JP2005093297A - Hydrogen storage alloy powder and its manufacturing method, hydrogen storage alloy electrode and nickel-hydrogen storage battery using the electrode - Google Patents

Hydrogen storage alloy powder and its manufacturing method, hydrogen storage alloy electrode and nickel-hydrogen storage battery using the electrode Download PDF

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JP2005093297A
JP2005093297A JP2003326755A JP2003326755A JP2005093297A JP 2005093297 A JP2005093297 A JP 2005093297A JP 2003326755 A JP2003326755 A JP 2003326755A JP 2003326755 A JP2003326755 A JP 2003326755A JP 2005093297 A JP2005093297 A JP 2005093297A
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hydrogen storage
storage alloy
alloy powder
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JP4815738B2 (en
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Manabu Kanemoto
学 金本
Mitsuhiro Kodama
充浩 児玉
Minoru Kurokuzuhara
実 黒葛原
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Yuasa Corp
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Yuasa Battery Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen storage alloy electrode and a nickel hydrogen storage battery which are not less than in discharge capacity compared with the conventional ones, and are superior in charging acceptance performance when quick charging is performed, and in charge discharge cycle performance. <P>SOLUTION: Hydrogen storage alloy powder is applied which has a CaCu<SB>5</SB>type crystal structure as active material for a hydrogen storage alloy electrode, and is composed of MmMgNiCoMnAl, and at least in which the minute separation phases composed of MgNiCoMnAl alloy phases exist dispersed. Moreover, it is desirable that hydrogen storage alloy powder having surface layers composed of an alloy of Ni and Co, be applied on the powder surfaces. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、水素吸蔵合金粉末とその製造方法、それを用いた水素吸蔵合金電極およびニッケル水素蓄電池に関するものである。   The present invention relates to a hydrogen storage alloy powder, a method for producing the same, a hydrogen storage alloy electrode and a nickel metal hydride storage battery using the same.

ニッケル水素蓄電池は、耐過充電、耐過放電特性に優れ、一般ユーザーにとって使い易い電池であるところから、携帯電話、小型電動工具および小型パーソナルコンピュータ等の携帯用小型電子機器類用の電源として広く利用されており、これらの小型電子機器類の普及とともに需要が飛躍的に増大している。また、ハイブリッド型電気自動車(HEV)の駆動用電源としても実用化されている。そして、アルカリ蓄電池に対してはさらなる急速充電における充電受け入れ性能および充放電サイクル性能のさらなる向上が求められている。   Nickel metal hydride storage batteries have excellent overcharge and overdischarge resistance characteristics, and are easy to use for general users, so they are widely used as power sources for portable small electronic devices such as mobile phones, small electric tools, and small personal computers. The demand is increasing drastically with the spread of these small electronic devices. In addition, it has been put into practical use as a driving power source for a hybrid electric vehicle (HEV). Further, further improvements in charge acceptance performance and charge / discharge cycle performance in quick charge are required for alkaline storage batteries.

前記ニッケル水素蓄電池の負極は、活物質となる水素吸蔵合金粉末を主成分とするペーストを、鉄、ニッケルや銅等、耐アルカリ性で良導電性金属の多孔性基板に担持させたものである。   The negative electrode of the nickel-metal hydride storage battery is obtained by supporting a paste mainly composed of hydrogen storage alloy powder as an active material on a porous substrate made of an alkali-resistant and highly conductive metal such as iron, nickel, or copper.

前記水素吸蔵合金粉末としてはLa-Ni系の他にMg系、Ti系、Zr系の合金があるが、合金の活性が高いこと、耐久性が良いところからLa-Ni系の合金とりわけMmNiCoMnAlからなる水素吸蔵合金粉末が重用されている。   As the hydrogen storage alloy powder, there are Mg-based, Ti-based, and Zr-based alloys in addition to La-Ni-based alloys. However, because of their high activity and durability, La-Ni-based alloys, particularly MmNiCoMnAl, are used. This hydrogen storage alloy powder is used heavily.

しかし、前記水素吸蔵合金粉末を、表面改質処理を施さないで水素吸蔵合金電極の活物質として用いた場合、充電過程における水素吸蔵反応や正極で発生する酸素吸収反応に対する活性が乏しく、充電受け入れ性能に劣る欠点があった。また、放電性能も満足できるものではなかった。   However, when the hydrogen storage alloy powder is used as an active material for the hydrogen storage alloy electrode without surface modification, it has poor activity for the hydrogen storage reaction in the charging process and the oxygen absorption reaction generated at the positive electrode, and thus accepts charging. There was a disadvantage of poor performance. Also, the discharge performance was not satisfactory.

前記水素吸蔵合金粉末の活性の乏しさを補うために、水素吸蔵合金電極にラネーニッケルやラネーコバルトなど、水素吸蔵反応や酸素吸収反応に対して触媒として働く物質を添加することが提案されている。(例えば特許文献1参照)   In order to compensate for the lack of activity of the hydrogen storage alloy powder, it has been proposed to add a substance that acts as a catalyst for hydrogen storage reaction or oxygen absorption reaction, such as Raney nickel or Raney cobalt, to the hydrogen storage alloy electrode. (For example, see Patent Document 1)

しかし、ラネーニッケルやラネーコバルトは高価であり、かつ、活性が高く空気雰囲気に放置すると酸化劣化を起こして変質するという欠点があった。   However, Raney nickel and Raney cobalt are expensive and have the disadvantage that they are highly active and deteriorate due to oxidative degradation when left in an air atmosphere.

また、水素吸蔵合金粉末を熱アルカリ水溶液中に浸漬し、水素吸蔵合金粉末の表面にNiに富む多孔性の層(Niリッチ層)を生成させることにより活性を高める方法も提案されている。該Niリッチ層は、主として水素吸蔵反応の触媒として作用するものと考えられる。(例えば特許文献2参照)   Also proposed is a method of increasing the activity by immersing the hydrogen storage alloy powder in a hot alkaline aqueous solution and forming a Ni-rich porous layer (Ni-rich layer) on the surface of the hydrogen storage alloy powder. The Ni-rich layer is considered to act mainly as a catalyst for the hydrogen storage reaction. (For example, see Patent Document 2)

しかし、水素吸蔵合金粉末を熱アルカリ水溶液中に浸漬する方法には処理後の合金粉末表面にMm(ミッシュメタル)が残存し、該Mmが折角生成させたNiリッチ層の触媒作用を阻害する虞があった。   However, in the method of immersing the hydrogen storage alloy powder in a hot alkaline aqueous solution, Mm (Misch metal) remains on the surface of the alloy powder after the treatment, and the Mm may inhibit the catalytic action of the Ni-rich layer that is bent. was there.

さらに、水素吸蔵合金粉末中に存在するMnやAlは特に水素吸蔵合金粉末の結晶粒界や表面に偏析し易く、偏析したMnやAlは水素吸蔵合金粉末に微細化などの劣化を引き起こす虞があった。水素吸蔵合金粉末の表面のMm、MnおよびAlを除去する方法として水素吸蔵合金粉末を塩酸等の酸の水溶液に浸漬する方法が提案されている。(例えば特許文献3参照)   Furthermore, Mn and Al present in the hydrogen storage alloy powder are particularly likely to segregate at the crystal grain boundaries and surfaces of the hydrogen storage alloy powder, and the segregated Mn and Al may cause deterioration of the hydrogen storage alloy powder, such as refinement. there were. As a method for removing Mm, Mn and Al on the surface of the hydrogen storage alloy powder, a method of immersing the hydrogen storage alloy powder in an aqueous solution of acid such as hydrochloric acid has been proposed. (For example, see Patent Document 3)

しかし、水素吸蔵合金粉末を塩酸等の酸の水溶液に浸漬する方法には、前記結晶粒界に偏析したMnやAlを除去することが難しい他に、該浸漬によって合金粉末表面に生成させたNi、Coリッチ層の母材からの剥離を引き起こしたり、合金が過剰に腐蝕し易いなどの欠点があった。   However, in the method of immersing the hydrogen storage alloy powder in an aqueous solution of an acid such as hydrochloric acid, it is difficult to remove Mn and Al segregated at the crystal grain boundaries, as well as Ni formed on the surface of the alloy powder by the immersion. There are disadvantages such as peeling of the Co-rich layer from the base material and excessive corrosion of the alloy.

近年、充放電を繰り返しても微細化し難い水素吸蔵合金として、MmMgNiCoMnAl系の水素吸蔵合金が提案されている。(例えば特許文献4参照)   In recent years, MmMgNiCoMnAl-based hydrogen storage alloys have been proposed as hydrogen storage alloys that are difficult to refine even after repeated charge and discharge. (For example, see Patent Document 4)

しかし、該合金をもってしても水素吸蔵合金の微細化を抑制することはできず、かつ、水素吸蔵反応および酸素吸収反応の活性が低いという欠点があった。   However, even if it has this alloy, refinement | miniaturization of a hydrogen storage alloy cannot be suppressed, and there existed a fault that the activity of hydrogen storage reaction and oxygen absorption reaction was low.

