Battery cell

Abstract

The invention belongs to the technical field of batteries, and particularly discloses a battery cell, at least one end of a shell of the battery cell is provided with an opening, a cover plate is arranged at the opening, and the cover plate and the shell jointly define an accommodating space for mounting a pole group. An abutted seam is formed between the circumferential side wall of the cover plate and the inner wall of the shell. In the first direction, the end face of the cover plate away from the pole group side is higher than the end face of the shell towards the cover plate side, so that a step part is formed therebetween. On the outer side, away from the containing space, of the abutted seam, the shell and the cover plate are welded and connected at the step part to form a welding part, an included angle is formed between the melting direction when the welding part is formed and the plane where the cover plate is located, the melting direction faces the circumferential side wall of the cover plate, and the plane where the cover plate is located is perpendicular to the first direction. By means of the welding mode that the laser for welding the shell and the cover plate inclines relative to the cover plate, the risk that the laser leaks into the containing space from the abutted seam when the shell and the cover plate are welded is reduced, the pole group is prevented from being burnt, and meanwhile reliable connection between the shell and the cover plate is guaranteed.

Description

A type of battery cell Technical Field

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

[0002] In steel-cased batteries, both the casing and the cover are made of stainless steel, a material with high hardness. Compared to conventional aluminum-cased batteries, it's difficult to machine a step on the inner wall of the casing near the opening to fit the cover. Typically, after the casing and cover are aligned, the seam between them is directly welded. However, due to the lack of a step to support the cover, it's difficult to position the cover, resulting in decreased welding quality and assembly accuracy. Furthermore, without a step to shield the laser, the laser can easily leak in through the seam between the cover and casing, potentially burning the internal electrode assembly and reducing product yield. Summary of the Invention

[0003] The purpose of this invention is to provide a battery cell in which laser leakage is less likely to burn the electrode assembly during the welding of the casing and the cover plate, and the welding quality between the casing and the cover plate is good, the welding yield is high, and the connection is reliable.

[0004] To achieve this objective, the present invention adopts the following technical solution: The present invention provides a battery cell, comprising: a housing, wherein at least one end of the housing is provided with an opening; a cover plate, wherein the cover plate is disposed at the opening, the cover plate and the housing together forming an accommodating space for mounting an electrode assembly, and a seam is formed between the circumferential sidewall of the cover plate and the inner wall of the housing; along a first direction, the end face of the cover plate opposite to the electrode assembly is higher than the end face of the housing facing the cover plate, and a step is formed between the end face of the cover plate opposite to the electrode assembly and the end face of the housing facing the cover plate; on the outer side of the seam away from the accommodating space, the housing and the cover plate are welded together at the step to form a welded portion, wherein the melting direction of the welded portion is set at an angle to the plane of the cover plate, the melting direction is toward the circumferential sidewall of the cover plate, and the plane of the cover plate is perpendicular to the first direction.

[0005] Optionally, the angle between the melting direction when the weld is formed and the plane of the cover plate is θ; the value of θ is in the range of 30°≤θ≤75°.

[0006] Optionally, the wall thickness of the shell is a; the value of a ranges from 0.1mm to a ≤ 0.3mm.

[0007] Optionally, the thickness of the cover plate is b; the value of b is in the range of 0.5mm≤b≤1.2mm.

[0008] Optionally, along the first direction, the height difference between the end face of the cover plate away from the pole group and the end face of the housing facing the cover plate is c; the relationship between c and a satisfies: 0.5≤c / a≤1.5.

[0009] Optionally, the portion of the welded part located on the shell is a first melting zone; along the first direction, the melting depth of the first melting zone is t; the relationship between t and b, c satisfies: 0.1mm≤t≤0.8×(bc).

[0010] Optionally, the portion of the welded part located on the cover plate is the second molten region; the weld width of the second molten region is w along a direction parallel to the cover plate; the value range of w is: 0.1mm≤w≤1mm.

[0011] Optionally, two cover plates are provided, and the housing has openings on opposite sides along the first direction. Each cover plate is fastened to one of the openings and welded to the housing.

