WO2020026623A1 - Electrode, metal air cell, and method for manufacturing metal air cell - Google Patents

Electrode, metal air cell, and method for manufacturing metal air cell Download PDF

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Publication number
WO2020026623A1
WO2020026623A1 PCT/JP2019/024181 JP2019024181W WO2020026623A1 WO 2020026623 A1 WO2020026623 A1 WO 2020026623A1 JP 2019024181 W JP2019024181 W JP 2019024181W WO 2020026623 A1 WO2020026623 A1 WO 2020026623A1
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electrode
hydrophilic polymer
metal
charging
porous
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PCT/JP2019/024181
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French (fr)
Japanese (ja)
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忍 竹中
宏隆 水畑
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シャープ株式会社
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Priority to JP2020534096A priority Critical patent/JP7106645B2/en
Publication of WO2020026623A1 publication Critical patent/WO2020026623A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M12/00—Hybrid cells; Manufacture thereof
    • H01M12/08—Hybrid cells; Manufacture thereof composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture

Definitions

  • the present disclosure relates to a metal-air battery and a method for manufacturing a metal-air battery.
  • a metal-air battery is provided with an air electrode (positive electrode), a metal negative electrode (negative electrode), and an electrolyte layer (electrolyte or solid electrolyte). Further, among the metal-air batteries which are secondary batteries, there is a three-electrode type battery further provided with a positive electrode for charging.
  • FIG. 9 is a schematic sectional view showing a general structure of a three-electrode metal-air battery 100.
  • the metal-air battery 100 includes, in a battery case 2 (casing), a metal negative electrode 3 containing a metal serving as a negative electrode active material, an air electrode 4 serving as a positive electrode for discharge, and an oxygen generating electrode 5 serving as a positive electrode for charging.
  • a separator 6 is provided between the metal negative electrode 3 and the oxygen generating electrode 5 and between the oxygen generating electrode 5 and the air electrode 4.
  • an air electrode 4, a metal negative electrode 3, and an oxygen generating electrode 5 are sequentially arranged in a battery case 2, and the battery case 2 is filled with an electrolyte 7 as an electrolyte layer.
  • the air electrode 4 includes an air electrode current collector 41, an air electrode catalyst layer 42, and an air electrode water repellent layer 43.
  • the cathode current collector 41 is porous and has electron conductivity.
  • the air electrode catalyst layer 42 is configured to include, for example, a conductive porous carrier and a catalyst supported on the porous carrier. Thereby, it becomes possible to form a three-phase interface where oxygen gas, water and electrons coexist on the catalyst, and the discharge reaction can proceed.
  • the air electrode water-repellent layer 43 is a porous material containing a water-repellent resin, and is disposed on the opposite side of the air electrode current collector 41 with respect to the air electrode catalyst layer 42 (that is, on the opposite side of the metal negative electrode 3). . By providing the air electrode water repellent layer 43, leakage of the electrolyte solution 7 can be suppressed.
  • a discharge reaction proceeds at a three-phase interface where oxygen (gas phase), water (liquid phase) and electron conductor (solid phase) coexist.
  • the air electrode 4 is provided so that oxygen gas contained in the atmosphere can diffuse.
  • the cathode 4 is provided such that at least a part of the surface of the cathode 4 is exposed to the atmosphere.
  • a large number of vents 21 are provided in the battery case 2, and oxygen gas contained in the atmosphere is diffused into the air electrode 4 through these vents 21.
  • the metal negative electrode 3 includes a negative electrode active material layer 31 and a negative electrode current collector 32.
  • the negative electrode current collector 32 is disposed substantially at the center of the negative electrode active material layer 31 in the thickness direction.
  • the negative electrode active material layer 31 includes an active material containing a metal element (negative electrode active material), and an oxidation reaction of the active material occurs during discharging, and a reduction reaction occurs during charging.
  • a metal element zinc, lithium, sodium, calcium, magnesium, aluminum, iron and the like are used.
  • the negative electrode current collector 32 is porous and has electronic conductivity.
  • the oxygen generating electrode 5 includes a charging electrode 510 and a charging electrode water-repellent layer 52.
  • the oxygen generating electrode 5 may include a charging electrode current collector (not shown).
  • the charging electrode 510 is a porous electrode. At the charging electrode 510, a charging reaction proceeds at a three-phase interface where oxygen (gas phase), water (liquid phase), and an electron conductor (solid phase) coexist.
  • the charging electrode 510 may be provided with oxygen generating catalyst particles for promoting a charging reaction on the surface.
  • the oxygen generating electrode 5 oxygen gas is generated as the charging reaction proceeds. Therefore, the oxygen generating electrode 5 is provided so that the oxygen gas can diffuse, and at least a part thereof is provided so as to communicate with the outside air. In the configuration of FIG. 9, a large number of vents 21 are provided in the battery case 2 also on the side where the oxygen generating electrode 5 is disposed, and a gas such as oxygen gas generated by a charging reaction is supplied through these vents 21. It is discharged from the oxygen generating electrode 5.
  • the charging electrode water-repellent layer 52 is provided for the oxygen generating electrode 5, similarly to the air electrode water-repellent layer 43 in the air electrode 4.
  • the charging electrode water-repellent layer 52 is a porous material containing a water-repellent resin, and is disposed on the opposite side of the charging electrode 510 from the metal negative electrode 3 (that is, on the battery case 2 side).
  • the separator 6 is made of an electronically insulating material, and secures the insulation between the air electrode 4 and the metal negative electrode 3 and between the oxygen generating electrode 5 and the metal negative electrode 3 while moving the charge carriers between these members. Make it possible. In particular, the separator 6 prevents a short circuit due to the formation of an electron conduction path between the electrodes. For example, a metal dendrite reduced and precipitated on the metal negative electrode 3 during charging reaches the oxygen generating electrode 5 and is prevented from being short-circuited.
  • the following problem occurs particularly in the oxygen generation electrode 5.
  • A Since the charging electrode 510 is porous and the electrolytic solution 7 entering the pores has high fluidity, it is difficult to reliably prevent the leakage of the electrolytic solution 7 only with the charging electrode water-repellent layer 52. . That is, the electrolyte 7 leaks from the back surface of the oxygen generating electrode 5.
  • B The discharge of oxygen gas generated during charging is inhibited by the electrolyte solution 7 that has entered the hole of the charging electrode 510, and bubbles are generated in the hole of the charging electrode 510. The bubbles reduce the three-phase interface at the charging electrode 510 and increase the charging voltage (charging overvoltage rise). As a result, uneven charging occurs, and the cyclability of the metal-air battery 100 also decreases.
  • Patent Literature 1 discloses that a charging positive electrode includes a foamed metal material and a hydrophilic particulate member included in a hole of the foamed metal material.
  • the electrolytic solution can be spread to all corners of the pores of the foamed metal material. It is said that the surface of the material can be used more effectively. Further, it is said that the hydrophilic particulate member containing the electrolytic solution also has an effect of preventing the electrolytic solution from passing through the positive electrode for charging, and suppressing the leakage of the electrolytic solution.
  • Patent Document 1 Although the technique disclosed in Patent Document 1 is considered to be effective for the problem (A), it cannot be said that the technology is sufficiently effective for the problem (B). The reason is as follows.
  • the charging positive electrode is made of a foamed metal material 200, and a water-repellent film 210 is arranged on the surface of the foamed metal material 200 on the outside air side.
  • the anion conductive film 220 is arranged on the surface on the electrolyte side.
  • the pores of the foamed metal material 200 include the hydrophilic particulate member 201.
  • the electrolyte 202 can be spread over the entire pores of the foamed metal material 200 by the hydrophilic particulate member 201.
  • the electrolytic solution 202 that has entered the hole without a gap also impedes the discharge of oxygen gas generated during charging. For this reason, the inside of the foamed metal material 200 tends to be in a state in which the bubbles 203 of the oxygen gas remain.
  • the hydrophilic particulate member 201 since the hydrophilic particulate member 201 has no effect of peeling the bubbles 203 from the inner wall surface of the foamed metal material 200, the bubbles 203 adhere to the inner wall surface of the foamed metal material 200 and reduce the area of the three-phase interface. This causes the problem (B).
  • the present disclosure has been made in view of the above problems, and has as its object to stably and efficiently perform a charging reaction at an oxygen generating electrode during charging in a three-electrode metal-air battery.
  • an electrode according to a first aspect of the present disclosure is an electrode used for a positive electrode for charging a metal-air battery, and a metal porous body having a large number of holes therein, And a hydrophilic polymer coating that covers at least the inner wall surface of the pores of the porous metal body.
  • the hydrophilic polymer coating covering the inner wall surface of the pores of the porous metal body does not completely fill the pores in the porous metal body, but leaves pores that serve as oxygen gas passages.
  • a coating is formed on the inner wall surface of the part.
  • the hydrophilic polymer preferably has a configuration having a hydrophilic group selected from a hydroxyl group, an amino group, a sulfo group and a carboxyl group.
  • the hydrophilic polymer preferably has a configuration having an anion exchange group. Thereby, carbonate precipitation at the oxygen generating electrode can be suppressed.
  • the hydrophilic polymer has a structure having a crosslinked structure.
  • the hydrophilic polymer film becomes strong and changes in shape over time are reduced, so that the effect of the hydrophilic polymer film can be maintained for a long time.
  • the hydrophilic polymer may have a structure in which a hydrogen atom of a hydrophilic group selected from a hydroxyl group, an amino group, a sulfo group, and a carboxyl group is eliminated, and the metal salt is ion-bonded to a metal ion. it can.
  • the metal porous body can be composed of any of the group consisting of Ni, Cr, Mn, Fe, Co, Cu, Ru, Rh, Pd, Ir, and Pt.
  • the electrode has a first surface and a second surface facing the first surface, and the hydrophilic polymer coating is formed of the metal porous body from the first surface to the second surface.
  • the film thickness on the second surface side is smaller than the film thickness on the first surface side, and on the first surface side of the electrode, the pores of the porous metal body have the hydrophilic property.
  • a configuration can be provided in which there is a filling region filled with a polymer coating.
  • the first surface is disposed so as to be in contact with the electrolyte while facing the metal negative electrode. Only the amount of the electrolyte diffused by the hydrophilic polymer film is allowed to penetrate into the charging electrode, and further permeation is suppressed by the filled region of the hydrophilic polymer film.
  • the second surface side since the film thickness of the hydrophilic polymer film is formed to be small, sufficient voids are formed, and the presence of the filling region on the second surface side allows the voids to be formed in the voids. The entry of the electrolytic solution is also suppressed. Therefore, oxygen gas generated during charging due to the void can be efficiently discharged.
  • the thickness of the filling region may be 1/20 to 1/2 of the thickness of the porous metal body.
  • the average pore diameter of the porous metal body may be 0.45 to 3.2 mm.
  • the electrode has a first surface, a second surface facing the first surface, and a first layer located on the first surface side and a first layer located on the second surface side.
  • the first surface is disposed so as to be in contact with the electrolyte while facing the metal negative electrode. Only the amount of the electrolyte diffused by the hydrophilic polymer film is allowed to penetrate into the charging electrode, and further penetration is suppressed by the hydrophilic polymer film of the first layer.
  • the hydrophilic polymer film is formed so as to have a small thickness, so that sufficient voids are formed, and the voids can efficiently discharge oxygen gas generated during charging.
  • a metal-air battery includes a housing, an electrolytic solution housed in the housing, and a part immersed in the electrolytic solution.
  • a metal negative electrode containing a metal to be a negative electrode active material, a part of the electrolytic solution is immersed in the electrolytic solution, disposed to face the metal negative electrode, an oxygen generating electrode having an oxygen generating ability, and a part of the electrolytic solution.
  • the metal-air battery may have a configuration in which a hydrophilic polymer layer is provided on a surface of the oxygen generating electrode facing the metal negative electrode.
  • a method for manufacturing an electrode according to a third aspect of the present disclosure is a method for manufacturing an electrode used for a positive electrode for charging a metal-air battery, wherein a large number of holes are provided inside.
  • a dipping step of dipping the porous metal body having a portion in a solution containing a hydrophilic polymer, and a drying step of pulling up and drying the porous metal body dipped in the solution containing a hydrophilic polymer in the dipping step It is characterized by.
  • the hydrophilic polymer film covering the inner wall surface of the hole of the porous metal body can be formed by the dipping step and the drying step, and the above-described electrode can be obtained.
  • a hydrophilic polymer film that covers the inner wall surface of the hole of the porous metal body of the electrode is formed.
  • oxygen gas generated by the charging reaction is caused by the action of a hydrophilic polymer film that coats the inner wall surface of the pores of the porous metal body. It is easily peeled off from the inner wall surface of the porous metal body, and is discharged to the outside through the void. Therefore, it is possible to suppress a decrease in the area of the three-phase interface due to bubbles of oxygen gas in the oxygen generating electrode of the metal-air battery, and to stably and efficiently perform a charging reaction at the oxygen generating electrode during charging. It works.
  • FIG. 2 is a schematic sectional view showing the structure of the metal-air battery according to Embodiment 1.
  • 3A and 3B are schematic diagrams illustrating an internal configuration of a charging electrode according to the first embodiment, where FIG. 3A is a diagram illustrating the entire charging electrode and FIG. 3B is a diagram illustrating a part of the charging electrode in an enlarged manner.
  • FIG. 4 is a process chart illustrating a method for manufacturing the charged electrode according to the first embodiment.
  • 9 is a graph showing changes in charging voltage during charging of an evaluation cell and a comparative evaluation cell.
  • FIG. 9 is a schematic diagram showing an internal configuration of a charging electrode according to Embodiment 2.
  • FIG. 9 is a schematic diagram showing an internal configuration of a charging electrode according to Embodiment 3.
  • FIG. 9 is a schematic sectional view illustrating a structure of a metal-air battery according to a third embodiment.
  • FIG. 1 is a schematic cross-sectional view showing a general structure of a three-electrode metal-air battery. It is a schematic diagram which shows the internal structure of the conventional charging electrode, (a) is a figure which shows the whole charging electrode, (b) is a figure which expands and shows a part of charging electrode.
  • FIG. 1 is a schematic sectional view showing the structure of the metal-air battery 10 according to the first embodiment.
  • the metal-air battery 10 is a tripolar secondary battery and has a configuration similar to that of the metal-air battery 100 shown in FIG. For this reason, in the metal-air battery 10 of FIG. 1, the same components as those of the metal-air battery 100 of FIG.
  • the metal-air battery 10 of FIG. 1 is different from the metal-air battery 100 of FIG. 9 only in the configuration of the oxygen generating electrode 5. Specifically, instead of the charging electrode 510 of FIG. Used. Therefore, in the first embodiment, a specific configuration and a manufacturing method of the charging electrode 51 will be described.
  • the configuration other than the oxygen generating electrode 5, for example, the configuration of the metal negative electrode 3 and the air electrode 4 is not limited to the same configuration as that of the metal-air battery 100. May be adopted.
  • FIGS. 2A and 2B are schematic diagrams showing the internal configuration of the charging electrode 51.
