Terminal for secondary battery and secondary battery having said terminal

Abstract

To provide a terminal for a secondary battery that can achieve welding with an external member without requiring surface treatment of a metal part pressure-welded by ultrasonic welding.SOLUTION: A terminal constituting either a positive or negative electrode of a secondary battery 1 includes a plate-shaped metal first member 72 and a metal second member 76 ultrasonically welded to one plate surface 72a of the first member. A recess 74 is formed in the first member 72 on the surface opposite the surface to which the second member 76 is welded. In the recess 74, ultrasonic welding of the first member 72 and the second member 76 is realized.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a terminal for a secondary battery, and more particularly to a terminal that is disposed at a predetermined position in a secondary battery and enables current to flow from the inside to the outside of the cell, and to a secondary battery using the terminal. [Background technology]

[0002] Since secondary batteries such as lithium-ion secondary batteries are lightweight and can provide high energy density, they are widely used as portable power sources for personal computers, mobile terminals, etc., and as on-board power sources for EVs (electric vehicles), HVs (hybrid vehicles), PHVs (plug-in hybrid vehicles), etc. In particular, since on-board power sources are required to have high output, battery packs in which a plurality of such secondary batteries (single cells) are electrically connected to each other are preferably used.

[0003] A battery pack is generally formed by electrically connecting the positive and negative terminals of a plurality of cells via a bus bar. However, when welding the bus bar to the positive and negative terminals of the cells, if the metal constituting the bus bar is different from the metal constituting the positive and negative terminals, it is difficult to perform proper welding because the thermal conductivity and melting point are different. In addition, electricity may be generated when water or the like comes into contact with the boundary between the different metals, which may cause corrosion and deterioration of the metal.

[0004] Therefore, Patent Document 1 discloses a battery pack using a positive terminal made of dissimilar metals so that the metal constituting the bus bar and the metal constituting the bus bar welded portion of the positive terminal are the same. The positive terminal is composed of a base mainly made of aluminum and a positive external terminal mainly made of copper, and the base and the positive external terminal are joined by ultrasonic bonding and crimping. This makes it possible to improve compatibility when welding the copper bus bar and the copper-based positive external terminal. Moreover, Patent Document 2 discloses a secondary battery in which a metal member made of the same metal as that constituting the bus bar is joined to an external terminal by ultrasonic welding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-124024 A [Patent Document 2] JP 2016-18675 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in both of the techniques of Patent Document 1 and Patent Document 2, unevenness is formed on the metal surface pressed for ultrasonic bonding, and burrs are generated at the same time. Therefore, before welding an external member such as a bus bar to the metal surface, a surface treatment is required to smooth out the unevenness formed on the metal surface, and a burr cleaning process is required. The existence of such additional processes is undesirable because it increases the cost and manufacturing time of the secondary battery.

[0007] The present invention has been made in consideration of the above problems, and a main object of the present invention is to provide a terminal that constitutes either the positive or negative electrode of a secondary battery, and that can be welded to an external member such as a bus bar without requiring surface treatment of the metal portion that is pressure-welded by ultrasonic welding. Another object of the present invention is to provide a secondary battery and a battery pack that include the terminal. [Means for solving the problem]

[0008] The terminal disclosed herein is a terminal constituting either the positive or negative electrode of a secondary battery, and includes a plate-shaped metal first member and a metal second member ultrasonically welded to one plate surface of the first member. A recess is formed on the surface of the first member opposite to the surface to which the second member is welded, and the first member and the second member are ultrasonically welded to each other in the recess. With this configuration, even after the first and second members are joined by ultrasonic welding, burrs and unevenness on the metal surface that can be caused by the ultrasonic welding occur in the recessed parts, so that a terminal is provided that does not require surface treatment and allows welding of an external member such as a bus bar to the plate surface having the recessed part of the first member.

[0009] In a preferred embodiment of the terminal disclosed herein, a weld residue generated when the ultrasonic welding is performed is present in the recess. With this configuration, a terminal is provided that can be welded to an external member such as a bus bar in a state where a weld residue generated when the ultrasonic welding is performed is present in the recess.

[0010] In a preferred embodiment of the terminal disclosed herein, the first member and the second member are made of different metals. This configuration provides a terminal that can satisfactorily weld the first member to an external member such as a bus bar and join the second member to an internal terminal electrically connected to the electrode body.

[0011] In a preferred embodiment of the terminal disclosed herein, the first member is made of aluminum or an alloy mainly made of aluminum, and the second member is made of copper or an alloy mainly made of copper. This configuration provides a terminal that can suitably join the first member to an external member such as a bus bar made of aluminum or an alloy mainly made of aluminum, and the second member to a negative electrode internal terminal made of copper or an alloy mainly made of copper and electrically connected to the negative electrode.

