Welding method and battery

Abstract

A welding method, comprising the following steps: attaching a cover plate (200) onto a housing (100), and welding the housing and the cover plate; and, after welding is complete, the width of a welding seam formed on the cover plate being L1, the weld width formed on the housing being L2, the wall thickness of the housing being L3, and the thickness of the cover plate being L4, said values satisfying: 30 μm≤(L1-L2)*L4 / L3≤70 μm. The present invention also relates to a battery prepared by the described welding method. According to said welding method, a good welding effect can be achieved when the housing and the cover plate are welded.

Description

Welding method and battery Technical Field

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

[0002] In the prior art, lithium-ion battery packaging comes in two main types: aluminum-plastic film and metal casing. While aluminum-plastic film packaging is simpler to manufacture and offers a more convenient design, it suffers from poor mechanical strength, resulting in poor dimensional consistency. Therefore, in some cases, lithium-ion batteries are packaged in steel casings.

[0003] A steel case typically consists of a shell and a cover plate, with the battery cells placed inside the shell and the cover plate sealing the shell opening. To ensure the seal and safety of the steel case, the shell and cover plate are typically connected by welding. However, existing techniques for welding the shell and cover plate have the problem of poor quality.

[0004] Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a welding method that can achieve better welding effect when welding a shell and a cover plate.

[0006] The present invention also provides a battery.

[0007] The welding method according to the first embodiment of the present invention comprises the following steps:

[0008] Laminating the cover plate on the shell, and welding the shell and the cover plate;

[0009] After welding is completed, the weld width formed on the cover plate is L1, the weld width formed on the shell is L2, the wall thickness of the shell is L3, and the thickness of the cover plate is L4, satisfying: 30μm≤(L1-L2)*L4 / L3≤70μm.

[0010] The welding method according to an embodiment of the present invention has at least the following beneficial effects: When welding a battery, the cover plate is attached to the housing, and then the housing and cover plate are welded. After welding, the weld seam width on the cover plate and the weld width on the housing are controlled to ensure that the weld seam width L1, weld width L2, housing wall thickness L3, and cover plate thickness L4 satisfy the following conditions: 30 μm ≤ (L1 - L2) * L4 / L3 ≤ 70 μm. This method achieves excellent welding results when welding the housing and cover plate.

[0011] According to the welding method of some embodiments of the present invention, L3 and L4 satisfy: 0.3≤L4 / L3≤1.

[0012] According to some embodiments of the welding method of the present invention, the welding method further includes the following steps: welding the shell and the cover plate from the direction of the cover plate to the shell.

[0013] According to the welding method of some embodiments of the present invention, the shell includes a main body and a protruding portion, the main body has a accommodating cavity for accommodating the battery cell, the protruding portion is connected to the outer edge of the main body, and the protruding portion protrudes outside the accommodating cavity, and the welding method also includes the following steps: welding the cover plate and the protruding portion.

[0014] According to the welding method of some embodiments of the present invention, the distance between the weld and the main body is L5, which satisfies: 0.25 mm ≤ L5 ≤ 0.35 mm.

[0015] According to the welding method of some embodiments of the present invention, the penetration depth formed on the shell is L6, and 0.3≤L6 / L3≤0.9.

[0016] A battery according to an embodiment of the second aspect of the present invention includes:

[0017] A housing having a cavity for accommodating the battery cell;

[0018] The cover plate is welded to the shell, wherein the weld width on the cover plate is L1, the weld width on the shell is L2, the wall thickness of the shell is L3, and the thickness of the cover plate is L4, satisfying: 30μm≤(L1-L2)*L4 / L3≤70μm.

[0019] The battery according to the embodiments of the present invention has at least the following beneficial effects: after the cover plate is welded to the shell, the weld seam width L1, weld width L2, shell wall thickness L3, and cover plate thickness L4 satisfy the following conditions: 30 μm ≤ (L1 - L2) * L4 / L3 ≤ 70 μm. Therefore, the shell and cover plate are welded effectively. Furthermore, due to the improved welding quality, the battery has higher reliability.

[0020] In batteries according to some embodiments of the present invention, L3 and L4 satisfy: 0.3≤L4 / L3≤1.