  • FIG. 2A is a diagram showing the entire charging electrode 51
  • FIG. 2B is an enlarged view of a part of the charging electrode 51.
  • the charging electrode 51 includes a porous metal body 511 and a hydrophilic polymer film 512.
  • the hydrophilic polymer coating 512 covers the inner wall surface of the hole in the porous metal body 511. That is, as shown in FIG. 2B, the hydrophilic polymer coating 512 does not completely fill the pores in the porous metal body 511, but leaves the voids 513 serving as oxygen gas passages. A film is formed on the surface.
  • oxygen generating catalyst particles that promote the charging reaction may be provided on the surface of the porous metal body 511.
  • the electrolytic solution 7 diffuses in the hydrophilic polymer film 512 and spreads over the entire inner wall surface of the porous metal body 511.
  • the oxygen gas generated by the charging reaction is easily peeled off from the inner wall surface of the porous metal body 511 by the action of the hydrophilic polymer film 512, and is discharged to the outside through the void 513.
  • oxygen gas generated at the charging electrode 51 is discharged from the charging electrode water-repellent layer 52 and the vent 21 of the battery case 2 to the outside of the metal-air battery 10.
  • the hydrophilic polymer coating 512 is formed on the inner wall surface of the hole in the porous metal body 511, the area of the three-phase interface is prevented from being reduced by oxygen gas bubbles in the oxygen generating electrode 5. it can. As a result, the charging reaction at the oxygen generating electrode 5 can be performed efficiently.
  • a porous metal body 511 and an aqueous solution containing a hydrophilic polymer are prepared (S1 and S2).
  • a metal foam for example, “Celmet (registered trademark)” manufactured by Sumitomo Electric Industries
  • a sintered body of metal particles or metal fibers can also be used.
  • the porous metal body 511 can be made of any metal having an oxygen generating ability, that is, any of the group consisting of Ni, Cr, Mn, Fe, Co, Cu, Ru, Rh, Pd, Ir, and Pt.
  • the dimensions of the porous metal body 511 are, for example, in the following ranges. ⁇ Thickness: 1.4 to 10.0 mm ⁇ Specific surface area: 250-5800m2 / m3 ⁇ Average pore diameter: 0.45 to 3.2 mm In addition, the average pore diameter of the pores in the porous metal body 511 can be calculated and specified by a pore diameter distribution measuring device (a palm porometer manufactured by PUI, USA).
  • Example 1 a metal foam, “Celmet” manufactured by Sumitomo Electric Co., Ltd. was used as the material, and a sheet-like metal sheet having a thickness of 1.4 mm, 50 mm ⁇ 50 mm, and an average pore diameter of 0.45 mm was used.
  • the hydrophilic polymer film 512 is a film containing at least a hydrophilic polymer.
  • Examples of the type of the hydrophilic polymer used for the hydrophilic polymer film 512 include a hydrogel having a hydrophilic group such as a hydroxyl group, an amino group, a sulfo group or a carboxyl group, and an anion exchange resin having an anion exchange group.
  • the hydrophilic polymer may form a salt with a metal ion by removing a hydrogen atom of a hydroxyl group, an amino group, a sulfo group, or a carboxyl group. Further, the hydrophilic polymer may have both a hydroxyl group or a carboxyl group and an anion exchange group.
  • the hydrophilic polymer contained in the hydrophilic polymer film 512 has a hydroxyl group, an amino group, a sulfo group or a carboxyl group, the effect of retaining the electrolyte solution 7 to be leaked is enhanced.
  • the hydrophilic polymer coating 512 has an anion exchange group, carbonate precipitation at the oxygen generating electrode 5 can be suppressed.
  • the hydrophilic polymer film 512 has a crosslinked structure (a monomer is bound by a covalent bond). When the hydrophilic polymer film 512 has a crosslinked structure, the hydrophilic polymer film 512 becomes strong and changes in shape over time are reduced, so that the effect of the hydrophilic polymer film 512 can be maintained for a long time.
  • the hydrogel has OH, COOH groups and the like, and has improved water retention by containing a polyhydric alcohol, acrylic acid or a metal salt of acrylic acid.
  • the polyhydric alcohol include diols such as ethylene glycol, propylene glycol, and butanediol; polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol; and polyhydric alcohol condensation such as polyethylene glycol, polypropylene glycol, diglycerin, and polyglycerin. And modified polyhydric alcohols such as polyoxyethylene glycerin.
  • the polyhydric alcohol may be only one kind or a mixture of plural kinds.
  • acrylic acid include polyacrylic acid
  • examples of polyacrylate include sodium polyacrylate and potassium polyacrylate.
  • anion exchange resin anion-conductive solid electrolyte resin
  • those having a quaternary ammonium group can be preferably used, and a known method (for example, see Japanese Patent Publication No. 03-12568) can be used. .
  • the hydrophilic polymer film 512 may contain a conductive auxiliary agent or a catalyst having an ability to generate oxygen, in addition to the hydrophilic polymer.
  • a conductive auxiliary agent and the catalyst having an oxygen generating ability known materials in the art may be used.
  • the amount of the hydrophilic polymer coating 512 contained in the oxygen generating electrode 5 is preferably 0.03 g to 0.3 g per 1 cm 3 of the porous metal body 511. If the amount of the hydrophilic polymer coating 512 contained in the oxygen generating electrode 5 is less than 0.03 g per 1 cm 3 of the metal porous body 511, the hydrophilic polymer coating 512 may become thin in the oxygen generating electrode 5 and may be insufficient. There is a possibility that a three-phase interface is not formed. When the hydrophilic polymer film 512 is thin, the charging overvoltage increases, and the effect of suppressing electrolyte leakage may not be obtained.
  • the voids 513 may be completely filled with the hydrophilic polymer coating 512. In this case, oxygen gas discharge is hindered by the hydrophilic polymer film 512 filling the void 513, and the three-phase interface is reduced.
  • Example 1 the hydrophilic polymer-containing aqueous solution was prepared by dissolving 1 g of “crosslinked sodium polyacrylate” in an aqueous solvent (100 cm 3) and stirring for 3 h.
  • the porous metal body 511 prepared in S1 was dipped in the hydrophilic polymer-containing aqueous solution prepared in S2 for 24 hours.
  • the metal porous body 511 immersed in the aqueous solution containing a hydrophilic polymer in S3 was pulled up and dried at 25 ° C. for 12 hours.
  • the charging electrode 51 of Example 1 in which the hydrophilic polymer film 512 is formed on the inner wall surface of the porous metal body 511 is obtained.
  • the hydrophilic polymer-containing aqueous solution is gelled, and the gelled hydrophilic polymer-containing aqueous solution is applied to one surface of the porous metal body 511, or the gelled hydrophilic polymer is applied to the metallic porous body 511. May be adopted.
  • a method of gelling to the extent that a hydrophilic polymer-containing aqueous solution can be applied or pressed there are (1) a method in which linear polyacrylic acid is mixed and gelled (thickened), and (2) a hydrophilic polymer.
  • a hydrophilic monomer eg, acrylic acid
  • a cross-linking agent eg, N′N-methylenebisacrylamide
  • a polymerization initiator eg, potassium peroxodisulfate powder
  • the charging electrode 51 of Example 1 formation of the hydrophilic polymer film 512 was confirmed by the following method. That is, the charging electrode 51 is impregnated with a solution containing a heavy metal cation or a Br anion, dried, and then subjected to cross-sectional TEM-EDX observation to detect a heavy metal or Br in a region other than the skeleton of the porous metal body 511, and to detect It was confirmed that the hydrophilic polymer coating 512 was present in the holes of the body 511.
  • a metal-air battery serving as an evaluation cell was manufactured using the charging electrode 51 of Example 1, and its charge / discharge characteristics were evaluated.
  • the evaluation cell (Example 1) had the structure of the metal-air battery 10 shown in FIG. 1, and the configuration other than the charging electrode 51 was as follows.
  • a comparative evaluation cell a metal-air battery using only the metal porous body 511 prepared in S1 as a charging electrode instead of the charging electrode 51 of Example 1 was manufactured.
  • the configuration of the comparative evaluation cell other than the charging electrode is as follows.
  • Metal negative electrode 3 Metal negative electrode containing zinc and zinc oxide particles “2 mm thick, 50 mm ⁇ 50 mm sheet”
  • Electrolyte solution 7 Zn-saturated KOH aqueous solution 10 ml (KOH 7M, zinc oxide 0.65M)
  • Air electrode 4 "Thickness 0.3 mm, 50 m” manufactured by QSI (Quantum Sphere) mx 50mm sheet " Separator 6: Nippon Shokubai Co., Ltd.
  • FIG. 4 is a graph showing a change in charging voltage during charging in a charge / discharge test during two cycles.
  • the charging voltage increases as the charging progresses, whereas in the evaluation cell (Example 1), the increase in the charging voltage is greatly suppressed even when the charging progresses. . Also, with respect to the maximum charge capacity, the evaluation cell (Example 1) is larger than the comparative evaluation cell.
  • the thickness of the hydrophilic polymer film 512 can be adjusted to some extent by adjusting the concentration of the hydrophilic polymer in the aqueous solution containing a hydrophilic polymer in the dipping step shown in FIG. That is, the film thickness of the hydrophilic polymer film 512 can be increased by increasing the concentration of the hydrophilic polymer, and the film thickness of the hydrophilic polymer film 512 can be decreased by decreasing the concentration of the hydrophilic polymer. However, it is considered that it is actually not easy to obtain an optimum film thickness of the hydrophilic polymer film 512 only by adjusting the concentration of the hydrophilic polymer-containing aqueous solution.
  • the film thickness of the hydrophilic polymer film 512 becomes too large, and the pores in the porous metal body 511 become the hydrophilic polymer film 512.
  • the hydrophilic polymer coating 512 that completely fills the pores of the porous metal body 511 is not actually a coating, but for convenience. , Hydrophilic polymer coating 512).
  • the voids 513 are formed, the voids 513 are too small to be connected, and most of the voids 513 may be divided by the hydrophilic polymer coating 512. If the void 513 is not sufficiently formed because the thickness of the hydrophilic polymer film 512 is too large, the effect of discharging oxygen gas generated during charging is significantly reduced, and the effect of preventing the problem (B) is reduced. I do.
  • the film thickness of the hydrophilic polymer film 512 becomes small, and the water retention effect of the hydrophilic polymer film 512 decreases.
  • the electrolyte solution 7 penetrates into a portion of the porous metal body 511 which originally becomes the void 513. Then, the discharge of oxygen gas generated during charging is inhibited by the electrolyte solution 7 that has entered the porous metal body 511, so that the effect of preventing the problem (B) is reduced. Furthermore, if the electrolytic solution 7 that is not retained by the hydrophilic polymer film 512 is present in the porous metal body 511, it causes a liquid leakage, and the effect of preventing the problem (A) is reduced.
  • FIG. 6 is a schematic diagram showing an internal configuration of the charging electrode 51 according to the second embodiment.
  • the charging electrode 51 according to the second embodiment includes a porous metal body 511 and a hydrophilic polymer film 512 as in the first embodiment.
  • the thickness of the hydrophilic polymer film 512 is not constant, and the hydrophilic polymer film 512 has a hydrophilic property from one surface (first surface) to the other surface (second surface) along the thickness direction of the charging electrode 51. It has a gradation structure in which the thickness of the polymer film 512 gradually decreases.
  • the pores of the porous metal body 511 are filled with the hydrophilic polymer film 512, and a filling region where no void 513 exists is generated.
  • the charging electrode 51 having such a gradation structure of the hydrophilic polymer film 512 has a second surface in contact with the charging electrode water-repellent layer 52 and a first surface facing the metal negative electrode 3 when applied to the metal-air battery 10. Then, it is arranged so as to be in contact with the electrolyte 7. In this case, on the first surface side of the charging electrode 51, there is a filling region in which the void 513 does not occur, so that only the amount of the electrolyte 7 diffused by the hydrophilic polymer film 512 penetrates into the charging electrode 51. And further penetration is suppressed.
  • the hydrophilic polymer film 512 is formed so as to have a small film thickness, so that a sufficient void 513 is formed.
  • the filling region exists on the second surface side, entry of the electrolyte 7 into the void 513 is also suppressed. Therefore, the void 513 can efficiently discharge oxygen gas generated during charging.
  • the charging electrode 51 according to Embodiment 2 does not immerse the entirety of the porous metal body 511 in the hydrophilic polymer-containing aqueous solution in the immersion step shown in FIG. It can be manufactured by immersing only a small amount. In this case, a filling region can be formed at a portion where the porous metal body 511 is immersed in the hydrophilic polymer-containing aqueous solution. In a portion that is not immersed in the hydrophilic polymer-containing aqueous solution, the hydrophilic polymer-containing aqueous solution can be sucked up by capillary action to form the hydrophilic polymer film 512, but the film thickness becomes small.
  • the concentration of the hydrophilic polymer-containing aqueous solution is set so that the portion in which the porous metal body 511 is immersed becomes a filling region having no void 513.
  • the thickness of the porous metal body 511 immersed in the aqueous solution containing a hydrophilic polymer is preferably in the range of 1/20 to 1/2 of the total thickness of the porous metal body 511, and 1/10 It is more preferable to set the range to 1 /.
  • the thickness of the filling region may be such that the penetration of the electrolyte solution 7 into the space 513 on the second surface side can be prevented, and it is preferable that the thickness is not excessively large. This is because, if the filling region is too thick, the region where the void 513 is formed decreases, and the oxygen gas discharge efficiency decreases.
  • the charging electrode 51 according to the second embodiment is not limited to the one in which the hydrophilic polymer film 512 is completely formed on the entire inner wall surface of the hole of the porous metal body 511, There may be a region where the hydrophilic polymer coating 512 is not formed on a part of the body 511. That is, the suction of the aqueous solution containing a hydrophilic polymer due to the capillary action may not completely reach the second surface, and there may be a region where the hydrophilic polymer coating 512 is not formed on the second surface.
  • the amount and thickness of the hydrophilic polymer film 512 formed inside the porous metal body 511 can be measured as follows.
  • the amount of the hydrophilic polymer film 512 can be determined by subtracting the weight of the metal porous body 511 alone from the metal porous body 511 on which the hydrophilic polymer film 512 is formed.
  • the method of measuring the film thickness of the hydrophilic polymer film 512 is as follows: the pore diameter distribution of the porous metal body 511 on which the hydrophilic polymer film 512 is formed is measured by a pore diameter distribution measuring device (U.S.A.
  • U.S.A pore diameter distribution measuring device
  • the difference from the pore diameter distribution of the porous metal body on which the hydrophilic polymer coating 512 is not formed can be determined as the thickness of the hydrophilic polymer coating 512.
  • FIG. 7 is a schematic diagram showing an internal configuration of the charging electrode 51 according to the third embodiment.
  • the charging electrode 51 according to the third embodiment has a two-layer structure using a metal porous body 511A and a metal porous body 511B in which the average pore diameters of the holes formed therein are different from each other.
  • the average pore diameter of the first layer made of the porous metal body 511A is smaller than the average pore diameter of the second layer made of the porous metal body 511B.
