JP7517060B2 - Storage cell and storage device - Google Patents

Description

The present invention relates to a storage cell and a storage device.

Patent Document 1 discloses a bipolar secondary battery having multiple bipolar electrodes. The bipolar secondary battery of Patent Document 1 has multiple bipolar electrodes and a seal portion that prevents leakage of the electrolyte layer. The bipolar electrode includes a current collector, a positive electrode located on a first surface of the current collector, and a negative electrode located on a second surface of the current collector. The seal portion is joined to adjacent current collectors.

JP 2008-97940 A

In bipolar secondary batteries, gas may be generated during charging and discharging. When gas is generated, the pressure in the space defined by adjacent current collectors and the seal increases. The increased pressure may cause the joint surface between the seal and the current collector to peel off from the edge, reducing the sealing ability.

The storage cell that solves the above problem is a storage cell that includes a first electrode having a first current collector, a second electrode having a second current collector, a first surface of the first current collector, a sealing member bonded to the first surface of the second current collector, and a space defined by the first current collector, the second current collector, and the sealing member, in which the direction in which the first electrode and the second electrode overlap is the stacking direction of the storage cell, and the direction along the first surface of the first current collector and the first surface of the second current collector is the stacking direction of the storage cell. In the cell surface direction, the sealing member has a first joint portion joined to the first surface of the first current collector, a second joint portion joined to the first surface of the second current collector, and a connection portion connecting the first joint portion and the second joint portion, and when the pressure in the space increases, a first end portion of the first joint portion closer to the inside of the space in the surface direction and a second end portion of the second joint portion closer to the inside of the space in the surface direction are spaced apart in the stacking direction compared to before the pressure in the space increases.

According to this, when the pressure in the space rises, the first end and the second end move apart in the stacking direction, thereby increasing the volume of the space in the storage cell. Therefore, compared to when the first end and the second end cannot be deformed to move apart in the stacking direction, the amount of pressure rise in the space for the same amount of gas generated is reduced, and the force peeling the first current collector from the first joint and the force peeling the second current collector from the second joint are reduced. Therefore, when the pressure in the space rises, the sealing member and the first and second current collectors are less likely to peel off from the ends of the joint surfaces, and a decrease in sealing performance can be suppressed.

In the above-described energy storage cell, the first end portion may have a non-bonded region that is not bonded to a member that faces the first end portion in the stacking direction.
According to this, when the pressure in the space increases, the first end can be separated in the stacking direction from the member opposite the first end, making it easier to separate the first end and the second end in the stacking direction than before the pressure in the space increased.

In the above-mentioned storage cell, the storage cell may include an intervening member interposed between the first joint and the second joint that overlap when viewed from the stacking direction, and the first end of the surface opposite to the surface of the first joint that is joined to the first current collector may not be joined to the intervening member.

According to this, by using the intervening member, it is easy to keep the first joint portion and the second joint portion in an unjoined state.
In the above-described energy storage cell, the interposed member may be a separator that is not joined to at least the first joint portion of the first joint portion and the second joint portion that overlap when viewed from the stacking direction.

According to this, by using the separator constituting the electricity storage cell as the intervening member, it is easy to form the non-bonded region without adding an intervening member.
In the above-described energy storage cell, the separator may be joined to the second joint portion.

According to this, in a storage cell in which a first current collector, a separator, and a second current collector are stacked in the stacking direction, the separator is joined to the sealing member, thereby suppressing misalignment of the separator within the storage cell along the surface direction.

In the above-mentioned storage cell, the connection portion may be located at a position that protrudes in the surface direction from an end face located at the outer edge of the surface direction of the first current collector and an end face located at the outer edge of the surface direction of the second current collector.

With this, when the pressure in the space increases, the connection part deforms, and the volume of the space can be increased more than when the connection part is located closer to the inside of the space than the outer end surface of the first current collector in the planar direction. Therefore, this is an ideal configuration for increasing the volume of the space.

The power storage device that solves the above problem may include a plurality of stacked power storage cells, and the plurality of power storage cells may include the power storage cell according to any one of claims 1 to 6.
According to this, when the pressure in the space of the stacked storage cells increases, the first end and the second end are separated in the stacking direction, thereby increasing the volume of the space in the storage cell. Therefore, compared to a case in which the first end and the second end cannot be deformed to separate in the stacking direction, the amount of pressure increase in the space for the same amount of gas generation is reduced, and the force to peel the first current collector from the first joint and the force to peel the second current collector from the second joint along the stacking direction are reduced. Therefore, when the pressure in the space increases, the seal member and the first and second current collectors are less likely to peel off from the ends of the joint surfaces, and a decrease in sealing performance can be suppressed.

The above-mentioned energy storage device further includes an extended seal portion interposed between the energy storage cells adjacent in the stacking direction and joined to each of the energy storage cells adjacent in the stacking direction, and in a plan view of the energy storage device seen from the outside in the stacking direction, the inner end surface of the extended seal portion in the surface direction is preferably located outside the inner end surface of the first joint located toward the inside of the space and the inner end surface of the second joint located toward the inside of the space.

With this, the extended seal portion can seal the gap between adjacent storage cells in the stacking direction, and can also fix multiple storage cells together in the stacking direction. In addition, by adjusting the position of the inner end face of the extended seal portion, the first joint portion and the second joint portion can be deformed so as to move away from each other when the pressure in the space increases.

This invention makes it possible to prevent deterioration of sealing performance.

