Terminal manufacturing method

Abstract

To provide a method for manufacturing an electrode terminal formed of different kinds of metals excellent in injunction strength.SOLUTION: A method for manufacturing a terminal includes the following steps: preparing a first member and a second member each made of a metal and forming the terminal, with the first member being formed in a sheet shape and having at one surface thereof a concave part allowing a part of the second member to be fitted therein, and with the second member having a flange part to be accommodated in the concave part; and fixing the first member and the second member to each other by ultrasonic pressure contact, with the ultrasonic pressure contact being performed by applying an ultrasonic wave vibration while applying a pressure in a direction of stacking of the first member and the second member in a state where the flange part of the second member is arranged in the concave part of the first member, thereby extending the flange part, and bringing a part of the extended flange part into pressure contact with an inner wall surface of the concave part.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a terminal used as an electrode terminal of a secondary battery and a method for manufacturing the same, and more particularly to a terminal made of two types of metal and a method for manufacturing the same. [Background technology]

[0002] Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries are lighter and have a higher energy density than existing batteries, and therefore in recent years have been used as power sources mounted on vehicles that use electricity as a driving source, or as power sources mounted on electrical products such as personal computers and mobile terminals. In particular, battery packs that are configured as single cells using sealed lithium-ion secondary batteries that are lighter and have a higher energy density are preferably used as high-output power sources for driving vehicles such as electric vehicles (EVs), plug-in hybrid vehicles (PHVs), and hybrid vehicles (HVs).

[0003] The sealed secondary battery constituting such a battery pack includes a battery case that houses an electrode assembly, and positive and negative electrode terminals. One end of each electrode terminal constituting the secondary battery is exposed to the outside of the battery case, and the other end is connected to the electrode assembly inside the battery case via a current collector. A plurality of such secondary batteries (hereinafter also referred to as "cells") are arranged along a predetermined arrangement direction, and an electrode terminal of one cell is electrically connected to another cell via a bus bar to form a battery pack.

[0004] Generally, the positive and negative electrode terminals of a lithium-ion secondary battery are made of different materials. When a bus bar made of the same material as one of the electrode terminals is used to connect unit cells, the electrical continuity and bonding strength between the other electrode terminal and the bus bar are relatively low compared to the one electrode terminal.

[0005] In order to establish electrical continuity between the electrode terminals and the bus bars, Patent Document 1 discloses a technique for constructing the electrode terminals using clad materials that match the metal types that constitute the bus bars and the current collector terminals. Patent Document 2 discloses a technique for joining connection terminals made of different types of metals by ultrasonic welding and then crimping to improve the electrical continuity and joint strength between the above-mentioned parts. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-85961 A [Patent Document 2] JP 2011-124024 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, electrode terminals made of clad materials as described in Patent Document 1 generally have high manufacturing costs. In addition, in the method described in Patent Document 2, in which connection terminals are joined by ultrasonic welding and then crimped, there is a risk that the parts will be deformed by crimping. There is a demand for the development of a technology for joining dissimilar metals to electrode terminals at lower cost and with sufficient joint strength.

[0008] The present invention has been made in view of the above-mentioned points, and has an object to provide a method for manufacturing an electrode terminal made of dissimilar metals having excellent bonding strength, and another main object is to provide a terminal manufactured by such a method, and a battery using the terminal. [Means for solving the problem]

[0009] The inventors discovered that when manufacturing an electrode terminal made of two types of metal by ultrasonic bonding, the pressure and vibration applied to the two types of metal causes one metal to stretch relative to the other metal and be pressed together, creating a crimped structure. It was found that the connection terminal produced in this manner has good electrical conductivity due to the metallurgical bonding between the two metals, and furthermore, that the first and second members are bonded with sufficient strength due to the crimped structure.

[0010] The method for manufacturing a terminal disclosed herein is a method for manufacturing a terminal constituting either a positive electrode or a negative electrode of a secondary battery, the method comprising the following steps: preparing a first member and a second member each made of metal constituting the terminal, wherein the first member is formed in a plate shape and has a recess on one surface into which a part of the second member is fitted, and the second member has a flange portion to be received in the recess; and The method includes a step of fixing the first member and the second member to each other by ultrasonic welding, wherein the ultrasonic welding is performed by applying ultrasonic vibrations while applying pressure in a stacking direction of the first member and the second member with a flange portion of the second member disposed in a recess of the first member, thereby stretching the flange portion and pressing a portion of the extended flange portion against an inner wall surface of the recess.