[0021] According to some embodiments of the battery of the present invention, the shell includes a main body and a protruding portion, the main body has the accommodating cavity, the protruding portion surrounds and is connected to the outer edge of the main body, and the protruding portion protrudes outside the accommodating cavity; the cover plate is welded to the protruding portion.

[0022] According to some embodiments of the battery of the present invention, a distance L5 between the weld and the main body satisfies the following condition: 0.25 mm ≤ L5 ≤ 0.35 mm.

[0023] In batteries according to some embodiments of the present invention, the penetration depth of the shell is L6, and 0.3≤L6 / L3≤0.9.

[0024] In batteries according to some embodiments of the present invention, the wall thickness of the shell is 0.05 mm to 0.5 mm.

[0025] In batteries according to some embodiments of the present invention, the cover plate has a thickness of 0.015 mm to 0.5 mm.

[0026] In the battery according to some embodiments of the present invention, the shell and the cover are both made of alloy.

[0027] In the battery according to some embodiments of the present invention, an explosion-proof valve is provided on the cover plate.

[0028] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0030] FIG1 is a flow chart of a welding method according to some embodiments of the present invention;

[0031] FIG2 is a schematic diagram of a cover plate and a housing in a welding method according to a first embodiment of the present invention;

[0032] FIG3 is a schematic diagram of a cover plate and a housing in a welding method according to a second embodiment of the present invention;

[0033] FIG4 is a schematic diagram of a cover plate and a shell in a welding method according to a third embodiment of the present invention.

[0034] Reference numerals: housing 100 , body 110 , protruding portion 120 , accommodating cavity 130 , cover plate 200 . DETAILED DESCRIPTION

[0035] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0036] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0037] In the description of the present invention, "several" means more than one, "plurality" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0038] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0039] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0040] Referring to FIG. 1 , in some embodiments, the welding method includes the following steps:

[0041] S100, attaching the cover plate 200 to the housing 100, and welding the housing 100 and the cover plate 200;

[0042] S200. After welding is completed, the weld width formed on the cover plate 200 is L1, the weld width formed on the shell 100 is L2, the wall thickness of the shell 100 is L3, and the thickness of the cover plate 200 is L4, satisfying: 30 μm ≤ (L1-L2)*L4 / L3 ≤ 70 μm.

[0043] Specifically, when welding a battery, the cover plate 200 is attached to the housing 100, and then the housing 100 and the cover plate 200 are welded. After welding, the weld seam width on the cover plate 200 and the weld width on the housing 100 are controlled to ensure that the weld seam width L1, weld width L2, housing wall thickness L3, and cover plate thickness L4 satisfy the following conditions: 30 μm ≤ (L1 - L2) * L4 / L3 ≤ 70 μm. This method achieves good welding results when welding the housing 100 and the cover plate 200.

[0044] The weld width mentioned above refers to the transverse width of the molten metal in the welding wire or rod during welding. Specifically, the weld width refers to the transverse width of the melted shell 100 when the cover plate 200 and the shell 100 are welded. The weld seam width mentioned above refers to the transverse width of the weld seam formed on the cover plate 200 during welding. L1 and L2 can be referred to in Figure 4.

[0045] As a supplementary explanation, when (L1-L2)*L4 / L3>70μm, the weld depth and width of the cover plate 200 and the housing 100 during welding will be too small, resulting in poor welding results. When (L1-L2)*L4 / L3<30μm, this may result in an excessively large weld width on the housing 100, further causing the weld depth to penetrate the housing 100 and affect its appearance. Furthermore, excessive laser power may cause the cover plate 200 and the housing 100 to be directly separated by the laser, preventing the intended connection of the cover plate 200 and the housing 100 by welding. For more details, please refer to the table below.

[0046] In the table above, "tensile force" represents the tensile force threshold required to separate the housing 100 and cover plate 200 during a tensile test. The table further demonstrates that when L1, L2, L3, and L4 satisfy the conditions of 30μm ≤ (L1-L2)*L4 / L3 ≤ 70μm, welds at locations meeting this condition achieve superior weld performance and withstand greater tensile forces. Specifically, when (L1-L2)*L4 / L3 exceeds 70μm, while the weld can withstand significant tensile forces, it can potentially penetrate the housing 100 and cover plate 200, a condition that does not meet process requirements. When (L1-L2)*L4 / L3 is less than 30μm, the weld can withstand greater tensile forces, but the connection strength between the housing 100 and cover plate 200 is lower.