FIG. 1 is a cross-sectional view showing a power storage device according to an embodiment. FIG. 3 is a cross-sectional view showing a portion of the storage cell. FIG. FIG. 4 is a cross-sectional view showing a portion of the energy storage cell after deformation. FIG. 11 is a cross-sectional view showing a portion of a storage cell according to another embodiment. FIG. 11 is a cross-sectional view showing a portion of a storage cell after deformation in another embodiment. FIG. 11 is a cross-sectional view showing a portion of a storage cell according to another embodiment. FIG. 11 is a cross-sectional view showing a portion of a storage cell according to another embodiment. FIG. 11 is a cross-sectional view showing a portion of a storage cell according to another embodiment.

Hereinafter, an embodiment of a power storage cell and a power storage device will be described with reference to FIGS.
As shown in FIG. 1, the energy storage device 1 includes a stack 2 in which a plurality of storage cells 10 are stacked. The energy storage device 1 is, for example, a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. In this embodiment, the energy storage device 1 is a lithium-ion secondary battery. The direction in which the storage cells 10 are stacked is the stacking direction of the energy storage device 1. Each storage cell 10 has a positive electrode 11 as a first electrode and a negative electrode 12 as a second electrode that overlap in the stacking direction. Each storage cell 10 also includes a seal member 14. If the direction in which the positive electrode 11 and the negative electrode 12 overlap is the stacking direction Z of the storage cell 10, the stacking direction Z of the storage cell 10 coincides with the stacking direction of the energy storage device 1. The storage cell 10 may include a separator 13 as an intervening member between the positive electrode 11 and the negative electrode 12 in the stacking direction Z. The separator 13 separates the positive electrode 11 and the negative electrode 12 to prevent a short circuit caused by contact between the two electrodes, while allowing charge carriers such as lithium ions to pass through. The separator 13 has a first surface 13a on one side in the stacking direction Z, and a second surface 13b on the other side in the stacking direction Z. The first surface 13a is treated so as not to be welded to a first bonding portion 30 of the sealing member 14 described later. For example, a ceramic layer is provided on at least the surface of the first surface 13a facing the first bonding portion 30.

The positive electrode 11 has a first current collector 20 and a positive electrode active material layer 22. The first current collector 20 has a first surface 20a on one side in the stacking direction Z, and a second surface 20b on the other side in the stacking direction Z. The first current collector 20 also has a first outer end surface 20c at its edge that intersects with the first surface 20a and the second surface 20b. The direction along the first surface 20a and the second surface 20b of the first current collector 20 is the surface direction X of the storage cell 10. The first outer end surface 20c is an end surface located at the outer edge of the surface direction X of the first current collector 20. The positive electrode active material layer 22 is located on the first surface 20a of the first current collector 20. The positive electrode active material layer 22 is not provided on the second surface 20b of the first current collector 20. The positive electrode 11 is, for example, a rectangular electrode.

The first current collector 20 has a first positive electrode portion 20d at a portion along the surface direction X that overlaps with the positive electrode active material layer 22 in the stacking direction Z. In the storage cell 10, the thickness of the storage cell 10 along the stacking direction Z at the first positive electrode portion 20d is the thickest.

The negative electrode 12 has a second current collector 21 and a negative electrode active material layer 23. The second current collector 21 has a first surface 21a on one side of the stacking direction Z and a second surface 21b on the other side of the stacking direction. The second current collector 21 also has a second outer end surface 21c at its edge that intersects with the first surface 21a and the second surface 21b. The direction along the first surface 21a and the second surface 21b of the second current collector 21 coincides with the surface direction X of the storage cell 10. The second outer end surface 21c is an end surface located at the outer edge of the surface direction X of the second current collector 21. The negative electrode active material layer 23 is located on the first surface 21a of the second current collector 21. The negative electrode active material layer 23 is not provided on the second surface 21b of the second current collector 21. The negative electrode 12 is, for example, a rectangular electrode.

The second current collector 21 has a first negative electrode portion 21d at a portion along the planar direction X that overlaps with the negative electrode active material layer 23 in the stacking direction Z.
In the energy storage cell 10, the first surface 20a of the first current collector 20 and the first surface 21a of the second current collector 21 face each other in the stacking direction Z. That is, the positive electrode 11 and the negative electrode 12 overlap each other when viewed from the stacking direction Z. The negative electrode active material layer 23 is disposed so as to face the positive electrode active material layer 22 in the stacking direction Z via the separator 13. Each of the positive electrode active material layer 22 and the negative electrode active material layer 23 has a rectangular shape. The negative electrode active material layer 23 is formed to be slightly larger than the positive electrode active material layer 22. In a plan view of the energy storage cell 10 viewed from the stacking direction Z, the entire formation region of the positive electrode active material layer 22 is located inside the formation region of the negative electrode active material layer 23.

A restraining load is applied to the storage cell 10 by a restraining member (not shown) so that the positive electrode active material layer 22 and the negative electrode active material layer 23 approach each other in the stacking direction Z. Therefore, at least the first positive electrode portion 20d of the first current collector 20 and the first negative electrode portion 21d of the second current collector 21 are restrained in the stacking direction by the restraining member.

The stack 2 is formed by stacking the adjacent storage cells 10 in the stacking direction such that the second surface 20b of the first positive electrode portion 20d of one storage cell 10 and the second surface 21b of the first negative electrode portion 21d of the other storage cell 10 are in contact with each other. This electrically connects the multiple storage cells 10 in series. In the stack 2, a pseudo bipolar electrode 3 is formed by the storage cells 10 adjacent in the stacking direction Z, with the first current collector 20 and the second current collector 21 in contact with each other as electrode bodies. That is, one bipolar electrode 3 includes the first current collector 20, the second current collector 21, the positive electrode active material layer 22, and the negative electrode active material layer 23.

