Secondary battery

Abstract

The disclosure provides a secondary battery capable of improving safety by discharging internal gas while preventing deformation of a cover plate including a vent unit when pressure inside a case increases. In an example, a secondary battery is disclosed, including a cylindrical case, an electrode assembly accommodated in the cylindrical case, and a cover plate electrically connected to the electrode assembly and sealing the cylindrical case, wherein the cover plate includes a first flat portion located at a center, a second flat portion located outside the first flat portion, and a vent portion located between the first flat portion and the second flat portion and having a thickness smaller than thicknesses of the first flat portion and the second flat portion.

Description

[0001] This application claims priority to and the benefit of Korean Patent Application No. 10-2022-0002679, filed on January 7, 2022, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to a secondary battery. BACKGROUND

[0003] Lithium ion secondary batteries are used as power sources for portable electronic devices, as well as hybrid or electric vehicles, due to advantages such as their high operating voltage and high energy density per unit weight.

[0004] These secondary batteries can be classified into cylindrical, prismatic, or pouch shapes. For example, a cylindrical secondary battery generally includes a cylindrical case, a cylindrical electrode assembly coupled to the case, an electrolyte (optional) injected into the case to enable movement of lithium ions, and a cap assembly coupled to one side of the case to prevent leakage of the electrolyte and separation of the electrode assembly.

[0005] The above information disclosed in this Background section is only for enhancing the understanding of the background of the application, and therefore it can contain information that does not constitute prior art. SUMMARY

[0006] The present disclosure provides a secondary battery that can improve safety by discharging internal gas while preventing deformation of a cover plate including a vent unit when pressure inside a case increases.

[0007] A secondary battery according to the present disclosure can include a cylindrical case, an electrode assembly accommodated in the cylindrical case, and a cover plate electrically connected to the electrode assembly and sealing the cylindrical case, wherein the cover plate can include a first flat portion located at a center, a second flat portion located outside the first flat portion, and a vent portion located between the first flat portion and the second flat portion and having a thickness smaller than thicknesses of the first flat portion and the second flat portion.

[0008] The first flat portion can have a thickness of 0.7 mm to 0.9 mm.

[0009] In this way, the present disclosure can provide a secondary battery that can secure a welding margin by limiting a thickness of a first flat portion located at a center of a cover plate.

[0010] A height of an upper surface of the second flat portion can be greater than a height of an upper surface of the first flat portion.

[0011] The height difference between the first flat portion and the second flat portion can be 0.1 mm to 0.4 mm.

[0012] In this way, the present disclosure can provide a secondary battery capable of improving the operating pressure distribution of the cover plate by generating a height difference between the first flat portion and the second flat portion of the cover plate when the pressure inside the case increases.

[0013] The electrode tab of the electrode assembly can be electrically connected to the lower surface of the first flat portion.

[0014] The upper surface of the first flat portion can be exposed to the outside.

[0015] The vent portion can include a notch formed on the lower surface thereof.

[0016] The vent portion can be formed to be inclined.

[0017] An insulating gasket disposed between the second flat portion and the cylindrical case can be further included. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a perspective view showing a secondary battery according to an embodiment of the present disclosure.

[0019] Figure 2 FIG. 2 is a cross-sectional view of the secondary battery according to an embodiment of the present disclosure.

[0020] Figure 3 FIG. 3 is an enlarged cross-sectional view of a cover plate in the secondary battery according to an embodiment of the present disclosure.

[0021] Figure 4A and Figure 4B FIG. 5 is a schematic view showing a method for manufacturing the cover plate in the secondary battery according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0023] The examples of the present disclosure are provided to more completely explain the present disclosure to those skilled in the art and can modify the following embodiments in various other forms. However, the present disclosure can be implemented in many different forms and should not be interpreted as being limited to the examples (or exemplary) embodiments set forth herein. Rather, these example embodiments are provided so that the present disclosure will be thorough and complete, and will convey the aspects and features of the present disclosure to those skilled in the art.

[0024] Also, in the drawings, the size or thickness of various components can be exaggerated for clarity and convenience. The same reference numbers can be used to denote the same elements throughout the specification. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In addition, it will be understood that when an element A is referred to as being "connected to" element B, element A can be directly connected to element B or an intervening element C can be present between element A and element B such that element A and element B are indirectly connected to each other.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0026] It will be understood that, although the terms first, second, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer and / or section from another element, component, region, layer and / or section. Thus, a first element, component, region, layer and / or section discussed below could be termed a second element, component, region, layer and / or section without departing from the teachings of the present disclosure.

