Battery cell and battery module including the same

Abstract

A battery cell according to the present invention includes an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, a cell case in which the electrode assembly is housed, and an electrode lead connected to the electrode assembly and protruding from one end of the cell case, the cell case including a housing portion in which the electrode assembly is housed and a sealing portion formed on a periphery of the cell case to seal the electrode assembly, and a reinforcing member is located on an outer surface of the cell case joined by the sealing portion.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0116869 dated September 2, 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 battery cell and a battery module including the same, and more particularly to a battery cell with an improved sealing level and a battery module including the same. [Background technology]

[0003] Due to the rapid development of mobile device technology and the increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Therefore, research into secondary batteries that can meet various demands is being actively conducted.

[0004] Currently, commercially available secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium secondary batteries. Among these, lithium secondary batteries are attracting attention due to their advantages of being freely chargeable and dischargeable, having a low self-discharge rate, and high energy density.

[0005] Depending on the shape of the battery case, secondary batteries are classified into cylindrical batteries and prismatic batteries, in which the electrode assembly is housed in a cylindrical or prismatic metal can, and pouch batteries, in which the electrode assembly is housed in a pouch-type case made of aluminum laminate sheet.

[0006] Secondary batteries can also be classified by the structure of the electrode assembly, which is a stacked structure consisting of a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. Representative examples include a jelly-roll (wound) electrode assembly, in which long sheet-type positive and negative electrodes are wound with a separator interposed between them, and a stacked (laminate) electrode assembly, in which multiple positive and negative electrodes cut to a predetermined size are stacked in order with a separator interposed between them. Recently, to address the issues inherent in the jelly-roll and stacked electrode assemblies, stacked / folded electrode assemblies, which are a hybrid of the jelly-roll and stacked types, have been developed. Among these, pouch-type batteries, which have a stacked or stacked / folded electrode assembly housed in a pouch-type battery case made of a laminate sheet, are increasingly being used due to their low manufacturing costs, light weight, and easy modification.

[0007] FIG. 1 is a perspective view of a conventional pouch-type battery cell.

[0008] 1, a conventional pouch-type battery cell may include a cell case 14 made of a laminate sheet that houses an electrode assembly including a positive electrode, a negative electrode, and a separator. Specifically, the electrode assembly mounted in a receiving portion 15 in the center of the cell case 14 is protected from the outside by heat-sealing a sealing portion 16 around the periphery of the cell case 14. Electrode leads 11 and 12 connected to electrode taps of the electrode assembly inside the cell case 14 are extended to the outside of the cell case 14 through the sealing portion 16, and lead films 18 are positioned between the upper and lower surfaces of the electrode leads 11 and 12 and the sealing portion 16.

[0009] Meanwhile, because the sealing portion 16 of the battery cell 10 is mainly joined by heat fusion, there is a problem that there is a large deviation in rigidity depending on the position, and therefore, it easily breaks when the internal pressure of the battery cell 10 increases. If the sealing portion 16 of the battery cell 10 or its surrounding area opens and gas inside the battery cell 10 is released, a fire may break out in the battery cell 10, and the fire may spread to adjacent battery cells 10.

[0010] Recently, as the energy density of battery cells has increased, the amount of gas generated inside the battery cells has also increased, making this problem even more serious. Summary of the Invention [Problem to be solved by the invention]

[0011] SUMMARY OF THE INVENTION An object of the present invention is to provide a battery cell and a battery module including the same, in which deviation in rigidity of a sealing portion is eliminated.

[0012] However, the problems to be solved by the embodiments of the present invention are not limited to the above problems, but may be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0013] A battery cell according to one embodiment of the present invention includes an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, a cell case in which the electrode assembly is housed, and an electrode lead connected to the electrode assembly and protruding from one end of the cell case, the cell case including a housing portion in which the electrode assembly is housed and a sealing portion formed around the periphery of the cell case to seal the electrode assembly, and a reinforcing member positioned on the outer surface of the cell case joined by the sealing portion.

[0014] The reinforcing member may be located at a position corresponding to the sealing portion.

