Terminal member, secondary battery, and method for manufacturing terminal member

Abstract

The present invention relates to a terminal member, a secondary battery, and a manufacturing method of a terminal member. A terminal member for a secondary battery disclosed herein has a plate-shaped head portion having a bottom surface and an upper surface on the side opposite to the bottom surface, and a shaft portion extending from the bottom surface. The terminal member contains a first metal and a second metal joined to the first metal and having higher ductility than the first metal. The bottom surface of the head portion is composed of the first metal. The upper surface of the head portion is composed of the second metal. An outer edge portion of the bottom surface of the head portion is provided with a chamfer portion continuous in the circumferential direction. A boundary between the first metal and the second metal is formed in the chamfer portion.

Description

Technical Field

[0001] This invention relates to terminal components, secondary batteries, and methods for manufacturing terminal components. Background Technology

[0002] Japanese Patent No. 6581440 discloses a battery terminal having a shaft portion and radially extending flange portions extending radially from the shaft portion. The battery terminal is composed of a cladding material formed by bonding a first metal layer and a second metal layer. In the shaft portion, the first metal layer has a portion protruding from the flange portion toward the shaft portion, at least at its central part. This protruding portion is significantly longer than the axial length of the flange portion. The battery terminal disclosed in this patent has a protruding portion, thereby resulting in a large interface area between the first and second metal layers. Therefore, the bonding strength between the first and second metal layers is high.

[0003] Japanese Patent Application Publication No. 2011-124024 discloses a battery pack consisting of multiple individual cells connected by a busbar. Each individual cell has a positive terminal and a negative terminal. The terminal of either the positive or negative terminal with lower weld quality to the busbar is configured as an external terminal comprising a base and a material with better weld quality to the busbar. This is believed to reduce the yield rate caused by defects due to short circuits between the positive and negative terminals.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6581440

[0007] Patent Document 2: Japanese Patent Application Publication No. 2011-124024 Summary of the Invention

[0008] The inventors have investigated improving the bonding strength between external connecting components such as busbars and electrode terminals by using terminal components made of multiple metals. Terminal components made of multiple metals can be shaped, for example, by press forming of the metal material. In the inventors' experiments, it was confirmed that burrs are generated in a portion of the terminal component when the shape of the multi-metal component is formed by press forming. The inventors believe that a technique for suppressing burr formation is desirable for terminal components used in secondary batteries.

[0009] The terminal component disclosed herein is a terminal component for a secondary battery, comprising: a plate-shaped head having a bottom surface and an upper surface opposite to the bottom surface; and a shaft extending from the bottom surface. The terminal component includes a first metal and a second metal bonded to the first metal and having higher ductility than the first metal. The bottom surface of the head is made of the first metal. The upper surface of the head is made of the second metal. A chamfered portion, continuous in the circumferential direction, is provided at the outer edge of the bottom surface of the head. A boundary between the first metal and the second metal is formed at the chamfered portion.

[0010] Terminal components with this structure can suppress the generation of burrs.

[0011] Terminal components may also be made of a covering material formed by joining a first metal and a second metal.

[0012] In at least one of the first metal and the second metal, the chamfered portion may be harder than the portion located on the inner side compared to the chamfered portion.

[0013] The head can also be a rectangle when viewed from above.

[0014] The average difference between the maximum and minimum distances from each side of the bottom surface of the head to the boundary can be within 200 μm.

[0015] As another aspect of the technology disclosed herein, a secondary battery is provided. The secondary battery includes a battery casing and a positive terminal and a negative terminal mounted on the battery casing. At least one of the positive terminal and the negative terminal has the aforementioned terminal component.

[0016] As another aspect of the technology disclosed herein, a method for manufacturing a terminal component is provided. The method for manufacturing a terminal component is a method for manufacturing a terminal component for a secondary battery, the terminal component having: a plate-shaped head having a bottom surface and an upper surface opposite to the bottom surface; and a shaft extending from the bottom surface. The method for manufacturing the terminal component includes: a preparation step in which a metal material comprising a first metal and a second metal with higher ductility than the first metal is prepared; and a plastic deformation step in which the metal material is plastically deformed into a shape corresponding to the shape of a mold, wherein the mold has a first forming portion for forming a head and a second forming portion for forming a shaft, the first forming portion having an abutment surface for the corner of the first metal to abut linearly, the abutment surface being used to form a chamfer continuously in the circumferential direction at the outer edge of the bottom surface. In the plastic deformation step, the first metal of the metal material is disposed on the abutment surface, and pressure is applied from the second metal side.

[0017] According to the manufacturing method of this terminal component, the generation of burrs can be suppressed.

[0018] In the preparation process, as a metal material, a coating material formed by joining a first metal and a second metal can also be prepared. Attached Figure Description

[0019] Figure 1 This is a partial cross-sectional view of the lithium-ion secondary battery 10.

[0020] Figure 2 yes Figure 1 Sectional view II-II.

[0021] Figure 3A This is a schematic diagram illustrating the manufacturing method of terminal component 61.

[0022] Figure 3B This is a schematic diagram illustrating the manufacturing method of terminal component 61.

[0023] Figure 3C This is a schematic diagram illustrating the manufacturing method of terminal component 61.

