JP3547980B2

JP3547980B2 - Nickel-hydrogen storage battery

Info

Publication number: JP3547980B2
Application number: JP07426798A
Authority: JP
Inventors: 光造野上; 睦矢野; 光紀徳田; 衛木本; 信幸東山; 伸藤谷; 晃治西尾
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1998-03-23
Filing date: 1998-03-23
Publication date: 2004-07-28
Anticipated expiration: 2018-03-23
Also published as: JPH11273716A

Description

【０００１】
【発明の属する技術分野】
この発明は、ニッケルの水酸化物を主成分とする正極活物質を用いた正極と、負極活物質に水素吸蔵合金を用いた負極とを備えたニッケル−水素蓄電池において、充電時に正極において酸素ガスが発生するのを抑制して、ガスリークや漏液等が発生するのを防止し、高い充電電流で急速充電を行う場合や、電池内における正極活物質や負極活物質の割合を多くして高エネルギー密度のニッケル−水素蓄電池を得る場合においても、優れた充放電サイクル特性が得られるようにした点に特徴を有するものである。
【０００２】
【従来の技術】
従来より、アルカリ蓄電池の一つとして、ニッケル−水素蓄電池が知られており、このニッケル−水素蓄電池は、エネルギー密度が大きい密閉型蓄電池として広く普及している。
【０００３】
ここで、このニッケル−水素蓄電池においては、一般にその正極における正極活物質にニッケルの水酸化物を主成分とするものを用い、またこのニッケル−水素蓄電池を充電させるにあたっては、上記の正極から酸素ガスが発生する状態まで充電を行い、充電時に発生する酸素ガスを負極における水素吸蔵合金中に吸蔵されている水素と反応させるようにしていた。
【０００４】
しかし、このように酸素ガスと水素吸蔵合金中に吸蔵されている水素とを反応させると発熱し、これによって水素吸蔵合金中に吸蔵されている水素が解離し、上記のように正極において発生する酸素ガスや、負極において発生する水素ガスによって、充電時にこのニッケル−水素蓄電池内における圧力が上昇し、特に、高い充電電流で急速充電を行うようにした場合には、ニッケル−水素蓄電池の内圧が高くなって、ガスリークや電解液の漏液等が発生し、ニッケル−水素蓄電池における充放電サイクル特性等が低下するという問題があった。
【０００５】
さらに、高エネルギー密度のニッケル−水素蓄電池を得るため、正極の中心部に空間を設け、この正極の中心部における空間に負極を収容させ、ニッケル−水素蓄電池内における正極活物質や負極活物質の割合を多くした、いわゆるインサイドアウト型構造のニッケル−水素蓄電池においては、正極において発生する酸素ガスが多くなると共に、負極において水素が解離するのを抑制することが困難であり、充電時にこのニッケル−水素蓄電池内における圧力が上昇し、ガスリークや電解液の漏液等が発生して、充放電サイクル特性等が低下するという問題があった。
【０００６】
このため、従来においても、特開昭６０−１００３８２号公報や、特開昭６０−１０９１８３号公報に示されるように、上記の負極の表面に酸素をイオン化させる触媒を設け、これにより正極において発生する酸素ガスと負極において発生する水素とを反応させて、ニッケル−水素蓄電池の内圧が上昇するのを抑制するようにしたものや、特開平６−１８７９８０号公報に示されるように、水素吸蔵合金電極の表面における結着剤を除去して、負極の表面に水素吸蔵合金の粒子を分散させ、負極における酸素ガス吸収能を向上させて、水素が解離するのを抑制するようにしたものが提案されている。
【０００７】
しかし、これらの公報に示されるものにおいても、上記のように高い充電電流で急速充電を行う場合や、インサイドアウト型構造のニッケル−水素蓄電池に利用する場合においては、必ずしも十分な効果が得られず、依然として、ガスリークや電解液の漏液等が発生し、ニッケル−水素蓄電池における充放電サイクル特性等が低下するという問題があった。
【０００８】
さらに、従来においては、正極において酸素が発生するのを抑制するため、特開昭６１−１６３５７０号公報に示されるように、その正極における正極活物質に二酸化マンガンを用いるようにしたものが提案されている。
【０００９】
しかし、二酸化マンガンはニッケルの水酸化物に比べて充放電の可逆性に乏しいため、深放電しない用途に限られ、高エネルギー密度の電池を得ることができないという問題があった。
【００１０】
【発明が解決しようとする課題】
