Energy storage element

Abstract

To provide a power storage element capable of improving a quality of bonding between a lamination part and a collector of an electrode.SOLUTION: A power storage element 10 comprises: an electrode body 300 having a lamination part 320; and a collector 400 connected to the lamination part 320. The lamination part 320 is nipped by a first part (an electrode connection part 420) as one part of the collector 400 in a first direction and a second part (a patch 500) as the other part of the collector 400 or the patch 500. At least one (the patch 500) of the first and second parts includes a projection part 510 in which a convex part 511 projected toward the other one (the electrode connection part 420) is formed. At least one part of the other one is arranged at a position nipping the lamination part 320 with the projection part 510 in the first direction. A gap 800 is formed at a position adjacent to the projection part 510 between the first and second parts. At a position overlapping with the projection part 510 when viewed from the first direction, a laser weld part 700 in which the first part and the lamination part 320 are welded with a laser is formed.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electricity storage element including an electrode body having a stacked portion where electrode plates are stacked and a current collector connected to the stacked portion.

Background Art

[0002] Conventionally, an electricity storage element including an electrode body having a stacked portion where electrode plates are stacked and a current collector, and in which the stacked portion of the electrode body and the current collector are laser welded, is widely known. For example, Patent Document 1 discloses a secondary battery (electricity storage element) in which a tab group (stacked portion) of an electrode assembly (electrode body) and a conductive member (current collector) are laser welded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above conventional electricity storage element, when joining the stacked portion of the electrode body and the current collector by laser welding, if a gap is generated in the laser welding target portion due to, for example, floating of the electrode plates in the stacked portion, the welding quality between the electrode body and the current collector may deteriorate. For example, if a gap is generated in the laser welding target portion, the melted portion of the electrode plate shrinks and solidifies to fill the gap during welding, so that breakage may occur at the interface between the melted portion and the unmelted portion of the electrode plate. If a gap is generated in the laser welding target portion, spatter or blowholes may also occur during welding. As a result, the quality of the joining between the stacked portion of the electrode body and the current collector may deteriorate.

[0005] An object of the present invention is to provide an electricity storage element capable of improving the quality of joining between the stacked portion of the electrode body and the current collector.

Means for Solving the Problems

[0006] To achieve the above objective, an energy storage element according to one aspect of the present invention comprises an electrode body having a laminated portion in which electrode plates are stacked, and a current collector connected to the laminated portion, wherein the laminated portion is arranged in a first direction sandwiched between a first portion which is a part of the current collector and a second portion which is another part of the current collector or a backing plate, and at least one of the first portion and the second portion has a protruding portion which has a convex portion that protrudes toward the other, and at least a part of the other portion is arranged in a position that sandwiches the laminated portion with the protruding portion in the first direction, and a gap is formed between the first portion and the second portion adjacent to the protruding portion, and a laser-welded portion is formed where the first portion and the laminated portion are laser-welded at a position that overlaps with the protruding portion when viewed from the first direction.

[0007] A different aspect of the present invention relates to an energy storage element comprising an electrode body having a laminated portion in which electrode plates are stacked, and a current collector connected to the laminated portion, wherein the laminated portion is arranged in a first direction adjacent to a first portion which is a part of the current collector, the first portion has a protruding portion which has a convex portion that protrudes toward the laminated portion, a gap is formed between the first portion and the laminated portion at a position adjacent to the protruding portion, a laser-welded portion is formed where the first portion and the laminated portion are laser-welded at a position which overlaps with the protruding portion when viewed from the first direction, and the laser-welded portion is formed to penetrate the first portion and the laminated portion in the first direction.

[0008] The present invention can be realized not only as such an energy storage element, but also as a method for manufacturing such an energy storage element, a method for joining the laminated portion of the electrode body to the current collector, or a combination of the laminated portion of the electrode body and the current collector. [Effects of the Invention]

[0009] The energy storage element of the present invention makes it possible to improve the quality of the bonding between the laminated portion of the electrode body and the current collector. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view showing the external appearance of an energy storage element according to an embodiment. [Figure 2] Figure 2 is a perspective view showing the components arranged inside the container of the energy storage element according to the embodiment. [Figure 3] Figure 3 is an exploded perspective view showing the individual components of the energy storage element according to the embodiment. [Figure 4] Figure 4 is a front view and a cross-sectional view showing the configuration of the electrode body, current collector, backing plate, and laser welding section according to the embodiment. [Figure 5] Figure 5 is a cross-sectional view showing a method for forming a laser-welded joint by laser welding an electrode body and a current collector according to an embodiment. [Figure 6] Figure 6 is a cross-sectional view showing the configuration of a laser-welded section according to a modified example 1 of the embodiment. [Figure 7] Figure 7 is a cross-sectional view showing the configuration of a laser-welded section according to a modified example 2 of the embodiment. [Figure 8] Figure 8 is a cross-sectional view showing the configuration of a laser-welded section according to a modified example 3 of the embodiment. [Figure 9A] Figure 9A is a cross-sectional view showing the configuration of a laser-welded section according to a modified example 4 of the embodiment. [Figure 9B] Figure 9B is a cross-sectional view showing the configuration of a laser-welded section according to a modified example 5 of the embodiment. [Modes for carrying out the invention]

[0011] An energy storage element according to one aspect of the present invention comprises an electrode body having a laminated portion in which electrode plates are stacked, and a current collector connected to the laminated portion, wherein the laminated portion is arranged in a first direction sandwiched between a first portion which is a part of the current collector and a second portion which is another part of the current collector or a backing plate, and at least one of the first portion and the second portion has a protruding portion which has a convex portion that protrudes toward the other, and at least a part of the other portion is arranged in a position that sandwiches the laminated portion with the protruding portion in the first direction, and a gap is formed between the first portion and the second portion adjacent to the protruding portion, and a laser-welded portion is formed where the first portion and the laminated portion are laser-welded at a position that overlaps with the protruding portion when viewed from the first direction.

[0012] According to this, the energy storage element includes having a laminated portion that is positioned in a state sandwiched between a first part, which is part of a current collector, and a second part, which is another part of the current collector or a backing plate, in a first direction. At least one of the first and second parts has a protruding portion that has a convex portion that projects toward the other, and at least a part of the other is positioned in a position that sandwiches the laminated portion with the protruding portion in the first direction. A gap is formed between the first and second parts at a position adjacent to the protruding portion, and a laser-welded portion is formed where the first part and the laminated portion are laser-welded at a position that overlaps with the protruding portion when viewed from the first direction. In other words, at least one of the first and second parts (current collector or backing plate) is provided with a protruding portion that has a convex portion that projects toward the other, and by applying it to the laminated portion and sandwiching the laminated portion with at least a part of the other, the interface between the members is compressed. At this time, a gap is formed between the first and second parts at a position adjacent to the protruding portion. This suppresses the floating of the electrode plates in the laminated portion. In other words, by suppressing the occurrence of gaps in the area to be laser-welded, the quality of the joint between the laminated portion of the electrode body and the current collector can be improved.

[0013] The protruding portion may have a recess that is indented toward the convex portion at a position opposite to the convex portion.

[0014] According to this, since the protruding portion has a recessed portion recessed toward the convex portion at a position facing the convex portion, the thickness of the protruding portion becomes thin, so the output during laser welding can be reduced. Therefore, the temperature rise of the laser welded portion can be suppressed. Accordingly, it is possible to further improve the quality of the joining between the laminated portion of the electrode body and the current collector.

[0015] The thickness of the protruding portion of the protruding part may be thinner than the thickness of at least one of the first part and the second part at a portion adjacent to the protruding portion.

[0016] According to this, since the thickness of the protruding portion of the protruding part is made thinner than the thickness of at least one of the first part and the second part at a portion adjacent to the protruding portion, the output during laser welding can be further reduced. Therefore, the temperature rise of the laser welded portion can be further suppressed. Accordingly, it is possible to further improve the quality of the joining between the laminated portion of the electrode body and the current collector.

[0017] One of the first part and the second part may have a first convex portion as the convex portion, and the other of the first part and the second part may have a plane larger than the first convex portion or a second convex portion as the convex portion protruding toward the first convex portion at a position facing the first convex portion.

[0018] According to this, one of the first part and the second part has a first convex portion as the convex portion, and the other of the first part and the second part has a plane larger than the first convex portion or a second convex portion as the convex portion protruding toward the first convex portion at a position facing the first convex portion, so that the protruding portion can be easily applied to the laminated portion and the boundary surface between the members can be easily brought into contact. Therefore, the floating of the electrode plate in the laminated portion is further suppressed, and the gap between the laser welding target portions can be suppressed. Accordingly, it is possible to further improve the quality of the joining between the laminated portion of the electrode body and the current collector.

[0019] In a second direction orthogonal to the first direction, a pair of the gaps may be formed at a position sandwiching the protruding portion between the first part and the second part.

[0020] According to this, in the second direction perpendicular to the first direction, a pair of gaps are formed at the position flanking the protrusion between the first and second parts, making it easier to bring the protrusion into contact with the laminated part. As a result, the protrusion can be compressed in a more balanced manner. Therefore, the quality of the bond between the laminated part of the electrode body and the current collector can be further improved.

[0021] The laser-welded portion may be formed to penetrate at least one of the first portion and the second portion in the first direction.

