Secondary battery and battery pack including this secondary battery

Abstract

The invention relates to a secondary battery and a battery pack comprising such a secondary battery. The secondary battery, in one aspect of the invention, may consist of: an electrode assembly extending in one direction; an outer membrane enclosing a portion of the electrode assembly; and caps covering the remainder of the electrode assembly, wherein the caps may consist of: a cap covering one side of the electrode assembly in the direction of extension of the electrode assembly; a coupling part consisting of a coupling part arranged on the outer surface of the cap and coupled to the outer membrane; and an electrode tip which at least part of it is exposed outside the cap and electrically connected to the electrode assembly, wherein the coupling part of the coupling part consists of a first layer comprising a first layer of resin and having an outer surface allowing coupling to the inner surface of the outer membrane and an inner surface allowing coupling to the outer surface of the cap.

Description

Secondary battery and battery pack including the same The present invention relates to a secondary battery and a battery pack including the same. In recent years, rising energy prices due to the depletion of fossil fuels and growing concerns about environmental pollution have made the demand for eco-friendly alternative energy sources essential for future living. Research is continuing into various power generation technologies, such as solar, wind, and tidal power. Furthermore, significant interest is being focused on power storage devices, such as batteries, to more efficiently utilize the generated electricity. Moreover, with the technological development and increasing demand for battery-powered electronic mobile devices and electric vehicles, the demand for batteries as an energy source is rapidly increasing, and accordingly, much research is being conducted on batteries that can meet various needs. Batteries that store electrical energy can generally be divided into primary and secondary batteries. Primary batteries are disposable, consumable batteries, whereas secondary batteries are rechargeable batteries manufactured using materials capable of repeatable oxidation and reduction processes between current and a substance. In other words, when current causes a reduction reaction in a material, the battery is charged, and when an oxidation reaction occurs in the material, the battery is discharged. This repeated charging and discharging process generates electricity. Secondary batteries can be classified into cylindrical cells, pouch cells, and prismatic cells based on their shape. Among them, pouch cells can be manufactured in a form in which an electrode assembly in which a positive electrode, a negative electrode, and a separator are laminated is accommodated inside a pouch, and the outer part of the pouch is sealed. Secondary batteries can be classified into cylindrical cells, pouch cells, and prismatic cells based on their shape. Among them, pouch cells can be manufactured in a form in which an electrode assembly in which a positive electrode, a negative electrode, and a separator are laminated is accommodated inside a pouch, and the outer part of the pouch is sealed. Conventional pouch cells have problems with cracks occurring in the pouch film during the forming process, and a lot of pouch film is discarded after the degassing process. Furthermore, the depth that can be formed is limited due to the material properties of the pouch film, which limits the increase in battery capacity. Furthermore, since existing pouch cells form upper and lower cases using pouch film as cups and seal the outer sides of the two cases together to form the cell, there is also the problem that there are limitations in controlling or predicting the venting direction of the cell in situations where the internal pressure of the cell increases or an explosion may occur due to abnormal cell behavior. Accordingly, there is a need for a secondary battery having a form that can improve battery capacity while having relatively few restrictions on shape, and furthermore, there is a need for a secondary battery that can control the direction of gas emission and flame generation inside the cell. The object of the present invention is to provide a secondary battery having improved battery capacity, reduced amount of moisture flowing in from the outside, and improved structural stability while having fewer restrictions on shape. The object of the present invention is to provide a secondary battery having improved durability by having excellent sealing strength and being able to withstand a high level of internal pressure due to gas generated inside the secondary battery. The object of the present invention is to provide a secondary battery with improved safety by controlling the direction in which gas or flame generated inside the secondary battery can be ejected. [1] According to one aspect of the present invention, a secondary battery is provided, comprising: an electrode assembly extending in one direction; an outer film covering a portion of the electrode assembly; and a cap covering the remainder of the electrode assembly, wherein the cap comprises: a cover portion covering one side of the electrode assembly in the extending direction; a connection portion including a coupling portion provided on an outer surface of the cover portion and coupled to the outer film; and a terminal portion at least partially exposed to the outside of the cover portion and electrically connected to the electrode assembly, wherein the coupling portion of the connection portion includes a first layer including a first resin and having an outer surface allowing coupling with an inner surface of the outer film and an inner surface allowing coupling with an outer surface of the cover portion. [2] In the above [1], the first resin has a melting point (T m ) resin having a melting point (T ) of 135°C to 150°C, a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and a melting point (T ) of m ) may include a resin selected from the group consisting of resins having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C and a melting point of 135°C to 150°C. [3] In the above [1] and / or [2], the first resin may include a modified polyolefin resin. [4] In at least one of the above [1] to [3], the joining portion of the connecting portion may include a first layer including a first resin and allowing joining with the outer surface of the cover portion, and a second layer including a second resin and laminated on the outer surface of the first layer and allowing joining with the inner surface of the outer film. [5] In the above [4], the first resin may include a resin selected from the group consisting of a resin having a melting point (Tm) of 135°C to 150°C, a resin having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and a resin having a melting point (Tm) of 135°C to 150°C and a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and the second resin may include a resin having a melting point (Tm) of 120°C to 145°C, a resin having a melt flow rate (MFR) of 5 g / 10 min to 18 g / 10 min at 230°C, and a resin having a melting point (Tm) of 120°C to 145°C and a melt flow rate (MFR) of 5 g / 10 min to It may include a resin selected from the group consisting of resins having a viscosity of 18 g / 10 min. [6] In the above [4] and / or [5], the first resin and the second resin can satisfy at least one selected from the relationship of the following formula 1 and the relationship of the following formula 2. [Formula 1] Tm2> Tm1 In the above equation 1, Tm1 is the melting point of the first resin, Tm2 is the melting point of the second resin, and the unit is ℃. [Formula 2] MFR2> MFR1 In the above equation 2, MFR1 is the melt flow rate of the first resin, MFR2 is the melt flow rate of the second resin, and the unit is g / 10 min. [7] In at least one of the above [4] to [6], the first resin may include a modified polyolefin-based resin, and the second resin may include a non-stretched polyolefin-based resin. [8] In at least one of the above [1] to [7], the joining portion of the connecting portion may include a first layer containing a first resin and allowing joining with the outer surface of the cover portion, a second layer containing a second resin and allowing joining with the inner surface of the outer film, and a third layer containing a third resin and disposed between the first layer and the second layer. [9] In the above [8], the first resin may include a resin selected from the group consisting of a resin having a melting point (Tm) of 135°C to 150°C, a resin having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and a resin having a melting point (Tm) of 135°C to 150°C and a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and the second resin may include a resin having a melting point (Tm) of 120°C to 145°C, a resin having a melt flow rate (MFR) of 5 g / 10 min to 18 g / 10 min at 230°C, and a resin having a melting point (Tm) of 120°C to 145°C and a melt flow rate (MFR) of 5 g / 10 min to 18 g / 10 min at 230°C. The third resin may include a resin selected from the group consisting of a resin having a melting point (Tm) of 145°C to 170°C, a resin having a melt flow rate (MFR) at 230°C of 2 g / 10 min to 4 g / 10 min, and a resin having a melting point (Tm) of 145°C to 170°C and a melt flow rate (MFR) at 230°C of 2 g / 10 min to 4 g / 10 min.

[0010] In the above [8] and / or [9], the first resin, the second resin, and the third resin can satisfy at least one selected from the relationship of the following formula 3 and the relationship of the following formula 4. [Formula 3] Tm3> Tm2> Tm1 In the above equation 3, Tm1 is the melting point of the first resin, Tm2 is the melting point of the second resin, and Tm3 is the melting point of the third resin, and the unit is ℃. [Formula 4] MFR2> MFR1> MFR3 In the above equation 4, MFR1 is the melt flow rate of the first resin, MFR2 is the melt flow rate of the second resin, and MFR3 is the melt flow rate of the third resin, and the unit is g / 10 min.

[0011] In at least one of the above [8] to

[0010] , the first resin may include a modified polyolefin-based resin, the second resin may include a non-stretched polyolefin-based resin, and the third resin may include a homopolyolefin-based resin.

[0012] In at least one of the above [1] to

[0011] , the connecting portion may include a connecting portion provided on at least one surface of the cover portion, excluding the outer surface of the cover portion on which the connecting portion is provided.

[0013] In the above

[0012] , the connecting portion of the connecting portion may include a first layer including a first resin and having an inner surface that allows bonding with one surface of the cover portion.

[0014] In the above

[0012] and / or

[0013] , the connecting portion of the connecting portion may include a first layer including a first resin and allowing bonding with one surface of the cover portion, and a second layer including a second resin and laminated on an outer surface of the first layer.

[0015] In at least one of the above

[0012] to

[0014] , the connecting portion of the connecting portion may include a first layer including a first resin and allowing bonding with one surface of the cover portion, a second layer including a second resin and disposed at the outermost portion, and a third layer including a third resin and disposed between the first layer and the second layer.

[0016] In at least one of the above [1] to

[0015] , the outer peripheral surface of the cover part may extend in the circumferential direction of the electrode assembly, and the joining portion may be provided on the outer peripheral surface of the cover part.

[0017] In at least one of the above [1] to

[0016] , the cover part includes a cover part having an outward surface facing the outside of the electrode assembly; and an extension part extending from the cover part toward the electrode assembly, and the joining part may be provided on the outer surface of the extension part.

[0018] In the above

[0017] , the cover portion has a plate shape, and the extension portion can extend from the edge of the cover portion.

