Small battery and method of manufacturing the same

Abstract

The application provides a small battery and a preparation method thereof. A positive or negative tab is connected to a welding piece, and the welding piece is welded at a pressure relief hole to form a pressure relief area. Thus, the positive or negative tab can be electrically connected to the shell, and the pressure relief area can be formed without other processes, thereby simplifying the processing of the small battery. The connection process of the positive or negative tab and the welding piece can be performed outside the pressure relief hole. After the connection is completed, the positive or negative tab is returned to the installation cavity, and then the welding piece is welded at the pressure relief hole. Thus, the connection difficulty of the positive or negative tab and the welding piece is reduced, and the influence of the positive or negative tab on the welding and fixing process of the cover and the shell is reduced, so as to ensure the consistency of the penetration depth of the welding position of the shell and the cover, and improve the welding strength. Thus, even if gas is generated in the small battery due to a short circuit, the cover will not be easily broken to cause harm to the application environment, thereby improving the safety performance of the small battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and particularly relates to a small battery and its preparation method. Background Technology

[0002] Small batteries are widely used in various aspects of life, especially in small portable electronic devices such as electronic watches, Bluetooth headsets, and hearing aids. In related technologies, the battery casing needs to form a pressure relief valve through a certain shaped concave section to release pressure when gas is generated inside the battery due to a short circuit. The negative electrode tab of the battery core needs to be welded to the battery casing wall to achieve a conductive connection. However, during the subsequent laser welding process between the battery cover and the battery casing, the negative electrode tab can obstruct the transmission of the laser, resulting in poor consistency of the weld depth between the battery cover and the battery casing, leading to a decrease in weld strength. Consequently, when gas is generated inside the battery due to a short circuit, the battery cover is prone to bursting open before the pressure can be released, increasing the safety hazard of small batteries. Summary of the Invention

[0003] This invention provides a small battery and its preparation method to address the significant safety hazards of existing small batteries.

[0004] In a first aspect, embodiments of the present invention provide a small battery, comprising:

[0005] The housing has an internal mounting cavity, an open end on one side, and a pressure relief hole on the housing. The open end and the pressure relief hole are respectively connected to the mounting cavity.

[0006] A cover body, which is provided on the open end, and the cover body has a mounting hole communicating with the mounting cavity;

[0007] A pole post, which is installed in the mounting hole and insulated from the cover;

[0008] A welded component, which is sealed and welded to the pressure relief hole to form a pressure relief zone at the pressure relief hole;

[0009] The core is installed in the mounting cavity. The core includes a stacked and wound positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet is connected to a positive electrode tab, and the negative electrode sheet is connected to a negative electrode tab. One of the positive electrode tab and the negative electrode tab is connected to the electrode post, and the other is connected to the welding component.

[0010] Optionally, the pressure relief hole is located on the peripheral wall of the housing.

[0011] Optionally, one of the positive and negative tabs is connected to the top of the winding core and the other is connected to the bottom of the winding core, and the pressure relief hole is located near the bottom of the housing.

[0012] Optionally, the positive or negative tab is connected to the welded component via a buffer structure.

[0013] Optionally, the buffer structure is formed by bending at least a portion of the positive or negative tab.

[0014] Optionally, at least a portion of the positive or negative tab is bent into one of a "Z", serrated, sawtooth, or wavy shape to form the buffer structure.

[0015] Optionally, the positive or negative electrode tab is welded to the weldment.

[0016] Optionally, insulating pads are provided at both ends of the winding core along its axial direction.

[0017] Optionally, the bottom of the housing is provided with a liquid injection hole, which communicates with the mounting cavity, and the small battery also includes a sealing element that seals the liquid injection hole.

[0018] Optionally, the portion of the cover near the edge is formed with an overlapping step, the overlapping step extending circumferentially along the cover and fixedly overlapping the end face of the opening.

