Battery welding methods, batteries, battery packs, and electrical equipment.

Abstract

This disclosure provides a battery welding method, a battery, a battery pack, and an electrical device. The welding method includes the following steps: providing a housing and a cover plate, the housing having a receiving cavity, the receiving cavity having an opening formed on a first surface of the housing, at least a portion of the cover plate extending from the opening into the receiving cavity, a predetermined gap forming between the cover plate extending into the receiving cavity and the housing; laser welding the cover plate and the housing, forming a weld mark at the weld joint, controlling the maximum offset between the laser focus and the predetermined gap along the first direction to be between 0.08 mm and 0.2 mm. This disclosure, by limiting the maximum offset between the laser focus and the predetermined gap, ensures that the molten pool fully fills the predetermined gap, guaranteeing the battery's sealing reliability, while preventing the laser beam from penetrating the predetermined gap and touching the battery cell inside the receiving cavity, reducing the risk of thermal short circuit in the battery cell, and improving the safety of the battery welding process.

Description

Technical Field

[0001] This disclosure relates to the field of battery technology, and in particular to a battery welding method, a battery, a battery pack, and an electrical device. Background Technology

[0002] In related technologies, batteries typically include a casing and a cover plate. The casing has a cavity for accommodating the battery and electrolyte. The cavity forms an opening on the surface of the casing. During assembly, the cover plate partially extends into the cavity through the opening, forming a preset gap between the cover plate and the casing. Laser welding needs to be precisely applied to the vicinity of the preset gap to form a weld mark. Existing battery laser welding methods lack precise control over the laser focus offset, resulting in insufficient weld mark strength or thermal melting damage to the internal battery cells. Summary of the Invention

[0003] The purpose of this disclosure is to provide a welding method for a battery, a battery, a battery pack, and an electrical device to solve the technical problems in the related art. It can improve the structural strength of the weld and avoid damage to the internal battery cells by thermal melting.

[0004] In a first aspect, this disclosure provides a method for welding a battery, comprising the following steps: A housing and a cover are provided. The housing has a receiving cavity, and the receiving cavity has an opening formed on a first surface of the housing. The first surface has a long side extending in a first direction and a short side extending in a second direction. The first direction, the second direction, and the third direction are perpendicular to each other. At least a portion of the cover extends from the opening into the receiving cavity, and a predetermined gap is formed between the cover extending into the receiving cavity and the housing. The cover plate is laser welded to the housing, and a weld mark is formed at the weld joint. The maximum offset between the laser focus and the preset gap along the first direction is controlled to be between 0.08mm and 0.2mm.

[0005] Secondly, this disclosure provides a battery formed by welding using the aforementioned welding method. At the short side of the preset surface, along the third direction upward, the lowest point of the weld is a first reference point, and the lowest point of the weld located within the preset gap is a second reference point. Along the first direction, the minimum distance between the first reference point and the second reference point is N mm, where N ≤ 0.2.

[0006] Thirdly, this disclosure provides a battery pack including the aforementioned battery.

[0007] Fourthly, this disclosure provides an electrical device including the aforementioned battery pack.

[0008] Compared with related technologies, this disclosure limits the maximum offset between the laser focus and the preset gap along the first direction, so that the molten pool can fully fill the preset gap, ensuring the reliability of battery sealing. At the same time, it avoids the laser beam penetrating the preset gap and touching the cell inside the cavity, reducing the risk of thermal melting and short circuit of the cell and improving the safety of the battery welding process. Attached Figure Description

[0009] Figure 1 This is a perspective view of the battery provided in an embodiment of this disclosure.

[0010] Figure 2 This is a perspective view of the battery casing provided in an embodiment of this disclosure.

[0011] Figure 3 yes Figure 1 A top view of the provided battery.

[0012] Figure 4 yes Figure 3 A sectional view along line AA.

[0013] Figure 5 yes Figure 4 A magnified structural diagram of point B, which has one of its annotation forms.

[0014] Figure 6 yes Figure 4 A magnified structural diagram of point B with another labeling format.

[0015] Explanation of reference numerals in the attached figures: 1. Shell; 2. Cover plate; 3. Receiving cavity; 4. Opening; 5. First surface; 51. Long side; 52. Short side; 6. Preset gap; 7. Weld mark; K1, first reference point; K2, second reference point; D1, First Direction; D2, Second Direction; D3, Third Direction. Detailed Implementation

[0016] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure.

