WO2003056047A1 - Hydrogen-occluding alloy, powder of hydrogen-occluding alloy, processes for producing these, and negative electrode for nickel-hydrogen secondary battery - Google Patents

Hydrogen-occluding alloy, powder of hydrogen-occluding alloy, processes for producing these, and negative electrode for nickel-hydrogen secondary battery Download PDF

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Publication number
WO2003056047A1
WO2003056047A1 PCT/JP2002/013607 JP0213607W WO03056047A1 WO 2003056047 A1 WO2003056047 A1 WO 2003056047A1 JP 0213607 W JP0213607 W JP 0213607W WO 03056047 A1 WO03056047 A1 WO 03056047A1
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Prior art keywords
alloy
hydrogen
hydrogen storage
formula
storage alloy
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PCT/JP2002/013607
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French (fr)
Japanese (ja)
Inventor
Kiyofumi Takamaru
Hiroki Hayashi
Hideaki Ikeda
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Santoku Corporation
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Priority to JP2003556563A priority Critical patent/JP4685353B2/en
Priority to AU2002360049A priority patent/AU2002360049A1/en
Publication of WO2003056047A1 publication Critical patent/WO2003056047A1/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
    • 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
    • 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
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0433—Nickel- or cobalt-based alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • 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
    • H01M10/345—Gastight metal hydride accumulators
    • 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

  • Hydrogen storage alloys Hydrogen storage alloys, hydrogen storage alloy powders, their production methods, and negative electrodes for nickel hydrogen secondary batteries
  • the present invention is useful as an electrode material for nickel-metal hydride secondary batteries and the like.
  • a hydrogen storage alloy having a good balance of good activity, corrosion resistance and life characteristics is provided.
  • the present invention relates to the powder, a method for producing the powder, and a negative electrode for a Huckel hydrogen secondary battery.
  • a metal oxide monohydrogen battery in which the hydrogen negative electrode is made of a hydrogen storage alloy.
  • Such batteries inherently have a high energy density, are excellent in volumetric efficiency, can operate safely, and are excellent in characteristics and reliability.
  • the AB 5 M7] containing storage alloy is mainly used as a negative electrode material of the battery, usually, in order to improve the characteristics of the battery, high hydrogen storage capacity, a variety of such low pressures, corrosion resistance, plateau flatness Characteristics are required. Since some of these properties are contradictory, research has been conducted on improving one property without sacrificing the other property, and some of them have been put to practical use.
  • nickel-metal hydride secondary batteries have come to be used for batteries that require high-rate discharge, such as power tool applications, and there is a need for further improvement in the properties of the hydrogen storage alloy used for these batteries.
  • An object of the present invention is to be useful as an electrode material of a nickel-hydrogen secondary battery, and by using it as a negative electrode material, it is possible to use a small amount of cobalt, to have an activity such as initial activity, high-rate discharge characteristics, corrosion resistance, and life.
  • An object of the present invention is to provide a hydrogen storage alloy having excellent characteristics in a well-balanced manner and excellent recyclability, a powder thereof, a method for producing the same, and a negative electrode for a nickel-metal hydride secondary battery using the hydrogen storage alloy powder.
  • the present inventors have conducted intensive studies on the correlation between the composition and structure of the alloy and the corrosion resistance and activity in order to solve the above-mentioned problems.
  • the B-site component of the alloy is set to a specific range
  • the B-site The inventors have found that the above problems can be solved by setting the amounts of A1 and Mn in the components to a specific range, and completed the present invention.
  • composition represented by the formula (1) is substantially a single phase, has an average crystallite diameter of 15 ⁇ or less, and each crystal has a short diameter (D1).
  • a hydrogen storage alloy having a ratio (D1 / D2) of 3 or more to the diameter (D2) is used.
  • R represents a rare earth element including yttrium or a mixed element thereof
  • M represents' Mg, Fe, Cu, Zr, Ti, Mo, W, B or a mixture thereof.
  • A represents 3.30 ⁇ a ⁇ 5.15, b is 0.10 ⁇ b ⁇ 0.50 N c is 0.15 ⁇ c ⁇ 0.35, d is 0.10 ⁇ d ⁇ 0.45, e is 0 ⁇ e ⁇ 0.50, 5.10 ⁇ a + b + c + d + e ⁇ 5.50, And the abundance ratio c / d of Al and Mn is from 0 to 5.0.
  • the average crystal grain size of the crystal having the composition represented by the formula (1) is included.
  • a hydrogen storage alloy powder having a diameter (D1ZD2) of 3 or more, which is 15 ⁇ or less, a ratio of a major axis (D1) to a minor axis D2) of 3 or more, and a particle diameter of ⁇ or greater.
  • the alloy melt was cooled and solidified to obtain a piece having an average thickness of 0.05 to 0.5 mm.
  • a negative electrode for a nickel hydrogen secondary battery including the above-mentioned hydrogen storage alloy powder and a conductive material as a negative electrode material.
  • the hydrogen storage alloy of the present invention has a composition represented by the above formula (1).
  • R in the formula (1) represents a rare earth element containing yttrium or a mixed element of two or more thereof. Specifically, for example, one or two selected from the group consisting of La, Ce, Pr and Nd from the viewpoint of improving corrosion resistance when used as a negative electrode active material of a nickel hydrogen secondary battery. It is desirable that the force includes at least one kind or at least one kind selected from the group consisting of La, Ce, Pr and Nd.
  • the ratio of each rare earth element is preferably 40 to 100% by mass of La, 0 to 50% by mass of Ce, 0 to 50% by mass of Pr, and 0 to 50% by mass of Nd.
  • a in the formula (1) which indicates the amount of Ni, is 3.30 to a ⁇ 5.15, preferably 3.90 a 4.75.
  • B indicating the amount of Co is 0.10 ⁇ b ⁇ 0.50, preferably 0.20 ⁇ b ⁇ 0.50. If b exceeds 0.50, the alloy price increases, and if it is less than 0.10, a decrease in corrosion resistance is inevitable.
  • C indicating the amount of A1 is 0.15 ⁇ c ⁇ 0.35, preferably 0.20 ⁇ c ⁇ 0.30.
  • D indicating the amount of Mn is 0.10 ⁇ d ⁇ 0.45, preferably 0.20 ⁇ d ⁇ 0.30.
  • cZd indicating the abundance ratio of A1 and Mn is 0: !! to 5.0, preferably 0.3 to 1.0.
  • M in the formula (1) is an additive element for adjusting the hydrogen storage properties of the alloy, and represents Mg, Fe, Cu, Zr, Ti, Mo, W, B, or a mixture of two or more thereof.
  • E which indicates the amount of M, is 0 ⁇ e ⁇ 0.50. If e exceeds 0.50, it may not be possible to improve properties corresponding to the added amount, and recycling may be difficult.
  • the value of a + b + c + d + e indicating the B-site element ratio is 5.10 to 5.50, preferably 5.20 to 5.40. If this value is less than 5.10, it becomes difficult to obtain a desired alloy structure, and if it exceeds 5.50, a decrease in capacity when used as a battery material is inevitable.
  • the hydrogen storage alloy structure of the present invention is substantially single-phase in order to obtain the desired effects of the present invention.
  • the fact that the alloy structure is substantially a single phase means that when there is a phase peak derived from a phase other than the desired phase by X-ray diffraction, the peak having the highest peak intensity is derived from the desired phase. It means that the value is within 5% of the peak intensity.
