JP3995385B2

JP3995385B2 - Paste type hydrogen storage alloy electrode

Info

Publication number: JP3995385B2
Application number: JP2000061512A
Authority: JP
Inventors: 喜裕増田; 佳文曲; 信幸東山; 靖彦伊藤
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 2000-03-07
Filing date: 2000-03-07
Publication date: 2007-10-24
Anticipated expiration: 2020-03-07
Also published as: JP2001250537A

Description

【０００１】
【発明が属する技術分野】
本発明は、ペースト式水素吸蔵合金電極に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
近年、ニッケル・カドミウム蓄電池に比べて２倍以上の容量を有し、しかも環境適合性にも優れる、負極に水素吸蔵合金電極を使用したニッケル・水素蓄電池が、次世代のアルカリ蓄電池として注目されており、各種ポータブル機器の普及に伴い、種々の改良技術が提案されている。
【０００３】
その一つとして、水素吸蔵合金電極を活性化して、安定した容量を取り出せる状態にするために必要な処理（充放電を数サイクル繰り返し行う活性化処理）に要する時間（サイクル）を短縮する技術がある。
【０００４】
例えば、特開平５−８２１２４号公報では、水素吸蔵合金に水酸化ニッケルを添加することにより、水素吸蔵合金電極の親液性が高められて、水素吸蔵合金電極の充放電サイクル初期の活性（初期活性）が向上することが報告されている。
【０００５】
しかしながら、本発明者らが検討したところ、上記の従来技術には、水素吸蔵合金電極の初期活性は若干向上するものの、水酸化ニッケルの添加により、酸素ガス吸収能が低下し、その結果、電池内圧が、無添加の場合と比べて、上昇し易くなるという問題があることが分かった。
【０００６】
ニッケル・水素蓄電池の如き密閉型電池においては、電池内圧が安全弁の作動圧を越えて高くなると、安全弁が作動して、電解液が電池内のガスとともに漏出する。その結果、内部抵抗が増大して、放電容量が低下する。また、電解液の漏出は、充放電サイクル特性低下の一因ともなる。
【０００７】
したがって、本発明は、充放電サイクル初期の放電容量が大きく、しかも電池内圧が上昇しにくい密閉型アルカリ蓄電池を与える、初期活性が高く、しかも酸素ガス吸収能が良いペースト式水素吸蔵合金電極を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明に係わる水素吸蔵合金電極（本発明電極）は、集電体と、当該集電体上に形成された活物質層とからなり、前記活物質層が、ＣａＣｕ₅型結晶構造を有する水素吸蔵合金と、Ｌｉ _p ＮｉＯ ₂ 〔０．０５≦ｐ≦０．９〕と、結着剤とを含む混合物である。
【０００９】
本発明電極は、水素吸蔵合金にＬｉ _p ＮｉＯ ₂ 〔０．０５≦ｐ≦０．９〕が添加されているので、初期活性が高く、しかも酸素ガス吸収能が良い。この理由は定かでないが、添加せるＬｉ _p ＮｉＯ ₂ 〔０．０５≦ｐ≦０．９〕が、電極の含液性を向上させるとともに、過充電時に正極で発生した酸素ガスが負極において水素と反応して水に還元される際の触媒として働くためと、考えられる。
【００１０】
ＣａＣｕ₅型結晶構造を有する水素吸蔵合金の具体例としては、ＭｍＮｉ_xＣｏ_yＭ_z〔式中、Ｍｍは希土類元素の混合物であるミッシュメタル、ＭはＡｌ、Ｍｇ、Ｍｎ、Ｆｅ、Ｓｎ、Ｓｉ、Ｗ、Ｚｎ、Ｃｒ及びＣｕからなる群から選ばれた少なくとも一種の元素、２．８≦ｘ≦４．４、０≦ｙ≦１．０、０≦ｚ≦１．５、４．５≦ｘ＋ｙ＋ｚ≦５．８である。〕で表される水素吸蔵合金が挙げられる。
【００１１】
Ｌｉ _p ＮｉＯ ₂ のｐが０．０５≦ｐ≦０．９に限定されるのは、初期活性が高く、しかも酸素ガス吸収能が良い水素吸蔵合金電極を得る上で、好ましいからである。
【００１２】
結着剤としては、ペースト式水素吸蔵合金電極の製造において従来使用されているものを特に制限無く使用することができる。具体例としては、ポリエチレンオキサイド、ポリビニルピロリドン及びカルボキシメチルセルロースが挙げられる。
【００１３】
初期活性が高く、しかも酸素ガス吸収能が良い水素吸蔵合金電極を得る上で、水素吸蔵合金に対するＬｉ _p ＮｉＯ ₂ 〔０．０５≦ｐ≦０．９〕の添加量は、水素吸蔵合金とニッケルとの重量比で、１００：０．１〜１００：５が好ましい。
【００１４】
【実施例】
以下、本発明を実施例に基づいてさらに詳細に説明するが、本発明は下記実施例に何ら限定されるものではなく、その要旨を変更しない範囲において適宜変更して実施することが可能なものである。
【００１５】
〔実験１〕
本発明電極及び比較電極を作製し、次いでそれらを使用してニッケル・水素蓄電池を作製し、各電池の充放電サイクル初期の放電容量及び過充電時の電池内圧特性を調べた。
【００１６】
（実施例１）
Ｍｍ（希土類元素の混合物であるミッシュメタルであり、Ｌａ２５重量％、Ｃｅ５０重量％、Ｐｒ７重量％、Ｎｄ１８重量％含有）と、Ｎｉ（純度９９．９％）と、Ｃｏ（純度９９．９％）と、Ｍｎ（純度９９．９％）と、Ａｌ（純度９９．９％）とを、モル比１：３．５：０．７：０．５：０．３で混合し、アルゴン雰囲気で加熱溶融し、双ロール法にて急冷し、アルゴン中で機械的に粉砕して、組成式：ＭｍＮｉ_3.5Ｃｏ_0.7Ｍｎ_0.5Ａｌ_0.3で表される平均粒径５０μｍの水素吸蔵合金粉末を作製した。
【００１７】
上記の水素吸蔵合金粉末と、Ｌｉ_0.5ＮｉＯ₂粉末とを、水素吸蔵合金とニッケルとの重量比１００：３で混合し、次いで、得られた混合粉末１００重量部と、結着剤としての、ＰＥＯ（ポリエチレンオキサイド）の５重量％水溶液１０重量部とを混合してペーストを調製し、このペーストをニッケルめっきを施したパンチングメタル（集電体）の両面に塗布し、室温で乾燥した後、所定の寸法に切断して、水素吸蔵合金電極ａ１（本発明電極）を作製した。
【００１８】
上記の本発明電極ａ１を負極として使用して、電池容量が正極容量により規制されるＡＡサイズのニッケル・水素蓄電池Ａ１（設計容量：１０００ｍＡｈ）を作製した。正極として従来公知の焼結式ニッケル極を、セパレータとして耐アルカリ性の不織布を、また電解液として水酸化カリウムの３０重量％水溶液を、それぞれ使用した。
【００１９】
図１は、作製したニッケル・水素蓄電池Ａ１を模式的に示す断面図であり、正極１、負極２、セパレータ３、正極リード４、負極リード５、正極外部端子６、負極缶７、封口蓋８、絶縁パッキング９、コイルスプリング１０などからなる。
【００２０】
正極１及び負極２は、セパレータ３を介して渦巻き状に巻取られた状態で負極缶７内に収容されており、正極１は正極リード４を介して封口蓋８に、また負極２は負極リード５を介して、負極缶７に接続されている。負極缶７と封口蓋８との接合部には絶縁パッキング９が装着されて電池の密閉化がなされている。正極外部端子６と封口蓋８との間には、コイルスプリング１０が設けられ、電池内圧が異常に上昇した際に圧縮されて、電池内部のガスを大気中に放出し得るようになっている。
【００２１】
（参考例１）
Ｌｉ_0.5ＮｉＯ₂粉末に代えて、ＬｉＮｉ₂Ｏ₃粉末を用いたこと以外は実施例１と同様にして、水素吸蔵合金電極ａ２（参考電極）を作製した。次いで、負極として水素吸蔵合金電極ａ２を使用して、負極のみがニッケル・水素蓄電池Ａ１と異なるニッケル・水素蓄電池Ａ２を作製した。
【００２２】
（参考例２）
Ｌｉ_0.5ＮｉＯ₂粉末に代えて、Ｌｉ_0.5ＮｉＯ粉末を用いたこと以外は実施例１と同様にして、水素吸蔵合金電極ａ３（参考電極）を作製した。次いで、負極として水素吸蔵合金電極ａ３を使用して、負極のみがニッケル・水素蓄電池Ａ１と異なるニッケル・水素蓄電池Ａ３を作製した。
【００２３】
（比較例１）
水素吸蔵合金粉末（実施例１で使用したものと同じもの）１００重量部と、ＰＥＯの５重量％水溶液１０重量部とを混合してペーストを調製し、このペーストをニッケルめっきを施したパンチングメタルの両面に塗布し、室温で乾燥した後、所定の寸法に切断して、水素吸蔵合金電極ｘ１（比較電極）を作製した。次いで、負極として比較電極ｘ１を使用して、負極のみがニッケル・水素蓄電池Ａ１と異なるニッケル・水素蓄電池Ｘ１を作製した。
【００２４】
（比較例２）
水素吸蔵合金粉末（実施例１で使用したものと同じもの）と、水酸化ニッケル粉末とを、水素吸蔵合金とニッケルとの重量比１００：３で混合し、次いで、得られた混合粉末１００重量部と、ＰＥＯの５重量％水溶液を１０重量部とを混合してペーストを調製し、このペーストをニッケルめっきを施したパンチングメタルの両面に塗布し、室温で乾燥した後、所定の寸法に切断して、水素吸蔵合金電極ｘ２（比較電極）を作製した。次いで、負極として比較電極ｘ２を使用して、負極のみがニッケル・水素蓄電池Ａ１と異なるニッケル・水素蓄電池Ｘ２を作製した。
【００２５】
〈充放電サイクル初期の放電容量〉
各電池を、常温にて、０．２Ｃで６時間充電した後、０．２Ｃで１．０Ｖまで放電した。次いで、１．０Ｃで１．２時間充電した後、１．０Ｃで１．０Ｖまで放電して、放電容量を求めた。結果を表１に示す。
【００２６】
〈電池内圧特性〉
０．２Ｃで６時間充電した後、０．２Ｃで１．０Ｖまで放電する充放電を、放電容量が設計容量（１０００ｍＡｈ）に達するまで繰り返し行なって、各電池を活性化した。次いで、１．０Ｃで連続充電し、電池内圧が８ｋｇｆ／ｃｍ²になるまでの充電時間を求めた。結果を表１に示す。この充電時間が長い電池ほど、過充電時に電池内圧が上昇しにくい、すなわち電池内圧特性の良い電池である。
【００２７】
【表１】

