Cylindrical battery cap assembly and cylindrical secondary battery

Abstract

The utility model relates to a cylindrical battery cap assembly and a cylindrical secondary battery, and belongs to the technical field of batteries. Wherein the cylindrical battery cap assembly comprises a top cover sheet, an anti-explosion sheet and an outer insulating ring; the anti-explosion piece and the top cover piece are oppositely arranged in the vertical direction. The anti-explosion piece is located below the top cover piece, and the outer edge of the anti-explosion piece makes contact with the outer edge of the top cover piece; the outer insulating ring is sleeved on the peripheries of the explosion-proof sheet and the top cover sheet; a connecting part is arranged at the lower end of the outer insulating ring, is positioned at the bottom of the explosion-proof sheet, and is in contact with one side, deviating from the top cover sheet, of the explosion-proof sheet; the connecting part is provided with a groove, the groove is located below the anti-explosion piece, and an opening of the groove faces upwards and is used for containing redundant glue between the contact faces of the anti-explosion piece and the connecting part. According to the cylindrical battery cap assembly provided by the utility model, the groove is formed in the bottom of the outer insulating ring, the groove is positioned below the anti-explosion sheet, and the notch of the groove is formed upwards, so that the groove can accommodate redundant glue between the anti-explosion sheet and the connecting part.

Description

Technical Field

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

[0002] Battery caps are an important component of lithium-ion batteries. Existing battery caps have explosion-proof functions by incorporating explosion-proof plates.

[0003] A patent (publication number CN207765485U) discloses a cylindrical battery explosion-proof edge-sealing combination cap, which discloses an outer insulating ring fitted around the outer periphery of a top cover, an explosion-proof sheet, and a perforated plate, and fixed with adhesive. In the prior art, the part where the explosion-proof sheet and the outer insulating ring of the cap meet is usually flat. When the top cover and the explosion-proof sheet are placed inside the outer insulating ring, the adhesive layer of the outer insulating ring is in complete contact with the explosion-proof sheet. However, due to the pressure exerted by the sealing pressure on the top cover and the explosion-proof sheet, the outer insulating ring is squeezed, which can easily cause adhesive to overflow, affecting the battery performance. Moreover, the bottom of the outer insulating ring on the cap is flat, resulting in limited overall structural strength and making it prone to deformation and sealing failure. Utility Model Content

[0004] In view of the shortcomings of the related technologies, the present invention provides a cylindrical battery cap assembly and a cylindrical secondary battery, wherein a groove is provided at the bottom of the outer insulating ring to accommodate excess glue and prevent glue from overflowing into the battery.

[0005] This utility model provides a cylindrical battery cap assembly, comprising:

[0006] Top cover plate;

[0007] The explosion-proof plate is vertically opposite to the top cover plate; the explosion-proof plate is located below the top cover plate, and the outer edge of the explosion-proof plate is in contact with the outer edge of the top cover plate.

[0008] An outer insulating ring is fitted around the outer periphery of the explosion-proof sheet and the top cover sheet. The lower end of the outer insulating ring is provided with a connecting part, which is located at the bottom of the explosion-proof sheet. The connecting part is in contact with the side of the explosion-proof sheet away from the top cover sheet. The connecting part is provided with a groove, which is located below the explosion-proof sheet. The groove opening is set upward to accommodate excess glue between the contact surface of the explosion-proof sheet and the connecting part.

[0009] This technical solution increases the contact area between the outer insulating ring and the explosion-proof sheet by providing a connecting part at the lower end of the outer insulating ring, so that the connecting part and the side of the explosion-proof sheet away from the top cover sheet come into contact with each other, thereby increasing the firmness of the explosion-proof sheet in the outer insulating ring; by providing a groove in the connecting part, with the groove located below the explosion-proof sheet and the groove opening facing upward, the groove can accommodate excess glue between the explosion-proof sheet and the connecting part.

