JP3952493B2

JP3952493B2 - Alkaline storage battery

Info

Publication number: JP3952493B2
Application number: JP2000199498A
Authority: JP
Inventors: 俊樹田中; 幸雄藤田; 佳克大谷; 達雄礒谷
Original assignee: 株式会社ユアサ開発
Priority date: 2000-06-30
Filing date: 2000-06-30
Publication date: 2007-08-01
Anticipated expiration: 2020-06-30
Also published as: JP2002015722A

Description

【０００１】
【発明の属する技術分野】
本発明は、電動工具や、ハイブリッド電気自動車（ＨＥＶ）電源用等の大電流での充放電を必要とする用途に適したアルカリ蓄電池に関するものであって、電気的特性に優れかつ生産性の高い電池に関するものである。
【０００２】
【従来の技術】
水素吸蔵合金を主材とした負極を用いた密閉形アルカリ蓄電池は、優れた充放電特性と、環境等の点から最近用途が拡大しつつある。中でも、電動工具やＨＥＶ用電池等の大電流充放電用電源としての需要が見込まれている。
【０００３】
従来、焼結式正極を用いたアルカリ蓄電池は、高率での充放電特性に優れるため、これらの大電流用途における主流電池であった。大電流用途に使用される電池は、渦巻きまたは積層式極群を採用し電流密度を下げている。また集電端子をインダイレクト溶接などで溶着させるタブレス方式を採用して、集電効果を高めている。
【０００４】
しかし、焼結式正極の容量密度は４５０ｍＡｈ／ｃｍ３程度であり、電池の容量を増加させることには限界があった。一方、フェルト状またはスポンジ状金属多孔体を基板とし、該基板に水酸化ニッケルを充填する方法を用いた非焼結式正極では５５０ｍＡｈ／ｃｍ３以上の容量密度が可能となり、ポータブル機器用の高容量ニッケル水素蓄電池や高容量ニッケルカドミウム蓄電池などに一般的に使用されている。最近では電気自動車用のニッケル水素蓄電池などにも使用され始めている。
【０００５】
前記のように、アルカリ蓄電池では集電端子をタブレス方式により極板の端部に溶接する。該極板端部は一般的に露出した基板から成る。非焼結式電極の基板は前記金属多孔体である。上記の非焼結式正極を使用した場合、焼結式電極を使用したものに比べて、集電端子と基板との溶接箇所の電気抵抗が高いため、高率放電特性に劣る欠点があった。
【０００６】
前記欠点改善のため、極板端部に帯状の活物質未充填部分を設け、該活物質未充填部分に帯状のニッケル板などを溶接した後に該極板端部に集電端子をシリーズ溶接するなどの提案（特開昭５６−８６４５９号公報）がなされている。また、工程を簡略化する目的で特開昭６２−１３９２５１号公報では、あらかじめ溶接部を圧縮した発泡性基板を用いて、タブレス方式に於ける集電端子の溶接強度を確保することができるとしている。
【０００７】
大電流での充放電を可能とするためには、集電端子の厚みを大きくする、集電端子と極板間の溶接点数を増やす、外部端子（円筒形電池においては電池蓋部分に相当する）と集電端子間を接続するリード片の長さを短くしたり、肉厚を厚くしたりして集電部分の電気抵抗を低減する方法がある。
【０００８】
しかしながら、従来の溶接方法を用いた場合、集電端子の厚みを厚くするとシリーズ溶接時の無効電流を増加させることになり、溶接強度を高めることが困難となる。また、従来の集電端子の構造で溶接点数を増加させようとするのは、溶接回数が多くなるので実際上困難である。また、リード片を短くしたり、肉厚を厚くすることは集電端子と外部端子の接続を難しくする。また、封口時にリード片が折り曲げられるため、リード片の剛性が大きいとリード片と集電端子あるいは集電端子と電極との溶着部が剥離するなどの問題が生じる。
【０００９】
特開昭６１−３２３５３公報には、渦巻き状極群を有するアルカリ蓄電池において集電体の下面に放射状の突部を設け、該突部と極板端部を溶接することにより極群と集電端子の溶接強度を高めることが提案されている。また特開平１１−３１４９７公報には集電端子の中央付近から外周縁部に至る切り欠き部複数個を放射状に設け、該切り欠き部の縁部に下向きのリブ状突起を設け、該リブ状突起が極板端部と交差しその一部分が端部に食い込み複数点で溶接されている構造が提案されている。本提案によれば、強固な溶接が得られる点に於いて優れている。本提案の場合リブ状突起の数を増せば、その分溶接点数を増やせる利点がある。しかし、リブ状突起の数に比例して多くの溶接回数を必要とする欠点がある。前記公報によれば、正極および負極の基板は焼結式ニッケル板や穿孔板、集電端子は鉄製鋼板で、いずれも硬質の材料である。そのため、極板端部と集電端子が溶接されずに単に接触しているのみでは電気的導通が確保されないため溶接が不可欠である。前記ＨＥＶ用等大形電池においては極群が大形になるため、極板と集電端子間に多数の電気的導通箇所を必要とする。大形電池の場合、従来の集電構造では多数回の溶接を必要とした。従って、少ない溶接回数で集電端子と極板との電気的導通箇所を多くできる集電構造が求められていた。
【００１０】
【発明が解決しようとする課題】
本発明はこのような課題を解決するために、電池内部の集電構造を改良することによって、集電端子と極群の溶接が少ない回数で済み、かつ集電機能に優れた大電流充放電が可能なアルカリ蓄電池を実現しようとするものである。
【００１１】
【課題を解決するための手段】
本発明は前記の課題を解決するため、渦巻き式又は積層式極群の相対向する外面に突出した正極板端部および負極板端部に集電端子を溶接してなるアルカリ蓄電池において、少なくとも一方の極板端部がフェルト状またはスポンジ状金属多孔体であり、該極板端部に溶接される集電端子が平面部にスリットおよび極群に面する側に高さが０．２〜１ｍｍのリブ状突起を有し、該集電端子の前記スリットを挟む平面部と極板端部に溶接されてなるとともに、前記リブ状突起が極板端部と交差し食い込んで接触している構造としたアルカリ蓄電池である。本構造によれば、集電端子平面部と極板端部の溶接箇所の他、溶接されていないリブ状突起と極板端部の接触箇所も電気的な導通を有する。該接触箇所で電気的導通を確保するので、溶接回数を増やさなくてもリブ状突起の数を増やすのみで導通箇所を多くすることができる。従って、少ない溶接回数で多くの導通箇所を確保できるので、特に大形極板の集電に有効である。
【００１２】
後述の如く、本発明によれば、前記溶接箇所は集電端子の平面部に設けられたスリットを挟む箇所のみである。従って本発明に係る集電構造は溶接回数が少なくて済みかつ集電効果の高い構造である。ここでいう高い集電効果とは極板の基板および集電端子を含む集電体の電気抵抗が小さいことは無論であるが、むしろ１枚の極板内および複数の極板間に集電体の電気抵抗に差がないことを指す。このことは充放電の際の電流分布が均一に保たれるための必要条件である。電流分布が均一に保たれれば、高率で放電した場合でも高い活物質利用率が得られる。そのためには集電端子と極板の基板との電気的接触点が多く、且つ該接触点が偏らずに分布していることが求められるが、本発明はそれに合致するものである。
【００１３】
