JP6364972B2 - Power storage device and method for manufacturing power storage device - Google Patents

Description

  The present invention relates to a power storage device and a method for manufacturing the power storage device.

  Conventionally, vehicles such as EVs (Electric Vehicles) and PHVs (Plug in Hybrid Vehicles) have been mounted with lithium-ion secondary batteries or nickel-hydrogen secondary batteries as power storage devices that store power supplied to electric motors and the like. . This type of secondary battery has an electrode assembly in which electrodes are stacked in layers over a plurality of layers.

  For example, as shown in Patent Document 1, a current collecting portion group in which core exposed portions (hereinafter referred to as “current collecting portions”) of each electrode overlap each other and a conductive member such as an electrode terminal include a laser or the like. It is welded using. In Patent Document 1, in a state in which the current collectors are stacked so that the front ends of the current collector groups become inclined surfaces, the inclined surfaces are welded to uniformly weld a wide area to reduce the resistance.

JP 2011-76776 A

  However, in Patent Document 1, since the conductive member is arranged on the side opposite to the inclined surface of the current collecting unit group, the current collecting unit that is closest to the conductive member among the current collecting units constituting the current collecting unit group. The current collector is welded to the conductive member, while the other current collector is welded to the adjacent current collector. For this reason, in patent document 1, there exists a possibility that it may become difficult to make the electrical resistance between a current collection part group and a electrically-conductive member uniform.

  This invention was made paying attention to the problem which exists in the said prior art, The objective is the electrical storage apparatus which can suppress that the electrical resistance between an electroconductive member and a current collection part group becomes non-uniform | heterogenous. And providing a method of manufacturing the power storage device.

  A power storage device that solves the above-described problem is a power storage device comprising: an electrode assembly in which electrodes are layered over a plurality of layers; and a conductive member that is electrically connected to the electrode assembly, The electrode has an active material layer, a conductive current collecting member that supports the active material layer, and a current collecting portion made of a metal foil connected to the current collecting member, and the electrode assembly includes: The current collector part of the electrode has a current collector part group that overlaps in layers, and the shape of the current collector part group is shifted in a predetermined direction in order of the tip of the current collector part for each layer or for each plurality of layers. The conductive member is arranged along the plurality of step portions, and the conductive member and the current collecting portion group include the plurality of step portions. It is summarized that it is welded at a plurality of steps that are part or all of the above.

  According to this configuration, the shape of the current collecting portion group is a stepped shape including a plurality of step portions, and the conductive member and the current collecting portion group include a plurality of steps that are part or all of the plurality of step portions. Welded at the part. For this reason, compared with the structure which arrange | positions a electrically-conductive member on the opposite side to the surface which is step-shaped among the current collection part groups conventionally, more current collection parts can be welded with a conductive member. Therefore, it can suppress that the electrical resistance between a electrically-conductive member and a current collection part group becomes nonuniform.

  About the said electrical storage apparatus, it is preferable that the said electrically-conductive member and the said current collection part group are welded by the opposing surface with the said electrically-conductive member in these step parts. According to this configuration, since the conductive member and the current collecting portion group are welded on the surface of each step portion in the current collecting portion group, the bonding strength can be improved.

  About the said electrical storage apparatus, it is preferable that the said electrically-conductive member and the said current collection part group are laser-welded. According to this configuration, by using laser welding, it is possible to reduce the range of heat generation when welding the conductive member and the current collecting unit group, and to suppress adverse effects on the active material layer of the electrode.

  About the said electrical storage apparatus, it is preferable that the said electrically-conductive member has a recessed part on the opposite side to the welding part of the said electrically-conductive member and the said current collection part group. According to this configuration, since the conductive member has the concave portion on the opposite side to the welded portion with the current collecting portion group, the conductive member can be easily and reliably welded through the concave portion. Therefore, it can suppress that the electrical resistance between a electrically-conductive member and a current collection part group becomes nonuniform.

  The power storage device further includes a sandwiching member that sandwiches the current collecting unit group from a direction in which the current collecting unit overlaps in the current collecting unit group, and the sandwiching member includes the conductive member and the current collecting unit group. It is preferable that it is arranged closer to the base end portion side of the current collecting portion group than the welded portion.

