WO2018190390A1 - Negative electrode material, negative electrode and iron-air battery - Google Patents

Negative electrode material, negative electrode and iron-air battery Download PDF

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Publication number
WO2018190390A1
WO2018190390A1 PCT/JP2018/015303 JP2018015303W WO2018190390A1 WO 2018190390 A1 WO2018190390 A1 WO 2018190390A1 JP 2018015303 W JP2018015303 W JP 2018015303W WO 2018190390 A1 WO2018190390 A1 WO 2018190390A1
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negative electrode
mass
iron
particles
surface modifying
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PCT/JP2018/015303
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French (fr)
Japanese (ja)
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基史 松田
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株式会社三徳
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Priority to JP2019512562A priority Critical patent/JP7141809B2/en
Publication of WO2018190390A1 publication Critical patent/WO2018190390A1/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
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • 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 a negative electrode material for an iron-air battery, and a negative electrode and an iron-air battery using the negative electrode material.
  • metal-air batteries can use oxygen in the atmosphere as the active material of the air electrode, the reaction material of the air electrode is considered to be zero, and most of the battery can be composed of the negative electrode reaction material, so it is relatively easy to achieve high energy density. Is possible. Therefore, the use as a vehicle-mounted secondary battery etc. which replaces a lithium ion battery is anticipated.
  • Metals such as zinc, lithium, magnesium, aluminum, and iron are used for the negative electrode of the metal-air battery.
  • a catalyst layer made of a carbon material, an oxide catalyst, a noble metal catalyst, or the like is used for the air electrode of the metal-air battery.
  • iron-air batteries such as zinc-air batteries have a problem that dendritic crystals are deposited on the negative electrode during charging, and a short circuit is likely to occur between the electrodes.
  • dendrite-like crystals are hardly formed on the negative electrode of the iron-air battery, and therefore the iron-air battery has relatively excellent cycle characteristics.
  • the negative electrode of an iron air battery has high corrosion resistance.
  • iron has the advantages of being abundant in resources, inexpensive, low in toxicity, easily reusable and environmentally friendly. For these reasons, iron-air batteries have recently attracted interest.
  • the negative electrode of the iron-air battery is made of an iron base material containing metallic iron or iron oxide.
  • the iron-air battery has a problem that it is difficult to increase the capacity.
  • Non-Patent Document 2 a method for distributing Fe 3 O 4 nanoparticles on the surface of carbon nanofibers has been proposed.
  • An object of the present invention is to provide a negative electrode material capable of improving discharge characteristics when used for a negative electrode of an iron-air battery.
  • Another object of the present invention is to provide a negative electrode capable of improving discharge characteristics when used in an iron-air battery.
  • the present inventor has improved discharge characteristics by using a negative electrode material in which a specific amount of a specific copper-based surface modifier is adhered to the surface of iron base particles.
  • the present inventors have found that an iron-air battery can be obtained, and have completed the present invention.
  • the negative electrode material of the present invention is used for an iron-air battery, and is composed of base particles and a surface modifying substance attached to the surface of the base particles, and the base particles contain 30 atomic% or more and 100 atomic% or less of Fe. And the surface modifying substance contains 20 atomic% or more and 100 atomic% or less of Cu, and the mass ratio of the surface modifying substance to 100% by mass of the substrate particles is 0.001% by mass or more and less than 30% by mass.
  • the negative electrode of the present invention includes the negative electrode material of the present invention, and the iron-air battery of the present invention has the negative electrode.
  • the iron-air battery of the present invention can achieve both a sufficient voltage and a large discharge capacity.
  • Example 4 is a SEM photograph of a negative electrode material prepared in Example 4.
  • the negative electrode material of the present invention comprises substrate particles and a surface modifying substance attached to the surface of the substrate particles, and is used for iron-air batteries.
  • the base particles contain iron alone (metallic iron), iron oxide, or a mixture thereof as a main component (iron base).
  • iron oxide include Fe 2 O 3 and Fe 3 O 4 .
  • the substrate particles have a large specific gravity, are fine, and have a large surface area.
  • metallic iron is preferable from the viewpoint of specific gravity, it is difficult to finely prepare metallic iron, and a larger discharge capacity may be obtained by preparing fine particles of iron oxide.
  • the base particles may contain impurities in an amount that does not significantly adversely affect the properties.
  • an “impurity” is a component that is not intentionally added but is mixed in the negative electrode material, and does not show any effect in the negative electrode material or means a component whose effect is unknown.
  • the impurities of the base particles Na, Ca, Nb, Cr, Mn, Co, Ni, Cu, Zn, Al, Ga, Si, P, S, Cl, rare earth elements (Pr, Nd, Dy, etc.) and the like are included. Can be mentioned. Rare earth oxides have a higher reduction potential than iron and remain inactive even when the iron-air battery is charged. Therefore, the present invention treats rare earth elements as impurities.
  • the mass ratio of the main component with respect to the whole substrate particles is usually 95% by mass or more, preferably 100% by mass.
  • the mass ratio of impurities with respect to the entire base particle is preferably 0% by mass, but if it is 5% by mass or less, the effect of improving the discharge characteristics of the present invention can be sufficiently obtained.
  • These mass ratios can be measured by X-ray diffraction, high frequency inductively coupled plasma (ICP) emission spectroscopy, or the like.
  • the atomic ratio of Fe with respect to all the constituent atoms of the substrate particles is 30 atomic% or more and 100 atomic% or less.
  • the atomic ratio is 100 atomic%.
  • the atomic ratio is 40 atomic%. This atomic ratio can be measured by X-ray diffraction, ICP emission spectroscopic analysis, or the like.
  • the substrate particles are preferably fine.
  • the D50 particle size of the substrate particles is preferably 5 ⁇ m or less.
  • the filling property filling density
  • the capacity density may not be improved. Therefore, in such a case, it is preferable that the D50 particle size of the base particle is 0.1 ⁇ m or more. This D50 particle size can be measured by a particle size distribution meter or the like.
  • the base particles preferably have a large surface area.
  • the BET specific surface area of the substrate particles is preferably 0.1 m 2 / g or more, more preferably 0.3 m 2 / g or more.
  • the BET specific surface area of the base particles is preferably 70 m 2 / g or less, more preferably 65 m 2 / g or less, from the viewpoint of improving the filling property of the negative electrode material, and thus the battery capacity per volume.
  • the BET specific surface area can be measured by, for example, nitrogen gas adsorption BET method using Macsorb HM-1210 (manufactured by MOUNTECH) or the like.
  • the shape of the substrate particles may be spherical or octahedral.
  • the base particles may be independent particles, a part thereof may be connected by sintering, or a part may be aggregated as secondary particles.
  • the base particles can be prepared by a uniform precipitation method using urea.
  • a residue generated in a rare earth magnet recycling process or the like can be used as a base particle.
  • such a residue contains an element derived from a rare earth magnet, but if the amount is within the range of the mass ratio of the impurities (5 mass% or less), the effect of the present invention can be sufficiently obtained.
  • the surface modifying substance contains, as a main component, copper alone (metal copper), a copper compound, or a mixture thereof.
  • the copper compound is CuO, Cu 2 O, Cu ( OH) 2 and the like.
  • the main component of the surface modifying material is preferably Cu.
  • the main component of the surface modifying material may contain CuO, Cu 2 O, or Cu (OH) 2 immediately after being attached to the base particle, before charging, or after discharging. When the iron-air battery is charged, CuO, Cu 2 O, and Cu (OH) 2 are reduced to the state of Cu.
  • the surface modifier may contain impurities in an amount that does not have a significant adverse effect on its properties.
  • the impurity of the surface modifying substance may be an element derived from a precursor or a neutralizing agent, and examples thereof include Li, Na, K, and S.
  • the mass ratio of the main component to the entire surface modifying substance is usually 95% by mass or more, preferably 100% by mass.
  • the mass ratio of impurities to the entire surface modifying substance is preferably 0% by mass, but if it is 5% by mass or less, the effect of improving the discharge characteristics of the present invention can be sufficiently obtained.
  • These mass ratios can be measured by X-ray diffraction, ICP emission spectroscopic analysis, or the like.
  • the atomic ratio of Cu with respect to all the constituent atoms of the surface modifier is 20 atomic% or more and 100 atomic% or less, and preferably 50 atomic% or more and 100 atomic% or less. That is, since Cu (OH) 2 has a small specific gravity, Cu, CuO, and Cu 2 O are more preferable from the viewpoint of the packing density of the negative electrode material.
  • This atomic ratio can be measured using a phase identified by X-ray diffraction, an energy dispersive X-ray analyzer (EDS), or the like.
  • the surface modifier may be granular.
  • the average particle diameter of the surface modifying substance is preferably 10 nm to 500 nm, more preferably 20 nm to 200 nm. That is, the surface modifying substance used in the present invention can be very fine particles.
  • the average particle diameter of the surface modifying substance can be measured by observation with a scanning electron microscope (SEM) or the like.
  • the surface modifier is attached to the surface of the base particle.
  • the surface modifying substance is preferably uniformly dispersed on the surface of the base particle, and may cover all or part of the surface of the base particle.
  • “the surface modifying substance is attached to the surface of the base particle” means that the surface modifying substance is held in contact with the surface.
  • the surface modifying substance may be physically adsorbed and / or chemically bonded to the surface, and the surface modifying substance and the base particle may form a solid solution in part or all of the contact interface.
  • the negative electrode material of the present invention has a specific adhesion state achieved by a production method including steps (a) to (c) described later.
  • This specific adhesion state cannot be obtained with a mixture obtained by simply mixing iron base particles and copper particles. Although it is difficult to specify the difference between the specific adhesion state of the present invention and the interface state in the mixture or the like by a numerical range, as shown in the examples described later, when the mixture is used in an iron-air battery, discharge characteristics are obtained. Decreases.
  • fine surface modifying substance particles can be easily attached onto the base particles by a production method including the steps (a) to (c) described later.
  • the mass ratio of the surface modifying substance to 100% by mass of the base particles is 0.001% by mass or more and less than 30% by mass.
  • the mass ratio of the surface modifying substance is too low, a sufficient conductivity improving effect cannot be obtained.
  • the mass ratio of the surface modifying substance is too high, the filling amount of the base material particles is reduced, so that the voltage of the iron-air battery is lowered.
  • the mass ratio of the surface modifying substance is preferably 0.005% by mass or more, more preferably 0.3% by mass or more.
  • the mass ratio is preferably 25% by mass or less. This content ratio can be measured by ICP emission spectroscopic analysis or the like.
  • the negative electrode material of the present invention includes (a) a step of stirring the substrate particles, the precursor of the surface modifier, and the neutralizing agent in a solvent to prepare a slurry, and (b) filtering the resulting slurry to obtain a cake. And (c) baking the cake.
  • step (a) for example, first, base particles are added to a solvent, a neutralizing agent is further added, and a solution of a surface modifying substance precursor is added dropwise thereto to perform a neutralization reaction, thereby forming a surface modifying substance. And can be attached to the surface of the substrate particles.
  • the amount of each component is adjusted so that the pH after dropping the surface modifying substance precursor solution is 4.0 or more.
  • the neutralization reaction may be performed by adding base particles to the solvent and simultaneously dropping the alkaline neutralizing agent solution and the acidic surface modifying substance precursor solution while adjusting the pH to 4.0 or more. .
  • the amount of the surface modifying substance is large (for example, when attaching 5% by mass or more of the surface modifying substance to 100% by mass of the base particles), it is difficult to dissolve a large amount of the neutralizing agent. It is preferable to simultaneously add the surface modifying substance precursor.
  • step (a) copper sulfate, copper nitrate, hydrates thereof, or the like can be used as the surface modifying substance precursor.
  • the neutralizing agent lithium hydroxide, sodium hydroxide, potassium hydroxide or the like can be used.
  • the solvent water, ethanol or the like can be used.
  • the addition speed of the surface modifying substance precursor solution, the addition speed of the neutralizing agent solution, the amount of the solvent, the stirring method and the like are not particularly limited as long as the base particles can be uniformly stirred and the surface modifying substance can be uniformly dispersed.
  • the stirring temperature is not particularly limited as long as the solvent does not evaporate.
  • step (b) it is preferable to wash the cake after filtering the slurry.
  • a suction filter, a filter press, a centrifuge, or the like can be used.
  • Liquids such as water and ethanol can be used for washing.
  • the washing after filtration is insufficient, Li, Na, K, etc. derived from the neutralizing agent may be mixed in the negative electrode material.
  • the degree of cleaning is confirmed by measuring the conductivity of the cleaning liquid.
  • the temperature for baking the cake is preferably 150 ° C. or higher and 800 ° C. or lower.
  • this firing temperature exceeds 800 ° C., Cu and Fe are excessively dissolved in the solid, and Cu diffuses into the inside of the substrate particles, so that the effect of surface modification is reduced.
  • the firing temperature is less than 150 ° C., the surface modifying substance does not sufficiently adhere to the base particles, so that the conductivity of the negative electrode material is not sufficiently improved, and the effect of improving the iron utilization rate is reduced.
  • the firing time is not particularly limited, but may be about 2 to 10 hours. Firing may be performed in the air, and may be performed using an electric furnace, a gas furnace, or the like.
  • step (a) when copper (II) sulfate pentahydrate is used as the precursor of the surface modifier, in step (a), at least part of the copper (II) sulfate pentahydrate can be converted to copper hydroxide. .
  • step (c) depending on conditions such as the firing temperature, copper oxide or metallic copper may be produced from the copper hydroxide, and at least a part of the copper hydroxide may remain as it is. That is, in this case, copper sulfate, copper hydroxide, copper oxide, and / or metal copper can be attached to the surface of the base particle as a surface modifier by appropriately selecting the conditions of each step. In particular, it is preferable to attach metallic copper, copper oxide, or a combination thereof to the surface of the base particle.
