Top cover assembly, preparation method of battery cell, battery cell and battery pack

Abstract

The invention provides a top cover assembly, a preparation method of a battery cell, the battery cell and a battery pack, the top cover assembly comprises a top cover provided with a liquid injection hole; the sealing plug is arranged to seal the liquid injection hole; wherein the sealing plug is configured to be puncturable, so that a vent hole is formed in the sealing plug.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a top cover assembly, a preparation method of a battery cell, the battery cell and a battery pack. BACKGROUND

[0002] In the related art, cylindrical battery cells need to be formed. In order to cooperate with the formation of the cylindrical battery cells, the top cover of the cylindrical battery cell is provided with a sealing plug. The sealing plug is arranged at the liquid injection hole of the top cover. A stable air hole is arranged on the sealing plug to facilitate exhaust during the formation process. After the liquid injection of the battery cell is completed and before the formation, dust can enter the battery cell through the air hole on the sealing plug to pollute the electrolyte. The electrolyte can volatilize through the air hole on the sealing plug, thereby affecting the performance of the battery cell. SUMMARY

[0003] Embodiments of the present application provide a top cover assembly, a preparation method of a battery cell, the 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, embodiments of the present application provide a top cover assembly, comprising: a top cover provided with a liquid injection hole; a sealing plug arranged to seal the liquid injection hole; wherein the sealing plug is configured to be puncturable to form an air hole on the sealing plug.

[0005] In an embodiment, the sealing plug is provided with a hollow groove, and a bottom wall of the hollow groove is configured to be puncturable. By arranging the hollow groove on the sealing plug, the overall structural strength of the sealing plug is weak, especially the bottom wall of the hollow groove, which is easily punctured by using a sharp puncturing piece.

[0006] In an embodiment, the hollow groove comprises a side wall, the side wall comprises an extension portion and a guide portion, the guide portion is arranged to be necked with respect to the extension portion, the extension portion abuts against the top cover, and the guide portion extends into the battery cell. By arranging the guide portion to be necked, the guide portion is facilitated to be inserted into the inside of the battery cell through the liquid injection hole.

[0007] In an embodiment, the side wall is further provided with an undercut structure, and the top cover is clamped between the top wall and the undercut structure, thereby preventing the sealing plug from being separated from the top cover.

[0008] In an embodiment, a top end surface of the top wall is arranged as a flat surface so as to facilitate the negative pressure extraction device to abut against the top end surface of the top wall.

[0009] In an embodiment, the bottom wall is arranged to be thinned relative to the side wall, and the thickness of the bottom wall is 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 the sealing plug is assembled to 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 difficult to be pierced, thereby affecting the formation of the vent hole.

[0010] In an embodiment, the diameter of the vent hole is 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 range of action between the piercing member and the sealing plug during the piercing of the bottom wall of the sealing plug is large, thereby causing the sealing plug to be separated from the top cover, which affects the fixation of the sealing plug. When the diameter of the vent hole of the sealing plug is less than 0.5 mm, the vent hole of the sealing plug is closed under the elastic recovery of the sealing plug after being pierced by the piercing member, thereby affecting the subsequent formation gas.

[0011] In an embodiment, the sealing plug comprises a top wall provided with an opening communicating with the hollow groove, and the top cover assembly further comprises a sealing sheet arranged to seal the opening after the formation of the battery cell. By sealing the opening of the hollow groove with the sealing sheet after the formation of the battery cell, the battery cell is formed as a whole sealed structure to prevent liquid leakage of the battery cell. At the same time, the gas generated during the use of the battery cell can be stored in the hollow groove, thereby improving the electrical performance and service life of the battery cell.

[0012] In an 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 an embodiment, the sealing sheet is arranged to compress the sealing plug, so 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 compression amount of the sealing plug is not enough, thereby causing the interference fit between the sealing plug and the top cover to be difficult to form, and causing the top cover assembly 100 of the battery cell to easily leak gas. When the compression rate of the sealing plug is greater than 70%, the sealing plug forms a large rebounding force on the sealing sheet, thereby easily causing the welding between the sealing sheet and the top cover to be poor.

[0014] In an embodiment, the sealing sheet forms a first abutting structure with the sealing plug, the sealing plug forms a second abutting structure with the top cover, and the first abutting structure and the second abutting structure overlap each other with a width c, and c is in a range of 1.0 mm to 6.5 mm. When the width c is less than 1.0 mm, the battery cell may be leaked. When the width c is greater than 6.5 mm, the sealing plug has a large size, and the injection hole has a large size, which affects the overall structure size of the battery cell.

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

[0016] In a second aspect, an embodiment of the present application provides a preparation method of a battery cell, the battery cell comprising the top cover assembly described above, and the preparation method of the battery cell comprising:

[0017] sealing the injection hole by the sealing plug;

[0018] piercing the sealing plug before the battery cell is formed, and the sealing plug forms a vent hole;

[0019] gas generated in the formation of the battery cell is discharged from the vent hole.

[0020] In an embodiment, the preparation method of the battery cell further comprises welding the sealing sheet on the top cover after the battery cell is formed.

[0021] In a third aspect, an embodiment of the present application provides a battery cell, which comprises the top cover assembly described above or is prepared by the preparation method of the battery cell described above.

[0022] In a fourth aspect, an embodiment of the present application provides a battery pack, which comprises the battery cell described above.

