WO2017002815A1

WO2017002815A1 - Zinc air battery cell pack and battery pack using same

Info

Publication number: WO2017002815A1
Application number: PCT/JP2016/069161
Authority: WO
Inventors: 裕一権田; 鬼頭　賢信
Original assignee: 日本碍子株式会社
Priority date: 2015-07-01
Filing date: 2016-06-28
Publication date: 2017-01-05
Also published as: JP7095991B2; JPWO2017002815A1

Abstract

Provided is a form of a cell pack that has excellent handling properties and that is extremely advantageous in assembling a battery pack, for a single battery (cell) of a zinc air battery in which an air electrode and a negative electrode have been reliably separated with a hydroxide ion conducting separator. This zinc air battery cell pack is provided with: a flexible bag body formed by a flexible film and provided with an opening; a separator structure including a separator that closes the opening in an air-tight and liquid-tight manner to form a closed space along with the flexible bag body, and has hydroxide ion-conductive properties but does not have water-permeable and breathable properties; an air electrode provided on a side opposite the closed space of the separator; a negative electrode that is housed in the closed space and is formed by including zinc, a zinc alloy and/or a zinc compound; and an electrolyte that is housed in the closed space, has the negative electrode immersed therein, and is formed by including an alkali metal hydroxide aqueous solution.

Description

Zinc-air battery cell pack and assembled battery using the same

The present invention relates to a zinc-air battery cell pack and an assembled battery using the same.

One of the innovative battery candidates is a metal-air battery. In metal-air batteries, the oxygen involved in the battery reaction is supplied from the air, so the space in the battery container can be used to fill the negative electrode active material to the maximum, thereby realizing a high energy density in principle. can do.

Many of the metal-air batteries currently proposed are lithium air batteries. However, there are many technical problems with lithium-air batteries, such as deposition of undesirable reaction products on the air electrode, carbon dioxide contamination, and short circuit between positive and negative electrodes due to the formation of lithium dendrite (dendritic crystals). ing.

On the other hand, a zinc-air battery using zinc as a negative electrode active material has also been conventionally known. In particular, zinc-air primary batteries have already been mass-produced and are widely used as power supplies for hearing aids and the like. In a zinc-air battery, an alkaline aqueous solution such as potassium hydroxide is used as an electrolytic solution, and a separator (partition) is used to prevent a short circuit between positive and negative electrodes. At the time of discharge, as shown in the following reaction formula, O ₂ is reduced on the air electrode (positive electrode) side to generate OH ^−, while zinc is oxidized on the negative electrode to generate ZnO.
Air electrode: O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻
Negative electrode: 2Zn + 4OH ⁻ → 2ZnO + 2H ₂ O + 4e ⁻

Attempts have also been made to use this zinc-air battery as a secondary battery, but during charging, ZnO is reduced at the negative electrode, and metallic zinc is deposited in a dendritic form to form dendrites, and these dendrites penetrate the separator through the air. There is a problem of causing a short circuit with the electrode, which greatly hinders the practical application of zinc-air batteries as secondary batteries. In addition, on the air electrode side, carbon dioxide in the air passes through the air electrode and dissolves in the electrolytic solution, and there is a problem in that the alkaline carbonate is precipitated to deteriorate the battery performance. Compared to lithium-air batteries, zinc-air batteries do not have much of a problem with reaction, so if the problems with short circuit between positive and negative electrodes due to zinc dendrite and carbon dioxide contamination are solved, it can be realized as a high-capacity secondary battery. It is said to have a high quality. Therefore, in a zinc-air secondary battery, a technique for preventing both short-circuiting by zinc dendrite and mixing of carbon dioxide is strongly desired.

As a technique for coping with such problems or requests, Patent Document 1 (International Publication No. 2013/073292) uses a hydroxide ion conductive inorganic solid electrolyte as a separator, and an inorganic solid electrolyte is used as a separator. There has been proposed an attempt to prevent both short-circuit between positive and negative electrodes due to zinc dendrite during charging and mixing of carbon dioxide into the electrolyte by providing the air electrode in close contact with one side. Further, this document inorganic solid electrolyte body has the general ^{_{^{_{_{formula: M 2+ 1-x M 3+}}}}} x (OH) 2 A n- x / n · mH 2 O ( ^{wherein, M 2+} is a divalent cation in ^{and, M 3+} is a trivalent ^{cation, a n-is} the n-valent anion, n represents an integer of 1 or more, x is has a basic composition of a is) 0.1 to 0.4 It is also described that what consists of a layered double hydroxide is preferable.

On the other hand, in order to obtain a high voltage and a large current, an assembled battery made by combining a plurality of single cells is widely used. The assembled battery has a configuration in which a stacked body in which a plurality of cells are connected in series or in parallel is housed in one battery container.

International Publication No. 2013/073292

The present applicant has succeeded in developing a ceramic separator (inorganic solid electrolyte separator) that has hydroxide ion conductivity but is highly densified to such an extent that it does not have water permeability and air permeability. Moreover, it has succeeded also in forming such a ceramic separator on a porous base material (for example, alumina porous base material). When a zinc-air secondary battery is configured using such a separator (or a separator with a porous substrate), the penetration of the separator by zinc dendrite generated during charging is physically blocked to prevent a short circuit between the positive and negative electrodes. In addition, the intrusion of carbon dioxide in the air can be prevented to prevent the precipitation of alkali carbonate (caused by carbon dioxide) in the electrolyte. In order to maximize this effect, it is desired to reliably partition the inside of the battery container into an air electrode side and a negative electrode side with a hydroxide ion conductive ceramic separator. In particular, it is extremely advantageous if an assembled battery can be efficiently assembled by combining a plurality of single cells in order to obtain a high voltage and a large current while securing such a configuration.

The present inventors have recently used a zinc-air battery in which the air electrode and the negative electrode are reliably separated by a hydroxide ion conductive separator by using a flexible film instead of a hard material as a constituent material of a battery container or the like. It has been found that the single cell (cell) can be provided in the form of a cell pack that is excellent in handling and extremely advantageous for assembling the assembled battery.

Accordingly, an object of the present invention is to provide a zinc-air battery cell (cell) in which the air electrode and the negative electrode are reliably separated by a hydroxide ion conductive separator, and is excellent in handleability and for assembling an assembled battery. It is to be provided in the form of a very advantageous cell pack.

According to one aspect of the present invention, a flexible bag formed of a flexible film and provided with an opening,
A separator structure including a separator having hydroxide ion conductivity but not having water permeability and air permeability, wherein the opening is hermetically and liquid-tightly closed to form a sealed space together with the flexible bag;
An air electrode provided on the side opposite to the sealed space of the separator;
A negative electrode containing zinc, a zinc alloy and / or a zinc compound, contained in the sealed space;
An electrolytic solution containing an aqueous alkali metal hydroxide solution that is housed in the sealed space and in which the negative electrode is immersed;
A zinc-air battery cell pack is provided.

According to another aspect of the present invention, an assembled battery is provided in which a plurality of zinc-air battery cell packs according to the above aspect are packed in a battery container.

It is a figure which shows typically an example of the zinc air battery cell pack by this invention. It is a figure which shows typically the example of arrangement | positioning of the several zinc air battery cell pack in the assembled battery by this invention. It is a schematic cross section showing one mode of a separator with a porous substrate. It is a schematic cross section which shows the other one aspect | mode of a separator with a porous base material. It is a schematic diagram which shows a layered double hydroxide (LDH) plate-like particle. 2 is a SEM image of the surface of an alumina porous substrate produced in Example 1. FIG. 3 is an XRD profile obtained for the crystal phase of the sample in Example 1. 2 is an SEM image showing a surface microstructure of a film sample observed in Example 1. 2 is an SEM image of a polished cross-sectional microstructure of a composite material sample observed in Example 1. FIG. 2 is an exploded perspective view of a denseness discrimination measurement system used in Example 1. FIG. 2 is a schematic cross-sectional view of a denseness discrimination measurement system used in Example 1. FIG. FIG. 3 is an exploded perspective view of a measurement sealed container used in the denseness determination test II of Example 1. 3 is a schematic cross-sectional view of a measurement system used in the denseness determination test II of Example 1. FIG. It is a top view which shows typically the positional relationship of each structural member of a partition sheet for manufacture of the nickel zinc battery cell pack in Example 3 (reference example). It is process drawing which shows the preparation procedures of the partition sheet in Example 3 (reference example). It is a photograph of the partition sheet produced in Example 3 (reference example). It is process drawing which shows the assembly procedure of the nickel zinc battery cell pack in Example 3 (reference example). It is the photograph which image | photographed from the positive electrode side the flexible bag body by which the outer periphery three sides produced by Example 3 (reference example) were heat-sealed and joined. It is the photograph which image | photographed from the negative electrode side the flexible bag body by which the outer periphery three sides produced in Example 3 (reference example) were heat-sealed and joined. It is an enlarged photograph of the part emphasized with the frame of the upper end part of the flexible bag body in Drawing 15A. It is the photograph which image | photographed the nickel zinc battery cell pack (what the open part of the upper end part was heat-seal-bonded) produced in Example 3 (reference example). It is a schematic cross section which shows an example of preferable arrangement | positioning of a separator, a porous base material, and a frame.

Zinc air battery cell pack present invention relates to zinc-air battery cell pack. In this specification, the “zinc-air battery cell pack” is a package including a single battery (cell) of a zinc-air battery (preferably a zinc-air secondary battery), and the packaging material constituting the package has flexibility. (Ie flexible). FIG. 1A schematically shows an example of a zinc-air battery cell pack according to the present invention. A zinc-air battery cell pack 10 shown in FIG. 1A includes a flexible bag 12, a separator structure 14, an air electrode 16, a negative electrode 18, and an electrolytic solution 20. The flexible bag 12 is formed of

flexible films

12a and 12b and includes an opening 12c. The separator structure 14 is a structure including a separator 28 that has hydroxide ion conductivity but does not have water permeability and air permeability. The separator 12 is closed in an airtight and liquid tight manner to form the flexible bag 12. In addition, a sealed space 22 is formed. The air electrode 16 is provided on the side of the separator 28 opposite to the sealed space 22. The negative electrode 18 includes zinc, a zinc alloy, and / or a zinc compound, and is accommodated in the sealed space 22. The electrolytic solution 20 is a solution containing an alkali metal hydroxide aqueous solution, and is accommodated in the sealed space 22 in which the negative electrode 18 is immersed. A current collector (air electrode current collector 17 and negative electrode current collector 19 in FIG. 1A), wiring and / or terminals are connected to the air electrode 16 and the negative electrode 18, respectively, and electricity is supplied to the outside of the cell pack 10. Needless to say, it is configured to be removable.