[0017] This disclosure provides a battery welding method, including the following steps: A housing 1 and a cover plate 2 are provided. The housing 1 and the cover plate 2 together constitute the outer casing of the battery. In one feasible embodiment, the outer casing of the battery is a cuboid structure. To better illustrate the structure of the battery, this disclosure defines a three-dimensional rectangular coordinate system, defining the direction of the long side 51 of the top surface of the battery as the first direction D1, the direction of the short side 52 of the top surface of the battery as the second direction D2, and the height direction of the battery as the third direction D3. The first direction D1, the second direction D2, and the third direction D3 are perpendicular to each other.

[0018] A receiving cavity 3 is integrally formed within the housing 1. The receiving cavity 3 is used to accommodate the battery cells and electrolyte. The housing 1 has a first surface 5, which has a long side 51 extending along a first direction D1 and a short side 52 extending along a second direction D2. The normal direction of the first surface 5 is the third direction D3. Among the multiple batteries constituting the battery pack, the multiple batteries are arranged in an array along the second direction D2, with the large surfaces of adjacent batteries in contact. The receiving cavity 3 forms an opening 4 on the first surface 5. The opening 4 is a through area of ​​the receiving cavity 3 on the first surface 5. The shape of the opening 4 matches the shape of the cover plate 2. The battery cells and electrolyte and other components are assembled into the receiving cavity 3 through the opening 4.

[0019] At least part of the cover plate 2 extends into the receiving cavity 3 through the opening 4 to form a nested fit. In one feasible embodiment, the cross section of the cover plate 2 along the third direction D3 is a "T" shaped structure or a flat plate structure, and there is a preset gap 6 between the cover plate 2 extending into the receiving cavity 3 and the housing 1.

[0020] The cover plate 2 is laser welded to the housing 1. The cover plate 2 and the housing 1 are connected into an integral structure, and the preset gap 6 between the cover plate 2 and the housing 1 is closed. The welding method can be top welding or side welding, preferably top welding.

[0021] A weld mark 7 is formed at the welding joint. The weld mark 7 is located at the welding interface between the cover plate 2 and the shell 1. The high temperature during welding melts the metal materials of the cover plate 2 and the shell 1, forming a molten pool. The molten pool fills the preset gap 6 between the cover plate 2 and the shell 1 and then solidifies to form the weld mark 7. The weld mark 7 can connect the cover plate 2 and the shell 1 into a whole and disperse the stress generated by the battery under vibration or impact conditions.

[0022] In the embodiments provided in this disclosure, at least at the short side 52 of the first surface 5, the maximum offset between the laser focus and the preset gap 6 along the first direction D1 is controlled to be between 0.08 mm and 0.2 mm. The value can be 0.08 mm, 0.09 mm, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, or 0.2 mm. Specifically, the value can be one of the aforementioned values ​​or any value between 0.08 mm and 0.2 mm. The laser focus is the center point of energy convergence in laser welding. The positioning accuracy of the laser focus determines the forming quality of the molten pool. Therefore, the maximum offset between the laser focus and the preset gap 6 is limited to a preset value range. This ensures that the laser focus is distributed around the preset gap 6, guaranteeing sufficient molten pool formation, thereby improving the structural strength and tear resistance of the weld mark 7. At the same time, it prevents the laser beam from penetrating the preset gap 6 and touching the battery cell inside the receiving cavity 3, reducing the risk of the battery cell thermally melting and short circuit, and improving the safety of the battery welding process.

[0023] If the maximum offset is too small, the laser focus will be too close to the inner boundary of the preset gap 6, or it may be able to directly penetrate the preset gap 6. Due to the high energy density and penetrability of the laser beam, this can lead to thermal melting and short circuit of the battery cell, causing safety hazards such as thermal runaway. At the same time, the concentrated laser energy acting on a local area of ​​the cover plate 2 or the shell 1 can easily cause excessive ablation, damage the structural rigidity of the welded area, and increase the risk of cracking of the weld mark 7.

[0024] If the maximum offset is too large, the laser focus will be too far away from the preset gap 6, and the laser energy will not be able to effectively act on the welding interface between the cover plate 2 and the shell 1. This will result in insufficient melting of the metal material at the welding interface, and the molten pool will not be able to fill the preset gap 6, resulting in defects such as false welding or lack of fusion. Consequently, the effective bearing area of ​​the weld mark 7 will be insufficient, and it will be easy to tear and crack under vibration or impact conditions.

