JP7642997B2 - Energy storage element - Google Patents

Description

The present invention relates to an energy storage element that includes an electrode body and a current collector connected to the electrode body.

Patent Document 1 discloses a method for manufacturing a secondary battery that includes a step of connecting an electrode body and a current collector by laser welding. In this secondary battery, the internal current collector terminal (current collector) includes a pair of joints that sandwich the exposed electrode portion of the wound electrode body from a direction intersecting the winding axis direction. The joints have 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 part along the inclined surface to give the connection part a stepped shape, and a step of welding and joining the stepped connection part and the inclined surface using laser light.

JP 2017-134910 A

In the above manufacturing method, the multiple exposed electrode portions (electrode plate ends) are stacked with the lower layers offset from the upper layers so that they protrude, which means that the connection portion, which is the laminate of the electrode plate ends, tends to protrude from the electrode body. In order to suppress this protrusion, it is necessary to reduce the amount of misalignment between the upper and lower layers of the electrode plate ends at the connection portion. In this case, however, it becomes 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.

The present invention was made by the inventors with a new focus on the above problem, and aims to provide an energy storage element with improved reliability of the fusion zone, which is the welded portion between the connection part of the electrode body and the current collector.

The energy storage element according to one aspect of the present invention comprises an electrode body having a connection portion at an end thereof, and a plate-shaped current collector that is overlapped with the connection portion in a first direction and welded at a fusion portion and that is arranged with its thickness direction facing the first direction, and the fusion portion includes a first fusion portion exposed on the side of the connection portion in the first direction, and a second fusion portion exposed on the side of the current collector in the first direction.

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.

The energy storage element may further include a backing plate arranged to sandwich the connection portion between the current collector and the backing plate with its thickness direction facing 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.

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 down with a backing plate. In this way, when the stacked electrode plate ends are pressed down with a backing plate, gaps are less likely to occur between adjacent electrode plate ends. Therefore, even when laser welding using laser light is used to form the first fusion portion and the second fusion portion, fusion portions in good condition can be formed efficiently. This makes it possible to form fusion portions with improved reliability in a short period of time.

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

This configuration improves the mechanical connection strength at the fusion zone, improving the reliability of not only the electrical connection at the fusion zone but also the mechanical connection.

In a second direction perpendicular to the first direction, the width of the portion of the first fusion portion exposed to the connection portion side is defined as a first width, and the width of the portion of the second fusion portion exposed to the current collector side is defined as a second width. The fusion portion may have a portion of 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.

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 one moves further in (as the melting depth increases). 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 throughout 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 flow 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.

When viewed from the first direction, if a virtual line passing through the 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 the 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, the first fusion portion and the second fusion portion may be arranged in positions where the first axis and the second axis are spaced apart in a second direction perpendicular to the first direction.

With this configuration, for example, the amount of melting in the area where the first molten part and the second molten part overlap is reduced, and this increases the overall amount of melting in the molten part (volume of the molten part). Therefore, for example, the amount of current flowing through the molten part is increased or the connection strength is improved, resulting in improved reliability of the molten part.

The present invention provides an energy storage element with improved reliability of the fusion zone, which is the welded portion between the connection part of the electrode body and the current collector.

1 is a perspective view showing the appearance of an energy storage element according to an embodiment; FIG. 2 is an exploded perspective view of an energy storage element according to an embodiment. FIG. 4 is a side view showing a simplified joint structure of a current collector and a connection portion according to the embodiment. 5A to 5C are diagrams illustrating a method for forming a fusion zone according to an embodiment. 5A to 5C are diagrams illustrating features of the shape of a fusion zone according to an embodiment. 10A and 10B are diagrams showing a configuration of a fusion zone according to a first modified example of the embodiment; 13 is a diagram showing a configuration of a fusion zone according to a second modified example of the embodiment; FIG.

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

In the following description and drawings, the X-axis direction is defined as the direction in which the pair of electrode terminals (positive and negative) of the storage element are arranged, the direction in which the pair of current collectors are arranged, the direction in which the pair of connection parts of the electrode body are arranged, or the direction in which the short side surfaces of the container face each other. The Y-axis direction is defined as the direction in which the long side surfaces of the container face each other, the short side of the container, or the thickness direction of the 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 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, depending on the mode of use, it is possible that the Z-axis direction is not the up-down direction, but for convenience of explanation, the Z-axis direction will be described as the up-down direction below. 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.

(Embodiment)
[1. General Description of Energy Storage Element]
First, an overall description of an energy storage element 10 according to the present embodiment will be given with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing the external 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.

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 as a battery for driving or starting an engine of a moving object 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 automobile. 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.

