Secondary battery and manufacturing method thereof

Abstract

A secondary battery according to an embodiment of the present invention may include a first electrode assembly having a plurality of first electrode tabs joined to each other, a second electrode assembly having a plurality of second electrode tabs joined to each other and stacked on the first electrode assembly, an electrode lead connected to the first electrode tabs, and a conductive connecting member connecting the second electrode tabs to the electrode lead. The electrode lead may include a tab connecting portion joined to the first electrode tabs, a bridge portion bent or folded in one rotational direction from the tab connecting portion, and a lead portion bent or folded in the other rotational direction from the bridge portion. One end of the conductive connecting member may be connected to the bridge portion or the lead portion.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0179053, filed December 20, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a secondary battery including a plurality of electrode assemblies and a method for manufacturing the same. [Background technology]

[0003] In recent years, with the depletion of fossil fuels causing rising energy costs and growing concerns about environmental pollution, the need for environmentally friendly alternative energy sources has become an essential factor for future life. Therefore, research into various electricity production technologies, such as solar, wind, and tidal power, is ongoing, and there is also great interest in energy storage devices such as batteries to more efficiently use the electrical energy produced in this way.

[0004] Furthermore, with the increasing technological development and demand for electronic mobile devices and electric vehicles that use secondary batteries, the demand for secondary batteries as an energy source is rapidly increasing, and as a result, much research is being conducted on secondary batteries that can meet various needs.

[0005] Secondary batteries can be classified into cylindrical secondary batteries, pouch-type secondary batteries, prismatic secondary batteries, etc. depending on the shape of the battery case. Among these, pouch-type secondary batteries can accommodate an electrode assembly in which a positive electrode, a negative electrode, a separator, etc. are stacked inside a pouch-type battery case. Pouch-type secondary batteries can be effectively used in various designs.

[0006] However, recently, pouch-type secondary batteries have been designed to be longer and thicker to increase energy density in line with the trend toward higher capacity and higher output. That is, the electrode assemblies included in pouch-type secondary batteries have become longer and thicker, and as a result, packaging materials and components are increasingly exposed to harsher process conditions and usage environments.

[0007] However, if the electrode assembly becomes too thick, the variation in length between the electrode tabs will increase, which may make it difficult to supply a stable current, and there may be a greater risk of the outermost electrode tabs being broken due to external impact or deformation of the electrode assembly. Summary of the Invention [Problem to be solved by the invention]

[0008] One problem that the present invention aims to solve is to provide a secondary battery and a manufacturing method thereof that can reduce variation in length between electrode tabs and prevent the risk of breakage in the outermost electrode tabs.

[0009] Another problem to be solved by the present invention is to provide a secondary battery having a simple structure and high energy density, and a method for manufacturing the same. [Means for solving the problem]

[0010] A secondary battery according to an embodiment of the present invention may include a first electrode assembly having a plurality of first electrode tabs joined to each other, a second electrode assembly having a plurality of second electrode tabs joined to each other and stacked on the first electrode assembly, an electrode lead connected to the first electrode tabs, and a conductive connecting member connecting the second electrode tabs to the electrode lead. The electrode lead may include a tab connecting portion joined to the first electrode tabs, a bridge portion bent or folded in one rotational direction from the tab connecting portion, and a lead portion bent or folded in the other rotational direction from the bridge portion. One end of the conductive connecting member may be connected to the bridge portion or the lead portion.

[0011] The secondary battery may further include an insulating member surrounding a portion of each of both ends of the electrode lead adjacent to one end thereof, and one end of the conductive connecting member may be joined between the other end of the electrode lead and the insulating member.

[0012] The other end of the electrode lead may be joined to the first electrode tab, and the other end of the conductive connecting member may be joined to the second electrode tab.

[0013] The secondary battery may further include a battery case that accommodates the first electrode assembly and the second electrode assembly, the insulating member may insulate the electrode lead from the battery case, and one end of the electrode lead may be located outside the battery case.

[0014] The electrode lead can be bent or folded at least two times in opposite directions.

[0015] The conductive connection member may include a tab joint portion joined to the second electrode tab, a bridge portion bent or folded at the tab joint portion, and a lead joint portion extending, bent, or folded at the bridge portion and joined to the electrode lead.

[0016] The thickness of the electrode lead and the conductive connecting member may be greater than the thickness of each of the first electrode tab and the second electrode tab.

