Battery cell and welding method thereof

Abstract

The invention discloses a battery monomer and a welding method thereof, the battery monomer comprises a shell and a cover plate, the shell is provided with an opening end, the opening edge of the opening end is provided with a notch groove, and the notch groove is provided with a groove bottom and an outer end; the cover plate comprises a cover plate main body part and lug parts uniformly distributed in the circumferential direction of the cover plate main body part, the cover plate main body part is embedded into the inner side of the open end, the lug parts are embedded into the notch grooves in a one-to-one correspondence manner, the edge of the cover plate and the opening edge of the open end are welded to form a closed accommodating cavity, and the size of the lug parts in the first direction is configured to be through welding during welding. The gap groove is formed in the shell, and the convex lug part is arranged on the cover plate, so that the technical obstacle that a continuous positioning step cannot be arranged on the thin-wall battery is solved, the top welding of the cover plate of the thin-wall battery is realized, and the welding efficiency of the thin-wall battery is improved.

Description

TECHNICAL FIELD

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

[0002] Since the development of lithium ion battery in the 20th century, due to its high specific energy, long cycle life, environmental friendliness and a series of advantages, especially with the continuous maturity of new materials and new technologies in the field, lithium ion battery is widely used in the field of large-scale power and energy storage. In the process of assembling the battery monomer, the cover plate of the battery needs to be welded to the shell of the battery. At present, there are mainly two methods for welding the cover plate, which are side welding and top welding. When side welding, the edge of the cover plate is roughly flush with the outer wall of the shell, the butt joint gap between the shell and the cover plate is directed to the four directions, and the welding needs to be carried out for four times, which needs a long working time and has low working efficiency. When top welding, a positioning step is arranged at the opening of the shell, the cover plate is embedded in the inner side of the opening of the shell, the butt joint gap between the shell and the cover plate is directed upward, and one-time welding can be carried out, which needs a short working time and has high working efficiency.

[0003] Since the shell of the thin-walled battery is thin, it is difficult to arrange a positioning step at the opening of the shell, therefore, the thin-walled battery currently usually adopts the side welding method for welding the cover plate. How to improve the welding efficiency of the thin-walled battery is a technical problem to be solved in the field. SUMMARY

[0004] Therefore, the present application provides a battery monomer and a welding method thereof, which realizes the top welding of the thin-walled battery and improves the welding efficiency.

[0005] To solve the above technical problems, the present application provides a battery monomer, which comprises: An outer shell assembly comprising a shell and a cover plate, the shell has an opening end in a first direction, the opening end is provided with at least two groups of notch grooves uniformly distributed at different positions in the circumferential direction of the opening end, the notch grooves are recessed on the opening edge of the opening end and penetrate the outer wall and the inner wall of the shell, the cover plate comprises a cover plate main body part, the edge of the cover plate main body part is provided with at least two groups of lug parts uniformly distributed at different positions in the circumferential direction of the edge, the cover plate main body part is embedded in the inner side of the edge, the lug parts are embedded in the notch grooves one by one, the edge of the cover plate is welded and connected with the opening edge of the opening end to form a closed containing cavity, and the size of the lug part in the first direction is configured to be penetrated by welding; An electrode assembly arranged in the containing cavity; A pole assembly comprising a positive pole and a negative pole, the positive pole and the negative pole are installed on the cover plate, and the positive pole and the negative pole are electrically connected with the electrode assembly.

[0006] Further, the notch groove has a groove depth dimension measured along the first direction, and the cover plate has a thickness dimension measured along the first direction, the groove depth dimension of the notch groove and the thickness dimension of the cover plate are between 0.2mm and 0.8mm.

[0007] Further, the notch groove has a groove width dimension measured along the length direction of the mouth along area where the notch groove is located, and a cross section perpendicular to the wall thickness direction of the housing area where the notch groove is located, the groove width dimension at the notch groove mouth is not less than the groove width dimension at the notch groove bottom, and the cross section of the notch groove is rectangular, trapezoidal or arc-shaped.

[0008] Further, the trapezoid is isosceles trapezoid or right-angle trapezoid.

[0009] Further, the mouth along of the opening end is rectangular, and the notch groove is arranged at the short side of the mouth along of the opening end.

[0010] Further, the lug portion has an outer end surface facing away from the cover plate main body portion and an outer surface facing away from the notch groove bottom, the outer end surface of the lug portion is arranged flush with the outer wall of the housing, and the outer surface of the lug portion is arranged flush with the rim.

