JP2014018810A - Resistance welding apparatus and resistance welding method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of working efficiency when a tab group and a conductive member are bonded to each other by resistance welding.SOLUTION: A first welding rod 31 of a resistance welding apparatus 30 includes: a tip end surface 32a of a body 32 opposed to a tab group 12c; and a welding part 33 projecting from the tip end surface 32a to the tab group 12c. The resistance welding apparatus 30 further includes an interposed member 35 that has a contact portion 35a contactable with the tip end surface 32a of the body 32 and is interposed between the tip end surface 32a of the body 32 and the tab group 12c.

Description

  The present invention relates to a resistance welding apparatus and a resistance welding method using the resistance welding apparatus.

  A secondary battery, which is a type of power storage device, has a sheet-like separator interposed between a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet and the negative electrode sheet are insulated by the separator, and a plurality of these are laminated alternately The laminated electrode assembly formed is housed in the case together with the electrolytic solution. Each positive electrode sheet and each negative electrode sheet have an active material layer in which an active material is applied to a metal foil, and a tab that is a portion where the active material in the metal foil is not applied. A tab group is formed on the electrode assembly by stacking the tabs. Each tab group is connected to a conductive member for extracting electricity from the tab group. Each conductive member is connected to an electrode terminal provided on the case.

  In order to connect the tab group and the conductive member, first, the tab group and the conductive member are connected by the first welding rod (electrode bar) arranged on the tab group side and the second welding rod arranged on the conductive member side. By sandwiching the member and energizing the tab group and the conductive member under pressure, a part of the tab group and a part of the conductive member are melted. Then, the tab group and the conductive member are connected by solidifying and adhering the melted portions (see, for example, Patent Document 1).

JP 2010-73408 A

  However, since the tab group is formed by laminating a plurality of tabs, when the tab group and the conductive member are to be connected, the first welding rod that directly contacts the tab group is the tab group. As the material melts, it sinks into the melted portion of the tab group. The molten part in the tab group adheres to the first welding rod. If the first welding rod excessively sinks into the molten portion of the tab group, the contact area between the molten portion of the tab group and the first welding rod increases, and the molten portion of the tab group There is a risk that the adhesion portion between the first welding rod and the first welding rod will expand, making it difficult to pull out the first welding rod from the molten portion of the tab group. As a result, workability when the tab group and the conductive member are connected by resistance welding is deteriorated.

  The present invention has been made in order to solve the above-described problems, and the purpose thereof is a resistance welding apparatus capable of suppressing deterioration in workability when connecting the tab group and the conductive member by resistance welding, And providing a resistance welding method using the same.

  In order to achieve the above object, the invention according to claim 1 is a tab group in which tabs projecting from one end of a metal foil constituting an electrode assembly configured in a layer shape of a power storage device are stacked; A resistance welding apparatus for connecting a conductive member electrically connected to the tab group by resistance welding, wherein the first welding rod is disposed on the tab group side, and is disposed on the conductive member side. A second welding rod, and the first welding rod has a facing surface that faces the tab group, and a welding portion that protrudes from the facing surface toward the tab group, The gist of the invention is that it has a contact portion that can come into contact with the opposing surface and includes an interposition member interposed between the opposing surface and the tab group.

  According to this invention, when the tab group and the conductive member are to be connected by resistance welding, the first welding rod sinks into the melted portion of the tab group as the tab group melts. Even so, it is possible to prevent the first welding rod from sinking excessively into the melted portion of the tab group by the contact surface of the first welding rod contacting the contact portion of the interposition member. . As a result, it is suppressed that the first welding rod is difficult to pull out from the melted portion of the tab group, and deterioration in workability when the tab group and the conductive member are connected by resistance welding can be suppressed. .

The gist of the invention described in claim 2 is the invention according to claim 1, further comprising a pressing mechanism that presses the interposition member toward the tab group.
According to this invention, since the tab group is pressed against the interposition member by pressing the interposition member toward the tab group side by the pressing mechanism, the tabs constituting the tab group can be brought into close contact with each other. As a result, compared to the case where the tabs are not in close contact with each other, the resistance of the current flowing through the tabs can be reduced, so that the tab group and the conductive member can be easily connected by resistance welding.

