Terminal parts, secondary batteries and battery packs

Abstract

To provide a terminal component suppressing deformation.SOLUTION: A terminal component 200 is equipped with a first metal 201, and a second metal 202 overlapped with the first metal 201. At a border between the first metal 201 and the second metal 202, a joint portion 203 where the first metal 201 and the second metal 202 are joined by metal-joining is provided. The second metal 202 has a groove 202c outside the joint portion 203, on a surface 202b opposite to a surface 202a overlapped with the first metal 201.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a terminal component, a secondary battery, and a battery pack. [Background technology]

[0002] JP 2016-18675 A discloses a secondary battery having positive and negative external terminals made of different materials. The secondary battery is connected in series by a bus bar made of the same material as one of the positive and negative external terminals. A metal member made of a material that is excellent in weldability to the material of one of the external terminals is ultrasonically bonded to the other external terminal. JP 2011-124024 A discloses a battery pack in which a plurality of cells are connected by a bus bar. Of the positive and negative terminals constituting the cells, the terminal of one polarity includes an external terminal having a better welding quality with the bus bar and a base to which a foil of one polarity is connected. The base and the external terminal are joined by ultrasonic welding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-18675 A [Patent Document 2] JP 2011-124024 A Summary of the Invention [Problem to be solved by the invention]

[0004] When joining dissimilar metals by ultrasonic bonding, one metal is joined to the other metal by applying ultrasonic vibrations while pressing a horn against the other metal. During this process, deformations may occur in the metal against which the horn is applied, such as protruding edges or partially curving. Such deformation may also occur when ultrasonic bonding is performed on a terminal used in a battery to bond dissimilar metals. According to the inventor's knowledge, if such deformation occurs in a terminal used in a battery, the deformed portion may penetrate a member such as a gasket that insulates the terminal from the lid body and interfere with other members. If the deformed portion becomes detached during the manufacturing process, the detached portion may enter the inside of the battery case and cause an internal short circuit. If deformation occurs in the portion that becomes the bus bar connection surface of the terminal, a gap may occur between the bus bar and the bus bar connection surface, which may cause poor welding. [Means for solving the problem]

[0005] The terminal component disclosed herein includes a first metal and a second metal overlaid on the first metal. At the boundary between the first metal and the second metal is a joint where the first metal and the second metal are joined by metallic bonding. The second metal has a groove on the outer side of the joint on the surface opposite to the surface overlaid on the first metal.

[0006] The second metal constituting the terminal component has a groove around the joint on the surface opposite to the joint, which serves to suppress deformation of the terminal component caused by ultrasonic bonding.

[0007] The groove of the terminal component may be continuous in the circumferential direction.The first metal and the second metal may be made of different metals.

[0008] A secondary battery including a battery case and an electrode terminal attached to the battery case may include a portion constituted by the above-mentioned terminal component.

[0009] An assembled battery including a plurality of secondary batteries having positive and negative external terminals, and a bus bar connecting the plurality of secondary batteries via the external terminals, may have a joint at the boundary between the external terminal of one of the external terminals and the bus bar, where the external terminal of one of the external terminals is joined to the bus bar by metal bonding, and the bus bar may have a groove on the outside of the joint on the surface opposite to the joint. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a partial cross-sectional view of a lithium-ion secondary battery 10. [Diagram 2] FIG. 2 is a cross-sectional view showing a cross section taken along line II-II of FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III of FIG. [Figure 4] FIG. 4 is a cross-sectional view that diagrammatically illustrates the terminal part 200. As shown in FIG. [Diagram 5] 5A to 5C are cross-sectional views illustrating a manufacturing method of the terminal component 200. As shown in FIG. [Figure 6] FIG. 6 is a perspective view showing a schematic diagram of the battery pack 100. As shown in FIG. [Figure 7] 1 is a cross-sectional view showing a schematic view of a portion of a battery pack 100 where a negative external terminal 43b and a bus bar 91 are connected. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the terminal component and secondary battery disclosed herein will be described. The embodiment described herein is, of course, not intended to limit the present invention. The present invention is not limited to the embodiment described herein unless otherwise specified. Each drawing is drawn typically and does not necessarily reflect the actual product. In addition, the same reference numerals are appropriately assigned to members and parts that perform the same function, and duplicated explanations are omitted.

