Power storage element

Abstract

To provide a power storage element in which reliability of a fusion part as a welding part of a connection part of an electrode body and a collector is improved.SOLUTION: A power storage element comprises: an electrode body 700 that includes a connection part 730 to an end part; and a plate-like collector 500 that is welded in a fusion part 600a in a state where it is overlapped with the connection part to a first direction, and is arranged so that a thickness direction is directed to a first direction Z. The fusion part includes: a first fusion part 610 that is exposed to the side of the connection part in the first direction; and a second fusion part 620 that is exposed to the side of the collector in the first direction. In the case of viewing it from the first direction, the first fusion part and the second fusion part are arranged at a position deviated to a second direction Y orthogonal to the first direction.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a power storage element including an electrode body and a current collector connected to the electrode body.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a secondary battery including a step of connecting an electrode body and a current collector by laser welding. In this secondary battery, an internal current collecting terminal (current collector) includes a pair of joining portions that sandwich an electrode exposed portion of a wound electrode body from a direction intersecting the winding axis direction. The joining portion has an inclined surface that expands outward as it moves away from the winding axis. The method for manufacturing the secondary battery includes a step of expanding the connection portion along the inclined surface to form a stepped shape, and a step of laser-welding and joining the stepped connection portion and the inclined surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above manufacturing method, since a plurality of electrode exposed portions (plate end portions) are shifted and laminated so that the lower layer protrudes with respect to the upper layer, the protruding length of the connection portion, which is a laminate of the plate end portions, from the electrode body main body tends to increase. In order to suppress this protruding length, it is necessary to reduce the shift amount between the upper layer and the lower layer of the plate end portions in the connection portion. In this case, however, in order to sufficiently melt and join a plurality of plate end portions, for example, it is necessary to increase the output of the laser beam. As a result, problems such as an increase in sputtering and melting of the plate end portions, which are metal foils, are likely to occur.

[0005] The present invention has been newly made by the inventor of the present application paying attention to the above problems, and an object thereof is to provide a power storage element in which the reliability of a melted portion, which is a welded portion between a connection portion of an electrode body and a current collector, is improved.

Means for Solving the Problems

[0006] A power storage element according to one aspect of the present invention includes an electrode body having a connection portion at an end, and a plate-shaped current collector welded in a melted portion in a state of being overlapped with the connection portion in a first direction, and the current collector is arranged with its thickness direction facing the first direction, and the melted portion includes a first melted portion exposed on the side of the connection portion in the first direction and a second melted portion exposed on the side of the current collector in the first direction, and when viewed from the first direction, the first melted portion and the second melted portion are arranged at positions shifted in a second direction orthogonal to the first direction. Further, a power storage element according to another aspect of the present invention includes an electrode body having a connection portion at an end, and a plate-shaped current collector welded in a melted portion in a state of being overlapped with the connection portion in a first direction, and the current collector is arranged with its thickness direction facing the first direction, and the melted portion includes a first melted portion exposed on the side of the connection portion in the first direction and a second melted portion exposed on the side of the current collector in the first direction, and the melted portion may have a portion with a width narrower than the widths of both ends in a second direction orthogonal to the first direction between both ends in the first direction.

[0007] A power storage element according to another aspect of the present invention includes an electrode body having a connection portion at an end, and a plate-shaped current collector welded in a melted portion in a state of being overlapped with the connection portion in a first direction, and the current collector is arranged with its thickness direction facing the first direction, and the melted portion may include a first melted portion exposed on the side of the connection portion in the first direction and a second melted portion exposed on the side of the current collector in the first direction.

[0008] According to this configuration, when welding the connection part of the electrode body and the current collector, the first melting part and the second melting part can be formed by the welding operation from the side of the connection part of the electrode body and the welding operation from the side of the current collector. That is, the welding operations for forming the first melting part and the second melting part respectively can be performed with relatively small energy, and the current collector and the connection part can be sufficiently melted together. Therefore, for example, sufficient electrical conductivity performance in the melting part can be ensured without causing sputtering scattering or melting of a part of the connection part. Therefore, the energy storage element according to this aspect is an energy storage element with improved reliability of the melting part which is the welded part between the connection part of the electrode body and the current collector.