[0019] In at least one of the above [1] to

[0018] , the outer film may have a predetermined flexibility so as to be bendable.

[0020] According to another aspect of the present invention, a method for manufacturing a secondary battery is provided, comprising the steps of: providing an electrode assembly including a positive electrode and a negative electrode and extending in one direction; surrounding a portion of the electrode assembly with an outer film; and covering a remaining portion of the electrode assembly with a cap, wherein the cap comprises: a cover portion covering one side of the electrode assembly in the extending direction; a connection portion including a coupling portion provided on an outer surface of the cover portion and coupled to the outer film; and a terminal portion at least partially exposed to the outside of the cover portion and electrically connected to the electrode assembly, wherein the coupling portion of the connection portion includes a first layer including a first resin and having an outer surface allowing coupling with an inner surface of the outer film and an inner surface allowing coupling with an outer surface of the cover portion.

[0021] According to another aspect of the present invention, there is provided a battery pack comprising: a secondary battery; and a packaging for accommodating the secondary battery, wherein the secondary battery comprises: an electrode assembly extending in one direction; an outer film covering a portion of the electrode assembly; and a cap covering the remainder of the electrode assembly, wherein the cap comprises: a cover portion covering one side of the electrode assembly in the extending direction; a connection portion including a coupling portion provided on an outer surface of the cover portion and coupled to the outer film; and a terminal portion at least partially exposed to the outside of the cover portion and electrically connected to the electrode assembly, wherein the coupling portion of the connection portion includes a first layer including a first resin and having an outer surface allowing coupling with an inner surface of the outer film and an inner surface allowing coupling with an outer surface of the cover portion. Since the secondary battery according to a preferred embodiment of the present invention does not have a process for forming an outer film, there are fewer restrictions on the shape in which the outer film accommodates the electrode assembly, the possibility of defects such as cracks occurring in the outer film is reduced, and the battery capacity can be improved. In addition, the safety of the secondary battery can be improved by reducing the degree to which moisture, etc., penetrates from the outside of the secondary battery into the inside of the secondary battery. In addition, since the sealing strength is excellent, it can withstand a high level of internal pressure due to gas generated inside the secondary battery, thereby improving the durability of the secondary battery. Additionally, the terminal portion and bus bar can be electrically connected to the electrode assembly in various forms. In addition, the structural stability of the secondary battery can be improved by the bonding relationship and arrangement of the connecting portion and the cover portion, and the structural stability can control the problem of venting to the cap portion in the event of an explosive increase in internal pressure or a flame eruption. In addition, the secondary battery can be efficiently electrically connected to the outside by the terminal portion penetrating the connecting portion. Additionally, the outer part of the connecting portion can protect the cover part of the cover portion from external contamination or impact. Additionally, the outer portion and the joining portion can be connected to improve the bonding between the joining portion and the cover portion. In addition, since the cover part is covered by the outer part, insulation between the cover part and other components can be improved, and heat transfer in a thermal runaway situation can be suppressed. Additionally, since the cover portion is entirely surrounded by the connecting portion, the cap can be easily manufactured by an insert injection process. The effects according to the present invention are not limited to the contents exemplified above, and more diverse effects are included in this specification. Figure 1 is a perspective view of a battery pack according to one embodiment of the present invention, viewed from above. Packaging is indicated by dotted lines, and components visible through the packaging are indicated by solid lines. Figure 2 is a perspective view of a secondary battery according to the first embodiment of the present invention as viewed from above. Figure 3 is an exploded perspective view of the secondary battery illustrated in Figure 2. Figure 4 is an exploded perspective view showing the state in which the connecting portion and the cover portion in Figure 3 are combined. Figure 5 is a drawing showing a part of a cross-sectional view along line A-A' of Figure 2. Figure 6 is a drawing showing a part of a cross-sectional view along line B-B' of Figure 2. Figure 7 is a perspective view of a secondary battery according to a second embodiment of the present invention viewed from above. Figure 8 is an exploded perspective view of the secondary battery illustrated in Figure 7. Fig. 9 is a drawing showing a part of a cross-sectional view along line C-C' of Fig. 7. FIG. 10 is a partial cross-sectional view of a secondary battery according to a third embodiment of the present invention taken along line C-C' of FIG. 7. FIG. 11 is a partial cross-sectional view of a secondary battery (first modified example of a bonding portion) according to a fourth embodiment of the present invention, taken along line C-C' of FIG. 7. FIG. 12 is a partial cross-sectional view taken along line C-C' of FIG. 7 of a secondary battery (a second modified example of a bonding portion) according to a fourth embodiment of the present invention. FIG. 13 is a partial cross-sectional view of a secondary battery (third modified example of a bonding portion) according to a fourth embodiment of the present invention, taken along line C-C' of FIG. 7. Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited or restricted by the following examples. In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification. In addition, terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way. Figure 1 is a perspective view of a battery pack according to one embodiment of the present invention, viewed from above. Packaging is indicated by dotted lines, and components visible through the packaging are indicated by solid lines. FIG. 1 discloses a battery pack according to one embodiment of the present invention. Referring to FIG. 1, a battery pack (1) according to one embodiment of the present invention may be a battery pack for charging and discharging electrical energy. A battery pack (1) according to one embodiment of the present invention may include a secondary battery (3). In this case, the secondary battery (3) may be configured in multiple units. Meanwhile, the battery pack (1) may include a packaging (2) that accommodates a plurality of secondary batteries (3) therein. The packaging (2) may be configured to protect the secondary battery (3) from external impact or contamination. In this embodiment, the packaging (2) may be provided as a box-shaped structure. The packaging (2) may be made of metal or plastic having a predetermined rigidity. The packaging (2) may have a structure in which a plurality of plates are combined. However, the shape or structure of the packaging (2) may be modified as needed. For example, at least a portion of the packaging (2) may have a curved shape. In addition, the packaging (2) may be additionally provided with other components. For example, the packaging (2) may be provided with a bus bar electrically connected to a plurality of secondary batteries (3) and / or a venting component that connects the inside and outside of the packaging (2). Below, a secondary battery according to an embodiment of the present invention is described. Example 1 Fig. 2 is a perspective view of a secondary battery according to a first embodiment of the present invention, viewed from above. Fig. 3 is an exploded perspective view of the secondary battery illustrated in Fig. 2. Fig. 4 is an exploded perspective view showing a state in which the connecting portion and the cover portion are combined in Fig. 3. Fig. 5 is a drawing showing a portion of a cross-sectional view taken along line A-A' of Fig. 2. Fig. 6 is a drawing showing a portion of a cross-sectional view taken along line B-B' of Fig. 2. Referring to FIGS. 2 to 6, a secondary battery (3) according to a first embodiment of the present invention may include an electrode assembly (10), an outer film (20), and a cap (30). Hereinafter, each component of the secondary battery (3) will be described in more detail. For reference, the contents of the first embodiment may be equally applied to other embodiments described later, as long as they do not conflict with each other. electrode assembly The electrode assembly (10) of the secondary battery (3) may include a positive electrode, a negative electrode, and a separator. Here, the separator may be disposed between the positive electrode and the negative electrode to physically separate the positive electrode and the negative electrode. The electrode assembly (10) may have a stacked form in which the positive electrode, the negative electrode, and the separator are laminated, or a jelly-roll form in which the positive electrode, the negative electrode, and the separator are wound. The type or structure of the electrode assembly (10) is not particularly limited. The electrode assembly (10) may extend in one direction (X-axis direction) to have a predetermined length. Meanwhile, the electrode assembly (10) may be provided with an electrode tab (11) connected to the electrode. The electrode tab (11) may be provided separately or as part of a current collector constituting the electrode. For reference, if the electrode assembly (10) is an all-solid-state battery, a solid electrolyte may be provided instead of a separator. exterior film Referring to FIGS. 1 to 6, the secondary battery (3) according to the first embodiment of the present invention may include an outer film (20). The outer film (20) of the secondary battery (3) may be provided to wrap a portion of the electrode assembly (10). Specifically, the outer film (20) may be provided to wrap the cap (30) and the electrode assembly (10), which will be described later. More specifically, the outer film (20) may be combined with the cap (30) to form an internal space, and the electrode assembly (10) may be accommodated in the internal space. As illustrated, in the present embodiment, the outer film (20) can wrap around the electrode assembly (10) in a circumferential direction. At this time, the circumferential direction may be a direction that wraps around an axis (X-axis) that is parallel to the extension direction of the electrode assembly (10). The outer film (20) may be made of a material that can be deformed in shape so as to wrap the electrode assembly (10). For example, the outer film (20) may have a predetermined flexibility so as to be bent by an external force. Additionally, the outer film (20) may be formed of a non-stretchy material. Conventionally, a pouch film was formed to form a space to accommodate the electrode assembly. However, since the outer film (20) does not need to change its shape through forming, it may be formed of a non-stretchy material. That is, the outer film (20) may not be stretchy. Of course, the outer film (20) may also have a certain degree of elasticity, as needed. The outer film (20) of the secondary battery (3) may have a shape in which a sheet or film is rolled along the side of the electrode assembly (10). That is, the outer film (20) may be arranged in a shape that wraps around the side of the electrode assembly (10). At this time, one end and the other end of the outer film (20) may be arranged in a shape that wraps around the electrode assembly (10) while meeting each other. With respect to the shape in which one end and the other end of the outer film (20) meet each other, one side of one end and the other side of the other end may be joined so as to be in contact with each other (see FIG. 2). This is merely an example, and the shape in which one end and the other end of the outer film (20) are joined to form a space that accommodates the electrode assembly (10) may vary. With regard to the method by which one end and the other end of the outer film (20) are joined, one