WO2024190570A1 - 空気二次電池 - Google Patents

空気二次電池 Download PDF

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WO2024190570A1
WO2024190570A1 PCT/JP2024/008596 JP2024008596W WO2024190570A1 WO 2024190570 A1 WO2024190570 A1 WO 2024190570A1 JP 2024008596 W JP2024008596 W JP 2024008596W WO 2024190570 A1 WO2024190570 A1 WO 2024190570A1
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air
air electrode
electrode
ruthenium oxide
secondary battery
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French (fr)
Japanese (ja)
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実紀 西
剛史 梶原
昇平 夘野木
賢大 遠藤
茂和 安岡
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FDK Corp
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FDK Corp
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Priority to CN202480018790.8A priority patent/CN120883425A/zh
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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
    • H01M4/90—Selection of catalytic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/44—Fibrous material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/454—Separators, membranes or diaphragms characterised by the material having a layered structure comprising a non-fibrous layer and a fibrous layer superimposed on one another
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to an air secondary battery.
  • air batteries which use oxygen in the air as the positive electrode active material, have been attracting attention due to their high energy density and the ease of making them small and lightweight.
  • zinc-air primary batteries have been put to practical use as a power source for hearing aids.
  • Air-hydrogen secondary battery which uses an alkaline aqueous solution (hereinafter also referred to as alkaline electrolyte) as the electrolyte and hydrogen as the negative electrode active material (see, for example, Patent Document 1).
  • Air-hydrogen secondary batteries such as those described in Patent Document 1 use a hydrogen storage alloy as the negative electrode metal, but the negative electrode active material in air-hydrogen secondary batteries is hydrogen that is stored and released by the above-mentioned hydrogen storage alloy, so that no dissolution or deposition reaction of the hydrogen storage alloy itself occurs during the chemical reaction (hereinafter also referred to as battery reaction) during charging and discharging in the battery.
  • air-hydrogen secondary batteries have the advantage that they do not cause problems such as internal short circuits caused by so-called dendrite growth, in which the negative electrode metal precipitates in a dendritic form, or a decrease in battery capacity due to shape change.
  • reaction formula (I) oxygen is generated at the air electrode during charging of an air secondary battery. This oxygen passes through the voids inside the air electrode and is released into the atmosphere from the part of the air electrode that is open to the atmosphere. On the other hand, during discharging, oxygen taken in from the atmosphere is reduced to produce hydroxide ions as shown in reaction formula (II).
  • the reactions at the air electrode shown in the above reaction formulas (I) and (II) have a relatively high overvoltage.
  • the air electrode which is the positive electrode of the above air secondary battery
  • a catalyst with excellent activity for both oxygen generation and oxygen reduction is required to promote the above charge/discharge reaction. Therefore, materials that are effective in reducing overvoltage have been studied as materials that can be used as catalysts for the air electrode.
  • Various metal oxides are promising materials that are effective in reducing such overvoltage.
  • pyrochlore-type bismuth ruthenium oxide can reduce overvoltage in both charge and discharge reactions, has a wide and stable potential window, and has a "dual function" of oxygen reduction and oxygen generation with high charge/discharge cycle resistance, so it is considered to be particularly effective as a catalyst for the air electrode.
  • the above-mentioned bismuth ruthenium oxide is produced, for example, by a manufacturing method in which a precursor is produced by a coprecipitation method using bismuth nitrate and ruthenium chloride as starting materials, and then this precursor is calcined.
  • the dissolution-precipitation reaction of the metal components (bismuth and ruthenium) derived from the by-products is repeated, and the metal components precipitate in a dendritic form on the negative electrode, so-called dendrite growth.
  • the metal components grow in this way, the metal components extend into the separator and eventually penetrate the separator to reach the positive electrode. As a result, the problem of an internal short circuit occurs.
  • an internal short circuit occurs in this way, not only ionic conductivity via the electrolyte but also electronic conductivity exists between the positive and negative electrodes inside the battery. When electronic conductivity exists, the battery is self-discharging.
  • Dendritic growth of the metal components increases with each charge/discharge cycle, so the amount of self-discharge also increases as the charge/discharge cycle progresses.
  • the discharge capacity of the battery decreases after a relatively small number of cycles, the battery reaches its end of life early, and the cycle characteristics deteriorate.
  • the resulting bismuth ruthenium oxide particles aggregate into relatively large lumps. Therefore, the aggregated lumps of bismuth ruthenium oxide particles are crushed to a predetermined particle size. This crushing operation is performed, for example, using a bead mill device.
  • clumps of aggregated bismuth ruthenium oxide particles may contain by-products that were not removed by the acid treatment.
  • clumps containing by-products like this are crushed, the by-products are exposed from the new surface, and there is a risk that the exposed by-products may cause an internal short circuit.
  • acid treatment requires crushing as a post-process, there is a problem that acid treatment alone cannot sufficiently suppress internal short circuits. For this reason, in the current situation, even acid treatment does not sufficiently improve the cycle characteristics of air secondary batteries.
  • the present invention was made based on the above circumstances, and its purpose is to provide an air secondary battery that suppresses internal short circuits caused by dendrites resulting from by-products of the oxygen catalyst, thereby providing excellent cycle life characteristics.
  • the present invention provides an air secondary battery comprising a container and an electrode group housed in the container together with an alkaline electrolyte, the electrode group including an air electrode and a negative electrode stacked with a separator interposed therebetween, the air electrode including a core and an air electrode mixture, the air electrode mixture including an oxygen catalyst and a manganese compound, and the separator being a composite of a microporous membrane and a nonwoven fabric aligned in the thickness direction.
  • the air secondary battery according to the present invention comprises a container and an electrode group housed in the container together with an alkaline electrolyte, the electrode group including an air electrode and a negative electrode stacked with a separator interposed therebetween, the air electrode including a core and an air electrode mixture, the air electrode mixture including an oxygen catalyst and a manganese compound, and the separator being configured as a composite of a microporous membrane and a nonwoven fabric aligned in the thickness direction.
  • This configuration blocks the extension of dendrites of the metal component of the by-product of the oxygen catalyst in the microporous membrane portion, and furthermore, the manganese compound dissolves in the alkaline electrolyte and precipitates on the air electrode side portion of the separator's microporous membrane to block the pores of the microporous membrane, thereby preventing the dendrites of the metal component of the by-product of the oxygen catalyst from penetrating to the air electrode side.
