Patent Publication Number: US-2022231386-A1

Title: Terminal component, secondary battery, and method for manufacturing terminal component

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a terminal component, a secondary battery, and a method for manufacturing a terminal component. The present application claims priority based on Japanese Patent Application No. 2021-008263 filed on Jan. 21, 2021, and the entire contents of the application are incorporated herein by reference. 
     2. Description of the Related Art 
     Japanese Patent Application Publication No. 2013-75297 discloses an electrode structure including a metal plate in which a bottomed hole is formed and a metal shaft press-fitted into the bottomed hole. Here, a plastically deformed portion of the metal plate enters a constricted space of the metal shaft. It is considered that this makes it possible to increase the joining force of the metal shaft to the metal plate. 
     Japanese Patent No. 6613346 discloses a non-penetration joint structure of metal members in which a joining member having a protruding portion and a member to be joined are joined to each other. The member to be joined is wrapped around the back surface of an undercut portion formed in the protruding portion, thereby increasing adhesion between the members. It is considered that this ensures a high strength in the axial direction. 
     SUMMARY OF THE INVENTION 
     In an in-vehicle battery, a running vibration of a vehicle is also transmitted to an electrode terminals of the battery through a bus bar. When an electrode terminal in which dissimilar metals are mechanically joined is used, a load caused by the vibration is applied to an interface where the dissimilar metals are joined. According to the findings of the present inventor, where such a load is continuously applied to the joining interface of dissimilar metals for a long period of time, a portion where the load is concentrated may be consumed and durability may be lowered. For example, there is a risk that a gap may be formed at the joining interface between dissimilar metals and the joining strength may be lowered, and that moisture may enter the gap and the resistance between dissimilar metals may be increased. 
     A terminal component disclosed herein includes a first metal and a second metal overlapped on the first metal. A biting portion where an edge of one of the first metal and the second metal bites into the other metal is provided in at least three locations on an interface where the first metal and the second metal are overlapped. 
     With such a configuration, a load applied to the joining interface of dissimilar metals can be dispersed, and durability of the terminal component can be improved. 
     Here, the biting portion provided in the terminal component may be wedge-shaped. 
     In at least one of the biting portions, one of the first metal and the second metal may have a recess in which an edge of an opening projects inward with respect to a bottom portion, and the edge of the opening of the recess may bite into the other metal. In at least one of the biting portions, one of the first metal and the second metal may have a protrusion in which an edge of a top portion projects outward with respect to a proximal end, and the edge of the top portion of the protrusion may bite into the other metal. The first metal may be higher in rigidity than the second metal. 
     In a secondary battery provided with a battery case and an electrode terminal attached to the battery case, the electrode terminal may include a part configured of the terminal component described above. 
     A method for manufacturing a terminal component disclosed herein includes a step of preparing a first metal, a step of preparing a second metal, and a step of pressurizing the first metal and the second metal. Here, the first metal is higher in rigidity than the second metal and is provided with at least one of a recess having a part in which an edge of an opening projects inward with respect to a bottom portion, and a protrusion having a part in which an edge of a top portion projects outward with respect to a proximal end. In the pressurizing step, the first metal and the second metal are pressed against each other, and the second metal is plastically deformed with respect to the first metal. As a result, at least three biting portions where an edge of one metal of the first metal and the second metal bites into the other metal are formed at an interface where the first metal and the second metal are overlapped. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view of a lithium ion secondary battery  10 ; 
         FIG. 2  is a cross-sectional view showing a II-II cross section of  FIG. 1 ; 
         FIG. 3  is a sectional view taken along line III-III of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view schematically showing a terminal component  200 ; 
         FIG. 5  is a cross-sectional view schematically showing a method for manufacturing the terminal component  200 ; 
         FIG. 6  is a cross-sectional view schematically showing a terminal component  200 A; and 
         FIG. 7  is a cross-sectional view schematically showing a terminal component  200 B. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment of the terminal component and secondary battery disclosed herein will be described. The embodiment described herein is, of course, not intended to specifically limit the present disclosure. The present disclosure is not limited to the embodiment described herein, unless otherwise specified. Each drawing is schematically drawn, and the dimensional relationship such as length and width does not necessarily reflect the actual dimensions. In addition, members and parts that perform the same action are designated, as appropriate, by the same reference numerals, and duplicate description thereof will be omitted. 
     Secondary Battery 
     In the present description, the “secondary battery” means a device capable of charging and discharging. The secondary battery is inclusive of a battery generally called a lithium ion battery, a lithium secondary battery, or the like, a lithium polymer battery, a lithium ion capacitor, or the like. Here, a lithium ion secondary battery will be illustrated as a form of the secondary battery. 
