Welding method and battery

Abstract

The invention discloses a welding method and a battery, the welding method is used for welding a side shell and a cover plate of a battery shell, and the welding method comprises the steps that a welding path of the side shell and the cover plate is at least divided into a starting section track and a tail section track; the laser is controlled to conduct welding in the starting section track at the starting section welding power and the starting section welding speed; the laser is controlled to conduct welding in the tail-section track at the tail-section welding power and the tail-section welding speed; wherein the tail-section welding power is smaller than the initial-section welding power, and the tail-section welding speed is smaller than the initial-section welding speed. The welding path of the side shell and the cover plate is at least divided into the starting section track and the tail section track, the tail section welding power is smaller than the starting section welding power, heat concentration can be avoided, thermal deformation of the side shell is reduced, meanwhile, the tail section welding speed is smaller than the starting section welding speed, the welding speed of the two sections of tracks is matched with the welding power, and the welding efficiency is improved. Enough welding penetration is obtained, and the welding quality is ensured, so that the welding yield is improved.

Description

Technical Field

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

[0002] In the battery production process, the battery shell needs to be welded and formed, wherein the battery shell includes a side shell for accommodating the battery cell and a cover plate covering the end of the side shell.

[0003] In the related art, the cover plate and the side shell are welded by laser. However, due to the thin thickness of the side shell, the heat generated during the welding process can easily cause the side shell to deform, thus affecting the welding yield. Summary of the invention

[0004] In view of this, the present application provides a welding method and a battery, aiming to improve the problem that the side shell is easily deformed during the existing welding process.

[0005] In a first aspect, an embodiment of the present application provides a welding method for welding a side shell and a cover plate of a battery housing, the welding method comprising:

[0006] Divide the welding path of the side shell and the cover plate into at least an initial track and an end track;

[0007] Controlling the laser to perform welding within the initial segment trajectory at an initial segment welding power and an initial segment welding speed;

[0008] Controlling the laser to perform welding within the final track at a final welding power and a final welding speed;

[0009] The welding power of the final section is smaller than the welding power of the initial section, and the welding speed of the final section is smaller than the welding speed of the initial section.

[0010] Optionally, in some embodiments of the present application, the laser output by the laser includes an inner ring spot and an outer ring spot;

[0011] Among them, the inner ring power of the inner ring light spot is smaller than the outer ring power of the outer ring light spot.

[0012] Optionally, in some embodiments of the present application, the initial welding power includes an initial inner ring power and an initial outer ring power;

[0013] The terminal welding power includes the terminal inner ring power and the terminal outer ring power;

[0014] The power of the inner ring at the end section is smaller than the power of the inner ring at the beginning section, and the power of the outer ring at the end section is smaller than the power of the outer ring at the beginning section.

[0015] Optionally, in some embodiments of the present application, the cover plate is configured as a square, and the cover plate includes two first sides disposed opposite to each other and two second sides disposed opposite to each other;

[0016] The welding path extends from one of the first sides to be welded to an adjacent second side to be welded, and the length of the first side is greater than the length of the second side.

[0017] Optionally, in some embodiments of the present application, an intersection of a first side edge to be welded and an adjacent second side edge to be welded is defined as a welding inflection point;

[0018] Wherein, the welding path of the side shell and the cover plate is divided into at least an initial track and an end track, including:

[0019] Setting the starting point of the initial track at an end of the first side to be welded away from the welding inflection point;

[0020] The end point of the last track is set at an end of the second side to be welded away from the welding inflection point.

[0021] Optionally, in some embodiments of the present application, the welding path of the side shell and the cover plate is divided into at least an initial track and an end track, including:

[0022] Dividing the welding path into a continuous initial track, a middle track and an end track;

[0023] The welding method further comprises:

[0024] The laser is controlled to perform welding within the middle track at a middle welding power and a middle welding speed.