  According to this configuration, it is possible to suppress the movement and deformation of the current collecting parts overlapping in layers from each other, so that the welded part between the current collecting part and the conductive member is accompanied by the movement or deformation of the current collecting part. It can suppress that a load is applied.

  A method of manufacturing a power storage device that solves the above problem includes forming a plurality of step portions by sequentially disposing a tip of the current collector in a predetermined direction for each layer or for each of a plurality of layers, thereby forming the current collector The shape of the group is stepped, and the conductive member and the current collector are irradiated by irradiating a surface of the conductive member arranged along the plurality of step portions on the side opposite to the current collecting portion group. The gist is to weld the group.

  According to this configuration, the conductive member and the current collecting portion group are welded by irradiating the laser on the surface opposite to the current collecting portion group among the conductive members arranged along the plurality of steps. Further, it is possible to omit a protective member for protecting the current collecting unit group while suppressing the electric resistance between the conductive member and the current collecting unit group from becoming non-uniform.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the electrical resistance between an electroconductive member and a current collection part group becomes non-uniform | heterogenous.

The perspective view which shows typically the electrical storage apparatus which decomposed | disassembled one part. FIG. 1 is a sectional view taken along line 1-1 shown in FIG. (A) is sectional drawing which shows an electrode assembly and an electrically-conductive member typically, (b) is sectional drawing which expands and a part of (a) is shown typically, (c) is a current collection tab The top view which shows a group and an electrically-conductive member typically. The schematic diagram for demonstrating the welding method of a current collection tab group and an electrically-conductive member. The schematic diagram for demonstrating the welding method of a current collection tab group and an electrically-conductive member. Sectional drawing which shows typically the electrode assembly and electroconductive member in another embodiment.

Hereinafter, an embodiment of a secondary battery and a method for manufacturing the secondary battery will be described.
As shown in FIG. 1, a secondary battery 10 as a power storage device has a rectangular parallelepiped case 11 made of metal. The case 11 is made of, for example, aluminum or aluminum alloy. The case 11 includes a bottomed square cylindrical case main body 11a and a lid 11b that closes an opening of the case main body 11a. An electrode assembly 12 is accommodated in the case 11. The case 11 is filled with an electrolyte (electrolytic solution) (not shown). The secondary battery 10 of this embodiment is a lithium ion secondary battery.

  The electrode assembly 12 has a substantially rectangular parallelepiped shape as a whole, and is a stacked electrode assembly in which a positive electrode 13 and a negative electrode 14 are alternately stacked over a plurality of layers with a separator 15 interposed therebetween. is there. The positive electrode 13, the negative electrode 14, and the separator 15 have a substantially rectangular sheet shape. The positive electrode 13 and the negative electrode 14 are insulated from each other by the separator 15. In the following description, the direction in which the electrodes 13 and 14 overlap in the electrode assembly 12 is simply referred to as “stacking direction DS”.

  As shown in FIG. 2, the positive electrode 13 includes a substantially rectangular metal foil 13a for a positive electrode, an active material layer 13b that covers a part of both surfaces thereof and includes a positive electrode active material, and a metal foil 13a. And a positive electrode tab 13c as a current collector protruding from one edge (one side). The metal foil 13a is, for example, an aluminum foil. The metal foil 13a serves as a conductive current collecting member that carries the active material layer 13b.

  The positive electrode tab 13c of this embodiment is a part of the metal foil 13a that is not covered with the active material layer 13b. All the positive electrodes 13 constituting the electrode assembly 12 have the same shape and the same configuration. That is, the positive electrode tab 13c of each positive electrode 13 has the same (or substantially the same) length along the protruding direction D1.

  The negative electrode 14 includes a substantially rectangular metal foil 14 a, an active material layer 14 b that covers a part of both surfaces of the metal foil 14 a and contains an active material for the negative electrode, and one edge (one side) of the metal foil 14 a. And a negative electrode tab 14c as a protruding current collector. The metal foil 14a is, for example, a copper foil. The metal foil 14a serves as a conductive current collecting member that carries the active material layer 14b.

  The negative electrode tab 14c of the present embodiment is a part of the metal foil 14a that is not covered with the active material layer 14b. All the negative electrodes 14 constituting the electrode assembly 12 have the same shape and the same configuration. That is, the negative electrode tab 14c of each negative electrode 14 has the same (or substantially the same) length along the protruding direction D1.