[0009] The energy storage element further includes a backing plate disposed so as to sandwich the connection part with the current collector and disposed with the thickness direction facing the first direction, and the first melting part may be exposed on the outer surface which is the surface of the backing plate opposite to the connection part.

[0010] According to this configuration, for example, the connection part formed by laminating the end parts of the electrode plates which are metal foils can be welded while being pressed by the backing plate. In this way, when the laminated end parts of the electrode plates are pressed by the backing plate, it becomes difficult for gaps to occur between adjacent end parts of the electrode plates. Therefore, even when laser welding using laser light is adopted for forming each of the first melting part and the second melting part, a melting part in a good state can be efficiently formed. Thereby, a melting part with improved reliability can be formed in a short time.

[0011] In the melting part, the first melting part and the second melting part may be arranged such that a part of each other overlaps.

[0012] According to this configuration, since the mechanical connection strength in the melting part is improved, the reliability can be improved not only in the electrical connection but also in the mechanical connection in the melting part.

[0013] In a second direction orthogonal to the first direction, when the width of the portion of the first molten part exposed on the side of the connection part is defined as a first width, and the width of the portion of the second molten part exposed on the side of the current collector is defined as a second width, the molten part may have a portion with a third width narrower than the first width and the second width between the position of the first width and the position of the second width in the first direction.

[0014] For example, when forming a molten part by laser welding, on the irradiation side of the laser light, relatively more of the object is melted, and as it goes deeper from there (as the melting depth increases), the amount of melting gradually decreases. Therefore, in order to form a molten part that penetrates the entire area of the object in the irradiation direction, it may be necessary to increase the output of the laser light. However, in this aspect, by irradiating laser light from both sides of the part to be melted, a relatively large amount of melting exists on both the side of the connection part and the side of the current collector, and a molten part can be formed that exists across the entire areas of the connection part and the current collector in the first direction. Therefore, a molten part with a sufficient amount of current conduction can be formed without increasing the output of the laser light used to form the molten part. That is, a molten part with improved reliability is formed.

[0015] When viewed from the first direction, when a virtual line parallel to the first direction passing through the center of the portion of the first molten part exposed on the side of the connection part is defined as a first axis, and a virtual line parallel to the first direction passing through the center of the portion of the second molten part exposed on the side of the current collector is defined as a second axis, in the molten part, the first molten part and the second molten part may be arranged at positions where the first axis and the second axis are separated in a second direction orthogonal to the first direction.

[0016] According to this configuration, for example, the amount of melting in the overlapping portion of the first molten part and the second molten part is reduced, and thereby the total amount of melting (the volume of the molten part) of the molten part increases. Therefore, for example, an increase in the amount of current conduction or an improvement in the connection strength in the molten part can be achieved, and as a result, the reliability of the molten part is improved.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide an energy storage element in which the reliability of a molten part, which is a welded part between a connection part of an electrode body and a current collector, is improved.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, an energy storage element according to an embodiment (and its modification) of the present invention will be described. Note that all of the embodiments described below show comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, manufacturing processes, order of manufacturing processes, etc. shown in the following embodiments are merely examples and are not intended to limit the present invention. Also, in each figure, the dimensions and the like are not strictly illustrated.

[0020] In the following description and drawings, the arrangement direction of a pair of electrode terminals (positive electrode side and negative electrode side) of the energy storage element, the arrangement direction of the pair of current collectors, the arrangement direction of the pair of connection parts of the electrode body, or the opposing direction of the short side surfaces of the container is defined as the X-axis direction. The opposing direction of the long side surfaces of the container, the short side direction of the short side surfaces of the container, or the thickness direction of the container is defined as the Y-axis direction. The arrangement direction of the electrode terminals, the current collectors, and the electrode body, the arrangement direction of the container body and the lid of the energy storage element, the long side direction of the short side surfaces of the container, the winding axis direction of the electrode body, or the vertical direction is defined as the Z-axis direction. These X-axis direction, Y-axis direction, and Z-axis direction are directions that intersect (orthogonal in this embodiment) with each other. Although there may be cases where the Z-axis direction does not become the vertical direction depending on the usage mode, hereinafter, for the sake of convenience of explanation, the Z-axis direction will be described as the vertical direction. Also, in the following description, for example, the X-axis plus direction indicates the arrow direction of the X-axis, and the X-axis minus direction indicates the direction opposite to the X-axis plus direction. The same applies to the Y-axis direction and the Z-axis direction.