[0012] The secondary battery disclosed herein comprises an electrode body including a positive electrode and a negative electrode, a battery case that houses the electrode body, and a positive electrode terminal and a negative electrode terminal electrically connected to the positive and negative electrodes in the electrode body, respectively, and at least one of the positive electrode terminal and the negative electrode terminal is constituted by the terminal disclosed herein. According to this configuration, a secondary battery is provided that can achieve good bonding between the positive and negative electrode terminals and external members.

[0013] The battery pack disclosed herein has a plurality of unit cells arranged and electrically connected to one another, and the secondary battery disclosed herein is used as the plurality of unit cells. According to this configuration, a battery pack is provided in which the terminals can be satisfactorily electrically connected to external members such as bus bars.

[0014] In addition, in a preferred embodiment of the battery pack disclosed herein, the plurality of single cells are electrically connected such that the positive terminal of one single cell and the negative terminal of another single cell are each electrically connected by a specified bus bar, and a terminal disclosed herein is used as either the positive terminal of the one single cell or the negative terminal of the other single cell, and the bus bar is formed from the same metal as the metal constituting the first member of the terminal. According to this configuration, a battery pack is provided in which the bus bars can be satisfactorily welded to the positive and negative terminals.

[0015] In addition, to achieve the above object, the present invention provides a method for manufacturing the terminal disclosed herein, which comprises preparing a plate-shaped metal first member and a metal second member, and joining the second member to one plate surface of the first member by ultrasonic welding, wherein a recess is formed in a plate surface of the first member opposite to the surface to which the second member is welded, and the ultrasonic welding is performed in the recess. According to a manufacturing method having such a configuration, burrs that may be generated by ultrasonic welding can be contained in the recess, and a terminal that does not require surface treatment after ultrasonic welding can be manufactured.

[0016] In a preferred embodiment of the terminal manufacturing method disclosed herein, the first member and the second member are made of different metals. According to a manufacturing method having such a configuration, it is possible to manufacture a terminal that can satisfactorily weld the first member to an external member such as a bus bar, and the second member to an internal terminal electrically connected to the electrode body.

[0017] In addition, in a preferred embodiment of the terminal manufacturing method disclosed herein, the first member is made of aluminum or an alloy mainly made of aluminum, and the second member is made of copper or an alloy mainly made of copper. According to a manufacturing method having such a configuration, it is possible to manufacture a terminal that can suitably join an external member such as a bus bar made of aluminum or an alloy mainly made of aluminum to a first member, and a negative electrode internal terminal made of copper or an alloy mainly made of copper and electrically connected to the negative electrode to a second member. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view illustrating a secondary battery according to an embodiment. [Diagram 2] FIG. 1 is a perspective view showing a schematic diagram of a battery pack according to an embodiment; [Diagram 3] 1 is a partially cutaway view illustrating a secondary battery according to an embodiment of the present invention; [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 2 is a cross-sectional view illustrating a schematic structure of a terminal according to one embodiment. [Figure 6] 1A to 1C are cross-sectional views illustrating a schematic diagram of a method for ultrasonically welding a terminal according to an embodiment of the present invention. [Figure 7] 3 is a cross-sectional view showing a schematic diagram of a connection portion of a terminal provided in a secondary battery constituting a battery pack according to one embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Below, an outline of a configuration example of a secondary battery and a battery pack having terminals according to this embodiment will be described with reference to the drawings. In the following drawings, members and parts having the same function will be denoted with the same reference numerals. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships. Furthermore, matters other than those specifically mentioned in this specification that are necessary for carrying out the present invention can be understood as design matters for a person skilled in the art based on the prior art in the field. In the drawings in this specification, the symbol X indicates the width direction (of the battery), the symbol Y indicates the thickness direction, and the symbol Z indicates the height direction. Note that these directions are determined for the convenience of explanation and are not intended to limit the installation mode of the battery.

[0020] In this specification, the term "secondary battery" refers generally to a storage device that can be repeatedly charged and discharged, and includes so-called storage batteries (i.e., chemical batteries) such as lithium ion secondary batteries, nickel metal hydride batteries, and nickel cadmium batteries, as well as capacitors (i.e., physical batteries) such as electric double layer capacitors. In addition, in this specification, the term "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and realizes charging and discharging by the transfer of charge associated with the lithium ions between the positive and negative electrodes.

