Electricity storage device

Abstract

The disclosed electricity storage device (10) is provided with: an electrode group (14) having a first electrode (14a) and a second electrode (14b); a plurality of tabs (15) that are respectively connected to the first electrodes (14a) and overlap each other; and a terminal member (17) provided on the opposite side of the electrode group (14) with the plurality of tabs (15) therebetween. The terminal member (17) is welded to the plurality of tabs (15) by a laser beam irradiated from the terminal member (17) in the direction of the electrode group (14). At least the tab (15) closest to the electrode group (14) among the plurality of tabs (15) has a folded portion (15a) formed by folding a part of the tab (15) and having a part of a laser mark (LM) caused by laser light. As a result, it is possible to easily achieve both the avoidance of damage to the electrode body and the avoidance of poor welding of the plurality of tabs at the same time.

Description

Technical Field

[0001] The present disclosure relates to a power storage device. Background Art

[0002] Conventionally, a power storage device that stores electric power for supply to a load device is known (e.g., Patent Document 1). The power storage device of Patent Document 1 includes a stacked electrode body having positive and negative electrodes, a positive tab group formed by stacking positive tabs protruding from the positive electrodes, and a negative tab group formed by stacking negative tabs protruding from the negative electrodes. The positive and negative tab groups each include an extension extending in a predetermined direction and a folded-back portion folded back toward the extension. The power storage device also includes a retaining portion that holds the folded-back portion in a state folded back toward the extension. An example of such a retaining portion is a welded portion formed by welding the overlapping region of the folded-back portion and the extension portion.

[0003] Prior art literature

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-44148 Summary of the Invention

[0005] However, depending on the structure of the energy storage device, multiple tabs connected to the electrodes of the electrode group may be welded together by irradiating the electrode group with a laser beam directed toward the electrode group. In this case, if the laser output is too high, the electrode body may be damaged. On the other hand, if the laser output is insufficient, some tabs (particularly those closest to the electrode group) may not be properly welded, resulting in weld defects. In such situations, one of the objectives of the present disclosure is to easily and simultaneously avoid damage to the electrode body and weld defects on multiple tabs.

[0006] One aspect of the present disclosure relates to an electricity storage device. The electricity storage device comprises: an electrode group including a first electrode and a second electrode; a plurality of electrode tabs respectively connected to the first electrode and overlapping with each other; and a terminal member disposed on an opposite side of the electrode group across the plurality of electrode tabs, the terminal member being welded to the plurality of electrode tabs by laser light irradiated from the terminal member toward the electrode group. At least the electrode tab closest to the electrode group among the plurality of electrode tabs has a folded portion formed by folding a portion of the electrode tab, and a portion of a laser mark caused by the laser light is formed on the folded portion.

[0007] According to the present disclosure, it is possible to easily achieve both avoiding damage to the electrode body and avoiding welding defects of a plurality of tabs.

[0008] While the novel features of the present disclosure are described in the appended claims, the present invention both in terms of organization and content, together with other objects and features of the application, can be better understood from the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a longitudinal sectional view schematically showing a power storage device according to one embodiment.

[0010] Figure 2 It is a longitudinal sectional view schematically showing a power storage device according to a modification. DETAILED DESCRIPTION

[0011] The following describes embodiments of the power storage device disclosed herein. However, the present disclosure is not limited to the following examples. While specific numerical values and materials are sometimes cited in the following description, other numerical values and materials may be used as long as the effects of the present disclosure are achieved.

[0012] The energy storage device disclosed herein may be a primary battery such as a lithium primary battery, a secondary battery such as an alkaline storage battery (nickel-metal hydride battery, nickel-cadmium battery, etc.), a lithium-ion secondary battery, or a lithium metal secondary battery. It may also be an energy storage device in which at least one of the positive and negative electrodes is a polarizable electrode that develops capacity through a non-Faradaic reaction (e.g., a lithium-ion capacitor or an electric double-layer capacitor). The energy storage device disclosed herein includes an electrode group, a plurality of tabs, and a terminal member.

[0013] The electrode group includes a first electrode and a second electrode. The electrode group may be, for example, a wound electrode group in which the first electrode and the second electrode are wound with a separator interposed therebetween. The outer shape of the electrode group may be, for example, cylindrical or prismatic. One of the first electrode and the second electrode is a positive electrode, and the other of the first electrode and the second electrode is a negative electrode.

[0014] The first electrode, the second electrode, and the separator may each be in the form of a long sheet (or strip). The first electrode may also include a long sheet-shaped first current collector and a first active material layer supported on the first current collector. The second electrode may also include a long sheet-shaped second current collector and further include a second active material layer supported on the second current collector. The separator may also be composed of a porous sheet having ion permeability and insulating properties. Examples of porous sheets include microporous films, woven fabrics, and non-woven fabrics.

