Secondary battery

Abstract

Embodiments of the present disclosure relate to secondary batteries, and can provide secondary batteries capable of protecting an electrode assembly and improving battery capacity relative to the same volume. Embodiments of the present disclosure include a secondary battery, the secondary battery comprising: an electrode assembly including a first electrode plate having a first substrate terminal tab, a second electrode plate having a second substrate terminal tab, and a separator inserted between the first electrode plate and the second electrode plate; a first lead welded to the first substrate terminal tab; a second lead welded to the second substrate terminal tab; a heat shrink tube around a thickness portion of the electrode assembly; and a housing accommodating the electrode assembly.

Description

Technical Field

[0001] Aspects of embodiments of the present disclosure relate to secondary batteries. Background Art

[0002] Unlike primary batteries that cannot be recharged, secondary batteries can be repeatedly recharged and discharged. Low-capacity secondary batteries including a single cell packaged in a group can be used in various portable small electronic devices, such as cellular phones or camcorders, and high-capacity secondary batteries in which dozens of cells are connected in a battery pack are widely used as power sources for motor drives, such as those in hybrid vehicles or electric vehicles.

[0003] A secondary battery may include: an electrode assembly including a negative electrode and a positive electrode; a housing for accommodating the electrode assembly; a terminal connected to the electrode assembly; and one or more other suitable components. Secondary batteries may be classified into circular, prismatic, and pouch types according to their shapes. Specifically, a pouch-type secondary battery may be formed of a pouch outer material that is easily deformed into various shapes and has a small weight.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore may contain information that does not constitute prior art. Summary of the invention

[0005] Embodiments of the present disclosure provide a secondary battery capable of protecting an electrode assembly.

[0006] In addition, the embodiments of the present disclosure provide a secondary battery capable of improving a battery capacity relative to the same volume.

[0007] A secondary battery according to an embodiment of the present disclosure may include: an electrode assembly, the electrode assembly including a first electrode plate including a first substrate terminal tab, a second electrode plate including a second substrate terminal tab, and a separator inserted between the first electrode plate and the second electrode plate; a first lead welded to the first substrate terminal tab; a second lead welded to the second substrate terminal tab; a heat shrink tube around a thickness portion of the electrode assembly; and a shell that accommodates the electrode assembly.

[0008] In addition, the heat shrink tube may have a width equal to or smaller than the thickness of the electrode assembly.

[0009] In addition, the electrode assembly may further include a plurality of first electrode plates, a plurality of second electrode plates and a plurality of separators, wherein each of the plurality of first electrode plates may have a first substrate terminal tab, and the first substrate terminal tab may include a first alignment portion bent and aligned in one direction and a first welding portion bent in a direction opposite to the one direction and welded to the first lead, wherein each of the plurality of second electrode plates may have a second substrate terminal tab, the second substrate terminal tab may include a second alignment portion bent and aligned in one direction and a second welding portion bent in a direction opposite to the one direction and welded to the second lead, and wherein the heat shrink tube may pass over the first welding portion and the second welding portion.

[0010] In addition, the electrode assembly may further include a plurality of first electrode plates, a plurality of second electrode plates and a plurality of separators, wherein each of the plurality of first electrode plates may have a first substrate terminal tab, the first substrate terminal tab may include a first alignment portion bent and aligned in one direction and a first welding portion bent in a direction opposite to the one direction and welded to the first lead, wherein each of the plurality of second electrode plates may have a second substrate terminal tab, and the second substrate terminal tab may include a second alignment portion bent and aligned in one direction and a second welding portion bent in a direction opposite to the one direction and welded to the second lead, and wherein the heat shrink tube may pass between the first alignment portion and the first welding portion and between the second alignment portion and the second welding portion.

[0011] In addition, the heat shrink tube may have a width equal to or greater than a width of the first welding portion and a width of the second welding portion.

[0012] In addition, the heat shrinkable tube may have a heat shrinkage temperature lower than that of the separator.