特開平11-1111304号公報{頁3、段落(0009)}JP 11-1111304 A {Page 3, paragraph (0009)} 特開平7-29568号公報{頁2、段落(0006)}JP-A-7-29568 {Page 2, Paragraph (0006)} 特開平6-88150号公報{頁2、段落(0010)〜(0011)}JP-A-6-88150 {Page 2, paragraphs (0010) to (0011)} 特開2002-80925号公報{頁2、段落(0004)〜(0005)}JP 2002-80925 A {Page 2, paragraphs (0004) to (0005)}

本発明は、前記従来技術の欠点に鑑みなされたものであって、従来のものに比べて急速充電を行ったときの充電受け入れ性能と充放電サイクル性能に優れた水素吸蔵合金電極およびそれを適用したニッケル水素蓄電池を提供せんとするものである。   The present invention has been made in view of the drawbacks of the prior art described above, and is a hydrogen storage alloy electrode excellent in charge acceptance performance and charge / discharge cycle performance when performing quick charge compared to the conventional one, and application thereof To provide a nickel-metal hydride storage battery.

MmMgNiCoMnAl合金系には、Mg、Mn、Al単独の偏析が生じ易く、該Mg、Mn、Alが単独に偏析すると合金の微細化が進む欠点があることが分かったが、鋭意検討した結果、MmMgNiCoMnAl合金中に微細なMgNiCoMnAlからなる合金相を分散した状態で生成させることによって、水素吸蔵合金粉末の微細化が抑制されることを見出して本発明に至った。また、表面にMgNiCoMnAl合金からなる層を生成させた水素粉末合金を熱アルカリ水溶液中に浸漬することによって、Mmを含まないNiとCoの合金が生成し、該合金層が水素吸蔵合金粉末の水素吸蔵反応や酸素吸収反応に対して極めて優れた触媒作用を有することを見出して本発明に至った。   The MmMgNiCoMnAl alloy system is prone to segregation of Mg, Mn, and Al alone, and it has been found that when the Mg, Mn, and Al segregate alone, there is a drawback that the alloy becomes finer. It has been found that by forming an alloy phase composed of fine MgNiCoMnAl in the alloy in a dispersed state, the refinement of the hydrogen storage alloy powder is suppressed, and the present invention has been achieved. In addition, by immersing a hydrogen powder alloy in which a layer made of MgNiCoMnAl alloy is formed on the surface in a hot alkaline aqueous solution, an alloy of Ni and Co not containing Mm is formed, and the alloy layer is a hydrogen storage alloy powder hydrogen. The inventors have found that the present invention has an extremely excellent catalytic action for the occlusion reaction and the oxygen absorption reaction, and have reached the present invention.

前記の課題を解決するために、本発明は、以下の構成を採用するものである。
(1)本発明に係る水素吸蔵合金粉末は、CaCu5型の結晶構造を有し、MmMgNiCoMnAl合金(Mmはミッシュメタルを表す)を主成分とする水素吸蔵合金粉末であって、少なくとも該粉末の内部にMgNiCoMnAlからなる合金相が分散して存在していることを特徴とする水素吸蔵合金粉末である。
(2)本発明に係る水素吸蔵合金粉末は、前記のようにCaCu5型の結晶構造を有し、MmMgNiCoMnAl合金を主成分とし、少なくとも該粉末の内部にMgNiCoMnAlからなる合金相が分散して存在する水素吸蔵合金粉末であって、水素吸蔵合金粉末に占める前記MgNiCoMnAlからなる合金相の比率が0.5〜1.5wt%であることを特徴とする水素吸蔵合金粉末である。
(3)本発明に係る水素吸蔵合金粉末は、前記のようにCaCu5型の結晶構造を有し、MmMgNiCoMnAl合金を主成分とし、少なくとも該粉末の内部にMgNiCoMnAlからなる合金相が分散して存在する水素吸蔵合金粉末であって、表面にNiとCoの合金からなる層を備えたことを特徴とする水素吸蔵合金粉末である。
(4)本発明に係る水素吸蔵合金粉末は、前記のようにCaCu5型の結晶構造を有し、MmMgNiCoMnAl合金を主成分とし、少なくとも該粉末の内部にMgNiCoMnAlからなる合金相が分散して存在し、表面にNiとCoの合金からなる層を備えた水素吸蔵合金粉末であって、比表面積が0.2〜2m2/gであることを特徴とする水素吸蔵合金粉末である。
(5)本発明に係る水素吸蔵合金粉末の製造方法は、CaCu5型の結晶構造を有し、MmMgNiCoMnAl合金を主成分とし、少なくとも該粉末の内部にMgNiCoMnAlからなる合金相が分散して存在する水素吸蔵合金粉末の製造方法であって、前記MmMgNiCoMnAl合金相を母相とし、該母相から偏析させることによって、前記MgNiCoMnAlからなる合金相を生成させることを特徴とする水素吸蔵合金粉末の製造方法である。
(6)本発明に係る水素吸蔵合金粉末の製造方法は、CaCu5型の結晶構造を有し、MmMgNiCoMnAl合金を主成分とし、少なくとも該粉末の内部にMgNiCoMnAlからなる合金相が分散して存在し、表面にNiとCoの合金からなる層を備えた水素吸蔵合金粉末の製造方法であって、MmMgNiCoMnAl合金からなる母相から偏析させることによって生成させたMgNiCoMnAl合金からなる層を表面に有する水素吸蔵合金粉末を、熱アルカリ水溶液中に浸漬処理することによって、前記NiとCoの合金からなる層を生成させることを特徴とする水素吸蔵合金粉末の製造方法である。
(7)本発明に係る水素吸蔵合金電極は、CaCu5型の結晶構造を有し、MmMgNiCoMnAl合金を主成分とする水素吸蔵合金粉末であって、少なくとも粉末の内部にMgNiCoMnAl合金相が分散して存在している水素吸蔵合金粉末、または、該水素吸蔵合金粉末の表面にNiおよびCoの合金からなる層を備えた水素吸蔵合金粉末を導電性基板に担持させたことを特徴とする水素吸蔵合金電極である。
(8)本発明に係るニッケル水素蓄電池は、ニッケル電極を正極とし、CaCu5型の結晶構造を有し、MmMgNiCoMnAl合金を主成分とする水素吸蔵合金粉末であって、MmMgNiCoMnAl合金相中にMgNiCoMnAlからなる合金相が分散している水素吸蔵合金粉末、または、該水素吸蔵合金粉末の表面にNiおよびCoからなる層を備えた水素吸蔵合金粉末を導電性基板に担持させた水素吸蔵合金電極を負極としたことを特徴とするニッケル水素蓄電池である。
In order to solve the above-described problems, the present invention employs the following configuration.
(1) The hydrogen storage alloy powder according to the present invention is a hydrogen storage alloy powder having a CaCu 5 type crystal structure and mainly composed of an MmMgNiCoMnAl alloy (Mm represents Misch metal), The hydrogen storage alloy powder is characterized in that an alloy phase composed of MgNiCoMnAl is dispersed inside.
(2) The hydrogen storage alloy powder according to the present invention has a CaCu 5 type crystal structure as described above, and is mainly composed of an MgMgNiCoMnAl alloy, and at least an alloy phase composed of MgNiCoMnAl is present inside the powder. The hydrogen storage alloy powder is characterized in that the ratio of the alloy phase composed of MgNiCoMnAl in the hydrogen storage alloy powder is 0.5 to 1.5 wt%.
(3) The hydrogen storage alloy powder according to the present invention has a CaCu 5 type crystal structure as described above, and is mainly composed of an MgMgNiCoMnAl alloy, and at least an alloy phase composed of MgNiCoMnAl is present inside the powder. The hydrogen storage alloy powder is characterized in that a layer made of an alloy of Ni and Co is provided on the surface.
(4) The hydrogen storage alloy powder according to the present invention has a CaCu 5 type crystal structure as described above, and is mainly composed of an MgMgNiCoMnAl alloy and at least an alloy phase composed of MgNiCoMnAl is present in the powder. The hydrogen storage alloy powder is provided with a layer made of an alloy of Ni and Co on the surface and has a specific surface area of 0.2 to 2 m 2 / g.
(5) The method for producing a hydrogen storage alloy powder according to the present invention has a CaCu 5 type crystal structure, the main component is an MgMgNiCoMnAl alloy, and at least the alloy phase composed of MgNiCoMnAl is dispersed inside the powder. A method for producing a hydrogen storage alloy powder, characterized in that the MmMgNiCoMnAl alloy phase is used as a parent phase, and an alloy phase composed of the MgNiCoMnAl is generated by segregation from the parent phase. It is.
(6) The method for producing a hydrogen storage alloy powder according to the present invention has a CaCu 5 type crystal structure, the main component is an MgMgNiCoMnAl alloy, and at least the alloy phase composed of MgNiCoMnAl is present in the powder. A method for producing a hydrogen storage alloy powder having a layer made of an alloy of Ni and Co on its surface, the surface comprising a layer made of MgNiCoMnAl alloy formed by segregation from a parent phase made of an MmMgNiCoMnAl alloy A method for producing a hydrogen-absorbing alloy powder, wherein the alloy powder is immersed in a hot alkaline aqueous solution to form a layer made of the alloy of Ni and Co.
(7) The hydrogen storage alloy electrode according to the present invention is a hydrogen storage alloy powder having a CaCu 5 type crystal structure and mainly composed of an MmMgNiCoMnAl alloy, wherein at least the MgNiCoMnAl alloy phase is dispersed inside the powder. An existing hydrogen storage alloy powder, or a hydrogen storage alloy powder comprising a surface of the hydrogen storage alloy powder having a layer made of an alloy of Ni and Co supported on a conductive substrate. Electrode.
(8) A nickel-metal hydride storage battery according to the present invention is a hydrogen storage alloy powder having a nickel electrode as a positive electrode, a CaCu 5 type crystal structure, and a MmMgNiCoMnAl alloy as a main component. A hydrogen storage alloy powder in which an alloy phase is dispersed, or a hydrogen storage alloy electrode in which a hydrogen storage alloy powder having a layer made of Ni and Co on the surface of the hydrogen storage alloy powder is supported on a conductive substrate This is a nickel-metal hydride storage battery.

