JP2004124132A - Hydrogen occlusion alloy powder, hydrogen occlusion alloy electrode, and nickel-hydrogen storage battery using the same - Google Patents
Hydrogen occlusion alloy powder, hydrogen occlusion alloy electrode, and nickel-hydrogen storage battery using the same Download PDFInfo
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、水素吸蔵合金粉末と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。
【０００２】
【従来の技術】
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容量アップ、充放電サイクル性能の向上が求められている。
【０００３】
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。
【０００４】
前記水素吸蔵合金としては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、耐久性が優れているところからＬａ−Ｎｉ系の合金が重用されている。しかし、ＨＥＶ用電源やパーソナルコンピューター用電源等高温で動作する機会が多くなり、電池に対して高温での耐久性など高温特性の更なる改良が求められており、従来の水素吸蔵合金電極を適用したニッケル水素蓄電池においては、水素吸蔵合金の耐久性が劣り、前記要求に対応仕切れない欠点があった。
【０００５】
従来、水素吸蔵合金の組成の改良によって水素吸蔵合金の耐久性を向上しようとする試みがなされてきた。（例えば、特許文献１参照。）
【０００６】
【特許文献１】
特開平５−６２６７４号公報（第２頁、第１４段落、第４頁、表１、表２）
【０００７】
上記特許文献１には、ＭｍＮｉ５（Ｍｍはミッシュメタル）で示され、ＭｍがＬａ０．２Ｃｅ０．４Ｐｒ０．１Ｎｄ０．１Ｒ０．２（Ｒは原子番号が６３以上のランタノイドのうちの１種の元素を示す）なる例が開示されている。しかし、特許文献１で示された組成の水素吸蔵合金は、単位重量当たりの容量が２５０ｍＡｈ／ｇ以下と低い値であり、該水素吸蔵合金を用いて作製した水素吸蔵合金電極を適用したニッケル水素蓄電池は容量が低い欠点があった。
【発明が解決しようとする課題】
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放電容量が劣らず、且つ、充放電サイクル特性に代表される耐久性において従来に勝る水素吸蔵合金電極およびニッケル水素蓄電池を提供せんとするものである。
【０００８】
【課題を解決するための手段】
前記課題を解決するため、本発明に係る水素吸蔵合金粉末を、ＣａＣｕ５型の結晶構造を有し、Ｌａ、Ｃｅ、Ｙと原子番号が６３以上のランタノイドのうちの少なくとも１種の元素、ＮｉおよびＣｏを必須成分とし、Ｒ１を原子番号５９〜６２のランタノイドのうちの少なくとも１種の元素とし、Ｒ２をＹと原子番号が６３以上のランタノイドのうちの少なくとも１種の元素とし、Ｘを希土類に属さない金属元素とし、組成式ＬａａＣｅｂＲ１ｃＲ２ｄＮｉｅＣｏｆＸｇで表した時に、前記ａ＋ｂ＋ｃ＋ｄ＝１．０であり、０．６≦ａ≦０．９、０．０５≦ｂ、０≦ｃ、０＜ｄ≦０．０６であり、５．０≦ｅ＋ｆ＋ｇ≦５．４であって、０．１≦ｆ≦１．２、０＜ｇで示される水素吸蔵合金粉末とする。
【０００９】
さらに、本発明においては、水素吸蔵合金粉末を、前記請求項１に記載の組成を有する水素吸蔵合金粉末であって、該粉末に含まれるＲ２（Ｒ２は、原子番号が６３以上のランタノイドのうちの少なくとも１種の元素を示す。該元素を総称して以下重希土類元素と記述する。）の濃度が、粉末の内部に比べて粉末の表面において高くすることが望ましい。
【００１０】
本発明に係る水素吸蔵合金電極は、前記請求項１〜請求項４に記載の水素吸蔵合金粉末を適用した電極である。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、請求項５に記載の水素吸蔵合金電極を負極とするニッケル水素蓄電池である。前記ニッケル電極が、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ｙのうちの少なくとも１種類の元素を含有したニッケル水素蓄電池がさらに望ましい。
【００１１】
【発明の実施の形態】
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、Ｌａ、Ｃｅ、原子番号が６３以上のランタノイドのうちの少なくとも１種の元素、ＮｉおよびＣｏを必須成分とし、Ｒ１を原子番号５９〜６２のランタノイドのうちの少なくとも１種の元素とし、Ｒ２をＹと原子番号が６３以上のランタノイドのうちの少なくとも１種の元素とし、Ｘを希土類に属さない金属元素とし、組成式ＬａａＣｅｂＲ１ｃＲ２ｄＮｉｅＣｏｆＸｇで表した時に、前記ａ＋ｂ＋ｃ＋ｄ＝１．０であり、０．６＜ａ＜０．９、０．０５≦ｂ、０≦ｃ、０＜ｄ＜０．０６であり、５．０≦ｅ＋ｆ＋ｇ≦５．４であって、０．１≦ｆ≦１．２、０＜ｇで示されることを特徴とする水素吸蔵合金粉末である。
【００１２】
該水素吸蔵合金粉末は、例えば前記組成の合金のインゴットを粉砕して得る。該水素吸蔵合金の平均粒径は、２０〜１００μｍとすることが望ましい。平均粒径が２０μｍ未満では充填性が劣る。また、平均粒径が１００μｍを超えると水素吸蔵合金電極の活物質としての活性が低い欠点がある。
【００１３】
前記Ｍｍ中のＬａの比率ａが０．６以下の場合は、該組成の合金粉末を水素吸蔵合金電極に適用した時に容量が低い欠点がある。前記Ｍｍ中のＬａの比率ａが０．９を超える場合は、アルカリ電解液中での耐食性が劣るために、該組成の合金粉末を水素吸蔵合金電極に適用した時に電極の耐久性が劣る欠点がある。
【００１４】
本発明に係る水素吸蔵合金は、Ｃｅの含有比率ｂを０．０５以上とする。さらに、該比率ｂを前記原子番号５９〜６２に属する希土類元素Ｒ１（以下該４種の元素の総称を示すときは軽希土類元素と記述する）の比率ｃより大きくすることが望ましい。前記ｂを０．０５≦ｂ、ｃ＜ｂとすることによって水素吸蔵合金の耐食性を高める効果がある。また、充電時に正極で発生する酸素を水素吸蔵合金が吸収するのを促進する効果がある。このことによって、水素吸蔵合金の腐食が抑制され、サイクル性能を高めることができる。
【００１５】
合金中の前記重希土類元素Ｒ２は、アルカリ電解液中での合金粉末の耐食性を向上させる作用がある。しかし、前記Ｍｍ中のＲ２の含有比率が大きくなるに従い、合金の水素の平行圧力が増大して該合金粉末を適用した水素吸蔵合金電極の容量が低下する。また、電極の活性化が遅くなる欠点がある。Ｒ２の比率ｄが０．０６を超えるとこの欠点が顕著に現れる。
【００１６】
前記ｅ＋ｆ＋ｇの値は５．０以上、５．４以下とする。該値が５．０未満の場合は、合金中にＭｍの偏析が生じ、耐食性が低い欠点がある。また、該値が５．４を超えると、水素吸蔵合金の水素吸蔵能が低下して該組成の合金粉末を水素吸蔵合金電極に適用した時に電極の容量が低い欠点がある。
【００１７】
前記のように、本発明においては、水素吸蔵合金粉末に含まれるＲ２（Ｒ２は重希土類元素のうちの少なくとも１種の元素を示す）の濃度を、粉末の内部に比べて粉末の表面において高くすることが望ましい。ここでいう粉末の表面とは、合金粉末がアルカリ電解液と接触した時に合金が腐食を受けて合金を構成する一部の成分が溶出するために、合金の組成が元の組成と異なる組成に変化する領域を意味し、このような変化を受ける領域であれば粉末の表面からの深さに拘束されない。しかし、通常は粉末の表面からの距離が約５００ナノメートル（ｎｍ）以下の領域をここでいう表面とみなすことができる。逆に、粉末の内部とは合金粉末がアルカリ電解液と接触しても組成の変化が起きない領域を意味し、具体的には粉末の表面からの距離が約６００ナノメートル（ｎｍ）以上の領域を粉末の内部とみなすことができる。
【００１８】
前記内部に比べて表面の重希土類元素Ｒ２がリッチな水素吸蔵合金粉末は、前記本発明に係る組成の合金粉末を高温、高濃度の化成アルカリ中に浸漬処理することによって得ることができる。該合金粉末は、アルカリ電解液中で表面に重希土類元素（Ｒ２）を含む不動態被膜を形成するため、耐食性が高いと考えられる。
【００１９】
前記合金粉末表面に含まれる重希土類元素は、ＴＥＭ（透過型電子顕微鏡）−ＥＤＳやＥＳＣＡ（光電子分光法）によって定量的に分析することができる。
【００２０】
本発明においては、水素吸蔵合金中に含まれるＮｉの比率ｅは３．３以上４．４以下とすることが望ましい。該比率ｅが３．３未満および４．４を超える場合は、合金粉末の耐食性が劣る欠点があり、水素吸蔵合金電極のサイクル特性が低い欠点がある。
【００２１】
本発明における水素吸蔵合金粉末に含まれるＣｏの比率ｆは、０．１以上１．２以下とする。ｆが０．１未満では合金粉末の耐食性が劣り、ｆが１．２を超えると水素吸蔵合金電極の活物質としての活性化が遅くなる欠点がある。
【００２２】
本発明における前記希土類元素に属さない金属元素であるＸは、Ａｌ、Ｃｕ、Ｆｅ、Ｍｎ、Ｔｉ、Ｚｒ、Ｃｒ、ＭｏおよびＢｅのうち少なくとも１種の元素であることが好ましい。これらの金属元素元素は水素吸蔵合金に添加することによって、水素吸蔵合金の水素吸蔵能力を高めたり、水素吸蔵合金電極としての活性化を速めたり、水素吸蔵合金の耐食性を高めたりする効果がある。
【００２３】
