Current collector structure and secondary battery using the same

Abstract

The problem to be solved by the present invention is to prevent the joint from breaking when the collector tabs are bundled and joined, and to seek to maintain the current path. In order to solve the above problems, the present invention provides a collector structure, including: a plurality of electrode collectors, composed of a metal porous body; a plurality of tabs, in each electrode collector, extending from one end of the metal porous body; and connecting tab leads to electrically connect different tabs to each other. The connecting tab leads are cross-joined with each tab to form a first compression joint, and further folded back from one tab toward the other tab, for example, configured in an accordion shape. At the tab bundling position where the first compression joint is overlapped, a second compression joint is formed by using ultrasound or the like for bundling.

Description

Technical Field

[0001] The present invention relates to a current collector structure and a secondary battery using the same. Background Art

[0002] In the past, lithium-ion secondary batteries have been widely used as secondary batteries with high energy density. Liquid lithium-ion secondary batteries have the following battery cell structure: there is a separator between the positive electrode and the negative electrode, and it is filled with a liquid electrolyte (electrolyte). In addition, when it is a solid-state battery in which the electrolyte is solid, it has a battery cell structure in which a solid electrolyte is present between the positive electrode and the negative electrode. A plurality of these single battery cells are laminated to form a lithium-ion secondary battery.

[0003] It is proposed to use a metal porous body as a current collector constituting a positive electrode and a negative electrode (for example, refer to Patent Document 1). The metal porous body has a mesh structure with fine pores and a large surface area. By filling an electrode composite material containing an electrode active substance into the interior of the mesh structure, the amount of the electrode active substance per unit area of ​​the electrode layer can be increased.

[0004] Furthermore, as a method of increasing the connection strength between porous metal bodies in an electrode, an electrode is also known in which another porous metal body is disposed between the ends of a porous metal body and the three are crimped together (for example, see Patent Document 2).

[0005] [Prior art literature]

[0006] (Patent Document)

[0007] Patent Document 1: Japanese Patent Application Publication No. 2012-186139

[0008] Patent Document 2: Japanese Patent Application Publication No. 2004-063398 Summary of the invention

[0009] [Problems to be solved by the invention]

[0010] Figure 7 is a perspective view showing an embodiment of a secondary battery using a conventional current collector structure. Figure 8 This is a three-dimensional image of a secondary battery before the tabs are assembled. Fig. 9 yes Figure 7 A cross-sectional view of the lug clustering area. Fig.10 yes Fig. 9 An enlarged cross-sectional view of the vicinity of the lug clustering portion.

[0011] like Figure 7As shown, the secondary battery 200 is an electrode laminate formed by alternately laminating a positive electrode 10, a solid electrolyte layer 30, and a negative electrode 20, with a positive electrode tab 11 extending from the positive electrode 10, and a negative electrode tab 21 extending from the negative electrode 20. The positive electrode 10 and the negative electrode 20 are formed of a metal porous body as a whole, and there are a composite material filled area filled with an electrode composite material and a composite material unfilled area not filled with an electrode composite material, and the positive electrode tab 11 and the negative electrode tab 21 constitute the composite material unfilled area. The positive electrode tab 11 and the negative electrode tab 21 are respectively bundled to form a joint 60. In addition, although Figure 7 Only the bundled state of the positive electrode tabs 11 is shown, and the bundled state of the negative electrode tabs 21 is omitted, but the negative electrode tabs are also bundled in the same manner.

[0012] Figure 8 yes Figure 7 The state of the lugs before they are assembled. Fig. 9 As shown in FIG. 1 , the ends of the positive electrode tab 11 and the negative electrode tab 21 are respectively bundled and compressed and joined by ultrasonic or resistance welding. The enlarged view of the joint 60 at this time is Fig.10 A plurality of positive electrode tabs 11 (three in this embodiment) are laminated at the joint 60 .

[0013] The porous metal body constituting the tab generally has pores of 90% or more by volume. Therefore, if compression bonding is performed, the thickness of the joint 60 will be reduced to about 1 / 10 (d0>d1). At this time, there is the following problem: a large height difference (thickness difference) is generated between the joint 60 and its surroundings. Fig.10 On the upper side of the joint 60 in the bonding process, the positive electrode tab 11 is in a shape that is pressed and cut by a pressure member such as an ultrasonic horn, and the positive electrode tab 11 in the laminated upper portion is particularly prone to breakage.

