Energy storage devices

Abstract

Provided is an electrical storage device that is compact and can be manufactured easily, while allowing for use of higher voltages.　In an electrical storage device 1, a winding structure 20 comprises: a central electrode body 21 in which a first extending part 21b and a second extending part 21c extending from either side of a central portion 21a are wound around the central portion in the same direction; a first electrode body 22 electrically connected to a first external terminal 6 and extending toward an outer peripheral side from a vicinity of the central portion; a second electrode body 23 electrically connected to a second external terminal 7 and extending toward the outer peripheral side from a vicinity of the central portion; a first separator 24 disposed between the central electrode body and the first electrode body; and a second separator 25 disposed between the central electrode body and the second electrode body.

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device, and more particularly to an internal electrode structure of an electricity storage device suitable for an element (capacitor-type electricity storage device) having an electricity storage function, such as an electric double layer capacitor, an electrolytic capacitor, or any other type of capacitor. [Background technology]

[0002] In recent years, there has been an increasing demand for high-voltage electric double-layer capacitors and electrolytic capacitors. Known high-voltage products include modular products in which multiple cells (energy storage elements) are connected in series (for example, multiple elements connected in series via a substrate, four-terminal types in which multiple elements are grouped together and the terminals of each element protrude directly, and internal connection types in which multiple elements are connected internally). However, these modular products have problems such as a large number of parts, a complicated manufacturing process, increased costs such as processing fees, low profit margins, and large size.

[0003] On the other hand, known examples of high-voltage products with a single cell structure include those disclosed in the following Patent Documents 1 and 2. Patent Document 1 describes an electric double layer capacitor in which multiple cylindrical conductors are concentrically arranged radially inside and outside with separators sandwiched between them (see Figure 4). Patent Document 2 also discloses a high-voltage supercapacitor having a bipolar element with three or four electrodes including an intermediate electrode that is not connected to an external terminal, and in which these electrodes are wound with three or four separators sandwiched between them (see Figures 1 to 3B). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 59-101433 [Patent Document 2] Special Publication No. 2010-524200 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the energy storage device described in the above-mentioned conventional Patent Document 1, when multiple energy storage functional units are connected in series within a single cell structure, it is necessary to arrange multiple cylindrical energy storage functional units concentrically, which results in a complex structure, difficult manufacturing, and an increased number of parts making up each section.

[0006] On the other hand, in the conventional electricity storage device described in Patent Document 2, three or four or more electrode bodies including an intermediate electrode are wound with the same number of separators interposed therebetween, and therefore, similar to the device described in Patent Document 1, the internal electrode structure lacks symmetry, and the number of layers in the wound structure increases, which causes problems such as the size easily becoming large.

[0007] The present invention is intended to solve the above problems, and an object of the present invention is to realize an electricity storage device that can be made compact and easily manufactured while achieving a high voltage. [Means for solving the problem]

[0008] In order to solve the above problem, the present invention provides an electric storage device comprising a winding structure, and a first external terminal and a second external terminal connected to the winding structure, wherein the winding structure comprises: a band-shaped intermediate electrode body in which a first extending portion and a second extending portion extending on both sides of an intermediate portion in an extension direction are wound in the same direction around the intermediate portion, the first extending portion and the second extending portion respectively winding around the intermediate portion in the same direction; a first electrode body conductively connected to the first external terminal, and disposed between the first extending portion located on the inner periphery and the second extending portion located on the outer periphery, and extending from the vicinity of the intermediate portion toward the outer periphery; a second electrode body conductively connected to the second external terminal, and disposed between the second extending portion located on the inner periphery and the first extending portion located on the outer periphery, and extending from the vicinity of the intermediate portion toward the outer periphery; a first separator disposed between the intermediate electrode body and the first electrode body; and a second separator disposed between the intermediate electrode body and the second electrode body.

[0009] In this electricity storage device, the first and second extending portions are wound in the same direction on either side of the intermediate portion of the band-shaped intermediate electrode body, the first electrode body is disposed in one of a pair of radial gaps between the first and second extending portions via a first separator, and the second electrode body is disposed in the other radial gap via a second separator. Then, by providing a first external terminal conductively connected to the first electrode body and a second external terminal conductively connected to the second electrode body, two electricity storage functional units are configured in series between the first and second external terminals via the intermediate electrode body. In this way, the first storage functional unit composed of the intermediate electrode body and the first electrode body, and the second storage functional unit composed of the intermediate electrode body and the second electrode body are arranged in a manner that they rotate on both sides of the intermediate portion as the center, so that at least two storage functional units can be connected in series, allowing for a higher voltage.In addition, the first storage functional unit and the second storage functional unit are not in a relationship where one is arranged on the inside and the other on the outside when viewed in the radial direction of the winding structure, but are arranged in parallel along the first extension portion and the second extension portion that are wound in the same direction on both sides of the intermediate portion.This simplifies the internal electrode structure, and since the structure can be manufactured by developing conventional technology and winding a stack of electrode bodies and separators, it is easy to manufacture, requires a small number of parts, and can be made more compact in the radial direction than the conventional method of simply winding three or more electrode bodies via three or more separators.

[0010] In the present invention, it is preferable that the outer edge (side edge) of the intermediate electrode body protrudes outward in the axial direction of the winding structure beyond the first electrode body and the second electrode body of the winding structure. This allows the widthwise outer edge (side edge) of the intermediate electrode body to suppress radial electrical leakage at the outer periphery beyond the axial outer edge (side edge) of the winding structure, thereby improving the insulating performance of the device. It is particularly preferable that both outer edge portions (side edges) on both sides of the widthwise direction of the intermediate electrode body protrude outward in the axial direction beyond the first electrode body and the second electrode body of the winding structure. In these cases, it is preferable that the winding structure is disposed within a storage space, and the outer edge (side edge) of the intermediate electrode body abuts against the boundary of the storage space of the winding structure that is located outside in the axial direction. This further reduces electrical leakage at the outer periphery in the axial direction within the storage space, thereby further improving the insulating performance. Here, the outer edge of the intermediate electrode body is preferably insulating.

[0011] Furthermore, it is desirable that the outer edge (edge) of the intermediate electrode body be positioned radially outward of the first electrode body and the second electrode body of the winding structure. This configuration can reduce electrical leakage in the circumferential direction at the outer periphery beyond the radial outer edge (periphery) of the winding structure by the outer edge (edge) of the intermediate electrode body in the extension direction, thereby improving insulation performance. It is particularly desirable that both outer edge (end edges) on both sides of the extension direction of the intermediate electrode body be positioned radially outward of the first electrode body and the second electrode body of the winding structure. In these cases, it is desirable that the winding structure be placed within a storage space, and that the outer edge (edge) of the intermediate electrode body abut against the boundary of the storage space of the winding structure that is located radially outward. This further reduces electrical leakage in the radial outer periphery of the storage space, thereby further improving insulation performance. Here, it is desirable that the outer edge of the intermediate electrode body be insulating.

[0012] Furthermore, when an electrolyte is introduced into the wound structure, it is preferable that at least the portion of the intermediate electrode body sandwiched between the first separator and the second separator does not allow the electrolyte and its ions to pass through. Furthermore, separately from this, when an electrolyte is introduced into the wound structure, it is preferable that the outer edge portion (side edge or end edge) of the intermediate electrode body is less likely to retain the electrolyte or its ions or to allow the electrolyte or its ions to pass through than the main body portion of the intermediate electrode body. This further enhances the separation of the electrolyte at the outer side in the axial or radial direction of the wound structure, thereby further improving the insulation performance. Here, it is even more preferable that the outer edge portion (side edge or end edge) is a portion that does not allow the electrolyte or its ions to pass through. This makes it possible to further reliably reduce leakage current through the electrolyte and further improve the insulation performance of the device.

[0013] In the present invention, it is preferable that the first extension portion and the second extension portion, and the first electrode body and the second electrode body, are formed rotationally symmetrically around the intermediate portion. This substantially ensures electrical symmetry between a pair of serially connected power storage functional units formed between the intermediate electrode body and the first and second electrode bodies, thereby improving durability and stability of characteristics. In this case, it is also preferable that the first separator and the second separator are formed rotationally symmetrically around the intermediate portion.

[0014] In the present invention, the intermediate electrode body is preferably composed of a plurality of electrode body layers arranged with separator layers between them, thereby forming one or more electricity storage functional units between the plurality of electrode body layers, thereby enabling a further increase in voltage.

[0015] In the present invention, the wound structure preferably has a structure in which the outer peripheries of the first electrode body and the second electrode body are covered from the radially outer periphery by the outer periphery of the intermediate electrode body. This makes it possible to suppress electrical leakage beyond the intermediate electrode body between the first electrode body and the second electrode body, thereby further improving insulation performance. In this case, it is desirable that the outer peripheries of the first separator and the second separator interposed between the intermediate electrode body and the first electrode body and the second electrode body are present over a wider angular range on the radially outer periphery side than the first electrode body and the second electrode body, respectively.

[0016] In the present invention, it is preferable that the first separator is disposed in one of a pair of radially inner and outer gaps between the intermediate electrode body and the first electrode body, the gaps being located radially inside and outside, respectively, and that a first partition member having electrical insulation and electrolyte blocking properties is disposed in the other gap, and that the second separator is disposed in one of a pair of radially inner and outer gaps between the intermediate electrode body and the second electrode body, the gaps being located radially inside and outside, respectively, and that a second partition member having electrical insulation and electrolyte blocking properties is disposed in the other gap. In this case, it is preferable that the first partition member is disposed in the gap on one of the radially inner and outer sides, and the second partition member is disposed in the gap on the same side as the first partition member.

