JP3838764B2

JP3838764B2 - Square sealed battery and method for manufacturing the same

Info

Publication number: JP3838764B2
Application number: JP29508197A
Authority: JP
Inventors: 直忠岡田; 克久本間; 昌浩加藤
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1997-10-28
Filing date: 1997-10-28
Publication date: 2006-10-25
Anticipated expiration: 2017-10-28
Also published as: JPH11135080A

Description

【０００１】
【発明の属する技術分野】
本発明は、角型の外装缶筐体の開口部に蓋体を挿入後に、蓋体と開口部とを溶接することによって作られる角型密閉電池及びその製造方法に関する。
【０００２】
【従来の技術】
近年、ポータブルＯＡ機器や通信機器の需要が高まるにつれ、その電源となるニッケル水素二次電池やリチウムイオン二次電池の中でも、特に小型化が可能で、しかも上記の各機器においての実装効率の高い、角型密閉電池の要求が高まっている。
【０００３】
角型密閉電池は、一般に角型の外装缶筐体の開口部を蓋体で溶接などを用いることで気密に閉塞して製造される。この電池では、図１０に示すような構造を採っている。なお、以下の説明においてこの図１０と同じ符号の構成は同じ作用をもつものとする。金属からなる角型で有底矩形形状をなす外装缶筐体１は、正極端子を兼ねており底部内面に絶縁フィルム６が配置されている。発電要素である電極体７は、外装缶筐体１内に収納されている。電極体７は、リチウムイオン二次電池の場合には炭素質物質を含有する活性物質が表裏両面に塗布されたアルミニウム薄膜の負極８と、多孔性のポリプロピレンシートであるセパレータ９と、リチウムニッケル酸化物やリチウムコバルト酸化物などを含有する活性物質が表裏両面に塗布された銅薄膜の正極１０とを、正極１０が最外周に配置されるようにして渦巻状に倦回した後、偏平状（非真円形）に整形することで作成したものである。
【０００４】
また蓋体２を介して電気的に外装缶筐体１と電極体７とを接合するために、正極１０から正極リード１１が延出されることによって、蓋体２での電極体７側の面に接合されている。自身の中心付近に負極端子１２の貫通穴を有し、合成樹脂からなるスペーサ１３は、外装缶筐体１内の電極体７上に設けられている。
【０００５】
そして蓋体２は、外装缶筐体１の上端の開口部３に溶接などで接合されている。蓋体２の中心付近には、負極端子１２の取出穴が開口されており、この取出穴から離れた箇所に電解液の注液孔１４が設けられている。負極端子１２は取出穴にガラス製又は樹脂製の絶縁材１５を介してハーメティックシールされている。負極端子１２の下端面には負極リード１６が接続され、この負極リード１６の他端は負極８に接続されている。
【０００６】
金属板材からなる封止蓋１６は、電解液を外装缶筐体１内へ注入して内部を満たした後に注液孔１４を含む蓋体２の外表面にシーム接合される。なお、この封止蓋１６を有しなくても電解液を外装缶筐体１内に注入した後に蓋体２を接合して封止する方法でも同様な作用が得られるのでよい。
【０００７】
ここで、電解液はリチウムイオン二次電池の場合には過塩素酸リチウム，ホウフッ化リチウム，六フッ化リチウム，六フッ化燐リチウムなどの電解質を含有する、エチレンカーボネート，プロピレンカーボネートなどの有機溶媒である。上部絶縁紙１７は、封止蓋１６を含む蓋体２の外表面全体に被覆されている。スリット１８を有する下部絶縁紙１９は外装缶筐体１の底面に配置されている。二つ折りされたＰＴＣ(Positive Thermal Coefficient)素子２０は、一方の面が外装缶筐体１の底面と下部絶縁紙１９との間に介挿され、かつ他方の面がスリット１８を通して下部絶縁紙１９の外側に延出されている。外装チューブ２１は、外装缶筐体１の側面から上部絶縁紙１７と下部絶縁紙１９の周辺まで延出するように配置され、上部絶縁紙１７及び下部絶縁紙１９を外装缶筐体１に固定している。このような外装チューブ２１の配置により、外部に延出されたＰＴＣ素子２０の上記した他方の面が下部絶縁紙１９の底面に向けて折り曲げられる。
【０００８】
しかしながら従来では、蓋体はレーザ溶接を用いて角型の外装缶筐体の開口部に気密に溶接される方法がある。キヤップ体をレーザ溶接して角型の外装缶筐体に固定する方法は、容積効率を低下させることなく、角型の外装缶筐体の開口部を閉塞できるために実用化がなされている。
【０００９】
一般には、レーザ光の照射により金属材料、例えばＪＩＳ規格のＡ３００３（Ｍｎ含有）やＡ３００４（Ｍｇ含有）のごとき、アルミニウム合金材料からなる被溶接部材の溶接を行なう場合、レーザ光の照射による溶融された部分が凝固する際に、クラック（ヒビ割れ）が発生しやすいので、レーザ溶接部分に凝固割れによって溶接不良が発生しやすいという問題がある。これについては、レーザ溶接時にレーザ溶接部分の凝固割れを防止するために、レーザ光のパルス状の波形を制御することによって、溶融された被溶接部材の溶融部の冷却速度を遅くすることが効果的であることが知られている。よって、できるだけこの溶融部の冷却速度を遅くすることで、良好な溶接が可能になる。
【００１０】
しかしその条件を満たしていても、図１１に第１の従来例として示すように蓋体２を角型外装缶筐体１の開口部３に装着し、側方からレーザ光を走査しながら接合部分をレーザ溶接する方法では外装缶筐体１のコーナー部Ｒの処理が困難である。即ち、図１２に要部拡大図を示すようにコーナー部Ｒでは、外装缶筐体１の構成部材に垂直にレーザ光が照射されるわけではなく、例えば曲率半径を２．０ｍｍ程度にすると、レーザ光の照射方向とコーナー部Ｒの接線（溶接面を含む）に垂直な面とがなす角度θが、最大４５度の角度をもって照射される。このときレーザ光の照射面積が（１／ｃｏｓ４５°＝）１．４１倍に増加する。よってレーザ光の照射エネルギー密度（フルエンス：Ｊ／ｃｍ² ）が溶接面へ垂直に入射する場合に比べて約４０％減少する。一般的にはレーザ溶接におけるフルエンスの変化に対する加工時の許容範囲は±１０％となっているために、上記のような条件では溶接部分の構成部材の溶融による溶け込みの深さも減少するので、接合強度が低くなり溶接部にクラックが生じてしまう。
【００１１】
特に、軽量化を図る為にその構成部材にアルミニウムまたはアルミニウム合金を使用した場合は、クラックが生じ易いために製品の製造における歩留まりが著しく低下する。良好に溶接を行なうには、ｃｏｓθ＞０．９を満たす必要があり、従ってθ＜２５°とすることが望まれる。よって、外装缶筐体の構成部材が鉄やステンレスの場合には、コーナー部Ｒを含んだ外装缶筐体全体の曲率半径を１．０〜１．３ｍｍ程度に小さくすることで、上記のような照射角度の偏りを防いで接合強度の低下という欠点の解決をしていた。しかし、アルミニウムまたはアルミニウム合金の場合には、上記のように曲率半径を小さくするとコーナー部Ｒに応力が集中して剛性が低下する。つまり、部材自体の強度が低いために曲率半径を大きくする必要があるので、上述した接合強度の低下が解決できない。
【００１２】
その他に溶接不良の発生を防ぐ具体的な技術として、例えば特開平８―７７９８３号公報に開示されているものがある。それによると、外装缶筐体の開口端に放熱除去部（切欠部）を設けるとともに、レーザビームの走査位置の中心をキヤップ体と外装缶筐体の境界から外側に偏在させてクラックの発生を防ぐものである。つまり、図１３に第２の従来例として示すように上方からレーザ光を照射して、蓋体２と外装缶筐体１とを溶接するもので、この様な構造を採ると溶接部分が上面に配置されるので、溶接面に垂直にレーザを照射できて、フルエンスの減少も無い。よって、コーナー部Ｒを含む外装缶筐体全体の曲率半径を１．７〜２．３ｍｍと大きくとることも可能になる。
【００１３】
しかし、図１４に示すように負極端子１２との絶縁をとるために、ハーメティックシール１５が外装缶筐体１の開口部３の内縁から１ｍｍ程度の距離で負極端子１２を囲んで配置されている。故に、レーザ照射によるハーメティックシール１５の損傷を防ぐために、ハーメティックシール１５と外装缶筐体の外縁からの距離ｔには下限かあることと、ハーメティックシール１２は絶縁性を保つために、負極端子１２からある程度（例えば３．５ｍｍ以上）の距離まで形成されていなければならないこととが原因となり、所定厚さ（例えば５．５ｍｍ）以下の外装缶筐体の設計は困難となっている。
【００１４】
また、従来の角型電池外装缶筐体では開口部に平行な断面が長方形（コーナー部Ｒがアールを持っているものも含む）に形成されており、その長辺部と短辺部とで板厚（外装缶筐体を構成する部材の厚さ）は等しくなっていた。そのため板厚が不十分な場合には外装缶筐体の剛性が低くなり、二次電池の発電要素に充電する際に、電解液の化学反応のためにガスが発生することで外装缶筐体の内圧が上昇すると、図１５に示す外装缶筐体１の断面に現れるような、曲げモーメント（点線矢印）に起因して外装缶筐体に歪みが生じる。つまりコーナー部Ｒを支点として、表面積の大きな（内圧を強く受ける）長辺部４が矢印で示すとおり外部へ膨らみ、応力の集中する短辺部５が矢印で示すとおり内部へ窪むのである。
