Cylindrical secondary battery

Abstract

To solve the technical problem according to the disclosure, a cylindrical secondary battery capable of preventing deformation of an assembly during manufacturing or use thereof is provided. To this end, the disclosure provides a cylindrical secondary battery including a cylindrical can, an electrode assembly accommodated in the cylindrical can, and a cap assembly for sealing the electrode assembly by covering the cylindrical can, wherein the cap assembly includes an upper cap portion, a lower cap portion disposed below the upper cap portion, and a safety vent hole disposed between the upper cap portion and the lower cap portion, and an elongation rate of the lower cap portion and an elongation rate of the safety vent hole are different from each other.

Description

Technical Field

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

[0002] Typically, a cylindrical secondary battery includes a cylindrical electrode assembly, a cylindrical can containing the electrode assembly and electrolyte, and a cover assembly attached to the upper opening of the can to seal the can and allow current generated from the electrode assembly to flow to an external device.

[0003] The cover assembly may include a safety vent through which internal gases are released when the internal pressure of the can exceeds a critical value. Since the internal pressure of the can is typically proportional to temperature, there is a risk that the safety vent may open unexpectedly and relatively quickly when the secondary battery is placed in a high-temperature environment.

[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 contain information that does not constitute prior art. Summary of the Invention

[0005] Technical issues

[0006] This disclosure provides a cylindrical secondary battery capable of delaying the opening time of a safety vent in high-temperature environments.

[0007] Technical solution

[0008] The cylindrical secondary battery according to this disclosure may include: a cylindrical can; an electrode assembly housed in the cylindrical can; and a cover assembly for sealing the electrode assembly by covering the cylindrical can, wherein the cover assembly includes: an upper cover portion; a lower cover portion disposed below the upper cover portion; and a safety vent disposed between the upper cover portion and the lower cover portion, and the elongation of the lower cover portion and the elongation of the safety vent portion are different from each other.

[0009] The elongation rate of the lower cover can be higher than that of the safety vent.

[0010] The safety vent and lower cover may be made of aluminum or aluminum alloy.

[0011] The safety vent may include an aluminum-manganese (Al-Mn) based alloy, and the lower cover may include pure aluminum with a purity of more than 99%.

[0012] The safety vent may be made of 3003 series aluminum alloy or 3005 series aluminum alloy, and the lower cover may be made of 1050 series aluminum alloy.

[0013] The safety vent and the lower cover can be connected to each other by laser welding.

[0014] The safety vent may include: a vent contact portion that contacts the upper cover portion; a vent inclined portion that slopes downward from the vent contact portion; a vent bottom portion that extends horizontally from the vent inclined portion; and a vent protrusion portion that protrudes from the vent bottom portion and connects to the lower cover portion.

[0015] The lower cover may include: a lower cover contact portion that contacts a safety vent via a connecting ring; a lower cover inclined portion that slopes downward from the lower cover contact portion; a lower cover bottom portion that extends horizontally from the lower cover inclined portion; a through hole that penetrates the lower cover bottom portion; and a lower cover recessed portion that is recessed from the lower surface of the lower cover bottom portion and connected to the vent protrusion.

[0016] Beneficial effects

[0017] This disclosure provides a cylindrical secondary battery capable of delaying the opening time of a safety vent in high-temperature environments. In some examples, the opening time of the safety vent can be delayed in high-temperature environments because the safety vent and the lower cover, which are connected to each other, have different elongation rates. In some examples, the lower cover has a higher elongation rate than the safety vent; therefore, when the internal pressure of the can increases in a high-temperature environment, the lower cover and the safety vent can separate (or rupture) after the lower cover has sufficiently elongated, thereby delaying the opening time of the safety vent in high-temperature environments. Attached Figure Description

[0018] Figure 1a , Figure 1b and Figure 1c These are perspective views, sectional views, and exploded perspective views illustrating an exemplary cylindrical secondary battery according to this disclosure.

[0019] Figure 2 This is a cross-sectional view showing an exemplary cover assembly in an exemplary cylindrical secondary battery according to the present disclosure.

[0020] Figure 3a and Figure 3b This is a half-sectional view illustrating the operation of an exemplary cover assembly in an exemplary cylindrical secondary battery according to the present disclosure.

[0021] Figure 4 This is a half-sectional view showing the operation of the cover assembly in a cylindrical secondary battery according to a comparative example.