[0012] Optionally, the shell is formed by bending the two ends of a long strip steel plate twice in opposite directions along its length, and then welding the two opposite sides of the long strip steel plate together to form a weld mark at the joint, thereby forming the cylindrical shell.

[0013] Optionally, both the housing and the cover are made of steel.

[0014] The beneficial effects of this invention are as follows: This invention provides a battery cell comprising a housing and a cover plate. At least one end of the housing has an opening, and the cover plate is disposed at the opening. The cover plate and the housing together form an accommodating space for mounting an electrode assembly. A seam is formed between the circumferential sidewall of the cover plate and the inner wall of the housing. Along a first direction, the end face of the cover plate facing away from the electrode assembly is higher than the end face of the housing facing the cover plate, forming a step between them. On the outer side of the seam away from the accommodating space, the housing and the cover plate are welded together at the step to form a welded portion. The melting direction during the formation of the welded portion is angled to the plane of the cover plate, with the melting direction pointing towards the circumferential sidewall of the cover plate. The plane of the cover plate is perpendicular to the first direction. By using a welding method where the laser used to weld the housing and the cover plate is tilted relative to the cover plate, the risk of laser leakage from the seam into the accommodating space during welding of the housing and the cover plate can be reduced, preventing the electrode assembly from being burned. Simultaneously, a reliable connection between the housing and the cover plate is ensured, resulting in better welding quality and higher connection strength. Attached Figure Description

[0015] Figure 1 is an exploded view of the battery cell provided in Embodiment 1 of the present invention; Figure 2 is a cross-sectional view of the battery cell provided in Embodiment 1 of the present invention; Figure 3 is a partial enlarged view of part I in Figure 2 (before welding); Figure 4 is a partial enlarged view of part I in Figure 2 (after welding); Figure 5 is an exploded view of the battery cell provided in Embodiment 2 of the present invention.

[0016] In the figure: 100, shell; 110, side wall; 1101, step; 111, opening; 112, weld mark; 200a, first cover plate; 200b, second cover plate; 210, positive electrode post; 220, negative electrode post; 300, welded part; 310, first melting zone; 320, second melting zone; 330, third melting zone. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0018] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0020] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, 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 present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0021] As shown in Figures 1-4, this embodiment provides a battery cell comprising a housing 100 and a cover plate. Both the housing 100 and the cover plate are made of steel. Steel has high hardness and mechanical strength, providing more reliable protection for the electrode assembly inside the battery cell. However, due to the high hardness and mechanical strength of steel, it is not easy to stamp a step on the housing 100 to support the cover plate. Therefore, the following installation scheme is adopted between the housing 100 and the cover plate in this embodiment.

[0022] Specifically, at least one end of the housing 100 has an opening 111, and a cover plate is disposed at the opening 111. The cover plate and the housing 100 together form an accommodating space for mounting the electrode assembly. A joint is formed between the circumferential sidewall of the cover plate and the inner wall of the housing 100. Along a first direction, the end face of the cover plate facing away from the electrode assembly is higher than the end face of the housing 100 facing the cover plate, so as to form a step portion 1101 between the two. The first direction is perpendicular to the plane where the cover plate is located, that is, the X-axis direction shown in FIG1. ​​On the outer side of the joint away from the accommodating space, the housing 100 and the cover plate are welded together at the step portion 1101 to form a weld portion 300. The melting direction of the weld portion 300 during its formation is set at an angle to the plane where the cover plate is located, and the melting direction is towards the circumferential sidewall of the cover plate. By tilting the laser of the welding housing 100 to the cover plate relative to the cover plate, the risk of laser leakage from the joint into the accommodating space during welding of the housing 100 and the cover plate can be reduced, avoiding burns to the electrode assembly. At the same time, it ensures a reliable connection between the housing 100 and the cover plate, resulting in better welding quality and higher connection strength.