[0012] 《Secondary battery》 In this specification, the term "secondary battery" refers to a device that can be charged and discharged. Secondary batteries include batteries generally called lithium ion batteries or lithium secondary batteries, as well as lithium polymer batteries and lithium ion capacitors. Here, a lithium ion secondary battery is exemplified as one form of secondary battery.

[0013] Lithium-ion secondary battery 10 FIG. 1 is a partial cross-sectional view of a lithium-ion secondary battery 10. FIG. 1 illustrates a state in which the inside is exposed along one wide surface of a substantially rectangular parallelepiped battery case 41. The lithium-ion secondary battery 10 illustrated in FIG. 1 is a so-called sealed battery. FIG. 2 is a cross-sectional view showing a cross section taken along line II-II in FIG. 1. FIG. 2 illustrates a schematic partial cross-sectional view of a state in which the inside is exposed along one narrow surface of a substantially rectangular parallelepiped battery case 41.

[0014] As shown in FIG. 1, the lithium ion secondary battery 10 includes an electrode assembly 20, a battery case 41, a positive electrode terminal 42, and a negative electrode terminal 43.

[0015] <Electrode body 20> The electrode body 20 is housed in a battery case 41 while being covered with an insulating film (not shown) or the like. The electrode body 20 includes a positive electrode sheet 21 as a positive electrode element, a negative electrode sheet 22 as a negative electrode element, and separator sheets 31 and 32 as separators. The positive electrode sheet 21, the first separator sheet 31, the negative electrode sheet 22, and the second separator sheet 32 ​​are each a long strip-shaped member.

[0016] The positive electrode sheet 21 is a positive electrode current collector foil 21a (e.g., aluminum foil) having a predetermined width and thickness, on both sides of which a positive electrode active material layer 21b containing a positive electrode active material is formed, except for an unformed portion 21a1 set at a certain width at one end of the width direction. For example, in a lithium ion secondary battery, the positive electrode active material is a material that can release lithium ions during charging and absorb lithium ions during discharging, such as a lithium transition metal composite material. In general, various positive electrode active materials have been proposed other than lithium transition metal composite materials, and there is no particular limitation.

[0017] The negative electrode sheet 22 is formed by forming a negative electrode active material layer 22b containing a negative electrode active material on both sides of a negative electrode current collector foil 22a (copper foil in this case) having a predetermined width and thickness, except for an unformed portion 22a1 set at a certain width on one edge in the width direction. The negative electrode active material is, for example, a material such as natural graphite in a lithium ion secondary battery that can absorb lithium ions during charging and release the absorbed lithium ions during charging during discharging. In general, various negative electrode active materials have been proposed other than natural graphite, and there is no particular limitation.

[0018] For example, a porous resin sheet having a required heat resistance and through which an electrolyte can pass is used for the separator sheets 31 and 32. Various types of separator sheets 31 and 32 have been proposed, and there is no particular limitation.

[0019] Here, the width of the negative electrode active material layer 22b is formed to be wider than that of the positive electrode active material layer 21b, for example. The width of the separator sheets 31 and 32 is wider than that of the negative electrode active material layer 22b. The unformed portion 21a1 of the positive electrode current collector foil 21a and the unformed portion 22a1 of the negative electrode current collector foil 22a are oriented in opposite directions in the width direction. The positive electrode sheet 21, the first separator sheet 31, the negative electrode sheet 22, and the second separator sheet 32 ​​are aligned in the length direction, and are stacked and wound in order. The negative electrode active material layer 22b covers the positive electrode active material layer 21b with the separator sheets 31 and 32 interposed therebetween. The negative electrode active material layer 22b is covered with the separator sheets 31 and 32. An unformed portion 21a1 of the positive current collector foil 21a protrudes from one width direction side of the separator sheets 31, 32. An unformed portion 22a1 of the negative current collector foil 22a protrudes from the separator sheets 31, 32 on the opposite width direction side.

[0020] 1, the electrode body 20 described above is in a flat state along one plane including the winding axis so that it can be housed in the case body 41a of the battery case 41. Then, along the winding axis of the electrode body 20, the unformed portion 21a1 of the positive electrode current collector foil 21a is arranged on one side, and the unformed portion 22a1 of the negative electrode current collector foil 22a is arranged on the opposite side.

[0021] <Battery case 41> 1, the battery case 41 houses the electrode assembly 20. The battery case 41 has a case body 41a having a substantially rectangular parallelepiped shape with one side open, and a lid 41b attached to the opening. In this embodiment, the case body 41a and the lid 41b are each formed of aluminum or an aluminum alloy mainly containing aluminum, from the viewpoints of reducing weight and ensuring the required rigidity.

