WO2018021361A1 - Magnesium-lithium alloy, and magnesium air battery - Google Patents

Magnesium-lithium alloy, and magnesium air battery Download PDF

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Publication number
WO2018021361A1
WO2018021361A1 PCT/JP2017/026941 JP2017026941W WO2018021361A1 WO 2018021361 A1 WO2018021361 A1 WO 2018021361A1 JP 2017026941 W JP2017026941 W JP 2017026941W WO 2018021361 A1 WO2018021361 A1 WO 2018021361A1
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mass
magnesium
negative electrode
lithium alloy
air battery
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PCT/JP2017/026941
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French (fr)
Japanese (ja)
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後藤　崇之
基史 松田
敦 作田
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株式会社三徳
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Priority to JP2018530321A priority Critical patent/JP6993337B2/en
Publication of WO2018021361A1 publication Critical patent/WO2018021361A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C23/00—Alloys based on magnesium
    • 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
    • H01M12/04—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type
    • H01M12/06—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode
    • 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
    • H01M4/46—Alloys based on magnesium or aluminium
    • 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 magnesium-lithium alloy suitable for use in a negative electrode of an air battery, and a negative electrode and a magnesium air battery using the alloy.
  • Metal-air batteries have attracted interest in recent years due to their high theoretical energy density, and various metals have been tried. Magnesium is abundant in resources, inexpensive, and has low toxicity, so a magnesium air battery using magnesium or a magnesium alloy as a negative electrode is expected.
  • the conventional magnesium-air battery has a problem that polarization tends to occur and the Coulomb efficiency is low.
  • magnesium in the negative electrode is easily corroded, and this corrosion is considered to cause polarization. Therefore, great efforts have been made to develop new magnesium alloy negative electrode materials mainly for the purpose of reducing the corrosion rate and improving the reaction activity.
  • Patent Document 1 discloses an alloy containing magnesium, aluminum, and calcium as essential components, and a magnesium air battery using the alloy as a negative electrode.
  • Patent Document 2 discloses an alloy composed of magnesium, lithium, and zinc, and a magnesium air battery using the alloy as a negative electrode active material.
  • the conventional magnesium-air battery although the corrosion rate of the negative electrode is improved to some extent, it is not sufficient, and as a result, the magnesium utilization efficiency is not high. Therefore, the conventional magnesium-air battery has a small discharge amount, and further improvement is desired.
  • An object of the present invention is to provide a magnesium-lithium alloy that can exhibit excellent discharge characteristics when used in a negative electrode of a magnesium-air battery.
  • Another object of the present invention is to provide a negative electrode capable of exhibiting excellent discharge characteristics when used in a magnesium-air battery.
  • a further object of the present invention is to provide a magnesium air battery exhibiting excellent discharge characteristics.
  • the present inventors have prepared a magnesium-lithium alloy by adding a specific element such as lithium to magnesium in a specific amount, and using the alloy for the negative electrode is excellent. It has been found that a magnesium-air battery exhibiting excellent discharge characteristics can be obtained, and the present invention has been completed.
  • the magnesium-lithium alloy for an air battery negative electrode of the present invention comprises 6.00 mass% to 10.50 mass% Li, 0 mass% to 15.00 mass% Al, 0 mass% to 5.00 mass%.
  • R represents one or more rare earth elements selected from the group consisting of Y, La, Ce, Nd, and Gd, and the total content of R and Mn is 0.02% by mass or more and 5.00% by mass. It is as follows.
  • the air battery negative electrode of the present invention contains the magnesium-lithium alloy of the present invention, and the magnesium air battery of the present invention has the negative electrode.
  • the magnesium-lithium alloy of the present invention has an ⁇ mixed phase structure because it contains a specific amount of Li. Moreover, a specific amount of at least one of R and Mn is contained. Therefore, a magnesium-air battery using the alloy for the negative electrode can exhibit very excellent discharge characteristics.
  • the magnesium-lithium alloy for an air battery negative electrode of the present invention contains Mg and Li as essential elements, and further contains at least one of R and Mn. Moreover, one or more elements selected from Al, Ca, Zn, Fe, Cu, and Ni may be contained as optional elements, and a small amount of impurities may be contained.
  • the magnesium-lithium alloy for air battery negative electrode is simply referred to as “magnesium-lithium alloy”.
  • the mass ratio of Li to the entire magnesium-lithium alloy (Li content ratio) is 6.00 mass% or more and 10.50 mass% or less. Therefore, this magnesium-lithium alloy has an ⁇ mixed phase structure and therefore exhibits sufficient corrosion resistance. In addition, other phases (for example, Al intermetallic compound phase) may precipitate in the ⁇ mixed phase structure. If the Li content exceeds 10.50% by mass, the corrosion resistance of the magnesium-lithium alloy tends to decrease. On the other hand, since it is considered that the higher Li content is suitable for long-term storage in the atmosphere, from the viewpoint of storage characteristics, the Li content is preferably 7.00 mass% or more, more preferably 8.00 mass. % Or more.
  • the mass ratio of Al to the whole magnesium-lithium alloy (Al content ratio) is 0 mass% or more and 15.00 mass% or less.
  • Al content ratio is 0 mass% or more and 15.00 mass% or less.
  • the Al content exceeds 15.00% by mass, the production of the negative electrode becomes difficult.
  • the Al content is as low as 1.70% by mass or less, excellent discharge characteristics may be obtained.
  • the mass ratio (Ca content ratio) of Ca to the entire magnesium-lithium alloy is 0% by mass or more and 5.00% by mass or less. Since the preferable range of the Ca content depends on the content of other elements, it cannot be defined unconditionally.
  • the mass ratio (Zn content ratio) of Zn to the entire magnesium-lithium alloy is 0% by mass or more and 3.00% by mass or less. When Zn is added, the workability of the magnesium-lithium alloy may be improved.
  • R is one or more rare earth elements selected from the group consisting of Y, La, Ce, Nd, and Gd.
  • R is known to easily form an intermetallic compound with Fe. Although the detailed mechanism is not clear, it is expected that the RFe compound generated in the magnesium-lithium alloy has an effect of suppressing or delaying the formation of the Mg (OH) 2 resistance film.
  • the mass ratio (R content ratio) of R to the entire magnesium-lithium alloy is 0% by mass or more and 3.00% by mass or less. Although the preferable range of the R content depends on the content of other elements and cannot be specified unconditionally, excellent workability is often obtained when the R content is 0% by mass or more and 1.00% by mass or less. .
  • Mn forms a stable intermetallic compound with Fe and improves the corrosion resistance of the magnesium-lithium alloy.
  • the mass ratio (Mn content ratio) of Mn to the entire magnesium-lithium alloy is 0% by mass or more and 2.00% by mass or less.
  • Mn content ratio depends on the content of other elements, it cannot be defined unconditionally, but when the Mn content is 0.001% by mass or more and 0.50% by mass or less, excellent corrosion resistance can be obtained. Many.
  • the mass ratio (Fe content ratio) of Fe to the entire magnesium-lithium alloy is 0% by mass or more and 0.10% by mass or less.
  • the preferable range of the Fe content depends on the content of other elements, it cannot be defined unconditionally, but more excellent discharge characteristics are often obtained when the Fe content is 0% by mass or more and 0.05% by mass or less. .
  • the corrosion resistance of the magnesium-lithium alloy may be lowered and the discharge characteristics of the battery may be deteriorated.
  • Li, Al, Ca, Zn, R, And by appropriately adjusting the content ratio of Mn sufficient discharge characteristics can be achieved even if the Fe content ratio exceeds 0.005 mass% or 0.007 mass%.
  • the mass ratio of Cu to the entire magnesium-lithium alloy (Cu content ratio) is 0 mass% or more and 0.10 mass% or less.
  • the preferable range of the Cu content depends on the content of other elements and cannot be defined unconditionally, excellent discharge characteristics are often obtained when the Cu content is 0% by mass or more and 0.05% by mass or less. .
  • the corrosion resistance of the magnesium-lithium alloy may be lowered and the discharge characteristics of the battery may be deteriorated.
  • Li, Al, Ca, Zn, R, And by appropriately adjusting the content ratio of Mn sufficient discharge characteristics can be achieved even if the Cu content ratio exceeds 0.005 mass% or 0.007 mass%.
  • Ni content ratio The mass ratio of Ni to the entire magnesium-lithium alloy (Ni content ratio) is 0% by mass or more and 0.10% by mass or less. Although the preferable range of the Ni content depends on the content of other elements, it cannot be defined unconditionally. However, when the Ni content is 0% by mass or more and 0.05% by mass or less, excellent discharge characteristics are often obtained. . Usually, when the Ni content exceeds 0.005 mass%, the corrosion resistance of the magnesium-lithium alloy may be lowered and the discharge characteristics of the battery may be deteriorated. However, in the present invention, Li, Al, Ca, Zn, R, In addition, by appropriately adjusting the content ratio of Mn, sufficient discharge characteristics can be achieved even if the Ni content ratio exceeds 0.005 mass% or 0.007 mass%.
  • the balance other than Li, Al, Ca, Zn, R, Mn, Fe, Cu, and Ni consists of Mg and impurities.
  • the “impurity” means an element mixed in the alloy, although not intentionally added to the magnesium-lithium alloy. That is, the “impurities” include elements that have been mixed in the alloy raw material and have not been removed in the alloy manufacturing process, and elements mixed in from the outside in the alloy manufacturing process. Although Al, Ca, Zn, R, Mn, Fe, Cu, and Ni may not be intentionally added, they may remain in the alloy, but in the present invention, these elements are not treated as impurities. . That is, in the present invention, the impurity is one or more elements other than Mg, Li, Al, Ca, Zn, R, Mn, Fe, Cu, and Ni. Examples of impurities include Si and the like.
