Method for manufacturing power storage device, and power storage device

Abstract

A method for manufacturing a power storage device includes preparing an electrode group (2) having a structure in which a plurality of exposed portions (12a) of a current collector (12) are arranged, bringing the plurality of arranged exposed portions (12a) into contact with current collector plates (20, 22), scanning a scanning region (58) of the current collector plates (20, 22) with laser light (L) from one end (58a) to the other end (58b), and bonding the plurality of exposed portions (12a) to the current collector plates (20, 22). In the scanning region (58), the other end (58b) is thicker than the one end (58a), and the thickness increases continuously or stepwise from the one end (58a) side toward the other end (58b) side in at least a partial section from the one end (58a) to the other end (58b).

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a power storage device and a power storage device. Background Art

[0002] Conventionally, a power storage device in which an electrode group is housed in an outer can has been known. In such a power storage device, a current collector plate is welded to an end portion of the electrode group (see, for example, Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-166030 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] The inventors of the present invention have repeatedly and thoroughly studied a power storage device in which an electrode group and a current collector plate are joined, and finally found that there is still room for improving the quality of existing power storage devices.

[0008] The present disclosure has been made in view of such a situation, and one of its objects is to provide a technology for improving the quality of a power storage device.

[0009] Method for Solving the Technical Problem

[0010] One aspect of the present disclosure is a method for manufacturing a power storage device. The manufacturing method includes: preparing an electrode group, which is an electrode group having a current collector in which electrode active material layers are laminated, and having a structure in which a plurality of exposed portions not covered by the electrode active material layers in the current collector are arranged, bringing the plurality of arranged exposed portions into contact with a current collector plate, scanning a scanning region extending in the arrangement direction of the exposed portions in the current collector plate with a laser from one end to the other end, and joining the plurality of exposed portions to the current collector plate. The other end of the scanning region is thicker than the one end, and in at least a part of the section from the one end to the other end, the thickness increases continuously or stepwise from the one end side toward the other end side.

[0011] Another aspect of the present disclosure is a power storage device. The power storage device includes: an electrode group having a current collector in which electrode active material layers are laminated; and a current collector plate joined to the current collector. The electrode group has a structure in which a plurality of exposed portions not covered by the electrode active material layers in the current collector are arranged, and the plurality of arranged exposed portions are joined to the current collector plate. In a region of the current collector plate that extends in the arrangement direction of the exposed portions and to which each exposed portion is joined, the other end is thicker than the one end, and in at least a part of the section from the one end to the other end, the thickness increases continuously or stepwise from the one end side toward the other end side.

[0012] Any combination of the above-described constituent elements, and a solution that converts the expression of the present disclosure between methods, apparatuses, systems, etc. is also effective as a solution of the present disclosure.

[0013] Advantageous Effects of the Invention

[0014] According to the present disclosure, improvement in the quality of the power storage device can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a cross-sectional view of the power storage device according to the embodiment.

[0016] Figure 2 (A) of is an exploded perspective view of the electrode assembly. Figure 2 (B) of is a top view of the electrode assembly to which the first current collector plate is joined.

[0017] Figure 3 (A) to Figure 3 (C) of is a view showing the joining process of the current collector and the current collector plate. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Summary of the Embodiment)

[0019] Hereinafter, the present disclosure will be described with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the present disclosure, and all features or combinations thereof described in the embodiments do not necessarily represent the essential content of the present disclosure. The same or equivalent constituent elements, components, and processes shown in the respective drawings are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. In addition, the scales or shapes of the respective parts shown in the respective drawings are set for convenience of explanation, and are not to be construed in a limiting sense unless otherwise specified. Further, when terms such as "first" and "second" are used in this specification or claims, they do not indicate any order or importance unless otherwise specified, but are used to distinguish one configuration from another. In addition, in each drawing, a part of the components that are not important in the description of the embodiment is omitted from the display.

[0020] Figure 1 is a cross-sectional view of the power storage device 1 according to the embodiment. Figure 2 (A) of is an exploded perspective view of the electrode assembly 2. Figure 2 (B) of is a top view of the electrode assembly 2 to which the first current collector plate 20 is joined. It should be noted that in Figure 1 , the shapes of the first current collector plate 20 and the second current collector plate 22 are simplified, and the illustration of the thickness change is omitted. In addition, in Figure 2 (A) of, the division of the current collector 12 and the electrode active material layer 14 is omitted.