  • the hydrophilic polymer coating 512 is formed on both the metal porous body 511A and the metal porous body 511B.
  • the pores are filled with the hydrophilic polymer coating 512, and the voids 513 are formed. Almost no occurrence.
  • the pores are covered with the hydrophilic polymer film 512, and voids 513 are generated.
  • the charging electrode 51 according to the third embodiment can be manufactured by performing a dipping step and a drying step shown in FIG. 3 on each of the porous metal bodies 511A and 511B, and then bonding them.
  • the first layer made of the porous metal body 511A is on the first surface side
  • the second layer made of the porous metal body 511B is on the second surface side.
  • the hydrophilic polymer coating 512 is formed in the first layer to such an extent that the void 513 is hardly generated, only the amount of the electrolyte solution 7 diffused by the hydrophilic polymer coating 512 enters the charging electrode 51 inside. Penetration is allowed and further penetration is suppressed.
  • a sufficient gap 513 is formed.
  • the hydrophilic polymer coating 512 of the first layer prevents the electrolyte solution 7 from entering the gap 513, the gap 513 allows the electrolyte solution 7 during charging. Emitted oxygen gas can be efficiently discharged.
  • the thickness of the first layer is 1/20 to 1/2 of the entire thickness of the porous metal body 511, similarly to the thickness of the important region in the second embodiment. It is preferably in the range, more preferably in the range of 1/10 to 1/5.
  • FIG. 8 is a schematic sectional view showing the structure of a metal-air battery 10 using the oxygen generating electrode 5 according to the third embodiment.
  • the configuration of the metal-air battery 10 shown in FIG. 8 is the same as that of the metal-air battery 10 shown in FIG.
  • the oxygen generating electrode 5 according to the fourth embodiment has a hydrophilic polymer layer 53 in addition to the charging electrode 51 and the charging electrode water-repellent layer 52.
  • the hydrophilic polymer layer 53 is disposed on the opposite side of the charging electrode 51 from the charging electrode water repellent layer 52, that is, on the side facing the metal negative electrode 3.
  • any of the charging electrodes 51 shown in FIG. 2, FIG. 6, or FIG. 7 may be used.
  • the oxygen generating electrode 5 according to the fourth embodiment When the oxygen generating electrode 5 according to the fourth embodiment is applied to the metal-air battery 10, only the amount of the electrolyte solution 7 diffused by the hydrophilic polymer layer 53 and the hydrophilic polymer film 512 is inside the charging electrode 51. Penetration is allowed and further penetration is suppressed. Therefore, in the charging electrode 51, the electrolyte 7 is prevented from entering the gap 513, and the oxygen gas generated during charging can be efficiently discharged by the gap 513.
  • the hydrophilic polymer layer 53 can be made of an anion exchange resin or a hydrogel as in the case of the hydrophilic polymer film 512. However, it is not necessary that the hydrophilic polymer layer 53 and the hydrophilic polymer film 512 be the same material.
  • the material of the hydrophilic polymer layer 53 can be an anion exchange resin
  • the material of the hydrophilic polymer coating 512 can be a hydrogel.

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Abstract

A charging electrode used in a positive electrode for charging of a metal air cell includes a metal porous body having a large number of pores in the interior, and a hydrophilic polymer coating covering the inner wall surface of the pores of the metal porous body. The hydrophilic polymer coating forms a coating on the inner wall surface of the pores while leaving gaps serving as passages for oxygen gas, instead of completely filling the pores of the metal porous body.

Description

電極、金属空気電池および金属空気電池の製造方法Electrode, metal-air battery and method of manufacturing metal-air battery
　本開示は、金属空気電池および金属空気電池の製造方法に関する。 The present disclosure relates to a metal-air battery and a method for manufacturing a metal-air battery.
　金属空気電池は、空気極（正極）と、金属負極（負極）と、電解質層（電解液または固体電解質）とを備えて構成されている。また、二次電池である金属空気電池には、さらに、充電用正極を備えた三極式のものもある。 A metal-air battery is provided with an air electrode (positive electrode), a metal negative electrode (negative electrode), and an electrolyte layer (electrolyte or solid electrolyte). Further, among the metal-air batteries which are secondary batteries, there is a three-electrode type battery further provided with a positive electrode for charging.
　図９は、三極式の金属空気電池１００の一般的な構造を示す概略断面図である。金属空気電池１００は、電池ケース２（筐体）内に、負極活物質となる金属を含む金属負極３と、放電用正極である空気極４と、充電用正極である酸素発生極５と、金属負極３と酸素発生極５との間、および酸素発生極５と空気極４との間に介装されたセパレータ６とを備えている。金属空気電池１００では、空気極４、金属負極３、酸素発生極５が電池ケース２内に順に配置されており、さらに電池ケース２内には電解質層として電解液７が満たされている。 FIG. 9 is a schematic sectional view showing a general structure of a three-electrode metal-air battery 100. The metal-air battery 100 includes, in a battery case 2 (casing), a metal negative electrode 3 containing a metal serving as a negative electrode active material, an air electrode 4 serving as a positive electrode for discharge, and an oxygen generating electrode 5 serving as a positive electrode for charging. A separator 6 is provided between the metal negative electrode 3 and the oxygen generating electrode 5 and between the oxygen generating electrode 5 and the air electrode 4. In the metal-air battery 100, an air electrode 4, a metal negative electrode 3, and an oxygen generating electrode 5 are sequentially arranged in a battery case 2, and the battery case 2 is filled with an electrolyte 7 as an electrolyte layer.
　空気極４は、空気極集電体４１、空気極触媒層４２、および空気極撥水層４３を備えて構成されている。空気極集電体４１は、多孔性でかつ電子伝導性を有する。空気極触媒層４２は、例えば、導電性の多孔性担体と、多孔性担体に担持された触媒とを含む構成とされる。これにより、触媒上において、酸素ガスと水と電子とが共存する三相界面を形成することが可能になり、放電反応を進行させることができる。空気極撥水層４３は、撥水性樹脂を含有する多孔性材料であり、空気極触媒層４２に対して空気極集電体４１と反対側（すなわち金属負極３の反対側）に配置される。空気極撥水層４３が配設されることにより電解液７の漏洩を抑制することができる。 The air electrode 4 includes an air electrode current collector 41, an air electrode catalyst layer 42, and an air electrode water repellent layer 43. The cathode current collector 41 is porous and has electron conductivity. The air electrode catalyst layer 42 is configured to include, for example, a conductive porous carrier and a catalyst supported on the porous carrier. Thereby, it becomes possible to form a three-phase interface where oxygen gas, water and electrons coexist on the catalyst, and the discharge reaction can proceed. The air electrode water-repellent layer 43 is a porous material containing a water-repellent resin, and is disposed on the opposite side of the air electrode current collector 41 with respect to the air electrode catalyst layer 42 (that is, on the opposite side of the metal negative electrode 3). . By providing the air electrode water repellent layer 43, leakage of the electrolyte solution 7 can be suppressed.
　この空気極４においては、酸素（気相）、水（液相）、電子伝導体（固相）が共存する三相界面で放電反応が進行する。空気極４は、大気に含まれる酸素ガスが拡散できるように設けられる。例えば、空気極４は、少なくとも空気極４の表面の一部が大気に曝されるように設けられている。図９の構成では、電池ケース２に多数の通気口２１が設けられており、これらの通気口２１を介して大気に含まれる酸素ガスが空気極４中に拡散される。 In the air electrode 4, a discharge reaction proceeds at a three-phase interface where oxygen (gas phase), water (liquid phase) and electron conductor (solid phase) coexist. The air electrode 4 is provided so that oxygen gas contained in the atmosphere can diffuse. For example, the cathode 4 is provided such that at least a part of the surface of the cathode 4 is exposed to the atmosphere. In the configuration of FIG. 9, a large number of vents 21 are provided in the battery case 2, and oxygen gas contained in the atmosphere is diffused into the air electrode 4 through these vents 21.
　金属負極３は、負極活物質層３１および負極集電体３２を備えて構成されている。図９の構成では、負極活物質層３１の厚み方向のほぼ中央に負極集電体３２が配置されている。負極活物質層３１は、金属元素を含む活物質（負極活物質）を含み、放電時には活物質の酸化反応が起こり、充電時には還元反応が起こる。金属元素としては、亜鉛、リチウム、ナトリウム、カルシウム、マグネシウム、アルミニウム、鉄などが用いられる。負極集電体３２は、多孔性でかつ電子伝導性を有する。 The metal negative electrode 3 includes a negative electrode active material layer 31 and a negative electrode current collector 32. In the configuration shown in FIG. 9, the negative electrode current collector 32 is disposed substantially at the center of the negative electrode active material layer 31 in the thickness direction. The negative electrode active material layer 31 includes an active material containing a metal element (negative electrode active material), and an oxidation reaction of the active material occurs during discharging, and a reduction reaction occurs during charging. As the metal element, zinc, lithium, sodium, calcium, magnesium, aluminum, iron and the like are used. The negative electrode current collector 32 is porous and has electronic conductivity.
　酸素発生極５は、充電極５１０および充電極撥水層５２を備えて構成されている。また、酸素発生極５は、図示しない充電極集電体を備える場合もある。充電極５１０は多孔性の電極であり、充電極５１０においては、酸素（気相）、水（液相）、電子伝導体（固相）が共存する三相界面で充電反応が進行する。充電極５１０は、表面に充電反応を促進する酸素発生触媒粒子が備えられてもよい。 The oxygen generating electrode 5 includes a charging electrode 510 and a charging electrode water-repellent layer 52. The oxygen generating electrode 5 may include a charging electrode current collector (not shown). The charging electrode 510 is a porous electrode. At the charging electrode 510, a charging reaction proceeds at a three-phase interface where oxygen (gas phase), water (liquid phase), and an electron conductor (solid phase) coexist. The charging electrode 510 may be provided with oxygen generating catalyst particles for promoting a charging reaction on the surface.
　酸素発生極５では、充電反応の進行により酸素ガスが生成される。このため、酸素発生極５は、この酸素ガスが拡散できるように設けられており、少なくともその一部が外気と連通するように設けられる。図９の構成では、酸素発生極５の配置側でも電池ケース２に多数の通気口２１が設けられており、これらの通気口２１を介して、充電反応により生成される酸素ガスなどのガスが酸素発生極５から排出される。 酸 素 At the oxygen generating electrode 5, oxygen gas is generated as the charging reaction proceeds. Therefore, the oxygen generating electrode 5 is provided so that the oxygen gas can diffuse, and at least a part thereof is provided so as to communicate with the outside air. In the configuration of FIG. 9, a large number of vents 21 are provided in the battery case 2 also on the side where the oxygen generating electrode 5 is disposed, and a gas such as oxygen gas generated by a charging reaction is supplied through these vents 21. It is discharged from the oxygen generating electrode 5.
　また、酸素発生極５に対しても、空気極４における空気極撥水層４３と同様に、充電極撥水層５２が備えられる。この充電極撥水層５２は、撥水性樹脂を含有する多孔性材料であり、充電極５１０に対して金属負極３と反対側（すなわち電池ケース２側）に配置されている。充電極撥水層５２が配設されることにより、酸素発生極５を介した電解液７の漏洩を抑制することができる。また、充電極撥水層５２が配設されることにより、充電反応により生成される酸素ガスなどのガスを電解液７と分離し、電池ケース２の外部へ通気口２１を介して排出することができる。 充電 Also, the charging electrode water-repellent layer 52 is provided for the oxygen generating electrode 5, similarly to the air electrode water-repellent layer 43 in the air electrode 4. The charging electrode water-repellent layer 52 is a porous material containing a water-repellent resin, and is disposed on the opposite side of the charging electrode 510 from the metal negative electrode 3 (that is, on the battery case 2 side). By providing the charging electrode water-repellent layer 52, leakage of the electrolyte solution 7 through the oxygen generating electrode 5 can be suppressed. Further, by providing the charging electrode water-repellent layer 52, a gas such as oxygen gas generated by a charging reaction is separated from the electrolytic solution 7 and discharged to the outside of the battery case 2 through the vent 21. Can be.
　セパレータ６は、電子的に絶縁性の材料で形成されて、空気極４と金属負極３、および酸素発生極５と金属負極３の絶縁を確保しつつ、これらの部材間の電荷担体の移動を可能とする。特に、セパレータ６は、電極間で電子伝導経路が形成されることによる短絡を防ぐ。例えば、充電時に金属負極３で還元析出した金属デンドライトが、酸素発生極５に到達し、短絡することを抑制する。 The separator 6 is made of an electronically insulating material, and secures the insulation between the air electrode 4 and the metal negative electrode 3 and between the oxygen generating electrode 5 and the metal negative electrode 3 while moving the charge carriers between these members. Make it possible. In particular, the separator 6 prevents a short circuit due to the formation of an electron conduction path between the electrodes. For example, a metal dendrite reduced and precipitated on the metal negative electrode 3 during charging reaches the oxygen generating electrode 5 and is prevented from being short-circuited.
　図９に示すような三極式の金属空気電池１００では、特に酸素発生極５において以下のような課題が発生する。
（Ａ）充電極５１０が多孔性であり、その孔部に入り込む電解液７は流動性が高いため、充電極撥水層５２のみでは電解液７の漏洩を確実に防止することが困難である。すなわち、酸素発生極５の背面から電解液７の漏洩が生じる。
（Ｂ）充電極５１０の孔部に入り込んだ電解液７により、充電中に発生する酸素ガスの排出が阻害され、充電極５１０の孔部に気泡が生じる。この気泡によって充電極５１０における三相界面が小さくなり、充電電圧が大きくなる（充電過電圧上昇）。その結果、不均一充電が生じ、金属空気電池１００のサイクル性も低下する。 In the three-electrode metal-air battery 100 as shown in FIG. 9, the following problem occurs particularly in the oxygen generation electrode 5.
(A) Since the charging electrode 510 is porous and the electrolytic solution 7 entering the pores has high fluidity, it is difficult to reliably prevent the leakage of the electrolytic solution 7 only with the charging electrode water-repellent layer 52. . That is, the electrolyte 7 leaks from the back surface of the oxygen generating electrode 5.
(B) The discharge of oxygen gas generated during charging is inhibited by the electrolyte solution 7 that has entered the hole of the charging electrode 510, and bubbles are generated in the hole of the charging electrode 510. The bubbles reduce the three-phase interface at the charging electrode 510 and increase the charging voltage (charging overvoltage rise). As a result, uneven charging occurs, and the cyclability of the metal-air battery 100 also decreases.
　上記課題に対して、特許文献１には、充電用正極を発泡金属材料と該発泡金属材料の孔部に含まれる親水性粒子状部材とを含んで構成することが開示されている。特許文献１に開示される構成では、発泡金属材料の孔部に親水性粒子状部材を含ませることで、発泡金属材料の孔部の隅々にまで電解液を行き渡らせることができ、発泡金属材料の表面をより有効に使用することができるとされている。また、電解液を含んだ親水性粒子状部材が、電解液が充電用の正極中を透過するのを阻止し、電解液の液漏れを抑制する効果も得られるとされている。 に 対 し て To solve the above problem, Patent Literature 1 discloses that a charging positive electrode includes a foamed metal material and a hydrophilic particulate member included in a hole of the foamed metal material. In the configuration disclosed in Patent Document 1, by including a hydrophilic particulate member in the pores of the foamed metal material, the electrolytic solution can be spread to all corners of the pores of the foamed metal material. It is said that the surface of the material can be used more effectively. Further, it is said that the hydrophilic particulate member containing the electrolytic solution also has an effect of preventing the electrolytic solution from passing through the positive electrode for charging, and suppressing the leakage of the electrolytic solution.
