Secondary battery

Abstract

The present invention relates to a secondary battery that can ensure sealing capability. Disclosed as an example is a secondary battery including an electrode assembly, a case in which the electrode assembly is accommodated, and a cover assembly coupled to a top of the case and including an upper cover, a safety vent disposed below the upper cover and having a vent extension extending to a top of the upper cover to cover an edge of the upper cover, and a lower cover disposed below the safety vent and electrically connected to the electrode assembly, wherein the vent extension has a welding area formed by welding the upper cover and the safety vent to each other, and the welding area is spaced apart from an end of the case.

Description

Technical Field

[0001] This invention relates to a secondary battery. Background Technology

[0002] Unlike non-rechargeable primary batteries, secondary batteries are rechargeable and dischargeable. Small-capacity batteries, where a single cell is packaged in a pack, are used in small portable electronic devices such as smartphones, feature phones, laptops, digital cameras, and camcorders. Large-capacity batteries, where dozens of cells are connected in a pack, are widely used as power sources for driving electric motors and for energy storage in hybrid and electric vehicles. Lithium-ion secondary batteries can be classified by shape into cylindrical, prismatic, and pouch-type secondary batteries.

[0003] Specifically, a cylindrical lithium-ion secondary battery typically includes a cylindrical electrode assembly, a cylindrical housing to which the electrode assembly is attached, an electrolyte injected into the housing to enable the movement of lithium ions, and a cover assembly attached to one side of the housing to prevent electrolyte leakage and to prevent the electrode assembly from separating.

[0004] The information disclosed in this background section is only intended to enhance the understanding of the background art of the invention, and therefore may include information that does not constitute prior art. Summary of the Invention

[0005] Technical issues This invention provides a secondary battery that can ensure sealing capability.

[0006] Technical solution The secondary battery according to the present invention may include: an electrode assembly; a housing in which the electrode assembly is housed; and a cover assembly coupled to the top of the housing and including an upper cover, a safety vent, and a lower cover, wherein the safety vent is disposed below the upper cover and has a vent extension extending to the top of the upper cover to cover the edge of the upper cover, and the lower cover is disposed below the safety vent and electrically connected to the electrode assembly, wherein the vent extension has a welded area formed by welding the upper cover and the safety vent to each other, and the welded area is spaced apart from the end of the housing.

[0007] The welding area can be spaced inward from the end of the housing.

[0008] The distance between the welded area and the end of the shell can be 0.2 mm or greater.

[0009] The welding area can be spaced outward from the end of the vent extension.

[0010] The gasket can be located between the welded area and the end of the housing.

[0011] The welding area can be circular in shape.

[0012] The welding area can be in the shape of at least one arc.

[0013] The housing may include a side plate and a bottom plate below the sealing side plate, and the end of the housing may be the uppermost part of the side plate.

[0014] The ends of the housing can be bent to form a press-fit portion for securing the cover assembly.

[0015] Beneficial effects In the secondary battery according to an embodiment of the present invention, by spacing the welded areas where the end of the casing is welded to the top cover and the safety vent by 0.2 mm or more, the sealing capability of the secondary battery can be ensured and the safety of the secondary battery can be improved. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view showing a secondary battery according to an embodiment of the present invention.

[0017] Figure 2 This is a cross-sectional view showing a cover assembly in a secondary battery according to an embodiment of the present invention.

[0018] Figure 3 It is shown Figure 2 An enlarged sectional view of part A.

[0019] Figure 4a and Figure 4b This is a plan view showing the welding area in the cover assembly. Detailed Implementation

[0020] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Examples of the invention are provided to explain it more fully to those skilled in the art, and the following examples can be modified in various other forms. However, the invention can be embodied in many different forms and should not be construed as limited to the examples (or exemplary) embodiments set forth herein. Rather, these exemplary embodiments are provided so that the invention will be thorough and complete, and will convey aspects and features of the invention to those skilled in the art.

[0022] Additionally, for the sake of brevity and clarity, the dimensions or thicknesses of various components are exaggerated in the accompanying drawings. The same reference numerals always refer to the same elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, it will be understood that when element A is referred to as being "connected to" element B, element A may be directly connected to element B, or an intermediary element C may exist between element A and element B, such that element A and element B are indirectly connected to each other.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising or including” and / or variations thereof are used in this specification, it indicates the presence of the stated features, quantities, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, quantities, steps, operations, elements, components, and / or groups thereof.

[0024] For ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” and “above” may be used herein to describe the relationship between one element or feature shown in the figures and another element(s). It will be understood that, in addition to the orientation depicted in the figures, the spatial relative terms are also intended to cover different orientations of the device during use or operation. For example, if an element or feature in the figures is flipped, an element described as “below” or “under” other elements or features would subsequently be oriented “above” or “above” said other elements or features. Thus, the exemplary term “below” can encompass both above and below orientations.

