Energy storage element

Abstract

To provide a power storage element with improved reliability of a molten part, which is a welding part between a connection part of an electrode body and a current collector.SOLUTION: A power storage element 10 has an electrode body 700 having a connection 730 at the end and a plate-shaped current collector 500 welded at a fusion section 600, overlapped in the Z-axis direction with the connection 730. The current collector 500 is arranged with its thickness direction facing the Z-axis direction. The fusion section 600 includes a first fusion section 610 exposed on the side of the connection 730 in the Z-axis direction and a second fusion section 620 exposed on the side of the current collector 500 in the Z-axis direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an energy storage element including an electrode assembly and a current collector connected to the electrode assembly. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a secondary battery, which includes a step of connecting an electrode body and a current collector by laser welding. In this secondary battery, an internal current collector terminal (current collector) includes a pair of joints that sandwich an exposed electrode portion of a wound electrode body from a direction intersecting the winding axis direction. The joints have inclined surfaces that expand outward as they move away from the winding axis. The method for manufacturing the secondary battery includes a step of expanding the connection portion along the inclined surfaces to give the connection portion a stepped shape, and a step of welding and joining the stepped connection portion and the inclined surface using laser light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-134910 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above manufacturing method, the multiple electrode exposed parts (electrode plate ends) are stacked with the lower layer projecting relative to the upper layer, so that the connection part, which is the laminate of the electrode plate ends, is likely to have a large protruding length from the electrode body. In order to suppress this protruding length, it is necessary to reduce the amount of deviation between the upper and lower layers of the electrode plate ends at the connection part, but in this case, it is necessary to increase the output of the laser light, for example, in order to sufficiently melt the multiple electrode plate ends together. As a result, problems such as increased spatter and melting of the electrode plate ends, which are metal foils, are likely to occur.

[0005] The present invention was made by the inventor of the present application with a new focus on the above-mentioned problem, and aims to provide an energy storage element in which the reliability of the fusion zone, which is the welded part between the connection part of the electrode body and the current collector, is improved. [Means for solving the problem]

[0006] An energy storage element according to one embodiment of the present invention comprises an electrode body having a connection portion at an end thereof, and a plate-shaped current collector welded to the connection portion at a fusion portion while being stacked in a first direction, and the current collector is arranged with its thickness direction facing the first direction, wherein 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.

[0007] According to this configuration, when welding the connection part of the electrode body and the current collector, the first fusion part and the second fusion part can be formed by welding from the side of the connection part of the electrode body and welding from the side of the current collector. In other words, the welding work for forming the first fusion part and the second fusion part can be performed with relatively small energy, and the current collector and the connection part can be sufficiently melted together. Therefore, it is possible to ensure sufficient current carrying performance in the fusion part without causing, for example, scattering of spatter or melting of a part of the connection part. Therefore, the energy storage element according to this embodiment is an energy storage element in which the reliability of the fusion part, which is the welded part between the connection part of the electrode body and the current collector, is improved.

[0008] The energy storage element may further include a backing plate arranged between the current collector and the connection portion and oriented with its thickness direction in the first direction, and the first molten portion may be exposed on an outer surface of the backing plate, which is the surface opposite the connection portion.

[0009] According to this configuration, the connection portion formed by stacking the electrode plate ends, which are, for example, metal foils, can be welded while being pressed with a backing plate. When the stacked electrode plate ends are pressed with a backing plate in this manner, gaps are less likely to occur between the adjacent electrode plate ends. Therefore, even when laser welding using a laser beam is adopted for forming each of the first fusion portion and the second fusion portion, a fusion portion in a good condition can be efficiently formed. This allows a fusion portion with improved reliability to be formed in a short time.

[0010] In the fusion zone, the first fusion zone and the second fusion zone may be arranged so as to partially overlap each other.

[0011] According to this configuration, the mechanical connection strength at the fusion zone is improved, so that the reliability can be improved not only in the electrical connection at the fusion zone but also in the mechanical connection.

[0012] In a second direction perpendicular to the first direction, when a width of a portion of the first molten portion exposed on the connection portion side is defined as a first width and a width of a portion of the second molten portion exposed on the current collector side is defined as a second width, the molten portion may have a portion of a third width narrower than the first width and the second width between a position of the first width and a position of the second width in the first direction.

