Top cover assembly, battery cell and battery pack

Abstract

The utility model provides a kind of top cover assembly, electric core and battery pack, the top cover assembly includes top cover, is equipped with liquid injection hole;Sealing plug is set to seal the liquid injection hole;Wherein, the sealing plug is configured to be punctured to form vent hole on the sealing plug.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a top cover assembly, a battery cell, and a battery pack. Background Technology

[0002] In related technologies, cylindrical cells need to undergo formation. To facilitate the formation of cylindrical cells, a sealing plug is provided on the top cover of the cylindrical cell. The sealing plug is located at the liquid injection hole of the top cover. Stable vents are provided on the sealing plug to facilitate the venting of air during the formation process. After the liquid injection of the cell is completed but before formation, dust will enter the cell through the vents on the sealing plug and contaminate the electrolyte. The electrolyte will also evaporate through the vents on the sealing plug, thereby affecting the performance of the cell. Utility Model Content

[0003] The embodiments of this utility model provide a top cover assembly, a battery cell, and a battery pack, which can improve the technical problem of poor sealing performance of the battery cell after liquid injection and before formation.

[0004] In a first aspect, an embodiment of the present invention provides a top cover assembly, comprising: a top cover having an injection hole; and a sealing plug configured to seal the injection hole; wherein the sealing plug is configured to be puncturable to form a vent hole on the sealing plug.

[0005] In one embodiment, the sealing plug has a hollow groove, the bottom wall of which is configured to be puncturable. By providing a hollow groove on the sealing plug, the overall structural strength of the sealing plug is weakened, especially the bottom wall of the hollow groove, which is easily punctured using a sharp piercing tool.

[0006] In one embodiment, the hollow slot includes a sidewall, the sidewall including an extension and a guide portion, the guide portion being necked relative to the extension portion, the extension portion abutting against the top cover, and the guide portion extending into the cell. By necking the guide portion, it is easier for the guide portion to be inserted into the cell through the injection hole.

[0007] In one embodiment, the sidewall is further provided with an inverted buckle structure, and the top cover is sandwiched between the top wall and the inverted buckle structure, thereby preventing the sealing plug from separating from the top cover.

[0008] In one embodiment, the top surface of the top wall is configured as a plane so that the negative pressure device abuts against the top surface of the top wall.

[0009] In one embodiment, the bottom wall is thinner than the side wall, and the thickness of the bottom wall accounts for 20% to 60% of the thickness of the side wall. When the thickness of the bottom wall of the sealing plug is less than 20% of the thickness of the side wall, the overall structural strength of the bottom wall of the sealing plug is poor, and the sealing plug is easily crushed when it is assembled onto the top cover. When the thickness of the bottom wall of the sealing plug is greater than 60% of the thickness of the side wall, the bottom wall of the sealing plug is more difficult to puncture, thus affecting the formation of the vent.

[0010] In one embodiment, the diameter of the vent hole ranges from 0.5 mm to 3.0 mm. When the diameter of the vent hole 25 of the sealing plug 2 is greater than 3.0 mm, the interaction range between the piercing element and the sealing plug is larger during the process of the piercing element piercing the bottom wall of the sealing plug, thereby causing the sealing plug to detach from the top cover and affecting the fixation of the sealing plug. When the diameter of the vent hole of the sealing plug is less than 0.5 mm, after the sealing plug is pierced by the piercing element, the vent hole on the sealing plug will close under its own elastic recovery, thereby affecting the subsequent formation venting.

[0011] In one embodiment, the sealing plug includes a top wall with an opening communicating with the hollow groove. The top cover assembly also includes a sealing sheet configured to seal the opening after cell formation. By sealing the opening of the hollow groove with a sealing sheet after cell formation, the entire cell forms a sealed structure, preventing leakage. Simultaneously, gases generated during cell use can be stored within the hollow groove, thereby improving the cell's electrical performance and lifespan.

[0012] In one embodiment, the sealing sheet is connected to the top cover and abuts against the top wall of the sealing plug, so that the sealing sheet, the top cover and the sealing plug form a double sealing structure.