     Lithium-Ion Secondary Battery  10   
       FIG. 1  is a partial cross-sectional view of a lithium ion secondary battery  10 . In  FIG. 1 , a state in which the inside is exposed is drawn along a wide surface on one side of a substantially rectangular parallelepiped battery case  41 . The lithium ion secondary battery  10  shown in  FIG. 1  is a so-called sealed battery.  FIG. 2  is a cross-sectional view showing a  11 -II cross section of  FIG. 1 . In  FIG. 2 , a partial cross-sectional view of a substantially rectangular parallelepiped battery case  41  in a state where the inside is exposed along a narrow surface on one side is schematically drawn. 
     As shown in  FIG. 1 , the lithium ion secondary battery  10  includes an electrode body  20 , a battery case  41 , a positive electrode terminal  42 , and a negative electrode terminal  43 . 
     Electrode Body  20   
     The electrode body  20  is accommodated in the battery case  41  in a state of being covered with an insulating film (not shown) or the like. The electrode body  20  includes a positive electrode sheet  21  as a positive electrode element, a negative electrode sheet  22  as a negative electrode element, and separator sheets  31  and  32  as separators. The positive electrode sheet  21 , the first separator sheet  31 , the negative electrode sheet  22 , and the second separator sheet  32  are long strip-shaped members, respectively. 
     In the positive electrode sheet  21 , a positive electrode active material layer  21   b  including a positive electrode active material is formed on both sides of a positive electrode current collecting foil  21   a  (for example, an aluminum foil) having a predetermined width and thickness, except for a non-formation portion  21   a   1  that is set to a constant width at one end in the width direction. For example, in a lithium ion secondary battery, the positive electrode active material is a material capable of releasing lithium ions during charging and absorbing lithium ions during discharging, such as a lithium transition metal composite material. Various positive electrode active materials have been generally proposed in addition to the lithium transition metal composite material, and the type of the positive electrode active material is not particularly limited. 
     In the negative electrode sheet  22 , a negative electrode active material layer  22   b  including a negative electrode active material is formed on both sides of a negative electrode current collecting foil  22   a  (here, a copper foil) having a predetermined width and thickness, except for a non-formation portion  22   a   1  that is set to a constant width at one end in the width direction. For example, in a lithium ion secondary battery, the negative electrode active material is a material capable of occluding lithium ions during charging and releasing the occluded lithium ions during discharging, such as natural graphite. Various negative electrode active materials have been generally proposed in addition to natural graphite, and the type of the negative electrode active material is not particularly limited. 
     For the separator sheets  31  and  32 , for example, a porous resin sheet which has a required heat resistance and through which an electrolyte can pass is used. Various separator sheets have been proposed for the separator sheets  31  and  32 , and the type thereof is not particularly limited. 
     Here, the negative electrode active material layer  22   b  is formed, for example, to be wider than the positive electrode active material layer  21   b . The width of the separator sheets  31  and  32  is larger than that of the negative electrode active material layer  22   b . The non-formation portion  21   a   1  of the positive electrode current collecting foil  21   a  and the non-formation portion  22   a   1  of the negative electrode current collecting foil  22   a  are directed to opposite sides in the width direction. Further, the positive electrode sheet  21 , the first separator sheet  31 , the negative electrode sheet  22 , and the second separator sheet  32  are oriented in the length direction, stacked in this order and wound. The negative electrode active material layer  22   b  covers the positive electrode active material layer  21   b  with the separator sheets  31  and  32  interposed therebetween. The negative electrode active material layer  22   b  is covered with separator sheets  31  and  32 . The non-formation portion  21   a   1  of the positive electrode current collecting foil  21   a  protrudes from one side of the separator sheets  31  and  32  in the width direction. The non-formation portion  22   a   1  of the negative electrode current collecting foil  22   a  protrudes from the separator sheets  31  and  32  on the opposite side in the width direction. 
     As shown in  FIG. 1 , the above-described electrode body  20  is flattened along one plane including the winding axis so as to be accommodated in the case body  41   a  of the battery case  41 . The non-formation portion  21   a   1  of the positive electrode current collecting foil  21   a  is arranged on one side, and the non-formation portion  22   a   1  of the negative electrode current collecting foil  22   a  is arranged on the opposite side along the winding axis of the electrode body  20 . 
     Battery Case  41   
     As shown in  FIG. 1 , the electrode body  20  is accommodated in the battery case  41 . The battery case  41  has a case body  41   a  having a substantially rectangular parallelepiped angular shape with one side open, and a lid  41   b  mounted on the opening. In this embodiment, the case body  41   a  and the lid  41   b  are formed of aluminum or an aluminum alloy mainly composed of aluminum, from the viewpoint of weight reduction and ensuring the required rigidity. 