end and the other end of the outer film (20) may be joined to each other by heat sealing or heat and pressure sealing. That is, the outer film (20) may include a material having heat sealing properties. As an example of the structure of the outer film (20), the outer film (20) may be formed in a film form. Specifically, the outer film (20) may be provided with a plurality of layers including a sealant layer, a barrier layer, and an insulating layer. More specifically, the outer film (20) may be arranged in the order of a sealant layer, a barrier layer, and an insulating layer from the inside closer to the electrode assembly (10). The sealant layer may include a material having a heat-sealing property so that one end and the other end of the outer film (20) can be bonded. For example, the sealant layer of the outer film (20) may include one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Mainly, a polyolefin resin such as polypropylene (PP) or polyethylene (PE) may be used. In particular, polypropylene (PP) may have excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance. The barrier layer may include a metal. For example, the metal of the barrier layer may be one or more materials selected from the group consisting of iron (Fe), carbon (C), chromium (Cr), manganese (Mn), nickel (Ni), and aluminum (Al). For example, the barrier layer may include stainless steel (STS). Additionally, the barrier layer may be formed of an alloy, such as an aluminum alloy. The insulating layer may include an insulating material. That is, the electrode assembly (10) may be insulated from the outside by the insulating layer. Therefore, the insulating layer may prevent a short circuit of the outer film (20), etc. For example, the insulating layer may include one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Mainly, a polymer such as nylon resin or polyethylene terephthalate (PET) having wear resistance and heat resistance may be used. Meanwhile, the outer film (20) may be arranged to wrap a portion of the electrode assembly (10) and the cap (30) may be arranged to wrap the remainder of the electrode assembly (10). Specifically, when the outer film (20) is arranged to wrap the electrode assembly (10) along the side (or outer periphery) of the electrode assembly (10), an opening formed by the edge of the outer film (20) may be formed at both ends of the electrode assembly (10). At this time, the opening may be located on both sides in the extension direction (X-axis direction) of the electrode assembly (10). The cap (30) of the secondary battery (3) can be combined with the outer film (20) in a form that covers the openings on both sides of the electrode assembly (10). In addition, the electrode assembly (10) can be accommodated in the internal space formed by the outer film (20) and the cap (30). The outer film (20) can be combined with the cap (30). As an example of a method of combining the cap (30) and the outer film (20), the cap (30) and the outer film (20) can be combined by welding. Specifically, the connecting portion (40) described below may include a metal material, and the outer film (20) may include a metal layer that can be combined with the connecting portion (40) by welding at a portion facing the connecting portion (40). As another example of a method of joining the cap (30) and the outer film (20), the cap (30) and the outer film (20) may be joined by sealing. Specifically, the connecting portion (40) may include a resin material having adhesiveness by heat, and the outer film (20) may include a resin layer that can be joined to the connecting portion (40) by heat and pressure at a portion facing the connecting portion (40). Here, the resin layer may include a material having sealing properties by heat as described above. Conventional pouch cells were formed by forming a cup portion to accommodate an electrode assembly (10) by forming a sheet or film. During the forming process of the cup portion, the depth that can be formed was limited depending on the material properties of the sheet or film, and the capacity that could accommodate the electrode assembly (10) was also limited. In addition, when forming a sheet or film, the thickness at the corners was the thinnest, so defects such as cracks frequently occurred. In addition, conventional pouch cells required a gas collection portion to collect gas in the degassing process to remove gas accumulated inside the pouch, and there were many cases where the gas collection portion was removed and discarded after the degassing process. On the other hand, in the secondary battery (3) according to the first embodiment of the present invention, since the outer film (20) can be used according to the volume of the electrode assembly (10), there may be no limitation on the capacity that can accommodate the electrode assembly (10). In addition, since molding of the cup portion is not required, the occurrence of defects such as cracks in the outer film (20) can be prevented, and the material and thickness of the outer film (20) can be selected relatively freely. In addition, since the electrolyte injection and degassing processes can be performed through the cap (30), the outer film (20) is not discarded, so the economic feasibility of the process can be improved. cap Referring to FIGS. 2 to 6, the cap (30) of the secondary battery (3) according to the first embodiment of the present invention may include a connection portion (40), a cover portion (50), and a terminal portion (60). In this embodiment, the cap (30) may seal the electrode assembly (10) together with the outer film (20). As a result, the emission of gas or flame due to an abnormal behavior inside may be guided (or concentrated) toward the outer film (20), thereby improving the stability of the secondary battery (3). The connecting portion (40) of the cap (30) may be combined with the outer film (20). In addition, the cover portion (50) of the cap (30) may be combined with the connecting portion (40) and may be provided so that a portion thereof is exposed to the outside of the connecting portion (40). Specifically, one surface of the cover portion (50) may be exposed to the outside of the connecting portion (40). Here, the inner side of the connecting portion (40) may mean a part of the internal space formed by the cap (30) and the outer film (20), and the outer side of the connecting portion (40) may mean a space outside the cap (30) and the outer film (20). And, one side of the cover portion (50) exposed to the outside of the connection portion (40) may be an outward-facing surface (51a) facing the outside. The outward-facing surface (51a) may be provided on the cover portion (51) of the cover portion (50) described later. The surface of the cover portion (51) facing the outward-facing surface (51a) may be referred to as an inward-facing surface (51b). The inward-facing surface (51b) may be a surface facing the electrode assembly (10). Referring to FIGS. 2 to 6, in the present embodiment, the connecting portion (40) may include a joining portion (41). The joining portion (41) may be a portion that directly joins the cover portion (50) and the outer film (20) described below. As needed, the joining portion (41) may be composed of a single layer including one material, a single layer including different materials, multiple layers each including different materials, or multiple layers each including different materials. In this embodiment, the joining portion (41) may be provided on the outer surface (54a) of the extension portion (54) of the cover portion (50). Here, the outer surface (54a) of the extension portion (54) may be a surface facing the outside (or an outer circumferential surface). The joining portion (41) may be provided between the extension portion (54) and the outer film (20) to join them. In the present embodiment, the joining portion (41) may be provided along the outer surface (54a) (or outer circumference) of the extension portion (54). As will be described in detail later, since the extension portion (54) in the present embodiment has a ring shape, the joining portion (41) may also have a ring shape corresponding to the extension portion (54). At this time, the ring shape may be a shape viewed in the longitudinal direction (X-axis direction) of the electrode assembly (10). The shape of the joining portion (41) may be appropriately modified depending on the structure of the cover portion (50). In addition, in the present embodiment, the connecting portion (40) may include an inner portion (43). The inner portion (43) may be provided on the inward surface (51b) of the cover portion (51). The inner portion (43) may cover the entire inward surface (51b). The inner portion (43) may have a plate shape having a predetermined thickness. Through this, heat transfer or moisture penetration through the cover portion (51) may be effectively suppressed. Meanwhile, the inner portion (43) may be provided with a terminal hole (43a). The terminal hole (43a) may be a hole through which a terminal portion (60) described below passes. Meanwhile, in the present embodiment, the connecting portion (40) may include an extension-side portion (44). The extension-side portion (44) may be provided on the inner surface (54b) (or inner circumferential surface) of the extension portion (54) in the cover portion (50) described below. At this time, the inner surface (54b) of the extension portion (54) may be a surface facing the outer surface (54a). The inner surface (54b) may be a surface facing the inside. In this embodiment, the extension-side portion (44) may be provided along the inner surface (54b) (or inner circumference) of the extension portion (54). At this time, since the extension portion (54) has a ring shape, the extension-side portion (44) may also have a ring shape corresponding to the extension portion (54). At this time, the ring shape may be a shape viewed in the longitudinal direction (X-axis direction) of the electrode assembly (10). The shape of the extension-side portion (44) may be appropriately modified depending on the structure of the cover portion (50). At this time, the extension-side portion (44) and the inner portion (43) can be connected to each other. In other words, the extension-side portion (44) can extend from the inner portion (43). The extension-side portion (44) can extend from the edge portion of the inner portion (43). Through this, the rigidity reinforcement, moisture penetration prevention, and heat transfer suppression effects of the cap (30) by the connection portion (40) can be increased. Meanwhile, as an example of a configuration for electrical connection with the outside, the cap (30) of the secondary battery (3) according to the first embodiment of the present invention may include a terminal portion (60). The terminal portion (60) may penetrate the connection portion (40) and the cover portion (50) and be exposed to the outside and inside of the connection portion (40), respectively. The terminal portion (60) may be electrically connected to the electrode assembly (10) at a portion exposed to the inside of the connection portion (40). Here, the electrical connection may include both a direct connection between the terminal portion (60) and the electrode assembly (10) and an indirect connection via another electrically conductive member. A portion of the terminal portion (60) exposed to the outside of the connection portion (40) may be electrically connected to the outside. The electrode assembly (10) and the terminal portion (60) for electrical connection to the outside may include an electrically conductive material. The terminal portion (60) may be arranged in a form that protrudes outward from the connection portion (40) (see FIG. 2). Accordingly, the secondary battery (3) can be electrically connected to the outside in a wider variety of forms and can efficiently provide electrical energy to the outside. Hereinafter, the structure of the terminal portion (60) will be described in more detail. The terminal portion (60) of the cap (30) according to the first embodiment of the present invention may extend from the inside of the connection portion (40) to the outside of the connection portion (40). At this time, the terminal portion (60) may be formed to have a constant cross-sectional area in the longitudinal direction. For example, the terminal portion (60) may have a cylindrical or rectangular parallelepiped shape. Here, a terminal portion (60) having a rectangular parallelepiped shape will be described as an example. A terminal portion (60) having a constant cross-sectional area in the longitudinal direction may be relatively easy to manufacture. The electrode assembly (10) may include electrodes and separators that are stacked in parallel. At this time, the