A type of battery cell

Abstract

This invention relates to the field of battery technology, specifically disclosing a battery cell. The battery cell includes a housing and an explosion-proof valve, the explosion-proof valve being disposed within a mounting hole on a mounting plate of the housing. A fixing portion of the explosion-proof valve extends away from the electrode assembly, and the outer peripheral wall of the fixing portion at least partially abuts against the inner wall of the mounting hole. Along a first direction, the end face of the fixing portion facing away from the electrode assembly is lower than the end face of the mounting plate facing away from the electrode assembly, thereby forming a step between the end face of the fixing portion facing away from the electrode assembly and the inner wall of the mounting hole. When welding the fixing portion to the mounting plate at the step, the laser is set at an angle relative to the mounting plate, and the fixing portion is welded to the inner wall of the mounting hole to form a welded portion. The melting direction during the formation of the welded portion is set at an angle to the plane of the mounting plate. By adopting the above welding method, the risk of laser leakage during welding of the fixing portion to the inner wall of the mounting hole is reduced, while ensuring a reliable connection between the fixing portion and the mounting plate, resulting in better welding quality.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more particularly to a battery cell. Background Technology

[0002] Currently, most battery cells use aluminum-plastic film encapsulation technology, commonly known as pouch cells. Aluminum-plastic film is thin and flexible, offering the advantage of versatile shapes, but its disadvantage is poor dimensional consistency after encapsulation. This issue can only be addressed by controlling process consistency, which is extremely difficult to achieve in practice. Therefore, some manufacturers have begun developing steel casings to improve the dimensional consistency of the encapsulated cells and simultaneously enhance their impact resistance.

[0003] However, in the manufacturing process of steel-cased battery cells, both the casing and the cover plate are made of stainless steel. To ensure the connection strength between the explosion-proof valve and the casing / cover plate, there is currently a solution to directly machine grooves onto the casing or cover plate to manufacture the explosion-proof valve. Although this can ensure a high connection strength between the explosion-proof valve and the casing / cover plate, the processing efficiency of this solution is low. When the casing or cover plate is thick, etching one explosion-proof valve can take several minutes or even tens of minutes, which is not conducive to mass production. Furthermore, aluminum explosion-proof valves cannot be directly welded to steel casings or cover plates; otherwise, potential corrosion is likely to occur at the weld joint, reducing the reliability of the connection between the explosion-proof valve and the casing / cover plate. If steel explosion-proof valves are directly welded to steel casings or cover plates, the problem of potential corrosion at the weld joint can be avoided. However, stainless steel is relatively hard, making it difficult to machine steps on the casing or cover plate, and it is not convenient to use the same step features as in the existing aluminum-cased battery cell and aluminum explosion-proof valve connection structures for welding. However, without a step to support the explosion-proof valve, the laser may leak during welding operations at the joint between the explosion-proof valve and the inner wall of the mounting hole, causing damage to the electrode assembly. Summary of the Invention

[0004] The purpose of this invention is to provide a battery cell that can directly weld a steel explosion-proof valve to a steel housing / cover plate, and avoid the problem of laser leakage at the welding point causing damage to the electrode assembly.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a battery cell, comprising:

[0007] The housing includes a mounting plate with mounting holes.

[0008] An explosion-proof valve includes a body and a fixing part surrounding the body. The fixing part extends away from the body in a direction away from the electrode group and forms an annular structure. The outer peripheral wall of the fixing part is at least partially in contact with the inner wall of the mounting hole. Along a first direction, the end face of the fixing part away from the electrode group is lower than the end face of the mounting plate away from the electrode group, and a step is formed between the end face of the fixing part away from the electrode group and the inner wall of the mounting hole.

[0009] Wherein, the end of the fixing part away from the electrode group is welded to the inner wall of the mounting hole and forms a welding part at the step portion. The melting direction of the welding part is set at an angle to the plane of the mounting plate, and the melting direction is towards the inner wall of the mounting hole. The plane of the mounting plate is perpendicular to the first direction. The angle between the central axis of the welding part and the plane of the mounting plate is θ.

[0010] The range of θ is: 30°≤θ≤75°.

[0011] Optionally, the fixing part includes two straight segments arranged opposite each other along the second direction and two arcuate segments arranged opposite each other along the third direction, the two straight segments and the two arcuate segments forming the annular structure; the mounting hole includes two straight wall surfaces arranged opposite each other along the second direction and two arcuate wall surfaces arranged opposite each other along the third direction, and the inner diameter of each arcuate wall surface is equal everywhere in a plane perpendicular to the first direction; the straight wall surface mates with the outer wall of the straight segment, and the arcuate wall surface mates with the outer wall of the arcuate segment;

[0012] Alternatively, the fixing part includes an arc segment that forms the annular structure; the mounting hole includes a cylindrical arc-shaped wall surface, and the inner diameter of the arc-shaped wall surface is equal everywhere in a plane perpendicular to the first direction; the arc-shaped wall surface mates with the outer wall of the arc segment.

