Secondary battery and method for manufacturing secondary battery

Abstract

Disclosed are a secondary battery and a method for manufacturing a secondary battery. According to one aspect of the present invention, there is provided a method for manufacturing a secondary battery, the method comprising: a first step of providing a top cover and a safety valve; a second step of bending an end portion of the safety valve upward; and a third step of inserting the top cover into the safety valve, wherein between the second step and the third step, an outer diameter (A) of the top cover is greater than an inner diameter (B) of the safety valve, and a contact pressure can be higher on an upper region or a lower region in an area where the side portion of the top cover and the bent portion of the safety valve contact each other, and can be relatively lower on a central region. According to another aspect of the present invention, there is provided a secondary battery in which a contact pressure can be higher on an upper region or a lower region in an area where the side portion of the top cover and the bent portion of the safety valve contact each other, and can be relatively lower on a central region.

Description

[0001] Divisional application

[0002] This application is a divisional application of Chinese invention patent application filed on November 20, 2019, with application number 201980008204.0 and entitled "Secondary Battery and Method for Manufacturing Secondary Battery".

[0003] Cross-reference to related applications

[0004] This application claims priority to Korean Patent Application No. 10-2018-0149832, filed on November 28, 2018, which is incorporated herein by reference in its entirety. Technical Field

[0005] This invention relates to a secondary battery and a method for manufacturing a secondary battery. Background Technology

[0006] Based on the structure of rechargeable and re-dischargeable batteries, they can be classified into pouch type, prismatic type, cylindrical type, etc.

[0007] Among these types, cylindrical secondary batteries have a structure in which a top cover is attached to the upper part of the battery can housing the electrode assembly. Furthermore, in cylindrical secondary batteries, a safety valve is typically attached to both the top cover and the battery can. This safety valve is located below the top cover and ruptures when the internal pressure of the secondary battery increases, releasing gas to the outside.

[0008] According to relevant technology, in the process of manufacturing a cylindrical secondary battery, the top cover is placed inside the safety valve, the outer periphery of the safety valve is bent upward, and then the outer periphery of the safety valve is bent again in the direction toward the top cover.

[0009] However, since the top cover must be positioned inside the safety valve as described above, its outer diameter must be smaller than the inner diameter of the safety valve. Therefore, in the manufactured cylindrical secondary battery, a gap may inevitably exist between the interior of the safety valve and the exterior of the top cover. According to related technologies, the electrolyte within the secondary battery may leak due to this gap. Summary of the Invention

[0010] Technical issues

[0011] Therefore, the object of the present invention is to solve the problem of electrolyte leakage that may occur in cylindrical secondary batteries manufactured according to related technologies.

[0012] Technical solution

[0013] According to one aspect of the present invention, a method for manufacturing a secondary battery is provided, the method comprising:

[0014] First step: Provide the top cover and safety valve;

[0015] The second step: bend the end of the safety valve upwards; and

[0016] Third step: Insert the top cover into the safety valve.

[0017] In the process between the second and third steps, the outer diameter (A) of the top cover is larger than the inner diameter (B) of the safety valve.

[0018] The contact pressure can be higher in the upper or lower region of the area where the side of the top cover and the bend of the safety valve come into contact with each other, and relatively lower in the central region.

[0019] According to another aspect of the present invention, a secondary battery is provided, the secondary battery comprising:

[0020] Battery can;

[0021] A top cover, the top cover being attached to the upper part of the battery canister; and

[0022] A safety valve, wherein the safety valve is located below the top cover.

[0023] The safety valve has an end that is bent upwards to form a bent portion.

[0024] The bent portion of the safety valve is in close contact with the side of the top cover, and

[0025] In the upper or lower region of the area where the side portion of the top cover and the bent portion of the safety valve come into contact with each other, the contact pressure can be higher, while in the central region, the contact pressure can be relatively lower.

[0026] To achieve the objectives described above, according to one aspect of the present invention, a method for manufacturing a secondary battery is provided, the method comprising: a first step of providing a top cover and a safety valve; a second step of bending the end of the safety valve upward; and a third step of inserting the top cover into the interior of the safety valve, wherein, between the second and third steps, the outer diameter (A) of the top cover is larger than the inner diameter (B) of the safety valve.

[0027] Between the second and third steps, the outer diameter (A) of the top cover can be 0.01 mm to 0.03 mm larger than the inner diameter (B) of the safety valve.