As described above, according to the present invention, the zinc ion in which the air electrode and the negative electrode are reliably separated by the hydroxide ion conductive separator by using a flexible film instead of a hard material as a constituent material of the battery container or the like. A single cell (cell) of an air battery can be provided in the form of a cell pack that is excellent in handleability and extremely advantageous for assembling an assembled battery. That is, the zinc-air battery cell pack 10 contains the air electrode 16, the negative electrode 18, and the electrolytic solution 20 in a compact manner in the flexible bag 12 in which the opening 12 c is airtight and liquid tightly closed by the separator structure 14. Because it can, it does not leak and is easy to carry, so it is easy to handle. In addition, since the zinc-air battery cell pack 10 contains the electrolytic solution 20 in the flexible bag 12 formed of the

flexible films

12a and 12b, the cell pack 10 as a whole is highly flexible. have. That is, although the air electrode 16, the negative electrode 18, and the separator structure 14 are not flexible or inferior, the flexibility of the

flexible films

12a and 12b is combined with the fluidity of the electrolyte solution, so that the cell pack 10 as a whole is an assembled battery. Flexibility that is convenient for assembly can be provided. In particular, when the assembled battery is configured, if the unit cell is made of a hard material, a dimensional tolerance tends to be a problem with the battery case for the assembled battery that houses a plurality of unit cells. That is, unless the dimensional accuracy of the unit cell is increased, it may occur that the battery cannot be stored well in the battery pack configuration. For example, excessive stress is generated when the cells are tightly packed in the battery container, while useless gaps can be formed when the cells are loosely assembled in the battery container. In particular, when excessive stress is applied to the unit cell, there is a concern that the battery performance may be adversely affected. In this regard, since the zinc-air battery cell pack 10 according to the present invention is highly flexible as a whole, a plurality of cell packs 10 are accommodated in the battery container 102 for the assembled battery 100 as schematically shown in FIG. 1B. In doing so, a plurality (preferably as many) of cell packs 10 can be easily packed into the battery container without much concern for design requirements such as dimensional tolerances. That is, since the desired function as a single cell (cell) of the zinc-air battery is sufficiently ensured in the unit of the cell pack 10, as long as the air supply path to the air electrode 16 is secured with a spacer or the like, the assembly A battery pack having a desired performance can be easily obtained simply by packing a plurality of cell packs 10 in a battery container for batteries relatively roughly and connecting them in series or in parallel. Even if the packing is relatively rough, the stress is easily dispersed by the flexibility in the cell pack 10 (and the fluidity of the electrolyte therein), and the structural stability and performance stability of the assembled battery and the single cells therein This is because the sex is secured. Moreover, in the cell pack 10, the air electrode 16 and the negative electrode 18 are reliably isolated by the separator structure 14 including the separator 28 having hydroxide ion conductivity but not water permeability and air permeability. Zinc dendrite that grows from the negative electrode 18 toward the air electrode 16 as a result of discharge is blocked by the separator 28, thereby effectively preventing a short circuit between the positive and negative electrodes due to the zinc dendrite. In addition, the infiltration of carbon dioxide in the air can be prevented and precipitation of alkali carbonate (caused by carbon dioxide) in the electrolyte can be effectively prevented.

Flexible bag body The flexible bag body 12 is a bag-like flexible package formed of a flexible film, and includes an opening 12c. The flexible film constituting the flexible bag body 12 preferably includes a resin film. It is preferable that the resin film has resistance to alkali metal hydroxides such as potassium hydroxide and can be joined by thermal fusion, for example, PP (polypropylene) film, PET (polyethylene terephthalate) film. And PVC (polyvinyl chloride) film. As a flexible film including a resin film, a commercially available laminate film can be used. As a preferable laminate film, a base film (for example, a PET film or a PP film) and a thermoplastic resin layer having two or more layers are provided. A heat laminate film is mentioned. A preferred thickness of the flexible film (for example, a laminate film) is 20 to 500 μm, more preferably 30 to 300 μm, and still more preferably 50 to 150 μm. As shown in FIG. 1A, the flexible bag 12 is composed of a pair of

flexible films

12a and 12b, and the outer peripheral edges of the pair of

flexible films

12a and 12b are sealed by heat sealing. Is preferred. By sealing the outer peripheral edge, coupled with the separator structure 14 that closes the opening 12c, the electrolyte solution 20 does not leak and there is no intrusion of outside air (for example, carbon dioxide in the air). It can hold | maintain in the sex bag body 12. FIG. Bonding or sealing by thermal fusion may be performed using a commercially available heat sealing machine or the like.

The separator structure separator structure 14 is a structure that closes the opening 12 c in an airtight and liquid-tight manner to form a sealed space 22 together with the flexible bag body 12. The separator structure 14 includes a separator having hydroxide ion conductivity but not water permeability and air permeability, thereby allowing hydroxide ions to be conducted between the air electrode 16 and the sealed space 22. However, it is configured not to allow liquid communication and gas communication. The separator structure 14 preferably includes a frame 32 along the outer peripheral edge of the separator 28, and the flexible film 12 b and the separator structure 14 are preferably bonded in a liquid-tight and air-tight manner via the frame 32. . The frame 32 is preferably a resin frame, and more preferably, the flexible film 12b and the resin frame 32 are bonded by an adhesive and / or heat fusion. An adhesive is preferable in that an epoxy resin adhesive is particularly excellent in alkali resistance. A hot melt adhesive may be used. In any case, it is desirable that liquid-tightness is secured at the joint between the flexible film 12b and the frame 32. The resin constituting the frame 32 is preferably a resin having resistance to an alkali metal hydroxide such as potassium hydroxide, more preferably a polyolefin resin, an ABS resin, a PP resin, a PE resin, or a modified polyphenylene ether. More preferred are ABS resin, PP resin, PE resin, or modified polyphenylene ether.

The separator 28 is a member having hydroxide ion conductivity but not water permeability and air permeability, and typically has a plate shape, a film shape, or a layer shape. In the present specification, “not having water permeability” means “measurement object (when the water permeability is evaluated by a“ denseness determination test I ”employed in Example 1 described later) or a technique or configuration according to the“ denseness determination test I ”. For example, it means that water that contacts one side of the LDH membrane and / or porous substrate does not permeate the other side. In other words, the fact that the separator 28 does not have water permeability and air permeability means that the separator 28 has a high degree of denseness that allows neither water nor gas to pass through, and a porous film having water permeability and air permeability. It means that it is not other porous material. For this reason, it has a very effective configuration for physically preventing penetration of the separator by zinc dendrite generated during charging and preventing a short circuit between the positive and negative electrodes. However, it goes without saying that the porous substrate 30 may be attached to the separator 28 as shown in FIG. 1A. In any case, since the separator 28 has hydroxide ion conductivity, it is possible to efficiently move the necessary hydroxide ions between the air electrode 16 and the electrolytic solution 20, so that in the air electrode 16 and the negative electrode 18. A charge / discharge reaction can be realized.

The separator 28 is preferably made of an inorganic solid electrolyte. By using a hydroxide ion conductive inorganic solid electrolyte as the separator 28, the electrolyte solution between the positive and negative electrodes is isolated and the hydroxide ion conductivity is ensured. And since the inorganic solid electrolyte which comprises the separator 28 is a dense and hard inorganic solid typically, the penetration of the separator by the zinc dendrite produced | generated at the time of charge is blocked | prevented, and the short circuit between positive and negative electrodes is prevented. Is possible. As a result, the reliability of the zinc-air battery can be greatly improved. It is desirable that the inorganic solid electrolyte body is densified to such an extent that it does not have water permeability and air permeability. For example, the inorganic solid electrolyte body preferably has a relative density of 90% or more, more preferably 92% or more, and even more preferably 95% or more, calculated by the Archimedes method, but prevents penetration of zinc dendrite. It is not limited to this as long as it is as dense and hard as possible. Such a dense and hard inorganic solid electrolyte body can be produced through a hydrothermal treatment. Therefore, a simple green compact that has not been subjected to hydrothermal treatment is not preferable as the inorganic solid electrolyte body of the present invention because it is not dense and is brittle in solution. Of course, any manufacturing method can be used as long as a dense and hard inorganic solid electrolyte body can be obtained, even if it has not undergone hydrothermal treatment.

The separator 28 or the inorganic solid electrolyte body may be a composite of a particle group including an inorganic solid electrolyte having hydroxide ion conductivity and an auxiliary component that assists densification and hardening of the particle group. Good. Alternatively, the separator 28 includes an open-pore porous body as a base material and an inorganic solid electrolyte (for example, a layered double hydroxide) deposited and grown in the pores so as to fill the pores of the porous body. It may be a complex. Examples of the substance constituting the porous body include ceramics such as alumina and zirconia, and insulating substances such as a porous sheet made of a foamed resin or a fibrous substance.

The inorganic solid electrolyte body preferably contains a layered double hydroxide (LDH), more preferably LDH. Typically, LDH is represented by the general formula: M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ _{x / n} · mH ₂ O (where M ²⁺ is a divalent cation and M ³⁺ is a trivalent ^{cation, a n-is} the n-valent anion, n is an integer of 1 or more, x is 0.1 ~ 0.4, m is 0 or more) Has a basic composition. In the above general formula, M ²⁺ may be any divalent cation, and preferred examples include Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , and more preferably Mg ²⁺ . M ³⁺ may be any trivalent cation, but preferred examples include Al ³⁺ or Cr ³⁺ , and more preferred is Al ³⁺ . A ^n- can be any anion, but preferred examples include OH ^- and CO ₃ ^2- . Therefore, in the general ^{formula, M 2+} comprises ^{Mg ^2+,} ^{M 3+} comprises ^{Al ^3+,} ^{A n-is} OH ^- and / or _CO preferably contains ^{3 2-.} n is an integer of 1 or more, preferably 1 or 2. x is 0.1 to 0.4, preferably 0.2 to 0.35. It is also possible to replace the part or all of the M ³⁺ in the general formula tetravalent or higher valency cation, in which case, the anion A ^n- coefficients x / n of the above general formula It may be changed as appropriate. m is an arbitrary number which means the number of moles of water, and is a real number or an integer of 0 or more, typically more than 0 or 1 or more.

It is preferable that the inorganic solid electrolyte body is densified by hydrothermal treatment. Hydrothermal treatment is extremely effective for the densification of layered double hydroxides, especially Mg—Al type layered double hydroxides. Densification by hydrothermal treatment is performed, for example, as described in Patent Document 1 (International Publication No. 2013/073292), in which pure water and a plate-shaped green compact are placed in a pressure vessel, and 120 to 250 ° C., preferably The reaction can be carried out at a temperature of 180 to 250 ° C., 2 to 24 hours, preferably 3 to 10 hours. However, a more preferable production method using hydrothermal treatment will be described later.

The inorganic solid electrolyte body may be in the form of a plate, a film, or a layer. When the inorganic solid electrolyte is in the form of a film or a layer, the film or layer of the inorganic solid electrolyte is on the porous substrate or its It is preferably formed in the inside. When the plate-like form is used, sufficient hardness can be secured and penetration of zinc dendrites can be more effectively prevented. On the other hand, if the film or layer form is thinner than the plate, there is an advantage that the resistance of the separator can be significantly reduced while ensuring the minimum necessary hardness to prevent the penetration of zinc dendrite. is there. The preferred thickness of the plate-like inorganic solid electrolyte body is 0.01 to 0.5 mm, more preferably 0.02 to 0.2 mm, and still more preferably 0.05 to 0.1 mm. Further, the higher the hydroxide ion conductivity of the inorganic solid electrolyte body is, the higher is desirable, but typically it has a conductivity of 10 ⁻⁴ to 10 ⁻¹ S / m. On the other hand, in the case of a film-like or layered form, the thickness is preferably 100 μm or less, more preferably 75 μm or less, still more preferably 50 μm or less, particularly preferably 25 μm or less, and most preferably 5 μm or less. Thus, the resistance of the separator 28 can be reduced. The lower limit of the thickness is not particularly limited because it varies depending on the application, but in order to ensure a certain degree of rigidity desired as a separator film or layer, the thickness is preferably 1 μm or more, more preferably 2 μm or more. is there.

