Terminal for secondary battery and secondary battery including the 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 of a secondary battery. Specifically, the present invention relates 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 single battery, and a secondary battery using the terminal.

Background Art

[0002] Secondary batteries such as lithium ion secondary batteries are widely used as portable power sources for personal computers, mobile terminals, etc., or vehicle-mounted power sources for EVs (electric vehicles), HVs (hybrid vehicles), PHVs (plug-in hybrid vehicles), etc. because they are lightweight and can obtain a high energy density. In particular, for vehicle-mounted power sources, since high output is required, a battery pack in which a plurality of such secondary batteries (single batteries) are electrically connected to each other is preferably used.

[0003] A battery pack is generally configured by electrically connecting the positive and negative terminals of a plurality of single batteries via bus bars, respectively. However, when welding the bus bar to the positive and negative terminals of the single battery, if the metal constituting the bus bar is different from the metals constituting the positive and negative terminals, it is difficult to perform appropriate 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 of dissimilar metals, and corrosion and deterioration of the metal may occur.

[0004] Therefore, Patent Document 1 discloses a battery pack using a positive terminal made of dissimilar metals in order to make the metal constituting the bus bar the same as the metal constituting the bus bar welding portion of the positive terminal. 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 caulking. Thereby, the compatibility when welding the copper bus bar and the positive external terminal mainly made of copper can be improved. In addition, Patent Document 2 discloses a secondary battery in which a metal member made of the same metal as the metal constituting the bus bar is joined to an external terminal by ultrasonic bonding.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in any of the techniques of Patent Document 1 and Patent Document 2, unevenness is formed on the metal surface pressed for ultrasonic bonding, and at the same time, burrs are generated. Therefore, before welding an external member such as a bus bar to the metal surface, a surface treatment for smoothing the unevenness formed on the metal surface and a burr cleaning process are required. The presence of such additional processes is not preferable because it will cost the cost and manufacturing time of the secondary battery.

[0007] Therefore, the present invention has been made in view of the above problems, and its main object is to provide a terminal that constitutes either the positive or negative electrode of a secondary battery, and can perform welding with an external member such as a bus bar without requiring surface treatment of the metal portion pressed by ultrasonic welding. Another object of the present invention is to provide a secondary battery and a battery pack including the terminal.

Means for Solving the Problems

[0008] The terminal disclosed herein is a terminal that constitutes either the positive or negative electrode of a secondary battery, and includes a plate-shaped first member made of metal, and a second member made of metal ultrasonically welded to one plate surface of the first member. A concave portion is formed on the surface of the first member opposite to the surface to which the second member is welded, and ultrasonic welding of the first member and the second member is realized in the concave portion. According to such a configuration, even after joining the first member and the second member by ultrasonic welding, burrs or unevenness on the metal surface that may be generated by the ultrasonic welding occur in the recessed portion, so that surface treatment is not required, and a terminal capable of performing welding of an external member such as a bus bar on the plate surface having the recessed portion of the first member is provided.

[0009] Further, in a preferred embodiment of the terminal disclosed herein, welding residues generated when the ultrasonic welding is performed in the recessed portion are present. According to such a configuration, a terminal capable of performing welding with an external member such as a bus bar in a state where welding residues generated when ultrasonic welding is performed in the recessed portion are present is provided.

[0010] Further, in a preferred embodiment of the terminal disclosed herein, the first member and the second member are made of different metals from each other. According to such a configuration, a terminal capable of favorably performing welding between the first member and an external member such as a bus bar, and joining between the second member and an internal terminal electrically connected to the electrode body is provided.

[0011] Further, in a preferred embodiment of the terminal disclosed herein, the first member is made of aluminum or an alloy mainly composed of aluminum, and the second member is made of copper or an alloy mainly composed of copper. According to such a configuration, a terminal capable of suitably performing joining between an external member such as a bus bar made of aluminum or an alloy mainly composed of aluminum and the first member, and joining between the second member and a negative electrode internal terminal made of copper or an alloy mainly composed of copper electrically connected to the negative electrode is provided.