[0021] <Secondary battery> FIG. 1 is a perspective view showing a secondary battery according to this embodiment. FIG. 3 is a partially cutaway view showing a secondary battery according to one embodiment. The secondary battery 1 according to this embodiment includes an electrode body 20, an electrolyte (not shown), a battery case 30, a positive electrode terminal 40, a negative electrode terminal 50, a gasket 60, and an insulator 62. The positive electrode terminal 40 includes a positive electrode internal terminal 42 and a positive electrode external terminal 44, and the negative electrode terminal 50 includes a negative electrode internal terminal 52 and a negative electrode external terminal 54. Here, as this embodiment, a secondary battery 1 including a terminal 70 disclosed herein as the negative electrode external terminal 54 is illustrated. However, this is merely an example, and other examples include a secondary battery 1 including a terminal 70 having a structure disclosed herein as the positive electrode external terminal 44. The configuration of the terminal 70 will be described later.

[0022] FIG. 2 is a perspective view showing a battery pack according to the present embodiment. As shown in FIG. 2, the battery pack 10 includes a plurality of secondary batteries (single cells) 1 electrically connected to each other and arranged, and the single cells are the secondary battery disclosed herein. The single cells 1 are arranged while being inverted one by one, so that the positive electrode terminals 40 and the negative electrode terminals 50 are arranged alternately. A spacer 12 is sandwiched between the arranged single cells 1. The spacer 12 can function as a heat dissipation means for efficiently dissipating heat, a length adjustment means, and the like. A pair of end plates (restraint plates) 17 are arranged on both ends of the arranged single cells 1. A tightening beam material 18 is attached so as to bridge between the two end plates 17. The ends of the beam material 18 are tightened and fixed to the end plates 17 by screws 19. As a result, the plurality of single cells 1 are restrained so that a restraint load is applied in the arrangement direction of the single cells 1.

[0023] The battery pack 10 includes a bus bar 14 between two adjacently arranged cells 1 that connects an external member joint of the positive electrode external terminal 44 of one cell 1 to an external member joint of the negative electrode external terminal 54 of the other cell 1. This forms a conductive path from the positive electrode internal terminal 42 of one cell 1 to the negative electrode internal terminal 52 of the other cell 1 via the bus bar 14 and the external terminal, and the cells 1 are electrically connected in series.

[0024] The busbar 14 is generally made of a metal having high electrical conductivity, such as aluminum, copper, tin, nickel, or an alloy mainly made of any of these metals. In a preferred embodiment, in the battery pack 10, a terminal 70 having the configuration disclosed herein is used as either one of the positive terminal 40 (positive external terminal 44) of one cell 1 connected by the busbar 14 and the negative terminal 50 (negative external terminal 54) of the other cell, and the busbar 14 is formed of the same metal as the metal constituting the first member 72 of the terminal 70. By making the busbar 14 and the first member 72 of the same metal, welding becomes stronger and good conduction can be achieved. More preferably, the busbar 14, the external member joint of the positive external terminal 44, and the external member joint of the negative external terminal 54 are made of the same metal. For example, when the positive electrode external terminal 44 of one cell is made of aluminum, and the negative electrode external terminal 54 of another cell is a terminal 70 having the structure disclosed herein, and the first member 72 (see FIG. 5) of the terminal 70 is made of aluminum, it is preferable that the bus bar 14 is made of aluminum. With such a configuration, the welding between the bus bar 14 and the positive electrode external terminal 44 and the negative electrode external terminal 54 becomes stronger, realizing even better conduction. Note that this is merely one preferred example, and does not limit the metals that make up the positive and negative electrode external terminals and bus bar.

[0025] Each element constituting the secondary battery 1 will be described below.

[0026] <Battery case> The battery case 30 is a container that houses the electrode assembly 20. As shown in FIG. 1, the battery case 30 in this embodiment is a flat rectangular container. However, the shape of the battery case 30 may be a box shape other than a rectangular shape (for example, a cylindrical box shape with a bottom). The battery case 30 includes a rectangular case body 32 with an open top and a plate-like lid body 34 that closes the opening of the case body 32. As shown in FIG. 3, the lid body 34 is provided with a safety valve 36 that releases the internal pressure when the internal pressure in the battery case 30 rises to a predetermined level or higher. In addition, the lid body 34 is provided with a terminal insertion hole 34a for inserting the negative electrode external terminal 54 and a terminal insertion hole 34b for inserting the positive electrode external terminal 44. As the material of the battery case 30, a metal material having a required strength is used, and for example, a metal material that is lightweight and has good thermal conductivity, such as aluminum, stainless steel, or nickel-plated steel, is used.

[0027] <Electrode body> The electrode body 20 is a power generating element accommodated inside the battery case 30 in a state where it is covered with an insulating film (not shown) or the like. The electrode body 20 in this embodiment includes a long sheet-like positive electrode 21, a long sheet-like negative electrode 22, and a long sheet-like separator 23. The electrode body 20 is a wound electrode body in which the long sheet-like member described above is wound up. The structure of the electrode body is not particularly limited, and various structures that can be adopted in general sealed batteries can be adopted without restriction. For example, the electrode body may be a laminated electrode body in which rectangular sheet-like positive and negative electrodes are laminated with a separator interposed therebetween.