金属元素Ｘは、前記金属元素のうちでも特にＭｎ、ＡｌおよびＦｅが好ましい。Ｍｎの存在は、水素吸蔵合金の水素吸蔵能力を高める効果がある。ただし、その反面合金の耐食性を低下させる。このような理由から、前記ａ＋ｂ＋ｃ＋ｄ＝１．０あるいはａ＋ｂ＋ｃ＋ｄ＋ｈ＝１．０と表した時に、合金に含有させるＭｎの比率を０．１以上０．５以下とすることが好ましい。Ａｌの存在は、水素吸蔵合金の耐食性を高めるのに有効である。その反面水素吸蔵合金電極の活性化が遅くなる欠点がある。このような理由から、前記ａ＋ｂ＋ｃ＋ｄ＝１．０あるいはａ＋ｂ＋ｃ＋ｄ＋ｈ＝１．０と表した時に、合金に含有させるＡｌの比率を０．１以上０．５以下とすることが好ましい。Ｆｅの存在は、水素吸蔵合金を水素吸蔵合金電極の活物質材料と適用したときに電極の活性を高める効果がある。但し、Ｆｅの比率が多くなるに従い合金の耐食性が顕著に低下する。このような理由から、前記ａ＋ｂ＋ｃ＋ｄ＝１．０あるいはａ＋ｂ＋ｃ＋ｄ＋ｈ＝１．０と表した時に、合金に含有させるＦｅの比率を０以上０．０５以下とすることが好ましい。
【００２４】
本発明に係る水素吸蔵合金に含有させる金属元素Ｘの比率ｇは０＜ｇとする。前記の理由により、該範囲のうちでも０．２＜ｇ≦１．０５とすることが好ましい。
【００２５】
本発明に係る水素吸蔵合金電極は、前記本発明に係る水素吸蔵合金粉末をニッケルやニッケルメッキを施した金属製の穿孔板や発泡メタル等の対電解液性の基板に担持させたものである。
【００２６】
本発明に係るニッケル水素蓄電池に適用するニッケル電極は、前記重希土類元素およびＹのうちの少なくとも１種類の元素を含有したニッケル電極とすることが望ましい。該ニッケル電極を適用したニッケル水素蓄電池を、高温下で充電すると、ニッケル電極における酸素の発生が抑制される。該ニッケル電極を本発明に係る水素吸蔵合金電極と組み合わせたニッケル水素蓄電池は、従来のニッケル水素蓄電池に比較して顕著に水素吸蔵合金の腐食が抑制され耐久性に優れ、サイクル性能が顕著に優れたニッケル水素蓄電池となる。
【００２７】
前記ニッケル電極に含まれる前記重希土類元素およびＹのうちの、少なくとも１種類の元素は酸化物、水酸化物として含まれる。前記重希土類元素は、酸化物や水酸化物（水和した水酸化物も適用できる）としてニッケル電極に添加することが好ましい。特に酸化物が安価に入手でき、好ましい化合物である。
【００２８】
【実施例】
以下実施例に基づいて本発明の詳細を説明する。
（実施例１）
（水素吸蔵合金の調整）
元素のモル比でＬａ０．６０、Ｃｅ０．２７、Ｐｒ０．０１、Ｎｄ０．０８、Ｙｂ０．０４、Ｎｉ４．０２、Ｃｏ０．５０、Ｍｎ０．３０、Ａｌ０．３２、Ｆｅ０．０１を秤量し坩堝に投入し高周波溶解炉を用いてアルゴン雰囲気（不活性雰囲気）にて金属を溶解させて合金のインゴットを得た。該インゴットを粉砕して平均粒径４０μｍの合金粉末を得た。
【００２９】
（水素吸蔵合金電極の作製）
前記水素吸蔵合金粉末１００重量部に対して、平均粒径１μｍのニッケルの微粉末３重量部、増粘剤であるメチルセルロース（ＭＣ）の１ｗｔ％水溶液２０重量部と、結着剤であるスチレンブタジエンゴム１重量部とを加えて混練してペーストを調製した。
【００３０】
水素吸蔵合金電極の基板には、ニッケル鍍金を施した厚さ７０μｍ、開口径１．５ｍｍ、開口率４０％の鋼板製の穿孔板を適用した。該基板の両面に前記ペーストを塗工した。塗工後の極板を乾燥し、厚さ１．１ｍｍの極板を得た。該極板を２本のロールの間を通して、極板の仕上がり厚さが０．４ｍｍになるようにプレス加工を施した。
【００３１】
（ニッケル電極材料粉末の作製）
所定の方法に従いコバルトおよび亜鉛をそれぞれ水酸化物換算で３重量％および５重量％固溶状態で含有させた高密度水酸化ニッケルを核とし、表面に水酸化コバルトの被覆層を形成させた平均粒径が１０μｍの水酸化ニッケルを主成分とするニッケル電極材料粉末を用意した。なお、該材料粉末の表面に形成させた前記水酸化コバルトの被覆層の比率を６重量％とした。
【００３２】
（ニッケル電極の作製）
得られたニッケル電極材料紛末８０重量部に、濃度が１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、ニッケル電極活物質ペーストを作製した。該ペーストを厚さ１．４ｍｍ、目付量５００ｇ／ｍ２の発泡ニッケル製多孔体基板に充填して乾燥した後、プレスして厚さを０．７５ｍｍに調整し、長尺帯状のニッケル電極用原板を得た。
【００３３】
（水素吸蔵合金電極単板試験用セルの作製）
前記ニッケル電極と水素吸蔵合金電極をサイズ３ｃｍ×３ｃｍに裁断し上辺の導電端縁に集電用タブを取り付けた。該水素吸蔵合金電極の両面に厚さ０．１２ｍｍの親水処理を施したポリプロピレン製不織布を介して所定寸法に裁断したニッケル電極を積層させた。ニッケル電極と水素吸蔵合金電極の充填容量の比、正極容量／負極容量の比が４になるように設定した。６．８モル／ｌのＫＯＨと０．８モル／ｌのＬｉＯＨを含む電解液を所定量注入し、参照電極として酸化水銀電極（Ｈｇ／ＨｇＯ）を挿入して水素吸蔵合金電極単板試験用セルとした。
【００３４】
（水素吸蔵合金電極単板試験用セルの化成）
得られたニッケル水素蓄電池を温度２０℃において１２時間エージングした後、以下に記述する条件にて化成をおこなった。初回の充電は、１／５０ＩｔＡの充電電流で１０時間充電し、その後、１／１０ＩｔＡの充電電流にて１０時間充電した。次いで１／５ＩｔＡの放電電流にて水素吸蔵合金電極の参照電極に対する電位が−０．６Ｖに至った時を放電終止として放電した。２サイクル目以降は、充電を１／１０ＩｔＡの充電電流にて１２時間充電、１／５ＩｔＡの放電電流にて前記の放電終止条件にて放電した。該サイクルを１サイクルとし、初回の充放電を含めて１０サイクル充放電を繰り返し実施した。
【００３５】
（円筒型ニッケル水素蓄電池の作製）
前記ニッケル電極の原板を所定の寸法に裁断してニッケル電極とした。活物質充填量から算定されるニッケル電極の容量は、１６００ｍＡｈであった。前記水素吸蔵電極の原板を所定の寸法に裁断して水素吸蔵合金電極とした。前記ニッケル電極と水素吸蔵合金電極を厚さ０．１２ｍｍの親水処理を施したポリプロピレ製不織布を介して積層し、これを捲回して極板群とした。該極板群の負極（水素吸蔵合金電極）と正極（ニッケル電極）の容量の比が１．６対１となるようにした。極板群に正極用集電端子を取り付け金属製電槽に挿入し、６．８モル／ｌのＫＯＨと０．８モル／ｌのＬｉＯＨを含む電解液を所定量注入した後封口して円筒型の密閉式ニッケル水素電池とした。
【００３６】
（円筒型ニッケル水素蓄電池の化成）
得られたニッケル水素蓄電池を温度４０℃において１２時間エージングした後、以下に記述する条件にて化成をおこなった。初回の充電は、１／５０ＩｔＡ（３２ｍＡ）の充電電流で１０時間充電し、その後、１／１０ＩｔＡ（１６０ｍＡ）の充電電流にて１０時間充電した。次いで１／５ＩｔＡ（３２０ｍＡ）の放電電流にて放電終止電圧を１．０Ｖとして放電した。２サイクル目以降は、充電を１／１０ＩｔＡ（１６０ｍＡ）の充電電流にて１２時間充電、１／５ＩｔＡ（３２０ｍＡ）の放電電流にて放電終止電圧を１．０Ｖとして放電した。該サイクルを１サイクルとし、初回の充放電を含めて１０サイクル充放電を繰り返し実施した。
【００３７】
（実施例２〜実施例６）
水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表１の実施例２〜実施例６に示した通りとした。それ以外は、実施例１と同じとした。
【００３８】
（比較例１〜比較例３）
水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表１の比較例１〜比較例４に示した通りとした。それ以外は、実施例１と同じとした。表１に実施例１〜実施例６と比較例１〜比較例３の試作内容をまとめて示す。なお、表１においては、Ｍｎ、Ａｌ、Ｆｅの比率であるＭｎ０．３０、Ａｌ０．３２、Ｆｅ０．０１を合わせてＸ０．６３として表示した。
【００３９】
【表１】
（実施例７、実施例８）
水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表２の実施例７、実施例８に示した通りとした。それ以外は、実施例１と同じとした。
【００４１】
（比較例４、比較例５）
水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表２の比較例４、比較例５に示した通りとした。それ以外は、実施例１と同じとした。比較例５は、従来の水素吸蔵合金組成の１典型例として示した。
【００４２】
【表２】
（実施例９〜実施例１９）
水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表３の実施例９〜実施例１９に示した通りとした。それ以外は、実施例１と同じとした。
【００４４】
【表３】
（実施例２０〜実施例２３）
水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表４の実施例２０〜実施例２３に示した通りとした。それ以外は、実施例１と同じとした。
【００４６】
（比較例６〜比較例９）
水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表４の比較例６〜比較例９に示した通りとした。それ以外は、実施例１と同じとした。
【００４７】
【表４】
（実施例２４〜実施例２７）
水素吸蔵合金の成分としてＭｇを加えた。水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表５の実施例２４〜実施例２７に示した通りとした。それ以外は、実施例１と同じとした。
【００４９】
【表５】
（実施例２８）
水素吸蔵合金を調整する時の金属元素の仕込量（モル比）を表１の実施例２と同じとした。得られた水素吸蔵合金粉末１００ｇを温度１００℃に保った６．８モル／ｌのＫＯＨと０．８モル／ｌのＬｉＯＨを含む水溶液２００ｍｌに１時間浸漬してその間溶液を撹拌した。その後水洗しアルカリを除去し、真空乾燥を行った。それ以外は実施例２と同じとした。
（水素吸蔵合金粉末中の重希土類元素の分析）
前記ＴＥＭ−ＥＤＳを用いて得られた水素吸蔵合金粉末に含まれる元素分析を行った。なお、ここではアルカリ浸漬直後の水素吸蔵合金を対象として分析したが、電池に組み込んだ後化成を含めて充放電サイクル数が３０サイクル以下の電池を解体して回収した水素吸蔵合金粉末を対象として分析してもほぼ同様の結果が得られる。