[0017] In this case, the partition member is preferably made of a synthetic resin. Examples of synthetic resins include polyphenylene sulfide (PPS), polyimide (PI), aramid (fully aromatic polyamide), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polypropylene (PP), and polyethylene (PE). The partition member is preferably in a sheet form for forming the wound structure. Furthermore, when an electrolyte is introduced into the wound structure, the partition member preferably does not allow the electrolyte and its ions to pass through. In particular, the partition member is preferably impermeable to and non-retaining of the electrolyte and its ions. For example, the partition member is preferably made of a sheet material without voids. This makes it possible to further reliably reduce leakage current through the electrolyte and further improve the insulating performance of the device. Desirable synthetic resin sheet materials from these viewpoints include fluororesin sheets such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (ETFE), and polychlorotrifluoroethylene (PCTFE). Furthermore, when the electrolyte is liquid, it is preferable that the surface of the partition member has a contact angle with the electrolyte of 80 degrees or more. In particular, it is desirable that the contact angle exceed 90 degrees (an obtuse angle).

[0018] In the present invention, it is preferable that the outer edge portions of the first partition member and the second partition member each protrude further in the axial direction of the winding structure than the intermediate electrode body and at least one of the first electrode body and the second electrode body. In this case, when the winding structure is placed in the storage space, it is preferable that the outer edge portions of the first partition member and the second partition member each abut (and more preferably are fixed to) a boundary of the storage space that is located outside in the axial direction.

[0019] In the present invention, it is preferable that the outer edge portions of the first partition member and the second partition member are respectively disposed radially outward of the intermediate electrode body and at least one of the first electrode body and the second electrode body in the winding structure. In this case, when the winding structure is disposed in a storage space, it is preferable that the outer edge portions of the first partition member and the second partition member each abut (preferably are fixed to) a boundary of the storage space that is located radially outward.

[0020] In the present invention, it is preferable that the inner edge of the first partition member is disposed so as to extend more inward than the inner edge of the first electrode body, and the inner edge of the second partition member is disposed so as to extend more inward than the inner edge of the second electrode body. In particular, it is preferable that the inner edge portions of the first partition member and the second partition member abut (and more preferably are fixed to) the inner periphery of the intermediate part of the intermediate electrode body, etc. [Effects of the Invention]

[0021] According to the present invention, it is possible to realize an electricity storage device that can be made compact and easily manufactured while achieving a high voltage. [Brief explanation of the drawings]

[0022] [Figure 1] 1A is a perspective view schematically showing the appearance of a first embodiment of an electricity storage device, and FIG. 1B is a perspective view schematically showing an internal winding structure. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the cross-sectional structure of the wound structure of the first embodiment. [Figure 3] FIG. 2 is an explanatory diagram schematically illustrating the overall configuration of the wound structure of the first embodiment before winding. [Figure 4] 2 is an enlarged cross-sectional view schematically showing the cross-sectional structure of each component of the winding structure of the first embodiment. FIG. [Figure 5] 3 is an enlarged cross-sectional view schematically showing a connection structure of a tab member for connecting an external terminal in the first electrode body or the second electrode body of the first embodiment. FIG. [Figure 6] 5A to 5D are explanatory views schematically showing a winding step for forming the wound structure of the first embodiment. [Figure 7] 1A is an explanatory cross-sectional view schematically showing the radial cross-sectional structure of the storage structure in the container of the wound structure of the first embodiment, and FIG. 1B is an explanatory cross-sectional view schematically showing the circumferential cross-sectional structure thereof. [Figure 8] 10A is a plan view schematically showing an expanded state of an intermediate electrode body of a second embodiment, and FIG. 10B is a perspective view schematically showing a wound structure. [Figure 9] 10A is an explanatory diagram schematically showing a radial cross-sectional structure of a storage structure in a container of a wound structure of a second embodiment, and FIG. 10B is an explanatory cross-sectional diagram schematically showing a circumferential cross-sectional structure thereof. [Figure 10] FIG. 10 is a schematic cross-sectional view showing a cross-sectional structure of a wound structure of a second embodiment. [Figure 11] FIG. 10 is a schematic cross-sectional view showing a cross-sectional structure of a wound structure according to a third embodiment. [Figure 12] FIG. 10 is a schematic cross-sectional view showing a cross-sectional structure of a wound structure of a fourth embodiment. [Figure 13] FIG. 10 is a schematic cross-sectional view showing a cross-sectional structure of a wound structure of a fifth embodiment. [Figure 14] FIG. 10 is a schematic cross-sectional view showing a cross-sectional structure of a wound structure of a sixth embodiment. [Figure 15] FIG. 13 is a schematic cross-sectional view showing a cross-sectional structure of a wound structure of a seventh embodiment. [Figure 16] 13A is a schematic cross-sectional view showing the cross-sectional structure of a wound structure of an eighth embodiment, and FIG. 13B is an explanatory view showing the overall configuration before winding. [Figure 17] 13A is a schematic cross-sectional view showing the cross-sectional structure of a wound structure of a ninth embodiment, and FIG. 13B is an explanatory view showing the overall configuration before winding. DETAILED DESCRIPTION OF THE INVENTION

[0023] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the embodiments of the present invention, an electric double layer capacitor will be used as an example of an electricity storage device. First, the overall configuration of a first embodiment of an electricity storage device according to the present invention will be described with reference to FIG.

[0024] First Embodiment FIG. 1A is a schematic perspective view of an electricity storage device 1 according to this embodiment, and FIG. 1B is a schematic perspective view of a wound capacitor element 2 housed inside the electricity storage device 1. The electricity storage device 1 includes a wound capacitor element 2 formed by introducing (impregnating) an electrolyte 5 into a winding structure 20 having a structure in which a strip material (sheet material) is wound, a bottomed (cylindrical) container 3 for housing the wound capacitor element 2, and a sealing body 4 for the container 3. The container 3 can be made of a metal such as aluminum. The sealing body 4 has through-holes through which the first external terminal 6 and the second external terminal 7 provided on the wound capacitor element 2 are inserted. The sealing body 4 seals the wound capacitor element 2 housed in the container 3 through the through-holes while allowing the first external terminal 6 and the second external terminal 7 to be led out. The sealing body 4 can be made of various synthetic rubbers, elastomers, or the like.

[0025] 2 is a schematic cross-sectional view showing a cross section of the winding structure 20. The winding structure 20 has a strip-shaped intermediate electrode body 21, which has a first extending portion 21b and a second extending portion 21c on either side of a middle portion 21a in the extending direction. The first extending portion 21b and the second extending portion 21c are both wound counterclockwise around the middle portion 21a in the illustrated example. A strip-shaped first separator 24 and a strip-shaped second separator 25 are arranged on the front and back sides of the intermediate electrode body 21, respectively, so as to cover the front and back sides of the intermediate electrode body 21.

[0026] Furthermore, when the intermediate region 21a is considered as the center, a strip-shaped first electrode body 22 is disposed in the gap between the first extending portion 21b on the inner periphery side and the second extending portion 21c on the outer periphery side. At this time, the first separator 24 is disposed between the first extending portion 21b and the first electrode body 22. In addition, the first separator 24 is disposed between the second extending portion 21c and the first electrode body 22. Meanwhile, a strip-shaped second electrode body 23 is disposed between the second extending portion 21c on the inner periphery side and the first extending portion 21b on the outer periphery side. At this time, the second separator 25 is disposed between the second extending portion 21c and the second electrode body 23. In addition, the second separator 25 is disposed between the first extending portion 21b and the second electrode body 23. The first separator 24 and the second separator 25 are both integrally formed on the front and back surfaces of the intermediate electrode body 21. That is, the first separator 24 and the second separator 25 are both continuous at a portion adjacent to the intermediate region 21a, and the portion along the first extending portion 21b and the portion along the second extending portion 21c are integrally formed. However, as in other embodiments described later, at least one of the first separator 24 and the second separator 25 may be separated at a portion adjacent to the intermediate region 21a, and the portion along the first extending portion 21b and the portion along the second extending portion 21c may be separate.

[0027] In the wound structure 20, the intermediate electrode assembly 21, first separator 24, first electrode 22, second separator 25, and second electrode 23 are wound in a stacked manner as shown in the illustrated example, and are finally held and fixed in the wound state by a holding member (e.g., a stop tape) 26 of the outermost layer. Note, however, that FIG. 2 is merely a schematic diagram and shows a different state from the actual wound state, for example, ignoring the reproducibility of the degree of adhesion between each layer and in many cases significantly reducing the number of turns. Furthermore, the outermost circle shown on the outside of the above structure originally indicates the boundary of the storage space of the wound structure 20, which corresponds to the container 3 and the holding member 26, i.e., the boundary of the space where the electrolyte 5 can exist in this embodiment. In other words, the circle shown in the figure is schematically shown as defining a space that has the storage function, shape-maintaining function, insulating function, etc. of the wound structure 20 required depending on the situation of the wound structure 20 having the above structure. Therefore, the shape (circular) itself is meaningless and is not limited. Furthermore, the pair of circles shown by the two-dot chain lines in the figure indicate the approximate positions of the joining portions (the portions where the tab members are formed) of the first electrode body 22 and the second electrode body 23 to be conductively connected to the first external terminal 6 and the second external terminal 7 shown in FIG. 1, respectively. The drawings attached to this specification, including but not limited to FIG. 2, should all be understood as schematic diagrams or enlarged views of portions, and the shapes depicted in the drawings do not directly represent the configuration of the actual embodiment. Here, the holding member 26 does not need to be formed from a single member but may be divided into multiple parts. Furthermore, the holding member 26 may be formed around the axis of the outer periphery of the winding structure 20 in a range of less than one revolution or more than one revolution. The fact that it does not need to be formed from a single member also applies to the other members constituting the winding structure 20.