[0022] Figure 5 It is a graph showing the relationship between internal pressure and displacement of an exemplary safety vent according to this disclosure and a safety vent according to a comparative example. Detailed Implementation

[0023] Examples of this disclosure are provided to explain it more fully to those skilled in the art, and the examples below may be modified in various other forms. However, this disclosure may be implemented in many different forms and should not be construed as limited to the exemplary (or exemplary) embodiments set forth herein. Rather, these exemplary embodiments are provided so that the invention will be thorough and complete, and will convey to those skilled in the art aspects and features of this disclosure.

[0024] Additionally, for the sake of brevity and clarity, the dimensions or thicknesses of various components are exaggerated in the accompanying drawings, and 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.

[0025] 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.

[0026] It will be understood that although the terms first, second, etc., may be used herein to describe various components, elements, regions, layers, and / or parts, these components, elements, regions, layers, and / or parts should not be limited by these terms. These terms are used only to distinguish one component, element, region, layer, and / or part from another component, element, region, layer, and / or part. Thus, for example, without departing from the teachings of this disclosure, the first component, first element, first region, first layer, and / or first part discussed below may be referred to as a second component, second element, second region, second layer, and / or second part.

[0027] For ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” and “upper” may be used herein to describe the relationship between one element or feature as 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 figure is flipped, an element described as “below” or “under” other elements or features would then be positioned “above” or “on” said other elements or features. Thus, the exemplary term “below” can encompass both above and below orientations.

[0028] Figure 1a , Figure 1b and Figure 1c These are perspective views, cross-sectional views, and exploded perspective views of a secondary battery 100 according to various embodiments of the present disclosure.

[0029] like Figure 1a , Figure 1b and Figure 1c As shown, the secondary battery 100 according to this disclosure may include a cylindrical can 110, a cylindrical electrode assembly 120, and a cap assembly 140. In some examples, the secondary battery 100 may also include a central pin 130 coupled to the electrode assembly 120.

[0030] The cylindrical can 110 may include a circular bottom 111 and a cylindrical side 112 extending upward from the bottom 111 for a predetermined length. During the manufacturing process of the secondary battery, the top of the cylindrical can 110 is open. Therefore, during the assembly process of the secondary battery, the electrode assembly 120 can be inserted into the cylindrical can 110 along with the electrolyte. In some examples, the cylindrical can 110 may include steel, steel alloy, aluminum, aluminum alloy, or equivalents thereof. In some examples, to prevent the electrode assembly 120 and the cover assembly 140 from detaching from the outside, the cylindrical can 110 may include a rolled edge portion 113 recessed into the lower portion relative to the cover assembly 140 and a crimped portion 114 bent into the upper portion relative to the cover assembly 140.

[0031] Electrode assembly 120 may be housed inside cylindrical container 110. Electrode assembly 120 may include a negative electrode plate 121 coated with a negative electrode active material (e.g., graphite, carbon, etc.) and a positive electrode plate 122 coated with a positive electrode active material (e.g., transition metal oxides (LiCoO2, LiNiO2, LiMn2O4, etc.)), and a separator 123 located between the negative electrode plate 121 and the positive electrode plate 122 to prevent short circuits and allow only lithium ion movement. In some examples, the negative electrode plate 121, the positive electrode plate 122, and the separator 123 may be wound in a generally cylindrical shape. In some examples, the negative electrode plate 121 may include copper (Cu) foil or nickel (Ni) foil, the positive electrode plate 122 may include aluminum (Al) foil, and the separator 123 may include polyethylene (PE) or polypropylene (PP). In some examples, the negative electrode tab 124, which protrudes downward and extends a certain length, can be soldered to the negative electrode plate 121, and the positive electrode tab 125, which protrudes upward and extends a certain length, can be soldered to the positive electrode plate 122, but the reverse is also possible. In some examples, the negative electrode tab 124 may comprise copper or nickel, and the positive electrode tab 125 may comprise aluminum.

[0032] In some examples, the negative electrode terminal 124 of the electrode assembly 120 can be soldered to the bottom 111 of the cylindrical can 110. Therefore, the cylindrical can 110 can function as a negative electrode. Conversely, the positive electrode terminal 125 can be soldered to the bottom 111 of the cylindrical can 110, in which case the cylindrical can 110 can function as a positive electrode.

[0033] In some examples, a first insulating plate 126, incorporated into the cylindrical can 110 and having a first hole 126a at its center and a second hole 126b on its outer side, can be inserted between the electrode assembly 120 and the bottom 111. The first insulating plate 126 prevents the electrode assembly 120 from making electrical contact with the bottom 111 of the cylindrical can 110. In some examples, the first insulating plate 126 prevents the positive electrode plate 122 of the electrode assembly 120 from making electrical contact with the bottom 111. In some examples, when a large amount of gas is generated due to an anomaly in the secondary battery, the first hole 126a allows the gas to move rapidly upward through the center pin 130, and the second hole 126b allows the negative electrode tab 124 to pass through and be soldered to the bottom 111.