[0025] Optionally, in some embodiments of the present application, the laser output by the laser includes an inner ring spot and an outer ring spot;

[0026] The initial welding power includes the initial inner ring power and the initial outer ring power;

[0027] The middle section welding power includes the middle section inner ring power and the middle section outer ring power;

[0028] The terminal welding power includes the terminal inner ring power and the terminal outer ring power;

[0029] The ratio of the initial inner ring power, the middle inner ring power and the final inner ring power is set to (7-9): (5-7): (3-5); and / or

[0030] The ratio of the initial outer ring power, the middle outer ring power and the final outer ring power is set to (13-15): (11-13): (9-11); and / or

[0031] The ratio of the initial welding speed, the middle welding speed and the final welding speed is set to (17-18): (16-17): (15-16).

[0032] In some embodiments, the value range of the initial inner ring power includes 700-900W, the value range of the initial outer ring power includes 1300-1500W, and the value range of the initial welding speed includes 170-180mm / s; and / or

[0033] The power of the middle section inner ring is in the range of 500-700W, the power of the middle section outer ring is in the range of 1100-1300W, and the welding speed of the middle section is in the range of 160-170mm / s; and / or

[0034] The value range of the power of the inner ring of the final section includes 300-500W, the value range of the power of the outer ring of the final section includes 900-1100W, and the value range of the welding speed of the final section includes 150-160mm / s.

[0035] Optionally, in some embodiments of the present application, the welding method further includes:

[0036] Controlling the battery housing to adjust to a first preset posture so that at least a portion of the middle track is located in a welding area of ​​the laser;

[0037] And / or, the welding method further comprises:

[0038] The battery housing is controlled to be adjusted to a second preset posture so that at least a portion of the final trajectory is located in a welding area of ​​the laser.

[0039] In a second aspect, an embodiment of the present application further provides a battery, comprising a battery casing; the battery casing is welded using the welding method as described above.

[0040] Beneficial effects of the embodiments of the present application:

[0041] In an embodiment of the present application, by dividing the welding path of the side shell and the cover plate into at least an initial trajectory and an end trajectory, and making the welding power of the end segment smaller than the welding power of the initial segment, heat concentration can be avoided and thermal deformation of the side shell can be reduced. At the same time, the welding speed of the end segment is smaller than the welding speed of the initial segment, so that the welding speeds of the two segments of the trajectory are matched with the welding power, sufficient welding penetration is obtained, the welding quality is guaranteed, and the welding yield is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 It is a flow chart of the main steps of a welding method provided in an embodiment of the present application;

[0044] Figure 2 yes Figure 1 The structural schematic diagram of the cover plate provided in the embodiment of the present application is shown;

[0045] Figure 3 is a specific flow chart of a welding method provided in an embodiment of the present application;

[0046] Figure 4 It is a welding product diagram using a continuous welding in the prior art;

[0047] Figure 5 This is a picture of a welding product obtained by welding using a welding method provided in an embodiment of the present application.

[0048] Reference numerals:

[0049] 110. Cover plate;

[0050] 111. First side edge; 112. Second side edge; 113. Rounded corner. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0053] In this application, unless otherwise stated, directional words such as "upper" and "lower" generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. In addition, in the description of this application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose numerical requirements or establish an order.

[0054] In this application, "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0055] In the present application, "at least one" means one or more, and "plurality" means two or more. "One or more", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0056] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0057] In the battery production process, the side shell (not shown) and the cover plate 110 of the battery shell (not shown) are welded. The side shell is made of aluminum or aluminum alloy to make the battery shell lighter. However, the heat generated during the welding process can easily cause the side shell to deform, affecting the flatness of the battery. The welding yield is low and leakage occurs. In addition, the deformation of the side shell increases the difficulty of welding. In order to improve the thermal deformation during welding, the prior art generally chooses to increase the thickness of the side shell. Under the same outer dimensions, the internal space of the side shell is reduced, resulting in a decrease in the energy density of the battery.

[0058] In a first aspect, the present application provides a welding method, referring to Figure 1 , including the following main steps:

[0059] S110: Divide the welding path of the side shell and the cover plate 110 into at least an initial track and an end track.

[0060] Specifically, the welding path includes a portion or the entirety of the weld between the side housing and the cover plate 110 .

[0061] S120: Control the laser to perform welding within the initial segment trajectory at the initial segment welding power and initial segment welding speed.

[0062] S130: Control the laser to perform welding within the final track at the final welding power and final welding speed.