[0022] According to this, the laser-welded portion is formed by penetrating one of the first and second portions in the first direction, thereby penetrating a protruding portion that projects toward the other. In other words, the lifting of the electrode plates in the laminated portion is further suppressed, and the gap in the laser-welded area can be suppressed. Therefore, the quality of the joint between the laminated portion of the electrode body and the current collector can be further improved.

[0023] A different aspect of the present invention relates to an energy storage element comprising an electrode body having a laminated portion in which electrode plates are stacked, and a current collector connected to the laminated portion, wherein the laminated portion is arranged in a first direction adjacent to a first portion which is a part of the current collector, the first portion has a protruding portion which has a convex portion that protrudes toward the laminated portion, a gap is formed between the first portion and the laminated portion at a position adjacent to the protruding portion, a laser-welded portion is formed where the first portion and the laminated portion are laser-welded at a position which overlaps with the protruding portion when viewed from the first direction, and the laser-welded portion is formed to penetrate the first portion and the laminated portion in the first direction.

[0024] According to this, the energy storage element has a laminated portion that is arranged in a state adjacent to a first portion which is part of the current collector in a first direction, and the first portion has a protruding portion which has a convex portion that protrudes toward the laminated portion. A gap is formed between the first portion and the laminated portion at a position adjacent to the protruding portion, and a laser-welded portion is formed where the first portion and the laminated portion are laser-welded at a position that overlaps with the protruding portion when viewed from the first direction, and the laser-welded portion is formed to penetrate the first portion and the laminated portion in the first direction. In other words, the first portion which has a protruding portion which has a convex portion that protrudes toward the laminated portion is brought into contact with the laminated portion, and the laminated portion is sandwiched between the first portion and the jig during joining, so that the interface between the members is compressed. At this time, a gap is formed between the first portion and the laminated portion at a position adjacent to the protruding portion. As a result, the floating of the electrode plate in the laminated portion is suppressed and the gap in the laser-welded area can be suppressed. Therefore, the quality of joining between the laminated portion of the electrode body and the current collector can be improved.

[0025] The following description of an energy storage element according to an embodiment (and its modifications) of the present invention will be given with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples and are not intended to limit the present invention. Dimensions and other specifications are not strictly illustrated in each figure. In each figure, the same or similar components are denoted by the same reference numerals.

[0026] In the following description and drawings, the direction in which the pair of electrode terminals (positive and negative, hereinafter the same) of the energy storage element are aligned, the direction in which the pair of current collectors are aligned, or the direction in which the short sides of the container face each other is defined as the X-axis direction. The direction in which the long sides of the container face each other, the thickness direction of the container, the stacking direction of the electrode plates at the joint (laser weld) between the electrode body and the current collector, the direction in which the current collector and electrode body are aligned at the joint, the direction in which the current collector, electrode body and backing plate are aligned at the joint, or the direction in which the laser light is irradiated at the joint is defined as the Y-axis direction. The direction in which the container body and lid of the energy storage element are aligned, the direction in which the electrode connection part (leg part) of the current collector extends, or the vertical direction is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect each other (orthogonal in this embodiment). Depending on the usage, the Z-axis direction may not be the vertical direction, but for the sake of explanation below, the Z-axis direction will be described as the vertical direction.

[0027] In the following explanation, the X-axis positive direction refers to the direction of the X-axis arrow, and the X-axis negative direction refers to the direction opposite to the X-axis positive direction. The same applies to the Y-axis and Z-axis directions. Below, the Y-axis direction will also be referred to as the first direction, and the X-axis direction as the second direction. Expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where they are not strictly those directions or orientations. Two directions being orthogonal does not only mean that the two directions are perfectly orthogonal, but also that they are substantially orthogonal, meaning that a difference of a few percent may be included. In the following explanation, when the term "insulation" is used, it means "electrical insulation".

[0028] (Embodiment) [1. General description of the energy storage element 10] First, a general description of the energy storage element 10 in this embodiment will be given using Figures 1 to 3. Figure 1 is a perspective view showing the external appearance of the energy storage element 10 according to this embodiment. Figure 2 is a perspective view showing the components arranged inside the container 100 of the energy storage element 10 according to this embodiment. Specifically, Figure 2 is a perspective view showing the configuration when the container body 110 is separated from the energy storage element 10, and shows the state after the current collector 400 is joined to the electrode body 300. Figure 3 is an exploded perspective view showing each component of the energy storage element 10 according to this embodiment when it is disassembled. Specifically, Figure 3 is a perspective view showing the components other than the container body 110 shown in Figure 2 disassembled, and shows the state before the current collector 400 is joined to the electrode body 300.

[0029] The energy storage element 10 is a secondary battery (single cell) capable of charging and discharging electricity, and specifically, is a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 may be used as a battery for driving or starting the engine of mobile vehicles such as automobiles, motorcycles, watercraft, ships, snowmobiles, agricultural machinery, construction machinery, or railway vehicles for electric railways. Examples of automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicles. Examples of railway vehicles for electric railways include electric trains, monorails, maglev trains, and hybrid trains equipped with both diesel engines and electric motors. The energy storage element 10 may also be used as a stationary battery for household or commercial use.

[0030] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, but may be a secondary battery other than a non-aqueous electrolyte secondary battery, or a capacitor. The energy storage element 10 may not be a secondary battery, but a primary battery that allows the user to use the stored electricity without charging. The energy storage element 10 may be a battery using a solid electrolyte. The energy storage element 10 may be a pouch-type energy storage element. In this embodiment, the energy storage element 10 is shown in a flat rectangular parallelepiped shape (square), but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, but may be cylindrical, oval cylindrical, or a polygonal prism shape other than a rectangular parallelepiped.

[0031] As shown in Figure 1, the energy storage element 10 comprises a container 100, a pair of electrode terminals 200 (positive and negative), and a pair of upper gaskets 210 (positive and negative). As shown in Figures 2 and 3, the container 100 houses a pair of lower gaskets 220 (positive and negative), an electrode body 300, a pair of current collectors 400 (404 and 405) (positive and negative), and a pair of backing plates 500 (positive and negative). An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but it is not shown in the illustration. There are no particular restrictions on the type of electrolyte as long as it does not impair the performance of the energy storage element 10, and various types can be selected. In addition to the above components, spacers placed to the side or below the electrode body 300, an insulating film enclosing the electrode body 300, etc., may be placed.

[0032] The container 100 is a rectangular parallelepiped (square or box-shaped) case having a container body 110 with an opening formed therein and a lid 120 that closes the opening of the container body 110. The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100. The container body 110 has a pair of flat, rectangular short sidewalls 111 on both sides (short sides) in the X-axis direction, a pair of flat, rectangular long sidewalls 112 on both sides (long sides) in the Y-axis direction, and a flat, rectangular bottom wall 113 in the negative Z-axis direction. The lid 120 is a rectangular plate-shaped member that constitutes the lid of the container 100 and is arranged extending in the X-axis direction in the positive Z-axis direction of the container body 110. The lid 120 is provided with a gas discharge valve 121 for releasing pressure when the pressure inside the container 100 rises excessively, and an injection section 122 for injecting electrolyte into the container 100, etc.

[0033] With this configuration, the container 100 is sealed inside by welding or other means to the container body 110 and the lid 120 after the electrode body 300 and the lid 120 have been placed inside the container body 110. The material of the container 100 (container body 110 and lid 120) is not particularly limited and may be a weldable metal such as stainless steel, aluminum, aluminum alloy, or iron, or it may be made of resin.

[0034] The electrode body 300 is an energy storage element (power generation element) that comprises a positive electrode plate, a negative electrode plate, and a separator, and is capable of storing electricity. The positive electrode plate is an electrode plate on which a positive electrode active material layer is formed on a positive electrode base layer which is a long strip-shaped current collector foil made of aluminum or an aluminum alloy. The negative electrode plate is an electrode plate on which a negative electrode active material layer is formed on a negative electrode base layer which is a long strip-shaped current collector foil made of copper or a copper alloy. As the current collector foil, any known material such as nickel, iron, stainless steel, titanium, calcined carbon, conductive polymer, conductive glass, or Al-Cd alloy can be used as appropriate. As the positive electrode active material and negative electrode active material used in the positive electrode active material layer and negative electrode active material layer, any known material can be used as long as it is an active material capable of intercalating and releasing lithium ions. The separator can be a microporous sheet or nonwoven fabric made of resin.

[0035] The electrode body 300 has a laminated portion 320 in which electrode plates 301 are stacked. In other words, the electrode body 300 is formed by stacking a positive electrode plate, a negative electrode plate, and a separator. Specifically, the electrode body 300 is formed by winding a separator between the positive electrode plate and the negative electrode plate. More specifically, the electrode body 300 is formed by winding the positive electrode plate and the negative electrode plate with the separator in between, offset from each other in the direction of the winding axis. The winding axis is a hypothetical axis that serves as the central axis when winding the positive electrode plate, the negative electrode plate, etc., and in this embodiment, it is a straight line parallel to the X-axis direction passing through the center of the electrode body 300. The positive electrode plate and the negative electrode plate have portions at their respective offset ends where the active material is not formed (coated) and the base material layer is exposed (non-active material layer portion).