[0023] Optionally, the angle between the melting direction (indicated by g in Figure 4) during the formation of the welded part 300 and the plane of the cover plate 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. By limiting the value of θ to the above range, a reliable connection between the housing 100 and the cover plate can be ensured, the welding quality of the welded part 300 can be good, and the welding laser can be shielded by the circumferential sidewall of the cover plate, preventing the welding laser from leaking into the accommodating space and causing damage to the electrode assembly. It should be noted that the value of θ should not be too small, otherwise part of the welding laser will be directly directed towards the circumferential sidewall of the cover plate, the welded part 300 on the housing 100 will have a small molten pool, the connection strength between the housing 100 and the cover plate will decrease, the connection will be unreliable, and the sealing performance will be poor; the value of θ should also not be too large, otherwise when the joint is large, the welding laser can easily leak into the accommodating space from the joint, thereby causing the electrode assembly to be burned and the yield of the finished product to decrease.

[0024] Furthermore, in this embodiment, the shell 100 has openings 111 on both opposite sides along the first direction, and two cover plates are provided. Each cover plate is fastened to one opening 111 and welded to the shell 100 using the connection method described above. One cover plate is designated as the first cover plate 200a, and the other cover plate is designated as the second cover plate 200b. In this embodiment, the welding connection between the first cover plate 200a and the shell 100 is used as an example for explanation. Furthermore, the shell 100 can be made using a long strip of steel plate. Specifically, after bending both ends of a long strip of steel plate towards each other along its length, the end of the long strip of steel plate is bent again along its length. Finally, the two opposite sides of the long strip of steel plate are welded together, forming a weld mark 112 at the joint, thereby forming a cylindrical shell 100. The cylindrical shell 100 includes four side walls 110, and the shell 100 has openings 111 at both ends along the first direction. The first direction is also the width direction of the elongated steel plate, which is perpendicular to its length direction. Optionally, in some embodiments, the weld mark 112 is located on the smaller side wall surface 110 of the housing 100.

[0025] Referring again to Figures 3 and 4, the wall thickness of the casing 100 is 'a', which is also the thickness of the elongated steel plate. The value of 'a' ranges from 0.1mm to 0.3mm. For example, the value of 'a' can be 0.1mm, 0.2mm, or 0.3mm, etc. By controlling the value of 'a' within the above range, the casing 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 'a' is too small, the wall thickness of the casing 100 is too thin, resulting in insufficient mechanical strength. On the one hand, the casing 100 is difficult to form during processing, and dimensional accuracy is difficult to guarantee; on the other hand, the casing 100 deforms severely when subjected to impact, reducing the protection effect for the electrode assembly. If the value of 'a' is too large, the wall thickness of the casing 100 is too thick, resulting in excessive design redundancy, large material usage, high cost, and increased weight of the battery cell.

[0026] The thickness of the first cover plate 200a is b, and the value of b ranges from 0.5mm to 1.2mm. For example, the value of b can be 0.5mm, 0.8mm, 1.0mm, or 1.2mm, etc. By controlling the value of b within the above range, the first cover plate 200a 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 b is too small, the first cover plate 200a is too thin, its mechanical strength is insufficient, it deforms severely when impacted, and its protection for the electrode assembly decreases. If the value of b is too large, the thickness of the first cover plate 200a is too large, resulting in excessive design redundancy, large material usage, high cost, and increased cell weight. Optionally, the thickness of the second cover plate 200b is equal to the thickness of the first cover plate 200a.

[0027] Optionally, along the first direction, the height difference between the end face of the first cover plate 200a facing away from the electrode group and the end face of the housing 100 facing the first cover plate 200a is c, and the relationship between c and a satisfies: 0.5 ≤ c / a ≤ 1.5. For example, the value of c / a can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5, etc. By limiting the value of c / a within the above range, welding operations are facilitated, while ensuring that sufficient melting space is formed at the step portion 1101, allowing the welded portion 300 to flow freely within the melting space. The welded portion 300 has good welding quality and appearance, without pores or incomplete welds, and the connection strength between the housing 100 and the first cover plate 200a is high. The c / a value should not be too small, otherwise the molten space formed at the step 1101 will be too small, making it inconvenient for the laser-emitting welding head to perform welding operations. Moreover, the molten material of the shell 100 and the first cover plate 200a will not have enough space to flow, and some of the molten material may flow along the outer wall of the shell 100. Furthermore, the edges of the shell 100 at the end along the first direction may not be melted, resulting in sharp corners and a poor appearance of the final battery cell. The c / a value should not be too large either, otherwise there may be a height difference between the welded part 300 formed after the shell 100 and the first cover plate 200a are welded and the end face of the first cover plate 200a on the side away from the electrode group. The edges where the circumferential sidewall of the first cover plate 200a intersects with the end face of the first cover plate 200a on the side away from the electrode group may not be melted, resulting in sharp corners and a poor appearance of the final battery cell.