[0010] In some embodiments, the ratio of the groove depth H1 to the connecting thickness H2 is greater than or equal to 12% and less than or equal to 22%; the groove depth H1 satisfies: 0.05mm≤H1≤0.25mm; the connecting thickness H2 satisfies: 0.8mm≤H2≤1mm.

[0011] In some embodiments, the groove has a structure that is wider at the top and narrower at the bottom, and the ratio of the bottom diameter W1 of the groove to the opening diameter W2 of the groove is greater than or equal to 40% and less than or equal to 60%.

[0012] In some embodiments, the bottom diameter W1 of the groove satisfies: 0.2mm≤W1≤0.4mm; the opening diameter W2 of the groove satisfies: 0.5mm≤W2≤0.7mm.

[0013] In some embodiments, the volume S of the groove satisfies: 0.04 mm 2 ≤S≤0.1mm 2 .

[0014] In some embodiments, the groove is recessed into the side of the connector facing the explosion-proof sheet, and the connector has a protrusion that forms the sidewall of the groove.

[0015] In some embodiments, the ratio of the top surface diameter W3 of the protrusion to the groove opening diameter W2 is greater than or equal to 75% and less than or equal to 95%.

[0016] In some embodiments, the ratio of the distance W4 from the central axis of the groove to the outer peripheral wall of the outer insulating ring to the length W0 of the connecting portion along the radial direction of the outer insulating ring is greater than or equal to 34% and less than or equal to 48%; the length W0 of the connecting portion along the radial direction of the outer insulating ring satisfies: 2mm≤W0≤4mm.

[0017] In some embodiments, a first included angle α is defined between the groove sidewall and the radial direction of the outer insulating ring, the first included angle α being greater than or equal to 35° and less than or equal to 55°.

[0018] In addition, this utility model also provides a cylindrical secondary battery, including the above-mentioned cylindrical battery cap assembly.

[0019] Based on the above technical solution, in this embodiment of the utility model, the cylindrical battery cap assembly has a groove on the bottom surface of the outer insulating ring to accommodate excess glue between the explosion-proof sheet and the outer insulating ring, preventing glue from overflowing onto the contact surface between the explosion-proof sheet and the outer insulating ring and affecting battery performance; and a protrusion is provided on the bottom surface of the outer insulating ring to reinforce the bottom of the outer insulating ring, preventing the bottom of the outer insulating ring from deforming and sagging, thereby increasing the structural strength of the battery and increasing the stability of the battery seal. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the present invention and form part of this application, illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the present invention and do not constitute an undue limitation thereof. In the drawings:

[0021] Figure 1 This is a schematic diagram of the structure of one embodiment of the cylindrical battery cap assembly of this utility model;

[0022] Figure 2 for Figure 1 Enlarged view of a portion of point A in the middle;

[0023] Figure 3 This is a partial dimensional diagram of the connecting part, protrusion, and groove in one embodiment of the cylindrical battery cap assembly of this utility model.

[0024] Figure 4 This is a dimension marking diagram of another part of the groove in one embodiment of the cylindrical battery cap assembly of this utility model.

[0025] In the picture:

[0026] 1. Top cover plate; 2. Explosion-proof plate; 3. Outer insulating ring;

[0027] 31. Connecting part; 311. Groove; 312. Protrusion. Detailed Implementation

[0028] The technical solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0029] In the description of this utility model, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0030] The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0031] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0032] As attached Figure 1 and Figure 2 As shown in an illustrative embodiment of the cylindrical battery cap assembly of this utility model, the cylindrical battery cap assembly includes a top cover plate 1, an explosion-proof plate 2, and an outer insulating ring 3; the explosion-proof plate 2 and the top cover plate 1 are arranged opposite each other in the vertical direction; the explosion-proof plate 2 is located below the top cover plate 1, and the outer edge of the explosion-proof plate 2 is in contact with the outer edge of the top cover plate 1; the outer insulating ring 3 has a through cavity arranged in the vertical direction, and the explosion-proof plate 2 and the top cover plate 1 are disposed in the through cavity, with the outer edges of the explosion-proof plate 2 and the outer edges of the top cover plate 1 respectively in contact with the inner wall of the through cavity. The outer insulating ring 3 is fitted around the outer periphery of the explosion-proof sheet 2 and the top cover sheet 1. The lower end of the outer insulating ring 3 is provided with a connecting part 31, which is located at the bottom opening of the cavity to reduce the opening at the bottom of the cavity. The connecting part 31 is located at the bottom of the explosion-proof sheet 2 and is in contact with the side of the explosion-proof sheet 2 away from the top cover sheet 1. The connecting part 31 is provided with a groove 311, which is located below the explosion-proof sheet 2 and has its opening facing upward to accommodate excess glue between the contact surfaces of the explosion-proof sheet 2 and the connecting part 31.