[0013] For example, when forming a molten part by laser welding, the object is melted relatively more on the side irradiated with the laser light, and the amount of melting gradually decreases as it goes deeper from there (as the melting depth becomes deeper). 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 embodiment, by irradiating the laser light from both sides of the part to be melted, it is possible to form a molten part that has a relatively large amount of melting on both the connection part side and the current collector side, and that exists over the entire area of ​​the connection part and the current collector in the first direction. Therefore, it is possible to form a molten part that ensures a sufficient amount of current without increasing the output of the laser light used to form the molten part. In other words, a molten part with improved reliability is formed.

[0014] When viewed from the first direction, if a virtual line passing through the center of a portion of the first molten portion exposed on the connection portion side and parallel to the first direction is defined as a first axis, and a virtual line passing through the center of a portion of the second molten portion exposed on the current collector side and parallel to the first direction is defined as a second axis, the first molten portion and the second molten portion may be positioned in the molten portion such that the first axis and the second axis are spaced apart in a second direction perpendicular to the first direction.

[0015] According to this configuration, for example, the melting amount of the portion where the first fusion zone and the second fusion zone overlap is reduced, and as a result, the melting amount of the fusion zone as a whole (volume of the fusion zone) is increased. Therefore, for example, the amount of current flowing through the fusion zone is increased or the connection strength is improved, and as a result, the reliability of the fusion zone is improved. Effect of the Invention

[0016] According to the present invention, it is possible to provide an energy storage element having improved reliability of the fusion zone, which is the welded portion between the connection portion of the electrode assembly and the current collector. [Brief description of the drawings]

[0017] [Figure 1]1 is a perspective view showing the appearance of an energy storage element according to an embodiment; [Diagram 2] FIG. 2 is an exploded perspective view of an energy storage element according to an embodiment. [Diagram 3] FIG. 4 is a side view showing a simplified joint structure between a current collector and a connection portion according to the embodiment. [Figure 4] 5A to 5C are diagrams illustrating a method for forming a fusion zone according to an embodiment. [Diagram 5] 5A to 5C are diagrams illustrating features of the shape of a fusion zone according to an embodiment. [Figure 6] FIG. 13 is a view showing a configuration of a fusion zone according to a first modified example of the embodiment. [Figure 7] FIG. 11 is a view showing a configuration of a fusion zone according to a second modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an energy storage element according to an embodiment (and its modified example) of the present invention will be described with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, the arrangement and connection forms of the components, manufacturing processes, the order of the manufacturing processes, and the like shown in the following embodiments are merely examples and are not intended to limit the present invention. Also, the dimensions, etc. are not strictly illustrated in each drawing.

[0019] In the following description and drawings, the X-axis direction is defined as the direction in which a pair of electrode terminals (positive and negative) of an energy storage element are arranged, the direction in which a pair of current collectors are arranged, the direction in which a pair of connecting parts of an electrode body are arranged, or the direction in which the short side surfaces of a container face each other. The Y-axis direction is defined as the direction in which the long side surfaces of a container face each other, the short side surface of a container, or the thickness direction of a container. The Z-axis direction is defined as the direction in which the electrode terminals, current collectors, and electrode body are arranged, the direction in which the container body and lid of the energy storage element are arranged, the longitudinal direction of the short side surface of the container, the winding axis direction of the electrode body, or the up-down direction. These X-axis direction, Y-axis direction, and Z-axis direction are directions that intersect with each other (orthogonal in this embodiment). Note that, although it is possible that the Z-axis direction is not the up-down direction depending on the mode of use, the following description will be made assuming that the Z-axis direction is the up-down direction for convenience of description. In the following description, for example, the positive X-axis direction indicates the direction of the arrow on the X-axis, and the negative X-axis direction indicates the opposite direction to the positive X-axis direction. The same applies to the Y-axis and Z-axis directions.

[0020] (Embodiment) [1. General description of energy storage elements] First, an energy storage device 10 according to the present embodiment will be generally described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing the appearance of the energy storage device 10 according to the embodiment. Fig. 2 is an exploded perspective view of the energy storage device 10 according to the embodiment.