特開２０１７－１６８３１２号公報JP-A-2017-168312
　上記特許文献１における技術は、上記（Ａ）の課題に対して効果はあると考えられるものの、上記（Ｂ）の課題に対して十分な効果があるとは言えない。その理由は以下の通りである。 技術 Although the technique disclosed in Patent Document 1 is considered to be effective for the problem (A), it cannot be said that the technology is sufficiently effective for the problem (B). The reason is as follows.
　特許文献１に開示される構成では、図１０（ａ）に示すように、充電用正極は発泡金属材料２００により構成され、発泡金属材料２００に対して外気側の面に撥水膜２１０を配置し、電解液側の面にアニオン伝導膜２２０を配置している。また、発泡金属材料２００の孔部に親水性粒子状部材２０１が含まれる。 In the configuration disclosed in Patent Document 1, as shown in FIG. 10A, the charging positive electrode is made of a foamed metal material 200, and a water-repellent film 210 is arranged on the surface of the foamed metal material 200 on the outside air side. The anion conductive film 220 is arranged on the surface on the electrolyte side. The pores of the foamed metal material 200 include the hydrophilic particulate member 201.
　特許文献１の充電用正極を用いる金属空気電池では、図１０（ｂ）に示すように、親水性粒子状部材２０１によって発泡金属材料２００の孔部の全体に電解液２０２を行き渡らせることができる。しかしながら、孔部に隙間なく入り込んだ電解液２０２は、充電中に発生する酸素ガスの排出を阻害することにもなる。このため、発泡金属材料２００の内部は、酸素ガスの気泡２０３が残存する状態となり易い。また、親水性粒子状部材２０１は、発泡金属材料２００の内壁面から気泡２０３を剥がすような効果は無いため、気泡２０３は発泡金属材料２００の内壁面に付着して三相界面の面積を減少させ、上記（Ｂ）の課題を発生させる要因になる。 In the metal-air battery using the charging positive electrode of Patent Document 1, as shown in FIG. 10B, the electrolyte 202 can be spread over the entire pores of the foamed metal material 200 by the hydrophilic particulate member 201. . However, the electrolytic solution 202 that has entered the hole without a gap also impedes the discharge of oxygen gas generated during charging. For this reason, the inside of the foamed metal material 200 tends to be in a state in which the bubbles 203 of the oxygen gas remain. In addition, since the hydrophilic particulate member 201 has no effect of peeling the bubbles 203 from the inner wall surface of the foamed metal material 200, the bubbles 203 adhere to the inner wall surface of the foamed metal material 200 and reduce the area of the three-phase interface. This causes the problem (B).
　本開示は、上記課題に鑑みてなされたものであり、三極式の金属空気電池において、充電時における酸素発生極での充電反応を安定して効率よく行うことを目的とする。 The present disclosure has been made in view of the above problems, and has as its object to stably and efficiently perform a charging reaction at an oxygen generating electrode during charging in a three-electrode metal-air battery.
　上記の課題を解決するために、本開示の第１の態様である電極は、金属空気電池の充電用正極に使用される電極であって、内部に多数の孔部を有する金属多孔体と、親水性ポリマーを含み、少なくとも前記金属多孔体の孔部の内壁面を被覆する親水性ポリマー被膜とを含むことを特徴としている。 In order to solve the above problems, an electrode according to a first aspect of the present disclosure is an electrode used for a positive electrode for charging a metal-air battery, and a metal porous body having a large number of holes therein, And a hydrophilic polymer coating that covers at least the inner wall surface of the pores of the porous metal body.
　上記の構成によれば、金属多孔体の孔部の内壁面を被覆する親水性ポリマー被膜は、金属多孔体における孔部を完全に埋めるのではなく、酸素ガスの通路となる空隙を残しながら孔部の内壁面に被膜を形成する。このような電極を金属空気電池の充電用正極（酸素発生極）に用いた場合、電池内の電解液は親水性ポリマー被膜内を拡散し、金属多孔体の内壁面の全体に行き渡る。また、充電反応によって発生する酸素ガスは、親水性ポリマー被膜の作用によって金属多孔体の内壁面から容易に剥がされ、空隙を通って外部に排出される。このため、金属空気電池では、酸素発生極において酸素ガスの気泡により三相界面の面積が減少することを抑制でき、充電時における酸素発生極での充電反応を安定して効率よく行うことができる。 According to the above configuration, the hydrophilic polymer coating covering the inner wall surface of the pores of the porous metal body does not completely fill the pores in the porous metal body, but leaves pores that serve as oxygen gas passages. A coating is formed on the inner wall surface of the part. When such an electrode is used as a charging positive electrode (oxygen generating electrode) of a metal-air battery, the electrolyte in the battery diffuses in the hydrophilic polymer film and spreads over the entire inner wall surface of the porous metal body. Oxygen gas generated by the charging reaction is easily peeled off from the inner wall surface of the porous metal body by the action of the hydrophilic polymer film, and is discharged to the outside through the void. For this reason, in the metal-air battery, it is possible to suppress a decrease in the area of the three-phase interface due to bubbles of oxygen gas in the oxygen generating electrode, and it is possible to stably and efficiently perform a charging reaction at the oxygen generating electrode during charging. .
　また、上記電極では、前記親水性ポリマーは、水酸基、アミノ基、スルホ基またはカルボキシル基から選択される親水基を有する構成とすることが好ましい。これにより、金属空気電池が漏出しようとする電解液を親水性ポリマー被膜によって保液する効果が高くなる。 In addition, in the above electrode, the hydrophilic polymer preferably has a configuration having a hydrophilic group selected from a hydroxyl group, an amino group, a sulfo group and a carboxyl group. Thereby, the effect of retaining the electrolyte that the metal-air battery is about to leak by the hydrophilic polymer film is enhanced.
　また、上記電極では、前記親水性ポリマーは、アニオン交換基を有する構成とすることが好ましい。これにより、酸素発生極での炭酸塩析出を抑制できる。 In addition, in the above electrode, the hydrophilic polymer preferably has a configuration having an anion exchange group. Thereby, carbonate precipitation at the oxygen generating electrode can be suppressed.
　また、上記電極では、前記親水性ポリマーは、架橋構造を有する構成とすることが好ましい。これにより、親水性ポリマー被膜が強固となり、経時的な形状変化が少なくなるため、親水性ポリマー被膜による効果が長期間維持できる。 In addition, in the above electrode, it is preferable that the hydrophilic polymer has a structure having a crosslinked structure. As a result, the hydrophilic polymer film becomes strong and changes in shape over time are reduced, so that the effect of the hydrophilic polymer film can be maintained for a long time.
　また、上記電極では、前記親水性ポリマーは、水酸基、アミノ基、スルホ基およびカルボキシル基から選択される親水基の水素原子が離脱し、金属イオンとイオン結合した金属塩を有する構成とすることができる。 In the above electrode, the hydrophilic polymer may have a structure in which a hydrogen atom of a hydrophilic group selected from a hydroxyl group, an amino group, a sulfo group, and a carboxyl group is eliminated, and the metal salt is ion-bonded to a metal ion. it can.
　また、上記電極では、前記金属多孔体は、Ｎｉ，Ｃｒ，Ｍｎ，Ｆｅ，Ｃｏ，Ｃｕ，Ｒｕ，Ｒｈ，Ｐｄ，Ｉｒ，Ｐｔからなる群の何れかから構成することができる。 In addition, in the above electrode, the metal porous body can be composed of any of the group consisting of Ni, Cr, Mn, Fe, Co, Cu, Ru, Rh, Pd, Ir, and Pt.
　また、上記電極は、第１面と、前記第１面と対向する第２面とを備えており、前記親水性ポリマー被膜は、前記第１面から前記第２面までの前記金属多孔体の厚み方向において、前記第２面側の膜厚が前記第１面側の膜厚よりも小さくされており、当該電極の前記第１面側には、前記金属多孔体の孔部が前記親水性ポリマー被膜によって埋められた充填領域が存在している構成とすることができる。 Further, the electrode has a first surface and a second surface facing the first surface, and the hydrophilic polymer coating is formed of the metal porous body from the first surface to the second surface. In the thickness direction, the film thickness on the second surface side is smaller than the film thickness on the first surface side, and on the first surface side of the electrode, the pores of the porous metal body have the hydrophilic property. A configuration can be provided in which there is a filling region filled with a polymer coating.
　上記の構成によれば、このような電極を金属空気電池の充電用正極（酸素発生極）に用いた場合、第１面を金属負極と対向させて電解液と接するように配置することで、電解液は親水性ポリマー被膜によって拡散される分だけが充電極に内部に浸透することを許容され、それ以上の浸透は親水性ポリマー被膜の充填領域によって抑制される。一方、第２面側では、親水性ポリマー被膜の膜厚が小さくなるように形成されているため、十分な空隙が形成され、第２面側に充填領域が存在していることでこの空隙に電解液が入り込むことも抑制される。このため、空隙により充電中に発生する酸素ガスの排出が効率よく行える。 According to the above configuration, when such an electrode is used as a charging positive electrode (oxygen generating electrode) of a metal-air battery, the first surface is disposed so as to be in contact with the electrolyte while facing the metal negative electrode. Only the amount of the electrolyte diffused by the hydrophilic polymer film is allowed to penetrate into the charging electrode, and further permeation is suppressed by the filled region of the hydrophilic polymer film. On the other hand, on the second surface side, since the film thickness of the hydrophilic polymer film is formed to be small, sufficient voids are formed, and the presence of the filling region on the second surface side allows the voids to be formed in the voids. The entry of the electrolytic solution is also suppressed. Therefore, oxygen gas generated during charging due to the void can be efficiently discharged.
　また、上記電極では、前記充填領域の厚みは、前記金属多孔体の厚みの１／２０～１／２である構成とすることができる。 In the above electrode, the thickness of the filling region may be 1/20 to 1/2 of the thickness of the porous metal body.
　また、上記電極では、記金属多孔体の平均孔径は、０．４５～３．２ｍｍである構成とすることができる。 In the above electrode, the average pore diameter of the porous metal body may be 0.45 to 3.2 mm.
　また、上記電極は、第１面と、前記第１面と対向する第２面とを備えており、かつ、前記第１面側に位置する第１層と、前記第２面側に位置する第２層とを有しており、前記第１層における前記金属多孔体の平均孔径は、前記第２層における前記金属多孔体の平均孔径よりも小さい構成とすることができる。 Further, the electrode has a first surface, a second surface facing the first surface, and a first layer located on the first surface side and a first layer located on the second surface side. A second layer, wherein the average pore size of the porous metal body in the first layer can be smaller than the average pore size of the porous metal body in the second layer.
　上記の構成によれば、このような電極を金属空気電池の充電用正極（酸素発生極）に用いた場合、第１面を金属負極と対向させて電解液と接するように配置することで、電解液は親水性ポリマー被膜によって拡散される分だけが充電極に内部に浸透することを許容され、それ以上の浸透は第１層の親水性ポリマー被膜によって抑制される。一方、第２層では、親水性ポリマー被膜の膜厚が小さくなるように形成されているため、十分な空隙が形成され、この空隙により充電中に発生する酸素ガスの排出が効率よく行える。 According to the above configuration, when such an electrode is used as a charging positive electrode (oxygen generating electrode) of a metal-air battery, the first surface is disposed so as to be in contact with the electrolyte while facing the metal negative electrode. Only the amount of the electrolyte diffused by the hydrophilic polymer film is allowed to penetrate into the charging electrode, and further penetration is suppressed by the hydrophilic polymer film of the first layer. On the other hand, in the second layer, the hydrophilic polymer film is formed so as to have a small thickness, so that sufficient voids are formed, and the voids can efficiently discharge oxygen gas generated during charging.
　また、上記の課題を解決するために、本開示の第２の態様である金属空気電池は、筐体と、前記筐体の内部に収容された電解液と、前記電解液に一部が浸漬され、負極活物質となる金属を含む金属負極と、前記電解液に一部が浸漬され、前記金属負極に対向して配され、酸素発生能を有する酸素発生極と、前記電解液に一部が浸漬され、前記金属負極に対向して配され、酸素還元能を有する空気極と、を備えた金属空気電池であって、前記酸素発生極に、上記記載の電極を用いたことを特徴としている。 Further, in order to solve the above-described problem, a metal-air battery according to a second aspect of the present disclosure includes a housing, an electrolytic solution housed in the housing, and a part immersed in the electrolytic solution. A metal negative electrode containing a metal to be a negative electrode active material, a part of the electrolytic solution is immersed in the electrolytic solution, disposed to face the metal negative electrode, an oxygen generating electrode having an oxygen generating ability, and a part of the electrolytic solution. Is immersed, disposed to face the metal negative electrode, and an air electrode having an oxygen reducing ability, a metal-air battery, comprising, in the oxygen generating electrode, using the electrode described above. I have.
　また、上記金属空気電池は、前記酸素発生極における前記金属負極との対向面側に親水性ポリマー層が設けられている構成とすることができる。 In addition, the metal-air battery may have a configuration in which a hydrophilic polymer layer is provided on a surface of the oxygen generating electrode facing the metal negative electrode.
　上記の構成によれば、電解液は親水性ポリマー層および親水性ポリマー被膜によって拡散される分だけが酸素発生極内部に浸透することを許容され、それ以上の浸透は抑制される。このため、酸素発生極では、空隙に電解液が入り込むことが抑制され、空隙によって充電中に発生する酸素ガスの排出が効率よく行える。 According to the above configuration, only the amount of the electrolyte solution diffused by the hydrophilic polymer layer and the hydrophilic polymer film is allowed to permeate into the oxygen generating electrode, and further permeation is suppressed. For this reason, in the oxygen generating electrode, entry of the electrolytic solution into the gap is suppressed, and oxygen gas generated during charging can be efficiently discharged by the gap.
　また、上記の課題を解決するために、本開示の第３の態様である電極の製造方法は、金属空気電池の充電用正極に使用される電極の製造方法であって、内部に多数の孔部を有する金属多孔体を、親水性ポリマーを含む溶液中に浸漬する浸漬工程と、前記浸漬工程で親水性ポリマーを含む溶液に浸漬させた金属多孔体を引き上げて乾燥させる乾燥工程とを含むことを特徴としている。 Further, in order to solve the above problem, a method for manufacturing an electrode according to a third aspect of the present disclosure is a method for manufacturing an electrode used for a positive electrode for charging a metal-air battery, wherein a large number of holes are provided inside. A dipping step of dipping the porous metal body having a portion in a solution containing a hydrophilic polymer, and a drying step of pulling up and drying the porous metal body dipped in the solution containing a hydrophilic polymer in the dipping step It is characterized by.
