Terminal member and method for manufacturing terminal member

Abstract

The present application relates to a terminal member and a manufacturing method of the terminal member. The terminal member disclosed herein is a terminal member used in a terminal for a secondary battery. The terminal member includes a first metal and a second metal having a recess. The first metal has a shaft portion having a pair of flat surfaces and an insertion portion formed at one end of the shaft portion in a longitudinal direction. A joining portion is formed by ultrasonic joining at a boundary between the first metal and the second metal, and a riveting portion is formed by the insertion portion of the first metal entering the recess of the second metal. In a plan view, a gap is formed between the recess and the insertion portion in an opposite direction opposite to the flat surfaces.

Description

TECHNICAL FIELD

[0001] The present application relates to a terminal member and a manufacturing method of a terminal member. BACKGROUND

[0002] As a terminal that constitutes a secondary battery, a technology related to a terminal composed of different kinds of metals has been proposed.

[0003] Japanese Patent Application Publication No. 2011-124024 discloses a battery pack in which a plurality of single cells are connected by a bus bar. As a method of manufacturing a positive electrode terminal used in the above-described battery pack, a positive electrode external terminal of copper is ultrasonically joined to an aluminum base, and foreign matter generated in the ultrasonic joining is cleaned, and further, rivet forming is performed. The rivet forming is performed by pressing with a punch tool of a male die and a cavity tool of a female die. According to the publication, the above-described positive electrode terminal has good weldability with the copper bus bar, and in addition, the joining strength of the base and the external terminal can be sufficiently ensured.

[0004] Japanese Patent No. 6216368 discloses a power storage element including an electrode body, a case that houses the electrode body, a rivet member that is fixed to a partition wall of the case and has a penetration portion at one end, and a conductive member that has the penetration portion and is electrically connected to the rivet member. The penetration portion of the rivet has a Vickers hardness that is greater than a Vickers hardness of a surrounding area of the penetration portion in the conductive member. The penetration portion is riveted in a state of penetrating the conductive member. Thus, the thickness of the surrounding area of the penetration portion is reduced, and an increase in the thickness of the conductive member is suppressed.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-124024

[0006] Patent Document 2: Japanese Patent No. 6216368

[0007] In addition, the different kinds of metals that constitute the external terminal are joined by ultrasonic joining or the like, and thus the conductivity between the different kinds of metals can be improved. In addition, the different kinds of metals are mechanically fastened by riveting or the like, and thus the joining strength between the different kinds of metals can be improved. The present inventors have researched a terminal in which these methods are combined and used in a secondary battery. However, when ultrasonic vibration is performed in a state in which the different kinds of metals are riveted, there is a concern that the rivet structure hinders the ultrasonic vibration performed in the ultrasonic joining. SUMMARY

[0008] The terminal member disclosed herein is a terminal member used in a terminal for a secondary battery. The terminal member includes: a first metal; and a second metal having a recess. The first metal has: a shaft portion having a pair of flat surfaces; and an insertion portion formed at one end in a long axis direction of the shaft portion. A joining portion is formed by ultrasonic joining at a boundary between the first metal and the second metal, and a riveting portion is formed by the insertion portion of the first metal entering the recess of the second metal. Here, a gap is formed between the recess and the insertion portion and in an opposite direction to the flat surfaces in a plan view.

[0009] The terminal member having the above-described structure has improved joining strength of the joining portion formed by ultrasonic joining.

[0010] A gap can be formed on both sides in the opposite direction. According to the above-described structure, the joining strength of the joining portion can be further improved.

[0011] A joining mark can be formed in the second metal, the joining mark being formed by applying vibration of ultrasonic joining in the opposite direction. The insertion portion can extend outward from the one end in the long axis direction of the shaft portion.

[0012] As another aspect of the technology disclosed herein, a secondary battery is provided, including: an electrode body including a positive electrode and a negative electrode; a battery case in which the electrode body is accommodated; a positive electrode terminal and a negative electrode terminal electrically connected to the positive electrode and the negative electrode in the electrode body, respectively. At least one of the positive electrode terminal and the negative electrode terminal of the secondary battery can include the terminal member disclosed herein.

[0013] As another aspect of the technology disclosed herein, a manufacturing method of a terminal member used in a secondary battery is provided. The manufacturing method of the terminal member includes: a preparation step of preparing a first metal and a second metal, wherein the second metal has a recess having a larger inner width than an opening, and the first metal has a shaft portion having a pair of flat surfaces and an insertion portion formed at one end in a long axis direction of the shaft portion and inserted into the recess of the second metal; a riveting step of riveting the first metal to the second metal by pressing the insertion portion of the first metal into the recess of the second metal, wherein the riveting is performed in such a manner that a gap is formed between the recess and the insertion portion and in an opposite direction to the flat surfaces in a plan view; and a joining step of joining the first metal to the second metal by ultrasonic joining, wherein vibration of the ultrasonic joining is applied in the opposite direction. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a partial cross-sectional view of a lithium-ion secondary battery 10.