[0021] The energy storage element 10 is a secondary battery capable of charging and discharging electricity, specifically a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. The energy storage element 10 is used as a battery for driving or starting an engine of a moving body such as an automobile, a motorcycle, a watercraft, a ship, a snowmobile, an agricultural machine, a construction machine, or a railway vehicle for an electric railway. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a gasoline vehicle. Examples of the railway vehicle for the electric railway include a train, a monorail, a linear motor car, and a hybrid train equipped with both a diesel engine and an electric motor. The energy storage element 10 can also be used as a stationary battery for home use or for a generator.

[0022] 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. The energy storage element 10 may not be a secondary battery, but may be a primary battery that allows the user to use stored electricity without charging it. The energy storage element 10 may be a battery using a solid electrolyte. In the present embodiment, the energy storage element 10 is illustrated as having a rectangular parallelepiped (corner) shape, 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 oval cylinder shape, or the like other than a rectangular parallelepiped shape.

[0023] As shown in FIG. 1, the energy storage element 10 includes a container 100, a pair of electrode terminals 200 (positive electrode side and negative electrode side), and a pair of upper gaskets 300 (positive electrode side and negative electrode side). As shown in FIG. 2, the container 100 contains a pair of lower gaskets 400 (positive electrode side and negative electrode side), a pair of current collectors 500 (positive electrode side and negative electrode side), and an electrode body 700. An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but is not shown. There is no particular limit to the type of electrolyte as long as it does not impair the performance of the energy storage element 10, and various electrolytes can be selected. In addition to the above components, a spacer disposed above or to the side of the electrode body 700, or an insulating film that wraps the electrode body 700, etc. may be disposed.

[0024] 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 this configuration, the container 100 has a structure in which the inside can be sealed by, for example, welding the container body 110 and the lid body 120 together after the electrode body 700 and the like are housed inside the container body 110. Note that 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 sheet.

[0025] The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100, and has an opening formed on the positive side of the Z axis. The lid body 120 is a plate-like member that is elongated and rectangular in the X axis direction that constitutes the lid of the container 100, and is disposed in a position to close the opening of the container body 110. The lid body 120 is provided with a gas exhaust valve 122 that exhausts gas from inside the container 100 when the internal pressure of the container 100 rises excessively.

[0026] The electrode body 700 is a storage element (power generating element) that includes a positive electrode plate, a negative electrode plate, and a separator and can store electricity. Specifically, the electrode body 700 is formed by winding a layered arrangement in which a separator is sandwiched between a positive electrode plate and a negative electrode plate. As a result, a plurality of tabs (plate ends) of the base layer (metal foil) of the positive electrode plate are stacked to form a connection part 720 on the positive electrode side, and a tab (plate end) of the base layer (metal foil) of the negative electrode plate is stacked to form a connection part 730 on the negative electrode side. In other words, the electrode body 700 has an electrode body main body 710 and connection parts 720 and 730 that protrude from a part of the electrode body main body 710 in the Z-axis positive direction (third direction) and extend in the Y-axis positive direction. Each of the connection parts 720 and 730 thus provided may be called a "tab part". In this embodiment, the electrode body 700 has an oval cross-sectional shape, but the cross-sectional shape of the electrode body 700 may be an ellipse or the like.

[0027] 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 crimping or the like, and is attached to the lid 120. Specifically, the electrode terminal 200 has an axis portion 201 (rivet portion) extending downward (Z-axis negative direction). The axis portion 201 is inserted into the through hole 301 of the upper gasket 300, the through hole 123 of the lid 120, the through hole 401 of the lower gasket 400, and the through hole 501 of the current collector 500, and is crimped. As a result, the electrode terminal 200 is fixed to the lid 120 together with the upper gasket 300, the lower gasket 400, and the current collector 500. 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. Moreover, it is not essential that the shaft portion 201 is provided on the electrode terminal 200. For example, the shaft portion 201 provided integrally with the current collector 500 may pass through the lower gasket 400, the cover 120, the upper gasket 300, and the electrode terminal 200, and may be crimped on the outside of the electrode terminal 200.