[0013] In addition, the heat shrink tube may be made of polyethylene, polypropylene, polyvinyl chloride, polyester, polyethylene terephthalate, ethylene propylene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, nitrile rubber, polytetrafluoroethylene, or a combination thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The features, aspects and principles of the present disclosure will be better understood by referring to the following detailed description when considered in conjunction with the following drawings. These drawings should not be construed as limiting the present disclosure, but are intended to be illustrative only.

[0015] Figure 1 is a schematic perspective view showing a secondary battery according to an embodiment of the present disclosure.

[0016] Figure 2 To illustrate the relationship between secondary batteries and Figure 1 Side view of the portion corresponding to region II.

[0017] Figure 3 A schematic perspective view illustrating a secondary battery according to another embodiment of the present disclosure.

[0018] Figure 4 To illustrate the relationship between secondary batteries and Figure 3 Side view of the portion corresponding to region IV. DETAILED DESCRIPTION

[0019] Hereinafter, illustrative embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0020] Examples of the present disclosure are provided to more completely explain the present disclosure to those skilled in the art, and the following examples may be modified in various other forms. However, the present disclosure may be embodied in many different forms and should not be construed as being limited to the example (or exemplary) embodiments set forth herein. On the contrary, these example embodiments are provided so that the present disclosure will be thorough and complete, and will convey the various aspects and features of the present disclosure to those skilled in the art. Therefore, processes, elements, and techniques that are unnecessary for those of ordinary skill in the art to fully understand the various aspects and features of the present invention may not be described.

[0021] In addition, in the accompanying drawings, for simplicity and clarity, the size or thickness of various parts is magnified. The same reference numerals refer to the same elements throughout the text, and unless otherwise noted, the description thereof may not be repeated. As used herein, the term "and / or" includes any and all combinations of one or more related enumerated items. In addition, it will be understood that when element A is referred to as "on" element B "or" being "connected to" element B, element A may be directly on element B or directly connected to element B, or there may be an intermediate element C between element A and element B, so that element A and element B are indirectly connected to each other or indirectly to each other. In addition, it will also be understood that when an element or layer is referred to as "between" two elements or layers, it may be the only element or layer between two elements or layers, or one or more intermediate elements or layers may also be present.

[0022] The terms used in this article are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. It will be further understood that the terms "comprise", "comprising", "include" and / or "including" when used in this specification indicate the presence of the narrated features, numbers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, parts and / or groups thereof.

[0023] It will be understood that although the terms first, second, etc. may be used herein to describe various members, elements, regions, layers, and / or parts, these members, elements, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one member, element, region, layer, and / or part from another member, element, region, layer, and / or part. Therefore, for example, without departing from the teachings of the present disclosure, a first member, a first element, a first region, a first layer, and / or a first part may be referred to as a second member, a second element, a second region, a second layer, and / or a second part.

[0024] For ease of description, spatially relative terms, such as "below," "beneath," "below," "above," and "on," may be used herein to describe the relationship of one element or feature to another element or feature 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 in a figure is turned over, an element described as "below" or "beneath" another element or feature would then be oriented "above" or "on" the other element or feature. Thus, the term "below" may encompass both above and below orientations.

[0025] As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation rather than as terms of degree, and are intended to take into account the inherent deviations of measurements or calculations that one of ordinary skill in the art will recognize. In addition, the use of "may" when describing embodiments of the present disclosure refers to "one or more embodiments of the present disclosure." As used herein, the terms "use," "using," and "used" may be considered synonymous with the terms "utilize," "utilizing," and "utilized," respectively. Also, the term "exemplary" is intended to indicate an example or illustration.

[0026] The electronic or electrical devices and / or any other related devices or components according to the embodiments of the present disclosure described herein may be implemented using any appropriate hardware, firmware (e.g., application specific integrated circuits), software, or a combination of software, firmware, and hardware. For example, the various components of these devices may be formed on an integrated circuit (IC) chip or formed on an independent IC chip. In addition, the various components of these devices may be implemented on a flexible printed circuit film, a tape carrier package (TCP), or a printed circuit board (PCB), or formed on a substrate. In addition, the various components of these devices may be processes or threads running on one or more processors in one or more computing devices (executing computer program instructions and interacting with other system components for performing the various functions described herein). Computer program instructions are stored in a memory, which may be implemented in a computing device using a standard memory device, such as, for example, a random access memory (RAM). Computer program instructions may also be stored in other non-temporary computer-readable media, such as, for example, a CD-ROM or a flash drive, etc. Furthermore, those skilled in the art will recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a dedicated computing device may be distributed across one or more other computing devices without departing from the spirit and scope of the exemplary embodiments of the present disclosure.

