JP4540045B2 - Hydrogen storage alloy, hydrogen storage electrode and nickel metal hydride storage battery - Google Patents

Hydrogen storage alloy, hydrogen storage electrode and nickel metal hydride storage battery Download PDF

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JP4540045B2
JP4540045B2 JP2004214376A JP2004214376A JP4540045B2 JP 4540045 B2 JP4540045 B2 JP 4540045B2 JP 2004214376 A JP2004214376 A JP 2004214376A JP 2004214376 A JP2004214376 A JP 2004214376A JP 4540045 B2 JP4540045 B2 JP 4540045B2
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学 金本
実 黒葛原
誠二郎 落合
俊樹 田中
充浩 児玉
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GS Yuasa International Ltd
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Description

本発明は、希土類元素とニッケル（Ｎｉ）を主構成成分とし、CaCu5形の結晶構造を主結晶構造とする水素吸蔵合金および該水素吸蔵合金を適用した水素吸蔵電極を備えた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 having a rare earth element and nickel (Ni) as main components and having a crystal structure of CaCu 5 type as a main crystal structure, and a nickel metal hydride storage battery including a hydrogen storage electrode to which the hydrogen storage alloy is applied. Is.

アルカリ蓄電池の１種であるニッケル水素蓄電池は、同じアルカリ蓄電池の１種であるニッケルカドミウム蓄電池に比べて高いエネルギー密度を有し、しかも有害なカドミウムを含まず環境汚染の虞が少ないことから、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、該小形電子機器用電源としての用途が広がるとともに更なる放電容量の向上が求められている。   Nickel metal hydride storage battery, a type of alkaline storage battery, has a higher energy density than nickel cadmium storage battery, which is one type of alkaline storage battery, and does not contain harmful cadmium. It is widely used as a power source for portable small electronic devices such as telephones, small electric tools, and small personal computers, and the demand is rapidly increasing with the spread of these small electronic devices. In addition, the use as a power source for small electronic devices has been expanded, and further improvement in discharge capacity has been demanded.

従来のニッケル水素蓄電池に用いる水素吸蔵合金電極には、希土類元素およびニッケルなどの遷移金属元素を主成分とし、CaCu5形の結晶構造を有する水素吸蔵合金が広く使用されている。該水素吸蔵合金を用いた水素吸蔵合金電極はサイクル性能に優れるものの放電容量が低く、前記求めに応じて更なる放電容量の向上をはかることが難しいという問題がある。 As a hydrogen storage alloy electrode used in a conventional nickel metal hydride storage battery, a hydrogen storage alloy having a CaCu 5 type crystal structure mainly composed of a transition metal element such as a rare earth element and nickel is widely used. Although the hydrogen storage alloy electrode using the hydrogen storage alloy is excellent in cycle performance, the discharge capacity is low, and there is a problem that it is difficult to further improve the discharge capacity according to the above demand.

高容量を有する水素吸蔵合金として従来広く用いられてきたＡＢ5形に替えて近年ＡＢ3形やＡＢ3.5形の水素吸蔵合金が提案されている。（例えば特許文献１） In recent years, AB 3 type and AB 3.5 type hydrogen storage alloys have been proposed in place of the AB 5 type which has been widely used as a high capacity hydrogen storage alloy. (For example, Patent Document 1)

特開平１１−３２３４６９号公報 特許文献１に記載の水素吸蔵合金を適用した水素吸蔵合金電極は、前記従来の水素吸蔵合金電極に比べて放電容量は大きいものの、耐久性に劣り、該水素吸蔵合金を用いた水素吸蔵合金電極はサイクル性能が劣る欠点があった。JP, 11-323469, A The hydrogen storage alloy electrode which applied the hydrogen storage alloy of patent documents 1 is inferior in durability, although a discharge capacity is large compared with the above-mentioned conventional hydrogen storage alloy electrode, and this hydrogen storage alloy However, the hydrogen storage alloy electrode using the material had a disadvantage that the cycle performance was inferior.

また、ＡＢ5形の水素吸蔵合金粉末において、水素吸蔵合金の組成をLaを２４〜３３重量％、MgまたはCaを０．１〜１．０重量％含む組成とすることにより高容量であって、繰り返し充放電を行っても微粉化の抑制された長寿命を有する水素吸蔵合金が提案されている。（例えば特許文献２参照）
特開2002-80925公報 しかし、該特許文献２において特に好ましいと記載されている元素Ｂと元素Ａの比（原子比）Ｂ／Ａが５〜６では水素吸蔵合金の水素吸蔵量が小さいためか放電容量向上において効果が不十分であるという欠点があった。 Further, in the AB 5 form of hydrogen-absorbing alloy powder, the composition of the hydrogen storage alloy La of 24 to 33 wt%, a high capacity by a composition containing Mg or Ca 0.1 to 1.0 wt% A hydrogen storage alloy having a long life in which pulverization is suppressed even after repeated charge and discharge has been proposed. (For example, see Patent Document 2)
However, if the ratio (atomic ratio) B / A between element B and element A, which is described as being particularly preferable in Patent Document 2, is 5 to 6, the hydrogen storage amount of the hydrogen storage alloy is small. There is a drawback that the effect is insufficient in improving the discharge capacity.

本発明は、前記従来の水素吸蔵合金およびニッケル水素蓄電池の欠点に鑑みなされたものであって、水素吸蔵合金電極のサイクル性能を低下させることなく、放電容量の大きい水素吸蔵合金およびそれを適用することによって放電容量が向上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 disadvantages of the conventional hydrogen storage alloy and nickel-metal hydride storage battery, and applies a hydrogen storage alloy having a large discharge capacity without reducing the cycle performance of the hydrogen storage alloy electrode. Therefore, a nickel-metal hydride storage battery with improved discharge capacity is provided.

本発明は、水素吸蔵合金およびニッケル水素蓄電池を以下の構成とすることによって前記課題を解決する。
本発明に係るニッケル水素蓄電池は、記号Ａが希土類元素であり、記号ＢがＭｇであり、記号ＣがＣｏ、Ｍｎ、Ａｌ、ＦｅおよびＣｕから選ばれる１種以上の元素であり、化学式ＡwＢxＮｉyＣzにおいて、ｗ＋ｘ＝１、０．０４≦ｘ≦０．０９、３．５≦ｙ≦４．３、４．０≦ｙ＋ｚ≦４．７、０＜ｚ、４．７５≦（ｘ＋ｙ＋ｚ）／ｗ≦５．３５で表される水素吸蔵合金を用いた水素吸蔵電極を備えたニッケル水素蓄電池である。
本発明に係るニッケル水素蓄電池の水素吸蔵電極は、水素吸蔵合金の粉末とセリウム（Ｃｅ）、デイスプロシウム（Ｄｙ）、ホルミウム（Ｈｏ）、エルビウム（Ｅｒ）、ツリウム（Ｔｍ）、イッテルビウム（Ｙｂ）、ルテチウム（Ｒｕ）およびイットリウム（Ｙ）から選ばれた少なくとも１種の希土類元素の水酸化物と酸化物の少なくとも１種を導電性基板に担持させたものであることが好ましい。 This invention solves the said subject by setting a hydrogen storage alloy and a nickel metal hydride storage battery as the following structures.
Nickel-metal hydride storage battery according to the present invention, the symbol A is a rare earth element, the symbol B is M g, at least one element symbol C is selected Co, Mn, Al, Fe and Cu, Formula AwBxNiyCz W + x = 1, 0.04 ≦ x ≦ 0.09, 3.5 ≦ y ≦ 4.3, 4.0 ≦ y + z ≦ 4.7, 0 < z, 4.75 ≦ (x + y + z) / w ≦ It is a nickel hydride storage battery provided with the hydrogen storage electrode using the hydrogen storage alloy represented by 5.35.
The hydrogen storage electrode of the nickel metal hydride storage battery according to the present invention includes a hydrogen storage alloy powder and cerium (Ce), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb). It is preferable that at least one kind of hydroxide and oxide of rare earth elements selected from lutetium (Ru) and yttrium (Y) are supported on a conductive substrate.

本発明によれば、従来のニッケル水素蓄電池に比べて放電容量が大きく、且つ、サイクル性能が従来のニッケル水素蓄電池と同等かまたは上回るニッケル水素蓄電池を得ることができる。 According to the onset bright, large discharge capacity as compared to conventional nickel-metal hydride storage battery, and can cycle performance obtain conventional nickel-metal hydride storage battery equal to or greater than the nickel-metal hydride storage battery.

