JP6429378B2 - Secondary battery using hydroxide ion conductive ceramic separator - Google Patents

Description

  The present invention relates to a secondary battery using a hydroxide ion conductive ceramic separator.

  Although zinc secondary batteries such as nickel-zinc secondary batteries and zinc-air secondary batteries have been developed and studied for a long time, they have not yet been put into practical use. This is because the zinc constituting the negative electrode produces dendritic crystals called dendrite during charging, and this dendrite breaks through the separator and causes a short circuit with the positive electrode. Therefore, a technique for preventing a short circuit due to zinc dendrite in a zinc secondary battery such as a nickel zinc secondary battery or a zinc-air secondary battery is strongly desired.

In order to deal with such problems and demands, a battery using a hydroxide ion conductive ceramic separator has been proposed. For example, in Patent Document 1 (International Publication No. 2013/118561), a separator made of a hydroxide ion conductive inorganic solid electrolyte is used as a positive electrode in a nickel zinc secondary battery for the purpose of preventing a short circuit due to zinc dendrite. And an inorganic solid electrolyte body having a general formula: M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ _{x / n} · mH ₂ O (wherein M ²⁺ is at least is at least one divalent cation, M ³⁺ is at least one or more trivalent cations, a ^n-is the n-valent anion, n represents an integer of 1 or more, x is 0 It is proposed to use a layered double hydroxide (LDH) having a basic composition of. Further, in Patent Document 2 (International Publication No. 2013/073292), in a zinc-air secondary battery, a separator made of layered double hydroxide (LDH) having the same basic composition as described above is brought into close contact with one side of the air electrode. It has been proposed that both the short circuit between the positive and negative electrodes due to zinc dendrite during charging and the mixing of carbon dioxide into the electrolyte can be prevented.

  As an application example of a hydroxide ion conductive ceramic separator other than a zinc secondary battery, Patent Document 3 (International Publication No. 2013/161516) describes a layered double hydroxide (LDH) having the same basic composition as described above. A lithium-air secondary battery using a constructed inorganic solid electrolyte as an anion exchanger is disclosed, and this anion exchanger can prevent carbon dioxide from being mixed into the battery.

International Publication No. 2013/118561 International Publication No. 2013/073292 International Publication No. 2013/161516

  The present applicant has succeeded in the development of 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. When such a separator (or a separator with a porous substrate) is used to form a secondary battery such as a zinc-nickel battery or a zinc-air secondary battery, a short circuit due to zinc dendrite (especially in the case of a metal-air secondary battery) (Problem) carbon dioxide contamination can be prevented. And in order to exhibit this effect for a long term, it is desired to suppress the deterioration of the ceramic separator. However, the electrolyte of a secondary battery (for example, a metal-air battery or a nickel-zinc battery) to which a hydroxide ion conductive ceramic separator is applied requires high hydroxide ion conductivity, and therefore has a pH of 14 It is desired that a strong alkaline aqueous KOH solution be used. For this reason, the ceramic separator is desired to have a high alkali resistance that hardly deteriorates even in such a strong alkaline electrolyte.

  The inventors of the present invention have now found that the deterioration of a hydroxide ion conductive ceramic separator caused by an alkaline electrolyte can be significantly reduced by adding an alcohol to the alkaline electrolyte. And the knowledge that the reliable secondary battery which can reduce significantly the deterioration by the alkaline electrolyte of a hydroxide ion conductive ceramic separator can be provided using this electrolyte was also obtained.

  Therefore, an object of the present invention is to provide a highly reliable secondary battery that can significantly reduce deterioration of a hydroxide ion conductive ceramic separator.

According to one aspect of the present invention, a secondary battery using a hydroxide ion conductive ceramic separator, the secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution containing an alkali metal hydroxide aqueous solution; A ceramic separator made of an inorganic solid electrolyte body having hydroxide ion conductivity, which is in contact with the electrolytic solution and separates the positive electrode and the negative electrode,
The 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, 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 to 0.4 basic, m is 0 or higher) A layered double hydroxide having a composition,
There is provided a secondary battery configured such that the electrolyte further includes alcohol, thereby preventing erosion of the layered double hydroxide by the electrolyte.

It is a conceptual diagram which shows typically an example of the nickel zinc battery by one aspect | mode of this invention, and shows a discharge end state. It is a figure which shows the full charge state of the nickel zinc battery shown by FIG. It is a conceptual diagram which shows typically an example of the zinc air secondary battery by 1 aspect of this invention. FIG. 3B is a perspective view of the zinc-air secondary battery shown in FIG. 3A. 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. 4 is a SEM image of the surface of an alumina porous substrate produced in Example 3. FIG. 3 is an XRD profile obtained for the crystal phase of the sample in Example 3. 10 is a SEM image showing the surface microstructure of the film sample observed in Example 3. 4 is a SEM image of a polished cross-sectional microstructure of a composite material sample observed in Example 3. FIG. FIG. 10 is an exploded perspective view of a denseness discrimination measurement system used in Example 3. 6 is a schematic cross-sectional view of a denseness discrimination measurement system used in Example 3. FIG. 6 is an exploded perspective view of a measurement sealed container used in a denseness determination test II of Example 3. FIG. 6 is a schematic cross-sectional view of a measurement system used in a denseness determination test II of Example 3. FIG.

Secondary battery The secondary battery of the present invention uses a hydroxide ion conductive ceramic separator. The secondary battery of the present invention includes a nickel zinc secondary battery, a silver zinc oxide secondary battery, a manganese zinc secondary battery, a zinc air secondary battery, various other alkaline zinc secondary batteries, and a lithium air secondary battery. And various secondary batteries to which a hydroxide ion conductive ceramic separator can be applied. In particular, a nickel zinc secondary battery and a zinc-air secondary battery are preferable. Therefore, in the following general description, reference may be made to FIG. 1 relating to a nickel zinc secondary battery and FIGS. 3A and 3B relating to a zinc-air secondary battery. The secondary battery should not be limited to the air secondary battery, and conceptually includes the various secondary batteries described above that can employ the hydroxide ion conductive ceramic separator.

A secondary battery according to one embodiment of the present invention includes a positive electrode, a negative electrode, an electrolytic solution, and a ceramic separator. The electrolytic solution comprises an alkali metal hydroxide aqueous solution. The ceramic separator is in contact with the electrolytic solution and separates the positive electrode and the negative electrode. Ceramic separator, an inorganic solid electrolyte having a hydroxide ion conductivity, the 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, 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 to 0.4, and m is 0 or more). The positive electrode may be appropriately selected according to the type of secondary battery, and may be an air electrode. The negative electrode may be appropriately selected according to the type of secondary battery. For example, in the case of various zinc secondary batteries, zinc, a zinc alloy, and / or a zinc compound may be included. If desired, a porous substrate (preferably a ceramic porous substrate) may be provided on one or both surfaces of the ceramic separator. Of the constituent members of the secondary battery described above, at least the negative electrode and the alkaline electrolyte can be accommodated in a container (preferably a resin container). Like the nickel-zinc battery 10 shown in FIG. 1, the container 22 can also accommodate the positive electrode 12 and the positive electrode electrolyte 14, but the positive electrode is configured as an air electrode 32 like the zinc-air secondary battery 30 shown in FIG. 3A. In this case, the air electrode 32 (positive electrode) does not need to be completely accommodated in the container 46, and is simply attached so as to close the opening 46a of the container 46 (for example, in the form of a lid). Good. It should be noted that the positive electrode and the alkaline electrolyte need not necessarily be separated, and may be configured as a positive electrode mixture in which the positive electrode and the alkaline electrolyte are mixed. No liquid is required. Moreover, the negative electrode and the alkaline electrolyte need not necessarily be separated, and may be configured as a negative electrode mixture in which the negative electrode and the alkaline electrolyte are mixed. If desired, a positive electrode current collector may be provided in contact with the positive electrode. If desired, a negative electrode current collector may be provided in contact with the negative electrode.

As described above, when a secondary battery such as a zinc-nickel battery or a zinc-air secondary battery is configured using such a ceramic separator, a short circuit due to zinc dendrite (particularly in the case of a metal-air secondary battery) Can prevent carbon dioxide contamination. And in order to exhibit this effect for a long term, it is desired to suppress the deterioration of the ceramic separator. However, the electrolyte of a secondary battery (for example, a metal-air battery or a nickel-zinc battery) to which a hydroxide ion conductive ceramic separator is applied requires high hydroxide ion conductivity, and therefore has a pH of 14 It is desired that a strong alkaline aqueous KOH solution be used. For this reason, the ceramic separator is desired to have a high alkali resistance that hardly deteriorates even in such a strong alkaline electrolyte. In this regard, the present inventors have recently obtained the knowledge that the deterioration due to the alkaline electrolyte of the hydroxide ion conductive ceramic separator can be significantly reduced by adding alcohol to the alkaline electrolyte. . That is, the secondary battery of the present invention is configured such that the electrolytic solution further contains alcohol, and thereby erosion of the layered double hydroxide by the electrolytic solution is suppressed. In particular, erosion by the electrolyte of the layered double hydroxide of the general formula of the layered double ^{_{hydroxide: M 2+ 1-x M 3+}} x (OH) M in _{2 A n- x / n · mH} 2 O 2+ and / Alternatively, elution of a metal element corresponding to M ³⁺ is accompanied by elution of such a metal element (for example, an element corresponding to M ³⁺ such as Al or Cr, particularly Al). Can be reduced. In particular, by suppressing the erosion of the layered double hydroxide by the electrolyte, the excellent hydroxide ion conductivity inherent in the layered double hydroxide and the excellent denseness of the ceramic separator are desirably maintained over a long period of time. can do. That is, according to the present invention, it is possible to provide a highly reliable secondary battery that can significantly reduce the deterioration of the hydroxide ion conductive ceramic separator due to the alkaline electrolyte.

