Manufacturing method of bipolar type power storage device

Abstract

To provide a manufacturing method of a bipolar power storage device capable of suppressing an electrolyte impregnation defect of an electrode.SOLUTION: A manufacturing method of a bipolar power storage device includes: a first pressure reduction step S20 of reducing a pressure in an internal space to a first pressure via an attachment; a first liquid injection step S40 of injecting a predetermined amount of electrolyte from a holding part in which the preset predetermined amount of electrolyte is held, through a liquid injection port to the internal space in which the pressure is reduced in the first pressure reduction step S20; a second pressure reduction step S50 of reducing a pressure in the internal space in which the predetermined amount of electrolyte is injection through the holding part and the liquid injection port, to a second pressure and causing a part of the electrolyte flow back from the internal space to the holding part; and a second liquid injection step S70 of increasing a pressure in the holding part where the flowing-back electrolyte is held, higher than the second pressure and injecting the electrolyte from the holding part through the liquid injection port to the internal space. The second pressure reduction step S50 includes an initial pressure reduction step S51 of reducing the pressure in the internal space at a pressure reduction speed lower than that in the first pressure reduction step S20.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a bipolar power storage device. [Background technology]

[0002] A known method for manufacturing a bipolar type electricity storage device includes a step of injecting an electrolyte solution into a space between electrodes arranged opposite each other with a separator sandwiched therebetween (see, for example, Patent Document 1). In a bipolar type electricity storage device, if the electrolyte solution is not sufficiently impregnated into the active material layer and the separator, the resistance value increases, resulting in poor battery performance.

[0003] In the manufacturing method described in Patent Document 1, an electrolyte is injected into a battery case, and the inside of the battery case is repeatedly pressurized and depressurized by a pump, and the electrolyte is injected, thereby impregnating the electrode group with the electrolyte. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-191450 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a bipolar type energy storage device using bipolar electrodes, the space between the metal plates of the electrodes becomes the internal space of the cell. In a bipolar type energy storage device, the internal space of the cell is narrower than that of a typical rectangular cell, so that the internal pressure easily rises when gas is generated due to a charge / discharge reaction or the like. In order to suppress the rise in internal pressure, it is necessary to reduce the amount of electrolyte injected into the internal space of the cell and provide an excess space to accommodate the gas. On the other hand, if the amount of electrolyte injected into the internal space of the cell is reduced, air may be taken into the cell during the impregnation process, which may cause poor electrolyte impregnation of the electrodes.

[0006] An object of the present disclosure is to provide a method for manufacturing a bipolar electricity storage device that can suppress poor electrolyte impregnation of electrodes. [Means for solving the problem]

[0007] A method for manufacturing a bipolar type electricity storage device according to one aspect of the present disclosure is a method for manufacturing a bipolar type electricity storage device including an electrode stack formed by stacking bipolar electrodes including a current collector, a positive electrode active material layer provided on one surface of the current collector, and a negative electrode active material layer provided on the other surface of the current collector, a seal that forms an internal space between adjacent current collectors in which an electrolyte solution is contained and seals the internal space, and a liquid injection port that is formed in the seal and communicates the internal space with the outside, the method including a first depressurization step of depressurizing the internal space to a first pressure lower than atmospheric pressure through an attachment attached to the liquid injection port, and a second depressurization step of depressurizing the internal space to a first pressure lower than atmospheric pressure through an attachment attached to the liquid injection port after the first depressurization step. a first liquid injection step of reducing the pressure inside the holding part to a pressure higher than the first pressure, and injecting a predetermined amount of electrolyte from the holding part through the liquid injection port into the internal space reduced in pressure in the first pressure reduction step; a second pressure reduction step of reducing, after the first pressure reduction step, the internal space into which the predetermined amount of electrolyte has been injected to a second pressure lower than atmospheric pressure, through the holding part and the liquid injection port, to cause a portion of the electrolyte to flow back from the internal space to the holding part; and a second liquid injection step of reducing, after the second pressure reduction step, reducing the pressure inside the holding part which holds the electrolyte that has flowed back in the second pressure reduction step to a pressure higher than the second pressure, and injecting the electrolyte from the holding part through the liquid injection port into the internal space, the second pressure reduction step including an initial pressure reduction step of reducing the pressure inside the internal space at a lower pressure reduction rate than the first pressure reduction step.

[0008] In the method for manufacturing a bipolar type electricity storage device, the internal space between adjacent metal plates is depressurized in the first depressurization step, and then the electrolyte is injected in the first liquid injection step, so that the electrolyte can be easily injected by the pressure difference. In addition, in the second depressurization step, the internal space is depressurized at a depressurization speed lower than that in the first depressurization step. In this way, the second depressurization step is performed while controlling the depressurization speed, so that the impregnation of the electrolyte into the electrodes is promoted and impregnation failure of the electrolyte into the electrodes is suppressed. In addition, scattering of the electrolyte that flows back into the holding part can be suppressed.

[0009] In the initial pressure reduction step, the internal space may be reduced in pressure at a constant pressure reduction rate, which can more reliably promote the impregnation of the electrodes with the electrolyte.

[0010] The second pressure may be higher than the first pressure. In this case, for example, by setting the second pressure to be equal to or higher than the saturated vapor pressure of the electrolyte, volatilization of the electrolyte can be suppressed.

[0011] The second pressure may be equal to or higher than the saturated vapor pressure of the electrolyte, in which case volatilization of the electrolyte can be suppressed.

[0012] In the second liquid injecting step, oxygen gas may be injected from the holder into the internal space by supplying oxygen gas into the holder.

[0013] The method for producing a bipolar electricity storage device may further include a repeating step of repeatedly carrying out the second pressure reducing step and the second liquid pouring step, whereby the active material layer and the separator can be more thoroughly impregnated with the electrolyte.

[0014] In the second liquid injecting step which is finally carried out, oxygen gas may be supplied into the holder, thereby injecting oxygen gas from the holder into the internal space.

[0015] The method for manufacturing the bipolar type electricity storage device may further include a maintaining step of maintaining the internal space at the second pressure after the second depressurization step, and the time during which the internal space is maintained at the second pressure in the maintaining step may be increased according to the number of times the second depressurization step is performed. In this case, the internal space is maintained in a depressurized state by the maintaining step, so that gas is easily exhausted from the non-impregnated parts of the active material layer and the separator. Furthermore, although the number of non-impregnated parts decreases as the second depressurization step is performed, the time during which the internal space is maintained in a depressurized state by the maintaining step is increased according to the number of times the second depressurization step is performed, so that gas is even more easily exhausted from the non-impregnated parts.

[0016] The method for producing a bipolar electricity storage device may further include a maintaining step of maintaining the internal space at the second pressure after the second depressurization step. In this case, the internal space is maintained in a depressurized state by the maintaining step, so that gas is easily discharged from the active material layer and the unimpregnated portion of the separator.

[0017] At least one of the first and second depressurization steps may be performed on one of a pair of internal spaces adjacent to each other in the stacking direction of the electrode stack, while the other internal space is not depressurized. In this case, one internal space receives a pressing force from the other internal space due to a pressure difference, so that depressurization can be easily performed.