本発明に係る水素吸蔵合金は、記号Ａが希土類元素であり、記号ＢがＭｇであり、記号ＣがＣｏ、Ｍｎ、Ａｌ、ＦｅおよびＣｕから選ばれる１種以上の元素であり、化学式ＡwＢxＮｉyＣzにおいて、ｗ＋ｘ＝１、０．０４≦ｘ≦０．０９、３．５≦ｙ≦４．３、４．０≦ｙ＋ｚ≦４．７、０＜ｚ、４．７５≦（ｘ＋ｙ＋ｚ）／ｗ≦５．３５で表される水素吸蔵合金である。 The hydrogen storage alloy according to the present invention, the symbol A is a rare earth element, the symbol B is M g, at least one element symbol C is selected Co, Mn, Al, Fe and Cu, the formula A In w B x Ni y C z , w + x = 1, 0.04 ≦ x ≦ 0.09, 3.5 ≦ y ≦ 4.3, 4.0 ≦ y + z ≦ 4.7, 0 < z, 4.75 It is a hydrogen storage alloy represented by ≦ (x + y + z) /w≦5.35.

該水素吸蔵合金の製造方法は特に限定されず、鋳造法、ガスアトマイズ法、メルトスピニング法、アーク溶解法の何れでも適用できるが、水素吸蔵合金を構成する元素のうちＭｇ、Ｃａは、溶解したときに蒸発によって逸散し易く、所定の組成の合金が得られない虞がある。Ｍｇ、Ｃａの蒸発による逸散を抑制するには鋳造法、ガスアトマイズ法、メルトスピニング法が好ましい方法である。 Method for producing a hydrogen-absorbing alloy is not particularly limited, casting, gas atomization, melt spinning method can be applied either in arc melting method, among Mg, Ca of elements constituting the hydrogen storage alloy were dissolved Sometimes, it tends to dissipate by evaporation, and an alloy having a predetermined composition may not be obtained. A casting method, a gas atomizing method, and a melt spinning method are preferable methods for suppressing dissipation due to evaporation of Mg and Ca.

本発明に係る水素吸蔵合金は、主としてCaCu5形の結晶構造を有する。ここで、主としてCaCu5形の結晶と記述したのは、粉末Ｘ線回折を用いた調査でCaCu5形結晶に混じって一部PuNi3形やCe2Ni7形の結晶を含むものが認められたからである。 The hydrogen storage alloy according to the present invention mainly has a CaCu 5 type crystal structure. Here, primarily that described with CaCu 5 form of crystals, it was observed to include an investigation CaCu 5 type crystal in mixed partially PuNi 3 shapes and Ce 2 Ni 7 crystalline form with a powder X-ray diffraction This is because the.

本発明に係る水素吸蔵合金は、前記組成表示においてＭｇの含有比（原子比）ｘが０．０４〜０．０９である。希土類元素を含む系にＭｇやＣａが存在すると水素吸蔵合金の水素吸蔵放出サイトが多くなり水素吸蔵合金の放電容量が増大する。また、ＭｇやＣａの存在は、水素吸蔵合金が水素を吸蔵・放出したときに水素吸蔵合金の結晶格子が膨張・収縮するのを緩和し結晶を安定化させる作用がある。該比ｘが０．０４未満では、Ｍｇ、Ｃａの添加効果が発現せず高容量が得られ難い。また、Ｍｇ、Ｃａはそれ自体アルカリ電解液中で溶出し易く、水素吸蔵合金中にＭｇ、Ｃａが存在すると水素吸蔵合金が腐蝕（溶出）し易くなる。このような理由からｘが０．１７を超えると高容量が得られるものの合金の耐久性が低くサイクル性能が劣る欠点があった。なお、前記ｘが０．０４〜０．０９であれば、良好なサイクル性能が得られるので好ましい。 The hydrogen storage alloy according to the present invention has an Mg content ratio (atomic ratio) x of 0.04 to 0.09 in the composition display. When Mg or Ca is present in a system containing a rare earth element, the number of hydrogen storage / release sites of the hydrogen storage alloy increases and the discharge capacity of the hydrogen storage alloy increases. Further, the presence of Mg and Ca has an action of stabilizing the crystal by relaxing the expansion and contraction of the crystal lattice of the hydrogen storage alloy when the hydrogen storage alloy absorbs and releases hydrogen. When the ratio x is less than 0.04, the effect of adding Mg and Ca is not exhibited, and it is difficult to obtain a high capacity. Further, Mg and Ca are easily eluted in an alkaline electrolyte per se, and if Mg and Ca are present in the hydrogen storage alloy, the hydrogen storage alloy is easily corroded (elution). For these reasons, when x exceeds 0.17, a high capacity can be obtained, but the alloy has low durability and poor cycle performance. In addition, if said x is 0.04-0.09, since favorable cycling performance is obtained, it is preferable.

本発明に係る水素吸蔵合金は、また、前記組成表示においてＮｉの含有比（原子比）ｙが３．５〜４．３であり、３．７〜４．１が好ましい。該比ｙが３．５未満では水素吸蔵合金のアルカリ電解液に対する耐食性が低いのと、且つ、充放電を繰り返し行ったときに微細化し易く該微細化に伴って水素吸蔵能力が低下するため耐久性が劣る。逆にｙが４．３を超えると水素吸蔵合金の水素吸蔵量が少なく放電容量が低くなる虞がある。なお、該比ｙが３．７〜４．１であれば、良好なサイクル性能が得られるので好ましい。   In the hydrogen storage alloy according to the present invention, the content ratio (atomic ratio) y of Ni in the composition display is 3.5 to 4.3, and preferably 3.7 to 4.1. If the ratio y is less than 3.5, the corrosion resistance of the hydrogen storage alloy to the alkaline electrolyte is low, and it is easy to miniaturize when repeated charge and discharge, and the hydrogen storage capacity decreases with the miniaturization. Inferior. On the other hand, if y exceeds 4.3, the hydrogen storage amount of the hydrogen storage alloy is small and the discharge capacity may be lowered. In addition, it is preferable if the ratio y is 3.7 to 4.1 because good cycle performance can be obtained.

本発明に係る水素吸蔵合金は、Ｃｏ、Ｍｎ、Ａｌ、ＦｅおよびＣｕから選ばれる１種以上の元素の含有比（原子比）ｚが０＜ｚを満たし、前記組成表示においてＮｉの含有比（原子比）ｙとｚの和ｙ＋ｚが４．０〜４．７であるのが良く、ｙ＋ｚが４．４５〜４．７であるのが好ましい。Ｃｏ、Ｍｎ、Ａｌ、ＦｅおよびＣｕから選ばれる１種以上の元素のうちＣｏは、水素吸蔵合金が水素を吸蔵・放出を繰り返したときに水素吸蔵合金が微細化して容量が低下するのを抑制する効果がある。Ｍｎの適量の存在は、水素吸蔵合金の水素平衡圧を低下させ、水素吸蔵能力を向上させる効果がある。Ａｌは、水素吸蔵合金の化学的安定性を向上させ耐久性を高める作用がある。また、ＦｅおよびＣｕを添加することによって低コスト化を図ることができる。
前記比ｙ＋ｚが４．０未満では水素吸蔵合金のアルカリ電解液に対する耐食性が低いため耐久性が劣り、且つ、容量も低い。ｙ＋ｚが４．７を超えると、水素吸蔵合金の水素吸蔵量が少なく放電容量が低下する。なお、該比ｙ＋ｚが４．４５〜４．７であれば、良好なサイクル性能が得られるので好ましい。 In the hydrogen storage alloy according to the present invention, the content ratio (atomic ratio) z of one or more elements selected from Co, Mn, Al, Fe and Cu satisfies 0 < z, and the content ratio of Ni ( Atomic ratio) The sum y + z of y and z is preferably 4.0 to 4.7, and y + z is preferably 4.45 to 4.7. Among one or more elements selected from Co, Mn, Al, Fe, and Cu, Co suppresses the reduction in capacity due to the miniaturization of the hydrogen storage alloy when the hydrogen storage alloy repeatedly stores and releases hydrogen. There is an effect to. The presence of an appropriate amount of Mn has the effect of reducing the hydrogen equilibrium pressure of the hydrogen storage alloy and improving the hydrogen storage capacity. Al has the effect of improving the chemical stability of the hydrogen storage alloy and increasing the durability. Moreover, cost reduction can be achieved by adding Fe and Cu.
When the ratio y + z is less than 4.0, the corrosion resistance of the hydrogen storage alloy to the alkaline electrolyte is low, so that the durability is inferior and the capacity is low. When y + z exceeds 4.7, the hydrogen storage amount of the hydrogen storage alloy is small and the discharge capacity is reduced. In addition, if this ratio y + z is 4.45 to 4.7, since favorable cycling performance is obtained, it is preferable.