[0012] Further, the secondary battery disclosed herein includes an electrode body including a positive electrode and a negative electrode, a battery case that houses the electrode body therein, and a positive electrode terminal and a negative electrode terminal that are 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 configured by the terminal disclosed herein. According to such a configuration, a secondary battery capable of realizing good joining between the positive electrode terminal and the negative electrode terminal and an external member is provided.

[0013] In addition, the assembled battery disclosed herein has a plurality of single cells electrically connected and arranged to each other, and the secondary battery disclosed herein is used as the plurality of single cells. According to such a configuration, an assembled battery in which electrical connection between a terminal and an external member such as a bus bar can be satisfactorily performed is provided.

[0014] In a preferred aspect of the assembled battery disclosed herein, in the plurality of single cells, a positive electrode terminal of one single cell and a negative electrode terminal of another single cell are electrically connected to each other by a predetermined bus bar. Here, as either one of the positive electrode terminal of the one single cell and the negative electrode terminal of the other single cell, the terminal disclosed herein is used, and the bus bar is formed of the same metal as the metal constituting the first member of the terminal. According to such a configuration, an assembled battery in which welding between the bus bar and the positive electrode terminal and the negative electrode terminal can be satisfactorily performed is provided.

[0015] In addition, to achieve the above object, a method for manufacturing the terminal disclosed herein is provided. That is, a method for manufacturing a terminal constituting either the positive or negative electrode of the secondary battery disclosed herein includes preparing a plate-shaped first member made of metal and a second member made of metal, and joining the second member to one plate surface of the first member by ultrasonic welding. Here, a concave portion is formed on the plate surface of the first member opposite to the surface where the second member is welded, and ultrasonic welding is performed in the concave portion. According to the manufacturing method having such a configuration, burrs that may be generated by ultrasonic welding can be retained in the concave portion, and a terminal that does not require surface treatment after ultrasonic welding can be manufactured.

[0016] In a preferred aspect of the terminal manufacturing method disclosed herein, the first member and the second member are made of different metals from each other. According to the manufacturing method with such a configuration, it is possible to manufacture a terminal capable of favorably performing welding between the first member and an external member such as a bus bar, and welding between the second member and an internal terminal electrically connected to the electrode body.

[0017] Further, in a preferred aspect of the terminal manufacturing method disclosed herein, the first member is made of aluminum or an alloy mainly composed of aluminum, and the second member is made of copper or an alloy mainly composed of copper. According to the manufacturing method with such a configuration, it is possible to manufacture a terminal capable of favorably performing joining between an external member such as a bus bar made of aluminum or an alloy mainly composed of aluminum and the first member, and joining between the second member and a negative electrode internal terminal made of copper or an alloy mainly composed of copper and electrically connected to the negative electrode.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0019] Hereinafter, a schematic configuration example of a secondary battery and a battery pack including the terminal according to the present embodiment will be described with reference to the drawings. In the following drawings, members and parts having the same function are denoted by the same reference numerals for description. In addition, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. In addition, matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. In the drawings in this specification, reference numeral X indicates the width direction (of the battery), reference numeral Y indicates the thickness direction, and reference numeral Z indicates the height direction. These directions are defined for convenience of explanation and are not intended to limit the installation mode of the battery.

[0020] In this specification, the "secondary battery" generally refers to a rechargeable power storage device, 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 "lithium-ion secondary battery" refers to a secondary battery that uses lithium ions as charge carriers and realizes charge and discharge by the movement of charges associated with lithium ions between the positive and negative electrodes.

[0021] <Secondary battery> FIG. 1 is a perspective view schematically showing a secondary battery according to the present embodiment. FIG. 3 is a partially cut-away view schematically showing a secondary battery according to an embodiment. The secondary battery 1 according to the present 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 an example of the present embodiment, a secondary battery 1 including the terminal 70 disclosed here as the negative electrode external terminal 54 is illustrated. However, this is only an example, and other examples include a secondary battery 1 including the terminal 70 having the structure disclosed here as the positive electrode external terminal 44. The configuration of the terminal 70 will be described later.