この発明は、ニッケルの水酸化物を主成分とする正極活物質を用いた正極と、負極活物質に水素吸蔵合金を用いた負極とを備えたニッケル−水素蓄電池における上記のような問題を解決することを課題とするものであり、充電時に正極において酸素ガスが発生するのを抑制し、高い充電電流で急速充電を行う場合や、電池内における正極活物質や負極活物質の割合を多くして高エネルギー密度のニッケル−水素蓄電池を得る場合においても、ガスリークや電解液の漏液等が発生して充放電サイクル特性等が低下するのを防止することを課題とするものである。
【００１１】
【課題を解決するための手段】
この発明におけるニッケル−水素蓄電池においては、上記のような課題を解決するため、α−Ｎｉ（ＯＨ） ₂ の結晶構造中に少なくともマンガンが固溶された複合水酸化物からなる正極活物質を用いた正極と、水素吸蔵合金からなる負極活物質を用いた負極とを備えたニッケル−水素蓄電池において、上記の正極活物質の全金属元素中におけるマンガンの割合が２５〜５０モル％の範囲になるようにした。
【００１２】
ここで、この発明におけるニッケル−水素蓄電池のように、α−Ｎｉ（ＯＨ） ₂ の結晶構造中に少なくともマンガンが固溶された複合水酸化物からなる正極活物質を用いると、充電状態ではγ−ＮｉＯＯＨの状態になり、酸素発生の過電圧が大きくなって、充電時における酸素ガスの発生が抑制され、高い充電電流で急速充電を行う場合や、電池内における正極活物質や負極活物質の割合を多くして高エネルギー密度のニッケル−水素蓄電池を得る場合においても、ガスリークや電解液の漏液等が抑制されて、充放電サイクル特性等の低下が防止される。特に、この発明におけるニッケル−水素蓄電池を充電させるにあたり、充電終止電圧を設定して、酸素発生が生じる電位に達する前に充電を終了させるように制御したり、充電電流を変化させて酸素発生が生じる電位より低い定電圧で充電されるようにようにすると、非常に高い効率での充電が行われ、正極における酸素の発生が防止されるようになる。
【００１３】
ここで、この発明におけるニッケル−水素蓄電池のように、正極活物質としてα−Ｎｉ（ＯＨ） ₂ の結晶構造中に少なくともマンガンが固溶された複合水酸化物を用いるにあたり、この正極活物質中におけるマンガンの量が少ないと、この正極活物質における結晶構造が変化しやすくなり、充電時における酸素ガスの発生を十分に抑制することができなくなる一方、マンガンの量が多くなり過ぎると、この正極活物質中におけるニッケルの量が少なくなって、ニッケル−水素蓄電池における電池容量が低下するため、正極活物質の全金属元素中におけるマンガンの割合を２５〜５０モル％の範囲、好ましくは２５〜４０モル％の範囲になるようにする。
【００１４】
【実施例】
以下、この発明に係るニッケル−水素蓄電池について実施例を挙げて具体的に説明すると共に、この実施例におけるニッケル−水素蓄電池においては、充放電を繰り返して行った場合におけるガスリークや電解液の漏液等が抑制されて、充放電サイクル特性に優れたニッケル−水素蓄電池が得られることを比較例を挙げて明らかにする。なお、この発明に係るニッケル−水素蓄電池は、下記の実施例に示したものに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できるものである。
【００１５】
（実施例１〜３及び参考例１，２）
実施例１〜３及び参考例１，２においては、下記のようにして作製した正極と負極とを用い、図１に示すようなスパイラル構造になった単３型のニッケル−水素蓄電池を作製した。
【００１６】
（正極の作製）
正極を作製するにあたっては、硫酸ニッケルと硫酸マンガンとをそれぞれ所定のモル比になるように混合し、硫酸塩濃度が１．３モル／ｌになるように調製した各混合液に、１０％のアンモニアと１０％の水酸化ナトリウムの混合液をｐＨが１０．０±０．４の範囲になるように加え、これによって生成した沈殿物を濾過し、これを室温下において２０％ＫＯＨ水溶液中に１週間保存した後、これを洗浄し濾過して、下記の表１に示す組成になった各正極活物質を得た。
【００１７】
ここで、これらの各正極活物質をＸ線回折法（ＸＲＤ）により解析してその結晶構造を調べたところ、これらの各正極活物質はα−Ｎｉ（ＯＨ）₂ の結晶構造を有しており、またこれらの各正極活物質を電子線プローブ微量分析法（ＥＰＭＡ）により解析したところ、マンガンが偏在することなくα−Ｎｉ（ＯＨ）₂ 中に均一に固溶されていた。
【００１８】
そして、正極を作製するにあたっては、上記の各正極活物質を７３重量％、導電剤である水酸化コバルトを７重量％、結着剤であるメチルセルロースが１重量％含有されたメチルセルロース水溶液を２０重量％の割合にし、これらを混練したペーストを、それぞれニッケルメッキを施した発泡メタル（導電性多孔体）に充填し、これを乾燥させ成形して各正極を得た。
【００１９】
（負極の作製）