[0017] The conductive connecting member may have a length shorter than that of the electrode lead.

[0018] A method for manufacturing a secondary battery according to another embodiment of the present invention may include stacking a first electrode assembly having a plurality of first electrode tabs joined to each other and a second electrode assembly having a plurality of second electrode tabs joined to each other, preparing a lead assembly, and connecting the lead assembly to the first electrode assembly and the second electrode assembly. The step of preparing the lead assembly may include wrapping a portion of both ends of an electrode lead adjacent to one end with an insulating member, and connecting one end of a conductive connecting member between the other end of the electrode lead and the insulating member. In the step of connecting the lead assemblies, the other end of the electrode lead may be connected to the first electrode tab and the other end of the conductive connecting member to the second electrode tab.

[0019] In the step of preparing the lead assembly, the length of the conductive connection member may be shorter than the length of the electrode lead.

[0020] The step of preparing the lead assembly may further include bending or folding the electrode lead at least twice in opposite directions and bending or folding the conductive connecting member at least once. [Effects of the Invention]

[0021] According to a preferred embodiment of the present invention, instead of a single thick electrode assembly, multiple electrode assemblies are stacked, thereby reducing the variation in length between the electrode tabs joined to each other in each electrode assembly, thereby enabling stable current supply and minimizing the risk of disconnection of the outermost electrode tabs due to external impact or deformation of the electrode assembly.

[0022] Furthermore, since the lead assembly is manufactured by welding the electrode lead and the conductive connecting member, there is an advantage that the structure and manufacturing of the lead assembly are simple.

[0023] Furthermore, since the conductive connecting member is formed shorter than the electrode lead, the space occupied by the conductive connecting member in the battery case can be reduced, thereby improving the energy density of the secondary battery and reducing the manufacturing costs of the lead assembly, especially the conductive connecting member.

[0024] In a manufacturing method according to a preferred embodiment of the present invention, a lead assembly may be prepared first, and then the lead assembly may be connected to a plurality of electrode assemblies, which has the advantages of reducing manufacturing tolerances for the lead assembly and simplifying manufacturing compared to a method in which electrode leads and conductive connecting members are first connected to a plurality of electrode assemblies, and then the conductive connecting members are connected to the electrode leads.

[0025] Furthermore, since the process of manufacturing the lead assembly and the process of manufacturing and stacking the electrode assembly can be separated, there is an advantage in that each process can be easily managed.

[0026] Other effects may be included that can be easily predicted by a person skilled in the art from the configuration according to the preferred embodiment of the present invention. [Brief explanation of the drawings]

[0027] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical concept of the present invention, and the present invention should not be interpreted as being limited solely to the matters shown in such drawings.

[0028] [Figure 1] 1 is a perspective view of a secondary battery according to an embodiment of the present invention; [Figure 2] 1 is a perspective view illustrating an electrode assembly and a lead assembly according to an embodiment of the present invention; [Figure 3] FIG. 2 is a partial cross-sectional view taken along line AA' in FIG. [Figure 4] FIG. 10 is a partial cross-sectional view of a secondary battery according to a comparative example. [Figure 5]1 is a plan view illustrating an electrode lead and a conductive connecting member according to an embodiment of the present invention in an unfolded state; [Figure 6a] FIG. 4 illustrates a modification of the lead assembly shown in FIG. 3. [Figure 6b] FIG. 4 illustrates a modification of the lead assembly shown in FIG. 3. [Figure 6c] FIG. 4 illustrates a modification of the lead assembly shown in FIG. 3. [Figure 7] 10 is a flowchart of a method for manufacturing a secondary battery according to another embodiment of the present invention. [Figure 8] 8 is a flowchart of steps for preparing the lead assembly shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will now be described in detail with reference to the accompanying drawings, in order to enable those skilled in the art to easily carry out the present invention. However, the present invention may be embodied in various different forms and should not be construed as being limited to the following embodiments.

[0030] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the description or related known technologies that may obscure the gist of the present invention will be omitted. In this specification, when referring to components in each drawing, the same or similar reference numerals will be used throughout the specification to refer to the same or similar components.

[0031] Furthermore, the terms and words used in this specification and claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0032] FIG. 1 is a perspective view of a secondary battery according to one embodiment of the present invention, FIG. 2 is a perspective view illustrating an electrode assembly and a lead assembly according to one embodiment of the present invention, and FIG. 3 is a partial cross-sectional view taken along line A-A' in FIG. 1.