[0022] FIG. 2 is a perspective view schematically showing the assembled battery according to the present embodiment. As shown in FIG. 2, in the assembled battery 10, a plurality of secondary batteries (single cells) 1 are electrically connected to each other and arranged, and the single cell is the secondary battery disclosed herein. By arranging the single cells 1 one by one while inverting them, the positive electrode terminals 40 and the negative electrode terminals 50 are alternately arranged. 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, or the like. A pair of end plates (constraint plates) 17 are arranged at both ends of the arranged single cells 1. A tightening beam member 18 is attached so as to bridge between both end plates 17. The end of the beam member 18 is tightened and fixed to the end plate 17 by a screw 19. Thereby, a plurality of single cells 1 are constrained so that a constraint load is applied in the arrangement direction of the single cells 1.

[0023] The assembled battery 10 includes a bus bar 14 that connects the external member joint portion of the positive electrode external terminal 44 of one single cell 1 and the external member joint portion of the negative electrode external terminal 54 of another single cell 1 between two adjacent single cells 1. Thereby, a conductive path is formed from the positive electrode internal terminal 42 of one single cell 1 to the negative electrode internal terminal 52 of another single cell 1 via the bus bar 14 and the external terminals, and each single cell 1 is electrically connected in series.

[0024] The bus bar 14 is generally made of a metal with high conductivity, and examples thereof include aluminum, copper, tin, nickel, or an alloy mainly composed of any of these metals. In a preferred embodiment, in the assembled battery 10, as one of the terminals of either the positive electrode terminal 40 (positive electrode external terminal 44) of one single battery 1 connected by the bus bar 14 or the negative electrode terminal 50 (negative electrode external terminal 54) of the other single battery, the terminal 70 having the configuration disclosed herein is used, and the bus bar 14 is formed of the same metal as the metal constituting the first member 72 of the terminal 70. Since the bus bar 14 and the first member 72 are made of the same metal, welding becomes stronger and good electrical conduction can be achieved. More preferably, the bus bar 14, the external member joint portion of the positive electrode external terminal 44, and the external member joint of the negative electrode external terminal 54 are made of the same metal. For example, if the positive electrode external terminal 44 of one single battery is made of aluminum and the negative electrode external terminal 54 of the other single battery is the terminal 70 having the structure disclosed herein, and the first member 72 (see FIG. 5) of the terminal 70 is made of aluminum, the bus bar 14 is preferably made of aluminum. With such a configuration, the welding between the bus bar 14, the positive electrode external terminal 44, and the negative electrode external terminal 54 becomes stronger, and even better electrical conduction is achieved. It should be noted that this is only a preferred specific example and does not limit the metals constituting the external terminals of the positive and negative electrodes and the bus bar.

[0025] Hereinafter, each element constituting the secondary battery 1 will be described.

[0026] <Battery case> The battery case 30 is a container for housing the electrode body 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 rectangular (for example, a bottomed cylindrical box shape, etc.). The battery case 30 includes a rectangular case body 32 with an open top surface 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 above a predetermined level. Further, 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 the required strength is used. For example, a lightweight and highly thermally conductive metal material such as aluminum, stainless steel, or nickel-plated steel is used.

[0027] <electrode body> The electrode body 20 is a power generation element housed inside the battery case 30 while being covered with an insulating film (not shown) or the like. The electrode body 20 in this embodiment includes a long sheet-shaped positive electrode 21, a long sheet-shaped negative electrode 22, and a long sheet-shaped separator 23. Such an electrode body 20 is a wound electrode body in which the above-described long sheet-shaped members are wound on top of each other. Note that the structure of the electrode body is not particularly limited, and various structures that can be adopted in a general sealed battery can be adopted without limitation. For example, the electrode body may be a laminated electrode body in which a rectangular sheet-shaped positive electrode and negative electrode are laminated with a separator interposed therebetween.

[0028] The positive electrode 21 includes a foil-shaped positive electrode current collector (e.g., aluminum foil) and a positive electrode active material layer formed on the surface (preferably both surfaces) of the positive electrode current collector. Further, on one side edge portion of the positive electrode 21 in the width direction X (the left side edge portion in FIG. 3), a positive electrode connection portion 21a is formed where the positive electrode active material layer is not formed and the positive electrode current collector is exposed. Note that the positive electrode active material layer contains various materials such as a positive electrode active material, a binder, and a conductive material. Regarding the materials contained in such a 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 since it does not limit the present invention, detailed description thereof is omitted.