[0063] Among them, the welding power of the last section is less than that of the first section, and the welding speed of the last section is less than that of the first section.

[0064] It is understandable that the laser can emit a single laser beam or multiple laser beams. For example, when the laser is configured to emit a single laser beam, the welding power of the single laser beam in the final track is less than the welding power in the initial track.

[0065] When the laser is configured to emit dual-beam lasers, the average power of the dual-beam lasers in welding in the final trajectory is less than the average power in welding in the initial trajectory; or, the power of each laser beam in welding in the final trajectory is less than the power in welding in the initial trajectory.

[0066] By adopting the above technical solution, the welding path of the side shell and the cover plate 110 is divided into at least the initial track and the final track, and the welding power of the final track is made smaller than the welding power of the initial track, so as to avoid heat concentration and reduce the thermal deformation of the side shell. At the same time, the welding speed of the final track is made smaller than the welding speed of the initial track, so that the welding speed of the two tracks matches the welding power, and sufficient welding penetration is obtained to ensure welding quality, thereby improving welding yield and avoiding battery leakage. In addition, the reduction of thermal deformation during welding can reduce the difficulty of welding.

[0067] At the same time, by adopting the welding method of the present application, there is no need to increase the thickness of the side shell, thereby ensuring that the side shell has a larger internal space, thereby improving the energy density.

[0068] In some embodiments, the laser output by the laser includes an inner ring spot and an outer ring spot, and the inner ring power of the inner ring spot is less than the outer ring power of the outer ring spot. Using such a laser form can achieve precise control of welding depth and improve welding quality.

[0069] Specifically, the inner ring spot acts on the joint between the cover plate 110 and the side shell to generate a keyhole to obtain welding penetration; while the outer ring spot provides energy during the welding process to increase the weld width, and can preheat and extend the keyhole closing time, which is beneficial to the escape of molten pool gas, thereby reducing the weld porosity.

[0070] In some embodiments, the initial welding power includes the initial inner ring power and the initial outer ring power; the final welding power includes the final inner ring power and the final outer ring power.

[0071] Among them, the power of the inner ring at the end section is less than the power of the inner ring at the beginning section, and the power of the outer ring at the end section is less than the power of the outer ring at the beginning section.

[0072] By adopting such a scheme, the power of the inner ring of the last section is reasonably controlled to be smaller than that of the inner ring of the first section, and the power of the outer ring of the last section is smaller than that of the outer ring of the first section, so as to reduce the accumulation of heat during the welding of the last section track, avoid the occurrence of deformation, and improve the welding yield.

[0073] In some embodiments, the cover plate 110 is configured in a square shape, and includes two oppositely disposed first side edges 111 and two oppositely disposed second side edges 112 .

[0074] The welding path extends from one of the first sides 111 to be welded to an adjacent second side 112 to be welded, and the length of the first side 111 is greater than the length of the second side 112 .

[0075] It can be understood that one of the initial track and the final track extends from the first side 111 to be welded to the adjacent second side 112 to be welded, and the end point of the final track is located at the second side 112 to be welded.

[0076] By adopting such a solution, the welding path is set to extend from the longer first side 111 to the shorter second side 112, and at least part of a first side 111 and at least part of a second side 112 are welded in one welding path, thereby improving welding efficiency. In addition, since the length of the second side 112 is relatively small, the area of ​​one side of the side shell to which it is connected is relatively small, and the deformation amount of the side of the side shell is relatively small when the same amount of heat is absorbed; the end point of the last segment of the track is set at the second side 112 to be welded, so that the heat generated by the entire welding path is mainly concentrated in the vicinity of the second side 112, thereby reducing the thermal deformation of the side shell.

[0077] As an optional solution, the welding between the cover plate 110 and the side housing includes at least two welding paths.

[0078] For example, refer to Figure 2The first welding path starts at point A and ends at point D. The second welding path starts at point D and ends at point A. By connecting the first welding path and the second welding path end to end, a full circle welding is formed between the cover plate 110 and the side shell.

[0079] In some embodiments, the intersection of the first side 111 to be welded and the adjacent second side 112 to be welded is defined as a welding inflection point M.

