiments of the present invention, the moving speed of the second laser beam 20b is less than the moving speed of the first laser beam 20a. By reducing the moving speed of the second laser beam 20b, it allows for a more sufficient irradiation time on the sharp protrusion 10a, thereby avoiding the risk that the sharp protrusion 10a may not be melted due to excessively fast movement of the second laser beam 20b, thus improving the effectiveness of eliminating the sharp protrusion 10a using the second laser beam 20b.

[0051] According to some embodiments of the present invention, the angle between the emission angle of the first laser beam 20a and the emission angle of the second laser beam 20b is in the range of 70° to 110°. This allows for a better increase in the distance between the emission positions of the first laser beam 20a and the second laser beam 20b. For example, the first laser beam 20a is emitted from the outer periphery of the top cover towards the cover body 2 and the shell body 1, while the second laser beam 20b is emitted from the side of the top cover away from the shell body 1 along a first direction towards the sharp protrusion 10a. This avoids interference between the laser emitter emitting the first laser beam 20a and the laser emitter emitting the second laser beam 20b, thereby reducing the difficulty of arranging the laser emitters emitting the first laser beam 20a and the second laser beam 20b.

[0052] Furthermore, when the first laser beam 20a is emitted from the outer periphery of the top cover towards the cover 2 and the shell body 1 to weld the cover 2 and the shell body 1, a second laser beam 20b is emitted from the side of the cover 2 away from the shell body 1 along the first direction towards the sharp protrusion 10a. This ensures that the distance between the second laser beam 20b and the cover 2 remains constant, thereby avoiding the impact of changes in defocusing amount or the difficulty of trajectory planning on the elimination of the sharp protrusion 10a on the elimination efficiency and effect. In other words, by controlling the angle between the emission angle of the first laser beam 20a and the emission angle of the second laser beam 20b within the range of 70° to 110°, the efficiency and effect of eliminating the sharp protrusion 10a by the second laser beam 20b can be improved. The angle between the emission angle of the first laser beam 20a and the emission angle of the second laser beam 20b can be 70°, 75°, 80°, 85°, 90°, 95°, 100°, 105°, 110°, etc.

[0053] According to some embodiments of the present invention, when the sharp protrusion 10a is irradiated by the second laser beam 20b to melt the sharp protrusion 10a, an inert gas is delivered to the location of the sharp protrusion 10a. The inert gas delivered to the sharp protrusion 10a isolates it from oxygen in the air, thereby avoiding the risk of oxidation and defects caused by the sharp protrusion 10a coming into contact with oxygen under the irradiation of the second laser beam 20b. In other words, it avoids generating other undesirable defects during the elimination of the sharp protrusion 10a, thus improving the effectiveness of eliminating the sharp protrusion 10a by the second laser beam 20b.

[0054] In a specific example, nitrogen is used as the inert gas, which can reduce the cost of using inert gases.

[0055] According to some embodiments of the present invention, such as Figure 3 and Figure 4As shown, welding the shell body 1 and the cover 2 using a first laser beam 20a includes: the first laser beam 20a being emitted from the outer periphery of the cover 2 toward the connection point between the cover 2 and the shell body 1; irradiating the sharp protrusion 10a using a second laser beam 20b includes: the second laser beam 20b being emitted from one side of the cover 2 along a first direction toward the sharp protrusion 10a. In other words, the welding method between the cover 2 and the shell body 1 is side welding, which can effectively improve the welding strength between the cover 2 and the shell body 1, and avoid the risk of damage to the battery cell caused by the welding laser irradiating the battery cell through the gap between the cover 2 and the shell body 1 during top welding. Furthermore, the second laser beam 20b being emitted from one side of the cover 2 along the first direction toward the sharp protrusion 10a allows for stable control of the defocusing amount of the second laser beam 20b, thereby improving the quality of the second laser beam 20b in eliminating the sharp protrusion 10a. For example, in some embodiments, the first direction is the up-down direction, the cover 2 is located on the top of the shell body 1, and the second laser beam 20b irradiates the sharp protrusion 10a from top to bottom. The laser emitter for emitting the second laser beam 20b is located above the cover 2, so that the distance between the laser emitter for emitting the second laser beam 20b and the cover 2 can remain consistent during the movement of the laser emitter, and the defocus amount remains constant. This can avoid welding defects caused by changes in the defocus amount, and thus improve the effect of eliminating the sharp protrusion 10a by the second laser beam 20b.