　上記の構成よれば、浸漬工程および乾燥工程によって金属多孔体の孔部の内壁面を被覆する親水性ポリマー被膜を形成することができ、上記記載の電極を得ることができる。 According to the above configuration, the hydrophilic polymer film covering the inner wall surface of the hole of the porous metal body can be formed by the dipping step and the drying step, and the above-described electrode can be obtained.
　また、上記電極の製造方法では、前記浸漬工程で前記金属多孔体の厚さの１／２０～１／２までのみを前記親水性ポリマーを含む溶液中に浸漬させる構成とすることができる。 In addition, in the above-described method for manufacturing an electrode, it is possible to adopt a configuration in which only 1/20 to 1/2 of the thickness of the porous metal body is immersed in the solution containing the hydrophilic polymer in the immersion step.
　本開示の電極、金属空気電池および電極の製造方法では、電極の金属多孔体の孔部の内壁面を被覆する親水性ポリマー被膜が形成される。このような電極を金属空気電池の充電用正極（酸素発生極）に用いた場合、充電反応によって発生する酸素ガスは、金属多孔体の孔部の内壁面を被覆する親水性ポリマー被膜の作用によって金属多孔体の内壁面から容易に剥がされ、空隙を通って外部に排出される。このため、金属空気電池の酸素発生極において酸素ガスの気泡により三相界面の面積が減少することを抑制でき、充電時における酸素発生極での充電反応を安定して効率よく行うことができるといった効果を奏する。 In the electrode, the metal-air battery, and the method for manufacturing an electrode according to the present disclosure, a hydrophilic polymer film that covers the inner wall surface of the hole of the porous metal body of the electrode is formed. When such an electrode is used as a positive electrode for charging a metal-air battery (oxygen generating electrode), oxygen gas generated by the charging reaction is caused by the action of a hydrophilic polymer film that coats the inner wall surface of the pores of the porous metal body. It is easily peeled off from the inner wall surface of the porous metal body, and is discharged to the outside through the void. Therefore, it is possible to suppress a decrease in the area of the three-phase interface due to bubbles of oxygen gas in the oxygen generating electrode of the metal-air battery, and to stably and efficiently perform a charging reaction at the oxygen generating electrode during charging. It works.
実施の形態１に係る金属空気電池の構造を示す概略断面図である。FIG. 2 is a schematic sectional view showing the structure of the metal-air battery according to Embodiment 1. 実施の形態１に係る充電極の内部構成を示す模式図であり、（ａ）は充電極の全体を示す図であり、（ｂ）は充電極の一部を拡大して示す図である。3A and 3B are schematic diagrams illustrating an internal configuration of a charging electrode according to the first embodiment, where FIG. 3A is a diagram illustrating the entire charging electrode and FIG. 3B is a diagram illustrating a part of the charging electrode in an enlarged manner. 実施の形態１に係る充電極の製造方法を示す工程図である。FIG. 4 is a process chart illustrating a method for manufacturing the charged electrode according to the first embodiment. 評価セルおよび比較用評価セルに対し、充電時の充電電圧の変化を示すグラフである。9 is a graph showing changes in charging voltage during charging of an evaluation cell and a comparative evaluation cell. （ａ）は親水性ポリマー被膜の膜厚が大きすぎる場合の充電極の模式図であり、（ｂ）は親水性ポリマー被膜の膜厚が小さすぎる場合の充電極の模式図である。(A) is a schematic diagram of the charging electrode when the thickness of the hydrophilic polymer film is too large, and (b) is a schematic diagram of the charging electrode when the film thickness of the hydrophilic polymer film is too small. 実施の形態２に係る充電極の内部構成を示す模式図である。FIG. 9 is a schematic diagram showing an internal configuration of a charging electrode according to Embodiment 2. 実施の形態３に係る充電極の内部構成を示す模式図である。FIG. 9 is a schematic diagram showing an internal configuration of a charging electrode according to Embodiment 3. 実施の形態３に係る金属空気電池の構造を示す概略断面図である。FIG. 9 is a schematic sectional view illustrating a structure of a metal-air battery according to a third embodiment. 三極式の金属空気電池の一般的な構造を示す概略断面図である。FIG. 1 is a schematic cross-sectional view showing a general structure of a three-electrode metal-air battery. 従来の充電極の内部構成を示す模式図であり、（ａ）は充電極の全体を示す図であり、（ｂ）は充電極の一部を拡大して示す図である。It is a schematic diagram which shows the internal structure of the conventional charging electrode, (a) is a figure which shows the whole charging electrode, (b) is a figure which expands and shows a part of charging electrode.
　〔実施の形態１〕
　以下、本開示の実施の形態について、図面を参照して詳細に説明する。図１は、本実施の形態１に係る金属空気電池１０の構造を示す概略断面図である。金属空気電池１０は、三極式の二次電池であり、図９に示す金属空気電池１００と類似した構成を示している。このため、図１の金属空気電池１０において、図９の金属空気電池１００と同様の構成については同じ部材番号を付し、詳細な説明は省略する。 [Embodiment 1]
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing the structure of the metal-air battery 10 according to the first embodiment. The metal-air battery 10 is a tripolar secondary battery and has a configuration similar to that of the metal-air battery 100 shown in FIG. For this reason, in the metal-air battery 10 of FIG. 1, the same components as those of the metal-air battery 100 of FIG.
　図１の金属空気電池１０は、酸素発生極５の構成のみが図９の金属空気電池１００とは異なるものであり、具体的には、図９の充電極５１０に代えて、充電極５１を用いている。このため、本実施の形態１では、充電極５１の具体的構成および製造方法について説明する。尚、酸素発生極５以外の構成、例えば金属負極３や空気極４の構成については、金属空気電池１００と同様の構成に限定されるものではなく、三極式の金属空気二次電池における他の公知の構成を採用してもよい。 The metal-air battery 10 of FIG. 1 is different from the metal-air battery 100 of FIG. 9 only in the configuration of the oxygen generating electrode 5. Specifically, instead of the charging electrode 510 of FIG. Used. Therefore, in the first embodiment, a specific configuration and a manufacturing method of the charging electrode 51 will be described. The configuration other than the oxygen generating electrode 5, for example, the configuration of the metal negative electrode 3 and the air electrode 4 is not limited to the same configuration as that of the metal-air battery 100. May be adopted.
　図２は充電極５１の内部構成を示す模式図であり、図２の（ａ）は充電極５１の全体を示す図であり、図２の（ｂ）は充電極５１の一部を拡大して示す図である。図２（ａ），（ｂ）に示すように、充電極５１は金属多孔体５１１および親水性ポリマー被膜５１２によって構成されている。親水性ポリマー被膜５１２は、金属多孔体５１１における孔部の内壁面を被覆する。すなわち、親水性ポリマー被膜５１２は、図２（ｂ）に示すように、金属多孔体５１１における孔部を完全に埋めるのではなく、酸素ガスの通路となる空隙５１３を残しながら孔部の内壁面に被膜を形成している。尚、充電極５１では、金属多孔体５１１の表面に充電反応を促進する酸素発生触媒粒子が備えられてもよい。 2A and 2B are schematic diagrams showing the internal configuration of the charging electrode 51. FIG. 2A is a diagram showing the entire charging electrode 51, and FIG. 2B is an enlarged view of a part of the charging electrode 51. FIG. As shown in FIGS. 2A and 2B, the charging electrode 51 includes a porous metal body 511 and a hydrophilic polymer film 512. The hydrophilic polymer coating 512 covers the inner wall surface of the hole in the porous metal body 511. That is, as shown in FIG. 2B, the hydrophilic polymer coating 512 does not completely fill the pores in the porous metal body 511, but leaves the voids 513 serving as oxygen gas passages. A film is formed on the surface. In the charging electrode 51, oxygen generating catalyst particles that promote the charging reaction may be provided on the surface of the porous metal body 511.
　このような充電極５１を用いた金属空気電池１０では、電解液７は親水性ポリマー被膜５１２内を拡散し、金属多孔体５１１の内壁面の全体に行き渡る。また、充電反応によって発生する酸素ガスは、親水性ポリマー被膜５１２の作用によって金属多孔体５１１の内壁面から容易に剥がされ、空隙５１３を通って外部に排出される。具体的には、充電極５１で発生する酸素ガスは、充電極撥水層５２および電池ケース２における通気口２１から金属空気電池１０の外部に排出される。 In the metal-air battery 10 using such a charging electrode 51, the electrolytic solution 7 diffuses in the hydrophilic polymer film 512 and spreads over the entire inner wall surface of the porous metal body 511. The oxygen gas generated by the charging reaction is easily peeled off from the inner wall surface of the porous metal body 511 by the action of the hydrophilic polymer film 512, and is discharged to the outside through the void 513. Specifically, oxygen gas generated at the charging electrode 51 is discharged from the charging electrode water-repellent layer 52 and the vent 21 of the battery case 2 to the outside of the metal-air battery 10.
　金属空気電池１０では、金属多孔体５１１における孔部の内壁面に親水性ポリマー被膜５１２が形成されることで、酸素発生極５において酸素ガスの気泡により三相界面の面積が減少することを抑制できる。その結果、酸素発生極５における充電反応を効率よく行うことができる。 In the metal-air battery 10, since the hydrophilic polymer coating 512 is formed on the inner wall surface of the hole in the porous metal body 511, the area of the three-phase interface is prevented from being reduced by oxygen gas bubbles in the oxygen generating electrode 5. it can. As a result, the charging reaction at the oxygen generating electrode 5 can be performed efficiently.
　続いて、充電極５１の製造方法について図３を参照して説明する。尚、以下の説明では、実際に製造した実施例１の充電極５１の製造条件を併せて示す。 Next, a method of manufacturing the charging electrode 51 will be described with reference to FIG. In the following description, manufacturing conditions of the actually manufactured charging electrode 51 of the first embodiment are also shown.
　まず、充電極５１の材料として、金属多孔体５１１と親水性ポリマー含有水溶液とを準備する（Ｓ１およびＳ２）。金属多孔体５１１としては、金属発泡体（例えば、住友電工製の「セルメット（登録商標）」）が好適に使用できるが、それ以外にも金属粒子や金属繊維の焼結体なども使用可能である。尚、金属多孔体５１１は、酸素発生能を有する金属、すなわちＮｉ，Ｃｒ，Ｍｎ，Ｆｅ，Ｃｏ，Ｃｕ，Ｒｕ，Ｒｈ，Ｐｄ，Ｉｒ，Ｐｔからなる群の何れから構成することができる。 First, as a material of the charging electrode 51, a porous metal body 511 and an aqueous solution containing a hydrophilic polymer are prepared (S1 and S2). As the metal porous body 511, a metal foam (for example, “Celmet (registered trademark)” manufactured by Sumitomo Electric Industries) can be preferably used, but a sintered body of metal particles or metal fibers can also be used. is there. The porous metal body 511 can be made of any metal having an oxygen generating ability, that is, any of the group consisting of Ni, Cr, Mn, Fe, Co, Cu, Ru, Rh, Pd, Ir, and Pt.
　金属多孔体５１１の寸法は、例えば、以下の範囲とされる。
・厚み：１．４～１０．０ｍｍ
・比表面積：２５０～５８００ｍ2／ｍ3
・平均孔径：０．４５～３．２ｍｍ
尚、金属多孔体５１１における孔部の平均孔径は、細孔直径分布測定装置（米国ＰＵＩ社製 パームポロメーター）により算出し、規定することができる。 The dimensions of the porous metal body 511 are, for example, in the following ranges.
・ Thickness: 1.4 to 10.0 mm
・ Specific surface area: 250-5800m2 / m3
・ Average pore diameter: 0.45 to 3.2 mm
In addition, the average pore diameter of the pores in the porous metal body 511 can be calculated and specified by a pore diameter distribution measuring device (a palm porometer manufactured by PUI, USA).
　実施例１においては、金属発泡体である住友電工製の「セルメット」を材料とし、厚さ１．４ｍｍ、５０ｍｍ×５０ｍｍのシート状、平均孔径０．４５ｍｍの金属多孔体５１１を用いた。 In Example 1, a metal foam, “Celmet” manufactured by Sumitomo Electric Co., Ltd. was used as the material, and a sheet-like metal sheet having a thickness of 1.4 mm, 50 mm × 50 mm, and an average pore diameter of 0.45 mm was used.
　親水性ポリマー被膜５１２は少なくとも親水性ポリマーを含む膜である。親水性ポリマー被膜５１２に用いられる親水性ポリマーの種類としては、水酸基、アミノ基、スルホ基またはカルボキシル基などの親水基を有するハイドロゲルや、アニオン交換基を有するアニオン交換樹脂等が挙げられる。また、親水性ポリマーは、水酸基、アミノ基、スルホ基、カルボキシル基の水素原子が離脱して、金属イオンと塩を形成していてもよい。また、親水性ポリマーは、水酸基またはカルボキシル基と、アニオン交換基との両方を有していてもよい。 The hydrophilic polymer film 512 is a film containing at least a hydrophilic polymer. Examples of the type of the hydrophilic polymer used for the hydrophilic polymer film 512 include a hydrogel having a hydrophilic group such as a hydroxyl group, an amino group, a sulfo group or a carboxyl group, and an anion exchange resin having an anion exchange group. The hydrophilic polymer may form a salt with a metal ion by removing a hydrogen atom of a hydroxyl group, an amino group, a sulfo group, or a carboxyl group. Further, the hydrophilic polymer may have both a hydroxyl group or a carboxyl group and an anion exchange group.
　親水性ポリマー被膜５１２に含まれる親水性ポリマーが水酸基、アミノ基、スルホ基またはカルボキシル基を有する場合、漏出しようとする電解液７を保液する効果が高くなる。また、親水性ポリマー被膜５１２がアニオン交換基を有する場合、酸素発生極５での炭酸塩析出を抑制できる。さらに、親水性ポリマー被膜５１２は架橋構造を有する（共有結合でモノマーが結合されている）ものとすることが好ましい。親水性ポリマー被膜５１２が架橋構造を有する場合、親水性ポリマー被膜５１２が強固となり、経時的な形状変化が少なくなるため、親水性ポリマー被膜５１２による効果が長期間維持できる。 (4) When the hydrophilic polymer contained in the hydrophilic polymer film 512 has a hydroxyl group, an amino group, a sulfo group or a carboxyl group, the effect of retaining the electrolyte solution 7 to be leaked is enhanced. In addition, when the hydrophilic polymer coating 512 has an anion exchange group, carbonate precipitation at the oxygen generating electrode 5 can be suppressed. Further, it is preferable that the hydrophilic polymer film 512 has a crosslinked structure (a monomer is bound by a covalent bond). When the hydrophilic polymer film 512 has a crosslinked structure, the hydrophilic polymer film 512 becomes strong and changes in shape over time are reduced, so that the effect of the hydrophilic polymer film 512 can be maintained for a long time.
