Energy storage device

Abstract

To provide a power storage device which can determine whether there is an abnormality in the internal pressure, from the outside.SOLUTION: A power storage device 10 has an electrode laminate part 20 and a seal part 30. In the electrode laminate part 20, a plurality of bipolar electrodes 22, in which a positive electrode 27 is formed on one surface 25A of a collector 25 and a negative electrode 28 is formed on the other surface 25B, are laminated through a separator 24. The seal part 30 is arranged to surround the electrode laminate part 20, holds the collector 25, forms a space S between two bipolar electrodes 22 adjacent to each other through the separator 24, and seals the space S. A space S1, which is formed in an outmost end part of the bipolar electrode 22 in a lamination direction D, is narrower than another space S.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a power storage device having a bipolar structure.

Background Art

[0002] Patent Document 1 discloses a power storage device having a bipolar structure in which a current collector coated with electrode active materials of a positive electrode and a negative electrode on both sides, respectively, and a separator are alternately stacked.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the power storage device having a bipolar structure described in Patent Document 1, for example, since the cells overlap each other, it is difficult to visually confirm whether the internal pressure of each cell is negative.

[0005] In consideration of the above fact, an object of the present invention is to provide a power storage device capable of determining the presence or absence of an abnormality in internal pressure from the outside.

Means for Solving the Problems

[0006] [[ID=?]] The power storage device according to the present invention described in claim 1 includes an electrode laminate portion in which a plurality of bipolar electrodes each having a positive electrode formed on one surface of a current collector and a negative electrode formed on the other surface are laminated via a separator, and is disposed so as to surround the electrode laminate portion, holds the current collector, forms a space between two adjacent bipolar electrodes via the separator, and seals the space. A seal portion, and the space formed at the outermost end in the stacking direction of the bipolar electrodes is narrower than the other spaces. The seal portion is formed such that the seal portion forming the space at the outermost end is longer inward than the seal portions forming other spaces, and the seal portion comprises a plurality of pairs of retaining seal materials that each hold the current collector of the stacked bipolar electrodes from both sides in the stacking direction, an outer peripheral retaining seal portion that holds the outer periphery of the pair of retaining seal materials, and a spacer interposed between two adjacent pairs of retaining seal materials in the stacking direction of the bipolar electrodes, wherein the inner ends of at least the retaining seal material forming the space at the outermost end and the spacer are in the same position in a direction substantially perpendicular to the stacking direction. .

[0007] In the energy storage device according to claim 1, the space formed at the outermost end in the stacking direction of the bipolar electrodes is narrower than other spaces. Therefore, when the pressure inside the battery rises, the space formed at the outermost end is more susceptible to the effects than other spaces. For this reason, by checking the internal pressure of the space formed at the outermost end, it is possible to determine from the outside whether or not there is an abnormality in the internal pressure.

[0009] Also, Claim 1 In the energy storage device according to the present invention as described above, the seal portion forming the space at the outermost end in the stacking direction of the bipolar electrodes is formed to be longer inward than the seal portions forming other spaces, so that the space formed at the outermost end can be narrowed by the seal portion. Therefore, by checking the internal pressure of the space formed at the outermost end, it is possible to determine from the outside whether or not there is an abnormality in the internal pressure.

[0011] Also, Claim 1 In the energy storage device according to the present invention described herein, the inner ends of the retaining seal material and spacer that form the space at the outermost end in the stacking direction of the bipolar electrodes are located at the same position in a direction substantially perpendicular to the stacking direction. Therefore, it is possible to suppress the complexity of the shape of the space formed at the outermost end in the stacking direction of the bipolar electrodes.

[0012] Claim 2 The energy storage device according to the present invention described herein is The electrode stack comprises a plurality of bipolar electrodes, each having a positive electrode on one side and a negative electrode on the other, stacked via a separator, and a sealing portion arranged to surround the electrode stack, holding the current collector, forming a space between two adjacent bipolar electrodes via the separator, and sealing the space, wherein the space formed at the outermost end in the stacking direction of the bipolar electrodes is narrower than the other spaces.The sealing portion comprises a plurality of pairs of retaining sealing materials that each hold the current collector of the stacked bipolar electrodes from both sides in the stacking direction, an outer peripheral retaining sealing portion that holds the outer peripheral of the pair of retaining sealing materials, and a spacer interposed between two adjacent pairs of retaining sealing materials in the stacking direction of the bipolar electrodes, wherein the space is formed by being surrounded by the spacer, two retaining sealing materials located on both sides of the spacer in the stacking direction, a first current collector held by a pair of retaining sealing materials including one of the two retaining sealing materials, a second current collector held by a pair of retaining sealing materials including the other of the two retaining sealing materials, the positive electrode formed on one side of the first current collector, and the negative electrode formed on the other side of the second current collector, wherein at least one of the positive electrode and the negative electrode forming the space at the outermost end is formed to be larger on the outer peripheral side than the other positive electrode and the other negative electrode.