  • the hydrogen storage alloy of the present invention has a crystal structure, and the average crystal grain size of the contained crystals is 15 111 or less, preferably 10 m or less, particularly preferably 1 to 10 m, and D1ZD2 Is 3 or more, preferably 10 or more, particularly preferably 10 to 40. If the average crystal grain size exceeds 15 ⁇ , it is difficult to obtain a desired activity when used for a negative electrode for a secondary battery. If the D1 / D2 force is less than S3, it is difficult to obtain the desired corrosion resistance.
  • D1 is the major axis of the crystal
  • the major axis means the maximum value in the longitudinal direction of the crystal grain
  • D2 is the minor axis of the crystal
  • the minor axis is a line indicating the major axis.
  • the line is divided into five equal parts, and the four straight lines perpendicular to the line indicating the major axis mean the average value of the lengths of the lines cut by the ends of the crystal grains.
  • the average crystal grain size means an average value of the minor axis.
  • the method for producing the hydrogen storage alloy of the present invention is not particularly limited as long as the composition and crystal of the obtained alloy can be controlled as described above, but the following production method of the present invention is preferable.
  • an alloy raw material having a composition represented by the above formula (1) is melted, and then the alloy melt is cooled and solidified to obtain a piece having a specific average thickness. It is characterized in that the piece is heat-treated under specific conditions.
  • the alloy raw material having the composition represented by the above formula (1) is not particularly limited as long as the obtained alloy composition is a mixture of a metal or an alloy satisfying the formula (1).
  • a mixture of metals having the composition represented by the formula (1) or a mother alloy having a desired composition prepared in advance can be used.
  • the alloy melt of the alloy raw material can be obtained, for example, by a known method such as high-frequency melting in an inert gas atmosphere using an alumina tube.
  • the above-mentioned alloy melt is solidified by cooling to obtain a piece having an average thickness of 0.05 to 0.5 mm.
  • the cooling rate is high, the crystal grain size becomes finer, and if the cooling speed is slow, the crystal grain size becomes coarse. Since the crystal grain size is not uniform during the preparation of the piece, ripening treatment is performed under specific conditions in a later step. Therefore, it is not preferable that the cooling rate at the time of producing the piece is too slow, because the crystal sizing diameter becomes large during the heat treatment described below.
  • the cooling rate is too high, the crystals are finely dispersed and the dispersed state is improved, but it is not preferable because the control of the heat treatment conditions becomes difficult or the productivity is reduced.
  • the cooling rate is further increased to become amorphous, it is not preferable because it is difficult to precipitate desired crystal grains even if heat treatment is performed thereafter.
  • the above-mentioned piece production is performed by a strip casting method using a single roll or a twin roll, a centrifugal production method, a rotating disk production method, or the like which can obtain a suitable cooling rate.
  • the cooling conditions are usually about 10 to 3000 ° C./sec, preferably 10 to 500 ° C./sec, and more preferably 10 to 200 ° C./sec.
  • the thickness of the obtained piece is controlled in the range of 0.05 to 0.5 mm in order to eliminate the variation of the crystal grain size in the cross-sectional direction of the piece and to make the crystal grain size after heat treatment described later uniform. There is a need.
  • a desired hydrogen storage alloy can be obtained by subjecting the obtained piece to a specific heat treatment.
  • the higher the heat treatment temperature and the longer the heat treatment time the smaller the grain size difference of each crystal in the piece can be.
  • the crystal grain size becomes too large and the desired characteristics cannot be obtained. There is fear. Therefore, in the production method of the present invention, it is necessary to set the ripening treatment conditions at 900 to: L100 ° C for 30 minutes to 10 hours.
  • the hydrogen storage alloy powder of the present invention has a composition represented by the above formula (1), the average crystal grain size of the included crystals is 15 m or less, preferably 10 m or less, and D1 / D2 of each crystal is It is an alloy powder having a particle size of 10 m or more, preferably 3 or more, preferably 10 or more.
  • the meaning of each configuration is the same as the above-described hydrogen storage alloy of the present invention.
  • the hydrogen storage alloy powder of the present invention When used as a negative electrode for a secondary battery, it may contain another alloy powder, and the average particle size of the alloy powder containing the hydrogen storage alloy powder of the present invention is as follows: 5 to; 100 ⁇ is preferred. Further, the composition of the alloy powder other than the hydrogen storage alloy of the present invention is preferably all compositions represented by the formula (1). However, the cZd value in equation (1) does not need to be satisfied! / ,.
  • the alloy powder containing the hydrogen storage alloy powder of the present invention has a crystal grain size of preferably 5 m or more, and more preferably 5 to 50 ⁇ , particularly when used as an electrode. It is preferable that the crystal grain size is 1/2 or less of the average particle size of the alloy powder used.
  • the surface is covered with plating or a high-molecular polymer, or a solution of an acid, alkaline solution, or the like.
  • a publicly known treatment such as a surface treatment can be performed.
  • the hydrogen storage alloy powder of the present invention for example, After production, it can be obtained by the production method of the present invention or the like in which the obtained heat-treated pieces are ground.
  • the step of pulverizing the piece after the heat treatment is not particularly limited as long as the alloy oxidation does not proceed during the pulverization of the piece and a specific particle size can be obtained, and a known method can be used.
  • a wet pulverization method using low oxygen water a dry pulverization method such as a pin mill or a disk mill, a hydrogen pulverization method using hydrogen gas, and the like are preferable.
  • the negative electrode for a nickel-hydrogen secondary battery of the present invention is not particularly limited as long as it contains the hydrogen storage alloy powder of the present invention and a conductive material as negative electrode materials. May contain other materials to achieve other purposes.
  • an alloy powder containing the hydrogen-absorbing alloy of the present invention ground to a specific particle size and a conductive material are used.
  • a negative electrode can be obtained by mixing and molding with an auxiliary agent and the like.
  • the conductive material, the binder, the conductive auxiliary agent and the like used at this time are not particularly limited, and known materials can be used.
  • the hydrogen storage alloy and the powder thereof of the present invention have a specific composition and a specific structure, they are useful as an electrode material for a nickel-metal hydride secondary battery. Discharge characteristics, corrosion resistance, and life characteristics are well-balanced, and these characteristics can be obtained with a small amount of Co, and recyclability can be considered. Further, according to the production method of the present invention, such a hydrogen storage alloy and its powder can be industrially easily obtained.
  • the negative electrode for a nickel-metal hydride secondary battery of the present invention uses the hydrogen-absorbing alloy powder of the present invention as an active material, so that the effect obtained when the negative electrode for a secondary battery is obtained is obtained, and the utility is rich.
  • the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited thereto.
  • Rare earth metals having the atomic ratios shown in Table 1 (Examples 1-1 to 1-4 used misch metal manufactured by Santoku Co., Ltd.) as the A site, and Ni, Co, Mn when the A site was 1.
  • a raw material metal or an alloy was blended so that the atomic ratio of Al, Al and X of ABx became the values shown in Table 1, and were subjected to high frequency melting in an argon atmosphere using an alumina tube to prepare an alloy melt.
  • the obtained alloy melt is continuously supplied to a single roll via a tundish, A 0.2 mm thick piece was prepared by rapid cooling at a cooling rate of 100 ° C / sec by the lip casting method.
  • the obtained piece was heat-treated in an argon gas atmosphere under the conditions shown in Table 1 to prepare a hydrogen storage alloy.