[0027] Unless otherwise defined, all terms (including technical and scientific terms) used in this article have the same meaning as those commonly understood by ordinary technicians in the field to which the present disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant field and / or this specification, and should not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0028] Figure 1 2 is a schematic perspective view showing a secondary battery 1000 according to an embodiment of the present disclosure. Figure 2 To explain the secondary battery 1000 and Figure 1 1 is a side view of the portion corresponding to region II in FIG. 1 , wherein the heat shrink tube 1300 is indicated by a dotted line.

[0029] refer to Figure 1 and Figure 2 , the secondary battery 1000 includes an electrode assembly 1100 , a first lead 1210 , a second lead 1220 , a heat shrink tube 1300 , and a case 1400 .

[0030] The electrode assembly 1100 includes a first electrode plate 1110 , a second electrode plate 1120 , and a separator 1130 .

[0031] The first electrode plate 1110 may be any one of a negative electrode plate and a positive electrode plate. When the first electrode plate 1110 is a negative electrode plate, the first electrode plate 1110 may include, for example, but not limited to, a negative electrode coated portion coated with a negative electrode active material on a negative electrode collector plate, the negative electrode collector plate being made of a thin conductive metal plate, for example, a copper foil or a nickel foil or a copper mesh or a nickel mesh; and a negative electrode uncoated portion on which a negative electrode active material is not coated. In some embodiments, the negative electrode active material may include, for example, but not limited to, a carbon-based material, Si, Sn, a tin alloy composite material, a transition metal oxide, a lithium metal nitrite, and / or a metal oxide (e.g., tin oxide). In addition, the first electrode plate 1110 may include a first substrate tab 1111 formed by stamping an uncoated portion of the negative electrode.

[0032] The second electrode plate 1120 may be any one of a negative electrode plate and a positive electrode plate. When the first electrode plate 1110 is a negative electrode plate, the second electrode plate 1120 may become a positive electrode plate. In this embodiment, the second electrode plate 1120 may include, for example, but not limited to, a positive electrode coated portion coated with a positive electrode active material on a positive electrode collector plate, the positive electrode collector plate being made of a thin metal plate having excellent electrical conductivity, for example, an aluminum foil or an aluminum mesh; and a positive electrode uncoated portion on which a positive electrode active material is not coated. Here, the positive electrode active material may include, for example, but not limited to, a chalcogenide compound, for example, a composite metal oxide, such as LiCoO2, LiMn2O4, LiNiO2 and / or LiNiMnO2. In addition, the second electrode plate 1120 may include a second substrate tab 1121 formed by stamping the positive electrode uncoated portion.

[0033] The separator 1130 is inserted between the first electrode plate 1110 and the second electrode plate 1120 to prevent or avoid an electrical short circuit between the first electrode plate 1110 and the second electrode plate 1120. The separator 1130 may be made of, for example, but not limited to, polyethylene, polypropylene, a porous copolymer of polyethylene and polypropylene, and / or one or more appropriate materials. In addition, in order to effectively prevent or avoid an electrical short circuit between the first electrode plate 1110 and the second electrode plate 1120, the separator 1130 may have a larger area than the first electrode plate 1110 and the second electrode plate 1120.

[0034] According to the manufacturing method, the electrode assembly 1100 can be divided into a winding type and a stacking type. In the drawings, the stacking type electrode assembly 1100 is explained by way of example, and for the convenience of understanding, the following description will be made based on the electrode assembly 1100 being a stacking type with reference to the drawings, however, the present disclosure is not limited thereto. In addition, hereinafter, for the convenience of explanation, the wide portion in the electrode assembly 1100 (based on the drawings, for example, Figure 1, the side surface parallel to the XY plane) is called the "plate surface portion", and the narrow portion (XZ plane, based on the drawings, for example, Figure 1 , the side surface parallel to the YZ plane) is called the “thickness portion”.