[0025] In the embodiments provided in this disclosure, welding is performed using a ring spot laser or a fiber + semiconductor laser, and the specific process steps include: S01: Battery loading process. This process completes the loading and pairing of batteries. Specifically, the battery is clamped by a battery gripper assembly, which is used to stably hold the battery and prevent damage or displacement of the battery casing 1 or cover plate 2 during loading. The loading is completed by a transport assembly, which is responsible for transferring the battery from the feeding area to the subsequent processing station to achieve automated loading. At the battery scanning station, the QR code on the cover plate 2 is scanned and paired to confirm the battery's identity information and ensure that the subsequent processing steps match the battery specifications and model.

[0026] S02: Battery positioning process. This process provides the positioning basis for laser welding, ensuring the accuracy of the welding position. Using the first surface 5 of the battery as the positioning reference, the battery is clamped in multiple directions, and the relevant gaps and clamping pressures are controlled to avoid excessive gaps affecting welding quality and excessive gaps causing deformation of the casing 1 or cover plate 2. This ensures the positioning fixture adapts to the battery contour, accommodating the positioning needs of batteries of different specifications and improving positioning versatility. Specifically, during battery welding, the first surface 5 of the battery is used as the positioning reference, and the battery is clamped along the first direction D1, the second direction D2, and the third direction D3. This restricts the battery's displacement during processing, ensuring a uniform posture. After clamping, the gap between the casing 1 and the cover plate 2 is ≤0.07mm, the height difference between the upper surface of the positioning fixture and the upper surface of the cover plate 2 is 0.5mm-1.5mm, and the clamping cylinder pressure of the positioning fixture is 0.1MPa-0.5MPa.

[0027] S03: Laser welding process. The laser is aligned with the preset gap 6 and offset towards the side of the cover plate 2 to ensure precise laser energy application to the welding interface, improving welding reliability. Welding is performed around the circumference of the cover plate 2 to achieve a full circumferential seal of the battery. Welding parameters, protective gas, and dust removal air velocity are controlled. The protective gas prevents oxidation in the welding area, and the dust removal air velocity promptly removes fumes generated during welding, preventing them from affecting the quality of the weld mark 7. Specifically, the laser is aligned with the preset gap 6 between the housing 1 and the cover plate 2, offset towards the side of the cover plate 2 by 0.95mm-1.05mm, and welded around the circumference of the cover plate 2. During welding, the welding speed is controlled at 100mm / s-300mm / s, the welding defocusing amount is 0-3mm, the welding power for the outer ring is 800W-2800W, the welding power for the inner ring is 400W-1400W, the protective nitrogen flow rate is 10L / min-50L / min, and the dust removal air velocity is ≥20m / s.

[0028] In this step, the maximum offset between the laser focus and the preset gap 6 along the first direction D1 is controlled to be between 0.08mm and 0.2mm.

[0029] S04: Welding Imprint 7 Appearance Inspection Process. This process inspects the appearance of the welding imprint 7 for defects, promptly removing batteries with substandard welding appearance to prevent them from entering subsequent processes, reducing subsequent processing costs, and ensuring the battery's sealing performance and structural stability. Specifically, the welded batteries are transferred to the appearance inspection station, where a CCD inspection device is used to inspect the appearance of the welding imprint 7. The inspection items include at least one of the following defects: welding imprint 7 burst points, pinholes, dents, broken welds, and misalignment.

[0030] S05: Solder Mark 7 Rolling Process. This process rolls the solder mark to improve its density and structural strength. Rolling parameters and dust removal air velocity are controlled to prevent over-rolling (damage to the solder mark) or under-rolling (failure to achieve optimal results). The dust removal air velocity removes debris generated during rolling, preventing it from affecting the battery's subsequent use. Specifically, batteries that have completed visual inspection are transferred to the solder mark rolling station. Two sets of rolling devices, one vertical and one horizontal, are used to roll the solder mark 7 on the long side 51 and top surface of the battery. Rolling eliminates protrusions and burrs on the surface of the solder mark 7, while also compacting any small voids that may exist inside. The solder mark 7 is rolled to below 0.05mm. During rolling, the dust removal air velocity is controlled to be ≥15m / s, the rolling angle is 2°-8°, and the rolling pressure is 0.1MPa-0.5MPa.