  • internal short circuits are suppressed and cycle life characteristics are improved.
  • FIG. 1 is a cross-sectional view illustrating an air hydrogen secondary battery according to an embodiment of the present invention
  • 1 is a graph showing the relationship between the open circuit voltage (OCV) after charging, which is the OCV 10 minutes after the start of a pause after charging, and the number of charge/discharge cycles.
  • FIG. 2 is a schematic diagram showing analysis points where elemental analysis was performed on the air electrode-side nonwoven fabric, the microporous membrane, and the negative electrode-side nonwoven fabric that constitute a separator located between the air electrode and the negative electrode.
  • 4 is a graph showing the distribution of Mn, Ru, and Bi from the atomic percentages of these elements at the analysis points shown in FIG. 3 for Example 1.
  • 4 is a graph showing the distribution state of Ru and Bi based on the atomic percentages of these elements at the analysis points shown in FIG. 3 for Comparative Example 1.
  • an air hydrogen secondary battery (hereinafter also referred to as battery) 2 including an air electrode for an air secondary battery according to one embodiment will be described with reference to the drawings.
  • the battery 2 includes a container 4 and an electrode group 10 housed in the container 4 together with an alkaline electrolyte 82.
  • the electrode group 10 is formed by stacking a negative electrode 12 and an air electrode (positive electrode) 16 with a separator 14 in between.
  • the negative electrode 12 includes a conductive negative electrode core having a porous structure and numerous pores, and a negative electrode mixture supported within the pores and on the surface of the negative electrode core.
  • foamed nickel can be used as the negative electrode core described above.
  • the negative electrode mixture contains hydrogen storage alloy powder, which is an aggregate of hydrogen storage alloy particles capable of absorbing and releasing hydrogen as the negative electrode active material, a conductive material, and a binder.
  • hydrogen storage alloy powder is an aggregate of hydrogen storage alloy particles capable of absorbing and releasing hydrogen as the negative electrode active material, a conductive material, and a binder.
  • graphite powder, carbon black powder, etc. can be used as the conductive material.
  • the hydrogen storage alloy constituting the hydrogen storage alloy particles is not particularly limited, but it is preferable to use, for example, a rare earth-Mg-Ni based hydrogen storage alloy.
  • the composition of this rare earth-Mg-Ni based hydrogen storage alloy can be freely selected, but for example, General formula: Ln 1-a Mg a Ni b-c-d Al c M d ...(III) It is preferable to use one represented by the following formula:
  • Ln represents at least one element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, Zr, and Ti
  • M represents at least one element selected from the group consisting of V, Nb, Ta, Cr, Mo, Mn, Fe, Co, Ga, Zn, Sn, In, Cu, Si, P, and B, and the subscripts a, b, c, and d represent numbers that satisfy the relationships 0.01 ⁇ a ⁇ 0.30, 2.8 ⁇ b ⁇ 3.9, 0.05 ⁇ c ⁇ 0.30, and 0 ⁇ d ⁇ 0.50, respectively.
  • the hydrogen storage alloy particles can be obtained, for example, as follows. First, metal raw materials are weighed and mixed to obtain a desired composition, and the mixture is melted in an inert gas atmosphere, for example in a high-frequency induction melting furnace, and then cooled to form an ingot. The resulting ingot is heated to 900 to 1200°C in an inert gas atmosphere and is homogenized by heat treatment in which it is held at that temperature for 5 to 24 hours. The ingot is then crushed and sieved to obtain a hydrogen storage alloy powder, which is an aggregate of hydrogen storage alloy particles of the desired particle size.
  • binders examples include sodium polyacrylate, carboxymethyl cellulose, and styrene butadiene rubber.
  • the negative electrode 12 can be produced, for example, as follows. First, a negative electrode mixture paste is prepared by kneading hydrogen storage alloy powder, which is an aggregate of hydrogen storage alloy particles, a conductive material, a binder, and water. The obtained negative electrode mixture paste is filled into a negative electrode core, and then a drying process is performed. After drying, the negative electrode core to which the hydrogen storage alloy particles and the like are attached is rolled to increase the amount of alloy per unit volume, and then cut, thereby obtaining a negative electrode 12. This negative electrode 12 has a plate shape as a whole. The negative electrode mixture layer included in the negative electrode 12 is formed by hydrogen storage alloy particles, conductive material particles, and the like, so that there are gaps between the particles and the negative electrode mixture layer has a porous structure as a whole.
  • the air electrode 16 includes a conductive air electrode core and an air electrode mixture layer (positive electrode mixture layer) formed by the air electrode mixture (positive electrode mixture) held on the air electrode core.
  • a metal porous body can be used as the air electrode core body as described above.
  • this metal porous body it is preferable to use a metal foam.
  • this metal foam it is preferable to use nickel foam.
  • a nickel mesh or a nickel sintered body made by sintering nickel powder can also be used.
  • the air electrode mixture contains an oxygen catalyst, a conductive material, a water repellent, and a manganese compound. In addition, it is preferable to add a viscosity adjuster to the air electrode mixture.
  • the oxygen catalyst used has the dual function of oxidation and reduction.
  • a catalyst with dual function contributes to reducing the overvoltage of the battery during both the charging and discharging processes.
  • a pyrochlore-type bismuth ruthenium oxide is preferably used as such an oxygen catalyst. This bismuth ruthenium oxide has the dual functions of oxygen generation and oxygen reduction.
  • Bismuth ruthenium oxide has a pyrochlore type crystal structure represented by the composition formula Bi 2-x Ru 2 O 7-z (where 0 ⁇ x ⁇ 1, z satisfies the relationship 0 ⁇ z ⁇ 1).
  • the pyrochlore-type bismuth ruthenium oxide described above can be produced, for example, as follows.
  • Bi(NO 3 ) 3.5H 2 O and RuCl 3.3H 2 O are prepared. Then, Bi(NO 3 ) 3.5H 2 O and RuCl 3.3H 2 O are weighed out so that the molar ratio of Ru is 1.00 and Bi is 0.50 or more and less than 0.80. The weighed Bi(NO 3 ) 3.5H 2 O and RuCl 3.3H 2 O are put into a predetermined solution and stirred to prepare a mixed aqueous solution of Bi(NO 3 ) 3.5H 2 O and RuCl 3.3H 2 O. At this time, examples of the predetermined solution include distilled water and a dilute nitric acid aqueous solution, and the temperature of these solutions is 60°C or more and 90° C or less.
