Welding method and battery

Abstract

The embodiment of the invention provides a welding method and a battery, and the welding method comprises the steps that a first material and a second material are provided, a welding seam is formed between the first material and the second material, the melting point of the first material is higher than that of the second material, and the laser absorptivity of the first material is lower than that of the second material; a welding device is provided, the welding device can generate a laser spot, the laser spot comprises an inner circle part and an outer ring part, the outer ring part surrounds the inner circle part, the outer ring part and the inner circle part are coaxial, and the power density of the inner circle part is higher than that of the outer ring part; the laser spot moves along the preheating path, so that the part, adjacent to the welding seam, of the first material is in a molten state; the laser spot moves along the welding path to weld the first material and the second material along the weld seam. The risk that the welding seam between the first material and the second material forms an incomplete fusion area, and air holes and deformation occur can be reduced, so that the risk that the electrical property of the battery is reduced can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of welding, and in particular to a welding method and a battery. Background Art

[0002] After the battery's electrodes and casing are riveted together, the gap between them needs to be welded, typically using laser welding. In existing technology, the melting point of the electrode's material is higher than that of the casing's material, and the electrode's material has a lower laser absorption rate than the casing's. During welding, while the casing's material melts, the electrode's material is not fully melted, forming an unfused zone. Furthermore, the material at the center of the laser vaporizes to generate high-pressure steam, creating a cavity within the molten material. Furthermore, the escape of high-pressure steam pushes the molten material, deforming the weld. This can lead to defects in the weld between the electrode and casing, which in turn reduces the battery's electrical performance. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a welding method and a battery that can reduce the risk of battery electrical performance degradation caused by defects in the weld between the electrode and the housing.

[0004] In a first aspect, an embodiment of the present invention provides a welding method, which includes: providing a first material and a second material to form a weld seam between the first material and the second material, wherein the melting point of the first material is higher than the melting point of the second material, and the absorption rate of the first material to laser is lower than that of the second material; providing a welding device, which can generate a laser spot, wherein the laser spot includes an inner circle part and an outer ring part, the outer ring part surrounds the inner circle part, the outer ring part is coaxial with the inner circle part, and the power density of the inner circle part is higher than the power density of the outer ring part; preheating the first material by the laser spot, defining the movement path of the laser spot when preheating the first material as a preheating path, and the laser spot moves along the preheating path so that the part of the first material adjacent to the weld seam is in a molten state; welding the first material and the second material along the weld seam by the laser spot, defining the movement path of the laser spot when welding the first material and the second material as a welding path, and the laser spot moves along the welding path to weld the first material and the second material along the weld seam.

[0005] The welding method provided by the first embodiment of the present invention has at least the following beneficial effects: On the one hand, preheating the first material with the laser spot before welding the first and second materials can reduce the risk of the first material not being fully melted while the second material is molten during welding, thereby reducing the risk of an unfused zone forming between the first and second materials. On the other hand, the outer ring portion of the laser spot surrounds the inner ring portion of the laser spot, and the power density of the inner ring portion is higher than that of the outer ring portion. This prevents heat from being concentrated in the center of the laser spot during welding and increases the fluidity of the molten material around the laser spot, thereby making it easier for the high-pressure steam generated by the vaporization of the material at the center of the laser spot to escape. Furthermore, after the molten material around the center of the laser spot is deformed by the escaping high-pressure steam, it has sufficient fluidity to deflect toward the bottom of the molten pool formed by the molten material to complete reset, thereby reducing the risk of porosity and deformation defects in the weld.

[0006] In an embodiment of this implementation, when the laser spot preheats the first material, the focal length of the outer ring part is 1.2mm-3.0mm, and the focal length of the inner circle part is 1.2mm-3.0mm; when the laser spot welds the first material and the second material, the focal length of the outer ring part is 1.2mm-3.0mm, and the focal length of the inner circle part is 1.2mm-3.0mm.

[0007] In an example of this implementation manner, the speed at which the laser spot moves along the preheating path is 320 mm / s-720 mm / s, and the speed at which the laser spot moves along the welding path is 368 mm / s-552 mm / s.

[0008] In an example of this implementation manner, when the laser spot preheats the first material, the power of the outer ring portion is 1.3kw-1.5kw, and the power of the inner circle portion is 0.9kw-1.1kw.

