Secondary batteries

Abstract

To provide a secondary battery including a vent to prevent thermal runaway, by preventing the decomposition of an electrolyte solution necessary in the progress of the thermal runaway in such a way that the electrolyte solution is discharged before the gas in the case is discharged.SOLUTION: A secondary battery according to an example of the present invention includes a rectangular case, an electrode assembly accommodated in the case together with an electrolyte solution, a cap assembly coupled to one end of the case and including at least one vent, and at least one discharge pipe included inside the case and having one end adjacent to a lower surface of the case, and the other end communicating with the vent.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a secondary battery having a vent for discharging electrolyte. [Background technology]

[0002] The secondary battery may include an electrode assembly formed by stacking or winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween, a case that houses the electrode assembly together with an electrolyte, and a cap assembly that seals the case.

[0003] A secondary battery can overheat when overcharged or physically damaged. Chemical reactions within the battery can also accelerate, generating additional heat. The heat causes chemicals within the battery to begin to decompose. Lithium salt, a commonly used electrolyte, decomposes at high temperatures to produce gas, increasing the battery's internal pressure. Furthermore, accelerated chemical and decomposition reactions can cause a rapid rise in the battery's internal temperature, resulting in thermal runaway. If the internal pressure of the battery continues to increase and exceeds a certain level, the battery case can eventually burst, causing a fire.

[0004] The vent automatically opens when the pressure exceeds a certain level, releasing the internal gas to the outside, and through this process, the internal pressure of the battery is maintained at a safe level. However, even if the vent opens and the gas is released, there is a high possibility of explosion and fire due to the residual electrolyte remaining inside the case.

[0005] The information disclosed in the above background of the invention is merely intended to enhance understanding of the background of the invention and may therefore include information that does not constitute prior art. Summary of the Invention [Problem to be solved by the invention]

[0006] An embodiment of the present invention provides a secondary battery having a vent that prevents thermal runaway by allowing the electrolyte to be discharged before the gas inside the case is discharged, thereby preventing decomposition of the electrolyte, which is essential for the progression of thermal runaway. [Means for solving the problem]

[0007] A secondary battery according to an embodiment of the present invention may include a rectangular case, an electrode assembly housed inside the case together with an electrolyte, a cap assembly coupled to one end of the case and having at least one vent, and at least one exhaust pipe provided inside the case, one end adjacent to a bottom surface of the case and the other end communicating with the vent.

[0008] When the pressure inside the case exceeds a certain pressure, the vent is opened to discharge the electrolyte, and then gas inside the case can be discharged.

[0009] The discharge tube may be in the form of a hollow tube.

[0010] The exhaust pipe may be positioned so as not to interfere with the electrode assembly.

[0011] The discharge pipe may be at least partially bent.

[0012] The exhaust pipe may include a connecting pipe connected to the vent, and a plurality of branch pipes branching from the connecting pipe and extending toward the bottom surface of the case.

[0013] A plurality of vents may be provided, and a plurality of exhaust pipes may be provided, each exhaust pipe being connected to a respective vent.

[0014] The drain tube may be made of an insulating material that does not react with the electrolyte.

[0015] A secondary battery according to an embodiment of the present invention may include a pouch-type case having a recess and at least one vent on one side for discharging gas, an electrode assembly housed inside the case together with an electrolyte, and at least one exhaust pipe provided inside the case, one end of which is adjacent to a lower surface of the recess and the other end of which is in communication with the vent.

[0016] When the pressure inside the case exceeds a certain pressure, the vent is opened to discharge the electrolyte, and then gas inside the case can be discharged.

[0017] The discharge tube may be in the form of a hollow tube.

[0018] The exhaust pipe may be positioned so as not to interfere with the electrode assembly.

[0019] The discharge pipe may be at least partially bent.

[0020] The discharge pipe may include a connecting pipe connected to the vent, and a plurality of branch pipes branching from the connecting pipe and extending toward the lower surface of the recess.

[0021] A plurality of vents may be provided, and a plurality of exhaust pipes may be provided, each exhaust pipe being connected to a respective vent.

