A cylindrical secondary battery

Abstract

The utility model relates to a cylindrical battery technical field, proposes a kind of cylindrical secondary battery, including shell, roll core, negative cover plate and negative current collector disc;The roll core is arranged in the shell;The negative cover plate is fixedly arranged on the shell;The negative current collector disc is S-shaped, and it includes the first bending portion, connecting portion and second bending portion connected in turn, the first bending portion is in close contact with the negative tab;The second bending portion is welded and fixed on the negative cover plate;The end face diameter of the shell is D 10 , the maximum length of the first bending portion is L 61 , L 61 / D 10 =77.2% to 85.8%.The utility model can improve the assembly efficiency of negative cover plate and negative current collector disc by setting negative current collector disc to S shape, by setting negative current collector disc to include the first bending portion, connecting portion and second bending portion, and limiting the length of the first bending portion, the flow capacity between negative current collector disc and negative tab can be guaranteed, so as to improve the overall performance of battery.

Description

Technical Field

[0001] This utility model relates to the field of cylindrical battery technology, and in particular to a cylindrical secondary battery. Background Technology

[0002] With the rapid development of technology, the demand for energy storage in various electronic devices, electric vehicles, and energy storage systems is increasing. Rechargeable batteries, due to their rechargeable nature, have become a key energy solution to meet these needs. Among them, cylindrical rechargeable batteries, with their compact structure, high energy density, and mature manufacturing processes, have been widely used in numerous application scenarios.

[0003] Cylindrical secondary batteries are mainly composed of a casing, a core, and positive and negative current collectors. The positive and negative current collectors are welded and fixed to the positive and negative tabs of the core using methods such as laser welding and ultrasonic welding, respectively, to collect and conduct current.

[0004] As disclosed in utility model publication CN222282192U, a cover plate and negative electrode current collector connection structure and a cylindrical battery are provided. A negative electrode current collector is set between the electrode assembly and the cover plate to achieve conductivity at the negative terminal of the battery. This negative electrode current collector has a disc-shaped structure. A micro-protrusion needs to be set on the cover plate, protruding into the battery and reversible under internal battery pressure, to weld the micro-protrusion to the negative electrode current collector. However, this micro-protrusion needs to support the negative electrode current collector. If the supporting force is too large, it will damage the winding core; if the supporting force is too small, it will reduce the welding reliability between the cover plate and the negative electrode current collector, resulting in greater assembly difficulty for the negative electrode current collector and the cover plate, thus affecting the battery assembly efficiency. Utility Model Content

[0005] In view of this, the present invention proposes a cylindrical secondary battery, which can not only improve the assembly efficiency of the negative electrode current collector and the cover plate, but also ensure the current carrying capacity of the negative electrode current collector and the winding core, thereby effectively improving the overall performance of the battery.

[0006] The technical solution of this utility model is implemented as follows: This utility model provides a cylindrical secondary battery, including a shell, a winding core, a negative electrode cover plate, and a negative electrode current collector, wherein the negative end of the shell is provided with an opening; the winding core is disposed inside the shell, and a negative electrode tab is provided at the end of the winding core; the negative electrode cover plate is fixedly disposed on the shell and seals the opening; the negative electrode current collector is S-shaped, and includes a first bent portion, a connecting portion, and a second bent portion connected in sequence, the first bent portion abutting against the negative electrode tab and being welded and fixed thereto; the second bent portion is welded and fixed to the negative electrode cover plate; the end face diameter of the shell is D. 10 The maximum length of the first bend is L 61 L61 / D 10 =77.2% - 85.8%.

[0007] Based on the above technical solution, preferably, the second bending portion is parallel to the first bending portion; the maximum length of the second bending portion is L. 63 L 63 / D 10 =61% - 69.7%.

[0008] More preferably, the minimum distance between the end of the first bent portion near the connecting portion and the inner wall of the housing is the first gap, and the minimum distance between the end of the second bent portion away from the connecting portion and the inner wall of the housing is the second gap; the first gap is greater than the second gap, and the difference between the two is L. 62 L 62 / L 63 =8.2% - 11.5%.