本発明によれば集電端子と極板端部との間で強固な溶接強度が得られる。本発明の場合極板端部に溶接しようとする集電端子の平面部にスリットを配置している。該スリットを挟んで両側に溶接器の電極を当接して溶接することにより無効電流を抑制し、溶接電流を高めることができる。このため溶接に不利な平面であっても良好な溶接が得られる。集電端子突起と極板端部の溶接は点での溶接であり、極板端部がフェルト状またはスポンジ状金属多孔体の場合には溶接箇所の機械的強度が弱いのに対して、本発明のように同基板端部と集電端子平面との溶接は面での溶接なので機械的強度が強く、衝撃や振動が加わった場合にも溶接箇所がはずれ難い利点がある。
【００１４】
本発明は更に、前記集電端子のリブ状突起と極板端部が略垂直に交差している構造である。極板端面とリブ状突起が略垂直に交差していると、突起が小さい応力で極板端部に食い込むため突起が変形せず、良好な食い込み状態が得られる。該食い込み箇所は溶接されずに接触しているのみであるが、電気的導通が良好である。従って本構造によれば、前記溶接箇所以外に基板と集電端子との電気的導通の良好な接触箇所を得ることができる。渦巻き式又は積層式極群に於いては、集電端子のリブ状突起と極板との接触箇所は多い。またリブ状突起を均等に配置することにより、前記接触箇所を極板の長さ方向に対して均等に配置することが可能である。このため、前記の高い集電効果が得られる。
【００１５】
本発明の場合、正極板と負極板の中少なくとも一方の基板は、ニッケル等の金属繊維マットから成るフェルト状又は発泡体から成るスポンジ状金属多孔体であって、集電端子と溶接される側の極板端部は、活物質が未充填であり前記基板が露出している。活物質が未充填状態の前記多孔体は柔軟で弾性に富む。従って、前記リブ状突起が基板に無理無く食い込むことにより、両者の接触箇所で電気的導通が確保される。活物質が充填された基板は柔軟性、弾性共に喪失するので好ましくない。
【００１６】
【発明の実施の形態】
本発明に係る集電構造は、少なくても一方の極板を構成する基板が前記フェルト状またはスポンジ状金属多孔体である電池に対して適用される。アルカリ蓄電池の場合、一般適に前記金属多孔体は正極の基板に適用され、負極の基板には穿孔板が適用されることが多い。従って本発明は少なくとも正極の集電構造に適用される。ここでは正極の集電構造に限って記述するが、負極の基板が前記金属多孔体である場合、本発明は負極の集電構造に対しても有効である。
【００１７】
本発明に係るアルカリ蓄電池に於ける正極は前記非焼結式正極である。帯状の正極、セパレータおよび負極の積層体が巻き込まれた渦巻き式かまたは矩形の正極、セパレータおよび負極が複数枚積層された積層式極群を有する。該極群を構成する正極板は繊維状ニッケルマットまたは発泡状ニッケル製基板に活物質が充填されている。極板長手方向の片側端部には、帯状に活物質未充填部分が形成され、基板が露出している。基板が露出した正極板の端部に集電端子が溶接されている。
【００１８】
前記集電端子は、平面部にスリットおよび極群に面する側に高さが０．２〜１ｍｍのリブ状突起を有している。極板端部と前記集電端子のスリットを挟む平面部が溶接されている。極板端部と前記リブ状突起は交差し、かつ、リブ状突起は極板端部に食い込んでいる。前記集電端子に配置されたスリットは、溶接工程において溶接電流値を高める役割を果たす。すなわち、溶接機の２本の電極を、前記スリットを挟んで対峙させて溶接することにより、無効電流が抑えられ、溶接電流値が高められるので良好な溶接が得られる。従って、スリットのない場合に比べ溶接箇所が少なくて済む。本発明においては、溶接は集電端子のスリットを挟む平面部においてのみ行われる。そのため溶接回数が少なくて済む。
【００１９】
極板端部と前記リブ状突起は略垂直に交差している。前記のようにリブ状突起は極板端部に食い込んでいる。該交差部の中には、極板端部とリブ状突起が弱く溶接されている例も認められる。これは意図して溶接したものでは無いが、前記極板端部と集電端子との溶接工程において、前記交差部に漏れ電流が流れたために溶接されたものと推定される。交差部が単なる接触あるいは弱い溶接の何れの場合であっても、該交差部において基板と集電端子との間に良好な電気的導通が得られる。このため少ない溶接回数で高い集電効果が達成できる。
【００２０】
【実施例】
以下、本発明の１実施例を図面に基づいて説明する。なお、本発明の形状、寸法等は以下に示した例に限定されるものではない。
【００２１】
図１は、本発明に係る円筒形電池の正極集電端子の１例を示す斜視図である。該集電端子１は、厚さ４μｍのニッケルメッキが施された鉄製である。集電端子１は、直径が２８ｍｍφ、厚さが０．５ｍｍの円盤状で、図の１ａに示すように幅２ｍｍの切り欠き部が存在する。切り欠き部１ａの両側にはリブ状突起１ｂがある。リブ状突起１ｂは、高さが０．５ｍｍであり図のように先端が尖っている。リブ状突起の高さは、極板上端部に設けられた帯状の活物質未充填部の幅０．５〜２ｍｍより小さくなければならない。前記リブ状突起が極板端部に容易に食い込み、極板と集電端子間に良好な電気的導通が得られるためには、リブ状突起の高さが０．２〜１ｍｍであって先端が尖っていることが望ましい。また、図の例では平面部１ｄに溶接効果を高めるために幅１ｍｍ、長さ４ｍｍのスリット１ｃが設けられている。
【００２２】
図２（Ａ）は、本発明に係る角形電池の正極集電端子２の斜視図である。該集電端子２は、厚さ４μｍのニッケルメッキが施された鉄製である。集電端子２は、幅１２ｍｍ、長さ１００ｍｍ、厚さ０．５ｍｍの矩形板で、図の２ａに示すように幅５ｍｍ、長さ１０ｍｍの切り欠き部がある。切り欠き部２ａの両側にはリブ状突起２ｂがある。図１に示した円筒形電池の集電端子と同様、集電端子の平面部２ｄにスリット２ｃが設けられている。図２（Ｂ）は、図２（Ａ）の一点鎖線Ａ−Ａ′で切断した断面図である。リブ状突起２ｂは高さが０．５ｍｍであり、先端が尖った形状であることを示す。
【００２３】
図３は本発明に係る円筒形電池用正極集電端子の別の例を示す斜視図である。集電端子３は、図１に示した例同様直径が２８ｍｍ、厚さが０．５ｍｍの円盤状で、Ｖ字状のリブ状突起３ｂを有する。該リブ状突起は高さが約０．５ｍｍであり、図のように先端が尖っていることが望ましい。リブ状突起の高さは図１に示した１ｂ同様０．２〜１ｍｍが適当である。また平面部３ｄには溶接効果を高めるためのスリット３ｃが配置されている。
【００２４】
図４は比較のために示した、従来の円筒形電池用正極集電端子４の平面図である。厚さ０．３ｍｍのニッケル製で、直径が２８ｍｍφの円盤状である。
【００２５】
図５は比較のために示した、従来の角形電池用正極集電端子５の平面図である。厚さ０．３ｍｍのニッケル製で、幅が１２ｍｍ、長さが１００ｍｍの矩形板である。
【００２６】
図６は円筒形アルカリ蓄電池の渦巻き状極群６の上面に集電端子１が取り付けられた状態を示す説明図である。渦巻き状極群６の上面に正極板端部６ａが突出しており、該正極板端部６ａに集電端子１が溶接されている。スリット１ｃの両側に位置する黒点６ｂに溶接機の電極が当接され抵抗溶接される。これによって正極板端面６ａと集電端子１のスリット１ｃを挟む平面が溶接される。本例では溶接点が６点で、溶接回数は３回である。
【００２７】
図７は図６に示した集電端子付きの極群を真上から見た説明図である。前記正極板端部６ａを波線で表した。スリット１ａの両側に設けられたリブ状突起１ｂは円の中心から略放射状に伸びており、渦巻き状の極板端部６ａと略垂直に交差接触している。前記の如く、極板上端部は活物質未充填であり、柔らかくて柔軟性のある繊維状又は発泡のニッケル製の多孔質基板である。尖った先端を有するリブ状突起１ｂは該正極板端部６ａに食い込むため、正極集電端子と正極板端部は良好に接触する。
