WO2011111699A1 - Hydrogen storage alloy and nickel-hydrogen storage battery - Google Patents

Hydrogen storage alloy and nickel-hydrogen storage battery Download PDF

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Publication number
WO2011111699A1
WO2011111699A1 PCT/JP2011/055368 JP2011055368W WO2011111699A1 WO 2011111699 A1 WO2011111699 A1 WO 2011111699A1 JP 2011055368 W JP2011055368 W JP 2011055368W WO 2011111699 A1 WO2011111699 A1 WO 2011111699A1
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Prior art keywords
hydrogen storage
storage alloy
formula
atomic
nickel
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PCT/JP2011/055368
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French (fr)
Japanese (ja)
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尾崎　哲也
学 金本
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株式会社Ｇｓユアサ
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Priority to JP2012504473A priority Critical patent/JP5796787B2/en
Publication of WO2011111699A1 publication Critical patent/WO2011111699A1/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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/34—Gastight accumulators
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/0005—Reversible uptake of hydrogen by an appropriate medium, i.e. based on physical or chemical sorption phenomena or on reversible chemical reactions, e.g. for hydrogen storage purposes ; Reversible gettering of hydrogen; Reversible uptake of hydrogen by electrodes
    • C01B3/001—Reversible uptake of hydrogen by an appropriate medium, i.e. based on physical or chemical sorption phenomena or on reversible chemical reactions, e.g. for hydrogen storage purposes ; Reversible gettering of hydrogen; Reversible uptake of hydrogen by electrodes characterised by the uptaking medium; Treatment thereof
    • C01B3/0031—Intermetallic compounds; Metal alloys; Treatment thereof
    • C01B3/0047—Intermetallic compounds; Metal alloys; Treatment thereof containing a rare earth metal; Treatment thereof
    • C01B3/0057—Intermetallic compounds; Metal alloys; Treatment thereof containing a rare earth metal; Treatment thereof also containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/023—Alloys based on nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0433—Nickel- or cobalt-based alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/007—Alloys based on nickel or cobalt with a light metal (alkali metal Li, Na, K, Rb, Cs; earth alkali metal Be, Mg, Ca, Sr, Ba, Al Ga, Ge, Ti) or B, Si, Zr, Hf, Sc, Y, lanthanides, actinides, as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • 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
    • H01M4/383—Hydrogen absorbing alloys
    • 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
    • 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
    • Y02E60/30—Hydrogen technology
    • Y02E60/32—Hydrogen storage

Definitions

  • the present invention relates to a hydrogen storage alloy and a nickel metal hydride storage battery including a negative electrode including the hydrogen storage alloy.
  • Nickel metal hydride storage batteries have high energy density, so they are used as power sources for small electronic devices such as digital cameras and notebook computers, and because the operating voltage is equivalent to and compatible with primary batteries such as alkaline manganese batteries. As a substitute for the primary battery, the battery is widely used, and the demand for the battery is expanding dramatically.
  • This type of nickel-metal hydride storage battery is usually configured to include a nickel electrode containing a positive electrode active material mainly composed of nickel hydroxide, a negative electrode mainly composed of a hydrogen storage alloy, a separator, and an alkaline electrolyte.
  • the hydrogen storage alloy which is the main material of the negative electrode, has a significant effect on the performance of nickel-metal hydride storage batteries such as discharge capacity and energy density, and various hydrogen storage alloys have been studied in the past. Has been.
  • rare earth-Mg a hydrogen storage alloy containing rare earth elements, Mg, and Ni
  • rare earth-Mg an alloy that can exhibit a discharge capacity that exceeds the discharge capacity when using an AB 5 rare earth-Ni hydrogen storage alloy.
  • Ni-based hydrogen storage alloy has attracted attention.
  • a rare earth element, Mg, and a combination of Ni and various metals have been proposed (Patent Document 1).
  • rare earth-Mg—Ni-based hydrogen storage alloys for example, in order to increase the discharge capacity of a nickel-metal hydride storage battery equipped with a negative electrode containing the hydrogen storage alloy, the type and amount of the metal blended in the hydrogen storage alloy are changed. Adjustments are made. However, the specific gravity of such rare earth-Mg—Ni-based hydrogen storage alloys may decrease depending on the type and amount of metal mixed in the hydrogen storage alloy, and the energy density of the battery cannot necessarily be increased.
  • the conventional rare earth-Mg-Ni-based hydrogen storage alloy has a relatively high specific gravity, so that the energy density of the battery can be made excellent, and the discharge capacity of the nickel-metal hydride storage battery is compared. There is a problem that it is not always possible to satisfy the high level.
  • the present invention is a hydrogen storage alloy that can be included in the negative electrode of a nickel-metal hydride storage battery, the specific gravity of which is relatively high, and the energy density of the battery is excellent, and It is an object of the present invention to provide a hydrogen storage alloy that simultaneously satisfies that the discharge capacity of a nickel metal hydride storage battery is relatively high. Another object of the present invention is to provide a nickel metal hydride storage battery including a negative electrode containing the hydrogen storage alloy.
  • the hydrogen storage alloy according to the present invention has a chemical composition represented by the following general formula (1): R1v Mgw Cax R2y Formula (1)
  • R1 is one or more elements selected from rare earth elements
  • R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn.
  • Formula (2) v, w, x, and y are the following formulas (3), (4), and (5).
  • the formula (5) is preferably represented by 1.0 ⁇ w / x ⁇ 2.5. According to the hydrogen storage alloy in which the formula (5) is represented by 1.0 ⁇ w / x ⁇ 2.5, it is possible to more reliably obtain the performance that the battery has an excellent energy density and a relatively high discharge capacity. Can do.
  • the hydrogen storage alloy according to the present invention is one or more elements selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr, and Zn in which a part of Ni of R2 is substituted. Is preferably more than 0 atomic% and 2.2 atomic% or less. With this configuration, the capacity maintenance rate of the battery can be improved.
  • a part of Ni in R2 is substituted with Al and the Al content is more than 0 atomic% and not more than 2.2 atomic%. With this configuration, the capacity maintenance rate of the battery can be improved.
  • Ce as R1 is contained in an amount of 0 atomic% to 2.3 atomic%. With this configuration, the capacity maintenance rate of the battery can be improved.
  • the hydrogen absorbing alloy according to the present invention preferably contains a crystal phase having a Pr 5 Co 19 type crystal structure 11 mass% or more.
  • the hydrogen storage alloy according to the present invention has a chemical composition represented by the following general formula (1 ′), R1v Mgw Cax R2y R3z Formula (1 ')
  • R1 is one or more elements selected from rare earth elements
  • R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn.
  • a hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
  • v, w, x, and y 100
  • Formula (2) v, w, x, and y are the following formulas (3), (4), and (5).
  • Formula (4) 0.8 ⁇ w / x ⁇ 2.5 (5)
  • z satisfies 0 ⁇ z ⁇ 0.4.
  • the hydrogen storage alloy according to the present invention has a chemical composition represented by the following general formula (1 ′), R1v Mgw Cax R2y R3z Formula (1 ')
  • R1 is one or more elements selected from rare earth elements
  • R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn.
  • a hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
  • v + w + x + y 100
  • Formula (2) v, w, x, y satisfy 13.0 ⁇ v ⁇ 18.0, 2.2 ⁇ w ⁇ 5.6, 2.0 ⁇ x ⁇ 5.0, 75.0 ⁇ y ⁇ 80.0
  • Z satisfies 0 ⁇ z ⁇ 0.4
  • w and x satisfy 0.8 ⁇ w / x ⁇ 2.5.
  • the nickel-metal hydride storage battery according to the present invention includes a negative electrode containing the hydrogen storage alloy.
  • the hydrogen storage alloy according to the present invention can be included in the negative electrode of a nickel metal hydride storage battery, and can have an excellent battery energy density due to its relatively high specific gravity, and discharge of the nickel metal hydride storage battery There is an effect of satisfying simultaneously that the capacity is relatively high.
  • the hydrogen storage alloy of the embodiment of the present invention has a chemical composition represented by the following general formula (1): R1v Mgw Cax R2y Formula (1)
  • R1 is one or more elements selected from rare earth elements
  • R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn.
  • Formula (2) v, w, x, and y are the following formulas (3), (4), and (5).
  • the hydrogen storage alloy of the embodiment of the present invention has a chemical composition represented by the following general formula (1 ′), R1v Mgw Cax R2y R3z Formula (1 ')
  • R1 is one or more elements selected from rare earth elements
  • R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn.
  • a hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
  • v, w, x, and y 100
  • Formula (2) v, w, x, and y are the following formulas (3), (4), and (5).
  • Formula (4) 0.8 ⁇ w / x ⁇ 2.5 (5)
  • z satisfies 0 ⁇ z ⁇ 0.4.
  • the hydrogen storage alloy contains rare earth elements, Mg, and Ni, and further Ca.
  • the number of Ni atoms is more than three times the total number of rare earth elements, Mg atoms, and Ca atoms. Greatly less than 5 times.
  • the number of Ni atoms is 3.4 times or more and 3.7 times or less of the total of the number of rare earth elements, the number of Mg atoms, and the number of Ca atoms. That is, the so-called B / A ratio is usually more than 3 and less than 5, preferably 3.4 or more and 3.7 or less.
  • A represents any element selected from the group consisting of rare earth elements and Mg
  • B represents any element selected from the group consisting of transition metal elements and Al.
  • a in the B / A ratio of the hydrogen storage alloy represents an element selected from the group consisting of rare earth elements such as La, Sm, Pr, and Nd, Mg, and Ca, and B represents Ni, It represents one or more elements selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn.
  • R1 is preferably one or more elements selected from the group consisting of La, Ce, Pr, Nd, Sm, and Y. More preferably, the element contains at least La or Nd.
  • the hydrogen storage alloy preferably contains 2.3 atomic% or less of Ce.
  • Ce is contained in an amount of 2.3 atomic% or less, there is an advantage that the cycle characteristics of the battery and the capacity retention rate of the battery can be further improved.
  • atomic% refers to the percentage of the number of specific atoms with respect to the total number of atoms present. Therefore, for example, an alloy containing 1 atomic% of calcium contains one calcium atom out of 100 atoms of the alloy.
  • R2 is preferably Ni or a part of Ni substituted by Al or Co, and is Ni or a part of Ni. More preferably, is substituted with Al.
  • the hydrogen storage alloy preferably contains more than 0 atomic% and 2.2 atomic% or less of elements other than Ni in the R2. With this configuration, the capacity maintenance rate of the battery can be improved.
  • an element other than Ni in R2 is Al, and the Al content is more than 0 atomic% and not more than 2.2 atomic%. More preferably, R2 is Ni without containing Al.
  • the hydrogen storage alloy can surely improve the energy density of the battery and can surely improve the discharge capacity of the battery. 3 is preferable, and z ⁇ 0.2 is more preferable.
  • z is very close to 0, that is, the chemical composition is substantially the same as that represented by the general formula (1).
  • z 0, that is, the chemical composition is represented by the general formula (1).
  • the hydrogen storage alloy is provided with two or more crystal phases having different crystal structures, and preferably these two or more crystal phases are laminated in the c-axis direction of the crystal structure.
  • the crystal phase include a crystal phase composed of a rhombohedral La 5 MgNi 24 type crystal structure (hereinafter also simply referred to as La 5 MgNi 24 phase), and a crystal phase composed of a hexagonal Pr 5 Co 19 type crystal structure (hereinafter simply referred to as simply “La 5 MgNi 24 phase”).
  • Pr 5 Co 19 phase crystal phase composed of rhombohedral Ce 5 Co 19 type crystal structure (hereinafter also simply referred to as Ce 5 Co 19 phase), crystal phase composed of hexagonal Ce 2 Ni 7 type crystal structure (Hereinafter also simply referred to as Ce 2 Ni 7 phase), crystal phase composed of rhombohedral Gd 2 Co 7 type crystal structure (hereinafter also simply referred to as Gd 2 Co 7 phase), and hexagonal CaCu 5 type crystal structure crystalline phase (hereinafter, simply referred to as CaCu 5 phase), crystal phase comprising a cubic AuBe 5 type crystal structure (hereinafter, simply referred to as AuBe 5 phase) crystal phase comprising a rhombohedral PuNi 3 type crystal structure Hereinafter also referred to simply as PuNi 3-phase), and the like.
  • Ce 5 Co 19 phase crystal phase composed of hexagonal Ce 2 Ni 7 type crystal structure (Hereinafter also simply referred to as Ce 2 Ni 7 phase)
  • La 5 MgNi 24 phase, Pr 5 Co 19 phase, Ce 5 Co 19 phase, and the hydrogen storage alloy having two or more selected from the group consisting of Ce 2 Ni 7 phase is preferably used.
  • the hydrogen storage alloy having these crystal phases has excellent characteristics that the difference between the expansion and contraction ratios between the crystal phases is small, so that the distortion is not easily generated and the deterioration is not easily caused by repeated storage and release of hydrogen.
  • the hydrogen storage alloy is formed by laminating two or more crystal phases having different crystal structures in the c-axis direction of the crystal structure, distortion of the crystal phase when hydrogen is stored by charging is adjacent to the hydrogen storage alloy. Can be relaxed by other crystalline phases. Therefore, the inclusion of the hydrogen storage alloy has the advantage that the negative electrode is less likely to be pulverized and is less likely to deteriorate even if the storage and release of hydrogen are repeated by charging and discharging.
  • the La 5 MgNi 24 type crystal structure is a crystal structure in which 4 units of AB 5 units are inserted between A 2 B 4 units, and the Pr 5 Co 19 type crystal structure is A 2 B It is a crystal structure in which 3 units of AB 5 units are inserted between 4 units, and Ce 5 Co 19 type crystal structure is that 3 units of AB 5 units are inserted between 4 units of A 2 B 4 It is a crystal structure, and the Ce 2 Ni 7 type crystal structure is a crystal structure in which two AB 5 units are inserted between A 2 B 4 units. What is the Gd 2 Co 7 type crystal structure? , 2 units of AB 5 units are inserted between A 2 B 4 units, and the AuBe 5 type crystal structure is a crystal structure composed of only A 2 B 4 units.
  • the A 2 B 4 unit is a structural unit having a hexagonal MgZn 2 type crystal structure (C14 structure) or a hexagonal MgCu 2 type crystal structure (C15 structure), and the AB 5 unit is a hexagonal CaCu 5 It is a structural unit with a type crystal structure.
  • the stacking order of the crystal phases is not particularly limited, and a combination of specific crystal phases may be stacked with repeating periodicity.
  • the phase may be laminated randomly and without periodicity.
  • each crystal phase is not particularly limited, but the content of the crystal phase having the La 5 MgNi 24 type crystal structure is 0 to 50% by mass, and the Pr 5 Co 19 type crystal structure.
  • the rate is preferably 0 to 65% by mass.
  • the hydrogen storage alloy preferably contains 11 to 73% by mass, more preferably 37 to 73% by mass, of a crystal phase having a Pr 5 Co 19 type crystal structure containing Ca.
  • the crystal phase having each crystal structure can be identified by performing X-ray diffraction measurement on the ground alloy powder and analyzing the obtained X-ray diffraction pattern by the Rietveld method. Moreover, the content rate of the crystal phase which has each crystal structure is determined by the method described in the Example.
  • the denominator on the left side of the above formula (3) is A for all the number of sites in the hydrogen storage alloy obtained based on the fact that the hydrogen storage alloy is composed of A 2 B 4 units and AB 5 units.
  • 2 B Indicates the ratio of the number of A sites in 4 units. That is, the denominator on the left side of the formula (3) represents the number of A sites of A 2 B 4 units when the total number of sites in the hydrogen storage alloy represented by the chemical composition of the formula (1) is represented by v + w + x + y. . In detail, it is calculated
  • the number of sites where the A side element is arranged is represented by v + w + x with respect to the number of all sites represented by v + w + x + y in the crystal of the hydrogen storage alloy, and the number of sites where the B side element is arranged is y It is represented by On the other hand, the ratio of the number of AB 5 units to the number of A 2 B 4 units k, i.e., the ratio between the A 2 B 4 units and AB 5 units 1: When k, site A side element is arranged The number can also be expressed as (2 + k) ⁇ n. The number of sites where the B-side element is arranged can also be expressed as (4 + 5k) ⁇ n.
  • n means the number of crystal units when one A 2 B 4 unit and k AB 5 units are crystal units. From the above relationship, the following equation (A) can be obtained.
  • k can be represented by the following formula (C) by modifying the formula (B).
  • the number of A sites of A 2 B 4 units when the number of all sites is represented by v + w + x + y is represented by the following formula (D). That is, since the the AB 5 units against A 2 B 4 units 1 exists k, the total number of A site is represented by (2 + k) ⁇ n, the number of A-site in A 2 B 4 units is represented by 2n The The total number of A sites is also expressed as v + w + x. Therefore, the number of A sites of A 2 B 4 units when the total number of sites is represented by v + w + x + y is represented by the following formula (D).