[0013] Optionally, the thickness of the fixing part along the second direction is b; along the first direction, the distance between the end face of the fixing part facing away from the electrode group and the end face of the mounting plate facing away from the electrode group is c.

[0014] The value of b is in the range of: 0.1mm ≤ b ≤ 0.5mm;

[0015] The range of values ​​for c is: b≤c≤1.0mm.

[0016] Optionally, the height of the fixing part extending along the first direction is a;

[0017] The range of values ​​for 'a' is: 0.5mm ≤ a ≤ 2.0mm.

[0018] Optionally, along the first direction, the distance between the lowest point of the melting direction when the welded portion is formed and the end face of the fixing portion on the side away from the electrode assembly is e;

[0019] The value range of e is: 0.2mm≤e≤1.0mm.

[0020] Optionally, along the first direction, the height f of the welded portion protruding from the end face of the mounting plate on the side opposite to the electrode assembly;

[0021] The value range of f is: 0mm≤f≤0.1mm.

[0022] Optionally, a groove is provided on the end face of the main body facing away from the pole group, and the residual thickness at the groove is t1;

[0023] The value range of t1 is: 0.01mm≤t1≤0.1mm.

[0024] Optionally, the housing includes a shell and two cover plates. The shell has openings on opposite sides along a first direction. Each cover plate is fastened to one of the openings and connected to the shell. One of the cover plates is the mounting plate.

[0025] Optionally, the wall thickness of the shell is t2;

[0026] The range of t2 is: 0.1mm ≤ t2 ≤ 0.3mm;

[0027] The thickness of the cover plate is d;

[0028] The value range of d is: 0.5mm≤d≤1.2mm.

[0029] Optionally, both the housing and the explosion-proof valve are made of stainless steel.

[0030] The beneficial effects of this invention are as follows:

[0031] This invention provides a battery cell, including a housing and an explosion-proof valve, the explosion-proof valve being disposed within a mounting hole on a mounting plate of the housing. The explosion-proof valve includes a body portion and a fixing portion surrounding the body portion. The fixing portion extends away from the body portion in a direction away from the electrode assembly, and its outer peripheral wall at least partially abuts against the inner wall of the mounting hole. Along a first direction, the end face of the fixing portion away from the electrode assembly is lower than the end face of the mounting plate away from the electrode assembly, thereby forming a step between the end face of the fixing portion away from the electrode assembly and the inner wall of the mounting hole. The fixing portion is welded to the inner wall of the mounting hole, forming a welded portion at the step. The melting direction during welded portion formation is angled to the plane of the mounting plate. By extending the fixing portion away from the electrode assembly and using a welding method where the laser for welding the fixing portion and the mounting plate is tilted relative to the mounting plate, the risk of laser leakage during welding of the fixing portion to the inner wall of the mounting hole can be reduced, preventing damage to the electrode assembly, while ensuring a reliable connection between the fixing portion and the mounting plate, resulting in better welding quality and higher connection strength. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the battery cell structure provided in Embodiment 1 of the present invention;

[0033] Figure 2 This is a schematic diagram of the separate structure of the cover plate and the explosion-proof valve provided in Embodiment 1 of the present invention;

[0034] Figure 3 This is a cross-sectional view of the cover plate and explosion-proof valve assembled according to Embodiment 1 of the present invention;

[0035] Figure 4 for Figure 3 Enlarged view of a section at point A (before welding);

[0036] Figure 5 for Figure 3 Enlarged view of a portion of point A (after welding);

[0037] Figure 6 This is a schematic diagram of the battery cell structure provided in Embodiment 2 of the present invention;

[0038] Figure 7 This is a schematic diagram of the battery cell provided in Embodiment 3 of the present invention.

[0039] In the picture:

[0040] 100. Housing; 110. Side wall; 111. Opening; 112. Weld mark; 200. Cover plate; 200a. First cover plate; 200b. Second cover plate; 210. Mounting hole; 211. Straight wall surface; 212. Curved wall surface; 220. Pole post; 300. Explosion-proof valve; 310. Body part; 311. Scoring groove; 320. Fixing part; 3201. Step part; 321. Straight section; 322. Curved section; 330. Transition part; 400. Welded part. Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions. Furthermore, "above," "on top of," and "over" the first feature in relation to the second feature includes the first feature directly above and diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "under," and "below" the first feature in relation to the second feature includes the first feature directly below and diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0043] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0045] Example 1

[0046] like Figures 1-5 As shown, this embodiment provides a battery cell, which includes a housing and an explosion-proof valve 300. The cover plate 200 of the housing is a mounting plate, and the cover plate 200 has mounting holes 210 for mounting the explosion-proof valve 300. Both the housing and the explosion-proof valve 300 are made of stainless steel. Stainless steel has high hardness and mechanical strength, which can provide more reliable protection for the electrode assembly inside the battery cell. However, because of the high hardness and mechanical strength of stainless steel, it is not easy to stamp and form. Therefore, the explosion-proof valve 300 and the cover plate 200 in this embodiment adopt the following installation scheme.