[0011] This manufacturing method makes it possible to manufacture a terminal including a connection terminal in which the first member and the second member are ultrasonically bonded to provide good electrical continuity, and the first member and the second member are bonded with sufficient strength by having a crimped structure.

[0012] In one embodiment, the first member and the second member are constructed from different metals. This manufacturing method makes it possible to manufacture terminals that have good joint strength and electrical continuity even if the terminals are made of different metal species.

[0013] In one embodiment, the first member is comprised of aluminum or an aluminum-based alloy, and the second member is comprised of copper or a copper-based alloy. This manufacturing method makes it possible to manufacture a terminal that has good electrical conductivity with a bus bar made of aluminum or an alloy mainly containing aluminum.

[0014] In another aspect of the technology disclosed herein, a terminal constituting either a positive electrode or a negative electrode of a secondary battery is provided. The terminal has a first member and a second member, each made of a metal, the first member being formed in a plate shape and having a recess on one surface thereof, and the second member having a flange portion accommodated in the recess of the first member. Here, the first member and the flange portion of the second member are at least partially joined to each other by metal joining, and an end of the flange portion is crimped to the inner wall surface of the recess without a through hole. A terminal having such a configuration has good electrical conductivity due to ultrasonic bonding between the first member and the second member, and the first member and the second member are bonded with sufficient strength due to the crimping structure.

[0015] In a preferred embodiment, the metal joint occurs closer to the center of the flange portion than the crimped portion. With this configuration, the above-mentioned effects can be more effectively achieved.

[0016] In one embodiment, the metallurgical bond interface between the first and second members comprises a bond surface produced by ultrasonic bonding. With this configuration, good electrical continuity can be achieved between the first member and the second member.

[0017] In one embodiment, the first member and the second member are constructed from different metals. With this configuration, even if the terminals are made of different metals, the joining strength and electrical continuity can be ensured.

[0018] In one embodiment, the first member is comprised of aluminum or an aluminum-based alloy, and the second member is comprised of copper or a copper-based alloy. With this configuration, good electrical conduction is achieved between the electrode terminal having the terminal and an external connecting part such as a bus bar made of aluminum or an alloy mainly containing aluminum.

[0019] As another aspect of the technology disclosed herein, there is provided a secondary battery comprising an electrode body including a positive electrode and a negative electrode, a battery case housing the electrode body therein, and a positive electrode terminal and a negative electrode terminal electrically connected to the positive electrode and negative electrode, respectively, in the electrode body, wherein at least one of the positive electrode terminal and the negative electrode terminal includes the terminal disclosed herein.

[0020] As another aspect of the technology disclosed herein, there is provided an assembled battery in which a plurality of single cells are arranged and electrically connected to each other, and the plurality of single cells each include a secondary battery having the terminal disclosed herein as at least one of the positive terminal and the negative terminal.

