WO2018123520A1 - Electricity storage device - Google Patents

Electricity storage device Download PDF

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Publication number
WO2018123520A1
WO2018123520A1 PCT/JP2017/044230 JP2017044230W WO2018123520A1 WO 2018123520 A1 WO2018123520 A1 WO 2018123520A1 JP 2017044230 W JP2017044230 W JP 2017044230W WO 2018123520 A1 WO2018123520 A1 WO 2018123520A1
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WO
WIPO (PCT)
Prior art keywords
separator
power storage
storage device
storage module
compression rate
Prior art date
Application number
PCT/JP2017/044230
Other languages
French (fr)
Japanese (ja)
Inventor
毅 真里谷
耕二郎 田丸
寿光 田中
Original Assignee
株式会社豊田自動織機
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社豊田自動織機 filed Critical 株式会社豊田自動織機
Publication of WO2018123520A1 publication Critical patent/WO2018123520A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/10—Multiple hybrid or EDL capacitors, e.g. arrays or modules
    • H01G11/12—Stacked hybrid or EDL capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/52—Separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G2/00—Details of capacitors not covered by a single one of groups H01G4/00-H01G11/00
    • H01G2/02—Mountings
    • H01G2/04—Mountings specially adapted for mounting on a chassis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/04—Construction or manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/24—Alkaline accumulators
    • H01M10/30—Nickel accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present disclosure relates to a power storage device.
  • a bipolar battery including a bipolar electrode in which a positive electrode is formed on one surface of a current collector plate and a negative electrode is formed on the other surface is known (see Patent Document 1).
  • a bipolar battery a plurality of bipolar electrodes are stacked in series across a separator holding an electrolyte layer.
  • a separator a microporous membrane separator or a nonwoven fabric separator is used.
  • the battery is pressed from above and below using an iron plate and bolts and nuts.
  • a restraining force is applied to the bipolar electrode by restraining plates provided at both ends in the stacking direction and restraining members such as bolts and nuts.
  • the restraint plate is designed so that fatigue failure does not occur due to the internal pressure fluctuation (load fluctuation) of the cell.
  • a deformable member such as a resin is not provided between the constraining plate and the bipolar electrode, so that the influence of fluctuations in the internal pressure of the cell is large.
  • Bipolar electrodes also tend to have a large area, and from this point of view, the influence of cell internal pressure fluctuations is large. Therefore, when using a restraint plate having a predetermined strength (thickness), it is necessary to carefully examine the pressure applied to the restraint plate.
  • This disclosure is intended to provide a power storage device that can suppress load fluctuations with respect to a restraining member such as a restraining plate for restraining stacked bipolar electrodes.
  • a power storage device includes a plurality of bipolar electrodes each including an electrode plate, a positive electrode provided on a first surface of the electrode plate, and a negative electrode provided on a second surface of the electrode plate, and a plurality of bipolar electrodes And at least one power storage module in which a plurality of bipolar electrodes are stacked in the stacking direction via the separator, and both ends of the at least one power storage module in the stacking direction.
  • a restraint structure that includes a first restraining member and a second restraining member provided in a portion, and applies a compressive force in a stacking direction to a portion provided with a positive electrode, a separator, and a negative electrode in at least one power storage module;
  • the separator is made of a porous resin, and the compressibility of the separator compressed by the constraining structure is greater than 0% and less than 40%.
  • the power storage module is formed by stacking a plurality of bipolar electrodes in the stacking direction via separators.
  • the restraint structure including the first restraining member and the second restraining member, a compressive force is applied to the portion where the positive electrode, the separator, and the negative electrode are provided.
  • the compression ratio of the separator is greater than 0% and less than 40%, deformation of the restraint member due to fluctuations in the internal pressure of the cell and relaxation of the separator compression amount (that is, crushing amount) occur simultaneously.
  • This compression rate range is a range suitable for a separator made of a porous resin.
  • the load fluctuation on the restraining member is suitably suppressed. This leads to a reduction in the stress amplitude of the restraining member.
  • the separator is not compressed (when it is not crushed, that is, when the compression rate is 0%), the stress amplitude tends to increase. Therefore, the said structure is advantageous from a viewpoint of the fatigue
  • the compression rate of the separator compressed by the restraint structure may be 10% or more.
  • the amount of compression of the separator that is, the amount of crushing
  • the separator may be separated from the bipolar electrode.
  • the distance between the bipolar electrodes cannot be controlled, and the ion conduction distance may become extremely long. These phenomena are not preferable because they increase the resistance in the power storage module. Therefore, if the compression ratio of the separator is 10% or more, the separation phenomenon of the separator from the bipolar electrode can be prevented, and an increase in resistance can be prevented. As a result, a desired output can be maintained.
  • the compression rate of the separator compressed by the constraining structure may be 30% or less. If the compression rate of the separator is increased too much, the surface pressure that the restraining member receives from the separator becomes high, so that it is necessary to increase the strength of the restraining member, that is, the plate thickness.
  • a plate thickness in an appropriate range can be set with respect to the assumed internal pressure of the cell.
  • the plate thickness in the proper range is a plate that does not deform the constraining member against the assumed internal pressure (it does not deform as far as the separator is separated) and that satisfies the desired thickness in terms of downsizing the power storage device. It is thick.
  • the compression ratio of the separator compressed by the constraining structure may be 20% or more and 30% or less.
  • the lower limit value and the upper limit value are set in this way, the possibility of various problems such as separation of the separator, enlargement of the restraint member due to increased surface pressure by the separator, and electrolyte diffusion failure is more reliably reduced. it can.
  • the porous resin may be made of non-woven fabric.
  • the storage module may be a nickel metal hydride secondary battery.
  • the above compression rate range is particularly suitable.
  • the management of the compression rate of the separator has a great effect in terms of the reliability and miniaturization of the nickel-hydrogen secondary battery.
  • the compression rate of the separator and the thicknesses of the first restraining member and the second restraining member may be set. Thereby, the separation of the separator from the bipolar electrode during normal operation can be suppressed. Moreover, it can suppress that a 1st restraint member and a 2nd restraint member yield by the reaction force from the compressed separator.
  • the compression ratio of the separator may be set so that the thickness of the first restraining member and the second restraining member is minimized under the above range. In this case, the physique of the power storage device with respect to the output can be reduced. Therefore, the power storage device can be highly integrated.
  • the separator compression rate and the thickness of the first and second restraining members may be set so that the initial minimum porosity of the separator is 33% or more.
  • the electrolyte solution can be diffused without any problem, and a desired output can be maintained. Further, it is possible to cause sufficient gas escape during gas generation.
  • the compression rate of the separator and the thickness of the first restraining member and the second restraining member are such that the stress generated in the restraining structure during the normal operation of the power storage module is less than the fatigue strength of the first restraining member and the second restraining member. It may be set. In this case, it is possible to prevent the first restraining member and the second restraining member from being fatigued and destroyed by the reaction force from the compressed separator.
  • FIG. 3A is a sectional view showing the bipolar electrode and the separator before compression
  • FIG. 3B is a sectional view showing the bipolar electrode and the separator after compression.
  • FIG. 3A is a sectional view showing the bipolar electrode and the separator before compression
  • FIG. 3B is a sectional view showing the bipolar electrode and the separator after compression.
  • the power storage device 10 shown in FIG. 1 is used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles.
  • the power storage device 10 includes a plurality (three in the present embodiment) of power storage modules 12, but may include a single power storage module 12.
  • the power storage module 12 is a bipolar battery.
  • the power storage module 12 is a secondary battery such as a nickel hydride secondary battery or a lithium ion secondary battery, but may be an electric double layer capacitor. In the following description, a nickel metal hydride secondary battery is illustrated.
  • the plurality of power storage modules 12 can be stacked via a conductive plate 14 such as a metal plate, for example.
  • a conductive plate 14 such as a metal plate, for example.
  • the conductive plates 14 are also arranged outside the power storage modules 12 positioned at both ends in the stacking direction (Z direction) of the power storage modules 12.
  • the conductive plate 14 is electrically connected to the adjacent power storage module 12. Thereby, the some electrical storage module 12 is connected in series in the lamination direction.
  • a positive electrode terminal 24 is connected to the conductive plate 14 located at one end
  • a negative electrode terminal 26 is connected to the conductive plate 14 located at the other end.
  • the positive terminal 24 may be integrated with the conductive plate 14 to be connected.
  • the negative electrode terminal 26 may be integrated with the conductive plate 14 to be connected.
  • the positive electrode terminal 24 and the negative electrode terminal 26 extend in a direction (X direction) intersecting the stacking direction.
  • the positive and negative terminals 24 and 26 can charge and discharge the power storage device 10.
  • the conductive plate 14 can also function as a heat radiating plate for releasing heat generated in the power storage module 12.
  • a refrigerant such as air passes through the plurality of gaps 14a provided inside the conductive plate 14, heat from the power storage module 12 can be efficiently released to the outside.
  • Each gap 14a extends, for example, in a direction (Y direction) intersecting the stacking direction.
  • the conductive plate 14 is smaller than the power storage module 12, but may be the same as or larger than the power storage module 12.
  • the power storage device 10 may include a restraining structure 16 that restrains the alternately stacked power storage modules 12 and conductive plates 14 in the stacking direction.
  • the restraint structure 16 connects, for example, a pair of restraint plates 16A and 16B (first restraint member and second restraint member) provided at both ends in the stacking direction of the plurality of power storage modules 12 and the restraint plates 16A and 16B. Connecting members (such as bolts 18 and nuts 20).
  • Constraint plates 16A and 16B are made of metal such as iron, for example. More specifically, the material constituting the restraining plates 16A and 16B is, for example, carbon steel such as S45C (JIS standard), aluminum die casting (aluminum alloy die casting) such as ADC10, or the like.
  • the restraint plates 16A and 16B have a predetermined plate thickness.
  • the plate thickness of the restraining plates 16A and 16B can be determined based on several criteria. For example, the plate thickness of the restraining plates 16A and 16B is determined so as to be deformed so as not to cause separation of the separator 40 described later with respect to the internal pressure assumed in the cell.
  • the plate thickness is designed so that the deformation of the constraining plates 16A and 16B is less than the design standard (criteria) up to an internal pressure of 4 MPa. Is done. As long as these criteria are satisfied, the restraining plates 16A and 16B should be as thin as possible.
  • An insulating film 22 such as a resin film is disposed between the constraining plates 16A and 16B and the conductive plate 14.
  • each of the restraining plates 16A and 16B and the insulating film 22 has, for example, a rectangular shape.
  • the insulating film 22 is larger than the conductive plate 14, and the restraining plates 16 ⁇ / b> A and 16 ⁇ / b> B are larger than the power storage module 12.
  • an insertion hole 16A1 through which the shaft portion of the bolt 18 is inserted is provided at a position on the outer side of the power storage module 12 at the edge of the restraint plate 16A.
  • an insertion hole 16 ⁇ / b> B ⁇ b> 1 through which the shaft portion of the bolt 18 is inserted is provided at a position on the outer side of the power storage module 12 at the edge of the restraining plate 16 ⁇ / b> B when viewed from the stacking direction.
  • the insertion hole 16A1 and the insertion hole 16B1 are located at the corners of the restraint plates 16A, 16B.
  • One constraining plate 16A is abutted against the conductive plate 14 connected to the negative electrode terminal 26 via the insulating film 22, and the other constraining plate 16B has the insulating film 22 applied to the conductive plate 14 connected to the positive electrode terminal 24.
  • the bolt 18 is passed through the insertion hole 16A1 and the insertion hole 16B1, for example, from one restraint plate 16A side toward the other restraint plate 16B side.
  • a nut 20 is screwed onto the tip of the bolt 18 protruding from the other restraining plate 16B.
  • the insulating film 22, the conductive plate 14, and the power storage module 12 are sandwiched and unitized, and a restraining load (compression force) is applied in the stacking direction.
  • the power storage module 12 illustrated in FIG. 2 includes a stacked body 30 in which a plurality of bipolar electrodes 32 are stacked. When viewed from the stacking direction of the bipolar electrode 32, the stacked body 30 has, for example, a rectangular shape. A separator 40 may be disposed between the adjacent bipolar electrodes 32.
  • Each bipolar electrode 32 includes an electrode plate 34, a positive electrode 36 provided on the first surface 34 c of the electrode plate 34, and a negative electrode 38 provided on the second surface 34 d of the electrode plate 34.
  • the positive electrode 36 of one bipolar electrode 32 faces the negative electrode 38 of one bipolar electrode 32 adjacent in the stacking direction across the separator 40, and the negative electrode 38 of one bipolar electrode 32 connects the separator 40. It faces the positive electrode 36 of the other bipolar electrode 32 that is adjacent in the stacking direction.
  • the separator 40 is sandwiched between the positive electrode 36 and the negative electrode 38.
  • an electrode plate 34 having a negative electrode 38 disposed on the inner surface (the lower surface in the drawing) is disposed at one end of the stacked body 30.
  • the electrode plate 34 corresponds to a negative terminal electrode.
  • an electrode plate 34 having a positive electrode 36 disposed on the inner surface (the upper surface in the drawing) is disposed at the other end of the stacked body 30.
  • This electrode plate 34 corresponds to a positive terminal electrode.
  • the negative electrode 38 of the negative electrode-side termination electrode faces the positive electrode 36 of the uppermost bipolar electrode 32 with the separator 40 interposed therebetween.
  • the positive electrode 36 of the positive terminal electrode is opposed to the negative electrode 38 of the lowermost bipolar electrode 32 with the separator 40 interposed therebetween.
  • the electrode plates 34 of these termination electrodes are connected to the adjacent conductive plates 14 (see FIG. 1).
  • the power storage module 12 includes a cylindrical resin portion 50 that extends in the stacking direction of the bipolar electrodes 32 and accommodates the stacked body 30.
  • the resin part 50 holds the peripheral edge part 34 a of the plurality of electrode plates 34.
  • the resin part 50 is configured to surround the laminated body 30.
  • the resin part 50 is joined to the peripheral part 34a of the electrode plate 34, and the first seal part 52 that holds the peripheral part 34a and the first seal part 52 in the direction (X direction and Y direction) intersecting the stacking direction. 2nd seal part 54 provided in the outside.
  • the 1st seal part 52 which constitutes the inner wall of resin part 50 is provided over the perimeter of peripheral part 34a of electrode board 34 in a plurality of bipolar electrodes 32 (namely, layered product 30).
  • the first seal portion 52 is welded, for example, to the peripheral portion 34a of the electrode plate 34, and seals the peripheral portion 34a.