[0019] Secondly, embodiments of the present invention also provide a method for manufacturing a small battery, the small battery comprising a casing, a cover, a core, and welded components, wherein the core is connected to a positive electrode tab and a negative electrode tab, and the method for manufacturing the small battery comprises:

[0020] The winding core is installed inside the housing, and a pressure relief hole is provided in the housing;

[0021] The end of the positive or negative electrode tab is passed through the pressure relief hole;

[0022] Connect one end of the positive or negative electrode tab that protrudes from the pressure relief hole to the welded component;

[0023] Put the positive or negative electrode tab back into the housing through the pressure relief hole;

[0024] The welded component is welded to the pressure relief hole to form a pressure relief zone at the pressure relief hole.

[0025] Optionally, before the step of returning the positive or negative electrode tab from the pressure relief hole back into the housing, the method further includes:

[0026] The portion of the positive or negative electrode that extends out of the pressure relief hole is bent into one of the following shapes: "Z", snake, sawtooth, or wave, to form a buffer structure.

[0027] The small battery provided in this invention connects the positive or negative tab to a welding component, and then welds the welding component to the pressure relief hole to form a pressure relief area. This achieves a conductive connection between the positive or negative tab and the casing without requiring additional processes to form the pressure relief area, simplifying the manufacturing process of the small battery. The connection process between the positive or negative tab and the welding component can be performed outside the pressure relief hole. After connection, the positive or negative tab is placed back into the mounting cavity, and then the welding component is welded to the pressure relief hole. This reduces the difficulty of connecting the positive or negative tab to the welding component and minimizes the impact of the positive or negative tab on the welding and fixing process between the cover and the casing, ensuring consistent weld depth and improving weld strength. Therefore, even if gas is generated inside the small battery due to a short circuit, the cover will not easily break open and cause harm to its application environment, thus improving the safety performance of the small battery. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0029] To gain a more complete understanding of the present invention and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0030] Figure 1 This is a schematic diagram of the structure of a small battery provided in an embodiment of the present invention.

[0031] Figure 2 This is a cross-sectional schematic diagram of a small battery provided in an embodiment of the present invention.

[0032] Figure 3 This is a schematic flowchart illustrating the method for preparing a small battery according to an embodiment of the present invention.

[0033] 10. Housing; 11. Mounting cavity; 12. Pressure relief area; 20. Cover; 30. Terminal post; 40. Core; 41. Positive electrode tab; 42. Negative electrode tab; 50. Welded component; 421. Buffer structure; 13. Injection hole; 50. Seal; 21. Overlap step. Detailed Implementation

[0034] The technical solutions of the embodiments of this application 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 application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0035] Small batteries are widely used in various aspects of life, especially in small portable electronic devices such as electronic watches, Bluetooth headsets, and hearing aids. In related technologies, the battery casing needs to form a pressure relief valve through a certain shaped concave section to release pressure when gas is generated inside the battery due to a short circuit. The negative electrode tab 42 of the core 40 needs to be welded to the battery casing wall to achieve a conductive connection. However, during the subsequent laser welding process between the battery cover and the battery casing, the negative electrode tab 42 can obstruct the transmission of the laser, resulting in poor consistency of the weld depth between the battery cover and the battery casing, leading to a decrease in weld strength. Consequently, when gas is generated inside the battery due to a short circuit, the battery cover is prone to bursting open before the pressure can be released, increasing the safety hazard of small batteries.

[0036] This invention provides a small battery to address the significant safety hazards of existing small batteries. The following description, in conjunction with the accompanying drawings, will illustrate this. The small battery provided by this invention can be applied to electronic devices. For example, please refer to... Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of a small battery provided in an embodiment of the present invention. Figure 2 This is a cross-sectional schematic diagram of a small battery provided in an embodiment of the present invention.

[0037] The small battery includes: a housing 10, which has a mounting cavity 11 inside, an open end on one side of the housing 10, and a pressure relief hole on the housing 10, the open end and the pressure relief hole communicating with the mounting cavity; a cover 20, which covers the open end and has a mounting hole communicating with the mounting cavity 11; a terminal post 30, which is installed in the mounting hole and insulated from the cover 20; a welded component 50, which covers and is welded to the pressure relief hole to form a pressure relief area 12 at the pressure relief hole; and a core 40, which is installed in the mounting cavity 11 and includes a stacked and wound positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet is connected to a positive electrode tab 41, and the negative electrode sheet is connected to a negative electrode tab 42. One of the positive electrode tab 41 and the negative electrode tab 42 is connected to the terminal post 30, and the other is connected to the welded component 50.

