US-20260128489-A1 - Sealing Structure of Liquid Injection Port of Battery Can, Battery Cell, Battery and Vehicle Including the Same

Abstract

A structure for sealing a liquid injection port of a battery cell may include a can with one open end; an electrode assembly accommodated in the can; a cap covering the open end of the can; a liquid injection port provided at the cap; and a closing member inserted in the liquid injection port. The closing member inserted in the liquid injection port seals and is fixed to the liquid injection port through a sealing and fixing material melting at a predetermined temperature. The closing member includes a ball made of metal material. The sealing and fixing material may include a synthetic resin layer coated on the surface of the ball, or a solder filled between the surface of the ball and the inner circumferential surface of the liquid injection port with the ball inserted in the liquid injection port to seal the liquid injection port and fix the ball to the liquid injection port.

Inventors

• Hangsoo SHIN
• Dongsung Hwang
• Sungmin Cho
• Do Gyun Kim

Assignees

• LG ENERGY SOLUTION, LTD.

Dates

Publication Date

20260507

Application Date

20230926

Priority Date

20220930

Claims (20)

1. 1 . A battery cell comprising: a can comprising an open end; an electrode assembly accommodated in the can; a cap covering the open end of the can, wherein the can or the cap comprises a liquid injection port; a closing member seated in the liquid injection port; and a sealing and fixing material fixing the closing member within the liquid injection port; wherein the liquid injection port has a perforated section extending in an axial direction, and the liquid injection port has a cross-section defined by an intersection of an imaginary plane extending in a radial plane orthogonal to the axial direction and an inner circumferential surface of the liquid injection port, wherein the closing member extends in the axial direction, and the closing member has a cross-section defined by an intersection of the imaginary plane extending in the radial plane and an outer circumferential surface of the closing member, wherein at least a portion of the closing member extending in the axial direction is within the perforated section of the liquid injection port, wherein the sealing and fixing material is interposed between the inner circumferential surface of the liquid injection port and the outer circumferential surface of the closing member, wherein the sealing and fixing material is configured to seal a space between the inner circumferential surface of the liquid injection port and the outer circumferential surface of the closing member such that a sealed section extending in the axial direction fixes the closing member within the injection port, and wherein the sealing and fixing material has a melting point lower than melting point of the can or a melting point of the cap and wherein the melting point of the sealing and fixing material is lower than a melting point of the closing member.
2. 2 . The battery cell of claim 1 , wherein a minimum cross-section of the liquid injection port is smaller than a maximum cross-section of the closing member, and wherein the minimum cross-section of the liquid injection port is disposed further inward toward an inside of the can in the axial direction than the sealed section.
3. 3 . The battery cell of claim 1 , wherein the inner circumferential surface of the liquid injection port is defined by an inner circumferential surface of a circular tube extending in the axial direction from the can or the cap.
4. 4 . The battery cell of claim 3 , wherein an inner end of the circular tube in the axial direction is positioned in a core hollow portion of the electrode assembly.
5. 5 . The battery cell of claim 4 , wherein the circular tube comprises an air hole configured to discharge an air in the can when an electrolyte solution is injected through the liquid injection port, wherein the air hole is disposed in the sealed section.
6. 6 . The battery cell of claim 1 , wherein the outer circumferential surface of the closing member is not in direct contact with the inner circumferential surface of the liquid injection port.
7. 7 . The battery cell of claim 6 , wherein the sealing and fixing material is integrally fixed to the outer circumferential surface of the closing member.
8. 8 . The battery cell of claim 7 , wherein the sealing and fixing material comprises a synthetic resin layer coating a surface of the closing member.
9. 9 . (canceled)
10. 10 . The battery cell of claim 1 , wherein the closing member comprises a metal material.
11. 11 . The battery cell of claim 1 , wherein the sealing and fixing material has a cross-section in the radial plane defined by an intersection of the imaginary plane and an outer circumferential surface of the sealing and fixing material, and wherein the cross-section of the sealing and fixing material at the sealed section is larger than the cross-section of the liquid injection port at the sealed section such that the sealing and fixing material is compressed inward in the radial plane by the inner circumferential surface of the liquid injection port.
12. 12 . The battery cell of claim 11 , wherein the cross-section of the sealing and fixing material at a location further inward toward an inside of the can in the axial direction than the sealed section gradually becomes smaller.
13. 13 . (canceled)
14. 14 . The battery cell of claim 11 , wherein the cross-section of the closing member at a location further inward toward an inside of the can in the axial direction than the sealed section gradually becomes smaller.
15. 15 . The battery cell of claim 6 , wherein the closing member includes a ball, and the sealing and fixing material is coated integrally on the ball.
16. 16 - 21 . (canceled)
17. 22 . The battery cell of claim 1 , wherein a rate at which the cross-section of the closing member decreases in the axial direction toward an inside of the can in the first direction at a rate that is greater than a rate at which the cross-section of the liquid injection port decreases in the axial direction toward the inside of the can in the first direction in a predetermined section of the perforated section of the liquid injection port, wherein inner than where the outer circumferential surface of the closing member and the inner circumferential surface of the liquid injection port are in contact with each other further outward from the inside of the can in the axial direction than the predetermined section of the liquid injection port.
