Welding method and battery

Abstract

The application discloses a welding method and a battery, wherein the welding method is used for welding a side shell and a cover plate of a battery shell, and the welding method comprises the following steps: dividing a welding path of the side shell and the cover plate into at least a start section track and an end section track; controlling a laser to perform welding in the start section track at a start section welding power and a start section welding speed; and controlling the laser to perform welding in the end section track at an end section welding power and an end section welding speed; wherein the end section welding power is less than the start section welding power, and the end section welding speed is less than the start section welding speed. By dividing the welding path of the side shell and the cover plate into at least the start section track and the end section track, and by making the end section welding power less than the start section welding power, heat concentration can be avoided, and thermal deformation of the side shell can be reduced. Meanwhile, by making the end section welding speed less than the start section welding speed, the welding speed and the welding power of the two section tracks are matched, sufficient welding penetration is obtained, the welding quality is ensured, and the welding yield is improved.

Description

TECHNICAL FIELD

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

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

[0003] In the related art, the cover plate and the side shell are welded by laser welding. However, due to the thin thickness of the side shell, the heat generated during the welding process is easy to cause the side shell to deform, thereby affecting the welding yield. SUMMARY

[0004] Therefore, the present application provides a welding method and a battery, aiming to improve the problem that the side shell is easy to deform in 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 shell, and the welding method comprises the following steps:

[0006] dividing a welding path of the side shell and the cover plate into at least a start section track and an end section track;

[0007] controlling a laser to weld in the start section track at a start section welding power and a start section welding speed;

[0008] controlling the laser to weld in the end section track at an end section welding power and an end section welding speed;

[0009] wherein the end section welding power is less than the start section welding power, and the end section welding speed is less than the start section welding speed.

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

[0011] wherein the inner ring power of the inner ring light spot is less than the outer ring power of the outer ring light spot.

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

[0013] the end section welding power includes an end section inner ring power and an end section outer ring power;

[0014] wherein the end section inner ring power is less than the start section inner ring power, and the end section outer ring power is less than the start section outer ring power.

[0015] Optionally, in some embodiments of the present application, the cover plate is configured as a square, and the cover plate comprises two oppositely arranged first sides and two oppositely arranged second sides;

[0016] Wherein, the welding path extends from one of the first sides to be welded to an adjacent one of the second sides 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, the intersection of the first side to be welded and the adjacent second side 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 a start segment trajectory and an end segment trajectory, comprising:

[0019] The starting point of the start segment trajectory is arranged at one end of the first side to be welded away from the welding inflection point;

[0020] The end point of the end segment trajectory is arranged at one 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 a start segment trajectory and an end segment trajectory, comprising:

[0022] The welding path is divided into a continuous start segment trajectory, a middle segment trajectory, and an end segment trajectory;

[0023] The welding method further comprises:

[0024] Controlling the laser to weld in the middle segment trajectory at a middle segment welding power and a middle segment welding speed.

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

[0026] The start segment welding power comprises a start segment inner ring power and a start segment outer ring power;

[0027] The middle segment welding power comprises a middle segment inner ring power and a middle segment outer ring power;

[0028] The end segment welding power comprises an end segment inner ring power and an end segment outer ring power;

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

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

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

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

[0033] The middle segment inner ring power ranges from 500-700W, the middle segment outer ring power ranges from 1100-1300W, and the middle segment welding speed ranges from 160-170mm / s; and / or

[0034] The final segment inner ring power ranges from 300-500W, the final segment outer ring power ranges from 900-1100W, and the final segment welding speed ranges from 150-160mm / s.

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

[0036] controlling the battery shell to adjust to a first preset posture so that at least part of the middle segment trajectory is located in the welding area of the laser;

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

[0038] controlling the battery shell to adjust to a second preset posture so that at least part of the final segment trajectory is located in the welding area of the laser.

[0039] In a second aspect, embodiments of the present application also provide a battery comprising a battery shell; the battery shell is welded by the welding method as described above.