[0036] As a result, the electrode body 300 has a positive electrode laminated portion 320 at one end in the winding axis direction, where the portions of the positive electrode plate that do not have an active material layer are laminated and bundled, and a negative electrode laminated portion 320 at the other end in the winding axis direction, where the portions of the negative electrode plate that do not have an active material layer are laminated and bundled. The laminated portion 320 is the part in which the electrode plates (positive electrode plate or negative electrode plate) are laminated in the lamination direction (Y axis direction). In other words, the electrode body 300 has an electrode body main body portion 310 that constitutes the main body of the electrode body 300, and a pair of laminated portions 320 (positive electrode and negative electrode) that protrude from the electrode body main body portion 310 on both sides in the X axis direction. The electrode body main body portion 310 is an oval-shaped portion (active material layer forming portion) formed by winding together the portions of the positive electrode plate and the negative electrode plate where the active material layer is formed (coated) and a separator. In this embodiment, the cross-sectional shape of the electrode body 300 (electrode body main body portion 310) is shown as an oval shape, but it may also be circular, elliptical, polygonal, or the like.

[0037] The electrode terminals 200 are terminal members (positive and negative terminals) that are electrically connected to the electrode body 300 via the current collector 400. In other words, the electrode terminals 200 are metal members that guide the electricity stored in the electrode body 300 to the external space of the energy storage element 10 and introduce electricity into the internal space of the energy storage element 10 to store electricity in the electrode body 300. The electrode terminals 200 are made of a conductive material such as aluminum, aluminum alloy, copper, or copper alloy. The electrode terminals 200 are connected (joined) to the current collector 400 by crimping or the like, and are attached to the cover 120.

[0038] Specifically, as shown in Figure 3, the electrode terminal 200 is fixed to the cover 120 together with the current collector 400 by inserting the shaft portion 201 into the through hole 211 of the upper gasket 210, the through hole 123 of the cover 120, the through hole 221 of the lower gasket 220, and the through hole 413 of the current collector 400, and then crimping them. The method of connecting (joining) the electrode terminal 200 and the current collector 400 is not limited to crimping, and welding methods such as ultrasonic welding, laser welding or resistance welding, or mechanical joining other than crimping, such as screw fastening, may also be used.

[0039] The upper gasket 210 is a plate-shaped, rectangular member (positive electrode upper gasket and negative electrode upper gasket) positioned between the lid 120 of the container 100 and the electrode terminal 200, insulating and sealing the space between the lid 120 and the electrode terminal 200. A through hole 211 is formed in the center of the upper gasket 210 into which the shaft portion 201 of the electrode terminal 200 is inserted. The lower gasket 220 is a plate-shaped, rectangular member (positive electrode lower gasket and negative electrode lower gasket) positioned between the lid 120 of the container 100 and the current collector 400, insulating the space between the lid 120 and the current collector 400. A through hole 221 is formed in the center of the lower gasket 220 into which the shaft portion 201 of the electrode terminal 200 is inserted.

[0040] The upper gasket 210 and the lower gasket 220 may be formed from any material that has insulating properties, but may also be formed from insulating materials such as polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyetherether ketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyethersulfone (PES), ABS resin, or composite materials thereof.

[0041] The current collector 400 is connected to the laminated portion 320 of the electrode body 300. Specifically, the current collector 400 is positioned on both sides of the electrode body 300 in the X-axis direction and is connected (joined) to the laminated portion 320 of the electrode body 300 and the electrode terminals 200, and is a current collecting member (positive electrode current collector and negative electrode current collector) having conductivity and rigidity that electrically connects the electrode body 300 and the electrode terminals 200. More specifically, the current collector 400 is a plate-shaped member that is bent and positioned along the side wall of the container body 110 and the lid 120. The current collector 400 is fixedly connected (joined) to the lid 120. With this configuration, the electrode body 300 is held (supported) suspended from the lid 120 by the current collector 400, and shaking due to vibrations and shocks is suppressed. The material of the current collector 400 is not particularly limited, but the positive electrode current collector 400 may be made of aluminum or an aluminum alloy, similar to the positive electrode base material layer of the electrode body 300, and the negative electrode current collector 400 may be made of copper or a copper alloy, similar to the negative electrode base material layer of the electrode body 300.

[0042] As shown in Figure 3, the current collectors 404 in the positive X-axis direction and 405 in the negative X-axis direction, of the positive and negative electrode current collectors 400, have shapes that are symmetrical with respect to the YZ plane. Each current collector 400 (404 and 405) has a terminal connection portion 414 and an electrode connection portion 420 which is a leg portion extending from the terminal connection portion 414 in the negative Z-axis direction.

[0043] The terminal connection portion 414 is the base of the current collector 400 that is connected (joined) to the electrode terminal 200. Specifically, the terminal connection portion 414 is located on the electrode terminal 200 side (upper side, Z-axis positive direction) of the current collector 400, and is a flat plate-shaped portion parallel to the XY plane in which the aforementioned circular through hole 413 is formed, and is electrically and mechanically connected (joined) to the electrode terminal 200. The electrode connection portion 420 is the leg portion of the current collector 400 that is connected (joined) to the electrode body 300. In other words, the electrode connection portion 420 is located on the electrode body 300 side (lower side, Z-axis negative direction) of the current collector 400, and is electrically and mechanically connected (joined) to the electrode body 300. Specifically, the electrode connection portion 420 is a long, flat plate-shaped portion extending in the Z-axis-negative direction from the Y-axis-positive end of the terminal connection portion 414, and is positioned in the Y-axis-positive direction of the laminated portion 320 of the electrode body 300 and joined to the laminated portion 320. The flat plate shape is not limited to a perfectly flat plate shape, and may have protrusions or holes, or may have a part missing.

[0044] In this embodiment, the electrode connection portion 420, which is part of the current collector 400, is an example of the first part, and the backing plate 500 is an example of the second part. The laminated portion 320 is positioned in a state where it is sandwiched between the electrode connection portion 420 (first part), which is part of the current collector 400, and the backing plate 500 (second part) in the first direction (Y-axis direction). Specifically, the backing plate 500 is positioned to sandwich the electrode body 300 between the current collector 400 and the backing plate 500, and is a member that is joined to the electrode body 300 together with the current collector 400 while the electrode body 300 is sandwiched between the backing plate 500 and the backing plate 500. In other words, the backing plate 500 is a cover that protects the laminated portion 320, positioned to sandwich the laminated portion 320 between the electrode connection portion 420 and the backing plate 500. The backing plate 500 has protrusions 510 in the Z-axis positive direction and the Z-axis negative direction, respectively.

[0045] Specifically, the backing plate 500 is a flat, rectangular metal member positioned in the negative Y-axis direction of the laminated portion 320 and extending in the Z-axis direction along the laminated portion 320. The protrusion 510 of the backing plate 500 is positioned to face the laminated portion 320 in the Y-axis direction. The material of the backing plate 500 is not particularly limited, but the backing plate 500 for the positive electrode may be made of aluminum or an aluminum alloy, similar to the positive electrode base layer of the electrode body 300, and the backing plate 500 for the negative electrode may be made of copper or a copper alloy, similar to the negative electrode base layer of the electrode body 300. The flat shape is not limited to a perfectly flat plate shape, and may have protrusions or holes, or may be partially missing.

[0046] With this configuration, the electrode connection portion 420, the laminated portion 320, and the backing plate 500 are joined together with the laminated portion 320 sandwiched between them, and a laser-welded portion 700 (see Figure 2) is formed on the protrusion 510 formed on the backing plate 500. In this embodiment, for one electrode connection portion 420, two laser-welded portions 700 are formed on two protrusions 510 aligned in the Z-axis direction. In other words, two laser-welded portions 700 are formed on one current collector 400, and four laser-welded portions 700 are formed on one energy storage element 10.

[0047] [2. Explanation of the laser-welded section 700] [2.1 Description of the configuration of the laser-welded section 700] Next, the configuration of the laser-welded portion 700 between the laminated portion 320 of the electrode body 300, the electrode connection portion 420 of the current collector 400, and the protruding portion 510 of the backing plate 500 will be described in detail. Figure 4 is a front view and a cross-sectional view showing the configuration of the electrode body 300, current collector 400, backing plate 500, and laser-welded portion 700 according to this embodiment. Specifically, Figure 4(a) is a front view showing an enlarged view of the laser-welded portion 700 and its surrounding configuration shown in Figure 2, viewed from the negative Y-axis direction. Figure 4(b) is a cross-sectional view showing the configuration when the configuration of Figure 4(a) is cut along the IV(b)-IV(b) section. Figure 4 shows the configuration of one of the laser-welded portions 700 and its surrounding configuration shown in Figure 2, but the other laser-welded portions 700 and their surrounding configurations have a similar configuration.

[0048] As shown in these figures, the electrode connection portion 420 of the current collector 400 is positioned in the positive Y-axis direction of the laminated portion 320 of the electrode body 300, and the backing plate 500 is positioned in the negative Y-axis direction of the laminated portion 320, thereby forming a laser-welded portion 700 to which the electrode body 300, the current collector 400, and the backing plate 500 are joined. In addition to the protruding portion 510 described above, the backing plate 500 has a flat portion 520, which is a flat portion (non-protruding portion), adjacent to the protruding portion 510. The protruding portion 510 is a circular portion (bulge) when viewed from the Y-axis direction, which bulges out from the flat portion 520 in the positive Y-axis direction. The flat portion 520 is an annular portion that surrounds the periphery (entire circumference) of the protruding portion 510 when viewed from the Y-axis direction. The flat portion is not limited to a perfectly flat shape. That is, the flat portion may have an uneven shape to the extent that it can be called flat, may have a part missing, or may be inclined.

