JP3625731B2

JP3625731B2 - Square battery

Info

Publication number: JP3625731B2
Application number: JP2000084118A
Authority: JP
Inventors: 雅雄井上; 太計男浜松; 敬長瀬; 英之浅沼
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1999-03-25
Filing date: 2000-03-24
Publication date: 2005-03-02
Anticipated expiration: 2020-03-24
Also published as: JP2000340251A

Description

【０００１】
【発明の属する技術分野】
本発明は角型電池にかかり、特にニッケル−水素蓄電池、ニッケル−カドミウム蓄電池などの正極板と負極板とをセパレータを介して積層した極板群を備えた角型電池に関するものである。
【０００２】
【従来の技術】
近年、正極板と負極板をセパレータを介して渦巻状に巻回した渦巻状電極群を備えた円筒型アルカリ蓄電池に代わり、電池使用機器内での体積効率を高めるために角型アルカリ蓄電池が開発されるようになった。この種の角型アルカリ蓄電池においては、正極板と負極板をセパレータを介して交互に積層した極板群を角型の外装缶内に挿入し、正極板より延出する正極リードを正極端子に接続し、負極板より延出する負極リードを負極端子に接続した後、電解液を注入し、開口部を封口体で封止して作製するようにしている。
【０００３】
この種の角型アルカリ蓄電池は携帯電話、ノートブック型パーソナルコンピュータ等の携帯機器用電源としての需要が急速に拡大し、これに伴って、角型アルカリ蓄電池のさらなる高容量化、長寿命化が要求されるようになった。このため、この種の角型アルカリ蓄電池は、例えば、帯状の芯体を共通にしてその左右に２つの負極板を形成した後、その中央部（連結部）をＵ字状に折曲し、Ｕ字状に折曲された２つの負極板間にセパレータを介して正極板を挟持させた極板組の間にセパレータを介して正極板を積層して極板群とし、この極板群を電解液とともに角型外装缶内に挿入して製造される。
【０００４】
【発明が解決しようとする課題】
ところで、上述した角型のアルカリ蓄電池のエネルギー密度をさらに増大させようとした場合、電池の充放電反応に関与しないセパレータを薄型にすれば、セパレータが薄くなった分だけ活物質の充填量を増加させることが可能となって高エネルギー密度で高容量の電池が得られるようになる。
しかしながら、高エネルギー密度で高容量な電池とするために、セパレータを薄型にすればするほどセパレータの機械的強度が減少し、内部短絡が発生するようになるので、セパレータの薄型化には限界があった。
【０００５】
ここで、例えば、図５に示すように、中央の折曲部（連結部）２３でＵ字状に折曲された２つの負極板２４，２５間にセパレータ３０，３０を介して正極板１０Ｄを挟持させて極板組とし、これらの２つ極板組の間にセパレータ３０，３０を介して正極板１０Ｄを積層して極板群とし、この極板群を電解液とともに角型外装缶内に挿入して角型アルカリ蓄電池を形成すると、セパレータ３０は６枚が必要となる。
【０００６】
ところが、セパレータを薄型化する代わりに電池内に配置するセパレータの枚数を減少させ、セパレータが減少した分だけ極板の厚みを増大させて活物質の充填量を増加させると、図６に示すように、中央の折曲部（連結部）２３でＵ字状に折曲された２つの負極板２６，２７間にセパレータ３０，３０を介して厚みの厚い正極板１０Ｅを挟持させて極板組とし、これらの２つ極板組を積層して極板群として、この極板群を電解液とともに角型外装缶内に挿入して角型アルカリ蓄電池を形成すると、セパレータは４枚だけで済むようになる。
【０００７】
このように、セパレータを薄型化する代わりに電池内に配置するセパレータの枚数を減少させれば、セパレータの挿入枚数が減少した分だけ極板の厚みを増加させて活物質の充填量を増加させることが可能となるので、高エネルギー密度で高容量の電池が得られるようになる。
【０００８】
しかしながら、活物質を高密度に充填して、厚みが厚い極板を作製することは困難であるという問題を生じた。また、三次元網目構造の多孔性基板（発泡ニッケルなど）を極板芯体として用いて極板を製造する場合、極板芯体自体の厚みを厚くすることが困難であるという問題も生じた。
そこで、本発明は前記実情にかんがみてなされたもので、極板の製造が容易であるとともに活物質の充填密度および体積エネルギー密度が大きい角型アルカリ蓄電池を提供することを目的としてなされたものである。
【０００９】
【課題を解決するための手段】
上記課題を解決するため、本発明の角型アルカリ蓄電池の極板群は、極板芯体からなる連結部の両側に一対の一方極の極板が形成されているとともに、該連結部がＵ字状に折曲されており、前記連結部にてＵ字状に折曲された一方極の一対の極板間にセパレータを介して他方極の複数の極板よりなる複合極板が挟持されて極板組が形成されているとともに、該極板組の複数組がセパレータを介することなく直接積層されて電極群が形成されており、前記複数の極板よりなる複合極板の各極板は金属多孔体からなる極板芯体に活物質が充填されて形成されていて、該各極板の少なくとも１つは該複合極板より延出して集電リード板が固着されており、前記電極群の最外側に配置された前記一方極の極板は前記金属外装缶の内側面に緊密に接触するとともに前記連結部が前記金属外装缶の内底面に緊密に接触するように前記電極群が前記金属外装缶に収容されている。このような極板群構成であると、極板組間にはセパレータを配置する必要が無くなるため、極板群内のセパレータの枚数を減少させることが可能となる。
【００１０】
そして、極板群内のセパレータの枚数を減少させると、セパレータの枚数を減少させた分だけ他方極および一方極の極板の厚みを増すことが可能になるが、極板の厚みを増加させる代わりに極板の枚数を増加させることにより、１枚当たりの極板の厚みを薄くすることが可能となる。この結果、活物質を高密度に充填することが可能になるとともに、三次元網目構造の多孔性基板（発泡ニッケルなど）を極板芯体として用いることも可能となり、極板の体積エネルギー密度が向上して、高容量の角型アルカリ蓄電池が得られるようになる。
【００１１】
また、複合極板の各極板の少なくとも１つは該複合極板より延出して集電リード板が固着されており、この集電リード板の固着面がセパレータに接しないように配置されていると、集電リード板の形成時に生じたバリ等に起因して発生するセパレータ貫通による短絡を防止できるようになる。そして、複合極板の各極板にそれぞれ集電リード板を設ける場合、これらの溶接面同士を対向させて、その反対側をセパレータに接するようにすれば、セパレータ貫通による短絡を防止できるようになる。
【００１２】
また、複合極板の各極板間に１つの集電リード板が固着されており、この集電リード板により複合極板の各極板からの集電がなされるようにすると、集電リード板の固着面がセパレータと接しないように配置されることとなるので、セパレータ貫通による短絡を防止できるようになるとともに、集電リード板の個数を減らすことが可能となる。
【００１３】