[0022] The drain tube may be made of an insulating material that does not react with the electrolyte. [Effects of the Invention]

[0023] According to the embodiment of the present invention, the electrolyte is discharged before the gas inside the case is discharged through the vent, thereby preventing the decomposition of the remaining electrolyte and preventing thermal runaway, which in turn prevents explosions and fires caused by thermal runaway. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a perspective view illustrating a secondary battery according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of the cap assembly and electrode assembly according to FIG. [Figure 3] FIG. 3 is a partial cross-sectional view of FIG. 2. [Figure 4] 2 is a front view schematically illustrating a first embodiment of a discharge pipe in the secondary battery shown in FIG. 1; [Figure 5] FIG. 5 is a front view schematically illustrating a state in which the vent in FIG. 4 is opened. [Figure 6] FIG. 10 is a side view schematically illustrating a second embodiment of the discharge pipe. [Figure 7] FIG. 10 is a side view schematically illustrating a third embodiment of the discharge pipe. [Figure 8] 10 is a side view schematically illustrating a discharge pipe of a secondary battery according to another embodiment of the present invention; [Figure 9] 9 is a front view schematically illustrating a discharge pipe of the secondary battery shown in FIG. 8. FIG. [Figure 10] 10 is a side view schematically illustrating a discharge pipe of a secondary battery according to still another embodiment of the present invention; [Figure 11] 11 is a front view schematically illustrating a discharge pipe of the secondary battery shown in FIG. 10. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] The examples of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples may be modified into various other forms, and the scope of the present invention is not limited to the following examples. Rather, these examples are provided to make the present disclosure more faithful and complete, and to fully convey the disclosure of the present invention to those skilled in the art.

[0026] In the following drawings, the thickness and size of each layer have been exaggerated for convenience and clarity of explanation, and the same reference numerals refer to the same elements throughout the drawings. As used herein, the term "and / or" includes any one and all combinations of one or more of the associated listed items. In addition, in this specification, the term "connected" refers not only to a case where member A and member B are directly connected, but also to a case where member A and member B are indirectly connected via member C interposed between them.

[0027] The terms used in this specification are used to describe particular embodiments and are not intended to limit the present invention. As used in this specification, the singular forms "a," "an," "the," and "the" can include the plural forms unless the context clearly dictates otherwise. Furthermore, as used in this specification, the words "comprise," "include," and / or "comprising," "including," specify the presence of a stated shape, number, step, operation, member, element, and / or group thereof, but do not exclude the presence or addition of one or more other shapes, numbers, operations, members, elements, and / or groups.

[0028] In this specification, terms such as "first," "second," etc. are used to describe various members, components, regions, layers, and / or portions, but it is clear that these members, components, regions, layers, and / or portions should not be limited by these terms. These terms are used only to distinguish one member, component, region, layer, or portion from another region, layer, or portion. Therefore, a first member, component, region, layer, or portion described in detail below can refer to a second member, component, region, layer, or portion without departing from the teachings of the present invention.

[0029] Space-related terms such as "beneath," "below," "lower," "above," and "upper" may be used to facilitate understanding of one element or feature from another element or feature illustrated in the drawings. These space-related terms are used to facilitate understanding of the present invention in various process or use states of the present invention and are not intended to limit the present invention. For example, if an element or feature in the drawing is turned over, an element or feature described as "beneath" or "below" becomes "upper" or "above." Therefore, "beneath" is a concept that encompasses "upper" or "below."

[0030] Hereinafter, a secondary battery according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0031] Fig. 1 is a perspective view illustrating an exemplary secondary battery. Fig. 2 is a perspective view of a cap assembly and an electrode assembly according to Fig. 1. Fig. 3 is a partial cross-sectional view of Fig. 2. For convenience, the description will be made with reference to Fig. 1, with the upper portion defined as the upward direction and the lower portion defined as the downward direction.

[0032] 1 to 3, a secondary battery 10 according to an embodiment of the present invention may include an electrode assembly 100, a case 200 that houses the electrode assembly 100, and a cap assembly 300 that is coupled to the case 200. Exemplarily, the secondary battery 10 may be a prismatic battery in which the case 200 is shaped like a rectangular parallelepiped. However, this is merely an example, and the present invention may be applied to various types of secondary batteries, such as pouch-type secondary batteries.

[0033] 2 and 3, the electrode assembly 100 may be formed by winding a unit laminate including a thin plate-like or film-like first electrode plate 110, a second electrode plate 120, and a separator 130 interposed therebetween, or by stacking a plurality of such units. When the electrode assembly 100 is wound, the winding shaft may be arranged in a horizontal direction substantially parallel to the longitudinal direction of the cap assembly 300 or in a vertical direction substantially perpendicular to the longitudinal direction of the cap assembly 300. When the electrode assembly 100 is stacked, the long sides of the plurality of unit laminates may be arranged adjacent to each other. An insulating sheet 140 may be attached to the exterior of the electrode assembly 100 with insulating tape 150 to insulate it from the case 200. For example, the first electrode plate may be a negative electrode and the second electrode plate may be a positive electrode. Alternatively, the opposite may be true.