18. 23 . The battery cell of claim 1 , wherein a rate at which the cross-section of the closing member decreases in the axial direction toward an inside of the can in the first direction at a rate that is greater than a rate at which the cross-section of the liquid injection port decreases in the axial direction toward the inside of the can in the first direction in a predetermined section of the perforated section of the liquid injection port, wherein the predetermined section is further outward from the inside of the can outer than a location where the outer circumferential surface of the closing member and the inner circumferential surface of the liquid injection port are in contact with each other.
19. 24 . (canceled)
20. 25 . The battery cell of claim 1 , wherein the sealed section is provided further outward from an inside of the can in the first axial direction than a location where the outer circumferential surface of the closing member and the inner circumferential surface of the liquid injection port are in contact with each other.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national stage entry under 35 U.S.C. § 371 of International Application No. PCT/KR 2023/014889 filed on Sep. 26, 2023, which claims priority to Korean Patent Application No. 10-2022-0124981 filed on Sep. 30, 2022, and Korean Patent Application No. 10-2023-0026246 filed on Feb. 27, 2023, the entire contents of each of which are incorporated by reference herein. TECHNICAL FIELD The present disclosure relates to sealing structure of a liquid injection port of a battery can, a battery cell to which the same is applied, a manufacturing method of the battery cell, a battery pack including the battery cell, and a vehicle equipped with the battery pack. BACKGROUND A cylindrical battery cell is a structure wherein a jelly-roll shaped electrode assembly is accommodated in a cylindrical metal can, and is more robust to shock and temperature than a pouch-type battery. Accordingly, the demand for using metal can-type cells as battery cells applied to vehicle battery packs is increasing. The process of manufacturing a battery cell using a cylindrical can includes deep drawing a metal sheet to form a circular bottom and a circular tube-shaped sidewall member connected to the circular bottom, accommodating the electrode assembly in the can, and covering the open end of the sidewall member with a cap. Crimping or seam welding may be applied to a structure wherein the open end of the battery can is covered with a cap and the cap and the battery can are fixed. Referring to FIG. 1, crimping is a method of fixing the cap 40 by physically pressing the edge of the cap 40 to the open end of the can 10 with the gasket 91 interposed therebetween. Since crimping is a physical fixing method without applying heat, crimping may be performed with the electrolyte solution filled in the can. Therefore, the crimping method is advantageous in that separate liquid injection port structure and sealing structure thereof are not required. However, since crimping is structurally more complex than welding, there are limits in securing the internal volume of the can that accommodates the electrode assembly 20. Contrarily, as shown in FIG. 2, seam welding is a process of bringing the perimeter of the tip of the sidewall portion 11 of the battery can 10 into contact with the perimeter of the edge of the cap 40 and welding the same along the circumferential direction of the cap 40 such that more volume of the electrode assembly that may be accommodated in the battery can is secured due to the simplicity of the fixing structure of the cap 40. Therefore, the seam welding is more advantageous in securing electric capacity with respect to the volume of battery can. However, when welding is performed by filling the battery can with an electrolyte solution and then covering the open end of the battery can with a cap, there is a possibility that the electrolyte solution may deteriorate or ignite due to the high-temperature generated by welding. During the seam welding, for example, the surface temperature may rise up to 1400 degrees Celsius which is the melting point of SUS when the battery can and the cap are made of SUS. Such high-temperature heat may cause ignition of the electrolyte solution. Thus, when the cap is to be fixed by subjecting the perimeter of the open end of the battery can and cap to seam welding, a method may be applied wherein a battery can 10 provided with a liquid injection port at the bottom portion or a cap 40 provided with a liquid injection port 42 are prepared; the electrolyte solution is injected through the liquid injection port 42 provided at the cap or the bottom portion of the battery can after accommodating the electrode assembly in the battery can and seam-welding the battery can 10 and the cap; and closing and sealing and the liquid injection port after completing the liquid injection. For example, as shown in FIG. 2, a closing member such as a metal ball 50 may be press-fitted into the liquid injection port 42 to be fixed to the liquid injection port 42 and to seal the liquid injection port 42. That is, a metal ball 50 with a diameter larger than that of the inner circumferential surface of the liquid injection port 42 is forcibly press-fitted into the liquid injection port 42 such that the inner circumferential surface of the liquid injection port 42 and the surface of the metal ball 50 are compressed together by elastic deformations thereof to achieve sealing. However, such structure is disadvantageous in securing the internal volume of the can since the sealing structure of the liquid injection port consumes the volume of the battery cell as much as the section where the ball is pressed in. Additionally, since a large pressure is applied toward the electrode to force the ball 50 into the liquid injection port 42, there is a possibility that the electrode may be damaged. Meanwhile, when thermal runaway occurs inside the can of a battery cell, the inner pressu