[0022] <Case body 41a> As shown in Fig. 1 and Fig. 2, the case body 41a has a substantially rectangular parallelepiped shape with one side open. The case body 41a has a substantially rectangular bottom surface portion 61, a pair of wide surface portions 62, 63, and a pair of narrow surface portions 64, 65. The pair of wide surface portions 62, 63 each rise from a long side of the bottom surface portion 61. The pair of narrow surface portions 64, 65 each rise from a short side of the bottom surface portion 61. An opening 41a1 surrounded by the pair of wide surface portions 62, 63 and the pair of narrow surface portions 64, 65 is formed on one side of the case body 41a.

[0023] <Lid 41b> The lid 41b is attached to the opening 41a1 of the case body 41a, which is surrounded by the long sides of the pair of wide surface portions 62, 63 and the short sides of the pair of narrow surface portions 64, 65. The peripheral edge of the lid 41b is then joined to the edge of the opening 41a1 of the case body 41a. This joining may be achieved, for example, by continuous welding without gaps. This welding may be achieved, for example, by laser welding.

[0024] In this embodiment, a positive electrode terminal 42 and a negative electrode terminal 43 are attached to the lid 41b. The positive electrode terminal 42 includes an internal terminal 42a and an external terminal 42b. The negative electrode terminal 43 includes an internal terminal 43a and an external terminal 43b. The internal terminals 42a and 43a are attached to the inside of the lid 41b via an insulator 72. The external terminals 42b and 43b are attached to the outside of the lid 41b via a gasket 71. The internal terminals 42a and 43a each extend into the inside of the case body 41a. The positive electrode internal terminal 42a is connected to the unformed portion 21a1 of the positive electrode current collector foil 21a. The negative electrode internal terminal 43a is connected to the unformed portion 22a1 of the negative electrode current collector foil 22a.

[0025] As shown in FIG. 1, the unformed portion 21a1 of the positive electrode current collector foil 21a of the electrode body 20 and the unformed portion 22a1 of the negative electrode current collector foil 22a are attached to the internal terminals 42a, 43a attached to both sides in the longitudinal direction of the lid 41b. The electrode body 20 is housed in the battery case 41 in a state where it is attached to the internal terminals 42a, 43a attached to the lid 41b. Here, a wound type electrode body 20 is illustrated. The structure of the electrode body 20 is not limited to this form. The structure of the electrode body 20 may be, for example, a laminated structure in which positive electrode sheets and negative electrode sheets are alternately laminated with a separator sheet interposed therebetween. In addition, a plurality of electrode bodies 20 may be housed in the battery case 41.

[0026] Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. Fig. 3 shows a cross section of a portion where the negative electrode terminal 43 is attached to the lid 41b. In this embodiment, a member formed by joining dissimilar metals is used for the negative electrode external terminal 43b. Fig. 3 does not show the structure of the metal grooves constituting the external terminal 43b or the interface between the dissimilar metals, but shows only a schematic cross-sectional shape of the external terminal 43b.

[0027] As shown in FIG. 3, the lid 41b has a mounting hole 41b1 for mounting the negative electrode external terminal 43b. The mounting hole 41b1 penetrates the lid 41b at a predetermined position of the lid 41b. The negative electrode internal terminal 43a and external terminal 43b are mounted in the mounting hole 41b1 of the lid 41b with a gasket 71 and an insulator 72 interposed therebetween. A step 41b2 is provided on the outside of the mounting hole 41b1, on which the gasket 71 is mounted around the mounting hole 41b1. The step 41b2 is provided with a seat 41b3 on which the gasket 71 is disposed. The seat 41b3 is provided with a protrusion 41b4 for positioning the gasket 71.

[0028] Here, as shown in FIG. 3, the negative electrode external terminal 43b includes a head 43b1, a shaft 43b2, and a crimping piece 43b3. The head 43b1 is a portion disposed on the outside of the lid 41b. The head 43b1 is a portion disposed on the gasket 71, which is larger than the mounting hole 41b1. The shaft 43b2 is a portion mounted on the mounting hole 41b1 via the gasket 71. The shaft 43b2 protrudes downward from the approximate center of the head 43b1. As shown in FIG. 3, the crimping piece 43b3 is a portion crimped to the negative electrode internal terminal 43a inside the lid 41b. The crimping piece 43b3 extends from the shaft 43b2, and is inserted into the lid 41b, and then bent and crimped to the negative electrode internal terminal 43a.