[0015] Figure 2 is a cross-sectional view showing a II-II cross section of Figure 1 .

[0016] Figure 3 is Figure 2 a III-III sectional view.

[0017] Figure 4 is a sectional view schematically showing the terminal member 200.

[0018] Figure 5 is a sectional view schematically showing the terminal member 200.

[0019] Figure 6 is a schematic view schematically showing the shapes of the recessed portion 202a and the embedded portion 201b.

[0020] Figure 7 is a schematic view schematically showing the shapes of the recessed portion 202a and the embedded portion 201b of the terminal member 200 according to another embodiment.

[0021] Figure 8 is a schematic view schematically showing the shapes of the recessed portion 202a and the embedded portion 201b of the terminal member 200 according to another embodiment. DETAILED DESCRIPTION

[0022] Hereinafter, one embodiment of a terminal member and a secondary battery disclosed herein will be described. The embodiment described herein is by no means intended to particularly limit the present application. Each drawing schematically depicts the embodiment and does not necessarily reflect the actual object. Also, for the expression "A to B" or the like indicating a numerical range, as long as not particularly mentioned, it means "A or more and B or less". Further, in the drawings described below, the same reference numerals are assigned to the components, parts that play the same roles, and the repeated description is sometimes omitted or simplified. Also, in the drawings referred to in the present specification, the reference numeral X indicates "width direction", the reference numeral Y indicates "length direction", the reference numeral Z indicates "height direction", and the reference numeral U indicates "vibration direction of ultrasonic wave".

[0023] In the present specification, the "secondary battery" refers to the entire power storage device that generates charge-discharge reactions by moving charge carriers between a pair of electrodes (positive electrode and negative electrode) via an electrolyte. The above secondary battery includes not only so-called storage batteries such as lithium-ion secondary batteries, nickel-hydrogen batteries, nickel-cadmium batteries, and the like, but also capacitors such as electric double layer capacitors and the like. Hereinafter, in the above secondary battery, an embodiment in a case where a lithium-ion secondary battery is taken as an object will be described.

[0024] 〈Lithium-ion secondary battery 10〉

[0025] Figure 1 is a partial sectional view of the lithium-ion secondary battery 10. In Figure 1In the present embodiment, a state in which the inside is exposed is schematically depicted along the narrow width surface of the single side of the substantially cuboid battery case 41. Figure 1 The lithium ion secondary battery 10 shown is a so-called closed type battery. Figure 2 is a cross-sectional view of the II-II section of Figure 1 Figure 2 In the present embodiment, a state in which the inside is exposed is schematically depicted along the narrow width surface of the single side of the substantially cuboid battery case 41.

[0026] As shown in Figure 1 , the lithium ion secondary battery 10 is provided with an electrode body 20, a battery case 41, a positive electrode terminal 42, and a negative electrode terminal 43.

[0027] 〈Electrode Body 20〉

[0028] The electrode body 20 is housed in the battery case 41 in a state covered by an insulating film (not shown) or the like. The electrode body 20 is provided with a positive electrode sheet 21 as a positive electrode element, a negative electrode sheet 22 as a negative electrode element, and separator sheets 31, 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.

[0029] For the positive electrode sheet 21, a positive electrode current collector foil 21a (for example, an aluminum foil) of a predetermined width and thickness has a positive electrode active material layer 21b including a positive electrode active material formed on both surfaces, except for an unformed portion 21al of a constant width provided on the edge of the single side in the width direction. For example, in a lithium ion secondary battery, the positive electrode active material is a material that can release lithium ions at the time of charging and absorb lithium ions at the time of discharging, such as a lithium transition metal composite material. For the positive electrode active material, various materials other than the lithium transition metal composite material can be proposed, and are not particularly limited.

[0030] For the negative electrode sheet 22, a negative electrode current collector foil 22a (here, a copper foil) of a predetermined width and thickness has a negative electrode active material layer 22b including a negative electrode active material formed on both surfaces, except for an unformed portion 22al of a constant width provided on the edge of the single side in the width direction. For example, in a lithium ion secondary battery, the negative electrode active material is a material that can occlude lithium ions at the time of charging and release the lithium ions occluded at the time of charging at the time of discharging, such as natural graphite. For the negative electrode active material, various materials other than natural graphite can be proposed, and are not particularly limited.

[0031] The separator sheets 31, 32 use, for example, a porous resin sheet that can pass an electrolyte having a required heat resistance. For the separator sheets 31, 32, various materials can be proposed, and are not particularly limited.