The porous substrate 30 may be provided on at least one side of the separator 28. Preferably, the porous substrate 30 is provided on the negative electrode 18 side (sealed space 22 side) of the separator 28, but the reverse may be used as described later. It goes without saying that the porous base material 30 has water permeability, and therefore the electrolytic solution 20 can reach the separator 28, but the presence of the porous base material 30 makes the hydroxylation more stable on the separator 28. It is also possible to retain product ions. Further, since the strength can be imparted by the porous base material 30, the separator 28 can be thinned to reduce the resistance. In addition, a dense film or a dense layer of an inorganic solid electrolyte (preferably LDH) can be formed on or in the porous substrate 30. In the case of providing a porous substrate on one side of the separator 28, a method of preparing a porous substrate and depositing an inorganic solid electrolyte on the porous substrate can be considered (this method will be described later). In FIG. 1A, the porous base material 30 is provided over the entire surface of one side of the separator 28. However, the porous base material 30 may be provided only on a part of one side of the separator 28 (for example, a region involved in the charge / discharge reaction). For example, when the inorganic solid electrolyte is formed in a film or a layer on or in the porous substrate 30, the porous substrate 30 is provided over the entire surface of one side of the separator 28 due to the manufacturing method. It is typical to become. On the other hand, when the inorganic solid electrolyte body is formed in a self-supporting plate shape (which does not require a base material), the porous base material 30 is formed only on a part of one side of the separator 28 (for example, a region involved in charge / discharge reaction). May be retrofitted, or the porous substrate 30 may be retrofitted over the entire surface of one side.

When the separator structure 14 includes the porous substrate 30 on one side of the separator 28, the separator 28 is provided on either the air electrode 16 side or the negative electrode 18 side (sealed space 22 side) of the porous substrate 30. Also good. For example, when the separator 28 is provided on the negative electrode 18 side (sealed space 22 side) of the porous base material 30, the separation of the separator 28 (for example, LDH dense film) from the porous base material 30 is more effectively suppressed. Can do. That is, when zinc dendrite grows from the negative electrode 18 and reaches the separator 28, the stress that can be generated as the zinc dendrite grows acts in a direction to press the separator 28 against the porous substrate 30. As a result, the separator 28 is difficult to peel off from the porous substrate 30. In this case, in order to ensure the hydroxide ion conductivity between the separator 28 and the air electrode 16, a part or all of the separator 28 is incorporated in the porous substrate 30 and / or the porous substrate 30. It is preferred that a hydroxide ion conductive material is incorporated therein.

As described above, the separator structure 14 preferably includes the frame 32 along the outer peripheral edge of the separator 28, and the frame 32 is more preferably a resin frame. FIG. 17 shows a separator structure provided with a frame 32 when the separator 28 is provided on the negative electrode 18 side of the porous substrate 30 (that is, when the porous substrate 30 is provided on the air electrode 16 side of the separator 28). Fourteen preferred embodiments are shown. The frame 32 in the embodiment shown in FIG. 17 includes an outer frame portion 32a having an opening that can accommodate the separator 28 and the porous substrate 30, and an end of the outer frame portion 32a on the air electrode 16 side and / or the vicinity thereof. And an inner frame portion 32b extending toward the opening. Then, the inner frame portion 32 b engages with the air electrode 16 side of the porous substrate 30. And between the porous substrate 30 and the frame 32 (that is, the outer frame portion 32a and the inner frame portion 32b), or both the porous substrate 30 and the separator 28 and the frame 32 (that is, the outer frame portion 32a and the inner frame portion). 32b) is preferably liquid-tightly sealed with an adhesive 31. According to this configuration, when zinc dendrite grows from the negative electrode 18 and reaches the separator 28, stress that can be generated as the zinc dendrite grows presses the porous substrate 30 against the inner frame portion 32 b. As a result, the adhesive 31 is compressed between the porous base material 30 and the inner frame portion 32b, and the liquid-tight sealing effect and the adhesive effect by the adhesive 31 can be improved. That is, since the stress can be applied in the compressing direction rather than the direction in which the adhesive 31 is pulled, even if the stress due to the zinc dendrite is applied, the peeling of the frame 32 due to the pulling of the adhesive 31 is effectively avoided. can do. However, it goes without saying that the frame 32 having the inner frame portion 32a and the outer frame portion 32b can be employed even when the separator 28 is provided on the air electrode 16 side of the porous substrate 30.

In addition, a second separator (resin separator) made of a water-absorbing resin such as a nonwoven fabric or a liquid-retaining resin is disposed between the negative electrode 18 and the separator 28, so that the electrolytic solution can be used even when the electrolytic solution is reduced. It is good also as a structure which can hold | maintain electrolyte solution in this reaction part. Preferable examples of the water absorbent resin or the liquid retaining resin include polyolefin resins.

The air electrode 16 may be a known air electrode used in metal-air batteries such as zinc-air batteries, and is not particularly limited. The air electrode 16 typically comprises an air electrode catalyst, an electronically conductive material, and optionally a hydroxide ion conductive material. However, when an air electrode catalyst that also functions as an electron conductive material is used, the air electrode 16 includes such an electron conductive material / air electrode catalyst and, optionally, a hydroxide ion conductive material. It may be a thing.

The air electrode catalyst is not particularly limited as long as it functions as a positive electrode in a metal-air battery, and various air electrode catalysts that can use oxygen as a positive electrode active material can be used. Preferred examples of the air electrode catalyst include carbon-based materials having a redox catalyst function such as graphite, metals having a redox catalyst function such as platinum and nickel, perovskite oxides, manganese dioxide, nickel oxide, cobalt oxide, spinel. Examples thereof include inorganic oxides having a redox catalyst function such as oxides. The shape of the air electrode catalyst is not particularly limited, but is preferably a particle shape. The content of the air electrode catalyst in the air electrode 16 is not particularly limited, but is preferably 5 to 70% by volume, more preferably 5 to 60% by volume, and still more preferably 5 to 50% by volume with respect to the total amount of the air electrode 16. %.

The electron conductive material is not particularly limited as long as it has conductivity and enables electron conduction between the air electrode catalyst and the separator 28 (or an intermediate layer to be described later if applicable). Preferred examples of the electron conductive material include carbon blacks such as ketjen black, acetylene black, channel black, furnace black, lamp black, and thermal black, natural graphite such as flake graphite, artificial graphite, and expanded graphite. Examples thereof include conductive fibers such as graphites, carbon fibers, and metal fibers, metal powders such as copper, silver, nickel, and aluminum, organic electron conductive materials such as polyphenylene derivatives, and any mixture thereof. The shape of the electron conductive material may be a particle shape or any other shape, but is used in a form that provides a continuous phase (that is, an electron conductive phase) in the thickness direction in the air electrode 16. Is preferred. For example, the electron conductive material may be a porous material. The electron conductive material may be in the form of a mixture or complex with an air electrode catalyst (for example, platinum-supported carbon). As described above, an air electrode catalyst (for example, a transition metal) that also functions as an electron conductive material. Perovskite-type compounds). The content of the electron conductive material in the air electrode 16 is not particularly limited, but is preferably 10 to 80% by volume, more preferably 15 to 80% by volume, and still more preferably 20 to 80% with respect to the total amount of the air electrode 16. % By volume.

The air electrode 16 may further include a hydroxide ion conductive material as an optional component. In particular, when the separator 28 is made of a hydroxide ion conductive inorganic solid electrolyte, which is a dense ceramic, on the separator 28 (with an intermediate layer having hydroxide ion conductivity if desired), conventionally. By forming the air electrode 16 containing not only the air electrode catalyst and the electron conductive material to be used but also the hydroxide ion conductive material, desired characteristics by the separator 28 made of dense ceramics can be secured. However, it is possible to reduce the reaction resistance of the air electrode in the metal-air battery. That is, not only the air electrode catalyst and the electron conductive material, but also the hydroxide ion conductive material is contained in the air electrode 16 so that the electron conductive phase (electron conductive material), the gas phase (air), The three-phase interface consisting of is present not only in the interface between the separator 28 (or the intermediate layer, if applicable) and the air electrode 16 but also in the air electrode 16, and exchanges hydroxide ions that contribute to the battery reaction. As a result, the reaction resistance of the air electrode is considered to be reduced in the metal-air battery. The hydroxide ion conductive material is not particularly limited as long as it is a material that can transmit hydroxide ions, and various materials and forms of materials can be used regardless of whether the material is an inorganic material or an organic material. It may be a layered double hydroxide having a basic composition. The hydroxide ion conductive material is not limited to the particle form, but may be in the form of a coating film that partially or substantially entirely covers the air electrode catalyst and the electron conductive material. However, also in the form of this coating film, the ion conductive material is not dense and has open pores, and the interface from the outer surface of the air electrode 16 to the separator 28 (or intermediate layer if applicable). It is desirable that O ₂ or H ₂ O can be diffused in the pores. The content of the hydroxide ion conductive material in the air electrode 16 is not particularly limited, but is preferably 0 to 95% by volume, more preferably 5 to 85% by volume, and still more preferably based on the total amount of the air electrode 16. 10 to 80% by volume.

The formation of the air electrode 16 may be performed by any method and is not particularly limited. For example, an air electrode catalyst, an electron conductive material, and optionally a hydroxide ion conductive material are wet-mixed using a solvent such as ethanol, dried and crushed, and then mixed with a binder to obtain a fibril. The fibrillar mixture is pressure-bonded to the current collector to form the air electrode 16, and the air electrode 16 side of the air electrode 16 / current collector laminated sheet is pressure-bonded to the separator 28 (or an intermediate layer if applicable). May be. Alternatively, an air electrode catalyst, an electron conductive material, and, if desired, a hydroxide ion conductive material are wet mixed with a solvent such as ethanol to form a slurry, and this slurry is applied to an intermediate layer and dried to form the air electrode 16. It may be formed. Therefore, the air electrode 16 may contain a binder. The binder may be a thermoplastic resin or a thermosetting resin and is not particularly limited.

The air electrode 16 is preferably in the form of a layer having a thickness of 5 to 200 μm, more preferably 5 to 100 μm, still more preferably 5 to 50 μm, and particularly preferably 5 to 30 μm. For example, when a hydroxide ion conductive material is included, if the thickness is within the above range, a relatively large area of the three-phase interface can be secured while suppressing an increase in gas diffusion resistance, and the reaction of the air electrode Reduction of resistance can be realized more preferably.

An intermediate layer may be provided between the separator 28 and the air electrode 16. The intermediate layer is not particularly limited as long as it improves the adhesion between the separator 28 and the air electrode 16 and has hydroxide ion conductivity, regardless of whether it is an organic material or an inorganic material. Layer. The intermediate layer preferably includes a polymer material and / or a ceramic material. In this case, at least one of the polymer material and the ceramic material included in the intermediate layer may have hydroxide ion conductivity. That's fine. A plurality of intermediate layers may be provided, and the plurality of intermediate layers may be the same type and / or different layers. That is, the intermediate layer may have a single layer structure or a structure having two or more layers. The intermediate layer preferably has a thickness of 1 to 200 μm, more preferably 1 to 100 μm, still more preferably 1 to 50 μm, and particularly preferably 1 to 30 μm. With such a thickness, the adhesion between the separator 28 and the air electrode 16 can be easily improved, and the battery resistance (particularly, the interface resistance between the air electrode and the separator) can be more effectively reduced in the zinc-air secondary battery. Can do.