[0018] The second depressurization step may include an additional depressurization step in which the internal space is depressurized at a higher depressurization rate than in the initial depressurization step after the initial depressurization step, which can shorten the manufacturing time and improve productivity compared to the case where the internal space is continuously depressurized at the same depressurization rate as in the initial depressurization step.

[0019] The method for producing the bipolar type electricity storage device may further include an installation step of attaching a holding part capable of holding an electrolyte to the electrolyte inlet via an attachment. In this case, a series of steps such as reducing the pressure of the internal space and injecting electrolyte can be performed via the attachment attached to the electrolyte inlet.

[0020] In the first injection step, the pressure inside the holder may be set higher than atmospheric pressure to inject the electrolyte into the internal space, which accelerates the injection and allows the electrolyte to be injected in a short period of time.

[0021] In the second injection step, the pressure inside the holder may be set higher than atmospheric pressure to inject the electrolyte into the internal space, which accelerates the injection and allows the electrolyte to be injected in a short time. Effect of the Invention

[0022] According to the present disclosure, it is possible to provide a manufacturing method for a bipolar electricity storage device that can suppress poor electrolyte impregnation of electrodes. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a configuration of a bipolar electricity storage device according to one embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing an internal configuration of the electricity storage module shown in FIG. [Diagram 3] FIG. 3 is a cross-sectional view perpendicular to the stacking direction of the electricity storage module shown in FIG. [Figure 4] FIG. 4 is a flowchart showing a method for manufacturing a bipolar power storage device according to one embodiment. [Diagram 5] FIG. 5 is a diagram for explaining the first liquid injection step. [Figure 6] FIG. 6 is a diagram for explaining the second depressurization step. [Figure 7] FIG. 7 is a diagram for explaining the second liquid injection step. [Figure 8] FIG. 8 is a diagram for explaining the second liquid injection step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicated descriptions will be omitted.

[0025] Fig. 1 is a schematic cross-sectional view showing the configuration of a bipolar type energy storage device according to one embodiment. The bipolar type energy storage device 1 (hereinafter also simply referred to as "energy storage device 1") shown in Fig. 1 is a device used as a battery for various vehicles such as a forklift, a hybrid car, an electric car, etc. The energy storage device 1 is a secondary battery such as a nickel-hydrogen secondary battery or a lithium-ion secondary battery. In this embodiment, the energy storage device 1 is a nickel-hydrogen secondary battery. The energy storage device 1 includes a module stack 2 and a restraining member 3 that applies a restraining load to the module stack 2 in the stacking direction of the module stack 2.

[0026] The module stack 2 includes a power storage module 4 and a conductive plate 5 stacked on the power storage module 4. The module stack 2 includes a plurality (three here) of power storage modules 4 and a plurality (four here) of conductive plates 5. The power storage module 4 is a bipolar battery and has a rectangular shape when viewed in the stacking direction.

[0027] The adjacent energy storage modules 4 in the stacking direction are electrically connected to each other via a conductive plate 5. The conductive plates 5 are respectively arranged between the adjacent energy storage modules 4 in the stacking direction and on the outside of the energy storage module 4 located at the stacking end. A positive electrode terminal 6 is connected to one of the conductive plates 5 arranged on the outside of the energy storage module 4 located at the stacking end. A negative electrode terminal 7 is connected to the other conductive plate 5 arranged on the outside of the energy storage module 4 located at the stacking end. The positive electrode terminal 6 and the negative electrode terminal 7 are drawn out, for example, from the edge of the conductive plate 5 in a direction intersecting with the stacking direction. The positive electrode terminal 6 and the negative electrode terminal 7 charge and discharge the energy storage device 1.

[0028] A plurality of flow paths 5a for circulating a coolant such as air are provided inside the conductive plate 5. The flow paths 5a extend, for example, along a direction intersecting (orthogonal to) the stacking direction and the drawing direction of the positive electrode terminal 6 and the negative electrode terminal 7. The conductive plate 5 functions as a connection member for electrically connecting the power storage modules 4 to each other, and also functions as a heat dissipation plate for dissipating heat generated in the power storage module 4 by circulating a coolant through these flow paths 5a. In the example of FIG. 1, the area of ​​the conductive plate 5 as viewed from the stacking direction is smaller than the area of ​​the power storage module 4. However, from the viewpoint of improving heat dissipation, the area of ​​the conductive plate 5 may be the same as the area of ​​the power storage module 4 or may be larger than the area of ​​the power storage module 4.

[0029] The restraining member 3 is composed of a pair of end plates 8 that sandwich the module stack 2 in the stacking direction, and fastening bolts 9 and nuts 10 that fasten the end plates 8 together. The end plates 8 are rectangular metal plates with an area slightly larger than the areas of the energy storage modules 4 and conductive plates 5 when viewed in the stacking direction. An electrically insulating film F is provided on the surface of the end plates 8 facing the module stack 2. The film F provides insulation between the end plates 8 and the conductive plates 5.

[0030] An insertion hole 8a is provided at an edge of the end plate 8 at a position outside the module stack 2. A fastening bolt 9 is passed from the insertion hole 8a of one end plate 8 to the insertion hole 8a of the other end plate 8, and a nut 10 is screwed onto the tip of the fastening bolt 9 protruding from the insertion hole 8a of the other end plate 8. As a result, the energy storage module 4 and the conductive plate 5 are sandwiched between the end plates 8 and unitized as the module stack 2, and a restraint load is applied to the module stack 2 in the stacking direction.

[0031] Next, the configuration of the electricity storage module 4 will be described in detail. Fig. 2 is a schematic cross-sectional view showing the internal configuration of the electricity storage module shown in Fig. 1. As shown in Fig. 2, the electricity storage module 4 includes an electrode stack 11 and a resin sealing body 12 that seals the electrode stack 11. The electricity storage module 4 is formed in, for example, a rectangular parallelepiped shape.

[0032] The electrode laminate 11 includes a plurality of electrodes laminated in a lamination direction D via separators 13, and current collectors (metal plates 20A, 20B) located at the stacking ends of the electrode laminate 11. The plurality of electrodes include a negative terminal electrode 18, a positive terminal electrode 19, and a plurality of bipolar electrodes 14 laminated between the negative terminal electrode 18 and the positive terminal electrode 19. The laminate of the plurality of bipolar electrodes 14 is provided between the negative terminal electrode 18 and the positive terminal electrode 19.

[0033] The bipolar electrode 14 has a current collector (metal plate 15) including one surface 15a and another surface 15b provided on the opposite side of the one surface 15a, a positive electrode 16 provided on the one surface 15a, and a negative electrode 17 provided on the other surface 15b. The one surface 15a is a surface facing one side of the stacking direction D. The one surface 15a faces, for example, upward in the direction of gravity. The other surface 15b is a surface facing the other side of the stacking direction D. The other surface 15b faces, for example, downward in the direction of gravity. The positive electrode 16 is a positive electrode active material layer formed by coating the metal plate 15 with a positive electrode active material. The negative electrode 17 is a negative electrode active material layer formed by coating the metal plate 15 with a negative electrode active material. In the electrode laminate 11, the positive electrode 16 of one bipolar electrode 14 faces the negative electrode 17 of another adjacent bipolar electrode 14 on one side of the stacking direction D, with the separator 13 in between. In the electrode laminate 11, the negative electrode 17 of one bipolar electrode 14 faces the positive electrode 16 of another adjacent bipolar electrode 14 on the other side of the stacking direction D, with the separator 13 in between.