  A ceramic separator (hereinafter, also simply referred to as “separator”) is provided so as to be in contact with an electrolytic solution and to separate a positive electrode and a negative electrode. For example, as in the nickel-zinc secondary battery 10 shown in FIG. 1, the separator 20 contains a positive electrode chamber 24 containing the positive electrode 12 and the positive electrode electrolyte solution 14, and a negative electrode 16 and a negative electrode electrolyte solution 18 in the container 22. The separator 40 may block the opening 46a of the container 46 so as to be in contact with the electrolytic solution 36, as in the zinc-air secondary battery 30 shown in FIG. 3A. The container 46 and the negative electrode side sealed space may be formed. The separator or the inorganic solid electrolyte constituting the separator preferably has hydroxide ion conductivity but does not have water permeability and air permeability. That is, the fact that the separator or inorganic solid electrolyte body does not have water permeability and air permeability means that the separator or inorganic solid electrolyte body has a high degree of denseness that does not allow water and gas to pass through. It means that it is not a porous film or other porous material having air permeability. For this reason, in the case of a zinc secondary battery, 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. Further, in the case of a metal-air secondary battery, a configuration that is extremely effective in preventing the infiltration of carbon dioxide in the air and preventing the precipitation of alkali carbonate (caused by carbon dioxide) in the electrolyte. It has become. In any case, since the ceramic separator has hydroxide ion conductivity, the efficiency of hydroxide ions required between the positive electrode side (for example, alkaline electrolyte or air electrode) and the negative electrode side (for example, alkaline electrolyte). Charge and discharge reactions at the positive electrode and the negative electrode can be realized.

  The ceramic separator is made of an inorganic solid electrolyte body having hydroxide ion conductivity. By using a hydroxide ion conductive inorganic solid electrolyte as a separator, the electrolyte solution between the positive and negative electrodes is isolated and hydroxide ion conductivity is ensured. 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 ceramic separator 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 is a composite of an open-pore porous material as a base material and an inorganic solid electrolyte (for example, layered double hydroxide) deposited and grown in the pores so as to fill the pores of the porous material. It may be a body. 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 has a 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 and M ³⁺ is 3 the valence of the ^{cation, a n-is} the n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, the basic composition of m is 0 or higher) It preferably comprises a layered double hydroxide (LDH) having, more preferably, such LDH. 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- may be any anion, preferred examples OH ^- and _CO ^{3 2-} and the like. 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. m is a real number or an integer of 0 or more, typically more than 0 or 1 or more. 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.

  The inorganic solid electrolyte is preferably 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. 2013/118561), in which pure water and a plate-like green compact are placed in a pressure vessel, and 120 to 250 ° C., preferably The reaction can be performed at a temperature of 180 to 250 ° C. for 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. Moreover, the higher the hydroxide ion conductivity of the inorganic solid electrolyte body, the better, but it typically 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 can be reduced by being thin. 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.

  A porous substrate may be provided on one side or both sides of the ceramic separator. It goes without saying that the porous substrate 28 has water permeability, and therefore, the alkaline electrolyte can reach the separator. However, the presence of the porous substrate allows hydroxide ions to be more stably formed on the separator. It can also be held. In addition, since the strength can be imparted by the porous base material, the resistance can be reduced by thinning the separator. Also, a dense film or a dense layer of an inorganic solid electrolyte (preferably LDH) can be formed on or in the porous substrate. When providing a porous substrate on one side of the separator, 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). On the other hand, when providing a porous base material on both surfaces of a separator, it can be considered that densification is performed by sandwiching a raw material powder of an inorganic solid electrolyte between two porous base materials. For example, in FIG. 1, the porous substrate 28 is provided over the entire surface of one side of the separator 20, but may be provided only on a part of one side of the separator 20 (for example, a region involved in the charge / discharge reaction). For example, when an inorganic solid electrolyte body is formed in a film or layer on or in a porous substrate, the porous substrate is provided over the entire surface of one side of the separator derived from the manufacturing method. Is typical. 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), a porous base material is retrofitted only on a part of one side of the separator (for example, a region involved in the charge / discharge reaction). Alternatively, a porous substrate may be retrofitted over the entire surface of one side.

  The electrolyte solution may be any alkaline electrolyte solution that can be used for the secondary battery as long as it contains an alkali metal hydroxide aqueous solution. As shown in FIG. 1, when the positive electrode electrolyte 14 and the negative electrode electrolyte 18 are present, an alkali metal hydroxide aqueous solution is preferably used as the positive electrode electrolyte 14 and the negative electrode electrolyte 18. Examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide and the like, and potassium hydroxide is more preferable. In the case of a zinc secondary battery, a zinc compound such as zinc oxide or zinc hydroxide may be added to the electrolytic solution in order to suppress self-dissolution of the zinc alloy. As described above, the alkaline electrolyte may be mixed with the positive electrode and / or the negative electrode to be present in the form of a positive 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.

  As described above, the electrolyte further includes alcohol. The alcohol is preferably added in advance to the electrolytic solution, and may be added, for example, at the time of manufacturing the battery or electrolytic solution or before using the battery. However, the alcohol may be added to the electrolyte later (for example, when the battery is used), and in this case, the alcohol may be gradually added as the battery is used. The alcohol is preferably an alcohol having 1 to 6 carbon atoms, more preferably 2 to 6 carbon atoms. When the number of carbon atoms is 6 or less, the hydrophilicity becomes strong and the alcohol is easily dissolved in the electrolytic solution. The alcohol, particularly an alcohol having a number of carbon atoms within the above range, is preferably an alcohol having 1 to 5 hydroxy groups, more preferably 2 to 5 hydroxy groups. When the number of hydroxy groups is 5 or less, the viscosity of the alkaline electrolyte decreases and the ionic conductivity increases.

  Examples of alcohols having 1 to 6 carbon atoms and 1 hydroxy group in the molecule include methanol, ethanol, 1-propanol, 1-butanol, 2-methyl-1-propanol, and 1-pentanol. 2-methyl-1-butanol, 3-methyl-1-butanol, 2,2-dimethyl-1-propanol, 2-propanol, 2-butanol, 2-methyl-2-propanol, 2-pentanol, 2- Methyl-2-butanol, 3-methyl-2-butanol, 3-pentanol, 3-hexanol, 2-methyl-3-pentanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2 -Methyl-1-pentanol, 4-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol 2,3-dimethyl-1-butanol, 2,2-dimethyl-1-butanol, 3,3-dimethyl-1-butanol, 2-hexanol, 2-methyl-2-pentanol, 4-methyl-2- Pentanol, 3-methyl-2-pentanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-2-butanol, cyclopentylmethanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methyl Cyclohexanol, and any combination thereof. Examples of alcohols having 1 to 6 carbon atoms and 2 to 3 hydroxy groups in the molecule include 1,2-ethanediol (ethylene glycol), 1,2-propanediol, 1, 3-propanediol, 1,2,3-propanetriol, and any combination thereof. Particularly preferred alcohols are ethanol, 1,2-ethanediol (ethylene glycol), and combinations thereof. In particular, 1,2-ethanediol (ethylene glycol) is most preferable because it is excellent in the effect of suppressing deterioration of the ceramic separator not only at normal temperature (eg, 30 ° C.) but also at high temperature (eg, 70 ° C.).

  The concentration of the alcohol in the electrolytic solution is not particularly limited as long as the deterioration of the ceramic separator can be reduced, but is preferably 0.1 to 20 mol / L, more preferably 0.1 to 10 mol / L. Within such a range, deterioration of the ceramic separator can be desirably reduced while maintaining good ionic conductivity of the electrolyte.

If desired, the electrolyte contains a metal corresponding to M ²⁺ and / or M ³⁺ in the general formula of layered double hydroxide: M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ^n- _{x / n} · mH ₂ O A metal compound containing an element may be dissolved. In this case, the metal compound is intentionally dissolved in the electrolytic solution, and is preferably dissolved before the alcohol is added to the electrolytic solution. The metal element only needs to be dissolved in the electrolyte solution in some form, and can typically be dissolved in the electrolyte solution in the form of metal ions, hydroxides and / or hydroxy complexes. For example, as ^the form in which Al is _{^{dissolved, Al 3+, Al (OH)}} 2+, Al (OH) 2 +, Al (OH) 3 0, Al (OH) 4 -, Al (OH) 5 2- etc. Can be mentioned. The metal compound preferably contains a metal element corresponding to M ³⁺ , and preferred examples of such a metal element include Al and Cr, and most preferably Al.