[0031] S06: Insulation testing process. This process tests the battery voltage drop and insulation resistance to ensure battery safety. Specifically, the rolled batteries are transferred to the insulation testing station, where a pulse-type lithium battery short-circuit tester is used to test the battery voltage drop and insulation resistance. The test results determine whether the battery has short circuits or poor insulation.

[0032] S07: Battery unloading process. This process separates qualified and unqualified batteries. Specifically, batteries that have completed insulation testing are transferred to the unloading station and then to the helium testing process for further testing of the battery's sealing performance. If the insulation test fails, the battery is transferred to the buffer position for subsequent unified processing, ensuring the overall quality of the battery products.

[0033] In the embodiments provided in this disclosure, at least at the short side 52 of the first surface 5, the weld mark 7 is controlled to protrude from the surface of the cover plate 2. Along the third direction D3, the maximum distance between the surface of the weld mark 7 furthest from the cover plate 2 and the cover plate 2 is R mm, where 0.01 ≤ R ≤ 0.3. The value can be 0.01, 0.05, 0.1, 0.13, 0.15, 0.17, 0.2, 0.23, 0.25, 0.27 or 0.3, and can specifically be the values ​​listed above, or any value between 0.01 and 0.3. If R is too small, the thickness of the weld mark 7 is insufficient, the effective bearing area of ​​the weld mark 7 is reduced, and it cannot effectively disperse and transmit the tearing stress generated under vibration or impact conditions, resulting in stress concentration of the weld mark 7 on the short side 52, which is prone to cracking. If R is too large, the solder mark 7 will be too thick, the welding time will be too long, resulting in excessive continuous input of welding heat, which will cause deformation of the shell 1 or the cover plate 2 and increase the risk of failure of the solder mark 7 on the short side 52.

[0034] In the embodiments provided in this disclosure, at least at the short side 52 of the first surface 5, along the first direction D1, the maximum distance between the surface of the weld mark 7 on the cover plate 2 furthest from the housing 1 and the preset gap 6 is T mm, where 0 ≤ T ≤ 0.15. The value can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, or 0.15. Specifically, the values ​​listed above can be any value between 0 and 0.15. If T is too small, the thickness of the weld mark 7 will be insufficient, the effective bearing area of ​​the weld mark 7 will decrease, and it will be unable to effectively disperse and transmit the tearing stress generated under vibration or impact conditions, resulting in stress concentration at the short side 52 of the weld mark 7, which is prone to cracking. If T is too large, the welding time will be too long, resulting in excessive continuous input of welding heat, causing deformation of the shell 1 and increasing the risk of failure of the weld mark 7 at the short side 52.

[0035] In the embodiments provided in this disclosure, at least at the short side 52 of the preset surface 5, the maximum cross-sectional area of ​​the solder mark 7 along the first direction D1 is controlled to be S mm. 2 Where 0.6 ≤ S ≤ 1.7. The value can be 0.6, 0.7, 0.8, 0.9, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or 1.7. The value can be one of the values ​​listed above, or any value between 0.6 and 1.7. If the maximum cross-sectional area is too small, the load-bearing area of ​​the weld mark 7 will be insufficient, failing to effectively transfer and disperse the tearing stress caused by vibration or impact, leading to stress concentration at the weld mark 7 and increasing the risk of cracking. If the maximum cross-sectional area is too large, the cross-sectional area of ​​the weld mark 7 will be excessive, expanding the welding heat-affected zone and causing welding deformation of the shell 1 and cover plate 2, reducing the structural strength of the shell 1 and cover plate 2.

[0036] In one feasible implementation, both the cover plate 2 and the shell 1 are made of aluminum. Compared to steel, aluminum covers 2 and shell 1 have lower strength, resulting in weaker structural stability and tear resistance in the welded connection area. Therefore, it is necessary to ensure that the weld 7 has sufficient strength to offset the weakening effect caused by the material. Thus, along the first direction D1, the maximum offset between the laser focus and the preset gap 6 is between 0.1mm and 0.2mm. The value can be 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, or 0.2mm. The value can be any value between 0.1mm and 0.2mm, specifically those listed above. While avoiding laser beam incident on the battery cell, the laser focus can be brought closer to the preset gap 6 to ensure sufficient molten pool formation, thereby improving the structural strength and tear resistance of the single-segment weld 7 and reducing the risk of weld 7 cracking.