[0038] In this embodiment, the housing 10 can be cylindrical with an open top, and is made of a conductive material, such as stainless steel. The cover 20 can be circular to fit the shape of the housing 10; the material of the cover 20 can be the same as that of the housing 10 to achieve electrical conductivity between the housing 10 and the cover 20. The housing 10 and the cover 20 can be fixed by laser welding. The pole post 30 can be insulated from the wall of the mounting hole by an insulating layer to achieve insulation between the core 40 and the cover 20. One end of the pole post 30 is connected to the positive electrode 41 or the negative electrode 42 in the mounting cavity 11, and the other end is used for connection to the electrical circuit outside the mounting cavity 11. Taking the positive electrode 41 connected to the pole post 30 and the negative electrode 42 connected to the welded part 50 as an example, the positive terminal of the electrical circuit can be connected to the pole post 30 and the negative terminal can be connected to the welded part 50, thereby forming a current loop between the core 40 and the electrical circuit.

[0039] The welding component 50 is used to connect the positive electrode tab 41 or the negative electrode tab 42, and is then welded to the pressure relief hole. The connection process between the positive electrode tab 41 or the negative electrode tab 42 and the welding component 50 can be carried out outside the mounting cavity 11, so that the operator has more operating space and the connection difficulty between the positive electrode tab 41 or the negative electrode tab 42 and the welding component 50 is reduced.

[0040] Specifically, taking the connection of the negative electrode tab 42 to the welded component 50 as an example, after installing the core 40 into the mounting cavity 11, one end of the negative electrode tab 42 can be passed through the pressure relief hole first, and then that end of the negative electrode tab 42 can be connected to the welded component 50. The connection method between the negative electrode tab 42 and the welded component 50 can be welding or bonding, and there is no limitation here. For example, the positive electrode tab 41 or the negative electrode tab 42 is welded to the welded component 50. After the negative electrode tab 42 and the welded component 50 are connected outside the mounting cavity 11, the negative electrode tab 42 can be pushed back into the mounting cavity 11 through the pressure relief hole, and then the welded component 50 can be sealed and welded to the pressure relief hole.

[0041] After welding the welded part 50 at the pressure relief hole, a weld seam is formed, which serves as the pressure relief area 12 of the casing 10. If gas is generated inside the small battery due to a short circuit, the weld seam can break open first under the action of gas pressure, thereby allowing the gas to be released and preventing the battery casing from exploding due to excessive internal gas pressure. As a result, the battery casing does not need to be equipped with an additional pressure relief structure for pressure relief, simplifying the structure of the small battery.

[0042] The process of fixing the cover 20 to the shell 10 can be carried out before the welding part 50 is welded to the pressure relief hole, that is, after the negative electrode tab 42 protrudes from the pressure relief hole. This reduces the impact of the negative electrode tab 42 on the uniformity of the weld depth between the cover 20 and the shell 10, thereby improving the weld strength. Even if gas is generated inside the small battery due to a short circuit, the cover 20 will not easily break open and cause harm to its application environment, thus improving the safety performance of the small battery.

[0043] The small battery provided in this embodiment of the invention connects the positive tab 41 or the negative tab 42 to the welding component 50, and then welds the welding component 50 to the pressure relief hole to form a pressure relief area 12. This achieves a conductive connection between the positive tab 41 or the negative tab 42 and the casing 10, and forms the pressure relief area 12 without requiring other processes, simplifying the manufacturing process of the small battery. The connection process between the positive tab 41 or the negative tab 42 and the welding component 50 can be performed outside the pressure relief hole. After the connection is completed, the positive tab 41 or the negative tab 42 is placed back into the mounting cavity 11, and then the welding component 50 is welded to the pressure relief hole. This reduces the difficulty of connecting the positive tab 41 or the negative tab 42 to the welding component 50 and minimizes the impact of the positive tab 41 or the negative tab 42 on the welding and fixing process between the cover 20 and the casing 10, ensuring consistent weld penetration at the weld between the casing 10 and the cover 20, thereby improving weld strength. Therefore, even if gas is generated inside the small battery due to a short circuit, the cover 20 will not be easily broken open and cause harm to its application environment, thereby improving the safety performance of the small battery.