[0047] Specifically, the mounting holes 210 on the cover plate 200 are directly formed by stamping or machining. No stepped structure is provided on the inner wall of the mounting holes 210. Along the first direction, the dimensions and shape of the mounting holes 210 are identical at all locations. The aforementioned first direction is... Figure 1 The X-axis direction is shown in the diagram. The explosion-proof valve 300 includes a body portion 310 and a fixing portion 320 surrounding the body portion 310. The fixing portion 320 extends away from the body portion 310 in a direction away from the electrode group and forms an annular structure. The outer peripheral wall of the fixing portion 320 is at least partially in contact with the inner wall of the mounting hole 210. Along the first direction, the end face of the fixing portion 320 away from the electrode group is lower than the end face of the cover plate 200 away from the electrode group, and a step portion 3201 is formed between the end face of the fixing portion 320 away from the electrode group and the inner wall of the mounting hole 210. The end of the fixing portion 320 away from the electrode group is laser welded to the inner wall of the mounting hole 210, and a molten pool is formed at the step portion 3201. After the molten pool cools and solidifies, a welded portion 400 is formed. It is important to note that, in order to prevent the welding laser from leaking through the gap between the fixing part 320 and the inner wall of the mounting hole 210, in this embodiment, when welding the fixing part 320 to the inner wall of the mounting hole 210, the welding laser is tilted relative to the plane of the cover plate 200. Consequently, the melting direction of the welding part 400 during formation forms an angle with the plane of the cover plate 200, and the plane of the cover plate 200 is perpendicular to the first direction. Since the direction of the welding laser is tilted relative to the cover plate 200 and towards the inner wall of the mounting hole 210, that is, the melting direction of the molten pool during welding is towards the inner wall of the mounting hole 210, the inner wall of the mounting hole 210 can shield the welding laser, preventing it from leaking in and causing damage to the electrode assembly.

[0048] Optionally, the central axis of the welded part 400 ( Figure 5 The angle between the plane containing the cover plate 200 and the plane marked with g is θ, and the value of θ is in the range of 30°≤θ≤75°. For example, the value of θ can be 30°, 40°, 50°, 60°, 70° or 75°, etc.

[0049] See also Figure 4 and Figure 5 To avoid the explosion-proof valve 300 occupying internal space and increasing the space for the electrode assembly, the end face of the body 310 of the explosion-proof valve 300 facing the electrode assembly can be flush with the end face of the cover plate 200 facing the electrode assembly, thereby improving the cell capacity. Alternatively, in some embodiments, the end face of the body 310 of the explosion-proof valve 300 facing the electrode assembly can be lower than the end face of the cover plate 200 facing the electrode assembly, achieving the same effect of avoiding the electrode assembly and saving space.

[0050] See also Figure 2 In this embodiment, the explosion-proof valve 300 is generally waist-shaped. The shape of the mounting hole 210 is adapted to the shape of the explosion-proof valve 300. There is a small assembly gap between the outer contour of the explosion-proof valve 300 and the inner wall of the mounting hole 210 to facilitate installation and positioning. The fixing part 320 includes two straight segments 321 arranged opposite each other along a second direction, and two arc-shaped segments 322 arranged opposite each other along a third direction. The straight segments 321 and the arc-shaped segments 322 are connected end to end in sequence, and the two straight segments 321 and the two arc-shaped segments 322 together form the above-mentioned annular structure. The second direction is... Figure 1 The Y-axis direction shown is the third direction. Figure 1 The Z-axis direction is shown in the diagram. Correspondingly, the mounting hole 210 includes two straight wall surfaces 211 arranged opposite each other along the second direction, and two arc-shaped wall surfaces 212 arranged opposite each other along the third direction. In a plane perpendicular to the first direction, the inner diameter of each arc-shaped wall surface 212 is uniform everywhere. The straight wall surface 211 mates with the outer wall of the straight segment 321, and the arc-shaped wall surface 212 mates with the outer wall of the arc-shaped segment 322. This allows for peripheral welding of the fixing part 320 to the inner wall of the mounting hole 210 around the circumference of the explosion-proof valve 300, ensuring a reliable connection and good sealing between the explosion-proof valve 300 and the cover plate 200. Alternatively, in some optional embodiments, the explosion-proof valve 300 can also be designed as circular, with the shape of the mounting hole 210 adapted to the shape of the explosion-proof valve 300, and a small assembly gap between the outer contour of the explosion-proof valve 300 and the inner wall of the mounting hole 210 to facilitate installation and positioning. The fixing part 320 includes only one arc segment, which forms a complete annular structure. The mounting hole 210 includes a cylindrical arc-shaped wall. In a plane perpendicular to the first direction, the inner diameter of the arc-shaped wall is equal everywhere, and the arc-shaped wall mates with the outer wall of the arc segment.