  • the denominator of the left side of Formula (3) can be obtained by substituting Formula (E) and Formula (F) into Formula (D).
  • the value of the left side of the above formula (3) exceeds 0.8, that is, when the ratio of Ca and Mg to the ratio of A site in the A 2 B 4 unit exceeds 0.8, it is clear However, it is considered that Ca and Mg are difficult to enter the A site of the A 2 B 4 unit, and Ca is arranged at the A site of the AB 5 unit. As a result, the crystal lattice may expand and the specific gravity of the alloy may be reduced.
  • the value on the left side of the above formula (3) is preferably more than 0, more preferably 0.4 or more, further preferably 0.5 or more, and most preferably 0.6 or more. preferable.
  • Mg can be arranged at the A site of the A 2 B 4 unit, but is not arranged at the A site of the AB 5 unit, and is considered to segregate when it cannot enter the A site of the A 2 B 4 unit.
  • the hydrogen storage alloy when the above formula (4) is not satisfied, that is, when x is less than 2.0, the discharge capacity of the nickel-metal hydride storage battery including the negative electrode including the hydrogen storage alloy becomes insufficient. If x exceeds 5.0, the specific gravity of the hydrogen storage alloy may not be sufficiently large.
  • x is preferably a number satisfying 2.2 ⁇ x, more preferably a number satisfying 2.3 ⁇ x, further preferably a number satisfying 2.8 ⁇ x. Most preferred is a number satisfying 1 ⁇ x. Further, x is preferably a number that satisfies x ⁇ 4.7, more preferably a number that satisfies x ⁇ 4.4, and even more preferably a number that satisfies x ⁇ 4.1. When x is 2.2 or more, there is an advantage that the discharge capacity of the battery can be improved, and when it is 4.7 or less, the specific gravity of the hydrogen storage alloy can be increased. There are advantages.
  • w is preferably a number satisfying 2.2 ⁇ w, and more preferably a number satisfying 3.3 ⁇ w. Moreover, it is preferable that it is a number which satisfy
  • fills w ⁇ 5.6, and it is more preferable that it is a number which satisfy
  • fills w ⁇ 4.7.
  • w is 2.2 or more, there is an advantage that the specific gravity of the hydrogen storage alloy can be larger, and when w is 5.6 or less, the discharge capacity of the battery becomes better. There is an advantage of getting.
  • w / x is less than 0.8, that is, the ratio of Mg to Ca is less than 0.8, or w / x is If it exceeds 2.5, the specific gravity of the hydrogen storage alloy may not be sufficiently large.
  • w / x is a number satisfying 1.0 ⁇ w / x.
  • fills w / x ⁇ 2.0.
  • v is preferably a number satisfying 13.0 ⁇ v ⁇ 18.0, and is a number satisfying 14.0 ⁇ v ⁇ 17.0. It is more preferable.
  • y is preferably a number satisfying 75.0 ⁇ y ⁇ 80.0, and a number satisfying 77.0 ⁇ y ⁇ 79.0. It is more preferable that
  • the hydrogen storage alloy according to another embodiment has a chemical composition represented by the following general formula (1 ′): R1v Mgw Cax R2y R3z Formula (1 ')
  • R1 is one or more elements selected from rare earth elements
  • R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn.
  • a hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
  • v + w + x + y 100
  • Formula (2) v, w, x, y satisfy 13.0 ⁇ v ⁇ 18.0, 2.2 ⁇ w ⁇ 5.6, 2.0 ⁇ x ⁇ 5.0, 75.0 ⁇ y ⁇ 80.0
  • Z satisfies 0 ⁇ z ⁇ 0.4
  • w and x satisfy 0.8 ⁇ w / x ⁇ 2.5.
  • the structure similar to the hydrogen storage alloy of embodiment mentioned above is employable.
  • the hydrogen storage alloy preferably has a hydrogen equilibrium pressure of 0.07 MPa or less.
  • Conventional hydrogen storage alloys have the property that they do not absorb hydrogen easily when the hydrogen equilibrium pressure is high and easily release the absorbed hydrogen. When the high-rate characteristics of the hydrogen storage alloy are improved, hydrogen self-releases. It is easy to do. However, it is a rare earth-Mg-Ni-based hydrogen storage alloy in which two or more crystal phases having different crystal structures are laminated, and particularly when the content of the crystal phase having a CaCu 5 type crystal structure is 15% by mass or less. In some hydrogen storage alloys, good high rate characteristics can be obtained even when the hydrogen equilibrium pressure is set to a low value of 0.07 MPa or less.
  • a nickel metal hydride battery using the hydrogen storage alloy as a negative electrode has excellent high rate characteristics and Hydrogen self-release (self-discharge in a battery) is unlikely to occur. This is considered to be because the diffusibility of hydrogen in the alloy was improved.
  • a cooling process for solidifying, an annealing process for annealing the cooled alloy in a pressurized inert gas atmosphere in a temperature range of 860 ° C. to 1000 ° C., and a pulverizing process for pulverizing the alloy are performed.
  • a predetermined amount of raw material ingot is weighed based on the chemical composition of the target hydrogen storage alloy.
  • the alloy raw material is put in a crucible and heated to, for example, 1200 ° C. or higher and 1600 ° C. or lower in an inert gas atmosphere or in a vacuum to melt the alloy raw material.
  • the cooling rate is preferably 1000 K / second or more (also called rapid cooling). By rapidly cooling at 1000 K / second or more, there is an effect that the alloy composition is refined and homogenized.
  • the cooling rate can be set in a range of 1000000 K / second or less.
  • a melt spinning method having a cooling rate of 100,000 K / sec or more, a gas atomizing method having a cooling rate of about 10,000 K / sec, or the like can be suitably used.
  • heating is performed at 860 ° C. or higher and 1000 ° C. or lower using, for example, an electric furnace in a pressurized state under an inert gas atmosphere.
  • the pressurizing condition is preferably 0.2 MPa (gauge pressure) or more and 1.0 MPa (gauge pressure) or less.
  • the processing time in this annealing process shall be 3 hours or more and 50 hours or less.
  • the pulverization step may be performed either before or after annealing, but since the surface area is increased by pulverization, it is desirable to perform the pulverization step after the annealing step from the viewpoint of preventing surface oxidation of the alloy.
  • the pulverization is preferably performed in an inert atmosphere to prevent oxidation of the alloy surface.
  • the pulverization means for example, mechanical pulverization, hydrogenation pulverization, or the like is used, and it is preferable that the particle size of the hydrogen storage alloy particles after pulverization is approximately 20 to 70 [ ⁇ m].
  • the nickel-metal hydride storage battery according to this embodiment includes a negative electrode containing the above-described hydrogen storage alloy as a hydrogen storage medium. That is, it is a nickel metal hydride storage battery provided with the negative electrode containing the hydrogen storage alloy mentioned above. Since the nickel-metal hydride storage battery of the present embodiment includes the hydrogen storage alloy in the negative electrode, the specific gravity of the hydrogen storage alloy is relatively high, the battery energy density is relatively high, and the discharge capacity of the battery is high. It can be relatively expensive.
  • the nickel metal hydride storage battery of the present embodiment includes a negative electrode mainly composed of the above-described hydrogen storage alloy, and further includes, for example, a positive electrode (nickel electrode) including a positive electrode active material mainly composed of nickel hydroxide, a separator, And an alkaline electrolyte.
  • a positive electrode nickel electrode
  • the negative electrode include those in which the hydrogen storage alloy powder is mixed with a conductive agent, a binder, a thickener, or the like, and pressed into a predetermined shape.
  • the nickel hydroxide composite which has nickel hydroxide as a main component and zinc hydroxide and cobalt hydroxide are mixed.
  • the positive electrode containing an oxide as a positive electrode active material is mentioned, Preferably, the positive electrode containing this nickel hydroxide complex oxide uniformly disperse
  • additives other than the nickel hydroxide composite oxide cobalt hydroxide, cobalt oxide and the like as a conductive modifier can be used, and the nickel hydroxide composite oxide is coated with cobalt hydroxide.
  • the positive electrode may contain a conductive agent, a binder, a thickener, and the like as other components in addition to the main components as described above.
  • the conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance.
  • natural graphite such as scaly graphite, scaly graphite, earthy graphite
  • artificial graphite carbon black, acetylene black
  • examples thereof include ketjen black, carbon whisker, carbon fiber, vapor-grown carbon, metal (nickel, gold, etc.) powder, one kind of conductive material such as metal fiber, or a mixture of two or more kinds.
  • ketjen black carbon whisker, carbon fiber, vapor-grown carbon, metal (nickel, gold, etc.) powder
  • one kind of conductive material such as metal fiber, or a mixture of two or more kinds.
  • a method of mixing them a method that can be as uniform as possible is preferable.
  • a powder mixer such as a V-type mixer, an S-type mixer, a grinder, a ball mill, a planetary ball mill, or the like may be dry or wet.
  • the method used in the above can be adopted.
  • the binder is usually a thermoplastic resin such as polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoro rubber.
  • PTFE polytetrafluoroethylene
  • EPDM ethylene-propylene-diene terpolymer
  • SBR styrene butadiene rubber
  • fluoro rubber examples thereof include a single type of polymer having rubber elasticity such as a single type or a mixture of two or more types.
  • the addition amount of the binder is preferably 0.1 to 3% by mass with respect to the total amount of the positive electrode or the negative electrode.
  • the thickener include one kind of a polysaccharide such as carboxymethylcellulose, methylcellulose, and xanthan gum, or a mixture of two or more kinds.
  • the addition amount of the thickener is preferably 0.1 to 0.3% by mass with respect to the total amount of the positive electrode or the negative electrode.
  • the positive electrode and the negative electrode are prepared by mixing the active material, the conductive agent, and the binder in an organic solvent such as water, alcohol, and toluene, and then applying the obtained mixed liquid onto a current collector and drying it.
  • an organic solvent such as water, alcohol, and toluene
  • a method of applying an arbitrary thickness and an arbitrary shape using means such as roller coating such as an applicator roll, screen coating, blade coating, spin coating, and per coating is preferable. It is not limited to.
  • an electron conductor that does not adversely affect the exchange of electrons with the active material in the battery that is configured can be used without any particular limitation.
  • the current collector include those made of nickel or nickel-plated steel plate as a material from the viewpoint of reduction resistance and oxidation resistance.
  • the shape of the current collector include a foam, a molded product of a fiber group, a three-dimensional base material subjected to uneven processing, or a two-dimensional base material such as a punching plate.
  • the thickness of the current collector is not particularly limited, and is usually 5 to 700 ⁇ m.
  • the positive electrode those made of nickel having excellent corrosion resistance and oxidation resistance to alkali and having a porous structure having a structure excellent in current collection are preferable.
  • a punching plate obtained by nickel plating on an iron foil that is inexpensive and excellent in conductivity is preferable.
  • the punching diameter is preferably 2.0 mm or less, and the opening ratio is preferably 40% or more. This makes it possible to improve the adhesion between the negative electrode active material and the current collector even with a small amount of binder.
  • the separator of the nickel metal hydride storage battery is preferably composed of a porous film or a nonwoven fabric exhibiting excellent rate characteristics alone or in combination of two or more.
  • the material constituting the separator include polyolefin resins such as polyethylene and polypropylene, and nylon.
  • the basis weight of the separator is preferably 40 g / m 2 to 100 g / m 2 . If it is less than 40 g / m 2 , the short circuit and the self-discharge performance may be deteriorated, and if it exceeds 100 g / m 2 , the ratio of the separator per unit volume increases, so the battery capacity tends to decrease.
  • the air permeability of the separator is preferably 1 cm / sec to 50 cm / sec. If it is less than 1 cm / sec, the internal pressure of the battery may increase, and if it exceeds 50 cm / sec, the short circuit and the self-discharge performance may be deteriorated.
  • the average fiber diameter of the separator is preferably 1 ⁇ m to 20 ⁇ m. When the thickness is less than 1 ⁇ m, the strength of the separator decreases, and the defect rate in the battery assembly process may increase. When the thickness exceeds 20 ⁇ m, the short circuit and the self-discharge performance may decrease. Further, the separator is preferably subjected to a hydrophilic treatment.
  • separator examples include those obtained by subjecting the surface of a polyolefin resin fiber such as polypropylene to a sulfonation treatment, a corona treatment, a fluorine gas treatment, a plasma treatment, or a mixture of those already subjected to these treatments. .
  • separators that have been sulfonated have a high ability to adsorb impurities such as NO 3 ⁇ , NO 2 ⁇ , and NH 3 ⁇ that cause the shuttle phenomenon and elements eluted from the negative electrode. ,preferable.
  • the alkaline electrolyte constituting the nickel metal hydride storage battery preferably contains at least one of sodium ion, potassium ion and lithium ion, and the total ion concentration is 9.0 mol / liter or less, and the total ion concentration is What is 5.0-8.0 mol / liter is still more preferable.
  • additives may be added to the electrolytic solution in order to improve the corrosion resistance of the alloy, improve the overvoltage at the positive electrode, improve the corrosion resistance of the negative electrode, and improve self-discharge.
  • the additive include oxides such as yttrium, ytterbium, erbium, calcium, and zinc, one kind of a hydroxide or the like, or a mixture of two or more kinds.
  • the nickel-metal hydride storage battery of this embodiment is an open-type nickel-metal hydride storage battery
  • the battery sandwiches the negative electrode with the positive electrode via a separator and fixes these electrodes so that a predetermined pressure is applied to these electrodes. Then, an electrolytic solution made of an aqueous solution containing KOH and LiOH is injected, and an open cell is assembled.
  • the nickel metal hydride storage battery of this embodiment is a sealed nickel metal hydride storage battery
  • the battery is injected with the electrolyte before or after the positive electrode, the separator, and the negative electrode are stacked, and is sealed with an exterior material.
  • the electrolyte is injected into the power generation element before or after winding.
  • an injection method it is possible to inject at normal pressure, but a vacuum impregnation method, a pressure impregnation method, and a centrifugal impregnation method can also be used.
  • examples of the material for the outer package of the sealed nickel-metal hydride storage battery include nickel-plated iron, stainless steel, polyolefin resin, and the like.
  • the configuration of the sealed nickel-metal hydride storage battery is not particularly limited, and batteries including a positive electrode, a negative electrode, and a single-layer or multi-layer separator, such as a coin battery, a button battery, a square battery, a flat battery, Alternatively, a cylindrical battery having a roll-shaped positive electrode, a negative electrode, and a separator can be given.
  • the present invention is not limited to the above exemplified hydrogen storage alloy and the above exemplified nickel metal hydride storage battery. That is, various forms used in a general hydrogen storage alloy can be adopted as long as the effects of the present invention are not impaired. Moreover, the various aspects used in a general nickel hydride storage battery can be employ
  • the hydrogen storage alloy whose chemical composition is represented by the formula (1) is an element not defined by the general formula as long as the general formula is satisfied as long as the effect of the present invention is not impaired. Can be included.
  • the chemical composition of the hydrogen storage alloy containing an element not defined by the formula (1) can also be represented by the formula (1 ′).
  • the content of R3 in the formula (1 ′) is an amount that does not impair the effects of the present invention. That is, it is proved that the effect of the present invention is not impaired if z defining the amount of R3 in the formula (1 ′) satisfies z ⁇ 0.4.
  • the reason why the R3 element is contained in the hydrogen storage alloy is that impurities are contained in the raw material ingot. Therefore, the amount of R3 in the hydrogen storage alloy can be controlled by controlling the purity of the raw material ingot.
  • Example 1 An open-type nickel metal hydride storage battery was produced by the method described below. Preparation of hydrogen storage alloy A predetermined amount of raw material ingot was weighed into a crucible so that the chemical composition would be Example 1 of Table 1, and heated to 1500 ° C. using a high frequency melting furnace in a reduced pressure argon gas atmosphere. Melted. After melting, it was quenched by applying a melt spinning method to solidify the alloy. Next, after heat-treating the obtained alloy at 910 ° C. in an argon gas atmosphere pressurized to 0.2 MPa (gauge pressure, the same applies hereinafter), the obtained hydrogen storage alloy was pulverized and averaged A hydrogen storage alloy powder having a particle size (D 50 ) of 20 ⁇ m was obtained.
  • D 50 particle size
  • An open-type nickel-metal hydride storage battery was manufactured by using the hydrogen storage alloy powder for the negative electrode. Specifically, after adding 3 parts by weight of nickel powder (INCO, # 210) to 100 parts by weight of the hydrogen storage alloy powder obtained as described above, the thickener (methylcellulose) is dissolved. After adding the prepared aqueous solution and further adding 1.5 parts by weight of a binder (styrene butadiene rubber) to a paste, it was applied to both sides of a 45 ⁇ m-thick perforated steel sheet (opening ratio 60%) and dried. , Pressed to a thickness of 0.36 mm to obtain a negative electrode.
