Energy storage device

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

Technical Field

[0001] The present disclosure relates to a power storage device.

Background Art

[0002] Patent Document 1 discloses a bipolar battery. This bipolar battery includes a bipolar electrode having a positive electrode provided on one surface of a current collector and a negative electrode provided on the other surface, a gel electrolyte sandwiched between the positive electrode and the negative electrode, and a seal layer provided between current collectors surrounding the periphery of a single battery composed of the positive electrode, the negative electrode, and the gel electrolyte.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the battery disclosed in Patent Document 1, the current collector is composed of a rectangular metal foil, and a rectangular frame-shaped seal layer made of resin is provided at the periphery of the current collector. In such a battery, when there is a large temperature change, due to the difference in the volume expansion coefficients of the seal layer and the current collector, stress may concentrate in the region of the current collector corresponding to the corner of the seal layer (current collector corner). When the temperature change is repeated, stress repeatedly concentrates at the current collector corner, and the current collector may be deformed, resulting in a risk of deterioration of battery performance.

[0005] An object of the present disclosure is to provide a power storage device capable of alleviating the deterioration of battery performance due to temperature changes.

Means for Solving the Problems

[0006] An energy storage device according to one aspect of the present disclosure comprises a laminate formed by stacking a plurality of electrodes, each having a rectangular, metallic current collector, 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 include 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. Each current collector of the plurality of bipolar electrodes has a rectangular first region on the first and second surfaces, where the active material layer is provided when viewed from the stacking direction, and a rectangular frame-shaped second region 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 seal layers are joined to the first and second surfaces at the periphery of each current collector of the plurality of electrodes. The plurality of spacer layers are located between adjacent seal layers in the stacking direction and, together with the plurality of seal layers, seal the internal space formed between adjacent current collectors in the stacking direction. The sealing portion includes an end-face welded portion formed by welding the outer edges of multiple seal layers and the outer edges of multiple spacer layers together. The outer edge of the rectangular first region is defined by a pair of opposing first sides and a pair of opposing second sides that connect the pair of first sides. 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 along the pair of second sides, a pair of second sections separated by the second partition lines along the first side, and four third sections separated by the first and second partition lines, connecting the first and second sections and including the four corners of the spacer layer. At least one of the multiple spacer layers is provided with a notched portion formed in at least one third section such that the widthwise length of the spacer layer from the end face weld to the internal space is shorter than the widthwise length of the spacer layer in the adjacent first or second section.

[0007] In the above-described energy storage device, a notched portion is formed in the third section, including the corner of the spacer layer that constitutes the resin sealing portion. As a result, the amount of resin in the corner is reduced by the volume corresponding to the notched portion. This reduction in the amount of resin in the corner reduces the dimensional change of the sealing portion at the corner when the ambient temperature changes. Consequently, 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, thus suppressing stress concentration at the corner of the current collector. Therefore, the deterioration of battery performance due to temperature changes can be mitigated.

[0008] The sealing portion may be provided with 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 notched 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 concentration at the corners located near the region in which the communication hole is formed is suppressed.

[0009] The widthwise length of the spacer layer in one of the pair of first sections in which a communication hole is formed may be greater than the widthwise length of the spacer layer in the other of the pair of first sections and the widthwise length of the spacer layer in the pair of second sections. When the width of the spacer layer is large, the volume ratio of the resin increases, and therefore the amount of dimensional change of the resin also increases. By forming a notched portion adjacent to one of the first sections in which the amount of dimensional change of the resin is likely to increase, it is possible to suppress the concentration of stress from that first section at the corner.

[0010] Multiple spacer layers may have overlapping portions that overlap the current collector and extended portions that extend outward beyond the edge of the current collector when viewed from the stacking direction. The end face welding portion is provided in the extended portion of the spacer layer when viewed from the stacking direction, and the notched portion may be provided in the overlapping portion that is inside the end face welding portion when viewed from the stacking direction. In this configuration, since the notched portion is formed at a distance from the end face welding portion, sealing performance at the end face welding portion can be ensured.

[0011] At least one of a pair of seal layers adjacent to a spacer layer with a notched portion may have a seal notch in the region corresponding to the notched portion of the spacer layer, where the contact width with the current collector is shorter than the contact width in other regions. This configuration makes it possible to reduce the amount of dimensional change at the seal notch when the ambient temperature changes.

[0012] The notched portion formed in the third section of the spacer layer may have a cut-like portion extending from the inner edge of the spacer to the end face welded portion. In this configuration, the presence of the cut-like portion divides the area where stress concentrates at the corner when the sealing portion expands and contracts in the direction of edge extension when viewed from the stacking direction, thereby mitigating thermal shock. [Effects of the Invention]

[0013] According to this disclosure, it is possible to provide an energy storage device that can mitigate the deterioration of battery performance due to temperature changes. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic plan view showing an example of an energy storage module. [Figure 2] Figure 2 is a schematic cross-sectional view along the line II-II in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view along the line III-III in Figure 1. [Figure 4] Figure 4 is a schematic cross-sectional view along the line IV-IV in Figure 3. [Figure 5] Figure 5 is a schematic cross-sectional view of another example of an energy storage module. [Figure 6] Figure 6 is a schematic cross-sectional view of yet another example of an energy storage module. [Figure 7] Figure 7 is a schematic cross-sectional view of yet another example of an energy storage module. [Figure 8] Figure 8 is a schematic cross-sectional view of yet another example of an energy storage module. [Modes for carrying out the invention]

[0015] 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 or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. In the description, an orthogonal coordinate system defined by the X-axis, Y-axis, and Z-axis may be referred to.