[0009] More preferably, the minimum distance between the end of the first bent portion away from the connecting portion and the inner wall of the housing is the third gap, and the minimum distance between the end of the second bent portion near the connecting portion and the inner wall of the housing is the fourth gap; the fourth gap is greater than the third gap, and the difference between the two is L. 64 L 64 / D 10 =20.5% - 24.8%.

[0010] Based on the above technical solution, preferably, a groove is provided on one side of the negative electrode cover, forming a convex ring on the other side of the negative electrode cover, and the end of the second bent portion away from the connecting portion is welded and fixed to the convex ring; the end face radius of the housing is R. 10 The minimum distance between the pressure groove and the axis of the housing is W. 11 W 11 / R 10 =52.8% - 61.5%.

[0011] More preferably, the pressing groove is an annular groove structure with a trapezoidal cross-section; the maximum annular width of the pressing groove is W. 12 W 12 / R 10 =24.3% - 33%.

[0012] More preferably, the minimum distance between the pressure groove and the periphery of the housing is W. 13 W 13 / R 10 =9.8% - 18.5%.

[0013] More preferably, the side of the second bent portion away from the core is flush with the side of the convex ring away from the negative electrode cover plate, and the end of the second bent portion near the connecting portion is located inside the convex ring; the distance between the end of the second bent portion near the connecting portion and the convex ring is L. 65 L 65 =1.81-2.41mm.

[0014] More preferably, the distance between the end of the second bent portion away from the connecting portion and the outer edge of the convex ring is W. 15 W 15 =0.55-0.95mm.

[0015] Based on the above technical solutions, the preferred option is D. 10 =44-48mm.

[0016] The cylindrical secondary battery of this invention has the following advantages over the prior art:

[0017] (1) By setting the negative current collector to an S-shape, the assembly efficiency of the negative current collector and the negative current collector can be improved. By setting the negative current collector to include a first bending part, a connecting part and a second bending part, and limiting the length of the first bending part, the current carrying capacity between the negative current collector and the negative electrode tab can be guaranteed, thereby improving the overall performance of the battery.

[0018] (2) By setting a convex ring on the negative electrode cover and limiting the specifications and installation position of the negative electrode cover, the capacity and energy density of the battery can be further improved, as well as the assembly quality and assembly efficiency of the battery can be further improved. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a cross-sectional view of a cylindrical secondary battery according to the present invention.

[0021] Figure 2 This is a cross-sectional view of the first gap in a cylindrical secondary battery according to the present invention.

[0022] Figure 3 This is a cross-sectional view of the third gap in a cylindrical secondary battery according to the present invention.

[0023] Figure 4 This is a cross-sectional view of the negative electrode cover and the casing of a cylindrical secondary battery according to the present invention.

[0024] Figure 5 This is a perspective view of a cylindrical secondary battery according to the present invention.

[0025] The components are: 1. Shell; 101. Opening; 2. Core; 201. Negative electrode tab; 3. Negative electrode cover plate; 31. Protruding ring; 301. Pressure groove; 4. Negative electrode collector plate; 41. First bend; 42. Connecting part; 43. Second bend. Detailed Implementation

[0026] The technical solutions of this utility model will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0027] The present invention relates to a cylindrical secondary battery, comprising a casing 1, a winding core 2, a negative electrode cover plate 3, and a negative electrode current collector 4.

[0028] The housing 1 is a cylindrical structure. Both the positive and negative ends of the housing 1 are provided with openings 101. The core 2 is placed inside the housing 1. The two ends of the core 2 are respectively provided with positive electrode tabs and negative electrode tabs 201. The negative electrode current collector 4 is welded and fixed between the negative electrode tabs 201 and the negative electrode cover plate 3. The negative electrode cover plate 3 is fixedly placed on the housing 1 and blocks the openings 101, thereby achieving the sealing of the negative end of the housing 1 and the conduction of the negative end of the cylindrical secondary battery.

[0029] The negative electrode current collector 4 has a long strip structure. First, one end of the negative electrode current collector 4 is welded and fixed to the negative electrode tab 201 inside the housing 1. Then, the other end of the negative electrode current collector 4 is welded and fixed to the negative electrode cover plate 3. Finally, by bending the negative electrode current collector 4, the negative electrode current collector 4 is formed into an S-shape, so that the negative electrode cover plate 3 can be installed at the opening 101 to realize the assembly of the battery.

