Secondary battery

Abstract

To provide a highly reliable secondary battery that can increase the energy density per volume even when using a negative electrode layer whose thickness changes significantly due to charging and discharging.SOLUTION: In a secondary battery, ends of a plurality of positive electrode current collector extensions drawn from each of a plurality of positive electrode current collectors are stacked at the center in the stacking direction of an electrode stack to form a positive electrode current collector extension laminate, a positive electrode tab lead includes a clamping portion that clamps the positive electrode current collector extension laminate from both end sides in the stacking direction of the positive electrode current collector extension laminate, ends of a negative electrode current collector extensions drawn from each of the negative electrode current collectors are stacked at the center in the stacking direction of the electrode stack to form a negative electrode current collector extension laminate, and a negative electrode tab lead includes a clamping portion that clamps the negative electrode current collector extension laminate from both end sides in the stacking direction of the negative electrode current collector extension laminate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] In recent years, research and development has been conducted on secondary batteries that contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. A known secondary battery is a stacked secondary battery having an electrode stack in which multiple positive electrode layers and multiple negative electrode layers are alternately stacked with separators interposed between them. A known electrode lead-out structure for stacked secondary batteries is a structure in which current collector extensions, which are extensions of portions of the current collectors of each electrode layer, are stacked, and the stack of current collector extensions is connected to a tab lead (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-110492 Summary of the Invention [Problem to be solved by the invention]

[0004] In secondary battery technology, increasing capacity and improving long-term reliability are key challenges. Lithium metal secondary batteries have been studied as a high-capacity secondary battery. Lithium metal secondary batteries use lithium ions as a charge transfer medium, depositing lithium metal in the negative electrode layer during charging, and transferring the deposited lithium metal to the positive electrode layer as lithium ions during discharging.

[0005] In laminated lithium metal secondary batteries, the thickness of the negative electrode layer changes significantly during charging and discharging. For this reason, laminated lithium metal secondary batteries typically use a laminate film as the exterior body, which can expand and contract in response to changes in the thickness of the negative electrode layer. When the exterior body is formed using a laminate film, the electrode laminate is sandwiched between two laminate films, and the two laminate films are sealed. In a lithium metal secondary battery with this configuration, the tab lead is preferably located between the two laminate films, i.e., in the center of the electrode laminate in the stacking direction. If the tab lead is located in the center of the electrode laminate in the stacking direction, the current collector extension portion of the laminate will be positioned off-center in the stacking direction of the electrode laminate.

[0006] If the current collector extension is positioned off-center in the stacking direction, the difference in length between the current collector closest to the stack and the current collector farther from the stack becomes significant. In particular, in lithium metal secondary batteries, the thickness of the negative electrode layer changes significantly during charging and discharging, so the current collector farther from the stack must have a longer extension. As the length of the current collector extension increases, a larger space is required to accommodate the current collector extension, resulting in a decrease in the energy density per volume of the secondary battery. Furthermore, as the length of the current collector extension increases, the shape of the current collector extension increases due to changes in the thickness of the negative electrode layer, which can lead to fracture of the joint between the current collector extension and the tab lead, reducing reliability, such as ensuring an electrical conduction path.

[0007] The present invention has been made in view of the above, and aims to provide a highly reliable secondary battery that can increase the energy density per volume even when using a negative electrode layer whose thickness changes significantly during charge and discharge, thereby contributing to improved energy efficiency. [Means for solving the problem]

[0008] The inventors discovered that by arranging the current collector extension laminate at the center of the stacking direction of the electrode laminate and sandwiching the current collector extension laminate with tab leads from both ends in the stacking direction, it is possible to center the positions of the current collector extension laminate and the tab leads in the stacking direction of the electrode laminate, thereby achieving the above-mentioned object and arriving at the present invention.

[0009] (1) An electrode laminate including a plurality of positive electrode layers and a plurality of negative electrode layers alternately stacked with separators interposed therebetween, a positive electrode tab lead, and a negative electrode tab lead, wherein each of the plurality of positive electrode layers has a positive electrode current collector and a positive electrode current collector extension drawn from one side of the positive electrode current collector, and ends of the plurality of positive electrode current collector extensions drawn from each of the plurality of positive electrode current collectors form a positive electrode current collector extension laminate stacked at the center in the stacking direction of the electrode laminate, and the positive electrode tab lead connects the positive electrode current collector extension laminate to each of the plurality of negative electrode layers has a negative electrode current collector and a negative electrode current collector extension drawn from one side of the negative electrode current collector, and ends of the negative electrode current collector extension drawn from each of the negative electrode current collectors form a negative electrode current collector extension laminate stacked at the center of the stacking direction of the electrode laminate; and the negative electrode tab lead has clamping portions that clamp the negative electrode current collector extension laminate from both ends of the negative electrode current collector extension laminate in the stacking direction.