[0013] In one embodiment, the sealing sheet is configured to compress the sealing plug, such that the compression rate of the sealing plug is 15% to 70%. When the compression rate of the sealing plug is less than 15%, the insufficient compression makes it difficult to form an interference fit between the sealing plug and the top cover, leading to easy air leakage in the top cover assembly 100 of the battery cell. When the compression rate of the sealing plug is greater than 70%, the sealing plug exerts a large rebound force on the sealing sheet, which can easily lead to poor welding between the sealing sheet and the top cover.

[0014] In one embodiment, the sealing sheet and the sealing plug form a first abutment structure, and the sealing plug and the top cover form a second abutment structure. The overlap width between the first and second abutment structures is c, which ranges from 1.0 mm to 6.5 mm. When the overlap width c is less than 1.0 mm, it will cause air leakage in the battery cell. When the overlap width c is greater than 6.5 mm, it will result in a larger overall size of the sealing plug, and correspondingly a larger size of the liquid injection hole, thereby affecting the overall structural dimensions of the battery cell.

[0015] In one embodiment, the sealing plug is made of one or more of fluororubber, PP, PBT, and EPDM, so that the sealing plug has a suitable compression amount, as well as a certain temperature resistance and a long service life.

[0016] Secondly, embodiments of this utility model provide a battery cell, which includes the top cover assembly described above, or is prepared using the battery cell preparation method described above.

[0017] Thirdly, embodiments of the present invention provide a battery pack, the battery pack including the aforementioned battery cells.

[0018] The beneficial effects of the embodiments of this utility model are as follows:

[0019] In an embodiment of this utility model, the sealing plug is configured to be puncturable. After the battery cell is injected with electrolyte, the sealing plug is configured to seal the electrolyte injection hole. Before the battery cell is prepared for formation, the sealing plug is punctured to form a vent hole, so that the gas generated during the battery cell formation process can be discharged through the vent hole, thereby ensuring that the battery cell is in a sealed state after electrolyte injection and before formation. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments 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.

[0021] Figure 1 This is a cross-sectional view of a portion of the battery cell structure provided in an embodiment of this utility model;

[0022] Figure 2 This is an exploded view of the top cover assembly provided in an embodiment of this utility model;

[0023] Figure 3 This is a perspective view of the sealing plug provided in an embodiment of this utility model;

[0024] Figure 4This is a cross-sectional view of the sealing plug of the top cover assembly provided in an embodiment of the present invention before it is punctured;

[0025] Figure 5 This is a cross-sectional view of the sealing plug of the top cover assembly provided in an embodiment of the present invention being punctured by the puncture component;

[0026] Figure 6 This is a cross-sectional view of the sealing plug of the top cover assembly provided in an embodiment of the present invention after it has been punctured;

[0027] Figure 7 This is a partial cross-sectional view of the battery cell provided in an embodiment of the present invention, showing the negative pressure being drawn using a negative pressure drawing device.

[0028] 100. Top cover assembly;

[0029] 1. Top cover; 11. Injection hole; 12. Base; 13. Boss;

[0030] 2. Sealing plug; 21. Hollow groove; 22. Top wall; 221. Opening; 23. Side wall; 231. Extension; 232. Guide; 24. Bottom wall; 25. Vent hole; 26. Inverted structure; 27. First abutting structure; 28. Second abutting structure;

[0031] 3. Sealing sheet; 31. Main body; 32. Recessed part;

[0032] 4. Sealing components;

[0033] 5. Negative pressure extraction device;

[0034] 6. Punctured parts;

[0035] 7. Shell;

[0036] 8. Electrode assembly; Detailed Implementation

[0037] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model. In addition, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present utility model and are not intended to limit the present utility model. In the present utility model, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0038] In related technologies, cylindrical cells need to undergo formation. To facilitate the formation of cylindrical cells, a sealing plug is provided on the top cover of the cylindrical cell. The sealing plug is located at the liquid injection hole of the top cover. The sealing plug has vent holes to facilitate the venting of air during the formation process. After the cell is filled with liquid but before formation, dust will enter the cell through the vent holes on the sealing plug and contaminate the electrolyte. The electrolyte will also evaporate through the vent holes on the sealing plug, thereby affecting the performance of the cell.

[0039] An embodiment of this application provides a battery pack, which includes a housing and a plurality of battery cells disposed within the housing. This battery pack can be a power battery pack or an energy storage battery pack.