[0011] Further, the cover plate has an outer surface facing the outside of the housing in the first direction, and the outer surface of the cover plate is flush with the mouth along of the opening end.

[0012] Further, the battery cell is a thin-walled battery.

[0013] The application also provides a welding method of the battery cell, comprising the following steps: S1, positioning the housing with the opening end facing upwards, and placing the electrode assembly inside the housing; S2, mounting the pole assembly on the cover plate; S3, pre-positioning and connecting the cover plate to the opening end, embedding the cover plate main body portion inside the mouth along, embedding the lug portion in the notch groove, and forming a joint gap between the rim of the cover plate and the mouth along of the opening end, the joint gap comprising a first gap section facing upwards and a second gap section facing sideways; S4, welding along the rim of the cover plate by a welding head, wherein when welding the first gap section, the welding head is aligned with the mouth along of the opening end and the rim of the cover plate on both sides of the first gap section; and when welding the second gap section, the welding head is aligned with the rim of the lug portion and the welding penetration is greater than the size of the lug portion along the first direction.

[0014] Further, in step S4, the housing and the cover plate are welded by laser welding.

[0015] Compared with the prior art, the above-mentioned technical solution of the present invention has the following advantages: The battery cell and its welding method of the present invention, by setting notches and grooves on the shell and setting lugs on the cover plate, solves the technical obstacle that thin-walled batteries cannot be set with continuous positioning steps, realizes the top welding of the cover plate of thin-walled batteries, and improves the welding efficiency of thin-walled batteries. Attached Figure Description

[0016] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0017] Figure 1 This is a front view of a battery cell disclosed in Embodiment 1 of the present invention; Figure 2 This is a top view of the battery cell disclosed in Embodiment 1 of the present invention; Figure 3 for Figure 2 A magnified view of a section at point A in the middle; Figure 4 This is a side view of a battery cell disclosed in Embodiment 1 of the present invention; Figure 5 for Figure 4 A magnified view of a section at point B in the middle; Figure 6 This is a schematic diagram of the opening end of the housing disclosed in Embodiment 1 of the present invention; Figure 7 This is a side view of a battery cell disclosed in Embodiment 2 of the present invention; Figure 8 for Figure 7 A magnified view of a section at point C; Figure 9 This is a side view of a battery cell disclosed in Embodiment 3 of the present invention; Figure 10 for Figure 9 A magnified view of a section at point D.

[0018] Explanation of reference numerals in the accompanying drawings: 11, housing; 111, rim; 112, notch; 12, cover plate; 121, main body of cover plate; 122, lug; 13, first slit section; 14, second slit section; 21, positive terminal; 22, negative terminal. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0020] Example 1: See Figures 1 to 6As shown, this is the first embodiment of the battery cell provided by the present invention.

[0021] The battery cell includes: The housing assembly includes a housing 11 and a cover plate 12. The housing 11 has an open end in a first direction. At least two sets of notches 112 are evenly distributed at different positions in the circumference of the opening edge 111. The notches 112 are recessed into the opening edge 111 and penetrate the outer wall and inner wall of the housing 11. The cover plate 12 includes a cover plate body 121. At least two sets of lugs 122 are evenly distributed at different positions in the circumference of the edge of the cover plate body 121. The cover plate body 121 is embedded in the inner side of the opening edge 111. The lugs 122 are correspondingly embedded in the notches 112. The edge of the cover plate 12 is welded to the opening edge 111 to form a closed receiving cavity. The lugs 122 are dimensionally configured in the first direction so that they can be welded through during welding. An electrode assembly (not shown in the figure) is disposed in the aforementioned receiving cavity; The electrode assembly includes a positive electrode 21 and a negative electrode 22, which are mounted on the cover plate 12 and are electrically connected to the electrode assembly.