[0024] Figure 4A This is a schematic cross-sectional view of a mold 190 having an arc-shaped contact surface 191a.

[0025] Figure 4B This is a schematic cross-sectional view of a mold 290 having a stepped abutment surface 291a. Detailed Implementation

[0026] The following describes one embodiment of the terminal component, secondary battery, and manufacturing method of the terminal component disclosed herein. This embodiment is not intended to limit the invention in any particular way. The accompanying drawings are schematic and do not necessarily reflect the actual objects. Furthermore, unless otherwise specified, expressions such as "A to B" indicating numerical ranges mean "A or more and B or less." It should be noted that in the accompanying drawings described below, the same reference numerals are used to denote components and parts that perform the same function, and sometimes repeated descriptions are omitted or simplified. Additionally, in the figures referenced in this specification, reference numeral X indicates the "long side direction," reference numeral Y indicates the "short side direction," and reference numeral Z indicates the "height direction."

[0027] In this specification, "secondary battery" generally refers to an energy storage device that undergoes a charging and discharging reaction by the movement of charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte. Besides so-called storage batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, secondary batteries also include capacitors such as electric double-layer capacitors. The following describes an embodiment using a lithium-ion secondary battery as an example.

[0028] <Lithium-ion secondary battery 10>

[0029] Figure 1 This is a partial cross-sectional view of a lithium-ion secondary battery 10 (hereinafter also simply referred to as secondary battery 10) having an external terminal 61, which serves as the negative electrode, as the terminal component disclosed herein. Figure 1 The image depicts a state where the interior is exposed along a wide surface on one side of the roughly rectangular battery casing 41. For example... Figure 1 As shown, the lithium-ion secondary battery 10 includes: an electrode body 20; a battery housing 41 having a housing body 41a and a cover 41b, the housing body 41a having an opening 41a1 and the cover 41b blocking the opening 41a1 of the housing body 41a; and a positive terminal 50 and a negative terminal 60 mounted on the battery housing 41.

[0030] <Electrode 20>

[0031] The electrode body 20 is housed in the battery casing 41 covered by an insulating film (not shown). The electrode body 20 includes a positive electrode plate 21 as a positive electrode element, a negative electrode plate 22 as a negative electrode element, and separator plates 31 and 32 as separators. The positive electrode plate 21, the first separator plate 31, the negative electrode plate 22, and the second separator plate 32 are all long strip-shaped components.

[0032] The positive electrode sheet 21 has a positive electrode active material layer 21b formed on both sides of a positive electrode current collector foil 21a (e.g., aluminum foil) of predetermined width and thickness, except for an unformed portion 21a1 of a certain width set at one end in the width direction. This layer contains the positive electrode active material. The positive electrode active material, for example in lithium-ion secondary batteries, such as lithium transition metal composite materials, is a material that releases lithium ions during charging and absorbs lithium ions during discharging. Various solutions for the positive electrode active material have been proposed besides lithium transition metal composite materials, and there is no particular limitation.

[0033] The negative electrode sheet 22 has a negative electrode active material layer 22b formed on both sides of a negative electrode current collector foil 22a (in this case, copper foil) of predetermined width and thickness, except for an unformed portion 22a1 of a certain width set on one edge in the width direction. This layer contains the negative electrode active material. The negative electrode active material, for example in lithium-ion secondary batteries, such as natural graphite, is a material that absorbs lithium ions during charging and releases the absorbed lithium ions during discharging. Various alternatives to natural graphite have been proposed for the negative electrode active material, and there is no particular limitation.

[0034] Diaphragm sheets 31 and 32 may be, for example, porous resin sheets through which an electrolyte with the required heat resistance can pass. Various designs for diaphragm sheets 31 and 32 have also been proposed, and there are no particular limitations.

[0035] Here, the width of the negative electrode active material layer 22b is, for example, wider than the width of the positive electrode active material layer 21b. The widths of the separators 31 and 32 are wider than 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 and sequentially overlapped and wound. The negative electrode active material layer 22b covers the positive electrode active material layer 21b with the separators 31 and 32 in between. The negative electrode active material layer 22b is covered by the separators 31 and 32. The unformed portions 21a1 of the positive electrode current collector foil 21a extend from one side in the width direction of the separators 31 and 32. The unformed portion 22a1 of the negative electrode current collector foil 22a extends from the diaphragm sheets 31 and 32 on the opposite side in the width direction.

[0036] like Figure 1 As shown, the electrode body 20 is flat along a plane including the winding axis, so as to be accommodated in the housing body 41a of the battery housing 41. Moreover, along the winding axis of the electrode body 20, an unformed portion 21a1 of the positive electrode current collector foil 21a is arranged on one side, and an unformed portion 22a1 of the negative electrode current collector foil 22a is arranged on the opposite side.

[0037] <Battery casing 41>

[0038] The battery casing 41 houses the electrode body 20. The battery casing 41 has: a generally rectangular casing body 41a with an opening on one side; and a cover 41b mounted on the opening 41a1. In this embodiment, from the viewpoint of lightweighting and ensuring the required rigidity, the casing body 41a and the cover 41b are respectively formed of aluminum or an aluminum-based alloy. It should be noted that... Figure 1 In the illustrated embodiment, a wound electrode body 20 is shown, but the structure of the electrode body 20 is not limited to this form. For example, the electrode body 20 can also be a laminated structure consisting of alternating layers of positive and negative electrode sheets sandwiching a separator. Furthermore, multiple electrode bodies 20 can be housed within the battery casing 41.