[0049] As shown in Figure 4, the protruding portion 510 has a convex portion 511 that protrudes in the positive Y-axis direction (towards the laminated portion 320) and a concave portion 512 formed at a position opposite to the convex portion 511 and recessed toward the convex portion 511. In other words, the protruding portion 510 has a concave portion 512 at a position opposite to the convex portion 511 and recessed toward the convex portion 511. The convex portion 511 is a circular convex portion that protrudes in the positive Y-axis direction from the Y-axis positive surface of the flat portion 520, when viewed from the Y-axis direction. The concave portion 512 is a circular concave portion that is recessed in the positive Y-axis direction from the Y-axis negative surface of the flat portion 520, when viewed from the Y-axis direction. The inner circumferential surface of the concave portion 512 is smaller than the outer circumferential surface of the convex portion 511 when viewed from the Y-axis direction. In other words, the surface of the backing plate 500 in the negative Y-axis direction is concave, forming a recess 512, and the surface of the backing plate 500 in the positive Y-axis direction protrudes, forming a convex portion 511 at the position opposite to the recess 512.

[0050] As shown in Figure 4(b), the thickness of the protruding portion of the protruding part 510 (thickness in the Y-axis direction) is thinner than the thickness (thickness in the Y-axis direction) of the portion adjacent to the protruding part 510 (flat portion 520 in this embodiment) of at least one of the electrode connection portion 420 (first portion) and the backing plate 500 (second portion) (backing plate 500 in this embodiment). Thus, at least one of the electrode connection portion 420 (first portion) and the backing plate 500 (second portion) (backing plate 500 in this embodiment) has a protruding part 510 with a convex portion 511 formed thereon that protrudes toward the other (electrode connection portion 420 in this embodiment). At least a portion of the other (electrode connection portion 420) is positioned in the first direction (Y-axis direction) to sandwich the laminated portion 320 with the protruding part 510. The laminated portion 320 is compressed by the protruding portion 410 of the backing plate 500, but the flat portion 520 of the backing plate 500 and the laminated portion 320 are not in contact, and there is a gap. Since the laser-welded portion 700 is formed on the protruding portion 510, there may or may not be a gap between the flat portion 520 and the laminated portion 320.

[0051] The laser-welded portion 700 is formed by laser welding. Therefore, the laser-welded portion 700 has the shape of a weld formed by laser welding. Specifically, as shown in Figure 4(b), the laser-welded portion 700 has a shape that tapers as it moves away from the surface on which the laser light was incident. In other words, the size of the laser-welded portion formed on the laser-irradiated surface of the laser-welded portion 700 is larger than the size of the tip of the laser-welded portion 700 formed at a position away from the laser light. Specifically, when the laser is irradiated from the negative Y-axis direction to the positive Y-axis direction, the size of the laser-welded portion formed on the negative Y-axis surface of the recess 512 (the width formed in the recess 512 of the laser-welded portion 700 in the X-axis direction in the XY plane) is larger than the size of the tip of the laser-welded portion 700 (the width of the tip of the laser-welded portion 700 in the X-axis direction in the XY plane).

[0052] As shown in Figure 4(b), one of the electrode connection portion 420 (first portion) and the backing plate 500 (second portion) (the backing plate 500 in this embodiment) has a first protrusion 511 as a convex portion 511. The other of the electrode connection portion 420 (first portion) and the backing plate 500 (second portion) (the electrode connection portion 420 in this embodiment) has a larger plane than the first protrusion 511 at a position opposite to the first protrusion 511. Specifically, the electrode connection portion 420 that faces the Y-axis positive plane of the protrusion 511 (corresponding to the first protrusion) 511 of the projection portion 510 across the stacked portion 320 is a plane that is larger in size (area) than the protrusion 511 when viewed from the Y-axis direction. As a result, the protruding portion 510 of the backing plate 500 can be more easily brought into contact with the laminated portion 320, and the interface surfaces of the members (the interface between the current collector 400 and the electrode plate 301, the interface between the electrode plates 301, the interface between the backing plate 500 and the electrode plate 301, or the interface between the current collector 400 and the backing plate 500) can be more easily brought into contact.

[0053] When the protrusion 510 is pressing against the laminated portion 320 (the state in which the laser-welded portion 700 is formed), a gap 800 is formed between the electrode connection portion 420 (first portion) and the backing plate 500 (second portion) at a position adjacent to the protrusion 510. As shown in Figure 4(a), the gap 800 is formed in an annular shape, surrounding the circular protrusion 510 when viewed from the negative Y-axis direction. In other words, the gap 800 is formed continuously around the entire circumference of the protrusion 510.

[0054] As shown in Figure 4(b), the gap 800 is a space located within the recess 330 formed in the laminated portion 320 by the protrusion 510. In other words, the gap 800 is a space enclosed by the inner circumferential surface of the recess 330 formed in the laminated portion 320, the outer circumferential surface of the protrusion 510, and the Y-axis positive direction surface of the flat portion 520. The gap 800 is larger than the gap between the multiple electrode plates 301 arranged between the protrusion 511 of the protrusion 510 and the current collector 400, and also larger than the gap between the multiple electrode plates 301 arranged between the flat portion 520 and the current collector 400. The multiple electrode plates 301 are electrode plates stacked to form the laminated portion 320. This makes it easier to bring the protrusion 510 into contact with the laminated portion 320, allowing for closer and more balanced compression between the multiple electrode plates 301. Therefore, the laser welded portion 700 can be formed more easily.

[0055] The laser-welded portion 700 is formed by laser welding the electrode connection portion 420 (first portion) and the laminated portion 320 at a position that overlaps with the protruding portion 510 when viewed from the first direction (Y-axis direction). In other words, the laser-welded portion 700 is a weld formed by laser welding the protruding portion 510, the laminated portion 320 of the electrode body 300, and the electrode connection portion 420 of the current collector 400 at the point where they overlap. As shown in Figure 4(a), the laser-welded portion 700 is formed in the central part of the protruding portion 510. As shown in Figure 4(b), the laser-welded portion 700 is a weld (molten portion) that penetrates the protruding portion 510 and the laminated portion 320 in the Y-axis direction and extends in the Y-axis direction up to the electrode connection portion 420. Specifically, the laser-welded portion 700 is a laser-welded mark formed by laser welding the protruding portion 510 of the backing plate 500, the laminated portion 320 of the electrode body 300, and the electrode connection portion 420 of the current collector 400 in the area where the protruding portion 510, the laminated portion 320, and the electrode connection portion 420 overlap.

[0056] The laser-welded portion 700 is formed in the first direction (Y-axis direction) by penetrating at least one of the electrode connection portion 420 (the first portion in this embodiment) and the backing plate 500 (the second portion in this embodiment) (the backing plate 500 in this embodiment). Specifically, the laser-welded portion 700 is formed in the region where the electrode plates 301 are in contact with each other when viewed from the Y-axis direction. More specifically, the laser-welded portion 700 is formed from the Y-axis negative direction surface of the recess 512 of the protrusion 510, penetrating the surface of the convex portion 511 facing the laminated portion 320, penetrating the laminated portion 320, and extending to a part of the electrode connection portion 420 (the Y-axis negative portion). In other words, the laser-welded portion 700 is a melted mark formed by the melting of the protrusion 510, the laminated portion 320, and the Y-axis negative portion of the electrode connection portion 420.

[0057] In this embodiment, the laser-welded portion 700 is formed up to the Y-axis negative portion of the electrode connection portion 420, but it may also be formed up to the Y-axis central portion of the electrode connection portion 420, or it may be formed penetrating the electrode connection portion 420 in the Y-axis direction. Specifically, the laser-welded portion 700 may melt the surface of the electrode connection portion 420 facing the laminated portion 320 and not penetrate the electrode connection portion 420, or it may penetrate to the opposite surface of the electrode connection portion 420 from the surface facing the laminated portion 320 (the Y-axis positive surface of the electrode connection portion 420). In this case, a laser welding mark may be formed on the opposite surface of the electrode connection portion 420 from the surface facing the laminated portion 320 (the Y-axis positive surface of the electrode connection portion 420).

[0058] [2.2 Description of the method for forming the laser-welded joint 700] Next, the method for forming the laser-welded portion 700, that is, the method for joining the electrode body 300 and the current collector 400, will be described in detail as part of the manufacturing method of the energy storage element 10. Figure 5 is a cross-sectional view showing the method for joining the electrode body 300 and the current collector 400 to form the laser-welded portion 700 according to this embodiment. Specifically, Figure 5(a) shows the state before the jig 20 is applied to the backing plate 500 as part of the manufacturing method of the energy storage element 10 (method for forming the laser-welded portion 700), Figure 5(b) shows the state in which the jig 20 is applied to the backing plate 500 and the laminated portion 320 is compressed, and Figure 5(c) shows the laser welding process.