[0015] The reinforcing member may be located at a position on the cell casing corresponding to the electrode lead.

[0016] The reinforcing member may have a predetermined length and a predetermined width.

[0017] The reinforcing member may include a bending portion bent to have a curvature, an extension portion extending from the bending portion, and a connection portion connecting both ends of the extension portion.

[0018] A bent portion may be formed between the bending portion and the extension portion.

[0019] The extension portion may include a first extension portion and a second extension portion extending from both ends of the bending portion, and a gap between the first extension portion and the second extension portion may have a value smaller than a maximum diameter of the bending portion.

[0020] The connecting portion may have a shape extending from the first extension portion to the second extension portion, and a locking portion may be formed at a portion of the connecting portion that contacts the second extension portion.

[0021] The connecting portion may be formed by twisting the portions extended from the first extension portion and the second extension portion together.

[0022] A reinforcing tape may be provided on the outer surface of the cell case joined by the sealing portion.

[0023] A battery module according to another embodiment of the present invention includes at least one battery cell as described above. [Effects of the Invention]

[0024] According to an embodiment, the present invention can eliminate rigidity deviation of the sealing portion and minimize gas emission from the battery cell by providing an additional member around the sealing portion of the battery cell.

[0025] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned above will be apparent to those skilled in the art from the claims. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a perspective view of a conventional pouch-type battery cell. [Figure 2] 1 is a perspective view of a battery cell according to an embodiment of the present invention; [Figure 3] 3 is a diagram showing a weak area in the battery cell of FIG. 2. [Figure 4] 4 is a diagram showing a cross section taken along the line AA in FIG. 3 when a gas pocket occurs. [Figure 5] and [Figure 6] 1 is a view showing a battery cell provided with a reinforcing tape according to an embodiment of the present invention. [Figure 7] 7 is a view showing the cross section BB of FIG. 6 when a gas pocket occurs. [Figure 8] 10 is a view showing an example in which a reinforcing member is provided in a battery cell according to another embodiment of the present invention; [Figure 9] 10 is a view showing another example in which a reinforcing member is provided in a battery cell according to another embodiment of the present invention; [Figure 10] 1 is a diagram showing an example of a battery cell according to another embodiment of the present invention. [Figure 11] 10 is a diagram showing another example of a battery cell according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily understand and practice the present invention. The present invention may be embodied in various different forms other than those described below, and the scope of the present invention is not limited to the embodiments described herein.

[0028] In order to clearly explain the present invention, parts not necessary for the explanation will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0029] Furthermore, the size and thickness of each component shown in the drawings are arbitrarily enlarged or reduced for the sake of convenience, and it is obvious that the contents of the present invention are not limited to those shown. In the following drawings, the thickness of each layer is enlarged to clearly show multiple layers and regions. In the following drawings, the thickness of some layers and regions is exaggerated for the sake of convenience.

[0030] Furthermore, when a layer, film, region, plate, etc. is described as being "above" or "on" another portion, this should be interpreted as including not only the case where the layer, film, region, plate, etc. is "directly above" the other portion, but also the case where there are other portions therebetween. Conversely, when a layer, film, region, plate, etc. is described as being "directly above" the other portion, it means that there are no other portions therebetween. Furthermore, being "above" or "on" a reference portion means being located above or below the reference portion, and does not necessarily mean being located "on" or "above" the direction opposite to gravity. Meanwhile, it should be clear from the above that just as something is described as being "above" or "on" another portion, something can also be described as being "below" or "below" another portion.

[0031] Also, throughout the specification, when a part "comprises" other elements, this does not mean that it excludes other elements, but that it can further include other elements, unless specifically stated to the contrary.

[0032] Furthermore, throughout the specification, "on a plane" means when the part in question is viewed from above, and "on a cross section" means when the part in question is cut vertically and viewed from the side.

[0033] Hereinafter, a battery cell according to an embodiment of the present invention will be described.

[0034] FIG. 2 is a perspective view of a battery cell according to one embodiment of the present invention.