【００２８】
図８は円筒形電池における極群６／正極集電端子１／金属リード片９／電池蓋８ｃ（正極端子を兼ねる）の接続構造を説明するための図であって、電槽に収納される以前の極群を横から見た図である。正極集電端子１電池蓋８ｃは金属リード片９により接続されている。図のようにリード片９は湾曲しているので、正極集電端子１に対してもリード片の剛性に応じた応力が加わるが、正極集電端子と正極板端部の溶接強度が高いため溶接がはずれる虞は無い。正極８ａは絶縁板、８ｂはガスケット、８ｄはガス排出弁である。図では省略したが、正極集電端子が溶接された極群の上面と対向する下面には負極板端部が突出しており、該負極板端部に負極集電端子が溶接される。
【００２９】
図９は集電端子と外部端子とを接続するための前記金属リ−ド片９の平面図である。本リード片９は幅が１５ｍｍ、長さが２０ｍｍ、厚さが０．５ｍｍのニッケル板を加工したものであり、黒点９ａで示した溶接用プロジェクションが設けられている。また２つのプロジェクションの間に溶接効果を高めるためのスリット９ｂを有する。
【００３０】
図１０は積層式の極群を有する角形電池における集電端子と極板との接続構造を示す説明図で、極群を横から見た図である。正極集電端子２は極群左側の正極板端部１０aに溶接されている。該正極板端部は活物質未充填の繊維状ニッケルマット又は発泡状ニッケル基板製である。正極集電端子のリブ状突起２bは極板端部１０ａと略垂直に交差接触し食い込んでいる。従って円筒形電池同様正極集電端子と正極板端部は良好に接触する。正極集電端子と対向する極群右側には負極板１０cの端部１０dが突出しており、該端面に負極集電端子１０ｂが溶接されている。１０eは正極板と負極板の間に狭持されたセパレータである。
【００３１】
（実施例１）
ニッケルの一部を亜鉛及びコバルトで置換した高密度水酸化ニッケルの表面にコバルト酸化物を被覆した活物質を３次元の発泡状ニッケル基板に充填し、高さ５０ｍｍ、長さ６５０ｍｍ、厚み０．４６ｍｍの正極板（公称容量８Ａｈ）を作製した。一方、水素吸蔵合金を主体とする活物質をニッケルメッキパンチング鋼板に塗着し、高さ５０ｍｍ、長さ７２０ｍｍ、厚み０．３３ｍｍの負極板（公称容量１４Ａｈ）を作製した。正極板端部が極群の上面に突出するように、正極板と負極板とを高さ方向に１．５ｍｍずらした状態で不織布を介して円筒形に巻きこみ、最外周をテープにより固定した電極群を作製した。この極群の正極板の上側端部には、幅１．５ｍｍの活物質未充填部分が設けられている。他方極群の下面に突出した負極板の下側端部にも活物質未充填部分が設けられている。
【００３２】
正極板端部に図１に示した集電端子を押圧して、集電端子のリブ状突起１ｂを極板端部に予め食い込ませた後、集電端子のスリット１ｃを挟む平面部にシリーズ溶接（溶接点数：６点）を行い図６の状態となるようにした。一方、負極端部には直径が２８ｍｍφ、厚さが０．３ｍｍのニッケル製負極集電端子をシリーズ溶接（溶接点数：１６点）した後、電槽に挿入し、電槽底部と負極集電端子とのスポット溶接を行った。
【００３３】
次に、この正極集電端子１と図５の金属リード片５及び電池蓋とを溶接し、図８に示すような接続構造となるようにした。
【００３４】
公知の方法を用いて水酸化カリウムを主体とする電解液を所定量注入した後、封口することによりＤサイズの本発明電池Ａを作製した。
【００３５】
次に比較例として、図１に示した集電端子１に替えて図４に示した集電端子３を用いて正極端部とシリーズ溶接（溶接点数：１６点）を行った。それ以外は本発明電池Ａと同様に作製した。該電池を比較例電池Ｂとした。
【００３６】
これらの電池を活性化した後、２５℃雰囲気下で４Ａの定電流で２時間充電した。次いで０℃雰囲気下で５時間の放置した後、同温度に於いて４０Ａの定電流でセル電圧が０．９Ｖになるまでの放電を行った。図１１に放電容量とセル電圧の関係を示す。
【００３７】
また、２５℃、４５℃、５５℃の各温度において４Ａの定電流で１時間３６分の充電（定格容量の８０％）を行った後、各温度雰囲気下で４Ａの定電流でセル電圧が０．９Ｖになるまでの放電を行った。図１２に温度と放電容量の関係を示す。
【００３８】
図１１の結果から、本発明電池Ａは比較例電池Ｂに比べて放電電圧が高いことが明らかである。これは前記に示した如く、本発明電池Ａが高い集電効果を有する為と考えられる。
【００３９】
図１２の結果では、雰囲気温度が上昇するにつれて本発明電池Ａと比較例電池Ｂとの放電容量に差が見られる。これは、本発明電池Ａの集電効果が高く、電池の内部抵抗が低い為充電電圧が低く抑えられ、水の電気分解等の副反応が抑えられることにより充電効率が向上したためと考えられる。
【００４０】
以上のように、本発明電池Ａは比較例電池Ｂに比べて充電及び放電の双方の反応効率が向上していることが明らかである。
【００４１】
（実施例２）
ニッケルの一部を亜鉛及びコバルトで置換した高密度水酸化ニッケルの表面にコバルト酸化物を被覆した活物質を３次元の発泡状ニッケル基板に充填し、５５０ｍＡｈ／ｃｍ２の理論容量密度の極板を作製した。正極板の端部には幅１．５ｍｍｘ７５ｍｍの活物質未充填部分を設けており、極板の大きさは４２ｍｍｘ７５ｍｍで厚みが０．４ｍｍのものである。一方、水素吸蔵合金を主体とする活物質をニッケルメッキパンチング鋼板に塗着し、１２００ｍＡｈ／ｃｍ２の理論容量密度の負極板を作製した。負極板の端部には幅１．５ｍｍｘ７５ｍｍの活物質未充填部分を設けており、極板の大きさは４２ｍｍｘ７５ｍｍで厚みが０．３ｍｍである。
【００４２】
これらの正極板と負極板とを不織布製のセパレータを介して積層した。積層に際しては幅方向に１．５ｍｍづつずらした状態で積層し、正極板が１２枚と負極板が１３枚の極群を作製した。正極板と負極板の端部に設けた活物質未充填部分は相対向する側辺にくるように積層されている。この極群を厚み方向に圧力をかけて固定した後、正極板の端部に図２に示した集電端子２を押圧してリブ状突起２ｂを極板端部に食い込ませた後、集電端子のスリット２ｃを挟む平面部にシリーズ溶接（溶接点数：６点）によって取り付けた。
【００４３】
一方、負極板端部には幅が１０ｍｍ、長さが１００ｍｍ、厚さが０．４ｍｍのニッケル製集電端子をシリーズ溶接（溶接点数：１６点）した。溶接機の棒状電極の直径は５ｍｍφであり、先端が平面な電極を使用した。以上により図１０に示した集電端子付き極群を作製した。
【００４４】
この電極群を角形の樹脂電槽に挿入し、水酸化カリウムを主成分とする電解液を所定量注入した後、蓋を溶着して本発明電池Ｃ（公称容量８Ａｈ）を作製した。電池外部と電池内部とは正極及び負極の集電端子により導通されており、密閉性を保つため隙間を樹脂で固定した。
【００４５】
（比較例２）
前記実施例２において、正極集電端子として図２に示したリブ状突起付き集電端子２に替えて図５に示した集電端子４を用いた以外は実施例２と同一の方法で電池を作製した。溶接点数も６点で実施例２と同一にした。本電池を比較例電池Ｄとした。
【００４６】
これらの電池を活性化した後、２５℃雰囲気下で４Ａの定電流で２時間充電した。その後０℃雰囲気下で５時間放置した後、同温度に於いて４０Ａの定電流でセル電圧が０．９Ｖになるまでの放電を行った。図１３に放電容量とセル電圧の関係を示す。
【００４７】
また、２５℃、４５℃、５５℃の各温度において４Ａの定電流で１時間３６分の充電（定格容量の８０％）を行った後、各温度雰囲気下で４Ａの定電流でセル電圧が０．９Ｖになるまでの放電を行った。図１４に温度と放電容量の関係を示す。