  • nickel powder INCO, # 210
  • the thickener methylcellulose
  • a binder styrene butadiene rubber
  • the positive electrode an excess capacity sintered nickel hydroxide electrode was used.
  • an electrode was manufactured as prepared above open type battery sandwiched between the positive electrode through the separator, it is bolted to a pressure of 1 kgf / cm 2 to these electrodes such, assembled into open type cell.
  • the electrolytic solution a mixed solution composed of a 6.8 mol / L KOH solution and a 0.8 mol / L LiOH solution was used.
  • Nickel-metal hydride storage batteries were produced in the same manner as in Example 1 except that the compositions of the hydrogen storage alloys were changed to those shown in Examples 2 to 15 in Table 1.
  • ⁇ Content of crystal phase in hydrogen storage alloy> The hydrogen storage alloy powders obtained in each example and each comparative example were measured by X-ray diffraction, and further analyzed by the Rietveld method to identify the crystal structure contained in the hydrogen storage alloy. As a result, a crystal phase having a Pr 5 Co 19 type crystal structure, a crystal phase having a Ce 2 Ni 7 type crystal structure, and a crystal phase having a Gd 2 Co 7 type crystal structure were identified. Also, measure factor of each phase obtained from the Rietveld analysis, the unit cell volume, formula number, by using a chemical formula weight to determine the content of the crystal phase having a Pr 5 Co 19 type crystal structure. Table 1 shows the results of the hydrogen storage alloys of the examples and comparative examples.
  • ⁇ Nickel metal hydride storage capacity maintenance rate Using each of the produced nickel metal hydride storage batteries, charging in a water bath at 20 ° C. under a condition of 150% at 0.1 It (A), and a stop potential of ⁇ 0.6 V (vs Hg / v) at 0.2 It (A) Charging / discharging was repeated 50 cycles, with the discharge under the condition of HgO) as one cycle. Then, the discharge capacity at the 50th cycle with respect to the discharge capacity at the 1st cycle was obtained as a capacity retention rate.
  • ⁇ Discharge capacity of nickel metal hydride storage battery> The maximum discharge capacity of the nickel-metal hydride storage batteries produced in each Example and each Comparative Example was measured by the method described below. Using each produced nickel metal hydride storage battery, a charge / discharge test was performed under the following conditions. The charging conditions were constant current and constant voltage charging with a charging current of 0.1 ItmA and a charging time of 15 hours, and the discharging conditions were constant current discharging with a discharge current of 0.1 ItmA.
  • Table 1 shows the specific gravity of the hydrogen storage alloys produced in each example and each comparative example, the initial maximum discharge capacity measured in the charge / discharge test using each nickel metal hydride storage battery, and the capacity retention rate of the battery. As can be seen from Table 1, in the examples, specific gravity of 7.5 or more and maximum discharge capacity of 370 mAh / g or more can be achieved. In addition, Example 10 and Example 18 in which the Al content was 2.2 atomic% or less were significantly superior in capacity retention compared to Example 19 in which the Al content was 3.3 atomic%. It is a thing.

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Abstract

Disclosed is a hydrogen storage alloy included in a negative electrode of a nickel-hydrogen storage battery. Specifically disclosed is a hydrogen storage alloy that simultaneously satisfies the conditions of superior energy density for the battery because of a comparatively high specific gravity for the hydrogen storage alloy and comparatively high discharge capacity for the nickel-hydrogen storage battery. Also disclosed is a nickel-hydrogen storage battery provided with a hydrogen storage alloy and negative electrode containing that hydrogen storage alloy wherein the chemical composition is represented by general formula (1). R1v Mgw Cax R2y (1). R1 is one or more elements selected from the rare earth elements. R2 is Ni or a hydrogen storage alloy wherein some Ni is substituted by one or more elements selected from a group composed of Al, Co, Cu, Mn, Fe, Cr and Zn. When v, w, x and y are set so as to satisfy formula (2), v, w, x and y for the disclosed hydrogen storage alloy and electrode containing that hydrogen storage alloy satisfy formula (3), formula (4) and formula (5). v+w+x+y=100 (2), 2.0≤x≤5.0 (4), 0.8≤w/x≤2.5 (5)

Description

水素吸蔵合金及びニッケル水素蓄電池Hydrogen storage alloy and nickel metal hydride storage battery
　本発明は、水素吸蔵合金及び該水素吸蔵合金を含む負極を備えたニッケル水素蓄電池に関する。 The present invention relates to a hydrogen storage alloy and a nickel metal hydride storage battery including a negative electrode including the hydrogen storage alloy.
　ニッケル水素蓄電池は、高エネルギー密度を有することから、デジタルカメラ、ノート型パソコン等の小型電子機器類の電源として、また、作動電圧がアルカリマンガン電池等の一次電池と同等で互換性があることから、該一次電池の代替として、広く利用されており、その需要は飛躍的に拡大している。 Nickel metal hydride storage batteries have high energy density, so they are used as power sources for small electronic devices such as digital cameras and notebook computers, and because the operating voltage is equivalent to and compatible with primary batteries such as alkaline manganese batteries. As a substitute for the primary battery, the battery is widely used, and the demand for the battery is expanding dramatically.
　この種のニッケル水素蓄電池は、通常、水酸化ニッケルを主成分とする正極活物質を含んでなるニッケル電極、水素吸蔵合金を主材料とする負極、セパレータ、及びアルカリ電解液を備えて構成されている。これらの電池構成材料のうち、特に、負極の主材料となる水素吸蔵合金は、放電容量やエネルギー密度といったニッケル水素蓄電池の性能に大きな影響を及ぼすものであり、従来、種々の水素吸蔵合金が検討されている。 This type of nickel-metal hydride storage battery is usually configured to include a nickel electrode containing a positive electrode active material mainly composed of nickel hydroxide, a negative electrode mainly composed of a hydrogen storage alloy, a separator, and an alkaline electrolyte. Yes. Among these battery constituent materials, the hydrogen storage alloy, which is the main material of the negative electrode, has a significant effect on the performance of nickel-metal hydride storage batteries such as discharge capacity and energy density, and various hydrogen storage alloys have been studied in the past. Has been.
　近年、ＡＢ５系希土類－Ｎｉ系の水素吸蔵合金を用いた場合の放電容量を上回る放電容量を示しうる合金として、希土類元素、Ｍｇ、およびＮｉを含んでいる水素吸蔵合金（以下、希土類－Ｍｇ－Ｎｉ系水素吸蔵合金ともいう）が注目されており、例えば、希土類元素、Ｍｇ、およびＮｉと各種の金属とを組み合わせてなるものなどが提案されている（特許文献１）。 In recent years, a hydrogen storage alloy containing rare earth elements, Mg, and Ni (hereinafter referred to as rare earth-Mg) is an alloy that can exhibit a discharge capacity that exceeds the discharge capacity when using an AB 5 rare earth-Ni hydrogen storage alloy. —Ni-based hydrogen storage alloy ”has attracted attention. For example, a rare earth element, Mg, and a combination of Ni and various metals have been proposed (Patent Document 1).
日本国特開平１１－３２３４６９号公報Japanese Unexamined Patent Publication No. 11-323469
　斯かる希土類－Ｍｇ－Ｎｉ系の水素吸蔵合金においては、例えば、その水素吸蔵合金を含む負極を備えたニッケル水素蓄電池の放電容量を上げるべく、水素吸蔵合金に配合される金属の種類や量を調整することなどがおこなわれている。しかしながら、斯かる希土類－Ｍｇ－Ｎｉ系の水素吸蔵合金は、水素吸蔵合金に配合する金属の種類や量によってその比重が低下することがあり、必ずしも電池のエネルギー密度を高め得るものではない。 In such rare earth-Mg—Ni-based hydrogen storage alloys, for example, in order to increase the discharge capacity of a nickel-metal hydride storage battery equipped with a negative electrode containing the hydrogen storage alloy, the type and amount of the metal blended in the hydrogen storage alloy are changed. Adjustments are made. However, the specific gravity of such rare earth-Mg—Ni-based hydrogen storage alloys may decrease depending on the type and amount of metal mixed in the hydrogen storage alloy, and the energy density of the battery cannot necessarily be increased.
　即ち、従来の希土類－Ｍｇ－Ｎｉ系の水素吸蔵合金においては、その比重が比較的高いものであることで電池のエネルギー密度を優れたものにし得ること、及び、ニッケル水素蓄電池の放電容量が比較的高いものであることを必ずしも同時に満たせないという問題がある。 In other words, the conventional rare earth-Mg-Ni-based hydrogen storage alloy has a relatively high specific gravity, so that the energy density of the battery can be made excellent, and the discharge capacity of the nickel-metal hydride storage battery is compared. There is a problem that it is not always possible to satisfy the high level.
　本発明は、上記の問題点等に鑑み、ニッケル水素蓄電池の負極に含まれ得る水素吸蔵合金であって、その比重が比較的高いことで電池のエネルギー密度が優れたものであること、及び、ニッケル水素蓄電池の放電容量が比較的高いものであることを同時に満足する水素吸蔵合金を提供することを課題とする。また、該水素貯蔵合金を含む負極を備えたニッケル水素蓄電池を提供することを課題とする。 In view of the above-described problems, the present invention is a hydrogen storage alloy that can be included in the negative electrode of a nickel-metal hydride storage battery, the specific gravity of which is relatively high, and the energy density of the battery is excellent, and It is an object of the present invention to provide a hydrogen storage alloy that simultaneously satisfies that the discharge capacity of a nickel metal hydride storage battery is relatively high. Another object of the present invention is to provide a nickel metal hydride storage battery including a negative electrode containing the hydrogen storage alloy.
　上記課題を解決すべく、本発明に係る水素吸蔵合金は、化学組成が、下記一般式（１）で表され、
　　　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y　　　　・・・式（１）
Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものである水素吸蔵合金であって、
　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
　ｖ，ｗ，ｘ，ｙが、下記の式（３）、式（４）、式（５）
Figure JPOXMLDOC01-appb-M000003
 　　　　２．０≦ｘ≦５．０　　　　　　　　・・・式（４）
　　　　０．８≦　ｗ／ｘ　≦２．５　　　　・・・式（５）
を満たすことを特徴とする。
　化学組成が上記一般式（１）で表される前記水素吸蔵合金においては、式（２）を満たすｖ，ｗ，ｘ，ｙが、上記式（３）、式（４）、及び式（５）を同時に満たす。そして、水素吸蔵合金を構成する結晶相に含まれるＡ２Ｂ４ユニットのＡサイトにＣａ及びＭｇが配置されることにより、Ａ２Ｂ４ユニットのＡサイトに配置されたＣａによって結晶格子の膨張が引き起こされ得る。ところが、明確にその作用原理が解明されているわけではないが、Ａ２Ｂ４ユニットのＡサイトに配置されたＭｇによって結晶格子の一部が収縮し、その分、合金全体における結晶格子の膨張が抑制されるものと考えられる。従って、合金の比重が小さくなることが抑制され得る。 In order to solve the above problems, the hydrogen storage alloy according to the present invention has a chemical composition represented by the following general formula (1):
R1v Mgw Cax R2y Formula (1)
R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements,
When v, w, x, and y are set to satisfy the following equation (2),
v + w + x + y = 100 Formula (2)
v, w, x, and y are the following formulas (3), (4), and (5).
Figure JPOXMLDOC01-appb-M000003
 2.0 ≦ x ≦ 5.0 Formula (4)
0.8 ≦ w / x ≦ 2.5 (5)
It is characterized by satisfying.
In the hydrogen storage alloy having the chemical composition represented by the general formula (1), v, w, x, and y satisfying the formula (2) are the above formulas (3), (4), and (5). ) At the same time. Then, when Ca and Mg are arranged at the A site of the A 2 B 4 unit included in the crystal phase constituting the hydrogen storage alloy, the crystal lattice is expanded by Ca arranged at the A site of the A 2 B 4 unit. Can be caused. However, although the principle of operation is not clearly clarified, a part of the crystal lattice contracts due to Mg arranged at the A site of the A 2 B 4 unit, and the crystal lattice expansion in the entire alloy is correspondingly reduced. Is considered to be suppressed. Therefore, it can be suppressed that the specific gravity of the alloy is reduced.
　また、本発明に係る水素吸蔵合金においては、前記式（５）が１．０≦　ｗ／ｘ　≦２．５　で表されることが好ましい。前記式（５）が１．０≦　ｗ／ｘ　≦２．５　で表される水素吸蔵合金によれば、電池のエネルギー密度に優れ電池の放電容量が比較的高いという性能をより確実に得ることができる。 Moreover, in the hydrogen storage alloy according to the present invention, the formula (5) is preferably represented by 1.0 ≦ w / x ≦ 2.5. According to the hydrogen storage alloy in which the formula (5) is represented by 1.0 ≦ w / x ≦ 2.5, it is possible to more reliably obtain the performance that the battery has an excellent energy density and a relatively high discharge capacity. Can do.
　また、本発明に係る水素吸蔵合金は、前記Ｒ２のＮｉの一部が置換されたＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素を、０原子％を超え２．２原子％以下含むことが好ましい。斯かる構成により、電池の容量維持率がより優れたものになり得る。
　また、本発明に係る水素吸蔵合金は、前記Ｒ２のＮｉの一部がＡｌで置換され該Ａｌを０原子％を超え２．２原子％以下含むことが好ましい。斯かる構成により、電池の容量維持率がより優れたものになり得る。
　また、前記Ｒ１としてのＣｅを０原子％以上２．３原子％以下含むことが好ましい。斯かる構成により、電池の容量維持率がより優れたものになり得る。 Further, the hydrogen storage alloy according to the present invention is one or more elements selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr, and Zn in which a part of Ni of R2 is substituted. Is preferably more than 0 atomic% and 2.2 atomic% or less. With this configuration, the capacity maintenance rate of the battery can be improved.
In the hydrogen storage alloy according to the present invention, it is preferable that a part of Ni in R2 is substituted with Al and the Al content is more than 0 atomic% and not more than 2.2 atomic%. With this configuration, the capacity maintenance rate of the battery can be improved.
Moreover, it is preferable that Ce as R1 is contained in an amount of 0 atomic% to 2.3 atomic%. With this configuration, the capacity maintenance rate of the battery can be improved.
　また、本発明に係る水素吸蔵合金は、Ｐｒ５Ｃｏ１９型結晶構造を有する結晶相を１１質量％以上含むことが好ましい。 The hydrogen absorbing alloy according to the present invention preferably contains a crystal phase having a Pr 5 Co 19 type crystal structure 11 mass% or more.
　本発明に係る水素吸蔵合金は、化学組成が、下記一般式（１’）で表され、
　　　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y Ｒ３z　　　　・・・式（１’）
Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものであり、Ｒ３が、前記Ｒ１、前記Ｍｇ、前記Ｃａ及び前記Ｒ２以外の元素である水素吸蔵合金であって、
　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
ｖ，ｗ，ｘ，ｙが、下記の式（３）、式（４）、及び、式（５）
Figure JPOXMLDOC01-appb-M000004
 　　　　２．０≦ｘ≦５．０　　　　　　　　・・・式（４）
　　　　０．８≦　ｗ／ｘ　≦２．５　　　　・・・式（５）
を満たし、ｚが０≦ｚ≦０．４を満たすことを特徴とする。 The hydrogen storage alloy according to the present invention has a chemical composition represented by the following general formula (1 ′),
R1v Mgw Cax R2y R3z Formula (1 ')
R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
When v, w, x, and y are set to satisfy the following equation (2),
v + w + x + y = 100 Formula (2)
v, w, x, and y are the following formulas (3), (4), and (5).
Figure JPOXMLDOC01-appb-M000004
 2.0 ≦ x ≦ 5.0 Formula (4)
0.8 ≦ w / x ≦ 2.5 (5)
And z satisfies 0 ≦ z ≦ 0.4.
　本発明に係る水素吸蔵合金は、化学組成が、下記一般式（１’）で表され、
　　　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y Ｒ３z　　　　・・・式（１’）
Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものであり、Ｒ３が、前記Ｒ１、前記Ｍｇ、前記Ｃａ及び前記Ｒ２以外の元素である水素吸蔵合金であって、
　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
ｖ，ｗ，ｘ，ｙが、１３．０≦ｖ≦１８．０、２．２≦ｗ≦５．６、２．０≦ｘ≦５．０、７５．０≦ｙ≦８０．０を満たし、ｚが０≦ｚ≦０．４を満たし、且つ、ｗ及びｘが０．８≦　ｗ／ｘ　≦２．５を満たすことを特徴とする。 The hydrogen storage alloy according to the present invention has a chemical composition represented by the following general formula (1 ′),
R1v Mgw Cax R2y R3z Formula (1 ')
R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
When v, w, x, and y are set to satisfy the following equation (2),
v + w + x + y = 100 Formula (2)
v, w, x, y satisfy 13.0 ≦ v ≦ 18.0, 2.2 ≦ w ≦ 5.6, 2.0 ≦ x ≦ 5.0, 75.0 ≦ y ≦ 80.0 , Z satisfies 0 ≦ z ≦ 0.4, and w and x satisfy 0.8 ≦ w / x ≦ 2.5.