[0028] The current collector 500 is a plate-like member that electrically connects the electrode body 700 and the electrode terminal 200. Specifically, the positive electrode side current collector 500 has a terminal connection part 510 that is joined to the positive electrode side electrode terminal 200 by crimping or the like, and an electrode connection part 520 that is connected (joined) to the positive electrode side connection part 720 of the electrode body 700 by welding. The negative electrode side current collector 500 is similar, and has a terminal connection part 510 that is joined to the negative electrode side electrode terminal 200 by crimping or the like, and an electrode connection part 520 that is connected (joined) to the negative electrode side connection part 730 of the electrode body 700 by welding. In this embodiment, the current collector 500 is approximately flat when it is welded to the connection part 720 or 730, and is then folded around an axis parallel to the X-axis direction and accommodated in the container 100. That is, in the present embodiment, current collector 500 is divided into terminal connection portion 510 and electrode connection portion 520 by the folding line as a boundary.

[0029] It should be noted that the term "plate-shaped member" includes, for example, a flat plate-shaped member and a flat plate-shaped member formed into an L-shape, a U-shape, a V-shape, an S-shape, etc. There are no particular limitations 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, and casting can be used.

[0030] The current collector 500 is formed of a metal such as aluminum, an aluminum alloy, copper, or a copper alloy. The method for connecting (joining) the current collector 500 and the electrode terminal 200 is not limited to crimping, and may be ultrasonic welding, laser welding, resistance welding, or other welding, or mechanical joining other than crimping, such as screw fastening. Laser welding, resistance welding, or the like is used as a method for connecting (joining) the current collector 500 and the connection portion 720 or 730. In this 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 this embodiment will be described later with reference to Figs. 3 to 5.

[0031] The upper gasket 300 is a flat, insulating sealing member disposed between the lid 120 of the container 100 and the electrode terminal 200. The lower gasket 400 is a flat, insulating sealing member disposed between the lid 120 and the current collector 500. The upper gasket 300 and the lower gasket 400 are formed of an insulating material such as a resin 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 polyether sulfone (PES), or a composite material containing these resins.

[0032] [2. Joint structure between current collector and electrode body] Next, the joint structure between the current collector 500 and the connection part 730 of the electrode assembly 700 will be described with reference to Fig. 3 to Fig. 6. In this embodiment, the joint structure between the current collector 500 and the connection part 720 on the positive electrode side and the joint structure between the current collector 500 and the connection part 730 on the negative electrode side are substantially the same, so the joint structure on the negative electrode side will be focused on and described below. In other words, various matters related to 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.

[0033] FIG. 3 is a side view showing a simplified joint structure of a current collector 500 and a connection part 730 according to an embodiment. In FIG. 3, the negative electrode side current collector 500 and its surrounding structure when viewed from the X-axis positive direction side of the energy storage element 10 (side view) are simply shown, the container 100 is shown by a dotted line, and the upper gasket 300 and the lower gasket 400 are omitted. FIG. 4 is a diagram showing a method for forming a fusion zone 600 according to an embodiment. FIG. 5 is a diagram showing characteristics of the shape of the fusion zone 600 according to an embodiment. In FIG. 3 to FIG. 5, the existence range of the fusion zone 600 in side view is shown by a region surrounded by a dashed line and dotted. This also applies to FIG. 6 and FIG. 7 described later.

[0034] As shown in FIG. 3, the connection portion 730 formed by stacking the ends (electrode plate ends 701) of the negative electrode plates of the electrode body 700 is welded to the current collector 500. Specifically, the connection portion 730 and the current collector 500 are stacked in the Z-axis direction, which is an example of a first direction, and are welded at the fusion portion 600. The fusion portion 600 is formed penetrating the connection portion 730 and the current collector 500 in the Z-axis direction, which is the stacking direction of the electrode plate ends 701. More specifically, the fusion portion 600 has a first fusion portion 610 exposed on the side of the connection portion 730 of the current collector 500 and the connection portion 730 stacked in the Z-axis direction, and a second fusion portion 620 exposed on the side of the current collector 500. Such a fusion portion 600 can be formed by irradiating the current collector 500 and the connection portion 730 stacked in the Z-axis direction with laser light from both sides in the Z-axis direction, as shown in FIG. 4, for example.