[0021] In one embodiment, the positive terminal of one of the multiple single cells is electrically connected to the negative terminal of another single cell by a specified bus bar, and the bus bar is made of the same metal as the metal constituting the first member of the terminal. With this configuration, a battery pack is provided in which the cells are better connected to each other. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a perspective view showing a schematic external shape of a secondary battery using a terminal according to one embodiment. [Diagram 2] FIG. 1 is a perspective view showing a schematic diagram of a battery pack formed from unit cells using a terminal according to one embodiment. [Diagram 3]1 is a cross-sectional view of a wide surface that illustrates a schematic internal structure of a secondary battery using a terminal according to one embodiment. [Figure 4] FIG. 2 is a cross-sectional view of a narrow surface, which is a schematic diagram showing an internal structure of a secondary battery using a terminal according to one embodiment. [Diagram 5] 1 is a cross-sectional view of a main portion that illustrates a structure of a terminal according to an embodiment of the present invention. [Figure 6] 4 is a flowchart showing a manufacturing procedure of a secondary battery including a terminal according to one embodiment. [Figure 7] 4 is a cross-sectional view showing a schematic configuration when a first member and a second member are crimped by ultrasonic welding. FIG. [Figure 8] 4 is a cross-sectional view showing a schematic state before a first member and a second member are joined by ultrasonic welding. FIG. [Figure 9] 4 is a cross-sectional view showing a schematic view of a state in which a first member and a second member are joined by ultrasonic welding; FIG. [Figure 10] 4 is a cross-sectional view showing a schematic state in which a first member and a second member are crimped by ultrasonic welding. FIG. [Figure 11] FIG. 2 is a cross-sectional view illustrating a structure of a first component according to one embodiment. [Figure 12] 1 is a cross-sectional photograph showing a state in which a first member and a second member are crimped together according to one embodiment. [Figure 13] 1 is a scanning electron microscope (SEM) image of a cross section of a terminal according to one embodiment after fracture. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, with reference to the drawings as appropriate, an embodiment of the terminal disclosed herein, a secondary battery including the terminal, a battery pack including a cell including the terminal, and a method for manufacturing the terminal will be described in detail using a rectangular lithium ion secondary battery including a wound electrode body as an example. Naturally, the following embodiment is not intended to particularly limit the technology disclosed herein. The secondary battery disclosed herein is not limited to the lithium ion secondary battery described below, and examples of the secondary battery herein include sodium ion secondary batteries, magnesium ion secondary batteries, and lithium ion capacitors included in so-called physical batteries. In addition, a lithium ion secondary battery having a wound electrode body having a structure in which a plurality of positive and negative electrode bodies are wound with a separator interposed therebetween is described here, but the electrode body is not limited to such a configuration, and may be configured such that a plurality of positive and negative electrode bodies are stacked with a separator interposed therebetween.

[0024] It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the technical common sense in the relevant field.

[0025] In the following drawings, the same reference numerals are used for components and parts having the same functions, and duplicated explanations may be omitted or simplified. The dimensional relationships such as length and width in the following drawings do not necessarily reflect the actual dimensional relationships. In this specification, when a numerical range is described as A to B (where A and B are arbitrary numerical values), it means A or more and B or less. In addition, in this specification, the term "main component" refers to a component that occupies 70% by weight or more of the total components.

[0026] FIG. 1 is a perspective view showing a schematic external shape of a secondary battery using a terminal according to one embodiment. The secondary battery 12 is a secondary battery that can be repeatedly charged and discharged, such as a lithium ion secondary battery. Although detailed structural description is omitted, the secondary battery 12 disclosed herein includes an electrode body having a structure in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, inside a battery case 30. Such an electrode body is housed in a battery case body 32 together with a nonaqueous electrolyte (not shown), and the edge of a lid body 34 is sealed by welding or the like while the inside is depressurized, and is hermetically sealed. For the battery case 30, for example, a metal material that is lightweight and has good thermal conductivity, such as aluminum, is used. The shape of the battery case 30 is not limited to the rectangular one as shown in FIG. 1, and may be, for example, a cylindrical type or the like.

[0027] The battery case 30 includes a positive electrode terminal 40 and a negative electrode terminal 50 that are electrically connected to the electrode body inside the battery case and are connected to external connection parts via a bus bar or the like. At least one of the positive electrode terminal 40 and the negative electrode terminal 50 has a connection terminal corresponding to the electrode terminal in question, either a positive electrode connection terminal 44 or a negative electrode connection terminal 54. The shapes of the positive electrode terminal 40 and the negative electrode terminal 50 exposed to the outside of the battery case are not particularly limited, and may be rectangular as shown in the figure, or may be circular, including elliptical, shapes, etc.

[0028] FIG. 2 is a perspective view showing a schematic diagram of a battery pack made up of unit cells using the terminal according to one embodiment. In a battery pack 100 in which a plurality of unit cells 12 are arranged as shown in Fig. 1, the unit cells 12 are arranged via spacers 11. A pair of end plates 17 are arranged further outboard of the outermost spacer 11. These are restrained by fastening beams 18 attached so as to bridge the end plates 17, and ends of the fastening beams 18 are fastened and fixed by screws 19.