[0051] See Figure 4 and Figure 5 In this embodiment, the fixing part 320 can be formed by bending the circumferential edge of the main body part 310. Along the second direction, the thickness of the fixing part 320 is b, and the value of b ranges from 0.1mm to 0.5mm. For example, the value of b can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, or 0.5mm, etc. By limiting the value of b to the above range, the fixing part 320 of the explosion-proof valve 300 is guaranteed to have high mechanical strength. Otherwise, if the value of b is too small, the thickness of the fixing part 320 will be thin, resulting in insufficient material to melt at the fixing part 320 when welding it to the inner wall of the mounting hole 210. This would lead to a weak weld between the fixing part 320 and the inner wall of the mounting hole 210, and the fixing part 320 itself would have low mechanical strength, making the explosion-proof valve 300 prone to deformation and other problems. Of course, the value of b should not be too large, otherwise the thickness of the fixing part 320 will be too thick, affecting the size design of the main body part 310, which may reduce the area of ​​the exhaust channel of the explosion-proof valve 300, reduce the exhaust efficiency, and also increase the processing difficulty, making it difficult to form the fixing part 320.

[0052] Along the first direction, the distance between the end face of the fixing part 320 away from the electrode group and the end face of the cover plate 200 away from the electrode group is c, and the value of c is in the range of: b≤c≤1.0mm. For example, when the value of b is 0.1mm, the value of c can be 0.1mm, 0.3mm, or 0.5mm, etc. When the value of b is 0.3mm, the value of c can be 0.3mm, 0.5mm, or 0.8mm, etc. When the value of b is 0.5mm, the value of c can be 0.5mm, 0.8mm, or 1.0mm, etc. By limiting the value of c to the above range, a step part 3201 can be formed between the end of the fixing part 320 away from the electrode group and the inner wall of the mounting hole 210. The step part 3201 can provide space for the molten pool formed during welding, and prevent the weld part 400 formed after subsequent welding from protruding too much from the end face of the cover plate 200 away from the electrode group, which would affect the installation of the explosion-proof valve protection patch on the end face of the cover plate 200 away from the electrode group.

[0053] Furthermore, the height of the fixing part 320 extending along the first direction is 'a', and the value of 'a' ranges from 0.5mm to 2.0mm. For example, the value of 'a' can be 0.5mm, 0.8mm, 1.0mm, 1.5mm, or 2.0mm, etc. By limiting the value of 'a' to the above range, on the one hand, it facilitates the processing and manufacturing of the fixing part 320; on the other hand, it provides sufficient space for welding, ensuring sufficient material for melting when welding the fixing part 320 to the inner wall of the mounting hole 210, thereby ensuring the reliability of the weld between the two and improving the connection strength. Otherwise, if the value of 'a' is too small, the bending difficulty when processing the fixing part 320 on the body part 310 is greater, making it difficult to ensure processing accuracy, which may affect the assembly of the explosion-proof valve 300 and the mounting hole 210. The assembly problems of the explosion-proof valve 300 and the mounting hole 210 include: the risk of scratching the inner wall of the mounting hole 210; and the excessive assembly gap between the fixing part 320 and the inner wall of the mounting hole 210 in some positions, affecting the welding quality and posing a risk of hole explosion. Of course, the value of a should not be too large. Otherwise, the height of the fixing part 320 along the first direction will be large, and the thickness of the cover plate 200 that needs to be matched with it will need to be designed to be large. The outer shell of the battery cell will be relatively thick, which is not conducive to the lightweight design of the battery cell. If the thickness of the matching cover plate 200 is small, the body part 310 of the explosion-proof valve 300 will encroach on the space inside the outer shell, and the arrangement space of the electrode group will be reduced, which is not conducive to increasing the capacity of the battery cell.

[0054] See also Figure 4 When the fixing part 320 is formed by bending the circumferential edge of the main body 310, due to limitations in the manufacturing process, a transition part 330 is formed between the main body 310 and the fixing part 320. The transition part 330 has an arc-shaped chamfered structure. Optionally, the radius of curvature of the outer wall surface of the transition part 330 near the pole group is R, and the value of R is in the range of 0.2mm ≤ R ≤ 1.0mm. For example, the value of R can be 0.2mm, 0.5mm, 0.8mm, or 1.0mm, etc.

[0055] See also Figure 5Along the first direction, the distance between the lowest point of the melting direction when the welded part 400 is formed and the end face of the fixing part 320 on the side away from the electrode assembly is denoted as e. The value of e ranges from 0.2mm to 1.0mm. For example, the value of e can be 0.2mm, 0.3mm, 0.5mm, 0.8mm, or 1.0mm. By limiting the value of e to the above range, a reliable connection between the fixing part 320 and the inner wall of the mounting hole 210 can be guaranteed, resulting in good welding quality. Otherwise, if the value of e is too small, the molten pool formed on the inner wall of the mounting hole 210 during welding will be small, the welding strength between the fixing part 320 and the inner wall of the mounting hole 210 will be insufficient, and the explosion-proof valve 300 will easily fall off the cover plate 200, reducing reliability. If the value of e is too large, the welding power required during welding will be large, and the risk of hole explosion will easily occur.