  Preferable examples of the metal compound containing Al include aluminum hydroxide, γ alumina, α alumina, boehmite, diaspore, hydrotalcite, and any combination thereof, more preferably aluminum hydroxide and / or γ alumina. And most preferably aluminum hydroxide. The concentration of Al in the electrolytic solution is preferably 0.001 mol / L or more, preferably 0.01 mol / L or more, more preferably 0.1 mol / L or more, still more preferably 1.0 mol / L or more, particularly preferably 2. 0 mol / L or more, particularly preferably more than 3.0 mol / L, most preferably 3.3 mol / L or more. Thus, it is preferable to intentionally dissolve a large amount of Al. For example, it is more preferable to dissolve a larger amount than Al contained in the ceramic separator. Therefore, the upper limit of the concentration of Al in the electrolytic solution is not particularly limited, and may reach the saturation solubility of the Al compound, but is, for example, 20 mol / L or less or 10 mol / L or less.

  The container contains at least a negative electrode and an alkaline electrolyte. As described above, the container 22 can also contain the positive electrode 12 and the positive electrode electrolyte 14 as in the nickel-zinc battery 10 shown in FIG. 1, but the positive electrode is used as the air electrode as in the zinc-air secondary battery 30 shown in FIG. 3A. When configured as 32, the air electrode 32 (positive electrode) does not need to be completely accommodated in the container 46, and is simply attached so as to close the opening 46a of the container 46 (for example, in the form of a lid). May be. In any case, the container preferably has a structure having liquid tightness and air tightness. The container is preferably a resin container, and the resin constituting the resin container is preferably a resin having resistance to an alkali metal hydroxide such as potassium hydroxide, more preferably a polyolefin resin and an ABS resin. More preferred is an ABS resin. It is preferable that a ceramic separator and / or a porous member be fixed to the container using a commercially available adhesive or by heat sealing.

Nickel-zinc battery According to a preferred embodiment of the present invention, a nickel-zinc secondary battery is provided. In FIG. 1, an example of the nickel zinc battery by this aspect is shown typically. The nickel zinc battery shown in FIG. 1 shows an initial state before charging, and corresponds to a discharged state. However, it goes without saying that the nickel-zinc battery of this embodiment may be configured in a fully charged state. As shown in FIG. 1, the nickel zinc battery 10 according to this embodiment includes a positive electrode 12, a positive electrode electrolyte 14, a negative electrode 16, a negative electrode electrolyte 18, and a ceramic separator 20 in a container 22. The positive electrode 12 includes nickel hydroxide and / or nickel oxyhydroxide. The positive electrode electrolyte 14 is an alkaline electrolyte containing an alkali metal hydroxide and alcohol, and the positive electrode 12 is immersed therein. The negative electrode 16 includes zinc and / or zinc oxide. The negative electrode electrolyte 18 is an alkaline electrolyte containing an alkali metal hydroxide, and the negative electrode 16 is immersed therein. The container 22 contains the positive electrode 12, the positive electrode electrolyte 14, the negative electrode 16, and the negative electrode electrolyte 18. The positive electrode 12 and the positive electrode electrolyte solution 14 are not necessarily separated from each other, and may be configured as a positive electrode mixture in which the positive electrode 12 and the positive electrode electrolyte solution 14 are mixed. Similarly, the negative electrode 16 and the negative electrode electrolyte 18 are not necessarily separated from each other, and may be configured as a negative electrode mixture in which the negative electrode 16 and the negative electrode electrolyte 18 are mixed. If desired, a positive electrode current collector 13 is provided in contact with the positive electrode 12. Further, if desired, a negative electrode current collector 17 is provided in contact with the negative electrode 16.

The separator 20 is provided in the container 22 so as to partition a positive electrode chamber 24 that accommodates the positive electrode 12 and the positive electrode electrolyte solution 14 and a negative electrode chamber 26 that accommodates the negative electrode 16 and the negative electrode electrolyte solution 18. The separator 20 has hydroxide ion conductivity but does not have water permeability. In other words, the fact that the separator 20 does not have water permeability means that the separator 20 has a high degree of denseness that does not allow water to pass through, and is not a porous film or other porous material having water permeability. Means. 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 28 may be attached to the separator 20 as shown in FIG. In any case, since the separator 20 has hydroxide ion conductivity, it is possible to efficiently move the required hydroxide ions between the positive electrode electrolyte 14 and the negative electrode electrolyte 18, and the positive electrode chamber 24 and the negative electrode. The charge / discharge reaction in the chamber 26 can be realized. The reaction at the time of charging in the positive electrode chamber 24 and the negative electrode chamber 26 is as shown below, and the discharge reaction is reversed.
-Positive electrode: Ni (OH) ₂ + OH ⁻ → NiOOH + H ₂ O + e ⁻
-Negative electrode: ZnO + H ₂ O + 2e ⁻ → Zn + 2OH ⁻

However, the negative electrode reaction is composed of the following two reactions.
-ZnO dissolution reaction: ZnO + H ₂ O + 2OH ⁻ → Zn (OH) ₄ ²⁻
-Zn precipitation reaction: Zn (OH) ₄ ^2- + 2e ⁻ → Zn + 4OH ⁻

  The nickel zinc battery 10 has a positive electrode-side surplus space 25 having a volume that allows an increase / decrease in the amount of water accompanying the positive electrode reaction during charge / discharge in the positive electrode chamber 24, and accompanies the negative electrode reaction during charge / discharge in the negative electrode chamber 26 It is preferable to have a negative electrode-side surplus space 27 having a volume that allows a decrease in the amount of moisture. This effectively prevents problems associated with the increase or decrease in the amount of moisture in the positive electrode chamber 24 and the negative electrode chamber 26 (for example, liquid leakage, deformation of the container due to changes in the container internal pressure, etc.), and further improves the reliability of the nickel zinc battery. Can be improved. That is, as can be seen from the above reaction formula, during charging, water increases in the positive electrode chamber 24 while water decreases in the negative electrode chamber 26. On the other hand, during discharge, water decreases in the positive electrode chamber 24 while water increases in the negative electrode chamber 26. In this respect, since most conventional separators have water permeability, water can freely pass through the separators. However, since the separator 20 used in this embodiment has a highly dense structure that does not have water permeability, water cannot freely pass through the separator 20, and the inside of the positive electrode chamber 24 and / or the negative electrode chamber accompanies charging / discharging. 26, the amount of the electrolyte may increase unilaterally and cause problems such as liquid leakage. Therefore, the positive electrode chamber 24 has a positive electrode-side surplus space 25 having a volume that allows an increase or decrease in the amount of water associated with the positive electrode reaction during charge / discharge, thereby increasing the positive electrolyte 14 during charging as shown in FIG. It can be made to function as a buffer that can cope with this. That is, as shown in FIG. 2, the positive electrode side excess space 25 functions as a buffer even after full charge, so that the increased amount of the positive electrode electrolyte solution 14 is reliably held in the positive electrode chamber 24 without overflowing. Can do. Similarly, the negative electrode chamber 26 has a negative electrode-side surplus space 27 having a volume that allows a decrease in the amount of water associated with the negative electrode reaction during charge / discharge, thereby functioning as a buffer that can cope with an increase in the negative electrode electrolyte 18 during discharge. Can be made.

The increase / decrease amount of the water | moisture content in the positive electrode chamber 24 and the negative electrode chamber 26 can be calculated based on the reaction formula mentioned above. As can be seen from the reaction formula described above, the amount of H ₂ O produced at the positive electrode 12 during charging corresponds to twice the amount of H ₂ O consumed at the negative electrode 16. Therefore, the volume of the positive electrode side surplus space 25 may be larger than that of the negative electrode side surplus space 27. In any case, the volume of the positive-side surplus space 25 can be generated not only from the amount of water increase expected in the positive electrode chamber 24 but also from the positive electrode 12 during overcharge or a gas such as air existing in the positive electrode chamber 24 in advance. It is preferable that the volume has a slight or some margin so that oxygen gas can be accommodated at an appropriate internal pressure. In this regard, it can be said that it is sufficient if the negative side surplus space 27 has the same volume as the positive side surplus space 25 as shown in FIG. It is desirable to provide a surplus space that exceeds the amount of water reduction. In any case, the negative electrode side surplus space 27 may be smaller than the positive electrode side surplus space 25 because the amount of water increases or decreases by about half of the amount in the positive electrode chamber 24.

  When the nickel-zinc battery 10 is constructed in a discharged state, the positive-side surplus space 25 has a volume that exceeds the amount of water expected to increase with the positive-electrode reaction during charging, and the positive-side surplus space 25 Is not filled with the positive electrode electrolyte 14 in advance, and the negative electrode side surplus space 27 has a volume exceeding the amount of water expected to decrease with the negative electrode reaction during charging, and the negative electrode side surplus space 27 Is preferably filled in advance with an amount of the negative electrode electrolyte 18 that is expected to decrease. On the other hand, when the nickel-zinc battery 10 is constructed in a fully charged state, the positive-side surplus space 25 has a volume exceeding the amount of water expected to decrease with the positive-electrode reaction during discharge, and the positive-side surplus The space 25 is preliminarily filled with an amount of the positive electrode electrolyte 14 that is expected to decrease, and the negative surplus space 27 exceeds the amount of water that is expected to increase with the negative electrode reaction during discharge. It is preferable that the negative electrode side excess space 27 is not filled with the negative electrode electrolyte 18 in advance.