[0040] The beneficial effects of embodiments of the present application are:

[0041] In embodiments of the present application, by dividing the welding path of the side shell and the cover plate into at least an initial segment trajectory and a final segment trajectory, and making the final segment welding power less than the initial segment welding power, heat concentration can be avoided, and thermal deformation of the side shell can be reduced. At the same time, by making the final segment welding speed less than the initial segment welding speed, the welding speed and welding power of the two segment trajectories are matched, sufficient welding penetration is obtained, and welding quality is guaranteed, thereby improving the welding yield. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments description will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0043] Figure 1 is a main step flow chart of a welding method provided by the embodiments of the present application;

[0044] Figure 2 is Figure 1 is a structure schematic diagram of a cover plate provided by the embodiments of the present application;

[0045] Figure 3 is a specific flow chart of a welding method provided by the embodiments of the present application;

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

[0047] Figure 5 is a welding product diagram of a welding product obtained by using a welding method provided by the embodiments of the present application.

[0048] Reference signs:

[0049] 110, cover plate;

[0050] 111, first side edge; 112, second side edge; 113, round corner. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application. In addition, it should be understood that the specific embodiments described herein are only for the purpose of illustration and explanation of the present application, and are not intended to limit the present application.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0053] In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower positions of the device in the actual use or working state, and specifically refer to the directions of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish an order.

[0054] In the present application, the association relationship of the associated objects is described by "and / or", which means that there can be three kinds of relationships, for example, A and / or B can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.

[0055] In the present application, "at least one" means one or more, and "multiple" means two or more. "One or more", "at least one of the following" or the like means any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0056] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has 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, regardless of the range. In addition, whenever a numerical range is indicated in this document, it means that any quoted number (fraction or integer) within the indicated range is included.

[0057] In the battery production process, the welding of the side shell (not shown) of the battery shell (not shown) and the cover plate 110 is involved. The material of the side shell is aluminum or aluminum alloy, so that the battery shell is lighter. However, the heat generated during the welding process easily causes the side shell to deform, affecting the flatness of the battery, resulting in a low welding yield and causing liquid leakage. Moreover, the deformation of the side shell increases the difficulty of welding. In order to improve the thermal deformation during welding, the prior art generally selects to increase the thickness of the side shell. Under the same outer size, 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 embodiments of the present application provide a welding method, referring to Figure 1 , comprising the following main steps:

[0059] S110: dividing the welding path of the side shell and the cover plate 110 into at least a start segment trajectory and an end segment trajectory.

[0060] Specifically, the welding path includes part or all of the weld between the side shell and the cover plate 110.

[0061] S120: controlling the laser to weld in the start segment trajectory at a start segment welding power and a start segment welding speed.

[0062] S130: controlling the laser to weld in the end segment trajectory at an end segment welding power and an end segment welding speed.

[0063] Wherein, the end segment welding power is less than the start segment welding power, and the end segment welding speed is less than the start segment welding speed.

[0064] It can be understood that the laser can emit a single beam or multiple beams, for example, when the laser is configured to emit a single beam, the power of the single beam for welding in the end segment trajectory is less than that for welding in the start segment trajectory.

[0065] When the laser is configured to emit double beams, the average power of the double beams for welding in the end segment trajectory is less than that for welding in the start segment trajectory; or the power of each beam for welding in the end segment trajectory is less than that for welding in the start segment trajectory.

[0066] With the above technical solution, by dividing the welding path of the side shell and the cover plate 110 into at least a start segment trajectory and an end segment trajectory, and making the end segment welding power less than the start segment welding power, heat concentration can be avoided, and thermal deformation of the side shell can be reduced, at the same time, making the end segment welding speed less than the start segment welding speed, the welding speed of the two segment trajectories is matched with the welding power, sufficient welding penetration is obtained, and welding quality is guaranteed, so as to improve the welding yield and avoid battery leakage. Moreover, the reduction of thermal deformation during the welding process can reduce the welding difficulty.