[0021] The power storage device 1 is, for example, a rechargeable secondary battery such as a lithium-ion battery, a nickel-hydrogen battery, or a nickel-cadmium battery, or a capacitor such as an electric double layer capacitor. The power storage device 1 has a structure in which an electrode group 2, an electrolyte (not shown), a first current collector plate 20, and a second current collector plate 22 are housed in an outer can 4. As an example, the electrode group 2 has a cylindrical shape and has a wound structure in which a strip-shaped first electrode plate 6 and a strip-shaped second electrode plate 8 are laminated with a strip-shaped spacer 10 in between and wound in a spiral shape. In the present embodiment, the first electrode plate 6 is set as the positive electrode plate and the second electrode plate 8 is set as the negative electrode plate. Alternatively, the first electrode plate 6 may be the negative electrode plate and the second electrode plate 8 may be the positive electrode plate. The spacer 10 is, for example, formed of a microporous membrane made of a polypropylene resin or the like.

[0022] The first electrode plate 6 and the second electrode plate 8 each have a current collector 12 and an electrode active material layer 14 laminated on the current collector 12. The current collector 12 and the electrode active material layer 14 are also strip-shaped and wound in a spiral shape. In a typical lithium-ion secondary battery, the positive electrode of the current collector 12 is made of aluminum foil or the like, and the negative electrode is made of copper foil or the like. The electrode active material layer 14 can also be formed by coating an electrode mixture on the surface of the current collector 12 using a known coating device and then drying and rolling. The electrode mixture is obtained by kneading materials such as an electrode active material, a binder material, and a conductive material in a dispersion medium to uniformly disperse them. In a typical lithium-ion secondary battery, the positive electrode of the electrode active material is lithium cobaltate or lithium iron phosphate, etc., and the negative electrode is graphite or the like.

[0023] The first electrode plate 6 and the second electrode plate 8 each have an exposed portion 12a of the current collector 12 at an end in the width direction A. The width direction A is a direction intersecting the length direction of the strip. The exposed portion 12a of the first electrode plate 6 and the exposed portion 12a of the second electrode plate 8 protrude in opposite directions from each other in the width direction A. The exposed portion 12a is a portion of the current collector 12 that is not covered by the electrode active material layer 14.

[0024] As described above, the electrode group 2 has a structure in which the first electrode plate 6 and the second electrode plate 8 are wound. Therefore, a plurality of ends of the current collector 12 in the width direction A, that is, the exposed portions 12a, are arranged in the radial direction B of the electrode group 2. That is, the electrode group 2 has a laminated structure of the exposed portions 12a. Alternatively, the electrode group 2 may have a structure in which a plurality of single-piece first electrode plates 6 and single-piece second electrode plates 8 are laminated with a spacer 10 in between.

[0025] As an example, the electrode group 2 has a first joining region 46 and a second joining region 48 where a plurality of exposed portions 12a arranged in the radial direction B are bent in the radial direction B. The first joining region 46 and the second joining region 48 are located on opposite sides in the width direction A. The plurality of exposed portions 12a included in the first joining region 46 are the exposed portions 12a of the current collector 12 provided in the first electrode plate 6. The plurality of exposed portions 12a included in the second joining region 48 are the exposed portions 12a of the current collector 12 provided in the second electrode plate 8.

[0026] For example, each exposed portion 12a is bent toward the winding center C of the electrode group 2, that is, toward the inside in the radial direction B. The winding center C is, for example, the geometric center of the outer shape of the electrode group 2 as viewed from the width direction A, in other words, the geometric center of the projection shape of the electrode group 2 in the width direction A. Further, in the electrode group 2 as an example, a plurality of first joining regions 46 and a plurality of second joining regions 48 are respectively arranged at a predetermined interval in the circumferential direction of the electrode group 2. In the present embodiment, four first joining regions 46 are arranged at an interval of 90° in the circumferential direction. Further, four second joining regions 48 are arranged at an interval of 90° in the circumferential direction.

[0027] The first current collector plate 20 and the second current collector plate 22 are arranged so as to sandwich the electrode group 2 in the width direction A. The first current collector plate 20 is arranged on the side of the first joining region 46. The second current collector plate 22 is arranged on the side of the second joining region 48.

[0028] The first current collector plate 20 is made of, for example, aluminum or the like. The plurality of exposed portions 12a bent at the first joining region 46 are in surface contact with the first current collector plate 20. Each exposed portion 12a is bent so that the contact area between each exposed portion 12a and the first current collector plate 20 increases. Then, laser welding or the like is performed at a position where the first joining region 46 and the first current collector plate 20 overlap. Thus, the exposed portions 12a of each winding layer and the first current collector plate 20 are joined to each other.