【００２８】
表１に示すように、ニッケル・水素蓄電池Ａ１〜Ａ３は、ニッケル・水素蓄電池Ｘ１及びＸ２に比べて、充放電サイクル初期の放電容量が大きく、しかも過充電時に電池内圧が上昇しにくい。この結果から、本発明電極ａ１及び参考電極ａ２、ａ３は、比較電極ｘ１及びｘ２に比べて、初期活性が高く、しかも酸素ガス吸収能が良いことが分かる。
【００２９】
〔実験２〕
Ｌｉ _p ＮｉＯ ₂ 中のｐの値と、水素吸蔵合金電極の初期活性及び酸素ガス吸収能との関係を調べた。
【００３０】
リチウム含有ニッケル酸化物として、Ｌｉ_0.01ＮｉＯ₂、Ｌｉ_0.05ＮｉＯ₂、Ｌｉ_0.9ＮｉＯ₂又はＬｉＮｉＯ₂を用いたこと以外は実施例１と同様にして、水素吸蔵合金電極ｂ１〜ｂ４を作製した。次いで、負極としてこれらの各水素吸蔵合金電極を使用して、負極のみがニッケル・水素蓄電池Ａ１と異なるニッケル・水素蓄電池Ｂ１〜Ｂ４を作製した。各ニッケル・水素蓄電池について、実験１で行ったものと同じ条件の試験を行い、負極の初期活性及び酸素ガス吸収能を調べた。結果を表２に示す。表２には、ニッケル・水素蓄電池Ａ１の結果も表１より転記して示してある。
【００３１】
【表２】