[0009] In an example of this implementation manner, when the laser spot welds the first material and the second material, the power of the outer ring part is 1.4kw-1.6kw, and the power of the inner circle part is 1.1kw-1.3kw.

[0010] In an example of this implementation manner, the first material is copper, and the second material is aluminum.

[0011] In an example of this embodiment, the welding path extends along the welding seam, the welding seam, the welding path and the preheating path are all annular, and the welding seam, the welding path and the preheating path are coaxial.

[0012] In an example of this embodiment, when the laser spot moves along the welding path, the axis of the inner circular portion remains intersecting with the welding seam.

[0013] In an example of this embodiment, the diameter of the preheating path is 7.7 mm, and the diameter of the welding path is 8.7 mm.

[0014] In a second aspect, an embodiment of the present invention provides a battery, comprising an electrode and a shell, wherein the electrode is made of the first material of any embodiment of the first aspect, and the shell is made of the second material of any embodiment of the first aspect, and the electrode is welded to the shell by the welding method of any embodiment of the first aspect.

[0015] The battery provided by the second embodiment of the present invention has at least the following beneficial effects: The battery electrodes are welded to the battery shell by the welding method in the embodiment of the first aspect of the present invention, which can reduce the risk of defects in the weld between the electrode and the shell, thereby facilitating improved electrical performance of the battery.

[0016] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which: Figure 1 A schematic diagram of a welding method according to an embodiment of the present invention; Figure 2 A schematic diagram of a laser spot trajectory of a welding method according to an embodiment of the present invention; Figure 3 Schematic diagram of the structure of a laser spot according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0019] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0020] In the description of the present invention, "several" means more than one, "plurality" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0021] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0022] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0023] The embodiment of the present invention provides a welding method, please refer to Figure 1 , Figure 1 Schematic diagram of a welding method according to an embodiment of the present invention. The welding method includes: In step S100 , a first material and a second material are provided to form a welding seam between the first material and the second material. The melting point of the first material is higher than that of the second material, and the absorption rate of the first material to laser is lower than that of the second material.

[0024] Specifically, the first material and the second material are brought into close proximity so that a gap is formed between the first material and the second material, and a portion of the gap constitutes a welding seam.

[0025] Step S200: provide a welding device, see Figure 3 , Figure 3Figure 3 is a schematic diagram of the structure of a laser spot according to an embodiment of the present invention. The welding device generates a laser spot 30 comprising an inner circular portion 32 and an outer ring portion 31. The outer ring portion 31 surrounds the inner circular portion 32 and is coaxial with the inner circular portion 32. The power density of the inner circular portion 32 is higher than that of the outer ring portion 31.

[0026] Specifically, the welding equipment includes a ring-shaped spot laser, an optical fiber, and a laser head. The ring-shaped spot laser can generate an outer ring laser and a center laser. The outer ring laser surrounds the center laser. The center laser is a Gaussian laser, and the outer ring laser is a multimode laser. The power density of the center laser is higher than that of the outer ring laser. The power of the center laser and the outer ring laser can be adjusted independently. The optical fiber has an inner portion and an outer portion. The inner portion transmits the center laser to the laser head, and the outer portion transmits the outer ring laser to the laser head, so that the laser head can generate an outer ring portion 31 and an inner circular portion 32 on the first material and / or the second material. The outer ring laser constitutes the outer ring portion 31, and the center laser constitutes the inner circular portion 32. The laser spot 30 composed of the outer ring portion 31 and the inner circular portion 32 is a coaxial laser beam.

[0027] Step S300: preheating the first material by laser spot 30. Figure 2 , Figure 2 Figure 2 is a schematic diagram of a laser spot trajectory for a welding method according to an embodiment of the present invention. The path of movement of the laser spot 30 during preheating of the first material is defined as a preheating path 20. The laser spot 30 moves along the preheating path 20 to molten the portion of the first material adjacent to the weld.

[0028] Specifically, when the laser spot 30 moves along the preheating path 20 , the laser spot 30 irradiates the portion of the first material adjacent to the weld seam. The area scanned by the laser spot 30 on the first material forms a preheating area 21 , melting the first material in the preheating area 21 .