[0028] The contact pressure applied between the top cover and the safety valve after the third step can be greater than or equal to the following pressure (P). v The pressure (P) v The pressure inside the secondary battery is when the gas inside the secondary battery begins to be discharged through the safety valve.

[0029] The top cover can be made of cold-rolled steel, stainless steel or aluminum, and the safety valve can be made of aluminum.

[0030] After the third step, the contact pressure applied between the side of the top cover and the safety valve can be 7.0 MPa or lower.

[0031] The ratio (AB) of the difference between the outer diameter (A) of the top cover and the inner diameter (B) of the safety valve to the outer diameter (A) of the top cover (AB) / A) can be 5.4 × 10⁻⁶. -4 Up to 1.62×10 -3 between.

[0032] The ratio of the difference (AB) between the outer diameter (A) of the top cover and the inner diameter (B) of the safety valve to the inner diameter (B) of the safety valve ((AB) / B) can be 5.4 × 10⁻⁶. -4 Up to 1.62×10 -3 between.

[0033] The method may also include a fourth step: additionally bending the end of the safety valve along the central direction of the safety valve.

[0034] After the third step, the contact pressure applied to the central area between the side of the top cover and the safety valve can be 3.5 MPa or lower.

[0035] To achieve the objectives described above, according to another aspect of the present invention, a secondary battery is provided, comprising: a battery canister; a top cover connected to the upper part of the battery canister; and a safety valve disposed below the top cover, wherein an end of the safety valve is bent upward to form a bend, the bend of the safety valve being in close contact with a side portion of the top cover, and the contact pressure between the bend of the safety valve and the side portion of the top cover being between 0.7 MPa and 7.0 MPa.

[0036] The contact pressure applied to the central area between the bend of the safety valve and the side of the top cover can be 3.5 MPa or lower.

[0037] Beneficial effects

[0038] According to the present invention, electrolyte leakage that may occur due to the gap between the safety valve and the top cover in the cylindrical secondary battery can be prevented. Attached Figure Description

[0039] Figure 1 This is a side cross-sectional view showing the structure of the top cover and safety valve according to the invention.

[0040] Figure 2 This is a side cross-sectional view illustrating the upper structure of the secondary battery according to the present invention.

[0041] Figure 3 These are simulation results, in which the stress inside the safety valve in the interconnected top cover and safety valve of the embodiments and comparative examples according to the present invention is shown in a visual manner. Detailed Implementation

[0042] The method for manufacturing a secondary battery according to the present invention will be described below with reference to the accompanying drawings.

[0043] Here, the secondary battery according to the present invention can be a cylindrical secondary battery.

[0044] Method for manufacturing secondary batteries

[0045] Figure 1 A side cross-sectional view showing the structure of the top cover and safety valve according to the invention is shown separately. Figure 2 This is a side cross-sectional view illustrating the upper structure of the secondary battery according to the present invention.

[0046] The method for manufacturing a secondary battery according to the present invention may include a first step of providing a top cover 200 and a safety valve 300. The top cover 200 may be configured to be attached to the upper part of the battery canister 100 (see...). Figure 2 Here, as Figure 1 As shown, the outer periphery of the top cover 200 can have a circular shape with an outer diameter of A. Furthermore, the top cover 200 can be made of cold-rolled steel, stainless steel, or aluminum.

[0047] Here, a notch 300a may be formed in the safety valve 300, the thickness of which is less than the thickness in other areas of the safety valve 300. Due to factors such as increased temperature inside the secondary battery, the internal pressure inside the secondary battery may increase. When the internal pressure of the secondary battery exceeds a certain pressure, the notch 300a of the safety valve 300 ruptures, thereby allowing gas inside the secondary battery to be discharged to the outside through the notch 300a and the vent (not shown) of the top cover 200. Therefore, it is possible to prevent the secondary battery from exploding due to increased internal pressure.

[0048] Furthermore, the method for manufacturing a secondary battery according to the present invention may further include a second step of bending the end of the safety valve 300 upwards. For example... Figure 1As shown, a bent portion 310 with an upwardly bent shape can be formed in the end of the safety valve 300 through a second step. Here, as... Figure 1 As shown, the interior of the safety valve 300, in which the bend 310 is formed, can have a circular shape with an inner diameter of B. Furthermore, the safety valve 300 can be made of aluminum.

[0049] Referring again to the accompanying drawings, the method for manufacturing a secondary battery according to the present invention may further include a third step of inserting a top cover 200 into a safety valve 300. Between the second and third steps, the outer diameter A of the top cover 200 may be larger than the inner diameter B of the safety valve 300.