  • one or a plurality of substances may be attached to the base particles as the surface modifying substance.
  • the iron-air battery of the present invention usually has a negative electrode, an air electrode, and an electrolyte, and may further have a separator, a current collector, a cell case, an opening, and the like.
  • the iron-air battery uses iron and oxygen as a negative electrode active material and oxygen as an air electrode active material.
  • the negative electrode contains the negative electrode material of the present invention, and may further contain a binder, a current collector, a core for holding the electrode, a conductive aid such as a carbon material, and the like.
  • a negative electrode is not specifically limited, For example, it can obtain by rolling the negative electrode material of this invention.
  • the size and shape of the negative electrode are not particularly limited, but usually the thickness of the negative electrode may be about 10 ⁇ m to 5 mm.
  • the air electrode may have a current collector for supplying electrons to oxygen, which is an active material, and a catalyst layer for promoting an oxygen reduction reaction.
  • the current collector includes a conductive material, and examples thereof include carbonaceous materials such as activated carbon, carbon fiber, carbon black, and graphite, and metal materials such as iron, copper, nickel, and aluminum.
  • the catalyst used for the catalyst layer include silver, platinum, ruthenium, palladium, carbon, oxide and the like. Among these, an oxide catalyst is preferable from the viewpoint of both abundant amount of resources and high reaction activity.
  • the current collector and the catalyst layer may each contain a binder, a water repellent material, and the like.
  • the air electrode may be prepared by stacking the current collector and the catalyst layer as separate components. Alternatively, the air electrode may be formed by mixing a conductive material for the current collector and a catalyst for the catalyst layer. That is, one component having both the function as a current collector and the function as a catalyst layer may be used as the air electrode.
  • the air electrode may further have a support (carrier), a water repellent layer, a gas diffusion layer and the like.
  • the support is made of a material having mechanical strength, and examples thereof include various foamed metals such as nickel, punching metal, and micromesh.
  • the water-repellent layer is made of a material that can transmit oxygen but can block water, and examples thereof include polytetrafluoroethylene (PTFE).
  • the gas diffusion layer preferably has high porosity and high conductivity, and examples of the material include carbon paper and carbon cloth.
  • the method for producing the air electrode is not particularly limited.
  • a slurry can be prepared by mixing a catalyst, a conductive material, a binder, and a solvent, and the slurry can be applied to a support and dried.
  • the solvent include water and organic solvents (N-methyl-2-pyrrolidone, ethanol, ethylene glycol, etc.).
  • the size and shape of the air electrode are not particularly limited, but usually the thickness of the air electrode may be about 20 ⁇ m to 1 cm.
  • the electrolyte may be used in the form of an electrolyte solution (electrolytic solution).
  • electrolytic solution examples include aqueous solutions of KOH, NaCl, NaOH, NaHCO 3 , Na 2 SO 4 , HCl, HNO 3 , NH 3 and the like.
  • the separator is disposed between the negative electrode and the air electrode, and prevents the short circuit between the two electrodes, holds the electrolyte, and conducts ions.
  • the separator material include polyethylene fiber, polypropylene fiber, glass fiber, resin nonwoven fabric, glass nonwoven fabric, and filter paper.
  • the iron-air battery of the present invention exhibits improved discharge characteristics. More specifically, the iron-air battery of the present invention can achieve both a sufficient voltage and a large discharge capacity.
  • the maximum discharge capacity obtained in 30 cycles is defined as the “maximum capacity” of the iron-air battery, and the maximum The average voltage at the time of discharging at which the capacity is obtained is referred to as “maximum capacity voltage”.
  • the iron-air battery of the present invention exhibits a higher maximum capacity than an iron-air battery using a negative electrode material that has not been subjected to surface modification treatment, and a sufficient maximum capacity voltage of 0.4 V or more.
  • the manufacturing method of the iron-air battery is not particularly limited, and for example, it can be manufactured by laminating a negative electrode case, a spacer, a current collector, a negative electrode, a separator, an air electrode, and an air electrode case in this order.
  • Example 1 Preparation of base particle
  • the residual iron material produced in the process of recycling the rare earth magnet was used as the base particle (A).
  • the base particles (A) mainly had an octahedral shape and contained Fe 3 O 4 as a main component.
  • the base particle (A) contained Nd, Dy, Co, and Al in addition to Fe 3 O 4 .
  • the entire substrate particle (A) is 100% by mass, the proportion of Fe is 70.5% by mass, Nd is 1.33% by mass, Dy is 0.46% by mass, Co is 0.51% by mass, Al is It was 0.19 mass%.
  • the mass ratio of the impurities to the entire base particle (A) was 2.49% by mass.
  • the atomic ratio of Fe with respect to all the constituent atoms of the base particle (A) was 42.6 atomic%.
  • the base particle (A) had a BET specific surface area of 8.8 m 2 / g and a D50 particle size of 4.1 ⁇ m.
  • the resulting slurry was filtered by Nutsche and washed with pure water. The washing was repeated until the conductivity of the washing liquid became 300 ⁇ S / cm or less. The obtained cake was baked at 250 ° C. for 2 hours to obtain a negative electrode material.
  • the obtained negative electrode material 0.01% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A).
  • the surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Further, the surface modified substance formed by this method was observed by using a field emission electron probe microanalyzer (FESEM) JXA-8530F manufactured by JEOL Ltd., and the average particle size of 56 particles was determined to be about 100 nm. Met. The same applies to Examples 2 to 17 and Comparative Examples 2, 6, 8, and 10 below.
  • the shape of the substrate particles was observed using a scanning electron microscope (SEM) S-3000N manufactured by Hitachi High-Technologies Corporation.
  • the composition of the base particles and the surface modifying substance was determined by ICP analysis using an ICP emission analyzer Optima 8300 manufactured by Perkin Elmer and XRD measurement using an X-ray diffractometer Ultrama IV manufactured by Rigaku Corporation.
  • the BET specific surface area of the substrate particles was measured using a specific surface area measuring device Macsorb HM-1210 manufactured by MOUNTECH.
  • the D50 particle size of the substrate particles was measured using a laser diffraction particle size distribution meter HRA (Microtrack) manufactured by LEEDS & NORTHUP.
  • Negative Electrode 1.5 g of the above negative electrode material and 0.3 mL of KOH aqueous solution (5 M) as an electrolyte solution (electrolytic solution) were kneaded in a mortar for 10 minutes to produce a negative electrode.
  • the amount of the negative electrode material used is shown in Table 1 as the negative electrode material filling amount in the iron-air battery.
  • a 2032 type coin cell part manufactured by Hosen Co., Ltd. was used as a battery member.
  • Negative electrode case, wave washer, spacer, copper foil cut to a diameter of 16 mm (CF-T8G-STD-18 manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.), negative electrode, filter paper cut to a diameter of 18 mm (ADVANTEC 5C), air electrode, And the air electrode case with an air hole was laminated
  • the copper foil functions as a current collector.
  • the filter paper functions as a separator and also has a role of holding an electrolyte solution.
  • Example 2 30 g of the base particles (A) were added to 50 mL of pure water and stirred, and 0.0064 g of lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved therein to obtain a slurry.
  • 0.0942 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 mL of pure water to prepare a surface modifying substance precursor solution. This surface modifying substance precursor solution was dropped into the slurry, and after confirming that there was no fluctuation in pH, the obtained slurry was Nutsche filtered and washed with pure water.
  • the washing was repeated until the conductivity of the washing liquid became 300 ⁇ S / cm or less.
  • the obtained cake was baked at 250 ° C. for 2 hours to obtain a negative electrode material.
  • the surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu.
  • an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
  • Example 3 50 g of base material particles (A) were added to 50 mL of pure water and stirred, and 0.1812 g of lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved therein to obtain a slurry.
  • 0.5392 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 mL of pure water to prepare a surface modifying substance precursor solution. This surface modifying substance precursor solution was dropped into the slurry, and after confirming that there was no fluctuation in pH, the obtained slurry was Nutsche filtered and washed with pure water.
  • the washing was repeated until the conductivity of the washing liquid became 300 ⁇ S / cm or less.
  • the obtained cake was baked at 250 ° C. for 2 hours to obtain a negative electrode material.
  • the surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu.
  • an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
  • Example 4 50 g of base material particles (A) were added to 50 mL of pure water and stirred to obtain a slurry.
  • 7.8474 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 35 mL of pure water to prepare a surface modifying substance precursor solution.
  • the surface modifying substance precursor solution was dropped into the slurry at a dropping rate of 1 mL / min using a tube pump.
  • the pH of the slurry was maintained at 9.0 by simultaneously dropping a 5% NaOH solution.
  • the resulting slurry was filtered by Nutsche and washed with pure water.
  • Example 4 An SEM photograph of the negative electrode material of Example 4 is shown in FIG. Relatively fine substrate particles (A) having a particle size of about 1 ⁇ m or less are generally coated with surface modifying substance particles. In the substrate particles (A) having a particle diameter of about several ⁇ m, surface modifying substance particles are present on the surface. It was uniformly dispersed.
  • the surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
  • Example 5 A negative electrode in the same manner as in Example 4 except that 15.69948 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 60 mL of pure water to prepare a surface modifying substance precursor solution. Obtained material. In the obtained negative electrode material, 10% by mass of the surface modifying substance adhered to 100% by mass of the base material particles (A). The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
  • Example 6 10 g of the above base particle (A) is added to 50 mL of pure water and stirred to prepare a slurry, and 6.2279 g of copper (II) sulfate pentahydrate (Wako Pure Chemical Industries, Ltd.) is added to 20 mL of pure water.
  • a negative electrode material was obtained in the same manner as in Example 4 except that the surface modification solution was prepared by dissolving the product. In the obtained negative electrode material, 20% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A).
  • the surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
  • Comparative Example 1 The surface modifying substance was not formed (the surface modification treatment was not performed), and the base material particle (A) was used as it was as the negative electrode material. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
  • Comparative Example 2 A negative electrode material was obtained in the same manner as in Example 6 except that 9.4169 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 30 mL of pure water to prepare a surface modification solution. It was. In the obtained negative electrode material, 30% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A). The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
  • Comparative Example 3 Same as Example 1 except that 1.04 g of the above base particle (A), 0.16 g of carbon black, and 0.3 mL of KOH aqueous solution (5M) were kneaded in a mortar for 10 minutes to produce a negative electrode. An iron-air battery was prepared and a charge / discharge test was conducted. The results are shown in Table 1.
  • Comparative Example 4 1.5 g of the above base particle (A) and 0.075 g of copper powder (pure copper 45 ⁇ m pass manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed, and 1.5 g of the obtained powder was 0.3 mL.
  • An iron-air battery was prepared and a charge / discharge test was conducted in the same manner as in Example 1 except that a negative electrode was prepared by kneading in a mortar with a KOH aqueous solution (5M) for 10 minutes. The results are shown in Table 1.
  • copper particles having a primary particle diameter of about 1 ⁇ m were mixed with the base material particles (A).
  • the mass ratio of the copper particles to 100% by mass of the base material particles (A) was 5% by mass.
  • Comparative Example 3 in which carbon was used as a conductive auxiliary agent without performing the surface modification treatment of the present invention, the amount of base material particles that could be filled in the battery case was reduced because the carbon was bulky, and the maximum capacity was reduced. .
  • Comparative Example 4 where the surface modification treatment of the present invention was not performed and copper powder was used as the conductive auxiliary agent, the maximum capacity was improved, but the voltage at the maximum capacity decreased.
  • surface modifying substances CuO or the like
  • iron-air batteries of Examples 7 to 10 and Comparative Examples 5 and 6 were produced and subjected to a charge / discharge test. The results are shown in Table 2.
  • the base particles (B) were BASF carbonyl iron SQ grade, had a spherical shape, and contained Fe as a main component.
  • the base particle (B) contained a small amount of Si in addition to Fe, and the total mass of the base particle (B) was 100% by mass. The ratio was 99.9% by mass and Si was 0.1% by mass.
  • the atomic ratio of Fe with respect to all the constituent atoms of the base particle (B) was 99.98 atomic%.
  • the base particle (B) had a BET specific surface area of 0.4 m 2 / g and a D50 particle size of 4.0 ⁇ m.
  • Examples 11 to 14 and Comparative Examples 7 and 8 Examples 1, 2, 4, and 6 and Comparative Example 1 and Comparative Example 1 except that the base particle (C) was used instead of the base particle (A), and the filling amount of the negative electrode material was changed as shown in Table 3.
  • iron-air batteries of Examples 11 to 14 and Comparative Examples 7 and 8 were produced and subjected to a charge / discharge test. The results are shown in Table 3.
  • the base particles (C) are Fe 2 O 3 particles (iron (III) oxide, Wako first grade, product code 096-04825) manufactured by Wako Pure Chemical Industries, Ltd., and contain Fe 2 O 3 as a main component. It was. When SQX analysis was performed, the base particle (C) contained Al, Si, P, S, Cl, Ca, Cr, Mn, Ni, Zn, and Nb in addition to Fe 2 O 3.
  • the mass ratio of Fe is 69.5% by mass
  • Al is 0.03% by mass
  • Si is 0.03% by mass
  • P is 0.01% by mass
  • S is 0.01% by mass
  • Cl 0.06% by mass
  • Ca 0.01% by mass
  • Cr 0.02% by mass
  • Mn 0.25% by mass
  • Ni 0.01% by mass
  • Zn 0. It was 02 mass%.
  • the atomic ratio of Fe with respect to all the constituent atoms of the base particles (C) was 39.96 atomic%.
  • the base material particle (C) had a BET specific surface area of 6.1 m 2 / g and a D50 particle size of 1.9 ⁇ m.
  • Examples 15 to 17 and Comparative Examples 9 and 10 Examples 2, 5, and 6 and Comparative Examples 1 and 2 except that the base particle (D) was used instead of the base particle (A), and the filling amount of the negative electrode material was changed as shown in Table 4.