     Case Body  41   a    
     As shown in  FIGS. 1 and 2 , the case body  41   a  has a substantially rectangular parallelepiped angular shape with one side open. The case body  41   a  has a substantially rectangular bottom surface portion  61 , a pair of wide surface portions  62  and  63 , and a pair of narrow surface portions  64  and  65 . Each of the pair of wide surface portions  62  and  63  rises from the long side of the bottom surface portion  61 . Each of the pair of narrow surface portions  64  and  65  rises from the short side of the bottom surface portion  61 . An opening  41   a   1  surrounded by a pair of wide surface portions  62  and  63  and a pair of narrow surface portions  64  and  65  is formed on one side surface of the case body  41   a.    
     Lid  41   b    
     The lid  41   b  is mounted on the opening  41   a   1  of the case body  41   a  surrounded by the long sides of the pair of wide surface portions  62  and  63  and the short sides of the pair of narrow surface portions  64  and  65 . The peripheral edge of the lid  41   b  is joined to the edge of the opening  41   a   1  of the case body  41   a . Such joining may be performed by, for example, continuous welding with no gaps. Such welding can be achieved, for example, by laser welding. 
     In this embodiment, a positive electrode terminal  42  and a negative electrode terminal  43  are attached to the lid  41   b . The positive electrode terminal  42  includes an internal terminal  42   a  and an external terminal  42   b . The negative electrode terminal  43  includes an internal terminal  43   a  and an external terminal  43   b . The internal terminals  42   a  and  43   a  are attached to the inside of the lid  41   b  with an insulator  72  interposed therebetween. The external terminals  42   b  and  43   b  are attached to the outside of the lid  41   b  with a gasket  71  interposed therebetween. The internal terminals  42   a  and  43   a  extend inside the case body  41   a . The internal terminal  42   a  of the positive electrode is connected to the non-formation portion  21   a   1  of the positive electrode current collecting foil  21   a . The internal terminal  43   a  of the negative electrode is connected to the non-formation portion  22   a   1  of the negative electrode current collecting foil  22   a.    
     As shown in  FIG. 1 , the non-formation portion  21   a   1  of the positive electrode current collecting foil  21   a  of the electrode body  20  and the non-formation portion  22   a   1  of the negative electrode current collecting foil  22   a  are attached to the internal terminals  42   a  and  43   a  that are attached to both sides of the lid  41   b  in the longitudinal direction. The electrode body  20  is accommodated in the battery case  41  in a state of being attached to the internal terminals  42   a  and  43   a  attached to the lid  41   b . Here, the wound electrode body  20  is illustrated by way of example. The structure of the electrode body  20  is not limited to such a form. The structure of the electrode body  20  may be, for example, a laminated structure in which a positive electrode sheet and a negative electrode sheet are alternately laminated with a separator sheet interposed therebetween. Further, a plurality of electrode bodies  20  may be accommodated in the battery case  41 . 
       FIG. 3  is a sectional view taken along line III-III of  FIG. 2 .  FIG. 3  shows a cross section of a part where the negative electrode terminal  43  is attached to the lid  41   b . In this embodiment, a member in which dissimilar metals are joined is used for the external terminal  43   b  of the negative electrode. In  FIG. 3 , the structure of dissimilar metals forming the external terminal  43   b , the interface between dissimilar metals, and the like are not shown, and the cross-sectional shape of the external terminal  43   b  is schematically shown. 
     As shown in  FIG. 3 , the lid  41   b  has an attachment hole  41   b   1  for attaching the external terminal  43   b  of the negative electrode. The attachment hole  41   b   1  penetrates the lid  41   b  at a predetermined position of the lid  41   b . The internal terminal  43   a  and the external terminal  43   b  of the negative electrode are attached to the attachment hole  41   b   1  of the lid  41   b  with the gasket  71  and the insulator  72  interposed therebetween. On the outside of the attachment hole  41   b   1 , a step  41   b   2  on which the gasket  71  is mounted is provided around the attachment hole  41   b   1 . The step  41   b   2  is provided with a seat surface  41   b   3  on which the gasket  71  is arranged. The seat surface  41   b   3  is provided with a projection  41   b   4  for positioning the gasket  71 . 