本発明に係る水素吸蔵合金は、前記組成表示において前記ｘとｙとｚの和ｘ＋ｙ＋ｚのｗに対する比（ｘ＋ｙ＋ｚ）／ｗが４．７５〜５．３５であり、４．８５〜５．１５が好ましい。該比が４．７５未満では水素吸蔵合金のアルカリ電解液に対する耐食性が低いため耐久性が劣る。逆に該比が５．３５を超えると水素吸蔵合金の水素吸蔵量が少なく放電容量が低い。なお、該比（ｘ＋ｙ＋ｚ）／ｗが４．８５〜５．１５であれば、良好なサイクル性能が得られるので好ましい。   In the hydrogen storage alloy according to the present invention, the ratio (x + y + z) / w of the sum x + y + z of x, y, and z (x + y + z) / w in the composition display is 4.75 to 5.35, and 4.85 to 5.15. preferable. If the ratio is less than 4.75, the corrosion resistance of the hydrogen storage alloy to the alkaline electrolyte is low, so the durability is poor. On the other hand, when the ratio exceeds 5.35, the hydrogen storage amount of the hydrogen storage alloy is small and the discharge capacity is low. In addition, if this ratio (x + y + z) / w is 4.85-5.15, since favorable cycling performance is obtained, it is preferable.

本発明に係る水素吸蔵電極は、前記請求項１に記載の高容量水素吸蔵合金の粉末の他にＣｅ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、ＲｕおよびＹから選ばれた少なくとも１種の希土類元素の水酸化物と酸化物の少なくとも１種を含有することによって、高容量を維持しながら水素吸蔵合金の耐食性を高めることによって優れたサイクル性能を達成することができる。該希土類元素の酸化物または水酸化物の水素吸蔵合金粉末に対する比率は特に限定されるものではないが、０．５〜３重量％が好ましく、０．５〜１．５重量％がさらに好ましい。該比率が０．５重量％未満ではこれらの化合物の添加効果が得にくく、３重量％を超えると水素吸蔵電極の導電性を低下させ集電を妨げる虞がある。   The hydrogen storage electrode according to the present invention includes at least one rare earth selected from Ce, Dy, Ho, Er, Tm, Yb, Ru and Y in addition to the powder of the high capacity hydrogen storage alloy according to claim 1. By containing at least one elemental hydroxide and oxide, excellent cycle performance can be achieved by increasing the corrosion resistance of the hydrogen storage alloy while maintaining a high capacity. The ratio of the rare earth element oxide or hydroxide to the hydrogen storage alloy powder is not particularly limited, but is preferably 0.5 to 3% by weight, more preferably 0.5 to 1.5% by weight. If the ratio is less than 0.5% by weight, the effect of adding these compounds is difficult to obtain, and if it exceeds 3% by weight, the conductivity of the hydrogen storage electrode may be reduced and current collection may be hindered.

以下に実施例により本発明の詳細を説明するが、本発明は前記構成の水素吸蔵合金およびそれを用いた水素吸蔵電極を備えるニッケル水素蓄電池全てに適用できるものであって、以下に記載の実施例に示す実施形態に限定されるものではない。
（水素吸蔵合金粉末の作製）
（実施例１〜９、参考例１〜１２）
表１の実施例１〜実施例９、参考例１〜１２に示した原子比で各金属元素を秤量し、高周波溶解法を用いて溶解させた後、水冷金型中で冷却した。得られた合金（インゴット）をアルゴン雰囲気下で、温度９００℃において３時間加熱し炉内で放置冷却した。得られたインゴットをアルゴン雰囲気下で機械粉砕し、平均粒径（Ｄ５０）が５０μｍの水素吸蔵合金粉末を作製した。それぞれの水素吸蔵合金粉末を実施例１〜実施例９、参考例１〜１２とする。なお、表１でMmはミッシュメタルを表し、原子比でLa65%、Ce25%、Pr2%、Nd8%からなる希土類元素の混合物である。
（比較例１〜４）
表１の比較例１〜比較例４に示した原子比で各金属元素を秤量し、以下前記実施例１〜実施例９、参考例１〜１２と同様の手順で水素吸蔵合金粉末を作製した。得られた水素吸蔵合金粉末をそれぞれ比較例１〜比較例４とする。
The details of the present invention will be described below with reference to examples, but the present invention can be applied to all nickel-metal hydride storage batteries including the hydrogen storage alloy having the above-described configuration and a hydrogen storage electrode using the same, and the following implementations It is not limited to the embodiment shown in the example.
(Preparation of hydrogen storage alloy powder)
(Examples 1-9 , Reference Examples 1-12 )
Each metal element was weighed in the atomic ratios shown in Examples 1 to 9 and Reference Examples 1 to 12 in Table 1, dissolved using a high-frequency dissolution method, and then cooled in a water-cooled mold. The obtained alloy (ingot) was heated at 900 ° C. for 3 hours in an argon atmosphere and allowed to cool in the furnace. The obtained ingot was mechanically pulverized under an argon atmosphere to produce a hydrogen storage alloy powder having an average particle size (D50) of 50 μm. The respective hydrogen storage alloy powders are referred to as Examples 1 to 9 and Reference Examples 1 to 12 . In Table 1, Mm represents Misch metal, which is a mixture of rare earth elements composed of La65%, Ce25%, Pr2%, and Nd8% in atomic ratio.
(Comparative Examples 1-4)
Each metal element was weighed at the atomic ratio shown in Comparative Example 1 to Comparative Example 4 in Table 1, and hydrogen storage alloy powders were prepared in the same manner as in Examples 1 to 9 and Reference Examples 1 to 12 below. . The obtained hydrogen storage alloy powders are referred to as Comparative Examples 1 to 4, respectively.

（粉末Ｘ線回折による調査）
銅管球を用いて実施例１〜９、参考例１〜１２、比較例１〜４に係る水素吸蔵合金粉末の粉末Ｘ線回折測定を行った。
(Investigation by powder X-ray diffraction)
The powder X-ray diffraction measurement of the hydrogen storage alloy powder which concerns on Examples 1-9, Reference Examples 1-12 , and Comparative Examples 1-4 was performed using the copper tube.

（実施例１〜９、参考例１〜１２）
（単極試験用水素吸蔵電極の作製１）
前記実施例１〜９、参考例１〜１２に係る水素吸蔵合金粉末１００重量部にインコ社製ニッケル粉末（INCO#210）１０重量部を添加混合した後、増粘剤であるメチルセルロースを０．５％の濃度で溶解した水溶液および結着剤であるスチレンブタジエンゴム（ＳＢＲ）の水性デイスパージョンを水素吸蔵合金粉末に対して固形分として０．７重量％添加混練してペーストにした。該ペーストを、厚さ３５μｍ、開口率６０％、開口径１ｍｍの穿孔鋼板（ニッケルメッキ済み）製の基板の両面に塗布し、乾燥後所定の厚さ（０．３ｍｍ）になるようにプレスした。該水素吸蔵電極をそれぞれ実施例１〜実施例９、参考例１〜１２とする。
（比較例１〜４）
前記比較例１〜４に係る水素吸蔵合金粉末を用い、実施例１〜９、参考例１〜１２と同様の手順で水素吸蔵電極を作製した。該水素吸蔵電極を比較例１〜４とする。
(Examples 1-9 , Reference Examples 1-12 )
(Preparation of hydrogen storage electrode for unipolar test 1)
After adding 10 parts by weight of Inco Corporation nickel powder (INCO # 210) to 100 parts by weight of the hydrogen storage alloy powders according to Examples 1 to 9 and Reference Examples 1 to 12 , 0. An aqueous solution dissolved at a concentration of 5% and an aqueous dispersion of styrene butadiene rubber (SBR) as a binder were added and kneaded as a solid content to the hydrogen storage alloy powder to obtain a paste. The paste was applied to both surfaces of a substrate made of a perforated steel plate (nickel plated) having a thickness of 35 μm, an aperture ratio of 60%, and an aperture diameter of 1 mm, and pressed to a predetermined thickness (0.3 mm) after drying. . The hydrogen storage electrodes are referred to as Examples 1 to 9 and Reference Examples 1 to 12 , respectively.
(Comparative Examples 1-4)
Using the hydrogen storage alloy powders according to Comparative Examples 1 to 4, hydrogen storage electrodes were prepared in the same procedure as in Examples 1 to 9 and Reference Examples 1 to 12 . Let this hydrogen storage electrode be Comparative Examples 1-4.

