JP2024080295A - Power storage device - Google Patents

Abstract

To provide a power storage device which can ease reduction of the performance of the battery caused by temperature change.SOLUTION: In a case where a spacer layer is divided in a short-side section (a first section) along a short side, a long-side section (a second section) along a long side, and an angular section (a third section) connecting the long-side section and the short-side section to each other when the spacer layer is seen from the lamination direction, there is a notch part in at least one angular part of the spacer layer.SELECTED DRAWING: Figure 4

Description

This disclosure relates to an electricity storage device.

Patent Document 1 discloses a bipolar battery. This bipolar battery has a bipolar electrode with a positive electrode on one side of a current collector and a negative electrode on the other side, a gel electrolyte sandwiched between the positive and negative electrodes, and a seal layer that surrounds the periphery of a single cell composed of the positive electrode, negative electrode, and gel electrolyte and is provided between the current collectors.

JP 2004-158343 A

In the battery disclosed in Patent Document 1, the current collector is made of rectangular metal foil, and a rectangular frame-shaped sealing layer made of resin is provided around the periphery of this current collector. In such a battery, if there is a large change in temperature, it is thought that stress will concentrate in the area of the current collector corresponding to the corner of the sealing layer (current collector corner) due to the difference in the volume expansion coefficient between the sealing layer and the current collector. If temperature changes are repeated, stress will repeatedly concentrate on the corner of the current collector, causing the current collector to deform and potentially reducing battery performance.

The purpose of this disclosure is to provide an energy storage device that can mitigate the degradation of battery performance caused by temperature changes.

The power storage device according to one aspect of the present disclosure includes a laminate in which a plurality of electrodes, each having a rectangular metal current collector, are stacked, and a resin sealing portion provided on the periphery of the current collector so as to surround the laminate when viewed from the stacking direction of the plurality of electrodes. The plurality of electrodes includes a plurality of bipolar electrodes. Each of the plurality of bipolar electrodes has an active material layer on a first surface of the current collector and on a second surface opposite to the first surface. The current collector of each of the plurality of bipolar electrodes has a rectangular first region on the first surface and a rectangular frame-shaped second region outside the first region when viewed from the stacking direction, on the first surface and the second surface. The sealing portion includes a plurality of rectangular frame-shaped sealing layers and a plurality of rectangular frame-shaped spacer layers. The plurality of sealing layers are bonded to the first surface and the second surface at the periphery of each current collector of the plurality of electrodes. The plurality of spacer layers are located between adjacent sealing layers in the stacking direction, and together with the plurality of sealing layers, seal the internal space formed between adjacent current collectors in the stacking direction. The sealing portion includes an end surface welding portion in which the outer peripheries of the plurality of sealing layers and the outer peripheries of the plurality of spacer layers are integrated by welding them to each other. The outer periphery of the rectangular first region is defined by a pair of first sides facing each other and a pair of second sides connecting the pair of first sides and facing each other. When the spacer layer is divided by a first partition line extending from the pair of first sides and a second partition line extending from the pair of second sides as viewed from the stacking direction, the spacer layer is divided into a pair of first sections separated by the first partition lines and extending along the pair of second sides, a pair of second sections separated by the second partition lines and extending along the first sides, and four third sections separated by the first partition line and the second partition line, connecting the first section and the second section, and including four corners of the spacer layer. At least one of the multiple spacer layers has a notched portion formed in at least one third section such that the widthwise length of the spacer layer from the end face welded portion to the internal space is shorter than the widthwise length of the spacer layer in the adjacent first section or second section.

In the above-mentioned energy storage device, a notch-shaped portion is formed in the third section including the corner of the spacer layer that constitutes the resin sealing portion. Therefore, the amount of resin at the corner is reduced by the volume equivalent to the notch-shaped portion. In this way, by reducing the amount of resin at the corner, the amount of dimensional change of the sealing portion at the corner when the environmental temperature changes is reduced. As a result, at the corner of the current collector corresponding to the corner of the spacer layer, the current collector is less likely to be pulled by the sealing portion, and stress concentration at the corner of the current collector is suppressed. Therefore, the deterioration of battery performance due to temperature change can be mitigated.

The sealing portion may have a communication hole that connects the internal space to the outside of the sealing portion. The communication hole may be formed in one of a pair of first sections of the spacer layer. The cutout portion may be formed in at least a pair of third sections adjacent to the first section in which the communication hole is formed. In this configuration, stress is prevented from concentrating in the corners located near the area in which the communication hole is formed.

The widthwise length of the spacer layer in one of the pair of first compartments in which a communicating hole is formed may be greater than the widthwise length of the spacer layer in the other of the pair of first compartments and the widthwise length of the spacer layer in the pair of second compartments. When the width of the spacer layer is large, the volumetric proportion of the resin increases, and the amount of dimensional change in the resin also increases. By forming a notched portion adjacent to one of the first compartments where the amount of dimensional change in the resin is likely to be large, it is possible to suppress the concentration of stress from that one of the first compartments at the corner.

The spacer layers may have overlapping portions that overlap the current collector when viewed from the stacking direction, and extending portions that extend outward beyond the edge of the current collector. The end face welding portions may be provided on the extending portions of the spacer layers when viewed from the stacking direction, and the cutout portions may be provided on the overlapping portions that are more inward than the end face welding portions when viewed from the stacking direction. In this configuration, the cutout portions are formed at a distance from the end face welding portions, ensuring sealing at the end face welding portions.

At least one of the pair of sealing layers adjacent to the spacer layer in which the cutout portion is formed may have a sealing cutout portion in a region corresponding to the cutout portion of the spacer layer, the bonding width with the current collector being shorter than the bonding width in other regions. With this configuration, it is possible to reduce the amount of dimensional change in the sealing cutout portion when the environmental temperature changes.