[0022] In the above text, the outer shell assembly refers to the sealed structure formed by welding the shell 11 and the cover plate 12. The opening end of the shell 11 is an open opening, and the edge 111 of the opening end is a straight opening, which is the transition surface between the inner wall and the outer wall of the shell 11. The notch 112 refers to the recessed structure that is circumferentially distributed along the edge 111 of the opening end. Its design, which penetrates the wall thickness of the shell 11, makes the size of the notch 112 along the wall thickness direction of the shell 11 as large as possible, so as to effectively support the cover plate 12. The main body 121 of the cover plate is the main part of the cover plate 12. After the cover plate 12 is assembled with the housing 11, the main body 121 is located inside the rim 111. The lug 122 is a protruding structure that matches the shape of the notch 112. The notch 112 of the housing 11 and the lug 122 on the cover plate 12 form a fitting and positioning. This structure allows the cover plate 12 to be pre-positioned without the need for positioning steps on the inner sidewall of the housing 11, and ensures that most of the weld gap is the top gap (first gap segment 13) facing the same direction. By controlling the size of the lug 122 along the first direction, the lug 122 can be fully welded during welding. When welding the cover plate 12, it is not necessary to align the welding head with the outer gap; it is only necessary to align the welding head with the edge of the lug 122 to achieve welding of the outer gap.

[0023] Electrode assembly refers to an electrochemical unit formed by winding or stacking positive and negative electrode plates and a separator. Specifically, it can adopt a winding or stacked structure, which is directly installed in the housing 11 and connected to the positive electrode post 21 and the negative electrode post 22 through electrode tabs.

[0024] In addition to the positive terminal 21 and the negative terminal 22, the electrode assembly also includes a seal and a conductive connector. The positive terminal 21 is connected to the positive tab of the electrode assembly, and the negative terminal 22 is connected to the negative tab of the electrode assembly. The positive terminal 21 and the negative terminal 22 are used for external electrical connection.

[0025] Specifically, the notches 112 of the housing 11 are evenly distributed circumferentially to form multiple positioning references. When the lugs 122 of the cover plate 12 are inserted into the corresponding notches 112, the cover plate 12 is supported and horizontally limited. During the welding process, the welding head performs circumferential welding along the edge of the cover plate 12.

[0026] By using the above technical solution, and by setting notches and grooves on the casing and lugs on the cover plate, the technical obstacle of not being able to set continuous positioning steps in thin-walled batteries is solved, enabling the top welding of the cover plate of thin-walled batteries and improving the welding efficiency of thin-walled batteries.

[0027] In this embodiment, the notch 112 has a groove depth dimension measured along the first direction, and the lug 122 has a thickness dimension measured along the first direction. The groove depth dimension of the notch 112 and the thickness dimension of the lug 122 are both between 0.2 mm and 0.8 mm.

[0028] In the above text, the groove depth of the notch 112 refers to the vertical distance from the bottom of the notch 112 to the opening of the groove, measured along the first direction of the shell 11. The thickness of the lug 122 refers to the vertical distance between the two surfaces of the lug 122, measured along the first direction of the shell 11. The thickness of the lug 122 directly affects whether it can be fully penetrated during welding.

[0029] Specifically, the depth of the notch 112 and the thickness of the lug 122 are generally set to be the same, both being H, for example, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, or 0.8 mm. When H is less than 0.2 mm, the notch 112 is too shallow and the lug 122 is too thin, resulting in the notch 112 being unable to effectively limit positioning, and the structural strength of the lug 122 being too low, which is not conducive to the mutual positioning of the two. When H is greater than 0.8 mm, the thickness of the lug 122 is too large, making it difficult to penetrate the weld, requiring an increase in welding power. Excessive welding power can lead to product deformation and other defects.

[0030] By setting the groove depth and lug thickness within a certain range, the effective positioning of both can be ensured, the lug can be fully welded, and the shell and cover plate will not deform.

[0031] In this embodiment, the notch 112 has a groove width dimension measured along the length direction of the region where it is located (the opening edge 111) and a cross-section perpendicular to the wall thickness direction of the region where it is located. The groove width dimension at the opening of the notch 112 is equal to the groove width dimension at the bottom of the notch 112, and the cross-section of the notch 112 is rectangular.

[0032] In the above text, the rim 111 is annular. Assuming that the notch 112 is set on a section of the rim extending along the second direction, the width of the notch 112 is the dimension of the notch 112 along the second direction. The cross-section of the notch 112 is perpendicular to the third direction, and the third direction, the second direction, and the first direction are all perpendicular to each other.

[0033] Specifically, when viewed from the outside of the housing area where the notch 112 is located, both the notch 112 and the lug are rectangular. This shape ensures that the lug 122 can enter the notch 112 along the first direction, and the lug 122 is not easy to slip out of the notch 112.