[0028] The positive electrode 21 includes a foil-shaped positive electrode collector (e.g., aluminum foil) and a positive electrode active material layer formed on the surface (preferably both surfaces) of the positive electrode collector. In addition, on one side edge portion (the left side edge portion in FIG. 3) of the positive electrode 21 in the width direction X, the positive electrode active material layer is not formed, and a positive electrode connection portion 21a where the positive electrode collector is exposed is formed. The positive electrode active material layer contains various materials such as a positive electrode active material, a binder, and a conductive material. As for the materials contained in the positive electrode active material layer, those that can be used in conventional general secondary batteries (e.g., lithium ion secondary batteries) can be used without particular limitation, and detailed description is omitted since they do not limit the present invention.

[0029] The negative electrode 22 includes a foil-shaped negative electrode collector (e.g., copper foil) and a negative electrode active material layer formed on the surface (preferably both surfaces) of the negative electrode collector. The other side edge portion (the right side edge portion in FIG. 3) of the negative electrode 22 in the width direction X does not have a negative electrode active material layer, and a negative electrode connection portion 22a is formed where the negative electrode collector is exposed. Like the positive electrode active material layer, the negative electrode active material layer also contains various materials such as a negative electrode active material and a binder. As for the materials contained in the negative electrode active material layer, those that can be used in conventional general secondary batteries can be used without particular limitation, and detailed description thereof will be omitted since they do not limit the present invention.

[0030] The separator 23 is 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, the separator 23 has a plurality of fine holes formed therein, and is configured so that lithium ions can move between the positive electrode 21 and the negative electrode 22 through the fine holes. A resin sheet or the like having required heat resistance is used for the separator 23, but since any material that can be used in conventional general secondary batteries can be used without particular restriction, detailed description thereof will be omitted.

[0031] The electrolyte (not shown) contained in the battery case 30 can be any electrolyte that can be used in conventional general secondary batteries without any particular restrictions. For example, the electrolyte can be a non-aqueous liquid electrolyte (nonaqueous electrolyte solution) containing a non-aqueous solvent and a supporting salt, but detailed description thereof is omitted as it does not limit the present invention.

[0032] <Electrode terminal> The negative electrode terminal 50 includes a negative electrode side current collector terminal (negative electrode internal terminal 52) and a negative electrode side external connection terminal (negative electrode external terminal 54). The negative electrode internal terminal 52 is an elongated metal member extending along the height direction Z. As shown in FIG. 3 and FIG. 4, a lower end portion 52b of the negative electrode internal terminal 52 is joined and electrically connected to the negative electrode 22 (specifically, the negative electrode connection portion 22a) inside the battery case 30. In addition, the negative electrode external terminal 54 is inserted through a terminal insertion hole 34a provided in the lid body 34, and a part of it is exposed to the outside of the battery case 30, and the other part is electrically connected to the upper end portion 52a of the negative electrode internal terminal 52 inside the battery case 30. A through hole for inserting the negative electrode external terminal 54 is provided in the upper end portion 52a, and a crimping portion of the negative electrode external terminal 54 is caused to protrude from the through hole and then the crimping portion is crimped, thereby achieving electrical connection between the negative electrode internal terminal 52 and the negative electrode external terminal 54. In order to prevent electrical conduction between the battery case 30 (lid body 34) and the negative electrode internal terminal 52 and the negative electrode external terminal 54, an insulator 62 is disposed between the lid body 34 and the negative electrode internal terminal 52, and further, a gasket 60 is disposed between the lid body 34 and the negative electrode external terminal 54.

[0033] The positive electrode terminal 40 has a structure substantially similar to that of the negative electrode terminal 50 described above. That is, it includes a positive electrode side current collector terminal (positive electrode internal terminal 42) and a positive electrode side external connection terminal (positive electrode external terminal 44). The positive electrode internal terminal 42 is a long metal member extending along the height direction Z. The lower end of the positive electrode internal terminal 42 is connected to the positive electrode 21 (specifically, the positive electrode connection portion 21a) inside the battery case 30. In addition, the positive electrode external terminal 44 is inserted through a terminal insertion hole 34b provided in the lid body 34, and a part of it is exposed to the outside of the battery case 30, and the other part is connected to the upper end of the positive electrode internal terminal 42 inside the battery case 30. A through hole for inserting the positive external terminal 44 is provided at the upper end, and a crimping portion of the positive external terminal 44 is protruded from the through hole and then the crimping portion is crimped to realize connection between the positive internal terminal 42 and the positive external terminal 44. In the positive terminal 40 of this embodiment, in order to prevent electrical conduction between the battery case 30 (lid 34) and the positive internal terminal 42 and the positive external terminal 44, an insulator 62 is disposed between the lid 34 and the positive internal terminal 42, and further, a gasket 60 is disposed between the lid 34 and the positive external terminal 44.