[0029] <Gasket 71> As shown in FIG. 3, the gasket 71 is a member that is attached to the mounting hole 41b1 and the seat surface 41b3 of the lid 41b. In this embodiment, the gasket 71 includes a seat portion 71a, a boss portion 71b, and a side wall 71c. The seat portion 71a is a portion that is attached to the seat surface 41b3 provided on the outer surface around the mounting hole 41b1 of the lid 41b. The seat portion 71a has a substantially flat surface that matches the seat surface 41b3. The seat portion 71a includes a recess that corresponds to the protrusion 41b4 of the seat surface 41b3. The boss portion 71b protrudes from the bottom surface of the seat portion 71a. The boss portion 71b has an outer shape that follows the inner side surface of the mounting hole 41b1 so that it can be attached to the mounting hole 41b1 of the lid 41b. The inner side surface of the boss portion 71b becomes a mounting hole into which the shaft portion 43b2 of the external terminal 43b is attached. The side wall 71c rises upward from the periphery of the seat portion 71a. The head 43b1 of the external terminal 43b is attached to the gasket 71 in a portion surrounded by the side wall 71c.

[0030] The gasket 71 is disposed between the lid 41b and the external terminal 43b, and ensures insulation between the lid 41b and the external terminal 43b. The gasket 71 also ensures airtightness of the mounting hole 41b1 of the lid 41b. From this viewpoint, it is preferable to use a material having excellent chemical resistance and weather resistance. In this embodiment, the gasket 71 is made of PFA. PFA is a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (Tetrafluoroethylene Perfluoroalkylvinylether Copolymer). The material used for the gasket 71 is not limited to PFA.

[0031] <Insulator 72> The insulator 72 is a member that is attached to the inside of the lid 41b around the mounting hole 41b1 of the lid 41b. The insulator 72 includes a base portion 72a, a hole 72b, and a side wall 72c. The base portion 72a is a portion that is arranged along the inner side surface of the lid 41b. In this embodiment, the base portion 72a is a substantially flat plate-shaped portion. The base portion 72a is arranged along the inner side surface of the lid 41b and has a size that does not protrude from the lid 41b so that it can be accommodated in the case body 41a. The hole 72b is a hole that is provided corresponding to the mounting hole 41b1. In this embodiment, the hole 72b is provided in the substantially central portion of the base portion 72a. On the side surface facing the inner side surface of the lid 41b, a recessed step 72b1 is provided around the hole 72b. The tip of the boss portion 71b of the gasket 71 attached to the mounting hole 41b1 is accommodated in the step 72b1. The side wall 72c rises downward from the periphery of the base portion 72a. The base portion 72a houses a base portion 43a1 provided at one end of the negative electrode internal terminal 43a. Since the insulator 72 is disposed inside the battery case 41, it is preferable that the insulator 72 has a required chemical resistance. In this embodiment, PPS is used for the insulator 72. PPS is polyphenylene sulfide resin. Note that the material used for the insulator 72 is not limited to PPS.

[0032] The negative electrode internal terminal 43a includes a base 43a1 and a connection piece 43a2 (see FIGS. 1 and 2). The base 43a1 is a portion that is attached to the base portion 72a of the insulator 72. In this embodiment, the base 43a1 has a shape that corresponds to the inside of the side wall 72c around the base portion 72a of the insulator 72. As shown in FIGS. 1 and 2, the connection piece 43a2 extends from one end of the base 43a1, extends into the case main body 41a, and is connected to the negative electrode unformed portion 22a1 of the electrode body 20.

[0033] In this embodiment, the gasket 71 is attached to the outside of the lid 41b while the boss portion 71b is attached to the mounting hole 41b1. The external terminal 43b is attached to the gasket 71. At this time, the shaft portion 43b2 of the external terminal 43b is inserted into the boss portion 71b of the gasket 71, and the head portion 43b1 of the external terminal 43b is placed in the seat portion 71a of the gasket 71. The insulator 72 and the internal terminal 43a are attached to the inside of the lid 41b. Then, as shown in FIG. 3, the crimping piece 43b3 of the external terminal 43b is bent and crimped to the base portion 43a1 of the internal terminal 43a. The crimping piece 43b3 of the external terminal 43b and the base portion 43a1 of the negative terminal 43 may be partially metal-jointed to improve electrical conductivity.