[0025] Figure 1 This is a cross-sectional view showing a secondary battery according to an embodiment of the present invention.

[0026] Reference Figure 1 According to an embodiment of the present invention, the secondary battery 100 may include an electrode assembly 110, a housing 120, a cover assembly 130, and a gasket 190.

[0027] The electrode assembly 110 includes a first electrode 111, a second electrode 112, and a diaphragm 113 disposed between the first electrode 111 and the second electrode 112. The electrode assembly 110 can be formed by winding a stack of the first electrode 111, the diaphragm 113, and the second electrode 112 into an electrode core shape. Here, the first electrode 111 can be used as a positive electrode, and the second electrode 112 can be used as a negative electrode. A first electrode tab 114 is connected to the cover assembly 130 at the top of the electrode assembly 110, and a second electrode tab 115 is connected to the bottom plate 122 of the housing 120 at the bottom of the electrode assembly 110.

[0028] The first electrode 111 is formed by applying a first electrode active material (such as a transition metal oxide) to a first electrode current collector formed of a metal foil (such as aluminum). An uncoated portion of the first electrode to which the first electrode active material is not applied is formed on the first electrode 111, and a first electrode tab 114 is attached to this uncoated portion. One end of the first electrode tab 114 is electrically connected to the first electrode 111, and the other end protrudes upward from the electrode assembly 110 and is electrically connected to the cover assembly 130.

[0029] The second electrode 112 is formed by applying a second electrode active material (such as graphite or carbon) to a second electrode current collector formed of a metal foil (such as copper or nickel). Uncoated portions of the second electrode where the second electrode active material is not applied are formed on the second electrode 112, and second electrode tabs 115 are attached to these uncoated portions. One end of the second electrode tab 115 is electrically connected to the second electrode 112, and the other end protrudes from the bottom of the electrode assembly 110 and is electrically connected to the base plate 122 of the housing 120.

[0030] A separator 113 is positioned between the first electrode 111 and the second electrode 112 to prevent short circuits and allow lithium ions to move. The separator 113 may be made of polyethylene, polypropylene, or a composite membrane of polyethylene and polypropylene.

[0031] The housing 120 includes a side plate 121 and a bottom plate 122. The side plate 121 is a cylinder with a predetermined diameter to form a space for accommodating the electrode assembly 110, and the bottom plate 122 seals the lower part of the side plate 121. The top opening of the housing 120 is open to be sealed after the electrode assembly 110 is inserted into the housing 120. Furthermore, a rolled edge portion 123 for preventing movement of the electrode assembly 110 is formed on the top of the housing 120. Additionally, a crimping portion 124 for securing the cover assembly 130 and the gasket 190 is formed at the uppermost portion of the housing 120. The crimping portion 124 has a gasket 190 disposed therein and is configured to press the cover assembly 130 to prevent separation of the cover assembly 130 and to prevent electrolyte leakage.

[0032] Figure 2 This is a cross-sectional view showing a cover assembly in a secondary battery according to an embodiment of the present invention.

[0033] Reference Figure 2 The cover assembly 130 may include an upper cover 140, a safety vent 150, an insulator 160, and a lower cover 170.

[0034] The top cover 140 is formed as a circular plate and includes a terminal portion 141 that protrudes upward from the center, a connecting portion 142 located on the outer periphery of the terminal portion 141, and a connecting portion 143 connecting the terminal portion 141 and the connecting portion 142. The terminal portion 141 protrudes upward relative to the connecting portion 142 and serves as a terminal for electrical connection to an external circuit. The terminal portion 141 is electrically connected to a first electrode tab 114 and can serve as, for example, a positive electrode. The connecting portion 142 is located on the outer periphery of the terminal portion 141, and a safety vent 150 is connected to the connecting portion 142. The vent extension 153 of the safety vent 150 is connected to the top of the connecting portion 142. The connecting portion 143 connects the terminal portion 141 and the connecting portion 142, and a vent hole 143a is formed in the connecting portion 143. A plurality of vent holes 143a can be formed in the connecting portion 143 and provide a path for venting gas generated inside the housing 120. Furthermore, some of the vent holes 143a may extend to the terminal portion 141 and the joint portion 142.

[0035] The safety vent 150 is formed as a circular plate corresponding to the upper cover 140 and is attached to the bottom of the upper cover 140. A downwardly protruding protrusion 151 is formed at the center of the safety vent 150. The safety vent 150 is electrically connected to a sub-plate 175 fixed to the lower surface of the lower cover 170 by means of the protrusion 151 passing through a through hole 171 in the lower cover 170. Here, the protrusion 151 of the safety vent 150 and the sub-plate 175 can be welded by laser welding, ultrasonic welding, resistance welding, or equivalent methods.

