JP3639494B2 - Nickel-hydrogen storage battery - Google Patents
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- JP3639494B2 JP3639494B2 JP2000078746A JP2000078746A JP3639494B2 JP 3639494 B2 JP3639494 B2 JP 3639494B2 JP 2000078746 A JP2000078746 A JP 2000078746A JP 2000078746 A JP2000078746 A JP 2000078746A JP 3639494 B2 JP3639494 B2 JP 3639494B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Description
【０００１】
【発明の属する技術分野】
本発明は、電気化学的に水素の吸蔵・放出を可逆的に行うことができる水素吸蔵合金からなる負極と、主活物質として水酸化ニッケルを含有する正極と、アルカリ電解液とを備えたニッケル−水素蓄電池に関するものである。
【０００２】
【従来の技術】
アルカリ蓄電池は各種の電源として広く使われており、小型電池は各種の携帯用の電子、通信機器に、大型電池は産業用にそれぞれ使われている。この種のアルカリ蓄電池を高容量とするために、水素吸蔵合金電極を用いたニッケル−水素蓄電池が実用化されるようになった。このニッケル−水素蓄電池の正極にはニツケル電極が用いられ、負極には水素吸蔵合金電極が用いられている。このニッケル−水素蓄電池の負極に用いられる水素吸蔵合金としては、Ｔｉ−Ｎｉ系合金、ＬａまたはＭｍ（ミッシュメタル）−Ｎｉ系合金等が用いられる。
【０００３】
上述したようなニッケル−水素蓄電池は高容量であるとともに長寿命にする必要があり、長寿命とするためには水素吸蔵合金の耐食性を向上させる必要がある。そこで、水素吸蔵合金負極にイットリウムあるいはイットリウム化合物を含有させることにより、水素吸蔵合金の酸化による劣化を抑制することが、特開平６−２１５７６５号公報にて提案されるようになった。
この特開平６−２１５７６５号公報にて提案された水素吸蔵合金負極にあっては、イットリウムあるいはイットリウム化合物の添加効果を充分に発揮させるためには、イットリウムあるいはイットリウム化合物の添加量（水素吸蔵合金１００質量部に対して０．１質量部以上）を多くする必要があり、イットリウムあるいはイットリウム化合物は非常に高価であるため、商業性が低いという問題があった。
【０００４】
これに対して、イットリウム、イッテルビウムなどの希土類元素の合金表面、負極内部、負極外表面への添加量を少なくするために、アルカリ電解液中にイットリウムイオンと他の希土類元素の少なくとも一種をイオンとして含有させることが、特開平１０−１０６６２０公報にて提案されるようになった。これにより、希土類元素の少なくとも一種のイオンが水素吸蔵合金負極を構成する粒子表面に均一に分散されて表面に吸着し、負極表面を被覆することで負極の酸化を抑制して、充放電サイクル特性の向上効果を得ることができるというものである。
【０００５】
【発明が解決しようとする課題】
ところで、この種の水素吸蔵合金負極を用いたニッケル−水素電池においては、高温（４５℃以上）の雰囲気で使用されることがあるため、高温雰囲気での充放電サイクルを繰り返しても、あるいは高温雰囲気で連続充電を行っても、水素吸蔵合金負極が酸化されないようにする必要がある。
【０００６】
しかしながら、一般にニッケル−水素電池に用いられるアルカリ電解液の水素イオン濃度（ｐＨ）は１３程度であって、この程度のｐＨではイットリウム、イッテルビウムなどの希土類元素は不溶もしくは難溶であるため、上記特開平１０−１０６６２０公報にて提案されるように添加しても、アルカリ電解液中には少量の希土類元素しか溶解することができず、負極表面をイットリウム、イッテルビウムなどの希土類元素で十分に被覆することが困難であった。このため、イットリウム、イッテルビウムなどの希土類元素の添加効果を十分に発揮することができず、特に、高温雰囲気で使用される場合には、負極の酸化を抑制することができず、充放電サイクル特性が向上しないという問題を生じた。
【０００７】
また、水素吸蔵合金にイットリウムおよびイッテルビウムからなる群から選択された少なくとも１つの元素の化合物を０．２〜１．０質量％添加して、低温時の電池特性を向上させることが特開平１０−２１９０８号公報に提案されているが、この場合においても、イットリウムおよびイッテルビウムからなる元素の添加量が多くなるため、非常に高価になって商業性が低いとともに、高温雰囲気で使用する場合には、負極の酸化を抑制することができず、充放電サイクル特性が向上しないという問題を生じた。
【０００８】
そこで、本発明は上記問題点を解消するためになされたものであって、イットリウムあるいはイッテルビウムの水素吸蔵合金負極への添加量が少量であっても、高温雰囲気で使用した場合でも、酸化抑制効果に優れ、かつサイクル特性に優れたアルカリ蓄電池を提供することを目的とするものである。
【０００９】
【課題を解決するための手段およびその作用・効果】
上記目的を達成するため、本発明のアルカリ蓄電池は、表面にイットリウムあるいはイッテルビウムの金属、金属酸化物あるいは金属水酸化物から選択される１種以上の粉末粒子と炭素粉末とを備えた負極と、主活物質として水酸化ニッケルを含有する正極と、アルカリ電解液とを備えるようにしている。
【００１０】
炭素粉末は非常に大きな比表面積を有するため、イットリウムあるいはイッテルビウムの金属、金属酸化物あるいは金属水酸化物から選択される１種以上の粉末粒子と炭素粉末とを負極表面に備えるようにすると、非常に大きな比表面積を有する炭素粉末の表面にイットリウムあるいはイッテルビウムの化合物（これらの金属の酸化物あるいは水酸化物）が吸着して、酸素ガス吸収の触媒として作用するため、少量の添加量であっても酸化抑制効果が得られるようになる。
【００１１】
この場合、炭素粉末としては比表面積が大きい粉末であれば何でもよいが、活性炭、黒鉛、アセチレンブラック、カーボンブラック、ケッチェンブラック等を用いるのが好ましい。また、イットリウムあるいはイッテルビウムの金属、金属酸化物あるいは金属水酸化物から選択される粉末粒子の添加量は、少なすぎると酸化抑制効果を発揮することができず、多すぎると水素吸蔵合金負極の表面を覆ってしまうことにより、円滑な酸素ガス吸収反応が阻害されるため、水素吸蔵合金の質量に対して１〜１００００ｐｐｍであることが望ましい。