【００５１】
（実施例２９〜実施例３３）
（ニッケル電極材料粉末の作製）
前記実施例２においてコバルトおよび亜鉛を固溶状態で含有させ、表面に水酸化コバルトからなる被覆層を形成させた水酸化ニッケル粉末９７重量部に、それぞれ平均粒径約５μｍのＥｒ２Ｏ３、Ｔｍ２Ｏ３、Ｙｂ２Ｏ３、Ｌｕ２Ｏ３、Ｙ２Ｏ３を３重量部を添加混合して正極材料粉末とした。それ以外は実施例２と同じとした。それぞれを実施例２９〜実施例２３とする。
【００５２】
（実施例３４）
正極には、前記実施例３１と同じＹｂ２Ｏ３を混合添加した正極材料粉末を適用したニッケル電極を用い、負極には前記実施例２８と同じＫＯＨとＬｉＯＨを含むアルカリ水溶液に浸漬処理した水素吸蔵合金粉末を適用した水素吸蔵合金を適用し、それ以外は実施例２と同様にしてニッケル水素蓄電池を作製した。
【００５３】
（比較例１０）
（ニッケル電極材料粉末の作製）
前記実施例３０と同じ水酸化ニッケル粉末９７重量部に、平均粒径約５μｍのＹｂ２Ｏ３を３重量部混合添加したニッケル電極と水素吸蔵合金電極には前記比較例１と同じ水素吸蔵合金電極を組み合わせてニッケ水素蓄電池を構成した。
表４に実施例２９〜実施例３４および比較例１０の試作内容をまとめて示す。
【００５４】
【表６】
（水素吸蔵合金電極の単板試験）
化成終了後の水素吸蔵合金電極の単板試験用セルを、温度２０℃において水素吸蔵合金電極の充填容量基準で０．２ＩｔＡの電流で１２０％充電し、同じく０．２ＩｔＡの電流で水素吸蔵合金電極の参照電極基準の電位が−０．６Ｖになるまで放電した。該充放電サイクルを５サイクル繰り返し行い、安定した容量が得られたことを確認した。後述の試験結果は化成終了後５サイクル目の容量を示した。
【００５６】
（円筒型ニッケル水素蓄電池の充放電サイクル試験）
化成終了後の実施例電池および比較例電池を、温度２０℃において充放電サイクル試験に供した。充電はＩｔＡの電流で１．２時間行い、放電はＩｔＡの電流にて放電終止電圧を１．０Ｖとして実施した。該充放電サイクルを１サイクルとして、サイクルを繰り返し実施した。放電容量が初期の８０％に低下した時点をもってサイクル寿命とした。
【００５７】
（高温における充放電試験）
化成終了後の実施例電池および比較例電池を６個用意し、３個を温度２０℃において別の３個を５０℃において充放電試験に供した。充電は０．２ＩｔＡの電流で６時間行い、放電は０．２ＩｔＡの電流にて放電終止電圧を１．０Ｖとして実施した。５サイクル充電放電を繰り返し行い安定した容量が得られたことを確認した。後述の試験結果は、化成終了後５サイクル目の５０℃の容量と２０℃の容量の比で示した。
【００５８】
（円筒型ニッケル水素蓄電池の高温での充放電サイクル試験）
化成終了後の実施例電池および比較例電池を、温度４０℃において充放電サイクル試験に供した。充電はＩｔＡの電流で１．２時間行い、放電はＩｔＡの電流にて放電終止電圧を１．０Ｖとして実施した。該充放電サイクルを１サイクルとして、サイクルを繰り返し実施した。
【００５９】
（水素吸蔵合金電極の単板試験および円筒型蓄電池のサイクル試験結果）
表７〜表１２に試験結果を示す。
【表７】
表７に示す通り、水素吸蔵合金電極の単板試験によれば本発明の実施例１〜実施例６に係る水素吸蔵合金電極は、水素吸蔵合金１ｇ当たり何れも２８０ｍＡｈ／ｇを超える容量を示し、従来の典型的な例（表２に示した比較例５）とほぼ同等かまたはそれを上回る容量を有する。且つ、本発明に係る水素吸蔵合金を用いて作製した水素吸蔵合金電極を適用した円筒型ニッケル水素蓄電池は、充放電サイクルが４００サイクルを超えており、前記比較例５や比較例３のサイクル性能を上回る性能を有している。水素吸蔵合金中のＬａの比率の小さい比較例１は、容量が小さく、逆にＬａの比率の大きい比較例２はサイクル性能が劣る。
【００６１】
図１に水素吸蔵合金のＬａの比率と水素吸蔵合金電極の単板試験における容量、ニッケル水素蓄電池のサイクル性能の関係を示した。図１に示す如く、Ｌａの比率ａが０．６〜０．９の領域で容量、サイクル性能共に優れており、０．６≦ａ≦０．９が良いことが判る。
【００６２】
表７に示す通り、水素吸蔵合金中のＣｅの比率ｂを０．０５≦ｂとした実施例３、実施例４、実施例５とｂ＝０．０１とした比較例３を比較すると何れの実施例も比較例１とほぼ同等の容量を有し、且つ比較例４に比べて優れたサイクル性能を示す。図２に水素吸蔵合金のＣｅの比率ｂと水素吸蔵合金電極の単板試験における容量、ニッケル水素蓄電池のサイクル性能の関係を示した。図２に示したように、水素吸蔵吸蔵合金中のＣｅの比率ｂは、０．０５≦ｂの範囲においてサイクル性能が良いことが判る。
【００６３】
【表８】
表８に示す通り、実施例７および実施例８は、サイクル性能において比較例４および比較例５を上回っている。このことから水素吸蔵合金中のＹｂの存在がサイクル性能向上に有効であることが判る、但し、Ｙｂの比率ｄを０．０８と大きくするとｄを０．０６とした実施例８や、ｄを０．０１とした実施例７と比べてサイクル性能が低下しており、ｄの値が高すぎても良くないことがわかる。図３に水素吸蔵合金のＹｂの比率ｄと水素吸蔵合金電極の単板試験における容量、ニッケル水素蓄電池のサイクル性能の関係を示した。図３に示したように、Ｙｂの比率ｄが０．０１〜０．０６の領域で容量、サイクル性能共に優れており、０．０１≦ｄ≦０．０６が良いことが判る。
【００６５】
【表９】
表９に示す通り、本発明の実施例９〜実施例１９に係る水素吸蔵合金電極は、何れも２８０ｍＡｈ／ｇを超える容量を示し、従来のものに比べて同等以上の容量を有する。且つ、本発明に係る水素吸蔵合金を用いて作製した水素吸蔵合金電極を適用した円筒型ニッケル水素蓄電池は、充放電サイクルが４００サイクルを超えており、前記いずれの比較例電池と比べても比較例を上回るサイクル性能を有している。このことから、前記Ｒ２としてＥｕ以下ＬｕおよびＹ、ＥｒとＴｍの２種類、ＥｒとＹｂの２種類の元素を含むいずれの場合も放電容量が従来と同等以上であり、サイクル性能において優れていることが判る。
【００６７】
【表１０】
表１０に示すように、Ｎｉの比率ｅ、Ｃｏの比率ｆ、Ｓの比率ｇの和ｅ＋ｆ＋ｇが４．９と低い比較例８は、放電容量は高いが、サイクル性能が劣る。逆にｅ＋ｆ＋ｇが５．５と高い比較例９は、容量が低い欠点があることが判る。図４にｅ＋ｆ＋ｇの値と水素吸蔵合金電極の単板試験における容量、ニッケル水素蓄電池のサイクル性能の関係を示した。ｅ＋ｆ＋ｇの値が５．０〜５．４の領域で容量、サイクル性能共に優れており、５．０≦ｅ＋ｆ＋ｇ≦５．４が良いことが判る。
【００６９】
Ｎｉの比率が３．１２と低く、Ｃｏの比率が１．４と高い比較例７は、放電容量、サイクル性能共に劣る。図５に水素吸蔵合金中のＣｏの比率ｆの値と水素吸蔵合金電極の単板試験における容量、ニッケル水素蓄電池のサイクル性能の関係を示した。Ｃｏの比率ｆが０．１０〜１．２の領域で容量、サイクル性能共に優れており、０．１≦ｆ≦１．２が良いことが判る。
【００７０】
また、図６に水素吸蔵合金中のＮｉの比率ｅの値と水素吸蔵合金電極の単板試験における容量、ニッケル水素蓄電池のサイクル性能の関係を示した。Ｎｉの比率ｅが３．３〜４．４の領域で容量、サイクル性能共に優れており、３．３≦ｅ≦４．４が好ましいことが判る。
【００７１】
【表１１】
表１１に示したように本発明の実施例２４〜実施例２７に係る水素吸蔵合金は、何れも２９０ｍＡｈ／ｇを超える容量を示し、従来のものに比べて同等以上の容量を有する。且つ、実施例２４、実施例２５および実施例２７に係る水素吸蔵合金を用いて作製した水素吸蔵合金電極を適用した円筒型ニッケル水素蓄電池は、５００サイクルを超えるサイクル性能を有しサイクル性能において従来に比べて高い性能を有する。実施例２４および実施例２５は、Ｍｇを含有しない水素吸蔵合金を用いた実施例１７に比べて容量、サイクル性能共に勝る。また、実施例２７もＭｇを含有しない実施例２に比べて容量、サイクル性能共に勝る。このことから、水素吸蔵合金中に希土類元素に加えてＭｇを含ませることが有効であることが判る。但し、水素吸蔵合金のＭｇの比率を０．０７と高くした実施例２６は、容量、サイクル性能共に実施例２４、実施例２５に比べて劣る。
【００７３】
図７にＭｇの比率ｈと水素吸蔵合金電極の単板試験における容量、ニッケル水素蓄電池のサイクル性能の関係を示した。ｈの値が０〜０．０４の領域で容量、サイクル性能共に優れており、０＜ｈ≦０．０４が望ましいことが判る。
【００７４】
表１２に実施例２および実施例２８に係る水素吸蔵合金の、粉末の表面および粉末の内部の分析結果を示す。
【表１２】
表１２に示す通り、実施例２の水素吸蔵合金粉末は，表面からの深さが２００ｎｍ、４００ｎｍ、６００ｎｍいずれの部分においてもＹｂの比率が同じである。これに対して実施例２８に係る水素吸蔵合金粉末においては、表面からの深さが２００ｎｍ、４００ｎｍにおけるＹｂの比率が６００ｎｍ前記粉末の表面のＹｂの含有比率が高い、つまり前記粉末内部に比べて表面のＹｂの含有比率高い値であることが判る。
【００７６】
表１３に実施例２および実施例２８の水素吸蔵合金電極の単板試験における容量、ニッケル水素蓄電池のサイクル性能を示した。
【表１３】
表１３に示す如く、本発明の実施例２８に係る水素吸蔵合金を適用したニッケル水素蓄電池は、サイクル性能が顕著に優れている。実施例２８の場合、合金粉末の表面がＹｂリッチであり、Ｙｂを含む不動態化被膜によって被覆されたことにより、合金の耐食性が向上したことによると考えられる。なお、実施例２８ではＲ２がＹｂの場合の例を示したが、Ｒ２がＹまたはＹｂ以外の前記重希土類元素の場合も同様の効果が得られる。
【００７８】
表１４に実施例２、実施例２９〜実施例３４および比較例１０に係るニッケル水素蓄電池の高温充放電試験結果とサイクル性能を示した。
【表１４】