The negative electrode

negative

electrode 18 includes zinc, a zinc alloy, and / or a zinc compound that functions as a negative electrode active material. The negative electrode 18 may have any shape or form such as a particle shape, a plate shape, or a gel shape, but it is preferable that the negative electrode 18 has a particle shape or a gel shape from the viewpoint of reaction rate. As the particulate negative electrode, those having a particle diameter of 30 to 350 μm can be preferably used. As the gelled negative electrode, a gelled negative electrode alloy powder having a particle diameter of 100 to 300 μm, an alkaline electrolyte, and a thickener (gelling agent) mixed and stirred can be preferably used. . The zinc alloy can be a hatched or non-hatched alloy such as magnesium, aluminum, lithium, bismuth, indium, lead, etc., and its content is not particularly limited as long as desired performance can be secured as a negative electrode active material. . Preferred zinc alloys are anhydrous silver and lead-free zinc-free zinc alloys, more preferably those containing aluminum, bismuth, indium or combinations thereof. More preferably, a zinc-free zinc alloy containing 50 to 1000 ppm of bismuth, 100 to 1000 ppm of indium and 10 to 100 ppm of aluminum and / or calcium, particularly preferably 100 to 500 ppm of bismuth, 300 to 700 ppm of indium, Contains 20 to 50 ppm of aluminum and / or calcium. Examples of preferred zinc compounds include zinc oxide.

The current collector zinc-air battery cell pack 10 further includes an air electrode current collector 17 provided on the opposite side of the air electrode 16 from the separator 28 and a negative electrode current collector 19 provided in contact with the negative electrode 18. preferable. In this case, the negative electrode current collector 19 preferably extends from the outer peripheral edge of the flexible bag body 12. The air electrode current collector 17 also preferably extends from a position corresponding to the outer peripheral edge of the flexible bag body 12. Alternatively, the air electrode 16 and the negative electrode 18 may be connected to the separately provided air electrode terminal and negative electrode terminal inside or outside the flexible bag body 12, respectively. The air electrode current collector 17 preferably has air permeability so that air is supplied to the air electrode 16. Preferred examples of the air electrode current collector 17 include metal plates or metal meshes such as stainless steel, copper, and nickel, carbon paper, carbon cloth, and electron conductive oxides, and the like in terms of corrosion resistance and air permeability. Stainless steel wire mesh is particularly preferred. Preferable examples of the negative electrode current collector 19 include a metal plate or metal mesh such as stainless steel, copper (for example, copper punching metal), nickel, carbon paper, and an oxide conductor. In this case, for example, a negative electrode comprising a negative electrode / negative electrode current collector by applying a mixture containing zinc oxide powder and / or zinc powder and optionally a binder (for example, polytetrafluoroethylene particles) on copper punching metal. A plate can be preferably produced. At that time, it is also preferable to press the dried negative electrode plate (that is, negative electrode 18 / negative electrode current collector 19) to prevent the electrode active material from falling off and to improve the electrode density.

If desired, the zinc-air battery cell pack 10 may include a third electrode (not shown) provided so as to be in contact with the electrolytic solution 20 but not to be in contact with the negative electrode 18. In this case, the third electrode Is connected to the air electrode 16 via an external circuit. With this configuration, hydrogen gas that can be generated from the negative electrode 18 by a side reaction is brought into contact with the third electrode, and the following reaction is performed:
Third electrode: H ₂ + 2OH ⁻ → 2H ₂ O + 2e ⁻
Air electrode discharge: It can be returned to water by O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ . In other words, the hydrogen gas generated at the negative electrode 18 is absorbed by the third electrode and self-discharged. As a result, an increase in internal pressure in the negative electrode-side sealed space due to the generation of hydrogen gas and the accompanying problems can be suppressed or avoided, and water (which will be reduced according to the above reaction formula along with the discharge reaction) is generated and the negative electrode-side sealed Water shortage in the space can be suppressed or avoided. That is, the hydrogen gas generated from the negative electrode can be recycled by returning it to water in the negative electrode-side sealed space. As a result, a highly reliable zinc-air secondary battery that can cope with the problem of hydrogen gas generation while having a configuration that is extremely effective in preventing both short-circuiting due to zinc dendrite and carbon dioxide contamination. Can be provided.

The third electrode is not particularly limited as long as it is an electrode capable of converting hydrogen gas (H ₂ ) into water (H ₂ O) by the reaction as described above by being connected to the air electrode 16 through an external circuit. It is desirable that the oxygen overvoltage is larger than that of the air electrode 16. It is also desirable that the third electrode does not participate in normal charge / discharge reactions. The third electrode preferably comprises platinum and / or a carbon material, and more preferably comprises a carbon material. Preferable examples of the carbon material include natural graphite, artificial graphite, hard carbon, soft carbon, carbon fiber, carbon nanotube, graphene, activated carbon, and any combination thereof. Although the shape of a 3rd electrode is not specifically limited, It is preferable to set it as the shape (for example, mesh shape or particle shape) that a specific surface area becomes large. More preferably, the third electrode (preferably the third electrode having a large specific surface area) is applied and / or disposed on the current collector. The current collector for the third electrode may have any shape, but preferable examples include a wire (for example, a wire), a punching metal, a mesh, a foam metal, and any combination thereof. The material for the current collector for the third electrode may be the same material as the material for the third electrode, or may be a metal (for example, nickel), an alloy, or other conductive material.

The third electrode is in contact with the electrolytic solution 20, but it is desirable that the third electrode be disposed at a place not directly related to the normal charge / discharge reaction. In this case, a water retaining member made of a water absorbent resin such as a nonwoven fabric or a liquid retaining resin is disposed in the negative electrode side sealed space so as to be in contact with the third electrode. It is preferable that the third electrode is held so as to be always contactable. A commercially available battery separator can also be used as the water retaining member. Preferable examples of the water absorbent resin or the liquid retaining resin include polyolefin resins. The third electrode does not necessarily need to be impregnated with a large amount of the electrolytic solution 20 and can exhibit a desired function even when it is wet with a small amount or a small amount of the electrolytic solution 20. The water retention member should just have.

Electrolytic solution Electrolytic solution 20 comprises an aqueous alkali metal hydroxide solution. Examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide, and potassium hydroxide is more preferable. In order to suppress self-dissolution of the zinc alloy, a zinc compound such as zinc oxide or zinc hydroxide may be added to the electrolytic solution. As described above, the electrolytic solution 20 may be mixed with the air electrode 16 and / or the negative electrode 18 to be present in the form of an air electrode mixture and / or a negative electrode mixture. Further, the electrolytic solution may be gelled in order to prevent leakage of the electrolytic solution. As the gelling agent, it is desirable to use a polymer that swells by absorbing the solvent of the electrolytic solution, and polymers such as polyethylene oxide, polyvinyl alcohol, and polyacrylamide, and starch are used.

The zinc-air battery cell pack 10 preferably includes in the sealed space 22 an excess space having a volume that allows a decrease in the amount of water accompanying the negative electrode reaction during charging and discharging. As a result, it is possible to effectively prevent problems associated with the increase or decrease in the amount of water in the sealed space 22 (for example, liquid leakage, deformation of the container accompanying changes in the container internal pressure, etc.), and further improve the reliability of zinc air. . That is, as can be seen from the reaction formula described above, water decreases in the sealed space 22 during charging. On the other hand, water increases in the sealed space 22 during discharge. In this respect, since most conventional separators have water permeability, water can freely pass through the separators. However, since the separator 28 used in the present invention has a highly dense structure that does not have water permeability, water cannot freely pass through the separator 28, and the amount of electrolytic solution in the sealed space 22 is increased due to charge / discharge. It may increase unilaterally and cause problems such as liquid leakage. Thus, by providing the closed space 22 with the excess space 22a having a volume that allows a decrease in the amount of water associated with the negative electrode reaction during charging and discharging, the sealed space 22 can function as a buffer that can cope with an increase in the electrolyte 20 during discharging. . The increase / decrease amount of the water | moisture content in the sealed space 22 can be calculated based on the reaction formula mentioned above.

When the zinc-air battery cell pack 10 is constructed in a discharged state, the surplus space 22a has a volume exceeding the amount of moisture expected to decrease with the negative electrode reaction during charging, and the surplus space 22a It is preferable that the amount of the electrolyte solution 20 that is expected to decrease is filled in advance. On the other hand, when the zinc-air battery cell pack 10 is constructed in a fully charged state, the surplus space 22a has a volume exceeding the amount of water expected to increase with the negative electrode reaction during discharge, and the surplus space 22a. It is preferable that the electrolyte solution 20 is not filled in advance.

In the zinc-air battery cell pack 10 of the present invention, the flexible bag 12, the separator structure 14, the air electrode 16, and the negative electrode 18 are preferably provided vertically. In this case, as shown in FIG. 1A, the sealed space 22 preferably has a surplus space 22a above it. However, when a gel electrolyte solution is used, the electrolyte solution can be held in the charge / discharge reaction portion of the sealed space 22 in spite of a decrease in the electrolyte solution. It is also possible to provide the surplus space 22a in the side portion and the lower portion), and the degree of freedom in design increases.

As the battery pack described above, since the rich in flexibility as a whole zinc-air battery cell pack 10 according to the present invention, a plurality of cell pack in the battery container 102 for the battery pack 100 as shown schematically in Figure 1B As long as the air supply path to the air electrode 16 is secured with a spacer or the like, a plurality of (preferably as many) as possible can be obtained without worrying about design requirements such as dimensional tolerances. The cell pack 10 can be easily packed in the battery container. That is, according to a preferred aspect of the present invention, there is provided an assembled battery 100 in which a plurality of zinc-air battery cell packs 10 of the present invention are packed in a battery container 102. Note that a current collector (air electrode current collector 17 and negative electrode current collector 19 in FIG. 1A), wiring, and / or terminals are connected to the air electrode 16 and the negative electrode 18 of each cell pack 10, respectively. Needless to say, the battery container 102 is configured so that electricity can be taken out. Further, it is preferable to provide an air supply path to the air electrode 16 and the air electrode current collector 17 by interposing a spacer (not shown) between the cell packs 10. In the battery container 102, the plurality of zinc-air battery cell packs 10 may be connected in series with each other or may be connected in parallel with each other. Further, as shown in FIG. 1B, the zinc-air battery cell pack 10 is preferably accommodated vertically in the battery container 102, but may be accommodated horizontally as long as no particular problem occurs.