【００１２】
また、イットリウムあるいはイッテルビウムの金属、金属酸化物あるいは金属水酸化物から選択される粉末粒子の平均粒径が大きくなるとサイクル寿命が低下する傾向があったため、その平均粒径（レーザー法による）は５μｍ以下とすることが望ましい。さらに、イットリウムあるいはイッテルビウムの金属、金属酸化物あるいは金属水酸化物から選択される粉末粒子の比表面積が小さくなるとサイクル寿命が低下する傾向があったため、その比表面積（ＢＥＴ窒素吸着法による）は１５ｍ2／ｇ以上とすることが望ましい。
【００１３】
【発明の実施の形態】
以下に、本発明のニッケル−水素蓄電池の実施の形態を説明する。
１．水素吸蔵合金の作製
ＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6（なお、Ｍｍはミッシュメタルである）となるように市販の各金属元素（Ｍｍ，Ｎｉ，Ｃｏ，Ａｌ，Ｍｎ）を秤量して混合する。このものを高周波溶解炉に投入して溶解させた後、鋳型に流し込み、冷却してＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金の塊（インゴット）を作製した。この水素吸蔵合金の塊を粗粉砕した後、不活性ガス雰囲気中で平均粒径が５０μｍ程度になるまで機械的に粉砕して、水素吸蔵合金粉末を作製した。
【００１４】
２．水素吸蔵合金塗着極板の作製
上述のようにして作製された水素吸蔵合金粉末９９質量％に、結着剤としてポリエチレンオキサイド（ＰＥＯ）粉末を水素吸蔵合金粉末質量に対して１％と、適量の水を加えて混練して、水素吸蔵合金スラリー▲１▼を作製した。この水素吸蔵合金スラリー▲１▼を、表面にニッケルメッキを施したパンチングメタル等からなる金属芯体の両面に塗着した後、乾燥させ、圧延することにより、水素吸蔵合金塗着極板ｚ1を作製した。なお、水素吸蔵合金スラリー▲１▼の塗着量は圧延後の水素吸蔵合金密度が５ｇ／ｃｍ3となるように調整した。
【００１５】
一方、上述のようにして作製された水素吸蔵合金粉末９９質量％と酸化イットリウム粉末０．５質量％との混合粉末９９質量％に、結着剤としてポリエチレンオキサイド（ＰＥＯ）粉末を水素吸蔵合金粉末質量に対して１質量％と、適量の水を加えて混練して、水素吸蔵合金スラリー▲２▼を作製した。この水素吸蔵合金スラリー▲２▼を、表面にニッケルメッキを施したパンチングメタル等からなる金属芯体の両面に塗着した後、乾燥させ、圧延することにより、水素吸蔵合金塗着極板ｗ1を作製した。なお、水素吸蔵合金スラリー▲２▼の塗着量は圧延後の水素吸蔵合金密度が５ｇ／ｃｍ3となるように調整した。
【００１６】
３．分散液の作製
ついで、レーザー法による平均粒径が３μｍで、ＢＥＴ窒素吸着法による比表面積が２０ｍ2／ｇの酸化イットリウム粉末を用意した後、この酸化イットリウム粉末５質量％と、アセチレンブラック粉末５質量％とを、９０質量％のポリビニルアルコール（ＰＶＡ）の４質量％水溶液に添加混合して分散液αを作製した。
また、同様に、レーザー法による平均粒径が３μｍで、ＢＥＴ窒素吸着法による比表面積が２０ｍ2／ｇの酸化イッテルビウム粉末を用意した後、この酸化イッテルビウム粉末５質量％と、アセチレンブラック粉末５質量％とを、９０質量％のポリビニルアルコール（ＰＶＡ）の４質量％水溶液に添加混合して分散液βを作製した。
【００１７】
また、アセチレンブラック粉末５質量％を９５質量％のポリビニルアルコール（ＰＶＡ）の４質量％水溶液に添加混合して分散液γを作製した。
さらに、レーザー法による平均粒径が３μｍで、ＢＥＴ窒素吸着法による比表面積が２０ｍ2／ｇの酸化イッテルビウム粉末を用意した後、この酸化イッテルビウム粉末５質量％を９５質量％のポリビニルアルコール（ＰＶＡ）の４質量％水溶液に添加混合して分散液δを作製した。
【００１８】
４．水素吸蔵合金電極の作製
ついで、上述のようにして作製した分散液αをローラー転写による方法で、上述のように作製した水素吸蔵合金塗着極板ｚ1の両面に塗布し、乾燥させた後、圧延を行って所定の寸法に切断して、被覆材を塗着した水素吸蔵合金電極ａ〜ｊを作製した。なお、分散液αの塗布量は水素吸蔵合金質量に対して酸化イットリウムが０．５〜２００００ｐｐｍとなるように調整して塗布した。ここで、水素吸蔵合金質量に対して酸化イットリウムが０．５ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ａとした。
【００１９】
同様に、酸化イットリウムが１ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｂとし、５ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｃとし、１０ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｄとし、１００ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｅとし、５００ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｆとし、１０００ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｇとし、５０００ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｈとし、１００００ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｉとし、２００００ｐｐｍとなるように塗布されたものを水素吸蔵合金電極ｊとした。
【００２０】
また、上述のようにして作製した分散液βをローラー転写による方法で、上述のように作製した水素吸蔵合金負極板ｚ1の両面に、水素吸蔵合金質量に対して酸化イッテルビウムが５０００ｐｐｍとなるように塗布し、乾燥させた後、圧延を行い、所定の寸法に切断して、被覆材を塗着した水素吸蔵合金電極ｋを作製した。
また、上述のようにして作製した分散液γをローラー転写による方法で、上述のように作製した水素吸蔵合金負極板ｚ1の両面に、水素吸蔵合金質量に対してアセチレンブラックが０．５質量％となるように塗布し、乾燥させた後、圧延を行い、所定の寸法に切断して、被覆材を塗着した水素吸蔵合金電極ｖを作製した。
【００２１】
また、上述のようにして作製した水素吸蔵合金塗着極板ｗ1を所定の寸法に切断して、水素吸蔵合金電極ｗを作製した。