[0035] That is, the energy storage element 10 according to this embodiment includes an electrode body 700 having a connection portion 730 at an end, and a plate-shaped current collector 500 welded to the connection portion 730 at a fusion portion 600 in a state where the current collector 500 is overlapped with the connection portion 730 in a first direction (Z-axis direction). The current collector 500 is disposed with its thickness direction facing the Z-axis direction. The fusion portion 600 includes a first fusion portion 610 exposed on the side of the connection portion 730 in the Z-axis direction, and a second fusion portion 620 exposed on the side of the current collector 500 in the Z-axis direction.

[0036] Thus, in the energy storage element 10 according to the present embodiment, the fusion zone 600, which is a 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 fusion zone 600, a state in which the connection portion 730 and the current collector 500 are sufficiently melted is formed. In addition, the first fusion zone 610 and the second fusion zone 620 of such a fusion zone 600 can be formed by a welding operation from the connection portion 730 side of the electrode body 700 and a welding operation from the current collector 500 side. That is, the welding operation for forming the first fusion zone 610 and the second fusion zone 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 fusion zone 600 is formed by laser welding using a laser beam as in the present embodiment, the laser beam can be irradiated to the plate-shaped current collector 500 from its thickness direction (normal direction). This allows energy to be efficiently concentrated at the location to be melted. Therefore, for example, scattering of spatter or melting of a part of the connection part 730 is not caused, and sufficient current-carrying performance in the fusion part 600 can be ensured. Therefore, the energy storage element 10 according to this embodiment is an energy storage element 10 in which the reliability of the fusion part 600, which is the welded part between the connection part 730 of the electrode body 700 and the current collector 500, is improved.

[0037] 3 and 4, in the present embodiment, the energy storage element 10 further includes a backing plate 550 disposed between the current collector 500 and the connection portion 730, and disposed with its thickness direction facing the first direction. The first fusion portion 610 is exposed on an outer surface 551 of the backing plate 550, which is the surface opposite to the connection portion 730. The backing plate 550 is a plate-like member formed of a metal such as aluminum, an aluminum alloy, copper, or a copper alloy, like the current collector 500.

[0038] In this way, by using the backing plate 550 for welding the connection portion 730 and the current collector 500, the connection portion 730 formed by stacking the electrode plate ends 701, which are metal foils, can be welded in a state in which gaps between the electrode plate ends 701 are unlikely to occur while being pressed by the backing plate 550. Therefore, even when laser welding using a laser beam is adopted for forming each of the first fusion portion 610 and the second fusion portion 620, the first fusion portion 610 and the second fusion portion 620 in a good condition can be efficiently formed. In other words, the fusion portion 600 with improved reliability can be formed in a short time.

[0039] In the present embodiment, the first fusion zone 610 and the second fusion zone 620 are arranged so as to overlap each other in part in the fusion zone 600. Specifically, as shown in FIG. 3, an overlapping portion of the first fusion zone 610 and the second fusion zone 620 exists in the center portion of the connection portion 730 in the thickness direction (Z-axis direction). The overlapping portion of the first fusion zone 610 and the second fusion zone 620 is a portion that is melted by the heat when the first fusion zone 610 is formed and melted by the heat when the second fusion zone 620 is formed during the formation process. In other words, when the formation range of the first fusion zone 610 and the formation range of the second fusion zone 620 are connected in the fusion zone 600, an overlapping portion of the first fusion zone 610 and the second fusion zone 620 exists in the connection portion.

[0040] According to this configuration, the fusion part 600 is formed in a state in which it penetrates all the electrode plate ends 701 included in the connection part 730 in the stacking direction, and penetrates the current collector 500 in the thickness direction. Therefore, the mechanical connection strength of the fusion part 600 is improved, and the reliability of not only the electrical connection but also the mechanical connection in the fusion part 600 can be improved.

[0041] 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 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 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 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 is defined as a width that satisfies W3 < W1 and W3 < W2.

[0042] 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 one through the current collector 500 and the connection portion 730 in the Z-axis direction, 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 electrode plate end portion 701 included in the connection portion 730 or damage to other members due to the scattering of spatter.