[0014] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to prevent the joint from breaking when the collector tabs are bundled and joined together, and to maintain the current path.

[0015] [Technical means to solve the problem]

[0016] The inventors of the present invention have found that the above-mentioned problem can be solved by configuring a connecting tab lead across the tabs in a specific state, thereby completing the present invention. That is, the present invention provides the following solutions.

[0017] (1) A current collector structure, comprising:

[0018] A plurality of electrode current collectors, composed of a porous metal body;

[0019] A plurality of tabs extending from one end of the aforementioned porous metal body in each electrode current collector; and

[0020] Connecting tab leads to electrically connect two or more tabs to each other; and

[0021] The aforementioned connecting tab lead is made of a metal porous body.

[0022] The connecting tab lead and the tab have a first compression joint at an intersection where the extension direction of the tab intersects the length direction of the connecting tab lead.

[0023] The connecting tab lead is configured to be bent back from the intersection with one tab and extend toward the intersection with the other tab.

[0024] A second compression joint is provided at the tab clustering position where a plurality of the aforementioned intersections are stacked.

[0025] According to the invention of (1), the first compression joint and the second compression joint have the tab and the connecting tab lead. Therefore, since the two are intertwined to form the compression joint, the density of the porous metal body in the compression joint becomes high. Therefore, the fracture of the joint can be effectively prevented.

[0026] (2) The current collector structure according to (1), wherein the second compression joint is connected to an external connection tab.

[0027] According to the invention of (2), the second compression joint portion can be joined to the external connection tab without breaking the tab.

[0028] (3) A secondary battery comprising the current collector structure described in (1) or (2), and comprising:

[0029] The positive electrode and / or the negative electrode has a composite material filled region filled with an electrode composite material and a composite material unfilled region not filled with the electrode composite material in the metal porous body of the electrode current collector; and

[0030] an electrolyte disposed between the electrodes; and

[0031] The region of the electrode current collector that is not filled with the composite material constitutes the electrode tab.

[0032] According to the invention of (3), a secondary battery capable of achieving the effect of (1) or (2) can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a perspective view showing one embodiment of a secondary battery using the current collector structure of the present invention.

[0034] Figure 2 It is a plan view showing a state where a plurality of tabs extending from electrodes are connected by connecting tab leads.

[0035] Figure 3 yes Figure 1 A three-dimensional image of a secondary battery before the tabs are bundled.

[0036] Figure 4 yes Figure 3 An enlarged stereogram of the vicinity of the pole ear.

[0037] Figure 5 It is a cross-sectional schematic diagram showing the arrangement state of the connection tab lead and its modification.

[0038] Figure 6 yes Figure 1 An enlarged cross-sectional view of the lug clustering portion.

[0039] Figure 7 This is a perspective view showing an embodiment of a secondary battery using a conventional current collector structure.

[0040] Figure 8 yes Figure 7 A three-dimensional image of a secondary battery before the tabs are bundled.

[0041] Fig. 9 yes Figure 7 A cross-sectional view near the lug clustering portion.

[0042] Fig.10 yes Fig. 9 An enlarged cross-sectional view of the vicinity of the lug clustering portion. DETAILED DESCRIPTION

[0043] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The content of the present invention is not limited to the description of the following embodiment. In addition, in the following embodiment, a lithium-ion battery of a solid-state battery is used as an example for description, but the present invention is not limited to a solid-state battery, and can also be applied to a secondary battery having a liquid electrolyte and a separator. In addition, it can also be applied to batteries other than lithium-ion batteries.

[0044] [First embodiment]

[0045] <Overall structure of lithium-ion secondary battery>

[0046] like Figure 1 As shown, the present embodiment Figure 1 The lithium-ion secondary battery 100 is a solid-state battery and is an electrode laminate in which a positive electrode 10, a solid electrolyte layer 30, and a negative electrode 20 are alternately laminated. Although not shown in the figure, the electrode laminate includes the following tabs and their bundled portion, which are vacuum-packaged together by an outer packaging film, and the lead tabs of the positive and negative electrodes electrically connected to the tab bundled portion extend out of the outer packaging film.

