JP2023046589A - power storage device - Google Patents

Abstract

To provide a power storage device capable of mitigating deterioration of a battery performance due to temperature changes.SOLUTION: A power storage device includes: a stacked body in which a plurality of current collectors is stacked, each current collector including a positive electrode active material layer provided on a first side thereof and a negative electrode active material layer provided on a second side thereof being opposite to the first side; and a sealing part sealing a periphery of the stacked body as viewed from a stacking direction of the current collectors. At least one of the positive electrode active material layer and the negative electrode active material layer has a notched part exhibiting a shape that is notched toward the inside as viewed from the stacking direction, in at least one side among four sides defining edges.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to power storage devices.

Patent Document 1 discloses a bipolar battery. This bipolar battery is composed of a bipolar electrode having a positive electrode on one side of a current collector and a negative electrode on the other side, a gel electrolyte sandwiched between the positive electrode and the negative electrode, and the positive electrode, the negative electrode, and the gel electrolyte. and a sealing layer surrounding the cell and between the current collectors.

Japanese Patent Application Laid-Open No. 2004-158343

In the battery disclosed in Patent Document 1, the current collector is made of a rectangular metal foil, and a rectangular frame-shaped sealing layer made of resin is provided around the periphery of the current collector. In such a battery, when there is a change in environmental temperature (for example, cooling from room temperature to about -40°), the corners of the seal layer may be affected due to the difference in linear expansion coefficient between the seal layer and the current collector. It is conceivable that the stress concentrates and the corners of the current collector are greatly deformed. If the current collector is repeatedly deformed, the current collector may be damaged and the battery performance may be degraded.

An object of the present disclosure is to provide a power storage device capable of alleviating deterioration in battery performance due to temperature changes.

A power storage device according to one aspect of the present disclosure is provided with a rectangular positive electrode active material layer on a first surface and a rectangular negative electrode active material layer on a second surface opposite to the first surface. and a rectangular frame-shaped sealing portion that seals the periphery of the laminate when viewed from the stacking direction of the current collector, when viewed from the stacking direction In addition, the four sides that define the edges of the negative electrode active material layer and the four sides that define the edges of the positive electrode active material layer are parallel to the inner edges of the sealing portions facing each other. At least one of the material layer and the negative electrode active material layer has a cut-out portion that is cut inward when viewed from the stacking direction, on at least one of the four sides defining the edge.

In the power storage device, the notch-shaped portion is formed on the side of the active material layer. Therefore, it is possible to disperse the stress due to environmental temperature changes, which tends to be concentrated on the corners of the sealing layer, to the notched portions. In this way, the stress concentrated on the corners of the seal layer is dispersed, thereby relieving the deformation of the corners of the current collector. Therefore, deterioration of battery performance due to temperature change can be alleviated.

The active material layer having the notched portion may be provided on the current collector via an adhesive layer. In this configuration, since the two-layer structure of the adhesive layer and the active material layer is formed, even if the current collector is deformed by stress, the active material layer is unlikely to come off.

When viewed from the stacking direction, the edge of the negative electrode active material layer surrounds the edge of the positive electrode active material layer, and the notched portions are formed in the positive electrode active material layer and the negative electrode active material layer, respectively. In the inner edge of the sealing portion, the region facing the notch-shaped portion of the positive electrode active material layer and the region facing the notch-shaped portion of the negative electrode active material layer may overlap each other when viewed from the stacking direction. With this configuration, it becomes easier to disperse the stress caused by environmental temperature changes, which tends to concentrate on the corners of the sealing layer, to the notch-shaped portions.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a power storage device capable of alleviating deterioration in battery performance due to temperature changes.

FIG. 1 is a schematic side view showing an example power storage device. FIG. 2 is a schematic cross-sectional view showing an example power storage module. FIG. 3 is a schematic plan view of an example electrode unit viewed from the positive electrode side.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and overlapping descriptions are omitted. In the description, reference may be made to a Cartesian coordinate system defined by X, Y and Z axes.

FIG. 1 is a side view schematically showing an example power storage device. The power storage device 1 can be used, for example, as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The electricity storage device 1 includes a module laminate 2 including an electricity storage module 11 , connecting members 3 and 4 electrically connected to the module laminate 2 , and a pair of ends for restraining the module laminate (laminate) 2 . It has plates 5, 5 and a fastening member 6 for fastening the end plates 5, 5 together.