[0039] The battery casing 41 may also contain an electrolyte (not shown) together with the electrode body 20. As the electrolyte, a non-aqueous electrolyte in which the supporting electrolyte is dissolved 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 supporting electrolytes include fluorinated lithium salts such as LiPF6.

[0040] <Shell Body 41a>

[0041] 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 42, a pair of wide faces 43, and a pair of narrow faces 44. The wide faces 43 rise from the long side of the base 42. The narrow faces 44 rise from the short side of the base 42. An opening 41a1, surrounded by the pair of wide faces 43 and the pair of narrow faces 44, is formed on one side of the main body 41a.

[0042] Cover 41b

[0043] The cover 41b seals the opening 41a1 of the housing body 41a. In this embodiment, the cover 41b is rectangular when viewed from above. The cover 41b is mounted on the opening 41a1 of the housing body 41a. Furthermore, the periphery of the cover 41b engages with the edge of the opening 41a1 of the housing body 41a. This engagement can be achieved, for example, by a continuous weld without gaps. This weld can be achieved, for example, by laser welding.

[0044] A positive terminal 50 and a negative terminal 60 are mounted on the cover 41b. The positive terminal 50 and the negative terminal 60 each have external terminals 51 and 61 and internal terminals 55 and 65, respectively. The external terminals 51 and 61 are mounted on the outside of the cover 41b via gaskets 70. The internal terminals 55 and 65 are mounted on the inside of the cover 41b via insulators 80. The internal terminals 55 and 65 extend into the interior of the housing body 41a. The unformed portions 21a1 of the positive current collector foil 21a and 22a1 of the negative current collector foil 22a of the electrode body 20 are mounted on the internal terminals 55 and 65, respectively, mounted on both sides of the cover 41b along its long side.

[0045] Figure 2 yes Figure 1 Sectional view II-II. Figure 2 The diagram shows a cross-section of the portion where the negative terminal 60 is mounted on the cover 41b. It should be noted that the positive terminal 50 can also be mounted on the cover 41b using the same structure; therefore, its description is omitted. Figure 2 As shown, the cover 41b has a mounting hole 41b1 for mounting an external terminal 61. The mounting hole 41b1 penetrates the cover 41b at a predetermined position. An internal terminal 65 and an external terminal 61 are mounted in the mounting hole 41b1, sandwiching a washer 70 and an insulator 80. A seat surface 41b2 for mounting the washer 70 is provided around the mounting hole 41b1 on the outside of the mounting hole 41b1. A protrusion 41b3 for positioning the washer 70 is provided on the seat surface 41b2.

[0046] <External terminal 61>

[0047] The external terminal 61 includes a head 62, a shaft 63, and a rivet 64. The head 62 is a plate-shaped portion that extends outward from one end of the shaft 63. The head 62 is the portion for connection with a busbar. The busbar can be connected to the upper surface 62a of the head 62, for example, by welding. The shaft 63 is the portion that is mounted in the mounting hole 41b1 with a washer 70 between it and the shaft. The rivet 64 is the portion that is riveted to the internal terminal 65 inside the cover 41b. The rivet 64 extends from the shaft 63, bends after being inserted into the cover 41b, and is riveted to the negative internal terminal 65.

[0048] <Washer 70>

[0049] The washer 70 is a component installed in the mounting hole 41b1 and the seat surface 41b2 of the cover 41b. The washer 70 is disposed between the cover 41b and the external terminal 61 to ensure insulation between the cover 41b and the external terminal 61. Additionally, the washer 70 is compressed and installed in the mounting hole 41b1 of the cover 41b to ensure the airtightness of the battery casing 41. The washer 70 has: a seat portion 71 disposed between the head 62 and the cover 41b; a side wall 72 that rises upward from the seat portion 71; and a boss portion 73 that protrudes from the bottom surface of the seat portion 71.

[0050] The seat portion 71 is the portion mounted on the outer side of the mounting hole 41b1 of the cover 41b, which is provided with a seat surface 41b2. When viewed from above, the seat portion 71 is larger than the head 62. The seat portion 71 has a generally flat surface corresponding to the seat surface 41b2. The seat portion 71 has a recess corresponding to the protrusion 41b3 of the seat surface 41b2. A boss portion 73 protrudes from the bottom surface of the seat portion 71. The boss portion 73 has an outline shape along the inner side of the mounting hole 41b1 for mounting into the mounting hole 41b1 of the cover 41b. The inner side of the boss portion 73 becomes a mounting hole for the shaft portion 63 of the external terminal 61. A sidewall 72 rises upward from the periphery of the seat portion 71. The head 62 of the external terminal 61 is surrounded by the sidewall 72 of the washer 70. The washer 70 can be made of a material with excellent chemical resistance and weather resistance. Although not specifically limited, gasket 70 may, for example, be a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA).

