JP2022123651A - Storage cell and power storage device - Google Patents

Abstract

[Problem] To provide a storage cell and a storage device capable of suppressing deterioration of sealing property. [Solution] The storage cell 2 includes a positive electrode 11 having a current collector 21 and a positive electrode active material layer 23 provided on a first surface 21a of the current collector 21, a current collector 22 and a negative electrode 12 having a negative electrode active material layer 24 provided on a first surface 22a of the current collector 22, facing the positive electrode active material layer 23 and having a polarity different from that of the positive electrode active material layer 23, a separator 13 arranged between the positive electrode active material layer 23 and the negative electrode active material layer 24, and a sealing part 14 that seals an electrolyte in a space S between the current collector 21 and the current collector 22. The sealing part 14 includes an outer peripheral region R1 bonded over the entire circumference of an edge portion 21c of the first surface 21a and the entire circumference of an edge portion 22c of the first surface 22a, and an inner peripheral region R2 arranged inside the outer peripheral region R1 and not bonded to the first surface 21a and the first surface 22a. An end portion 13a of the separator 13 is fixed to the inner peripheral region R2. [Selected Figure] FIG.

Description

The present disclosure relates to a power storage cell and a power storage device.

Patent Document 1 discloses a bipolar electrode including a current collector, a positive electrode active material layer formed on one side of the current collector, and a negative electrode active material layer formed on the other side of the current collector. describes a bipolar secondary battery in which are stacked with a separator interposed therebetween. In this bipolar secondary battery, seal portions are provided on the peripheral edge portions of one surface and the other surface of the current collector, respectively.

Japanese Unexamined Patent Application Publication No. 2011-9039

In the battery described in Patent Document 1, in order to suppress a short circuit between the positive electrode and the negative electrode, the peripheral edge portion of the separator is sandwiched between the seal portions adjacent to each other in the stacking direction, and the seal portions and the current collector are attached to each other. is welded. In order to bond the seal portion to the current collector, it is necessary to apply pressure and heat to the welding range where the current collector and the seal portion overlap to melt the seal portion. By the way, when the edge of the separator is located in the welding range of the seal portion and the current collector, the seal portion does not exist outside the edge surface of the separator before heat is applied due to the thickness of the separator. A minute space is formed. When pressure and heat are applied to the welding area while the end of the separator is positioned in the welding area, part of the molten resin also flows into this minute space. However, due to the thickness of the separator, it is difficult to sufficiently apply pressure to the portion where the minute space is formed. For this reason, a weakly bonded portion, in which the bonding between the seal portions is insufficient, is formed at the end of the region sealed to seal the cell. Since the weakly bonded portion is formed adjacent to the peripheral portion of the separator, in a state in which the electrolyte is sealed in the battery, the electrolyte easily penetrates into the weakly bonded portion via the separator. When the resin of the weakly-bonded portion is swollen by the electrolytic solution through the edge of the separator, the adhesive strength of the weakly-bonded portion is reduced, and the seal portions are separated from each other. Since the weakly bonded portion is continuous with the portion where the seal portions are strongly bonded together, peeling of the weakly bonded portion may start and spread to the strongly bonded portion. As a result, the sealing portion may be cleaved, and the sealing performance of the battery may deteriorate.

An object of the present disclosure is to provide a power storage cell and a power storage device capable of suppressing deterioration in sealing performance.

A storage cell according to one aspect of the present disclosure includes a first current collector, a first electrode having a first active material layer provided on a first surface of the first current collector, a second current collector, and a second electrode provided on the second surface of the second current collector, facing the first active material layer and having a second active material layer having a polarity different from that of the first active material layer; and In the facing direction in which the second active material layers face each other, an electrolytic solution is provided in the space between the separator disposed between the first active material layer and the second active material layer and the first current collector and the second current collector. and a sealing portion that seals the edge of the first surface and the entire periphery of the edge of the second surface, and the outer peripheral region bonded over the entire periphery of the edge of the second surface, and the outer periphery when viewed from the opposite direction and an inner peripheral region located inside the region and not adhered to the first surface and the second surface, the inner peripheral region having the ends of the separator fixed thereto.