[0023] Advantages of the embodiments of the present application:

[0024] In the embodiments of the present application, the sealing plug is configured to be pierceable, the sealing plug is arranged to seal the injection hole after the battery cell is injected, and the sealing plug forms a vent hole after being pierced before the battery cell is formed, so that the gas generated in the formation of the battery cell can be discharged through the vent hole, and the battery cell is in a sealed state after being injected and before being formed. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to make the technical solutions in the embodiments of the present application clearer, the accompanying drawings needed in the embodiments will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only show some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0026] Figure 1 is a sectional view of a partial structure of an electric core provided by an embodiment of the present application;

[0027] Figure 2 is an exploded view of a top cover assembly provided by an embodiment of the present application;

[0028] Figure 3 is a perspective view of a sealing plug provided by an embodiment of the present application;

[0029] Figure 4 is a sectional view of the sealing plug of the top cover assembly before being punctured by a puncturing member provided by an embodiment of the present application;

[0030] Figure 5 is a sectional view of the sealing plug of the top cover assembly being punctured by the puncturing member provided by an embodiment of the present application;

[0031] Figure 6 is a sectional view of the sealing plug of the top cover assembly after being punctured provided by an embodiment of the present application;

[0032] Figure 7 is a partial sectional view of an electric core using a negative pressure extraction device to extract negative pressure provided by an embodiment of the present application.

[0033] 100, top cover assembly;

[0034] 1, top cover; 11, liquid injection hole; 12, base portion; 13, boss portion;

[0035] 2, sealing plug; 21, hollow groove; 22, top wall; 221, opening; 23, side wall; 231, extension portion; 232, guide portion; 24, bottom wall; 25, air hole; 26, undercut structure; 27, first abutting structure; 28, second abutting structure;

[0036] 3, sealing sheet; 31, main body portion; 32, recessed portion;

[0037] 4, sealing member;

[0038] 5, negative pressure extraction device;

[0039] 6, puncturing member;

[0040] 7, shell;

[0041] 8, pole piece assembly; DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower in the actual use or working state of the device, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device.

[0043] In the related art, the cylindrical battery cell needs to be formed. In order to cooperate with the formation of the cylindrical battery cell, the top cover of the cylindrical battery cell is provided with a sealing plug, the sealing plug is arranged at the liquid injection hole of the top cover, and a gas hole is arranged on the sealing plug to facilitate exhaust during the formation process. After the liquid injection of the battery cell is completed and before the formation is performed, dust can enter the battery cell through the gas hole on the sealing plug to contaminate the electrolyte, and the electrolyte can volatilize through the gas hole on the sealing plug, thereby affecting the performance of the battery cell.

[0044] Embodiments of the present application provide a battery pack, which includes a box body and a plurality of battery cells arranged in the box body. The battery pack can be a power battery pack or an energy storage battery pack.

[0045] Embodiments of the present application provide a battery cell, which can be a cylindrical battery cell or a square battery cell. As shown in Figure 1 and Figure 2 The battery cell includes a shell 7, a top cover assembly 100, a pole piece assembly 8, and an electrolyte.

[0046] The shell 7 can be a steel shell, and the top end of the shell 7 is open to facilitate the installation of the pole piece assembly 8.

[0047] The top cover assembly 100 is connected to the top opening of the shell 7.

[0048] The pole piece assembly 8 can be a winding core assembly formed by winding a plurality of positive pole pieces, a plurality of separators, and a plurality of negative pole pieces, or a laminated core assembly formed by stacking a plurality of positive pole pieces, a plurality of separators, and a plurality of negative pole pieces. The electrolyte is injected into the pole piece assembly 8, and the electrolyte is a medium for the migration of lithium ions between the positive pole pieces and the negative pole pieces, and is the basis for the electrochemical reaction of the battery cell.

[0049] Embodiments of the present 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 shell 7.

[0050] 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.

[0051] 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 6 As 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.

[0052] 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.

[0053] 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.

[0054] 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%.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] Table 1 Verification Table of Vent Hole Diameter Range for Sealing Plugs

[0064]

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] like Figure 4 As shown, the thickness of the top wall 22 of the sealing plug 2 before it is 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.

[0070] Table 2 Comparison Table of the Compressibility Performance of Sealing Plates on Sealing Plugs

[0071]

[0072] 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.

[0073] 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.

[0074] 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.

[0075] Table 3: Comparison of the overlap widths of the first and second abutment structures.

[0076]

[0077] 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.

[0078] 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.

[0079] Embodiments of this application also provide a method for preparing a battery cell, the method comprising:

[0080] Seal the injection hole 11 with the sealing plug 2;

[0081] 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;

[0082] The battery cells undergo formation.

[0083] 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.

[0084] 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.

[0085] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. 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 the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

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. The top cover assembly according to any one of claims 1 to 5, characterized in that, The sealing plug (2) is made of one or more of the following materials: fluororubber, PP, PBT, and EPDM.

13. A method for manufacturing a battery cell, the battery cell comprising the top cover assembly according to any one of claims 1 to 10, characterized in that, The method for preparing the battery cell includes: Seal the injection hole (11) with the sealing plug (2); Before the cell is formed, the sealing plug (2) is punctured, and a vent hole (25) is formed on the sealing plug; The gas generated during the cell formation is discharged from the vent (25).

14. The method for preparing a battery cell according to claim 13, characterized in that, The method for preparing the battery cell further includes: after the battery cell is formed, welding the sealing sheet (3) onto the top cover (1).

15. A battery cell, characterized in that, The battery cell includes the top cover assembly as described in any one of claims 1 to 12, or is prepared using the battery cell preparation method described in claim 13 or 14.

16. A battery pack, characterized in that, The battery pack includes the battery cell as described in claim 15.

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