　ハイドロゲルは、ＯＨ，ＣＯＯＨ基等を有するものであり、多価アルコールまたはアクリル酸またはアクリル酸金属塩を含むことで保水性を向上させたものである。多価アルコールとしては、エチレングリコール、プロピレングリコール、ブタンジオール等のジオールの他、グリセリン、ペンタエリスリトール、ソルビトール等の多価アルコール類、ポリエチレングリコール、ポリプロピレングリコール、ジグリセリン、ポリグリセリン等の多価アルコール縮合体、ポリオキシエチレングリセリン等の多価アルコール変成体が挙げられる。多価アルコールは、１種のみであってもよく、複数種の混合物であってもよい。また、アクリル酸としては、ポリアクリル酸などが挙げられ、ポリアクリル酸塩としてはポリアクリル酸ナトリウム、ポリアクリル酸カリウムなどが挙げられる。 The hydrogel has OH, COOH groups and the like, and has improved water retention by containing a polyhydric alcohol, acrylic acid or a metal salt of acrylic acid. Examples of the polyhydric alcohol include diols such as ethylene glycol, propylene glycol, and butanediol; polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol; and polyhydric alcohol condensation such as polyethylene glycol, polypropylene glycol, diglycerin, and polyglycerin. And modified polyhydric alcohols such as polyoxyethylene glycerin. The polyhydric alcohol may be only one kind or a mixture of plural kinds. Examples of acrylic acid include polyacrylic acid, and examples of polyacrylate include sodium polyacrylate and potassium polyacrylate.
　アニオン交換樹脂（アニオン伝導性固体電解質樹脂）は、４級アンモニウム基を有するものが好適に使用でき、その製造方法は公知の方法（例えば特公平０３－１２５６８号公報を参照）が使用可能である。 As the anion exchange resin (anion-conductive solid electrolyte resin), those having a quaternary ammonium group can be preferably used, and a known method (for example, see Japanese Patent Publication No. 03-12568) can be used. .
　親水性ポリマー被膜５１２には、親水性ポリマーの他に、導電助剤や酸素発生能を有する触媒が含まれてもよい。導電助剤および酸素発生能を有する触媒は、当該分野の公知の材料を用いてよい。 The hydrophilic polymer film 512 may contain a conductive auxiliary agent or a catalyst having an ability to generate oxygen, in addition to the hydrophilic polymer. As the conductive auxiliary agent and the catalyst having an oxygen generating ability, known materials in the art may be used.
　酸素発生極５に含まれる親水性ポリマー被膜５１２の量は、金属多孔体５１１の１ｃｍ3あたり、０．０３ｇ～０．３ｇであることが好ましい。酸素発生極５に含まれる親水性ポリマー被膜５１２の量が金属多孔体５１１の１ｃｍ3あたり０．０３ｇよりも少ないと、酸素発生極５内で親水性ポリマー被膜５１２が薄くなる場合があり、十分な三相界面が形成されない虞がある。親水性ポリマー被膜５１２が薄い場合、充電過電圧が高くなると共に、電解液漏出抑制の効果が得られない場合がある。酸素発生極５に含まれる親水性ポリマー被膜５１２の量が金属多孔体５１１の１ｃｍ3あたり、０．３ｇよりも多い場合は、親水性ポリマー被膜５１２で空隙５１３がすべて埋まってしまう虞がある。この場合、空隙５１３を埋める親水性ポリマー被膜５１２によって酸素ガス排出が阻害され三相界面が低下してしまう。 量 The amount of the hydrophilic polymer coating 512 contained in the oxygen generating electrode 5 is preferably 0.03 g to 0.3 g per 1 cm 3 of the porous metal body 511. If the amount of the hydrophilic polymer coating 512 contained in the oxygen generating electrode 5 is less than 0.03 g per 1 cm 3 of the metal porous body 511, the hydrophilic polymer coating 512 may become thin in the oxygen generating electrode 5 and may be insufficient. There is a possibility that a three-phase interface is not formed. When the hydrophilic polymer film 512 is thin, the charging overvoltage increases, and the effect of suppressing electrolyte leakage may not be obtained. If the amount of the hydrophilic polymer coating 512 contained in the oxygen generating electrode 5 is more than 0.3 g per 1 cm 3 of the metal porous body 511, the voids 513 may be completely filled with the hydrophilic polymer coating 512. In this case, oxygen gas discharge is hindered by the hydrophilic polymer film 512 filling the void 513, and the three-phase interface is reduced.
　実施例１において、親水性ポリマー含有水溶液は、水溶媒（１００ｃｍ3）に、「架橋型ポリアクリル酸ナトリウム」を１ｇ溶かし、３ｈ撹拌することで準備した。 に お い て In Example 1, the hydrophilic polymer-containing aqueous solution was prepared by dissolving 1 g of “crosslinked sodium polyacrylate” in an aqueous solvent (100 cm 3) and stirring for 3 h.
　Ｓ３の浸漬工程では、Ｓ１で準備した金属多孔体５１１を、Ｓ２で準備した親水性ポリマー含有水溶液に２４ｈ浸漬させた。Ｓ４の乾燥工程では、Ｓ３で親水性ポリマー含有水溶液に浸漬させた金属多孔体５１１を引き上げ、２５℃の環境下で１２ｈ乾燥させた。乾燥工程後、金属多孔体５１１の内壁面に親水性ポリマー被膜５１２が形成された実施例１の充電極５１が得られる。尚、浸漬工程においては、親水性ポリマー含有水溶液をゲル化させ、ゲル化させた親水性ポリマー含有水溶液を金属多孔体５１１の片面に塗布する、またはゲル化させた親水性ポリマーを金属多孔体５１１の片面に圧着させるような方法を採用してもよい。親水性ポリマー含有水溶液を塗布または圧着できる程度にゲル化する方法としては、(1) 直鎖型ポリアクリル酸などを混ぜてゲル化させる（増粘化させる）方法や、(2) 親水性ポリマー含有水溶液に、親水性モノマー（例：アクリル酸）、架橋剤（例：Ｎ'Ｎ－メチレンビスアクリルアミド）、重合開始剤（例：ペルオキソ二硫酸カリウム粉末）を溶かし、３０ｍｉｎ攪拌、１２ｈ静置してゲル化させる方法などが挙げられる。 In the dipping step of S3, the porous metal body 511 prepared in S1 was dipped in the hydrophilic polymer-containing aqueous solution prepared in S2 for 24 hours. In the drying step of S4, the metal porous body 511 immersed in the aqueous solution containing a hydrophilic polymer in S3 was pulled up and dried at 25 ° C. for 12 hours. After the drying step, the charging electrode 51 of Example 1 in which the hydrophilic polymer film 512 is formed on the inner wall surface of the porous metal body 511 is obtained. In the immersion step, the hydrophilic polymer-containing aqueous solution is gelled, and the gelled hydrophilic polymer-containing aqueous solution is applied to one surface of the porous metal body 511, or the gelled hydrophilic polymer is applied to the metallic porous body 511. May be adopted. As a method of gelling to the extent that a hydrophilic polymer-containing aqueous solution can be applied or pressed, there are (1) a method in which linear polyacrylic acid is mixed and gelled (thickened), and (2) a hydrophilic polymer. A hydrophilic monomer (eg, acrylic acid), a cross-linking agent (eg, N′N-methylenebisacrylamide), and a polymerization initiator (eg, potassium peroxodisulfate powder) are dissolved in the aqueous solution, and the mixture is stirred for 30 minutes and left to stand for 12 hours. Gelation method.
　製造した実施例１の充電極５１においては、以下の方法により親水性ポリマー被膜５１２の形成を確認した。すなわち、充電極５１を、重金属カチオンやＢｒアニオンを含む溶液に含浸・乾燥後、断面ＴＥＭ－ＥＤＸ観察を行うことで、金属多孔体５１１の骨格以外の領域に重金属またはＢｒを検出し、金属多孔体５１１の孔部内に親水性ポリマー被膜５１２が存在することを確認した。 形成 In the manufactured charging electrode 51 of Example 1, formation of the hydrophilic polymer film 512 was confirmed by the following method. That is, the charging electrode 51 is impregnated with a solution containing a heavy metal cation or a Br anion, dried, and then subjected to cross-sectional TEM-EDX observation to detect a heavy metal or Br in a region other than the skeleton of the porous metal body 511, and to detect It was confirmed that the hydrophilic polymer coating 512 was present in the holes of the body 511.
　実施例１の充電極５１を用いて評価セルとなる金属空気電池を製造し、その充放電特性を評価した。評価セル（実施例１）は、図１に示す金属空気電池１０の構造とし、充電極５１以外の構成は以下のようにした。また、比較用評価セルとして、実施例１の充電極５１に代えて、上記Ｓ１で準備した金属多孔体５１１のみを充電極として用いた金属空気電池を製造した。比較用評価セルにおいても、充電極以外の構成は以下の通りである。 金属 A metal-air battery serving as an evaluation cell was manufactured using the charging electrode 51 of Example 1, and its charge / discharge characteristics were evaluated. The evaluation cell (Example 1) had the structure of the metal-air battery 10 shown in FIG. 1, and the configuration other than the charging electrode 51 was as follows. Further, as a comparative evaluation cell, a metal-air battery using only the metal porous body 511 prepared in S1 as a charging electrode instead of the charging electrode 51 of Example 1 was manufactured. The configuration of the comparative evaluation cell other than the charging electrode is as follows.
　　金属負極３：亜鉛および酸化亜鉛粒子を含む金属負極「厚さ２ｍｍ、５０ｍｍ×５０ｍｍのシート状」
　　電解液７：Ｚｎ飽和ＫＯＨ水溶液　１０ｍｌ　（ＫＯＨ７Ｍ、酸化亜鉛０．６５Ｍ）
　　空気極４：ＱＳＩ（Ｑｕａｎｔｕｍ Ｓｐｈｅｒｅ）社製「厚さ０．３ｍｍ、５０ｍ
ｍ×５０ｍｍのシート状」
　　セパレータ６：日本触媒社製「厚さ０．３ｍｍ、５０ｍｍ×５０ｍｍのシート状」
　　充電極撥水層５２：日東電工社製「厚さ０．２ｍｍ、５０ｍｍ×５０ｍｍのシート状」
　評価セルおよび比較用評価セルに対し、バッテリーテスター（菊水電子工業社製：ＳＰＥＣ２０５２６－ＰＦＸ２０１１Ｓ）を用いた充放電試験を、温度２５℃の環境下で電池端子間開路電圧が１．０Ｖ‐３．０Ｖの範囲において、０．１Ｃの定電流で１０サイクルの充放電を行った。図４は、２サイクル時の充放電試験における充電時の充電電圧の変化を示すグラフである。 Metal negative electrode 3: Metal negative electrode containing zinc and zinc oxide particles “2 mm thick, 50 mm × 50 mm sheet”
Electrolyte solution 7: Zn-saturated KOH aqueous solution 10 ml (KOH 7M, zinc oxide 0.65M)
Air electrode 4: "Thickness 0.3 mm, 50 m" manufactured by QSI (Quantum Sphere)
mx 50mm sheet "
Separator 6: Nippon Shokubai Co., Ltd. “Sheet 0.3 mm thick, 50 mm × 50 mm”
Charging electrode water-repellent layer 52: Nitto Denko Corporation “0.2 mm thick, 50 mm × 50 mm sheet”
A charge / discharge test using a battery tester (SPEC20526-PFX2011S, manufactured by Kikusui Electronics Corporation) was performed on the evaluation cell and the comparative evaluation cell under an environment of a temperature of 25 ° C. 10 cycles of charging and discharging were performed at a constant current of 0.1 C in a range of 0 V. FIG. 4 is a graph showing a change in charging voltage during charging in a charge / discharge test during two cycles.
　図４に示すように、比較用評価セルでは充電が進むにつれて充電電圧が増加しているのに対し、評価セル（実施例１）では充電が進んでも充電電圧の増加は大幅に抑制されている。また、最大充電容量についても、評価セル（実施例１）は比較用評価セルよりも増加している。 As shown in FIG. 4, in the comparative evaluation cell, the charging voltage increases as the charging progresses, whereas in the evaluation cell (Example 1), the increase in the charging voltage is greatly suppressed even when the charging progresses. . Also, with respect to the maximum charge capacity, the evaluation cell (Example 1) is larger than the comparative evaluation cell.
　さらに、充電極撥水層５２からの液漏れに関しても、目視で確認による確認では、評価セル（実施例１）において液漏れは発生していなかった。一方で、比較用評価セルにおいて液漏れは発生していた。これは、充電極５１の内部において、電解液７が親水性ポリマー被膜５１２内を拡散することでその流動性が抑えられ、その結果、充電極撥水層５２からの液漏れが無くなったためと考えられる。 {Circle around (5)} Further, with respect to the liquid leakage from the charged extreme water-repellent layer 52, liquid leakage did not occur in the evaluation cell (Example 1) by visual confirmation. On the other hand, liquid leakage occurred in the comparative evaluation cell. This is because the electrolyte 7 diffuses inside the hydrophilic polymer film 512 inside the charging electrode 51 to suppress its fluidity, and as a result, liquid leakage from the charging electrode water-repellent layer 52 is eliminated. Can be
　〔実施の形態２〕
　上記実施の形態１では、充電極５１を金属多孔体５１１および親水性ポリマー被膜５１２によって構成することで、背景技術にて説明した課題（Ａ）および（Ｂ）を解決できることを説明した。しかしながら、実際には、図２に示す充電極５１の構成にて課題（Ａ）および（Ｂ）を解決するためには、親水性ポリマー被膜５１２が適切な膜厚を有するように形成されることが必要である。 [Embodiment 2]
In the first embodiment, it has been described that the problems (A) and (B) described in the background art can be solved by configuring the charging electrode 51 with the porous metal body 511 and the hydrophilic polymer film 512. However, in practice, in order to solve the problems (A) and (B) with the configuration of the charging electrode 51 shown in FIG. 2, the hydrophilic polymer film 512 must be formed to have an appropriate film thickness. is necessary.
　親水性ポリマー被膜５１２の膜厚は、図３に示す浸漬工程において、親水性ポリマー含有水溶液の親水性ポリマー濃度を調整することで、ある程度は調整可能である。すなわち、親水性ポリマー濃度を高くすれば親水性ポリマー被膜５１２の膜厚を大きくすることができ、親水性ポリマー濃度を低くすれば親水性ポリマー被膜５１２の膜厚を小さくすることができる。しかしながら、親水性ポリマー含有水溶液の濃度調整のみで親水性ポリマー被膜５１２の最適な膜厚を得ることは実際には容易でないと考えられる。 (3) The thickness of the hydrophilic polymer film 512 can be adjusted to some extent by adjusting the concentration of the hydrophilic polymer in the aqueous solution containing a hydrophilic polymer in the dipping step shown in FIG. That is, the film thickness of the hydrophilic polymer film 512 can be increased by increasing the concentration of the hydrophilic polymer, and the film thickness of the hydrophilic polymer film 512 can be decreased by decreasing the concentration of the hydrophilic polymer. However, it is considered that it is actually not easy to obtain an optimum film thickness of the hydrophilic polymer film 512 only by adjusting the concentration of the hydrophilic polymer-containing aqueous solution.