  • the peripheral edge 34 a of the electrode plate 34 of each bipolar electrode 32 is held in a state of being buried in the first seal portion 52.
  • the peripheral portions 34 a of the electrode plates 34 disposed at both ends of the stacked body 30 are also held in a state of being buried in the first seal portion 52.
  • an internal space that is airtightly partitioned by the electrode plates 34 and 34 and the first seal portion 52 is formed between the electrode plates 34 and 34 adjacent in the stacking direction.
  • An electrolytic solution (not shown) made of an alkaline solution such as an aqueous potassium hydroxide solution is accommodated in the internal space.
  • the second seal part 54 constituting the outer wall of the resin part 50 covers the outer peripheral surface 52a of the first seal part 52 extending in the stacking direction of the bipolar electrodes 32.
  • the inner peripheral surface 54a of the second seal portion 54 is welded, for example, to the outer peripheral surface 52a of the first seal portion 52, and seals the outer peripheral surface 52a.
  • the welding surface (joint surface) of the second seal portion 54 with respect to the first seal portion 52 forms, for example, four rectangular planes.
  • the resin part 50 (the first seal part 52 and the second seal part 54) is formed in a rectangular cylindrical shape by, for example, injection molding using an insulating resin.
  • the resin material constituting the resin portion 50 include polypropylene (PP), polyphenylene sulfide (PPS), and modified polyphenylene ether (modified PPE).
  • the resin part 50 regulates the movement of gas and electrolyte from one cell to another cell. Thereby, the insulation between adjacent cells is ensured.
  • the electrode plate 34 is a rectangular metal foil made of nickel, for example.
  • the peripheral edge 34a of the electrode plate 34 is an uncoated region where the positive electrode active material and the negative electrode active material are not coated. In the uncoated region, the electrode plate 34 is exposed. The uncoated region is buried and held in the first seal portion 52 constituting the inner wall of the resin portion 50.
  • An example of the positive electrode active material constituting the positive electrode 36 is nickel hydroxide.
  • Examples of the negative electrode active material constituting the negative electrode 38 include a hydrogen storage alloy.
  • the formation region of the negative electrode 38 on the second surface 34 d of the electrode plate 34 may be slightly larger than the formation region of the positive electrode 36 on the first surface 34 c of the electrode plate 34.
  • the separator 40 is formed in a sheet shape, for example.
  • the separator 40 has a rectangular shape, for example.
  • the separator 40 is made of a porous resin.
  • Separator 40 consists of a nonwoven fabric which is a kind of porous resin, for example.
  • the material forming the separator 40 is a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), a woven fabric or a non-woven fabric made of polypropylene, polyethylene terephthalate (PET), methylcellulose or the like. Etc. are exemplified.
  • the electrolyte is alkaline, and thus the material forming the separator 40 is required to have alkali resistance.
  • a glass fiber separator cannot be used.
  • the fibers of the nonwoven fabric may be made of polypropylene (PP) and polyethylene (PE). Surface treatment for imparting affinity to the electrolyte solution may be performed on the fibers of the nonwoven fabric.
  • PP polypropylene
  • PE polyethylene
  • Surface treatment for imparting affinity to the electrolyte solution may be performed on the fibers of the nonwoven fabric.
  • the separator 40 may be reinforced with a vinylidene fluoride resin compound.
  • the separator 40 is not limited to a sheet shape, and may be a bag shape.
  • the conductive plate 14 connected to the power storage module 12 is disposed, for example, inside the resin portion 50.
  • the conductive plate 14 abuts on the electrode plates 34 provided at both ends of the stacked body 30 in the stacking direction, and transmits the compressive force from the restraining structure 16 to the stacked body 30.
  • the restraint structure 16 applies a compressive force in the stacking direction to the positive electrode 36, the separator 40, and the negative electrode 38 in each power storage module 12.
  • the separator 40 disposed between the positive electrode 36 and the negative electrode 38 of the bipolar electrode 32 is compressed at a predetermined compression rate.
  • the surface pressure (compression surface pressure and load surface pressure) received by the constraining plates 16A and 16B by the compressed separator 40 is considered. Since the separator 40 is compressed with an appropriate compression rate, the stress amplitude of the restraining plates 16A and 16B is reduced.
  • the compression rate is easy to manage. The compression rate is a ratio indicating how much the thickness in the stacking direction of the separator 40 after compression is reduced (the amount of compression and crushing) with respect to the thickness in the stacking direction of the separator 40 before compression.
  • FIG. 4 is a diagram illustrating the compressive load characteristics of the separator 40.
  • the compression surface pressure is a surface pressure that the constraining plates 16A and 16B receive from the separator 40 only because the separator 40 is compressed without taking the cell internal pressure into consideration.
  • the compression rate compressing amount
  • the compression surface pressure tends to increase rapidly. This means that the higher the compression ratio, the higher the possibility of exceeding the deformation criteria of the restraining plates 16A and 16B. For example, if the compression rate is 40% or more, the compression surface pressure exceeds 6 MPa, which is not preferable.
  • FIG. 5 is a diagram showing the load surface pressure of the restraining plates 16A and 16B with respect to the cell internal pressure.
  • This load surface pressure is the surface pressure that the restraining plates 16A and 16B receive when the cell internal pressure is taken into consideration.
  • FIG. 5 is a simulation result regarding the surface pressure in the nickel-hydrogen secondary battery. In this simulation, the compressive load characteristic of the separator 40 shown in FIG. 4 is considered. As shown in FIG. 5, the higher the initial compression ratio, the smaller the increase width of the restraint plate load surface pressure, that is, the stress amplitude. Further, when the initial compression ratio is 10%, 17%, and 23%, the restraint plate load surface pressure is always higher than the cell internal pressure.
  • FIG. 6 is a diagram illustrating a change in the output of the power storage device 10 when the compression rate of the separator 40 is changed.
  • the change in output is shown as a ratio, with the maximum output being 100%.
  • FIG. 6 shows a case where SOC (State Of Charge) 60%, temperature 25 ° C., output 10 seconds, 1.0 V cut, and initial porosity of separator 40 is 65%.
  • SOC State Of Charge
  • the compression rate exceeds 40%
  • the output is rapidly reduced. It is considered that this is because, when the compressibility of the separator 40 is increased too much, the gaps in the separator 40 are reduced and the diffusion of the electrolytic solution is hindered.
  • “1.0V cut” means that the output is taken out to 1.0V. If the value is less than that, it is judged as overdischarge, and no output is taken out.
  • the compression rate of the separator 40 compressed by the constraining structure 16 is greater than 0% and less than 40%. More preferably, the compression rate of the separator 40 compressed by the constraining structure 16 may be 10% or more. More preferably, the compression rate of the separator 40 compressed by the constraining structure 16 may be 30% or less. More preferably, the compression rate of the separator 40 compressed by the constraining structure 16 may be 20% or more and 30% or less. The compressibility of the separator 40 compressed by the constraining structure 16 may be 25% or less, 20% or less, or 15% or less.
  • the compression surface pressure is about 0.1 MPa.
  • the compression surface pressure is about 0.3 MPa.
  • the compression rate of the separator 40 is 20%, the compression surface pressure is about 0.6 MPa.
  • the compression rate of the separator 40 is 25%, the compression surface pressure is about 1.1 MPa.
  • the compression rate of the separator 40 is 30%, the compression surface pressure is about 1.9 MPa.
  • the compression rate of the separator 40 is 35%, the compression surface pressure is about 3.3 MPa.
  • the positive electrode 36 is formed on the first surface 34 c of the electrode plate 34, and the negative electrode 38 is formed on the second surface 34 d of the electrode plate 34 to obtain the bipolar electrode 32.
  • the bipolar electrode 32 is stacked via the separator 40 to obtain the stacked body 30.
  • sticker part 52 is formed in the peripheral part 34a of the electrode plate 34 of each bipolar electrode 32 by hot press or injection molding.
  • the second seal portion 54 is formed by, for example, injection molding.
  • the second seal portion 54 can be formed by pouring a resin material of the second seal portion 54 having fluidity into the mold.
  • the first seal portion 52 that is a part of the resin portion 50 is formed before the lamination step, and the second seal portion 54 that is the remaining portion of the resin portion 50 is formed after the lamination step.
  • an electrolytic solution is injected into the resin part 50 through an injection port or the like.
  • the storage module 12 is manufactured by sealing the injection port.
  • a plurality of power storage modules 12 are stacked via the conductive plate 14.
  • a positive electrode terminal 24 and a negative electrode terminal 26 are connected in advance to the conductive plates 14 located at both ends in the stacking direction.
  • a pair of restraint plates 16A and 16B are respectively disposed at both ends in the stacking direction via the insulating film 22, and the restraint plates 16A and 16B are connected to each other using the bolt 18 and the nut 20.
  • a restraint load compression force
  • the distance between the restraining plates 16A and 16B can be adjusted so that the compression rate of the separator 40 becomes the above-described predetermined compression rate.
  • power storage device 10 shown in FIG. 1 is manufactured.
  • a compressive force is applied to the portion where the positive electrode 36, the separator 40, and the negative electrode 38 are provided by the constraining structure 16 including the constraining plates 16A and 16B. If the compression rate of the separator 40 is greater than 0% and less than 40%, deformation of the restraint plates 16A and 16B due to fluctuations in the internal pressure of the cells and relaxation of the compression amount (that is, crushing amount) of the separator 40 occur simultaneously. That is, the compression state of the separator 40 reduces the internal pressure fluctuation.
  • the range of the compression rate is a range suitable for the separator 40 made of a porous resin.
  • the compression rate range suitable for the separator 40 made of porous resin By setting the compression rate range suitable for the separator 40 made of porous resin, load fluctuations on the restraining plates 16A and 16B are suitably suppressed. This leads to a reduction in the stress amplitude of the restraining plates 16A and 16B.
  • the separator 40 When the separator 40 is not compressed (when it is not crushed, that is, when the compression rate is 0%), the stress amplitude tends to increase (see FIG. 5). Therefore, the said structure is advantageous from a viewpoint of the fatigue
  • the compression rate of the separator 40 is too large, due to the surface pressure received from the compressed separator 40, a load higher than that when the internal pressure of the cell is increased is applied to the restraining plates 16A and 16B (see FIG. 4). ). This is disadvantageous from the viewpoint of fatigue of the restraining plates 16A and 16B. Further, the deformation criteria of the restraining plates 16A and 16B may be exceeded. By making the compression rate of the separator 40 less than 40%, these various problems that may occur with respect to the restraining plates 16A and 16B are solved.
  • the separator 40 may be separated from the bipolar electrode 32 (see FIG. 5).
  • the distance between the bipolar electrodes 32 cannot be controlled, and the ion conduction distance may become extremely long. These phenomena are not preferable because they increase the resistance in the power storage module 12. Therefore, when the compressibility of the separator 40 is 10% or more, the separation phenomenon of the separator 40 from the bipolar electrode 32 can be prevented, and an increase in resistance can be prevented. As a result, a desired output can be maintained (see FIG. 6).
  • the compression rate of the separator 40 is 30% or less, a plate thickness in an appropriate range can be set with respect to the assumed internal pressure of the cell.
  • the plate thickness in an appropriate range is such that the constraining plate does not deform with respect to the assumed internal pressure (it does not deform as far as the separator 40 is separated) and satisfies the desired thickness from the viewpoint of miniaturization of the power storage device 10. Thickness.
  • the compression rate of the separator 40 when the compression rate of the separator 40 is increased too much, the gaps in the separator 40 are reduced, and the diffusion of the electrolytic solution may be hindered. Also from this viewpoint, when the compression rate of the separator is 30% or less, the electrolyte solution can be diffused without any problem, and a desired output can be maintained (see FIG. 6).
  • the size of the restraining plates 16A and 16B is increased due to the separation of the separator 40 and the increase in the surface pressure by the separator 40. , And the possibility of various problems such as poor diffusion of the electrolyte solution is more reliably reduced.
  • the separator 40 made of porous resin is used, so the above-described compression rate range is particularly suitable.
  • a nickel metal hydride secondary battery provided with a bipolar electrode since a deformable member such as a resin is not provided between the restraining plates 16A and 16B and the bipolar electrode 32, the influence of fluctuations in the internal pressure of the cell is great.
  • a case with a fixed shape may be provided for each cell, but a bipolar nickel-hydrogen secondary battery does not have such a case. Therefore, the pressure receiving area is large and stress is easily applied.
  • the bipolar electrode 32 tends to have a large coating area, and from this point of view, the influence of cell internal pressure fluctuations is large.
  • the management of the compression rate of the separator 40 has a great effect in terms of reliability and miniaturization in the bipolar nickel-hydrogen secondary battery.
  • the separator 40 made of a polymorphic resin can adjust the thickness variation of the first seal portion 52 and the distance between the electrode plates 34 and 34 by reducing the amount of compression after compression.
  • the first restraining member and the second restraining member are not limited to plate-like members such as restraining plates 16A and 16B. What is used as the first restraining member and the second restraining member as long as a structure that is provided at both ends in the stacking direction of the electricity storage module and can apply a compressive force to the electricity storage module is realized. Also good.
  • the compression rate of the separator 40 is always greater than 0% during normal operation of the power storage module 12.
  • the stress generated in the restraint structure 16 when the power storage module 12 is abnormal is less than the yield stress of the restraint plates 16A and 16B.
  • the following two criteria (3) and (4) are further satisfied regarding the compression rate of the separator 40 and the optimal setting of the restraining plates 16A and 16B.
  • (3) The initial minimum porosity of the separator 40 is 33% or more.
  • the stress generated in the restraint structure 16 during the normal operation of the power storage module 12 is less than the fatigue strength of the restraint plates 16A and 16B.
  • FIG. 7 is a diagram showing an example of the establishment range of the above four criteria.
  • the horizontal axis indicates the thickness of the separator before compression
  • the vertical axis indicates the thickness of the restraint plate.
  • the thickness of the separator after compression is 75 ⁇ m. Therefore, when the horizontal axis is converted into the compression rate of the separator, the range where the thickness of the separator before compression is 75 ⁇ m to 125 ⁇ m corresponds to the range where the compression rate of the separator is 0% to 40%.
  • the right region of the graph A is a region that satisfies the criterion (1)
  • the left region of the graph B is a region that satisfies the criterion (2).
  • the left region of the graph C is a region satisfying the criterion (3)
  • the left region of the graph D is a region satisfying the criterion (4).