本発明によれば、水素の吸蔵および放出を繰り返し行っても、微細化による劣化が生じにくい水素吸蔵合金粉末とすることができる。(請求項1、請求項2)
本発明によれば、水素吸蔵反応や酸素吸収反応に対する活性が高い水素吸蔵合金粉末とすることができる。(請求項3、請求項4)
本発明によれば、水素の吸蔵および放出を繰り返し行っても、微細化による劣化が生じにくい水素吸蔵合金粉末を容易に得ることができる。(請求項5)
本発明によれば、水素吸蔵反応や酸素吸収反応に対する活性が高い水素吸蔵合金粉末を容易に得ることができる。(請求項6)
本発明に係る水素吸蔵電極は、充放電サイクル性能に優れ、かつ、急速充電において充電受け入れ性が良いアルカリ蓄電池用水素吸蔵電極である。(請求項7)
本発明に係るニッケル水素蓄電池は充放電サイクル性能に優れ、且つ、急速充電において充電受け入れ性が良いニッケル水素蓄電池である。(請求項8)
According to the present invention, it is possible to obtain a hydrogen storage alloy powder that is unlikely to deteriorate due to miniaturization even if hydrogen storage and release are repeated. (Claim 1, Claim 2)
According to the present invention, a hydrogen storage alloy powder having high activity for hydrogen storage reaction and oxygen absorption reaction can be obtained. (Claim 3 and Claim 4)
According to the present invention, it is possible to easily obtain a hydrogen storage alloy powder that hardly deteriorates due to miniaturization even if hydrogen is repeatedly stored and released. (Claim 5)
ADVANTAGE OF THE INVENTION According to this invention, the hydrogen storage alloy powder with high activity with respect to hydrogen storage reaction or oxygen absorption reaction can be obtained easily. (Claim 6)
The hydrogen storage electrode according to the present invention is a hydrogen storage electrode for an alkaline storage battery that has excellent charge / discharge cycle performance and good charge receptivity in rapid charging. (Claim 7)
The nickel-metal hydride storage battery according to the present invention is a nickel-metal hydride storage battery that has excellent charge / discharge cycle performance and good charge acceptability in rapid charging. (Claim 8)

図1は、本発明に係る水素吸蔵合金粉末の構成を模式的に示す、水素吸蔵合金粉末の断面図である。該水素吸蔵合金粉末は複数の結晶粒子の集合体からなる多結晶体であり、結晶粒子と結晶粒子の境目には結晶の粒界(図示せず)が存在する。図1の1は、水素吸蔵合金粉末の主成分であるCaCu5型の結晶構造を有し、MmMgNiCoMnAl合金からなる母相である。2は前記粒界に位置し、水素吸蔵合金の内部に分散して存在するMgNiCoMnAlからなる微細な合金相である。水素吸蔵合金粉末の平均粒径が数十μm(20〜80μm)であるのに対して、MgNiCoMnAlからなる合金相2は、直径が数μm(1〜5μm)の小さな塊状である。 FIG. 1 is a cross-sectional view of a hydrogen storage alloy powder schematically showing the configuration of the hydrogen storage alloy powder according to the present invention. The hydrogen storage alloy powder is a polycrystal composed of an aggregate of a plurality of crystal particles, and a crystal grain boundary (not shown) exists at the boundary between the crystal particles. 1 in FIG. 1 is a parent phase having a CaCu 5 type crystal structure which is a main component of the hydrogen storage alloy powder and made of an MmMgNiCoMnAl alloy. Reference numeral 2 denotes a fine alloy phase made of MgNiCoMnAl which is located at the grain boundary and is dispersed inside the hydrogen storage alloy. Whereas the average particle diameter of the hydrogen storage alloy powder is several tens of μm (20 to 80 μm), the alloy phase 2 made of MgNiCoMnAl is a small lump having a diameter of several μm (1 to 5 μm).

前記、MgNiCoMnAlからなる微細な合金相2は、MmMgNiCoMnAl合金からなる水素吸蔵合金を溶融状態から冷却固化する過程において、後記の特定の冷却速度で冷却したときに前記母相から偏析させることによって生成した相である。即ち、母相を構成する元素のうち、融点の低いMg、Mn、Alが冷却の過程で結晶粒界に移行し、Mmを含まないMgNiCoMnAl 合金相が生成したものと考えられる。   The fine alloy phase 2 made of MgNiCoMnAl was generated by segregating from the matrix phase when the hydrogen storage alloy made of MgMgNiCoMnAl alloy was cooled and solidified from the molten state at a specific cooling rate described later. Is a phase. That is, it is considered that Mg, Mn, and Al having a low melting point among the elements constituting the parent phase migrate to the grain boundary during the cooling process, and an MgNiCoMnAl alloy phase not containing Mm is generated.

MgNiCoMnAl合金を外部添加するのとは異なり、前記のように母相から MgNiCoMnAlからなる合金相を生成させると、母相の組成に変化が生じ、Mg、Mn、Al単独の偏析が抑制されるものと考えられる。また、偏析によって生成させたMgNiCoMnAl合金相2(以下偏析相と記述する)は、前記のように微細な塊状であって、かつ水素吸蔵合金粉末の内部に分散しているので、水素吸蔵合金粉末内における水素の拡散を妨げない点でも好ましい形態であると考えられる。   Unlike the case where MgNiCoMnAl alloy is added externally, when the alloy phase composed of MgNiCoMnAl is generated from the parent phase as described above, the composition of the parent phase changes, and segregation of Mg, Mn, and Al alone is suppressed. it is conceivable that. Further, the MgNiCoMnAl alloy phase 2 (hereinafter referred to as a segregation phase) produced by segregation is a fine lump as described above and is dispersed inside the hydrogen storage alloy powder. It is also considered to be a preferable form in that it does not hinder the diffusion of hydrogen inside.

前記図1の2に示したMgNiCoMnAlからなる微細な合金相(以下偏析相という)が水素吸蔵合金に占める比率は、0.5〜1.5wt%が好ましく、0.8〜1.2wt%がさらに好ましい。該偏析相の比率が0.5wt%を下回るとMmMgNiCoMnAl合金相に含まれるMg、Mn、Alが単独で偏析する虞があり、1.5wt%を超えると水素吸蔵合金の容量(mAh/g)が低くなる虞がある。   The ratio of the fine alloy phase (hereinafter referred to as segregation phase) composed of MgNiCoMnAl shown in 2 of FIG. 1 to the hydrogen storage alloy is preferably 0.5 to 1.5 wt%, and 0.8 to 1.2 wt%. Further preferred. If the ratio of the segregation phase is less than 0.5 wt%, Mg, Mn, and Al contained in the MmMgNiCoMnAl alloy phase may be segregated alone. If the ratio exceeds 1.5 wt%, the capacity of the hydrogen storage alloy (mAh / g) May decrease.

本発明に係るMmMgNiCoMnAl合金からなる水素吸蔵合金粉末において、前記偏析相はMmMgNiCoMnAl合金を溶融させた状態から適度の冷却速度で冷却固化することによって生成させることができる。前記偏析相を生成させるためには、MmuMgvNiwCoxMnyAlzのu、v、w、x、y、zが、それぞれu:0.94〜0.98、v:0.02〜0.06、w:3.5〜4.0、x:0.2〜1.0、y:0.1〜0.6、z:0.1〜0.4であることが好ましい。uが0.94未満では合金の容量(mAh/g)が低くなる虞があり、0.98を超えるとMgNiCoMnAl系の合金形成が困難となる虞がある。vが0.02未満ではMgNiCoMnAl系の合金形成が困難となる虞があり、0.06を超えると合金の容量(mAh/g)が低くなる虞がある。wが3.5未満では合金の容量(mAh/g)が低くなる虞があり、4.4を超えると合金の耐久性が低くなる虞がある。xが0.2未満では合金の耐久性が低くなり、1.0を超えると合金の容量(mAh/g)が低くなる虞がある。yが0.1未満では合金の容量(mAh/g)が低くなる虞があり、0.6を超えると合金の耐久性が低くなる虞がある。zが0.1未満では合金の耐久性が低くなる虞があり、0.4を超えると合金の容量(mAh/g)が低くなる虞がある。 In the hydrogen storage alloy powder made of the MmMgNiCoMnAl alloy according to the present invention, the segregation phase can be generated by cooling and solidifying the MmMgNiCoMnAl alloy from a molten state at an appropriate cooling rate. To produce the segregation phase is, Mm u Mg v Ni w Co x Mn y Al z of u, v, w, x, y, z are each u: 0.94~0.98, v: 0 0.02-0.06, w: 3.5-4.0, x: 0.2-1.0, y: 0.1-0.6, z: 0.1-0.4 preferable. If u is less than 0.94, the alloy capacity (mAh / g) may be low, and if it exceeds 0.98, formation of an MgNiCoMnAl-based alloy may be difficult. If v is less than 0.02, MgNiCoMnAl-based alloy formation may be difficult, and if it exceeds 0.06, the capacity (mAh / g) of the alloy may be reduced. If w is less than 3.5, the capacity (mAh / g) of the alloy may be low, and if it exceeds 4.4, the durability of the alloy may be low. If x is less than 0.2, the durability of the alloy is low, and if it exceeds 1.0, the capacity (mAh / g) of the alloy may be low. If y is less than 0.1, the capacity (mAh / g) of the alloy may be low, and if it exceeds 0.6, the durability of the alloy may be low. If z is less than 0.1, the durability of the alloy may be lowered, and if it exceeds 0.4, the alloy capacity (mAh / g) may be lowered.