表１４に示した如く、実施例２９〜実施例３３に係る希土類元素を含むニッケル電極を適用したニッケル水素蓄電池は、希土類元素を含まないニッケル電極を適用した実施例２のニッケル水素蓄電池と比較して５０℃での充放電性能、４０℃での充放電サイクル性能共に優れている。実施例２９〜実施例３３の場合は、ニッケル電極の充電受け入れ性が良く、充電の過程においてニッケル電極での酸素発生が抑制されたことと耐久性に優れた水素吸蔵合金電極を適用することによって、サイクル性能が顕著に向上したと考えられる。
【００８０】
なお、実施例２９〜実施例３３においては、ニッケル電極に添加する物質としてＹｂ等表６に示した重希土類元素およびＹの酸化物を適用したが、該希土類元素の水酸化物を適用することも有効である。また実施例では水酸化ニッケル粉末９７重量部に前記希土類元素の酸化物を３重量部を混合添加したが、本発明はこれに限定されるものではなく、水酸化ニッケル粉末９０〜９９重量部、Ｙｂ等前記希土類元素の化合物のうちの少なくとも１種類を１〜１０重量部の範囲で混合添加するのが有効である。
【００８１】
実施例３４に係るニッケル水素蓄電池は、５０℃放電での放電容量は実施例２９〜実施例３３とほぼ同等であるが、４０℃におけるサイクル性能において実施例２９〜実施例３３を顕著に上回る性能（サイクル寿命）を示す。また、前記２０℃での充放電サイクル試験においても、サイクル寿命が前記実施例２８の６８０サイクル、実施例３１の５７０サイクルに比べて７２０サイクルと顕著に上回るサイクル性能を示す。
【００８２】
この結果は、前記実施例２８の評価結果において記述した水素吸蔵合金の耐食性向効果と、実施例２９〜実施例３３の評価結果で記述したニッケル電極の酸素発生抑制効果が相俟ってサイクル性能向上において顕著な効果が得られたことを示すものと考えられる。
【発明の効果】
【００８３】
本発明の請求項１に係る水素吸蔵合金粉末は、従来の水素吸蔵合金粉末に比べて単位重量あたりの容量が同等以上であり、耐久性が良く充放電サイクル特性に優れたニッケル水素蓄電池を可能にするものである。
【００８４】
本発明の請求項２に係る水素吸蔵合金粉末は、特に耐久性に優れた水素吸蔵合金粉末である。
【００８５】
本発明の請求項３に係るアルカリ蓄電池用負極は、耐久性に優れ、容量および活性化の速さにおいても従来の水素吸蔵合金に同等以上の水素吸蔵合金である。
【００８６】
本発明の請求項４に係る水素吸蔵合金は、アルカリ電解液に対する耐食性において特に優れ、充放電サイクル特性に優れたニッケル水素蓄電池を可能にするものである。
【００８７】
本発明の請求項５に係る水素吸蔵合金電極は、従来の水素吸蔵電極に比べて同等以上の容量を保持し、サイクル性能の優れた水素吸蔵合金電極である。
【００８８】
本発明の請求項６に係るニッケル水素蓄電池は、従来の電池に比べて同等以上の容量を保持し、サイクル性能の優れたニッケル水素蓄電池である。
【００８９】
本発明の請求項７に係るニッケル水素蓄電池は、高温での充放電性能および高温および常温での充放電サイクル性能の優れたニッケル水素蓄電池である。
【図面の簡単な説明】
【図１】水素吸蔵合金に含まれるＬａの比率ａと水素吸蔵合金粉末の容量、およびニッケル水素蓄電池のサイクル性能の関係を示すグラフである。
【図２】水素吸蔵合金に含まれるＣｅの比率ｂと水素吸蔵合金粉末の容量、およびニッケル水素蓄電池のサイクル性能の関係を示すグラフである。
【図３】水素吸蔵合金に含まれるＹｂの比率ｄと水素吸蔵合金粉末の容量、およびニッケル水素蓄電池のサイクル性能の関係を示すグラフである。
【図４】水素吸蔵合金に含まれるＮｉ、ＣｏおよびＳの比率の和ｅ＋ｆ＋ｇと水素吸蔵合金粉末の容量、およびニッケル水素蓄電池のサイクル性能の関係を示すグラフである。
【図５】水素吸蔵合金に含まれるＣｏの比率ｆと水素吸蔵合金粉末の容量、およびニッケル水素蓄電池のサイクル性能の関係を示すグラフである。
【図６】水素吸蔵合金に含まれるＮｉの比率ｅと水素吸蔵合金粉末の容量、およびニッケル水素蓄電池のサイクル性能の関係を示すグラフである。
【図７】水素吸蔵合金に含まれるＭｇの比率ｈと水素吸蔵合金粉末の容量、およびニッケル水素蓄電池のサイクル性能の関係を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrogen storage alloy powder, a hydrogen storage alloy electrode using the same, and a nickel-metal hydride storage battery.
[0002]
[Prior art]
Nickel-metal hydride storage batteries have excellent resistance to overcharge and overdischarge and are easy to use for general users.Therefore, they are widely used as power sources for portable small electronic devices such as mobile phones, small power tools and small personal computers. The demand is increasing dramatically with the spread of these small electronic devices. Further, it has been put to practical use as a power supply for driving a hybrid electric vehicle (HEV). Further, there is a demand for further increase in capacity and improvement in charge / discharge cycle performance of alkaline storage batteries.
[0003]
The negative electrode of the nickel-metal hydride storage battery is one in which a paste mainly composed of a hydrogen storage alloy serving as an active material is supported on a porous substrate of an alkali-resistant and highly conductive metal such as iron, nickel, and copper.
[0004]
As the hydrogen storage alloy, there are Mg-based alloys, Ti-based alloys, and Zr-based alloys in addition to La-Ni-based alloys. La-Ni-based alloys are frequently used because of their high activity and excellent durability. Have been. However, there are many opportunities to operate at high temperature such as power supply for HEV and personal computer, and further improvement of high temperature characteristics such as durability at high temperature is required for batteries, and conventional hydrogen storage alloy electrodes are applied. In the nickel-metal hydride storage battery described above, there is a disadvantage that the durability of the hydrogen storage alloy is inferior and the above-mentioned demand cannot be satisfied.
[0005]
Conventionally, attempts have been made to improve the durability of the hydrogen storage alloy by improving the composition of the hydrogen storage alloy. (For example, refer to Patent Document 1.)
[0006]
[Patent Document 1]
JP-A-5-62674 (page 2, page 14, paragraph 4, page 1, Table 1 and Table 2)
[0007]
Patent Document 1 discloses that MmNi 5 (Mm is misch metal) and Mm is La 0.2 Ce 0.4 Pr 0.1 Nd 0.1 R 0.2 (R represents one element of a lanthanoid having an atomic number of 63 or more). However, the hydrogen storage alloy having the composition described in Patent Document 1 has a low capacity per unit weight of 250 mAh / g or less, and a nickel-metal hydride using a hydrogen storage alloy electrode manufactured using the hydrogen storage alloy. Storage batteries have the disadvantage of low capacity.
