Secondary battery

Abstract

The present invention provides a secondary battery, comprising: an electrode assembly in which a positive electrode, a separator and a negative electrode are stacked, a positive electrode tab protrudes toward one side, a negative electrode tab protrudes toward the other side, and a through hole is formed in the electrode assembly; an upper can provided with a flat surface portion and a peripheral portion protruding in a vertical direction along the edge of the surface portion; a lower can provided with a flat surface portion and a peripheral portion protruding in a vertical direction along the edge of the surface portion, wherein the peripheral portion is assembled in parallel with the peripheral portion of the upper can; and a center pin, which applies an elastic force in a longitudinal direction when inserted into the through hole. Wherein, in a state where the negative electrode tab is arranged parallel to the plane portion of the lower can and the positive electrode tab is arranged parallel to the plane portion of the upper can, when the upper can and the lower can are engaged with each other, the center pin applies an elastic force to allow the negative electrode tab to be in close contact with the lower can and allow the positive electrode tab to be in close contact with the upper can. The secondary battery according to the present invention having the above configuration has the effect of removing the welding process for the positive electrode tab and the negative electrode tab.

Description

Technical Field

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2020-0041760, filed on April 6, 2020, which is hereby incorporated by reference herein in its entirety.

[0002] The present invention relates to a secondary battery, and more particularly, to a secondary battery in which a process of welding a positive electrode tab and a negative electrode tab to an upper can and a lower can, respectively, is eliminated to reduce production costs and also reduce a defect rate due to a difficult welding process. Background Art

[0003] A button type battery, which is generally used as a coin type battery or a button type battery, has a thin button shape and is widely used in various devices such as remote controllers, clocks, toys, computer parts, and the like.

[0004] Such button-type batteries are mainly manufactured as non-rechargeable primary batteries, but with the development of miniaturized devices, button-type batteries are also widely manufactured as rechargeable and dischargeable secondary batteries. In addition, similar to button-type secondary batteries or cylindrical or pouch-type secondary batteries, button-type secondary batteries also have a structure in which an electrode assembly and an electrolyte are embedded in a housing to repeatedly perform charge and discharge.

[0005] Figure 1 is a cross-sectional view showing a state in which, in assembling a button-type secondary battery according to the related art, a negative electrode tab and a lower can are welded to each other, a positive electrode tab and an upper can are welded to each other, and then, the lower can and the upper can are joined to each other.

[0006] As shown in the drawings, the button type secondary battery has a structure in which an upper can 30 and a lower can 20 are joined to each other. Here, each of the upper can 30 and the lower can 20 has a flat cylindrical shape, and the diameter of the upper can 30 is slightly larger than that of the lower can 20.

[0007] The electrode assembly 10 in which the positive electrode, the separator, and the negative electrode are stacked, and the electrolyte are installed in the lower can 20. Here, the electrode assembly 10 is configured such that: the negative electrode tab 12 protruding from the negative electrode extends from the side surface of the negative electrode to protrude downward, and the positive electrode tab 11 protruding from the positive electrode extends from the side surface of the positive electrode to protrude upward.

[0008] In addition, when the electrode assembly 10 is placed on the lower can 20, with the extended portion of the negative electrode tab 12 bent into contact with the bottom surface of the electrode assembly 10, the upper welding gun A enters the hole 13 formed in the center of the electrode assembly 10, and current is applied to the lower welding gun B, so that the negative electrode tab 12 is joined to the lower can 20 by resistance welding.

[0009] On the other hand, the positive electrode tab 11 is welded to the bottom surface of the flat portion of the upper can 30 before being completely bent. In addition, when the upper can 30 and the lower can 20 are joined to each other, the positive electrode tab 11 is bent one more time than the negative electrode tab 12 (see FIG. Figure 1 The positive electrode tab is bent twice in the figure below).