A first current collector 20 is arranged as a terminal electrode at one end 6 of the storage device 1 in the stacking direction Z. A second current collector 21 is arranged as a terminal electrode at the other end 7 of the storage device 1 in the stacking direction Z.

The energy storage device 1 includes a positive electrode current-carrying plate 60 and a negative electrode current-carrying plate 70 arranged to sandwich the laminate 2 in the stacking direction Z. The energy storage device 1 includes a pair of current-carrying bodies consisting of a positive electrode current-carrying plate 60 and a negative electrode current-carrying plate 70. Each of the positive electrode current-carrying plate 60 and the negative electrode current-carrying plate 70 is made of a conductive material. The positive electrode current-carrying plate 60 is electrically connected to the first current-carrying plate 20 arranged on the outermost side at one end 6 of the stacking direction Z. The negative electrode current-carrying plate 70 is electrically connected to the second current-carrying plate 21 arranged on the outermost side at the other end 7 of the stacking direction Z. The energy storage device 1 is charged and discharged through terminals provided on the positive electrode current-carrying plate 60 and the negative electrode current-carrying plate 70. The material constituting the first current-carrying plate 20 can be used as the material constituting the positive electrode current-carrying plate 60. The positive electrode current-carrying plate 60 may be made of a metal plate thicker than the first current-carrying plate 20 used in the laminate 2. The material constituting the negative electrode current-carrying plate 70 can be the same as the material constituting the second current collector 21. The negative electrode current-carrying plate 70 may be made of a metal plate that is thicker than the second current collector 21 used in the laminate 2.

The first current collector 20 and the second current collector 21 are chemically inactive electrical conductors. Examples of materials constituting the first current collector 20 and the second current collector 21 include metal materials, conductive resin materials, conductive inorganic materials, and the like. Examples of conductive resin materials include resins in which a conductive filler is added as necessary to a conductive polymer material or a non-conductive polymer material. The first current collector 20 and the second current collector 21 may have multiple layers including one or more layers containing the above-mentioned metal material or conductive resin material. A coating layer may be formed on the surface of the first current collector 20 and the second current collector 21 by a known method such as plating or spray coating. The first current collector 20 and the second current collector 21 may be formed in the form of, for example, a plate, foil, sheet, film, mesh, or the like. When the first current collector 20 and the second current collector 21 are made of metal foil, for example, aluminum foil, copper foil, nickel foil, titanium foil, or stainless steel foil can be used. When stainless steel foil is used as the first current collector 20 and the second current collector 21, the mechanical strength of the first current collector 20 and the second current collector 21 can be ensured by using, for example, SUS304, SUS316, SUS301, SUS304, etc., as specified in JIS G 4305:2015. The first current collector 20 and the second current collector 21 may be an alloy foil or clad foil of the above metals. In this embodiment, the first current collector 20 is an aluminum foil, and the second current collector 21 is a copper foil. When the first current collector 20 and the second current collector 21 are in the form of foil, the thickness may be, for example, 1 μm to 100 μm.

The positive electrode active material layer 22 includes a positive electrode active material capable of absorbing and releasing charge carriers such as lithium ions. As the positive electrode active material, a lithium composite metal oxide having a layered rock salt structure, a metal oxide having a spinel structure, a polyanion-based compound, or the like may be used. In addition, two or more types of positive electrode active materials may be used in combination as the positive electrode active material. In this embodiment, the positive electrode active material layer 22 includes olivine-type lithium iron phosphate (LiFePO ₄ ) as a composite active material.

The negative electrode active material layer 23 may be an element capable of absorbing and releasing charge carriers such as lithium ions, an alloy, carbon, a metal compound, an element capable of alloying with lithium, or a compound thereof. Examples of carbon include natural graphite, artificial graphite, hard carbon (hardly graphitizable carbon), or soft carbon (easily graphitizable carbon). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements capable of alloying with lithium include silicon and tin. In this embodiment, the negative electrode active material layer 23 includes graphite as a carbon-based material.

The positive electrode active material layer 22 and the negative electrode active material layer 23 may further contain a conductive assistant, a binder, an electrolyte (polymer matrix, ion-conductive polymer, electrolyte solution, etc.) for increasing electrical conductivity, an electrolyte supporting salt (lithium salt) for increasing ion conductivity, etc., as necessary. The components or the mixing ratio of the components contained in the active material layer and the thickness of the active material layer are not particularly limited, and known knowledge about lithium ion secondary batteries may be appropriately referred to. The thickness of the active material layer is, for example, 2 μm to 150 μm. A known method such as a roll coating method may be used to form an active material layer on the surface of the first current collector 20 and the second current collector 21. In order to improve the thermal stability of the positive electrode 11 or the negative electrode 12, a heat-resistant layer may be provided on the surface (one side or both sides) of the first current collector 20 and the second current collector 21 or on the surface of the positive electrode active material layer 22 and the negative electrode active material layer 23. The heat-resistant layer may contain, for example, inorganic particles and a binder, and may also contain additives such as a thickener.

The conductive assistant is added to increase the conductivity of the positive electrode 11 or the negative electrode 12. Examples of the conductive assistant include acetylene black, carbon black, graphite, and the like.
Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorinated rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamide, alkoxysilyl group-containing resins, acrylic resins such as poly(meth)acrylic acid, styrene-butadiene rubber (SBR), carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked bodies, and starch-acrylic acid graft polymers. These binders can be used alone or in combination. Examples of the solvent include water and N-methyl-2-pyrrolidin (NMP).

The separator 13 may be, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte. Examples of materials that constitute the separator 13 include polypropylene, polyethylene, polyolefin, polyester, and the like. The separator 13 may have a single-layer structure or a multi-layer structure. The multi-layer structure may have, for example, an adhesive layer, a ceramic layer as a heat-resistant layer, and the like. The separator 13 may be impregnated with an electrolyte, or the separator 13 itself may be composed of an electrolyte such as a polymer gel electrolyte or an inorganic electrolyte.