terminal portion (60) may be formed with one side and the other side formed on both ends of the portion exposed to the inside of the connection portion (40) based on the stacking direction of the electrode and the separator, as a plane. Referring to Fig. 4, the one side and the other side formed on both ends of the terminal portion (60) may be surfaces that come into contact with the electrode tab (11) of the electrode assembly (10). With such a shape, the terminal portion (60) can be more efficiently connected to the electrode tab (11). In addition, when the secondary battery (3) includes a plurality of electrode assemblies (10), the electrode tabs (11) of the plurality of electrode assemblies (10) can be electrically connected to one side and the other side of the terminal portion (60), respectively. Through this, the secondary battery (3) can efficiently increase the battery capacity. In addition to the shape described in the first embodiment of the present invention, the terminal portion (60) may have various shapes for efficient electrical connection. Meanwhile, although not specifically illustrated in the drawing, a predetermined gasket may be provided on the outer periphery of the terminal portion (60). The gasket may be configured to prevent leakage of the electrolyte. The gasket may be interposed between the outer periphery of the terminal portion (60) and the cover portion (50). The gasket may be made of a polymer material such as plastic or rubber. Below, the structure of the cover part (50) is described in more detail. As an example of a configuration for improving the structural stability of the cap (30), at least a portion of the cover portion (50) of the cap (30) according to the first embodiment of the present invention may be embedded in the connecting portion (40). In this regard, the cover portion (50) of the cap (30) may include a cover portion (51) and an extension portion (54). The cover portion (51) of the cover part (50) can be positioned on one side of the length direction (X-axis direction) of the electrode assembly (10). The cover portion (51) can cover the one side of the electrode assembly (10). The cover portion (51) can have a square plate shape, but the shape of the cover portion (51) is not particularly limited as long as it can partially cover the electrode assembly (10). The outward surface (51a) of the cover portion (51) may be provided to be exposed to the outside of the connection portion (40). Here, the outward surface (51a) may be a surface of the outer surface of the cover portion (51) that faces the outside of the electrode assembly (10). At this time, the outward surface (51a) of the cover portion (51) may be disposed on the same surface as one surface of the connection portion (40). More specifically, the outward surface (51a) may be disposed on the same surface as one surface of the joining portion (41) of the connection portion (40) described later. Of course, the outward surface (51a) may be positioned further outward than the above-described surface of the joining portion (41). By this configuration, space utilization can be improved when arranging a plurality of secondary batteries (3). Here, the outward surface (51a) may refer to a surface facing forward (positive direction of the X-axis) from the cover portion (51) based on Fig. 6, and one surface of the joining portion (41) may refer to an end surface facing forward (positive direction of the X-axis). The extension portion (54) of the cover portion (50) may extend toward the electrode assembly (10). That is, the extension portion (54) may extend from the cover portion (51) toward the electrode assembly (10). Specifically, the extension portion (54) may be provided so that the end surface (54c) on the electrode assembly (10) side is exposed to the inside of the connection portion (40). At this time, the extension portion (54) may extend from the edge of the cover portion (51). Referring to FIGS. 5 and 6, the extension portion (54) of the cover portion (50) may be formed in a plurality. Here, at least one extension portion (54) may be provided such that the end surface (54c) on the electrode assembly (10) side is exposed to the inside of the connection portion (40). Specifically, among the plurality of extension portions (54) extending from the cover portion (51) toward the electrode assembly (10), some may be embedded in the connection portion (40), and other some may be exposed to the inside of the connection portion (40). However, in the first embodiment of the present invention, an example is given in which all of the plurality of extension portions (54) are exposed to the inside of the connecting portion (40). Specifically, the plurality of extension portions (54) may include first to fourth extension portions (55 to 58). Referring to FIGS. 5 and 6, the first and second extension portions (55, 56) may extend in parallel from both sides of the cover portion (51) in the width direction (Y-axis direction). The first extension portion (55) and the second extension portion (56) may be arranged at a predetermined distance in the width direction. At this time, the width direction (Y-axis direction) may be a direction perpendicular to the direction in which the electrodes and the separator are laminated (Z-axis direction). The first and second extension portions (55, 56) may have a partition (or plate) shape having a predetermined thickness. The third and fourth extension portions (57, 58) may extend in parallel from both sides of the cover portion (51) in the height direction (Z-axis direction). The third extension portion (57) and the fourth extension portion (58) may be arranged at a predetermined distance in the height direction. At this time, the height direction (Z-axis direction) may be a direction parallel to the direction in which the electrodes and the separator are laminated (Z-axis direction). The third and fourth extension portions (57, 58) may have a partition (or plate) shape having a predetermined thickness. At this time, the first to fourth extension portions (55 to 58) may be connected to each other. As a result, when viewed in the longitudinal direction (X-axis direction) of the electrode assembly (10), the first to fourth extension portions (55 to 58) may have an overall ring shape. In other words, the first to fourth extension portions (55 to 58) may have a ring shape that follows the circumferential direction of the electrode assembly (10). At this time, the ring shape may be a shape viewed in the longitudinal direction (X-axis direction) of the electrode assembly (10). Referring to Fig. 5, the end face (54c) of the extended portion (54) exposed to the inside of the connecting portion (40) can be positioned at a predetermined distance from the electrode assembly (10). Accordingly, damage to the electrode assembly (10) by the extended portion (54) can be prevented. Meanwhile, in the present embodiment, the extension portion (54) has been described as being composed of first to fourth extension portions (55 to 58). However, if necessary, the extension portion (54) may be configured to include only some of the first to fourth extension portions (55 to 58). For example, the extension portion (54) may be configured to be composed of first and second extension portions (55, 56) and be open in the height direction (Z-axis direction). Referring to FIGS. 2 to 6, the extension portion (54) can be embedded in the connection portion (40) in a form that fits into a groove formed in the connection portion (40). The connection portion (40) and the cover portion (50) can be coupled as the cover portion (51) and a portion of the extension portion (54) are fitted into the connection portion (40) (see FIGS. 2 to 6). At this time, the connection portion (40) and the extension portion (54) can be bonded to each other by heat sealing. In addition, the connection portion (40) and the extension portion (54) can also be bonded to each other through an adhesive applied therebetween. Here, the type and application form of the adhesive for bonding the connection portion (40) and the extension portion (54) can vary. Preferably, the adhesive can be composed of a material with relatively high hydrophobicity. When the connecting portion (40) and the extension portion (54) are bonded by sealing, the connecting portion (40) may include a resin material that has adhesive properties due to heat. That is, the resin material of the connecting portion (40) that has adhesive properties due to heat melts, and the connecting portion (40) can be bonded to the extension portion (54) by pressure. Through this, the connecting portion (40) and the cover portion (50) can be joined. Meanwhile, although not described in detail in the present invention, the cap (30) may further include an electrolyte injection port for injecting an electrolyte or a gas discharge port for discharging gas in a degassing process. The cap (30) of the secondary battery (3) according to the first embodiment of the present invention may cover the electrode assembly (10) with a connecting portion (40) and a cover portion (50) at least partially embedded in the connecting portion (40). Depending on the material of the connecting portion (40), moisture or the like on the outside of the connecting portion (40) may penetrate into the connecting portion (40) through the connecting portion (40). The penetration of moisture may cause a defect in the secondary battery (3). According to the first embodiment of the present invention, the secondary battery (3) has a cap (30) that includes a cover portion (50) having excellent waterproof properties, such as metal, and can cover the electrode assembly (10) together with the connection portion (40). Therefore, the cap (30) can reduce the area of ​​the connection portion (40) through which moisture can penetrate. In addition, since at least a portion of the cover portion (50) is disposed in a shape in which it is embedded in the connection portion (40), it can be difficult for moisture to penetrate between the cover portion (50) and the connection portion (40). Therefore, the secondary battery (3) according to the first embodiment of the present invention can reduce the phenomenon in which problems occur in the performance of the secondary battery (3) by reducing the amount of moisture penetrating into the interior. In addition, the cap (30) of the secondary battery (3) according to the first embodiment of the present invention can be placed in a state where the extension portion (54) of the cover portion (50) is embedded in the connecting portion (40). Accordingly, the connecting portion (40) restricts the movement of the cover portion (50) and prevents the cover portion (50) from coming off, so that the structural stability of the secondary battery (3) can be improved. In addition, since the cap (30) of the secondary battery (3) includes a terminal portion (60), it can be efficiently electrically connected to the outside. In addition, the terminal portion (60) can be connected to various types of electrode assemblies (10) through changes in shape and arrangement, and can be efficiently connected to the electrode tabs (11) even when the number of electrode tabs (11) increases. Although not described in detail in this embodiment, the cap (30) may further include a gas discharge member (not shown) for discharging gas inside the secondary battery (3) or a venting member (not shown) for inducing venting in a specific direction. Example 2 Fig. 7 is a perspective view of a secondary battery according to a second embodiment of the present invention, viewed from above. Fig. 8 is an exploded perspective view of the secondary battery illustrated in Fig. 7. Fig. 9 is a drawing showing a portion of a cross-sectional view taken along line C-C' of Fig. 7. Hereinafter, a detailed description of the configuration identical to that of the secondary battery (3) (illustrated in FIG. 2) according to the first embodiment of the present invention will be omitted, and the differences between the first embodiment and the second embodiment will be specifically described. Referring to FIGS. 7 to 9, a secondary battery (103) according to a second embodiment of the present invention may differ from the secondary battery (3) (shown in FIG. 2) according to the first embodiment in the shape of the connection portion (140), the shape of the terminal portion (160), the presence or absence of a bus bar (170), the method of combining the configuration, etc. The secondary battery (103) according to the second embodiment of the present invention may include an electrode assembly (10), an outer film (20), and a cap (130). At this time, the outer film (20) of the secondary battery (103) may have a shape in which a sheet or film is rolled along the side of the