Power storage element

Abstract

This power storage element includes an electrode body. The electrode body includes an electrode plate that includes a current collector foil and an active material layer. The electrode plate is wound around a winding axis that extends in a first direction, and includes an active material formation part in which the active material layer is formed on the current collector foil in a second direction that is orthogonal to the first direction. The active material formation part comprises a plurality of layers in the second direction. Among the plurality of layers, each of two or more consecutive layers is provided with one or more electrode holes which are through holes that penetrate both of the current collector foil and the active material layer. The opening area of each of the electrode holes is 0.02 mm2 or less. When viewed from the second direction, the electrode body is provided with an electrode hole group in which the electrode holes in each layer are closely packed within a specific region over two or more layers.

Description

Energy storage element

[0001] The present invention relates to an energy storage element.

[0002] Patent Document 1 discloses a wound-type energy storage device including a wound electrode assembly formed by stacking and winding positive and negative electrode plates with a separator interposed therebetween. The positive electrode plate has a plurality of positive electrode through-holes aligned in the longitudinal direction, and the negative electrode plate has a plurality of negative electrode through-holes aligned in the longitudinal direction. The positive electrode through-holes and negative electrode through-holes overlap each other with the separator interposed therebetween, thereby forming an air passage that runs from the inside of the electrode assembly to the outer periphery.

[0003] Japanese Patent Application Laid-Open No. 2006-210031

[0004] In an energy storage element including an electrode body in which electrode plates are wound, it may be difficult to inject the electrolyte into the electrode body, so it is considered to form a through-hole in the electrode body. In the wound-type energy storage device disclosed in the above-mentioned Patent Document 1, an air passage is formed in the wound-type electrode body, so it is considered to inject the electrolyte into the wound-type electrode body through the air passage. However, in this wound-type energy storage device, there is a risk of problems such as the generation of burrs or contamination (metal powder, etc.) due to the formation of the air passage, or a decrease in capacity. Therefore, a configuration that allows the electrolyte to easily infiltrate the electrode body while suppressing the occurrence of such problems is desired.

[0005] The present invention was made by the inventor of the present application by focusing on the above-mentioned problem, and aims to provide an energy storage element that allows electrolyte to easily penetrate into the electrode body while suppressing the occurrence of defects.

[0006] An energy storage element according to one aspect of the present invention includes an electrode body, the electrode body including an electrode plate having a current collecting foil and an active material layer, the electrode plate being wound around a winding axis extending in a first direction, and including an active material forming portion in which the active material layer is formed in a second direction of the current collecting foil perpendicular to the first direction, the active material forming portion constituting a plurality of layers in the second direction, and each of two or more consecutive layers among the plurality of layers includes one or more electrode holes which are through holes penetrating both the current collecting foil and the active material layer, and the opening area of ​​the electrode hole is 0.02 mm ２The electrode body has an electrode hole group formed across each of the two or more layers when viewed from the second direction, with the electrode holes of each layer being densely packed within a predetermined region.

[0007] According to the energy storage element of the present invention, the electrolyte can easily permeate the electrode body while suppressing the occurrence of defects.

[0008] FIG. 1 is a perspective view showing the appearance of an energy storage element according to an embodiment. FIG. 2 is an exploded perspective view showing each component of the energy storage element according to the embodiment. FIG. 3 is a perspective view and a cross-sectional view showing the configuration of an electrode assembly according to an embodiment. FIG. 4 is a perspective view showing the configuration of an electrode assembly according to an embodiment in a partially developed state, in which the wound state of electrode plates is wound. FIG. 5 is a front view showing the configuration of electrode holes and electrode hole groups of an electrode assembly according to an embodiment. FIG. 6 is a front view and a cross-sectional view showing, in enlarged form, a portion of the configuration of electrode holes and electrode hole groups of an electrode assembly according to an embodiment. FIG. 7 is a front view showing the configuration of electrode holes and electrode hole groups of an electrode assembly according to a first modified example of the embodiment. FIG. 8 is a front view showing the configuration of electrode holes and electrode hole groups of an electrode assembly according to a second modified example of the embodiment. FIG. 9 is a front view showing the configuration of electrode holes and electrode hole groups of an electrode assembly according to a third modified example of the embodiment. FIG. 10 is a front view showing the configuration of electrode holes and electrode hole groups of an electrode assembly according to a fourth modified example of the embodiment. FIG. 11 is a perspective view showing the configuration of electrode holes formed in electrode hole groups of an electrode assembly according to a fifth modified example of the embodiment. FIG. 12 is a plan view showing an example of an energy storage device according to a sixth modified example of the embodiment.

[0009] (1) An energy storage element according to one aspect of the present invention includes an electrode body, the electrode body including an electrode plate including a current collecting foil and an active material layer, the electrode plate being wound around a winding axis extending in a first direction, and including an active material forming portion in which the active material layer is formed in a second direction of the current collecting foil perpendicular to the first direction, the active material forming portion constituting a plurality of layers in the second direction, and each of two or more consecutive layers among the plurality of layers includes one or more electrode holes that are through-holes penetrating both the current collecting foil and the active material layer, and the opening area of ​​the electrode hole is 0.02 mm ２The electrode body has an electrode hole group formed across each of the two or more layers when viewed from the second direction, with the electrode holes of each layer being densely packed within a predetermined region.

[0010] According to this, in the energy storage element, each of the two or more consecutive layers that constitute the active material forming portion of the wound electrode plate of the electrode body has an opening area of ​​0.02 mm ２ The electrode body has the following electrode holes, and when viewed from the second direction, an electrode hole group is formed in which the electrode holes of each layer are densely packed within a predetermined area. An electrode body in which electrode plates are wound is difficult to penetrate with an electrolyte, but by forming an electrode hole group in this way in which the electrode holes of each layer of the active material forming portion are densely packed within a predetermined area in the electrode body, the electrolyte can easily penetrate into the electrode body through each electrode hole of the electrode hole group. The electrode holes have an opening area of ​​0.02 mm ２ Because the electrode holes are so minute, the risk of micro-short circuits caused by burrs or contamination, or problems such as a decrease in capacity (decrease in energy density) due to a decrease in the effective electrode area, can be reduced. This allows the electrolyte to easily penetrate into the electrode body while preventing problems from occurring.

[0011] (2) In the energy storage device described in (1) above, the maximum width of the predetermined region as viewed from the second direction may be smaller than 50 mm.

[0012] According to this, by making the maximum width of the specified area in which the electrode holes of each layer in the electrode hole group are densely arranged smaller than 50 mm, the electrode holes of each layer are closer to each other, thereby improving the permeability of the electrolyte into each layer through the electrode holes.

[0013] (3) In the energy storage element according to (1) or (2) above, in the electrode hole group, each of the two or more layers may include a plurality of the electrode holes.

[0014] According to this, by providing a plurality of electrode holes in each layer of the electrode hole group, the electrolyte can efficiently permeate into each layer through the plurality of electrode holes.

[0015] (4) In the energy storage element described in any one of (1) to (3) above, the electrode plate may include a positive electrode plate and a negative electrode plate, and the electrode hole group may include the electrode holes in all of the layers of the active material forming portion of the positive electrode plate and the layers of the active material forming portion of the negative electrode plate.

[0016] According to this, by providing electrode holes in all layers of the active material forming portion of the positive electrode plate and the negative electrode plate in the electrode hole group, the electrolyte can penetrate into all layers of the positive electrode plate and the negative electrode plate, allowing the electrolyte to penetrate into the electrode body more effectively.

[0017] (5) In the energy storage element described in any one of (1) to (4) above, the ratio of the total opening area of ​​all the electrode holes provided in the active material forming portion to the area of ​​the active material forming portion may be 3% or less.

[0018] According to this, by reducing the ratio of the total opening area of ​​all the electrode holes to the area of ​​the active material forming portion to 3% or less, it is possible to suppress a decrease in the effective electrode area caused by providing the electrode holes in the active material forming portion.

[0019] (6) In the energy storage element described in any one of (1) to (5) above, two or more electrode hole groups may be formed in the electrode body, and when viewed from the second direction, the distance between the electrode holes within the electrode hole group may be smaller than the distance between two adjacent electrode hole groups.

[0020] According to this, the distance between the electrode holes in the electrode hole group is relatively small, which allows the electrolyte to penetrate into the electrode body effectively, and the distance between two adjacent electrode hole groups is relatively large, which prevents damage to the electrode plate, such as breakage of the electrode plate, between the two electrode hole groups.

[0021] (7) In the energy storage element described in (6) above, the distance between the two electrode hole groups in the first direction may be a first distance, the distance between the two electrode hole groups in a third direction perpendicular to the first direction and the second direction may be a second distance, and the first distance may be greater than the second distance.

[0022] According to this, the first distance between two electrode hole groups in the first direction is set to be larger than the second distance between two electrode hole groups in the third direction. In this way, by distributing the electrode hole groups at a constant distance (the first distance in the first direction and the second distance in the third direction), it is possible to suppress a reduction in the effective electrode area due to the provision of the electrode holes. By increasing the distance between the electrode hole groups in the first direction (the first distance), it is possible to further suppress damage to the electrode plates, such as tearing of the electrode plates between the electrode hole groups.

[0023] (8) In the energy storage device described in (7) above, the first distance may be greater than 10 times the second distance.

[0024] According to this, by making the first distance greater than 10 times the second distance, the electrode hole groups are distributed at large intervals in the first direction, which further suppresses a reduction in the effective electrode area due to the provision of the electrode holes. By making the first distance greater than 10 times the second distance, the distance between the electrode hole groups in the first direction is further increased, which further suppresses damage to the electrode plates, such as breakage of the electrode plates between the electrode hole groups.