[0010] In addition, the method for joining the positive electrode tab 11 to the negative electrode tab 12 according to the related art has the following problems: each of the positive electrode tab 11 and the negative electrode tab 12 is welded, thereby reducing productivity. In addition, since the positive electrode tab 11 must have a sufficiently long length for welding, production costs may increase, and additional bending may be performed, thereby increasing the thickness of the secondary battery. Summary of the invention

[0011] Technical issues

[0012] Therefore, an object of the present invention is to provide a secondary battery in which the problems of the above-mentioned structure according to the related art (reduction in productivity due to separate joining of positive electrode tabs and negative electrode tabs, increase in product cost due to increase in length of the positive electrode tab, and increase in thickness due to additional bending of the positive electrode tab) can be solved.

[0013] Technical Solutions

[0014] The present invention for achieving the above-mentioned purpose provides a secondary battery, which includes: an electrode assembly, in which a positive electrode, a separator and a negative electrode are stacked, a positive electrode tab protrudes toward one side, a negative electrode tab protrudes toward the other side, and a through hole is formed in the electrode assembly; an upper can, which is provided with a flat plane portion and a surrounding portion protruding in a vertical direction along an edge of the plane portion; a lower can, which is provided with a flat plane portion and a surrounding portion protruding in a vertical direction along an edge of the plane portion, wherein the surrounding portion is assembled in parallel with the surrounding portion of the upper can; and a center pin, which is configured to apply an elastic force in a longitudinal direction when inserted into the through hole, wherein, in a state in which the negative electrode tab is arranged to be parallel to the plane portion of the lower can and the positive electrode tab is arranged to be parallel to the plane portion of the upper can, when the upper can and the lower can are engaged with each other, the center pin applies an elastic force to allow the negative electrode tab to be in close contact with the lower can and allow the positive electrode tab to be in close contact with the upper can.

[0015] The center pin may include one or more springs that resist a compressive force, and the compressive force may be applied to the springs when the upper and lower cans engage each other.

[0016] The spring may include a first spring and a second spring disposed to be connected to each other in a longitudinal direction, and an insulator interrupting power may be disposed between the first spring and the second spring to electrically insulate the first spring and the second spring from each other.

[0017] The end of the first spring pressing the positive electrode tab and the end of the second spring pressing the negative electrode tab can be provided with a wedge having a sharp shape with a diameter gradually decreasing toward the end of the wedge. In addition, two wedges can be arranged parallel to each other at the end of each of the first spring and the second spring.

[0018] The length and elasticity of each of the first spring and the second spring may be determined to be within a range in which one or more of the positive electrode tab and the negative electrode tab are separated from the upper tank or the lower tank before the upper tank and the lower tank are completely separated from each other. When the upper tank rises a predetermined distance from its initial position joined to the lower tank, the positive electrode tab may switch from a state of contacting with the bottom surface of the upper tank to a state of not contacting with the bottom surface of the upper tank.

[0019] When the upper tank and the lower tank are joined to each other, a gasket for interrupting power may be provided between the peripheral portion of the upper tank and the peripheral portion of the lower tank. The gasket may be configured to not only insulate electricity but also prevent leakage of the built-in electrolyte, and contain an adhesive component to allow the upper tank and the lower tank to be bonded to each other.

[0020] In the present invention, the diameter of the upper tank can be larger than the diameter of the lower tank, the surrounding part of the lower tank can enter the surrounding part of the upper tank, and each of the upper tank and the lower tank can be formed in the form of a shell (schale), in which the diameter of the planar part of each of the upper tank and the lower tank is larger than the height of the surrounding part of each of the upper tank and the lower tank.

[0021] The electrode assembly may have a cylindrical shape, and the through hole may be formed at a position passing through the center of the electrode assembly. When the upper can is joined to the lower can in a state where the electrode assembly is inserted into the lower can, the negative electrode tab may be extended from the side surface of the electrode assembly and bent to be led to the lower side of the electrode assembly, the positive electrode tab may be extended from the side surface of the electrode assembly and bent to be led to the upper side of the electrode assembly, and the point where the negative electrode tab is connected to the side surface of the electrode assembly and the point where the positive electrode tab is connected to the side surface of the electrode assembly may be set at sides opposite to each other.