[0034] The negative electrode terminal electrode 18 has a metal plate 15 and a negative electrode 17 provided on the other surface 15b of the metal plate 15. The negative electrode terminal electrode 18 is arranged on one end side of the stacking direction D so that the other surface 15b faces the center side of the stacking direction D in the electrode stack 11. A metal plate 20A is further laminated on one surface 15a of the metal plate 15 of the negative electrode terminal electrode 18, and is electrically connected to one conductive plate 5 adjacent to the power storage module 4 via the metal plate 20A. The negative electrode 17 provided on the other surface 15b of the metal plate 15 of the negative electrode terminal electrode 18 faces the positive electrode 16 of the bipolar electrode 14 at one end of the stacking direction D via the separator 13.

[0035] The positive electrode terminal electrode 19 has a metal plate 15 and a positive electrode 16 provided on one surface 15a of the metal plate 15. The positive electrode terminal electrode 19 is disposed on the other end side of the stacking direction D such that the one surface 15a faces the center side of the stacking direction D in the electrode stack 11. A metal plate 20B is further laminated on the other surface 15b of the metal plate 15 of the positive electrode terminal electrode 19, and is electrically connected to the other conductive plate 5 adjacent to the power storage module 4 via the metal plate 20B. The positive electrode 16 provided on the one surface 15a of the metal plate 15 of the positive electrode terminal electrode 19 faces the negative electrode 17 of the bipolar electrode 14 at the other end of the stacking direction D via the separator 13.

[0036] The metal plate 15 is made of a metal such as nickel or a nickel-plated steel plate. As an example, the metal plate 15 is a rectangular metal foil made of nickel. Each metal plate 15 is one of the metal plates included in the electrode stack 11. The edge portion 15c of the metal plate 15 has a rectangular frame shape and is a part of an uncoated region 15d (see FIG. 3) where the positive electrode active material and the negative electrode active material are not coated. For example, nickel hydroxide is used as the positive electrode active material constituting the positive electrode 16. For example, a hydrogen storage alloy is used as the negative electrode active material constituting the negative electrode 17. In this embodiment, the formation area of ​​the negative electrode 17 on the other surface 15b of the metal plate 15 is one size larger than the formation area of ​​the positive electrode 16 on the one surface 15a of the metal plate 15. The electrode stack 11 has a plurality of stacked metal plates 15, 20A, and 20B.

[0037] The separator 13 is a member for preventing short circuits between the metal plates 15, and is formed, for example, in a sheet shape. Examples of the separator 13 include a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), and a woven or nonwoven fabric made of polypropylene, methylcellulose, or the like. The separator 13 may be reinforced with a vinylidene fluoride resin compound. The separator 13 is not limited to a sheet shape, and a bag-shaped one may be used.

[0038] The metal plates 20A and 20B are substantially the same member as the metal plate 15, and are made of a metal such as nickel or a nickel-plated steel plate. Both the metal plates 20A and 20B are one of the metal plates included in the electrode stack 11. As an example, the metal plates 20A and 20B are rectangular metal foils made of nickel. The metal plates 20A and 20B are uncoated electrodes in which neither the positive electrode active material layer nor the negative electrode active material layer is coated on the one surface 20a nor the other surface 20b. In other words, the metal plates 20A and 20B are uncoated electrodes in which no active material layer is provided on both surfaces.

[0039] The metal plate 20A is located at one end of the electrode laminate 11. The metal plate 20A causes the negative terminal electrode 18 to be disposed between the metal plate 20A and the bipolar electrode 14 along the lamination direction D. The other surface 20b of the metal plate 20A and one surface 15a of the metal plate 15 of the negative terminal electrode 18 are in direct contact with each other without any intervening space. This allows the metal plate 20A and the negative terminal electrode 18 to be electrically connected. The metal plate 20B is located at the other end of the electrode laminate 11. The metal plate 20B causes the positive terminal electrode 19 to be disposed between the metal plate 20B and the bipolar electrode 14 along the lamination direction D. The one surface 20a of the metal plate 20B and the other surface 15b of the metal plate 15 of the positive terminal electrode 19 are in direct contact with each other without any intervening space. This allows the metal plate 20B and the positive terminal electrode 19 to be electrically connected.

[0040] In the electrode laminate 11, the central region of the electrode laminate 11 (the region where the active material layers are arranged in the bipolar electrode 14, the negative terminal electrode 18, and the positive terminal electrode 19) bulges out in the stacking direction D compared to the surrounding regions. Therefore, the metal plates 20A, 20B are bent in a direction in which the central regions of the metal plates 20A, 20B are separated from each other. The central regions of one surface 20a of the metal plate 20A and the other surface 20b of the metal plate 20B abut (contact) with the conductive plate 5. In other words, the conductive plate 5 is arranged in contact with the metal plates 20A, 20B at the stacking ends of the electrode laminate 11.

[0041] The sealing body 12 is formed of, for example, an insulating resin into a rectangular tubular shape as a whole. The sealing body 12 is formed into, for example, a rectangular tubular shape having a pair of short side portions 12a and a pair of long side portions 12b (see FIG. 3). The sealing body 12 is provided so as to surround the side surface 11a of the electrode stack 11. The sealing body 12 holds an edge portion 15c on the side surface 11a.

[0042] The sealing body 12 has a plurality of frame-shaped first sealing portions 21 (resin portions) provided on the edge portions of the metal plates included in the electrode laminate 11 (i.e., the edge portion 15c of the metal plate 15 and the edge portions 20c of the metal plates 20A and 20B), and second sealing portions 22 surrounding the first sealing portions 21 from the outside along the side surface 11a and joined to each of the first sealing portions 21. The first sealing portions 21 and the second sealing portions 22 are, for example, insulating resins having alkali resistance. Examples of materials constituting the first sealing portions 21 and the second sealing portions 22 include polypropylene (PP), polyphenylene sulfide (PPS), and modified polyphenylene ether (modified PPE).

[0043] The first sealing portion 21 is provided continuously around the entire periphery of the edge portion 15c of the metal plate 15 and the edge portions 20c of the metal plates 20A and 20B, and has a rectangular frame shape when viewed from the stacking direction D. The first sealing portion 21 is welded to the edge portion 15c of the metal plate 15 and the edge portions 20c of the metal plates 20A and 20B, respectively, by, for example, ultrasonic welding or hot plate welding. This allows the first sealing portion 21 and the metal plate 15, and the first sealing portion 21 and the metal plates 20A and 20B to be hermetically joined, respectively. The first sealing portion 21 extends outward beyond the edge portion 15c of the metal plate 15 or the edge portions 20c of the metal plates 20A and 20B when viewed from the stacking direction D. The first sealing portion 21 includes an outer portion 21a that protrudes outward from the edge of the metal plate 15 or the metal plates 20A, 20B, and an inner portion 21b that is located inside the edge of the metal plate 15 or the metal plates 20A, 20B. A welding layer 23 is formed on the tip portion (outer edge portion) of the outer portion 21a of the first sealing portion 21. The welding layer 23 is formed by bonding the tip portions of the first sealing portions 21 that have been melted by, for example, hot plate welding to each other.