[0016] FIG. 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 FIG. 1 can be used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage module 11 is, for example, a secondary battery such as a nickel-hydrogen 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.

[0017] FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, schematically showing the layer structure of the power storage module 11. FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1, schematically showing the layer structure of the power storage module 11. The power storage module 11 is a unit cell having a flat rectangular parallelepiped shape in the Z-axis direction. In this embodiment, a bipolar type lithium-ion secondary battery is exemplified as the power storage module 11. The power storage module 11 includes an electrode laminate (laminate) 12 including a plurality of bipolar electrodes 14 and a sealing portion 30. The bipolar electrodes 14 in the electrode laminate 12 are laminated along the Z-axis direction. The lamination direction of the bipolar electrodes 14 is along the Z-axis direction and coincides with the lamination direction of the power storage module 11 in the module laminate 2.

[0018] 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 inert electrical conductor for continuously passing an electric current through the positive electrode active material layer 22 and the negative electrode active material layer 23 during discharge or charging of the lithium-ion secondary battery.

[0019] The current collector 21 is a sheet-like conductive member having a rectangular shape in plan view, and has a first surface 21a and a second surface 21b located on the opposite side of the first surface 21a. The current collector 21 is composed of, for example, a metal foil or an alloy foil. Examples of the metal foil include copper foil, aluminum foil, titanium foil, nickel foil, etc. Examples of the alloy foil include stainless steel foil (such as SUS304, SUS316, SUS301, etc. defined in JIS G 4305:2015), steel foil or stainless steel foil subjected to plating treatment, etc. The alloy foil may be an alloy foil of the metals exemplified as the materials of the above metal foil. The current collector 21 may be formed by integrating or laminating and attaching a plurality of metal foils, or may be formed by plating another metal layer on the surface of one metal foil.

[0020] In the illustrated example, the current collector 21 is formed by joining an aluminum foil 21A and a copper foil 21B such 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 overlapping and roll-bonding an aluminum foil 21A and a copper foil 21B. The current collector 21 may be a laminated foil. That is, the current collector 21 may be formed by joining and integrating an aluminum foil 21A and a copper foil 21B with a conductive adhesive resin (adhesive layer) such 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 vapor-depositing or plating copper on one side of an aluminum foil such that the first surface 21a is an aluminum layer and the second surface 21b is a copper layer. Note that, on the first surface 21a of the current collector 21, a chromate treatment may be performed on the aluminum layer. Also, on the second surface 21b of the current collector 21, nickel plating may be performed on the copper layer. In this case, the nickel plating layer may be a roughened surface which is a protrusion-like plated surface provided with fine protrusions on the surface. Note that the roughened surface only needs to have a rougher surface than the unprocessed metal foil, and may be formed by roughness processing such as etching or electroplating, for example. For example, the thickness of the current collector 21 may be about 30 μm to 150 μm, but is not limited thereto.

[0021] 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 periphery 21c of the current collector 21 is exposed.

[0022] In one example, 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. In one example, the adhesive layer may be provided over the entire surface of the first surface 21a of the current collector 21. The edges of the adhesive layer may also be formed along the edges of the negative electrode active material layer 23 surrounding the positive electrode active material layer 22 when viewed from the lamination direction.

[0023] The positive electrode active material layer 22 is a layered member containing a positive electrode active material, a conductive additive, and a binder. Examples of positive electrode active materials include composite oxides, metallic lithium, and sulfur. The composition of the composite oxide includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of composite oxides include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2.

[0024] The binder plays a role in maintaining the conductive network within the electrode by tying the active material or conductive additive to the surface of the current collector 21. Examples of binders include fluororesins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; acrylic resins containing monomer units such as acrylic acid and methacrylic acid; styrene-butadiene rubber (SBR); alginates such as carboxymethylcellulose, sodium alginate, and ammonium alginate; water-soluble cellulose ester crosslinked polymers; and starch-acrylic acid graft polymers. These binders can be used individually or in combination. Examples of conductive additives include acetylene black, carbon black, and graphite. Viscosity-adjusting solvents such as N-methyl-2-pyrrolidone (NMP) may be used in the positive electrode active material layer 22.

[0025] 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 such that the periphery 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. That is, 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.