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 that uses a solid electrolyte. In this 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.

As shown in FIG. 1, the energy storage element 10 includes a container 100, a pair of electrode terminals 200 (positive and negative), and a pair of upper gaskets 300 (positive and negative). As shown in FIG. 2, the container 100 contains a pair of lower gaskets 400 (positive and negative), a pair of current collectors 500 (positive and negative), and an electrode body 700. An electrolyte (non-aqueous electrolyte) is enclosed 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 encases the electrode body 700, etc. may be disposed.

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 is structured so that 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 other components are housed inside the container body 110. 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.

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 positioned 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 if the internal pressure of the container 100 rises excessively.

The electrode body 700 is a storage element (power generation 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 layers arranged so that the separator is sandwiched between the positive electrode plate and the 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 the 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 the 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.

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 body 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 body 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 body 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 material 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 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.

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 almost 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 stored in the container 100. In other words, in this embodiment, the current collector 500 is divided into a terminal connection portion 510 and an electrode connection portion 520 by the folding line.

Note that the term "plate-shaped member" includes, for example, flat plate-shaped members and flat plate-shaped members formed into L-shapes, U-shapes, V-shapes, S-shapes, etc. There are no particular limitations on the method of forming the shape to produce members of various shapes such as an L-shape, and various forming methods such as bending, cutting, drawing, and casting can be used.

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. The method for connecting (joining) the current collector 500 and the connection portion 720 or 730 may be laser welding or resistance welding. 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 Figures 3 to 5.

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.

[2. Joint structure between current collector and electrode assembly]
Next, the joint structure between the current collector 500 and the connection portion 730 of the electrode assembly 700 will be described with reference to Figures 3 to 6. In this embodiment, the joint structure between the current collector 500 and the connection portion 720 on the positive electrode side and the joint structure between the current collector 500 and the connection portion 730 on the negative electrode side are substantially the same, so the following description will focus on the joint structure on the negative electrode side. In other words, various matters related to the current collector 500 and the connection portion 730 on the negative electrode side described below may also be applied to the current collector 500 and the connection portion 720 on the positive electrode side.

Figure 3 is a side view showing a simplified joint structure of the current collector 500 and the connection part 730 according to the embodiment. In Figure 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. Figure 4 is a diagram showing a method for forming the fusion part 600 according to the embodiment. Figure 5 is a diagram showing the characteristics of the shape of the fusion part 600 according to the embodiment. In Figures 3 to 5, the range of the fusion part 600 in side view is shown by the area surrounded by a dashed line and dotted. This also applies to Figures 6 and 7 described later.

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 to the side of the connection portion 730 in the current collector 500 and the connection portion 730 stacked in the Z-axis direction, and a second fusion portion 620 exposed to the side of the current collector 500. Such a fusion portion 600 can be formed, for example, as shown in FIG. 4, 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.

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 that is welded to the connection portion 730 at a fusion portion 600 in a state where the current collector 500 is overlapped in a first direction (Z-axis direction). The current collector 500 is arranged 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.

In this way, in the energy storage element 10 according to the present embodiment, the fusion zone 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 of 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 fused 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 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. In other words, the welding work for forming each of 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 fused together. Furthermore, when the fusion zone 600 is formed by laser welding using a laser beam as in the present embodiment, the plate-shaped current collector 500 can be irradiated with laser beam from its thickness direction (normal direction). This allows energy to be efficiently concentrated at the location to be melted. Therefore, for example, it is possible to ensure sufficient electrical conductivity in the fusion zone 600 without causing scattering of spatter or melting of a portion of the connection zone 730. Therefore, the energy storage element 10 according to this embodiment is an energy storage element 10 with improved reliability in the fusion zone 600, which is the welded portion between the connection zone 730 of the electrode body 700 and the current collector 500.

In addition, in this embodiment, as shown in Figs. 3 and 4, the energy storage element 10 further includes a backing plate 550 arranged to sandwich the connection portion 730 between the current collector 500 and the backing plate 550, 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 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, just like the current collector 500.

In this way, by using the backing plate 550 to weld 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 down by the backing plate 550. Therefore, even if laser welding using laser light is used to form the first fusion portion 610 and the second fusion portion 620, the first fusion portion 610 and the second fusion portion 620 in good condition can be efficiently formed. In other words, a fusion portion 600 with improved reliability can be formed in a short time.