【００４８】
図１３の結果に示した如く、本発明電池Ｃは比較例電池Ｄに比べて高い放電電圧を示す。これは本発明電池Ｃにおいては、前記本発明電池Ａと同様、比較例電池Ｄと比べて集電効果が高められた結果であると考えられる。
【００４９】
図１４の結果では、高温雰囲気において、本発明電池Ｃが比較例電池Ｄに比べて大きい放電容量を示している。これは、本発明電池Ｃにおいては、前記本発明電池Ａと同様に集電効果が高められたことにより充電効率が向上したためと考えられる。以上のように、本発明電池Ｃは、比較例電池Ｄに比べて充電および放電の双方の特性が向上している。
【００５０】
本実施例では集電端子と金属リード片とを溶接により接続したが、一体成形することによりさらに工程の簡略化及び抵抗の低減を図ることが可能である。本実施例では集電端子の厚み及び金属リード片の厚みが０．５ｍｍ以下のものを用いたが、電池に要求される最大電流値により適切な厚みを選択することができる。集電端子の平面部の溶接を考慮するとその範囲は０．２〜１．２ｍｍであることが望ましい。
【００５１】
本実施例ではコストの低減を図るために鉄にニッケルメッキされている材料を用いたが、金属ニッケル単体などの耐アルカリ性材料を使用することによりさらに抵抗の低減を図ることが可能である。
【００５２】
【発明の効果】
本発明の請求項１によれば、少ない溶接点数で正極集電端子と正極板端部との電気的接続点数を多く、かつ偏り無く設置することができるので、集電効果が高く電気的特性に優れたアルカリ蓄電池を生産性良く提供することができる。本発明の請求項２によれば、集電端子のリブ状突起を正極板端部に無理無く食い込ませることができるので、正極集電端子と正極板の間で接触による良好な電気的接続を得ることができる。そのために集電効果を高めることができる。以上のように本発明は高容量の非焼結式正極を用いたアルカリ蓄電池において、高率放電特性に優れた電池を実現するもので、工業的価値は大きい。
【図面の簡単な説明】
【図１】本発明に係る円筒形電池用集電端子の１例を示す斜視図である。
【図２】（Ａ）は本発明に係る角形電池用集電端子の１例を示す斜視図、（Ｂ）は（Ａ）のＡ−Ａ′に於ける断面図である。
【図３】本発明に係る円筒形電池用集電端子の１例を示す斜視図である。
【図４】従来の円筒形電池用集電端子を示す平面図である。
【図５】従来の角形電池用集電端子を示す平面図である。
【図６】本発明に係る円筒形電池における集電端子と正極板端部との溶接状態を示す説明図である。
【図７】本発明に係る円筒形電池における集電端子付き極群を真上から見た状態を示す説明図である。
【図８】本発明に係る円筒形電池における極群／集電端子／金属リード片／電池蓋の接続構造を示す説明図である。
【図９】本発明に係る金属リード片を示す図である。
【図１０】本発明に係る角形電池における集電端子と電極との接続構造を示す説明図である。
【図１１】本発明電池Ａと比較例電池Ｂの放電特性を示すグラフである。
【図１２】本発明電池Ａと比較例電池Ｂの温度特性を示すグラフである。
【図１３】本発明電池Ｃと比較例電池Ｄの放電特性を示すグラフである。
【図１４】本発明電池Ｃと比較例電池Ｄの温度特性を示すグラフである。
【符号の説明】
１、２、３集電端子
１ｂ、２ｂ、３ｂリブ状突起
１ｃ、２ｃ、３ｃスリット
６ａ、１０ａ正極板の端部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an alkaline storage battery suitable for applications requiring charging / discharging with a large current, such as for power tools and hybrid electric vehicle (HEV) power supplies, and has excellent electrical characteristics and high productivity. It relates to batteries.
[0002]
[Prior art]
A sealed alkaline storage battery using a negative electrode mainly composed of a hydrogen storage alloy has recently been expanded in terms of excellent charge / discharge characteristics and environment. In particular, demand as a power source for large current charging / discharging such as electric tools and HEV batteries is expected.
[0003]
Conventionally, an alkaline storage battery using a sintered positive electrode has been excellent in charge and discharge characteristics at a high rate, and thus has been a mainstream battery in these large current applications. Batteries used for high current applications employ spirals or stacked pole groups to reduce current density. In addition, the current collection effect is enhanced by adopting a tabless system in which the current collector terminals are welded by indirect welding.
[0004]
However, the capacity density of the sintered positive electrode is about 450 mAh / cm 3, and there is a limit to increasing the capacity of the battery. On the other hand, a non-sintered positive electrode using a felt-like or sponge-like metal porous body as a substrate and filling the substrate with nickel hydroxide enables a capacity density of 550 mAh / cm3 or more, and has a high capacity for portable equipment. It is generally used for nickel metal hydride storage batteries and high capacity nickel cadmium storage batteries. Recently, it has begun to be used for nickel-metal hydride storage batteries for electric vehicles.