（水素吸蔵電極単極試験）
前記実施例１〜９、参考例１〜１２、比較例１〜４に係る水素吸蔵電極を３０×３０ｍｍに裁断し、端部にリード片を接合して単極試験用の水素吸蔵電極とした。水素吸蔵電極１枚を真ん中にしてその両側に２枚のニッケル電極を配置し開放形セルを組み立てた。なお、ニッケル電極の容量が水素吸蔵電極の容量に対して大過剰（ニッケル電極の容量／水素吸蔵電極の容量＝３．５）になるようにした。電解液には６．８Ｍ／ｌのＫＯＨと０．８Ｍ／ｌのＬｉＯＨを含む水溶液を用いた。該セルを周囲温度２０℃において充放電を行った。０．１ItA（40mA）にて水素吸蔵電極の容量に対して１５０％充電した後、０．２ItA（80mA）にて放電した。なお、水素吸蔵電極の参照電極（Hg/HgO電極）に対する電位が−０．６Ｖになった時点で放電を打ち切った。該充放電を1サイクルとして、該サイクルを繰り返し行い、１０サイクル目の放電容量を該水素吸蔵電極の放電容量とし、該放電容量（mAh）を水素吸蔵合金の充填量（g）で除した値（mAh/g）をもって放電容量を評価する指標とした。
(Hydrogen storage electrode single electrode test)
The hydrogen storage electrodes according to Examples 1 to 9, Reference Examples 1 to 12 , and Comparative Examples 1 to 4 were cut to 30 × 30 mm, and lead pieces were joined to the end portions to form hydrogen storage electrodes for a single electrode test. . An open cell was assembled with one hydrogen storage electrode in the middle and two nickel electrodes on each side. It should be noted that the capacity of the nickel electrode was excessively large relative to the capacity of the hydrogen storage electrode (the capacity of the nickel electrode / the capacity of the hydrogen storage electrode = 3.5). An aqueous solution containing 6.8 M / l KOH and 0.8 M / l LiOH was used as the electrolytic solution. The cell was charged and discharged at an ambient temperature of 20 ° C. After charging 150% of the capacity of the hydrogen storage electrode at 0.1 ItA (40 mA), the battery was discharged at 0.2 ItA (80 mA). The discharge was stopped when the potential of the hydrogen storage electrode relative to the reference electrode (Hg / HgO electrode) became −0.6V. The charge / discharge cycle is repeated, the cycle is repeated, the discharge capacity at the 10th cycle is defined as the discharge capacity of the hydrogen storage electrode, and the discharge capacity (mAh) is divided by the filling amount (g) of the hydrogen storage alloy. (MAh / g) was used as an index for evaluating the discharge capacity.

（水素吸蔵合金粉末の質量飽和磁化の測定）
放電試験終了後の開放形セル（放電済み）を解体して取り出した負極板から水素吸蔵合金粉末を回収し、それぞれの粉末の質量飽和磁化を測定した。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た後、（株）理研電子製、振動試料形磁力計（モデルBHV-30)を用い５ｋエルステッドの磁場をかけて測定して得られた値を該水素吸蔵合金粉末の質量飽和磁化とした。 (Measurement of mass saturation magnetization of hydrogen storage alloy powder)
The hydrogen storage alloy powder was recovered from the negative electrode plate taken out after dismantling the open cell (discharged) after the end of the discharge test, and the mass saturation magnetization of each powder was measured. After precisely weighing 0.3 g of hydrogen storage alloy powder and filling the sample holder, it is obtained by applying a 5 k Oersted magnetic field using a vibrating sample magnetometer (model BHV-30) manufactured by Riken Denshi Co., Ltd. The obtained value was defined as the mass saturation magnetization of the hydrogen storage alloy powder.

（水素吸蔵合金粉末の比表面積の測定）
放電試験終了後の開放形セル（放電済み）を解体して取り出した負極板から水素吸蔵合金粉末を回収し、水素吸蔵合金粉末１．０ｇを精秤し、ＢＥＴ法にて測定した値を該水素吸蔵合金粉末の比表面積とした。 (Measurement of specific surface area of hydrogen storage alloy powder)
The hydrogen storage alloy powder was recovered from the negative electrode plate taken out by dismantling the open cell (discharged) after the discharge test was completed, 1.0 g of the hydrogen storage alloy powder was precisely weighed, and the value measured by the BET method was The specific surface area of the hydrogen storage alloy powder was used.

図１に実施例３、参考例４及び比較例２に係る水素吸蔵合金粉末の粉末Ｘ線回折図を、図２に比較例１に係る水素吸蔵合金粉末の粉末Ｘ線回折図を示す。
また、表１に実施例１〜９、参考例１〜１２、比較例１〜４に係る水素吸蔵合金粉末の組成、水素吸蔵電極単極試験結果、質量飽和磁化測定結果、比表面積測定結果を示す。
FIG. 1 shows a powder X-ray diffraction diagram of the hydrogen storage alloy powder according to Example 3, Reference Example 4 and Comparative Example 2, and FIG. 2 shows a powder X-ray diffraction diagram of the hydrogen storage alloy powder according to Comparative Example 1.
Table 1 shows the compositions of hydrogen storage alloy powders according to Examples 1 to 9, Reference Examples 1 to 12 , and Comparative Examples 1 to 4, hydrogen storage electrode monopolar test results, mass saturation magnetization measurement results, and specific surface area measurement results. Show.

図１（イ）は、参考例４に係る水素吸蔵合金粉末、図１（ロ）は、実施例３、図１（ハ）は比較例２に係る水素吸蔵合金粉末の粉末Ｘ線回折図である。比較例２がMgを含有しないのに対して、実施例３および参考例４の水素吸蔵合金粉末は、共にMgを含有し、また実施例３と参考例４がMgの含有比率を異にするが、図１に示すように実施例３、参考例４ともに比較例２と同様CaCu5形の結晶構造を有している。詳細は省略するが、表１に示した他の実施例、他の参考例もCaCu5形を主とする結晶構造を有していた。
これに対して、Mgの含有比率を高くした比較例１の場合は図２に示す粉末Ｘ線回折図からCaCu5形とは異なる結晶構造を有していることが分かった。
1A is a powder X-ray diffraction diagram of the hydrogen storage alloy powder according to Reference Example 4 , FIG. 1B is Example 3 and FIG. 1C is a powder X-ray diffraction pattern of the hydrogen storage alloy powder according to Comparative Example 2. is there. While Comparative Example 2 does not contain Mg, the hydrogen storage alloy powders of Example 3 and Reference Example 4 both contain Mg, and Example 3 and Reference Example 4 have different Mg content ratios. However, as shown in FIG. 1, both Example 3 and Reference Example 4 have a CaCu 5 type crystal structure as in Comparative Example 2. Although details are omitted , other examples and other reference examples shown in Table 1 also had a crystal structure mainly composed of CaCu 5 type .
On the other hand, in the case of Comparative Example 1 in which the Mg content ratio was increased, it was found from the powder X-ray diffraction diagram shown in FIG. 2 that the crystal structure was different from that of the CaCu 5 form.