[0028] Furthermore, the portion of the welded part 300 located on the housing 100 is the first melting region 310, the portion of the welded part 300 located on the first cover plate 200a is the second melting region 320, and the portion of the welded part 300 located at the step portion 1101 is the third melting region 330. The welded part 300 is composed of the first melting region 310, the second melting region 320, and the third melting region 330.

[0029] Along the first direction, the melting depth of the first molten region 310 is t, and the relationship between t and b, c satisfies: 0.1mm ≤ t ≤ 0.8 × (bc). For example, when the value of b is 0.5mm and the value of c is 0.3mm, the value of t can be 0.1mm, 0.12mm, 0.14mm, or 0.16mm, etc. When the value of b is 1.0mm and the value of c is 0.3mm, the value of t can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, or 0.56mm, etc. When the value of b is 1.2mm and the value of c is 0.45mm, the value of t can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, or 0.6mm, etc. By limiting the value of t within the aforementioned range, the depth of the first molten region 310 of the welded part 300 on the housing 100 is ensured to be large, the connection between the housing 100 and the first cover plate 200a is reliable and well-sealed, and the housing 100 does not deform. If the value of t is too small, the connection strength between the housing 100 and the first cover plate 200a is low, and the sealing performance is poor; if the value of t is too large, the welding power required is large, the housing 100 is prone to deformation, which in turn leads to a larger joint between the housing 100 and the first cover plate 200a. Molten beads generated during welding may fall from the joint into the accommodating space, causing damage to the electrode assembly.

[0030] Along the direction parallel to the first cover plate 200a (i.e., the second direction, as shown by the Y-axis in Figure 4), the weld width of the second molten region 320 is w, and the value of w ranges from 0.1mm to 1mm. For example, the value of w can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1.0mm, etc. By limiting the value of w to the above range, it is ensured that the weld width of the second molten region 320 of the welded part 300 on the first cover plate 200a is large, and the connection between the shell 100 and the first cover plate 200a is reliable and well-sealed. If the value of w is too small, the connection strength between the shell 100 and the first cover plate 200a is low, and the sealing performance is poor; if the value of w is too large, the welding power required is large, and there is a risk of welding defects such as porosity, resulting in poor welding quality.

[0031] Further referring to Figures 1 and 2, the battery cell also includes a positive terminal 210 and a negative terminal 220. Both the positive terminal 210 and the negative terminal 220 are disposed on the first cover plate 200a, and the positive terminal 210 and the negative terminal 220 are respectively placed on both sides of the first cover plate 200a along the second direction, and the positive terminal 210 and the negative terminal 220 are symmetrically arranged about the center of the first cover plate 200a.

[0032] The following uses samples from specific implementation cases to verify the relevant dimensional design of the above-mentioned battery cells. See Table 1 for details.

[0033] Table 1

[0034] As can be seen from the above results, the values ​​of parameters c, a, and c / a in Examples 1 to 5 all meet their corresponding size limitations. The welding quality of the welded part 300 between the shell 100 and the first cover plate 200a is good, and there are no welding defects such as false welding or bursting. The sealing effect of the joint between the shell 100 and the first cover plate 200a is good. After long-term use, it can still pass the helium test, with a long service life, high reliability, and good product quality.

[0035] In Comparative Examples 1 and 2, the value of parameter c / a is less than the minimum value of its range 0.5 ≤ c / a ≤ 1.5. In this case, the battery cell has a poor appearance; the edges of the casing 100 along the first direction are sharp and easily cut the insulating film covering the battery cell (e.g., the blue film commonly used in the industry), resulting in a defective product.

[0036] In Comparative Examples 3 and 4, the value of parameter c / a is greater than the maximum value in its range of 0.5 ≤ c / a ≤ 1.5. In this case, the cell has a defective appearance; the edge where the circumferential sidewall of the first cover plate 200a intersects with the end face of the first cover plate 200a on the side opposite to the electrode assembly is not melted; the first cover plate 200a has sharp edges that can easily cut the insulating film covering the cell (e.g., the blue film commonly used in the industry), resulting in a defective product.