[0029] Step S400: The first material and the second material are welded along the welding seam by the laser spot 30. Figure 2 The movement path of the laser spot 30 when welding the first material and the second material is defined as a welding path 10. The laser spot 30 moves along the welding path 10 to weld the first material and the second material along the welding seam.

[0030] Specifically, when the laser spot 30 moves along the welding path 10, the laser spot 30 irradiates the weld seam. The laser spot 30 moves along the extension path of the weld seam. The area scanned by the laser spot 30 on the first material and the second material forms a welding area 11. The welding area 11 covers part of the first material and part of the second material adjacent to the weld seam, so that part of the first material and part of the second material adjacent to the weld seam are converted into a molten state and fused.

[0031] The welding method provided by the first embodiment of the present invention has at least the following beneficial effects: On the one hand, preheating the first material via laser spot 30 before welding the first and second materials can reduce the risk of the first material not being fully melted while the second material is molten during welding, thereby reducing the risk of an unfused zone forming between the first and second materials. On the other hand, the outer ring portion 31 of laser spot 30 surrounds the inner ring portion 32 of laser spot 30, and the power density of inner ring portion 32 is higher than the power density of outer ring portion 31. This prevents heat from being concentrated at the center of laser spot 30 during welding and improves the fluidity of the molten material around laser spot 30, thereby facilitating the escape of high-pressure steam generated by the vaporization of the material at the center of laser spot 30. Furthermore, after being deformed by the escaping high-pressure steam, the molten material surrounding the center of laser spot 30 has sufficient fluidity to deflect toward the bottom of the molten pool formed by the molten material to complete reset, thereby reducing the risk of porosity and deformation defects in the weld.

[0032] In one embodiment of this embodiment, please refer to Figure 3 When the laser spot 30 preheats the first material, the focal length of the outer ring part 31 is 1.2mm-3.0mm, and the focal length of the inner circle part 32 is 1.2mm-3.0mm. When the laser spot 30 welds the first material and the second material, the focal length of the outer ring part 31 is 1.2mm-3.0mm, and the focal length of the inner circle part 32 is 1.2mm-3.0mm.

[0033] Specifically, in the vertical direction, the position of the welding device relative to the first material and the second material is fixed. During the welding process and the preheating process, the welding device is located above the first material and the second material. The laser spot 30 generated by the welding device extends in the vertical direction. The focal lengths of the inner circle part 32 and the outer ring part 31 remain unchanged. The focal points of the inner circle part 32 and the outer ring part 31 are located below the welding device and on the side of the first material and the second material facing the welding device. When the laser spot 30 preheats the first material, the focal length of the outer ring part 31 can be 1.2mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, and the focal length of the inner circle part 32 can be 1.2mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm. When the laser spot 30 welds the first material and the second material, the focal length of the outer ring part 31 can be 1.2mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm, and the focal length of the inner circle part 32 can be 1.2mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm.

[0034] It is understandable that such a setting is conducive to improving welding quality. It should be noted that during the preheating process of the laser spot 30 on the first material, if the focal length of the outer ring portion 31 is too short, the defocus of the first material is too large, which will reduce the energy density of the outer ring portion 31, thereby causing the first material irradiated by the outer ring portion 31 to have insufficient fluidity. If the focal length of the outer ring portion 31 is too long, the defocus of the outer ring portion 31 is too small, which will cause the energy density of the outer ring portion 31 to be too high, causing the first material irradiated by the outer ring portion 31 to generate a large amount of high-pressure steam. When the high-pressure steam escapes outward, the molten first material will splash. The splashed first material will adhere to other parts of the first material after falling, causing the first material to deform. If the focal length of the inner circle portion 32 is too short, the defocus of the inner circle portion 32 is too large, which will cause the energy density of the inner circle portion 32 to be too low, which may cause the first material irradiated by the inner circle portion 32 to fail to fully melt, thereby reducing the preheating effect. When the focal length of the inner circular part 32 is too long and the defocus amount of the inner circular part 32 is too small, the energy density of the inner circular part 32 will be too large, and the first material irradiated by the inner circular part 32 will generate a large amount of high-pressure steam that escapes outward. During the escape process, the high-pressure steam pushes the molten first material, thereby causing the first material to deform.