[0026] The negative electrode active material layer 23 is a layered member containing a negative electrode active material, a conductive additive, and a binder. Examples of negative electrode active materials include graphite, artificial graphite, highly oriented graphite, carbon such as mesocarbon microbeads, hard carbon, and soft carbon, metal compounds, elements that can alloy with lithium or compounds of such elements, and boron-doped carbon. Examples of elements that can alloy with lithium include silicon and tin. The conductive additive and binder can be the same as those used in the positive electrode active material layer 22.

[0027] To form the positive electrode active material layer 22 and the negative electrode active material layer 23 on the current collector 21, conventionally known methods such as the roll coating method, die coating method, dip coating method, doctor blade method, spray coating method, and curtain coating method can be used. Specifically, an active material, solvent, and optionally a binder and conductive additive are mixed to produce a slurry-like active material layer forming composition, and this active material layer forming composition is applied to the first surface 21a and the second surface 21b and then dried. Examples of solvents include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. To increase the electrode density, the dried material may be compressed.

[0028] In the electrode stack 12, adjacent bipolar electrodes 14, 14 in the stacking direction are arranged such that the positive electrode active material layer 22 of one bipolar electrode 14 and the negative electrode active material layer 23 of the other bipolar electrode 14 face each other. A separator 15 is placed between adjacent bipolar electrodes 14, 14 in the stacking direction. In this embodiment, the separator 15 is a sheet-like member that has a rectangular shape in plan view and prevents short circuits between adjacent bipolar electrodes 14, 14 in the stacking direction.

[0029] The separator 15 has a rectangular shape, which, when viewed from the stacking direction, 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. 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.

[0030] The separator 15 is formed, for example, in the form of a sheet. The separator 15 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains electrolytes. Examples of materials constituting the separator 15 include polypropylene, polyethylene, polyolefin, and polyester. The separator 15 may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, the separator 15 may include, for example, a base 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 also include a ceramic layer that serves as a heat-resistant layer. The separator 15 may be reinforced with a vinylidene fluoride resin compound.

[0031] The separator 15 is formed by stretching molten resin using a dry or wet process. In this case, depending on the stretching process, the separator 15 has a direction of greater shrinkage and a direction of less shrinkage. The separator 15 may have a rectangular shape, with the direction of greater shrinkage along the shorter side and the direction of less shrinkage along the longer side. One example of a separator 15 is formed by a wet process, where the TD (Transverse Direction) direction of greater shrinkage is along the shorter side and the MD (Machine Direction) direction of less shrinkage is along the longer side.

[0032] Examples of electrolytes to be impregnated into the separator 15 include a liquid electrolyte (electrolyte solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, or a polymer gel electrolyte containing an electrolyte held in a polymer matrix. When the separator 15 is impregnated with an electrolyte, known lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, LiFSi, and LiN(CF3SO2)2 can be used as the electrolyte salt. In addition, known solvents such as cyclic carbonates, cyclic esters, linear carbonates, linear esters, and ethers can be used as the non-aqueous solvent. Two or more of these known solvent materials may be used in combination.

[0033] The electrode stack 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 electrode active material layer 22 provided on the first surface 21a of the current collector 21. The positive terminal electrode 16 is positioned on one end of the electrode stack 12 in the stacking direction such that the positive electrode active material layer 22 on the first surface 21a faces the negative electrode active material layer 23 of the end bipolar electrode 14. In the positive terminal electrode 16, the positive electrode active material layer 22 and the negative electrode active material layer 23 are not provided on the second surface 21b of the current collector 21, and this 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 made of aluminum foil.

[0034] The negative electrode terminal electrode 17 is composed of a current collector 21 and a negative electrode active material layer 23 provided on the second surface 21b of the current collector 21. The negative electrode terminal electrode 17 is positioned on the other end side in the stacking direction of the electrode stack 12 such that the negative electrode active material layer 23 on the second surface 21b faces the positive electrode active material layer 22 of the end bipolar electrode 14. In the negative electrode terminal electrode 17, the positive electrode active material layer 22 and the negative electrode active material layer 23 are not provided on the first surface 21a of the current collector 21, and this first surface 21a is electrically connected to an adjacent conductive plate (not shown).

[0035] The separator 15 described above is placed not only between adjacent bipolar electrodes 14, 14 in the stacking direction, but also between the bipolar electrode 14 and the positive terminal electrode 16, and between the bipolar electrode 14 and the negative terminal electrode 17. The placement of the separator 15 prevents short circuits between the bipolar electrode 14 and the positive terminal electrode 16, and between the bipolar electrode 14 and the negative terminal electrode 17.

[0036] The sealing portion 30 is a member that seals the internal space S between adjacent current collectors 21 in the stacking direction. The sealing portion 30 has electrical insulating properties. The sealing portion 30 is bonded (joined) to the edge of the current 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 positioned between adjacent current collectors 21 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 energy storage module 11, the internal space S is defined by the adjacent current collectors 21 and the sealing portion 30 in the stacking direction. An electrolyte (not shown) is housed in the internal space S. By being positioned between adjacent current collectors in the stacking direction, the sealing portion 30 also functions as a spacer that maintains the distance between adjacent current collectors.