  • the composition of the obtained hydrogen storage alloy was quantitatively analyzed by X-ray fluorescence analysis (SMX-10, manufactured by Rigaku Denki Kogyo). As a result, it was confirmed that the composition was the same as the composition. Also, the alloy structure was observed with a scanning electron microscope, and it was confirmed by X-ray diffraction whether or not the alloy was substantially a single phase. Furthermore, the average crystal grain size, D1 and D2 were measured from the alloy structure observed with a scanning electron microscope. Table 1 shows the results.
  • composition of the obtained hydrogen-absorbing alloy powder was quantitatively analyzed by X-ray fluorescence analysis (SMX-10, manufactured by Rigaku Denki Kogyo), and as a result, Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1 It was confirmed that the composition was the same as the composition of the hydrogen storage alloy prepared in -2.
  • Table 2 shows the results of the measurements performed in the same manner as in Examples 1-1 to L-5.
  • the capacity at the time of discharging at 1 C at the 11th cycle was measured, and the ratio of the value at this time to the discharge capacity at the 10th cycle was evaluated.

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Abstract

A hydrogen-occluding alloy which is reduced in cobalt content, has a satisfactory balance among activity, corrosion resistance, and life characteristics, and has excellent suitability for recycling. The hydrogen-occluding alloy has a composition represented by the formula (1), is constituted substantially of a single phase, and has an average crystal grain diameter of 15 µm or smaller and a major axis/minor axis ratio in each crystal of 3 or higher. RNiaCobAlcMndMe (1) (R is any of rare earth elements including yttrium, etc.; M is magnesium, iron, copper, zirconium, etc.; and 3.30<a≤5.15, 0.10≤b≤0.50, 0.15≤c<0.35, 0.10≤d≤0.45, 0≤e≤0.50, 5.10≤a+b+c+d+e≤5.50, and 0.1≤c/d≤5.0.)

Description

水素吸蔵合金、 水素吸蔵合金粉末、 それらの製造法及び-ッケル水素二次電池用負極 技術分野 Hydrogen storage alloys, hydrogen storage alloy powders, their production methods, and negative electrodes for nickel hydrogen secondary batteries
本発明は、 ニッケル水素二次電池等の電極材料として有用であり、 特に、 二次電池 用負極材料に用いることにより、 良好な活性度、 耐食性並びに寿命特性をバランス良 く備えた水素吸蔵合金、 その粉末、 それらの製造法及ぴュッケル水素二次電池用負極 に関する。  INDUSTRIAL APPLICABILITY The present invention is useful as an electrode material for nickel-metal hydride secondary batteries and the like.In particular, when used as a negative electrode material for secondary batteries, a hydrogen storage alloy having a good balance of good activity, corrosion resistance and life characteristics is provided. The present invention relates to the powder, a method for producing the powder, and a negative electrode for a Huckel hydrogen secondary battery.
背景技術 Background art
現在、 金属酸化物一水素電池において、 水素負極を水素吸蔵合金で構成した形式の 電池が注目を集めている。 このような電池は、 元来高エネルギー密度を有し、 容積効 率に優れ、 しかも安全作動が可能であって、 特性的にも信頼度の点でも優れている。 該電池の負極材料として主に使用される AB5M7]素吸蔵合金には、通常、電池の特性 を向上させるために、 高水素吸蔵量、 低 圧、 耐食性、 プラトーの平坦性等の様々 な特性が要求される。 これら特性のうちのいくつかは、 相反する性質であるため、一 方の特性を犠牲にせずに他方の特性を向上させるという点についての研究が進められ、 一部実用化に至っている。 At present, attention has been focused on a metal oxide monohydrogen battery in which the hydrogen negative electrode is made of a hydrogen storage alloy. Such batteries inherently have a high energy density, are excellent in volumetric efficiency, can operate safely, and are excellent in characteristics and reliability. The AB 5 M7] containing storage alloy is mainly used as a negative electrode material of the battery, usually, in order to improve the characteristics of the battery, high hydrogen storage capacity, a variety of such low pressures, corrosion resistance, plateau flatness Characteristics are required. Since some of these properties are contradictory, research has been conducted on improving one property without sacrificing the other property, and some of them have been put to practical use.
電池のサイクル特性を向上させる要因となる水素吸蔵合金の耐食性を向上させると いう面においては、 コバルトを添加する方法が効果を上げ、 実用化に至っている。 し かし、 コバルトは非常に高価な金属であるため、 合金の価格が高くなる。 そこで、 コ バルトの添加量を低減しながら合金の耐食性を維持する技術の開発が進められている。 例えば、 コバルトと共に他の添加元素を多数使用する方法が検討されている。 しか し、 該方法では、 合金を構成する元素数が増えるため、 電池のリサイクルが困難にな り、 リサイクルにかかるコストが増加するという問題が新たに浮上している。 また、 希土類元素を主体とする Aサイト成分に対し、 Niを主体とする Bサイト成分の割合 を多くする方法が試みられている。 該方法では、 合金組織を均質化することが困難と なり、 PCT曲線におけるブラトー部の傾斜が大きくなりすぎたり、多段ブラトーにな る傾向が高いため、電池容量の低下や、電池の内圧特性が低下する等の問題が生じる。 電池の活性度を向上させる要因となる水素吸蔵合金の活性度を向上させるという面 においては、 合金に対して、 酸やアルカリによる表面処理を施す方法、 Aサイト成分 の割合を多くする方法が試みられている。 しカゝし、 活性度は前述の耐食性とは相反す る要因であるため、 活性度を向上させるこれらの方法は同時に耐食性を低下させると いう問題がある。 In terms of improving the corrosion resistance of the hydrogen storage alloy, which is a factor that improves the cycle characteristics of batteries, the method of adding cobalt is effective and has been put to practical use. However, cobalt is a very expensive metal, which increases the price of the alloy. Therefore, technology to maintain the corrosion resistance of the alloy while reducing the amount of cobalt added is being developed. For example, a method of using a large number of other additive elements together with cobalt is being studied. However, this method has a new problem that the number of elements constituting the alloy increases, which makes it difficult to recycle the battery and increases the cost of recycling. Attempts have been made to increase the ratio of B-site components mainly composed of Ni to A-site components mainly composed of rare earth elements. According to this method, it is difficult to homogenize the alloy structure, and the inclination of the blast plateau in the PCT curve becomes too large, and the tendency toward multi-stage blast plateau is high, so that the battery capacity is reduced and the internal pressure characteristics of the battery are reduced. Problems such as lowering occur. In terms of improving the activity of the hydrogen storage alloy, which is a factor that improves the activity of the battery, attempts have been made to apply a surface treatment to the alloy with an acid or alkali and to increase the proportion of the A-site component to the alloy. Have been. The activity is contradictory to the aforementioned corrosion resistance Therefore, these methods for improving the activity have a problem that the corrosion resistance is reduced at the same time.
最近ではパヮ一ツール用途等の高率放電を必要とする電池についてもニッケル水素 二次電池が使われるようになり、 これに使用する水素吸蔵合金の特性の更なる向上が 求められている。  Recently, nickel-metal hydride secondary batteries have come to be used for batteries that require high-rate discharge, such as power tool applications, and there is a need for further improvement in the properties of the hydrogen storage alloy used for these batteries.