[0035] It should be noted that when laser spot 30 welds the first and second materials, if the focal length of outer ring portion 31 is too short, the defocus of the first material is too large, which reduces the energy density of outer ring portion 31 and reduces the fluidity of the first and second materials irradiated by outer ring portion 31. This makes it difficult for the high-pressure steam generated by the first or second material irradiated by inner ring portion 32 to escape, and easily causes pores. If the focal length of outer ring portion 31 is too long, the defocus of the first material is too small, which increases the energy density of outer ring portion 31. The first material irradiated by outer ring portion 31 generates a large amount of high-pressure steam. When the high-pressure steam escapes, the molten first and second materials are splashed. The splashed material may then adhere to other parts of the first or second material that have not been fully melted and have low fluidity, causing deformation of the first or second material at the location where the splashed material adheres. If the focal length of inner ring portion 32 is too short, the defocus of inner ring portion 32 is too large, resulting in too low energy density in inner ring portion 32, which prevents the first and second materials from fully fusing. When the focal length of the inner circular part 32 is too long, the defocus amount of the inner circular part 32 is too small, which will make the energy density of the inner circular part 32 too large, and the first material or the second material irradiated by the inner circular part 32 will generate a large amount of high-pressure steam that escapes outward. During the escape process, the high-pressure steam pushes the molten first material or the molten second material, thereby causing the first material or the second material to deform.

[0036] In one embodiment of this embodiment, please refer to Figure 2 and Figure 3The speed at which the laser spot 30 moves along the preheating path 20 is 320 mm / s-720 mm / s, and the speed at which the laser spot 30 moves along the welding path 10 is 368 mm / s-552 mm / s.

[0037] Specifically, the speed at which the laser spot 30 moves along the preheating path 20 can be 320 mm / s, 400 mm / s, 500 mm / s, 600 mm / s, or 720 mm / s, and the speed at which the laser spot 30 moves along the welding path 10 can be 368 mm / s, 390 mm / s, 460 mm / s, 530 mm / s, or 552 mm / s. It is understood that if the laser spot 30 moves too slowly along the preheating path 20, the preheating time will be too long, thereby reducing efficiency. If the laser spot 30 moves too quickly along the preheating path 20, the preheating will be insufficient, thereby causing the first material in the preheating area 21 to not be fully melted. If the laser spot 30 moves too quickly along the welding path 10, the first and second materials in the welding area 11 may not be fully fused, resulting in weld defects. If the laser spot 30 moves too slowly along the welding path 10, welding efficiency will be reduced and localized overheating of the first and second materials will occur, thereby reducing welding quality. Setting the speed of the laser spot 30 along the preheating path 20 to 320 mm / s-720 mm / s and the speed of the laser spot 30 along the welding path 10 to 368 mm / s-552 mm / s can help improve welding quality and efficiency.

[0038] In one embodiment of this embodiment, please refer to Figure 2 and Figure 3 When the laser spot 30 preheats the first material, the power of the outer ring part 31 is 1.3kw-1.5kw, and the power of the inner circle part 32 is 0.9kw-1.1kw.

[0039] Specifically, when the laser spot 30 preheats the first material, the power of the outer ring part 31 can be 1.30kw, 1.35kw, 1.40kw, 1.45kw, 1.50kw, and the power of the inner circle part 32 can be 0.9kw, 0.95kw, 1.00kw, 1.05kw, 1.1kw.

[0040] It is understood that when laser spot 30 preheats the first material, if the power of outer ring portion 31 is too high, a large amount of high-pressure steam will be generated within the first material illuminated by outer ring portion 31. The escape of high-pressure steam will cause the molten first material to splash outward, and the splashed first material may adhere to the first material outside the preheating area 21, causing deformation of the first material. If the power of outer ring portion 31 is too low, the first material illuminated by outer ring portion 31 will have insufficient fluidity, making it difficult for the high-pressure steam generated by the first material illuminated by inner circle portion 32 to escape, and thus easily forming pores. If the power of inner circle portion 32 is too high, a large amount of high-pressure steam will be generated in the first material illuminated by inner circle portion 32, and the high-pressure steam will push the molten first material during the escape process, causing deformation. If the power of inner circle portion 32 is too low, the first material will not be fully melted. Setting the power of outer ring portion 31 to 1.3 kW to 1.5 kW and the power of inner circle portion 32 to 0.9 kW to 1.1 kW will help improve the preheating quality of the first material.