[Problems to be solved by the invention]
The present invention has been made in view of the drawbacks of the prior art, and has a discharge capacity that is not inferior to the conventional one, and a hydrogen storage alloy electrode that is superior to the conventional one in durability represented by charge and discharge cycle characteristics. And a nickel-metal hydride storage battery.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the hydrogen storage alloy powder according to the present invention is 5 Having at least one element of La, Ce, Y and a lanthanoid having an atomic number of 63 or more, Ni and Co as essential components, and R1 of a lanthanoid having an atomic number of 59 to 62. At least one element; R2 at least one of Y and lanthanoids having an atomic number of 63 or more; X as a metal element not belonging to a rare earth element; a Ce b R1 c R2 d Ni e Co f X g A + b + c + d = 1.0, 0.6 ≦ a ≦ 0.9, 0.05 ≦ b, 0 ≦ c, 0 <d ≦ 0.06, and 5.0 ≦ e + f + g ≦ 5.4, and a hydrogen storage alloy powder represented by 0.1 ≦ f ≦ 1.2 and 0 <g.
[0009]
Furthermore, in the present invention, the hydrogen storage alloy powder is a hydrogen storage alloy powder having the composition according to claim 1, wherein R2 (R2 is a lanthanoid having an atomic number of 63 or more contained in the powder). It is preferable that the concentration of the element be higher at the surface of the powder than at the inside of the powder.
[0010]
The hydrogen storage alloy electrode according to the present invention is an electrode to which the hydrogen storage alloy powder according to any one of claims 1 to 4 is applied. A nickel-metal hydride storage battery according to the present invention is a nickel-metal hydride storage battery having a nickel electrode as a positive electrode and the hydrogen storage alloy electrode according to claim 5 as a negative electrode. It is further desirable that the nickel electrode contains at least one element of Er, Tm, Yb, Lu and Y.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The hydrogen storage alloy powder according to the present invention comprises CaCu 5 Having at least one element selected from the group consisting of La, Ce, and a lanthanoid having an atomic number of 63 or more, Ni and Co as essential components, and R1 having at least one of lanthanoids having an atomic number of 59 to 62. R2 is at least one element of Y and a lanthanoid having an atomic number of 63 or more, X is a metal element not belonging to a rare earth element, and a composition formula La a Ce b R1 c R2 d Ni e Co f X g A + b + c + d = 1.0, 0.6 <a <0.9, 0.05 ≦ b, 0 ≦ c, 0 <d <0.06, and 5.0 ≦ e + f + g ≦ 5.4, wherein 0.1 ≦ f ≦ 1.2 and 0 <g.
[0012]
The hydrogen storage alloy powder is obtained by, for example, grinding an ingot of an alloy having the above composition. The average particle size of the hydrogen storage alloy is desirably 20 to 100 μm. If the average particle size is less than 20 μm, the filling property is inferior. On the other hand, when the average particle size exceeds 100 μm, there is a disadvantage that the activity of the hydrogen storage alloy electrode as an active material is low.
[0013]
When the ratio a of La in Mm is 0.6 or less, there is a disadvantage that the capacity is low when the alloy powder of the composition is applied to a hydrogen storage alloy electrode. When the ratio a of La in Mm exceeds 0.9, corrosion resistance in an alkaline electrolyte is inferior, so that when the alloy powder of the composition is applied to a hydrogen storage alloy electrode, the durability of the electrode is inferior. There is.
[0014]
In the hydrogen storage alloy according to the present invention, the content ratio b of Ce is set to 0.05 or more. Further, it is preferable that the ratio b is larger than the ratio c of the rare earth element R1 belonging to the atomic numbers 59 to 62 (hereinafter referred to as a light rare earth element when the four elements are collectively referred to). By setting b to 0.05 ≦ b and c <b, there is an effect of increasing the corrosion resistance of the hydrogen storage alloy. In addition, there is an effect of promoting absorption of oxygen generated at the positive electrode during charging by the hydrogen storage alloy. Thereby, corrosion of the hydrogen storage alloy is suppressed, and cycle performance can be improved.
[0015]
The heavy rare earth element R2 in the alloy has an effect of improving the corrosion resistance of the alloy powder in the alkaline electrolyte. However, as the content ratio of R2 in the Mm increases, the parallel pressure of hydrogen in the alloy increases, and the capacity of the hydrogen storage alloy electrode using the alloy powder decreases. Further, there is a disadvantage that activation of the electrode is delayed. When the ratio d of R2 exceeds 0.06, this defect becomes remarkable.
[0016]
The value of e + f + g is 5.0 or more and 5.4 or less. When the value is less than 5.0, Mm segregates in the alloy, and there is a defect that the corrosion resistance is low. On the other hand, if the value exceeds 5.4, the hydrogen storage capacity of the hydrogen storage alloy decreases, and when the alloy powder of the composition is applied to a hydrogen storage alloy electrode, the capacity of the electrode is low.
[0017]
As described above, in the present invention, the concentration of R2 (R2 represents at least one of heavy rare earth elements) contained in the hydrogen storage alloy powder is higher on the surface of the powder than inside the powder. It is desirable to do. The powder surface here means that when the alloy powder comes in contact with the alkaline electrolyte, the alloy is corroded and some of the constituents of the alloy are eluted. It means a region that changes, and any region that undergoes such a change is not restricted by the depth from the surface of the powder. However, usually, a region having a distance from the surface of the powder of about 500 nanometers (nm) or less can be regarded as the surface here. Conversely, the inside of the powder means a region where the composition does not change even when the alloy powder comes in contact with the alkaline electrolyte, and specifically, the distance from the powder surface is about 600 nanometers (nm) or more. The area can be considered as inside the powder.
[0018]
The hydrogen-absorbing alloy powder in which the surface heavy rare earth element R2 is richer than the inside can be obtained by immersing the alloy powder having the composition according to the present invention in a high-temperature, high-concentration chemical conversion alkali. The alloy powder is considered to have high corrosion resistance because it forms a passive film containing a heavy rare earth element (R2) on the surface in an alkaline electrolyte.
[0019]
The heavy rare earth element contained in the surface of the alloy powder can be quantitatively analyzed by TEM (transmission electron microscope) -EDS or ESCA (photoelectron spectroscopy).
[0020]
In the present invention, it is desirable that the ratio e of Ni contained in the hydrogen storage alloy is 3.3 or more and 4.4 or less. When the ratio e is less than 3.3 or more than 4.4, there is a disadvantage that the corrosion resistance of the alloy powder is inferior and that the cycle characteristics of the hydrogen storage alloy electrode are low.
[0021]
In the present invention, the ratio f of Co contained in the hydrogen storage alloy powder is set to 0.1 or more and 1.2 or less. If f is less than 0.1, the corrosion resistance of the alloy powder is inferior. If f exceeds 1.2, activation of the hydrogen storage alloy electrode as an active material is delayed.
[0022]
In the present invention, X, which is a metal element that does not belong to the rare earth element, is preferably at least one element of Al, Cu, Fe, Mn, Ti, Zr, Cr, Mo, and Be. The addition of these metal elements to the hydrogen storage alloy has the effect of increasing the hydrogen storage capacity of the hydrogen storage alloy, speeding up the activation of the hydrogen storage alloy electrode, and increasing the corrosion resistance of the hydrogen storage alloy. .
[0023]
The metal element X is particularly preferably Mn, Al and Fe among the above-mentioned metal elements. The presence of Mn has the effect of increasing the hydrogen storage capacity of the hydrogen storage alloy. However, it reduces the corrosion resistance of the alloy. For these reasons, when a + b + c + d = 1.0 or a + b + c + d + h = 1.0, it is preferable that the ratio of Mn contained in the alloy be 0.1 or more and 0.5 or less. The presence of Al is effective in increasing the corrosion resistance of the hydrogen storage alloy. On the other hand, there is a disadvantage that activation of the hydrogen storage alloy electrode is delayed. For these reasons, when a + b + c + d = 1.0 or a + b + c + d + h = 1.0, it is preferable that the ratio of Al contained in the alloy be 0.1 or more and 0.5 or less. The presence of Fe has the effect of increasing the activity of the hydrogen storage alloy when the hydrogen storage alloy is used as the active material of the hydrogen storage alloy electrode. However, as the proportion of Fe increases, the corrosion resistance of the alloy significantly decreases. For such a reason, when a + b + c + d = 1.0 or a + b + c + d + h = 1.0, it is preferable that the ratio of Fe contained in the alloy be 0 or more and 0.05 or less.
[0024]
The ratio g of the metal element X contained in the hydrogen storage alloy according to the present invention is set to 0 <g. For the above-mentioned reason, it is preferable that 0.2 <g ≦ 1.05 in the above range.
[0025]
The hydrogen storage alloy electrode according to the present invention is one in which the hydrogen storage alloy powder according to the present invention is supported on a substrate having an anti-electrolyte property such as a perforated plate made of nickel or nickel plated metal or a foamed metal. .
[0026]
The nickel electrode applied to the nickel-metal hydride storage battery according to the present invention is preferably a nickel electrode containing at least one of the heavy rare earth element and Y. When a nickel-metal hydride storage battery to which the nickel electrode is applied is charged at a high temperature, generation of oxygen at the nickel electrode is suppressed. A nickel-metal hydride storage battery in which the nickel electrode is combined with the hydrogen storage alloy electrode according to the present invention has remarkably suppressed corrosion of the hydrogen storage alloy, excellent durability, and excellent cycle performance as compared with the conventional nickel-metal hydride storage battery. Nickel-metal hydride storage battery.