  • the magnesium-lithium alloy of the present invention preferably does not usually contain impurities, but may contain impurities in an amount that does not have a significant adverse effect on the properties of the alloy. That is, the mass ratio (impurity content ratio) of impurities to the entire magnesium-lithium alloy is preferably 0% by mass, but is acceptable if it is 0.1% by mass or less. When a general alloy raw material and alloy manufacturing method are used, the impurity content is usually 0.001% by mass or more and 0.5% by mass or less.
  • a magnesium air battery using magnesium or a magnesium alloy for the negative electrode has a problem that polarization easily occurs. Since corrosion of the negative electrode can cause polarization, many studies have been made on reducing the amount of corrosion of the negative electrode material as described in Non-Patent Document 1, for example.
  • the performance of the battery is improved by suppressing or delaying the formation of the resistance film with Li, R, or the like, or stabilizing the resistance film by adjusting the content ratio of Mn or the like.
  • the total content of R and Mn is 0.02% by mass or more and 5.00% by mass or less.
  • the total content is preferably 0.025% by mass or more, more preferably 0.030% by mass or more.
  • the method for producing the magnesium-lithium alloy is not particularly limited as long as the alloy having the above composition and physical properties can be obtained.
  • a method including the step (a) of obtaining the alloy raw material melt by melting the raw materials of each element and the step (b) of obtaining an alloy ingot by cooling and solidifying the alloy raw material melt.
  • the magnesium-air battery of the present invention usually has a negative electrode, a positive electrode, and an electrolyte, and the negative electrode contains the magnesium-lithium alloy of the present invention.
  • the electrolyte may be used in the form of an electrolyte solution (electrolytic solution).
  • a magnesium air battery uses oxygen as a positive electrode active material and magnesium as a negative electrode active material. Magnesium in the negative electrode emits electrons to become magnesium ions and elutes into the electrolyte. On the other hand, in the positive electrode, oxygen and water receive electrons and become hydroxide ions. As a whole, an electromotive force is generated between both electrodes due to the production of magnesium hydroxide Mg (OH) 2 from magnesium, oxygen, and water.
  • the electrolytic solution elutes magnesium ions generated at the negative electrode and supplies water that reacts with oxygen to the positive electrode.
  • the magnesium-air battery may be stored in a state that does not contain an electrolytic solution, and the electrolytic solution may be added at the time of use. That is, in the present invention, a structure having a negative electrode and a positive electrode in a state before adding an electrolytic solution is also referred to as a magnesium-air battery.
  • the negative electrode includes the magnesium-lithium alloy of the present invention, and may further include a component for ensuring current collection. It may be formed by applying a carbon paste to a magnesium-lithium alloy or sputtering a dissimilar metal such as platinum or copper. Alternatively, a laminate of a current collector and a magnesium-lithium alloy may be used. One component having both a function as a current collector and a function as a negative electrode active material may be used as the negative electrode.
  • the method for producing the negative electrode is not particularly limited, and can be obtained, for example, by rolling the alloy ingot obtained in any of the steps (b) to (d).
  • the rolled alloy ingot may be polished or roughened using sandpaper or the like. In the case of polishing, it is preferably performed immediately before the production of the battery.
  • 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 positive electrode may have a current collector for supplying electrons to oxygen, which is a positive electrode 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 positive electrode may be obtained by preparing a current collector and a catalyst layer as separate components and laminating them.
  • the positive electrode may be formed by mixing a conductive material for the current collector and a catalyst for the catalyst layer. That is, a single component having both a function as a current collector and a function as a catalyst layer may be used as the positive electrode.
  • the positive 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 positive 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 positive electrode are not particularly limited, but usually the thickness of the positive electrode may be about 20 ⁇ m to 1 cm.
  • electrolytic solution examples include aqueous solutions of NaCl, NaOH, NaHCO 3 , Na 2 SO 4 , HCl, HNO 3 , NH 3 and the like. Among these, a highly safe NaCl aqueous solution is preferable.
  • the magnesium air battery may further have a separator, a current collector, and the like.
  • a separator is arrange
  • the separator material include polyethylene fiber, polypropylene fiber, glass fiber, resin nonwoven fabric, glass nonwoven fabric, and filter paper.
  • the magnesium-air battery of the present invention exhibits excellent discharge characteristics.
  • a negative electrode is produced by processing a magnesium-lithium alloy into a shape having a diameter of 16 mm and a thickness of 1 mm, and MnO 2 , acetylene black, and polyvinylidene fluoride are used at 2: 0.05: A catalyst layer containing 0.1 mass ratio is supported on nickel foam having a diameter of 14 mm to produce a catalyst layer, and a magnesium-air battery having a diameter of 20 mm and a thickness of 3.2 mm is manufactured using the anode and the catalyst layer.
  • a discharge amount evaluation test in which a discharge process of injecting a NaCl aqueous solution as an electrolyte into the magnesium-air battery and discharging at a constant current of 5 mA is repeated 8 times, a discharge amount of 45C or more (obtained in 8 discharge processes) Sum of coulomb amounts).
  • a discharge amount of 70 C or more is obtained, and in a more preferred embodiment, a discharge amount of 100 C or more is obtained.
  • a very high discharge amount exceeding 200 C can be achieved.
  • a negative electrode is produced by processing a magnesium-lithium alloy into a shape having a diameter of 14 mm and a thickness of 1 mm, and a catalyst mixture containing carbon black and polytetrafluoroethylene is foamed with a diameter of 14 mm.
  • the magnesium-air battery of the present invention can be repeatedly discharged 20 times or more. In a preferred embodiment of the present invention, it can be repeated 90 times or more, and in a more preferred embodiment, it can be repeated 150 times or more.
  • the R content is 0.25% by mass or less and the Mn content is 0.20% by mass or less.
  • the total content of R and Mn is preferably 0.02% by mass or more and 0.25% by mass or less, the R content is 0.15% by mass or less, and the Mn content is 0.05.
  • the total content of R and Mn is particularly preferably 0.02% by mass or more and 0.15% by mass or less.
  • the magnesium-air battery of the present invention can be used as an emergency standby power source, an outdoor power source, a power source in a non-electrified area, and the like. When it is stored in a dry state without adding an electrolyte, it can be stored for a long time. In this case, it functions as a battery by adding an electrolyte during use.
  • the manufacturing method of the magnesium-air battery is not particularly limited.
  • the negative electrode case, the spacer, the current collector, the magnesium-lithium alloy negative electrode, the separator, the positive electrode, and the positive electrode case can be stacked in this order.
  • Example 1 A raw material for each element was prepared and melted by heating to obtain a molten alloy raw material. Subsequently, the melt was cast into a 150 mm ⁇ 300 mm ⁇ 500 mm mold and cooled and solidified to produce a magnesium-lithium alloy alloy ingot. The composition of the obtained magnesium-lithium alloy was quantitatively analyzed by ICP (Inductively Coupled Plasma) emission spectrometry. The results are shown in Table 1. The magnesium-lithium alloy of Example 1 was confirmed to contain impurities such as Si, but the impurity content was a trace amount that did not satisfy the lower limit of quantification. That is, this magnesium-lithium alloy substantially consists of the elements shown in Table 1 and the balance Mg.
  • ICP Inductively Coupled Plasma
  • Examples 2 to 5 and Comparative Examples 1 to 6 Alloy ingots of Examples 2 to 5 and Comparative Examples 1 to 6 were produced in the same manner as Example 1 except that the content ratio of each element was changed as shown in Table 1. The composition of the obtained alloy was quantitatively analyzed in the same manner as in Example 1. The results are shown in Table 1. The alloys of Examples 2 to 5 and Comparative Examples 1 to 6 were confirmed to contain impurities such as Si, but the impurity content was a trace amount that did not satisfy the lower limit of quantification. That is, these alloys are substantially composed of the elements shown in Table 1 and the balance Mg.
  • the foamed nickel thus coated with the catalyst slurry was dried on a hot plate heated to 160 ° C. for 3 hours or more.
  • An electrolyte injection hole having a diameter of 3 mm was formed in the central portion, and pressed at 64 MPa for 30 seconds to produce a positive electrode.
  • the thickness of the positive electrode was 150 ⁇ m, and the supported amount of MnO 2 catalyst was 100 mg ⁇ cm ⁇ 2 .
  • a 2032 type coin cell part manufactured by Hosen Co., Ltd. As a battery member, a 2032 type coin cell part manufactured by Hosen Co., Ltd. was used. 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 Co., Ltd.), the above magnesium-lithium alloy negative electrode, filter paper cut to a diameter of 18 mm (5C made by ADVANTEC) 3) The above positive electrode and the positive electrode case with air holes were laminated in this order, and caulking was performed to produce a magnesium air battery.
  • 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.
  • the magnesium-air battery was installed in a thermostatic chamber (temperature 25 ° C., relative humidity 30%).
  • a 0.1 M NaCl aqueous solution was prepared as an electrolytic solution, and 0.1 mL of the NaCl aqueous solution was injected into the battery from the positive electrode electrolyte injection hole using a syringe.
  • a discharge test was conducted at a constant current of 5 mA.
  • BLS5516-5V100 mA manufactured by Keiki Keiki Center Co., Ltd. was used.