The gist of the invention according to claim 3 is that, in the invention according to claim 1 or claim 2, the tab group side of the interposition member is flat.
According to the present invention, since the tab group can be pressed by the flat interposition member, even if the tabs constituting the tab group are wrinkled, the wrinkle can be extended, and the tab group and the conductive member Can be easily connected by resistance welding.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the interposed member has an insertion hole through which the welded portion can be inserted, and the contact The gist is that the portion is formed around the insertion hole on the surface facing the facing surface.

  According to the present invention, for example, the contact area between the facing surface and the contact portion can be increased as compared with the case where the interposition member is provided in a part of the periphery of the weld portion, and the weld portion is a tab group. It is possible to easily prevent the material from sinking excessively into the melted portion.

  The invention according to claim 5 is the invention according to claim 2, wherein the pressing mechanism has one end connected to the interposition member and the other end connected to a support portion supporting the first welding rod. And a moving means for moving the support portion and the first welding rod toward the tab group.

  According to this invention, by moving the support portion toward the tab group by the moving means, the interposition member moves toward the tab group via the spring member, and the interposition member contacts the tab group. Then, in a state where the interposition member is in contact with the tab group, the tab group can be pressed by the interposition member by further moving the support portion toward the tab group by the moving means. Furthermore, when the support portion is moved toward the tab group by the moving means, the spring member is bent, so that the first welding rod can be moved toward the tab group. Therefore, the pressing to the tab group in the interposition member and the contact to the tab group in the first welding rod can be performed by one apparatus, the resistance welding apparatus can be simplified, and the tab group Connection work with the conductive member can be simplified.

  A sixth aspect of the present invention is the invention according to any one of the first to fifth aspects, wherein the interposition member is formed of a material having a lower conductivity than the metal foil. And

  According to this invention, when the tab group and the conductive member are to be connected by resistance welding, even if the opposing surface of the first welding rod and the contact portion of the interposition member are in contact, the current is greater than that of the interposition member. Since it becomes easy to flow into a tab group, it can control that an interposed member is welded to a tab group.

The gist of the invention according to claim 7 is that, in the invention according to any one of claims 1 to 6, the interposition member has an insulating property.
According to this invention, when the tab group and the conductive member are to be connected by resistance welding, even if the opposing surface of the first welding rod and the contact portion of the interposition member come into contact, the interposition member becomes a tab group. It is possible to prevent welding.

  According to an eighth aspect of the present invention, there is provided a tab group in which tabs protruding from one end of a metal foil constituting an electrode assembly configured in a layer form of a power storage device are stacked, and electrically connected to the tab group A resistance welding method using a resistance welding apparatus for connecting a conductive member to be connected by resistance welding, wherein the resistance welding apparatus includes a first welding rod disposed on the tab group side, and the conductive member side. An interposition member having a contact portion that can contact an opposing surface of the first welding rod facing the tab group, the opposing surface, and the tab group. The gist is to have an intervening step interposed between the two.

  According to this invention, when the tab group and the conductive member are connected by resistance welding, it is possible to suppress the first welding rod from sinking excessively into the melted portion of the tab group. This prevents the welding rod from becoming difficult to pull out from the melted portion of the tab group. As a result, it is possible to suppress deterioration in workability when the tab group and the conductive member are connected by resistance welding.

The gist of the invention described in claim 9 is the invention according to claim 8, further comprising a pressing step of pressing the interposition member toward the tab group.
According to this invention, the tabs constituting the tab group can be brought into close contact with each other, and the resistance of the current flowing through each tab can be reduced as compared with the case where the tabs are not in close contact with each other. The group and the conductive member can be easily connected by resistance welding.

  According to this invention, the deterioration of workability | operativity at the time of connecting a tab group and an electrically-conductive member by resistance welding can be suppressed.

The disassembled perspective view of the secondary battery in embodiment. The perspective view which shows a positive electrode sheet, a negative electrode sheet, and a separator. Sectional drawing which shows a resistance welding apparatus, a tab group, and a conductive member. Sectional drawing which shows the state by which the tab group was pressed by the interposition member. Sectional drawing which shows the state which the welding part of the 1st welding rod contact | abutted to the tab group. Sectional drawing which shows the state which a part of tab group is fuse | melting.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
First, the secondary battery 10 as a power storage device will be described.
As shown in FIG. 1, the secondary battery 10 includes an electrode assembly 11 and an aluminum case 20 that houses the electrode assembly 11. The case 20 includes a bottomed rectangular box-shaped case main body 21 in which an opening 21 a into which the electrode assembly 11 can be inserted is formed, and a flat lid 28 that closes the opening 21 a of the case main body 21. Yes. The lid 28 has a positive terminal 25 and a negative terminal 26 protruding outward.