The cutout portion formed in the third section of the spacer layer may have a notch-like portion extending from the inner edge of the spacer toward the end face welded portion. In this configuration, the presence of the notch-like portion separates the area of stress concentration at the corner when the sealing portion expands and contracts in the extension direction of the side as viewed from the stacking direction, thereby mitigating thermal shock.

This disclosure provides an energy storage device that can mitigate the degradation of battery performance caused by temperature changes.

FIG. 1 is a schematic plan view showing an example of an electricity storage module. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a schematic cross-sectional view of another example of an electricity storage module. FIG. 6 is a schematic cross-sectional view of a power storage module according to still another embodiment. FIG. 7 is a schematic cross-sectional view of a power storage module according to still another embodiment. FIG. 8 is a schematic cross-sectional view of a power storage module according to still another embodiment.

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicated descriptions will be omitted. In the description, a Cartesian coordinate system defined by the X-axis, Y-axis, and Z-axis may be referenced.

Figure 1 is a schematic plan view of a power storage module according to this embodiment. The power storage module 11 (power storage device) shown in Figure 1 can be used as a battery for various vehicles, such as a forklift, a hybrid vehicle, or an electric vehicle. The power storage module 11 is, for example, a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The power storage module 11 may be an electric double layer capacitor or an all-solid-state battery. Here, the case where the power storage module 11 is a lithium-ion secondary battery is shown.

Figure 2 is a cross-sectional view taken along line II-II in Figure 1, and shows a schematic layer structure of the storage module 11. Figure 3 is a cross-sectional view taken along line III-III in Figure 1, and shows a schematic layer structure of the storage module 11. The storage module 11 is a single cell having a flat rectangular parallelepiped shape in the Z-axis direction. In this embodiment, a bipolar lithium-ion secondary battery is exemplified as the storage module 11. The storage module 11 is configured to include an electrode stack (stack) 12 including a plurality of bipolar electrodes 14, and a sealing portion 30. The bipolar electrodes 14 in the electrode stack 12 are stacked along the Z-axis direction. The stacking direction of the bipolar electrodes 14 is along the Z-axis direction and coincides with the stacking direction of the storage modules 11 in the module stack 2.

The bipolar electrode 14 includes a current collector 21, a positive electrode active material layer 22, and a negative electrode active material layer 23. The current collector 21 is a chemically inactive electrical conductor that continues to pass current to the positive electrode active material layer 22 and the negative electrode active material layer 23 during discharging or charging of the lithium ion secondary battery.

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

In the illustrated example, the current collector 21 is formed by bonding an aluminum foil 21A and a copper foil 21B together so that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. The current collector 21 may be, for example, a clad foil formed by stacking and rolling-bonding an aluminum foil 21A and a copper foil 21B together. The current collector 21 may be a laminated foil. That is, the current collector 21 may be formed by bonding and integrating an aluminum foil 21A and a copper foil 21B together with a conductive adhesive resin (adhesive layer) so that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. The current collector 21 may be formed by copper vapor deposition or copper plating on one side of an aluminum foil so that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. In addition, the aluminum layer on the first surface 21a of the current collector 21 may be chromated. In addition, the copper layer on the second surface 21b of the current collector 21 may be nickel-plated. In this case, the nickel-plated layer may be a roughened surface that is a protruding plated surface with fine protrusions on the surface. The roughened surface may be rougher than the unprocessed metal foil, and may be formed by roughening processing such as etching or electrolytic plating. For example, the thickness of the current collector 21 may be about 30 μm to 150 μm, but is not limited to this.

The positive electrode active material layer 22 is provided on the first surface 21a of the current collector 21. The current collector 21 and the positive electrode active material layer 22 provided on the first surface 21a of the current collector 21 constitute the positive electrode of the bipolar electrode 14. The positive electrode active material layer 22 is formed in a rectangular shape in the center of the first surface 21a so that the peripheral edge 21c of the current collector 21 is exposed.

The positive electrode active material layer 22 is provided on the first surface 21a of the current collector 21 via an adhesive layer. For example, the adhesive layer may be formed of an adhesive such as acetylene black. The adhesive layer may be provided on the entire surface of the first surface 21a of the current collector 21. The edge of the adhesive layer may be formed along the edge of the negative electrode active material layer 23 that surrounds the positive electrode active material layer 22 when viewed from the stacking direction.

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

The binder serves to anchor the active material or conductive assistant to the surface of the current collector 21 and maintain the conductive network in the electrode. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, acrylic resins containing monomer units such as acrylic acid and methacrylic 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 conductive assistant include acetylene black, carbon black, and graphite. The positive electrode active material layer 22 may contain a viscosity adjusting solvent such as N-methyl-2-pyrrolidone (NMP).

The negative electrode active material layer 23 is provided on the second surface 21b of the current collector 21. The current collector 21 and the negative electrode active material layer 23 provided on the second surface 21b of the current collector 21 constitute the negative electrode of the bipolar electrode 14. The negative electrode active material layer 23 is formed in a rectangular shape in the center of the second surface 21b so that the peripheral edge 21c of the current collector 21 is exposed. In one example, when viewed from the stacking direction, the positive electrode active material layer 22 is contained within the region of the negative electrode active material layer 23. In other words, the outer edge of the positive electrode active material layer 22 is slightly smaller than the outer edge of the negative electrode active material layer 23.

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

To form the positive electrode active material layer 22 and the negative electrode active material layer 23 on the current collector 21, a conventionally known method such as roll coating, die coating, dip coating, doctor blade, spray coating, curtain coating, etc. is used. Specifically, an active material, a solvent, and optionally a binder and a conductive assistant are mixed to produce a slurry-like active material layer forming composition, which is then applied to the first surface 21a and the second surface 21b and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The dried product may be compressed to increase the electrode density.