[0029] The second current collector plate 22 is made of, for example, iron with nickel plating or the like. The plurality of exposed portions 12a bent at the second joining region 48 are in surface contact with the second current collector plate 22. Each exposed portion 12a is bent so that the contact area between each exposed portion 12a and the second current collector plate 22 increases. And, laser welding or the like is performed at a position where the second joining region 48 and the second current collector plate 22 overlap. Thus, the exposed portions 12a of each winding layer and the second current collector plate 22 are joined to each other.

[0030] The electrode group 2 after the first current collector plate 20 and the second current collector plate 22 are joined is housed together with the electrolyte in a bottomed cylindrical outer can 4. The outer can 4 is made of, for example, copper, nickel, iron, aluminum, or an alloy thereof. The second current collector plate 22 is joined to the inner bottom surface of the outer can 4 by welding or the like. The first current collector plate 20 is joined to a sealing plate 26 made of the same metal as the outer can 4 by welding or the like. The sealing plate 26 is inserted into the opening of the outer can 4 via an insulating gasket 24. Thus, the electrode group 2 and the electrolyte are sealed inside the outer can 4.

[0031] Next, a method for manufacturing the power storage device 1 will be described. Figure 3 (A) to Figure 3 (C) of FIG. are diagrams showing the joining process of the current collector 12 and the current collector plate. In addition, in Figure 3 (A) to Figure 3 (C) of FIG., only a part of the exposed portion 12a is shown. In addition, only a part of the current collector plate is shown.

[0032] First, as shown in Figure 2 (A) of FIG., strip-shaped first electrode plates 6, second electrode plates 8, and spacers 10 are prepared respectively. And the spacers 10, the first electrode plates 6, the spacers 10, and the second electrode plates 8 are laminated in this order. The obtained laminate is wound in a spiral shape to form a wound-type electrode group 2.

[0033] Next, the electrode group 2 is set in a processing device (not shown). Then, by the processing device, the end of the current collector 12 provided in the first electrode plate 6 is bent in the radial direction B. Thus, a first joining region 46 including a plurality of exposed portions 12a bent in the radial direction B is formed. Thereafter, the first current collector plate 20 is pressed against the first joining region 46. And the exposed portions 12a arranged in plurality in the first joining region 46 and the first current collector plate 20 are joined by laser welding.

[0034] Specifically, as shown in Figure 3 (A) of FIG., in a state where the plurality of arranged exposed portions 12a are in contact with the first current collector plate 20, laser L is irradiated from the first current collector plate 20 side. The laser L is irradiated to one end 58a of a scanning region 58 in the first current collector plate 20. The scanning region 58 overlaps with the plurality of arranged exposed portions 12a and extends in the arrangement direction of the exposed portions 12a, that is, in the radial direction B of the electrode group 2. In the present embodiment, four scanning regions 58 extend radially from the winding center C (see Figure 2 (B) of FIG.). Each scanning region 58 is arranged so as to overlap with the first joining region 46 in the width direction A and not to overlap with the winding center C. Therefore, both ends of each scanning region 58 are offset in the same direction with respect to the winding center C in the radial direction of the electrode group 2.

[0035] By irradiating the first current collector plate 20 with a laser beam L, a molten portion 54 (molten pool) is formed. And, as shown in (B) of Figure 3 and (C) of Figure 3 , by shifting the irradiation position of the laser beam L, the molten portion 54 moves from one end 58a to the other end 58b within the scanning region 58. At a position where the current collector 12 is absent, the molten portion 54 is substantially composed only of the melt of the first current collector plate 20, and at a position where the current collector 12 is present, the molten portion 54 is composed of the melt of the first current collector plate 20 and the melt of the current collector 12. By scanning the scanning region 58 with the laser beam L from one end 58a to the other end 58b, the joint portions 52 between the respective exposed portions 12a and the first current collector plate 20 are formed. As a result, the plurality of exposed portions 12a are joined to the scanning region 58 of the first current collector plate 20.

[0036] After scanning the laser beam L over all the scanning regions 58, the joining of the first current collector plate 20 to the electrode group 2 is completed. Next, the end portion of the current collector 12 provided on the second electrode plate 8 is bent by a processing device. Thereby, a second joint region 48 including a plurality of exposed portions 12a bent in the radial direction B is formed. Thereafter, the second current collector plate 22 is pressed against the second joint region 48. And, by the same process as in the case of joining the first current collector plate 20 to the electrode group 2, the plurality of exposed portions 12a arranged in the second joint region 48 and the second current collector plate 22 are joined by laser welding. As a result, each of the exposed portions 12a is joined to the second current collector plate 22.