  • a region satisfying all the four criteria is a portion indicated by a region R in FIG. Among the portions indicated by the region R, the compression rate and the restraint plate thickness of the separator indicated by the point Ra where the restraint plate thickness is the smallest are the optimum design conditions that satisfy the above criteria (1) to (4).
  • Criterion (1) relates to deformation of the constraining plate due to fluctuations in the internal pressure of the cell and relaxation of the compression amount of the separator.
  • the thickness of the restraint plate is reduced, the amount of deformation of the restraint plate due to fluctuations in the internal pressure of the cell is increased, so that the compression rate of the separator satisfying the criterion (1) is also increased.
  • the storage module is provided with an open valve when the internal pressure rises, the storage module is operating at an internal pressure within a predetermined range that is less than the operating pressure of the open valve. Refers to the case.
  • Criterion (2) relates to the yield stress of the restraint plate.
  • the criterion (1) is abnormal, for example, when the storage module is provided with an open valve at the time when the internal pressure increases, the internal pressure of the storage module reaches the operating pressure of the open valve.
  • Criterion (3) relates to the diffusion of electrolyte between cells.
  • the boundary line of the criterion (3) in FIG. 7 is shifted to the left side of the graph.
  • the boundary line of the criterion (3) in FIG. Shift to the right refers to the time when the power storage module is tightened by the restraint structure.
  • Criterion (4) relates to the fatigue strength of the restraint plate. When the fatigue strength setting is increased, the boundary line of the criterion (4) in FIG. 7 shifts to the left side of the graph, and when the fatigue strength setting is decreased, the boundary line of the criterion (4) in FIG. Shift to.
  • FIG. 8 is a diagram showing an example of the compression characteristics of the separator.
  • the horizontal axis indicates the surface pressure
  • the vertical axis indicates the compression rate.
  • a graph E in FIG. 8 shows a compression characteristic of a separator having a thickness of 70 ⁇ m
  • a graph F shows a compression characteristic of a separator having a thickness of 80 ⁇ m
  • a graph G shows a compression characteristic of the separator having a thickness of 90 ⁇ m.
  • These compression characteristics are obtained using an autograph based on the load and stroke of the autograph.
  • the basis weight of each separator is 31 g / m2. From these compression characteristics, it is understood that when the basis weight is the same, the surface pressure for the same compression rate can be controlled by changing the thickness of the separator.
  • the reaction force can be calculated by converting the surface pressure from the pressure receiving area applied to the restraining plate.
  • FIG. 9 is a diagram illustrating an example of the relationship between the thickness of the separator and the porosity.
  • the horizontal axis represents the separator thickness
  • the vertical axis represents the porosity
  • the change in the porosity when the thickness of the separator having a basis weight of 31 g / m 2 is increased is plotted. From the results shown in the figure, it is understood that the porosity can be controlled by changing the thickness of the separator when the basis weight is the same.
  • the restraint plate include carbon steel for machine structure represented by S45C.
  • the physical properties after quenching and tempering are, for example, Young's modulus 205 MPa, Poisson's ratio 0.3, yield stress 490 MPa, tensile strength 690 MPa, and fatigue strength 305 MPa.
  • the minimum compression rate of the separator 40 is always greater than 0% during normal operation of the power storage module 12, and the stress generated in the restraint structure 16 when the power storage module 12 is abnormal is caused by the restraint plate 16A.
  • the compression rate of the separator 40 and the thicknesses of the restraining plates 16A and 16B may be set under a range that is equal to or less than the yield stress of 16B.
  • the compression rate of the separator 40 may be set so that the thicknesses of the restraining plates 16A and 16B are minimized within the above range. In this case, the physique of the power storage device 10 with respect to the output can be reduced. Therefore, the power storage device 10 can be highly integrated.
  • the compression rate of the separator 40 and the thickness of the restraining plates 16A and 16B may be set so that the initial minimum porosity of the separator 40 is 33% or more.
  • the electrolyte solution can be diffused without any problem, and a desired output can be maintained. Further, it is possible to cause sufficient gas escape during gas generation.
  • the compressibility of the separator 40 and the thickness of the restraint plates 16 ⁇ / b> A and 16 ⁇ / b> B are set so that the stress generated in the restraint structure 16 during the normal operation of the power storage module 12 is less than the fatigue strength of the restraint plates 16 ⁇ / b> A and 16 ⁇ / b> B. Sato may be set. In this case, it is possible to prevent the restraint plates 16A and 16B from being fatigued by the reaction force from the compressed separator 40.
  • SYMBOLS 10 Power storage device, 12 ... Power storage module, 16 ... Restraint structure, 16A, 16B ... Restraint plate (first restraint member, second restraint member), 32 ... Bipolar electrode, 34 ... Electrode plate, 34a ... Peripheral part, 34c ... 1st surface, 34d ... 2nd surface, 36 ... positive electrode, 38 ... negative electrode, 40 ... separator, 50 ... resin part, 52 ... 1st seal

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Abstract

This electricity storage device 10 is provided with: at least one electricity storage module 12 in which a plurality of bipolar electrodes 32 are laminated in a lamination direction, with separators 40 being interposed therebetween; and a constraining structure 16 which comprises constraining members 16A, 16B that are arranged on both ends of the at least one electricity storage module 12 in the lamination direction, and which applies a compressive force to a portion of the at least one electricity storage module 12 in the lamination direction, in said portion a positive electrode 36, a separator 40 and a negative electrode 38 being provided. Each separator 40 which is sandwiched between the positive electrode 36 and the negative electrode 38, while being arranged between the plurality of bipolar electrodes 32 is formed from a porous resin. The compression rate of each separator 40 compressed by the constraining structure 16 is more than 0% but less than 40%.

Description

蓄電装置Power storage device
　本開示は、蓄電装置に関する。 The present disclosure relates to a power storage device.
　集電板の一方の面に正極が形成され、他方の面に負極が形成されたバイポーラ電極を備えるバイポーラ電池が知られている（特許文献１参照）。このバイポーラ電池では、電解質層が保持されたセパレータを挟んで複数のバイポーラ電極が直列に積層されている。セパレータとして、微多孔膜セパレータまたは不織布セパレータが用いられている。この電池では、鉄板とボルト・ナットとを用いて電池を上下から押さえている。 A bipolar battery including a bipolar electrode in which a positive electrode is formed on one surface of a current collector plate and a negative electrode is formed on the other surface is known (see Patent Document 1). In this bipolar battery, a plurality of bipolar electrodes are stacked in series across a separator holding an electrolyte layer. As the separator, a microporous membrane separator or a nonwoven fabric separator is used. In this battery, the battery is pressed from above and below using an iron plate and bolts and nuts.
特開２０１１－１５１０１６号公報JP 2011-151016 A
　バイポーラ電極を備えた蓄電装置では、積層方向の両端部に設けられた拘束板と、ボルト及びナット等の拘束部材とによって、バイポーラ電極に拘束力を付与している。このような蓄電装置では、拘束板は、セルの内圧変動（負荷変動）に起因して疲労破壊が生じないように設計される。特に、バイポーラ電極を備えた蓄電装置では、拘束板とバイポーラ電極との間に樹脂などの変形し得る部材が設けられないため、セルの内圧変動の影響は大きい。バイポーラ電極は、面積が大きくなる傾向ももっており、この観点でも、セルの内圧変動の影響は大きい。よって、所定の強度（厚み）を有する拘束板を用いる場合に、その拘束板に加わる圧力を慎重に検討する必要がある。 In a power storage device provided with a bipolar electrode, a restraining force is applied to the bipolar electrode by restraining plates provided at both ends in the stacking direction and restraining members such as bolts and nuts. In such a power storage device, the restraint plate is designed so that fatigue failure does not occur due to the internal pressure fluctuation (load fluctuation) of the cell. In particular, in a power storage device including a bipolar electrode, a deformable member such as a resin is not provided between the constraining plate and the bipolar electrode, so that the influence of fluctuations in the internal pressure of the cell is large. Bipolar electrodes also tend to have a large area, and from this point of view, the influence of cell internal pressure fluctuations is large. Therefore, when using a restraint plate having a predetermined strength (thickness), it is necessary to carefully examine the pressure applied to the restraint plate.
　本開示は、積層されたバイポーラ電極を拘束するための拘束板等の拘束部材に対する負荷変動を抑制することができる蓄電装置を提供することを目的とする。 This disclosure is intended to provide a power storage device that can suppress load fluctuations with respect to a restraining member such as a restraining plate for restraining stacked bipolar electrodes.
　本開示に係る蓄電装置は、電極板と電極板の第１面に設けられた正極と電極板の第２面に設けられた負極とをそれぞれ含む複数のバイポーラ電極と、複数のバイポーラ電極の間に配置されて正極と負極とによって挟まれるセパレータと、を有し、複数のバイポーラ電極がセパレータを介して積層方向に積層された少なくとも１つの蓄電モジュールと、少なくとも１つの蓄電モジュールの積層方向の両端部に設けられた第１拘束部材および第２拘束部材を含み、少なくとも１つの蓄電モジュールにおける正極、セパレータ、及び負極が設けられた部分に対して積層方向に圧縮力を付与する拘束構造と、を備え、セパレータは多孔性樹脂からなり、拘束構造により圧縮されたセパレータの圧縮率は０％より大きく４０％未満である。 A power storage device according to the present disclosure includes a plurality of bipolar electrodes each including an electrode plate, a positive electrode provided on a first surface of the electrode plate, and a negative electrode provided on a second surface of the electrode plate, and a plurality of bipolar electrodes And at least one power storage module in which a plurality of bipolar electrodes are stacked in the stacking direction via the separator, and both ends of the at least one power storage module in the stacking direction. A restraint structure that includes a first restraining member and a second restraining member provided in a portion, and applies a compressive force in a stacking direction to a portion provided with a positive electrode, a separator, and a negative electrode in at least one power storage module; The separator is made of a porous resin, and the compressibility of the separator compressed by the constraining structure is greater than 0% and less than 40%.
　この蓄電装置によれば、蓄電モジュールは、複数のバイポーラ電極がセパレータを介して積層方向に積層されてなる。第１拘束部材および第２拘束部材を含む拘束構造によって、正極、セパレータ、及び負極が設けられた部分に圧縮力が付与される。セパレータの圧縮率が０％より大きく４０％未満であると、セルの内圧変動による拘束部材の変形と、セパレータの圧縮量（すなわち潰し量）の緩和とが同時に起こる。この圧縮率の範囲は、多孔性樹脂からなるセパレータに適した範囲である。多孔性樹脂からなるセパレータに適した圧縮率の範囲とすることで、拘束部材に対する負荷変動が好適に抑制される。このことは、拘束部材の応力振幅の低減をもたらす。セパレータを圧縮しない場合（潰さない場合すなわち圧縮率が０％の場合）は、応力振幅が大きくなる傾向にある。よって、上記構成は、セパレータを圧縮しない場合に比べて、拘束部材の疲労の観点で有利である。 According to this power storage device, the power storage module is formed by stacking a plurality of bipolar electrodes in the stacking direction via separators. By the restraint structure including the first restraining member and the second restraining member, a compressive force is applied to the portion where the positive electrode, the separator, and the negative electrode are provided. When the compression ratio of the separator is greater than 0% and less than 40%, deformation of the restraint member due to fluctuations in the internal pressure of the cell and relaxation of the separator compression amount (that is, crushing amount) occur simultaneously. This compression rate range is a range suitable for a separator made of a porous resin. By setting the compression rate range suitable for the separator made of the porous resin, the load fluctuation on the restraining member is suitably suppressed. This leads to a reduction in the stress amplitude of the restraining member. When the separator is not compressed (when it is not crushed, that is, when the compression rate is 0%), the stress amplitude tends to increase. Therefore, the said structure is advantageous from a viewpoint of the fatigue | exhaustion of a restraint member compared with the case where a separator is not compressed.
　拘束構造により圧縮されたセパレータの圧縮率は１０％以上であってもよい。内圧変動によってセパレータの圧縮量（すなわち潰し量）が緩和された場合、セパレータがバイポーラ電極から離れてしまう可能性がある。セパレータが離れると、バイポーラ電極間の距離が制御できなくなり、イオン伝導距離が極端に長くなる可能性がある。これらの現象は、蓄電モジュールにおける抵抗を増大させるため、好ましくない。そこで、セパレータの圧縮率が１０％以上であると、バイポーラ電極からのセパレータの離間現象を防止でき、抵抗の増大を防止することができる。その結果として、所望の出力を維持することができる。 The compression rate of the separator compressed by the restraint structure may be 10% or more. When the amount of compression of the separator (that is, the amount of crushing) is relaxed due to fluctuations in internal pressure, the separator may be separated from the bipolar electrode. When the separator is separated, the distance between the bipolar electrodes cannot be controlled, and the ion conduction distance may become extremely long. These phenomena are not preferable because they increase the resistance in the power storage module. Therefore, if the compression ratio of the separator is 10% or more, the separation phenomenon of the separator from the bipolar electrode can be prevented, and an increase in resistance can be prevented. As a result, a desired output can be maintained.
　拘束構造により圧縮されたセパレータの圧縮率は３０％以下であってもよい。セパレータの圧縮率を高めすぎると、拘束部材がセパレータから受ける面圧が高くなるため拘束部材の強度すなわち板厚を高める必要がある。セパレータの圧縮率が３０％以下であると、想定されるセルの内圧に対して、適正な範囲の板厚を設定することができる。適正な範囲の板厚とは、想定内圧に対して拘束部材が変形せず（セパレータが離れるほどには変形せず）、かつ蓄電装置の小型化の観点で所望の薄さを満たすような板厚である。また、セパレータの圧縮率を高めすぎると、セパレータの空隙が少なくなり、電解液の拡散に支障が生じ得る。この観点でも、セパレータの圧縮率が３０％以下であると、電解液の拡散が支障なく行われ、所望の出力を維持することができる。 The compression rate of the separator compressed by the constraining structure may be 30% or less. If the compression rate of the separator is increased too much, the surface pressure that the restraining member receives from the separator becomes high, so that it is necessary to increase the strength of the restraining member, that is, the plate thickness. When the compression rate of the separator is 30% or less, a plate thickness in an appropriate range can be set with respect to the assumed internal pressure of the cell. The plate thickness in the proper range is a plate that does not deform the constraining member against the assumed internal pressure (it does not deform as far as the separator is separated) and that satisfies the desired thickness in terms of downsizing the power storage device. It is thick. Moreover, when the compression rate of a separator is raised too much, the space | gap of a separator will decrease and a problem may arise in the spreading | diffusion of electrolyte solution. Also from this viewpoint, when the compressibility of the separator is 30% or less, the electrolyte solution can be diffused without any problem, and a desired output can be maintained.