[0037] An example of a sealing portion 30 includes a first seal layer 31, a second seal layer 32, and a spacer layer 33. The first seal layer 31, the second seal layer 32, and the spacer layer 33 each form a frame shape when viewed from the stacking direction. For example, the thickness of the first seal layer 31 and the second seal layer 32 may be about 50 μm to 200 μm. The thickness of the first seal layer 31 and the thickness of the second seal layer 32 may be the same as each other. The thickness of the spacer layer 33 may be thicker than the thickness of the first seal layer 31 and the second seal layer 32, for example, about 200 μm to 500 μm.

[0038] 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 overlapping regions 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 apart from the positive electrode active material layer 22.

[0039] 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 overlapping regions. 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 apart from the negative electrode active material layer 23.

[0040] The first seal layer 31, the second seal layer 32, and the spacer layer 33 are welded to each other by the end face welding portion R1. The outer edge 33b of the spacer layer 33 may be in 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 should 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. Also, the outer edge 33b of the spacer layer 33 should 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. In other words, the first seal layer 31, the second seal layer 32, and the spacer layer 33 are welded to each other by the end face welding portion R1 in the region outside the edge 21d of the current collector 21.

[0041] The end face weld portion R1 is formed by welding together the ends (outer peripheral edges) of the multiple first seal layers 31, multiple second seal layers 32, and multiple spacer layers 33 that are opposite to the internal space S, thereby integrating them. In other words, the first seal layers 31 and spacer layers 33 are not welded together in any part other than the end face weld portion R1, but are only in contact with each other. Similarly, the second seal layers 32 and spacer layers 33 are not welded together in any part other than the end face weld portion R1, but are only in contact with each other. In this way, since the spacer layers 33 are connected to the first seal layers 31 and second seal layers 32 by the end face weld portion R1, stress due to the expansion and contraction of the spacer layers 33 can affect the current collectors 21 joined to the first seal layers 31 and second seal layers 32.

[0042] The end face welding portion R1, when viewed from the stacking direction, has a rectangular frame shape that surrounds the electrode stack 12. The end face welding portion R1 is formed outside the outer edge of the current collector 21 when viewed from the stacking direction. That is, the first seal layer, the second seal layer and the spacer layer 33 have an overlapping portion that overlaps the current collector 21 when viewed from the stacking direction and an extended portion that extends outside the edge 21d of the current collector 21, and the end face welding portion R1 is provided in the extended portion. The side of the end face welding portion R1 opposite to the internal space S extends along the stacking direction and constitutes the outer surface of the sealing portion 30. In other words, the sealing portion 30 includes an inner surface facing the internal space S and an outer surface opposite to the inner surface.

[0043] The sealing portion 30 has communication holes 35 that communicate with each of the multiple internal spaces S. For example, the communication holes 35 are formed by partially cutting out the spacer layer 33 and penetrate the spacer layer 33 and the end face welding portion R1. The communication holes 35 have one opening in the internal space S and the other opening on the outer surface of the sealing portion 30. In the energy storage module 11, a cell containing one internal space S is formed between a pair of adjacent current collectors 21. Here, one communication hole 35 is formed for each cell. The communication holes 35 can be used as an injection port for pouring electrolyte into the internal space S. That is, an injection port (opening of the communication hole 35) is provided on the outer surface of the sealing portion 30. In an energy storage module 11 that is rectangular when viewed from the stacking direction, the side on which the communication holes 35 are provided is called the injection port side.

[0044] Viewed from the stacking direction, the inner edge 33a of the spacer layer 33 at the injection port is located inward (towards the internal space S) than 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 injection port is located, for example, 1 mm or more inward from the inner edges 31a and 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, viewed from the stacking direction, the inner edge 33a of the spacer layer 33 at locations other than the injection port may be located outward from the inner edge 31a of the first seal layer 31 and the inner edge 32a of the second seal layer 32.

[0045] The end portion 15a of the separator 15 described above is fixed between the second seal layer 32 and the spacer layer 33, near the inner edge 32a of the second seal layer 32. The end portion 15a may be partially bonded (welded) to the second seal layer 32, for example, by spot welding.

[0046] Viewed from the stacking direction, the first seal layer 31 is spaced apart from the positive electrode active material layer 22, and its inner edge 31a is located outside the positive electrode active material layer 22. Viewed from the stacking direction, the second seal layer 32 is spaced apart from the negative electrode active material layer 23, and its inner edge 32a is located outside the negative electrode active material layer 23. In this embodiment, 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 with the negative electrode active material layer 23 as long as it is spaced apart from the positive electrode active material layer 22.

[0047] 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 sandwiched between the current collector 21 and the spacer layer 33. The thickness of the second seal layer 32 is the thickness of the portion of the second seal layer 32 sandwiched between the current collector 21 and the spacer layer 33. The thickness of the spacer layer 33 is the thickness of the portion of the spacer layer 33 sandwiched between the first 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 to 1 / 2 of the thickness of the spacer layer 33, or they 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 they may be different. Furthermore, the thicknesses of the first seal layer 31 and the second seal layer 32 may be thicker than the spacer layer 33.