[0047] Specifically, the positive electrode tab 11 and the negative electrode tab 21 extend from one end of the current collector of each electrode of the electrode laminate and are bundled and compressed and joined at the second compression joint 17 to form an integrated body. Figure 6 ). In addition, the details of the collector structure will be described below.

[0048] Next, each component will be described.

[0049] <Positive and negative electrodes>

[0050] In this embodiment, in each of the positive electrode 10 and the negative electrode 20 , the current collector is constituted by a porous metal body having pores (interconnected pores) that are continuous with each other.

[0051] The holes of each current collector are material-filled regions filled with electrode materials (positive electrode materials and negative electrode materials) containing electrode active materials, while the positive electrode tabs 11 and negative electrode tabs 21 are material-unfilled regions not filled with electrode materials.

[0052] (Current Collector)

[0053] The current collector is composed of a metal porous body having mutually continuous pores. By having mutually continuous pores, the positive electrode composite material and the negative electrode composite material containing the electrode active material can be filled inside the pores, thereby increasing the amount of the electrode active material per unit area of ​​the electrode layer. As the above-mentioned metal porous body, there is no particular limitation as long as it has mutually continuous pores, and examples thereof include foamed metal, metal mesh, porous metal, punched metal, metal nonwoven fabric, etc. having pores formed by foaming.

[0054] The metal used for the metal porous body is not particularly limited as long as it has conductivity, and examples thereof include nickel, aluminum, stainless steel, titanium, copper, silver, etc. Among them, as the current collector constituting the positive electrode, in a battery using a solid electrolyte, preferably foamed aluminum, foamed nickel, and foamed stainless steel are used, and in a battery using an electrolyte, foamed aluminum is used. As the current collector constituting the negative electrode, whether it is a battery using a solid electrolyte or a battery using an electrolyte, foamed copper, foamed nickel, and foamed stainless steel can be preferably used.

[0055] By using a current collector of a metal porous body, the amount of active material per unit area of ​​the electrode can be increased, and as a result, the volume energy density of the lithium ion secondary battery can be improved. In addition, since the positive electrode composite material and the negative electrode composite material are easily fixed, it is different from the previous electrode using a metal foil as a current collector. When the electrode composite material layer is thickened, it is not necessary to thicken the coating slurry forming the electrode composite material layer. Therefore, it is possible to reduce the adhesive such as the organic polymer compound required for thickening. Therefore, it is possible to increase the capacity per unit area of ​​the electrode, thereby realizing the high capacity of the lithium ion secondary battery.

[0056] (Electrode Composite Material)

[0057] The positive electrode composite material and the negative electrode composite material are respectively arranged in the hole formed in the current collector. The positive electrode composite material and the negative electrode composite material contain a positive electrode active material and a negative electrode active material as essential components, respectively.

[0058] (Electrode Active Material)

[0059] The positive electrode active material is not particularly limited as long as it can absorb and release lithium ions, and examples thereof include LiCoO2, Li(Ni 5 / 10 Co 2 / 10 Mn 3 / 10 )O2、Li(Ni 6 / 10 Co 2 / 10 Mn 2 / 10 )O2、Li(Ni 8 / 10 Co 1 / 10 Mn 1 / 10 )O2、Li(Ni 0.8 Co 0.15 Al 0.05 )O2、Li(Ni 1 / 6 Co 4 / 6 Mn 1 / 6 )O2、Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2, LiCoO4, LiMn2O4, LiNiO2, LiFePO4, lithium sulfide, sulfur, etc.

[0060] The negative electrode active material is not particularly limited as long as it can absorb and release lithium ions, and examples thereof include metallic lithium, lithium alloys, metal oxides, metal sulfides, metal nitrides, Si, SiO, and carbon materials such as artificial graphite, natural graphite, hard carbon, and soft carbon.

[0061] (Other ingredients)

[0062] The electrode composite material may also contain any other components except the electrode active material and the ion conductive particles. As other components, there is no particular limitation, as long as they are components that can be used when making lithium ion secondary batteries. For example, conductive aids, adhesives, etc. can be listed. As conductive aids for the positive electrode, acetylene black, etc. can be exemplified, and as adhesives for the positive electrode, polyvinylidene fluoride, etc. can be exemplified. As adhesives for the negative electrode, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium polyacrylate, etc. can be exemplified.