In the storage cell, the sealing portion has an outer peripheral region bonded to the first current collector and the second current collector, and the outer peripheral region defines a space between the first current collector and the second current collector. Seal. The seal further has an inner peripheral region to which the ends of the separator are fixed. Unlike the case where the end of the separator is fixed to the outer peripheral region, which is the adhesive portion between the sealing portion and the first current collector and the second current collector, in this configuration, the sealing portion is attached to the first current collector. And the end of the separator is fixed at a portion other than the adhesion portion adhered to the second current collector. Therefore, a weakly bonded portion is not formed at the end of the bonded portion. Therefore, peeling of the sealing portion caused by peeling of the weakly bonded portion is suppressed. Thereby, the deterioration of the sealing property can be suppressed.

When viewed from the opposing direction, the end of the separator may be positioned inside the inner circumference of the outer peripheral region, separated from the outer peripheral region. In this case, since the bonded portion between the first current collector and the second current collector in the outer peripheral region and the end portion of the separator are separated from each other with the non-bonded portion interposed therebetween, the weakly bonded portion is formed at the end portion of the bonded portion. In addition to not being formed, the effect of the swelling of the sealing portion by the electrolytic solution through the edge of the separator further affects the bonding portion between the first current collector and the second current collector in the outer peripheral region. hard.

In the opposing direction, the inner peripheral region may sandwich the end of the separator between the first surface and the first surface. In this case, it is possible to prevent displacement of the separator when the active material of the first electrode or the second electrode expands or contracts without bonding the separator to the inner peripheral region.

The outer peripheral region is formed by laminating a first resin layer adhered to the edge of the first surface and a second resin layer adhered to the edge of the second surface. The inner circumference of the layer is positioned inside the inner circumference of the second resin layer, and the area of the first resin layer positioned inside the inner circumference of the second resin layer constitutes the inner circumference area. You may have In this case, the inner peripheral region can be thinned by the thickness of the second resin layer. Therefore, the space can be kept wide.

The first resin layer may be thinner than the second resin layer in the facing direction. In this case, the space can be kept even wider.

The inner peripheral region may be spaced apart from the first surface in the facing direction. In this case, it is difficult for the electrolyte to accumulate between the first surface and the inner peripheral region.

The first current collector may be arranged above the second current collector in the direction of gravity. In this case, it is even more difficult for the electrolyte to accumulate between the first surface and the inner peripheral region.

A power storage device according to the present disclosure includes a laminate in which the above power storage cells are stacked.

Since the power storage device includes a laminate in which the power storage cells are stacked, it is possible to suppress deterioration in sealing performance.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a power storage cell and a power storage device capable of suppressing deterioration in sealing performance.

FIG. 1 is a schematic cross-sectional view showing a power storage device according to one embodiment. 2 is a schematic cross-sectional view of the storage cell shown in FIG. 1. FIG. FIG. 3 is a schematic cross-sectional view of a storage cell according to a first modified example. FIG. 4 is a schematic cross-sectional view of a storage cell according to a second modification.

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.

FIG. 1 is a schematic cross-sectional view showing a power storage device according to one embodiment. A power storage device 1 shown in FIG. 1 is, for example, a power storage module used in batteries of various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 1 is, for example, a secondary battery such as a nickel-hydrogen secondary battery or a lithium-ion secondary battery. The power storage device 1 may be an electric double layer capacitor or an all-solid battery. In this embodiment, the case where the power storage device 1 is a lithium ion secondary battery is illustrated.

The power storage device 1 includes a cell stack 3 (laminated body) in which a plurality of power storage cells 2 are stacked. 2 is a schematic cross-sectional view of the storage cell shown in FIG. 1. FIG. As shown in FIGS. 1 and 2 , each storage cell 2 includes a positive electrode 11 , a negative electrode 12 , a separator 13 and a sealing portion 14 . The positive electrode 11 and the negative electrode 12 are arranged facing each other. A facing direction D of the positive electrode 11 and the negative electrode 12 coincides with the stacking direction of the plurality of storage cells 2 . The positive electrode 11 and the negative electrode 12 are, for example, rectangular electrodes when viewed from the opposing direction D. As shown in FIG. The facing direction D is, for example, the direction of gravity, and the positive electrode 11 is arranged above the negative electrode 12 in the direction of gravity.

The positive electrode 11 includes a current collector 21 and a positive electrode active material layer 23 . The current collector 21 has a first surface 21a and a second surface 21b facing opposite to each other. A positive electrode active material layer 23 is provided on the first surface 21a. The positive electrode active material layer 23 is not provided on the edge portion 21c of the first surface 21a. The edge portion 21c is located outside the region where the positive electrode active material layer 23 is provided on the first surface 21a when viewed from the facing direction D. As shown in FIG. The positive electrode active material layer 23 is not provided on the entire second surface 21b.