  • the electrolyte solution was injected again to perform the same discharge process, and a total of eight discharge processes were performed. Table 1 shows the total amount of coulombs obtained in these eight discharge processes as “discharge amount”.
  • the magnesium-air battery was placed in a thermostatic chamber (temperature: 25 ° C.), discharged at a constant current of 10 mA for 5 minutes, and then rested for 30 minutes. This discharge and rest were repeated until no discharge was possible, and the number of repetitions at which discharge was possible was measured. This number is shown in Table 1 as “the number of discharges”.
  • As an evaluation apparatus BLS5516-5V100 mA manufactured by Keiki Keiki Center Co., Ltd. was used.

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Abstract

A magnesium-lithium alloy suitable for use in the negative electrode of an air battery, a negative electrode using said alloy, and a magnesium air battery are provided. This magnesium-lithium alloy comprises 6.00-10.50 mass% of Li, 0-15.00 mass% of Al, 0-5.00 mass% of Ca, 0-3.00 mass% of Zn, 0-3.00 mass% of R, 0-2.00 mass% of Mn, 0-0.10 mass% of Fe, 0-0.10 mass% of Cu, 0-0.10 mass% of Ni, with the remainder being Mg and unavoidable impurities, wherein R represents one or more rare earth elements selected from Y, La, Ce, Nd and Gd, and the content ratio of the total of R and Mn is 0.02-5.00 mass%.

Description

マグネシウム－リチウム合金及びマグネシウム空気電池Magnesium-lithium alloy and magnesium air battery
　本発明は、空気電池の負極での使用に適したマグネシウム－リチウム合金、並びに該合金を用いた負極及びマグネシウム空気電池に関する。 The present invention relates to a magnesium-lithium alloy suitable for use in a negative electrode of an air battery, and a negative electrode and a magnesium air battery using the alloy.
　金属空気電池は理論エネルギー密度が高いため近年関心を集めており、様々な金属が試されている。マグネシウムは比較的資源が豊富であり、安価であり、毒性が低いため、マグネシウム又はマグネシウム合金を負極に用いたマグネシウム空気電池が期待されている。 Metal-air batteries have attracted interest in recent years due to their high theoretical energy density, and various metals have been tried. Magnesium is abundant in resources, inexpensive, and has low toxicity, so a magnesium air battery using magnesium or a magnesium alloy as a negative electrode is expected.
　従来のマグネシウム空気電池は分極が起こりやすくクーロン効率が低いという問題を有する。マグネシウム空気電池では負極中のマグネシウムが腐食しやすく、この腐食が分極を引き起こすと考えられている。従って、主に腐食速度の低下と反応活性の向上を目的として、新たなマグネシウム合金負極材料の開発に多大な努力がなされてきた。 The conventional magnesium-air battery has a problem that polarization tends to occur and the Coulomb efficiency is low. In the magnesium-air battery, magnesium in the negative electrode is easily corroded, and this corrosion is considered to cause polarization. Therefore, great efforts have been made to develop new magnesium alloy negative electrode materials mainly for the purpose of reducing the corrosion rate and improving the reaction activity.
　非特許文献１等に記載されているように、マグネシウム空気電池の負極材料として、マグネシウム－リチウム合金、マグネシウム－アルミニウム合金、マグネシウム－アルミニウム－亜鉛合金、マグネシウム－アルミニウム－マンガン合金といった、様々なマグネシウム合金が検討されてきた。例えば、特許文献１は、マグネシウム、アルミニウム、及びカルシウムを必須成分として含む合金、並びに該合金を負極に用いたマグネシウム空気電池を開示している。また、特許文献２は、マグネシウム、リチウム、及び亜鉛からなる合金、並びに該合金を負極活物質として用いたマグネシウム空気電池を開示している。 As described in Non-Patent Document 1, etc., various magnesium alloys such as magnesium-lithium alloy, magnesium-aluminum alloy, magnesium-aluminum-zinc alloy, magnesium-aluminum-manganese alloy are used as negative electrode materials for magnesium-air batteries. Has been studied. For example, Patent Document 1 discloses an alloy containing magnesium, aluminum, and calcium as essential components, and a magnesium air battery using the alloy as a negative electrode. Patent Document 2 discloses an alloy composed of magnesium, lithium, and zinc, and a magnesium air battery using the alloy as a negative electrode active material.
ＷＯ２０１２／１４４３０１WO2012 / 144301 特開２０１６－８５８５０号JP 2016-85850 A
　しかしながら、従来のマグネシウム空気電池においては、負極の腐食速度についてはある程度改善されているものの十分ではなく、その結果としてマグネシウム利用効率は高くない。そのため、従来のマグネシウム空気電池は放電量が小さく、更なる向上が望まれている。 However, in the conventional magnesium-air battery, although the corrosion rate of the negative electrode is improved to some extent, it is not sufficient, and as a result, the magnesium utilization efficiency is not high. Therefore, the conventional magnesium-air battery has a small discharge amount, and further improvement is desired.
　本発明の目的は、マグネシウム空気電池の負極に使用した際に優れた放電特性を示し得るマグネシウム－リチウム合金を提供することである。 An object of the present invention is to provide a magnesium-lithium alloy that can exhibit excellent discharge characteristics when used in a negative electrode of a magnesium-air battery.
　本発明の他の目的は、マグネシウム空気電池に使用した際に優れた放電特性を示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 exhibiting excellent discharge characteristics when used in a magnesium-air battery.
　本発明の更なる目的は、優れた放電特性を示すマグネシウム空気電池を提供することである。 A further object of the present invention is to provide a magnesium air battery exhibiting excellent discharge characteristics.
　本発明者らは、上記課題を解決するべく鋭意検討した結果、マグネシウムにリチウム等の特定元素を特定量だけ添加してマグネシウム－リチウム合金を調製し、該合金を負極に使用することによって、優れた放電特性を示すマグネシウム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 inventors have prepared a magnesium-lithium alloy by adding a specific element such as lithium to magnesium in a specific amount, and using the alloy for the negative electrode is excellent. It has been found that a magnesium-air battery exhibiting excellent discharge characteristics can be obtained, and the present invention has been completed.
　本発明の空気電池負極用マグネシウム－リチウム合金は、６．００質量％以上１０．５０質量％以下のＬｉ、０質量％以上１５．００質量％以下のＡｌ、０質量％以上５．００質量％以下のＣａ、０質量％以上３．００質量％以下のＺｎ、０質量％以上３．００質量％以下のＲ、０質量％以上２．００質量％以下のＭｎ、０質量％以上０．１０質量％以下のＦｅ、０質量％以上０．１０質量％以下のＣｕ、０質量％以上０．１０質量％以下のＮｉ、並びに残部のＭｇ及び不純物からなる。ここで、ＲはＹ、Ｌａ、Ｃｅ、Ｎｄ、及びＧｄからなる群から選ばれる１種以上の希土類元素を表し、Ｒ及びＭｎの合計の含有割合は０．０２質量％以上５．００質量％以下である。 The magnesium-lithium alloy for an air battery negative electrode of the present invention comprises 6.00 mass% to 10.50 mass% Li, 0 mass% to 15.00 mass% Al, 0 mass% to 5.00 mass%. The following Ca, Zn of 0 to 3.00 mass%, R of 0 to 3.00 mass%, M of 0 to 2.00 mass%, 0 to 0.10 mass% It consists of Fe of 0 mass% or less, Cu of 0 mass% or more and 0.10 mass% or less, Ni of 0 mass% or more and 0.10 mass% or less, and the remaining Mg and impurities. Here, R represents one or more rare earth elements selected from the group consisting of Y, La, Ce, Nd, and Gd, and the total content of R and Mn is 0.02% by mass or more and 5.00% by mass. It is as follows.
　本発明の空気電池負極は上記本発明のマグネシウム－リチウム合金を含み、本発明のマグネシウム空気電池は該負極を有する。 The air battery negative electrode of the present invention contains the magnesium-lithium alloy of the present invention, and the magnesium air battery of the present invention has the negative electrode.
　本発明のマグネシウム－リチウム合金は、特定量のＬｉを含有するためαβ混相構造を有する。また、Ｒ及びＭｎの少なくとも一方を特定量含有する。そのため、該合金を負極に用いたマグネシウム空気電池は非常に優れた放電特性を示し得る。 The magnesium-lithium alloy of the present invention has an αβ mixed phase structure because it contains a specific amount of Li. Moreover, a specific amount of at least one of R and Mn is contained. Therefore, a magnesium-air battery using the alloy for the negative electrode can exhibit very excellent discharge characteristics.
　本発明の空気電池負極用マグネシウム－リチウム合金は、必須元素としてＭｇ及びＬｉを含有し、更にＲ及びＭｎの少なくとも１つを含有する。また、任意元素としてＡｌ、Ｃａ、Ｚｎ、Ｆｅ、Ｃｕ、及びＮｉから選ばれる１種以上の元素を含有していてもよく、更に少量の不純物を含有してもよい。以下、空気電池負極用マグネシウム－リチウム合金を単に「マグネシウム－リチウム合金」と称する。 The magnesium-lithium alloy for an air battery negative electrode of the present invention contains Mg and Li as essential elements, and further contains at least one of R and Mn. Moreover, one or more elements selected from Al, Ca, Zn, Fe, Cu, and Ni may be contained as optional elements, and a small amount of impurities may be contained. Hereinafter, the magnesium-lithium alloy for air battery negative electrode is simply referred to as “magnesium-lithium alloy”.