[0034] In some examples, a second insulating plate 127, incorporated into the cylindrical container 110 and having a first hole 127a at its center and a plurality of second holes 127b on its outer side, can be inserted between the electrode assembly 120 and the cover assembly 140. The second insulating plate 127 prevents the electrode assembly 120 from electrically contacting the cover assembly 140. In some examples, the second insulating plate 127 prevents the negative electrode plate 121 of the electrode assembly 120 from electrically contacting the cover assembly 140. In some examples, when a large amount of gas is generated due to an anomaly in the secondary battery, the first hole 127a allows the gas to move rapidly into the cover assembly 140, and the second holes 127b allow the positive electrode terminal piece 125 to pass through and be soldered to the cover assembly 140. Additionally, the remaining second holes 127b allow electrolyte to flow rapidly into the electrode assembly 120 during an electrolyte injection process.

[0035] In some examples, the first hole 126a of the first insulating plate 126 and the first hole 127a of the second insulating plate 127 are formed to be smaller than the diameter of the center pin 130, thereby preventing the center pin 130 from making electrical contact with the bottom 111 of the cylindrical can 110 or the cover assembly 140 due to external impact.

[0036] In some examples, the center pin 130 has the shape of a hollow cylindrical tube and can be coupled to approximately the center of the electrode assembly 120. In some examples, the center pin 130 may comprise steel, a steel alloy, aluminum, an aluminum alloy, or polybutylene terephthalate. The center pin 130 serves to suppress deformation of the electrode assembly 120 during battery charging and discharging and acts as a channel for gases generated inside the secondary battery. In some cases, the center pin 130 may be omitted.

[0037] The cover assembly 140 may include an upper cover portion 141 having a plurality of through holes 141a, a safety vent 142 positioned below the upper cover portion 141, a connecting ring 143 positioned below the safety vent 142, and a lower cover portion 144 positioned below the safety vent 142 and the connecting ring 143, having a plurality of through holes 144a and electrically connected to the positive electrode terminal piece 125. In some examples, the cover assembly 140 may also include an insulating gasket 145 that insulates the upper cover portion 141, the safety vent 142, and the lower cover portion 144 from the sides of the cylindrical can 110.

[0038] In some examples, the insulating gasket 145 may be substantially pressed between the crimped portion 113 and the crimped portion 114 formed on the side 112 of the cylindrical can 110. In some examples, when abnormal pressure is generated inside the cylindrical can 110, the through-hole 141a of the upper cover 141 and the through-hole 144a of the lower cover 144 can release internal gas to the outside. In some examples, internal gas can cause the safety vent 142 to flip upward through the through-hole 144a of the lower cover 144, and thus electrically disconnect the safety vent 142 from the lower cover 144. Then, as the safety vent 142 is torn (opened), internal gas can be released to the outside through the through-hole 141a of the upper cover 141.

[0039] In some examples, an electrolyte (not shown) may be injected into a cylindrical container 110, allowing lithium ions generated during charging and discharging by electrochemical reactions in the negative electrode plate 121 and positive electrode plate 122 inside the battery. The electrolyte may include a non-aqueous organic electrolyte as a mixture of lithium salt and a high-purity organic solvent. In some examples, the electrolyte may include a polymeric electrolyte or a solid electrolyte using a polymer.

[0040] Figure 2 This is a cross-sectional view showing an exemplary cover assembly 140 in an exemplary cylindrical secondary battery 100 according to the present disclosure.

[0041] like Figure 2 As shown, the cover assembly 140 may include an upper cover portion 141, a safety vent 142 disposed below the upper cover portion 141, a connecting ring 143 disposed below the safety vent 142, and a lower cover portion 144 disposed below the connecting ring 143.

[0042] In some examples, the cover portion 141 may include a cover contact portion 141b that contacts the safety vent 142, a cover inclined portion 141c that slopes upward from the cover contact portion 141b and has a plurality of through holes 141a, and a cover top plate portion 141d that extends horizontally from the cover inclined portion 141c. In some examples, an external device may be electrically connected to the cover top plate portion 141d.

[0043] In some examples, the safety vent 142 may include a vent contact portion 142a that contacts the upper cover contact portion 141b of the upper cover portion 141, a vent inclined portion 142b that slopes downward from the vent contact portion 142a, a vent bottom portion 142c that extends horizontally from the vent inclined portion 142b, and a vent protrusion portion 142d that protrudes from the vent bottom portion 142c and contacts (connects to or links to) the lower cover portion 144.