[0025] Hereinafter, with reference to the drawings, an energy storage element according to an embodiment of the present invention (including its modified examples) will be described. The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples only and are not intended to limit the present invention. In each drawing, dimensions and the like are not strictly illustrated. In each drawing, the same or similar components are designated by the same reference numerals.

[0026] In the following description and drawings, the X-axis direction is defined as the arrangement direction of a pair of terminals (positive and negative electrodes, hereinafter the same) of the energy storage element, the arrangement direction of a pair of current collectors, the winding axis direction of the electrode body, the extension direction (widest width) of the electrode body or the container, or the direction in which a pair of short side surfaces of the container face each other. The Y-axis direction is defined as the thickness direction of the container (the direction in which the container width is narrowest), the direction in which a pair of long side surfaces of the container face each other, or the direction in which a pair of flat portions of the electrode body face each other. The Z-axis direction is defined as the arrangement direction of the container body and lid of the container, the direction in which a pair of curved portions of the electrode body face each other, or the up-down direction. The X-axis direction, Y-axis direction, and Z-axis direction intersect each other (orthogonal in this embodiment). Depending on the usage mode, the Z-axis direction may not be the up-down direction; however, for convenience of explanation, the Z-axis direction will be described below as the up-down direction.

[0027] In the following description, the positive X-axis direction refers to the direction of the arrow on the X-axis, and the negative X-axis direction refers to the direction opposite to the positive X-axis direction. Simply referring to the X-axis direction refers to both or either of the positive X-axis direction and the negative X-axis direction. The same applies to the Y-axis and Z-axis directions. Hereinafter, the X-axis direction will also be referred to as the first direction, the Y-axis direction as the second direction, and the Z-axis direction as the third direction. Expressions indicating relative directions or orientations, such as parallel and perpendicular, also include cases where the directions or orientations are not strictly the same. Two directions being parallel not only means that the two directions are completely parallel, but also means that the directions are substantially parallel, i.e., there is a difference of, for example, a few percent. In the following description, the term "insulating" means "electrically insulating." An insulating material has a volume resistivity of 1×10 １０ It is preferable that the material be made of a material with a resistance of Ωm or more.

[0028] (Embodiment) [1 General Description of Energy Storage Device 10] First, an overall description of the energy storage device 10 according to the present embodiment will be given using Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing the appearance of the energy storage device 10 according to the present embodiment. Fig. 2 is an exploded perspective view showing the components of the energy storage device 10 according to the present embodiment.

[0029] The energy storage element 10 is a secondary battery (single cell) capable of charging and discharging electricity, more specifically, a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used as a battery for driving or starting the engine of a moving object such as an automobile, motorcycle, personal watercraft, ship, snowmobile, agricultural machinery, construction machinery, automatic guided vehicle (AGV), or electric railway vehicle. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicle. Examples of the electric railway vehicle include a train, a monorail, a linear motor car, and a hybrid train equipped with both a diesel engine and an electric motor. The energy storage element 10 can also be used as a stationary battery for home or business use.

[0030] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage element 10 may be a primary battery instead of a secondary battery. The energy storage element 10 may be a pouch-type energy storage element. In the present embodiment, the energy storage element 10 is illustrated as having a rectangular parallelepiped (square) shape that is flattened in the Y-axis direction, but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, and may be a polygonal prism shape other than a rectangular parallelepiped, an elongated cylinder shape, an elliptical cylinder shape, a cylindrical shape, or the like.

[0031] As shown in Fig. 1, the energy storage element 10 includes a container 100, a pair of (positive and negative) terminals 300, and a pair of (positive and negative) upper gaskets 400. As shown in Fig. 2, the energy storage element 10 further includes a pair of (positive and negative) lower gaskets 500, a pair of (positive and negative) current collectors 600, and an electrode assembly 700, all of which are housed inside the container 100. In addition to the above components, spacers disposed on the sides or below the electrode assembly 700, an insulating film wrapping the electrode assembly 700, etc. may also be disposed.

[0032] An electrolyte solution (nonaqueous electrolyte) is sealed inside the container 100, but is not shown in the figure. There are no particular limitations on the type of electrolyte solution, and various types can be selected as long as they do not impair the performance of the energy storage element 10. The electrolyte solution contains a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. The nonaqueous solvent can be appropriately selected from known nonaqueous solvents. Examples of nonaqueous solvents include cyclic carbonates such as ethylene carbonate (EC) or propylene carbonate (PC), chain carbonates such as ethyl methyl carbonate (EMC), carboxylic acid esters, phosphate esters, sulfonic acid esters, ethers, amides, and nitriles. Compounds in which some of the hydrogen atoms contained in these compounds are substituted with halogens may also be used as nonaqueous solvents. The electrolyte salt can be appropriately selected from known electrolyte salts. Examples of the electrolyte salt include LiPF ６ Examples of inorganic lithium salts include lithium salts, sodium salts, potassium salts, magnesium salts, and onium salts, such as those mentioned above. Among these, lithium salts are preferred. The electrolytic solution may contain an additive such as biphenyl in addition to the non-aqueous solvent and the electrolyte salt.

[0033] The container 100 is a rectangular parallelepiped (square or box-shaped) case that includes a container body 110 with an opening facing in the positive direction of the Z axis, and a lid 120 that closes the opening of the container body 110. The lid 120 is a flat, rectangular member that forms the lid portion of the container 100, and is disposed in the positive direction of the Z axis of the container body 110. The lid 120 is a wall that extends in the direction of the winding axis of the electrode body 700. The winding axis direction of the electrode body 700 is the direction in which a winding axis L of the electrode body 700, which will be described later, extends, and in this embodiment is the X-axis direction.

[0034] The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100. The container body 110 has a pair of long side walls 111 on both sides (side surfaces) in the Y-axis direction, a pair of short side walls 112 on both sides (side surfaces) in the X-axis direction, and a bottom wall 113 on the surface (bottom surface) in the negative Z-axis direction. The long side walls 111 are flat, rectangular wall portions extending in the X-axis direction (winding axis direction of the electrode body 700) and include the long side surfaces of the container 100. The long side walls 111 are adjacent to the short side walls 112, the bottom wall 113, and the lid 120, and have a larger area than the short side walls 112. The short side walls 112 are flat, rectangular wall portions extending in the Z-axis direction and include the short side surfaces of the container 100. The short side wall portion 112 is adjacent to the long side wall portion 111, the bottom wall portion 113, and the lid body 120, and has a smaller area than the long side wall portion 111. The bottom wall portion 113 is a flat, rectangular wall portion extending in the X-axis direction (the winding axis direction of the electrode body 700), and includes the bottom surface of the container 100. The bottom wall portion 113 is disposed adjacent to the long side wall portion 111 and the short side wall portion 112.

[0035] After the electrode assembly 700 and the like are housed inside the container body 110, the container body 110 and the lid 120 are joined by welding or the like, thereby sealing the interior of the container 100. The material of the container 100 (container body 110 and lid 120) is not particularly limited, and may be a weldable (joinable) metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet, or a resin. The container body 110 and the lid 120 may be formed of the same material or different materials. When the energy storage element 10 is a pouch-type energy storage element, the container 100 may be a laminate film composed of multiple layers including a metal layer and a resin layer.

[0036] The container 100 is formed with a liquid injection part 130 and a gas exhaust valve 140. In this embodiment, the liquid injection part 130 and the gas exhaust valve 140 are formed in the lid 120. That is, the liquid injection part 130 and the gas exhaust valve 140 are formed in a wall extending in the direction of the winding axis (X-axis direction) of the electrode body 700. The gas exhaust valve 140 is a safety valve that releases pressure when the pressure inside the container 100 increases excessively. In this embodiment, the gas exhaust valve 140 is disposed at the center of the lid 120 in the X-axis direction and the Y-axis direction, but may be disposed at any position on the lid 120.

[0037] The liquid injection unit 130 is a portion for injecting an electrolyte into the container 100 during the manufacture of the energy storage element 10. The liquid injection unit 130 is used during the manufacture of the energy storage element 10 to evacuate the container 100, inject an electrolyte into the container 100 to impregnate the electrode body 700 with the electrolyte, and remove gas from the electrode body 700. In the present embodiment, the liquid injection unit 130 is disposed near the negative X-axis direction of the lid body 120 and at the center in the Y-axis direction, but may be disposed at any position on the lid body 120.

[0038] The liquid filling section 130 includes a liquid filling port 131 and a liquid filling tap 132. The liquid filling port 131 is a through-hole formed in the lid 120 for injecting the electrolyte into the container 100, and in this embodiment, has a circular shape. The liquid filling tap 132 is a member that closes the liquid filling port 131. Specifically, the liquid filling tap 132 is a closing member (lid member) that is joined to the lid 120 to close the liquid filling port 131 after the container 100 is evacuated through the liquid filling port 131 and the electrolyte is injected into the container 100 during the manufacture of the energy storage device 10. The material of the liquid filling tap 132 is not particularly limited, and any metal that can be used for the container 100 (lid 120) can be used. In particular, the liquid filling tap 132 is formed of a material that can be welded to the lid 120, such as the same material as the lid 120.

[0039] The terminals 300 are electrode terminals (positive and negative terminals) electrically connected to the electrode body 700 via the current collector 600. The terminals 300 are metal members for conducting electricity stored in the electrode body 700 to the external space of the energy storage element 10 and for introducing electricity into the internal space of the energy storage element 10 to store electricity in the electrode body 700. The terminals 300 are formed of a conductive member such as a metal, such as aluminum, an aluminum alloy, copper, or a copper alloy. The terminals 300 are connected (joined) to the current collector 600 by crimping, welding, or the like, and are attached to the lid 120. The terminals 300 are arranged so as to protrude in the positive Z-axis direction from the outer surface (the surface facing the positive Z-axis direction) of the lid 120. In this embodiment, terminal 300 is a welding terminal that is joined to an external conductive member such as a bus bar by welding, but terminal 300 may also be a bolt terminal that has a bolt portion formed with a male thread portion that protrudes in the positive direction of the Z axis and is joined to the conductive member by a bolt connection.