【００１５】
【発明が解決しようとする課題】
以上のような外装缶筐体の側面でキャップ体を溶接する方法は、外装缶筐体と蓋体との接合不良が起こりやすくなる。それに加えて外装缶筐体は膨張を起こすが、構成部材としてアルミニウムまたはアルミニウム合金を用いた場合には、鉄やステンレスに比して強度が劣るために、電池の使用者による過充電時などには破裂を起こす可能性もある。特に引張強度としては、例えばアルミニウム合金Ａ３００３（ＪＩＳ規格）を用いた場合には鉄の約３０％程度でしかない。よって、外装缶の重量増加を防ぎながら外装缶筐体の膨張を抑制するには、蓋体の外装缶筐体への溶接不良を抑制しつつ溶接部の形状を工夫して外装缶の剛性を高める必要がある。しかし、剛性を高くしようとすると上記したようなコーナー部の曲率半径を大きくする必要もあり、このコーナー部へのレーザ溶接時に溶接部でのフルエンスの低下が生じるために、クラックの発生が生じるという不具合がある。
【００１６】
また、外装缶筐体自体の内部からの膨張による変形を防ぐには外装缶筐体の構成部材の板厚を大きくして剛性を高くする必要もある。しかし、外装缶筐体の内部の容積の減少を防ぐ必要があるとともに、発電要素などを含む電池全体での重量の軽量化が望まれているために、上記の短辺部を構成する部材の板厚は小さく保つことが好ましい。
【００１７】
本発明は上記の事情に着目してなされたもので、その目的は、主として二次電池の充電時に、内部の圧力上昇に起因した膨張に耐えられるだけの剛性の高い外装缶筐体を提供できる角型密閉電池と角型密閉電池の製造方法とを提供することにある。
【００１８】
【課題を解決するための手段】
請求項１によれば、開口部を有し、コーナー部をもった金属製の外装缶筐体と、この外装缶筐体内に収納され、セパレータを挟んで対向した正極及び負極を有する発電要素と、前記開口部に溶接によって接合された金属製の蓋体と、前記発電要素に電気的に接続された電極素子とを具備する角型密閉電池において、前記開口部のコーナー部の外周部の一部に、前記開口部以外のコーナー部の前記開口部と平行な断面の外周部の曲率半径より小さい曲率半径を有する部分が形成されるように、前記開口部のコーナー部が整形されているとともに、前記蓋体は、この開口部のコーナー部が整形された前記開口部に対応して気密に溶接可能な形状に形成されていることを特徴とする。
【００１９】
請求項２によれば、請求項１に記載の角型密閉電池において、前記開口部のコーナー部
は、前記開口部の前記コーナー部が所定の角度で面取りがなされて形成されるとともに、
前記蓋体は、この面取りがなされた前記開口部に対応して気密に溶接可能な形状に形成さ
れていることを特徴とする。
【００２０】
請求項３によれば、開口部を有し、コーナー部をもった金属製の外装缶筐体と、この外装缶筐体内に収納され、セパレータを挟んで対向した正極及び負極を有する発電要素と、前記開口部に溶接によって接合された金属製の蓋体と、前記発電要素に電気的に接続された電極素子とを具備する角型密閉電池において、前記外装缶筐体は、前記開口部に平行な断面が長方形に形成されるとともに、この長方形の短辺部の板厚が長辺部の板厚よりも大きいことを特徴とする。
【００２１】
請求項４によれば、請求項１乃至請求項３のうちのいづれか１項に記載の角型密閉電池において、前記外装缶筐体又は前記蓋体のうちの少なくとも一方は、アルミニウムあるいは、０．０５重量％以下のＭｇ及び０．２重量％以下のＣｕを含むアルミニウム系金属により構成されることを特徴とする。
【００２２】
請求項５によれば、開口部を有する金属製で角型の外装缶筐体の内部に、セパレータを挟んで対向した正極及び負極を有する発電要素を収納する工程と、前記発電要素と電気的に接続された電極端子を形成する工程と、前記開口部に対して金属製の蓋体をレーザ溶接により接合する工程と、前記蓋体を接合する前又は後に電解液を前記外装缶筐体の内部に注入する工程とを具備する角型密閉電池の製造方法において、前記レーザ溶接により接合する工程の前に前記開口部のコーナー部の外周部の一部に、前記開口部以外のコーナー部の前記開口部と平行な断面の外周部の曲率半径より小さい曲率半径を有する部分が形成されるように、前記開口部のコーナー部を整形する工程を具備することを特徴とする。
【００２３】
請求項６によれば、請求項５に記載の角型密閉電池の製造方法において、前記開口部の前記コーナー部を整形する工程は、前記開口部のコーナー部を所定の角度で面取りする方法を用いることを特徴とする。
【００２４】
請求項７によれば、請求項５に記載の角型密閉電池の製造方法において、前記開口部の前記コーナー部を整形する工程は、前記開口部のコーナー部の曲率半径をプレス加工により小さくする方法を用いることを特徴とする。
【００２５】
請求項８によれば、開口部を有し、この開口部に平行な断面が長方形に形成されている金属製で角型の外装缶筐体の内部に、セパレータを挟んで対向した正極及び負極を有する発電要素を収納する工程と、前記発電要素と電気的に接続された電極端子を形成する工程と、前記開口部に対して金属製の蓋体をレーザ溶接により接合する工程と、前記蓋体を接合する前又は後に電解液を前記外装缶筐体の内部に注入する工程とを具備する角型密閉電池の製造方法において、前記長方形の短辺部の板厚が前記長方形の長辺部の板厚よりも大きく形成される工程を具備することを特徴とする。
【００２６】
上記の発明によれば、短辺部の板厚を長辺部の板厚よりも大きくすることで、内部からの圧力の上昇に起因する膨張に耐えられるだけの剛性の高い外装缶筐体を形成できる。それにより、密閉度の高い角型密閉電池とその製造方法とを提供することができる。
【００２７】
【発明の実施の形態】
以下に、本発明の実施形態に関して図面を参照して説明する。なお、ここで「角型」とは外装缶筐体の開口部に平行な断面がほぼ長方形であるが、コーナー部にアールがつけられている形状も許容するものである。
【００２８】
さて一般に、角型密閉電池は図１に示したように、外装缶筐体１と蓋体２との密閉容器構造で形成されている。図１は本発明の一実施形態の角型密閉電池を示す斜視図であり、外装缶筐体の構造以外は先に説明した図１０の角型密閉電池と同様の構造をしている。外装缶筐体１は、上記の発電要素を収納した後に蓋体２が接合される、開口部３に対して平行な断面が長方形であり、長辺部４の板厚を０．５ｍｍで、短辺部５の板厚を０．７ｍｍとしている。外装缶筐体１を構成するアルミニウム系金属として、例えば０．０５重量％以下のＭｇ及び０．２重量％以下のＣｕを含むものとすると、レーザ溶接がなされた後の冷却固化が起こっても、凝固点におけるクラックが抑制される。具体的には、ＪＩＳ規格のＡ３００３，Ａ３００４，Ａ１０５０，Ａ１１００，Ａ１２００などが好ましい。これらの材料を上記の板厚になるように、深絞りや冷間衝撃加工といったプレス加工によって、外装缶筐体１の形状を形成する。
【００２９】
また図２に示すように、開口部３には板厚が１．０ｍｍの蓋体２が蓋をするように挿入されて係合している。蓋体２は角型の薄板状で周辺部に０．３ｍｍの段差が設けられ、外装缶筐体１との係合部では外側の段は厚さ方向の端面が外装缶筐体１の外面と面一になるように設定されている。蓋体２は、０．８ｍｍ以上で好ましくは０．９〜１．５ｍｍの厚さを有することが望ましい。０．８ｍｍ未満では、強度が低下してしまうからである。
【００３０】
この状態で、外装缶筐体１と蓋体２との接合部（溶接面）に向けて、図１における点線の矢印方向に沿って走査しながら、集束径（レーザスポット径）０．４〜０．５ｍｍでＹＡＧレーザからのレーザ光を照射する。そうすることによって、接合部に対して溶融径が０．８ｍｍ程度の溶融部を連続的に形成するシーム溶接を行ない、外装缶筐体１を蓋体２で密閉する。この際の条件としては、ＹＡＧレーザ（波長：１．０６μｍ）は、繰返し周期が２０〜３０Ｈｚ，パルス幅が３〜５ｍｓ，移動（走査）速度が５〜１０ｍｍ／ｓ，オーバーラップ率が７０〜８０％とした。また、溶接部に窒素ガスを吹き付けてながら溶接することによって、溶接の際に外装缶筐体１の構成部材が酸化することによって引き起こされる気泡の発生を防止している。
【００３１】
なお、レーザ光としてＹＡＧレーザを用いたのは、波長が炭酸ガスレーザよりも短波長であるため、アルミニウムやその合金に対する反射率が炭酸ガスレーザに比べて小さく、より効率のよい溶接が可能な為である。そして、このレーザ光は、レーザ発振器から光ファイバを通じてレンズで接合部へ集光される。このレーザ光の光軸は、接合部に対して垂直から２０°の許容範囲で設定されて溶接をする。ここでは上記のレンズが長辺部４又は短辺部５の接合部に対して一定の角度及び距離を保つようにして走査されて、一辺ずつ溶接を行なう。
【００３２】
上記の様な、内部の圧力が上昇しても変形を抑えながら外装缶筐体１の重量を抑制するための、外装缶筐体１の寸法を導くに際して、発明者は実験を行ない以下に説明する図３と図４に示すような結果を得た。この実験の基準となった、外装缶筐体１の寸法例を以下の［表１］に示す。なお、この表では「幅」とは長辺部４の長さであり、「厚み」とは短辺部５の長さであり、「高さ」とは外装缶筐体１の底部から蓋体２との接合部までの長さである。
【００３３】
【表１】