[0036] Furthermore, a notch 152 is formed on the outer periphery of the protrusion 151 to guide the rupture of the safety vent 150. When abnormal internal pressure is generated inside the housing 120, the safety vent 150 discharges internal gas while interrupting the current. In the safety vent 150, when the internal pressure of the housing 120 exceeds the operating pressure of the safety vent 150, the protrusion 151 rises upward due to the gas discharged through the vent hole 172 of the lower cover 170 and is electrically separated from the sub-plate 175. Here, the sub-plate 175 is electrically separated from the safety vent 150 due to the tearing of the weld of the protrusion 151. Furthermore, in the safety vent 150, when the internal pressure of the housing 120 exceeds a rupture pressure higher than the operating pressure of the safety vent 150, the notch 152 ruptures to prevent the secondary battery 100 from exploding. The safety vent 150 may be made of aluminum (Al).

[0037] The safety vent 150 is mounted to make tight contact with the joint 142 at the bottom of the upper cover 140. Furthermore, the edge of the safety vent 150 surrounds the upper cover 140 and extends to the top of the upper cover 140. Here, the portion of the safety vent 150 extending upward from the upper cover 140 is defined as the vent extension 153. Furthermore, the upper part of the vent extension 153 is welded to secure the safety vent 150 to the upper cover 140. The safety vent 150 and a portion of the upper cover 140 can be melted by this welding to form a weld area 155. Here, the safety vent 150 and the upper cover 140 can be welded by laser welding, ultrasonic welding, resistance welding, or equivalent methods. The welding method between the safety vent 150 and the upper cover 140, and the weld area 155, will be described in more detail below.

[0038] An insulator 160 is positioned between the safety vent 150 and the lower cover 170 to insulate the safety vent 150 and the lower cover 170 from each other. Specifically, the insulator 160 is formed in an annular shape and positioned between the outer periphery of the safety vent 150 and the outer periphery of the lower cover 170. The insulator 160 may be made of a resin material such as polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET).

[0039] The lower cover 170 is formed as a circular plate. A through hole 171 is formed at the center of the lower cover 170, and a protrusion 151 of the safety vent 150 passes through the through hole 171. Furthermore, a vent 172 is formed on one side of the lower cover 170, and a sub-plate 175 is attached to the bottom of the lower cover 170. The vent 172 is used to release internal gas when excessive internal pressure is generated inside the housing 120. Here, the protrusion 151 of the safety vent 150 is raised due to the gas discharged through the vent 172, and the protrusion 151 can be separated from the sub-plate 175. The sub-plate 175 is welded between the protrusion 151 of the safety vent 150 passing through the through hole 171 of the lower cover 170 and the first electrode contact 114. Therefore, the sub-plate 175 can electrically connect the first electrode contact 114 and the safety vent 150 to each other.

[0040] Gasket 190 is installed in the top opening of housing 120. That is, gasket 190 is tightly assembled between the outer periphery of top cover 140 and safety vent 150 and the top opening of housing 120. Gasket 190 may be formed of a resin material such as polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET). Gasket 190 provides electrical insulation between housing 120 and cover assembly 130.

[0041] Figure 3 It is shown Figure 2 An enlarged sectional view of part A. Figure 4a and Figure 4bThis is a plan view showing the welding area in the cover assembly.

[0042] Reference Figure 3 The welding area 155 can be formed by melting a portion of the safety vent 150 and a portion of the top cover 140. The welding area 155 can be formed to be spaced apart from the end 125 of the housing 120, and the upper part of the welding area 155 can be covered by a gasket 190. In other words, the gasket 190 is positioned on the welding area 155 to prevent a short circuit between the safety vent 150 and the housing 120. The welding area 155 is located internally relative to the end 125 of the housing 120 (in the direction toward the center). In other words, the welding area 155 can be spaced apart from the end 125 of the housing 120 in the inward direction. Here, the end 125 of the housing 120 refers to the uppermost end of the side plate 121 of the housing 120. When the crimping portion 124 is formed to secure the cover assembly 130 to the housing 120, the end 125 can be bent and positioned above the vent extension 153. Figure 4a As shown, the welding area 155 can be formed in a concentric circle shape on the upper surface of the vent extension 153. In some examples, such as Figure 4b As shown, the welding area 155 can be formed as an arc shape spaced at predetermined intervals, rather than a circular shape that connects the entire upper surface of the vent extension 153. Furthermore, the sealing capability (or sealing pressure) of the secondary battery 100 (i.e., the sealing capability between the housing 120 and the cover assembly 130) can be varied.

[0043] In some examples, the closer the end 125 of the housing 120 and the welded area 155 are, the worse the sealing capability of the secondary battery 100. The reason for this is that, since the welded area 155 is formed by melting a portion of the safety vent 150 and a portion of the top cover 140 and protrudes upwards, there is a separation space between the welded area 155 and the gasket 190. Therefore, only when the end 125 of the housing 120 and the welded area 155 are separated by a certain distance can the sealing capability of the secondary battery 100 be prevented from deteriorating due to the separation space between the welded area 155 and the gasket 190.