The module laminate 2 is configured by stacking a plurality of power storage modules 11 and a plurality of conductive plates P in the Z-axis direction. In the example of FIG. 1, the module laminate 2 includes two power storage modules 11 and three conductive plates P. In the example of FIG. The three conductive plates P are arranged between the power storage modules 11 and at both ends of the module stack 2 in the stacking direction. These conductive plates P are electrically connected to electrodes that constitute the storage module 11 . Here, the two power storage modules 11 are connected in series by a conductive plate P. As shown in FIG.

Inside the conductive plate P, a plurality of flow paths (not shown) for circulating a cooling medium such as air may be provided. By circulating the cooling medium in the flow paths in the conductive plate P, the conductive plate P functions as a connection member that electrically connects the plurality of power storage modules 11 to each other, and also dissipates heat generated in the power storage modules 11. It also has a function as a heat sink that dissipates heat. In the example of FIG. 1 , the area of the conductive plate P is one size smaller than the area of the power storage module 11 . From the viewpoint of improving heat dissipation, the area of the conductive plate P may be equal to the area of the power storage module 11 or may be slightly larger than the area of the power storage module 11 .

The connection members 3 and 4 are conductive members (bus bars) that function as a positive terminal and a negative terminal of the power storage device 1 . The connecting member 3 is electrically connected to the conductive plate P on the positive electrode side, and the connecting member 4 is electrically connected to the conductive plate P on the negative electrode side. The connecting members 3 and 4 are made of, for example, metal material or alloy material. Examples of metal materials include copper, aluminum, titanium, and nickel. Examples of alloy materials include stainless steel plates (SUS301, SUS304, etc.) and alloys of the above metal materials. At least one of the connection members 3 and 4 may be attached with heat radiation fins (not shown) having excellent thermal conductivity. In this case, the heat generated in the power storage module 11 can be effectively dissipated through the conductive plate P, the connection members 3 and 4, and the heat dissipation fins.

The pair of end plates 5, 5 and the fastening member 6 constitute a restraining member that applies a restraining load to the module stack 2 in the stacking direction. A pair of end plates 5, 5 are provided so as to sandwich the module stack 2 in the stacking direction. The end plate 5 is made of, for example, a metal plate. Materials for forming the end plate 5 include, for example, alloys such as copper, aluminum, titanium, nickel, and stainless steel. As shown in FIGS. 1 and 2, the end plate 5 has a rectangular shape that is one size larger than the shape (here, rectangular shape) when the module stack 2 is viewed from the stacking direction. The end plate 5 is arranged concentrically with the module stack 2 when viewed in the stacking direction. As a result, the edges of the four sides of the end plate 5 form overhanging portions 5a that overhang the sandwiched portion of the module stack 2 to the outside.

The fastening member 6 is composed of, for example, a bolt 6A and a nut 6B. The bolt 6A is passed through an insertion hole 5b provided in each overhanging portion 5a of the pair of end plates 5, 5, and the pair of end plates 5, 5 are fastened by screwing a nut 6B. As a result, a binding load is applied to the module stack 2 in the stacking direction via the pair of end plates 5 , 5 . In this embodiment, when viewed from the stacking direction, the fastening members 6 are arranged at equal intervals along the four edges of the overhanging portion 5a of the end plate 5 so as to include the positions corresponding to the corners of the end plate 5. are placed.

FIG. 2 is a schematic cross-sectional view showing the layer structure of the power storage module 11. As shown in FIG. The power storage module 11 is a single cell having a rectangular parallelepiped shape flattened in the Z-axis direction. In this embodiment, a bipolar lithium ion secondary battery is exemplified as the power storage module 11 . The power storage module 11 includes an electrode laminate (laminate) 12 including a plurality of bipolar electrodes 14 and a sealing portion 30 . The bipolar electrodes 14 in the electrode laminate 12 are laminated along the Z-axis direction. The stacking direction of the bipolar electrodes 14 is along the Z-axis direction and coincides with the stacking direction of the power storage modules 11 in the module stack 2 .