[0010] According to the secondary battery (1), the positive electrode current collector extension laminate and the negative electrode current collector extension laminate are disposed at the center of the stacking direction of the electrode laminate, and the structure is symmetrical about the center of the stacking direction of the electrode laminate. Therefore, even if the thickness of the negative electrode layer changes significantly due to charge and discharge, there is no need to excessively extend the lengths of the positive electrode current collector extension and the negative electrode current collector extension. This allows for a large capacity per volume. Furthermore, the positive electrode current collector extension laminate is clamped by the clamping portion of the positive electrode tab lead, so it is difficult to detach from the positive electrode tab lead, and the negative electrode current collector extension laminate is clamped by the clamping portion of the negative electrode tab lead, so it is difficult to detach from the negative electrode tab lead. This improves reliability. Furthermore, because the positive electrode tab lead and the negative electrode tab lead are disposed at the center of the stacking direction of the electrode laminate, it is easy to form an exterior body using a laminate film.

[0011] (2) The secondary battery according to (1), wherein the clamping portion of the positive electrode tab lead has a first bent portion bent to one side in the stacking direction of the positive electrode current collector extension laminate and a second bent portion bent to the other side, and the electrode laminate is clamped by the first bent portion and the second bent portion; the clamping portion of the negative electrode tab lead has a third bent portion bent to one side in the stacking direction of the positive electrode current collector extension laminate and a fourth bent portion bent to the other side, and the negative electrode current collector extension laminate is clamped by the third bent portion and the fourth bent portion.

[0012] According to the secondary battery (2), the clamping portions of the positive electrode tab lead and the negative electrode tab lead have the above-described structure, so that the positive electrode current collector extension laminate and the negative electrode current collector extension laminate can be securely clamped.

[0013] (3) The secondary battery described in (2), wherein the clamping portion of the positive electrode tab lead has two or more of at least one of the first bent portion and the second bent portion, and the clamping portion of the negative electrode tab lead has two or more of at least one of the third bent portion and the fourth bent portion.

[0014] According to the secondary battery (3), the clamping portions of the positive electrode tab lead and the negative electrode tab lead have the above-described structure, so that the positive electrode current collector extension laminate and the negative electrode current collector extension laminate can be firmly clamped.

[0015] (4) The secondary battery according to (2) or (3), wherein the first bent portion and the second bent portion of the positive electrode tab lead have flat portions facing each other, the positive electrode current collector extension laminate is welded to the flat portion of the first bent portion and the flat portion of the second bent portion, the first bent portion and the second bent portion of the positive electrode tab lead have flat portions facing each other, and the negative electrode current collector extension laminate is welded to the flat portion of the third bent portion and the flat portion of the fourth bent portion.

[0016] According to the secondary battery (4), since the positive electrode tab lead and the negative electrode tab lead have the above-described structure, the positive electrode current collector extension laminate and the negative electrode current collector extension laminate can be more firmly sandwiched between them.

[0017] (5) The secondary battery according to any one of (1) to (4), wherein at least one of the positive electrode current collector and the negative electrode current collector is a laminated current collector in which a first metal layer, a resin layer, and a second metal layer are laminated in this order.

[0018] According to the secondary battery of (5), at least one of the positive electrode current collector and the negative electrode current collector is a laminated current collector. Therefore, when the temperature of the secondary battery rises excessively, the resin layer of the laminated current collector melts, electrically insulating at least one of the positive electrode current collector and the positive electrode tab lead and the negative electrode current collector and the negative electrode tab lead, thereby improving safety when the temperature rises.

[0019] (6) The secondary battery according to (5), wherein the positive electrode current collector is the laminated current collector, and ends of the plurality of positive electrode current collector extensions are divided into a plurality of positive electrode current collector extension pieces by slits formed along the extension direction of the positive electrode current collector extensions, at least one of the plurality of positive electrode current collector extension pieces is folded so that the first metal layer is on the outside and the second metal layer is on the inside, and the other is folded so that the first metal layer is on the inside and the second metal layer is on the outside, and a first positive electrode current collector extension laminate is formed by stacking a plurality of the positive electrode current collector extension pieces folded so that the first metal layer is on the outside in contact with each other, and a second positive electrode current collector extension laminate is formed by stacking a plurality of the positive electrode current collector extension pieces folded so that the second metal layer is on the outside in contact with each other, and the first positive electrode current collector extension laminate and the second positive electrode current collector extension laminate are sandwiched by the negative electrode tab lead.