Examples of the electrolyte impregnated into the separator 13 include a liquid electrolyte (electrolyte 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.

When the separator 13 _is impregnated with an electrolyte solution, _known lithium salts such as _LiClO4 , _{LiAsF6LiPF6 , LiBF4} , _LiCF3SO3 , LiN( _FSO2 ) ₂ , and LiN( _CF3SO2 ) ₂ can be used as the electrolyte salt. In addition, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used as the non-aqueous solvent. Two or more of these known solvent materials may be used in combination.

2 or 3, in a plan view of the storage cell 10 seen from the outside along the stacking direction Z, the sealing member 14 extends along the edge of the first current collector 20 and the edge of the second current collector 21. In a plan view of the storage cell 10 seen from the outside along the stacking direction Z, the sealing member 14 has a rectangular frame shape surrounding the periphery of the positive electrode active material layer 22 and the negative electrode active material layer 23. The sealing member 14 is located between the first current collector 20 and the second current collector 21 in the stacking direction Z. The sealing member 14 is bonded to the first current collector 20 and the second current collector 21. The sealing member 14 contains an insulating material and prevents a short circuit by insulating between the first current collector 20 and the second current collector 21.

The sealing member 14 has a first joint 30, a second joint 31, and a connection portion 32. The first joint 30 is located between the first current collector 20 and the separator 13 in the stacking direction Z.

The first joint 30 has a first surface 30a facing the separator 13 in the stacking direction Z. The first joint 30 has a second surface 30b facing the first current collector 20 in the stacking direction Z. The first surface 30a of the first joint 30 is located on the opposite side of the stacking direction Z to the second surface 30b. The first joint 30 has a first inner end surface 30c near the positive electrode active material layer 22 in the planar direction X, and the first surface 30a has a first end 30d at a portion intersecting with the first inner end surface 30c. In other words, the first end 30d is one end of the first surface 30a of the first joint 30 near the inner side of the space S in the planar direction X. The first surface 30a is not joined to the first surface 13a of the separator 13. The second surface 30b is joined to the first surface 20a of the first current collector 20. The first surface 30a of the first joint portion 30 is not welded to the separator 13 by the ceramic layer formed on the first surface 13a of the separator 13. In other words, the first joint portion 30 and the separator 13 are not joined. In addition, the second surface 30b of the first joint portion 30 is welded and joined to the first surface 20a of the first current collector 20. The second surface 30b of the first joint portion 30 and the first surface 20a of the first current collector 20 form the joint surfaces between the first joint portion 30 and the first current collector 20.
Here, the first current collector 20 will be described. The first current collector 20 has a second positive electrode portion 20e at a portion along the planar direction X that overlaps with the first joint portion 30 when viewed from the stacking direction Z. In the energy storage cell 10, the thickness of the energy storage cell 10 along the stacking direction Z at the second positive electrode portion 20e is the thinnest. Furthermore, the first current collector 20 has a third positive electrode portion 20f at a portion along the planar direction X that connects the first positive electrode portion 20d and the second positive electrode portion 20e.

The second joint 31 is located between the second current collector 21 and the separator 13 in the stacking direction Z. The second joint 31 has a first surface 31a that faces the separator 13 in the stacking direction Z. The second joint 31 also has a second surface 31b that faces the second current collector 21 in the stacking direction Z. The first surface 31a of the second joint 31 is located on the opposite side of the stacking direction Z to the second surface 31b. The second joint 31 also has a second inner end surface 31c closer to the negative electrode active material layer 23 in the planar direction X, and the first surface 31a has a second end surface 31d at a portion where it intersects with the second inner end surface 31c. In other words, the second end surface 31d is one end of the first surface 31a of the second joint 31 closer to the inside of the space S in the planar direction X. The first surface 31a is joined to the second surface 13b of the separator 13. The second surface 31b is joined to the first surface 21a of the second current collector 21. For example, the first surface 31a of the second joint 31 is welded and joined to the second surface 13b of the separator 13, and the second surface 31b is welded and joined to the first surface 21a of the second current collector 21. The second surface 31b of the second joint 31 and the first surface 21a of the second current collector 21 form the joint surface between the second joint 31 and the second current collector 21.

The second current collector 21 will now be described. The second current collector 21 has a second negative electrode portion 21e at a portion along the surface direction X that overlaps with the second joint 31 when viewed from the stacking direction Z. The second positive electrode portion 20e and the second negative electrode portion 21e overlap when viewed from the stacking direction Z. The second current collector 21 also has a third negative electrode portion 21f at a portion along the surface direction X that connects the first negative electrode portion 21d and the second negative electrode portion 21e.

In the sealing member 14, the first joint 30 and the second joint 31 overlap when viewed from the stacking direction Z. In this embodiment, the entire first joint 30 and the entire second joint 31 overlap when viewed from the stacking direction Z via a portion of the separator 13.