[0056] Furthermore, along the first direction, the height of the welded part 400 protruding from the end face of the cover plate 200 on the side away from the electrode group is f, and the value of f is in the range of 0mm ≤ f ≤ 0.1mm. For example, the value of f can be 0mm, 0.05mm, or 0.1mm, etc. By limiting the value of f to the above range, the height of the welded part 400 protruding from the end face of the cover plate 200 on the side away from the electrode group is not too large, so as not to affect the setting of the explosion-proof valve protection patch on the end face of the cover plate 200 on the side away from the electrode group. The setting of the explosion-proof valve protection patch can prevent electrolyte or external dust from contacting the explosion-proof valve 300, which has a good protective effect on the explosion-proof valve 300 and helps to ensure its stable valve opening pressure.

[0057] See also Figure 2 and Figure 4 The main body 310 has a groove 311 on the end face facing away from the electrode group, with the groove opening facing away from the electrode group. Optionally, the groove 311 can be annular. In some embodiments, the groove 311 can also be a racetrack shape or C-shape with a notch, that is, the first and last ends of the groove 311 are not connected when the groove 311 is processed. This is to prevent the inner part of the groove 311 from flying out after the explosion-proof valve 300 is opened, causing a safety hazard. The inner side of the groove 311 forms an opening. When the pressure on one side of the explosion-proof valve 300 reaches the opening pressure, the groove 311 breaks, and an exhaust channel is formed at the opening formed by the inner side of the groove 311. The exhaust channel allows gas to pass through, realizing the pressure relief function of the explosion-proof valve 300. For example, the residual thickness at the groove 311 is t1, and the value range of t1 is: 0.01mm≤t1≤0.1mm. For example, the value of t1 can be 0.01mm, 0.02mm, 0.05mm, 0.08mm, or 0.1mm. By limiting the value of t1 to the above range, the body part 310 can still have sufficient connection strength at the groove 311 after machining, ensuring the stability and reliability of the opening pressure of the explosion-proof valve 300.

[0058] See also Figure 1 In this embodiment, the outer casing includes a housing 100 and two cover plates 200. The housing 100 has openings 111 on both opposite sides along a first direction. Each cover plate 200 is fastened to one opening 111 and welded to the housing 100. One of the cover plates 200 is a mounting plate. That is, one of the cover plates 200 has a mounting hole 210, and the explosion-proof valve 300 is mounted on one of the cover plates 200. For ease of explanation, the cover plate 200 with the explosion-proof valve 300 is designated as the first cover plate 200a, and the other cover plate 200 is designated as the second cover plate 200b.

[0059] The battery cell also includes two terminals 220, one of which is a positive terminal and the other is a negative terminal. Both the positive and negative terminals are located on the first cover plate 200a, and are positioned on opposite sides of the explosion-proof valve 300. The mounting hole 210 on the first cover plate 200a is located at the center of the first cover plate 200a along the second direction, and the positive and negative terminals are symmetrically arranged about the explosion-proof valve 300.

[0060] Furthermore, the casing 100 of the battery cell can be made using a long strip of steel. Specifically, after bending both ends of a long strip of steel towards each other along its length, the ends of the long strip of steel are bent again along its length. Finally, the two opposite sides of the long strip of steel are welded together, forming a weld mark 112 at the joint, thereby forming a cylindrical casing 100. The cylindrical casing 100 includes four side walls 110, and the casing 100 has openings 111 at both ends along a first direction. The first direction is also the width direction of the long strip of steel, which is perpendicular to the length direction. Optionally, in some embodiments, the weld mark 112 is located on the smaller side wall 110 of the casing 100.

[0061] Optionally, the wall thickness of the housing 100 is t2, which is the thickness of the elongated steel plate. The value of t2 ranges from 0.1mm to 0.3mm. For example, the value of t2 can be 0.1mm, 0.2mm, or 0.3mm, etc. By controlling the value of t2 within the above range, the housing 100 is guaranteed to have high mechanical strength, be able to resist a certain impact, and provide good protection for the electrode assembly. If the value of t2 is too small, the wall thickness of the housing 100 is too thin, and the mechanical strength is insufficient. On the one hand, the housing 100 is difficult to form during processing, and the dimensional accuracy is difficult to guarantee; on the other hand, the housing 100 deforms severely when impacted, and the protection effect for the electrode assembly decreases. If the value of t2 is too large, the wall thickness of the housing 100 is too thick, resulting in excessive design redundancy, large material usage, high cost, and increased weight of the battery cell.

[0062] See also Figure 4In this embodiment, the thickness of the cover plate 200 (i.e., the first cover plate 200a) is d, and the value of d ranges from 0.5mm to 1.2mm. For example, the value of d can be 0.5mm, 0.8mm, 1.0mm, or 1.2mm, etc. By controlling the value of d within the above range, the cover plate 200 is guaranteed to have high mechanical strength, be able to resist a certain impact, and provide good protection for the electrode assembly. If the value of d is too small, the cover plate 200 is too thin, the mechanical strength is insufficient, and it will deform severely when impacted, reducing the protection effect for the electrode assembly. If the value of d is too large, the thickness of the cover plate 200 is too large, resulting in excessive design redundancy, large material usage, high cost, and increased weight of the battery cell. Optionally, the thickness of the second cover plate 200b is equal to the thickness of the first cover plate 200a.