[0020] According to the secondary battery (6), the first metal layers of the positive electrode current collectors are connected to each other at the first positive electrode current collector extension laminate, and the second metal layers of the positive electrode current collectors are connected to each other at the second positive electrode current collector extension laminate, so that the first metal layers and the second metal layers of the positive electrode current collectors can be reliably electrically connected to each other.

[0021] (7) The secondary battery according to (5) or (6), wherein the negative electrode current collector is the laminated current collector, and ends of the plurality of negative electrode current collector extensions are divided into a plurality of negative electrode current collector extension pieces by slits formed along the extension direction of the negative electrode current collector extensions, at least one of the plurality of negative electrode current collector extension pieces is folded so that the first metal layer is on the outside and the second metal layer is on the inside, and the other is folded so that the first metal layer is on the inside and the second metal layer is on the outside, a plurality of the negative electrode current collector extension pieces folded so that the first metal layer is on the outside are stacked so as to be in contact with each other to form a first negative electrode current collector extension laminate, a plurality of the negative electrode current collector extension pieces folded so that the second metal layer is on the outside are stacked so as to be in contact with each other to form a second negative electrode current collector extension laminate, and the first negative electrode current collector extension laminate and the second negative electrode current collector extension laminate are sandwiched by the negative electrode tab lead.

[0022] According to the secondary battery (7), the first metal layers of the negative electrode current collectors are connected to each other at the first negative electrode current collector extension laminate, and the second metal layers of the negative electrode current collectors are connected to each other at the second negative electrode current collector extension laminate, so that the first metal layers and the second metal layers of the negative electrode current collectors can be reliably electrically connected to each other. [Effects of the Invention]

[0023] According to the present invention, even if a negative electrode layer that undergoes large changes in thickness due to charge and discharge is used, it is possible to provide a highly reliable secondary battery that can increase the energy density per volume. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view of a secondary battery according to a first embodiment of the present invention. [Figure 2] 2 is a plan view of the secondary battery shown in FIG. 1 with the exterior body thereof omitted. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is a perspective view of a positive electrode tab lead used in the secondary battery shown in FIG. [Figure 5] 10 is a plan view of the positive electrode tab lead side of a secondary battery according to a second embodiment of the present invention, with the exterior body omitted. FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 5. [Figure 8] FIG. 6 is an exploded perspective view of the positive electrode tab lead side of the secondary battery shown in FIG. 5. [Figure 9] FIG. 1 is a perspective view of an example of a positive electrode tab lead that can be used in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are merely examples of the present invention, and the present invention is not limited to the following.

[0026] [First embodiment] Fig. 1 is a cross-sectional view of a secondary battery according to a first embodiment of the present invention, Fig. 2 is a plan view of the secondary battery shown in Fig. 1 with the exterior body thereof omitted, Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2, and Fig. 4 is a perspective view of a positive electrode tab lead used in the secondary battery shown in Fig. 1.

[0027] The secondary battery 100 of the first embodiment has an electrode laminate 4, an electrolyte 5, a positive electrode tab lead 6, a negative electrode tab lead 7, and an exterior body 8. The electrode laminate 4 is a laminate in which a plurality of positive electrode layers 1 and a plurality of negative electrode layers 2 are alternately stacked with separators 3 interposed therebetween. The positive electrode tab lead 6 and the negative electrode tab lead 7 are arranged in positions facing each other with the electrode laminate 4 interposed therebetween.

[0028] The positive electrode layer 1 has a positive electrode current collector 10 and a positive electrode active material layer 15. The positive electrode active material layers 15 are laminated on both surfaces of the positive electrode current collector 10. Each positive electrode current collector 10 of the multiple positive electrode layers 1 has a positive electrode current collector extension 10a extended to the positive electrode tab lead 6 side. The ends of each positive electrode current collector extension 10a are laminated at the center of the stacking direction of the electrode laminate 4 to form a positive electrode current collector extension laminate 11. Note that the center of the stacking direction of the electrode laminate 4 does not necessarily have to be the exact center point; the center includes the range from the center point to 1 / 10 of the length of the electrode laminate 4 in the stacking direction.