比較例２は、MmNiCoMnAl系のMgやCaを含まない組成の水素吸蔵合金粉末であって、従来ひろく用いられているものである。これに対して、実施例１〜９、参考例１〜１２に示す水素吸蔵合金粉末は、新規な組成を有する水素吸蔵合金粉末であって、MgまたはCaを含み、その含有比（原子比ｘ）が0.04〜0.17である水素吸蔵合金粉末である。
表１に示すように、実施例１〜９、参考例１〜１２に係る水素吸蔵合金は、比較例２に比べて、単位重量当たりの放電容量(mAh/g)が1.13〜1.25倍である。比較例２に比べて、実施例の放電容量が大きいのは、水素吸蔵合金中にMg、Caを存在させたことと、Ni、Co、Alの含有比率(y+z)を4.70以下と比較例２の5.00に比べて低く抑えたことによって水素吸蔵合金の水素吸蔵能力を高めたことによる。因みに実施例に比べて更にMgの含有比率を高くし、(y+z)の値3.50と低くした比較例１の場合は、放電容量が380mAh/gと高い値を示している。(y+z)が大きい比較例３は、比較例２と比べて放電容量が低い。因みに図３に水素吸蔵合金の容量と(y+z)の関係を示す。図３に示したように、(y+z)が小さい方が水素吸蔵合金の容量が大きい傾向にあることが分かる。また、Mg+Ni+Co+AlとLaの比｛(x+y+z)/w｝が4.51と小さい比較例４も水素吸蔵合金の水素吸蔵能力が小さいためか、放電容量が小さい結果となった。
表１に示した試験結果によれば、前記ｘを0.04〜0.17、ｙを3.5〜4.3、(y+z)を4.0〜4.7、(x+y+z)/wを4.75〜5.35とした実施例１〜９、参考例１〜１２が比較例２〜４と比較して放電容量が大きいことが分かる。なお、詳細は省くがNiの含有比ｙが4.3を超えた場合、放電容量が低い欠点がある。
 Comparative Example 2 is an MmNiCoMnAl-based hydrogen storage alloy powder having a composition that does not contain Mg or Ca, and has been widely used in the past. In contrast, Example 1-9, the hydrogen storage alloy powder as in Reference Example 1 to 12, a hydrogen-absorbing alloy powder having a new composition comprises Mg or Ca, the content ratio (atomic ratio x) is a hydrogen storage alloy powder having 0.04 to 0.17.
As shown in Table 1, the hydrogen storage alloys according to Examples 1 to 9 and Reference Examples 1 to 12 have a discharge capacity (mAh / g) per unit weight of 1.13 to 1.25 times that of Comparative Example 2. . Compared with Comparative Example 2, the discharge capacity of the Example is larger than the presence of Mg and Ca in the hydrogen storage alloy and the content ratio (y + z) of Ni, Co and Al is 4.70 or less. This is because the hydrogen storage capacity of the hydrogen storage alloy was increased by keeping it lower than 5.00 in Example 2. Incidentally, in the case of Comparative Example 1 in which the Mg content ratio is further increased and the value of (y + z) is as low as 3.50 as compared with the Examples, the discharge capacity is as high as 380 mAh / g. Comparative Example 3 with a large (y + z) has a lower discharge capacity than Comparative Example 2. FIG. 3 shows the relationship between the capacity of the hydrogen storage alloy and (y + z). As shown in FIG. 3, it can be seen that the smaller the (y + z), the larger the capacity of the hydrogen storage alloy. Further, Comparative Example 4 in which the ratio of Mg + Ni + Co + Al and La {(x + y + z) / w} is as small as 4.51 is also because the hydrogen storage capacity of the hydrogen storage alloy is small or the discharge capacity is small. became.
According to the test results shown in Table 1, the x was 0.04 to 0.17, y was 3.5 to 4.3, (y + z) was 4.0 to 4.7, and (x + y + z) / w was 4.75 to 5.35. It turns out that Examples 1-9 and Reference Examples 1-12 have a large discharge capacity compared with Comparative Examples 2-4. Although not described in detail, when the Ni content ratio y exceeds 4.3, the discharge capacity is low.

実施例、比較例共に水素吸蔵電極単極試験にかける前の水素吸蔵合金粉末の質量飽和磁化は、0.1Am2/kg未満であり、比表面積は0.3m2/g未満であった。水素吸蔵電極単極試験中に電解液によって水素吸蔵合金粉末の表面が腐蝕され、Ni、Coが単離すると水素吸蔵合金粉末の質量飽和磁化が増大する。また表面がエッチングされると水素吸蔵合金粉末の比表面積が増大する。このことから、試験後の水素吸蔵合金粉末の質量飽和磁化、比表面積が小さい方が、水素吸蔵合金粉末の電解液に対する耐食性が高いことを示唆していると考えることができる。試験後に於いて、実施例に係る水素吸蔵合金粉末の質量飽和磁化が4.2Am2/kg以下であり、比表面積が1.1m2/g以下であるのに対して、NiまたはNi+Co+Mnの比(y+z)が小さい（3.80以下）比較例１、４と希土類元素の含有比が小さい｛(x+y+z)/wが5.55と大きい｝比較例３の場合は、質量飽和磁化が5.7Am2/kg以上、比表面積が1.2m2/g以上と高い値を示し、これらの比較例の水素吸蔵合金の耐食性が、(y+z)が4.0 以上、(x+y+z)/wが5.35以下である実施例に比べて劣っていることを示唆している。
また、前記図１に示したように実施例１〜９、参考例１〜１２、比較例２に係る水素吸蔵合金の質量飽和磁化、比表面積が比較例１に比べて小さいところから、CaCu5形の結晶構造を有する水素吸蔵合金がCaCu5形とは異なる結晶構造を有する水素吸蔵合金に比べて耐食性が優れていると考えられる。
図１と表１に示した結果から、高容量で、且つ、耐食性に優れた水素吸蔵合金粉末とするためには、前記ｘが0.04〜0.17、(y+z)が4.0〜4.7であって(x+y+z)/wが4.75〜5.35であり、且つ、主としてCaCu5形の結晶構造を有する水素吸蔵合金が良いことが分かる。
なお、詳細は省くがNiの含有比ｙが3.5未満の場合、水素吸蔵合金の電解液に対する耐食性が劣る欠点がある。
In both the examples and comparative examples, the mass saturation magnetization of the hydrogen storage alloy powder before the hydrogen storage electrode single electrode test was less than 0.1 Am 2 / kg, and the specific surface area was less than 0.3 m 2 / g. During the hydrogen storage electrode unipolar test, the surface of the hydrogen storage alloy powder is corroded by the electrolyte, and when Ni and Co are isolated, the mass saturation magnetization of the hydrogen storage alloy powder increases. Further, when the surface is etched, the specific surface area of the hydrogen storage alloy powder increases. From this, it can be considered that the smaller the mass saturation magnetization and the specific surface area of the hydrogen storage alloy powder after the test suggests that the corrosion resistance of the hydrogen storage alloy powder to the electrolytic solution is higher. After the test, the mass saturation magnetization of the hydrogen storage alloy powder according to the example is 4.2 Am 2 / kg or less and the specific surface area is 1.1 m 2 / g or less, whereas Ni or Ni + Co + Mn In the case of Comparative Example 3 where the ratio (y + z) is small (3.80 or less) and Comparative Example 3 where the content ratio of rare earth elements is small {(x + y + z) / w is large as 5.55} Magnetization is as high as 5.7 Am 2 / kg and specific surface area is as high as 1.2 m 2 / g or more.The corrosion resistance of the hydrogen storage alloys of these comparative examples is (y + z) is 4.0 or more, (x + y + This suggests that z) / w is inferior to that of 5.35 or less.
In addition, as shown in FIG. 1, since the mass saturation magnetization and specific surface area of the hydrogen storage alloys according to Examples 1 to 9, Reference Examples 1 to 12 and Comparative Example 2 are smaller than those of Comparative Example 1, CaCu 5 It is considered that the hydrogen storage alloy having the crystal structure of the shape has better corrosion resistance than the hydrogen storage alloy having a crystal structure different from the CaCu 5 type .
From the results shown in FIG. 1 and Table 1, in order to obtain a hydrogen storage alloy powder having a high capacity and excellent corrosion resistance, x is 0.04 to 0.17, and (y + z) is 4.0 to 4.7. It can be seen that a hydrogen storage alloy having (x + y + z) / w of 4.75 to 5.35 and mainly having a CaCu 5 type crystal structure is good.
Although not described in detail, when the Ni content ratio y is less than 3.5, there is a drawback that the corrosion resistance of the hydrogen storage alloy to the electrolyte is poor.

（ニッケル水素蓄電池による評価）
（実施例１〜９、参考例１〜１２）
（正極板の作製）
亜鉛３重量％、コバルト１重量％を固溶状態で含有する水酸化ニッケル粉末表面に４重量％のオキシ水酸化コバルトからなる被覆層を形成したニッケル電極活物質粉末８０重量部に、濃度が０．７重量％のカルボキシメチルセルロース（ＣＭＣ）水溶液２０重量部を添加混練して、ペーストにした。該ペーストを面密度４５０ｇ／ｍ２、厚さ１．３ｍｍの発泡ニッケル基板に充填した後乾燥し、所定の厚さ（０．７５ｍｍ）になるようにプレスした。該ニッケル極板を所定の寸法に裁断し活物質の充填量から算定される容量が2450mAhの正極板（ニッケル電極）とした。
(Evaluation using nickel metal hydride storage battery)
(Examples 1-9 , Reference Examples 1-12 )
(Preparation of positive electrode plate)
A concentration of 0 is added to 80 parts by weight of a nickel electrode active material powder in which a coating layer made of 4% by weight of cobalt oxyhydroxide is formed on the surface of a nickel hydroxide powder containing 3% by weight of zinc and 1% by weight of cobalt in a solid solution state. 20 parts by weight of a 7 wt% carboxymethylcellulose (CMC) aqueous solution was added and kneaded to obtain a paste. The paste was filled in a foam nickel substrate having a surface density of 450 g / m 2 and a thickness of 1.3 mm, dried, and pressed to a predetermined thickness (0.75 mm). The nickel electrode plate was cut into a predetermined size to obtain a positive electrode plate (nickel electrode) having a capacity calculated from the filling amount of the active material of 2450 mAh.