[0044] The multiple first sealing portions 21 include multiple first sealing portions 21A provided on the bipolar electrode 14 and the positive terminal electrode 19, a first sealing portion 21B provided on the negative terminal electrode 18, a first sealing portion 21C provided on the metal plate 20A, and first sealing portions 21D and 21E provided on the metal plate 20B.

[0045] The first sealing portion 21A is joined to one surface 15a of the metal plate 15 of the bipolar electrode 14 and the positive terminal electrode 19. The inner portion 21b of the first sealing portion 21A is located between the edge portions 15c of the metal plates 15 adjacent to each other in the stacking direction D. The region where the edge portions 15c on one surface 15a of the metal plate 15 overlap with the first sealing portion 21A is a bonding region between the metal plate 15 and the first sealing portion 21A.

[0046] In this embodiment, the first sealing portion 21A is formed in a two-layer structure by folding one film in two. The outer edge of the first sealing portion 21A embedded in the second sealing portion 22 is a folded portion (bent portion) of the film. The first layer of film constituting the first sealing portion 21A is bonded to one surface 15a. The inner edge of the second layer of film is located outside the inner edge of the first layer of film, forming a step portion on which the separator 13 is placed. The inner edge of the second layer of film is located inside the edge of the metal plate 15.

[0047] The first sealing portion 21B is joined to one surface 15a of the metal plate 15 of the negative terminal electrode 18. The inner portion 21b of the first sealing portion 21B is located between the edge portion 15c of the metal plate 15 of the negative terminal electrode 18 and the edge portion 20c of the metal plate 20A, which are adjacent to each other in the stacking direction D. The area where the edge portion 15c on the one surface 15a of the metal plate 15 and the inner portion 21b of the first sealing portion 21B overlap is the bonding area between the metal plate 15 and the first sealing portion 21B. The first sealing portion 21B is also joined to the other surface 20b of the metal plate 20A. The area where the edge portion 20c on the other surface 20b of the metal plate 20A and the first sealing portion 21B overlap is the bonding area between the metal plate 20A and the first sealing portion 21B. In this embodiment, the first sealing portion 21B is also joined to the edge portion 20c on the other surface 20b of the metal plate 20A. It can be said that the first sealing portion 21B is provided not only on the negative terminal electrode 18 but also on the metal plate 20A.

[0048] The first sealing portion 21C is joined to one surface 20a (outer surface) of the metal plate 20A. In this embodiment, the first sealing portion 21C is located at the end-most side in the stacking direction D among the multiple first sealing portions 21. The region where the edge portion 20c on the one surface 20a of the metal plate 20A and the first sealing portion 21C overlap is the bonding region between the metal plate 20A and the first sealing portion 21C. The one surface 20a of the metal plate 20A has an exposed surface 20d exposed from the first sealing portion 21C. The conductive plate 5 is arranged in contact with the exposed surface 20d.

[0049] In this embodiment, the outer edges of the first sealing parts 21B, 21C embedded in the second sealing part 22 are continuous with each other. That is, the first sealing parts 21B, 21C are formed by folding one film in two with the edge part 20c of the metal plate 20A sandwiched therebetween. The outer edges of the first sealing parts 21B, 21C are folded parts (bent parts) of the film. The film constituting the first sealing parts 21B, 21C is joined to the edge part 20c on both the one side 20a and the other side 20b of the metal plate 20A. In this way, by joining both sides of the metal plate 20A to the first sealing parts 21B, 21C, it is possible to suppress the seepage of the electrolyte due to the so-called alkaline creep phenomenon.

[0050] The first sealing portion 21D is joined to one surface 20a of the metal plate 20B. The inner portion 21b of the first sealing portion 21D is located between the edge portion 15c of the metal plate 15 of the positive terminal electrode 19 adjacent to each other in the stacking direction D and the edge portion 20c of the metal plate 20B. The region where the edge portion 20c on the one surface 20a of the metal plate 20B overlaps with the first sealing portion 21D is a bonding region between the metal plate 20B and the first sealing portion 21D.

[0051] The first sealing portion 21E is disposed at an edge portion 20c on the other surface 20b (outer surface) of the metal plate 20B. In this embodiment, the first sealing portion 21E is located at the other end side of the multiple first sealing portions 21 in the stacking direction D. In this embodiment, the first sealing portion 21E is not joined to the metal plate 20B. The other surface 20b of the metal plate 20B has an exposed surface 20d exposed from the first sealing portion 21E. The conductive plate 5 is disposed in contact with (in contact with) the exposed surface 20d.

[0052] In this embodiment, the outer edges of the first sealing portions 21D, 21E embedded in the second sealing portion 22 are continuous with each other. That is, the first sealing portions 21D, 21E are formed by folding one film in two with the edge portion 20c of the metal plate 20B sandwiched between them. The outer edges of the first sealing portions 21D, 21E are folded-back portions (bent portions) of the film. The films constituting the first sealing portions 21D, 21E are joined to the edge portion 20c on one surface 20a of the metal plate 20B.

[0053] In the bonding region, the surfaces of the metal plates 15, 20A, and 20B are roughened. Although the roughened region may be only the bonding region, in this embodiment, the entire one side 15a of the metal plate 15 is roughened. Moreover, the entire one side 20a and the other side 20b of the metal plate 20A are roughened. Moreover, the entire one side 20a of the metal plate 20B is roughened.

[0054] The roughening can be achieved by forming a plurality of protrusions by, for example, electrolytic plating. By forming a plurality of protrusions in the bonding region, the molten resin penetrates between the plurality of protrusions formed by the roughening at the bonding interface with the first sealing portion 21 in the bonding region, and an anchor effect is exhibited. This can improve the bonding strength between the metal plates 15, 20A, 20B and the first sealing portion 21. The protrusions formed during the roughening have a shape that is tapered from the base end side to the tip end side, for example. This makes the cross-sectional shape between adjacent protrusions an undercut shape, which can enhance the anchor effect.

[0055] A plurality of internal spaces V are provided within the electrode laminate 11. Each internal space V is provided between adjacent metal plates. The internal space V is a space between adjacent metal plates in the lamination direction D, which is partitioned in an airtight and liquid-tight manner by the metal plates and the sealing body 12. The internal space V contains an electrolyte (not shown) made of an alkaline aqueous solution such as an aqueous potassium hydroxide solution. The electrolyte is impregnated into the separator 13, the positive electrode 16, and the negative electrode 17. Since the electrolyte is strongly alkaline, the sealing body 12 is made of a resin material having strong alkali resistance.

