Energy storage device

Abstract

Provided is a power storage device that is made compact and can be manufactured easily, while ensuring voltage endurance characteristics.　A power storage device 1 comprises a winding structure 20 and a housing 3, 4 forming an accommodating space. The winding structure comprises: an electrically insulating, band-shaped partitioning member 21 that has an electrolyte-shielding property and is wound so as to divide the accommodating space into a plurality of accommodating regions; and a plurality of power-storage function bodies 20A, 20B which are each separately disposed in the plurality of accommodating regions so as to be wound along the partitioning member. The power-storage function bodies are provided with first electrode bodies 22A, 22B, second electrode bodies 23A, 23B, and separators 24A, 24B disposed between the first electrode bodies and the second electrode bodies, each of which is configured in the form of a band wound along the partitioning member.

Description

Technical Field

[0001] The present invention relates to a power storage device, and particularly to an internal structure of a power storage device suitable as an element having a power storage function such as an electric double layer capacitor, an electrolytic capacitor, and other various capacitors (capacitor type power storage device).

Background Art

[0002] In electric double layer capacitors and electrolytic capacitors, in recent years, the demand for high voltage products has been increasing. As high voltage products, module products in which a plurality of cells (power storage elements) are connected in series (for example, those in which a plurality of elements are connected in series via a substrate, a 4-terminal type in which a plurality of elements are grouped together and the terminals of each element protrude as they are, an internal connection type in which a plurality of elements are connected internally, etc.) are known, but these module products have a problem that the number of parts is large, the manufacturing process is complicated, the cost such as processing cost increases, the profit rate is poor, and the size also becomes large.

[0003] On the other hand, as those configured with a single cell structure as a high voltage product, those disclosed in Patent Document 1 and Patent Document 2 below are known. Patent Document 1 describes an electric double layer capacitor in which a plurality of cylindrical conductors are arranged concentrically in the radial direction inside and outside with a separator interposed therebetween (see FIG. 4). Further, Patent Document 2 discloses a bipolar element having three or four electrodes including an intermediate electrode not connected to an external terminal, and a high voltage supercapacitor in which these electrodes are wound through three or four separators (see FIGS. 1 to 3B).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the power storage device described in the above-mentioned conventional Patent Document 1, since it is necessary to arrange a plurality of cylindrical power storage functional units concentrically, due to the spatial constraints in the radial direction, variations or biases in characteristics, or a decrease in withstand voltage characteristics, etc. between the respective power storage functional units are inevitable problems.

[0006] On the other hand, in the power storage device described in the above-mentioned conventional Patent Document 2, since three or four or more electrode bodies including an intermediate electrode are wound through the same number of separators, similar to the device described in Patent Document 1, variations or biases in characteristics, etc. cannot be avoided due to the spatial constraints in the radial direction, it is difficult to improve the withstand voltage characteristics such as reducing leakage current, and since the number of layers of the winding structure value increases, there is a problem that the size tends to increase.

[0007] Therefore, the present invention solves the above problems, and the problem is to realize a power storage device that can ensure withstand voltage characteristics and can achieve miniaturization and ease of manufacturing.

Means for Solving the Problems

[0008] In order to solve the above problems, the power storage device of the present invention is a power storage device including a wound structure body and a housing that constitutes a housing space for housing the wound structure body, wherein the wound structure body is wound so as to partition the housing space into a plurality of housing regions, and includes an electrically insulating belt-shaped partition member having electrolyte blocking properties, and a plurality of power storage functional bodies that are separately arranged in each of the plurality of housing regions in a manner of being wound along the partition member. Here, each of the power storage functional bodies includes a first electrode body, a second electrode body, and a separator disposed between the first electrode body and the second electrode body, each of which is configured in a belt shape wound along the partition member. Note that each of the above housing regions does not necessarily need to be a sealed region, and may be a region configured to be able to individually house a plurality of power storage functional bodies.

[0009] According to this power storage device, the storage space is partitioned into a plurality of storage regions by a wound, electrically insulating strip-shaped partition member having electrolyte blocking properties, and a plurality of power storage functional bodies are respectively arranged in a wound manner along the partition member within each storage region. By doing so, a plurality of power storage functional structures can be compactly accommodated and the manufacturing can be facilitated. Moreover, the leakage current can be reduced by the electrically insulating partition member having electrolyte blocking properties, and the withstand voltage characteristics can be improved.

[0010] In the present invention, it is preferable that an outer edge portion (side edge) of the partition member protrudes outward in the axial direction of the winding structure body more than the first electrode body and the second electrode body belonging to the plurality of power storage functional bodies. According to this, the radial electrical leakage in the outer peripheral portion beyond the outer edge (side edge) in the axial direction of the winding structure body can be suppressed by the outer edge portion (side edge) in the width direction of the electrically insulating partition member having electrolyte blocking properties, so that the insulation performance of the device can be improved. In particular, it is more desirable that the outer edge portions (both side edges) on both sides in the width direction of the partition member both protrude outward in the axial direction more than the first electrode body and the second electrode body in the winding structure body. In these cases, it is desirable that the outer edge portion (side edge) of the partition member abuts against the boundary outside the axial direction of the accommodation space of the winding structure body. Thereby, since the electrical leakage in the outer peripheral portion in the axial direction within the accommodation space is further reduced by the outer edge portion of the partition member, the insulation performance can be further improved.