また、上述のようにして作製した分散液δをローラー転写による方法で、上述のように作製した水素吸蔵合金負極板ｚ1の両面に、水素吸蔵合金質量に対して酸化イットリウムが０．５質量％となるように塗布し、乾燥させた後、圧延を行い、所定の寸法に切断して、被覆材を塗着した水素吸蔵合金電極ｘを作製した。
さらに、上述のようにして作製した水素吸蔵合金塗着極板ｚ1を所定の寸法に切断して、水素吸蔵合金電極ｚを作製した。
【００２２】
３．ニッケル正極の作製
共沈成分として亜鉛を２．５質量％とコバルトを１．０質量％含有する水酸化ニッケル粉末を硫酸コバルト水溶液に投入し、撹拌しながら１モルの水酸化ナトリウム水溶液を徐々に滴下し、反応中のｐＨを１１に調整した後、撹拌を続けて反応させた。この時のｐＨの監視は自動温度補償付きガラス電極（ｐＨメータ）にて行った。次いで、沈殿物をろ別し、水洗し、真空乾燥して水酸化ニッケル粒子の表面が５質量％の水酸化コバルトで被覆された粉末を得た。
【００２３】
ついで、得られた粉末をビーカー中で撹拌しながら、これに２５質量％の水酸化ナトリウム水溶液を質量比が１：１０となるように加えて含浸させ、８時間撹拌しながら８５℃の温度雰囲気で加熱処理することによるアルカリ熱処理を施した後、水洗して、６５℃で乾燥した。このアルカリ熱処理により水酸化コバルトの一部が高次化されると共に、ナトリウムが含有される。これにより、水酸化コバルト被覆層中に１質量％のナトリウムを含有する複合体粒子が得られた。
【００２４】
ついで、上述のようにして得られた複合体粒子を９５質量％と酸化亜鉛３質量％と水酸化コバルト２質量％とからなる混合粉末に、結着剤としてのヒドロキシプロピルセルロースの０．２質量％水溶液を混合粉末の質量に対して５０質量％を添加、混合して、正極活物質スラリーを作製した。この後、この正極活物質スラリーをニッケル発泡体（例えば、面密度（目付）が約６００ｇ／ｍ2で、多孔度が９５％で、厚みが約２ｍｍのもの）からなる発泡ニッケル基板の空孔内に充填し、乾燥させ、圧延を行った後、所定の寸法に切断して、非焼結式ニッケル正極板を得た。なお、正極活物質スラリーの充填量は、圧延後の活物質密度が約２．９ｇ／ｃｍ3−ｖｏｉｄとなるように調整した。
【００２５】
４．ニッケル−水素蓄電池の作製
上述のように作製した各水素吸蔵合金負極板ａ〜ｋ、ｖ，ｗ，ｘ，ｚと上述のように作製した非焼結式ニッケル正極板にそれぞれ集電タブを取り付けた後、これらの各極板を厚みが０．２ｍｍのポリプロピレン製不織布からなるセパレータを介して渦巻状に巻回して渦巻状電極群をそれぞれ作製した。この後、各渦巻状極板群をそれぞれＡＡサイズの有底円筒状の金属外装缶内に挿入し、負極集電タブを外装缶の内底面に溶接するとともに、正極集電タブを封口体の底面に溶接した。ついで、各金属外装缶内にそれぞれアルカリ電解液（ＬｉＯＨとＮａＯＨを含有した８ＮのＫＯＨ水溶液）を注入した後、封口体で密封して、公称容量が１３００ｍＡｈのニッケル−水素蓄電池をそれぞれ作製した。
【００２６】
なお、水素吸蔵合金負極板ａを用いたニッケル−水素蓄電池を電池Ａとし、水素吸蔵合金負極板ｂを用いたニッケル−水素蓄電池を電池Ｂとし、水素吸蔵合金負極板ｃを用いたニッケル−水素蓄電池を電池Ｃとし、水素吸蔵合金負極板ｄを用いたニッケル−水素蓄電池を電池Ｄとし、水素吸蔵合金負極板ｅを用いたニッケル−水素蓄電池を電池Ｅとし、水素吸蔵合金負極板ｆを用いたニッケル−水素蓄電池を電池Ｆとし、水素吸蔵合金負極板ｇを用いたニッケル−水素蓄電池を電池Ｇとし、水素吸蔵合金負極板ｈを用いたニッケル−水素蓄電池を電池Ｈとし、水素吸蔵合金負極板ｉを用いたニッケル−水素蓄電池を電池Ｉとし、水素吸蔵合金負極板ｊを用いたニッケル−水素蓄電池を電池Ｊとし、水素吸蔵合金負極板ｋを用いたニッケル−水素蓄電池を電池Ｋとした。
【００２７】
また、水素吸蔵合金負極板ｖを用いたニッケル−水素蓄電池を電池Ｖとし、水素吸蔵合金負極板ｗを用いたニッケル−水素蓄電池を電池Ｗとし、水素吸蔵合金負極板ｘを用いたニッケル−水素蓄電池を電池Ｘとし、水素吸蔵合金負極板ｚを用いたニッケル−水素蓄電池を電池Ｚとした。
また、水素吸蔵合金負極板ｚを用いて、上述と同様に渦巻状電極群を作製した後、上述と同様にＡＡサイズの有底円筒状の金属外装缶内に挿入し、負極集電タブを外装缶の内底面に溶接するとともに、正極集電タブを封口体の底面に溶接した。ついで、酸化イットリウムを室温（２５℃）で飽和させたアルカリ電解液を注入した後、封口体で密封して、公称容量が１３００ｍＡｈのニッケル−水素蓄電池を作製した。このニッケル−水素蓄電池を電池Ｙとした。
【００２８】
５．電池試験
（１）活性化
上述のように作製した各電池Ａ〜ＫおよびＶ〜Ｚを、室温（２５℃）で１３０ｍＡ（０．１Ｃ）の充電々流で１６時間充電した後、１時間休止させる。その後、２６０ｍＡ（０．２Ｃ）の放電々流で終止電圧が１．０Ｖになるまで放電させた後、１時間休止させる。この充放電を室温（２５℃）で５サイクル繰り返して、各ニッケル−水素蓄電池Ａ〜ＫおよびＶ〜Ｚを活性化した。
【００２９】
（２）高温連続充電特性試験
ついで、上述のように活性化した各電池Ａ〜ＫおよびＶ〜Ｚを、室温（２５℃）で１３０ｍＡ（０．１Ｃ）の充電々流で１６時間充電し、室温（２５℃）で１時間休止させた後、室温（２５℃）で１３００ｍＡ（１．０Ｃ）の放電々流で終止電圧が１．０Ｖになるまで放電させて、放電時間から室温（２５℃）での放電容量を求めて、初期電池容量とした。
【００３０】
次に、上述のように初期電池容量を測定した後の各電池Ａ〜ＫおよびＶ〜Ｚを、６０℃の恒温槽内に配置し、２６０ｍＡ（０．２Ｃ）の充電々流で連続充電を開始した。連続充電を開始してから、２日間隔（１日おき）に恒温槽から各電池Ａ〜ＫおよびＶ〜Ｚを取り出して、室温（２５℃）にて３時間放置した後、室温（２５℃）で１３００ｍＡ（１Ｃ）の放電々流で終止電圧が１．０Ｖになるまで放電させて、このときの各電池Ａ〜ＫおよびＶ〜Ｚの放電容量を求めた。
ついで、予め求めた初期電池容量との比率を算出し、その割合が３０％以下になった時点で電池寿命として求めると、下記の表１に示すような結果となった。なお、表１の添加量（ＰＰＭ）、平均粒径（μｍ）および比表面積（ｍ2／ｇ）は、酸化イットリウムまたは酸化イッテルビウムの添加量（ＰＰＭ）、平均粒径（μｍ）および比表面積（ｍ2／ｇ）をそれぞれ示している。
【００３１】
【表１】