また、水素吸蔵合金を溶融状態から冷却して固化させる時の冷却速度は、5〜100℃/sec.が好ましく、10〜50℃/sec.がさらに好ましい。冷却速度が5℃/sec.未満では合金の耐久性が低くなる虞があり、100℃/sec.を超えると、MgNiCoMnAl系の合金相(偏析相)の形成が困難となる虞があるので好ましくない。   The cooling rate when the hydrogen storage alloy is cooled and solidified from the molten state is preferably 5 to 100 ° C./sec., More preferably 10 to 50 ° C./sec. If the cooling rate is less than 5 ° C./sec., The durability of the alloy may be lowered. If it exceeds 100 ° C./sec., Formation of an MgNiCoMnAl-based alloy phase (segregation phase) may be difficult. Absent.

本発明に係る水素吸蔵合金粉末の好ましい実施形態によれば、図1に示すように合金粉末の表面にNiおよびCoの合金からなる層3(以下表面層と記述する)が形成されている。該表面層3は、以下のような機構で生成すると考えられる。前記結晶粒界にMgNiCoMnAl合金相を生成した合金のインゴットを粉砕し粉末を得る過程で、インゴットは合金の結晶粒界に沿って粉砕され、得られた粉末の表面にはMgNiCoMnAl合金相からなる層が形成される。該合金粉末を熱アルカリ水溶液に浸漬処理すると、Mg、Mn、Alがアルカリ水溶液中に溶出し、合金粉末の表面にMmを含まないNiとCoからなる合金の層が形成する。   According to a preferred embodiment of the hydrogen storage alloy powder according to the present invention, a layer 3 (hereinafter referred to as a surface layer) made of an alloy of Ni and Co is formed on the surface of the alloy powder as shown in FIG. The surface layer 3 is considered to be generated by the following mechanism. In the process of pulverizing an alloy ingot that has produced an MgNiCoMnAl alloy phase at the crystal grain boundary to obtain a powder, the ingot is pulverized along the crystal grain boundary of the alloy, and the surface of the obtained powder is a layer composed of an MgNiCoMnAl alloy phase. Is formed. When the alloy powder is immersed in a hot alkaline aqueous solution, Mg, Mn and Al are eluted in the alkaline aqueous solution, and an alloy layer made of Ni and Co not containing Mm is formed on the surface of the alloy powder.

前記浸漬処理するための処理液は、濃度が数モル/l(5〜10モル/l)のNaOH、KOH、LiOHのおのおの単独または混合水溶液が好ましい。該アルカリ水溶液は、塩酸等の酸の水溶液がNi、Coも溶出する傾向が強いのと異なり、Mg、Mn、Alを選択的に溶出する性質を持つ。従って、アルカリ処理液に浸漬すると水素吸蔵合金粉末表面のMg、Mn、Alが選択的に溶出する。アルカリ処理液には表面層の触媒作用を阻害するMmを溶出し難い欠点があるが、本発明に係る水素吸蔵合金粉末は、前記のように表面にMmを含まないMgNiCoMnAl合金相からなる層が形成されているので、アルカリ水溶液浸漬処理をすることによって、表面にNiとCoの合金からなる表面層が生成する。前記のように、アルカリ処理液はNiおよびCoを溶出し難く、Mg、Mn、Alを選択的に溶出するので、前記表面層は、Mg、Mn、Alが溶出した後が微細な孔をなした活性度の高い多孔質の層と考えられ、そのために、水素吸蔵合金粉末が水素を吸蔵する反応および酸素を吸収する反応を促進する触媒として作用するものと考えられる。   The treatment liquid for the immersion treatment is preferably a single or mixed aqueous solution of NaOH, KOH, or LiOH having a concentration of several mol / l (5 to 10 mol / l). The aqueous alkaline solution has a property of selectively eluting Mg, Mn, and Al, unlike an aqueous solution of an acid such as hydrochloric acid, which has a strong tendency to elute Ni and Co. Therefore, when immersed in an alkali treatment liquid, Mg, Mn and Al on the surface of the hydrogen storage alloy powder are selectively eluted. Alkaline treatment liquid has a defect that it is difficult to elute Mm which inhibits the catalytic action of the surface layer, but the hydrogen storage alloy powder according to the present invention has a layer made of MgNiCoMnAl alloy phase not containing Mm as described above. Since it is formed, a surface layer made of an alloy of Ni and Co is generated on the surface by immersion treatment with an alkaline aqueous solution. As described above, the alkaline treatment liquid hardly elutes Ni and Co, and selectively elutes Mg, Mn, and Al. Therefore, the surface layer has fine pores after the elution of Mg, Mn, and Al. Therefore, it is considered that the hydrogen storage alloy powder acts as a catalyst for promoting the hydrogen storage reaction and the oxygen absorption reaction.

前記表面層3の水素吸蔵合金粉末に占める比率が大きくなると、水素吸蔵合金粉末の質量飽和磁化が大きくなり、前記層3の生成量と質量飽和磁化との間に相関性がある。本発明においては、水素吸蔵合金粉末の質量飽和磁化が0.5〜3.1A・m2/g(約3A・m2/kg)であることが好ましい。質量飽和磁化が0.5A・m2/g未満では、表面層の形成が不足し、水素吸蔵合金粉末の水素吸蔵反応や酸素吸収反応に対する活性が低く、高率充電を行ったときの充電受け入れ性能が劣ったり、充電時に電池の内圧が高くなる虞がある。また、質量飽和磁化が約4A・m2/gを超えると、表面層の形成が過剰となり、合金の容量(mAh/g)が低くなる虞がある。 When the ratio of the surface layer 3 to the hydrogen storage alloy powder increases, the mass saturation magnetization of the hydrogen storage alloy powder increases, and there is a correlation between the generation amount of the layer 3 and the mass saturation magnetization. In the present invention, the mass saturation magnetization of the hydrogen storage alloy powder is preferably 0.5 to 3.1 A · m 2 / g (about 3 A · m 2 / kg). When the mass saturation magnetization is less than 0.5 A · m 2 / g, the formation of the surface layer is insufficient, the hydrogen storage alloy powder has low activity for hydrogen storage reaction and oxygen absorption reaction, and charge acceptance when performing high rate charging There is a possibility that the performance is inferior or the internal pressure of the battery becomes high during charging. On the other hand, if the mass saturation magnetization exceeds about 4 A · m 2 / g, the surface layer is excessively formed, and the capacity (mAh / g) of the alloy may be lowered.

本発明に係るMmMgNiCoMnAl合金相を主成分とする水素吸蔵合金粉末の比表面積は、0.2〜2m2/gであることが好ましく、0.2〜1m2/gであることがさらに好ましい。比表面積が0.2m2/gを下回ると、水素吸蔵合金粉末の水素吸蔵反応や酸素吸収反応の速度が低くなるする虞があり、2m2/gを超えると電解液に対する耐食性が低くなる虞がある。 The specific surface area of the hydrogen-absorbing alloy powder based on MmMgNiCoMnAl alloy phase according to the present invention is preferably 0.2~2m 2 / g, more preferably from 0.2~1m 2 / g. If the specific surface area is less than 0.2 m 2 / g, the hydrogen storage reaction or oxygen absorption reaction rate of the hydrogen storage alloy powder may decrease, and if it exceeds 2 m 2 / g, the corrosion resistance to the electrolyte solution may decrease. There is.

(実施例1)
(水素吸蔵合金粉末の作製)
Mm0.95Mg0.05Ni3.7Co0.75Mn0.4Al0.3(Mm:La50wt%、Ce25wt%、Pr5wt%、Nd20wt%からなる合金)からなる合金塊を高周波誘導炉内においてアルゴン雰囲気下で溶融させた。生成した溶湯を鋳型に注入することによって徐冷し、水素吸蔵合金の1kgのインゴットを得た。該冷却固化の過程で溶湯の注入速度を制御することによって、溶湯が冷えて固化に至るまでの冷却速度を20℃/sec.になるように制御した。得られたインゴットを、雰囲気炉を用いてアルゴン雰囲気下において、1050℃に加熱し、該温度に6時間保持した後、前記インゴットを雰囲気炉に隣接する内部をアルゴン雰囲気に保った予備室に引き出し、インゴットの温度が約100℃になるまで冷却した。前記の手順で得られたインゴットを、ミルを用いて粉砕し、平均粒径(D50)が50μmの水素吸蔵合金粉末を得た。
(Example 1)
(Preparation of hydrogen storage alloy powder)
An alloy lump made of Mm 0.95 Mg 0.05 Ni 3.7 Co 0.75 Mn 0.4 Al 0.3 (Mm: an alloy consisting of La 50 wt%, Ce 25 wt%, Pr 5 wt%, Nd 20 wt%) was melted in an induction furnace in an argon atmosphere. The produced molten metal was gradually cooled by pouring it into a mold to obtain a 1 kg ingot of hydrogen storage alloy. By controlling the injection rate of the molten metal during the cooling and solidification process, the cooling rate until the molten metal cooled and solidified was controlled to 20 ° C./sec. The obtained ingot was heated to 1050 ° C. in an argon atmosphere using an atmosphere furnace and held at that temperature for 6 hours, and then the ingot was drawn out into a preliminary chamber in which the interior adjacent to the atmosphere furnace was kept in an argon atmosphere. The ingot was cooled to about 100 ° C. The ingot obtained by the above procedure was pulverized using a mill to obtain a hydrogen storage alloy powder having an average particle size (D50) of 50 μm.