The separator 13 also has an intervening portion 33 at its outer edge that is interposed between the second positive electrode portion 20e and the first joint 30, and the second negative electrode portion 21e and the second joint 31. In a plan view of the storage cell 10 seen from the outside along the stacking direction Z, the intervening portion 33 is a rectangular frame that surrounds the positive electrode active material layer 22 and the negative electrode active material layer 23. The intervening portion 33 is not joined to the first joint 30. The intervening portion 33 is joined to the second joint 31. That is, the first end 30d of the first surface 30a and the first surface 13a of the separator 13 facing the first end 30d are not joined. Therefore, the first end 30d has a non-jointed region that is not joined to the separator 13 facing the first end 30d in the stacking direction Z. In the energy storage cell 10, the dimension in the stacking direction Z between the first end 30d of the first bonding portion 30 and the second end 31d of the second bonding portion 31 at the internal pressure P1 of the space S in a state where there is no gas generation or the like and the pressure in the space S is not rising is defined as dimension L1. In the state of the internal pressure P1, for example, the dimension L1 is approximately equal to the thickness of the separator 13 interposed between the first bonding portion 30 and the second bonding portion 31 in the stacking direction Z. In particular, when the internal pressure P1 is negative with respect to the atmospheric pressure, the first bonding portion 30 and the second bonding portion 31 are pressed by the atmospheric pressure so as to approach each other in the stacking direction Z, so that the dimension L1 is equal to the thickness of the separator 13 in the stacking direction Z.

The connection portion 32 connects the first joint portion 30 and the second joint portion 31. The connection portion 32 is a portion that protrudes in the planar direction X from the first outer end surface 20c of the first current collector 20 and the second outer end surface 21c of the second current collector 21. The connection portion 32 has a first continuous portion 15 that is continuous with the first joint portion 30 in the planar direction X, a second continuous portion 16 that is continuous with the second joint portion 31 in the planar direction X, and a third continuous portion 17 that is continuous with the first continuous portion 15 and the second continuous portion 16.

The cross-sectional shape of the connection portion 32 along the stacking direction Z is a shape bent from the first joint portion 30 to the second joint portion 31. In the connection portion 32, a part of the separator 13 is interposed between the first continuous portion 15 and the second continuous portion 16 in the stacking direction Z.

The first continuous portion 15 has a first inner surface 15a closer to the separator 13 in the stacking direction Z. The first continuous portion 15 also has a first outer surface 15b closer to the first current collector 20 in the stacking direction Z. The first inner surface 15a is not joined to the first surface 13a of the separator 13. The first outer surface 15b is exposed to the outside of the storage cell 10.

The second continuous portion 16 has a second inner surface 16a closer to the separator 13 in the stacking direction Z. The second continuous portion 16 also has a second outer surface 16b closer to the second current collector 21 in the stacking direction Z. The second inner surface 16a is joined to the second surface 13b of the separator 13. The second outer surface 16b is exposed to the outside of the storage cell 10.

The sealing member 14 configured as described above seals the space S defined by the first current collector 20, the second current collector 21, and the sealing member 14. The sealing member 14 prevents the electrolyte contained in the space S from leaking out to the outside. The sealing member 14 also prevents moisture from entering the space S from the outside. In this embodiment, the material of the sealing member 14 is acid-modified polyethylene. The material of the sealing member 14 may also be acid-modified polypropylene. The sealing member 14 is flexible.

The storage cell 10 includes a cylindrical member 18 as a cell component. Although not shown, the cylindrical member 18 has a flat shape in an axial view of the cylindrical member 18 from the outside along the axial direction. In this embodiment, the cylindrical member 18 is used to inject an electrolyte. The cylindrical member 18 is interposed between the seal member 14 and the first current collector 20. The cylindrical member 18 has a passage 18a and a blocking portion 18b. The passage 18a is formed by a peripheral wall 18e. The outer end 18c of the cylindrical member 18, which is closer to the outside of the space S in the axial direction, is located outside the third outer surface 17b of the third continuous portion 17. The outer end 18c of the cylindrical member 18 is blocked by the blocking portion 18b. The blocking portion 18b is formed by welding the outer end 18c of the cylindrical member 18 by heat. The blocking portion 18b blocks the passage 18a outside the third outer surface 17b of the third continuous portion 17. An inner end 18d opposite to the outer end 18c in the axial direction of the cylindrical member 18 is located inside a first inner end surface 30c of the first joint portion 30. The inner end 18d of the cylindrical member 18 opens toward the space S. The passages 18a are provided penetrating the seal member 14 in the planar direction X from the blocking portion 18b toward the inside of the space S. A portion of the passages 18a that overlaps with the seal member 14 and the first current collector 20 in the stacking direction Z is joined to the first current collector 20 and the seal member 14 by being welded to them. That is, in the portion where the passages 18a overlap, the seal member 14 and the first current collector 20 are not directly joined to each other, but are joined via the cylindrical member 18. A portion of the tubular member 18 near the inner end 18d is located between the second positive electrode portion 20e and the third positive electrode portion 20f of the first current collector 20 and the second negative electrode portion 21e and the third negative electrode portion 21f of the second current collector 21 in the stacking direction Z.

Therefore, a portion of the tubular member 18 near the inner end 18d overlaps with the first current collector 20 and the second current collector 21 in the stacking direction Z. A portion of the tubular member 18 near the inner end 18d is not joined to the first surface 20a of the third positive electrode portion 20f of the first current collector 20. The inner end 18d of the tubular member 18 is open.