[0035] In some embodiments, the electrode assembly 1100 is formed by stacking the first electrode plate 1110, the separator 1130, the second electrode plate 1120, and the separator 1130 in this order, and the stacking may be performed so that the first substrate terminal tab 1111 (including a plurality of first substrate terminal tabs 1111, such as Figure 2 ) are arranged layer by layer in the Z-axis direction, and the second substrate wiring piece 1121 is also arranged layer by layer in the Z-axis direction, wherein the first substrate wiring piece 1111 and the second substrate wiring piece 1121 are arranged side by side in the Y-axis direction.

[0036] The first lead 1210 may have one end fixed (eg, welded) to the first substrate tab 1111, and the other end protruding and extending to the outside. A process for fixing the first lead 1210 and the first substrate tab 1111 will now be described in more detail.

[0037] The process for fixing the first lead 1210 and the first substrate tab 1111 may be performed as follows: a first bending step of bending and aligning a plurality of first substrate tabs 1111 in one direction; a cutting and spot welding step of gathering the aligned portions into one and cutting and spot welding the ends thereof together; a welding step of welding the spot welded portions to the first lead 1210; and a second bending step of bending the welded portions in a direction opposite to the bending direction in the first bending step. Hereinafter, for convenience of explanation, the portion where the first substrate tab 1111 is bent and aligned in one direction is referred to as the first alignment portion 1111A, and the portion of the first substrate tab 1111 welded to the first lead 1210 is referred to as the first welding portion 1111B (see, for example, Figure 2 The first lead 1210 may include a first insulating member 1211 for preventing (or avoiding) a short circuit with the housing 1400 .

[0038] The second lead 1220 may have one end fixed (e.g., welded) to the second substrate tab 1121, and another end protruding and extending to the outside. Similarly, the process for fixing the second lead 1220 and the second substrate tab 1121 may also be performed as follows: a first bending step of bending and aligning a plurality of second substrate tabs 1121 in one direction; a cutting and spot welding step of gathering the aligned portions into one and cutting and spot welding the ends thereof together; a welding step of welding the spot welded portion to the second lead 1220; and a second bending step of bending the welded portion in a direction opposite to the bending direction in the first bending step. Hereinafter, for convenience of explanation, the portion in which the second substrate tab 1121 is bent and aligned in one direction is referred to as the second alignment portion, and the portion of the second substrate tab 1121 welded to the second lead 1220 is referred to as the second welding portion. The second lead 1220 may include a second insulating member 1221 for preventing (or avoiding) a short circuit with the housing 1400.

[0039] The heat shrink tube 1300 surrounds the thickness portion of the electrode assembly 1100 (or around the thickness portion of the electrode assembly 1100). In the process of manufacturing the secondary battery 1000, during a fall and safety assessment, a portion of the electrode assembly 1100 (for example, in the case of a stacked type electrode assembly 1100, the thickness portion of the electrode plate exposed therein) may become weakened. In some embodiments, the heat shrink tube 1300 may surround the thickness portion of the electrode assembly 1100 or around the thickness portion of the electrode assembly 1100 and protect the thickness portion of the electrode assembly 1100.

[0040] In some embodiments, in the secondary battery 1000 according to the embodiment of the present disclosure, the heat shrink tube 1300 surrounds the thickness portion of the electrode assembly 1100 (or around the thickness portion of the electrode assembly 1100) so as to pass over the first welding portion 1111B and the second welding portion. Therefore, because the heat shrink tube 1300 covers the first welding portion 1111B and the second welding portion, it is possible to prevent (or avoid) the housing 1400 from being damaged due to burrs that may occur during welding. In addition, the heat shrink tube 1300 can squeeze the first substrate tab 1111 and the second substrate tab 1121 and thus allow the first substrate tab 1111 and the second substrate tab 1121 to be bent more firmly, thereby reducing the space occupied by the first substrate tab 1111 and the second substrate tab 1121 inside the housing 1400.