[0080] Wherein, step S110 includes the following specific steps:

[0081] S111: setting the starting point of the initial track at an end of the first side edge 111 to be welded away from the welding inflection point.

[0082] S112: setting the end point of the last track at an end of the second side edge 112 to be welded away from the welding inflection point.

[0083] For example, refer to Figure 2 The starting point of the initial trajectory is point A and the end point is point B; the starting point of the final trajectory is point C and the end point is point D.

[0084] Point B and point C may be different points on the first side 111 to be welded, and at least one welding track is provided between the initial track and the final track. Alternatively, point B and point C may be the same point on the first side 111 to be welded, and at this time, the welding path is composed of the initial track and the final track.

[0085] By adopting such a solution, the welding path of the present application includes the adjacent first side edge 111 and the second side edge 112 , thereby avoiding heat concentration at the first side edge 111 that causes thermal deformation and improving welding efficiency.

[0086] As a specific plan, refer to Figure 2 , a fillet 113 is formed between the adjacent first side 111 and the second side 112. Specifically, the starting point A of the initial segment trajectory may be a proximal end point, a midpoint, or a distal end point of the fillet 113 adjacent to the first side 111 and far away from the welding inflection point M, wherein the proximal end point is the intersection point of the fillet 113 and the first side 111, the distal end point is the point where the fillet 113 is far away from the first side 111, and the midpoint is the point where the fillet 113 is equally divided.

[0087] Similarly, the end point D of the last track may be a proximal end point, a midpoint, or a distal end point of the fillet 113 adjacent to the second side 112 and away from the welding inflection point M.

[0088] In some embodiments, step S110 includes the following specific steps:

[0089] The welding path is divided into a continuous initial trajectory, a middle trajectory and an end trajectory.

[0090] For example, refer to Figure 2 The starting point of the initial trajectory is point A and the end point is point B; the starting point of the middle trajectory is point B and the end point is point C; the starting point of the final trajectory is point C and the end point is point D.

[0091] Welding methods also include:

[0092] The laser is controlled to perform welding within the middle track at the middle welding power and the middle welding speed.

[0093] By adopting this solution, the welding path is divided into a continuous initial trajectory, a middle trajectory and an end trajectory, and the welding power and welding speed of each trajectory are reasonably controlled, which can effectively control heat concentration, reduce thermal deformation of the side shell, and improve welding yield.

[0094] In a specific embodiment of the present application, refer to Figure 3 , the welding method includes the following specific steps:

[0095] St101: The welding path is divided into a continuous initial trajectory, a middle trajectory and an end trajectory.

[0096] St102: Control the laser to weld within the initial segment trajectory at the initial segment welding power and initial segment welding speed.

[0097] St103: Control the laser to weld in the middle track at the middle welding power and middle welding speed.

[0098] St104: Control the laser to weld within the final trajectory at the final welding power and final welding speed.

[0099] As an optional solution, the laser has equal welding power and equal welding speed in each trajectory to facilitate welding control.

[0100] As another optional solution, the welding power and welding speed of the laser are gradually reduced within at least one section of the trajectory to further reduce heat concentration.

[0101] In some embodiments, the initial welding power includes the initial inner ring power and the initial outer ring power; the middle welding power includes the middle inner ring power and the middle outer ring power; and the final welding power includes the final inner ring power and the final outer ring power.

[0102] Specifically, the ratio of the inner ring power at the beginning, the inner ring power at the middle, and the inner ring power at the end is set to (7-9): (5-7): (3-5).

[0103] The ratio of the initial outer ring power, the middle outer ring power and the final outer ring power is set to (13-15): (11-13): (9-11).

[0104] The ratio of the initial welding speed, the middle welding speed and the final welding speed is set to (17-18): (16-17): (15-16).

[0105] By adopting this solution, the welding power and welding speed of the initial trajectory, the middle trajectory and the final trajectory can be reasonably controlled, and the welding speed can be adjusted to effectively reduce the temperature rise during the welding process. By reducing the welding power of the middle trajectory and the final trajectory, heat concentration can be avoided, thermal deformation can be greatly reduced, the welding yield can be improved, and battery cell leakage can be avoided.