     Here, as shown in  FIG. 3 , the external terminal  43   b  of the negative electrode includes a head  43   b   1 , a shaft  43   b   2 , and a caulking piece  43   b   3 . The head  43   b   1  is a part arranged outside the lid  41   b . The head  43   b   1  is a substantially flat part larger than the attachment hole  41   b   1 . The shaft  43   b   2  is a part mounted in the attachment hole  41   b   1  with the gasket  71  interposed therebetween. The shaft  43   b   2  protrudes downward from a substantially central portion of the head  43   b   1 . As shown in  FIG. 3 , the caulking piece  43   b   3  is a part caulked to the internal terminal  43   a  of the negative electrode inside the lid  41   b . The caulking piece  43   b   3  extends from the shaft  43   b   2  and is bent and caulked to the internal terminal  43   a  of the negative electrode after being inserted into the lid  41   b.    
     Gasket  71   
     As shown in  FIG. 3 , the gasket  71  is a member attached to the attachment hole  41   b   1  and the seat surface  41   b   3  of the lid  41   b . In this embodiment, the gasket  71  includes a seat  71   a , a boss  71   b , and a side wall  71   c . The seat  71   a  is a part mounted on the seat surface  41   b   3  provided on the outer surface around the attachment hole  41   b   1  of the lid  41   b . The seat  71   a  has a substantially flat surface corresponding to the seat surface  41   b   3 . The seat  71   a  is provided with a depression corresponding to the projection  41   b   4  of the seat surface  41   b   3 . The boss  71   b  projects from the bottom surface of the seat  71   a . The boss  71   b  has an outer shape along the inner side surface of the attachment hole  41   b   1  so as to be mounted on the attachment hole  41   b   1  of the lid  41   b . The inner surface of the boss  71   b  serves as a mounting hole for mounting the shaft  43   b   2  of the external terminal  43   b . The side wall  71   c  rises upward from the peripheral edge of the seat  71   a . The head  43   b   1  of the external terminal  43   b  is mounted on a part surrounded by the side wall  71   c  of the gasket  71 . 
     The gasket  71  is arranged between the lid  41   b  and the external terminal  43   b  to ensure insulation between the lid  41   b  and the external terminal  43   b . Further, the gasket  71  ensures the airtightness of the attachment hole  41   b   1  of the lid  41   b . From this point of view, it is preferable to use a material having excellent chemical resistance and weather resistance. In this embodiment, PFA is used for the gasket  71 . PFA is a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (Tetrafluoroethylene Perfluoroalkylvinylether Copolymer). The material used for the gasket  71  is not limited to PFA. 
     Insulator  72   
     The insulator  72  is a member mounted inside the lid  41   b  around the attachment hole  41   b   1  of the lid  41   b . The insulator  72  includes a base  72   a , a hole  72   b , and a side wall  72   c . The base  72   a  is a part arranged along the inner surface of the lid  41   b . In this embodiment, the base  72   a  is a substantially flat plate-shaped part. The base  72   a  is arranged along the inner side surface of the lid  41   b , and has a size such that the base does not protrude from the lid  41   b  so that it can be housed in the case body  41   a . The hole  72   b  is provided correspondingly to the attachment hole  41   b   1 . In this embodiment, the hole  72   b  is provided in a substantially central portion of the base  72   a . On the side surface of the lid  41   b  facing the inner side surface, a recessed step  72   b   1  is provided around the hole  72   b . The step  72   b   1  accommodates the distal end of the boss  71   b  of the gasket  71  mounted in the attachment hole  41   b   1 . The side wall  72   c  rises downward from the peripheral edge of the base  72   a . A proximal portion  43   a   1  provided at one end of the internal terminal  43   a  of the negative electrode is accommodated in the base  72   a . Since the insulator  72  is arranged inside the battery case  41 , it is preferable that the insulator  72  have a required chemical resistance. In this embodiment, PPS is used for the insulator  72 . PPS is a polyphenylene sulfide resin. The material used for the insulator  72  is not limited to PPS. 
     The internal terminal  43   a  of the negative electrode includes the proximal portion  43   a   1  and a connection piece  43   a   2  (see  FIGS. 1 and 2 ). The proximal portion  43   a   1  is a part mounted on the base  72   a  of the insulator  72 . In this embodiment, the proximal portion  43   a   1  has a shape corresponding to the inside of the side wall  72   c  around the base  72   a  of the insulator  72 . As shown in  FIGS. 1 and 2 , the connection piece  43   a   2  extends from one end of the proximal portion  43   a   1  and extends into the case body  41   a  to be connected to the non-formation portion  22   a   1  of the negative electrode of the electrode body  20 . 