[0021] (Embodiment) [1. General description of the energy storage element] First, a general description of the energy storage element 10 in this embodiment will be given with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing the appearance of the energy storage element 10 according to the embodiment. FIG. 2 is an exploded perspective view of the energy storage element 10 according to the embodiment.

[0022] The energy storage element 10 is a secondary battery that can charge and discharge electricity, specifically a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used, for example, as a battery for driving a moving body such as an automobile, motorcycle, watercraft, ship, snowmobile, agricultural machinery, construction machinery, or a railway vehicle for electric railways for engine starting, etc. Examples of the above-mentioned automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and gasoline vehicles. Examples of the above-mentioned railway vehicles for electric railways include trains, monorails, linear motor cars, and hybrid trains equipped with both a diesel engine and an electric motor. Further, the energy storage element 10 can also be used as a stationary battery for household use or for generators, etc.

[0023] Note that the energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. Further, the energy storage element 10 may be a primary battery that can use the stored electricity without the user charging it, rather than a secondary battery. Further, the energy storage element 10 may be a battery using a solid electrolyte. In the present embodiment, a rectangular parallelepiped-shaped (square-shaped) energy storage element 10 is illustrated, but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, and may be a polygonal prism shape, an elliptical cylinder shape, etc. other than a rectangular parallelepiped shape.

[0024] As shown in Fig. 1, the energy storage element 10 includes a container 100, a pair of (positive electrode side and negative electrode side) electrode terminals 200, and a pair of (positive electrode side and negative electrode side) upper gaskets 300. Further, as shown in Fig. 2, inside the container 100, a pair of (positive electrode side and negative electrode side) lower gaskets 400, a pair of (positive electrode side and negative electrode side) current collectors 500, and an electrode body 700 are accommodated. Also, although an electrolytic solution (non-aqueous electrolyte) is enclosed inside the container 100, its illustration is omitted. The type of the electrolytic solution is not particularly limited as long as it does not impair the performance of the energy storage element 10, and various types can be selected. Further, in addition to the above-described components, a spacer disposed above or on the side of the electrode body 700, or an insulating film that wraps the electrode body 700 or the like may be disposed.

[0025] The container 100 is a rectangular parallelepiped (box-shaped) case having a container body 110 with an opening formed therein and a lid body 120 that closes the opening of the container body 110. With such a configuration, after the electrode body 700 and the like are accommodated inside the container body 110, the container body 110 and the lid body 120 are welded or the like, so that the interior can be sealed. The materials of the container body 110 and the lid body 120 are not particularly limited, but are preferably weldable metals such as stainless steel, aluminum, aluminum alloy, iron, and plated steel sheets.

[0026] The container body 110 is a member having a rectangular cylindrical shape with a bottom that constitutes the main body of the container 100, and an opening is formed on the +Z-axis direction side. The lid body 120 is a plate-shaped member that is long in the X-axis direction and rectangular and constitutes the lid portion of the container 100, and is disposed at a position that closes the opening of the container body 110. A gas discharge valve 122 for discharging the gas inside the container 100 when the internal pressure of the container 100 rises excessively is disposed on the lid body 120.

[0027] The electrode body 700 includes a positive electrode plate, a negative electrode plate, and a separator, and is a power storage element (power generation element) capable of storing electricity. Specifically, the electrode body 700 is formed by winding a layered structure in which a separator is sandwiched between a positive electrode plate and a negative electrode plate. As a result, a plurality of tabs (electrode plate ends) of the base material layer (metal foil) of the positive electrode plate are stacked to form a connection portion 720 on the positive electrode side, and tabs (electrode plate ends) of the base material layer (metal foil) of the negative electrode plate are stacked to form a connection portion 730 on the negative electrode side. That is, the electrode body 700 has an electrode body main body portion 710 and connection portions 720 and 730 that protrude from a part of the electrode body main body portion 710 in the +Z-axis direction (third direction) and extend in the +Y-axis direction. Each of the connection portions 720 and 730 provided in this way may also be referred to as a "tab portion". In this embodiment, an electrode body 700 having an oval cross-sectional shape is employed, but the cross-sectional shape of the electrode body 700 may also be an elliptical shape or the like.