[0044] In some examples, the diameter (length or width) of the vent protrusion 142d can be approximately 60% to approximately 100% of the diameter (length or width) of the vent bottom portion 142c. In some examples, the vent protrusion 142d can be laser- or ultrasonically welded to the lower cover portion 144, so that the vent protrusion 142d and the lower cover portion 144 can contact (connect or link) each other.

[0045] In some examples, the vent contact portion 142a can be bent multiple times to contact the bottom surface, side surface, and top surface of the cover contact portion 141b, respectively. In some examples, the vent bottom portion 142c may also include a substantially flat vent recess 142e formed on the upper surface opposite the vent protrusion 142d. In some examples, the flat vent recess 142e can be formed by pressing using a mold for forming the vent protrusion 142d on the vent bottom portion 142c. In some examples, the vent bottom portion 142c of the safety vent 142 may also include a substantially linear vent groove 142f formed on the upper surface opposite the vent protrusion 142d. In some examples, when the internal pressure of the battery exceeds a preset pressure, the linear vent groove 142f ruptures (opens), thus releasing internal gas to the outside.

[0046] In some examples, the lower cover 144 may include a lower cover contact portion 144b that contacts the connecting ring 143, a lower cover inclined portion 144c that slopes downward from the lower cover contact portion 144b, and a lower cover bottom portion 144d that extends horizontally from the lower cover inclined portion 144c. In some examples, the connecting ring 143 may be inserted between the vent contact portion 142a and the lower cover contact portion 144b. In some examples, the upper cover 141, the safety vent 142, and the lower cover 144 are made of metallic materials (e.g., aluminum, copper, or nickel), while the connecting ring 143 is made of insulating materials (e.g., polypropylene or polyethylene). Here, the metallic materials forming the safety vent 142 and the lower cover 144 and their elongation will be described again below.

[0047] In some examples, the bottom portion 144d of the lower cover may also include a through hole 144a penetrating the bottom portion 144d. In some examples, the separation space S may be provided between the bottom portion 142c of the vent and the bottom portion 144d of the lower cover. In some examples, the vertical separation distance between the bottom portion 142c of the vent and the bottom portion 144d of the lower cover may be from about 0.20 mm to about 30 mm. As the separation distance increases, it can be ensured that the lower cover portion 144 has a wider extension space in the upward direction. In some examples, the lower cover portion 144 may also include a flat lower cover recess 144e recessed from the lower surface of the bottom portion 144d of the lower cover. In some examples, the negative electrode terminal piece 125 (see...) Figure 1b It can be welded to the bottom portion 144d of the lower cover outside the flat lower cover recess 144e.

[0048] In some examples, the elongation (%) of the lower cover 144 and the elongation (%) of the safety vent 142 may be different from each other.

[0049] In some examples, the elongation (%) of the lower cover 144 may be higher than the elongation (%) of the safety vent 142.

[0050] In some examples, the safety vent 142 and the lower cover 144 may comprise aluminum or an aluminum alloy, but the elongation (%) of the lower cover 144 may be greater than the elongation (%) of the safety vent 142.

[0051] In some examples, the lower cover 144 may comprise 1000 series aluminum, and the safety vent 142 may be an aluminum alloy from any of the 2000, 3000, 4000, 5000, 6000, and 7000 series.

[0052] In some examples, the lower cover 144 may include pure aluminum with a purity greater than 99%, and the safety vent 142 may include any one of Al-Cu-based alloys, Al-Mn-based alloys, Al-Si-based alloys, Al-Mg-based alloys, Al-Mg-Si-based alloys, and Al-Zn-(Mg,Cu)-based alloys.

[0053] In some examples, the lower cover 144 may include 1050 series aluminum alloy, and the safety vent 142 may include 3003 series aluminum alloy or 3005 series aluminum alloy.

[0054] Figure 3a and Figure 3b This is a half-sectional view illustrating the operation of an exemplary cover assembly in an exemplary cylindrical secondary battery according to the present disclosure. Figure 4 This is a half-sectional view showing the operation of the cover assembly in a cylindrical secondary battery according to a comparative example.

[0055] here, Figure 4 The diagram illustrates the operation of the safety vent 142 according to an increase in internal pressure when the materials of the safety vent 142 and the lower cover 144 are the same (e.g., when the materials of the safety vent 142 and the lower cover 144 are both aluminum alloys of 3000 series rigid materials).