[0029] The negative electrode 22 includes a foil-shaped negative electrode current collector (e.g., copper foil) and a negative electrode active material layer formed on the surface (preferably both surfaces) of the negative electrode current collector. Further, on the other side edge portion of the negative electrode 22 in the width direction X (the right side edge portion in FIG. 3), a negative electrode connection portion 22a is formed where the negative electrode active material layer is not formed and the negative electrode current collector is exposed. Note that, similar to 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. Regarding the materials contained in such a negative electrode active material layer, those that can be used in conventional general secondary batteries can be used without particular limitation, and since it does not limit the present invention, detailed description thereof is omitted.

[0030] The separator 23 is interposed between the positive electrode 21 and the negative electrode 22 to prevent these electrodes from directly contacting each other. Although illustration is omitted, a plurality of fine holes are formed in the separator 23, and it is configured such that lithium ions 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 those that can be used in conventional general secondary batteries can be used without particular limitation, detailed description thereof is omitted.

[0031] The electrolyte (not shown) accommodated in the battery case 30 can be used without particular limitation as long as it can be used in a conventional general secondary battery. For example, the electrolyte can be a non-aqueous liquid electrolyte (non-aqueous electrolyte solution) containing a non-aqueous solvent and a supporting salt, but a detailed description is omitted because the present invention is not limited thereto.

[0032] <Electrode terminal> The negative electrode terminal 50 includes a current collecting terminal on the negative electrode side (negative electrode internal terminal 52) and an external connection terminal on the negative electrode side (negative electrode external terminal 54). The negative electrode internal terminal 52 is a long metal member extending along the height direction Z. As shown in FIGS. 3 and 4, the lower end portion 52b of the negative electrode internal terminal 52 is joined to the negative electrode 22 (specifically, the negative electrode connection portion 22a) inside the battery case 30 and is electrically connected. Further, the negative electrode external terminal 54 passes through a terminal insertion hole 34a provided in the lid body 34. A part of it is exposed outside the battery case 30, and another 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. After the caulking portion provided on the negative electrode external terminal 54 protrudes from the through hole, the caulking portion is caulked, whereby electrical connection between the negative electrode internal terminal 52 and the negative electrode external terminal 54 is realized. In order to prevent energization 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 substantially the same structure as the negative electrode terminal 50 described above. That is, it includes a current collecting terminal on the positive electrode side (positive electrode internal terminal 42) and an external connection terminal on the positive electrode side (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 portion 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. Further, the positive electrode external terminal 44 passes through the terminal insertion hole 34b provided in the lid body 34. A part of it is exposed outside the battery case 30, and the other part is connected to the upper end portion of the positive electrode internal terminal 42 inside the battery case 30. A through hole for inserting the positive electrode external terminal 44 is provided in the upper end portion. After the caulking portion provided on the positive electrode external terminal 44 protrudes from the through hole, the caulking portion is caulked to realize the connection between the positive electrode internal terminal 42 and the positive electrode external terminal 44. Further, in the positive electrode terminal 40 in the present embodiment, in order to prevent energization between the battery case 30 (lid body 34) and the positive electrode internal terminal 42 and the positive electrode external terminal 44, an insulator 62 is disposed between the lid body 34 and the positive electrode internal terminal 42. Further, a gasket 60 is disposed between the lid body 34 and the positive electrode external terminal 44.