[0047] Furthermore, in order to control the size of the weld, the size of the weld width and the size of the weld depth, the voltage, current and welding speed can be controlled to achieve the effect of controlling the size of the weld, the size of the weld width and the size of the weld depth.

[0048] Furthermore, in some embodiments, the width of the weld is in the range of 0.06 mm to 0.2 mm. Specifically, when the weld width is less than 0.06 mm, the weld strength is insufficient, causing the housing 100 and the cover plate 200 to break easily. When the weld width is greater than 0.2 mm, the weld joint is too fragile and prone to breakage.

[0049] Referring to FIG. 4 , in some embodiments, the depth of penetration on the housing 100 is L6, where 0.3 ≤ L6 / L3 ≤ 0.9. When the depth of penetration exceeds 0.9L3 mm, the weld quality may be degraded, leading to weld fracture. When the depth of penetration is less than 0.3L3 mm, the weld strength may be too low to meet requirements.

[0050] In some embodiments, the weld width on the housing 100 is 0.06 mm to 0.12 mm. When the weld width is greater than 0.12 mm, cracking may occur during welding, affecting the quality of the weld. When the weld width is less than 0.06 mm, the weld strength may be too low and may not meet the requirements.

[0051] Furthermore, the wall thickness of the shell 100 and the thickness of the cover plate 200 can be limited. Specifically, referring to Figure 2, in some embodiments, the wall thickness of the shell 100 is L3, and the thickness of the cover plate 200 is L4, satisfying: 0.3≤L4 / L3≤1. The wall thickness of the shell 100 can be 0.05mm~0.5mm. The thickness of the cover plate 200 can be 0.015mm~0.5mm. The thickness of the cover plate 200 can be less than the thickness of the shell 100. In the case where the thickness of the cover plate 200 is less than the wall thickness of the shell 100, compared with the case where the thickness of the cover plate 200 is equal to the wall thickness of the shell 100, the case where the thickness of the cover plate 200 is less than the wall thickness of the shell 100 can further reduce the size of the battery and increase the battery life. Specifically, by thinning the thickness of the cover plate 200, the thickness of the battery cell can be increased, thereby improving the battery life. In addition, if the strength of the housing 100 and the cover plate 200 meets the requirements, the battery life can be improved by reducing the wall thickness of the housing 100.

[0052] Furthermore, when the thickness of the cover plate 200 is less than the wall thickness of the shell 100, the shell 100 and the cover plate 200 can be welded from the direction of the cover plate 200 to the shell 100. That is, the laser can pass through the cover plate 200 first, and then pass through the shell 100. During the laser welding process, since the thickness of the cover plate 200 is relatively small, the laser consumes relatively low energy to melt through the cover plate 200. In this process, the laser uses relatively low energy, which can effectively avoid the problem of large fluctuations in the weld width due to excessive laser energy and poor control. That is, the smaller the laser energy, the higher the control accuracy of the weld. Specifically, in some embodiments, the welding method further includes the following steps: welding the shell 100 and the cover plate 200 from the direction of the cover plate 200 to the shell 100.

[0053] Further, referring to Figure 2, in some embodiments, the shell 100 includes a main body 110 and a protrusion 120, the main body 110 has a receiving cavity 130 for receiving the battery cell, the protrusion 120 surrounds and is connected to the outer edge of the main body 110, and the protrusion 120 protrudes from the receiving cavity 130, and the welding method further includes the following steps: welding the cover plate 200 and the protrusion 120. Specifically, the shell 100 can be formed by a stamping process. After being manufactured by the stamping process, the shell 100 includes a main body 110 and a protrusion 120. Among them, after the protrusion 120 protrudes from the receiving cavity 130, the protrusion 120 can be directly welded to the cover plate 200. This method can improve the efficiency of the staff because the staff does not have to cut the protrusion 120, and can directly use the protrusion 120 and the cover plate 200 for welding, thereby saving the cutting step. In addition, when the housing 100 does not have the protruding portion 120 , the cover plate 200 can be directly welded to the top surface of the housing 100 , as shown in FIG. 3 .