[0015] In the following description, using a lithium-ion secondary battery as an example, the first active material layer can be provided on both surfaces of the first current collector, or on a single surface. When the first electrode is a positive electrode, the first current collector is a positive electrode current collector (e.g., aluminum foil or aluminum alloy foil), and the first active material layer is a positive electrode active material layer (e.g., a lithium-containing transition metal oxide). When the first electrode is a negative electrode, the first current collector is a negative electrode current collector (e.g., copper foil or copper alloy foil), and a negative electrode active material layer (e.g., a carbonaceous material) can also be provided as the first active material layer.

[0016] The plurality of tabs are respectively connected to the first electrode and overlap with each other. The plurality of tabs may be separate from the first electrode or may be integral with the first electrode. The plurality of tabs may also be composed of a conductor such as a metal foil. The number of tabs is not particularly limited, and for example, it may be more than 2, more than 3, or more than 4 or 5. In addition, the number of tabs may be 15 or less. The thickness of the tabs is not particularly limited, and for example, it may be more than 40 μm and less than 120 μm.

[0017] The terminal member is disposed on the opposite side of the electrode group across the plurality of tabs. The terminal member is welded to the plurality of tabs by laser light directed from the terminal member toward the electrode group. Thus, the terminal member is electrically connected to the first electrode via the plurality of tabs. The terminal member may also be formed of a conductor.

[0018] When laser welding the terminal member and multiple tabs, it is necessary to obtain a laser output sufficient to weld all the tabs. On the other hand, if the laser output becomes too high, there is a risk that the electrode body will be damaged by the laser penetrating the tab closest to the electrode group. In other words, the laser output is required to reach the tab closest to the electrode group among the multiple tabs without penetrating it. However, in actual manufacturing processes that include various tolerances, it is difficult to consistently obtain such a laser output.

[0019] In contrast, in the storage device disclosed herein, at least the tab closest to the electrode group among the multiple tabs has a folded portion, which is formed by folding a portion of the tab and forms a portion of a laser mark caused by the laser. In this case, as long as at least a portion of the folded portion of the tab closest to the electrode group is laser welded, it becomes easy to meet the requirements of the laser output. For example, in the case where the folded portion is formed by doubly folding a portion of the tab, the allowable range of the laser output for not penetrating the tab closest to the electrode group is essentially doubled compared to the case where there is no folded portion. Therefore, it is easy to simultaneously avoid damage to the electrode body and avoid poor welding of multiple tabs.

[0020] It is also possible that only the tab closest to the electrode group among the multiple tabs has a folded portion. In this case, the effect of the present disclosure of increasing the allowable range of laser output can be obtained with the necessary minimum space. That is, although the tab with a folded portion occupies more space in the power storage device than the tab without a folded portion, in order to obtain the effect of the present disclosure, it is sufficient for the tab closest to the electrode group to have a folded portion, so it is preferred that only the tab closest to the electrode group has a folded portion. However, tabs other than the tab closest to the electrode group may also have a folded portion, and the number and arrangement of tabs with folded portions are not particularly limited.

[0021] The folded portion can also be formed by doubly folding a portion of the tab. In this case, the advantages of the present disclosure can be achieved, such as increasing the allowable range of laser output while suppressing the disadvantage of occupying space caused by the folded portion. Furthermore, there is no particular limit on the number of times a portion of the tab is folded to form the folded portion.

[0022] As described above, according to the present disclosure, for example, by providing a folded portion in the tab closest to the electrode body, it is possible to easily achieve both avoiding damage to the electrode body and avoiding poor welding of the plurality of tabs.

[0023] Hereinafter, an example of the power storage device disclosed herein will be described in detail with reference to the accompanying drawings. The above-mentioned components can be applied to the components of the power storage device of the example described below. The components of the power storage device of the example described below can be changed based on the above description. In addition, the matters described below can also be applied to the above-mentioned embodiment. Among the components of the power storage device of the example described below, components that are not essential to the power storage device of the present invention can also be omitted. Furthermore, the figures shown below are schematic diagrams and do not accurately reflect the shape and number of actual components.

[0024] An embodiment of the present disclosure will be described. The power storage device 10 of this embodiment is a secondary battery that can be repeatedly charged and discharged, for example, a lithium ion secondary battery or a lithium secondary battery (lithium metal secondary battery). Figure 1 As shown, the electricity storage device 10 includes a case 11 , an electrode group 14 , a plurality of tabs 15 , a positive electrode terminal 16 , an end current collecting plate 19 , a negative electrode current collecting plate 22 , and a sealing plate 23 .

[0025] The housing 11 is formed at one end ( Figure 1 The housing 11 has an open bottomed cylindrical shape (at its lower end). The housing 11 is made of metal. A through-hole 12 is formed in the center of the bottom of the housing 11, through which a positive electrode terminal 16 is inserted. The housing 11 houses an electrolyte (not shown) along with an electrode assembly 14. A recess 13 is formed near the opening of the housing 11, recessed radially inward.