　拘束構造により圧縮されたセパレータの圧縮率は２０％以上かつ３０％以下であってもよい。このように下限値と上限値を設定した場合、上記したセパレータの離間、セパレータによる面圧増大による拘束部材の大型化、及び電解液の拡散不良等といった諸問題が生じる可能性をより確実に低減できる。 The compression ratio of the separator compressed by the constraining structure may be 20% or more and 30% or less. When the lower limit value and the upper limit value are set in this way, the possibility of various problems such as separation of the separator, enlargement of the restraint member due to increased surface pressure by the separator, and electrolyte diffusion failure is more reliably reduced. it can.
　多孔性樹脂は不織布からなってもよい。 The porous resin may be made of non-woven fabric.
　蓄電モジュールはニッケル水素二次電池であってもよい。多孔性樹脂からなるセパレータが用いられるニッケル水素電池では、上記した圧縮率の範囲が特に適している。セパレータの圧縮率の管理は、ニッケル水素二次電池の信頼性や小型化の観点において、大きな効果を奏させる。 The storage module may be a nickel metal hydride secondary battery. In the nickel metal hydride battery in which a separator made of a porous resin is used, the above compression rate range is particularly suitable. The management of the compression rate of the separator has a great effect in terms of the reliability and miniaturization of the nickel-hydrogen secondary battery.
　蓄電モジュールの通常動作時においてセパレータの最小圧縮率が常に０％より大きく、かつ蓄電モジュールの異常時において拘束構造に発生する応力が第１拘束部材および第２拘束部材の降伏応力以下となる範囲下で、セパレータの圧縮率と第１拘束部材および第２拘束部材の厚さとが設定されていてもよい。これにより、通常動作時におけるバイポーラ電極からのセパレータの乖離を抑制できる。また、圧縮されたセパレータからの反力によって第１拘束部材および第２拘束部材が降伏してしまうことを抑制できる。 Under the range where the minimum compression rate of the separator is always greater than 0% during normal operation of the power storage module and the stress generated in the restraint structure when the power storage module is abnormal is less than the yield stress of the first restraint member and the second restraint member Thus, the compression rate of the separator and the thicknesses of the first restraining member and the second restraining member may be set. Thereby, the separation of the separator from the bipolar electrode during normal operation can be suppressed. Moreover, it can suppress that a 1st restraint member and a 2nd restraint member yield by the reaction force from the compressed separator.
　上記範囲下で第１拘束部材および第２拘束部材の厚さが最小となるように、セパレータの圧縮率が設定されていてもよい。この場合、出力に対する蓄電装置の体格を小さくすることができる。したがって、蓄電装置の高集積化が可能となる。 The compression ratio of the separator may be set so that the thickness of the first restraining member and the second restraining member is minimized under the above range. In this case, the physique of the power storage device with respect to the output can be reduced. Therefore, the power storage device can be highly integrated.
　セパレータの初期の最小空隙率が３３％以上となるように、セパレータの圧縮率と第１拘束部材および第２拘束部材の厚さとが設定されていてもよい。この場合、電解液の拡散が支障なく行われ、所望の出力を維持することができる。また、ガス発生時におけるガスの抜けを十分に生じさせることが可能となる。 The separator compression rate and the thickness of the first and second restraining members may be set so that the initial minimum porosity of the separator is 33% or more. In this case, the electrolyte solution can be diffused without any problem, and a desired output can be maintained. Further, it is possible to cause sufficient gas escape during gas generation.
　蓄電モジュールの通常動作時において拘束構造に発生する応力が第１拘束部材および第２拘束部材の疲労強度以下となるように、セパレータの圧縮率と第１拘束部材および第２拘束部材の厚さとが設定されていてもよい。この場合、圧縮されたセパレータからの反力によって第１拘束部材および第２拘束部材が疲労破壊してしまうことを抑制できる。 The compression rate of the separator and the thickness of the first restraining member and the second restraining member are such that the stress generated in the restraining structure during the normal operation of the power storage module is less than the fatigue strength of the first restraining member and the second restraining member. It may be set. In this case, it is possible to prevent the first restraining member and the second restraining member from being fatigued and destroyed by the reaction force from the compressed separator.
　この蓄電装置によれば、拘束部材に対する負荷変動を低減することができる。 According to this power storage device, it is possible to reduce load fluctuations on the restraining member.
蓄電モジュールを備える蓄電装置の実施形態を示す概略断面図である。It is a schematic sectional drawing which shows embodiment of an electrical storage apparatus provided with an electrical storage module. 図１の蓄電装置を構成する蓄電モジュールを示す概略断面図である。It is a schematic sectional drawing which shows the electrical storage module which comprises the electrical storage apparatus of FIG. 図３（ａ）は圧縮前のバイポーラ電極およびセパレータを示す断面図であり、図３（ｂ）は圧縮後のバイポーラ電極およびセパレータを示す断面図である。FIG. 3A is a sectional view showing the bipolar electrode and the separator before compression, and FIG. 3B is a sectional view showing the bipolar electrode and the separator after compression. セパレータの圧縮荷重特性を示す図である。It is a figure which shows the compressive load characteristic of a separator. セル内圧に対する拘束部材の負荷面圧を示す図である。It is a figure which shows the load surface pressure of the restraint member with respect to cell internal pressure. セパレータの圧縮率を変化させた場合の出力の変化を示す図である。It is a figure which shows the change of the output at the time of changing the compression rate of a separator. セパレータの圧縮率に関するクライテリアの成立範囲の一例を示す図である。It is a figure which shows an example of the establishment range of the criteria regarding the compression rate of a separator. セパレータの圧縮特性の一例を示す図である。It is a figure which shows an example of the compression characteristic of a separator. セパレータの厚みと空隙率の関係の一例を示す図である。It is a figure which shows an example of the relationship between the thickness of a separator, and the porosity.
　以下、本開示について、図面を参照しながら説明する。なお、図面の説明において同一要素には同一符号を付し、重複する説明は省略する。図面にはＸＹＺ直交座標系が示される。 Hereinafter, the present disclosure will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted. In the drawing, an XYZ orthogonal coordinate system is shown.
　図１を参照して、蓄電装置の実施形態について説明する。図１に示される蓄電装置１０は、例えばフォークリフト、ハイブリッド自動車、電気自動車等の各種車両のバッテリとして用いられる。蓄電装置１０は、複数（本実施形態では３つ）の蓄電モジュール１２を備えるが、単一の蓄電モジュール１２を備えてもよい。蓄電モジュール１２は、バイポーラ電池である。蓄電モジュール１２は、例えばニッケル水素二次電池、リチウムイオン二次電池等の二次電池であるが、電気二重層キャパシタであってもよい。以下の説明では、ニッケル水素二次電池を例示する。 With reference to FIG. 1, an embodiment of a power storage device will be described. The power storage device 10 shown in FIG. 1 is used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 10 includes a plurality (three in the present embodiment) of power storage modules 12, but may include a single power storage module 12. The power storage module 12 is a bipolar battery. The power storage module 12 is a secondary battery such as a nickel hydride secondary battery or a lithium ion secondary battery, but may be an electric double layer capacitor. In the following description, a nickel metal hydride secondary battery is illustrated.
　複数の蓄電モジュール１２は、例えば金属板等の導電板１４を介して積層され得る。積層方向から見て、蓄電モジュール１２及び導電板１４は例えば矩形形状を有する。各蓄電モジュール１２の詳細については後述する。導電板１４は、蓄電モジュール１２の積層方向（Ｚ方向）において両端に位置する蓄電モジュール１２の外側にもそれぞれ配置される。導電板１４は、隣り合う蓄電モジュール１２と電気的に接続される。これにより、複数の蓄電モジュール１２が積層方向に直列に接続される。積層方向において、一端に位置する導電板１４には正極端子２４が接続されており、他端に位置する導電板１４には負極端子２６が接続されている。正極端子２４は、接続される導電板１４と一体であってもよい。負極端子２６は、接続される導電板１４と一体であってもよい。正極端子２４及び負極端子２６は、積層方向に交差する方向（Ｘ方向）に延在している。これらの正極端子２４及び負極端子２６により、蓄電装置１０の充放電を実施できる。 The plurality of power storage modules 12 can be stacked via a conductive plate 14 such as a metal plate, for example. When viewed from the stacking direction, the power storage module 12 and the conductive plate 14 have, for example, a rectangular shape. Details of each power storage module 12 will be described later. The conductive plates 14 are also arranged outside the power storage modules 12 positioned at both ends in the stacking direction (Z direction) of the power storage modules 12. The conductive plate 14 is electrically connected to the adjacent power storage module 12. Thereby, the some electrical storage module 12 is connected in series in the lamination direction. In the stacking direction, a positive electrode terminal 24 is connected to the conductive plate 14 located at one end, and a negative electrode terminal 26 is connected to the conductive plate 14 located at the other end. The positive terminal 24 may be integrated with the conductive plate 14 to be connected. The negative electrode terminal 26 may be integrated with the conductive plate 14 to be connected. The positive electrode terminal 24 and the negative electrode terminal 26 extend in a direction (X direction) intersecting the stacking direction. The positive and negative terminals 24 and 26 can charge and discharge the power storage device 10.
　導電板１４は、蓄電モジュール１２において発生した熱を放出するための放熱板としても機能し得る。導電板１４の内部に設けられた複数の空隙１４ａを空気等の冷媒が通過することにより、蓄電モジュール１２からの熱を効率的に外部に放出できる。各空隙１４ａは例えば積層方向に交差する方向（Ｙ方向）に延在する。積層方向から見て、導電板１４は、蓄電モジュール１２よりも小さいが、蓄電モジュール１２と同じかそれより大きくてもよい。 The conductive plate 14 can also function as a heat radiating plate for releasing heat generated in the power storage module 12. When a refrigerant such as air passes through the plurality of gaps 14a provided inside the conductive plate 14, heat from the power storage module 12 can be efficiently released to the outside. Each gap 14a extends, for example, in a direction (Y direction) intersecting the stacking direction. When viewed from the stacking direction, the conductive plate 14 is smaller than the power storage module 12, but may be the same as or larger than the power storage module 12.
　蓄電装置１０は、交互に積層された蓄電モジュール１２及び導電板１４を積層方向に拘束する拘束構造１６を備え得る。拘束構造１６は、たとえば、複数の蓄電モジュール１２の積層方向の両端部に設けられた一対の拘束板１６Ａ，１６Ｂ（第１拘束部材および第２拘束部材）と、拘束板１６Ａ，１６Ｂ同士を連結する連結部材（ボルト１８及びナット２０等）とを備える。 The power storage device 10 may include a restraining structure 16 that restrains the alternately stacked power storage modules 12 and conductive plates 14 in the stacking direction. The restraint structure 16 connects, for example, a pair of restraint plates 16A and 16B (first restraint member and second restraint member) provided at both ends in the stacking direction of the plurality of power storage modules 12 and the restraint plates 16A and 16B. Connecting members (such as bolts 18 and nuts 20).
　拘束板１６Ａ，１６Ｂは、例えば鉄等の金属によって構成されている。より詳しくは、拘束板１６Ａ，１６Ｂを構成する材料は、たとえば、Ｓ４５Ｃ（ＪＩＳ規格）等の炭素鋼や、ＡＤＣ１０等のアルミダイカスト（アルミ合金ダイカスト）等である。拘束板１６Ａ，１６Ｂは、所定の板厚を有する。拘束板１６Ａ，１６Ｂの板厚は、いくつかの基準をもって決められ得る。たとえば、拘束板１６Ａ，１６Ｂの板厚は、セルに想定される内圧に対し、後述するセパレータ４０の離間を発生させない程度の変形となるように決められる。たとえば、想定内圧が最大２ＭＰａ以下（異常ガス発生時）であれば、安全率をとって、内圧４ＭＰａまで拘束板１６Ａ，１６Ｂの変形が設計基準（クライテリア）以下となるように、板厚が設計される。このような基準を満たす限りにおいて、拘束板１６Ａ，１６Ｂはできるだけ薄い方がよい。 Constraint plates 16A and 16B are made of metal such as iron, for example. More specifically, the material constituting the restraining plates 16A and 16B is, for example, carbon steel such as S45C (JIS standard), aluminum die casting (aluminum alloy die casting) such as ADC10, or the like. The restraint plates 16A and 16B have a predetermined plate thickness. The plate thickness of the restraining plates 16A and 16B can be determined based on several criteria. For example, the plate thickness of the restraining plates 16A and 16B is determined so as to be deformed so as not to cause separation of the separator 40 described later with respect to the internal pressure assumed in the cell. For example, if the assumed internal pressure is 2 MPa or less at the maximum (when abnormal gas is generated), the plate thickness is designed so that the deformation of the constraining plates 16A and 16B is less than the design standard (criteria) up to an internal pressure of 4 MPa. Is done. As long as these criteria are satisfied, the restraining plates 16A and 16B should be as thin as possible.
　各拘束板１６Ａ，１６Ｂと導電板１４との間には、例えば樹脂フィルム等の絶縁フィルム２２が配置される。積層方向から見て、各拘束板１６Ａ，１６Ｂ及び絶縁フィルム２２は例えば矩形形状を有する。絶縁フィルム２２は、導電板１４よりも大きくなっており、各拘束板１６Ａ，１６Ｂは、蓄電モジュール１２よりも大きくなっている。積層方向から見て、拘束板１６Ａの縁部には、ボルト１８の軸部を挿通させる挿通孔１６Ａ１が蓄電モジュール１２よりも外側となる位置に設けられている。同様に、積層方向から見て、拘束板１６Ｂの縁部には、ボルト１８の軸部を挿通させる挿通孔１６Ｂ１が蓄電モジュール１２よりも外側となる位置に設けられている。積層方向から見て各拘束板１６Ａ，１６Ｂが矩形形状を有している場合、挿通孔１６Ａ１及び挿通孔１６Ｂ１は、拘束板１６Ａ，１６Ｂの角部に位置する。 An insulating film 22 such as a resin film is disposed between the constraining plates 16A and 16B and the conductive plate 14. When viewed from the stacking direction, each of the restraining plates 16A and 16B and the insulating film 22 has, for example, a rectangular shape. The insulating film 22 is larger than the conductive plate 14, and the restraining plates 16 </ b> A and 16 </ b> B are larger than the power storage module 12. When viewed from the stacking direction, an insertion hole 16A1 through which the shaft portion of the bolt 18 is inserted is provided at a position on the outer side of the power storage module 12 at the edge of the restraint plate 16A. Similarly, an insertion hole 16 </ b> B <b> 1 through which the shaft portion of the bolt 18 is inserted is provided at a position on the outer side of the power storage module 12 at the edge of the restraining plate 16 </ b> B when viewed from the stacking direction. When each restraint plate 16A, 16B has a rectangular shape when viewed from the stacking direction, the insertion hole 16A1 and the insertion hole 16B1 are located at the corners of the restraint plates 16A, 16B.