[0028] The electrode terminal 200 is a member electrically connected to the electrode body 700 via the current collector 500. The electrode terminal 200 is connected to the current collector 500 by caulking or the like and is attached to the lid body 120. Specifically, the electrode terminal 200 has a shaft portion 201 (rivet portion) extending downward (in the -Z-axis direction). Then, the shaft portion 201 is inserted into the through-hole 301 of the upper gasket 300, the through-hole 123 of the lid body 120, the through-hole 401 of the lower gasket 400, and the through-hole 501 of the current collector 500 and is caulked. As a result, the electrode terminal 200 is fixed to the lid body 120 together with the upper gasket 300, the lower gasket 400, and the current collector 500. Note that the electrode terminal 200 is formed of a conductive member such as a metal such as aluminum, an aluminum alloy, copper, or a copper alloy. Also, it is not essential that the shaft portion 201 be provided on the electrode terminal 200. For example, a shaft portion 201 provided integrally with the current collector 500 may penetrate the lower gasket 400, the lid body 120, the upper gasket 300, and the electrode terminal 200 and be caulked outside the electrode terminal 200.

[0029] The current collector 500 is a plate-shaped member that electrically connects the electrode body 700 and the electrode terminal 200. Specifically, the current collector 500 on the positive electrode side has a terminal connection portion 510 joined to the positive electrode side electrode terminal 200 by caulking or the like, and an electrode connection portion 520 connected (joined) to the positive electrode side connection portion 720 of the electrode body 700 by welding. The same applies to the current collector 500 on the negative electrode side, which has a terminal connection portion 510 joined to the negative electrode side electrode terminal 200 by caulking or the like, and an electrode connection portion 520 connected (joined) to the negative electrode side connection portion 730 of the electrode body 700 by welding. Further, in the present embodiment, the current collector 500 is substantially flat when welded to the connection portion 720 or 730, and is then folded about an axis parallel to the X-axis direction and housed in the container 100. That is, in the current collector 500 in the present embodiment, the terminal connection portion 510 and the electrode connection portion 520 are separated with the folding line as a boundary.

[0030] Note that the term "plate-shaped member" includes, for example, a flat plate-shaped member and a member formed by a flat plate-shaped member being formed into an L-shape, U-shape, V-shape, or S-shape, etc. There is no particular limitation on the method of forming the shape for producing members of various shapes such as an L-shape, and various forming methods such as bending, cutting, drawing, or casting can be adopted.

[0031] The current collector 500 is formed of a metal such as aluminum, an aluminum alloy, copper, or a copper alloy. Note that the method of connecting (joining) the current collector 500 and the electrode terminal 200 is not limited to caulking, and welding such as ultrasonic welding, laser welding, or resistance welding, or mechanical joining other than caulking such as screw fastening may be used. Also, for the method of connecting (joining) the current collector 500 and the connection portion 720 or 730, laser welding or resistance welding or the like is adopted. In the present embodiment, the current collector 500 and the connection portion 720 or 730 are welded by laser welding. The joining structure between the current collector 500 and the connection portion 730 in the present embodiment will be described later with reference to FIGS. 3 to 5.

[0032] The upper gasket 300 is a flat and insulating sealing member disposed between the lid 120 of the container 100 and the electrode terminal 200. The lower gasket 400 is a flat and insulating sealing member disposed between the lid 120 and the current collector 500. Note that the upper gasket 300 and the lower gasket 400 are formed of an insulating material such as, for example, resins such as polypropylene (PP), polyethylene (PE), polyphenylene sulfide resin (PPS), polyethylene terephthalate (PET), polyether ether ketone (PEEK), tetrafluoroethylene·perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polybutylene terephthalate (PBT), or polyethersulfone (PES), or composite materials containing these resins.

[0033] [2. Bonding Structure between Current Collector and Connection Part of Electrode Body] Next, the bonding structure between the current collector 500 and the connection part 730 of the electrode body 700 will be described with reference to FIGS. 3 to 6. In the present embodiment, since the bonding structures of the current collector 500 and the connection part 720 on the positive electrode side and the current collector 500 and the connection part 730 on the negative electrode side are substantially the same, the bonding structure on the negative electrode side will be focused on and described below. That is, various matters regarding the current collector 500 and the connection part 730 on the negative electrode side described below may also be applied to the current collector 500 and the connection part 720 on the positive electrode side.