[0026] The electrode assembly 14 includes a positive electrode 14a and a negative electrode 14b. The electrode assembly 14 is a wound-type electrode assembly in which the positive electrode 14a and the negative electrode 14b are wound with a separator (not shown) interposed therebetween. The electrode assembly 14 is generally cylindrical. The positive electrode 14a is an example of a first electrode, and the negative electrode 14b is an example of a second electrode.

[0027] The plurality of tabs 15 are connected to the positive electrode 14a and overlap each other. The plurality of tabs 15 may also extend along the direction of the winding axis of the electrode group 14 ( Figure 1 The plurality of tabs 15 are formed of a conductor. In this embodiment, the number of tabs 15 is 8, but is not limited thereto. Figure 1 , only four of the eight tabs 15 are shown. The thickness of each tab 15 may be 60 μm or more and 80 μm or less.

[0028] An insulating member 24 is disposed between the electrode group 14 and the bottom of the case 11 to electrically insulate the two. The insulating member 24 is made of, for example, an insulating resin. The insulating member 24 may also be attached to the bottom of the case 11.

[0029] Positive terminal 16 is provided on the opposite side of electrode group 14, with multiple tabs 15 interposed therebetween. Positive terminal 16 is inserted through through-hole 12 in the bottom of case 11, penetrating the bottom of case 11. Positive terminal 16 is made of metal and is insulated from case 11 using a rivet or other similar material. Positive terminal 16 is insulated from case 11 by a positive electrode gasket 26 made of an insulating material. An insulating plate 25 is disposed between positive terminal 16 and electrode group 14 to electrically insulate the two.

[0030] The positive terminal 16 includes a first terminal member 17 extending throughout the interior and exterior of the housing 11, and a disc-shaped second terminal member 18 joined to the first terminal member 17 and exposed outside the housing 11. The first terminal member 17 includes a disc-shaped first portion 17a, a hollow, cylindrical second portion 17b formed continuously with the first portion 17a and inserted through the through-hole 12, and a third portion 17c extending radially outward from the end of the second portion 17b and joined to the second terminal member 18. The first terminal member 17 is welded to the plurality of tabs 15 in the first portion 17a by laser light directed from the first terminal member 17 toward the electrode group 14. Thus, the positive terminal 16 is electrically connected to the positive electrode 14a via the plurality of tabs 15, functioning as an external positive terminal for the power storage device 10. The first terminal member 17 is an example of a terminal member.

[0031] At least the tab 15 closest to the electrode group 14 among the plurality of tabs 15 ( Figure 1The lowermost tab 15 has a folded portion 15a. This folded portion 15a is formed by folding a portion of the tab 15 (specifically, a portion on the front end) and bears a portion of the laser mark LM caused by the laser. The folded portion 15a is located on the opposite side of the electrode assembly 14, with the insulating plate 25 interposed therebetween. The laser mark LM may be formed on only one of the two tabs forming the folded portion 15a, the one closest to the first terminal member 17, or on both tabs.

[0032] It is preferred that only the tab 15 closest to the electrode group 14 among the plurality of tabs 15 have the folded portion 15a. It is preferred that the folded portion 15a is formed by doubly folding a portion of the tab 15.

[0033] The folded portion 15a of this embodiment is formed by moving a portion of the tab 15 closest to the electrode group 14 in a direction away from the electrode group 14 ( Figure 1 Furthermore, if Figure 2 As shown in the modified example, the folded portion 15a may be formed by moving a portion of the tab 15 closest to the electrode group 14 toward the electrode group 14 ( Figure 2 It is formed by folding back (below the center).

[0034] The end collector plate 19 is made of metal. The shape of the end collector plate 19 is not particularly limited, and may be, for example, generally cross-shaped. The end collector plate 19 is connected to the negative electrode 14b of the electrode assembly 14 by, for example, laser welding.

[0035] The negative electrode current collector plate 22 is electrically connected to the end current collector plate 19 via a metal connecting plate 21 (which may be ring-shaped, for example). Thus, the negative electrode current collector plate 22 is electrically connected to the negative electrode 14b. The negative electrode current collector plate 22 and connecting plate 21 may be welded together (e.g., by laser welding). The connecting plate 21 and the end current collector plate 19 may also be welded together (e.g., by laser welding). Furthermore, the negative electrode current collector plate 22 may be directly connected to the end current collector plate 19. In this case, the connecting plate 21 is not required. The negative electrode current collector plate 22 has one or more injection holes 22a for injecting electrolyte into the case 11. The negative electrode current collector plate 22 is welded to the recessed portion 13 of the case 11 at its outer edge (e.g., by laser welding). Thus, the case 11 is electrically connected to the negative electrode 14b via the negative electrode current collector plate 22 and other components.