[0011] Further, it is desirable that the outer edge (end edge) of the partition member is disposed outside the first electrode body and the second electrode body in the winding structure in the radial direction of the winding structure. According to this, the circumferential electrical leakage in the outer peripheral portion beyond the outer edge (periphery) in the radial direction of the winding structure can be reduced by the outer edge (end edge) in the extending direction of the partition member, so that the insulation performance can be improved. In this case, it is desirable that the winding structure is disposed in the accommodation space and the outer edge (end edge) of the partition member abuts on the boundary outside the accommodation space of the winding structure in the radial direction. Thereby, since the electrical leakage in the outer peripheral portion in the radial direction in the accommodation space is further reduced, the insulation performance can be further improved. Further, it is preferable that the inner edge portion in the radial direction of the partition member is disposed on the inner peripheral side in the radial direction rather than the first electrode body and the second electrode body in the winding structure. In this case, it is desirable that the inner edge portion of the partition member abuts on (more preferably, is fixed to) the inner edge portion of the first separator or the second separator.

[0012] In the present invention, it is preferable that the partition member is made of a synthetic resin. Examples of the synthetic resin include polyphenylene sulfide (PPS), polyimide (PI), aramid (fully aromatic polyamide), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polypropylene (PP), polyethylene (PE), and the like. Further, as a preferable form for constituting the winding structure, the partition member is preferably in a sheet shape. Furthermore, when an electrolyte is introduced into the winding structure, it is preferable that the partition member does not allow the electrolyte and its ions to pass through. In particular, it is desirable that the partition member has impermeability and non-retention properties with respect to the electrolyte and its ions. For example, it is preferably composed of a sheet material having no voids. By these means, it becomes possible to more reliably reduce the leakage current through the electrolyte, and the insulation performance of the device can be further improved. Desirable sheet materials made of synthetic resin in these respects include fluororesin sheets such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylene propene copolymer (FEP), polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene copolymer (ETFE), and polychlorotrifluoroethylene (PCTFE). Further, when the electrolyte is in a liquid state, the surface of the partition member preferably has a surface with a contact angle of 80 degrees or more with respect to the electrolyte. In particular, it is desirable that the contact angle exceeds 90 degrees (is an obtuse angle).

[0013] In the present invention, it is preferable that the partition member has a plurality of extending portions extending to the outer peripheral side around an intermediate portion, each of which is wound around the intermediate portion in the same direction, and the accommodating region is formed so as to circulate from an inner peripheral portion adjacent to the intermediate portion to an outer peripheral portion between the plurality of extending portions. According to this, since a plurality of accommodating regions are separated at the inner peripheral portion by the plurality of extending portions extending around the intermediate portion of the partition member, it becomes possible to further improve the insulation characteristics between the plurality of power storage functional bodies.

[0014] In the present invention, it is preferable that the partition member (the plurality of extending portions) and the plurality of power storage functional bodies are formed to be rotationally symmetric about the axis (the intermediate portion) of the winding structure. Thereby, since the electrical symmetry between the plurality of power storage functional bodies configured via the partition member can be substantially ensured, the durability and the stability of characteristics can be improved. In this case, between the plurality of power storage functional bodies, the first electrode body, the second electrode body, and the separator belonging to each power storage functional body are also preferably formed to be rotationally symmetric about the axis (the intermediate portion).

[0015] In the present invention, it is preferable that the winding structure has a structure in which the outer peripheral portions of the plurality of power storage functional bodies are covered from the outer peripheral side in the radial direction by the outer peripheral portion of the partition member. Thereby, since each power storage functional body extends to the outer peripheral portion while being sandwiched between the first extending portion and the second extending portion of the partition member, an equal electrical insulation environment can be realized over the entire length of each power storage functional body, so that electrical leakage can be further suppressed, and the insulation performance can be further improved. In this case, it is desirable that the outer peripheral portions of the separator interposed between the first electrode body and the second electrode body exist over a wider angular range on the outer peripheral side in the radial direction than the first electrode body and the second electrode body, respectively. Further, in the present invention, it is preferable that the intermediate portion of the partition member and the inner peripheral end of the separator of the power storage functional body are connected. According to this, in the power storage functional body partitioned by the plurality of extending portions of the partition member, since the inner peripheral end of the separator is connected to the intermediate portion, the insulation characteristics are not deteriorated even when the power storage functional body is arranged from the inner peripheral side, so that the accommodation efficiency of the power storage functional body can be increased, and further compactification can be achieved.

Effects of the Invention

[0016] According to the present invention, it is possible to realize a power storage device that can achieve compactification and ease of manufacture while ensuring withstand voltage characteristics.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] 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 taken as an example of the energy storage device and described below. First, with reference to FIGS. 1 and 2, the overall configuration of the first embodiment of the energy storage device according to the present invention will be described.

[0019] <First Embodiment> FIG. 1 is a schematic perspective view (a) of the energy storage device 1 of the present embodiment and a perspective view (b) schematically showing the wound capacitor element 2 housed inside the energy storage device 1. The energy storage device 1 includes a wound capacitor element 2 in which an electrolyte 5 is introduced (impregnated) into a wound structure 20 having a structure formed by winding a strip material (sheet material), a bottomed-shaped (bottomed cylindrical) container 3 that houses 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 is provided with through holes for inserting a first external terminal 6 and a second external terminal 7 provided on the wound capacitor element 2. The sealing body 4 seals the wound capacitor element 2 housed in the container 3 through the through holes, and leads out two sets of first external terminals 6A, 6B and second external terminals 7A, 7B of A and B to the outside. The sealing body 4 can be made of various synthetic rubbers, elastomers, etc. The container 3 and the sealing body 4 constitute a housing.