[0022] Beneficial effects

[0023] In the present invention having the above technical features, when the upper tank and the lower tank are engaged with each other, the center pin can be elastically compressed so that the center pin allows the negative electrode tab to be in close contact with the lower tank and allows the positive electrode tab to be in close contact with the upper tank. Therefore, the welding process of the negative electrode tab and the positive electrode tab can be removed to simplify the manufacturing process and reduce the defect rate.

[0024] Each of the ends of the first spring and the second spring may be provided with a wedge having a sharp shape with a diameter gradually decreasing toward the ends thereof, so that the contact area between the center pin and the negative and positive electrode tabs can be minimized. Thus, the occurrence of leakage current and the increase of resistance can be prevented.

[0025] Two wedges may be provided on the end of each of the first spring and the second spring to prevent shaking and bending.

[0026] In addition, the length and elasticity of each of the first spring and the second spring can be determined to be within a range in which one or more of the positive electrode tab and the negative electrode tab are separated from the upper tank or the lower tank before the upper tank and the lower tank are completely separated from each other. Therefore, when expansion occurs, the positive electrode tab and the upper tank or the negative electrode tab and the lower tank can be spaced apart from each other to interrupt the current, thereby preventing an explosion or fire due to high temperature from occurring.

[0027] The gasket may be configured to not only electrically insulate but also prevent leakage of the built-in electrolyte, and contain an adhesive component to allow the upper tank and the lower tank to be bonded to each other. That is, the upper tank and the lower tank may be bonded to each other by welding, bonding, crimping, etc., and may provide an additional bonding force in addition to the bonding force acting in the main bonding. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a cross-sectional view showing a state in which, in an assembly process of a button-type secondary battery according to the related art, a negative electrode tab and a lower can are welded to each other, a positive electrode tab and an upper can are welded to each other, and then the lower can and the upper can are coupled to each other.

[0029] Figure 2 is a cross-sectional view of a secondary battery according to the present invention.

[0030] Figure 3 It shows that Figure 2 0 is a cross-sectional view of a state in which a secondary battery is exploded.

[0031] Figure 4 is a cross-sectional view showing a state before the upper tank is lowered to be joined to the lower tank.

[0032] Figure 5is a sectional view showing a state in which the positive electrode tab and the upper can are spaced apart from each other when the internal pressure increases to allow the upper can to move a certain distance spaced apart from the lower can in a state in which the upper can and the lower can are engaged with each other. DETAILED DESCRIPTION

[0033] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that a person skilled in the art can easily implement the technical ideas of the present invention. However, the present invention can be implemented in different forms and should not be construed as being limited to the embodiments described herein.

[0034] In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or like components throughout the specification.

[0035] In addition, the terms or words used in the present specification and claims should not be restrictively interpreted as ordinary meanings or dictionary-based meanings, but should be interpreted as meanings and concepts consistent with the scope of the present invention based on the principle that the inventor can appropriately define the concepts of the terms to best describe and interpret his or her invention.

[0036] The present invention relates to a button-type secondary battery, which is configured to solve problems such as reduced productivity, increased product cost due to increased length of a positive electrode tab, and increased thickness due to additional bending. Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0037] Figure 2 is a cross-sectional view of a secondary battery according to the present invention, and Figure 3 It is shown Figure 2 , which is a cross-sectional view of a secondary battery in an exploded state. As shown in the drawings, a secondary battery according to the present invention includes an electrode assembly 10, an upper can 30, a lower can 20, and a center pin 50.

[0038] The electrode assembly 10 has a structure in which a positive electrode, a separator, and a negative electrode are stacked, a positive electrode tab 11 protrudes toward one side, a negative electrode tab 12 protrudes toward the other side, and a through hole 13 is formed at the center of the electrode assembly. In more detail, the electrode assembly 10 has a cylindrical shape having a diameter greater than a height, and the through hole 13 is formed at a position passing through the center of the electrode assembly 10.

[0039] In addition, the positive electrode tab 11 protrudes upward from one side of the side surface of the electrode assembly 10, and the negative electrode tab 12 protrudes downward from the other side of the side surface. When the upper can 30 is joined to the lower can 20 in a state where the electrode assembly 10 is inserted into the lower can 20, the negative electrode tab 12 is bent to be directed toward the lower side of the electrode assembly 10, and the positive electrode tab 11 is bent to be directed toward the upper side of the electrode assembly 10.