[0034] Incidentally, the required level of oxidation-reduction resistance for the positive electrode internal terminal 42a of the lithium ion secondary battery 10 is not as high as that for the negative electrode. From the viewpoints of the required oxidation-reduction resistance and weight reduction, aluminum may be used for the positive electrode internal terminal 42a. In contrast, the required level of oxidation-reduction resistance for the negative electrode internal terminal 43a is higher than that for the positive electrode. From this viewpoint, copper may be used for the negative electrode internal terminal 43a. On the other hand, aluminum or an aluminum alloy may be used for the bus bar to which the external terminal 43b is connected, from the viewpoints of weight reduction and cost reduction.

[0035] The inventors have considered using copper or a copper alloy for the portion of the external terminal 43b that is joined to the internal terminal 43a, and using aluminum or an aluminum alloy for the portion of the external terminal 43b that is connected to the bus bar. In order to realize such a structure, in this embodiment, a member in which copper and aluminum are joined together as dissimilar metals is used as the external terminal 43b. The structure of a terminal part 200 used as the external terminal 43b will be described below.

[0036] Terminal Part 200 Fig. 4 is a cross-sectional view showing a schematic diagram of the terminal component 200. Fig. 4 shows a schematic diagram of a process for joining a first metal 201 and a second metal 202 which constitute the terminal component 200. The terminal component 200 as the external terminal 43b is attached to the battery case 41 such that a portion of the terminal component 200 is connected to the internal terminal 43a inside the battery case 41 and a portion of the terminal component 200 is exposed to the outside of the battery case 41, as shown in Fig. 3.

[0037] 4, the terminal component 200 includes a first metal 201 and a second metal 202 superimposed on the first metal 201. The first metal 201 and the second metal 202 are made of different metals.

[0038] The first metal 201 is a portion that is connected to the internal terminal 43a inside the battery case 41 when the terminal part 200 is used as the external terminal 43b (see FIG. 3). In this embodiment, the first metal is made of copper. The first metal 201 has a shaft portion 201a and a flange portion 201b. The shaft portion 201a is a portion that becomes the shaft portion 43b2 that is inserted into the mounting hole 41b1 of the lid 41b. The flange portion 201b is a flat portion that is provided at one end of the shaft portion 201a and is wider than the shaft portion 201a. The shaft portion 201a is provided with a portion 201c that becomes a crimping piece 43b3 that is crimped to the internal terminal 43a on the side opposite to the side where the flange portion 201b is provided.

[0039] The second metal 202 is a portion exposed to the outside of the battery case 41 when the terminal part 200 is used as the external terminal 43b (see FIG. 3). A metal having ductility and lower rigidity than the first metal 201 is used for the second metal 202. In this embodiment, the second metal 202 is made of aluminum. The second metal 202 is a flat metal member overlapped on the first metal 201. The surface 202a of the second metal 202 overlapped on the first metal 201 has a substantially rectangular shape corresponding to the end surface 201b1 of the first metal 201.

[0040] The terminal component 200 has a joint 203 at the boundary between the first metal 201 and the second metal 202, where the first metal 201 and the second metal 202 are joined by metallic joining. In the joint 203, the first metal 201 and the second metal 202 are solid-state joined without an adhesive layer such as an adhesive or solder. Such a joint 203 can be formed by joining the first metal 201 and the second metal 202 by a method such as ultrasonic welding, friction welding, or resistance welding.

[0041] The second metal 202 has a groove 202c on the outer side of the joint 203 on a surface 202b opposite to the surface 202a overlapped with the first metal 201. The groove 202c is formed outside the portion of the joint 203 vertically projected onto the surface 202b. The joint 203 and the groove 202c may partially overlap. The joint 203 may be partially outside the groove 202c. When the groove 202c is formed continuously outside the joint 203, it is preferable that the area inside the groove 202c is larger than the area of ​​the joint 203 vertically projected onto the surface 202b.