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

The separator 15 has a rectangular shape that is larger than the positive electrode active material layer 22 and the negative electrode active material layer 23 and smaller than the current collector 21 when viewed from the stacking direction. The end 15a of the separator 15 is located outside the positive electrode active material layer 22 and the negative electrode active material layer 23 when viewed from the stacking direction. In other words, the end 15a of the separator 15 does not overlap with either the positive electrode active material layer 22 or the negative electrode active material layer 23 when viewed from the stacking direction.

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

The separator 15 is formed by stretching molten resin using a dry process or a wet process. In this case, the separator 15 has a direction in which it shrinks more and a direction in which it shrinks less, depending on the stretching process. The separator 15 may be rectangular, with the direction in which it shrinks more along the short side and the direction in which it shrinks less along the long side. One example of the separator 15 is formed by a wet process, with the TD (Transverse Direction) direction in which it shrinks more along the short side and the MD (Machine Direction) direction in which it shrinks less along the long side.

Examples of the electrolyte impregnated in the separator 15 include a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, or a polymer gel electrolyte containing an electrolyte held in a polymer matrix. When the separator 15 is impregnated with an electrolyte, known lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(FSO ₂ ) ₂ , LiFSi, and LiN(CF ₃ SO ₂ ) 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. Note that two or more of these known solvent materials may be used in combination.

The electrode laminate 12 has a positive terminal electrode 16 and a negative terminal electrode 17 in addition to the bipolar electrode 14. The positive terminal electrode 16 is composed of a current collector 21 and a positive active material layer 22 provided on the first surface 21a of the current collector 21. The positive terminal electrode 16 is arranged at one end side in the stacking direction of the electrode laminate 12 so that the positive active material layer 22 of the first surface 21a faces the negative active material layer 23 of the terminal bipolar electrode 14. In the positive terminal electrode 16, the positive active material layer 22 and the negative active material layer 23 are not provided on the second surface 21b of the current collector 21, and the second surface 21b is electrically connected to an adjacent conductive plate (not shown). The current collector 21 used in the positive terminal electrode 16 may be composed of aluminum foil.

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

The separators 15 are arranged between the bipolar electrodes 14, 14 adjacent to each other in the stacking direction, as well as between the bipolar electrodes 14 and the positive terminal electrode 16, and between the bipolar electrodes 14 and the negative terminal electrode 17. The arrangement of the separators 15 prevents short circuits between the bipolar electrodes 14 and the positive terminal electrode 16, and between the bipolar electrodes 14 and the negative terminal electrode 17.

The sealing portion 30 is a member that seals the internal space S between the collectors 21 adjacent to each other in the stacking direction. The sealing portion 30 has electrical insulation properties. The sealing portion 30 is bonded (joined) to the edge of the collector 21. When viewed from the stacking direction, the sealing portion 30 is spaced apart from the positive electrode active material layer 22 and the negative electrode active material layer 23. When viewed from the stacking direction, the sealing portion 30 is frame-shaped and is disposed between the collectors 21 adjacent to each other in the stacking direction so as to surround the periphery of the positive electrode active material layer 22 and the negative electrode active material layer 23. In the storage module 11, an internal space S is defined by the collectors 21 adjacent to each other in the stacking direction and the sealing portion 30. The internal space S contains an electrolyte (not shown). The sealing portion 30 is disposed between the collectors adjacent to each other in the stacking direction, and therefore also functions as a spacer that maintains the distance between the adjacent collectors.

An example of the sealing portion 30 has a first sealing layer 31, a second sealing layer 32, and a spacer layer 33. The first sealing layer 31, the second sealing layer 32, and the spacer layer 33 each have a frame shape when viewed from the stacking direction. For example, the thickness of the first sealing layer 31 and the second sealing layer 32 may be about 50 μm to 200 μm. The thickness of the first sealing layer 31 and the thickness of the second sealing layer 32 may be the same. In addition, the thickness of the spacer layer 33 may be thicker than the thickness of the first sealing layer 31 and the second sealing layer 32, and may be, for example, about 200 μm to 500 μm.

The first seal layer 31 is bonded to the first surface 21a along the periphery 21c of the current collector 21. In one example, when viewed from the stacking direction, the outer edge 31b of the first seal layer 31 is larger than the edge 21d of the current collector 21 and surrounds the current collector 21. Also, when viewed from the stacking direction, the edge 21d of the current collector 21 is larger than the inner edge 31a of the first seal layer 31 and surrounds the inner edge 31a of the first seal layer 31. The first seal layer 31 and the current collector 21 are bonded to each other in the overlapping region when viewed from the stacking direction. That is, the first seal layer 31 and the current collector 21 are bonded to each other in the region from the inner edge 31a of the first seal layer 31 to the edge 21d of the current collector 21. When viewed from the stacking direction, the inner edge 31a of the first seal layer 31 is spaced from the positive electrode active material layer 22.

The second seal layer 32 is bonded to the second surface 21b along the periphery 21c of the current collector 21. In one example, the outer edge 32b of the second seal layer 32 is larger than the edge 21d of the current collector 21 and surrounds the current collector 21 when viewed from the stacking direction. For example, the second seal layer 32 and the current collector 21 are bonded to each other in the overlapping region. That is, the second seal layer 32 and the current collector 21 are bonded to each other in the region from the inner edge 32a of the second seal layer 32 to the edge 21d of the current collector 21. When viewed from the stacking direction, the inner edge 32a of the second seal layer 32 is spaced from the negative electrode active material layer 23.