  • iron-air batteries of Examples 15 to 17 and Comparative Examples 9 and 10 were produced and subjected to charge / discharge tests. The results are shown in Table 4.
  • the base particles (D) were prepared by the uniform precipitation method as follows. First, iron (II) sulfate heptahydrate and urea (both manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in pure water, and the pH was controlled by promoting decomposition of urea using a hot plate heated to 120 ° C. . This solution was maintained at a solution temperature of 90 ° C. for 10 minutes to form a precipitate, and then 24% NaOH was added to raise the pH to 10 to fix the particle size. The resulting precipitate was separated by filtration and washed to obtain substrate particles (D). The base particle (D) contained Fe 3 O 4 as a main component.
  • the base particle (D) contained Na, Si, P, S, Mn, Ni, and Cu in addition to Fe 3 O 4 , and the entire base particle (D) was 100.
  • the mass ratio of Fe is 72.1% by mass, Na is 0.05% by mass, Si is 0.02% by mass, S is 0.10% by mass, Mn is 0.02% by mass, Ni is 0.02 mass% and Cu was 0.01 mass%.
  • the atomic ratio of Fe with respect to all the constituent atoms of the base particle (D) was 42.59 atomic%.
  • the base particle (D) had a BET specific surface area of 59.1 m 2 / g and a D50 particle size of 1.2 ⁇ m.
  • Example 15 to 18 the maximum capacity of the iron-air battery was improved by attaching 0.1 to 20% by mass of the surface modifying substance to 100% by mass of the base particles. did.
  • the maximum capacity improvement effect was somewhat low when the mass ratio of the surface modifying substance was low. Since the base particle (D) has a relatively large surface area, it is considered that the effect is hardly exhibited with a small amount of the surface modifying substance.
  • Comparative Example 10 in which the mass ratio of the surface modifying substance was increased to 30% by mass, the maximum capacity was improved but the maximum capacity voltage was greatly reduced.
  • Example 17 the maximum capacity is lower than that in Comparative Example 9, but this is due to the different filling amounts.
  • the capacity per unit mass of the negative electrode material is 16.3 mAh / g in Example 17, and 13.7 mAh / g in Comparative Example 9, and Example 17 also shows the capacity improvement effect by the surface modifier.

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Abstract

Provided are: a negative electrode material which is suitable for use in a negative electrode of an iron-air battery; and a negative electrode and an iron-air battery, each of which uses this negative electrode material. This negative electrode material is composed of base material particles and a surface modification substance which adheres to the surfaces of the base material particles; the base material particles contain from 30% by atom to 100% by atom (inclusive) of Fe; and the surface modification substance contains from 20% by atom to 100% by atom (inclusive) of Cu. The mass ratio of the surface modification substance to 100% by mass of the base material particles is 0.001% by mass or more but less than 30% by mass.

Description

負極材料、負極、及び鉄空気電池Negative electrode material, negative electrode, and iron-air battery
　本発明は、鉄空気電池用の負極材料、並びに該負極材料を用いた負極及び鉄空気電池に関する。 The present invention relates to a negative electrode material for an iron-air battery, and a negative electrode and an iron-air battery using the negative electrode material.
　金属空気電池は空気極の活物質として大気中の酸素を利用できることから、空気極の反応物質をゼロと考え、電池の大部分を負極の反応物質で構成できるので、比較的容易に高エネルギー密度化が可能である。そのため、リチウムイオン電池に代わる車載用二次電池等としての利用が期待されている。金属空気電池の負極には、亜鉛、リチウム、マグネシウム、アルミニウム、鉄等の金属が用いられる。金属空気電池の空気極には、カーボン材料や、酸化物触媒、貴金属触媒等で構成された触媒層が用いられる。 Since metal-air batteries can use oxygen in the atmosphere as the active material of the air electrode, the reaction material of the air electrode is considered to be zero, and most of the battery can be composed of the negative electrode reaction material, so it is relatively easy to achieve high energy density. Is possible. Therefore, the use as a vehicle-mounted secondary battery etc. which replaces a lithium ion battery is anticipated. Metals such as zinc, lithium, magnesium, aluminum, and iron are used for the negative electrode of the metal-air battery. A catalyst layer made of a carbon material, an oxide catalyst, a noble metal catalyst, or the like is used for the air electrode of the metal-air battery.
　亜鉛空気電池等の多くの金属空気電池では、充電時に負極上にデンドライト状結晶が析出し、電極間で短絡が発生しやすくなるという問題がある。これに対し、鉄空気電池の負極ではデンドライト状結晶が形成されにくく、そのため鉄空気電池は比較的サイクル特性に優れている。また、リチウム空気電池やアルミニウム空気電池等と比較すると、鉄空気電池の負極は耐腐食性が高い。更に、鉄は資源が豊富であり、安価であり、毒性が低く、容易に再利用でき、環境に優しいという利点を有する。このような理由から、近年、鉄空気電池が関心を集めている。 Many metal-air batteries such as zinc-air batteries have a problem that dendritic crystals are deposited on the negative electrode during charging, and a short circuit is likely to occur between the electrodes. On the other hand, dendrite-like crystals are hardly formed on the negative electrode of the iron-air battery, and therefore the iron-air battery has relatively excellent cycle characteristics. Moreover, compared with a lithium air battery, an aluminum air battery, etc., the negative electrode of an iron air battery has high corrosion resistance. In addition, iron has the advantages of being abundant in resources, inexpensive, low in toxicity, easily reusable and environmentally friendly. For these reasons, iron-air batteries have recently attracted interest.
　通常、鉄空気電池の負極は、金属鉄又は酸化鉄を含む鉄基材からなる。鉄空気電池の充放電過程においては、鉄基材の表面領域のみが反応すると考えられている（非特許文献１）。そのため、鉄空気電池は大容量化が困難であるという問題を有する。 Usually, the negative electrode of the iron-air battery is made of an iron base material containing metallic iron or iron oxide. In the charge / discharge process of the iron-air battery, it is considered that only the surface region of the iron base material reacts (Non-Patent Document 1). Therefore, the iron-air battery has a problem that it is difficult to increase the capacity.
　そこで、反応に寄与する鉄の量（鉄利用率）を改善する方法が検討されており、カーボン材料を用いて負極の導電性を改善する方法が知られている。例えば、Ｆｅ３Ｏ４ナノ粒子をカーボンナノ繊維の表面に分布させる方法が提案されている（非特許文献２）。 Thus, methods for improving the amount of iron contributing to the reaction (iron utilization rate) have been studied, and methods for improving the conductivity of the negative electrode using a carbon material are known. For example, a method for distributing Fe 3 O 4 nanoparticles on the surface of carbon nanofibers has been proposed (Non-Patent Document 2).
　しかしながら、上記カーボン材料を用いる方法では、得られる負極が非常に嵩高いため、鉄空気電池の容量密度が低下する。鉄空気電池を実用化するためには、鉄基材の充填密度を損なわずに導電性を向上させ、放電特性を更に改善することが必要とされている。 However, in the method using the carbon material, since the obtained negative electrode is very bulky, the capacity density of the iron-air battery is lowered. In order to put the iron-air battery into practical use, it is necessary to improve the electrical conductivity and further improve the discharge characteristics without impairing the packing density of the iron base material.
　本発明の目的は、鉄空気電池の負極に使用した際に放電特性を改善し得る負極材料を提供することである。 An object of the present invention is to provide a negative electrode material capable of improving discharge characteristics when used for a negative electrode of an iron-air battery.
　本発明の他の目的は、鉄空気電池に使用した際に放電特性を改善し得る負極を提供することである。 Another object of the present invention is to provide a negative electrode capable of improving discharge characteristics when used in an iron-air battery.
　本発明の更なる目的は、改善された放電特性を示す鉄空気電池を提供することである。 It is a further object of the present invention to provide an iron-air battery that exhibits improved discharge characteristics.
　本発明者は、上記課題を解決するべく鋭意検討した結果、鉄基材粒子の表面に特定の銅系表面修飾物質を特定量だけ付着させてなる負極材料を使用することによって、放電特性が改善された鉄空気電池が得られることを見出し、本発明を完成するに至った。 As a result of intensive studies to solve the above problems, the present inventor has improved discharge characteristics by using a negative electrode material in which a specific amount of a specific copper-based surface modifier is adhered to the surface of iron base particles. The present inventors have found that an iron-air battery can be obtained, and have completed the present invention.
　本発明の負極材料は、鉄空気電池に用いられ、基材粒子と該基材粒子の表面に付着した表面修飾物質とからなり、前記基材粒子が３０原子％以上１００原子％以下のＦｅを含み、前記表面修飾物質が２０原子％以上１００原子％以下のＣｕを含み、１００質量％の前記基材粒子に対する前記表面修飾物質の質量比が０．００１質量％以上３０質量％未満である。 The negative electrode material of the present invention is used for an iron-air battery, and is composed of base particles and a surface modifying substance attached to the surface of the base particles, and the base particles contain 30 atomic% or more and 100 atomic% or less of Fe. And the surface modifying substance contains 20 atomic% or more and 100 atomic% or less of Cu, and the mass ratio of the surface modifying substance to 100% by mass of the substrate particles is 0.001% by mass or more and less than 30% by mass.
　本発明の負極は上記本発明の負極材料を含み、本発明の鉄空気電池は該負極を有する。 The negative electrode of the present invention includes the negative electrode material of the present invention, and the iron-air battery of the present invention has the negative electrode.
　本発明の負極材料では特定量の表面修飾物質が基材粒子の表面に付着しており、そのため該負極材料を用いた本発明の鉄空気電池は改善された放電特性を示す。より詳しくは、本発明の鉄空気電池は、十分な電圧と大きな放電容量の両方を達成し得る。 In the negative electrode material of the present invention, a specific amount of the surface modifying substance is adhered to the surface of the base particle, and therefore the iron-air battery of the present invention using the negative electrode material exhibits improved discharge characteristics. More specifically, the iron-air battery of the present invention can achieve both a sufficient voltage and a large discharge capacity.
実施例４で調製した負極材料のＳＥＭ写真である。4 is a SEM photograph of a negative electrode material prepared in Example 4.
　本発明の負極材料は、基材粒子と該基材粒子の表面に付着した表面修飾物質とからなり、鉄空気電池に用いられる。 The negative electrode material of the present invention comprises substrate particles and a surface modifying substance attached to the surface of the substrate particles, and is used for iron-air batteries.
　基材粒子は主成分（鉄基材）として鉄単体（金属鉄）、酸化鉄、又はこれらの混合物を含有する。酸化鉄の例としてはＦｅ２Ｏ３、Ｆｅ３Ｏ４等が挙げられる。本発明の負極材料を鉄空気電池に用いた際に高い容量密度を得るためには、基材粒子は比重が大きく、微細であり、表面積が大きいことが好ましい。比重の観点からは金属鉄が好ましいが、金属鉄を微細に調製することは難しく、酸化鉄の微細粒子を調製することでより大きな放電容量が得られる場合もある。 The base particles contain iron alone (metallic iron), iron oxide, or a mixture thereof as a main component (iron base). Examples of iron oxide include Fe 2 O 3 and Fe 3 O 4 . In order to obtain a high capacity density when the negative electrode material of the present invention is used in an iron-air battery, it is preferable that the substrate particles have a large specific gravity, are fine, and have a large surface area. Although metallic iron is preferable from the viewpoint of specific gravity, it is difficult to finely prepare metallic iron, and a larger discharge capacity may be obtained by preparing fine particles of iron oxide.
　基材粒子はその特性に大きな悪影響を与えない範囲の量で不純物を含んでいてもよい。本発明において、「不純物」は、意図的に添加したわけではないが負極材料に混入した成分であり、負極材料中で何ら効果を示さないか、或いは効果が不明な成分を意味する。基材粒子の不純物としては、Ｎａ、Ｃａ、Ｎｂ、Ｃｒ、Ｍｎ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ａｌ、Ｇａ、Ｓｉ、Ｐ、Ｓ、Ｃｌ、希土類元素（Ｐｒ、Ｎｄ、Ｄｙ等）等が挙げられる。希土類酸化物は鉄よりも高い還元電位を示すため、鉄空気電池を充電しても不活性なままである。従って、本発明では希土類元素を不純物として扱う。 The base particles may contain impurities in an amount that does not significantly adversely affect the properties. In the present invention, an “impurity” is a component that is not intentionally added but is mixed in the negative electrode material, and does not show any effect in the negative electrode material or means a component whose effect is unknown. As the impurities of the base particles, Na, Ca, Nb, Cr, Mn, Co, Ni, Cu, Zn, Al, Ga, Si, P, S, Cl, rare earth elements (Pr, Nd, Dy, etc.) and the like are included. Can be mentioned. Rare earth oxides have a higher reduction potential than iron and remain inactive even when the iron-air battery is charged. Therefore, the present invention treats rare earth elements as impurities.
　基材粒子全体に対する主成分の質量比は、通常は９５質量％以上であり、好ましくは１００質量％である。基材粒子全体に対する不純物の質量比は、好ましくは０質量％であるが、５質量％以下であれば本発明の放電特性改善効果が十分に得られる。これら質量比はＸ線回折法、高周波誘導結合プラズマ（ＩＣＰ）発光分光分析法等によって測定できる。 The mass ratio of the main component with respect to the whole substrate particles is usually 95% by mass or more, preferably 100% by mass. The mass ratio of impurities with respect to the entire base particle is preferably 0% by mass, but if it is 5% by mass or less, the effect of improving the discharge characteristics of the present invention can be sufficiently obtained. These mass ratios can be measured by X-ray diffraction, high frequency inductively coupled plasma (ICP) emission spectroscopy, or the like.