　本発明に係るニッケル水素蓄電池は、前記水素吸蔵合金を含む負極を備えたことを特徴とする。 The nickel-metal hydride storage battery according to the present invention includes a negative electrode containing the hydrogen storage alloy.
　本発明に係る水素吸蔵合金は、ニッケル水素蓄電池の負極に含まれ得るものであって、その比重が比較的高いことで電池のエネルギー密度を優れたものとし得ること、及び、ニッケル水素蓄電池の放電容量を比較的高いものにすることを同時に満足するという効果を奏する。 The hydrogen storage alloy according to the present invention can be included in the negative electrode of a nickel metal hydride storage battery, and can have an excellent battery energy density due to its relatively high specific gravity, and discharge of the nickel metal hydride storage battery There is an effect of satisfying simultaneously that the capacity is relatively high.
　以下、本発明に係る水素吸蔵合金の実施形態について説明する。 Hereinafter, embodiments of the hydrogen storage alloy according to the present invention will be described.
　本発明の実施形態の水素吸蔵合金は、化学組成が、下記一般式（１）で表され、
　　　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y　　　　・・・式（１）
Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものである水素吸蔵合金であって、
　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
　ｖ，ｗ，ｘ，ｙが、下記の式（３）、式（４）、式（５）
Figure JPOXMLDOC01-appb-M000005
 　　　　２．０≦ｘ≦５．０　　　　　　　　・・・式（４）
　　　　０．８≦　ｗ／ｘ　≦２．５　　　　・・・式（５）
を満たすものである。 The hydrogen storage alloy of the embodiment of the present invention has a chemical composition represented by the following general formula (1):
R1v Mgw Cax R2y Formula (1)
R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements,
When v, w, x, and y are set to satisfy the following equation (2),
v + w + x + y = 100 Formula (2)
v, w, x, and y are the following formulas (3), (4), and (5).
Figure JPOXMLDOC01-appb-M000005
 2.0 ≦ x ≦ 5.0 Formula (4)
0.8 ≦ w / x ≦ 2.5 (5)
It satisfies.
　また、本発明の実施形態の水素吸蔵合金は、化学組成が、下記一般式（１’）で表され、
　　　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y Ｒ３z　　　　・・・式（１’）
Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものであり、Ｒ３が、前記Ｒ１、前記Ｍｇ、前記Ｃａ及び前記Ｒ２以外の元素である水素吸蔵合金であって、
　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
ｖ，ｗ，ｘ，ｙが、下記の式（３）、式（４）、及び、式（５）
Figure JPOXMLDOC01-appb-M000006
 　　　　２．０≦ｘ≦５．０　　　　　　　　・・・式（４）
　　　　０．８≦　ｗ／ｘ　≦２．５　　　　・・・式（５）
を満たし、ｚが０≦ｚ≦０．４を満たすものである。 Moreover, the hydrogen storage alloy of the embodiment of the present invention has a chemical composition represented by the following general formula (1 ′),
R1v Mgw Cax R2y R3z Formula (1 ')
R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
When v, w, x, and y are set to satisfy the following equation (2),
v + w + x + y = 100 Formula (2)
v, w, x, and y are the following formulas (3), (4), and (5).
Figure JPOXMLDOC01-appb-M000006
 2.0 ≦ x ≦ 5.0 Formula (4)
0.8 ≦ w / x ≦ 2.5 (5)
And z satisfies 0 ≦ z ≦ 0.4.
　前記水素吸蔵合金は、希土類元素、Ｍｇ、およびＮｉ、さらにはＣａを含有し、通常、Ｎｉ原子の数が、希土類元素の数、Ｍｇ原子の数、並びにＣａ原子の数の合計の３倍より大きく５倍未満である。また、Ｎｉ原子の数が、希土類元素の数、Ｍｇ原子の数、並びにＣａ原子の数の合計の３．４倍以上３．７倍以下であることが好ましい。即ち、いわゆるＢ／Ａ比が、通常、３より大きく５未満であり、好ましくは３．４以上３．７以下である。
　なお、前記水素吸蔵合金におけるＡは、希土類元素とＭｇからなる群より選択される何れかの元素を表し、Ｂは、遷移金属元素とＡｌからなる群より選択される何れかの元素を表すものである。
　具体的には、前記水素吸蔵合金のＢ／Ａ比におけるＡは、Ｌａ、Ｓｍ、Ｐｒ、Ｎｄなどの希土類元素、Ｍｇ、及びＣａからなる群より選択される元素を表し、Ｂは、Ｎｉ、Ａｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択される１種又は２種以上の元素を表す。 The hydrogen storage alloy contains rare earth elements, Mg, and Ni, and further Ca. Usually, the number of Ni atoms is more than three times the total number of rare earth elements, Mg atoms, and Ca atoms. Greatly less than 5 times. Moreover, it is preferable that the number of Ni atoms is 3.4 times or more and 3.7 times or less of the total of the number of rare earth elements, the number of Mg atoms, and the number of Ca atoms. That is, the so-called B / A ratio is usually more than 3 and less than 5, preferably 3.4 or more and 3.7 or less.
In the hydrogen storage alloy, A represents any element selected from the group consisting of rare earth elements and Mg, and B represents any element selected from the group consisting of transition metal elements and Al. It is.
Specifically, A in the B / A ratio of the hydrogen storage alloy represents an element selected from the group consisting of rare earth elements such as La, Sm, Pr, and Nd, Mg, and Ca, and B represents Ni, It represents one or more elements selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn.
　前記一般式（１）又は一般式（１’）において、Ｒ１は、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、ＳｍおよびＹからなる群より選択される１種又は２種以上の元素であることが好ましく、少なくともＬａ又はＮｄを含む元素であることがより好ましい。 In the general formula (1) or general formula (1 ′), R1 is preferably one or more elements selected from the group consisting of La, Ce, Pr, Nd, Sm, and Y. More preferably, the element contains at least La or Nd.
　前記水素吸蔵合金には、Ｃｅが２．３原子％以下含まれていることが好ましい。Ｃｅが２．３原子％以下含まれていることにより、電池のサイクル特性及び電池の容量維持率がより優れたものになり得るという利点がある。また、前記水素吸蔵合金の微粉化が大幅に抑制され電池の容量維持率が大幅に優れたものになり得るという点で、Ｃｅの含有量が実質的に０原子％であることがより好ましく、Ｃｅが含まれていないことがさらに好ましい。 The hydrogen storage alloy preferably contains 2.3 atomic% or less of Ce. When Ce is contained in an amount of 2.3 atomic% or less, there is an advantage that the cycle characteristics of the battery and the capacity retention rate of the battery can be further improved. In addition, it is more preferable that the content of Ce is substantially 0 atomic% in that the pulverization of the hydrogen storage alloy can be significantly suppressed and the capacity retention rate of the battery can be greatly improved. More preferably, Ce is not contained.
　なお、本明細書において、原子％とは、存在する原子の全数に対する特定の原子の数の百分率をいう。従って、例えばカルシウムを１原子％含む合金は、合金の原子１００個のうちカルシウム原子を１個含むものである。 In this specification, atomic% refers to the percentage of the number of specific atoms with respect to the total number of atoms present. Therefore, for example, an alloy containing 1 atomic% of calcium contains one calcium atom out of 100 atoms of the alloy.
　前記一般式（１）又は一般式（１’）において、Ｒ２は、Ｎｉであるか又はＮｉの一部をＡｌ若しくはＣｏで置換したものであることが好ましく、Ｎｉであるか又はＮｉの一部をＡｌで置換したものであることがより好ましい。 In the general formula (1) or the general formula (1 ′), R2 is preferably Ni or a part of Ni substituted by Al or Co, and is Ni or a part of Ni. More preferably, is substituted with Al.
　前記水素吸蔵合金は、前記Ｒ２におけるＮｉ以外の元素を０原子％を超え２．２原子％以下含むことが好ましい。斯かる構成により、電池の容量維持率がより優れたものになり得る。
　前記水素吸蔵合金は、具体的には、前記Ｒ２におけるＮｉ以外の元素がＡｌであり、該Ａｌを０原子％を超え２．２原子％以下含むことが好ましい。さらに好ましくは、前記Ｒ２がＡｌを含まずＮｉである。 The hydrogen storage alloy preferably contains more than 0 atomic% and 2.2 atomic% or less of elements other than Ni in the R2. With this configuration, the capacity maintenance rate of the battery can be improved.
Specifically, in the hydrogen storage alloy, it is preferable that an element other than Ni in R2 is Al, and the Al content is more than 0 atomic% and not more than 2.2 atomic%. More preferably, R2 is Ni without containing Al.
　前記一般式（１’）において、ｚは、ｖ，ｗ，ｘ，ｙの合計数１００部に対する値を示す。即ち、ｖ，ｗ，ｘ，ｙがｖ＋ｗ＋ｘ＋ｙ＝１００を満たすように設定されたときのｚの数を示す。
　前記水素吸蔵合金は、電池のエネルギー密度をより確実に優れたものとし、且つ電池の放電容量をより確実に優れたものにできるという点で、前記一般式（１’）において、ｚ≦０．３であることが好ましく、ｚ≦０．２であることがより好ましい。また、ｚが極めて０に近いこと、即ち、化学組成が前記一般式（１）で表されるものと実質的に同じであることがさらに好ましい。さらには、ｚ＝０であること、即ち、化学組成が前記一般式（１）で表されることが最も好ましい。 In the general formula (1 ′), z represents a value for a total number of 100 parts of v, w, x, and y. That is, it indicates the number of z when v, w, x, and y are set so as to satisfy v + w + x + y = 100.
In the general formula (1 ′), the hydrogen storage alloy can surely improve the energy density of the battery and can surely improve the discharge capacity of the battery. 3 is preferable, and z ≦ 0.2 is more preferable. Further, it is further preferable that z is very close to 0, that is, the chemical composition is substantially the same as that represented by the general formula (1). Furthermore, it is most preferable that z = 0, that is, the chemical composition is represented by the general formula (1).
　前記水素吸蔵合金は、互いに異なる結晶構造を有する２以上の結晶相を備えたものであり、好ましくは、これら２以上の結晶相が、該結晶構造のｃ軸方向に積層されてなるものである。
　前記結晶相としては、菱面体晶Ｌａ５ＭｇＮｉ２４型結晶構造からなる結晶相（以下、単にＬａ５ＭｇＮｉ２４相ともいう）、六方晶Ｐｒ５Ｃｏ１９型結晶構造からなる結晶相（以下、単にＰｒ５Ｃｏ１９相ともいう）、菱面体晶Ｃｅ５Ｃｏ１９型結晶構造からなる結晶相（以下、単にＣｅ５Ｃｏ１９相ともいう）、六方晶Ｃｅ２Ｎｉ７型の結晶構造からなる結晶相（以下、単にＣｅ２Ｎｉ７相ともいう）、菱面体晶Ｇｄ２Ｃｏ７型の結晶構造からなる結晶相（以下、単にＧｄ２Ｃｏ７相ともいう）、六方晶ＣａＣｕ５型結晶構造からなる結晶相（以下、単にＣａＣｕ５相ともいう）、立方晶ＡｕＢｅ５型結晶構造からなる結晶相（以下、単にＡｕＢｅ５相ともいう）菱面体晶ＰｕＮｉ３型結晶構造からなる結晶相（以下、単にＰｕＮｉ３相ともいう）などを挙げることができる。 The hydrogen storage alloy is provided with two or more crystal phases having different crystal structures, and preferably these two or more crystal phases are laminated in the c-axis direction of the crystal structure. .
Examples of the crystal phase include a crystal phase composed of a rhombohedral La 5 MgNi 24 type crystal structure (hereinafter also simply referred to as La 5 MgNi 24 phase), and a crystal phase composed of a hexagonal Pr 5 Co 19 type crystal structure (hereinafter simply referred to as simply “La 5 MgNi 24 phase”). Pr 5 Co 19 phase), crystal phase composed of rhombohedral Ce 5 Co 19 type crystal structure (hereinafter also simply referred to as Ce 5 Co 19 phase), crystal phase composed of hexagonal Ce 2 Ni 7 type crystal structure (Hereinafter also simply referred to as Ce 2 Ni 7 phase), crystal phase composed of rhombohedral Gd 2 Co 7 type crystal structure (hereinafter also simply referred to as Gd 2 Co 7 phase), and hexagonal CaCu 5 type crystal structure crystalline phase (hereinafter, simply referred to as CaCu 5 phase), crystal phase comprising a cubic AuBe 5 type crystal structure (hereinafter, simply referred to as AuBe 5 phase) crystal phase comprising a rhombohedral PuNi 3 type crystal structure Hereinafter also referred to simply as PuNi 3-phase), and the like.
　なかでも、Ｌａ５ＭｇＮｉ２４相、Ｐｒ５Ｃｏ１９相、Ｃｅ５Ｃｏ１９相、及びＣｅ２Ｎｉ７相からなる群より選択される２種以上を有する水素吸蔵合金が好適に使用される。これらの結晶相を有する水素吸蔵合金は、各結晶相間の膨張収縮率の差が小さいために歪みが生じ難く、水素の吸蔵放出を繰り返した際の劣化が起こりにくいという優れた特性を有する。
　また、前記水素吸蔵合金が、互いに異なる結晶構造を有する２以上の結晶相を該結晶構造のｃ軸方向に積層したものである場合、充電によって水素を吸蔵した際の結晶相の歪みが、隣接する他の結晶相によって緩和され得る。従って、該水素吸蔵合金を含むことにより、負極は、充放電によって水素の吸蔵及び放出を繰り返しても合金の微粉化が生じにくく、劣化が進行しにくいという利点がある。 Among them, La 5 MgNi 24 phase, Pr 5 Co 19 phase, Ce 5 Co 19 phase, and the hydrogen storage alloy having two or more selected from the group consisting of Ce 2 Ni 7 phase is preferably used. The hydrogen storage alloy having these crystal phases has excellent characteristics that the difference between the expansion and contraction ratios between the crystal phases is small, so that the distortion is not easily generated and the deterioration is not easily caused by repeated storage and release of hydrogen.
Further, when the hydrogen storage alloy is formed by laminating two or more crystal phases having different crystal structures in the c-axis direction of the crystal structure, distortion of the crystal phase when hydrogen is stored by charging is adjacent to the hydrogen storage alloy. Can be relaxed by other crystalline phases. Therefore, the inclusion of the hydrogen storage alloy has the advantage that the negative electrode is less likely to be pulverized and is less likely to deteriorate even if the storage and release of hydrogen are repeated by charging and discharging.
　ここで、Ｌａ５ＭｇＮｉ２４型結晶構造とは、Ａ２Ｂ４ユニット間に、ＡＢ５ユニットが４ユニット分、挿入された結晶構造であり、Ｐｒ５Ｃｏ１９型結晶構造とは、Ａ２Ｂ４ユニット間に、ＡＢ５ユニットが３ユニット分、挿入された結晶構造であり、Ｃｅ５Ｃｏ１９型結晶構造とは、Ａ２Ｂ４ユニット間に、ＡＢ５ユニットが３ユニット分、挿入された結晶構造であり、Ｃｅ２Ｎｉ７型の結晶構造とは、Ａ２Ｂ４ユニット間に、ＡＢ５ユニットが２ユニット分、挿入された結晶構造であり、Ｇｄ２Ｃｏ７型の結晶構造とは、Ａ２Ｂ４ユニット間に、ＡＢ５ユニットが２ユニット分、挿入された結晶構造であり、ＡｕＢｅ５型結晶構造とは、Ａ２Ｂ４ユニットのみで構成された結晶構造である。 Here, the La 5 MgNi 24 type crystal structure is a crystal structure in which 4 units of AB 5 units are inserted between A 2 B 4 units, and the Pr 5 Co 19 type crystal structure is A 2 B It is a crystal structure in which 3 units of AB 5 units are inserted between 4 units, and Ce 5 Co 19 type crystal structure is that 3 units of AB 5 units are inserted between 4 units of A 2 B 4 It is a crystal structure, and the Ce 2 Ni 7 type crystal structure is a crystal structure in which two AB 5 units are inserted between A 2 B 4 units. What is the Gd 2 Co 7 type crystal structure? , 2 units of AB 5 units are inserted between A 2 B 4 units, and the AuBe 5 type crystal structure is a crystal structure composed of only A 2 B 4 units.