  • a NaOH aqueous solution of 1 mol/L or more and 3 mol/L or less is added to this mixed aqueous solution to precipitate the precursor (coprecipitation process).
  • the mixed aqueous solution is stirred. This stirring operation is performed for 12 to 60 hours with oxygen bubbling.
  • the pH of the mixed aqueous solution is maintained at 10 to 12, and the temperature is maintained at 60°C or more and 90°C or less.
  • the mixed aqueous solution is left to stand for 12 to 60 hours. After being left to stand, the resulting precipitate is collected by suction filtration.
  • the collected precipitate is kept at 80°C or more and 100°C or less to evaporate a part of the water and form a paste.
  • This paste is transferred to an evaporating dish, heated to 100°C or more and 150°C or less, and dried by keeping it in that state for 1 hour or more and 5 hours or less to obtain a dried paste.
  • the obtained dried paste is placed in a mortar and crushed with a pestle to obtain a precursor powder.
  • the precursor powder is heated to a temperature of 400°C or higher and 700°C or lower in an air atmosphere and held for 0.5 hours or higher and 4 hours or lower, thereby carrying out a heat treatment (calcination step).
  • the powder is washed with distilled water at a temperature of 60°C or higher and 90°C or lower, and then dried. This drying treatment is carried out by holding the washed powder at a temperature of 60°C or higher and 130°C or lower for 1 hour or higher and 12 hours or lower. This results in the production of pyrochlore-type bismuth ruthenium oxide (Bi2 - xRu2O7 -z ).
  • the procedure is as follows.
  • the concentration of the aqueous solution of nitric acid is preferably 5 mol/L or less.
  • the amount of the aqueous solution of nitric acid is preferably 20 mL per 1 g of bismuth ruthenium oxide.
  • the temperature of the aqueous solution of nitric acid is preferably set to 20°C or higher and 25°C or lower.
  • bismuth ruthenium oxide is immersed in the prepared nitric acid aqueous solution and stirred for at least 1 hour and not more than 6 hours. After stirring for the specified time, the bismuth ruthenium oxide is suction filtered from the nitric acid aqueous solution. The filtered bismuth ruthenium oxide is placed in distilled water set to at least 60°C and not more than 80°C and washed.
  • the washed bismuth ruthenium oxide is then dried by keeping it at a temperature of 60°C or higher and 130°C or lower for 1 hour or longer and 12 hours or shorter.
  • acid-treated bismuth ruthenium oxide is obtained.
  • by-products that are generated in the calcination process of the bismuth ruthenium oxide can be removed.
  • the acidic aqueous solution used in the acid treatment is not limited to an aqueous nitric acid solution, and in addition to an aqueous nitric acid solution, an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution can also be used. These aqueous hydrochloric acid and sulfuric acid solutions also have the effect of removing by-products, similar to the aqueous nitric acid solution.
  • the method of disintegration is not particularly limited, but it is preferable to use a wet bead mill device to perform the disintegration process.
  • the procedure for performing the disintegration process using a wet bead mill device is as follows: first, ion-exchanged water and a dispersant are added to the bismuth ruthenium oxide after the acid treatment and stirred to prepare a dispersion liquid. Next, this dispersion liquid is pumped into the disintegration chamber of the wet bead mill device at a predetermined flow rate. Zirconia beads having a predetermined diameter, for example, a diameter of 0.1 mm, are placed in the disintegration chamber.
  • the beads are energized by centrifugal force generated by driving the stirring mechanism in the disintegration chamber at a predetermined speed, and act on the lumps of bismuth ruthenium oxide particles that are the object to be disintegrated.
  • the lumps of bismuth ruthenium oxide particles are disintegrated.
  • the dispersion liquid thus subjected to the disintegration process is discharged from the disintegration chamber.
  • the dispersion liquid discharged from the disintegration chamber is sent back into the disintegration chamber and subjected to the disintegration process again. In this way, the procedure of feeding, crushing, and discharging the dispersion liquid is considered to be one pass, and by repeating this one-pass procedure several times, the agglomerates of bismuth ruthenium oxide particles can be crushed into smaller particles.
  • the bismuth ruthenium oxide when the bismuth ruthenium oxide is subjected to an acid treatment, it is necessary to carry out a crushing treatment as a set.
  • a crushing treatment by subjecting the bismuth ruthenium oxide that has been subjected to the calcination process to an acid treatment, most of the by-products are removed.
  • the particles of bismuth ruthenium oxide aggregate and form a mass during the acid treatment, the by-products may be incorporated into the mass without being removed.
  • the by-products incorporated into the mass of bismuth ruthenium oxide remain as they are, but may be exposed from the new surface formed by the crushing treatment after the acid treatment.
  • the by-products thus exposed may repeatedly dissolve and precipitate with the charge/discharge reaction of the battery, forming dendrites and causing an internal short circuit.
  • the conductive material is used to reduce the internal resistance in order to increase the output of the air secondary battery. Furthermore, the conductive material is also used as a carrier for supporting the oxygen catalyst mentioned above.
  • graphite or nickel is used as such a conductive material (catalyst-supporting conductive material). It is particularly preferable to use graphite powder made of graphite particles. There is no particular limitation on the average particle size of the graphite particles, but it is preferable to set the size so as to impart the desired conductivity to the air electrode.
  • graphite powder in which the average particle size (median diameter, hereinafter also referred to as D50) of the graphite particles measured by a laser diffraction/scattering type particle size distribution measuring device is 1 ⁇ m or more and 5 ⁇ m or less.
  • the conductive material described above is preferably contained in the air electrode mixture in an amount of 20% by weight or more.
  • the upper limit of the conductive material content is preferably set to 50% by weight or less in relation to the other constituent materials in the air electrode mixture.
  • the water repellent imparts appropriate water repellency to the air electrode 16.
  • a fluororesin is used as the water repellent.
  • the fluororesin include perfluoroethylene propene copolymer (FEP), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane polymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF).