[0028] 3 is a schematic diagram showing the arrangement of the intermediate electrode assembly 21, first separator 24, first electrode 22, second separator 25, and second electrode 23 in an expanded state. As can be seen from this expanded view, the first separator 24 is disposed between the intermediate electrode assembly 21 and the first electrode assembly 22. Furthermore, the second separator 25 is disposed between the intermediate electrode assembly 21 and the second electrode assembly 23.

[0029] 4 is a cross-sectional view schematically showing the detailed structure of each of the intermediate electrode body 21, first separator 24, first electrode 22, second separator 25, and second electrode 23. The intermediate electrode body 21 includes a current collector 211 made of metal foil or the like, and polarizable electrode layers 212, 213 made of a carbon-containing porous material or the like formed on both sides of the current collector 211. The first electrode body 22 includes a current collector 221 made of metal foil or the like, and polarizable electrode layers 222, 223 made of a carbon-containing porous material or the like formed on both sides of the current collector 221. The second electrode body 23 includes a current collector 231 made of metal foil or the like, and polarizable electrode layers 232, 233 made of a carbon-containing porous material or the like formed on both sides of the current collector 231.

[0030] The current collectors 211, 221, and 231 can be, for example, aluminum foils with a thickness of 20 μm to 50 μm. The polarizable electrode layers 212, 213, 222, 223, 232, and 233 can be formed, for example, by mixing activated carbon powder and carbon black with a binder to prepare a paste containing carbon fine particles, applying the paste to a thickness of 10 μm to 200 μm on both sides of the current collectors 211, 221, and 231, and then drying the applied paste. The polarizable electrode layer may be formed on only one of the current collectors 211, 221, and 231, rather than on both sides.

[0031] For example, a cellulose nonwoven fabric having a thickness of 20 μm to 100 μm can be used as the first separator 24 and the second separator 25. In addition to a cellulose nonwoven fabric, separators made of nonwoven fabrics of polyimide (PI), aramid (wholly aromatic polyamide), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polypropylene (PP), or polyethylene (PE) can also be used. The materials constituting the separators are not limited to the above-mentioned various nonwoven fabrics, and they may be made of, for example, paper made only from cellulose pulp.

[0032] The holding member (stop tape) 26 may be an adhesive tape made of resin such as polypropylene (PP), polyphenylene sulfide (PPS), or polyimide (PI), which has excellent solvent resistance, heat resistance, and insulating properties.

[0033] The electrolyte 5 introduced into the wound structure 20 can be any of a variety of electrolytes required depending on the type of electricity storage device. For example, in the case of the electric double layer capacitor of this embodiment, tetraethylammonium salt can be used as the cation, and boron tetrafluoride, bistrifluoromethylsulfonylimide, or the like can be used as the anion. A liquid or gel electrolyte can be used as the electrolyte. When configuring other capacitor-type electricity storage devices, such as an electrolytic capacitor, various electrolyte solutions using boric acid, adipic acid, maleic acid, benzoic acid, phthalic acid, salicylic acid, ammonia, triethylamine, tetramethylammonium hydroxide, or the like can be used as the electrolyte. Furthermore, the electrolyte 5 can also be a solid electrolyte such as manganese dioxide or an organic semiconductor, or a conductive polymer or other conductive solid (e.g., a conductive inorganic material).

[0034] Furthermore, by disposing a non-fluidic ion conductor between the intermediate electrode assembly and the first / second electrode assembly, it is possible to prevent contact and short-circuiting between the electrodes. Examples of non-fluidic ion conductors include a sheet-like structure in which a solid electrolyte is mixed with a support material such as a resin, and a gel-like electrolyte. The non-fluidic ion conductor in this case ensures ionic conductivity while also functioning as a separator to prevent contact and short-circuiting between the electrodes.

[0035] FIG. 5 schematically shows an example of a conductive connection portion of the first electrode body 22 to the first external terminal 6 and an example of a conductive connection portion of the second electrode body 23 to the second external terminal 7. Note that while FIG. 5 shows an example of the first electrode body 22 and the first external terminal 6, the second electrode body 23 and the second external terminal 7 can also be configured in a similar manner. As shown in the figure, at least one of the polarizable electrode layers 222, 223 (222 in the illustrated example) is partially removed from a portion of the first electrode body 22 to form a region 221a in which a portion of the current collector 221 is exposed. A tab member 214 conductively connected to the current collector 221 is joined to this region 221a. The position of this tab member 214 is set in advance together with the formation position of the region 221a so that it will be located in a predetermined position when the winding structure 20 is formed.

[0036] In this case, a protective film 215 that is insulating and has properties that prevent the passage of electrolytes and ions can be placed in the gap between the first separator 24 facing the tab member 214 and the intermediate electrode body 21. For example, in the illustrated example, the protective film 215 can be attached to the surface of the first separator 24 on the side of the intermediate electrode body 21. In this way, the separator is less likely to deteriorate, and the characteristics of the electricity storage device are less likely to deteriorate. The protective film 215 can be made of polyphenylene sulfide (PPS) having a thickness of, for example, 1 μm to 200 μm, preferably 5 μm to 50 μm.

[0037] 6A to 6D are schematic process diagrams illustrating steps for forming the wound structure 20. First, as shown in FIG. 6A, an intermediate electrode body 21 and a first separator 24 and a second separator 25, which are disposed on both the front and back surfaces of the intermediate electrode body 21, are arranged between a detachable winding core material 10 (a pair of winding cores 10a and 10b). At this time, the intermediate electrode body 21 and the first separator 24 and second separator 25 are held so as to be reeled out by left and right tape supply systems (not shown) (supply mechanisms including a supply reel with a rotational resistance applying mechanism, a tension roller, a guide roller, etc.; the same applies below). Thereafter, as shown in FIG. 6(b), the middle portion 21a of the intermediate electrode assembly 21 and the middle portions of the first separator 24 and second separator 25 are sandwiched between a pair of winding cores 10a and 10b, and by rotating the winding core 10 as shown in FIG. 6(c), the intermediate electrode assembly 21 and the first separator 24 and second separator 25 can be wound around the middle portion 21a sandwiched between the winding core 10 as shown in FIG. 6(d). At this time, the respective electrode bodies are unwound by left and right tape supply systems (not shown) as the winding core 10 rotates, so that the first electrode assembly 22 is wound inside the first separator 24 and the second electrode assembly 23 is wound inside the second separator 25. Finally, a holding member (winding stop tape) 26 is attached (adhered) to the outermost layer to maintain the wound state.

[0038] When the winding structure 20 is formed as described above, the first external terminal 6 and the second external terminal 7 are each joined to the corresponding tab member 214, thereby making a conductive connection, and are then inserted into the through-holes of the sealing body 4. Then, the winding structure 20 is housed in the container 3 while being impregnated with, for example, an electrolytic solution as the electrolyte 5, and finally, the opening of the container 3 is sealed with the sealing body 4.

[0039] 7A and 7B are schematic cross-sectional views showing the overall configuration of the electricity storage device 1 of this embodiment formed as described above. Here, FIG. 7A shows the relative positional relationship in the radial direction of the winding structure 20 (internal electrode structure) of the electricity storage device 1, and FIG. 7B shows the relative positional relationship around the axis (circumferential direction) of the winding structure 20 (internal electrode structure) of the electricity storage device 1. As shown in FIG. 7 , the interior (cell structure) of the electricity storage device 1 is provided with a first electricity storage functional unit formed by a portion where the intermediate electrode body 21 and the first electrode body 22 face each other with a first separator 24 interposed therebetween, and a second electricity storage functional unit formed by a portion where the intermediate electrode body 21 and the second electrode body 23 face each other with a second separator 25 interposed therebetween, in an introduction (impregnation) region of the electrolyte 5. These two power storage functional units are connected in series with each other between the first external terminal 6 and the second external terminal 7, making it possible to obtain a voltage nearly twice as high as in the case of a cell structure having only a single power storage functional unit. Note that although this embodiment is an electric double layer capacitor that stores electric charge using the electric double layers generated at the interfaces between the electrode bodies 21, 22, 23 and the electrolyte 5 as a dielectric, the above-mentioned series structure can also be used in electrolytic capacitors and other capacitors.

[0040] 2 , the first extension portion 21b and the second extension portion 21c are wound in the same direction on both sides of the intermediate region 21a of the strip-shaped intermediate electrode body 21, and the first electrode body 22 is disposed in one of a pair of radial gaps between the first extension portion 21b and the second extension portion 21c with a first separator 24 interposed therebetween, and the second electrode body 23 is disposed in the other of the pair of radial gaps with a second separator 25 interposed therebetween. Then, by providing a first external terminal 6 conductively connected to the first electrode body 22 and a second external terminal 7 conductively connected to the second electrode body 23, two electricity storage functional units are configured in series between the first external terminal 6 and the second external terminal 7 with the intermediate electrode body 21 interposed therebetween. In this case, the first power storage functional unit formed by the intermediate electrode body 21 and the first electrode body 22 and the second power storage functional unit formed by the intermediate electrode body 21 and the second electrode body 23 are not configured to overlap each other radially inside and outside, and therefore the first power storage functional unit and the second power storage functional unit are not in a relationship where one is located on the inside and the other on the outside when viewed in the radial direction. That is, in the winding structure 20 of this embodiment, the first electrode body 22 and the second electrode body 23 are arranged alternately or in parallel within an angular range around the intermediate portion 21a, thereby reducing bias in structural symmetry in the radial direction. Furthermore, the first electrode body 22 and the second electrode body 23 are configured to respectively follow the first extending portion 21b and the second extending portion 21c that are wound in the same direction on both sides of the intermediate portion 21a. Although the winding techniques are different, the present invention is able to develop conventional technology and manufacture the laminate of the electrode body and separator by winding it, which makes manufacturing easy and requires a small number of parts.