[0043] However, in the present embodiment, the laser light is applied from both sides of the portions to be melted in the overlapped connection portion 730 and current collector 500. This makes it possible to form a fusion portion 600 that has a relatively large amount of melt on both the connection portion 730 side and the current collector 500 side and exists over the entire area of ​​the connection portion 730 and the current collector 500 in the Z-axis direction. Therefore, it is possible to form a fusion portion 600 that ensures a sufficient amount of current flow without increasing the output of the laser light used to form the fusion portion 600. In other words, a fusion portion 600 with improved reliability is formed.

[0044] Although the energy storage element 10 according to the embodiment has been described above, the energy storage element 10 may have a fusion part having a configuration different from that shown in Figures 3 to 5 as a fusion part that is a welded portion between the connection part 730 of the electrode body 700 and the current collector 500. Therefore, below, modified examples of the fusion part of the energy storage element 10 will be described, focusing on the differences from the above embodiment.

[0045] (Variation 1) Fig. 6 is a diagram showing the configuration of a fusion zone 600a according to the first modification of the embodiment. As shown in Fig. 6, the fusion zone 600a according to this modification includes a first fusion zone 610 exposed on the side of the connection portion 730 in the Z-axis direction, and a second fusion zone 620 exposed on the side of the current collector 500 in the Z-axis direction. This configuration is common to the fusion zone 600 according to the embodiment. This modification differs from the above embodiment in that the positions of the first fusion zone 610 and the second fusion zone 620 in the Y-axis direction are clearly shifted.

[0046] Specifically, when viewed from the Z-axis direction, a virtual line passing through the center of a portion of the first fusion zone 610 exposed to the connection portion 730 side and parallel to the Z-axis direction is assumed to be a first axis A1, and a virtual line passing through the center of a portion of the second fusion zone 620 exposed to the current collector 500 side and parallel to the Z-axis direction is assumed to be a second axis A2. In this case, in the fusion zone 600, the first fusion zone 610 and the second fusion zone 620 are arranged at positions where the first axis A1 and the second axis A2 are spaced apart in a second direction (e.g., the Y-axis direction) perpendicular to the Z-axis direction. The fusion zone 600a having such a configuration can be formed, for example, by shifting the optical axis of the laser light for forming the first fusion zone 610 and the optical axis of the laser light for forming the second fusion zone 620 in a direction perpendicular to the Z-axis direction. This is also true for the fusion zone 600b according to Modification 2 described later.

[0047] According to this configuration, the melting amount of the overlapping portion of the first fusion zone 610 and the second fusion zone 620 is reduced, and as a result, the melting amount of the fusion zone 600 as a whole (volume of the fusion zone 600) is increased. Therefore, for example, the amount of current flowing through the fusion zone 600 is increased or the connection strength is improved, and as a result, the reliability of the fusion zone 600 is improved. In the example shown in FIG. 6, the first axis line A1 and the second axis line A2 are offset in the Y-axis direction, but the first axis line A1 and the second axis line A2 may be offset in a direction perpendicular to the Z-axis direction. In other words, for example, the first axis line A1 and the second axis line A2 may coincide in the Y-axis direction and be offset in the X-axis direction.

[0048] (Variation 2) FIG. 7 is a diagram showing the configuration of the fusion zone 600b according to the second modification of the embodiment. As shown in FIG. 7, the fusion zone 600b according to this modification includes a first fusion zone 610 exposed on the side of the connection portion 730 in the Z-axis direction, and a second fusion zone 620 exposed on the side of the current collector 500 in the Z-axis direction. Furthermore, the first axis A1, which is the central axis of the first fusion zone 610, and the second axis A2, which is the central axis of the second fusion zone 620, are arranged at positions spaced apart in a second direction (for example, the Y-axis direction) perpendicular to the Z-axis direction. These configurations are common to the fusion zone 600a according to the first modification. In the fusion zone 600b according to this modification, there is no overlapping portion between the first fusion zone 610 and the second fusion zone 620, and in this respect, it differs from the fusion zone 600a according to the first modification.

[0049] Even in this case, the first fusion zone 610 and the second fusion zone 620 may be arranged so that at least a part of the arrangement range in the Z-axis direction of each of the first fusion zone 610 and the second fusion zone 620 overlaps with each other. As a result, a part of each of the multiple electrode plate ends 701 stacked in the connection portion 730 is included in at least one of the first fusion zone 610 and the second fusion zone 620. Therefore, all of the multiple electrode plate ends 701 are electrically connected to the current collector 500. Therefore, the electrode body 700 can be efficiently charged and discharged via the connection portion 730 and the current collector 500.