（負極板の作製）
水素吸蔵合金粉末１００重量部にインコ社製ニッケル粉末（INCO#210）１重量部を添加混合したこと以外、前記水素吸蔵電極の単極試験用の極板と同様にして作製した水素吸蔵電極（実施例１〜１０、参考例１〜２０）を所定の寸法に裁断し負極板（水素吸蔵電極）とした。負極板の水素吸蔵合金粉末の充填量を一定量（8.93g）とした。
（円筒形ニッケル水素蓄電池の作製）
前記正極板と親水化処理を施したポリプロピレン製不織布からなるセパレータ、負極板を積層し、積層体を正極板が内側になるように捲回して捲回式極板群とした。該極板群を金属製電槽缶に挿入し、正極板と正極端子（キャップ）、負極板と負極端子（電槽缶）をそれぞれ接続し、7.8M/lのKOHと0.8M/lLiOHを含む水溶液からなる電解液を2.55ｇ注入した後所定の方法で電槽缶の開放端を気密に封止してAAサイズ、円筒形の密閉形ニッケル水素蓄電池を作製した。このようにして作製した円筒形のニッケル水素蓄電池を実施例１〜１０、参考例１〜２０とする。
(Preparation of negative electrode plate)
A hydrogen storage electrode produced in the same manner as the electrode plate for the monopolar test of the hydrogen storage electrode except that 1 part by weight of Inco Corporation nickel powder (INCO # 210) was added to and mixed with 100 parts by weight of the hydrogen storage alloy powder. Examples 1 to 10 and Reference Examples 1 to 20 ) were cut into predetermined dimensions to form negative electrode plates (hydrogen storage electrodes). The filling amount of the hydrogen storage alloy powder in the negative electrode plate was a constant amount (8.93 g).
(Production of cylindrical nickel-metal hydride storage battery)
The positive electrode plate and a separator made of a polypropylene nonwoven fabric subjected to a hydrophilic treatment and a negative electrode plate were laminated, and the laminate was wound so that the positive electrode plate was on the inside to form a wound electrode plate group. Insert the electrode plate group into a metal battery case, connect the positive electrode plate and the positive electrode terminal (cap), connect the negative electrode plate and the negative electrode terminal (battery can) respectively, and add 7.8M / l KOH and 0.8M / l LiOH After injecting 2.55 g of the electrolyte solution comprising the aqueous solution, the open end of the battery case can be hermetically sealed by a predetermined method to produce an AA size, cylindrical sealed nickel-metal hydride storage battery. The thus produced cylindrical nickel-metal hydride storage batteries are referred to as Examples 1 to 10 and Reference Examples 1 to 20 .

（比較例１〜４）
前記水素吸蔵電極の単極試験用の極板と同様にして作製した水素吸蔵電極（比較例１〜５）を用い、前記実施例１〜１０、参考例１〜２０と同様の手順にてAAサイズ、円筒形の密閉形ニッケル水素蓄電池を作製した。作製したニッケル水素蓄電池を比較例１〜５とする。
(Comparative Examples 1-4)
Using a hydrogen storage electrode (Comparative Examples 1 to 5) produced in the same manner as the electrode plate for a single electrode test of the hydrogen storage electrode , the same procedure as in Examples 1 to 10 and Reference Examples 1 to 20 was used. A size and cylindrical sealed nickel-metal hydride storage battery was produced. The produced nickel metal hydride storage batteries are referred to as Comparative Examples 1-5.

（化成および放電容量の測定）
前記実施例１〜１０、参考例１〜２０および比較例１〜５に係る密閉形ニッケル水素蓄電池を周囲温度２０℃にて化成した。初回、０．１ItA（245mA)にて１０時間充電した後、０．２ItAにて放電カット電圧１．０Ｖとして放電した。２回〜１０回目は、０．１ItA（230mA)にて１５時間充電したのち０．２ItAにて放電カット電圧１．０Ｖとして放電した。該１０回目の放電で得られた放電容量をもって当該電池の放電容量とした。
(Measurement of chemical conversion and discharge capacity)
The sealed nickel-metal hydride storage batteries according to Examples 1 to 10, Reference Examples 1 to 20, and Comparative Examples 1 to 5 were formed at an ambient temperature of 20 ° C. After first charging at 0.1 ItA (245 mA) for 10 hours, the battery was discharged at 0.2 ItA with a discharge cut voltage of 1.0 V. In the second to tenth cycles, the battery was charged with 0.1 ItA (230 mA) for 15 hours, and then discharged with a discharge cut voltage of 1.0 V at 0.2 ItA. The discharge capacity obtained by the tenth discharge was used as the discharge capacity of the battery.

（充放電サイクル試験）
実施例１〜１０、参考例１〜２０、比較例１〜５に係る密閉形ニッケル水素蓄電を周囲温度２０℃にて充放電サイクル試験に供した。充電レート0.5ItAにて5mVの電圧降下が認められる (dV=-5mV)まで充電し、３０分間休止した後、放電レート0.3ItAにて放電カット電圧を１．０Ｖとして放電した。該充放電を１サイクルとし、充放電を繰り返し行い、放電容量が１サイクル目の放電容量の６０％に低下した時点をもってサイクル寿命とした。
(Charge / discharge cycle test)
The sealed nickel-metal hydride electricity storage according to Examples 1 to 10, Reference Examples 1 to 20 , and Comparative Examples 1 to 5 was subjected to a charge / discharge cycle test at an ambient temperature of 20 ° C. The battery was charged until a voltage drop of 5 mV was observed at a charge rate of 0.5 ItA (dV = -5 mV), paused for 30 minutes, and then discharged with a discharge cut voltage of 1.0 V at a discharge rate of 0.3 ItA. The charging / discharging was set as one cycle, charging / discharging was repeated, and the cycle life was defined as the time when the discharge capacity was reduced to 60% of the discharge capacity at the first cycle.

表２に実施例１〜９、参考例１〜１２、比較例１〜４の密閉形ニッケル水素蓄電池のＮＰ比（Ｎ／Ｐ、Ｎは負極の容量を表し、Ｐは正極の容量を表す）、充放電サイクル試験結果を示す。なお、前記Ｎは、前記単極試験で得られた容量(mAh/g)と負極の活物質充填量(8.93g)の積として求めた値であり、Ｐは、前記正極板の容量（2450mAh）である。
Table 2 shows the NP ratio of the sealed nickel-metal hydride storage batteries of Examples 1 to 9, Reference Examples 1 to 12 , and Comparative Examples 1 to 4 (N / P, N represents the capacity of the negative electrode, and P represents the capacity of the positive electrode) The charge / discharge cycle test results are shown. N is a value obtained as a product of the capacity (mAh / g) obtained in the monopolar test and the active material filling amount (8.93 g) of the negative electrode, and P is the capacity of the positive electrode plate (2450 mAh). ).

負極板の放電容量を大きくするとＮＰ比（Ｎ／Ｐ）を大きくすることができる。ＮＰ比が大きいと負極板に大きい充電リザーブを確保することができ、充放電サイクル性能を高めることが可能となる。前記表１に示した結果（水素吸蔵合金粉末の質量飽和磁化、比表面積の大きさ）を比較すると、実施例１〜９、参考例１〜１２に係る水素吸蔵合金粉末の耐食性が比較例２に比べて高いとは言えない。にも拘わらず、表２に示すように実施例１〜９、参考例１〜１２に係るニッケル水素蓄電池は、比較例２に比べ比べて良好なサイクル性能を達成することができた。このような結果が得られたのは、実施例１〜９、参考例１〜１２のＮＰ比（Ｎ／Ｐ）が比較例２に比べて大きいためであり、ＮＰ比（Ｎ／Ｐ）が大きいのは、水素吸蔵合金粉末の単位重量当たりの容量(mAh/g)を比較例２に比べて高くすることができたためである。そしてこのような水素吸蔵合金粉末自身の高容量は、水素吸蔵合金の組成を表１の実施例１〜９、参考例１〜１２に示した新規な組成とすることによって達成できたものである。
 When the discharge capacity of the negative electrode plate is increased, the NP ratio (N / P) can be increased. When the NP ratio is large, a large charge reserve can be secured in the negative electrode plate, and charge / discharge cycle performance can be improved. When the results shown in Table 1 (mass saturation magnetization of hydrogen storage alloy powder, specific surface area) are compared, the corrosion resistance of the hydrogen storage alloy powders according to Examples 1 to 9 and Reference Examples 1 to 12 is Comparative Example 2. It cannot be said that it is expensive compared to. Nevertheless, as shown in Table 2, the nickel hydride storage batteries according to Examples 1 to 9 and Reference Examples 1 to 12 were able to achieve better cycle performance than Comparative Example 2. Such a result was obtained because the NP ratio (N / P) of Examples 1 to 9 and Reference Examples 1 to 12 was larger than that of Comparative Example 2, and the NP ratio (N / P) was high. The reason is that the capacity per unit weight (mAh / g) of the hydrogen storage alloy powder could be increased as compared with Comparative Example 2. And the high capacity | capacitance of such hydrogen storage alloy powder itself was able to be achieved by making the composition of a hydrogen storage alloy into the novel composition shown in Examples 1-9 of Table 1 and Reference Examples 1-12. .