　一方の拘束板１６Ａは、負極端子２６に接続された導電板１４に絶縁フィルム２２を介して突き当てられ、他方の拘束板１６Ｂは、正極端子２４に接続された導電板１４に絶縁フィルム２２を介して突き当てられている。ボルト１８は、例えば一方の拘束板１６Ａ側から他方の拘束板１６Ｂ側に向かって挿通孔１６Ａ１及び挿通孔１６Ｂ１に通される。他方の拘束板１６Ｂから突出するボルト１８の先端には、ナット２０が螺合されている。これにより、絶縁フィルム２２、導電板１４及び蓄電モジュール１２が挟持されてユニット化されると共に、積層方向に拘束荷重（圧縮力）が付与される。 One constraining plate 16A is abutted against the conductive plate 14 connected to the negative electrode terminal 26 via the insulating film 22, and the other constraining plate 16B has the insulating film 22 applied to the conductive plate 14 connected to the positive electrode terminal 24. Has been hit through. The bolt 18 is passed through the insertion hole 16A1 and the insertion hole 16B1, for example, from one restraint plate 16A side toward the other restraint plate 16B side. A nut 20 is screwed onto the tip of the bolt 18 protruding from the other restraining plate 16B. Thus, the insulating film 22, the conductive plate 14, and the power storage module 12 are sandwiched and unitized, and a restraining load (compression force) is applied in the stacking direction.
　図２を参照して、蓄電装置を構成する蓄電モジュールについて説明する。図２に示される蓄電モジュール１２は、複数のバイポーラ電極３２が積層された積層体３０を備える。バイポーラ電極３２の積層方向から見て、積層体３０は、例えば矩形形状を有する。隣り合うバイポーラ電極３２間にはセパレータ４０が配置され得る。 With reference to FIG. 2, a power storage module constituting the power storage device will be described. The power storage module 12 illustrated in FIG. 2 includes a stacked body 30 in which a plurality of bipolar electrodes 32 are stacked. When viewed from the stacking direction of the bipolar electrode 32, the stacked body 30 has, for example, a rectangular shape. A separator 40 may be disposed between the adjacent bipolar electrodes 32.
　各バイポーラ電極３２は、電極板３４と、電極板３４の第１面３４ｃに設けられた正極３６と、電極板３４の第２面３４ｄに設けられた負極３８とを含む。積層体３０において、一のバイポーラ電極３２の正極３６は、セパレータ４０を挟んで積層方向に隣り合う一方のバイポーラ電極３２の負極３８と対向し、一のバイポーラ電極３２の負極３８は、セパレータ４０を挟んで積層方向に隣り合う他方のバイポーラ電極３２の正極３６と対向している。セパレータ４０は、正極３６と負極３８とによって挟まれている。 Each bipolar electrode 32 includes an electrode plate 34, a positive electrode 36 provided on the first surface 34 c of the electrode plate 34, and a negative electrode 38 provided on the second surface 34 d of the electrode plate 34. In the stacked body 30, the positive electrode 36 of one bipolar electrode 32 faces the negative electrode 38 of one bipolar electrode 32 adjacent in the stacking direction across the separator 40, and the negative electrode 38 of one bipolar electrode 32 connects the separator 40. It faces the positive electrode 36 of the other bipolar electrode 32 that is adjacent in the stacking direction. The separator 40 is sandwiched between the positive electrode 36 and the negative electrode 38.
　積層方向において、積層体３０の一端には、内側面（図示下側の面）に負極３８が配置された電極板３４が配置される。この電極板３４は負極側終端電極に相当する。積層方向において、積層体３０の他端には、内側面（図示上側の面）に正極３６が配置された電極板３４が配置される。この電極板３４は正極側終端電極に相当する。負極側終端電極の負極３８は、セパレータ４０を介して最上層のバイポーラ電極３２の正極３６と対向している。正極側終端電極の正極３６は、セパレータ４０を介して最下層のバイポーラ電極３２の負極３８と対向している。これら終端電極の電極板３４はそれぞれ隣り合う導電板１４（図１参照）に接続される。 In the stacking direction, an electrode plate 34 having a negative electrode 38 disposed on the inner surface (the lower surface in the drawing) is disposed at one end of the stacked body 30. The electrode plate 34 corresponds to a negative terminal electrode. In the stacking direction, an electrode plate 34 having a positive electrode 36 disposed on the inner surface (the upper surface in the drawing) is disposed at the other end of the stacked body 30. This electrode plate 34 corresponds to a positive terminal electrode. The negative electrode 38 of the negative electrode-side termination electrode faces the positive electrode 36 of the uppermost bipolar electrode 32 with the separator 40 interposed therebetween. The positive electrode 36 of the positive terminal electrode is opposed to the negative electrode 38 of the lowermost bipolar electrode 32 with the separator 40 interposed therebetween. The electrode plates 34 of these termination electrodes are connected to the adjacent conductive plates 14 (see FIG. 1).
　蓄電モジュール１２は、バイポーラ電極３２の積層方向に延在し、積層体３０を収容する筒状の樹脂部５０を備える。樹脂部５０は、複数の電極板３４の周縁部３４ａを保持する。樹脂部５０は、積層体３０を取り囲むように構成されている。樹脂部５０は、電極板３４の周縁部３４ａに接合されて、その周縁部３４ａを保持する第１シール部５２と、積層方向に交差する方向（Ｘ方向及びＹ方向）において第１シール部５２の外側に設けられた第２シール部５４とを有する。 The power storage module 12 includes a cylindrical resin portion 50 that extends in the stacking direction of the bipolar electrodes 32 and accommodates the stacked body 30. The resin part 50 holds the peripheral edge part 34 a of the plurality of electrode plates 34. The resin part 50 is configured to surround the laminated body 30. The resin part 50 is joined to the peripheral part 34a of the electrode plate 34, and the first seal part 52 that holds the peripheral part 34a and the first seal part 52 in the direction (X direction and Y direction) intersecting the stacking direction. 2nd seal part 54 provided in the outside.
　樹脂部５０の内壁を構成する第１シール部５２は、複数のバイポーラ電極３２（すなわち積層体３０）における電極板３４の周縁部３４ａの全周にわたって設けられている。第１シール部５２は、電極板３４の周縁部３４ａに例えば溶着されており、その周縁部３４ａをシールする。各バイポーラ電極３２の電極板３４の周縁部３４ａは、第１シール部５２に埋没した状態で保持されている。積層体３０の両端に配置された電極板３４の周縁部３４ａも、第１シール部５２に埋没した状態で保持されている。これにより、積層方向に隣り合う電極板３４，３４間には、当該電極板３４，３４と第１シール部５２とによって気密に仕切られた内部空間が形成されている。当該内部空間には、例えば水酸化カリウム水溶液等のアルカリ溶液からなる電解液（不図示）が収容されている。 The 1st seal part 52 which constitutes the inner wall of resin part 50 is provided over the perimeter of peripheral part 34a of electrode board 34 in a plurality of bipolar electrodes 32 (namely, layered product 30). The first seal portion 52 is welded, for example, to the peripheral portion 34a of the electrode plate 34, and seals the peripheral portion 34a. The peripheral edge 34 a of the electrode plate 34 of each bipolar electrode 32 is held in a state of being buried in the first seal portion 52. The peripheral portions 34 a of the electrode plates 34 disposed at both ends of the stacked body 30 are also held in a state of being buried in the first seal portion 52. Thus, an internal space that is airtightly partitioned by the electrode plates 34 and 34 and the first seal portion 52 is formed between the electrode plates 34 and 34 adjacent in the stacking direction. An electrolytic solution (not shown) made of an alkaline solution such as an aqueous potassium hydroxide solution is accommodated in the internal space.
　樹脂部５０の外壁を構成する第２シール部５４は、バイポーラ電極３２の積層方向に延在する第１シール部５２の外周面５２ａを覆っている。第２シール部５４の内周面５４ａは、第１シール部５２の外周面５２ａに例えば溶着されており、その外周面５２ａをシールする。第１シール部５２に対する第２シール部５４の溶着面（接合面）は、例えば４つの矩形平面をなす。 The second seal part 54 constituting the outer wall of the resin part 50 covers the outer peripheral surface 52a of the first seal part 52 extending in the stacking direction of the bipolar electrodes 32. The inner peripheral surface 54a of the second seal portion 54 is welded, for example, to the outer peripheral surface 52a of the first seal portion 52, and seals the outer peripheral surface 52a. The welding surface (joint surface) of the second seal portion 54 with respect to the first seal portion 52 forms, for example, four rectangular planes.
　樹脂部５０（第１シール部５２及び第２シール部５４）は、例えば絶縁性の樹脂を用いた射出成形によって矩形の筒状に形成されている。樹脂部５０を構成する樹脂材料としては、例えばポリプロピレン（ＰＰ）、ポリフェニレンサルファイド（ＰＰＳ）、又は変性ポリフェニレンエーテル（変性ＰＰＥ）等が挙げられる。 The resin part 50 (the first seal part 52 and the second seal part 54) is formed in a rectangular cylindrical shape by, for example, injection molding using an insulating resin. Examples of the resin material constituting the resin portion 50 include polypropylene (PP), polyphenylene sulfide (PPS), and modified polyphenylene ether (modified PPE).
　蓄電装置１０では、第１面３４ｃの第１面３４ｃ側の正極３６と、隣接する電極板３４の第２面３４ｄ側の負極３８と、正極３６及び負極３８の間のセパレータ４０と、第１面３４ｃ及び第２面３４ｄの間の空間を密閉する樹脂部５０とによって、一層のセルが構成されている。樹脂部５０は、あるセルから他のセルへとガスおよび電解液が移動することを規制している。これにより、隣接するセル間における絶縁性が確保されている。 In the power storage device 10, the positive electrode 36 on the first surface 34 c side of the first surface 34 c, the negative electrode 38 on the second surface 34 d side of the adjacent electrode plate 34, the separator 40 between the positive electrode 36 and the negative electrode 38, A single cell is formed by the resin portion 50 that seals the space between the surface 34c and the second surface 34d. The resin part 50 regulates the movement of gas and electrolyte from one cell to another cell. Thereby, the insulation between adjacent cells is ensured.
　電極板３４は、例えばニッケルからなる矩形の金属箔である。電極板３４の周縁部３４ａは、正極活物質及び負極活物質の塗工されない未塗工領域となっている。未塗工領域では、電極板３４が露出している。その未塗工領域が、樹脂部５０の内壁を構成する第１シール部５２に埋没して保持されている。正極３６を構成する正極活物質としては、例えば水酸化ニッケルが挙げられる。負極３８を構成する負極活物質としては、例えば水素吸蔵合金が挙げられる。電極板３４の第２面３４ｄにおける負極３８の形成領域は、電極板３４の第１面３４ｃにおける正極３６の形成領域に対して一回り大きくてもよい。 The electrode plate 34 is a rectangular metal foil made of nickel, for example. The peripheral edge 34a of the electrode plate 34 is an uncoated region where the positive electrode active material and the negative electrode active material are not coated. In the uncoated region, the electrode plate 34 is exposed. The uncoated region is buried and held in the first seal portion 52 constituting the inner wall of the resin portion 50. An example of the positive electrode active material constituting the positive electrode 36 is nickel hydroxide. Examples of the negative electrode active material constituting the negative electrode 38 include a hydrogen storage alloy. The formation region of the negative electrode 38 on the second surface 34 d of the electrode plate 34 may be slightly larger than the formation region of the positive electrode 36 on the first surface 34 c of the electrode plate 34.
　セパレータ４０は、例えばシート状に形成されている。セパレータ４０は、例えば矩形形状を有する。セパレータ４０は、多孔性樹脂からなる。セパレータ４０は、たとえば、多孔性樹脂の一種である不織布からなる。セパレータ４０を形成する材料としては、具体的には、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）等のポリオレフィン系樹脂からなる多孔質フィルム、ポリプロピレン、ポリエチレンテレフタレート（ＰＥＴ）、メチルセルロース等からなる織布又は不織布等が例示される。蓄電モジュール１２がニッケル水素二次電池である場合、電解液はアルカリ性であるため、セパレータ４０を形成する材料にはアルカリ耐性が求められる。たとえば、蓄電モジュール１２がニッケル水素二次電池である場合には、ガラス繊維製のセパレータは使用できない。 The separator 40 is formed in a sheet shape, for example. The separator 40 has a rectangular shape, for example. The separator 40 is made of a porous resin. Separator 40 consists of a nonwoven fabric which is a kind of porous resin, for example. Specifically, the material forming the separator 40 is a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), a woven fabric or a non-woven fabric made of polypropylene, polyethylene terephthalate (PET), methylcellulose or the like. Etc. are exemplified. When the power storage module 12 is a nickel metal hydride secondary battery, the electrolyte is alkaline, and thus the material forming the separator 40 is required to have alkali resistance. For example, when the power storage module 12 is a nickel metal hydride secondary battery, a glass fiber separator cannot be used.
　セパレータ４０が不織布からなる場合、不織布の繊維は、ポリプロピレン（ＰＰ）及びポリエチレン（ＰＥ）からなってもよい。不織布の繊維に、電解液に対する親和性をもたせるための表面処理が施され得る。セパレータ４０が不織布である場合には、このような親和性をもたせるための表面処理を施しやすい。なお、セパレータ４０は、フッ化ビニリデン樹脂化合物で補強されたものであってもよい。セパレータ４０は、シート状に限られず、袋状であってもよい。 When the separator 40 is made of a nonwoven fabric, the fibers of the nonwoven fabric may be made of polypropylene (PP) and polyethylene (PE). Surface treatment for imparting affinity to the electrolyte solution may be performed on the fibers of the nonwoven fabric. When the separator 40 is a nonwoven fabric, it is easy to perform a surface treatment for giving such an affinity. The separator 40 may be reinforced with a vinylidene fluoride resin compound. The separator 40 is not limited to a sheet shape, and may be a bag shape.