[0040] Embodiments of this application provide a battery cell, which can be a cylindrical battery cell or a prismatic battery cell. For example... Figure 1 and Figure 2 As shown, the battery cell includes a housing 7, a top cover assembly 100, an electrode assembly 8, and an electrolyte.

[0041] The housing 7 can be a steel housing, with an open top to facilitate the installation of the electrode assembly 8.

[0042] The top cover assembly 100 is connected to the top opening of the housing 7.

[0043] The electrode assembly 8 can be a wound core assembly formed by winding multiple positive electrode sheets, multiple separators, and multiple negative electrode sheets, or a stacked assembly formed by stacking multiple positive electrode sheets, multiple separators, and multiple negative electrode sheets. An electrolyte is injected into the electrode assembly 8. The electrolyte serves as the medium for the migration of lithium ions between the positive and negative electrode sheets and is fundamental to the electrochemical reactions within the battery cell.

[0044] Embodiments of this application also provide a top cover assembly 100, which includes a top cover 1 and a sealing plug 2. The top cover 1 is connected to the top opening of the housing 7.

[0045] An injection hole 11 is provided on the top cover 1. Electrolyte is injected into the housing 7 through the injection hole 11 and fills the electrode assembly 8.

[0046] The sealing plug 2 is configured to seal the injection hole 11. The sealing plug 2 is puncturable; when punctured, it creates a vent hole 25 (e.g., ...). Figure 6As shown, the gas generated during the cell formation process can be discharged through the vent 25 to prevent the gas generated during cell formation from accumulating inside the casing 7 and causing the cell to expand in size. Furthermore, if the gas generated during cell formation is not discharged in time, it can lead to excessive internal pressure in the later stages of the cell's lifespan, resulting in a shortened cell lifespan. In the embodiments of this application, because the gas generated during cell formation can be discharged through the vent 25 on the sealing plug 2, a stable and uniform SEI film is formed inside the cell.

[0047] Understandably, during the cell manufacturing process, after the electrolyte is injected into the cell casing, the cell is left to stand to allow the electrolyte to fully wet the electrode assembly before formation. Since the sealing plug 2 seals the injection hole 11 after the electrolyte is injected, the injection hole 11 remains sealed during the cell wetting process, and the sealing plug 2 remains unpunctured. Therefore, the cell is completely sealed, making it difficult for dust to enter and for the electrolyte to evaporate. Before formation, the sealing plug 2 is punctured to create a vent hole 25, allowing gases generated during formation to escape through the vent hole 25.

[0048] In some embodiments, such as Figure 3 and Figure 4 As shown, a hollow groove 21 is provided on the sealing plug 2. The hollow groove 21 includes a connected side wall 23 and a bottom wall 24, wherein the bottom wall 24 of the hollow groove 21 is configured to be puncturable. By providing a hollow groove 21 on the sealing plug 2, the overall structural strength of the sealing plug 2 is relatively weak, especially the bottom wall 24 of the hollow groove 21, which is easily punctured by using a sharp piercing element 6.

[0049] In some embodiments, the sealing plug 2 is made of an elastomeric material with a suitable compression ratio. Suitable materials for preparing the sealing plug 2 include one or more of FKM (fluororubber), PP (polypropylene), PBT (polybutylene terephthalate), and EPDM (ethylene propylene diene monomer rubber), so that the sealing plug 2 has a suitable compression ratio while also possessing certain temperature resistance and a long service life. The suitable compression ratio of the sealing plug 2 is 10% to 80%.

[0050] In some embodiments, the bottom wall 24 of the sealing plug 2 is thinned relative to the side wall 23 so that the bottom wall 24 of the sealing plug 2 is easily punctured. In specific embodiments, the thickness of the bottom wall 24 is 20% to 60% of the thickness of the side wall 23. In some specific embodiments, the percentage of the thickness of the bottom wall 24 to the thickness of the side wall 23 can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any two of the above values, or a range between any two of the above values.

[0051] The inventors discovered through research that when the thickness of the bottom wall 24 of the sealing plug 2 is less than 20% of the thickness of the side wall 23, the overall structural strength of the bottom wall 24 of the sealing plug 2 is poor, and the sealing plug 2 is easily crushed when it is assembled onto the top cover 1. When the thickness of the bottom wall 24 of the sealing plug 2 is greater than 60% of the thickness of the side wall 23, the bottom wall 24 of the sealing plug 2 is more difficult to puncture, thus affecting the formation of the vent hole 25.