[0034] <Gasket> The gasket 60 is disposed between the lid 34 and the positive external terminal 44 and between the lid 34 and the negative external terminal 54 in the terminal insertion holes 34a, 34b provided on the outside of the battery case 30 and the lid 34. As a result, the gasket 60 insulates the lid 34 from the positive external terminal 44 and the negative external terminal 54. The gasket 60 has a through hole through which the external terminal is inserted. As shown in FIG. 7, the gasket 60 has a hollow cylindrical portion 60a provided along the periphery of the through hole, through which a part of the external terminal is inserted. This prevents the inner circumferential surface of the terminal insertion holes 34a, 34b provided in the lid 34 from directly contacting the external terminal. Furthermore, by crimping the crimped portion of the positive electrode external terminal 44 or the negative electrode external terminal 54, the gasket 60 is compressed in the height direction Z between the outer surface of the lid body 34 and the positive electrode external terminal 44 or the negative electrode external terminal 54. This seals the gap between the outer surface of the lid body 34 and the positive electrode external terminal 44 or the negative electrode external terminal 54, and can prevent leakage of liquid and the like from the inside of the battery case 30 and intrusion of moisture and the like from the outside of the battery case 30. The gasket 60 is made of an insulating material capable of elastic deformation, and examples of the material that can be used include fluorinated resin such as perfluoroalkoxy fluorine resin (PFA), polyphenylene sulfide resin (PPS), and aliphatic polyamide.

[0035] <Insulator> The insulator 62 is disposed inside the battery case 30 between the lid body 34 and the positive electrode internal terminal 42 and between the lid body 34 and the negative electrode internal terminal 52, and insulates the lid body 34 from the internal terminals. The insulator 62 has a through hole for inserting the positive electrode external terminal 44 or the negative electrode external terminal 54, and a part of the external terminal is inserted into the through hole. The insulator 62 is compressed and fixed in the height direction Z between the outer surface of the lid body 34 and the positive electrode external terminal 44 or the negative electrode external terminal 54 by crimping the crimped portion of the positive electrode external terminal 44 or the negative electrode external terminal 54. The insulator 62 is made of an insulating material capable of elastic deformation, such as polyphenylene sulfide resin (PPS) or aliphatic polyamide.

[0036] <Terminal> In the secondary battery 1 according to this embodiment, at least one of the positive electrode external terminal 44 and the negative electrode external terminal 54 employs a terminal 70 having the structure disclosed herein. As shown in Fig. 5, the terminal 70 includes a first member 72 and a second member 76. When the terminal 70 is provided in the secondary battery 1, at least a portion of the first member 72 is disposed outside the battery case 30, and at least a portion of the second member 76 is disposed inside the battery case 30.

[0037] The first member 72 is formed in a plate shape. One plate surface 72a of the first member 72 is ultrasonically welded to the second member 76, and a recess 74 is formed in the other plate surface 72b. The first member 72 and the second member 76 are ultrasonically welded to each other in the recess 74.

[0038] One plate surface 72a of the first member 72 may have a recess 73 for fitting with a part of the second member 72. As shown in Fig. 5, by fitting the recess 73 with a part of the second member, it is possible to easily align the first member 72 and the second member 76 when performing ultrasonic welding, and a strong bond can be achieved by the fitting.

[0039] The recess 74 is provided for ultrasonic welding between the first member 72 and the second member 76. By performing ultrasonic welding on the bottom surface 74a of the recess 74, welding residue (burrs) that may occur during ultrasonic welding can be retained in the recess 74. In addition, unevenness on the metal surface caused by the ultrasonic welding is formed on the bottom surface 74a of the recess. That is, even after ultrasonic welding between the first member 72 and the second member 76 is performed, it is possible to prevent burrs 75 and unevenness caused by the ultrasonic welding from being formed on the other plate surface 72b excluding the recess 74. Therefore, the other plate surface 72b can be welded to an external member (e.g., bus bar 14) without performing surface treatment after ultrasonic welding.

[0040] In a preferred embodiment, when an external member is welded to the other plate surface 72b, the recess 74 is sealed by the external member. For example, as shown in FIG. 7, the bus bar 14 can be disposed so as to seal the recess 74, and the bus bar 14 and the first member 72 can be welded together. This allows welding residue (burrs 75) that may be generated by ultrasonic welding to be trapped in the recess 74. That is, an external member such as a bus bar can be joined to the terminal 70 without the need for a cleaning process for the burrs 75 that may be generated in the recess 74 after ultrasonic welding.