　本実施形態の蓄電装置１０では、蓄電モジュール１２に対して接続される導電板１４は、たとえば樹脂部５０の内側に配置される。導電板１４は、積層体３０の積層方向の両端部に設けられた電極板３４に当接し、拘束構造１６からの圧縮力を積層体３０に伝達する。これにより、拘束構造１６は、各蓄電モジュール１２における正極３６、セパレータ４０、および負極３８に対して積層方向に圧縮力を付与する。 In the power storage device 10 of the present embodiment, the conductive plate 14 connected to the power storage module 12 is disposed, for example, inside the resin portion 50. The conductive plate 14 abuts on the electrode plates 34 provided at both ends of the stacked body 30 in the stacking direction, and transmits the compressive force from the restraining structure 16 to the stacked body 30. As a result, the restraint structure 16 applies a compressive force in the stacking direction to the positive electrode 36, the separator 40, and the negative electrode 38 in each power storage module 12.
　図３（ａ）および図３（ｂ）に示されるように、バイポーラ電極３２の正極３６と負極３８との間に配置されて挟まれたセパレータ４０は、所定の圧縮率で圧縮されている。本実施形態では、圧縮されたセパレータ４０によって拘束板１６Ａ，１６Ｂが受ける面圧（圧縮面圧および負荷面圧）が考慮されている。セパレータ４０が適切な圧縮率をもって圧縮されていることで、拘束板１６Ａ，１６Ｂの応力振幅が小さくなっている。特に、セパレータ４０の圧縮前の厚みが１００μｍといったオーダーであって分厚い場合、圧縮率は管理の対象としやすい。圧縮率とは、圧縮前のセパレータ４０の積層方向の厚みに対して、圧縮後のセパレータ４０の積層方向の厚みがどれくらい減少したか（圧縮量、潰し量）を示す割合である。 3A and 3B, the separator 40 disposed between the positive electrode 36 and the negative electrode 38 of the bipolar electrode 32 is compressed at a predetermined compression rate. In the present embodiment, the surface pressure (compression surface pressure and load surface pressure) received by the constraining plates 16A and 16B by the compressed separator 40 is considered. Since the separator 40 is compressed with an appropriate compression rate, the stress amplitude of the restraining plates 16A and 16B is reduced. In particular, when the thickness of the separator 40 before compression is on the order of 100 μm and thick, the compression rate is easy to manage. The compression rate is a ratio indicating how much the thickness in the stacking direction of the separator 40 after compression is reduced (the amount of compression and crushing) with respect to the thickness in the stacking direction of the separator 40 before compression.
　続いて、セパレータ４０の圧縮率が面圧および出力に及ぼす各種影響について説明する。図４は、セパレータ４０の圧縮荷重特性を示す図である。圧縮面圧とは、セル内圧を考慮に入れず、セパレータ４０が圧縮されたことのみに起因して、拘束板１６Ａ，１６Ｂがセパレータ４０から受ける面圧である。図４に示されるように、圧縮率（潰し量）が大きくなると、圧縮面圧が急激に増加する傾向にある。これは、圧縮率が高ければ高いほど、拘束板１６Ａ，１６Ｂの変形クライテリアを超える可能性が高まることを意味する。たとえば、圧縮率が４０％以上であると圧縮面圧は６ＭＰａを超えるので、好ましくない。 Subsequently, various effects of the compressibility of the separator 40 on the surface pressure and output will be described. FIG. 4 is a diagram illustrating the compressive load characteristics of the separator 40. The compression surface pressure is a surface pressure that the constraining plates 16A and 16B receive from the separator 40 only because the separator 40 is compressed without taking the cell internal pressure into consideration. As shown in FIG. 4, when the compression rate (crushing amount) increases, the compression surface pressure tends to increase rapidly. This means that the higher the compression ratio, the higher the possibility of exceeding the deformation criteria of the restraining plates 16A and 16B. For example, if the compression rate is 40% or more, the compression surface pressure exceeds 6 MPa, which is not preferable.
　図５は、セル内圧に対する拘束板１６Ａ，１６Ｂの負荷面圧を示す図である。この負荷面圧は、セル内圧を考慮に入れた場合に、拘束板１６Ａ，１６Ｂが受ける面圧である。図５は、ニッケル水素二次電池における面圧に関するシミュレーション結果である。このシミュレーションでは、図４に示されるセパレータ４０の圧縮荷重特性が考慮されている。図５に示されるように、初期圧縮率が高いほど、拘束板負荷面圧の上昇幅すなわち応力振幅は小さくなっている。また、初期圧縮率が１０％、１７％、および２３％の場合では、セル内圧よりも、拘束板負荷面圧の方が常に高い。これは、セルの内圧変動による拘束板の変形に対し、セパレータの圧縮量（すなわち潰し量）の緩和が生じ、セパレータがバイポーラ電極３２に当接していることを示す。すなわち、これは、セパレータ４０はバイポーラ電極３２から離れていない（浮いていない）ことを示す。一方、初期圧縮率が５％の場合では、セル内圧が０～０．１ＭＰａの範囲では、セパレータがバイポーラ電極３２に当接していると考えられる。しかし一方で、セル内圧が０．１ＭＰａを超えた範囲では、拘束板負荷面圧はセル内圧と等しくなっており、セパレータがバイポーラ電極３２から離れている（浮いている）と思われる。このようなセパレータ４０の離間は、蓄電モジュール１２における抵抗を増大させるため、好ましくない。 FIG. 5 is a diagram showing the load surface pressure of the restraining plates 16A and 16B with respect to the cell internal pressure. This load surface pressure is the surface pressure that the restraining plates 16A and 16B receive when the cell internal pressure is taken into consideration. FIG. 5 is a simulation result regarding the surface pressure in the nickel-hydrogen secondary battery. In this simulation, the compressive load characteristic of the separator 40 shown in FIG. 4 is considered. As shown in FIG. 5, the higher the initial compression ratio, the smaller the increase width of the restraint plate load surface pressure, that is, the stress amplitude. Further, when the initial compression ratio is 10%, 17%, and 23%, the restraint plate load surface pressure is always higher than the cell internal pressure. This indicates that the amount of compression (that is, the amount of crushing) of the separator is relaxed against deformation of the constraining plate due to fluctuations in the internal pressure of the cell, and the separator is in contact with the bipolar electrode 32. That is, this indicates that the separator 40 is not separated (not floating) from the bipolar electrode 32. On the other hand, when the initial compression rate is 5%, it is considered that the separator is in contact with the bipolar electrode 32 when the cell internal pressure is in the range of 0 to 0.1 MPa. However, on the other hand, in the range where the cell internal pressure exceeds 0.1 MPa, the constraining plate load surface pressure is equal to the cell internal pressure, and the separator seems to be separated (floating) from the bipolar electrode 32. Such separation of the separator 40 is not preferable because it increases resistance in the power storage module 12.
　図６は、セパレータ４０の圧縮率を変化させた場合の蓄電装置１０の出力の変化を示す図である。図６では、最大の出力を１００％として、出力の変化が割合で示されている。図６では、ＳＯＣ（Ｓｔａｔｅ　Ｏｆ　Ｃｈａｒｇｅ）６０％、温度２５℃、出力は１０秒間、１．０Ｖカット、セパレータ４０の初期空隙率が６５％の場合を示している。図６に示されるように、圧縮率が４０％を超えると、急激に出力が低下している。これは、セパレータ４０の圧縮率を高めすぎた場合、セパレータ４０の空隙が少なくなって電解液の拡散に支障が生じることに起因すると考えられる。なお、「１．０Ｖカット」とは、出力を取り出すのを１．０Ｖまでとすることを意味する。それ以下の値では過放電と判断され、出力は取り出されない。 FIG. 6 is a diagram illustrating a change in the output of the power storage device 10 when the compression rate of the separator 40 is changed. In FIG. 6, the change in output is shown as a ratio, with the maximum output being 100%. FIG. 6 shows a case where SOC (State Of Charge) 60%, temperature 25 ° C., output 10 seconds, 1.0 V cut, and initial porosity of separator 40 is 65%. As shown in FIG. 6, when the compression rate exceeds 40%, the output is rapidly reduced. It is considered that this is because, when the compressibility of the separator 40 is increased too much, the gaps in the separator 40 are reduced and the diffusion of the electrolytic solution is hindered. “1.0V cut” means that the output is taken out to 1.0V. If the value is less than that, it is judged as overdischarge, and no output is taken out.
　上記の各種影響を考慮し、本実施形態の蓄電装置１０においては、拘束構造１６により圧縮されたセパレータ４０の圧縮率は、０％より大きく４０％未満になっている。より好ましくは、拘束構造１６により圧縮されたセパレータ４０の圧縮率は、１０％以上であってもよい。より好ましくは、拘束構造１６により圧縮されたセパレータ４０の圧縮率は、３０％以下であってもよい。更に好ましくは、拘束構造１６により圧縮されたセパレータ４０の圧縮率は、２０％以上かつ３０％以下であってもよい。拘束構造１６により圧縮されたセパレータ４０の圧縮率は、２５％以下であってもよく、２０％以下であってもよく、１５％以下であってもよい。 In consideration of the various effects described above, in the power storage device 10 of the present embodiment, the compression rate of the separator 40 compressed by the constraining structure 16 is greater than 0% and less than 40%. More preferably, the compression rate of the separator 40 compressed by the constraining structure 16 may be 10% or more. More preferably, the compression rate of the separator 40 compressed by the constraining structure 16 may be 30% or less. More preferably, the compression rate of the separator 40 compressed by the constraining structure 16 may be 20% or more and 30% or less. The compressibility of the separator 40 compressed by the constraining structure 16 may be 25% or less, 20% or less, or 15% or less.
　図４に示されるように、セパレータ４０の圧縮率が１０％の場合、圧縮面圧は約０．１ＭＰａである。セパレータ４０の圧縮率が１５％の場合、圧縮面圧は約０．３ＭＰａである。セパレータ４０の圧縮率が２０％の場合、圧縮面圧は約０．６ＭＰａである。セパレータ４０の圧縮率が２５％の場合、圧縮面圧は約１．１ＭＰａである。セパレータ４０の圧縮率が３０％の場合、圧縮面圧は約１．９ＭＰａである。セパレータ４０の圧縮率が３５％の場合、圧縮面圧は約３．３ＭＰａである。 As shown in FIG. 4, when the compression rate of the separator 40 is 10%, the compression surface pressure is about 0.1 MPa. When the compression rate of the separator 40 is 15%, the compression surface pressure is about 0.3 MPa. When the compression rate of the separator 40 is 20%, the compression surface pressure is about 0.6 MPa. When the compression rate of the separator 40 is 25%, the compression surface pressure is about 1.1 MPa. When the compression rate of the separator 40 is 30%, the compression surface pressure is about 1.9 MPa. When the compression rate of the separator 40 is 35%, the compression surface pressure is about 3.3 MPa.
　ここで、蓄電モジュール１２の製造方法について説明する。まず、電極板３４の第１面３４ｃに正極３６を形成し、電極板３４の第２面３４ｄに負極３８を形成して、バイポーラ電極３２を得る。次に、例えばセパレータ４０を介してバイポーラ電極３２を積層して積層体３０を得る。本実施形態では、この積層工程前に、各バイポーラ電極３２の電極板３４の周縁部３４ａにおいて、第１シール部５２が熱プレス又は射出成形により形成されている。 Here, a method for manufacturing the power storage module 12 will be described. First, the positive electrode 36 is formed on the first surface 34 c of the electrode plate 34, and the negative electrode 38 is formed on the second surface 34 d of the electrode plate 34 to obtain the bipolar electrode 32. Next, for example, the bipolar electrode 32 is stacked via the separator 40 to obtain the stacked body 30. In this embodiment, before this lamination process, the 1st seal | sticker part 52 is formed in the peripheral part 34a of the electrode plate 34 of each bipolar electrode 32 by hot press or injection molding.
　次に、第２シール部５４を例えば射出成形により形成する。例えば、モールド内に、流動性を有する第２シール部５４の樹脂材料を流し込むことによって、第２シール部５４が形成され得る。 Next, the second seal portion 54 is formed by, for example, injection molding. For example, the second seal portion 54 can be formed by pouring a resin material of the second seal portion 54 having fluidity into the mold.
　なお、本実施形態では、積層工程前に樹脂部５０の一部である第１シール部５２を形成し、積層工程後に樹脂部５０の残部である第２シール部５４を形成しているが、積層工程後に樹脂部５０の一部である第１シール部５２を形成してもよい。 In the present embodiment, the first seal portion 52 that is a part of the resin portion 50 is formed before the lamination step, and the second seal portion 54 that is the remaining portion of the resin portion 50 is formed after the lamination step. You may form the 1st seal | sticker part 52 which is a part of resin part 50 after a lamination process.
　次に、注液口等を通じて、樹脂部５０内に電解液を注入する。電解液を注入した後、注液口を封止することによって、蓄電モジュール１２が製造される。その後、図１に示されるように、導電板１４を介して複数の蓄電モジュール１２を積層する。積層方向の両端に位置する導電板１４にはそれぞれ正極端子２４及び負極端子２６が予め接続されている。その後、積層方向の両端に、絶縁フィルム２２を介して一対の拘束板１６Ａ，１６Ｂをそれぞれ配置し、ボルト１８及びナット２０を用いて、拘束板１６Ａ，１６Ｂ同士を連結する。これにより、各蓄電モジュール１２に拘束荷重（圧縮力）が付与される。この拘束工程においては、セパレータ４０の圧縮率が上記した所定の圧縮率となるよう、拘束板１６Ａ，１６Ｂ間の距離が調節され得る。上記のようにして、図１に示される蓄電装置１０が製造される。 Next, an electrolytic solution is injected into the resin part 50 through an injection port or the like. After injecting the electrolytic solution, the storage module 12 is manufactured by sealing the injection port. Thereafter, as shown in FIG. 1, a plurality of power storage modules 12 are stacked via the conductive plate 14. A positive electrode terminal 24 and a negative electrode terminal 26 are connected in advance to the conductive plates 14 located at both ends in the stacking direction. Then, a pair of restraint plates 16A and 16B are respectively disposed at both ends in the stacking direction via the insulating film 22, and the restraint plates 16A and 16B are connected to each other using the bolt 18 and the nut 20. Thereby, a restraint load (compression force) is applied to each power storage module 12. In this restraining step, the distance between the restraining plates 16A and 16B can be adjusted so that the compression rate of the separator 40 becomes the above-described predetermined compression rate. As described above, power storage device 10 shown in FIG. 1 is manufactured.