LDH separator with porous base material As described above, the separator with a porous base material preferably used for the zinc-air battery cell pack of the present invention includes a separator composed of an inorganic solid electrolyte having hydroxide ion conductivity, And a porous substrate provided on at least one surface. The inorganic solid electrolyte body is in the form of a film or a layer that is so dense that it does not have water permeability and air permeability. A particularly preferable separator with a porous substrate includes a porous substrate and a separator layer formed on and / or in the porous substrate, and the separator layer is in the form of a layer as described above. It comprises double hydroxide (LDH). The separator layer preferably does not have water permeability and air permeability. That is, the porous material can have water permeability and air permeability due to the presence of pores, but the separator layer is preferably densified with LDH to such an extent that it does not have water permeability and air permeability. The separator layer is preferably formed on a porous substrate. For example, as shown in FIG. 2, the separator layer 28 is preferably formed on the porous substrate 30 as an LDH dense film. In this case, needless to say, LDH may be formed on the surface of the porous substrate 30 and in the pores in the vicinity thereof as shown in FIG. 2 due to the nature of the porous substrate 30. Alternatively, as shown in FIG. 3, LDH is densely formed in the porous substrate 30 (for example, the surface of the porous substrate 30 and the pores in the vicinity thereof), whereby at least one of the porous substrates 30 is formed. The part may constitute separator layer 28 '. In this regard, the embodiment shown in FIG. 3 has a configuration in which the film equivalent portion in the separator layer 28 of the embodiment shown in FIG. 2 is removed, but is not limited to this, and is parallel to the surface of the porous substrate 30. A separator layer only needs to be present. In any case, since the separator layer is densified with LDH to such an extent that it does not have water permeability and air permeability, it has hydroxide ion conductivity but does not have water permeability and air permeability (ie basically It can have a unique function of passing only hydroxide ions).

The porous substrate is preferably one that can form an LDH-containing separator layer on and / or in the porous substrate, and the material and porous structure are not particularly limited. Typically, an LDH-containing separator layer is formed on and / or in a porous substrate, but an LDH-containing separator layer is formed on a non-porous substrate and then non-porous by various known techniques. The porous substrate may be made porous. In any case, it is preferable that the porous base material has a porous structure having water permeability in that the electrolyte solution can reach the separator layer when incorporated into the battery as a battery separator.

The porous substrate is preferably composed of at least one selected from the group consisting of ceramic materials, metal materials, and polymer materials. More preferably, the porous substrate is made of a ceramic material. In this case, preferable examples of the ceramic material include alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, silicon carbide, and any combination thereof, and more preferable. Is alumina, zirconia, titania, and any combination thereof, particularly preferably alumina and zirconia, most preferably alumina. When these porous ceramics are used, it is easy to form an LDH-containing separator layer having excellent denseness. Preferable examples of the metal material include aluminum and zinc. Preferable examples of the polymer material include polystyrene, polyether sulfone, polypropylene, epoxy resin, polyphenylene sulfide, hydrofluorinated fluororesin (tetrafluorinated resin: PTFE, etc.), and any combination thereof. It is more preferable to appropriately select a material excellent in alkali resistance as the resistance to the battery electrolyte from the various preferable materials described above.

The porous substrate preferably has an average pore diameter of 0.001 to 1.5 μm, more preferably 0.001 to 1.25 μm, still more preferably 0.001 to 1.0 μm, and particularly preferably 0.001. 0.75 μm, most preferably 0.001 to 0.5 μm. By setting it within these ranges, it is possible to form an LDH-containing separator layer that is so dense that it does not have water permeability while ensuring desired water permeability in the porous substrate. In the present invention, the average pore diameter can be measured by measuring the longest distance of the pores based on an electron microscope (SEM) image of the surface of the porous substrate. The magnification of the electron microscope (SEM) image used for this measurement is 20000 times, and all obtained pore diameters are arranged in order of size, and the top 15 points and the bottom 15 points from the average value, with 30 points per field of view in total. The average pore diameter can be obtained by calculating an average value for two visual fields. For the length measurement, a length measurement function of SEM software, image analysis software (for example, Photoshop, manufactured by Adobe) or the like can be used.

The surface of the porous substrate preferably has a porosity of 10 to 60%, more preferably 15 to 55%, still more preferably 20 to 50%. By setting it within these ranges, it is possible to form an LDH-containing separator layer that is so dense that it does not have water permeability while ensuring desired water permeability in the porous substrate. Here, the porosity of the surface of the porous substrate is adopted because it is easy to measure the porosity using the image processing described below, and the porosity of the surface of the porous substrate. This is because it can be said that it generally represents the porosity inside the porous substrate. That is, if the surface of the porous substrate is dense, the inside of the porous substrate can be said to be dense as well. In the present invention, the porosity of the surface of the porous substrate can be measured as follows by a technique using image processing. That is, 1) An electron microscope (SEM) image of the surface of the porous substrate (acquisition of 10,000 times or more) is obtained, and 2) a grayscale SEM image is read using image analysis software such as Photoshop (manufactured by Adobe). 3) Create a black-and-white binary image by the procedure of [Image] → [Tonal Correction] → [Turn Tone], and 4) The value obtained by dividing the number of pixels occupied by the black part by the total number of pixels in the image Rate (%). The porosity measurement by this image processing is preferably performed for a 6 μm × 6 μm region on the surface of the porous substrate. In order to obtain a more objective index, three arbitrarily selected regions are used. It is more preferable to employ the average value of the obtained porosity.

The separator layer is formed on the porous substrate and / or in the porous substrate, preferably on the porous substrate. For example, when the separator layer 28 is formed on the porous substrate 30 as shown in FIG. 2, the separator layer 28 is in the form of an LDH dense film, typically from the LDH. Become. As shown in FIG. 3, when the separator layer 28 'is formed in the porous substrate 30, the surface of the porous substrate 30 (typically the surface of the porous substrate 30 and the vicinity thereof). Since the LDH is densely formed in the pores), the separator layer 28 'is typically composed of at least a part of the porous substrate 30 and LDH. The separator layer 28 ′ shown in FIG. 3 can be obtained by removing a portion corresponding to the film in the separator layer 28 shown in FIG. 2 by a known method such as polishing or cutting.

The separator layer preferably has no water permeability and air permeability. For example, the separator layer does not allow permeation of water even if one side of the separator layer is brought into contact with water at 25 ° C. for 1 week, and does not allow permeation of helium gas even if helium gas is pressurized on the one side with a pressure difference of 0.5 atm. . That is, the separator layer is preferably densified with LDH to such an extent that it does not have water permeability and air permeability. However, when a defect having water permeability locally and / or accidentally exists in the functional film, the defect is filled with an appropriate repair agent (for example, epoxy resin) to repair the water impermeability and Gas impermeability may be ensured and such repair agents need not necessarily have hydroxide ion conductivity. In any case, the surface of the separator layer (typically the LDH dense film) preferably has a porosity of 20% or less, more preferably 15% or less, still more preferably 10% or less, and particularly preferably 7%. It is as follows. It means that the lower the porosity of the surface of the separator layer, the higher the density of the separator layer (typically the LDH dense film), which is preferable. Here, the porosity of the surface of the separator layer is adopted because it is easy to measure the porosity using the image processing described below, and the porosity of the surface of the separator layer is determined inside the separator layer. It is because it can be said that the porosity of is generally expressed. That is, if the surface of the separator layer is dense, it can be said that the inside of the separator layer is also dense. In the present invention, the porosity of the surface of the separator layer can be measured as follows by a technique using image processing. That is, 1) An electron microscope (SEM) image (10,000 times or more magnification) of the surface of the separator layer is acquired, and 2) a gray-scale SEM image is read using image analysis software such as Photoshop (manufactured by Adobe). ) Create a black-and-white binary image by the procedure of [Image] → [Tone Correction] → [2 Gradation], and 4) Porosity (the value obtained by dividing the number of pixels occupied by the black part by the total number of pixels in the image) %). The porosity measurement by this image processing is preferably performed for a 6 μm × 6 μm region on the surface of the separator layer. In order to obtain a more objective index, it is obtained for three arbitrarily selected regions. It is more preferable to adopt the average value of the porosity.

The layered double hydroxide is composed of an aggregate of a plurality of plate-like particles (that is, LDH plate-like particles), and the plurality of plate-like particles have their plate surfaces perpendicular to the surface of the porous substrate (substrate surface). It is preferably oriented in such a direction as to cross each other at an angle. As shown in FIG. 2, this embodiment is a particularly preferable and feasible embodiment when the separator layer 28 is formed as an LDH dense film on the porous substrate 30, but as shown in FIG. 3, LDH is densely formed in the porous substrate 30 (typically in the surface of the porous substrate 30 and in the pores in the vicinity thereof), whereby at least a part of the porous substrate 30 forms the separator layer 28 ′. This can be realized even in the case of configuration.

That is, the LDH crystal is known to have the form of a plate-like particle having a layered structure as shown in FIG. 4, but the vertical or oblique orientation is determined by the LDH-containing separator layer (for example, an LDH dense film). This is a very advantageous property for the user. This is because, in an oriented LDH-containing separator layer (for example, an oriented LDH dense film), the hydroxide ion conductivity in the direction in which the LDH plate-like particles are oriented (that is, the direction parallel to the LDH layer) is perpendicular to this. This is because there is a conductivity anisotropy that is much higher than the conductivity in the direction. In fact, the present applicant has obtained knowledge that the conductivity (S / cm) in the alignment direction is one order of magnitude higher than the conductivity (S / cm) in the direction perpendicular to the alignment direction in the LDH oriented bulk body. ing. That is, the vertical or oblique orientation in the LDH-containing separator layer of the present embodiment indicates the conductivity anisotropy that the LDH oriented body can have in the layer thickness direction (that is, the direction perpendicular to the surface of the separator layer or the porous substrate). As a result, the conductivity in the layer thickness direction can be maximized or significantly increased. In addition, since the LDH-containing separator layer has a layer form, lower resistance can be realized than a bulk form LDH. An LDH-containing separator layer having such an orientation is easy to conduct hydroxide ions in the layer thickness direction. In addition, since it is densified, it is extremely suitable for a separator that requires high conductivity and denseness in the layer thickness direction.

Particularly preferably, the LDH plate-like particles are highly oriented in the vertical direction in the LDH-containing separator layer (typically the LDH dense film). This high degree of orientation is confirmed by the fact that when the surface of the separator layer is measured by an X-ray diffraction method, the peak of the (003) plane is not substantially detected or smaller than the peak of the (012) plane. (However, when a porous substrate in which a diffraction peak is observed at the same position as the peak due to the (012) plane is used, the peak of the (012) plane due to the LDH plate-like particle is used. This is not the case). This characteristic peak characteristic indicates that the LDH plate-like particles constituting the separator layer are oriented in a direction perpendicular to the separator layer. Here, it is needless to say that the “vertical direction” in this specification includes not only a strict vertical direction but also a substantially vertical direction similar thereto. That is, the (003) plane peak is known as the strongest peak observed when X-ray diffraction is performed on non-oriented LDH powder. In the oriented LDH-containing separator layer, the LDH plate-like particles are separated from the separator. Due to the orientation in the direction perpendicular to the layer, the peak of the (003) plane is not substantially detected or is smaller than the peak of the (012) plane. This is because the c-axis direction (00l) plane (l is 3 and 6) to which the (003) plane belongs is a plane parallel to the layered structure of the LDH plate-like particles. On the other hand, when oriented in the vertical direction, the LDH layered structure also faces the vertical direction. As a result, when the separator layer surface is measured by the X-ray diffraction method, the (00l) plane (l is 3 and 6). This is because the peak does not appear or becomes difficult to appear. In particular, the (003) plane peak tends to be stronger than the (006) plane peak when it exists, so it can be said that it is easier to evaluate the presence of vertical orientation than the (006) plane peak. . Therefore, in the oriented LDH-containing separator layer, the (003) plane peak is substantially not detected or smaller than the (012) plane peak, suggesting a high degree of vertical orientation. It can be said that it is preferable.