The negative electrode 12 includes a current collector 22 and a negative electrode active material layer 24 having a polarity different from that of the positive electrode active material layer 23 . The current collector 22 has a first surface 22a and a second surface 22b facing opposite to each other. A negative electrode active material layer 24 is provided on the first surface 22a. The negative electrode active material layer 24 faces the positive electrode active material layer 23 in the facing direction D. As shown in FIG. The negative electrode active material layer 24 is not provided on the edge portion 22c of the first surface 22a. The edge portion 22c is located outside the region where the negative electrode active material layer 24 is provided on the first surface 22a when viewed from the opposing direction D. As shown in FIG. The negative electrode active material layer 24 is not provided on the entire second surface 22b.

The positive electrode 11 and the negative electrode 12 are arranged such that the positive electrode active material layer 23 and the negative electrode active material layer 24 face each other in the facing direction D. As shown in FIG. In this embodiment, both the positive electrode active material layer 23 and the negative electrode active material layer 24 are formed in a rectangular shape when viewed from the facing direction D. As shown in FIG. The negative electrode active material layer 24 is formed one size larger than the positive electrode active material layer 23 . As viewed from the opposing direction D, the entire positive electrode active material layer 23 is located inside the outer edge of the negative electrode active material layer 24 .

The cell stack 3 is configured by stacking the storage cells 2 such that the second surface 21b of the current collector 21 and the second surface 22b of the current collector 22 are in contact with each other. Thereby, the plurality of storage cells 2 are electrically connected in series. In the storage cells 2, 2 adjacent to each other in the stacking direction, the current collector 21 of one storage cell 2 and the current collector 22 of the other storage cell 2 are in contact with each other.

In the cell stack 3, the storage cells 2, 2 adjacent to each other in the stacking direction form a pseudo bipolar electrode 10 in which the current collectors 21 and 22 that are in contact with each other are used as one current collector. At one end of the cell stack 3 in the stacking direction, a terminating electrode (positive terminating electrode in this embodiment) including a current collector 21 is arranged. A terminating electrode (a negative terminating electrode in this embodiment) including a current collector 22 is arranged at the other end of the cell stack 3 in the stacking direction.

Current collectors 21 and 22 are chemically inactive electrical conductors for continuing current flow through positive electrode active material layer 23 and negative electrode active material layer 24 during discharge or charge of the lithium ion secondary battery. Examples of materials that can be used for the current collectors 21 and 22 include metal materials, conductive resin materials, and conductive inorganic materials. Examples of conductive resin materials include resins obtained by adding conductive fillers to conductive polymer materials and non-conductive polymer materials. The current collectors 21 and 22 may have multiple layers including one or more layers containing the aforementioned metal material or conductive resin material. A coating layer may be formed on the surfaces of the current collectors 21 and 22 by a known method such as plating or spray coating. The current collectors 21 and 22 may be formed in a plate-like, foil-like, sheet-like, film-like, or mesh-like shape, for example. When the current collectors 21 and 22 are made of metal foil, for example, aluminum foil, copper foil, nickel foil, titanium foil, stainless steel foil, or the like is used. The current collectors 21 and 22 may be alloy foils or clad foils of the above metals. When the current collectors 21 and 22 are foil-shaped, the thickness of the current collectors 21 and 22 may be in the range of 1 μm or more and 100 μm or less. The current collectors 21 and 22 may be integrated by, for example, plating one side of an aluminum foil with copper. In this embodiment, the current collector 21 is aluminum foil and the current collector 22 is copper foil.

The positive electrode active material layer 23 contains a positive electrode active material capable of intercalating and deintercalating charge carriers such as lithium ions. 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 negative electrode active material layer 24 contains a negative electrode active material capable of intercalating and deintercalating charge carriers such as lithium ions. 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 thereof, boron-added carbon, and the like. mentioned. Examples of elements that can be alloyed with lithium include silicon (silicon) and tin.

The positive electrode active material layer 23 and the negative electrode active material layer 24 may contain a binder and a conductive aid in addition to the active material. The binder serves to bind the active material or conductive aid to each other and maintain the conductive network in the electrode. 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; resins containing alkoxysilyl groups; Examples include acrylic resins such as acids and polymethacrylic acid, styrene-butadiene rubber (SBR), carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked products, and starch-acrylic acid graft polymers. be able to. These binders may be used singly or in combination. Conductive aids are conductive materials such as acetylene black, carbon black, and graphite, and can increase electrical conductivity. As the viscosity adjusting solvent, for example, N-methyl-2-pyrrolidone or the like is used.