[0044] Table 1 below shows the measurement results of the sealing pressure of the secondary battery 100 based on the separation distance D1 between the end 125 of the housing 120 and the welding area 155.

[0045] First, secondary batteries 100 with different separation distances D1 between the end 125 of the housing 120 and the welding area 155 are prepared. The secondary batteries 100 are discharged, and all secondary batteries 100 are identical except for the separation distance. Next, holes are drilled in the side of each secondary battery 100, a clamp for injecting nitrogen is inserted, and a gas (or water) testing agent is placed on the secondary battery 100. The gas (or water) testing agent is positioned to completely cover the upper part of the secondary battery 100. Then, while injecting nitrogen into the secondary battery 100 at a rate of 0.5 kgf / s, the sealing pressure is checked by measuring the pressure gauge at the moment the bubbles rise through the gas (or water) testing agent. For experimental accuracy, a total of 5 measurements are performed for each separation distance, and the average value is taken. Furthermore, the separation distance D1 is the distance between the end 125 of the housing 120 and the center point of the welding area 155.

[0046] Table 1

[0047] Furthermore, regarding sealing pressure, a secondary battery 100 that remains sealed until the burst pressure at the safety vent 150 is determined to be a good product. A secondary battery 100 with a sealing pressure of approximately 27 kgf to approximately 33 kgf, taking into account a tolerance of ±3 kgf based on the burst pressure, is determined to be a good product when the burst pressure is approximately 30 kgf. As shown in Table 1, when the distance D1 between the end 125 of the housing 120 and the welded area 155 is less than 0.2 mm, the sealing pressure is less than 27 kgf, indicating that the secondary battery 100 is not completely sealed. Specifically, when the welded area 155 is located outside the end 125 of the housing 120, the sealing pressure decreases to 23.6 kgf, indicating poor sealing capability. Furthermore, when the distance D1 between the end 125 of the housing 120 and the welded area 155 is 0.2 mm or greater, the measured sealing pressure is approximately 29.2 kgf to 30.2 kgf, indicating that the secondary battery 100 is completely sealed. Therefore, it can be seen that in order to ensure the sealing capability of the secondary battery 100, the distance D1 between the end 125 of the casing 120 and the welding area 155 should be 0.2 mm or greater.

[0048] In some examples, the welded area 155 may be formed at the end 154 of the vent extension 153. While the sealing capability is good when the welded area 155 is formed at the end 154 of the vent extension 153, an appearance defect occurs due to the step between the vent extension 153 and the top cover 140. Therefore, the welded area 155 is preferably spaced apart from the end 154 of the vent extension 153.

[0049] As described above, in the secondary battery 100 according to the present invention, by separating the end 125 of the casing 120 from the welding area 155 by 0.2 mm or more, the sealing capability of the secondary battery 100 can be ensured, and the safety of the secondary battery 100 can be improved.

[0050] While the foregoing embodiments for implementing the secondary battery according to the invention have been provided, it should be understood that the embodiments described herein should be considered in a descriptive sense only and not for limiting purposes, and various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims.

[0051] Industrial applicability This invention relates to a secondary battery that can ensure sealing capability.

Claims

1. A secondary battery, the secondary battery comprising: Electrode assembly; A housing in which the electrode assembly is housed; as well as A cover assembly, joined to the top of the housing, includes an upper cover, a safety vent, and a lower cover. The safety vent is disposed below the upper cover and has a vent extension extending to the top of the upper cover to cover its edge. The lower cover is disposed below the safety vent and is electrically connected to the electrode assembly. The exhaust port extension has an upwardly protruding welding area formed by welding the upper cover and the safety exhaust port together, and the welding area is spaced apart from the end of the housing. Wherein, the welding area is spaced apart from the end of the housing in the inward direction, and The distance between the welding area and the end of the housing is 0.2 mm or greater.

2. The secondary battery according to claim 1, wherein, The welding area is spaced apart from the end of the exhaust port extension in the outward direction.

3. The secondary battery according to claim 1, wherein, The gasket is located between the welded area and the end of the housing, wherein the sealing pressure of the secondary battery is 29.2 kgf to 30.2 kgf.

4. The secondary battery according to claim 1, wherein, The welding area is circular in shape, and is formed at the end of the exhaust port extension.

5. The secondary battery according to claim 1, wherein, The welding area is in the shape of at least one arc.

6. The secondary battery according to claim 1, wherein, The housing includes a side plate and a bottom plate that seals the lower part of the side plate, and the end of the housing is the uppermost part of the side plate.

7. The secondary battery according to claim 1, wherein, The end of the housing is bent to form a press-fit portion that secures the cover assembly.

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