Next, the operation of this embodiment will be described.
For example, gas may be generated in the space S due to charging and discharging of the storage cell 10, and the pressure in the space S may increase. As shown in FIG. 2 or FIG. 4, when the pressure in the space S increases, a force is generated from the space S toward the outside of the space S. Then, the storage cell 10 deforms so as to increase the volume of the space S. At this time, a force acts on the first current collector 20 and the second current collector 21 to separate them from each other along the stacking direction Z. The second positive electrode portion 20e and the third positive electrode portion 20f, which are not restrained by the restraining member, and the second negative electrode portion 21e and the third negative electrode portion 21f deform so as to separate from each other along the stacking direction Z. The first joint portion 30 joined to the second positive electrode portion 20e, including the first end portion 30d, is not joined to the separator 13, which is a member facing the first surface 30a of the first joint portion 30, and therefore deforms following the second positive electrode portion 20e. The second joint 31 joined to the second negative electrode portion 21e and the separator 13 is deformed together with the separator 13, following the second negative electrode portion 21e. That is, the first end 30d of the first joint 30 and the second end 31d of the second joint 31 are separated in the stacking direction Z. At this time, the connection portion 32 of the seal member 14 is deformed so as to expand in the stacking direction Z and shrink in the surface direction X. As a result, in the energy storage cell 10, the first joint 30 and the second joint 31 overlapping in the stacking direction Z are allowed to deform in a direction separating them in the stacking direction Z. As a result, the dimension in the stacking direction Z between the first end 30d of the first joint 30 and the second end 31d of the second joint 31 becomes larger than that before the pressure in the space S increases. That is, the internal pressure of the space S in a state in which the pressure in the space S increases due to the generation of gas or the like becomes an internal pressure P2 that is larger than the internal pressure P1. If the dimension in the stacking direction Z between the first end 30d of the first joint 30 and the second end 31d of the second joint 31 at internal pressure P2 is dimension L2, dimension L2 is greater than dimension L1.

By deforming the sealing member 14, the first current collector 20, and the second current collector 21 in this manner, the volume of the space S increases, suppressing the amount of pressure increase in the space S and reducing the force to peel the first current collector 20 from the first joint 31 along the stacking direction Z and the force to peel the second current collector 21 from the second joint 31 along the stacking direction Z.

In this embodiment, the following effects can be obtained.
(1) When the pressure in the space S increases, the first joint 30 and the second joint 31 in the energy storage cell 10 can be deformed so that the dimension L1 increases. As the dimension L1 in the energy storage cell 10 increases, the first joint 30 and the second joint 31 can be deformed so as to move away from each other, and the volume of the space S in the energy storage cell 10 can be increased. Therefore, compared to a case in which the first joint 30 and the second joint 31 cannot be deformed so as to move away from each other, the amount of pressure increase in the space S for the same amount of gas generation is reduced, and the force to peel the first current collector 20 from the first joint 30 along the stacking direction Z and the force to peel the second current collector 21 from the second joint 31 along the stacking direction Z are reduced. Therefore, when the pressure in the space S increases, the seal member 14 and the first and second current collectors 20 and 21 are less likely to peel off from the ends of the joint surfaces, and a decrease in sealing performance can be suppressed.

(2) Because the first end 30d has a non-bonded region with respect to the separator 13, when the pressure in the space S increases, the first bonding portion 30 including the first end 30d can be separated from the separator 13, and the first end 30d and the second end 31d can be more easily separated in the stacking direction Z than before the pressure in the space S increases.

(3) Because the interposition portion 33 of the separator 13 is interposed between the first joint portion 30 and the second joint portion 31, it is easy to make the first joint portion 30 and the second joint portion 31 unjoined from each other without special processing of the sealing member 14.

(4) By using the separator 13 constituting the energy storage cell 10 as an intervening member, it is easy to form a non-bonded region at the first end 30d without adding an intervening member, and it is easy to make the first bonding portion 30 and the second bonding portion 31 not bonded to each other.

(5) In a storage cell 10 in which the first current collector 20, the separator 13, and the second current collector 21 overlap in the stacking direction Z, the second surface 13b of the separator 13 is joined to the first surface 31a of the second joint 31, thereby suppressing misalignment of the separator 13 in the planar direction X within the storage cell 10.

(6) In this embodiment, the connection portion 32 protrudes in the planar direction X beyond the first outer end surface 20c of the first current collector 20 and the second outer end surface 21c of the second current collector 21. For example, when the pressure in the space S increases, the connection portion 32 deforms, thereby making it possible to further increase the volume of the space S, compared to when the connection portion 32 is located closer to the inside of the space S than the first outer end surface 20c and the second outer end surface 21c in the planar direction X. Therefore, this is a suitable configuration for increasing the volume of the space S.

The above embodiment can be modified as follows. The above embodiment and the following modified examples can be combined with each other to the extent that there is no technical contradiction. The seal member 14 in the embodiment may be referred to as the first seal member 14.

As shown in FIG. 5 or 6, the energy storage device 1 may include a second seal member 40. The second seal member 40 has a seal portion main body 41 and a plurality of extended seal portions 42. The seal portion main body 41 has a rectangular frame shape in a plan view when the energy storage device 1 is viewed from the outside in the stacking direction Z. The seal portion main body 41 also surrounds the first seal member 14. The inner surface 41a of the seal portion main body 41 is joined to the outer end surface 32c of the connection portion 32 of each first seal member 14.

Each of the extended seal parts 42 extends from the inner surface 41a of the seal part main body 41 toward the inside of the energy storage device 1 along the surface direction X. Each of the extended seal parts 42 has a rectangular frame shape that is slightly smaller than the seal part main body 41 in a plan view of the energy storage device 1 from the outside in the stacking direction Z. Each of the extended seal parts 42 has a base 43 located between the first seal members 14 adjacent to each other in the stacking direction Z, and a tip part 44 that protrudes from the base 43 in the surface direction X and is located between the first current collector 20 and the second current collector 21 adjacent to each other in the stacking direction Z.

Each base 43 has a first surface 43a facing the first continuous portion 15 in the stacking direction Z, and a second surface 43b facing the second continuous portion 16 in the stacking direction Z. Each tip 44 has a first surface 44a facing the second current collector 21 in the stacking direction Z, and a second surface 44b facing the first current collector 20 in the stacking direction Z. Each extended seal portion 42 has a first step surface 42a connecting the second surface 43b of the base 43 and the first surface 44a of the tip 44. Similarly, each extended seal portion 42 has a second step surface 42b connecting the first surface 43a of the base 43 and the second surface 44b of the tip 44.