[0041] The shape of the recess 74 is not particularly limited, and may be, for example, a shape in which the other plate surface 74b is cut into a rectangular parallelepiped, hemispherical, cylindrical, triangular pyramid, or prismatic shape, but it is preferable that the cross section of the recess 74 perpendicular to the other plate surface 74b is rectangular. That is, when the other plate surface 74b is cut into a rectangular parallelepiped, cylindrical, or prismatic shape, the cross section may be rectangular. This makes it easier to ultrasonically weld the first member 72 and the second member 76 at the bottom surface 74a of the recess, and provides a terminal 70 that is firmly welded.

[0042] The number of recesses 74 to be formed is not particularly limited as long as it is within a range that can be sealed by an external member, and one or more recesses 74 may be formed. By forming a plurality of recesses 74, the number of places where ultrasonic welding is performed can be increased, and the bondability by ultrasonic welding can be improved. Furthermore, the size of the recess 74 to be formed is not particularly limited as long as it is within a range that allows it to be sealed by an external member.

[0043] 5, the second member 76 has a crimping portion 76a, and the terminal 70 can be electrically connected to the positive electrode internal terminal 42 or the negative electrode internal terminal 52 by crimping the crimping portion 76a. Specifically, as shown in Fig. 7, the second member 76 constituting the terminal 70 is inserted through the tubular portion 60a of the gasket 60, the terminal insertion hole 34a of the lid 34, the through hole of the insulator 62, and the through hole at the upper end of the internal terminal (here, the negative electrode internal terminal 52) in this order, and the crimping portion 76a is caused to protrude from the through hole at the upper end of the internal terminal, and then the crimping portion 76a is crimped so that a compressive force is applied in the height direction Z, thereby crimping and fixing the gasket 60, the lid 34, the insulator 62, and the internal terminal.

[0044] A part of the second member 76 may have a shape that can be fitted into a recess 73 that the first member 72 may have. For example, as shown in FIG. 5, the second member 76 may have a flange portion that can fit the first member 72 into the recess 73, although this is not particularly limited. The flange portion has a shape that spreads outward from the shaft portion of the second member 76. This makes it easier to align the first member 72 and the second member 76 during ultrasonic welding. Furthermore, by performing joining by fitting in addition to joining by ultrasonic welding, the joinability between the first member 72 and the second member 76 may be improved.

[0045] Both the first member 72 and the second member 76 are made of a metal having high electrical conductivity, for example, aluminum, an alloy mainly made of aluminum, copper, an alloy mainly made of copper, or the like. The first member 72 and the second member 76 may be made of the same metal or different metals, but preferably, the first member 72 and the second member 76 are made of metals different from each other. That is, the metal constituting the second member 76 and the metal constituting the internal terminal (positive electrode internal terminal 42 or negative electrode internal terminal 52) that can be electrically connected to the second member 76 can be made of the same metal, and the metal constituting the first member 72 and the metal constituting the external member (for example, the bus bar 14) that can be electrically connected to the first member 72 can be made of the same metal. Therefore, the reliability of welding between the first member 72 and the external member is improved, and good electrical conductivity and bonding are achieved between the second member 76 and the internal terminal. In this specification, the term "aluminum-based alloy" refers to an alloy composed of at least 70% aluminum. Other constituent elements contained in the alloy are not particularly limited, but may include silicon, iron, copper, manganese, magnesium, zinc, chromium, titanium, lead, zirconium, etc. In this specification, the term "copper-based alloy" refers to an alloy composed of at least 50% copper. Other constituent elements contained in the alloy are not particularly limited, but may include silicon, iron, manganese, magnesium, zinc, chromium, titanium, lead, tin, phosphorus, aluminum, nickel, cobalt, beryllium, zirconium, etc.

[0046] Among the terminals 70 in which the first member 72 and the second member 76 are made of different metals, it is particularly preferable that the first member 72 is made of aluminum or an alloy mainly made of aluminum, and the second member 76 is made of copper or an alloy mainly made of copper. The terminal 70 having such a configuration can be suitably used as the negative electrode external terminal 54. Typically, the negative electrode current collector is made of copper foil, and the negative electrode internal terminal 52 is preferably made of the same metal as the negative electrode current collector, and is therefore made of copper. Therefore, the terminal 70 having the above configuration provides a good connection between the second member 76 and the negative electrode internal terminal 52. In addition, as a typical example, the positive electrode current collector, the positive electrode internal terminal 42, and the positive electrode external terminal 44 are made of an alloy mainly made of aluminum. Therefore, the terminal 70 having the above configuration can more suitably join the external members made of the same metal as the positive electrode external terminal 44 and the negative electrode external terminal 54, since the first member 72 is made of aluminum or an alloy mainly made of aluminum.