[0013] In the energy storage device according to claim 2, the space formed at the outermost end in the stacking direction of the bipolar electrodes is narrower than the other spaces. Therefore, when the internal pressure of the battery rises, the space formed at the outermost end is more susceptible to the effects than the other spaces. For this reason, by checking the internal pressure of the space formed at the outermost end, it is possible to determine from the outside whether or not there is an abnormality in the internal pressure. Furthermore, Claim 2 In the energy storage device according to the present invention as described above, at least one of the positive electrode and the negative electrode that forms the space at the outermost end in the stacking direction of the bipolar electrodes is formed to be larger on the outer circumference than the other positive electrode and the other negative electrode. Therefore, the space formed at the outermost end can be narrowed by at least one of the positive electrode and the negative electrode without changing the shape of the seal portion. Accordingly, by checking the internal pressure of the space formed at the outermost end, it is possible to determine from the outside whether or not there is an abnormality in the internal pressure.

[0014] Claim 3 The energy storage device according to the present invention described herein is The electrode stack comprises a plurality of bipolar electrodes, each having a positive electrode on one side and a negative electrode on the other, stacked via a separator, and a sealing portion arranged to surround the electrode stack, holding the current collector, forming a space between two adjacent bipolar electrodes via the separator, and sealing the space, wherein the space formed at the outermost end in the stacking direction of the bipolar electrodes is narrower than the other spaces.The sealing portion comprises a plurality of pairs of retaining sealing materials that each hold the current collector of the stacked bipolar electrodes from both sides in the stacking direction, an outer peripheral retaining sealing portion that holds the outer peripheral portion of the pair of retaining sealing materials, and a spacer interposed between two adjacent pairs of retaining sealing materials in the stacking direction of the bipolar electrodes. The space is formed by the spacer, two retaining sealing materials located on both sides of the spacer in the stacking direction, a first current collector held by a pair of retaining sealing materials including one of the two retaining sealing materials, a second current collector held by a pair of retaining sealing materials including the other of the two retaining sealing materials, the positive electrode formed on one side of the first current collector, and the negative electrode formed on the other side of the second current collector. An electrolyte-resistant member is disposed at the outer peripheral end of at least one of the positive electrode and the negative electrode that form the space at the outermost end.

[0015] In the energy storage device according to claim 3, the space formed at the outermost end in the stacking direction of the bipolar electrodes is narrower than the other spaces. Therefore, when the internal pressure of the battery rises, the space formed at the outermost end is more susceptible to the effects than the other spaces. For this reason, by checking the internal pressure of the space formed at the outermost end, it is possible to determine from the outside whether or not there is an abnormality in the internal pressure. Furthermore, Claim 3 In the energy storage device according to the present invention as described above, an electrolyte-resistant member is placed at the outer peripheral end of at least one of the positive electrode and the negative electrode that forms a space at the outermost end in the stacking direction of the bipolar electrodes. Therefore, the space formed at the outermost end can be narrowed by the member without changing the shape of the electrode stacking portion and the sealing portion. Accordingly, by checking the internal pressure of the space formed at the outermost end, it is possible to determine from the outside whether or not there is an abnormality in the internal pressure. [Effects of the Invention]

[0016] As described above, the energy storage device according to the present invention has the excellent effect of being able to determine from the outside whether or not there is an abnormality in the internal pressure. [Brief explanation of the drawing]

[0017] [Figure 1] This is a perspective view showing the appearance of the energy storage device before it is packed, according to the first embodiment of the present invention. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3]It is a cross-sectional view corresponding to FIG. 2 of the power storage device according to the second embodiment of the present invention. [Figure 4] It is a cross-sectional view corresponding to FIG. 2 of the power storage device according to the third embodiment of the present invention. [Figure 5] It is a cross-sectional view corresponding to FIG. 2 of the power storage device according to the fourth embodiment of the present invention. [Figure 6] It is a cross-sectional view corresponding to FIG. 2 of the conventional power storage device.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, referring to the drawings, the power storage device 10 according to the first embodiment of the present invention will be described. FIG. 1 is a perspective view showing the appearance of the power storage device 10 before packaging according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. The power storage device 10 of the present embodiment is a bipolar type power storage device and is used, for example, as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 10 is a secondary battery such as a nickel-hydrogen secondary battery or a lithium-ion secondary battery, for example. The power storage device 10 may be an electric double layer capacitor, for example. In the present embodiment, the case where the power storage device 10 is a lithium-ion secondary battery will be exemplified.