　従来から、マグネシウム－リチウム合金において、Ｌｉは合金表面にＬｉ2ＣＯ3を形成することでＭｇ（ＯＨ）2抵抗被膜の生成を遅延させると考えられている（ジャーナル・オブ・ザ・エレクトロケミカル・ソサエティ（Journal of The Electrochemical Society），１６３（６），Ｃ３２４－Ｃ３２９（２０１６）参照）。また、Ｍｇの結晶構造はα相構造（ｈｃｐ構造）であるが、Ｌｉ含有割合が６～１０．５質量％のマグネシウム－リチウム合金はα相構造とβ相構造（ｂｃｃ構造）のαβ混相構造を有し、Ｌｉ含有割合が１０．５質量％を超えるマグネシウム－リチウム合金はβ単相構造を有することが知られている。β相は多くのすべり系を有するため、Ｌｉ含有割合を高くするに従ってマグネシウム－リチウム合金の加工性が向上する。 Conventionally, in a magnesium-lithium alloy, Li is thought to delay the formation of a Mg (OH) 2 resistive film by forming Li 2 CO 3 on the alloy surface (Journal of the Electrochemical. Society (The Journal of The Electrochemical Society), 163 (6), C324-C329 (2016)). The crystal structure of Mg is an α phase structure (hcp structure), but a magnesium-lithium alloy having a Li content of 6 to 10.5% by mass is an αβ mixed phase structure of an α phase structure and a β phase structure (bcc structure). It is known that a magnesium-lithium alloy having a Li content exceeding 10.5% by mass has a β single-phase structure. Since the β phase has many slip systems, the workability of the magnesium-lithium alloy improves as the Li content increases.
　本発明において、マグネシウム－リチウム合金全体に対するＬｉの質量比（Ｌｉ含有割合）は６．００質量％以上１０．５０質量％以下である。従って、このマグネシウム－リチウム合金はαβ混相構造を有し、そのため十分な耐食性を示す。なお、αβ混相構造中に他の相（例えばＡｌ金属間化合物相等）が析出していてもよい。Ｌｉ含有割合が１０．５０質量％を超えると、マグネシウム－リチウム合金の耐食性が低下する傾向がある。一方、Ｌｉ含有割合が高いほうが大気中での長期保存に適していると考えられるため、保存特性の観点からは、Ｌｉ含有割合は好ましくは７．００質量％以上、さらに好ましくは８．００質量％以上である。 In the present invention, the mass ratio of Li to the entire magnesium-lithium alloy (Li content ratio) is 6.00 mass% or more and 10.50 mass% or less. Therefore, this magnesium-lithium alloy has an αβ mixed phase structure and therefore exhibits sufficient corrosion resistance. In addition, other phases (for example, Al intermetallic compound phase) may precipitate in the αβ mixed phase structure. If the Li content exceeds 10.50% by mass, the corrosion resistance of the magnesium-lithium alloy tends to decrease. On the other hand, since it is considered that the higher Li content is suitable for long-term storage in the atmosphere, from the viewpoint of storage characteristics, the Li content is preferably 7.00 mass% or more, more preferably 8.00 mass. % Or more.
　マグネシウム－リチウム合金全体に対するＡｌの質量比（Ａｌ含有割合）は０質量％以上１５．００質量％以下である。Ａｌ含有割合が１５．００質量％を超えると負極の製造が困難となる。本発明では、Ａｌ含有割合が１．７０質量％以下という低い割合であっても、優れた放電特性が得られる場合がある。 The mass ratio of Al to the whole magnesium-lithium alloy (Al content ratio) is 0 mass% or more and 15.00 mass% or less. When the Al content exceeds 15.00% by mass, the production of the negative electrode becomes difficult. In the present invention, even when the Al content is as low as 1.70% by mass or less, excellent discharge characteristics may be obtained.
　マグネシウム－リチウム合金全体に対するＣａの質量比（Ｃａ含有割合）は０質量％以上５．００質量％以下である。Ｃａ含有割合の好ましい範囲は他の元素の含有割合に依るため一概に規定できない。 The mass ratio (Ca content ratio) of Ca to the entire magnesium-lithium alloy is 0% by mass or more and 5.00% by mass or less. Since the preferable range of the Ca content depends on the content of other elements, it cannot be defined unconditionally.
　マグネシウム－リチウム合金全体に対するＺｎの質量比（Ｚｎ含有割合）は０質量％以上３．００質量％以下である。Ｚｎを添加するとマグネシウム－リチウム合金の加工性が改善される場合がある。 The mass ratio (Zn content ratio) of Zn to the entire magnesium-lithium alloy is 0% by mass or more and 3.00% by mass or less. When Zn is added, the workability of the magnesium-lithium alloy may be improved.
　ＲはＹ、Ｌａ、Ｃｅ、Ｎｄ、及びＧｄからなる群から選ばれる１種以上の希土類元素である。ＲはＦｅと金属間化合物を形成しやすいことが知られている。詳細な機構は明らかではないが、マグネシウム－リチウム合金中で生じたＲＦｅ化合物はＭｇ（ＯＨ）2抵抗被膜の生成を抑制又は遅延させる効果があると予想される。マグネシウム－リチウム合金全体に対するＲの質量比（Ｒ含有割合）は０質量％以上３．００質量％以下である。Ｒ含有割合の好ましい範囲は他の元素の含有割合に依るため一概に規定できないが、Ｒ含有割合が０質量％以上１．００質量％以下である場合により優れた加工性が得られることが多い。 R is one or more rare earth elements selected from the group consisting of Y, La, Ce, Nd, and Gd. R is known to easily form an intermetallic compound with Fe. Although the detailed mechanism is not clear, it is expected that the RFe compound generated in the magnesium-lithium alloy has an effect of suppressing or delaying the formation of the Mg (OH) 2 resistance film. The mass ratio (R content ratio) of R to the entire magnesium-lithium alloy is 0% by mass or more and 3.00% by mass or less. Although the preferable range of the R content depends on the content of other elements and cannot be specified unconditionally, excellent workability is often obtained when the R content is 0% by mass or more and 1.00% by mass or less. .
　ＭｎはＦｅと安定な金属間化合物を形成し、マグネシウム－リチウム合金の耐食性を改善することが知られている。詳細な機構は明らかではないが、マグネシウム－リチウム合金が過剰量のＭｎを含有すると、上記ＲＦｅ化合物によるＭｇ（ＯＨ）2生成を抑制又は遅延させる効果が制限されると予想される。マグネシウム－リチウム合金全体に対するＭｎの質量比（Ｍｎ含有割合）は０質量％以上２．００質量％以下である。Ｍｎ含有割合の好ましい範囲は他の元素の含有割合に依るため一概に規定できないが、Ｍｎ含有割合が０．００１質量％以上０．５０質量％以下である場合により優れた耐食性が得られることが多い。 It is known that Mn forms a stable intermetallic compound with Fe and improves the corrosion resistance of the magnesium-lithium alloy. Although the detailed mechanism is not clear, it is expected that when the magnesium-lithium alloy contains an excessive amount of Mn, the effect of suppressing or delaying the production of Mg (OH) 2 by the RFe compound is limited. The mass ratio (Mn content ratio) of Mn to the entire magnesium-lithium alloy is 0% by mass or more and 2.00% by mass or less. Although the preferable range of the Mn content depends on the content of other elements, it cannot be defined unconditionally, but when the Mn content is 0.001% by mass or more and 0.50% by mass or less, excellent corrosion resistance can be obtained. Many.
　マグネシウム－リチウム合金全体に対するＦｅの質量比（Ｆｅ含有割合）は０質量％以上０．１０質量％以下である。Ｆｅ含有割合の好ましい範囲は他の元素の含有割合に依るため一概に規定できないが、Ｆｅ含有割合が０質量％以上０．０５質量％以下である場合により優れた放電特性が得られることが多い。通常、Ｆｅ含有割合が０．００５質量％を超えると、マグネシウム－リチウム合金の耐食性が低下し、電池の放電特性が悪化する場合があるが、本発明ではＬｉ、Ａｌ、Ｃａ、Ｚｎ、Ｒ、及びＭｎの含有割合を適宜調整することで、０．００５質量％或いは０．００７質量％を超えるＦｅ含有割合であっても十分な放電特性を達成し得る。 The mass ratio (Fe content ratio) of Fe to the entire magnesium-lithium alloy is 0% by mass or more and 0.10% by mass or less. Although the preferable range of the Fe content depends on the content of other elements, it cannot be defined unconditionally, but more excellent discharge characteristics are often obtained when the Fe content is 0% by mass or more and 0.05% by mass or less. . Usually, when the Fe content exceeds 0.005% by mass, the corrosion resistance of the magnesium-lithium alloy may be lowered and the discharge characteristics of the battery may be deteriorated. However, in the present invention, Li, Al, Ca, Zn, R, And by appropriately adjusting the content ratio of Mn, sufficient discharge characteristics can be achieved even if the Fe content ratio exceeds 0.005 mass% or 0.007 mass%.