[0032] ​Here, the width of the negative electrode active material layer 22b is, for example, wider than that of the positive electrode active material layer 21b. The widths of the separator sheets 31 and 32 are wider than that of the negative electrode active material layer 22b. The unformed portions 21a1 of the positive electrode current collector foil 21a and the unformed portions 22a1 of the negative electrode current collector foil 22a face opposite sides in the width direction. Furthermore, 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, sequentially overlapped, and wound. The negative electrode active material layer 22b covers the positive electrode active material layer 21b in a state where the separator sheets 31 and 32 are positioned between them. The negative electrode active material layer 22b is covered by the separator sheets 31 and 32. The unformed portions 21a1 of the positive electrode current collector foil 21a are exposed from one side in the width direction of the separator sheets 31 and 32. The unformed portion 22a1 of the negative electrode current collector foil 22a is exposed from the partition sheet 31, 32 on the opposite side in the width direction.

[0033] like Figure 1 As shown, the electrode body 20 is flat along a plane including the winding axis so that it can be housed in the housing body 41a of the battery housing 41. Furthermore, an unformed portion 21a1 of the positive electrode current collector foil 21a is arranged on one side along the winding axis of the electrode body 20, and an unformed portion 22a1 of the negative electrode current collector foil 22a is arranged on the opposite side.

[0034] <Battery casing 41>

[0035] like Figure 1 As shown, the battery casing 41 houses the electrode body 20. The battery casing 41 has: a casing body 41a, which is a generally rectangular shape with an opening on one side; and a cover 41b, which is mounted on the opening. In this embodiment, for the viewpoint of ensuring lightweight and the required rigidity, the casing body 41a and the cover 41b are respectively formed of aluminum or an aluminum alloy mainly composed of aluminum.

[0036] <Shell Body 41a>

[0037] The main body 41a has a generally rectangular, cuboid shape with an opening on one side. The main body 41a has a generally rectangular base portion 61 and a pair of wide portions 62 and 63 (see reference). Figure 2 A pair of narrow faces 64 and 65 are formed on one side of the main body 41a. A pair of wide faces 62 and 63 rise from the long side of the bottom face 61. A pair of narrow faces 64 and 65 rise from the short side of the bottom face 61. An opening 41a1 is formed on one side of the main body 41a by the pair of wide faces 62 and 63 and the pair of narrow faces 64 and 65.

[0038] Cover 41b

[0039] Cover 41b is mounted on a pair of wide faces 62, 63 (see reference) Figure 2The opening 41a1 of the shell body 41a is formed by the long side of the cover 41b and the short sides of a pair of narrow facets 64 and 65. Furthermore, the periphery of the cover 41b joins the edge of the opening 41a1 of the shell body 41a. This joining can be achieved, for example, through a seamless, continuous weld. This weld can be achieved, for example, by laser welding.

[0040] In this embodiment, a positive terminal 42 and a negative terminal 43 are mounted on the cover 41b. The positive terminal 42 has an internal terminal 42a and an external terminal 42b. The negative terminal 43 has an internal terminal 43a and an external terminal 43b. The internal terminals 42a and 43a are respectively mounted on the inner side of the cover 41b via an insulator 72. The external terminals 42b and 43b are respectively mounted on the outer side of the cover 41b via a washer 71. The internal terminals 42a and 43a extend into the interior of the housing body 41a. The internal terminal 42a of the positive terminal is connected to the unformed portion 21a1 of the positive current collector foil 21a. The internal terminal 43a of the negative terminal is connected to the unformed portion 22a1 of the negative current collector foil 22a.

[0041] like Figure 1 As shown, the unformed portions 21a1 of the positive current collector foil 21a and the unformed portions 22a1 of the negative current collector foil 22a of the electrode body 20 are mounted on internal terminals 42a and 43a, which are respectively mounted on both sides of the cover 41b along its length. The electrode body 20 is housed in the battery casing 41 with the internal terminals 42a and 43a mounted on the cover 41b. Furthermore, a wound type electrode body 20 is illustrated here. The structure of the electrode body 20 is not limited to the above-described manner. For example, the electrode body 20 can also be constructed by alternating layers of positive and negative electrode sheets separated by separator sheets. Additionally, multiple electrode bodies 20 can be housed within the battery casing 41.

[0042] Additionally, the battery casing 41 can house the electrode body 20 and an electrolyte (not shown). As the electrolyte, a non-aqueous electrolyte prepared by dissolving an auxiliary salt in a non-aqueous solvent can be used. Examples of non-aqueous solvents include carbonate solvents such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of auxiliary salts include fluorinated lithium salts such as LiPF6.

[0043] Figure 3 yes Figure 2 Sectional view III-III. In Figure 3 The image shows a cross-section of the portion where the negative terminal 43 is mounted on the cover 41b. In this embodiment, the external terminal 43b of the negative terminal uses a component made of joined different types of metals. Figure 3 The structure of the different types of metals constituting the external terminal 43b and the interfaces of the different types of metals are not shown in the figure, but the cross-sectional shape of the external terminal 43b is schematically shown.