[0063] (Method for manufacturing positive electrode and negative electrode)

[0064] The positive electrode 10 and the negative electrode 20 are obtained by filling the pores of a metal porous body having mutually continuous pores as a current collector with an electrode composite. First, the electrode active material and, if necessary, a binder or an auxiliary agent are uniformly mixed using a conventionally known method to obtain a paste-like electrode composite composition adjusted to a specific viscosity.

[0065] Next, the electrode composite composition is filled as an electrode composite into the pores of the metal porous body as a current collector. The method of filling the electrode composite into the current collector is not particularly limited, and the following method can be cited, for example: using a plunger-type die coater to apply pressure to fill the slurry containing the electrode composite into the pores of the current collector. In addition to the above, the interior of the metal porous body can also be impregnated with an ion conductor layer by an impregnation method.

[0066] <Solid electrolyte layer>

[0067] like Figure 1 As shown, in the present invention, a solid electrolyte layer 30 is formed between the positive electrode 10 and the negative electrode 20 .

[0068] The solid electrolyte constituting the solid electrolyte layer 30 is not particularly limited, and examples thereof include sulfide-based solid electrolyte materials, oxide-based solid electrolyte materials, nitride-based solid electrolyte materials, and halide-based solid electrolyte materials. As sulfide-based solid electrolyte materials, for example, if it is a lithium-ion battery, LPS-based halogens (Cl, Br, I), or Li2S-P2S5, Li2S-P2S5-LiI, etc. can be listed. In addition, the above-mentioned "Li2S-P2S5" record refers to a sulfide-based solid electrolyte material formed using a raw material composition containing Li2S and P2S5, and the other records are the same. As oxide-based solid electrolyte materials, for example, if it is a lithium-ion battery, sodium superion conductor (NASICON) type oxides, garnet-type oxides, perovskite-type oxides, etc. can be listed. As NASICON-type oxides, for example, oxides containing Li, Al, Ti, P, and O (such as Li 1.5 Al 0.5 Ti 1.5(PO4)3). Examples of garnet-type oxides include oxides containing Li, La, Zr, and O (e.g., Li7La3Zr2O 12 ). Examples of perovskite-type oxides include oxides containing Li, La, Ti, and O (eg, LiLaTiO 3 ).

[0069] <Liquid Electrolyte>

[0070] The electrolyte dissolved in the non-aqueous solvent is not particularly limited, and examples thereof include LiPF6, LiBF4, LiClO4, LiN(SO2CF3), LiN(SO2C2F5)2, LiCF3SO3, LiC4F9SO3, LiC(SO2CF3)3, LiF, LiCl, LiI, Li2S, Li3N, Li3P, Li 10 GeP2S 12 (LGPS), Li3PS4, Li6PS5Cl, Li7P2S8I, Li x PO y N z (x=2y+3z-5, LiPON), Li7La3Zr2O 12 (LLZO), Li 3x La 2 / 3-x TiO3(LLTO), Li 1+x Al x Ti 2-x (PO4)3(0≦x≦1, LATP), Li 1.5 Al 0.5 Ge 1.5 (PO4)3(LAGP), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 , Li 1+x+y Al x (Ti,Ge) 2-x Si y P 3-y O 12 , Li 4- 2x Zn x GeO4 (LISICON), etc. The above-mentioned materials may be used alone or in combination of two or more.

[0071] The non-aqueous solvent contained in the electrolyte is not particularly limited, and non-protonic solvents such as carbonates, esters, ethers, nitriles, sulfones, and lactones can be listed. Specifically, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), tetrahydrofuran (THF), 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, acetonitrile (AN), propionitrile, nitromethane, N,N-dimethylformamide (DMF), dimethyl sulfoxide, cyclopentane, γ-butyrolactone, etc. can be listed. The above can be used alone or in combination of two or more.

[0072] (Diaphragm)

[0073] In particular, when a liquid electrolyte is used, the lithium ion secondary battery of this embodiment may also include a separator. The separator is located between the positive electrode and the negative electrode. Its material and thickness are not particularly limited, and a known separator such as polyethylene or polypropylene that can be used in a lithium ion secondary battery can be used.