　本実施形態の蓄電装置１０によれば、拘束板１６Ａ，１６Ｂを含む拘束構造１６によって、正極３６、セパレータ４０、及び負極３８が設けられた部分に圧縮力が付与される。セパレータ４０の圧縮率が０％より大きく４０％未満であると、セルの内圧変動による拘束板１６Ａ，１６Ｂの変形と、セパレータ４０の圧縮量（すなわち潰し量）の緩和とが同時に起こる。すなわち、セパレータ４０の圧縮状態が、内圧変動を緩和する。上記の圧縮率の範囲は、多孔性樹脂からなるセパレータ４０に適した範囲になっている。多孔性樹脂からなるセパレータ４０に適した圧縮率の範囲とすることで、拘束板１６Ａ，１６Ｂに対する負荷変動が好適に抑制される。このことは、拘束板１６Ａ，１６Ｂの応力振幅の低減をもたらす。セパレータ４０を圧縮しない場合（潰さない場合すなわち圧縮率が０％の場合）は、応力振幅が大きくなる傾向にある（図５参照）。よって、上記構成は、セパレータを圧縮しない場合に比べて、拘束板の疲労の観点で有利である。セパレータ４０の圧縮率が大きすぎると、圧縮されたセパレータ４０から受ける面圧に起因して、セルの内圧の負荷が高まったとき以上の負荷が拘束板１６Ａ，１６Ｂに加わってしまう（図４参照）。これは拘束板１６Ａ，１６Ｂの疲労の観点で不利である。また、拘束板１６Ａ，１６Ｂの変形クライテリアを超えてしまうこともある。セパレータ４０の圧縮率を４０％未満とすることにより、拘束板１６Ａ，１６Ｂに対して生じ得るこれらの諸問題が解決される。 According to the power storage device 10 of the present embodiment, a compressive force is applied to the portion where the positive electrode 36, the separator 40, and the negative electrode 38 are provided by the constraining structure 16 including the constraining plates 16A and 16B. If the compression rate of the separator 40 is greater than 0% and less than 40%, deformation of the restraint plates 16A and 16B due to fluctuations in the internal pressure of the cells and relaxation of the compression amount (that is, crushing amount) of the separator 40 occur simultaneously. That is, the compression state of the separator 40 reduces the internal pressure fluctuation. The range of the compression rate is a range suitable for the separator 40 made of a porous resin. By setting the compression rate range suitable for the separator 40 made of porous resin, load fluctuations on the restraining plates 16A and 16B are suitably suppressed. This leads to a reduction in the stress amplitude of the restraining plates 16A and 16B. When the separator 40 is not compressed (when it is not crushed, that is, when the compression rate is 0%), the stress amplitude tends to increase (see FIG. 5). Therefore, the said structure is advantageous from a viewpoint of the fatigue | exhaustion of a restraint plate compared with the case where a separator is not compressed. If the compression rate of the separator 40 is too large, due to the surface pressure received from the compressed separator 40, a load higher than that when the internal pressure of the cell is increased is applied to the restraining plates 16A and 16B (see FIG. 4). ). This is disadvantageous from the viewpoint of fatigue of the restraining plates 16A and 16B. Further, the deformation criteria of the restraining plates 16A and 16B may be exceeded. By making the compression rate of the separator 40 less than 40%, these various problems that may occur with respect to the restraining plates 16A and 16B are solved.
　また、内圧変動によってセパレータ４０の圧縮量（すなわち潰し量）が緩和された場合、セパレータ４０がバイポーラ電極３２から離れてしまう可能性がある（図５参照）。セパレータ４０が離れると、バイポーラ電極３２間の距離が制御できなくなり、イオン伝導距離が極端に長くなる可能性がある。これらの現象は、蓄電モジュール１２における抵抗を増大させるため、好ましくない。そこで、セパレータ４０の圧縮率が１０％以上であると、バイポーラ電極３２からのセパレータ４０の離間現象を防止でき、抵抗の増大を防止することができる。その結果として、所望の出力を維持することができる（図６参照）。 Further, when the compression amount (that is, the crushing amount) of the separator 40 is relaxed due to fluctuations in internal pressure, the separator 40 may be separated from the bipolar electrode 32 (see FIG. 5). When the separator 40 is separated, the distance between the bipolar electrodes 32 cannot be controlled, and the ion conduction distance may become extremely long. These phenomena are not preferable because they increase the resistance in the power storage module 12. Therefore, when the compressibility of the separator 40 is 10% or more, the separation phenomenon of the separator 40 from the bipolar electrode 32 can be prevented, and an increase in resistance can be prevented. As a result, a desired output can be maintained (see FIG. 6).
　また、セパレータ４０の圧縮率を高めすぎると、拘束板１６Ａ，１６Ｂがセパレータ４０から受ける面圧が高くなるため（図４参照）、拘束板１６Ａ，１６Ｂの強度すなわち板厚を高める必要がある。セパレータ４０の圧縮率が３０％以下であると、想定されるセルの内圧に対して、適正な範囲の板厚を設定することができる。適正な範囲の板厚とは、想定内圧に対して拘束板が変形せず（セパレータ４０が離れるほどには変形せず）、かつ蓄電装置１０の小型化の観点で所望の薄さを満たすような板厚である。また、セパレータ４０の圧縮率を高めすぎると、セパレータ４０の空隙が少なくなり、電解液の拡散に支障が生じ得る。この観点でも、セパレータの圧縮率が３０％以下であると、電解液の拡散が支障なく行われ、所望の出力を維持することができる（図６参照）。 Also, if the compression rate of the separator 40 is increased too much, the surface pressure received by the constraining plates 16A and 16B from the separator 40 becomes high (see FIG. 4), so the strength of the constraining plates 16A and 16B, that is, the plate thickness needs to be increased. When the compression rate of the separator 40 is 30% or less, a plate thickness in an appropriate range can be set with respect to the assumed internal pressure of the cell. The plate thickness in an appropriate range is such that the constraining plate does not deform with respect to the assumed internal pressure (it does not deform as far as the separator 40 is separated) and satisfies the desired thickness from the viewpoint of miniaturization of the power storage device 10. Thickness. Moreover, when the compression rate of the separator 40 is increased too much, the gaps in the separator 40 are reduced, and the diffusion of the electrolytic solution may be hindered. Also from this viewpoint, when the compression rate of the separator is 30% or less, the electrolyte solution can be diffused without any problem, and a desired output can be maintained (see FIG. 6).
　セパレータ４０の圧縮率を２０％以上かつ３０％以下とし、このような下限値と上限値を設定した場合、上記したセパレータ４０の離間、セパレータ４０による面圧増大による拘束板１６Ａ，１６Ｂの大型化、及び電解液の拡散不良等といった諸問題が生じる可能性がより確実に低減される。 When the compression rate of the separator 40 is 20% or more and 30% or less, and such lower and upper limits are set, the size of the restraining plates 16A and 16B is increased due to the separation of the separator 40 and the increase in the surface pressure by the separator 40. , And the possibility of various problems such as poor diffusion of the electrolyte solution is more reliably reduced.
　蓄電モジュール１２がニッケル水素二次電池であると、多孔性樹脂からなるセパレータ４０が用いられるので、上記した圧縮率の範囲が特に適している。特に、バイポーラ電極を備えたニッケル水素二次電池では、拘束板１６Ａ，１６Ｂとバイポーラ電極３２との間に樹脂などの変形し得る部材が設けられないため、セルの内圧変動の影響が大きい。他の二次電池であれば、セル毎に形状の決まったケースが設けられる場合があるが、バイポーラ型のニッケル水素二次電池にはそのようなケースがない。そのため、受圧面積が大きく、応力が付加されやすい。しかも、バイポーラ電極３２は、塗工面積が大きくなる傾向ももっており、この観点でも、セルの内圧変動の影響は大きい。セパレータ４０の圧縮率の管理は、バイポーラ型のニッケル水素二次電池における信頼性や小型化の観点において、大きな効果を奏させる。 When the power storage module 12 is a nickel metal hydride secondary battery, the separator 40 made of porous resin is used, so the above-described compression rate range is particularly suitable. In particular, in a nickel metal hydride secondary battery provided with a bipolar electrode, since a deformable member such as a resin is not provided between the restraining plates 16A and 16B and the bipolar electrode 32, the influence of fluctuations in the internal pressure of the cell is great. For other secondary batteries, a case with a fixed shape may be provided for each cell, but a bipolar nickel-hydrogen secondary battery does not have such a case. Therefore, the pressure receiving area is large and stress is easily applied. In addition, the bipolar electrode 32 tends to have a large coating area, and from this point of view, the influence of cell internal pressure fluctuations is large. The management of the compression rate of the separator 40 has a great effect in terms of reliability and miniaturization in the bipolar nickel-hydrogen secondary battery.
　なお、多項性樹脂からなるセパレータ４０は、圧縮後に圧縮量が緩和されることにより、第１シール部５２の厚みや電極板３４，３４同士の距離のばらつきを調整することができる。 In addition, the separator 40 made of a polymorphic resin can adjust the thickness variation of the first seal portion 52 and the distance between the electrode plates 34 and 34 by reducing the amount of compression after compression.
　本開示について説明したが、本開示は上記実施形態に限られない。たとえば、拘束構造は、上記した構造に限られない。また、第１拘束部材および第２拘束部材は、拘束板１６Ａ，１６Ｂのような板状の部材に限られない。蓄電モジュールの積層方向の両端部に設けられて、蓄電モジュールに対して圧縮力を付与し得る構造が実現されていれば、第１拘束部材および第２拘束部材としてどのような部材が用いられてもよい。 Although the present disclosure has been described, the present disclosure is not limited to the above embodiment. For example, the constraint structure is not limited to the above-described structure. The first restraining member and the second restraining member are not limited to plate-like members such as restraining plates 16A and 16B. What is used as the first restraining member and the second restraining member as long as a structure that is provided at both ends in the stacking direction of the electricity storage module and can apply a compressive force to the electricity storage module is realized. Also good.
　また、蓄電装置１０では、セパレータ４０の圧縮率及び拘束板１６Ａ，１６Ｂの最適設定に関し、次の２つのクライテリア（１）（２）を満たすことが好ましい。
（１）蓄電モジュール１２の通常動作時においてセパレータ４０の最小圧縮率が常に０％より大きい
（２）蓄電モジュール１２の異常時において拘束構造１６に発生する応力が拘束板１６Ａ，１６Ｂの降伏応力以下 Moreover, in the electrical storage apparatus 10, it is preferable that the following two criteria (1) and (2) are satisfied regarding the compression rate of the separator 40 and the optimal setting of the restraining plates 16A and 16B.
(1) The minimum compression rate of the separator 40 is always greater than 0% during normal operation of the power storage module 12. (2) The stress generated in the restraint structure 16 when the power storage module 12 is abnormal is less than the yield stress of the restraint plates 16A and 16B.
　また、蓄電装置１０では、セパレータ４０の圧縮率及び拘束板１６Ａ，１６Ｂの最適設定に関し、次の２つのクライテリア（３）（４）を更に満たすことが好ましい。
（３）セパレータ４０の初期の最小空隙率が３３％以上
（４）蓄電モジュール１２の通常動作時において拘束構造１６に発生する応力が拘束板１６Ａ，１６Ｂの疲労強度以下 Moreover, in the electrical storage apparatus 10, it is preferable that the following two criteria (3) and (4) are further satisfied regarding the compression rate of the separator 40 and the optimal setting of the restraining plates 16A and 16B.
(3) The initial minimum porosity of the separator 40 is 33% or more. (4) The stress generated in the restraint structure 16 during the normal operation of the power storage module 12 is less than the fatigue strength of the restraint plates 16A and 16B.
　図７は、上記４つのクライテリアの成立範囲の一例を示す図である。同図に示す例では、横軸に圧縮前のセパレータの厚みを示し、縦軸に拘束板厚を示している。この例では、セパレータの圧縮後の厚みは７５μｍである。したがって、横軸をセパレータの圧縮率で換算すると、圧縮前のセパレータの厚みが７５μｍ～１２５μｍとなる範囲が、セパレータの圧縮率が０％～４０％となる範囲に相当する。図７において、グラフＡの右側領域がクライテリア（１）を満たす領域であり、グラフＢの左側領域がクライテリア（２）を満たす領域である。また、グラフＣの左側領域がクライテリア（３）を満たす領域であり、グラフＤの左側領域がクライテリア（４）を満たす領域である。上記４つのクライテリアを全て満たす領域は、図７における領域Ｒで示された部分となる。この領域Ｒで示された部分のうち、拘束板厚が最も小さくなる点Ｒａで示されるセパレータの圧縮率及び拘束板厚が上記クライテリア（１）～（４）を満たす最適設計条件となる。 FIG. 7 is a diagram showing an example of the establishment range of the above four criteria. In the example shown in the figure, the horizontal axis indicates the thickness of the separator before compression, and the vertical axis indicates the thickness of the restraint plate. In this example, the thickness of the separator after compression is 75 μm. Therefore, when the horizontal axis is converted into the compression rate of the separator, the range where the thickness of the separator before compression is 75 μm to 125 μm corresponds to the range where the compression rate of the separator is 0% to 40%. In FIG. 7, the right region of the graph A is a region that satisfies the criterion (1), and the left region of the graph B is a region that satisfies the criterion (2). Further, the left region of the graph C is a region satisfying the criterion (3), and the left region of the graph D is a region satisfying the criterion (4). A region satisfying all the four criteria is a portion indicated by a region R in FIG. Among the portions indicated by the region R, the compression rate and the restraint plate thickness of the separator indicated by the point Ra where the restraint plate thickness is the smallest are the optimum design conditions that satisfy the above criteria (1) to (4).
　クライテリア（１）は、セルの内圧変動による拘束板の変形と、これに伴うセパレータの圧縮量の緩和に関する。拘束板厚が小さくなると、セルの内圧変動による拘束板の変形量が大きくなるため、クライテリア（１）を満たすセパレータの圧縮率も大きくなる。クライテリア（１）における通常動作時とは、例えば蓄電モジュールに内圧上昇時の開放弁が設けられている場合には、開放弁の動作圧未満の所定の範囲の内圧で蓄電モジュールが動作している場合を指す。 Criterion (1) relates to deformation of the constraining plate due to fluctuations in the internal pressure of the cell and relaxation of the compression amount of the separator. When the thickness of the restraint plate is reduced, the amount of deformation of the restraint plate due to fluctuations in the internal pressure of the cell is increased, so that the compression rate of the separator satisfying the criterion (1) is also increased. In normal operation in the criterion (1), for example, when the storage module is provided with an open valve when the internal pressure rises, the storage module is operating at an internal pressure within a predetermined range that is less than the operating pressure of the open valve. Refers to the case.