[0041] 2, the first extension portion 21b and the second extension portion 21c, as well as the first electrode body 22 and the second electrode body 23, are preferably formed rotationally symmetrically around the intermediate portion 21a of the intermediate electrode body 21. This allows the first power storage functional unit and the second power storage functional unit to have substantially the same structure, thereby substantially ensuring electrical symmetry between a pair of power storage functional units connected in series between the intermediate electrode body 21 and the first electrode body 22 and second electrode body 23. Furthermore, the above-mentioned configuration can reduce bias in the applied voltage, etc., thereby improving the durability and characteristic stability of the power storage device.

[0042] More specifically, in Patent Documents 1 and 2, structural issues such as differences in radial arrangement and dimensions between multiple power storage functional units result in significant differences in characteristics, potentially leading to problems with durability and characteristic stability. For example, if the leakage current between each power storage functional unit differs significantly, self-discharge can cause significant voltage variation over time. As a result, in power storage functional units with low leakage current, the voltage increases over time, eventually reaching the decomposition voltage of the solvent, potentially resulting in problems such as gas generation and increased resistance. Furthermore, when multiple power storage functional units are enclosed in a single container, the leakage current can increase due to short circuits between the electrodes caused by the electrolyte. This increased leakage current can further deteriorate the aforementioned durability and characteristic stability.

[0043] In contrast, in the energy storage device of this embodiment, the first energy storage functional unit composed of the intermediate electrode body 21 and the first electrode body 22 and the second energy storage functional unit composed of the intermediate electrode body 21 and the second electrode body 23 are arranged in parallel, rotating on both sides of the intermediate region 21a. This makes it easier to achieve uniformity and balance in the characteristics of the first energy storage functional unit and the second energy storage functional unit. In particular, by configuring the intermediate electrode body 21, the first electrode body 22, and the second electrode body 23 in rotational symmetry about the intermediate region 21a as described above, the characteristics of both units can be balanced. As a result, voltage is less likely to concentrate on one side, significantly improving durability and characteristic stability. In this case, it is even more effective to configure the first separator 24 and the second separator 25 in rotational symmetry with respect to each other.

[0044] 7 shows the outer periphery of the wound structure 20 covered by the holding member 26, with the inner surface of the container 3 disposed outside of that, but FIG. 7 only shows a schematic configuration, and even if the outer periphery is configured as shown, it is merely an example. For example, unlike the configuration shown, a gap may be provided between the container 3 and the electrolyte 5, or the inner surface of the container 3 may be coated with an insulating coating. Furthermore, because FIG. 7 is a schematic diagram, it is illustrated as if the first separator 24, the second separator 25, and the intermediate electrode body 21 are not disposed radially outside the first electrode body 22 and the second electrode body 23, in a manner that does not match the cross-sectional structure shown in FIG. 2. However, such a configuration of the outer periphery can also be considered to be configured so that the first separator 24 is arranged radially outside the first electrode body 22, and / or the second separator 25 is arranged radially outside the second electrode body 23, corresponding to the cross-sectional structure shown in Figure 2, or so that the intermediate electrode body 21 is arranged further radially outside the above-mentioned separators 24, 25.

[0045] Second Embodiment Next, an electricity storage device according to a second embodiment of the present invention will be described with reference to Figures 8 to 10. In this second embodiment, the configuration is the same as that of the first embodiment except for the wound capacitor element 2', and the overall configuration of the winding structure 20' shown in Figure 8 and the schematic cross-sectional structure of the winding structure 20' shown in Figure 10 can also be basically configured in the same way as the winding structure 20, so parts that can be configured in the same way are given the same reference numerals and their description will be omitted.

[0046] In this second embodiment, as shown in FIG. 8(a), of the outer peripheral portion 21d of the intermediate electrode body 21′, a side edge 21f, which is the outer peripheral portion in the width direction, is configured to protrude further outward in the axial direction of the winding structure 20′ than the first electrode body 22 and the second electrode body 23 (see FIG. 9(a)). Here, it is more preferable that the side edge 21f be arranged in the same axial position as the outer peripheral positions of the first separator 24 and the second separator 25, or be configured to protrude further outward in the axial direction than the outer peripheral positions. Note that, unlike this embodiment, the side edge 21f may be arranged in the same axial position as the outer peripheral positions of the first separator 24 and the second separator 25, or be configured to protrude further outward in the axial direction than the outer peripheral positions, regardless of the relationship between the first electrode body 22 and the second electrode body 23, thereby improving the separation of the electrolyte and thereby reducing the leakage current between a pair of power storage functional units.

[0047] Furthermore, the edge 21e, which is the outer edge in the extension direction of the outer peripheral portion 21d of the intermediate electrode body 21′, is configured to be positioned radially outward of the first electrode body 22 and the second electrode body 23 (see FIG. 10 ). Here, it is more preferable that the edge 21e be positioned at the same radial position as the outer peripheral positions of the first separator 24 and the second separator 25, or positioned radially outward of the outer peripheral positions. Note that, unlike the present embodiment, the edge 21e can be positioned at the same radial position as the outer peripheral positions of the first separator 24 and the second separator 25, or positioned radially outward of the outer peripheral positions, regardless of the relationship between the first electrode body 22 and the second electrode body 23, thereby improving the separation of the electrolyte and thereby reducing the leakage current between a pair of power storage functional units.

[0048] The two-dot chain lines shown in Figure 8(a) indicate the outer edges of the first electrode body 22 and the second electrode body 23. These outer edges also indicate reference positions that indicate the relative positional relationship between the end edge 21e and the side edge 21f of the outer edge portion 21d of the intermediate electrode body 21' in the winding structure 20'. These points will be explained in more detail later. In the illustrated example, the outer edge portion 21d of the intermediate electrode body 21' is formed in a frame shape outside the polarizable electrode layers 212, 213 of the intermediate electrode body 21'. Furthermore, the end edge 21e and the side edge 21f are both formed on both sides in the extension direction and width direction.

[0049] In this embodiment, the outer edge portion 21d is formed on the outside of the main body portion consisting of the electrode region made up of the current collector 211 and the polarizable electrode layers 212, 213. The outer edge portion 21d is not particularly limited, but is preferably made of a portion that is less able to retain the electrolyte 5 and / or its ions or less able to pass the electrolyte 5 and / or its ions than the main body portion (the laminated structure of the current collector 211 and the polarizable electrode layers 212, 213) that makes up the intermediate electrode body 21′. The outer edge portion 21d can be, for example, an extension of a portion that is less able to retain the electrolyte 5 and / or its ions or less able to pass the electrolyte 5 and / or its ions than the (porous) polarizable electrode layers 212, 213 that are more able to retain the electrolyte 5 and / or its ions. For example, the outer edge portion 21d can be made of a synthetic resin sheet, film, tape, or the like, as described below. The outer edge portion 21d may be formed by exposing the current collector 211 without or after peeling off the polarizable electrode layers 212, 213, which easily retain the electrolyte 5 and / or its ions. Furthermore, the outer edge portion 21d may have the same structure as the laminated structure of the current collector 211 and the polarizable electrode portions 212, 213 of the main body portion, but the current collector 211, which serves as the core material, may be thicker or the polarizable electrode layers 212, 213 may be thinner than those of the main body portion. As a result, the outer edge portion 21d may be less able to retain the electrolyte 5 and / or its ions or less able to pass the electrolyte 5 and / or its ions than the main body portion. These outer edge portions 21d are provided to reduce electrical leakage from the outer periphery of the wound structure 20′. In this embodiment, the outer edge portions 21d are provided particularly to enhance the isolation between the first electrode body 22 side and the second electrode body 23 side with respect to the electrolyte 5 and its ions introduced into the wound structure 20′.

[0050] Furthermore, by making the outer edge 21d (end edge 21e, side edge 21f) an insulator, the periphery of the intermediate electrode body 21′ can be covered with an insulator, thereby suppressing internal conduction between the first electrode body 22 and the second electrode body 23, improving insulation performance, and further effectively reducing leakage current. Examples of such insulating, different-property edge 21d include sheets, films, tapes, and the like made of polyphenyl sulfide (PPS), polyimide (PI), aramid (wholly aromatic polyamide), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polypropylene (PP), or polyethylene (PE). These materials are not only insulating but also impermeable to the electrolyte 5 and ions, further improving the characteristics (insulation performance) of the electricity storage device, such as reducing leakage current.

[0051] FIG. 9, in comparison with FIG. 7 showing the first embodiment, is a diagram (a) schematically illustrating the relative positional relationship in the radial direction of the internal electrode structure of the power storage device 1 of the second embodiment, and a diagram (b) schematically illustrating the relative positional relationship around the axis of the electrode structure of the power storage device. As shown in these figures, the side edge 21f of the outer edge portion 21d facilitates the division of the electrolyte 5 in the radial direction of the winding structure 20′, thereby suppressing a decrease in insulating performance via the electrolyte 5. In particular, as shown in the figure, the side edge 21f abuts against the inner surface of the container 3 or the holding member 26 disposed therein, or the sealing body 4, the sealing resin, etc. (i.e., the boundary of the storage space of the winding structure 20′, i.e., the boundary of the space where the electrolyte 5 may exist in this embodiment). In this way, the side edge 21f abuts against the boundary located outside the axial direction of the storage space of the winding structure 20′, thereby substantially dividing the storage space in the radial direction of the winding structure 20′, thereby further improving insulating performance.