[0027] For ease of description, spatially relative terms, such as "beneath", "below", "lower", "above", "upper" and the like, can be used herein for describing an element's or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if an element or feature is depicted as being "below" or "beneath" another element or feature, it can be positioned "above" or "over" such other element or feature as viewed in a different orientation. Thus, the exemplary term "below" can encompass both an orientation of above and below. The terms "first", "second", "third", etc. can be used herein to describe various elements, components, regions, layers and / or sections but do not need to have a specific relationship to each other.

[0028] Figure 1 FIG. 1 is a perspective view showing a secondary battery according to an embodiment of the present disclosure. Figure 2 FIG. 2 is a cross-sectional view of the secondary battery according to the embodiment of the present disclosure. Figure 3 FIG. 3 is an enlarged cross-sectional view of a cover plate in the secondary battery according to the embodiment of the present disclosure. FIG. 4 is a perspective view showing a secondary battery according to another embodiment of the present disclosure.

[0029] Reference Figures 1 to 3 A secondary battery 100 according to an embodiment of the disclosure can include a cylindrical case 110, an electrode assembly 120, and a cover plate 130.

[0030] The cylindrical case 110 can include a substantially circular bottom 111 and a sidewall 112 extending upward from the bottom 111 by a predetermined length. In some examples, the cylindrical case 110 can include or be referred to as a can, a case, or a housing.

[0031] During a manufacturing process of the secondary battery, a top of the cylindrical case 110 can be opened. Accordingly, during an assembly process of the secondary battery, the electrode assembly 120 can be integrated as a single structure and inserted into the cylindrical case 110. Of course, an electrolyte can be later additionally injected into the cylindrical case 110.

[0032] The cylindrical case 110 can be made of steel, a steel alloy, nickel-plated steel, nickel-plated steel alloy, aluminum, or an aluminum alloy.

[0033] In addition, to prevent the cover plate 130 from being detached to the outside, the cylindrical case 110 can be provided with a crimped portion 113 inwardly recessed at a lower portion of the cover plate 130 and a crimped portion 114 inwardly bent at an upper portion of the cover plate 130.

[0034] The electrode assembly 120 can be accommodated inside the cylindrical case 110. The electrode assembly 120 can include or be referred to as an electrode, an electrode group, or a jelly roll. The electrode assembly 120 can include a negative electrode plate 121 coated with a negative electrode active material (e.g., graphite, carbon, etc.), a positive electrode plate 122 coated with a positive electrode active material (e.g., a transition metal oxide (LiCoO2, LiNiO2, LiMn2O4, etc.)), and a separator 123 located between the negative electrode plate 121 and the positive electrode plate 122 to prevent a short circuit and to allow only lithium ions to move. The negative electrode plate 121, the positive electrode plate 122, and the separator 123 can be wound in a substantially cylindrical shape. In some examples, the negative electrode plate 121 can be a copper (Cu) foil, the positive electrode plate 122 can be an aluminum (Al) foil, and the separator 123 can be polyethylene (PE) or polypropylene (PP).

[0035] In addition, a negative electrode tab 124 protruding downward and extending by a predetermined length can be welded to the negative electrode plate 121, and a positive electrode tab 125 protruding upward and extending by a predetermined length can be welded to the positive electrode plate 122. In addition, the negative electrode tab 124 can be copper (Cu) or nickel (Ni), and the positive electrode tab 125 can be aluminum (Al).

[0036] In addition, the negative electrode tab 124 of the electrode assembly 120 can be welded to the bottom 111 of the cylindrical case 110. Accordingly, the cylindrical case 110 can serve as a negative electrode. In some examples, the negative electrode tab 124 can be ultrasonically or laser welded to the bottom 111 of the cylindrical case 110. Of course, conversely, the positive electrode tab 125 can be welded to the bottom 111 of the cylindrical case 110, in which case the cylindrical case 110 can serve as a positive electrode.

[0037] In addition, a first insulating plate 126 coupled to the cylindrical case 110 and having a first hole 126a in the center and a second hole 126b outside the center can be interposed between the electrode assembly 120 and the bottom 111. In some examples, the first insulating plate 126 prevents the electrode assembly 120 from electrically contacting the bottom 111 of the cylindrical case 110. In some examples, the first insulating plate 126 prevents the positive electrode plate 122 of the electrode assembly 120 from electrically contacting the bottom 111. In some examples, when a large amount of gas is generated due to an abnormality of the secondary battery, the first hole 126a allows the gas to quickly move upward through the center pin 140, and the second hole 126b allows the negative electrode tab 124 to pass through and be welded to the bottom 111.

[0038] In addition, a second insulating plate 127 coupled to the cylindrical case 110 and having a first hole 127a in the center and a plurality of second holes 127b outside the center can be interposed between the electrode assembly 120 and the cover plate 130. In some examples, the second insulating plate 127 prevents the electrode assembly 120 from electrically contacting the cover plate 130. In some examples, the second insulating plate 127 prevents the negative electrode plate 121 of the electrode assembly 120 from electrically contacting the cover plate 130. In some examples, when a large amount of gas is generated due to an abnormality of the secondary battery, the first hole 127a allows the gas to quickly move to the cover plate 130, and the second holes 127b allow the positive electrode tab 125 to pass through and be welded to the cover plate 130. In addition, the remaining second holes 127b serve to allow the electrolyte to quickly flow into the cylindrical case 110 in an electrolyte injection process.