[0037] The electrode group 2 to which the first current collector plate 20 and the second current collector plate 22 are joined is housed together with the electrolytic solution in an outer can 4. In addition, processes such as joining the second current collector plate 22 to the outer can 4, joining the first current collector plate 20 to the sealing plate 26, and fitting the sealing plate 26 into the opening of the outer can 4 are performed to obtain the power storage device 1. In addition, the processing order of joining of each part, housing in the outer can 4, fitting of the sealing plate 26, etc. can be appropriately changed. For example, in the case where a liquid injection port is provided in the sealing plate 26 or the like, the electrolytic solution may be injected into the outer can 4 after the sealing plate 26 is fitted into the opening portion of the outer can 4. In addition, it may be that first the first joint region 46 and the second joint region 48 are formed, then the first current collector plate 20 and the second current collector plate 22 are pressed against the electrode group 2, and thereafter the laser beam L is irradiated to the first current collector plate 20 and the second current collector plate 22.

[0038] The inventors of the present invention have repeatedly and deeply studied the bonding process between the current collector 12 and the current collecting plate, and finally found that by improving the current collecting plate, the quality of the power storage device 1 can be improved. That is, generally, at the start end side and the end end side of laser welding, the heat input in the current collecting plate, in other words, the heat from the laser L supplied to each welding part of the current collecting plate, may be different. Specifically, as the irradiation time of the laser L extends, the heat accumulated in the current collecting plate increases, so the heat supplied to the end end side tends to increase compared with the start end side. Therefore, when scanning a current collecting plate with a certain thickness at a certain scanning speed using a laser L with a certain intensity, the state of the molten part 54 will be different between the start end side and the end end side, and the welding quality of the entire scanning area 58 may deviate.

[0039] In addition, as a method of suppressing the deviation of the welding quality in the entire scanning area 58, it can be considered to change the intensity or scanning speed of the laser L as the laser L moves, thereby adjusting the power density of the laser L input to the current collecting plate. However, in this method, when switching the intensity or scanning speed of the laser L, the flow of the melt inside the molten part 54 is disordered, sputtering may occur, or the laser L may penetrate the current collecting plate.

[0040] In contrast, in the present embodiment, as shown in (A) to Figure 3 and (C) of Figure 3 , the thickness T of the scanning area 58 is different between one end 58a side and the other end 58b side. The thickness T of the scanning area 58 in the present embodiment refers to the size of the scanning area 58 in the width direction A or the direction in which the electrode group and the current collecting plate are arranged. In addition, the thickness T of the scanning area 58 is, for example, the average value of the thicknesses at any 10 points, that is, the average thickness. For example, the thickness T of one end 58a is the average value of the thicknesses at 10 points arranged in the direction orthogonal to the scanning direction of the laser L at one end 58a.

[0041] Specifically, in the scanning area 58, the other end 58b located on the end end side of laser welding is thicker than one end 58a located on the start end side of laser welding. In addition, in at least a part of the interval from one end 58a to the other end 58b of the scanning area 58, the thickness T continuously or stepwise increases from the one end 58a side toward the other end 58b side.

[0042] Figure 3 and (A) to Figure 3In the scanning region 58 shown in (C), as an example, the thickness T continuously increases from one end 58a to the other end 58b. In addition, the manner in which the thickness T of the scanning region 58 changes is not limited to this. For example, the thickness T can change by only one step, or can change in multiple steps. In addition, it can also be that in one or more partitions within the scanning region 58, the thickness T changes continuously or stepwise, and in one or more other partitions, the thickness T is uniform. The thickness T of the scanning region 58 can be appropriately set based on the designer's experiments or simulations according to the composition of the current collector plate, the intensity of the laser L, or the scanning speed, etc. For example, the thickness T of each partition of the scanning region 58 is adjusted within the range of 0.1 mm or more and 0.8 mm or less.

[0043] By making the thickness T of the scanning region 58 thin on the start end side of the laser welding and thick on the end side of the laser welding, it is possible to easily make the supplied heat uniform throughout the scanning region 58. Thereby, in a state where the intensity of the laser L or the scanning speed is constant, it is possible to achieve the homogenization of the welding quality throughout the scanning region 58. In addition, it is also possible to suppress the occurrence of sputtering caused by the flow disorder of the molten material. Therefore, it is possible to improve the quality of the power storage device 1.