[0042] In this embodiment, the groove 202c is formed in a circumferential shape and is continuous in the circumferential direction. In this embodiment, the outer side wall 202c1 of the groove 202c is perpendicular to the surface 202b. The inner side wall 202c2 of the groove 202c is perpendicular to the surface 202b near the boundary with the bottom 202c3, but is inclined to approach the outer side wall 202c1 as it moves away from the bottom 202c3. That is, the inner part 202d on the inner side of the groove 202c widens as it moves toward the top 202d1. Therefore, the area of ​​the bottom 202c3 of the groove 202c is larger than the area of ​​the opening 202c4. The shape of the groove 202c is not particularly limited. The groove 202c may be formed in a polygonal shape such as a rectangle. The groove 202c may not be formed continuously, and may be formed intermittently. Also, the opening 202c4 of the groove 202c may be partially or wholly blocked by the widening of the top 202d1 of the inner portion 202d.

[0043] In the embodiment shown in Fig. 4, the surface 202b of the second metal 202 and the apex 202d1 of the inner portion 202d are flush with each other. However, the present invention is not limited to such a configuration. The apex 202d1 may protrude from the surface 202b. Also, the apex 202d1 may be recessed from the surface 202b.

[0044] In the embodiment shown in FIG. 4 and FIG. 5, the first metal 201 and the second metal 202 are ultrasonically welded together. As shown in FIG. 5, the second metal 202 has a groove 202e on the surface 202b, which will later become the groove 202c. The groove 202e is formed in a circumferential shape. The groove 202e is provided continuously in the circumferential direction. Here, the bottom 202e1 of the groove 202e is parallel to the surface 202b. The outer side wall 202e2 of the groove 202e is perpendicular to the surface 202b. The second metal 202 is provided with a protruding portion 202f, which will become the inner portion 202d. The top 202f1 of the protruding portion 202f is parallel to the surface 202b. The side wall 202f2 of the protruding portion 202f is perpendicular to the surface 202b. The height of the protruding portion 202f is greater than the depth of the groove 202e. The protrusion 202f protrudes from the surface 202b.

[0045] FIG. 5 is a cross-sectional view for explaining a manufacturing method of the terminal component 200. FIG. 5 shows a state before the first metal 201 and the second metal 202 are ultrasonically welded together. First, the first metal 201 is placed on the anvil 301. The second metal 202 is placed on the first metal 201. The horn 302 is attached to the apex 202f1 of the convex portion 202f of the second metal 202. The second metal 202 is pressurized while applying vibration required for ultrasonic welding to the horn 302. The pressure and ultrasonic vibration applied to the horn 302 are appropriately set according to the metal type and dimensions of the first metal 201 and the second metal 202. By applying pressure to the second metal 202 while applying ultrasonic vibration to it, a joint 203 is formed at the boundary between the first metal 201 and the second metal 202. At that time, a crush mark may be formed at a position corresponding to the joint 203 of the apex 201d1 by pressing the horn 302 against it.

[0046] When the horn 302 is pressed against the second metal 202, the second metal 202 is plastically deformed. At this time, due to the provision of the groove 202e, the plastic deformation of the second metal 202 occurs within the groove 202e. In other words, the deformation of the protrusion 202f against which the horn 302 is in contact extends only within the groove 202e. This suppresses the deformation of the terminal component 200. In the embodiment shown in FIG. 4, deformation occurs mainly in a portion close to the top 202d1 of the protrusion 202d so that the area of ​​the opening 202c4 is smaller than the area of ​​the bottom 202c3. The joint portion 203 may be joined by resistance welding, friction welding, etc. In the case of metal joining by such a method, deformation of the terminal part 200 due to pressure application is similarly suppressed.

[0047] The dimensions of the groove 202e and the protruding portion 202f are preferably set so that the groove 202c is not filled after metal bonding. The volume of the groove 202e is preferably set so as to be larger than the volume of the portion 202f3 of the protruding portion 202f protruding from the surface 202b. By setting the volume of the groove 202e in this manner, the deformation caused by applying pressure to the top portion 202f1 of the protruding portion 202f is contained within the groove 202e. This makes it possible to reduce the effect of the deformation of the second metal 202 caused by pressure on the external shape of the terminal component 200.