[0019] As shown in FIG. 1, the power storage device 10 is formed in a substantially rectangular parallelepiped shape and includes a liquid injection port frame 12 formed with a liquid injection port (not shown) into which an electrolytic solution described later is injected, and a substrate portion 14 for detecting the voltage of each battery cell constituting the power storage device 10. The substrate portion 14 includes an FPC (Flexible Printed Circuits) substrate 14A which is an example of a voltage detection circuit board including a circuit for detecting voltage, and both ends of the FPC substrate 14A in one direction are held by an FPC housing 14B. Although not shown, the power storage device 10 is housed in a battery case.

[0020] The energy storage device 10 comprises an electrode stacking section 20 and a sealing section 30 arranged to surround the electrode stacking section 20. As shown in Figure 2, the electrode stacking section 20 is formed by stacking multiple bipolar electrodes 22 with separators 24 in between. That is, separators 24 are interposed between adjacent bipolar electrodes 22 in the stacking direction D (up and down direction in Figure 2). In this embodiment, at least three or more bipolar electrodes 22 are stacked. As shown in Figure 1, the electrode stacking section 20 has, for example, a rectangular shape when viewed from the stacking direction.

[0021] The bipolar electrode 22 includes a current collector 25 and an electrode layer 26. The current collector 25 is formed in the shape of a rectangular sheet and in this embodiment has one surface 25A on the lower surface in the stacking direction D and the other surface 25B on the upper surface. The current collector 25 is a chemically inert electrical conductor that allows current to continue to flow through the electrode layer 26, for example, during the discharge or charging of the energy storage device 10. In this embodiment, the current collector 25 is formed from a rectangular metal foil made of a metal such as Al, SUS, Ni, or Cu.

[0022] The electrode layer 26 is formed on the inner side of the periphery of the current collector 25, and is formed on at least one of the two surfaces 25A and 25B of the current collector 25. That is, the peripheral edge 25C of the current collector 25 has a rectangular frame shape and is an uncoated area where the electrode layer 26 is not applied. In Figure 2, the peripheral side of the electrode stacking portion 20 (left side in the figure) is referred to as the outside, and the inner side of the electrode stacking portion 20 (right side in the figure) is referred to as the inside, and so on.

[0023] The electrode layer 26 includes at least one of a positive electrode 27 and a negative electrode 28. The positive electrode 27 is formed on one surface 25A of the current collector 25, and the negative electrode 28 is formed on the other surface 25B of the current collector 25. In the case of the bipolar electrode 22A that constitutes the lower end of the electrode stacked portion 20 in the stacking direction D, the positive electrode 27 is not provided on one surface 25A. Also, in the case of the bipolar electrode 22B that constitutes the upper end of the electrode stacked portion 20 in the stacking direction D, the negative electrode 28 is not provided on the other surface 25B.

[0024] The positive electrode 27 is a positive electrode active material layer formed by coating one surface 25A of the current collector 25 with positive electrode active material. Examples of positive electrode active materials that constitute the positive electrode 27 include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Rock salt layered active materials such as O2, LiMn2O4, Li(Ni 0.5 Mn 1.5 Examples of active materials include spinel-type active materials such as O4, and olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCuPO4. The positive electrode active material layer forming the positive electrode 27 may contain a conductive material and a binder in addition to the positive electrode active material.

[0025] The negative electrode 28 is a negative electrode active material layer formed by coating the other surface 25B of the current collector 25 with a negative electrode active material. Examples of negative electrode active materials that make up the negative electrode 28 include carbon active materials, oxide active materials, and metal active materials.

[0026] In the electrode stacking section 20, the positive electrode 27 of one bipolar electrode 22 faces the negative electrode 28 of another bipolar electrode 22 adjacent to it in one direction of the stacking direction D, separated by a separator 24. In addition, in the electrode stacking section 20, the negative electrode 28 of one bipolar electrode 22 faces the positive electrode 18 of another bipolar electrode 22 adjacent to it in the other direction of the stacking direction D, separated by a separator 24.

[0027] In this embodiment, the region where the negative electrode 28 is formed on the other surface 25B of the current collector 25 is slightly larger than the region where the positive electrode 27 is formed on one surface 25A of the current collector 25.