(水素吸蔵合金粉末の熱アルカリ水溶液中への浸漬処理)
前記水素吸蔵合金粉末100gを、6.8M/lのKOHと0.8M/lのLiOHを溶解した温度100℃の水溶液中に2時間浸漬し、撹拌した。該溶液を濾別し、得られた水素吸蔵合金粉末を、洗浄水のpHが9になるまで繰り返し水洗した。
(Immersion treatment of hydrogen storage alloy powder in hot alkaline aqueous solution)
100 g of the hydrogen storage alloy powder was immersed in an aqueous solution at a temperature of 100 ° C. in which 6.8 M / l KOH and 0.8 M / l LiOH were dissolved and stirred. The solution was separated by filtration, and the obtained hydrogen storage alloy powder was repeatedly washed with water until the pH of the washing water reached 9.

(偏析相の生成量および組成の定量分析)
熱アルカリ水溶液中への浸漬処理を施さない水素吸蔵合金粉末および浸漬処理を施した後の水素吸蔵合金粉末を別々にエポキシ樹脂に混ぜて硬化させ、硬化物を切断研磨して、切断面に合金粉末の断面を露出させた。該切断面をX線マイクロアナライザー(EPMA)を用いて元素分析を行った。走査範囲を0.5×0.5mm、ステップ幅を0.001mmとした。
(Quantitative analysis of segregation phase production and composition)
The hydrogen-absorbing alloy powder not subjected to immersion treatment in a hot alkaline aqueous solution and the hydrogen-absorbing alloy powder after immersion treatment are separately mixed in an epoxy resin and cured, and the cured product is cut and polished, and the cut surface is alloyed. A cross section of the powder was exposed. The cut surface was subjected to elemental analysis using an X-ray microanalyzer (EPMA). The scanning range was 0.5 × 0.5 mm and the step width was 0.001 mm.

分析の結果、熱アルカリ水溶液中への浸漬処理を施さない水素吸蔵合金粉末においてはMmMgNiCoMnAlからなる合金相(母相)と、粉末の表面にMgNiCoMnAlからなる合金相(表面層)および粉末の内部に直径約3μmのMgNiCoMnAlからなる合金相(偏析相)が分散して存在するのを認めた。他方、熱アルカリ水溶液中への浸漬処理を施した後の水素吸蔵合金粉末においては、粉末の表面にNiとCoからなる合金相(表面層)が存在し、粉末の内部には熱アルカリ水溶液中への浸漬処理を施さないものと同じMgNiCoMnAlからなる合金相(偏析相)が分散して存在するのを認めた。組成分析により、前記偏析相および表面層の構成元素の定量をおこなった。また、前記元素分析において、粉末の内部に存在する領域であって、Mmが検出されず、MnとAlの濃度が、MmMgNiCoMnAl合金相中のMnとAlの濃度の3倍以上の領域をMgNiCoMnAl合金相(偏析相)領域とし、該領域の面積のサンプルの切断面に占める比率(%)からサンプルに含まれる偏析相の比率を算定した。   As a result of the analysis, in the hydrogen storage alloy powder that is not immersed in the hot alkaline aqueous solution, the alloy phase (parent phase) composed of MmMgNiCoMnAl, the alloy phase (surface layer) composed of MgNiCoMnAl on the surface of the powder, and the inside of the powder It was observed that an alloy phase (segregation phase) made of MgNiCoMnAl having a diameter of about 3 μm was dispersed. On the other hand, in the hydrogen storage alloy powder after the immersion treatment in the hot alkaline aqueous solution, an alloy phase (surface layer) composed of Ni and Co is present on the surface of the powder, and in the hot alkaline aqueous solution inside the powder It was observed that the same alloy phase (segregation phase) composed of MgNiCoMnAl was not dispersed. The constituent elements of the segregation phase and the surface layer were quantified by composition analysis. Further, in the elemental analysis, a region existing in the powder, where Mm is not detected, and a region where the concentration of Mn and Al is more than three times the concentration of Mn and Al in the MmMgNiCoMnAl alloy phase is MgNiCoMnAl alloy. The phase (segregation phase) region was determined, and the ratio of the segregation phase contained in the sample was calculated from the ratio (%) of the area of the region to the cut surface of the sample.

(質量飽和磁化、比表面積の測定および結晶構造解析)
前記水素吸蔵合金粉末0.3gを精秤し、サンプルホルダーに充填して(株)理研電子製、試料振動磁力計(モデルBHV−30)を用いて5kエルステッドの磁場をかけて測定した。さらに、窒素吸着法により比表面積(BET表面積)を測定した。また、前記水素吸蔵合金粉末の結晶構造を粉末X線回折(XRD)によって分析した。その結果、得られた水素吸蔵合金粉末はCaCu5形の結晶構造を持つことが確認された。
(Mass saturation magnetization, measurement of specific surface area and crystal structure analysis)
The hydrogen storage alloy powder 0.3 g was precisely weighed, filled in a sample holder, and measured by applying a magnetic field of 5 k Oersted using a sample vibration magnetometer (model BHV-30) manufactured by Riken Denshi Co., Ltd. Furthermore, the specific surface area (BET surface area) was measured by the nitrogen adsorption method. The crystal structure of the hydrogen storage alloy powder was analyzed by powder X-ray diffraction (XRD). As a result, it was confirmed that the obtained hydrogen storage alloy powder had a CaCu 5 type crystal structure.

(水素吸蔵合金電極の作製)
前記水素吸蔵合金粉末100重量部に結着剤としてスチレンブタジエンラバー(SBR)1重量部、増粘剤として濃度1wt%のメチルセルロース(MC)水溶液13重量部を加えて混練し、ペースト状とした。該負極ペーストを厚さ0.05mm、開口率40%のニッケルメッキを施した穿孔鋼板の両面に塗布乾燥した後ロール掛けして、厚さ0.4mmの帯状の原板を得た。該原板を所定の寸法に裁断して負極板とした。該負極板の活物質(水素吸蔵合金)の充填量は9.3gであった。
(Production of hydrogen storage alloy electrode)
1 part by weight of styrene butadiene rubber (SBR) as a binder and 13 parts by weight of an aqueous methylcellulose (MC) solution having a concentration of 1 wt% as a thickener were added to 100 parts by weight of the hydrogen storage alloy powder and kneaded to obtain a paste. The negative electrode paste was applied to and dried on both sides of a nickel-plated perforated steel sheet having a thickness of 0.05 mm and an aperture ratio of 40%, and then rolled to obtain a strip-shaped original sheet having a thickness of 0.4 mm. The original plate was cut into a predetermined size to obtain a negative electrode plate. The filling amount of the active material (hydrogen storage alloy) of the negative electrode plate was 9.3 g.

(ニッケル水素蓄電池の作製)
亜鉛を3wt%、コバルトを3wt%固溶状態で含有し、表面に水酸化コバルトの被覆層を形成した平均粒径10μmの水酸化ニッケル粉末80重量部に、増粘材であるカルボキシルメチルセルロース(CMC)の濃度が1wt%の水溶液20重量部を添加混練してペースト状とした。該正極ペーストを、厚さ1.4mm、面密度450g/m2の発泡ニッケル基板に充填し、乾燥後ロール掛けして厚さ0.8mmの原板とした。該原板を所定の寸法に裁断し、集電用タブを取り付けて正極板とした。該正極板の活物質充填量から算定される正極板の容量は1600mAhであった。該正極板と前記負極板を、親水処理を施したポリプロピレン繊維からなる厚さ100μmの不織布(セパレータ)を間に挟んで積層し、該積層体を捲回して捲回式極板群とした。該捲回式極板群を金属製電槽に挿入した後、正極板のタブの一端に正極端子兼キャップを接合し、電解液として6.8M/lのKOHと0.8M/lのLiOHを溶解させたアルカリ水溶液を注入した後、前記キャップにより電槽の開口端を気密に封口してAAサイズの円筒形ニッケル水素蓄電池とした。
(Production of nickel metal hydride storage battery)
3 parts by weight of zinc and 3 parts by weight of cobalt in a solid solution state, and 80 parts by weight of nickel hydroxide powder having an average particle size of 10 μm and having a coating layer of cobalt hydroxide formed on the surface, carboxymethyl cellulose (CMC) as a thickener And 20 parts by weight of an aqueous solution having a concentration of 1 wt% was added and kneaded to obtain a paste. The positive electrode paste was filled in a foamed nickel substrate having a thickness of 1.4 mm and a surface density of 450 g / m 2 , dried and then rolled to obtain an original plate having a thickness of 0.8 mm. The original plate was cut into a predetermined size, and a current collecting tab was attached to form a positive electrode plate. The capacity of the positive electrode plate calculated from the active material filling amount of the positive electrode plate was 1600 mAh. The positive electrode plate and the negative electrode plate were laminated with a nonwoven fabric (separator) having a thickness of 100 μm made of polypropylene fibers subjected to hydrophilic treatment, and the laminate was wound to form a wound electrode plate group. After inserting the wound electrode plate group into a metal battery case, a positive electrode terminal / cap was joined to one end of the tab of the positive electrode plate, and 6.8 M / l KOH and 0.8 M / l LiOH were used as electrolytes. After injecting an alkaline aqueous solution in which the battery was dissolved, the open end of the battery case was hermetically sealed with the cap to obtain an AA size cylindrical nickel-metal hydride storage battery.