【００３４】
この基準寸法の外装缶筐体１を用いて、図１１などで示したコーナー部Ｒと外装缶筐体１の長辺部４の膨らみ量との関係を求めた結果を図３に示す。外装缶筐体１の内部の圧力は０．１９１３ＭＰａ（大気圧＋０．０９ＭＰａ）とし、膨らみ量は大気圧である０．１０１３ＭＰａのときの外装缶筐体１の形状を基準として、図１５に示す長辺部４の外側への最大変位量で定義されるものとする。この図３からコーナー部Ｒの曲率半径を大きくすると膨らみ量は減少し、外装缶筐体１の変形を効果的に抑制できることがわかる。同時に、外装缶筐体１の表面積も減少するので重量も減少するという利点もある。
【００３５】
次に上記の基準寸法の外装缶筐体１を用いて、短辺部５の板厚と長辺部４の膨らみ量との関係を求めた結果を図４に示す。ここでも外装缶筐体１の内部の圧力は０．１９１３ＭＰａとし、膨らみ量は大気圧である０．１０１３ＭＰａのときの外装缶筐体１の形状を基準として、図１４に示す長辺部４の外側への最大変位量で定義されるものとする。
【００３６】
この図４から、例えば短辺部５の板厚を０．５ｍｍから０．７ｍｍに増加させると、長辺部４の膨らみ量が約２０％減少することがわかる。そしてこの場合には、表１に示す寸法において外装缶筐体１全体の重量が４．５ｇから４．６ｇへと０．１ｇだけの増加に抑えることができたので、発電要素などを含む電池全体での軽量化にも寄与する。
【００３７】
また実際の製品としては、短辺部５（外装缶筐体缶１の厚み）の８％程度が長辺部４（外装缶筐体缶１の幅）の膨らみ量として許容されているので、厚みが大きくなるほど短辺部５の板厚も少なくてすむ。よって、下記の［表２］のような短辺部５の板厚が長辺部４の板厚よりも大きくなっている寸法が、適切な例として挙げられる。
【００３８】
【表２】