上記表１から明らかなように、アセチレンブラック（炭素粉末）も酸化イットリウムまたは酸化イッテルビウムも無添加の負極板を用いた電池Ｚの電池寿命が６８日で、アセチレンブラック（炭素粉末）のみを負極板の表面に塗布した負極板を用いた電池Ｖの電池寿命が７０日で、酸化イットリウムを負極板に添加した負極板を用いた電池Ｗの電池寿命が７２日で、酸化イットリウムのみを負極板の表面に塗布した負極板を用いた電池Ｘの電池寿命が７４日で、無添加の負極板を用い電解液中に酸化イットリウムを添加した電池Ｙの電池寿命が７２日であることからすると、アセチレンブラック（炭素粉末）のみを添加しても、酸化イットリウムまたは酸化イッテルビウムのみを添加しても、電池寿命がそれほど向上しないことが分かる。
【００３３】
これに対して、アセチレンブラック（炭素粉末）と酸化イットリウムまたは酸化イッテルビウムとを同時に負極板の表面に塗布した負極板を用いた電池Ａ〜Ｋにあっては、電池寿命が８０日以上に向上していることが分かる。これは、同時に添加された非常に大きな比表面積を有するアセチレンブラックの表面に酸化イットリウムまたは酸化イッテルビウムが吸着して、酸素ガス吸収の触媒として作用し、結果として、水素吸蔵合金の酸化が抑制されて電池寿命が向上したと考えられる。
【００３４】
また、酸化イットリウムまたは酸化イッテルビウムの添加量を１〜１００００ｐｐｍに制限した電池Ｂ〜Ｉおよび電池Ｋにあっては、９０日〜１２０日となり、電池寿命が飛躍的に向上していることが分かる。これは、酸化イットリウムまたは酸化イッテルビウムの添加量が１ｐｐｍ未満であると、添加量が少なすぎて、添加効果を発揮させることができないためである。
逆に、添加量が１００００ｐｐｍを越えると、酸化イットリウムまたは酸化イッテルビウムが水素吸蔵合金の表面を覆ってしまうことにより、円滑な酸素ガス吸収反応が阻害されるためと考えられる。
なお、表１においては、酸化イッテルビウムの添加量が５０００ｐｐｍの場合しか示されていないが、酸化イッテルビウムの添加量を変化させても酸化イットリウムの場合とほぼ同様な結果が得られた。
【００３５】
６．酸化イットリウムの物性値の検討
レーザー法による平均粒径が１０μｍで、ＢＥＴ窒素吸着法による比表面積が１８ｍ2／ｇの酸化イットリウム粉末を用意した後、この酸化イットリウム粉末５質量％と、アセチレンブラック粉末５質量％とを、９０質量％のポリビニルアルコール（ＰＶＡ）の４質量％水溶液に添加混合して分散液を作製した後、ローラー転写による方法で、上述のように作製した水素吸蔵合金塗着極板ｚ1の両面に塗布し、乾燥させた後、圧延を行って所定の寸法に切断して、被覆材を塗着した水素吸蔵合金電極ｌを作製した。
【００３６】
同様に、平均粒径が５μｍで、比表面積が１９ｍ2／ｇの酸化イットリウム粉末を用いて水素吸蔵合金電極ｍを作製し、平均粒径が３μｍで、比表面積が１０ｍ2／ｇの酸化イットリウム粉末を用いて水素吸蔵合金電極ｎを作製し、平均粒径が３μｍで、比表面積が１５ｍ2／ｇの酸化イットリウム粉末を用いて水素吸蔵合金電極ｏを作製した。なお、これらの分散液の塗布量は水素吸蔵合金質量に対して酸化イットリウムが５０００ｐｐｍとなるように調整して塗布した。
【００３７】
ついで、各水素吸蔵合金負極板ｌ〜ｏと上述のように作製した非焼結式ニッケル正極板にそれぞれ集電タブを取り付けた後、これらの各極板を厚みが０．２ｍｍのポリプロピレン製不織布からなるセパレータを介して渦巻状に巻回して渦巻状電極群をそれぞれ作製した。この後、各渦巻状極板群をそれぞれＡＡサイズの有底円筒状の金属外装缶内に挿入し、各金属外装缶内にそれぞれアルカリ電解液（ＬｉＯＨとＮａＯＨを含有した８ＮのＫＯＨ水溶液）を注入した後、封口体で密封して、公称容量が１３００ｍＡｈのニッケル−水素蓄電池Ｌ〜Ｏをそれぞれ作製した。
ついで、これらの各電池Ｌ〜Ｏを用いて、上述と同様に活性化した後、上述と同様な連続充電を行って電池寿命を測定すると、下記の表２に示すような結果となった。なお、表２の添加量（ＰＰＭ）、平均粒径（μｍ）および比表面積（ｍ2／ｇ）は、酸化イットリウムの添加量（ＰＰＭ）、平均粒径（μｍ）および比表面積（ｍ2／ｇ）をそれぞれ示している。また、表２には上述した電池Ｈについても併せて示している。
【００３８】
【表２】
上記表２より明らかなように、酸化イットリウムの平均粒径が５μｍを越えると電池寿命が短くなる傾向が認められ、また、酸化イットリウムの比表面積が１５ｍ2/ｇより小さくなると電池寿命が短くなる傾向が認められる。このことから、酸化イットリウムの平均粒径は５μｍ以下であることが望ましく、酸化イットリウムの比表面積は１５ｍ2/ｇ以上であることが望ましいということができる。なお、このことは、酸化イッテルビウムについても同様である。
【００４０】
上述したように、本発明においては、アセチレンブラック（炭素粉末）と酸化イットリウムまたは酸化イッテルビウムとを同時に負極板の表面に塗布しているので、非常に大きな比表面積を有するアセチレンブラックの表面に酸化イットリウムまたは酸化イッテルビウムが吸着する。そして、アセチレンブラックの表面に吸着した酸化イットリウムまたは酸化イッテルビウムは酸素ガス吸収の触媒として作用するため、水素吸蔵合金の酸化が抑制され、電池寿命が向上する。
【００４１】
なお、上述した実施の形態においては、炭素粉末としてアセチレンブラックを用いる例について説明したが、炭素粉末としては比表面積が大きい粉末であれば何でもよく、活性炭、黒鉛、アセチレンブラック、カーボンブラック、ケッチェンブラック等を用いるのが好ましい。
【００４２】
また、上述した実施の形態においては、水素吸蔵合金としてＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6を用いる例について説明したが、水素吸蔵合金としてはＴｉ−Ｎｉ系あるいはＬａ（もしくはＭｍ）−Ｎｉ系の多元合金から適宜選択して使用することができる。また、上述した実施の形態においては、機械的に粉砕した水素吸蔵合金を用いる例について説明したが、アトマイズ法により作製した水素吸蔵合金を用いてもよい。この場合、アトマイズ法により作製した水素吸蔵合金は比表面積が小さいため、本発明を適用するとさらに効果的である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a negative electrode made of a hydrogen storage alloy capable of reversibly storing and releasing hydrogen electrochemically, a positive electrode containing nickel hydroxide as a main active material, and a nickel having an alkaline electrolyte. -Relating to hydrogen storage batteries.