(初期化成)
前記ニッケル水素蓄電池を周囲温度20℃において0.02ItAで10時間充電し、引き続き0.25ItAで5時間充電した。続いて0.2ItAで放電し電圧が1.0Vになった時点で放電を打ち切った。次いで0.2ItAで6時間充電した後、放電打ち切り電圧を1.0Vとして0.2ItAで放電した。該充放電を1サイクルとして、該充放電サイクルを9回繰り返し実施した。
(Initialization)
The nickel hydride storage battery was charged at 0.02 ItA for 10 hours at an ambient temperature of 20 ° C., and subsequently charged for 5 hours at 0.25 ItA. Subsequently, the battery was discharged at 0.2 ItA, and the discharge was stopped when the voltage reached 1.0V. Next, the battery was charged with 0.2 ItA for 6 hours, and then discharged at 0.2 ItA with a discharge cutoff voltage of 1.0 V. The charging / discharging cycle was repeated nine times with one charging / discharging cycle.

(充放電サイクル試験)
前記初期化成済みの電池を10個用意し、周囲温度20℃において充放電サイクル試験に供した。1ItAで1.05時間(63分間)充電した後、0.5時間休止し、引き続いて放電打ち切り電圧を1.0Vとして1ItAで放電した。該充放電サイクル試験の1サイクル目の放電容量に対して放電容量が80%に低下したサイクル数をもってその電池のサイクル寿命とした。
(Charge / discharge cycle test)
Ten pre-initialized batteries were prepared and subjected to a charge / discharge cycle test at an ambient temperature of 20 ° C. The battery was charged at 1 ItA for 1.05 hours (63 minutes), then rested for 0.5 hours, and subsequently discharged at 1 ItA at a discharge cutoff voltage of 1.0 V. The cycle life of the battery was defined as the cycle number at which the discharge capacity decreased to 80% of the discharge capacity of the first cycle of the charge / discharge cycle test.

(急速充電試験)
前記初期化成済みの電池を10個用意し、該10個の電池のうち5個について、周囲温度20℃において急速充電を行ったときの充電受け入れ性能を評価した。用意した電池を、4ItAで13.5分間充電し、引き続き、放電打ち切り電圧を1.0Vとして1ItAで放電した。放電持続時間より算定された放電容量の前記充電(4ItAで13.5分間充電)における充電電気量に対する比率を充電受け入れ(%)とした。前記10個の電池のうち、残りの5個の電池に電池の内部圧力を測定するための圧力センサーを取り付け、前記と同じ上面で急速充電を行ったときの電池の内部圧力をモニターし、最高到達圧力を測定した。
(Quick charge test)
Ten batteries that had been initialized and prepared were prepared, and five of the ten batteries were evaluated for charge acceptance performance when quick charging was performed at an ambient temperature of 20 ° C. The prepared battery was charged with 4 ItA for 13.5 minutes, and subsequently discharged at 1 ItA with a discharge cutoff voltage of 1.0 V. The ratio of the discharge capacity calculated from the discharge duration to the amount of charge in the charge (charging at 4 ItA for 13.5 minutes) was defined as charge acceptance (%). Among the 10 batteries, a pressure sensor for measuring the internal pressure of the battery is attached to the remaining 5 batteries, and the internal pressure of the battery when the quick charge is performed on the same upper surface as described above is monitored. The ultimate pressure was measured.

(負極の単極試験)
前記負極の原板を裁断して、30mm×30mmの大きさの極板を採取した。該負極板1枚の両側にセパレータを介して35mm×35mmのニッケル電極板(正極板)2枚を配置し(正極板の容量を負極板の容量の約3倍になるように設定した)、前記円筒形ニッケル水素蓄電池と同一組成の電解液を注入し、開放形セルを作製した。また、該セルに参照電極としてHg/HgO電極を挿入した。該セルを、周囲温度20℃において、0.1ItAにて16時間充電し、0.2ItAにて負極の参照電極に対する電位が−0.6Vになるまで放電した。該充放電サイクルを10サイクル繰り返し行い、安定した放電容量が得られることを確認した。前記セルを5個用意し、5個のセルの、前記10サイクル目の放電容量の平均値を供試負極板の単極試験での放電容量とした。
(Single electrode test of negative electrode)
The negative plate was cut to obtain a 30 mm × 30 mm plate. Two nickel electrode plates (positive electrode plates) of 35 mm × 35 mm are disposed on both sides of the negative electrode plate via a separator (the capacity of the positive electrode plate is set to be about three times the capacity of the negative electrode plate), An electrolyte having the same composition as that of the cylindrical nickel-metal hydride storage battery was injected to produce an open cell. In addition, an Hg / HgO electrode was inserted into the cell as a reference electrode. The cell was charged at 0.1 ItA for 16 hours at an ambient temperature of 20 ° C. and discharged at 0.2 ItA until the potential of the negative electrode with respect to the reference electrode was −0.6 V. The charge / discharge cycle was repeated 10 times, and it was confirmed that a stable discharge capacity was obtained. Five cells were prepared, and the average value of the discharge capacity at the tenth cycle of the five cells was taken as the discharge capacity in the single electrode test of the test negative electrode plate.

(実施例2)
前記実施例1において溶融した水素吸蔵合金を冷却し固化するまでの冷却速度を50℃/sec.とした。それ以外は、実施例1と同じとした。該例を実施例2とする。
(実施例3)
前記実施例1において溶融した水素吸蔵合金を冷却し固化するまでの冷却速度を10℃/sec.とした。それ以外は、実施例1と同じとした。該例を実施例3とする。
(Example 2)
The cooling rate until the molten hydrogen storage alloy in Example 1 was cooled and solidified was 50 ° C./sec. Otherwise, it was the same as Example 1. This example is referred to as Example 2.
(Example 3)
The cooling rate for cooling and solidifying the molten hydrogen storage alloy in Example 1 was set to 10 ° C./sec. Otherwise, it was the same as Example 1. This example is referred to as Example 3.

(比較例1)
前記実施例1において溶融した水素吸蔵合金を、高速で回転する金属製ロールの表面に滴下し、急冷固化(双ロール法、冷却速度は約1000℃/sec.)した。それ以外は、実施例1と同じとした。該例を比較例1とする。
(Comparative Example 1)
The hydrogen storage alloy melted in Example 1 was dropped on the surface of a metal roll rotating at high speed, and rapidly cooled and solidified (double roll method, cooling rate was about 1000 ° C./sec.). Otherwise, it was the same as Example 1. This example is referred to as Comparative Example 1.

(比較例2)
前記実施例1において、水素吸蔵合金粉末を作製するするための水素吸蔵合金塊として、Mm1.0Ni3.7Co0.75Mn0.4Al0.3(Mm:La50wt%、Ce25wt%、Pr5wt%、Nd20wt%からなる合金)で示される組成の合金を用いた。それ以外は実施例1と同じとした。該例を比較例2とする。
(Comparative Example 2)
In Example 1, as a hydrogen storage alloy lump for producing a hydrogen storage alloy powder, Mm 1.0 Ni 3.7 Co 0.75 Mn 0.4 Al 0.3 (Mm: an alloy comprising La 50 wt%, Ce 25 wt%, Pr 5 wt%, Nd 20 wt%) An alloy having the composition indicated by Otherwise, it was the same as Example 1. This example is referred to as Comparative Example 2.

(実施例4)
前記実施例1において、水素吸蔵合金粉末の熱アルカリ水溶液中への浸漬時間を0.5時間とした。それ以外は実施例1と同じとした。該例を実施例4とする。
(実施例5)
前記実施例1において、水素吸蔵合金粉末の熱アルカリ水溶液中への浸漬時間を10時間とした。それ以外は実施例1と同じとした。該例を実施例5とする。
(参考例1)
前記実施例1において、水素吸蔵合金粉末の熱アルカリ水溶液中への浸漬時間を15時間とした。それ以外は実施例1と同じとした。該例を参考例1とする。
(参考例2)
前記実施例1において、水素吸蔵合金粉末の熱アルカリ水溶液中への浸漬を行わなかった。それ以外は実施例1と同じとした。該例を参考例2とする。
Example 4
In Example 1, the immersion time of the hydrogen storage alloy powder in the hot alkaline aqueous solution was 0.5 hour. Otherwise, it was the same as Example 1. This example is referred to as Example 4.
(Example 5)
In Example 1, the immersion time of the hydrogen storage alloy powder in the hot alkaline aqueous solution was 10 hours. Otherwise, it was the same as Example 1. This example is referred to as Example 5.
(Reference Example 1)
In Example 1, the immersion time of the hydrogen storage alloy powder in the hot alkaline aqueous solution was 15 hours. Otherwise, it was the same as Example 1. This example is referred to Reference Example 1.
(Reference Example 2)
In Example 1, the hydrogen storage alloy powder was not immersed in a hot alkaline aqueous solution. Otherwise, it was the same as Example 1. This example is referred to Reference Example 2.