[0048] FIG. 6 is a perspective view showing a schematic diagram of a battery pack 100. The battery pack 100 includes a plurality of secondary batteries 10 and a plurality of spacers 90. The battery pack 100 also includes a restraining mechanism. Specifically, as shown in the figure, the battery pack 100 includes a pair of end plates 92A, 92B, a restraining band 94, and a plurality of screws 96. The pair of end plates 92A, 92B are disposed at both ends of the battery pack 100 in the arrangement direction of the secondary batteries 10. The restraining band 94 is stretched across the pair of end plates 92A, 92B, and is attached to the pair of end plates 92A, 92B by the screws 96. The spacer 90 is sandwiched between two adjacent secondary batteries 10. End spacers 98 are disposed between the secondary batteries 10 and the end plates 92A and between the secondary batteries 10 and the end plates 92B, respectively. The positive electrode terminal 42 and the negative electrode terminal 43 of the secondary batteries 10 constituting the battery pack 100 are electrically connected by a bus bar 91. As a result, the secondary batteries 10 constituting the battery pack 100 are electrically connected in series in sequence. However, the shape, size, number, arrangement, connection method, etc. of the secondary batteries 10 constituting the battery pack 100 are not limited to the embodiments disclosed herein and can be changed as appropriate.

[0049] The terminal part 200 shown in FIG. 4 is used as the negative electrode external terminal 43b of the lithium ion secondary battery 10. The external terminal 43b is connected to a bus bar 91. The external terminal 43b and the bus bar 91 can be welded by, for example, laser welding. The bus bar 91 is made of aluminum from the viewpoint of weight reduction. According to the terminal part 200 proposed here, the first metal 201 of the negative electrode external terminal 43b exposed to the outside of the lithium ion secondary battery 10 can be made of aluminum. The positive electrode external terminal 42b is made of aluminum. Therefore, dissimilar metal joints do not occur in the joint between the bus bar 91 and the negative electrode external terminal 43b and the joint between the bus bar 91 and the positive electrode external terminal 42b, and joints with high reliability in terms of strength can be realized. Furthermore, according to this terminal part 200, the portion 201c of the negative electrode external terminal 43b that is joined to the internal terminal 43a (see FIGS. 2 and 3) inside the battery case 41 is made of the first metal 201, that is, copper. Therefore, no dissimilar metal junction occurs in the junction between the negative electrode external terminal 43b and the internal terminal 43a, and a junction with high reliability in terms of strength can be realized.

[0050] As shown in FIG. 4, the terminal component 200 proposed here has a groove 202c on a surface 202b of the second metal 202 opposite to a surface 202a overlapping the first metal 201. The groove 202c is provided on the outside of the joint 203. The joint 203 is a portion where the metal is joined by a method such as ultrasonic welding, friction welding, or resistance welding. By forming the groove 202c, the deformation of the second metal 202 due to the pressure applied when forming the joint 203 is unlikely to extend to the outside of the groove 202c. Therefore, the terminal component 200 with good dimensional accuracy is provided. In such a terminal component 200, the risk that the deformed portion will come off or that the deformed portion will interfere with other components is reduced. In addition, the busbar connection surface of the terminal component 200 is not curved, and a good connection with the busbar can be realized.

[0051] Here, the groove 202c is continuous in the circumferential direction. When metal bonding is performed, deformation due to pressure does not always occur at the same position. By having the groove 202c continuous around the periphery of the bonding portion 203, deformation of the outer shape of the terminal component 200 can be more suitably suppressed.

[0052] In the above-described embodiment, the groove 202c is provided outside the joint 203 where the first metal 201 and the second metal 202 are metallurgically bonded, but the present invention is not limited to such an embodiment. For example, for the purpose of improving the bonding strength between the first metal 201 and the second metal 202, there may be a portion where the first metal 201 and the second metal 202 are metallurgically bonded also outside the groove 202c. The first metal 201 and the second metal 202 may have a portion bonded by a bond other than metallic bonding. For example, in order to improve the bonding strength, a structure in which one metal is crimped to the other metal may be provided at the boundary between the first metal 201 and the second metal 202. The combination of metals constituting the first metal 201 and the second metal 202 is not limited to copper and aluminum, and various combinations of metals can be used. In addition, the first metal 201 and the second metal 202 may be subjected to a treatment such as plating.