The bipolar electrode 14 includes a current collector 21, a positive electrode active material layer (first active material layer) 22 provided on a first surface 21a of the current collector 21, and a second surface 21b of the current collector 21. and a negative electrode active material layer (second active material layer) 23 . The current collector 21 and the positive electrode active material layer 22 provided on the first surface 21 a of the current collector 21 constitute the positive electrode of the bipolar electrode 14 . The negative electrode active material layer 23 provided on the second surface 21 b constitutes the negative electrode of the bipolar electrode 14 . The positive electrode active material layer 22 is formed in a rectangular shape at the center of the first surface 21a so that the peripheral edge 21c of the current collector 21 is exposed. The negative electrode active material layer 23 is formed in a rectangular shape at the center of the second surface 21b so that the peripheral edge 21c of the current collector 21 is exposed. In one example, the cathode active material layer 22 is contained within the area of the anode active material layer 23 when viewed in the stacking direction. That is, the outer edge of the positive electrode active material layer 22 is one size smaller than the outer edge of the negative electrode active material layer 23 .

The current collector 21 is a sheet-like conductive member having a rectangular shape in plan view, and has a first surface 21a and a second surface 21b located on the opposite side of the first surface 21a. The current collector 21 is made of, for example, metal foil or alloy foil. Examples of metal foil include copper foil, aluminum foil, titanium foil, nickel foil and the like. As the alloy foil, for example, stainless steel foil (e.g. SUS304, SUS316, SUS301, etc. specified by JIS G 4305:2015), plated steel plate (e.g., JIS G 3141: Cold foil specified by 2005) rolled steel plate (SPCC, etc.), plated stainless steel plate, and the like. The alloy foil may be an alloy foil of the metals exemplified as the material of the metal foil. The current collector 21 may be formed by integrating or laminating a plurality of metal foils, or may be formed by plating the surface of a metal foil with another metal.

The current collector 21 in the illustrated example may be, for example, a clad foil in which an aluminum foil and a copper foil are joined such that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. In addition, on the first surface 21 a of the current collector 21 , the aluminum layer may be subjected to chromate treatment. In addition, on the second surface 21b of the current collector 21, the copper layer may be plated with nickel. In this case, the nickel plating layer may be a roughened surface, which is a projection-like plating surface on which fine projections are provided.

The positive electrode active material layer 22 is a layered member containing a positive electrode active material, a conductive aid, and a binder. Examples of positive electrode active materials include composite oxides, metallic lithium, and sulfur. The composition of the composite oxide includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Composite oxides include olivine-type lithium iron phosphate (LiFePO ₄ ), LiCoO ₂ , LiNiMnCoO ₂ and the like.

The binder serves to bind the active material or conductive aid to the surface of the current collector 21 and maintain the conductive network in the electrode. Examples of binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; Acrylic resins containing monomer units such as acid and methacrylic acid, styrene-butadiene rubber (SBR), carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked products, starch-acrylic acid graft polymers, etc. is mentioned. These binders can be used singly or in combination. Examples of conductive aids include acetylene black, carbon black, and graphite. A viscosity adjusting solvent such as N-methyl-2-pyrrolidone (NMP) may be used for the positive electrode active material layer 22 .

The negative electrode active material layer 23 is a layered member containing a negative electrode active material, a conductive aid, and a binder. Examples of the negative electrode active material include graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, carbon such as hard carbon and soft carbon, metal compounds, elements that can be alloyed with lithium or compounds of such elements, and boron-added carbon. etc. Elements that can be alloyed with lithium include silicon (silicon) and tin. As the conductive aid and the binder, the same ones as those used for the positive electrode active material layer 22 can be used.

In order to form the positive electrode active material layer 22 and the negative electrode active material layer 23 on the current collector 21, conventionally known methods such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, a curtain coating method, and the like can be used. method is used. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive aid are mixed to produce a slurry composition for forming an active material layer, and the composition for forming an active material layer is prepared in the first step. After being applied to the first surface 21a and the second surface 21b, it is dried. Solvents are, for example, N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, water. After drying, they may be compressed to increase electrode density.