  It is preferable that the positive electrode side surplus space 25 is not filled with the positive electrode 12 and / or the negative electrode side surplus space 27 is not filled with the negative electrode 16, and the positive electrode side surplus space 25 and the negative electrode side surplus space 27 are filled with the positive electrode 12. More preferably, the negative electrode 16 and the negative electrode 16 are not filled. In these surplus spaces, electrolyte can be depleted due to a decrease in the amount of water during charging and discharging. That is, even if these surplus spaces are filled with the positive electrode 12 and the negative electrode 16, they cannot be sufficiently involved in the charge / discharge reaction, which is inefficient. Therefore, the positive electrode 12 and the negative electrode 16 can be more efficiently and stably involved in the battery reaction without waste by not filling the positive electrode 12 and the negative electrode 16 in the positive electrode side excess space 25 and the negative electrode side excess space 27, respectively.

  The separator 20 is a member having hydroxide ion conductivity but not water permeability, and typically has a plate shape, a film shape, or a layer shape. The separator 20 is provided in the container 22 and partitions a positive electrode chamber 24 that accommodates the positive electrode 12 and the positive electrode electrolyte solution 14 and a negative electrode chamber 26 that accommodates the negative electrode 16 and the negative electrode electrolyte solution 18. Further, as described above, 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 positive electrode 12 and the separator 20 and / or between the negative electrode 16 and the separator 20, Even when the electrolyte is decreased, the electrolyte may be held in the reaction portion of the positive electrode and / or the negative electrode. Preferable examples of the water absorbent resin or the liquid retaining resin include polyolefin resins.

  The positive electrode 12 comprises nickel hydroxide and / or nickel oxyhydroxide. For example, nickel hydroxide may be used as the positive electrode 12 when the nickel-zinc battery is configured in the end-of-discharge state as shown in FIG. 1, and positive electrode when configured in the fully charged state as shown in FIG. 12 may be nickel oxyhydroxide. Nickel hydroxide and nickel oxyhydroxide (hereinafter referred to as nickel hydroxide or the like) are positive electrode active materials generally used in nickel zinc batteries, and are typically in the form of particles. In nickel hydroxide or the like, different elements other than nickel may be dissolved in the crystal lattice, thereby improving the charging efficiency at high temperatures. Examples of such different elements include zinc and cobalt. In addition, nickel hydroxide or the like may be mixed with a cobalt-based component, and examples of such a cobalt-based component include granular materials of metallic cobalt and cobalt oxide (for example, cobalt monoxide). . Furthermore, the surface of particles such as nickel hydroxide (which may contain different elements in solid solution) may be coated with a cobalt compound. Examples of such cobalt compounds include cobalt monoxide, divalent α-type. Examples include cobalt hydroxide, divalent β-type cobalt hydroxide, compounds of higher-order cobalt exceeding 2 valences, and any combination thereof.

  The positive electrode 12 may further contain an additional element in addition to the nickel hydroxide compound and the different element that can be dissolved therein. Examples of such additional elements include scandium (Sc), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), Gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), elpium (Er), thulium (Tm), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), Examples include rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au) and mercury (Hg), and any combination thereof. The inclusion form of the additional element is not particularly limited, and may be contained in the form of a simple metal or a metal compound (for example, oxide, hydroxide, halide, and carbonate). When adding a single metal or a metal compound containing an additional element, the addition amount is preferably 0.5 to 20 parts by weight, more preferably 2 to 5 parts by weight, with respect to 100 parts by weight of the nickel hydroxide compound. It is.

  The positive electrode 12 may be configured as a positive electrode mixture by further including an electrolytic solution or the like. The positive electrode mixture can include nickel hydroxide compound particles, an electrolytic solution, and optionally a conductive material such as carbon particles, a binder, and the like.

  A positive electrode current collector 13 is preferably provided in contact with the positive electrode 12. As shown in FIG. 1, the positive electrode current collector 13 may penetrate the container 22 and extend to the outside thereof to constitute the positive electrode terminal itself, or the positive electrode terminal provided separately may be provided in the container 22. Or it is good also as a structure connected outside. A preferable example of the positive electrode current collector 13 is a nickel porous substrate such as a foamed nickel plate. In this case, for example, a positive electrode plate made of positive electrode 12 / positive electrode current collector 13 is preferably prepared by uniformly applying a paste containing an electrode active material such as nickel hydroxide on a nickel porous substrate and drying the paste. Can do. At that time, it is also preferable to press the dried positive electrode plate (that is, positive electrode 12 / positive electrode current collector 13) to prevent the electrode active material from falling off and to improve the electrode density.

  The negative electrode 16 includes zinc and / or zinc oxide. Zinc may be contained in any form of zinc metal, zinc compound and zinc alloy as long as it has an electrochemical activity suitable for the negative electrode. Preferable examples of the negative electrode material include zinc oxide, zinc metal, calcium zincate and the like, and a mixture of zinc metal and zinc oxide is more preferable. The negative electrode 16 may be formed in a gel form, or may be mixed with an electrolytic solution to form a negative electrode mixture. For example, a gelled negative electrode can be easily obtained by adding an electrolytic solution and a thickener to the negative electrode active material. Examples of the thickener include polyvinyl alcohol, polyacrylate, CMC, alginic acid and the like. Polyacrylic acid is preferable because it has excellent chemical resistance to strong alkali.

  As the zinc alloy, a zinc alloy containing no mercury and lead, which is known as a non-free zinc alloy, can be used. For example, a zinc alloy containing 0.01 to 0.06 mass% indium, 0.005 to 0.02 mass% bismuth, and 0.0035 to 0.015 mass% aluminum has an effect of suppressing hydrogen gas generation. Therefore, it is preferable. In particular, indium and bismuth are advantageous in improving the discharge performance. The use of the zinc alloy for the negative electrode can improve the safety by suppressing the generation of hydrogen gas by slowing the self-dissolution rate in the alkaline electrolyte.

  The shape of the negative electrode material is not particularly limited, but it is preferably a powder form, which increases the surface area and can cope with a large current discharge. In the case of a zinc alloy, the preferable average particle diameter of the negative electrode material is in the range of 90 to 210 μm. If the average particle diameter is within this range, the surface area is large, so that it is suitable for dealing with a large current discharge. Easy to mix evenly and easy to handle during battery assembly.

  A negative electrode current collector 17 is preferably provided in contact with the negative electrode 16. As shown in FIG. 1, the negative electrode current collector 17 penetrates the container 22 and extends to the outside thereof, and the negative electrode terminal itself may be configured. Or it is good also as a structure connected outside. A preferred example of the negative electrode current collector 17 is copper punching metal. In this case, for example, a mixture containing zinc oxide powder and / or zinc powder and, optionally, a binder (for example, polytetrafluoroethylene particles) is applied onto copper punching metal, and the negative electrode 16 / negative electrode current collector 17 is used. A negative electrode plate can be preferably produced. At that time, it is also preferable to press the dried negative electrode plate (that is, negative electrode 16 / negative electrode current collector 17) to prevent the electrode active material from falling off and to improve the electrode density.

Zinc Air Secondary Battery According to another preferred embodiment of the present invention, a zinc air secondary battery is provided. 3A and 3B schematically show an example of the zinc-air secondary battery according to this embodiment. As shown in FIGS. 3A and 3B, the zinc-air secondary battery 30 according to this embodiment includes an air electrode 32, a negative electrode 34, an alkaline electrolyte 36, a ceramic separator 40, a container 46, and a third electrode 38 as desired. Become. The air electrode 32 functions as a positive electrode. The negative electrode 34 includes zinc, a zinc alloy, and / or a zinc compound. The electrolytic solution 36 is an aqueous electrolytic solution in which the negative electrode 34 is immersed, and includes an alkali metal hydroxide and alcohol. The container 46 has an opening 46 a and accommodates the negative electrode 34, the electrolytic solution 36, and the third electrode 38. The separator 40 closes the opening 46a so as to be in contact with the electrolyte solution 36 to form a container 46 and a negative electrode side sealed space, thereby isolating the air electrode 32 and the electrolyte solution 36 so that hydroxide ions can be conducted. If desired, a positive electrode current collector 42 may be provided in contact with the air electrode 32. Further, if desired, the negative electrode current collector 44 may be provided in contact with the negative electrode 34, and in that case, the negative electrode current collector 44 can also be accommodated in the container 46.