The first seal layer 31, the second seal layer 32, and the spacer layer 33 are welded to each other by the end surface welded portion R1. The outer edge 33b of the spacer layer 33 may be at the same position as the outer edge 31b of the first seal layer 31 and the outer edge 32b of the second seal layer 32 when viewed from the stacking direction. The outer edge 33b of the spacer layer 33 may be welded to the outer edge 31b of the first seal layer 31 outside the edge 21d of the current collector 21 when viewed from the stacking direction. The outer edge 33b of the spacer layer 33 may be welded to the outer edge 32b of the second seal layer 32 outside the edge 21d of the current collector 21 when viewed from the stacking direction. That is, the first seal layer 31, the second seal layer 32, and the spacer layer 33 are welded to each other by the end surface welded portion R1 in the region outside the edge 21d of the current collector 21.

The end face welded portion R1 is formed by welding together the end portions (peripheral edges) of the multiple first seal layers 31, the multiple second seal layers 32, and the multiple spacer layers 33 on the opposite side of the internal space S. In other words, the first seal layer 31 and the spacer layer 33 are not welded to each other except at the end face welded portion R1, and are only in contact with each other. Similarly, the second seal layer 32 and the spacer layer 33 are not welded to each other except at the end face welded portion R1, and are only in contact with each other. In this way, since the spacer layer 33 is connected to the first seal layer 31 and the second seal layer 32 by the end face welded portion R1, the stress due to the expansion and contraction of the spacer layer 33 may affect the current collector 21 joined to the first seal layer 31 and the second seal layer 32.

The end surface welded portion R1 has a rectangular frame shape surrounding the electrode laminate 12 when viewed from the stacking direction. When viewed from the stacking direction, the end surface welded portion R1 is formed outside the outer edge of the current collector 21. That is, the first seal layer, the second seal layer, and the spacer layer 33 have an overlapping portion that overlaps with the current collector 21 when viewed from the stacking direction, and an extending portion that extends outside the edge 21d of the current collector 21, and the end surface welded portion R1 is provided in the extending portion. The side of the end surface welded portion R1 opposite the internal space S extends along the stacking direction and constitutes the outer side of the sealing portion 30. In other words, the sealing portion 30 includes an inner side facing the internal space S and an outer side opposite the inner side.

The sealing portion 30 has a communication hole 35 that communicates with each of the multiple internal spaces S. As an example, the communication hole 35 is formed by partially cutting out the spacer layer 33 and penetrates the spacer layer 33 and the end face welding portion R1. The communication hole 35 has one opening in the internal space S and the other opening on the outer surface of the sealing portion 30. In the storage module 11, a cell including one internal space S is formed between a pair of adjacent current collectors 21. Here, one communication hole 35 is formed for one cell. The communication hole 35 can be used as a liquid injection port for injecting an electrolyte into the internal space S. That is, a liquid injection port (opening of the communication hole 35) is provided on the outer surface of the sealing portion 30. In the storage module 11 that is rectangular when viewed from the stacking direction, the side on which the communication hole 35 is provided is called the liquid injection port side.

When viewed from the stacking direction, the inner edge 33a of the spacer layer 33 at the inlet edge is located inside (toward the internal space S) of the inner edge 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32. The inner edge 33a of the spacer layer 33 at the inlet edge is located, for example, 1 mm or more inside the inner edges 31a, 32a, and is exposed from the first seal layer 31 and the second seal layer so as to face the internal space S. Note that when viewed from the stacking direction, the inner edge 33a of the spacer layer 33 at a portion other than the inlet edge may be located outside the inner edge 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32.

The end 15a of the separator 15 is fixed near the inner edge 32a of the second seal layer 32 between the second seal layer 32 and the spacer layer 33. The end 15a may be partially adhered (welded) to the second seal layer 32 by, for example, spot welding.

When viewed from the stacking direction, the first seal layer 31 is spaced apart from the positive electrode active material layer 22, and the inner edge 31a is located outside the positive electrode active material layer 22. When viewed from the stacking direction, the second seal layer 32 is spaced apart from the negative electrode active material layer 23, and the inner edge 32a is located outside the negative electrode active material layer 23. In this embodiment, when viewed from the stacking direction, the first seal layer 31 is also spaced apart from the negative electrode active material layer 23, but the first seal layer 31 may overlap the negative electrode active material layer 23 as long as it is spaced apart from the positive electrode active material layer 22.

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

The first seal layer 31, the second seal layer 32, and the spacer layer 33 are made of, for example, acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, or a resin material having electrolyte resistance such as polyethylene. The resin materials making up the first seal layer 31, the second seal layer 32, and the spacer layer 33 may be the same as or different from each other. In this embodiment, the first seal layer 31 and the second seal layer 32 are made of acid-modified polyethylene or acid-modified polypropylene. The spacer layer 33 is made of polyethylene or polypropylene.

Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3, and shows a schematic cross-section of the energy storage module. In Figure 4, the first seal layer 31 and the second seal layer 32 hidden by the spacer layer 33 are collectively shown as seal layer 34. For ease of explanation, the separator 15 is not shown.

4, the second surface 21b of the bipolar electrode 14 is divided into a rectangular first region 21T in which the negative electrode active material layer 23 is formed, and a second region 21M outside the first region 21T. In this case, the seal layer 34 and the spacer layer 33 can be divided by an extension line L1 (first partition line) of the long side (first side) of the first region 21T and an extension line L2 (second partition line) of the short side (second side). The sealing layer 34 and the spacer layer 33 are divided into short side portions (first sections) 34S, 33S along the short sides, which are separated by a pair of extension lines L1, long side portions (second sections) 34L, 33L along the long sides, which are separated by a pair of extension lines L2, and corner portions (third sections) 33C, 34C that are separated by extension lines L1 and L2 and connect the long side portions 34L, 33L and the short side portions 34S, 33S.