[0030] When assembling the battery using the above process, the welding convenience between the negative electrode current collector 4 and related components can be improved, thereby effectively improving the assembly quality and efficiency of the battery.

[0031] like Figures 1-3As shown, the negative electrode current collector 4 includes a first bent portion 41, a connecting portion 42, and a second bent portion 43. The connecting portion 42 is integrally formed between the first bent portion 41 and the second bent portion 43, and the two ends of the connecting portion 42 are continuously disposed with the ends of the first bent portion 41 and the second bent portion 43, respectively.

[0032] When the negative electrode current collector 4 is not bent, the first bent part 41, the connecting part 42 and the second bent part 43 are located in the same plane and are connected in sequence. When bending the negative electrode current collector 4, it is preferable that the first bent part 41 and the second bent part 43 are both bent 180° relative to the connecting part 42, that is, the first bent part 41, the connecting part 42 and the second bent part 43 are parallel to each other, and the connecting part 42 is located between the first bent part 41 and the second bent part 43.

[0033] The negative electrode cover plate 3 is a circular plate structure. A pressure groove 301 is provided on one side of the negative electrode cover plate 3. By stamping the pressure groove 301, a convex ring 31 is formed on the other side of the negative electrode cover plate 3. Both the pressure groove 301 and the convex ring 31 are ring structures.

[0034] When welding the negative electrode current collector 4 and the negative electrode tab 201, the entire first bent portion 41 abuts against the negative electrode tab 201, and the first bent portion 41 is welded and fixed to the negative electrode tab 201; when welding the negative electrode current collector 4 and the negative electrode cover plate 3, the end of the second bent portion 43 away from the connecting portion 42 is welded and fixed to the convex ring 31.

[0035] like Figure 1 As shown, since the second bent portion 43 is welded and fixed on the convex ring 31, the side of the second bent portion 43 away from the core 2 is flush with the side of the convex ring 31 away from the negative electrode cover plate 3. In order to avoid the second bent portion 43 interfering with the inner wall of the housing 1 during the assembly process, it is preferable to place the end of the second bent portion 43 near the connecting portion 42 inside the convex ring 31.

[0036] like Figure 2 As shown, in order to facilitate the stamping of the pressure groove 301 and improve the processing quality of the convex ring 31, it is preferable to make the pressure groove 301 an annular groove structure with a trapezoidal cross-section.

[0037] like Figure 1 and Figure 4 As shown, the end face radius of housing 1 is R. 10 The end face diameter of shell 1 is D. 10 The maximum length of the first bend 41 is L 61 The maximum length of the second bend 43 is L 63 .

[0038] In some embodiments, D 10 =44-48mm, that is, the end face diameter of shell 1 is 44mm, 46mm or 48mm, etc.

[0039] In some embodiments, L 61 / D 10 =77.2%-85.8%, meaning the maximum length of the first bend 41 is 77.2%, 81.5%, or 85.8% of the diameter of the end face of the shell 1, etc. If L 61 / D 10 If the value is less than 77.2%, then the length of the first bend 41 is too small, reducing the effective welding area between the negative electrode current collector 4 and the negative electrode tab 201, increasing the temperature rise at the welding position, and affecting the battery performance; if L 61 / D 10 If the length of the first bend 41 is greater than 85.8%, then the length of the first bend 41 is too large. During the battery assembly process, the first bend 41 is prone to interference with the inner wall of the housing 1 or the opening 101, which affects the assembly quality and efficiency of the battery.

[0040] In some embodiments, L 63 / D 10 =61%-69.7%, meaning the maximum length of the second bend 43 is 61%, 65.3%, or 69.7% of the diameter of the end face of the shell 1, etc. If L 63 / D 10 If L < 61%, then the length of the second bend 43 is too small, and the total length of the negative electrode current collector 4 becomes smaller. This causes the negative electrode cover plate 3 to be too close to the opening 101 when welding with the negative electrode current collector 4, affecting the welding quality between the negative electrode cover plate 3 and the negative electrode current collector 4, and reducing the production quality and efficiency of the battery; if L 63 / D 10 If the length of the second bending section 43 is greater than 69.7%, the total length of the negative electrode current collector 4 will increase, which will not only increase the production cost of the negative electrode current collector 4, but also increase its weight and affect the energy density of the battery.