[0044] The pressure relief hole is located at the same position as the welded part 50, which is also the position where the negative electrode tab 42 is connected to the housing 10. The pressure relief hole can be located on the bottom wall of the housing 10, or at other locations on the housing 10. For example,... Figure 2 As shown, the pressure relief hole is located on the peripheral wall of the housing 10, so that the negative electrode tab 42 can extend along the width direction of the housing 10 to connect with the welding piece 50 without occupying the space of the mounting cavity 11 in the height direction. This provides more mounting space for the winding core 40 in the height direction, thereby increasing the effective height of the winding core 40 and improving the energy density of the small battery.

[0045] The pressure relief port can be located near the top opening of the housing 10 or near the bottom wall of the housing 10. For example, as shown... Figure 2 As shown, one of the positive electrode tab 41 and the negative electrode tab 42 is connected to the top end of the winding core 40, and the other is connected to the bottom end of the winding core 40. The pressure relief hole is located near the bottom of the housing 10. The positive electrode tab 41 extends from the top end of the winding core 40 to connect with the pole post 30, while the negative electrode tab 42 extends from the bottom end of the winding core 40 to connect with the welding piece 50. This reduces the extension length of the positive electrode tab 41 and the negative electrode tab 42 within the mounting cavity 11, preventing the positive electrode tab 41 and the negative electrode tab 42 from coming into contact with each other and short-circuiting.

[0046] If the negative electrode tab 42 is directly connected to the welded part 50, when the small battery vibrates, the vibration will be transmitted to the negative electrode tab 42, which may easily cause the negative electrode tab 42 to break. For example, Figure 2As shown, the positive electrode tab 41 or the negative electrode tab 42 is connected to the welded part 50 through a buffer structure 421. The buffer structure 421 can be a spring, or other elastic shapes or materials; there are no restrictions, as long as the buffer structure 421 has the function of absorbing and buffering vibrations. When the small battery vibrates, the buffer structure 421 can absorb and buffer the vibration transmitted to the negative electrode tab 42, thereby preventing the negative electrode tab 42 from breaking due to concentrated force, thus improving the structural stability of the small battery.

[0047] The buffer structure 421 can be an additional component connected between the negative electrode tab 42 and the welded component 50, or it can be formed by bending the negative electrode tab 42 itself. For example, the buffer structure 421 is formed by bending at least a portion of the positive electrode tab 41 or the negative electrode tab 42, thus reducing the cost of the buffer structure 421 and simplifying the internal structure of the small battery. In conjunction with the embodiment described above where the negative electrode tab 42 is connected to the welded component 50 outside the pressure relief hole, the portion of the negative electrode tab 42 outside the pressure relief hole can be first bent into the buffer structure 421, and then the buffer structure 421 is connected to the welded component 50 and inserted back into the mounting cavity 11. This simplifies the bending process of the buffer structure 421 and improves processing efficiency. In practical applications, at least a portion of the positive electrode tab 41 or the negative electrode tab 42 is bent into one of the following shapes: "Z", serrated, sawtooth, or wavy, to form the buffer structure 421.

[0048] For example, the core 40 has insulating pads (not shown) at both ends in the axial direction. The core 40 can be fixed to the bottom wall of the housing 10, and an insulating gap is formed between the peripheral wall of the core 40 and the peripheral wall of the housing 10. The insulating pads are made of insulating materials, such as CPP film (cast polypropylene film), PPA film (polyphthalamide), modified PP film (polypropylene), composite film layer of PPA and PP, etc. The insulating pads can separate the two ends of the core 40 from the bottom wall of the housing 10 and the cover 20, thereby preventing the core 40 from directly short-circuiting with the housing 10 or the cover 20.