In the electrode laminate 12, the bipolar electrodes 14, 14 adjacent in the stacking direction are arranged such that the positive electrode active material layer 22 and the negative electrode active material layer 23 face each other. A separator 15 is arranged between the bipolar electrodes 14 , 14 . In this embodiment, the separator 15 is a sheet-like member having a rectangular shape in plan view, and prevents a short circuit between the bipolar electrodes 14, 14 adjacent in the stacking direction.

The separator 15 has a rectangular shape that is one size larger than the positive electrode active material layer 22 and the negative electrode active material layer 23 and one size smaller than the current collector 21 when viewed in the stacking direction. The end portion 15a of the separator 15 is located outside the positive electrode active material layer 22 and the negative electrode active material layer 23 when viewed in the stacking direction. The end portion 15a of the separator 15 overlaps neither the positive electrode active material layer 22 nor the negative electrode active material layer 23 when viewed from the stacking direction.

The separator 15 is formed in a sheet shape, for example. The separator 15 is, for example, a porous sheet or non-woven fabric containing a polymer that absorbs and retains electrolyte. Examples of materials that constitute the separator 15 include polypropylene, polyethylene, polyolefin, and polyester. The separator 15 may have a single layer structure or a multilayer structure. In the case of a multilayer structure, the separator 15 may include, for example, a base material layer and a pair of adhesive layers, and may be adhered and fixed to the positive electrode active material layer 22 and the negative electrode active material layer 23 by the pair of adhesive layers. The separator 15 may include a ceramic layer that serves as a heat resistant layer. The separator 15 may be reinforced with a vinylidene fluoride resin compound.

Examples of the electrolyte impregnated in the separator 15 include a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, or a polymer gel electrolyte containing an electrolyte held in a polymer matrix. is mentioned. When the separator 15 is impregnated with an electrolyte, known electrolyte salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(FSO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ and the like are used. can be used. As the non-aqueous solvent, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters and ethers can be used. Two or more of these known solvent materials may be used in combination.

In addition to the bipolar electrode 14, the electrode laminate 12 has a positive terminal electrode 16 and a negative terminal electrode 17. The positive terminal electrode 16 includes a current collector 21 and a and the positive electrode active material layer 22 provided. The positive terminal electrode 16 is arranged on one end side of the electrode stack 12 in the stacking direction so that the positive electrode active material layer 22 on the first surface 21 a faces the negative electrode active material layer 23 of the terminal bipolar electrode 14 . In the positive terminal electrode 16, the second surface 21b of the current collector 21 is not provided with the negative electrode active material layer 23, and the second surface 21b is electrically connected to the adjacent conductive plate P. there is

The negative terminal electrode 17 is composed of a current collector 21 and a negative electrode active material layer 23 provided on the second surface 21 b of the current collector 21 . The negative terminal electrode 17 is arranged on the other end side of the electrode laminate 12 in the stacking direction such that the negative electrode active material layer 23 on the second surface 21b faces the positive electrode active material layer 22 of the terminal bipolar electrode 14 . In the negative terminal electrode 17, the positive electrode active material layer 22 is not provided on the first surface 21a of the current collector 21, and the first surface 21a is electrically connected to the adjacent conductive plate P. there is

In addition to the bipolar electrodes 14 , 14 adjacent in the stacking direction, the separators 15 described above are arranged between the bipolar electrode 14 and the positive terminal electrode 16 and between the bipolar electrode 14 and the negative terminal electrode 17 . The placement of the separator 15 prevents short circuits between the bipolar electrode 14 and the positive terminal electrode 16 and short circuits between the bipolar electrode 14 and the negative terminal electrode 17 .

The sealing portion 30 is a member that seals the space S between the current collectors 21 adjacent in the stacking direction. The sealing portion 30 has electrical insulation. The sealing portion 30 is adhered (bonded) to the edge of the current collector 21 . The sealing portion 30 is separated from the positive electrode active material layer 22 and the negative electrode active material layer 23 when viewed in the stacking direction. The sealing portion 30 has a frame shape when viewed in the stacking direction, and is arranged between the current collectors 21 adjacent to each other in the stacking direction so as to surround the positive electrode active material layer 22 and the negative electrode active material layer 23 . In the storage module 11, a space S is defined by the current collector 21 and the sealing portion 30 that are adjacent to each other in the stacking direction. The space S accommodates an electrolyte (not shown). The sealing portion 30 is arranged between the current collectors adjacent to each other in the stacking direction, and thus functions as a spacer that maintains the interval between the adjacent current collectors.