[0051] <Insulator 80>

[0052] The insulator 80 is a component installed inside the cover 41b around the mounting hole 41b1. The insulator 80 includes a base portion 81, a hole 82, and a sidewall 83. The base portion 81 is a portion disposed along the inner surface of the cover 41b. In this embodiment, the base portion 81 is a generally flat portion. The base portion 81 is disposed along the inner surface of the cover 41b and is sized to not protrude from the cover 41b so as to be housed within the housing body 41a. The hole 82 is a hole provided corresponding to the inner surface of the boss portion 73 of the washer 70. In this embodiment, the hole 82 is provided approximately at the center of the base portion 81. A recessed step is provided around the hole 82 on the side facing the inner surface of the cover 41b. The front end of the boss portion 73 of the washer 70, which is mounted in the mounting hole 41b1, is housed in the step in a non-interfering manner. The sidewall 83 rises downward from the periphery of the base portion 81. A base 65a, which is provided at one end of the internal terminal 65, is housed in the base portion 81. The insulator 80 is disposed inside the battery casing 41, and therefore only needs to have the required chemical resistance. In this embodiment, polyphenylene sulfide resin (PPS) is used for the insulator 80. It should be noted that the material used for the insulator 80 is not limited to PPS.

[0053] <Internal Terminal 65>

[0054] The internal terminal 65 has a base 65a and a connecting piece 65b (see reference). Figure 1 The base 65a is the portion mounted on the base portion 81 of the insulator 80. In this embodiment, the base 65a has a shape corresponding to the inner side of the sidewall 83 surrounding the base portion 81 of the insulator 80. A connecting piece 65b extends from one end of the base 65a, extends within the housing body 41a, and connects to the unformed portion 22a1 of the negative electrode of the electrode body 20 (see reference). Figure 1 ).

[0055] In this embodiment, a boss 73 is installed in the mounting hole 41b1, and a washer 70 is installed on the outer side of the cover 41b. Next, an external terminal 61 is installed on the washer 70. At this time, the shaft portion 63 of the external terminal 61 is inserted into the boss portion 73 of the washer 70, and the head 62 of the external terminal 61 is disposed on the seat portion 71 of the washer 70. An insulator 80 and an internal terminal 65 are installed on the inner side of the cover 41b. Furthermore, the rivet tab 64 of the external terminal 61 is bent and riveted to the base 65a of the internal terminal 65. The rivet tab 64 of the external terminal 61 and the base 65a of the internal terminal 65 can be partially welded to improve conductivity.

[0056] However, the required level of oxidation-reduction resistance for the internal terminal 55 of the positive electrode of the lithium-ion secondary battery 10 is not as high as that for the negative electrode. Furthermore, from the viewpoints of required oxidation-reduction resistance and lightweight design, the internal terminal 55 of the positive electrode can be made of aluminum, aluminum alloy, etc. In contrast, the required level of oxidation-reduction resistance for the internal terminal 65 of the negative electrode is higher than that of the positive electrode. From this viewpoint, the internal terminal 65 of the negative electrode can be made of copper, copper alloy, etc. Additionally, from the viewpoints of lightweight design and cost reduction, aluminum or aluminum alloy can be used as the busbar connecting to the external terminals 51 and 61. The external terminals 51 and 61 connecting to the internal terminals 55 and 65 are made of metal. The metal used for the external terminals 51 and 61 is appropriately selected based on the type of busbar, internal terminals 55 and 65, etc.

[0057] When the internal terminal 55 and the busbar are made of the same type of metal, from the viewpoint of improving connectivity, the external terminal 51 of the positive electrode is preferably made of the same type of metal as the internal terminal 55 and the busbar. The external terminal 51 is preferably made of aluminum or an aluminum alloy.

[0058] On the other hand, in the negative terminal 60, the internal terminal 65 and the busbar can be made of different metals. The inventors investigated using the same type of metal as the internal terminal 65 for the portion of the external terminal 61 that engages with the internal terminal 65 (in this embodiment, the rivet 64), and the same type of metal as the busbar for the portion that engages with the busbar (in this embodiment, the upper surface 62a of the head 62). Here, the terminal component of the present invention will be described as an example of a terminal component 61 that can be used as the external terminal 61 and has portions made of aluminum and copper. It should be noted that the metal constituting the terminal component 61 is not limited to copper and aluminum. The type of metal constituting the terminal component 61 can be appropriately set according to the type of secondary battery 10, the type of metal used for engaging the internal terminal 65, the busbar, etc. Hereinafter, the terminal component 61 disclosed herein will be described together with its manufacturing method.

[0059] Terminal component 61

[0060] Terminal component 61 can be used as an external terminal 61 for a secondary battery. Figure 2The diagram schematically shows a cross-section of the terminal component 61. The terminal component 61 has: a plate-shaped head 62 having a bottom surface 62b and an upper surface 62a opposite to the bottom surface 62b; and a shaft portion 63 extending from the bottom surface 62b. In this embodiment, the head 62 is a rectangular plate. The head 62 has a side peripheral surface 62c extending from the upper surface 62a toward the bottom surface 62b. A chamfered portion 62d, continuous in the circumferential direction, is provided at the outer edge of the bottom surface 62b of the head 62. The chamfered portion 62d is continuously formed in the circumferential direction to connect the side peripheral surface 62c to the bottom surface 62b.