表1に、実施例1〜実施例5,参考例1、参考例2、比較例1、比較例2に係る水素吸蔵合金粉末の分析結果を示す。   Table 1 shows the analysis results of the hydrogen storage alloy powders according to Examples 1 to 5, Reference Example 1, Reference Example 2, Comparative Example 1, and Comparative Example 2.

Figure 2005093297
表1に示したとおり、実施例1〜実施例5、参考例1、参考例2に係る水素吸蔵合金粉末においては、CaCu5形の結晶構造を持つMmMgNiCoMnAlからなる合金相(母相)の内部に MgNiCoMnAlからなり、直径が3μmの塊状の合金相(偏析相)が偏析し、水素吸蔵合金粉末の内部に分散して存在するのを認めた。これに対して、比較例1に係る水素吸蔵合金粉末においては、前記MgNiCoMnAlからなる、合金相の偏析は認められず、水素吸蔵合金粉末の内部にMg、MnおよびAlが単独に偏析しているのが認められた。また、Mgを含まない水素吸蔵合金粉末を適用した比較例2においては水素吸蔵合金粉末の内部にMnおよびAlが単独に偏析しているのが認められた。さらに、実施例1〜実施例5、参考例1に係る水素吸蔵合金粉末においては、その表面にMmを含まず、NiとCoからなる合金相の層の生成が認められたのに対して、水素吸蔵合金粉末の熱アルカリ水溶液中への浸漬処理を施していない参考例2では、水素吸蔵合金粉末の表面に前記偏析相と同じMgNiCoMnAl合金からなる層が観察された。また、比較例1および比較例2に係る水素吸蔵合金粉末においては、表面の層にNiとCo以外にMmの存在が認められた。
Figure 2005093297
As shown in Table 1, in the hydrogen storage alloy powders according to Examples 1 to 5, Reference Example 1, and Reference Example 2, the inside of the alloy phase (matrix) composed of MmMgNiCoMnAl having a CaCu 5 type crystal structure. It was observed that a bulk alloy phase (segregation phase) made of MgNiCoMnAl and having a diameter of 3 μm was segregated and dispersed inside the hydrogen storage alloy powder. On the other hand, in the hydrogen storage alloy powder according to Comparative Example 1, segregation of the alloy phase composed of MgNiCoMnAl is not recognized, and Mg, Mn, and Al are segregated independently in the hydrogen storage alloy powder. It was recognized. Further, in Comparative Example 2 in which the hydrogen storage alloy powder not containing Mg was applied, it was recognized that Mn and Al were segregated independently inside the hydrogen storage alloy powder. Furthermore, in the hydrogen storage alloy powders according to Examples 1 to 5 and Reference Example 1, the surface does not contain Mm, whereas the formation of an alloy phase layer composed of Ni and Co was observed, In Reference Example 2 in which the hydrogen storage alloy powder was not immersed in a hot alkaline aqueous solution, a layer made of the same MgNiCoMnAl alloy as the segregation phase was observed on the surface of the hydrogen storage alloy powder. In the hydrogen storage alloy powders according to Comparative Example 1 and Comparative Example 2, the presence of Mm in addition to Ni and Co was recognized in the surface layer.

表2に、実施例1〜実施例5、参考例1、参考例2,比較例1、比較例2に係る円筒形ニッケル水素蓄電池および負極板単極試験結果を示す。なお、負極板単極試験結果は、実施例1の放電容量を100%とした相対的な数値で示した。   Table 2 shows the cylindrical nickel-metal hydride storage battery and negative electrode plate monopolar test results according to Examples 1 to 5, Reference Example 1, Reference Example 2, Comparative Example 1, and Comparative Example 2. In addition, the negative electrode single electrode test result was shown by the relative numerical value which made the discharge capacity of Example 1 100%.

Figure 2005093297
表2に示したとおり、実施例および参考例に係るニッケル水素蓄電池は、比較例電池に比べて充放電サイクル性能に優れる。このように優れたサイクル性能は、実施例電池においては、充放電を繰り返し行っても水素吸蔵合金粉末の微細化が抑制されて水素吸蔵合金粉末の容量低下が低減したことによるものであり、このことは実施例および参考例の場合、水素吸蔵合金粉末内部にMg、Mn、Alが単独に析出した偏析相の生成が抑制されたためと考えられる。
Figure 2005093297
As shown in Table 2, the nickel metal hydride storage batteries according to the examples and the reference examples are superior in charge / discharge cycle performance compared to the comparative example batteries. Thus, the excellent cycle performance is due to the fact that in the example battery, the hydrogen storage alloy powder was prevented from being refined even after repeated charge and discharge, and the capacity reduction of the hydrogen storage alloy powder was reduced. This is presumably because, in the case of the examples and reference examples, the generation of segregated phases in which Mg, Mn, and Al were separately precipitated inside the hydrogen storage alloy powder was suppressed.

また、実施例1〜実施例5および参考例1に係るニッケル水素蓄電池は、急速充電時の内圧上昇が抑制され、かつ、充電受け入れ性能が良い。これは、ニッケル水素吸蔵合金粉末の表面に形成された、NiとCoの合金相からなる多孔性表面層が、水素吸蔵合金の水素吸蔵反応および酸素吸収反応に対して良好な触媒作用を有するためと考えられる。これに対して、参考例2においては、水素吸蔵合金粉末の表面に実施例のようなNiとCoの合金相からなる表面層が形成されていないために、電池の内圧上昇が大きく、セパレータに含まれる電解液が押し出されて、セパレータが液涸れ現象をおこしたことが一因となって、容量低下が速くなったものと考えられる。比較例1、比較例2においては、前記セパレータの液涸れに加えて、水素吸蔵合金粉末の微細化が起きたために、さらにサイクル性能が低くなったものと考えられる。   In addition, the nickel-metal hydride storage batteries according to Examples 1 to 5 and Reference Example 1 are suppressed from increasing in internal pressure during rapid charging and have good charge acceptance performance. This is because the porous surface layer formed of the alloy phase of Ni and Co formed on the surface of the nickel hydrogen storage alloy powder has a good catalytic action for the hydrogen storage reaction and oxygen absorption reaction of the hydrogen storage alloy. it is conceivable that. On the other hand, in Reference Example 2, since the surface layer made of the alloy phase of Ni and Co as in the example is not formed on the surface of the hydrogen storage alloy powder, the increase in the internal pressure of the battery is large, and the separator It is considered that the decrease in capacity was accelerated due to the fact that the electrolyte contained was pushed out and the separator spilled. In Comparative Example 1 and Comparative Example 2, it is considered that the cycle performance was further lowered because the hydrogen storage alloy powder was refined in addition to the liquid dripping of the separator.

表2に示したように、負極単極試験における参考例1の放電容量が実施例や参考例2および比較例に比べて少し低い。参考例1は、水素吸蔵合金粉末を15時間という長時間に亘って熱アルカリ水溶液中に浸漬処理したために、水素吸蔵合金粉末表面の浸食が進んだものとなった。このことは、前記表1に示したように、参考例1の水素吸蔵合金粉末の比表面積が3.7m2/gと大きく、質量飽和磁化が4A・m2/kgを超えており、水素吸蔵合金粉末の比表面積と質量飽和磁化が実施例、参考例2、比較例の水素吸蔵合金粉末に比べて大きくなると同時に、水素吸蔵合金自体の放電容量(mAh/g)の低下をもたらしたものと考えられる。参考例1の場合、水素吸蔵合金粉末の放電容量が低かったために、円筒形ニッケル水素蓄電池を作製したときに充電リザーブ量が小さくなり、実施例に比べてサイクル性能が少し低くなったものと考えられる。これに対して、水素吸蔵合金粉末の比表面積が2m2/g、質量飽和磁化が、3.1A・m2/kgである実施例5の場合は、水素吸蔵合金粉末の容量およびサイクル寿命が実施例1〜実施例3に比べて僅かに低いが参考例1を上回っている。また、水素吸蔵合金粉末の比表面積が0.03m2/g、質量飽和磁化が、0.2A・m2/kgである参考例2においては実施例に比べてサイクル性能、急速充電受け入れ性能が少し劣り、電池内圧も高いのに対して、水素吸蔵合金粉末の比表面積が0.2m2/g、質量飽和磁化が、0.5A・m2/kgである実施例4においては、サイクル性能、急速充電受け入れ性能、電池内圧上昇が抑制されている点において良好な性能を示した。このことから、水素吸蔵合金粉末の水素吸蔵合金粉末の比表面積は、0.2〜2m2/gが好ましく、質量飽和磁化は、0.5〜3.1A・m2/kg(約3A・m2/kg)が好ましいことが分かる。 As shown in Table 2, the discharge capacity of Reference Example 1 in the negative electrode single electrode test is slightly lower than that of Examples, Reference Example 2 and Comparative Example. In Reference Example 1, since the hydrogen storage alloy powder was immersed in a hot alkaline aqueous solution for a long time of 15 hours, the surface of the hydrogen storage alloy powder was eroded. As shown in Table 1, the hydrogen storage alloy powder of Reference Example 1 has a large specific surface area of 3.7 m 2 / g and a mass saturation magnetization exceeding 4 A · m 2 / kg. The specific surface area and mass saturation magnetization of the storage alloy powder are larger than those of the hydrogen storage alloy powders of Example, Reference Example 2 and Comparative Example, and at the same time, the discharge capacity (mAh / g) of the hydrogen storage alloy itself is reduced. it is conceivable that. In the case of Reference Example 1, since the discharge capacity of the hydrogen storage alloy powder was low, when the cylindrical nickel metal hydride storage battery was produced, the charge reserve amount was reduced, and the cycle performance was considered to be slightly lower than in the example. It is done. On the other hand, in the case of Example 5 where the specific surface area of the hydrogen storage alloy powder is 2 m 2 / g and the mass saturation magnetization is 3.1 A · m 2 / kg, the capacity and cycle life of the hydrogen storage alloy powder are Although slightly lower than Examples 1 to 3, it is higher than Reference Example 1. Moreover, in the reference example 2 in which the specific surface area of the hydrogen storage alloy powder is 0.03 m 2 / g and the mass saturation magnetization is 0.2 A · m 2 / kg, the cycle performance and the rapid charge acceptance performance are higher than those of the examples. In Example 4 in which the specific surface area of the hydrogen storage alloy powder is 0.2 m 2 / g and the mass saturation magnetization is 0.5 A · m 2 / kg, although the battery internal pressure is slightly high, the cycle performance is It showed good performance in that the rapid charge acceptance performance and the increase in battery internal pressure were suppressed. Therefore, the specific surface area of the hydrogen storage alloy powder is preferably 0.2 to 2 m 2 / g, and the mass saturation magnetization is 0.5 to 3.1 A · m 2 / kg (about 3 A · m 2 / kg) is preferred.