electrode assembly (10). That is, the outer film (20) may be arranged in a shape that wraps around the side of the electrode assembly (10). At this time, one end and the other end of the outer film (20) may be arranged in a shape that wraps around the electrode assembly (10) while meeting each other. With regard to the shape in which one end and the other end of the outer film (20) meet each other, one side of one end and one side of the other end may be joined so as to be in contact with each other (see FIG. 7). This is merely an example, and the shape in which one end and the other end of the outer film (20) are joined to form a space that accommodates the electrode assembly (10) may vary. Referring to FIGS. 7 to 9, the cap (130) of the secondary battery (103) may include a connecting portion (140), a cover portion (50), and a terminal portion (160). The connecting portion (140) of the cap (130) may be coupled with an outer film (20), and the cover portion (50) of the cap (130) may be coupled to the connecting portion (140) such that a portion thereof is exposed to the outside of the connecting portion (140). The terminal portion (160) of the cap (130) may be arranged to penetrate the connecting portion (140) and the cover portion (50). In addition, one end and the other end of the terminal portion (160) may be exposed to the outside and inside of the connecting portion (140). Below, each component of the cap (130) will be described in more detail. In the present embodiment, the cover portion (50) may be configured in the same manner as the cover portion of the secondary battery according to the first embodiment. Specifically, the cover portion (50) may include a cover portion (51) and an extension portion (54). One side of the cover portion (51) may be arranged to be exposed to the outside of the connection portion (140). Hereinafter, the one side is referred to as an outward-facing side (51a), and the side opposite to the outward-facing side (51a) is referred to as an inward-facing side (51b). The inward-facing side (51b) may be a side facing the electrode assembly (10). At this time, in the present embodiment, the extension portion (54) may be embedded in the connecting portion (140). That is, one end of the extension portion (54) may not be exposed to the inside of the connecting portion (140). To this end, the connecting portion (140) may include an end-side portion (145) provided on the end side of the extension portion (54) to connect the extension-side portion (44) and the joining portion (41). The end-side portion (145) may be a portion that covers the end surface (54c) of the extension portion (54). This structure can secure not only the structural stability of the cap (30), but also the stability of the joint portion (41) where the cap (30) and the outer film (20) are sealed. In particular, the advantage of being able to control the venting direction can be expected. In the case where the extension portion (54) is completely buried by the connection portion (140) and there is no part exposed on the inside, the possibility of the joint portion (41) being separated from the extension portion (54) of the cover portion (50) can be eliminated. That is, in a situation where the internal pressure of the secondary battery (3) rapidly increases and the internal gas is explosively ejected, or in a situation where a fire occurs and flames are ejected to the outside, since there is no crack in the direction of the cap (30) that could eject flames or gas, it is possible to control that venting does not occur in the direction of the cap (30). Therefore, there is an advantage in that it is possible to resolve the heat transfer phenomenon that may occur due to venting in the direction of the cap (30) when assembled into a battery pack. At this time, in the present embodiment, the short-side portion (145) may have a ring shape corresponding to the shape of the extension portion (54). At this time, the ring shape may be a shape viewed in the extension direction (X-axis direction) of the electrode assembly (10). Meanwhile, in the present embodiment, the short-side portion (145) can be connected to the connecting portion (41) and the extending portion (44), respectively. As a result, the extending portion (54) can be completely buried by the connecting portion (140). With this configuration, moisture infiltration into the space where the electrode assembly (10) is accommodated can be further suppressed. This is because a predetermined gap through which moisture can infiltrate may be generated at the joint portion between the outer surface (54a) of the extending portion (54) and the connecting portion (41), and this gap is blocked by the short-side portion (145). In addition, by the above configuration, in an abnormal situation such as an increase in internal pressure or an explosion, the discharge of gas or flame can be directed toward the outer film (20). This is because the gap between the outer surface (54a) of the extension portion (54) and the joining portion (41) is blocked by the end portion (145), so the discharge of gas or flame through the cap (130) is suppressed. In this way, in the second embodiment of the present invention, the extension portion (54) is disposed in a form completely embedded in the connection portion (140), thereby improving the structural stability of the cap (30) and effectively controlling the direction of gas or flame discharge. In addition, there is no protruding shape on the other surface of the connection portion (140) facing the electrode assembly. A portion of the bus bar (170), which will be described later, can be disposed in this portion. Regarding the structure of the terminal portion (160) of the cap (130), the terminal portion (160) may include a body portion (161), an outer portion (162), and an inner portion (163). Specifically, the outer portion (162) may be connected to one end of the body portion (161), and the inner portion (163) may be connected to the other end. The body portion (161) of the terminal portion (160) may be arranged to penetrate the connection portion (140) and the cover portion (50). That is, the outer peripheral surface of the body portion (161) may be in contact with the connection portion (140) and the cover portion (50). A predetermined gasket may be provided on the outer peripheral surface of the body portion (161) to prevent leakage of electrolyte. The outer portion (162) of the terminal portion (160) may be exposed to the outside of the connection portion (140). Therefore, when the secondary battery (103) is electrically connected to the outside to provide electrical energy, the outer portion (162) may be connected to the outside. The inner portion (163) of the terminal portion (160) may be exposed to the inside of the connection portion (140). Therefore, the inner portion (163) may be electrically connected to the electrode assembly (10). Meanwhile, the outer portion (162) and the inner portion (163) of the terminal portion (160) according to the second embodiment of the present invention may be formed to have a cross-sectional area larger than the cross-sectional area of ​​the body portion (161). Referring to Fig. 9, the terminal portion (160) may be fitted into the connection portion (140) and the cover portion (50) by the outer portion (162) and the inner portion (163). Accordingly, separation of the terminal portion (160) may be prevented, thereby improving the structural stability of the cap (130). The body portion (161), the outer portion (162), and the inner portion (163) of the terminal portion (160) according to the second embodiment of the present invention may each have an approximately cylindrical shape. That is, the body portion (161), the outer portion (162), and the inner portion (163) may have a cross-section that is approximately circular. This is merely an example, and the body portion (161), the outer portion (162), and the inner portion (163) may have a cross-section of a different shape. As previously described, the inner portion (163) of the terminal portion (160) extending to the inner side of the connection portion (140) can be electrically connected to the electrode assembly (10). Here, the electrical connection can include both a direct connection between the inner portion (163) and the electrode assembly (10) and an indirect connection via another electrically conductive member. When the inner part (163) and the electrode assembly (10) are directly connected, the electrode tab (11) of the electrode assembly (10) can be connected to the inner part (163). In addition, when the inner part (163) and the electrode assembly (10) are indirectly connected, as an example of an electrically conductive member that serves as an intermediary, the secondary battery (103) can include a bus bar (170). A bus bar (170) is arranged between the connecting portion (140) and the electrode assembly (10) to connect the inner portion (163) exposed to the inside of the connecting portion (140) and the electrode assembly (10). The bus bar (170) may be made of metal so as to have electrical conductivity. In addition, the bus bar (170) may be arranged in various shapes depending on the extended length of the inner portion (163), etc. As an example of a configuration for efficient arrangement, a bus bar (170) according to the second embodiment of the present invention may include a first metal portion (171), a second metal portion (172), a third metal portion (173), and a fourth metal portion (174). Referring to FIG. 9, the first metal portion (171) can be in contact with the connecting portion (140) and the inner portion (163). One surface of the first metal portion (171) facing the connecting portion (140) can be arranged to be in contact with the connecting portion (140). In addition, the other surface of the first metal portion (171) facing the inner portion (163) can be arranged to be in contact with the inner portion (163). In this regard, the first metal portion (171) has a substantially plate shape and a hole can be formed in the center. The body portion (151) of the terminal portion (160) can penetrate the hole of the first metal portion (171), and the other surface of the first metal portion (171) facing the inner portion (163) can be in contact with the inner portion (163). That is, the first metal portion (171) of the bus bar (170) can be arranged in a manner that it is caught on the inner portion (163) so that movement in the direction toward the electrode assembly (10) is limited by the inner portion (163). Therefore, effective fixation of the bus bar (170) is possible. Meanwhile, the terminal portion (160) includes a metal material, and the inner portion (163) of the terminal portion (160) and the first metal portion (171) can be joined to each other through welding. The second metal portion (172) may extend from the first metal portion (171) toward the electrode assembly (10). At this time, the second metal portion (172) may extend in a direction approximately orthogonal to the extension direction of the first metal portion (171). In addition, one surface of the second metal portion (172) facing the connection portion (140) may be in contact with the connection portion (140). The third metal portion (173) may extend from the second metal portion (172) toward the outer film (20). At this time, the third metal portion (173) may extend in a direction approximately orthogonal to the extension direction of the second metal portion (172). Specifically, the third metal portion (173) may extend in a direction away from the inner portion (163). In addition, one surface of the third metal portion (173) facing the connection portion (140) may be in contact with the connection portion (140). The fourth metal portion (174) may extend from the third metal portion (173) toward the electrode assembly (10). In addition, the fourth metal portion (174) may have a surface facing the outer film (20) that may be in contact with the outer film (20). Meanwhile, one end of the fourth metal portion (174) may be connected to the electrode assembly (10). Specifically, one end of the fourth metal portion (174) may be connected to the electrode tab (11) of the electrode assembly (10). In this regard, the second metal portion (172), the third metal portion (173), and the fourth metal portion (174) may be formed as a pair. Here, the plurality of electrode tabs (11) of the electrode assembly (10) may be connected to the fourth metal portion (174) that are relatively close to each other. Therefore, even if the secondary battery (103) includes a plurality of electrode assemblies (10) and the number of electrode tabs (11) increases, the fourth metal portion (174) may be efficiently connected to the electrode tabs (11). The bus bar (170) according to the second