[0034] FIG. 3 is a side view schematically showing the joining structure of the current collector 500 and the connection part 730 according to the embodiment. In FIG. 3, the current collector 500 on the negative electrode side and the surrounding structure when viewed from the +X-axis direction side of the power storage element 10 (side view) are schematically illustrated. The container 100 is represented by a dotted line, and the illustration of the upper gasket 300 and the lower gasket 400 is omitted. FIG. 4 is a diagram showing a method for forming the melting part 600 according to the embodiment. FIG. 5 is a diagram showing the characteristics of the shape of the melting part 600 according to the embodiment. In FIGS. 3 to 5, the existing range of the melting part 600 in side view is represented by a region surrounded by a broken line and marked with dots. This also applies to FIGS. 6 and 7 described later.

[0035] As shown in FIG. 3, the connection part 730 formed by laminating the end parts (plate end parts 701) of the negative electrode plates of the electrode body 700 is welded to the current collector 500. Specifically, the connection part 730 and the current collector 500 are overlapped in the Z-axis direction which is an example of the first direction, and are welded in the melting part 600. Further, the melting part 600 is formed so as to penetrate the connection part 730 and the current collector 500 in the Z-axis direction which is the lamination direction of the plate end parts 701. More specifically, the melting part 600 has a first melting part 610 exposed on the side of the connection part 730 in the current collector 500 and the connection part 730 overlapped in the Z-axis direction, and a second melting part 620 exposed on the side of the current collector 500. Such a melting part 600 can be formed, for example, as shown in FIG. 4, by irradiating laser light from both sides in the Z-axis direction to the current collector 500 and the connection part 730 overlapped in the Z-axis direction.

[0036] That is, the power storage element 10 according to the present embodiment includes an electrode body 700 having a connection part 730 at an end, and a plate-shaped current collector 500 welded in the melting part 600 in a state of being overlapped with the connection part 730 in the first direction (Z-axis direction). The current collector 500 is arranged with its thickness direction facing the Z-axis direction. The melting part 600 includes a first melting part 610 exposed on the side of the connection part 730 in the Z-axis direction and a second melting part 620 exposed on the side of the current collector 500 in the Z-axis direction.

[0037] Thus, in the power storage element 10 according to the present embodiment, the melted portion 600, which is the welded portion between the connection portion 730 of the electrode body 700 and the current collector 500, is exposed on both sides in the overlapping direction (Z-axis direction) of the connection portion 730 and the current collector 500. That is, in the melted portion 600, a state in which the connection portion 730 and the current collector 500 are sufficiently melted is formed. Further, the first melted portion 610 and the second melted portion 620 of such a melted portion 600 can be formed by welding work from the side of the connection portion 730 of the electrode body 700 and welding work from the side of the current collector 500. That is, the welding work for forming each of the first melted portion 610 and the second melted portion 620 can be performed with relatively small energy, and the current collector 500 and the connection portion 730 can be sufficiently melted together. Furthermore, when the melted portion 600 is formed by laser welding using laser light as in the present embodiment, the laser light can be irradiated from the thickness direction (normal direction) to the plate-shaped current collector 500. Thereby, energy can be efficiently concentrated on the portion to be melted. Therefore, for example, sufficient electrical conduction performance in the melted portion 600 can be ensured without causing scattering of sputter or melting of a part of the connection portion 730. Therefore, the power storage element 10 according to the present embodiment is a power storage element 10 in which the reliability of the melted portion 600, which is the welded portion between the connection portion 730 of the electrode body 700 and the current collector 500, is improved.

[0038] Also, in the present embodiment, as shown in FIGS. 3 and 4, the power storage element 10 further includes a backing plate 550 that is disposed so as to sandwich the connection portion 730 with the current collector 500 and is disposed with the thickness direction facing the first direction. The first melted portion 610 is exposed on the outer surface 551, which is the surface of the backing plate 550 opposite to the connection portion 730. The backing plate 550 is a plate-shaped member formed of a metal such as aluminum, an aluminum alloy, copper, or a copper alloy, like the current collector 500.