[0054] Specifically, referring to FIG2 , in some embodiments, the distance between the weld and the main body 110 is L5, satisfying the following: 0.25 mm ≤ L5 ≤ 0.35 mm. When L5 is less than 0.25 mm, this will cause the weld to overlap with the bend of the housing 100, resulting in poor fit between the housing 100 and the cover plate 200, affecting the welding effect. More specifically, the cover plate 200 is welded to the protrusion 120, and the protrusion 120 is connected to the main body 110. There is a circular arc corner at the connection between the protrusion 120 and the main body 110. The circular arc corner is formed when the housing 100 is stamped to form the main body 110 and the protrusion 120. It is conceivable that the overlap of the weld and the circular arc corner will cause the above-mentioned problems. When L5 is greater than 0.35 mm, the weld is located farther from the main body 110, which will significantly increase the size of the battery, thereby reducing the battery life.

[0055] The following describes a battery in another embodiment. In some embodiments, the battery includes: a housing 100 and a cover plate 200. The housing 100 has a receiving cavity 130 for accommodating a battery cell. The cover plate 200 is welded to the housing 100, wherein the weld width on the cover plate 200 is L1, the weld width on the housing 100 is L2, the wall thickness of the housing 100 is L3, and the thickness of the cover plate 200 is L4, satisfying: 30μm≤(L1-L2)*L4 / L3≤70μm. Specifically, since after the cover plate 200 is welded to the housing 100, the weld width L1 on the cover plate 200, the weld width L2 on the housing 100, the wall thickness L3 of the housing 100, and the thickness L4 of the cover plate 200 satisfy 30μm≤(L1-L2)*L4 / L3≤70μm, the welding effect of the housing 100 and the cover plate 200 is good. Furthermore, due to the good welding effect, the battery has high reliability.

[0056] The aforementioned weld width refers to the lateral width of the molten metal of the welding wire or welding rod during the welding process. Specifically, the weld width refers to the lateral width of the melted shell 100 when the cover plate 200 and the shell 100 are welded. The aforementioned weld seam width refers to the lateral width of the weld seam formed on the cover plate 200 during welding. After the welding of the cover plate 200 and the shell 100 is completed, the weld depth and weld width can be observed by cutting the welded part. Please refer to Figure 4, which is a schematic diagram of the cover plate 200 and the shell 100 in the welding method. Figure 4 also shows a schematic diagram of the cover plate 200 and the shell 100 of the battery.

[0057] As a supplementary explanation, when (L1-L2)*L4 / L3>70μm, the weld depth and width of the cover plate 200 and the housing 100 during welding will be too small, resulting in poor welding results. When (L1-L2)*L4 / L3<30μm, this may result in an excessively large weld width on the housing 100, further causing the weld depth to penetrate the housing 100 and affect its appearance. Furthermore, excessive laser power may cause the cover plate 200 and the housing 100 to be directly separated by the laser, preventing the intended connection of the cover plate 200 and the housing 100 by welding. For more details, please refer to the table below.

[0058] In the table above, "tensile force" represents the tensile force threshold required to separate the housing 100 and cover plate 200 during a tensile test. The table further demonstrates that when L1, L2, L3, and L4 satisfy the conditions of 30μm ≤ (L1-L2)*L4 / L3 ≤ 70μm, welds at locations meeting this condition achieve superior weld performance and withstand greater tensile forces. Specifically, when (L1-L2)*L4 / L3 exceeds 70μm, while the weld can withstand significant tensile forces, it can potentially penetrate the housing 100 and cover plate 200, a condition that does not meet process requirements. When (L1-L2)*L4 / L3 is less than 30μm, the weld can withstand greater tensile forces, but the connection strength between the housing 100 and cover plate 200 is lower.