[0034] When the first electrode plate 110 is a negative electrode plate, the first electrode plate may be formed by coating a first electrode active material, such as graphite or carbon, on a first electrode current collector provided as a metal foil such as copper, copper alloy, nickel, or nickel alloy. The first electrode plate may have a first uncoated portion, which is an area where the first electrode active material is not coated. The first uncoated portion serves as a tab electrically connected to the first current collector plate 330 (described below), and may be defined as a first substrate tab. A plurality of first substrate tabs may be bent to one side and welded to the first current collector plate 330. The first current collector plate 330 may be electrically connected to the cap assembly 300.

[0035] When the second electrode plate 120 is a positive electrode plate, the second electrode plate may be formed by coating a second electrode active material, such as a transition metal oxide, on a second electrode current collector provided as a metal foil, such as aluminum or an aluminum alloy. The second electrode plate may have a second uncoated portion 122, which is an area where the second electrode active material is not coated. The second uncoated portion serves as a tab electrically connected to the second current collector plate 340, which will be described later, and may be defined as a second substrate tab. A plurality of second substrate tabs may be bent to one side and welded to the second current collector plate 340. The second current collector plate 340 may be electrically connected to the cap assembly 300.

[0036] The separator 130 is disposed between the first electrode plate 110 and the second electrode plate 120 to prevent short circuits and allow lithium ions to move. For example, the separator may be made of polyethylene, polypropylene, or a composite film of polyethylene and polypropylene. However, the separator is not limited to the aforementioned materials.

[0037] The electrode assembly 100 having the above-described structure may be housed in a case 200 together with an electrolyte. In some examples, the electrolyte may contain a lithium salt such as LiPF or LiBF in an organic solvent such as EC (ethylene carbonate), PC (propylene carbonate), DEC (diethyl carbonate), EMC (ethylmethyl carbonate), or DMC (dimethyl carbonate). The electrolyte may be liquid or gel-like.

[0038] Referring to FIG. 1 , the case 200 has a substantially rectangular parallelepiped box shape and may have an opening at the top in the longitudinal direction to form an internal storage space. The electrode assembly 100 and an electrolyte may be housed inside the case 200 through the opening at the top. Some components of the cap assembly 300 may be exposed to the outside of the case 200, while other components may be housed inside the case 200. The case 200 may have a rectangular bottom 210 and four side surfaces connected to the bottom 210. The sides with a relatively larger area are defined as long sides 220, and the sides with a relatively smaller area are defined as short sides 230. For example, the electrode assembly 100 may be disposed such that its plate surface faces the long sides 220. When the electrode assembly 100 is housed in the case 200, the cap assembly 300 is coupled to the case 200 and electrically connected to the electrode assembly 100.

[0039] Referring to Figures 1 and 2, the cap assembly 300 may include a cap plate 310 coupled to the case 200, a plurality of insulating members, a first current collecting plate 330 and a second current collecting plate 340, and a first terminal portion 350 and a second terminal portion 360.

[0040] The cap plate 310 has a generally rectangular plate shape and may be made of the same material as the case 200. The cap plate 310 may be formed with terminal holes for coupling to the first terminal portion 350 and the second terminal portion 360, a liquid injection hole 314, and a vent hole for coupling to the vent 316. A plurality of insulating members (not shown in the drawings), such as an insulating plate 320, may be provided to insulate the cap plate 310 from the electrode assembly 100.

[0041] The first current collecting plate 330 electrically connects the first electrode plate 110, which is a negative electrode plate, to the first terminal unit 350. To this end, the first current collecting plate 330 may be made of the same material as the first electrode plate 110. Exemplarily, the first current collecting plate 330 may be electrically connected to the first substrate tab of the first electrode plate 110 by laser welding.

[0042] The second current collecting plate 340 is disposed symmetrically to the first current collecting plate 330 and electrically connects the second electrode plate 120, which is a positive electrode plate, to the second terminal portion 360. To this end, the second current collecting plate 340 may be made of the same material as the second substrate tab of the second electrode plate 120.

[0043] The first terminal portion 350 may include a first terminal pin 352 and a first terminal plate 354. The first terminal plate 354 may be insulated from the cap plate 310 by an insulating member 328. The first terminal pin 352 is electrically connected to the first current collecting plate 330, and thereby electrically connected to the first electrode plate 110 of the electrode assembly 100.