A notch 33K is formed in at least one corner 33C of the spacer layer 33. In the illustrated example, the notch 33K is formed in a pair of corners 33C connected to the short side 33Sa along the injection port side among the four corners 33C. The notch may be an area that has a notched or cut-out shape when viewed from the stacking direction in the spacer layer 33 defined by the inner and outer edges of a rectangular shape.

In other words, when viewed from the stacking direction, at least one side of the spacer layer 33 may include a wide portion 33W having a large widthwise length and a notched portion 33K having a widthwise length smaller than that of the wide portion 33W. The widthwise length may be the widthwise length of each side of the spacer layer 33 perpendicular to the longitudinal direction of the side. That is, the widthwise length of the short side portion 34S is the length in the X-axis direction, and the widthwise length of the long side portion 34L is the length in the Y-axis direction. When a cutout portion such as a hole is formed in the spacer layer 33, the widthwise length of the spacer layer 33 may be defined as the length from the inner edge to the outer edge minus the length of the cutout portion. In the following description, the "widthwise length" may simply be referred to as "width".

When viewed from the stacking direction, the inner edge 33a of the spacer layer 33 in the short side portion 33Sa that constitutes the liquid inlet side is formed at different positions in the wide portion 33W and the notched portion 33K. In one example, the wide portion 33W is provided in the center of the longitudinal direction of the spacer layer 33 when viewed from the stacking direction, and the notched portion 33K is provided at both ends of the wide portion 33W. When the notched portion 33K is provided on the liquid inlet side, the liquid inlet (communication hole 35) is provided in the wide portion 33W.

The cutout portion 33K shown in FIG. 3 has a cutout shape in which the width direction length of the spacer layer 33 narrows from the inner edge to the outer edge of the spacer layer 33. The cutout portion 33K is formed in an area of the spacer layer 33 other than the end face welding portion R1, and is provided in an area where the spacer layer 33 and the current collector 21 overlap when viewed from the stacking direction. That is, when viewed from the stacking direction, the cutout portion 33K and the end face welding portion R1 do not overlap each other. The cutout portion 33K in one example has a rectangular shape including the corner of the inner edge of the corner portion 33C of the spacer layer 33. That is, the inner edge of the rectangular frame-shaped spacer layer is originally a rectangular shape with four corners, but the inner edge of the spacer layer 33 shown in FIG. 4 has a shape in which two of the corners of the inner edge are cut off by the cutout portion 33K. In this embodiment, the notch 33K is provided inside the edge 21d of the current collector 21 when viewed from the stacking direction, and does not reach the end surface welded portion R1. The notch 33K in the illustrated example is defined by a side along the inner edge of the long side portion 33L of the spacer layer 33, a side facing said side, and a side parallel to the inner edge of the short side portion 33S of the spacer layer 33.

As described above, the example of the storage module 11 includes an electrode stack 12 in which a plurality of rectangular metal collectors 21 are stacked, each having an active material layer on its first surface 21a and second surface 21b, and a rectangular frame-shaped resin sealing portion 30 that seals the periphery of the electrode stack 12 when viewed from the stacking direction of the plurality of collectors 21. The first surface 21a and second surface 21b of each of the plurality of collectors 21 have a rectangular first region 21T in which an active material layer is provided when viewed from the stacking direction, and a rectangular frame-shaped second region 21M that is outside the first region 21T. The sealing portion 30 has a plurality of rectangular frame-shaped seal layers 34 that are joined to the first surface 21a and second surface 21b at the periphery of each of the plurality of collectors 21, and a plurality of rectangular frame-shaped spacer layers 33 that are positioned between the seal layers 34 adjacent to each other in the stacking direction and form an internal space S between the collectors 21 together with the plurality of seal layers 34.

The sealing layers 34 and the spacer layers 33 include end surface welded portions R1 that are integrated by welding the outer peripheries on the side opposite to the internal space S when viewed from the stacking direction. The outer edge of the rectangular first region 21T is defined by a pair of long sides that face each other and a pair of short sides that connect the pair of long sides and face each other. When the spacer layer 33 is divided by an extension line L1 extending the pair of long sides and an extension line L2 extending the pair of short sides when viewed from the stacking direction, the spacer layer 33 is divided into a pair of short side portions 33S that are separated by the extension line L1 and extend along the short side, a pair of long side portions 33L that are separated by the extension line L2 and extend along the long side, and four corner portions 33C that are separated by the extension line L1 and the extension line L2 and connect the short side portions 33S and the long side portions 33L, and include the four corner portions of the spacer layer 33. At least one corner portion 33C has a notched portion 33K formed in the spacer layer 33. The width direction length of the cutout portion 33K is shorter than the width direction length of the spacer layer 33 in the adjacent short side portion 33S or long side portion 33L.

In general, from the viewpoint of energy density, it is desirable for the electrodes constituting the storage module 11 to have a thin current collector 21 and a thick active material layer. In addition, from the viewpoint of ensuring internal space S, it is desirable for the resin constituting the sealing portion 30 to have a thickness at least equal to that of the active material layer. In one example, when viewed from the viewpoint of one cell in the storage module, the thickness of the current collector 21 contained in one cell is about 30 μm to 150 μm, and the total thickness of the seal layer 34 and spacer layer 33 contained in one cell is about 100 μm to 900 μm. In addition, the volume expansion coefficient of the resin constituting the sealing portion 30 is about 10 to 30 times larger than that of the metal constituting the current collector 21. Here, the amount of dimensional change accompanying a change in temperature is expressed by the product of the volume expansion coefficient and the volume.

As mentioned above, in each cell included in the energy storage module, the thickness of the metal collector is overwhelmingly thinner than the resin sealing portion. Also, because the thermal expansion coefficient of the resin that makes up the sealing portion is greater than that of the metal that makes up the current collector, when there is a temperature change in the energy storage module, the sealing portion deforms more than the current collector. In this case, when the sealing portion expands and contracts, stress is generated in the current collector that is pulled by the sealing portion. In particular, stress is concentrated at the corners of the sealing portion because the stress vectors overlap.