[0052] In particular, since electrolyte 5 tends to pool outside the axial direction of the winding structure 20' (particularly at the bottom), the side edges 21f are effective in dividing the electrolyte 5. Here, in the illustrated example, the side edges 21f are provided on both sides in the width direction of the intermediate electrode body 21', but only one of them may be provided. However, it goes without saying that it is more effective if the pair of side edges 21f on both sides in the width direction both protrude or both abut against the boundary (the inner surface, etc.) as in the illustrated example.

[0053] As shown in FIG. 10 , the edge 21e of the outer edge portion 21d is disposed radially outward of the winding structure 20′ relative to the first electrode body 22, the second electrode body 23, and the first separator 24 and the second separator 25. This peripheral arrangement of the edge 21e can further enhance the circumferential separation of the electrolyte 5 in the winding structure 20′, as shown in FIG. 10 . In particular, as shown in the figure, the edge 21e abuts against the container 3 or a holding member 26 disposed inside the container 3, or the inner surface of the sealing body 4, sealing resin, or the like (the boundary of the storage space of the winding structure 20′, i.e., the boundary of the space in which the electrolyte 5 can exist in this embodiment), on the radially outer side (outer peripheral side) of the winding structure 20′, thereby further enhancing the circumferential separation of the electrolyte 5. Here, as shown in FIG. 8 , the edge 21e is provided on both sides of the intermediate electrode body 21′ in the extension direction, but it may be provided on only one side. However, it goes without saying that it is more effective if, as in the illustrated example, a pair of end edges 21e on both sides of the extension direction of the intermediate electrode body 21' are both positioned on the outer periphery or both abut against the above-mentioned boundary (the above-mentioned inner surface, etc.).

[0054] In this embodiment, the outer edge 21d of the intermediate electrode body 21′, such as the side edge 21f shown in FIG. 9 and the edge 21e shown in FIG. 10, is formed of a different structure and / or material from the main body portion in the illustrated example. However, even when the entire intermediate electrode body 21 is formed of a uniform structure and / or uniform material as in the first embodiment, the leakage current is reduced and the insulation performance is improved by arranging the outer edge of the intermediate electrode body 20 in such a manner that the edge shown by the two-dot chain line in FIG. 2 is located on the radial outer periphery or the side edge shown by the two-dot chain line in FIG. 7 protrudes in the axial direction. In this case, if a portion having a material or structure that has a high separating effect for the electrolyte 5, such as the current collector 211 that is the core material of the intermediate electrode body 20, reaches the end surface of the outer edge 21d (edge ​​21e or side edge 21f) and is exposed at the end surface of the outer edge 21d, the leakage current reduction effect can be more effectively obtained. In particular, if the above-mentioned portion is configured to be relatively thicker than the surface layer portion of the polarizable electrode layer or the like, it is more effective because it also enhances the separation from the electrolyte 5. As in the present embodiment, it is more desirable for the side edges of the intermediate electrode body 20 to abut against the outer boundary in the axial direction of the storage space, or for the end edges to abut against the outer boundary in the radial direction of the storage space.

[0055] In this embodiment, as shown in FIG. 9( a), of the outer peripheral portion 21d of the intermediate electrode body 21′, the side edge 21f, which is the outer edge in the width direction, is positioned axially outward of the first electrode body 22 and the second electrode body 23, and the first separator 24 and the second separator 25. However, if the side edge 21f protrudes outward in the axial direction of the winding structure 20′ more than at least one of the first electrode body 22 and the second electrode body 23, it is considered effective in reducing leakage current between a pair of power storage functional units and improving insulation performance. Furthermore, if the side edge 21f protrudes outward in the axial direction of the winding structure 20′ more than at least one of the first separator 24 and the second separator 25, it is considered effective in reducing leakage current between a pair of power storage functional units and improving insulation performance.

[0056] In this embodiment, as shown in FIG. 10 , the edge 21e, which is the outer edge in the extension direction of the outer edge 21d of the intermediate electrode body 21′, is positioned radially outward of the winding structure 20′ relative to the first electrode body 22 and the second electrode body 23. However, if the edge 21e is positioned radially outward of at least one of the first electrode body 22 and the second electrode body 23, it is possible to increase the separation between the pair of power storage function units, which is thought to be effective in improving insulation performance. Furthermore, if the edge 21e is positioned radially outward of at least one of the first separator 24 and the second separator 25, it is possible to increase the separation between the pair of power storage function units, which is thought to be effective in improving insulation performance.

[0057] When at least one of the intermediate electrode body 21′, the first electrode body 22, and the second electrode body 23 abuts against the boundary of the storage space (the inner surface, etc.), the boundary (the inner surface, etc.) is preferably insulating. However, even if the boundary (the inner surface, etc.) is conductive, it is sufficient to avoid any of the following: a plurality of different electrode bodies abutting against the same member that constitutes the boundary; a situation in which the first electrode body 22 and the electrolyte in the second power storage functional unit abut against the same member that constitutes the boundary; or a situation in which the second electrode body 23 and the electrolyte in the first power storage functional unit abut against the same member that constitutes the boundary.

[0058] <Third embodiment> Next, with reference to FIG. 11 , an electricity storage device according to a third embodiment of the present invention will be described. In this embodiment, the configuration other than the first separator 24′ and the second separator 25′ can be similar to that of the first or second embodiment. Therefore, the same reference numerals are used for similarly configured parts, and their description will be omitted. In this embodiment, the first separator 24′ is formed by providing a cutout portion 24a′ adjacent to the vicinity of the middle portion 21a of the intermediate electrode body 21, thereby dividing the separator 24′ into a separator portion 24b′ along the first extension portion 21b and a separator portion 24c′ along the second extension portion 21c. Furthermore, the second separator 25′ is formed by providing a cutout portion 25a′ adjacent to the vicinity of the middle portion 21a of the intermediate electrode body 21, thereby dividing the separator 25b′ along the first extension portion 21b and a separator portion 25c′ along the second extension portion 21c.

[0059] The above-described configuration does not pose a problem as long as the insulation between the intermediate electrode body 21 and the first electrode body 22 and the insulation between the intermediate electrode body 21 and the second electrode body 23 are ensured. In this case, even if the notched portions 24a' and 25a' are provided, insulation performance is ensured as long as the inner ends of the separator portions 24b', 24c', 25b', and 25c' are positioned closer to the center (closer to the intermediate region 21a) than the inner ends of the first electrode body 22 and the second electrode body 23, i.e., as long as the inner end portions of the first separator 24b' and the second separator 25' extend over an angular range that extends beyond the inner ends of the first electrode body 22 and the second electrode body 23. Furthermore, an insulator or an extended portion of the insulator may be disposed at the inner ends of the first electrode body 22 and the second electrode body 23 using the same structure and material as the different-characteristics edge portion 21d having the above-described insulating performance.

[0060] 11, leakage current can be reduced and insulation performance can be improved by having the outer edge (side edge) of the intermediate electrode body 20 protrude outward in the axial direction of the winding structure 20 and / or by locating the outer edge (edge) on the radial outside of the winding structure 20. In these cases, it is more desirable to have the outer edge abut against the outer boundary (the above-mentioned inner surface, etc.) in the axial and / or radial direction of the accommodation space of the winding structure 20.

[0061] <Fourth embodiment> Next, with reference to FIG. 12 , an electricity storage device according to a fourth embodiment of the present invention will be described. In this embodiment, the configuration other than the intermediate electrode body 21, the first separator 24, and the second separator 25 can be the same as in the first to third embodiments. Therefore, the same reference numerals are used for similarly configured parts, and their description will be omitted. In this embodiment, adhesive layers 27, 28 are provided between the intermediate electrode body 21 and the first separator 24 and the second separator 25, thereby integrally configuring the intermediate electrode body 21, the first separator 24, and the second separator 25. This integral intermediate electrode body 21, the first separator 24, and the second separator 25 are then wound together with the first electrode body 22 and the second electrode body 23 as described above to form the wound structure 20. Here, the adhesive layers 27, 28 can be made of various adhesive materials or bonding materials. In this way, the winding process is facilitated and the winding pattern of the wound structure can be formed in an orderly and reproducible manner. In the illustrated example described above, the intermediate electrode body 21 is configured to be integrated with the first separator 24 and the second separator 25. However, for example, in addition to or instead of the above configuration, a configuration in which the first separator 24 is integrated with the first electrode body 22 and / or a configuration in which the second separator 25 is integrated with the second electrode body 25 may be adopted.

[0062] 12, leakage current can be reduced and insulation performance can be improved by having the outer edge (side edge) of the intermediate electrode body 20 protrude outward in the axial direction of the winding structure 20 and / or by locating the outer edge (edge) on the radial outside of the winding structure 20. In these cases, it is more desirable to have the outer edge abut against the outer boundary (the above-mentioned inner surface, etc.) in the axial and / or radial direction of the accommodation space of the winding structure 20.

[0063] Fifth Embodiment Next, with reference to FIG. 13 , an electricity storage device according to a fifth embodiment of the present invention will be described. In this embodiment, the configuration other than the intermediate electrode body 31 (intermediate portion 31a, first extension portion 31b, second extension portion 31c) can be configured similarly to the first to fourth embodiments. Therefore, the same reference numerals are used for similarly configured parts, and their description will be omitted. The intermediate electrode body 31 of this embodiment is configured by multiple electrode body layers 31h, 31i arranged in the thickness direction with a separator layer 31g interposed between them. In the illustrated example, two electrode body layers 31h, 31i are arranged inside and outside with one separator layer 31g interposed between them, but three or more electrode body layers may be arranged with a separator layer interposed between them. In this way, since the intermediate electrode body 31 is configured by multiple electrode bodies, it is possible for the intermediate electrode body 31 alone to constitute one or more electricity storage functional units (third electricity storage functional units), thereby enabling even higher voltages. Here, the separator layer 31g can be made of the same material as the first separator 24 and the second separator 25.