  • FEP perfluoroethylene propene copolymer
  • PTFE polytetrafluoroethylene
  • PFA perfluoroalkoxyalkane polymer
  • ETFE ethylene-tetrafluoroethylene copolymer
  • PVDF polyvinylidene fluoride
  • PVDF polyvinylidene fluoride
  • PVDF polyvinyl fluoride
  • the above-mentioned fluororesin is preferably contained in the air electrode mixture at 19.8% by weight or more. If the content of this fluororesin exceeds 40% by weight, the content of the oxygen catalyst that contributes to the charge/discharge reaction will relatively decrease, resulting in a deterioration of the battery characteristics, so it is preferable that the upper limit of the fluororesin content in the air electrode mixture be 40% by weight or less.
  • a binder may be added to the air electrode mixture if necessary.
  • some of the fluororesins mentioned above also function to bind other constituent materials of the air electrode mixture, and can therefore also serve as binders.
  • a fluororesin that also functions to bind other constituent materials in this way there is no need to add a separate binder.
  • the viscosity adjuster adjusts the viscosity of the air electrode mixture slurry when preparing the air electrode mixture slurry described below. It is preferable to use hydroxypropyl cellulose (HPC) as this viscosity adjuster.
  • HPC hydroxypropyl cellulose
  • manganese dioxide is preferably used.
  • manganese dioxide powder which is an aggregate of manganese dioxide particles.
  • this manganese dioxide powder it is preferable to use manganese dioxide powder having an average particle size (median diameter, hereinafter also referred to as D50) of manganese dioxide particles measured by a laser diffraction/scattering type particle size distribution measuring device of 1 ⁇ m or more and 10 ⁇ m or less.
  • This manganese dioxide is preferably used after being subjected to a calcination treatment in which it is heated to 400°C or more and 500°C or less in an air atmosphere and held for 5 hours or more and 10 hours or less.
  • Mn dissolves from the manganese compound into the electrolyte, and this dissolved Mn precipitates in the microporous membrane contained in the separator, blocking the pores of the microporous membrane to some extent. This suppresses the penetration of dendrites derived from by-products of bismuth ruthenium oxide.
  • the manganese compound is preferably added in an amount of 5% by weight or more relative to the bismuth ruthenium oxide. This is because if the amount of manganese compound added is less than 5% by weight relative to the bismuth ruthenium oxide, the effect of suppressing the penetration of dendrites described above cannot be fully exerted.
  • the upper limit of the amount of manganese compound added is preferably 150% by weight or less relative to the bismuth ruthenium oxide.
  • the air electrode 16 can be manufactured, for example, as follows. First, a catalyst powder which is an aggregate of bismuth ruthenium oxide particles, a conductive powder which is an aggregate of carbon material particles as a conductive material, a water repellent, a viscosity adjuster, manganese dioxide powder, and water are prepared. Then, the catalyst powder, conductive powder, water repellent, viscosity adjuster, manganese dioxide powder, and water are kneaded to prepare an air electrode mixture slurry.
  • a sheet of porous metal is prepared as an air electrode core.
  • the prepared porous metal sheet is rolled in advance to adjust it to a predetermined thickness.
  • the porous metal sheet is filled with the air electrode mixture slurry obtained as described above.
  • the air electrode mixture slurry is filled and held inside the pores of the porous metal body, and is also held on the surface of the porous metal body.
  • the air electrode core holding the air electrode mixture slurry is held in an atmosphere of 50°C or higher and 80°C or lower for 10 minutes or more and 2 hours or less, and is subjected to a drying process. After the drying process, the moisture in the air electrode mixture slurry evaporates, and the air electrode mixture is held in the air electrode core. Then, the air electrode core holding the air electrode mixture is subjected to a roll rolling process. After the roll rolling process, the air electrode core holding the air electrode mixture is cut into a predetermined shape, thereby obtaining an air electrode 16.
  • the obtained air electrode 16 is put into a heat treatment furnace and subjected to heat treatment (sintering treatment).
  • This sintering treatment is preferably performed in an inert gas atmosphere for manufacturing purposes, but it may be performed in an air atmosphere.
  • the inert gas for example, nitrogen gas or argon gas is used.
  • the conditions for the sintering treatment are to heat to a temperature of 200°C or more and 400°C or less, and to hold this state for 10 minutes or more and 40 minutes or less.
  • the air electrode 16 is naturally cooled in the heat treatment furnace, and when the temperature of the air electrode 16 becomes 150°C or less, it is taken out into the air. In this way, the air electrode 16 that has been subjected to the sintering treatment is obtained.
  • This air electrode 16 has an air electrode mixture layer formed from an air electrode mixture.
  • the air electrode mixture layer formed from such an air electrode mixture has a porous structure containing a large number of fine pores as a whole.
  • the air electrode core body holding the air electrode mixture may be rolled, sintered, and then cut into a desired shape to form the air electrode 16.
  • the air electrode 16 and negative electrode 12 obtained as described above are stacked with a separator 14 interposed therebetween, thereby forming an electrode group 10.
  • the separator 14 is arranged to prevent short circuits between the air electrode 16 and the negative electrode 12, and is made of an electrically insulating material.
  • This separator 14 is a composite of a microporous membrane and a nonwoven fabric laminated in the thickness direction.
  • the composite has a two-layer structure in which one microporous membrane and one nonwoven fabric are stacked. More preferably, the composite has a three-layer structure in which one microporous membrane is sandwiched between two nonwoven fabrics.
  • microporous membrane generally refers to a polymer film containing many pores with an average pore size of 0.1 ⁇ m or less.
  • a microporous membrane separator made of polyolefin for lithium ion batteries is known as this type of microporous membrane, and in this embodiment, this microporous membrane separator for lithium ion batteries can be used.
  • an alkaline aqueous solution is used as the electrolyte in an air secondary battery, it is preferable to perform a hydrophilization treatment on the microporous membrane.
  • hydrophilization treatment examples include plasma treatment in which polar functional groups are added to the surface by surface modification using oxygen radicals, sulfonation treatment in which sulfone groups are created on the surface by treatment in sulfur trioxide gas or fuming sulfuric acid, and treatment with a surfactant.
  • plasma treatment in which polar functional groups are added to the surface by surface modification using oxygen radicals
  • sulfonation treatment in which sulfone groups are created on the surface by treatment in sulfur trioxide gas or fuming sulfuric acid
  • treatment with a surfactant it is preferable to select hydrophilization treatment with a surfactant as the hydrophilization treatment in order to suppress damage to the microporous membrane.