[0059] Further, please refer to Figure 2, which is a schematic diagram of the cover plate 200 and housing 100 during the welding method. Figure 2 also illustrates a schematic diagram of the cover plate 200 and housing 100 of the battery. In some embodiments, the wall thickness of the housing 100 is L3, and the thickness of the cover plate 200 is L4, satisfying the following relationship: 0.3 ≤ L4 / L3 ≤ 0.95. Specifically, the wall thickness of the housing 100 can be 0.05 mm to 0.5 mm. The thickness of the cover plate 200 can be 0.015 mm to 0.5 mm. The thickness of the cover plate 200 can be less than the thickness of the housing 100. When the thickness of the cover plate 200 is less than the wall thickness of the housing 100, compared to when the thickness of the cover plate 200 is equal to the wall thickness of the housing 100, the smaller thickness of the cover plate 200 can further reduce the size of the battery and increase its battery life. Specifically, by reducing the thickness of the cover plate 200, the thickness of the battery cell can be increased, thereby improving the battery life. In addition, if the strength of the housing 100 and the cover plate 200 meets the requirements, the battery life can be improved by reducing the wall thickness of the housing 100.

[0060] Further, please refer to Figure 2, which is a schematic diagram of the cover plate 200 and housing 100 during the welding method. Figure 2 also illustrates a schematic diagram of the cover plate 200 and housing 100 of a battery. In some embodiments, the housing 100 includes a body 110 and a protrusion 120. The body 110 has a receiving cavity 130. The protrusion 120 surrounds and connects to the outer edge of the body 110, protruding from the receiving cavity 130. The cover plate 200 is welded to the protrusion 120. Specifically, the housing 100 can be formed by a stamping process. After the stamping process, the housing 100 includes the body 110 and the protrusion 120. After the protrusion 120 protrudes from the receiving cavity 130, it can be directly welded to the cover plate 200. This method improves worker efficiency because the protrusion 120 does not need to be cut out and can be directly welded to the cover plate 200. In addition, when the housing 100 does not have the protrusion 120 , the cover plate 200 can be directly welded to the top surface of the housing 100 .

[0061] Further, please refer to Figure 2, which is a schematic diagram of the cover plate 200 and the shell 100 in the welding method. Figure 2 also shows a schematic diagram of the cover plate 200 and the shell 100 of the battery. In some embodiments, the distance between the weld and the main body 110 is L5, satisfying: 0.25mm≤L5≤0.35mm. When L5 is less than 0.25mm, this will cause the weld and the bending part of the shell 100 to overlap, resulting in poor fit between the shell 100 and the cover plate 200, affecting the welding effect. More specifically, the cover plate 200 is welded to the protrusion 120, and the protrusion 120 is connected to the main body 110. There will be an arc corner at the connection between the protrusion 120 and the main body 110. The arc corner is formed when the shell 100 is stamped to form the main body 110 and the protrusion 120. It is conceivable that the overlap of the weld and the arc corner will cause the above-mentioned problems. When L5 is greater than 0.35 mm, the weld is farther away from the main body 110 , which significantly increases the size of the battery, thereby reducing the battery life.

[0062] Furthermore, in some embodiments, the width of the weld is in the range of 0.06 mm to 0.2 mm. Specifically, when the weld width is less than 0.06 mm, the weld strength is insufficient, causing the housing 100 and the cover plate 200 to break easily. When the weld width is greater than 0.2 mm, the weld joint is too fragile and prone to breakage.

[0063] Referring to FIG. 4 , in some embodiments, the depth of penetration on the housing 100 is L6, where 0.3 ≤ L6 / L3 ≤ 0.9. When the depth of penetration exceeds 0.9L3 mm, the weld quality may be degraded, leading to weld fracture. When the depth of penetration is less than 0.3L3 mm, the weld strength may be too low to meet requirements.

[0064] In some embodiments, the weld width on the housing 100 is 0.06 mm to 0.12 mm. When the weld width is greater than 0.12 mm, cracking may occur during welding, affecting the quality of the weld. When the weld width is less than 0.06 mm, the weld strength may be too low and may not meet the requirements.

[0065] Furthermore, in some embodiments, the wall thickness of the housing 100 is 0.05 mm to 0.5 mm. When the wall thickness of the housing 100 is greater than 0.5 mm, although the thicker housing 100 can provide higher strength, if the housing 100 already meets the strength requirements, increasing the wall thickness of the housing 100 without limit will lead to increased manufacturing costs. When the wall thickness of the housing 100 is less than 0.05, this will result in the strength of the housing 100 being too low, and the housing 100's ability to protect the battery cells will be insufficient.