　マグネシウム－リチウム合金全体に対するＣｕの質量比（Ｃｕ含有割合）は０質量％以上０．１０質量％以下である。Ｃｕ含有割合の好ましい範囲は他の元素の含有割合に依るため一概に規定できないが、Ｃｕ含有割合が０質量％以上０．０５質量％以下である場合により優れた放電特性が得られることが多い。通常、Ｃｕ含有割合が０．００５質量％を超えると、マグネシウム－リチウム合金の耐食性が低下し、電池の放電特性が悪化する場合があるが、本発明ではＬｉ、Ａｌ、Ｃａ、Ｚｎ、Ｒ、及びＭｎの含有割合を適宜調整することで、０．００５質量％或いは０．００７質量％を超えるＣｕ含有割合であっても十分な放電特性を達成し得る。 The mass ratio of Cu to the entire magnesium-lithium alloy (Cu content ratio) is 0 mass% or more and 0.10 mass% or less. Although the preferable range of the Cu content depends on the content of other elements and cannot be defined unconditionally, excellent discharge characteristics are often obtained when the Cu content is 0% by mass or more and 0.05% by mass or less. . Usually, if the Cu content exceeds 0.005% by mass, the corrosion resistance of the magnesium-lithium alloy may be lowered and the discharge characteristics of the battery may be deteriorated. However, in the present invention, Li, Al, Ca, Zn, R, And by appropriately adjusting the content ratio of Mn, sufficient discharge characteristics can be achieved even if the Cu content ratio exceeds 0.005 mass% or 0.007 mass%.
　マグネシウム－リチウム合金全体に対するＮｉの質量比（Ｎｉ含有割合）は０質量％以上０．１０質量％以下である。Ｎｉ含有割合の好ましい範囲は他の元素の含有割合に依るため一概に規定できないが、Ｎｉ含有割合が０質量％以上０．０５質量％以下である場合により優れた放電特性が得られることが多い。通常、Ｎｉ含有割合が０．００５質量％を超えると、マグネシウム－リチウム合金の耐食性が低下し、電池の放電特性が悪化する場合があるが、本発明ではＬｉ、Ａｌ、Ｃａ、Ｚｎ、Ｒ、及びＭｎの含有割合を適宜調整することで、０．００５質量％或いは０．００７質量％を超えるＮｉ含有割合であっても十分な放電特性を達成し得る。 The mass ratio of Ni to the entire magnesium-lithium alloy (Ni content ratio) is 0% by mass or more and 0.10% by mass or less. Although the preferable range of the Ni content depends on the content of other elements, it cannot be defined unconditionally. However, when the Ni content is 0% by mass or more and 0.05% by mass or less, excellent discharge characteristics are often obtained. . Usually, when the Ni content exceeds 0.005 mass%, the corrosion resistance of the magnesium-lithium alloy may be lowered and the discharge characteristics of the battery may be deteriorated. However, in the present invention, Li, Al, Ca, Zn, R, In addition, by appropriately adjusting the content ratio of Mn, sufficient discharge characteristics can be achieved even if the Ni content ratio exceeds 0.005 mass% or 0.007 mass%.
　本発明のマグネシウム－リチウム合金において、上記Ｌｉ、Ａｌ、Ｃａ、Ｚｎ、Ｒ、Ｍｎ、Ｆｅ、Ｃｕ、及びＮｉ以外の残部はＭｇ及び不純物からなる。 In the magnesium-lithium alloy of the present invention, the balance other than Li, Al, Ca, Zn, R, Mn, Fe, Cu, and Ni consists of Mg and impurities.
　本発明において「不純物」とは、マグネシウム－リチウム合金に意図的に加えたわけではないが該合金に混入した元素を意味する。すなわち、「不純物」は、合金の原料に混入していた元素であって合金製造過程において除去されなかった元素や、合金製造過程において外部から混入した元素を包含する。上記Ａｌ、Ｃａ、Ｚｎ、Ｒ、Ｍｎ、Ｆｅ、Ｃｕ、及びＮｉを意図的に加えていないにも関わらず合金中に残存する場合があるが、本発明ではこれらの元素を不純物としては扱わない。すなわち、本発明において、不純物はＭｇ、Ｌｉ、Ａｌ、Ｃａ、Ｚｎ、Ｒ、Ｍｎ、Ｆｅ、Ｃｕ、及びＮｉ以外の１種以上の元素である。不純物の例としてはＳｉ等が挙げられる。 In the present invention, the “impurity” means an element mixed in the alloy, although not intentionally added to the magnesium-lithium alloy. That is, the “impurities” include elements that have been mixed in the alloy raw material and have not been removed in the alloy manufacturing process, and elements mixed in from the outside in the alloy manufacturing process. Although Al, Ca, Zn, R, Mn, Fe, Cu, and Ni may not be intentionally added, they may remain in the alloy, but in the present invention, these elements are not treated as impurities. . That is, in the present invention, the impurity is one or more elements other than Mg, Li, Al, Ca, Zn, R, Mn, Fe, Cu, and Ni. Examples of impurities include Si and the like.
　本発明のマグネシウム－リチウム合金は、通常は不純物を含まないことが好ましいが、合金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。すなわち、マグネシウム－リチウム合金全体に対する不純物の質量比（不純物含有割合）は０質量％であるのが好ましいが、０．１質量％以下であれば許容される。一般的な合金原料及び合金製造方法を用いた場合は、不純物含有割合は通常０．００１質量％以上０．５質量％以下である。 The magnesium-lithium alloy of the present invention preferably does not usually contain impurities, but may contain impurities in an amount that does not have a significant adverse effect on the properties of the alloy. That is, the mass ratio (impurity content ratio) of impurities to the entire magnesium-lithium alloy is preferably 0% by mass, but is acceptable if it is 0.1% by mass or less. When a general alloy raw material and alloy manufacturing method are used, the impurity content is usually 0.001% by mass or more and 0.5% by mass or less.
　負極にマグネシウム又はマグネシウム合金を用いたマグネシウム空気電池は分極が起こりやすいという問題を有している。負極の腐食は分極の原因となり得るため、例えば上記非特許文献１等に記載されているように、従来から負極材料の腐食量を減らすことについて研究が数多くなされてきた。一方、本発明においては、Ｌｉ、Ｒ等で抵抗被膜の生成を抑制又は遅延することや、Ｍｎ等の含有割合を調整して抵抗被膜を安定化することによって、電池性能を改善する。Ｒ及びＭｎの合計の含有割合は０．０２質量％以上５．００質量％以下である。当該合計含有割合は、好ましくは０．０２５質量％以上、より好ましくは０．０３０質量％以上である。また、好ましくは１．００質量％以下、より好ましくは０．６０質量％以下である。 A magnesium air battery using magnesium or a magnesium alloy for the negative electrode has a problem that polarization easily occurs. Since corrosion of the negative electrode can cause polarization, many studies have been made on reducing the amount of corrosion of the negative electrode material as described in Non-Patent Document 1, for example. On the other hand, in the present invention, the performance of the battery is improved by suppressing or delaying the formation of the resistance film with Li, R, or the like, or stabilizing the resistance film by adjusting the content ratio of Mn or the like. The total content of R and Mn is 0.02% by mass or more and 5.00% by mass or less. The total content is preferably 0.025% by mass or more, more preferably 0.030% by mass or more. Moreover, Preferably it is 1.00 mass% or less, More preferably, it is 0.60 mass% or less.
　マグネシウム－リチウム合金を製造する方法は、上述の組成及び物性を有する合金が得られる方法であれば特に限定されない。例えば、各元素の原料を溶融し合金原料溶融物を得る工程（ａ）と、合金原料溶融物を冷却固化して合金鋳塊を得る工程（ｂ）とを含む方法が挙げられる。工程（ｂ）で得られた合金鋳塊を均質化熱処理する工程（ｃ）を行ってもよい。また、工程（ｂ）又は（ｃ）で得られた合金鋳塊を熱間圧延する工程（ｄ）を行ってもよい。 The method for producing the magnesium-lithium alloy is not particularly limited as long as the alloy having the above composition and physical properties can be obtained. For example, there is a method including the step (a) of obtaining the alloy raw material melt by melting the raw materials of each element and the step (b) of obtaining an alloy ingot by cooling and solidifying the alloy raw material melt. You may perform the process (c) of homogenizing heat processing the alloy ingot obtained at the process (b). Moreover, you may perform the process (d) which hot-rolls the alloy ingot obtained by the process (b) or (c).
　本発明のマグネシウム空気電池は、通常は負極、正極、及び電解質を有し、該負極が上記本発明のマグネシウム－リチウム合金を含む。電解質は電解質溶液（電解液）の形態で使用してよい。マグネシウム空気電池は酸素を正極活物質として利用し、マグネシウムを負極活物質として利用する。負極中のマグネシウムは電子を放出してマグネシウムイオンとなり、電解液中に溶出する。一方、正極では酸素と水が電子を受け取って水酸化物イオンとなる。全体で見ると、マグネシウム、酸素、及び水から水酸化マグネシウムＭｇ（ＯＨ）2が生じることで両極間に起電力が発生する。電解液は負極で発生したマグネシウムイオンを溶出させるともに、酸素と反応する水を正極に供給する。電解液を含まない状態でマグネシウム空気電池を保管し、使用する時点で電解液を加えてもよい。即ち、本発明では、電解液を加える前の状態の負極及び正極を有する構造体も、マグネシウム空気電池と称する。 The magnesium-air battery of the present invention usually has a negative electrode, a positive electrode, and an electrolyte, and the negative electrode contains the magnesium-lithium alloy of the present invention. The electrolyte may be used in the form of an electrolyte solution (electrolytic solution). A magnesium air battery uses oxygen as a positive electrode active material and magnesium as a negative electrode active material. Magnesium in the negative electrode emits electrons to become magnesium ions and elutes into the electrolyte. On the other hand, in the positive electrode, oxygen and water receive electrons and become hydroxide ions. As a whole, an electromotive force is generated between both electrodes due to the production of magnesium hydroxide Mg (OH) 2 from magnesium, oxygen, and water. The electrolytic solution elutes magnesium ions generated at the negative electrode and supplies water that reacts with oxygen to the positive electrode. The magnesium-air battery may be stored in a state that does not contain an electrolytic solution, and the electrolytic solution may be added at the time of use. That is, in the present invention, a structure having a negative electrode and a positive electrode in a state before adding an electrolytic solution is also referred to as a magnesium-air battery.