[0040] The current collectors 600 are conductive current collecting members (positive electrode current collector and negative electrode current collector) arranged on both sides of the electrode body 700 in the X-axis direction and connected (joined) to the electrode body 700 and the terminal 300, electrically connecting the electrode body 700 and the terminal 300. The current collectors 600 are connected (joined) to an active material non-forming portion 720 of the electrode body 700 (described later) by welding, crimping, or the like, and are also connected (joined) to the terminal 300 by crimping, welding, or the like, as described above, and fixed to the lid 120. The material of the current collectors 600 is not particularly limited, but in this embodiment, the positive electrode current collector 600 is formed of aluminum, an aluminum alloy, or the like, similar to a positive electrode current collector foil 741 of the electrode body 700 (described later), and the negative electrode current collector 600 is formed of copper, a copper alloy, or the like, similar to a negative electrode current collector foil 751 of the electrode body 700 (described later).

[0041] The upper gasket 400 is a plate-like, rectangular gasket that is disposed between the lid 120 of the container 100 and the terminal 300 and provides insulation and sealing between the lid 120 and the terminal 300. The lower gasket 500 is a plate-like, rectangular gasket that is disposed between the lid 120 and the current collector 600 and provides insulation between the lid 120 and the current collector 600. The upper gasket 400 and the lower gasket 500 are formed from an insulating material such as polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyethersulfone (PES), polyamide (PA), ABS resin, or a composite material thereof.

[0042] The electrode body 700 is an electricity storage element (power generating element) that can store electricity and is formed by stacking electrode plates and separators. In this embodiment, the electrode body 700 is formed by winding the electrode plates and separators. The electrode body 700 has an elongated shape extending in the X-axis direction and has an oval cylindrical shape (an elliptical shape when viewed from the X-axis direction). The electrode body 700 includes an electrode body main body 710 and active material non-forming portions 720 that protrude from the electrode body main body 710 on both sides in the X-axis direction. As described above, the active material non-forming portions 720 are connected (joined) to the current collector 600. The electrode body main body 710 has an electrode hole group 730 formed therein, which includes a plurality of electrode holes 731, which will be described later. The configuration of this electrode body 700 will be described in detail below.

[0043] [2 Description of the configuration of the electrode assembly 700] Figure 3 is a perspective view and a cross-sectional view showing the configuration of the electrode assembly 700 according to this embodiment. Figure 3(a) is a perspective view showing the appearance of the electrode assembly 700, and Figure 3(b) is a cross-sectional view showing the stacked state of the electrode plates by enlarging a cross section of a portion of the electrode assembly 700. Figure 4 is a perspective view showing the configuration of the electrode assembly 700 according to this embodiment in a partially developed state where the wound state of the electrode plates is

[0044] [2.1 General Description of Electrode Assembly 700] As shown in Figures 3 and 4, the electrode assembly 700 includes two electrode plates, a positive electrode plate 740 and a negative electrode plate 750, and two separators 760, separators 761 and 762.

[0045] The positive electrode plate 740 is an electrode plate in which a positive electrode active material layer 742 is formed on the surface of a positive electrode current collector foil 741, which is a long, strip-shaped current collector foil (metal foil) made of a metal such as aluminum or an aluminum alloy. The negative electrode plate 750 is an electrode plate in which a negative electrode active material layer 752 is formed on the surface of a negative electrode current collector foil 751, which is a long, strip-shaped current collector foil (metal foil) made of a metal such as copper or a copper alloy. The positive electrode current collector foil 741 and the negative electrode current collector foil 751 may be made of any known material that is stable against oxidation-reduction reactions during charge and discharge, such as nickel, iron, stainless steel, titanium, baked carbon, conductive polymers, conductive glass, or an Al—Cd alloy. The positive electrode active material used in the positive electrode active material layer 742 and the negative electrode active material used in the negative electrode active material layer 752 may be any known material that is capable of absorbing and releasing charge-transport ions.

[0046] As a positive electrode active material, LiMPO ４ , LiMSiO ４ , LiMBO ３ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.), polyanion compounds such as lithium titanate, LiMn ２ O ４ or LiMn １．５ Ni ０．５ O ４ Spinel-type lithium manganese oxides such as LiMO ２(M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) and the like can be used. Examples of the negative electrode active material include lithium metal, lithium alloys (lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and lithium metal-containing alloys such as Wood's alloy), alloys capable of absorbing and releasing lithium, carbon materials (graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature fired carbon, amorphous carbon, etc.), silicon oxides, metal oxides, and lithium metal oxides (Li ４ Ti ５ O １２ etc.), polyphosphate compounds, or Co, commonly called conversion anodes ３ O ４ or Fe ２ Examples of the metal include compounds of transition metals such as P and elements of Groups 14 to 16.

[0047] The separator 760 (separators 761 and 762) is a microporous insulating sheet made of resin or the like. Any known material can be used as the material for the separator 760 as long as it does not impair the performance of the energy storage device 10. Examples of the separator 760 include woven fabric, nonwoven fabric, and porous resin film. Among these examples, porous resin film is preferred from the viewpoint of strength, and nonwoven fabric is preferred from the viewpoint of electrolyte retention. Polyolefins such as polyethylene and polypropylene are preferred from the viewpoint of shutdown function, and polyimide, aramid, and the like are preferred from the viewpoint of oxidative decomposition resistance. A composite material of these resins may also be used for the separator 760. The separators 761 and 762 may be formed of the same material or different materials.

[0048] The electrode assembly 700 is formed by alternately stacking and winding the positive electrode plates 740 and negative electrode plates 750 configured as described above and the separators 761 and 762. That is, the electrode assembly 700 is formed by stacking and winding the positive electrode plates 740, the separator 761, the negative electrode plates 750, and the separator 762 in this order (see FIG. 3B , etc.). In this embodiment, the electrode assembly 700 is a wound electrode assembly formed by winding the positive electrode plates 740, the negative electrode plates 750, etc. around a winding axis L extending in the X-axis direction (first direction). The winding axis L is an imaginary axis that serves as the central axis when winding the positive electrode plates 740, the negative electrode plates 750, etc., and in this embodiment, is a straight line that passes through the center of the electrode assembly 700 and is parallel to the X-axis direction.

[0049] Specifically, the electrode body 700 is wound with a positive electrode plate 740 and a negative electrode plate 750 interposed between separators 761 and 762, offset from each other in a direction along the winding axis L (the winding axis direction, the X-axis direction in this embodiment). The positive electrode plate 740 and the negative electrode plate 750 have active material-free portions 720 at their respective ends in the offset direction, where the positive electrode active material layer 742 and the negative electrode active material layer 752 are not formed (coated) and the positive electrode current collector foil 741 and the negative electrode current collector foil 751 are exposed. In other words, the electrode body 700 has, at one end in the winding axis direction, the positive electrode active material-free portions 720 formed by stacking and bundling the ends of the positive electrode current collector foil 741, and has, at the other end in the winding axis direction, the negative electrode active material-free portions 720 formed by stacking and bundling the ends of the negative electrode current collector foil 751.

[0050] As described above, the electrode body 700 includes an electrode body main body portion 710 that constitutes the main body of the electrode body 700, and a pair of active material non-forming portions 720 (positive and negative) that protrude from the electrode body main body portion 710 on both sides in the X-axis direction. The electrode body main body portion 710 is an elongated cylindrical portion formed by winding an active material forming portion 713 provided on the electrode plates (positive electrode plate 740 and negative electrode plate 750) and a separator 760. The active material forming portion 713 is a portion of the electrode plates (positive electrode plate 740 and negative electrode plate 750) where an active material layer (a positive electrode active material layer 742 and a negative electrode active material layer 752) is formed (coated) in a second direction (the Y-axis direction in FIG. 3B ) that is perpendicular to the first direction of the current collecting foils (a positive electrode current collecting foil 741 and a negative electrode current collecting foil 751) of the electrode plates (a positive electrode plate 740 and a negative electrode plate 750). As a result, the electrode body main body 710 has a pair of curved portions 711 on both sides in the Z-axis direction and a pair of flat portions 712 on both sides in the Y-axis direction (see FIG. 3A). In other words, the electrode body 700 has the curved portions 711 and flat portions 712 formed by winding the positive electrode plate 740 and the negative electrode plate 750 around the winding axis L.

[0051] The curved portions 711 are curved in a semicircular arc shape so as to protrude in the Z-axis direction when viewed from the X-axis direction, and are curved portions extending in the X-axis direction, and are disposed opposite the bottom wall portion 113 and the lid body 120 of the container body 110. That is, when viewed from the X-axis direction, the pair of curved portions 711 are curved portions so as to protrude on both sides in the Z-axis direction toward the bottom wall portion 113 and the lid body 120 of the container body 110. The flat portions 712 are rectangular and flat portions extending parallel to the XZ plane facing the Y-axis direction, connecting the ends of the pair of curved portions 711, and are disposed opposite the long side wall portions 111 on both sides in the Y-axis direction of the container body 110. The curved shape of the curved portions 711 is not limited to a semicircular arc shape and may be a part of an ellipse, for example, and may be any other curved shape. The outer surface of the flat portion 712 facing the Y-axis direction is not limited to being flat, and the outer surface may be slightly concave or slightly convex.