  • a polyethylene microporous membrane with a melting point of 130 to 140°C is mainly used to enhance safety. This is intended to provide a shutdown function in the event of an abnormal rise in battery temperature due to a short circuit or the like, in which the polyethylene that constitutes the microporous membrane melts to close the pores and stop the permeation of ions through the separator.
  • air secondary batteries use an alkaline aqueous solution, so a polypropylene microporous membrane, which has a lower risk of combustion and a higher melting point, can be used.
  • a polyethylene microporous membrane can also be used in this embodiment.
  • a microporous membrane alone as the separator.
  • the liquid replenishment properties of the separator are important, so a composite made by combining a microporous membrane with a nonwoven fabric, which is used as a separator in nickel-metal hydride secondary batteries, is used as the separator.
  • Nonwoven fabric is characterized by a higher porosity and better liquid replenishment properties than microporous membranes, so it is ideal for complementing the liquid replenishment properties of the microporous membrane.
  • nonwoven fabrics examples include polyamide fiber nonwoven fabrics to which hydrophilic functional groups have been added, and polyolefin fiber nonwoven fabrics such as polyethylene and polypropylene to which hydrophilic functional groups have been added.
  • the formed electrode group 10 is placed in a container 4.
  • the container 4 there are no particular limitations on the container 4 as long as it can accommodate the electrode group 10 and the alkaline electrolyte, and for example, a box-shaped container 4 is used.
  • this container 4 includes a container body 6 and a lid 8.
  • the material of the container 4 as long as it can withstand the alkaline electrolyte, and examples of the material include acrylic resin and metal materials.
  • the container body 6 is box-shaped and has a bottom wall 18 and side walls 20 that extend upward from the periphery of the bottom wall 18.
  • the portion surrounded by the upper edge 21 of the side walls 20 is open.
  • an opening 22 is provided on the opposite side of the bottom wall 18.
  • the side walls 20 have through holes at predetermined positions on the right side wall 20R and the left side wall 20L, which serve as lead wire withdrawal openings 24, 26, which will be described later.
  • an electrolyte storage unit 80 is attached to the container body 6.
  • This electrolyte storage unit 80 is a container that contains an alkaline electrolyte 82, and is attached, for example, via a connection unit 84 that communicates with a through hole 19 provided in the bottom wall 18.
  • the connection unit 84 is a flow path for the alkaline electrolyte 82 that communicates between the inside of the container 4 and the electrolyte storage unit 80. In this way, since the inside of the container 4 and the electrolyte storage unit 80 are connected, the alkaline electrolyte 82 can move between the inside of the container 4 and the electrolyte storage unit 80.
  • the lid 8 has the same shape as the container body 6 when viewed from above, and is placed on the top of the container body 6 to close the opening 22.
  • the gap between the lid 8 and the upper edge 21 of the side wall 20 is liquid-tightly sealed.
  • the lid 8 has an air passage 30 on the inner surface 28 facing the inside of the container body 6.
  • the air passage 30 is open at the portion facing the inside of the container body 6, and has a serpentine shape as a whole. Furthermore, an inlet air hole 32 and an outlet air hole 34 are provided at predetermined positions of the lid 8, penetrating in the thickness direction.
  • the inlet air hole 32 communicates with one end of the air passage 30, and the outlet air hole 34 communicates with the other end of the air passage 30.
  • the air passage 30 is open to the atmosphere through the inlet air hole 32 and the outlet air hole 34. It is preferable to attach a pressure pump (not shown) to the inlet air hole 32. By driving this pressure pump, air can be sent from the inlet air hole 32 to the air passage 30.
  • an adjustment member 36 is placed on the bottom wall 18 of the container body 6.
  • the adjustment member 36 is used to align the electrode group 10 in the height direction inside the container 4.
  • a foamed nickel sheet is used as the adjustment member 36.
  • the electrode group 10 is disposed on the adjustment member 36. At this time, the negative electrode 12 of the electrode group 10 is disposed so as to be in contact with the adjustment member 36.
  • a water-repellent ventilation member 40 is disposed on the air electrode 16 side of the electrode group 10 so as to contact the air electrode 16.
  • This water-repellent ventilation member 40 is a combination of a PTFE porous membrane 42 and a nonwoven diffusion paper 44.
  • the water-repellent ventilation member 40 exerts a water-repellent effect due to the PTFE, and allows gas to pass through.
  • the water-repellent ventilation member 40 is interposed between the lid 8 and the air electrode 16, and is in close contact with both the lid 8 and the air electrode 16. This water-repellent ventilation member 40 is large enough to cover the entire ventilation path 30, inlet ventilation hole 32, and outlet ventilation hole 34 of the lid 8.
  • the container body 6 housing the electrode group 10, the adjustment member 36, and the water-repellent and breathable member 40 as described above is covered with the lid 8. Then, as shown diagrammatically in FIG. 1, the peripheral edge portions 46, 48 of the container 4 (container body 6 and lid 8) are sandwiched from above and below by connectors 50, 52. After that, a predetermined amount of alkaline electrolyte 82 is injected from the electrolyte storage portion 80, and the alkaline electrolyte 82 is introduced into the container 4. In this manner, the battery 2 is formed.
  • alkaline electrolyte 82 a typical alkaline electrolyte used in alkaline secondary batteries is preferably used, specifically an aqueous solution containing at least one of NaOH, KOH, and LiOH as a solute.
  • the ventilation passage 30 of the lid 8 faces the water-repellent ventilation member 40.
  • the water-repellent ventilation member 40 allows gas to pass through but blocks moisture, so the air electrode 16 is open to the atmosphere via the water-repellent ventilation member 40, the ventilation passage 30, the inlet ventilation hole 32, and the outlet ventilation hole 34. In other words, the air electrode 16 comes into contact with the atmosphere through the water-repellent ventilation member 40.
  • an air electrode lead (positive electrode lead) 54 is electrically connected to the air electrode (positive electrode) 16, and a negative electrode lead 56 is electrically connected to the negative electrode 12.
  • These air electrode lead 54 and negative electrode lead 56 are illustrated diagrammatically in FIG. 1, but are pulled out of the container 4 from the outlets 24, 26 while maintaining airtightness and liquid tightness.
  • An air electrode terminal (positive electrode terminal) 58 is provided at the tip of the air electrode lead 54, and a negative electrode terminal 60 is provided at the tip of the negative electrode lead 56. Therefore, in the battery 2, the air electrode terminal 58 and negative electrode terminal 60 are used to input and output current during charging and discharging.