[0039] In this way, by using the pressing plate 550 for welding the connection part 730 and the current collector 500, the connection part 730 formed by the lamination of the electrode plate end parts 701 which are metal foils can be welded in a state where the gap between the electrode plate end parts 701 is not likely to occur while being pressed by the pressing plate 550. Therefore, even when laser welding using laser light is adopted for the formation of each of the first melting part 610 and the second melting part 620, the first melting part 610 and the second melting part 620 in good condition can be efficiently formed. That is, the melting part 60 with improved reliability can be formed in a short time.

[0040] Also, in the present embodiment, in the melting part 600, a part of the first melting part 610 and the second melting part 620 overlap each other. Specifically, as shown in FIG. 3, an overlapping part of the first melting part 610 and the second melting part 620 exists in the central part in the thickness direction (Z-axis direction) of the connection part 730. The overlapping part of the first melting part 610 and the second melting part 620 is a part that is melted by the heat during the formation of the first melting part 610 and is also melted by the heat during the formation of the second melting part 620 in the process of its formation. That is, when the formation range of the first melting part 610 and the formation range of the second melting part 620 are connected in the melting part 600, an overlapping part of the first melting part 610 and the second melting part 620 exists at the connection part.

[0041] According to this configuration, the melting part 600 is formed in a state of penetrating all the electrode plate end parts 701 included in the connection part 730 in its lamination direction and penetrating the current collector 500 in its thickness direction. Therefore, since the mechanical connection strength in the melting part 600 is improved, the reliability can be improved not only in the electrical connection but also in the mechanical connection in the melting part 600.

[0042] Also, in the present embodiment, as shown in FIG. 5, in a second direction (for example, the Y-axis direction) orthogonal to the first direction (Z-axis direction), assume a case where the width of the portion exposed on the side of the connection portion 730 of the first melting portion 610 is defined as a first width (W1), and the width of the portion exposed on the side of the current collector 500 of the second melting portion 620 is defined as a second width (W2). In this case, the melting portion 600 has a portion with a third width (W3) that is narrower than W1 and W2 between the position of W1 and the position of W2 in the Z-axis direction. In other words, the melting portion 600 has a portion with a width (W3) that is narrower than the widths (W1, W2) of both ends between both ends in the Z-axis direction. When the first melting portion 610 and the second melting portion 620 are formed while moving the laser beam in a predetermined direction orthogonal to the first direction, each of the first melting portion 610 and the second melting portion 620 is formed in an elongated shape in the predetermined direction. In this case, the first width (W1) is defined as the width in the short side direction of the exposed portion of the first melting portion 610 when viewed from the first direction, and the second width (W2) is defined as the width in the short side direction of the exposed portion of the second melting portion 620 when viewed from the first direction. Further, the third width (W3) is defined as the width in the short side direction in a cross section (a cross section parallel to the XY plane) perpendicular to the first direction in the melting portion 600, and satisfies W3 < W1 and W3 < W2.

[0043] When forming the melting portion 600 by laser welding as in the present embodiment, the object on the irradiation side of the laser beam is relatively more melted, and the melting amount gradually decreases as it goes deeper from there. Therefore, in order to form the melting portion 600 so as to penetrate the entire area of the object in the irradiation direction, it may be necessary to increase the output of the laser beam. That is, as shown in FIGS. 3 to 5, for example, when focusing on only one of the first melting portion 610 and the second melting portion 620, the one is formed in a mountain shape with the irradiation side of the laser beam as the base. Therefore, when melting only the current collector 500 and the connection portion 730 in the Z-axis direction with only the one, it is necessary to increase the output of the laser beam for forming the one. This may cause factors such as the occurrence of melting of the end plate end portion 701 included in the connection portion 730 or damage to other members due to scattering of spatter.

[0044] However, in the present embodiment, laser light is irradiated from both sides of the portion to be melted in the overlapping connection portion 730 and the current collector 500. As a result, a melted portion 600 having a relatively large amount of melting on both the connection portion 730 side and the current collector 500 side and existing over the entire connection portion 730 and current collector 500 in the Z-axis direction can be formed. Therefore, the melted portion 600 that ensures a sufficient amount of current conduction can be formed without increasing the output of the laser light used for forming the melted portion 600. That is, the melted portion 600 with improved reliability is formed.