  As shown in FIG. 1, the electrode assembly 12 protrudes from the edge portion 12 a of the electrode assembly 12 by laminating the plurality of positive electrodes 13, and the positive electrode tabs 13 c of the positive electrode 13 overlap each other in layers. A positive electrode tab group 13d as a current collecting unit group. In addition, the electrode assembly 12 has a plurality of negative electrodes 14 stacked so that the electrode assembly 12 protrudes from the edge 12a of the electrode assembly 12 and the negative electrode tabs 14c of the negative electrode 14 overlap each other in layers. As a negative electrode tab group 14d.

  The secondary battery 10 has a positive electrode terminal 17 fixed to the lid 11 b so as to protrude outside the case 11, and a negative electrode terminal 18 fixed to the lid 11 b so as to protrude outside the case 11. The positive electrode terminal 17 and the negative electrode terminal 18 are insulated from the lid 11b by an annular insulating member 19.

  The secondary battery 10 includes a conductive member 21 that electrically connects the electrode assembly 12 (positive electrode tab group 13 d) and the positive electrode terminal 17. The positive electrode terminal 17 and the conductive member 21 are electrically connected at the base end portion of the conductive member 21. Further, the positive electrode tab group 13d is a state in which all the positive electrode tabs 13c constituting the positive electrode tab group 13d are gathered together on one end face 12b side of the both end faces of the electrode assembly 12 in the stacking direction DS, and The tip of the conductive member 21 is welded in a state of being bent so as to extend along the edge 12a.

  Further, the secondary battery 10 includes a conductive member 22 that electrically connects the electrode assembly 12 (negative electrode tab group 14 d) and the negative electrode terminal 18. The negative electrode terminal 18 and the conductive member 22 are electrically connected at the base end portion of the conductive member 22. The negative electrode tab group 14d is a state in which all the negative electrode tabs 14c constituting the negative electrode tab group 14d are gathered to the end surface 12b side of the electrode assembly 12, and is bent so as to extend along the edge 12a. And is welded to the tip of the conductive member 22.

  Hereinafter, the shape of the negative electrode tab group 14d and the conductive member 22 and the joining structure of the negative electrode tab group 14d and the conductive member 22 will be described in detail. The shape of the positive electrode tab group 13d and the conductive member 21 and the joining structure between the positive electrode tab group 13d and the conductive member 21 are the same as those of the negative electrode tab group 14d and the conductive member 22, and therefore a detailed description thereof will be given. Omitted.

  As shown in FIGS. 3A to 3C, in the negative electrode tab group 14d, the plurality of negative electrode tabs 14c are sloped in the shape of the tip portion of the negative electrode tab group 14d and stepped in a cross section when enlarged. Are stacked. In other words, the shape of the negative electrode tab group 14d is a staircase shape including a plurality of step portions 14e by shifting the tip of the negative electrode tab 14c sequentially in the protruding direction D1 as a predetermined direction for each layer with respect to the edge portion 12a. It is the shape. In other words, with respect to the tip of the negative electrode tab 14c that protrudes most in the protruding direction D1, the tip of the negative electrode tab 14c is sequentially shifted in the direction opposite to the protruding direction D1 (direction toward the edge 12a) for each layer. It can also be grasped. In addition, that the shape of a front-end | tip part is a slope shape (inclined surface) means that the virtual plane which contacts each negative electrode tab 14c turns into an inclined surface.

  The conductive member 22 is a substantially rectangular metal plate such as copper. The conductive member 22 has a shape slightly twisted so that the base end side thereof is parallel to the lid 11b and the tip end side thereof is along the inclined surface of the negative electrode tab group 14d. The positive electrode conductive member 21 is, for example, a metal plate of aluminum or aluminum alloy.

  The conductive member 22 and the negative electrode tab group 14d are welded to the inclined surface of the negative electrode tab group 14d, that is, a plurality of step portions 14e, which are all of the plurality of step portions 14e, as shown in black in the drawing. Yes. More specifically, the conductive member 22 and the negative electrode tab group 14d are welded to each other at the facing surface 14f facing the conductive member 22 of the stepped portions 14e. In addition, as will be described later, in the present embodiment, the conductive member 22 and the negative electrode tab group 14d are welded (laser welding) using a welding laser. In the following description, a portion welded to the conductive member 22 in each negative electrode tab 14c is referred to as a welded portion 14g.