[0029] A positive electrode terminal 40 and a negative electrode terminal 50 are provided on the upper portion of the single battery 12. At least one of the positive electrode terminal 40 and the negative electrode terminal 50 has a connection terminal corresponding to the electrode terminal, either a positive electrode connection terminal 44 or a negative electrode connection terminal 54. The positive electrode terminal 40 and the negative electrode terminal 50 are electrically connected to the adjacent cells 12 via the bus bar 14. The bus bar 14 is generally made of a metal having high electrical conductivity and high mechanical strength, such as aluminum or copper.

[0030] The internal structure of a secondary battery using the terminal disclosed herein will be described with reference to FIG. 3 is a cross-sectional view of a wide surface, which is a schematic diagram showing the structure of a secondary battery using the terminal according to one embodiment. The secondary battery 12 includes an electrode assembly 20, a battery case 30, a positive electrode terminal 40, and a negative electrode terminal 50. The structure of each of these components will be described below.

[0031] The electrode body 20 is a power generating element that is covered with an insulating film (not shown) or the like and is accommodated inside the battery case 30. The electrode body 20 includes a long sheet-like positive electrode 21, a long sheet-like negative electrode 22, and long sheet-like separators 23 and 24. The electrode body 20 is a wound electrode body in which the long sheet-like members described above are wound and stacked.

[0032] The positive electrode 21 includes a foil-shaped positive electrode collector 21A and a positive electrode active material layer 21B formed along the longitudinal direction on one or both sides of the positive electrode collector 21A. In addition, on one side edge of the electrode body 20 in the width direction of the secondary battery 12, the positive electrode active material layer 21B is not formed, and a positive electrode collector exposed portion 21C where the positive electrode collector 21A is exposed is provided. The positive electrode active material layer 21B contains various materials such as a positive electrode active material, a binder, and a conductive material. For example, aluminum foil or the like is used as the positive electrode current collector terminal 42. As for the material contained in the positive electrode active material layer 21B, any material that can be used in a conventional general lithium ion secondary battery can be used without any particular limitation, and detailed description thereof is omitted since it does not characterize the present invention.

[0033] The negative electrode 22 includes a foil-shaped negative electrode collector 22A and a negative electrode active material layer 22B formed along the longitudinal direction on one or both sides of the negative electrode collector 22A. In addition, the negative electrode active material layer 22B is not formed on the other side edge of the electrode body 20 in the width direction, and a negative electrode collector exposed portion 22C where the negative electrode collector 22A is exposed is provided. As with the positive electrode active material layer 21B, the negative electrode active material layer 22B contains various materials such as a negative electrode active material and a binder. For example, copper foil or the like is used as the negative electrode current collector terminal 52. As for the material contained in the negative electrode active material layer 22B, any material that can be used in a conventional general lithium ion secondary battery can be used without any particular limitation, and detailed description thereof is omitted since it does not characterize the present invention.

[0034] The separators 23, 24 are interposed between the positive electrode 21 and the negative electrode 22 to prevent these electrodes from coming into direct contact with each other. Although not shown in the figure, a plurality of fine pores are formed in the separators 23, 24. The fine pores are configured to allow charge carriers (lithium ions in the case of a lithium ion secondary battery) to move between the positive electrode 21 and the negative electrode 22. A resin sheet or the like having required heat resistance is used for the separators 23, 24. As the separators 23, 24, any separator that can be used in a conventional general lithium ion secondary battery can be used without any particular limitation, and detailed description thereof is omitted since it does not characterize the present invention.

[0035] The nonaqueous electrolyte contained in the battery case 30 may be any electrolyte that can be used in conventional lithium ion secondary batteries, typically containing a nonaqueous solvent and a supporting salt, without any particular restrictions. Detailed description of the electrolyte is omitted here as it does not characterize the present invention.