In order to form the positive electrode active material layer 23 and the negative electrode active material layer 24 on the first surfaces 21a and 22a, conventional methods such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method are used. A method known from the US Pat. 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 one surface 21a, 22a, 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.

The separator 13 is arranged between the positive electrode 11 and the negative electrode 12 in the opposing direction D. As shown in FIG. A separator 13 is interposed between the positive electrode 11 and the negative electrode 12 . The separator 13 is a member that separates the adjacent positive electrode 11 and negative electrode 12 when the storage cells 2 are stacked, thereby preventing an electrical short circuit due to contact between the two electrodes and allowing charge carriers such as lithium ions to pass through. The separator 13 is arranged between the positive electrode active material layer 23 and the negative electrode active material layer 24 facing each other.

The separator 13 has a rectangular shape that is one size larger than the positive electrode active material layer 23 and the negative electrode active material layer 24 and one size smaller than the current collectors 21 and 22 when viewed from the opposing direction D. As shown in FIG. The end portion 13 a of the separator 13 is arranged outside the positive electrode active material layer 23 and the negative electrode active material layer 24 when viewed from the opposing direction D. As shown in FIG. The end portion 13 a of the separator 13 overlaps neither the positive electrode active material layer 23 nor the negative electrode active material layer 24 when viewed from the opposing direction D. As shown in FIG.

The separator 13 is formed in a sheet shape, for example. The separator 13 is, for example, a porous sheet or non-woven fabric containing a polymer that absorbs and retains electrolyte. Materials constituting the separator 13 include, for example, polypropylene, polyethylene, polyolefin, and polyester. The separator 13 has, for example, a multilayer structure. The separator 13 includes a base material layer (not shown) and a pair of adhesive layers (not shown), and is adhered and fixed to the positive electrode active material layer 23 and the negative electrode active material layer 24 by the pair of adhesive layers. The separator 13 may include a ceramic layer that serves as a heat-resistant layer. The separator 13 may be reinforced with a vinylidene fluoride resin compound. The separator 13 may have a single layer structure.

Examples of the electrolyte impregnated in the separator 13 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. are mentioned. When the separator 13 is impregnated with an electrolyte, the electrolyte salt may be LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(FSO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ or the like. Known lithium salts 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.

The sealing portion 14 is a resin member that seals the electrolytic solution in the space S between the current collectors 21 and 22 . The sealing portion 14 is formed between the first surface 21a of the current collector 21 and the first surface 22a of the current collector 22 so as to surround the positive electrode active material layer 23 and the negative electrode active material layer 24 when viewed from the opposing direction D. placed in between. The sealing portion 14 is separated from the positive electrode active material layer 23 and the negative electrode active material layer 24 when viewed from the opposing direction D. As shown in FIG.

In the storage cell 2 , a space S is defined by the current collector 21 , the current collector 22 , and the sealing portion 14 . The space S contains an electrolytic solution (not shown). The sealing portion 14 is arranged between the current collector 21 and the current collector 22 and thus functions as a spacer that maintains a gap between the current collector 21 and the current collector 22 . The sealing portion 14 has a facing surface 14a facing the first surface 21a, a facing surface 14b facing the first surface 22a, and an inner peripheral surface 14c facing the space S.

The sealing portion 14 includes an outer peripheral region R1 and an inner peripheral region R2. The outer peripheral region R1 is adhered to the entire periphery of the edge 21c of the first surface 21a and the entire periphery of the edge 22c of the first surface 22a by, for example, thermocompression bonding or ultrasonic waves. Of the facing surfaces 14a and 14b, portions included in the outer peripheral region R1 are adhered to the edge portions 21c and 22c, respectively. The sealing portion 14 seals the space S with the outer peripheral region R1. The inner peripheral region R2 is adjacent to the outer peripheral region R1 when viewed from the opposing direction D, and is arranged inside the outer peripheral region R1. The inner peripheral region R2 is in contact with the first surface 21a and the first surface 22a, but is not adhered to the first surface 21a and the first surface 22a. Therefore, the inner peripheral region R2 does not contribute to the sealing of the space S.