  As described above, the separator 40 is preferably 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. The separator 40 closes the opening 46a so as to be in contact with the electrolytic solution 36 to form the container 46 and the negative electrode side sealed space, thereby isolating the air electrode 32 and the electrolytic solution 36 so that hydroxide ions can be conducted. The porous substrate 48 may be provided on one side or both sides of the separator 40, preferably on one side (electrolyte side). Further, even when the water retention member made of a water absorbent resin such as a nonwoven fabric or a liquid retention resin is disposed between the negative electrode 34 and the separator 40 and the electrolyte solution 36 is reduced, the electrolyte solution 36 is replaced with the negative electrode 34 and the separator 40. It is good also as a structure hold | maintained so that contact is always possible. This water retaining member may also serve as the water retaining member for the third electrode 38 described above, or a water retaining member for the separator 40 may be used separately. 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 air electrode 32 may be a known air electrode used in a metal air battery such as a zinc-air battery, and is not particularly limited. The air electrode 32 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 32 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. Although content of the air electrode catalyst in the air electrode 12 is not specifically limited, 5-70 volume% is preferable with respect to the total amount of the air electrode 12, More preferably, it is 5-60 volume%, More preferably, it is 5-50 volume. %.

  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 40 (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 other shapes, but is used in a form that provides a continuous phase in the thickness direction (that is, an electron conductive phase) in the air electrode 32. 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). Although content of the electron conductive material in the air electrode 32 is not specifically limited, 10-80 volume% is preferable with respect to the total amount of the air electrode 32, More preferably, it is 15-80 volume%, More preferably, it is 20-80. % By volume.

The air electrode 32 may further contain a hydroxide ion conductive material as an optional component. In particular, when the separator 40 is made of a hydroxide ion conductive inorganic solid electrolyte, which is a dense ceramic, on the separator 40 (with an intermediate layer having hydroxide ion conductivity if desired), conventionally. By forming the air electrode 32 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 40 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 32, 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 40 (or the intermediate layer, if applicable) and the air electrode 32 but also in the air electrode 32, and exchange of hydroxide ions contributing 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, even in the form of the coating film, the ion conductive material is not dense and has open pores, and the interface from the outer surface of the air electrode 32 to the separator 40 (or an 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 32 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 32. 10 to 80% by volume.

  The formation of the air electrode 32 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 32, and the air electrode 32 side of the air electrode 32 / current collector laminated sheet is pressure-bonded to the separator 40 (or an intermediate layer if applicable). May be. Alternatively, an air electrode catalyst, an electron conductive material, and optionally 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 32. It may be formed. Therefore, the air electrode 32 may contain a binder. The binder may be a thermoplastic resin or a thermosetting resin and is not particularly limited.

  The air electrode 32 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.

  A positive electrode current collector 42 having air permeability is preferably provided on the side of the air electrode 32 opposite to the separator 40. In this case, the positive electrode current collector 42 preferably has air permeability so that air is supplied to the air electrode 32. Preferable examples of the positive electrode current collector 42 include metal plates or metal meshes such as stainless steel, copper and nickel, carbon paper, carbon cloth, and electron conductive oxide. Stainless steel is used in terms of corrosion resistance and air permeability. A wire mesh is particularly preferred.

  An intermediate layer may be provided between the separator 40 and the air electrode 32. The intermediate layer is not particularly limited as long as it improves the adhesion between the separator 40 and the air electrode 32 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, it is easy to improve the adhesion between the separator 40 and the air electrode 32, and the battery resistance (especially the interface resistance between the air electrode and the separator) is more effectively reduced in the zinc-air secondary battery. Can do.

  The negative electrode 34 includes zinc, a zinc alloy, and / or a zinc compound that functions as a negative electrode active material. The negative electrode 34 may have any shape or form such as a particle shape, a plate shape, or a gel shape, but a particle shape or a gel shape is preferable in terms 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 having a particle size of 100 to 300 μm, an alkaline electrolyte and a thickener (gelling agent) mixed and stirred to form a gel 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.

  A negative electrode current collector 44 is preferably provided in contact with the negative electrode 34. As shown in FIGS. 3A and 3B, the negative electrode current collector 44 may penetrate the container 46 and extend to the outside thereof to constitute the negative electrode terminal itself, or the negative electrode terminal provided separately may It is good also as a structure connected within 46 or outside. Preferable examples of the negative electrode current collector include a metal plate or metal mesh such as stainless steel, copper (for example, copper punching metal), nickel, carbon paper, and an oxide conductor. For example, a negative electrode plate comprising a negative electrode 34 / a negative electrode current collector 44 by applying a mixture containing zinc oxide powder and / or zinc powder and optionally a binder (for example, polytetrafluoroethylene particles) on copper punching metal. Can be preferably produced. At that time, it is also preferable to press the dried negative electrode plate (that is, the negative electrode 34 / negative electrode current collector 44) to prevent the electrode active material from falling off and to improve the electrode density.

If desired, the third electrode 38 may be provided so as to be in contact with the electrolytic solution 36 but not to be in contact with the negative electrode 34. In this case, the third electrode 38 is connected to the air electrode 32 through an external circuit. With this configuration, hydrogen gas that can be generated from the negative electrode 34 by a side reaction is brought into contact with the third electrode 38, and the following reaction is performed:
Third electrode: H ₂ + 2OH ⁻ → 2H ₂ O + 2e ⁻
Positive electrode discharge: O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻
Can be returned to the water. In other words, the hydrogen gas generated at the negative electrode 34 is absorbed by the third electrode 38 and self-discharge occurs. 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 38 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 32 through an external circuit. However, it is desirable that the oxygen overvoltage is larger than that of the air electrode 32. It is also desirable that the third electrode 38 does not participate in normal charge / discharge reactions. The third electrode 38 preferably comprises platinum and / or a carbon material, more preferably 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 the 3rd electrode 38 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 38 (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 38 may have any shape, but preferred examples include wire (eg, wire), punching metal, mesh, foam metal, and any combination thereof. The material of the current collector for the third electrode 38 may be the same material as that of the third electrode 38, or may be a metal (for example, nickel), an alloy, or other conductive material.

  The third electrode 38 is in contact with the electrolytic solution 36, but it is desirable that the third electrode 38 be disposed at a place not directly related to the normal charge / discharge reaction. In this case, even when the electrolyte solution is reduced by disposing a water-holding member made of a water-absorbing resin such as a nonwoven fabric or a liquid-retaining resin so as to be in contact with the third electrode 38 in the negative electrode side sealed space Is preferably configured to be held in contact with the third electrode 38 at all times. 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 38 does not necessarily need to be impregnated with a large amount of electrolytic solution 36, and can exhibit a desired function even when wet with a small amount or a small amount of electrolytic solution 36. As long as the water retaining member has.

LDH separator with porous substrate As described above, the inorganic solid electrolyte body constituting the separator in the present invention can be in the form of a film or a layer. In this case, it is preferable to use a separator with a porous substrate, in which a film-like or layered inorganic solid electrolyte is formed on or in the porous substrate. A particularly preferred separator with a porous substrate comprises a porous substrate and a separator layer formed on and / or in the porous substrate, and the separator layer is layered 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. 4, the separator layer 20 is preferably formed as an LDH dense film on the porous substrate 28. In this case, needless to say, LDH may also be formed on the surface of the porous substrate 28 and in the pores in the vicinity thereof as shown in FIG. 4 due to the nature of the porous substrate 28. Alternatively, as shown in FIG. 5, LDH is densely formed in the porous substrate 28 (for example, the surface of the porous substrate 28 and the pores in the vicinity thereof), whereby at least one of the porous substrates 28 is formed. The part may constitute separator layer 20 '. In this regard, the embodiment shown in FIG. 5 has a configuration in which the membrane equivalent portion of the separator layer 20 of the embodiment shown in FIG. 4 is removed, but is not limited to this, and is parallel to the surface of the porous substrate 28. 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 capable of forming an LDH-containing separator layer on and / or in the porous substrate, and the material and the 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, aluminum nitride, silicon nitride, and any combination thereof. More preferred are alumina, zirconia, titania, and any combination thereof, particularly preferred are alumina and zirconia, and most preferred is alumina. In particular, when an alumina porous substrate is used together with an electrolyte solution in which alcohol or Al is dissolved, an Al elution suppression effect from the alumina porous substrate can be expected, and deterioration of the porous substrate can also be suppressed. . 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. Preferred examples of the polymer material include polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, 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. It is -0.75 micrometer, Most preferably, it is 0.001-0.5 micrometer. 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 the electron microscope image of the surface of the porous substrate. The magnification of the electron microscope image used for this measurement is 20000 times or more, and all obtained pore diameters are arranged in the order of size, and the upper 15 points and the lower 15 points from the average value. The average pore size can be obtained by calculating the average value of minutes. 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%, and 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 20 is formed on the porous substrate 28 as shown in FIG. 4, the separator layer 20 is in the form of an LDH dense film, which is typically made from LDH. Become. Further, when the separator layer 20 ′ is formed in the porous substrate 28 as shown in FIG. 5, the surface of the porous substrate 28 (typically the surface of the porous substrate 28 and the vicinity thereof). Since the LDH is densely formed in the pores), the separator layer 20 ′ is typically composed of at least a part of the porous substrate 28 and LDH. The separator layer 20 ′ shown in FIG. 5 can be obtained by removing a portion corresponding to the film in the separator layer 20 shown in FIG. 4 by a known method such as polishing or cutting.