[0002]
[Prior art]
Alkaline storage batteries are widely used as various power sources, small batteries are used for various portable electronic and communication devices, and large batteries are used for industrial purposes. In order to increase the capacity of this type of alkaline storage battery, nickel-hydrogen storage batteries using hydrogen storage alloy electrodes have come into practical use. A nickel electrode is used for the positive electrode of the nickel-hydrogen storage battery, and a hydrogen storage alloy electrode is used for the negative electrode. As the hydrogen storage alloy used for the negative electrode of the nickel-hydrogen storage battery, Ti—Ni alloy, La or Mm (Misch metal) —Ni alloy, or the like is used.
[0003]
The nickel-hydrogen storage battery as described above has a high capacity and needs to have a long life, and in order to have a long life, it is necessary to improve the corrosion resistance of the hydrogen storage alloy. Therefore, it has been proposed in Japanese Patent Application Laid-Open No. 6-215765 to suppress deterioration due to oxidation of the hydrogen storage alloy by containing yttrium or an yttrium compound in the negative electrode of the hydrogen storage alloy.
In the hydrogen storage alloy negative electrode proposed in Japanese Patent Application Laid-Open No. 6-215765, the addition amount of yttrium or an yttrium compound (hydrogen storage alloy 100) is required in order to fully exhibit the effect of adding yttrium or an yttrium compound. It is necessary to increase 0.1 parts by mass or more with respect to parts by mass, and yttrium or an yttrium compound is very expensive.
[0004]
On the other hand, in order to reduce the addition amount of rare earth elements such as yttrium and ytterbium to the alloy surface, the inside of the negative electrode, and the outer surface of the negative electrode, at least one of yttrium ions and other rare earth elements is used as ions in the alkaline electrolyte. Inclusion has been proposed in JP-A-10-106620. As a result, at least one kind of ions of rare earth elements are uniformly dispersed on the surface of the particles constituting the hydrogen storage alloy negative electrode and adsorbed on the surface, and the negative electrode surface is coated to suppress oxidation of the negative electrode, and charge / discharge cycle characteristics The improvement effect can be obtained.
[0005]
[Problems to be solved by the invention]
By the way, in a nickel-hydrogen battery using this type of hydrogen storage alloy negative electrode, it may be used in an atmosphere of high temperature (45 ° C. or higher). It is necessary to prevent the hydrogen storage alloy negative electrode from being oxidized even if continuous charging is performed in an atmosphere.
[0006]
However, in general, the hydrogen ion concentration (pH) of an alkaline electrolyte used in a nickel-hydrogen battery is about 13, and rare earth elements such as yttrium and ytterbium are insoluble or sparingly soluble at this pH. Even if added as proposed in Kaihei 10-106620, only a small amount of rare earth elements can be dissolved in the alkaline electrolyte, and the negative electrode surface is sufficiently covered with rare earth elements such as yttrium and ytterbium. It was difficult. For this reason, the effect of adding rare earth elements such as yttrium and ytterbium cannot be sufficiently exerted, and in particular, when used in a high temperature atmosphere, the oxidation of the negative electrode cannot be suppressed, and charge / discharge cycle characteristics. Caused the problem of not improving.
[0007]
It is also possible to improve the battery characteristics at low temperature by adding 0.2 to 1.0% by mass of a compound of at least one element selected from the group consisting of yttrium and ytterbium to the hydrogen storage alloy. In this case, the amount of elements consisting of yttrium and ytterbium is increased, so that it becomes very expensive and low in commerciality, and when used in a high-temperature atmosphere, There was a problem that the oxidation of the negative electrode could not be suppressed and the charge / discharge cycle characteristics were not improved.
[0008]
Therefore, the present invention has been made to solve the above problems, and even if the amount of yttrium or ytterbium added to the hydrogen storage alloy negative electrode is small, even when used in a high-temperature atmosphere, the effect of suppressing oxidation. It is an object of the present invention to provide an alkaline storage battery that is excellent in performance and cycle characteristics.
[0009]
[Means for solving the problems and their functions and effects]
In order to achieve the above object, the alkaline storage battery of the present invention comprises a negative electrode provided on the surface with one or more powder particles selected from yttrium or ytterbium metal, metal oxide or metal hydroxide, and carbon powder, A positive electrode containing nickel hydroxide as a main active material and an alkaline electrolyte are provided.
[0010]
Since carbon powder has a very large specific surface area, it is very difficult to provide one or more powder particles selected from yttrium or ytterbium metal, metal oxide or metal hydroxide and carbon powder on the negative electrode surface. Since yttrium or ytterbium compounds (oxides or hydroxides of these metals) are adsorbed on the surface of carbon powder having a large specific surface area and act as a catalyst for oxygen gas absorption, a small amount is added. As a result, an oxidation inhibiting effect can be obtained.
[0011]
In this case, any carbon powder may be used as long as it has a large specific surface area, but activated carbon, graphite, acetylene black, carbon black, ketjen black, or the like is preferably used. Further, if the amount of powder particles selected from yttrium or ytterbium metal, metal oxide or metal hydroxide is too small, the effect of inhibiting oxidation cannot be exhibited, and if too large, the surface of the hydrogen storage alloy negative electrode As a result, the smooth oxygen gas absorption reaction is hindered. Therefore, the content is preferably 1 to 10,000 ppm with respect to the mass of the hydrogen storage alloy.
[0012]
In addition, since the cycle life tends to decrease as the average particle size of powder particles selected from yttrium or ytterbium metal, metal oxide or metal hydroxide increases, the average particle size (by the laser method) is 5 μm. The following is desirable. Furthermore, since the cycle life tends to decrease when the specific surface area of the powder particles selected from yttrium or ytterbium metal, metal oxide or metal hydroxide is reduced, the specific surface area (by BET nitrogen adsorption method) is 15 m. 2 / g or more is desirable.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the nickel-hydrogen storage battery of the present invention will be described below.
1. Production of Hydrogen Storage Alloy Each commercially available metal element (Mm, Ni, Co, Al, Mn) is weighed and mixed so as to be MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 (Mm is Misch metal). This was put into a high frequency melting furnace and melted, then poured into a mold and cooled to prepare a hydrogen storage alloy lump (ingot) composed of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 . This lump of hydrogen storage alloy was coarsely pulverized and then mechanically pulverized in an inert gas atmosphere until the average particle size became about 50 μm to prepare a hydrogen storage alloy powder.