[0059] First, as shown in Figure 5(a), the electrode body 300 is positioned so as to sandwich it between the backing plate 500 and the current collector 400. Specifically, the protruding portion 510 of the backing plate 500 and the electrode connection portion 420 of the current collector 400 sandwich the laminated portion 320 in which the electrode plates 301 of the electrode body 300 are stacked. More specifically, the surface of the convex portion 511 of the protruding portion 510, which is positioned in the negative Y-axis direction of the laminated portion 320, and the electrode connection portion 420, which is positioned in the positive Y-axis direction of the laminated portion 320, sandwich the laminated portion 320 in the stacking direction of the electrode plates 301 (Y-axis direction). A jig 20 for compressing the laminated portion 320 is positioned so as to face the surface of the backing plate 500 in the negative Y-axis direction. Specifically, the jig 20 is positioned so as to face the surface of the flat portion 520, which is a flat portion (non-protruding portion) adjacent to the protruding portion of the backing plate 500 in the X-axis direction, in the negative Y-axis direction.

[0060] As shown in Figure 5(b), the jig 20 is placed against the backing plate 500, compressing the laminated portion 320 in the Y-axis direction, thereby forming a gap 800 adjacent to the protrusion 510 in the X-axis direction. Specifically, the jig 20 pushes the backing plate 500 in the positive Y-axis direction, causing the Y-axis positive surface of the protrusion 511 of the protrusion 510 (the surface facing the laminated portion 320) to be pushed in the positive Y-axis direction. This compresses the interface between the members facing the protrusion 510 (the interface between the current collector 400 and the laminated portion 320, the interface between the laminated electrode plates 301 of the laminated portion 320, and the interface between the protrusion 510 and the laminated portion 320). As a result, the gap at the interface between these members becomes smaller, and a gap 800 is formed adjacent to the protrusion 510 in the X-axis direction.

[0061] Next, as shown in Figure 5(c), in the laser welding process, with the backing plate 500, electrode body 300, and current collector 400 superimposed in the Y-axis direction, laser light L is irradiated toward the Y-axis negative surface of the protruding portion 510. As a result, the backing plate 500, electrode body 300, and current collector 400 are laser-welded together, forming the laser-welded portion 700. Specifically, in the laser welding process, the laser light L is irradiated from the Y-axis negative surface of the recess 512 of the protruding portion 510, passes through the Y-axis positive surface of the convex portion 511, penetrates the area where the electrode plates 301 of the laminated portion 320 are in contact, and melts a part of the electrode connection portion 420 of the current collector 400, thereby forming the laser-welded portion 700. The laser welding marks of the laser-welded portion 700 are formed on the Y-axis negative surface of the recess 512. In this embodiment, the laser-welded portion 700 is formed in the center of the recess 512 of the protruding portion 510 when viewed from the direction of irradiation of the laser beam L (Y-axis direction), but it does not have to be in the center.

[0062] The recess 512 of the protruding portion 510 is recessed in the positive Y-axis direction compared to the flat portion 520, which is the portion of the backing plate 500 adjacent to the protruding portion 510 (non-protruding portion) in the X-axis direction. Therefore, the thickness of the protruding portion of the protruding portion 510 (thickness in the Y-axis direction) is thinner than the thickness of the flat portion 520 adjacent to the protruding portion 510 (thickness in the Y-axis direction). Because the laminated portion 320 is compressed by the protruding portion 510, the distance between the protruding portion 510 and the electrode connection portion 420 in the Y-axis direction is smaller than the distance between the flat portion 520 and the electrode connection portion 420. In other words, the thickness of the laminated portion 320 is thinner than before it was compressed by the protruding portion 510. Because the thickness of the protruding portion 510 and the thickness of the laminated portion 320 are thin in the Y-axis direction, the output of the laser light L during laser irradiation can be reduced. Therefore, the temperature rise of the laser-welded portion 700 can be suppressed.

[0063] In the Y-axis direction, the position of the protrusion 510 is lower in the negative Y-axis direction than the position of the flat portion 520 (a recess 512 is formed in the protrusion 510). This allows the position of the laser beam L to be adjusted more accurately during laser irradiation using the recess 512 as a guide. As in this embodiment, even if the jig 20 does not have a space for laser irradiation that matches the size of the recess 512 of the protrusion 510, the position of the protrusion 510 can be easily confirmed using the recess 512 as a guide, and the laser welded portion 700 can be formed.

[0064] [3. Explanation of Effects] As described above, the energy storage element 10 according to the embodiment of the present invention has a laminated portion 320 that is sandwiched in a first direction (Y-axis direction) between a first part (electrode connection portion 420 in this embodiment), which is a part of the current collector 400, and a second part (backing plate 500 in this embodiment), which is another part of the current collector 400 or a backing plate 500. At least one of the first and second parts (backing plate 500 in this embodiment) has a protruding portion 510 on which a convex portion 511 is formed that protrudes toward the other part (electrode connection portion 420 in this embodiment). At least a part of the other part (electrode connection portion 420) is positioned in the first direction (Y-axis direction) to sandwich the laminated portion 320 with the protruding portion 510. A gap 800 is formed between the first part (electrode connection portion 420) and the second part (backing plate 500) at a position adjacent to the protruding portion 510. A laser-welded portion 700 is formed where the first portion (electrode connection portion 420) and the laminated portion 320 are laser-welded together at a position that overlaps with the protruding portion 510 when viewed from the first direction (Y-axis direction).

[0065] In other words, a protruding portion 510 is provided on at least one of the first part (electrode connection part 420) and the second part (backing plate 500), with a convex portion 511 projecting toward the other part (electrode connection part 420), and is applied to the laminated part 320. By sandwiching the laminated part 320 between at least a part of the other part (electrode connection part 420) and the protruding portion 510, the interface between the members is compressed. At this time, a gap 800 is formed between the first part (electrode connection part 420) and the second part (backing plate 500) at a position adjacent to the protruding portion 510. As a result, the jig 20 can easily compress each of the multiple electrode plates 301 laminated in the laminated part 320, and by fixing the electrode plates 301 with a higher surface pressure than in the conventional structure, the floating of the electrode plates 301 in the laminated part 320 is suppressed. In other words, the occurrence of gaps in the laser welding target area is suppressed. This suppresses deformation of the electrode plate 301 during melting and improves the quality of the joint between the laminated portion 320 of the electrode body and the current collector 400. The gap 800 is larger than the gap between the multiple electrode plates 301 arranged between the protruding portion 510 and the current collector 400, and is also larger than the gap between the multiple electrode plates 301 arranged between the flat portion 520 and the current collector 400. The laser welded portion 700 may be point-shaped, linear, or annular.

[0066] The protruding portion 510 has a recess 512 that is recessed toward the protrusion 511 at a position opposite to the protrusion 511. In this way, because the protruding portion 510 has a recess 512 that is recessed toward the protrusion 511 at a position opposite to the protrusion 511, the thickness of the protruding portion 510 in the first direction (Y-axis direction) is reduced, so the output during laser welding can be reduced. As a result, the temperature rise of the laser-welded area 700 can be suppressed, and the quality of the joint between the laminated portion 320 of the electrode body 300 and the current collector 400 can be further improved. In this embodiment, the laser was irradiated toward the laminated portion 320 from the second part having the protruding portion 510 (in this embodiment, the backing plate 500), but even when the laser is irradiated toward the laminated portion 320 from the second part without the protruding portion 510, the heat capacity can be reduced. Therefore, even when the laser is irradiated from the second part, which does not have the protruding portion 510, toward the laminated portion 320, the temperature rise of the laser-welded portion 700 can be suppressed in the same way as when the laser is irradiated from the first part, which has the protruding portion 510, toward the laminated portion 320.

[0067] The thickness of the protruding portion of the protruding portion 510 is thinner than the thickness of the protruding portion 510 and the flat portion 520 of at least one of the first part (electrode connection portion 420 in this embodiment) and the second part (backing plate 500 in this embodiment). As a result, when a laser is irradiated from the second part (backing plate 500) having the protruding portion 510 toward the laminated portion 320, the thickness of the protruding portion of the protruding portion 510 of at least one of the first part (electrode connection portion 420) and the second part (backing plate 500) is thinner than the thickness of the flat portion 520, thereby further reducing the output during laser welding. Therefore, the temperature rise of the laser-welded portion 700 can be further suppressed. Consequently, the quality of the joining between the laminated portion 320 of the electrode body 300 and the current collector 400 can be improved.

[0068] If the first part has a protrusion 510 and the second part does not have a protrusion 510, even when the laser is irradiated from the second part toward the laminated part 320, the heat capacity can be reduced, and the temperature rise of the laser-welded part 700 can be suppressed, similar to when the laser is irradiated from the first part toward the laminated part 320. The thickness of the protruding portion of the protrusion 510 is preferably 30-80%, more preferably 40-60%, and even more preferably about 50% of the thickness of the flat portion 520, which is the non-protruding part of the backing plate 500 (the part adjacent to the protrusion). If the thickness of the protruding portion of the protrusion 510 is 30-80% of the thickness of the flat portion 520, the temperature rise of the laser-welded part 700 can be suppressed by reducing the laser output when laser welding. If the thickness of the protruding portion of the protruding part 510 is 40-60% of the thickness of the flat portion 520, the temperature rise of the laser-welded area 700 can be suppressed more effectively, and the backing plate 500 can be compressed while maintaining the strength of the protruding portion 510. If the thickness of the protruding portion of the protruding part 510 is about 50% of the thickness of the flat portion 520, the temperature rise of the laser-welded area 700 can be suppressed even further, and the backing plate 500 can be compressed while maintaining the strength of the protruding portion 510, thus achieving a good balance of these effects.