[0045] As described above, the power storage element 10 according to the embodiment has been described. However, the power storage element 10 may have a melted portion having a configuration different from the configuration shown in FIGS. 3 to 5 as the melted portion that is the welded portion between the connection portion 730 of the electrode body 700 and the current collector 500. Therefore, hereinafter, a modified example of the melted portion included in the power storage element 10 will be described centering on the differences from the above-described embodiment.

[0046] (Modification Example 1) FIG. 6 is a diagram showing the configuration of the melted portion 600a according to Modification Example 1 of the embodiment. As shown in FIG. 6, the melted portion 600a according to the present modification example includes a first melted portion 610 exposed on the connection portion 730 side in the Z-axis direction and a second melted portion 620 exposed on the current collector 500 side in the Z-axis direction. This configuration is common to the melted portion 600 according to the embodiment. In the present modification example, it is different from the above-described embodiment in that the positions of the first melted portion 610 and the second melted portion 620 in the Y-axis direction are clearly shifted.

[0047] Specifically, when viewed from the Z-axis direction, assume a case where a virtual line parallel to the Z-axis passing through the center of the exposed portion on the side of the connection portion 730 of the first melting portion 610 is defined as the first axis A1, and a virtual line parallel to the Z-axis passing through the center of the exposed portion on the side of the current collector 500 of the second melting portion 620 is defined as the second axis A2. In this case, in the melting portion 600, the first melting portion 610 and the second melting portion 620 are arranged at positions where the first axis A1 and the second axis A2 are separated in a second direction (for example, the Y-axis direction) orthogonal to the Z-axis direction. The melting portion 600a having such a configuration can be formed, for example, by shifting the optical axis of the laser beam for forming the first melting portion 610 and the optical axis of the laser beam for forming the second melting portion 620 in a direction orthogonal to the Z-axis direction. This also applies to the melting portion 600b according to Modification Example 2 described later.

[0048] According to this configuration, the melting amount of the overlapping portion of the first melting portion 610 and the second melting portion 620 is reduced, and thereby, the overall melting amount (volume of the melting portion 600) of the melting portion 600 increases. Therefore, for example, an increase in the energization amount or an improvement in the connection strength in the melting portion 600 can be achieved, and as a result, the reliability of the melting portion 600 is improved. In the example shown in FIG. 6, the first axis A1 and the second axis A2 are displaced in the Y-axis direction, but the first axis A1 and the second axis A2 only need to be displaced in a direction orthogonal to the Z-axis direction. That is, for example, the first axis A1 and the second axis A2 may coincide in the Y-axis direction and be displaced in the X-axis direction.

[0049] (Modification Example 2) FIG. 7 is a diagram showing the configuration of the melting part 600b according to Modification 2 of the embodiment. As shown in FIG. 7, the melting part 600b according to this modification includes a first melting part 610 exposed on the side of the connection part 730 in the Z-axis direction and a second melting part 620 exposed on the side of the current collector 500 in the Z-axis direction. Further, a first axis A1 which is the central axis of the first melting part 610 and a second axis A2 which is the central axis of the second melting part 620 are arranged at positions spaced apart in a second direction (for example, the Y-axis direction) orthogonal to the Z-axis direction. These configurations are common to the melting part 600a according to Modification 1. In the melting part 600b according to this modification, there is no overlapping part between the first melting part 610 and the second melting part 620, and in this respect, it is different from the melting part 600a according to Modification 1.

[0050] Even in this case, the first melting part 610 and the second melting part 620 may be arranged such that at least a part of the arrangement ranges of the first melting part 610 and the second melting part 620 in the Z-axis direction overlap each other. Thereby, a part of each of the plurality of electrode plate ends 701 laminated in the connection part 730 is included in at least one of the first melting part 610 and the second melting part 620. Therefore, all of the plurality of electrode plate ends 701 are electrically connected to the current collector 500. Accordingly, the electrode body 700 can be efficiently charged and discharged via the connection part 730 and the current collector 500.