[0035] 2, the battery cell 110 may be provided in a pouch type, which maximizes the number of cells stacked per unit area. The pouch type battery cell 110 may be manufactured by placing an electrode assembly in a cell case 114 and then heat-sealing the periphery of the cell case 114. Here, the electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, and may be provided in a jelly-roll type (wound type), stack type (layered type), or composite type (stack / folded type) structure.

[0036] The cell casing 114 may include a receiving portion 115 for receiving the electrode assembly and a sealing portion 116 formed around the periphery of the cell casing 114 to seal the electrode assembly. The cell casing 114 may have a laminate structure of a resin layer / metal thin film layer / resin layer.

[0037] The cell case 114 may be provided in a form in which the laminate sheet is folded and the periphery of the adjacent corners is sealed. In this case, the internal space formed by folding the sheet may be a receiving portion 115 for accommodating the electrode assembly, and the three open corners of the folded sheet may be sealed to form a sealing portion 116.

[0038] Here, the sealing portion 116 is shown as being formed on both ends 114a, 114b of the cell casing 114 and one side 114c connecting them, but this is not necessarily the case, and it can also be formed on all corners of the cell casing 114.

[0039] The electrode leads 111 and 112 protrude outward from the cell case 114 through the sealing portion 116. Specifically, one end of each electrode lead 111 and 112 is located inside the battery cell 110 and electrically connected to a positive or negative electrode tab of the electrode assembly, and the other end of each electrode lead 111 and 112 is led out of the battery cell 110 and electrically connected to a separate member, for example, a bus bar.

[0040] The lead film 118 may be positioned on the upper or lower surface of the electrode leads 111, 112 corresponding to the sealing portion 116. The lead film 118 may prevent a short circuit from occurring in the electrode leads 111, 112 when the sealing portion 116 is heat-sealed or press-sealed. In addition, the lead film 118 may improve the sealing performance between the sealing portion 116 and the electrode leads 111, 112 by being positioned between the sealing portion 116 and the electrode leads 111, 112.

[0041] The lead film 118 may have a width wider than that of the electrode leads 111 and 112. The lead film 118 may have a length greater than that of the sealing portion 116 based on the protruding direction of the electrode leads 111 and 112, and may have a length smaller than that of the electrode leads 111 and 112. As a result, the lead film 118 does not interfere with the electrical connection of the electrode leads 111 and 112, and can prevent the sides of the electrode leads 111 and 112 from being exposed to the outside.

[0042] Figure 3 is a diagram showing a weak area in the battery cell of Figure 2. Figure 4 is a diagram showing a cross section taken along the line AA in Figure 3 when a gas pocket occurs.

[0043] 3 and 4, a battery cell 110 may include electrode leads 111 and 112 that protrude from one end of a cell casing 114 via a sealing portion 116. Because the electrode leads 111 and 112 pass through the sealing portion 116, the sealing portions 116 formed at both ends 114a and 114b where the electrode leads 111 and 112 are located may have a greater rigidity deviation than the sealing portion 116 formed at one side 114c. Thus, the areas around the sealing portions 116 formed at both ends 114a and 114b may be referred to as weak areas 120 that are easily opened by internal pressure.

[0044] Here, through the drawings and explanation, the fragile area 120 of the present invention may be described based on one end of the battery cell, but it is not necessarily limited to this, and it is to be made clear in advance that the same or similar content may be described in the case of the other end of the battery cell.

[0045] 4, when a gas pocket is formed inside the battery cell 110 due to heat generation of the battery cell 110, thereby increasing the internal pressure of the battery cell 110, the weak area 120 may be opened more easily than other areas of the battery cell 110. Therefore, it may be desirable to provide the battery cell 110 with a member to supplement the rigidity of the weak area 120.

[0046] The following describes the reinforcing tape 210 and reinforcing member 220 of the present invention, which are provided to supplement the rigidity of the weakened region 120.

[0047] 5 and 6 are views showing a battery cell provided with a reinforcing tape according to an embodiment of the present invention, and Fig. 7 is a view showing a cross section BB of Fig. 6 when a gas pocket occurs.