【００３２】
表２より、Ｌｉ_pＮｉＯ₂を使用する場合は、初期活性が高く、しかも酸素ガス吸収能が良い水素吸蔵合金電極を得る上で、０．０５≦ｐ≦０．９のＬｉ_pＮｉＯ₂を使用することが好ましいことが分かる。
【００３３】
〔実験３〕
リチウム含有ニッケル酸化物の好適な添加量を調べた。
【００３４】
水素吸蔵合金粉末（実施例１で使用したものと同じもの）と、Ｌｉ_0.5ＮｉＯ₂粉末とを、水素吸蔵合金とニッケルとの重量比１００：０．０５、１００：０．１、１００：５又は１００：１０で混合し、次いで、得られた混合粉末１００重量部と、ＰＥＯの５重量％水溶液１０重量部とを混合してペーストを調製し、このペーストをニッケルめっきを施したパンチングメタルの両面に塗布し、室温で乾燥した後、所定の寸法に切断して、水素吸蔵合金電極ｃ１〜ｃ４を作製した。次いで、負極としてこれらの各水素吸蔵合金電極を使用して、負極のみがニッケル・水素蓄電池Ａ１と異なるニッケル・水素蓄電池Ｃ１〜Ｃ４を作製した。各ニッケル・水素蓄電池について、実験１で行ったものと同じ条件の試験を行い、負極の初期活性及び酸素ガス吸収能を調べた。結果を表３に示す。表３には、ニッケル・水素蓄電池Ａ１の結果も表１より転記して示してある。
【００３５】
【表３】