　クライテリア（２）は、拘束板の降伏応力に関する。セパレータの圧縮率が大きいほど、反力による拘束板への荷重が大きくなる。このため、セパレータの圧縮率が大きいほど、拘束板厚を大きくする必要がある。クライテリア（１）における異常時とは、例えば蓄電モジュールに内圧上昇時の開放弁が設けられている場合には、蓄電モジュールの内圧が開放弁の動作圧に到達した場合を指す。 Criterion (2) relates to the yield stress of the restraint plate. The larger the compression rate of the separator, the greater the load on the restraining plate due to the reaction force. For this reason, it is necessary to increase the restraint plate thickness as the separator compressibility increases. When the criterion (1) is abnormal, for example, when the storage module is provided with an open valve at the time when the internal pressure increases, the internal pressure of the storage module reaches the operating pressure of the open valve.
　クライテリア（３）は、セル間の電解液の拡散に関する。最小空隙率の設定を大きくすると、図７におけるクライテリア（３）の境界線は、グラフの左側にシフトし、最小空隙率の設定を小さくすると、図７におけるクライテリア（３）の境界線は、グラフの右側にシフトする。クライテリア（３）における初期とは、拘束構造による蓄電モジュールの締付時を指す。また、クライテリア（４）は、拘束板の疲労強度に関する。疲労強度の設定を高くすると、図７におけるクライテリア（４）の境界線は、グラフの左側にシフトし、疲労強度の設定を低くすると、図７におけるクライテリア（４）の境界線は、グラフの右側にシフトする。 Criterion (3) relates to the diffusion of electrolyte between cells. When the setting of the minimum porosity is increased, the boundary line of the criterion (3) in FIG. 7 is shifted to the left side of the graph. When the setting of the minimum porosity is decreased, the boundary line of the criterion (3) in FIG. Shift to the right. The initial stage in the criterion (3) refers to the time when the power storage module is tightened by the restraint structure. Criterion (4) relates to the fatigue strength of the restraint plate. When the fatigue strength setting is increased, the boundary line of the criterion (4) in FIG. 7 shifts to the left side of the graph, and when the fatigue strength setting is decreased, the boundary line of the criterion (4) in FIG. Shift to.
　図８は、セパレータの圧縮特性の一例を示す図である。同図に示す例では、横軸に面圧を示し、縦軸に圧縮率を示している。図８におけるグラフＥは、厚み７０μｍのセパレータの圧縮特性、グラフＦは、厚み８０μｍのセパレータの圧縮特性、グラフＧは、厚み９０μｍのセパレータの圧縮特性を示している。これらの圧縮特性は、オートグラフを用い、オートグラフの荷重とストロークに基づいて取得されたものである。各セパレータの目付は、いずれも３１ｇ／ｍ２である。これらの圧縮特性から、目付を同じ条件とした場合には、セパレータの厚みを変えることで、同一の圧縮率に対する面圧を制御できることが分かる。面圧を拘束板にかかる受圧面積から換算することで反力を算出することができる。 FIG. 8 is a diagram showing an example of the compression characteristics of the separator. In the example shown in the figure, the horizontal axis indicates the surface pressure, and the vertical axis indicates the compression rate. A graph E in FIG. 8 shows a compression characteristic of a separator having a thickness of 70 μm, a graph F shows a compression characteristic of a separator having a thickness of 80 μm, and a graph G shows a compression characteristic of the separator having a thickness of 90 μm. These compression characteristics are obtained using an autograph based on the load and stroke of the autograph. The basis weight of each separator is 31 g / m2. From these compression characteristics, it is understood that when the basis weight is the same, the surface pressure for the same compression rate can be controlled by changing the thickness of the separator. The reaction force can be calculated by converting the surface pressure from the pressure receiving area applied to the restraining plate.
　図９は、セパレータの厚みと空隙率の関係の一例を示す図である。同図に示す例では、横軸にセパレータ厚み、縦軸に空隙率を示し、目付が３１ｇ／ｍ２であるセパレータの厚みを増加させた場合の空隙率の変化をプロットしている。同図の結果から、目付を同じ条件とした場合には、セパレータの厚みを変えることで空隙率を制御できることが分かる。拘束板としては、例えばＳ４５Ｃに代表される機械構造用炭素鋼が挙げられる。焼き入れ及び焼き戻し後の物性値は、例えばヤング率２０５ＭＰａ、ポアソン比０．３、降伏応力４９０ＭＰａ、引張強さ６９０ＭＰａ、疲労強度３０５ＭＰａである。 FIG. 9 is a diagram illustrating an example of the relationship between the thickness of the separator and the porosity. In the example shown in the figure, the horizontal axis represents the separator thickness, the vertical axis represents the porosity, and the change in the porosity when the thickness of the separator having a basis weight of 31 g / m 2 is increased is plotted. From the results shown in the figure, it is understood that the porosity can be controlled by changing the thickness of the separator when the basis weight is the same. Examples of the restraint plate include carbon steel for machine structure represented by S45C. The physical properties after quenching and tempering are, for example, Young's modulus 205 MPa, Poisson's ratio 0.3, yield stress 490 MPa, tensile strength 690 MPa, and fatigue strength 305 MPa.
　以上のように、蓄電装置１０では、蓄電モジュール１２の通常動作時においてセパレータ４０の最小圧縮率が常に０％より大きく、かつ蓄電モジュール１２の異常時において拘束構造１６に発生する応力が拘束板１６Ａ，１６Ｂの降伏応力以下となる範囲下で、セパレータ４０の圧縮率と拘束板１６Ａ，１６Ｂの厚さとが設定されていてもよい。これにより、通常動作時におけるバイポーラ電極３２からのセパレータ４０の乖離を抑制できる。また、圧縮されたセパレータ４０からの反力によって拘束板１６Ａ，１６Ｂが降伏してしまうことを抑制できる。 As described above, in the power storage device 10, the minimum compression rate of the separator 40 is always greater than 0% during normal operation of the power storage module 12, and the stress generated in the restraint structure 16 when the power storage module 12 is abnormal is caused by the restraint plate 16A. The compression rate of the separator 40 and the thicknesses of the restraining plates 16A and 16B may be set under a range that is equal to or less than the yield stress of 16B. Thereby, the deviation of the separator 40 from the bipolar electrode 32 during normal operation can be suppressed. Moreover, it can suppress that restraint board 16A, 16B yields by the reaction force from the compressed separator 40. FIG.
　また、蓄電装置１０では、上記範囲下で拘束板１６Ａ，１６Ｂの厚さが最小となるように、セパレータ４０の圧縮率が設定されていてもよい。この場合、出力に対する蓄電装置１０の体格を小さくすることができる。したがって、蓄電装置１０の高集積化が可能となる。 In the power storage device 10, the compression rate of the separator 40 may be set so that the thicknesses of the restraining plates 16A and 16B are minimized within the above range. In this case, the physique of the power storage device 10 with respect to the output can be reduced. Therefore, the power storage device 10 can be highly integrated.
　また、蓄電装置１０では、セパレータ４０の初期の最小空隙率が３３％以上となるように、セパレータ４０の圧縮率と拘束板１６Ａ，１６Ｂの厚さとが設定されていてもよい。この場合、電解液の拡散が支障なく行われ、所望の出力を維持することができる。また、ガス発生時におけるガスの抜けを十分に生じさせることが可能となる。 Further, in the power storage device 10, the compression rate of the separator 40 and the thickness of the restraining plates 16A and 16B may be set so that the initial minimum porosity of the separator 40 is 33% or more. In this case, the electrolyte solution can be diffused without any problem, and a desired output can be maintained. Further, it is possible to cause sufficient gas escape during gas generation.
　また、蓄電装置１０では、蓄電モジュール１２の通常動作時において拘束構造１６に発生する応力が拘束板１６Ａ，１６Ｂの疲労強度以下となるように、セパレータ４０の圧縮率と拘束板１６Ａ，１６Ｂの厚さとが設定されていてもよい。この場合、圧縮されたセパレータ４０からの反力によって拘束板１６Ａ，１６Ｂが疲労破壊してしまうことを抑制できる。 In the power storage device 10, the compressibility of the separator 40 and the thickness of the restraint plates 16 </ b> A and 16 </ b> B are set so that the stress generated in the restraint structure 16 during the normal operation of the power storage module 12 is less than the fatigue strength of the restraint plates 16 </ b> A and 16 </ b> B. Sato may be set. In this case, it is possible to prevent the restraint plates 16A and 16B from being fatigued by the reaction force from the compressed separator 40.
　１０…蓄電装置、１２…蓄電モジュール、１６…拘束構造、１６Ａ、１６Ｂ…拘束板（第１拘束部材、第２拘束部材）、３２…バイポーラ電極、３４…電極板、３４ａ…周縁部、３４ｃ…第１面、３４ｄ…第２面、３６…正極、３８…負極、４０…セパレータ、５０…樹脂部、５２…第１シール部、５４…第２シール部。 DESCRIPTION OF SYMBOLS 10 ... Power storage device, 12 ... Power storage module, 16 ... Restraint structure, 16A, 16B ... Restraint plate (first restraint member, second restraint member), 32 ... Bipolar electrode, 34 ... Electrode plate, 34a ... Peripheral part, 34c ... 1st surface, 34d ... 2nd surface, 36 ... positive electrode, 38 ... negative electrode, 40 ... separator, 50 ... resin part, 52 ... 1st seal | sticker part, 54 ... 2nd seal | sticker part.

Claims (10)

  1. 　電極板と前記電極板の第１面に設けられた正極と前記電極板の第２面に設けられた負極とをそれぞれ含む複数のバイポーラ電極と、前記複数のバイポーラ電極の間に配置されて前記正極と前記負極とによって挟まれるセパレータと、を有し、前記複数のバイポーラ電極が前記セパレータを介して積層方向に積層された少なくとも１つの蓄電モジュールと、
    　前記少なくとも１つの蓄電モジュールの前記積層方向の両端部に設けられた第１拘束部材および第２拘束部材を含み、前記少なくとも１つの蓄電モジュールにおける前記正極、前記セパレータ、及び前記負極が設けられた部分に対して前記積層方向に圧縮力を付与する拘束構造と、を備え、
    　前記セパレータは多孔性樹脂からなり、
    　前記拘束構造により圧縮された前記セパレータの圧縮率は０％より大きく４０％未満である、蓄電装置。     A plurality of bipolar electrodes each including an electrode plate, a positive electrode provided on a first surface of the electrode plate, and a negative electrode provided on a second surface of the electrode plate; and disposed between the plurality of bipolar electrodes, A separator sandwiched between a positive electrode and the negative electrode, and at least one power storage module in which the plurality of bipolar electrodes are stacked in the stacking direction via the separator;
    A portion including a first restraining member and a second restraining member provided at both ends in the stacking direction of the at least one power storage module, wherein the positive electrode, the separator, and the negative electrode are provided in the at least one power storage module A constraining structure that applies a compressive force in the stacking direction to
    The separator is made of a porous resin,
    The power storage device, wherein the compression ratio of the separator compressed by the constraining structure is greater than 0% and less than 40%.
  2. 　前記拘束構造により圧縮された前記セパレータの前記圧縮率は１０％以上である、請求項１に記載の蓄電装置。 The power storage device according to claim 1, wherein the compression rate of the separator compressed by the constraining structure is 10% or more.
  3. 　前記拘束構造により圧縮された前記セパレータの前記圧縮率は３０％以下である、請求項１または２に記載の蓄電装置。 The power storage device according to claim 1 or 2, wherein the compression rate of the separator compressed by the constraining structure is 30% or less.
  4. 　前記拘束構造により圧縮された前記セパレータの前記圧縮率は２０％以上かつ３０％以下である、請求項１に記載の蓄電装置。 The power storage device according to claim 1, wherein the compression ratio of the separator compressed by the constraining structure is 20% or more and 30% or less.
  5. 　前記多孔性樹脂は不織布からなる、請求項１～４のいずれか一項に記載の蓄電装置。 The power storage device according to any one of claims 1 to 4, wherein the porous resin is made of a nonwoven fabric.
  6. 　前記蓄電モジュールはニッケル水素二次電池である、請求項１～５のいずれか一項に記載の蓄電装置。 The power storage device according to any one of claims 1 to 5, wherein the power storage module is a nickel metal hydride secondary battery.
  7. 　前記蓄電モジュールの通常動作時において前記セパレータの最小圧縮率が常に０％より大きく、かつ前記蓄電モジュールの異常時において前記拘束構造に発生する応力が前記第１拘束部材および前記第２拘束部材の降伏応力以下となる範囲下で、前記セパレータの圧縮率と前記第１拘束部材および前記第２拘束部材の厚さとが設定されている、請求項１記載の蓄電装置。 The minimum compression rate of the separator is always greater than 0% during normal operation of the power storage module, and the stress generated in the restraint structure when the power storage module is abnormal is yielded by the first restraining member and the second restraining member. The power storage device according to claim 1, wherein a compression rate of the separator and thicknesses of the first restraining member and the second restraining member are set under a range where the stress is equal to or lower than the stress.
  8. 　前記範囲下で前記第１拘束部材および前記第２拘束部材の厚さが最小となるように、前記セパレータの圧縮率が設定されている、請求項７記載の蓄電装置。 The power storage device according to claim 7, wherein a compression rate of the separator is set so that a thickness of the first restraining member and the second restraining member is minimized under the range.
  9. 　前記セパレータの初期の最小空隙率が３３％以上となるように、前記セパレータの圧縮率と前記第１拘束部材および前記第２拘束部材の厚さとが設定されている、請求項７又は８記載の蓄電装置。 The compression rate of the separator and the thicknesses of the first and second restraining members are set so that the initial minimum porosity of the separator is 33% or more. Power storage device.
  10. 　前記蓄電モジュールの通常動作時において前記拘束構造に発生する応力が前記第１拘束部材および前記第２拘束部材の疲労強度以下となるように、前記セパレータの圧縮率と前記第１拘束部材および前記第２拘束部材の厚さとが設定されている、請求項７～９のいずれか一項記載の蓄電装置。 The compressibility of the separator, the first restraining member, and the first restraint so that the stress generated in the restraining structure during normal operation of the power storage module is less than the fatigue strength of the first restraining member and the second restraining member. The power storage device according to any one of claims 7 to 9, wherein a thickness of the two restraining members is set.
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