また、表２に示すように実施例１〜９、参考例１〜１２に係るニッケル水素蓄電池は、比較例１、比較例３、４に比べてサイクル性能が優れている。因みに、図４に前記表２に示した試験後の水素吸蔵合金粉末の質量飽和磁化とサイクル寿命、図５に比表面積とサイクル寿命の関係を示す。図４は、質量飽和磁化が小さい方が、サイクル寿命が良く、図５は、比表面積が小さい方が、サイクル寿命が良いことを示している。このことから、実施例に係るニッケル水素蓄電池の場合は、比較例１、比較例３、４に比べて水素吸蔵合金の耐食性が向上したためにサイクル寿命が良くなったものと考えられる。
As shown in Table 2, the nickel-metal hydride storage batteries according to Examples 1 to 9 and Reference Examples 1 to 12 are superior in cycle performance to Comparative Examples 1 and 3 and 4. 4 shows the mass saturation magnetization and cycle life of the hydrogen storage alloy powder after the test shown in Table 2 above, and FIG. 5 shows the relationship between the specific surface area and the cycle life. FIG. 4 shows that the cycle life is better when the mass saturation magnetization is smaller, and FIG. 5 shows that the cycle life is better when the specific surface area is smaller. From this, in the case of the nickel-metal hydride storage battery according to the example, it is considered that the cycle life was improved because the corrosion resistance of the hydrogen storage alloy was improved as compared with Comparative Examples 1, 3 and 4 .

因みに図６は、ニッケル水素蓄電池のサイクル寿命とそれに適用した水素吸蔵合金粉末の(y+z)の関係を示すグラフである。図６によれば、(y+z)が4.0〜4.7の範囲にあって、4.7に近い方がサイクル寿命が良いことが分かる。
なお、表２に示した結果によれば、ｘが0.04〜0.09、ｙが3.7〜4.1、(y+z)が4.45〜4.7、(x+y+z)/wが4.85〜5.15であれば、特に優れたサイクル性能が得られるので好ましいことが分かる。 FIG. 6 is a graph showing the relationship between the cycle life of a nickel metal hydride storage battery and (y + z) of the hydrogen storage alloy powder applied thereto. According to FIG. 6, it can be seen that (y + z) is in the range of 4.0 to 4.7, and the cycle life is better when it is closer to 4.7.
According to the results shown in Table 2, if x is 0.04 to 0.09, y is 3.7 to 4.1, (y + z) is 4.45 to 4.7, and (x + y + z) / w is 4.85 to 5.15. It can be seen that this is preferable because particularly excellent cycle performance can be obtained.

（実施例１０、参考例１３〜２０）
（水素吸蔵電極の作製と水素吸蔵電極単極試験）
前記参考例４の水素吸蔵合金粉末１００重量部に対してY2O3粉末、CeO2粉末、Dy2O3粉
末、Ho2O3粉末、Er2O3粉末、Tm2O3粉末、Yb2O3粉末、Lu2O3粉末をそれぞれ１重量部混合添加した。それ以外は参考例４（水素吸蔵電極単極試験）と同様の手順で水素吸蔵電極を作製した。作製した電極を参考例１３〜２０とする。
（比較例５）
前記比較例１に係る水素吸蔵合金粉末１００重量部に対してYb2O3粉末１重量部を混合添加した。それ以外は比較例１（水素吸蔵電極単極試験）と同様の手順で水素吸蔵電極を作製した。作製した電極を比較例５とする。
前記実施例１〜９、参考例１〜１２と同様にして、実施例１０、参考例１３〜２０、比較例５に係る水素吸蔵電極の単極試験を実施した。
(Example 10, Reference Examples 13 to 20 )
(Preparation of hydrogen storage electrode and hydrogen storage electrode unipolar test)
Y 2 O 3 powder, CeO 2 powder, Dy 2 O 3 powder, Ho 2 O 3 powder, Er 2 O 3 powder, Tm 2 O 3 powder, Yb with respect to 100 parts by weight of the hydrogen storage alloy powder of Reference Example 4 1 part by weight of 2 O 3 powder and Lu 2 O 3 powder were mixed and added. Otherwise, a hydrogen storage electrode was produced in the same procedure as in Reference Example 4 (hydrogen storage electrode single electrode test). The produced electrodes are referred to as Reference Examples 13 to 20.
(Comparative Example 5)
1 part by weight of Yb 2 O 3 powder was mixed and added to 100 parts by weight of the hydrogen storage alloy powder according to Comparative Example 1. Otherwise, a hydrogen storage electrode was produced in the same procedure as in Comparative Example 1 (hydrogen storage electrode single electrode test). The produced electrode is referred to as Comparative Example 5.
In the same manner as in Examples 1 to 9 and Reference Examples 1 to 12 , a unipolar test of the hydrogen storage electrode according to Example 10, Reference Examples 13 to 20 and Comparative Example 5 was performed.

表３に実施例３、実施例１０、参考例４、参考例１３〜２０および比較例１、５に係る水素吸蔵電極単極試験結果を示す。
実施例３と実施例１０、参考例４と参考例１３〜２０、比較例１と比較例５は、それぞれ適用した水素吸蔵合金の組成が同じである。実施例３と実施例１０、参考例４と実施例１３〜２０を比較すると、実施例１０は実施例３と、参考例１３〜２０は参考例４とほぼ同等の容量を有し、水素吸蔵合金粉末の質量飽和磁化が小さい。このことは実施例１０、参考例１３〜２０において水素吸蔵電極に表２に示した希土類元素の化合物を添加することによって放電容量を低下させることなく、水素吸蔵合金の耐食性を向上させることができることを示唆している。一方、水素吸蔵合金中のMgの含有比率が高い比較例５の場合は、希土類元素の化合物を添加しても耐食性向上に効果がないためか比較例１に比べて、試験後の質量飽和磁化、比表面積共に大差がない結果となった。
Table 3 shows the hydrogen storage electrode monopolar test results according to Example 3, Example 10, Reference Example 4, Reference Examples 13 to 20, and Comparative Examples 1 and 5.
Example 3 and Example 10, Reference Example 4 and Reference Examples 13 to 20 , Comparative Example 1 and Comparative Example 5 have the same compositions of applied hydrogen storage alloys. Examples 3 and 10, a comparison of Example 4 and Example 13 to 20, Example 10 Example 3, Reference Example 13 to 20 have substantially the same volume as in Reference Example 4, the hydrogen storage The mass saturation magnetization of the alloy powder is small. This means that the corrosion resistance of the hydrogen storage alloy can be improved without reducing the discharge capacity by adding the rare earth element compounds shown in Table 2 to the hydrogen storage electrode in Example 10 and Reference Examples 13 to 20. It suggests. On the other hand, in the case of Comparative Example 5 in which the content ratio of Mg in the hydrogen storage alloy is high, the addition of a rare earth element compound is not effective in improving the corrosion resistance. As a result, the specific surface area was not significantly different.