[0048] 5 and 6 , a reinforcing tape 210 may be provided in the vulnerable region 120 of the battery cell 110 according to this embodiment. Specifically, the reinforcing tape 210 may be provided on the outer surface of the cell casing 114 to secure the two surfaces of the cell casing 114 joined by the sealing portion 116. The reinforcing tape 210 may be provided to correspond to the sealing portions 116 formed on both ends 114a and 114b of the cell casing 114. The reinforcing tape 210 may be provided inside the cell casing 114 to correspond to the portion where the electrode leads 111 and 112 are located or the portion where the lead film 118 is located. Although the drawings illustrate the reinforcing tape 210 being provided on one surface of the battery cell 110, it is obvious that the reinforcing tape 210 may also be provided on the other surface of the battery cell 110. For example, the reinforcing tape 210 may be provided in a form that wraps around both surfaces of the vulnerable region.

[0049] The reinforcing tape 210 in Fig. 5 is illustrated as an example that entirely covers the area corresponding to the lead film 118, and the reinforcing tape 210 in Fig. 6 is illustrated as an example that partially covers the area corresponding to the lead film 118. Thus, although Figs. 5 and 6 show the reinforcing tape 210 being provided in part of the weakened area 120, this is not necessarily the case, and the reinforcing tape 210 may be provided in the entire weakened area 120 or may be provided to cover an area different from that shown in the drawings.

[0050] The reinforcing tape 210 may be coated with adhesive on one side. The inclusion of adhesive allows the reinforcing tape 210 to be easily attached to the cell casing 114. The reinforcing tape 210 may be easy to process. The reinforcing tape 210 can be easily adjusted in size by cutting, etc., so that when applied to the cell casing 114, the size can be easily adjusted to fit the size intended by the designer. In addition, the reinforcing tape 210 may be made of a material having a certain level of toughness. For example, the reinforcing tape 210 may be a PET tape, a silicone tape, or an aluminum (AL) tape.

[0051] 7, the reinforcing tape 210 can supplement the rigidity of the sealing portion 116. If a gas pocket occurs inside the battery cell 110 due to overheating of the battery cell 110, the reinforcing tape 210 can minimize the shear force applied to the sealing portion 116. In addition, the reinforcing tape 210 can prevent the gas inside the battery cell 110 from escaping to the outside by preventing the sealing portion 116 from opening. Therefore, it may be desirable to provide the reinforcing tape 210 at the outermost end of the sealing portion 116, outside the sealing portion 116, or at the outermost end of the cell casing 114, specifically, near the protruding electrode leads 111 and 112.

[0052] On the other hand, if a large gas pocket is formed inside the battery cell 110, causing a large pressure, the stiffness of the reinforcing tape 210 may not be sufficient to minimize the shear force applied to the sealing portion 116. Therefore, a reinforcing member 220 having a stiffness higher than that of the reinforcing tape 210 will be described below.

[0053] Fig. 8 is a view showing an example in which a reinforcing member is provided in a battery cell according to another embodiment of the present invention, and Fig. 9 is a view showing another example in which a reinforcing member is provided in a battery cell according to another embodiment of the present invention.

[0054] 8 and 9, a reinforcing member 220 may be provided in the weak area 120 of the battery cell 110 according to this embodiment. The reinforcing member 220 is provided on the outer surface of the cell casing 114, and the reinforcing member 220 can firmly support the outer surface of the cell casing 114 and minimize the shear force applied to the sealing portion 116.

[0055] The reinforcing member 220 may be formed by molding a long member so that both ends in the length direction abut and then connecting the ends. The reinforcing member 220 may have a folded shape. The reinforcing member 220 may be provided to have a width as shown in Fig. 8. Alternatively, the reinforcing member 220 may be provided in the form of a line having only a narrow width or length as shown in Fig. 9.

[0056] The reinforcing member 220 may be made of a material that has high rigidity but is also flexible, for example, the reinforcing member 220 may be made of metal, plastic, or other materials.