[0056] 3 is a cross-sectional view perpendicular to the stacking direction of the electricity storage module shown in FIG. 2. As shown in FIG. 3, a liquid inlet P is provided in one short side portion 12a of the sealing body 12. The liquid inlet P penetrates the sealing body 12 in the long side direction of the sealing body 12. The liquid inlet P communicates with the internal space V and the external space. The position at which the liquid inlet P is provided in one short side portion 12a of the sealing body 12 varies depending on the position of the corresponding internal space V in the stacking direction D (see FIG. 2). The liquid inlet P is provided offset in the short side direction of the sealing body 12 so that adjacent liquid inlet ports P in the stacking direction D (see FIG. 2) do not overlap with each other. In the example of FIG. 3, the liquid inlet P is provided at one end of one short side portion 12a of the sealing body 12.

[0057] The positive electrode 16 includes a plurality of divided regions 16a divided by grooves 16b on the one surface 15a. The grooves 16b extend along the long side of the one surface 15a. The bottom surface of the grooves 16b is formed by the one surface 15a.

[0058] The divided regions 16a are spaced apart from one another in the short side direction of the one surface 15a. In this embodiment, the positive electrode 16 is divided into five divided regions 16a by four grooves 16b. The divided regions 16a have a rectangular shape with the long side direction of the one surface 15a as the long side direction and the short side direction of the one surface 15a as the short side direction. The grooves 16b have, for example, the same shape as one another.

[0059] Although not shown in the figure, the negative electrode 17 also includes a plurality of divided regions divided by grooves, similar to the positive electrode 16. The grooves of the negative electrode 17 are provided so as to overlap with the grooves 16b of the positive electrode 16 when viewed from the stacking direction D (see FIG. 2). When the electrolyte is poured into the internal space V, a gap formed by combining the grooves of the positive electrode 16 and the grooves of the negative electrode 17 functions as a flow path for the electrolyte, similar to the gap between the uncoated region 15d of one surface 15a and the uncoated region 15d of the other surface 15b.

[0060] Fig. 4 is a flow chart showing a method for manufacturing a bipolar type electricity storage device according to one embodiment. As shown in Fig. 4, the method for manufacturing the electricity storage device 1 includes an installation step S10, a first pressure reduction step S20, a first maintenance step S30, a first liquid injection step S40, a second pressure reduction step S50, a second maintenance step S60, a second liquid injection step S70, and a repeat step S80. Each step will be described below.

[0061] The installation step S10 is a step of attaching the supply device 30 shown in FIG. 5 to the liquid injection port P. The supply device 30 includes a syringe C, an attachment 31, pipes L1 and L2, valves 32 to 34, a pressure reducing pump (vacuum pump) 35, and an electropneumatic regulator (precision regulator) 36. The syringe C is a holder capable of holding an electrolyte. The syringe C is attached to the liquid injection port P via the attachment 31. The syringe C and the pipe L1 are connected to the attachment 31. The attachment 31 is configured to be able to switch between a path connecting the liquid injection port P and the syringe C and a path connecting the liquid injection port P and the pipe L1. For example, the attachment 31 includes a switching valve, and the path to which the liquid injection port P is connected is switched by operating the switching valve. Moreover, the attachment 31 is attached to the liquid-filling port P in a liquid-tight and airtight manner, and in this attached state, the connection between the attachment 31 and the liquid-filling port P is in a sealed state.

[0062] The pipe L1 is a pipe for reducing the pressure of the internal space V. The pipe L1 connects the attachment 31 and the decompression pump 35. A valve 32 is disposed in the pipe L1. The pipe L2 is a pipe for opening the inside of the syringe C to the atmosphere. The pipe L2 connects the syringe C to the outside. A valve 33 is disposed in the pipe L2. The pipe L3 is a pipe for reducing the pressure of the internal space V through the syringe C. The pipe L3 connects the syringe C to the decompression pump 35. A valve 34 and an electropneumatic regulator 36 are disposed in the pipe L3. The electropneumatic regulator 36 is disposed between the valve 34 and the decompression pump 35. In the installation process S10, the syringe C is attached to the liquid inlet P via the attachment 31.

[0063] The first depressurization step S20 is a step of depressurizing the internal space V to a first pressure lower than atmospheric pressure through the liquid inlet P and the attachment 31. In this embodiment, the first depressurization step S20 depressurizes the internal space V through the liquid inlet P, the attachment 31, and the pipe L1 without using the syringe C. The first pressure is, for example, 0.01 kPa or more and 2 kPa or less. In the first depressurization step S20, the attachment 31 switches the connection destination of the liquid inlet P to the pipe L1 and connects the liquid inlet P and the pipe L1 so that they can communicate with each other. Furthermore, the valve 32 is opened to connect the depressurization pump 35 to the liquid inlet P. The depressurization pump 35 exhausts the gas in the internal space V to the outside through the liquid inlet P. The first depressurization step S20 depressurizes the internal space V from atmospheric pressure (101.3 kPa) to the first pressure in, for example, 0.1 seconds or more and 20 seconds or less. Therefore, the depressurization speed in the first depressurization step S20 is, for example, 5 kPa / sec or more and 1000 kPa / sec or less.

[0064] The first maintaining step S30 is a step of maintaining the internal space V at the first pressure after the first depressurization step S20. The first maintaining step S30 is performed immediately after the first depressurization step S20. In the first maintaining step S30, the time for which the internal space V is maintained at the first pressure is, for example, 10 seconds or more and 30 minutes or less.

[0065] The first liquid injection step S40 is a step of injecting an electrolyte into the internal space V depressurized in the first depressurization step S20. In the electricity storage module 4, gas is generated due to charge / discharge reactions and the like, so it is necessary to provide an excess space in the internal space V for accommodating the generated gas. Therefore, a preset amount of electrolyte is injected into the internal space V so that an excess space is formed in the internal space when impregnation of the electrodes with the electrolyte is completed.

[0066] FIG. 5 is a diagram for explaining the first liquid injection step. In the first liquid injection step S40, a syringe C shown in FIG. 5 is used as a holding part for holding a predetermined amount of electrolyte solution set in advance. The electrolyte solution may be supplied to the syringe C in the first liquid injection step S40, or may be supplied to the syringe C before the first liquid injection step S40. In the first liquid injection step S40, the attachment 31 switches the connection destination of the liquid injection port P to the syringe C, and connects the liquid injection port P and the syringe C so that they can communicate with each other. Furthermore, the valve 33 is opened to connect the syringe C to the outside. As a result, the inside of the syringe C becomes atmospheric pressure, and the electrolyte solution is injected from the syringe C through the liquid injection port P into the internal space V due to the pressure difference between the atmospheric pressure and the pressure of the internal space V reduced to a first pressure lower than the atmospheric pressure. The electrolyte solution is impregnated into the positive electrode 16, the negative electrode 17, and the separator 13 in the internal space V.