　基材粒子の全構成原子に対するＦｅの原子比は、３０原子％以上１００原子％以下である。例えば、基材粒子が金属鉄のみからなる場合、当該原子比は１００原子％である。基材粒子がＦｅ２Ｏ３のみからなる場合、当該原子比は４０原子％である。この原子比はＸ線回折法、ＩＣＰ発光分光分析法等によって測定できる。 The atomic ratio of Fe with respect to all the constituent atoms of the substrate particles is 30 atomic% or more and 100 atomic% or less. For example, when the substrate particles are composed only of metallic iron, the atomic ratio is 100 atomic%. When the substrate particles are composed of only Fe 2 O 3 , the atomic ratio is 40 atomic%. This atomic ratio can be measured by X-ray diffraction, ICP emission spectroscopic analysis, or the like.
　上述のとおり、基材粒子は微細であることが好ましい。具体的には、基材粒子のＤ５０粒径は５μｍ以下であるのが好ましい。負極材料を電池ケース等に充填する場合は、基材粒子が過剰に微細であると充填性（充填密度）が低下し、容量密度が向上しないことがある。従って、このような場合は、基材粒子のＤ５０粒径を０．１μｍ以上とするのが好ましい。このＤ５０粒径は粒度分布計等によって測定できる。 As described above, the substrate particles are preferably fine. Specifically, the D50 particle size of the substrate particles is preferably 5 μm or less. When the negative electrode material is filled in a battery case or the like, if the substrate particles are excessively fine, the filling property (filling density) may be lowered and the capacity density may not be improved. Therefore, in such a case, it is preferable that the D50 particle size of the base particle is 0.1 μm or more. This D50 particle size can be measured by a particle size distribution meter or the like.
　上述のとおり、基材粒子は大きな表面積を有することが好ましい。具体的には、基材粒子のＢＥＴ比表面積は、好ましくは０．１ｍ２／ｇ以上、より好ましくは０．３ｍ２／ｇ以上である。一方、負極材料の充填性、ひいては容積あたりの電池容量を向上させる観点からは、基材粒子のＢＥＴ比表面積は、好ましくは７０ｍ２／ｇ以下、より好ましくは６５ｍ２／ｇ以下である。このＢＥＴ比表面積は、例えばＭａｃｓｏｒｂ　ＨＭ－１２１０（ＭＯＵＮＴＥＣＨ社製）等を用いて、窒素ガス吸着ＢＥＴ法等によって測定できる。 As described above, the base particles preferably have a large surface area. Specifically, the BET specific surface area of the substrate particles is preferably 0.1 m 2 / g or more, more preferably 0.3 m 2 / g or more. On the other hand, the BET specific surface area of the base particles is preferably 70 m 2 / g or less, more preferably 65 m 2 / g or less, from the viewpoint of improving the filling property of the negative electrode material, and thus the battery capacity per volume. The BET specific surface area can be measured by, for example, nitrogen gas adsorption BET method using Macsorb HM-1210 (manufactured by MOUNTECH) or the like.
　基材粒子の形状は球状や八面体状等であってよい。基材粒子はそれぞれが独立した粒子であってもよく、一部が焼結により繋がっていてもよく、一部が二次粒子として凝集していてもよい。 The shape of the substrate particles may be spherical or octahedral. The base particles may be independent particles, a part thereof may be connected by sintering, or a part may be aggregated as secondary particles.
　基材粒子は尿素を用いた均一沈殿法等によって調製できる。基材粒子は市販品であってもよく、その例としては、ＢＡＳＦ製カルボニル鉄ＳＱグレード（Ｄ５０＝４．０μｍ）、和光純薬工業株式会社製Ｆｅ２Ｏ３粒子（Ｄ５０＝１．９μｍ）等が挙げられる。また、本発明では、例えば希土類磁石のリサイクル工程等で生じた残渣を基材粒子として用いることも可能である。通常このような残渣は希土類磁石に由来する元素を含有するが、その量が上記不純物の質量比の範囲（５質量％以下）内であれば、本発明の効果が十分に得られる。 The base particles can be prepared by a uniform precipitation method using urea. The base particle may be a commercially available product, and examples thereof include BASF carbonyl iron SQ grade (D50 = 4.0 μm), Wako Pure Chemical Industries, Ltd. Fe 2 O 3 particles (D50 = 1.9 μm). Etc. Further, in the present invention, for example, a residue generated in a rare earth magnet recycling process or the like can be used as a base particle. Usually, such a residue contains an element derived from a rare earth magnet, but if the amount is within the range of the mass ratio of the impurities (5 mass% or less), the effect of the present invention can be sufficiently obtained.
　表面修飾物質は主成分として銅単体（金属銅）、銅化合物、又はこれらの混合物を含有する。銅化合物の例としてはＣｕＯ、Ｃｕ２Ｏ、Ｃｕ（ＯＨ）２等が挙げられる。負極の導電性を向上させるためには、表面修飾物質の主成分はＣｕであることが好ましい。しかしながら、基材粒子に付着させた直後、充電前、或いは放電後の時点では、表面修飾物質の主成分はＣｕＯ、Ｃｕ２Ｏ、又はＣｕ（ＯＨ）２を含んでいてもよい。鉄空気電池を充電すると、ＣｕＯ、Ｃｕ２Ｏ、及びＣｕ（ＯＨ）２はＣｕの状態まで還元される。 The surface modifying substance contains, as a main component, copper alone (metal copper), a copper compound, or a mixture thereof. Examples of the copper compound is CuO, Cu 2 O, Cu ( OH) 2 and the like. In order to improve the conductivity of the negative electrode, the main component of the surface modifying material is preferably Cu. However, the main component of the surface modifying material may contain CuO, Cu 2 O, or Cu (OH) 2 immediately after being attached to the base particle, before charging, or after discharging. When the iron-air battery is charged, CuO, Cu 2 O, and Cu (OH) 2 are reduced to the state of Cu.
　表面修飾物質はその特性に大きな悪影響を与えない範囲の量で不純物を含んでいてもよい。表面修飾物質の不純物は、その前駆体又は中和剤に由来する元素であってよく、その例としてはＬｉ、Ｎａ、Ｋ、Ｓ等が挙げられる。 The surface modifier may contain impurities in an amount that does not have a significant adverse effect on its properties. The impurity of the surface modifying substance may be an element derived from a precursor or a neutralizing agent, and examples thereof include Li, Na, K, and S.
　表面修飾物質全体に対する主成分の質量比は、通常は９５質量％以上であり、好ましくは１００質量％である。表面修飾物質全体に対する不純物の質量比は、好ましくは０質量％であるが、５質量％以下であれば本発明の放電特性改善効果が十分に得られる。これら質量比はＸ線回折法、ＩＣＰ発光分光分析法等によって測定できる。 The mass ratio of the main component to the entire surface modifying substance is usually 95% by mass or more, preferably 100% by mass. The mass ratio of impurities to the entire surface modifying substance is preferably 0% by mass, but if it is 5% by mass or less, the effect of improving the discharge characteristics of the present invention can be sufficiently obtained. These mass ratios can be measured by X-ray diffraction, ICP emission spectroscopic analysis, or the like.
　表面修飾物質の全構成原子に対するＣｕの原子比は、２０原子％以上１００原子％以下であり、好ましくは５０原子％以上１００原子％以下である。すなわち、Ｃｕ（ＯＨ）２は比重が小さいため、負極材料の充填密度の観点からはＣｕ、ＣｕＯ、及びＣｕ２Ｏのほうが好ましい。この原子比は、Ｘ線回折により同定された相やエネルギー分散型Ｘ線分析装置（ＥＤＳ）等を用いて測定できる。 The atomic ratio of Cu with respect to all the constituent atoms of the surface modifier is 20 atomic% or more and 100 atomic% or less, and preferably 50 atomic% or more and 100 atomic% or less. That is, since Cu (OH) 2 has a small specific gravity, Cu, CuO, and Cu 2 O are more preferable from the viewpoint of the packing density of the negative electrode material. This atomic ratio can be measured using a phase identified by X-ray diffraction, an energy dispersive X-ray analyzer (EDS), or the like.
　表面修飾物質は粒状であってよい。表面修飾物質の平均粒径は、好ましくは１０ｎｍ以上５００ｎｍ以下であり、より好ましくは２０ｎｍ以上２００ｎｍ以下である。すなわち、本発明で用いる表面修飾物質は非常に微細な粒子であり得る。表面修飾物質の平均粒径は走査型電子顕微鏡（ＳＥＭ）観察等によって測定できる。 The surface modifier may be granular. The average particle diameter of the surface modifying substance is preferably 10 nm to 500 nm, more preferably 20 nm to 200 nm. That is, the surface modifying substance used in the present invention can be very fine particles. The average particle diameter of the surface modifying substance can be measured by observation with a scanning electron microscope (SEM) or the like.
　本発明の負極材料において、表面修飾物質は基材粒子の表面に付着している。表面修飾物質は基材粒子の表面上で均一に分散していることが好ましく、基材粒子の表面全て又は一部を被覆していてもよい。なお、本発明において「表面修飾物質が基材粒子の表面に付着している」とは、表面修飾物質が該表面に接触して保持されていることを意味する。表面修飾物質が該表面に物理吸着及び／又は化学結合していてもよく、また表面修飾物質と基材粒子がその接触界面の一部又は全体で固溶体を形成していてもよい。ただし、本発明の負極材料は、後述する工程（ａ）～（ｃ）を含む製造方法によって達成される特定の付着状態を有する。この特定の付着状態は、鉄基材粒子と銅粒子とを単に混ぜて得られる混合物では得られない。本発明の特定の付着状態と該混合物等における界面状態との違いを数値範囲により特定することは困難であるが、後述する実施例に示すように、該混合物を鉄空気電池に用いると放電特性が低下する。 In the negative electrode material of the present invention, the surface modifier is attached to the surface of the base particle. The surface modifying substance is preferably uniformly dispersed on the surface of the base particle, and may cover all or part of the surface of the base particle. In the present invention, “the surface modifying substance is attached to the surface of the base particle” means that the surface modifying substance is held in contact with the surface. The surface modifying substance may be physically adsorbed and / or chemically bonded to the surface, and the surface modifying substance and the base particle may form a solid solution in part or all of the contact interface. However, the negative electrode material of the present invention has a specific adhesion state achieved by a production method including steps (a) to (c) described later. This specific adhesion state cannot be obtained with a mixture obtained by simply mixing iron base particles and copper particles. Although it is difficult to specify the difference between the specific adhesion state of the present invention and the interface state in the mixture or the like by a numerical range, as shown in the examples described later, when the mixture is used in an iron-air battery, discharge characteristics are obtained. Decreases.
　また、鉄基材粒子と銅粒子とを単に混合する場合、上述した平均粒径５００ｎｍ以下の微細な銅粒子を工業的に製造することは技術的に困難であり、また高コストである。更に、この場合、微細な銅粒子を鉄基材粒子上に均一に分散させ付着させることは実質的に不可能である。微細な酸化銅粒子として古河ケミカルズ株式会社製ＦＲＣ－Ｎ１０が市販されているが、顕微鏡観察によってこの粒子は二次凝集していることが確認できる。二次凝集粒子を基材粒子上に均一に分散させ付着させるには、非常に煩雑な工程が必要であると考えられる。本発明では、後述する工程（ａ）～（ｃ）を含む製造方法によって、微細な表面修飾物質粒子を基材粒子上に容易に付着させることができる。 Also, when iron base particles and copper particles are simply mixed, it is technically difficult and expensive to industrially produce the above-described fine copper particles having an average particle size of 500 nm or less. Further, in this case, it is substantially impossible to uniformly disperse and adhere fine copper particles onto the iron base particles. Although FRC-N10 manufactured by Furukawa Chemicals Co., Ltd. is commercially available as fine copper oxide particles, it can be confirmed by microscopic observation that the particles are secondary aggregated. In order to uniformly disperse and adhere the secondary agglomerated particles onto the substrate particles, it is considered that a very complicated process is required. In the present invention, fine surface modifying substance particles can be easily attached onto the base particles by a production method including the steps (a) to (c) described later.
　本発明の負極材料において、１００質量％の基材粒子に対する表面修飾物質の質量比は、０．００１質量％以上３０質量％未満である。表面修飾物質の質量比が低すぎる場合は、十分な導電性改善効果が得られない。一方、表面修飾物質の質量比が高すぎる場合は、基材粒子の充填量が減少するため鉄空気電池の電圧が低下する。表面修飾物質の質量比は、好ましくは０．００５質量％以上、より好ましくは０．３質量％以上である。また、該質量比は好ましくは２５質量％以下である。この含有割合はＩＣＰ発光分光分析法等によって測定できる。 In the negative electrode material of the present invention, the mass ratio of the surface modifying substance to 100% by mass of the base particles is 0.001% by mass or more and less than 30% by mass. When the mass ratio of the surface modifying substance is too low, a sufficient conductivity improving effect cannot be obtained. On the other hand, when the mass ratio of the surface modifying substance is too high, the filling amount of the base material particles is reduced, so that the voltage of the iron-air battery is lowered. The mass ratio of the surface modifying substance is preferably 0.005% by mass or more, more preferably 0.3% by mass or more. The mass ratio is preferably 25% by mass or less. This content ratio can be measured by ICP emission spectroscopic analysis or the like.
　本発明の負極材料は、（ａ）基材粒子、表面修飾物質の前駆体、及び中和剤を溶媒中で撹拌し、スラリーを調製する工程、（ｂ）得られたスラリーをろ過してケーキを得る工程、及び（ｃ）ケーキを焼成する工程を含む方法によって製造できる。 The negative electrode material of the present invention includes (a) a step of stirring the substrate particles, the precursor of the surface modifier, and the neutralizing agent in a solvent to prepare a slurry, and (b) filtering the resulting slurry to obtain a cake. And (c) baking the cake.