[0069] The protruding portion of the protruding portion 510 is the part of the protruding portion 510 that contacts the laminated portion 320 of the electrode body 300. The thickness of the protruding portion 510 that is not laser-welded may be thin or not. Even if the protruding portion 510 has a convex portion 511 but no concave portion 512, if the thickness of the convex portion 511 in the first direction (Y-axis direction) is equal to or thinner than the thickness of the flat portion 520, laser welding can be performed while compressing the laminated portion 320 with a higher surface pressure than in the conventional structure, without increasing the laser output.

[0070] One of the first part (electrode connection part 420 in this embodiment) and the second part (backing plate 500 in this embodiment) (the backing plate 500 in this embodiment) has a protrusion 511 (first protrusion 511). The other of the first part (electrode connection part 420) and the second part (backing plate 500) (the electrode connection part 420 in this embodiment) has a flat surface that is larger than the first protrusion 511 at a position opposite to the first protrusion 511. In other words, one of the first and second parts (backing plate 500) has the first protrusion 511, and the other (electrode connection part 420) has a flat surface that is larger than the first protrusion 511 at a position opposite to the first protrusion 511.

[0071] This makes it easier to bring the protruding portion 510 into contact with the laminated portion 320, and to bring the interface surfaces between the members (the interface between the current collector 400 and the electrode plate 301, the interface between the electrode plates 301 themselves, the interface between the backing plate 500 and the electrode plate 301, or the interface between the current collector 400 and the backing plate 500) into contact more easily. As a result, the jig 20 can easily compress each of the electrode plates 301 laminated in the laminated portion 320, and by fixing the laminated portion with a higher surface pressure than in the conventional structure, the floating of the electrode plates 301 in the laminated portion 320 is suppressed. Therefore, the quality of the bond between the laminated portion 320 of the electrode body 300 and the current collector 400 can be further improved.

[0072] In the second direction (X-axis direction) perpendicular to the first direction (Y-axis direction), a pair of gaps 800 are formed at positions that sandwich the protruding portion 510 between the first part (electrode connection part 420 in this embodiment) and the second part (backing plate 500 in this embodiment). As a result, in the second direction (X-axis direction) perpendicular to the first direction (Y-axis direction), a pair of gaps 800 are formed at positions that sandwich the protruding portion 510 between the first part (electrode connection part 420) and the second part (backing plate 500), making it easier to bring the protruding portion 510 into contact with the laminated part 320. Therefore, the protruding portion 510 can be compressed in a more balanced manner. Consequently, the quality of the bond between the laminated part 320 of the electrode body 300 and the current collector 400 can be further improved.

[0073] The laser-welded portion 700 is formed by penetrating one of the above-mentioned parts (in this embodiment, the backing plate 500) in the first direction (Y-axis direction). As a result, the laser-welded portion 700 is formed by penetrating at least one of the first part and the second part (in this embodiment, the backing plate 500) in the first direction (Y-axis direction), and by penetrating the protruding portion 510 which has a convex portion 511 that protrudes toward the other part (in this embodiment, the electrode connection portion 420). This makes it easier to laser-weld the laminated portion 320 which is fixed with a higher surface pressure than in the conventional structure. Therefore, it is possible to further improve the quality of the joint between the laminated portion 320 of the electrode body 300 and the current collector 400.

[0074] [4. Explanation of variations] Next, modifications of the above embodiment will be described. Figure 6 is a cross-sectional view showing the configuration of the laser welded section 701 according to modification 1 of this embodiment. Figure 7 is a cross-sectional view showing the configuration of the laser welded section 702 according to modification 2 of this embodiment. Figure 8 is a cross-sectional view showing the configuration of the laser welded section 703 according to modification 3 of this embodiment. Figure 9A is a cross-sectional view showing the configuration of the laser welded section 704 according to modification 4 of this embodiment. Figure 9B is a cross-sectional view showing the configurations of the laser welded sections 704 and 705 according to modification 5 of this embodiment. Specifically, Figures 6 to 9B all correspond to Figure 4(b).

[0075] As shown in Figure 6, the laser-welded portion 701 in Modification 1 is formed in place of the laser-welded portion 700 in the above embodiment. In the above embodiment, the laser-welded portion 700 is laser-welded from the negative Y-axis direction, but the laser-welded portion 701 is laser-welded from the positive Y-axis direction. In other words, the laser-welded portion 701 has a laser-welded mark on the positive Y-axis direction surface of the electrode connection portion 420 of the current collector 400.

[0076] The laser-welded portion 701 may have a welding depth in the Y-axis direction that is the same as or shallower than that of the laser-welded portion 700. In Figure 6, the laser-welded portion 701 is shown not to penetrate the protrusion 510 of the backing plate 500, but the laser-welded portion 701 may be formed by penetrating the backing plate 500. In other words, a laser welding mark may be formed on the Y-axis negative surface of the recess 512 of the protrusion 510 of the backing plate 500.

[0077] As shown in Figure 7, the electrode connection portion 421 of the current collector 401 in Modified Example 2 has a protrusion 410. The backing plate 501 in this modified example does not have the protrusion 510 as in the above embodiment. In other words, the protrusion may be formed on the current collector 401 or on the backing plate 501. Specifically, in Figure 7, the laser-welded portion 702 is formed by irradiating the recess 412 of the protrusion 410 with a laser from the Y-axis negative direction, penetrating the convex portion 411, penetrating the laminated portion 320, and melting a part of the backing plate 501.

[0078] The laser-welded portion 702 may have a welding depth in the Y-axis direction that is the same as or shallower than that of the laser-welded portion 700. In Figure 7, the laser-welded portion 702 is shown not to penetrate the backing plate 501, but the laser-welded portion 702 may be formed by penetrating the backing plate 501. The laser-welded portion 702 may be formed by laser irradiation from the Y-axis positive direction surface of the backing plate 501.

[0079] As shown in Figure 8, the electrode connection portion 422 of the current collector 402 in Modification 3 has a protruding portion 410, similar to Modification 2 described above. In other words, Figure 8 shows the energy storage element 10 with the backing plate 501 removed from Modification 2 shown in Figure 7. In this modification, similar to Modification 2 described above, the laser-welded portion 703 is formed by penetrating the protruding portion 410 and the laminated portion 320. Specifically, in Figure 8, the laser-welded portion 703 is formed by laser irradiation from the Y-axis negative direction surface of the recess 412 of the protruding portion 410, penetrating the convex portion 411 and the laminated portion 320. Laser welding marks are formed on the Y-axis negative direction surface of the recess 412 and the Y-axis positive direction surface of the laminated portion 320.

[0080] The laser-welded section 703 shown in Figure 8 may be formed by removing the backing plate after laser welding. If the backing plate is made of a material with a high melting point, such as tungsten, it can be removed even after laser welding, allowing it to be used for laser welding multiple times. This reduces the number of parts and the weight of the energy storage element. Reducing the area occupied by the parts within the container 100 improves the energy density.

[0081] With reference to Figure 5 of the above embodiment, the method for forming the laser-welded portion 703 (method for manufacturing an energy storage element) will be described. As shown in Figure 5(a), the laminated portion 320 is sandwiched in the Y-axis direction (first direction) between the protrusion 410 of the current collector 402 and the backing plate, and the jig 20 is positioned in the negative Y-axis direction of the current collector 402. As shown in Figure 5(b), the jig 20 approaches the backing plate so as to compress the laminated portion 320 in the Y-axis direction, and a gap 800 is formed in the X-axis direction adjacent to the protrusion 410. As shown in Figure 5(c), the laser-welded portion 703 is formed by laser irradiation from the Y-axis negative direction surface of the recess 412 of the protrusion 410, penetrating the convex portion 411 and penetrating the laminated portion 320. At this time, since the backing plate is made of a material with a high melting point that does not melt when irradiated with laser, the laser-welded portion 703 is not formed on the backing plate. As a result, a laser-welded portion 703 without a backing plate is formed as shown in Figure 8.

[0082] The backing plate can be any member that sandwiches the current collector 402 and the laminated portion 320 between the jig 20 during laser welding. The laser-welded portion 703 may be formed by sandwiching the laminated portion 320 between a base-like member made of a material with a high melting point that does not melt at the laser welding temperature and laser welding the current collector 402, and then separating the current collector 402 and the laminated portion 320 from the base after laser welding. Even if the laser-welded portion 703 is formed in this way, as shown in Figure 8, it is sufficient that the laser-welded portion 703 penetrates the protruding portion 410 of the electrode connection portion 422 of the current collector 402 and the laminated portion 320 in the Y-axis direction (first direction).

[0083] As shown in Figure 8, the energy storage element 10 in the modified example 3 includes an electrode body 300 having a laminated portion 320 in which electrode plates 301 are stacked, and a current collector 402 connected to the laminated portion 320. The laminated portion 320 is arranged in a first direction (Y-axis direction) adjacent to a first part (electrode connection portion 422 in this modified example) which is part of the current collector 402. The first part (electrode connection portion 422) has a protruding portion 410 with a convex portion 411 that protrudes toward the laminated portion 320, and a gap 800 is formed between the first part (electrode connection portion 422) and the laminated portion 320 at a position adjacent to the protruding portion 410. A laser-welded portion 703 is formed at a position overlapping with the protruding portion 410 when viewed from the first direction (Y-axis direction), where the first portion (electrode connection portion 422) and the laminated portion 320 are laser-welded, and the laser-welded portion 703 is formed penetrating the first portion (electrode connection portion 422) and the laminated portion 320 in the first direction (Y-axis direction).