[0037] In another feasible implementation, both the cover plate 2 and the shell 1 are made of steel, which has higher strength than aluminum. This results in higher structural stability and tear resistance in the welded joint area, eliminating the need to increase the area of ​​the weld mark 7 to improve connection reliability. Therefore, along the first direction D1, the maximum offset between the laser focus and the preset gap 6 is between 0.08mm and 0.18mm. The value can be 0.08mm, 0.09mm, 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, or 0.18mm, specifically any of the values ​​listed above or any value between 0.08mm and 0.18mm. While ensuring sufficient filling of the molten pool and meeting the structural strength requirements of the weld mark 7, the laser focus can be moved further away from the preset gap 6 to minimize the risk of battery thermal short circuits.

[0038] Secondly, this disclosure provides a battery formed by welding using the aforementioned welding method. At the short side 52 of the preset surface 5, along the third direction D3, the lowest point of the weld mark 7 is the first reference point K1, which is the lowest point in the entire weld mark 7 in the melting depth direction. The lowest point of the weld mark 7 located within the preset gap 6 is the second reference point K2, which is the lowest point of the weld mark 7 located within the preset gap 6.

[0039] In the embodiments provided in this disclosure, the positional relationship between the first reference point K1 and the second reference point K2 at the short side 52 of the battery is defined to precisely control the forming shape of the solder mark 7. Specifically, the minimum distance between the first reference point K1 and the second reference point K2 along the first direction D1 is defined as N mm, where N ≤ 0.2. The value can be 0, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, or 0.2. The value can be one of the aforementioned values ​​or any value between 0 and 0.2. If this minimum spacing is too large, during the laser welding process, the distance between the laser focus and the preset gap 6 will be too large, making it difficult for the molten pool to fully fill the gap space, resulting in defects such as incomplete welding and lack of fusion. This reduces the welding strength between the shell 1 and the cover plate 2, and at the same time, it will aggravate the stress concentration in the area where the preset gap 6 is located. The weld mark 7 at the preset gap 6 will be difficult to fully disperse and transmit tearing stress, increasing the risk of damage and cracking of the weld mark 7.

[0040] By controlling this minimum spacing within a preset value range, the thickness and distribution of the solder mark 7 at the preset gap 6 can be optimized. The thickness distribution of the solder mark 7 at the preset gap 6 is uniform, and the thicker areas of the solder mark 7 are close to or located within the preset gap 6. The structural strength and tear resistance of the solder mark 7 at the preset gap 6 are guaranteed. The tearing stress on the solder mark 7 at the preset gap 6 can be effectively dispersed and transmitted, avoiding excessive local stress accumulation and reducing the risk of solder mark 7 damage and cracking under vibration or impact conditions.

[0041] Preferably, the distance between the first reference point K1 and the second reference point K2 satisfies: N ≤ 0.15 mm, making the lowest position of the weld 7 within the preset gap 6 closer to the lowest position of the weld 7, while maintaining a misalignment between the lowest position of the weld 7 within the preset gap 6 and the preset gap 6. When the welding method is top welding, the maximum penetration depth of the weld 7 can be made close to but misaligned with the area where the preset gap 6 is located, thereby preventing laser energy from potentially passing through the preset gap 6 and directly acting on the internal battery cell, causing damage to the battery cell and avoiding laser leakage during the welding process. At the same time, it can further enhance the structural strength and tear resistance of the weld 7 at the preset gap 6, reducing the risk of cracking of the weld 7 under vibration or impact conditions.

[0042] In the embodiments provided in this disclosure, when the first reference point K1 is not kept at a certain distance from the second reference point K2, the thickness of the weld 7 at the first reference point K1 on the third direction D3 is H1, which is limited to 0.5≤H1≤1.9. The value can be 0.5, 0.7, 1, 1.2, 1.5, 1.7 or 1.9, and the value can be any value between 0.5 and 1.9, specifically the values ​​listed above. If H1 is too small, the thickness of the weld 7 at the first reference point K1 is insufficient, the effective bearing area of ​​the weld 7 is reduced, and it cannot effectively disperse and transmit the tearing stress generated under vibration or impact conditions, resulting in stress concentration at the weld 7 on the short side 52, which is prone to cracking. If H1 is too large, the weld 7 is too thick, the welding time is too long, resulting in excessive continuous input of welding heat, causing deformation of the shell 1 or the cover plate 2, and exacerbating the failure risk of the weld 7 on the short side 52.