[0067] The syringe C may be connected to the liquid injection port P at least in the first liquid injection step S40. Since the syringe C is attached to the liquid injection port P via the attachment 31 in the installation step S10, in the first depressurization step S20, the syringe C before the electrolyte is supplied may be connected to the liquid injection port P, and the internal space V may be depressurized to the first pressure through the liquid injection port P, the attachment 31, and the syringe C.

[0068] The electrolyte injected from the inlet P into the internal space V spreads through the positive electrode 16, the negative electrode 17, and the separator 13 in order from the part closest to the inlet P. As described above, the gap between the uncoated area 15d on the one side 15a and the uncoated area 15d on the other side 15b, and the gap formed by combining the groove of the positive electrode 16 and the groove of the negative electrode 17 each function as a flow path for the electrolyte. Therefore, the electrolyte easily reaches the part of the positive electrode 16, the negative electrode 17, and the separator 13 that is close to the flow path, and the electrolyte does not easily reach the part far from the flow path. In addition, the electrolyte easily reaches the part of the positive electrode 16, the negative electrode 17, and the separator 13 that is close to the inlet P, and the electrolyte does not easily reach the part far from the inlet P.

[0069] In the first liquid injection step S40, the liquid is injected by pressurizing the inside of the syringe C holding the electrolyte with gas. The electrolyte is injected from the syringe C into the internal space V and gas is injected into the syringe C until the pressure difference between the pressure in the internal space V and the pressure inside the syringe C disappears. The gas used in this embodiment is the atmosphere (air). When all of the electrolyte held in the syringe C before the start of liquid injection is injected into the internal space V, the pressure in the internal space V becomes equal to atmospheric pressure. At this time, air also enters the internal space V, and the progress of impregnation of the electrolyte stops. In the positive electrode 16, the negative electrode 17, and the separator 13, the parts into which the atmosphere enters before the electrolyte becomes unimpregnated parts N that are not impregnated with the electrolyte. The gap between the uncoated region 15d on one surface 15a and the uncoated region 15d on the other surface 15b is wider than the gap formed by the combination of the grooves of the positive electrode 16 and the negative electrode 17, so the electrolyte can easily pass through. Therefore, the portion far from the pouring port P and also from the uncoated region 15d is less likely to become wetted with the electrolyte and is likely to become an unimpregnated portion N.

[0070] 6 is a diagram for explaining the second depressurization step. The second depressurization step S50 is a step of depressurizing the internal space V into which a predetermined amount of electrolyte has been injected to a second pressure lower than atmospheric pressure through the liquid injection port P, the syringe C, the pipe L3, and the electropneumatic regulator 36. In the second depressurization step S50, the attachment 31 switches the connection destination of the liquid injection port P to the syringe C, and connects the liquid injection port P and the syringe C so as to be communicable. Furthermore, the valve 34 is opened, and the depressurization pump 35 is connected to the liquid injection port P via the electropneumatic regulator 36. In the second depressurization step S50, the depressurization pump 35 is used. The depressurization pump 35 is connected to the syringe C, and discharges gas from the internal space V through the liquid injection port P, and causes a part of the electrolyte to flow back from the internal space V to the syringe C.

[0071] The second pressure is higher than the first pressure. The second pressure is equal to or higher than the saturated vapor pressure of the electrolyte. This suppresses the volatilization of the electrolyte. The saturated vapor pressure of the electrolyte varies depending on the components constituting the electrolyte. The second pressure is, for example, 2 kPa or more and 20 kPa or less. By setting the second pressure to 20 kPa or less, more preferably 10 kPa or less, in the subsequent second liquid injection step S70, the pressure difference between the reduced pressure of the internal space V and the pressure inside the syringe C (for example, atmospheric pressure) can be increased. This promotes the impregnation of the electrolyte into the positive electrode 16, the negative electrode 17, and the separator 13 in the second liquid injection step S70.

[0072] The second depressurization step S50 includes an initial depressurization step S51 and an additional depressurization step S52. The initial depressurization step S51 is a step performed first in the second depressurization step S50, and depressurizes the internal space V from atmospheric pressure to the third pressure. The third pressure is lower than the atmospheric pressure and higher than the second pressure. The third pressure is, for example, 10 kPa or more and 50 kPa or less. In the initial depressurization step S51, the internal space V is depressurized at a depressurization speed lower than that of the first depressurization step S20. In the initial depressurization step S51, the internal space V is depressurized at a constant depressurization speed. The depressurization speed of the initial depressurization step S51 is adjusted, for example, by an electropneumatic regulator. In the initial depressurization step S51, the internal space V is depressurized from atmospheric pressure to the third pressure in, for example, 5 seconds or more and 100 seconds or less. Therefore, the depressurization speed of the initial depressurization step S51 is, for example, 0.2 kPa / sec or more and 18 kPa / sec or less.

[0073] The additional depressurization step S52 is a step performed following the initial depressurization step S51, and depressurizes the internal space V from the third pressure to the second pressure. The additional depressurization step S52 performs depressurization at a higher depressurization speed than the initial depressurization step S51. The additional depressurization step S52 may perform depressurization at the same depressurization speed as the first depressurization step S20. The first depressurization step S20 and the additional depressurization step S52 are performed, for example, without using an electropneumatic regulator. The additional depressurization step S52 depressurizes the internal space V from the third pressure to the second pressure in, for example, 0.1 seconds or more and 20 seconds or less. Therefore, the depressurization speed of the additional depressurization step S52 is, for example, 2 kPa / second or more and 500 kPa / second or less.

[0074] The second maintaining step S60 is a step of maintaining the internal space V at the second pressure after the second depressurization step S50. The second maintaining step S60 is performed immediately after the second depressurization step S50. In the second maintaining step S60, the time for maintaining the internal space V at the second pressure is, for example, 10 minutes or less. By providing such a maintaining time, the electrolyte remaining in the internal space V without being impregnated into the positive electrode 16, the negative electrode 17, and the separator 13 can be reliably sucked back (backflowed) into the syringe C.

[0075] 7 and 8 are diagrams for explaining the second liquid injection step. FIG. 7 shows the state during the second liquid injection step S70, and FIG. 8 shows the state after the second liquid injection step S70. The second liquid injection step S70 is a step of re-injecting a part of the electrolyte solution that has been caused to flow back from the internal space V to the syringe C in the second depressurization step S50 into the internal space V through the liquid injection port P. In the second liquid injection step S70, the attachment 31 switches the connection destination of the liquid injection port P to the syringe C, and connects the liquid injection port P and the syringe C so that they can communicate with each other. Furthermore, the valve 33 is opened to connect the syringe C to the outside.

[0076] In the second liquid injection step S70, the inside of the syringe C is made equal to or higher than the second pressure, and re-injection is performed by utilizing the difference in pressure between the internal space V and the internal pressure of the syringe C. In the second liquid injection step S70, for example, the inside of the syringe C, which has been depressurized to the second pressure in the immediately preceding step, is opened to the atmosphere, thereby allowing the atmosphere (air) to flow into the inside of the syringe C and making the internal pressure of the syringe C atmospheric pressure. When the internal pressure of the syringe C becomes atmospheric pressure, a pressure difference occurs between the syringe C and the internal space V, which has been depressurized to the second pressure. Using this pressure difference, the electrolyte that was caused to flow back into the inside of the syringe C in the second depressurization step S50 is re-injected into the internal space V through the liquid injection port P. Due to the re-injection, the unimpregnated portion N shrinks.