[0084] In other words, the first part (electrode connection part 422), which is provided with a protruding part 410 having a convex part 411 that protrudes toward the laminated part 320, is brought into contact with the laminated part 320, and the laminated part 320 is sandwiched between the first part (electrode connection part 422) and the jig 20 during laser welding. As a result, the interface between the members (the interface between the current collector 400 and the electrode plate 301, the interface between the electrode plates 301 themselves, the interface between the backing plate 500 and the electrode plate 301, or the interface between the current collector 400 and the backing plate 500) is compressed. At this time, a gap 800 is formed between the first part (electrode connection part 422) and the laminated part 320 at a position adjacent to the protruding part 410.

[0085] The gap 800 is a space located within the recess 330 formed in the laminated portion 320 by the protrusion 410. In other words, the gap 800 is a space enclosed by the inner circumferential surface of the recess 330 formed in the laminated portion 320, the outer circumferential surface of the protrusion 410, and the Y-axis positive direction surface of the flat portion 430. The gap 800 is larger than the gap between the multiple electrode plates 301 arranged between the convex portion 411 of the protrusion 410 and the current collector 402, and also larger than the gap between the multiple electrode plates 301 arranged between the flat portion 430 and the current collector 402. As a result, the jig 20 can easily compress each of the multiple electrode plates 301 laminated in the laminated portion 320, and by fixing the laminated portion 320 with a higher surface pressure than in the conventional structure, the floating of the electrode plates 301 in the laminated portion 320 is suppressed. Therefore, the quality of the bond between the laminated portion 320 of the electrode body 300 and the current collector 402 can be improved.

[0086] As shown in Figure 9A, the current collector 403 in the modified example 4 has two electrode connection portions 423, and a protrusion is formed on each electrode connection portion 423. Specifically, similar to the current collector 400 shown in Figure 3, the current collector 403 has a terminal connection portion 414 and two electrode connection portions (for example, legs) 423 extending from the terminal connection portion 414 in the negative Z-axis direction. One electrode connection portion 423 located in the negative Y-axis direction is also referred to as electrode connection portion 4231, and the other electrode connection portion 423 located in the positive Y-axis direction is also referred to as electrode connection portion 4232.

[0087] With the laminated portion 320 sandwiched between the protrusion 4101 of the electrode connection portion 4231 and the protrusion 4102 of the electrode connection portion 4232, a laser is irradiated from the Y-axis negative direction surface of the recess 4121 of the protrusion 4101 to form the laser-welded portion 704. In other words, the laminated portion 320 is positioned in a state where it is sandwiched between a first part (electrode connection portion 4231), which is part of the current collector 403, and a second part (electrode connection portion 4232), which is another part of the current collector 403, in the first direction (Y-axis direction). By compressing the laminated portion 320 in this way, a gap 800 is formed in the X-axis direction at a position adjacent to each of the protrusions. In other words, one of the first part (electrode connection part 4231) and the second part (electrode connection part 4232) (electrode connection part 4231) has a first protrusion 4111 as a convex part, and the other of the first and second parts (electrode connection part 4232) has a second protrusion 4112 that is positioned opposite to the first protrusion 4111 and protrudes toward the first protrusion 4111. With the protrusions 4101 and 4102 facing each other in the Y-axis direction and sandwiching the laminated part 320, the laminated part 320 can be compressed more strongly than in the conventional design.

[0088] The laser-welded portion 704 may be formed by penetrating the Y-axis positive plane of the recess 4122 of the protrusion 4102 of the electrode connection portion 4232, or it may be formed by irradiating the Y-axis positive plane of the recess 4122 of the protrusion 4102 of the electrode connection portion 4232 with a laser. In this modified example, the current collector 403 has two electrode connection portions 423, the electrode connection portion 4231 has a protrusion 4101, and the electrode connection portion 4232 has a protrusion 4102, but the combination of members sandwiching the laminated portion 320 is not limited to this. The laminated portion may also be sandwiched between the protrusions of the electrode connection portion of the current collector and the protrusions of the backing plate.

[0089] As shown in Figure 9B, in Modification 5, laser welded sections 704 and 705 are formed. Specifically, in this Modification, similar to Modification 4, the current collector 403 has two electrode connection sections 423, and each electrode connection section 423 has a protrusion. The laser welded section 704 is formed by irradiating the recess 4121 of the protrusion 4101 of the electrode connection section 4231 with a laser from the Y-axis negative direction. The laser welded section 705 is formed by irradiating the recess 4122 of the protrusion 4102 of the electrode connection section 4232 with a laser from the Y-axis positive direction. Since the two electrode connection sections 423 are each provided with protrusions (4101 and 4102) and recesses (4121 and 4122), laser welding can be performed with a low laser power regardless of which protrusion (4101 and 4102) recess (4121 and 4122) the laser is irradiated from. Even if the recess 412 is not provided, the protrusions (4111, 4112) of the protrusions (4101, 4102) compress the laminated portion 320 more strongly than when there are no protrusions (4101, 4102). This makes it easier to suppress deformation of the foil during melting and reduce the quality of the bond. As a result, it is easier to improve the quality of the bond between the electrode body 300 and the current collector 403.

[0090] (Other variations) Although embodiments of the present invention (including modifications thereof) of an energy storage element and a method for manufacturing the same have been described above, the present invention is not limited to these embodiments. The embodiments disclosed herein are illustrative in all respects, and the scope of the present invention includes all modifications in the sense and scope equivalent to the claims. Since the other configurations of the modifications shown below are the same as those of the embodiments described above, a detailed description is omitted.

[0091] In the above embodiment, there may or may not be a gap between the backing plate 500 and the laminated portion 320. In either case, the protruding portion 510 of the backing plate 500 can compress the laminated portion 320, so the laminated portion 320 can be fixed with a higher surface pressure than in the conventional structure. Similarly, as shown in Modification 2, when the electrode connection portion 421 has a protruding portion 410, there may or may not be a gap between the electrode connection portion 421 and the laminated portion 320. The same applies to other modifications.

[0092] In the above embodiment, the protruding portion 510 has a recess 512 that is recessed toward the convex portion 511 at a position opposite to the convex portion 511. However, the protruding portion 510 does not have to have a recess 512. Even in this case, the protruding portion 510 can compress the laminated portion 320, and the laminated portion 320 can be fixed with a higher surface pressure than in the conventional structure.

[0093] In the above embodiment, the thickness of the protruding portion of the protruding portion 510 may be thinner than the thickness of the flat portion 520 adjacent to the protruding portion 510 in at least one of the first and second parts. The thickness of the protruding portion of the protruding portion 510 does not have to be thinner than the thickness of the flat portion 520 adjacent to the protruding portion 510. In other words, the thickness of the protruding portion of the protruding portion 510 may be thicker than the thickness of the flat portion 520 adjacent to the protruding portion 510, or it may be the same as the thickness of the adjacent flat portion 520. The protruding portion is the part of the protruding portion that contacts the laminated portion 320 of the electrode body 300, but the thickness of the protruding portion that does not form a laser weld may be thinner than or not thinner than the thickness of the part adjacent to the protruding portion. When the laser is irradiated from the direction in which the second part, which is facing the laminated portion on either side, is arranged, the first part having the protruding portion does not have to be penetrated, so the thickness of the protruding portion may be thick.

[0094] In the above embodiment, one of the first and second parts has a first protrusion as a convex portion 511, and the other of the first and second parts may have a larger plane than the first protrusion, or a second protrusion as a convex portion 511 projecting toward the first protrusion, at a position opposite to the first protrusion. It is not necessary for there to be a plane larger than the first protrusion at the position opposite to the first protrusion, and the second protrusion may not be present. Even when the laminated portion 320 is sandwiched between the first protrusion and a plane smaller than the first protrusion, the laminated portion 320 can be compressed by the first protrusion, and the laminated portion 320 can be fixed with a higher surface pressure than in the conventional structure. The other of the first and second parts may have a recess that is indented toward the protrusion at a position opposite to the protrusion. If one of the first and second parts has a protrusion, the laminated portion 320 can be sandwiched between the protrusion and the recess, and the laminated portion 320 can be compressed by the protrusion, resulting in the effect of fixing the laminated portion 320 with a higher surface pressure than in the conventional structure.

[0095] In the above embodiment, a pair of gaps 800 may be formed in a second direction (X-axis direction) perpendicular to the first direction (Y-axis direction), at positions that sandwich the protrusion 510 between the first and second parts. More specifically, the gaps 800 are formed continuously around the entire circumference so as to surround the protrusion 510. The gaps 800 may be located anywhere adjacent to the protrusion 510 between the first and second parts. The gaps 800 may be formed intermittently as long as they are adjacent to the protrusion 510, and do not have to be formed in an annular shape. In other words, the gaps 800 may be formed so as to surround the laser-welded part 700, or they may be formed in only one place adjacent to the protrusion 510. The gaps 800 may be formed in two opposite places on either side of the protrusion 510. The second direction may be the X-axis direction or the Z-axis direction.