[0033] It should be noted that the outer insulating ring 3 is made of a relatively soft material. The outer insulating ring 3 deforms so that it fits around the outer periphery of the explosion-proof sheet 2 and the top cover sheet 1.

[0034] The aforementioned cylindrical battery cap assembly features a connecting portion 31 at the lower end of the outer insulating ring 3, allowing the connecting portion 31 to contact the side of the explosion-proof sheet 2 facing away from the top cover 1. This increases the contact area between the outer insulating ring 3 and the explosion-proof sheet 2, enhancing the stability of the explosion-proof sheet 2 within the outer insulating ring 3. Furthermore, a groove 311 is provided in the connecting portion 31, positioned below the explosion-proof sheet 2 with its opening facing upwards. This allows the groove 311 to accommodate excess adhesive between the explosion-proof sheet 2 and the connecting portion 31, preventing adhesive from overflowing the contact surface between the explosion-proof sheet 2 and the outer insulating ring 3, thus avoiding any impact on battery performance.

[0035] like Figure 3 As shown, the ratio of the depth H1 of the groove 311 to the thickness H2 of the connecting part 31 is greater than or equal to 12% and less than or equal to 22%; the depth H1 of the groove 311 satisfies: 0.05mm≤H1≤0.25mm; the thickness H2 of the connecting part 31 also satisfies: 0.8mm≤H2≤1mm.

[0036] If the ratio of H1 to H2 is too small, the depth H1 of the groove 311 will be small, the amount of glue that the groove 311 can hold will be small, and the glue will easily overflow from the groove 311. Furthermore, when the top cover 1 and the explosion-proof sheet 2 are installed into the outer insulating ring 3, too much glue will overflow to the outside of the outer insulating ring 3, resulting in poor battery performance.

[0037] If the ratio of H1 to H2 is too large, the depth H1 of the groove 311 will be larger, and the amount of glue that the groove 311 can hold will be larger, which will cause glue waste and increase the manufacturing cost of the battery. Moreover, if the depth H1 of the groove 311 is larger, with a certain thickness of the connecting part 31, the thickness of the bottom of the groove 311 will be smaller. When the battery is sealed, the outer insulating ring 3 will be compressed at the casing groove. The bottom of the groove 311 will not have enough extra thickness for compression, which may cause poor battery sealing and increase the probability of battery leakage.

[0038] In some embodiments, the depth H1 of the groove 311 is 0.15 mm, the thickness H2 of the connecting portion 31 is 0.9 mm, and the ratio of H1 to H2 is 17%.

[0039] like Figure 2 As shown, the groove 311 has a structure that is wider at the top and narrower at the bottom, so that the sidewalls of the groove 311 can guide the glue. The ratio of the bottom diameter W1 of the groove 311 to the opening diameter W2 of the groove 311 is greater than or equal to 40% and less than or equal to 60%.

[0040] If the ratio of W1 to W2 is too small, the bottom diameter W1 of the groove 311 becomes smaller and the opening diameter W2 of the groove 311 becomes larger, reducing the contact area between the explosion-proof sheet 2 and the outer insulating ring 3. When the cap is squeezed, the glue easily overflows from the groove 311, and the connecting part 31 does not have enough contact surface to adhere the glue, making the adhesion between the explosion-proof sheet 2 and the outer insulating ring 3 unreliable. The explosion-proof sheet 2 and the outer insulating ring 3 are prone to shaking and displacement, resulting in a decrease in sealing performance. If the ratio of W1 to W2 is too large, the bottom diameter W1 of the groove 311 becomes larger and the opening diameter W2 of the groove 311 becomes smaller. The guiding effect of the side wall of the groove 311 on the glue overflow is reduced, and the position of the glue overflow is uncontrollable and the thickness is uneven.

