Secondary battery and battery module including said secondary battery

Abstract

A secondary battery according to an embodiment of the present invention includes an electrode assembly, and a pouch-type case including an upper case and a lower case in which the electrode assembly is incorporated and which are heat-sealed to each other, the pouch-type case including a sealing portion formed along at least a portion of an edge of the pouch-type case and formed by heat-sealing the upper case and the lower case, an electrode lead connected to the electrode assembly protrudes from one side of the pouch-type case, the sealing portion including a notch portion formed at any one end of the side from which the electrode lead protrudes, and the notch portion has a curvature that is concave toward the inside of the pouch-type case.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0159972 dated November 19, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a secondary battery and a battery module including the secondary battery, and more particularly to a pouch-type secondary battery with improved safety and a battery module including the secondary battery. [Background technology]

[0003] Demand for secondary batteries as an energy source is rapidly increasing due to technological developments and increasing demand for mobile devices. In response to this increase, much research is being conducted on secondary batteries to meet various demands.

[0004] Secondary batteries are attracting much attention as an energy source for power devices such as electric bicycles, electric vehicles, and hybrid electric vehicles, as well as for mobile devices such as mobile phones, digital cameras, and notebook computers.

[0005] Small devices such as mobile phones and cameras use small battery packs that contain a single battery cell, while medium- to large-sized devices such as laptops and electric vehicles use medium- to large-sized battery packs that contain two or more battery cells connected in parallel and / or series.

[0006] In terms of shape, there is high demand for prismatic and pouch-type secondary batteries, which are thin and suitable for use in products such as mobile phones. Prismatic lithium secondary batteries are advantageous in protecting the electrode assembly from external impact and facilitate the liquid injection process, but their fixed shape makes it difficult to reduce their volume. In contrast, pouch-type lithium secondary batteries have the advantage of being suitable for the production of thin cells as they are not limited in shape or size, are easy to assemble using heat fusion, and are highly safe as they easily vent gas or liquid in the event of abnormal behavior.

[0007] However, in such pouch-type secondary batteries, electrolyte decomposition can occur due to factors such as overcharging, exposure to high temperatures, and internal short circuits, which can result in the generation of large amounts of gas or internal fire, resulting in an increase in internal pressure. FIG. 1 illustrates an electrode lead portion of a conventional pouch-type secondary battery. As shown in FIG. 1, in a conventional secondary battery 10, a lead portion 21 extending from an electrode assembly 20 protrudes to the outside of a pouch-type case, and a sealing portion 34 is formed along the edge of the pouch-type case. The sealing portion 34 is uniformly formed along the entire edge and is symmetrically shaped relative to the lead portion 21. In this case, if the internal pressure increases, the entire battery can suddenly become engulfed in flames. Venting often occurs in the area corresponding to the lead portion 21. If venting occurs in the lead portion 21, the entire battery can become engulfed in flames even more rapidly. Therefore, even if gas or flames are generated inside the battery, it is necessary to appropriately control them and slow down the heat propagation. Summary of the Invention [Problem to be solved by the invention]

[0008] The embodiment provides a pouch-type secondary battery that can safely discharge gas in a desired direction to prevent explosion even if a large amount of gas is generated inside.

[0009] However, the problems to be solved by the embodiments of the present invention are not limited to the above problems, and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0010] A secondary battery according to an embodiment of the present invention includes an electrode assembly and a pouch-type case including an upper case and a lower case in which the electrode assembly is incorporated and which are heat-sealed to each other, the pouch-type case including a sealing portion formed along at least a portion of an edge of the pouch-type case and formed by heat-sealing the upper case and the lower case, an electrode lead connected to the electrode assembly protruding from one side of the pouch-type case, the sealing portion including a notch portion formed at one end of the side from which the electrode lead protrudes, the notch portion having a curvature that is concave toward the inside of the pouch-type case.

[0011] The other end portion located opposite the end portion where the notch portion is formed may not have the notch portion formed therein, and the electrode lead may be inserted between the end portion and the other end portion.

[0012] The width of the notch may be equal to or smaller than the width of the sealing portion excluding the notch.

[0013] The electrode leads may protrude from both longitudinal sides of the pouch-type case.