[0048] 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 an electrolyte-resistant resin material such as polyethylene. The resin materials constituting the first seal layer 31, the second seal layer 32, and the spacer layer 33 may be the same or different. 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.

[0049] Figure 4 is a cross-sectional view along the line IV-IV in Figure 3, schematically showing the cross-section of the energy storage module. In Figure 4, the first seal layer 31 and the second seal layer 32, which are hidden by the spacer layer 33, are combined and shown as the seal layer 34. Also, the separator 15 is omitted from the illustration for the sake of explanation.

[0050] As shown in Figure 4, the second surface 21b of the bipolar electrode 14 is divided into a rectangular first region 21T on 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 separated by the extension line L1 (first partition line) of the long side (first side) and the extension line L2 (second partition line) of the short side (second side) of the first region 21T. The seal layer 34 and the spacer layer 33 are divided into short-side portions (first section) 34S, 33S along the short side, separated by a pair of extension lines L1; long-side portions (second section) 34L, 33L along the long side, separated by a pair of extension lines L2; ​​and corner portions (third section) 33C, 34C connecting the long-side portions 34L, 33L and the short-side portions 34S, 33S, separated by extension lines L1 and L2.

[0051] A notched portion 33K is formed in at least one corner portion 33C of the spacer layer 33. In the illustrated example, a notched portion 33K is formed in a pair of corner portions 33C connected to the short side portion 33Sa along the edge of the liquid injection port, out of the four corner portions 33C. The notched portion may be a region in the spacer layer 33, which is defined by a rectangular inner and outer edge, that has a cut-out or cut-out shape when viewed from the stacking direction.

[0052] In other words, when viewed from the stacking direction, at least one side of the spacer layer 33 may include a wide portion 33W with a larger widthwise length and a notched portion 33K with a smaller widthwise length than the wide portion 33W. The widthwise length may be the length in the widthwise direction perpendicular to the longitudinal direction of each side of the spacer layer 33. That is, the widthwise length in the short side portion 34S is the length in the X-axis direction, and the widthwise length in the long side portion 34L is the length in the Y-axis direction. If 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 explanation, "widthwise length" may sometimes be simply referred to as "width".

[0053] 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 injection port is formed at different positions in the wide portion 33W and the notched portion 33K. In one example, the wide portion 33W is located in the center of the longitudinal direction of the spacer layer 33 when viewed from the stacking direction, and the notched portions 33K are located at both ends of the wide portion 33W. When the notched portions 33K are located on the liquid injection port side, the liquid injection port (communication hole 35) is located in the wide portion 33W.

[0054] The notched portion 33K shown in Figure 3 has a cut-out shape in which the widthwise length of the spacer layer 33 narrows from the inner edge to the outer edge of the spacer layer 33. The notched portion 33K is formed in the area of ​​the spacer layer 33 other than the end face welding portion R1, and is provided in the area where the spacer layer 33 and the current collector 21 overlap when viewed from the stacking direction. In other words, when viewed from the stacking direction, the notched portion 33K and the end face welding portion R1 do not overlap with each other. In one example, the notched portion 33K has a rectangular shape that includes the inner corner of the corner portion 33C of the spacer layer 33. That is, the inner edge of the original rectangular frame-shaped spacer layer has a rectangular shape with four corners, but the inner edge of the spacer layer 33 shown in Figure 4 has a shape in which two of the inner corners are cut off by the notched portion 33K. In this embodiment, the notched portion 33K is located inside the edge 21d of the current collector 21 when viewed from the stacking direction and does not reach the end face welding portion R1. In the illustrated example, the notched portion 33K is defined by an edge along the inner edge of the long side portion 33L of the spacer layer 33, an edge opposite to that edge, and an edge parallel to the inner edge of the short side portion 33S of the spacer layer 33.

[0055] As described above, one example of a power storage module 11 includes an electrode stack 12 in which a plurality of rectangular metal current collectors 21, each having an active material layer on a first surface 21a and a second surface 21b, are stacked, 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 current collectors 21. Each of the plurality of current collectors 21 has a rectangular first region 21T on 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 includes a plurality of rectangular frame-shaped seal layers 34 joined to the first surface 21a and the second surface 21b at the periphery of each of the plurality of current collectors 21, and a plurality of rectangular frame-shaped spacer layers 33 located between adjacent seal layers 34 in the stacking direction, which together with the plurality of seal layers 34 form an internal space S between the current collectors 21.

[0056] The multiple seal layers 34 and the multiple spacer layers 33 include an end-face welded portion R1 which is integrated by welding the outer peripheral edges opposite to the internal space S to each other when viewed from the stacking direction. The outer edge of the rectangular first region 21T is defined by a pair of opposing long sides and a pair of opposing short sides that connect the pair of long sides. When the spacer layer 33 is divided by extension lines L1 extending the pair of long sides and extension lines 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 along the short sides separated by the extension lines L1, a pair of long side portions 33L along the long sides separated by the extension lines L2, and four corner portions 33C which connect the short side portions 33S and the long side portions 33L separated by extension lines L1 and L2, and include the four corners of the spacer layer 33. At least one corner portion 33C has a notched portion 33K formed in the spacer layer 33. The widthwise length of the notched portion 33K is shorter than the widthwise length of the spacer layer 33 in the adjacent short side portion 33S or long side portion 33L.