[0034] By using the above technical solution, the notch is set as a rectangular notch, which ensures that the lug can be embedded into the notch along the first direction and that the lug is not easy to slip out of the notch.

[0035] In this embodiment, the opening edge 111 of the opening end is rectangular, and the notch 112 is located at the short side of the opening edge 111 of the opening end.

[0036] In the above text, the rectangular shape of the opening edge 111 means that the opening edge of the shell 11 has a geometric shape with four straight sides and adjacent sides perpendicularly connected. The notch 112 is located at the short side of the opening edge 111, which means that the notch 112 is arranged in the side area of ​​the rectangular edge 111 with a shorter length. Choosing the short side area can avoid the problem of insufficient mechanical strength in the long side area due to the shell wall being too thin.

[0037] Specifically, the shell 11 is formed into a square tube shape by four thin plates. The larger plate forms the long side of the rim 111, and the smaller plate forms the short side of the rim 111. The larger the plate area, the easier it is to deform, and the smaller the plate area, the less likely it is to deform. The notch 112 is set at the short side of the rim 111, forming symmetrically distributed support points along the short side. When supporting the cover plate 12, the shell 11 is not easily deformed by the support of the smaller plate area.

[0038] By using the above technical solution, the notch is located on the short side of the opening, which can reduce or avoid shell deformation when supporting the cover plate.

[0039] In this embodiment, the lug 122 has an outer end face away from the cover plate main body 121 and an outer surface away from the bottom of the notch 112. The outer end face of the lug 122 is configured to be flush with the outer wall of the housing 11, and the outer surface of the lug 122 is configured to be flush with the edge 111 of the opening end.

[0040] In the above text, the outer end face of the lug 122 is flush with the outer wall of the housing 11. The outer surface of the lug 122 is configured to be flush with the edge 111 of the opening end, which means that the two form a coplanar structure with no height difference when they are welded together, so that the welding interface remains continuous and flat.

[0041] Specifically, during the welding process, after the lug 122 is inserted into the notch 112, the outer end face of the lug 122 and the flush structure of the outer wall of the shell 11 form a continuous welding contact surface. The outer surface of the lug 122 and the edge 111 of the opening end remain flush, ensuring the uniformity and consistency of the weld and making the welding quality more stable.

[0042] By using the above technical solution, the outer end face of the lug is flush with the outer wall of the shell, and the outer surface of the lug is flush with the edge of the opening, ensuring the uniformity and consistency of the weld and making the welding quality more stable.

[0043] In this embodiment, the cover plate 12 has an outer surface facing the outside of the housing 11 in a first direction, and the outer surface of the cover plate 12 is flush with the edge 111 of the opening end.

[0044] In the above text, the first direction refers to the axial extension direction of the opening end of the housing 11, which defines the assembly reference direction when the cover plate 12 is embedded in the housing 11. The fact that the outer surface of the cover plate 12 is flush with the edge 111 of the opening end means that the outer surface of the cover plate 12 and the edge 111 of the housing 11 are in the same plane.

[0045] Specifically, after the cover plate body 121 is embedded inside the opening edge 111, the cover plate body 121 is flush with the opening edge 111, which can ensure the uniformity and consistency of the weld and make the welding quality more stable.

[0046] The above technical solution ensures that the outer surface of the cover plate is flush with the rim to form a top welding interface, thus guaranteeing welding quality.

[0047] In this embodiment, the aforementioned battery cell is a thin-walled battery.

[0048] In the above text, thin-walled batteries refer to batteries with a casing wall thickness that is significantly lower than that of conventional batteries, and their wall thickness can be controlled within a specific thinning range.

[0049] Specifically, the collaborative design of the thin-walled battery and the notch overcomes the technical limitation of traditional casings requiring positioning steps. When the cover plate is pre-installed into the opening of the casing, the lugs embed into the notch to form a mechanical limit, replacing the constraint function of traditional positioning steps. During the welding process, the welding head performs continuous welding along the edge of the cover plate, allowing the thin-walled battery to be welded at the top without the need for additional positioning steps.

[0050] Through the above technical solution, by combining the thin-walled battery with the notch and slot structure, single continuous welding is achieved while maintaining the advantage of thin casing.