[0052] With the above configuration, the electrode assembly 700 has an elongated (horizontally elongated) shape with a long length in the winding axis direction (X-axis direction). That is, the length of the electrode assembly 700 in the X-axis direction is longer than the lengths of the electrode assembly 700 in both the Y-axis direction and the Z-axis direction. In this embodiment, the length of the electrode assembly 700 in the X-axis direction is preferably 300 mm or more, more preferably 500 mm or more, and even more preferably 1000 mm or more, but may be shorter than 300 mm. In this embodiment, the length of the electrode assembly 700 in the X-axis direction is 1500 mm or less, but may be longer than 1500 mm.

[0053] Furthermore, as shown in FIG. 4 , a plurality of electrode holes 731 are formed in the active material forming portion 713 of the electrode body main body 710 of the electrode body 700. In FIGS. 2 and 3 , the electrode holes 731 are not shown because they are hidden by the separator 760. In FIG. 4 , the electrode holes 731 hidden by the separator 760 are indicated by dotted lines. FIG. 4 is an image diagram showing the arrangement and shape of the electrode holes 731, and the size of the electrode holes 731 is illustrated larger than the actual size compared to FIG. 5 and other figures described below. In this embodiment, the plurality of electrode holes 731 are densely arranged within a predetermined region as viewed from the Y-axis direction, when viewed through the electrode plates (positive electrode plate 740 and negative electrode plate 750) and separator 760 of the electrode body 700, thereby forming an electrode hole group 730 (see FIG. 5 ) consisting of the plurality of electrode holes 731. The configuration of the electrode holes 731 and the electrode hole group 730 will be described in detail below, also with reference to FIGS. 5 and 6 .

[0054] [2.2 Description of Electrode Holes 731 and Electrode Hole Groups 730] Figure 5 is a front view showing the configuration of the electrode holes 731 and electrode hole groups 730 of the electrode assembly 700 according to this embodiment. Figure 5(a) is a view of the electrode assembly 700 as seen from the negative Y-axis direction, and Figure 5(b) is an enlarged view of the configuration of the electrode holes 731 and electrode hole groups 730. For ease of explanation, Figure 5 illustrates each electrode hole 731 and each electrode hole group 730 formed in the flat portion 712 of the electrode assembly main body 710 in the negative Y-axis direction, with the electrode plates (positive electrode plate 740 and negative electrode plate 750) of the electrode assembly 700 and the separator 760 visible through. Figure 6 is a front view and a cross-sectional view showing an enlarged view of a portion of the configuration of the electrode holes 731 and electrode hole groups 730 of the electrode assembly 700 according to this embodiment. Fig. 6(a) is a front view of a portion of the configuration of the electrode hole 731 and the electrode hole group 730 as viewed from the negative Y-axis direction, and Fig. 6(b) is a cross-sectional view showing the VIb-VIb cross section in Fig. 6(a). Other electrode holes 731 and electrode hole groups 730 not shown in Fig. 6 also have the same configuration as the electrode hole 731 and electrode hole group 730 shown in Fig. 6.

[0055] As described above, the electrode plate included in the electrode body 700 includes an active material forming portion 713 in which an active material layer is formed in the second direction (Y-axis direction in FIG. 6 ) of the current collector foil. The electrode plate includes a positive electrode plate 740 and a negative electrode plate 750. Therefore, the positive electrode plate 740 includes a positive electrode active material forming portion 713 in which a positive electrode active material layer 742 is formed in the second direction (Y-axis direction in FIG. 6 ) of the positive electrode current collector foil 741, and the negative electrode plate 750 includes a negative electrode active material forming portion 713 in which a negative electrode active material layer 752 is formed in the second direction (Y-axis direction in FIG. 6 ) of the negative electrode current collector foil 751. In other words, the positive electrode current collector foil 741 and the positive electrode active material layer 742, excluding the positive electrode active material non-forming portion 720 of the positive electrode plate 740, are referred to as the positive electrode active material forming portion 713. The negative electrode current collector foil 751 and the negative electrode active material layer 752 excluding the negative electrode active material non-forming portion 720 of the negative electrode plate 750 are referred to as the negative electrode active material forming portion 713. In other words, the portion of the positive electrode plate 740 other than the positive electrode active material non-forming portion 720 is referred to as the positive electrode active material forming portion 713, and the portion of the negative electrode plate 750 other than the negative electrode active material non-forming portion 720 is referred to as the negative electrode active material forming portion 713.

[0056] In this embodiment, since the electrode plates (positive electrode plate 740 and negative electrode plate 750) are wound, the active material forming portion 713 is also wound. As a result, as shown in FIG. 6 , the active material forming portion 713 is configured to have a plurality of layers 713a in the Y-axis direction (second direction). In other words, the active material forming portion 713 includes a plurality of layers 713a stacked in the Y-axis direction (second direction). That is, in the positive electrode plate 740, three layers each in which positive electrode active material layers 742 (two layers) are formed on both surfaces of a positive electrode current collector foil 741 (one layer) in the Y-axis direction are defined as one unit, and are referred to as one layer 713a (positive electrode layer 713a). In the negative electrode plate 750, three layers each in which negative electrode active material layers 752 (two layers) are formed on both surfaces of a negative electrode current collector foil 751 (one layer) in the Y-axis direction are defined as one unit, and are referred to as one layer 713a (negative electrode layer 713a). In this way, by winding the positive electrode plate 740 and the negative electrode plate 750, a plurality of positive electrode layers 713a and a plurality of negative electrode layers 713a are stacked with the separator 761 or 762 disposed between the positive electrode layer 713a and the negative electrode layer 713a. The electrode body main body 710 is formed by stacking these plurality of positive electrode layers 713a, a plurality of negative electrode layers 713a, and the separators 761 and 762.

[0057] Of the multiple layers 713a, each of two or more consecutive layers 713a has one or more electrode holes 731, which are through-holes that penetrate both the current collector foil and the active material layer. Figure 6 illustrates four consecutive layers 713a (two positive electrode layers 713a and two negative electrode layers 713a). Each of the two positive electrode layers 713a has one or more electrode holes 731 (three positive electrode holes 740a in Figure 6) that are through-holes that penetrate both the positive electrode current collector foil 741 and the positive electrode active material layer 742. The positive electrode hole 731 (electrode hole 740a) is a circular through-hole that penetrates in the Y-axis direction through the positive electrode current collector foil 741 and the positive electrode active material layer 742 provided on both sides of the positive electrode current collector foil 741 in the Y-axis direction. Each of the two negative electrode layers 713a has one or more electrode holes 731 (three negative electrode holes 750a in FIG. 6 ) that are through-holes that penetrate both the negative electrode current collector foil 751 and the negative electrode active material layer 752. The negative electrode hole 731 (electrode hole 750a) is a circular through-hole that penetrates in the Y-axis direction through the negative electrode current collector foil 751 and the negative electrode active material layers 752 provided on both sides of the negative electrode current collector foil 751 in the Y-axis direction. The shape of the electrode holes 731 (electrode holes 740a, electrode holes 750a) is not limited to a circular shape and may be any shape, such as an elliptical shape, an oval shape, a polygonal shape such as a rectangle, or a slit.

[0058] The opening area of ​​the electrode hole 731 (electrode hole 740a, electrode hole 750a) is 0.02 mm ２ If the electrode holes 731 are circular, the diameter of the electrode holes 731 is 0.16 mm or less (the radius is 0.08 mm or less). If the electrode holes 731 are of this size, two adjacent electrode holes 731 are connected, and the opening area is 0.04 mm ２ Even if an electrode hole with an opening area of ​​0.02 mm (or an electrode hole with a width of 0.16 mm and a length of 0.32 mm) is formed, the electrode hole is still small, so defects such as lithium electrodeposition are unlikely to occur. ２ In the case of electrode holes larger than 0.01 mm, if two adjacent electrode holes are connected, problems such as lithium electrodeposition may occur. ２ Preferably, the diameter is 0.002 mm or less (or 100 μm or less in diameter), ２It is more preferable that the diameter is 0.0003 mm or less (or 50 μm or less in diameter). ２ It is more preferable that the diameter is 20 μm or less.

[0059] From the viewpoint of the permeability of the electrolyte into the electrode body 700, the opening area of ​​the electrode hole 731 is set to 0.00002 mm ２ The opening area of ​​the electrode hole 731 is preferably 0.00005 mm or more (or a diameter of 5 μm or more). ２ More preferably, the diameter is 10 μm or more, and 0.0002 mm ２ It is more preferable that the diameter is 15 μm or more (or a diameter of 15 μm or more). The method for forming (processing) the electrode holes 731 is not particularly limited, but by using a high-power-density ultrashort pulse laser such as a picosecond laser or a femtosecond laser, it is possible to process electrode holes 731 with a small opening area (small diameter). The separator 760 disposed between two or more consecutive layers 713 a (adjacent positive electrode plates 740 and negative electrode plates 750) has micropores, which facilitates the penetration of electrolyte and the exhaust of gas within the separator 760. Therefore, it is not necessary to form through-holes in the separator 760. If the micropores are considered to be through-holes, it can also be said that through-holes are disposed in the separator 760 between two or more consecutive layers 713 a. For this reason, in the present embodiment, no through-holes such as electrode hole 731 are formed in separator 760, but through-holes such as electrode hole 731 may also be formed in separator 760 (one or both of separators 761 and 762). When such through-holes are formed in separator 760, the arrangement of the through-holes in separator 760 may be within the range of electrode hole group 730 or may be outside the range of electrode hole group 730.