[0074] <Current Collector Structure>

[0075] Next, use Figures 1 to 6 The collector structure which is a characteristic of the present invention is described in detail. Figures 7 to 10 The same components as those in the prior art are denoted by the same reference numerals, and their description is omitted.

[0076] Figure 1 is a perspective view showing an embodiment of a secondary battery using the current collector structure of the present invention, Figure 2 is a top view showing a state where a plurality of tabs extending from an electrode are connected by connecting tab leads, Figure 3 yes Figure 1 A three-dimensional image of a secondary battery before the tabs are assembled. Figure 4 yes Figure 3 The enlarged stereogram near the pole ear in the figure, Figure 5 is a cross-sectional schematic diagram showing the configuration state of the connecting tab lead and its modification example, Figure 6 yes Figure 1 An enlarged cross-sectional view of the lug clustering portion.

[0077] like Figure 1As shown, the lithium-ion secondary battery 100 is an electrode laminate formed by alternately laminating a positive electrode 10, a solid electrolyte layer 30, and a negative electrode 20. A positive electrode tab 11 extends from the positive electrode 10, and a negative electrode tab 21 extends from the negative electrode 20. The positive electrode 10 and the negative electrode 20 are formed of a metal porous body as a whole, and there are composite material filled areas filled with electrode composite materials and composite material unfilled areas not filled with electrode composite materials. The positive electrode tab 11 and the negative electrode tab 21 constitute the composite material unfilled area. The positive electrode tab 11 and the negative electrode tab 21 are respectively bundled to form a second compression joint 17. In addition, Figure 1 Only the positive electrode tabs 11 are shown in a bundled state, and the negative electrode tabs 21 are omitted. The negative electrode tabs 21 are also bundled in the same manner. Next, the current collector structure of the positive electrode 10 will be described. The negative electrode 20 also has the same structure.

[0078] Figure 2 It is extracted Figure 1 FIG. 1 is a top view of a connection member 10 a composed of a positive electrode 10 and a connection tab lead 15 .

[0079] The positive electrode tab 11 extending from one side of the substantially rectangular positive electrode 10 with a width narrower than the side is also substantially rectangular. As described above, the positive electrode tab 11 is a region of the porous metal body that is not filled with the alloy material.

[0080] The connecting tab lead 15 is not integral with the positive tab 11, but is made of the same metal porous body (the material or size may be different from the positive tab 11). When viewed from above, the whole is in the shape of a flat plate (lead) of a specific width, and has a length direction and a width direction. In this embodiment, the extension direction of the positive tab 11 and the length direction of the connecting tab lead 15 are arranged in a substantially orthogonal direction, and the two are overlapped at a position including the extension end of the positive tab 11 to form an intersection P. In addition, regarding the "intersection point" in the present invention, as long as Figure 2 At least a portion of the diagrams shown may overlap, or they may cross each other.

[0081] exist Figure 2 At the three intersection points P of the electrode, the connecting tab lead 15 and the positive electrode tab 11 have a first compression joint 16, thereby electrically connecting the connecting tab lead 15 and the positive electrode tab 11. Therefore, even when the positive electrode tab 11 is broken at a specific position, the overall electrical conduction is ensured. The first compression joint 16 is a state in which each metal porous body is meshed and crimped and entangled with each other, thereby ensuring reliable electrical and physical bonding. The formation of the first compression joint 16 can be carried out by a conventionally known pressing step.

[0082] Figure 3 Yes Figure 2 The connecting member 10a is folded and arranged to form an electrode laminate, and is a diagram showing Figure 1 A diagram of the state of the tabs before they are clustered. Figure 4 yes Figure 3 A magnified image of Figure 3 , Figure 4 In the figure, the connecting ear lead 15 is configured in a folded manner, extending from one side of the first positive electrode ear in the top layer of the laminated state, and folding back to one side of the second positive electrode ear in the lower layer through the folding portion 18, and then extending from the other side of the second positive electrode ear, and further folding back to the other side of the third positive electrode ear in the lower layer through the folding portion 18.

[0083] Figure 5 yes Figure 3 The schematic diagram of the XX cross-sectional view is a diagram showing an example of a folded state. In the present invention, the folded state is not particularly limited, and can be as follows Figure 5 (a) and (b) are folded back into a bellows shape, or Figure 5 (c) is folded back into a Z-shape. The number of foldings is not particularly limited, as long as the tab leads 15 are connected to connect two or more positive tabs 11. That is, all tabs may be bundled together or separately.