In each of the extended seal sections 42, the first surface 43a of the base 43 is joined to the first outer surface 15b of the first continuous section 15. In each of the extended seal sections 42, the second surface 43b of the base 43 is joined to the second outer surface 16b of the second continuous section 16.

In each of the extended seal parts 42, the first surface 44a of the tip 44 is joined to a portion of the second surface 21b of the second current collector 21 that is located at the second negative electrode portion 21e. In addition, in each of the extended seal parts 42, the second surface 44b of the tip 44 is joined to a portion of the second surface 20b of the first current collector 20 that is located at the second positive electrode portion 20e.

In each of the extended seal portions 42, the first step surface 42a is joined to the second outer end surface 21c of the second current collector 21. In each of the extended seal portions 42, the second step surface 42b is joined to the first outer end surface 20c of the first current collector 20.

Therefore, each of the extended seal portions 42 seals the gaps G between the energy storage cells 10 adjacent to each other in the stacking direction Z.
In a plan view of the electricity storage device 1 seen from the outside in the stacking direction Z, the inner end surface 42c of the extended seal portion 42 in the surface direction X is located outside the first inner end surface 30c of the first joint portion 30 and the second inner end surface 31c of the second joint portion 31, and inside the first outer end surface 20c of the first current collector 20 and the second outer end surface 21c of the second current collector 21. The extended seal portion 42 may not have a tip portion 44 and may be configured only by the base portion 43. In this case, the inner end surface 42c of the extended seal portion 42 is located at the same position as or outside the first outer end surface 20c of the first current collector 20 and the second outer end surface 21c of the second current collector 21 in the surface direction X.

Now, in the above configuration, when the pressure in the space S increases, a force is generated from the space S toward the outside of the space S. Then, the storage cell 10 deforms so as to increase the volume of the space S at a portion closer to the space S than the inner end surface 42c of the extended seal portion 42 in the surface direction X. At this time, a force acts on a part of the second positive electrode portion 20e and the third positive electrode portion 20f of the first current collector 20, and a part of the second negative electrode portion 21e and the third negative electrode portion 21f of the second current collector 21 to separate them from each other along the stacking direction Z. The first joint 30 joined to the second positive electrode portion 20e deforms following the second positive electrode portion 20e. The second joint 31 joined to the second negative electrode portion 21e deforms following the second negative electrode portion 21e. In other words, the first end 30d of the first joint 30 and the second end 31d of the second joint 31 are separated in the stacking direction Z. As a result, in the energy storage cell 10, a part of the first joint 30 and a part of the second joint 31 that overlap in the stacking direction Z are allowed to deform in a direction separating them in the stacking direction Z. As a result, the dimension in the stacking direction Z between the first end 30d of the first joint 30 and the second end 31d of the second joint 31 becomes larger than before the pressure in the space S increases. In other words, the dimension L2 at the internal pressure P2 in the pressure-increased state is larger than the dimension L1 at the internal pressure P1 in the pressure-not-increased state.

Therefore, the extended seal portion 42 of the second seal member 40 can seal the gap G between the adjacent energy storage cells 10 in the stacking direction Z. Furthermore, the second seal member 40 can fix the multiple energy storage cells 10 to each other in the stacking direction Z. Also, by adjusting the position of the inner end surface 42c of the extended seal portion 42, the first joint portion 30 and the second joint portion 31 can be deformed so as to move away from each other when the pressure in the space S increases.

The energy storage device 1 may not have the second seal member 40. For example, in a configuration in which the energy storage cells 10 having the first seal member 14 are integrated in the stacking direction Z, the first seal members 14 adjacent to each other in the stacking direction Z may be integrated by welding. Specifically, heat is applied to the connection portions 32 of the energy storage cells 10 adjacent to each other in the stacking direction Z. Then, the connection portions 32 adjacent to each other in the stacking direction Z are integrated to form the extended seal portion 42. In this case, the extended seal portion 42 is located between the second current collector 21 of one energy storage cell 10 and the first current collector 20 of the other energy storage cell 10.

As shown in FIG. 7, in the portion where the first joint 30 and the second joint 31 overlap in the stacking direction Z in the seal member 14, the separator 13 may not be interposed between the first joint 30 and the second joint 31. In this case, a slit 45 is formed so that the first surface 30a of the first joint 30 and the first surface 31a of the second joint 31 are not joined. The slit 45 does not join the first joint 30 and the second joint 31 to each other in the stacking direction Z, and does not join the first end 30d and the second end 31d. The slit 45 can be formed, for example, by welding or adhering the first current collector 20 and the first joint 30 and the second current collector 21 and the second joint 31 to each other so that the first surface 30a of the first joint 30 and the first surface 31a of the second joint 31 are not welded to each other.

As shown in FIG. 8, the seal member 14 may have a first joint 30, a second joint 31, and an intervening seal portion 50 interposed between the first joint 30 and the second joint 31. When constructing this seal member 14, the first joint 30 is pre-joined to the first surface 20a of the first current collector 20, and the second joint 31 is pre-joined to the first surface 21a of the second current collector 21. Then, when stacking the first current collector 20 and the second current collector 21, the intervening seal portion 50 is disposed between the first joint 30 and the second joint 31, and heat is applied to the first joint 30, the second joint 31, and the intervening seal portion 50. Then, the first joint 30, the second joint 31, and the intervening seal portion 50 are integrated to form the seal member 14.