[0044] Preferably, the scanning region 58 is scanned with a laser L of constant intensity from one end 58a to the other end 58b. More preferably, the scanning region 58 is scanned with a laser L of constant intensity and constant scanning speed from one end 58a to the other end 58b. Thereby, it is possible to suppress the occurrence of sputtering caused by the flow disorder of the molten material, and it is possible to improve the quality of the power storage device 1. In addition, it is possible to suppress the complication of the control of the laser L.

[0045] The other end 58b of the scanning region 58 can also be located closer to the winding center C side of the electrode group 2 than one end 58a. That is, it can also be that the partition of the scanning region 58 close to the center of the electrode group 2 is thick and the partition close to the outside of the electrode group 2 is thin. At this time, each scanning region 58 is scanned with the laser L from the outside of the electrode group 2 toward the winding center C. Generally speaking, in the power storage device 1, current collection is performed from the outside of the electrode group 2 toward the winding center C side. Therefore, by making the winding center C side in the scanning region 58 thicker than the outside, the resistance of the part where more electrical concentration occurs can be reduced. Thereby, it is possible to suppress the heat generation accompanying current collection and improve the energy efficiency of the power storage device 1. Therefore, it is possible to improve the quality of the power storage device 1.

[0046] In addition, the other end 58b of the scanning region 58 may also be located on the side farther from the winding center C of the electrode group 2 than one end 58a. That is, it may also be that the partition closer to the outside of the electrode group 2 in the scanning region 58 is thick, and the partition closer to the center of the electrode group 2 is thin. At this time, each scanning region 58 is scanned with the laser L from the winding center C side of the electrode group 2 toward the outside. When a force is applied from the outside during the manufacturing process, transportation process, or use of the power storage device 1, a force (torque) in the circumferential direction or winding direction tends to be applied to the outside of the electrode group 2. In addition, since the scanning region 58 extends in the radial direction B, the force in the circumferential direction of the electrode group 2 tends to be weaker than the force in the radial direction B. In addition, for the thicker current collector plate, the bonding strength between the current collector plate and the exposed portion 12a is more likely to increase. Therefore, by making the outside in the scanning region 58 thicker than the winding center C side, the torque strength of the electrode group 2 can be improved. Therefore, an improvement in the quality of the power storage device 1 can be achieved.

[0047] As described above, the embodiments of the present disclosure have been described in detail. The foregoing embodiments merely show specific examples when implementing the present disclosure. The content of the embodiments does not limit the technical scope of the present disclosure, and various design changes such as changes, additions, and deletions of components can be made without departing from the idea of the invention defined in the claims. The new embodiments with design changes have the effects of both the combined embodiments and the deformations. In the foregoing embodiments, for the content that can be subject to such design changes, expressions such as "in this embodiment" and "in the present embodiment" are given to emphasize, and design changes are allowed even for the content without such expressions. In addition, any combination of the components included in each embodiment is also effective as a solution of the present disclosure. The hatching marked on the cross-section of the drawings does not limit the material of the object marked with hatching.

[0048] The embodiments can also be determined by the items described below.

[0049] [First item]

[0050] A method for manufacturing a power storage device (1), comprising:

[0051] Preparing an electrode group (2), which is an electrode group (2) having a current collector (12) with electrode active material layers (14) laminated thereon, and having a structure in which a plurality of exposed portions (12a) not covered by the electrode active material layers (14) in the current collector (12) are arranged,

[0052] Bringing the plurality of arranged exposed portions (12a) into contact with a current collector plate (20, 22), and scanning the scanning region (58) extending along the arrangement direction of the exposed portions (12a) in the current collector plate (20, 22) with a laser (L) from one end (58a) to the other end (58b) to bond the plurality of exposed portions (12a) to the current collector plate (20, 22);

[0053] The other end (58b) of the scanning region (58) is thicker than one end (58a), and in at least a part of the interval from one end (58a) to the other end (58b), the thickness (T) continuously or stepwise increases from the side of one end (58a) toward the side of the other end (58b).

[0054] [Second item]

[0055] The manufacturing method of the power storage device (1) as described in the first item,

[0056] The electrode group (2) has a wound structure in which a strip-shaped current collector (12) is wound.

[0057] The other end (58b) is located closer to the winding center (C) side of the electrode group (2) than one end (58a).