　工程（ａ）において、例えば、まず溶媒に基材粒子を加え、更に中和剤を加え、これに表面修飾物質前駆体の溶液を滴下して中和反応を行うことで、表面修飾物質を形成して基材粒子の表面に付着させることができる。このとき、表面修飾物質前駆体溶液を滴下した後のｐＨが４．０以上となるように各成分の量を調整する。或いは、溶媒に基材粒子を加え、アルカリ性の中和剤溶液と酸性の表面修飾物質前駆体溶液とを、ｐＨを４．０以上に調整しながら同時に滴下し、中和反応を行ってもよい。表面修飾物質の量が多い場合（例えば、１００質量％の基材粒子に対し５質量％以上の表面修飾物質を付着させる場合）、多量の中和剤を溶解させることが難しいため、中和剤と表面修飾物質前駆体とを同時に添加することが好ましい。 In step (a), for example, first, base particles are added to a solvent, a neutralizing agent is further added, and a solution of a surface modifying substance precursor is added dropwise thereto to perform a neutralization reaction, thereby forming a surface modifying substance. And can be attached to the surface of the substrate particles. At this time, the amount of each component is adjusted so that the pH after dropping the surface modifying substance precursor solution is 4.0 or more. Alternatively, the neutralization reaction may be performed by adding base particles to the solvent and simultaneously dropping the alkaline neutralizing agent solution and the acidic surface modifying substance precursor solution while adjusting the pH to 4.0 or more. . When the amount of the surface modifying substance is large (for example, when attaching 5% by mass or more of the surface modifying substance to 100% by mass of the base particles), it is difficult to dissolve a large amount of the neutralizing agent. It is preferable to simultaneously add the surface modifying substance precursor.
　工程（ａ）において、表面修飾物質前駆体としては硫酸銅、硝酸銅、これらの水和物等を用いることができる。中和剤としては水酸化リチウム、水酸化ナトリウム、水酸化カリウム等を用いることができる。溶媒としては水、エタノール等を用いることができる。表面修飾物質前駆体溶液の添加速度、中和剤溶液の添加速度、溶媒の量、撹拌方法等は、基材粒子を均一に撹拌でき、表面修飾物質を均一に分散できれば特に限定されない。撹拌温度は溶媒が蒸発しない温度であれば特に限定されない。 In step (a), copper sulfate, copper nitrate, hydrates thereof, or the like can be used as the surface modifying substance precursor. As the neutralizing agent, lithium hydroxide, sodium hydroxide, potassium hydroxide or the like can be used. As the solvent, water, ethanol or the like can be used. The addition speed of the surface modifying substance precursor solution, the addition speed of the neutralizing agent solution, the amount of the solvent, the stirring method and the like are not particularly limited as long as the base particles can be uniformly stirred and the surface modifying substance can be uniformly dispersed. The stirring temperature is not particularly limited as long as the solvent does not evaporate.
　工程（ｂ）において、スラリーをろ過した後、ケーキを洗浄するのが好ましい。ろ過及び洗浄には、吸引ろ過器、フィルタープレス、遠心分離機等を使用できる。洗浄には水、エタノール等の液体を用いることができる。ろ過後の洗浄が不十分な場合、負極材料に中和剤由来のＬｉ、Ｎａ、Ｋ等が混入する場合がある。通常、洗浄液の導電率を測定することによって、洗浄度合いを確認する。 In step (b), it is preferable to wash the cake after filtering the slurry. For filtration and washing, a suction filter, a filter press, a centrifuge, or the like can be used. Liquids such as water and ethanol can be used for washing. When the washing after filtration is insufficient, Li, Na, K, etc. derived from the neutralizing agent may be mixed in the negative electrode material. Usually, the degree of cleaning is confirmed by measuring the conductivity of the cleaning liquid.
　工程（ｃ）において、ケーキを焼成する温度は、好ましくは１５０℃以上８００℃以下である。この焼成温度が８００℃を超えると、ＣｕとＦｅが過剰に固溶し、Ｃｕが基材粒子内部まで拡散するため、表面修飾による効果が低下する。焼成温度が１５０℃未満であると、表面修飾物質が基材粒子に十分に付着しないため、負極材料の導電性が十分に向上せず、鉄利用率の向上効果が小さくなる。焼成時間は特に限定されないが、２～１０時間程度であってよい。焼成は大気中で行ってよく、電気炉やガス炉等を用いて行ってよい。 In step (c), the temperature for baking the cake is preferably 150 ° C. or higher and 800 ° C. or lower. When this firing temperature exceeds 800 ° C., Cu and Fe are excessively dissolved in the solid, and Cu diffuses into the inside of the substrate particles, so that the effect of surface modification is reduced. When the firing temperature is less than 150 ° C., the surface modifying substance does not sufficiently adhere to the base particles, so that the conductivity of the negative electrode material is not sufficiently improved, and the effect of improving the iron utilization rate is reduced. The firing time is not particularly limited, but may be about 2 to 10 hours. Firing may be performed in the air, and may be performed using an electric furnace, a gas furnace, or the like.
　例えば、表面修飾物質の前駆体として硫酸銅（ＩＩ）五水和物を用いる場合、工程（ａ）において、硫酸銅（ＩＩ）五水和物の少なくとも一部が水酸化銅へと変換され得る。工程（ｃ）では、焼成温度等の条件に依っては、水酸化銅から酸化銅や金属銅が生じることがあり、また水酸化銅の少なくとも一部がそのまま残ることもある。すなわち、この場合、各工程の条件を適宜選択することによって、表面修飾物質として硫酸銅、水酸化銅、酸化銅、及び／又は金属銅を基材粒子表面に付着させることができる。特に、金属銅、酸化銅、又はこれらの組み合わせを基材粒子表面に付着させるのが好ましい。このように、本発明では、表面修飾物質として一種又は複数の物質を基材粒子に付着させてよい。 For example, when copper (II) sulfate pentahydrate is used as the precursor of the surface modifier, in step (a), at least part of the copper (II) sulfate pentahydrate can be converted to copper hydroxide. . In the step (c), depending on conditions such as the firing temperature, copper oxide or metallic copper may be produced from the copper hydroxide, and at least a part of the copper hydroxide may remain as it is. That is, in this case, copper sulfate, copper hydroxide, copper oxide, and / or metal copper can be attached to the surface of the base particle as a surface modifier by appropriately selecting the conditions of each step. In particular, it is preferable to attach metallic copper, copper oxide, or a combination thereof to the surface of the base particle. Thus, in the present invention, one or a plurality of substances may be attached to the base particles as the surface modifying substance.
　本発明の鉄空気電池は、通常は負極、空気極、及び電解質を有し、更にセパレータ、集電体、セルケース、開孔部等を有していてもよい。鉄空気電池は負極活物質として鉄及び酸素を利用し、空気極活物質として酸素を利用する。 The iron-air battery of the present invention usually has a negative electrode, an air electrode, and an electrolyte, and may further have a separator, a current collector, a cell case, an opening, and the like. The iron-air battery uses iron and oxygen as a negative electrode active material and oxygen as an air electrode active material.
　負極は上記本発明の負極材料を含み、更にバインダー、集電体、電極を保持するための芯体、カーボン材料等の導電補助剤等を含んでいてもよい。負極の作製方法は特に限定されないが、例えば本発明の負極材料を圧延加工して得られる。負極の大きさや形状も特に限定されないが、通常、負極の厚みは１０μｍ～５ｍｍ程度であってよい。 The negative electrode contains the negative electrode material of the present invention, and may further contain a binder, a current collector, a core for holding the electrode, a conductive aid such as a carbon material, and the like. Although the manufacturing method of a negative electrode is not specifically limited, For example, it can obtain by rolling the negative electrode material of this invention. The size and shape of the negative electrode are not particularly limited, but usually the thickness of the negative electrode may be about 10 μm to 5 mm.
　空気極は、活物質である酸素に電子を供給するための集電体と、酸素還元反応を促進するための触媒層とを有してよい。集電体は導電性材料を含み、その例としては活性炭、炭素繊維、カーボンブラック、黒鉛等のような炭素質材料や、鉄、銅、ニッケル、アルミニウム等のような金属材料等が挙げられる。触媒層に用いられる触媒の例としては、銀、白金、ルテニウム、パラジウム、カーボン、酸化物等が挙げられる。中でも、資源量の豊富さと反応活性の高さの両立の観点から酸化物系触媒が好ましい。集電体及び触媒層はそれぞれバインダーや撥水材料等を含んでいてもよい。空気極は集電体と触媒層とを別個の構成要素として用意しこれらを積層したものであってよい。或いは、空気極は集電体用の導電性材料と触媒層用の触媒とを混合してなるものであってもよい。即ち、集電体としての機能と触媒層としての機能とを併せ持つ１つの構成要素を空気極として使用してもよい。 The air electrode may have a current collector for supplying electrons to oxygen, which is an active material, and a catalyst layer for promoting an oxygen reduction reaction. The current collector includes a conductive material, and examples thereof include carbonaceous materials such as activated carbon, carbon fiber, carbon black, and graphite, and metal materials such as iron, copper, nickel, and aluminum. Examples of the catalyst used for the catalyst layer include silver, platinum, ruthenium, palladium, carbon, oxide and the like. Among these, an oxide catalyst is preferable from the viewpoint of both abundant amount of resources and high reaction activity. The current collector and the catalyst layer may each contain a binder, a water repellent material, and the like. The air electrode may be prepared by stacking the current collector and the catalyst layer as separate components. Alternatively, the air electrode may be formed by mixing a conductive material for the current collector and a catalyst for the catalyst layer. That is, one component having both the function as a current collector and the function as a catalyst layer may be used as the air electrode.
　空気極は更に支持体（担体）、撥水層、ガス拡散層等を有していてもよい。支持体は機械的強度を有する材料からなり、その例としてはニッケル等の各種発泡金属、パンチングメタル、マイクロメッシュ等が挙げられる。撥水層は酸素を透過可能であるが水を遮断できる材料からなり、その例としてはポリテトラフルオロエチレン（ＰＴＦＥ）等が挙げられる。ガス拡散層は好ましくは高い多孔性及び高い導電性を有し、その材料の例としてはカーボンペーパー、カーボンクロス等が挙げられる。 The air electrode may further have a support (carrier), a water repellent layer, a gas diffusion layer and the like. The support is made of a material having mechanical strength, and examples thereof include various foamed metals such as nickel, punching metal, and micromesh. The water-repellent layer is made of a material that can transmit oxygen but can block water, and examples thereof include polytetrafluoroethylene (PTFE). The gas diffusion layer preferably has high porosity and high conductivity, and examples of the material include carbon paper and carbon cloth.
　空気極の作製方法は特に限定されないが、例えば、触媒、導電性材料、バインダー、及び溶媒を混合してスラリーを調製し、このスラリーを支持体に塗付し、乾燥して作製できる。溶媒の例としては水や有機溶媒（Ｎ－メチル－２－ピロリドン、エタノール、エチレングリコール等）が挙げられる。空気極の大きさや形状も特に限定されないが、通常、空気極の厚みは２０μｍ～１ｃｍ程度であってよい。 The method for producing the air electrode is not particularly limited. For example, a slurry can be prepared by mixing a catalyst, a conductive material, a binder, and a solvent, and the slurry can be applied to a support and dried. Examples of the solvent include water and organic solvents (N-methyl-2-pyrrolidone, ethanol, ethylene glycol, etc.). The size and shape of the air electrode are not particularly limited, but usually the thickness of the air electrode may be about 20 μm to 1 cm.
　電解質は電解質溶液（電解液）の形態で使用してよい。電解液としては、ＫＯＨ、ＮａＣｌ、ＮａＯＨ、ＮａＨＣＯ３、Ｎａ２ＳＯ４、ＨＣｌ、ＨＮＯ３、ＮＨ３等の水溶液が挙げられる。 The electrolyte may be used in the form of an electrolyte solution (electrolytic solution). Examples of the electrolytic solution include aqueous solutions of KOH, NaCl, NaOH, NaHCO 3 , Na 2 SO 4 , HCl, HNO 3 , NH 3 and the like.
　通常、セパレータは負極と空気極との間に配置され、両電極間の短絡を防止するとともに、電解質を保持し、イオンを伝導させる役割を有する。セパレータの材料としては、ポリエチレン繊維、ポリプロピレン繊維、ガラス繊維、樹脂不織布、ガラス不織布、濾紙等が挙げられる。 Usually, the separator is disposed between the negative electrode and the air electrode, and prevents the short circuit between the two electrodes, holds the electrolyte, and conducts ions. Examples of the separator material include polyethylene fiber, polypropylene fiber, glass fiber, resin nonwoven fabric, glass nonwoven fabric, and filter paper.
　本発明の鉄空気電池は改善された放電特性を示す。より詳しくは、本発明の鉄空気電池は十分な電圧と大きな放電容量の両方を達成し得る。以下、後述する実施例に示すように鉄空気電池を作製し充放電を３０サイクル行ったとき、３０サイクル中で得られた最大の放電容量を当該鉄空気電池の「最大容量」とし、この最大容量が得られた放電時の平均電圧を「最大容量時電圧」とする。本発明の鉄空気電池は、表面修飾処理を行っていない負極材料を用いた鉄空気電池よりも高い最大容量を示し、且つ０．４Ｖ以上という十分な最大容量時電圧を示す。なお、この最大容量時電圧が０．４Ｖ未満であると、機器を動作させる等の目的で実際に使用する際に、鉄空気電池を多直列化する必要がある。即ち、最大容量時電圧が０．４Ｖ未満の鉄空気電池を実用化しようとすると、煩雑な製造工程が必要となり、コストが増加する。 The iron-air battery of the present invention exhibits improved discharge characteristics. More specifically, the iron-air battery of the present invention can achieve both a sufficient voltage and a large discharge capacity. Hereinafter, when an iron-air battery is manufactured and charged and discharged for 30 cycles as shown in the examples described later, the maximum discharge capacity obtained in 30 cycles is defined as the “maximum capacity” of the iron-air battery, and the maximum The average voltage at the time of discharging at which the capacity is obtained is referred to as “maximum capacity voltage”. The iron-air battery of the present invention exhibits a higher maximum capacity than an iron-air battery using a negative electrode material that has not been subjected to surface modification treatment, and a sufficient maximum capacity voltage of 0.4 V or more. When the maximum capacity voltage is less than 0.4V, it is necessary to serialize iron-air batteries in actual use for the purpose of operating the device. That is, if an iron-air battery having a maximum capacity voltage of less than 0.4 V is to be put into practical use, a complicated manufacturing process is required, and the cost increases.
