Secondary battery and method of manufacturing the same

Abstract

The present invention provides a secondary battery in which an electrode assembly is built into a pouch, and a lead electrically connected to the electrode assembly has one side protruding to the outside of the pouch. The secondary battery includes: a pouch containing the electrode assembly, which is sealed along the edge of the pouch; a lead having one end connected to the electrode assembly and another end protruding to the outside of the pouch; and a lead film disposed between the lead and the pouch and adhering to each of the pouch and the lead when the pouch is sealed, wherein an extension of a predetermined length is formed on the pouch, and the lead film has a region therein that accommodates the entire extension.

Description

Technical Field

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0154998, filed on November 18, 2020, which is incorporated herein by reference in its entirety.

[0002] This invention relates to a secondary battery and a method for manufacturing the secondary battery, and more specifically, to a secondary battery and a method for manufacturing the secondary battery in which an extension is formed at the protruding portion of the lead wire in the bag to increase the sealing area, thereby improving the sealing performance. Background Technology

[0003] The demand for secondary batteries as an energy source is rapidly increasing across various sectors, including personal portable devices and electric vehicles.

[0004] Unlike primary batteries, rechargeable secondary batteries have been developed not only for digital devices but also for vehicles such as electric vehicles.

[0005] Secondary batteries are classified in various ways based on the materials and shapes of their positive and negative electrodes. Among them, lithium secondary batteries, which use lithium compound materials, are widely used as a replacement for nickel-cadmium secondary batteries based on related technologies due to their large capacity and low self-discharge rate.

[0006] Furthermore, lithium secondary batteries can be manufactured in various shapes. Typically, lithium secondary batteries can be manufactured as cylindrical, prismatic, or pouch types.

[0007] like Figure 1 a and Figure 1 b The diagram illustrates the state of the electrode assembly before and after it is installed on a bag with a conventional structure. The bag-type secondary battery includes a bag 4 and an electrode assembly 1 built into the bag 4 for charging and discharging energy.

[0008] Electrode assembly 1 is constructed by alternately stacking negative and positive electrodes with a diaphragm between them, and electrode contacts 1a and 1b, including a negative electrode contact protruding from the negative electrode and a positive electrode contact protruding from the positive electrode, are respectively welded to leads 2a and 2b on both sides of electrode assembly 1. As shown in the figure, according to the manufacturing method of the positive and negative electrodes, the positive electrode contact and the negative electrode contact can be disposed on opposite sides of each other.

[0009] In addition, the ends of leads 2a and 2b protrude beyond the bag 4 for electrical connection with external devices.

[0010] The pouch 4 is divided into an upper portion 5 and a lower portion 6, which can accommodate the electrode assembly 1 by covering one side and the other side of the electrode assembly 1, and is provided in a structure in which the upper portion 5 and the lower portion 6 are connected to each other at one side.

[0011] Grooves 5a and 6a are formed in the upper portion 5 and the lower portion 6 of the pouch 4 to accommodate the electrode assembly 1, respectively, and each of edges 5b and 6b of the grooves 5a and 6a is formed flat along the outer periphery of the pouch 4. Thus, after the electrode assembly 1 is installed, when the upper portion 5 and the lower portion 6 of the pouch 4 are closed, the edges 5b and 6b of the upper portion 5 and the lower portion 6 come into contact with each other in this state, and heat fusion is performed by applying heat and pressure to form a sealing portion.

[0012] Here, when the electrode assembly 1 is installed, one end of each of the lead wires 2a and 2b protrudes outside the pouch 4, and in order to prevent deterioration of the sealing performance of the pouch 4 and at the same time ensure electrical insulation, the lead film 3a and 3b are installed in a state of being attached to the lead wires 2a and 2b.

[0013] As the capacity of the secondary battery increases and is miniaturized, the size of the edges 5b and 6b forming the sealing portion of the pouch 4 tends to gradually decrease. Thus, there is a problem that the sealing strength is reduced, and in particular, when the sealing strength is reduced, electrolyte leakage or the like can occur in the portion in which each of the lead wires 2a and 2b protrudes. SUMMARY

[0014] TECHNICAL PROBLEM

[0015] Therefore, the main object of the present application is to provide a secondary battery capable of increasing the sealing strength of a portion in which a lead wire of a pouch protrudes, and a method of manufacturing the same.

[0016] TECHNICAL SOLUTION

[0017] In order to achieve the above object, in the present application, a method of manufacturing a secondary battery in which an electrode assembly is built in a pouch and a lead wire electrically connected to the electrode assembly has one side protruding to the outside of the pouch, the method including: a pouch setting process of setting the pouch having an internal space in which the electrode assembly is built, and performing sealing along an edge in the pouch, wherein an extension is protruding from a position where the lead wire is seated, the lead wire having one end connected to the electrode assembly and the other end protruding to the outside; and a sealing process of applying heat along the edge of the pouch to seal the pouch in a state in which the electrode assembly and the lead wire are installed in the pouch, and the pouch is closed, wherein, in the sealing process, sealing is performed so that the extension is bonded to the lead wire.