[0077] The repeating step S80 is a step of repeatedly performing the second depressurization step S50 and the second liquid injection step S70. In this embodiment, the repeating step S80 repeats the second depressurization step S50, the second maintaining step S60, and the second liquid injection step S70. The number of repetitions is, for example, two. According to the repeating step S80, the unimpregnated portion N is further reduced. In the second maintaining step S60, the time for maintaining the internal space V at the second pressure is lengthened according to the number of times the second depressurization step S50 is performed. For example, when the number of repetitions is three, the maintenance time in the second maintaining step S60 is longer after the second depressurization step S50 than after the first depressurization step S50, and is even longer after the third depressurization step S50.

[0078] In the second liquid injection step S70, which is performed last, oxygen gas may be supplied into the syringe C, thereby injecting oxygen gas from the syringe C into the internal space V. The inside of the syringe C is purged with oxygen to a pressure higher than the second pressure (for example, atmospheric pressure), whereby oxygen gas is injected into the internal space V together with a part of the electrolyte held in the syringe C. For example, as in this embodiment, when the battery is a nickel-hydrogen secondary battery, the excess space in the internal space V can be expanded by reacting the oxygen gas injected into the internal space V with hydrogen absorbed in the hydrogen storage alloy, which is the active material of the negative electrode 17. When oxygen is supplied into the syringe C, the inside of the syringe C may be pressurized with oxygen to a pressure higher than atmospheric pressure. By achieving such a state, the reinjection is accelerated, and the reinjection can be performed in a short time.

[0079] In the manufacturing method of the electricity storage device 1, the above steps S10 to S80 are performed for each internal space V. At this time, at least one of the first depressurization step S20 and the second depressurization step S50 is performed for one internal space V of a pair of internal spaces V adjacent to each other in the stacking direction D (see FIG. 2) in a state in which the other internal space V is not depressurized. The non-depressurized state is, for example, a state of atmospheric pressure.

[0080] Since the metal plate 15 is thin and easily deformed, when there is a pressure difference between adjacent internal spaces V, it deforms so as to be recessed toward the internal space V with the lower pressure. Therefore, a pressing force caused by the deformation of the metal plate 15 is applied to the internal space V with the lower pressure from the stacking direction D. In other words, when depressurizing one of the adjacent internal spaces V, it is easier to depressurize the internal space V when the other internal space V is not depressurized.

[0081] In this embodiment, both the first depressurization step S20 and the second depressurization step S50 are performed on one of a pair of adjacent internal spaces V in a state where the other internal space V is not depressurized. This allows for easy depressurization in both steps. Furthermore, when internal spaces V are arranged on both sides in the stacking direction of the internal space V to be depressurized, the internal space V to be depressurized is depressurized in a state where the internal spaces V on both sides are not depressurized. This allows for even easier depressurization, since a pressing force is applied to the internal space V to be depressurized from both sides in the stacking direction.

[0082] For example, the steps S20 to S80 may be performed on the odd-numbered internal spaces V in the stacking direction, and then on the even-numbered internal spaces V. Alternatively, for example, the steps S20 to S40 and the steps S50 to S80 may be separated and performed in order on the odd-numbered internal spaces V and the even-numbered internal spaces V.

[0083] As described above, the manufacturing method of the electricity storage device 1 includes a first depressurization step S20 of depressurizing the internal space V to a first pressure through the liquid injection port P, and a first liquid injection step S40 of injecting a predetermined amount of electrolyte solution from a syringe C holding a preset amount of electrolyte solution into the internal space V depressurized in the first depressurization step S20 through the liquid injection port P. In this way, the internal space V is depressurized to the first pressure through the first depressurization step S20, and then the electrolyte solution is injected through the first liquid injection step S40, so that the electrolyte solution can be easily injected into the internal space V by the pressure difference.

[0084] The manufacturing method of the electricity storage device 1 includes a second depressurization step S50 of reducing the pressure of the internal space V into which a predetermined amount of electrolyte has been injected to a second pressure through the injection port P and causing a part of the electrolyte to flow back into the syringe C, and a second liquid injection step S70 of reinjecting the electrolyte that has flowed back from the internal space V to the syringe C in the second depressurization step S50 into the space through the injection port P. In this way, the second depressurization step S50 reduces the pressure of the internal space V into which a predetermined amount of electrolyte has been injected and causes a part of the electrolyte to flow back into the syringe C, and then the second liquid injection step S70 reinjects the electrolyte into the internal space V, so that the electrolyte can be sufficiently impregnated into the positive electrode 16, the negative electrode 17, and the separator 13.

[0085] The second depressurization step S50 includes an initial depressurization step S51 in which the internal space V is depressurized at a depressurization rate lower than that of the first depressurization step S20. If the depressurization is performed without controlling the depressurization rate in a state in which the electrolyte is injected into the internal space V, impregnation of the electrolyte into the positive electrode 16, the negative electrode 17, and the separator 13 may be insufficient. In addition, the electrolyte flowing back into the syringe C may be scattered. The electrolyte attached to the inner wall of the syringe C due to the scattering of the electrolyte may not be reinjected into the internal space V. As a result, the amount of electrolyte in the internal space V may fall below a predetermined amount. The amount of electrolyte is set to a minimum amount that can impregnate the positive electrode 16, the negative electrode 17, and the separator 13 in order to form an excess space in the internal space V. If the amount of electrolyte falls below a predetermined amount, an unimpregnated portion N may be generated in the positive electrode 16, the negative electrode 17, and the separator 13, and the battery performance may be deteriorated. In this embodiment, the second depressurization step S50 is performed by controlling the depressurization speed, which promotes impregnation of the electrolyte into the positive electrode 16, the negative electrode 17, and the separator 13, and suppresses impregnation failure of the electrolyte into the positive electrode 16, the negative electrode 17, and the separator 13. In addition, scattering of the electrolyte flowing back into the syringe C can be suppressed, and deterioration of battery performance can be suppressed.

[0086] In the initial depressurization step S51, the internal space V is depressurized at a constant depressurization rate, which makes it possible to more reliably suppress scattering of the electrolyte.

[0087] The second pressure is higher than the first pressure and is equal to or higher than the saturated vapor pressure of the electrolyte. Therefore, in the second depressurization step S50, the volatilization of the electrolyte can be suppressed. In the first depressurization step S20, the electrolyte is not injected into the internal space V, so the first pressure can be set within the range of the depressurization capacity of the depressurization pump 35, regardless of the saturated vapor pressure of the electrolyte. The lower the first pressure, the larger the pressure difference with the atmospheric pressure, so that in the first liquid injection step S40, the electrolyte can be easily impregnated into the positive electrode 16, the negative electrode 17, and the separator 13.