  The separator layer preferably does not have 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 are substantially the same as the surface of the porous substrate (substrate surface). It is preferably oriented in a direction that intersects perpendicularly or diagonally. As shown in FIG. 4, this embodiment is a particularly preferable and feasible embodiment when the separator layer 20 is formed as an LDH dense film on the porous substrate 28. As shown in FIG. LDH is densely formed in the porous substrate 28 (typically in the surface of the porous substrate 28 and in the pores in the vicinity thereof), whereby at least a part of the porous substrate 28 forms the separator layer 20 ′. 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. 6, but the above-mentioned substantially vertical or oblique orientation is obtained by using an LDH-containing separator layer (for example, an LDH dense film). This is a very advantageous property. 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 substantially 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 a substantially vertical direction in the LDH-containing separator layer (typically an 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 substantially vertical direction (that is, a vertical direction or an oblique direction similar thereto, preferably a vertical direction) with respect to the separator layer. 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. By being oriented in a direction substantially perpendicular to the layer, the peak of the (003) plane is not substantially detected or detected 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 a substantially vertical direction, the LDH layered structure also faces in a substantially vertical direction. As a result, when the separator layer surface is measured by an X-ray diffraction method, the (00l) plane (l is 3 and 6). This is because the peak of) does not appear or becomes difficult to appear. In particular, the peak of the (003) plane tends to be stronger than the peak of the (006) plane when it exists, so it is easier to evaluate the presence / absence of orientation in the substantially vertical direction than the peak of the (006) plane I can say that. 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, further 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 above-mentioned LDH separator with a porous substrate 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, aluminum nitride, silicon nitride, and any combination thereof. More preferred are alumina, zirconia, titania, and any combination thereof, particularly preferred are alumina and zirconia, and most preferred is 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, LDH is substantially perpendicular to or close to the porous substrate (that is, the LDH plate-like particles have their plate surfaces intersecting the surface (substrate surface) of the porous substrate substantially perpendicularly or obliquely. It is preferable to adopt a configuration or arrangement in which growth is performed in such a 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 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 (urea / NO ₃ ⁻ ) of urea to nitrate ions (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 performed at 60 to 150 ° C. in a closed container, more preferably 65 to 120 ° C., still more 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, the porous substrate is preferably taken out from the sealed container and washed with ion exchange 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 oriented in a substantially vertical direction advantageous for conduction. Therefore, it can be said that it is extremely suitable for a nickel-zinc 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.

Method for Producing LDH Dense Plate A preferred form of the plate-like inorganic solid electrolyte is a layered double hydroxide (LDH) dense body. Although the LDH dense body may be produced by any method, an embodiment of a preferable production method will be described below. This production method is carried out by forming and firing LDH raw material powder typified by hydrotalcite to form an oxide fired body, regenerating it into a layered double hydroxide, and then removing excess water. . According to this method, a high-quality layered double hydroxide dense body having a relative density of 88% or more can be provided and produced easily and stably.

(1) as prepared raw material powder of the raw material powder, 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, M ³⁺ is a trivalent ^{cation, a n-n-valent} anion, n represents an integer of 1 or more, x is a layered double hydroxide represented by a is) 0.1 to 0.4 powder Prepare. 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- may be any anion, preferred examples OH ^- and _CO ^{3 2-} and the like. Accordingly, the general formula is at least ^{M 2+} is ^{Mg 2+,} include ^{M 3+} is ^{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. Such a raw material powder may be a commercially available layered double hydroxide product, or may be a raw material produced by a known method such as a liquid phase synthesis method using nitrate or chloride. The particle size of the raw material powder is not limited as long as a desired layered double hydroxide dense body is obtained, but the volume-based D50 average particle size is preferably 0.1 to 1.0 μm, more preferably 0.3. ~ 0.8 μm. This is because if the particle size of the raw material powder is too fine, the powder tends to aggregate, and there is a high possibility that pores will remain during molding, and if it is too large, the moldability will deteriorate.

If desired, the raw material powder may be calcined to obtain an oxide powder. The calcining temperature at this time is somewhat different depending on the constituent M ²⁺ and M ³⁺ , but is preferably 500 ° C. or lower, more preferably 380 to 460 ° C., in a region where the raw material particle size does not change significantly.

(2) Production of molded body A raw material powder is molded to obtain a molded body. In this molding, a molded body after molding and before firing (hereinafter referred to as a molded body) is 43 to 65%, more preferably 45 to 60%, and even more preferably 47% to 58%. For example, it is preferably performed by pressure molding. The relative density of the molded body is calculated by calculating the density from the size and weight of the molded body and dividing by the theoretical density, but the weight of the molded body is affected by the adsorbed moisture. It is preferable to measure the relative density after the molded body using the raw material powder stored for 24 hours or more in a desiccator having a room temperature and a relative humidity of 20% or less, or after storing the molded body under the above conditions. However, when the raw material powder is calcined to form an oxide powder, the relative density of the compact is preferably 26 to 40%, more preferably 29 to 36%. The relative density in the case of using oxide powder is based on the assumption that each metal element constituting the layered double hydroxide has changed to oxide by calcining, and the converted density obtained as a mixture of each oxide is the denominator. As sought. The pressure forming described as an example may be performed by a uniaxial press of a mold, or may be performed by cold isostatic pressing (CIP). In the case of using cold isostatic pressing (CIP), it is preferable to put the raw material powder in a rubber container and vacuum-seal it or use a preformed one. In addition, you may shape | mold by well-known methods, such as slip casting and extrusion molding, and it does not specifically limit about a shaping | molding method. However, when the raw material powder is calcined to obtain an oxide powder, it is limited to the dry molding method. The relative density of these compacts not only affects the strength of the resulting compact, but also affects the degree of orientation of the layered double hydroxides that usually have a plate shape. The relative density is preferably set within the above range.

(3) Firing step The molded body obtained in the above step is fired to obtain an oxide fired body. This firing is preferably performed so that the oxide fired body has a weight of 57 to 65% of the weight of the compact and / or a volume of 70 to 76% or less of the volume of the compact. When it is 57% or more of the weight of the molded product, it is difficult to generate a heterogeneous phase that cannot be regenerated during regeneration to a layered double hydroxide in the subsequent step, and when it is 65% or less, sufficient firing is performed in the subsequent step. Densify. Further, when it is 70% or more of the volume of the molded body, it is difficult to generate a heterogeneous phase when regenerating into a layered double hydroxide in a subsequent process, and cracks are hardly generated. Done and fully densified in later steps. When the raw material powder is calcined to obtain an oxide powder, it is preferable to obtain an oxide fired body of 85 to 95% of the weight of the compact and / or 90% or more of the volume of the compact. Regardless of whether or not the raw material powder is calcined, the firing is preferably performed so that the oxide fired body has a relative density of 20 to 40% in terms of oxide, more preferably 20 to 35. %, More preferably 20-30%. Here, the relative density in terms of oxide means that each metal element constituting the layered double hydroxide is changed to an oxide by firing, and the converted density obtained as a mixture of each oxide is used as the denominator. It is the obtained relative density. A preferable baking temperature for obtaining the oxide fired body is 400 to 850 ° C, more preferably 700 to 800 ° C. It is preferable to hold | maintain for 1 hour or more with the calcination temperature in this range, and more preferable holding time is 3 to 10 hours. Further, in order to prevent moisture and carbon dioxide from being released due to rapid temperature rise and cracking the molded body, the temperature rise for reaching the firing temperature is preferably performed at a rate of 100 ° C./h or less. Preferably it is 5-75 degreeC / h, More preferably, it is 10-50 degreeC / h. Therefore, it is preferable to secure a total firing time from temperature increase to temperature decrease (100 ° C. or lower) of 20 hours or more, more preferably 30 to 70 hours, and further preferably 35 to 65 hours.

(4) Regeneration step to layered double hydroxide The oxide fired body obtained in the above step is held in or directly above the aqueous solution containing the n-valent anion (A ⁿ⁻ ) and layered double hydroxide. It regenerates into a product, thereby obtaining a layered double hydroxide solidified body rich in moisture. That is, the layered double hydroxide solidified body obtained by this production method inevitably contains excess moisture. The anion contained in the aqueous solution may be the same kind of anion as that contained in the raw material powder, or may be a different kind of anion. It is preferable that the oxide fired body is held in an aqueous solution or immediately above the aqueous solution by a hydrothermal synthesis method in a sealed container, and an example of such a sealed container is a sealed container made of Teflon (registered trademark). More preferably, it is a closed container provided with a jacket made of stainless steel or the like on the outside thereof. The layered double hydroxide is preferably formed by maintaining the oxide fired body at 20 ° C. or more and less than 200 ° C. so that at least one surface of the oxide fired body is in contact with the aqueous solution, and a more preferable temperature is 50 to 180. And a more preferable temperature is 100 to 150 ° C. It is preferable that the oxide sintered body is maintained at such a layered double hydroxide formation temperature for 1 hour or more, more preferably 2 to 50 hours, and further preferably 5 to 20 hours. With such a holding time, it is possible to avoid or reduce the occurrence of a heterogeneous phase by sufficiently regenerating the layered double hydroxide. The holding time is not particularly problematic if it is too long, but it may be set in a timely manner with emphasis on efficiency.