[0036] In one embodiment, the positive electrode terminal 40 is composed of a positive electrode connection terminal 44 and a positive electrode current collector terminal 42. As shown in Fig. 4, a portion of the positive electrode connection terminal 44 is exposed to the outside of the battery case 30, and a portion of the positive electrode current collector terminal 42 is connected to the positive electrode current collector terminal 42 inside the battery case 30. The positive electrode current collector terminal 42 is disposed inside the battery case 30, and is connected to the positive electrode 21 via the positive electrode current collector exposed portion 21C.

[0037] In one embodiment, the negative electrode terminal 50 is composed of a negative electrode connection terminal 54 and a negative electrode current collector terminal 52. As shown in Fig. 4, a portion of the negative electrode connection terminal 54 is exposed to the outside of the battery case 30, and a portion of the negative electrode current collector terminal 54 is connected to the negative electrode current collector terminal 52 inside the battery case 30. The negative electrode current collector terminal 52 is disposed inside the battery case 30, and is connected to the negative electrode 22 via the negative electrode current collector exposed portion 22C.

[0038] At least one of the positive electrode terminal 40 and the negative electrode terminal 50 has a connection terminal corresponding to the electrode terminal, either the positive electrode connection terminal 44 or the negative electrode connection terminal 54. Below, a detailed description will be given with reference to Fig. 5 on the basis of a configuration in which the negative electrode terminal 50 has the negative electrode connection terminal 54. The configuration in which the positive electrode terminal 40 has the positive electrode connection terminal 44 is similar to the configuration in which the negative electrode terminal 50 has the negative electrode connection terminal 54, and therefore a detailed description will be omitted.

[0039] FIG. 5 is a cross-sectional view of a main part that typically illustrates the structure of a terminal according to one embodiment. The negative electrode terminal 50 is composed of a negative electrode connection terminal 54 and a negative electrode current collecting terminal 52. The negative electrode connection terminal 54 is composed of a first member 56 and a second member 58. The negative electrode current collector terminal 52 is connected to the second member 58 by welding or the like. The negative electrode current collector terminal 52 connected to the negative electrode current collector 22A is preferably made of the same metal as the negative electrode current collector 22A, for example, copper. The second member 58 connected to the negative electrode current collector terminal 52 is preferably made of the same metal as the negative electrode current collector terminal 52, for example, copper.

[0040] As shown in FIG. 5, the negative electrode connection terminal 54 is inserted into a lid 34 having a through hole, and the lid 34 and the negative electrode connection terminal 54 are insulated from each other by a gasket 60 . The gasket 60 is made of an insulating material, for example, a fluororesin such as perfluoroalkoxyalkane (PFA). As shown in the figure, the negative electrode collector terminal 52 is insulated by an insulator 61. The insulator 61 is made of an insulating material, for example, polycarbonate. Resin materials such as polyphenylene sulfide resin (PPS) are used.

[0041] The manufacturing method of the above-mentioned terminal and the manufacturing method of the secondary battery having the terminal will be described. In the following, the manufacturing method of the negative electrode terminal will be described as an example. The manufacturing method of the positive electrode terminal can be the same as the manufacturing method of the negative electrode terminal, so the description will be omitted.

[0042] FIG. 6 is a flowchart of a method for manufacturing a secondary battery including a terminal according to one embodiment. In this manufacturing method, first, a first member 56 and a second member 58 each made of metal and constituting a connection terminal are prepared (S1). The first member 56 is formed in a plate shape, and has a recess 56R on one surface thereof into which a part of the second member 58 fits. The second member 58 has a flange portion 58F that fits into the recess 56R of the first member 56. The second member 58 further has a shaft portion 58S that is inserted into a through hole of the lid body 34. The second member 58 may have a leg portion 58L that is connected to the negative electrode current collector terminal 52 by welding or the like, and is fixed to the lid body 34 by crimping or the like. A flange portion 58F that is shaped to expand outward from the shaft portion 58S in a flange-like shape as shown in FIG. 5 is provided at the end of the shaft portion 58S facing the recess 56R.