負極を作製するにあたっては、負極活物質として、ＭｍＮｉ_3.2 ＣｏＡｌ_0.2Ｍｎ_0.6 の組成からなる水素吸蔵合金粉末を用い、この水素吸蔵合金粉末に結着剤であるポリエチレンオキサイドの水溶液を加えてペーストを調製し、このペーストをニッケルメッキを施したパンチングメタルの両面に塗着させ、これを乾燥させて負極を作製した。なお、Ｍｍは希土類の混合物であるミッシュメタルを示す。
【００２０】
（電池の作製）
電池を作製するにあたっては、上記のようにして作製した各正極と負極とを用い、図１に示すように、正極１と負極２との間にナイロン不織布で構成されたセパレータ３を介在させてスパイラル状に巻き、これを電池缶４内に収容させた後、この電池缶４内に水酸化カリウムが７ｍｏｌ／ｌ，水酸化リチウムが０．４ｍｏｌ／ｌ含有されたアルカリ電解液を注液して封口し、正極１を正極リード５を介して正極蓋６に接続させる一方、負極２を負極リード７を介して電池缶４に接続させ、電池缶４と正極蓋６とをパッキン８によって電気的に絶縁させて各ニッケル−水素蓄電池を得た。また、各ニッケル−水素蓄電池においては、正極蓋６と正極外部端子９との間にコイルスプリング１０を設け、電池の内圧が上昇した場合には、このコイルスプリング１０が圧縮されて、電池内部のガスが外部に放出されるようにした。
【００２１】
（比較例１）
この比較例１においては、正極の作製において、正極活物質を得るにあたり、硫酸ニッケルと硫酸コバルトと硫酸亜鉛とを９６：３：１のモル比になるように混合した混合液に、１０％のアンモニアと１０％の水酸化ナトリウムの混合液をｐＨが１１．５±０．２の範囲になるように加え、これによって生成した沈殿物を濾過し、これを室温下において２０％ＫＯＨ水溶液中に１週間保存した後、これを洗浄し濾過して、下記の表１に示す組成になった正極活物質を得た。
【００２２】
そして、このようにして得た正極活物質を用いる以外は、上記の実施例１〜３、参考例１，２の場合と同様にして、ニッケル−水素蓄電池を作製した。
【００２３】
次に、上記のようにして作製した実施例１〜３、参考例１，２及び比較例１の各ニッケル−水素蓄電池をそれぞれ５．０Ａの高い定電流で電池電圧が１．５５Ｖに達するまで充電させ、その後、１．５５Ｖの定電圧で１０分間保持させた。そして、１時間休止した後、１．０Ａの放電電流で電池電圧が１．０Ｖに達するまで放電を行い、これを１サイクルとして充放電を繰り返し、２サイクル目と５０サイクル目とにおいて、それぞれその充電容量及び充電後の放電容量、各ニッケル−水素蓄電池の内部抵抗及び電池作製時からの各ニッケル−水素蓄電池における重量減少を求め、これらの結果を下記の表１に示した。
【００２４】
【表１】

【００２５】
この結果、上記のように高い電流で急速充電を行った場合、比較例１のニッケル−水素蓄電池においては、５０サイクル時における充電容量や放電容量の低下が大きく、また電池の内部抵抗が大きく上昇すると共にガスリークや漏液による重量減も大きくなっていたのに対して、実施例１〜３、参考例１，２の各ニッケル−水素蓄電池においては、比較例１のニッケル−水素蓄電池に比べ、５０サイクル時における充電容量や放電容量の低下が著しく少なくなっており、また電池の内部抵抗の上昇やガスリークや漏液による重量減も非常に少なく、急速充電を行った場合における充放電サイクル特性が著しく向上していた。特に、正極活物質の全金属元素中におけるマンガンの割合が１１〜５０モル％の範囲になった実施例１〜３及び参考例２においては、電池の内部抵抗の上昇やガスリークや漏液による重量減がなく、急速充電を行った場合における充放電サイクル特性がさらに向上していた。
【００２６】
（実施例４〜６、参考例３及び比較例２）
実施例４〜６、参考例３及び比較例２においては、下記のようにして作製した正極と負極とを用い、図２に示すようなインサイドアウト型構造になった単３型のニッケル−水素蓄電池を作製した。
【００２７】
（正極の作製）
正極を作製するにあたっては、その正極活物質として、下記の表２に示すように、参考例３では参考例２と、実施例４では実施例１と、実施例５では実施例２と、実施例６では実施例３と、比較例２では比較例１と同じ正極活物質を用いるようにした。
【００２８】
そして、これらの正極活物質９０重量部に対してグラファイトを１０重量部の割合で加え、少量の水を加えて顆粒状とした後、これらを外径が１３．３ｍｍ、内径が１０．３ｍｍの円筒状に加圧成形して、図２に示すような各正極１を得た。
【００２９】
（負極の作製）
負極を作製するにあたっては、その負極活物質として、ＭｍＮｉ_3.3 Ｃｏ_0.9Ａｌ_0.3 Ｍｎ_0.5 の組成からなる合金塊を粉砕し、平均粒径が約３０μｍになった水素吸蔵合金粉末を用いた。
【００３０】