The intervening seal portion 50 is interposed only outside the space S, beyond the first end 30d of the first joint 30 closer to the inside of the space S, and the second end 31d of the second joint 31 closer to the inside of the space S, and a part of it protrudes along the surface direction X beyond the first outer end surface 20c of the first current collector 20 and the second outer end surface 21c of the second current collector 21. That is, the intervening seal portion 50 is not integrated at the first end 30d of the first joint 30 closer to the inside of the space S, and the second end 31d of the second joint 31 closer to the inside of the space S. In this case, the connection portion 32 is constituted by the intervening seal portion 50, and when viewed from the stacking direction Z, the first joint 30 and the second joint 31 and the connection portion 32 partially overlap. The separator 13 is joined to a part of the first surface 31a of the second joint 31 closer to the inside of the space S than the intervening seal portion 50. The first surface 30a of the first joint portion 30 and the separator 13 are separated by the thickness of the intervening seal portion 50 along the stacking direction Z, and are not joined to each other. That is, in this embodiment, the dimension L1 at the internal pressure P1 is approximately equal to the thickness of the intervening seal portion 50 along the stacking direction Z.

As shown in FIG. 9, in a configuration in which the storage cells 10 having the first seal member 14 shown in FIG. 8 are integrated in the stacking direction Z, the intervening seal portions 50 adjacent to each other in the stacking direction Z may be integrated by welding them together. In this case, when the intervening seal portions 50 are welded together, a part of the intervening seal portion 50 penetrates into the portion located between the first current collector 20 of one storage cell 10 and the second current collector 21 of the other storage cell 10 among the storage cells 10 adjacent to each other in the stacking direction Z, and the extended seal portion 42 is formed by the penetrated portion.

In the above embodiment, the positive electrode 11 is the first electrode and the negative electrode 12 is the second electrode, but this is not limited to the above. For example, the negative electrode 12 may be the first electrode and the positive electrode 11 may be the second electrode.
In the above embodiment, the separator 13 is not limited to be disposed between the first joint portion 30 and the second joint portion 31 . A separate plate-shaped member may be disposed between the first joint portion 30 and the second joint portion 31 .

The first current collector 20, the second current collector 21, and the seal member 14 may have a circular, elliptical, or hexagonal shape in a plan view.
The cell constituent member may be used to exhaust gas generated in the space S to the outside.

In the sealing member 14, the connection portion 32 does not have to protrude from the first outer end surface 20c of the first current collector 20 and the second outer end surface 21c of the second current collector 21. In this case, the connection portion 32 is located between the second positive electrode portion 20e and the second negative electrode portion 21e in the stacking direction Z.

The intermediate portion 33 of the separator 13 does not have to be joined to the second joining portion 31 .
In the embodiment, the entire first joint 30 and the entire second joint 31 overlap in the stacking direction Z, but the first joint 30 and the second joint 31 may only partially overlap in the stacking direction Z.

1...electricity storage device, 10...electricity storage cell, 11...positive electrode as first electrode, 12...negative electrode as second electrode, 13...separator as intervening member, 13a...first surface, 13b...second surface, 14...sealing member, 18...tubular member, 20...first current collector, 20a...first surface, 20c...first outer end surface as end surface, 21...second current collector, 21a...first surface, 21c...second outer end surface as end surface, 30...first joint, 30c...first inner end surface as inner end surface, 30d...first end, 31...second joint, 31c...second inner end surface as inner end surface, 31d...second end, 32...connection, 42...extended seal portion, S...space, X...surface direction, Z...stacking direction.

Claims (8)

a first electrode having a first current collector;
a second electrode having a second current collector;
a seal member bonded to a first surface of the first current collector and a first surface of the second current collector;
A storage cell including a space defined by the first current collector, the second current collector, and the seal member,
a direction in which the first electrode and the second electrode overlap each other is defined as a stacking direction of the power storage cell;
a direction along the first surface of the first current collector and the first surface of the second current collector is defined as a surface direction of the power storage cell,
The sealing member includes a first bonding portion bonded to the first surface of the first current collector,
a second bonding portion bonded to the first surface of the second current collector;
a connection portion that connects the first joint portion and the second joint portion,
A storage cell characterized in that, when pressure in the space increases, a first end of the first joint toward the inside of the space in the planar direction and a second end of the second joint toward the inside of the space in the planar direction become farther apart in the stacking direction than they were before the pressure in the space increased. The energy storage cell according to claim 1, characterized in that the first end has a non-bonded region that is not bonded to a member that faces the first end in the stacking direction. the energy storage cell includes an interposition member interposed between the first joint portion and the second joint portion that overlap when viewed from the stacking direction,
3 . The energy storage cell according to claim 2 , wherein the end of the first joint portion on a surface opposite to the surface joined to the first current collector is not joined to the interposition member. The energy storage cell according to claim 3, characterized in that the intervening member is a separator that is not joined to at least the first joint portion of the first joint portion and the second joint portion that overlap when viewed from the stacking direction. The storage cell according to claim 4, characterized in that the separator is joined to the second joint. The storage cell according to any one of claims 1 to 5, characterized in that the connection portion is located at a position protruding in the surface direction from an end face located at the outer edge of the surface direction of the first current collector and an end face located at the outer edge of the surface direction of the second current collector. The battery has a plurality of stacked storage cells,
The power storage device includes a plurality of the power storage cells, the power storage cell according to any one of claims 1 to 6. Further, an extended seal portion is provided between the storage cells adjacent to each other in the stacking direction and is joined to each of the storage cells adjacent to each other in the stacking direction,
The energy storage device according to claim 7, characterized in that, in a planar view of the energy storage device from the outside in the stacking direction, an inner end surface of the extended seal portion in the surface direction is located outside an inner end surface of the first joint portion located toward the inside of the space and an inner end surface of the second joint portion located toward the inside of the space.