[0040] In addition, the negative electrode tab 12 and the positive electrode tab 11 may be disposed on opposite sides of the electrode assembly 10. In some cases, the negative electrode tab 12 and the positive electrode tab 11 may be disposed closer to each other (e.g., the negative electrode tab 12 and the positive electrode tab 11 may be disposed at a point where the negative electrode tab 12 and the positive electrode tab 11 form a right angle with respect to the through hole).

[0041] In addition, the upper can 30 and the lower can 20 have flat plane parts 30 b and 20 b and peripheral parts 30 a and 20 a protruding in the vertical direction along the edges of the plane parts 30 b and 20 b , respectively.

[0042] Each of the upper tank 30 and the lower tank 20 is formed in the form of a shell, in which each of the plane parts 30b and 20b has a diameter greater than the height of each of the peripheral parts 30a and 20a, and the diameter of the upper tank 30 is approximately as large as the thickness of the lower tank 20 so that the lower tank 20 is fitted in the upper tank 30. Therefore, the peripheral part 20a of the lower tank 20 can enter and be fixed to the inside of the peripheral part 30a of the upper tank 30.

[0043] In addition, the center pin 50 is inserted into the through hole 13 of the electrode assembly 10 to press the bent positive electrode tab 11 upward and the bent negative electrode tab 12 downward. Figure 4 As shown, in a state where the center pin 50 is disposed between the positive electrode tab 11 and the negative electrode tab 12, the center pin 50 is elastically compressed by the pressure applied when the upper can 30 and the lower can 20 are engaged with each other. Therefore, the center pin 50 presses the positive electrode tab 11 and the negative electrode tab 12 so that the positive electrode tab 11 and the negative electrode tab 12 are in close contact with the plane portions 30b and 20b of the upper can 30 and the lower can 20, respectively.

[0044] That is, in a state where the bent portion of the negative electrode tab 12 is arranged to be parallel to the planar portion 20 b of the lower can 20 and the bent portion of the positive electrode tab 11 is arranged to be parallel to the planar portion 30 b of the upper can 30, since the center pin 50 configured to apply an elastic restoring force in the longitudinal direction presses the negative electrode tab 12 and the positive electrode tab 11 into close contact with the lower can 20 and the upper can 30, in the configuration of the present invention, a process of welding each of the negative electrode tab 12 and the positive electrode tab 11 is unnecessary.

[0045] In the center pin 50 according to the present invention, two springs 51 and 52 that resist the compressive force are connected to each other, and the springs are insulated from each other by an insulator 53 provided therebetween.

[0046] That is, the spring includes a first spring 51 and a second spring 52, the first spring 51 and the second spring 52 are connected to each other in the longitudinal direction, and an insulator 53 for interrupting power is provided between the first spring 51 and the second spring 52 to insulate the first spring 51 and the second spring 52 from each other. Here, it is preferred that the first spring 51 and the second spring 52 are made of the same material and have the same size so as to have the same elastic restoring force. The insulator 53 is manufactured to have a rigidity that can fully support the connection point between the first spring 51 and the second spring 52.

[0047] Furthermore, in the present invention, each of the end of the first spring 51 pressing the positive electrode tab 11 and the end of the second spring 52 pressing the negative electrode tab 12 is provided with a wedge 54 having a sharp shape with a diameter gradually decreasing toward the end thereof, so as to minimize the contact between the first spring 51 and the positive electrode tab 11 and between the second spring 52 and the negative electrode tab 12, thereby suppressing current leakage and preventing resistance increase.

[0048] The wedge 54 has a mechanical property of not damaging the surface when contacting each of the positive electrode tab 11 and the negative electrode tab 12. In addition, two wedges 54 are provided in parallel with each other at the end of each of the first spring 51 and the second spring 52 to disperse the pressure (alternatively, the wedge 54 may be provided in more than two and may be provided not only in a wedge shape but also in other shapes such as an edge type).