[0029] The positive electrode tab lead 6 has a base 61 and a clamping portion 62. A portion of the base 61 is exposed from the exterior body 8. The positive electrode tab lead 6 is disposed in the center of the stacking direction of the electrode laminate 4. The clamping portion 62 has a first bent portion 62a bent to one side (upper side in FIG. 4 ) in the stacking direction of the positive electrode current collector extension laminate 11, and a second bent portion 62b bent to the other side (lower side in FIG. 4 ). The first bent portion 62a has one end connected to the base 61 and the other end including a first inclined portion 63a extending obliquely upward, and a first flat portion 64a connected to the other end of the first inclined portion 63a. The second bent portion 62b has one end connected to the base portion 61 and the other end extending diagonally downward, forming a second inclined portion 63b, and a second flat portion 64b connected to the other end of the second inclined portion 63b. The first flat portion 64a and the second flat portion 64b are perpendicular to the stacking direction of the positive current collector extension laminate 11. The positive current collector extension laminate 11 is sandwiched between the first flat portion 64a and the second flat portion 64b. Because the first flat portion 64a and the second flat portion 64b are in surface contact with the positive current collector extension laminate 11, the positive tab lead 6 can more firmly sandwich the positive current collector extension laminate 11. Each positive electrode current collector extension 10a of the positive electrode current collector extension laminate 11, the positive electrode current collector extension laminate 11 and the first flat portion 64a, and the positive electrode current collector extension laminate 11 and the second flat portion 64b are welded together. Examples of welding methods that can be used include resistance welding and ultrasonic welding.

[0030] The negative electrode layer 2 has a negative electrode current collector 20 and a lithium metal-containing layer 25. The lithium metal-containing layer 25 is laminated on both side surfaces of the negative electrode current collector 20. Each negative electrode current collector 20 of the multiple negative electrode layers 2 has a negative electrode current collector extension 20a extended to the negative electrode tab lead 7 side. The ends of each negative electrode current collector extension 20a are laminated at the center in the stacking direction of the electrode laminate 4 to form a negative electrode current collector extension laminate 21.

[0031] The negative electrode tab lead 7 has a base portion 71 and a clamping portion 72. The negative electrode tab lead 7 is disposed at the center of the electrode laminate 4 in the stacking direction. The clamping portion 72 has a third bent portion 72a bent to one side in the stacking direction of the negative electrode current collector extension laminate 21 and a fourth bent portion 72b bent to the other side. The third bent portion 72a has one end connected to the base portion 71 and the other end extending obliquely upward to form a third inclined portion 73a, and a third flat portion 74a connected to the other end of the third inclined portion 73a. The fourth bent portion 72b has one end connected to the base portion 71 and the other end extending obliquely downward to form a fourth inclined portion 73b, and a fourth flat portion 74b connected to the other end of the fourth inclined portion 73b. The third flat portion 74a and the fourth flat portion 74b are perpendicular to the stacking direction of the negative electrode current collector extension laminate 21. The negative electrode current collector extension laminate 21 is sandwiched between the third flat portion 74a and the fourth flat portion 74b. The third flat portion 74a and the fourth flat portion 74b are in surface contact with the negative electrode current collector extension laminate 21, so that the negative electrode tab lead 7 can more firmly sandwich the negative electrode current collector extension laminate 21. Each negative electrode current collector extension 20a of the negative electrode current collector extension laminate 21, the negative electrode current collector extension laminate 21 and the third flat portion 74a, and the negative electrode current collector extension laminate 21 and the fourth flat portion 74b are welded together. Examples of welding methods that can be used include resistance welding and ultrasonic welding.

[0032] The secondary battery 100 of this embodiment is a lithium metal secondary battery that uses lithium ions as a charge transfer medium, deposits lithium metal on the surface of the lithium metal-containing layer 25 of the negative electrode layer 2 during charging, and transfers the lithium metal as lithium ions to the positive electrode active material layer 15 of the positive electrode layer 1 during discharging. The materials of each component of the secondary battery 100 are as follows.

[0033] Examples of materials for the positive electrode current collector 10 include aluminum, aluminum alloy, stainless steel, nickel, iron, and titanium.

[0034] The positive electrode active material layer 15 contains a positive electrode active material. For example, a layered active material containing lithium, a spinel-type active material, or an olivine-type active material can be used as the positive electrode active material. Specific examples of the positive electrode active material include lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), and LiNi p Mn q Co r O2(p+q+r=1), LiNi p Al q Co r O2 (p+q+r=1), lithium manganese oxide (LiMn2O4), Li 1+x Mn 2-x-y Examples of such an element-substituted Li-Mn spinel are MO4 (x+y=2, M=at least one selected from Al, Mg, Co, Fe, Ni, and Zn), lithium titanate (oxide containing Li and Ti), and lithium metal phosphate (LiMPO4, M=at least one selected from Fe, Mn, Co, and Ni). The positive electrode active material layer 15 may further contain a conductive additive and a binder.