[0028] The separator 24 is positioned between adjacent bipolar electrodes 22 in the stacking direction D, and is interposed between the positive electrode 27 and the negative electrode 28. By isolating the positive electrode 27 and the negative electrode 28, the separator 24 prevents short circuits caused by contact between adjacent electrode layers 26 while allowing charge carriers such as lithium ions to pass through. The separator 24 is formed, for example, in the form of a sheet. Examples of the separator 24 include porous films made of polyolefin resins such as polyethylene (PE) and polypropylene (PP), and woven or nonwoven fabrics made of polypropylene, methylcellulose, etc. The separator 24 may also be reinforced with a vinylidene fluoride resin compound. Note that the separator 24 is not limited to a sheet, and a bag-shaped separator may also be used.

[0029] The sealing portion 30 is formed in a frame shape on the periphery of the electrode stacking portion 20 so as to surround the electrode stacking portion 20, and comprises a pair of retaining sealing materials 32, an outer peripheral retaining sealing portion 34, and a spacer 36. The pair of retaining sealing materials 32 hold at least the outer peripheral region of the peripheral edge 25C of one surface 25A and the other surface 25B of each current collector 25 from both sides in the stacking direction D. The pair of retaining sealing materials 32 comprises a first retaining sealing material 32A joined to the peripheral edge 25C of one surface 25A of the current collector 25, and a second retaining sealing material 32B joined to the peripheral edge 25C of the other surface 25B of the current collector 25.

[0030] The first retaining seal material 32A and the second retaining seal material 32B are formed in a two-layer structure, for example, by folding a single film in half. That is, the peripheral side, which is the region not connected to the current collector 25, is the folded portion (bent portion) of the film, and they are joined to each other at this peripheral portion. In addition, at least one of the surfaces of the first retaining seal material 32A and the second retaining seal material 32B that are opposite each other is joined to one surface 25A or the other surface 25B of the current collector 25.

[0031] In this embodiment, the pair of retaining seal materials 32 are made of a single film, but the present invention is not limited to this, and may be made of two films. That is, the first retaining seal material 32A and the second retaining seal material 32B may be formed separately. In this case, the peripheral edges of the first retaining seal material 32A and the second retaining seal material 32B are joined together.

[0032] The outer peripheral retaining seal portion 34 holds the outer periphery of multiple pairs of retaining seal materials 32. Specifically, the outer peripheral retaining seal portion 34 is a welded layer formed by welding the overlapping portions of multiple pairs of retaining seal materials 32 and multiple spacers 36 (described later) in the stacking direction, thereby integrating multiple pairs of retaining seal materials 32 and multiple spacers 36 (described later).

[0033] The spacer 36 is interposed between two pairs of adjacent retaining seal materials 32 in the stacking direction D. Specifically, the spacer 36 is positioned between the first retaining seal material 32A of one pair of adjacent retaining seal materials 32 and the second retaining seal material 32B of the other pair of adjacent retaining seal materials 32. This spacer 36 maintains the gap between two adjacent pairs of retaining seal materials 32 in the stacking direction D. In other words, the spacer 36 maintains the gap between adjacent current collectors 25 in the stacking direction D at a desired distance.

[0034] The spacer 26 is formed in a frame shape and is positioned on the peripheral edge 25C of the current collector 25 when viewed from the stacking direction D. The spacer 36 is welded to at least one of the first retaining seal material 32A and the second retaining seal material 32B adjacent to each other in the stacking direction D. In this embodiment, the inner surface of the spacer 36 is formed to be longer than the inner surfaces of the first retaining seal material 32A and the second retaining seal material 32B. In this embodiment, the peripheral edge of each separator 24 is fixed by being sandwiched between the spacer 36 and the second retaining seal material 32B, for example. The separator 24 may be joined to either the spacer 36 or the second retaining seal material 32B.

[0035] The sealing portion 30 is formed of, for example, an insulating resin, and examples of resin constituent materials include polypropylene (PP), polyphenylene sulfide (PPS), and modified polyphenylene ether (modified PPE).