【００３６】
表３より、初期活性が高く、しかも酸素ガス吸収能が良い水素吸蔵合金電極を得る上で、水素吸蔵合金に対するリチウム含有ニッケル酸化物の添加量は、水素吸蔵合金とニッケルとの重量比で、１００：０．１〜１００：５が好ましいことが分かる。
【００３７】
【発明の効果】
充放電サイクル初期の放電容量が大きく、しかも電池内圧が上昇しにくい密閉型アルカリ蓄電池を与える、初期活性が高く、しかも酸素ガス吸収能が良いペースト式水素吸蔵合金電極が提供される。
【図面の簡単な説明】
【図１】実施例で作製したニッケル・水素蓄電池の断面図である。
【符号の説明】
Ａ１ニッケル・水素蓄電池
１正極
２負極
３セパレータ
４正極リード
５負極リード
６正極外部端子
７負極缶
８封口蓋
９絶縁パッキング
１０コイルスプリング[0001]
[Technical field to which the invention belongs]
The present invention relates to a paste-type hydrogen storage alloy electrode.
[0002]
[Prior art and problems to be solved by the invention]
In recent years, nickel-hydrogen storage batteries that use hydrogen storage alloy electrodes for the negative electrode, which have more than twice the capacity of nickel-cadmium storage batteries and have excellent environmental compatibility, are attracting attention as next-generation alkaline storage batteries. With the spread of various portable devices, various improved techniques have been proposed.
[0003]
One of the technologies is to shorten the time (cycle) required for the process necessary to activate the hydrogen storage alloy electrode so that a stable capacity can be taken out (activation process in which charging and discharging are repeated several cycles). is there.
[0004]
For example, in Japanese Patent Application Laid-Open No. 5-82124, by adding nickel hydroxide to a hydrogen storage alloy, the lyophilicity of the hydrogen storage alloy electrode is enhanced, and the initial charge / discharge cycle activity of the hydrogen storage alloy electrode (initial Activity) has been reported to improve.
[0005]
However, as a result of investigations by the present inventors, the above-described prior art shows that although the initial activity of the hydrogen storage alloy electrode is slightly improved, the addition of nickel hydroxide decreases the oxygen gas absorption capacity. It has been found that there is a problem that the internal pressure is likely to rise as compared with the case of no addition.
[0006]
In a sealed battery such as a nickel-hydrogen storage battery, when the battery internal pressure exceeds the operating pressure of the safety valve, the safety valve is activated and the electrolyte leaks together with the gas in the battery. As a result, the internal resistance increases and the discharge capacity decreases. In addition, leakage of the electrolyte also contributes to deterioration of charge / discharge cycle characteristics.
[0007]
Therefore, the present invention provides a paste-type hydrogen storage alloy electrode that provides a sealed alkaline storage battery that has a large discharge capacity at the beginning of the charge / discharge cycle and is less likely to increase the internal pressure of the battery, has a high initial activity, and has a good oxygen gas absorption capacity. The purpose is to do.
[0008]
[Means for Solving the Problems]
A hydrogen storage alloy electrode according to the present invention (electrode of the present invention) comprises a current collector and an active material layer formed on the current collector, and the active material layer is a hydrogen having a CaCu ₅ type crystal structure. It is a mixture containing an occlusion alloy, Li _p NiO ₂ [0.05 ≦ p ≦ 0.9], and a binder.
[0009]
In the electrode of the present invention, since Li _p NiO ₂ [0.05 ≦ p ≦ 0.9] is added to the hydrogen storage alloy, the initial activity is high and the oxygen gas absorption ability is good. The reason for this is not clear, but Li _p NiO ₂ [0.05 ≦ p ≦ 0.9] to be added improves the liquid-containing property of the electrode, and oxygen gas generated at the positive electrode during overcharge is reduced with hydrogen at the negative electrode. This is thought to be because it acts as a catalyst when reacted and reduced to water.
[0010]
Specific examples of the hydrogen-absorbing alloy having a CaCu ₅ type crystal structure, MmNi _x Co _y M _z wherein misch metal Mm is a mixture of rare earth elements, M is Al, Mg, Mn, Fe, Sn, Si At least one element selected from the group consisting of W, Zn, Cr and Cu, 2.8 ≦ x ≦ 4.4, 0 ≦ y ≦ 1.0, 0 ≦ z ≦ 1.5, 4.5 ≦ x + y + z ≦ 5.8. ] The hydrogen storage alloy represented by these is mentioned.
[0011]
The reason why _{p of} Li _p NiO ₂ is limited to 0.05 ≦ p ≦ 0.9 is that it is preferable for obtaining a hydrogen storage alloy electrode having high initial activity and good oxygen gas absorption ability.
[0012]
As the binder, those conventionally used in the production of paste-type hydrogen storage alloy electrodes can be used without any particular limitation. Specific examples include polyethylene oxide, polyvinyl pyrrolidone, and carboxymethyl cellulose.
[0013]
In order to obtain a hydrogen storage alloy electrode having high initial activity and good oxygen gas absorption ability, the amount of Li _p NiO ₂ [0.05 ≦ p ≦ 0.9] added to the hydrogen storage alloy is such that the hydrogen storage alloy and nickel Is preferably 100: 0.1 to 100: 5.
[0014]
【Example】
Hereinafter, the present invention will be described in more detail on the basis of examples. However, the present invention is not limited to the following examples, and can be implemented with appropriate modifications without departing from the scope of the present invention. It is.
[0015]
[Experiment 1]
The electrode of the present invention and the comparative electrode were prepared, and then a nickel-hydrogen storage battery was prepared using them, and the discharge capacity at the beginning of the charge / discharge cycle of each battery and the internal pressure characteristics of the battery during overcharge were examined.
[0016]
Example 1