[0005]
As described above, in the alkaline storage battery, the current collecting terminal is welded to the end of the electrode plate by the tabless method. The end of the electrode plate generally consists of an exposed substrate. The substrate of the non-sintered electrode is the metal porous body. When the above non-sintered positive electrode is used, the electrical resistance of the welded portion between the current collecting terminal and the substrate is higher than that using the sintered electrode, and thus there is a disadvantage inferior to the high rate discharge characteristics. .
[0006]
In order to improve the defect, a strip-shaped active material unfilled portion is provided at the end of the electrode plate, and a current collector terminal is welded in series to the end of the electrode plate after welding a strip-shaped nickel plate or the like to the unfilled portion of the active material (Japanese Patent Laid-Open No. 56-86459) has been made. Further, in order to simplify the process, Japanese Patent Laid-Open No. 62-139251 discloses that the weld strength of the current collecting terminal in the tabless method can be secured by using a foamable substrate in which a welded portion is compressed in advance. Yes.
[0007]
In order to enable charging / discharging with a large current, the thickness of the current collecting terminal is increased, the number of welding points between the current collecting terminal and the electrode plate is increased, and the external terminal (corresponding to the battery lid portion in a cylindrical battery) ) And the current collector terminal, there is a method of reducing the electrical resistance of the current collector part by shortening the length of the lead piece or increasing the wall thickness.
[0008]
However, when the conventional welding method is used, increasing the thickness of the current collector terminal increases the reactive current during series welding, making it difficult to increase the welding strength. In addition, it is practically difficult to increase the number of welding points in the conventional current collecting terminal structure because the number of weldings increases. Also, shortening the lead piece or increasing the thickness makes it difficult to connect the current collecting terminal and the external terminal. Further, since the lead piece is bent at the time of sealing, if the rigidity of the lead piece is large, there arises a problem that the welded portion between the lead piece and the current collecting terminal or the current collecting terminal and the electrode is peeled off.
[0009]
In JP-A-61-32353, in an alkaline storage battery having a spiral pole group, a radial protrusion is provided on the lower surface of the current collector, and the protrusion and the end of the electrode plate are welded to each other to collect the pole group and the current collector. It has been proposed to increase the welding strength of the terminals. Japanese Patent Application Laid-Open No. 11-31497 discloses a plurality of cutout portions radially extending from the vicinity of the center of the current collecting terminal to the outer peripheral edge, and downward rib-like projections on the edges of the cutout portions. There has been proposed a structure in which the protrusion intersects with the end portion of the electrode plate and a part thereof bites into the end portion and is welded at a plurality of points. According to this proposal, it is excellent in that strong welding can be obtained. In the case of this proposal, if the number of rib-shaped projections is increased, there is an advantage that the number of welding points can be increased accordingly. However, there is a drawback that a large number of weldings are required in proportion to the number of rib-like projections. According to the publication, the positive and negative substrates are sintered nickel plates and perforated plates, and the current collecting terminals are iron steel plates, both of which are hard materials. For this reason, welding is indispensable because electrical continuity is not ensured simply by contacting the electrode plate end and the current collecting terminal without being welded. In the HEV isobaric battery, since the pole group becomes large, a large number of electrical conduction points are required between the electrode plate and the current collecting terminal. In the case of a large battery, the conventional current collecting structure required many times of welding. Accordingly, there has been a demand for a current collecting structure that can increase the number of electrical continuity points between the current collecting terminal and the electrode plate with a small number of weldings.
[0010]
[Problems to be solved by the invention]
In order to solve such problems, the present invention improves the current collecting structure inside the battery, so that the current collecting terminal and the electrode group need only be welded few times and has a large current charging / discharging function. It is intended to realize an alkaline storage battery that can be used.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides at least one of an alkaline storage battery in which a positive electrode plate end and a negative electrode plate end protruding on opposite surfaces of a spiral or stacked electrode group are welded to a current collecting terminal. The electrode plate end is a felt-like or sponge-like metal porous body, and a current collecting terminal welded to the electrode plate end is On the flat surface On the side facing the slit and pole group Height is 0.2-1mm A rib-like projection, welded to the flat plate portion sandwiching the slit of the current collector terminal and the end of the electrode plate, and the rib-like projection intersects and contacts the electrode plate end portion; Alkaline storage battery. According to this structure, in addition to the welded portion between the current collecting terminal plane portion and the electrode plate end portion, the contact portion between the unwelded rib-like protrusion and the electrode plate end portion also has electrical continuity. Since electrical continuity is ensured at the contact points, the number of conductive points can be increased only by increasing the number of rib-like protrusions without increasing the number of weldings. Therefore, since many conduction | electrical_connection places can be ensured with few frequency | counts of welding, it is effective especially for the current collection of a large-sized electrode plate.
[0012]
As will be described later, according to the present invention, the welding location is only the location sandwiching the slit provided in the flat portion of the current collecting terminal. Therefore, the current collecting structure according to the present invention is a structure that requires a small number of weldings and has a high current collecting effect. The high current collecting effect here is of course that the electric resistance of the current collector including the substrate of the electrode plate and the current collecting terminal is small, but rather the current collecting in one electrode plate and between a plurality of electrode plates. It means that there is no difference in the electrical resistance of the body. This is a necessary condition for maintaining a uniform current distribution during charging and discharging. If the current distribution is kept uniform, a high active material utilization rate can be obtained even when discharging is performed at a high rate. For this purpose, there are many electrical contact points between the current collecting terminal and the substrate of the electrode plate, and the contact points are required to be distributed without being biased, but the present invention conforms to this.
[0013]
According to the present invention, strong welding strength can be obtained between the current collecting terminal and the electrode plate end. In the case of this invention, the slit is arrange | positioned in the plane part of the current collection terminal which is going to weld to the electrode plate edge part. By reacting and welding the electrodes of the welder on both sides of the slit, the reactive current can be suppressed and the welding current can be increased. For this reason, even if it is a plane which is disadvantageous to welding, favorable welding is obtained. The welding of the current collector terminal protrusion and the end of the electrode plate is a point welding. When the end of the electrode plate is a felt-like or sponge-like porous metal, the mechanical strength of the welded portion is weak. As in the invention, since the welding between the end of the substrate and the flat surface of the current collector terminal is performed on the surface, the mechanical strength is strong, and there is an advantage that the welded portion is not easily detached even when an impact or vibration is applied.
[0014]
The present invention further has a structure in which the rib-like protrusions of the current collecting terminal and the end portion of the electrode plate intersect substantially vertically. If the end face of the electrode plate and the rib-like protrusion intersect substantially perpendicularly, the protrusion will bite into the end of the electrode plate with a small stress, so that the protrusion will not be deformed and a good biting state will be obtained. The biting portion is not welded but is in contact, but the electrical continuity is good. Therefore, according to this structure, the contact location with favorable electrical continuity between the substrate and the current collector terminal can be obtained in addition to the weld location. In the spiral type or laminated type electrode group, there are many contact points between the rib-like protrusions of the current collecting terminal and the electrode plate. Further, by arranging the rib-like projections evenly, the contact portions can be evenly arranged in the length direction of the electrode plate. For this reason, the said high current collection effect is acquired.