[0052] In some embodiments, the thickness of the bottom wall 24 of the sealing plug 2 is 0.3 mm to 2.0 mm, thereby ensuring that the bottom wall 24 of the sealing plug 2 has suitable structural strength while being easily punctured by the puncturing member 6. In specific embodiments, the thickness of the bottom wall 24 of the sealing plug 2 can be 0.3 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2.0 mm, 2.3 mm, 2.5 mm, 2.8 mm, 3.0 mm, or any value between the above, or a range between any two of the above values.

[0053] In some embodiments, continue to refer to Figure 3 and Figure 4 The sealing plug 2 includes a top wall 22 and a bottom wall 24 opposite to each other, and a side wall 23 connecting the top wall 22 and the bottom wall 24. An opening 221 is provided on the top wall 22, and the side wall 23 and the bottom wall 24 enclose a hollow groove 21, and the opening 221 communicates with the hollow groove 21.

[0054] The sidewall 23 includes an extension 231 and a guide 232 connected together. The extension 231 connects the top wall 22 and the guide 232, and the guide 232 connects the extension 231 and the bottom wall 24. The guide 232 is necked relative to the extension 231. The extension 231 abuts against the sidewall of the liquid injection hole 11 of the top cover 1, and the guide 232 extends into the cell. By necking the guide 232, it is easier for the guide 232 to be inserted into the cell through the liquid injection hole 11. In a specific embodiment, the guide 232 is inclined relative to the extension 231 to form a guide angle.

[0055] In some embodiments, continue to refer to Figure 3 and Figure 4 The sealing plug 2 also has an inverted buckle structure 26, which is disposed on the side wall 23. The top wall 22 of the sealing plug 2 abuts against the upper end face of the top cover 1, and the inverted buckle structure 26 abuts against the lower end face of the top cover 1, thereby preventing the sealing plug 2 from separating from the top cover 1. The inverted buckle structure 26 is disposed on the guide portion 232 of the side wall 23.

[0056] In some embodiments, such as Figures 5 to 7 As shown, the top wall 22 of the sealing plug 2 is set as a plane so that the negative pressure device 5 can abut against the top surface of the top wall 22. Specifically, after the bottom wall 24 of the hollow groove 21 is punctured by the piercing piece 6, the negative pressure device 5 is abutted against the top surface of the top wall 22. The negative pressure device 5 connects to the inner cavity of the housing 7 through the vent hole 25 on the hollow groove 21, so that a negative pressure cavity is formed inside the housing 7, and the air brought in during the electrolyte injection process is discharged to the outside of the battery cell by the negative pressure device 5.

[0057] In some embodiments, the diameter of the vent hole 25 on the bottom wall 24 of the sealing plug 2 ranges from 0.5 mm to 3.0 mm. The inventors discovered through research that when the diameter of the vent hole 25 of the sealing plug 2 is greater than 3.0 mm, the piercing element 6, during the process of piercing the bottom wall 24 of the sealing plug 2, has a larger interaction range with the sealing plug 2, thereby causing the sealing plug 2 to detach from the top cover 1 and affecting the fixation of the sealing plug 2. Since the sealing plug 2 is made of a material with a certain degree of elasticity, when the diameter of the vent hole 25 of the sealing plug 2 is less than 0.5 mm, after the sealing plug 2 is pierced by the piercing element 6, the vent hole 25 on the sealing plug 2 will close under its own elastic recovery, thus affecting subsequent formation venting. The applicant set up two sets of comparative examples and three sets of experimental cases, using different models of piercing elements 6 to pierce the same sealing plug 2, to observe whether the sealing plug 2 would be pulled out by the piercing element 6, and whether the vent hole 25 on the sealing plug 2 would close after piercing.

[0058] Table 1 Verification Table of Vent Hole Diameter Range for Sealing Plugs

[0059]

[0060] It should be noted that the diameter of the vent 25 after the sealing plug 2 is punctured is measured using a two-dimensional measuring instrument. Due to the elastic recovery property of the material of the sealing plug 2, the diameter of the vent 25 after puncture will be smaller than the diameter of the puncturing part 6. Through the three sets of embodiments numbered 2 to 5 and the two sets of comparative examples numbered 1 and 6, it can be concluded that the suitable diameter range of the vent 25 of the sealing plug 2 is 0.5 mm to 3.0 mm.