さらに、一方極の各極板間にはこれらの各極板の極板芯体からなる連結部が一体的に形成されているとともに、この連結部が略Ｕ字状に折曲されていると、略Ｕ字状に折曲された一方極の各極板間にセパレータを介して複合極板を配置するだけで極板組が容易に構成できるようになるため、この種の極板群の構成が容易となる。
【００２８】
【発明の実施の形態】
以下に、本発明をニッケル−水素蓄電池に適用した場合の一実施形態を図に基づいて説明する。
なお、図１は第１実施例の複合正極板を示す図であり、図１（ａ）は２枚の正極板をずらして重ね合わせた状態を示す図であり、図１（ｂ）はその側面を示す図である。図２は第２実施例の複合正極板を示す図であり、図２（ａ）は２枚の正極板をずらして重ね合わせた状態を示す図であり、図２（ｂ）はその側面を示す図である。図３は第３実施例の複合正極板を示す図であり、図３（ａ）は３枚の正極板をずらして重ね合わせた状態を示す図であり、図３（ｂ）はその側面を示す図である。また、図４は本発明の各実施例の極板群を示す断面図であり、図５は第１比較例の極板群を示す図であり、図６は第２比較例の極板群を示す図である。
【００２９】
１．複合正極板の作製
（１）実施例１
発泡ニッケル等よりなる三次元的に連続する空間を有する金属多孔体（例えば、厚みが１．２ｍｍのもの）よりなる芯体に水酸化ニッケルを主成分とする活物質スラリーを充填し、乾燥した後、所定の厚み（例えば、０．６３ｍｍ）になるように圧延して第１のニッケル正極板１１および第２のニッケル正極板１２を作製した。
【００３０】
ついで、第１のニッケル正極板１１および第２のニッケル正極板１２の上端部に充填された活物質の一部を除去して活物質の剥離部をそれぞれ形成した後、これらの剥離部に第１の集電リード板１１ａあるいは第２の集電リード板１２ａをそれぞれ溶接して固着した。この後、図１（なお、図１（ａ）は両極板をずらして配置（極板完成時には完全に重なった状態となっている）した状態を示す正面図であり、図１（ｂ）はその側面図である）に示すように、第１の集電リード板１１ａと第２の集電リード板１２ａとがそれぞれ対向するようにして、第１のニッケル正極板１１の上に第２のニッケル正極板１２を重ね合わせて実施例１の複合正極板１０Ａを作製した。
【００３１】
なお、水酸化ニッケルを主成分とする活物質スラリーとしては、例えば、共沈成分として亜鉛２．５重量％とコバルト１重量％を含有する水酸化ニッケル粉末１０重量部と、酸化亜鉛粉末３重量部との混合粉末に、ヒドロキシプロピルセルロースの０．２重量％水溶液を加えて撹拌、混合したものを使用した。以下、同様に、水酸化ニッケルを主成分とする活物質スラリーはこの方法で作成したものを使用した。
【００３２】
（２）実施例２
発泡ニッケル等よりなる三次元的に連続する空間を有する金属多孔体（例えば、厚みが１．２ｍｍのもの）よりなる芯体に水酸化ニッケルを主成分とする活物質スラリーを充填し、乾燥した後、所定の厚み（例えば、０．６３ｍｍ）になるように圧延して第１のニッケル正極板１３および第２のニッケル正極板１４を作製した。
【００３３】
ついで、第２のニッケル正極板１４の上端部に充填された活物質の一部を除去して活物質の剥離部を形成した後、この剥離部に集電リード板１４ａを溶接して固着した。この後、図２（なお、図２（ａ）は両極板をずらして配置（極板完成時には完全に重なった状態となっている）した状態を示す正面図であり、図２（ｂ）はその側面図である）に示すように、第２のニッケル正極板１４の集電リード板１４ａが第１のニッケル正極板１３に対向するようにして、第１のニッケル正極板１３の上に第２のニッケル正極板１４を重ね合わせた後、固着して実施例２の複合正極板１０Ｂを作製した。
【００３４】
（３）比較例１
発泡ニッケル等よりなる三次元的に連続する空間を有する金属多孔体（例えば、厚みが１．５ｍｍのもの）よりなる芯体に水酸化ニッケルを主成分とする活物質スラリーを充填し、乾燥した後、所定の厚み（例えば、０．８３ｍｍ）になるように圧延してニッケル正極板を作製した。ついで、ニッケル正極板の上端部に充填された活物質の一部を除去して活物質の剥離部を形成した後、この剥離部に集電リード板を溶接して比較例１の正極板１０Ｄを作製した。
【００３５】
（４）比較例２
発泡ニッケル等よりなる三次元的に連続する空間を有する金属多孔体（例えば、厚みが２．２ｍｍのもの）よりなる芯体に水酸化ニッケルを主成分とする活物質スラリーを充填し、乾燥した後、所定の厚み（例えば、１．２９ｍｍ）になるように圧延してニッケル正極板を作製した。ついで、ニッケル正極板の上端部に充填された活物質の一部を除去して活物質の剥離部を形成した後、この剥離部に集電リード板を溶接して比較例２の正極板１０Ｅを作製した。
【００３６】
２．連結負極板の作製
Ｔｉ−Ｎｉ系あるいはＬａ（もしくはＭｍ）−Ｎｉ系の多元合金、例えば、ＭｍＮｉ_３．４Ｃｏ_０．８Ａｌ_０．２Ｍｎ_０．６合金よりなる水素吸蔵合金粉末に結着剤としてポリテトラフルオロエチレン（ＰＴＦＥ）粉末を水素吸蔵合金粉末に対して５重量％加えて混練して、負極活物質ペーストを作製した。この負極活物質ペーストを、パンチングメタル等からなる金属芯体にその中央部（連結部）２３が露出するように左右両側に塗着した後、両面から加圧して中央部（連結部）２３で接続された２個の水素吸蔵合金負極板２１，２２（２４，２５あるいは２６，２７）からなる連結負極板２０Ａ（２０Ｂ，２０Ｃ）を作製した。
なお、上述した各実施例および比較例で作製した正極板と負極板の容量比が同一となるように、負極活物質ペーストの各々調整した。
【００３７】
３．電極群の作製
（１）実施例１〜２
上述のように作製した２個の水素吸蔵合金負極板２１，２２からなる連結負極板２０Ａの中央部（連結部）２３をそれぞれＵ字状に折曲した後、厚み０．１５ｍｍのポリプロピレン製不織布からなるセパレータ３０を介して上述のように作製した各複合正極板１０Ａおよび１０Ｂをそれぞれ挟持させて、極板組を作製した（図４参照）。このように作製した極板組をそれぞれ２組づつ用意し、これらの２組の極板組をそれぞれ積層して、実施例１〜２の極板群を作製した。なお、実施例１の複合正極板１０Ａを用いた極板群を実施例１の極板群Ａとし、実施例２の複合正極板１０Ｂを用いた極板群を実施例２の極板群Ｂとした。
【００３８】
（２）比較例１
上述のように作製した２個の水素吸蔵合金負極板２４，２５からなる連結負極板２０Ｂの中央部（連結部）２３をそれぞれＵ字状に折曲した後、厚み０．１５ｍｍのポリプロピレン製不織布からなるセパレータ３０を介して上述のように作製した正極板１０Ｄを挟持させて極板組を作製した。このように作製した極板組をそれぞれ２組づつ用意し、これらの２組の極板組を積層して、比較例１の極板群Ｄを作製した。
【００３９】
（３）比較例２
上述のように作製した２個の水素吸蔵合金負極板２６，２７からなる連結負極板２０Ｃの中央部（連結部）２３をそれぞれＵ字状に折曲した後、厚み０．１５ｍｍのポリプロピレン製不織布からなるセパレータ３０を介して上述のように作製した正極板１０Ｅを挟持させて極板組を作製した。このように作製した極板組をそれぞれ２組づつ用意し、これらの２組の極板組を積層して、比較例２の極板群Ｅを作製した。
【００４０】
なお、上述のようにして作製された極板群の各実施例１〜２の複合正極板１０Ａ，１０Ｂおよび各比較例１，２の正極板１０Ｄ，１０Ｅの極板厚み、正極活物質密度、正極活物質量および各負極活物質量を測定すると、下記の表１に示すような結果となった。
【００４１】
【表１】