  • Example 1 Battery Production (Example 1) (1) Synthesis of oxygen catalyst for air secondary battery 1) Coprecipitation process Bi(NO 3 ) 3.5H 2 O and RuCl 3.3H 2 O were prepared. Then, Bi(NO 3 ) 3.5H 2 O and RuCl 3.3H 2 O were weighed so that the molar concentration ratio of Ru was 1.00 and Bi was 0.75. The weighed Bi(NO 3 ) 3.5H 2 O and RuCl 3.3H 2 O were put together into a dilute nitric acid aqueous solution at 75 ° C. and stirred to prepare a mixed aqueous solution of Bi(NO 3 ) 3.5H 2 O and RuCl 3.3H 2 O.
  • a 2 mol/L NaOH aqueous solution was prepared. Then, the above-mentioned mixed aqueous solution and the NaOH aqueous solution were simultaneously dropped into a glass reaction vessel with a volume of 300 mL. At this time, the dripping time was adjusted so that the mixed aqueous solution and the NaOH aqueous solution would overflow when the average residence time in the reaction vessel reached 30 minutes.
  • the dripping time of the solution was adjusted so that the solution dripped at a predetermined dripping amount would overflow.
  • the average residence time is 30 minutes when dripping at a dripping speed that causes a 300 mL reaction vessel to overflow after 30 minutes.
  • the precursor was precipitated by reacting the mixed aqueous solution with the NaOH aqueous solution as described above. After that, the overflowed mixed aqueous solution containing the precursor was placed in a stirring vessel and stirred. This stirring was performed for 24 hours while oxygen bubbling was performed. During this stirring, the pH of the mixed aqueous solution was maintained at 10.7 and the temperature was maintained at 70°C. After the stirring was completed, the mixed aqueous solution was left to stand for 24 hours. After standing, the resulting precipitate was collected by filtration. The collected precipitate was kept at 85°C to evaporate part of the water and make it into a paste. The obtained paste was transferred to an evaporating dish, heated to 120°C, and dried by keeping it in that state for 3 hours to obtain a dried precursor. The obtained dried precursor was placed in a mortar and crushed with a pestle to obtain a powder.
  • nitric acid aqueous solution was prepared in a ratio of 20 mL per 1 g of bismuth ruthenium oxide powder. Then, this nitric acid aqueous solution and the bismuth ruthenium oxide powder were placed in a stirring tank of a stirrer, and the nitric acid aqueous solution was stirred for 1 hour while maintaining the temperature of the nitric acid aqueous solution at 25° C., thereby performing an acid treatment.
  • the concentration of the nitric acid aqueous solution was 2 mol/L.
  • the bismuth ruthenium oxide powder was extracted from the nitric acid aqueous solution by suction filtration.
  • the extracted bismuth ruthenium oxide powder was washed with 1 liter of distilled water heated to 70°C. After washing, the bismuth ruthenium oxide powder was dried by holding it in an atmosphere at 120°C for 3 hours. In this way, acid-treated bismuth ruthenium oxide powder, i.e., oxygen catalyst powder for air secondary batteries, was obtained.
  • the powder of bismuth ruthenium oxide that has undergone the acid treatment process is agglomerated and has a relatively large mass, so a crushing process is required.
  • An amount of ion-exchanged water such that the solid content ratio per weight of the powder of bismuth ruthenium oxide that has undergone the acid treatment process is 10% by weight, and an amount of dispersant (ammonium polycarboxylate, manufactured by San Nopco Co., Ltd., SN Dispersant 5468) such that the solid content ratio per weight of the powder of bismuth ruthenium oxide that has also undergone the acid treatment process is 1% by weight were prepared.
  • the ion-exchanged water and dispersant prepared as described above were added to a predetermined amount of bismuth ruthenium oxide powder, and the catalyst dispersion was prepared by mixing them.
  • the obtained catalyst dispersion was pumped at a flow rate of 200 mL/min into the crushing chamber of a wet bead mill device (manufactured by Ashizawa Finetech Co., Ltd., Labo Star Mini DMS65) from the inlet of the crushing chamber.
  • Beads made of partially stabilized zirconia (PSZ) with a diameter of 0.1 mm were placed in advance in this crushing chamber.
  • the stirring mechanism in the disintegration chamber was driven at a peripheral speed of 8 m/s, and the lumps of bismuth ruthenium oxide particles were subjected to disintegration treatment for 9 minutes.
  • the catalyst dispersion discharged from the outlet of the disintegration chamber was again fed into the disintegration chamber from the inlet of the disintegration chamber, and the second stage of disintegration treatment was performed.
  • the procedure of feeding, disintegration, and discharging the catalyst dispersion was one pass, and this one pass was repeated a total of five times (5 passes).
  • the catalyst dispersion was concentrated by holding it in an atmosphere of 60° C. for 12 hours.
  • the solid ratio of the catalyst dispersion after concentration was 27% by weight.
  • Graphite powder which is an aggregate of graphite particles, was prepared as a conductive material.
  • the graphite particles had an average particle size (D50) of 3.3 ⁇ m measured by a laser diffraction/scattering particle size distribution measuring device.
  • manganese dioxide powder which is an aggregate of manganese dioxide particles (FMH, manufactured by Tosoh Corporation, average particle size (D50) of 5 ⁇ m), was prepared. This manganese dioxide powder was subjected to a baking treatment in which it was heated to 450° C. in an air atmosphere and held for 7 hours.
  • FEP perfluoroethylene propene copolymer
  • the concentrated catalyst dispersion obtained as described above was weighed out to prepare an amount of 50 parts by weight of bismuth ruthenium oxide powder (oxygen catalyst).
  • oxygen catalyst oxygen catalyst
  • the foamed nickel sheet with the adjusted thickness was filled with the slurry of the air electrode mixture obtained as described above.
  • the foamed nickel sheet holding the slurry of the air electrode mixture was then held in an atmosphere of 80°C for 20 minutes to dry. After this drying process, the foamed nickel sheet holding the air electrode mixture was rolled to compress it to a thickness of 0.20 mm, and then cut to a length of 40 mm and a width of 40 mm. This resulted in an intermediate air electrode product.