[0049] Furthermore, the present invention has a structure in which the length of each of the first spring 51 and the second spring 52 and the length of each of the positive electrode tab 11 and the negative electrode tab 12 are limited to suppress interruption of current before heat generation or explosion occurs when the internal temperature rises due to overcharging or the like to evaporate the electrolyte.

[0050] That is, when the pressure in each of the upper can 30 and the lower can 20 increases in a state where the upper can 30 and the lower can 20 are engaged with each other to allow the upper can 30 to move a certain distance from the lower can 20, referring to the state showing the positive electrode tab 11 and the upper can 30 are spaced apart from each other. Figure 5 , when heat generation occurs due to abnormal operation of the secondary battery and thus internal electrolyte is evaporated by the heat so that internal pressure increases, the upper can 30 and the lower can 20 are separated from each other to move in the vertical direction.

[0051] like Figure 5 As shown in, in the secondary battery according to the present invention, when each of the upper tank 30 and the lower tank 20 moves a predetermined distance before the upper tank 30 and the lower tank 20 are completely separated from each other, the positive electrode tab 11 and the upper tank 30 are spaced apart from each other by a distance "t" to interrupt the current. Since the current is interrupted before the upper tank 30 and the lower tank 20 are completely separated from each other, heat generation can be suppressed, and the increase in internal pressure can be stopped, so that the explosion of the secondary battery can be suppressed. Here, the distance "t" can be determined in the design step. In addition, the length and elasticity of each of the first spring 51 and the second spring 52 can be set, and the length of each of the positive electrode tab 11 and the negative electrode tab 12 can be determined according to the distance "t".

[0052] That is, the length and elasticity of each of the first spring 51 and the second spring 52 can be determined to be within the following range: within this range, one or more of the positive electrode tab 11 and the negative electrode tab 12 are separated from the upper can 30 or the lower can 20 before the upper can 30 and the lower can 20 are completely separated from each other.

[0053] In addition, in the present invention, when the upper tank 30 and the lower tank 20 are joined to each other, a gasket 40 for electrically insulating the upper tank 30 and the lower tank 20 from each other is provided between the peripheral portion 30a of the upper tank 30 and the peripheral portion 20a of the lower tank 20. The gasket 40 may be configured to not only electrically insulate but also prevent leakage of the built-in electrolyte, and contain an adhesive component to allow the upper tank 30 and the lower tank 20 to be bonded to each other.

[0054] For example, the upper tank 30 and the lower tank 20 may be mainly joined to each other by welding or crimping, which are typical joining methods. Alternatively, an adhesive component may be added to the gasket 40 to provide additional joining force in addition to the main joining.

[0055] In the present invention having the above technical features, when the upper can 30 and the lower can 20 are engaged with each other, the center pin can be elastically compressed so that the center pin 50 allows the negative electrode tab 12 to be in close contact with the lower can 20 and allows the positive electrode tab 11 to be in close contact with the upper can 30. Therefore, the welding process of the negative electrode tab 12 and the positive electrode tab 11 can be removed to simplify the manufacturing process and reduce the defect rate.

[0056] Each of the ends of the first spring 51 and the second spring 52 may be provided with a wedge 54 having a sharp shape with a diameter gradually decreasing toward the ends thereof, and thus, the contact area between the center pin 50 and the negative electrode tab 12 and the positive electrode tab 11 may be minimized. Therefore, the occurrence of leakage current and the increase of resistance may be prevented.

[0057] Two wedges 54 may be provided on the end of each of the first spring 51 and the second spring 52 to prevent shaking and bending.

[0058] In addition, the length and elasticity of each of the first spring 51 and the second spring 52 may be determined to be within a range in which one or more of the positive electrode tab 11 and the negative electrode tab 12 are separated from the upper can 30 or the lower can 20 before the upper can 30 and the lower can 20 are completely separated from each other. Therefore, when expansion occurs, the positive electrode tab 11 and the upper can 30 or the negative electrode tab 12 and the lower can 20 may be spaced apart from each other to interrupt current, thereby preventing an explosion or fire due to high temperature from occurring.