[0044] As Figure 3 shown, the lid 41b has a mounting hole 41b1 for mounting the external terminal 43b of the negative electrode. The mounting hole 41b1 penetrates the lid 41b at a predetermined position of the lid 41b. The internal terminal 43a and the external terminal 43b of the negative electrode are mounted in the mounting hole 41b1 of the lid 41b in a manner of being sandwiched by the washer 71 and the insulator 72. Outside the mounting hole 41b1, a step 41b2 for mounting the washer 71 is provided around the mounting hole 41b1. A seating surface 41b3 for arranging the washer 71 is provided in the step 41b2. A protrusion 41b4 for positioning the washer 71 is provided in the seating surface 41b3.

[0045] Here, as Figure 3 shown, the external terminal 43b of the negative electrode has a head portion 43b1, a shaft portion 43b2, and a rivet portion 43b3. The head portion 43b1 is a portion arranged outside the lid 41b. The head portion 43b1 is a substantially flat portion larger than the mounting hole 41b1. The shaft portion 43b2 is a portion mounted to the mounting hole 41b1 via the washer 71. The shaft portion 43b2 protrudes downward from a substantially central portion of the head portion 43b1. As Figure 3 shown, the rivet portion 43b3 is a portion riveted to the internal terminal 43a of the negative electrode inside the lid 41b. The rivet portion 43b3 extends from the shaft portion 43b2, is bent after being inserted through the lid 41b, and is riveted to the internal terminal 43a of the negative electrode.

[0046] 〈Washer 71〉

[0047] As Figure 3 shown, the washer 71 is a member mounted to the mounting hole 41b1 and the seating surface 41b3 of the lid 41b. In this embodiment, the washer 71 has a seating portion 71a, a protruding portion 71b, and a side wall 71c. The seating portion 71a is a portion mounted to the seating surface 41b3 provided on the outer side surface around the mounting hole 41b1 of the lid 41b. The seating portion 71a has a substantially flat surface in cooperation with the seating surface 41b3. The seating portion 71a has a recess corresponding to the protrusion 41b4 of the seating surface 41b3. The protruding portion 71b protrudes from the bottom surface of the seating portion 71a. The protruding portion 71b has an outer shape along the inner side surface of the mounting hole 41b1 so as to be mounted to the mounting hole 41b1 of the lid 41b. The inner side surface of the protruding portion 71b becomes a mounting hole for mounting the shaft portion 43b2 of the external terminal 43b. The side wall 71c stands upward from the peripheral edge of the seating portion 71a. The head portion 43b1 of the external terminal 43b is mounted to a portion surrounded by the side wall 71c of the washer 71.

[0048] The gasket 71 is arranged between the lid 41b and the external terminal 43b, and ensures insulation of the lid 41b and the external terminal 43b. In addition, the gasket 71 ensures airtightness of the mounting hole 41b1 of the lid 41b. From this viewpoint, a material excellent in chemical resistance and durability can be used. In this embodiment, the gasket 71 uses PFA. PFA is a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether. In addition, the material used for the gasket 71 is not limited to PFA.

[0049] <Insulator 72>

[0050] The insulator 72 is a member mounted to the inner side of the lid 41b around the mounting hole 41b1 of the lid 41b. The insulator 72 has a base portion 72a, a hole 72b, and a side wall 72c. The base portion 72a is a portion arranged along the inner side surface of the lid 41b. In this embodiment, the base portion 72a is a substantially flat portion. The base portion 72a is arranged along the inner side surface of the lid 41b, and has a size not exposed from the lid 41b so as to be accommodated in the case main body 41a. The hole 72b is a hole provided to correspond to the inner side surface of the protruding portion 71b of the gasket 71. In this embodiment, the hole 72b is provided at the substantially central portion of the base portion 72a. A recessed step 72b1 is provided around the hole 72b at the side surface opposite to the inner side surface of the lid 41b. The front end of the protruding portion 71b of the gasket 71 mounted to the mounting hole 41b1 is accommodated in the step 72b1 in a manner to interfere with the portion. The side wall 72c stands downward from the peripheral portion of the base portion 72a. The base portion 43a1 of the internal terminal 43a of the negative electrode is accommodated in the base portion 72a. The insulator 72 is arranged in the inside of the battery case 41, and thus has only to have required chemical resistance. In this embodiment, the insulator 72 uses PPS. PPS is a polyphenylene sulfide resin. In addition, the material used for the insulator 72 is not limited to PPS.

[0051] The internal terminal 43a of the negative electrode has a base portion 43a1 and a connecting piece 43a2 (see Figure 1 and Figure 2 ). The base portion 43a1 is a portion mounted to the base portion 72a of the insulator 72. In this embodiment, the base portion 43a1 has a shape corresponding to the inner side of the side wall 72c around the base portion 72a of the insulator 72. The connecting piece 43a2 extends from one end of the base portion 43a1, extends into the case main body 41a, and is connected to the unformed portion 22a1 of the negative electrode of the electrode body 20 (see Figure 1 and Figure 2 ).