The sealing portion 14 may have a substantially uniform thickness (length in the opposing direction D) in the outer peripheral region R1 and the inner peripheral region R2 as shown in FIG. In addition, in the sealing portion 14, the thickness of the outer peripheral region R1 bonded to the current collectors 21 and 22 may be thinner than the thickness of the inner peripheral region R2 that is not bonded. It may be thicker than the thickness of the peripheral region R2.

An end portion 13a of the separator 13 is welded to the inner peripheral region R2. In the facing direction D, the inner peripheral region R2 sandwiches the end portion 13a with the first surface 22a of the current collector 22 . This also fixes the position of the end portion 13a. When viewed from the facing direction D, the end portion 13a is located inside the inner circumference of the outer peripheral region R1 and is spaced apart from the inner circumference of the outer peripheral region R1. Since the end portion 13a overlaps the inner peripheral region R2 when viewed from the opposing direction D, a sufficient contact area between the end portion 13a and the inner peripheral region R2 can be ensured. Although the thickness is emphasized in FIGS. 1 and 2, the actual sealing portion 14 is thin and the inner peripheral surface 14c is narrow.

The width of the inner peripheral region R2 is, for example, narrower than the width of the outer peripheral region R1. The width of the inner peripheral region R2 is, for example, 1 mm or more and 10 mm or less. With a width of 1 mm or more, the contact area between the end portion 13a of the separator 13 and the inner peripheral region R2 is ensured, and the position of the end portion 13a can be firmly fixed. The space S can be kept wide because the width is 10 mm or less. The widths of the outer peripheral region R1 and the inner peripheral region R2 are the same as those in the direction orthogonal to the outer edges 21d and 22d or the inner peripheral surface 14c of the current collectors 21 and 22 when viewed from the facing direction D. is the length of

The sealing portion 14 is made of a resin material having electrolyte resistance and electrical insulation. Examples of the resin material forming the sealing portion 14 include acid-denatured polypropylene (acid-denatured PP), acid-denatured polyethylene (acid-denatured PE), polystyrene, ABS resin, and acrylonitrile styrene (AS) resin. In this embodiment, the sealing portion 14 is made of acid-modified polypropylene. Since acid-modified polypropylene adheres more easily to metals than polypropylene that has not been acid-modified, the sealing property can be improved. Acid-modified polyethylene also adheres better to metal than non-acid-modified polyethylene.

In this embodiment, a plurality of sealing portions 14 arranged in the stacking direction of the cell stack 3 are integrated with each other by welding to form the rectangular cylindrical member 4 . In the present embodiment, portions of the sealing portion 14 protruding from the outer edges 21d and 22d of the current collectors 21 and 22 are integrated with each other by welding. The tubular member 4 extends in the stacking direction from a current collector 21 arranged at one end in the stacking direction of the cell stack 3 to a current collector 22 arranged at the other end in the stacking direction.

Actions and effects of the storage cell 2 and the storage device 1 will be described below. In the storage cell 2, the sealing portion 14 has an outer peripheral region R1 bonded to the current collector 21 and the current collector 22, and the space S between the current collector 21 and the current collector 22 is defined by the outer peripheral region R1. Sealed. The space S contains an electrolytic solution. Since the electrolyte permeates into the separator 13 , in a configuration in which the end portion 13 a of the separator 13 abuts against the sealing portion 14 , the electrolyte may swell the sealing portion 14 through the end portion 13 a of the separator 13 . If the edge 13a of the separator 13 is fixed to the outer peripheral region R1 where the current collectors 21 and 22 and the sealing portion 14 are bonded, the separator 13 is fixed as in the invention described in Patent Document 1. A weakly bonded portion is formed on the outside of the end face of the . The adhesiveness of the resin of the weakly bonded portion is likely to be lowered due to the swelling of the electrolyte. Therefore, when the resin of the weakly-bonded portion swells through the separator 13 and peeling occurs, the peeling of the weakly-bonded portion becomes a starting point, and the current collectors 21 and 22 and the sealing portion 14 that are continuous with the weakly-bonded portion are separated from each other. The detachment may also propagate to the adhesion portion where the two are strongly adhered to each other, and the sealing performance of the storage cell 2 may be deteriorated.