[0027]
At least one of the heavy rare earth element and Y included in the nickel electrode is included as an oxide or a hydroxide. The heavy rare earth element is preferably added to the nickel electrode as an oxide or a hydroxide (a hydrated hydroxide can also be applied). In particular, oxides are inexpensive and are preferred compounds.
[0028]
【Example】
Hereinafter, the present invention will be described in detail based on examples.
(Example 1)
(Adjustment of hydrogen storage alloy)
La0.60, Ce0.27, Pr0.01, Nd0.08, Yb0.04, Ni4.02, Co0.50, Mn0.30, Al0.32, Fe0.01 are weighed and put into the crucible in the molar ratio of the elements. Then, the metal was melted in an argon atmosphere (inert atmosphere) using a high frequency melting furnace to obtain an alloy ingot. The ingot was pulverized to obtain an alloy powder having an average particle size of 40 μm.
[0029]
(Preparation of hydrogen storage alloy electrode)
For 100 parts by weight of the hydrogen storage alloy powder, 3 parts by weight of nickel fine powder having an average particle diameter of 1 μm, 20 parts by weight of a 1 wt% aqueous solution of methylcellulose (MC) as a thickener, and styrene butadiene as a binder One part by weight of rubber was added and kneaded to prepare a paste.
[0030]
As the substrate of the hydrogen storage alloy electrode, a perforated plate made of a steel plate having a thickness of 70 μm, an opening diameter of 1.5 mm, and an opening ratio of 40% plated with nickel was applied. The paste was applied to both sides of the substrate. The coated electrode plate was dried to obtain an electrode plate having a thickness of 1.1 mm. The electrode plate was pressed between two rolls so that the finished thickness of the electrode plate was 0.4 mm.
[0031]
(Preparation of nickel electrode material powder)
According to a predetermined method, an average having a high density nickel hydroxide containing 3% by weight and 5% by weight of a solid solution in terms of hydroxide in the form of hydroxide as a nucleus and forming a coating layer of cobalt hydroxide on the surface. A nickel electrode material powder having a particle size of 10 μm and containing nickel hydroxide as a main component was prepared. The ratio of the cobalt hydroxide coating layer formed on the surface of the material powder was 6% by weight.
[0032]
(Preparation of nickel electrode)
To 80 parts by weight of the obtained nickel electrode material powder, 20 parts by weight of a 1% by weight aqueous solution of carboxymethyl cellulose (CMC) was added and kneaded to prepare a nickel electrode active material paste. The paste was 1.4 mm thick and the basis weight was 500 g / m. 2 After filling in a porous nickel foam substrate and drying, the thickness was adjusted to 0.75 mm by pressing to obtain a long strip-shaped original plate for nickel electrodes.
[0033]
(Preparation of cell for single plate test of hydrogen storage alloy electrode)
The nickel electrode and the hydrogen storage alloy electrode were cut into a size of 3 cm × 3 cm, and a current collecting tab was attached to the upper conductive edge. A nickel electrode cut to a predetermined size was laminated on both surfaces of the hydrogen storage alloy electrode via a polypropylene nonwoven fabric having a thickness of 0.12 mm and subjected to a hydrophilic treatment. The ratio of the filling capacity of the nickel electrode and the hydrogen storage alloy electrode and the ratio of the positive electrode capacity / negative electrode capacity were set to 4. A predetermined amount of an electrolyte containing 6.8 mol / l KOH and 0.8 mol / l LiOH is injected, and a mercury oxide electrode (Hg / HgO) is inserted as a reference electrode to test a hydrogen storage alloy electrode single plate. Cell.
[0034]
(Formation of test cell for hydrogen storage alloy electrode single plate)
After aging the obtained nickel-metal hydride storage battery at a temperature of 20 ° C. for 12 hours, formation was performed under the following conditions. In the first charging, the battery was charged at a charging current of 1/50 ItA for 10 hours, and then charged at a charging current of 1/10 ItA for 10 hours. Then, when the potential of the hydrogen storage alloy electrode with respect to the reference electrode reached −0.6 V at a discharge current of ５ ItA, discharge was terminated. From the second cycle on, the charge was performed at a charge current of 1/10 ItA for 12 hours and discharged at a discharge current of 1/5 ItA under the above-mentioned discharge termination condition. The cycle was defined as one cycle, and the charge and discharge were repeated for 10 cycles including the first charge and discharge.
[0035]
(Production of cylindrical nickel-metal hydride battery)
The original plate of the nickel electrode was cut into a predetermined size to obtain a nickel electrode. The capacity of the nickel electrode calculated from the active material filling amount was 1600 mAh. The original plate of the hydrogen storage electrode was cut into a predetermined size to obtain a hydrogen storage alloy electrode. The nickel electrode and the hydrogen storage alloy electrode were laminated via a non-woven fabric made of polypropylene having a thickness of 0.12 mm and subjected to a hydrophilic treatment, and this was wound to form an electrode plate group. The capacity ratio of the negative electrode (hydrogen storage alloy electrode) and the positive electrode (nickel electrode) of the electrode plate group was set to 1.6 to 1. A current collecting terminal for a positive electrode is attached to the electrode plate group, inserted into a metal battery case, a predetermined amount of an electrolytic solution containing 6.8 mol / l of KOH and 0.8 mol / l of LiOH is injected, and then sealed and sealed. Type sealed nickel-metal hydride battery.
[0036]
(Formation of cylindrical nickel-metal hydride storage battery)
After aging the obtained nickel-metal hydride storage battery at a temperature of 40 ° C. for 12 hours, formation was performed under the following conditions. The first charging was performed at a charging current of 1/50 ItA (32 mA) for 10 hours, and thereafter, charging was performed at a charging current of 1/10 ItA (160 mA) for 10 hours. Next, the battery was discharged at a discharge current of 1/5 ItA (320 mA) with a discharge end voltage of 1.0 V. After the second cycle, the battery was charged at a charge current of 1/10 ItA (160 mA) for 12 hours, and discharged at a discharge current of 1/5 ItA (320 mA) with a discharge end voltage of 1.0 V. The cycle was defined as one cycle, and the charge and discharge were repeated for 10 cycles including the first charge and discharge.
[0037]
(Examples 2 to 6)
The charged amounts (molar ratios) of the metal elements when adjusting the hydrogen storage alloy were as shown in Examples 2 to 6 in Table 1. Other than that, it was the same as Example 1.
[0038]
(Comparative Examples 1 to 3)
The amounts (molar ratios) of metal elements charged when adjusting the hydrogen storage alloy were as shown in Comparative Examples 1 to 4 in Table 1. Other than that, it was the same as Example 1. Table 1 summarizes the trial production contents of Examples 1 to 6 and Comparative Examples 1 to 3. In Table 1, Mn0.30, Al0.32, and Fe0.01, which are the ratios of Mn, Al, and Fe, are collectively indicated as X0.63.
[0039]
[Table 1]
(Examples 7 and 8)
The amounts (molar ratios) of metal elements charged when adjusting the hydrogen storage alloy were as shown in Examples 7 and 8 in Table 2. Other than that, it was the same as Example 1.
[0041]
(Comparative Example 4, Comparative Example 5)
The amounts (molar ratios) of the metal elements used for preparing the hydrogen storage alloy were as shown in Comparative Examples 4 and 5 in Table 2. Other than that, it was the same as Example 1. Comparative Example 5 is shown as a typical example of a conventional hydrogen storage alloy composition.
[0042]
[Table 2]
(Examples 9 to 19)
The amounts (molar ratios) of metal elements charged when adjusting the hydrogen storage alloy were as shown in Examples 9 to 19 in Table 3. Other than that, it was the same as Example 1.
[0044]
[Table 3]
(Examples 20 to 23)
The amounts (molar ratios) of metal elements charged when adjusting the hydrogen storage alloy were as shown in Examples 20 to 23 in Table 4. Other than that, it was the same as Example 1.
[0046]
(Comparative Examples 6 to 9)
The amounts (molar ratios) of metal elements charged when adjusting the hydrogen storage alloy were as shown in Comparative Examples 6 to 9 in Table 4. Other than that, it was the same as Example 1.
[0047]
[Table 4]
(Examples 24 to 27)
Mg was added as a component of the hydrogen storage alloy. The preparation amounts (molar ratios) of metal elements when adjusting the hydrogen storage alloy were as shown in Examples 24 to 27 of Table 5. Other than that, it was the same as Example 1.
[0049]
[Table 5]
(Example 28)
The amount (molar ratio) of the metal element charged when adjusting the hydrogen storage alloy was the same as in Example 2 in Table 1. 100 g of the obtained hydrogen-absorbing alloy powder was immersed in 200 ml of an aqueous solution containing 6.8 mol / l KOH and 0.8 mol / l LiOH maintained at a temperature of 100 ° C. for 1 hour, and the solution was stirred during the immersion. Thereafter, the resultant was washed with water to remove alkali, and vacuum-dried. The other conditions were the same as in Example 2.
(Analysis of heavy rare earth elements in hydrogen storage alloy powder)
Elemental analysis included in the obtained hydrogen storage alloy powder using the TEM-EDS was performed. In this case, the analysis was performed on the hydrogen storage alloy immediately after immersion in the alkali, but the analysis was performed on the hydrogen storage alloy powder recovered by disassembling the battery having a charge / discharge cycle number of 30 cycles or less, including formation after forming the battery. The analysis yields almost the same results.
[0051]
(Examples 29 to 33)
(Preparation of nickel electrode material powder)
In the above Example 2, 97 parts by weight of nickel hydroxide powder containing cobalt and zinc in a solid solution state and having a coating layer made of cobalt hydroxide formed on the surface was added to each of Er having an average particle size of about 5 μm. 2 O 3 , Tm 2 O 3 , Yb 2 O 3 , Lu 2 O 3 , Y 2 O 3 Was added and mixed to obtain a positive electrode material powder. The other conditions were the same as in Example 2. These are referred to as Examples 29 to 23, respectively.