[0041] The bottom diameter W1 of groove 311 satisfies: 0.2mm≤W1≤0.4mm; the opening diameter W2 of groove 311 satisfies: 0.5mm≤W2≤0.7mm.

[0042] In some embodiments, the bottom diameter W1 of the groove 311 is 0.3 mm, the opening diameter W2 of the groove 311 is 0.6 mm, and the ratio of W1 to W2 is 50%.

[0043] The volume S of groove 311 satisfies: 0.04mm 2 ≤S≤0.1mm 2 .

[0044] If the volume S of the groove 311 is too large, a large amount of glue can be stored in the groove 311. However, the amount of glue squeezed out by the cap is limited, and the remaining glue is still stored in the groove 311, which easily leads to glue waste. If the volume S of the groove 311 is too small, a small amount of glue can be stored in the groove 311. When the cap is squeezed, not enough glue is squeezed out from the groove 311, so the bonding surface of the outer insulating ring 3 and the explosion-proof sheet 2 cannot be completely covered with glue. This easily leads to a poor adhesion between the explosion-proof sheet 2 and the outer insulating ring. During transportation / handling, due to factors such as shaking and vibration, the top cover plate and the explosion-proof sheet 2 may detach from the outer insulating ring 3, resulting in the scrapping of the cap.

[0045] In some embodiments, the volume S of the groove 311 is 0.7 mm. 2 .

[0046] like Figure 2 As shown, the connecting part 31 has a protrusion 312, which strengthens the bottom of the outer insulating ring 3, making the bottom of the outer insulating ring 3 less prone to deformation and sagging. This not only increases the structural strength of the battery but also ensures the stability of the battery seal. The groove 311 is recessed into the connecting part 31 on the side facing the explosion-proof sheet 2, and the protrusion 312 forms the sidewall of the groove 311.

[0047] The ratio of the top surface diameter W3 of the protrusion 312 to the groove diameter W2 of the groove 311 is greater than or equal to 75% and less than or equal to 95%.

[0048] If the ratio of the top surface diameter W3 of the protrusion 312 to the groove diameter W2 of the recess 311 is too small, the top surface diameter W3 of the protrusion 312 will become smaller, and the groove diameter W2 of the recess 311 will become larger. This reduces the contact area between the explosion-proof sheet 2 and the outer insulating ring 3. When the cap is compressed, the adhesive is prone to overflowing from the groove 311, and the connecting part 31 will not have sufficient contact surface to hold the adhesive. This can easily lead to unreliable adhesion between the explosion-proof sheet 2 and the outer insulating ring 3, causing them to easily wobble and shift, thus compromising sealing performance. If the ratio of the top surface diameter W3 of the protrusion 312 to the groove diameter W2 of the groove 311 is too large, the top surface diameter W3 of the protrusion 312 will become larger and the groove diameter W2 of the groove 311 will become smaller. As a result, the amount of glue stored in the groove 311 will be less. After the cap is squeezed, there will not be enough glue in the groove 311 to overflow and coat the contact surface between the explosion-proof sheet 2 and the outer insulating ring 3. This may cause the explosion-proof sheet 2 to be not firmly fixed and may shake inside the insulating ring, resulting in problems such as poor airtightness.

[0049] like Figure 4 As shown, the ratio of the distance W4 from the central axis of the groove 311 to the outer peripheral wall of the outer insulating ring 3 to the length W0 of the connecting part 31 along the radial direction of the outer insulating ring 3 is greater than or equal to 34% and less than or equal to 48%.