[0014]
2. Preparation of hydrogen storage alloy-coated electrode plate 99% by mass of the hydrogen storage alloy powder prepared as described above, polyethylene oxide (PEO) powder as a binder, 1% with respect to the mass of the hydrogen storage alloy powder, an appropriate amount Was added and kneaded to prepare a hydrogen storage alloy slurry (1). This hydrogen storage alloy slurry {circle around (1)} is applied to both surfaces of a metal core made of punched metal or the like with nickel plated on the surface, then dried and rolled to obtain a hydrogen storage alloy coated electrode plate z 1. Was made. The coating amount of the hydrogen storage alloy slurry (1) was adjusted so that the density of the hydrogen storage alloy after rolling was 5 g / cm 3 .
[0015]
On the other hand, 99% by mass of the hydrogen storage alloy powder 99% by mass and 0.5% by mass of yttrium oxide powder prepared as described above, and polyethylene oxide (PEO) powder as a binder were added to the hydrogen storage alloy powder. An appropriate amount of water, 1% by mass with respect to the mass, was added and kneaded to prepare a hydrogen storage alloy slurry (2). This hydrogen storage alloy slurry {circle around (2)} is applied to both surfaces of a metal core made of a punching metal or the like whose surface is nickel plated, and then dried and rolled to obtain a hydrogen storage alloy coated electrode plate w 1. Was made. The coating amount of the hydrogen storage alloy slurry (2) was adjusted so that the density of the hydrogen storage alloy after rolling was 5 g / cm 3 .
[0016]
3. Next, after preparing a dispersion, an yttrium oxide powder having an average particle diameter of 3 μm by a laser method and a specific surface area of 20 m 2 / g by a BET nitrogen adsorption method was prepared, and 5% by mass of this yttrium oxide powder and an acetylene black powder 5 The dispersion liquid α was prepared by adding and mixing the mass% with a 4 mass% aqueous solution of 90 mass% polyvinyl alcohol (PVA).
Similarly, after preparing an ytterbium oxide powder having an average particle diameter of 3 μm by a laser method and a specific surface area of 20 m 2 / g by a BET nitrogen adsorption method, 5% by mass of this ytterbium oxide powder and 5% by mass of acetylene black powder % Was added to and mixed with a 4% by mass aqueous solution of 90% by mass polyvinyl alcohol (PVA) to prepare a dispersion β.
[0017]
Further, 5% by mass of acetylene black powder was added to and mixed with a 4% by mass aqueous solution of 95% by mass of polyvinyl alcohol (PVA) to prepare a dispersion γ.
Furthermore, after preparing an ytterbium oxide powder having an average particle diameter of 3 μm by a laser method and a specific surface area of 20 m 2 / g by a BET nitrogen adsorption method, 5% by mass of this ytterbium oxide powder is 95% by mass of polyvinyl alcohol (PVA). A dispersion δ was prepared by adding to and mixing with a 4% by mass aqueous solution.
[0018]
4). Preparation of hydrogen storage alloy electrode Next, the dispersion α prepared as described above was applied to both surfaces of the hydrogen storage alloy coated electrode plate z 1 prepared as described above by a roller transfer method and dried. The hydrogen storage alloy electrodes a to j coated with a coating material were produced by rolling and cutting into predetermined dimensions. The amount of dispersion α applied was adjusted so that the amount of yttrium oxide was 0.5 to 20000 ppm relative to the mass of the hydrogen storage alloy. Here, what was apply | coated so that yttrium oxide might be 0.5 ppm with respect to the hydrogen storage alloy mass was set as the hydrogen storage alloy electrode a.
[0019]
Similarly, a hydrogen storage alloy electrode b was applied so that yttrium oxide was 1 ppm, and a hydrogen storage alloy electrode c was applied so as to be 5 ppm. The hydrogen storage alloy electrode d, which was applied to 100 ppm, was the hydrogen storage alloy electrode e, and the one applied to 500 ppm was the hydrogen storage alloy electrode f, and was applied to 1000 ppm. The hydrogen storage alloy electrode g was applied to 5000 ppm, the hydrogen storage alloy electrode h was applied to 10,000 ppm, the hydrogen storage alloy electrode i was applied to 10,000 ppm, and was applied to 20000 ppm. This was used as a hydrogen storage alloy electrode j.
[0020]
Further, the dispersion β prepared as described above is transferred by roller transfer so that the ytterbium oxide is 5000 ppm on both sides of the hydrogen storage alloy negative electrode plate z 1 prepared as described above with respect to the mass of the hydrogen storage alloy. After being applied to and dried, it was rolled, cut to a predetermined size, and a hydrogen storage alloy electrode k coated with a coating material was produced.
Further, the dispersion γ prepared as described above was transferred by roller transfer to the hydrogen storage alloy negative electrode plate z 1 prepared as described above on both sides of the hydrogen storage alloy negative electrode plate z 1 with 0.5 mass of acetylene black relative to the mass of the hydrogen storage alloy. %, And then dried, cut to a predetermined size, and produced a hydrogen storage alloy electrode v coated with a coating material.
[0021]
Further, the hydrogen storage alloy coated electrode plate w 1 manufactured as described above was cut into a predetermined size to prepare a hydrogen storage alloy electrode w.
In addition, the dispersion liquid δ produced as described above was transferred onto the both surfaces of the hydrogen storage alloy negative electrode plate z 1 produced as described above by a method using roller transfer, and 0.5 mass of yttrium oxide was added to the mass of the hydrogen storage alloy. %, And dried, cut to a predetermined size, and produced a hydrogen storage alloy electrode x coated with a coating material.
Further, the hydrogen storage alloy-coated electrode plate z 1 manufactured as described above was cut into a predetermined size to prepare a hydrogen storage alloy electrode z.
[0022]
3. Nickel hydroxide powder containing 2.5% by mass of zinc and 1.0% by mass of cobalt as a coprecipitation component for nickel positive electrode was added to a cobalt sulfate aqueous solution, and 1 mol of sodium hydroxide aqueous solution was gradually added while stirring. After dropwise addition and adjusting the pH during the reaction to 11, the reaction was continued with stirring. The pH at this time was monitored with a glass electrode (pH meter) with automatic temperature compensation. Next, the precipitate was separated by filtration, washed with water, and vacuum dried to obtain a powder in which the surface of nickel hydroxide particles was coated with 5% by mass of cobalt hydroxide.
[0023]
Next, while stirring the obtained powder in a beaker, a 25 mass% sodium hydroxide aqueous solution was added to impregnate the mass ratio to 1:10, and the temperature atmosphere at 85 ° C. was stirred for 8 hours. After performing an alkali heat treatment by heat treatment with, the product was washed with water and dried at 65 ° C. This alkali heat treatment increases a part of the cobalt hydroxide and contains sodium. As a result, composite particles containing 1% by mass of sodium in the cobalt hydroxide coating layer were obtained.