[0015]
In the case of the present invention, at least one of the positive electrode plate and the negative electrode plate is a felt-like or foam-like porous metal body made of a metal fiber mat such as nickel, and is welded to the current collector terminal. The end portion of the electrode plate is not filled with an active material and the substrate is exposed. The porous body in an active material unfilled state is flexible and rich in elasticity. Therefore, the rib-like protrusions can easily bite into the substrate, so that electrical conduction is ensured at the contact point between the two. A substrate filled with an active material is not preferable because it loses both flexibility and elasticity.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The current collecting structure according to the present invention is applied to a battery in which the substrate constituting at least one of the electrode plates is the felt-like or sponge-like metal porous body. In the case of alkaline storage batteries, the metal porous body is generally suitably applied to a positive electrode substrate, and a perforated plate is often applied to the negative electrode substrate. Therefore, the present invention is applied to at least the positive electrode current collecting structure. Here, only the current collecting structure of the positive electrode will be described, but when the negative electrode substrate is the porous metal body, the present invention is also effective for the current collecting structure of the negative electrode.
[0017]
The positive electrode in the alkaline storage battery according to the present invention is the non-sintered positive electrode. It has a spiral pole type in which a laminate of a strip-like positive electrode, a separator and a negative electrode is wound, or a laminated pole group in which a plurality of rectangular positive electrodes, separators and negative electrodes are laminated. In the positive electrode plate constituting the electrode group, a fibrous nickel mat or a foamed nickel substrate is filled with an active material. An active material unfilled portion is formed in a strip shape at one end in the longitudinal direction of the electrode plate, and the substrate is exposed. A current collecting terminal is welded to the end of the positive electrode plate where the substrate is exposed.
[0018]
The current collecting terminal is On the flat surface On the side facing the slit and pole group Height is 0.2-1mm It has rib-like projections. A flat portion sandwiching the end of the electrode plate and the slit of the current collecting terminal is welded. The end of the electrode plate and the rib-shaped protrusion intersect each other, and the rib-shaped protrusion bites into the end of the electrode plate. The slit arranged in the current collecting terminal plays a role of increasing the welding current value in the welding process. That is, by welding the two electrodes of the welding machine facing each other across the slit, the reactive current can be suppressed and the welding current value can be increased, so that good welding can be obtained. Therefore, there are fewer welding locations than when there is no slit. In the present invention, welding is performed only at a flat portion sandwiching the slit of the current collecting terminal. Therefore, the number of weldings can be reduced.
[0019]
The end portion of the electrode plate and the rib-like projection intersect each other substantially perpendicularly. As described above, the rib-like protrusions are biting into the end portion of the electrode plate. An example in which the end portion of the electrode plate and the rib-like projection are weakly welded is also observed in the intersection. This is not intended to be welded, but it is presumed that welding was performed because leakage current flowed through the intersection in the welding process of the electrode plate end and the current collecting terminal. Regardless of whether the intersecting portion is merely contact or weak welding, good electrical conduction can be obtained between the substrate and the current collecting terminal at the intersecting portion. Therefore, a high current collecting effect can be achieved with a small number of weldings.
[0020]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the shape, dimension, etc. of this invention are not limited to the example shown below.
[0021]
FIG. 1 is a perspective view showing an example of a positive electrode current collecting terminal of a cylindrical battery according to the present invention. The current collecting terminal 1 is made of iron having a nickel plating thickness of 4 μm. The current collecting terminal 1 has a disk shape with a diameter of 28 mmφ and a thickness of 0.5 mm, and has a width of 2 mm as shown in FIG. Notch Exists. Notch There are rib-like protrusions 1b on both sides of 1a. The rib-like protrusion 1b has a height of 0.5 mm and has a sharp tip as shown in the figure. The height of the rib-shaped protrusions must be smaller than the width of 0.5 to 2 mm of the band-shaped active material unfilled portion provided at the upper end of the electrode plate. In order for the rib-like projections to easily bite into the end of the electrode plate and to obtain good electrical continuity between the electrode plate and the current collecting terminal, the height of the rib-like projection is 0.2 to 1 mm and the tip It is desirable that is sharp. In the example shown in the figure, a slit 1c having a width of 1 mm and a length of 4 mm is provided in the flat portion 1d to enhance the welding effect.
[0022]
FIG. 2A is a perspective view of the positive electrode current collecting terminal 2 of the rectangular battery according to the present invention. Current collector terminal 2 Is made of iron with a nickel plating thickness of 4 μm. The current collecting terminal 2 is a rectangular plate having a width of 12 mm, a length of 100 mm, and a thickness of 0.5 mm, and has a width of 5 mm and a length of 10 mm as shown in FIG. Notch There is. Notch There are rib-like protrusions 2b on both sides of 2a. Similar to the current collecting terminal of the cylindrical battery shown in FIG. 1, a slit 2c is provided in the flat portion 2d of the current collecting terminal. FIG. 2B is a cross-sectional view taken along one-dot chain line AA ′ in FIG. The rib-shaped protrusion 2b has a height of 0.5 mm and indicates a pointed shape.
[0023]
FIG. 3 is a perspective view showing another example of the positive electrode current collecting terminal for a cylindrical battery according to the present invention. As in the example shown in FIG. 1, the current collecting terminal 3 has a disk shape with a diameter of 28 mm and a thickness of 0.5 mm, and has a V-shaped rib-shaped protrusion 3b. The rib-like projections are about 0.5 mm in height, and it is desirable that the tips are sharp as shown in the figure. The height of the rib-like protrusion is suitably 0.2 to 1 mm as in 1b shown in FIG. In addition, a slit 3c for enhancing the welding effect is disposed in the flat portion 3d.
[0024]
FIG. 4 is a plan view of a conventional positive electrode current collecting terminal 4 for a cylindrical battery, shown for comparison. It is made of nickel with a thickness of 0.3 mm and has a disk shape with a diameter of 28 mmφ.
[0025]
FIG. 5 is a plan view of a conventional positive electrode current collecting terminal 5 for a square battery, shown for comparison. This is a rectangular plate made of nickel having a thickness of 0.3 mm, a width of 12 mm, and a length of 100 mm.
[0026]
FIG. 6 is an explanatory view showing a state where the current collecting terminal 1 is attached to the upper surface of the spiral pole group 6 of the cylindrical alkaline storage battery. A positive electrode plate end 6 a protrudes from the upper surface of the spiral pole group 6, and the current collecting terminal 1 is welded to the positive electrode plate end 6 a. The electrodes of the welding machine are brought into contact with the black spots 6b located on both sides of the slit 1c and resistance welding is performed. As a result, a plane sandwiching the positive electrode end face 6a and the slit 1c of the current collecting terminal 1 is welded. In this example, the number of welding points is 6, and the number of weldings is 3.
[0027]
FIG. 7 is an explanatory view of the pole group with current collecting terminals shown in FIG. 6 viewed from directly above. The positive electrode plate end 6a is represented by a wavy line. The rib-like protrusions 1b provided on both sides of the slit 1a extend substantially radially from the center of the circle, and are in cross contact with the spiral electrode plate end 6a substantially perpendicularly. As described above, the upper end of the electrode plate is not filled with an active material, and is a soft and flexible fibrous or foamed nickel porous substrate. Since the rib-like protrusion 1b having a sharp tip bites into the positive plate end 6a, the positive collector terminal and the positive plate end are in good contact.