The separator layer preferably has a thickness of 100 μm or less, more preferably 75 μm or less, still more preferably 50 μm or less, particularly preferably 25 μm or less, and most preferably 5 μm or less. Thus, the resistance of the separator can be reduced by being thin. The separator layer is preferably formed as an LDH dense film on the porous substrate. In this case, the thickness of the separator layer corresponds to the thickness of the LDH dense film. When the separator layer is formed in the porous substrate, the thickness of the separator layer corresponds to the thickness of the composite layer composed of at least part of the porous substrate and LDH, and the separator layer is porous. When formed over and in the substrate, this corresponds to the total thickness of the LDH dense film and the composite layer. In any case, when the thickness is as described above, a desired low resistance suitable for practical use in battery applications and the like can be realized. The lower limit of the thickness of the LDH alignment film is not particularly limited because it varies depending on the application, but in order to ensure a certain degree of hardness desired as a functional film such as a separator, the thickness is preferably 1 μm or more. Preferably it is 2 micrometers or more.

The LDH separator with a porous substrate described above is (1) a porous substrate is prepared, and (2) a total of 0.20 to 0.40 mol / L of magnesium ions (Mg ²⁺ ) and aluminum ions (Al ³⁺ ). A separator comprising a layered double hydroxide by immersing the porous substrate in a raw material aqueous solution containing urea at a concentration and (3) hydrothermally treating the porous substrate in the raw material aqueous solution It can be produced by forming a layer on and / or in a porous substrate.

(1) Preparation of porous substrate The porous substrate is as described above, and is preferably composed of at least one selected from the group consisting of ceramic materials, metal materials, and polymer materials. More preferably, the porous substrate is made of a ceramic material. In this case, preferable examples of the ceramic material include alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, silicon carbide, and any combination thereof, and more preferable. Is alumina, zirconia, titania, and any combination thereof, particularly preferably alumina and zirconia, most preferably alumina. When these porous ceramics are used, the density of the LDH-containing separator layer tends to be improved. When using a porous substrate made of a ceramic material, it is preferable to subject the porous substrate to ultrasonic cleaning, cleaning with ion exchange water, and the like.

(2) Immersion in raw material aqueous solution Next, the porous substrate is immersed in the raw material aqueous solution in a desired direction (for example, horizontally or vertically). When the porous substrate is held horizontally, the porous substrate may be suspended, floated, or disposed so as to be in contact with the bottom of the container. For example, the porous substrate is suspended from the bottom of the container in the raw material aqueous solution. The material may be fixed. When the porous substrate is held vertically, a jig that can set the porous substrate vertically on the bottom of the container may be placed. In any case, the LDH is perpendicular to or close to the porous substrate (that is, the LDH plate-like particles are such that their plate surfaces intersect the surface (substrate surface) of the porous substrate perpendicularly or obliquely. It is preferable to adopt a configuration or arrangement in which the growth is performed in any direction. The raw material aqueous solution contains magnesium ions (Mg ²⁺ ) and aluminum ions (Al ³⁺ ) at a predetermined total concentration, and contains urea. By the presence of urea, ammonia is generated in the solution by utilizing hydrolysis of urea, so that the pH value increases, and the coexisting metal ions form hydroxides to obtain LDH. Further, since carbon dioxide is generated in the hydrolysis, LDH in which the anion is carbonate ion type can be obtained. The total concentration (Mg ²⁺ + Al ³⁺ ) of magnesium ions and aluminum ions contained in the raw material aqueous solution is preferably 0.20 to 0.40 mol / L, more preferably 0.22 to 0.38 mol / L, still more preferably The amount is 0.24 to 0.36 mol / L, particularly preferably 0.26 to 0.34 mol / L. When the concentration is within such a range, nucleation and crystal growth can proceed in a well-balanced manner, and an LDH-containing separator layer that is excellent not only in orientation but also in denseness can be obtained. That is, when the total concentration of magnesium ions and aluminum ions is low, crystal growth becomes dominant compared to nucleation, and the number of particles decreases and particle size increases. It is considered that the generation becomes dominant, the number of particles increases, and the particle size decreases.

Preferably, magnesium nitrate and aluminum nitrate are dissolved in the raw material aqueous solution, so that the raw material aqueous solution contains nitrate ions in addition to magnesium ions and aluminum ions. In this case, the molar ratio of urea to nitrate ions (NO ₃ ⁻ ) (urea / NO ₃ ⁻ ) in the raw material aqueous solution is preferably 2 to 6, and more preferably 4 to 5.

(3) Formation of LDH-containing separator layer by hydrothermal treatment Then, the porous substrate is hydrothermally treated in the raw material aqueous solution, and the separator layer containing LDH is placed on the porous substrate and / or in the porous substrate. Let it form. This hydrothermal treatment is preferably carried out in a closed container at 60 to 150 ° C., more preferably 65 to 120 ° C., further preferably 65 to 100 ° C., and particularly preferably 70 to 90 ° C. The upper limit temperature of the hydrothermal treatment may be selected so that the porous substrate (for example, the polymer substrate) is not deformed by heat. The rate of temperature increase during the hydrothermal treatment is not particularly limited, and may be, for example, 10 to 200 ° C./h, preferably 100 to 200 ° C./h, more preferably 100 to 150 ° C./h. The hydrothermal treatment time may be appropriately determined according to the target density and thickness of the LDH-containing separator layer.

After the hydrothermal treatment, it is preferable to take out the porous substrate from the sealed container and wash it with ion-exchanged water.

The LDH-containing separator layer in the LDH-containing composite material produced as described above is one in which LDH plate-like particles are highly densified and are oriented in the vertical direction advantageous for conduction. Therefore, it can be said that it is extremely suitable for a zinc-air secondary battery in which the progress of zinc dendrite has become a major barrier to practical use.

By the way, the LDH containing separator layer obtained by the said manufacturing method can be formed in both surfaces of a porous base material. For this reason, in order to make the LDH-containing composite material suitable for use as a separator, the LDH-containing separator layer on one side of the porous substrate is mechanically scraped after film formation, or on one side during film formation. It is desirable to take measures so that the LDH-containing separator layer cannot be formed.

The present invention will be described more specifically with reference to the following examples.

Example 1 : Production and evaluation of LDH separator with porous substrate (1) Production of porous substrate Boehmite (manufactured by Sasol, DISPAL 18N4-80), methylcellulose, and ion-exchanged water (boehmite): (methylcellulose) : (Ion-exchanged water) mass ratio was 10: 1: 5, and then kneaded. The obtained kneaded product was subjected to extrusion molding using a hand press and molded into a plate shape having a size sufficiently exceeding 5 cm × 8 cm and a thickness of 0.5 cm. The obtained molded body was dried at 80 ° C. for 12 hours and then calcined at 1150 ° C. for 3 hours to obtain an alumina porous substrate. The porous substrate thus obtained was cut into a size of 5 cm × 8 cm.

For the obtained porous substrate, the porosity of the surface of the porous substrate was measured by a technique using image processing, and it was 24.6%. The porosity is measured by 1) observing the surface microstructure with an accelerating voltage of 10 to 20 kV using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL Co., Ltd.). SEM) image (magnification of 10,000 times or more) is obtained, 2) a grayscale SEM image is read using image analysis software such as Photoshop (manufactured by Adobe), etc. 3) [Image] → [Tone Correction] → [2 A monochrome binary image was created by the procedure of [gradation], and 4) the porosity (%) was obtained by dividing the number of pixels occupied by the black portion by the total number of pixels in the image. This porosity measurement was performed on a 6 μm × 6 μm region on the surface of the porous substrate. FIG. 5 shows an SEM image of the porous substrate surface.

Further, when the average pore diameter of the porous substrate was measured, it was about 0.1 μm. In the present invention, the average pore diameter was measured by measuring the longest distance of the pores based on an electron microscope (SEM) image of the surface of the porous substrate. The magnification of the electron microscope (SEM) image used for this measurement is 20000 times, and all the obtained pore diameters are arranged in order of size, and the top 15 points and the bottom 15 points from the average value, and 30 points per visual field in total. The average value for two visual fields was calculated to obtain the average pore diameter. For length measurement, the length measurement function of SEM software was used.

(2) Cleaning of porous substrate The obtained porous substrate was ultrasonically cleaned in acetone for 5 minutes, ultrasonically cleaned in ethanol for 2 minutes, and then ultrasonically cleaned in ion-exchanged water for 1 minute.

(3) As the manufacturing raw material of the raw aqueous solution, magnesium nitrate hexahydrate _{_{(Mg (NO 3) 2 ·}} 6H 2 O, manufactured by Kanto Chemical Co., Inc.), aluminum nitrate nonahydrate (Al _(NO ₃₎ 3 · 9H ₂ O, manufactured by Kanto Chemical Co., Ltd.) and urea ((NH ₂ ) ₂ CO, manufactured by Sigma-Aldrich) were prepared. Weigh magnesium nitrate hexahydrate and aluminum nitrate nonahydrate so that the cation ratio (Mg ²⁺ / Al ³⁺ ) is 2 and the total metal ion molar concentration (Mg ²⁺ + Al ³⁺ ) is 0.320 mol / L. In a beaker, ion exchange water was added to make a total volume of 600 ml. After stirring the obtained solution, urea weighed at a ratio of urea / NO ₃ ⁻ = 4 was added to the solution, and further stirred to obtain an aqueous raw material solution.

(4) Film formation by hydrothermal treatment The Teflon (registered trademark) sealed container (with an internal volume of 800 ml, the outside is a stainless steel jacket), the raw material aqueous solution prepared in (3) above and the porous substrate washed in (2) above Both were enclosed. At this time, the base material was fixed by being floated from the bottom of a Teflon (registered trademark) sealed container, and placed horizontally so that the solution was in contact with both surfaces of the base material. Thereafter, hydrothermal treatment was performed at a hydrothermal temperature of 70 ° C. for 168 hours (7 days) to form a layered double hydroxide alignment film (separator layer) on the substrate surface. After the elapse of a predetermined time, the substrate is taken out from the sealed container, washed with ion-exchanged water, dried at 70 ° C. for 10 hours, and a dense layer of layered double hydroxide (hereinafter referred to as LDH) (hereinafter referred to as a membrane sample). ) Was obtained on a substrate. The thickness of the obtained film sample was about 1.5 μm. Thus, a layered double hydroxide-containing composite material sample (hereinafter referred to as a composite material sample) was obtained. Although the LDH film was formed on both surfaces of the porous substrate, the LDH film on one surface of the porous substrate was mechanically scraped to give the composite material a form as a separator.

(5) Various evaluations (5a) Identification of film sample Film sample with X-ray diffractometer (RINT TTR III manufactured by Rigaku Corporation) under voltage: 50 kV, current value: 300 mA, measurement range: 10-70 ° As a result, the XRD profile shown in FIG. 6 was obtained. About the obtained XRD profile, JCPDS card NO. It was identified using the diffraction peak of the layered double hydroxide (hydrotalcite compound) described in 35-0964. As a result, it was confirmed that the film sample was a layered double hydroxide (LDH, hydrotalcite compound). In addition, in the XRD profile shown in FIG. 6, a peak (peak marked in the figure) due to alumina constituting the porous substrate on which the film sample is formed is also observed. .