　なお、Ａ２Ｂ４ユニットとは、六方晶ＭｇＺｎ２型結晶構造（Ｃ１４構造）又は六方晶ＭｇＣｕ２型結晶構造（Ｃ１５構造）を持つ構造ユニットであり、ＡＢ５ユニットとは、六方晶ＣａＣｕ５型結晶構造を持つ構造ユニットである。 The A 2 B 4 unit is a structural unit having a hexagonal MgZn 2 type crystal structure (C14 structure) or a hexagonal MgCu 2 type crystal structure (C15 structure), and the AB 5 unit is a hexagonal CaCu 5 It is a structural unit with a type crystal structure.
　該結晶相が積層されたものである場合、各結晶相の積層順については特に限定されず、特定の結晶相の組み合わせが繰返し周期性をもって積層されたようなものであってもよく、各結晶相が無秩序に周期性なく積層されたものであってもよい。 When the crystal phases are stacked, the stacking order of the crystal phases is not particularly limited, and a combination of specific crystal phases may be stacked with repeating periodicity. The phase may be laminated randomly and without periodicity.
　また、前記各結晶相の含有量については特に限定されるものではないが、前記Ｌａ５ＭｇＮｉ２４型結晶構造を有する結晶相の含有率は０～５０質量％、前記Ｐｒ５Ｃｏ１９型結晶構造を有する結晶相の含有率は１１～８０質量％、前記Ｇｄ２Ｃｏ７型結晶構造を有する結晶相の含有率は１５～８０質量％、前記Ｃｅ２Ｎｉ７型結晶構造を有する結晶相の含有率は０～６５質量％であることが好ましい。 The content of each crystal phase is not particularly limited, but the content of the crystal phase having the La 5 MgNi 24 type crystal structure is 0 to 50% by mass, and the Pr 5 Co 19 type crystal structure The content of the crystal phase having 11 to 80% by mass, the content of the crystal phase having the Gd 2 Co 7 type crystal structure is 15 to 80% by mass, and the content of the crystal phase having the Ce 2 Ni 7 type crystal structure The rate is preferably 0 to 65% by mass.
　特に、前記水素吸蔵合金は、Ｃａを含有してなるＰｒ５Ｃｏ１９型結晶構造を有する結晶相を１１～７３質量％含むことが好ましく、３７～７３質量％含むことがより好ましい。 In particular, the hydrogen storage alloy preferably contains 11 to 73% by mass, more preferably 37 to 73% by mass, of a crystal phase having a Pr 5 Co 19 type crystal structure containing Ca.
　なお、前記各結晶構造を有する結晶相は、粉砕した合金粉末についてＸ線回折測定を行い、得られたＸ線回折パターンをリートベルト法により解析することによって結晶構造を特定することができる。
　また、各結晶構造を有する結晶相の含有率は、実施例に記載された方法によって決定されるものである。 The crystal phase having each crystal structure can be identified by performing X-ray diffraction measurement on the ground alloy powder and analyzing the obtained X-ray diffraction pattern by the Rietveld method.
Moreover, the content rate of the crystal phase which has each crystal structure is determined by the method described in the Example.
　また、互いに異なる結晶構造を有する２以上の結晶相が、該結晶構造のｃ軸方向に積層されていることは、ＴＥＭを用いて合金の格子像を観察することによって確認することができる。 Further, it can be confirmed by observing the lattice image of the alloy using TEM that two or more crystal phases having different crystal structures are laminated in the c-axis direction of the crystal structure.
　前記水素吸蔵合金においては、水素吸蔵合金を構成する結晶相に含まれるＡ２Ｂ４ユニットのＡサイトにＣａ及びＭｇが配置されることにより、Ａ２Ｂ４ユニットのＡサイトに配置されたＣａによって結晶格子の膨張が引き起こされるとも考えられる。ところが、ｖ，ｗ，ｘ，ｙが上記式（３）、式（４）、及び式（５）を同時に満たす前記水素吸蔵合金によれば、明確にその作用原理が解明されているわけではないが、Ａ２Ｂ４ユニットのＡサイトに配置されたＭｇによって結晶格子の一部が収縮し、その分、合金全体における結晶格子の膨張が抑制され得ると考えられる。従って、合金の比重が小さくなることが抑制され得る。 In the hydrogen storage alloy, Ca and Mg are arranged at the A site of the A 2 B 4 unit contained in the crystal phase constituting the hydrogen storage alloy, whereby the Ca arranged at the A site of the A 2 B 4 unit. It is also considered that the crystal lattice is caused to expand. However, according to the hydrogen storage alloy in which v, w, x, and y satisfy the above equations (3), (4), and (5) at the same time, the principle of operation is not clearly clarified. However, it is considered that a part of the crystal lattice contracts due to Mg arranged at the A site of the A 2 B 4 unit, and the expansion of the crystal lattice in the entire alloy can be suppressed accordingly. Therefore, it can be suppressed that the specific gravity of the alloy is reduced.
　ここで、上記式（３）の左辺の分母は、前記水素吸蔵合金がＡ２Ｂ４ユニット及びＡＢ５ユニットで構成されていることに基づいて求めた、水素吸蔵合金における全てのサイト数に対するＡ２Ｂ４ユニットのＡサイト数の割合を表す。
　即ち、上記式（３）の左辺の分母は、上記式（１）の化学組成で表される水素吸蔵合金における全サイト数をｖ＋ｗ＋ｘ＋ｙで表したときのＡ２Ｂ４ユニットのＡサイト数を表す。詳しくは、下記の方法によって求められるものである。
　Ａ側元素が配置されるサイトの数は、水素吸蔵合金の結晶においてｖ＋ｗ＋ｘ＋ｙで表される全てのサイトの数に対して、ｖ＋ｗ＋ｘで表され、Ｂ側元素が配置されるサイトの数は、ｙで表される。
　一方、Ａ２Ｂ４ユニットの数に対するＡＢ５ユニットの数の比をｋ、即ち、Ａ２Ｂ４ユニットとＡＢ５ユニットとの比を１：ｋとすると、Ａ側元素が配置されるサイトの数は、（２＋ｋ）×ｎと表すこともできる。また、Ｂ側元素が配置されるサイトの数は、（４＋５ｋ）×ｎと表すこともできる。ここで、ｎは、１個のＡ２Ｂ４ユニットとｋ個のＡＢ５ユニットとを結晶単位としたときのその結晶単位の数を意味する。
　以上の関係から、次の式（Ａ）を得ることができる。 Here, the denominator on the left side of the above formula (3) is A for all the number of sites in the hydrogen storage alloy obtained based on the fact that the hydrogen storage alloy is composed of A 2 B 4 units and AB 5 units. 2 B Indicates the ratio of the number of A sites in 4 units.
That is, the denominator on the left side of the formula (3) represents the number of A sites of A 2 B 4 units when the total number of sites in the hydrogen storage alloy represented by the chemical composition of the formula (1) is represented by v + w + x + y. . In detail, it is calculated | required by the following method.
The number of sites where the A side element is arranged is represented by v + w + x with respect to the number of all sites represented by v + w + x + y in the crystal of the hydrogen storage alloy, and the number of sites where the B side element is arranged is y It is represented by
On the other hand, the ratio of the number of AB 5 units to the number of A 2 B 4 units k, i.e., the ratio between the A 2 B 4 units and AB 5 units 1: When k, site A side element is arranged The number can also be expressed as (2 + k) × n. The number of sites where the B-side element is arranged can also be expressed as (4 + 5k) × n. Here, n means the number of crystal units when one A 2 B 4 unit and k AB 5 units are crystal units.
From the above relationship, the following equation (A) can be obtained.
Figure JPOXMLDOC01-appb-M000007
 　そして、式（Ａ）を変形することにより、下記の式（Ｂ）を得ることができる。
Figure JPOXMLDOC01-appb-M000007
 And the following formula (B) can be obtained by modifying the formula (A).
Figure JPOXMLDOC01-appb-M000008
 　さらに、式（Ｂ）を変形することにより、ｋを下記の式（Ｃ）で表すことができる。
Figure JPOXMLDOC01-appb-M000008
 Furthermore, k can be represented by the following formula (C) by modifying the formula (B).
Figure JPOXMLDOC01-appb-M000009
 　他方、全てのサイト数をｖ＋ｗ＋ｘ＋ｙで表したときのＡ２Ｂ４ユニットのＡサイトの数は、次の式（Ｄ）で表される。即ち、Ａ２Ｂ４ユニット１に対してＡＢ５ユニットはｋ存在することから、Ａサイトの総数は（２＋ｋ）×ｎで表され、Ａ２Ｂ４ユニットにおけるＡサイトの数は２ｎで表される。また、Ａサイトの総数は、ｖ＋ｗ＋ｘでも表される。従って、全サイト数をｖ＋ｗ＋ｘ＋ｙで表したときのＡ２Ｂ４ユニットのＡサイトの数は、下記式（Ｄ）で表される。
Figure JPOXMLDOC01-appb-M000009
 On the other hand, the number of A sites of A 2 B 4 units when the number of all sites is represented by v + w + x + y is represented by the following formula (D). That is, since the the AB 5 units against A 2 B 4 units 1 exists k, the total number of A site is represented by (2 + k) × n, the number of A-site in A 2 B 4 units is represented by 2n The The total number of A sites is also expressed as v + w + x. Therefore, the number of A sites of A 2 B 4 units when the total number of sites is represented by v + w + x + y is represented by the following formula (D).
Figure JPOXMLDOC01-appb-M000010
 　また、式（Ｃ）を変形することにより式（Ｅ）が求められ、ｖ＋ｗ＋ｘ＋ｙ＝１００を変形することにより式（Ｆ）が求められる。そして、式（Ｅ）及び式（Ｆ）を式（Ｄ）に代入することにより、式（３）の左辺の分母を得ることができる。
Figure JPOXMLDOC01-appb-M000010
 Further, the equation (E) is obtained by modifying the equation (C), and the equation (F) is obtained by modifying v + w + x + y = 100. And the denominator of the left side of Formula (3) can be obtained by substituting Formula (E) and Formula (F) into Formula (D).
Figure JPOXMLDOC01-appb-M000011
Figure JPOXMLDOC01-appb-M000011
Figure JPOXMLDOC01-appb-M000012
Figure JPOXMLDOC01-appb-M000012
　前記水素吸蔵合金において、上記式（３）の左辺の値が０．８を超えると、即ち、Ａ２Ｂ４ユニットにおけるＡサイトの割合に対するＣａ及びＭｇの割合が０．８を超えると、明確にその作用原理が解明されているわけではないが、Ｃａ及びＭｇが該Ａ２Ｂ４ユニットのＡサイトに入ることが困難となり、ＣａがＡＢ５ユニットのＡサイトに配置されると考えられ、結果として結晶格子が膨張し、合金の比重が小さくなるというおそれがある。上記式（３）の左辺の値は０を超えていることが好ましく、０．４以上であることがより好ましく、０．５以上であることがさらに好ましく、０．６以上であることが最も好ましい。
　なお、Ｍｇは、Ａ２Ｂ４ユニットのＡサイトには配置され得るが、ＡＢ５ユニットのＡサイトには配置されず、Ａ２Ｂ４ユニットのＡサイトに入れなくなると、偏析すると考えられる。 In the hydrogen storage alloy, when the value of the left side of the above formula (3) exceeds 0.8, that is, when the ratio of Ca and Mg to the ratio of A site in the A 2 B 4 unit exceeds 0.8, it is clear However, it is considered that Ca and Mg are difficult to enter the A site of the A 2 B 4 unit, and Ca is arranged at the A site of the AB 5 unit. As a result, the crystal lattice may expand and the specific gravity of the alloy may be reduced. The value on the left side of the above formula (3) is preferably more than 0, more preferably 0.4 or more, further preferably 0.5 or more, and most preferably 0.6 or more. preferable.
Mg can be arranged at the A site of the A 2 B 4 unit, but is not arranged at the A site of the AB 5 unit, and is considered to segregate when it cannot enter the A site of the A 2 B 4 unit.
　前記水素吸蔵合金において、上記式（４）が満たされなくなると、即ち、ｘが２．０未満であると、水素吸蔵合金を含む負極を備えたニッケル水素蓄電池の放電容量が十分でないものになり得るというおそれがあり、ｘが５．０を超えると、水素吸蔵合金の比重が十分に大きいものにならないというおそれがある。 In the hydrogen storage alloy, when the above formula (4) is not satisfied, that is, when x is less than 2.0, the discharge capacity of the nickel-metal hydride storage battery including the negative electrode including the hydrogen storage alloy becomes insufficient. If x exceeds 5.0, the specific gravity of the hydrogen storage alloy may not be sufficiently large.
　また、ｘは、２．２≦ｘを満たす数であることが好ましく、２．３＜ｘを満たす数であることがより好ましく、２．８＜ｘを満たす数であることがさらに好ましく、３．１＜ｘを満たす数であることが最も好ましい。また、ｘは、ｘ≦４．７を満たす数であることが好ましく、ｘ≦４．４を満たす数であることがより好ましく、ｘ≦４．１を満たす数であることがさらに好ましい。
　ｘが２．２以上であることにより、電池の放電容量がより優れたものになり得るという利点があり、４．７以下であることにより、水素吸蔵合金の比重がより大きいものになり得るという利点がある。 Further, x is preferably a number satisfying 2.2 ≦ x, more preferably a number satisfying 2.3 <x, further preferably a number satisfying 2.8 <x. Most preferred is a number satisfying 1 <x. Further, x is preferably a number that satisfies x ≦ 4.7, more preferably a number that satisfies x ≦ 4.4, and even more preferably a number that satisfies x ≦ 4.1.
When x is 2.2 or more, there is an advantage that the discharge capacity of the battery can be improved, and when it is 4.7 or less, the specific gravity of the hydrogen storage alloy can be increased. There are advantages.
　前記水素吸蔵合金において、ｗは、２．２≦ｗを満たす数であることが好ましく、３．３≦ｗを満たす数であることがより好ましい。また、ｗ≦５．６を満たす数であることが好ましく、ｗ≦４．７を満たす数であることがより好ましい。
　ｗが２．２以上であることにより、水素吸蔵合金の比重がより大きいものになり得るという利点があり、ｗが５．６以下であることにより、電池の放電容量がより優れたものになり得るという利点がある。 In the hydrogen storage alloy, w is preferably a number satisfying 2.2 ≦ w, and more preferably a number satisfying 3.3 ≦ w. Moreover, it is preferable that it is a number which satisfy | fills w <= 5.6, and it is more preferable that it is a number which satisfy | fills w <= 4.7.
When w is 2.2 or more, there is an advantage that the specific gravity of the hydrogen storage alloy can be larger, and when w is 5.6 or less, the discharge capacity of the battery becomes better. There is an advantage of getting.
　前記水素吸蔵合金において、上記式（５）が満たされなくなると、詳しくは、ｗ／ｘが０．８未満、即ちＣａに対するＭｇの比率が０．８未満であるか、又は、ｗ／ｘが２．５を超えると、水素吸蔵合金の比重が十分に大きいものにならないというおそれがある。
　また、ｗ／ｘは、１．０≦　ｗ／ｘを満たす数であることが好ましい。また、ｗ／ｘ　≦２．０を満たす数であることが好ましい。 When the above formula (5) is not satisfied in the hydrogen storage alloy, specifically, w / x is less than 0.8, that is, the ratio of Mg to Ca is less than 0.8, or w / x is If it exceeds 2.5, the specific gravity of the hydrogen storage alloy may not be sufficiently large.
Moreover, it is preferable that w / x is a number satisfying 1.0 ≦ w / x. Moreover, it is preferable that it is a number which satisfy | fills w / x <= 2.0.
　前記一般式（１）又は一般式（１’）において、ｖは、１３．０≦ｖ≦１８．０を満たす数であることが好ましく、１４．０≦ｖ≦１７．０を満たす数であることがより好ましい。 In the general formula (1) or the general formula (1 ′), v is preferably a number satisfying 13.0 ≦ v ≦ 18.0, and is a number satisfying 14.0 ≦ v ≦ 17.0. It is more preferable.
　また、前記一般式（１）又は一般式（１’）において、ｙは、７５．０≦ｙ≦８０．０を満たす数であることが好ましく、７７．０≦ｙ≦７９．０を満たす数であることがより好ましい。 In the general formula (1) or general formula (1 ′), y is preferably a number satisfying 75.0 ≦ y ≦ 80.0, and a number satisfying 77.0 ≦ y ≦ 79.0. It is more preferable that
　ここで、本発明の水素吸蔵合金の他の実施形態について説明する。
　他の実施形態の水素吸蔵合金は、化学組成が、下記一般式（１’）で表され、
　　　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y Ｒ３z　　　　・・・式（１’）
Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものであり、Ｒ３が、前記Ｒ１、前記Ｍｇ、前記Ｃａ及び前記Ｒ２以外の元素である水素吸蔵合金であって、
　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
ｖ，ｗ，ｘ，ｙが、１３．０≦ｖ≦１８．０、２．２≦ｗ≦５．６、２．０≦ｘ≦５．０、７５．０≦ｙ≦８０．０を満たし、ｚが０≦ｚ≦０．４を満たし、且つ、ｗ及びｘが０．８≦　ｗ／ｘ　≦２．５を満たすことを特徴とする。
　他の実施形態の水素吸蔵合金においては、上述した実施形態の水素吸蔵合金と同様の構成を採用することができる。 Here, another embodiment of the hydrogen storage alloy of the present invention will be described.