  Next, a method for manufacturing a secondary battery will be described together with its operation, focusing on a method for welding the conductive member 22 and the negative electrode tab 14c. The secondary battery 10 of the present embodiment is manufactured through a manufacturing process including a stacking process, a molding process, an arrangement process, and a welding process described below.

  As shown in FIGS. 4 and 5, first, in the laminating step, the electrode assembly 12 is obtained by alternately laminating the positive electrode 13 and the negative electrode 14 with the separator 15 interposed therebetween. Next, in the molding process, all the negative electrode tabs 14c constituting the negative electrode tab group 14d are gathered together toward the end surface 12b side of the electrode assembly 12, thereby forming the shape of the tip portion of the negative electrode tab group 14d into an inclined surface (inclined surface). To form.

  As described above, the lengths of the negative electrode tabs 14c along the protruding direction D1 are the same (or substantially the same). For this reason, in the molding process, the tips of the negative electrode tabs 14c of the negative electrode 14 that are stacked at a position separated from the end surface 12b by gathering the negative electrode tabs 14c toward the end surface 12b are closer to the edge 12a. It arranges so that it may adjoin sequentially. That is, in the forming step, the tips of the negative electrode tabs 14c are sequentially shifted in the protruding direction D1 for each layer to form a plurality of step portions 14e, and the shape of the negative electrode tab group 14d is stepped.

  Next, in the arranging step, the conductive member 22 is arranged so that the tip side is along the inclined surface of the negative electrode tab group 14d. That is, in the arrangement step, the conductive member 22 is arranged along the plurality of step portions 14e. At this time, the facing surface 14f of each step 14e is in surface contact with the conductive member 22, respectively.

  Next, in the welding process, the conductive member 22 and the negative electrode tab 14c are melted by irradiating the surface of the conductive member 22 opposite to the negative electrode tab group 14d with a laser 25a for welding from the laser irradiation device 25. The negative electrode tab group 14d and the conductive member 22 are welded together. In the welding process, as indicated by an arrow in the figure, the irradiation position of the laser 25a is reciprocated along the protruding direction D1, thereby welding the conductive member 22 and the opposing surface 14f of each negative electrode tab 14c, and welding portions 14g is formed (indicated in black in the figure).

  In the welding process, the intensity (output) of the laser 25a and the irradiation time of the laser 25a at each part are set such that the portion of each negative electrode tab 14c that contacts the conductive member 22 and the conductive member 22 melt. Yes. In laser welding, for example, it is possible to generate heat in a narrower range compared to resistance welding or the like, and therefore, the heat generated by welding has an adverse effect on the active material layer 14b constituting the negative electrode 14. Can be suppressed.

  Through such a welding process, the conductive member 22 and the negative electrode tab group 14d are welded at the facing surface 14f of each stepped portion 14e. Therefore, since the conductive member 22 and the negative electrode tab group 14d are electrically connected by the plurality of negative electrode tabs 14c, the conventional conductive member 22 and the negative electrode tab group 14d are electrically connected to the conductive member 22 by the single negative electrode tab 14c. Compared with the configuration, the electrical resistance between the conductive member 22 and the negative electrode tab group 14d can be made small and uniform.

  Further, if the conductive member 22 and the negative electrode tab group 14d are welded by resistance welding or the like, a protective member made of, for example, a copper metal plate is required. For example, the protective member is interposed between the electrode rod of spot welding and the negative electrode tab group 14d, thereby suppressing the negative electrode tab 14c constituting the negative electrode tab group 14d from being broken by pressurization from the electrode bar. . On the other hand, in this embodiment, since the welding is performed by the laser 25a, the protective member as described above can be omitted. In addition, since the shaping | molding process, arrangement | positioning process, and welding process about the positive electrode tab group 13d and the electrically-conductive member 21 are the same as that of the case of the negative electrode tab group 14d and the electrically-conductive member 22, the detailed description is abbreviate | omitted.

  Thereafter, the positive electrode tab group 13d and the negative electrode tab group 14d are bent along the edge 12a of the electrode assembly 12 to be in the state shown in FIGS. The conductive members 21 and 22 are electrically connected to the terminals 17 and 18, respectively. And the electrode assembly 12 is accommodated in the case 11 with the electrolyte, and the secondary battery 10 is completed.