[0033] A secondary battery 1 according to an embodiment of the present invention may include a battery case 10, a plurality of electrode assemblies 20 housed in the battery case 10, and a lead assembly 30 connecting the plurality of electrode assemblies 20.

[0034] The battery case 10 may be a pouch-type battery case manufactured by molding a laminate film. More specifically, the battery case 10 may include a receiving portion 11 that receives a plurality of electrode assemblies 20 and a sealing portion 12 located on the periphery of the receiving portion 11.

[0035] The battery case 10 may be manufactured by forming a pair of cases, at least one of which has a recessed receiving portion 11, facing each other with the plurality of electrode assemblies 20 interposed therebetween, and sealing the periphery of the receiving portion 11 to form a sealing portion 12. The pair of cases may be connected by a folding portion on one side, or may be separate cases. This is a well-known technique, so a detailed description thereof will be omitted.

[0036] Each electrode assembly 20 may be formed by interposing a separator between alternatingly arranged positive and negative electrodes. That is, each electrode assembly 20 may include a plurality of electrodes and separators interposed between the plurality of electrodes to insulate the plurality of electrodes from each other. The electrode assembly 20 may be housed in the housing 11 of the battery case 10 together with an electrolyte.

[0037] The electrode assembly 20 may be of a stack type, a jelly roll type, a stack and folding type, or the like, and the type of the electrode assembly 20 is not limited.

[0038] Each electrode assembly 20 may include a plurality of electrode tabs 21 joined to one another. The electrode tabs 21 may act as a path through which electrons can move between the inside and outside of the electrode assembly 20.

[0039] The electrode tabs 21 may be joined together by welding them together, which may be called "pre-welding." Pre-welding may be performed by ultrasonic welding, laser welding, or resistance welding.

[0040] More specifically, each electrode assembly 20 may include a plurality of joined positive electrode tabs and a plurality of joined negative electrode tabs. The positive electrode tabs and the negative electrode tabs may protrude in different directions from the electrode assembly 20, but are not limited thereto, and may protrude in various directions, such as protruding in parallel in the same direction from one side.

[0041] A plurality of electrode assemblies 20 may be stacked on one another. The thickness of the stack of the plurality of electrode assemblies 20 may be 30 mm or more. This allows the secondary battery 1 to have a high output.

[0042] However, to prevent each electrode assembly 20 from becoming excessively thick, the number of electrodes included in each electrode assembly 20 may be 30 to 50. That is, each electrode assembly 20 may be formed by stacking 30 to 50 electrodes alternately with separators. Here, the thickness of each electrode, more specifically, the current collector of each electrode, may be 5 to 20 μm. Each electrode tab 21 is formed by cutting out a portion of the current collector, and the thickness of the electrode tab 21 may be 5 to 20 μm.

[0043] The plurality of electrode assemblies 20 may include a first electrode assembly 20A and a second electrode assembly 20B stacked on the first electrode assembly 20A. If necessary, the plurality of electrode assemblies 20 may further include a third electrode assembly, a fourth electrode assembly, and so on.

[0044] As described above, the electrode tabs 21 of each electrode assembly 20 may be joined to one another. The electrode tab 21 of the first electrode assembly 20A may be referred to as the first electrode tab 21A, and the electrode tab 21 of the second electrode assembly 20B may be referred to as the second electrode tab 21B.

[0045] The lead assemblies 30 may be provided in pairs. One lead assembly 30 may be a positive electrode lead assembly that connects the positive electrode tabs of the plurality of electrode assemblies 20 to each other, and the other lead assembly 30 may be a negative electrode lead assembly that connects the negative electrode tabs of the plurality of electrode assemblies 20 to each other.

[0046] The lead assembly 30 may connect the electrode tabs 21 of the plurality of electrode assemblies 20 to each other. The lead assembly 30 may connect the first electrode tab 21A and the second electrode tab 21B.

[0047] The lead assembly 30 may include an electrode lead 40 connected to the electrode tab 21 of one of the electrode assemblies 20, and a conductive connection member 50 connecting the electrode lead 40 to the electrode tab 21 of another electrode assembly 20.