[0041] like Figure 2 As shown, the minimum distance between the end of the first bent portion 41 near the connecting portion 42 and the inner wall of the housing 1 is the first gap, and the minimum distance between the end of the second bent portion 43 away from the connecting portion 42 and the inner wall of the housing 1 is the second gap. The first gap is greater than the second gap, and the difference between the first gap and the second gap is L. 62 ,like Figure 3 As shown, the minimum distance between the end of the first bent portion 41 away from the connecting portion 42 and the inner wall of the housing 1 is the third gap, and the minimum distance between the end of the second bent portion 43 near the connecting portion 42 and the inner wall of the housing 1 is the fourth gap. The fourth gap is greater than the third gap, and the difference between the fourth gap and the third gap is L. 64 .

[0042] In some embodiments, L 62 / L 63=8.2%-11.5%, meaning the difference between the first gap and the second gap is 8.2%, 9.9%, or 11.5% of the maximum length of the second bending portion 43, etc. The position between the first bending portion 41 and the connecting portion 42 is the first bending position of the negative electrode current collector 4. Given a fixed maximum length of the second bending portion 43, if L... 62 / L 63 If the difference between the first and second gaps is less than 8.2%, then the difference is too small, meaning the length of the first bend 41 is too large. During battery assembly, the negative electrode current collector 4 will interfere with the casing 1, affecting the battery assembly quality and efficiency. 62 / L 63 If the difference between the first gap and the second gap is greater than 11.5%, it means that the length of the first bending part 41 is too small, which leads to a reduction in the welding area between the first bending part 41 and the negative electrode tab 201, and an increase in the temperature rise at the welding position, thus affecting the performance of the battery.

[0043] In some embodiments, L 64 / D 10 =20.5%-24.8%, meaning the difference between the fourth gap and the third gap is 20.5%, 22.6%, or 24.8% of the diameter of the end face of the housing 1, etc. The position between the second bend 43 and the connecting part 42 is the second bend position of the negative electrode current collector 4. If L 64 / D 10 If L < 20.5%, the difference between the fourth gap and the third gap is too small. Under the premise of ensuring the welding positions of the first bending part 41 and the second bending part 43 remain unchanged, the overall length of the negative electrode current collector 4 will increase. This will not only increase the production cost of the negative electrode current collector 4 but also increase its weight and affect the energy density of the battery. 64 / D 10 If the difference between the fourth gap and the third gap is greater than 24.8%, the overall length of the negative electrode current collector 4 will be shortened while ensuring that the welding positions of the first bending part 41 and the second bending part 43 remain unchanged. This will cause the negative electrode cover plate 3 to be too close to the opening 101 when welding with the negative electrode current collector 4, affecting the welding quality between the negative electrode cover plate 3 and the negative electrode current collector 4, and reducing the production quality and efficiency of the battery.

[0044] like Figure 4 As shown, the minimum distance between the pressure groove 301 and the axis of the housing 1 is W. 11 The maximum circumferential width of the pressure groove 301 is W. 12 The minimum distance between the pressure groove 301 and the periphery of the housing 1 is W. 13 ,like Figure 3 As shown, the distance between the end of the second bent portion 43 near the connecting portion 42 and the protruding ring 31 is L. 65 ,like Figure 2As shown, the distance between the end of the second bent portion 43 away from the connecting portion 42 and the outer edge of the convex ring 31 is W. 15 .

[0045] In some embodiments, W 11 / R 10 =52.8%-61.5%, meaning the minimum distance between the pressure groove 301 and the axis of the housing 1 is 52.8%, 57.1%, or 61.5% of the radius of the end face of the housing 1, etc. If W 11 / R 10 If the pressure groove 301 is less than 52.8%, the distance between the pressure groove 301 and the axis of the housing 1 is too small. The pressure groove 301 moves towards the center of the negative electrode cover 3. Since the groove of the explosion-proof valve is usually set on the negative electrode cover 3 inside the pressure groove 301, when the pressure groove 301 moves inward, it will affect the opening area of ​​the explosion-proof valve groove, affecting the safety performance of the battery. If W 11 / R 10 If the distance between the pressure groove 301 and the axis of the housing 1 is greater than 61.5%, the distance between the pressure groove 301 and the axis of the housing 1 will be too large. When the position of the second bending part 43 remains unchanged, the welding area between the second bending part 43 and the convex ring 31 will be reduced, resulting in a decrease in the current carrying capacity of the second bending part 43 and the convex ring 31, and an increase in the temperature rise at the welding position, which will affect the performance of the battery.