  • the intermediate product was subjected to a heat treatment (sintering treatment). Specifically, the intermediate product was placed in an electric furnace for sintering. The conditions for the sintering treatment were that it was heated to a sintering temperature of 250°C in an air atmosphere and held at this temperature for 13 minutes. In this way, an air electrode 16 was obtained.
  • the weight of the resulting air electrode 16 was measured. The result was taken as the air electrode weight. The weight of the foamed nickel, which had been measured beforehand, was then subtracted from this air electrode weight to calculate the weight of the air electrode mixture after drying that was held in the foamed nickel. Furthermore, the amount of bismuth ruthenium oxide (oxygen catalyst) was calculated from the weight ratio of bismuth ruthenium oxide added to the air electrode mixture. As a result, the amount of bismuth ruthenium oxide in the air electrode of Example 1 was 0.12 g.
  • the ingot was subjected to a heat treatment in an argon gas atmosphere at a temperature of 1000°C for 10 hours, and then cooled to room temperature of 25°C. After cooling, the ingot was mechanically crushed in an argon gas atmosphere to obtain rare earth-Mg-Ni hydrogen storage alloy powder.
  • the volume average particle size (MV) of the obtained rare earth-Mg-Ni hydrogen storage alloy powder was measured using a laser diffraction/scattering particle size distribution measuring device. As a result, the volume average particle size (MV) was 60 ⁇ m.
  • composition of this hydrogen storage alloy powder was analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) and found to be Nd 0.89 Mg 0.11 Ni 3.33 Al 0.17 .
  • This negative electrode mixture paste was filled into a sheet of foamed nickel with an areal density (weight per unit area) of 300 g/m 2 and a thickness of 1.7 m.
  • the negative electrode mixture paste was then dried to obtain a sheet of foamed nickel filled with the negative electrode mixture.
  • the obtained sheet was rolled to increase the amount of alloy per unit volume, and then cut into a length of 40 mm and a width of 40 mm. In this way, the negative electrode 12 was obtained.
  • the thickness of the negative electrode 12 was 0.75 mm.
  • the negative electrode capacity calculated from the electrochemical alloy capacity was 2500 mAh.
  • the obtained air electrode 16 and negative electrode 12 were stacked with a separator 14 sandwiched between them to produce an electrode group 10.
  • the separator 14 used in producing this electrode group 10 was made of a three-layer composite in which one microporous membrane was sandwiched between two nonwoven fabrics.
  • the microporous membrane is a polymer film made of polypropylene and contains many pores. The average pore size of the pores is 36 nm. The microporous membrane is 25 ⁇ m thick and has a porosity of 41%.
  • the microporous membrane has been subjected to a hydrophilic treatment. Specifically, the microporous membrane is immersed in an aqueous solution containing a surfactant to make it hydrophilic.
  • the nonwoven fabric used was made of polypropylene fibers having sulfonic groups, and had a thickness of 0.2 mm (basis weight 100 g/m 2 ).
  • a container body 6 made of acrylic resin was prepared, and the above-mentioned electrode group 10 was housed in this container body 6.
  • a sheet of foamed nickel serving as an adjustment member 36 was placed on the bottom wall 18 of the container body 6, and the electrode group 10 was placed on this adjustment member 36.
  • the foamed nickel sheet serving as the adjustment member 36 was 1 mm thick and had a square shape measuring 40 mm in length and 40 mm in width.
  • a water-repellent ventilation member 40 was placed on top of the electrode group 10 (on top of the air electrode 16).
  • the water-repellent ventilation member 40 was formed by combining a PTFE porous membrane 42 that was 45 mm long, 45 mm wide, and 0.1 mm thick, and a nonwoven fabric diffusion paper 44 that was 40 mm long, 40 mm wide, and 0.2 mm thick.
  • the container body 6 was covered with the acrylic resin lid 8 so as to close the opening 22.
  • the water-repellent ventilation member 40 was brought into close contact with the area on the inner surface 28 of the lid 8, including the ventilation passage 30, the inlet ventilation hole 32, and the outlet ventilation hole 34, so that the area was entirely covered with the water-repellent ventilation member 40.
  • the ventilation passage 30 has a single serpentine shape as a whole.
  • the cross section of the ventilation passage 30 is rectangular, with the vertical dimension of the rectangle being 1 mm and the horizontal dimension being 1 mm.
  • the ventilation passage 30 is open on the water-repellent ventilation member 40 side.
  • the container 4 is formed by combining the container body 6 and the lid 8, and the peripheral edge portions 46, 48 are sandwiched from above and below by connectors 50, 52.
  • a resin packing (not shown) is provided at the contact portion between the container body 6 and the lid 8 to prevent leakage of the alkaline electrolyte.
  • An air electrode lead 54 is electrically connected to the air electrode 16, and an anode lead 56 is electrically connected to the anode 12.
  • the air electrode lead 54 and the anode lead 56 extend appropriately from the lead wire outlets 24, 26 to the outside of the container 4 while maintaining the airtightness and liquid tightness of the container 4.
  • An air electrode terminal 58 is attached to the tip of the air electrode lead 54, and an anode terminal 60 is attached to the tip of the anode lead 56.
  • Example 2 In producing the air electrode mixture slurry, the concentrated catalyst dispersion was prepared by weighing out an amount of bismuth ruthenium oxide powder (oxygen catalyst) contained therein to be 25 parts by weight, and the manganese dioxide powder was adjusted to 25 parts by weight, except that an air-hydrogen secondary battery was produced in the same manner as in Example 1.
  • the amount of bismuth ruthenium oxide in the air electrode in Example 2 was 0.06 g.
  • Comparative Example 1 Except for not adding manganese dioxide powder when preparing the slurry of the air electrode mixture, an air-hydrogen secondary battery was prepared in the same manner as in Example 1. The amount of bismuth ruthenium oxide in the air electrode of Comparative Example 1 was 0.11 g.
  • Comparative Example 2 An air-hydrogen secondary battery was produced in the same manner as in Example 1, except that a microporous membrane was not used and two layers of polypropylene fiber nonwoven fabric (thickness: 0.2 mm, basis weight: 100 g/ m2 ) were used as the separator.
  • the amount of bismuth ruthenium oxide in the air electrode of Comparative Example 2 was 0.11 g.