【００３９】
そして、本実施形態では開口部３ではコーナー部Ｒの曲率半径を外装缶筐体１の膨らみ抑制の理由から大きくとっているので、本明細書中の［従来の技術］の項に説明したように、溶接部へのレーザ光の入射角度が大きくなり蓋体２と開口部３との溶接部が不良になる可能性が高い。よって、外装缶筐体１自体はコーナー部Ｒの開口部と平行な前記外装缶筐体の断面の外周部での曲率を大きくとることで剛性を高めるとともに、開口部３のコーナー部の外周部の一部に、前記開口部以外のコーナー部の前記開口部と平行な断面の外周部の曲率半径より小さい曲率半径を有する開口部のコーナー部Ｑに整形されるようにすれば、蓋体２との溶接も不良が抑制されると考えられる。ここで、開口部のコーナー部Ｑとはコーナー部Ｒよりも小さな曲率半径を持っている部分があれば足りる。要は、いかにして溶接部分に対するレーザ光の入射角を直角に近づけるかを目的としているからである。
【００４０】
図５にて図１のＡ−Ａ’線での断面を示すように、開口部３のコーナー部の外周部の一部に、前記開口部以外のコーナー部の前記開口部と平行な断面の外周部の曲率半径より小さいな曲率半径を有するコーナー部Ｑが形成されている。長辺部４の板厚をａとおき、短辺部５の板厚をｂとおくと、上述した通りに外装缶筐体１の内圧による膨らみを抑えるためにａ＜ｂとなっている。斜線部は開口部のコーナー部Ｑをもった開口部３の前記外装缶筐体の断面であり、点線部が曲率をもったコーナー部Ｒを有する外装缶筐体１自体（開口部３を除く）の断面である。この点線部のみを図６に示す。
【００４１】
さて、この開口部以外のコーナー部の開口部と平行な断面の外周部の曲率半径より小さい曲率半径を有する開口部のコーナー部Ｑを形成するに際して、図５に示す長辺部４又は短辺部５と開口部のコーナー部Ｑとがなす角度θを１５°とした。ここで幾何学的な計算から、長辺部４及び短辺部５と開口部のコーナー部Ｑとがなす角度は、溶接面とレーザ光の照射方向に垂直な面とがなす角度と等しくθとなる。そうすると図５の要部を拡大した図７に示すθを本明細書中の［従来の技術］の項で説明した条件である、θ＜２５°を満たし、従ってｃｏｓθ＞０．９とするように設定すれば良好に溶接を行なうことが可能となる。実際にθ＝１５°として上記の板厚の条件で開口部のコーナー部Ｑを加工した場合１５０個溶接を行なってクラックの発生は０個であったが、このような加工を行なわないものでは全てクラックが発生した。
【００４２】
この開口部以外の外装缶筐体のコーナー部の曲率半径より小さな曲率半径を有する開口
部のコーナー部Ｑは、本実施形態では、深絞りなどのプレス加工によって形成される。つ
まり、外装缶筐体１を形成後に金型へ開口部３を挿入して面取りのプレス加工をするので
ある。この際には、レーザ光による蓋体２と開口部３との溶接条件を一定に保つために、
開口部３においては上記のようにａ＜ｂとするのではなくａ＝ｂとしてもよい。外装缶筐
体１での開口部３の占める面積は少ないので開口部３に限れば長辺部４と短辺部５とで同
一の板厚にプレス加工しても差し支えないからである。
【００４３】
図８はこの実施形態の変形例の斜視図を示すものであり、この変形例では外装缶筐体１のうちの開口部３のみのコーナー部Ｒの前記開口部と平行な断面の外周部の曲率半径が大きく形成されている。そして、図９は図８のＢ−Ｂ’線での断面を示したもので開口部３に前記開口部以外のコーナー部の前記開口部と平行な断面の外周部の曲率半径より小さい曲率半径を有する開口部のコーナー部Ｑが形成されている。図７と同様に斜線部は開口部のコーナー部Ｑをもった開口部３の断面であり、点線部が曲率をもったコーナー部Ｒを有する外装缶筐体１自体（開口部３を除く）の断面であり、図６と同様の形状をしている。この開口部のコーナー部Ｑを形成するに際して、上述した条件であるθ＜２５°を満たし、従ってｃｏｓθ＞０．９とするように設定すれば、良好に溶接を行なうことが可能となる。
【００４４】
この開口部のコーナー部Ｑは、この変形例でも深絞りなどのプレス加工によって形成される。つまり、外装缶筐体１を形成後に金型へ開口部３を挿入して押し出しのプレス加工をするのである。この際も、ａ＜ｂとするのではなくａ＝ｂとしてもよい。
【００４５】
なお、本実施形態では溶接にはパルス発振のレーザ光を用いたが、連続発振（ＣＷ：Continuous Wave ）のレーザ光を用いても、照射エネルギーを溶接に適当な値に設定すれば、同様な効果が得られる。
【００４６】
また、本各実施形態ではリチウムイオン二次電池を例にして角型二次電池用の外装缶筐体１に適用した場合を示したが、ニッケル水素二次電池などの他の種類の二次電池でもよく、更には剛性を高めるという本発明の効果から一次電池にも適用可能である。
【００４７】
【発明の効果】
本発明によれば、短辺部の板厚を長辺部の板厚よりも大きくすることで、内部からの圧力の上昇に起因する膨張に耐えられるだけの剛性の高い外装缶筐体を形成できるので、密閉度の高い角型密閉電池とその製造方法とを提供することができる。
【００４８】
更には、外装缶筐体全体の剛性を落とさないために、外装缶筐体のコーナー部の曲率半径を大きくとりつつ開口部のみのコーナー部を角部に加工することによって、外装缶筐体と蓋体との溶接部を確実に封止することができる。そして内部からの膨張に耐えられるだけの剛性の高い外装缶筐体を形成でき、密閉度の高い角型密閉電池とその製造方法とを提供することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示す斜視図。
【図２】本発明の一実施形態での外装缶筐体と蓋体との溶接状態を示す要部断面図。
【図３】コーナー部と外装缶筐体の長辺部の膨らみ量との関係を示すグラフ。
【図４】短辺部の板厚と長辺部の膨らみ量との関係を示すグラフ。
【図５】図１のＡ−Ａ’線に沿った外装缶筐体の断面図。
【図６】開口部を除いた外装缶筐体の断面図。
【図７】図５の要部拡大断面図。
【図８】本発明の一実施形態の変形例を示す斜視図。
【図９】図７のＢ−Ｂ’線に沿った外装缶筐体の断面図。
【図１０】角型密閉電池としてのリチウムイオン二次電池を示す部分切欠斜視図。
【図１１】本発明の第１の従来例を示す斜視図。
【図１２】図１１のコーナー部の要部拡大断面図。
【図１３】本発明の第２の従来例を示す斜視図。
【図１４】図１３の負極端子近傍の要部拡大上面図。
【図１５】外装缶筐体の変形を示す模式断面図。
【符号の説明】
１…外装缶筐体，２…蓋体，３…開口部，４…長辺部，５…短辺部
６…絶縁フィルム，７…電極体，８…負極，９…セパレータ，１０…正極
１１…正極リード，１２…負極端子，１３…スペーサ，１４…注液孔
１５…封止蓋，１６…負極リード，１７…上部絶縁紙，１８…スリット
１９…下部絶縁紙，２０…ＰＣＴ素子，２１…外装チューブ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rectangular sealed battery made by welding a lid and an opening after inserting the lid into an opening of a rectangular outer can housing and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, as demand for portable OA equipment and communication equipment increases, among nickel-hydrogen secondary batteries and lithium-ion secondary batteries that serve as power sources, the size can be particularly reduced, and the mounting efficiency in each of the above-described equipment is high. The demand for square sealed batteries is increasing.
[0003]
A rectangular sealed battery is generally manufactured by airtightly closing an opening of a rectangular outer can casing by using a lid or the like by welding. This battery has a structure as shown in FIG. In the following description, the same reference numerals as those in FIG. 10 have the same functions. An outer can case 1 having a rectangular shape and a bottomed rectangular shape made of metal also serves as a positive electrode terminal, and an insulating film 6 is disposed on the inner surface of the bottom. The electrode body 7 as a power generation element is housed in the outer can casing 1. In the case of a lithium ion secondary battery, the electrode body 7 is composed of an aluminum thin film negative electrode 8 coated with an active material containing a carbonaceous material on both front and back surfaces, a separator 9 made of a porous polypropylene sheet, lithium nickel oxide A copper thin film positive electrode 10 coated with an active material containing a product or lithium cobalt oxide on both front and back surfaces is wound in a spiral shape so that the positive electrode 10 is disposed on the outermost periphery, It is created by shaping it into a non-round shape.
[0004]
Further, in order to electrically join the outer can casing 1 and the electrode body 7 through the lid body 2, the positive electrode lead 11 is extended from the positive electrode 10, whereby the surface on the electrode body 7 side of the lid body 2. It is joined to. A spacer 13 having a through hole for the negative electrode terminal 12 near its center and made of synthetic resin is provided on the electrode body 7 in the outer can casing 1.
[0005]
The lid 2 is joined to the opening 3 at the upper end of the outer can casing 1 by welding or the like. An extraction hole for the negative electrode terminal 12 is opened near the center of the lid 2, and an electrolyte injection hole 14 is provided at a location away from the extraction hole. The negative electrode terminal 12 is hermetically sealed in the extraction hole via an insulating material 15 made of glass or resin. A negative electrode lead 16 is connected to the lower end surface of the negative electrode terminal 12, and the other end of the negative electrode lead 16 is connected to the negative electrode 8.
[0006]
The sealing lid 16 made of a metal plate is seam-bonded to the outer surface of the lid body 2 including the liquid injection hole 14 after the electrolyte is injected into the outer can casing 1 to fill the inside. Even if the sealing lid 16 is not provided, the same effect can be obtained by a method in which the lid 2 is joined and sealed after injecting the electrolyte into the outer can casing 1.
[0007]
Here, in the case of a lithium ion secondary battery, the electrolyte is an organic solvent such as ethylene carbonate or propylene carbonate containing an electrolyte such as lithium perchlorate, lithium borofluoride, lithium hexafluoride, or lithium hexafluoride. It is. The upper insulating paper 17 is covered on the entire outer surface of the lid body 2 including the sealing lid 16. A lower insulating paper 19 having a slit 18 is disposed on the bottom surface of the outer can casing 1. The PTC (Positive Thermal Coefficient) element 20 folded in half is inserted between the bottom surface of the outer can casing 1 and the lower insulating paper 19 on one side, and the other side through the slit 18 on the lower insulating paper 19 on the other side. Is extended outside. The outer tube 21 is disposed so as to extend from the side surface of the outer can casing 1 to the periphery of the upper insulating paper 17 and the lower insulating paper 19, and the upper insulating paper 17 and the lower insulating paper 19 are fixed to the outer can casing 1. is doing. With such an arrangement of the exterior tube 21, the other surface of the PTC element 20 extended to the outside is bent toward the bottom surface of the lower insulating paper 19.
[0008]
However, conventionally, there is a method in which the lid is hermetically welded to the opening of the rectangular outer can casing using laser welding. The method of laser welding the cap body to fix it to the square outer can casing has been put to practical use because the opening of the square outer can casing can be closed without reducing the volumetric efficiency.
[0009]
In general, when welding a welded member made of an aluminum alloy material such as JIS standard A3003 (Mn-containing) or A3004 (Mg-containing) by laser light irradiation, it is melted by laser light irradiation. When the part is solidified, cracks (cracks) are likely to occur, so that there is a problem that poor welding is likely to occur due to solidification cracks in the laser welded part. Regarding this, in order to prevent solidification cracking of the laser welded part during laser welding, it is effective to slow down the cooling rate of the melted part of the melted welded member by controlling the pulsed waveform of the laser beam. Is known to be. Therefore, good welding is possible by slowing down the cooling rate of the melted portion as much as possible.
[0010]
However, even if the conditions are satisfied, the lid 2 is attached to the opening 3 of the rectangular outer can case 1 as shown in FIG. 11 as the first conventional example, and joined while scanning the laser beam from the side. It is difficult to process the corner portion R of the outer can casing 1 by the method of laser welding the portion. That is, as shown in the enlarged view of the main part in FIG. 12, the corner portion R does not irradiate the laser beam perpendicularly to the constituent members of the outer can casing 1. For example, when the curvature radius is about 2.0 mm, An angle θ formed by the laser beam irradiation direction and a plane perpendicular to the tangent line (including the welded surface) of the corner portion R is irradiated with a maximum angle of 45 degrees. At this time, the irradiation area of the laser light increases by (1 / cos 45 ° =) 1.41 times. Therefore, the irradiation energy density of the laser beam (fluence: J / cm² ) Is reduced by about 40% as compared to the case where it is perpendicularly incident on the weld surface. In general, the allowable range during processing with respect to the change in fluence in laser welding is ± 10%. Therefore, under the above conditions, the depth of penetration due to melting of the components of the welded portion is also reduced. The strength is lowered and cracks are generated in the weld.
[0011]
In particular, when aluminum or an aluminum alloy is used as a constituent member in order to reduce the weight, cracks are likely to occur, and the yield in manufacturing the product is significantly reduced. In order to perform welding well, cos θ> 0.9 needs to be satisfied, and therefore θ <25 ° is desired. Therefore, when the constituent member of the outer can casing is iron or stainless steel, the radius of curvature of the entire outer can casing including the corner portion R is reduced to about 1.0 to 1.3 mm as described above. The problem of a decrease in bonding strength was prevented by preventing the uneven irradiation angle. However, in the case of aluminum or an aluminum alloy, if the radius of curvature is reduced as described above, stress concentrates on the corner portion R and the rigidity decreases. That is, since the strength of the member itself is low, it is necessary to increase the radius of curvature, and thus the above-described decrease in the bonding strength cannot be solved.
[0012]
As another specific technique for preventing the occurrence of poor welding, there is a technique disclosed in, for example, Japanese Patent Application Laid-Open No. 8-77783. According to this, a heat radiation removal part (notch part) is provided at the opening end of the outer can casing, and the center of the scanning position of the laser beam is unevenly distributed outward from the boundary between the cap body and the outer can casing to prevent generation of cracks. It is something to prevent. That is, as shown in FIG. 13 as a second conventional example, laser light is irradiated from above and the lid 2 and the outer can casing 1 are welded. Therefore, it is possible to irradiate a laser perpendicular to the welding surface, and there is no reduction in fluence. Therefore, the curvature radius of the entire outer can casing including the corner portion R can be increased to 1.7 to 2.3 mm.
[0013]
However, as shown in FIG. 14, a hermetic seal 15 is disposed to surround the negative electrode terminal 12 at a distance of about 1 mm from the inner edge of the opening 3 of the outer can housing 1 in order to insulate from the negative electrode terminal 12. ing. Therefore, in order to prevent damage to the hermetic seal 15 due to laser irradiation, there is a lower limit to the distance t from the outer edge of the hermetic seal 15 and the outer can housing, and the hermetic seal 12 maintains insulation. For this reason, it must be formed to a certain distance (for example, 3.5 mm or more) from the negative electrode terminal 12, and it is difficult to design an outer can casing having a predetermined thickness (for example, 5.5 mm) or less. It has become.