[0046] In some embodiments, W 12 / R 10 =24.3%-33%, meaning the maximum circumferential width of the pressure groove 301 is 24.3%, 28.7%, or 33% of the radius of the end face of the shell 1, etc. If W 12 / R 10 If W < 24.3%, the ring width of the pressure groove 301 is too small, the area of ​​the convex ring 31 becomes smaller, and the welding area between the negative electrode current collector 4 and the negative electrode cover plate 3 is reduced, resulting in a decrease in the current carrying capacity at the welding position and an increase in the temperature rise at the welding position, affecting the battery performance; if W 12 / R 10 If the width of the groove is greater than 33%, the circumference of the groove 301 is too large. The groove 301 moves towards the center of the negative electrode cover plate 3. Since the groove of the explosion-proof valve is usually set on the negative electrode cover plate 3 inside the groove 301, when the groove 301 moves inward, it will affect the opening area of ​​the groove of the explosion-proof valve and affect the safety performance of the battery.

[0047] In some embodiments, W 13 / R 10 =9.8%-18.5%, meaning the minimum distance between the pressure groove 301 and the periphery of the shell 1 is 9.8%, 14.1%, or 18.5% of the radius of the end face of the shell 1, etc. If W 13 / R 10If the negative electrode fill factor is less than 9.8%, the distance between the pressure groove 301 and the periphery of the casing 1 is too small, and the protruding ring 31 is too close to the edge of the negative electrode cover plate 3. When the negative electrode cover plate 3 is installed at the opening 101, the protruding ring 31 is prone to interference with the inner wall of the opening 101, affecting the assembly quality and assembly efficiency of the battery; if W 13 / R 10 If the value is greater than 18.5%, the distance between the pressure groove 301 and the periphery of the shell 1 is too large, and the convex ring 31 moves inward toward the center of the negative electrode cover plate 3. When the position of the second bending part 43 remains unchanged, the welding area between the second bending part 43 and the convex ring 31 is reduced, resulting in a decrease in the current carrying capacity of the second bending part 43 and the convex ring 31, an increase in the temperature rise at the welding position, and an impact on the performance of the battery.

[0048] In some embodiments, L 65 =1.81-2.41mm, meaning the distance between the end of the second bend 43 near the connecting part 42 and the protruding ring 31 is 1.81mm, 2.11mm, or 2.41mm, etc. If L 65 If the distance is less than 1.81mm, the gap between the end of the second bend 43 near the connecting part 42 and the convex ring 31 is too small, increasing the overall length of the negative electrode current collector 4. This not only increases the production cost of the negative electrode current collector 4 but also increases its weight and affects the energy density of the battery. 65 If the distance is greater than 2.41mm, the distance between the second bending part 43 and the convex ring 31 near the connecting part 42 is too large, the overall length of the negative electrode current collector 4 becomes smaller, and the negative electrode cover plate 3 is too close to the opening 101 when welding with the negative electrode current collector 4, which affects the welding quality of the negative electrode cover plate 3 and the negative electrode current collector 4, and reduces the production quality and production efficiency of the battery.

[0049] In some embodiments, W 15 =0.55-0.95mm, meaning the distance between the end of the second bend 43 furthest from the connecting part 42 and the outer edge of the convex ring 31 is 0.55mm, 0.75mm, or 0.95mm, etc. If W 15 If the distance is less than 0.55mm, the gap between the end of the second bend 43 away from the connecting part 42 and the outer edge of the convex ring 31 is too small, increasing the overall length of the negative electrode current collector 4. This not only increases the production cost of the negative electrode current collector 4 but also increases its weight and affects the energy density of the battery. Simultaneously, when the end of the second bend 43 away from the connecting part 42 is close to the rounded corner of the outer edge of the convex ring 31, a gap will exist between the second bend 43 and the convex ring 31, affecting the welding quality. If W 15 If the distance is greater than 0.95mm, the distance between the end of the second bend 43 away from the connecting part 42 and the outer edge of the convex ring 31 is too large. This reduces the welding area between the second bend 43 and the convex ring 31, resulting in a decrease in the current carrying capacity of the second bend 43 and the convex ring 31, an increase in the temperature rise at the welding position, and an impact on the battery performance.