　負極は本発明のマグネシウム－リチウム合金を含み、更に集電性を確保するための構成要素を含んでいてもよい。マグネシウム－リチウム合金にカーボンペーストを塗布したり、白金や銅等の異種金属をスパッタしてなるものであってもよい。或いは、集電体とマグネシウム－リチウム合金とを積層したものであってもよい。集電体としての機能と負極活物質としての機能とを併せ持つ１つの構成要素を負極として使用してもよい。 The negative electrode includes the magnesium-lithium alloy of the present invention, and may further include a component for ensuring current collection. It may be formed by applying a carbon paste to a magnesium-lithium alloy or sputtering a dissimilar metal such as platinum or copper. Alternatively, a laminate of a current collector and a magnesium-lithium alloy may be used. One component having both a function as a current collector and a function as a negative electrode active material may be used as the negative electrode.
　負極の作製方法は特に限定されないが、例えば上記工程（ｂ）～（ｄ）のいずれかで得られた合金鋳塊を圧延加工して得られる。サンドペーパー等を用いて、圧延加工した合金鋳塊を研磨又は粗面化してもよい。研磨する場合は電池を作製する直前に行うのが好ましい。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 method for producing the negative electrode is not particularly limited, and can be obtained, for example, by rolling the alloy ingot obtained in any of the steps (b) to (d). The rolled alloy ingot may be polished or roughened using sandpaper or the like. In the case of polishing, it is preferably performed immediately before the production of the battery. 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.
　正極は、正極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。正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、正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つの構成要素を正極として使用してもよい。 The positive electrode may have a current collector for supplying electrons to oxygen, which is a positive electrode 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 positive electrode may be obtained by preparing a current collector and a catalyst layer as separate components and laminating them. Alternatively, the positive electrode may be formed by mixing a conductive material for the current collector and a catalyst for the catalyst layer. That is, a single component having both a function as a current collector and a function as a catalyst layer may be used as the positive electrode.
　正極は更に支持体（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 positive 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.
　正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。正極の大きさや形状も特に限定されないが、通常、正極の厚みは２０μｍ～１ｃｍ程度であってよい。 The method for producing the positive 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 positive electrode are not particularly limited, but usually the thickness of the positive electrode may be about 20 μm to 1 cm.
　電解液としては、ＮａＣｌ、ＮａＯＨ、ＮａＨＣＯ3、Ｎａ2ＳＯ4、ＨＣｌ、ＨＮＯ3、ＮＨ3等の水溶液が挙げられる。中でも、安全性の高いＮａＣｌ水溶液が好ましい。 Examples of the electrolytic solution include aqueous solutions of NaCl, NaOH, NaHCO 3 , Na 2 SO 4 , HCl, HNO 3 , NH 3 and the like. Among these, a highly safe NaCl aqueous solution is preferable.
　マグネシウム空気電池は、更にセパレータや集電体等を有していてもよい。通常、セパレータは負極と正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。 The magnesium air battery may further have a separator, a current collector, and the like. Usually, a separator is arrange | positioned between a negative electrode and a positive electrode, and while having a role which hold | maintains electrolyte and conducts an ion while preventing the short circuit between both electrodes. Examples of the separator material include polyethylene fiber, polypropylene fiber, glass fiber, resin nonwoven fabric, glass nonwoven fabric, and filter paper.
　本発明のマグネシウム空気電池は優れた放電特性を示す。例えば、後述する実施例に示すように、マグネシウム－リチウム合金を直径１６ｍｍ且つ厚さ１ｍｍの形状に加工して負極を作製し、ＭｎＯ2、アセチレンブラック、及びポリフッ化ビニリデンを２：０．０５：０．１の質量比で含む触媒合材を直径１４ｍｍの発泡ニッケルに担持させて触媒層を作製し、該負極及び触媒層を用いて直径２０ｍｍ且つ厚さ３．２ｍｍのマグネシウム空気電池を製造し、このマグネシウム空気電池の内部に電解液としてＮａＣｌ水溶液を注入して５ｍＡ定電流にて放電させる放電過程を８回繰り返す放電量評価試験において、４５Ｃ以上の放電量（８回の放電過程で得られるクーロン量の総和）を示し得る。本発明の好ましい態様においては７０Ｃ以上の放電量が得られ、より好ましい態様においては１００Ｃ以上の放電量が得られる。更に、本発明では２００Ｃを超える非常に高い放電量を達成することも可能である。 The magnesium-air battery of the present invention exhibits excellent discharge characteristics. For example, as shown in the examples described later, a negative electrode is produced by processing a magnesium-lithium alloy into a shape having a diameter of 16 mm and a thickness of 1 mm, and MnO 2 , acetylene black, and polyvinylidene fluoride are used at 2: 0.05: A catalyst layer containing 0.1 mass ratio is supported on nickel foam having a diameter of 14 mm to produce a catalyst layer, and a magnesium-air battery having a diameter of 20 mm and a thickness of 3.2 mm is manufactured using the anode and the catalyst layer. In a discharge amount evaluation test in which a discharge process of injecting a NaCl aqueous solution as an electrolyte into the magnesium-air battery and discharging at a constant current of 5 mA is repeated 8 times, a discharge amount of 45C or more (obtained in 8 discharge processes) Sum of coulomb amounts). In a preferred embodiment of the present invention, a discharge amount of 70 C or more is obtained, and in a more preferred embodiment, a discharge amount of 100 C or more is obtained. Furthermore, in the present invention, a very high discharge amount exceeding 200 C can be achieved.
　また、後述する実施例に示すように、マグネシウム－リチウム合金を直径１４ｍｍ且つ厚さ１ｍｍの形状に加工して負極を作製し、カーボンブラック及びポリテトラフルオロエチレンを含む触媒合材を直径１４ｍｍの発泡ニッケルに担持させて触媒層を作製し、該負極及び触媒層の下半分をＮａＣｌ水溶液に浸漬してマグネシウム空気電池を製造し、１０ｍＡ定電流にて５分間放電させた後に３０分間休止させる過程を繰り返す放電回数評価試験において、本発明のマグネシウム空気電池は放電を２０回以上繰り返して行うことが可能である。本発明の好ましい態様においては９０回以上繰り返すことが可能であり、より好ましい態様においては１５０回以上繰り返すことが可能である。 Further, as shown in the examples described later, a negative electrode is produced by processing a magnesium-lithium alloy into a shape having a diameter of 14 mm and a thickness of 1 mm, and a catalyst mixture containing carbon black and polytetrafluoroethylene is foamed with a diameter of 14 mm. A process of producing a catalyst layer by carrying it on nickel, manufacturing a magnesium air battery by immersing the lower half of the negative electrode and the catalyst layer in an NaCl aqueous solution, discharging for 5 minutes at a constant current of 10 mA, and resting for 30 minutes. In the repeated discharge number evaluation test, the magnesium-air battery of the present invention can be repeatedly discharged 20 times or more. In a preferred embodiment of the present invention, it can be repeated 90 times or more, and in a more preferred embodiment, it can be repeated 150 times or more.
　上述の放電回数評価試験において優れた放電回数を得る観点からは、本発明のマグネシウム－リチウム合金において、Ｒ含有割合が０．２５質量％以下であり、Ｍｎ含有割合が０．２０質量％以下であり、且つＲ及びＭｎの合計の含有割合が０．０２質量％以上０．２５質量％以下であることが好ましく、Ｒ含有割合が０．１５質量％以下であり、Ｍｎ含有割合が０．０５質量％以下であり、且つＲ及びＭｎの合計の含有割合が０．０２質量％以上０．１５質量％以下であることが特に好ましい。また、Ｒ及びＭｎの両方を含有することが好ましい。特に、０．０１質量％以上のＲと０．００５質量％以上のＭｎとの組み合わせを含有するのが好ましい。 From the viewpoint of obtaining an excellent number of discharges in the discharge number evaluation test described above, in the magnesium-lithium alloy of the present invention, the R content is 0.25% by mass or less and the Mn content is 0.20% by mass or less. And the total content of R and Mn is preferably 0.02% by mass or more and 0.25% by mass or less, the R content is 0.15% by mass or less, and the Mn content is 0.05. The total content of R and Mn is particularly preferably 0.02% by mass or more and 0.15% by mass or less. Moreover, it is preferable to contain both R and Mn. In particular, it is preferable to contain a combination of 0.01 mass% or more of R and 0.005 mass% or more of Mn.
　本発明のマグネシウム空気電池は、緊急時用の予備電源、アウトドア用電源、未電化地域における電源等として使用できる。電解液を加えずに乾燥状態で保管する場合は長期間の保管が可能である。この場合、使用時に電解液を加えることで電池として機能する。 The magnesium-air battery of the present invention can be used as an emergency standby power source, an outdoor power source, a power source in a non-electrified area, and the like. When it is stored in a dry state without adding an electrolyte, it can be stored for a long time. In this case, it functions as a battery by adding an electrolyte during use.
　マグネシウム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、マグネシウム－リチウム合金負極、セパレータ、正極、及び正極ケースをこの順に積層して製造できる。 The manufacturing method of the magnesium-air battery is not particularly limited. For example, the negative electrode case, the spacer, the current collector, the magnesium-lithium alloy negative electrode, the separator, the positive electrode, and the positive electrode case can be stacked in this order.