【００４２】
なお、上記表１において、比較例１の極板群Ｄの正極板１０Ｄの極板厚み、正極活物質密度、正極活物質量および連結負極板２０Ｂの各水素吸蔵合金負極板２４，２５の負極活物質量をそれぞれ１００として算出した。また、各複合正極板１０Ａ，１０Ｂの極板厚みにおいては各ニッケル正極板１１（１２），１３（１４）のそれぞれの厚みを求めた値である。
上記表１より明らかなように、各実施例１〜２の複合正極板１０Ａ，１０Ｂは厚みを低減できたことから、高密度化が可能となることが分かる。
【００４３】
４．角型ニッケル−水素蓄電池の作製
上述のように作製した各極板群Ａ，Ｂ，Ｄ，Ｅをそれぞれ有底角型の金属外装缶内に挿入し、各極板群Ａ，Ｂ，Ｄ，Ｅの両端部の水素吸蔵合金負極板２２（２５あるいは２７）と金属外装缶の内側面とを緊密に接触させるとともに、金属芯体が露出した中央部（連結部）２３が金属外装缶の内底面に緊密に接触させる。ついで、これらの各金属外装缶内にそれぞれ３０重量％の水酸化カリウム（ＫＯＨ）水溶液よりなる電解液を注液することにより、Ｂ１サイズ（幅１７．０ｍｍ、高さ４８．０ｍｍ、厚み６．１ｍｍ）の角型ニッケル−水素蓄電池Ａ，Ｂ，Ｄ，Ｅをそれぞれ作製した。
【００４４】
なお、実施例１の極板群Ａを用いた角型ニッケル−水素蓄電池を実施例１の電池Ａとし、実施例２の極板群Ｂを用いた角型ニッケル−水素蓄電池を実施例２の電池Ｂとし、比較例１の極板群Ｄを用いた角型ニッケル−水素蓄電池を比較例１の電池Ｄとし、比較例２の極板群Ｅを用いた角型ニッケル−水素蓄電池を比較例２の電池Ｅとした。
【００４５】
５．放電容量試験
上述のように作製した各電池Ａ，Ｂ，Ｄ，Ｅを０．１Ｃ（６０ｍＡ）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、０．２Ｃ（１２０ｍＡ）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。この充放電を室温で５サイクル繰り返して、各角型ニッケル−水素蓄電池Ａ，Ｂ，Ｄ，Ｅを活性化した。
【００４６】
ついで、上述のように活性化した各角型ニッケル−水素蓄電池Ａ，Ｂ，Ｄ，Ｅを、０．１Ｃ（６０ｍＡ）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、０．２Ｃ（１２０ｍＡ）の放電々流で終止電圧が１．０Ｖになるまで放電させたときの放電時間より放電容量を求め、比較例１の電池Ｄの放電容量を１００とした場合の容量比を求めると、下記の表２に示すような結果が得られた。
【００４７】
【表２】

【００４８】
なお、上記表２より明らかなように、比較例１の電池Ｄと比較例２の電池Ｅとを比較すると、比較例２の電池の方が放電容量が大きいことが分かる。これは、連結負極板２０Ａの各水素吸蔵合金負極板２１，２２の間に正極板１０Ｅを挟持させた２つの極板組を積層して極板群を形成した方が、２つの極板組間にセパレータ３０を介して正極板１０Ｄを積層するより、セパレータ３０の使用枚数を減少させることが可能となるため、その分、正極板１０Ｅおよび負極板２６，２７の厚みを増加させることができ、放電容量が増加したためである。
【００４９】
また、実施例１〜２の各電池Ａ，Ｂと比較例２の電池Ｅとを比較すると、実施例１〜２の各電池Ａ，Ｂの方が放電容量が大きいことが分かる。これは、セパレータ３０の使用枚数が同じであっても、実施例１〜２の各電池Ａ，Ｂは、複合正極板１０Ａ，１０Ｂを用いたことにより、各正極板１１，１２（１３，１４）の活物質の充填密度が増加し、各正極板１１，１２（１３，１４）に充填される活物質量が増大したためである。
【００５０】
６．変形例
上述した各実施例においては、２枚の正極板を用いて複合極板とする例について説明したが、本発明の複合極板は２枚に限られることはなく、３枚でも、４枚でも複合させることが可能である。ついで、図３（なお、図３（ａ）は３枚の極板をずらして配置（極板完成時には完全に重なった状態となっている）した状態を示す正面図であり、図３（ｂ）はその側面図である）に基づいて本変形例の複合極板を説明する。
【００５１】
まず、発泡ニッケル等よりなる三次元的に連続する空間を有する金属多孔体（例えば、厚みが０．８ｍｍのもの）よりなる芯体に水酸化ニッケルを主成分とする活物質スラリーを充填し、乾燥した後、所定の厚み（例えば、０．４２ｍｍ）になるように圧延して第１のニッケル正極板１５、第２のニッケル正極板１６および第３のニッケル正極板１７をそれぞれ作製した。
【００５２】
ついで、第１のニッケル正極板１５および第３のニッケル正極板１７の上端部に充填された活物質の一部をそれぞれ除去して活物質の剥離部を形成した後、これらの剥離部に第１の集電リード板１５ａあるいは第２の集電リード板１７ａをそれぞれ溶接して固着した。この後、図３に示すように、第１のニッケル正極板１５の第１の集電リード板１５ａと第２のニッケル正極板１６とが対向するとともに、第２のニッケル正極板１６と第３のニッケル正極板１７の第２の集電リード板１７ａとが対向するようにして、第１のニッケル正極板１５の上に第２のニッケル正極板１６および第３のニッケル正極板１７を重ね合わせた後、固着して変形例の複合正極板１０Ｃを作製した。
【００５３】
一方、上述のように作製した２個の水素吸蔵合金負極板２１，２２からなる連結負極板２０Ａの中央部（連結部）２３をそれぞれＵ字状に折曲した後、厚み０．１５ｍｍのポリプロピレン製不織布からなるセパレータ３０を介して上述のように作製した複合正極板１０Ｃを挟持させて、極板組を作製した。このように作製した極板組をそれぞれ２組づつ用意し、これらの２組の極板組をそれぞれ積層して、変形例の極板群Ｃを作製した。
【００５４】
この極板群Ｃを有底角型の金属外装缶内に挿入し、極板群Ｃの両端部の水素吸蔵合金負極板２２と金属外装缶の内側面とを緊密に接触させるとともに、金属芯体が露出した中央部（連結部）２３が金属外装缶の内底面に緊密に接触させる。ついで、金属外装缶内に３０重量％の水酸化カリウム（ＫＯＨ）水溶液よりなる電解液を注液することにより、Ｂ１サイズ（幅１７．０ｍｍ、高さ４８．０ｍｍ、厚み６．１ｍｍ）の角型ニッケル−水素蓄電池Ｃを作製した。
【００５５】
７．集電リード板の取付位置の検討
ついで、複合正極板より延出して固着された集電リード板の取付位置と短絡の発生具合との関係を検討した。上述した実施例１〜２の各電池Ａ，Ｂおよび変形例の電池Ｃの他に、新たに、実施例１と同様なニッケル正極板１１，１２に溶接された集電リード板１１ａ，１２ａが互いに対向しないように重ね合わせて作製した比較例３の複合正極板１０Ｆ（図示せず）を用いた比較例３の電池Ｆと、実施例２と同様なニッケル正極板１４に溶接された集電リード板１４ａがニッケル正極板１３に対向しないように重ね合わせて作製した比較例４の複合正極板１０Ｇ（図示せず）を用いた比較例４の電池Ｆとを作製した。これらの実施例１〜２の各電池Ａ，Ｂと、変形例の電池Ｃと、比較例３の電池Ｆと、比較例４の電池Ｇとをそれぞれ１０００個ずつ用意し、これらの各電池Ａ，Ｂ，Ｃ，Ｄ，Ｅ，Ｆ，Ｇの内部抵抗を測定して短絡率を求めると下記の表３に示すような結果となった。
【００５６】
【表３】