[0061] It should be noted that, in this specification, "chamfered portion" refers to the portion formed on the outer edge of the bottom surface, which is a portion where the corner is chamfered. The shape of the chamfered portion is not particularly limited; for example, it can be a C-face shape where the corner is cut off at a specified angle, an R-face shape where the corner is rounded, a recessed surface shape where the corner cross-section is recessed into a roughly rectangular shape, or a combination of these shapes. In this embodiment, the chamfered portion 62d is a C-face shape that is inclined at an angle of approximately 45 degrees from the lower end of the side peripheral surface 62c toward the outer periphery of the bottom surface 62b.

[0062] Terminal component 61 includes a first metal 61a and a second metal 61b bonded to the first metal 61a and having higher ductility than the first metal 61a. In other words, terminal component 61 has a portion made of the first metal 61a and a portion made of the second metal 61b. In this embodiment, the first metal 61a is copper. The second metal 61b is aluminum.

[0063] The upper surface 62a of the head 62 is made of a second metal 61b. The side peripheral surface 62c of the head is made of a second metal 61b. The bottom surface 62b of the head 62 is made of a first metal 61a. A boundary 61c between the first metal 61a and the second metal 61b is formed at the chamfer 62d. The boundary 61c is continuously formed circumferentially along the chamfer 62d. The boundary 61c is not formed at least on the bottom surface 62b.

[0064] The boundary 61c is formed so that it does not curve significantly along the chamfer 62d. In this embodiment, as described above, the head 62 is rectangular when viewed from above. In this case, although not particularly limited, the average difference between the maximum and minimum distances from each side of the bottom surface 62b of the head 62 to the boundary 61c can be within 200 μm.

[0065] A boundary surface 61d between a first metal 61a and a second metal 61b is formed inside the terminal component 61. In this embodiment, as... Figure 2 As shown, the boundary surface 61d is formed into a curved surface. In this embodiment, the terminal component 61 is made of a covering material formed by joining a first metal 61a and a second metal 61b.

[0066] <Method for manufacturing terminal component 61>

[0067] A method for manufacturing a terminal component 61 having the above structure includes:

[0068] (a) A preparation step, wherein a metal material 161 comprising a first metal 61a and a second metal 61b having a higher ductility than the first metal 61a is prepared; and

[0069] (b) Plastic deformation process, in which the metal material 161 is plastically deformed into a shape corresponding to the shape of the mold 90.

[0070] Figure 3A , Figure 3B as well as Figure 3C This is a schematic diagram illustrating the manufacturing method of terminal component 61. Figure 3A The figure shows a cross-section of the mold 90 used in manufacturing the terminal component 61 and the side surface of the metal material 161 disposed on the mold 90. Figure 3B The cross-sectional shape of the metal material 161 under pressure is schematically shown in the diagram. Figure 3C The figure shows a cross-section of the mold 90 and the side of the formed terminal component 61.

[0071] <Process (a): Preparation Process>

[0072] In the preparation process, a metal material 161, which will become the material for the terminal component 61, is prepared. In this embodiment, the metal material 161 is a covering material 161 formed by bonding a first metal 61a and a second metal 61b. The covering material 161 is a rectangular plate, with one side formed by the first metal 61a and the other side formed by the second metal 61b. In this embodiment, the covering material 161 is a so-called covering type covering material. A flat boundary surface is formed on the covering material 161 in a plane orthogonal to the thickness direction. On this boundary surface, the first metal 61a and the second metal 61b are bonded together over the entire surface by diffusion bonding.

[0073] The first metal 61a and the second metal 61b of the covering material 161 are made of the same metal as the metal used in the terminal component 61. The structure of the covering material 161 is not particularly limited and can be appropriately set according to the shape of the terminal component 61, etc. The thickness of the portion made of the first metal 61a and the portion made of the second metal 61b can be the same or different. Furthermore, the covering material 161 is not limited to the aforementioned covering type covering material; for example, so-called embedded type covering materials, edge-laying type covering materials, etc., can also be used.

[0074] Although not specifically limited, the cladding material 161 can be manufactured, for example, according to the following method. First, prepare a metal sheet made of a first metal 61a and a metal sheet made of a second metal 61b. Next, overlap the prepared metal sheets and roll them together using a rolling mill. The cladding material 161 can also be manufactured by adjusting the shape of the rolled and joined metal sheets, such as by punching. In order to improve the bonding strength between dissimilar metals, the rolled and joined metal sheets can also be heat-treated.

[0075] <Process (b): Plastic Deformation Process>

[0076] In the plastic deformation process, a mold 90 corresponding to the shape of the terminal component 61 is used. For example... Figure 3A As shown, the mold 90 used in manufacturing the terminal component 61 has a lower mold 90a and an upper mold 90b. The mold 90 has a first forming portion 91 forming a head 62 and a second forming portion 92 forming a shaft portion 63. In addition, the mold 90 has a third forming portion 93 forming a riveting piece 64. The first forming portion 91 to the third forming portion 93 are provided in the lower mold 90a. The lower mold 90a has a side wall 90a1 at a position higher than the first forming portion 91, corresponding to the shape of the side peripheral surface 62c. An opening for introducing metal material 161 is formed at the upper end of the side wall 90a1.