[0051] The welding method for the above-mentioned battery cells is described below, including the following steps: S1. Position the housing 11 so that the opening end faces upward, and place the electrode assembly into it. S2. Install the above-mentioned pole assembly onto the above-mentioned cover plate 12; S3. The cover plate 12 is prepositioned and connected to the opening end, so that the main body 121 of the cover plate is embedded in the inner side of the opening edge 111, the lug 122 is embedded in the notch 112, and a splicing gap is formed between the edge of the cover plate 12 and the opening edge 111. The splicing gap includes a first gap segment 13 facing upward and a second gap segment 14 facing sideways. S4. Weld a ring around the edge of the cover plate 12 using a welding head, wherein the welding head is aligned with the first gap segment so that the generated molten material fills the first gap segment 13; the welding head is aligned with the intersection of the outer end face and the outer surface of the lug 122 so that the generated molten material spreads to the second gap segment 14.

[0052] In the above description, the housing 11 is pre-positioned to facilitate the placement of the electrode assembly and the supporting cover 12. Pre-positioning connection means that the cover 12 and the housing 11 maintain a relative position. This pre-positioning of the cover 12 and housing 11 does not require external force and is achieved through the notch 112 and the lug 122. Welding the welding head around the edge of the cover 12 means that the welding head moves only on one side of the cover 12 and does not need to move around the entire housing 11.

[0053] Specifically, the upward-facing positioning of the shell 11 ensures the welding operation surface is horizontal, facilitating continuous circumferential movement of the welding head. During the pre-positioning stage, the engagement of the lug 122 and the notch 112 creates splicing gaps with different orientations, with the first gap segment 13 and the second gap segment 14 forming a continuous welding path. During welding, as the welding head moves in a circular motion along the edge of the cover plate 12, molten material fills the first gap segment 13 and the second gap segment 14, achieving continuous welding in a single operation.

[0054] The above-mentioned protection scheme enables a single continuous operation for welding thin-walled battery cover plates, eliminating the need for multiple process switching required in traditional side welding.

[0055] In this embodiment, in step S4 above, the shell 11 and the cover plate 12 are welded by laser welding.

[0056] As mentioned above, laser welding is the mainstream method for connecting the battery casing 11 and the cover plate 12, which can effectively ensure the battery's sealing performance and structural strength.

[0057] Specifically, when the welding head is aligned with the first weld gap, the edge 111 of the shell and the edge of the cover plate melt and flow into the first weld gap, thus achieving connection, fixation, and sealing of the first weld gap. When the welding head is aligned with the junction of the outer end face and the outer surface of the lug 122, the junction of the outer end face and the outer surface melts and flows into the second weld gap, thus achieving connection, fixation, and sealing of the second weld gap.

[0058] The advantages of laser welding, as described above, directly match the core requirements of batteries and are suitable as a welding method for batteries.

[0059] Example 2: See Figure 7 and Figure 8 As shown, this is the second embodiment of the battery cell provided by the present invention.

[0060] The rest is the same as in Embodiment 1, except that the cross-section of the notch 112 is an isosceles trapezoid.

[0061] In the above text, the isosceles trapezoid refers to a trapezoidal structure with symmetrically inclined sides, which facilitates the guidance of the lug 122 and makes it easier for the lug 122 to enter the notch groove 112.

[0062] Specifically, the isosceles trapezoid has an inclined surface structure. If there is a slight misalignment when it is assembled with the notch 112, the inclined surface of the trapezoid of the notch 112 will generate a guiding force. During the process of the lug 122 being inserted into the notch 112, the inclined surface will guide the lug 122 to automatically slide to the correct center position without the need for repeated manual adjustment.

[0063] The above technical solution sets the notch groove as an isosceles trapezoid, which facilitates the quick insertion of the convex lug into the notch groove.

[0064] Example 3: See Figure 9 and Figure 10 As shown, this is the third embodiment of the battery cell provided by the present invention.

[0065] The rest is the same as in Embodiment 1, except that the cross-section of the notch groove is a right trapezoid.

[0066] In the above text, a right trapezoid refers to a trapezoidal structure in which one side of the groove wall is vertical and the other side of the groove wall is inclined.

[0067] Specifically, when the cross-section of the notch 112 is rectangular, the lug 122 is less likely to slip out of the notch when subjected to external force, but precise relative positioning is required during insertion. When the cross-section of the notch 112 is trapezoidal, the lug 122 is easier to position with the notch 112, but because the notch 112 is shallow, the lug 122 is prone to slip out of the notch 112 under external force, leading to positioning failure. Setting the cross-section of the notch 112 as a right-angled trapezoid prevents the lug 122 from slipping out, while the inclined side guides the lug 122 into the notch 112.