　鉄空気電池の製造方法は特に限定されないが、例えば、負極ケース、スペーサー、集電体、負極、セパレータ、空気極、及び空気極ケースをこの順に積層して製造できる。 The manufacturing method of the iron-air battery is not particularly limited, and for example, it can be manufactured by laminating a negative electrode case, a spacer, a current collector, a negative electrode, a separator, an air electrode, and an air electrode case in this order.
　以下、実施例及び比較例により本発明をより詳細に説明するが、本発明はそれらに限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
実施例１
基材粒子の準備
　希土類磁石のリサイクル過程で生じた残渣鉄材を基材粒子（Ａ）として用いた。この基材粒子（Ａ）は主に八面体状の形状を有し、Ｆｅ３Ｏ４を主成分として含有していた。Ｘ線回折測定を行ったところ、Ｆｅ３Ｏ４以外の相に起因するピークは確認されなかった。また、ＩＣＰ発光分光分析の結果、基材粒子（Ａ）はＦｅ３Ｏ４に加えてＮｄ、Ｄｙ、Ｃｏ、及びＡｌを含有していた。基材粒子（Ａ）全体を１００質量％とすると、Ｆｅの割合は７０．５質量％、Ｎｄは１．３３質量％、Ｄｙは０．４６質量％、Ｃｏは０．５１質量％、Ａｌは０．１９質量％であった。従って、基材粒子（Ａ）全体に対する不純物の質量比は２．４９質量％であった。基材粒子（Ａ）の全構成原子に対するＦｅの原子比は４２．６原子％であった。また、基材粒子（Ａ）のＢＥＴ比表面積は８．８ｍ２／ｇ、Ｄ５０粒径は４．１μｍであった。 Example 1
Preparation of base particle The residual iron material produced in the process of recycling the rare earth magnet was used as the base particle (A). The base particles (A) mainly had an octahedral shape and contained Fe 3 O 4 as a main component. When X-ray diffraction measurement was performed, no peak due to a phase other than Fe 3 O 4 was confirmed. As a result of ICP emission spectroscopic analysis, the base particle (A) contained Nd, Dy, Co, and Al in addition to Fe 3 O 4 . Assuming that the entire substrate particle (A) is 100% by mass, the proportion of Fe is 70.5% by mass, Nd is 1.33% by mass, Dy is 0.46% by mass, Co is 0.51% by mass, Al is It was 0.19 mass%. Therefore, the mass ratio of the impurities to the entire base particle (A) was 2.49% by mass. The atomic ratio of Fe with respect to all the constituent atoms of the base particle (A) was 42.6 atomic%. Further, the base particle (A) had a BET specific surface area of 8.8 m 2 / g and a D50 particle size of 4.1 μm.
負極材料の調製
　５０ｍＬの純水に１０ｇの基材粒子（Ａ）を加えて撹拌し、これに５％ＮａＯＨ溶液を滴下してｐＨを９．０に調整し、スラリーを得た。一方、１０ｍＬの純水に０．０３１４ｇの硫酸銅（ＩＩ）五水和物（和光純薬工業株式会社製）を溶解させて表面修飾物質前駆体溶液を調製した。表面修飾物質前駆体溶液のうち１ｍＬを分取してスラリーに滴下し、更に５％ＮａＯＨ溶液を滴下しｐＨを９．０に調整した。ｐＨの変動が無いことを確認した後、得られたスラリーをヌッチェろ過し、純水で洗浄した。洗浄は洗浄液の導電率が３００μＳ／ｃｍ以下になるまで繰り返した。得られたケーキを２５０℃で２時間焼成して負極材料を得た。 Preparation of negative electrode material 10 g of base material particles (A) were added to 50 mL of pure water and stirred, and 5% NaOH solution was added dropwise thereto to adjust the pH to 9.0 to obtain a slurry. On the other hand, 0.0314 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 mL of pure water to prepare a surface modifying substance precursor solution. 1 mL of the surface modifying substance precursor solution was collected and added dropwise to the slurry, and a 5% NaOH solution was added dropwise to adjust the pH to 9.0. After confirming that there was no change in pH, the resulting slurry was filtered by Nutsche and washed with pure water. The washing was repeated until the conductivity of the washing liquid became 300 μS / cm or less. The obtained cake was baked at 250 ° C. for 2 hours to obtain a negative electrode material.
　得られた負極材料では、１００質量％の基材粒子（Ａ）に対して０．０１質量％の表面修飾物質が付着していた。表面修飾物質はＣｕＯを主成分とし、５０原子％のＣｕを含有していた。また、日本電子株式会社製フィールドエミッション電子プローブマイクロアナライザ（ＦＥＳＥＭ）ＪＸＡ－８５３０Ｆを用いて、この方法によって形成した表面修飾物質を観察し、５６個の粒子の平均粒径を求めたところ、約１００ｎｍであった。以下の実施例２～１７並びに比較例２、６、８、及び１０でも同様であった。 In the obtained negative electrode material, 0.01% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A). The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Further, the surface modified substance formed by this method was observed by using a field emission electron probe microanalyzer (FESEM) JXA-8530F manufactured by JEOL Ltd., and the average particle size of 56 particles was determined to be about 100 nm. Met. The same applies to Examples 2 to 17 and Comparative Examples 2, 6, 8, and 10 below.
　なお、実施例において、基材粒子の形状は、株式会社日立ハイテクノロジーズ製走査型電子顕微鏡（ＳＥＭ）Ｓ－３０００Ｎを用いて観察した。基材粒子及び表面修飾物質の組成は、パーキンエルマー社製ＩＣＰ発光分析装置Ｏｐｔｉｍａ８３００を用いたＩＣＰ分析及び株式会社リガク製Ｘ線回折装置ＵｌｔｉｍａＩＶを用いたＸＲＤ測定によって決定した。基材粒子のＢＥＴ比表面積は、ＭＯＵＮＴＥＣＨ社製比表面積測定装置Ｍａｃｓｏｒｂ　ＨＭ－１２１０を用いて測定した。基材粒子のＤ５０粒径は、ＬＥＥＤＳ＆ＮＯＲＴＨＲＵＰ製レーザー回折式粒度分布計ＨＲＡ（マイクロトラック）を用いて測定した。 In the examples, the shape of the substrate particles was observed using a scanning electron microscope (SEM) S-3000N manufactured by Hitachi High-Technologies Corporation. The composition of the base particles and the surface modifying substance was determined by ICP analysis using an ICP emission analyzer Optima 8300 manufactured by Perkin Elmer and XRD measurement using an X-ray diffractometer Ultrama IV manufactured by Rigaku Corporation. The BET specific surface area of the substrate particles was measured using a specific surface area measuring device Macsorb HM-1210 manufactured by MOUNTECH. The D50 particle size of the substrate particles was measured using a laser diffraction particle size distribution meter HRA (Microtrack) manufactured by LEEDS & NORTHUP.
負極の作製
　１．５ｇの上記負極材料及び電解質溶液（電解液）である０．３ｍＬのＫＯＨ水溶液（５Ｍ）を乳鉢中で１０分間混練し、負極を作製した。この負極材料の使用量を、鉄空気電池中の負極材料の充填量として表１に示す。 Production of Negative Electrode 1.5 g of the above negative electrode material and 0.3 mL of KOH aqueous solution (5 M) as an electrolyte solution (electrolytic solution) were kneaded in a mortar for 10 minutes to produce a negative electrode. The amount of the negative electrode material used is shown in Table 1 as the negative electrode material filling amount in the iron-air battery.
空気極の作製
　ＭｎＯ２（東ソー株式会社製ＨＭＨ）と、アセチレンブラック（デンカ株式会社製デンカブラック）と、ポリフッ化ビニリデン溶液（株式会社クレハ製ＫＦポリマーＬ＃１１２０）とを、ＭｎＯ２：アセチレンブラック：ポリフッ化ビニリデンの質量比が２：０．０５：０．１となるよう秤量し、溶媒として１ｍＬのＮ－メチル－２－ピロリドンを加え、２時間混合して触媒スラリーを調製した。直径１４ｍｍに切り出した発泡ニッケル（住友電気工業株式会社製セルメット＃８）をこの触媒スラリーに浸漬した。このようにして触媒スラリーが塗布された発泡ニッケルを１６０℃に加熱したホットプレート上で３時間以上乾燥した後、６４ＭＰａで３０秒間プレスして、空気極（触媒層）を作製した。 Production of air electrode MnO 2 (HMH manufactured by Tosoh Corporation), acetylene black (Denka Black manufactured by Denka Co., Ltd.), and a polyvinylidene fluoride solution (KF Polymer L # 1120 manufactured by Kureha Co., Ltd.), MnO 2 : Acetylene Black : Polyvinylidene fluoride was weighed so that the mass ratio was 2: 0.05: 0.1, and 1 mL of N-methyl-2-pyrrolidone was added as a solvent and mixed for 2 hours to prepare a catalyst slurry. Foamed nickel cut out to a diameter of 14 mm (Celmet # 8 manufactured by Sumitomo Electric Industries, Ltd.) was immersed in this catalyst slurry. The nickel foam coated with the catalyst slurry in this way was dried on a hot plate heated to 160 ° C. for 3 hours or more and then pressed at 64 MPa for 30 seconds to produce an air electrode (catalyst layer).
鉄空気電池の作製
　電池部材として宝泉株式会社製２０３２型コインセルパーツを用いた。負極ケース、ウェーブワッシャー、スペーサー、直径１６ｍｍに切り出した銅箔（福田金属箔粉工業株式会社製ＣＦ－Ｔ８Ｇ－ＳＴＤ－１８）、負極、直径１８ｍｍに切り出した濾紙（ＡＤＶＡＮＴＥＣ製５Ｃ）、空気極、及び空気孔付き空気極ケースをこの順に積層し、かしめ処理を行って鉄空気電池を作製した。ここで、銅箔は集電体として機能する。また、濾紙はセパレータとして機能し、且つ電解液を保持する役割も有する。 Production of iron-air battery A 2032 type coin cell part manufactured by Hosen Co., Ltd. was used as a battery member. Negative electrode case, wave washer, spacer, copper foil cut to a diameter of 16 mm (CF-T8G-STD-18 manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.), negative electrode, filter paper cut to a diameter of 18 mm (ADVANTEC 5C), air electrode, And the air electrode case with an air hole was laminated | stacked in this order, the caulking process was performed, and the iron air battery was produced. Here, the copper foil functions as a current collector. Further, the filter paper functions as a separator and also has a role of holding an electrolyte solution.
充放電試験
　作製した鉄空気電池を用いて、温度２５℃、相対湿度１００％、充電電流３０ｍＡ、充電時間１時間、放電電流１０ｍＡ、放電下限電圧０Ｖ、及び充放電後休止時間３分の条件下、充放電を行った。この充放電を３０サイクル実施して、３０サイクル中で得られた最大の放電容量を当該鉄空気電池の「最大容量」とし、この最大容量が得られた放電時の平均電圧を「最大容量時電圧」とした。結果を表１に示す。 Charge / Discharge Test Using the produced iron-air battery, temperature 25 ° C., relative humidity 100%, charge current 30 mA, charge time 1 hour, discharge current 10 mA, discharge lower limit voltage 0 V, and post-charge / discharge rest period 3 minutes Then, charging / discharging was performed. This charging / discharging is carried out for 30 cycles, and the maximum discharge capacity obtained during the 30 cycles is defined as the “maximum capacity” of the iron-air battery. Voltage ”. The results are shown in Table 1.