[0035] Examples of materials for the negative electrode current collector 20 include nickel, copper, and stainless steel.

[0036] The material of the lithium metal-containing layer 25 includes either or both of lithium and a metal that forms an alloy with lithium. Examples of the metal that forms an alloy with lithium include Mg, Si, Au, Ag, In, Ge, Sn, Pb, Al, and Zn.

[0037] The separator 3 is not particularly limited, and may be any known material used as a separator for lithium metal secondary batteries, such as a porous sheet or a nonwoven fabric sheet. Examples of materials for the porous sheet include polyolefins such as polyethylene and polypropylene, aramid, polyimide, and fluororesin. Examples of materials for the nonwoven fabric sheet include glass fiber and cellulose fiber.

[0038] The electrolytic solution 5 contains an organic solvent and an electrolyte. Examples of the organic solvent include cyclic carbonates, chain carbonates, cyclic ethers, chain ethers, hydrofluoroethers, aromatic ethers, sulfones, cyclic esters, chain carboxylic acid esters, and nitriles. Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, vinylene carbonate, and fluoroethylene carbonate. Examples of chain carbonates include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, and 4-methyl-1,3-dioxolane. Examples of chain ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, and diethyl ether. Examples of hydrofluoroethers include 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl)ether, and 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane. Examples of aromatic ethers include anisole. Examples of sulfones include sulfolane and methylsulfolane. Examples of cyclic esters include γ-butyrolactone. Examples of chain carboxylic acid esters include acetate esters, butyrate esters, and propionate esters. Examples of nitriles include acetonitrile and propionitrile. The organic solvents may be used alone or in combination of two or more.

[0039] The electrolyte is a source of lithium ions, which are a charge transfer medium, and contains a lithium salt. Examples of lithium salts include LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC(CF3SO2)3, LiN(CF3SO2)2 (LiTFSI), LiN(FSO2)2 (LiFSI), and LiBC4O8. The lithium salts may be used alone or in combination of two or more. The concentration of the electrolyte is, for example, within the range of 1.5 to 4.0 mol / L.

[0040] Examples of materials for the positive electrode tab lead 6 and the negative electrode tab lead 7 include copper, copper alloy, aluminum, aluminum alloy, stainless steel, nickel, iron, and titanium.

[0041] The exterior body 8 is expandable and contractible in accordance with changes in the thickness of the negative electrode layer 2 due to charging and discharging. A laminate film can be used as the material for the exterior body 8. The laminate film can be a three-layered film having an inner resin layer, a metal layer, and an outer resin layer stacked in this order from the inside. The outer resin layer can be, for example, a polyamide (nylon) layer or a polyethylene terephthalate (PET) layer, the metal layer can be, for example, an aluminum layer, and the inner resin layer can be, for example, a polyethylene layer or a polypropylene layer.

[0042] The secondary battery 100 can be manufactured, for example, as follows. Positive electrode layers 1 and negative electrode layers 2 are alternately stacked with separators 3 interposed therebetween to obtain an electrode laminate 4. Next, the ends of the positive electrode current collector extensions 10a of the positive electrode layers 1 are stacked to form a positive electrode current collector extension laminate 11. Next, the positive electrode current collector extension laminate 11 is inserted between the first bent portion 62a and the second bent portion 62b of the positive electrode tab lead 6, and the upper flat surface and the first flat portion 64a and the lower flat surface and the second flat portion 64b of the positive electrode current collector extension laminate 11 are joined. In this way, the positive electrode current collector extension laminate 11 is sandwiched between the clamping portions 62 of the positive electrode tab lead 6. Similarly, the negative electrode current collector extension laminate 21 is sandwiched between the clamping portions 72 of the negative electrode tab lead 7. Next, the electrode laminate 4 is sandwiched between laminate films, and three sides of the laminate films are sealed to form a bag, after which the electrolyte 5 is poured into the bag. Then, the remaining side of the laminate film is sealed to form the exterior body 8.

[0043] In the secondary battery 100 of the first embodiment configured as described above, the positive electrode current collector extension laminate 11 and the negative electrode current collector extension laminate 12 are disposed at the center of the electrode laminate 4 in the stacking direction, and the structure is symmetrical about the center of the electrode laminate 4 in the stacking direction. Therefore, even if the thickness of the negative electrode layer 2 changes significantly due to charge and discharge, the lengths of the positive electrode current collector extension 10a and the negative electrode current collector extension 20a do not need to be excessively extended. This increases the capacity per volume. Furthermore, the positive electrode current collector extension laminate 11 is clamped by the clamping portion 62 of the positive electrode tab lead 6, so it is unlikely to come off the positive electrode tab lead 6. The negative electrode current collector extension laminate 21 is clamped by the clamping portion 72 of the negative electrode tab lead 7, so it is unlikely to come off the negative electrode tab lead 7. This improves reliability. Furthermore, because the positive electrode tab lead 6 and the negative electrode tab lead 7 are disposed at the center of the electrode laminate 4 in the stacking direction, it is easy to form the exterior body 8 using a laminate film.