[0063] Of course, in other embodiments, the housing and explosion-proof valve 300 may also be made of aluminum or other metal materials, and the installation structure between the housing and explosion-proof valve 300 may also adopt the above-mentioned structure and design parameters. There is no limitation on the specific materials of the housing and explosion-proof valve 300.

[0064] The following uses samples from specific implementation cases to verify the range of values ​​for relevant parameters b and c in the assembly structure between the explosion-proof valve 300 and the cover plate 200. See Table 1 for details.

[0065] Table 1

[0066]

[0067] As can be seen from the above results, the values ​​of parameters b and c in Examples 1 to 5 all meet their corresponding dimensional limitations. The fixing part 320 of the explosion-proof valve 300 has high forming precision, and its outer contour is smooth and rounded. The fixing part 320 of the explosion-proof valve 300 fits well with the inner wall of the mounting hole 210 of the cover plate 200. Therefore, after welding, the welding trajectory of the welded part 400 formed between the fixing part 320 and the inner wall of the mounting hole 210 of the cover plate 200 is flat and has a good appearance. At the same time, the welded part 400 does not protrude from the end face of the cover plate 200 away from the electrode group, and does not affect the setting of the explosion-proof valve protective patch on the end face of the cover plate 200 away from the electrode group, indicating a good product.

[0068] In Comparative Example 1, the value of parameter c is greater than the maximum value of its range b≤c≤1.0mm. The height difference between one end of the fixing part 320 away from the electrode group and the end face of the cover plate 200 away from the electrode group is large. When the fixing part 320 and the inner wall of the mounting hole 210 are welded in an inclined manner, the welding head used to emit the welding laser is not easy to penetrate into the mounting hole 210, the welding operation is inconvenient, the final welded part 400 has an uneven appearance, the welding quality is reduced, and the product is defective.

[0069] In Comparative Example 2, the value of parameter c is less than the minimum value within its range of b ≤ c ≤ 1.0 mm, i.e., c < b. The height difference between the end of the fixing part 320 away from the electrode assembly and the end face of the cover plate 200 away from the electrode assembly is too small. The space at the stepped part 3201 formed by the end of the fixing part 320 away from the electrode assembly and the inner wall of the mounting hole 210 is too small to accommodate the welded part 400 formed after the molten pool cools and solidifies. This results in the welded part 400 protruding excessively from the end face of the cover plate 200 away from the electrode assembly, affecting the installation of the explosion-proof valve protective patch and leading to product defects.

[0070] The following uses samples from specific implementation cases to verify the range of values ​​for the relevant parameter θ of the assembly structure between the explosion-proof valve 300 and the cover plate 200. See Table 2 for details.

[0071] Table 2

[0072]

[0073] As can be seen from the above results, the values ​​of parameter θ in Examples 1 to 5 meet their size limitations, the welding quality between the fixing part 320 of the explosion-proof valve 300 and the inner wall of the mounting hole 210 on the cover plate 200 is good, the welding trajectory is flat, there are no explosion points, and the product is good.

[0074] In Comparative Examples 1 and 2, the value of parameter θ is less than the minimum value of its range of 30°≤θ≤75°. When the fixing part 320 of the explosion-proof valve 300 is welded to the inner wall of the mounting hole 210 on the cover plate 200, the welding angle is too small. The welding head used to emit the welding laser is not easy to penetrate into the mounting hole 210, making the operation difficult. As a result, the welded part 400 formed after welding has an uneven appearance and the weld width of the welded part 400 fluctuates greatly, the welding quality is reduced, and the product is defective.

[0075] In Comparative Example 3, the value of θ is greater than its maximum value within the range of 30°≤θ≤75°. The weld quality of the welded part 400 formed by welding the fixing part 320 of the explosion-proof valve 300 to the inner wall of the mounting hole 210 on the cover plate 200 is poor, the penetration depth of the welded part 400 fluctuates greatly, the weld quality is reduced, and the product is defective.

[0076] In Comparative Example 4, the value of θ is 90°, which is greater than the maximum value of its range of 30°≤θ≤75°. At this time, the fixing part 320 of the explosion-proof valve 300 and the inner wall of the mounting hole 210 on the cover plate 200 are welded by conventional butt welding. During welding, there is a risk of molten beads dripping and burning the electrode assembly. Moreover, problems such as hole bursting and incomplete welding are prone to occur during welding. The welding quality of the welding part 400 is poor, and the cover plate 200 is at risk of being burned, resulting in product defects.

[0077] In Comparative Example 5, the value of θ is greater than 90°, which is greater than the maximum value of its range of 30°≤θ≤75°. At this time, the welding laser is directed towards the explosion-proof valve 300, and the melting direction is also towards the explosion-proof valve 300. When welding the fixing part 320 of the explosion-proof valve 300 to the inner wall of the mounting hole 210 on the cover plate 200, the cover plate 200 is easily burned, and the weld strength of the welded part 400 is poor after welding, making it prone to cracking and resulting in defective products.