そして、上記の水素吸蔵合金粉末をニッケルメッシュを用いた負極集電体で包み、これを直径が６．５ｍｍ、高さが３６ｍｍの成形金型内に入れて加圧成形した後、これを７００℃で２時間の熱処理により焼結させて、図２に示すように、負極活物質２ａが上記のニッケルメッシュからなる負極集電体２ｂで包まれた負極２を得た。また、上記の負極集電体２ｂの一部を負極２より延出させて、これをリード部２ｃとして用いるようにした。
【００３１】
（電池の作製）
電池を作製するにあたっては、図２に示すように、上記の円筒状になった各正極１をそれぞれ電池缶４内の外周側に収容させると共に、セロファンとビニロン不織布をラミネートしたセパレータ３を介して上記の負極２をそれぞれ円筒状になった正極１の内周側に収容させ、この状態で各電池缶４内に４０重量％のＫＯＨ水溶液からなるアルカリ電解液５を３．５ｇ注液した後、これを封口させて各ニッケル−水素蓄電池を得た。なお、この各ニッケル−水素蓄電池においては、図示していないがガス等を排出させる逆止弁を設けた。
【００３２】
次に、上記のようにして作製した実施例４〜６、参考例３及び比較例２の各ニッケル−水素蓄電池を、それぞれ１５０ｍＡの充電電流で電池電圧が１．５５Ｖに達するまで充電させた後、１５０ｍＡの放電電流で電池電圧が１．０Ｖに達するまで放電を行い、これを１サイクルとして充放電を繰り返し、２サイクル目と５０サイクル目とにおいて、それぞれ各ニッケル−水素蓄電池における充電容量と、放電容量と、電池の内部抵抗と、電池作製時からの各ニッケル−水素蓄電池における重量減少とを求め、これらの結果を下記の表２に示した。
【００３３】
【表２】

【００３４】
この結果、上記のようにニッケル−水素蓄電池をインサイドアウト型構造にして、電池内における正極活物質や負極活物質の量を多くした場合においても、上記の実施例４〜６、参考例３の各ニッケル−水素蓄電池においては、比較例２のニッケル−水素蓄電池に比べて、５０サイクル時における充電容量や放電容量の低下が著しく少なくなっていると共に、電池の内部抵抗の上昇も非常に少なく、またガスリークや漏液による重量減も殆どなく、高い電池容量を有すると共に、充放電サイクル特性に優れたニッケル−水素蓄電池が得られた。
【００３５】
【発明の効果】
以上詳述したように、この発明におけるニッケル−水素蓄電池においては、正極にα−Ｎｉ（ＯＨ） ₂ の結晶構造中に少なくともマンガンが固溶された複合水酸化物からなる正極活物質を用い、この正極活物質の全金属元素中におけるマンガンの割合が２５〜５０モル％の範囲になるようにしたため、この正極活物質における酸素発生の過電圧が高くなり、充電時に正極において酸素ガスが発生するのが抑制されて、ニッケル−水素蓄電池におけるガスリークや電解液の漏液等が防止されるようになった。
【００３６】
この結果、この発明によると、高い充電電流で急速充電を行う場合や、電池内における正極活物質や負極活物質の割合を多くして高エネルギー密度のニッケル−水素蓄電池を得るようにした場合においても、充放電サイクル特性に優れたニッケル−水素蓄電池が得られるようになった。
【図面の簡単な説明】
【図１】この発明の実施例１〜３、参考例１，２及び比較例１において作製したニッケル−水素蓄電池の概略説明図である。
【図２】この発明の実施例４〜６、参考例３及び比較例２において作製したニッケル−水素蓄電池の概略説明図である。
【符号の説明】
１正極
２負極
３セパレータ
４電池缶[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a nickel-hydrogen storage battery including a positive electrode using a positive electrode active material mainly containing a hydroxide of nickel and a negative electrode using a hydrogen storage alloy as a negative electrode active material. To prevent gas leaks and liquid leakage, etc., and to perform rapid charging with a high charging current, or to increase the ratio of the positive electrode active material and the negative electrode active material in the battery to increase the It is characterized in that even when a nickel-hydrogen storage battery having an energy density is obtained, excellent charge / discharge cycle characteristics are obtained.