[0059] The gasket 40 may be configured to not only electrically insulate but also prevent leakage of the built-in electrolyte, and contain an adhesive component to allow the upper tank and the lower tank to be bonded to each other. That is, the upper tank 30 and the lower tank 20 may be bonded to each other by welding, bonding, crimping, etc., and may provide an additional bonding force in addition to the bonding force acting in the main bonding.

[0060] While embodiments of the present invention have been described with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

[0061] [Description of Reference Signs]

[0062] 10: Electrode assembly

[0063] 11: Positive terminal

[0064] 12: Negative terminal

[0065] 20: Lower the tank

[0066] 30: Canning

[0067] 50: Center pin

Claims

1. A secondary battery comprising: an electrode assembly in which a positive electrode, a separator, and a negative electrode are stacked, a positive electrode tab protrudes toward one side, a negative electrode tab protrudes toward the other side, and a through hole is formed in the electrode assembly; an upper tank, the upper tank being provided with a flat plane portion and a peripheral portion protruding in a vertical direction along an edge of the plane portion; a lower tank provided with a flat plane portion and a peripheral portion protruding in the vertical direction along an edge of the plane portion, wherein the peripheral portion is assembled in parallel with the peripheral portion of the upper tank; and a center pin configured to apply an elastic force in a longitudinal direction when inserted into the through hole, wherein, in a state where the negative electrode tab is arranged parallel to the plane portion of the lower tank and the positive electrode tab is arranged parallel to the plane portion of the upper tank, when the upper tank and the lower tank are engaged with each other, the center pin applies the elastic force to allow the negative electrode tab to be in close contact with the lower tank and the positive electrode tab to be in close contact with the upper tank, wherein the center pin includes one or more springs that resist compression forces, When the upper tank and the lower tank are engaged with each other, the compressive force is applied to the spring, The spring comprises a first spring and a second spring, and the first spring and the second spring are arranged to be connected to each other in the longitudinal direction, An insulator that interrupts power is provided between the first spring and the second spring to electrically insulate the first spring and the second spring from each other, and Wherein, the length and elasticity of each of the first spring and the second spring are determined to be within the following range: in the range, one or more of the positive electrode tab and the negative electrode tab are separated from the upper tank or the lower tank before the upper tank and the lower tank are completely separated from each other.

2. The secondary battery according to claim 1, wherein Each of the end of the first spring pressing the positive electrode tab and the end of the second spring pressing the negative electrode tab is provided with a wedge having a sharp shape with a diameter gradually decreasing toward the end of the wedge.

3. The secondary battery according to claim 2, wherein: Two wedges are provided parallel to each other at an end of each of the first spring and the second spring.

4. The secondary battery according to claim 1, wherein When the upper tank rises a predetermined distance from its initial position joined to the lower tank, the positive electrode tab switches from a state of contact with the bottom surface of the upper tank to a state of not contacting the bottom surface of the upper tank.

5. The secondary battery according to claim 1, wherein When the upper tank and the lower tank are coupled to each other, a gasket that interrupts power is provided between a peripheral portion of the upper tank and a peripheral portion of the lower tank.

6. The secondary battery according to claim 5, wherein The diameter of the upper tank is greater than the diameter of the lower tank, and The surrounding portion of the lower tank enters the surrounding portion of the upper tank.

7. The secondary battery according to claim 6, wherein Each of the upper tank and the lower tank is formed in the form of a shell sheet, and in each of the upper tank and the lower tank, the diameter of the planar portion of each of the upper tank and the lower tank is greater than the height of the surrounding portion of each of the upper tank and the lower tank.

8. The secondary battery according to claim 1, wherein The electrode assembly has a cylindrical shape, and The through hole is formed at a position passing through the center of the electrode assembly.

9. The secondary battery according to claim 1, wherein When the upper can is joined to the lower can in a state where the electrode assembly is inserted into the lower can, the negative electrode tab is extended from the side surface of the electrode assembly and is bent to be led to the lower side of the electrode assembly, The positive electrode tab extends from a side surface of the electrode assembly and is bent to be directed toward an upper side of the electrode assembly, and A point at which the negative electrode tab is connected to a side surface of the electrode assembly and a point at which the positive electrode tab is connected to a side surface of the electrode assembly are opposite to each other.

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