[0060] In this embodiment, the three electrode holes 740a provided in the positive electrode layer 713a and the three electrode holes 750a provided in the negative electrode layer 713a, which sandwich the separator 761, are arranged at positions offset (different positions) in the X-axis direction and the Z-axis direction when viewed from the Y-axis direction. Any one of the three electrode holes 740a and any one of the three electrode holes 750a may be arranged at the same position (partially or completely overlapping) in one or both of the X-axis direction and the Z-axis direction when viewed from the Y-axis direction. The same applies to the three electrode holes 740a and the three electrode holes 750a provided in the positive electrode layer 713a and the negative electrode layer 713a, which sandwich the separator 762. The same applies to the electrode holes 740a in different positive electrode layers 713a, and the same applies to the electrode holes 750a in different negative electrode layers 713a. In other words, in two or more consecutive layers 713a, the electrode holes 731 provided in different layers 713a may be positioned at the same position when viewed from the Y-axis direction, or may be positioned at offset positions (partially overlapping positions or spaced apart positions).

[0061] In this way, by forming electrode holes 731 in the multiple layers 713a of the active material forming portion 713 and stacking the multiple layers 713a, an electrode hole group 730 is formed in the electrode body 700, as shown in FIG. 5 . Specifically, in the electrode body 700, when viewed from the Y-axis direction (second direction), the electrode hole group 730 is formed in each of two or more layers 713a, with the electrode holes 731 of each layer 713a densely concentrated in a predetermined region R1. In other words, in the electrode hole group 730, the electrode holes 731 of each layer 713a are arranged concentratedly (intensively) in the predetermined region R1 when viewed from the Y-axis direction. In other words, the electrode holes 731 are more densely concentrated (concentrated) in the predetermined region R1 than in the region surrounding the predetermined region R1. The density of the electrode holes 731 is higher (the number of electrode holes 731 per unit area is greater) in the predetermined region R1 than in the region surrounding the predetermined region R1.

[0062] In this embodiment, the maximum width of the predetermined region R1 is smaller than 50 mm when viewed from the Y-axis direction (second direction). The predetermined region R1 is smaller than the region R2, which has a diameter of 50 mm. In FIG. 5 , the width of the predetermined region R1 in the Z-axis direction is the longest and is smaller than 50 mm. That is, the width of the predetermined region R1 in the Z-axis direction is longer than the width of the predetermined region R1 in the X-axis direction. This allows multiple electrode holes 731 to be positioned within the predetermined region R1 even when the electrode plates (positive electrode plate 740 and negative electrode plate 750) are wound and the positions of the electrode holes 731 are shifted in the Z-axis direction (the electrode plates do not need to be wound precisely). In this embodiment, the electrode hole group 730 has a substantially elliptical shape that is elongated in the Z-axis direction when viewed from the Y-axis direction. The electrode hole group 730 may have a circular, polygonal, or any other shape when viewed from the Y-axis direction. By adjusting the formation position of the electrode hole 731, the width of the predetermined region R1 in the Z-axis direction may be made shorter than the width of the predetermined region R1 in the X-axis direction. The maximum width of the predetermined region R1 is preferably 30 mm or less, more preferably 10 mm or less, and even more preferably 5 mm or less. The minimum width of the predetermined region R1 is preferably 0.1 mm or more, more preferably 1 mm or more, and even more preferably 2 mm or more.

[0063] As shown in FIGS. 4 to 6 , in the electrode hole group 730, each layer 713 a of two or more consecutive layers 713 a has a plurality of electrode holes 731 (three electrode holes 731 in this embodiment). In FIG. 6 , each positive electrode layer 713 a has three electrode holes 740 a, and each negative electrode layer 713 a has three electrode holes 750 a. Furthermore, in the electrode hole group 730, electrode holes 731 are provided in all of the layers 713 a included in the positive electrode plate 740 and the negative electrode plate 750. Specifically, in the electrode hole group 730, electrode holes 731 are provided in all of the layers 713 a included in the active material forming portion 713 included in the positive electrode plate 740 and the active material forming portion 713 included in the negative electrode plate 750. That is, in the electrode hole group 730, a plurality of electrode holes 731 are provided in all layers 713a of the positive electrode plate 740 and the negative electrode plate 750.

[0064] Two or more electrode hole groups 730 are formed in the electrode body 700. In this embodiment, nine electrode hole groups 730 (electrode hole groups 730a to 730i) are formed in each flat portion 712 of the electrode body main body 710 of the electrode body 700. Specifically, in the flat portion 712 in the negative Y-axis direction of the electrode body main body 710, electrode hole groups 730a, 730b, and 730c are arranged side by side in the Z-axis direction at the end of the electrode body main body 710 in the negative X-axis direction. Electrode hole groups 730d, 730e, and 730f are arranged side by side in the Z-axis direction at the center of the electrode body main body 710 in the X-axis direction. Electrode hole groups 730g, 730h, and 730i are arranged side by side in the Z-axis direction at the end of the electrode body main body 710 in the positive X-axis direction. In other words, electrode hole groups 730a, 730d, and 730g are arranged side by side in the X-axis direction at the positive Z-axis end of the electrode body main body 710. Electrode hole groups 730b, 730e, and 730h are arranged side by side in the X-axis direction at the center of the electrode body main body 710 in the Z-axis direction. Electrode hole groups 730c, 730f, and 730i are arranged side by side in the X-axis direction at the negative Z-axis end of the electrode body main body 710.

[0065] In the flat portion 712 of the electrode body main body 710 in the positive Y-axis direction, the arrangement positions of the nine electrode hole groups 730 (electrode hole groups 730a to 730i) formed in the flat portion 712 of the electrode body main body 710 in the negative Y-axis direction are upside down (the positions in the Z-axis direction are reversed). That is, in the flat portion 712 of the electrode body main body 710 in the positive Y-axis direction, the electrode hole groups 730a, 730d, and 730g are arranged side by side in the X-axis direction at the end of the electrode body main body 710 in the negative Z-axis direction, and the electrode hole groups 730c, 730f, and 730i are arranged side by side in the X-axis direction at the end of the electrode body main body 710 in the positive Z-axis direction. The electrode hole groups 730 formed in the flat portion 712 of the electrode body main body 710 in the negative Y-axis direction and the electrode hole groups 730 formed in the flat portion 712 of the electrode body main body 710 in the positive Y-axis direction have the same configuration. Figure 5 shows nine electrode hole groups 730 (electrode hole groups 730a to 730i) formed on the flat portion 712 of the electrode body main body 710 in the negative Y-axis direction, and the following describes these nine electrode hole groups 730.

[0066] In each of these nine electrode hole groups 730 (electrode hole groups 730a to 730i), the electrode holes 731 (electrode holes 731a to 731i) provided in each layer 713a are densely arranged within a predetermined region R1. Because the electrode holes 731 are densely arranged within the electrode hole group 730, the distance between the electrode holes 731 within the electrode hole group 730 is smaller than the distance between two adjacent electrode hole groups 730 (such as a first distance A1 or a second distance A2, which will be described later). In other words, when viewed from the Y-axis direction (second direction) (when viewed perspectively), the distance between the electrode holes 731 within the electrode hole group 730 is smaller than the distance between two adjacent electrode hole groups 730. In Figures 4 and 5, in the electrode hole groups 730a to 730i, the electrode holes 731a to 731i are each densely arranged in a similar position, but the electrode holes 731a to 731i only need to be densely arranged when the electrode body 700 is formed, and their individual arrangement positions are not particularly limited.

[0067] The distance between two adjacent electrode hole groups 730 in the X-axis direction (first direction) is defined as a first distance A1. The distance between two adjacent electrode hole groups 730 in the Z-axis direction (third direction perpendicular to the first and second directions) is defined as a second distance A2. The distance between two electrode hole groups 730 in the X-axis direction is the distance in the X-axis direction between the edge of the electrode hole group 730 in the negative X-axis direction in the positive X-axis direction and the edge of the electrode hole group 730 in the positive X-axis direction in the negative X-axis direction. The same applies to the distance between two electrode hole groups 730 in the Z-axis direction.

[0068] That is, when two predetermined adjacent electrode hole groups 730 among the plurality of electrode hole groups 730 (nine electrode hole groups 730 in this embodiment) are considered, the distance in the X-axis direction between the two electrode hole groups 730 is defined as a first distance A1, and the distance in the Z-axis direction between the two electrode hole groups 730 is defined as a second distance A2. In FIG. 5 , electrode hole group 730a and electrode hole group 730e are considered as an example of two adjacent electrode hole groups 730, and the distance in the X-axis direction between electrode hole group 730a and electrode hole group 730e is illustrated as a first distance A1, and the distance in the Z-axis direction between electrode hole group 730a and electrode hole group 730e is illustrated as a second distance A2. When electrode hole group 730a and electrode hole group 730d are considered as an example of two adjacent electrode hole groups 730, the distance in the X-axis direction between electrode hole group 730a and electrode hole group 730d is defined as the first distance A1 in FIG. 5 , but the second distance A2 in the Z-axis direction is zero.

[0069] In this configuration, the first distance A1 is greater than the second distance A2. Specifically, the first distance A1 is greater than 10 times the second distance A2. The first distance A1 is more preferably greater than 20 times the second distance A2, and even more preferably greater than 50 times the second distance A2. In this embodiment, the first distance A1 is 100 mm or greater. The first distance A1 is preferably 125 mm or greater, and more preferably 150 mm or greater. From the viewpoint of the permeability of the electrolyte solution into the electrode assembly 700, the first distance A1 is preferably 90 times or less, and more preferably 70 times or less, the second distance A2. The first distance A1 is preferably 250 mm or less, and more preferably 200 mm or less. In this way, the multiple electrode hole groups 730 (in this embodiment, nine electrode hole groups 730) include two electrode hole groups 730 in which the first distance A1 is greater than the second distance A2 (greater than 10 times the second distance A2, for example).