[0048] That is, the lead assembly 30 may include an electrode lead 40 connected to the first electrode tab 21A, and a conductive connecting member 50 connecting the second electrode tab 21B and the electrode lead 40. The lead assembly 30 may further include an insulating member 60 surrounding a portion of the electrode lead 40.

[0049] The electrode lead 40 and conductive connecting member 50 may act as a path for electrical current to travel between the electrode assembly 20 and an external component.

[0050] The electrode lead 40 and the conductive connecting member 50 included in the positive electrode lead assembly may be made of the same material as the positive electrode current collector, for example, aluminum.

[0051] The electrode lead 40 and the conductive connecting member 50 included in the negative electrode lead assembly may be made of the same material as the negative electrode current collector, for example, nickel (Ni) and / or copper (Cu). In particular, when the secondary battery 1 is used in an electric vehicle (EV) or an energy storage system (ESS), the electrode lead 40 and the conductive connecting member 50 included in the negative electrode lead assembly may be made of nickel-plated copper.

[0052] Furthermore, the electrode lead 40 and the conductive connecting member 50 may be surface-treated to ensure corrosion resistance to the electrolyte and adhesion to the insulating member 60, which will be described later. For example, the surfaces of the electrode lead 40 and the conductive connecting member 50 may be treated with at least one of a chromium coating, an oxide film (Al2O3) coating, a chemical conversion coating, and an organic film coating.

[0053] The electrode lead 40 and the conductive connecting member 50 may be connected to the electrode tab 21 by being welded to the electrode tab 21. This process may be referred to as main welding. Main welding may be performed by ultrasonic welding, laser welding, or resistance welding.

[0054] The electrode lead 40 may protrude to the outside through the sealing portion 12 of the battery case 10. More specifically, one end 40a of the electrode lead 40 may be located outside the battery case 10, and the other end 40b of the electrode lead 40 may be joined to the first electrode tab 21A.

[0055] The conductive connection member 50 may connect the second electrode tab 21B and the electrode lead 40 inside the battery case 10. The conductive connection member 50 may be connected to the electrode lead 40 by welding. The welding between the conductive connection member 50 and the electrode lead 40 may be performed by ultrasonic welding, laser welding, or resistance welding.

[0056] More specifically, one end 50a of the conductive connecting member 50 can be joined between the other end 40b of the electrode lead 40 and the insulating member 60, and the other end 50b of the conductive connecting member 50 can be joined to the second electrode tab 21B.

[0057] The thickness of the electrode lead 40 and the conductive connecting member 50 can be thicker than the thickness of each electrode tab 21. More specifically, the thickness of the electrode lead 40 and the conductive connecting member 50 can be 200 μm or more, and the thickness of the electrode tab 21 can be 5 to 20 μm, as described above. In other words, the thickness of the electrode lead 40 and the conductive connecting member 50 can be 10 times or more the thickness of the electrode tab 21.

[0058] This allows the electrode lead 40 and the conductive connecting member 50 to have high strength, reducing the risk of breakage due to deformation caused by external impact or swelling of the electrode assembly.

[0059] For smooth current flow, the width of the electrode lead 40 and the conductive connecting member 50 can be 30 mm or more.

[0060] The electrode lead 40 may be bent or folded at least twice in opposite directions, and the conductive connecting member 50 may be bent or folded at least once.

[0061] For this reason, the length of the electrode lead 40 and the conductive connecting member 50 can be 60 mm or more. If the length of the electrode lead 40 and the conductive connecting member 50 is shorter than 60 mm, bending or folding may be difficult.

[0062] As a result, even if each electrode assembly 20 expands or deforms, the electrode leads 40 and the conductive connecting members 50 are not broken and can be gradually deployed. In addition, tension applied to the electrode tabs 21 of each electrode assembly 20 is minimized, thereby preventing breakage of the electrode tabs 21.

[0063] More specifically, the electrode lead 40 may include a tab joint 41 joined to the first electrode tab 21A, a bridge portion 42 bent or folded in one rotational direction (e.g., clockwise with reference to FIG. 3) at the tab joint 41, and a lead portion 43 bent or folded in the other rotational direction (e.g., counterclockwise with reference to FIG. 3) at the bridge portion 42. The lead portion 43 may include one end 40a of the electrode lead 40, and the tab joint 41 may include the other end 40b of the electrode lead 40.