In the storage cell 2, the sealing portion 14 has an inner peripheral region R2 to which the end portion 13a of the separator 13 is welded in a portion different from the outer peripheral region R1. The inner peripheral region R2 sandwiches the end portion 13a of the separator 13 between itself and the current collector 22 . The inner peripheral region R2 is not adhered to the current collector 21 and the current collector 22 . That is, when viewed from the opposing direction D, the outer edge of the welded portion of the inner peripheral region R2 and the inner edge of each bonded portion of the outer peripheral region R1 are separated from each other via the non-bonded portion that is not bonded anywhere. . Therefore, unlike the case where the end portion 13a of the separator 13 is fixed to the outer peripheral region R1, a weakly bonded portion is not formed at the end portion of the adhesive portion in the outer peripheral region R1. For this reason, separation of the sealing portion 14 from the current collectors 21 and 22, which occurs when the electrolyte swells the resin of the weakly bonded portion through the separator 13, is suppressed. Further, even if the resin of the inner peripheral region R2 swells due to the electrolytic solution through the end portion 13a of the separator 13, the adhesive portion of the outer peripheral region R1 is hardly affected. In other words, the swelling of the resin in the inner peripheral region R2 due to the electrolytic solution does not directly cause the deterioration of the adhesiveness of the adhesive portion in the outer peripheral region R1. Therefore, the separation of the sealing portion 14 from the current collectors 21 and 22 is suppressed. Thereby, in the storage cell 2, deterioration of sealing performance can be suppressed. In the storage cell 2, the end 13a of the separator 13 is located inside the inner periphery (inner edge) of the outer peripheral region R1, separated from the outer peripheral region R1, as viewed from the facing direction D.

When the outer peripheral region R1 and the inner peripheral region R2 are adhered to the current collectors 21 and 22 with the end portion 13a of the separator 13 sandwiched between the inner peripheral region R2 and the current collector 22, the inner peripheral region R2 side In this case, the thickness of the separator 13 is increased by the end portion 13a. Therefore, the end portion 13a of the separator 13 can be sandwiched and fixed without welding the end portion 13a of the separator 13 to the inner peripheral region R2. Since the end portion 13a of the separator 13 is welded and fixed to the inner peripheral region R2 so that the current collector 21 of the positive electrode 11 and the current collector 22 of the negative electrode 12 do not directly face each other in the facing direction D, the positive electrode 11 and the negative electrode 12 is suppressed.

The power storage device 1 includes a cell stack 3 in which power storage cells 2 are stacked.

FIG. 3 is a schematic cross-sectional view of a storage cell according to a first modified example. As shown in FIG. 3, a storage cell 2A according to the first modification differs from the storage cell 2 (see FIG. 2) mainly in that a sealing portion 14A is provided. 14 A of sealing parts have the 1st resin layer 15 and the 2nd resin layer 16 which were laminated|stacked in the opposing direction D. As shown in FIG. The first resin layer 15 is adhered to the edge portion 21c. The second resin layer 16 is adhered to the edge portion 22c. The first resin layer 15 and the second resin layer 16 are welded (adhered) to each other. The first resin layer 15 and the second resin layer 16 may be made of the same resin material. The first resin layer 15 and the second resin layer 16 may be made of different resin materials. In the facing direction D, the first resin layer 15 is thinner than the second resin layer 16 .

The first resin layer 15 has a facing surface 15a facing the first surface 21a, a facing surface 15b facing the first surface 22a via the second resin layer 16, and an inner peripheral surface 15c facing the space S. have. The second resin layer 16 has a facing surface 16a facing the first surface 22a, a facing surface 16b facing the first surface 21a via the first resin layer 15, and an inner peripheral surface 16c facing the space S. have.

When viewed from the facing direction D, the width of the first resin layer 15 is wider than the width of the second resin layer 16, and the inner peripheral surface 15c (inner periphery of the first resin layer 15) is wider than the inner peripheral surface 16c (second It is positioned inside the inner circumference of the resin layer 16). The outer peripheral surface of the first resin layer 15 and the outer peripheral surface of the second resin layer 16 are at the same position when viewed from the opposing direction D. As shown in FIG. The first resin layer 15 has an extension portion 15d that extends inward from the inner peripheral surface 16c. The extending portion 15 d is a region of the first resin layer 15 located inside the second resin layer 16 when viewed from the opposing direction D. As shown in FIG. The thickness of the extension portion 15d is thinner than the thickness of the space S. The extending portion 15d is separated from at least one of the first surface 21a and the first surface 22a. The width of the first resin layer 15 and the second resin layer 16 is the width of the first resin layer in the direction perpendicular to the outer edges 21d and 22d or the inner peripheral surfaces 15c and 16c of the current collectors 21 and 22 when viewed from the facing direction D. It is the length of the layer 15 and the second resin layer 16 .