[0057] The reinforcing member 220 may include a bending portion 222, an extension portion 224, and a connecting portion 226. Here, the bending portion 222 refers to the portion bent to form the reinforcing member 220, the connecting portion 226 refers to the portion where both ends of the member are connected, and the extension portion 224 refers to the portion extending from the bending portion 222 to the connecting portion 226. For ease of explanation, the two portions of the reinforcing member 220 that face each other due to being bent by the bending portion 222, i.e., the two portions of the extension portion 224 extending from both ends of the bending portion 222, may be referred to as a first extension portion 224a and a second extension portion 224b.

[0058] The reinforcing member 220 may be fitted between the bending portion 222 and the connecting portion 226 to fix the two surfaces of the cell casing 114. The reinforcing member 220 may be provided to correspond to the sealing portions 116 formed on both ends 114a and 114b of the cell casing 114. The reinforcing member 220 may be provided inside the cell casing 114 to correspond to the portion where the electrode leads 111 and 112 are located or the portion where the lead film 118 is located.

[0059] The reinforcing member 220 may have a gap between the first extension 224a and the second extension 224b for fitting two surfaces of the cell casing 114, i.e., the ends of the battery cells 110. In this case, the size of the gap must be wide enough to allow the ends of the battery cells 110 to be inserted, but narrow enough to prevent the ends of the fitted battery cells 110 from slipping out. In this case, it may be desirable for the gap between the first extension 224a and the second extension 224b to be constant depending on its position. This may be so that the reinforcing member 220 can support two surfaces of the cell casing 114 evenly.

[0060] A bent portion 223 may be formed between the bending portion 222 and the extension portion 224. The bent portion 223 may be a portion bent toward the inside of the reinforcing member 220 between the bending portion 222 and the extension portion 224. Because the bending portion 222 has a round shape with a curvature, if the extension portion 224 is connected to the bending portion 222 without the bent portion 223, the maximum diameter of the bending portion 222 may be the size of the gap between the first extension portion 224a and the second extension portion 224b. However, if the bent portion 223 is formed between the bending portion 222 and the extension portion 224, the maximum diameter of the bending portion 222 and the size of the gap between the first extension portion 224a and the second extension portion 224b may be different, allowing for more flexible design. Here, the maximum diameter may refer to the inner diameter of the bending portion 222. Also, if the bending portion 222 does not form a perfect circle or semicircle, the maximum distance in the bending portion 222 from the first extension portion 224a toward the second extension portion 224b may be replaced with the above-mentioned maximum diameter.

[0061] Meanwhile, if the gap is slightly narrower than the thickness of the end of the battery cell 110, the first extension 224a and the second extension 224b may become separated. In this case, the bending portion 222 is subjected to tension, reducing its curvature. As a result, the distance between the first extension 224a and the second extension 224b increases, and the connecting portion 226 located at the end of the extension 224 may receive excessive pressure. However, if the reinforcing member 220 has a bent portion 223, the bent portion 223 deforms as the curvature of the bent portion 222 decreases, thereby expanding the gap between the first extension 224a and the second extension 224b overall, thereby minimizing the above-mentioned problem.

[0062] The connecting portion 226 may be a portion for connecting one end of the first extension portion 224a and one end of the second extension portion 224b to each other. Through the connecting portion 226, the reinforcing member 220 can maintain its shape and stably support the end of the battery cell 110.

[0063] The connector 226 can be provided in a variety of shapes.

[0064] 8, the connecting portion 226 may have a shape that extends from one of the first extension portion 224a and the second extension portion 224b to the other. For example, the connecting portion 226 may be fixed to the first extension portion 224a and extend toward the second extension portion 224b. In this case, a locking portion may be formed at the portion of the connecting portion 226 that contacts the second extension portion 224b, and the locking portion may be hooked onto the second extension portion 224b, thereby stably connecting the first extension portion 224a and the second extension portion 224b.

[0065] As another example, the connection portion 226 may extend from each of the first extension portion 224a and the second extension portion 224b, as shown in FIG. 9, and be formed by twisting the ends of these extension portions. This may be referred to as a twisted shape. The connection portion 226 provided in a twisted shape may be formed by twisting the ends of the first extension portion 224a and the second extension portion 224b, so the position of the connection portion 226 may be flexible. Specifically, even if the first extension portion 224a and the second extension portion 224b are formed somewhat long, the reinforcing member 220 and the battery cell 110 can be coupled to fit snugly by adjusting the position of the connection portion 226.