[0014]
In addition, in the conventional rectangular battery outer can case, the cross section parallel to the opening is formed in a rectangle (including those in which the corner portion R has a round shape), and the long side portion and the short side portion The plate thickness (the thickness of the members constituting the outer can casing) was equal. Therefore, when the plate thickness is insufficient, the rigidity of the outer can casing becomes low, and when the power generation element of the secondary battery is charged, gas is generated due to a chemical reaction of the electrolytic solution, so that the outer can casing When the internal pressure increases, the outer can casing is distorted due to a bending moment (dotted arrow) that appears in the cross section of the outer can casing 1 shown in FIG. That is, with the corner portion R as a fulcrum, the long side portion 4 having a large surface area (subject to strong internal pressure) bulges outward as indicated by an arrow, and the short side portion 5 where stress concentrates is recessed toward the inside as indicated by an arrow.
[0015]
[Problems to be solved by the invention]
The method of welding the cap body on the side surface of the outer can casing as described above tends to cause poor bonding between the outer can casing and the lid. In addition, the outer can housing expands. However, when aluminum or aluminum alloy is used as a component, the strength is inferior to that of iron or stainless steel. Can also rupture. In particular, the tensile strength is only about 30% of iron when aluminum alloy A3003 (JIS standard) is used, for example. Therefore, in order to suppress the expansion of the outer can casing while preventing the weight of the outer can from increasing, the shape of the welded portion is devised while suppressing the poor welding of the lid to the outer can casing, and the rigidity of the outer can can be increased. Need to increase. However, if the rigidity is to be increased, it is necessary to increase the radius of curvature of the corner portion as described above, and the fluence at the welded portion is reduced during laser welding to the corner portion, so that cracking occurs. There is a bug.
[0016]
Further, in order to prevent deformation due to expansion from the inside of the outer can casing itself, it is necessary to increase the plate thickness of the constituent members of the outer can casing to increase the rigidity. However, since it is necessary to prevent a reduction in the volume of the inside of the outer can housing and to reduce the weight of the entire battery including the power generation element and the like, the members constituting the short side portion described above are desired. The plate thickness is preferably kept small.
[0017]
The present invention has been made paying attention to the above-mentioned circumstances, and its purpose is to provide a highly rigid outer can casing that can withstand expansion caused by an increase in internal pressure mainly when charging a secondary battery. An object of the present invention is to provide a square sealed battery and a method for manufacturing the square sealed battery.
[0018]
[Means for Solving the Problems]
  According to claim 1, a metal outer can housing having an opening and a corner portion, and a power generation element having a positive electrode and a negative electrode housed in the outer can housing and facing each other with a separator interposed therebetween, In the rectangular sealed battery comprising a metal lid joined to the opening by welding and an electrode element electrically connected to the power generation element, the corner of the openingOn part of the outer periphery, Smaller than the radius of curvature of the outer peripheral portion of the cross section parallel to the opening at the corner other than the openingNoHas a radius of curvatureThe corner of the opening is shaped so that a part is formedIn addition, the lid body is characterized in that it is formed in a shape that can be air-tightly welded corresponding to the opening portion in which the corner portion of the opening portion is shaped.
[0019]
  According to claim 2, in the square sealed battery according to claim 1,Corner of opening
Is formed by chamfering the corner portion of the opening at a predetermined angle,
The lid is formed in a shape that can be air-tightly welded in correspondence with the chamfered opening.
It is characterized by being.
[0020]
According to claim 3, a metal outer can case having an opening and having a corner portion, and a power generation element having a positive electrode and a negative electrode that are accommodated in the outer can case and face each other with a separator interposed therebetween. The prismatic sealed battery comprising a metal lid joined to the opening by welding and an electrode element electrically connected to the power generating element, wherein the outer can casing is disposed at the opening. The parallel cross section is formed in a rectangular shape, and the thickness of the short side portion of the rectangle is larger than the thickness of the long side portion.
[0021]
According to a fourth aspect of the present invention, in the square sealed battery according to any one of the first to third aspects, at least one of the outer can casing and the lid body is made of aluminum, or 0. It is characterized by being composed of an aluminum-based metal containing not more than 05 wt% Mg and not more than 0.2 wt% Cu.
[0022]
  According to the fifth aspect, the step of housing the power generation element having the positive electrode and the negative electrode opposed to each other with the separator sandwiched inside the metal-made square outer can housing having the opening, and the power generation element and the electrical A step of forming an electrode terminal connected to the opening, a step of joining a metal lid to the opening by laser welding, and an electrolyte solution before or after joining the lid. In the method of manufacturing a rectangular sealed battery comprising a step of injecting into the inside of the corner portion of the opening before the step of joining by laser welding.In part of the outer periphery,Smaller than the radius of curvature of the outer periphery of the cross section parallel to the opening at the corner other than the openingNoHas radius of curvatureThe corner of the opening is formed so that a portion to be formed is formed.A step of shaping is provided.
[0023]
  According to claim 6, in the method of manufacturing a rectangular sealed battery according to claim 5, the step of shaping the corner portion of the opening portion includes:The openingA method of chamfering the corner portion at a predetermined angle is used.
[0024]
  According to Claim 7, in the manufacturing method of the square sealed battery according to Claim 5, the corner portion of the opening portion.TheThe shaping process isThe openingThe method is characterized in that a method of reducing the radius of curvature of the corner portion of this by pressing is used.
[0025]
According to the eighth aspect of the present invention, a positive electrode and a negative electrode which have an opening and are opposed to each other with a separator sandwiched inside a metal-made square outer can housing having a rectangular cross section parallel to the opening. A step of housing a power generation element having a step, a step of forming an electrode terminal electrically connected to the power generation element, a step of joining a metal lid to the opening by laser welding, and the lid And a step of injecting an electrolyte into the outer can housing before or after joining the bodies, in the method of manufacturing a rectangular sealed battery, wherein the rectangular short side portion has a plate thickness of the rectangular long side portion The method is characterized by comprising a step of forming a thickness larger than the plate thickness.
[0026]
According to the above invention, by making the plate thickness of the short side portion larger than the plate thickness of the long side portion, the highly rigid outer can casing that can withstand expansion caused by an increase in pressure from the inside is provided. Can be formed. Thereby, it is possible to provide a square sealed battery having a high sealing degree and a method for manufacturing the same.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. Here, the “square shape” has a substantially rectangular cross section parallel to the opening of the outer can casing, but also allows a shape with a rounded corner.
[0028]
In general, the rectangular sealed battery is formed in a sealed container structure of an outer can casing 1 and a lid 2 as shown in FIG. FIG. 1 is a perspective view showing a prismatic sealed battery according to an embodiment of the present invention, which has the same structure as the prismatic sealed battery of FIG. 10 described above except for the structure of the outer can casing. The outer can housing 1 has a rectangular cross-section parallel to the opening 3 to which the lid 2 is joined after housing the power generation element, and the plate thickness of the long side portion 4 is 0.5 mm. The plate thickness of the short side portion 5 is 0.7 mm. As an aluminum-based metal constituting the outer can casing 1, for example, if it contains 0.05 wt% or less of Mg and 0.2 wt% or less of Cu, even if cooling and solidification after laser welding is performed, Cracks at the freezing point are suppressed. Specifically, JIS standard A3003, A3004, A1050, A1100, A1200 and the like are preferable. The shape of the outer can casing 1 is formed by press working such as deep drawing or cold impact processing so that these materials have the above plate thickness.
[0029]
As shown in FIG. 2, a lid 2 having a plate thickness of 1.0 mm is inserted into and engaged with the opening 3 so as to cover it. The lid 2 has a rectangular thin plate shape and is provided with a step of 0.3 mm in the peripheral portion. In the engaging portion with the outer can case 1, the outer step has an end face in the thickness direction on the outer surface of the outer can case 1. And is set to be flush with each other. The lid body 2 has a thickness of 0.8 mm or more, preferably 0.9 to 1.5 mm. This is because if the thickness is less than 0.8 mm, the strength decreases.
[0030]
In this state, while scanning along the dotted arrow direction in FIG. 1 toward the joint portion (welded surface) between the outer can casing 1 and the lid 2, the focusing diameter (laser spot diameter) 0.4 to Laser light from a YAG laser is irradiated at 0.5 mm. By doing so, seam welding for continuously forming a melted portion having a melt diameter of about 0.8 mm is performed on the joint, and the outer can casing 1 is sealed with the lid 2. In this case, the YAG laser (wavelength: 1.06 μm) has a repetition period of 20 to 30 Hz, a pulse width of 3 to 5 ms, a moving (scanning) speed of 5 to 10 mm / s, and an overlap rate of 70 to 70. 80%. Further, by welding while blowing nitrogen gas to the welded portion, generation of bubbles caused by oxidation of the constituent members of the outer can casing 1 during welding is prevented.
[0031]
The reason why the YAG laser was used as the laser beam is that the wavelength is shorter than that of the carbon dioxide gas laser, so the reflectivity for aluminum and its alloys is smaller than that of the carbon dioxide laser, and more efficient welding is possible. is there. And this laser beam is condensed to a junction part with a lens through an optical fiber from a laser oscillator. The optical axis of this laser beam is set within an allowable range of 20 ° from the perpendicular to the joint, and welding is performed. Here, the above-mentioned lens is scanned so as to maintain a certain angle and distance with respect to the joint portion of the long side portion 4 or the short side portion 5, and welding is performed one by one.
[0032]
As described above, the inventor conducted an experiment to derive the dimensions of the outer can casing 1 for suppressing the weight of the outer can casing 1 while suppressing deformation even when the internal pressure increases. The results shown in FIGS. 3 and 4 were obtained. The following [Table 1] shows an example of the dimensions of the outer can casing 1 that is the basis of this experiment. In this table, “width” is the length of the long side portion 4, “thickness” is the length of the short side portion 5, and “height” is the lid from the bottom of the outer can casing 1. This is the length to the joint with the body 2.
[0033]
[Table 1]