[0078] The following uses samples from specific implementation cases to verify the range of values ​​for the relevant parameter e of the assembly structure between the explosion-proof valve 300 and the cover plate 200. See Table 3 for details.

[0079] Table 3

[0080]

[0081] As can be seen from the above results, the values ​​of parameter e in Examples 1 to 5 meet their size limitations. The welding between the fixing part 320 of the explosion-proof valve 300 and the inner wall of the mounting hole 210 of the cover plate 200 is good. The connection strength of the welded part 400 formed after the two are welded is high. When the explosion-proof valve 300 is opened, the welded part 400 does not crack. The reliability is high and the product is good.

[0082] In Comparative Examples 1 and 2, the value of parameter e is less than the minimum value of its range of 0.2mm≤e≤1.0mm. The welding quality between the fixing part 320 of the explosion-proof valve 300 and the inner wall of the mounting hole 210 of the cover plate 200 is poor. The connection strength of the welded part 400 formed after the two are welded is low, and there are cases of false welding in some places. When the explosion-proof valve 300 is opened, the welded part 400 cracks, resulting in poor reliability and product defects.

[0083] In Comparative Examples 3 and 4, the value of parameter e is greater than the maximum value within its range of 0.2 mm ≤ e ≤ 1.0 mm. The welding quality between the fixing part 320 of the explosion-proof valve 300 and the inner wall of the mounting hole 210 of the cover plate 200 is poor. During welding, there are cases of cratering and dripping of molten beads, which can easily damage the electrode group inside the battery cell, reduce the processing yield, and result in defective products.

[0084] Taking all factors into consideration, when the assembly structure between the explosion-proof valve 300 and the cover plate 200 meets the aforementioned dimensional limitations, it can be ensured that the weld trajectory of the welded part 400 formed between the fixing part 320 of the explosion-proof valve 300 and the inner wall of the mounting hole 210 of the cover plate 200 is smooth, with a good appearance, and the welded part 400 has high strength and is not prone to cracking. At the same time, it does not affect the setting of the explosion-proof valve protective patch on the end face of the cover plate 200 away from the electrode group, resulting in a good product.

[0085] Example 2

[0086] This embodiment provides a battery cell that differs from the battery cell in Embodiment 1 in that the positions of the terminals 220 and the explosion-proof valve 300 are different in this embodiment.

[0087] See Figure 6 In this embodiment, the outer casing of the battery cell includes a housing 100 and two cover plates 200, with the housing 100 along a first direction ( Figure 6 Openings 111 are provided on both sides of the cover plate 200 (in the X-axis direction shown). Each cover plate 200 is fastened to one opening 111 and welded to the housing 100. One of the cover plates 200 is a mounting plate. The mounting plate has mounting holes 210, and the explosion-proof valve 300 is mounted on one of the cover plates 200. For ease of explanation, the cover plate 200 with the explosion-proof valve 300 is named the first cover plate 200a, and the other cover plate 200 is named the second cover plate 200b.

[0088] The first cover plate 200a has a mounting hole 210, and an explosion-proof valve 300 is disposed in the mounting hole 210. The explosion-proof valve 300 is located at the middle position of the first cover plate 200a along the second direction. Of course, in other embodiments, the explosion-proof valve 300 can also be eccentrically disposed on the first cover plate 200a as needed. For example, the explosion-proof valve 300 can also be disposed on the first cover plate 200a along the second direction ( Figure 6 One end of the cell (in the Y-axis direction shown). The second cover plate 200b of the battery cell is provided with two terminals 220, one of which is a positive terminal and the other is a negative terminal. The positive terminal and the negative terminal are respectively located at both ends of the second cover plate 200b along the second direction.

[0089] The remaining structures in this embodiment are the same as those in Embodiment 1, and will not be described in detail here.

[0090] Example 3

[0091] This embodiment provides a battery cell that differs from the battery cell in Embodiment 1 in that the positions of the terminals 220 and the explosion-proof valve 300 are different in this embodiment.

[0092] See Figure 7 In this embodiment, the outer casing of the battery cell includes a housing 100 and two cover plates 200, with the housing 100 along a first direction ( Figure 7 Openings 111 are provided on both sides of the cover plate 200 (in the X-axis direction shown). Each cover plate 200 is fastened to one opening 111 and welded to the housing 100. One of the cover plates 200 is a mounting plate. The mounting plate has mounting holes 210, and the explosion-proof valve 300 is mounted on one of the cover plates 200. For ease of explanation, the cover plate 200 with the explosion-proof valve 300 is named the first cover plate 200a, and the other cover plate 200 is named the second cover plate 200b.