[0066] The shape of the connection portion 226 is not limited to the above examples and drawings, and may be provided in various shapes not mentioned.

[0067] Figure 10 is a diagram showing an example of a battery cell according to another embodiment of the present invention, and Figure 11 is a diagram showing another example of a battery cell according to another embodiment of the present invention.

[0068] 10 and 11 , a reinforcing tape 210 and a reinforcing member 220 may be provided in the weakened region 120 of the battery cell 110 according to this embodiment. When the reinforcing tape 210 and the reinforcing member 220 are provided on the battery cell 110, if a gas pocket is formed inside the battery cell 110, the reinforcing member 220 minimizes the shear force applied to the sealing portion 116, and the reinforcing tape 210 can prevent the sealing portion 116 from opening. Here, it may be preferable to provide the reinforcing tape 210 at the outermost end of the sealing portion 116, outside the sealing portion 116, or the outermost end of the cell casing 114, specifically, in a position close to the protruding electrode leads 111 and 112. Meanwhile, detailed descriptions of the reinforcing tape 210 and the reinforcing member 220 have been provided in the above-described embodiments, and therefore will not be repeated in this embodiment.

[0069] Meanwhile, the above-mentioned battery cells 110 may be included in a battery module or a battery pack. Here, a battery pack may be formed by packaging one or more battery modules in a pack case. Also, a battery module may be formed by modularizing one or more battery cells 110. However, the battery cells 110 included in the battery pack may not be packaged in a separate frame like a battery module, but may be directly installed in the pack case of the battery pack. Also, the battery pack may additionally include a Battery Management System (BMS) that manages the temperature and voltage of the battery, a cooling device, etc.

[0070] The battery module including the above-described battery cell 110 and the battery pack including the same are applicable to various devices. Such devices are applicable to 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 the battery module and the battery pack including the same, which also fall within the scope of the present invention.

[0071] 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]

[0072] 110 battery cells 111, 112 Electrode leads 114 Cell Case 115 Storage section 116 Sealing part 118 Lead Film 120 Vulnerable Area 210 Reinforcement tape 220 Reinforcement member

Claims

1. an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a cell case in which the electrode assembly is housed; an electrode lead connected to the electrode assembly and protruding from one end of the cell case; In a battery cell including: the cell case includes a receiving portion that receives the electrode assembly and a sealing portion that is formed on a periphery of the cell case and seals the electrode assembly; the electrode lead protrudes outward from the inside of the cell casing through the sealing portion, a reinforcing member is positioned on an outer surface of the cell case joined by the sealing portion; the reinforcing member is externally attached to a position corresponding to the sealing portion of the one end of the cell casing where the electrode lead is located, The reinforcing member includes a bending portion bent to have a curvature, an extension portion extending from the bending portion, and a connection portion to which both ends of the extension portion are connected. Battery cell.

2. The battery cell according to claim 1 , wherein the reinforcing member is located inside the cell case at a position corresponding to the electrode lead.

3. The battery cell of claim 1 , wherein the reinforcing member has a predetermined length and a predetermined width.

4. The battery cell according to claim 1 , wherein a bent portion is formed between the bent portion and the extension portion.

5. the extension portion includes a first extension portion and a second extension portion extending from both ends of the bent portion, The battery cell according to claim 1 , wherein a gap between the first extension portion and the second extension portion has a value smaller than a maximum diameter of the bent portion.

6. The battery cell according to claim 5 , wherein the connection portion has a shape extending from the first extension portion to the second extension portion, and a locking portion is formed at a portion of the connection portion that contacts the second extension portion.

7. The battery cell according to claim 5 , wherein the connection portion is formed by twisting portions extended from the first extension portion and the second extension portion together.

8. The battery cell according to claim 1 , wherein a reinforcing tape is provided on the outer surface of the cell case joined by the sealing portion.

9. A battery module comprising at least one battery cell according to any one of claims 1 to 8.

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