[0052]
(Example 34)
The same Yb as in Example 31 was used for the positive electrode. 2 O 3 Using a nickel electrode to which a cathode material powder mixed with and added is applied, and a hydrogen storage alloy to which a hydrogen storage alloy powder applied by immersion treatment in the same alkaline aqueous solution containing KOH and LiOH as in Example 28 is applied to the negative electrode, A nickel-metal hydride storage battery was fabricated in the same manner as in Example 2 except for the above.
[0053]
(Comparative Example 10)
(Preparation of nickel electrode material powder)
97 parts by weight of the same nickel hydroxide powder as in Example 30 was mixed with Yb having an average particle size of about 5 μm. 2 O 3 Was mixed and added to the nickel electrode and the hydrogen storage alloy electrode, and the same hydrogen storage alloy electrode as in Comparative Example 1 was combined to form a nickel hydrogen storage battery.
Table 4 summarizes the trial production contents of Examples 29 to 34 and Comparative Example 10.
[0054]
[Table 6]
(Single plate test of hydrogen storage alloy electrode)
After the formation, the single cell test cell of the hydrogen storage alloy electrode is charged at a temperature of 20 ° C. with a current of 0.2 ItA based on the filling capacity of the hydrogen storage alloy electrode at 120%, and the hydrogen storage alloy is also charged with a current of 0.2 ItA. Discharge was performed until the reference potential of the electrode became −0.6 V. The charge / discharge cycle was repeated five times, and it was confirmed that a stable capacity was obtained. The test results described below showed the capacity at the fifth cycle after the formation was completed.
[0056]
(Charge / discharge cycle test of cylindrical nickel-metal hydride battery)
The battery of Example and the battery of Comparative Example after the formation were subjected to a charge / discharge cycle test at a temperature of 20 ° C. Charging was performed with an ItA current for 1.2 hours, and discharging was performed with an ItA current with a discharge end voltage of 1.0 V. The cycle was repeated with the charge / discharge cycle as one cycle. The cycle life was defined as the point at which the discharge capacity decreased to 80% of the initial value.
[0057]
(Charge / discharge test at high temperature)
After completion of the formation, six Example batteries and Comparative Example batteries were prepared, and three were subjected to a charge / discharge test at a temperature of 20 ° C. and another three at 50 ° C. Charging was performed at a current of 0.2 ItA for 6 hours, and discharging was performed at a current of 0.2 ItA with a discharge end voltage of 1.0 V. It was confirmed that a stable capacity was obtained by repeating charge and discharge for 5 cycles. The test results described below are shown as the ratio of the capacity at 50 ° C. to the capacity at 20 ° C. in the fifth cycle after the formation.
[0058]
(Charge / discharge cycle test of cylindrical nickel-metal hydride storage battery at high temperature)
The battery of Example and the battery of Comparative Example after the formation were subjected to a charge / discharge cycle test at a temperature of 40 ° C. Charging was performed with an ItA current for 1.2 hours, and discharging was performed with an ItA current with a discharge end voltage of 1.0 V. The cycle was repeated with the charge / discharge cycle as one cycle.
[0059]
(Single plate test of hydrogen storage alloy electrode and cycle test result of cylindrical storage battery)
Tables 7 to 12 show the test results.
[Table 7]
As shown in Table 7, according to the single plate test of the hydrogen storage alloy electrode, the hydrogen storage alloy electrodes according to Examples 1 to 6 of the present invention all showed a capacity exceeding 280 mAh / g per 1 g of the hydrogen storage alloy. Has a capacity almost equal to or greater than that of a typical conventional example (Comparative Example 5 shown in Table 2). In addition, the cylindrical nickel-metal hydride storage battery using the hydrogen storage alloy electrode manufactured using the hydrogen storage alloy according to the present invention has a charge / discharge cycle exceeding 400 cycles, and the cycle performance of Comparative Examples 5 and 3 described above. It has performance exceeding that of Comparative Example 1, in which the ratio of La in the hydrogen storage alloy is small, has a small capacity, and conversely, Comparative Example 2, in which the ratio of La is large, is inferior in cycle performance.
[0061]
FIG. 1 shows the relationship between the ratio of La in the hydrogen storage alloy, the capacity of the hydrogen storage alloy electrode in the single plate test, and the cycle performance of the nickel-metal hydride storage battery. As shown in FIG. 1, in the region where the ratio a of La is 0.6 to 0.9, both the capacity and the cycle performance are excellent, and it can be seen that 0.6 ≦ a ≦ 0.9 is good.
[0062]
As shown in Table 7, when comparing Example 3, Example 4, and Example 5 in which the ratio b of Ce in the hydrogen storage alloy was 0.05 ≦ b with Comparative Example 3 in which b = 0.01, The example also has substantially the same capacity as the comparative example 1 and shows superior cycle performance as compared with the comparative example 4. FIG. 2 shows the relationship between the ratio b of Ce in the hydrogen storage alloy, the capacity of the hydrogen storage alloy electrode in a single plate test, and the cycle performance of the nickel-metal hydride storage battery. As shown in FIG. 2, it can be seen that the cycle performance is good when the ratio b of Ce in the hydrogen storage alloy is 0.05 ≦ b.
[0063]
[Table 8]
As shown in Table 8, Examples 7 and 8 are superior to Comparative Examples 4 and 5 in cycle performance. This indicates that the presence of Yb in the hydrogen storage alloy is effective for improving the cycle performance. However, when the ratio d of Yb is increased to 0.08, Example 8 in which d is 0.06 and The cycle performance was lower than that of Example 7 in which the value was 0.01, and it can be seen that the value of d may not be too high. FIG. 3 shows the relationship between the ratio d of Yb in the hydrogen storage alloy, the capacity of the hydrogen storage alloy electrode in the single plate test, and the cycle performance of the nickel-metal hydride storage battery. As shown in FIG. 3, it is found that the capacity and the cycle performance are excellent in the range where the ratio d of Yb is 0.01 to 0.06, and that 0.01 ≦ d ≦ 0.06 is good.
[0065]
[Table 9]
As shown in Table 9, each of the hydrogen storage alloy electrodes according to Examples 9 to 19 of the present invention has a capacity exceeding 280 mAh / g, and has a capacity equal to or higher than that of the conventional one. Moreover, the cylindrical nickel-metal hydride storage battery to which the hydrogen storage alloy electrode manufactured using the hydrogen storage alloy according to the present invention is applied has a charge / discharge cycle exceeding 400 cycles, and is compared with any of the comparative example batteries. It has cycle performance that exceeds that of the examples. From this, the above R 2 It can be seen that the discharge capacity is equal to or higher than that of the conventional one and the cycle performance is excellent in any case including Lu and Y below Eu and two types of elements Er and Tm and two types of elements Er and Yb.
[0067]
[Table 10]
As shown in Table 10, Comparative Example 8 in which the sum e + f + g of the ratio e of Ni, the ratio f of Co, and the ratio g of S is as low as 4.9 has a high discharge capacity, but is inferior in cycle performance. Conversely, it can be seen that Comparative Example 9 having a high e + f + g of 5.5 has a disadvantage of low capacity. FIG. 4 shows the relationship between the value of e + f + g, the capacity of the hydrogen storage alloy electrode in a single plate test, and the cycle performance of the nickel-metal hydride storage battery. In the region where the value of e + f + g is 5.0 to 5.4, both the capacity and the cycle performance are excellent, and it can be seen that 5.0 ≦ e + f + g ≦ 5.4 is good.
[0069]
Comparative Example 7 in which the ratio of Ni is as low as 3.12 and the ratio of Co is as high as 1.4 is inferior in both discharge capacity and cycle performance. FIG. 5 shows the relationship between the value of the ratio f of Co in the hydrogen storage alloy, the capacity of the hydrogen storage alloy electrode in the single plate test, and the cycle performance of the nickel-metal hydride storage battery. In the region where the Co ratio f is 0.10 to 1.2, both capacity and cycle performance are excellent, and it can be seen that 0.1 ≦ f ≦ 1.2 is good.
[0070]
FIG. 6 shows the relationship between the value of the ratio e of Ni in the hydrogen storage alloy, the capacity of the hydrogen storage alloy electrode in a single plate test, and the cycle performance of the nickel-metal hydride storage battery. In the region where the ratio e of Ni is 3.3 to 4.4, both capacity and cycle performance are excellent, and it can be seen that 3.3 ≦ e ≦ 4.4 is preferable.
[0071]
[Table 11]
As shown in Table 11, each of the hydrogen storage alloys according to Examples 24 to 27 of the present invention has a capacity exceeding 290 mAh / g, and has a capacity equal to or greater than that of the conventional one. In addition, the cylindrical nickel-metal hydride storage battery using the hydrogen storage alloy electrode manufactured using the hydrogen storage alloy according to Example 24, Example 25 or Example 27 has a cycle performance exceeding 500 cycles and has a conventional cycle performance. Has higher performance than. Examples 24 and 25 are superior in both capacity and cycle performance as compared with Example 17 using a hydrogen storage alloy containing no Mg. In addition, Example 27 also excels in both capacity and cycle performance as compared to Example 2 containing no Mg. This indicates that it is effective to include Mg in the hydrogen storage alloy in addition to the rare earth element. However, Example 26 in which the ratio of Mg in the hydrogen storage alloy was increased to 0.07 was inferior to Examples 24 and 25 in both capacity and cycle performance.
[0073]
FIG. 7 shows the relationship between the Mg ratio h, the capacity of the hydrogen storage alloy electrode in a single plate test, and the cycle performance of the nickel-metal hydride storage battery. In the range of h from 0 to 0.04, both capacity and cycle performance are excellent, and it is understood that 0 <h ≦ 0.04 is desirable.
[0074]
Table 12 shows the results of analysis of the surface of the powder and the inside of the powder for the hydrogen storage alloys according to Example 2 and Example 28.