[0050] 7, the first axis A1 and the second axis A2 are offset in the Y-axis direction, but the first axis A1 and the second axis A2 may be offset in a direction perpendicular to the Z-axis direction. In other words, for example, the first axis A1 and the second axis A2 may coincide in the Y-axis direction and be offset in the X-axis direction.

[0051] (Other embodiments) Although the energy storage element according to the embodiment and its modified examples of the present invention have been described above, the present invention is not limited to the above-mentioned embodiment and its modified examples. In other words, the embodiment and its modified examples disclosed herein are illustrative in all respects, and include all modifications within the meaning and scope equivalent to the claims.

[0052] For example, the connection portion welded to the current collector 500 in the fusion zone 600 having the characteristics described with reference to Figures 3 to 5 does not have to be a tab portion provided protruding from a part of the end of the electrode body main body 710 as shown in Figure 2. For example, a portion protruding from the entire end of the electrode body main body in the winding axis direction may be the connection portion. Even in this case, it is possible to form a fusion zone including a first fusion zone exposed on the side of the connection portion in the overlapping direction (first direction) of the connection portion and the current collector, and a second fusion zone exposed on the side of the current collector in the first direction.

[0053] In addition, it is not necessary to provide the fusion part 600 on both the positive electrode side and the negative electrode side. For example, when a metal container is used as a positive electrode terminal, that is, when the positive electrode of the electrode body 700 is connected to the container, the fusion part 600, which is the welded part between the current collector 500 and the connection part 730, may be provided only on the negative electrode side.

[0054] The above-mentioned various supplementary points regarding the fusion zone 600 according to the embodiment may be applied to the fusion zone 600a or 600b according to the first or second modification.

[0055] Furthermore, the current collector connected to the electrode assembly 700 does not necessarily have to be folded like the current collector 500 shown in Fig. 3. For example, when the connection part 730 of the electrode assembly 700 is housed in a container in a state in which it stands along the winding axis direction (Z-axis direction), a simple flat or L-shaped current collector may be welded to the connection part 730. In other words, the overall shape and size of the current collector joined to the connection part 730 are not particularly limited as long as it has a portion where the fusion part 600 can be formed.

[0056] The type of electrode body included in the energy storage element 10 is not limited to a wound type. For example, the energy storage element 10 may be provided with a laminated type electrode body in which flat electrode plates are laminated, or an electrode body having a structure in which long strip-shaped electrode plates are laminated in a bellows shape by repeatedly folding in peaks and valleys.

[0057] Additionally, configurations constructed by arbitrarily combining the multiple components described above are also included within the scope of the present invention. [Industrial Applicability]

[0058] The present invention can be applied to storage elements such as lithium ion secondary batteries. [Explanation of symbols]

[0059] 10 Energy storage element 100 containers 500 Current collector 550 Backing plate 551 External surface 600, 600a, 600b fusion zone 610 First fusion zone 620 Second fusion zone 700 Electrode body 701 Plate end 710 Electrode body part 720, 730 Connection

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, In a second direction perpendicular to the first direction, when a width of a portion of the first fusion portion exposed on the connection portion side is defined as a first width and a width of a portion of the second fusion portion exposed on the current collector side is defined as a second width, The molten portion has a portion having a third width narrower than the first width and the second width between a position of the first width and a position of the second width in the first direction. Energy storage element.

2. Further, a backing plate is provided that is disposed so as to sandwich the connection portion between the current collector and the backing plate and has a thickness direction oriented in the first direction, The first fusion portion is exposed on an outer surface of the backing plate, which is the surface opposite to the connection portion. The energy storage element according to claim 1.

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. 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, a virtual line passing through a center of a portion of the first fusion portion exposed to the connection portion side and parallel to the first direction is defined as a first axis, and a virtual line passing through a center of a portion of the second fusion portion exposed to the current collector side and parallel to the first direction is defined as a second axis. In the fusion zone, the first fusion zone and the second fusion zone are arranged at positions where the first axis and the second axis are spaced apart in a second direction perpendicular to the first direction. Energy storage element.

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