[0043] The dimensions of the recess 56R of the first member 56 and the flange portion 58F of the second member 58 are appropriately set according to the type of metal used, etc. These dimensions are not particularly limited as long as they do not impair the effects of the present invention. For example, when the first member 56 is made of aluminum and the second member 58 is made of copper, from the viewpoint of ease of pressure welding of the two members in a later process, it is preferable that the gap between the recess 56R and the flange portion 58F formed when the flange portion 58F is fitted into the recess 56R is 1 mm or less at maximum. The gap is more preferably 0.8 mm or less, and even more preferably 0.5 mm or less. From the viewpoint of ease of fitting, the gap is preferably 0.1 mm or more.

[0044] From the viewpoint of ease in pressing the two members together in a later process, the depth of the recess 56R is set to D R The thickness of the flange part 58F is T F Then, D R is 0.5×T F Larger, 0.7×T F Preferably larger than 0.9×T F It is preferable that the value is larger than the value of D. R is 1.2×T F Preferably smaller than 1.1 x T F Smaller is more preferable.

[0045] The shape of the recess 56R of the first member 56 is not particularly limited as long as the flange portion 58F of the second member 58 can fit into it; however, for example, as shown in FIG. 11, the first member 56 and the second member 58 can be joined more strongly by providing a groove in the inner wall of the recess 56R for pressing in the end of the flange portion 58F. The shape of the groove may be, for example, a rectangular shape in the cross section as shown in FIG. 11, or a shape that widens on the side surface of the recess toward the bottom surface.

[0046] The first member 56 and the second member 58 constituting the negative electrode connection terminal 54 may be made of the same metal, but in cases where the negative electrode current collector 22A and the bus bar 14 are made of different metals, for example, it is preferable that the first member 56 and the second member 58 are made of different metals. In that case, it is preferable from the viewpoint of ensuring electrical continuity that the first member 56 and the bus bar 14 are made of the same metal, and the second member 58 and the negative electrode current collector 22A are made of the same metal.

[0047] For example, when the bus bar 14 connected to the negative terminal 54 is made of aluminum or an alloy mainly made of aluminum, and the negative collector terminal 52 is made of copper or an alloy mainly made of copper, it is preferable that the first member 56 is made of aluminum or an alloy mainly made of aluminum, and the second member 58 is made of copper or an alloy mainly made of copper. In this way, by selecting the metal type of the first member 56 and the second member 58 based on the metal type of the bus bar and the current collecting terminal, the conductivity and bonding strength of external connection parts such as the negative terminal and the bus bar can be improved.

[0048] Next, the first member 56 and the second member 58 are fitted together (S2), and the first member 56 and the second member 58 are fixed to each other by ultrasonic pressure welding (S3). 7, flange portion 58F of second member 58 is fitted into recess 56R of first member 56, and sandwiched between horn 70 and anvil 71 (S2). The shapes of horn 70 and anvil 71 are not limited as long as the effects of the present invention are achieved.

[0049] In one embodiment, the anvil 71 on which the second member 58 is disposed has a recess through which the shaft portion 58S of the second member 58 is inserted and into which the flange portion 58F is disposed. The horn 70 applied from the upper surface of the first member 56 has a shape that allows pressure to be applied over an area approximately equal to the area of ​​the surface where the recessed portion 56R and the flange portion 58F face each other. The shape of the horn 70 is not limited thereto, and can be appropriately selected according to the shapes of the first member 56 and the second member 58. Although not limited thereto, the shape of the horn 70 may be, for example, cylindrical so that the surface of the upper surface of the first member 56 that is supported by the anvil 71 via the flange portion 58F can be pressed, or may have a shape in which a plurality of pressing portions are evenly arranged in the circumferential direction.

[0050] Horn 70 is attached to a press (not shown) equipped with a vibration generator. The vibration generator is a device that applies the required vibration required for ultrasonic welding to horn 70. In order to efficiently stretch flange portion 58F, it is preferable to position horn 70 and anvil 71 so that ultrasonic vibration is applied to the end of flange portion 58F.

[0051] As described above, the first member 56 and the second member 58 are sandwiched between the horn 70 and the anvil 71, and then ultrasonic pressure welding is performed to fix the first member 56 and the second member 58 together (S3). A pressure is applied to the first member 56 and the second member 58 by a press. The pressure applied here can be set appropriately depending on the metal types and dimensions of the first member 56 and the second member 58, the shape of the horn 70, and the like. Although not limited thereto, the pressure applied to the first member 56 and the second member 58 can be set to about 200 to 1600 N, for example.