     In this embodiment, the gasket  71  is attached to the outside of the lid  41   b  while the boss  71   b  is being mounted on the attachment hole  41   b   1 . The external terminal  43   b  is mounted on the gasket  71 . At this time, the shaft  43   b   2  of the external terminal  43   b  is inserted into the boss  71   b  of the gasket  71 , and the head  43   b   1  of the external terminal  43   b  is arranged on the seat  71   a  of the gasket  71 . The insulator  72  and the internal terminal  43   a  are attached to the inside of the lid  41   b . As shown in  FIG. 3 , the caulking piece  43   b   3  of the external terminal  43   b  is bent and caulked to the proximal portion  43   a   1  of the internal terminal  43   a . The caulking piece  43   b   3  of the external terminal  43   b  and the proximal portion  43   a   1  of the negative electrode terminal  43  may be partially metal-joined in order to improve conductivity. 
     For the internal terminal  42   a  of the positive electrode of the lithium ion secondary battery  10 , the required level of oxidation-reduction resistance is not higher than that of the negative electrode. From the viewpoint of required oxidation-reduction resistance and weight reduction, aluminum can be used for the internal terminal  42   a  of the positive electrode. By contrast, for the internal terminal  43   a  of the negative electrode, the required level of oxidation-reduction resistance is higher than that of the positive electrode. From this point of view, copper may be used for the internal terminal  43   a  of the negative electrode. Meanwhile, as the bus bar to which the external terminal  43   b  is connected, aluminum or an aluminum alloy is used from the viewpoint of weight reduction and cost reduction. 
     The present inventor has studied the use of copper for a part of the external terminal  43   b  that is joined to the internal terminal  43   a , and the use of aluminum or an aluminum alloy for a part of the external terminal  43   b  that is connected to the bus bar. In order to realize such a structure, in this embodiment, a member made of copper and aluminum is used as the external terminal  43   b . Hereinafter, the structure of a terminal component  200  used as the external terminal  43   b  will be described. 
     Terminal Component  200   
       FIG. 4  is a cross-sectional view schematically showing the terminal component  200 .  FIG. 5  is a cross-sectional view schematically showing a method for manufacturing the terminal component  200  shown in  FIG. 4 .  FIG. 4  schematically shows the structure of the first metal  201  and the second metal  202  constituting the terminal component  200 , and how these metals are joined.  FIG. 5  shows the first metal  201  and the second metal  202  before joining. 
     In this embodiment, the terminal component  200  may constitute the external terminal  43   b  to be attached to the battery case  41 , for example, as shown in  FIG. 3 . As shown in  FIG. 3 , a part of the terminal component  200  as the external terminal  43   b  is connected to the internal terminal  43   a  inside the battery case  41 , and a part is exposed to the outside of the battery case  41 . As shown in  FIG. 4 , the terminal component  200  includes the first metal  201  and the second metal  202 . The first metal  201  has a part to be connected to the internal terminal  43   a . The second metal  202  has a part to be exposed to the outside of the battery case  41 . 
     In this embodiment, the first metal  201  has a shaft  201   a  and a flange  201   b , as shown in  FIG. 4 . The shaft  201   a  is a part serving as the shaft  43   b   2  (see  FIG. 3 ) to be inserted into the attachment hole  41   b   1  of the lid  41   b . The flange  201   b  is a part provided at one end of the shaft  201   a  and is wider than the shaft  201   a . The shaft  201   a  is provided with a part  201   c  that serves as the caulking piece  43   b   3  (see  FIG. 3 ) that is to be further caulked to the internal terminal  43   a  on the side opposite to the side on which the flange  201   b  is provided. The second metal  202  is overlapped on the end surface of the first metal  201  where the flange  201   b  is provided. 
     In this embodiment, the first metal  201  is configured of copper. As shown in  FIG. 5 , the first metal  201  is provided with a recess  201   d  and a protrusion  201   e  on the surface on the side on which the second metal  202  is to be overlapped. That is, the first metal  201  includes the recess  201   d  and the protrusion  201   e  on the end surface on the side where the flange  201   b  is provided. 
     In the recess  201   d , an edge  201   d   2  of an opening  201   dl  projects inward with respect to a bottom portion  201   d   3 . In this embodiment, the recess  201   d  is a depression in which the bottom portion  201   d   3  has a flat, substantially truncated cone space. The inner diameter of the recess  201   d  increases from the opening  201   d   1  toward the bottom portion  201   d   3 . The vertical cross section of the edge  201   d   2  of the opening  201   d   1  of the recess  201   d  has a wedge shape having an angle smaller than 90 degrees. The edge  201   d   2  of the recess  201   d  is continuous in the circumferential direction of the recess  201   d . In the present description, a “vertical cross section” means a cross section perpendicular to the interface where the first metal  201  and the second metal  202  are overlapped. 