An example seal 30 includes a first sealing layer 31 , a second sealing layer 32 and a spacer layer 33 . The first seal layer 31, the second seal layer 32, and the spacer layer 33 each have a rectangular frame shape when viewed from the stacking direction. The first sealing layer 31 is bonded to the first surface 21a along the peripheral edge 21c of the current collector 21 . In one example, the outer edge 31 b of the first seal layer 31 is larger than the edge 21 d of the current collector 21 and surrounds the current collector 21 when viewed in the stacking direction. Further, when viewed from the stacking direction, the edge 21d of the current collector 21 is larger than the inner edge 31a of the first seal layer 31 and surrounds the inner edge 31a of the first seal layer 31 . The first seal layer 31 and the current collector 21 are bonded to each other in overlapping regions when viewed in the stacking direction. That is, the first sealing layer 31 and the current collector 21 are bonded to each other in the region from the inner edge 31a of the first sealing layer 31 to the edge 21d of the current collector 21 . The inner edge 31 a of the first seal layer 31 is separated from the positive electrode active material layer 22 when viewed from the stacking direction.

The second sealing layer 32 is bonded to the second surface 21b along the peripheral edge 21c of the current collector 21. As shown in FIG. In one example, the outer edge 32b of the second seal layer 32 is larger than the edge 21d of the current collector 21 and surrounds the current collector 21 when viewed in the stacking direction. For example, the second sealing layer 32 and the current collector 21 are bonded to each other in the overlapping regions. In other words, the second sealing layer 32 and the current collector 21 are joined together in the region from the inner edge 32a of the second sealing layer 32 to the edge 21d of the current collector 21 . The inner edge 32 a of the second seal layer 32 is separated from the negative electrode active material layer 23 when viewed from the stacking direction.

In the positive terminal electrode 16, the first sealing layer 31 is bonded to the first surface 21a of the current collector 21, and the second sealing layer 32 is not bonded to the second surface 21b. Further, in the negative terminal electrode 17, the second sealing layer 32 is bonded to the second surface 21b of the current collector 21, and the first sealing layer 31 is not bonded to the first surface 21a.

The spacer layer 33 is provided between the first sealing layer 31 and the second sealing layer 32 and welded to the first sealing layer 31 and the second sealing layer 32 . The inner edge 31 a of the first seal layer 31 and the inner edge 32 a of the second seal layer 32 are located inside the inner edge 33 a of the spacer layer 33 when viewed from the stacking direction. The inner edges 31a and 32a are located inside the inner edge 33a by, for example, 1 mm or more. That is, the inner edge 31 a of the first seal layer 31 is exposed from the spacer layer 33 so as to face the space S. An inner edge 32 a of the second seal layer 32 is exposed from the spacer layer 33 so as to face the space S.

The spacer layer 33 is welded to the first seal layer 31 outside the inner edge 31a of the first seal layer 31 when viewed in the stacking direction. The spacer layer 33 is welded to the second seal layer 32 outside the inner edge 32a of the second seal layer 32 as viewed in the lamination direction. That is, the bonding region R1 where the first sealing layer 31, the second sealing layer 32 and the spacer layer 33 are welded together is outside the inner edge 31a of the first sealing layer 31 and the inner edge 32a of the second sealing layer 32. . In one example, the bonding region R<b>1 is outside the inner edge 33 a of the spacer layer 33 . In the illustrated example, the region outside the edge 21d of the current collector 21 is the junction region R1. That is, the first seal layer 31, the second seal layer 32, and the spacer layer 33 are separated from the edge 21d of the current collector 21 when viewed from the stacking direction. They are welded together in the region up to their respective outer edges. Therefore, the portion of the spacer layer 33 inside the bonding region R1 is not welded (adhered) to the first seal layer 31 and the second seal layer 32 when viewed in the stacking direction.