[0041] In one embodiment of this embodiment, please refer to Figure 3 When the laser spot 30 welds the first and second materials, the power of the outer ring portion 31 is 1.4 kW to 1.6 kW, and the power of the inner circle portion 32 is 1.1 kW to 1.3 kW. Specifically, the power of the outer ring portion 31 can be 1.4 kW, 1.45 kW, 1.5 kW, 1.55 kW, or 1.6 kW, and the power of the inner circle portion 32 can be 1.1 kW, 1.15 kW, 1.20 kW, 1.25 kW, or 1.3 kW.

[0042] It is understood that if the power of the outer ring portion 31 is too high, the first material irradiated by the outer ring portion 31 will generate a large amount of high-pressure steam. When the high-pressure steam escapes, the molten first material and the molten second material will splash. After the splash falls, it may adhere to the first material or the second material that has not been fully melted and has low fluidity outside the welding area 11, causing the first material or the second material at the location where the splash adheres to deform. If the power of the outer ring portion 31 is too low, the first material and the second material irradiated by the outer ring portion 31 will have insufficient fluidity, making it difficult for the high-pressure steam generated by the first material or the second material irradiated by the inner circle portion 32 to escape, which can easily lead to the formation of pores. If the power of the inner circle portion 32 is too high, the first material or the second material irradiated by the inner circle portion 32 will generate a large amount of high-pressure steam that escapes outward. During the escape process, the high-pressure steam pushes the molten first material or the molten second material, causing the first material or the second material to deform. If the power of the inner circle portion 32 is too low, the first material and the second material at the center of the laser spot 30 will not be fully fused. Setting the power of the outer ring portion 31 to 1.4 kW-1.6 kW and the power of the inner circle portion 32 to 1.1 kW-1.3 kW is beneficial to improving the welding quality of the first material and the second material.

[0043] In one embodiment of this embodiment, the first material is copper and the second material is aluminum. It is understood that copper has a higher melting point than aluminum and a lower laser absorptivity than aluminum. Therefore, selecting copper as the first material and aluminum as the second material is beneficial for improving weld quality.

[0044] In one embodiment of this embodiment, please refer to Figure 2 and Figure 3 , the welding path 10 extends along the welding seam, and the welding seam, welding path 10 and preheating path 20 are all annular, and the welding seam, welding path 10 and preheating path 20 are coaxial. Specifically, the first material is cylindrical, and the second material has a hole. During welding and preheating, the first material is arranged in the hole in the second material, and the gap between the outer peripheral surface of the first material and the hole wall of the second material constitutes the welding seam. It can be understood that under the condition of the same path length, the displacement distance of the laser spot 30 moving along the annular path is smaller than the displacement distance of the laser spot 30 moving along the straight path. Setting the welding seam, welding path 10 and preheating path 20 to be annular can reduce the requirements for the welding size supported by the welding equipment.

[0045] In one embodiment of this embodiment, please refer to Figure 2 and Figure 3As the laser spot 30 moves along the welding path 10, the axis of the inner circular portion 32 remains intersecting with the weld seam. Specifically, the diameter of the weld seam is equal to the diameter D2 of the welding path 10. It can be understood that the energy density at the axis of the inner circular portion 32 is higher, and the molten first material and the molten second material fuse at the weld seam. The intersection of the axis of the inner circular portion 32 and the weld seam facilitates full fusion of the first and second materials.

[0046] In one embodiment of this embodiment, please refer to Figure 2 and Figure 3 The diameter D1 of the preheating path 20 is 7.7 mm, and the diameter D2 of the welding path 10 is 8.7 mm. It is understood that if the diameter D1 of the preheating path 20 is too large, the laser spot 30 will take a longer time to complete one revolution along the preheating path 20. For ease of explanation, the first and second points are defined as being located on the preheating path 20 and symmetrically distributed about the center of the preheating path 20. If the diameter D1 of the preheating path 20 is too large, the first material at the second point may have cooled by the time the laser spot 30 reaches the first point, preventing the first material along the preheating path 20 from remaining molten, thereby reducing the preheating effect. If the diameter D1 of the preheating path 20 is too small, it will indirectly limit the size of the first and second materials, making it unsuitable for welding under certain conditions. If the diameter D2 of the welding path 10 is too large, some of the preheated first material will cool before the weld is completed, resulting in incomplete fusion of the first and second materials. If the diameter D2 of the welding path 10 is too small, it will indirectly limit the size of the first and second materials, making it unsuitable for welding under certain conditions. Setting the diameter D1 of the preheating path 20 to 7.7 mm and the diameter D2 of the welding path 10 to 8.7 mm not only improves welding quality, but also meets welding requirements under more conditions.