  When carbon dioxide (carbonate ion) in the air is assumed as an anion species of an aqueous solution containing an n-valent anion used for regeneration into a layered double hydroxide, ion-exchanged water can be used. In the hydrothermal treatment in the sealed container, the fired oxide body may be submerged in the aqueous solution, or the treatment may be performed in a state where at least one surface is in contact with the aqueous solution using a jig. When the treatment is performed in a state where at least one surface is in contact with the aqueous solution, the amount of excess water is small compared to complete submergence, so that the subsequent steps may be completed in a short time. However, if the amount of the aqueous solution is too small, cracks are likely to occur. Therefore, it is preferable to use moisture equal to or greater than the weight of the fired body.

(5) Dehydration process Excess water is removed from the water-rich layered double hydroxide solidified product obtained in the above process. Thus, the layered double hydroxide dense body of the present invention is obtained. The step of removing excess water is preferably performed in an environment of 300 ° C. or lower and an estimated relative humidity of 25% or higher at the maximum temperature of the removal step. In order to prevent rapid evaporation of moisture from the layered double hydroxide solidified body, when dehydrating at a temperature higher than room temperature, it should be re-enclosed in the sealed container used in the regeneration process to the layered double hydroxide. preferable. The preferable temperature in that case is 50-250 degreeC, More preferably, it is 100-200 degreeC. Moreover, the more preferable relative humidity at the time of spin-drying | dehydration is 25 to 70%, More preferably, it is 40 to 60%. Dehydration may be performed at room temperature, and there is no problem as long as the relative humidity is within a range of 40 to 70% in a normal indoor environment.

  The present invention is more specifically described by the following examples.

Example 1 : Production and evaluation of LDH dense body (1) Production of LDH dense body As raw material powder, hydrotalcite powder (DHT-4H, manufactured by Kyowa Chemical Industry Co., Ltd.), which is a commercially available layered double hydroxide, is prepared. did. The composition of this raw material powder was Mg ²⁺ _0.68 Al ³⁺ _0.32 (OH) ₂ CO ₃ ^{2 −} _0.16 · mH ₂ O. The raw material powder was filled into a 16 mm diameter mold and uniaxial press molding was performed at a molding pressure of 500 kgf · cm ² to obtain a molded body having a relative density of 53% and a thickness of about 2 mm. The relative density was measured on a molded article stored at room temperature and a relative humidity of 20% or less for 24 hours. The obtained molded body was fired in an alumina sheath. This firing is performed at a rate of 100 ° C./h or less to prevent moisture and carbon dioxide from being released due to a sudden rise in temperature, and when the temperature reaches a maximum temperature of 750 ° C., 5 After holding for a period of time, cooling was performed. The total firing time from the temperature increase to the temperature decrease (100 ° C. or less) was 62 hours, and the weight, volume and relative density of the obtained sintered body were 59% by weight, 72% by volume and 23%, respectively. It was. The “weight” and “volume” are relative values (%) calculated with the compact before firing as 100%, and the “relative density” is the constituent metal elements of hydrotalcite, Mg and Al. It is a relative density in terms of oxide obtained using the theoretical density calculated as an oxide. The fired body thus obtained was sealed in a sealed container made of Teflon (registered trademark) with a stainless steel jacket on the outside together with ion-exchanged water in the atmosphere, and kept at 100 ° C. for 5 hours (regeneration conditions (temperature and its temperature). The sample was obtained by performing a hydrothermal treatment with the retention time at (5). Since the sample cooled to room temperature contained excess moisture, the moisture on the surface was gently wiped off with a filter paper or the like. The sample thus obtained was naturally dehydrated (dried) in a room at 25 ° C. and a relative humidity of about 50% to obtain an LDH dense sample.

(2) Measurement of relative density The density was calculated by calculating the density from the size and weight of the LDH dense body sample, and dividing this density by the theoretical density, and it was 91%. In calculating the theoretical density, JCPDS card No. 1 was used as the theoretical density of Mg / Al = 2 hydrotalcite. 2.09 g / cm ³ described in 70-2151 was used.

(3) Determination of cracks When the LDH dense body sample was observed with the naked eye, no cracks were observed.

(4) Identification of crystal phase The crystal phase of the LDH dense body sample was measured with an X-ray diffractometer (D8 ADVANCE, manufactured by Bulker AXS) under the measurement conditions of voltage: 40 kV, current value: 40 mA, measurement range: 5-70 °. JCPDS card NO. It was identified using the hydrotalcite diffraction peak described in 35-0965. As a result, only peaks due to hydrotalcite were observed.

Example 2 : Alkali resistance test of LDH dense bodies in various electrolytic solutions LDH dense bodies were immersed in various alcohol-containing / non-containing electrolytic solutions (KOH aqueous solution) to determine alkali resistance (particularly, whether or not Al was eluted) as follows: I investigated. Further, when the composition of the LDH dense body sample prepared in Example 1 was analyzed by energy dispersive X-ray analysis (EDX) prior to immersion in the electrolytic solution, the Al / Mg ratio shown in Table 1 was obtained. It was.

  KOH powder and ethylene glycol or ethanol were added to ion exchange water and stirred to prepare electrolyte samples 1 to 5. For comparison, an electrolytic solution sample 5 was prepared in the same manner as above except that no alcohol was added. As a result of ICP analysis, each of the alcohol-added KOH aqueous solutions obtained had a KOH concentration of 9M, and the alcohol concentration was as shown in Table 1. The LDH dense body produced in Example 1 was immersed in each of the electrolyte samples 1 to 5 thus obtained at 30 ° C. for 1 week. The dense LDH after immersion for 1 week was taken out and the composition was analyzed by energy dispersive X-ray analysis (EDX). As a result, the Al / Mg ratio of the LDH dense body after immersion was as shown in Table 1. From the results shown in Table 1, by adding alcohol to the electrolyte (KOH aqueous solution), the change in the Al / Mg ratio of the LDH dense body is significantly suppressed (that is, the elution of Al from the LDH dense body is significantly reduced). As a result, it can be seen that the alkali resistance of LDH is significantly improved.

Example 3 : 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.

  With respect to the obtained porous substrate, the porosity on 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 using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL) at an acceleration voltage of 10 to 20 kV, and an electron microscope on the surface of the porous substrate ( 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. 7 shows an SEM image of the porous substrate surface.

  Moreover, it was about 0.1 micrometer when the average hole diameter of the porous base material was measured. 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 a raw material aqueous 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 membrane sample Membrane sample was measured with X-ray diffractometer (RINT TTR III manufactured by Rigaku Corporation) under the measurement conditions of voltage: 50 kV, current value: 300 mA, measurement range: 10-70 °. As a result, the XRD profile shown in FIG. 8 was obtained. About the obtained XRD profile, JCPDS card NO. It 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. 8, a peak (a peak marked with a circle 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 at an acceleration voltage of 10 to 20 kV using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL). FIG. 9 shows an SEM image (secondary electron image) of the surface microstructure of the obtained film sample.

  Further, 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 at an acceleration voltage of 10 to 20 kV using a scanning electron microscope (SEM). 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 using a scanning electron microscope (SEM, JSM-6610LV, manufactured by JEOL) at an acceleration voltage of 10 to 20 kV, and 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.

  Further, 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. 11A, the composite material sample 120 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 122 provided with the opening 122a was adhered, and the obtained laminate was adhered between two acrylic containers 124 and 126. The bottom of the acrylic container 124 disposed on the silicon rubber 122 side is pulled out, whereby the silicon rubber 122 is bonded to the acrylic container 124 with the opening 122a open. On the other hand, the acrylic container 126 disposed on the porous substrate side of the composite material sample 120 has a bottom, and ion-exchanged water 128 is contained in the container 126. That is, by assembling the components upside down after assembly, the constituent members are arranged so that the ion exchange water 128 is in contact with the porous substrate side of the composite material sample 120. After assembling these components, the total weight was measured. Needless to say, the container 126 has a closed vent hole (not shown) and is opened after being turned upside down. The assembly was placed upside down as shown in FIG. 11B and held at 25 ° C. for 1 week, and then the total weight was measured again. At this time, when water droplets were attached to the inner side surface of the acrylic container 124, 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. 12A and 12B, an acrylic container 130 without a lid and an alumina jig 132 having a shape and size that can function as a lid for the acrylic container 130 were prepared. The acrylic container 130 is formed with a gas supply port 130a for supplying gas therein. The alumina jig 132 is formed with an opening 132a having a diameter of 5 mm, and a depression 132b for placing a film sample is formed along the outer periphery of the opening 132a. An epoxy adhesive 134 was applied to the depression 132 b of the alumina jig 132, and the film sample 136 b side of the composite material sample 136 was placed in the depression 132 b and adhered to the alumina jig 132 in an air-tight and liquid-tight manner. Then, the alumina jig 132 to which the composite material sample 136 is bonded is adhered to the upper end of the acrylic container 130 in a gas-tight and liquid-tight manner using a silicone adhesive 138 so as to completely close the open portion of the acrylic container 130. A measurement sealed container 140 was obtained. The measurement sealed container 140 was placed in a water tank 142, and the gas supply port 130 a of the acrylic container 130 was connected to a pressure gauge 144 and a flow meter 146 so that helium gas could be supplied into the acrylic container 130. Water 143 was put into the water tank 142 and the measurement sealed container 140 was completely submerged. At this time, the inside of the measurement sealed container 140 is sufficiently airtight and liquid tight, and the membrane sample 136b side of the composite material sample 136 is exposed to the internal space of the measurement sealed container 140, while the composite material sample The porous substrate 136 a side of 136 is in contact with the water in the water tank 142. In this state, helium gas was introduced into the measurement sealed container 140 into the acrylic container 130 via the gas supply port 130a. The pressure gauge 144 and the flow meter 146 are controlled so that the differential pressure inside and outside the membrane sample 136a 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 were generated in the water from the composite material sample 136 was observed. As a result, generation of bubbles due to helium gas was not observed. Therefore, it was confirmed that the membrane sample 136b has high density so as not to have air permeability.