[0056] like Figure 3a and Figure 3bAs shown, when the elongation rate of the lower cover 144 is greater than that of the safety vent 142 (i.e., when the material of the lower cover is a flexible material), as the internal pressure of the can 110 increases, the safety vent 142 can separate from the lower cover 144 after the lower cover 144 extends upward by a predetermined length. Subsequently, when the internal pressure of the can 110 increases further, the safety vent 142 eventually ruptures and opens, thus releasing the gas inside the can 110 to the outside. Specifically, when the internal pressure of the can 110 reaches a critical value in a high-temperature environment, such as approximately 80°C to approximately 100°C, the safety vent 142 does not immediately operate. However, as described above, after the lower cover 144 extends upward, the safety vent 142 can separate from the lower cover 144, and then the safety vent 142 can open, thereby delaying the operation of the safety vent 142 when the secondary battery 100 is in a high-temperature environment.

[0057] However, as in Figure 4 In the comparative example shown, for example, when both the safety vent 142 and the lower cover 144 are made of aluminum alloy as a rigid 3000 series material, the safety vent 142 immediately separates from the lower cover 144 without causing the lower cover 144 to extend, and the safety vent 142 opens immediately, so the safety vent 142 opens too quickly.

[0058] Figure 5 This is a graph showing the relationship between internal pressure and displacement of an exemplary safety vent according to this disclosure and a safety vent according to a comparative example. Figure 5 In the middle, the X-axis indicates the internal pressure (kgf / cm). 2 ), and the Y-axis indicates the displacement of the safety vent.

[0059] like Figure 5 As shown, in a high-temperature environment, when both the lower cover and the safety vent are made of rigid materials, as in the comparative example, the safety vent opens under an internal pressure of approximately 14. Conversely, when the lower cover is made of a flexible material and the safety vent is made of a rigid material, as in the example embodiment, the safety vent opens under an internal pressure of approximately 17. Therefore, in a high-temperature environment, when the material of the lower cover is softer than the material of the safety vent, the opening time of the safety vent can be delayed, thereby improving the high-temperature characteristics of the secondary battery.

[0060] Although the foregoing embodiments have been described to practice this disclosure, these embodiments are set forth for illustrative purposes and are not intended to limit the disclosure. It will be readily understood by those skilled in the art that many modifications and variations may be made without departing from the spirit and scope of the disclosure as defined in the appended claims, and that such modifications and variations are covered within the scope and spirit of this disclosure.

Claims

1. A cylindrical secondary battery, the cylindrical secondary battery comprising: Cylindrical can; The electrode assembly is housed in the cylindrical container; as well as A cover assembly for sealing the electrode assembly by covering the cylindrical canister. The cover assembly includes: an upper cover portion; a lower cover portion disposed below the upper cover portion; and a safety vent disposed between the upper cover portion and the lower cover portion, wherein the elongation rate of the lower cover portion is greater than the elongation rate of the safety vent. The safety vent includes: a vent contact portion that contacts the upper cover; a vent inclined portion that slopes downward from the vent contact portion; a vent bottom portion that extends horizontally from the vent inclined portion; and a vent protruding portion that protrudes from the vent bottom portion and connects to the lower cover. The lower cover includes: a lower cover contact portion that contacts the safety vent via a connecting ring; a lower cover inclined portion that slopes downward from the lower cover contact portion; a lower cover bottom portion that extends horizontally from the lower cover inclined portion; a through hole that penetrates the lower cover bottom portion; and a lower cover recessed portion that is recessed from the lower surface of the lower cover bottom portion and connected to the vent protrusion portion.

2. The cylindrical secondary battery according to claim 1, wherein, The safety vent and the lower cover are made of aluminum or aluminum alloy.

3. The cylindrical secondary battery according to claim 1, wherein, The safety vent is made of an aluminum-manganese based alloy, and the lower cover is made of pure aluminum with a purity of more than 99%.

4. The cylindrical secondary battery according to claim 1, wherein, The safety vent is made of 3003 series aluminum alloy or 3005 series aluminum alloy, and the lower cover is made of 1050 series aluminum alloy.

5. The cylindrical secondary battery according to claim 1, wherein, The safety vent and the lower cover are connected to each other by laser welding.

6. The cylindrical secondary battery according to claim 1, wherein, The diameter of the protruding portion of the exhaust port is 60% to 100% of the diameter of the bottom portion of the exhaust port.

7. The cylindrical secondary battery according to claim 1, wherein, The recessed portion of the lower cover is flat, and one of the positive electrode terminal and the negative electrode terminal is welded to the bottom portion of the lower cover.

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