[0052] Next, ultrasonic vibration is applied via the horn 70 while pressure is being applied to the first member 56 and the second member 58. As shown in FIG. 8, before ultrasonic vibration is applied to the first member 56 and the second member 58, a gap exists between the inner wall surface of the recess 56R and the end of the flange portion 58F. By applying vibration as shown in FIG. 9, the flange portion 58F is extended toward the inner wall surface of the recess 56R. As a result, as shown in FIG. 10, a part of the flange portion 58F extended toward the inner wall surface of the recess 56R is pressed against the inner wall surface of the recess 56R, and the first member 56 and the second member 58 are fixed together.

[0053] A metal bond can be formed on at least a portion of the opposing surfaces of the flange portion 58F and the recessed portion 56R that are pressed against each other by being sandwiched between the horn 70 and the anvil 71. Here, the conditions of the ultrasonic vibration applied via horn 70 can be appropriately set depending on the metal types and dimensions of first member 56 and second member 58, the shape of horn 70, etc. Although not limited thereto, for example, the amplitude can be set to about 20 to 80 μm, the frequency to about 15 to 150 kHz, and the amount of energy applied to first member 56 and second member 58 to about 20 to 500 J. By the above manufacturing method, a terminal having the connection terminal 54 disclosed herein as a component part can be manufactured.

[0054] A battery assembly can be constructed using the connection terminals 54 manufactured through the above-mentioned steps (S4). In this step, first, the above-mentioned electrode assembly 20, non-aqueous electrolyte, battery case 30, positive electrode terminal 40, negative electrode current collector terminal 52, and negative electrode connection terminal 54 are prepared. The battery case 30 includes a battery case body 32 having an opening, and a lid 34 having a liquid injection port for injecting the non-aqueous electrolyte. The lid 34 has through holes for inserting the positive electrode terminal 40 and the negative electrode connection terminal 54, respectively.

[0055] Next, the electrode assembly 20 is housed in a battery case 30 . The positive electrode terminal 40 is inserted into one of the through-holes of the lid body 34 and attached. The negative electrode connection terminal 54 is inserted into the other through-hole of the lid body 34 and connected to the negative electrode current collector terminal 52, thereby attaching the negative electrode terminal 50 to the lid body 34. The connection between the negative electrode connection terminal 54 and the negative electrode current collector terminal 52 is performed by a known method. Although not limited thereto, the connection between the negative electrode connection terminal 54 and the negative electrode current collector terminal 52 may be made by crimping as shown in FIG. 5. The positive electrode terminal 40 and the negative electrode current collector terminal 50 are welded to the positive electrode current collector exposed portion 21C and the negative electrode current collector exposed portion 22C, respectively, that are exposed at the ends of the electrode body 20. Then, the electrode body 20 is housed inside the battery case 30 body through its opening, and the body and the lid of the battery case 30 are welded together.

[0056] Next, a non-aqueous electrolyte is injected through the injection port. After the non-aqueous electrolyte is injected, the injection port is sealed to obtain a battery assembly. The battery assembly is subjected to an initial charging process to produce a lithium ion secondary battery.

[0057] A negative electrode connecting terminal 54 manufactured by the manufacturing method disclosed herein has a first member 56 and a second member 58, each made of metal. The first member 56 is formed in a plate shape and has a recess 56R on one surface thereof, and the second member 58 has a flange portion 58F that is received in the recess 56R of the first member 56. The first member 56 and the flange portion 58F of the second member 58 are at least partially joined to each other by metal joining, and an end of the flange portion 58F is crimped to the inner wall surface of the recess 56R without a through hole.

[0058] Here, "the end of flange portion 58F is crimped against the inner wall surface of recess 56R" refers to a state in which first member 56 is fixed to second member 58, for example, by the end of flange portion 58F being pressed against the inner wall surface of recess 56R. 12 is a cross-sectional photograph of the first member 56 made of aluminum and the second member 58 made of copper after ultrasonic welding. The dashed line in the figure indicates the position of the inner wall surface of the recess 56R before ultrasonic welding. It can be seen that the end of the flange 58F is extended, so that the flange 58F is pressed into the inner wall surface of the recess 56R.