[0106] As a preferred solution, the ratio of the inner ring power of the initial section, the inner ring power of the middle section and the inner ring power of the final section is set to 8:6:5.

[0107] The ratio of the initial outer ring power, the middle outer ring power and the final outer ring power is set to 7:6:5.

[0108] The ratio of the initial welding speed, the middle welding speed and the final welding speed is set to 3.5:3.3:3.1.

[0109] In some embodiments, the value range of the initial inner ring power includes 700-900W, the value range of the initial outer ring power includes 1300-1500W, and the value range of the initial welding speed includes 170-180mm / s.

[0110] The power range of the middle section inner ring includes 500-700W, the power range of the middle section outer ring includes 1100-1300W, and the power range of the middle section welding speed includes 160-170mm / s.

[0111] The power of the inner ring of the final stage ranges from 300 to 500 W, the power of the outer ring of the final stage ranges from 900 to 1100 W, and the welding speed of the final stage ranges from 150 to 160 mm / s.

[0112] Using this welding parameter range,

[0113] As a preferred solution, the value range of the initial inner ring power includes 800W, the value range of the initial outer ring power includes 1400W, and the value range of the initial welding speed includes 175mm / s.

[0114] The value range of the middle section inner ring power includes 600W, the value range of the middle section outer ring power includes 1200W, and the value range of the middle section welding speed includes 165mm / s.

[0115] The value range of the power of the inner ring of the final stage includes 500W, the value range of the power of the outer ring of the final stage includes 1000W, and the value range of the welding speed of the final stage includes 155mm / s.

[0116] In some embodiments, the ratio of the lengths of the initial trajectory, the middle trajectory, and the final trajectory is set to (1-3): (1-3): (1-3).

[0117] In a specific embodiment of the present application, the lengths of the initial track, the middle track and the final track are equal. It has been verified through experiments that based on the above welding parameters, when the lengths of the initial track, the middle track and the final track are equal, the welding yield is improved while ensuring the welding speed.

[0118] In some embodiments, after welding the initial track and before welding the middle track, the laser is controlled to collect light for a first preset time, so that the heat accumulated on a part of the side shell can be dissipated, effectively avoiding heat concentration.

[0119] Specifically, the value range of the first preset time includes 30-60 seconds.

[0120] After welding the middle track and before welding the last track, the laser is controlled to collect light for a second preset time. In this way, the heat accumulated on a part of the side shell can be dissipated, effectively avoiding heat concentration.

[0121] Specifically, the value range of the second preset time includes 30-60 seconds.

[0122] In some embodiments, the welding method further comprises:

[0123] The battery housing is controlled to be adjusted to a first preset posture so that at least a portion of the middle track is located in a welding area of ​​the laser.

[0124] That is, after welding the initial track and before welding the middle track, the battery housing needs to be adjusted to a first preset posture so that at least a portion of the middle track is located in the welding area of ​​the laser.

[0125] In a specific embodiment of the present application, within the first preset time of laser light collection, the battery housing is controlled to adjust to a first preset posture, and the first preset time is reused for heat dissipation and posture adjustment to avoid heat concentration while improving welding efficiency.

[0126] Accordingly, the welding method further comprises:

[0127] The battery housing is controlled to be adjusted to a second preset posture so that at least a portion of the last segment of the trajectory is located in a welding area of ​​the laser.

[0128] That is, after welding the middle track and before welding the last track, the battery housing needs to be adjusted to a second preset posture so that at least a portion of the last track is located in the welding area of ​​the laser.

[0129] In a specific embodiment of the present application, within the second preset time of laser light collection, the battery housing is controlled to adjust to a second preset posture, and the second preset time is reused for heat dissipation and posture adjustment to avoid heat concentration while improving welding efficiency.

[0130] Figure 4 The figure shows a welding product in which a continuous welding is applied to the first side 111. Figure 5 A picture of a welded product welded using the welding method of the present application is shown.

[0131] contrast Figure 4 and Figure 5 It can be seen that Figure 4 The side shell in the Figure 5 The flatness of the side shell shown is relatively good, so the welding method of the present application can effectively avoid thermal deformation during the welding process of the battery shell.