[0034] <Gasket> The gasket 60 is disposed between the lid body 34 and the positive external terminal 44 and between the lid body 34 and the negative external terminal 54 at the terminal insertion holes 34a and 34b provided on the outside of the battery case 30 and the lid body 34. Thereby, the gasket 60 insulates the lid body 34 from the positive external terminal 44 and the negative external terminal 54. The gasket 60 has through holes through which the external terminals are inserted. Further, as shown in FIG. 7, the gasket 60 has a hollow cylindrical tube portion 60a provided along the periphery of the through hole, and a part of the external terminal is inserted through the tube portion. Thereby, it is possible to prevent the inner peripheral surfaces of the terminal insertion holes 34a and 34b provided in the lid body 34 from coming into direct contact with the external terminals. Further, when the caulking portion of the positive external terminal 44 or the negative external terminal 54 is caulked, the gasket 60 is compressed in the height direction Z between the outer surface of the lid body 34 and the positive external terminal 44 or the negative external terminal 54. Thereby, the space between the outer surface of the lid body 34 and the positive external terminal 44 or the negative external terminal 54 is sealed, and leakage of liquid or the like from the inside of the battery case 30 and intrusion of moisture or the like from the outside of the battery case 30 can be prevented. The gasket 60 is formed of an insulating material capable of elastic deformation, and for example, fluorinated resins such as perfluoroalkoxy fluororesin (PFA), polyphenylene sulfide resin (PPS), aliphatic polyamide, etc. are used.

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

[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 part of the first member 72 is disposed outside the battery case 30, and at least a part 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. And in the recess 74, ultrasonic welding between the first member 72 and the second member 76 is realized.

[0038] One plate surface 72a of the first member 72 may be provided with a depression 73 for fitting with a part of the second member 72. As shown in FIG. 5, by fitting the depression 73 and a part of the second member, the alignment of the first member 72 and the second member 76 can be facilitated when performing ultrasonic welding, and a strong joint by fitting can be realized.

[0039] The recess 74 is provided for ultrasonic welding of the first member 72 and the second member 76. By performing ultrasonic welding on the bottom surface 74a of the recess 74, welding residues (burrs) that may occur during the ultrasonic welding can be retained in the recess 74. Further, unevenness on the metal surface caused by the ultrasonic welding is formed on the bottom surface 74a of the recess. That is, even after performing ultrasonic welding between the first member 72 and the second member 76, it is possible to prevent burrs 75 and unevenness due to 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 (for example, the bus bar 14) without performing surface treatment after ultrasonic welding.

[0040] In a preferred embodiment, when welding an external member 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 is arranged so as to seal the recess 74, and the bus bar 14 and the first member 72 can be welded. Thereby, welding residues (burrs 75) that may occur due to ultrasonic welding can be confined in the recess 74. That is, after ultrasonic welding, it is not necessary to perform a cleaning process on the burrs 75 that may occur in the recess 74, and an external member such as a bus bar can be joined to the terminal 70.

[0041] The shape of the recess 74 is not particularly limited, and for example, the other plate surface 74b may be cut out in a rectangular parallelepiped shape, a hemispherical shape, a cylindrical shape, a triangular pyramid shape, a prismatic shape, etc. However, it is preferable that the cross section of the recess 74 in a direction perpendicular to the other plate surface 74b is rectangular. That is, when the other plate surface 74b is cut out in a rectangular parallelepiped shape, a cylindrical shape, a prismatic shape, etc., the above cross section can be rectangular. Thereby, it becomes easy to perform ultrasonic welding between the first member 72 and the second member 76 on the bottom surface 74a of the recess, and a firmly welded terminal 70 can be provided.

[0042] The number of recesses 74 formed is not particularly limited as long as it can be sealed by an external member, and one or two or more recesses 74 can be formed. By forming a plurality of recesses 74, the locations where ultrasonic welding is performed can be increased, and the jointability by ultrasonic welding can be improved. Moreover, the size of the recess 74 to be formed is not particularly limited as long as it can be sealed by the external member.

[0043] As shown in FIG. 5, the second member 76 includes a caulking portion 76a. By caulking the caulking portion 76a, the terminal 70 can be electrically connected to the positive internal terminal 42 or the negative internal terminal 52. Specifically, 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 internal terminal 52) in this order. After the caulking portion 76a protrudes from the through hole at the upper end of the internal terminal, the caulking portion 76a is caulked 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 the recess 73 that the first member 72 may have. Although not particularly limited, for example, as shown in FIG. 5, the second member 76 may be provided with a flange portion having a shape that can be fitted into the recess 73 of the first member 72. The flange portion has a shape that spreads outward from the shaft portion of the second member 76. This facilitates the alignment of the first member 72 and the second member 76 during ultrasonic welding. In addition to the joining by ultrasonic welding, the joining by fitting can be performed, thereby improving the joinability between the first member 72 and the second member 76.