[0051] In the example shown in FIG. 7, the first axis A1 and the second axis A2 are displaced in the Y-axis direction, but the first axis A1 and the second axis A2 may be displaced in a direction orthogonal to the Z-axis direction. That is, for example, the first axis A1 and the second axis A2 may coincide in the Y-axis direction and be displaced in the X-axis direction.

[0052] (Other Embodiments) As described above, the energy storage element according to the embodiment of the present invention and its modifications have been described, but the present invention is not limited to the above embodiment and its modifications. That is, the embodiments and their modifications disclosed this time are illustrative in all respects, and all changes within the meaning and scope equivalent to the claims are included.

[0053] For example, in the melting part 600 having the features described with reference to FIGS. 3 to 5, the connecting part welded to the current collector 500 does not have to be a tab part provided to protrude from a part of the end of the electrode body main part 710 as shown in FIG. 2. For example, a part protruding from the entire end in the winding axis direction of the electrode body main part may be the connecting part. Even in this case, it is possible to form a melting part including a first melting part exposed on the side of the connecting part in the overlapping direction (first direction) of the connecting part and the current collector, and a second melting part exposed on the side of the current collector in the first direction.

[0054] Also, it is not necessary to provide the melting parts 600 on both the positive electrode side and the negative electrode side. For example, when a metal container is used as the positive electrode terminal, that is, when the positive electrode of the electrode body 700 is connected to the container, the melting part 600 which is the welded part between the current collector 500 and the connecting part 730 may be provided only on the negative electrode side.

[0055] In addition, the various supplementary matters regarding the melting part 600 according to the above embodiment may be applied to the melting parts 600a or 600b according to Modification 1 or 2.

[0056] Also, the current collector connected to the electrode body 700 does not have to be folded like the current collector 500 shown in FIG. 3. For example, when the connecting part 730 of the electrode body 700 is housed in a container in a state of being erected along the winding axis direction (Z-axis direction), a simple flat plate-shaped or L-shaped current collector may be welded to the connecting part 730. That is, the current collector joined to the connecting part 730 is not particularly limited in the overall shape and size as long as it has a part where the melting part 600 can be formed.

[0057] Also, the type of the electrode body included in the energy storage element 10 is not limited to the wound type. For example, a stacked type electrode body in which flat plate-shaped electrode plates are stacked, or an electrode body having a structure in which long strip-shaped electrode plates are stacked in a bellows shape by repeating mountain folds and valley folds may be provided in the energy storage element 10.

[0058] Also, a form constructed by arbitrarily combining the plurality of components described above is also included within the scope of the present invention.

Industrial Applicability

[0059] The present invention can be applied to power storage elements such as lithium-ion secondary batteries.

Explanation of Reference Numerals

[0060] 10 Power storage element 100 Container 500 Current collector 550 Pad 551 Outer surface 600, 600a, 600b Molten part 610 First molten part 620 Second molten part 700 Electrode body 701 Electrode plate end 710 Electrode body main body part 720, 730 Connection part

Claims

1. An electrode body having a connection portion at an end thereof; a plate-shaped current collector that is welded to the connection portion at a fusion portion in a state where the current collector is overlapped with the connection portion in a first direction, and the current collector is arranged with a thickness direction oriented in the first direction; the fusion portion includes a first fusion portion exposed on a side of the connection portion in the first direction and a second fusion portion exposed on a side of the current collector in the first direction, When viewed from the first direction, the first fusion portion and the second fusion portion are arranged at positions shifted from each other in a second direction perpendicular to the first direction. Energy storage element.

2. An electrode body having a connection portion at an end thereof; a plate-shaped current collector that is welded to the connection portion at a fusion portion in a state where the current collector is overlapped with the connection portion in a first direction, and the current collector is arranged with a thickness direction oriented in the first direction; the fusion portion includes a first fusion portion exposed on a side of the connection portion in the first direction and a second fusion portion exposed on a side of the current collector in the first direction, The fusion portion has a portion between both ends in the first direction, the portion having a width narrower than the width of both ends in a second direction perpendicular to the first direction. Energy storage element.

3. In the fusion zone, the first fusion zone and the second fusion zone are arranged to overlap each other. The energy storage element according to claim 1 or 2.

4. In the fusion zone, the first fusion zone and the second fusion zone are arranged apart from each other. The energy storage element according to claim 1.

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