[0050] Based on the structure of the cylindrical secondary battery according to the related technology, since the top cover must be housed inside the safety valve, the outer diameter of the top cover must be smaller than the inner diameter of the safety valve. Therefore, in the cylindrical secondary battery manufactured according to the related technology, a gap may inevitably exist between the inner side of the safety valve and the outer side of the top cover. This poses a risk of electrolyte leakage.

[0051] However, according to the present invention, the outer diameter of the top cover is manufactured to be larger than the inner diameter of the safety valve. Therefore, when the top cover and the safety valve are connected to each other in the third step, there can be no gap between the outer side of the top cover and the inner side of the safety valve. Thus, unlike related technologies, since there is no gap between the outer side of the top cover and the inner side of the safety valve, leakage of electrolyte from the space located between the outer side of the top cover and the inner side of the safety valve can be prevented.

[0052] Here, the ratio of the difference (AB) between the outer diameter A of the top cover 200 and the inner diameter B of the safety valve 300 to the outer diameter A of the top cover 200 (AB) / (A) or to the inner diameter B of the safety valve 300 (AB) / (B) can be within 5.4 × 10⁻⁶. -4 Up to 1.62×10 -3 between.

[0053] When (AB) / A or (AB) / B is less than 5.4 × 10 -4 At this time, the contact pressure between the top cover 200 and the safety valve 300 becomes too small. Therefore, the top cover 200 may separate from the safety valve 300 and fly out as the internal pressure of the secondary battery 10 increases. Additionally, when (AB) / A or (AB) / B is greater than 1.62 × 10⁻⁶... -3 At this time, due to the excessive increase in contact pressure between the top cover 200 and the safety valve 300, the internal stress of the top cover 200 or the safety valve 300 is excessively increased. Therefore, the top cover 200 or the safety valve 300 may be damaged during the connection of the top cover 200 to the safety valve 300 or when the secondary battery 10 is used.

[0054] As described above, in the method for manufacturing a secondary battery according to the present invention, since the outer diameter A of the top cover 200 is larger than the inner diameter B of the safety valve 300 between the second and third steps, an interference fit connection can be established between the top cover 200 and the safety valve 300 through the third step. Therefore, after the third step, pressure can be applied to the area where the top cover 200 and the safety valve 300 are in close contact with each other. That is, as Figure 2 As shown, contact pressure can be applied between the side portion 210 of the top cover 200 and the bend portion 310 of the safety valve 300.

[0055] The contact pressure needs to be greater than the pressure inside the secondary battery 10. This is because if the contact pressure is less than the pressure inside the secondary battery 10, the top cover 200 may be separated from the safety valve 300 due to the pressure inside the secondary battery 10.

[0056] Specifically, the top cover 200 is connected to the safety valve 300 not only when the secondary battery 10 is operating normally, but also in the event that the notch 300a ruptures due to an abnormal increase in the internal pressure of the secondary battery 10, causing gas inside the secondary battery 10 to be released to the outside. This is because if the top cover 200 detaches from the safety valve 300 and flies out due to an abnormal increase in the internal pressure of the secondary battery 10, a safety accident caused by the top cover 200 may occur.

[0057] Therefore, in the method for manufacturing a secondary battery according to the present invention, the contact pressure applied between the top cover 200 and the safety valve 300 after the third step can be greater than or equal to the pressure P. v The pressure P v This refers to the pressure inside the secondary battery 10 when gas begins to be released through the safety valve 300. In this situation, even if the internal pressure of the secondary battery 10 rises abnormally, it can prevent a safety accident that may occur when the top cover 200 separates from the safety valve 300. Here, P... v Between 1.3 MPa and 3.0 MPa.

[0058] Here, the outer diameter A of the top cover 200 can be 0.01 mm to 0.03 mm larger than the inner diameter B of the safety valve 300.

[0059] When the outer diameter A is less than 0.01 mm larger than the inner diameter B, the contact pressure between the top cover 200 and the safety valve 300 becomes too low. Therefore, as the internal pressure of the secondary battery 10 increases, the top cover 200 may separate from the safety valve 300 and fly out. On the other hand, when the outer diameter A is more than 0.03 mm larger than the inner diameter B, the contact pressure between the top cover 200 and the safety valve 300 increases excessively. As a result, the internal stress of the top cover 200 or the safety valve 300 increases excessively. Therefore, the top cover 200 or the safety valve 300 may be damaged during the connection of the top cover 200 to the safety valve 300 or when the secondary battery 10 is used. More preferably, the outer diameter A of the top cover 200 may be 0.01 mm to 0.02 mm larger than the inner diameter B of the safety valve 300.