【００５７】
上記表３から明らかなように、実施例１〜２の各電池Ａ，Ｂおよび変形例の電池Ｃにおいては短絡は発生しなかったが、比較例３の電池Ｆにあっては７個（０．７％）の電池に短絡が発生し、比較例４の電池Ｇにあっては３個（０．３％）の電池に短絡が発生した。これは、比較例４の電池Ｇの複合正極板１０Ｇは集電リード板１４ａのみが片面のセパレータに接触しているため、この集電リード板１４ａの製造時に生じたバリによりセパレータ貫通が生じて短絡したためである。一方、比較例３の電池Ｆの複合正極板１０Ｆは集電リード板１１ａ，１２ａのそれぞれがセパレータに接触しているため、これらの集電リード板１１ａ，１２ａの製造時に生じたバリにより複合正極板１０Ｆの片面または両面のセパレータにセパレータ貫通が生じて短絡したためである。
【００５８】
なお、極板芯体として金属多孔体を用いた場合、この極板芯体の厚さは、０．５−３ｍｍ程度が望ましく、さらに望ましくは１−２．５ｍｍ程度である。例えば極板芯体として発泡ニッケルを用いた場合について考える。まず、厚くなりすぎると、活物質を充填して圧延する際、均一な圧延が不可能であるという問題がある。さらに単位面積当たり重量一定で、厚くした場合は、厚くなりすぎると、芯体骨格部が細くなり、強度が低下してしまう。あるいは活物質から集電体としての芯体までの距離が長くなり、反応性が低下するという問題がある。さらにまた、単位面積当たり重量一定という条件なしに、厚くした場合、芯体重量が増加するため軽量極板が作製できない。あるいはポア数が多くなりすぎるために、各ポアに均一に活物質を充填できないという問題がある。
【００５９】
さらにまた極板芯体については厚さのみならず、開口率の観点から、単位面積当たりの重量を２００ｇ／ｍ^２〜１０００ｇ／ｍ^２とするのが望ましい。さらに望ましくは３００ｇ／ｍ^２〜６００ｇ／ｍ^２とするのが望ましい。つまり、極板芯体は、活物質を十分に含有でき、かつ集電体として十分に機能できるようにするように形成する必要がある。
【００６０】
また、セパレータの厚さは０．０５−０．３ｍｍさらに望ましくは０．０７−０．２ｍｍである。
さらに、前記複合極板は隣接する２枚の極板間の一端縁に挟持された集電リードを介して固着されており、固着面は活物質が除去され極板芯体が露呈しており、前記極板芯体と前記集電リードとの固着によって接続されているため、厚さを大幅に増大することなく、電極面積を最大限に大きく利用する事が可能となる。
【００６１】
このように、本発明によれば、最適の条件で極板芯体の厚さを決定し、これを積層構造体として使用することにより、必要な厚さの極板を得ることができる。したがって、製造が容易で体積エネルギー密度の大きい角型電池を提供することが可能となる。
【００６３】
【発明の効果】
上述したように、本発明の極板群においては、極板群内に配置されるセパレータの枚数を低減することが可能となるため、その分、極板の厚みを増加させることが可能になり、高容量の電池が得られるようになる。また、極板の厚みを増加させる手段として、厚みが薄い複数の極板からなる複合極板を使用するようにしているので、各極板に充填される活物質の充填密度を高くすることが可能となるため、高エネルギー密度で、高容量の角型アルカリ蓄電池を得ることが可能となる。
【００６４】
なお、上述した実施形態においては、本発明をニッケル−水素蓄電池に適用する例について説明したが、ニッケル−水素蓄電池に限らず、ニッケル−カドミウム蓄電池など他の角型電池に本発明を適用しても同様な効果を得ることが可能となる。
【図面の簡単な説明】
【図１】本発明の第１実施例の複合正極板を示す図であり、図１（ａ）は２枚の正極板をずらして重ね合わせた状態を示す図であり、図１（ｂ）はその側面を示す図である。
【図２】本発明の第２実施例の複合正極板を示す図であり、図２（ａ）は２枚の正極板をずらして重ね合わせた状態を示す図であり、図２（ｂ）はその側面を示す図である。
【図３】本発明の変形例の複合正極板を示す図であり、図３（ａ）は３枚の正極板をずらして重ね合わせた状態を示す図であり、図３（ｂ）はその側面を示す図である。
【図４】本発明の極板群を示す図である。
【図５】従来例（第１比較例）の極板群を示す図である。
【図６】他の従来例（第２比較例）の極板群を示す図である。
【符号の説明】
１０Ａ，１０Ｂ，１０Ｃ…複合正極板、１１…第１のニッケル正極板、１１ａ…第１の集電リード板、１２…第２のニッケル正極板、１２ａ…第２の集電リード板、１３…第１のニッケル正極板、１４…第２のニッケル正極板、１４ａ…集電リード板、１５…第１のニッケル正極板、１５ａ…第１の集電リード板、１６…第２のニッケル正極板、１７…第３のニッケル正極板、１７ａ…第２の集電リード板、２０Ａ…連結負極板、２１，２２…水素吸蔵合金負極板、２３…連結部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a prismatic battery, and more particularly to a prismatic battery including an electrode plate group in which a positive electrode plate and a negative electrode plate such as a nickel-hydrogen storage battery and a nickel-cadmium storage battery are stacked via a separator.
[0002]
[Prior art]
In recent years, instead of a cylindrical alkaline storage battery that has a spiral electrode group in which a positive electrode plate and a negative electrode plate are spirally wound via a separator, a rectangular alkaline storage battery has been developed to increase volumetric efficiency in battery-operated equipment. It came to be. In this type of prismatic alkaline storage battery, an electrode plate group in which positive and negative electrode plates are alternately stacked via a separator is inserted into a rectangular outer can, and a positive electrode lead extending from the positive electrode plate is used as a positive electrode terminal. After connecting and connecting a negative electrode lead extending from the negative electrode plate to the negative electrode terminal, an electrolytic solution is injected and the opening is sealed with a sealing body.
[0003]
This type of prismatic alkaline storage battery has rapidly expanded the demand for power sources for portable devices such as mobile phones and notebook personal computers, and this has led to further increases in capacity and longer life of prismatic alkaline storage batteries. It came to be required. Therefore, this type of prismatic alkaline storage battery, for example, after forming two negative plates on the left and right with a strip-shaped core body in common, bend the center (connecting portion) into a U-shape, A positive electrode plate is laminated via a separator between two electrode plates each having a positive electrode plate sandwiched between two negative electrode plates bent in a U-shape. It is manufactured by being inserted into a rectangular outer can together with an electrolytic solution.
[0004]
[Problems to be solved by the invention]
By the way, when trying to further increase the energy density of the above-mentioned rectangular alkaline storage battery, if the separator that does not participate in the charge / discharge reaction of the battery is made thin, the amount of active material filling increases as the separator becomes thinner. Therefore, a battery having a high energy density and a high capacity can be obtained.
However, in order to obtain a battery with high energy density and high capacity, the thinner the separator, the lower the mechanical strength of the separator and the occurrence of an internal short circuit. there were.
[0005]
Here, for example, FIG. As shown in FIG. 4, the positive electrode plate 10D is sandwiched between the two