  As shown in FIG. 2, the electrode assembly 11 insulates the positive electrode sheet 12 and the negative electrode sheet 13 by interposing a sheet-like separator 14 between the positive electrode sheet 12 and the negative electrode sheet 13. A plurality of layers are laminated. That is, the electrode assembly 11 of the present embodiment is a stacked electrode assembly in which a plurality of positive electrode sheets 12, negative electrode sheets 13, and separators 14 are stacked in a certain direction (stacking direction).

  The positive electrode sheet 12 has an active material layer 12 a configured by applying an active material to the metal foil 121, and a tab 12 b protruding from one end of the metal foil 121. The negative electrode sheet 13 has an active material layer 13 a configured by applying an active material to the metal foil 131, and a tab 13 b protruding from one end of the metal foil 131. Each positive electrode sheet 12 is laminated in a certain direction so that each tab 12b overlaps, and each negative electrode sheet 13 is laminated in a certain direction so that each tab 13b overlaps. The metal foil of the positive electrode sheet 12 is an aluminum foil, and the metal foil of the negative electrode sheet 13 is a copper foil.

  As shown in FIG. 1, the electrode assembly 11 is formed with a tab group 12c in which tabs 12b of the respective positive electrode sheets 12 are laminated. A rectangular plate-like conductive member 19a electrically connected to the tab group 12c is joined (connected) to the tab group 12c by resistance welding. The electrode assembly 11 is formed with a tab group 13c in which tabs 13b of the negative electrode sheets 13 are laminated. A rectangular plate-like conductive member 19b electrically connected to the tab group 13c is joined (connected) to the tab group 13c by resistance welding. The tab group 12 c of the positive electrode sheet 12 and the tab group 13 c of the negative electrode sheet 13 extend from one side of the electrode assembly 11 in the same direction (one direction).

  The conductive member 19 a is connected to the positive terminal 25 and the conductive member 19 b is connected to the negative terminal 26. Accordingly, the tab group 12c of the positive electrode sheet 12 and the positive electrode terminal 25 are electrically connected via the conductive member 19a, and the tab group 13c of the negative electrode sheet 13 and the negative electrode terminal 26 are electrically connected via the conductive member 19b. Connected. Then, the lid 28 and the case main body 21 are joined by laser welding, and the opening 21a of the case main body 21 is closed and sealed by the lid 28, whereby the secondary battery 10 is configured. An electrolyte is injected into the case 20.

  Next, a resistance welding apparatus used when the tab group 12c of the positive electrode sheet 12 and the conductive member 19a are connected by resistance welding will be described. A similar resistance welding apparatus is also used when the tab group 13c of the negative electrode sheet 13 and the conductive member 19b are connected by resistance welding.

  As shown in FIG. 3, the resistance welding apparatus 30 includes a first welding rod 31 and a second welding rod 41. The first welding rod 31 and the second welding rod 41 are disposed to face each other. The front end surface 32 a of the main body portion 32 of the first welding rod 31 has a flat surface shape, and the welded portion 33 protrudes from the front end surface 32 a of the main body portion 32. The welded portion 33 has a substantially hemispherical shape that bulges from the distal end surface 32 a of the main body portion 32. A flat plate-like support portion 34 is fixed to the base end side of the main body portion 32, and the first welding rod 31 is supported by the support portion 34.

  A plurality of (only two are shown in FIG. 3) spring members 36 are arranged on the surface of the support portion 34 on the first welding rod 31 side, and on the opposite side of the spring member 36 from the support portion 34, A flat interposition member 35 is provided. That is, one end of the spring member 36 is connected to the interposition member 35 and the other end is connected to the support portion 34. The interposition member 35 is formed of a resin material. That is, the interposition member 35 has an insulating property. An insertion hole 35 h is formed at the center of the interposed member 35. The inner diameter of the insertion hole 35h is larger than the outer diameter of the welded portion 33, and the welded portion 33 can be inserted inside the inserted hole 35h. In addition, a contact portion 35a that can come into contact with the distal end surface 32a of the main body 32 is formed around the insertion hole 35h on the upper surface of the intermediate member 35 (the surface of the intermediate member 35 that faces the distal end surface 32a of the main body 32). Yes. The contact part 35a has a flat surface shape. The length H in the thickness direction of the interposed member 35 (the thickness of the interposed member 35) is shorter than the protruding length L of the welded portion 33 from the distal end surface 32a of the main body portion 32. Furthermore, the resistance welding apparatus 30 includes a moving unit 37 that moves the support portion 34 and the first welding rod 31 in a direction in which the supporting portion 34 and the second welding rod 41 are moved toward and away from each other.