[0018] The lead can be mounted with the lead film, and when the sealing of the extension portion is performed, the extension portion can be heat-fused to the lead film, and the lead film can be heat-fused to the surface of the lead.

[0019] The lead film can have an area in which the entire extension portion is accommodated. The lead film can have a width greater than the width of the lead.

[0020] The length of the extension portion protruding from the side of the pouch in which the extension portion is formed can be less than 50% of the length of the lead protruding from the side of the pouch in which the extension portion is formed.

[0021] A secondary battery according to the present application manufactured by the manufacturing method, in which an electrode assembly is built in a pouch, and a lead electrically connected to the electrode assembly has one side protruding to the outside of the pouch, includes the pouch in which the electrode assembly is built, sealing is performed along the edge of the pouch, the lead having one end connected to the electrode assembly and the other end protruding to the outside of the pouch, and a lead film disposed between the lead and the pouch and adhered to each of the pouch and the lead when the sealing of the pouch is performed, in which an extension portion extending a predetermined length in the length direction of the lead is formed on the pouch, and the lead film has an area in which the entire extension portion is accommodated.

[0022] The extension portion can be heat-fused to the lead film, and the lead film can be heat-fused to the surface of the lead.

[0023] The extension portion can have a width less than or equal to the width of the lead, and the width of the lead film can be greater than the width of the lead.

[0024] The length of the extension portion protruding from the side of the pouch in which the extension portion is formed can be less than 50% of the length of the lead protruding from the side of the pouch in which the extension portion is formed.

[0025] Advantageous effects

[0026] In the present application having the above-described configuration, since the extension portion is formed on the pouch, and the sealing area is increased by the area of the extension portion, the sealing performance in the portion in which the lead is provided can be further improved, and thus the possibility of electrolyte leakage and the possibility of lead damage can be further reduced.

[0027] The lead film can be heat-fused to the extension portion of the pouch and the lead. Here, since the area and the width of the lead film are greater than the area and the width of the extension portion, an effect in which the width of the sealing point is increased can be expected. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 a is a view illustrating a state in which the electrode assembly is installed in a pouch having a conventional structure.

[0029] Figure 1 b is a view illustrating a state in which the electrode assembly is installed in a pouch having a conventional structure, and then sealing is performed, and is an enlarged view of a region in which a lead protrudes.

[0030] Figure 2 is a view illustrating a state before the electrode assembly according to the present application is installed in a pouch,

[0031] Figure 3 is a view illustrating a state in which the electrode assembly according to the present application is installed in a pouch, and then sealing is performed, and is an enlarged view of a region in which a lead protrudes.

[0032] Figure 4 is a plan view illustrating a region S in which sealing is performed in a secondary battery according to the present application. DETAILED DESCRIPTION

[0033] Hereinafter, preferred embodiments of the present application will be described in detail with reference to the accompanying drawings so as to be easily practiced by one of ordinary skill in the art to which the present application pertains. However, the present application can be embodied in different forms and should not be construed as limited to the embodiments set forth herein.

[0034] In order to clearly describe the present application, portions unrelated to the description are omitted, and the same reference numerals denote the same or similar components throughout the application.

[0035] Further, the terms or words used in the present specification and claims should not be interpreted as being limited to the commonly used meanings or meanings based on the dictionary, but should be interpreted based on the meanings and concepts according to the principle of the present application on the basis of the concept of the inventor's ability to define the terms appropriately to best describe and explain the present application.

[0036] The present application relates to a secondary battery and a method of manufacturing the same, and more particularly, to a secondary battery in which expansion portions 51a, 51b, 61a, and 61b are formed at portions in which leads 20a and 20b of a pouch 40 protrude to increase a sealing area, thereby improving sealing performance, and a method of manufacturing the same. Hereinafter, embodiments according to the present application will be described in more detail with reference to the accompanying drawings.

[0037] First embodiment

[0038] Figure 2 is a view illustrating a state before the electrode assembly according to the present application is installed in a pouch, Figure 3is a diagram illustrating a state in which the electrode assembly according to the present application is installed in a pouch, and then sealing is performed, and is an enlarged view of a region in which a lead is protruded.

[0039] Referring to Figure 2 and Figure 3 The secondary battery according to the present embodiment has a structure in which the electrode assembly 10 is built in a pouch 40, and one side of each of leads 20a and 20b electrically connected to the electrode assembly 10 is protruded to the outside of the pouch 40.