[0077] The first forming portion 91 is provided with an abutment surface 91a for the corner of the first metal 61a to abut linearly. This abutment surface 91a is used to form a chamfered portion 62d that is continuous in the circumferential direction on the outer edge of the bottom surface 62b of the head 62. The abutment surface 91a is provided continuously in the circumferential direction in such a way that it connects the portion 91b of the formed bottom surface 62b with the portion (side wall 90a1) of the formed side peripheral surface 62c. In this embodiment, the abutment surface 91a is an inclined surface that is inclined at about 45 degrees relative to the portion 91b of the formed bottom surface 62b and the side wall 90a1.

[0078] The upper die 90b is inserted into the lower die 90a through the opening. Therefore, the dimensions of the side surface of the upper die 90b are smaller than the dimensions of the opening and the side wall 90a1. From the viewpoint of preventing the flow of the plastically deformed metal material 161 into the space between the lower die 90a and the upper die 90b during stamping, it is preferable that the difference between the dimensions of the inner side surface of the upper die 90b and the dimensions of the side wall 90a1 be as small as possible. In addition, a pressure surface 90b1 corresponding to the upper surface 62a of the head 62 of the terminal component 61 is formed on the upper die 90b. In this embodiment, the pressure surface 90b1 is a flat surface corresponding to the upper surface 62a. The shape of the pressure surface 90b1 is not limited to this form. For example, protrusions, recesses, or other structures for mounting or positioning the busbar can be provided on the upper surface 62a of the head 62 of the terminal component 61. In this case, the shape of the pressure surface 90b1 can be set according to the shape of the upper surface 62a.

[0079] In the plastic deformation process, a first metal 61a, on which a metal material 161 (in this embodiment, a coating material 161) is placed at the contact surface 91a, is pressurized from the second metal 61b side. In this embodiment, the coating material 161 is pressurized by so-called cold forging, which is performed by compression forming at room temperature using a die 90.

[0080] First, the covering material 161 is introduced into the lower mold 90a through the opening and positioned on the abutment surface 91a. At this time, the covering material 161 is introduced with the first metal 61a facing downwards. The corner of the first metal 61a is continuous in the circumferential direction and abuts against the abutment surface 91a linearly. The covering material 161 is supported on the abutment surface 91a where the corner of the first metal 61a abuts linearly. By supporting the covering material 161 on the abutment surface 91a, a gap 101 is formed between the surface of the first metal 61a and the portion 91b of the bottom surface 62b of the forming head 62 of the lower mold 90a. Additionally, a gap 102 is formed between the side peripheral surface of the covering material 161 and the sidewall 90a1.

[0081] Next, the covering material 161 is pressurized within the mold 90. A stamping press (not shown) is mounted on the upper mold 90b. The stamping mechanism is capable of setting stamping conditions such as stamping load, stamping speed, and stamping time. The upper mold 90b is lowered relative to the lower mold 90a to pressurize the covering material 161. Although not particularly limited, the stamping load can be set to approximately 20kN to 100kN. When continuously manufacturing multiple terminal components 61, the stamping speed can be set to approximately 30 shots / min to 80 shots / min. When the covering material 161 is pressurized within the mold 90, the covering material 161 plastically deforms into a shape corresponding to the internal shape of the mold 90. At this time, the boundary surface 61d between the first metal 61a and the second metal 61b (refer to...) Figure 2 It forms a curved surface.

[0082] However, when a metal material is plastically deformed under pressure, a gap exists between the formed metal material and the mold before pressure is applied. For example, to place the metal material in the mold, the side dimension of the metal material needs to be set smaller than the opening dimension of the mold, thus creating a gap between the side dimension of the metal material and the mold. Additionally, tiny gaps also form at the surfaces where the metal material contacts the mold (e.g., the surfaces where the metal material is placed in the mold), making it difficult to completely eliminate these gaps. In the inventors' experiments, when a metal material containing multiple metals was plastically deformed under pressure, sometimes the relatively soft metal (e.g., a highly ductile metal) plastically deformed earlier and entered the gap between the relatively hard metal and the mold. This metal entering the gap becomes a burr, and if it peels off and remains in the mold, this fragment may cause indentations on the terminal components manufactured later. Furthermore, if burrs remain on the terminal components, defects may occur when manufacturing secondary batteries using those terminal components. Additionally, if burrs remain on the terminal components, defects may also occur when the secondary batteries using those terminal components are finalized as products.

[0083] In this embodiment, the covering material 161 is arranged such that the corner of the first metal 61a continuously abuts the contact surface 91a in a linear manner in the circumferential direction, and is pressed against the upper mold 90b from the side of the highly ductile second metal. For example... Figure 3B As shown, the plastic deformation of the highly ductile second metal occurs rapidly, and the second metal 61b flows in the direction of the arrow in the figure. The gap 102 between the covering material 161 and the sidewall 90a1 (see reference) Figure 3A It was buried by a second metal. Then, as... Figure 3C As shown, the first metal 61a flows sequentially into the first forming part 91, the second forming part 92, the third forming part 93, forming the head 62, the shaft part 63, and the riveting piece 64. As a result, a terminal component 61 with a boundary 61c is formed at the part of the chamfered part 62d that abuts against the corner of the first metal 61a.