negative electrode plates

24, 25 bent in a U shape at the central bent portion (connecting portion) 23 via the

separators

30, 30. The positive electrode plate 10D is laminated between the two electrode plate sets via the

separators

30 and 30 to form an electrode plate group, and this electrode plate group is inserted into the rectangular outer can together with the electrolyte. When an alkaline storage battery is formed, six separators 30 are required.
[0006]
However, instead of reducing the thickness of the separator, the number of separators arranged in the battery is decreased, and the thickness of the electrode plate is increased by the amount of the decrease in the separator to increase the active material filling amount. FIG. As shown in FIG. 3, a thick positive electrode plate 10E is sandwiched between two

negative electrode plates

26, 27 bent in a U shape by a central bent portion (connecting portion) 23 via

separators

30, 30. When an electrode plate assembly is formed, and these two electrode plate assemblies are laminated to form an electrode plate group, and this electrode plate group is inserted into the prismatic outer can together with the electrolytic solution to form a prismatic alkaline storage battery, four separators are formed. You just need to.
[0007]
In this way, if the number of separators disposed in the battery is reduced instead of reducing the thickness of the separator, the thickness of the electrode plate is increased by the amount corresponding to the decrease in the number of separators inserted, and the active material filling amount is increased. Therefore, a battery having a high energy density and a high capacity can be obtained.
[0008]
However, there is a problem that it is difficult to fill the active material with a high density to produce a thick electrode plate. Also ,three A porous substrate with a three-dimensional network structure (foamed nickel, etc.) is used as an electrode plate core. The When manufacturing an electrode plate, there also arises a problem that it is difficult to increase the thickness of the electrode plate core itself.
Accordingly, the present invention has been made in view of the above circumstances, and has been made for the purpose of providing a prismatic alkaline storage battery that is easy to manufacture an electrode plate and has a high active material filling density and a large volume energy density. is there.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the electrode plate group of the prismatic alkaline storage battery of the present invention is: A pair of one-electrode plates are formed on both sides of the connecting portion made of the electrode plate core, and the connecting portion is bent in a U shape, and is bent in a U shape at the connecting portion. A composite electrode plate made up of a plurality of electrode plates of the other electrode is sandwiched between a pair of electrode plates of the one electrode, with a separator interposed therebetween to form an electrode plate assembly. The electrode group is formed by directly laminating without any interposition, and each electrode plate of the composite electrode plate made of the plurality of electrode plates is formed by filling an active material into an electrode plate core made of a metal porous body. At least one of the electrode plates extends from the composite electrode plate and has a current collecting lead plate fixed thereto, and the electrode plate of the one electrode disposed on the outermost side of the electrode group is the metal outer can. The inner surface of the metal outer can is in close contact with the inner surface of the metal outer can. The electrode group is housed in the metal outer can to. With such an electrode plate group configuration, there is no need to arrange separators between the electrode plate groups, and the number of separators in the electrode plate group can be reduced.
[0010]
When the number of separators in the electrode plate group is reduced, it is possible to increase the thickness of the other electrode and the electrode plate of the one electrode by an amount corresponding to the decrease in the number of separators, but increase the thickness of the electrode plate. Instead, by increasing the number of electrode plates, the thickness of each electrode plate can be reduced. As a result, it becomes possible to fill the active material with a high density, and it is also possible to use a porous substrate (such as foamed nickel) having a three-dimensional network structure as the electrode plate core, and the volume energy density of the electrode plate is reduced. As a result, a high capacity prismatic alkaline storage battery can be obtained.
[0011]
Also, At least one of the electrode plates of the composite electrode plate extends from the composite electrode plate, and the current collecting lead plate is fixed. In addition, if the current collecting lead plate is disposed so that the fixing surface does not contact the separator, it is possible to prevent a short circuit due to the penetration of the separator caused by burrs or the like generated when the current collecting lead plate is formed. . And when providing a current collecting lead plate on each electrode plate of the composite electrode plate, if these welding surfaces are made to face each other and the opposite side is in contact with the separator, a short circuit due to the penetration of the separator can be prevented. Become.
[0012]
In addition, one current collecting lead plate is fixed between each electrode plate of the composite electrode plate, and when current collecting from each electrode plate of the composite electrode plate is performed by this current collecting lead plate, the current collecting lead plate Since the fixed surface of the plate is arranged so as not to contact the separator, it is possible to prevent a short circuit due to the penetration of the separator and to reduce the number of current collecting lead plates.
[0013]
Further, a connecting portion composed of a plate core body of each of these electrode plates is integrally formed between each electrode plate of one electrode, and this connecting portion is bent in a substantially U shape. In this type of electrode plate group, the electrode plate assembly can be easily configured simply by arranging a composite electrode plate between each electrode plate of one electrode bent in a substantially U shape via a separator. Configuration becomes easy.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Below, one embodiment at the time of applying the present invention to a nickel-hydrogen storage battery is described based on figures.
1 is a diagram showing the composite positive electrode plate of the first embodiment, FIG. 1 (a) is a diagram showing a state in which two positive electrode plates are shifted and overlapped, and FIG. It is a figure which shows a side surface. FIG. 2 is a diagram showing a composite positive electrode plate of a second embodiment, FIG. 2 (a) is a diagram showing a state in which two positive electrode plates are shifted and overlapped, and FIG. 2 (b) is a side view thereof. FIG. FIG. 3 is a view showing a composite positive electrode plate according to a third embodiment, FIG. 3 (a) is a view showing a state in which three positive electrode plates are shifted and overlapped, and FIG. 3 (b) is a side view thereof. FIG. Also, Figure 4 It is a cross-sectional view showing an electrode plate group of each example of the present invention, FIG. Is a diagram showing an electrode plate group of a first comparative example, FIG. These are figures which show the electrode group of a 2nd comparative example.
[0029]
1. Preparation of composite positive electrode plate
(1) Example 1
An active material slurry mainly composed of nickel hydroxide was filled into a core made of a porous metal body (for example, having a thickness of 1.2 mm) having a three-dimensionally continuous space made of foamed nickel or the like and dried. Then, it rolled so that it might become predetermined | prescribed thickness (for example, 0.63 mm), and the 1st nickel positive electrode plate 11 and the 2nd nickel positive electrode plate 12 were produced.
[0030]
Next, after removing a part of the active material filled in the upper end portions of the first nickel positive electrode plate 11 and the second nickel positive electrode plate 12 to form the active material separation portions, One current collecting lead plate 11a or the second current collecting lead plate 12a was welded and fixed. After this, FIG. 1 (note that FIG. 1 (a) is a front view showing a state in which both electrode plates are shifted and arranged (when the electrodes are completed, they are completely overlapped), FIG. 1 (b) is a front view. As shown in the side view of FIG. 2, the first current collecting lead plate 11a and the second current collecting lead plate 12a are opposed to each other on the first nickel positive electrode plate 11, respectively. A composite positive electrode plate 10A of Example 1 was manufactured by superimposing the nickel positive electrode plates 12.
[0031]
The active material slurry containing nickel hydroxide as a main component includes, for example, 10 parts by weight of nickel hydroxide powder containing 2.5% by weight of zinc and 1% by weight of cobalt as a coprecipitation component, and 3% by weight of zinc oxide powder. A 0.2 wt% aqueous solution of hydroxypropylcellulose was added to the mixed powder and the mixture was stirred and mixed. Hereinafter, similarly, an active material slurry mainly composed of nickel hydroxide was prepared by this method.
[0032]
(2) Example 2
An active material slurry mainly composed of nickel hydroxide was filled into a core made of a porous metal body (for example, having a thickness of 1.2 mm) having a three-dimensionally continuous space made of foamed nickel or the like and dried. Then, it rolled so that it might become predetermined | prescribed thickness (for example, 0.63 mm), and the 1st nickel positive electrode plate 13 and the 2nd nickel positive electrode plate 14 were produced.
[0033]
Next, after removing a part of the active material filled in the upper end portion of the second nickel positive electrode plate 14 to form a peeled portion of the active material, the current collecting lead plate 14a was welded and fixed to the peeled portion. . After this, FIG. 2 (FIG. 2 (a) is a front view showing a state in which the two electrode plates are shifted and arranged (the electrodes are completely overlapped when the electrode plates are completed), and FIG. 2 (b) is a front view. As shown in the side view), the current collecting lead plate 14a of the second nickel positive electrode plate 14 is placed on the first nickel positive electrode plate 13 so that the current collector lead plate 14a faces the first nickel positive electrode plate 13. The two nickel positive electrode plates 14 were superposed and then fixed to produce a composite positive electrode plate 10B of Example 2.
[0034]
(3) Comparative Example 1
An active material slurry mainly composed of nickel hydroxide was filled into a core made of a porous metal body (for example, having a thickness of 1.5 mm) having a three-dimensionally continuous space made of foamed nickel or the like and dried. Then, it rolled so that it might become predetermined | prescribed thickness (for example, 0.83 mm), and the nickel positive electrode plate was produced. Next, after removing a part of the active material filled in the upper end portion of the nickel positive electrode plate to form a peeled portion of the active material, a current collecting lead plate is welded to the peeled portion, and the positive electrode plate 10D of Comparative Example 1 is used. Was made.
[0035]
(4) Comparative Example 2
An active material slurry mainly composed of nickel hydroxide was filled into a core made of a metal porous body (for example, having a thickness of 2.2 mm) having a three-dimensionally continuous space made of foamed nickel or the like and dried. Then, it rolled so that it might become predetermined | prescribed thickness (for example, 1.29 mm), and the nickel positive electrode plate was produced. Next, after removing a part of the active material filled in the upper end portion of the nickel positive electrode plate to form a peeled portion of the active material, a current collecting lead plate is welded to the peeled portion, and the positive electrode plate 10E of Comparative Example 2 is used. Was made.
[0036]
2. Production of connected negative plates
Ti-Ni-based or La (or Mm) -Ni-based multi-component alloys such as MmNi _3.4 Co _0.8 Al _0.2 Mn _0.6 An anode active material paste was prepared by adding 5% by weight of polytetrafluoroethylene (PTFE) powder as a binder to the hydrogen storage alloy powder made of an alloy and kneading the hydrogen storage alloy powder. This negative electrode active material paste is applied to a metal core made of punched metal or the like on both the left and right sides so that the central portion (connecting portion) 23 is exposed. A connected negative electrode plate 20A (20B, 20C) composed of two connected hydrogen storage alloy negative electrode plates 21, 22 (24, 25 or 26, 27) was produced.
In addition, each of the negative electrode active material paste was adjusted so that the capacity ratios of the positive electrode plate and the negative electrode plate produced in each of the above-described Examples and Comparative Examples were the same.
[0037]
3. Fabrication of electrode group
(1) Examples 1-2
After folding the central portion (connecting portion) 23 of the connecting negative electrode plate 20A composed of the two hydrogen storage alloy negative electrode plates 21 and 22 prepared as described above into a U-shape, a polypropylene non-woven fabric having a thickness of 0.15 mm Each of the composite