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

[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 composed of aluminum, and the second member 76 is made of copper or an alloy mainly composed 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 a copper foil, and it is preferable that the negative electrode internal terminal 52 is made of the same metal as the negative electrode current collector, so it is made of copper. Therefore, according to the terminal 70 having the above configuration, the connection between the second member 76 and the negative electrode internal terminal 52 is improved. Further, 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 aluminum or an alloy mainly composed of aluminum. Therefore, according to the terminal 70 having the above configuration, since the first member 72 is made of aluminum or an alloy mainly composed of aluminum, an external member made of the same kind of metal as the positive electrode external terminal 44 and the negative electrode external terminal 54 can be more suitably joined.

[0047] One surface 72a of the first member 72 and a part of the second member 76 of the first member 72 and the second member 76 are joined by ultrasonic welding, and the pressure contact portion of the ultrasonic welding is the recess 74. In a preferred embodiment, there is welding residue generated when ultrasonic welding is performed at the recess 74. Thereby, after ultrasonic welding, an external member such as a bus bar can be welded to the other plate surface 72b of the first member 72 without performing a surface treatment. Further, it can be visually confirmed that the ultrasonic welding is performed at the recess 74.

[0048] Hereinafter, a method for manufacturing the terminal 70 will be described. The method for manufacturing 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 such a manufacturing method, first, a plate-shaped metal first member 72 constituting the terminal 70 and a metal second member 76 are prepared. A recess 74 is formed in the plate surface (the other plate surface 72b) of the first member 72 on the side opposite to the surface where 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 from each other. Thereby, the first member 72 and an external member such as a bus bar joined to the first member 72 can be made of the same kind of metal, and the weldability can be improved. Furthermore, since the second member 76 and an internal terminal joined to the second member 76 can be made of the same kind of metal, a good connection can be achieved. Particularly preferably, the first member 72 prepared here is made of aluminum or an alloy mainly composed of aluminum, and the second member 76 is made of copper or an alloy mainly composed of copper. By using the terminal 70 manufactured by the above members as the negative terminal 50 (negative external terminal 54), the conductivity on the negative electrode side can be improved, and the weldability with an external member such as an aluminum bus bar can be improved.

[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 at the recess 74 to join the first member 72 and the second member 76. Specifically, as shown in FIG. 6, the horn 80 is applied to the bottom surface 74a of the recess 74, and the 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 for ultrasonic welding to the horn 80. Also, the shape of the pressure contact portion of the horn 80 is not particularly limited as long as it can enter the recess 74. Although not particularly limited, in a preferred example of the arrangement position of the anvil 82, as shown in FIG. 6, the anvil 82 is arranged in the hollow structure of the caulking portion 76a of the second member 76. Thereby, the alignment of the anvil 82 can be facilitated.

[0052] After arranging the horn 80 and the anvil 82, pressure is applied to the first member 72 and the second member 76 by a press. Then, while applying such pressure, ultrasonic vibration is imparted to the horn 80. Note that the conditions of the pressure by the press and the ultrasonic vibration of the horn can be appropriately set according to the metal type, dimensions, shape of the horn 80, etc. that constitute the first member 72 and the second member 76. 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 applied to the pressure contact portion of the horn 80 is set to 30 to 500 J. Thereby, ultrasonic welding in the recess 74 is realized, and the terminal 70 having the structure disclosed herein can be manufactured.

[0053] By ultrasonic welding, burrs 75 and unevenness may occur on the metal surface. However, according to such a manufacturing method, welding residues (typically burrs 75) that may be generated by ultrasonic welding and unevenness that may occur on the surface to which the horn 80 is pressure - contacted can be retained in the recess 74. Therefore, the terminal 70 manufactured by such a manufacturing method can be welded to an external member such as a bus bar on the plate surface (the other plate surface 72b) on the side opposite to the surface of the first member 72 where the second member 76 is welded without performing surface treatment after ultrasonic welding.