[0020] FIG. 2 is a schematic cross-sectional view schematically showing a cross-section of the wound structure 20. The wound structure 20 has a strip-shaped partition member 21, and the partition member 21 includes a first extending portion 21b and a second extending portion 21c on both sides of an intermediate portion 21a in the extending direction. The first extending portion 21b and the second extending portion 21c are each wound counterclockwise around the intermediate portion 21a in the illustrated example. On both the front and back sides of the partition member 21, energy storage functional bodies 20A and 20B are respectively arranged between the first extending portion 21b and the second extending portion 21c of the partition member 21. These energy storage functional bodies 20A and 20B each have a structure in which strip-shaped first electrode bodies 22A, 22B, second electrode bodies 23A, 23B, and separators 24A, 24B arranged therebetween are laminated.

[0021] Further, in the winding structure 20, a plurality of accommodating regions are defined by the partition member 21. Here, each accommodating region does not necessarily have to be a sealed region, and it may be a region configured to be able to individually accommodate a plurality of power storage functional bodies 20A and 20B. More specifically, when considering the intermediate portion 21a as the center, in the gap between the first extending portion 21b on the inner peripheral side and the second extending portion 21c on the outer peripheral side, which is one of the above-mentioned accommodating regions, the belt-shaped power storage functional body 20B is disposed. At this time, in the power storage functional body 20B, the first electrode body 22B, the separator 24B, and the second electrode body 23B are laminated in this order from the inner peripheral side to the outer peripheral side, and extend in a manner wound from the inner peripheral side to the outer peripheral side along the partition member 21. On the other hand, in the gap between the second extending portion 21c on the inner peripheral side and the first extending portion 21b on the outer peripheral side, which is the other above-mentioned accommodating region, the belt-shaped power storage functional body 20A is disposed. At this time, in the power storage functional body 20A, the first electrode body 22A, the separator 24A, and the second electrode body 23A are laminated in this order from the inner peripheral side to the outer peripheral side, and extend in a manner wound from the inner peripheral side to the outer peripheral side along the partition member 21. In these cases, at the inner peripheral ends of each of the power storage functional bodies 20A and 20B, the inner peripheral ends of the separators 24A and 24B extend to the inner peripheral side of the inner peripheral ends of the first electrode bodies 22A and 22B and the second electrode bodies 23A and 23B. Also, at the outer peripheral ends of each of the power storage functional bodies 20A and 20B, the outer peripheral ends of the separators 24A and 24B extend to the outer peripheral side of the outer peripheral ends of the first electrode bodies 22A and 22B and the second electrode bodies 23A and 23B.

[0022] In the above-described winding structure 20, the partition member 21 and the two power storage functional bodies 20A and 20B are wound in a mutually laminated manner as shown in the illustrated example, and finally held and fixed in a wound state by the outermost holding member (for example, a winding tape) 26. However, it should be noted that FIG. 2 is merely a schematic diagram and is shown in a manner different from the actual winding state. For example, the reproducibility of the adhesion degree between layers is ignored, and in many cases, the number of windings is significantly reduced. Further, the outermost circular shape shown outside the above structure originally represents the boundary of the accommodation space of the winding structure 20 corresponding to the container 3 and the holding member 26, that is, the boundary of the space where the electrolyte 5 can exist in the present embodiment. That is, the above circular shape shown in the figure is schematically shown as defining a space having functions such as an accommodation function, a shape maintenance function, and an insulation function of the winding structure 20 required according to the situation of the winding structure 20 having the above structure. Therefore, the shape (circular) itself has no meaning and is not limited. Furthermore, the pair of circular shapes shown by the two-dot chain line in the figure indicates the approximate positions of the joining portions (formation sites of tab members) of the first electrode bodies 22A and 22B and the second electrode bodies 23A and 23B that should be electrically connected to the first external terminals 6A and 6B and the second external terminals 7A and 7B shown in FIG. 2, respectively. It should be noted that the drawings attached to this specification should be understood not only as FIGS. 1 and 2 but also as schematic diagrams or diagrams showing a partial enlargement, and the shapes drawn in the drawings do not directly (limitatively) show the configurations of actual examples.

[0023] FIG. 3 schematically shows the arrangement in the unfolded state before winding of the partition member 21, the first electrode bodies 22A and 22B, the second electrode bodies 23A and 23B, and the separators 24A and 24B. As can be seen from this unfolded state diagram, the partition member 21 is disposed between the power storage functional bodies 20A and 20B. The partition member 21 is configured with a material and shape (structure) that can reduce the leakage current between the power storage functional bodies 20A and 20B as much as possible and ensure the withstand voltage characteristics. For this purpose, the partition member 21 preferably has electrolyte blocking properties and electrical insulation properties. That is, the partition member 21 has a blocking property that does not allow the passage of electrolytes (ions), and itself has electrical insulation properties. As the partition member 21, a synthetic resin is preferably used. Examples of the synthetic resin include polyphenylene sulfide (PPS), polyimide (PI), aramid (fully aromatic polyamide), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polypropylene (PP), polyethylene (PE), and the like.