[0036] In this embodiment, a plurality of spaces S are provided within the energy storage device 10. Each space S is provided between adjacent bipolar electrodes 22 in the stacking direction D via a separator 24, and is a space sealed airtight and liquidtight by a seal portion 30. Specifically, as an example, space S2 is defined by one surface 25A of the current collector 25 (first current collector) of the upper bipolar electrode 22-1, one of the bipolar electrodes 22-1 and 12-2 adjacent in the stacking direction D, the outer peripheral surface of the positive electrode 27, and the inner surface of the first retaining seal material 32A, the other surface 25B of the current collector 25 (second current collector) of the lower bipolar electrode 22-2, the outer peripheral surface of the negative electrode 28, and the inner surface of the second retaining seal material 32B, as well as the inner surface of the spacer 36 interposed between the bipolar electrodes 22-1 and 12-2, and the upper and lower surfaces of the spacer 36 protruding from the pair of retaining seal materials 32. Other spaces S in space S2 are defined in the same manner.

[0037] Each of these spaces S contains, for example, an electrolyte (not shown). The electrolyte contains, for example, a non-aqueous solvent and a supporting salt. Examples of non-aqueous solvents include organic solvents such as carbonates, ethers, esters, nitriles, sulfones, and lactones. Examples of supporting salts include lithium salts such as LiPF6. The electrolyte is impregnated into the separator 24, the positive electrode 27, and the negative electrode 28.

[0038] As shown in Figure 1, the energy storage device 10 is provided with an injection port frame 12, and this injection port frame 12 has multiple injection ports (not shown) arranged in the cross-sectional direction D that connect each space S to the external space. Each injection port is provided offset in the direction of the short side of the seal portion 30, for example, so that adjacent injection ports do not overlap in the stacking direction D (see Figure 2).

[0039] In this embodiment, as shown in Figure 2, the space S1 formed at the uppermost end (upper side in Figure 2) as the outermost end in the stacking direction D is formed to be narrower than the other spaces S (including space S2). Specifically, the seal portion 30 forming space S1 is formed to be longer inward than the seal portions 30 forming the other spaces S. More specifically, the inner surface of the first retaining seal material 32A facing space S1, the inner surface of the spacer 36 facing space S1, and the inner surface of the second retaining seal material 32B facing space S1 are formed to be longer inward than the inner surfaces facing the other spaces S.

[0040] In other words, when viewed from the stacking direction D, the width of the frame portion of the first retaining seal material 32A, spacer 36, and second retaining seal material 32B that form space S1 is wider than the width of the frame portion of the first retaining seal material 32A, spacer 36, and second retaining seal material 32B that form other spaces S. To put it another way, when viewed from the stacking direction D, the area of ​​the first retaining seal material 32A, spacer 36, and second retaining seal material 32B that form space S1 is wider than the area of ​​the first retaining seal material 32A, spacer 36, and second retaining seal material 32B that form other spaces S.

[0041] Next, the effects and benefits of the energy storage device 10 in the first embodiment will be described.

[0042] Here, Figure 6 shows a cross-sectional view of a conventional energy storage device 100 corresponding to Figure 2. In Figure 6, components similar to those in Figure 2 are indicated by the same reference numerals and their explanation is omitted here; only the different structures will be explained in detail.

[0043] As shown in Figure 6, in the structure of the conventional energy storage device 100, the electrode stacking portion 20, the seal portion 30, and the spacer 36 of each bipolar electrode 22 stacked in the stacking direction D are identical in shape. Therefore, the size of each space S formed inside the energy storage device 100 is uniform. In the structure of the conventional energy storage device 100, since each space S of the same size overlaps in the stacking direction D, it is difficult to visually confirm whether the pressure inside each space S is negative.

[0044] In contrast to the structure of the conventional energy storage device 100, the energy storage device 10 in this embodiment, as shown in Figure 2, has a seal portion 30 that forms the space S1 at the uppermost end in the stacking direction D of the bipolar electrodes 22, which is longer inward than the seal portions 30 that form other spaces S. Therefore, the space S1 formed at the uppermost end can be narrowed by the seal portion 30 and the spacer 36.

[0045] In this embodiment, the space S1 formed at the uppermost end, which is the outermost end in the stacking direction D of the bipolar electrodes 22, is narrower than the other spaces S in the energy storage device 10. Therefore, when the pressure inside the energy storage device 10 rises, the space S1 formed at the uppermost end is more susceptible to the effects than the other spaces S. As a result, by checking the internal pressure of the space S1 formed at the uppermost end, it is possible to determine from the outside whether there is an abnormality in the internal pressure. In other words, by monitoring only the internal pressure of the space S1 formed at the uppermost end, without monitoring the internal pressure of all spaces S, it is possible to determine whether there is an abnormality in the internal pressure of the energy storage device 10.