In the example energy storage module 11, a notch 33K is formed in a corner 33C of the spacer layer 33 that constitutes the resin sealing portion 30. Therefore, the amount of resin in the corner 33C of the spacer layer 33 is reduced by the volume equivalent to the notch 33K. By reducing the amount of resin in the corner 33C in this way, the amount of dimensional change in the corner 33C is reduced. This makes it difficult for the current collector 21 to be pulled by the sealing portion 30, which deforms with temperature changes, and suppresses stress concentration at the corner of the current collector 21. Therefore, it is possible to mitigate the deterioration of battery performance due to temperature changes.

In addition, at the position where the notched portion 33K is formed, the width of the spacer layer 33 is narrower than the wide portion 33W. That is, in the above example, the notched portion 33K is formed at the corner portion 33C, and thus the continuity between the long side portion 33L and the short side portion 33S of the spacer layer 33 is partially lost. Therefore, even if a dimensional change occurs due to a temperature change, the spacer layer 33 is unlikely to be distorted, and stress concentration at the corner of the current collector 21 is suppressed.

The width of the spacer layer 33 at the short side portion 33Sa where the communication hole 35 is formed may be greater than the width of the spacer layer 33 at the other short side portion 33S. In this configuration, by forming the notched portion 33K close to the short side portion 33Sa where the dimensional change of the resin is likely to be large, it is possible to prevent stress from concentrating on the corner portion 33C of the spacer layer 33.

The spacer layers 33 may have overlapping portions that overlap the current collector 21 and extending portions that extend outward beyond the edge 21d of the current collector 21 when viewed from the stacking direction. The end surface welded portion R1 may be provided on the extending portion of the spacer layer 33 when viewed from the stacking direction, and the cutout portion 33K may be provided on the overlapping portion that is more inward than the end surface welded portion R1 when viewed from the stacking direction. In this configuration, the cutout portion 33K is not formed in the end surface welded portion R1, so that sealing performance at the end surface welded portion R1 can be ensured.

In one example, the sealing portion 30 and the current collector 21 can be sufficiently bonded to each other because the first sealing layer 31 and the second sealing layer 32 do not have any notch-shaped portions. In another example, the spacer layer 33 is thicker than the first sealing layer 31 and the second sealing layer 32, so the volume of the sealing portion 30 can be sufficiently reduced by only forming the notch-shaped portions 33K in the spacer layer 33.

The above describes in detail an example of the present disclosure, but the present disclosure is not limited to the above example.

Figure 5 is a schematic cross-sectional view of another example of a storage module. Figure 5 shows a cross-sectional view of the storage module cut at the same position as in Figure 4. The storage module shown in Figure 5 differs from the storage module shown in Figure 4 and the like only in that it has a notch-shaped portion 33KS. As shown in Figure 5, the spacer layer 33 has a notch-shaped portion 33KS in which the spacer layer 33 is cut from the notch-shaped portion 33K toward the end face welding portion R1 at the corner portion 33C where the notch-shaped portion 33K is formed. Among the spacer layers 33, the spacer layers 33 cut by the notch-shaped portion 33KS are only in contact with each other and are not directly connected. That is, the spacer layer 33 is cut at the notch-shaped portion 33KS. The notch-shaped portion 33KS may be formed by making a cut in the spacer layer 33. The notch-like portion 33KS in the illustrated example is formed along the side along the extension line L2 of the notch-like portion 33K, and extends to the end face welded portion R1. That is, the notch-like portion 33K formed in the corner portion 33C has a notch-like portion 33KS that extends from the inner edge 33a of the spacer layer 33 toward the end face welded portion R1. Note that the notch-like portion 33KS reaches the end face welded portion R1, but is not formed in the end face welded portion R1. In this configuration, the presence of the notch-like portion 33KS separates the area where stress concentrates at the corner when the sealing portion 30 expands and contracts in the extension direction of the side as viewed from the stacking direction, thereby mitigating thermal shock.

Figure 6 is a schematic cross-sectional view of a storage module of yet another example. Figure 6 shows the state in which the storage module is cut at the same position as in Figure 4. In the example of Figure 6, a spacer layer 133 is shown instead of the spacer layer 33. This spacer layer 133 is divided into a long side portion 133L, a short side portion 133S, and a corner portion 133C, similar to the spacer layer 33. One short side portion 133Sa forms the liquid injection port side and has a communication hole 135. In the illustrated example, a notch-shaped portion 133K is formed in all four corner portions 133C. The width of the spacer layer 133 is different between the notch-shaped portion 133K and the wide portion 133W. The notch-shaped portion 133K has a shape in which the inner edge 133a of the spacer layer 133 is notched toward the edge 21d of the current collector 21 when viewed from the stacking direction. The cutout portion 133K has a rectangular shape including the inner corner of the corner portion 133C of the spacer layer 133. The extension direction of each side defining the rectangular cutout portion 133K is along the long side direction or short side direction of the spacer layer 133. The cutout portion 133K in the illustrated example is defined by a side offset toward the outside from the inner edge of the long side portion 133L of the spacer layer 133, a side facing the side, and a side parallel to the inner edge of the short side portion 133S of the spacer layer 133. The cutout portion 133K does not reach the end face welded portion R1.