[0039] In addition, the first hole 126a of the first insulating plate 126 and the first hole 127a of the second insulating plate 127 have a diameter smaller than that of the center pin 140, thereby preventing the center pin 140 from electrically contacting the bottom 111 of the cylindrical case 110 or the cover plate 130 due to an external impact.

[0040] The center pin 140 has a shape of a hollow circular tube and can be combined to a general center of the electrode assembly 120. The center pin 140 can be made of steel, stainless steel, aluminum, aluminum alloy, or polybutylene terephthalate, but the material is not limited to those listed here. The center pin 140 serves to suppress deformation of the electrode assembly 120 during charging and discharging of the secondary battery, and serves as a passage for gas generated inside the secondary battery.

[0041] The cover plate 130 seals the opening of the cylindrical case 110 to protect the electrode assembly 120 from the external environment, and when the internal pressure of the cylindrical case 110 is higher than the reference pressure (or the operating pressure of the cover plate), the cover plate 130 can be broken and the internal gas of the cylindrical case 110 can be discharged to the outside. In some examples, the cover plate 130 can also serve as a positive electrode terminal. In some examples, the cover plate 130 can be made of aluminum or an aluminum alloy.

[0042] Referring to Figure 3 The cover plate 130 can include a first flat portion 131 that is substantially flat and located at the center, a second flat portion 132 that is located outside the first flat portion 131 and is substantially flat, and a vent portion 133 located between the first flat portion 131 and the second flat portion 132.

[0043] In some examples, the cover plate 130 can include or be referred to as a cap, a conductor plate, a curved plate, a cover, or a lid.

[0044] In some examples, the thickness of the first flat portion 131 and the second flat portion 132 can be substantially similar or the same as each other.

[0045] The first flat portion 131 is located at the center of the cover plate 130, and the positive electrode tab 125 of the electrode assembly 120 can be welded to the lower portion of the first flat portion 131. In some examples, the lower surface of the first flat portion 131 can be ultrasonically or laser welded to the positive electrode tab 125. In addition, the upper surface of the first flat portion 131 is exposed to the outside and can be electrically connected to an external device to serve as a terminal.

[0046] The first flat portion 131 can have a thickness of 0.7 to 0.9 mm. If the thickness of the first flat portion 131 is less than 0.7 mm, pinholes can occur during welding of the cover plate 130 and the positive electrode tab 125, thereby reducing the bonding force between the two. In addition, if the thickness of the first flat portion 131 is greater than 0.9 mm, deformation distribution can occur during welding of the cover plate 130 and the positive electrode tab 125, thereby reducing the quality of the secondary battery 100.

[0047] As such, the secondary battery 100 according to the disclosure can secure a welding margin by limiting the thickness of the first flat portion 131.

[0048] The second flat portion 132 is located outside the first flat portion 131 and can be fixed to the cylindrical case 110 through the insulating gasket 150. The height of the second flat portion 132 can be higher than the height of the first flat portion 131. The upper surface of the second flat portion 132 can be higher than the upper surface of the first flat portion 131. In other words, the upper surface of the second flat portion 132 and the upper surface of the first flat portion 131 are not located on the same plane. Accordingly, a height difference H is generated between the upper surface of the second flat portion 132 and the upper surface of the first flat portion 131.

[0049] As such, when the second flat portion 132 is formed to have a height greater than the height of the first flat portion 131, the distribution of the operating pressure of the cover plate 130 can be enhanced and / or improved.

[0050] The height difference H between the upper surface of the second flat portion 132 and the upper surface of the first flat portion 131 can be 0.1 mm to 0.4 mm. If the height difference H between the upper surface of the second flat portion 132 and the upper surface of the first flat portion 131 is less than 0.1 mm or greater than 0.4 mm, deformation and fracture distribution of components can occur during the operation of the cover plate 130.

[0051] In some examples, the height difference H between the upper surface of the second flat portion 132 and the upper surface of the first flat portion 131 can be 0.15 mm to 0.35 mm. If the height difference H between the upper surface of the second flat portion 132 and the upper surface of the first flat portion 131 is 0.15 mm to 0.35 mm, deformation and fracture distribution and deformation distribution can be prevented from occurring during the operation of the cover plate 130.