[0028]
FIG. 8 is a diagram for explaining a connection structure of a pole group 6 / positive electrode current collecting terminal 1 / metal lead piece 9 / battery cover 8c (also serving as a positive electrode terminal) in a cylindrical battery, and is housed in a battery case. It is the figure which looked at the former pole group from the side. The positive electrode current collecting terminal 1 battery lid 8 c is connected by a metal lead piece 9. Since the lead piece 9 is curved as shown in the figure, stress corresponding to the rigidity of the lead piece is also applied to the positive electrode current collecting terminal 1, but the weld strength between the positive electrode current collecting terminal and the positive electrode plate end is high. There is no risk of welding coming off. The positive electrode 8a is an insulating plate, 8b is a gasket, and 8d is a gas discharge valve. Although omitted in the figure, the negative electrode plate end protrudes from the lower surface facing the upper surface of the pole group to which the positive electrode current collector terminal is welded, and the negative electrode current collector terminal is welded to the negative electrode plate end.
[0029]
FIG. 9 is a plan view of the metal lead piece 9 for connecting the current collecting terminal and the external terminal. This lead piece 9 is obtained by processing a nickel plate having a width of 15 mm, a length of 20 mm, and a thickness of 0.5 mm, and is provided with a welding projection indicated by a black dot 9a. Further, a slit 9b for enhancing the welding effect is provided between the two projections.
[0030]
FIG. 10 is an explanatory view showing a connection structure between a current collecting terminal and an electrode plate in a prismatic battery having a stacked type electrode group, and is a view of the electrode group viewed from the side. The positive electrode current collecting terminal 2 is welded to the positive electrode plate end portion 10a on the left side of the electrode group. The end of the positive electrode plate is made of a fibrous nickel mat or a foamed nickel substrate not filled with an active material. The rib-shaped protrusion 2b of the positive electrode current collecting terminal intersects and bites into the electrode plate end portion 10a substantially perpendicularly. Therefore, like the cylindrical battery, the positive electrode current collecting terminal and the positive electrode plate end are in good contact. An end 10d of the negative electrode plate 10c protrudes on the right side of the electrode group facing the positive electrode current collector terminal, and the negative electrode current collector terminal 10b is welded to the end surface. A separator 10e is sandwiched between the positive electrode plate and the negative electrode plate.
[0031]
Example 1
A three-dimensional foamed nickel substrate is filled with an active material in which cobalt oxide is coated on the surface of high-density nickel hydroxide in which a part of nickel is replaced with zinc and cobalt. A 46 mm positive electrode plate (nominal capacity 8 Ah) was produced. On the other hand, an active material mainly composed of a hydrogen storage alloy was applied to a nickel-plated punched steel plate to produce a negative electrode plate (nominal capacity 14 Ah) having a height of 50 mm, a length of 720 mm, and a thickness of 0.33 mm. An electrode in which the positive electrode plate and the negative electrode plate are wound in a cylindrical shape through a non-woven fabric in a state shifted by 1.5 mm in the height direction so that the end of the positive electrode plate protrudes from the upper surface of the electrode group, and the outermost periphery is fixed with a tape Groups were made. An active material unfilled portion having a width of 1.5 mm is provided at the upper end portion of the positive electrode plate of this pole group. An active material unfilled portion is also provided at the lower end of the negative electrode plate protruding from the lower surface of the other electrode group.
[0032]
The current collector terminal shown in FIG. 1 is pressed to the end of the positive electrode plate, and the rib-shaped protrusion of the current collector terminal 1b Is inserted into the end of the electrode plate in advance, and then the slit of the current collector terminal 1c Series welding (the number of welding points: 6 points) was performed on the flat portion sandwiching the wire, and the state shown in FIG. 6 was obtained. On the other hand, a negative electrode current collector terminal made of nickel having a diameter of 28 mmφ and a thickness of 0.3 mm was series welded (number of welding points: 16 points) to the negative electrode end portion, and then inserted into the battery case, and the bottom of the battery case and the negative electrode current collector Spot welding with the terminal was performed.
[0033]
Next, the positive electrode current collecting terminal 1 was welded to the metal lead piece 5 and the battery lid of FIG. 5 so that a connection structure as shown in FIG. 8 was obtained.
[0034]
Using a known method, a predetermined amount of an electrolyte mainly composed of potassium hydroxide was injected, and then sealed, thereby producing a D-sized present invention battery A.
[0035]
Next, as a comparative example, the current collector terminal 3 shown in FIG. 4 was used instead of the current collector terminal 1 shown in FIG. 1, and series welding (the number of welding points: 16 points) was performed with the positive electrode end. Other than that was produced similarly to the battery A of the present invention. This battery was referred to as Comparative Example Battery B.
[0036]
After activating these batteries, they were charged with a constant current of 4 A for 2 hours in an atmosphere at 25 ° C. Next, after standing for 5 hours in an atmosphere of 0 ° C., discharging was performed until the cell voltage became 0.9 V at a constant current of 40 A at the same temperature. FIG. 11 shows the relationship between the discharge capacity and the cell voltage.
[0037]
In addition, after charging for 1 hour and 36 minutes at a constant current of 4 A at each temperature of 25 ° C., 45 ° C., and 55 ° C. (80% of the rated capacity), the cell voltage is maintained at a constant current of 4 A in each temperature atmosphere. Discharge to 0.9V was performed. FIG. 12 shows the relationship between temperature and discharge capacity.
[0038]
From the results of FIG. 11, it is clear that the battery A of the present invention has a higher discharge voltage than the battery B of the comparative example. As described above, this is considered because the battery A of the present invention has a high current collecting effect.
[0039]
In the results of FIG. 12, a difference is seen in the discharge capacity between the battery A of the present invention and the comparative battery B as the ambient temperature rises. This is probably because the battery A of the present invention has a high current collecting effect, the internal resistance of the battery is low, the charging voltage is kept low, and the side reaction such as the electrolysis of water is suppressed, thereby improving the charging efficiency.
[0040]
As described above, it is apparent that the battery A of the present invention has improved both charging and discharging reaction efficiency as compared with the comparative battery B.
[0041]
(Example 2)
A three-dimensional foamed nickel substrate is filled with an active material in which cobalt oxide is coated on the surface of high-density nickel hydroxide in which a part of nickel is replaced with zinc and cobalt, and an electrode plate having a theoretical capacity density of 550 mAh / cm 2 is formed. Produced. An active material unfilled portion having a width of 1.5 mm × 75 mm is provided at the end of the positive electrode plate, and the size of the electrode plate is 42 mm × 75 mm and the thickness is 0.4 mm. On the other hand, an active material mainly composed of a hydrogen storage alloy was applied to a nickel-plated punched steel plate to produce a negative electrode plate having a theoretical capacity density of 1200 mAh / cm 2. An end portion of the negative electrode plate is provided with an active material unfilled portion having a width of 1.5 mm × 75 mm. The size of the electrode plate is 42 mm × 75 mm and the thickness is 0.3 mm.
[0042]
These positive electrode plate and negative electrode plate were laminated via a non-woven separator. When laminating, the electrodes were laminated in a state shifted by 1.5 mm in the width direction, and a pole group of 12 positive plates and 13 negative plates was produced. The active material unfilled portions provided at the end portions of the positive electrode plate and the negative electrode plate are laminated so as to be on opposite sides. After fixing the pole group by applying pressure in the thickness direction, the current collector terminal 2 shown in FIG. 2 is pressed to the end of the positive electrode plate to cause the rib-like protrusion 2b to bite into the end of the electrode plate, Electrical terminal slit 2c It attached to the plane part which pinches | interposes by series welding (the number of welding points: 6 points).