Therefore, according to the above embodiment, the following effects can be obtained.
(1) The shape of the negative electrode tab group 14d is stepped, and the conductive member 22 and the negative electrode tab group 14d are welded by a plurality of step portions 14e. For this reason, compared with the structure which arrange | positions the electrically-conductive member 22 on the opposite side to the inclined surface which is step shape among the negative electrode tab groups 14d conventionally, more negative electrode tabs 14c are directly welded with the electrically-conductive member 22. it can. Therefore, it is possible to prevent the electrical resistance between the conductive member 22 and the negative electrode tab group 14d from becoming uneven. The same applies to the positive electrode tab group 13d and the conductive member 21.

  (2) Since the negative electrode tab group 14d and the conductive member 22 are welded at the facing surface 14f of each step portion 14e in the negative electrode tab group 14d, compared with the configuration in which welding is performed at the tip of the negative electrode tab 14c, Strength can be improved.

  (3) By using the laser 25a for welding, it is possible to reduce the range of heat generation when welding the negative electrode tab group 14d and the conductive member 22, and to suppress adverse effects on the active material layer 14b of the negative electrode 14. . The same applies to the positive electrode tab group 13d and the conductive member 21.

  (4) Of the conductive members 22 arranged along the plurality of step portions 14e, the negative electrode tab group 14d and the conductive member 22 are welded by irradiating the surface opposite to the negative electrode tab group 14d with the laser 25a. . For this reason, in this embodiment, it becomes possible to omit the protective member for protecting the negative electrode tab group 14d.

The embodiment is not limited to the above, and may be embodied as follows, for example.
As shown in FIG. 6, for the secondary battery 10, the conductive member 22 may have a recess 22 a on the opposite side of the welded portion 14 g with the negative electrode tab group 14 d. In this case, the recess 22a may be formed in a long groove shape extending along the protruding direction D1 from the stepped portion 14e closest to the edge 12a to the stepped portion 14e closest to the edge 12a in the protruding direction D1 of the negative electrode tab 14c. According to this configuration, by irradiating the concave portion 22a with the laser 25a, the laser 25a having a lower intensity can be uniformly and reliably welded as compared with the case where the concave portion 22a is not provided. Therefore, it is possible to prevent the electrical resistance between the conductive member 22 and the negative electrode tab group 14d from becoming uneven. The conductive member 21 can be similarly changed.

  As shown in FIG. 6, the secondary battery 10 further includes a sandwiching member 27 that sandwiches the negative electrode tab group 14d from the stacking direction DS, and the sandwiching member 27 is a welded portion between the conductive member 22 and the negative electrode tab group 14d. 14g may be arrange | positioned at the base end part side (edge part 12a side) of the negative electrode tab group 14d. According to this configuration, since the negative electrode tabs 14c that are layered can be prevented from moving or deforming in a direction away from each other, welding of the negative electrode tab 14c and the conductive member 22 is accompanied by the movement or deformation of the negative electrode tab 14c. It can suppress that a load is applied to the part 14g.

  In addition, the above-described holding member 27 may be removed after the welding process is finished, or may be housed in the case 11 without being removed as it is, and may be the secondary battery 10 provided with the holding member 27. It can change similarly about the positive electrode tab group 13d.

  In addition to or instead of the clamping member 27 described above, the negative electrode tabs 14c constituting the negative electrode tab group 14d may be temporarily fixed by resistance welding or the like. It can change similarly about the positive electrode tab group 13d.

(Circle) the positive electrode tab 13c and the negative electrode tab 14c may be gathered near the end surface side on the opposite side to the end surface 12b of the electrode assembly 12. FIG.
The electrode assembly 12 may have a plurality of negative electrode tab groups 14d by dividing the plurality of negative electrode tabs 14c and gathering them together. It can change similarly about the positive electrode tab group 13d.

  O It is good also considering the front-end | tip part of 14 d of negative electrode tab groups as step shape by laminating | stacking the negative electrode 14 from which the length of the negative electrode tab 14c along the protrusion direction D1 differs. It can change similarly about the positive electrode tab group 13d.

  The shape of the negative electrode tab group 14d may be a stepped shape including a plurality of step portions 14e by shifting the tip of the negative electrode tab 14c in the protruding direction D1 in order for each of a plurality of layers with respect to the edge portion 12a. . It can change similarly about the positive electrode tab group 13d.