[0024] Also, as a preferable form for constituting the winding structure 20, the partition member 21 is desirably in a sheet shape. Further, when an electrolyte is introduced into the winding structure, it is preferable that the partition member does not allow the electrolyte and its ions to pass through. In particular, it is desirable to have impermeability and non-retention of the electrolyte and its ions. For example, it is composed of a sheet material having no voids. By these, it becomes possible to more reliably reduce the leakage current through the electrolyte, and the insulation performance of the device can be further improved. Desirable synthetic resin sheet materials in these respects include fluororesin sheets such as polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), perfluoroethylene propene copolymer (FEP), polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene copolymer (ETFE), and polychlorotrifluoroethylene (PCTFE).

[0025] As described later, when using a highly fluid electrolyte such as an electrolytic solution, it is desirable for the partition member 21 to have a surface with a property of repelling the electrolyte. As the surface material at this time, for example, the above-mentioned fluororesin sheet is preferable. Also, a surface layer having a property of repelling the electrolyte may be formed on the surface by applying a coating or the like. As for the degree of repelling the electrolyte, it is preferable that the contact angle θ with respect to the target electrolyte (liquid) is 80 degrees or more, and particularly preferably an angle exceeding 90 degrees (obtuse angle). Usually, the contact angle of the fluororesin is about 100 degrees. Thus, by making the surface of the partition member 21 less wettable to the electrolyte, even if there is a slight gap between the partition member 21 and the surrounding members, it becomes difficult for the electrolyte to cross the accommodation region partitioned by the partition member 21 (difficult to pass through the gap), so that an effect of improving insulation characteristics such as reduction of leakage current can be obtained.

[0026] FIG. 4 is a cross-sectional view schematically showing the more detailed structures of the above-mentioned partition member 21 and the power storage functional bodies 20A and 20B, respectively. In the partition member 21, it is composed of a sheet having electrical insulation without voids as described above. When the partition member 21 is composed of a synthetic resin sheet as described above, in order to ensure electrical insulation and impermeability to the electrolyte (ions) and to make the structure as compact as possible, its thickness is preferably in the range of 5 μm to 1 mm, and particularly preferably in the range of 10 μm to 500 μm. More preferably, it is in the range of 20 μm to 200 μm. If the thickness is below the above ranges, the electrolyte and its ions are likely to pass through. If the thickness exceeds the above ranges, the winding property during manufacturing deteriorates, which is also disadvantageous for making the power storage device compact.

[0027] On one hand, the first electrode bodies 22A and 22B of the power storage functional bodies 20A and 20B include a current collector 22A1, 22B1 made of a metal foil or the like, and a polarizable electrode layer 22A2, 22B2 made of a carbon-containing porous material or the like laminated on the surface of the current collector 22A1, 22B1 facing the second electrode bodies 23A and 23B. Also, in the second electrode bodies 23A and 23B, there are a current collector 23A1, 23B1 made of a metal foil or the like, and a polarizable electrode layer 23A2, 23B2 made of a carbon-containing porous material or the like laminated on the surface of the current collector 23A1, 23B1 facing the second electrode bodies 22A and 23A.

[0028] As the current collectors 22A1, 22B1, 23A1, and 23B1, for example, an aluminum foil with a thickness of 20 μm to 50 μm can be used. Also, as the polarizable electrode layers 22A2, 22B2, 23A2, and 23B2, for example, activated carbon powder and carbon black are kneaded with a binder to prepare a carbon fine particle-containing paste, and the paste is applied onto the surfaces of the current collectors 22A1, 22B1, 23A1, and 23B1 with a thickness of 10 μm to 200 μm and dried to form them.

[0029] As the separators 24A and 24B, for example, a cellulose nonwoven fabric with a thickness of 20 μm to 100 μm can be used. Also, in addition to the cellulose nonwoven fabric, separators made of nonwoven fabrics of polyimide (PI), aramid (fully aromatic polyamide), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polypropylene (PP), and polyethylene (PE) can also be used. Note that the material constituting the separator is not limited to the above various nonwoven fabrics, and for example, it may be composed of paper made only of cellulose pulp.

[0030] As the holding member (winding tape) 26, an adhesive tape made of a resin such as polypropylene (PP), polyphenylene sulfide (PPS), or polyimide (PI), which is excellent in solvent resistance, heat resistance, and insulation performance, can be used. Here, as the holding member 26, it is preferable that the adhesive layer does not prevent electrical insulation, and that the electrode bodies (especially the polarizable electrode layers) and the separators are not connected via the adhesive layer between the regions partitioned by the partitioning member 21.

[0031] As the electrolyte 5 introduced into the winding structure 20, various ones required according to the type of the power storage device can be used. For example, in the case of the electric double layer capacitor of the present embodiment, tetraethylammonium salt can be used as the cation, and boron tetrafluoride, bis(trifluoromethylsulfonyl)imide, etc. can be used as the anion. As the electrolyte at this time, a liquid or gel electrolyte can be used. In addition, as another capacitor type power storage device, for example, when configuring an electrolytic capacitor, various electrolytic solutions using boric acid, adipic acid, maleic acid, benzoic acid, phthalic acid, salicylic acid, ammonia, triethylamine, tetramethylammonium hydroxide, etc. as the electrolyte can be used. Further, as the electrolyte 5, a solid electrolyte such as manganese dioxide or an organic semiconductor, or a conductive solid such as a conductive polymer or others (for example, a conductive inorganic material, etc.) can also be used.