（ニッケル水素蓄電池による評価）
前記水素吸蔵電極単極試験の参考例１３〜２０において水素吸蔵合金粉末１００重量部に対してインコ社製ニッケル粉末（INCO#210）１重量部混合添加した。また、水素吸蔵合金粉末の充填量を8.85gとし、それ以外は水素吸蔵電極単極試験の参考例１３〜２０と同様の手順で作製した負極板（水素吸蔵電極板）を適用してニッケル水素蓄電池を作製した。作製したニッケル水素蓄電池を参考例１３〜２０とする。
（実施例１０）
前記水素吸蔵電極単極試験の実施例１０の水素吸蔵合金粉末１００重量部に対してインコ社製ニッケル粉末（INCO#210）を１重量部混合添加した。また、水素吸蔵合金粉末の充填量を8.85gとし、それ以外は水素吸蔵電極単極試験の実施例１０と同様の手順で作製した負極板（水素吸蔵電極板）を適用してニッケル水素蓄電池を作製した。作製したニッケル水素蓄電池を実施例１０とする。
（比較例５）
前記水素吸蔵電極単極試験の比較例５の水素吸蔵合金粉末１００重量部に対してインコ社製ニッケル粉末（INCO#210)を１重量部混合添加した。また、水素吸蔵合金粉末の充填量を8.85gとし、それ以外は水素吸蔵電極単極試験の比較例５と同様の手順で作製した負極板（水素吸蔵電極板）を適用してニッケル水素蓄電池を作製した。作製したニッケル水素蓄電池を比較例５とする。
表４に実施例３、実施例１０、参考例４、参考例１３〜２０、比較例１、５に係るニッケル水素蓄電池の、ＮＰ比（Ｎ／Ｐ）、充放電サイクル試験結果を示す。
(Evaluation using nickel metal hydride storage battery)
In Reference Examples 13 to 20 of the hydrogen storage electrode single electrode test, 1 part by weight of Inco Corporation nickel powder (INCO # 210) was added to 100 parts by weight of the hydrogen storage alloy powder. In addition, the filling amount of the hydrogen storage alloy powder was 8.85 g, and nickel hydrogen was applied by applying a negative electrode plate (hydrogen storage electrode plate) prepared in the same manner as in Reference Examples 13 to 20 of the hydrogen storage electrode single electrode test. A storage battery was produced. The produced nickel metal hydride storage batteries are referred to as Reference Examples 13-20 .
(Example 10 )
One part by weight of Inco nickel powder (INCO # 210) was mixed and added to 100 parts by weight of the hydrogen storage alloy powder of Example 10 of the hydrogen storage electrode single electrode test. In addition, the filling amount of the hydrogen storage alloy powder was 8.85 g, and other than that, the negative electrode plate (hydrogen storage electrode plate) produced by the same procedure as in Example 10 of the hydrogen storage electrode single electrode test was applied to form a nickel metal hydride storage battery. Produced. The produced nickel metal hydride storage battery is referred to as Example 10 .
(Comparative Example 5)
One part by weight of Inco nickel powder (INCO # 210) was mixed and added to 100 parts by weight of the hydrogen storage alloy powder of Comparative Example 5 of the hydrogen storage electrode single electrode test. In addition, the filling amount of the hydrogen storage alloy powder was 8.85 g, and a nickel hydride storage battery was applied by applying a negative electrode plate (hydrogen storage electrode plate) manufactured in the same manner as in Comparative Example 5 of the hydrogen storage electrode single electrode test. Produced. The produced nickel metal hydride storage battery is referred to as Comparative Example 5.
Table 4 shows the NP ratio (N / P) and charge / discharge cycle test results of the nickel-metal hydride storage batteries according to Example 3, Example 10, Reference Example 4, Reference Examples 13 to 20 , and Comparative Examples 1 and 5.

表４に示すように、実施例１０は実施例３に比べて高いサイクル寿命を有し、参考例１３〜２０は参考例４に比べて高いサイクル寿命を有している。実施例１０、参考例１３〜２０においては水素吸蔵電極に希土類の化合物を添加することにより、水素吸蔵合金粉末の耐食性を向上させることができたために、それぞれ実施例３、参考例４に比べて電池のサイクル寿命が向上したものと考えられる。
比較例５のサイクル特性は、比較例１に比べて向上しているものの、実施例に比べて劣っている。比較例１に示したMgの含有率が高くCaCu5形とは異なる結晶構造を有する水素吸蔵合金粉末は、容量は高いものの電解液に対する耐食性が劣るために、防食効果がある希土類元素を添加してもサイクル特性が劣るという欠点が解消されない。これに対して、本発明に係る水素吸蔵合金を適用した水素吸蔵電極、ニッケル水素蓄電池は、従来広く用いられているMgを含有しない水素吸蔵合金を適用した水素吸蔵合金電極、ニッケル水素蓄電池に比べて、高容量で、且つ、サイクル特性に優れた水素吸蔵合金電極、ニッケル水素蓄電池であり、前記希土類元素の酸化物または水酸化物を添加することにより、サイクル特性を一層向上させた水素吸蔵合金電極、ニッケル水素蓄電池である。
 As shown in Table 4, Example 10 has a higher cycle life than that of Example 3 , and Reference Examples 13 to 20 have a higher cycle life than that of Reference Example 4 . In Example 10 and Reference Examples 13 to 20 , the corrosion resistance of the hydrogen storage alloy powder could be improved by adding a rare earth compound to the hydrogen storage electrode, so that compared to Example 3 and Reference Example 4 , respectively. It is considered that the cycle life of the battery has been improved.
Although the cycle characteristics of Comparative Example 5 are improved as compared with Comparative Example 1, they are inferior to those of Examples. The hydrogen storage alloy powder having a high Mg content and a crystal structure different from the CaCu 5 type shown in Comparative Example 1 has a high capacity but is poor in corrosion resistance to an electrolytic solution. However, the disadvantage of poor cycle characteristics cannot be resolved. On the other hand, the hydrogen storage electrode and nickel metal hydride storage battery to which the hydrogen storage alloy according to the present invention is applied are compared with the hydrogen storage alloy electrode and nickel metal hydride storage battery to which a hydrogen storage alloy not containing Mg, which has been widely used conventionally, is applied. A hydrogen storage alloy electrode and nickel-metal hydride storage battery with high capacity and excellent cycle characteristics, and the addition of the rare earth element oxide or hydroxide further improves the cycle characteristics. Electrode, nickel metal hydride storage battery.

本発明は、水素吸蔵合金粉末を活物質に用いた水素吸蔵電極を備えるニッケル水素蓄電池において、従来電池と同等か、あるいは同等以上のサイクル性能を有し、且つ、高容量のニッケル水素蓄電池を提供するもので工業的な価値の高いものである。   The present invention provides a nickel-metal hydride storage battery having a hydrogen storage electrode using a hydrogen storage alloy powder as an active material, and having a cycle performance equivalent to or higher than that of a conventional battery and having a high capacity. It has high industrial value.

本発明および比較例に係り、CaCu5形の結晶構造を有する水素吸蔵合金粉末の粉末Ｘ線回折図である。FIG. 4 is a powder X-ray diffraction diagram of a hydrogen storage alloy powder having a CaCu 5 type crystal structure according to the present invention and a comparative example. 比較例係り、CaCu5形とは異なる結晶構造を有する水素吸蔵合金粉末の粉末Ｘ線回折図である。Comparative Example relates, is a powder X-ray diffraction pattern of a hydrogen storage alloy powder having a crystal structure different from the CaCu 5 form. 水素吸蔵合金の放電容量と(y+z)の関係を示すグラフである。4 is a graph showing the relationship between the discharge capacity of a hydrogen storage alloy and (y + z). ニッケル水素蓄電池のサイクル寿命と水素吸蔵合金の質量飽和磁化の関係を示すグラフである。It is a graph which shows the relationship between the cycle life of a nickel hydride storage battery, and the mass saturation magnetization of a hydrogen storage alloy. ニッケル水素蓄電池のサイクル寿命と水素吸蔵合金の比表面積の関係をすグラフである。It is a graph which shows the relationship between the cycle life of a nickel metal hydride storage battery and the specific surface area of a hydrogen storage alloy. ニッケル水素蓄電池のサイクル寿命と水素吸蔵合金の(y+z)の関係をすグラフである。3 is a graph showing the relationship between the cycle life of a nickel metal hydride storage battery and (y + z) of a hydrogen storage alloy.

Claims (1)

記号Ａがイットリウム（Ｙ）を含む希土類元素のうちから選ばれた１種以上の元素であり、記号ＢがＭｇであり、記号ＣがＣｏ、Ｍｎ、Ａｌ、ＦｅおよびＣｕから選ばれる１種以上の元素であり、化学式ＡwＢxＮｉyＣzにおいて、ｗ＋ｘ＝１、０．０４≦ｘ≦０．０９、３．５≦ｙ≦４．３、４．０≦ｙ＋ｚ≦４．７、０＜ｚ、４．７５≦（ｘ＋ｙ＋ｚ）／ｗ≦５．３５で表される水素吸蔵合金の粉末を用いた水素吸蔵電極を備えたニッケル水素蓄電池。 Symbol A is at least one element selected from among rare earth elements including yttrium (Y), the symbol B is M g, one that symbol C is Co, Mn, Al, selected from Fe and Cu In the chemical formula A w B x Ni y C z , w + x = 1, 0.04 ≦ x ≦ 0.09, 3.5 ≦ y ≦ 4.3, 4.0 ≦ y + z ≦ 4.7 , 0 < z, 4.75 ≦ (x + y + z) /w≦5.35, a nickel-metal hydride storage battery provided with a hydrogen storage electrode using a powder of a hydrogen storage alloy represented by
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