[0014] The electrode leads may each include a notch at an end of each of the two sides from which the electrode leads protrude, the end being in the same direction relative to the electrode leads.

[0015] The notch may have a radius of curvature of 2 mm or less.

[0016] A portion of the upper case and the lower case that is not heat-sealed may be disposed between the notch and the edge of the pouch-type case.

[0017] The upper case and the lower case may be integrally formed with a bend line therebetween, and the notch may be disposed adjacent to the bend line.

[0018] A battery module according to another embodiment of the present invention may include a plurality of the above-described secondary batteries.

[0019] The notches of the plurality of secondary batteries may all be arranged in the same direction. [Effects of the Invention]

[0020] According to the embodiment, in a pouch-type secondary battery, even if a large amount of gas is generated inside, the gas can be safely guided to be discharged in the intended direction, thereby preventing explosion, and thus a secondary battery with improved safety can be provided. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing an electrode lead portion of a conventional pouch-type secondary battery. [Figure 2] 1 is an exploded perspective view showing a secondary battery according to an embodiment of the present invention; [Figure 3] FIG. 2 is a diagram showing the secondary battery of FIG. 1 in an assembled state. [Figure 4] FIG. 4 is a view showing one electrode lead portion of FIG. 3. [Figure 5] FIG. 10 is a diagram showing a secondary battery according to a first modified example of the present invention. [Figure 6] FIG. 10 is a diagram showing a secondary battery according to a second modified example of the present invention. [Figure 7] FIG. 10 is a diagram showing a secondary battery according to a third modified example of the present invention. [Figure 8] 10A and 10B are diagrams for explaining the state of secondary batteries according to an example of the present invention and a comparative example during testing. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention may be embodied in various different forms and should not be construed as limited to the embodiments set forth herein.

[0023] In order to clearly explain the present invention, parts that are not relevant to the description will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0024] Furthermore, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to those shown. In the drawings, thicknesses are exaggerated to clearly show multiple layers and regions. In the drawings, thicknesses of some layers and regions are exaggerated for the convenience of explanation.

[0025] Furthermore, when a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes not only the case where it is "directly above" that part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "above" or "above" the opposite direction of gravity.

[0026] Also, throughout the specification, when a part is said to "comprise" a certain element, this means that it may further include other elements, not excluding other elements, unless otherwise specified to the contrary.

[0027] Also, throughout the specification, "on a plane" means when the subject part is viewed from above, and "on a cross section" means when the subject part is cut vertically and viewed from the side.

[0028] Hereinafter, a secondary battery according to an embodiment of the present invention will be described with reference to FIGS.

[0029] FIG. 2 is an exploded perspective view showing a secondary battery according to one embodiment of the present invention, FIG. 3 is a view showing the secondary battery of FIG. 1 in an assembled state, and FIG. 4 is a view showing one electrode lead portion of FIG. 3.

[0030] 2 to 4, a secondary battery 100 according to an embodiment of the present invention includes an electrode assembly 200 and a pouch-type case 300 that houses the electrode assembly 200. The pouch-type case 300 includes an upper case 310 and a lower case 320. While FIG. 2 illustrates the case in which the upper case 310 and the lower case 320 are formed separately, they may also be connected to each other to form an integrated unit. The shape of the pouch-type case 300 is not limited to the example shown in FIG. 2, and it may have any shape that can house and seal the electrode assembly 200.

[0031] The electrode assembly 200 may be configured in such a way that a positive electrode plate and a negative electrode plate are disposed with a separator interposed therebetween. The electrode assembly 200 may have a structure in which one positive electrode plate and one negative electrode plate are wound with a separator interposed therebetween, or a structure in which multiple positive electrode plates and multiple negative electrode plates are stacked with a separator interposed therebetween. The positive electrode plate and the negative electrode plate may each be formed by applying an active material slurry to an electrode current collector. The slurry is typically formed by stirring an active material, a conductive material, a binder, a plasticizer, and the like in a solvent.