[0067] At the same time, by using the welding method of the present application, the thickness of the side shell does not need to be increased, the side shell has a large internal space, and the energy density is improved.

[0068] In some embodiments, the laser output by the laser includes an inner ring light spot and an outer ring light spot, and the inner ring power of the inner ring light spot is less than the outer ring power of the outer ring light spot. With such a laser form, the welding depth can be accurately controlled, and the welding quality is improved.

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

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

[0071] The final-stage inner ring power is less than the initial-stage inner ring power, and the final-stage outer ring power is less than the initial-stage outer ring power.

[0072] With such a scheme, by reasonably controlling the final-stage inner ring power to be less than the initial-stage inner ring power and the final-stage outer ring power to be less than the initial-stage outer ring power, the accumulation of heat during the final-stage track welding is reduced, and the generation of deformation is avoided, thereby improving the welding yield.

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

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

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

[0076] With such a scheme, the welding path is arranged to extend from the longer first side edge 111 to the shorter second side edge 112, so that at least part of the first side edge 111 and at least part of the second side edge 112 are welded in one welding path, thereby improving the welding efficiency. Moreover, since the length of the second side edge 112 is smaller, the area of the side edge of the side shell connected to the second side edge 112 is smaller, and the deformation amount of the side edge of the side shell is smaller under the absorption of the same amount of heat. The end point of the final-stage track is arranged on the second side edge 112 to be welded, so that the heat generated by the entire welding path is mainly concentrated in the vicinity of the second side edge 112, thereby reducing the thermal deformation of the side shell.

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

[0078] Exemplarily, with reference to Figure 2The first welding path has A point as the path starting point and D point as the path ending point. The second welding path has D point as the path starting point and A point as the path ending point. The first welding path and the second welding path are connected in series to form a whole-circle welding on the cover plate 110 and the side shell.

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

[0080] The step S110 includes the following specific steps.

[0081] S111: The starting point of the initial segment is set at one end of the first side edge 111 to be welded away from the welding inflection point M.

[0082] S112: The ending point of the final segment is set at one end of the second side edge 112 to be welded away from the welding inflection point M.

[0083] Exemplarily, referring to Figure 2 The starting point of the initial segment is A point, and the ending point is B point. The starting point of the final segment is C point, and the ending point is D point.

[0084] B point and C point can be different points on the first side edge 111 to be welded, and at least one welding track is arranged between the initial segment and the final segment. Alternatively, B point and C point can be the same point on the first side edge 111 to be welded, and the welding path is composed of the initial segment and the final segment.

[0085] By adopting such a scheme, the welding path of the present application contains the adjacent first side edge 111 and the second side edge 112, thereby avoiding heat concentration at the first side edge 111 to cause thermal deformation while improving the welding efficiency.

[0086] As a specific scheme, referring to Figure 2 A round corner 113 is formed between the adjacent first side edge 111 and the second side edge 112. Specifically, the starting point A of the initial segment can be adjacent to the first side edge 111 and can be a near-end point, a middle point or a far-end point of the round corner 113 away from the welding inflection point M. The near-end point is the intersection of the round corner 113 and the first side edge 111, the far-end point is the point of the round corner 113 away from the first side edge 111, and the middle point is the bisecting point of the round corner 113.

[0087] Similarly, the ending point D of the final segment can be adjacent to the second side edge 112 and can be a near-end point, a middle point or a far-end point of the round corner 113 away from the welding inflection point M.

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

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

[0090] Exemplarily, referring to Figure 2 , the initial point of the initial segment trajectory is point A, and the terminal point is point B; the initial point of the middle segment trajectory is point B, and the terminal point is point C; the initial point of the final segment trajectory is point C, and the terminal point is point D.

[0091] The welding method further comprises:

[0092] controlling the laser to weld in the middle segment trajectory at a middle segment welding power and a middle segment welding speed.