[0054] The terminal 70 manufactured by such a manufacturing method may have burrs 75 formed in the recess 74 as described above. However, by sealing the recess 74 with an external member, the step of cleaning the burrs 75 is not required, and the secondary battery 1 and the assembled battery 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 body 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. After the caulking portion 76a is made to protrude from the through hole at the upper end of the internal terminal, the caulking portion 76a is caulked so that a compressive force is applied in the height direction Z, thereby crimping and fixing the gasket 60, the lid body 34, the insulator 62, and the negative electrode internal terminal 52, and the terminal 70 can be provided to the secondary battery 1 (lid body 34). Then, the bus bar 14 (external member) is disposed 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. By providing the bus bar welded portion 14a around the recess 74, the burrs 75 can be sealed in the recess 74. Thereby, it is possible to realize welding of the external member (bus bar) and the terminal 70 without performing surface treatment after ultrasonic welding.

[0055] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The invention disclosed herein includes various modifications and changes of the above specific examples.

Explanation of Reference Numerals

[0056] 1 Secondary battery (single cell) 10 Assembled battery 12 Spacer 14 Bus bar 14a Bus bar welded portion 17 End plate 18 Beam material 19 Screw 20 Electrode body 21 Positive electrode 21a Positive electrode connection portion 22 Negative electrode 22a Negative electrode connection portion 23 Separator 30 Battery case 32 Case body 34 Cover 34a, b Terminal insertion holes 36 Safety valve 40 Positive terminal 42 Positive internal terminal 44 Positive external terminal 50 Negative terminal 52 Negative internal terminal 52a Upper end portion 52b Lower end portion 54 Negative external terminal 60 Gasket 60a Cylindrical portion 62 Insulator 70 Terminal 72 First member 72a One plate surface 72b The other plate surface 73 Depression 74 Recess 74a Bottom surface 75 Burr 76 Second member 76a Crimping portion 80 Horn 82 Anvil

Claims

1. A terminal that constitutes an electrode terminal for external connection of either the positive or negative electrode of a secondary battery, A first member made of metal containing a first metal, A second member made of metal containing a second metal different from the first metal and welded to the surface of the first member, and comprising: A recess having a flat bottom surface is provided on the surface of the first member opposite to the surface in contact with the second member, An ultrasonic bonding portion where the first metal and the second metal are joined is provided at a portion facing the recess at the interface between the first member and the second member, Terminal.

2. The terminal according to claim 1, wherein welding residues are present in the recess.

3. The terminal according to claim 1 or 2, wherein the first member and the second member are made of different metals from each other.

4. The terminal according to claim 3, wherein the first member is made of aluminum or an alloy mainly composed of aluminum, and the second member is made of copper or an alloy mainly composed of copper.

5. The terminal according to any one of claims 1 to 4, wherein the first member is plate-shaped.

6. An electrode body 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 body respectively A secondary battery comprising: At least one of the positive electrode terminal and the negative electrode terminal is constituted by the terminal according to any one of claims 1 to 5, Secondary battery.

7. A battery pack in which a plurality of single cells are electrically connected to each other and arranged, A battery pack comprising the secondary battery according to claim 6 as the plurality of single cells.

8. The plurality of single cells are electrically connected to each other such that the positive electrode terminal of one single cell and the negative electrode terminal of another single cell are respectively connected by a predetermined bus bar. Here, as either one of the positive electrode terminal of the one single cell and the negative electrode terminal of the other single cell, the terminal according to any one of claims 1 to 5 is used, and the bus bar is formed of the same metal as the metal constituting the first member of the terminal. The battery pack according to claim 7.

9. A method for manufacturing a terminal constituting an electrode terminal for external connection of either the positive or negative electrode of a secondary battery, preparing a first member made of metal containing a first metal and a second member made of metal containing a second metal different from the first metal, and joining the second member to the surface of the first member by ultrasonic welding to provide an ultrasonic joint where the first metal and the second metal are joined, wherein a recess having a flat bottom surface is formed on the surface of the first member opposite to the surface to which the second member is welded, A terminal manufacturing method for performing the ultrasonic welding in the recess.

10. The terminal manufacturing method according to claim 9, wherein the first member and the second member are made of different metals from each other.

11. The terminal manufacturing method according to claim 10, wherein the first member is made of aluminum or an alloy mainly composed of aluminum, and the second member is made of copper or an alloy mainly composed of copper.

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