[0049] When manufacturing a small battery, after encapsulating the winding core 40, it is necessary to fill the mounting cavity 11 with electrolyte. The electrolyte can be filled through the injection hole 13 opened on the housing 10 or the cover 20. For example, Figure 2 As shown, the bottom of the housing 10 is provided with a liquid injection hole 13, which is connected to the mounting cavity 11. The small battery also includes a sealing member 50 that seals the liquid injection hole 13.

[0050] For example, such as Figure 2As shown, the portion of the cover 20 near its edge has an overlapping step 21. The overlapping step 21 extends circumferentially along the cover 20 and is fixedly overlapped to the end face of the opening. The overlapping step 21 can play a positioning role in the welding and fixing process between the cover 20 and the housing 10, thereby preventing the cover 20 from shifting or misaligning relative to the housing 10, thus improving the production yield of small batteries.

[0051] For example, such as Figure 3 As shown, Figure 3 This is a schematic flowchart illustrating the fabrication method of a small battery provided in an embodiment of the present invention. The present invention also provides a method for fabricating a small battery, the small battery comprising a casing 10, a cover 20, a core 40, and a welded component 50, wherein the core 40 is connected to a positive electrode tab 41 and a negative electrode tab 42, and the fabrication method of the small battery includes:

[0052] S100. Install the winding core 40 into the housing 10, and open a pressure relief hole in the housing 10;

[0053] S200, pass the end of the positive electrode tab 41 or the negative electrode tab 42 through the pressure relief hole;

[0054] S300, Connect one end of the positive electrode tab 41 or negative electrode tab 42 that protrudes from the pressure relief hole to the welded part 50;

[0055] S400: Put the positive electrode tab 41 or the negative electrode tab 42 back into the housing 10 from the pressure relief hole;

[0056] S500, the welding component 50 is welded to the pressure relief hole to form a pressure relief zone 12 at the pressure relief hole.

[0057] As can be seen from the above embodiments, the housing 10 can form a mounting cavity 11 with an opening to one side, and the core 40 is installed in the mounting cavity 11. Taking the connection of the negative electrode tab 42 to the welded component 50 as an example, after the core 40 is installed in the mounting cavity 11, one end of the negative electrode tab 42 can be passed through the pressure relief hole first, and then that end of the negative electrode tab 42 can be connected to the welded component 50. The connection method between the negative electrode tab 42 and the welded component 50 can be welding or bonding, and there is no limitation here. For example, the positive electrode tab 41 or the negative electrode tab 42 is welded to the welded component 50. After the negative electrode tab 42 and the welded component 50 are connected outside the mounting cavity 11, the negative electrode tab 42 can be pushed back into the mounting cavity 11 through the pressure relief hole, and then the welded component 50 can be sealed and welded to the pressure relief hole.

[0058] After welding the welded part 50 at the pressure relief hole, a weld seam is formed, which serves as the pressure relief area 12 of the casing 10. If gas is generated inside the small battery due to a short circuit, the weld seam can break open first under the action of gas pressure, thereby allowing the gas to be released and preventing the battery casing from exploding due to excessive internal gas pressure. As a result, the battery casing does not need to be equipped with an additional pressure relief structure for pressure relief, simplifying the structure of the small battery.

[0059] The process of fixing the cover 20 to the shell 10 can be carried out before the welding part 50 is welded to the pressure relief hole, that is, after the negative electrode tab 42 protrudes from the pressure relief hole. This reduces the impact of the negative electrode tab 42 on the uniformity of the weld depth between the cover 20 and the shell 10, thereby improving the weld strength. Even if gas is generated inside the small battery due to a short circuit, the cover 20 will not easily break open and cause harm to its application environment, thus improving the safety performance of the small battery.

[0060] For example, before the step of returning the positive electrode tab 41 or the negative electrode tab 42 from the pressure relief hole back into the housing 10, the method further includes:

[0061] The portion of the positive electrode tab 41 or the negative electrode tab 42 that extends out of the pressure relief hole is bent into one of the following shapes: "Z", snake, sawtooth, or wave, to form a buffer structure 421.