     In the protrusion  201   e , an edge  201   e   2  of a top portion  201   e   1  projects outward with respect to a proximal end  201   e   3 . In this embodiment, the protrusion  201   e  is provided so as to protrude upward from the center of the bottom portion  201   d   3  of the recess  201   d . The outer diameter of the protrusion  201   e  gradually increases from the proximal end  201   e   3  provided on the bottom portion  201   d   3  of the recess  201   d  toward the top portion  201   e   1 . In other words, the protrusion  201   e  has a substantially inverted truncated cone shape spreading in the radial direction from the proximal end  201   e   3  toward the top portion  201   e   1 . The edge  201   e   2  of the top portion  201   e   1  of the protrusion  201   e  projects outward with respect to the proximal end  201   e   3 . The vertical cross section of the edge  201   e   2  of the protrusion  201   e  has a wedge shape having an angle smaller than 90 degrees. The edge  201   e   2  of the protrusion  201   e  is continuous in the circumferential direction of the protrusion  201   e . In this embodiment, the top portion  201   e   1  of the protrusion  201   e  is higher than the opening  201   d   1  of the recess  201   d.    
     The second metal  202  is overlapped on the end surface of the first metal  201  provided with the recess  201   d  and the protrusion  201   e , and is joined to the first metal  201 . In this embodiment, the second metal  202  may be a metal having malleability and lower rigidity than the first metal  201 . Specifically, in this embodiment, the first metal  201  is configured of copper, while the second metal  202  is configured of aluminum. 
     The second metal  202  is a substantially flat plate-shaped member, and is overlapped an end surface provided with the flange  201   b  of the first metal  201  provided with the recess  201   d  and the protrusion  201   e . Where the second metal  202  is strongly pressed against the end surface of the first metal  201 , as shown in  FIG. 4 , the second metal  202  is deformed into a shape along the recess  201   d  and the protrusion  201   e  of the end surface of the first metal  201 . As a result, biting portions A 1  and B 1  where the edge of the first metal  201  bites into the second metal  202  and the biting portions A 2  and B 2  where the edge the second metal  202  bites into the first metal  201  are formed at the interface F where the first metal  201  and the second metal  202  are overlapped. 
     In the biting portion A 1 , the edge  201   e   2  of the top portion  201   e   1  of the protrusion  201   e  provided on the first metal  201  bites into the second metal  202 . 
     In the biting portion B 1 , the edge  201   d   2  of the opening  201   d   1  of the recess  201   d  provided in the first metal  201  bites into the second metal  202 . 
     In the biting portion A 2 , the second metal  202  enters the bottom of the substantially truncated cone recess  201   d  provided in the first metal  201 . In other words, a part of the second metal  202  that has entered the substantially truncated cone recess  201   d  formed in the first metal  201  becomes a protrusion  202   a  in which the edge of the top portion projects outward with respect to the proximal end. The edge of the top portion of the protrusion  202   a  is in a state of biting into the first metal  201 . 
     In the biting portion B 2 , the second metal  202  enters the proximal end of the substantially inverted truncated cone protrusion  201   e  provided on the first metal  201 . In other words, a part of the second metal  202  that has entered the substantially inverted truncated cone protrusion  201   e  provided on the first metal  201  becomes a recess  202   b  in which the edge of the opening projects inward with respect to the bottom portion. The edge of the opening of the recess  202   b  is in a state of biting into the first metal  201 . 
     The biting portions A 1 , A 2 , B 1 , and B 2  have a shape that follows the shape of the other metal. In this embodiment, as shown in  FIG. 4 , the vertical cross section of the biting portions A 1 , A 2 , B 1 , and B 2  that passes through the center of the interface F where the first metal  201  and the second metal  202  are overlapped has a wedge shape. In this embodiment, the angle of the wedges of the biting portions A 1 , A 2 , B 1 , and B 2  is about 60 degrees. The angle of the wedge is set, as appropriate, according to the required joint strength and the like. Although not particularly limited, the angle of the wedge of the biting portion is usually 30 degrees or more, but may be 40 degrees or more, or 50 degrees or more. The angle of the wedge of the biting portion is usually less than 90 degrees, and may be 80 degrees or less, or 70 degrees or less. 
     Further, in this embodiment, the biting portion is continuously provided in the circumferential direction. The biting portion is not limited to this, and may be formed intermittently. It is preferable that the first metal  201  and the second metal  202  are in close contact with each other at the interface where the first metal  201  and the second metal  202  are overlapped, but a gap is allowed to be present. 