[0064] The conductive connection member 50 may include a tab joint 51 joined to the second electrode tab 21B, a bridge portion 52 bent or folded at the tab joint 51, and a lead joint 53 extending from the bridge portion 52 or bent or folded to be joined to the electrode lead 40. The lead joint 53 may include one end 50a of the conductive connection member 50, and the tab joint 51 may include the other end 50b of the conductive connection member 50.

[0065] Although not shown in the drawings, the portion where the first electrode tab 21A and the electrode lead 40 are joined to each other and / or the portion where the second electrode tab 21B and the conductive connecting member 50 are joined may be surrounded by a protective member (e.g., protective tape).

[0066] The lead joint portion 53 of the conductive connection member 50 can be joined to the bridge portion 42 or the lead portion 43 of the electrode lead 40. Figure 3 shows the state in which the lead joint portion 53 is joined to the lead portion 43.

[0067] The tab joint 41 of the electrode lead 40 and the tab joint 51 of the conductive connecting member 50 can be substantially parallel.

[0068] The tab joint 41 of the electrode lead 40 and the tab joint 51 of the conductive connecting member 50 may have the same or similar lengths. Also, the bridge portion 42 of the electrode lead 40 and the bridge portion 52 of the conductive connecting member 50 may have the same or similar lengths.

[0069] The direction in which the bridge portion 52 of the conductive connection member 50 is bent or folded at the tab joint 51 can be opposite to the direction in which the bridge portion 42 of the electrode lead 40 is bent or folded at the tab joint 41. Therefore, the tab joint 41 and bridge portion 42 of the electrode lead 40 and the tab joint 51 and bridge portion 52 of the conductive connection member 50 are both shaped like a rotated "U" or

number

[0070] The insulating member 60 can insulate the battery case 10 and the electrode lead 40 from each other. The insulating member 60 can be bonded to the electrode lead 40. The insulating member 60 can also be sealed to the battery case 10, more specifically, to the inner surface of the sealing portion 12. This allows the battery case 10 to be reliably sealed, and the electrode lead 40 can protrude to the outside of the battery case 10 through the sealing portion 12.

[0071] The insulating member 60 may surround the electrode lead 40, more specifically, a portion of the lead portion 43. The insulating member 60 may surround a portion of both ends 40a, 40b of the electrode lead 40 that is adjacent to the one end 40a. For example, the insulating member 60 may be an insulating film.

[0072] The insulating member 60 can include at least one, preferably two or more, polypropylene (PP) layers.

[0073] The insulating member 60 may be formed to be long in the width direction of the electrode lead 40, and the length of the insulating member 60 may be greater than the width of the electrode lead 40. More specifically, the length of the insulating member 60 may be 35 mm or more. This allows the insulating member 60 to reliably insulate the electrode lead 40 from the battery case 10.

[0074] The thickness of the insulating member 60 may be thicker than the thickness of the electrode tab 21 and thinner than the thickness of the electrode lead 40. More specifically, the thickness of the insulating member 60 may be 100 μm or greater.

[0075] The lead assembly 30 electrically connects the stacked electrode assemblies 20. In addition, since the variation in length between the joined electrode tabs 21 of each electrode assembly 20 is reduced, a stable current can be supplied and the risk of disconnection of the outermost electrode tab due to external impact or deformation of the electrode assembly 20 can be minimized.

[0076] Furthermore, since the lead assembly 30 is manufactured by welding the electrode lead 40 to which the insulating member 60 is attached and the conductive connecting member 50, the lead assembly 30 has the advantage of being simple in structure and manufacturing.

[0077] FIG. 4 is a partial cross-sectional view of a secondary battery according to a comparative example.

[0078] The secondary battery according to the comparative example may include a battery case 10 and a single electrode assembly 20' housed in the battery case 10. In this case, the thickness of the electrode assembly 20' may correspond to the stack thickness of the plurality of electrode assemblies 20 according to an embodiment of the present invention.

[0079] The electrode assembly 20' may include a plurality of electrode tabs 21' joined to each other, and an electrode lead 40' may be welded to the electrode tabs 21'. An insulating member 60 may insulate the electrode lead 40' from the battery case 10, and the electrode lead 40' may pass through the insulating member 60 and protrude to the outside of the battery case 10.