[0044] The second terminal unit 360 may include a second terminal pin 362, a second terminal plate 364, and a conductive plate 366. The second terminal unit 360 is disposed symmetrically with the first terminal unit 350. The conductive plate 366 electrically connects the cap plate 310 to the second terminal plate 364, which is electrically connected to the second terminal pin 362. Therefore, the cap plate 310 is connected to the second current collecting plate 340 through the second terminal unit 360, and can therefore be electrically connected to the second electrode plate 120. Therefore, the cap plate 310 has the same positive polarity as the second current collecting plate 340, and the case 200 welded to the cap plate 310 also has a positive polarity.

[0045] Meanwhile, when the pressure inside the case 200 exceeds a certain pressure, the vent 316 opens to discharge the gas inside the case 200 to the outside. The vent 316 may be designed as a fusion joint, or may have a variety of structures, such as a mechanical valve or a device that is activated by heat.

[0046] In the secondary battery of the present invention, at least one exhaust pipe 400 may be provided inside the case 200, as shown in FIGS. 4 and 5. FIG. 4 is a front view schematically illustrating a first embodiment of the exhaust pipe in the secondary battery of FIG. 1, and FIG. 5 is a front view schematically illustrating the state in which the vent in FIG. 4 is open. The exhaust pipe 400 is shaped like a hollow pipe. One end of the exhaust pipe 400 is adjacent to the bottom of the case 200, and the other end of the exhaust pipe 400 is connected to the vent 316. Here, the bottom of the case 200 refers to the bottom surface facing the direction of gravity where the electrolyte is accumulated. One end of the exhaust pipe 400 does not contact the bottom of the case 200, but is adjacent to it at a certain distance. Accordingly, the vent 316 is located at the top end of the case 200 but is connected to the bottom end of the case 200.

[0047] 4 and 5 illustrate a single exhaust pipe 400, but this is not limiting. The exhaust pipe 400 is installed so as not to interfere with the electrode assembly 100. That is, the exhaust pipe 400 may be installed in the space between the electrode assembly 100 and the case 200. To this end, if the exhaust pipe 400 must avoid the electrode assembly 100 due to the position of the vent 316, at least a portion of the exhaust pipe 400 may be bent. For example, if the vent 316 is located in the center of the cap plate 310, the exhaust pipe 400 may extend downward from the vent 316 before contacting the electrode assembly 100. Thereafter, to avoid the electrode assembly 100, the exhaust pipe 400 may be bent to the side of the electrode assembly 100 and then extend downward again from the side of the electrode assembly 100 toward the bottom of the case 200. However, if the vent 316 is provided on the cap plate 310 at a position corresponding to the space between the electrode assembly 100 and the case 200, the discharge pipe 400 may not be bent.

[0048] As described above, the discharge pipe 400 comes into contact with the electrolyte, and therefore, it is preferable that the discharge pipe 400 be made of an insulating material that does not react with the electrolyte.

[0049] Before thermal runaway occurs, if gas is generated inside case 200 due to decomposition of the electrolyte, causing an increase in internal pressure, the gas inside case 200 pushes the heated residual electrolyte downward, as shown in FIG. 4. As a result, the residual electrolyte flows into exhaust pipe 400 and moves toward vent 316. When the pressure inside case 200 subsequently exceeds a certain pressure (critical pressure), vent 316 opens and the electrolyte is discharged to the outside. As shown in FIG. 5, if the electrolyte is continuously discharged through vent 316, the level of the residual electrolyte inside case 200 becomes lower than one end of exhaust pipe 400. In other words, if most of the residual electrolyte is discharged, the gas inside case 200 may be discharged to the outside through exhaust pipe 400 following the discharge of the electrolyte.

[0050] In this way, when the pressure inside the case 200 exceeds a certain pressure, the vent 316 is opened, and the residual electrolyte is first discharged, followed by the gas. Therefore, since there is no residual electrolyte remaining inside the case 200, additional decomposition of the residual electrolyte that may occur after the vent is opened and the resulting thermal runaway can be prevented.

[0051] Next, another embodiment of the discharge pipe will be described with reference to Fig. 6. Fig. 6 is a side view that schematically illustrates a second embodiment of the discharge pipe.