     In the terminal component  200 , the biting portions A 1 , A 2 , B 1 , and B 2  where the edge of one of the first metal  201  and the second metal  202  bites into the other metal are provided at four locations at the interface F where the first metal  201  and the second metal  202  are overlapped. With such terminal component  200 , for example, even when a vibration of the lithium ion secondary battery  10  is transmitted to the terminal component  200 , the load applied to the interface F between the first metal  201  and the second metal  202  is dispersed. Further, since the interface F between the first metal  201  and the second metal  202  meshes in a complicated manner, the durability is improved. From this point of view, the present inventor has found that at the interface F where the first metal  201  and the second metal  202  of one terminal component  200  are overlapped, the biting portion where the edge of one of the first metal  201  and the second metal  202  bites into the other metal is preferably provided in at least three locations in the vertical cross section along an arbitrary radial direction from the center of the interface F where the first metal  201  and the second metal  202  are overlapped. 
     From the above viewpoint, the biting portions A 1 , A 2 , B 1 , and B 2  may have, for example, a wedge shape. Because of such shape, the biting portions A 1 , A 2 , B 1 , and B 2  bite deeply into the other metal, so that the above-mentioned effect is likely to be advantageously exhibited. 
     An example of the method for manufacturing the terminal component  200  described above will be described hereinbelow. The method for manufacturing the terminal component  200  includes a step of preparing a first metal, a step of preparing a second metal, and a step of pressurizing the first metal and the second metal. 
     The first metal prepared in the step of preparing the first metal has at least one of a recess having a part where the edge of an opening projects inward with respect to a bottom portion, and a protrusion having a part where the edge of a top portion projects outward with respect to a proximal end. In this embodiment, in the step of preparing the first metal, the first metal  201  having the above-mentioned shape is prepared. 
     In the embodiment shown in  FIG. 5 , the second metal  202  prepared in the step of preparing the second metal is a substantially flat member. The second metal  202  has a depression  202   c  corresponding to the end surface of the first metal  201  provided with the flange  201   b . The bottom portion of the depression  202   c  is flat, and the center of the depression  202   c  is provided with a substantially cylindrical projection  202   d  corresponding to the recess  201   d  and the protrusion  201   e  of the first metal  201 . The projection  202   d  extends vertically from the bottom portion. The projection  202   d  has a substantially cylindrical shape. A depression  202   e  is formed on the end surface of the projection  202   d . The depression  202   e  is a substantially columnar space. 
     The projection  202   d  is a part that becomes the protrusion  202   a  corresponding to the recess  201   d  of the first metal  201 . The depression  202   e  is a part that becomes the recess  202   b  corresponding to the protrusion  201   e  of the first metal  201  (see  FIG. 4 ). The shape of the second metal  202  is not limited to this as long as the shape is plastically deformed along the shape of the first metal  201  in a subsequent step. The shape of the second metal  202  is selected, as appropriate, according to the shape of the first metal  201 , the rigidity of the second metal, and the like. Such first metal  201  and second metal  202  can be manufactured by, for example, known metal processing such as forging or cutting. 
     In the pressurizing step, the first metal  201  and the second metal  202  are pressed against each other, and the second metal  202  is plastically deformed with respect to the first metal  201 . 
     Here, a press machine (not shown) is used to press-fit the second metal  202  into the first metal  201 . A press jig  301  is attached to the surface of the first metal  201  opposite to the side on which the flange  201   b  is provided. A press jig  302  is attached to the surface of the second metal  202  opposite to the surface on which the projection  202   d  is provided. The projection  202   d  and the depression  202   e  of the second metal  202  and the recess  201   d  and the protrusion  201   e  of the first metal  201  face each other. The press machine is operated to press the first metal  201  and the second metal  202  against each other. Here, the pressure applied by the press machine is set, as appropriate, according to the metal type and dimensions of the first metal  201  and the second metal  202 . Although not limited to this, the press pressure can be set to, for example, about 200 N to 1600 N. 
     By pressing the first metal  201  and the second metal  202  against each other, the second metal  202  is plastically deformed along the surface where the recess  201   d  and the protrusion  201   e  are formed. The recess  201   d  and the protrusion  201   e  of the first metal  201  enter the second metal  202 . In other words, the surface of the second metal  202  overlapped with the first metal  201  enters the recess  201   d  and the protrusion  201   e  of the first metal  201 . As a result, the biting portions A 1 , A 2 , B 1 , and B 2  are formed, and the terminal component  200  is manufactured. 
     In the embodiment shown in  FIG. 5 , the first metal  201  and the second metal  202  are pressed against each other to plastically deform the second metal  202  having low rigidity and to form the biting portions A 1 , A 2 , B 1 , and B 2 . However, the method of forming the biting portion is not limited to this. For example, one or both of the first metal and the second metal may be composed of a plurality of members. A biting portion may be formed by fitting one metal composed of a plurality of members to the other metal. At this time, the plurality of members may be assembled by fitting the members together, and then the respective members may be joined by welding, press-fitting, or the like. A caulking piece may be provided on one of the metals, and the caulking piece may be bent to form a biting portion. By hitting a part of one of the metals, the metal having low rigidity among the first metal and the second metal may be plastically deformed to form a biting portion. A biting portion may be also formed by combining these methods. 