[0080] The electrode assembly 20' according to this comparative example is formed to be very thick, and therefore, in order for the electrode tabs 21' provided in the electrode assembly 20' to be joined to each other, there must be a large variation in the lengths of the electrode tabs 21'. In this case, there is a risk that the current supply through the electrode tabs 21' will become unstable.

[0081] Furthermore, since a high tension is applied to the outermost electrode tab among the plurality of electrode tabs 21', there is a high risk that the outermost electrode tab may be broken due to an external impact or deformation of the electrode assembly 20'.

[0082] The secondary battery 1 according to one embodiment of the present invention can eliminate the risks that may occur in the secondary battery according to the comparative example.

[0083] FIG. 5 is a plan view illustrating an unfolded state of an electrode lead and a conductive connecting member according to one embodiment of the present invention.

[0084] The length L2 of the conductive connecting member 50 may be shorter than the length L1 of the electrode lead 40. This is because the electrode lead 40 must extend from the first electrode tab 21A to the outside of the battery case 10, whereas the conductive connecting member 50 connects the second electrode tab 21B and the electrode lead 40 inside the battery case 10.

[0085] This reduces the space occupied by the conductive connecting member 50 inside the battery case 10, thereby improving the energy density of the secondary battery 1. Furthermore, the manufacturing costs of the lead assembly 30, particularly the conductive connecting member 50, can be reduced.

[0086] 6a to 6c are diagrams illustrating modifications of the lead assembly shown in FIG.

[0087] 3, in the lead assembly 30 according to one embodiment, the bridge portion 42 of the electrode lead 40 can be bent or folded to form an angle of approximately 90 degrees with respect to the tab joint 41, and the lead portion 43 can be bent or folded to form an angle of approximately 90 degrees with respect to the bridge portion 42. The bridge portion 42 and the lead portion 43 can be bent or folded in opposite directions.

[0088] Furthermore, the bridge portion 52 of the conductive connecting member 50 may be bent or folded to form an angle of approximately 90 degrees with respect to the tab joint portion 51, and the lead joint portion 53 may be bent or folded to form an angle of approximately 90 degrees with respect to the bridge portion 52. The bridge portion 52 and the lead joint portion 53 may be bent or folded in opposite directions. Furthermore, the lead joint portion 53 may be welded to the lead portion 43.

[0089] 6a, in the lead assembly 30a according to the first modification, compared to the lead assembly 30 according to the embodiment, the lead joint portion 53 of the conductive connecting member 50 can extend without being bent or folded at the bridge portion 52. The lead joint portion 53 can be welded to the bridge portion 42 of the electrode lead 40.

[0090] 6b, in the case of a lead assembly 30b according to the second modification, the bridge portion 42 of the electrode lead 40 may be bent or folded to form an obtuse angle with respect to the tab joint portion 41, and the lead portion 43 may be bent or folded to form an obtuse angle with respect to the bridge portion 42. The bridge portion 42 and the lead portion 43 may be bent or folded in opposite directions.

[0091] Furthermore, the bridge portion 52 of the conductive connecting member 50 may be bent or folded to form an obtuse angle with respect to the tab joint portion 51, and the lead joint portion 53 may be bent or folded to form an obtuse angle with respect to the bridge portion 52. The bridge portion 52 and the lead joint portion 53 may be bent or folded in opposite directions. Furthermore, the lead joint portion 53 may be welded to the lead portion 43.

[0092] 6c, in the lead assembly 30a according to the third modification, compared to the lead assembly 30b according to the second modification, the bridge portion 52 and the lead joint portion 53 of the conductive connecting member 50 may be bent or folded in the same direction. The lead joint portion 53 may be welded to the bridge portion 42 of the electrode lead 40.

[0093] As shown in the embodiment and modified examples of the present invention, the lead assembly 30 can be manufactured in various ways, allowing an appropriate lead assembly 30 to be used depending on the size and shape of the battery case and electrode assembly.

[0094] FIG. 7 is a flowchart of a method for manufacturing a secondary battery according to another embodiment of the present invention, and FIG. 8 is a flowchart of steps for preparing the lead assembly shown in FIG.

[0095] A method for manufacturing the above-described secondary battery will now be described as another embodiment of the present invention.

[0096] A method for manufacturing a secondary battery (hereinafter, "manufacturing method") according to another embodiment of the present invention may include the steps of stacking a plurality of electrode assemblies 20 (S10), preparing a lead assembly 30 (S20), and connecting the lead assembly 30 to the plurality of electrode assemblies 20 (S30). The manufacturing method may also include the step of placing the plurality of electrode assemblies 10 in a battery case 10 (S40).