  Next, the operation of this embodiment will be described while describing a resistance welding method for connecting the tab group 12c of the positive electrode sheet 12 and the conductive member 19a using the resistance welding apparatus 30 having the above-described configuration. Since the resistance welding method for connecting the tab group 13c of the negative electrode sheet 13 and the conductive member 19b is the same, the description thereof is omitted.

  First, in a state where the tab group 12c and the conductive member 19a are overlapped, the first welding rod 31 is disposed on the tab group 12c side, and the second welding rod 41 is disposed on the conductive member 19a side. At this time, the front end surface 32a of the main body 32 is opposed to the tab group 12c. Therefore, the front end surface 32a of the main body portion 32 corresponds to a facing surface that faces the tab group 12c. Further, an interposition member 35 is interposed between the front end surface 32a of the main body 32 and the tab group 12c (intervening step).

  Subsequently, as shown in FIG. 4, the support unit 34 and the first welding rod 31 are moved toward the tab group 12 c by the moving unit 37. Then, the interposition member 35 moves to the tab group 12c side via the spring member 36, and the interposition member 35 contacts (contacts) the tab group 12c. When the support member 34 and the first welding rod 31 are further moved toward the tab group 12c by the moving means 37 in a state where the interposition member 35 is in contact with the tab group 12c, the spring member 36 is bent, The interposing member 35 is pressed toward the tab group 12c by the spring force of the spring member 36 (pressing step). Therefore, in the present embodiment, the spring member 36 and the moving means 37 constitute a pressing mechanism that presses the interposition member 35 toward the tab group 12c. By this pressing step, the tabs 12b constituting the tab group 12c are pressed while being sandwiched between the interposition member 35 and the conductive member 19a, and the tabs 12b are brought into close contact with each other.

  Subsequently, as shown in FIG. 5, when the support portion 34 and the first welding rod 31 are further moved toward the tab group 12 c by the moving means 37, the spring member 36 is further bent, and the first welding rod 31. Moves toward the tab group 12c. And while the welding part 33 enters into the insertion hole 35h of the interposition member 35, the front-end | tip of the welding part 33 contacts the tab group 12c. Thus, the tab group 12c and the conductive member 19a are sandwiched between the first welding rod 31 and the second welding rod 41. Further, in a state where the tab group 12c and the conductive member 19a are sandwiched between the first welding rod 31 and the second welding rod 41 and pressed, the gap between the first welding rod 31 and the second welding rod 41 is increased. Current is passed through.

  Then, as shown in FIG. 6, resistance heat is generated between the first welding rod 31, the tab group 12c, the conductive member 19a, and the second welding rod 41, and this resistance heat causes the tab group 12c and the conductive layer to be conductive. The member 19a is heated and melted. Here, as the tab group 12c is melted, the welded portion 33 sinks into the melted portion of the tab group 12c, but the front end surface 32a of the main body portion 32 comes into contact with the contact portion 35a of the interposition member 35. Thus, the movement of the first welding rod 31 toward the tab group 12c is restricted, and the welding portion 33 is prevented from excessively sinking into the melted portion of the tab group 12c. Then, the welded portion 33 is pulled out from the melted portion of the tab group 12c, and the tab portion 12c and the conductive member 19a are cooled to join the tab group 12c and the conductive member 19a.

In the above embodiment, the following effects can be obtained.
(1) Between the front end surface 32a of the main body 32 and the tab group 12c, an interposition member 35 having a contact portion 35a that can contact the front end surface 32a is interposed. When the tab group 12c and the conductive member 19a are to be connected by resistance welding, the first welding rod 31 sinks into the melted portion of the tab group 12c as the tab group 12c melts. However, when the front end surface 32a of the main body 32 comes into contact with the contact portion 35a, the first welding rod 31 can be prevented from excessively sinking into the melted portion of the tab group 12c. As a result, it is suppressed that the first welding rod 31 is difficult to be pulled out from the melted portion of the tab group 12c, and deterioration in workability when the tab group 12c and the conductive member 19a are connected by resistance welding is suppressed. can do.