[0046] In this embodiment, as an example, as shown in Figures 1 and 2, the change in internal pressure of space S1 can be detected by detecting the amount of bulging on the other side 25B of the current collector 25 of the bipolar electrode 22B that constitutes the uppermost end of the electrode stacking portion 20 in the stacking direction D. Here, the sensor used for detection can be a known sensor such as a laser displacement sensor, but the type of sensor is not particularly limited.

[0047] In the energy storage device 10 of the first embodiment described above, as shown in Figure 2, the inner surfaces of the first retaining seal material 32A, spacer 36, and second retaining seal material 32B facing the space S1 formed at the uppermost end of the stacking direction D of the bipolar electrode 22 are formed to be longer inward than their respective inner surfaces facing other spaces S. However, the present invention is not limited to this. It is sufficient that the inner surface of one or more of the first retaining seal material 32A, spacer 36, and second retaining seal material 32B facing the space S1 formed at the uppermost end of the stacking direction D of the bipolar electrode 22 is formed to be longer inward than their respective inner surfaces facing other spaces S.

[0048] Next, a second embodiment of the energy storage device 10A of the present invention will be described. Figure 3 is a cross-sectional view of the energy storage device 10A of the second embodiment of the present invention, corresponding to Figure 2. In the second embodiment, components similar to those in the first embodiment described above are indicated by the same reference numerals and their descriptions are omitted, and only the different structures will be described in detail.

[0049] In the first embodiment described above, the inner surface of the spacer 36 is formed to be longer than the inner surfaces of the first retaining seal material 32A and the second retaining seal material 32B. In contrast, in the energy storage device 10A of the second embodiment, as shown in Figure 3, the inner surface of the spacer 36 that forms the space S1 formed at the uppermost end, which is the outermost end of the stacking direction D of the bipolar electrodes 22, is formed to be the same length as the inner surfaces of the first retaining seal material 32A and the second retaining seal material 32B. That is, the positions of the inner ends of the spacer 36, the first retaining seal material 32A, and the second retaining seal material 32B that form the space S1 are the same in a direction substantially perpendicular to the stacking direction D.

[0050] Next, the effects and benefits of the energy storage device 10A in the second embodiment will be described.

[0051] In the energy storage device 10A of the second embodiment, the same effects as those of the energy storage device 10 of the first embodiment described above can be obtained. Furthermore, in the energy storage device 10A of the second embodiment, the positions of the inner ends of the first retaining seal material 32A, the second retaining seal material 32B, and the spacer 36 that form the space S1 formed at the uppermost end, which is the outermost end of the stacking direction D of the bipolar electrodes 22, are the same in a direction substantially perpendicular to the stacking direction D. Therefore, it is possible to suppress the complexity of the shape of the space S1 formed at the uppermost end of the stacking direction D of the bipolar electrodes 22.

[0052] In the second embodiment described above, the lengths of the inner surfaces of the first retaining seal material 32A, the second retaining seal material 32B, and the spacer 36 are the same only in the space S1 formed at the uppermost end, which is the outermost end in the stacking direction D of the bipolar electrode 22. However, the present invention is not limited to this. Similarly, the lengths of the inner surfaces of the first retaining seal material 32A, the second retaining seal material 32B, and the spacer 36 may be the same in spaces S other than the uppermost space S1. However, in the uppermost space S1, the lengths of the inner surfaces of the first retaining seal material 32A, the second retaining seal material 32B, and the spacer 36 are formed to be longer than in the other spaces S.

[0053] Next, a third embodiment of the present invention, the energy storage device 10B, will be described. Figure 4 is a cross-sectional view of the energy storage device 10B according to the third embodiment of the present invention, corresponding to Figure 2. In the third embodiment, components similar to those in the first embodiment described above are indicated by the same reference numerals and their descriptions are omitted; only the different structures will be described in detail.

[0054] In the first embodiment described above, the seal portion 30 that forms the space S1 at the uppermost end of the bipolar electrode 22 in the stacking direction D is formed to be longer inward than the seal portions 30 that form the other spaces S. In contrast, in the energy storage device 10B of the third embodiment, the seal portion 30 that forms the space S1 at the uppermost end of the bipolar electrode 22 in the stacking direction D is formed to be the same length inward as the seal portions 30 that form the other spaces S.

[0055] In the third embodiment of the energy storage device 10B, as shown in Figure 4, the positive electrode 27 and negative electrode 28 that form the space S1 formed at the uppermost end in the stacking direction D of the bipolar electrode 22 are formed to be larger towards the outer periphery than the positive electrode 27 and negative electrode 28 that form the other spaces S. That is, when viewed from the stacking direction D, the area of ​​the positive electrode 27 and negative electrode 28 that form space S1 is formed to be larger than the area of ​​the positive electrode 27 and negative electrode 28 that form the other spaces S.