Mm (Misch metal which is a mixture of rare earth elements, containing La 25% by weight, Ce 50% by weight, Pr 7% by weight, Nd 18% by weight), Ni (purity 99.9%), Co (purity 99.9%) Mn (purity 99.9%) and Al (purity 99.9%) are mixed at a molar ratio of 1: 3.5: 0.7: 0.5: 0.3 and heated in an argon atmosphere. The mixture was melted, rapidly cooled by a twin roll method, and mechanically pulverized in argon to prepare a hydrogen storage alloy powder having an average particle size of 50 μm represented by a composition formula: MmNi _3.5 Co _0.7 Mn _0.5 Al _0.3 .
[0017]
The above-mentioned hydrogen storage alloy powder and Li _0.5 NiO ₂ powder are mixed at a weight ratio of 100: 3 of the hydrogen storage alloy and nickel, and then 100 parts by weight of the obtained mixed powder is used as a binder. A paste was prepared by mixing 10 parts by weight of a 5% by weight aqueous solution of PEO (polyethylene oxide). This paste was applied to both sides of a nickel-plated punching metal (current collector) and dried at room temperature. It cut | disconnected to the predetermined dimension and produced hydrogen storage alloy electrode a1 (this invention electrode).
[0018]
Using the above-described electrode a1 of the present invention as a negative electrode, an AA size nickel-hydrogen storage battery A1 (design capacity: 1000 mAh) whose battery capacity is regulated by the positive electrode capacity was produced. A conventionally known sintered nickel electrode was used as the positive electrode, an alkali-resistant non-woven fabric as the separator, and a 30% by weight aqueous solution of potassium hydroxide as the electrolyte.
[0019]
FIG. 1 is a cross-sectional view schematically showing the produced nickel-hydrogen storage battery A1. The positive electrode 1, the negative electrode 2, the separator 3, the positive electrode lead 4, the negative electrode lead 5, the positive electrode external terminal 6, the negative electrode can 7, and the sealing lid 8 , Insulating packing 9, coil spring 10 and the like.
[0020]
The positive electrode 1 and the negative electrode 2 are accommodated in a negative electrode can 7 while being wound in a spiral shape via a separator 3. The positive electrode 1 is accommodated in a sealing lid 8 via a positive electrode lead 4, and the negative electrode 2 is a negative electrode. The lead 5 is connected to the negative electrode can 7. An insulating packing 9 is attached to the joint between the negative electrode can 7 and the sealing lid 8 to seal the battery. A coil spring 10 is provided between the positive electrode external terminal 6 and the sealing lid 8, and is compressed when the battery internal pressure rises abnormally so that the gas inside the battery can be released into the atmosphere. .
[0021]
( Reference Example 1 )
A hydrogen storage alloy electrode a2 ( reference electrode ) was produced in the same manner as in Example 1 except that LiNi ₂ O ₃ powder was used instead of Li _0.5 NiO ₂ powder. Next, using the hydrogen storage alloy electrode a2 as the negative electrode, a nickel / hydrogen storage battery A2 in which only the negative electrode was different from the nickel / hydrogen storage battery A1 was produced.
[0022]
( Reference Example 2 )
A hydrogen storage alloy electrode a3 ( reference electrode ) was produced in the same manner as in Example 1 except that Li _0.5 NiO powder was used instead of Li _0.5 NiO ₂ powder. Next, using the hydrogen storage alloy electrode a3 as a negative electrode, a nickel / hydrogen storage battery A3 having only the negative electrode different from the nickel / hydrogen storage battery A1 was produced.
[0023]
(Comparative Example 1)
A paste was prepared by mixing 100 parts by weight of hydrogen storage alloy powder (the same as that used in Example 1) and 10 parts by weight of a 5% by weight aqueous solution of PEO, and this paste was subjected to nickel plating. After being coated on both sides and dried at room temperature, it was cut to a predetermined size to produce a hydrogen storage alloy electrode x1 (comparative electrode). Next, using the comparative electrode x1 as the negative electrode, a nickel / hydrogen storage battery X1 having only the negative electrode different from the nickel / hydrogen storage battery A1 was produced.
[0024]
(Comparative Example 2)
Hydrogen storage alloy powder (same as that used in Example 1) and nickel hydroxide powder were mixed at a weight ratio of 100: 3 of hydrogen storage alloy and nickel, and then obtained mixed powder 100 weight Part and 10 parts by weight of a 5% by weight aqueous solution of PEO were prepared, and this paste was applied to both sides of a nickel-plated punching metal, dried at room temperature, and then cut into predetermined dimensions Thus, a hydrogen storage alloy electrode x2 (comparative electrode) was produced. Next, using the comparative electrode x2 as a negative electrode, a nickel / hydrogen storage battery X2 in which only the negative electrode was different from the nickel / hydrogen storage battery A1 was produced.
[0025]
<Discharge capacity at the beginning of charge / discharge cycle>
Each battery was charged at 0.2 C for 6 hours at room temperature, and then discharged to 1.0 V at 0.2 C. Next, after charging at 1.0 C for 1.2 hours, the battery was discharged at 1.0 C to 1.0 V, and the discharge capacity was determined. The results are shown in Table 1.
[0026]
<Battery pressure characteristics>
After charging at 0.2 C for 6 hours, charging / discharging at 0.2 C to 1.0 V was repeated until the discharge capacity reached the design capacity (1000 mAh) to activate each battery. Next, the battery was continuously charged at 1.0 C, and the charging time until the battery internal pressure reached 8 kgf / cm ² was determined. The results are shown in Table 1. A battery having a longer charging time is less likely to increase the battery internal pressure during overcharging, that is, a battery having good battery internal pressure characteristics.
[0027]
[Table 1]