発明の開示 Disclosure of the invention
本発明の目的は、 二ッケル水素二次電池の電極材料として有用であり、 負極材料と して使用することにより、少ないコバルト量で、初期活性、高率放電特性等の活性度、 耐食性並びに寿命特性を良好にバランス良く備え、 かつリサイクル性にも優れた水素 吸蔵合金、 その粉末、 それらの製造法、 並びに該水素吸蔵合金粉末を用いたニッケル 水素二次電池用負極を提供することにある。  An object of the present invention is to be useful as an electrode material of a nickel-hydrogen secondary battery, and by using it as a negative electrode material, it is possible to use a small amount of cobalt, to have an activity such as initial activity, high-rate discharge characteristics, corrosion resistance, and life. An object of the present invention is to provide a hydrogen storage alloy having excellent characteristics in a well-balanced manner and excellent recyclability, a powder thereof, a method for producing the same, and a negative electrode for a nickel-metal hydride secondary battery using the hydrogen storage alloy powder.
本発明者らは、 上記課題を解決するため、 合金の組成や組織と、 耐食性及び活性度 との相関について鋭意検討を行った結果、合金の Bサイト成分を特定の範囲にすると 共に、 Bサイト成分のうち A1及び Mn量を特定の範囲とすることによって、 上記課 題が解決できることを知見し、 本発明を完成した。  The present inventors have conducted intensive studies on the correlation between the composition and structure of the alloy and the corrosion resistance and activity in order to solve the above-mentioned problems. As a result, the B-site component of the alloy is set to a specific range, and the B-site The inventors have found that the above problems can be solved by setting the amounts of A1 and Mn in the components to a specific range, and completed the present invention.
すなわち本宪明によれば、式 (1)で表される組成を有し、実質的に単相で、含まれる 結晶の平均結晶立径が 15μ ηι以下、 各結晶の長径 (D1)と短径 (D2)との比 (D1/D2)が 3以上である水素吸蔵合金が ¾される。  That is, according to the present invention, it has a composition represented by the formula (1), is substantially a single phase, has an average crystallite diameter of 15 μηι or less, and each crystal has a short diameter (D1). A hydrogen storage alloy having a ratio (D1 / D2) of 3 or more to the diameter (D2) is used.
RN i a C o bA l 0Mn dMe · · · (1) RN i a C o b A l 0 Mn d M e
(式中、 Rはィットリゥムを含む希土類元素又はこれらの混合元素を示し、 Mは' Mg、 Fe、 Cu、 Zr、 Ti、 Mo、 W、 B又はこれらの混合物を示す。 aは 3.30<a≤5.15、 bは 0.10≤b≤0.50N cは 0.15≤c<0.35、 dは 0.10≤d≤0.45、 eは 0≤e≤0.50、 5.10≤a +b+c+d+e≤5.50であり、 且つ Al及ぴ Mnの存在比 c/dが 0ユ〜 5.0である。 '） また本発明によれば、式 (1)で表される組成を有し、含まれる結晶の平均結晶粒径が 15μ πι以下であり、 各結晶の長径 (D1)と短径 D2)との比 (D1ZD2)が 3以上であり、 粒径が ΙΟμ πι以上である水素吸蔵合金粉末が提供される。 (Wherein, R represents a rare earth element including yttrium or a mixed element thereof, M represents' Mg, Fe, Cu, Zr, Ti, Mo, W, B or a mixture thereof. A represents 3.30 <a≤ 5.15, b is 0.10≤b≤0.50 N c is 0.15≤c <0.35, d is 0.10≤d≤0.45, e is 0≤e≤0.50, 5.10≤a + b + c + d + e≤5.50, And the abundance ratio c / d of Al and Mn is from 0 to 5.0. ') According to the present invention, the average crystal grain size of the crystal having the composition represented by the formula (1) is included. Provided is a hydrogen storage alloy powder having a diameter (D1ZD2) of 3 or more, which is 15 μπι or less, a ratio of a major axis (D1) to a minor axis D2) of 3 or more, and a particle diameter of ΙΟμπι or greater.
更に本発明によれば、式 (1)で示される組成となる合金原料を溶融した後、該合金溶 融物を冷却凝固し、平均厚さ 0.05〜0.5mmの铸片を得、得られた铸片を 900〜1100°C で 30分間〜 10時間熱処理する上記水素吸蔵合金の製造法、 更に粉砕工程を行う上記 水素吸蔵合金粉末の製造法が される。 また本発明によれば、 上記水素吸蔵合金粉末と導電材とを負極材料として含む二ッ ケル水素二次電池用負極が提供される。 Furthermore, according to the present invention, after melting the alloy raw material having the composition represented by the formula (1), the alloy melt was cooled and solidified to obtain a piece having an average thickness of 0.05 to 0.5 mm. The above-mentioned method for producing a hydrogen storage alloy in which a piece is heat-treated at 900 to 1100 ° C. for 30 minutes to 10 hours, and the method for producing a hydrogen storage alloy powder in which a pulverizing step is performed. Further, according to the present invention, there is provided a negative electrode for a nickel hydrogen secondary battery including the above-mentioned hydrogen storage alloy powder and a conductive material as a negative electrode material.
発明の好ましい実施の態様 Preferred embodiments of the invention
以下、 本発明について詳細に説明する。  Hereinafter, the present invention will be described in detail.
本発明の水素吸蔵合金は、 上記式 (1)で表される組成を有する。 式 (1)中の Rは、 ィ ットリゥムを含む希土類元素又はこれらの 2種以上の混合元素を示す。 具体的には例 えば、 二ッケル水素二次電池の負極活物質として使用した際に耐食性等を向上させる 点から、 主に La、 Ce、 Pr及び Ndからなる群より選択される 1種又は 2種以上を含 む力 \ 若しくは La、 Ce、 Pr及び Ndからなる群より選択される 1種又は 2種以上で あることが望ましい。 この際の各希土類元素の比率は、 Laが 40〜100質量％、 Ceが 0〜50質量％、 Prが 0〜50質量％、 Ndが 0〜50質量％であることが好ましい。  The hydrogen storage alloy of the present invention has a composition represented by the above formula (1). R in the formula (1) represents a rare earth element containing yttrium or a mixed element of two or more thereof. Specifically, for example, one or two selected from the group consisting of La, Ce, Pr and Nd from the viewpoint of improving corrosion resistance when used as a negative electrode active material of a nickel hydrogen secondary battery. It is desirable that the force includes at least one kind or at least one kind selected from the group consisting of La, Ce, Pr and Nd. In this case, the ratio of each rare earth element is preferably 40 to 100% by mass of La, 0 to 50% by mass of Ce, 0 to 50% by mass of Pr, and 0 to 50% by mass of Nd.