[0036] The sealing plate 23 seals the opening of the housing 11. The sealing plate 23 is made of metal and is generally disk-shaped. The sealing plate 23 is insulated from the housing 11 by a negative electrode gasket 27. In this embodiment, the sealing plate 23 is not electrically connected to either the positive electrode 14a or the negative electrode 14b of the electrode assembly 14, but this is not the only limitation. The sealing plate 23 includes an explosion-proof mechanism (not shown) that activates when the internal pressure of the housing 11 exceeds a predetermined value.

[0037] -Method for manufacturing an electricity storage device-

[0038] The method for manufacturing the power storage device 10 of this embodiment includes: a first step of preparing an electrode group 14 having a first electrode 14a and a second electrode 14b, with a plurality of tabs 15 connected to the first electrode 14a; a second step of partially overlapping the plurality of tabs 15; a third step of folding at least a portion of the tab 15 closest to the electrode group 14 to form a folded portion 15a; a fourth step of disposing a first terminal member 17 on the opposite side of the electrode group 14 with the plurality of tabs 15 interposed therebetween; and a fifth step of welding the overlapping plurality of tabs 15 and the first terminal member 17 by irradiating a laser beam from the first terminal member 17 toward the electrode group 14. In the fourth and / or fifth steps, for example, a rod-shaped jig may be inserted into the hollow space of the electrode group 14 to sandwich the plurality of tabs 15 between the jig and the first terminal member 17. In the fifth step, a portion of the laser mark LM is formed on at least a portion of the folded portion 15a of the tab 15 closest to the electrode assembly 14. The order of executing the steps is not particularly limited, and multiple steps may be executed simultaneously.

[0039] Postscript

[0040] The following technology is disclosed through the description of the above embodiments.

[0041] (Technique 1)

[0042] A power storage device comprising:

[0043] an electrode group comprising a first electrode and a second electrode;

[0044] a plurality of tabs respectively connected to the first electrode and overlapping with each other; and

[0045] A terminal member is provided on the opposite side of the electrode group with the plurality of tabs interposed therebetween, and the terminal member is welded to the plurality of tabs by laser irradiation from the terminal member toward the electrode group.

[0046] At least the tab closest to the electrode group among the plurality of tabs has a folded portion formed by folding a portion of the tab, and a portion of a laser mark caused by the laser is formed in the folded portion.

[0047] (Technique 2)

[0048] According to the power storage device of technique 1, only the tab closest to the electrode group among the plurality of tabs has the folded portion.

[0049] (Technique 3)

[0050] In the power storage device according to technology 1 or 2, the folded portion is formed by doubly folding the portion of the tab.

[0051] Although the present invention has been described in terms of presently preferred embodiments, this disclosure should not be construed in a limiting sense. Various modifications and variations will undoubtedly become apparent to those skilled in the art upon reading the above disclosure. Therefore, the appended claims should be construed to include all modifications and variations that do not depart from the true spirit and scope of this disclosure.

[0052] Industrial applicability

[0053] The present disclosure can be used in a power storage device.

[0054] Description of Reference Numerals

[0055] 10: Power storage device

[0056] 11: Shell

[0057] 12: Through hole

[0058] 13: concave part

[0059] 14: Electrode group

[0060] 14a: Positive electrode (first electrode)

[0061] 14b: Negative electrode (second electrode)

[0062] 15: Tab

[0063] 15a: Folding part

[0064] 16: Positive terminal

[0065] 17: First terminal member (terminal member)

[0066] 17a: Part 1

[0067] 17b: Part 2

[0068] 17c: Part 3

[0069] 18: Second terminal component

[0070] 19: End collector plate

[0071] 21: Connecting plate

[0072] 22: Negative electrode collector plate

[0073] 22a: Injection hole

[0074] 23: Sealing plate

[0075] 24: Insulation components

[0076] 25: Insulation board

[0077] 26: Positive electrode gasket

[0078] 27: Negative electrode liner

[0079] LM: Laser Mark

Claims

1. A power storage device comprising: an electrode group comprising a first electrode and a second electrode; a plurality of tabs respectively connected to the first electrode and overlapping with each other; and A terminal member is provided on the opposite side of the electrode group with the plurality of tabs interposed therebetween, and the terminal member is welded to the plurality of tabs by laser irradiation from the terminal member toward the electrode group. At least the tab closest to the electrode group among the plurality of tabs has a folded portion formed by folding a portion of the tab, and a portion of a laser mark caused by the laser is formed in the folded portion. 2 . The power storage device according to claim 1 , wherein only the tab closest to the electrode group among the plurality of tabs has the folded portion. 3 . The power storage device according to claim 1 , wherein the folded portion is formed by doubly folding the portion of the tab.

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