[0061] In some embodiments, such as Figure 1 , Figure 3 and Figure 6 As shown, the top cover assembly 100 also includes a sealing sheet 3, which is configured to seal the opening 221 of the hollow groove 21 after the cell is formed. By sealing the opening 221 of the hollow groove 21 with the sealing sheet 3 after the cell is formed, the entire cell forms a sealed structure, preventing leakage. Simultaneously, gases generated during cell use can be stored within the hollow groove 21, thereby improving the cell's electrical performance and lifespan.

[0062] In some embodiments, such as Figure 5 and Figure 6 As shown, the sealing sheet 3 is connected to the top cover 1 and abuts against the top wall 22 of the sealing plug 2, so that the sealing sheet 3, the top cover 1, and the sealing plug 2 form a double sealing structure, which helps to improve the overall sealing performance of the battery cell. The sealing sheet 3 includes a steel sheet and is connected to the upper end face of the top cover 1 by welding. In a specific embodiment, the top cover 1 includes a base portion 12 and a boss portion 13 connected to the base portion 12. The boss portion 13 protrudes outward relative to the base portion 12 toward the outside of the battery cell. The sealing plug 2 is connected to the base portion 12 of the top cover 1, and the sealing sheet 3 is connected to the boss portion 13. The sealing sheet 3 includes a main body portion 31 and a recessed portion 32 connected to the main body portion 31, wherein the recessed portion 32 is recessed inward relative to the main body portion 31 toward the inside of the battery cell. The main body portion 31 of the sealing sheet 3 is connected to the boss portion 13 of the top cover 1, and the recessed portion 32 of the sealing sheet 3 is connected to the top wall 22 of the sealing plug 2.

[0063] In some embodiments, the sealing sheet 3 abuts against and compresses the sealing plug 2, such that the compression rate of the sealing plug 2 is 15% to 70%. The applicant has found through research that when the compression rate of the sealing plug 2 is less than 15%, the insufficient compression makes it difficult to form an interference fit between the sealing plug 2 and the top cover 1, leading to easy air leakage in the top cover assembly 100 of the battery cell. When the compression rate of the sealing plug 2 is greater than 70%, it causes a large rebound force on the sealing sheet 3, which can easily lead to poor welding between the sealing sheet 3 and the top cover 1.

[0064] like Figure 4 As shown, the thickness of the top wall 22 of the sealing plug 2 before being compressed by the sealing sheet 3 is set to a, such as Figure 6 As shown, the thickness of the top wall 22 of the sealing plug 2 after being compressed by the sealing sheet 3 is set to b, and the compression ratio of the sealing plug 2 is (ab) / a. The applicant verified the suitable compression ratio range of the sealing plug 2 by compressing the sealing sheet 3 by measuring the airtightness of the battery cell using sealing plug 2 with different compression ratios, as shown in Table 2 below.

[0065] Table 2 Comparison Table of the Compressibility Performance of Sealing Plates on Sealing Plugs

[0066]

[0067] Among them, the air tightness value of the battery cell measured by helium mass spectrometer must be no greater than 1*10^-7 for the air tightness test to be judged as leak-free.

[0068] In a specific embodiment, the sealing sheet 3 compresses the sealing plug 2. The compression rate of the sealing plug 2 can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any value between any two of the above values ​​or a range between any two of the above values. These are not listed one by one in the embodiments of this application.

[0069] In some embodiments, along the radial or width direction of the top cover assembly 100, the sealing sheet 3 and the sealing plug 2 form a first abutting structure 27, and the sealing plug 2 and the top cover 1 form a second abutting structure 28. The first abutting structure 27 and the second abutting structure 28 have an overlapping width along the radial or width direction of the top cover assembly 100, and this overlapping width is c, ranging from 1.0 mm to 6.5 mm. The applicant has found through research that when the overlapping width c is less than 1.0 mm, it leads to air leakage in the battery cell. When the overlapping width c is greater than 6.5 mm, it results in a larger overall size for the sealing plug 2, and correspondingly a larger size for the injection hole 11, thus affecting the overall structural dimensions of the battery cell. The applicant conducted experiments by setting different overlapping widths on the battery cell and testing whether the battery cell leaked air, as shown in Table 3 below.