Example 4 (Reference): Preparation and Evaluation of Nickel-Zinc Battery (1) Preparation of Separator with Porous Substrate Hydrotalcite membrane on alumina substrate (size) as a separator with porous substrate by the same procedure as Example 1. : 5 cm × 8 cm).

(2) Preparation of positive electrode plate Nickel hydroxide particles to which zinc and cobalt were added so as to form a solid solution were prepared. The nickel hydroxide particles were coated with cobalt hydroxide to obtain a positive electrode active material. The obtained positive electrode active material was mixed with a 2% aqueous solution of carboxymethyl cellulose 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 an area of 5 cm × 5 cm was obtained. At this time, the coating amount was adjusted so that nickel hydroxide particles corresponding to 4 Ah were included in the active material.

(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 was obtained in which the active material portion was coated over an area of 5 cm × 5 cm at 50%. At this time, the coating amount was adjusted so that the zinc oxide powder corresponding to the positive electrode plate capacity of 4 Ah was included in the active material.

(4) Battery assembly Using the positive electrode plate, the negative electrode plate, and the separator with a porous substrate obtained above, a nickel zinc battery as shown in FIG. 1 was assembled in the following procedure.

  First, a rectangular parallelepiped case body made of ABS resin with the case upper lid removed was prepared. A separator with a porous substrate (a hydrotalcite film on an alumina substrate) was inserted near the center of the case body, and three sides thereof were fixed to the inner wall of the case body using a commercially available adhesive. The positive electrode plate and the negative electrode plate were inserted into the positive electrode chamber and the negative electrode chamber, respectively. At this time, the positive electrode plate and the negative electrode plate were arranged so that the positive electrode current collector and the negative electrode current collector were in contact with the inner wall of the case body. A 6 mol / L aqueous KOH solution in an amount that sufficiently hides the positive electrode active material coating portion was injected into the positive electrode chamber as an electrolyte. The liquid level in the positive electrode chamber was about 5.2 cm from the case bottom. On the other hand, in the negative electrode chamber, not only the negative electrode active material coating part was sufficiently hidden, but also an excessive amount of 6 mol / L KOH aqueous solution was injected as an electrolyte considering the amount of water expected to decrease during charging. . The liquid level in the negative electrode chamber was about 6.5 cm from the case bottom. The terminal portions of the positive electrode current collector and the negative electrode current collector were connected to external terminals at the top of the case. The case upper lid was fixed to the case body by heat sealing, and the battery case container was sealed. Thus, a nickel zinc battery was obtained. In this battery, since the size of the separator is 5 cm wide × 8 cm high, and the size of the active material coated portion of the positive electrode plate and the negative electrode plate is 5 cm wide × 5 cm high, the positive electrode chamber and the negative electrode The space equivalent to 3 cm above the chamber can be said to be the positive electrode side excess space and the negative electrode side excess space.

(5) Evaluation The manufactured nickel zinc battery was subjected to constant current charging for 10 hours at a current of 0.4 mA corresponding to 0.1 C with a design capacity of 4 Ah. After charging, no deformation of the case or leakage of the electrolyte was observed. When the amount of the electrolyte after charging was observed, the electrolyte level in the positive electrode chamber was about 7.5 cm from the bottom of the case, and the electrolyte level in the negative electrode chamber was about 5.2 cm from the bottom of the case. It was. Although the positive electrode chamber electrolyte increased and the negative electrode chamber electrolyte decreased due to charging, there was sufficient electrolyte in the negative electrode active material coating part, and the applied positive electrode active material and negative electrode active material were charged and discharged. The electrolyte that causes a sufficient charge / discharge reaction could be held in the case.

Example 5 (Reference): Preparation of a zinc-air secondary battery (1) Preparation of separator with porous substrate An alumina substrate as a separator with a porous substrate (hereinafter simply referred to as a separator) by the same procedure as in Example 1 An upper hydrotalcite membrane was prepared.

(2) Production of air electrode layer α-MnO ₂ particles as an air electrode catalyst were produced 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. In this way, 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 earlier 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)) in a sheet form 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 hydrotalcite 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) Assembling the battery Using the obtained air electrode with separator, negative electrode plate, and third electrode, a zinc-air secondary battery having a horizontal structure as shown in FIG. 3A is produced by 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. Seal the opening of the resin container with an air electrode with a separator so that the air electrode side is on the outside, and apply a commercially available adhesive to the outer periphery of the opening to provide air tightness and liquid tightness. Stop and bond. 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 34 can be brought into contact with the third electrode 38 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. .

DESCRIPTION OF SYMBOLS 10 Nickel zinc battery 12 Positive electrode 13 Positive electrode collector 14 Positive electrode electrolyte 16 Negative electrode 17 Negative electrode collector 18 Negative electrode electrolyte 20 Ceramic separator 22 Container 24 Positive electrode chamber 25 Positive electrode side surplus space 26 Negative electrode chamber 27 Negative electrode side surplus space 28 Porous Base material 30 Zinc-air secondary battery 32 Air electrode 34 Negative electrode 36 Electrolytic solution 38 Third electrode 40 Ceramic separator 42 Positive electrode current collector 44 Negative electrode current collector 46 Container 46a Opening 48 Porous base material

Claims (12)

A secondary battery using a hydroxide ion conductive ceramic separator, wherein the secondary battery is in contact with the positive electrode, the negative electrode, an electrolyte containing an alkali metal hydroxide aqueous solution, and the electrolyte. A ceramic separator made of an inorganic solid electrolyte body having hydroxide ion conductivity, which separates the positive electrode and the negative electrode,
The 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, 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 to 0.4 basic, m is 0 or higher) A layered double hydroxide having a composition,
The electrolyte further includes alcohol, and is configured to suppress erosion of the layered double hydroxide by the electrolyte,
In the general ^{formula, M 2+} comprises ^{Mg 2+,} include ^{M 3+} is ^{Al 3+, A n-is} OH ^- and / or _CO ³ includes ^2-, alcohol concentration in the electrolytic solution at 2 to 5 mol / L There is a secondary battery.   The secondary battery according to claim 1, wherein the alcohol is an alcohol having 1 to 6 carbon atoms.   The secondary battery according to claim 2, wherein the alcohol is an alcohol having 1 to 5 hydroxy groups.   The alcohol is methanol, ethanol, 1-propanol, 1-butanol, 2-methyl-1-propanol, 1-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2,2-dimethyl. -1-propanol, 2-propanol, 2-butanol, 2-methyl-2-propanol, 2-pentanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 3-pentanol, 3-hexanol 2-methyl-3-pentanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-methyl-1-pentanol, 4-methyl-1-pentanol, 3-methyl-1 -Pentanol, 2-ethyl-1-butanol, 2,3-dimethyl-1-butanol, 2,2-dimethyl-1-butane 3,3-dimethyl-1-butanol, 2-hexanol, 2-methyl-2-pentanol, 4-methyl-2-pentanol, 3-methyl-2-pentanol, 2,3-dimethyl- 2-butanol, 3,3-dimethyl-2-butanol, cyclopentylmethanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol (ethylene glycol), 1,2- The secondary battery according to claim 3, wherein the secondary battery is at least one selected from the group consisting of propanediol, 1,3-propanediol, and 1,2,3-propanetriol.   The secondary battery according to claim 4, wherein the alcohol is at least one selected from the group consisting of ethanol and 1,2-ethanediol (ethylene glycol). The secondary battery according to any one of claims 1 to 5 , wherein the inorganic solid electrolyte body has a relative density of 90% or more. The secondary battery according to any one of claims 1 to 6 , wherein the inorganic solid electrolyte body has a plate shape, a film shape, or a layer shape. The secondary battery according to any one of claims 1 to 7 , further comprising a porous substrate on one or both surfaces of the ceramic separator. The secondary battery according to claim 8 , wherein the porous substrate is made of alumina or zirconia. The inorganic solid electrolyte body is in the form of a film-like or layered, in which the inorganic solid electrolyte body of the film-like or layered is formed on or in a said porous substrate, according to claim 8 or 9 Secondary battery. The inorganic solid electrolyte body is one that has been densified to extent no water permeability and air permeability, the secondary battery according to any one of claims 1-10. The secondary battery according to any one of claims 1 to 11 , wherein the inorganic solid electrolyte body is densified by hydrothermal treatment.