The outer peripheral region R1 is formed by stacking the first resin layer 15 and the second resin layer 16 . The outer peripheral region R1 includes a portion of the first resin layer 15 (a portion other than the extension portion 15d) and the entirety of the second resin layer 16. As shown in FIG. Of the facing surfaces 15a and 16a, portions included in the outer peripheral region R1 are adhered to the edge portions 21c and 22c, respectively. Portions of the facing surfaces 15b and 16b included in the outer peripheral region R1 are welded to each other.

The inner peripheral region R2 is configured by the extension portion 15d. An end portion 13a of the separator 13 is welded (bonded) to the inner peripheral region R2. The end portion 13a is welded to the facing surface 15a of the first resin layer 15 and faces the first surface 21a. The end portion 13a is partially adhered to the inner peripheral region R2 by, for example, spot welding or the like. The inner peripheral region R2 is thinner than the outer peripheral region R1. As described above, when the sealing portion 14 is attached to the current collectors 21 and 22 by adhesion, the thickness of the outer peripheral region R1 is thinner than before welding, but is thicker than the thickness of the inner peripheral region R2. The inner peripheral region R2 is pulled by gravity and the separator 13 and hangs down, and is spaced apart from the first surface 21a in the facing direction D. As shown in FIG. The inner peripheral region R2 may be in contact with the first surface 21a.

FIG. 4 is a schematic cross-sectional view of a storage cell according to a second modification. As shown in FIG. 4, a storage cell 2B according to the second modification differs from the storage cell 2 (see FIG. 2) mainly in that a sealing portion 14B is provided. Since the sealing portion 14B has the same shape as the sealing portion 14A (see FIG. 3), description thereof is omitted. In the storage cell 2B, the end portion 13a of the separator 13 is welded to the facing surface 15b of the first resin layer 15 and faces the first surface 22a, unlike the storage cell 2A (see FIG. 3). there is

Also in the storage cells 2A and 2B, when viewed from the opposing direction D, the outer edge of the welded portion of the inner peripheral region R2 and the inner edge of each bonded portion of the outer peripheral region R1 are separated from each other via the non-bonded portion. Therefore, since a weakly bonded portion is not formed at the end of each bonded portion in the outer peripheral region R1, the electrolyte swells the resin of the weakly bonded portion through the separator 13, thereby peeling off the sealing portion 14 from the current collectors 21 and 22. No fear. Further, even if the resin of the inner peripheral region R2 swells due to the electrolytic solution through the end portion 13a of the separator 13, the adhesive portion of the outer peripheral region R1 is hardly affected. In other words, the swelling of the resin in the inner peripheral region R2 due to the electrolytic solution does not directly cause the deterioration of the adhesiveness of the adhesive portion in the outer peripheral region R1. Therefore, it is possible to suppress the peeling of the sealing portion 14 from the current collectors 21 and 22, and to suppress the deterioration of the sealing performance of the storage cells 2A and 2B. In the storage cells 2A and 2B, the inner peripheral region R2 is composed only of the extending portion 15d of the first resin layer 15. As shown in FIG. Therefore, the inner peripheral region R2 can be made thinner by the thickness of the second resin layer 16 . Since the inner peripheral region R2 is thinner than the outer peripheral region R1 in the facing direction D, it is possible to suppress an increase in the size of the storage cell while securing a surplus space for accommodating gas generated by battery reaction in the storage cell. can.

The inner peripheral region R2 is separated from at least one of the first surface 21a and the first surface 22a. In FIG. 4, in the storage cells 2A and 2B, the inner peripheral region R2 hangs down toward the first surface 22a and is separated from both the first surface 21a and the first surface 22a. Therefore, it is possible to further suppress swelling of the adhesive portion of the outer peripheral region R1 of the sealing portion 14 by the electrolytic solution through the end portion 13a of the separator 13, and to further suppress deterioration of the sealing performance.

In the storage cells 2A and 2B, the current collector 21 may be arranged above the current collector 22 in the gravitational direction. Since the electrolyte moves downward in the gravitational direction, it is difficult for the electrolyte to accumulate between the current collector 22 and the inner peripheral region R2 where the end portion 13a of the separator 13 is welded. Therefore, deterioration of the sealing performance can be further suppressed.

The present disclosure is not limited to the above embodiments and modifications.