[0002]
[Prior art]
Conventionally, a nickel-hydrogen storage battery has been known as one of the alkaline storage batteries, and the nickel-hydrogen storage battery is widely used as a sealed storage battery having a large energy density.
[0003]
Here, in this nickel-metal hydride storage battery, generally, a material having a nickel hydroxide as a main component is used as a positive electrode active material in the positive electrode. Charging was performed until gas was generated, and oxygen gas generated during charging was reacted with hydrogen stored in the hydrogen storage alloy in the negative electrode.
[0004]
However, when the oxygen gas reacts with the hydrogen stored in the hydrogen storage alloy as described above, heat is generated, whereby the hydrogen stored in the hydrogen storage alloy is dissociated and generated at the positive electrode as described above. Oxygen gas and hydrogen gas generated at the negative electrode increase the pressure in the nickel-hydrogen storage battery during charging, and particularly when the rapid charging is performed with a high charging current, the internal pressure of the nickel-hydrogen storage battery increases. As a result, a gas leak or a leakage of an electrolytic solution occurs, and the charge-discharge cycle characteristics of the nickel-hydrogen storage battery deteriorate.
[0005]
Furthermore, in order to obtain a nickel-hydrogen storage battery with a high energy density, a space is provided at the center of the positive electrode, and the negative electrode is accommodated in the space at the center of the positive electrode. In a so-called inside-out type nickel-hydrogen storage battery having an increased ratio, the amount of oxygen gas generated at the positive electrode increases, and it is difficult to suppress the dissociation of hydrogen at the negative electrode. There has been a problem that the pressure in the hydrogen storage battery rises, gas leaks and electrolyte leakage occur, and the charge / discharge cycle characteristics and the like deteriorate.
[0006]
Therefore, conventionally, as disclosed in JP-A-60-100382 and JP-A-60-109183, a catalyst for ionizing oxygen is provided on the surface of the above-mentioned negative electrode, thereby producing a catalyst at the positive electrode. In which the internal pressure of a nickel-hydrogen storage battery is prevented from increasing by reacting oxygen gas generated at the negative electrode with hydrogen generated at the negative electrode, or a hydrogen storage alloy as disclosed in JP-A-6-187980. It is proposed to remove the binder on the surface of the electrode, disperse the particles of the hydrogen storage alloy on the surface of the negative electrode, improve the oxygen gas absorption capacity of the negative electrode, and suppress the dissociation of hydrogen. Have been.
[0007]
However, even in those disclosed in these publications, a sufficient effect is not necessarily obtained when rapid charging is performed with a high charging current as described above, or when the battery is used for a nickel-hydrogen storage battery having an inside-out type structure. However, there still remains a problem that gas leakage, electrolyte leakage, and the like occur, and the charge-discharge cycle characteristics of the nickel-hydrogen storage battery deteriorate.
[0008]
Further, conventionally, in order to suppress the generation of oxygen in the positive electrode, there has been proposed a method in which manganese dioxide is used as a positive electrode active material in the positive electrode as shown in Japanese Patent Application Laid-Open No. 61-163570. ing.
[0009]
However, manganese dioxide has poor charge / discharge reversibility as compared with nickel hydroxide, and is therefore limited to applications in which deep discharge is not performed, and there has been a problem that a battery with high energy density cannot be obtained.
[0010]
[Problems to be solved by the invention]
The present invention solves the above-described problems in a nickel-hydrogen storage battery including a positive electrode using a positive electrode active material mainly containing a hydroxide of nickel and a negative electrode using a hydrogen storage alloy as a negative electrode active material. The problem is to suppress the generation of oxygen gas at the positive electrode during charging and to increase the ratio of the positive electrode active material and the negative electrode active material in the battery when performing rapid charging with a high charging current. It is also an object of the present invention to prevent a gas leak, a leakage of an electrolyte solution, or the like from occurring and a decrease in charge / discharge cycle characteristics or the like even when a nickel-hydrogen storage battery having a high energy density is obtained.
[0011]
[Means for Solving the Problems]
In the nickel-hydrogen storage battery according to the present invention, α-Ni (OH) ₂ In a nickel-hydrogen storage battery provided with a positive electrode using a positive electrode active material composed of a composite hydroxide in which at least manganese is dissolved in the crystal structure of the crystal structure and a negative electrode using a negative electrode active material composed of a hydrogen storage alloy, The ratio of manganese in all the metal elements of the positive electrode active material was adjusted to be in the range of 25 to 50 mol% .