　例えば、親水性ポリマー含有水溶液の濃度が高すぎる場合、図５（ａ）に示すように、親水性ポリマー被膜５１２の膜厚が大きくなりすぎ、金属多孔体５１１における孔部が親水性ポリマー被膜５１２によって完全に埋められて空隙５１３が形成されないことが起こり得る（尚、金属多孔体５１１の孔部を完全に埋めるような親水性ポリマー被膜５１２は、実際には被膜と言えるものではないが、便宜上、親水性ポリマー被膜５１２との名称を用いている）。あるいは、空隙５１３が形成されたとしても、空隙５１３が小さすぎて繋がらず、親水性ポリマー被膜５１２によって殆どの空隙５１３が分断されてしまうことも起こり得る。このように親水性ポリマー被膜５１２の膜厚が大きすぎて空隙５１３が十分に形成されなければ、充電中に発生する酸素ガスの排出効果が大幅に低下し、課題（Ｂ）の防止効果が低下する。 For example, when the concentration of the aqueous solution containing a hydrophilic polymer is too high, as shown in FIG. 5A, the film thickness of the hydrophilic polymer film 512 becomes too large, and the pores in the porous metal body 511 become the hydrophilic polymer film 512. (The hydrophilic polymer coating 512 that completely fills the pores of the porous metal body 511 is not actually a coating, but for convenience. , Hydrophilic polymer coating 512). Alternatively, even if the voids 513 are formed, the voids 513 are too small to be connected, and most of the voids 513 may be divided by the hydrophilic polymer coating 512. If the void 513 is not sufficiently formed because the thickness of the hydrophilic polymer film 512 is too large, the effect of discharging oxygen gas generated during charging is significantly reduced, and the effect of preventing the problem (B) is reduced. I do.
　一方、親水性ポリマー含有水溶液の濃度が低すぎる場合、図５（ｂ）に示すように、親水性ポリマー被膜５１２の膜厚が小さくなり、親水性ポリマー被膜５１２による保水効果が低下する。この場合、金属多孔体５１１内の、本来は空隙５１３となる部分にまで電解液７が入り込んでしまう。そして、金属多孔体５１１内に入り込んだ電解液７によって、充電中に発生する酸素ガスの排出が阻害されるため、課題（Ｂ）の防止効果が低下する。さらには、金属多孔体５１１内に親水性ポリマー被膜５１２によって保水されない電解液７が存在すると液漏れの原因ともなり、課題（Ａ）の防止効果も低下する。 On the other hand, when the concentration of the aqueous solution containing a hydrophilic polymer is too low, as shown in FIG. 5B, the film thickness of the hydrophilic polymer film 512 becomes small, and the water retention effect of the hydrophilic polymer film 512 decreases. In this case, the electrolyte solution 7 penetrates into a portion of the porous metal body 511 which originally becomes the void 513. Then, the discharge of oxygen gas generated during charging is inhibited by the electrolyte solution 7 that has entered the porous metal body 511, so that the effect of preventing the problem (B) is reduced. Furthermore, if the electrolytic solution 7 that is not retained by the hydrophilic polymer film 512 is present in the porous metal body 511, it causes a liquid leakage, and the effect of preventing the problem (A) is reduced.
　本実施の形態２では、上述した課題（Ａ）および（Ｂ）をより確実に解決し得る充電極５１の構成および製造方法について説明する。 In the second embodiment, a configuration and a manufacturing method of the charging electrode 51 that can more reliably solve the above-described problems (A) and (B) will be described.
　図６は、本実施の形態２に係る充電極５１の内部構成を示す模式図である。本実施の形態２に係る充電極５１は、実施の形態１と同様に、金属多孔体５１１および親水性ポリマー被膜５１２によって構成されている。但し、親水性ポリマー被膜５１２は、その膜厚が一定ではなく、充電極５１の厚さ方向に沿って、一方の面（第１面）から他方の面（第２面）に向かって親水性ポリマー被膜５１２の膜厚が徐々に小さくなるようなグラデーション構造を有している。この時、親水性ポリマー被膜５１２の膜厚が大きくなる第１面側では、金属多孔体５１１の孔部が親水性ポリマー被膜５１２によって埋まり、空隙５１３が存在しない充填領域が発生する。 FIG. 6 is a schematic diagram showing an internal configuration of the charging electrode 51 according to the second embodiment. The charging electrode 51 according to the second embodiment includes a porous metal body 511 and a hydrophilic polymer film 512 as in the first embodiment. However, the thickness of the hydrophilic polymer film 512 is not constant, and the hydrophilic polymer film 512 has a hydrophilic property from one surface (first surface) to the other surface (second surface) along the thickness direction of the charging electrode 51. It has a gradation structure in which the thickness of the polymer film 512 gradually decreases. At this time, on the first surface side where the film thickness of the hydrophilic polymer film 512 is large, the pores of the porous metal body 511 are filled with the hydrophilic polymer film 512, and a filling region where no void 513 exists is generated.
　このような親水性ポリマー被膜５１２のグラデーション構造を有する充電極５１は、金属空気電池１０への適用時、第２面を充電極撥水層５２と接触させ、第１面を金属負極３と対向させて電解液７と接するように配置される。この場合、充電極５１の第１面側では、空隙５１３が生じない充填領域が存在しているため、電解液７は親水性ポリマー被膜５１２によって拡散される分だけが充電極５１に内部に浸透することを許容され、それ以上の浸透は抑制される。 The charging electrode 51 having such a gradation structure of the hydrophilic polymer film 512 has a second surface in contact with the charging electrode water-repellent layer 52 and a first surface facing the metal negative electrode 3 when applied to the metal-air battery 10. Then, it is arranged so as to be in contact with the electrolyte 7. In this case, on the first surface side of the charging electrode 51, there is a filling region in which the void 513 does not occur, so that only the amount of the electrolyte 7 diffused by the hydrophilic polymer film 512 penetrates into the charging electrode 51. And further penetration is suppressed.
　一方、充電極５１の第２面側では、親水性ポリマー被膜５１２の膜厚が小さくなるように形成されているため、十分な空隙５１３が形成される。また、第２面側に充填領域が存在していることで、空隙５１３に電解液７が入り込むことも抑制される。このため、空隙５１３により、充電中に発生する酸素ガスの排出も効率よく行える。 On the other hand, on the second surface side of the charging electrode 51, the hydrophilic polymer film 512 is formed so as to have a small film thickness, so that a sufficient void 513 is formed. In addition, since the filling region exists on the second surface side, entry of the electrolyte 7 into the void 513 is also suppressed. Therefore, the void 513 can efficiently discharge oxygen gas generated during charging.
　本実施の形態２に係る充電極５１は、図３に示す浸漬工程において、金属多孔体５１１の全体を親水性ポリマー含有水溶液に浸漬させず、金属多孔体５１１の第１面側のみを一定厚さ分だけ浸漬させることで製造可能である。この場合、金属多孔体５１１を親水性ポリマー含有水溶液に浸漬させた部分で充填領域を形成することができる。親水性ポリマー含有水溶液に浸漬させていない部分では、毛細管現象によって親水性ポリマー含有水溶液を吸い上げさせて親水性ポリマー被膜５１２を形成することができるが、その膜厚は小さくなる。また、親水性ポリマー含有水溶液の濃度は、金属多孔体５１１を浸漬させた部分が空隙５１３を有さない充填領域となる程度の濃度とされる。 The charging electrode 51 according to Embodiment 2 does not immerse the entirety of the porous metal body 511 in the hydrophilic polymer-containing aqueous solution in the immersion step shown in FIG. It can be manufactured by immersing only a small amount. In this case, a filling region can be formed at a portion where the porous metal body 511 is immersed in the hydrophilic polymer-containing aqueous solution. In a portion that is not immersed in the hydrophilic polymer-containing aqueous solution, the hydrophilic polymer-containing aqueous solution can be sucked up by capillary action to form the hydrophilic polymer film 512, but the film thickness becomes small. The concentration of the hydrophilic polymer-containing aqueous solution is set so that the portion in which the porous metal body 511 is immersed becomes a filling region having no void 513.
　親水性ポリマー含有水溶液に浸漬させる金属多孔体５１１の厚み（すなわち、充填領域の厚み）は、金属多孔体５１１の厚み全体の１／２０～１／２の範囲とすることが好ましく、１／１０～１／５の範囲とすることがより好ましい。充填領域の厚みは、第２面側の空隙５１３内への電解液７の浸透を防止できる程度であればよく、必要以上に厚くないことが好ましい。これは、充填領域が厚くなりすぎると、空隙５１３の形成領域が少なくなり、酸素ガスの排出効率が低下するためである。 The thickness of the porous metal body 511 immersed in the aqueous solution containing a hydrophilic polymer (that is, the thickness of the filling region) is preferably in the range of 1/20 to 1/2 of the total thickness of the porous metal body 511, and 1/10 It is more preferable to set the range to １ ／. The thickness of the filling region may be such that the penetration of the electrolyte solution 7 into the space 513 on the second surface side can be prevented, and it is preferable that the thickness is not excessively large. This is because, if the filling region is too thick, the region where the void 513 is formed decreases, and the oxygen gas discharge efficiency decreases.
　尚、本実施の形態２に係る充電極５１は、金属多孔体５１１の孔部の内壁面の全体に親水性ポリマー被膜５１２が完全に形成されているものに限定されるものではなく、金属多孔体５１１の一部に親水性ポリマー被膜５１２の形成されていない領域があってもよい。すなわち、毛細管現象による親水性ポリマー含有水溶液の吸い上げが第２面にまで完全には到達しておらず、第２面側で親水性ポリマー被膜５１２の形成されていない領域があってもよい。 The charging electrode 51 according to the second embodiment is not limited to the one in which the hydrophilic polymer film 512 is completely formed on the entire inner wall surface of the hole of the porous metal body 511, There may be a region where the hydrophilic polymer coating 512 is not formed on a part of the body 511. That is, the suction of the aqueous solution containing a hydrophilic polymer due to the capillary action may not completely reach the second surface, and there may be a region where the hydrophilic polymer coating 512 is not formed on the second surface.
　また、金属多孔体５１１の内部に形成される親水性ポリマー被膜５１２の量および膜厚は、以下のように測定可能である。親水性ポリマー被膜５１２の量は、親水性ポリマー被膜５１２が形成された金属多孔体５１１から金属多孔体５１１単体の重量を差し引く計算により求めることができる。親水性ポリマー被膜５１２の膜厚の測定方法は、孔直径分布測定装置（米国ＰＵＩ社製 パームポロメーター）により、親水性ポリマー被膜５１２が形成された金属多孔体５１１の孔直径分布を測定し、親水性ポリマー被膜５１２が形成されていない金属多孔体の孔直径分布との差分を親水性ポリマー被膜５１２の膜厚として求めることができる。 量 The amount and thickness of the hydrophilic polymer film 512 formed inside the porous metal body 511 can be measured as follows. The amount of the hydrophilic polymer film 512 can be determined by subtracting the weight of the metal porous body 511 alone from the metal porous body 511 on which the hydrophilic polymer film 512 is formed. The method of measuring the film thickness of the hydrophilic polymer film 512 is as follows: the pore diameter distribution of the porous metal body 511 on which the hydrophilic polymer film 512 is formed is measured by a pore diameter distribution measuring device (U.S.A. The difference from the pore diameter distribution of the porous metal body on which the hydrophilic polymer coating 512 is not formed can be determined as the thickness of the hydrophilic polymer coating 512.
　〔実施の形態３〕
　本実施の形態３では、上述した課題（Ａ）および（Ｂ）をより確実に解決し得る充電極５１の他の構成および製造方法について説明する。 [Embodiment 3]
In the third embodiment, another configuration and a manufacturing method of the charging electrode 51 that can more reliably solve the problems (A) and (B) described above will be described.
　図７は、本実施の形態３に係る充電極５１の内部構成を示す模式図である。本実施の形態３に係る充電極５１は、内部に形成される孔部の平均孔径が互いに異なる金属多孔体５１１Ａおよび金属多孔体５１１Ｂを用いた２層構造とされている。図７では、金属多孔体５１１Ａからなる第１層の平均孔径が、金属多孔体５１１Ｂからなる第２層の平均孔径よりも小さくなっている。親水性ポリマー被膜５１２は、金属多孔体５１１Ａおよび金属多孔体５１１Ｂの両方に形成されるが、孔部の平均孔径が小さい金属多孔体５１１Ａでは孔部が親水性ポリマー被膜５１２によって埋まり、空隙５１３が殆ど生じない。一方、孔部の平均孔径が大きい金属多孔体５１１Ｂでは孔部が親水性ポリマー被膜５１２によって被膜され、空隙５１３が生じる。 FIG. 7 is a schematic diagram showing an internal configuration of the charging electrode 51 according to the third embodiment. The charging electrode 51 according to the third embodiment has a two-layer structure using a metal porous body 511A and a metal porous body 511B in which the average pore diameters of the holes formed therein are different from each other. In FIG. 7, the average pore diameter of the first layer made of the porous metal body 511A is smaller than the average pore diameter of the second layer made of the porous metal body 511B. The hydrophilic polymer coating 512 is formed on both the metal porous body 511A and the metal porous body 511B. In the metal porous body 511A having a small average pore diameter, the pores are filled with the hydrophilic polymer coating 512, and the voids 513 are formed. Almost no occurrence. On the other hand, in the metal porous body 511B having a large average pore diameter, the pores are covered with the hydrophilic polymer film 512, and voids 513 are generated.
　本実施の形態３に係る充電極５１は、金属多孔体５１１Ａおよび金属多孔体５１１Ｂのそれぞれに図３に示す浸漬工程および乾燥工程を施した後、これらを貼り合わせることで製造可能である。 充電 The charging electrode 51 according to the third embodiment can be manufactured by performing a dipping step and a drying step shown in FIG. 3 on each of the porous metal bodies 511A and 511B, and then bonding them.
　図７に示す充電極５１は、金属空気電池１０への適用時、金属多孔体５１１Ａからなる第１層が第１面側、金属多孔体５１１Ｂからなる第２層が第２面側となるように配置される。この場合、第１層では空隙５１３が殆ど生じない程度にまで親水性ポリマー被膜５１２が形成されているため、電解液７は親水性ポリマー被膜５１２によって拡散される分だけが充電極５１に内部に浸透することを許容され、それ以上の浸透は抑制される。 When the charging electrode 51 shown in FIG. 7 is applied to the metal-air battery 10, the first layer made of the porous metal body 511A is on the first surface side, and the second layer made of the porous metal body 511B is on the second surface side. Placed in In this case, since the hydrophilic polymer coating 512 is formed in the first layer to such an extent that the void 513 is hardly generated, only the amount of the electrolyte solution 7 diffused by the hydrophilic polymer coating 512 enters the charging electrode 51 inside. Penetration is allowed and further penetration is suppressed.
　一方、第２層では、十分な空隙５１３が形成されているが、第１層の親水性ポリマー被膜５１２によって空隙５１３に電解液７が入り込むことが抑制されるため、空隙５１３により、充電中に発生する酸素ガスの排出が効率よく行える。 On the other hand, in the second layer, a sufficient gap 513 is formed. However, since the hydrophilic polymer coating 512 of the first layer prevents the electrolyte solution 7 from entering the gap 513, the gap 513 allows the electrolyte solution 7 during charging. Emitted oxygen gas can be efficiently discharged.