An end portion 15 a of the separator 15 is fixed to the second seal layer 32 inside the inner edge 33 a of the spacer layer 33 . The end portion 15a is partially adhered (welded) to the second seal layer 32 by, for example, spot welding or the like.

The first sealing layer 31 is separated from the positive electrode active material layer 22 when viewed from the stacking direction, and the inner edge 31 a is positioned outside the positive electrode active material layer 22 . The second sealing layer 32 is separated from the negative electrode active material layer 23 when viewed from the stacking direction, and the inner edge 32 a is positioned outside the negative electrode active material layer 23 . In the present embodiment, the first sealing layer 31 is also separated from the negative electrode active material layer 23 when viewed from the stacking direction. It may overlap with the negative electrode active material layer 23 .

In the stacking direction, the thickness of the first sealing layer 31 and the thickness of the second sealing layer 32 are thinner than the thickness of the spacer layer 33, for example. The thickness of the first seal layer 31 is the thickness of the portion of the first seal layer 31 sandwiched between the current collector 21 and the spacer layer 33 . The thickness of the second seal layer 32 is the thickness of the portion of the second seal layer 32 sandwiched between the current collector 21 and the spacer layer 33 . The thickness of the spacer layer 33 is the thickness of the portion of the spacer layer 33 sandwiched between the first sealing layer 31 and the second sealing layer 32 . The thickness of the first sealing layer 31 and the second sealing layer 32 may be, for example, 1/10 or more and 1/2 or less of the thickness of the spacer layer 33 . The thicknesses of the first sealing layer 31 and the second sealing layer 32 may be equal to each other, or may be different from each other. Also, the thickness of the first sealing layer 31 and the second sealing layer 32 may be thicker than the spacer layer 33 .

The first seal layer 31, the second seal layer 32, and the spacer layer 33 are, for example, acid-denatured polyethylene (acid-denatured PE), acid-denatured polypropylene (acid-denatured PP), polyethylene, or electrolyte-resistant polyethylene or the like. It is made of a resin material. The resin materials forming the first sealing layer 31, the second sealing layer 32, and the spacer layer 33 may be the same or different. In this embodiment, the first sealing layer 31 and the second sealing layer 32 are made of acid-denatured polyethylene or acid-denatured polypropylene. The spacer layer 33 is made of polyethylene or polypropylene.

FIG. 3 is a plan view of the electrode unit 40 configured by the bipolar electrode 14, the first seal layer 31 and the second seal layer 32, viewed from the positive electrode side. In FIG. 3, the joint region R1 where the first seal layer 31, the second seal layer 32 and the spacer layer 33 are welded together is indicated by a chain double-dashed line. In one example, the position of this two-dot chain line coincides with the edge 21 d of the current collector 21 . In this case, the bonding region R2 between the current collector 21 and the first seal layer 31 extends from the inner edge 31a of the first seal layer 31 to the edge 21d of the current collector 21 (that is, the position of the two-dot chain line in FIG. 3). area. The bonding region R1 is a region outside the inner edge of the bonding region R2 when viewed from the stacking direction, and particularly in the example of FIG. 3, it is a region outside the outer edge of the bonding region R2.

An example of the positive electrode active material layer 22 is provided on the first surface 21a of the current collector 21 with an adhesive layer 24 interposed therebetween. For example, the adhesive layer 24 may be made of an adhesive such as acetylene black. The edge 24a of the adhesive layer 24 in the example is formed along the edge of the negative electrode active material layer 23 surrounding the positive electrode active material layer 22 when viewed from the stacking direction. The edge 24a of the adhesive layer 24 in the illustrated example is formed in a rectangular shape when viewed from the stacking direction. When viewed from the stacking direction, the four sides defining the edge 22b of the positive electrode active material layer 22 are parallel to the inner edge 31a of the first sealing layer 31 facing each other. Similarly, the four sides defining the edge 23b of the negative electrode active material layer 23 may be parallel to the opposing inner edge 32a of the second seal layer 32, respectively.