  (2) When the tab group 12c and the conductive member 19a are connected by resistance welding, the interposition member 35 is pressed toward the tab group 12c. Therefore, since the tab group 12c is pressed by the interposition member 35 when the interposition member 35 is pressed by the tab group 12c side, each tab 12b which comprises the tab group 12c can be closely_contact | adhered. As a result, compared to the case where the tabs 12b are not in close contact with each other, the resistance of the current flowing through the tabs 12b can be reduced, so that the tab group 12c and the conductive member 19a can be easily connected by resistance welding. Can do.

  (3) The interposition member 35 has a flat plate shape. Accordingly, since the tab group 12c can be pressed by the flat interposition member 35, even if the tabs 12b constituting the tab group 12c are wrinkled, the wrinkles can be extended, and the tab group 12c can be electrically connected. The member 19a can be easily connected by resistance welding.

  (4) An insertion hole 35h through which the welded portion 33 can be inserted is formed in the interposed member 35, and a contact portion 35a that can contact the distal end surface 32a of the main body 32 is formed around the insertion hole 35h on the upper surface of the interposed member 35. . Therefore, for example, compared with the case where the interposition member 35 is provided in a part of the periphery of the welded portion 33, the contact area between the tip surface 32a of the main body portion 32 and the contact portion 35a can be increased, and welding is performed. It is possible to easily prevent the portion 33 from sinking excessively into the melted portion of the tab group 12c.

  (5) In this embodiment, the spring member 36 having one end connected to the interposition member 35 and the other end connected to the support portion 34, and the moving means 37 that moves the support portion 34 toward the tab group 12c. A pressing mechanism that presses the interposition member 35 toward the tab group 12c is configured. Therefore, by moving the support portion 34 and the first welding rod 31 toward the tab group 12 c by the moving means 37, the interposition member 35 moves to the tab group 12 c side via the spring member 36, and the interposition member 35. Comes into contact with the tab group 12c. Then, in a state where the interposition member 35 is in contact with the tab group 12c, the support member 34 and the first welding rod 31 are further moved toward the tab group 12c by the moving means 37, whereby the interposition member 35 causes the tab group 12c to move. Can be pressed. Further, when the support portion 34 and the first welding rod 31 are moved toward the tab group 12c by the moving means 37, the spring member 36 is bent, so that the first welding rod 31 is moved toward the tab group 12c. be able to. Therefore, the pressing of the interposition member 35 to the tab group 12c and the contact of the first welding rod 31 to the tab group 12c can be performed by one apparatus, and the resistance welding apparatus 30 can be simplified. In addition, the connection work between the tab group 12c and the conductive member 19a can be simplified.

  (6) The interposition member 35 has insulating properties. Therefore, when the tab group 12c and the conductive member 19a are to be connected by resistance welding, the interposition member 35 is welded to the tab group 12c even if the distal end surface 32a of the main body 32 and the contact portion 35a come into contact with each other. Can be prevented.

In addition, you may change the said embodiment as follows.
In the embodiment, the interposition member 35 only needs to be formed of a material having lower conductivity than the metal foils 121 and 131. According to this, when trying to connect the tab groups 12c, 13c and the conductive members 19a, 19b by resistance welding, even if the tip surface 32a of the main body portion 32 and the contact portion 35a of the interposition member 35 come into contact, Since the current flows more easily through the tab groups 12c and 13c than through the interposition member 35, the interposition member 35 can be prevented from being welded to the tab groups 12c and 13c. Moreover, when the interposition member 35 is formed of a metal material having a lower conductivity than the metal foils 121 and 131, the interposition member 35 is preferably flat. According to this, when the tab groups 12c and 13c are pressed by the interposition member 35, it is difficult to apply local surface pressure to the tab groups 12c and 13c. If there is a portion where the surface pressure is locally high, current may flow between the interposed member 35 and the tab group 12c, 13c at that location, and welding may occur. However, by making the interposition member 35 into a flat plate shape, the surface pressure is made uniform, and the current can hardly flow through the interposition member 35 to the tab groups 12c and 13c. As a result, the interposed member 35 can be prevented from being welded to the tab groups 12c and 13c.

In the embodiment, the interposition member 35 may be, for example, an insulating coating on the entire outer surface of the metal plate. In short, it is sufficient that the interposition member 35 has an insulating property.
In the embodiment, the interposed member 35 may be provided on a part of the periphery of the welded portion 33.