　以下、実施例及び比較例を挙げて本発明を具体的に説明するが、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 specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
実施例１
　各元素の原料を準備し、加熱溶解して合金原料溶融物を得た。続いてこの溶融物を１５０ｍｍ×３００ｍｍ×５００ｍｍの金型中に鋳込んで冷却固化し、マグネシウム－リチウム合金の合金鋳塊を作製した。得られたマグネシウム－リチウム合金の組成をＩＣＰ（Ｉｎｄｕｃｔｉｖｅｌｙ　Ｃｏｕｐｌｅｄ　Ｐｌａｓｍａ）発光分光分析により定量分析した。結果を表１に示す。なお、実施例１のマグネシウム－リチウム合金はＳｉ等の不純物を含んでいることが確認されたが、不純物の含有割合は定量下限値に満たない微量であった。即ち、このマグネシウム－リチウム合金は実質的に表１に示す元素と残部のＭｇとからなる。 Example 1
A raw material for each element was prepared and melted by heating to obtain a molten alloy raw material. Subsequently, the melt was cast into a 150 mm × 300 mm × 500 mm mold and cooled and solidified to produce a magnesium-lithium alloy alloy ingot. The composition of the obtained magnesium-lithium alloy was quantitatively analyzed by ICP (Inductively Coupled Plasma) emission spectrometry. The results are shown in Table 1. The magnesium-lithium alloy of Example 1 was confirmed to contain impurities such as Si, but the impurity content was a trace amount that did not satisfy the lower limit of quantification. That is, this magnesium-lithium alloy substantially consists of the elements shown in Table 1 and the balance Mg.
実施例２～５及び比較例１～６
　各元素の含有割合を表１に示す通り変更したこと以外は実施例１と同様に、実施例２～５及び比較例１～６の合金鋳塊を作製した。得られた合金の組成を実施例１と同様に定量分析した。結果を表１に示す。なお、実施例２～５及び比較例１～６の合金はＳｉ等の不純物を含んでいることが確認されたが、不純物の含有割合は定量下限値に満たない微量であった。即ち、これらの合金は実質的に表１に示す元素と残部のＭｇとからなる。 Examples 2 to 5 and Comparative Examples 1 to 6
Alloy ingots of Examples 2 to 5 and Comparative Examples 1 to 6 were produced in the same manner as Example 1 except that the content ratio of each element was changed as shown in Table 1. The composition of the obtained alloy was quantitatively analyzed in the same manner as in Example 1. The results are shown in Table 1. The alloys of Examples 2 to 5 and Comparative Examples 1 to 6 were confirmed to contain impurities such as Si, but the impurity content was a trace amount that did not satisfy the lower limit of quantification. That is, these alloys are substantially composed of the elements shown in Table 1 and the balance Mg.
　実施例１～５及び比較例１～６の合金鋳塊を用いて、以下のとおり放電量評価試験及び放電回数評価試験を行った。 Using the alloy ingots of Examples 1 to 5 and Comparative Examples 1 to 6, a discharge amount evaluation test and a discharge number evaluation test were performed as follows.
［放電量評価試験］
（負極の作製）
　合金鋳塊を厚み１ｍｍに圧延し、直径１６ｍｍに切り出し、両面を＃６００サンドペーパーで研磨して、負極を作製した。なお、研磨は電池を作製する直前に行った。 [Discharge evaluation test]
(Preparation of negative electrode)
The alloy ingot was rolled to a thickness of 1 mm, cut to a diameter of 16 mm, and both surfaces were polished with # 600 sandpaper to produce a negative electrode. The polishing was performed immediately before manufacturing the battery.
（正極の作製）
　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。中央部分に直径３ｍｍの電解液注入孔をあけ、６４ＭＰａで３０秒間プレスして、正極を作製した。なお、正極の厚みは１５０μｍであり、ＭｎＯ2触媒担持量は１００ｍｇ・ｃｍ-2であった。 (Preparation of positive electrode)
MnO 2 (Tosoh Corporation HMH), acetylene black (Denka Corporation Denka Black), and polyvinylidene fluoride solution (Kureha KF Polymer L # 1120), MnO 2 : acetylene black: polyvinylidene fluoride The mass ratio was 2: 0.05: 0.1, 1 mL of N-methyl-2-pyrrolidone was added as a solvent, and the mixture was 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 foamed nickel thus coated with the catalyst slurry was dried on a hot plate heated to 160 ° C. for 3 hours or more. An electrolyte injection hole having a diameter of 3 mm was formed in the central portion, and pressed at 64 MPa for 30 seconds to produce a positive electrode. The thickness of the positive electrode was 150 μm, and the supported amount of MnO 2 catalyst was 100 mg · cm −2 .
（マグネシウム空気電池の作製）
　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）、上記マグネシウム－リチウム合金負極、直径１８ｍｍに切り出した濾紙（ＡＤＶＡＮＴＥＣ製５Ｃ）３枚、上記正極、及び空気孔付き正極ケースをこの順に積層し、かしめ処理を行ってマグネシウム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 magnesium air battery)
As a battery member, a 2032 type coin cell part manufactured by Hosen Co., Ltd. was used. 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 Co., Ltd.), the above magnesium-lithium alloy negative electrode, filter paper cut to a diameter of 18 mm (5C made by ADVANTEC) 3) The above positive electrode and the positive electrode case with air holes were laminated in this order, and caulking was performed to produce a magnesium air battery. 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.
（放電量の測定）
　上記マグネシウム空気電池を恒温槽（温度２５℃、相対湿度３０％）内に設置した。電解液として０．１ＭのＮａＣｌ水溶液を調製し、注射器を用いて０．１ｍＬの当該ＮａＣｌ水溶液を正極の電解液注入孔より電池内部に注入した。注入後速やかに５ｍＡ定電流にて放電試験を実施した。評価装置としては株式会社計測器センター製ＢＬＳ５５１６－５Ｖ１００ｍＡを使用した。放電過程終了後、再度電解液を注入して同様の放電過程を行い、合計で８回の放電過程を実施した。これら８回の放電過程で得られたクーロン量の総和を「放電量」として表１に示す。 (Measurement of discharge amount)
The magnesium-air battery was installed in a thermostatic chamber (temperature 25 ° C., relative humidity 30%). A 0.1 M NaCl aqueous solution was prepared as an electrolytic solution, and 0.1 mL of the NaCl aqueous solution was injected into the battery from the positive electrode electrolyte injection hole using a syringe. Immediately after injection, a discharge test was conducted at a constant current of 5 mA. As an evaluation apparatus, BLS5516-5V100 mA manufactured by Keiki Keiki Center Co., Ltd. was used. After completion of the discharge process, the electrolyte solution was injected again to perform the same discharge process, and a total of eight discharge processes were performed. Table 1 shows the total amount of coulombs obtained in these eight discharge processes as “discharge amount”.
［放電回数評価試験］
（負極の作製）
　合金鋳塊を厚み１ｍｍに圧延し、直径１４ｍｍに切り出し、負極を作製した。 [Discharge frequency evaluation test]
(Preparation of negative electrode)
The alloy ingot was rolled to a thickness of 1 mm, cut into a diameter of 14 mm, and a negative electrode was produced.
（正極の作製）
　０．２ｇのカーボンブラック（デンカ株式会社製デンカブラック）と、０．０６７ｇの６０％ポリテトラフルオロエチレン液（ＡＧＣ　Ｃｈｅｍｉｃａｌｓ製Ｆｌｕｏｎ　ＡＤ－９１１Ｌ）とを秤量し、溶媒として１０ｍＬの純水を加え、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１３０℃に加熱したホットプレート上で３時間以上乾燥し、２７０℃で３時間焼成した。得られた焼成体を６４ＭＰａで３０秒間プレスして、正極を作製した。なお、正極の厚みは１５０μｍであった。 (Preparation of positive electrode)
0.2 g of carbon black (Denka Black manufactured by Denka Co., Ltd.) and 0.067 g of 60% polytetrafluoroethylene liquid (Fluon AD-911L manufactured by AGC Chemicals) were weighed, and 10 mL of pure water was added as a solvent. A catalyst slurry was prepared by mixing for 2 hours. 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 foamed nickel thus coated with the catalyst slurry was dried for 3 hours or more on a hot plate heated to 130 ° C. and calcined at 270 ° C. for 3 hours. The obtained fired body was pressed at 64 MPa for 30 seconds to produce a positive electrode. The positive electrode had a thickness of 150 μm.
（マグネシウム空気電池の作製）
　５０ｍＬガラス瓶（ＵＭサンプル瓶）の蓋に２箇所穴をあけ、それぞれの穴にクリップ付きリード線を通して固定した。一方のクリップに上記正極を接続し、他方のクリップに上記負極を接続し、正極と負極が同じ高さになるよう調整した。ガラス瓶に１０ｗｔ％ＮａＣｌ水溶液を入れ、正極及び負極を接続したクリップ付きの蓋を閉め、マグネシウム空気電池を作製した。ここで、ＮａＣｌ水溶液の量は、正極及び負極の下半分がＮａＣｌ水溶液に浸漬され、クリップとの接続部分がＮａＣｌ水溶液に触れないように調整した。クリップと負極の接続部分がＮａＣｌ水溶液に浸された場合、接続部分で電流集中が生じて腐食が進行するため、正確な評価ができない。 (Production of magnesium air battery)
Two holes were made in the lid of a 50 mL glass bottle (UM sample bottle), and a lead wire with a clip was fixed to each hole. The positive electrode was connected to one clip, the negative electrode was connected to the other clip, and the positive electrode and the negative electrode were adjusted to have the same height. A 10 wt% NaCl aqueous solution was placed in a glass bottle, the lid with a clip connecting the positive electrode and the negative electrode was closed, and a magnesium-air battery was produced. Here, the amount of the NaCl aqueous solution was adjusted so that the lower half of the positive electrode and the negative electrode was immersed in the NaCl aqueous solution, and the connection portion with the clip did not touch the NaCl aqueous solution. When the clip and the negative electrode connection part are immersed in an aqueous NaCl solution, current concentration occurs in the connection part and corrosion proceeds, so accurate evaluation cannot be performed.