[0052] In this embodiment, the discharge pipe 1400 may include a connecting pipe 1420 connected to the vent 316, and a plurality of branch pipes 1440 branching from the connecting pipe 1420 and extending toward the bottom of the case 200. In this embodiment, the vent 316 is located at the center of the cap plate 310. Therefore, the connecting pipe 1420 may extend downward from the vent 316 before contacting the electrode assembly 100. Then, the plurality of branch pipes 1440 may be bent from the connecting pipe 1420 to opposite sides of the electrode assembly 100, and then extend downward toward the bottom of the case 200.

[0053] As described above, by providing the exhaust pipe 1400, when the pressure inside the case 200 exceeds a certain pressure, the vent 316 is opened, and the residual electrolyte is exhausted, followed by the gas.

[0054] Another embodiment of the discharge pipe will be described with reference to Fig. 7. Fig. 7 is a side view that schematically illustrates a third embodiment of the discharge pipe.

[0055] In this embodiment, a plurality of vents 316 and a plurality of exhaust pipes 2400 may be provided, and each exhaust pipe 2400 may be connected to a respective vent 316. Specifically, in this embodiment, two vents 316 are provided, and each vent 316 may be provided at a position on the cap plate 310 corresponding to the space between the electrode assembly 100 and the case 200. Also, although two exhaust pipes 2400 are provided, each exhaust pipe 2400 may extend in a straight line from the respective vent 316 toward the bottom surface of the case 200. Here, the position and number of vents 316 may be designed in various ways depending on the embodiment.

[0056] As described above, by providing a plurality of exhaust pipes 2400, when the pressure inside the case 200 exceeds a certain pressure, a plurality of vents 316 are opened, and the residual electrolyte is discharged, followed by the gas.

[0057] Although the above-described embodiment has been described with reference to a prismatic secondary battery, the present invention can also be applied to a pouch-type secondary battery.

[0058] FIG. 8 is a side view schematically illustrating a discharge pipe of a secondary battery according to another embodiment of the present invention. FIG. 9 is a front view schematically illustrating a discharge pipe of the secondary battery according to FIG. 8. Referring to FIGS. 8 and 9, an exemplary pouch-type secondary battery 10a includes a recess 210a serving as a storage space. The pouch-type secondary battery 10a may include a pouch-type case 200a having at least one vent 316a on one side for gas discharge, an electrode assembly 100a accommodated in the recess 210a together with an electrolyte, and at least one discharge pipe 1400a disposed inside the pouch-type case 200a, one end of which is adjacent to the bottom surface of the recess 210a and the other end of which is in communication with the vent 316a. The electrode assembly 100a may include a first electrode tab 102a electrically connected to a first electrode plate and a second electrode tab 104a electrically connected to a second electrode plate. The vent 316a may be disposed between the first electrode tab 102a and the second electrode tab 104a. Here, the lower surface of the recess 210a refers to the lower surface facing the direction of gravity where the electrolyte is collected. The structure of the exhaust pipe 1400a of the pouch-type secondary battery 10a may be the same as the structure of the exhaust pipe 1400 described for the prismatic battery of FIG. 6. That is, the exhaust pipe 1400a may include a connecting pipe 1420a connected to the vent 316a and a plurality of branch pipes 1440a branching from the connecting pipe 1420a and extending toward the lower surface of the pouch-type case 200a. Because the vent 316a is disposed between the first electrode tab 102a and the second electrode tab 104a, the exhaust pipe 1400a is also disposed between the first electrode tab 102a and the second electrode tab 104a. The connecting pipe 1420a may extend downward from the vent 316a before contacting the electrode assembly 100a. One of the branch pipes 1440a may be disposed on one side of the electrode assembly 100a and extend toward the bottom surface of the pouch-type case 200a. The other of the branch pipes 1440a may pass between the first electrode tab 102a and the second electrode tab 104a and extend toward the bottom surface of the pouch-type case 200a.

[0059] 10 is a side view schematically illustrating a discharge pipe of a secondary battery according to still another embodiment of the present invention, and FIG. 11 is a front view schematically illustrating the discharge pipe of the secondary battery according to FIG.

[0060] 10 and 11, an exemplary pouch-type secondary battery 10b includes a recess 210b serving as a storage space. The pouch-type secondary battery 10b may include a pouch-type case 200b having a plurality of vents 316b on one side for gas release, an electrode assembly 100b housed in the recess 210b together with an electrolyte, and a plurality of exhaust pipes 1400b disposed inside the pouch-type case 200b, one end of which is adjacent to the bottom surface of the recess 210b and the other end of which is in communication with the vent 316b. The electrode assembly 100b may include a first electrode tab 102b electrically connected to the first electrode plate and a second electrode tab 104b electrically connected to the second electrode plate. The vent 316b may be located outside the first electrode tab 102b and the second electrode tab 104b. The structure of the exhaust pipe 1400b of the pouch-type secondary battery 10b may be the same as the structure of the exhaust pipe 2400 described for the prismatic battery of FIG. 7. That is, in this embodiment, two exhaust pipes 1400b may be connected to two vents 316b, respectively. The two exhaust pipes 1400b may extend in a straight line from each vent 316b toward the bottom surface of the pouch-type case 200b. The exhaust pipes 1400b may be spaced apart from the electrode assembly 100b. The position and number of the vents 316b may be variously designed depending on the embodiment.