[0047] The first member 72 and the second member 76 are joined by ultrasonic welding between one plate surface 72a of the first member 72 and a part of the second member 76, and the pressure-welded portion of the ultrasonic welding is the recess 74. In a preferred embodiment, a welding residue is present in the recess 74 when ultrasonic welding is performed. This allows an external member such as a bus bar to be welded to the other plate surface 72b of the first member 72 without performing a surface treatment after ultrasonic welding. In addition, it is possible to visually confirm that ultrasonic welding has been performed in the recess 74.

[0048] The following describes a manufacturing method of the terminal 70. The manufacturing method of the terminal 70 includes preparing a plate-shaped metal first member 72 and a metal second member 76, and joining the second member 76 to one plate surface 72a of the first member 72 by ultrasonic welding.

[0049] In this manufacturing method, first, a plate-shaped metal first member 72 and a metal second member 76 that constitute the terminal 70 are prepared. A recess 74 is formed in a plate surface (other plate surface 72b) opposite to the surface of the first member 72 to which the second member 76 is welded.

[0050] In a preferred embodiment, the first member 72 and the second member 76 prepared here are made of different metals. This allows the first member 72 and an external member such as a bus bar joined to the first member 72 to be made of the same metal, improving weldability. Furthermore, the second member 76 and an internal terminal joined to the second member 76 can be made of the same metal, which can achieve good connection. Particularly preferably, the first member 72 prepared here is made of aluminum or an alloy mainly made of aluminum, and the second member 76 is made of copper or an alloy mainly made of copper. By using the terminal 70 manufactured from the above members as the negative electrode terminal 50 (negative electrode external terminal 54), it is possible to improve the electrical continuity on the negative electrode side and improve the weldability with an external member such as an aluminum bus bar.

[0051] Next, the second member 76 is joined to one plate surface 72a of the first member 72 by ultrasonic welding. The ultrasonic welding is performed in the recess 74 to join the first member 72 and the second member 76. In detail, as shown in FIG. 6, a horn 80 is applied to the bottom surface 74a of the recess 74, and an anvil 82 is applied to the second member 76 so as to sandwich the first member 72 and the second member 76 in the height direction Z. The horn 80 is attached to a press machine (not shown) equipped with a vibration generator. The vibration generator is a device that applies the required vibration required for ultrasonic welding to the horn 80. The shape of the pressure-welded portion of the horn 80 is not particularly limited as long as it is large enough to fit into the recess 74. Although not particularly limited, in a preferred example of the position of the anvil 82, the anvil 82 is disposed within the hollow structure of the crimping portion 76a of the second member 76, as shown in Fig. 6. This makes it possible to easily align the position of the anvil 82.

[0052] After the horn 80 and the anvil 82 are placed, pressure is applied to the first member 72 and the second member 76 by a press machine. Then, while the pressure is being applied, ultrasonic vibration is applied to the horn 80. The conditions of the pressure by the press machine and the ultrasonic vibration of the horn can be appropriately set according to the metal types and dimensions constituting the first member 72 and the second member 76, the shape of the horn 80, and the like. For example, the pressure is applied in the range of 80 to 1600 N, the ultrasonic vibration is set to an amplitude of 20 to 80 μm and a frequency of 15 to 150 kHz, and the energy to the pressure-welded portion of the horn 80 is set to 30 to 500 J. This realizes ultrasonic welding in the recess 74, and the terminal 70 having the structure disclosed herein can be manufactured.

[0053] Although ultrasonic welding can cause burrs 75 and irregularities on the metal surface, this manufacturing method can keep the welding residue (typically burrs 75) that may be caused by ultrasonic welding and the irregularities that may be caused on the surface to which the horn 80 is pressed, in the recess 74. Therefore, in the terminal 70 made by this manufacturing method, it is possible to weld an external member such as a bus bar to the plate surface (other plate surface 72b) opposite to the surface to which the second member 76 of the first member 72 is welded, without performing surface treatment after ultrasonic welding.