[0028]
As shown in Table 1, the nickel-hydrogen storage batteries A1 to A3 have a larger discharge capacity at the beginning of the charge / discharge cycle than the nickel-hydrogen storage batteries X1 and X2, and the internal pressure of the battery is unlikely to increase during overcharge. From this result, it can be seen that the present invention electrode a1 and the reference electrodes a2 and a3 have higher initial activity and better oxygen gas absorption capacity than the comparison electrodes x1 and x2.
[0029]
[Experiment 2]
The relationship between the value of p in Li _p NiO ₂ and the initial activity and oxygen gas absorption capacity of the hydrogen storage alloy electrode was examined.
[0030]
Hydrogen storage alloy electrodes b1 to b4 were produced in the same manner as in Example 1 except that Li _0.01 NiO ₂ , Li _0.05 NiO ₂ , Li _0.9 NiO _2, or LiNiO ₂ was used as the lithium-containing nickel oxide. Next, using each of these hydrogen storage alloy electrodes as a negative electrode, nickel / hydrogen storage batteries B1 to B4 differing only in the negative electrode from the nickel / hydrogen storage battery A1 were produced. Each nickel-hydrogen storage battery was tested under the same conditions as in Experiment 1, and the initial activity and oxygen gas absorption capacity of the negative electrode were examined. The results are shown in Table 2. Table 2 also shows the results of nickel-hydrogen storage battery A1 transcribed from Table 1.
[0031]
[Table 2]