　尚、本実施の形態３に係る充電極５１では、第１層の厚みは、実施の形態２における重点領域の厚みと同様に、金属多孔体５１１の厚み全体の１／２０～１／２の範囲とすることが好ましく、１／１０～１／５の範囲とすることがより好ましい。 In the charging electrode 51 according to the third embodiment, the thickness of the first layer is 1/20 to 1/2 of the entire thickness of the porous metal body 511, similarly to the thickness of the important region in the second embodiment. It is preferably in the range, more preferably in the range of 1/10 to 1/5.
　〔実施の形態４〕
　本実施の形態４では、上述した課題（Ａ）および（Ｂ）をより確実に解決し得る酸素発生極５の他の構成および製造方法について説明する。図８は、本実施の形態３に係る酸素発生極５を用いた場合の金属空気電池１０の構造を示す概略断面図である。図８に示す金属空気電池１０では、酸素発生極５以外の構成は図１に示す金属空気電池１０と同じである。 [Embodiment 4]
In the fourth embodiment, another configuration and a manufacturing method of the oxygen generating electrode 5 that can more reliably solve the above-described problems (A) and (B) will be described. FIG. 8 is a schematic sectional view showing the structure of a metal-air battery 10 using the oxygen generating electrode 5 according to the third embodiment. The configuration of the metal-air battery 10 shown in FIG. 8 is the same as that of the metal-air battery 10 shown in FIG.
　図８に示すように、本実施の形態４に係る酸素発生極５は、充電極５１および充電極撥水層５２以外に、親水性ポリマー層５３を有している。親水性ポリマー層５３は、充電極５１に対して充電極撥水層５２とは反対側、すなわち金属負極３と対向する側に配置されている。また、本実施の形態４に係る酸素発生極５では、充電極５１は、図２、図６または図７に示す充電極５１の何れが使用されてもよい。 As shown in FIG. 8, the oxygen generating electrode 5 according to the fourth embodiment has a hydrophilic polymer layer 53 in addition to the charging electrode 51 and the charging electrode water-repellent layer 52. The hydrophilic polymer layer 53 is disposed on the opposite side of the charging electrode 51 from the charging electrode water repellent layer 52, that is, on the side facing the metal negative electrode 3. Further, in the oxygen generating electrode 5 according to the fourth embodiment, as the charging electrode 51, any of the charging electrodes 51 shown in FIG. 2, FIG. 6, or FIG. 7 may be used.
　本実施の形態４に係る酸素発生極５は、金属空気電池１０への適用時、電解液７は親水性ポリマー層５３および親水性ポリマー被膜５１２によって拡散される分だけが充電極５１に内部に浸透することを許容され、それ以上の浸透は抑制される。このため、充電極５１では、空隙５１３に電解液７が入り込むことが抑制され、空隙５１３によって充電中に発生する酸素ガスの排出が効率よく行える。 When the oxygen generating electrode 5 according to the fourth embodiment is applied to the metal-air battery 10, only the amount of the electrolyte solution 7 diffused by the hydrophilic polymer layer 53 and the hydrophilic polymer film 512 is inside the charging electrode 51. Penetration is allowed and further penetration is suppressed. Therefore, in the charging electrode 51, the electrolyte 7 is prevented from entering the gap 513, and the oxygen gas generated during charging can be efficiently discharged by the gap 513.
　親水性ポリマー層５３は、親水性ポリマー被膜５１２と同様に、アニオン交換樹脂やハイドロゲルを材料とすることができる。但し、親水性ポリマー層５３と親水性ポリマー被膜５１２とが同じ材料である必要は無い。例えば、親水性ポリマー層５３の材料をアニオン交換樹脂とし、親水性ポリマー被膜５１２の材料をハイドロゲルとすることが可能である。 The hydrophilic polymer layer 53 can be made of an anion exchange resin or a hydrogel as in the case of the hydrophilic polymer film 512. However, it is not necessary that the hydrophilic polymer layer 53 and the hydrophilic polymer film 512 be the same material. For example, the material of the hydrophilic polymer layer 53 can be an anion exchange resin, and the material of the hydrophilic polymer coating 512 can be a hydrogel.
　今回開示した実施形態はすべての点で例示であって、限定的な解釈の根拠となるものではない。したがって、本開示の技術的範囲は、上記した実施形態のみによって解釈されるものではなく、特許請求の範囲の記載に基づいて画定される。また、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれる。 The embodiment disclosed this time is an example in all respects, and is not a basis for restrictive interpretation. Therefore, the technical scope of the present disclosure is not interpreted only by the above-described embodiments, but is defined based on the description in the claims. In addition, all changes within the meaning and scope equivalent to the claims are included.
　〔援用の記載〕
　本国際出願は、２０１８年７月３１日に日本特許庁に出願された日本国特許出願第２０１８－１４３９４４号に基づく優先権を主張するものであり、日本国特許出願第２０１８－１４３９４４号の全内容を参照により本国際出願に援用する。 [Description of incorporation]
This international application claims priority based on Japanese Patent Application No. 2018-143944 filed with the Japan Patent Office on July 31, 2018, and discloses the entirety of Japanese Patent Application No. 2018-143944. The contents are incorporated by reference into this international application.
２　　電池ケース（筐体）
２１　　通気口
３　　金属負極
３１　　負極活物質層
３２　　負極集電体
４　　空気極
４１　　空気極集電体
４２　　空気極触媒層
４３　　空気極撥水層
５　　酸素発生極
５１　　充電極
５１１、５１１Ａ、５１１Ｂ　　金属多孔体
５１２　　親水性ポリマー被膜
５１３　　空隙
５２　　充電極撥水層
５３　　親水性ポリマー層
６　　セパレータ
７　　電解液
１０　　金属空気電池 2 Battery case (housing)
21 vent 3 metal negative electrode 31 negative electrode active material layer 32 negative electrode current collector 4 air electrode 41 air electrode current collector 42 air electrode catalyst layer 43 air electrode water repellent layer 5 oxygen generating electrode 51 charging electrode 511, 511A, 511B metal porous Body 512 Hydrophilic polymer coating 513 Void 52 Charging electrode water repellent layer 53 Hydrophilic polymer layer 6 Separator 7 Electrolyte 10 Metal-air battery

Claims (14)

  1. 　金属空気電池の充電用正極に使用される電極であって、
    　内部に多数の孔部を有する金属多孔体と、
    　親水性ポリマーを含み、少なくとも前記金属多孔体の孔部の内壁面を被覆する親水性ポリマー被膜とを含むことを特徴とする電極。     An electrode used for a positive electrode for charging a metal-air battery,
    A metal porous body having a large number of pores inside,
    An electrode, comprising: a hydrophilic polymer; and a hydrophilic polymer coating covering at least an inner wall surface of a hole of the porous metal body.
  2. 　請求項１に記載の電極であって、
    　前記親水性ポリマーは、少なくとも水酸基、アミノ基、スルホ基およびカルボキシル基から選択される親水基を有することを特徴とする電極。     The electrode according to claim 1, wherein
    An electrode, wherein the hydrophilic polymer has at least a hydrophilic group selected from a hydroxyl group, an amino group, a sulfo group and a carboxyl group.
  3. 　請求項１または２に記載の電極であって、
    　前記親水性ポリマーは、アニオン交換基を有することを特徴とする電極。     The electrode according to claim 1 or 2,
    The electrode, wherein the hydrophilic polymer has an anion exchange group.
  4. 　請求項１から３の何れか１項に記載の電極であって、
    　前記親水性ポリマーは、架橋構造を有することを特徴とする電極。     The electrode according to any one of claims 1 to 3, wherein
    The electrode, wherein the hydrophilic polymer has a crosslinked structure.
  5. 　請求項１から４の何れか１項に記載の電極であって、
    　前記親水性ポリマーは、水酸基、アミノ基、スルホ基およびカルボキシル基から選択される親水基の水素原子が離脱し、金属イオンとイオン結合した金属塩を有することを特徴とする電極。     The electrode according to any one of claims 1 to 4, wherein
    An electrode, wherein the hydrophilic polymer has a metal salt in which a hydrogen atom of a hydrophilic group selected from a hydroxyl group, an amino group, a sulfo group, and a carboxyl group is eliminated and ion-bonded to a metal ion.
  6. 　請求項１から５の何れか１項に記載の電極であって、
    　前記金属多孔体は、Ｎｉ，Ｃｒ，Ｍｎ，Ｆｅ，Ｃｏ，Ｃｕ，Ｒｕ，Ｒｈ，Ｐｄ，Ｉｒ，Ｐｔからなる群の何れかから構成されることを特徴とする電極。     The electrode according to any one of claims 1 to 5, wherein
    The electrode, wherein the porous metal body is formed of any one of a group consisting of Ni, Cr, Mn, Fe, Co, Cu, Ru, Rh, Pd, Ir, and Pt.
  7. 　請求項１から６の何れか１項に記載の電極であって、
    　第１面と、前記第１面と対向する第２面とを備えており、
    　前記親水性ポリマー被膜は、前記第１面から前記第２面までの前記金属多孔体の厚み方向において、前記第２面側の膜厚が前記第１面側の膜厚よりも小さくされており、
    　当該電極の前記第１面側には、前記金属多孔体の孔部が前記親水性ポリマー被膜によって埋められた充填領域が存在していることを特徴とする電極。     The electrode according to any one of claims 1 to 6, wherein
    A first surface, and a second surface facing the first surface,
    In the hydrophilic polymer film, in the thickness direction of the porous metal body from the first surface to the second surface, the film thickness on the second surface side is smaller than the film thickness on the first surface side. ,
    An electrode, wherein a filling region in which a hole of the porous metal body is filled with the hydrophilic polymer film exists on the first surface side of the electrode.
  8. 　請求項７に記載の電極であって、
    　前記充填領域の厚みは、前記金属多孔体の厚みの１／２０～１／２であることを特徴とする電極。     The electrode according to claim 7, wherein
    The electrode according to claim 1, wherein a thickness of the filling region is 1/20 to 1/2 of a thickness of the porous metal body.
  9. 　請求項１から８の何れか１項に記載の電極であって、
    　前記金属多孔体の平均孔径は、０．４５～３．２ｍｍであることを特徴とする電極。     The electrode according to any one of claims 1 to 8, wherein
    An electrode, wherein the average pore diameter of the porous metal body is 0.45 to 3.2 mm.
  10. 　請求項１から６の何れか１項に記載の電極であって、
    　第１面と、前記第１面と対向する第２面とを備えており、かつ、前記第１面側に位置する第１層と、前記第２面側に位置する第２層とを有しており、
    　前記第１層における前記金属多孔体の平均孔径は、前記第２層における前記金属多孔体の平均孔径よりも小さいことを特徴とする電極。     The electrode according to any one of claims 1 to 6, wherein
    It has a first surface and a second surface facing the first surface, and has a first layer located on the first surface side and a second layer located on the second surface side. And
    The electrode according to claim 1, wherein an average pore diameter of the porous metal body in the first layer is smaller than an average pore diameter of the porous metal body in the second layer.
  11. 　筐体と、
    　前記筐体の内部に収容された電解液と、
    　前記電解液に一部が浸漬され、負極活物質となる金属を含む金属負極と、
    　前記電解液に一部が浸漬され、前記金属負極に対向して配され、酸素発生能を有する酸素発生極と、
    　前記電解液に一部が浸漬され、前記金属負極に対向して配され、酸素還元能を有する空気極と、を備えた金属空気電池であって、
    　前記酸素発生極に、前記請求項１から１０の何れか１項に記載の電極を用いたことを特徴とする金属空気電池。     A housing,
    An electrolytic solution housed inside the housing,
    A metal negative electrode that is partially immersed in the electrolytic solution and contains a metal that becomes a negative electrode active material,
    An oxygen generating electrode partially immersed in the electrolytic solution, disposed to face the metal negative electrode, and having an oxygen generating ability,
    A part is immersed in the electrolytic solution, disposed to face the metal negative electrode, and an air electrode having oxygen reduction ability,
    A metal-air battery using the electrode according to any one of claims 1 to 10 for the oxygen generating electrode.
  12. 　請求項１１に記載の金属空気電池であって、
    　前記酸素発生極における前記金属負極との対向面側に親水性ポリマー層が設けられていることを特徴とする金属空気電池。     The metal-air battery according to claim 11, wherein
    A metal-air battery, wherein a hydrophilic polymer layer is provided on a side of the oxygen generating electrode facing the metal negative electrode.
  13. 　金属空気電池の充電用正極に使用される電極の製造方法であって、
    　内部に多数の孔部を有する金属多孔体を、親水性ポリマーを含む溶液中に浸漬する浸漬工程と、
    　前記浸漬工程で親水性ポリマーを含む溶液に浸漬させた金属多孔体を引き上げて乾燥させる乾燥工程とを含むことを特徴とする電極の製造方法。     A method for producing an electrode used for a positive electrode for charging a metal-air battery,
    An immersion step of immersing a metal porous body having a large number of pores therein in a solution containing a hydrophilic polymer,
    A drying step of lifting and drying the porous metal body immersed in the solution containing a hydrophilic polymer in the immersion step.
  14. 　請求項１３に記載の電極の製造方法であって、
    　前記浸漬工程で前記金属多孔体の厚さの１／２０～１／２までのみを前記親水性ポリマーを含む溶液中に浸漬させることを特徴とする電極の製造方法。     It is a manufacturing method of the electrode of Claim 13, Comprising:
    A method for manufacturing an electrode, wherein in the immersion step, only 1/20 to 1/2 of the thickness of the porous metal body is immersed in a solution containing the hydrophilic polymer.
PCT/JP2019/024181 2018-07-31 2019-06-19 Electrode, metal air cell, and method for manufacturing metal air cell WO2020026623A1 (en)

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JP2014165056A (en) * 2013-02-26 2014-09-08 Imura Zairyo Kaihatsu Kenkyusho:Kk Positive electrode for metal air secondary battery
JP2016058211A (en) * 2014-09-09 2016-04-21 株式会社イムラ材料開発研究所 Positive electrode for aqueous lithium-air secondary battery
JP2016081572A (en) * 2014-10-09 2016-05-16 トヨタ自動車株式会社 Air battery
JP2017168312A (en) * 2016-03-16 2017-09-21 株式会社日本触媒 Metal air battery

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Publication number Priority date Publication date Assignee Title
JP2010198798A (en) * 2009-02-23 2010-09-09 Toyota Motor Corp Metal air battery and method of manufacturing the same
US20120040254A1 (en) * 2010-08-10 2012-02-16 Steven Amendola Bifunctional (rechargeable) air electrodes
JP2014165056A (en) * 2013-02-26 2014-09-08 Imura Zairyo Kaihatsu Kenkyusho:Kk Positive electrode for metal air secondary battery
JP2016058211A (en) * 2014-09-09 2016-04-21 株式会社イムラ材料開発研究所 Positive electrode for aqueous lithium-air secondary battery
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