embodiment of the present invention can be arranged in contact with the outer film (20) or the cap (130). Accordingly, the structural stability of the secondary battery (103) can be improved. In addition, since the bus bar (170) includes a first metal portion (171), a second metal portion (172), a third metal portion (173), and a fourth metal portion (174), it can be applied in various forms depending on the number, arrangement, shape, etc. of the electrode assembly (10). The shape of the bus bar (170) described in the present invention is only one preferred example. Therefore, the shape and arrangement of the bus bar (170) may vary. Example 3 FIG. 10 is a partial cross-sectional view of a secondary battery according to a third embodiment of the present invention taken along line C-C' of FIG. 7. The electrode assembly, outer film, cover part of the cap, terminal part, and bus bar of the secondary battery (203) according to the third embodiment of the present invention may be configured identically to the electrode assembly, outer film, cover part of the cap, terminal part, and bus bar of the secondary battery (103) (shown in FIGS. 7 to 9) according to the second embodiment of the present invention. Referring to Fig. 10, in the secondary battery (203) according to the third embodiment of the present invention, the connection portion (240) of the cap (230) may further include an outer portion (242). The outer portion (242) may be configured to cover an outward surface (51a) facing the outside of the electrode assembly (10) among the outer surfaces of the cover portion (51). Accordingly, the cover portion (51) may have the outward surface (51a) and the inward surface (51b) covered by the outer portion (242) and the inward portion (43), respectively. That is, the cover portion (51) may be entirely embedded in the connection portion (240). In this embodiment, the outer portion (242) may have a plate shape that entirely covers the outward-facing surface (51a). Through this, the cover portion (50) can be protected from external impacts and contamination. However, the shape of the outer portion (242) is not particularly limited as long as it can cover the outward-facing surface (51a). Meanwhile, in the present embodiment, the edge portion of the outer portion (242) may be connected to the joining portion (41). The outer portion (242) may be provided integrally with the joining portion (41). The outer portion (242) may be made of the same material as the joining portion (41). Through this, since the cover part (50) can be entirely surrounded by the connecting part (240), the bonding property between the connecting part (240) and the cover part (50) can be improved. In addition, since the gap between the connecting part (41) and the outer surface (54a) of the extension part (54) is blocked by the outer part (242), moisture penetration into the space where the electrode assembly (10) is accommodated can also be very effectively suppressed. Meanwhile, in the present embodiment, the body portion (161) of the terminal portion (160) can pass through the cover portion (50) and the inner portion (43) and penetrate the outer portion (242). The outer portion (162) of the terminal portion (160) can be provided at an end of the body portion (161). Here, the end of the body portion (161) can be a part facing the outer portion (242). At this time, the outer portion (162) may have a larger cross-sectional area than the body portion (161). As a result, one side of the outer portion (162) may be caught on the outer part (242), so that movement (or, detachment) of the terminal portion (160) may be restricted. In this way, in the present embodiment, since the outward surface (51a) of the cover portion (50) is covered by the outer portion (242), not only durability and bonding properties are improved, but also insulation between the terminal portion (160) and other components can be improved. In addition, in a thermal runaway situation, thermal transfer can be suppressed by the outer portion (242). Furthermore, in this embodiment, since the cover portion (50) made of a metal material is surrounded by the connecting portion (240), the cap (230) can be easily manufactured using an insert injection process. This improves the productivity of the secondary battery, simplifies the manufacturing process, and reduces manufacturing costs. Example 4 Fig. 11 is a partial cross-sectional view taken along line C-C' of Fig. 7 of a secondary battery according to a fourth embodiment of the present invention. Referring to Fig. 11, the electrode assembly (10), outer film (20), cover portion (50), terminal portion (160), and bus bar (170) of the secondary battery (303) according to the fourth embodiment of the present invention may be configured in the same manner as the electrode assembly, outer film, cover portion, terminal portion, and bus bar of the secondary battery according to the second embodiment. At this time, the connecting portion (340) in the cap (330) of the secondary battery (303) according to the fourth embodiment of the present invention may include a joining portion (41). In addition, the outward surface (51a) and the inward surface (51b) of the cover portion (51) and the inner surface (54b) and the end surface (54c) of the extension portion (54) may not be covered by the connecting portion (340). In other words, the outer surface (51a), the inner surface (51b), the inner surface (54b), and the end surface (54c) may be exposed. Of course, if necessary, the inner surface (51b), the inner surface (54b), and / or the end surface (54c) may be at least partially covered by a bus bar (170). In the present embodiment, the connecting portion (340) may have a ring shape surrounding the outer surface (54a) (or outer circumference) of the extension portion (54). In this way, in the present embodiment, the connecting portion (340) can be simply and compactly configured with only the joining portion (41). Accordingly, the secondary battery (303) can be made lightweight while achieving rigidity reinforcement by the cover portion (50). Connections (40, 140, 240, 340) of Examples 1 to 4 Modifications of the connecting portions (40, 140, 240, 340) according to Embodiments 1 to 4 of the present invention, for example, modifications of the joining portion (41) of the connecting portion (40), will be described in more detail. The description of the modifications can be applied to all Embodiments 1 to 4 according to the present invention and can include modifications possible for those skilled in the art. Hereinafter, Embodiment 4 will be described as a representative example. First, referring to FIG. 11, the connecting portion (41) of the connecting portion (340) according to the first embodiment of the present invention may, as a first modified example, include a first layer (41a) having an outer surface that includes a first resin and allows for bonding with the inner surface of the outer film (20) and an inner surface that allows for bonding with the outer surface of the cover portion (50). The first resin included in the first layer (41a) may be a material that facilitates the bonding of the cover portion (50) and the outer film (20), for example, a material having a melting point (T m ) resin having a melting point (T ) of 135°C to 150°C, a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and a melting point (T ) of m ) may include a resin selected from the group consisting of resins having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C and a melting point of 135°C to 150°C. When the first resin having the above properties is applied to the first layer (41a), the first layer (41a) has excellent heat resistance and can withstand heat sealing at high temperatures without change in appearance, thereby ensuring excellent sealing strength, and can have excellent durability in response to pressure increase due to gas generated inside the secondary battery. For example, the first resin may include a modified polyolefin-based resin. The first resin may be included in the first layer in an amount exceeding 50 wt%, preferably 70 wt% or more, 80 wt% or more, or 90 wt% or more, and the first resin may be applied alone, and when mixed, the remainder may be an appropriate resin such as another polyolefin-based resin. The above-mentioned modified polyolefin resin may be modified by an acid or a siloxane, preferably modified by an acid, and more preferably may be a polyolefin copolymerized with a monomer including acrylic acid or post-treated with an acid. For example, it may be acid-modified polypropylene or acid-modified polyethylene, and plasma-treated polypropylene or polyethylene may be applied, and more preferably, acid-modified polypropylene may be included. When applying such a modified polyolefin, since the functional group introduced by the modification improves the bonding strength with the surface of the metal, it may be more advantageous for the adhesion between the metal and the resin, and considering that a metal may be applied as the material of the cover portion (50), it may be preferable to apply a resin such as the one described above as the connecting portion (40). Referring to FIG. 12, the connecting portion (41) of the connecting portion (340) may, as a second modified example, include a first layer (41a) that includes a first resin and allows for bonding with the outer surface of the cover portion (50), and a second layer (41b) that includes a second resin and is laminated on the outer surface of the first layer and allows for bonding with the inner surface of the outer film (20). For example, the first resin included in the first layer (41a) may be as described above, and the second resin included in the second layer (41b) may include a resin selected from the group consisting of a resin having a melting point (Tm) of 120°C to 145°C, a resin having a melt flow rate (MFR) at 230°C of 5 g / 10 min to 18 g / 10 min, and a resin having a melting point (Tm) of 120°C to 145°C and a melt flow rate (MFR) at 230°C of 5 g / 10 min to 18 g / 10 min. As another example, the first resin and the second resin may satisfy at least one selected from the relationship of the following Equation 1 and the relationship of the following Equation 2. [Formula 1] Tm2> Tm1 In the above equation 1, Tm1 is the melting point of the first resin, Tm2 is the melting point of the second resin, and the unit is ℃. [Formula 2] MFR2> MFR1 In the above equation 2, MFR1 is the melt flow rate of the first resin, MFR2 is the melt flow rate of the second resin, and the unit is g / 10 min. When the above-mentioned connecting portion (340) is configured as a double layer, the bonding strength with the cover portion (50) and the bonding strength with the outer film (20) can be increased compared to when it is configured as a single layer, which has the advantage of ensuring a higher sealing strength. In particular, when a resin having a higher melting point or higher melt flow rate than the first resin applied to the first layer (41a) is included as the second resin in the second layer (41b), the physical properties thereof can become more similar to those of the outer film (20), and thus, not only the sealing processability can be improved, but also the bonding strength due to heat fusion can be expected to be improved, so that the sealing strength can be increased and the durability against the resulting increase in internal pressure can be greatly improved. For example, the first resin included in the first layer (41a) may be the same as described above, and the second resin included in the second layer (41b) may be, for example, a polyolefin-based resin. The polyolefin-based resin may differ from the first resin in the presence or absence of a modification group, and the second resin may be an unmodified polyolefin-based resin, and may include, for example, polypropylene or polyethylene, and may be a homopolymer thereof, or may be a block copolymer or random copolymer copolymerized with a small amount of comonomer. In addition, when the second resin is included in the second layer, the content thereof may be the same as when the first resin is included in the first layer. The polyolefin resin may be, for example, a non-stretched polyolefin resin. The non-stretched polyolefin resin is manufactured through casting without being stretched in a specific direction during the manufacturing or processing process, and is more flexible than a stretched polyolefin resin, does not have a problem of tearing in a specific direction, and can be relatively easy to process. However, since the connecting portion (40) may be manufactured by insert injection together with the cover portion (50), and a certain level of rigidity or higher may be required due to the characteristics of the cap (30), the