positive electrode plates

10A and 10B prepared as described above was sandwiched via a separator 30 made of the above, thereby preparing an electrode plate assembly (see FIG. 4). Two sets of electrode plates prepared in this way were prepared, and these two electrode plate groups were laminated to prepare the electrode plate groups of Examples 1 and 2. An electrode plate group using the composite positive electrode plate 10A of Example 1 is referred to as an electrode plate group A of Example 1, and an electrode plate group using the composite positive electrode plate 10B of Example 2 is used as an electrode plate group B of Example 2. It was.
[0038]
(2) Comparative Example 1
After bending the central portion (connecting portion) 23 of the connecting negative electrode plate 20B composed of the two hydrogen storage alloy

negative electrode plates

24 and 25 produced as described above into a U-shape, a polypropylene non-woven fabric having a thickness of 0.15 mm The positive electrode plate 10 </ b> D prepared as described above was sandwiched through the separator 30 made of the electrode plate, and an electrode plate assembly was prepared. Two pairs of electrode plates thus prepared were prepared, and these two electrode plate groups were laminated to prepare the electrode plate group D of Comparative Example 1.
[0039]
(3) Comparative Example 2
After bending the central portion (connecting portion) 23 of the connecting negative electrode plate 20C composed of the two hydrogen storage alloy

negative electrode plates

26 and 27 prepared as described above into a U-shape, a polypropylene non-woven fabric having a thickness of 0.15 mm The positive electrode plate 10E manufactured as described above was sandwiched through the separator 30 made of the electrode plate, and an electrode plate assembly was manufactured. Two electrode plate assemblies prepared in this way were prepared, and these two electrode plate assemblies were laminated to prepare the electrode plate group E of Comparative Example 2.
[0040]
In addition, the electrode plate thickness of each of the composite

positive electrode plates

10A and 10B of Examples 1-2 and the positive electrode plates 10D and 10E of Comparative Examples 1 and 2 of the electrode plate group manufactured as described above, the positive electrode active material density, When the amount of the positive electrode active material and the amount of each negative electrode active material were measured, the results shown in Table 1 below were obtained.
[0041]
[Table 1]