[0043] On the third direction D3, the thickness of the weld mark 7 at the second reference point K2 is H2, limited to 0.5 ≤ H2 ≤ 1.45. The value can be 0.5, 0.7, 1, 1.2, or 1.45, specifically the values ​​listed above, or any value between 0.5 and 1.45. If H2 is too small, the thickness of the weld mark 7 at the second reference point K2 is insufficient, reducing the effective bearing area of ​​the weld mark 7 in the preset gap 6. This makes it unable to effectively disperse and transmit the tearing stress generated under vibration or impact conditions, leading to stress concentration at the weld mark 7 on the short side 52, which is prone to cracking. If H2 is too large, the weld mark 7 is too thick, resulting in excessive welding time and continuous excessive input of welding heat, causing deformation of the shell 1 or cover plate 2, and exacerbating the failure risk of the weld mark 7 on the short side 52.

[0044] The constraint expression satisfies H1-H2≤1.2. If the values ​​of H1 and H2 differ too much, the thickness difference between the weld mark 7 at the first reference point K1 and the second reference point K2 will be too large, causing a significant abrupt change in thickness between the weld mark 7 in the area of ​​the preset gap 6 and other areas. This will result in significant stress concentration at the thickness transition point. Under vibration or impact conditions, cracking is likely to occur in this thickness transition area, reducing the structural strength and tear resistance of the weld mark 7.

[0045] By limiting the difference between H1 and H2 to a preset range, the thickness difference of the solder mark 7 at the first reference point K1 and the second reference point K2 is reduced, so that the solder mark 7 forms a smooth transition between the area where the preset gap 6 is located and other areas, effectively reducing stress concentration caused by sudden thickness changes and reducing the risk of solder mark 7 being damaged and cracked.

[0046] Thirdly, this disclosure provides a battery pack including the aforementioned battery.

[0047] Fourthly, this disclosure provides an electrical device that may include the aforementioned battery pack.

[0048] Battery packs can serve as operating power for electrical equipment or as driving power for electrical equipment, replacing or partially replacing fuel or natural gas to provide driving power for vehicles. By way of example only, electrical equipment can be, but is not limited to, vehicles, ships, aircraft, household appliances, and industrial equipment. For example, vehicles can be passenger cars, trucks, construction vehicles, etc.

[0049] In addition, electrical equipment can also be used for the storage, conversion, and release of recyclable electrical energy.

[0050] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of this disclosure. The above description is only a preferred embodiment of this disclosure, but this disclosure does not limit the scope of implementation to what is shown in the figures. Any changes made in accordance with the concept of this disclosure, or modifications to equivalent embodiments with equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of this disclosure.

Claims

1. A method of welding a battery, characterized by, Includes the following steps: A housing and a cover are provided. The housing has a receiving cavity, and the receiving cavity has an opening formed on a first surface of the housing. The first surface has a long side extending in a first direction and a short side extending in a second direction. The first direction, the second direction, and the third direction are perpendicular to each other. At least a portion of the cover extends from the opening into the receiving cavity, and a predetermined gap is formed between the cover extending into the receiving cavity and the housing. The cover plate is laser welded to the housing, and a weld mark is formed at the weld joint. The maximum offset between the laser focus and the preset gap along the first direction is controlled to be between 0.08mm and 0.2mm.

2. The welding method according to claim 1, characterized in that, It also includes the following steps: S01: Battery loading process, completing the loading and identity matching of the battery; S02: Battery positioning process, using the first surface of the battery as the positioning reference, positioning and clamping the battery in multiple directions, and controlling the relevant gaps and clamping pressure, the positioning fixture adapts to the outline of the battery and moves accordingly; S03: Laser welding process, the laser is aligned with the preset gap and deflected towards the cover plate side, and welding is performed along the perimeter of the cover plate, while controlling the welding parameters, protective gas and dust removal wind speed; S04: Solder stamp appearance inspection process, which performs defect inspection on the appearance of the solder stamp; S05: Welding stamp rolling process, wherein the welding stamp is rolled, and the rolling parameters and dust removal wind speed are controlled; S06: Insulation testing process, which tests the voltage drop and insulation resistance of the battery; S07: Battery unloading process, which separates qualified and unqualified batteries; In step S03, the cover plate and the housing are laser welded together, and a weld mark is formed at the weld joint. The maximum offset between the laser focus and the preset gap along the first direction is controlled to be between 0.08mm and 0.2mm.