[0088] In the second injection process S70, oxygen gas is supplied into the syringe C, and the oxygen gas is injected from the syringe C into the internal space V. As a result, oxygen gas is taken into the negative electrode 17, and the excess space in the internal space V can be expanded.

[0089] The method for manufacturing the electricity storage device 1 further includes a repeating step S80 in which the second pressure reducing step S50 and the second liquid pouring step S70 are repeatedly performed. This allows the positive electrode 16, the negative electrode 17, and the separator 13 to be more sufficiently impregnated with the electrolyte.

[0090] In the second injection process S70 which is finally performed, oxygen gas is supplied into the syringe C, and the oxygen gas is injected from the syringe C into the internal space V. This causes the oxygen gas to be taken into the negative electrode 17. As a result, the surplus space in the internal space V can be expanded.

[0091] The manufacturing method of the electricity storage device 1 further includes a second maintaining step S60 for maintaining the internal space V at the second pressure after the second depressurization step 40. Therefore, the space is maintained in a depressurized state by the second maintaining step S60, and gas is easily discharged from the unimpregnated portion N of the positive electrode 16, the negative electrode 17, and the separator 13. Furthermore, the time for which the internal space V is maintained at the second pressure in the second maintaining step S60 is lengthened according to the number of times the second depressurization step S50 is performed. Although the unimpregnated portion N decreases as the second depressurization step S50 is performed more frequently, the time for which the internal space V is maintained in a depressurized state by the second maintaining step S60 is lengthened according to the number of times the second depressurization step S50 is performed, and gas is further easily discharged from the unimpregnated portion N.

[0092] At least one of the first depressurization step S20 and the second depressurization step S50 is performed on one of a pair of internal spaces V adjacent to each other in the stacking direction D, in a state in which the other internal space V is not depressurized. Therefore, one internal space V receives a pressing force from the other internal space V due to a pressure difference, so that depressurization can be easily performed.

[0093] The second depressurization step S50 includes an additional depressurization step S52 in which the internal space V is depressurized at a depressurization speed higher than that of the initial depressurization step S51. Therefore, compared to the case where the depressurization is continued at the same depressurization speed as the initial depressurization step S51, it is possible to shorten the manufacturing time and improve productivity.

[0094] The present disclosure is not limited to the above embodiments.

[0095] The manufacturing method of the power storage device 1 does not necessarily have to include the repeating step S80. The first pressure may be equal to the second pressure depending on the pressure reducing capacity of the pressure reducing pump 35. The manufacturing method of the power storage device 1 does not necessarily have to include the second maintenance step S60.

[0096] In the first liquid injection step S40, the pressure inside the syringe C may be set higher than atmospheric pressure, and the electrolyte may be injected into the internal space V. In this case, the electrolyte is injected from the syringe C through the liquid injection port P into the internal space V due to the pressure difference between the pressure inside the syringe C and the pressure inside the internal space V. By pressurizing the inside of the syringe C to a pressure higher than atmospheric pressure in this way, the injection is accelerated and the injection can be performed in a short time. As in the first liquid injection step S40, in the second liquid injection step S70, the pressure inside the syringe C may be set higher than atmospheric pressure, and the electrolyte may be reinjected into the internal space V. In this case, the reinjection is accelerated and the reinjection can be performed in a short time. [Explanation of symbols]

[0097] 1...bipolar type energy storage device, 11...electrode stack, 12...sealing body, 14...bipolar electrode, 15...metal plate (current collector), 15a...one side, 15b...other side, 16...positive electrode, 17...negative electrode, 31...attachment, C...syringe (holding part), D...stacking direction, P...pouring port, V...internal space.

Claims

1. A method for manufacturing a bipolar type electricity storage device comprising: an electrode stack formed by stacking bipolar electrodes each including a current collector, a positive electrode active material layer provided on one surface of the current collector, and a negative electrode active material layer provided on the other surface of the current collector; a seal that forms an internal space between adjacent current collectors for containing an electrolyte and seals the internal space; and a liquid injection port that is formed in the seal and communicates the internal space with the outside, a first depressurization step of depressurizing the internal space to a first pressure lower than atmospheric pressure through an attachment attached to the liquid inlet; a first liquid injection step of, after the first depressurization step, bringing an inside of a holding part that holds a preset amount of the electrolyte solution to a pressure higher than the first pressure, and injecting the predetermined amount of the electrolyte solution from the holding part through the liquid injection port into the internal space depressurized in the first depressurization step; a second depressurization step of depressurizing the internal space into which the predetermined amount of the electrolyte solution has been injected through the holding portion and the injection port to a second pressure lower than atmospheric pressure after the first electrolyte injection step, thereby causing a portion of the electrolyte solution to flow back from the internal space to the holding portion; a second liquid injection step of, after the second depressurization step, setting the inside of the holding part that holds the electrolyte solution that has flowed back in the second depressurization step to a pressure higher than the second pressure, and injecting the electrolyte solution from the holding part through the liquid injection port into the internal space, The second pressure reduction step includes an initial pressure reduction step of reducing the pressure in the internal space at a pressure reduction rate lower than that in the first pressure reduction step.

2. In the initial depressurization step, the internal space is depressurized at a constant depressurization rate. A method for manufacturing the bipolar type electricity storage device according to claim 1.

3. The second pressure is higher than the first pressure. A method for manufacturing the bipolar type electricity storage device according to claim 1 or 2.

4. The second pressure is equal to or greater than the saturated vapor pressure of the electrolyte. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 3.

5. In the second liquid injection step, oxygen gas is supplied into the holding portion, thereby injecting the oxygen gas from the holding portion into the internal space. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 4.

6. The method further includes a repeating step of repeatedly performing the second depressurization step and the second liquid injection step. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 4.

7. In the second liquid injection step, oxygen gas is supplied into the holding part, so that the oxygen gas is injected from the holding part into the internal space. A method for manufacturing the bipolar type electricity storage device according to claim 6.

8. The method further includes a maintaining step of maintaining the internal space at the second pressure after the second depressurization step, The time for which the internal space is maintained at the second pressure in the maintaining step is increased according to the number of times the second depressurization step is performed. A method for manufacturing the bipolar type electricity storage device according to claim 6 or 7.

9. The method further includes a maintaining step of maintaining the internal space at the second pressure after the second depressurization step. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 7.

10. At least one of the first depressurization step and the second depressurization step is performed in a state in which one of a pair of internal spaces adjacent to each other in a stacking direction of the electrode stack is not depressurized in the other internal space. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 9.

11. The second depressurization step includes an additional depressurization step of depressurizing the internal space at a depressurization rate higher than that of the initial depressurization step after the initial depressurization step. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 10.

12. The method further includes an installation step of attaching the holding portion capable of holding the electrolyte to the liquid injection port via the attachment. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 11.

13. In the first liquid injection step, the inside of the holding part is made to have a pressure higher than atmospheric pressure, and the electrolyte is injected into the internal space. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 12.

14. In the second liquid injection step, the inside of the holding part is made to have a pressure higher than atmospheric pressure, and the electrolyte is injected into the internal space. A method for manufacturing the bipolar type electricity storage device according to any one of claims 1 to 13.

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