The hydrogen storage alloy according to another embodiment has a chemical composition represented by the following general formula (1 ′):
R1v Mgw Cax R2y R3z Formula (1 ')
R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
When v, w, x, and y are set to satisfy the following equation (2),
v + w + x + y = 100 Formula (2)
v, w, x, y satisfy 13.0 ≦ v ≦ 18.0, 2.2 ≦ w ≦ 5.6, 2.0 ≦ x ≦ 5.0, 75.0 ≦ y ≦ 80.0 , Z satisfies 0 ≦ z ≦ 0.4, and w and x satisfy 0.8 ≦ w / x ≦ 2.5.
In the hydrogen storage alloy of other embodiment, the structure similar to the hydrogen storage alloy of embodiment mentioned above is employable.
　前記水素吸蔵合金は、水素平衡圧が０．０７ＭＰａ以下のものであることが好ましい。従来の水素吸蔵合金は、水素平衡圧が高い場合には水素を吸収し難く、吸収した水素を放出し易いという性質を有しており、水素吸蔵合金のハイレート特性を高めると、水素が自己放出しやすいものである。
　ところが、互いに異なる結晶構造を有する結晶相が２以上積層されてなる希土類－Ｍｇ－Ｎｉ系の水素吸蔵合金であって、特にＣａＣｕ５型結晶構造を有する結晶相の含有率が１５質量％以下である水素吸蔵合金においては、水素平衡圧を０．０７ＭＰａ以下という低い値に設定した場合でも良好なハイレート特性が得られ、該水素吸蔵合金を負極として用いたニッケル水素蓄電池は、ハイレート特性に優れ且つ水素の自己放出（電池においては、自己放電）の生じ難いものとなる。これは、合金中の水素の拡散性が向上したためであると考えられる。 The hydrogen storage alloy preferably has a hydrogen equilibrium pressure of 0.07 MPa or less. Conventional hydrogen storage alloys have the property that they do not absorb hydrogen easily when the hydrogen equilibrium pressure is high and easily release the absorbed hydrogen. When the high-rate characteristics of the hydrogen storage alloy are improved, hydrogen self-releases. It is easy to do.
However, it is a rare earth-Mg-Ni-based hydrogen storage alloy in which two or more crystal phases having different crystal structures are laminated, and particularly when the content of the crystal phase having a CaCu 5 type crystal structure is 15% by mass or less. In some hydrogen storage alloys, good high rate characteristics can be obtained even when the hydrogen equilibrium pressure is set to a low value of 0.07 MPa or less. A nickel metal hydride battery using the hydrogen storage alloy as a negative electrode has excellent high rate characteristics and Hydrogen self-release (self-discharge in a battery) is unlikely to occur. This is considered to be because the diffusibility of hydrogen in the alloy was improved.
　なお、水素平衡圧とは、８０℃のＰＣＴ曲線（圧力－組成等温線）において、Ｈ／Ｍ＝０．５の平衡圧（放出側）を意味するものである。 The hydrogen equilibrium pressure means an equilibrium pressure (release side) of H / M = 0.5 in the 80 ° C. PCT curve (pressure-composition isotherm).
　次に、本発明の実施形態の水素吸蔵合金の製造方法について説明する。 Next, a method for producing a hydrogen storage alloy according to an embodiment of the present invention will be described.
　前記水素吸蔵合金の製造方法においては、例えば、上述のような所定の組成比となるように配合された合金原料を溶融する溶融工程と、溶融した合金原料を１０００Ｋ／秒以上の冷却速度で急冷凝固する冷却工程と、冷却された合金を加圧状態の不活性ガス雰囲気下で８６０℃以上１０００℃以下の温度範囲で焼鈍する焼鈍工程と、該合金を粉砕する粉砕工程とをおこなう。 In the method for producing the hydrogen storage alloy, for example, a melting step of melting an alloy raw material blended to have a predetermined composition ratio as described above, and a rapid cooling of the molten alloy raw material at a cooling rate of 1000 K / second or more. A cooling process for solidifying, an annealing process for annealing the cooled alloy in a pressurized inert gas atmosphere in a temperature range of 860 ° C. to 1000 ° C., and a pulverizing process for pulverizing the alloy are performed.
　各工程についてより具体的に説明すると、まず、目的とする水素吸蔵合金の化学組成に基づいて、原料インゴッド（合金原料）を所定量秤量する。 More specifically, each step will be described. First, a predetermined amount of raw material ingot (alloy raw material) is weighed based on the chemical composition of the target hydrogen storage alloy.
　溶融工程においては、前記合金原料をルツボに入れ、不活性ガス雰囲気中又は真空中で高周波溶融炉を用い、例えば、１２００℃以上１６００℃以下に加熱して合金原料を溶融させる。 In the melting step, the alloy raw material is put in a crucible and heated to, for example, 1200 ° C. or higher and 1600 ° C. or lower in an inert gas atmosphere or in a vacuum to melt the alloy raw material.
　冷却工程においては、溶融した合金原料を冷却して固化させる。冷却速度は、１０００Ｋ／秒以上（急冷ともいう）が好ましい。１０００Ｋ／秒以上で急冷することにより、合金組成が微細化し、均質化するという効果がある。また、該冷却速度は、１００００００Ｋ／秒以下の範囲に設定することができる。 In the cooling process, the molten alloy material is cooled and solidified. The cooling rate is preferably 1000 K / second or more (also called rapid cooling). By rapidly cooling at 1000 K / second or more, there is an effect that the alloy composition is refined and homogenized. The cooling rate can be set in a range of 1000000 K / second or less.
　該冷却方法としては、具体的には、冷却速度が１０００００Ｋ／秒以上であるメルトスピニング法、冷却速度が１００００Ｋ／秒程度であるガスアトマイズ法などを好適に用いることができる。 As the cooling method, specifically, a melt spinning method having a cooling rate of 100,000 K / sec or more, a gas atomizing method having a cooling rate of about 10,000 K / sec, or the like can be suitably used.
　焼鈍工程においては、不活性ガス雰囲気下の加圧状態において、例えば、電気炉等を用いて８６０℃以上１０００℃以下に加熱する。加圧条件としては、０．２ＭＰａ（ゲージ圧）以上１．０ＭＰａ（ゲージ圧）以下が好ましい。また、該焼鈍工程における処理時間は、３時間以上５０時間以下とすることが好ましい。 In the annealing step, heating is performed at 860 ° C. or higher and 1000 ° C. or lower using, for example, an electric furnace in a pressurized state under an inert gas atmosphere. The pressurizing condition is preferably 0.2 MPa (gauge pressure) or more and 1.0 MPa (gauge pressure) or less. Moreover, it is preferable that the processing time in this annealing process shall be 3 hours or more and 50 hours or less.
　前記粉砕工程は、焼鈍の前後のどちらで行ってもよいが、粉砕により表面積が大きくなるため、合金の表面酸化を防止する観点から、焼鈍工程の後に粉砕工程を実施するのが望ましい。粉砕は、合金表面の酸化防止のために不活性雰囲気中で行うことが好ましい。
　粉砕手段としては、例えば、機械粉砕、水素化粉砕などが用いられ、粉砕後の水素吸蔵合金粒子の粒径が、概ね２０～７０［μｍ］となるように行うことが好ましい。 The pulverization step may be performed either before or after annealing, but since the surface area is increased by pulverization, it is desirable to perform the pulverization step after the annealing step from the viewpoint of preventing surface oxidation of the alloy. The pulverization is preferably performed in an inert atmosphere to prevent oxidation of the alloy surface.
As the pulverization means, for example, mechanical pulverization, hydrogenation pulverization, or the like is used, and it is preferable that the particle size of the hydrogen storage alloy particles after pulverization is approximately 20 to 70 [μm].
　さらに、本発明に係るニッケル水素蓄電池の一実施形態について説明する。 Furthermore, an embodiment of a nickel metal hydride storage battery according to the present invention will be described.
　本実施形態のニッケル水素蓄電池は、上述の水素吸蔵合金を水素吸蔵媒体として含む負極を備えたものである。即ち、上述した水素吸蔵合金を含む負極を備えたニッケル水素蓄電池である。
　本実施形態のニッケル水素蓄電池は、前記水素吸蔵合金を負極に備えているため、前記水素吸蔵合金の比重が比較的高く、電池のエネルギー密度が比較的高いものとなり、且つ、電池の放電容量が比較的高いものとなり得る。 The nickel-metal hydride storage battery according to this embodiment includes a negative electrode containing the above-described hydrogen storage alloy as a hydrogen storage medium. That is, it is a nickel metal hydride storage battery provided with the negative electrode containing the hydrogen storage alloy mentioned above.
Since the nickel-metal hydride storage battery of the present embodiment includes the hydrogen storage alloy in the negative electrode, the specific gravity of the hydrogen storage alloy is relatively high, the battery energy density is relatively high, and the discharge capacity of the battery is high. It can be relatively expensive.
　本実施形態のニッケル水素蓄電池は、詳しくは、上述の水素吸蔵合金を主材料とする負極を備え、さらに例えば、水酸化ニッケルを主成分とする正極活物質を含む正極（ニッケル電極）、セパレータ、及びアルカリ電解液を備えて構成されている。
　前記負極としては、例えば、前記水素吸蔵合金の粉末が導電剤、結着剤、又は増粘剤等と混合され、所定形状に加圧成形されたものが挙げられる。 Specifically, the nickel metal hydride storage battery of the present embodiment includes a negative electrode mainly composed of the above-described hydrogen storage alloy, and further includes, for example, a positive electrode (nickel electrode) including a positive electrode active material mainly composed of nickel hydroxide, a separator, And an alkaline electrolyte.
Examples of the negative electrode include those in which the hydrogen storage alloy powder is mixed with a conductive agent, a binder, a thickener, or the like, and pressed into a predetermined shape.
　本実施形態のニッケル水素蓄電池の正極としては、特に限定されるものではないが、一般的には、水酸化ニッケルを主成分とし且つ水酸化亜鉛や水酸化コバルトが混合されてなる水酸化ニッケル複合酸化物を正極活物質として含む正極が挙げられ、好ましくは、共沈法によって均一分散した該水酸化ニッケル複合酸化物を含む正極が挙げられる。
　水酸化ニッケル複合酸化物以外の添加物としては、導電改質剤としての水酸化コバルト、酸化コバルト等を用いることができ、また、前記水酸化ニッケル複合酸化物に水酸化コバルトをコートしたものや、これらの水酸化ニッケル複合酸化物の一部を酸素又は酸素含有気体、又は、Ｋ2Ｓ2Ｏ8、次亜塩素酸などの薬剤を用いて酸化したものが挙げられる。
　また、添加剤としては、酸素過電圧を向上させる物質として、Ｙ、Ｙｂ等の希土類元素の化合物や、Ｃａ化合物が例示される。Ｙ、Ｙｂ等の希土類元素は、その一部が溶解して、負極表面に配置されるため、負極活物質の腐食を抑制する効果も期待できる。なお、前記正極には、上述したような主要構成成分の他に、導電剤、結着剤、増粘剤等が、他の構成成分として含有されていてもよい。 Although it does not specifically limit as a positive electrode of the nickel hydride storage battery of this embodiment, In general, the nickel hydroxide composite which has nickel hydroxide as a main component and zinc hydroxide and cobalt hydroxide are mixed. The positive electrode containing an oxide as a positive electrode active material is mentioned, Preferably, the positive electrode containing this nickel hydroxide complex oxide uniformly disperse | distributed by the coprecipitation method is mentioned.
As additives other than the nickel hydroxide composite oxide, cobalt hydroxide, cobalt oxide and the like as a conductive modifier can be used, and the nickel hydroxide composite oxide is coated with cobalt hydroxide. And those obtained by oxidizing a part of these nickel hydroxide composite oxides using oxygen or an oxygen-containing gas, or a chemical such as K2S2O8 or hypochlorous acid.
Examples of the additive include compounds of rare earth elements such as Y and Yb, and Ca compounds as substances that improve oxygen overvoltage. Since some of rare earth elements such as Y and Yb are dissolved and disposed on the negative electrode surface, an effect of suppressing corrosion of the negative electrode active material can be expected. The positive electrode may contain a conductive agent, a binder, a thickener, and the like as other components in addition to the main components as described above.
　導電剤としては、電池性能に悪影響を及ぼさない電子伝導性材料であれば限定されないが、通常、天然黒鉛（鱗状黒鉛、鱗片状黒鉛、土状黒鉛等）、人造黒鉛、カーボンブラック、アセチレンブラック、ケッチェンブラック、カーボンウィスカー、炭素繊維、気相成長炭素、金属（ニッケル、金等）粉、金属繊維等の導電性材料の１種単独物又は２種以上を混合したものが挙げられる。
　これらを混合する方法としては、できる限り均一な状態とし得るものが好ましく、例えば、Ｖ型混合機、Ｓ型混合機、擂かい機、ボールミル、遊星ボールミルといった粉体混合機を、乾式、あるいは湿式で用いる方法を採用しうる。
　前記結着剤としては、通常、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリエチレン、ポリプロピレン等の熱可塑性樹脂、エチレン－プロピレン－ジエンターポリマー（ＥＰＤＭ）、スルホン化ＥＰＤＭ、スチレンブタジエンゴム（ＳＢＲ）、フッ素ゴム等のゴム弾性を有するポリマーの１種単独物又は２種以上を混合したものが挙げられる。該結着剤の添加量は、正極又は負極の総量に対して、０．１～３質量％が好ましい。
　前記増粘剤としては、通常、カルボキシメチルセルロース、メチルセルロース、キサンタンガム等の多糖類等の１種単独物又は２種以上を混合したものが挙げられる。増粘剤の添加量は、正極又は負極の総量に対して、０．１～０．３質量％が好ましい。 The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance. Usually, natural graphite (such as scaly graphite, scaly graphite, earthy graphite), artificial graphite, carbon black, acetylene black, Examples thereof include ketjen black, carbon whisker, carbon fiber, vapor-grown carbon, metal (nickel, gold, etc.) powder, one kind of conductive material such as metal fiber, or a mixture of two or more kinds.
As a method of mixing them, a method that can be as uniform as possible is preferable. For example, a powder mixer such as a V-type mixer, an S-type mixer, a grinder, a ball mill, a planetary ball mill, or the like may be dry or wet. The method used in the above can be adopted.
The binder is usually a thermoplastic resin such as polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluoro rubber. Examples thereof include a single type of polymer having rubber elasticity such as a single type or a mixture of two or more types. The addition amount of the binder is preferably 0.1 to 3% by mass with respect to the total amount of the positive electrode or the negative electrode.
Examples of the thickener include one kind of a polysaccharide such as carboxymethylcellulose, methylcellulose, and xanthan gum, or a mixture of two or more kinds. The addition amount of the thickener is preferably 0.1 to 0.3% by mass with respect to the total amount of the positive electrode or the negative electrode.
　正極及び負極は、前記活物質、導電剤および結着剤を、水やアルコール、トルエン等の有機溶媒に混合した後、得られた混合液を集電体の上に塗布し、乾燥することによって好適に作製される。前記塗布方法としては、例えば、アプリケーターロールなどのローラーコーティング、スクリーンコーティング、ブレードコーティング、スピンコーティング、パーコーティング等の手段を用い、任意の厚み及び任意の形状に塗布する方法が好適であるが、これらに限定されるものではない。 The positive electrode and the negative electrode are prepared by mixing the active material, the conductive agent, and the binder in an organic solvent such as water, alcohol, and toluene, and then applying the obtained mixed liquid onto a current collector and drying it. Produced suitably. As the application method, for example, a method of applying an arbitrary thickness and an arbitrary shape using means such as roller coating such as an applicator roll, screen coating, blade coating, spin coating, and per coating is preferable. It is not limited to.
　前記集電体としては、構成された電池において前記活物質との電子の授受に悪影響を及ぼさない電子伝導体が特に制限されることなく使用され得る。該集電体としては、例えば、耐還元性及び耐酸化性の観点から、ニッケルやニッケルメッキした鋼板をその材料としたものが挙げられる。該集電体の形状としては、発泡体、繊維群の成形体、凹凸加工を施した３次元基材、或いは、パンチング板等の２次元基材が挙げられる。また、該集電体の厚みについても特に限定はなく、通常、５～７００μｍのものが例示される。
　これらの集電体のうち、正極用としては、アルカリに対する耐食性と耐酸化性に優れたニッケルを材料とし、集電性に優れた構造である多孔体構造の発泡体としたものが好ましい。また、負極用としては、安価で、且つ導電性に優れる鉄箔に、ニッケルメッキを施した、パンチング板が好ましい。
　パンチング径は２．０ｍｍ以下、開口率は４０％以上であることが好ましく、これにより、少量の結着剤でも負極活物質と集電体との密着性を高めることができる。 As the current collector, an electron conductor that does not adversely affect the exchange of electrons with the active material in the battery that is configured can be used without any particular limitation. Examples of the current collector include those made of nickel or nickel-plated steel plate as a material from the viewpoint of reduction resistance and oxidation resistance. Examples of the shape of the current collector include a foam, a molded product of a fiber group, a three-dimensional base material subjected to uneven processing, or a two-dimensional base material such as a punching plate. Further, the thickness of the current collector is not particularly limited, and is usually 5 to 700 μm.