non-stretched polyolefin resin and the stretched polyolefin resin may be appropriately selected by considering the properties of each resin depending on the required degree. Referring to FIG. 13, the connecting portion (41) of the connecting portion (340) may, as a third modified example, include a first layer (41a) containing a first resin and allowing for bonding with the outer surface of the cover portion (50), a second layer (41b) containing a second resin and allowing for bonding with the inner surface of the outer film (20), and a third layer (41c) containing a third resin and disposed between the first layer (41a) and the second layer (41b). For example, the first resin and the second resin are as described above, and the third resin may include a resin selected from the group consisting of a resin having a melting point (Tm) of 145°C to 170°C, a resin having a melt flow rate (MFR) at 230°C of 2 g / 10 min to 4 g / 10 min, and a resin having a melting point (Tm) of 145°C to 170°C and a melt flow rate (MFR) at 230°C of 2 g / 10 min to 4 g / 10 min. As another example, the first resin, the second resin, and the third resin may satisfy at least one selected from the relationship of Equation 3 below and the relationship of Equation 4 below. [Formula 3] Tm3> Tm2> Tm1 In the above equation 3, Tm1 is the melting point of the first resin, Tm2 is the melting point of the second resin, and Tm3 is the melting point of the third resin, and the unit is ℃. [Formula 4] MFR2> MFR1> MFR3 In the above equation 4, MFR1 is the melt flow rate of the first resin, MFR2 is the melt flow rate of the second resin, and MFR3 is the melt flow rate of the third resin, and the unit is g / 10 min. When the above-mentioned connecting portion (340) is composed of a triple layer, the third layer (41c) provided between the first layer (41a) and the second layer (41b) can be selected to have a higher melting point and a lower melting flow rate than the other layers. In this case, deformation due to heat of the connecting portion (40) can be minimized, so that not only sealing strength but also insulation can be secured. The third resin that can be applied to the third layer (41c) can be, for example, a resin that satisfies the above-described melting point and melt flow rate range within the same type of resin range as the second resin, and for example, the third resin can be selected as a homopolyolefin resin that is a single polymer. According to embodiments 1 to 4 of the present invention, the connecting portion (40, 140, 240, 340) may be provided on one surface of the cover portion (50), and may include a connecting portion (242, 43, 44, 145) provided on at least one surface (e.g., inner surface (54b), end surface (54c), outward surface (51a), inward surface (51b)) of one surface of the cover portion (50) excluding one surface (e.g., outer surface (54a)) of the cover portion (50) on which the connecting portion (41) is provided. The connecting portion (242, 43, 44, 145) of the above connecting portion (40, 140, 240, 340) may include a first layer including a first resin and having an inner surface that allows for bonding with one surface of the cover portion, as in the first modified example of the above connecting portion (41). In addition, the connecting portion (242, 43, 44, 145) of the connecting portion (40, 140, 240, 340) may include a first layer including a first resin and allowing bonding with one surface of the cover portion, and a second layer including a second resin and laminated on the outer surface of the first layer. In addition, the connecting portion (242, 43, 44, 145) of the connecting portion (40, 140, 240, 340) may include a first layer including a first resin and allowing bonding with one surface of the cover portion, a second layer including a second resin and arranged at the outermost portion, and a third layer including a third resin and arranged between the first layer and the second layer. In more detail, the connecting portion (40) further includes a connecting portion covering one surface of the cover portion (50) in addition to the joining portion (41), and the connecting portion may include, as in Embodiment 1 of FIG. 5, an inner portion (43) provided on the inward surface (51b) of the cover portion (51) of the cover portion (50), and an extension portion-side portion (44) provided on the inner surface (54b) (or inner circumferential surface) of the extension portion (54) of the cover portion (50). The inner portion (43) and the extension portion-side portion (44) may be applied with variations identical to or different from the first to third variations of the joining portion (41) independently of the joining portion (41), and in general, the same variations may be applied in that the cap (30) is manufactured by insert injection. As another example, the connecting portion (40) may further include a connecting portion covering one side of the cover portion (50) in addition to the joining portion (41), and the connecting portion may include an inner portion (43) provided on the inward surface (51b) of the cover portion (51) of the cover portion (50), an extension portion-side portion (44) provided on the inner surface (54b) (or inner circumferential surface) of the extension portion (54) of the cover portion (50), and an end-side portion (145) covering the end surface (54c) of the extension portion (54) of the cover portion (50), as in the embodiment 2 illustrated in FIG. 9. The inner portion (43), the extension-side portion (44) and the end-side portion (145) may be applied with variations identical to or different from the first to third variations of the coupling portion (41) independently of the coupling portion (41), and in general, the same variations may be applied in that the cap (30) is manufactured by insert injection. As another example, the connecting portion (40) may further include, in addition to the joining portion (41), a connecting portion covering one surface of the cover portion (50), and the connecting portion may include, as in the embodiment 3 illustrated in FIG. 10, an inner portion (43) provided on the inward surface (51b) of the cover portion (51) of the cover portion (50), an extension portion-side portion (44) provided on the inner surface (54b) (or inner circumferential surface) of the extension portion (54) of the cover portion (50), an end-side portion (145) covering the end surface (54c) of the extension portion (54) of the cover portion (50), and an outer portion (242) covering the outward surface (51a) facing the outside of the electrode assembly (10) among the outer surfaces of the cover portion (51) of the cover portion (50). The inner portion (43), the extension portion (44), the end portion (145) and the outer portion (242) may be applied with the same or different modifications as the first to third modifications of the coupling portion (41) independently of the coupling portion (41), and in general, the same modifications may be applied in that the cap (30) is manufactured by insert injection. Evaluation example Below, evaluation examples of the connecting portion (41) of the connecting portion (340) illustrated in FIGS. 11 to 13 are described in detail so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in various different forms and is not limited to the evaluation examples described herein. Evaluation Example 1 A polyethylene terephthalate (PET) film measuring 266 mm wide, 50 m long, and 12 ㎛ thick and a nylon film measuring 266 mm wide, 50 m long, and 25 ㎛ thick were laminated on one side of an aluminum alloy film measuring 266 mm wide, 50 m long, and 60 ㎛ thick, and a polypropylene film measuring 266 mm wide, 50 m long, and 80 ㎛ thick was laminated on the other side, thereby preparing an outer film having a polyethylene terephthalate / nylon / aluminum alloy film / polypropylene film structure. Here, the polyethylene terephthalate film and the nylon film are substrate layers, the aluminum alloy film is a gas barrier layer, and the polypropylene film is a sealant layer. Next, the joint portions (41, 41a) of the cover portion (50) and the connecting portion (340) of the same shape as in Fig. 11 were prepared by insert injection using a 1 mm thick aluminum metal plate and a 2 mm thick maleic anhydride-modified acid-modified polypropylene resin (Tm 135°C, MFR 6 g / 10 min), respectively. An electrode assembly was prepared by simulating the stacking method of assembling a cathode, anode, and a porous polyethylene separator, and after wrapping this with the outer film, a secondary battery having the shape shown in Fig. 2 was manufactured using the assembly of the cover part and the connecting part. At this time, the sealing of the outer film and the connecting part was performed for 5 seconds under the conditions of 240°C and 0.3 MPa. Evaluation Example 2 When manufacturing the cover part (50) and the connection part (340) by insert injection, a heterogeneous insert injection using a non-stretched polypropylene resin (cPP, Tm 140°C, MFR 10 g / 10 min) randomly copolymerized with ethylene and an acid-modified polypropylene resin (PPa, Tm 135°C, MFR 6 g / 10 min) modified with maleic anhydride was applied as the material of the connection part (340), so that an acid-modified polypropylene resin layer (first layer (41a), 1 mm) was formed at a position in contact with the cover part (50), and an ethylene copolymerized polypropylene resin layer (second layer (41b), 1 mm) was formed at a position in contact with the inner surface of the outer film, as shown in FIG. 12, and a secondary battery was manufactured in the same manner as in Evaluation Example 1, except that the same method was used. Experimental Example 1: Evaluation of Sealing Strength For each secondary battery manufactured in the evaluation example, the sealing strength was evaluated using the following method. After cutting the joint portion of the connecting portion and the outer film at 15 mm intervals, the connecting portion was joined to the lower jig of the UTM and the outer film was joined to the upper jig, and then the sealing strength was measured by pulling in the 180° direction at a speed of 5 mm / min at room temperature and 60°C, and the low-speed sealing strength was calculated by calculating the average value in the 8 mm section from the point exceeding 4.5 N / 15 mm among the graphs of the sealing strength. Room temperature sealing strength (N / 15mm) Breakage area 60℃ sealing strength (N / 15mm) Breakage area Evaluation example 178.08 Outer film - connection 30.80 Outer film - connection Evaluation example 2141.59 Outer film 121.97 Outer film Referring to Table 1 above, in the case of Evaluation Example 1, the sealing strength was evaluated for the joint portion of the connection part manufactured according to the first modified example, and when the room temperature sealing strength and the high temperature sealing strength were confirmed, it was confirmed that the required level of sealing strength was exceeded, and through this, it was confirmed that the minimum sealing strength to withstand internal pressure can be secured when the joint portion of the connection part is composed of a resin having the characteristics described above. In addition, in the case of Evaluation Example 2, the joint portion of the connecting portion was manufactured according to the second modified example, and since the sealing strength was strong, it was observed that the outer film was torn rather than the joint portion of the connecting portion being peeled off, confirming that the sealing strength was excellent. In addition, when configured as a double layer, it was confirmed that the sealing strength was excellent even at high temperatures, similar to that at room temperature. Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various embodiments are possible within the scope equivalent to the technical idea of ​​the present invention and the claims to be described below by a person having ordinary skill in the art to which the present invention pertains. [Explanation of symbols] 1: Battery pack 2: Packaging 3, 103, 203, 303: Secondary battery 10: Electrode assembly 11: Electrode tab 20: Outer film 30, 130, 230, 330: Cap 40, 140, 240: Connector 41: Joint section 41a: First floor 41b: 2nd floor 41c: 3rd floor 242: Outer part 43: Inner part 44: Extension part 145: end side part 50: cover part 51: Cover part 51a: Outward facing surface 51b: Inward surface 54: Extended part 54a: Exterior 54b: Interior 54c: End face 55: First extension part 56: Second extension section 57: Third extension section 58: 4th extension section 60, 160: Terminal section 161: Body 162: Outer part 163: Inner side 170: Bus bar 171: First metal section 172: Second metal section 173: Third metal section 174: Fourth metal section