The positive electrode active material layer 22 includes a low-rigidity region 22r. The low-rigidity region 22r is a region in which the peripheral rigidity of the electrode unit 40 is partially reduced. An example of the low-rigidity region 22r is configured by a notched portion 22k formed in the peripheral edge 22a of the positive electrode active material layer 22 . The notched portion 22k is a recessed portion in which the edge 22b of the positive electrode active material layer 22 formed in a straight line is notched inward when viewed from the stacking direction. The adhesive layer 24 is exposed at the notched portion 22k. The notch-shaped portion 22k in the illustrated example has an arc shape that draws a substantially semicircular shape when viewed from the stacking direction. The boundary between the notched portion 22k and the linear portion of the edge 22b is connected with a curved locus. The notch-like portion 22k may have a notch-like shape, and does not need to be actually formed by notching. The shortest distance from the notched portion 22k to the inner edge 31a of the first seal layer 31 is longer than the shortest distance from the edge 22b other than the notched portion 22k to the inner edge 31a of the first seal layer 31.

The size of the semi-circular cut-out portion 22k is sufficiently larger than the recess of the edge 22b caused by the machining accuracy. Note that the size of the notch-shaped portion 22k may be defined, for example, as the size of the radius of a semicircle along the notch-shaped portion 22k. Moreover, when the notch-shaped portion is not semicircular, the size of the notch-shaped portion may be the length of the notch-shaped portion in the direction perpendicular to the edge 22b in plan view.

For example, the size of the notched portion 22k may be determined according to the coefficient of linear expansion of the active material layer. That is, the size of the notch-like portion 22k may be a size that allows the notch-like portion to maintain its shape when the active material layer expands and contracts. In this case, even if the active material layer expands and contracts, the edge 22b and the notched portion 22k can be clearly distinguished. For example, the size of the notched portion may be equal to or greater than the length of the active material layer that changes due to expansion and contraction. For example, when the change length of the active material layer is about 5 mm, the size of the notched portion 22k may be 5 mm to 20 mm, and may be about 15 mm as an example. Moreover, the size of the notch-shaped portion 22 k may be approximately the same as the size of the width between the inner edge 31 a of the first seal layer 31 and the edge 22 b of the positive electrode active material layer 22 .

In the illustrated example, one notch-like portion 22k is formed on each of the two short sides 22S and the two long sides 22L that define the edge 22b of the positive electrode active material layer 22 . For example, the cut-out portion 22k formed on the short side 22S is positioned in the longitudinal center of the short side 22S. Similarly, the cut-out portion 22k formed on the long side 22L is positioned in the longitudinal center of the long side 22L. That is, the cutout portion 22k is formed at a position that divides the long side 22L or the short side 22S that constitutes the positive electrode active material layer 22 into equal parts.

As described above, in the power storage device 1 of the example, the positive electrode active material layer 22 is provided on the first surface 21a, and the negative electrode active material layer 23 is provided on the second surface 21b opposite to the first surface 21a. An electrode laminate 12 in which a plurality of current collectors 21 are laminated, and a sealing portion 30 for sealing the peripheral edge of the electrode laminate 12 when viewed from the stacking direction of the current collectors 21, viewed from the stacking direction Sometimes, the edge 23b of the negative electrode active material layer 23 surrounds the edge 22b of the positive electrode active material layer 22, and defines the edge 23b of the negative electrode active material layer 23 when viewed from the stacking direction. The four sides and the four sides defining the edge 22b of the positive electrode active material layer 22 are parallel to the inner edges of the sealing layers facing each other, and the four sides defining the edge 22b of the positive electrode active material layer 22 are parallel to each other. At least one of the sides has a notched portion 22k that is notched inward when viewed in the stacking direction.

In the power storage device 1, since the notch-shaped portion 22k is formed on the side of the positive electrode active material layer 22, the stress caused by environmental temperature changes, which tends to concentrate on the corners of the seal layer, is transferred to the notch-shaped portion 22k. can be dispersed. In this way, the stress concentrated on the corners of the sealing layer is dispersed, so that the deformation of the corners of the current collector 21 is alleviated. Therefore, deterioration of battery performance due to temperature change can be alleviated.

Moreover, the positive electrode active material layer 22 in which the notched portion 22k is formed is provided on the current collector 21 with the adhesive layer 24 interposed therebetween. In this configuration, a two-layer structure of the adhesive layer 24 and the positive electrode active material layer 22 is formed, so even if the current collector 21 is deformed by stress, the positive electrode active material layer 22 is unlikely to come off.