[0052] In this embodiment, the protruding portion 71b is installed in the installation hole 41b1, and the grommet 71 is installed on the outer side of the cover 41b. The external terminal 43b is installed to the grommet 71. At this time, the shaft portion 43b2 of the external terminal 43b is inserted through the protruding portion 71b of the grommet 71, and the head portion 43b1 of the external terminal 43b is disposed in the seat portion 71a of the grommet 71. The inner side of the cover 41b is installed with the insulator 72 and the negative electrode terminal 43. Further, as shown in Figure 3 , the rivet portion 43b3 of the external terminal 43b is bent and riveted to the base portion 43a1 of the negative electrode terminal 43. In order to improve the conductivity, the rivet portion 43b3 of the external terminal 43b and the base portion 43a1 of the negative electrode terminal 43 can be joined by spot welding or metal joining.

[0053] However, in the internal terminal 42a of the positive electrode of the lithium ion secondary battery 10 (refer to Figure 1 ), the required level of oxidation-reduction resistance is not higher than that of the negative electrode. Further, from the viewpoint of the required oxidation-reduction resistance and lightweight, the internal terminal 42a of the positive electrode can use aluminum. In contrast, in the internal terminal 43a of the negative electrode, the required level of oxidation-reduction resistance is higher than that of the positive electrode. According to the above viewpoint, the internal terminal 43a of the negative electrode can use copper. On the other hand, in the bus bar to which the external terminal 43b is connected, from the viewpoint of lightweight and low cost, aluminum or an aluminum alloy can be used.

[0054] The present inventors have studied the case where different kinds of metals are used at the portion connected to the internal terminal 43a and the portion connected to the bus bar. That is, the case where metals having high weldability with respect to each are used at the portion connected to the bus bar and the portion connected to the internal terminal 43a in the external terminal 43b has been studied. However, based on the insight of the present inventors, joining different kinds of metals has problems in conductivity and joining strength. The present inventors have studied the case where the metals are joined metallurgically in order to ensure conductivity between the metals, and the case where the metals are riveted in order to improve the joining strength between the metals. Hereinafter, the terminal member 200 disclosed herein will be described together with the manufacturing method of the terminal member 200.

[0055] 〈Terminal Member 200〉

[0056] Figure 4 and Figure 5 is a schematic view schematically showing the terminal member 200. Figure 6 is a schematic view schematically showing the shape of the recess portion 202a and the embedded portion 201b. The terminal member 200 can be used as the external terminal 43b of the negative electrode as shown in Figure 3 . In Figure 4 and Figure 5The diagram schematically illustrates the process of joining the first metal 201 and the second metal 202 constituting the terminal component 200 by ultrasonic bonding. Figure 4 The terminal component 200 is shown as viewed from the Y direction (i.e., the length direction of the second metal 202). Figure 5 The terminal component 200 is shown as viewed from the X direction (i.e., the width direction of the second metal 202). Figure 4 as well as Figure 5 The image shows a cross-section of the second metal 202. Figure 4 The illustration of the fixing fixture 320 is omitted in the text.

[0057] like Figure 4 As shown, the terminal component 200 includes a first metal 201 and a second metal 202 having a recess 202a. A joint portion 204, formed by ultrasonic bonding, and a riveting portion 203, formed by the insertion portion 201b of the first metal 201 entering the recess 202a of the second metal 202, are formed at the boundary between the first metal 201 and the second metal 202. In a top view, a gap 205 is formed between the recess 202a and the insertion portion 201b, in an opposing direction opposite to the flat surface 201a1 described later (see reference). Figure 5 The first metal 201 is configured to face the battery housing 41 in the terminal component 200 (see reference). Figure 1 as well as Figure 2 The interior of the terminal 43a (refer to) is configured with the internal terminal of the negative electrode. Figure 3 The connection point. The second metal 202 is in the battery housing 41 of the terminal component 200 (see reference). Figure 1 The exposed portion forms a connection point with external components such as busbars. In this embodiment, the first metal 201 is made of copper, and the second metal is made of aluminum.

[0058] The method for manufacturing the terminal component 200 disclosed herein includes the following steps (a) to (c):

[0059] (a) Preparation process for preparing the first metal 201 and the second metal 202;

[0060] (b) A riveting process in which the first metal 201 and the second metal 202 are riveted together by pressing the first metal 201 into the recess 202a of the second metal 202.

[0061] (c) A bonding process of joining the first metal 201 and the second metal 202 by ultrasonic bonding.

[0062] <Process (a): Preparation Process>

[0063] In the process (a), the first metal 201 and the second metal 202 are prepared. The second metal 202 prepared here has a recess 202a whose inner portion is wider than an opening 202a1. The first metal 201 prepared here has a shaft portion 201a having a pair of flat surfaces 201a1 and an embedded portion 201b formed at one end in the longitudinal direction of the shaft portion 201a. The embedded portion 201b is a portion that is embedded in the recess 202a of the second metal 202.