Claims

1. Electrode assembly extending in one direction; An outer film covering a portion of the electrode assembly; and comprising a cap surrounding the remainder of the electrode assembly; The above cap is, A cover portion covering one side of the extension direction of the electrode assembly; A connecting portion including a connecting portion provided on the outer surface of the cover portion and connected to the outer film; and At least a portion of the cover portion is exposed to the outside and includes a terminal portion electrically connected to the electrode assembly, The joining part of the above connecting part is, A secondary battery comprising a first layer including a first resin and having an outer surface allowing bonding with an inner surface of the outer film and an inner surface allowing bonding with an outer surface of the cover portion.

2. In claim 1, The above first resin has a melting point (T m ) resin having a melting point (T ) of 135°C to 150°C, a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and a melting point (T ) of m ) A secondary battery comprising a resin selected from the group consisting of resins having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C and a melting point of 135°C to 150°C.

3. In claim 1, A secondary battery, wherein the first resin comprises a modified polyolefin resin.

4. In claim 1, The joining part of the above connecting part is, A first layer comprising a first resin and allowing bonding with the outer surface of the cover portion, A secondary battery comprising a second resin, a second layer laminated on the outer surface of the first layer, and allowing bonding with the inner surface of the outer film.

5. In claim 4, The above first resin has a melting point (T m ) resin having a melting point (T ) of 135°C to 150°C, a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and a melting point (T ) of m ) comprises a resin selected from the group consisting of resins having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C and a melting point of 135°C to 150°C, The above second resin has a melting point (T m ) resin having a melting point (T ) of 120°C to 145°C, a melt flow rate (MFR) of 5 g / 10 min to 18 g / 10 min at 230°C, and a melting point (T ) of m ) A secondary battery comprising a resin selected from the group consisting of resins having a melt flow rate (MFR) of 5 g / 10 min to 18 g / 10 min at 230°C and a melting point of 120°C to 145°C.

6. In claim 4, The above first resin and second resin, A secondary battery that satisfies at least one of the relationships in Equation 1 below and Equation 2 below: [Formula 1] T m2 > T m1 In the above equation 1, T m1 is the melting point of the first resin, and T m2 is the melting point of the second resin, and the unit is ℃. [Formula 2] MFR2> MFR1 In the above equation 2, MFR1 is the melt flow rate of the first resin, MFR2 is the melt flow rate of the second resin, and the unit is g / 10 min.

7. In claim 4, The first resin comprises a modified polyolefin resin, A secondary battery, wherein the second resin comprises a non-stretchy polyolefin resin.

8. In claim 1, The joining part of the above connecting part is, A first layer comprising a first resin and allowing bonding with the outer surface of the cover portion, A second layer comprising a second resin and allowing bonding with the inner surface of the outer film, A secondary battery comprising a third resin and a third layer disposed between the first layer and the second layer.

9. In claim 8, The above first resin has a melting point (T m ) resin having a melting point (T ) of 135°C to 150°C, a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C, and a melting point (T ) of m ) comprises a resin selected from the group consisting of resins having a melt flow rate (MFR) of 4 g / 10 min to 10 g / 10 min at 230°C and a melting point of 135°C to 150°C, The above second resin has a melting point (T m ) resin having a melting point (T ) of 120°C to 145°C, a melt flow rate (MFR) of 5 g / 10 min to 18 g / 10 min at 230°C, and a melting point (T ) of m ) comprises a resin selected from the group consisting of resins having a melt flow rate (MFR) of 5 g / 10 min to 18 g / 10 min at 230°C and a melting point of 120°C to 145°C, The above third resin has a melting point (T m ) resin having a melting point (T ) of 145°C to 170°C, a melt flow rate (MFR) of 2 g / 10 min to 4 g / 10 min at 230°C, and a melting point (T ) of m ) A secondary battery comprising a resin selected from the group consisting of resins having a melt flow rate (MFR) of 2 g / 10 min to 4 g / 10 min at 230°C and a melting point of 145°C to 170°C.

10. In claim 8, The first resin, the second resin and the third resin are, A secondary battery that satisfies at least one of the relationships in Equation 3 below and Equation 4 below: [Formula 3] T m3 > T m2 > T m1 In the above equation 3, T m1 is the melting point of the first resin, and T m2 is the melting point of the second resin, and T m3 is the melting point of the third resin, and the unit is ℃. [Formula 4] MFR2> MFR1> MFR3 In the above equation 4, MFR1 is the melt flow rate of the first resin, MFR2 is the melt flow rate of the second resin, and MFR3 is the melt flow rate of the third resin, and the unit is g / 10 min.

11. In claim 8, The first resin comprises a modified polyolefin resin, The above second resin includes a non-stretchy polyolefin resin, A secondary battery, wherein the third resin comprises a homopolyolefin resin.

12. In claim 1, The above connection part is, A secondary battery comprising a connecting portion provided on at least one surface of the cover portion, excluding the outer surface of the cover portion having the connecting portion, provided on one surface of the cover portion.

13. In claim 12, The connecting part of the above connecting part is, A secondary battery comprising a first layer including a first resin and having an inner surface that allows bonding with one surface of the cover portion.

14. In claim 12, The connecting part of the above connecting part is, A first layer comprising a first resin and allowing bonding with one side of the cover portion, A secondary battery comprising a second layer comprising a second resin and laminated on the outer surface of the first layer.

15. In claim 12, The connecting part of the above connecting part is, A first layer comprising a first resin and allowing bonding with one side of the cover portion, A second layer containing a second resin and arranged at the outermost end, A secondary battery comprising a third resin and a third layer disposed between the first layer and the second layer.

16. In claim 1, The outer circumferential surface of the above cover portion extends in the circumferential direction of the electrode assembly, A secondary battery, wherein the above-mentioned connecting portion is provided on the outer circumferential surface of the cover portion.

17. In claim 1, The above cover part, A cover portion having an outwardly facing surface facing the outside of the electrode assembly; and Including an extension portion extending from the cover portion toward the electrode assembly, A secondary battery, wherein the above-mentioned connecting portion is provided on the outer surface of the above-mentioned extension portion.

18. In claim 17, The above cover portion has a plate shape, The above extension portion is a secondary battery extending from the edge of the cover portion.

19. In claim 1, A secondary battery, wherein the outer film has a predetermined flexibility so that it can be bent.

20. Secondary battery; and A packaging comprising a secondary battery, The above secondary battery, An electrode assembly extending in one direction; An outer film covering a portion of the electrode assembly; and comprising a cap surrounding the remainder of the electrode assembly; The above cap is, A cover portion covering one side of the extension direction of the electrode assembly; A connecting portion including a connecting portion provided on the outer surface of the cover portion and connected to the outer film; and At least a portion of the cover portion is exposed to the outside and includes a terminal portion electrically connected to the electrode assembly, The joining part of the above connecting part is, A battery pack comprising a first layer comprising a first resin and having an outer surface allowing bonding with an inner surface of the outer film and an inner surface allowing bonding with an outer surface of the cover portion.

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