[0097] The step S10 of stacking the plurality of electrode assemblies 20 and the step S20 of preparing the lead assembly 30 may be performed in order, in reverse order, or simultaneously.

[0098] In the step (S10) of stacking the plurality of electrode assemblies 20, the first electrode assembly 20A and the second electrode assembly 20B may be stacked.

[0099] In the step (S20) of preparing the lead assembly 30, the lead assembly 30 can be formed using an electrode lead 40 and a conductive connecting member 50 having a predetermined length and width. The electrode lead 40 and the conductive connecting member 50 can be separate members. The length L2 of the conductive connecting member 50 can be formed to be shorter than the length L1 of the electrode lead 40.

[0100] The step of preparing the lead assembly 30 (S20) may include the step of wrapping a portion of the electrode lead 40 with an insulating member 60 (S21) and the step of connecting the conductive connecting member 50 to the electrode lead 40 (S23). The step of preparing the lead assembly 30 may further include the step of bending or folding the electrode lead 40 and the conductive connecting member 50 (S22).

[0101] In the step S21 of wrapping a portion of the electrode lead 40 with the insulating member 60, the insulating member 60 may wrap a portion of both ends 40a, 40b of the electrode lead 40 that is further adjacent to the one end 40a. The insulating member 60 may be heat-sealed or adhered to the electrode lead 40.

[0102] In the step (S22) of bending or folding the electrode lead 40 and the conductive connecting member 50, the electrode lead 40 may be bent or folded at least twice in opposite directions. As a result, the electrode lead 40 may be divided into a tab joint portion 41, a bridge portion 42, and a lead portion 43. The bridge portion 42 may be bent or folded to form an angle of 90 degrees or more with respect to the tab joint portion 41, and the lead portion 43 may be bent or folded to form an angle of 90 degrees or more with respect to the bridge portion 42.

[0103] In addition, in the step (S22) of bending or folding the electrode lead 40 and the conductive connecting member 50, the conductive connecting member 50 may be bent or folded at least once.

[0104] When the conductive connecting member 50 is bent or folded two or more times, the conductive connecting member 50 can be divided into a tab joint 51, a bridge portion 52, and a lead joint 53. The bridge portion 52 can be bent or folded to form an angle of 90 degrees or more with respect to the tab joint 51, and the lead joint 53 can be bent or folded to form an angle of 90 degrees or more with respect to the bridge portion 52.

[0105] When the conductive connecting member 50 is bent or folded once, the conductive connecting member 50 may be divided into a tab joint portion 51 and a remaining section (see FIG. 6a). The remaining section may be bent or folded to form an angle of 90 degrees or more with respect to the tab joint portion 51. The remaining section may be the section that will be subsequently divided into a bridge portion 52 and a lead joint portion 53.

[0106] In the step (S23) of connecting the conductive connection member 50 to the electrode lead 40, one end 50a of the conductive connection member 50 may be connected between the other end 40b of the electrode lead 40 and the insulating member 60. More specifically, the one end 50a of the conductive connection member 50 may be connected to the bridge portion 42 or the lead portion 43 of the electrode lead 40. The conductive connection member 50 and the electrode lead 40 may be connected by welding. In this way, the lead assembly 30 may be formed.

[0107] In the step (S30) of connecting the lead assembly 30, the lead assembly 30 may be connected to the first electrode assembly 20A and the second electrode assembly 20B. More specifically, the other end 40b of the electrode lead 40 may be connected to the first electrode tab 21A, and the other end 50b of the conductive connecting member 50 may be connected to the second electrode tab 21B. The electrode lead 40 and the first electrode tab 21A, and the conductive connecting member 50 and the second electrode tab 21B may be connected to each other by welding.

[0108] In the step S40 of accommodating a plurality of electrode assemblies 20 into a battery case 10, the stacked electrode assemblies 10 may be accommodated in a receiving portion 11 formed in at least one of the pair of cases while the pair of cases is separated or unfolded. Then, with the pair of cases aligned to abut against each other, the periphery of the receiving portion 11 may be sealed to form a sealing portion 12, thereby sealing the battery case 10. Here, a portion of the sealing portion 12 may be sealed with the insulating member 60 of the lead assembly 30, and the electrode leads 40 may protrude to the outside of the battery case 20 through the insulating member 60.