[0037] Taking all factors into consideration, when the dimensions of the cell's c, a, and c / a all meet the above-mentioned dimensional requirements, it can be ensured that the connection strength between the housing 100 and the first cover plate 200a is high, the sealing performance at the connection between the housing 100 and the first cover plate 200a is good, and the appearance of the cell is good.

[0038] Example 2 This example provides a battery cell, which differs from the battery cell in Example 1 in that the positions of the positive terminal 210 and the negative terminal 220 on the cover plate of the battery cell in this example are different.

[0039] Referring to Figure 5, in this embodiment, the battery cell includes a housing 100 and two cover plates. The housing 100 has openings 111 on opposite sides along a first direction (the X-axis direction shown in Figure 5). Each cover plate is fastened to one opening 111 and welded to the housing 100. One cover plate is designated as the first cover plate 200a, and the other as the second cover plate 200b. The positive terminal 210 can be eccentrically positioned on the first cover plate 200a along a second direction (the Y-axis direction shown in Figure 5). Alternatively, the positive terminal 210 can be positioned at the center of the first cover plate 200a along the second direction. The negative terminal 220 can be eccentrically positioned on the second cover plate 200b along the second direction. Alternatively, the negative terminal 220 can also be positioned at the center of the second cover plate 200b along the second direction.

[0040] The remaining structures in this embodiment are the same as those in Embodiment 1, and will not be described in detail here.

[0041] 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 will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. 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: A housing, wherein at least one end of the housing is provided with an opening; A cover plate is disposed at the opening, and the cover plate and the housing together form an accommodating space for installing the electrode assembly, and a joint is formed between the circumferential sidewall of the cover plate and the inner wall of the housing; Along the first direction, the end face of the cover plate facing away from the electrode group is higher than the end face of the housing facing the cover plate, and a step is formed between the end face of the cover plate facing away from the electrode group and the end face of the housing facing the cover plate; on the outer side of the joint away from the accommodating space, the housing and the cover plate are welded together at the step to form a welded part, and the melting direction when the welded part is formed is set at an angle to the plane of the cover plate, the melting direction is towards the circumferential sidewall of the cover plate, and the plane of the cover plate is perpendicular to the first direction.

2. The battery cell according to claim 1, characterized in that, The angle between the melting direction when the weld is formed and the plane of the cover plate is θ; the value of θ is in the range of 30°≤θ≤75°.

3. The battery cell according to claim 1, characterized in that, The wall thickness of the shell is a; the value of a ranges from 0.1mm to a and from 0.3mm to 0.1mm to 0.3mm.

4. The battery cell according to claim 3, characterized in that, The thickness of the cover plate is b; the value of b is in the range of 0.5mm≤b≤1.2mm.

5. The battery cell according to claim 4, characterized in that, Along the first direction, the height difference between the end face of the cover plate away from the pole group and the end face of the housing facing the cover plate is c; the relationship between c and a satisfies: 0.5≤c / a≤1.

5.

6. The battery cell according to claim 5, characterized in that, The portion of the welded part located on the shell is the first melting zone; Along the first direction, the melting depth of the first molten region is t; the relationship between t and b and c satisfies: 0.1mm≤t≤0.8×(bc).

7. The battery cell according to claim 1, characterized in that, The portion of the weld located on the cover plate is the second molten region; the weld width of the second molten region is w along the direction parallel to the cover plate; the value range of w is: 0.1mm≤w≤1mm.

8. The battery cell according to claim 1, characterized in that, The cover plate is provided in two parts, and the shell has openings on both sides of the opposite side along the first direction. Each cover plate is fastened to one of the openings and welded to the shell.

9. The battery cell according to claim 8, characterized in that, The shell is formed by bending the two ends of a long strip of steel plate twice in opposite directions along its length, and then welding the two opposite sides of the long strip of steel plate together to form a weld mark at the joint, thus forming the cylindrical shell.

10. The battery cell according to claim 1, characterized in that, Both the housing and the cover plate are made of steel.

Images