[0032] The electrode assembly 200 may have uncoated portions where no slurry is applied to the electrode plates, and electrode tabs corresponding to each electrode plate may be formed in these uncoated portions. That is, each of the multiple positive electrodes and multiple negative electrodes included in the electrode assembly 200 may include a positive electrode tab and a negative electrode tab, and electrode leads 210, 220 are connected to the electrode assembly 200. Specifically, the electrode leads 210, 220 include a positive electrode lead 210 and a negative electrode lead 220. The electrode leads 210, 220 connected to the electrode assembly 200 protrude from both ends of the pouch-type case 300 and are exposed to the outside of the pouch-type case 300. Although the positive electrode lead 210 and the negative electrode lead 220 protrude in opposite directions in this embodiment, the protruding directions are not particularly limited. That is, the positive electrode lead 210 and the negative electrode lead 220 may both be exposed in the same direction from one side of the secondary battery 100.

[0033] The pouch-type case 300 includes an upper case 310 and a lower case 320 that are heat-sealed to each other. Although not specifically shown, the pouch-type case 300 including the upper case 310 and the lower case 320 may be a laminate sheet including a resin layer and a metal layer. Specifically, each of the upper case 310 and the lower case 320 may include an inner resin layer for sealing, a metal layer for preventing penetration of substances, and an outermost outer resin layer.

[0034] The outer resin layer may have excellent tensile strength and weather resistance relative to its thickness and may have electrical insulation properties to protect the secondary battery 100 from the outside. The outer resin layer may include polyethylene terephthalate (PET) resin or nylon resin. The metal layer may prevent air, moisture, etc. from entering the interior of the secondary battery 100. The metal layer may include aluminum (Al). The inner resin layers may be heat-sealed to each other by applying heat and pressure with the electrode assembly 200 inside. The inner resin layer may include a thermoplastic resin such as cast polypropylene (CPP) or polypropylene (PP).

[0035] Each of the upper case 310 and the lower case 320 may have a recessed receiving portion 300ST in which the electrode assembly 200 can be seated. Rim portions 300S1 and 300S2 including an area where a sealing portion 340 is to be formed are provided along the outer periphery of the receiving portion 300ST for each of the upper case 310 and the lower case 320. The rim portion 300S1 of the upper case 310 and the rim portion 300S2 of the lower case 320 are in contact with each other, and the area corresponding to the sealing portion 340 is heat-sealed to form the sealing portion 340, thereby sealing the pouch-type case 300.

[0036] The sealing portion 340 includes a notch 330 formed at one end of one side of the pouch-type case 300 where the electrode leads 210 and 220 protrude outward. The notch 330 has a shape that is recessed toward the inside of the pouch-type case 300. That is, as shown in Figures 2 to 4, the notch 330 has a shape with a concave curvature toward the inside of the pouch-type case 300.

[0037] In this case, the notch 330 is formed only at one end of one side from which the electrode leads 210 and 220 protrude, and not at the other end located on the opposite side. For example, in FIG. 4, one side of the pouch-type case 300 from which the electrode leads 210 protrude is aligned with the x-axis direction, and the notch 330 is formed at the end on the positive side of the x-axis direction, i.e., the lower end in the drawing, and not the end on the negative side, i.e., the upper end in the drawing. With this configuration, if a fire breaks out inside the pouch-type case 300, causing a rise in temperature and generating gas, the flame and gas can be vented through the notch 330 before the sealing part 340 on the electrode leads 210 and 220 side is damaged by pressure. That is, if notch portion 330 is not formed, it is difficult to predict the position where the flame and gas will vent, and in particular, the portion where electrode leads 210 and 220 are arranged may have slightly weaker sealing than other portions, and if the flame vents through this portion, other components connected adjacent to electrode leads 210 and 220 may be rapidly engulfed in flame, and as a result, the secondary battery 100 and the entire battery module including the secondary battery 100 may also be engulfed in flame. However, by forming notch portion 330 only on one side of the positions where electrode leads 210 and 220 are formed as in this embodiment, the vent of the flame and gas can be guided to the specific position where notch portion 330 is formed, thereby delaying heat propagation.