[0050] The convex ring 31 is preferably circular, and the convex ring 31 is preferably concentrically arranged with the negative electrode cover plate 3.

[0051] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A cylindrical secondary battery, characterized in that: It includes a housing (1), a core (2), a negative electrode cover plate (3), and a negative electrode current collector (4), wherein, The negative end of the housing (1) is provided with an opening (101); The core (2) is disposed inside the housing (1), and the end of the core (2) is provided with a negative electrode tab (201); The negative electrode cover plate (3) is fixedly installed on the housing (1) and blocks the opening (101); The negative electrode current collector (4) is S-shaped and includes a first bent part (41), a connecting part (42), and a second bent part (43) connected in sequence. The first bent part (41) abuts against the negative electrode tab (201) and is welded and fixed thereto; the second bent part (43) is welded and fixed to the negative electrode cover plate (3). The end face diameter of the shell (1) is D 10 The maximum length of the first bent portion (41) is L 61 L 61 / D 10 =77.2% - 85.8%.

2. The cylindrical secondary battery as described in claim 1, characterized in that: The second bend (43) is parallel to the first bend (41); The maximum length of the second bend (43) is L 63 L 63 / D 10 =61% - 69.7%.

3. A cylindrical secondary battery as described in claim 2, characterized in that: The minimum distance between the end of the first bent portion (41) near the connecting portion (42) and the inner wall of the housing (1) is the first gap, and the minimum distance between the end of the second bent portion (43) away from the connecting portion (42) and the inner wall of the housing (1) is the second gap; The first gap is larger than the second gap, and the difference between them is L. 62 L 62 / L 63 =8.2% - 11.5%.

4. A cylindrical secondary battery as described in claim 3, characterized in that: The minimum distance between the end of the first bent portion (41) away from the connecting portion (42) and the inner wall of the housing (1) is the third gap, and the minimum distance between the end of the second bent portion (43) near the connecting portion (42) and the inner wall of the housing (1) is the fourth gap; The fourth gap is larger than the third gap, and the difference between them is L. 64 L 64 / D 10 =20.5% - 24.8%.

5. A cylindrical secondary battery as described in claim 1, characterized in that: A groove (301) is provided on one side of the negative electrode cover plate (3), so that a convex ring (31) is formed on the other side of the negative electrode cover plate (3), and the end of the second bent part (43) away from the connecting part (42) is welded and fixed on the convex ring (31). The end face radius of the shell (1) is R 10 The minimum distance between the pressure groove (301) and the axis of the housing (1) is W. 11 W 11 / R 10 =52.8% - 61.5%.

6. A cylindrical secondary battery as described in claim 5, characterized in that: The pressure groove (301) is an annular groove structure with a trapezoidal cross-section; The maximum circumferential width of the pressure groove (301) is W. 12 W 12 / R 10 =24.3% - 33%.

7. A cylindrical secondary battery as described in claim 6, characterized in that: The minimum distance between the pressure groove (301) and the periphery of the shell (1) is W. 13 W 13 / R 10 =9.8% - 18.5%.

8. A cylindrical secondary battery as described in claim 5, characterized in that: The side of the second bend (43) away from the core (2) is flush with the side of the convex ring (31) away from the negative electrode cover plate (3), and the end of the second bend (43) near the connecting part (42) is located inside the convex ring (31); The distance between the second bent portion (43) near the end of the connecting portion (42) and the protruding ring (31) is L. 65 L 65 =1.81-2.41mm.

9. A cylindrical secondary battery as described in claim 8, characterized in that: The distance between the end of the second bent portion (43) away from the connecting portion (42) and the outer edge of the convex ring (31) is W. 15 W 15 =0.55-0.95mm.

10. A cylindrical secondary battery as described in any one of claims 1-9, characterized in that: D 10 =44-48mm。

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