[0093] With such a scheme, the welding path is divided into a continuous initial segment trajectory, a middle segment trajectory, and a final segment trajectory, and the welding power and welding speed of each segment trajectory are reasonably controlled, which can effectively control heat concentration, reduce thermal deformation of the side shell, and improve the welding yield.

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

[0095] St101: dividing the welding path into a continuous initial segment trajectory, a middle segment trajectory, and a final segment trajectory.

[0096] St102: controlling the laser to weld in the initial segment trajectory at an initial segment welding power and an initial segment welding speed.

[0097] St103: controlling the laser to weld in the middle segment trajectory at a middle segment welding power and a middle segment welding speed.

[0098] St104: controlling the laser to weld in the final segment trajectory at a final segment welding power and a final segment welding speed.

[0099] As an optional scheme, the welding power of the laser in each segment trajectory is equal, and the welding speed is equal, which facilitates welding control.

[0100] As another optional scheme, in at least one segment trajectory, both the welding power and the welding speed of the laser gradually decrease, further reducing heat concentration.

[0101] In some embodiments, the initial segment welding power comprises an initial segment inner ring power and an initial segment outer ring power; the middle segment welding power comprises a middle segment inner ring power and a middle segment outer ring power; and the final segment welding power comprises a final segment inner ring power and a final segment outer ring power.

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

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

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

[0105] With such a scheme, by reasonably controlling the welding power and welding speed of the initial-stage trajectory, the middle-stage trajectory and the final-stage trajectory, by adjusting the welding speed, the temperature rise in the welding process is effectively reduced, and by reducing the welding power of the middle-stage trajectory and the final-stage trajectory, heat concentration is avoided, thermal deformation is greatly reduced, welding yield is improved, and battery leakage is avoided.

[0106] As a preferred scheme, the ratio of the initial-stage inner ring power, the middle-stage inner ring power and the final-stage inner ring power is set as 8:6:5.

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

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

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

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

[0111] The final-stage inner ring power has a value range of 300-500W, the final-stage outer ring power has a value range of 900-1100W, and the final-stage welding speed has a value range of 150-160mm / s.

[0112] With such a welding parameter range,

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

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

[0115] The end segment inner ring power has a value range including 500W, the end segment outer ring power has a value range including 1000W, and the end segment welding speed has a value range including 155mm / s.

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

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

[0118] In some embodiments, after the welding of the initial segment trajectory is performed and before the welding of the middle segment trajectory is performed, the laser is controlled to receive light for a first preset time. In this way, a part of the heat accumulated on the side shell can be dissipated, effectively avoiding heat concentration.

[0119] Specifically, the first preset time has a value range including 30-60 seconds.

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

[0121] Specifically, the second preset time has a value range including 30-60 seconds.

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

[0123] The battery shell is controlled to be adjusted to a first preset posture so that at least a part of the middle segment trajectory is located in the welding area of the laser.

[0124] That is, after the welding of the initial segment trajectory is performed and before the welding of the middle segment trajectory is performed, the battery shell needs to be adjusted to the first preset posture so that at least a part of the middle segment trajectory is located in the welding area of the laser.

[0125] In a specific embodiment of the present application, within the first preset time during which the laser receives light, the battery shell is controlled to be adjusted to the first preset posture, and the first preset time is reused for heat dissipation and posture adjustment, thereby avoiding heat concentration and improving welding efficiency.

[0126] Correspondingly, the welding method further comprises:

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

[0128] That is, after the welding of the middle section trajectory is performed, and before the welding of the end section trajectory is performed, the battery shell needs to be adjusted to the second preset posture, so that at least part of the end section trajectory is located in the welding area of the laser.

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

[0130] Figure 4 A welding product diagram using a continuous welding on the first side edge 111 is shown, Figure 5 A welding product diagram welded by the welding method of the present application is shown.

[0131] Comparison Figure 4 and Figure 5 It can be seen that, Figure 4 the side shell in the prior art has obvious deformation, while Figure 5 the side shell shown in the present application has relatively good flatness, so that the welding method of the present application can effectively avoid thermal deformation of the battery shell during welding.