[0109] As described above, the manufacturing method according to another embodiment of the present invention is characterized in that the lead assembly 30 is first prepared and then connected to a plurality of electrode assemblies 20. This has the advantage of reducing manufacturing tolerances for the lead assembly 30 and simplifying manufacturing compared to a method in which the electrode leads 40 and conductive connecting members 50 are first connected to a plurality of electrode assemblies 20 and then the conductive connecting members 50 are connected to the electrode leads 40. In addition, the process of manufacturing the lead assembly 30 can be separated from the process of manufacturing and stacking the electrode assemblies 20, which has the advantage of facilitating management of each process.

[0110] The above description is merely an illustrative example of the technical concept of the present invention, and various modifications and variations can be made by a person having ordinary knowledge in the technical field to which the present invention pertains without departing from the essential characteristics of the present invention.

[0111] Therefore, the embodiments disclosed in the present invention are intended to illustrate, not limit, the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by such embodiments.

[0112] The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention. [Explanation of symbols]

[0113] 1 Secondary battery 10 Battery case 11 Storage area 12 Sealing part 20 Electrode assembly 21 Electrode tab 30 Lead Assembly 40 electrode leads 41 Tab joint 42 Bridge section 43 Lead section 50 Conductive connecting member 51 Tab joint 52 Bridge section 53 Lead joint 60 Insulating material

Claims

1. a first electrode assembly having a plurality of first electrode tabs joined together; a second electrode assembly having a plurality of second electrode tabs joined to each other and stacked on the first electrode assembly; an electrode lead connected to the first electrode tab; a conductive connection member connecting the second electrode tab and the electrode lead, The electrode lead is a tab joint portion joined to the first electrode tab; a bridge portion bent or folded in one rotation direction at the tab joint; a lead portion bent or folded in the opposite rotation direction at the bridge portion, A secondary battery, wherein one end of the conductive connecting member is joined to the bridge portion or the lead portion.

2. The electrode lead further includes an insulating member surrounding a portion of both ends of the electrode lead that is adjacent to one end of the electrode lead, The secondary battery according to claim 1 , wherein one end of the conductive connecting member is joined between the other end of the electrode lead and the insulating member.

3. The other end of the electrode lead is joined to the first electrode tab, The secondary battery according to claim 2 , wherein the other end of the conductive connecting member is joined to the second electrode tab.

4. a battery case that accommodates the first electrode assembly and the second electrode assembly, the insulating member insulates the electrode lead from the battery case; The secondary battery according to claim 2 , wherein one end of the electrode lead is located outside the battery case.

5. The secondary battery according to claim 1 , wherein the electrode lead is bent or folded at least twice in opposite directions.

6. The conductive connecting member is a tab joint portion joined to the second electrode tab; a bridge portion bent or folded at the tab joint; 2. The secondary battery according to claim 1, further comprising: a lead joint portion that is extended, bent, or folded at the bridge portion and joined to the electrode lead.

7. The secondary battery according to claim 1 , wherein the thickness of the electrode lead and the conductive connecting member is greater than the thickness of each of the first electrode tab and the second electrode tab.

8. The secondary battery according to claim 1 , wherein the conductive connecting member has a length shorter than that of the electrode lead.

9. stacking a first electrode assembly having a plurality of first electrode tabs joined to each other and a second electrode assembly having a plurality of second electrode tabs joined to each other; providing a lead assembly; connecting the lead assembly to the first electrode assembly and the second electrode assembly; The step of providing the lead assembly includes: wrapping a portion of the electrode lead adjacent to one end of both ends of the electrode lead with an insulating material; and connecting one end of a conductive connecting member between the other end of the electrode lead and the insulating member; In the step of connecting the lead assembly, the other end of the electrode lead is connected to the first electrode tab, and the other end of the conductive connecting member is connected to the second electrode tab.

10. The method of manufacturing a secondary battery according to claim 9 , wherein in the step of preparing the lead assembly, the length of the conductive connection member is formed to be shorter than the length of the electrode lead.

11. The step of providing the lead assembly includes: The method for manufacturing a secondary battery according to claim 9 , further comprising the steps of bending or folding the electrode lead at least twice in opposite directions and bending or folding the conductive connecting member at least once.

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