Figure 7 is a schematic cross-sectional view of a storage module in yet another example. Figure 7 shows the state in which the storage module is cut at the same position as in Figure 4. In the example of Figure 7, a spacer layer 233 is shown instead of the spacer layer 33. This spacer layer 233 is divided into a long side portion 233L, a short side portion 233S, and a corner portion 233C, similar to the spacer layer 33. One short side portion 233Sa forms the liquid injection port side and has a communication hole 235. In the illustrated example, a notch-shaped portion 233K is formed in all four corner portions 233C. The notch-shaped portion 233K has a V-shaped cutout shape from the inner edge to the outer edge at the corner of the spacer layer 233. In addition, the notch-shaped portion 233K has a triangular shape including the inner corner of the corner portion 233C of the spacer layer 233. The width of the cutout portion 233K is smaller than the width of the wide portion 233W located at the center of the short side portion 233S. The triangular cutout portion 233K is defined by two sides that are inclined in both the long side direction and the short side direction of the spacer layer 233, and its tip extends toward the corner of the outer edge of the spacer layer 233. Note that the cutout portion 233K does not reach the end face welded portion R1.

Figure 8 is a schematic cross-sectional view of a storage module of yet another example. Figure 8 shows a state in which the storage module is cut at the same position as in Figure 4. In the example of Figure 8, a spacer layer 333 is shown instead of the spacer layer 33. This spacer layer 333 is divided into a long side portion 333L, a short side portion 333S, and a corner portion 333C, similar to the spacer layer 33. One short side portion 333Sa forms the liquid injection port side and has a communication hole 335. In the illustrated example, a punched-out portion 333H that is circularly cut out is formed in all four corner portions 333C. In addition, a V-shaped cut-out portion 333K is formed in the corner portion 333C that is continuous with the short side portion 333Sa. The punched-out portion 333H has a shape in which a part between the inner edge and the outer edge of the spacer layer 333 is cut out. In the illustrated example, a punched-out portion 333H that is circularly cut out is shown, but the shape is not particularly limited. The cutout portion 233K does not reach the end face welded portion R1.

Although the modified examples of the present disclosure have been described above with reference to the drawings, the present disclosure is not limited to the above-described forms.

For example, in the example shown, the inner edge of the end surface welded portion R1 is located outside the edge 21d of the current collector 21, but the inner edge of the end surface welded portion R1 may be located at the edge 21d of the current collector 21, or may be located inside the edge 21d of the current collector 21.

In addition, although an example has been shown in which the sealing layer and the spacer layer are divided based on the extension lines of the long and short sides of the negative electrode active material layer, the sealing layer and the spacer layer may be divided based on the extension lines of the long and short sides of the positive electrode active material layer.

Although an active material layer having a rectangular shape has been exemplified, the shape of the active material layer is not particularly limited as long as it can be regarded as a rectangle. For example, the active material layer may be divided into a plurality of regions spaced apart from each other, or may have a shape other than a rectangle. In this case, the shape of the active material layer may be regarded as a rectangle having a long side along the long side of the current collector and a short side along the short side of the current collector, among the smallest rectangles including all the regions in which the active material layer is formed.

In addition, FIG. 5 shows an example in which a notch-like portion 33KS is formed in the cutout portion 33K shown in FIG. 4, but the notch-like portion may be formed in any area in which the spacer layer 33 is cut, and may also be formed in the other examples in FIG. 6 to FIG. 8.

In addition, although an example in which the notch-shaped portion, the cut-shaped portion, and the punch-shaped portion are formed only in the spacer layer has been shown, the notch-shaped portion, the cut-shaped portion, and the punch-shaped portion may be formed not only in the spacer layer but also in the seal layer. The notch-shaped portion (seal notch), the cut-shaped portion, and the punch-shaped portion formed in the seal layer may have the same shape as the notch-shaped portion, the cut-shaped portion, and the punch-shaped portion formed in the spacer layer, or may have a different shape. In addition, the notch-shaped portion, the cut-shaped portion, and the punch-shaped portion formed in the seal layer may be formed at a position corresponding to the position of the notch-shaped portion, the cut-shaped portion, and the punch-shaped portion formed in the spacer layer, or may be formed at a different position. For example, in the notch-shaped portion formed in the seal layer, the joint width (width direction length) between the current collector and the seal layer may be smaller than other regions.