[0024]
Subsequently, the composite particles obtained as described above were mixed with 95% by mass, 3% by mass of zinc oxide and 2% by mass of cobalt hydroxide, and 0.2% by mass of hydroxypropylcellulose as a binder. A positive electrode active material slurry was prepared by adding and mixing 50% by weight of an aqueous solution with respect to the weight of the mixed powder. Thereafter, the positive electrode active material slurry is made of a nickel foam (for example, having a surface density (weight per unit area) of about 600 g / m 2 , a porosity of 95%, and a thickness of about 2 mm). It was filled in, dried, rolled, and then cut into predetermined dimensions to obtain a non-sintered nickel positive electrode plate. The filling amount of the positive electrode active material slurry was adjusted so that the active material density after rolling was about 2.9 g / cm 3 -void.
[0025]
4). Production of Nickel-Hydrogen Storage Battery Attaching a current collecting tab to each of the hydrogen storage alloy negative electrode plates a to k, v, w, x, z produced as described above and the non-sintered nickel positive electrode plate produced as described above. After that, each of these electrode plates was spirally wound through a separator made of a polypropylene nonwoven fabric having a thickness of 0.2 mm to produce a spiral electrode group. Thereafter, each spiral electrode group is inserted into an AA size bottomed cylindrical metal outer can, the negative electrode current collecting tab is welded to the inner bottom surface of the outer can, and the positive electrode current collecting tab is attached to the sealing body. Welded to the bottom. Next, an alkaline electrolyte (8N KOH aqueous solution containing LiOH and NaOH) was injected into each metal outer can, and then sealed with a sealing body to produce a nickel-hydrogen storage battery having a nominal capacity of 1300 mAh.
[0026]
The nickel-hydrogen storage battery using the hydrogen storage alloy negative electrode plate a is battery A, the nickel-hydrogen storage battery using the hydrogen storage alloy negative electrode plate b is battery B, and the nickel-hydrogen storage using the hydrogen storage alloy negative electrode plate c. The storage battery is battery C, the nickel-hydrogen storage battery using the hydrogen storage alloy negative electrode plate d is battery D, the nickel-hydrogen storage battery using the hydrogen storage alloy negative electrode plate e is battery E, and the hydrogen storage alloy negative electrode plate f is used. The nickel-hydrogen storage battery used as battery F, the nickel-hydrogen storage battery using hydrogen storage alloy negative electrode plate g as battery G, the nickel-hydrogen storage battery using hydrogen storage alloy negative electrode plate h as battery H, and the hydrogen storage alloy negative electrode. Nickel-hydrogen storage battery using plate i is battery I, nickel-hydrogen storage battery using hydrogen storage alloy negative electrode plate j is battery J, and nickel-water using hydrogen storage alloy negative electrode plate k The battery was a battery K.
[0027]
The nickel-hydrogen storage battery using the hydrogen storage alloy negative electrode plate v is referred to as battery V, the nickel-hydrogen storage battery using the hydrogen storage alloy negative electrode plate w is referred to as battery W, and nickel-hydrogen using the hydrogen storage alloy negative electrode plate x. The storage battery was designated as battery X, and the nickel-hydrogen storage battery using the hydrogen storage alloy negative electrode plate z was designated as battery Z.
In addition, after preparing a spiral electrode group in the same manner as described above using the hydrogen storage alloy negative electrode plate z, it is inserted into an AA size bottomed cylindrical metal outer can in the same manner as described above, and a negative electrode current collecting tab is provided. While welding to the inner bottom face of an exterior can, the positive electrode current collection tab was welded to the bottom face of the sealing body. Next, after injecting an alkaline electrolyte saturated with yttrium oxide at room temperature (25 ° C.), it was sealed with a sealing body to produce a nickel-hydrogen storage battery having a nominal capacity of 1300 mAh. This nickel-hydrogen storage battery was designated as battery Y.
[0028]
5. Battery Test (1) Activation Each battery AK and VZ prepared as described above was charged at room temperature (25 ° C.) with a charging current of 130 mA (0.1 C) for 16 hours, and then rested for 1 hour. Let Thereafter, the battery is discharged at a discharge current of 260 mA (0.2 C) until the final voltage reaches 1.0 V, and then rested for 1 hour. This charging / discharging was repeated 5 cycles at room temperature (25 ° C.) to activate the nickel-hydrogen storage batteries A to K and V to Z.
[0029]
(2) High-temperature continuous charge characteristics test Next, the batteries A to K and V to Z activated as described above were charged for 16 hours at room temperature (25 ° C.) with a charging current of 130 mA (0.1 C), After resting at room temperature (25 ° C.) for 1 hour, the battery was discharged at room temperature (25 ° C.) with a discharge current of 1300 mA (1.0 C) until the final voltage reached 1.0 V, and from the discharge time to room temperature (25 ° C. ) To obtain the initial battery capacity.
[0030]
Next, the batteries A to K and V to Z after measuring the initial battery capacity as described above are placed in a constant temperature bath of 60 ° C., and continuous charging is performed at a charging current of 260 mA (0.2 C). Started. After starting continuous charging, the batteries A to K and V to Z were taken out from the thermostat at intervals of 2 days (every other day) and left at room temperature (25 ° C.) for 3 hours. ) At a discharge current of 1300 mA (1C) until the final voltage reached 1.0 V, and the discharge capacities of the batteries A to K and V to Z at this time were determined.
Next, when the ratio with the initial battery capacity obtained in advance was calculated and the battery life was obtained when the ratio became 30% or less, the results shown in Table 1 below were obtained. The addition amount (PPM), average particle diameter (μm) and specific surface area (m 2 / g) in Table 1 are the addition amount (PPM), average particle diameter (μm) and specific surface area (m / g) of yttrium oxide or ytterbium oxide. m 2 / g), respectively.
[0031]
[Table 1]
As apparent from Table 1 above, the battery life of the battery Z using the negative electrode plate to which neither acetylene black (carbon powder) nor yttrium oxide or ytterbium oxide was added was 68 days, and only acetylene black (carbon powder) was used as the negative electrode plate. The battery life of the battery V using the negative electrode plate coated on the surface of the battery is 70 days, the battery life of the battery W using the negative electrode plate added with yttrium oxide to the negative electrode plate is 72 days, and only the yttrium oxide is used for the negative electrode plate. The battery life of the battery X using the negative electrode plate coated on the surface is 74 days, and the battery life of the battery Y using the additive-free negative electrode plate with yttrium oxide added to the electrolyte is 72 days. It can be seen that even when only black (carbon powder) is added or only yttrium oxide or ytterbium oxide is added, the battery life is not improved so much.
[0033]
On the other hand, in the batteries A to K using the negative electrode plate in which acetylene black (carbon powder) and yttrium oxide or ytterbium oxide are simultaneously applied to the surface of the negative electrode plate, the battery life is improved to 80 days or more. I understand that This is because yttrium oxide or ytterbium oxide is adsorbed on the surface of acetylene black having a very large specific surface area added at the same time, and acts as a catalyst for oxygen gas absorption. As a result, oxidation of the hydrogen storage alloy is suppressed. The battery life is considered to have improved.