[0056] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," 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 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 invention according to the specific circumstances.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0058] Although embodiments of the invention have been shown and described, those skilled in the art will understand 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 claims and their equivalents.

Claims

1. A welding method for a battery casing, characterized in that, The battery casing includes a casing body and a cover. The casing body has a casing opening on one side along a first direction, and the cover is disposed at the casing opening of the casing body. The welding method includes: The cover is placed at the opening of the shell body and the shell body and the cover are welded together by the first laser beam; Identify sharp protrusions on the outer surface of the welding position between the cover and the shell body, wherein the sharp protrusions are protrusions with pointed tips; The sharp protrusion is irradiated by a second laser beam to melt it.

2. The welding method for a battery casing according to claim 1, characterized in that, The step of melting the sharp protrusion by irradiating it with a second laser beam includes: the movement trajectory of the second laser beam extends along the circumference of the cover body, and along the circumference of the cover body, the movement trajectory of the second laser beam has an elimination start point and an elimination end point located on opposite sides of the sharp protrusion, and the distance between the elimination start point and the elimination end point and the sharp protrusion is not less than 2 mm.

3. The welding method for a battery casing according to claim 2, characterized in that, The battery casing has a rounded rectangular cross-section. When a sharp protrusion is detected at the rounded corner where the casing body and the cover are welded, the second laser beam irradiates the sharp protrusion at the rounded corner to melt it, including: The second laser beam moves along the first moving trajectory along the circumference of the cover. The first moving trajectory has a first elimination start point and a first elimination end point located on both sides of the rounded corner in the circumferential direction. The distance between the first elimination start point and the first elimination end point and the rounded corner is 10~20mm.

4. The welding method for a battery casing according to claim 3, characterized in that, When a sharp protrusion is detected on the straight side of the welding position between the shell body and the cover body, the sharp protrusion located on the straight side is irradiated with the second laser beam to melt the sharp protrusion, including: The second laser beam moves along a second moving trajectory, which has a second elimination start point and a second elimination end point located on opposite sides of the sharp protrusion. Along the circumference of the cover, the distance between the second elimination start point and the second elimination end point and the sharp protrusion ranges from 2 to 5 mm.

5. The welding method for a battery casing according to claim 1, characterized in that, The sharp protrusions on the outer surface that identify the welding position between the cover and the shell body include: The outer surface of the welding position between the cover and the shell body is scanned by a 3D profilometer to form a detection profile. Multiple detection points are set on the detection profile. When the included angle between the tangents corresponding to two adjacent detection points is less than a preset angle, the area between the two detection points is marked as the sharp protrusion.

6. The welding method according to claim 5, characterized in that, The preset angle is no greater than 160°.

7. The welding method for a battery casing according to claim 1, characterized in that, The power of the second laser beam is greater than 500W; and / or the moving speed of the second laser beam is not less than 50mm / s.

8. The welding method for a battery casing according to claim 1, characterized in that, The power of the second laser beam is less than the power of the first laser beam.

9. The welding method for a battery casing according to claim 1, characterized in that, The second laser beam moves at a speed less than that of the first laser beam.

10. The welding method for a battery casing according to claim 1, characterized in that, The angle between the emission angle of the first laser beam and the emission angle of the second laser beam is in the range of 70°~110°.

11. The welding method for a battery casing according to claim 1, characterized in that, When the sharp protrusion is irradiated by the second laser beam and melted, inert gas is delivered to the location of the sharp protrusion.

12. The welding method for a battery casing according to any one of claims 1-11, characterized in that, Welding the shell body and the cover body by the first laser beam includes: the first laser beam is emitted from the outer peripheral side of the cover body toward the connection position of the cover body and the shell body; Irradiating the sharp protrusion with a second laser beam includes: the second laser beam being emitted from one side of the cover along the first direction toward the sharp protrusion.

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