式 (1)中の Ni量を示す aは、 3.30く a≤5.15、 好ましくは 3.90 a 4.75である。 Co量を示す bは 0.10≤b≤0.50、好ましくは 0.20≤b≤0.50である。 bが 0.50を超え ると合金価格が高くなり、 0.10未満では耐食性の低下が避けられない。 A1量を示す c は 0.15≤cく 0.35、好ましくは 0.20≤c≤0.30である。 Mn量を示す dは 0.10≤d≤0.45、 好ましくは 0.20≤d≤0.30である。 また、 A1及ぴ Mnの存在比を示す cZdは 0.：!〜 5.0、 好ましくは 0.3〜1.0である。 cZdが前記範囲外では所望の合金が得られない。 式 (1)中の Mは、合金の水素吸蔵特性を調整するための添加元素であり、 Mg、 Fe、 Cu、 Zr、 Ti、 Mo、 W、 B又はこれらの 2種以上の混合物を示す。 M量を示す eは 0 ≤e≤0.50である。 eが 0.50を超える場合は、 添加量に見合う特性の向上が望めず、 リサイクルが困難になる恐れがある。  A in the formula (1), which indicates the amount of Ni, is 3.30 to a≤5.15, preferably 3.90 a 4.75. B indicating the amount of Co is 0.10≤b≤0.50, preferably 0.20≤b≤0.50. If b exceeds 0.50, the alloy price increases, and if it is less than 0.10, a decrease in corrosion resistance is inevitable. C indicating the amount of A1 is 0.15 ≦ c ≦ 0.35, preferably 0.20 ≦ c ≦ 0.30. D indicating the amount of Mn is 0.10≤d≤0.45, preferably 0.20≤d≤0.30. Also, cZd indicating the abundance ratio of A1 and Mn is 0: !! to 5.0, preferably 0.3 to 1.0. If cZd is out of the above range, a desired alloy cannot be obtained. M in the formula (1) is an additive element for adjusting the hydrogen storage properties of the alloy, and represents Mg, Fe, Cu, Zr, Ti, Mo, W, B, or a mixture of two or more thereof. E, which indicates the amount of M, is 0 ≤ e ≤ 0.50. If e exceeds 0.50, it may not be possible to improve properties corresponding to the added amount, and recycling may be difficult.
本発明の合金において Bサイト元素比を示す a+b+c+d+eの値は、 5.10〜5.50、 好ましくは 5.20〜5.40である。 この値が 5.10未満では所望の合金組織とすることが 困難になり、 5.50を超えると電池材料とした際の容量低下が避けられない。  In the alloy of the present invention, the value of a + b + c + d + e indicating the B-site element ratio is 5.10 to 5.50, preferably 5.20 to 5.40. If this value is less than 5.10, it becomes difficult to obtain a desired alloy structure, and if it exceeds 5.50, a decrease in capacity when used as a battery material is inevitable.
本発明の水素吸蔵合金組織は、 本発明の所望の効果を得るために実質的に単相であ る。 合金組織が実質的に単相であるとは、 X線回折により、 所望の相以外に由来する 相のピークが存在した場合、 そのうちのピーク強度が最も高いものが、 所望の相に由 来するピーク強度の 5%以内の値になる場合を意味する。  The hydrogen storage alloy structure of the present invention is substantially single-phase in order to obtain the desired effects of the present invention. The fact that the alloy structure is substantially a single phase means that when there is a phase peak derived from a phase other than the desired phase by X-ray diffraction, the peak having the highest peak intensity is derived from the desired phase. It means that the value is within 5% of the peak intensity.
本発明の水素吸蔵合金は、結晶構造を含み、含まれる結晶の平均結晶粒径が 15 111 以下、好ましくは 10 m以下、特に好ましくは 1〜10 mであり、各結晶の D1ZD2 が 3以上、 好ましくは 10以上、 特に好ましくは 10〜40である。 平均結晶粒径が 15 μ πιを超えると二次電池用負極に用いた場合に所望の活性度が得られ難い。また、 D1 /D2力 S 3未満では、 所望の耐食性が得られ難い。 The hydrogen storage alloy of the present invention has a crystal structure, and the average crystal grain size of the contained crystals is 15 111 or less, preferably 10 m or less, particularly preferably 1 to 10 m, and D1ZD2 Is 3 or more, preferably 10 or more, particularly preferably 10 to 40. If the average crystal grain size exceeds 15 μπι, it is difficult to obtain a desired activity when used for a negative electrode for a secondary battery. If the D1 / D2 force is less than S3, it is difficult to obtain the desired corrosion resistance.
本発明において D1は結晶の長径であって、 該長径とは、 結晶粒の長手方向の最大 値を意味し、 D2は結晶の短径であって、 該短径とは、 前記長径を示す線分を 5等分 し、長径を示す線分と直交する 4本の直線がそれぞれ結晶粒の端により切り取られた 線分の長さの平均値を意味する。 また、 本発明において平均結晶粒径とは、 上記短径 の平均値を意味する。  In the present invention, D1 is the major axis of the crystal, and the major axis means the maximum value in the longitudinal direction of the crystal grain, and D2 is the minor axis of the crystal, and the minor axis is a line indicating the major axis. The line is divided into five equal parts, and the four straight lines perpendicular to the line indicating the major axis mean the average value of the lengths of the lines cut by the ends of the crystal grains. In the present invention, the average crystal grain size means an average value of the minor axis.
本発明の水素吸蔵合金を製造するには、 得られる合金の組成及び結晶が上述のとお り制御しうる方法であれば特に限定されないが、 以下の本発明の製造法が好ましい。 本発明の水素吸蔵合金の製造法は、上記式 (1)で示される組成となる合金原料を溶融 した後、 該合金溶融物を冷却凝固し、 特定平均厚さの铸片を得、 得られた鎳片を特定 条件で熱処理することを特徴とする。  The method for producing the hydrogen storage alloy of the present invention is not particularly limited as long as the composition and crystal of the obtained alloy can be controlled as described above, but the following production method of the present invention is preferable. In the method for producing a hydrogen storage alloy of the present invention, an alloy raw material having a composition represented by the above formula (1) is melted, and then the alloy melt is cooled and solidified to obtain a piece having a specific average thickness. It is characterized in that the piece is heat-treated under specific conditions.
本発明の製造法において、上記式 (1)で示される組成となる合金原料としては、得ら れる合金組成が式 (1)を充足する金属や合金の混合物であれば特に限定されないが、通 常、式 (1)で示す組成となる各金属の混合物又は予め調製した所望組成の母合金が使用 できる。 該合金原料の合金溶融物は、 例えば、 アルミナルツポを用いて不活性ガス雰 囲気中、 高周波溶融等の公知の方法により得ることができる。  In the production method of the present invention, the alloy raw material having the composition represented by the above formula (1) is not particularly limited as long as the obtained alloy composition is a mixture of a metal or an alloy satisfying the formula (1). In general, a mixture of metals having the composition represented by the formula (1) or a mother alloy having a desired composition prepared in advance can be used. The alloy melt of the alloy raw material can be obtained, for example, by a known method such as high-frequency melting in an inert gas atmosphere using an alumina tube.
本発明の製造法では、次に、上記合金溶融物を冷却凝固し、平均厚さ 0.05〜0.5mm の铸片を得る。 この際、 冷却速度が速ければ結晶粒径は微細化し、 遅ければ粗大化す る。 該铸片作製時には結晶粒径が均一でないため、 後工程において特定条件で熟処理 を行う。 従って、 铸片作製時の冷却速度が遅すぎると、 後述する熱処理時に結晶求立径 が粗大化するので好ましくない。 逆に冷却速度が速すぎると、 結晶が微細ィ匕し分散状 態は良くなるが、 熱処理条件の制御が困難となったり、 生産性が低下するので好まし くない。 また、 冷却速度が更に速くなり非晶質となった場合には、 その後に熱処理を 行っても所望結晶粒を析出させることが困難であるので好ましくない。  Next, in the production method of the present invention, the above-mentioned alloy melt is solidified by cooling to obtain a piece having an average thickness of 0.05 to 0.5 mm. At this time, if the cooling rate is high, the crystal grain size becomes finer, and if the cooling speed is slow, the crystal grain size becomes coarse. Since the crystal grain size is not uniform during the preparation of the piece, ripening treatment is performed under specific conditions in a later step. Therefore, it is not preferable that the cooling rate at the time of producing the piece is too slow, because the crystal sizing diameter becomes large during the heat treatment described below. Conversely, if the cooling rate is too high, the crystals are finely dispersed and the dispersed state is improved, but it is not preferable because the control of the heat treatment conditions becomes difficult or the productivity is reduced. In addition, when the cooling rate is further increased to become amorphous, it is not preferable because it is difficult to precipitate desired crystal grains even if heat treatment is performed thereafter.