(5b) Observation of microstructure The surface microstructure of the film sample was observed with a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL) at an acceleration voltage of 10 to 20 kV. FIG. 7 shows an SEM image (secondary electron image) of the surface microstructure of the obtained film sample.

Also, the cross section of the composite material sample was polished by CP polishing to form a polished cross section, and the microstructure of the polished cross section was observed with a scanning electron microscope (SEM) at an acceleration voltage of 10 to 20 kV. An SEM image of the polished cross-sectional microstructure of the composite material sample thus obtained is shown in FIG.

(5c) Measurement of porosity The porosity of the surface of the membrane was measured for the membrane sample by a technique using image processing. The porosity is measured by 1) observing the surface microstructure with a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL) at an acceleration voltage of 10 to 20 kV, and observing an electron microscope (SEM) on the surface of the film. An image (magnification of 10,000 times or more) is acquired, 2) a grayscale SEM image is read using image analysis software such as Photoshop (manufactured by Adobe), and 3) [image] → [tone correction] → [2 gradations] A black and white binary image was created by the procedure of 4), and 4) the value obtained by dividing the number of pixels occupied by the black portion by the total number of pixels of the image was taken as the porosity (%). This porosity measurement was performed on a 6 μm × 6 μm region of the alignment film surface. As a result, the porosity of the film surface was 19.0%. Further, using the porosity of the film surface, the density D when viewed from the film surface (hereinafter referred to as the surface film density) was calculated by D = 100% − (porosity of the film surface). %Met.

In addition, the porosity of the polished cross section of the film sample was also measured. The measurement of the porosity of the polished cross section is the same as that described above except that an electron microscope (SEM) image (magnification of 10,000 times or more) of the cross-section polished surface in the thickness direction of the film was obtained according to the procedure shown in (5b) above. It carried out similarly to the porosity of the film | membrane surface. The measurement of the porosity was performed on the film portion of the alignment film cross section. Thus, the porosity calculated from the cross-sectional polished surface of the film sample is 3.5% on average (average value of the three cross-sectional polished surfaces), and a very high-density film is formed on the porous substrate. It was confirmed that

(5d) Denseness determination test I
In order to confirm that the membrane sample has a denseness that does not have water permeability, a denseness determination test was performed as follows. First, as shown in FIG. 9A, the composite material sample 220 obtained in (1) above (cut to 1 cm × 1 cm square) has a center of 0.5 cm × 0.5 cm square on the film sample side. The silicon rubber 222 provided with the opening 222a was bonded, and the obtained laminate was bonded between two

acrylic containers

224 and 226. The bottom of the acrylic container 224 disposed on the silicon rubber 222 side is removed, and thereby the silicon rubber 222 is bonded to the acrylic container 224 with the opening 222a opened. On the other hand, the acrylic container 226 disposed on the porous substrate side of the composite material sample 220 has a bottom, and ion-exchanged water 228 is contained in the container 226. At this time, Al and / or Mg may be dissolved in the ion exchange water. That is, the constituent members are arranged so that the ion-exchanged water 228 is in contact with the porous substrate side of the composite material sample 220 by turning upside down after assembly. After assembling these components, the total weight was measured. After assembling these components, the total weight was measured. Needless to say, the container 226 has a closed vent hole (not shown) and is opened after being turned upside down. As shown in FIG. 9B, the assembly was placed upside down and held at 25 ° C. for 1 week, after which the total weight was measured again. At this time, when water droplets adhered to the inner side surface of the acrylic container 224, the water droplets were wiped off. Then, the density was determined by calculating the difference in the total weight before and after the test. As a result, no change was observed in the weight of ion-exchanged water even after holding at 25 ° C. for 1 week. From this, it was confirmed that the membrane sample (that is, the functional membrane) has high density so as not to have water permeability.

(5e) Denseness determination test II
In order to confirm that the film sample has a denseness that does not have air permeability, a denseness determination test was performed as follows. First, as shown in FIGS. 10A and 10B, an acrylic container 230 without a lid and an alumina jig 232 having a shape and size that can function as a lid for the acrylic container 230 were prepared. The acrylic container 230 is formed with a gas supply port 230a for supplying gas therein. The alumina jig 232 has an opening 232a having a diameter of 5 mm, and a recess 232b for placing a film sample is formed along the outer periphery of the opening 232a. An epoxy adhesive 234 was applied to the depression 232b of the alumina jig 232, and the film sample 236b side of the composite material sample 236 was placed in the depression 232b to adhere to the alumina jig 232 in an airtight and liquid-tight manner. Then, the alumina jig 232 to which the composite material sample 236 is bonded is adhered to the upper end of the acrylic container 230 in a gas-tight and liquid-tight manner using a silicone adhesive 238 so as to completely close the opening of the acrylic container 230. A measurement sealed container 240 was obtained. The measurement sealed container 240 was placed in a water tank 242, and the gas supply port 230 a of the acrylic container 230 was connected to the pressure gauge 244 and the flow meter 246 so that helium gas could be supplied into the acrylic container 230. Water 243 was put into the water tank 242 and the measurement sealed container 240 was completely submerged. At this time, the inside of the measurement sealed container 240 is sufficiently airtight and liquid-tight, and the membrane sample 236b side of the composite material sample 236 is exposed to the internal space of the measurement sealed container 240, while the composite material sample The porous base material 236 a side of 236 is in contact with the water in the water tank 242. In this state, helium gas was introduced into the measurement sealed container 240 into the acrylic container 230 via the gas supply port 230a. The pressure gauge 244 and the flow meter 246 are controlled so that the differential pressure inside and outside the membrane sample 236b is 0.5 atm (that is, the pressure applied to the side in contact with the helium gas is 0.5 atm higher than the water pressure applied to the opposite side). Whether or not helium gas bubbles are generated in the water from the composite material sample 236 was observed. As a result, generation of bubbles due to helium gas was not observed. Therefore, it was confirmed that the membrane sample 236b has high density so as not to have air permeability.

Example 2 (Reference): Production of Zinc-Air Secondary Battery This example is a reference example based on a unit cell provided with a pair of air electrode plate / separator / negative electrode plate. Although this example is not an example relating to a zinc-air battery cell pack using a flexible bag body, it is an example of producing a zinc-air secondary battery using an LDH separator, and therefore the zinc-air battery cell pack of the present invention. It can be used as a reference when manufacturing the above.

(1) Preparation of separator with porous substrate By the same procedure as in Example 1, an LDH film on an alumina substrate was prepared as a separator with a porous substrate (hereinafter simply referred to as a separator).

(2) Preparation of air electrode layer α-MnO ₂ particles as an air electrode catalyst were prepared as follows. First, Mn (SO ₄ ) · 5H ₂ O and KMnO ₄ were dissolved in deionized water at a molar ratio of 5:13 and mixed. The obtained mixed liquid is put into a stainless steel sealed container with Teflon (registered trademark) attached thereto, and hydrothermal synthesis is performed at 140 ° C. for 2 hours. The precipitate obtained by hydrothermal synthesis was filtered, washed with distilled water, and dried at 80 ° C. for 6 hours. Thus, α-MnO ₂ powder was obtained.

Layered double hydroxide particles (hereinafter referred to as LDH particles) as hydroxide ion conductive materials were produced as follows. First, Ni (NO ₃ ) ₂ · 6H ₂ O and Fe (NO ₃ ) ₃ · 9H ₂ O were dissolved and mixed in deionized water to a molar ratio of Ni: Fe = 3: 1. The resulting mixture was added dropwise to a 0.3 M Na ₂ CO ₃ solution at 70 ° C. with stirring. At this time, the pH of the mixed solution is adjusted to 10 while adding a 2M NaOH solution and maintained at 70 ° C. for 24 hours. The precipitate formed in the mixed solution was filtered, washed with distilled water, and then dried at 80 ° C. to obtain LDH powder.

The α-MnO ₂ particles and LDH particles obtained above and carbon black (product number VXC72, manufactured by Cabot Co., Ltd.) as an electron conductive material are weighed so as to have a predetermined blending ratio, and in the presence of an ethanol solvent. Wet mixed. The resulting mixture is dried at 70 ° C. and then crushed. The obtained pulverized powder was mixed with a binder (PTFE, manufactured by Electrochem, product number EC-TEF-500ML) and water for fibrillation. At this time, the amount of water added was 1% by mass with respect to the air electrode. The fibrillar mixture thus obtained was pressure-bonded to a current collector (carbon cloth (manufactured by Electrochem, product number EC-CC1-060T)) so as to have a thickness of 50 μm, and the air electrode layer / current collector A laminated sheet was obtained. The air electrode layer thus obtained has an electron conductive phase (carbon black) of 20% by volume, a catalyst layer (α-MnO ₂ particles) of 5% by volume, a hydroxide ion conductive phase (LDH particles) of 70% by volume and It contained 5% by volume of a binder phase (PTFE).

(3) Production of air electrode with separator An anion exchange membrane (Astom Corp., Neocepta AHA) was immersed in 1M NaOH aqueous solution overnight. This anion exchange membrane is laminated as an intermediate layer on the LDH membrane of the separator to obtain a separator / intermediate layer laminate. The thickness of the intermediate layer is 30 μm. The separator / intermediate layer laminate thus obtained is pressure-bonded with the air electrode layer / current collector laminated sheet prepared previously so that the air electrode layer side is in contact with the intermediate layer, thereby obtaining an air electrode sample with a separator.

(4) Production of Negative Electrode Plate A mixture of 80 parts by weight of zinc oxide powder, 20 parts by weight of zinc powder and 3 parts by weight of polytetrafluoroethylene particles was applied onto a current collector made of copper punching metal, and the porosity was about A negative electrode plate coated with an active material portion at 50% is obtained.

(5) Production of third electrode A platinum paste is applied on a current collector made of nickel mesh to obtain a third electrode.

(6) Assembly of battery Using the obtained air electrode with separator, negative electrode plate, and third electrode, a zinc-air secondary battery having a horizontal structure is manufactured in the following procedure. First, a container without a lid (hereinafter referred to as a resin container) made of ABS resin and having a rectangular parallelepiped shape is prepared. The negative electrode plate is placed on the bottom of the resin container so that the side on which the negative electrode active material is coated faces upward. At this time, the negative electrode current collector is in contact with the bottom of the resin container, and the end of the negative electrode current collector is connected to an external terminal provided through the side surface of the resin container. Next, a third electrode is provided at a position higher than the upper surface of the negative electrode plate on the inner wall of the resin container (that is, a position that does not contact the negative electrode plate and does not participate in the charge / discharge reaction), and the nonwoven fabric separator contacts the third electrode. Deploy. The opening of the resin container is closed with an air electrode with a separator so that the air electrode side is on the outside. At that time, an epoxy resin-based adhesive (EP008, manufactured by Cemedine Co., Ltd.) is applied to the outer peripheral portion of the opening to Seal and bond to give liquid tightness. A 6 mol / L aqueous solution of KOH is injected as an electrolyte into the resin container through a small inlet provided near the upper end of the resin container. In this way, the separator comes into contact with the electrolyte solution, and the electrolyte solution can always contact the third electrode regardless of the increase or decrease of the electrolyte solution due to the liquid retaining property of the nonwoven fabric separator. At this time, the amount of electrolyte to be injected is the amount of water expected not only to sufficiently hide the negative electrode active material coating part in the resin container but also to decrease during charging in order to produce a battery in a discharged state. Use an excess amount in consideration. Therefore, the resin container is designed so as to accommodate the excessive amount of the electrolytic solution. Finally, the inlet of the resin container is sealed. Thus, the internal space defined by the resin container and the separator is hermetically and liquid-tightly sealed. Finally, the third electrode and the current collecting layer of the air electrode are connected via an external circuit. In this way, a zinc-air secondary battery is obtained.