[0057] In general, from the viewpoint of energy density, it is desirable for the electrodes constituting the energy storage module 11 to have a thin current collector 21 and a thick active material layer. Furthermore, from the viewpoint of securing internal space S, it is desirable for the resin constituting the sealing portion 30 to have at least the same thickness as the active material layer. In one example, when looking at a single cell in the energy 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. Also, 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 due to temperature change is expressed by the product of the volume expansion coefficient and the volume.

[0058] As described above, in each cell of the energy storage module, the thickness of the current collector, which is made of metal, is overwhelmingly thinner than the thickness of the encapsulation, which is made of resin. Furthermore, because the thermal expansion coefficient of the resin that makes up the encapsulation is larger than that of the metal that makes up the current collector, when there is a temperature change in the energy storage module, the encapsulation deforms much more than the current collector. In this case, stress is generated in the current collector that is pulled by the encapsulation as it expands and contracts. In particular, stress concentrates at the corners of the encapsulation because the stress vectors overlap.

[0059] In one example of a power storage module 11, a notched portion 33K is formed in the corner portion 33C of the spacer layer 33 that constitutes the resin sealing portion 30. As a result, the amount of resin in the corner portion 33C of the spacer layer 33 is reduced by the volume corresponding to the notched portion 33K. This reduction in the amount of resin in the corner portion 33C reduces the dimensional change in the corner portion 33C. This makes it less likely for the current collector 21 to be pulled by the sealing portion 30 which deforms with temperature changes, thus suppressing stress concentration at the corners of the current collector 21. Therefore, the deterioration of battery performance due to temperature changes can be mitigated.

[0060] Furthermore, at the location where the notched portion 33K is formed, the width of the spacer layer 33 is narrower than that of the wider portion 33W. In other words, in the above example, the formation of the notched portion 33K at the corner portion 33C partially disrupts the continuity between the long side portion 33L and the short side portion 33S of the spacer layer 33. Therefore, even if dimensional changes occur due to temperature changes, distortion is less likely to occur in the spacer layer 33, thus suppressing stress concentration at the corners of the current collector 21.

[0061] The width of the spacer layer 33 in the short side portion 33Sa where the communication hole 35 is formed may be greater than the width of the spacer layer 33 in the other short side portion 33S. In this configuration, by forming a notched portion 33K close to the short side portion 33Sa where the dimensional change of the resin tends to be large, it is possible to suppress stress concentration at the corner portion 33C of the spacer layer 33.

[0062] The multiple spacer layers 33 may have overlapping portions that overlap the current collector 21 and extended portions that extend outward from the edge 21d of the current collector 21 when viewed from the stacking direction. The end face welding portion R1 is provided in the extended portion of the spacer layer 33 when viewed from the stacking direction, and the notched portion 33K may be provided in the overlapping portion that is inside the end face welding portion R1 when viewed from the stacking direction. In this configuration, since the notched portion 33K is not formed in the end face welding portion R1, sealing performance at the end face welding portion R1 can be ensured.

[0063] In one example, since no notched portions are formed in the first seal layer 31 and the second seal layer 32, the sealing portion 30 and the current collector 21 can be sufficiently joined. Also, in one example, since the thickness of the spacer layer 33 is greater than that of the first seal layer 31 and the second seal layer 32, the volume of the sealing portion 30 can be sufficiently reduced by forming the notched portion 33K only in the spacer layer 33.

[0064] The above describes in detail one example of the form of this disclosure, but this disclosure is not limited to the above form.

[0065] Figure 5 is a schematic cross-sectional view of another example of a battery storage module. Figure 5 shows a cross-sectional view obtained by cutting the battery storage module at the same position as in Figure 4. The battery storage module shown in Figure 5 differs from the battery storage modules shown in Figure 4, etc., only in that it has a notched portion 33KS. As shown in Figure 5, the spacer layer 33 has a notched portion 33KS at the corner portion 33C where the notched portion 33K is formed, where the spacer layer 33 is cut from the notched portion 33K toward the end face weld portion R1. The spacer layers 33 that are cut by the notched portion 33KS are only in contact with each other and are not directly connected. That is, the spacer layer 33 is cut at the notched portion 33KS. The notched portion 33KS may be formed by making a cut in the spacer layer 33. In the illustrated example, the notched portion 33KS is formed along the edge along the extension line L2 of the notched portion 33K and extends to the end face weld portion R1. In other words, the notched portion 33K formed in the corner portion 33C has a notched portion 33KS extending from the inner edge 33a of the spacer layer 33 to the end face weld portion R1. The notched portion 33KS reaches the end face weld portion R1, but is not formed in the end face weld portion R1. In this configuration, the presence of the notched portion 33KS divides the area where stress concentrates at the corner when the sealing portion 30 expands and contracts in the direction of edge extension when viewed from the stacking direction, thereby mitigating thermal shock.