[0032] FIG. 5 is a schematic process diagram (a) to (f) schematically showing the process of forming the winding structure 20. First, as shown in FIG. 5(a), between the separably configured winding core materials 10 (a pair of winding cores 10a and 10b), a partition member 21 and power storage functional bodies 20A and 20B disposed on both the front and back surfaces thereof are arranged. At this time, the partition member 21 and the power storage functional bodies 20A and 20B are held so as to be fed out by left and right tape supply systems (supply mechanisms including supply reels with rotation resistance imparting mechanisms, tension rollers, guide rollers, etc., not shown), and the like. Then, as shown in FIG. 5(b), the intermediate portion 21a of the partition member 21 is sandwiched between the pair of winding cores 10a and 10b, and by rotating the winding core material 10 as shown in FIG. 5(c), as shown in FIG. 5(d), the intermediate electrode body 21 can be wound around the intermediate portion 21a sandwiched by the winding core material 10. At this time, the respective power storage functional bodies 20A and 20B are fed out by left and right tape supply systems (not shown) according to the rotation of the winding core material 10 so that the power storage functional bodies 20A and 20B supplied from the left and right are wound in. Finally, a holding member (winding tape) 26 is attached (stuck) to the outermost layer to hold the above winding state.

[0033] When the winding structure 20 is formed as described above, each of the first external terminals 6A, 6B and the second external terminals 7A, 7B is conductively connected by being joined to the corresponding first electrode bodies 22A, 22B and the second electrode bodies 23A, 23B via tab members (not shown) and is inserted into the through holes of the sealing body 4. Then, the winding structure 20 is accommodated in the container 3 in a state where, for example, the electrolyte 5 is impregnated with an electrolytic solution, and finally, the opening of the container 3 is sealed with the sealing body 4. In the winding process shown in FIG. 5, the first electrode bodies 22A, 22B, the second electrode bodies 23A, 23B, and the separators 24A, 24B of the power storage functional bodies 20A, 20B may be integrated in a laminated state in advance (before winding) and wound together with the partition member 21. Further, the power storage functional body 20A may be integrated on one surface of the first extending portion 21b of the partition member 21 in advance (before winding), and / or the power storage functional body 20B may be integrated on the other surface of the second extending portion 21c, and then the winding process may be performed.

[0034] FIG. 6 is a schematic cross-sectional view (a) and (b) schematically showing the overall configuration of the power storage device 1 of the present embodiment formed as described above. Here, FIG. 6(a) schematically shows the relative positional relationship in the radial direction of the wound structure 20 (internal structure) of the power storage device 1, and FIG. 6(b) schematically shows the relative positional relationship around the axis (circumferential direction) of the wound structure 20 (internal structure) of the power storage device 1. As shown in FIG. 6, inside the power storage device 1 (cell structure), in the introduction (impregnation) region of the electrolyte 5, the first electrode body 22A and the second electrode body 23A, which are respectively arranged in the regions partitioned by the partition member 21, face each other through the separator 24A. A first power storage functional body 20A constituted by the facing portions and a second power storage functional body 20B constituted by the facing portions of the first electrode body 22B and the second electrode body 23B through the separator 24B are provided. These two sets of power storage functional bodies 20A and 20B are connected to the first external terminals 6A and 6B and the second external terminals 7A and 7B, respectively. Therefore, the two sets of power storage functional bodies are formed in a state where each has a corresponding two sets of external terminals. These two sets of power storage functional bodies 20A and 20B can be connected in series or in parallel through a pair of external terminals of each set, but the usage mode is not particularly limited. In addition, although the present embodiment is an electric double layer capacitor that stores charges using the electric double layer generated at the interface between each of the electrode bodies 22A, 22B, 23A, 23B and the electrolyte 5 as a dielectric, the above structure can be similarly configured for an electrolytic capacitor or other capacitors.

[0035] In the first embodiment described above, as shown in FIG. 2, the first extending portion 21b and the second extending portion 21c on both sides of the intermediate portion 21a of the strip-shaped partition member 21 are wound in the same direction, and the two power storage functional bodies 20A and 20B arranged between the first extending portion 21b and the second extending portion 21c are accommodated in the accommodation region partitioned from each other by the partition member 21. At this time, since the power storage functional bodies 20A and 20B arranged in the accommodation region partitioned by the partition member 21 are not configured to overlap each other radially inward and outward, the power storage functional body 20A and the power storage functional body 20B are not in a relationship where one is arranged inside and the other is arranged outside in the radial direction. That is, in the winding structure 20 of the present embodiment, by arranging the first electrode bodies 22A and 22B and the second electrode bodies 23A and 23B alternately or in parallel in the angular range around the intermediate portion 21a, structural and arrangement constraints between a plurality of power storage functional bodies can be relaxed, and the bias of the radial structural symmetry can be reduced. Further, since the first power storage functional body 20A and the second power storage functional body 20B 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 methods are different, the prior art can be developed, and a plurality of power storage functional bodies (a laminate in which the first electrode body and the second electrode body are laminated via a separator) can be wound and manufactured, so the manufacturing is easy and the number of parts is small.

[0036] In the present embodiment, as shown in FIG. 2, it is preferable that the first extending portion 21b, the second extending portion 21c, the first power storage functional body 20A, and the second power storage functional body 20b are rotationally symmetrically formed around the intermediate portion 21a of the partition member 21. Thereby, since the first power storage functional body 20A and the second power storage functional body 20B have substantially the same structure in substantially the same accommodation space, the electrical symmetry between the pair of power storage functional bodies can be substantially ensured. And when configured as described above, even when a plurality of power storage functional bodies are connected in series, the bias such as the applied voltage can be reduced, so the durability and characteristic stability of the power storage device can be improved.