[0012]
Here, as in the nickel-hydrogen storage battery of the present invention, α-Ni (OH) ₂ When a positive electrode active material comprising a composite hydroxide in which at least manganese is dissolved in the crystal structure of γ is used, the charged state becomes γ-NiOOH, the overvoltage of oxygen generation increases, and oxygen gas during charging increases. In the case where rapid charging is performed with a high charging current and the rate of the positive electrode active material and the negative electrode active material in the battery is increased to obtain a nickel-hydrogen storage battery with a high energy density, gas leakage and electrolytic Liquid leakage and the like are suppressed, and deterioration of charge / discharge cycle characteristics and the like is prevented. In particular, when charging the nickel-hydrogen storage battery of the present invention, a charge end voltage is set to control charging to be completed before reaching a potential at which oxygen generation occurs, or oxygen current is generated by changing a charging current. If the charging is performed at a constant voltage lower than the generated potential, the charging is performed with extremely high efficiency, and the generation of oxygen at the positive electrode is prevented.
[0013]
Here, as in the nickel-hydrogen storage battery of the present invention, α-Ni (OH) _{2 is} used as a positive electrode active material. When using a composite hydroxide in which at least manganese is dissolved in the crystal structure of the positive electrode active material, if the amount of manganese in the positive electrode active material is small, the crystal structure of the positive electrode active material is likely to change, and oxygen during charging is reduced. While the generation of gas cannot be sufficiently suppressed, when the amount of manganese is too large, the amount of nickel in the positive electrode active material decreases, and the battery capacity of the nickel-hydrogen storage battery decreases. The proportion of manganese in all the metal elements of the active material is in the range of 25 to 50 mol%, preferably in the range of 25 to 40 mol%.
[0014]
【Example】
Hereinafter, the nickel-hydrogen storage battery according to the present invention will be specifically described with reference to examples. In the nickel-hydrogen storage battery according to this example, gas leakage and electrolyte leakage when charging and discharging are repeatedly performed will be described. It will be clarified that a nickel-hydrogen storage battery having excellent charge-discharge cycle characteristics can be obtained by suppressing the above-mentioned conditions and the like with reference to comparative examples. It should be noted that the nickel-hydrogen storage battery according to the present invention is not limited to those shown in the following embodiments, but can be appropriately modified and implemented without changing the gist thereof.
[0015]
(Examples 1 to 3 and Reference Examples 1 and 2 )
In Examples 1 to 3 and Reference Examples 1 and 2 , an AA nickel-hydrogen storage battery having a spiral structure as shown in FIG. 1 was manufactured using the positive electrode and the negative electrode manufactured as described below. .
[0016]
(Preparation of positive electrode)
In preparing the positive electrode, nickel sulfate and manganese sulfate were mixed at a predetermined molar ratio, and 10% of each mixed solution was prepared so that the sulfate concentration was 1.3 mol / l. A mixture of ammonia and 10% sodium hydroxide was added so that the pH was in the range of 10.0 ± 0.4, and the resulting precipitate was filtered, and this was added to a 20% aqueous KOH solution at room temperature. After storing for one week, this was washed and filtered to obtain each positive electrode active material having the composition shown in Table 1 below.
[0017]
Here, when each of these positive electrode active materials was analyzed by X-ray diffraction (XRD) to examine the crystal structure, each of these positive electrode active materials had an α-Ni (OH) ₂ crystal structure. When each of these positive electrode active materials was analyzed by electron beam probe microanalysis (EPMA), manganese was uniformly dissolved in α-Ni (OH) ₂ without uneven distribution.
[0018]
In preparing the positive electrode, 73% by weight of each of the above positive electrode active materials, 7% by weight of cobalt hydroxide as a conductive agent, and 20% by weight of a methylcellulose aqueous solution containing 1% by weight of methylcellulose as a binder were used. %, And kneaded pastes were filled into nickel-plated foamed metal (conductive porous body), dried and molded to obtain each positive electrode.
[0019]
(Preparation of negative electrode)
In preparing the negative electrode, a hydrogen storage alloy powder having a composition of MmNi _3.2 CoAl _0.2 Mn _0.6 was used as a negative electrode active material, and an aqueous solution of polyethylene oxide as a binder was added to the hydrogen storage alloy powder to prepare a paste. Then, this paste was applied on both surfaces of a punched metal plated with nickel, and dried to produce a negative electrode. Here, Mm indicates a misch metal which is a mixture of rare earth elements.