[0066] Figure 6 is a schematic cross-sectional view of yet another example of a storage module. Figure 6 shows the storage module cut at the same position as in Figure 4. In the example of Figure 6, a spacer layer 133 is shown instead of 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 spacer layer 33. One of the short side portions 133Sa forms the liquid injection port side and has a communication hole 135. In the illustrated example, notched portions 133K are formed in all four corner portions 133C. The width of the spacer layer 133 differs between the notched portions 133K and the wide portions 133W. The notched portions 133K have a shape in which the inner edge 133a of the spacer layer 133 is cut out toward the end edge 21d of the current collector 21 when viewed from the stacking direction. Furthermore, the notched portion 133K has a quadrilateral shape that includes the inner edge corner of the corner portion 133C of the spacer layer 133. The extension direction of each side defining the quadrilateral notched portion 133K is along the long side direction or the short side direction of the spacer layer 133. In the illustrated example, the notched portion 133K is defined by a side offset outward from the inner edge of the long side portion 133L of the spacer layer 133, a side opposite to that side, and a side parallel to the inner edge of the short side portion 133S of the spacer layer 133. Note that the notched portion 133K does not reach the end face welding portion R1.

[0067] Figure 7 is a schematic cross-sectional view of yet another example of a storage module. Figure 7 shows the storage module cut at the same position as in Figure 4. In the example of Figure 7, a spacer layer 233 is shown instead of 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 spacer layer 33. One of the short side portions 233Sa forms the liquid injection port side and has a communication hole 235. In the illustrated example, notched portions 233K are formed in all four corner portions 233C. The notched portions 233K have a V-shaped cutout at the corner of the spacer layer 233, extending from the inner edge to the outer edge. The notched portions 233K also have a triangular shape, including the inner corner of the corner portion 233C of the spacer layer 233. The widthwise length of the notched portion 233K is smaller than the widthwise length of the wide portion 233W located in the center of the short side portion 233S. The triangular notched portion 233K is defined by two sides that inclined in both the long and short side directions of the spacer layer 233, and its tip extends toward the corner of the outer edge of the spacer layer 233. The notched portion 233K does not reach the end face welded portion R1.

[0068] Figure 8 is a schematic cross-sectional view of yet another example of a storage module. Figure 8 shows the storage module cut at the same position as in Figure 4. In the example of Figure 8, a spacer layer 333 is shown instead of 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 spacer layer 333. One of the short side portions 333Sa forms the liquid injection port side and has a communication hole 335. In the illustrated example, circularly cut-out punched portions 333H are 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 portions 333H have a shape in which a part between the inner and outer edges of the spacer layer 333 is cut out. In the illustrated example, a circularly cut-out punched portion 333H is shown, but the shape is not particularly limited. Note that the notched portion 233K does not reach the end face welded portion R1.

[0069] Although modifications of the present disclosure have been described above with reference to the drawings, the present disclosure is not limited to the above-described forms.

[0070] For example, although we have shown an example where the inner edge of the end face welded portion R1 is outside the edge 21d of the current collector 21, the inner edge of the end face welded portion R1 may be at the same position as the edge 21d of the current collector 21, or it may be inside the edge 21d of the current collector 21.

[0071] Furthermore, while an example was shown in which the seal layer and spacer layer are separated based on the extensions of the long and short sides of the negative electrode active material layer, the seal layer and spacer layer may also be separated based on the extensions of the long and short sides of the positive electrode active material layer.

[0072] Furthermore, although a rectangular active material layer was given as an example, the shape of the active material layer is not particularly limited as long as it can be considered rectangular. For example, the active material layer may be divided into multiple regions spaced apart from each other, or it may have a shape other than a rectangle. In this case, the shape of the active material layer may be considered to be the smallest rectangle that includes all the regions in which the active material layer is formed, having a long side along the long side of the current collector and a short side along the short side of the current collector.

[0073] Furthermore, Figure 5 shows an example in which a notched portion 33KS is formed in the notched portion 33K shown in Figure 4. However, the notched portion can be formed in any region where the spacer layer 33 is cut, and therefore can also be formed in the other examples in Figures 6 to 8.

[0074] Furthermore, although examples have been shown in which notched portions, cut portions, and punched portions are formed only on the spacer layer, notched portions, cut portions, and punched portions may also be formed on the seal layer as well as the spacer layer. The notched portions (seal notches), cut portions, and punched portions formed on the seal layer may be the same shape as the notched portions, cut portions, and punched portions formed on the spacer layer, or they may be different shapes. In addition, the notched portions, cut portions, and punched portions formed on the seal layer may be formed at positions corresponding to the positions of the notched portions, cut portions, and punched portions formed on the spacer layer, or they may be formed at different positions. For example, in the notched portions formed on the seal layer, the joint width (widthwise length) between the current collector and the seal layer may be smaller than in other areas.