[0037] More specifically, in Patent Document 1 and Patent Document 2, due to structural problems such as different radial arrangements and dimensions between a plurality of power storage functional units, the characteristic differences become large, so problems are likely to occur in durability and characteristic stability. For example, if the leakage currents are significantly different between the respective power storage functional units, the voltage variation increases with the passage of the voltage application time due to the influence of self-discharge. As a result, in the power storage functional unit with a small leakage current, the voltage increases with the passage of the voltage application time, and ultimately rises to the decomposition voltage of the solvent, risking problems such as gas generation and increased resistance. Further, when a plurality of power storage functional units are enclosed in one container, the leakage current may increase due to a short circuit between the electrode bodies caused by the electrolyte. This increase in the leakage current also becomes a factor that further deteriorates the aforementioned durability, characteristic stability, or withstand voltage characteristics.

[0038] On the other hand, according to the power storage device of the present embodiment, the first power storage functional bodies 20A and 20B are arranged in parallel in separate accommodation regions partitioned by the electrically insulating partition member 21 having electrolyte blocking properties in a manner of rotating around the intermediate portion 21a on both sides thereof. Therefore, it becomes easier to equalize and balance the characteristics between these power storage functional bodies. In particular, as described above, by configuring the partition member 21 and the two power storage functional bodies 20A and 20B to be rotationally symmetric about the intermediate portion 21a, the balance of the characteristics of both power storage functional bodies can be achieved. As a result, voltage concentration on one side is less likely to occur, and thus durability and characteristic stability are significantly improved. In this case, it is more effective if the respective electrode bodies 22A, 22B, 23A, 23B and separators 24A, 24B inside the power storage functional bodies 20A and 20B are also configured to be rotationally symmetric with each other.

[0039] Further, in the present embodiment, as shown in FIG. 2, in the winding structure 20, the outer peripheral portions of the power storage functional bodies 20A and 20B have a structure in which they are covered from the outer peripheral side in the radial direction by the outer peripheral portion of the partition member 21. For this reason, each of the power storage functional bodies 20A and 20B is arranged between the first extending portion 21b and the second extending portion 21c of the partition member 21 over the entire length from the inner peripheral portion to the outer peripheral portion. For this reason, since each of the power storage functional bodies 20A and 20B is placed in an equivalent insulation environment over the entire length from the inner peripheral portion to the outer peripheral portion, electrical leakage can be further reduced and the insulation characteristics can be improved.

[0040] Furthermore, in the present embodiment, in a situation where a plurality of power storage functional bodies 20A and 20B are partitioned by the electrically insulating partition member 21 having electrolyte blocking properties, as shown in FIG. 6, the side edge 21e, which is the outer edge portion of the partition member 21, is arranged outside the first electrode bodies 22A and 22B and the second electrode bodies 23A and 23B in the axial direction of the winding structure 20 (the vertical direction in the drawing of FIG. 6). Thereby, the electrical insulation between the power storage functional bodies 20A and 20B can be enhanced. In particular, since the side edge 21e is arranged on both outer sides in the axial direction of the winding structure 20 (both upper and lower sides in the drawing), the insulation characteristics can be further improved. Also, in the present embodiment, the end edges 21be and 21ce, which are the outer edge portions in the winding direction of the outer peripheral portion of the partition member 21, are arranged on the outer peripheral side, that is, on the outer side in the radial direction, when viewed in the circumferential direction of the winding structure 20 with respect to the first electrode bodies 22A and 22B and the second electrode bodies 23A and 23B. Thereby, the electrical insulation between the power storage functional bodies 20A and 20B can be enhanced.

[0041] In these cases, when the winding structure 20 is arranged in the accommodation space as in the present embodiment, it is desirable for the outer edge portion (side edge 21e or end edges 21be, 21ce) of the partition member 21 to contact the boundary on the outer side in the axial direction or the radial direction of the accommodation space of the winding structure in order to further improve the insulation characteristics. Further, it is more desirable that the contact state is fixed by adhesion or the like. In FIG. 6, as the configuration of the accommodation space, a state is depicted in which the outer peripheral portion of the winding structure 20 is covered by the holding member 26 and the inner surface of the container 3 is disposed outside thereof. However, FIG. 6 shows only a schematic configuration, and even if the configuration of the outer peripheral portion is as illustrated, it is merely an example. For example, different from the illustrated configuration, a gap may be provided between the container 3 and the electrolyte 5, or the inner surface of the container 3 may be provided with an insulating coating. Further, since FIG. 6 is a schematic diagram, note that it only partially illustrates the characteristics of the radial arrangement modes of the partition member 21, the power storage functional bodies 20A and 20B in a mode that is not consistent with the cross-sectional structure shown in FIG. 2.

[0042] <Second Embodiment> Next, with reference to FIG. 7, a power storage device according to a second embodiment of the present invention will be described. This second embodiment is the same as the first embodiment in that it is a wound capacitor element, and the overall configuration and cross-sectional structure of the winding structure 20' shown in FIG. 7 can basically be configured in the same manner as the winding structure 20. Therefore, the same reference numerals are given to the parts that can be configured in the same manner, and the description thereof is omitted.