Among these current collectors, for the positive electrode, those made of nickel having excellent corrosion resistance and oxidation resistance to alkali and having a porous structure having a structure excellent in current collection are preferable. For the negative electrode, a punching plate obtained by nickel plating on an iron foil that is inexpensive and excellent in conductivity is preferable.
The punching diameter is preferably 2.0 mm or less, and the opening ratio is preferably 40% or more. This makes it possible to improve the adhesion between the negative electrode active material and the current collector even with a small amount of binder.
　ニッケル水素蓄電池のセパレータとしては、優れたレート特性を示す多孔膜や不織布等を、単独で、あるいは２以上併用して構成されていることが好ましい。該セパレータを構成する材料としては、例えば、ポリエチレン、ポリプロピレン等のポリオレフィン系樹脂や、ナイロンを挙げることができる。
　該セパレータの目付は、４０ｇ／ｍ２から１００ｇ／ｍ２が好ましい。４０ｇ／ｍ２未満であると、短絡や自己放電性能が低下する虞があり、１００ｇ／ｍ２を超えると単位体積当たりに占めるセパレータの割合が増加するため、電池容量が下がる傾向にある。該セパレータの通気度は、１ｃｍ／ｓｅｃから５０ｃｍ／ｓｅｃが好ましい。１ｃｍ／ｓｅｃ未満であると、電池内圧が上昇する虞があり、５０ｃｍ／ｓｅｃを超えると、短絡や自己放電性能が低下する虞がある。該セパレータの平均繊維径は、１μｍから２０μｍが好ましい。１μｍ未満であるとセパレータの強度が低下し、電池組み立て工程での不良率が増加する虞があり、２０μｍを超えると、短絡や自己放電性能が低下する虞がある。
　また、該セパレータは、親水化処理が施されていることが好ましい。該セパレータとしては、例えば、ポリプロピレンなどのポリオレフィン系樹脂繊維の表面にスルフォン化処理、コロナ処理、フッ素ガス処理、プラズマ処理を施したり、これらの処理を既に施されたものを混合したものが挙げられる。特に、スルフォン化処理を施されたセパレータは、シャトル現象を引き起こすＮＯ3 -、ＮＯ2 -、ＮＨ3 -等の不純物や負極からの溶出元素を吸着する能力が高いため、自己放電抑制効果が高く、好ましい。 The separator of the nickel metal hydride storage battery is preferably composed of a porous film or a nonwoven fabric exhibiting excellent rate characteristics alone or in combination of two or more. Examples of the material constituting the separator include polyolefin resins such as polyethylene and polypropylene, and nylon.
The basis weight of the separator is preferably 40 g / m 2 to 100 g / m 2 . If it is less than 40 g / m 2 , the short circuit and the self-discharge performance may be deteriorated, and if it exceeds 100 g / m 2 , the ratio of the separator per unit volume increases, so the battery capacity tends to decrease. The air permeability of the separator is preferably 1 cm / sec to 50 cm / sec. If it is less than 1 cm / sec, the internal pressure of the battery may increase, and if it exceeds 50 cm / sec, the short circuit and the self-discharge performance may be deteriorated. The average fiber diameter of the separator is preferably 1 μm to 20 μm. When the thickness is less than 1 μm, the strength of the separator decreases, and the defect rate in the battery assembly process may increase. When the thickness exceeds 20 μm, the short circuit and the self-discharge performance may decrease.
Further, the separator is preferably subjected to a hydrophilic treatment. Examples of the separator include those obtained by subjecting the surface of a polyolefin resin fiber such as polypropylene to a sulfonation treatment, a corona treatment, a fluorine gas treatment, a plasma treatment, or a mixture of those already subjected to these treatments. . In particular, separators that have been sulfonated have a high ability to adsorb impurities such as NO 3 − , NO 2 − , and NH 3 − that cause the shuttle phenomenon and elements eluted from the negative electrode. ,preferable.
　ニッケル水素蓄電池を構成するアルカリ電解液としては、ナトリウムイオン、カリウムイオン、リチウムイオンの少なくとも何れか一方を含み、イオン濃度の合計が９．０ｍｏｌ／リットル以下であるものが好ましく、イオン濃度の合計が５．０～８．０ｍｏｌ／リットルであるものがより一層好ましい。 The alkaline electrolyte constituting the nickel metal hydride storage battery preferably contains at least one of sodium ion, potassium ion and lithium ion, and the total ion concentration is 9.0 mol / liter or less, and the total ion concentration is What is 5.0-8.0 mol / liter is still more preferable.
　また、該電解液には、合金への防食性向上、正極での過電圧向上、負極の耐食性の向上、自己放電向上のため、種々の添加剤が添加され得る。該添加剤としては、イットリウム、イッテルビウム、エルビウム、カルシウム、亜鉛などの酸化物、水酸化物等の１種単独物又は２種以上混合したものが挙げられる。 In addition, various additives may be added to the electrolytic solution in order to improve the corrosion resistance of the alloy, improve the overvoltage at the positive electrode, improve the corrosion resistance of the negative electrode, and improve self-discharge. Examples of the additive include oxides such as yttrium, ytterbium, erbium, calcium, and zinc, one kind of a hydroxide or the like, or a mixture of two or more kinds.
　本実施形態のニッケル水素蓄電池が開放型ニッケル水素蓄電池である場合、該電池は、例えば、セパレータを介して負極を正極で挟み込み、これらの電極に所定の圧力がかかるようにこれらの電極を固定して、ＫＯＨ及びＬｉＯＨを含む水溶液でなる電解液を注液し、開放形セルを組み立てることにより作製できる。 When the nickel-metal hydride storage battery of this embodiment is an open-type nickel-metal hydride storage battery, the battery, for example, sandwiches the negative electrode with the positive electrode via a separator and fixes these electrodes so that a predetermined pressure is applied to these electrodes. Then, an electrolytic solution made of an aqueous solution containing KOH and LiOH is injected, and an open cell is assembled.
　本実施形態のニッケル水素蓄電池が密閉型ニッケル水素蓄電池である場合、該電池は、前記電解液を、前記正極、セパレータ及び負極を積層する前又は積層した後に注液し、外装材で封止することにより、好適に作製される。また、正極と負極とが前記セパレータを介して積層された発電要素を巻回してなる密閉型ニッケル水素蓄電池においては、前記電解液は、巻回の前又は後に発電要素に注液されるのが好ましい。注液法としては、常圧で注液することも可能であるが、真空含浸法、加圧含浸法、遠心含浸法も使用可能である。また、該密閉型ニッケル水素蓄電池の外装体の材料としては、ニッケルメッキした鉄やステンレススチール、ポリオレフィン系樹脂等が一例として挙げられる。 When the nickel metal hydride storage battery of this embodiment is a sealed nickel metal hydride storage battery, the battery is injected with the electrolyte before or after the positive electrode, the separator, and the negative electrode are stacked, and is sealed with an exterior material. Thus, it can be suitably manufactured. In a sealed nickel-metal hydride storage battery in which a power generation element in which a positive electrode and a negative electrode are stacked via the separator is wound, the electrolyte is injected into the power generation element before or after winding. preferable. As an injection method, it is possible to inject at normal pressure, but a vacuum impregnation method, a pressure impregnation method, and a centrifugal impregnation method can also be used. Further, examples of the material for the outer package of the sealed nickel-metal hydride storage battery include nickel-plated iron, stainless steel, polyolefin resin, and the like.
　該密閉型ニッケル水素蓄電池の構成については特に限定されるものではなく、正極、負極および単層又は複層のセパレータを備えた電池、例えば、コイン電池、ボタン電池、角型電池、扁平型電池、あるいは、ロール状の正極、負極及びセパレータを有する円筒型電池等を挙げることができる。 The configuration of the sealed nickel-metal hydride storage battery is not particularly limited, and batteries including a positive electrode, a negative electrode, and a single-layer or multi-layer separator, such as a coin battery, a button battery, a square battery, a flat battery, Alternatively, a cylindrical battery having a roll-shaped positive electrode, a negative electrode, and a separator can be given.
　本発明は、上記例示の水素吸蔵合金、及び上記例示のニッケル水素蓄電池に限定されるものではない。
　即ち、一般的な水素吸蔵合金において用いられる種々の形態を、本発明の効果を損ねない範囲において、採用することができる。また、一般的なニッケル水素蓄電池において用いられる種々の態様を、本発明の効果を損ねない範囲において、採用することができる。
　例えば、上述のごとく化学組成が前記式（１）で表される水素吸蔵合金は、該一般式を満たしている限り、本発明の効果を損ねない範囲において、該一般式で規定されていない元素が含まれ得る。前記式（１）で規定されていない元素を含む水素吸蔵合金の化学組成は、前記式（１’）で表すこともできる。該式（１’）におけるＲ３の含有量は、本発明の効果を損ねない範囲の量である。即ち、式（１’）のＲ３の量を規定するｚがｚ≦０．４を満たせば、本発明の効果が損なわれないことが証明されている。前記水素吸蔵合金にＲ３の元素が含まれる原因としては、原料インゴット中に不純物が含まれていることが挙げられる。従って、原料インゴットの純度を制御することにより前記水素吸蔵合金中のＲ３の量を制御することができる。 The present invention is not limited to the above exemplified hydrogen storage alloy and the above exemplified nickel metal hydride storage battery.
That is, various forms used in a general hydrogen storage alloy can be adopted as long as the effects of the present invention are not impaired. Moreover, the various aspects used in a general nickel hydride storage battery can be employ | adopted in the range which does not impair the effect of this invention.
For example, as described above, the hydrogen storage alloy whose chemical composition is represented by the formula (1) is an element not defined by the general formula as long as the general formula is satisfied as long as the effect of the present invention is not impaired. Can be included. The chemical composition of the hydrogen storage alloy containing an element not defined by the formula (1) can also be represented by the formula (1 ′). The content of R3 in the formula (1 ′) is an amount that does not impair the effects of the present invention. That is, it is proved that the effect of the present invention is not impaired if z defining the amount of R3 in the formula (1 ′) satisfies z ≦ 0.4. The reason why the R3 element is contained in the hydrogen storage alloy is that impurities are contained in the raw material ingot. Therefore, the amount of R3 in the hydrogen storage alloy can be controlled by controlling the purity of the raw material ingot.
　次に実施例を挙げて本発明をさらに詳しく説明するが、本発明はこれらに限定されるものではない。 Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
（実施例１）
　以下に示す方法により、開放形ニッケル水素蓄電池を作製した。
・水素吸蔵合金の作製
　化学組成が表１の実施例１となるように原料インゴットを所定量秤量してルツボに入れ、減圧アルゴンガス雰囲気下で高周波溶融炉を用いて１５００℃に加熱し、材料を溶融した。溶融後、メルトスピニング法を適用して急冷し、合金を固化させた。
　次に、得られた合金を０．２ＭＰａ（ゲージ圧、以下同じ）に加圧されたアルゴンガス雰囲気下で、９１０℃にて熱処理を行った後、得られた水素吸蔵合金を粉砕して平均粒径（Ｄ５０）が２０μｍの水素吸蔵合金粉末とした。
・電極の作製
　前記水素吸蔵合金粉末を負極に用いることによって開放形のニッケル水素蓄電池を製作した。具体的には、上記のようにして得られた水素吸蔵合金粉末１００重量部に、ニッケル粉末（ＩＮＣＯ社製、＃２１０）３重量部を加えて混合した後、増粘剤（メチルセルロース）を溶解した水溶液を加え、さらに、結着剤（スチレンブタジエンゴム）を１．５重量部加えてペースト状にしたものを厚み４５μｍの穿孔鋼板（開口率６０％）の両面に塗布して乾燥させた後、厚さ０．３６ｍｍにプレスし、負極とした。一方、正極としては、容量過剰のシンター式水酸化ニッケル電極を用いた。
・開放形電池の作製
　上述のようにして作製した電極をセパレータを介して正極で挟み込み、これらの電極に１ｋｇｆ／ｃｍ２の圧力がかかるようにボルトで固定し、開放形セルに組み立てた。電解液としては、６．８ｍｏｌ／ＬのＫＯＨ溶液および０．８ｍｏｌ／ＬのＬｉＯＨ溶液からなる混合液を使用した。 Example 1
An open-type nickel metal hydride storage battery was produced by the method described below.
Preparation of hydrogen storage alloy A predetermined amount of raw material ingot was weighed into a crucible so that the chemical composition would be Example 1 of Table 1, and heated to 1500 ° C. using a high frequency melting furnace in a reduced pressure argon gas atmosphere. Melted. After melting, it was quenched by applying a melt spinning method to solidify the alloy.
Next, after heat-treating the obtained alloy at 910 ° C. in an argon gas atmosphere pressurized to 0.2 MPa (gauge pressure, the same applies hereinafter), the obtained hydrogen storage alloy was pulverized and averaged A hydrogen storage alloy powder having a particle size (D 50 ) of 20 μm was obtained.
-Preparation of electrode An open-type nickel-metal hydride storage battery was manufactured by using the hydrogen storage alloy powder for the negative electrode. Specifically, after adding 3 parts by weight of nickel powder (INCO, # 210) to 100 parts by weight of the hydrogen storage alloy powder obtained as described above, the thickener (methylcellulose) is dissolved. After adding the prepared aqueous solution and further adding 1.5 parts by weight of a binder (styrene butadiene rubber) to a paste, it was applied to both sides of a 45 μm-thick perforated steel sheet (opening ratio 60%) and dried. , Pressed to a thickness of 0.36 mm to obtain a negative electrode. On the other hand, as the positive electrode, an excess capacity sintered nickel hydroxide electrode was used.
- an electrode was manufactured as prepared above open type battery sandwiched between the positive electrode through the separator, it is bolted to a pressure of 1 kgf / cm 2 to these electrodes such, assembled into open type cell. As the electrolytic solution, a mixed solution composed of a 6.8 mol / L KOH solution and a 0.8 mol / L LiOH solution was used.
（実施例２～１５）
　水素吸蔵合金の組成を表１の実施例２～１５に示した組成とした以外は、実施例１と同様にしてニッケル水素蓄電池を作製した。 (Examples 2 to 15)
Nickel-metal hydride storage batteries were produced in the same manner as in Example 1 except that the compositions of the hydrogen storage alloys were changed to those shown in Examples 2 to 15 in Table 1.
（比較例１～１７）
　水素吸蔵合金の組成を表１の比較例１～１７に示した組成とした以外は、実施例１と同様にしてニッケル水素蓄電池を作製した。 (Comparative Examples 1 to 17)
A nickel-metal hydride storage battery was produced in the same manner as in Example 1 except that the composition of the hydrogen storage alloy was changed to the composition shown in Comparative Examples 1 to 17 in Table 1.
＜水素吸蔵合金の比重＞
　以下に示す方法により、各実施例及び各比較例で作製した水素吸蔵合金の比重を測定した。
　なお、各合金の比重は真密度測定装置（商品名「ＵＬＴＲＡ　ＰＹＣＮＯＭＥＴＥＲ　１０００」Quantachrome社製）を用いて測定した。 <Specific gravity of hydrogen storage alloy>
By the method shown below, the specific gravity of the hydrogen storage alloy produced in each Example and each comparative example was measured.
The specific gravity of each alloy was measured using a true density measuring device (trade name “ULTRA PYCNOMETER 1000” manufactured by Quantachrome).
＜水素吸蔵合金における結晶相の含有率＞
　各実施例、各比較例で得られた水素吸蔵合金粉末をＸ線回折測定し、さらにリートベルト法で解析することにより、水素吸蔵合金に含まれる結晶構造を特定した。その結果、Ｐｒ５Ｃｏ１９型結晶構造を有する結晶相、Ｃｅ２Ｎｉ７型結晶構造を有する結晶相、及びＧｄ２Ｃｏ７型結晶構造を有する結晶相を特定した。
　また、リートベルト解析から求められた各相の尺度因子、単位胞体積、化学式数、化学式量を用いることによって、Ｐｒ５Ｃｏ１９型結晶構造を有する結晶相の含有率を求めた。各実施例、各比較例の水素吸蔵合金におけるその結果を表１に示す。 <Content of crystal phase in hydrogen storage alloy>
The hydrogen storage alloy powders obtained in each example and each comparative example were measured by X-ray diffraction, and further analyzed by the Rietveld method to identify the crystal structure contained in the hydrogen storage alloy. As a result, a crystal phase having a Pr 5 Co 19 type crystal structure, a crystal phase having a Ce 2 Ni 7 type crystal structure, and a crystal phase having a Gd 2 Co 7 type crystal structure were identified.