[0042]
In Table 1 above, the electrode plate thickness of the positive electrode plate 10D of the electrode plate group D of Comparative Example 1, the positive electrode active material density, the positive electrode active material amount, and the negative electrodes of the hydrogen storage alloy

negative electrode plates

24 and 25 of the connected negative electrode plate 20B. Each active material amount was calculated as 100. Moreover, in the electrode plate thickness of each composite

positive electrode plate

10A, 10B, it is the value which calculated | required each thickness of each nickel positive electrode plate 11 (12), 13 (14).
As is clear from Table 1 above, it can be seen that the composite

positive plates

10A and 10B of Examples 1 and 2 can be reduced in thickness because the thickness can be reduced.
[0043]
4). Fabrication of prismatic nickel-hydrogen storage battery
Each electrode plate group A, B, D, E produced as described above Bottomed square type And in close contact with the hydrogen storage alloy negative electrode plate 22 (25 or 27) at both ends of each electrode plate group A, B, D, E and the inner surface of the metal outer can, The central portion (connecting portion) 23 where the metal core is exposed is brought into close contact with the inner bottom surface of the metal outer can. Next, an electrolytic solution composed of a 30% by weight potassium hydroxide (KOH) aqueous solution was poured into each of these metal outer cans to obtain a B1 size (width 17.0 mm, height 48.0 mm, thickness 6. 1 mm) square nickel-hydrogen storage batteries A, B, D, and E were produced.
[0044]
In addition, the prismatic nickel-hydrogen storage battery using the electrode plate group A of Example 1 is referred to as the battery A of Example 1, and the prismatic nickel-hydrogen storage battery using the electrode plate group B of Example 2 is that of Example 2. A prismatic nickel-hydrogen storage battery using the electrode plate group D of Comparative Example 1 as a battery B and a prismatic nickel-hydrogen storage battery using the electrode plate group E of Comparative Example 2 as a comparative example Battery E of No. 2 was obtained.
[0045]
5. Discharge capacity test
Each battery A, B, D, E produced as described above is charged for 16 hours with a charging current of 0.1 C (60 mA) and then rested for 1 hour. Thereafter, the battery is discharged at a discharge current of 0.2 C (120 mA) until the final voltage reaches 1.0 V, and then rested for 1 hour. This charging / discharging was repeated at room temperature for 5 cycles to activate each prismatic nickel-hydrogen storage battery A, B, D, E.
[0046]
Next, each of the prismatic nickel-hydrogen storage batteries A, B, D, E activated as described above is charged for 16 hours with a charging current of 0.1 C (60 mA), and then rested for 1 hour. Thereafter, the discharge capacity was obtained from the discharge time when the discharge was discharged at a discharge current of 0.2 C (120 mA) until the final voltage reached 1.0 V, and the discharge capacity of the battery D of Comparative Example 1 was set to 100. When the capacity ratio was determined, the results shown in Table 2 below were obtained.
[0047]
[Table 2]

[0048]
As is clear from Table 2 above, when the battery D of Comparative Example 1 and the battery E of Comparative Example 2 are compared, it can be seen that the battery of Comparative Example 2 has a larger discharge capacity. This is because two electrode plate groups are formed by laminating two electrode plate groups in which the positive electrode plate 10E is sandwiched between the hydrogen storage alloy negative electrode plates 21 and 22 of the connecting negative electrode plate 20A. Since the number of separators 30 used can be reduced rather than laminating the positive electrode plate 10D with the separator 30 interposed therebetween, the thickness of the positive electrode plate 10E and the

negative electrode plates

26 and 27 can be increased accordingly. This is because the discharge capacity has increased.
[0049]
Moreover, when each battery A and B of Examples 1-2 and the battery E of the comparative example 2 are compared, it turns out that each battery A and B of Examples 1-2 has a larger discharge capacity. Even if the number of separators 30 used is the same, each of the batteries A and B of Examples 1 and 2 uses the composite

positive plates

10A and 10B, so that the positive plates 11 and 12 (13 and 14). This is because the packing density of the active material in () increased, and the amount of active material filled in each of the positive electrode plates 11, 12 (13, 14) increased.
[0050]
6). Modified example
In each of the above-described embodiments, an example in which a composite electrode plate is formed using two positive electrode plates has been described. However, the composite electrode plate of the present invention is not limited to two plates, and three or four plates may be used. It is possible to combine them. Next, FIG. 3 (note that FIG. 3 (a) is a front view showing a state in which the three electrode plates are shifted and arranged (when the electrode plates are completely overlapped)), FIG. ) Is a side view of the composite electrode plate of the present modification.
[0051]
First, an active material slurry mainly composed of nickel hydroxide is filled into a core body made of a porous metal body (for example, having a thickness of 0.8 mm) having a three-dimensionally continuous space made of nickel foam or the like, After drying, the first nickel positive electrode plate 15, the second nickel positive electrode plate 16, and the third nickel positive electrode plate 17 were produced by rolling to a predetermined thickness (for example, 0.42 mm).
[0052]
Next, a part of the active material filled in the upper end portions of the first nickel positive electrode plate 15 and the third nickel positive electrode plate 17 is respectively removed to form an active material peeling portion. The first current collecting lead plate 15a or the second current collecting lead plate 17a was welded and fixed. Thereafter, as shown in FIG. 3, the first current collecting lead plate 15a of the first nickel positive electrode plate 15 and the second nickel positive electrode plate 16 face each other, and the second nickel positive electrode plate 16 and the third nickel positive electrode plate 16 The second nickel positive electrode plate 16 and the third nickel positive electrode plate 17 are superimposed on the first nickel positive electrode plate 15 so that the second current collecting lead plate 17a of the nickel positive electrode plate 17 faces the second current collecting lead plate 17a. After that, the composite positive electrode plate 10C of a modified example was produced by fixing.
[0053]
On the other hand, after bending the central portion (connecting portion) 23 of the connecting negative electrode plate 20A composed of the two hydrogen storage alloy negative electrode plates 21 and 22 produced as described above into a U-shape, polypropylene having a thickness of 0.15 mm is obtained. The composite positive electrode plate 10C produced as described above was sandwiched through a separator 30 made of a non-woven fabric to produce an electrode plate assembly. Prepare two sets of electrode plates prepared in this way, and laminate these two sets of electrode plates, Modified example Electrode plate group C was prepared.
[0054]
This plate group C Bottomed square type The metal storage can is inserted into the metal outer can, and the hydrogen storage alloy negative electrode plates 22 at both ends of the electrode plate group C and the inner surface of the metal outer can are brought into close contact with each other, and the central portion (connecting portion) where the metal core is exposed 23 is brought into close contact with the inner bottom surface of the metal outer can. Next, by injecting an electrolytic solution comprising a 30 wt% potassium hydroxide (KOH) aqueous solution into the metal outer can, a B1 size (width 17.0 mm, height 48.0 mm, thickness 6.1 mm) corner is obtained. Type nickel-hydrogen storage battery C was produced.
[0055]
7). Examination of current collector lead plate mounting position
Next, the relationship between the mounting position of the current collector lead plate extended from the composite positive electrode plate and fixed and the occurrence of a short circuit was examined. In addition to the batteries A and B of Examples 1 and 2 described above and the battery C of the modified example, current collecting lead plates 11a and 12a newly welded to nickel

positive plates

11 and 12 similar to Example 1 are provided. A current collector welded to a battery F of Comparative Example 3 using a composite positive electrode plate 10F (not shown) of Comparative Example 3 which is produced by being overlapped so as not to face each other, and a nickel positive electrode plate 14 similar to Example 2. A battery F of Comparative Example 4 was produced using a composite positive electrode plate 10G (not shown) of Comparative Example 4 which was produced by overlapping the lead plate 14a so as not to face the nickel positive electrode plate 13. Each of the batteries A and B of Examples 1 and 2, the battery C of the modified example, the battery F of the comparative example 3, and the battery G of the comparative example 4 are each prepared in a quantity of 1,000. , B, C, D, E, F, and G were measured to determine the short-circuit rate, and the results shown in Table 3 below were obtained.
[0056]
[Table 3]