According to such a configuration, since the separator has a high degree of denseness that does not allow water and gas to pass through, the penetration of the separator by the zinc dendrite generated during charging is physically blocked to prevent a short circuit between the positive and negative electrodes, In addition, it is possible to prevent the infiltration of carbon dioxide in the air and to prevent the precipitation of alkali carbonate (caused by carbon dioxide) in the electrolyte. In addition, hydrogen gas that can be generated by a side reaction from the negative electrode can be brought into contact with the third electrode and returned to water through the above-described reaction. That is, a highly reliable zinc-air secondary battery that can cope with the problem of hydrogen gas generation while having a configuration suitable for preventing both short-circuiting due to zinc dendrite and mixing of carbon dioxide is provided. .

Example 3 (Reference): Preparation of nickel zinc battery cell pack (Reference)
This example is a reference example regarding a nickel zinc battery cell pack. Although this example is not an example relating to a zinc-air battery, it is also an example in which a battery cell pack is produced using a zinc negative electrode and a flexible bag formed of a flexible film and an LDH separator. Thus, it can be used as a reference when producing the zinc-air battery cell pack of the present invention.

(1) Production of partition sheet In the same procedure as in Example 1, an LDH film on an alumina substrate was prepared as a separator with a porous substrate. As shown in FIGS. 11A and 11B, a modified polyphenylene ether resin frame 332 was placed along the outer periphery of the separator 328 with the porous substrate 330 on the separator 328 side (that is, the LDH film side). At this time, the frame 332 is a square frame, and a step is provided on the inner periphery thereof, and the outer periphery of the porous substrate 330 and the separator 328 is fitted to the step. On this frame 332, a laminate film (manufactured by AS ONE, product name: polybag for vacuum sealer, thickness: 50 μm, material: PP resin (base film) and PE resin (thermoplastic resin)) is formed as a flexible film 324. Placed. The flexible film 324 has an opening 324 a formed in the center in advance, and the flexible film 324 is disposed so that the opening 324 a corresponds to an open area in the frame 332. The joint part of the flexible film 324, the frame 332, and the separator 328 with the porous base material 330 was heat-sealed and sealed at about 200 ° C. using a commercially available heat sealer. A photograph of the partition sheet thus produced is shown in FIG. A region H indicated by a dotted line in FIG. 12 is a region where heat sealing has been performed, and liquid tightness in this region is ensured.

(2) Preparation of positive electrode plate Nickel hydroxide particles to which zinc and cobalt are added so as to form a solid solution are prepared. The nickel hydroxide particles are coated with cobalt hydroxide to obtain a positive electrode active material. The obtained positive electrode active material and a 2% aqueous solution of carboxymethylcellulose are mixed to prepare a paste. The paste obtained above is uniformly applied to a current collector made of a nickel metal porous substrate having a porosity of about 95% and dried so that the porosity of the positive electrode active material is 50%. A positive electrode plate coated over a predetermined area is obtained.

(3) Production of negative electrode plate A mixture of 80 parts by weight of zinc oxide powder, 20 parts by weight of zinc powder and 3 parts by weight of polytetrafluoroethylene particles was applied on a current collector made of copper punching metal, and the porosity was about A negative electrode plate in which the active material portion is applied over a predetermined region at 50% is obtained.

(4) Production of Nickel Zinc Battery Cell Pack A nickel zinc battery cell pack 310 as shown in FIG. 13 was assembled by the following procedure using the partition sheet 314, the positive electrode 316 and the negative electrode 320 obtained above. First, as a pair of

flexible films

312a and 312b, a laminate film (manufactured by AS ONE, product name: plastic bag for vacuum sealer, thickness: 50 μm, material: PP resin (base film) and PE resin (thermoplastic resin) ) Was prepared. As shown in FIG. 13, the negative electrode 320, the partition sheet 314, the positive electrode 316, and the flexible film 312b were laminated in this order on the flexible film 312a. At this time, the partition sheet 314 was disposed so that the porous base material 330 and the frame 332 were positioned on the positive electrode 316 side. The outer periphery 3 sides (sides other than the upper end) of the

flexible films

312a and 312b and the outer periphery 3 sides (sides other than the upper end) of the flexible film 324 constituting the partition sheet 314 overlap, The overlapping portions (outer peripheral edge 3 sides) of the

flexible films

312a, 323, 312b were heat-sealed and bonded at about 200 ° C. using a commercially available heat sealer. A photograph taken from the positive electrode 316 side of the flexible bag 312 sealed in a liquid-tight manner by heat fusion bonding is shown in FIG. In FIG. 14, a region H on the three outer peripheral edges surrounded by a dotted line is a portion that is heat sealed. At this point, as can be seen from FIG. 14, the upper end portion of the flexible bag is opened without being heat-sealed, and the positive electrode current collector and the negative electrode current collector are flexible at different positions. It extends from the outer periphery of the bag at different positions (corresponding to two metal pieces visually recognized in the figure). In FIG. 14, the positive electrode current collector and the negative electrode current collector are provided with a considerably longer length, but this is for the purpose of trial manufacture, and in actuality, the surplus space is not increased unnecessarily. It is preferable that the length is shorter than that shown in FIG. The photograph which image | photographed the flexible bag body heat-sealed and sealed from the negative electrode side is shown to FIG. 15A. As shown in FIG. 15A as a gray line in the portion highlighted by the frame at the upper end of the flexible bag (an enlarged photograph of that portion is shown in FIG. 15B), On the portion to be brought into contact with the upper end of the flexible bag body, a heat-sealing flexible film and a heat-sealing sealant film that promotes welding (product name: tab lead MINUS LEAD, material: (Polyolefin resin) is disposed, so that heat fusion bonding can be reliably performed at the contact portion with the current collector (metal piece) (that is, between different materials) at the time of heat fusion bonding of the upper end portion performed later. Has been. Thus, the flexible bag 312 containing the partition sheet 314, the positive electrode 316, and the negative electrode 320 is placed in a vacuum desiccator and placed in each of the positive electrode chamber 315 and the negative electrode chamber 319 in the flexible bag 312 in a vacuum atmosphere. As an electrolytic solution, a 6 mol / L aqueous KOH solution was injected as an electrolytic solution. The electrolyte solution was injected from the open part of the upper end of the flexible bag 312. Finally, the open portion at the upper end of the flexible bag body 312 was heat-sealed and bonded at about 200 ° C. using a commercially available heat sealer, to obtain a nickel zinc battery cell pack 310. The photograph which image | photographed the nickel zinc battery cell pack 310 by which the upper end part was heat-seal-bonded in this way is shown in FIG. In FIG. 16, a region H on one side of the upper end that is the outer periphery surrounded by a dotted line is a portion that is heat-sealed.

Claims

A flexible bag formed of a flexible film and provided with an opening;
A separator structure including a separator having hydroxide ion conductivity but not having water permeability and air permeability, wherein the opening is hermetically and liquid-tightly closed to form a sealed space together with the flexible bag;
An air electrode provided on the side opposite to the sealed space of the separator;
A negative electrode containing zinc, a zinc alloy and / or a zinc compound, contained in the sealed space;
An electrolytic solution containing an aqueous alkali metal hydroxide solution that is housed in the sealed space and in which the negative electrode is immersed;
A zinc-air battery cell pack comprising:
The zinc-air battery cell pack according to claim 1, wherein the flexible film comprises a resin film.
The zinc-air battery cell pack according to claim 1 or 2, wherein the flexible bag is made of a pair of flexible films, and the outer peripheral edges of the pair of flexible films are sealed by heat sealing. .
The separator structure includes a frame along an outer peripheral edge of the separator, and the flexible film and the separator structure are bonded in a liquid-tight and air-tight manner through the frame. 4. The zinc-air battery cell pack according to claim 3.
The zinc-air battery cell pack according to claim 4, wherein the frame is a resin frame, and the flexible film and the resin frame are bonded by an adhesive and / or heat fusion.
The zinc-air battery cell pack according to any one of claims 1 to 5, wherein the sealed space includes a surplus space having a volume that allows a decrease in water amount accompanying a negative electrode reaction during charge and discharge.
The zinc-air battery cell pack according to claim 6, wherein the flexible bag, the separator structure, the air electrode, and the negative electrode are provided vertically, and the sealed space has the excess space above it.
The zinc-air battery cell pack according to any one of claims 1 to 7, wherein the separator is made of an inorganic solid electrolyte body.
The zinc-air battery cell pack according to claim 8, wherein the inorganic solid electrolyte body has a relative density of 90% or more.
The zinc-air battery cell pack according to claim 8 or 9, wherein the inorganic solid electrolyte body is composed of a layered double hydroxide.
The zinc-air battery cell pack according to any one of claims 8 to 10, wherein the inorganic solid electrolyte body has a plate shape, a film shape, or a layer shape.
The zinc-air battery cell pack according to any one of claims 1 to 11, wherein the separator structure further includes a porous substrate on at least one side of the separator.
The zinc according to claim 12, wherein the inorganic solid electrolyte body is in the form of a film or a layer, and the film or layered inorganic solid electrolyte is formed on or in the porous substrate. Air battery cell pack.
The zinc-air battery cell pack according to claim 12 or 13, wherein the separator is provided on the sealed space side of the porous substrate.
The separator structure includes a frame along an outer peripheral edge of the separator, and the frame includes:
An outer frame portion having an opening capable of accommodating the separator and the porous substrate;
An inner frame portion extending from the end of the outer frame portion on the air electrode side and / or the vicinity thereof toward the opening, and engaging with the air electrode side of the porous substrate;
The space between the porous substrate and the frame or between the porous substrate and the separator and the frame is liquid-tightly sealed with an adhesive. Zinc-air battery cell pack.
The inorganic solid electrolyte body is composed of a layered double hydroxide, and the layered double hydroxide is composed of an assembly of a plurality of plate-like particles, and the plate surfaces of the plurality of plate-like particles are the porous group. The zinc-air battery cell pack according to any one of claims 8 to 15, wherein the zinc-air battery cell pack is oriented in a direction perpendicular to or obliquely intersecting the surface of the material.
The zinc-air battery cell pack further comprises a breathable air electrode current collector provided on the air electrode opposite to the separator, and a negative electrode current collector provided in contact with the negative electrode. The zinc-air battery cell pack according to any one of claims 1 to 16.
The zinc-air battery cell pack according to any one of claims 1 to 17, wherein the negative electrode current collector extends from an outer peripheral edge of the flexible bag.
The zinc-air battery cell pack includes a third electrode provided so as to be in contact with the electrolyte but not in contact with the negative electrode, and the third electrode is connected to the air electrode via an external circuit, The zinc-air battery cell pack according to any one of claims 1 to 18.
An assembled battery in which a plurality of zinc-air battery cell packs according to any one of claims 1 to 19 are packed in a battery container.