[0084] The upper and lower relationship between the connecting tab lead 15 and the positive tab 11 is also not particularly limited. Figure 5 As shown in (a) and (b), the positive electrode tab 11 may have the first compression joint 16 formed on the upper surface of the tab lead 15 or on the lower surface of the tab lead 15 .

[0085] Next, according to Figure 3 status, such as Figure 6 As shown, the ends of the positive electrode tab 11 and the negative electrode tab 21 are respectively bundled, and at the tab bundling position, the first compression joints 16 of each tab are stacked in a manner of overlapping multiple sheets. At this position, compression bonding is performed by ultrasonic welding or resistance welding, thereby forming a second compression joint 17, and bonding with the external connection tab 50, thereby obtaining Figure 1 The enlarged view of the vicinity of the second compression joint 17 is as follows: Figure 6 .

[0086] In the second compression joint 17, the joint of the connecting tab lead 15 having the first compression joint 16 and the positive tab 11 is laminated in a manner of overlapping multiple sheets (three layers in this embodiment, a total of three sheets), and compression bonding is performed using an ultrasonic horn 40. Similar to the first compression joint 16, the second compression joint 17 is in a state of being intertwined by the respective metal porous bodies meshing with each other and being crimped, thereby ensuring reliable electrical and physical bonding.

[0087] and Fig. 9 , Fig.10 Compared with the prior art, in the prior art, the joint 60 is composed of only three positive electrode tabs. In contrast, in this embodiment, the second compression joint 17 is formed by connecting the tab lead 15 and the positive electrode tab 11 to form the first compression joint 16 in advance, and the three first compression joints 16 are overlapped, so that there are actually six layers alternately laminated. Therefore, Figure 6 The thickness d2 is greater than Fig.10 The thickness d1 (d2>d1) is greater than that of the first compression joint 16. In addition, since the first compression joint 16 is formed in advance, the density of the porous metal body is also high, and the fracture strength is increased. Thus, the tab can be effectively prevented from being fractured during ultrasonic or resistance welding.

[0088] In addition, before forming the second compression joint 17, the pressing step may be performed again at the tab clustering position to obtain a joint surface with the external connection tab 50. In this case, when viewed from above, the pressing area of ​​the re-pressing step is preferably larger than the joint area of ​​the first compression joint 16. As a result, the height difference of the joint portion caused by the presence of the first compression joint 16 can be eliminated, thereby obtaining a smooth joint surface, and therefore, the joint with the external connection tab 50 becomes reliable.

[0089] As mentioned above, although the preferred embodiment of the present invention was described, the content of the present invention is not limited to the above-mentioned embodiment, and it can be modified appropriately.

[0090] Reference numerals

[0091] 10 Positive electrode

[0092] 10a Connecting member

[0093] 11. Positive electrode tab

[0094] 15 Connect the lead wire

[0095] 16 first compression joint

[0096] 17 Second compression joint

[0097] 18 Turnaround

[0098] 20 Negative electrode

[0099] 21. Negative electrode tab

[0100] 40 Ultrasonic welding head

[0101] 50 External connection tabs

[0102] 100 Lithium-ion secondary battery

Claims

1. A current collector structure, comprising: a plurality of electrode current collectors, each of which is composed of a metal porous body; A plurality of tabs extending from one end of the aforementioned porous metal body in each electrode current collector; and Connecting tab leads to electrically connect two or more tabs to each other; and The aforementioned connecting tab lead is made of a metal porous body. The connecting tab lead and the tab have a first compression joint at an intersection where the extension direction of the tab intersects the length direction of the connecting tab lead. The connecting tab lead is configured to be bent back from the intersection with one tab and extend toward the intersection with the other tab. The connecting tab lead forms a first compression joint with the first tab on the upper surface of the first tab, and forms a first compression joint with the second tab on the lower surface of the second tab. A second compression joint is provided at the tab clustering position where a plurality of the aforementioned intersections are stacked.

2. The current collector structure according to claim 1, wherein: The second compression joint is connected to an external connection tab.

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