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

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

In this embodiment, as shown in FIG. 5, in a second direction (for example, Y-axis direction) perpendicular to the first direction (Z-axis direction), the width of the portion of the first fusion portion 610 exposed to the connection portion 730 side is assumed to be the first width (W1), and the width of the portion of the second fusion portion 620 exposed to the current collector 500 side is assumed to be the second width (W2). In this case, the fusion portion 600 has a portion of a third width (W3) narrower than W1 and W2 between the positions W1 and W2 in the Z-axis direction. In other words, the fusion portion 600 has a portion of a width (W3) narrower than the widths (W1, W2) of both ends between both ends in the Z-axis direction. In addition, when the first fusion portion 610 and the second fusion portion 620 are formed while moving the laser light in a predetermined direction perpendicular to the first direction, each of the first fusion portion 610 and the second fusion portion 620 is formed in an elongated shape in the predetermined direction. In this case, the first width (W1) is defined as the width of the exposed portion of the first fusion zone 610 in the short side direction when viewed from the first direction, and the second width (W2) is defined as the width of the exposed portion of the second fusion zone 620 in the short side direction when viewed from the first direction. Furthermore, the third width (W3) is defined as the width of the fusion zone 600 in the short side direction in a cross section perpendicular to the first direction (a cross section parallel to the XY plane), and is defined as a width that satisfies W3<W1 and W3<W2.

When forming the molten part 600 by laser welding as in this embodiment, 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. Therefore, in order to form the molten part 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 light. That is, as shown in Figures 3 to 5, for example, when focusing on only one of the first molten part 610 and the second molten part 620, the one is formed in a mountain shape with the side irradiated with the laser light as the base. Therefore, when melting the current collector 500 and the connection part 730 in the Z-axis direction with only the one, it is necessary to increase the output of the laser light for forming the one. This can cause the electrode plate end part 701 included in the connection part 730 to melt, or damage to other members due to scattering of spatter.

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

The above describes the energy storage element 10 according to the embodiment, but the energy storage element 10 may have a fusion part having a configuration different from that shown in Figures 3 to 5 as the fusion part that is the 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.

(Variation 1)
6 is a diagram showing the configuration of a fusion zone 600a according to the first modified example of the embodiment. As shown in FIG. 6, the fusion zone 600a according to this modified example 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 modified example 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.

Specifically, when viewed from the Z-axis direction, a virtual line passing through the center of the part of the first fusion zone 610 exposed to the connection part 730 side and parallel to the Z-axis direction is assumed to be the first axis A1, and a virtual line passing through the center of the part of the second fusion zone 620 exposed to the current collector 500 side and parallel to the Z-axis direction is assumed to be the 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 separated 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 the modified example 2 described later.

According to this configuration, the amount of melting at the overlapping portion of the first fusion zone 610 and the second fusion zone 620 is reduced, and as a result, the overall amount of melting of the fusion zone 600 (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 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.

(Variation 2)
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 (e.g., 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.

Even in this case, the first fusion zone 610 and the second fusion zone 620 only need to be arranged so that at least a portion of the arrangement range in the Z-axis direction of each of the first fusion zone 610 and the second fusion zone 620 overlaps. As a result, a portion 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.

In the example shown in FIG. 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.

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.

For example, the connection portion welded to the current collector 500 in the fusion portion 600 having the characteristics described using Figures 3 to 5 does not have to be a tab portion protruding from a portion of the end of the electrode body main body 710 as shown in Figure 2. For example, the connection portion may be a portion protruding from the entire end of the electrode body main body in the winding axis direction. Even in this case, it is possible to form a fusion portion that includes a first fusion portion 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 portion exposed on the side of the current collector in the first direction.

Furthermore, 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 the 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.

The various supplementary points regarding the fusion zone 600 according to the embodiment described above may also be applied to the fusion zone 600a or 600b according to the modified example 1 or 2.

In addition, the current collector connected to the electrode body 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 body 700 is stored in a container in a state where it is erected 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.

The type of electrode body provided in the energy storage element 10 is not limited to the wound type. For example, the energy storage element 10 may be provided with a laminated electrode body in which flat 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 repeatedly folding in peaks and valleys.

In addition, configurations constructed by combining multiple components described above in any desired manner are also included within the scope of the present invention.

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

REFERENCE SIGNS LIST 10 Energy storage element 100 Container 500 Current collector 550 Cover plate 551 Outer surface 600, 600a, 600b Melted portion 610 First melted portion 620 Second melted portion 700 Electrode body 701 Electrode plate end portion 710 Electrode body main body portion 720, 730 Connection portion

Claims (4)

An electrode body having a connection portion at an end thereof;
a plate-shaped current collector that is overlapped with the connection portion in a first direction and welded to the connection portion at a fusion portion, and the current collector is disposed 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. 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. 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. An electrode body having a connection portion at an end thereof;
a plate-shaped current collector that is overlapped with the connection portion in a first direction and welded to the connection portion at a fusion portion, and the current collector is disposed 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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