[0044] [Second embodiment] Fig. 5 is a plan view of the positive electrode tab lead side of a secondary battery according to a second embodiment of the present invention, with the exterior body omitted. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5, and Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 5. Fig. 8 is an exploded perspective view of the positive electrode tab lead side of the secondary battery shown in Fig. 5.

[0045] In the secondary battery 100a of this embodiment, the positive electrode current collector 110 is a laminated current collector in which a first metal layer 111, a resin layer 112, and a second metal layer 113 are laminated in this order. Other configurations are the same as those of the secondary battery 100 of the first embodiment, and therefore the same components are denoted by the same reference numerals and their description will be omitted.

[0046] The positive electrode layer 1 has a positive electrode current collector 110 and a positive electrode active material layer 15. The positive electrode active material layers 15 are laminated on both side surfaces of the positive electrode current collector 110. Each positive electrode current collector 110 of the multiple positive electrode layers 1 has a positive electrode current collector extension 110a extended to the positive electrode tab lead 6 side.

[0047] The end of each positive electrode current collector extension 110a is divided into two pieces, a first positive electrode current collector extension piece 110c and a second positive electrode current collector extension piece 110d, by a slit 110b formed along the extension direction of the positive electrode current collector extension 110a. The first positive electrode current collector extension piece 110c is folded so that the first metal layer 111 faces outward and the second metal layer 113 faces inward. The second positive electrode current collector extension piece 110d is folded so that the first metal layer 111 faces inward and the second metal layer 113 faces outward.

[0048] As shown in FIG. 6 , the first positive current collector extension pieces 110c of each positive current collector extension 110a are stacked to form a first positive current collector extension laminate 114. The first positive current collector extension laminate 114 is disposed at the center of the stacking direction of the electrode laminate 4. The first positive current collector extension laminate 114 is connected to the first flat portion 64a of the first bent portion 62a of the positive tab lead 6. Each of the first positive current collector extension pieces 110c of the first positive current collector extension laminate 114 and the first positive current collector extension laminate 114 are welded to the first flat portion 64a. Examples of welding methods that can be used include resistance welding and ultrasonic welding, with resistance welding being preferred. Resistance welding allows the first positive current collector extension pieces 110c to be welded without partially deteriorating the resin layer 112 of the positive current collector 110.

[0049] As shown in FIG. 7 , the second positive electrode current collector extension pieces 110d of the respective positive electrode current collector extensions 110a are stacked to form a second positive electrode current collector extension laminate 115. The second positive electrode current collector extension laminate 115 is disposed at the center of the stacking direction of the electrode laminate 4. The second positive electrode current collector extension laminate 115 is connected to the second flat portion 64b of the second bent portion 62b of the positive electrode tab lead 6. Each second positive electrode current collector extension piece 110d of the second positive electrode current collector extension laminate 115 and the second positive electrode current collector extension laminate 115 are welded to the second flat portion 64b. Examples of welding methods that can be used include resistance welding and ultrasonic welding, with resistance welding being preferred.

[0050] In the secondary battery 100a of this embodiment, the first metal layers 111 of each positive electrode layer 1 are electrically connected by a first positive electrode current collector extension laminate 114, and the second metal layers 113 of each positive electrode layer 1 are electrically connected by a second positive electrode current collector extension laminate 115. The first positive electrode current collector extension laminate 114 and the second positive electrode current collector extension laminate 115 are sandwiched by the sandwiching portion 62 of the positive electrode tab lead 6, thereby electrically connecting the first metal layer 111 and the second metal layer 113 of each positive electrode layer 1.

[0051] The first metal layer 111 and the second metal layer 113 of the positive electrode current collector 110 may be made of the same material as that of the positive electrode current collector 10 of the secondary battery 100 of the first embodiment. Examples of materials for the resin layer 112 include thermoplastic resins such as polyethylene terephthalate (PET) and polypropylene (PP).