[0084] It should be noted that the degree of plastic deformation tends to be greater at the location where the material is pressed against the contact surface 91a, and work hardening is more likely to occur at this location. Therefore, in at least one of the first metal 61a and the second metal 61b, the chamfered portion 62d may be harder than the portion further inward compared to the chamfered portion 62d. The degree of hardness variation varies depending on the type of metal, the shape of the terminal component 61, etc., and is therefore not particularly limited. However, compared to the portion further inward compared to the chamfered portion 62d, the hardness can be, for example, 8% or more, and furthermore, 10% or more. The method for evaluating hardness is not particularly limited, and various methods can be used depending on the type of metal, the shape and size of the terminal component 61, etc. Hardness can be evaluated, for example, by Vickers hardness testing, Brinell hardness testing, Knoop hardness testing, Rockwell hardness testing, etc.

[0085] As described above, terminal component 61 can be obtained. As described above, by providing an abutment surface 91a on the first forming portion 91 where the corner of the first metal 61a abuts linearly, even with continued pressure, the entry of the second metal into the lower part of the mold 90 can be prevented. Therefore, the second metal will not enter the gap 101 (see reference). Figure 3A The gap 101 is filled by the first metal after plastic deformation. The result is, as... Figure 3C As shown, a chamfered portion 62d formed by the abutment surface 91a is formed on the terminal component 61. A boundary 61c between the first metal 61a and the second metal 61b is formed on the chamfered portion 62d. By this manufacturing method, it is possible to suppress the second metal from entering the bottom surface 62b of the head 62, and to manufacture a terminal component 61 that suppresses the generation of burrs on the second metal 61b.

[0086] Furthermore, the terminal component 61 disclosed herein offers a high degree of freedom in shape processing. For example, when manufacturing a terminal component using a mold without an abutment surface 91a, it is necessary to improve the fit between the metal material and the mold on which the metal material is placed to prevent burrs. Therefore, the metal material and the area on which the metal material is placed can be flat surfaces. In the terminal component 61 disclosed herein, by providing an abutment surface 91a, the shape of the mold 90 can be set at a position below the abutment surface 91a, corresponding to the desired shape. For example, protrusions, steps, etc., for positioning the terminal component relative to a washer can be provided. Such a structure can be provided in the terminal component without additional processing such as cutting.

[0087] In the above embodiment, the metal material 161 is a coating material 161 formed by bonding a first metal 61a and a second metal 61b. That is, the boundary surface 61d of the first metal 61a and the second metal 61b is bonded by diffusion bonding. Therefore, the first metal 61a and the second metal 61b are firmly bonded at the boundary surface 61d. In addition, by performing diffusion bonding over a wider range, the on-resistance of the first metal 61a and the second metal 61b is suppressed to a lower level.

[0088] The terminal component manufactured as described above can be used in various secondary batteries. It should be noted that the terminal component disclosed herein is not limited to the structure described above and can be modified in various ways. For example, in the above embodiment, the chamfered portion 62d has a C-surface shape, but it is not limited to this form. Figure 4A This is a schematic cross-sectional view of a mold 190 having an arc-shaped abutment surface 191a. (See diagram below.) Figure 4A As shown, a mold 190 with a cross-sectional shape of arc-shaped contact surface 191a can also be used to form the chamfered portion into an arc-shaped recessed shape. Alternatively, the chamfered portion can be formed into an R-surface shape. Figure 4B This is a schematic cross-sectional view of a mold 290 having a stepped abutment surface 291a. (See attached image.) Figure 4B As shown, a mold 290 with a stepped abutment surface 291a can also be used to form the chamfered portion into a stepped shape. In the above embodiment, a cladding material is used as a metal material, but it is not limited to this form. For example, a metal material formed by metallurgically joining or mechanically fastening multiple metal materials can also be used. Multiple unjoined metals can also be used. When using unjoined metals, they can be joined by welding or other methods after forming.

[0089] The following describes embodiments of the terminal components disclosed herein, but it is not intended to limit this disclosure to the contents shown in these embodiments.

[0090] <Example>

[0091] Using a cladding material composed of a first metal (copper in this embodiment) and a second metal (aluminum in this embodiment), the terminal component of the embodiment is manufactured using a mold with the same structure as the mold 90 described above. The mold has an abutment surface. It should be noted that the abutment surface has different dimensions in the short and long sides. The abutment surface is configured such that the chamfered portion in the long side direction has a C-surface shape of C0.25, and the chamfered portion in the short side direction has a C-surface shape of C0.5. The terminal component of the embodiment has the same structure as terminal component 61. Specifically, the terminal component of the embodiment includes a shaft portion, a head, and a rivet tab. The head is a rectangular plate. A chamfered portion that is continuous in the circumferential direction is provided on the outer edge of the bottom surface of the head.

[0092] <Comparative Example>

[0093] The comparative example terminal component was manufactured using a mold with the same structure as the mold described above, except that it lacks an abutment surface. The comparative example terminal component differs from the example terminal component in that it does not have a chamfered portion.