[0054] The terminal 70 manufactured by this manufacturing method may have burrs 75 formed in the recesses 74 as described above, but by sealing the recesses 74 with an external member, a step of cleaning the burrs 75 is not required, and a secondary battery 1 and a battery pack 10 including the terminal 70 can be manufactured. As shown in Fig. 7, the second member 76 constituting the terminal 70 is inserted through the cylindrical portion 60a of the gasket 60, the terminal insertion hole 34a of the lid 34, the through hole of the insulator 62, and the through hole at the upper end of the internal terminal (here, the negative electrode internal terminal 52) in this order, and the crimping portion 76a is made to protrude from the through hole at the upper end of the internal terminal, and then the crimping portion 76a is crimped so that a compressive force is applied in the height direction Z, thereby crimping and fixing the gasket 60, the lid 34, the insulator 62, and the negative electrode internal terminal 52 together, thereby making it possible to attach the terminal 70 to the secondary battery 1 (lid 34). Then, the bus bar 14 (external member) is placed on the plate surface (the other plate surface 72b) having the recess 74 of the first member 72 so as to seal the recess 74, and the bus bar 14 and the first member 72 are welded together. By providing the bus bar welded portion 14a around the recess 74, the burr 75 can be sealed in the recess 74. This makes it possible to weld the external member (bus bar) and the terminal 70 together without performing surface treatment after ultrasonic welding.

[0055] 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]

[0056] 1. Secondary battery (single cell) 10 Battery pack 12 Spacer 14 Bus bar 14a Busbar welded section 17 End Plate 18 Beam material 19 Bis 20 Electrode body 21 Positive electrode 21a Positive electrode connection part 22 Negative electrode 22a Negative electrode connection part 23 Separator 30 Battery case 32 Case body 34 Lid 34a, b Terminal insertion hole 36 Safety valve 40 Positive terminal 42 Positive inner terminal 44 Positive external terminal 50 Negative terminal 52 Negative internal terminal 52a Upper end 52b Bottom end 54 Negative external terminal 60 Gasket 60a cylinder part 62 Insulator 70 Terminals 72 First member 72a One plate surface 72b Other plate surface 73 Depression 74 Recess 74a Bottom 75 Bali 76 Second member 76a Crimping part 80 Horn 82 Anvil

Claims

1. A terminal constituting either the positive or negative electrode of a secondary battery, A first member made of metal and having a depression on a surface thereof; a second member made of metal having a flange portion, the flange portion being fitted into the recess of the first member, A recess is provided on a surface of the first member opposite to the surface on which the recess is provided, a metal joint is provided at a portion of a boundary surface between the first member and the second member facing the recess; Terminal.

2. The terminal of claim 1 , wherein the recess has a weld residue therein.

3. The terminal according to claim 1 or 2, wherein the metal joint is an ultrasonic joint.

4. The terminal according to any one of claims 1 to 3, wherein a cross section of the recess in a direction perpendicular to a surface of the first member on which the recess is provided is rectangular.

5. a cylindrical portion having an internal space and a side wall surrounding the internal space is provided at an end of the second member opposite to the end where the second member is fitted with the first member, The terminal according to any one of claims 1 to 4, wherein in a plan view, the internal space and the recess overlap, and the recess is located inside the internal space.

6. The terminal according to any one of claims 1 to 5, wherein no welding residue is present on the surface surrounding the recess except for the recess.

7. The terminal according to any one of claims 1 to 6, wherein the first member and the second member are made of different metals.

8. 8. The terminal according to claim 7, wherein the first member is made of aluminum or an aluminum-based alloy, and the second member is made of copper or a copper-based alloy.

9. An electrode assembly including a positive electrode and a negative electrode; a battery case that houses the electrode body therein; a positive electrode terminal and a negative electrode terminal electrically connected to the positive and negative electrodes of the electrode assembly, respectively; A secondary battery comprising: At least one of the positive terminal and the negative terminal is constituted by the terminal according to any one of claims 1 to 8. Secondary battery.

10. A battery pack in which a plurality of unit cells are electrically connected to each other and arranged, A battery pack comprising the secondary battery according to claim 9 as the plurality of single cells.

11. The plurality of single cells are each electrically connected to a positive terminal of one single cell and a negative terminal of another single cell by a predetermined bus bar, The terminal according to any one of claims 1 to 8 is used as either one of the positive terminal of the one cell and the negative terminal of the other cell, and the recess of the terminal is sealed with the bus bar. The battery pack according to claim 10.

12. A method for manufacturing a terminal constituting either a positive or negative electrode of a secondary battery, comprising the steps of: Preparing a first metal member having a recess on one surface and a concave portion on a surface opposite to the first metal member, and a second metal member having a flange portion; fitting a flange portion of the second member into the recess; and A terminal manufacturing method comprising: welding the recess of the first member to join the first member and the second member.

13. The method of claim 12, wherein the welding is ultrasonic welding.

14. The terminal manufacturing method according to claim 12 or 13, wherein the first member and the second member are made of different metals.

15. 15. The method for manufacturing a terminal according to claim 14, wherein the first member is made of aluminum or an alloy mainly made of aluminum, and the second member is made of copper or an alloy mainly made of copper.

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