[0052] The vent portion 133 can be located between the first flat portion 131 and the second flat portion 132. The vent portion 133 can be provided to have a thickness smaller than the thickness of the first flat portion 131 and the second flat portion 132. In some examples, the vent portion 133 can have a relatively small thickness than the thickness of the first flat portion 131 and the second flat portion 132 by partially removing the lower surface of the cover plate 130. In some examples, the vent portion 133 can be shaped as a ring spaced apart from the center of the cover plate 130 by a certain distance.

[0053] In addition, the vent portion 133 can be disposed to be inclined by the height difference H between the first flat portion 131 and the second flat portion 132. The vent portion 133 can further include a notch 134 formed at a predetermined depth on the lower surface. In some examples, the notch 134 can be formed in a continuous form along the lower surface of the vent portion 133.

[0054] In this way, when the internal pressure of the secondary battery 100 is greater than the operating pressure of the cover plate 130, the notch 134 of the vent portion 133 is broken, such that the gas inside the cylindrical case 110 is released to the outside, thereby improving the safety of the secondary battery 100.

[0055] In addition, the secondary battery 100 according to the disclosure is provided with only the cover plate 130 as an assembly that seals the upper portion of the cylindrical case 110, and eliminates the existing assembly having a current blocking function, thereby reducing the internal resistance and lightening the weight of the secondary battery 100.

[0056] The insulating gasket 150 can be interposed between the cover plate 130 and the cylindrical case 110. The insulating gasket 150 can insulate the cover plate 130 and the cylindrical case 110 from each other. In some examples, the insulating gasket 150 can cover the outer periphery of the second flat portion 132 of the cover plate 130. The outer surface of the insulating gasket 150 can be in close contact with the crimped portion 113 and the press-contact portion 114, and the inner surface of the insulating gasket 150 can be in close contact with the second flat portion 132. In some examples, the insulating gasket 150 can include or be referred to as a sealing gasket, an insulating member, or a resin.

[0057] The insulating gasket 150 can be made of a resin material such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), or the like, but the material is not limited thereto.

[0058] Figure 4A and Figure 4B is a schematic view illustrating a method for manufacturing a cover plate in a secondary battery according to an embodiment of the disclosure. As shown in Figure 4A and Figure 4B As shown in FIGS. 1A and 1B, for example, the cover plate 130 in which the first flat portion 131 and the second flat portion 132 are located on the same plane is provided, and a pressure is applied to the first flat portion 131, thereby manufacturing the cover plate 130 in which the upper surface of the second flat portion 132 is higher than the upper surface of the first flat portion 131. In some examples, by increasing the thickness of the portion of the second flat portion 132 adjacent to the vent portion 133, the thickness by which the second flat portion 132 extends downward together with the vent portion 133 when the first flat portion 131 is pressed can be compensated for.

[0059] As described above, the present disclosure provides a secondary battery capable of improving safety by discharging internal gas while preventing deformation of a cover plate including a vent portion when pressure inside a case increases.

[0060] Although the foregoing embodiment is merely one embodiment for implementing a secondary battery according to the present disclosure, it is not limited to this embodiment, and those skilled in the art will understand that various changes in form and details can be made without departing from the spirit and scope of the present disclosure defined by the claims.

Claims

1. A secondary battery, the secondary battery comprising: Cylindrical shell; The electrode assembly is housed within the cylindrical housing; as well as A cover plate, electrically connected to the electrode assembly and sealing the cylindrical housing. The cover plate includes a first flat portion located at the center, a second flat portion located outside the first flat portion, and a ventilated portion located between the first flat portion and the second flat portion and having a thickness smaller than that of the first flat portion and the second flat portion. Wherein, the height of the upper surface of the second flat portion is greater than the height of the upper surface of the first flat portion. The upper parts of the first flat portion and the upper parts of the second flat portion are connected to each other via the ventilated portion. The height difference between the first flat portion and the second flat portion is 0.1 mm to 0.4 mm. The ventilation section includes a notch formed on its lower surface.

2. The secondary battery according to claim 1, wherein, The first flat portion has a thickness of 0.7 mm to 0.9 mm.

3. The secondary battery according to claim 1, wherein, The thickness of the first flat portion and the thickness of the second flat portion are the same.

4. The secondary battery according to claim 1, wherein, The electrode terminals of the electrode assembly are electrically connected to the lower surface of the first flat portion.

5. The secondary battery according to claim 1, wherein, The upper surface of the first flat portion is exposed to the outside.

6. The secondary battery according to claim 1, wherein, The ventilation section is angled.

7. The secondary battery according to claim 1, wherein the secondary battery further comprises an insulating gasket disposed between the second flat portion and the cylindrical housing.

8. The secondary battery according to claim 1, wherein, The notch is spaced apart from the first flat portion and the second flat portion by a portion of the venting portion.

9. The secondary battery according to claim 1, wherein, The thickness of the venting section is greater than the depth of the notch.

Images