[0068] By using the above technical solution, the notch is set as a right-angled trapezoid, which can not only prevent the lug from slipping off, but also allow it to be quickly fitted with the lug.

[0069] Example 4: The rest is the same as Example 1, except that the cross-section of the notch groove is arc-shaped.

[0070] In the above text, "arch" refers to the arc-shaped surface where the bottom and wall of the notch groove are integral. This type of groove is also called an arc-shaped groove.

[0071] Specifically, curved grooves avoid stress concentration at right angles or sharp corners, and can evenly distribute external forces throughout the groove, extending the structure's service life. With the same materials and dimensions, curved grooves offer stronger resistance to bending and impact, making them particularly suitable for applications requiring pressure or vibration resistance.

[0072] The above technical solutions can reduce stress concentration in the notch groove and improve the impact resistance of the shell.

[0073] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A battery cell, characterized in that, include: An outer casing assembly includes a housing and a cover plate. The housing has an open end in a first direction. At least two sets of notches are evenly distributed at different positions in the circumference of the open end. The notches are recessed into the circumference of the open end and penetrate the outer wall and inner wall of the housing. The cover plate includes a cover plate body. At least two sets of lugs are evenly distributed at different positions in the circumference of the edge of the cover plate body. The cover plate body is embedded in the inner side of the edge. The lugs are embedded in the notches one by one. The lugs have an outer end face away from the cover plate body and an outer surface away from the bottom of the notch. The lugs are configured such that molten material at the junction of the outer end face and the outer surface can spread into the gap between the outer end face and the outer wall of the housing. The edge of the cover plate is welded to the edge of the open end to form a closed receiving cavity. The lugs are configured in the first direction such that they can be welded through during welding. The electrode assembly is disposed within the receiving cavity; The electrode assembly includes a positive electrode and a negative electrode, which are mounted on the cover plate and electrically connected to the electrode assembly.

2. The battery cell according to claim 1, characterized in that, The notch has a depth dimension measured along the first direction, and the lug has a thickness dimension measured along the first direction. The depth dimension of the notch and the thickness dimension of the lug are between 0.2 mm and 0.8 mm.

3. The battery cell according to claim 1, characterized in that, The notch has a width dimension measured along the length of its opening region and a cross-section perpendicular to the wall thickness of its shell region. The width dimension at the opening of the notch is not less than the width dimension at the bottom of the notch. The cross-section of the notch is rectangular, trapezoidal, or arc-shaped.

4. The battery cell according to claim 3, characterized in that, The trapezoid is an isosceles trapezoid or a right trapezoid.

5. The battery cell according to claim 1, characterized in that, The opening edge is rectangular, and the notch is located at the short side of the opening edge.

6. The battery cell according to claim 1, characterized in that, The lug has an outer end face away from the main body of the cover plate and an outer surface away from the bottom of the notch. The outer end face of the lug is configured to be flush with the outer wall of the housing, and the outer surface of the lug is configured to be flush with the rim.

7. The battery cell according to claim 1, characterized in that, The cover plate has an outer surface facing the outside of the housing in a first direction, and the outer surface of the cover plate is flush with the edge of the opening end.

8. The battery cell according to claim 1, characterized in that, The battery cell is a thin-walled battery.

9. The welding method for a battery cell according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Position the housing so that the opening end faces upward, and place the electrode assembly inside the housing; S2. Install the pole assembly onto the cover plate; S3. The cover plate is pre-positioned and connected to the opening end, so that the main body of the cover plate is embedded in the inner side of the opening edge, the lug is embedded in the notch groove, and a splicing gap is formed between the edge of the cover plate and the opening edge of the opening end. The splicing gap includes a first gap segment facing upward and a second gap segment facing sideways. S4. Weld a circle around the edge of the cover plate using a welding head, wherein when welding the first gap segment, the welding head is aligned with the opening edge of the opening end on both sides of the first gap segment and the edge of the cover plate; when welding the second gap segment, the welding head is aligned with the edge of the lug and the welding penetration depth is greater than the size of the lug along the first direction.

10. The welding method for a battery cell according to claim 9, characterized in that, In step S4, the housing and the cover plate are welded using laser welding.

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