実施例２
　５０ｍＬの純水に３０ｇの基材粒子（Ａ）を加えて撹拌し、これに０．００６４ｇの水酸化リチウム一水和物（和光純薬工業株式会社製）を溶解させてスラリーを得た。一方、１０ｍＬの純水に０．０９４２ｇの硫酸銅（ＩＩ）五水和物（和光純薬工業株式会社製）を溶解させて表面修飾物質前駆体溶液を調製した。この表面修飾物質前駆体溶液をスラリーに滴下し、ｐＨの変動が無いことを確認した後、得られたスラリーをヌッチェろ過し、純水で洗浄した。洗浄は洗浄液の導電率が３００μＳ／ｃｍ以下になるまで繰り返した。得られたケーキを２５０℃で２時間焼成して負極材料を得た。得られた負極材料では、１００質量％の基材粒子（Ａ）に対して０．１質量％の表面修飾物質が付着していた。表面修飾物質はＣｕＯを主成分とし、５０原子％のＣｕを含有していた。この負極材料を用いて、実施例１と同様に鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。 Example 2
30 g of the base particles (A) were added to 50 mL of pure water and stirred, and 0.0064 g of lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved therein to obtain a slurry. On the other hand, 0.0942 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 mL of pure water to prepare a surface modifying substance precursor solution. This surface modifying substance precursor solution was dropped into the slurry, and after confirming that there was no fluctuation in pH, the obtained slurry was Nutsche filtered and washed with pure water. The washing was repeated until the conductivity of the washing liquid became 300 μS / cm or less. The obtained cake was baked at 250 ° C. for 2 hours to obtain a negative electrode material. In the obtained negative electrode material, 0.1% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A). The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
実施例３
　５０ｍＬの純水に５０ｇの基材粒子（Ａ）を加えて撹拌し、これに０．１８１２ｇの水酸化リチウム一水和物（和光純薬工業株式会社製）を溶解させてスラリーを得た。一方、１０ｍＬの純水に０．５３９２ｇの硫酸銅（ＩＩ）五水和物（和光純薬工業株式会社製）を溶解させて表面修飾物質前駆体溶液を調製した。この表面修飾物質前駆体溶液をスラリーに滴下し、ｐＨの変動が無いことを確認した後、得られたスラリーをヌッチェろ過し、純水で洗浄した。洗浄は洗浄液の導電率が３００μＳ／ｃｍ以下になるまで繰り返した。得られたケーキを２５０℃で２時間焼成して負極材料を得た。得られた負極材料では、１００質量％の基材粒子（Ａ）に対して０．３質量％の表面修飾物質が付着していた。表面修飾物質はＣｕＯを主成分とし、５０原子％のＣｕを含有していた。この負極材料を用いて、実施例１と同様に鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。 Example 3
50 g of base material particles (A) were added to 50 mL of pure water and stirred, and 0.1812 g of lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved therein to obtain a slurry. On the other hand, 0.5392 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 mL of pure water to prepare a surface modifying substance precursor solution. This surface modifying substance precursor solution was dropped into the slurry, and after confirming that there was no fluctuation in pH, the obtained slurry was Nutsche filtered and washed with pure water. The washing was repeated until the conductivity of the washing liquid became 300 μS / cm or less. The obtained cake was baked at 250 ° C. for 2 hours to obtain a negative electrode material. In the obtained negative electrode material, 0.3% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A). The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
実施例４
　５０ｍＬの純水に５０ｇの基材粒子（Ａ）を加えて撹拌し、スラリーを得た。一方、３５ｍＬの純水に７．８４７４ｇの硫酸銅（ＩＩ）五水和物（和光純薬工業株式会社製）を溶解させて表面修飾物質前駆体溶液を調製した。チューブポンプを用いて滴下速度１ｍＬ／分で表面修飾物質前駆体溶液をスラリーに滴下した。このとき、５％ＮａＯＨ溶液を同時に滴下することで、スラリーのｐＨを９．０に保持した。ｐＨの変動が無いことを確認した後、得られたスラリーをヌッチェろ過し、純水で洗浄した。洗浄は洗浄液の導電率が３００μＳ／ｃｍ以下になるまで繰り返した。得られたケーキを２５０℃で２時間焼成して負極材料を得た。得られた負極材料では、１００質量％の基材粒子（Ａ）に対して５質量％の表面修飾物質が付着していた。実施例４の負極材料のＳＥＭ写真を図１に示す。粒径約１μｍ以下の比較的微細な基材粒子（Ａ）は概ね表面修飾物質粒子によって被覆されており、粒径が数μｍ程度の基材粒子（Ａ）では表面上に表面修飾物質粒子が均一に分散されていた。表面修飾物質はＣｕＯを主成分とし、５０原子％のＣｕを含有していた。この負極材料を用いて、実施例１と同様に鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。 Example 4
50 g of base material particles (A) were added to 50 mL of pure water and stirred to obtain a slurry. On the other hand, 7.8474 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 35 mL of pure water to prepare a surface modifying substance precursor solution. The surface modifying substance precursor solution was dropped into the slurry at a dropping rate of 1 mL / min using a tube pump. At this time, the pH of the slurry was maintained at 9.0 by simultaneously dropping a 5% NaOH solution. After confirming that there was no change in pH, the resulting slurry was filtered by Nutsche and washed with pure water. The washing was repeated until the conductivity of the washing liquid became 300 μS / cm or less. The obtained cake was baked at 250 ° C. for 2 hours to obtain a negative electrode material. In the obtained negative electrode material, 5% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A). An SEM photograph of the negative electrode material of Example 4 is shown in FIG. Relatively fine substrate particles (A) having a particle size of about 1 μm or less are generally coated with surface modifying substance particles. In the substrate particles (A) having a particle diameter of about several μm, surface modifying substance particles are present on the surface. It was uniformly dispersed. The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
実施例５
　６０ｍＬの純水に１５．６９４８ｇの硫酸銅（ＩＩ）五水和物（和光純薬工業株式会社製）を溶解させて表面修飾物質前駆体溶液を調製したこと以外は実施例４と同様に負極材料を得た。得られた負極材料では、１００質量％の基材粒子（Ａ）に対して１０質量％の表面修飾物質が付着していた。表面修飾物質はＣｕＯを主成分とし、５０原子％のＣｕを含有していた。この負極材料を用いて、実施例１と同様に鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。 Example 5
A negative electrode in the same manner as in Example 4 except that 15.69948 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 60 mL of pure water to prepare a surface modifying substance precursor solution. Obtained material. In the obtained negative electrode material, 10% by mass of the surface modifying substance adhered to 100% by mass of the base material particles (A). The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
実施例６
　５０ｍＬの純水に１０ｇの上記基材粒子（Ａ）を加えて撹拌してスラリーを調製し、２０ｍＬの純水に６．２７７９ｇの硫酸銅（ＩＩ）五水和物（和光純薬工業株式会社製）を溶解させて表面修飾液を調製したこと以外は実施例４と同様に負極材料を得た。得られた負極材料では、１００質量％の基材粒子（Ａ）に対して２０質量％の表面修飾物質が付着していた。表面修飾物質はＣｕＯを主成分とし、５０原子％のＣｕを含有していた。この負極材料を用いて、実施例１と同様に鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。 Example 6
10 g of the above base particle (A) is added to 50 mL of pure water and stirred to prepare a slurry, and 6.2279 g of copper (II) sulfate pentahydrate (Wako Pure Chemical Industries, Ltd.) is added to 20 mL of pure water. A negative electrode material was obtained in the same manner as in Example 4 except that the surface modification solution was prepared by dissolving the product. In the obtained negative electrode material, 20% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A). The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
比較例１
　表面修飾物質を形成せず（表面修飾処理を行わず）、上記基材粒子（Ａ）をそのまま負極材料として用いた。この負極材料を用いて、実施例１と同様に鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。 Comparative Example 1
The surface modifying substance was not formed (the surface modification treatment was not performed), and the base material particle (A) was used as it was as the negative electrode material. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
比較例２
　３０ｍＬの純水に９．４１６９ｇの硫酸銅（ＩＩ）五水和物（和光純薬工業株式会社製）を溶解させて表面修飾液を調製したこと以外は実施例６と同様に負極材料を得た。得られた負極材料では、１００質量％の基材粒子（Ａ）に対して３０質量％の表面修飾物質が付着していた。表面修飾物質はＣｕＯを主成分とし、５０原子％のＣｕを含有していた。この負極材料を用いて、実施例１と同様に鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。 Comparative Example 2
A negative electrode material was obtained in the same manner as in Example 6 except that 9.4169 g of copper (II) sulfate pentahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 30 mL of pure water to prepare a surface modification solution. It was. In the obtained negative electrode material, 30% by mass of a surface modifying substance adhered to 100% by mass of the base material particles (A). The surface modifying material was mainly composed of CuO and contained 50 atomic% of Cu. Using this negative electrode material, an iron-air battery was produced in the same manner as in Example 1, and a charge / discharge test was conducted. The results are shown in Table 1.
比較例３
　１．０４ｇの上記基材粒子（Ａ）、０．１６ｇのカーボンブラック、及び０．３ｍＬのＫＯＨ水溶液（５Ｍ）を乳鉢中で１０分間混練して負極を作製したこと以外は実施例１と同様に鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。 Comparative Example 3
Same as Example 1 except that 1.04 g of the above base particle (A), 0.16 g of carbon black, and 0.3 mL of KOH aqueous solution (5M) were kneaded in a mortar for 10 minutes to produce a negative electrode. An iron-air battery was prepared and a charge / discharge test was conducted. The results are shown in Table 1.
比較例４
　１．５ｇの上記基材粒子（Ａ）と０．０７５ｇの銅粉末（株式会社高純度化学研究所製純銅４５μｍ　ｐａｓｓ）とを混合し、得られた粉末のうち１．５ｇを０．３ｍＬのＫＯＨ水溶液（５Ｍ）と共に乳鉢中で１０分間混練して負極を作製したこと以外は実施例１と同様に、鉄空気電池を作製し、充放電試験を行った。結果を表１に示す。なお、得られた負極では、一次粒子径１μｍ程度の銅粒子が基材粒子（Ａ）と混合されていた。１００質量％の基材粒子（Ａ）に対する銅粒子の質量比は５質量％であった。 Comparative Example 4
1.5 g of the above base particle (A) and 0.075 g of copper powder (pure copper 45 μm pass manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed, and 1.5 g of the obtained powder was 0.3 mL. An iron-air battery was prepared and a charge / discharge test was conducted in the same manner as in Example 1 except that a negative electrode was prepared by kneading in a mortar with a KOH aqueous solution (5M) for 10 minutes. The results are shown in Table 1. In the obtained negative electrode, copper particles having a primary particle diameter of about 1 μm were mixed with the base material particles (A). The mass ratio of the copper particles to 100% by mass of the base material particles (A) was 5% by mass.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１から明らかなように、実施例１～６においては、１００質量％の基材粒子に０．０１～２０質量％の表面修飾物質を付着させたことによって、鉄空気電池の最大容量が向上した。一方、表面修飾物質の質量比を３０質量％まで増加させた比較例２では、最大容量は向上したものの最大容量時電圧が大きく低下した。表面修飾物質の割合が増えるに従い基材粒子の割合が減少し、本来の鉄空気電池の反応に由来する放電成分が減少したと考えられる。また、本発明の表面修飾処理を行わず、導電助剤としてカーボンを用いた比較例３では、カーボンが嵩高いため電池ケース内に充填できる基材粒子の量が減少し、最大容量が低下した。本発明の表面修飾処理を行わず、導電助剤として銅粉末を用いた比較例４では、最大容量は向上したものの最大容量時電圧が低下した。本発明で基材粒子に付着させる表面修飾物質（ＣｕＯ等）と比較して、このような銅粉末は非常に粗大であり、また銅粉末は単に基材粒子と混合された状態で基材粒子表面に保持されていなかったため、導電性改善効果が不十分であった。 As is apparent from Table 1, in Examples 1 to 6, the maximum capacity of the iron-air battery was improved by attaching 0.01 to 20% by mass of the surface modifying substance to 100% by mass of the base particles. did. On the other hand, in Comparative Example 2 in which the mass ratio of the surface modifying substance was increased to 30% by mass, the maximum capacity was improved, but the maximum capacity voltage was greatly reduced. It is considered that as the proportion of the surface modifying substance increases, the proportion of the base particles decreases, and the discharge components derived from the reaction of the original iron-air battery decrease. Further, in Comparative Example 3 in which carbon was used as a conductive auxiliary agent without performing the surface modification treatment of the present invention, the amount of base material particles that could be filled in the battery case was reduced because the carbon was bulky, and the maximum capacity was reduced. . In Comparative Example 4 where the surface modification treatment of the present invention was not performed and copper powder was used as the conductive auxiliary agent, the maximum capacity was improved, but the voltage at the maximum capacity decreased. Compared with surface modifying substances (CuO or the like) to be adhered to the base particles in the present invention, such copper powder is very coarse, and the copper powder is simply mixed with the base particles. Since it was not held on the surface, the effect of improving conductivity was insufficient.
実施例７～１０並びに比較例５及び６
　基材粒子（Ａ）に替えて基材粒子（Ｂ）を使用し、負極材料の充填量を表２に示すとおり変更したこと以外は実施例２、３、５、及び６並びに比較例１及び２と同様に、実施例７～１０並びに比較例５及び６の鉄空気電池をそれぞれ作製し、充放電試験を行った。結果を表２に示す。 Examples 7 to 10 and Comparative Examples 5 and 6
Examples 2, 3, 5, and 6 and Comparative Example 1 and Comparative Example 1 except that the base particle (B) was used instead of the base particle (A), and the filling amount of the negative electrode material was changed as shown in Table 2. In the same manner as in Example 2, iron-air batteries of Examples 7 to 10 and Comparative Examples 5 and 6 were produced and subjected to a charge / discharge test. The results are shown in Table 2.