[0053] As another aspect of the technology disclosed herein, a battery pack 100 is provided in which a first metal 201 is used as an external terminal and a second metal 202 is used as a bus bar 91. FIG. 7 is a cross-sectional view showing a schematic diagram of a portion of the battery pack 100 where a negative external terminal 43b and a bus bar 91 are connected. In the embodiment shown in FIG. 7, the first metal 201 is used as the negative external terminal 43b, and the second metal 202 is used as the bus bar 91. Here, the second metal 202 is a long plate-shaped metal member made of aluminum. The second metal 202 has a surface 202a provided at one end thereof superposed on an end surface 201b1 of the first metal 201. Although not shown, the second metal 202 has the other end connected to the positive external terminal 42b. At the boundary between the external terminal 43b and the bus bar 91, a joint 203 is provided where the external terminal 43b and the bus bar 91 are joined by metal joining. Bus bar 91 has groove 202c on the outer side of joint portion 203 on surface 201b opposite joint portion 203. In the battery pack 100 having such a configuration, the external terminal 43b is made of one type of metal. The fewer number of parts reduces manufacturing costs. The bus bar 91 and the external terminal 43b are metallically joined, thereby keeping the conduction resistance low. The bus bar 91 also has a groove 202c on the outside of the joint 203. This prevents deformation or bending of the surface of the bus bar 91 that is joined to the external terminal 43b, and can achieve good joining with the external terminal 43b.

[0054] The terminal components, secondary batteries, and assembled batteries disclosed herein have been described above. The embodiments of the terminal components and batteries described herein do not limit the present invention unless otherwise specified. The batteries disclosed herein may be modified in various ways, and the components and processes described herein may be omitted or combined as appropriate unless any particular problems arise. [Explanation of symbols]

[0055] 10 Lithium-ion secondary battery 20 Electrode body 21 Positive electrode sheet 22 Negative electrode sheet 31,32 Separator sheet 41 Battery case 41a Case body 41a1 opening 41b Lid 41b1 Mounting hole 41b2 Step 41b3 Seat 41b4 protrusion 42 Positive terminal 42a Positive inner terminal 42b Positive external terminal 43 Negative terminal 43a Negative internal terminal 43a1 base 43a2 Connection piece 43b Negative external terminal 43b1 Head 43b2 Shaft 43b3 Crimp piece 61 Bottom part 62,63 Wide surface section 64,65 Narrow side part 71 Gasket 71a Seat part 71b Boss part 71c side wall 72 Insulator 72a Base 72b hole 72b1 Step 72c side wall 90 Spacer 91 Bus Bar 92A, 92B End plate 94 Restraint Band 96 bis 98 End Spacer 100 battery packs 200 Terminal parts 201 First metal 201a Shaft 201b Flange part 201b1 End face 201c part 202 Second metal 202a side 202b side 202c groove 202c1 outer wall 202c2 Inner wall 202c3 bottom 202c4 opening 202d Internal part 202d1 Top 202e Groove 202e1 bottom 202e2 outer wall 202f Convex 202f1 top 202f2 side wall 203 Joint 301 Anvil 302 Horn

Claims

1. A terminal part attached to a battery case, A first metal; a second metal overlying the first metal; Equipped with At the boundary between the first metal and the second metal, a joint portion in which the first metal and the second metal are joined by metal joining; The boundary between the first metal and the second metal is a flat surface without any step around the joint, The second metal is a groove extending in a circumferential direction around a position corresponding to the joint on a surface opposite to the surface overlapping the first metal; At the top of the area surrounded by the groove, A crush mark is formed due to the pressure being applied to the top portion, and a plastically deformed portion is formed in the area surrounded by the groove so as to expand outward toward the groove as a result of pressure being applied to the top portion, The plastically deformed portion is contained in the groove, The terminal part, wherein the joint is an ultrasonic joint.

2. The terminal component according to claim 1 , wherein the first metal and the second metal are made of different metals.

3. A battery case; An electrode terminal attached to the battery case; Equipped with A secondary battery, wherein the electrode terminal comprises the terminal part according to claim 1 or 2.

4. A plurality of secondary batteries having positive and negative external terminals; a bus bar that connects the plurality of secondary batteries via the external terminal; A battery pack comprising: Among the external terminals, an external terminal of one pole is overlapped with the bus bar, a joint portion at a boundary between the external terminal of the one pole and the bus bar, where the external terminal of the one pole and the bus bar are joined by metal joining, a boundary between the external terminal of the one pole and the bus bar is abutted on a flat surface without a step around the joint, the bus bar has, on a surface opposite to the joint portion, a groove that is continuous in a circumferential direction around a position corresponding to the joint portion, At the top of the area surrounded by the groove, A crush mark is formed due to the pressure being applied to the top portion, and a plastically deformed portion is formed in the area surrounded by the groove so as to expand outward toward the groove as a result of pressure being applied to the top portion, The plastically deformed portion is contained in the groove, The battery pack, wherein the joint is an ultrasonic joint.

Images