以上の点より、 上記铸片作製は、 好適な冷却速度が得られる単ロールや双ロールに よるストリップキャスト法、 遠心铸造法、 回転円盤鎵造法等により行うことが好まし い。 冷却条件は、 通常 10〜3000°C/秒程度、 好ましくは 10〜500°C/秒、 更に好ま しくは 10〜200°CZ秒の冷却速度で行なうことができる。 得られる铸片の厚さは、 鎳片の断面方向における結晶粒径のサイズのばらつきをな くし、後述する熱処理後の結晶粒径を均一にするために、 0.05〜0.5mmの範囲に制御 する必要がある。 この場合、 上記冷却方法を揉用することにより、 得られる铸片の厚 さ方向に柱状晶が成長する。 単ロールストリップキャストをはじめとする片面冷却で は、 冷却媒体に接触する面の結晶粒径が一番小さく、 対面に向かって結晶粒径が大き くなる。 双ロールストリップキャストをはじめとする両面冷却では冷却媒体に接触す る表面の結晶粒径が小さく、 铸片の中心部に向かって結晶粒径が大きくなる。 鍀片の 厚さが 0.5mmを超えると、 結晶粒径の小さい部分と大きい部分とで粒径の差が大き くなりすぎ、 後述する熱処理によっても前述の所望の組織にすることが困難になる。 本発明の製造法では、 次に、 得られた铸片を特定の熱処理に供することにより所望 の水素吸蔵合金を得ることができる。 一般に、 熱処理温度を高くして、 熱処理時間を 長くするほど铸片内の各結晶の粒径差を小さくすることができるが、 結晶粒径が大き くなりすぎて、 所望の特性が得られない恐れがある。 従って、 本発明の製造法におい ては、 熟処理条件を、 900〜： L100°Cで 30分間〜 10時間とする必要がある。 From the above points, it is preferable that the above-mentioned piece production is performed by a strip casting method using a single roll or a twin roll, a centrifugal production method, a rotating disk production method, or the like which can obtain a suitable cooling rate. The cooling conditions are usually about 10 to 3000 ° C./sec, preferably 10 to 500 ° C./sec, and more preferably 10 to 200 ° C./sec. The thickness of the obtained piece is controlled in the range of 0.05 to 0.5 mm in order to eliminate the variation of the crystal grain size in the cross-sectional direction of the piece and to make the crystal grain size after heat treatment described later uniform. There is a need. In this case, columnar crystals grow in the thickness direction of the obtained piece by rubbing the cooling method. In single-sided cooling such as single roll strip casting, the crystal grain size on the surface that comes into contact with the cooling medium is the smallest, and the crystal grain size increases toward the opposite surface. In double-sided cooling, such as twin roll strip casting, the crystal grain size on the surface in contact with the cooling medium is small, and the crystal grain size increases toward the center of the piece.と If the thickness of the piece exceeds 0.5 mm, the difference in grain size between the portion with a small crystal grain size and the portion with a large crystal grain size becomes too large, making it difficult to obtain the desired structure by the heat treatment described below. . Next, in the production method of the present invention, a desired hydrogen storage alloy can be obtained by subjecting the obtained piece to a specific heat treatment. In general, the higher the heat treatment temperature and the longer the heat treatment time, the smaller the grain size difference of each crystal in the piece can be. However, the crystal grain size becomes too large and the desired characteristics cannot be obtained. There is fear. Therefore, in the production method of the present invention, it is necessary to set the ripening treatment conditions at 900 to: L100 ° C for 30 minutes to 10 hours.
本発明の水素吸蔵合金粉末は、上記式 (1)で表される組成を有し、含まれる結晶の平 均結晶粒径が 15 m以下、好ましくは 10 m以下、 各結晶の D1/D2が 3以上、好 ましくは 10以上である粒径 10 m以上の合金粉末である。 ここで、 各構成の意味す るところは上述の本発明の水素吸蔵合金と同様である。  The hydrogen storage alloy powder of the present invention has a composition represented by the above formula (1), the average crystal grain size of the included crystals is 15 m or less, preferably 10 m or less, and D1 / D2 of each crystal is It is an alloy powder having a particle size of 10 m or more, preferably 3 or more, preferably 10 or more. Here, the meaning of each configuration is the same as the above-described hydrogen storage alloy of the present invention.
本発明の水素吸蔵合金粉末を二次電池用負極として用いる場合には、 他の合金粉末 を含んでいても良く、 その際の本発明の水素吸蔵合金粉末を含む合金粉末の平均粒径 は、 5〜； 100 μ πιが好ましい。 また、本発明の水素吸蔵合金以外の合金粉末の組成は、 全てが式 (1)で表される組成であることが好ましレ、。 但し、 式 (1)における cZd値は必 ずしも充足する必要は無！/、。  When the hydrogen storage alloy powder of the present invention is used as a negative electrode for a secondary battery, it may contain another alloy powder, and the average particle size of the alloy powder containing the hydrogen storage alloy powder of the present invention is as follows: 5 to; 100 μπι is preferred. Further, the composition of the alloy powder other than the hydrogen storage alloy of the present invention is preferably all compositions represented by the formula (1). However, the cZd value in equation (1) does not need to be satisfied! / ,.
前記二次電池用負極に用いる際の本発明の水素吸蔵合金粉末を含む合金粉末の結晶 粒径は 5 m以上、 更には 5〜50 ί πιが好ましく、 特に、 電極として使用する際には、 結晶粒径が、 用いる合金粉末の平均粒径の 1/2以下であることが好ましい。  When used as the secondary battery negative electrode, the alloy powder containing the hydrogen storage alloy powder of the present invention has a crystal grain size of preferably 5 m or more, and more preferably 5 to 50 μπι, particularly when used as an electrode. It is preferable that the crystal grain size is 1/2 or less of the average particle size of the alloy powder used.
このような水素吸蔵合金粉末は、 電極材料とする場合、 例えば、 電極諸特性の更な る向上を目的として、 メッキゃ高分子ポリマー等で表面ネ皮覆したり、 酸、 アル力リ等 の溶液による表面処理等、 公知の処理を施すことができる。  When such a hydrogen storage alloy powder is used as an electrode material, for example, for the purpose of further improving various electrode characteristics, the surface is covered with plating or a high-molecular polymer, or a solution of an acid, alkaline solution, or the like. A publicly known treatment such as a surface treatment can be performed.
本発明の水素吸蔵合金粉末を製造するには、 例えば、 上記本発明の水素吸蔵合金を 製造した後、 得られた熱処理後の鎳片を粉碎する本発明の製造法等により得ることが できる。 In order to produce the hydrogen storage alloy powder of the present invention, for example, After production, it can be obtained by the production method of the present invention or the like in which the obtained heat-treated pieces are ground.
前記熱処理後の铸片を粉碎する工程は、 铸片の粉砕時に合金酸化が進まず、 特定の 粒度が得られる方法であれば特に限定されず公知の方法を用いることができる。 例え ば、 低酸素水を用いた湿式粉碎法、 ピンミルやディスクミル等の乾式粉碎法、 水素ガ スを用いた水素粉砕法等が好ましく挙げられる。  The step of pulverizing the piece after the heat treatment is not particularly limited as long as the alloy oxidation does not proceed during the pulverization of the piece and a specific particle size can be obtained, and a known method can be used. For example, a wet pulverization method using low oxygen water, a dry pulverization method such as a pin mill or a disk mill, a hydrogen pulverization method using hydrogen gas, and the like are preferable.