[0064] In this embodiment, the shaft portion 201a of the first metal 201 is a substantially cylindrical shape in which a pair of flat surfaces 201a1 are formed at a portion thereof. The pair of flat surfaces 201a1 are surfaces that are pressed from both sides in the Y direction by a fixing jig 320 (refer to Figure 5 ) at the time of ultrasonic joining. The embedded portion 201b extends outward in the radial direction from one end in the longitudinal direction of the shaft portion 201a and is a so-called flange shape. The embedded portion 201b is formed so as to be continuous in the circumferential direction of the shaft portion 201a. The end portion 201b1 of the embedded portion 201b is an elliptical shape with the X direction as the major axis direction and the Y direction as the minor axis direction (refer to Figure 6 ). The outer edge 201b2 of the embedded portion 201b is a tapered surface in which the outer diameter gradually decreases toward the inside in the axial direction from the end portion 201b1. In addition, the first metal 201 has a portion 201c on the side opposite to the side on which the embedded portion 201b is provided, and the portion 201c further becomes a rivet piece 43b3 (refer to Figure 3 ) that is riveted to the inner terminal 43a.

[0065] In this embodiment, the second metal 202 is a substantially rectangular plate shape in which a circular arc is processed at the corners in the top view (refer to Figure 6 ). The recess 202a that accommodates the embedded portion 201b of the first metal 201 is provided at the central portion of the one face 202f1 of the second metal 202. As described above, the inner portion of the recess 202a of the second metal 202 is wider than the opening 202a1. In other words, a space that expands in the radial direction from the opening 202a1 is formed in the inner portion of the recess 202a. In this embodiment, the opening 202a1 and the bottom portion 202a2 of the recess 202a are circular shapes. That is, the recess 202a is a space that is formed in a circular truncated cone shape. The side peripheral surface 202a3 of the recess 202a is a tapered surface that gradually narrows toward the opening 202a1 from the bottom portion 202a2.

[0066] In the joining process thereafter, a horn 300 for performing ultrasonic joining is abutted against the face 202f2 of the second metal 202 on the side opposite to the face 202f1 on which the recess 202a is provided. A recess for positioning the portion to which the horn 300 is abutted can be provided at the face 202f2.

[0067] The size relationship of the embedded portion 201b of the first metal 201 and the recessed portion 202a of the second metal 202 is set to a size that allows riveting and fixing the first metal 201 and the second metal 202 in a subsequent process. In this embodiment, the length-diameter ratio of the end portion 201b1 is slightly longer than the diameter of the bottom portion 202a2, so as to form a rivet portion 203 at both ends in the length-diameter direction (i.e., the X direction) of the end portion 201b1 of the embedded portion 201b. The first metal 201 and the second metal 202 having such a shape can be prepared by known metal processing such as forging processing, cutting processing, and the like on a metal that is the material of each component (in this embodiment, copper and aluminum).

[0068] <Process (b): Riveting Process>

[0069] In the process (b), the first metal 201 and the second metal 202 are riveted by pressing the embedded portion 201b of the first metal 201 into the recessed portion 202a of the second metal 202. Here, the riveting is performed in such a manner that a gap 205 is formed between the recessed portion 202a and the embedded portion 201b in a plan view and in an opposite direction to the flat surface 201a1.

[0070] First, the end portion 201b1 of the embedded portion 201b of the first metal 201 and the bottom portion 202a2 of the recessed portion 202a of the second metal 202 are made to face each other, and the first metal 201 and the second metal 202 are overlapped. In this embodiment, the first metal 201 and the second metal 202 are overlapped in a state where the opposite direction of the flat surface 201a1 of the shaft portion 201a of the first metal 201 coincides with the length direction Y of the second metal 202 (see FIG. 6). Figure 6 Next, the first metal 201 and the second metal 202 are pressed against each other with a desired pressing pressure using a press machine or the like. As a result, one of the first metal 201 and the second metal 202 plastically deforms with respect to the other. The embedded portion 201b of the first metal 201 enters the recessed portion 202a, and a rivet portion 203 is formed. In the rivet portion 203, the outer edge 201b2 of the embedded portion 201b and the side peripheral surface 202a3 of the recessed portion 202a are in a pressed-in state. The sizes of the first metal 201 and the second metal 202 are appropriately adjusted so as to form such a rivet portion 203. The pressing pressure can be appropriately set according to the shapes of the first metal 201 and the second metal 202, the types of metals.

[0071] In this embodiment, as described above, the bottom 202a2 of the recessed portion 202a of the second metal 202 is a circular shape, and the end portion 201b1 of the embedded portion 201b of the first metal 201 is an elliptical shape. Therefore, the rivet portion 203 is formed on both sides in the long diameter direction of the end portion 201b1. The first metal 201 and the second metal 202 are fixed to each other by the rivet portion 203. In this embodiment, the second metal 202 made of aluminum is plastically deformed with respect to the first metal 201 made of copper, and the rivet portion 203 is formed. In this way, the first metal 201 and the second metal 202 are riveted and mechanically fastened, and thus the joining strength between the first metal 201 and the second metal 202 can be ensured.