An embodiment of the present disclosure can be shown as follows.
[1]
a laminate including a plurality of electrodes stacked together, each of the electrodes having a rectangular metal current collector;
a resin sealing portion provided on a periphery of the current collector so as to surround the stack when viewed from the stacking direction of the plurality of electrodes,
the plurality of electrodes includes a plurality of bipolar electrodes;
Each of the plurality of bipolar electrodes has an active material layer on a first surface of the current collector and on a second surface opposite to the first surface,
the current collector of each of the plurality of bipolar electrodes has, on the first surface and the second surface, a rectangular first region in which the active material layer is provided, as viewed from the stacking direction, and a rectangular frame-shaped second region that is outside the first region;
the sealing portion includes a plurality of rectangular frame-shaped seal layers and a plurality of rectangular frame-shaped spacer layers,
the plurality of sealing layers are joined to the first surface and the second surface at a periphery of the current collector of each of the plurality of electrodes;
the plurality of spacer layers are positioned between the seal layers adjacent to each other in the stacking direction and seal, together with the seal layers, internal spaces formed between the current collectors adjacent to each other in the stacking direction;
the sealing portion includes end surface welded portions in which outer peripheral edges of the plurality of seal layers and outer peripheral edges of the plurality of spacer layers are welded to each other to be integrated together,
an outer edge of the rectangular first region is defined by a pair of first sides opposed to each other and a pair of second sides connected to each other and opposed to each other,
When the spacer layer is divided by first partition lines extending from the pair of first sides and second partition lines extending from the pair of second sides as viewed from the stacking direction, the spacer layer is divided into a pair of first sections separated by the first partition lines and extending along the pair of second sides, a pair of second sections separated by the second partition lines and extending along the first sides, and four third sections separated by the first partition lines and the second partition lines, connecting the first sections and the second sections, and including four corners of the spacer layer,
an energy storage device, wherein at least one of the plurality of spacer layers has a cutout portion formed in at least one of the third compartments so that the widthwise length of the spacer layer from the end face welding portion to the internal space is shorter than the widthwise length of the spacer layer in the adjacent first compartment or the adjacent second compartment.
[2]
The sealing portion includes a communication hole that communicates the internal space with the outside of the sealing portion,
the communication hole is formed in one of the pair of first sections of the spacer layer,
The power storage device according to [1], wherein the cutout portions are formed in at least a pair of the third compartments adjacent to the first compartment in which the communication hole is formed.
[3]
The energy storage device described in [2], wherein the widthwise length of the spacer layer in one of the pair of first compartments in which the communicating hole is formed is greater than the widthwise length of the spacer layer in the other of the pair of first compartments and the widthwise length of the spacer layer in the pair of second compartments.
[4]
the plurality of spacer layers each include an overlapping portion overlapping the current collector and an extending portion extending outward beyond an edge of the current collector when viewed from the stacking direction,
the end surface welded portion is provided on the extending portion of the spacer layer as viewed from the stacking direction,
The energy storage device according to any one of [1] to [3], wherein the cutout portion is provided in the overlapping portion that is on the inner side of the end surface welded portion when viewed from the stacking direction.
[5]
The energy storage device according to any one of [1] to [4], wherein at least one of a pair of the sealing layers adjacent to the spacer layer in which the cutout portion is formed has a sealing cutout portion in a region of the spacer layer corresponding to the cutout portion, the bonding width with the current collector being shorter than the bonding width in other regions.
[6]
The storage device according to any one of [1] to [5], wherein the cutout portion formed in the third section of the spacer layer has a notch portion extending from an inner edge of the spacer toward the end face welded portion.

11...electricity storage module, 12...electrode laminate (laminate), 21...current collector, 21a...first surface, 21b...second surface, 22...positive electrode active material layer, 23...negative electrode active material layer, 30...sealing portion, 31...first seal layer, 32...second seal layer, 33...spacer layer, 33C...corner portion, 33L...long side portion, 33K...notched portion, 33S...short side portion, 34...seal layer.

Claims (6)

a laminate including a plurality of electrodes stacked together, each of the electrodes having a rectangular metal current collector;
a resin sealing portion provided on a periphery of the current collector so as to surround the stack when viewed from the stacking direction of the plurality of electrodes,
the plurality of electrodes includes a plurality of bipolar electrodes;
Each of the plurality of bipolar electrodes has an active material layer on a first surface of the current collector and on a second surface opposite to the first surface,
the current collector of each of the plurality of bipolar electrodes has, on the first surface and the second surface, a rectangular first region in which the active material layer is provided, as viewed from the stacking direction, and a rectangular frame-shaped second region that is outside the first region;
the sealing portion includes a plurality of rectangular frame-shaped seal layers and a plurality of rectangular frame-shaped spacer layers,
the plurality of sealing layers are joined to the first surface and the second surface at a periphery of the current collector of each of the plurality of electrodes;
the plurality of spacer layers are positioned between the seal layers adjacent to each other in the stacking direction and seal, together with the seal layers, internal spaces formed between the current collectors adjacent to each other in the stacking direction;
the sealing portion includes end surface welded portions in which outer peripheral edges of the plurality of seal layers and outer peripheral edges of the plurality of spacer layers are welded to each other to be integrated together,
an outer edge of the rectangular first region is defined by a pair of first sides opposed to each other and a pair of second sides connected to each other and opposed to each other,
When the spacer layer is divided by first partition lines extending from the pair of first sides and second partition lines extending from the pair of second sides as viewed from the stacking direction, the spacer layer is divided into a pair of first sections separated by the first partition lines and extending along the pair of second sides, a pair of second sections separated by the second partition lines and extending along the first sides, and four third sections separated by the first partition lines and the second partition lines, connecting the first sections and the second sections, and including four corners of the spacer layer,
an energy storage device, wherein at least one of the plurality of spacer layers has a cutout portion formed in at least one of the third compartments so that the widthwise length of the spacer layer from the end face welding portion to the internal space is shorter than the widthwise length of the spacer layer in the adjacent first compartment or the adjacent second compartment. The sealing portion includes a communication hole that communicates the internal space with the outside of the sealing portion,
the communication hole is formed in one of the pair of first sections of the spacer layer,
The power storage device according to claim 1 , wherein the cutout portions are formed in at least a pair of the third compartments adjacent to the first compartment in which the communication hole is formed. The electric storage device according to claim 2, wherein the widthwise length of the spacer layer in one of the pair of first compartments in which the communication hole is formed is greater than the widthwise length of the spacer layer in the other of the pair of first compartments and the widthwise length of the spacer layer in the pair of second compartments. the plurality of spacer layers each include an overlapping portion overlapping the current collector and an extending portion extending outward beyond an edge of the current collector when viewed from the stacking direction,
the end surface welded portion is provided on the extending portion of the spacer layer as viewed from the stacking direction,
The power storage device according to claim 1 , wherein the cutout portion is provided in the overlapping portion that is located on an inner side than the end surface welded portion when viewed from the stacking direction. The electric storage device according to any one of claims 1 to 4, wherein at least one of the pair of sealing layers adjacent to the spacer layer in which the cutout portion is formed has a sealing cutout portion in a region of the spacer layer corresponding to the cutout portion, the bonding width with the current collector being formed shorter than the bonding width in other regions. The energy storage device according to claim 1, wherein the cutout portion formed in the third section of the spacer layer has a cut-like portion extending from the inner edge of the spacer toward the end face welded portion.

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