[0070] Table 3. Comparison of the overlap widths of the first and second abutment structures.

[0071]

[0072] In item 3, the sealing plug 2 was too large, preventing its assembly on the top cover assembly 100 and thus hindering verification. The airtightness value of the battery cell measured by helium mass spectrometry must not exceed 1*10^-7 for the airtightness test to determine it as leak-free.

[0073] In specific embodiments, the width c of the double sealing structure formed by the sealing sheet 3, the sealing plug 2, and the top cover 1 can be 1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm, 6.5 mm, or any value between any two of the above, or a range between any two of the above values. These are not listed individually in the embodiments of this application.

[0074] Embodiments of this application also provide a method for preparing a battery cell, the method comprising:

[0075] Seal the injection hole 11 with the sealing plug 2;

[0076] Before the battery cell is formed, the piercing component 6 pierces the sealing plug 2, and the sealing plug 2 forms a vent hole 25;

[0077] The battery cells undergo formation.

[0078] After the electrolyte is injected, the injection hole is sealed by the sealing plug 2. Before the cell is formed, it needs to stand for a period of time. During this period, the sealing plug 2 seals the injection hole 11, so that the cell is in a sealed state. External dust is difficult to enter the cell through the injection hole 11, and the electrolyte is difficult to evaporate to the outside through the injection hole 11.

[0079] In some embodiments, after the cell is formed, the sealing sheet 3 is welded to the top cover 1 and the sealing plug 2 is sealed, thereby forming a sealed structure for the cell.

[0080] The embodiments of this utility model have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this utility model. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A top cover assembly, characterized in that, include: The top cover (1) is provided with a liquid injection hole (11); A sealing plug (2) is configured to seal the injection hole (11); The sealing plug (2) is configured to be puncturable to form a vent hole (25) on the sealing plug (2).

2. The top cover assembly according to claim 1, characterized in that, The sealing plug (2) is provided with a hollow groove (21), and the bottom wall (24) of the hollow groove (21) is configured to be puncturable.

3. The top cover assembly according to claim 2, characterized in that, The hollow slot (21) includes a sidewall (23), the sidewall (23) includes an extension (231) and a guide (232), the guide (232) is necked relative to the extension (231), the extension (231) abuts against the top cover (1), and the guide (232) extends into the cell.

4. The top cover assembly according to claim 3, characterized in that, The side wall (23) is also provided with an inverted structure (26), and the sealing plug (2) also includes a top wall (22) connected to the side wall (23), and the top cover (1) abuts between the top wall (22) and the inverted structure (26).

5. The top cover assembly according to claim 3, characterized in that, The sealing plug (2) also includes a top wall (22) connected to the side wall (23), and the top surface of the top wall (22) is set as a plane so that the negative pressure device can abut against the top surface of the top wall (22).

6. The top cover assembly according to any one of claims 3 to 5, characterized in that, The bottom wall (24) is thinner than the side wall (23), and the thickness of the bottom wall (24) is 20% to 60% of the thickness of the side wall (23).

7. The top cover assembly according to any one of claims 1 to 5, characterized in that, The diameter of the vent (25) ranges from 0.5 mm to 3.0 mm.

8. The top cover assembly according to claim 4 or 5, characterized in that, The hollow groove (21) is provided with an opening (221), and the top cover assembly also includes a sealing sheet (3), which is configured to seal the opening (221) after the cell is formed.

9. The top cover assembly according to claim 8, characterized in that, The sealing sheet (3) is connected to the top cover (1) and abuts against the top wall (22) of the sealing plug (2).

10. The top cover assembly according to claim 9, characterized in that, The sealing sheet (3) is configured to compress the sealing plug (2) such that the compression rate of the sealing plug (2) is 15% to 70%.

11. The top cover assembly according to claim 9, characterized in that, The sealing sheet (3) and the sealing plug (2) form a first abutting structure, and the sealing plug (2) and the top cover (1) form a second abutting structure. The overlap width of the first abutting structure and the second abutting structure is c, and the range of c is 1.0 mm to 6.5 mm.

12. A battery cell, characterized in that, The battery cell includes the top cover assembly as described in any one of claims 1 to 11.

13. A battery pack, characterized in that, The battery pack includes the battery cell as described in claim 12.

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