[0041] The heat shrink tube 1300 may have a width equal to or smaller than the thickness of the electrode assembly 1100 (based on the drawings, for example, Figure 1, length in the Z-axis direction). In other words, the heat shrink tube 1300 may surround only the thickness portion of the electrode assembly 1100 (or only around the thickness portion of the electrode assembly 1100), and may not surround the plate surface portion of the electrode assembly 1100 (or not around the plate surface portion of the electrode assembly 1100). When the heat shrink tube 1300 surrounds the plate surface portion of the electrode assembly 1100 (or around the plate surface portion of the electrode assembly 1100), due to the thickness of the heat shrink tube 1300, the total thickness of the electrode assembly 1100 and the heat shrink tube 1300 may increase, thereby correspondingly reducing the battery capacity relative to the same volume. Therefore, by preventing the heat shrink tube 1300 from surrounding the plate surface portion of the electrode assembly 1100 (or around the plate surface portion of the electrode assembly 1100), the battery capacity may be improved. However, the heat shrink tube 1300 may have a width equal to or greater than the width of the first welding portion 1111B and the width of the second welding portion (based on the drawings, for example, Figure 1 , in the Z-axis direction). This is to effectively protect the housing 1400 by allowing the heat shrink tube 1300 to completely cover the first welding portion 1111B and the second welding portion. In addition, the heat shrink tube 1300 may include, for example, but not limited to, an insulating polymer resin such as polyethylene, polypropylene, polyvinyl chloride, polyester, polyethylene terephthalate, ethylene propylene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, nitrile rubber, polytetrafluoroethylene (PTFE) and / or combinations thereof. is a registered trademark of The Chemours Company FC, LLC of Wilmington Delaware. In addition, in some embodiments, the heat shrink tube 1300 has a heat shrink temperature lower than the heat shrink temperature of the separator 1130. Considering that the separator 1130 generally undergoes heat shrinkage at a temperature above about 130°C, the heat shrink tube 1300 may have a heat shrink temperature of 130°C or lower, for example, about 60°C to about 130°C.

[0042] The case 1400 accommodates the electrode assembly 1100 and may be formed into a so-called pouch shape by thermal fusion along a circumference. The case 1400 may be formed into a multi-layer or laminate structure including, for example, but not limited to, a first insulating layer, a metal layer, and / or a second insulating layer.

[0043] Figure 3 A schematic perspective view of a secondary battery 2000 is provided to explain another embodiment of the present disclosure, and Figure 4 To explain the secondary battery 2000 and Figure 3 A side view of the portion corresponding to region IV in FIG. 2 , wherein the heat shrink tube 2300 is indicated by a dotted line.

[0044] The secondary battery 2000 according to the present embodiment is different from the secondary battery 1000 in the position where the heat shrink tube 2300 is installed. The other parts are substantially the same or to the extent that those skilled in the art naturally change in response to the difference, so their repeated description will be omitted. The following description will focus on the heat shrink tube 2300.

[0045] refer to Figure 3 and Figure 4 The heat shrink tube 2300 surrounds a thickness portion of the electrode assembly 1100 (or around a thickness portion of the electrode assembly 1100) so as to pass between the first alignment portion 1111A and the first welding portion 1111B and between the second alignment portion and the second welding portion.

[0046] In order to respectively fix the first lead 1210 and the second lead 1220 and the first substrate terminal piece 1111 and the second substrate terminal piece 1121, the fixing process can be performed as follows: a first bending step of bending and aligning multiple first substrate terminal pieces 1111 and multiple second substrate terminal pieces 1121 in one direction; a cutting and spot welding step of gathering the aligned parts into one and cutting and spot welding the ends thereof together; a welding step of welding the spot welded parts to the first lead 1210 and the second lead 1220; and a second bending step of bending the welded parts in a direction opposite to the bending direction in the first bending step, and a heat shrink tube 2300 can be installed between the first bending step and the cutting and spot welding step. That is, after aligning the first substrate tab 1111 and the second substrate tab 1121 by bending them in one direction respectively, the heat shrink tube 2300 may be heat shrunk by surrounding the thickness portion of the electrode assembly 1100 with the heat shrink tube 2300 (or placing the heat shrink tube 2300 around the thickness portion of the electrode assembly 1100) so that the heat shrink tube 2300 passes over the alignment portion (the first alignment portion 1111A and the second alignment portion). Then, cutting and spot welding steps may be performed.