[0059] The metal joint occurs on the surfaces of the first member 56 and the second member 58 where the recess 56R and the flange portion 58F face each other, and can occur, for example, closer to the center of the flange portion 58F than the crimped portion.

[0060] In this embodiment, the occurrence of metal bonding between the first member 56 and the second member 58 can be confirmed, for example, by fracturing the interface between the first member 56 and the second member 58 and observing the fracture surface. Fig. 13 is an SEM image of a fracture surface of the first member 56 made of aluminum and the second member 58 made of copper. The arrow in the figure indicates adhesion of the first member 56 made of aluminum to the second member 58 made of copper. In this way, when adhesion of the other metal can be confirmed on the fracture surface of at least one of the first member 56 and the second member 58, it can be confirmed that the above-mentioned bonding surface exists.

[0061] The first member 56 and the second member 58 constituting the negative electrode connection terminal 54 may be made of the same metal, but in cases where the negative electrode current collector 22A and the bus bar 14 are made of different metals, it is preferable that the first member 56 and the second member 58 are made of different metals. In that case, it is preferable from the viewpoint of ensuring electrical continuity that the first member 56 and the bus bar 14 are made of the same metal, and the second member 58 and the negative electrode current collector 22A are made of the same metal. With this configuration, the electrical continuity and bonding strength between the negative electrode terminal 50 including the negative electrode connection terminal 54 and the bus bar 14 can be improved.

[0062] For example, when the bus bar 14 connected to the negative terminal 54 is made of aluminum or an alloy mainly made of aluminum, and the negative collector terminal 52 is made of copper or an alloy mainly made of copper, it is preferable that the first member 56 is made of aluminum or an alloy mainly made of aluminum, and the second member 58 is made of copper or an alloy mainly made of copper. With this configuration, the electrical continuity and bonding strength between the negative electrode terminal 50 including the negative electrode connection terminal 54 and the bus bar 14 connected to the negative electrode terminal 50 can be improved.

[0063] Although the specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The invention disclosed herein includes various modifications and alterations of the above specific examples. [Explanation of symbols]

[0064] 11 Spacer 12 Secondary battery (single cell) 14 Bus bar 17 End Plate 18 Fastening beam 19 Bis 20 Electrode body 21 Positive electrode 21A positive electrode current collector 21B Positive electrode active material layer 21C Exposed part of positive electrode current collector 22 Negative electrode 22A negative electrode current collector 22B Negative electrode active material layer 22C Negative electrode current collector exposed part 23 Separator 24 Separator 30 Battery case 32 Battery case body 34 Lid 40 Positive terminal 42 Positive collector terminal 44 Positive connection terminal 50 Negative terminal 52 Negative current collector terminal 54 Negative connection terminal 56 First member 56R Recess 58 Second member 58F Flange 58L legs 58S shaft part 60 Gasket 61 Insulator 70 Horn 71 Anvil 100 battery packs

Claims

1. A method for manufacturing a terminal constituting either a positive electrode or a negative electrode of a secondary battery, comprising the steps of: preparing a first member made of aluminum or an alloy mainly containing aluminum, the first member having a recess and formed in a plate shape; preparing a second member made of copper or a copper-based alloy and having a flange portion to be received in the recess; disposing the flange portion of the second member in the recess of the first member; a step of applying pressure while applying ultrasonic vibration along a depth direction of the recess, thereby crimping the first member and the second member such that a side peripheral surface of the recess of the first member and the flange portion of the second member disposed in the recess are in pressure contact with each other; a step of metal-joining the flange portion of the second member disposed in the recess and the first member at portions facing each other along a depth direction of the recess; A method for manufacturing a terminal comprising the steps of:

2. The method for manufacturing a terminal according to claim 1 , wherein in the crimping step, the flange portion of the second member and an inner wall surface of the recess of the first member are pressed against each other in a radial direction relative to a center of the recess.

Images