Also, measure factor of each phase obtained from the Rietveld analysis, the unit cell volume, formula number, by using a chemical formula weight to determine the content of the crystal phase having a Pr 5 Co 19 type crystal structure. Table 1 shows the results of the hydrogen storage alloys of the examples and comparative examples.
＜水素吸蔵合金における結晶相の構造の観察＞
　透過型電子顕微鏡（ＴＥＭ）を用いることにより、合金の格子像を観察した。その結果、各実施例、各比較例の水素吸蔵合金において、結晶相がｃ軸方向に積層されていることが確認された。 <Observation of crystal phase structure in hydrogen storage alloy>
The lattice image of the alloy was observed by using a transmission electron microscope (TEM). As a result, it was confirmed that the crystal phases were laminated in the c-axis direction in the hydrogen storage alloys of the examples and comparative examples.
＜ニッケル水素蓄電池の容量維持率＞
　作製した各ニッケル水素蓄電池を用いて、２０℃の水槽中において、０．１Ｉｔ（Ａ）で１５０％の条件での充電、及び、０．２Ｉｔ（Ａ）で停止電位－０．６Ｖ（ｖｓＨｇ／ＨｇＯ）の条件での放電を１サイクルとして、充放電を５０サイクル繰り返した。そして、１サイクル目の放電容量に対する５０サイクル目の放電容量を容量維持率として求めた。 <Nickel metal hydride storage capacity maintenance rate>
Using each of the produced nickel metal hydride storage batteries, charging in a water bath at 20 ° C. under a condition of 150% at 0.1 It (A), and a stop potential of −0.6 V (vs Hg / v) at 0.2 It (A) Charging / discharging was repeated 50 cycles, with the discharge under the condition of HgO) as one cycle. Then, the discharge capacity at the 50th cycle with respect to the discharge capacity at the 1st cycle was obtained as a capacity retention rate.
＜ニッケル水素蓄電池の放電容量＞
　以下に示す方法により、各実施例及び各比較例で作製したニッケル水素蓄電池の最大放電容量を測定した。
　作製した各ニッケル水素蓄電池を用いて、次の条件で充放電試験をおこなった。充電条件は、充電電流０．１ＩｔｍＡ、充電時間１５時間の定電流定電圧充電とし、放電条件は、放電電流０．１ＩｔｍＡの定電流放電とした。 <Discharge capacity of nickel metal hydride storage battery>
The maximum discharge capacity of the nickel-metal hydride storage batteries produced in each Example and each Comparative Example was measured by the method described below.
Using each produced nickel metal hydride storage battery, a charge / discharge test was performed under the following conditions. The charging conditions were constant current and constant voltage charging with a charging current of 0.1 ItmA and a charging time of 15 hours, and the discharging conditions were constant current discharging with a discharge current of 0.1 ItmA.
　各実施例及び各比較例で作製した水素吸蔵合金の比重、各ニッケル水素蓄電池を用いた充放電試験において測定された初回の最大放電容量、及び電池の容量維持率を表１に示す。
　表１からわかるように、実施例のものでは、比重７．５以上及び最大放電容量３７０ｍＡｈ／ｇ以上を達成できる。また、Ａｌの含有量が２．２原子％以下の実施例１０及び実施例１８は、Ａｌの含有量が３．３原子％の実施例１９と比較して、容量維持率が大幅に優れたものになっている。 Table 1 shows the specific gravity of the hydrogen storage alloys produced in each example and each comparative example, the initial maximum discharge capacity measured in the charge / discharge test using each nickel metal hydride storage battery, and the capacity retention rate of the battery.
As can be seen from Table 1, in the examples, specific gravity of 7.5 or more and maximum discharge capacity of 370 mAh / g or more can be achieved. In addition, Example 10 and Example 18 in which the Al content was 2.2 atomic% or less were significantly superior in capacity retention compared to Example 19 in which the Al content was 3.3 atomic%. It is a thing.
Figure JPOXMLDOC01-appb-T000013
Figure JPOXMLDOC01-appb-T000013

Claims (19)

  1. 　化学組成が、下記一般式（１）で表され、
    　　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y　　　　・・・式（１）
    Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものである水素吸蔵合金であって、
    　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
    　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
    ｖ，ｗ，ｘ，ｙが、下記の式（３）、式（４）、及び、式（５）
    Figure JPOXMLDOC01-appb-I000001
    　　　　２．０≦ｘ≦５．０　　　　　　　　・・・式（４）
    　　　　０．８≦　ｗ／ｘ　≦２．５　　　　・・・式（５）
    を満たすことを特徴とする水素吸蔵合金。     The chemical composition is represented by the following general formula (1):
    R1v Mgw Cax R2y Formula (1)
    R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements,
    When v, w, x, and y are set to satisfy the following equation (2),
    v + w + x + y = 100 Formula (2)
    v, w, x, and y are the following formulas (3), (4), and (5).
    Figure JPOXMLDOC01-appb-I000001
    2.0 ≦ x ≦ 5.0 Formula (4)
    0.8 ≦ w / x ≦ 2.5 (5)
    The hydrogen storage alloy characterized by satisfy | filling.
  2. 　前記式（５）が１．０≦　ｗ／ｘ　≦２．５　で表されることを特徴とする請求項１記載の水素吸蔵合金。 2. The hydrogen storage alloy according to claim 1, wherein the formula (5) is represented by 1.0 ≦ w / x ≦ 2.5.
  3. 　前記Ｒ２のＮｉの一部が置換されたＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素を、０原子％を超え２．２原子％以下含むことを特徴とする請求項１又は２に記載の水素吸蔵合金。 One or two or more elements selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr, and Zn in which a part of Ni in R2 is substituted include more than 0 atomic% and 2.2 atoms % Or less, The hydrogen storage alloy of Claim 1 or 2 characterized by the above-mentioned.
  4. 　前記Ｒ２のＮｉの一部がＡｌで置換され該Ａｌが０原子％を超え２．２原子％以下含まれていることを特徴とする請求項１～３のいずれか１項に記載の水素吸蔵合金。 The hydrogen occlusion according to any one of claims 1 to 3, wherein a part of Ni in R2 is substituted with Al and the Al content is more than 0 atomic percent and not more than 2.2 atomic percent. alloy.
  5. 　前記Ｒ１としてのＣｅを０原子％以上２．３原子％以下含むことを特徴とする請求項１～４のいずれか１項に記載の水素吸蔵合金。 The hydrogen storage alloy according to any one of claims 1 to 4, wherein Ce as R1 is contained in an amount of 0 atomic% to 2.3 atomic%.
  6. 　Ｐｒ５Ｃｏ１９型結晶構造を有する結晶相を１１質量％以上含むことを特徴とする請求項１～５のいずれか１項に記載の水素吸蔵合金。 The hydrogen storage alloy according to any one of claims 1 to 5, comprising a crystal phase having a Pr 5 Co 19 type crystal structure in an amount of 11 mass% or more.
  7. 　化学組成が、下記一般式（１’）で表され、
    　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y Ｒ３z　　　　・・・式（１’）
    Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものであり、Ｒ３が、前記Ｒ１、前記Ｍｇ、前記Ｃａ及び前記Ｒ２以外の元素である水素吸蔵合金であって、
    　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
    　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
    ｖ，ｗ，ｘ，ｙが、下記の式（３）、式（４）、及び、式（５）
    Figure JPOXMLDOC01-appb-I000002
    　　　　２．０≦ｘ≦５．０　　　　　　　　・・・式（４）
    　　　　０．８≦　ｗ／ｘ　≦２．５　　　　・・・式（５）
    を満たし、ｚが０≦ｚ≦０．４を満たすことを特徴とする水素吸蔵合金。     The chemical composition is represented by the following general formula (1 ′),
    R1v Mgw Cax R2y R3z Formula (1 ')
    R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
    When v, w, x, and y are set to satisfy the following equation (2),
    v + w + x + y = 100 Formula (2)
    v, w, x, and y are the following formulas (3), (4), and (5).
    Figure JPOXMLDOC01-appb-I000002
    2.0 ≦ x ≦ 5.0 Formula (4)
    0.8 ≦ w / x ≦ 2.5 (5)
    And z satisfies 0 ≦ z ≦ 0.4.
  8. 　前記式（５）が１．０≦　ｗ／ｘ　≦２．５　で表されることを特徴とする請求項７記載の水素吸蔵合金。 8. The hydrogen storage alloy according to claim 7, wherein the formula (5) is expressed by 1.0 ≦ w / x ≦ 2.5.
  9. 　前記Ｒ２のＮｉの一部が置換されたＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素を、０原子％を超え２．２原子％以下含むことを特徴とする請求項７又は８に記載の水素吸蔵合金。 One or two or more elements selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr, and Zn in which a part of Ni in R2 is substituted include more than 0 atomic% and 2.2 atoms % Or less, The hydrogen storage alloy of Claim 7 or 8 characterized by the above-mentioned.
  10. 　前記Ｒ２のＮｉの一部がＡｌで置換され該Ａｌが０原子％を超え２．２原子％以下含まれていることを特徴とする請求項７～９のいずれか１項に記載の水素吸蔵合金。 The hydrogen storage according to any one of claims 7 to 9, wherein a part of Ni in R2 is substituted with Al and the Al is contained in an amount of more than 0 atomic% and not more than 2.2 atomic%. alloy.
  11. 　前記Ｒ１としてのＣｅを０原子％以上２．３原子％以下含むことを特徴とする請求項７～１０のいずれか１項に記載の水素吸蔵合金。 The hydrogen storage alloy according to any one of claims 7 to 10, wherein Ce as R1 is contained in an amount of 0 atomic% to 2.3 atomic%.
  12. 　Ｐｒ５Ｃｏ１９型結晶構造を有する結晶相を１１質量％以上含むことを特徴とする請求項７～１１のいずれか１項に記載の水素吸蔵合金。 The hydrogen storage alloy according to any one of claims 7 to 11, comprising 11 mass% or more of a crystal phase having a Pr 5 Co 19 type crystal structure.
  13. 　化学組成が、下記一般式（１’）で表され、
    　　　　Ｒ１v Ｍｇw Ｃａx Ｒ２y Ｒ３z　　　　・・・式（１’）
    Ｒ１が、希土類元素より選択される１種又は２種以上の元素であり、Ｒ２が、Ｎｉであるか又はＮｉの一部をＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素で置換したものであり、Ｒ３が、前記Ｒ１、前記Ｍｇ、前記Ｃａ及び前記Ｒ２以外の元素である水素吸蔵合金であって、
    　ｖ，ｗ，ｘ，ｙが下記の式（２）を満たすように設定されたとき、
    　　　　ｖ＋ｗ＋ｘ＋ｙ＝１００　　　　　　・・・式（２）
    ｖ，ｗ，ｘ，ｙが、１３．０≦ｖ≦１８．０、２．２≦ｗ≦５．６、２．０≦ｘ≦５．０、７５．０≦ｙ≦８０．０を満たし、ｚが０≦ｚ≦０．４を満たし、且つ、ｗ及びｘが０．８≦ｗ／ｘ≦２．５を満たすことを特徴とする水素吸蔵合金。     The chemical composition is represented by the following general formula (1 ′),
    R1v Mgw Cax R2y R3z Formula (1 ')
    R1 is one or more elements selected from rare earth elements, and R2 is Ni or a part of Ni is selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr and Zn. A hydrogen storage alloy that is substituted with one or more selected elements, and R3 is an element other than R1, Mg, Ca, and R2,
    When v, w, x, and y are set to satisfy the following equation (2),
    v + w + x + y = 100 Formula (2)
    v, w, x, y satisfy 13.0 ≦ v ≦ 18.0, 2.2 ≦ w ≦ 5.6, 2.0 ≦ x ≦ 5.0, 75.0 ≦ y ≦ 80.0 , Z satisfies 0 ≦ z ≦ 0.4, and w and x satisfy 0.8 ≦ w / x ≦ 2.5.
  14. 　前記式（５）が１．０≦　ｗ／ｘ　≦２．５　で表されることを特徴とする請求項１３記載の水素吸蔵合金。 14. The hydrogen storage alloy according to claim 13, wherein the formula (5) is represented by 1.0 ≦ w / x ≦ 2.5.
  15. 　前記Ｒ２のＮｉの一部が置換されたＡｌ、Ｃｏ、Ｃｕ、Ｍｎ、Ｆｅ、ＣｒおよびＺｎからなる群より選択された１種または２種以上の元素を、０原子％を超え２．２原子％以下含むことを特徴とする請求項１３又は１４に記載の水素吸蔵合金。 One or two or more elements selected from the group consisting of Al, Co, Cu, Mn, Fe, Cr, and Zn in which a part of Ni in R2 is substituted include more than 0 atomic% and 2.2 atoms % Or less, The hydrogen storage alloy of Claim 13 or 14 characterized by the above-mentioned.
  16. 　前記Ｒ２のＮｉの一部がＡｌで置換され該Ａｌが０原子％を超え２．２原子％以下含まれていることを特徴とする請求項１３～１５のいずれか１項に記載の水素吸蔵合金。 The hydrogen occlusion according to any one of claims 13 to 15, wherein a part of Ni in R2 is substituted with Al and the Al is contained in an amount of more than 0 atomic% and not more than 2.2 atomic%. alloy.
  17. 　前記Ｒ１としてのＣｅを０原子％以上２．３原子％以下含むことを特徴とする請求項１３～１６のいずれか１項に記載の水素吸蔵合金。 The hydrogen storage alloy according to any one of claims 13 to 16, wherein Ce as R1 is contained in an amount of 0 atomic% to 2.3 atomic%.
  18. 　Ｐｒ５Ｃｏ１９型結晶構造を有する結晶相を１１質量％以上含むことを特徴とする請求項１３～１７のいずれか１項に記載の水素吸蔵合金。 The hydrogen storage alloy according to any one of claims 13 to 17, comprising a crystal phase having a Pr 5 Co 19 type crystal structure of 11 mass% or more.
  19. 　請求項１～１８のいずれか１項に記載の水素吸蔵合金を含む負極を備えたことを特徴とするニッケル水素蓄電池。 A nickel-metal hydride storage battery comprising a negative electrode containing the hydrogen storage alloy according to any one of claims 1 to 18.
PCT/JP2011/055368 2010-03-12 2011-03-08 Hydrogen storage alloy and nickel-hydrogen storage battery WO2011111699A1 (en)

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JP2013199703A (en) * 2012-02-20 2013-10-03 Gs Yuasa Corp Hydrogen storage alloy, electrode, nickel-hydrogen storage battery and method for producing hydrogen storage alloy
JP2014114476A (en) * 2012-12-07 2014-06-26 Gs Yuasa Corp Hydrogen storage alloy, electrode, nickel-hydrogen storage battery, and method for manufacturing hydrogen storage alloy
JP2015187301A (en) * 2014-03-27 2015-10-29 株式会社Ｇｓユアサ Hydrogen storage alloy, electrode, and electrical storage element
CN106854715A (en) * 2015-12-08 2017-06-16 北京有色金属研究总院 A kind of lanthanum-magnesium containing yttrium-nickel system AB3Type hydrogen storage alloy and its preparation technology
CN108493436A (en) * 2018-03-09 2018-09-04 燕山大学 Ni-based quaternary hydrogen-storing alloy electrode material of a kind of super stacking provisions lanthanum-M-magnesium-of 2H types A5B19 and preparation method thereof

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2628812A1 (en) * 2012-02-20 2013-08-21 GS Yuasa International Ltd. Hydrogen storage alloy, electrode, nickel-metal hydride rechargeable battery and method for producing hydrogen storage alloy
JP2013199703A (en) * 2012-02-20 2013-10-03 Gs Yuasa Corp Hydrogen storage alloy, electrode, nickel-hydrogen storage battery and method for producing hydrogen storage alloy
JP2014114476A (en) * 2012-12-07 2014-06-26 Gs Yuasa Corp Hydrogen storage alloy, electrode, nickel-hydrogen storage battery, and method for manufacturing hydrogen storage alloy
JP2015187301A (en) * 2014-03-27 2015-10-29 株式会社Ｇｓユアサ Hydrogen storage alloy, electrode, and electrical storage element
CN106854715A (en) * 2015-12-08 2017-06-16 北京有色金属研究总院 A kind of lanthanum-magnesium containing yttrium-nickel system AB3Type hydrogen storage alloy and its preparation technology
CN108493436A (en) * 2018-03-09 2018-09-04 燕山大学 Ni-based quaternary hydrogen-storing alloy electrode material of a kind of super stacking provisions lanthanum-M-magnesium-of 2H types A5B19 and preparation method thereof

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