       FIGS. 6 and 7  show terminal components, which are other forms of the terminal component  200 . 
       FIG. 6  is a cross-sectional view schematically showing a terminal component  200 A. In the embodiment shown in  FIG. 6 , one end of the shaft  201   a  of the first metal  201  is provided with an inclined portion  201   f  that expands toward the end portion. The inclined portion  201   f  is continuous in the circumferential direction of the shaft  201   a . The first metal  201  has a recess  201   g  on the end surface including the inclined portion  201   f . The recess  201   g  is a space having a substantially truncated cone shape. The edge of the opening of the recess  201   g  projects inward with respect to the bottom portion. 
     The second metal  202  is overlapped with the end surface of the first metal  201  provided with the inclined portion  201   f . The second metal  202  is provided with a depression  202   f  in which a part of the inclined portion  201   f  is accommodated. The second metal  202  is further provided with a protrusion  202   g  that follows the shape of the recess  201   g.    
     Biting portions B 11  and C 11  where the edge of the first metal  201  bites into the second metal  202 , and a biting portion A 11  where the edge of the second metal  202  bites into the first metal  201  are provided at the interface F where the first metal  201  and the second metal  202  are overlapped. 
     In the biting portion A 11 , the edge of the top portion of the protrusion  202   g  provided on the second metal  202  bites into the first metal  201 . 
     In the biting portion B 11 , the edge of the opening of the recess  201   g  provided in the first metal  201  bites into the second metal  202 . 
     In the biting portion C 11 , an edge  201   f   1  of the inclined portion  201   f  provided on the first metal  201  bites into the second metal  202 . 
     As described above, in the embodiment shown in  FIG. 6 , the biting portions A 11 , B 11 , and C 11  are provided at three locations. 
       FIG. 7  is a cross-sectional view schematically showing the terminal component  200 B. 
     In this embodiment, the first metal  201  is provided with a projection  201   h  on an end surface  201   a   1  at one end of the shaft  201   a . The projection  201   h  has a circular cross section parallel to the end surface  201   a   1 . The projection  201   h  has a cylindrical portion  201   hl  extending from a part of the end surface  201   a   1  of the shaft  201   a , and a head  201   h   2  extending from the end portion of the cylindrical portion  201   h   1 . The projection  201   h  is formed with a gently curved edge toward the outside at a top portion  201   h   3  of the head  201   h   2 . The edge of the projection  201   h  projects outward with respect to the proximal end of the projection. The first metal  201  further has a recess  201   i  at the top portion  201   h   3  of the head  201   h   2 . The edge of the opening of the recess  201   i  projects inward with respect to the bottom portion. 
     The second metal  202  is overlapped with the end surface of the first metal  201  provided with the projection  201   h . As shown in  FIG. 7 , the second metal  202  is provided with a depression  202   h  in which the projection  201   h  is accommodated and which follows the shape of the projection  201   h . The edge of the opening of the depression  202   h  is bent at a right angle toward the bottom portion. The edge of the opening of the depression  202   h  projects inward with respect to the bottom portion. 
     Biting portions B 21  and C 21  where the edge of the first metal  201  bites into the second metal  202 , and biting portions A 21  and C 22  where the edge of the second metal  202  bites into the first metal  201  are provided at the interface F where the first metal  201  and the second metal  202  are overlapped. 
     In the biting portion A 21 , the edge of the top portion of the protrusion  202   i  provided on the second metal  202  bites into the first metal  201 . 
     In the biting portion B 21 , the edge of the opening of the recess  201   i  provided in the first metal  201  bites into the second metal  202 . 
     In the biting portion C 21 , the edge of the projection  201   h  provided on the first metal  201  bites into the second metal  202 . 
     In the biting portion C 22 , the edge of the opening of the depression  202   h  provided in the second metal  202  bites into the first metal  201 . 
     As described above, in the embodiment shown in  FIG. 7 , the biting portions A 21 , B 21 , C 21 , and C 22  are provided at four locations. 
     The terminal component and secondary battery disclosed herein have been described in various ways. Unless otherwise specified, the terminal components and the embodiments of the secondary battery mentioned herein do not limit the present disclosure. Further, the secondary battery disclosed herein can be variously modified, and constituent elements thereof and processing referred to herein can be omitted, as appropriate, or combined, as appropriate, unless a specific problem occurs.