[0057]
As apparent from Table 3 above, no short circuit occurred in the batteries A and B of Examples 1 and 2 and the battery C of the modified example, but 7 batteries (0 in the battery F of Comparative Example 3) .7%), a short circuit occurred, and in the battery G of Comparative Example 4, three (0.3%) batteries were short circuited. This is because, in the composite positive electrode plate 10G of the battery G of Comparative Example 4, only the current collector lead plate 14a is in contact with the separator on one side, so that the separator penetrates due to the burr generated during the production of the current collector lead plate 14a. This is because of a short circuit. On the other hand, in the composite positive electrode plate 10F of the battery F of Comparative Example 3, since the current collector lead plates 11a and 12a are in contact with the separator, the composite positive electrode plate 10F is caused by burrs generated during the production of the current collector lead plates 11a and 12a. This is because the separator penetration has occurred in the separator on one or both sides of the plate 10F, resulting in a short circuit.
[0058]
In addition, when a metal porous body is used as the electrode plate core, the thickness of the electrode plate core is preferably about 0.5 to 3 mm, more preferably about 1 to 2.5 mm. For example, when foamed nickel is used as the electrode plate core In Think about it. First, if it is too thick, there is a problem that uniform rolling is impossible when rolling with filling of the active material. Further, when the weight per unit area is constant and the thickness is increased, if the thickness is too large, the core skeleton is thinned and the strength is lowered. Alternatively, there is a problem that the distance from the active material to the core as a current collector is increased, and the reactivity is lowered. Furthermore, when the thickness is increased without the condition of constant weight per unit area, the weight of the core increases, so that a lightweight electrode plate cannot be produced. Alternatively, since the number of pores becomes too large, there is a problem that the active material cannot be uniformly filled in each pore.
[0059]
Furthermore, with respect to the electrode plate core, not only the thickness but also the weight per unit area is 200 g / m from the viewpoint of the aperture ratio. ² ~ 1000g / m ² Is desirable. More desirably 300 g / m ² ~ 600g / m ² Is desirable. That is, the electrode plate core needs to be formed so that it can sufficiently contain the active material and can sufficiently function as a current collector.
[0060]
The thickness of the separator is 0.05-0.3 mm, more preferably 0.07-0.2 mm.
Further, the composite electrode plate is fixed via a current collecting lead sandwiched at one end edge between two adjacent electrode plates, the active material is removed from the fixing surface, and the electrode plate core is exposed. Since the electrode plate core body and the current collecting lead are connected to each other, the electrode area can be maximized without significantly increasing the thickness.
[0061]
Thus, according to the present invention, an electrode plate having a required thickness can be obtained by determining the thickness of the electrode plate core body under optimum conditions and using this as a laminated structure. Therefore, it is possible to provide a prismatic battery that is easy to manufacture and has a large volumetric energy density.
[0063]
【The invention's effect】
As described above, in the electrode plate group of the present invention, the number of separators arranged in the electrode plate group can be reduced, and accordingly, the thickness of the electrode plate can be increased accordingly. A high capacity battery can be obtained. In addition, as a means for increasing the thickness of the electrode plate, a composite electrode plate composed of a plurality of thin electrode plates is used, so that the packing density of the active material filled in each electrode plate can be increased. Therefore, it becomes possible to obtain a prismatic alkaline storage battery having a high energy density and a high capacity.
[0064]
In the above-described embodiment, an example in which the present invention is applied to a nickel-hydrogen storage battery has been described. However, the present invention is not limited to a nickel-hydrogen storage battery, but is applied to other prismatic batteries such as a nickel-cadmium storage battery. The same effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing a composite positive electrode plate according to a first embodiment of the present invention. FIG. 1 (a) is a diagram showing a state in which two positive electrode plates are shifted and overlapped, and FIG. FIG.
FIG. 2 is a view showing a composite positive electrode plate according to a second embodiment of the present invention. FIG. 2 (a) is a view showing a state in which two positive electrode plates are shifted and overlapped, and FIG. FIG.
FIG. 3 is a view showing a composite positive electrode plate according to a modification of the present invention. FIG. 3 (a) is a view showing a state in which three positive electrode plates are shifted and overlapped, and FIG. It is a figure which shows a side surface.
FIG. 4 is a diagram showing an electrode plate group according to the present invention.
[Figure 5] It is a figure which shows the electrode group of a prior art example (1st comparative example).
[Fig. 6] It is a figure which shows the electrode group of another prior art example (2nd comparative example).
[Explanation of symbols]
10A, 10B, 10C ... composite positive electrode plate, 11 ... first nickel positive electrode plate, 11a ... first current collecting lead plate, 12 ... second nickel positive electrode plate, 12a ... second current collecting lead plate, 13 ... 1st nickel positive electrode plate, 14 ... 2nd nickel positive electrode plate, 14a ... current collecting lead plate, 15 ... 1st nickel positive electrode plate, 15a ... 1st current collecting lead plate, 16 ... 2nd nickel positive electrode plate , 17 ... third nickel positive electrode plate, 17a ... second current collecting lead plate, 20A ... connection negative electrode plate, 21, 22 ... hydrogen storage alloy negative electrode plate, 23 ... connection portion

Claims

A prismatic battery in which a group of electrode plates in which one electrode plate and the other electrode plate are stacked via a separator is housed in a rectangular metal outer can,
  A pair of unipolar electrode plates are formed on both sides of the connecting portion made of the electrode plate core, and the connecting portion is bent in a U shape,
  A composite electrode plate composed of a plurality of electrode plates of the other electrode is sandwiched between a pair of electrode plates of the one electrode bent in a U shape at the connecting portion via a separator to form an electrode plate assembly. And the electrode group is formed by directly laminating a plurality of sets of electrode plates without using a separator,
  Each electrode plate of the composite electrode plate made of the plurality of electrode plates is formed by filling an active material into an electrode plate core body made of a metal porous body, and at least one of the electrode plates is more than the composite electrode plate. Extending and the current collector lead plate is fixed,
  The electrode plate disposed on the outermost side of the electrode group is in close contact with the inner surface of the metal outer can, and the connecting portion is in close contact with the inner bottom surface of the metal outer can. A square battery characterized in that a group is accommodated in the metal outer can.

2. The prismatic battery according to claim 1, wherein the current collecting lead plate is fixed to a peeling portion where the active material is removed and the electrode plate core made of the metal porous body is exposed. 3.

The square battery according to claim 1 or 2, wherein the porous metal body is nickel foam.

The square battery according to any one of claims 1 to 3, wherein the composite electrode plate constitutes a positive electrode.

5. The electrode plate according to claim 1, wherein the electrode plate of the one electrode is formed by applying an active material paste to both surfaces excluding the connecting portion of a metal core made of punch metal. Square battery.