[0034]
FIG. 3 shows the result of determining the relationship between the corner portion R shown in FIG. 11 and the bulging amount of the long side portion 4 of the outer can case 1 using the outer can case 1 having the reference dimensions. The pressure inside the outer can case 1 is 0.1913 MPa (atmospheric pressure + 0.09 MPa), and the bulge amount is 0.1013 MPa, which is the atmospheric pressure, with reference to the shape of the outer can case 1 shown in FIG. It is defined by the maximum displacement amount to the outside of the long side portion 4. It can be seen from FIG. 3 that when the radius of curvature of the corner portion R is increased, the amount of swelling is reduced and deformation of the outer can casing 1 can be effectively suppressed. At the same time, since the surface area of the outer can casing 1 is reduced, there is an advantage that the weight is also reduced.
[0035]
Next, FIG. 4 shows the result of determining the relationship between the plate thickness of the short side portion 5 and the bulge amount of the long side portion 4 using the outer can casing 1 having the above-mentioned reference dimensions. Again, the pressure inside the outer can case 1 is 0.1913 MPa, and the amount of swelling is 0.101 MPa, which is the atmospheric pressure, with reference to the shape of the outer can case 1 as shown in FIG. It shall be defined by the maximum outward displacement.
[0036]
As can be seen from FIG. 4, for example, when the plate thickness of the short side portion 5 is increased from 0.5 mm to 0.7 mm, the bulge amount of the long side portion 4 is reduced by about 20%. In this case, the weight of the entire outer can casing 1 in the dimensions shown in Table 1 can be suppressed to an increase of only 0.1 g from 4.5 g to 4.6 g. Contributes to overall weight reduction.
[0037]
Further, as an actual product, about 8% of the short side portion 5 (thickness of the outer can case casing can 1) is allowed as a bulge amount of the long side portion 4 (width of the outer can case casing can 1). As the thickness increases, the plate thickness of the short side portion 5 can be reduced. Therefore, a dimension in which the plate thickness of the short side portion 5 as shown in [Table 2] below is larger than the plate thickness of the long side portion 4 is given as a suitable example.
[0038]
[Table 2]