[0043] In this second embodiment, as shown in Fig. 7(a), the structure of the partition member 21 is basically the same as that of the first embodiment. However, in the power storage functional bodies 20A' and 20B', on both the front and back sides of the second electrode bodies 23A and 23B, the first electrode bodies 22A' and 22B' face each other via the separators 24A' and 24B'. Specifically, the lengths of the first electrode bodies 22A' and 22B' and the separators 24A' and 24B' in the winding direction are configured to be at least twice the lengths of the second electrode bodies 23A and 23B in the winding direction. And the middle portions of the first electrode bodies 22A' and 22B' and the separators 24A' and 24B' are folded back so as to wrap the inner peripheral ends of the second electrode bodies 23A and 23B near the central portion of the wound structure body 20', as shown in Fig. 7(b). At this time, different from the first embodiment, in this second embodiment, it is preferable that the second electrode bodies 23A and 23B are those in which the polarizing electrode layers 23A2 and 23B2 are laminated on both the front and back sides of the current collectors 23A1 and 23B1. At this time, for the first electrode bodies 22A' and 22B', the polarizing electrode layers 22A2 and 22B2 need only be laminated on the surfaces facing the second electrode bodies 23A and 23B via the separators 24A and 24B on the current collectors 22A1 and 22B1. By doing so, since the polarizing electrode layers are formed only in the regions where the first electrode layers 22A' and 22B' and the second electrode layers 23A and 23B face each other, the non-facing regions of the polarizing electrode layers can be reduced. Therefore, the deterioration of durability and the variation in durability between the front and back can be suppressed.

[0044] In this embodiment, in each of the power storage functional bodies 20A' and 20B', the first electrode bodies 22A' and 22B' are configured to face the front and back of the second electrode bodies 23A and 23B via the separators 24A' and 24B'. Therefore, while maintaining the compactness, by increasing the facing area between the electrodes, the capacitance can be increased. In this embodiment, it is also possible to adopt a structure in which at least one of the above-mentioned separators 24A' and 24B' and the first electrode bodies 22A' and 22B' is cut at the folded inner peripheral end portion. However, in this case, it is desirable to extend the separators 24A' and 24B' so as to extend to the inner peripheral side of the inner peripheral ends of the second electrode bodies 23A and 23B to ensure insulation between the two electrode bodies.

[0045] <Third Embodiment> Next, with reference to FIG. 8, a power storage device according to the third embodiment of the present invention will be described. In this embodiment, in the wound structure 20″, the structure of the partition member 21 is the same as that of the first embodiment. However, in each power storage functional body 20A″, 20B″, the laminate of the first electrode bodies 22A″, 22B″, the second electrode bodies 23A″, 23B″, and the separators 24A″, 24B″ is folded back at an intermediate portion adjacent to the intermediate portion 21a of the partition member 21, and its inner and outer double laminate is configured to extend to the outer peripheral side. Note that the configurations other than the above can be configured in the same manner as the first embodiment or the second embodiment. Therefore, the same reference numerals are given to the portions that can be configured in the same manner, and the description thereof is omitted.

[0046] In this embodiment, although not shown, if the polarized electrode layer is formed only on one side facing each other through the separators 24A″, 24B″ in the current collectors of the first electrode bodies 22A″, 22B″ and the second electrode bodies 23A″, 23B″, the unopposed region of the polarized electrode layer can be reduced as described above. Also, similar to the second embodiment, the capacitance can be increased by increasing the opposing area between the electrodes while maintaining the compactness. Note that in this embodiment, at least one of the above-described separators 24A″, 24B″, the first electrode bodies 22A″, 22B″, and the second electrode bodies 23A″, 23B″ may have a structure cut at the folded inner peripheral end. However, in this case, it is desirable to extend the separators 24A″, 24B″ to extend to the inner peripheral side of the inner peripheral ends of the second electrode bodies 23A″, 23B″ to ensure insulation between the two electrode bodies.

[0047] <Fourth Embodiment> Next, with reference to FIG. 9, a power storage device according to a fourth embodiment of the present invention will be described. In this embodiment, as shown in FIG. 9(a), the partition member 31 in the wound structure 30 branches into three extending portions 31b, 31c, 31d from the intermediate portion 31a, and each of the extending portions 31b, 31c, 31d is wound in the same direction. As a result, in the wound structure 30, three storage regions are partitioned by the partition member 31, so that a total of three power storage functional bodies 30A, 30B, and 30C can be arranged in their respective storage regions. Similarly, the partition member may be configured such that four or more extending portions branch from the intermediate portion, and the power storage functional bodies may be arranged in the respective storage regions partitioned by the partition member.

[0048] Note that even when there are three or more power storage functional bodies 30A, 30B, and 30C, as shown in FIG. 9(b), each power storage functional body 30A, 30B, and 30C may be inserted while winding the partition member 31. Further, the winding process may be performed in a state where the laminated structure of each power storage functional body is fixed in advance as described above, or in a state where each power storage functional body is fixed in advance to each of the extending portions 31b, 31c, 31d of the partition member 31. Furthermore, in each of the embodiments described above, the partition members 21 and 31 are configured to be integral or connected to each other, but they may be arranged in a wound state inside the wound structures 20 and 30 in a state of being divided into two or more bodies. For example, in this fourth embodiment, the wound structure 30 may be formed by winding with each power storage functional body arranged between three partition members. In this case, it is preferable that the inner peripheral ends of the partition members are configured to contact or be close to each other.