[0050] If the ratio of the distance W4 from the central axis of the groove 311 to the outer peripheral wall of the outer insulating ring 3 to the radial length W0 of the connecting part 31 along the outer insulating ring 3 is too small, then the distance W4 from the central axis of the groove 311 to the outer peripheral wall of the outer insulating ring 3 will be too small. In this case, the glue will be squeezed out and will have difficulty overflowing to the entire contact surface between the explosion-proof sheet 2 and the outer insulating ring 3. It will be difficult to fix the entire explosion-proof sheet 2, and it will be easy to shake inside the outer insulating ring 3, causing problems such as poor airtightness.

[0051] If the ratio of the distance W4 from the central axis of the groove 311 to the outer peripheral wall of the outer insulating ring 3 to the radial length W0 of the connecting part 31 along the outer insulating ring 3 is too large, then the distance W4 from the central axis of the groove 311 to the outer peripheral wall of the outer insulating ring 3 will be too large, and the distance between the central axis of the groove 311 and the central axis of the outer insulating ring 3 will be too small. When the cap is squeezed, the glue will easily overflow in the direction of the central axis of the outer insulating ring 3. The glue will easily overflow, and after the battery is sealed, the glue will easily come into contact with the electrolyte and enter the battery, affecting the battery performance.

[0052] The length W0 of the connecting part 31 along the radial direction of the outer insulating ring 3 satisfies: 2mm≤W0≤4mm.

[0053] The distance W4 from the central axis of groove 311 to the outer peripheral wall of outer insulating ring 3 satisfies: 0.9mm≤W0≤1.5mm.

[0054] In some embodiments, the length W0 of the connecting portion 31 along the radial direction of the outer insulating ring 3 is 3 mm, the distance W4 from the central axis of the groove 311 to the outer peripheral wall of the outer insulating ring 3 is 1.2 mm, and the ratio of the distance W4 from the central axis of the groove 311 to the outer peripheral wall of the outer insulating ring 3 to the length W0 of the connecting portion 31 along the radial direction of the outer insulating ring 3 is 40%.

[0055] like Figure 4 As shown, a first included angle α is defined between the sidewall of the groove 311 and the radial direction of the outer insulating ring 3, and the angle of the first included angle α is greater than or equal to 35° and less than or equal to 55°.

[0056] If the first included angle α is too small, it will occupy the contact area between the explosion-proof sheet 2 and the outer insulating ring 3, resulting in a reduction in the contact area between the explosion-proof sheet 2 and the outer insulating ring 3. After the cap is squeezed, the glue is easy to overflow from the groove 311, and the connecting part 31 does not have enough contact surface to adhere the glue, which makes the adhesion between the explosion-proof sheet 2 and the outer insulating ring 3 unreliable. The explosion-proof sheet 2 and the outer insulating ring 3 are easy to shake and shift, resulting in a decrease in sealing performance. If the first included angle α is too large, the guiding effect of glue overflow is reduced, the position of glue overflow is uncontrollable, and the thickness is uneven.

[0057] The working principle of the above-mentioned cylindrical battery cap assembly is as follows: glue is injected into the groove 311, and the outer insulating ring 3 is squeezed during the sealing process, which squeezes out the glue in the groove 311 and spreads the glue on the contact surface of the explosion-proof sheet 2 and the connecting part 31, thereby achieving the adhesion and fixation between the explosion-proof sheet 2 and the outer insulating ring 3. Excess glue is still stored in the groove 311 and will not overflow into the battery, thus not affecting the battery performance.

[0058] Based on the above-described cylindrical battery cap assembly, this utility model also provides a cylindrical secondary battery, which includes the above-described cylindrical battery cap assembly.

[0059] Through the description of several embodiments of the cylindrical battery cap assembly of this utility model, it can be seen that the embodiments of the cylindrical battery cap assembly of this utility model have at least one or more of the following advantages:

[0060] (1) The above-mentioned cylindrical battery cap assembly has a connecting part 31 at the lower end of the outer insulating ring 3, so that the connecting part 31 and the side of the explosion-proof sheet 2 away from the top cover sheet 1 are in contact with each other, thereby increasing the contact area between the outer insulating ring 3 and the explosion-proof sheet 2 and increasing the firmness of the explosion-proof sheet 2 in the outer insulating ring 3.