[0070] The nine electrode hole groups 730 in this embodiment are arranged in a lattice pattern, with three electrode hole groups 730 spaced a first distance A1 apart in the X-axis direction, and three sets of three electrode hole groups 730 spaced a second distance A2 apart in the Z-axis direction. Therefore, it can be said that the distance between any two adjacent electrode hole groups 730 in the X-axis direction is the first distance A1 and the distance between any two adjacent electrode hole groups 730 in the Z-axis direction is the second distance A2, and that the first distance A1 is greater than the second distance A2. In Figure 5, the distance in the X-axis direction between electrode hole group 730a and electrode hole group 730d adjacent in the X-axis direction is the first distance A1, and the distance in the Z-axis direction between electrode hole group 730a and electrode hole group 730b adjacent in the Z-axis direction is the second distance A2, and the first distance A1 is greater than the second distance A2. Thus, the multiple electrode hole groups 730 (in this embodiment, nine electrode hole groups 730) include at least three electrode hole groups 730 in which the first distance A1 is greater than the second distance A2 (greater than 10 times the second distance A2, for example).

[0071] Forming the electrode hole group 730 (electrode holes 731) in the electrode body 700 reduces the effective electrode area of ​​the electrode body 700, thereby reducing the capacity of the energy storage device 10 (causing capacity loss). The effective electrode area of ​​the electrode body 700 is the area of ​​the region in the electrode plate where the active material layer is disposed (the region in which the active material forming portion 713 is disposed). The rate at which this effective electrode area is reduced is referred to as the open area ratio. The open area ratio is the ratio of the total open area of ​​all the electrode holes 731 provided in the active material forming portion 713 to the area of ​​the active material forming portion 713. In detail, when the wound state of the electrode body 700 is unfolded to unfold the electrode plate and the electrode plate is viewed in plan, the open area ratio is the ratio of the total open area of ​​all the electrode holes 731 provided in the active material forming portion 713 to the area of ​​the active material forming portion 713.

[0072] The opening area ratio is preferably 3% or less, more preferably 1% or less, and even more preferably 0.5% or less, from the viewpoint of suppressing a decrease in the capacity of the energy storage element 10. The opening area ratio is preferably 0.001% or more, and even more preferably 0.01% or more, from the viewpoint of improving the permeability of the electrolyte into the electrode body 700. As described above, the opening area ratio can also be said to be the ratio of the amount of capacity decrease (capacity loss) of the energy storage element 10 due to the electrode holes 731. Therefore, the ratio of the amount of capacity decrease (capacity loss) of the energy storage element 10 is also preferably 3% or less, more preferably 1% or less, and even more preferably 0.5% or less. The ratio of the amount of capacity decrease (capacity loss) of the energy storage element 10 is preferably 0.001% or more, and even more preferably 0.01% or more.

[0073] [3 Description of Effects] As described above, according to the energy storage device 10 according to the embodiment of the present invention, each of the two or more continuous layers 713a constituting the active material forming portion 713 of the wound electrode plates (positive electrode plate 740 and negative electrode plate 750) of the electrode body 700 has an opening area of ​​0.02 mm ２ The electrode body 700 has the following electrode holes 731. When viewed from the second direction (Y-axis direction), the electrode body 700 has an electrode hole group 730 formed therein, in which the electrode holes 731 of each layer 713a are densely packed within a predetermined region R1. Thus, the electrode body 700, in which the electrode plates are wound, has an electrode hole group 730 formed therein, in which the electrode holes 731 of each layer 713a of the active material forming portion 713 are densely packed within a predetermined region R1. This allows the electrolyte to easily permeate the electrode body 700 through each electrode hole 731 of the electrode hole group 730. The electrode body 700 has an elongated shape with a long length in the winding axis direction (X-axis direction), making it difficult for the electrolyte to permeate. However, as described above, the electrode hole group 730 formed in the electrode body 700 allows the electrolyte to easily permeate the electrode body 700. The electrode hole 731 has an opening area of ​​0.02 mm. ２ Because the electrode holes 731 are so minute as to be no larger than 1 / 4 of a micrometer, it is possible to suppress the risk of micro-short circuits due to burrs or contamination, or problems such as a decrease in capacity (decrease in energy density) due to a decrease in the effective electrode area. This allows the electrolyte to easily penetrate the electrode body 700 while suppressing the occurrence of problems.

[0074] If gas is generated and accumulates inside the electrode body 700 during use of the energy storage element 10, the gas can be exhausted from the electrode hole groups 730 (particularly, the electrode hole groups 730a, 730d, and 730g), thereby preventing a decrease in capacity due to an expansion of the inactive region caused by the formation of gas pockets. When the electrolyte inside the electrode body 700 is consumed and the electrolyte runs out, the electrolyte can be replenished into the electrode body 700 from the electrode hole groups 730 (particularly, the electrode hole groups 730c, 730f, and 730i), thereby preventing a decrease in capacity due to an expansion of the inactive region caused by the electrolyte running out at the end of life.

[0075] Because the electrode holes 731 are minute through-holes, lithium electrodeposition is unlikely to occur even without alignment of the electrode holes 731. In other words, electrodeposition is unlikely to occur even when there is no negative electrode active material facing the positive electrode active material. Even if minute electrodeposition does occur, it is localized and is likely to be resolved by self-diffusion of lithium ions in the electrode plate during use of the energy storage device 10. When forming minute electrode holes 731 using a laser (such as a picosecond laser or femtosecond laser), the components of the electrode plate evaporate, making it less likely that contamination of several tens of microns in size, which could cause micro-short circuit defects, will occur. When forming minute electrode holes 731 in the electrode plate, the thermal effect of the laser is small, preventing thermal alteration of the surrounding active material. When forming electrode holes 731 with a diameter of 5 μm or more, electrolyte can penetrate the electrode body 700 relatively easily, but holes with a diameter of 5 μm or more can be formed using a laser (such as a picosecond laser or femtosecond laser). By forming minute electrode holes 731 in the electrode plate, it is possible to prevent the paste from passing through the electrode holes 731 and soiling the support roll during application of the active material, thereby enabling stable application.

[0076] By making the size of the predetermined region R1 where the electrode holes 731 of each layer 713a in the electrode hole group 730 are densely arranged smaller than 50 mm, the electrode holes 731 of each layer 713a are closer to each other, thereby improving the permeability of the electrolyte into each layer 713a through the electrode holes 731. The proximity of two or more electrode holes 731 in one layer 713a can also improve the permeability of the electrolyte, and the proximity of the electrode holes 731 provided in two or more adjacent layers 713a can also improve the permeability of the electrolyte. If the number of electrode holes 731 can be reduced by densely arranging the electrode holes 731 in a small predetermined region R1, the reduction in the effective electrode area can be suppressed.

[0077] By providing a plurality of electrode holes 731 in each layer 713a in the electrode hole group 730, the electrolyte can efficiently permeate into each layer 713a via the plurality of electrode holes 731. By providing a plurality of electrode holes 731 in each layer 713a, gas can be efficiently exhausted from the electrode hole group 730 when gas is generated inside the electrode body 700, and the electrolyte can be efficiently replenished from the electrode hole group 730 to the inside of the electrode body 700 when the electrolyte runs out.

[0078] In the electrode hole group 730, by providing electrode holes 731 in all layers 713a of the active material forming portions 713 provided on the positive electrode plates 740 and the negative electrode plates 750, the electrolyte can permeate all layers 713a of the positive electrode plates 740 and the negative electrode plates 750, thereby more effectively permeating the electrolyte into the electrode body 700. By providing electrode holes 731 in all layers 713a of the positive electrode plates 740 and the negative electrode plates 750, gas can be more effectively exhausted from the electrode hole group 730 when gas is generated inside the electrode body 700, and the electrolyte can be more effectively replenished from the electrode hole group 730 to the inside of the electrode body 700 when the electrolyte runs out.

[0079] By reducing the ratio of the total opening area of ​​all electrode holes 731 to the area of ​​the active material forming portion 713 to 3% or less, it is possible to suppress a decrease in the effective electrode area caused by providing electrode holes 731 in the active material forming portion 713. When reducing the ratio of the total opening area of ​​the electrode holes 731, the opening area of ​​the electrode holes 731 is reduced or the number of electrode holes 731 is reduced, which reduces the risk of micro-short circuits caused by burrs or contamination.

[0080] When viewed from the second direction (Y-axis direction), the distance between the electrode holes 731 within the electrode hole group 730 is smaller than the distance between two adjacent electrode hole groups 730. In this way, the relatively small distance between the electrode holes 731 within the electrode hole group 730 allows the electrolyte to effectively permeate the electrode body 700. When viewed from the second direction (Y-axis direction), the distance between two adjacent electrode hole groups 730 is larger than the distance between the electrode holes 731 within the electrode hole group 730. In this way, the relatively large distance between the two adjacent electrode hole groups 730 can suppress damage to the electrode plate, such as tearing of the electrode plate (positive electrode plate 740 or negative electrode plate 750) between the two electrode hole groups 730.

[0081] The first distance A1 between two electrode hole groups 730 in the first direction (X-axis direction) is set to be larger than the second distance A2 between two electrode hole groups 730 in the third direction (Z-axis direction). By distributing the electrode hole groups 730 at a constant distance (first distance A1 in the first direction and second distance A2 in the third direction), a reduction in the effective electrode area due to the provision of the electrode holes 731 can be suppressed. By increasing the distance (first distance A1) between the electrode hole groups 730 in the first direction (X-axis direction), damage to the electrode plates (positive electrode plate 740 or negative electrode plate 750), such as breakage of the electrode plates between the electrode hole groups 730, can be further suppressed. In particular, since the electrode body 700 is formed by winding the electrode plates (positive electrode plate 740 and negative electrode plate 750), the electrode plates are wound while being pulled in a direction perpendicular to the winding axis L, i.e., in the second direction (Y-axis direction). For this reason, if the distance (first distance A1) between the electrode hole groups 730 in the first direction (X-axis direction) is small, tension is concentrated on the active material forming portions 713 between adjacent electrode hole groups 730, making them prone to tearing. Therefore, by increasing the first distance A1, damage to the electrode plates, such as tearing of the electrode plates between the electrode hole groups 730, can be further suppressed.