[0047] In a second aspect, an embodiment of the present invention provides a battery, comprising an electrode and a shell, wherein the electrode is made of the first material of any embodiment of the first aspect, and the shell is made of the second material of any embodiment of the first aspect, and the electrode is welded to the shell by the welding method of any embodiment of the first aspect.

[0048] Specifically, the electrode is columnar, the shell has a hole, the electrode is arranged in the hole of the shell, and the gap between the outer peripheral surface of the electrode and the hole wall of the shell constitutes a welding seam.

[0049] The battery provided by the second embodiment of the present invention has at least the following beneficial effects: The battery electrodes are welded to the battery shell by the welding method in the embodiment of the first aspect of the present invention, which can reduce the risk of defects in the weld between the electrode and the shell, thereby facilitating improved electrical performance of the battery.

[0050] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A welding method, characterized in that: include: Providing a first material and a second material so that a welding seam is formed between the first material and the second material, wherein the melting point of the first material is higher than that of the second material, and the absorption rate of the first material to laser light is lower than that of the second material; A welding device is provided, wherein the welding device can generate a laser spot, wherein the laser spot includes an inner circular portion and an outer ring portion, wherein the outer ring portion surrounds the inner circular portion and is coaxial with the inner circular portion, and the power density of the inner circular portion is higher than the power density of the outer ring portion; preheating the first material by the laser spot, defining a movement path of the laser spot when preheating the first material as a preheating path, and moving the laser spot along the preheating path so that a portion of the first material adjacent to the weld is in a molten state; The first material and the second material are welded along the welding seam by the laser spot. The movement path of the laser spot when welding the first material and the second material is defined as the welding path. The laser spot moves along the welding path to weld the first material and the second material along the welding seam.

2. The welding method according to claim 1, characterized in that When the laser spot preheats the first material, the focal length of the outer ring part is 1.2mm-3.0mm, and the focal length of the inner circle part is 1.2mm-3.0mm. When the laser spot welds the first material and the second material, the focal length of the outer ring part is 1.2mm-3.0mm, and the focal length of the inner circle part is 1.2mm-3.0mm.

3. The welding method according to claim 1, wherein: The speed at which the laser spot moves along the preheating path is 320 mm / s-720 mm / s, and the speed at which the laser spot moves along the welding path is 368 mm / s-552 mm / s.

4. The welding method according to claim 1, wherein: When the laser spot preheats the first material, the power of the outer ring portion is 1.3kw-1.5kw, and the power of the inner circle portion is 0.9kw-1.1kw.

5. The welding method according to claim 1, wherein: When the laser spot welds the first material and the second material, the power of the outer ring part is 1.4kw-1.6kw, and the power of the inner circle part is 1.1kw-1.3kw.

6. The welding method according to claim 1, characterized in that The first material is copper, and the second material is aluminum.

7. The welding method according to claim 1, wherein: The welding path extends along the welding seam, the welding seam, the welding path and the preheating path are all annular, and the welding seam, the welding path and the preheating path are coaxial.

8. The welding method according to claim 7, characterized in that: When the laser spot moves along the welding path, the axis of the inner circular portion keeps intersecting with the welding seam.

9. The welding method according to claim 7, characterized in that: The diameter of the preheating path is 7.7 mm, and the diameter of the welding path is 8.7 mm.

10. A battery, characterized in that: The invention comprises an electrode and a shell, wherein the electrode is made of the first material according to any one of claims 1 to 9, the shell is made of the second material according to any one of claims 1 to 9, and the electrode is welded to the shell by the welding method according to any one of claims 1 to 9.

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