[0039]
  In the present embodiment, the radius of curvature of the corner portion R is made large in the opening 3 for the reason of suppressing the swelling of the outer can casing 1, so that it has been described in the section of “PRIOR ART” in this specification. In addition, there is a high possibility that the incident angle of the laser beam to the welded portion becomes large and the welded portion between the lid 2 and the opening 3 becomes defective. Therefore, the outer can casing 1 itself has increased rigidity by increasing the curvature at the outer periphery of the cross section of the outer can casing parallel to the opening of the corner R, and the corner of the opening 3In part of the outer periphery,In corners other than the openingSaidSmaller than the radius of curvature of the outer periphery of the cross section parallel to the openingNoIf it is shaped to the corner portion Q of the opening having a radius of curvature, it is considered that defects in welding with the lid 2 are also suppressed. Here, the corner portion Q of the opening is sufficient if there is a portion having a smaller radius of curvature than the corner portion R. The point is that the purpose is to make the incident angle of the laser beam to the welded portion close to a right angle.
[0040]
  As shown in FIG. 5 as a cross-section taken along line A-A ′ of FIG.In part of the outer periphery,Smaller than the radius of curvature of the outer periphery of the cross section parallel to the opening at the corner other than the openingNoA corner portion Q having a large radius of curvature is formed. Assuming that the plate thickness of the long side portion 4 is a and the plate thickness of the short side portion 5 is b, as described above, a <b is satisfied in order to suppress the swelling due to the internal pressure of the outer can casing 1. The hatched portion is a cross section of the outer can case of the opening 3 having the corner portion Q of the opening, and the outer can case 1 itself (excluding the opening 3) having a corner portion R having a curved portion of the dotted line portion. ). Only this dotted line is shown in FIG.
[0041]
  Now, it is smaller than the curvature radius of the outer peripheral part of the cross section parallel to the opening part of the corner part other than this opening part.NoWhen forming the corner Q of the opening having a radius of curvature, the angle θ formed by the long side 4 or the short side 5 shown in FIG. 5 and the corner Q of the opening was set to 15 °. Here, from the geometric calculation, the angle formed by the long side portion 4 and the short side portion 5 and the corner portion Q of the opening portion is equal to the angle formed by the welding surface and the plane perpendicular to the laser beam irradiation direction θ. It becomes. Then, θ shown in FIG. 7 which is an enlarged view of the main part of FIG. 5 satisfies θ <25 °, which is the condition described in the section of “PRIOR ART” in this specification, so that cos θ> 0.9. If set to, good welding can be performed. Actually, when θ = 15 ° and the corner portion Q of the opening was processed under the above plate thickness conditions, 150 were welded and no cracks were generated. However, such processing is not performed. All cracks occurred.
[0042]
  It has a radius of curvature smaller than the radius of curvature of the corner portion of the outer can casing other than the opening.Opening
Corner partIn this embodiment, Q is formed by press working such as deep drawing. One
In other words, after forming the outer can casing 1, the opening 3 is inserted into the mold and the chamfering is pressed.
is there. At this time, in order to keep the welding condition between the lid 2 and the opening 3 by laser light constant,
In the opening 3, a = b may be used instead of a <b as described above. Exterior can case
Since the area occupied by the opening 3 in the body 1 is small, the long side 4 and the short side 5 are the same as long as the opening 3 is limited.
This is because it can be pressed to the same thickness.
[0043]
  FIG. 8 shows a perspective view of a modified example of this embodiment. In this modified example, the outer peripheral portion of the outer peripheral portion of the outer side of the corner portion R of only the opening 3 of the outer can casing 1 is parallel to the opening. A large radius of curvature is formed. FIG. 9 shows a cross section taken along line B-B ′ of FIG. 8. The opening 3 is smaller than the radius of curvature of the outer peripheral portion of the cross section parallel to the opening at the corner other than the opening.NoA corner Q of the opening having a radius of curvature is formed. As in FIG. 7, the hatched portion is a cross section of the opening 3 having the corner portion Q of the opening, and the outer can case 1 itself (excluding the opening 3) having the corner portion R with the dotted line portion having a curvature. And has the same shape as FIG. When the corner portion Q of the opening is formed, if the condition θ <25 °, which is the above-described condition, is set to satisfy cos θ> 0.9, welding can be performed satisfactorily.
[0044]
  The corner portion Q of the opening is also formed by press working such as deep drawing in this modified example. That is, after the outer can casing 1 is formed, the opening 3 is inserted into the mold, and extrusion pressing is performed. In this case, a = b may be used instead of a <b.
[0045]
In this embodiment, pulsed laser light is used for welding, but even if continuous wave (CW: Continuous Wave) laser light is used, if the irradiation energy is set to an appropriate value for welding, the same applies. An effect is obtained.
[0046]
In each of the embodiments, a lithium ion secondary battery is taken as an example and applied to the outer can casing 1 for a prismatic secondary battery. However, other types of secondary batteries such as a nickel hydrogen secondary battery are shown. A battery may be used, and further, it can be applied to a primary battery because of the effect of the present invention to increase rigidity.
[0047]
【The invention's effect】
According to the present invention, by forming the plate thickness of the short side portion larger than the plate thickness of the long side portion, a highly rigid outer can casing that can withstand expansion caused by an increase in pressure from the inside is formed. Therefore, it is possible to provide a square sealed battery having a high sealing degree and a method for manufacturing the same.
[0048]
Furthermore, in order not to reduce the rigidity of the entire outer can casing, by processing the corner portion of only the opening into a corner portion while increasing the radius of curvature of the corner portion of the outer can casing, The welded portion with the lid can be reliably sealed. A highly rigid outer can casing capable of withstanding expansion from the inside can be formed, and a highly sealed prismatic sealed battery and a manufacturing method thereof can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of an essential part showing a welded state between an outer can casing and a lid in an embodiment of the present invention.
FIG. 3 is a graph showing a relationship between a corner portion and a bulge amount of a long side portion of an outer can casing.
FIG. 4 is a graph showing a relationship between a plate thickness of a short side part and a bulge amount of a long side part.
FIG. 5 is a cross-sectional view of the outer can housing taken along the line A-A ′ of FIG. 1;
FIG. 6 is a cross-sectional view of an outer can housing excluding an opening.
7 is an enlarged cross-sectional view of a main part of FIG.
FIG. 8 is a perspective view showing a modification of one embodiment of the present invention.
9 is a cross-sectional view of the outer can housing taken along line B-B ′ of FIG. 7;
FIG. 10 is a partially cutaway perspective view showing a lithium ion secondary battery as a square sealed battery.
FIG. 11 is a perspective view showing a first conventional example of the present invention.
12 is an enlarged cross-sectional view of a main part of a corner portion in FIG.
FIG. 13 is a perspective view showing a second conventional example of the present invention.
14 is an enlarged top view of the main part in the vicinity of the negative electrode terminal in FIG. 13;
FIG. 15 is a schematic cross-sectional view showing a deformation of the outer can housing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Exterior can housing | casing, 2 ... Cover body, 3 ... Opening part, 4 ... Long side part, 5 ... Short side part
6 ... Insulating film, 7 ... Electrode body, 8 ... Negative electrode, 9 ... Separator, 10 ... Positive electrode
DESCRIPTION OF SYMBOLS 11 ... Positive electrode lead, 12 ... Negative electrode terminal, 13 ... Spacer, 14 ... Injection hole
15 ... sealing lid, 16 ... negative electrode lead, 17 ... upper insulating paper, 18 ... slit
19 ... Lower insulating paper, 20 ... PCT element, 21 ... Exterior tube