[0082] By making the first distance A1 greater than 10 times the second distance A2, the electrode hole groups 730 are distributed at large intervals in the first direction (X-axis direction), which further reduces the reduction in effective electrode area caused by the provision of the electrode holes 731. By making the first distance A1 greater than 10 times the second distance A2, the distance between the electrode hole groups 730 in the first direction (X-axis direction) becomes even greater, which further reduces damage to the electrode plates (positive electrode plate 740 or negative electrode plate 750) between the electrode hole groups 730, such as tearing of the electrode plates.

[0083] [4 Description of Modifications] While the energy storage device 10 according to the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The embodiment disclosed herein is illustrative in all respects, and the scope of the present invention includes all modifications within the meaning and scope of the claims.

[0084] (Variations 1 to 5) In the above-described embodiments, there are no particular limitations on the number and positions of the electrode holes 731 and electrode hole groups 730 formed in the electrode body 700. In other words, any number of electrode hole groups 730 may be formed at any position on the electrode body 700, and any number of electrode holes 731 may be formed at any position within the electrode hole group 730.

[0085] FIG. 7 is a front view showing the configuration of the electrode holes 731 and electrode hole groups 730 of an electrode body 701 according to Modification 1 of the present embodiment. FIG. 8 is a front view showing the configuration of the electrode holes 731 and electrode hole groups 730 of an electrode body 702 according to Modification 2 of the present embodiment. FIG. 9 is a front view showing the configuration of the electrode holes 731 and electrode hole groups 730 of an electrode body 703 according to Modification 3 of the present embodiment. FIG. 10 is a front view showing the configuration of the electrode holes 731 and electrode hole groups 730 of an electrode body 704 according to Modification 4 of the present embodiment. FIGS. 7 to 10 correspond to FIG. 5(a). As with FIG. 5, for convenience of explanation, FIGS. 7 to 10 illustrate the electrode holes 731 and electrode hole groups 730 formed in the flat portion 712 of the electrode body main body 710 in the negative Y-axis direction, as seen through the electrode plates (positive electrode plate 740 and negative electrode plate 750) of the electrode bodies 701 to 704 and the separator 760. In each of the modified examples, electrode holes 731 and electrode hole groups 730 having the same configuration as the flat portion 712 in the negative Y-axis direction of the electrode body main body 710 are also formed in the flat portion 712 in the positive Y-axis direction of the electrode body main body 710. Fig. 11 is a perspective view showing the configuration of the electrode holes 731 formed in the electrode hole group 730 of the electrode body 705 according to modified example 5 of the present embodiment. Fig. 11 is a view corresponding to Fig. 4.

[0086] As shown in FIG. 7 , the electrode body 701 of the first modification has three electrode hole groups 730 (electrode hole groups 730a, 730d, and 730g) formed at the end of the electrode body 700 in the positive Z-axis direction in the above-described embodiment. In this modification, too, in the flat portion 712 in the negative Y-axis direction, the first distance A1, which is the distance in the X-axis direction between two adjacent electrode hole groups 730 (electrode hole group 730a and electrode hole group 730d in FIG. 7 ), is greater than the second distance A2 (not shown because it is zero), which is the distance in the Z-axis direction (greater than 10 times the second distance A2). The same is true for the flat portion 712 in the positive Y-axis direction. The other configurations of this modification are similar to those of the above-described embodiment, and therefore detailed description will be omitted. This modification can achieve the same effects as the above-described embodiment. In particular, the reduced number of electrode hole groups 730 can reduce the risk of micro-short circuits due to burrs or contamination caused by the formation of the electrode holes 731, or problems such as reduced capacitance due to a reduced effective electrode area. If gas is generated and accumulates inside the electrode body 701 during use of the energy storage element 10, the gas can be exhausted through the electrode hole group 730, thereby preventing a decrease in capacity due to the expansion of the inactive area caused by the formation of gas accumulation.

[0087] As shown in FIG. 8 , the electrode body 702 of the second modification has three electrode hole groups 730 (electrode hole groups 730c, 730f, and 730i) formed at the end of the electrode body 700 in the negative Z-axis direction in the above-described embodiment. In this modification, too, in the flat portion 712 in the negative Y-axis direction, the first distance A1, which is the distance in the X-axis direction between two adjacent electrode hole groups 730 (electrode hole group 730c and electrode hole group 730f in FIG. 8 ), is greater than the second distance A2 (not shown because it is zero), which is the distance in the Z-axis direction (greater than 10 times the second distance A2). The same is true for the flat portion 712 in the positive Y-axis direction. The other configurations of this modification are similar to those of the above-described embodiment, and therefore detailed description will be omitted. This modification can achieve the same effects as the above-described embodiment. In particular, the reduced number of electrode hole groups 730 can reduce the risk of micro-short circuits due to burrs or contamination caused by the formation of the electrode holes 731, or problems such as reduced capacitance due to a reduced effective electrode area. When the electrolyte inside the electrode body 702 is consumed and the electrolyte runs out, the electrolyte can be replenished inside the electrode body 702 through the electrode hole group 730, thereby preventing a decrease in capacity due to the expansion of the inactive area caused by the electrolyte running out at the end of the life of the electrode body 702.

[0088] As shown in FIG. 9 , the electrode body 703 in the third modification has five electrode hole groups 730 (electrode hole groups 730j, 730k, 730l, 730m, and 730n) formed in a flat portion 712 in the negative Y-axis direction, each of which has an electrode hole 731 (electrode holes 731j, 731k, 731l, 731m, and 731n). The five electrode hole groups 730 are aligned in the X-axis direction and arranged in a staggered manner in the Z-axis direction (a staggered arrangement). In this modification, the distance between two adjacent electrode hole groups 730 in the X-axis direction (first direction) is defined as a first distance A1, and the distance between two adjacent electrode hole groups 730 in the Z-axis direction (third direction) is defined as a second distance A2, with the first distance A1 being greater than the second distance A2. FIG. 9 illustrates two adjacent electrode hole groups 730, ie, electrode hole group 730j and electrode hole group 730k, with the distance between electrode hole group 730j and electrode hole group 730k in the X-axis direction as a first distance A1 and the distance in the Z-axis direction as a second distance A2. The first distance A1 is greater than 10 times the second distance A2. The same applies to the flat portion 712 in the positive Y-axis direction. The remaining configuration of this modification is similar to that of the above-described embodiment, and therefore detailed description will be omitted. This modification can achieve the same effects as the above-described embodiment. In particular, reducing the number of electrode hole groups 730 can reduce the risk of micro-short circuits due to burrs or contamination caused by the formation of the electrode holes 731, or problems such as reduced capacitance due to a reduced effective electrode area.

[0089] As shown in FIG. 10 , the electrode body 704 in Variation 4 has three electrode hole groups 730 (electrode hole groups 730o, 730p, and 730q) formed in a flat portion 712 in the negative Y-axis direction, each of which includes an electrode hole 731 (electrode holes 731o, 731p, and 731q). These three electrode hole groups 730 are elongated in the Z-axis direction and arranged side by side in the X-axis direction. In this variation, a first distance A1, which is the distance in the X-axis direction between two adjacent electrode hole groups 730 (electrode hole group 730o and electrode hole group 730p in FIG. 10 ), is greater than a second distance A2 (not shown because it is zero), which is the distance in the Z-axis direction (more than 10 times the second distance A2). In this variation, each electrode hole group 730 is formed in a strip shape extending in the Z-axis direction, and the width A3 of each electrode hole group 730 in the X-axis direction is approximately 20 mm. Within each electrode hole group 730, a circular or elliptical group of multiple electrode holes 731 is arranged in the Z-axis direction. In each electrode hole group 730, each layer 713a of the active material forming portion 713 may have at least one of the multiple electrode holes 731 shown in FIG. 10 formed therein, and any number of electrode holes 731 may be formed. In one electrode hole group 730, multiple electrode holes 731 may be arranged in a zigzag pattern. The same applies to the flat portion 712 in the positive Y-axis direction. The other configurations of this modified example are similar to those of the above-described embodiment, and therefore detailed description thereof will be omitted. This modified example can achieve the same effects as those of the above-described embodiment. In particular, by extending each electrode hole group 730 in the Z-axis direction, gas can be efficiently exhausted from the electrode holes 731 in the positive Z-axis direction, and electrolyte can be replenished into the electrode body 704 from the electrode holes 731 in the negative Z-axis direction.

[0090] As shown in FIG. 11 , the electrode body 705 in Modification 5 is formed with the electrode holes 731 (electrode holes 731a to 731i) that are provided in the electrode body 700 in the above embodiment. However, in this modification, only one electrode hole 731 is formed in one electrode hole group 730 in each layer 713a of the active material forming portion 713. In other words, in this modification, one of the three electrode holes 731 included in one electrode hole group 730 and provided in each layer 713a in the above embodiment is formed in each layer 713a. In FIG. 11 , as in FIG. 4 , the size of the electrode hole 731 is exaggerated. The electrode holes 731 formed in each layer 713a are densely packed within a predetermined region when viewed from the Y-axis direction, thereby forming the electrode hole group 730. The electrode hole group 730 formed in the electrode body 705 has a similar configuration to that shown in FIG. 5 due to the electrode holes 731 of each layer 713a being closely spaced, and therefore illustration and detailed description of the electrode hole group 730 are omitted. The other configurations of this modified example are similar to those of the above-described embodiment, and therefore detailed description is omitted. This modified example can achieve the same effects as the above-described embodiment. In particular, by reducing the number of electrode holes 731, it is possible to suppress the risk of micro-short circuits due to burrs or contamination associated with the formation of the electrode holes 731, or problems such as reduced capacity due to a reduced effective electrode area.