[0094] Evaluation of the distance from the bottom to the boundary

[0095] The comparative example terminal component has its head's upper surface and side peripheral surfaces covered with a second metal. A burr of the second metal is formed on a portion of the bottom surface of the head of the comparative example terminal component. In the embodiment terminal component, both the upper surface and side peripheral surfaces are covered with the second metal. On the other hand, the embodiment terminal component does not have a burr of the second metal formed on the bottom surface of its head. A boundary between the first and second metals is formed at the chamfer of the embodiment terminal component. The boundary is not a perfectly straight line, but rather forms with a slight curve. For the embodiment terminal component without burrs, the distance from the bottom surface to the boundary is evaluated. Here, a dimensional measuring instrument is used to measure the distance from each side of the bottom surface of the rectangle to the boundary. First, the terminal component is arranged with one face of the chamfer parallel to the measuring surface of the dimensional measuring instrument. Next, using the boundary between the chamfer and the bottom surface as a reference line, the maximum and minimum values ​​of the distance to the boundary between the first and second metals are measured. The maximum and minimum values ​​are also measured for the other three faces of the chamfer. The average values ​​are calculated for the long side and the short side respectively. The results are shown in Table 1.

[0096] [Table 1]

[0097] Long side Short side Average of the maximum value 0.301mm 0.455mm The average of the minimum values 0.198mm 0.271mm

[0098] <Hardness Test>

[0099] In the terminal component of this embodiment, the hardness of the chamfered portion and the portion inside the chamfered portion (hereinafter also referred to as the "inner portion") was compared using a Vickers hardness test. The hardness of these portions was tested on both the first metal and the second metal. First, a section perpendicular to the bottom surface was exposed. The Vickers hardness was measured at a depth of 0.2 mm from the surface of the chamfered portion in the portion made of the first metal. Measurements were taken at three locations under the same conditions, and the average value was calculated as the hardness of the chamfered portion of the first metal. Next, the Vickers hardness was measured at a depth of 2 mm from the circumferential surface in the portion made of the first metal. Measurements were taken at three locations under the same conditions, and the average value was calculated as the hardness of the inner portion of the first metal. The second metal was also subjected to a hardness test under the same conditions, and the hardness of the chamfered portion and the inner portion of the second metal were measured. The results are shown in Table 2.

[0100] [Table 2]

[0101] chamfered part inner side First Metal 131Hv 121Hv Second metal 50Hv 45Hv

[0102] The head is rectangular when viewed from above. According to Table 1, the average difference between the maximum and minimum distances from each side of the head's bottom surface to the boundary is within 200 μm on both the long and short sides. According to Table 2, for the first metal (copper in this embodiment), the hardness of the chamfered portion is 8.2% higher than that of the inner portion. For the second metal (aluminum in this embodiment), the hardness of the chamfered portion is 11.1% higher than that of the inner portion.

[0103] The above provides various descriptions of the secondary battery disclosed herein. Unless otherwise specified, the embodiments of the terminal components, secondary batteries, and manufacturing methods of the terminal components listed herein are not limited to the present invention. Furthermore, the terminal components, secondary batteries, and manufacturing methods of the terminal components disclosed herein can be modified in various ways, and each component and each process mentioned herein can be appropriately omitted or appropriately combined without causing particular problems.

Claims

1. A terminal member that is a terminal member for a secondary battery, the terminal member having: a head portion that is a plate-shaped head portion having a bottom surface and an upper surface on the side opposite the bottom surface. and a shaft portion extending from the bottom surface, wherein the terminal member includes: a first metal; and a second metal joined to the first metal and higher in ductility than the first metal, the bottom surface of the head portion is composed of the first metal, the upper surface of the head portion is composed of the second metal, a chamfer portion that is continuous in the circumferential direction is provided at an outer edge portion of the bottom surface of the head portion, a boundary between the first metal and the second metal is formed at the chamfer portion.

2. The terminal member according to claim 1, wherein the terminal member is composed of a clad material in which the first metal and the second metal are joined.

3. The terminal member according to claim 1 or 2, wherein in at least either of the first metal and the second metal, the chamfer portion is harder than a portion inside compared to the chamfer portion.

4. The terminal member according to any one of claims 1 to 3, wherein the head portion is rectangular when viewed from above, an average of a difference between a maximum value and a minimum value of a distance from each side of the bottom surface of the head portion to the boundary is within 200 μm.

5. A secondary battery, wherein, the secondary battery is provided with: a battery case; and a positive electrode terminal and a negative electrode terminal mounted to the battery case, at least either of the positive electrode terminal and the negative electrode terminal is provided with the terminal member according to any one of claims 1 to 4.

6. A method of manufacturing a terminal member, which is a method of manufacturing a terminal member for a secondary battery, the terminal member having: a head portion that is plate-shaped, the head portion having a bottom surface and an upper surface on the side opposite the bottom surface; and a shaft portion extending from the bottom surface, wherein the manufacturing method of the terminal member includes: a preparation step in which a metal material including a first metal and a second metal higher in ductility than the first metal is prepared; and a plastic deformation step in which the metal material is plastically deformed into a shape corresponding to a shape of a mold, wherein the mold has a first molding portion that molds the head portion and a second molding portion that molds the shaft portion, and an abutting surface that allows a corner portion of the first metal to abut linearly is provided at the first molding portion, and the abutting surface is used to mold a chamfer portion that is continuous in the circumferential direction at an outer edge portion of the bottom surface, in the plastic deformation step, the first metal of the metal material is arranged at the abutting surface, and pressing is performed from the second metal side.

7. The manufacturing method of the terminal member according to claim 6, wherein in the preparation step, as the metal material, a clad material in which the first metal and the second metal are joined is prepared.

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