本発明のニッケル水素二次電池用負極は、 本発明の水素吸蔵合金粉末と、 導電材と を負極材料として含むものであれば特に限定されず、 所望の目的を更に向上させるた めに、 また他の目的を達成するために他の材料を含んでいても良 、。  The negative electrode for a nickel-hydrogen secondary battery of the present invention is not particularly limited as long as it contains the hydrogen storage alloy powder of the present invention and a conductive material as negative electrode materials. May contain other materials to achieve other purposes.
本発明のニッケル水素二次電池用負極を調製するには、 例えば、 特定粒度に粉碎し た本発明の水素吸蔵合金を含む合金粉末及び導電材を使用し、 の方法により、 結 着剤、 導電助剤等と共に混合、 成形して負極を得ることができる。 この際用いる導電 材、 結着剤、 導電助剤等は特に限定されず、 公知のものが使用できる。  In order to prepare the negative electrode for a nickel-metal hydride secondary battery of the present invention, for example, an alloy powder containing the hydrogen-absorbing alloy of the present invention ground to a specific particle size and a conductive material are used. A negative electrode can be obtained by mixing and molding with an auxiliary agent and the like. The conductive material, the binder, the conductive auxiliary agent and the like used at this time are not particularly limited, and known materials can be used.
本発明の水素吸蔵合金及びその粉末は、 特定の組成及ぴ特定の組織を有するので、 ニッケル水素二次電池の電極材料として有用であり、 該負極材料として使用すること により、 初期活性、 高率放電特性、 耐食性及び寿命特性を良好にパランス良く備え、 更に、少ない Co量でこのような特性が得られ、 かつリサイクル性も考慮しうるので、 実用性に優れている。 また、 本発明の製造法では、 このような水素吸蔵合金及ぴその 粉末を工業的に容易に得ることができる。  Since the hydrogen storage alloy and the powder thereof of the present invention have a specific composition and a specific structure, they are useful as an electrode material for a nickel-metal hydride secondary battery. Discharge characteristics, corrosion resistance, and life characteristics are well-balanced, and these characteristics can be obtained with a small amount of Co, and recyclability can be considered. Further, according to the production method of the present invention, such a hydrogen storage alloy and its powder can be industrially easily obtained.
本発明のニッケル水素二次電池用負極は、 活物質として上記本発明の水素吸蔵合金 粉末を用いるので、 上記二次電池用負極とした際の効果が得られ、 実用性に富む。 以下、 本発明を実施例及び比較例により更に詳細に説明する力 本発明はこれらに 限定されない。  The negative electrode for a nickel-metal hydride secondary battery of the present invention uses the hydrogen-absorbing alloy powder of the present invention as an active material, so that the effect obtained when the negative electrode for a secondary battery is obtained is obtained, and the utility is rich. Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited thereto.
実施例 1-1〜1-5及ぴ比較例 1-1〜： 1-2  Examples 1-1 to 1-5 and Comparative Examples 1-1 to: 1-2
表 1に示す原子比の希土類金属 (実施例 1-1〜1-4は株式会社三徳製のミッシュメタ ルを用いた)を Aサイトとし、 該 Aサイトを 1とした場合の Ni、 Co、 Mn、 Alの原子 比及び ABxの Xが表 1に示す値となるように原料金属又は合金を配合し、 アルミナ ルツポを用いてアルゴン雰囲気中、 高周波溶融して合金溶融物を調製した。 次いで、 得られた合金溶融物を、 タンディッシュを介して、 単ロールに連続的に供給し、 スト リップキャスト法により冷却速度 100°C/秒で急冷して厚さ 0.2mmの铸片を調製し た。 次いで、 得られた铸片をアルゴンガス雰囲気中で表 1に示す条件で熱処理を行い、 水素吸蔵合金を調製した。 Rare earth metals having the atomic ratios shown in Table 1 (Examples 1-1 to 1-4 used misch metal manufactured by Santoku Co., Ltd.) as the A site, and Ni, Co, Mn when the A site was 1. A raw material metal or an alloy was blended so that the atomic ratio of Al, Al and X of ABx became the values shown in Table 1, and were subjected to high frequency melting in an argon atmosphere using an alumina tube to prepare an alloy melt. Next, the obtained alloy melt is continuously supplied to a single roll via a tundish, A 0.2 mm thick piece was prepared by rapid cooling at a cooling rate of 100 ° C / sec by the lip casting method. Next, the obtained piece was heat-treated in an argon gas atmosphere under the conditions shown in Table 1 to prepare a hydrogen storage alloy.
得られた水素吸蔵合金について、 蛍光 X線分析 (理学電機工業製 SMX-10)によって 組成を定量分析した結果、 配合組成と同一であることが確認できた。 また、 走查型電 子顕微鏡で合金組織を観察し、 X線回折によって、 実質的に単相であるカゝ否かを確認 した。 更に、 走査型電子顕微鏡で観察した合金組織から、 平均結晶粒径、 D1及ぴ D2 を測定した。 結果を表 1に示す。 The composition of the obtained hydrogen storage alloy was quantitatively analyzed by X-ray fluorescence analysis (SMX-10, manufactured by Rigaku Denki Kogyo). As a result, it was confirmed that the composition was the same as the composition. Also, the alloy structure was observed with a scanning electron microscope, and it was confirmed by X-ray diffraction whether or not the alloy was substantially a single phase. Furthermore, the average crystal grain size, D1 and D2 were measured from the alloy structure observed with a scanning electron microscope. Table 1 shows the results.
表 1 table 1
Figure imgf000010_0001
Figure imgf000010_0001
実施例 2-l〜2-5及び比較例 2-1〜2-2 Examples 2-l to 2-5 and Comparative examples 2-1 to 2-2
実施例 1-1〜1-5又は比較例 1-：！〜 1-2で調製した水素吸蔵合金を機械的に粉砕し、 平均粒径が 60 m以下の水素吸蔵合金粉末をそれぞれ調製した。  Examples 1-1 to 1-5 or Comparative Example 1- :! The hydrogen storage alloys prepared in Steps 1 to 2 were mechanically pulverized to prepare hydrogen storage alloy powders having an average particle diameter of 60 m or less.
得られた水素吸蔵合金粉末について、 蛍光 X線分析 (理学電機工業製 SMX-10)によ つて組成を定量分析した結果、 実施例 1-1〜1-5及ぴ比較例 1-1〜1-2で調製した水素 吸蔵合金組成と同一であることが確認できた。また、実施例 1-1〜： L-5と同様に各測定 を行なった結果を表 2に示す。  The composition of the obtained hydrogen-absorbing alloy powder was quantitatively analyzed by X-ray fluorescence analysis (SMX-10, manufactured by Rigaku Denki Kogyo), and as a result, Examples 1-1 to 1-5 and Comparative Examples 1-1 to 1 It was confirmed that the composition was the same as the composition of the hydrogen storage alloy prepared in -2. Table 2 shows the results of the measurements performed in the same manner as in Examples 1-1 to L-5.