[0040] That is, in the present embodiment, the secondary battery includes the electrode assembly 10, the pouch 40 (50 and 60), the leads 20 (20a and 20b), and the lead film 30 (30a and 30b), and the pouch 40 has a structure in which extension portions 51 and 61 (51a, 51b, 61a, and 61b) are formed.

[0041] The electrode assembly 10 is constructed by alternately stacking negative electrodes and positive electrodes having a separator therebetween, and a negative tab protruded from the negative electrode and a positive tab protruded from the positive electrode are respectively welded to the leads 20a and 20b at both sides of the electrode assembly 10.

[0042] Further, end portions of the leads 20a and 20b are installed in the pouch 40 to be protruded to the outside of the pouch 40, so that the leads 20a and 20b are electrically connected to an external device. The pouch 40 is divided into an upper portion 50 and a lower portion 60, the upper portion 50 and the lower portion 60 are capable of accommodating the electrode assembly 10 by covering one side and the other side of the electrode assembly 10, and are provided in a structure in which the upper portion 50 and the lower portion 60 are connected to each other at one side. Alternatively, in some cases, the upper portion 50 and the lower portion 60 can be provided in a state of being completely separated.

[0043] Grooves 50a and 60a are formed in the upper portion 50 and the lower portion 60 of the pouch 40 to accommodate the electrode assembly 10, respectively, and each of edges 50b and 60b of the grooves 50a and 60a is formed flat along the outer periphery of the pouch 40. When the upper portion 50 and the lower portion 60 of the pouch 40 are closed after the electrode assembly 10 is installed, the edges 50b and 60b of the upper portion 50 and the lower portion 60 come into contact with each other in this state, and heat fusion is performed by applying heat and pressure to form a sealing portion.

[0044] Accordingly, one end of each of the leads 20a and 20b is connected to the electrode assembly 10, and the other end is protruded to the outside of the pouch 40. Here, the lead film 30 (30a and 30b) is attached to the side of the lead 20 protruded to the outside of the pouch 40, respectively. Accordingly, as Figure 3As shown in FIG. 1, when sealing is performed, each lead film 30 is disposed between each lead 20 and the pouch 40 (between the edges of the pouch), and when heat fusion is performed, one surface of each lead film 30 is adhered to the pouch 40, and the other side of each lead film 30 is adhered to each lead 20.

[0045] Further, the extensions 51 and 61 are formed on the pouch 40, each of the extensions 51 and 61 extending a predetermined length in the length direction of the lead 20. Here, the lead film 30 is formed in a size in which the entire extensions 51 and 61 are accommodated therein.

[0046] In the secondary battery provided in the present embodiment, the width of the extension 51 is less than or equal to the width of the lead 20, and the width of the lead film 30 is greater than the width of the lead 20. The width used here refers to the length in the direction perpendicular to the length direction of the lead.

[0047] Further, preferably, the protruding length d1 of each of the extensions 51 and 61 from the side of the pouch 40 on which the extensions 51 and 61 are formed is less than 50% of the protruding length d2 of the lead 20 from the side of the pouch 40 on which the extensions 51 and 61 are formed.

[0048] More specifically, preferably, the protruding length d1 of each of the extensions 51 and 61 is formed in a range of 20% to 40% of the protruding length d2 of the lead 20.

[0049] When the protruding length d1 of each of the extensions 51 and 61 is formed to be less than 20% of the protruding length d2 of the lead 20, there is a problem in that the effect of increasing the sealing force is reduced due to the formation of the extensions 51 and 61. When the protruding length d1 exceeds 40% of the protruding length d2, the exposed area of the lead 20 is excessively covered, and thus there is a possibility that interference occurs when the lead 20 is electrically connected to an external device. Therefore, it is preferable to form within the above range so as to take into account such a state.

[0050] Therefore, when heat and pressure are applied to the pouch 40, the heat and pressure are transmitted in the order of the extensions 51 and 61, the lead film 30, and the lead 20. As a result, the extensions 51 and 61 are heat-fused to the lead film 30, and the lead film 30 is heat-fused to the surface of the lead 20.

[0051] Second embodiment

[0052] Further, the present application provides a method of manufacturing a secondary battery having the above structure as a second embodiment.

[0053] The manufacturing method according to the embodiment includes a pouch disposing step and a sealing step.

[0054] In the bag setting process, a bag 40 with an internal space is provided, in which the electrode assembly 10 is built, and the bag 40 is sealed along edges 50b and 60b. Here, each of the extensions 51 and 61 protrudes from the position where the lead 20 is placed, one end of the lead 20 is connected to the electrode assembly 10 and the other end protrudes to the outside.