[0047] Alternatively, the heat shrink tube 2300 may be installed between the cutting and spot welding steps and the welding step. That is, the cutting and spot welding steps may be performed, and then the heat shrink tube 2300 may be heat-shrunk by surrounding the thickness portion of the electrode assembly 1100 with the heat shrink tube 2300 (or placing the heat shrink tube 2300 around the thickness portion of the electrode assembly 1100) so that the heat shrink tube 2300 passes over the first alignment portion 1111A and the second alignment portion. Then, the welding step may be performed.

[0048] Alternatively, the heat shrink tube 2300 may be installed between the welding step and the second bending step. That is, the welding step may be performed, and then the heat shrink tube 2300 may be heat-shrunk by surrounding the thickness portion of the electrode assembly 1100 with the heat shrink tube 2300 (or placing the heat shrink tube 2300 around the thickness portion of the electrode assembly 1100) so that the heat shrink tube 2300 passes over the first alignment portion 1111A and the second alignment portion. Then, the second bending step may be performed.

[0049] Embodiments of the present disclosure provide a secondary battery that may be protected by a heat shrinkable tube surrounding (or around) a thickness portion of an electrode assembly.

[0050] In an embodiment of the present disclosure, by preventing the heat shrink tube from surrounding the plate surface portion of the electrode assembly, the volume increase can be minimized. In addition, the heat shrink tube can squeeze the first substrate terminal tab and the second substrate terminal tab, and thus the first substrate terminal tab and the second substrate terminal tab can be bent more firmly, thereby reducing the space occupied by the first substrate terminal tab and the second substrate terminal tab inside the housing. This can help improve the battery capacity relative to the same volume.

[0051] Although the present disclosure describes illustrative embodiments of secondary batteries implementing the present disclosure, the present disclosure is not limited thereto, and those skilled in the art will understand that various changes in form and details may be made herein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

1. A secondary battery comprising: an electrode assembly including a first electrode plate including a first substrate terminal tab, a second electrode plate including a second substrate terminal tab, and a separator interposed between the first electrode plate and the second electrode plate; a first lead welded to the first substrate terminal tab; a second lead welded to the second substrate terminal tab; a heat shrink tube around a thickness portion of the electrode assembly and not around a plate surface portion of the electrode assembly; and a casing for accommodating the electrode assembly, wherein the electrode assembly further comprises a plurality of the first electrode plates, a plurality of the second electrode plates and a plurality of the separators, wherein each of the plurality of first electrode plates has the first substrate tab, and the first substrate tab includes a first alignment portion bent and aligned in one direction and a first welding portion bent in a direction opposite to the one direction and welded to the first lead, wherein each of the plurality of second electrode plates has a second substrate tab, and the second substrate tab includes a second alignment portion bent and aligned in one direction and a second welding portion bent in a direction opposite to the one direction and welded to the second lead, and The heat shrink tube covers middle portions of the first alignment portion and the second alignment portion and compresses the first substrate tab and the second substrate tab. 2 . The secondary battery according to claim 1 , wherein the heat shrink tube has a width equal to or smaller than a thickness of the electrode assembly. 3 . The secondary battery according to claim 1 , wherein the heat shrink tube goes over the first welding portion and the second welding portion. 4 . The secondary battery according to claim 1 , wherein the heat shrink tube passes between the first alignment portion and the first welding portion and between the second alignment portion and the second welding portion. 5 . The secondary battery according to claim 3 , wherein the heat shrinkable tube has a width equal to or larger than a width of the first welding portion and a width of the second welding portion. 6 . The secondary battery according to claim 1 , wherein the heat shrinkage tube has a heat shrinkage temperature lower than that of the separator. 7 . The secondary battery according to claim 1 , wherein the heat shrinkable tube is made of polyethylene, polypropylene, polyvinyl chloride, polyester, polyethylene terephthalate, ethylene propylene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, nitrile rubber, polytetrafluoroethylene, or a combination thereof.

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