[0049] <Fifth Embodiment> Next, referring to FIG. 10, the fifth embodiment will be described. In this embodiment, separators 24A and 24B are fixed to the intermediate portion 21a of the partition member 21 similar to that in the first embodiment by adhesion or the like from both the front and back sides, and the first electrode bodies 22A and 22B and the second electrode bodies 23A and 23B are laminated on both sides of these separators 24A and 24B and then wound to form a wound structure 20. Other configurations can be made exactly the same as those in the first embodiment.

[0050] In this embodiment, since the inner peripheral ends of the separators 24A and 24B are fixed to the intermediate portion 21a of the partition member 21, the insulation between the first electrode bodies 22A and 22B and the second electrode bodies 23A and 23B can be surely ensured, and thus the insulation characteristics of the wound structure 20 can be improved. Note that such a structure can be applied between any partition member and separator in the first to fourth embodiments described above. Further, in this embodiment, as shown by the dotted line in FIG. 10, the separators 24A and 24B may be further extended to the outer peripheral side and abutted (fixed) to the boundary of the accommodation space to further enhance the insulation characteristics.

[0051] Note that the power storage device of the present invention is not limited to the above-described illustrated examples, and it goes without saying that various changes can be made without departing from the gist of the present invention. For example, in each of the above embodiments, an example of an electric double layer capacitor has been described. However, it is obvious to those skilled in the art that the internal structure of the wound structure can be easily applied to an electrolytic capacitor by forming an insulating film such as an oxide film on the surface of each electrode body. Further, the internal structure according to the present invention is applicable to various capacitor-type power storage devices such as other various capacitors. Furthermore, the internal structure according to the present invention is also applicable to chemical power storage devices such as batteries. Note that the configurations (or characteristic points) of each part in the above embodiments can be arbitrarily combined with each other as long as there is no particular problem.

[0052] Also, in each of the above embodiments, a plurality of sets of first external terminals and second external terminals are provided, and each of the plurality of power storage functional bodies is conductively connected to a separate set of corresponding first external terminals and second external terminals. However, in the power storage device according to the present invention, it may be provided with first external terminals and second external terminals to which a plurality of power storage functional bodies are commonly conductively connected. For example, a plurality of power storage functional bodies may be configured to be conductively connected in series or in parallel to a set of first external terminals and second external terminals.

Explanation of Reference Numerals

[0053] 1... Power 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, 20', 20'', 30... Wound structure, 21, 21', 31... Partition member, 21a, 31a... Intermediate part, 21b, 31b... First extending part, 21c, 31c... Second extending part, 31d... Third extending part, 21e... Outer edge part (side edge), 21be, 21ce... Outer edge part (end edge), 22A, 22B... First electrode body, 23A, 23B... Second electrode body, 24A, 24B... Separator, 26... Holding member, 22A1, 22B1, 23A1, 23B1... Current collector, 22A2, 22B2, 23A2, 23B2... Polarized electrode layer

Claims

1. A power storage device comprising a wound structure and a housing that constitutes a storage space for housing the wound structure, wherein the wound structure is a strip-shaped partition member having electrolyte blocking properties and being electrically insulating, wound so as to partition the storage space into a plurality of storage regions, and a plurality of power storage functional bodies, each of which is separately arranged in each of the plurality of storage regions in a manner wound along the partition member, and has each of the power storage functional bodies includes a first electrode body, a second electrode body, and a separator disposed between the first electrode body and the second electrode body, and is configured in a strip shape wound along the partition member, a power storage device.

2. The outer edge portion of the partition member protrudes outward in the axial direction of the wound structure beyond the first electrode body and the second electrode body in the wound structure. The power storage device according to Claim 1.

3. The outer edge portion of the partition member abuts against a boundary outside the storage space in the axial direction. The power storage device according to Claim 2.

4. The outer edge portion of the partition member is disposed outside the first electrode body and the second electrode body in the wound structure in the radial direction of the wound structure. The power storage device according to any one of Claims 1 to 3.

5. The outer edge portion of the partition member abuts against a boundary outside the storage space in the radial direction. The power storage device according to Claim 4.

6. An electrolyte is introduced into the wound structure, and the partition member has impermeability and non-retainability to the electrolyte and its ions. The power storage device according to any one of Claims 1 to 5.

7. The electrolyte is configured in a liquid state, and the partition member has a surface with a contact angle of 80 degrees or more with respect to the electrolyte. The power storage device according to Claim 6.

8. In the partition member, a plurality of extending portions extending to the outer peripheral side around an intermediate portion are each wound in the same direction around the intermediate portion, and the storage region is formed to circulate from an inner peripheral portion adjacent to the intermediate portion between the plurality of extending portions to an outer peripheral portion. The power storage device according to any one of Claims 1 to 7.

9. The partition member and the plurality of power storage functional bodies are formed rotationally symmetric about the axis of the wound structure. The power storage device according to any one of Claims 1 to 8.

10. The first electrode body, the second electrode body, and the separator in the plurality of power storage functional bodies are also formed to be rotationally symmetric about the axis. The power storage device according to claim 9. **Claim 11** The wound structure has a structure in which the outer peripheral portions of the first electrode body and the second electrode body are covered from the outer peripheral side in the radial direction by the outer peripheral portion of the partition member. The power storage device according to any one of claims 8 to 10. **Claim 12** The outer peripheral portions of the separators are each present over a wider angular range on the outer peripheral side in the radial direction of the wound structure than the first electrode body and the second electrode body. The power storage device according to claim 11.

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