[0091] (Variation 6) The energy storage elements 10 may be used in an energy storage device. In this case, the technology of the present invention may be applied to at least one energy storage element 10 included in the energy storage device. FIG. 12 is a plan view showing an example of an energy storage device 30 according to Variation 6 of the present embodiment. As shown in FIG. 12 , a plurality of energy storage units 20 are arranged inside the energy storage device 30. The energy storage unit 20 is composed of a plurality of electrically connected energy storage elements 10. The energy storage device 30 may include a bus bar (not shown) that electrically connects the plurality of energy storage elements 10, a bus bar (not shown) that electrically connects the plurality of energy storage units 20, and the like. The energy storage unit 20 or the energy storage device 30 may include a state monitoring device (not shown) that monitors the state of one or more energy storage elements 10. The energy storage device 30 may include only one energy storage unit 20 (that is, the energy storage unit 20 may be referred to as an energy storage device).

[0092] (Other Modifications) In the above embodiment (and the above Modifications 1 to 6, and the same applies hereinafter), the electrode hole groups 730 are formed in both the flat portion 712 in the negative Y-axis direction and the flat portion 712 in the positive Y-axis direction of the electrode body main body 710. However, they may be formed in only one of the flat portions 712. The configurations of the electrode hole groups 730 (such as the arrangement position, shape, number, or number of electrode holes 731 in one electrode hole group 730) may be different between the flat portion 712 in the negative Y-axis direction and the flat portion 712 in the positive Y-axis direction. The electrode hole groups 730 may be formed in the curved portion 711 of the electrode body main body 710. In Modification 1, the electrode hole groups 730 may be formed in the curved portion 711 of the electrode body main body 710 in the positive Z-axis direction. In Modification 2, the electrode hole groups 730 may be formed in the curved portion 711 of the electrode body main body 710 in the negative Z-axis direction. When the electrode hole group 730 is formed in the curved portion 711, the second direction (the stacking direction of the multiple layers 713a) is defined as the Z-axis direction, or a direction between the Y-axis direction and the Z-axis direction, rather than the Y-axis direction.

[0093] In the above embodiment, the multiple electrode hole groups 730 provided in the electrode body main body 710 all have the same configuration, but any of the electrode hole groups 730 may have a different configuration.

[0094] In the above embodiment, the electrode holes 731 (electrode holes 740a, 750a) are all the same shape and size (opening area), but any of the electrode holes 731 may have a different shape or size (opening area). The size of the electrode hole 740a may be larger or smaller than the size of the electrode hole 750a.

[0095] In the above embodiment, the electrode hole group 730 includes a plurality of electrode holes 731 in all of the layers 713a included in the positive electrode plate 740 and the negative electrode plate 750. However, this is not limited to this. The electrode holes 731 may be provided in only half of the consecutive layers 713a of all of the layers 713a included in the positive electrode plate 740 and the negative electrode plate 750, or only one-third of the consecutive layers 713a, or only one-quarter of the consecutive layers 713a. Only one electrode hole 731 may be provided in any of the layers 713a included in the positive electrode plate 740 and the negative electrode plate 750. In other words, it is sufficient that one or more electrode holes 731 are provided in each of two or more consecutive layers 713a included in the positive electrode plate 740 and the negative electrode plate 750.

[0096] In the above embodiment, when priority is given to reducing time and costs during manufacturing, the opening area ratio may be set to more than 3%.

[0097] In the above embodiment, the maximum width of the predetermined region R1 as viewed in the Y-axis direction (second direction) is set to be smaller than 50 mm, but it may be set to be 50 mm or larger.

[0098] In the above embodiment, in two adjacent electrode hole groups 730, the first distance A1 is greater than 10 times the second distance A2, but it may be less than 10 times the second distance A2 or may be smaller than the second distance A2.

[0099] In the above embodiment, only one electrode hole group 730 may be formed in the electrode assembly 700 .

[0100] In the above embodiment, the liquid injection part 130 is arranged in the lid 120 of the container 100, but it may also be arranged in the container body 110. The liquid injection part 130 may be arranged in the long side wall part 111 or the bottom wall part 113 (a wall part extending in the winding axis direction of the electrode body 700) of the container body 110, or may also be arranged in the short side wall part 112. The gas exhaust valve 140 is arranged in the lid 120, but it may also be arranged in any wall part of the container body 110.

[0101] In the above embodiment, an inorganic coating layer may be provided on the separator 760 (separators 761, 762). The inorganic coating layer is a coating layer containing inorganic particles and a binder (binding material), and the inorganic coating layer may be coated on the entire or part of the surface (one or both sides) of the separator 760 with the binder. Any known material may be used as the binder. The inorganic coating layer preferably contains at least one of aluminum silicate, barium sulfate, and alumina (boehmite) as inorganic particles. The inorganic coating layer has a permeation area of ​​80 mm 300 seconds after the electrolytic solution is dropped. ２ or more. When a sheet-like member is disposed on the outer surface of the electrode assembly 700, an insulating sheet-like porous body may be disposed. The porous body preferably has larger pores (100 μm or more) than the separator 760, and thus has lower air permeability than the separator 760 (air permeability of 250 sec / 100 mL or less). The porous body is preferably formed from a nonwoven fabric such as a polymer nonwoven fabric made of PP. This improves the permeability of the electrolyte solution into the electrode assembly 700, allowing the number of electrode hole groups 730 or the number of electrode holes 731 formed in the electrode assembly 700 to be reduced.

[0102] In the above embodiment, the pair of terminals 300 are arranged to protrude from the container 100 in the positive direction of the Z axis, but there are no particular limitations on the protruding direction of the terminals 300. The pair of terminals 300 may protrude from the container 100 in either one direction in the X axis direction, or in both directions in the X axis direction.

[0103] In the above embodiment, the electrode body 700 has an elongated cylindrical shape (flat shape) including a curved portion 711 and a flat portion 712, but it may have a cylindrical or elliptical cylindrical shape, etc., and the shape is not particularly limited as long as it is a wound electrode body. In the electrode body 700, the active material non-forming portion 720 may be a tab portion (a portion where multiple tabs of electrode plates are stacked) protruding from a part of the electrode body main body portion 710. The electrode body 700 does not have to have a shape that is elongated in the X-axis direction.

[0104] Any combination of the components included in the above-described embodiment and its modifications is also included within the scope of the present invention. The various supplementary notes regarding the above-described embodiment may be applied to any of Modifications 1 to 6.

[0105] The present invention can be applied to an energy storage device such as a lithium ion secondary battery.

[0106] DESCRIPTION OF SYMBOLS 10 Energy storage element 20 Energy storage unit 30 Energy storage device 100 Container 130 Liquid injection portion 300 Terminal 600 Current collector 700, 701, 702, 703, 704, 705 Electrode body 710 Electrode body main body portion 711 Curved portion 712 Flat portion 713 Active material formed portion 713a Layer 720 Active material non-formed portion 730, 730a, 730b, 730c, 730d, 730e, 730f, 730g, 730h, 730i, 730j, 730k, 730l, 730m, 730n, 730o, 730p, 730q Electrode hole group 731, 731a, 731b, 731c, 731d, 731e, 731f, 731g, 731h, 731i, 731j, 731k, 731l, 731m, 731n, 731o, 731p, 731q, 740a, 750a Electrode hole 740 Positive electrode plate 741 Positive electrode current collector foil 742 Positive electrode active material layer 750 Negative electrode plate 751 Negative electrode current collector foil 752 Negative electrode active material layer 760, 761, 762 Separator

Claims

1. An electrode body, the electrode body comprising an electrode plate having a current collecting foil and an active material layer, the electrode plate being wound around a winding axis extending in a first direction, and comprising an active material forming section in which the active material layer is formed in a second direction of the current collecting foil perpendicular to the first direction, the active material forming section constituting a plurality of layers in the second direction, each of two or more consecutive layers among the plurality of layers having one or more electrode holes which are through holes penetrating both the current collecting foil and the active material layer, the opening area of ​​the electrode hole being 0.02 mm ２ the electrode body has an electrode hole group formed across each of the two or more layers when viewed from the second direction, in which the electrode holes of each of the layers are densely packed within a predetermined region.

2. The energy storage element according to claim 1, wherein the maximum width of the specified region when viewed from the second direction is less than 50 mm.

3. The energy storage element according to claim 1 or 2, wherein in the electrode hole group, each of the two or more layers has a plurality of the electrode holes.

4. The energy storage element according to claim 1 or 2, wherein the electrode plates comprise positive and negative electrode plates, and the electrode holes are provided in all of the layers of the active material forming portion of the positive electrode plate and the layers of the active material forming portion of the negative electrode plate in the electrode hole group.

5. The energy storage element according to claim 1 or 2, wherein the ratio of the total opening area of ​​all the electrode holes provided in the active material forming portion to the area of ​​the active material forming portion is 3% or less.

6. A storage element as described in claim 1 or 2, wherein two or more electrode hole groups are formed in the electrode body, and the distance between the electrode holes within the electrode hole group is smaller than the distance between two adjacent electrode hole groups when viewed from the second direction.

7. The storage element as described in claim 6, wherein a distance between the two electrode hole groups in the first direction is a first distance, and a distance between the two electrode hole groups in a third direction perpendicular to the first direction and the second direction is a second distance, and the first distance is greater than the second distance.

8. The energy storage element according to claim 7, wherein the first distance is greater than 10 times the second distance.

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