  • Example 3 An air-hydrogen secondary battery was produced in the same manner as in Example 1, except that no manganese dioxide powder was added when producing the air electrode mixture slurry, and that no microporous membrane was used, and instead, two layers of polypropylene fiber nonwoven fabric (thickness: 0.2 mm, basis weight: 100 g/ m2 ) were used as the separator.
  • the amount of bismuth ruthenium oxide in the air electrode of Comparative Example 3 was 0.10 g.
  • Example 1 Elemental Analysis After the above-mentioned battery characteristics were evaluated, the air hydrogen secondary batteries of Example 1 and Comparative Example 1 were disassembled to take out the separators. The separators were immersed in ion-exchanged water, and the ion-exchanged water was replaced with new ion-exchanged water every 30 minutes, and the separators were washed by repeating this operation seven times. After drying the washed separators, the separators were disassembled into the air electrode side nonwoven fabric, the microporous membrane, and the negative electrode side nonwoven fabric.
  • the surfaces of the air electrode side nonwoven fabric, the microporous membrane, and the negative electrode side nonwoven fabric were observed with a scanning electron microscope, and elemental analysis was performed by energy dispersive X-ray spectroscopy, so-called SEM/EDS, to analyze the state of bismuth, ruthenium, and manganese present in which parts of the separator and to what extent. Specifically, as shown in FIG.
  • analysis point A on the surface of the air electrode side of the air electrode-side nonwoven fabric located on the air electrode side analysis point B on the surface of the negative electrode side
  • analysis point C on the surface of the air electrode side of the microporous membrane analysis point D on the surface of the negative electrode side
  • analysis point E on the surface of the air electrode side of the negative electrode-side nonwoven fabric located on the negative electrode side analysis point F on the surface of the negative electrode side.
  • a scanning electron microscope JSM-6510 manufactured by JEOL Ltd.
  • EDS energy dispersive X-ray analyzer
  • composition analysis was performed by mapping the entire surface of two fields of view under conditions of an acceleration voltage of 15 kV, a measurement magnification of 500 times, and an accumulation number of 20 times.
  • the ratio of the amount of bismuth, ruthenium, and manganese in the bulk was calculated using the average measured in two fields of view.
  • the atomic percentages [at%] of Mn, Ru, and Bi were calculated with the total of Mn, Bi, Ru, and other elements (C, O, Al, Si, K, Ni, Nd, Au) being 100%.
  • the average composition analysis results of the samples measured at each measurement point are shown in Figures 4 and 5.
  • Example 1 (3) Observations From Table 1 and Fig. 2, in Example 1, no decrease in the OCV value after charging was observed up to the number of cycles of 78. In Example 2, no decrease in the OCV value after charging was observed up to the number of cycles of 67. For this reason, it is considered that no internal short circuit occurred in Examples 1 and 2.
  • Comparative Example 1 the OCV value after charging was below 1.2 V at 29 cycles, in Comparative Example 2 at 28 cycles, and in Comparative Example 3 at 20 cycles. For this reason, it is believed that an internal short circuit occurred at the above-mentioned number of cycles in Comparative Examples 1 to 3. From these results, it can be seen that even with the addition of Mn compound, Comparative Example 2, which contains only nonwoven fabric, showed only a change of about 8 cycles in the resistance to internal short circuits compared to Comparative Example 3, which does not contain Mn compound, and Comparative Example 3, which contains only nonwoven fabric without the addition of Mn compound, showed the same short circuit suppression effect when compared to Comparative Example 1, which uses a microporous membrane.
  • Mn was detected in large amounts on the air electrode side of the microporous membrane (part C) and on the air electrode side nonwoven fabric (parts A and B), while Ru and Bi were found in large amounts on the negative electrode side of the microporous membrane (part D), and were hardly detected on the side of the microporous membrane from the air electrode side (part C) to the side where the air electrode is located. This is thought to be because Mn clogs the pores on the air electrode side of the microporous membrane, making it difficult for Bi and Ru to reach the air electrode side.
  • Comparative Example 1 a microporous membrane was also used, but the detected amounts of Bi and Ru on the air electrode side (part C) and the negative electrode side (part D) of the microporous membrane were greater than in Example 1. This is thought to be because in Comparative Example 1, no Mn compound was added, and therefore the effect of Mn in suppressing the penetration of dendrites was not exerted.
  • Example 1 As in Example 1, by adding a Mn compound to the air electrode mixture and using a separator containing a microporous membrane, Mn dissolves and precipitates in the microporous membrane, preventing the dendrites of Bi and Ru derived from the by-products from easily penetrating through the separator to the air electrode side. As a result, it is believed that the occurrence of internal short circuits is suppressed and the cycle life is extended.
  • the negative electrode metal is not limited to hydrogen storage alloys, and the present invention can be applied to air secondary batteries in which the negative electrode metal is changed to Li, Zn, Al, Mg, etc.
  • Battery air hydrogen secondary battery
  • Container Container body
  • Lid Electrode group 12
  • Negative electrode Separator
  • Air electrode positive electrode
  • Ventilation path 40 Water-repellent ventilation member

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09190827A (ja) * 1995-12-29 1997-07-22 Sony Corp 空気電池用空気極
JP2005123059A (ja) * 2003-10-17 2005-05-12 Matsushita Electric Ind Co Ltd 空気亜鉛電池
JP2017016901A (ja) * 2015-07-01 2017-01-19 日本碍子株式会社 亜鉛空気電池
JP2017183110A (ja) * 2016-03-30 2017-10-05 株式会社Ｇｓユアサ 亜鉛電極、及びその亜鉛電極を備えた蓄電池
WO2022209010A1 (ja) * 2021-03-30 2022-10-06 日本碍子株式会社 空気極／セパレータ接合体及び金属空気二次電池

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09190827A (ja) * 1995-12-29 1997-07-22 Sony Corp 空気電池用空気極
JP2005123059A (ja) * 2003-10-17 2005-05-12 Matsushita Electric Ind Co Ltd 空気亜鉛電池
JP2017016901A (ja) * 2015-07-01 2017-01-19 日本碍子株式会社 亜鉛空気電池
JP2017183110A (ja) * 2016-03-30 2017-10-05 株式会社Ｇｓユアサ 亜鉛電極、及びその亜鉛電極を備えた蓄電池
WO2022209010A1 (ja) * 2021-03-30 2022-10-06 日本碍子株式会社 空気極／セパレータ接合体及び金属空気二次電池

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