[0060] Here, after the third step, the contact pressure between the side portion 210 of the top cover 200 and the bend portion 310 of the safety valve 300 facing each other in the entire area can be 7.0 MPa or lower. Furthermore, the contact pressure applied to the central region of the area where the side portion 210 of the top cover 200 and the bend portion 310 of the safety valve 300 face each other after the third step can be 3.5 MPa or lower.

[0061] When the contact pressure on the entire area where the side portion 210 of the top cover 200 and the bent portion 310 of the safety valve 300 face each other is 7.0 MPa or lower, damage to the top cover 200 or the safety valve 300 due to the interference fit connection between the top cover 200 and the safety valve 300 can be prevented.

[0062] Here, the contact pressure may be particularly high in the upper or lower region of the area where the side portion 210 of the top cover 200 contacts the bend portion 310 of the safety valve 300, but relatively low in the central region. Therefore, when the contact pressure in the central region of the area where the side portion 210 of the top cover contacts the bend portion 310 of the safety valve is 3.5 MPa or less, the contact pressure in the entire area where the side portion 210 of the top cover contacts the bend portion 310 of the safety valve is 7.0 MPa or less.

[0063] Here, the bend 310 of the safety valve 300 can be U-shaped, rather than... Figure 1 and Figure 2 The L-shape is bent upwards as shown. Therefore, the method for manufacturing a secondary battery according to the invention may further include a fourth step in which the end of the safety valve is additionally bent in a direction toward the center of the safety valve.

[0064] The structure of the secondary battery according to the present invention will be described below with reference to the accompanying drawings.

[0065] Secondary batteries

[0066] like Figure 1 and Figure 2 As shown, the secondary battery 10 according to the present invention may include a battery canister 100, a top cover 200 and a safety valve 300. The top cover 200 is connected to the upper part of the battery canister 100, and the safety valve 300 is disposed below the top cover 200.

[0067] Here, the end of the safety valve 300 can be bent upward to form a bent portion 310, and the bent portion 310 of the safety valve 300 can contact the side portion 210 of the top cover 200. In addition, a gasket 400 can be provided between the side portion of the safety valve 300 and the inner surface of the battery canister 100.

[0068] Furthermore, according to the present invention, a contact pressure can be applied between the bend 310 of the safety valve and the side portion 210 of the top cover. Here, the contact pressure can be 0.7 MPa or 7.0 MPa. Additionally, the contact pressure applied to the central region of the area between the bend 310 of the safety valve and the side portion 210 of the top cover can be 3.5 MPa or lower.

[0069] Example 1

[0070] In the Abaqus program, the safety valve and its cap are connected by inserting a cap into the safety valve, which has bends extending upwards from both ends. The safety valve is made of aluminum, and the cap is made of cold-rolled steel. Furthermore, the aluminum used in the safety valve has a yield strength of 125 MPa, and the cold-rolled steel used in the cap has a yield strength of 250 MPa.

[0071] The safety valve has a thickness of 0.3 mm, and the top cover has a thickness of 0.7 mm. A notch is formed in the safety valve.

[0072] In Example 1, the inner diameter of the safety valve is 18.495 mm, and the outer diameter of the top cover is 18.505 mm.

[0073] Example 2

[0074] Except that the inner diameter of the safety valve is 18.49 mm and the outer diameter of the top cover is 18.51 mm, the safety valve and the top cover are connected to each other in the same manner as in Example 1.

[0075] Example 3

[0076] Except that the inner diameter of the safety valve is 18.485 mm and the outer diameter of the top cover is 18.515 mm, the safety valve and the top cover are connected to each other in the same manner as in Example 1.

[0077] Comparison Examples

[0078] Except that the inner diameter of the safety valve is 18.48 mm and the outer diameter of the top cover is 18.52 mm, the safety valve and the top cover are connected to each other in the same manner as in Example 1.

[0079] Experimental Example

[0080] In the Abaqus program, the stresses acting on the interconnected safety valves and top covers are measured in the various embodiments and comparative examples. Figure 3 These are simulation results, in which the stress inside the safety valve in the interconnected top cover and safety valve of the embodiment and comparative example according to the present invention is shown visually. The various recessed areas are notches.