表 2  Table 2
Figure imgf000011_0001
Figure imgf000011_0001
実施例 3-1〜3-5及ぴ比較例 3-1〜3-2  Example 3-1 to 3-5 and Comparative Example 3-1 to 3-2
実施例 2-1〜2-5又は比較例 2-1〜2-2で調製した水素吸蔵合金粉末をそれぞれ 1.2g 計量し、 導電材としてのカルポニルニッケル lg及ぴ結着材としてのフッ素樹脂粉末 0.2gと混合し、繊維状物をそれぞれ調製した。 得られた鶸锥状物を、 ニッケルメッシ ュで包み込み、 2.8ton//cm2の圧力で加圧成形し、 ニッケル水素二次電池用負極を作 製した。 各電極について、 30%の KOH中、 5気圧の加圧容器中で充放電テストを行 い、 以下に示す初期活性、 高率放電特性及ぴ耐食性を評価した。 結果を表 3に示す。 初期活性は、 0.2Cの放電電流で 10サイクル行い、 10サイクル目の放電容量に対す る 3サイクノレ目の放電容量を評価することにより行なった。 1.2 g of each of the hydrogen storage alloy powders prepared in Examples 2-1 to 2-5 or Comparative Examples 2-1 to 2-2 were weighed, and carbonyl carbon lg as a conductive material and a fluororesin powder as a binder were weighed. The mixture was mixed with 0.2 g to prepare fibrous materials. The obtained whisker-like material was wrapped in a nickel mesh and pressed under a pressure of 2.8 ton // cm 2 to produce a negative electrode for a nickel-metal hydride secondary battery. Each electrode was subjected to a charge / discharge test in a pressurized vessel at 5 atm in 30% KOH to evaluate the initial activity, high rate discharge characteristics and corrosion resistance shown below. Table 3 shows the results. The initial activity was carried out for 10 cycles at a discharge current of 0.2 C, and the discharge capacity at the third cycle was evaluated with respect to the discharge capacity at the tenth cycle.
高率放電特性は、 11サイクル目に 1Cで放電したときの容量を測定し、 10サイクル 目の放電容量に対するこの時の値の割合を評価した。  As for the high rate discharge characteristics, the capacity at the time of discharging at 1 C at the 11th cycle was measured, and the ratio of the value at this time to the discharge capacity at the 10th cycle was evaluated.
耐食性は、 12サイクル目以降、再ぴ 0.2Cの放電電流で放電し、 10サイクル目の放 電容量に対する 600サイクル目の容量維持率を Hffiした。 表 3 With respect to the corrosion resistance, after the 12th cycle, the battery was discharged at a discharge current of 0.2 C, and the capacity retention ratio at the 600th cycle with respect to the discharge capacity at the 10th cycle was Hffi. Table 3
初期活性 高率放電 耐食性 (%) 特性 (％) (%) 実施例 3-1 96.6 93.3 95.6 実施例 3-2 95.0 92.5 96.8 実施例 3-3 97.5 94.1 96.2 実施例 3-4 97.9 95.0 96.6 実施例 3-5 95.7 93.2 94.2 比較例 3-1 89.4 84.2 95.5 比較例 3-2 96.2 82.2 82.2  Initial activity High rate discharge Corrosion resistance (%) Characteristics (%) (%) Example 3-1 96.6 93.3 95.6 Example 3-2 95.0 92.5 96.8 Example 3-3 97.5 94.1 96.2 Example 3-4 97.9 95.0 96.6 Example 3-5 95.7 93.2 94.2 Comparative example 3-1 89.4 84.2 95.5 Comparative example 3-2 96.2 82.2 82.2

Claims

請求の範囲 The scope of the claims
1 .式 (1)で表される組成を有し、実質的に単相で、含まれる結晶の平均結晶粒径が 15 m以下、 各結晶の長径 (D1)と短径 (D2)との比 (D1ZD2)が 3以上である水素吸蔵 合金。  1.has a composition represented by the formula (1), is substantially a single phase, and has an average crystal grain size of 15 m or less, and the major axis (D1) and minor axis (D2) of each crystal Hydrogen storage alloy with a ratio (D1ZD2) of 3 or more.
RN i a C o b A 1 0Mn dMe · · · (1) RN i a C o b A 1 0 Mn d M e (1)
(式中、 Rはィットリゥムを含む希土類元素又はこれらの混合元素を示し、 Mは Mg、 Fe、 CuN Zr、 Ti、 Mo、 W、 B又はこれらの混合物を示す。 aは 3.30<a≤5.15、 b tt 0.10≤b≤0.50% cは 0.15≤c<0.35、 dは 0.10≤d 0.45、 eは 0≤e 0.50、 5.10 ≤a+b+c+d+e≤5.50であり、且つ Al及ぴ Mnの存在比 c/dが 0.：!〜 5.0である。）(In the formula, R represents a rare earth element or a mixture elements including Ittoriumu, M is Mg, Fe, Cu N Zr, shows Ti, Mo, W, B or mixtures thereof. A is 3.30 <a≤5.15 B tt 0.10≤b≤0.50 % c is 0.15≤c <0.35, d is 0.10≤d 0.45, e is 0≤e 0.50, 5.10 ≤a + b + c + d + e≤5.50, and Al and存在 Mn abundance c / d is 0:! ~ 5.0.)
2 . 式 (1)で表される組成を有し、含まれる結晶の平均結晶粒径が 15 m以下であり、 各結晶の長径 (D1)と短径 (D2)との比 (D1/D2)が 3以上であり、 粒径が 10μ m以上 である水素吸蔵合金粉末。 2. Having the composition represented by the formula (1), the average crystal grain size of the contained crystals is 15 m or less, and the ratio of the major axis (D1) to the minor axis (D2) of each crystal (D1 / D2 ) Is 3 or more and the particle diameter is 10 μm or more.
3 . 式 (1)で示される組成となる合金原料を溶融した後、該合金溶融物を冷却凝固し、 平均厚さ 0.05〜0.5mmの铸片を得、 得られた铸片を 900〜： L100。Cで 30分間〜 10 時間熱処理する請求の範囲 1の水素吸蔵合金の製造法。  3. After melting the alloy raw material having the composition represented by the formula (1), the alloy melt is cooled and solidified to obtain a piece having an average thickness of 0.05 to 0.5 mm. L100. The method for producing a hydrogen storage alloy according to claim 1, wherein the heat treatment is performed at 30 minutes to 10 hours at C.
4. 式 (1)で示される組成となる合金原料を溶融した後、該合金溶融物を冷却凝固し、 平均厚さ 0.05〜0.5mmの铸片を得、 得られた铸片を 900〜： 1100°Cで 30分間〜 10 時間熱処理した後、 粉碎する請求の範囲 2の水素吸蔵合金粉末の製造法。  4. After melting the alloy raw material having the composition represented by the formula (1), the alloy melt is cooled and solidified to obtain a piece having an average thickness of 0.05 to 0.5 mm. The method for producing a hydrogen storage alloy powder according to claim 2, wherein the powder is heat-treated at 1100 ° C for 30 minutes to 10 hours and then pulverized.
5 . 請求の範囲 2の水素吸蔵合金粉末と導電材とを負極材料として含むニッケル水素 二次電池用負極。  5. A negative electrode for a nickel-metal hydride secondary battery, comprising the hydrogen storage alloy powder of claim 2 and a conductive material as a negative electrode material.
PCT/JP2002/013607 2001-12-27 2002-12-26 Hydrogen-occluding alloy, powder of hydrogen-occluding alloy, processes for producing these, and negative electrode for nickel-hydrogen secondary battery WO2003056047A1 (en)

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