[0055] Bag 40 is manufactured by molding and cutting the raw material of bag 40. Here, the portions of the upper part 50 and the lower part 60 of bag 40 with grooves 50a and 60a are formed by deforming the raw material by pressing with a punch, and the portions of the edges 50b and 60b are processed to a predetermined size by cutting the raw material. Here, when cutting is performed to form the edges 50b and 60b of the upper part 50 and the lower part 60, extensions 51 and 61 are processed to be provided, each of the extensions 51 and 61 protruding to a predetermined size from each portion of the placement lead 20 of the edges 50b and 60b.

[0056] Furthermore, the sealing process includes a receiving process that houses the electrode assembly 10 within the bag 40. During the receiving process, when the electrode assembly 10 is housed within the bag 40, a portion of the lead film 30 and the end of the lead 20 are received and protrude into the extensions 51 and 61.

[0057] Furthermore, during the sealing process, heat is applied to the edges 50b and 60b of the upper part 50 and the lower part 60 of the bag 40 when they are in contact with each other, so as to perform a seal.

[0058] When sealing edges 50b and 60b, extensions 51 and 61 are also sealed to connect to lead 20.

[0059] Since the lead 20 is installed in a state of being bonded to the lead film 30, when the sealing of the extensions 51 and 61 is performed, the extensions 51 and 61 are thermally fused to the lead film 30, and the lead film 30 is thermally fused to the surface of the lead 20.

[0060] The lead film 30 has a region that accommodates the entire extension portions 51 and 61. The width of the lead film 30 is greater than the width of the lead 20.

[0061] like Figure 4 As shown, a sealed region S is displayed in the secondary battery according to the invention. In the invention with the above-described structure, extensions 51 and 61 can be formed in the pouch 40, and the sealing area can be increased by the area increased by the extensions 51 and 61, thereby further improving the sealing performance at the portion where the lead 20 is provided. Therefore, the possibility of electrolyte leakage and the possibility of lead damage can be further reduced.

[0062] The lead film 30 can be heat-fused to the extensions 51 and 61 of the bag 40 and the lead 20. Here, since the area and width of the lead film 30 are larger than the area and width of each of the extensions 51 and 61, the effect of increasing the width of the sealing point is expected.

[0063] Although embodiments of the invention have been described with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

[0064] [Label Explanation]

[0065] 10: Electrode assembly

[0066] 40: bag

[0067] 50: The upper part of the bag

[0068] 60: The bottom of the bag

[0069] 30 (30a, 30b): Lead film

[0070] 51a, 51b, 61a, 61b: Extension section.

Claims

1. A secondary battery, wherein an electrode assembly is housed within a pouch, and a lead electrically connected to the electrode assembly has a side protruding to the outside of the pouch, the secondary battery comprising: The bag containing the electrode assembly is sealed along its edges; The lead wire has one end connected to the electrode assembly and the other end protruding to the outside of the bag; as well as A lead film is disposed between the lead and the bag, a portion of the lead film protruding to the outside of the bag, and adhering to each of the bag and the lead when the bag is sealed. The lead wire and lead wire film on the bag have extension portions that extend a predetermined length along the length direction of the lead wire at the protruding positions, thereby increasing the fusion area between the lead wire film and the bag. The lead film has a region therein that accommodates the entire extension. The extension portion is thermally fused to the lead film, and The lead film is thermally fused to the surface of the lead.

2. The secondary battery according to claim 1, wherein the extension portion has a width less than or equal to the width of the lead.

3. The secondary battery according to claim 2, wherein the width of the lead film is greater than the width of the lead.

4. The secondary battery according to claim 1, wherein the length of the extension protruding from the side of the pouch where the extension is formed is less than 50% of the length of the lead protruding from the side of the pouch where the extension is formed.

5. A method of manufacturing a secondary battery, wherein an electrode assembly is housed within a pouch, and a lead electrically connected to the electrode assembly has a side protruding to the outside of the pouch, the method comprising: The bag setting process involves setting a bag having an internal space, housing the electrode assembly within the internal space, and sealing the bag along its edges, wherein an extension protrudes from the location where the lead wire is placed, the lead wire having one end connected to the electrode assembly and another end protruding to the outside; as well as In the sealing process, heat is applied along the edge of the bag to seal the bag while the electrode assembly and the leads are mounted inside, and the bag is then closed. In the sealing process, a seal is performed to attach the extension to the lead. The lead wire is mounted together with the lead wire film. When the sealing of the extension is performed, the extension is thermally fused to the lead film, and the lead film is thermally fused to the surface of the lead. The lead film has a region therein that accommodates the entire extension.

6. The method of claim 5, wherein the lead film has a width greater than the width of the lead.

7. The method of claim 5, wherein the length of the extension protruding from the side of the bag where the extension is formed is less than 50% of the length of the lead protruding from the side of the bag where the extension is formed.

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