In the storage cell 2 , the positive electrode 11 is arranged above the negative electrode 12 in the direction of gravity, but the positive electrode 11 may be arranged below the negative electrode 12 in the direction of gravity. In this case, the electrolytic solution is less likely to accumulate on the current collector 22 side. Also in the storage cells 2A and 2B, the positive electrode 11 may be arranged below the negative electrode 12 in the direction of gravity.

In the storage cell 2, the inner peripheral region R2 sandwiches the end portion 13a of the separator 13 between the first surface 22a of the current collector 22 and the first surface 21a of the current collector 21. 13 may be sandwiched between the ends 13a. In this case, since the positive electrode 11 is arranged above the negative electrode 12 in the gravitational direction, it is difficult for the electrolytic solution to accumulate on the current collector 21 side.

In the storage cells 2A and 2B, the first resin layer 15 has the extension portion 15d, and the extension portion 15d constitutes the inner peripheral region R2, while the second resin layer 16 has the extension portion (not shown). You may The second resin layer 16 may be thinner than the first resin layer 15, or the first resin layer 15 and the second resin layer 16 may have the same thickness.

In the storage cells 2A and 2B, the first resin layer 15 and the second resin layer 16 are separate members, but may be formed as one member. For example, one resin layer may be folded and laminated, and the first layer may be used as the first resin layer 15 and the second layer may be used as the second resin layer 16 . In this case, the first resin layer 15 and the second resin layer 16 are configured to be continuous with each other at the outer edge.

The power storage device 1 may include a cell stack 3 in which the power storage cells 2A are stacked instead of the power storage cells 2, or may include a cell stack 3 in which the power storage cells 2B are stacked. The cell stack 3 may include two or more types of storage cells 2, 2A, and 2B. Even in these cases, deterioration of the sealing performance can be suppressed.

REFERENCE SIGNS LIST 1 power storage device, 2, 2A, 2B power storage cell, 3 cell stack (laminate), 11 positive electrode, 12 negative electrode, 13 separator, 13a end, 14, 14A, 14B sealing portion, DESCRIPTION OF SYMBOLS 15... 1st resin layer, 16... 2nd resin layer, 16c... Inner peripheral surface, 21... Current collector, 21a... First surface, 21c... Edge, 22... Current collector, 22a... First surface, 22c Edge portion 23 Positive electrode active material layer 24 Negative electrode active material layer R1 Outer peripheral region R2 Inner peripheral region S Space.

Claims (8)

a first electrode having a first current collector and a first active material layer provided on a first surface of the first current collector;
a second current collector, and a second current collector provided on the second surface of the second current collector, facing the first active material layer, and having a second active material layer having a polarity different from that of the first active material layer; two electrodes;
a separator disposed between the first active material layer and the second active material layer in the facing direction in which the first active material layer and the second active material layer face each other;
a sealing portion that seals an electrolytic solution in the space between the first current collector and the second current collector;
The sealing portion is arranged inside an outer peripheral region bonded over the entire periphery of the edge of the first surface and the entire periphery of the edge of the second surface, and inside the outer peripheral region when viewed from the opposite direction, an inner peripheral region that is not adhered to the first surface and the second surface;
An edge of the separator is fixed to the inner peripheral region,
storage cell. When viewed from the facing direction, the end of the separator is located inside the inner circumference of the outer peripheral area and is spaced apart from the inner circumference of the outer peripheral area.
The storage cell according to claim 1. In the facing direction, the inner peripheral region sandwiches an end portion of the separator between the first surface and the first surface.
The storage cell according to claim 1 or 2. The outer peripheral region is formed by laminating a first resin layer adhered to the edge of the first surface and a second resin layer adhered to the edge of the second surface,
When viewed from the facing direction, the inner circumference of the first resin layer is located inside the inner circumference of the second resin layer, and the inner circumference of the first resin layer is positioned further than the inner circumference of the second resin layer. The area located inside constitutes the inner peripheral area,
The storage cell according to claim 1 or 2. The first resin layer is thinner than the second resin layer in the facing direction,
The storage cell according to claim 4. In the facing direction, the inner peripheral region is separated from the first surface,
The storage cell according to claim 4 or 5. The first current collector is arranged above the second current collector in the direction of gravity,
The storage cell according to any one of claims 3 to 6. An electricity storage device comprising a laminate in which the electricity storage cells according to any one of claims 1 to 7 are laminated.

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