In the embodiment, the interposition member 35 only needs to be interposed between the distal end surface 32a of the main body 32 and the tab groups 12c and 13c, and the shape thereof is not particularly limited.
In the embodiment, the length H in the thickness direction of the interposed member 35 and the protruding length L of the welded portion 33 from the distal end surface 32a of the main body portion 32 may be the same length.

  In the embodiment, the pressing mechanism is provided separately with moving means for moving the interposition member 35 toward the tab groups 12c and 13c and moving means for moving the first welding rod 31 toward the tab groups 12c and 13c. Also good.

In the embodiment, the interposition member 35 may be fixed to the distal end surface 32 a of the main body 32 in advance.
In the embodiment, it is not necessary to provide a pressing mechanism that presses the interposed member 35 toward the tab groups 12c and 13c.

In the embodiment, the interposition member 35 may not be flat, and only the tab groups 12c and 13c may be flat.
In embodiment, the welding part 33 may be cylindrical, for example, and the shape of the welding part 33 is not specifically limited.

  In the embodiment, the stacked electrode assembly 11 configured by interposing the separator 14 between the positive electrode sheet 12 and the negative electrode sheet 13 and laminating a plurality of these in a certain direction is used. Absent. For example, a wound-type electrode assembly configured by interposing a strip-shaped separator between a strip-shaped positive electrode sheet and a negative electrode sheet and winding them around a winding axis in a spiral manner may be used. . Here, the wound electrode assembly refers to an electrode assembly obtained by winding a series of positive electrode sheets, negative electrode sheets, and separators in layers. In the case of the wound electrode assembly, the metal foil is wound, whereby the tabs are stacked at the same location to form a tab group.

  In the embodiment, the secondary battery 10 is applied as the power storage device. However, the present invention is not limited thereto, and may be a power storage device such as an electric double layer capacitor.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery as a power storage device, 11 ... Electrode assembly, 12b, 13b ... Tab, 12c, 13c ... Tab group, 19a, 19b ... Conductive member, 30 ... Resistance welding device, 31 ... First welding rod, 32a ... a tip surface corresponding to the facing surface, 33 ... a welded portion, 34 ... a support portion, 35 ... an interposition member, 35a ... a contact portion, 35h ... an insertion hole, 36 ... a spring member constituting a pressing mechanism, 37 ... a pressing mechanism. Constructing moving means, 41 ... second welding rod, 121, 131 ... metal foil.

Claims (9)

Resistance welding a tab group formed by laminating tabs projecting from one end of a metal foil constituting a layered electrode assembly of a power storage device, and a conductive member electrically connected to the tab group A resistance welding device connected by
A first welding rod arranged on the tab group side;
A second welding rod disposed on the conductive member side,
The first welding rod has a facing surface that faces the tab group, and a welding portion that protrudes from the facing surface toward the tab group,
A resistance welding apparatus comprising: a contact portion that can contact the facing surface; and an interposed member interposed between the facing surface and the tab group.   The resistance welding apparatus according to claim 1, further comprising a pressing mechanism that presses the interposition member toward the tab group.   The resistance welding apparatus according to claim 1 or 2, wherein the tab group side of the interposition member is flat.   The insertion member is formed with an insertion hole through which the welded portion can be inserted, and the contact portion is formed around the insertion hole on a surface facing the facing surface. The resistance welding apparatus according to any one of claims 1 to 3.   The pressing mechanism includes a spring member having one end connected to the interposition member and the other end connected to a support portion supporting the first welding rod, and the support portion and the first welding rod connected to the tab. The resistance welding apparatus according to claim 2, further comprising a moving unit that moves the group toward the group.   The resistance welding apparatus according to claim 1, wherein the interposition member is made of a material having a lower conductivity than the metal foil.   The resistance welding apparatus according to claim 1, wherein the interposition member has an insulating property. Resistance welding a tab group formed by laminating tabs projecting from one end of a metal foil constituting a layered electrode assembly of a power storage device, and a conductive member electrically connected to the tab group A resistance welding method using a resistance welding apparatus to be connected by
The resistance welding apparatus includes:
A first welding rod arranged on the tab group side;
A second welding rod disposed on the conductive member side,
A resistor comprising an interposing step of interposing an interposition member having a contact portion capable of contacting an opposing surface facing the tab group in the first welding rod between the opposing surface and the tab group. Welding method.   The resistance welding method according to claim 8, further comprising a pressing step of pressing the interposition member toward the tab group side.