[0052] In the secondary battery 100a of this embodiment, the first positive electrode current collector extension laminate 114 and the second positive electrode current collector extension laminate 115 are disposed at the center of the stacking direction of the electrode laminate 4, and the first positive electrode current collector extension laminate 114 and the second positive electrode current collector extension laminate 115 are sandwiched by the clamping portion 62 of the positive electrode tab lead 6, with the positive electrode tab lead 6 being disposed at the center of the stacking direction of the electrode laminate. Therefore, the same effects as those of the secondary battery 100 of the first embodiment are obtained. Furthermore, in the secondary battery 100a of this embodiment, the positive electrode current collector 110 is a laminated current collector having a resin layer 112. Therefore, when the temperature of the secondary battery rises excessively, the resin layer 112 melts, electrically insulating the positive electrode current collector 110 and the positive electrode tab lead 6. This improves safety during temperature rises. Furthermore, the first metal layers 111 of the positive electrode current collectors 110 are connected to each other at the first positive electrode current collector extension laminate 114, and the second metal layers 113 of the positive electrode current collectors 110 are connected to each other at the second positive electrode current collector extension laminate 115, so that the first metal layers 111 and second metal layers 113 of the positive electrode current collectors 110 can be reliably electrically connected to each other.

[0053] In this embodiment, the secondary battery 100a of this embodiment has a laminated current collector as the positive electrode current collector 110. The negative electrode current collector may also be a laminated current collector, or both the positive electrode current collector and the negative electrode current collector may be laminated current collectors.

[0054] The positive electrode tab lead 6 used in this embodiment has a structure in which the clamping portion 62 has one first bent portion 62a and one second bent portion 62b, but there is no limit to the number of bent portions. The same applies to the negative electrode tab lead 7.

[0055] Fig. 9 is a perspective view of an example of a positive electrode tab lead that can be used in the present invention. The positive electrode tab lead 6a shown in Fig. 9 has two first bent portions 62a and two second bent portions 62b arranged alternately.

[0056] In this embodiment, the clamping portion 62 of the positive electrode tab lead 6 has flat portions (first flat portion 64a, second flat portion 64b), and the flat end portions are in surface contact with the positive electrode current collector extensions 10a, 110a, but there are no limitations on the method of contact between the clamping portion 62 and the positive electrode current collector extensions 10a, 110a. The clamping portion 62 of the positive electrode tab lead 6 may not have flat portions, and the clamping portion 62 may be in point contact with the positive electrode current collector extensions 10a, 110a. The same applies to the negative electrode tab lead 7.

[0057] In this embodiment, the secondary batteries 100 and 100a are non-aqueous solvent lithium metal secondary batteries containing the electrolytic solution 5, but the secondary battery of the present invention is not limited to this. For example, the secondary battery of the present invention may be an all-solid-state lithium metal secondary battery using a solid electrolyte as the electrolyte.

[0058] In the second embodiment, the end of the positive electrode current collector extension 110a is divided by the slit 110b into two pieces, the first positive electrode current collector extension piece 110c and the second positive electrode current collector extension piece 110d, but the positive electrode current collector extension 110a may be divided into three or more pieces. Alternatively, instead of dividing the positive electrode current collector extension 110a, the ends of the positive electrode current collector extension 110a may be stacked and the resin layer 112 of the stacked positive electrode current collector extension 110a may be partially dissolved to electrically connect the first metal layer 111 and the second metal layer 113.

[0059] Although the secondary batteries 100 and 100a are non-aqueous solvent lithium metal secondary batteries containing the electrolytic solution 5, the secondary battery of the present invention is not limited thereto. For example, the secondary battery of the present invention may be an all-solid-state lithium metal secondary battery using a solid electrolyte as the electrolyte. [Explanation of symbols]

[0060] 1 Positive electrode layer 2. Negative electrode layer 3 Separator 4-electrode laminate 5 Electrolyte 6, 6a Positive electrode tab lead 8. Exterior body 10 Positive electrode current collector 10a Positive electrode current collector extension 11 Positive electrode current collector extension laminate 12 Negative electrode current collector extension laminate 15 Cathode active material layer 20 Negative electrode current collector 20a Negative electrode current collector extension 21 Negative electrode current collector extension laminate 25 Lithium metal-containing layer 61 Base 62 Clamping part 62a First bending part 62b Second bending part 63a 1st slope part 63b 2nd slope part 64a 1st flat part 64b 2nd flat part 71 Base 72 Clamping part 72a Third bending part 72b Fourth bending part 73a 3rd slope 73b 4th slope 74a 3rd flat part 74b 4th flat part 100, 100a secondary battery 110 Positive electrode current collector 110a Positive electrode current collector extension 110b slit 110c 1st positive electrode current collector extension piece 110d 2nd positive electrode current collector extension piece 111 1st metal layer 112 Resin layer 113 Second metal layer 114 First positive electrode current collector extension laminate 115 Second positive electrode current collector extension laminate