[0058] [Third item]

[0059] The manufacturing method of the power storage device (1) as described in the first item,

[0060] The electrode group (2) has a wound structure in which a strip-shaped current collector (12) is wound.

[0061] The other end (58b) is located farther from the winding center (C) of the electrode group (2) than one end (58a).

[0062] [Fourth item]

[0063] The manufacturing method of the power storage device (1) as described in any one of the first item to the third item includes:

[0064] Scanning a laser (L) with a constant intensity from one end (58a) to the other end (58b).

[0065] [Fifth item]

[0066] A power storage device (1) includes:

[0067] An electrode group (2) having a current collector (12) with an electrode active material layer (14) laminated thereon, and

[0068] Current collector plates (20, 22) joined to the current collector (12);

[0069] The electrode group (2) has a structure in which a plurality of exposed portions (12a) not covered by the electrode active material layer (14) in the current collector (12) are arranged, and the plurality of arranged exposed portions (12a) are joined to the current collector plates (20, 22).

[0070] The region (58) that extends along the arrangement direction of the exposed portions (12a) in the current collectors (20, 22) and joins the respective exposed portions (12a) has a thickness where the other end (58b) is thicker than the one end (58a), and in at least a part of the interval from the one end (58a) to the other end (58b), the thickness (T) increases continuously or stepwise from the one end (58a) side toward the other end (58b) side.

[0071] [Item 6]

[0072] The power storage device (1) as described in Item 5,

[0073] The electrode assembly (2) has a wound structure in which a strip-shaped current collector (12) is wound.

[0074] The other end (58b) is located closer to the winding center (C) side of the electrode assembly (2) than the one end (58a).

[0075] [Item 7]

[0076] The power storage device (1) as described in Item 5,

[0077] The electrode assembly (2) has a wound structure in which a strip-shaped current collector (12) is wound.

[0078] The other end (58b) is located farther from the winding center (C) of the electrode assembly (2) than the one end (58a).

[0079] Industrial availability

[0080] The present disclosure can be used in a method for manufacturing a power storage device and a power storage device.

[0081] Explanation of reference numerals

[0082] 1 Power storage device, 2 Electrode assembly, 12 Current collector, 12a Exposed portion, 14 Electrode active material layer, 20 First current collector, 22 Second current collector, 58 Scanning region, 58a One end, 58b Other end, C Winding center, L Laser.

Claims

1. A manufacturing method of an electricity storage device, comprising: Preparing an electrode assembly, which is an electrode assembly having a current collector with electrode active material layers laminated thereon, and which has a structure in which a plurality of exposed portions not covered by the electrode active material layers in the current collector are arranged; Bringing the plurality of arranged exposed portions into contact with a current collector plate, and scanning a scanning region extending along the arrangement direction of the exposed portions in the current collector plate with a laser from one end to the other end to join the plurality of exposed portions to the current collector plate; In the scanning region, the other end is thicker than the one end, and in at least a part of the interval from the one end to the other end, the thickness increases continuously or stepwise from the one end side toward the other end side.

2. The manufacturing method of the electricity storage device according to claim 1, The electrode assembly has a wound structure in which the strip-shaped current collector is wound, The other end is located on a side closer to the winding center of the electrode assembly than the one end.

3. The manufacturing method of the electricity storage device according to claim 1, The electrode assembly has a wound structure in which the strip-shaped current collector is wound, The other end is located on a side farther from the winding center of the electrode assembly than the one end.

4. The manufacturing method of the electricity storage device according to any one of claims 1 to 3, including: Scanning the laser with a constant intensity from the one end to the other end.

5. An electricity storage device, comprising: An electrode assembly, which has a current collector with electrode active material layers laminated thereon, and A current collector plate, joined to the current collector; The electrode assembly has a structure in which a plurality of exposed portions not covered by the electrode active material layers in the current collector are arranged, and the plurality of arranged exposed portions are joined to the current collector plate, In a region extending along the arrangement direction of the exposed portions in the current collector plate and joining each exposed portion, the other end is thicker than the one end, and in at least a part of the interval from the one end to the other end, the thickness increases continuously or stepwise from the one end side toward the other end side.

6. The electricity storage device according to claim 5, The electrode assembly has a wound structure in which the strip-shaped current collector is wound, The other end is located on a side closer to the winding center of the electrode assembly than the one end.

7. The electricity storage device according to claim 5, The electrode assembly has a wound structure in which the strip-shaped current collector is wound, and the other end is located on a side farther from the winding center of the electrode assembly than the one end.

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