[0072] In addition, as shown in Figure 5 , with respect to the diameter of the recessed portion 202a of the second metal 202, a gap 205 is formed on the shorter diameter portion of the embedded portion 201b of the first metal 201. In this embodiment, the gap 205 is formed on both sides in the short diameter direction of the end portion 201b1 of the embedded portion 201b (that is, in the opposite direction to the flat surface 201a1 in the plan view).

[0073] <Process (c): joining process>

[0074] In the process (c), the first metal 201 and the second metal 202 are joined by ultrasonic joining. Here, vibration of the ultrasonic joining is applied in the above-described opposite direction. Thus, the joining portion 204 is formed. In addition, the joining conditions of the ultrasonic joining can be appropriately set according to the metal types, sizes, and the like of the first metal 201 and the second metal 202. Although not limited thereto, for example, it can be set to an amplitude of about 20 μm to 80 μm, a frequency of about 15 kHz to 150 kHz, and an energy amount of about 50 J to 500 J applied to the joined objects.

[0075] The ultrasonic joining is performed using the welding horn 300, the anvil 310, and the fixing jig 320. First, the first metal 201 on which the second metal 202 is overlapped is disposed on the anvil 310. Next, as shown in Figure 5 , the first metal 201 is fixed by the fixing jig 320 so as to be sandwiched from both sides of the pair of flat surfaces 201a1. In the state where the first metal 201 is fixed, the welding horn 300 is abutted to the second metal 202, and ultrasonic vibration is applied while being pressed. In this embodiment, the welding horn 300 is abutted to the center portion 206 of the second metal 202 (see Figure 6 ). The vibration direction U of the ultrasonic vibration is parallel to the direction (Y direction) in which the pair of flat surfaces 201a1 is fixed by the fixing jig 320. Thus, the loss of energy when the ultrasonic vibration is applied can be reduced.

[0076] As shown in Figure 6As shown, in a plan view, the vibration direction U and the direction in which the gap 205 opposes the flat surface 201a1 coincide. That is, the vibration direction U coincides with the direction in which the gap 205 is formed as viewed from the center portion 206. However, based on the inventor's insight, when two components are joined by ultrasonic joining, vibration is also transmitted to the entire joined component in correspondence with ultrasonic vibration applied to the joining interface with which the horn abuts. In the case where the two components are fastened without a gap, the vibration is difficult to transmit as the entire component. As a result, the vibration of the joining interface is impeded, and there is concern that the joining strength of the joining interface resulting from ultrasonic joining will decrease. In this embodiment, as described above, the vibration direction U coincides with the direction in which the gap 205 is formed. Thereby, the vibration is difficult to be impeded, and the joining portion 204 is formed with high joining strength. In addition, since the gap 205 is formed, even in the case where a large amount of energy is given to the first metal 201 and the second metal 202 at the time of ultrasonic joining, it is possible to suppress deformation within the gap 205. Thereby, it is possible to reduce deformation of the outer shape of the first metal 201 and the second metal 202.

[0077] The joining portion 204 is formed at a position corresponding to the center portion 206 with which the horn 100 abuts. In addition, in the second metal 202, a joining trace can be formed at the center portion 206. The joining trace can be formed when vibration of ultrasonic joining is applied in the above-mentioned opposing direction. Therefore, for the joining trace, a large burr can be formed on both sides in the vibration direction U compared to the direction perpendicular to the vibration direction U.

[0078] The terminal component 200 can be manufactured as described above. The terminal component 200 forms the riveting portion 203 and the joining portion 204 joined by ultrasonic joining at the boundary of the first metal 201 and the second metal 202. In the riveting portion 203, the joining strength of the first metal 201 and the second metal 202 can be ensured. In the joining portion 204, solid joining by ultrasonic joining can ensure low resistance conduction. The terminal component 200 can be utilized as a positive electrode terminal or a negative electrode terminal of a secondary battery.

[0079] The above-described terminal component 200 forms the gap 205 in a plan view between the recess portion 202a and the embedded portion 201b and in the opposing direction opposing the flat surface 201a1. Thereby, the joining strength of the joining portion 204 joined by ultrasonic joining can be improved. The joining strength of the joining portion 204 is improved, and thereby the conduction of the first metal 201 and the second metal 202 can be maintained for a long period of time. In addition, deformation caused by energy given at the time of ultrasonic joining can also be reduced.

[0080] In the above embodiment, gaps 205 are formed on both sides of the opposing direction. According to the above structure, the relative vibration of the first metal 201 and the second metal 202 is less likely to be hindered. Therefore, the bonding strength of the joint 204 can be improved.

[0081] In the above embodiment, the bottom 202a2 of the recess 202a of the second metal 202 is circular, and the end 201b1 of the insert portion 201b of the first metal 201 is elliptical, but it is not limited to the above-described manner. For example, the end 201b1 of the insert portion 201b may also be a partially cut circular shape.