[0075] The form of this disclosure may be shown as follows: [1] A laminate in which multiple electrodes, each having a rectangular shape and a metal current collector, are stacked, The current collector comprises 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 include a plurality of bipolar electrodes, Each of the plurality of bipolar electrodes has an active material layer on the first surface of the current collector and on the second surface opposite to the first surface, Each of the current collectors of the plurality of bipolar electrodes has a rectangular first region on its first and second surfaces, where the active material layer is provided when viewed from the stacking direction, and a rectangular frame-shaped second region outside the first region. 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 and second surfaces at the periphery of the current collector of each of the plurality of electrodes, The plurality of spacer layers are positioned between adjacent seal layers in the stacking direction and, together with the plurality of seal layers, seal the internal space formed between adjacent current collectors in the stacking direction. The sealing portion includes an end-face welded portion formed by welding the outer edges of the plurality of sealing layers and the outer edges of the plurality of spacer layers together, The outer edge 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 the pair of first sides and a second partition line extending the pair of second sides, as viewed from the stacking direction, the spacer layer is divided into a pair of first sections along the pair of second sides, separated by the first partition lines, a pair of second sections along the first sides, separated by the second partition lines, and four third sections connecting the first and second sections, and including the four corners of the spacer layer, separated by the first and second partition lines. An energy storage device wherein at least one of the plurality of spacer layers is provided with a notched portion in at least one of the third compartments such 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 or second compartment. [2] The sealing portion is provided with a communication hole that connects 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 energy storage device according to [1], wherein the notched portion is formed in at least a pair of third sections adjacent to the first section in which the communication hole is formed. [3] The energy storage device according to [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. [4] The plurality of spacer layers, when viewed from the stacking direction, include an overlapping portion that overlaps the current collector and an extending portion that extends outward beyond the edge of the current collector. The end face welding portion is provided on the extended portion of the spacer layer when viewed from the stacking direction, The energy storage device according to any one of [1] to [3], wherein the notched portion is provided in the overlapping portion which is on the inside of the end face 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 seal layers adjacent to the spacer layer in which the notched portion is formed has a seal notch in the region of the spacer layer corresponding to the notched portion, the width of the contact with the current collector being shorter than the width of the contact in other regions. [6] The energy storage device according to any one of [1] to [5], wherein the notched portion formed in the third section of the spacer layer has a notched portion extending from the inner edge of the spacer toward the end face welding portion. [Explanation of Symbols]

[0076] 11... Energy storage module, 12... Electrode laminate (laminated body), 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

1. A laminate in which multiple electrodes, each having a rectangular shape and a metal current collector, are stacked, The current collector comprises 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 include a plurality of bipolar electrodes, Each of the plurality of bipolar electrodes has an active material layer on the first surface of the current collector and on the second surface opposite to the first surface, Each of the current collectors of the plurality of bipolar electrodes has a rectangular first region on its first and second surfaces, where the active material layer is provided when viewed from the stacking direction, and a rectangular frame-shaped second region outside the first region. 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 and second surfaces at the periphery of the current collector of each of the plurality of electrodes, The plurality of spacer layers are positioned between adjacent seal layers in the stacking direction and, together with the plurality of seal layers, seal the internal space formed between adjacent current collectors in the stacking direction. The sealing portion includes an end-face welded portion formed by welding the outer edges of the plurality of sealing layers and the outer edges of the plurality of spacer layers together, The outer edge 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 the pair of first sides and a second partition line extending the pair of second sides, as viewed from the stacking direction, the spacer layer is divided into a pair of first sections along the pair of second sides, separated by the first partition lines, a pair of second sections along the first sides, separated by the second partition lines, and four third sections connecting the first and second sections, including the four corners of the spacer layer, separated by the first and second partition lines. An energy storage device wherein at least one of the plurality of spacer layers is provided with a notched portion in at least one of the third compartments such 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 or second compartment.

2. The sealing portion is provided with a communication hole that connects 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 energy storage device according to claim 1, wherein the notched portion is formed in at least a pair of third sections adjacent to the first section in which the communication hole is formed.

3. The energy 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.

4. The plurality of spacer layers, when viewed from the stacking direction, include an overlapping portion that overlaps the current collector and an extending portion that extends outward beyond the edge of the current collector. The end face welding portion is provided on the extended portion of the spacer layer when viewed from the stacking direction, The energy storage device according to claim 1, wherein the notched portion is provided in the overlapping portion which is located inside the end face welded portion when viewed from the stacking direction.

5. The energy storage device according to any one of claims 1 to 4, wherein at least one of the pair of seal layers adjacent to the spacer layer in which the notched portion is formed has a seal notch in the region of the spacer layer corresponding to the notched portion, the width of the contact with the current collector being shorter than the width of the contact in other regions.

6. The energy storage device according to claim 1, wherein the notched portion formed in the third section of the spacer layer has a notched portion extending from the inner edge of the spacer layer toward the end face welding portion.

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