[0062] When the small battery vibrates, the buffer structure 421 absorbs and buffers the vibration transmitted to the negative electrode tab 42, thereby preventing the negative electrode tab 42 from breaking due to concentrated force, thus improving the structural stability of the small battery. The buffer structure 421 is formed by bending at least a portion of the positive electrode tab 41 or the negative electrode tab 42, thus reducing the cost of the buffer structure 421 and simplifying the internal structure of the small battery. In the embodiment described above where the negative electrode tab 42 is connected to the welded part 50 outside the pressure relief hole, the portion of the negative electrode tab 42 outside the pressure relief hole can be first bent into the buffer structure 421, and the buffer structure 421 is connected to the welded part 50 and then inserted back into the mounting cavity 11. This simplifies the bending process of the buffer structure 421 and improves processing efficiency.

[0063] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0064] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more features. The small battery provided by the embodiments of this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application; at the same time, for those skilled in the art, based on the ideas of this application, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A small battery, characterized in that, include: The housing has an internal mounting cavity, an open end on one side, and a pressure relief hole on the housing. The open end and the pressure relief hole are respectively connected to the mounting cavity. A cover body, which is provided on the open end, and the cover body has a mounting hole communicating with the mounting cavity; A pole post, which is installed in the mounting hole and insulated from the cover; A welded component, which is sealed and welded to the pressure relief hole to form a pressure relief zone at the pressure relief hole; The core is installed in the mounting cavity. The core includes a stacked and wound positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet is connected to a positive electrode tab, and the negative electrode sheet is connected to a negative electrode tab. One of the positive electrode tab and the negative electrode tab is connected to the electrode post, and the other is connected to the welding component. The pressure relief hole is located on the peripheral wall of the housing; The positive or negative electrode tab is connected to the welded component via a buffer structure.

2. The small battery according to claim 1, characterized in that, One of the positive and negative tabs is connected to the top of the winding core, and the other is connected to the bottom of the winding core. The pressure relief hole is located near the bottom of the housing.

3. The small battery according to claim 1, characterized in that, The buffer structure is formed by bending at least a portion of the positive or negative tab.

4. The small battery according to claim 3, characterized in that, At least a portion of the positive or negative tab is bent to form one of a "Z", a serrated, a sawtooth, or a wavy shape to form the buffer structure.

5. The small battery according to any one of claims 1 to 2, characterized in that, The positive or negative electrode tab is welded to the welded component.

6. The small battery according to any one of claims 1 to 2, characterized in that, Insulating pads are provided at both ends of the winding core along the axial direction.

7. The small battery according to any one of claims 1 to 2, characterized in that, The bottom of the housing has a liquid injection hole, which communicates with the mounting cavity. The small battery also includes a seal that plugs the liquid injection hole.

8. The small battery according to any one of claims 1 to 2, characterized in that, The portion of the cover near the edge has an overlapping step, which extends circumferentially along the cover and is fixedly overlapped to the end face of the opening.

9. A method for preparing a small battery, characterized in that, The small battery includes a casing, a cover, a winding core, and welded components. The winding core is connected to a positive electrode tab and a negative electrode tab. The method for manufacturing the small battery includes: The winding core is installed inside the housing, and pressure relief holes are opened on the peripheral wall of the housing; The end of the positive or negative electrode tab is passed through the pressure relief hole; One end of the positive or negative electrode tab that protrudes from the pressure relief hole is connected to the welded part through a buffer structure; Put the positive or negative electrode tab back into the housing through the pressure relief hole; The welded component is welded to the pressure relief hole to form a pressure relief zone at the pressure relief hole.

10. The method for preparing a small battery according to claim 9, characterized in that, Before the step of returning the positive or negative electrode tab back into the housing from the pressure relief hole, the method further includes: The portion of the positive or negative electrode that extends out of the pressure relief hole is bent into one of the following shapes: "Z", snake, sawtooth, or wave, to form a buffer structure.

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