[0132] In a second aspect, an embodiment of the present application provides a battery, including a battery housing; the battery housing is welded using the above welding method. The battery has all the beneficial effects achieved by the above welding method, which will not be described in detail in this application.

[0133] In a specific embodiment of the present application, the battery of the present application is a square battery.

[0134] The embodiments of the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A welding method for welding the side shell and cover plate of a battery housing, characterized in that: The welding method comprises: Divide the welding path of the side shell and the cover plate into at least an initial track and an end track; Controlling the laser to perform welding within the initial segment trajectory at an initial segment welding power and an initial segment welding speed; Controlling the laser to perform welding within the final track at a final welding power and a final welding speed; The welding power of the final section is smaller than the welding power of the initial section, and the welding speed of the final section is smaller than the welding speed of the initial section.

2. The welding method according to claim 1, characterized in that: The laser output by the laser includes an inner ring light spot and an outer ring light spot; Among them, the inner ring power of the inner ring light spot is smaller than the outer ring power of the outer ring light spot.

3. The welding method according to claim 2, characterized in that: The initial welding power includes the initial inner ring power and the initial outer ring power; The terminal welding power includes the terminal inner ring power and the terminal outer ring power; The power of the inner ring at the end section is smaller than the power of the inner ring at the beginning section, and the power of the outer ring at the end section is smaller than the power of the outer ring at the beginning section.

4. The welding method according to claim 1, characterized in that: The cover plate is constructed in a square shape, and comprises two first sides arranged opposite to each other and two second sides arranged opposite to each other; The welding path extends from one of the first sides to be welded to an adjacent second side to be welded, and the length of the first side is greater than the length of the second side.

5. The welding method according to claim 4, characterized in that: defining an intersection of a first side edge to be welded and an adjacent second side edge to be welded as a welding inflection point; Wherein, the welding path of the side shell and the cover plate is divided into at least an initial track and an end track, including: Setting the starting point of the initial track at an end of the first side to be welded away from the welding inflection point; The end point of the last track is set at an end of the second side to be welded away from the welding inflection point.

6. The welding method according to any one of claims 1 to 5, characterized in that: The step of dividing the welding path of the side shell and the cover plate into at least an initial track and an end track comprises: Dividing the welding path into a continuous initial track, a middle track and an end track; The welding method further comprises: The laser is controlled to perform welding within the middle track at a middle welding power and a middle welding speed.

7. The welding method according to claim 6, characterized in that: The laser output by the laser includes an inner ring light spot and an outer ring light spot; The initial welding power includes the initial inner ring power and the initial outer ring power; The middle section welding power includes the middle section inner ring power and the middle section outer ring power; The terminal welding power includes the terminal inner ring power and the terminal outer ring power; The ratio of the initial inner ring power, the middle inner ring power and the final inner ring power is set to (7-9): (5-7): (3-5); and / or The ratio of the initial outer ring power, the middle outer ring power and the final outer ring power is set to (13-15): (11-13): (9-11); and / or The ratio of the initial welding speed, the middle welding speed and the final welding speed is set to (17-18): (16-17): (15-16).

8. The welding method according to claim 7, characterized in that: The value range of the initial inner ring power includes 700-900W, the value range of the initial outer ring power includes 1300-1500W, and the value range of the initial welding speed includes 170-180mm / s; and / or The power of the middle section inner ring is in the range of 500-700W, the power of the middle section outer ring is in the range of 1100-1300W, and the welding speed of the middle section is in the range of 160-170mm / s; and / or The value range of the power of the inner ring of the final section includes 300-500W, the value range of the power of the outer ring of the final section includes 900-1100W, and the value range of the welding speed of the final section includes 150-160mm / s.

9. The welding method according to claim 6, characterized in that: The welding method further comprises: Controlling the battery housing to adjust to a first preset posture so that at least a portion of the middle track is located in a welding area of ​​the laser; And / or, the welding method further comprises: The battery housing is controlled to be adjusted to a second preset posture so that at least a portion of the final trajectory is located in a welding area of ​​the laser.

10. A battery, comprising a battery housing; characterized in that: The battery casing is welded using the welding method according to any one of claims 1 to 9.

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