Although an example form of the present disclosure has been described in detail above, the present disclosure is not limited to the above form.

Also, although the low-rigidity region formed by the substantially semicircular notch-shaped portion is shown, the notch-shaped portion may be substantially rectangular, substantially triangular, or the like, for example.

Moreover, although an example in which the inner edge of the bonding region R1 is aligned with the edge of the current collector has been shown, the inner edge of the bonding region R1 may be inside or outside the edge of the current collector. may be

Moreover, although the example in which the notch-like portions are formed on both the short and long sides of the active material layer has been shown, the notch-like portions may be formed on either the short side or the long side. Moreover, the number of notch-like portions is not particularly limited. For example, two or more notch-like portions may be formed on the long side or the short side of the active material layer. In addition, although an example in which the notch-shaped portion is formed at a position that divides the long side or the short side of the active material layer into equal parts has been shown, the notch-shaped portion may be formed at any position on the long side or the short side. good. When the low-rigidity regions are formed at least on the long sides, the stress can be appropriately controlled on the long sides, which are more susceptible to contraction of the sealing layer than on the short sides.

In addition, although an example in which the notch-shaped portion is formed in the positive electrode active material layer has been shown, the notch-shaped portion defines the edge of the active material layer that is at least one of the positive electrode active material layer and the negative electrode active material layer. It is sufficient if it is formed on at least one of the four sides. Note that the notched portions may be formed in the positive electrode active material layer and the negative electrode active material layer, respectively. In this case, the notch-shaped portion of the positive electrode active material layer and the notch-shaped portion of the negative electrode active material layer may overlap each other when viewed from the stacking direction. That is, in the inner edge of the sealing portion, the region facing the notch-shaped portion of the positive electrode active material layer and the region facing the notch-shaped portion of the negative electrode active material layer may overlap each other when viewed in the stacking direction. For example, when the edge of the negative electrode active material layer surrounds the edge of the positive electrode active material layer, when viewed from the stacking direction, the four sides defining the edge of the positive electrode active material layer are the edges of the negative electrode active material layer. They extend adjacent to each other on the inside of the four sides that define the edge. Of the four sides forming the edge of the positive electrode active material layer and the four sides forming the edge of the negative electrode active material layer, when the notched portions are formed on adjacent sides, the extension of the side The positions of the respective notch-like portions in the direction (extension direction common to mutually adjacent sides) may overlap. With this configuration, it becomes easier to disperse the stress caused by environmental temperature changes, which tends to concentrate on the corners of the sealing layer, to the notch-shaped portions.

Reference Signs List 1 power storage device 12 electrode laminate (laminate) 21 current collector 21a first surface 21b second surface 22 positive electrode active material layer 22k notch portion 23 negative electrode active material Material layer 30 Sealing portion 31 First sealing layer 32 Second sealing layer 40 Electrode unit.

Claims (3)

A plurality of rectangular current collectors each having a rectangular positive electrode active material layer provided on a first surface and a rectangular negative electrode active material layer provided on a second surface opposite to the first surface are stacked. a laminate;
A rectangular frame-shaped sealing portion that seals the periphery of the laminate when viewed from the stacking direction of the current collector,
When viewed from the stacking direction, the four sides defining the edges of the negative electrode active material layer and the four sides defining the edges of the positive electrode active material layer correspond to inner edges of the sealing portion facing each other. are parallel to each other,
At least one of the positive electrode active material layer and the negative electrode active material layer has a notch formed in at least one side of four sides defining the edge so as to have a shape that is cut inward when viewed from the stacking direction. A power storage device having a shaped portion. 2. The power storage device according to claim 1, wherein the active material layer having the notched portion is provided with respect to the current collector via an adhesive layer. When viewed from the stacking direction, the edge of the negative electrode active material layer surrounds the edge of the positive electrode active material layer,
The notched portion is formed in each of the positive electrode active material layer and the negative electrode active material layer,
In the inner edge of the sealing portion, the region facing the notch-shaped portion of the positive electrode active material layer and the region facing the notch-shaped portion of the negative electrode active material layer overlap each other when viewed in the stacking direction. , The power storage device according to claim 1 or 2.

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