[0043]
On the other hand, a nickel current collector terminal having a width of 10 mm, a length of 100 mm, and a thickness of 0.4 mm was series-welded to the end portion of the negative electrode plate (the number of welding points: 16 points). The diameter of the rod-shaped electrode of the welding machine was 5 mmφ, and an electrode having a flat tip was used. Thus, the pole group with current collecting terminals shown in FIG. 10 was produced.
[0044]
This electrode group was inserted into a rectangular resin battery case, and a predetermined amount of an electrolytic solution containing potassium hydroxide as a main component was injected. Then, a lid was welded to produce a battery C of the present invention (nominal capacity 8 Ah). The outside of the battery and the inside of the battery are electrically connected by the current collector terminals of the positive electrode and the negative electrode, and the gap is fixed with a resin in order to maintain hermeticity.
[0045]
(Comparative Example 2)
The battery of Example 2 was the same as that of Example 2 except that the current collecting terminal 4 shown in FIG. 5 was used instead of the current collecting terminal 2 with rib-like projections shown in FIG. Was made. The number of welding points was also the same as Example 2 with 6 points. This battery was referred to as Comparative Example Battery D.
[0046]
After activating these batteries, they were charged with a constant current of 4 A for 2 hours in an atmosphere at 25 ° C. Thereafter, the sample was allowed to stand for 5 hours in an atmosphere of 0 ° C., and then discharged at the same temperature until the cell voltage became 0.9 V with a constant current of 40 A. FIG. 13 shows the relationship between the discharge capacity and the cell voltage.
[0047]
In addition, after charging for 1 hour and 36 minutes at a constant current of 4 A at each temperature of 25 ° C., 45 ° C., and 55 ° C. (80% of the rated capacity), the cell voltage is maintained at a constant current of 4 A in each temperature atmosphere. Discharge to 0.9V was performed. FIG. 14 shows the relationship between temperature and discharge capacity.
[0048]
As shown in the results of FIG. 13, the battery C of the present invention exhibits a higher discharge voltage than the comparative battery D. This is considered to be a result of the current collection effect being enhanced in the battery C of the present invention as compared with the battery D of the comparative example, like the battery A of the present invention.
[0049]
FIG. 4 Results in In high temperature atmosphere The present invention battery C is a comparative battery D Compared to Shows large discharge capacity . This is presumably because, in the present invention battery C, the charging efficiency was improved by increasing the current collecting effect as in the case of the present invention battery A. As described above, the battery C of the present invention is a comparative battery. D Compared to both charging and discharging Characteristic Has improved.
[0050]
In the present embodiment, the current collecting terminal and the metal lead piece are connected by welding. However, it is possible to further simplify the process and reduce the resistance by integrally forming the current collecting terminal and the metal lead piece. In this embodiment, the current collecting terminal and the metal lead piece have a thickness of 0.5 mm or less, but an appropriate thickness can be selected according to the maximum current value required for the battery. In consideration of welding of the flat portion of the current collecting terminal, the range is preferably 0.2 to 1.2 mm.
[0051]
In this embodiment, in order to reduce the cost, a material plated with nickel on iron is used. However, resistance can be further reduced by using an alkali-resistant material such as metallic nickel alone.
[0052]
【The invention's effect】
According to the first aspect of the present invention, the number of electrical connection points between the positive electrode current collector terminal and the positive electrode plate end can be increased with a small number of welding points and can be installed without any bias. Can provide an alkaline storage battery with excellent productivity. According to the second aspect of the present invention, the rib-like protrusions of the current collecting terminal can be forced into the end portion of the positive electrode plate, so that a good electrical connection can be obtained by contact between the positive electrode current collecting terminal and the positive electrode plate. Can do. Therefore, the current collection effect can be enhanced. As described above, the present invention realizes a battery excellent in high rate discharge characteristics in an alkaline storage battery using a high-capacity non-sintered positive electrode, and has a great industrial value.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a collector terminal for a cylindrical battery according to the present invention.
2A is a perspective view showing an example of a current collecting terminal for a rectangular battery according to the present invention, and FIG. 2B is a cross-sectional view taken along line AA ′ of FIG.
FIG. 3 is a perspective view showing an example of a current collecting terminal for a cylindrical battery according to the present invention.
FIG. 4 is a plan view showing a conventional cylindrical battery current collecting terminal.
FIG. 5 is a plan view showing a conventional current collecting terminal for a rectangular battery.
FIG. 6 is an explanatory diagram showing a welded state between a current collecting terminal and a positive electrode plate end in a cylindrical battery according to the present invention.
FIG. 7 is an explanatory diagram showing a state in which a pole group with current collecting terminals is viewed from directly above in a cylindrical battery according to the present invention.
FIG. 8 is an explanatory view showing a connection structure of a pole group / current collecting terminal / metal lead piece / battery cover in a cylindrical battery according to the present invention.
FIG. 9 is a view showing a metal lead piece according to the present invention.
FIG. 10 is an explanatory view showing a connection structure between a current collecting terminal and an electrode in a prismatic battery according to the present invention.
11 is a graph showing discharge characteristics of the battery A of the present invention and the comparative battery B. FIG.
12 is a graph showing temperature characteristics of the battery A of the present invention and the comparative battery B. FIG.
13 is a graph showing discharge characteristics of the battery C of the present invention and the comparative battery D. FIG.
14 is a graph showing temperature characteristics of the battery C of the present invention and the comparative battery D. FIG.
[Explanation of symbols]
1, 2, 3 Current collector terminal
1b, 2b, 3b Rib projection
1c, 2c, 3c slit
6a, 10a End of positive electrode plate

Claims

極群の相対向する外面に突出した正極板端部および負極板端部に集電端子が溶接されてなるアルカリ蓄電池において、前記極板端部の中少なくとも一方の極板端部がフェルト状またはスポンジ状金属多孔体であり、該極板端部に溶接された集電端子が平面部にスリットおよび極群に面する側に高さが０．２〜１ｍｍのリブ状突起を有する平板であって、前記スリットを挟む平面部が極板端部に溶接され、前記リブ状突起が極板端部と交差し食い込んで接触していることを特徴とするアルカリ蓄電池。In an alkaline storage battery in which a current collector terminal is welded to a positive electrode plate end portion and a negative electrode plate end portion that project to opposite outer surfaces of a pole group, at least one of the electrode plate end portions is felt-like or Sponge-like metal porous body, a current collector terminal welded to the end of the electrode plate is a flat plate having slits in the flat part and rib-like protrusions having a height of 0.2 to 1 mm on the side facing the electrode group. An alkaline storage battery, wherein a flat portion sandwiching the slit is welded to an end portion of the electrode plate, and the rib-shaped protrusion intersects and contacts the end portion of the electrode plate.

前記集電端子のリブ状突起と極板端部が略垂直に交差していることを特徴とする請求項１記載のアルカリ蓄電池。 2. The alkaline storage battery according to claim 1, wherein the rib-like protrusions of the current collecting terminal and the end of the electrode plate intersect substantially perpendicularly.