[0064] 13, by having the outer edge (side edge) of the intermediate electrode assembly 20 protrude outward in the axial direction of the winding structure 20 and / or by disposing the outer edge (edge) radially outward of the winding structure 20, leakage current can be reduced and insulation performance can be improved. In these cases, it is more desirable to have the outer edge abut against the outer boundary (the above-mentioned inner surface, etc.) in the axial direction and / or radial direction of the accommodation space of the winding structure 20. In this case, it is desirable to configure each of the multiple electrode body layers 31h, 31i in a stepped manner so that the separator layer 31g extends to the outer periphery of the winding structure 30 and the separator layer 31g and the electrode body layers 31h, 31i abut against the boundary (the above-mentioned inner surface, etc.) of the accommodation space.

[0065] Sixth Embodiment Next, with reference to FIG. 14, an electricity storage device according to a sixth embodiment of the present invention will be described. In this embodiment, the configuration other than the intermediate electrode body 41 (the intermediate portion 41a, the first extension portion 41b, and the second extension portion 41c) can be configured similarly to the first to fifth embodiments. Therefore, the same reference numerals are used for similarly configured parts, and their description will be omitted. In this embodiment, as shown in FIG. 14, the first electrode body 22 and the second electrode body 23 are respectively covered from the outer periphery in the radial direction by outer peripheries 41j and 41k of the intermediate electrode body 41, via the first separator 24 and the second separator 25, respectively. In other words, the outer peripheries 41j and 41k of the first extension portion 41b and the second extension portion 41c are formed over a wider angular range on the outer periphery side than the outer peripheries of the first electrode body 22 and the second electrode body 23. In this way, the first electrode body 22 and the second electrode body 23 are surrounded by the intermediate electrode body 41 over the entire circumference (all angular range) when viewed in the radial direction. This makes it possible to suppress electrical leakage beyond the intermediate electrode body 41 between the first electrode body 22 and the second electrode body 23, thereby further improving the insulating characteristics. In particular, as in the illustrated example, it is desirable that the outer peripheral portions 41j, 41k of the intermediate electrode body 41 abut against the boundary of the accommodation space (such as the inner surface). Furthermore, in addition to or instead of the above configuration, if the outer peripheral portions 41j, 41k (e.g., their ends) of the intermediate electrode body 41 abut against (hold or adhere) the intermediate portions of the intermediate electrode body 41 arranged radially inward of the outer peripheral portions 41j, 41k in the ranges 41L, 41M surrounded by the two-dot chain lines in the illustration, the effect of confining the electrolyte 5 inside the wound structure can be strengthened, thereby further improving the insulating performance.

[0066] In this case, in order to ensure insulation between the electrodes, it is desirable that, as in the illustrated example, the outer peripheries of the first separator 24 and the second separator 25 are interposed between the intermediate electrode body 41 and the first electrode body 22 and the second electrode body 23 over a wider angular range on the outer periphery side than the first electrode body 22 and the second electrode body 23. Note that, in order to ensure insulation of the intermediate electrode body 41, the outer peripheries of the first separator 24 and the second separator 25 may be configured to extend further outward from the intermediate electrode body 41 over a wider angular range, or insulation may be ensured by the boundary of the storage space (the above-mentioned inner surface, etc.).

[0067] Seventh Embodiment Next, with reference to FIG. 15 , an electricity storage device according to a seventh embodiment of the present invention will be described. In this embodiment, the configuration other than the intermediate electrode body 21″ (intermediate region 21a, first extension portion 21b″, second extension portion 21c″), first electrode body 22″, and second electrode body 23″ can be configured in the same manner as in the first to sixth embodiments. Therefore, the same reference numerals are used for similarly configured parts, and descriptions thereof will be omitted. In this embodiment, as shown in FIG. 15 , in the first extension portion 21b″ and the second extension portion 21c″ of the intermediate electrode body 21″, the polarized electrode layer is not formed on the outer peripheral surface that does not face the first electrode body 22″ and the second electrode body 23″ within the outermost angular range of the outer periphery of the wound structure, and therefore, outer peripheral exposed regions 21bs, 21cs are provided in which the current collector 211 is exposed. In addition, in the first electrode body 22″, the polarized electrode layer is not formed on the outer peripheral surface that does not face the intermediate electrode body 21″ within the outermost angular range of the outer periphery of the wound structure, so that an outer peripheral exposed region 22s is provided where the current collector 221 is exposed. Furthermore, in the second electrode body 23″, the polarized electrode layer is not formed on the outer peripheral surface that does not face the intermediate electrode body 21″ within the outermost angular range of the outer periphery of the wound structure, so that an outer peripheral exposed region 23s is provided where the current collector 231 is exposed.

[0068] With the above-described configuration, it is possible to suppress deterioration in durability and variations in durability between the front and back sides, which occur when polarized electrode layers facing the electrodes and polarized electrode layers not facing the electrodes are present on the front and back sides of each electrode body 21", 22", 23". That is, in this embodiment, polarized electrode layers are not formed on the parts of each electrode body 21", 22", 23" that do not face other electrode bodies, and therefore it is possible to avoid problems caused by deterioration in durability. However, the ends of both electrode bodies may be aligned at the same angular position so that there is no portion on the outer periphery of the wound structure where the intermediate electrode body 21'' does not face the first electrode body 22'' and the second electrode body 23''. For example, if the outer periphery ends of the first electrode body 22'' and the second electrode body 23'' are aligned at the angular position of the outer periphery ends of the first extending portion 21b'' and the second extending portion 21c'' of the intermediate electrode body 21'', there is no need to provide the above-mentioned outer periphery exposed region in the first electrode body 22'' and the second electrode body 23'', and it is sufficient to form the outer periphery exposed regions 21bs, 21cs only in the first extending portion 21b'' and the second extending portion 21c''.

[0069] Eighth Embodiment Next, an eighth embodiment of the present invention will be described with reference to FIG. 16. This embodiment differs from the previously described embodiments in that partition members 56 and 57 are disposed in a portion of the internal structure of a winding structure 50. However, other configurations can be formed similarly to the previously described embodiments and the configurations described therein. Therefore, a description of similar configurations that can be adopted to the extent that they do not cause any particular problems will be omitted. As shown in FIG. 16(a), the winding structure 50 of this embodiment includes components that can be configured similarly to the previously described embodiments, such as an intermediate electrode assembly 51 (intermediate portion 51a, first extension portion 51b, second extension portion 51c), a first electrode assembly 52, a second electrode assembly 53, a first separator 54, a second separator 55, a container 3, a holding member 26, a sealing body 4 (not shown), an electrolyte 5 (not shown), a first external electrode 6, and a second external electrode 7.

[0070] However, in this embodiment, the first separator 54 is disposed between the first electrode body 52 and the second extending portion 51c, similar to the first separator 24 in each of the above-described embodiments, but is not disposed between the first electrode body 52 and the first extending portion 51b, unlike the first separator 24 in each of the above-described embodiments. Furthermore, the second separator 55 is disposed between the second electrode body 53 and the first extending portion 51b, similar to the second separator 25 in each of the above-described embodiments, but is not disposed between the second electrode body 53 and the second extending portion 51c, unlike the second separator 25 in each of the above-described embodiments.

[0071] A feature of this embodiment is that in the winding structure 50, a partition member 56 is disposed between the first electrode body 52 and the first extension portion 51b, and a partition member 57 is disposed between the second electrode body 53 and the second extension portion 51c. These partition members 56, 57 are disposed in one of the radially inner and outer gaps between the intermediate electrode body 51 and the first electrode body 52 or the second electrode body 53 (in the illustrated example, both are the radially outer gaps), thereby functioning as an electrically insulating barrier so that an opposing region between the electrodes is formed only in the other gap between the intermediate electrode body 51 and the first electrode body 52 or the second electrode body 53. For this reason, the partition members 56, 57 are configured with a material and shape (structure) that minimizes leakage current between the intermediate electrode body 51 and the first electrode body 52 or the second electrode body 53 in one of the gaps and ensures voltage resistance characteristics. For this reason, the partition members 56, 57 are preferably made of a material that has electrolyte blocking properties and electrical insulation. That is, the partition members 56, 57 have blocking properties that prevent the passage of electrolytes (ions) and are themselves electrically insulating. The partition members 56, 57 are preferably made of a synthetic resin. Examples of synthetic resins include polyphenylene sulfide (PPS), polyimide (PI), aramid (wholly aromatic polyamide), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polypropylene (PP), and polyethylene (PE).

[0072] Furthermore, the partition members 56, 57 are preferably in a sheet form as a preferred form for constructing the wound structure 50. Furthermore, when an electrolyte is introduced into the wound structure, the partition members preferably do not allow the electrolyte and its ions to pass through. In particular, it is desirable for the partition members to be impermeable to and non-retaining of the electrolyte and its ions. For example, the partition members may be made of a sheet material without voids. This makes it possible to further reliably reduce leakage current through the electrolyte and further improve the insulating performance of the device. Examples of desirable synthetic resin sheet materials from these perspectives include fluororesin sheets such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (ETFE), and polychlorotrifluoroethylene (PCTFE).