[0034]
In addition, in the batteries B to I and the battery K in which the addition amount of yttrium oxide or ytterbium oxide is limited to 1 to 10000 ppm, it is 90 days to 120 days, which shows that the battery life is dramatically improved. This is because if the addition amount of yttrium oxide or ytterbium oxide is less than 1 ppm, the addition amount is too small to exhibit the effect of addition.
On the contrary, when the addition amount exceeds 10,000 ppm, it is considered that yttrium oxide or ytterbium oxide covers the surface of the hydrogen storage alloy, thereby inhibiting a smooth oxygen gas absorption reaction.
In Table 1, although only the case where the amount of ytterbium oxide added is 5000 ppm, the same results as in the case of yttrium oxide were obtained even when the amount of ytterbium oxide added was changed.
[0035]
6). Examination of physical property values of yttrium oxide After preparing an yttrium oxide powder having an average particle diameter of 10 μm by a laser method and a specific surface area of 18 m 2 / g by a BET nitrogen adsorption method, 5% by mass of this yttrium oxide powder and an acetylene black powder 5 wt% was added to and mixed with a 4 wt% aqueous solution of 90 wt% polyvinyl alcohol (PVA) to prepare a dispersion, and then a hydrogen storage alloy coated electrode prepared as described above by a roller transfer method. After applying and drying on both surfaces of the plate z 1 , rolling was performed and cut to a predetermined size to produce a hydrogen storage alloy electrode l coated with a coating material.
[0036]
Similarly, a hydrogen storage alloy electrode m was prepared using yttrium oxide powder having an average particle diameter of 5 μm and a specific surface area of 19 m 2 / g, and yttrium oxide having an average particle diameter of 3 μm and a specific surface area of 10 m 2 / g. A hydrogen storage alloy electrode n was prepared using the powder, and a hydrogen storage alloy electrode o was prepared using an yttrium oxide powder having an average particle diameter of 3 μm and a specific surface area of 15 m 2 / g. The coating amount of these dispersions was adjusted and applied so that yttrium oxide was 5000 ppm with respect to the mass of the hydrogen storage alloy.
[0037]
Next, after attaching a current collecting tab to each of the hydrogen storage alloy negative electrode plates l to o and the non-sintered nickel positive electrode plate prepared as described above, each of these electrode plates is made of a polypropylene nonwoven fabric having a thickness of 0.2 mm. Each of the spiral electrode groups was produced by spirally winding through a separator made of After that, each spiral electrode group is inserted into an AA size bottomed cylindrical metal outer can, and an alkaline electrolyte (8N KOH aqueous solution containing LiOH and NaOH) is placed in each metal outer can. After the injection, the nickel-hydrogen storage batteries L to O having a nominal capacity of 1300 mAh were prepared by sealing with a sealing body.
Next, when these batteries L to O were activated in the same manner as described above, and the battery life was measured by performing continuous charging in the same manner as described above, the results shown in Table 2 below were obtained. The addition amount in Table 2 (PPM), the average particle diameter ([mu] m) and the specific surface area (m 2 / g), the amount of yttrium oxide (PPM), the average particle diameter ([mu] m) and a specific surface area (m 2 / g) respectively. Table 2 also shows the battery H described above.
[0038]
[Table 2]
As is apparent from Table 2 above, when the average particle diameter of yttrium oxide exceeds 5 μm, the battery life tends to be shortened, and when the specific surface area of yttrium oxide is less than 15 m 2 / g, the battery life is shortened. A trend is observed. From this, it can be said that the average particle diameter of yttrium oxide is desirably 5 μm or less, and the specific surface area of yttrium oxide is desirably 15 m 2 / g or more. This also applies to ytterbium oxide.
[0040]
As described above, in the present invention, since acetylene black (carbon powder) and yttrium oxide or ytterbium oxide are simultaneously coated on the surface of the negative electrode plate, the surface of acetylene black having a very large specific surface area is yttrium oxide. Alternatively, ytterbium oxide is adsorbed. Since yttrium oxide or ytterbium oxide adsorbed on the surface of acetylene black acts as a catalyst for absorbing oxygen gas, oxidation of the hydrogen storage alloy is suppressed, and the battery life is improved.
[0041]
In the above-described embodiment, an example in which acetylene black is used as the carbon powder has been described. However, the carbon powder may be any powder having a large specific surface area, such as activated carbon, graphite, acetylene black, carbon black, ketjen. It is preferable to use black or the like.
[0042]
In the above-described embodiment, an example in which MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 is used as the hydrogen storage alloy has been described. However, as the hydrogen storage alloy, a Ti—Ni-based or La (or Mm) -Ni-based multiple element is used. It can be used by appropriately selecting from alloys. In the above-described embodiment, an example in which a mechanically pulverized hydrogen storage alloy is used has been described. However, a hydrogen storage alloy manufactured by an atomizing method may be used. In this case, since the hydrogen storage alloy produced by the atomization method has a small specific surface area, it is more effective when the present invention is applied.
Claims (4)
前記負極はその表面にレーザー法による平均粒径が５μｍ以下であるイットリウムあるいはイッテルビウムの金属、金属酸化物あるいは金属水酸化物から選択される１種以上の粉末粒子と炭素粉末とを備えたことを特徴とするニッケル−水素蓄電池。A nickel-hydrogen storage battery comprising a negative electrode made of a hydrogen storage alloy capable of reversibly storing and releasing hydrogen electrochemically, a positive electrode containing nickel hydroxide as a main active material, and an alkaline electrolyte. There,
The negative electrode is provided with at least one kind of powder particles selected from yttrium or ytterbium metal, metal oxide or metal hydroxide having an average particle diameter by laser method of 5 μm or less on the surface thereof and carbon powder. Nickel-hydrogen storage battery characterized.
前記負極はその表面にＢＥＴ窒素吸着法による比表面積が１５ｍ 2 ／ｇ以上であるイットリウムあるいはイッテルビウムの金属、金属酸化物あるいは金属水酸化物から選択される１種以上の粉末粒子と炭素粉末とを備えたことを特徴とするニッケル−水素蓄電池。A nickel-hydrogen storage battery comprising a negative electrode made of a hydrogen storage alloy capable of reversibly storing and releasing hydrogen electrochemically, a positive electrode containing nickel hydroxide as a main active material, and an alkaline electrolyte. There,
The negative electrode has one or more powder particles selected from yttrium or ytterbium metal, metal oxide or metal hydroxide having a specific surface area of 15 m 2 / g or more by the BET nitrogen adsorption method on the surface thereof and carbon powder. A nickel-hydrogen storage battery comprising:
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| JP5944854B2 (en) * | 2013-03-27 | 2016-07-05 | プライムアースＥｖエナジー株式会社 | Manufacturing method of nickel metal hydride storage battery |
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