[Table 12]
As shown in Table 12, the hydrogen storage alloy powder of Example 2 has the same Yb ratio at any part of the depth from the surface of 200 nm, 400 nm, and 600 nm. On the other hand, in the hydrogen storage alloy powder according to Example 28, the depth from the surface was 200 nm, the Yb ratio at 400 nm was 600 nm, and the Yb content at the surface of the powder was high, that is, compared to the inside of the powder. It can be seen that the content ratio of Yb on the surface is high.
[0076]
Table 13 shows the capacity of the hydrogen storage alloy electrodes of Example 2 and Example 28 in the single plate test and the cycle performance of the nickel-metal hydride storage battery.
[Table 13]
As shown in Table 13, the nickel-metal hydride storage battery using the hydrogen storage alloy according to Example 28 of the present invention has remarkably excellent cycle performance. In the case of Example 28, it is considered that the surface of the alloy powder was Yb-rich and was coated with the passivation film containing Yb, thereby improving the corrosion resistance of the alloy. Although the example in which R2 is Yb is shown in Example 28, the same effect can be obtained when R2 is the heavy rare earth element other than Y or Yb.
[0078]
Table 14 shows the high-temperature charge / discharge test results and the cycle performance of the nickel-metal hydride storage batteries according to Example 2, Examples 29 to 34, and Comparative Example 10.
[Table 14]
As shown in Table 14, the nickel-metal hydride storage batteries using the nickel electrodes containing rare earth elements according to Examples 29 to 33 were compared with the nickel-metal hydride storage batteries of Example 2 using nickel electrodes containing no rare earth elements. The charge / discharge performance at 50 ° C. and the charge / discharge cycle performance at 40 ° C. are both excellent. In the case of Examples 29 to 33, the charge acceptance of the nickel electrode is good, and the generation of oxygen at the nickel electrode is suppressed in the charging process, and the hydrogen storage alloy electrode with excellent durability is applied. It is considered that the cycle performance was significantly improved.
[0080]
In Examples 29 to 33, the heavy rare earth elements and the oxides of Y shown in Table 6 such as Yb were applied as the materials to be added to the nickel electrode, but the hydroxides of the rare earth elements were applied. Is also effective. In the examples, 3 parts by weight of the oxide of the rare earth element was mixed and added to 97 parts by weight of nickel hydroxide powder, but the present invention is not limited to this, and 90 to 99 parts by weight of nickel hydroxide powder, It is effective to mix and add at least one of the rare earth element compounds such as Yb in the range of 1 to 10 parts by weight.
[0081]
Although the nickel-metal hydride storage battery according to Example 34 had a discharge capacity at 50 ° C. discharge substantially equal to those of Examples 29 to 33, the cycle performance at 40 ° C. remarkably exceeded that of Examples 29 to 33. (Cycle life). Also, in the charge / discharge cycle test at 20 ° C., the cycle life is remarkably superior to the 680 cycles of Example 28 and 720 cycles compared to the 570 cycles of Example 31.
[0082]
This result is due to the combination of the corrosion resistance effect of the hydrogen storage alloy described in the evaluation results of Example 28 and the effect of suppressing the oxygen generation of the nickel electrode described in the evaluation results of Examples 29 to 33. This is considered to indicate that a remarkable effect was obtained in the improvement.
【The invention's effect】
[0083]
The hydrogen storage alloy powder according to claim 1 of the present invention has a capacity per unit weight equal to or greater than that of the conventional hydrogen storage alloy powder, and enables a nickel-metal hydride storage battery having excellent durability and excellent charge / discharge cycle characteristics. It is to be.
[0084]
The hydrogen storage alloy powder according to claim 2 of the present invention is a hydrogen storage alloy powder having particularly excellent durability.
[0085]
The negative electrode for an alkaline storage battery according to the third aspect of the present invention is a hydrogen storage alloy having excellent durability and a capacity and an activation speed that are equal to or higher than those of the conventional hydrogen storage alloy.
[0086]
The hydrogen storage alloy according to claim 4 of the present invention is particularly excellent in corrosion resistance to an alkaline electrolyte and enables a nickel-metal hydride storage battery having excellent charge / discharge cycle characteristics.
[0087]
The hydrogen storage alloy electrode according to claim 5 of the present invention is a hydrogen storage alloy electrode that has a capacity equal to or higher than that of a conventional hydrogen storage electrode and has excellent cycle performance.
[0088]
The nickel-metal hydride storage battery according to claim 6 of the present invention is a nickel-metal hydride storage battery that has a capacity equal to or higher than that of a conventional battery and has excellent cycle performance.
[0089]
The nickel-metal hydride storage battery according to claim 7 of the present invention is a nickel-metal hydride storage battery excellent in charge / discharge performance at high temperatures and charge / discharge cycle performance at high temperatures and normal temperatures.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the ratio a of La contained in a hydrogen storage alloy, the capacity of a hydrogen storage alloy powder, and the cycle performance of a nickel-metal hydride storage battery.
FIG. 2 is a graph showing the relationship between the ratio b of Ce contained in the hydrogen storage alloy, the capacity of the hydrogen storage alloy powder, and the cycle performance of the nickel-metal hydride storage battery.
FIG. 3 is a graph showing the relationship between the ratio d of Yb contained in the hydrogen storage alloy, the capacity of the hydrogen storage alloy powder, and the cycle performance of the nickel-metal hydride storage battery.
FIG. 4 is a graph showing a relationship between the sum e + f + g of the ratio of Ni, Co and S contained in the hydrogen storage alloy, the capacity of the hydrogen storage alloy powder, and the cycle performance of the nickel-metal hydride storage battery.
FIG. 5 is a graph showing the relationship between the ratio f of Co contained in the hydrogen storage alloy, the capacity of the hydrogen storage alloy powder, and the cycle performance of the nickel-metal hydride storage battery.
FIG. 6 is a graph showing the relationship between the ratio e of Ni contained in the hydrogen storage alloy, the capacity of the hydrogen storage alloy powder, and the cycle performance of the nickel-metal hydride storage battery.
FIG. 7 is a graph showing the relationship between the ratio h of Mg contained in the hydrogen storage alloy, the capacity of the hydrogen storage alloy powder, and the cycle performance of the nickel-metal hydride storage battery.
Claims (7)
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| JP2002287749A JP3861788B2 (en) | 2002-09-30 | 2002-09-30 | Hydrogen storage alloy powder, hydrogen storage alloy electrode and nickel metal hydride storage battery using the same. |
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| JP2002287749A JP3861788B2 (en) | 2002-09-30 | 2002-09-30 | Hydrogen storage alloy powder, hydrogen storage alloy electrode and nickel metal hydride storage battery using the same. |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006085542A1 (en) * | 2005-02-08 | 2006-08-17 | Mitsui Mining & Smelting Co., Ltd. | Hydrogen-occluding alloy with low cobalt content |
| JP2008084668A (en) * | 2006-09-27 | 2008-04-10 | Sanyo Electric Co Ltd | Hydrogen storage alloy and sealed alkaline storage battery using the same |
| CN105463256A (en) * | 2015-12-03 | 2016-04-06 | 内蒙古稀奥科贮氢合金有限公司 | Hydrogen storage alloy for nickel-metal hydride battery and manufacturing method of hydrogen storage alloy |
| JP2016528676A (en) * | 2013-06-25 | 2016-09-15 | オヴォニック バッテリー カンパニー インコーポレイテッド | Synergistic multiphase hydride alloy |
| WO2016157669A1 (en) * | 2015-03-31 | 2016-10-06 | パナソニックＩｐマネジメント株式会社 | Alloy powder for electrodes, negative electrode for nickel-metal hydride storage batteries using same, and nickel-metal hydride storage battery |
| US9490477B2 (en) | 2012-09-27 | 2016-11-08 | Gs Yuasa International Ltd. | Nickel-metal hydride storage battery including negative electrode containing yttrium substituted hydrogen storage alloy and electrolyte solution containing sodium hydroxide |
| JP2021120954A (en) * | 2016-06-30 | 2021-08-19 | 南通沃▲徳▼材料科技有限公司Nantong Volta Materials Ltd. | Method of preparing battery electrode plate |
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006085542A1 (en) * | 2005-02-08 | 2006-08-17 | Mitsui Mining & Smelting Co., Ltd. | Hydrogen-occluding alloy with low cobalt content |
| JP2008084668A (en) * | 2006-09-27 | 2008-04-10 | Sanyo Electric Co Ltd | Hydrogen storage alloy and sealed alkaline storage battery using the same |
| US9490477B2 (en) | 2012-09-27 | 2016-11-08 | Gs Yuasa International Ltd. | Nickel-metal hydride storage battery including negative electrode containing yttrium substituted hydrogen storage alloy and electrolyte solution containing sodium hydroxide |
| JP2016528676A (en) * | 2013-06-25 | 2016-09-15 | オヴォニック バッテリー カンパニー インコーポレイテッド | Synergistic multiphase hydride alloy |
| WO2016157669A1 (en) * | 2015-03-31 | 2016-10-06 | パナソニックＩｐマネジメント株式会社 | Alloy powder for electrodes, negative electrode for nickel-metal hydride storage batteries using same, and nickel-metal hydride storage battery |
| JPWO2016157669A1 (en) * | 2015-03-31 | 2017-10-12 | パナソニックＩｐマネジメント株式会社 | Alloy powder for electrode, negative electrode for nickel metal hydride storage battery and nickel metal hydride storage battery using the same |
| CN105463256A (en) * | 2015-12-03 | 2016-04-06 | 内蒙古稀奥科贮氢合金有限公司 | Hydrogen storage alloy for nickel-metal hydride battery and manufacturing method of hydrogen storage alloy |
| JP2021120954A (en) * | 2016-06-30 | 2021-08-19 | 南通沃▲徳▼材料科技有限公司Nantong Volta Materials Ltd. | Method of preparing battery electrode plate |
| JP7427149B2 (en) | 2016-06-30 | 2024-02-05 | 合肥集新能源科技有限公司 | How to prepare battery plates |
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