3. The welding method of claim 2, wherein, In step S01, the battery is clamped by the battery gripper assembly, the material is loaded by the conveying assembly, and the battery QR code is scanned and paired at the battery scanning station.

4. The welding method of claim 2, wherein, In step S02, during battery welding, the first surface of the battery is used as the positioning reference, and the battery is positioned and clamped along the first direction, the second direction, and the third direction. After clamping, the gap between the shell and the cover plate is ≤0.07mm, the height difference between the upper surface of the positioning fixture and the upper surface of the cover plate is 0.5mm-1.5mm, and the clamping cylinder pressure of the positioning fixture is 0.1MPa-0.5MPa.

5. The welding method of claim 2, wherein, In step S03, the laser is aligned with the preset gap between the housing and the cover plate, and offset towards the cover plate by 0.95mm-1.05mm, and a weld is performed around the perimeter of the cover plate.

6. The welding method of claim 5, wherein, In step S03, the welding speed is controlled at 100mm / s-300mm / s, the welding decoking amount is 0-3mm, the welding power of the outer ring is 800W-2800W, the welding power of the inner ring is 400W-1400W, the protective nitrogen flow rate is 10L / min-50L / min, and the dust removal wind speed is ≥20m / s.

7. The welding method of claim 2, wherein, In step S04, the welded battery is transferred to the appearance inspection station, where a CCD inspection device is used to inspect the appearance of the weld. The inspection items include at least one of the following defects: weld bursts, pinholes, dents, broken welds, and misalignment.

8. The welding method of claim 2, wherein, In step S05, the battery that has completed the appearance inspection is transferred to the soldering and pressing station. Two sets of pressing devices, one vertical and one horizontal, are used to press the solder marks on the side and top of the battery to a thickness of less than 0.05mm. During the pressing process, the dust removal wind speed is controlled to be ≥15m / s, the pressing angle is 2°-8°, and the pressing pressure is 0.1MPa-0.5MPa.

9. The welding method of claim 2, wherein, In step S06, the battery that has completed rolling is transferred to the insulation testing station, where a pulse-type lithium battery short-circuit tester is used to test the voltage drop and insulation resistance of the battery.

10. The welding method of claim 2, wherein, In step S07, the battery that has completed the insulation test is transferred to the unloading station and then to the helium testing process; if the insulation test fails, the battery is transferred to the buffer position.

11. The welding method of claim 1, wherein, At least at the short side of the first surface, the solder mark is controlled to protrude from the surface of the cover plate. Along the third direction upward, the maximum distance between the surface of the solder mark farthest from the cover plate and the cover plate is R mm, where 0.01≤R≤0.

3.

12. The welding method of claim 1, wherein, At least at the short side of the first surface, the solder mark is controlled to protrude from the surface of the cover plate. Along the first direction, the maximum distance between the surface of the solder mark on the cover plate furthest from the housing and the preset gap is T mm, where 0 ≤ T ≤ 0.

15.

13. The welding method of claim 1, wherein, At least at the short side of the preset surface, the maximum cross-sectional area of ​​the solder mark along the first direction is controlled to be S mm. 2 Where 0.6≤S≤1.

7.

14. The welding method of claim 1, wherein, When both the cover plate and the housing are made of aluminum, at least on the short side of the preset surface, the maximum offset between the laser focus and the preset gap along the first direction is controlled to be between 0.1mm and 0.2mm.

15. The welding method of claim 1, wherein, When both the cover plate and the housing are made of steel, at least at the short side of the preset surface, the maximum offset between the laser focus and the preset gap along the first direction is controlled to be between 0.08mm and 0.18mm.

16. A battery, which is formed by welding using the welding method according to any one of claims 1 to 15, characterized by At the short side of the preset surface, along the third direction upwards, the lowest point of the solder mark is the first reference point, and the lowest point of the solder mark located within the preset gap is the second reference point. Along the first direction, the minimum distance between the first reference point and the second reference point is N mm, where N ≤ 0.

2.

17. The battery according to claim 16, characterized in that, The distance between the first reference point and the second reference point satisfies: N≤0.15, unit mm.

18. The battery of claim 16, wherein, In the third direction, the thickness of the solder mark at the first reference point is H1, and the thickness of the solder mark at the second reference point is H2, wherein H1-H2≤1.

2.

19. A battery pack, characterized by Includes the battery as described in any one of claims 16 to 18.

20. An electrical device, comprising: Includes the battery pack as described in claim 19.

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