[0132] In a second aspect, the embodiments of the present application provide a battery, which comprises a battery shell; the battery shell is welded by the welding method as above. The battery has all the beneficial effects of the welding method as above, which will not be described herein again.

[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 described in detail above, and the principles and embodiments of the present application are described by applying specific examples in this paper; the above embodiment descriptions are only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific embodiments and application range will be changed; in view of the above, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A welding method for welding a side shell and a cover plate of a battery case, the welding method comprising: dividing a welding path of the side shell and the cover plate into at least a start section and an end section; controlling a laser to weld in the start section at a start section welding power and a start section welding speed; controlling the laser to weld in the end section at an end section welding power and an end section welding speed; wherein the end section welding power is less than the start section welding power, and the end section welding speed is less than the start section welding speed; wherein the laser outputs laser light comprising an inner ring light spot and an outer ring light spot; wherein an inner ring power of the inner ring light spot is less than an outer ring power of the outer ring light spot; wherein the cover plate is square-shaped, and comprises two first sides and two second sides; the welding path extends from one of the first sides to be welded to one of the second sides to be welded adjacently; wherein an intersection of the first side to be welded and the second side to be welded adjacently is defined as a welding inflection point; wherein the dividing the welding path into at least the start section and the end section comprises: setting a start point of the start section at an end of the first side to be welded away from the welding inflection point; and setting an end point of the end section at an end of the second side to be welded away from the welding inflection point; wherein the start section welding power comprises a start section inner ring power and a start section outer ring power; wherein the end section welding power comprises an end section inner ring power and an end section outer ring power; wherein the end section inner ring power is less than the start section inner ring power, and the end section outer ring power is less than the start section outer ring power; wherein a length of the first side is greater than a length of the second side; wherein the dividing the welding path into at least the start section and the end section comprises: dividing the welding path into a continuous start section, a middle section, and an end section; wherein the welding method further comprises: controlling the laser to weld in the middle section at a middle section welding power and a middle section welding speed. 2.The welding method of claim 1, wherein the start section welding power comprises a start section inner ring power and a start section outer ring power; the middle section welding power comprises a middle section inner ring power and a middle section outer ring power; the end section welding power comprises an end section inner ring power and an end section outer ring power; the ratio of the start section inner ring power, the middle section inner ring power, and the end section inner ring power is set to (7-9):(5-7):(3-5); and / or the ratio of the start section outer ring power, the middle section outer ring power, and the end section outer ring power is set to (13-15):(11-13):(9-11); and / or the ratio of the start section welding speed, the middle section welding speed, and the end section welding speed is set to (17-18):(16-17):(15-16). 3.The welding method of claim 1 or 2, wherein the start section inner ring power is in a range of 700-900W, the start section outer ring power is in a range of 1300-1500W, and the start section welding speed is in a range of 170-180mm / s. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The welding method according to claim 1, characterized in that, ​ ​ ​ 3. The welding method of claim 1, wherein, ​ 4. The welding method according to any one of claims 1 to 3, characterized in that, ​ ​ ​ ​ 5. The welding method of claim 4, wherein, ​ ​ ​ ​ ​ ​ ​ 6. The welding method of claim 5, wherein, ​ The middle section inner ring power value range includes 500-700W, the middle section outer ring power value range includes 1100-1300W, and the middle section welding speed value range includes 160-170mm / s; and / or The end section inner ring power value range includes 300-500W, the end section outer ring power value range includes 900-1100W, and the end section welding speed value range includes 150-160mm / s.

7. The welding method of claim 4, wherein, The welding method further includes: controlling the battery shell to adjust to a first preset posture, so that at least part of the middle section trajectory is located in the welding area of the laser; and / or, the welding method further includes: controlling the battery shell to adjust to a second preset posture, so that at least part of the end section trajectory is located in the welding area of the laser.

Images