Claims

1. an electrode stack in which a plurality of positive electrode layers and a plurality of negative electrode layers are alternately stacked with separators interposed therebetween, a positive electrode tab lead, and a negative electrode tab lead; Each of the plurality of positive electrode layers has a positive electrode current collector and a positive electrode current collector extension drawn out from one side of the positive electrode current collector, end portions of the positive electrode current collector extension portions drawn out from the positive electrode current collectors, respectively, form a positive electrode current collector extension stack stacked at the center in the stacking direction of the electrode stack; the positive electrode tab lead has clamping portions that clamp the positive electrode current collector extension laminate from both end sides in the stacking direction of the positive electrode current collector extension laminate, Each of the plurality of negative electrode layers has a negative electrode current collector and a negative electrode current collector extension drawn out from one side of the negative electrode current collector, end portions of the negative electrode current collector extensions drawn out from the respective negative electrode current collectors form a negative electrode current collector extension stack stacked at the center in the stacking direction of the electrode stack; the negative electrode tab lead has a clamping portion that clamps the negative electrode current collector extension laminate from both ends in the stacking direction of the negative electrode current collector extension laminate.

2. the clamping portion of the positive electrode tab lead has a first bent portion bent to one side in a stacking direction of the positive electrode current collector extension laminate and a second bent portion bent to the other side, the electrode laminate being clamped by the first bent portion and the second bent portion, 2. The secondary battery according to claim 1, wherein the clamping portion of the negative electrode tab lead has a third bent portion bent to one side in a stacking direction of the positive electrode current collector extension laminate and a fourth bent portion bent to the other side, and the negative electrode current collector extension laminate is clamped by the third bent portion and the fourth bent portion.

3. the clamping portion of the positive electrode tab lead has two or more of at least one of the first bent portion and the second bent portion, The secondary battery according to claim 2 , wherein the clamping portion of the negative electrode tab lead has two or more of at least one of the third bent portion and the fourth bent portion.

4. the first bent portion and the second bent portion of the positive electrode tab lead have flat portions facing each other, and the positive electrode current collector extension laminate is welded to the flat portion of the first bent portion and the flat portion of the second bent portion, 3. The secondary battery of claim 2, wherein the first bent portion and the second bent portion of the positive electrode tab lead have flat portions facing each other, and the negative electrode current collector extension laminate is welded by the flat portion of the third bent portion and the flat portion of the fourth bent portion.

5. 3. The secondary battery according to claim 1, wherein at least one of the positive electrode current collector and the negative electrode current collector is a laminated current collector in which a first metal layer, a resin layer, and a second metal layer are laminated in this order.

6. The positive electrode current collector is the laminated current collector, end portions of the plurality of positive electrode current collector extension portions are divided into a plurality of positive electrode current collector extension pieces by slits formed along the extension direction of the positive electrode current collector extension portions, at least one of the plurality of positive electrode current collector extension pieces is folded so that the first metal layer is on the outside and the second metal layer is on the inside, and the other is folded so that the first metal layer is on the inside and the second metal layer is on the outside, a plurality of the positive electrode current collector extension pieces folded so that the first metal layer faces outward are stacked in contact with each other to form a first positive electrode current collector extension stack; and a plurality of the positive electrode current collector extension pieces folded so that the second metal layer faces outward are stacked in contact with each other to form a second positive electrode current collector extension stack; The secondary battery according to claim 5 , wherein the first positive electrode current collector extension laminate and the second positive electrode current collector extension laminate are sandwiched by the negative electrode tab lead.

7. The negative electrode current collector is the laminated current collector, end portions of the plurality of negative electrode current collector extension portions are divided into a plurality of negative electrode current collector extension pieces by slits formed along an extension direction of the negative electrode current collector extension portions, at least one of the plurality of negative electrode current collector extension pieces is folded so that the first metal layer is on the outer side and the second metal layer is on the inner side, and the other is folded so that the first metal layer is on the inner side and the second metal layer is on the outer side, a plurality of the negative electrode current collector extension pieces folded so that the first metal layer faces outward are stacked in contact with each other to form a first negative electrode current collector extension stack; and a plurality of the negative electrode current collector extension pieces folded so that the second metal layer faces outward are stacked in contact with each other to form a second negative electrode current collector extension stack. The secondary battery according to claim 5 , wherein the first negative electrode current collector extension laminate and the second negative electrode current collector extension laminate are sandwiched by the negative electrode tab lead.

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