Claims

A metal outer can housing having an opening and a corner;
A power generation element having a positive electrode and a negative electrode that are housed in this outer can housing and are opposed to each other with a separator interposed therebetween,
A metal lid joined by welding to the opening;
In a square sealed battery comprising an electrode element electrically connected to the power generation element,
Some of the outer peripheral portion of the corner portion of the opening, so that the opening parallel to the outer peripheral portion the curvature portion having more have smaller curvature radius of the cross section of the corner portion other than the opening is formed,
The Rutotomoni corner portion of the opening portion is shaped, the lid has a feature in that corners of the opening portion is formed in weldable shape hermetically in correspondence to the opening that is shaped Square sealed battery.

The corner portion of the opening portion is formed by chamfering the corner portion of the opening portion at a predetermined angle, and the lid body can be welded in an airtight manner corresponding to the chamfered opening portion. The square sealed battery according to claim 1, wherein the prismatic sealed battery is formed in a simple shape.

A metal outer can housing having an opening and a corner;
A power generation element having a positive electrode and a negative electrode that are housed in this outer can housing and are opposed to each other with a separator interposed therebetween,
A metal lid joined by welding to the opening;
In a square sealed battery comprising an electrode element electrically connected to the power generation element,
The outer can case has a rectangular cross section parallel to the opening, and a rectangular sealed battery characterized in that the rectangular short side is thicker than the long side. .

At least one of the outer can casing or the lid is made of aluminum or an aluminum-based metal containing 0.05 wt% or less Mg and 0.2 wt% or less Cu. The square sealed battery according to any one of claims 1 to 3.

Storing a power generation element having a positive electrode and a negative electrode facing each other with a separator sandwiched inside a metal-made square outer can housing having an opening;
Forming an electrode terminal electrically connected to the power generation element;
Joining a metal lid to the opening by laser welding;
In the method for manufacturing a rectangular sealed battery comprising a step of injecting an electrolyte into the exterior can housing before or after joining the lid,
Before the step of joining by laser welding, a part of the outer periphery of the corner of the opening ,
As the opening parallel to the outer peripheral portion the curvature portion chromatic small have a radius of curvature than the radius of the cross section of the corner portion other than the opening is formed, comprising the step of shaping the corner portions of the opening A method for producing a rectangular sealed battery, characterized in that:

6. The method for manufacturing a rectangular sealed battery according to claim 5, wherein the step of shaping the corner portion of the opening portion uses a method of chamfering the corner portion of the opening portion at a predetermined angle.

6. The method for manufacturing a rectangular sealed battery according to claim 5, wherein the step of shaping the corner portion of the opening uses a method of reducing a radius of curvature of the corner of the opening by pressing.

A power generation element having a positive electrode and a negative electrode facing each other with a separator interposed is housed inside a metal-made square outer can housing having an opening and a rectangular cross section parallel to the opening. Process,
Forming an electrode terminal electrically connected to the power generation element;
Joining a metal lid to the opening by laser welding;
In the method for manufacturing a rectangular sealed battery comprising a step of injecting an electrolyte into the exterior can housing before or after joining the lid,
A method for manufacturing a rectangular sealed battery, comprising a step of forming a plate thickness of the short side of the rectangle larger than a plate thickness of the long side of the rectangle.