[0073] As will be described later, when a highly fluid electrolyte such as an electrolytic solution is used, it is desirable that the partition members 56, 57 have a surface that repels the electrolyte. In this case, for example, the fluororesin sheet described above is a preferred surface material. Alternatively, a surface layer that repels the electrolyte may be formed on the surface by coating or the like. The degree of electrolyte repellency is preferably such that the contact angle θ with the target electrolyte (liquid) is 80 degrees or more, and particularly, an angle exceeding 90 degrees (obtuse angle) is desirable. Typically, the contact angle of fluororesin is approximately 100 degrees. By providing the surfaces of the partition members 56, 57 with low electrolyte wettability, even if there is a small gap between the partition members 56, 57 and the surrounding components, the electrolyte is less likely to cross the storage area defined by the partition members 56, 57 (it is less likely to pass through the gap), thereby improving insulation properties such as reducing leakage current.

[0074] As described above, the partition members 56, 57 are made of electrically insulating sheets with no voids. When the partition members 56, 57 are made of synthetic resin sheets as described above, in order to ensure electrical insulation and electrolyte (ion) impermeability while being as compact as possible, the thickness is preferably in the range of 5 μm to 1 mm, and more preferably in the range of 10 μm to 500 μm. In particular, it is even more desirable that the thickness be in the range of 20 μm to 200 μm. If the thickness is below the above ranges, the electrolyte and its ions will easily pass through, while if the thickness is above the above ranges, the winding ability during manufacturing will be poor, which will be disadvantageous in making the electricity storage device compact.

[0075] Incidentally, in this embodiment as well, as described above, the intermediate electrode body 51, the first electrode body 52, and the second electrode body 53 can be configured with a laminated structure of current collectors 511, 521, and 531 and polarizable electrode layers 512, 513, 522, and 532. However, in this embodiment, as described above, the partition member 56 is interposed between the first electrode body 52 and the first extending portion 51b, and the partition member 57 is interposed between the second electrode body 53 and the second extending portion 51c. Therefore, as shown in Fig. 16(b), the opposing regions of the intermediate electrode body 51, the first electrode body 52, and the second electrode body 53 that exhibit the electricity storage function are only on the sides where the first separator 54 and the second separator 55 are interposed (the inner peripheral side in the illustrated example), and no opposing regions that exhibit the electricity storage function are configured on the sides where the partition members 56 and 57 are interposed (the outer peripheral side in the illustrated example). For this reason, in this embodiment, polarizable electrode layers 512, 513, 522, and 532 are laminated only on the opposing region side, and no polarizable electrode layer is formed on the side of partition members 56 and 57. This makes it possible to reduce the non-opposing region of the polarizable electrode layers, thereby suppressing deterioration in durability due to the non-opposing region and variations in durability between the front and back sides.

[0076] According to the present embodiment, by providing electrically insulating partition members 56, 57 with electrolyte blocking properties in one of the two gaps between the intermediate electrode body 51 and the first and second electrode bodies 52 and 53, it is possible to reduce electrical leakage between the two electricity storage structural units provided in series in the winding structure 50. In particular, when the electrolyte 5 is contained in the winding structure 50 as in the present embodiment, electrical short circuits via the electrolyte 5 can be suppressed, thereby reducing leakage current and improving voltage resistance characteristics. In particular, as in the present embodiment, by arranging both the partition members 56 and 57 in the gaps between the intermediate electrode body 51 and the first and second electrode bodies 52 and 53 on the same radially inner or outer side (the outer peripheral side in the illustrated example), it is possible to reduce structural and functional imbalances between the electricity storage functional unit formed between the intermediate electrode body and the first electrode body 52 and the electricity storage functional unit formed between the intermediate electrode body and the second electrode body 53, and to enhance the symmetry of the electricity storage functional units as in the illustrated example.

[0077] From the viewpoint of improving insulation characteristics, the positions of the outer edge portions (side edges) of the partition members 56 and 57 in this embodiment preferably protrude further outward in the axial direction of the winding structure 50 than the intermediate electrode body 51 and at least one (preferably both) of the first electrode body 52 or the second electrode body 53. In particular, the positions of both outer edge portions (side edges) of the partition members 56 and 57 in the axial direction preferably protrude further outward in the axial direction of the winding structure 50 than the intermediate electrode body 51 and at least one (preferably both) of the first electrode body 52 or the second electrode body 53. Furthermore, when the winding structure 50 is accommodated in an accommodation space formed by a housing such as the container 3 and the sealing body 4 and the holding member 26 inside the housing, it is preferable that the outer edge portions (side edges) abut (be fixed to) a boundary located on the outside in the axial direction of the accommodation space.

[0078] From the viewpoint of improving insulation characteristics, the positions of the outer edge portions (edges) 56e, 57e of the partition members 56, 57 preferably protrude radially outward of the winding structure 50 further than the intermediate electrode body 51 and at least one of (preferably both of) the first electrode body 52 and the second electrode body 53. As shown in the illustrated example, the outer edge portions (outer edges) of the intermediate electrode body 51, the first electrode body 52, and the second electrode body 53 are preferably covered from the outer periphery by the outer peripheral portions (portions extending to the edges 56e, 57e) of the partition members 56, 57. Furthermore, when the winding structure 50 is housed in a housing formed by a housing including the container 3 and the sealing body 4 and a holding member 26 inside the housing, as shown in the illustrated example, the outer edge portions (radial edges) 56e, 57e preferably abut (and more preferably are fixed to) a boundary located radially outward of the housing space. Furthermore, from the viewpoint of improving insulation characteristics, it is preferable that the radial inner edges (inner end edges) of the partition members 56 and 57 are positioned so as to extend further inward of the winding structure 50 than the first electrode body 52 or the second electrode body 53. It is also preferable that the inner edges (inner end edges) of the intermediate electrode body 51, the first electrode body 52, or the second electrode body 53 are covered from the inner periphery by the inner edges of the partition members 56 and 57. In particular, as shown in FIG. 16( a), it is preferable for the inner edges of the partition members 56 and 57 to abut (more preferably, be connected and fixed to) the inner periphery of the intermediate section 51a or the like of the intermediate electrode body 51, in order to further improve insulation characteristics. Furthermore, the inner edges of the partition members 56 and 57 may abut (more preferably, be connected and fixed to) the inner periphery of the first separator 54 or the second separator 55, respectively. However, the inner edges of the partition members 56 and 57 may be spaced apart from the intermediate electrode body 51 and the separators 54 and 55, as shown by the dotted lines in FIG. 16(b).

[0079] In this embodiment, the wound structure 50 preferably has a structure in which the outer peripheries of the intermediate electrode body 51, the first electrode body 52, and the second electrode body 53 are covered from the outer periphery in the radial direction by the outer peripheries (portions extending to the radial edges 56e, 57e) of the partition members 56, 57. It is to be noted that, regardless of the outer peripheries of the partition members 56, 57, it is desirable that the outer peripheries of the first separator 54 and the second separator 55 extend further outward than the outer peripheries of the intermediate electrode body 51, the first electrode body 52, and the second electrode body 53.

[0080] In addition, it is preferable that the holding member 26 is configured so that the electrode bodies (particularly the polarizable electrode layers) and separators are not connected via an adhesive layer between the areas partitioned by the partition members 56, 57, so that the adhesive layer does not interfere with electrical insulation.

[0081] Ninth Embodiment Next, with reference to FIG. 17 , an electricity storage device according to a ninth embodiment of the present invention will be described. In this embodiment, partition members 56′ and 57′ are arranged in a part of the internal structure of a winding structure 50′, as in the eighth embodiment. However, this embodiment differs from the eighth embodiment in the following respects. Specifically, in this embodiment, a partition member 56′ is arranged between the first electrode body 52 and the second extension portion 51c, and a partition member 57′ is arranged between the second electrode body 53 and the first extension portion 51b. Meanwhile, a first separator 54′ is arranged between the first electrode body 52 and the first extension portion 51b, and a second separator 55′ is arranged between the second electrode body 53 and the second extension portion 51c. In this embodiment, the partition members 56′ and 57′ are arranged in the inner gaps of a pair of radially inner and outer gaps between the intermediate electrode body 51 and the first electrode body 52 or the second electrode body 53.

[0082] The other configurations of the above-mentioned partition members 56', 57' can be formed in the same manner as in the previously described eighth embodiment, and it is clear that similar configurations can be adopted to the extent that they do not cause any particular problems, so a description of these will be omitted. Furthermore, the winding structure 50' of this embodiment can also achieve the same effects as in the eighth embodiment. Furthermore, with regard to the lamination of the polarizable electrode layers 512, 513, 521, 531 on the current collectors 511, 521, 531 shown in FIG. 17(b), the polarizable electrode layers are formed in portions that face each other via the first separator 54' and the second separator 55', and the configuration and effects in the case where no unfacing portions of the polarizable electrode layers are formed are also the same as in the eighth embodiment. [Industrial Applicability]

[0083] The power storage device of the present invention is not limited to the illustrated examples described above, and various modifications can be made without departing from the spirit and scope of the present invention. For example, while the above embodiments have been described with reference to an electric double layer capacitor, it will be obvious to those skilled in the art that the internal electrode structure of the wound structure can also be easily applied to an electrolytic capacitor by forming an insulating film such as an oxide film on the surface of each electrode body. Furthermore, the internal electrode structure of the present invention can be applied to various capacitor-type power storage devices, such as various other capacitors. Furthermore, the internal electrode structure of the present invention can also be applied to chemical power storage devices such as batteries. The configurations of the various parts of the above embodiments can be configured in any combination with each other, as long as no particular problems arise.