[0081] like Figure 3 As shown, it is confirmed that relatively high stress is generated in the region of the recess in each safety valve in the interconnected safety valves and top cover according to the embodiments and comparative examples. In particular, it is confirmed that relatively high stress is generated in the recess and the region below the recess of each safety valve in the embodiments and comparative examples compared to other regions.

[0082] More specifically, when comparing Example 1 with Example 2, it was confirmed that a relatively higher stress was generated in the safety valve of Example 2 compared to Example 1. Furthermore, when comparing Example 2 with Example 3, it was confirmed that a relatively higher stress was generated in the safety valve of Example 3 compared to Example 2.

[0083] However, as Figure 3 As shown, it is confirmed that the stress generated in the various safety valves including the notch in Embodiments 1 to 3 of the present invention is relatively low compared to the yield strength of the aluminum used in the safety valve. That is, it is confirmed that the yield strength of the aluminum used in each safety valve of the embodiments of the present invention and the comparative examples is 125 MPa as described above, but the stress generated in the safety valve over the entire area of ​​each safety valve in Embodiments 1 to 3 is less than 100 MPa. In particular, it is confirmed that the stress generated in the safety valve over the entire area of ​​the safety valve in Embodiment 1 is less than 25 MPa.

[0084] On the other hand, it is confirmed that, Figure 3 As shown, the stress generated in the safety valve in the comparative example increases rapidly. In particular, it is confirmed that a stress exceeding 100 MPa is generated in the region below the notch of the safety valve, which is 80% of the yield strength of the aluminum used in the safety valve. Therefore, the durability of the safety valve is significantly degraded.

[0085] Although the present invention has been described with reference to the specific embodiments and accompanying drawings described above, the present invention is not limited thereto. Obviously, those skilled in the art can make various changes and modifications within the technical concept of the present invention and the equivalent scope of the appended claims.

Claims

1. A method for manufacturing a secondary battery, the method comprising: First step: Provide the top cover and safety valve; Second step: Bend the end of the safety valve upwards; as well as Third step: Insert the top cover into the safety valve. In the process between the second and third steps, the outer diameter (A) of the top cover is larger than the inner diameter (B) of the safety valve. In the upper or lower region of the area where the side of the top cover and the bent portion of the safety valve contact each other, the contact pressure can be higher, while in the central region, the contact pressure can be relatively lower. The contact pressure applied between the side of the top cover and the safety valve is 7.0 MPa or lower. The contact pressure applied to the center region of the area between the side of the top cover and the safety valve is 3.5 MPa or lower. The method further includes a fourth step: additionally bending the end of the safety valve along the center direction of the safety valve.

2. The method according to claim 1, wherein, Between the second step and the third step, the outer diameter (A) of the top cover is 0.01 mm to 0.03 mm larger than the inner diameter (B) of the safety valve.

3. The method according to claim 1, wherein, After the third step, the contact pressure applied between the top cover and the safety valve is greater than or equal to the following pressure (P). v The pressure (P) v The pressure inside the secondary battery is when the gas inside the secondary battery begins to be discharged through the safety valve.

4. The method according to claim 1, wherein, The top cover is made of cold-rolled steel, stainless steel, or aluminum, and The safety valve is made of aluminum.

5. The method according to claim 1, wherein, The ratio of the difference (AB) between the outer diameter (A) of the top cover and the inner diameter (B) of the safety valve to the outer diameter (A) of the top cover ((AB) / A) is 5.4 × 10⁻⁶. -4 Up to 1.62×10 -3 between.

6. The method according to claim 1, wherein, The ratio of the difference (AB) between the outer diameter (A) of the top cover and the inner diameter (B) of the safety valve to the inner diameter (B) of the safety valve ((AB) / B) is 5.4 × 10⁻⁶. -4 Up to 1.62×10 -3 between.

7. A secondary battery, the secondary battery comprising: Battery canister; A top cover, which is attached to the upper part of the battery canister; as well as A safety valve, wherein the safety valve is located below the top cover. The safety valve has an end that is bent upwards to form a bent portion. The bent portion of the safety valve is in close contact with the side of the top cover, and In the upper or lower region of the area where the side portion of the top cover and the bent portion of the safety valve contact each other, the contact pressure can be higher, while in the central region, the contact pressure can be relatively lower. The contact pressure applied between the side of the top cover and the safety valve is 7.0 MPa or lower. The contact pressure applied to the center region of the area between the side of the top cover and the safety valve is 3.5 MPa or lower. The end of the safety valve is additionally bent along the central direction of the safety valve.

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