[0066] Furthermore, the above description is about the wall thickness of the shell 100, and the following description is about the thickness of the cover plate 200. In some embodiments, the thickness of the cover plate 200 is 0.015mm to 0.5mm. When the thickness of the cover plate 200 is greater than 0.5mm, although the thicker cover plate 200 can make the cover plate 200 have higher strength, if the cover plate 200 already meets the strength requirements, increasing the thickness of the cover plate 200 without limit will lead to an increase in manufacturing costs. When the thickness of the cover plate 200 is less than 0.015, this will cause the strength of the cover plate 200 to be too low, and the ability of the cover plate 200 to protect the battery cell will be insufficient.

[0067] Furthermore, in some embodiments, the housing 100 is formed by a stamping process. Specifically, the stamping process has the characteristic of high processing precision and is suitable for processing smaller housings 100. Thus, the stamping process can ensure high processing precision when processing the housing 100, and can also ensure high processing efficiency.

[0068] Furthermore, in some embodiments, the housing 100 and the cover plate 200 are both made of an alloy. The alloy can be stainless steel. When the housing 100 and the cover plate 200 are made of an alloy, the housing 100 and the cover plate 200 can withstand a certain amount of pressure, thereby protecting the battery cells and preventing them from failing when subjected to external forces.

[0069] Furthermore, in some embodiments, an explosion-proof valve is provided on the cover plate 200. Specifically, the explosion-proof valve can be opened when the pressure in the accommodating cavity 130 is too high, thereby allowing the gas in the accommodating cavity 130 to escape, effectively avoiding the problem of battery explosion.

[0070] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A welding method, characterized in that, Including the following steps: Attach the cover plate to the housing and weld the housing and the cover plate; After welding, the weld width formed on the cover plate is L1, the fusion width formed on the housing is L2, the wall thickness of the housing is L3, and the thickness of the cover plate is L4, satisfying: 30μm ≤ (L1 - L2) * L4 / L3 ≤ 70μm.

2. The welding method according to claim 1, wherein, L3 and L4 satisfy: 0.3 ≤ L4 / L3 ≤ 1.

3. The welding method according to claim 2, wherein, The welding method further includes the following steps: Weld the housing and the cover plate in the direction from the cover plate to the housing.

4. The welding method according to claim 2, characterized in that, The housing includes a body part and a protruding part. The body part has a receiving cavity for accommodating an electric core. The protruding part is connected around the outer edge of the body part and protrudes outside the receiving cavity. The welding method further includes the following steps: Weld the cover plate and the protruding part.

5. The welding method according to claim 4, wherein, The distance between the weld and the body part is L5, satisfying: 0.25mm ≤ L5 ≤ 0.35mm.

6. The welding method according to claim 2, wherein The penetration depth formed on the housing is L6, 0.3 ≤ L6 / L3 ≤ 0.

9.

7. Battery, characterized in that, Including: A housing having a receiving cavity for accommodating an electric core; A cover plate welded to the housing, wherein the weld width on the cover plate is L1, the fusion width on the housing is L2, the wall thickness of the housing is L3, and the thickness of the cover plate is L4, satisfying: 30μm ≤ (L1 - L2) * L4 / L3 ≤ 70μm.

8. The battery according to claim 7, characterized in that, L3 and L4 satisfy: 0.3 ≤ L4 / L3 ≤ 1.

9. The battery according to claim 7, characterized in that, The housing includes a body part and a protruding part. The body part has the receiving cavity. The protruding part is connected around the outer edge of the body part and protrudes outside the receiving cavity; the cover plate is welded to the protruding part.

10. The battery according to claim 9, characterized in that, The distance between the weld and the body part is L5, satisfying: 0.25mm ≤ L5 ≤ 0.35mm.

11. The battery according to claim 7, wherein The penetration depth of the housing is L6, 0.3 ≤ L6 / L3 ≤ 0.

9.

12. The battery according to claim 7, characterized in that, The wall thickness of the housing is 0.05mm to 0.5mm.

13. The battery according to claim 7, characterized in that, The thickness of the cover plate is 0.015mm to 0.5mm.

14. The battery according to claim 7, characterized in that, The materials of the housing and the cover plate are both alloys.

15. The battery according to claim 7, characterized in that, An explosion-proof valve is provided on the cover plate.

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