（放電回数の測定）
　上記マグネシウム空気電池を恒温槽（温度２５℃）内に設置し、１０ｍＡ定電流にて５分間放電させた後、３０分間休止した。この放電及び休止を放電できなくなるまで繰り返し、放電が可能な繰り返し回数を測定した。この回数を「放電回数」として表１に示す。評価装置としては株式会社計測器センター製ＢＬＳ５５１６－５Ｖ１００ｍＡを用いた。 (Measurement of the number of discharges)
The magnesium-air battery was placed in a thermostatic chamber (temperature: 25 ° C.), discharged at a constant current of 10 mA for 5 minutes, and then rested for 30 minutes. This discharge and rest were repeated until no discharge was possible, and the number of repetitions at which discharge was possible was measured. This number is shown in Table 1 as “the number of discharges”. As an evaluation apparatus, BLS5516-5V100 mA manufactured by Keiki Keiki Center Co., Ltd. was used.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示すように、比較例１～３では既に知られているマグネシウム－アルミニウム－亜鉛合金を使用し、比較例４では上記特許文献２が開示しているＬＺ９１を使用し、比較例５及び６ではＬｉ含有割合が低くα単相構造を有する合金を使用した結果、放電量は非常に少なかった。これに対し、実施例１～４では、各元素の組成比を特定範囲内に制御した結果、非常に優れた放電量を示すマグネシウム空気電池が得られた。 As shown in Table 1, in Comparative Examples 1 to 3, a known magnesium-aluminum-zinc alloy was used, and in Comparative Example 4, LZ91 disclosed in Patent Document 2 was used. In No. 6, as a result of using an alloy having a low Li content and an α single phase structure, the amount of discharge was very small. On the other hand, in Examples 1 to 4, the composition ratio of each element was controlled within a specific range, and as a result, magnesium-air batteries showing a very excellent discharge amount were obtained.
　特に、比較例４の結果より、Ｌｉ含有割合が本発明の範囲内であっても、Ｒ及びＭｎの合計含有割合が本発明の範囲を外れていると、放電量を改善する効果は得られないことが分かる。また、比較例６の結果より、Ｒ及びＭｎの合計含有割合が本発明の範囲内であっても、Ｌｉ含有割合が本発明の範囲より低いと、放電量を改善する効果は得られないことが分かる。すなわち、本発明においては、Ｌｉ含有割合、Ｒ含有割合、Ｍｎ含有割合、並びにＲ及びＭｎの合計含有割合を全て特定範囲内に制御することによって、相乗的に顕著な放電量改善効果を奏する。 In particular, from the results of Comparative Example 4, even if the Li content is within the range of the present invention, if the total content of R and Mn is out of the range of the present invention, the effect of improving the discharge amount is obtained. I understand that there is no. Further, from the result of Comparative Example 6, even if the total content ratio of R and Mn is within the range of the present invention, if the Li content ratio is lower than the range of the present invention, the effect of improving the discharge amount cannot be obtained. I understand. That is, in the present invention, by controlling the Li content ratio, the R content ratio, the Mn content ratio, and the total content ratio of R and Mn all within a specific range, a remarkable discharge amount improvement effect is exhibited synergistically.
　放電回数評価試験では、実施例１～５のマグネシウム空気電池は十分な結果を示した。特に、ＲとＭｎを併用し、且つＲ及びＭｎの合計含有割合を０．０２質量％以上０．２５質量％以下とした実施例１及び５では、顕著に優れた結果が得られた。 In the discharge number evaluation test, the magnesium-air batteries of Examples 1 to 5 showed sufficient results. In particular, in Examples 1 and 5 in which R and Mn were used in combination, and the total content ratio of R and Mn was 0.02% by mass or more and 0.25% by mass or less, remarkable results were obtained.

Claims (5)

  1. 　６．００質量％以上１０．５０質量％以下のＬｉ、
    　０質量％以上１５．００質量％以下のＡｌ、
    　０質量％以上５．００質量％以下のＣａ、
    　０質量％以上３．００質量％以下のＺｎ、
    　０質量％以上３．００質量％以下のＲ、
    　０質量％以上２．００質量％以下のＭｎ、
    　０質量％以上０．１０質量％以下のＦｅ、
    　０質量％以上０．１０質量％以下のＣｕ、
    　０質量％以上０．１０質量％以下のＮｉ、並びに
    　残部のＭｇ及び不純物からなり、
    　前記ＲがＹ、Ｌａ、Ｃｅ、Ｎｄ、及びＧｄからなる群から選ばれる１種以上の希土類元素を表し、
    　前記Ｒ及びＭｎの合計の含有割合が０．０２質量％以上５．００質量％以下である、
    　空気電池負極用マグネシウム－リチウム合金。     6.00% by mass or more and 10.50% by mass or less of Li,
    Al of 0 mass% or more and 15.00 mass% or less,
    0 mass% or more and 5.00 mass% or less of Ca,
    Zn of 0 mass% or more and 3.00 mass% or less,
    0 mass% or more and 3.00 mass% or less of R,
    Mn from 0% by mass to 2.00% by mass,
    Fe of 0 mass% or more and 0.10 mass% or less,
    0 mass% or more and 0.10 mass% or less of Cu,
    Consisting of 0 mass% or more and 0.10 mass% or less of Ni, and the balance of Mg and impurities,
    R represents one or more rare earth elements selected from the group consisting of Y, La, Ce, Nd, and Gd;
    The total content of R and Mn is 0.02% by mass or more and 5.00% by mass or less.
    Magnesium-lithium alloy for air battery negative electrode.
  2. 　前記マグネシウム－リチウム合金を直径１４ｍｍ且つ厚さ１ｍｍの形状に加工して負極を作製し、カーボンブラック及びポリテトラフルオロエチレンを含む触媒合材を直径１４ｍｍの発泡ニッケルに担持させて触媒層を作製し、前記負極及び前記触媒層の下半分をＮａＣｌ水溶液に浸漬してマグネシウム空気電池を製造し、１０ｍＡ定電流にて５分間放電させた後に３０分間休止させる過程を放電できなくなるまで繰り返す放電回数評価試験において、放電回数が２０回以上である、請求項１に記載のマグネシウム－リチウム合金。 The magnesium-lithium alloy is processed into a shape having a diameter of 14 mm and a thickness of 1 mm to produce a negative electrode, and a catalyst mixture containing carbon black and polytetrafluoroethylene is supported on foamed nickel having a diameter of 14 mm to produce a catalyst layer. The negative electrode and the lower half of the catalyst layer are immersed in a NaCl aqueous solution to produce a magnesium-air battery, and the process of discharging for 5 minutes at a constant current of 10 mA and then resting for 30 minutes is repeated until the discharge cannot be performed. The magnesium-lithium alloy according to claim 1, wherein the number of discharges is 20 or more.
  3. 　前記マグネシウム－リチウム合金を直径１６ｍｍ且つ厚さ１ｍｍの形状に加工して負極を作製し、ＭｎＯ2、アセチレンブラック、及びポリフッ化ビニリデンを２：０．０５：０．１の質量比で含む触媒合材を直径１４ｍｍの発泡ニッケルに担持させて触媒層を作製し、前記負極及び前記触媒層を用いて直径２０ｍｍ且つ厚さ３．２ｍｍのマグネシウム空気電池を製造し、前記マグネシウム空気電池の内部に電解液としてＮａＣｌ水溶液を注入して５ｍＡ定電流にて放電させる放電過程を８回繰り返す放電量評価試験において、前記８回の放電過程で得られるクーロン量の総和が４５Ｃ以上である、請求項１又は２に記載のマグネシウム－リチウム合金。 A negative electrode is fabricated by processing the magnesium-lithium alloy into a shape having a diameter of 16 mm and a thickness of 1 mm, and a catalyst composition containing MnO 2 , acetylene black, and polyvinylidene fluoride in a mass ratio of 2: 0.05: 0.1. A catalyst layer is prepared by supporting the material on foamed nickel having a diameter of 14 mm, a magnesium air battery having a diameter of 20 mm and a thickness of 3.2 mm is manufactured using the negative electrode and the catalyst layer, and electrolysis is performed inside the magnesium air battery. In a discharge amount evaluation test in which a discharge process of injecting an NaCl aqueous solution as a liquid and discharging at a constant current of 5 mA is repeated 8 times, the total amount of coulombs obtained in the 8 discharge processes is 45C or more. 2. The magnesium-lithium alloy according to 2.
  4. 　請求項１～３のいずれかに記載のマグネシウム－リチウム合金を含む空気電池負極。 An air battery negative electrode comprising the magnesium-lithium alloy according to any one of claims 1 to 3.
  5. 　請求項４に記載の負極を有するマグネシウム空気電池。 A magnesium-air battery having the negative electrode according to claim 4.
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