The shape of the tip may be stepped only for either one of the negative electrode tab group 14d and the positive electrode tab group 13d.
The negative electrode tab group 14d and the conductive member 22 may be welded at a plurality of step portions 14e that are a part of the plurality of step portions 14e. The positive electrode tab group 13d and the conductive member 21 can be similarly changed.

  (Circle) between the inclined surface of the negative electrode tab group 14d, and the electrically-conductive member 22, the welding part 14g may be continuously formed along the protrusion direction D1. The positive electrode tab group 13d and the conductive member 21 can be similarly changed.

The negative electrode tab group 14d and the conductive member 22 may be joined by resistance welding or ultrasonic welding. The positive electrode tab group 13d and the conductive member 21 can be similarly changed.
The shape of the conductive member 21 or the conductive member 22 may be a flat plate shape. That is, the shape of each conductive member 21, 22 can be changed as appropriate.

The electrode assembly 12 may be a wound electrode assembly in which a belt-like positive electrode 13 and a belt-like negative electrode 14 are wound.
The negative electrode 14 may have the active material layer 14b only on one side. The positive electrode 13 can be similarly changed.

  The negative electrode tab 14c may be provided by bonding another metal foil to the metal foil 14a. It can change similarly about the positive electrode tab 13c. Moreover, the positive electrode 13 or the negative electrode 14 may use metal fiber or a foam metal instead of metal foil as a current collection member. And the positive electrode tab 13c or the negative electrode tab 14c should just consist of metal foil, and should be connected to the current collection member.

The secondary battery 10 is not limited to a lithium ion secondary battery, and may be another secondary battery such as a nickel hydrogen secondary battery or a nickel cadmium secondary battery.
O Not only the secondary battery 10, but also a power storage device such as an electric double layer capacitor or a lithium ion capacitor may be used.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery (electric storage apparatus), 12 ... Electrode assembly, 12a ... Edge, 13 ... Positive electrode (electrode), 13a ... Metal foil (current collection member), 13b ... Active material layer, 13c ... Positive electrode tab ( Current collecting part), 13d ... positive electrode tab group, 14 ... negative electrode (electrode), 14a ... metal foil (current collecting member), 14b ... active material layer, 14c ... negative electrode tab (current collecting part), 14d ... negative electrode tab group , 14e: stepped portion, 14f: facing surface, 14g: welded portion, 21: conductive member, 22: conductive member, 22a: concave portion, 27: clamping member.

Claims (6)

A power storage device comprising: an electrode assembly in which electrodes are stacked in layers over a plurality of layers; and a conductive member electrically connected to the electrode assembly,
The electrode has an active material layer, a conductive current collecting member carrying the active material layer, and a current collecting portion made of a metal foil connected to the current collecting member,
The electrode assembly has a current collecting portion group in which current collecting portions of the electrodes overlap each other, and the shape of the current collecting portion group is the tip of the current collecting portion for each layer or for each plurality of layers. Is a staircase shape including a plurality of step portions by sequentially shifting in a predetermined direction,
The conductive member is disposed along the inclined surface of one of the more formed on the plurality of step portions,
The power storage device, wherein the conductive member and the current collecting unit group are welded at a plurality of step portions that are part or all of the plurality of step portions.
  The power storage device according to claim 1, wherein the conductive member and the current collecting unit group are welded on a surface of the plurality of stepped portions facing the conductive member.   The power storage device according to claim 1, wherein the conductive member and the current collecting unit group are laser-welded.   The power storage device according to any one of claims 1 to 3, wherein the conductive member has a recess on a side opposite to a welded portion between the conductive member and the current collecting unit group. A clamping member that clamps the current collecting unit group from a direction in which the current collecting unit overlaps the current collecting unit group;
5. The power storage device according to claim 1, wherein the clamping member is disposed closer to a proximal end portion of the current collecting portion group than a welded portion between the conductive member and the current collecting portion group. apparatus. A method for manufacturing a power storage device according to any one of claims 1 to 5,
A plurality of step portions are formed by sequentially shifting the tips of the current collecting portions in a predetermined direction for each layer or for each of a plurality of layers, thereby forming the current collecting portion group in a step shape, and The conductive member and the current collector portion are welded to each other by irradiating a laser to a surface opposite to the current collector portion among the conductive members arranged along the step of Device manufacturing method.