[0061] (2) By setting a groove 311 on the bottom surface of the outer insulating ring 3, excess glue between the explosion-proof sheet 2 and the outer insulating ring 3 can be accommodated, so as to avoid glue overflowing from the contact surface between the explosion-proof sheet 2 and the outer insulating ring 3 and affecting the battery performance.

[0062] (3) By setting a protrusion 312 at the bottom of the outer insulating ring 3, the bottom of the outer insulating ring 3 is reinforced, making the bottom of the outer insulating ring 3 less prone to deformation and sagging, thereby increasing the structural strength of the battery and ensuring the stability of the battery seal.

[0063] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0064] The above embodiments are only used to illustrate the technical solution of this utility model and not to limit it; although the utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of this utility model or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solution of this utility model, and all such modifications and substitutions should be covered within the scope of the technical solution claimed by this utility model.

Claims

1. A cylindrical battery cap assembly, characterized in that, include: Top cover plate; An explosion-proof sheet is vertically opposite to the top cover sheet; the explosion-proof sheet is located below the top cover sheet, and the outer edge of the explosion-proof sheet is in contact with the outer edge of the top cover sheet. An outer insulating ring is fitted around the outer periphery of the explosion-proof sheet and the top cover sheet; the lower end of the outer insulating ring is provided with a connecting part, which is located at the bottom of the explosion-proof sheet and is in contact with the side of the explosion-proof sheet away from the top cover sheet; the connecting part is provided with a groove, which is located below the explosion-proof sheet and the groove opening is set upward.

2. The cylindrical battery cap assembly according to claim 1, characterized in that, The ratio of the groove depth H1 to the connecting part thickness H2 is greater than or equal to 12% and less than or equal to 22%; the groove depth H1 satisfies: 0.05mm≤H1≤0.25mm; the connecting part thickness H2 satisfies: 0.8mm≤H2≤1mm.

3. The cylindrical battery cap assembly according to claim 1 or 2, characterized in that, The groove has a structure that is wider at the top and narrower at the bottom, and the ratio of the bottom diameter W1 of the groove to the opening diameter W2 of the groove is greater than or equal to 40% and less than or equal to 60%.

4. The cylindrical battery cap assembly according to claim 3, characterized in that, The bottom diameter W1 of the groove satisfies: 0.2mm≤W1≤0.4mm; the opening diameter W2 of the groove satisfies: 0.5mm≤W2≤0.7mm.

5. The cylindrical battery cap assembly according to claim 1, characterized in that, The volume S of the groove satisfies: 0.04 mm 2 ≤S≤0.1mm 2 .

6. The cylindrical battery cap assembly according to claim 1, characterized in that, The groove is recessed on the side of the connecting part facing the explosion-proof sheet, and the connecting part is provided with a protrusion, which is used to form the sidewall of the groove.

7. The cylindrical battery cap assembly according to claim 6, characterized in that, The ratio of the top surface diameter W3 of the protrusion to the groove opening diameter W2 of the groove is greater than or equal to 75% and less than or equal to 95%.

8. The cylindrical battery cap assembly according to claim 1, characterized in that, The ratio of the distance W4 from the central axis of the groove to the outer peripheral wall of the outer insulating ring to the length W0 of the connecting part along the radial direction of the outer insulating ring is greater than or equal to 34% and less than or equal to 48%; the length W0 of the connecting part along the radial direction of the outer insulating ring satisfies: 2mm≤W0≤4mm.

9. The cylindrical battery cap assembly according to claim 1, characterized in that, A first included angle α is defined between the sidewall of the groove and the radial direction of the outer insulating ring, wherein the angle α is greater than or equal to 35° and less than or equal to 55°.

10. A cylindrical secondary battery, characterized in that, Includes the cylindrical battery cap assembly as described in any one of claims 1-9.

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