[0020]
(Production of battery)
In producing the battery, each positive electrode and the negative electrode produced as described above were used, and a separator 3 composed of a nonwoven nylon fabric was interposed between the positive electrode 1 and the negative electrode 2 as shown in FIG. After winding in a spiral shape and storing it in the battery can 4, an alkaline electrolyte containing 7 mol / l of potassium hydroxide and 0.4 mol / l of lithium hydroxide was poured into the battery can 4. The positive electrode 1 is connected to the positive electrode lid 6 via the positive electrode lead 5, while the negative electrode 2 is connected to the battery can 4 via the negative electrode lead 7, and the battery can 4 and the positive electrode lid 6 are electrically connected by the packing 8. Each nickel-hydrogen storage battery was obtained by being electrically insulated. Further, in each nickel-hydrogen storage battery, a coil spring 10 is provided between the positive electrode cover 6 and the positive electrode external terminal 9, and when the internal pressure of the battery increases, the coil spring 10 is compressed and the inside of the battery is compressed. The gas was released to the outside.
[0021]
(Comparative Example 1)
In Comparative Example 1, 10% of a mixed solution of nickel sulfate, cobalt sulfate, and zinc sulfate was mixed at a molar ratio of 96: 3: 1 to obtain a positive electrode active material. A mixture of ammonia and 10% sodium hydroxide was added so that the pH was in the range of 11.5 ± 0.2, and the resulting precipitate was filtered, and this was added to a 20% aqueous KOH solution at room temperature. After storing for one week, this was washed and filtered to obtain a positive electrode active material having the composition shown in Table 1 below.
[0022]
Then, a nickel-hydrogen storage battery was produced in the same manner as in Examples 1 to 3 and Reference Examples 1 and 2 except that the thus obtained positive electrode active material was used.
[0023]
Next, each of the nickel-hydrogen storage batteries of Examples 1 to 3, Reference Examples 1 and 2, and Comparative Example 1 produced as described above was charged at a high constant current of 5.0 A until the battery voltage reached 1.55 V. The battery was charged and then kept at a constant voltage of 1.55 V for 10 minutes. After a pause of one hour, the battery is discharged at a discharge current of 1.0 A until the battery voltage reaches 1.0 V, and this is repeated as one cycle, and charging and discharging are repeated. The charge capacity and the discharge capacity after charging, the internal resistance of each nickel-metal hydride storage battery, and the weight reduction of each nickel-metal hydride battery from the time of battery production were obtained. The results are shown in Table 1 below.
[0024]
[Table 1]

[0025]
As a result, when the rapid charging was performed at a high current as described above, in the nickel-hydrogen storage battery of Comparative Example 1, the charge capacity and the discharge capacity at 50 cycles decreased significantly, and the internal resistance of the battery increased significantly. In addition, while the weight loss due to gas leak and liquid leakage was large , the nickel-hydrogen storage batteries of Examples 1 to 3 and Reference Examples 1 and 2 were compared with the nickel-hydrogen storage battery of Comparative Example 1. The decrease in charge capacity and discharge capacity at the time of 50 cycles is significantly reduced, the weight loss due to increase in internal resistance of the battery, gas leak and liquid leakage is also very small, and the charge / discharge cycle characteristics when rapid charging is performed It was significantly improved. In particular, in Examples 1 to 3 and Reference Example 2 in which the ratio of manganese in all the metal elements of the positive electrode active material was in the range of 11 to 50 mol%, the weight due to an increase in the internal resistance of the battery, gas leak and liquid leakage was observed. There was no decrease, and the charge / discharge cycle characteristics when quick charging was performed were further improved.
[0026]
(Examples 4 to 6, Reference Example 3 and Comparative Example 2)
In Examples 4 to 6, Reference Example 3 and Comparative Example 2, using the positive electrode and the negative electrode manufactured as described below, an AA nickel-hydrogen having an inside-out structure as shown in FIG. 2 was used. A storage battery was manufactured.
[0027]
(Preparation of positive electrode)
In manufacturing the positive electrode, as shown in Table 2 below, as a positive electrode active material, Reference Example 2 in Reference Example 3 , Example 1 in Example 4 , Example 2 in Example 5 , In Example 6 , the same positive electrode active material as in Example 3 and Comparative Example 2 was used.
[0028]
Then, graphite was added at a ratio of 10 parts by weight to 90 parts by weight of these positive electrode active materials, and a small amount of water was added to obtain granules, and then these were made to have an outer diameter of 13.3 mm and an inner diameter of 10.3 mm. Each positive electrode 1 as shown in FIG. 2 was obtained by pressure molding into a cylindrical shape.
[0029]
(Preparation of negative electrode)
In producing the negative electrode, a hydrogen storage alloy powder having an average particle size of about 30 μm was obtained by pulverizing an alloy lump having a composition of MmNi _3.3 Co _0.9 Al _0.3 Mn _0.5 as the negative electrode active material.