[0038] The shape of the notch 330 can achieve the aforementioned effect by having a concave curvature toward the inside, as shown in FIGS. 2 to 4. In other words, simply making the corners more steep or narrower than the width of the remaining sealing portion 340 is not sufficient to induce flame and gas venting. In this case, the radius of curvature of the notch 330 may be 2 mm or less. If the radius of curvature is greater than 2 mm, the notch 330 may not be fully formed, and venting may occur in other areas where the notch 330 is not formed. Furthermore, the width of the notch 330 may be the same as or smaller than the width of the remaining portion of the sealing portion 340, i.e., the width of the remaining portion of the sealing portion 340 excluding the notch 330. Furthermore, the shape of the notch portion 330 may be formed so that the sealing portion 340 extending along the edge of the pouch-type case 300 is recessed inward to form a generally right-angled shape, with the apex of the right-angled shape having a radius of curvature of 2 mm or less. That is, for example, in FIG. 4, the notch portion 330 may extend inward along the negative y-axis direction and then extend along the positive x-axis direction to form a generally right-angled shape, with the apex, which is the innermost portion, having a curved shape with a radius of curvature of 2 mm or less. Furthermore, in this shape, the lengths of the portions extending inward along each axis may be, but are not limited to, approximately 7 mm or more and approximately 13 mm or less, and may vary depending on the width and shape of the sealing portion 340 and the rim portions 300S1 and 300S2.

[0039] In this way, by providing a notch portion 330 having a curvature that is concave toward the inside of the pouch-type case 300 only at one end of the protruding sides of the electrode leads 210, 220, if gas is generated inside the pouch-type case 300 or pressure increases due to an internal fire, venting can be induced through the notch portion 330, thereby preventing the rapid spread of flames and delaying the spread of heat.

[0040] Next, first to third modified examples of the embodiment of the present invention will be described with reference to FIGS.

[0041] FIG. 5 is a diagram showing a secondary battery according to a first modified example of the present invention, FIG. 6 is a diagram showing a secondary battery according to a second modified example of the present invention, and FIG. 7 is a diagram showing a secondary battery according to a third modified example of the present invention.

[0042] 5, in the secondary battery according to the first modified example of the present invention, the edge portion of the pouch-type case 300 where the notch portion 330 is formed is not cut along the shape of the notch portion 330. That is, the sealing portion 340 is completed through a sealing process using heat fusion, and at this time, the notch portion 330 can be formed in the sealing portion 340 by performing heat fusion along the shape of the notch portion 330. Therefore, the remaining portion of the pouch-type case 300 that is not heat fused remains as it is. That is, because the shape of the notch portion 330 is not obtained by deformation such as cutting or trimming, but is a part of the shape of the sealing portion 340 obtained by heat fusion, it is possible to easily provide the notch portion 330 without an additional molding process.

[0043] 6, the secondary battery according to the second modified example of the present invention has a configuration in which the upper case 310 and the lower case 320 of the pouch-type case 300 are connected rather than separated from each other. That is, the pouch-type case 300 can be completed by folding either the upper case 310 or the lower case 320. In this case, the folded portion can be sealed without the sealing unit 340, and therefore, the sealing unit 340 is formed along three sides of the pouch-type case 300 as shown in FIG. 6. Therefore, the notch 330 can be formed adjacent to the folding line (the line constituting the bottommost part in FIG. 6), and in this case, the end of the notch 330 located farther from the electrode lead 210 can be formed to abut the folding line as shown in FIG. 6.

[0044] Referring to FIG. 7, the secondary battery according to the third modified example of the present invention may include notches 330 on both longitudinal end portions of the secondary battery 100. That is, notches 330 may be included on both end portions from which the electrode leads 210 and 220 protrude. In this case, the vent position can be controlled by forming the notch 330 on only one side of the electrode leads 210 and 220. For example, in FIG. 7, the notch 330 can be formed only on the corner of the end portion in the positive x-axis direction. With this configuration, when a plurality of secondary batteries 100 are stacked upright to form a battery module, the portions with the notches 330 can be collectively arranged on the lower side. In the event of thermal runaway, the vent direction can be controlled to the lower side of the module, thereby preventing rapid flame waves and slowing heat propagation.

[0045] Next, with reference to FIG. 8, the results of testing the vent induction effect depending on the shape of the notch will be described.

[0046] 8(a) and 8(b) are diagrams for explaining the state of the secondary batteries according to the example of the present invention and the comparative example during testing, respectively.

[0047] The corner portions in (a) and (b) of FIG. 8 are both based on the second modified example, ie, the example shown in FIG.