[0093] The first cover plate 200a is provided with a mounting hole 210 and a positive terminal post. An explosion-proof valve 300 is provided in the mounting hole 210. The explosion-proof valve 300 is located on the first cover plate 200a along the second direction ( Figure 7 The positive terminal is located at one end of the first cover plate 200a along the second direction (as shown in the Y-axis direction). The second cover plate 200b of the battery cell has a negative terminal located at the middle position along the second direction. Alternatively, in other embodiments, the negative terminal can be mounted on the first cover plate 200a, and the positive terminal on the second cover plate 200b.

[0094] The remaining structures in this embodiment are the same as those in Embodiment 1, and will not be described in detail here.

[0095] Example 4

[0096] This embodiment provides a battery cell that differs from the battery cell in Embodiment 1 in that the explosion-proof valve 300 is positioned differently in this embodiment.

[0097] In this embodiment, the outer casing of the battery cell includes a housing 100 and two cover plates 200. The housing 100 has openings 111 on both opposite sides along a first direction. Each cover plate 200 is fastened to one opening 111 and welded to the housing 100. One side wall 110 of the housing 100 serves as a mounting plate. A mounting hole 210 is provided on one side wall 110 of the housing 100, and an explosion-proof valve 300 is installed within the mounting hole 210. The positive and negative terminals are both mounted on the same cover plate 200. Alternatively, in other embodiments, the positive and negative terminals may each be mounted on a separate cover plate 200.

[0098] The remaining structures in this embodiment are the same as those in Embodiment 1, and will not be described in detail here.

[0099] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A battery cell, characterized in that, include: The housing includes a mounting plate with mounting holes. An explosion-proof valve includes a body and a fixing part surrounding the body. The fixing part extends away from the body in a direction away from the electrode group and forms an annular structure. The outer peripheral wall of the fixing part is at least partially in contact with the inner wall of the mounting hole. Along a first direction, the end face of the fixing part away from the electrode group is lower than the end face of the mounting plate away from the electrode group, and a step is formed between the end face of the fixing part away from the electrode group and the inner wall of the mounting hole. Wherein, the end of the fixing part away from the pole group is welded to the inner wall of the mounting hole and forms a welding part at the step portion. The melting direction of the welding part is set at an angle to the plane of the mounting plate, and the melting direction is towards the inner wall of the mounting hole. The plane of the mounting plate is perpendicular to the first direction. The angle between the central axis of the welding part and the plane of the mounting plate is θ. The range of θ is: 30°≤θ≤75°.

2. The battery cell according to claim 1, characterized in that, The fixing part includes two straight segments arranged opposite each other along a second direction and two arc-shaped segments arranged opposite each other along a third direction, the two straight segments and the two arc-shaped segments forming the annular structure; the mounting hole includes two straight wall surfaces arranged opposite each other along the second direction and two arc-shaped wall surfaces arranged opposite each other along the third direction, and the inner diameter of each arc-shaped wall surface is equal everywhere in a plane perpendicular to the first direction; the straight wall surface mates with the outer wall of the straight segment, and the arc-shaped wall surface mates with the outer wall of the arc-shaped segment; Alternatively, the fixing part includes an arc segment that forms the annular structure; the mounting hole includes a cylindrical arc-shaped wall surface, and the inner diameter of the arc-shaped wall surface is equal everywhere in a plane perpendicular to the first direction; the arc-shaped wall surface mates with the outer wall of the arc segment.

3. The battery cell according to claim 1, characterized in that, The thickness of the fixing part along the second direction is b; along the first direction, the distance between the end face of the fixing part facing away from the electrode group and the end face of the mounting plate facing away from the electrode group is c. The value of b is in the range of: 0.1mm ≤ b ≤ 0.5mm; The range of values ​​for c is: b≤c≤1.0mm.

4. The battery cell according to claim 1, characterized in that, The height of the fixing part extending along the first direction is a, and the value of a is in the range of 0.5mm≤a≤2.0mm.

5. The battery cell according to claim 1, characterized in that, Along the first direction, the distance between the lowest point of the melting direction when the welded part is formed and the end face of the fixing part on the side away from the electrode group is e; The value range of e is: 0.2mm≤e≤1.0mm.

6. The battery cell according to claim 1, characterized in that, Along the first direction, the height f of the welded portion protruding from the end face of the mounting plate opposite to the electrode assembly is . The value range of f is: 0mm≤f≤0.1mm.

7. The battery cell according to claim 1, characterized in that, The end face of the main body away from the pole group is provided with a groove, and the residual thickness at the groove is t1; The value range of t1 is: 0.01mm≤t1≤0.1mm.

8. The battery cell according to claim 1, characterized in that, The outer casing includes a housing and two cover plates. The housing has openings on opposite sides along a first direction. Each cover plate is fastened to one of the openings and connected to the housing. One of the cover plates is the mounting plate.

9. The battery cell according to claim 8, characterized in that, The wall thickness of the shell is t2; The range of t2 is: 0.1mm ≤ t2 ≤ 0.3mm; The thickness of the cover plate is d; The value range of d is: 0.5mm≤d≤1.2mm.

10. The battery cell according to claim 1, characterized in that, Both the outer casing and the explosion-proof valve (300) are made of stainless steel.

Images