[0061] Accordingly, when the pressure inside the pouch-type case reaches a certain pressure or more, the vent is opened to discharge the residual electrolyte, and then the gas inside the pouch-type case can be discharged.

[0062] The above description is merely one example for carrying out the present invention, and the present invention is not limited to the above example. It can be said that the technical spirit of the present invention lies within the scope of the following claims, to the extent that anyone having ordinary skill in the art to which the invention pertains can make various modifications without departing from the gist of the present invention. [Explanation of symbols]

[0063] 10: Secondary battery 10a, 10b: Pouch-type secondary battery 100, 100a, 100b: Electrode assembly 102a, 102b: first electrode tabs 104a, 104b: second electrode tabs 110: First electrode plate 120: Second electrode plate 122: Second plain area 130: Separator 140: Insulating material sheet 150:Insulating tape 200: Case 200a, 200b: Pouch-type case 210: Bottom 210a, 210b: Recess 220: Long side 230: Short side 300: Cap assembly 310: Cap plate 314: Injection hole 316, 316a, 316b: Vent 320: Insulation plate 328: Insulating materials 330: First current collecting plate 340: Second current collecting plate 350: First terminal part 352: First terminal pin 354: First terminal plate 360: Second terminal 362: Second terminal pin 364: Second terminal plate 366: Conductive plate 400, 1400, 1400a, 1400b, 2400: Discharge pipe 1420, 1420a: Connecting pipe 1440, 1440a: Branch pipe

Claims

1. A rectangular case and an electrode assembly housed inside the case together with an electrolyte; a cap assembly coupled to one end of the case and having at least one vent; at least one exhaust pipe provided inside the case, one end of which is adjacent to the lower surface of the case and the other end of which is in communication with the vent; When the pressure inside the case reaches or exceeds a certain pressure, the vent is opened to discharge the electrolyte and then discharge gas inside the case.

2. The secondary battery according to claim 1 , wherein the discharge pipe is a hollow tube.

3. The secondary battery according to claim 2 , wherein the exhaust pipe is installed so as not to interfere with the electrode assembly.

4. The secondary battery according to claim 3, wherein at least a portion of the discharge pipe is bent.

5. The discharge pipe is The secondary battery of claim 4 , further comprising: a connecting pipe connected to the vent; and a plurality of branch pipes branching from the connecting pipe and extending toward a bottom surface of the case.

6. The secondary battery of claim 4 , wherein a plurality of the vents are provided, and a plurality of the exhaust pipes are provided, each exhaust pipe being connected to a respective vent.

7. 2. The secondary battery according to claim 1, wherein the discharge pipe is made of an insulating material that does not react with the electrolyte.

8. A pouch-type case having a recess as a storage space and at least one vent for gas discharge on one side; an electrode assembly accommodated in the recess inside the pouch-type case together with an electrolyte; at least one exhaust pipe provided inside the pouch-shaped case, one end of which is adjacent to a lower surface of the recess and the other end of which is in communication with the vent; When the pressure inside the pouch-type case reaches or exceeds a certain pressure, the vent is opened to discharge the electrolyte and then discharge gas inside the pouch-type case.

9. The secondary battery according to claim 8 , wherein the discharge pipe is a hollow tube.

10. The secondary battery according to claim 9, wherein the exhaust pipe is installed so as not to interfere with the electrode assembly.

11. The secondary battery according to claim 10, wherein at least a portion of the discharge pipe is bent.

12. The discharge pipe is The secondary battery of claim 11 , comprising: a connecting pipe connected to the vent; and a plurality of branch pipes branching from the connecting pipe and extending toward a lower surface of the recess.

13. The secondary battery of claim 11, wherein a plurality of the vents are provided, and a plurality of the exhaust pipes are provided, each exhaust pipe being connected to a respective vent.

14. 9. The secondary battery according to claim 8, wherein the discharge pipe is made of an insulating material that does not react with the electrolyte.

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