[0030]
Then, the above-mentioned hydrogen storage alloy powder is wrapped with a negative electrode current collector using a nickel mesh, placed in a molding die having a diameter of 6.5 mm and a height of 36 mm, and subjected to pressure molding. Sintering was performed by heat treatment at 2 ° C. for 2 hours to obtain a negative electrode 2 in which the negative electrode active material 2a was wrapped with the negative electrode current collector 2b made of the above-mentioned nickel mesh, as shown in FIG. Further, a part of the negative electrode current collector 2b was extended from the negative electrode 2, and this was used as the lead portion 2c.
[0031]
(Production of battery)
In producing the battery, as shown in FIG. 2, each of the above-mentioned cylindrical positive electrodes 1 is housed on the outer peripheral side in a battery can 4, respectively, and via a separator 3 in which cellophane and vinylon nonwoven fabric are laminated. Each of the negative electrodes 2 was accommodated in the inner peripheral side of the cylindrical positive electrode 1, and in this state, 3.5 g of an alkaline electrolyte 5 composed of a 40% by weight KOH aqueous solution was injected into each battery can 4. This was sealed to obtain each nickel-hydrogen storage battery. Although not shown, each nickel-hydrogen storage battery was provided with a check valve for discharging gas and the like.
[0032]
Next, each of the nickel-hydrogen storage batteries of Examples 4 to 6, Reference Example 3 and Comparative Example 2 produced as described above was charged at a charging current of 150 mA until the battery voltage reached 1.55 V. , A discharge current of 150 mA until the battery voltage reaches 1.0 V, and charging and discharging are repeated as one cycle. In the second cycle and the 50th cycle, the charge capacity of each nickel-metal hydride storage battery, The discharge capacity, the internal resistance of the battery, and the weight loss of each nickel-hydrogen storage battery from the time of battery production were determined. The results are shown in Table 2 below.
[0033]
[Table 2]

[0034]
As a result, even when the nickel-hydrogen storage battery has the inside-out type structure as described above and the amount of the positive electrode active material or the negative electrode active material in the battery is increased, the above Examples 4 to 6 and Reference Example 3 In each nickel-hydrogen storage battery, the decrease in the charge capacity and the discharge capacity at the time of 50 cycles was significantly smaller than that of the nickel-hydrogen storage battery of Comparative Example 2, and the increase in the internal resistance of the battery was very small. In addition, a nickel-hydrogen storage battery having high battery capacity and excellent charge / discharge cycle characteristics was obtained with almost no weight loss due to gas leak or liquid leakage.
[0035]
【The invention's effect】
As described in detail above, in the nickel-hydrogen storage battery of the present invention , α-Ni (OH) ₂ A positive electrode active material comprising a composite hydroxide in which at least manganese is dissolved in the crystal structure of the positive electrode active material was used, and the ratio of manganese in all the metal elements of the positive electrode active material was adjusted to be in the range of 25 to 50 mol%. Overvoltage of oxygen generation in the positive electrode active material is increased, and generation of oxygen gas in the positive electrode during charging is suppressed, so that gas leakage and electrolyte leakage in the nickel-hydrogen storage battery are prevented. .
[0036]
As a result, according to the present invention, in the case of performing rapid charging with a high charging current, or in the case of increasing the proportion of the positive electrode active material or the negative electrode active material in the battery to obtain a nickel-hydrogen storage battery having a high energy density Thus, a nickel-hydrogen storage battery having excellent charge-discharge cycle characteristics has been obtained.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view of nickel-hydrogen storage batteries manufactured in Examples 1 to 3, Reference Examples 1 and 2, and Comparative Example 1 of the present invention.
FIG. 2 is a schematic explanatory view of the nickel-hydrogen storage batteries manufactured in Examples 4 to 6, Reference Example 3 and Comparative Example 2 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery can

Claims

α-Ni (OH) ₂ In a nickel-hydrogen storage battery provided with a positive electrode using a positive electrode active material composed of a composite hydroxide in which at least manganese is dissolved in the crystal structure of the crystal structure and a negative electrode using a negative electrode active material composed of a hydrogen storage alloy, Wherein the proportion of manganese in all the metal elements of the positive electrode active material is in the range of 25 to 50 mol% .

2. The nickel-hydrogen storage battery according to claim 1, wherein a space is provided in a central portion of the positive electrode, and the negative electrode is provided in the space via a separator .

The nickel-hydrogen storage battery according to claim 1 or 2, wherein a negative electrode obtained by sintering a hydrogen storage alloy is used .