[0032]
From Table 2, when using Li _p NiO ₂ , in order to obtain a hydrogen storage alloy electrode having high initial activity and good oxygen gas absorption capacity, Li _p NiO ₂ of 0.05 ≦ p ≦ 0.9 is used. It can be seen that it is preferable to use it.
[0033]
[Experiment 3]
A suitable addition amount of lithium-containing nickel oxide was investigated.
[0034]
Hydrogen storage alloy powder (the same as that used in Example 1) and Li _0.5 NiO ₂ powder were used in a weight ratio of hydrogen storage alloy to nickel of 100: 0.05, 100: 0.1, 100: 5. Or 100: 10, and then mixing 100 parts by weight of the obtained mixed powder and 10 parts by weight of a 5% by weight aqueous solution of PEO to prepare a paste, and this paste is made of nickel-plated punching metal After apply | coating to both surfaces and drying at room temperature, it cut | disconnected to the predetermined dimension and produced hydrogen storage alloy electrode c1-c4. Next, using each of these hydrogen storage alloy electrodes as the negative electrode, nickel / hydrogen storage batteries C1 to C4 having only the negative electrode different from the nickel / hydrogen storage battery A1 were produced. Each nickel-hydrogen storage battery was tested under the same conditions as in Experiment 1, and the initial activity and oxygen gas absorption capacity of the negative electrode were examined. The results are shown in Table 3. Table 3 also shows the results of nickel-hydrogen storage battery A1 transcribed from Table 1.
[0035]
[Table 3]

[0036]
From Table 3, in order to obtain a hydrogen storage alloy electrode with high initial activity and good oxygen gas absorption capacity, the amount of lithium-containing nickel oxide added to the hydrogen storage alloy is the weight ratio of the hydrogen storage alloy and nickel. It turns out that 100: 0.1-100: 5 is preferable.
[0037]
【The invention's effect】
Provided is a paste-type hydrogen storage alloy electrode that provides a sealed alkaline storage battery that has a large discharge capacity at the beginning of the charge / discharge cycle and is less likely to increase the internal pressure of the battery, has a high initial activity, and has a good oxygen gas absorption capability.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a nickel-hydrogen storage battery manufactured in an example.
[Explanation of symbols]
A1 Nickel-hydrogen storage battery 1 Positive electrode 2 Negative electrode 3 Separator 4 Positive electrode lead 5 Negative electrode lead 6 Positive electrode external terminal 7 Negative electrode can 8 Sealing lid 9 Insulating packing 10 Coil spring

Claims

In a paste-type hydrogen storage alloy electrode comprising a current collector and an active material layer formed on the current collector, the active material layer comprises a hydrogen storage alloy having a CaCu ₅ type crystal structure, and Li _p NiO ₂ A paste-type hydrogen storage alloy electrode, which is a mixture containing [0.05 ≦ p ≦ 0.9] and a binder.

A nickel-hydrogen storage battery comprising the paste-type hydrogen storage alloy electrode according to claim 1 as a negative electrode.