以上実施例によって、本発明の詳細な説明を行ったが、本発明は、上記実施例と記載したものに限定されるものではない。本発明は、例えば、正極活物質を予め酸化剤を用いて酸化する方法や充電することによって部分的に酸化して、負極に生成する放電リザーブ量を低減させたり、正極にイッテルビウム(Yb)、イットリウム(Y)などの希土類元素を添加して充電効率を高めたり、あるいは、負極にイッテルビウム(Yb)、イットリウム(Y)などの希土類元素を添加して、水素吸蔵合金粉末の腐蝕を抑制したアルカリ蓄電池に対しても適用できる。   Although the present invention has been described in detail with reference to the examples, the present invention is not limited to the examples described above. The present invention is, for example, a method of oxidizing the positive electrode active material in advance using an oxidizing agent or by partially oxidizing the battery by charging, thereby reducing the amount of discharge reserve generated in the negative electrode, ytterbium (Yb) on the positive electrode, Alkaline that suppresses corrosion of hydrogen storage alloy powder by adding rare earth elements such as yttrium (Y) to increase charging efficiency, or adding rare earth elements such as ytterbium (Yb) and yttrium (Y) to the negative electrode It can also be applied to storage batteries.

本発明に係る水素吸蔵合金粉末の構成を模式的に示すための水素吸蔵合金粉末の切断面を示す図である。It is a figure which shows the cut surface of the hydrogen storage alloy powder for showing typically the structure of the hydrogen storage alloy powder which concerns on this invention.

符号の説明Explanation of symbols

1 水素吸蔵合金粉末
2 偏析層
3 表面層



1 Hydrogen storage alloy powder 2 Segregation layer 3 Surface layer



Claims (8)

CaCu5型の結晶構造を有し、MmMgNiCoMnAl合金(Mmはミッシュメタルを表す)を主成分とする水素吸蔵合金粉末であって、少なくとも該粉末の内部にMgNiCoMnAlからなる合金相が分散して存在していることを特徴とする水素吸蔵合金粉末。 A hydrogen storage alloy powder having a CaCu 5 type crystal structure and mainly composed of an MmMgNiCoMnAl alloy (Mm represents Misch metal), and at least an alloy phase composed of MgNiCoMnAl is present in the powder. A hydrogen storage alloy powder characterized by 水素吸蔵合金粉末に占める前記MgNiCoMnAlからなる合金相の比率が0.5〜1.5wt%であることを特徴とする請求項1記載の水素吸蔵合金粉末。 The hydrogen storage alloy powder according to claim 1, wherein a ratio of the alloy phase composed of MgNiCoMnAl in the hydrogen storage alloy powder is 0.5 to 1.5 wt%. 表面にNiとCoの合金からなる層を備えたことを特徴とする請求項1または請求項2に記載の水素吸蔵合金粉末。 The hydrogen storage alloy powder according to claim 1 or 2, further comprising a layer made of an alloy of Ni and Co on the surface. 比表面積が0.2〜2m2/gであることを特徴とする請求項3に記載の水素吸蔵合金粉末。 The hydrogen storage alloy powder according to claim 3, wherein the specific surface area is 0.2 to 2 m 2 / g. 前記MmMgNiCoMnAl合金相を母相とし、該母相から偏析させることによって前記MgNiCoMnAlからなる合金相を生成させることを特徴とする請求項1または請求項2記載の水素吸蔵合金粉末の製造方法。 The method for producing a hydrogen storage alloy powder according to claim 1 or 2, wherein the MmMgNiCoMnAl alloy phase is used as a parent phase, and the alloy phase comprising the MgNiCoMnAl is generated by segregation from the parent phase. 表面に、MmMgNiCoMnAl合金からなる母相から偏析させることによって生成させたMgNiCoMnAl合金からなる層を有する水素吸蔵合金粉末を、熱アルカリ水溶液中に浸漬処理することを特徴とする請求項4または請求項5に記載の水素吸蔵合金粉末の製造方法。 6. The hydrogen storage alloy powder having a layer made of MgNiCoMnAl alloy produced by segregating from a matrix phase made of MmMgNiCoMnAl alloy on the surface is immersed in a hot alkaline aqueous solution. The manufacturing method of the hydrogen storage alloy powder of description. CaCu5型の結晶構造を有し、MmMgNiCoMnAl合金を主成分とする水素吸蔵合金粉末であって、少なくとも粉末の内部にMgNiCoMnAl合金相が分散して存在している水素吸蔵合金粉末、または、該水素吸蔵合金粉末の表面にNiとCoの合金からなる層を備えた水素吸蔵合金粉末を導電性基板に担持させたことを特徴とする水素吸蔵合金電極。 A hydrogen storage alloy powder having a CaCu 5 type crystal structure and mainly composed of an MmMgNiCoMnAl alloy, wherein at least the MgNiCoMnAl alloy phase is dispersed in the powder, or the hydrogen storage alloy powder A hydrogen storage alloy electrode, characterized in that a hydrogen storage alloy powder having a layer made of an alloy of Ni and Co on the surface of the storage alloy powder is supported on a conductive substrate. ニッケル電極を正極とし、CaCu5型の結晶構造を有し、MmMgNiCoMnAlを主成分とする水素吸蔵合金粉末であって、少なくとも粉末の内部にMgNiCoMnAl合金相が分散して存在している水素吸蔵合金粉末、または、該水素吸蔵合金粉末の表面にNiとCoの合金からなる層を備えた水素吸蔵合金粉末を導電性基板に担持させた水素吸蔵合金電極を負極としたことを特徴とするニッケル水素蓄電池。




A hydrogen storage alloy powder having a nickel electrode as a positive electrode, a CaCu 5 type crystal structure, and mainly composed of MmMgNiCoMnAl, in which the MgNiCoMnAl alloy phase is dispersed at least inside the powder. Or a nickel hydride storage battery characterized in that a hydrogen storage alloy electrode comprising a conductive substrate and a hydrogen storage alloy powder comprising a layer made of an alloy of Ni and Co on the surface of the hydrogen storage alloy powder is used as a negative electrode. .




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JP2007056309A (en) * 2005-08-24 2007-03-08 Japan Metals & Chem Co Ltd Hydrogen storage alloy, its manufacturing method and nickel hydrogen secondary battery
JP4634256B2 (en) * 2005-08-24 2011-02-16 日本重化学工業株式会社 Hydrogen storage alloy, method for producing the same, and nickel metal hydride secondary battery
JP2009054514A (en) * 2007-08-29 2009-03-12 Sanyo Electric Co Ltd Hydrogen storage alloy electrode, and alkaline storage battery using the same
WO2009144873A1 (en) * 2008-05-30 2009-12-03 パナソニック株式会社 Hyrogen occluding alloy powder and method for surface treatment of same, negative pole for an alkali storage battery, and alkali storage battery
JP2010007177A (en) * 2008-05-30 2010-01-14 Panasonic Corp Hydrogen storage alloy powder, surface treatment method therefor, negative electrode for alkali storage battery, and alkali storage battery
JP4667513B2 (en) * 2008-05-30 2011-04-13 パナソニック株式会社 Hydrogen storage alloy powder and surface treatment method thereof, negative electrode for alkaline storage battery, and alkaline storage battery
JP2010050011A (en) * 2008-08-25 2010-03-04 Gs Yuasa Corporation Nickel-hydrogen storage battery and manufacturing method therefor
JP2012102343A (en) * 2010-11-05 2012-05-31 National Institute Of Advanced Industrial Science & Technology Hydrogen-storage alloy, hydrogen-storage alloy electrode, and nickel-hydrogen secondary battery
CN108588495A (en) * 2018-04-26 2018-09-28 吉林大学 A kind of AB having both high power capacity and long-life4.5Type hydrogen storage alloy and preparation method thereof
JP7333358B2 (en) 2021-03-03 2023-08-24 プライムアースEvエナジー株式会社 Nickel metal hydride storage battery

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