[0084] In this specification, an example of an induction-type electricity storage device in which lead wires (first external terminals and second external terminals) are attached to internal electrodes (first electrode body and second electrode body) and the device is wound up is illustrated and described as an embodiment, but the electricity storage device of the present invention is not limited to the induction type, and it is also possible to configure it as a non-induction-type electricity storage device in which lead wires (first external terminals and second external terminals) are attached to the axial edge portions of the internal electrodes (first electrode body and second electrode body) of the wound structure.

[0085] Furthermore, in the energy storage device of the present invention, as described above, two energy storage functional units are configured in series via the intermediate electrode body 21, such as a first energy storage functional unit configured by the intermediate electrode body 21 and the first electrode body 22, and a second energy storage functional unit configured by the intermediate electrode body 21 and the second electrode body 23. In this case, by using an anisotropic ion conductor having high ionic conductivity in the thickness direction and low ionic conductivity in the planar direction as the electrolyte 5, problems due to the common electrolyte effect, such as self-discharge current occurring between the energy storage functional units via a short circuit through the electrolyte 5, can be reduced, thereby further reducing electrical leakage in the above embodiment. The anisotropic ion conductor must have a lower electrical conductivity in the direction along the surface of each electrode body than in the direction perpendicular to the surface of each electrode body. In particular, it is preferable to use an anisotropic ion conductor whose electrical conductivity in the direction along the surface of each electrode body is 10% or less of the electrical conductivity in the direction perpendicular to the surface of each electrode body. [Explanation of symbols]

[0086] 1...electricity storage device (electric double layer capacitor), 2...wound capacitor element, 3...container (case), 4...sealing body, 5...electrolyte, 6...first external terminal, 7...second external terminal, 20, 50...wound structure, 21, 21', 31, 41, 51...intermediate electrode body, 21a, 31a, 41a, 51a...intermediate portion, 21b, 31b, 41b, 51b...first extension portion, 21c, 31c, 41c, 51c...second extension portion, 21d...outer edge portion, 21e...end edge, 21f...side edge, 31g...cell separator layer, 31h, 31i...electrode body layer, 41j, 41k...periphery portion, 22, 52...first electrode body, 23, 53...second electrode body, 24, 54, 54'...first separator, 25, 55, 55'...second separator, 26...holding member, 27, 28...adhesive layer, 211, 221, 231, 511, 521, 531...current collector, 212, 213, 222, 223, 232, 233, 512, 513, 522, 532...polarizable electrode layer, 56, 57, 56', 57'...partition member

Claims

1. An electricity storage device comprising a winding structure and a first external terminal and a second external terminal connected to the winding structure, The winding structure includes: a strip-shaped intermediate electrode body in which a first extending portion and a second extending portion extending on both sides of a middle portion in an extending direction are wound around the middle portion in the same direction; a first electrode body that is conductively connected to the first external terminal, that is disposed between the first extending portion located on the inner periphery side and the second extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a second electrode body that is conductively connected to the second external terminal, that is disposed between the second extending portion located on the inner periphery side and the first extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a first separator disposed between the intermediate electrode body and the first electrode body; a second separator disposed between the intermediate electrode body and the second electrode body; and an outer edge portion of the intermediate electrode body protrudes further outward in the axial direction of the wound structure than the first electrode body and the second electrode body in the wound structure;

2. The winding structure is disposed in the accommodation space, an outer edge portion of the intermediate electrode body abuts against a boundary of the accommodation space that is located outside in the axial direction; The electricity storage device according to claim 1 .

3. An electricity storage device comprising a winding structure and a first external terminal and a second external terminal connected to the winding structure, The winding structure includes: a strip-shaped intermediate electrode body in which a first extending portion and a second extending portion extending on both sides of a middle portion in an extending direction are wound around the middle portion in the same direction; a first electrode body that is conductively connected to the first external terminal, that is disposed between the first extending portion located on the inner periphery side and the second extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a second electrode body that is conductively connected to the second external terminal, that is disposed between the second extending portion located on the inner periphery side and the first extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a first separator disposed between the intermediate electrode body and the first electrode body; a second separator disposed between the intermediate electrode body and the second electrode body; and an outer edge portion of the intermediate electrode body is disposed radially outward of the wound structure relative to the first electrode body and the second electrode body in the wound structure;

4. an outer edge portion of the intermediate electrode body protrudes outward in the axial direction of the winding structure beyond the first electrode body and the second electrode body in the winding structure; The electricity storage device according to claim 3 .

5. The winding structure is disposed in the accommodation space, an outer edge portion of the intermediate electrode body abuts against a boundary of the accommodation space that is located outside in the axial direction; The electricity storage device according to claim 4 .

6. The winding structure is disposed in the accommodation space, an outer edge portion of the intermediate electrode body abuts against a boundary of the accommodation space on the outer side in the radial direction; The electricity storage device according to any one of claims 3 to 5.

7. The outer edge of the intermediate electrode body has insulating properties. The electricity storage device according to any one of claims 1 to 6.

8. an electrolyte is introduced into the wound structure; the outer edge portion of the intermediate electrode body is a portion that is less likely to retain the electrolyte or its ions or to allow the electrolyte or its ions to pass through than the main body portion of the intermediate electrode body; The electricity storage device according to any one of claims 1 to 7.

9. An electricity storage device comprising a winding structure and a first external terminal and a second external terminal connected to the winding structure, The winding structure includes: a strip-shaped intermediate electrode body in which a first extending portion and a second extending portion extending on both sides of a middle portion in an extending direction are wound around the middle portion in the same direction; a first electrode body that is conductively connected to the first external terminal, that is disposed between the first extending portion located on the inner periphery side and the second extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a second electrode body that is conductively connected to the second external terminal, that is disposed between the second extending portion located on the inner periphery side and the first extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a first separator disposed between the intermediate electrode body and the first electrode body; a second separator disposed between the intermediate electrode body and the second electrode body; and The winding structure has a structure in which the outer peripheries of the first electrode body and the second electrode body are covered from the outer periphery in the radial direction by the outer periphery of the intermediate electrode body.

10. the outer peripheral portions of the first separator and the second separator are present over a wider angular range on the outer peripheral side than the first electrode body and the second electrode body, respectively; The electricity storage device according to claim 9 .

11. An electricity storage device comprising a winding structure and a first external terminal and a second external terminal connected to the winding structure, The winding structure includes: a strip-shaped intermediate electrode body in which a first extending portion and a second extending portion extending on both sides of a middle portion in an extending direction are wound around the middle portion in the same direction; a first electrode body that is conductively connected to the first external terminal, that is disposed between the first extending portion located on the inner periphery side and the second extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a second electrode body that is conductively connected to the second external terminal, that is disposed between the second extending portion located on the inner periphery side and the first extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a first separator disposed between the intermediate electrode body and the first electrode body; a second separator disposed between the intermediate electrode body and the second electrode body; and The intermediate electrode body is an electricity storage device comprising a plurality of electrode body layers arranged with separator layers interposed between them.

12. An electricity storage device comprising a winding structure and a first external terminal and a second external terminal connected to the winding structure, The winding structure includes: a strip-shaped intermediate electrode body in which a first extending portion and a second extending portion extending on both sides of a middle portion in an extending direction are wound around the middle portion in the same direction; a first electrode body that is conductively connected to the first external terminal, that is disposed between the first extending portion located on the inner periphery side and the second extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a second electrode body that is conductively connected to the second external terminal, that is disposed between the second extending portion located on the inner periphery side and the first extending portion located on the outer periphery side, and that extends from the vicinity of the intermediate portion toward the outer periphery side; a first separator disposed between the intermediate electrode body and the first electrode body; a second separator disposed between the intermediate electrode body and the second electrode body; and the first separator is disposed in one of a pair of radially inner and outer gaps between the intermediate electrode body and the first electrode body, the gaps being disposed radially inner and outer, respectively, and an electrically insulating first partition member having electrolyte blocking properties is disposed in the other gap; An electricity storage device, wherein the second separator is disposed in one of a pair of radially inner and outer gaps between the intermediate electrode body and the second electrode body, the gaps being disposed radially inner and outer, respectively, and a second partition member having electrical insulation properties and electrolyte blocking properties is disposed in the other gap.

13. the first partition member is disposed in the gap on one of the inner and outer sides in the radial direction, and the second partition member is disposed in the gap on the same side as the first partition member. The electricity storage device according to claim 12.

14. an electrolyte is introduced into the wound structure; the first partition member and the second partition member are impermeable to and non-retaining the electrolyte and its ions; The electricity storage device according to claim 12 or 13.

15. The electrolyte is configured in a liquid state, the first partition member and the second partition member have surfaces with contact angles with the electrolyte of 80 degrees or more; The electricity storage device according to claim 14.

16. outer edge portions of the first partition member and the second partition member each protrude in the axial direction of the winding structure beyond the intermediate electrode body and at least one of the first electrode body and the second electrode body; The electricity storage device according to any one of claims 12 to 15.

17. The winding structure is disposed in the accommodation space, outer edge portions of the first partition member and the second partition member abut against boundaries of the accommodation space that are located outside in the axial direction; The electricity storage device according to claim 16.

18. outer edge portions of the first partition member and the second partition member are respectively disposed radially outward of the intermediate electrode body and at least one of the first electrode body and the second electrode body in the winding structure. The electricity storage device according to any one of claims 12 to 17.

19. The winding structure is disposed in the accommodation space, outer edge portions of the first partition member and the second partition member abut against boundaries of the accommodation space that are located on the outside in the radial direction; The power storage device according to claim 18.

20. the inner edge portions of the first partition member and the second partition member are disposed so as to extend more inward than the inner edge portions of the first electrode body and the second electrode body, respectively; The electricity storage device according to any one of claims 12 to 19.

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