[0096] In the above embodiment, the laser-welded portion 700 may be formed in the first direction (Y-axis direction) by penetrating at least one of the first portion and the second portion, which have a protrusion 510. The laser-welded portion 700 does not have to be formed by penetrating the one having the protrusion 510. The laser-welded portion 700 may be formed in the first direction by penetrating a current collector or backing plate (which may also be a clamping member) that does not have a protrusion, and by penetrating the laminated portion 320. A current collector or backing plate that does not have a protrusion and is facing the laminated portion 320 on either side of the current collector or backing plate has a protrusion. In this form as well, the laminated portion 320 is compressed by the convex portion 511 of the protrusion 510, so the heat capacity can be reduced and the temperature rise of the laser-welded portion 700 can be suppressed. Therefore, the quality of the joint between the laminated portion of the electrode body and the current collector can be improved.

[0097] In the above embodiment, one laser-welded portion 700 is formed. However, there is no limit to one laser-welded portion 700. Two or more laser-welded portions 700 may be formed. As shown in Figure 9B, a laser-welded portion 704 and a laser-welded portion 705 may be formed. In Figure 9B, the laser-welded portions 704 and 705 are formed by laser irradiation from the recesses (4121, 4122) of the two electrode connection portions (4231, 4232), but they may also be formed by laser irradiation from a single electrode connection portion (for example, 4231). Both the laser-welded portion 704 and the laser-welded portion 705 may be formed by laser irradiation from the Y-axis negative direction plane of the recess 4121 of the electrode connection portion 4231. The laser-welded portion 700 may be circumferentially irradiated with a laser to match the shape of the protruding portion 510, and two laser-welded portions may be formed. In this embodiment, the laser-welded portion 700 is formed in the center of the recess 512, but it may be formed in a protruding portion or not in the center. The laser-welded portion may be formed in two places in the X-axis direction (second direction), or it may be formed by intermittently hitting points to form a circular shape.

[0098] In the above embodiment, the current collector 400 has a shape that includes a terminal connection portion 414 and an electrode connection portion 420, but it may also have a clip-like shape. The current collector 400 may also be a member that sandwiches the laminated portion 320 in the Y-axis direction (first direction). The laminated portion 320 is positioned sandwiched between a first portion, which is part of the clip, and a second portion, which is another part of the clip. Even in this case, the laminated portion 320 is compressed by the protrusions of the protruding portion, so the quality of the bond between the laminated portion of the electrode body and the current collector can be improved. The first portion, which is part of the clip, and the electrode connection portion 420 of the current collector 400 may be superimposed in the Y-axis direction and joined together. With this configuration, the electrode terminals 200 of the energy storage element 10 and the current collector 400 can be connected after the laser welded portion is formed.

[0099] In the above embodiment, the current collector 403 has a terminal connection portion 414 and two electrode connection portions (for example, legs) 423 extending from the terminal connection portion 414 in the negative Z-axis direction. The current collector 403 may have a part of the electrode connection portion 420 extending from the terminal connection portion 414 in the negative Z-axis direction connected to a part of the backing plate 500. The backing plate 500 and the electrode connection portion 420 do not have to be separate parts, and the backing plate 500 and the electrode connection portion 420 may be integrally formed (integrated). Even if a part of the electrode connection portion 420 and a part of the backing plate 500 are connected, the laminated portion 320 is compressed by the convex portion 511 of the protruding portion 510, so the quality of the joint between the laminated portion 320 of the electrode body 300 and the current collector 400 can be improved. By reducing the area occupied by the parts in the container 100, the effect of improving energy density can be obtained. Since the number of parts is reduced, costs can be reduced.

[0100] In the above embodiment, one electrode connection portion 420 is provided on the current collector 400, and one backing plate 500 is placed on one electrode connection portion 420 to form two laser welded portions 700. The number of electrode connection portions 420 provided on the current collector 400, the number of laser welded portions 700 formed on one electrode connection portion 420, and the number of backing plates 500 placed on one electrode connection portion 420 are not particularly limited.

[0101] In the above embodiment, the protruding portion 510, the convex portion 511, the recessed portion 512, the laser-welded portion 700, and the gap 800, etc., are assumed to have a circular shape when viewed from the Y-axis direction (first direction). These shapes are not particularly limited and may be elliptical, oblong, rectangular, or other polygonal shapes when viewed from the Y-axis direction.

[0102] In the above embodiment, the current collector 400, the electrode body 300, and the backing plate 500 are joined together, but other members may also be joined together. The backing plate 500 may not be provided, and the electrode body 300 and the current collector 400 may be joined together.

[0103] In the above embodiment, the electrode body 300 is a wound-type electrode body whose winding axis is parallel to the lid 120. The electrode body 300 may also be a wound-type electrode body whose winding axis is perpendicular to the lid 120. The shape of the electrode body 300 is not limited to a wound type, but may be a stacked type in which flat electrode plates are stacked, or a shape in which the electrode plates and / or separators are folded in a bellows shape (a form in which the separator is made into a bellows shape and sandwiches a rectangular electrode plate, a form in which the electrode plates and separators are stacked and then made into a bellows shape, etc.). The stacked portion 320 may be a tab protruding from the electrode body main portion 310 of the electrode body 300. Specifically, the stacked portion 320 may be a tab that protrudes from the electrode body main portion 310 of the electrode body 300 toward the lid 120 and is integrally formed with the electrode body main portion 310. This tab may be a tab that protrudes from the electrode body main portion 310 away from the container body 110 in the X-axis direction.

[0104] In the above embodiment, the above configuration is applied to all laser welded parts 700, but the above configuration may not be applied to any of the laser welded parts 700. Protrusions may not be provided on all laser welded parts 700.

[0105] The present invention also includes forms constructed by arbitrarily combining the components included in the above embodiments and their modified examples.

[0106] The present invention can be realized not only as a method for manufacturing such an energy storage element and as an energy storage element, but also as a method for joining the electrode body 300 and the current collector 400, a combination of the electrode body 300 and the current collector 400, a joint between the electrode body 300 and the current collector 400, or a combination of the laminated portion 320 of the electrode body 300 and the current collector 400. [Industrial applicability]

[0107] This invention can be applied to energy storage elements such as lithium-ion secondary batteries. [Explanation of Symbols]

[0108] 10 Energy storage elements 20 jigs 100 containers 110 Container body 111 Short side wall section 112 Long side wall section 113 Bottom wall section 120 Lid 200 electrode terminal 201 Shaft 300 Electrode body 301 Pole plate 310 Electrode body part 320 Laminated section 330 recess 400, 401, 402, 403, 404, 405 current collectors 410, 4101, 4102, 510 protrusion 411 Convex part 511, 4111 Convex part (First convex part) 4112 Convex part (Second convex part) 412, 512, 4121, 4122 recess 414 Terminal connection section 420, 421, 422, 423, 4231, 4232 Electrode connection section 430, 520 flat area 500, 501 backing plate 700, 701, 702, 703, 704, 705 Laser Welded Sections 800 gap

Claims

1. A power storage element comprising an electrode body having a laminated portion in which electrode plates are stacked, and a current collector connected to the laminated portion, The laminated portion is arranged in a first direction, sandwiched between a first part which is a part of the current collector and a second part which is another part of the current collector or a backing plate. At least one of the first part and the second part has a protruding portion that projects toward the other, At least a portion of the other is positioned so as to overlap with the protrusion when viewed from the first direction, and is positioned in the first direction so as to sandwich the stacked portion between the protrusion and the other. A gap is formed between the first part and the second part at a position adjacent to the protruding portion. A laser-welded portion is formed where the part and the laminated portion are laser-welded together at a position that overlaps with the protruding portion when viewed from the first direction. Energy storage element.

2. The aforementioned protruding portion has a recess that is indented toward the convex portion at a position opposite to the convex portion. The energy storage element according to claim 1.

3. The thickness of the protruding portion of the aforementioned protrusion is thinner than the thickness of the portion adjacent to the protrusion in at least one of the first and second parts. The energy storage element according to claim 2.

4. One of the first part and the second part has the first protrusion as the protrusion, The other of the first and second parts has a plane larger than the first protrusion, or a second protrusion that protrudes toward the first protrusion, at a position opposite to the first protrusion. The energy storage element according to any one of claims 1 to 3.

5. In a second direction perpendicular to the first direction, a pair of gaps are formed at positions that sandwich the protruding portion between the first and second parts. The energy storage element according to any one of claims 1 to 4.

6. The laser-welded portion is formed to penetrate at least one of the first part and the second part in the first direction. The energy storage element according to any one of claims 1 to 5.

7. A power storage element comprising an electrode body having a laminated portion in which electrode plates are stacked, and a current collector connected to the laminated portion, The stacked portion is arranged in a state parallel to the first portion, which is part of the current collector, in the first direction. The aforementioned part has a protruding portion having a convex portion that protrudes toward the laminated portion, A gap is formed between the aforementioned part and the laminated portion at a position adjacent to the protruding portion. A laser-welded portion is formed at a position that overlaps with the protruding portion when viewed from the first direction, where the part and the laminated portion are laser-welded together. The laser-welded portion is formed to penetrate the part and the laminated portion in the first direction. Energy storage element.

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