[0056] Next, the effects and benefits of the energy storage device 10B in the third embodiment will be described.

[0057] In the third embodiment of the energy storage device 10B, the positive electrode 27 and negative electrode 28 that form the space S1 formed at the uppermost end of the stacking direction D of the bipolar electrodes 22 are formed to extend further outward than the positive electrode 27 and negative electrode 28 that each form other spaces S. Therefore, without changing the shape of the seal portion 30, the space S1 formed at the uppermost end of the stacking direction D of the bipolar electrodes 22 can be narrowed by the positive electrode 27 and negative electrode 28. Accordingly, similar to the energy storage device 10 of the first embodiment described above, the presence or absence of an abnormality in the internal pressure can be determined from the outside by checking the internal pressure of the space S1 formed at the uppermost end.

[0058] In the third embodiment described above, the positive electrode 27 and negative electrode 28 that form the space S1 formed at the uppermost end in the stacking direction D of the bipolar electrode 22 are formed to be larger on the outer circumference than the positive electrode 27 and negative electrode 28 that form the other spaces S, respectively, but the present invention is not limited thereto. Only the positive electrode 27 that forms space S1 may be formed to be larger on the outer circumference than the positive electrode 27 that forms the other spaces S, or only the negative electrode 28 that forms space S1 may be formed to be larger on the outer circumference than the negative electrode 28 that forms the other spaces S.

[0059] Next, a fourth embodiment of the present invention, the energy storage device 10C, will be described. Figure 5 is a cross-sectional view of the energy storage device 10C according to the fourth embodiment of the present invention, corresponding to Figure 2. In the fourth embodiment, components similar to those in the first embodiment described above are indicated by the same reference numerals and their descriptions are omitted; only the different structures will be described in detail.

[0060] In the first embodiment described above, the seal portion 30 that forms the space S1 formed at the uppermost end of the bipolar electrode 22 in the stacking direction D is formed to be longer inward than the seal portions 30 that form the other spaces S. In contrast, in the energy storage device 10B of the fourth embodiment, the seal portion 30 that forms the space S1 formed at the uppermost end of the bipolar electrode 22 in the stacking direction D is formed to be the same length inward as the seal portions 30 that form the other spaces S.

[0061] In the fourth embodiment of the energy storage device 10C, as shown in Figure 5, an electrolyte-resistant member 19 is arranged at the outer peripheral end of the positive electrode 27 that forms a space S1 at the uppermost end of the bipolar electrode 22 in the stacking direction D. Examples of constituent materials for the member 19 include polypropylene (PP), polyethylene (PE), perfluoroalkoxyalkane (PFA), and polytetrafluoroethylene (PTFT).

[0062] The member 19 may be provided at all of the outer ends of the positive electrode 27, that is, surrounding the positive electrode 27, or it may be provided at multiple locations with gaps in between.

[0063] Next, the effects and advantages of the energy storage device 10C in the fourth embodiment will be described.

[0064] In the fourth embodiment of the energy storage device 10C, an electrolyte-resistant member 19 is placed at the outer peripheral end of the positive electrode 27, which forms a space S1 at the uppermost end of the bipolar electrode 22 in the stacking direction D. Therefore, without changing the shape of the seal portion 30, the positive electrode 27, and the negative electrode 28, the space S1 formed at the uppermost end of the bipolar electrode 22 in the stacking direction D can be narrowed by the member 19. Accordingly, similar to the energy storage device 10 of the first embodiment described above, it is possible to determine from the outside whether there is an abnormality in the internal pressure by checking the internal pressure of the space S1 formed at the uppermost end.

[0065] In the fourth embodiment described above, the member 19 was placed only at the outer peripheral end of the positive electrode 27 that forms the space S1 formed at the uppermost end of the bipolar electrode 22 in the stacking direction D. However, the present invention is not limited to this. The member 19 may be placed only at the outer peripheral end of the negative electrode 28 that forms the space S1, or the member 19 may be placed at both ends of the positive electrode 27 and the negative electrode 28.

[0066] [remarks] In the embodiments described above, the space S1 formed at the uppermost end of the bipolar electrode 22 in the stacking direction D is made narrower than the other spaces S. However, the present invention is not limited to this, and the space S formed at the lowermost end of the bipolar electrode 22 in the stacking direction D may also be made narrower than the other spaces S. Furthermore, both the uppermost and lowermost spaces S1 formed at the bipolar electrode 22 in the stacking direction D may be made narrower than the other spaces S.