[0082] Figure 7 This is a schematic diagram illustrating the shapes of the recess 202a and the insert 201b of the terminal component 200 according to other embodiments. Figure 7 In the illustrated embodiment, the recess 202a is a space formed in the shape of a frustum. The insert 201b has the same shape as the recess 202a except for its two ends in the Y direction. The insert 201b has a shape in which its two ends in the Y direction are cut (so-called D-cut) into a straight line.

[0083] Figure 8 This is a schematic diagram illustrating the shapes of the recess 202a and the insert 201b of the terminal component 200 according to other embodiments. Figure 8 In the illustrated embodiment, the recess 202a is a space formed in the shape of a frustum. The insert 201b has the same shape as the recess 202a except for its two ends in the Y direction. The insert 201b has a shape in which its two ends in the Y direction are cut into an arc shape.

[0084] exist Figure 7 as well as Figure 8 In the illustrated embodiment, a gap 205 is formed in the cut portion in the circumferential direction, and a riveting portion 203 is formed in the portion other than the cut portion. By aligning the direction in which the gap 205 is formed with the vibration direction U, the bonding strength of the joint joined by ultrasonic bonding can be improved.

[0085] exist Figures 6-8 In the illustrated embodiment, gaps 205 are formed at both ends in the Y direction, but the embodiment is not limited to the manner described above. For example, gaps 205 may be formed only in one of the opposing directions of the flat surface 201a1. Alternatively, gaps may be formed in portions of the flat surface 201a1 other than the opposing directions described above.

[0086] exist Figures 6-8In the illustrated embodiment, the recess 202a of the second metal 202 is a space formed in a truncated cone shape, and a gap 205 is formed on the inner side of the truncated cone shape between the recess 202a and the embedded portion 201b, but the present application is not limited to the above-described manner. For example, the embedded portion can be formed in a truncated cone shape, and a portion wider than the embedded portion can be provided at a portion of the recess to form a gap on the outer side of the truncated cone shape.

[0087] The terminal member, the secondary battery, and the manufacturing method of the terminal member disclosed herein have been described above. The embodiments of the terminal member and the battery and the like presented herein are not limiting of the present application, as long as not particularly mentioned. In addition, the battery disclosed herein can be variously changed, and each component, each process mentioned herein can be appropriately omitted or can be appropriately combined, as long as no particular problem occurs.

Claims

1. A terminal member used in a terminal for a secondary battery, characterized by comprising: Possessing: a first metal; and a second metal having a recess, and being a different kind of metal from the first metal, the first metal has: a shaft portion having a pair of flat surfaces; and an insertion portion formed at one end of the shaft portion in the longitudinal direction and inserted into the recess of the second metal, a joining portion and a riveting portion are formed at the boundary between the first metal and the second metal, the joining portion is joined by ultrasonic joining, the riveting portion is formed by the insertion portion of the first metal entering the recess of the second metal, wherein, in a plan view, a gap is formed between the recess and the insertion portion and in an opposite direction opposite the flat surfaces, and the riveting portion is formed in a direction perpendicular to the opposite direction, the pair of flat surfaces are surfaces pressed by a fixed jig from both sides of the opposite direction at the time of ultrasonic joining, the direction in which the gap is formed coincides with the vibration direction of ultrasonic vibration at the time of ultrasonic joining in a plan view.

2. The terminal member according to claim 1, wherein the gap is formed on both sides of the opposite direction.

3. The terminal member according to claim 1, wherein a joining mark is formed in the second metal, the joining mark being formed by applying vibration of the ultrasonic joining in the opposite direction.

4. The terminal member according to any one of claims 1 to 3, wherein the insertion portion extends outward from one end of the shaft portion in the longitudinal direction.

5. A secondary battery comprising: an electrode body including a positive electrode and a negative electrode; a battery case in which the electrode body is housed; and a positive electrode terminal and a negative electrode terminal electrically connected to the positive electrode and the negative electrode in the electrode body, the secondary battery being characterized in that at least one of the positive electrode terminal and the negative electrode terminal includes the terminal member according to any one of claims 1 to 4.

6. A method of manufacturing a terminal member used in a secondary battery, characterized by comprising: including: a preparation step of preparing a first metal and a second metal that are different kinds of metal, the second metal having a recess with a wider inner portion than an opening, and the first metal having a shaft portion having a pair of flat surfaces and an insertion portion formed at one end of the shaft portion in the longitudinal direction and inserted into the recess of the second metal; a riveting step of riveting the first metal to the second metal by pressing the insertion portion of the first metal into the recess of the second metal, the riveting being performed in such a manner that a gap is formed between the recess and the insertion portion and in an opposite direction opposite the flat surfaces in a plan view, and a riveting portion is formed in a direction perpendicular to the opposite direction; and a joining step of joining the first metal to the second metal by ultrasonic joining by pressing the pair of flat surfaces from both sides of the opposite direction with a fixed jig, vibration of the ultrasonic joining being applied in the opposite direction, and the direction in which the gap is formed coinciding with the vibration direction of ultrasonic vibration at the time of ultrasonic joining in a plan view.

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