　なお、基材粒子（Ｂ）はＢＡＳＦ製カルボニル鉄ＳＱグレードであり、球状の形状を有し、Ｆｅを主成分として含有していた。蛍光Ｘ線分析（ＳＱＸ分析）を行ったところ、基材粒子（Ｂ）はＦｅに加えて微量のＳｉを含有しており、基材粒子（Ｂ）全体を１００質量％とすると、Ｆｅの質量比は９９．９質量％、Ｓｉは０．１質量％であった。基材粒子（Ｂ）の全構成原子に対するＦｅの原子比は９９．９８原子％であった。また、基材粒子（Ｂ）のＢＥＴ比表面積は０．４ｍ２／ｇ、Ｄ５０粒径は４．０μｍであった。 The base particles (B) were BASF carbonyl iron SQ grade, had a spherical shape, and contained Fe as a main component. When fluorescent X-ray analysis (SQX analysis) was performed, the base particle (B) contained a small amount of Si in addition to Fe, and the total mass of the base particle (B) was 100% by mass. The ratio was 99.9% by mass and Si was 0.1% by mass. The atomic ratio of Fe with respect to all the constituent atoms of the base particle (B) was 99.98 atomic%. In addition, the base particle (B) had a BET specific surface area of 0.4 m 2 / g and a D50 particle size of 4.0 μm.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２から明らかなように、実施例７～１０においては、１００質量％の基材粒子に０．１～２０質量％の表面修飾物質を付着させたことによって、鉄空気電池の最大容量が向上した。基材粒子（Ｂ）を用いた場合、表面修飾物質の質量比が低いと最大容量改善効果はやや低かった。カルボニル鉄は酸化鉄よりも高い導電性を有するため、少量の表面修飾物質では効果が現れにくいものと考えられる。一方、表面修飾物質の質量比を３０質量％まで増加させた比較例６では、最大容量は向上したものの最大容量時電圧が大きく低下した。基材粒子（Ｂ）はＢＥＴ比表面積が小さいにもかかわらず、実施例１０では実施例１～６よりも大きな最大容量が得られた。基材粒子（Ｂ）は比重が大きいため、充填量を増やすことができ、そのため高容量となったと考えられる。 As is apparent from Table 2, in Examples 7 to 10, the maximum capacity of the iron-air battery was improved by attaching 0.1 to 20% by mass of the surface modifying substance to 100% by mass of the base particles. did. When the substrate particles (B) were used, the maximum capacity improvement effect was somewhat low when the mass ratio of the surface modifying substance was low. Since carbonyl iron has higher conductivity than iron oxide, it is considered that the effect is difficult to appear with a small amount of a surface modifying substance. On the other hand, in Comparative Example 6 in which the mass ratio of the surface modifying substance was increased to 30% by mass, the maximum capacity was improved, but the maximum capacity voltage was greatly reduced. Although the base particle (B) had a small BET specific surface area, the maximum capacity was larger in Example 10 than in Examples 1 to 6. Since base material particle (B) has large specific gravity, it can be considered that the filling amount can be increased, and therefore the capacity is increased.
実施例１１～１４並びに比較例７及び８
　基材粒子（Ａ）に替えて基材粒子（Ｃ）を使用し、負極材料の充填量を表３に示すとおり変更したこと以外は実施例１、２、４、及び６並びに比較例１及び２と同様に、実施例１１～１４並びに比較例７及び８の鉄空気電池をそれぞれ作製し、充放電試験を行った。結果を表３に示す。 Examples 11 to 14 and Comparative Examples 7 and 8
Examples 1, 2, 4, and 6 and Comparative Example 1 and Comparative Example 1 except that the base particle (C) was used instead of the base particle (A), and the filling amount of the negative electrode material was changed as shown in Table 3. In the same manner as in Example 2, iron-air batteries of Examples 11 to 14 and Comparative Examples 7 and 8 were produced and subjected to a charge / discharge test. The results are shown in Table 3.
　なお、基材粒子（Ｃ）は和光純薬工業株式会社製Ｆｅ２Ｏ３粒子（酸化鉄（ＩＩＩ）、和光一級、商品コード０９６－０４８２５）であり、Ｆｅ２Ｏ３を主成分として含有していた。ＳＱＸ分析を行ったところ、基材粒子（Ｃ）はＦｅ２Ｏ３に加えてＡｌ、Ｓｉ、Ｐ、Ｓ、Ｃｌ、Ｃａ、Ｃｒ、Ｍｎ、Ｎｉ、Ｚｎ、及びＮｂを含有しており、基材粒子（Ｃ）全体を１００質量％とすると、Ｆｅの質量比は６９．５質量％、Ａｌは０．０３質量％、Ｓｉは０．０３質量％、Ｐは０．０１質量％、Ｓは０．０１質量％、Ｃｌは０．０６質量％、Ｃａは０．０１質量％、Ｃｒは０．０２質量％、Ｍｎは０．２５質量％、Ｎｉは０．０１質量％、Ｚｎは０．０２質量％であった。基材粒子（Ｃ）の全構成原子に対するＦｅの原子比は３９．９６原子％であった。また、基材粒子（Ｃ）のＢＥＴ比表面積は６．１ｍ２／ｇ、Ｄ５０粒径は１．９μｍであった。 The base particles (C) are Fe 2 O 3 particles (iron (III) oxide, Wako first grade, product code 096-04825) manufactured by Wako Pure Chemical Industries, Ltd., and contain Fe 2 O 3 as a main component. It was. When SQX analysis was performed, the base particle (C) contained Al, Si, P, S, Cl, Ca, Cr, Mn, Ni, Zn, and Nb in addition to Fe 2 O 3. Assuming that the entire material particle (C) is 100% by mass, the mass ratio of Fe is 69.5% by mass, Al is 0.03% by mass, Si is 0.03% by mass, P is 0.01% by mass, and S is 0.01% by mass, Cl: 0.06% by mass, Ca: 0.01% by mass, Cr: 0.02% by mass, Mn: 0.25% by mass, Ni: 0.01% by mass, Zn: 0. It was 02 mass%. The atomic ratio of Fe with respect to all the constituent atoms of the base particles (C) was 39.96 atomic%. The base material particle (C) had a BET specific surface area of 6.1 m 2 / g and a D50 particle size of 1.9 μm.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表３から明らかなように、実施例１１～１４においては、１００質量％の基材粒子に０．０１～２０質量％の表面修飾物質を付着させたことによって、鉄空気電池の最大容量が向上した。一方、表面修飾物質の質量比を３０質量％まで増加させた比較例８では、最大容量は向上したものの最大容量時電圧が大きく低下した。 As is apparent from Table 3, in Examples 11 to 14, the maximum capacity of the iron-air battery is improved by attaching 0.01 to 20% by mass of the surface modifying substance to 100% by mass of the base particles. did. On the other hand, in Comparative Example 8 in which the mass ratio of the surface modifying substance was increased to 30% by mass, the maximum capacity was improved but the maximum capacity voltage was greatly reduced.
実施例１５～１７並びに比較例９及び１０
　基材粒子（Ａ）に替えて基材粒子（Ｄ）を使用し、負極材料の充填量を表４に示すとおり変更したこと以外は実施例２、５、及び６並びに比較例１及び２と同様に、実施例１５～１７並びに比較例９及び１０の鉄空気電池をそれぞれ作製し、充放電試験を行った。結果を表４に示す。 Examples 15 to 17 and Comparative Examples 9 and 10
Examples 2, 5, and 6 and Comparative Examples 1 and 2 except that the base particle (D) was used instead of the base particle (A), and the filling amount of the negative electrode material was changed as shown in Table 4. Similarly, iron-air batteries of Examples 15 to 17 and Comparative Examples 9 and 10 were produced and subjected to charge / discharge tests. The results are shown in Table 4.
　なお、基材粒子（Ｄ）は次のとおり均一沈殿法によって調製した。まず、硫酸鉄（ＩＩ）七水和物及び尿素（共に和光純薬工業株式会社製）を純水に溶解し、１２０℃に加熱したホットプレートを用いて尿素の分解を促してｐＨを制御した。この溶液を溶液温度９０℃で１０分間保持して沈殿を生成させた後、２４％ＮａＯＨを添加してｐＨを１０まで上昇させ、粒径を固定した。得られた沈殿をろ過により分離し、洗浄して基材粒子（Ｄ）を得た。基材粒子（Ｄ）はＦｅ３Ｏ４を主成分として含有していた。ＳＱＸ分析を行ったところ、基材粒子（Ｄ）はＦｅ３Ｏ４に加えてＮａ、Ｓｉ、Ｐ、Ｓ、Ｍｎ、Ｎｉ、及びＣｕを含有しており、基材粒子（Ｄ）全体を１００質量％とすると、Ｆｅの質量比は７２．１質量％、Ｎａは０．０５質量％、Ｓｉは０．０２質量％、Ｓは０．１０質量％、Ｍｎは０．０２質量％、Ｎｉは０．０２質量％、Ｃｕは０．０１質量％であった。基材粒子（Ｄ）の全構成原子に対するＦｅの原子比は４２．５９原子％であった。また、基材粒子（Ｄ）のＢＥＴ比表面積は５９．１ｍ２／ｇ、Ｄ５０粒径は１．２μｍであった。 The base particles (D) were prepared by the uniform precipitation method as follows. First, iron (II) sulfate heptahydrate and urea (both manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in pure water, and the pH was controlled by promoting decomposition of urea using a hot plate heated to 120 ° C. . This solution was maintained at a solution temperature of 90 ° C. for 10 minutes to form a precipitate, and then 24% NaOH was added to raise the pH to 10 to fix the particle size. The resulting precipitate was separated by filtration and washed to obtain substrate particles (D). The base particle (D) contained Fe 3 O 4 as a main component. When SQX analysis was performed, the base particle (D) contained Na, Si, P, S, Mn, Ni, and Cu in addition to Fe 3 O 4 , and the entire base particle (D) was 100. The mass ratio of Fe is 72.1% by mass, Na is 0.05% by mass, Si is 0.02% by mass, S is 0.10% by mass, Mn is 0.02% by mass, Ni is 0.02 mass% and Cu was 0.01 mass%. The atomic ratio of Fe with respect to all the constituent atoms of the base particle (D) was 42.59 atomic%. Further, the base particle (D) had a BET specific surface area of 59.1 m 2 / g and a D50 particle size of 1.2 μm.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　表４から明らかなように、実施例１５～１８においては、１００質量％の基材粒子に０．１～２０質量％の表面修飾物質を付着させたことによって、鉄空気電池の最大容量が向上した。基材粒子（Ｄ）を用いた場合、表面修飾物質の質量比が低いと最大容量改善効果はやや低かった。基材粒子（Ｄ）は比較的大きな表面積を有するため、少量の表面修飾物質では効果が現れにくいものと考えられる。一方、表面修飾物質の質量比を３０質量％まで増加させた比較例１０では、最大容量は向上したものの最大容量時電圧が大きく低下した。なお、実施例１７では最大容量が比較例９よりも低くなっているが、これは充填量が異なることに起因する。負極材料の単位質量あたりの容量は、実施例１７では１６．３ｍＡｈ／ｇ、比較例９では１３．７ｍＡｈ／ｇであり、実施例１７でも表面修飾物質による容量改善効果が示されている。 As is apparent from Table 4, in Examples 15 to 18, the maximum capacity of the iron-air battery was improved by attaching 0.1 to 20% by mass of the surface modifying substance to 100% by mass of the base particles. did. When the base particles (D) were used, the maximum capacity improvement effect was somewhat low when the mass ratio of the surface modifying substance was low. Since the base particle (D) has a relatively large surface area, it is considered that the effect is hardly exhibited with a small amount of the surface modifying substance. On the other hand, in Comparative Example 10 in which the mass ratio of the surface modifying substance was increased to 30% by mass, the maximum capacity was improved but the maximum capacity voltage was greatly reduced. In Example 17, the maximum capacity is lower than that in Comparative Example 9, but this is due to the different filling amounts. The capacity per unit mass of the negative electrode material is 16.3 mAh / g in Example 17, and 13.7 mAh / g in Comparative Example 9, and Example 17 also shows the capacity improvement effect by the surface modifier.

Claims (6)

  1. 　基材粒子と該基材粒子の表面に付着した表面修飾物質とからなり、
    　前記基材粒子が３０原子％以上１００原子％以下のＦｅを含み、
    　前記表面修飾物質が２０原子％以上１００原子％以下のＣｕを含み、
    　１００質量％の前記基材粒子に対する前記表面修飾物質の質量比が０．００１質量％以上３０質量％未満である、
    　鉄空気電池用負極材料。     It consists of base material particles and a surface modifying substance attached to the surface of the base material particles,
    The base particle contains 30 atomic% or more and 100 atomic% or less of Fe,
    The surface modifying material contains 20 atomic% or more and 100 atomic% or less of Cu,
    The mass ratio of the surface modifying substance to 100% by mass of the substrate particles is 0.001% by mass or more and less than 30% by mass,
    Anode material for iron-air batteries.
  2. 　１００質量％の前記基材粒子に対する前記表面修飾物質の質量比が０．００５質量％以上２５質量％以下である、請求項１に記載の負極材料。 2. The negative electrode material according to claim 1, wherein a mass ratio of the surface modifying substance to 100% by mass of the base material particles is 0.005% by mass or more and 25% by mass or less.
  3. 　前記基材粒子のＢＥＴ比表面積が０．１ｍ２／ｇ以上７０ｍ２／ｇ以下である、請求項１又は２に記載の負極材料。 The negative electrode material according to claim 1 or 2, wherein the base particle has a BET specific surface area of 0.1 m 2 / g or more and 70 m 2 / g or less.
  4. 　前記表面修飾物質の平均粒径が１０ｎｍ以上５００ｎｍ以下である、請求項１～３のいずれか一項に記載の負極材料。 The negative electrode material according to any one of claims 1 to 3, wherein an average particle diameter of the surface modifying substance is 10 nm or more and 500 nm or less.
  5. 　請求項１～４のいずれか一項に記載の負極材料を含む、鉄空気電池用負極。 An iron-air battery negative electrode comprising the negative electrode material according to any one of claims 1 to 4.
  6. 　請求項５に記載の負極を有する、鉄空気電池。 An iron-air battery having the negative electrode according to claim 5.
PCT/JP2018/015303 2017-04-12 2018-04-11 Negative electrode material, negative electrode and iron-air battery WO2018190390A1 (en)

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JP2013165052A (en) * 2012-01-11 2013-08-22 Kobe Steel Ltd Material for air cell and all-solid air cell using the same
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JP2012094509A (en) * 2010-10-01 2012-05-17 Kyushu Univ Composite electrode material and method for producing the same, negative electrode for metal air battery, and metal air battery
JP2013165052A (en) * 2012-01-11 2013-08-22 Kobe Steel Ltd Material for air cell and all-solid air cell using the same
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Publication number Priority date Publication date Assignee Title
CN113390800A (en) * 2020-03-13 2021-09-14 宁德新能源科技有限公司 Method for detecting content of copper simple substance in lithium battery positive electrode material
CN113390800B (en) * 2020-03-13 2022-05-20 宁德新能源科技有限公司 Method for detecting content of copper simple substance in lithium battery positive electrode material

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