[0067] Furthermore, while the above-described embodiment uses a liquid-based battery in which an electrolyte is injected into space S as an example, the present invention is not limited to this and can also be applied to all-solid-state batteries as long as they have a bipolar structure.

[0068] Furthermore, the configuration of this disclosure is not limited to the embodiments described above, and the configuration can be modified as appropriate, as long as the problem can be solved. [Explanation of Symbols]

[0069] 10,10A~10C energy storage device, 20 electrode stacked section, 22, 22A, 22B Bipolar electrodes, 24 Separator, 25 Current collector, 25A One side, 25B The other side, 26 Electrode layer, 27 Positive electrode, 28 Negative electrode, 29 Component, 30 sealing portion, 32 pair of retaining sealing materials, 34 outer peripheral retaining sealing material, 36 Spacer, S Space, S1 Space formed at the uppermost end (space formed at the outermost end)

Claims

1. A stacked electrode section is formed by stacking multiple bipolar electrodes, each having a positive electrode on one side of the current collector and a negative electrode on the other side, separated by a separator. The electrode stack is surrounded by a sealing portion which holds the current collector and forms a space between two adjacent bipolar electrodes via the separator and seals the space, The space formed at the outermost end in the stacking direction of the bipolar electrode is formed to be narrower than the other spaces. The sealing portion that forms the space formed at the outermost end is formed to be longer inward than the sealing portions that form other spaces, The sealing portion comprises a plurality of pairs of retaining sealing materials that hold the current collectors of the stacked bipolar electrodes from both sides in the stacking direction, and an outer peripheral retaining sealing portion that holds the outer peripheral portion of the pair of retaining sealing materials. The bipolar electrodes are further comprising a spacer interposed between two adjacent pairs of retaining seal materials in the stacking direction, An energy storage device in which the inner ends of the retaining seal material and the spacer that form the space formed at least at the outermost end are in the same position in a direction substantially perpendicular to the stacking direction.

2. A stacked electrode section is formed by stacking multiple bipolar electrodes, each having a positive electrode on one side of the current collector and a negative electrode on the other side, separated by a separator. The electrode stack is surrounded by a sealing portion which holds the current collector and forms a space between two adjacent bipolar electrodes via the separator and seals the space, The space formed at the outermost end in the stacking direction of the bipolar electrode is formed to be narrower than the other spaces. The sealing portion comprises a plurality of pairs of retaining sealing materials that hold the current collectors of the stacked bipolar electrodes from both sides in the stacking direction, and an outer peripheral retaining sealing portion that holds the outer peripheral portion of the pair of retaining sealing materials. The bipolar electrodes are further comprising a spacer interposed between two adjacent pairs of retaining seal materials in the stacking direction, The space is formed by being surrounded by the spacer, two retaining seals located on both sides of the spacer in the stacking direction, a first current collector held by a pair of retaining seals including one of the two retaining seals, a second current collector held by a pair of retaining seals including the other of the two retaining seals, the positive electrode formed on one surface of the first current collector, and the negative electrode formed on the other surface of the second current collector. An energy storage device in which at least one of the positive electrode and the negative electrode forming the space at the outermost end is formed to be larger on the outer circumference than the other positive electrode and the other negative electrode.

3. A stacked electrode section is formed by stacking multiple bipolar electrodes, each having a positive electrode on one side of the current collector and a negative electrode on the other side, separated by a separator. The electrode stack is surrounded by a sealing portion which holds the current collector and forms a space between two adjacent bipolar electrodes via the separator and seals the space, The space formed at the outermost end in the stacking direction of the bipolar electrode is formed to be narrower than the other spaces. The sealing portion comprises a plurality of pairs of retaining sealing materials that each hold the current collector of the stacked bipolar electrodes from both sides in the stacking direction, an outer peripheral retaining sealing portion that holds the outer peripheral of the pair of retaining sealing materials, and a spacer interposed between two adjacent pairs of retaining sealing materials in the stacking direction of the bipolar electrodes. The space is formed by the spacer, two retaining seals located on both sides of the spacer in the stacking direction, a first current collector held by a pair of retaining seals including one of the two retaining seals, a second current collector held by a pair of retaining seals including the other of the two retaining seals, the positive electrode formed on one surface of the first current collector, and the negative electrode formed on the other surface of the second current collector. An energy storage device wherein an electrolyte-resistant member is disposed at the outer peripheral end of at least one of the positive electrode and the negative electrode that form the space at the outermost end.

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