[0048] As shown in Fig. 8(a), in the example, the notch portion 330 was designed to have a curvature radius, and experiments were conducted by setting the widths a, b, and c of each portion to different values. Furthermore, as shown in Fig. 8(b), in the comparative example, the sealing portion 34 was formed to have an inclination at the corner adjacent to the electrode lead 21, and experiments were conducted by setting the width (b) of the inclined portion to different values.

[0049] In each example and comparative example, when the internal temperature of the secondary battery was increased to increase the internal pressure, if venting occurred first at notch 330 or a position corresponding to notch 330, it was determined to have passed, but if venting occurred first at another position other than notch 330, such as a position corresponding to an electrode lead, it was determined to have failed. The dimensions of each part, the pressure at the time of venting, and the test results for each example and comparative example are shown in Table 1 below.

[0050] [Table 1]

[0051] As shown in Table 1, when a notch portion 330 having a curvature is formed as in Examples 1 to 4, it was confirmed that venting occurs first through the notch portion 330 before venting occurs in other areas, regardless of the widths of the sealing portion and notch portion. In contrast, as shown in Comparative Examples 1 and 2, even when the width (b) of a corner (inclined portion) is modified to be smaller than the width (c) of the sealing portion 34 in order to induce venting in the corner (inclined portion), venting occurs in other areas before venting in the corner (inclined portion), and thus there is no vent-inducing effect.

[0052] In addition, a plurality of pouch-type secondary batteries according to embodiments of the present invention may be assembled to form a battery module. In this case, by arranging the notches included in the secondary batteries in the battery module in the same direction (e.g., at the bottom of the battery module), the vent direction can be controlled in a fixed direction when thermal runaway occurs, thereby preventing rapid flame propagation and delaying heat propagation.

[0053] Furthermore, one or more such battery modules can be packaged within a pack case to form a battery pack.

[0054] The above-described battery module and battery pack including the battery module can be applied to various devices, including transportation means such as electric bicycles, electric cars, and hybrid cars, but the present invention is not limited thereto and can be applied to various devices that can use a battery module and a battery pack including the battery module, which also fall within the scope of the present invention.

[0055] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0056] 10 Secondary battery 20 Electrode assembly 21 Electrode lead (lead part) 34 Sealing section 100 Secondary battery 200 electrode assembly 210 Electrode lead (positive lead) 220 Electrode lead (negative electrode lead) 300 pouch-type case 300S1 rim 300S2 rim 300ST storage area 310 Upper Case 320 Lower Case 330 Notch 340 Sealing section a width b Width c width

Claims

1. an electrode assembly; and a pouch-type case incorporating the electrode assembly and including an upper case and a lower case that are heat-sealed to each other; A secondary battery comprising: the pouch-type case includes a sealing portion formed along at least a portion of an edge of the pouch-type case by heat-sealing the upper case and the lower case, an electrode lead connected to the electrode assembly protrudes from one side of the pouch-type case; the sealing portion includes a notch portion formed at one end of the side from which the electrode lead protrudes, the notch portion has a curvature that is concave toward the inside of the pouch-type case, The other end portion located opposite to the end portion having the notch portion is not formed with the notch portion, and the electrode lead is inserted between the end portion and the other end portion, The radius of curvature of the notch portion is 2 mm or less. Secondary battery.

2. The secondary battery of claim 1 , wherein the width of the notch is equal to or smaller than the width of the sealing portion excluding the notch.

3. The secondary battery according to claim 1 , wherein the electrode leads protrude from both longitudinal sides of the pouch-shaped case.

4. The secondary battery according to claim 3 , wherein the electrode leads are provided on both sides of the battery, the electrode leads being projected from the both sides, and each of the electrode leads includes a notch at an end thereof on the same side relative to the electrode leads.

5. The secondary battery according to claim 1 , wherein a portion of the upper case and the lower case that is not heat-sealed is disposed between the notch and the edge of the pouch-shaped case.

6. The upper case and the lower case are integrally formed across a bending line, The secondary battery according to claim 1 , wherein the notch is disposed adjacent to the folding line.

7. A battery module comprising a plurality of secondary batteries according to any one of claims 1 to 6.

8. The battery module according to claim 7 , wherein the notches of the plurality of secondary batteries are all arranged in the same direction.

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