JP4219661B2

JP4219661B2 - Battery sealing plate

Info

Publication number: JP4219661B2
Application number: JP2002340022A
Authority: JP
Inventors: 正明金田; 和彦渡▲邉▼; 兼人増本; 靖平川
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2002-11-22
Filing date: 2002-11-22
Publication date: 2009-02-04
Anticipated expiration: 2022-11-22
Also published as: JP2004178820A

Description

【０００１】
【発明の属する技術分野】
本発明は、電池内圧上昇時のケースの変形により破断する電池用封口板およびそれを用いた密閉型電池に関する。
【０００２】
【従来の技術】
密閉型電池を異常な条件で取り扱うと、電池内部にガスが発生し、内圧が上昇することがある。そこで、このような場合に、電池内圧の過剰な上昇を防ぐための安全弁が開発されている。安全弁は、電池内圧が所定値以上に達したときに作動し、電池内部のガスを外部へ放出する。このような安全弁としては、例えば以下に示すものが提案されている。
【０００３】
まず、電池ケースの開口部を封口する金属板に、所定の輪郭を有する肉薄部を形成し、その肉薄部を金属板の表面側に膨出させた安全弁が開発されている（例えば、特許文献１、２参照）。また、長辺と短辺を有する矩形または長円形の一方の長辺を除く輪郭に沿って、肉薄部を形成し、電池の内部圧力の上昇により、上部に向かって蝶番式に開裂する安全弁が開発されている（例えば、特許文献３参照）。
【０００４】
【特許文献１】
特許第３２２２４１８号公報（請求項１、図７）
【特許文献２】
特開２００１−３２５９３４公報（請求項１、図１、２）
【特許文献３】
特開２００２−８６１５号公報（請求項１、図１、２）
【０００５】
しかし、上記安全弁は、いずれも、電池内部のガスが弁体を上方に押し上げる力によって破断するものである。これらの安全弁は、電池内部のガス圧そのものによって作動する。そのため、肉薄部を膨出させたり、ドーム状にしたりして、破断させる部分がガスによる上方への圧力を受けやすいように設計されている。しかし、このような安全弁は、肉薄部を非常に薄くする必要がある上、性能の均一性を保つことが困難である。従って、安全弁の作動圧力が安定せず、電池内圧の過剰な上昇を十分に防ぐことは困難である。
【０００６】
【発明が解決しようとする課題】
本発明は、電池内圧上昇時のケースの変形により破断する安全弁を提供するものであり、上述のような従来の安全弁の欠点を改善するものである。
【０００７】
【課題を解決するための手段】
本発明は、電池ケースの開口部を封口する板状材料からなる封口板であって、前記封口板は、安全弁を有し、前記安全弁は、前記板状材料に座押し加工により形成された下面が平坦な肉薄部からなり、前記肉薄部は、座押し加工により形成されたさらに肉薄な平坦部を有し、前記平坦部は、矩形の輪郭または一対の平行な直線部を有する略長円形の輪郭に沿って溝を形成しており、かつ電池内圧上昇時の前記ケースの変形により、前記板状材料の面方向への張力により破断する電池用封口板に関する。
また、本発明は、電池ケースの開口部を封口する板状材料からなる封口板であって、前記封口板は、安全弁を有し、前記安全弁は、前記板状材料に座押し加工により形成された下面が平坦な肉薄部からなり、前記肉薄部は、座押し加工により形成されたさらに肉薄な平坦部を有し、前記平坦部は、矩形の輪郭または一対の平行な直線部を有する略長円形の輪郭で囲まれた凹部を形成しており、かつ電池内圧上昇時の前記ケースの変形により、前記板状材料の面方向への張力により破断する電池用封口板に関する。
【０００８】
前記平坦部の厚さは３０〜８０μｍであることが好ましい。
前記平坦部の幅は０．１ｍｍ以上であることが好ましい。
【０００９】
本発明は、また、電極群、電解液、前記電極群と前記非水電解液とを収容する角形電池ケース、ならびに前記ケースの開口部を封口する板状材料からなる封口板からなり、前記封口板が上記安全弁を有する密閉型電池に関する。
前記ケースの壁材の厚さは、１〜０．１ｍｍであることが好ましい。
【００１０】
【発明の実施の形態】
本発明の封口板およびそれを用いた密閉型電池の好ましい実施形態について説明する。
本発明の封口板は、板状材料からなり、安全弁を有する。板状材料には、金属板が好ましく用いられ、なかでもアルミニウム、鉄などからなる金属板が好ましく用いられる。板状材料の厚さは０．６〜２ｍｍであることが好ましい。板状材料が厚すぎると、肉薄部にかかる面方向への張力が小さくなり、薄すぎると、肉薄部以外での変形が大きくなり、安全弁の安定した作動が達成されないことがある。
【００１１】
安全弁は、板状材料に座押し加工により形成された下面が平坦な肉薄部からなる。また、肉薄部は、座押し加工により形成された、さらに肉薄な平坦部（以下、平坦部という。）を有する。平坦部以外の肉薄部の厚さは、５０〜１００μｍであることが好ましい。平坦部以外の肉薄部が厚すぎると、加工が困難になり、薄すぎると、安全弁の破断部分が定まらず安定した作動が達成されないことがある。
【００１２】
平坦部は、電池内圧上昇時の前記ケースの変形により、板状材料の面方向への張力により破断する。このような面方向への張力によれば、平坦部が多少厚くても比較的容易に破断され得る。従って、本発明の安全弁の平坦部は、従来の上方への力によって破断する安全弁の破断部分に比べて、より厚くすることができる。例えば、従来の上方への力によって破断する安全弁の場合、破断部分の厚さを２０μｍ以下にする必要がある。一方、本発明の安全弁の平坦部の厚さは３０〜８０μｍ、より好ましくは３５〜５０μｍとすることが可能である。
【００１３】
本発明の安全弁は、破断部分を従来よりも厚くすることができるため、多少の厚さの変動があっても、その変動が作動圧力に与える影響は小さく、結果として安全弁の作動圧力が安定する。また、封口板の大きさにもよるが、作動圧力を、より安定させる観点から、平坦部の幅は０．１ｍｍ以上、さらには１ｍｍ以上とすることが好ましい。ある程度までは、平坦部の幅が広い程、作動圧力は安定する。
【００１４】
以下、好ましい平坦部を有する封口板を例示する。
実施形態１
本実施形態に係る封口板の上面図を図１に示す。また、図１に示す封口板のII−II線拡大断面図を図２に、III−III線拡大部分断面図を図３に示す。
本実施形態に係る封口板の安全弁は、図１〜３に示すように、板状材料１２に座押し加工により形成された下面が平坦な肉薄部１１からなる。図１では、肉薄部１１は、略長円形の輪郭１０を有するが、肉薄部の輪郭に、特に限定はない。肉薄部１１には、一対の平行な直線部を有する略長円形の輪郭に沿って、溝状の平坦部１３が形成されている。溝状の平坦部１３は、このような略長円形の他に、矩形の輪郭に沿った形状でもよい。なお、封口板の中央には、電極端子を挿入するための端子孔１４ａが設けられており、その周囲には、電極端子と封口板とを絶縁する絶縁材料を嵌め込むための凹部１４ｂが設けられている。また、封口板の安全弁のない他端には、電解液を注液するための注液孔１５ａが設けられており、その周囲には、封栓を嵌め込むための凹部１５ｂが設けられている。
【００１５】
溝幅は、上述のように、０．１ｍｍ以上であることが好ましく、１ｍｍ以下であることが特に好ましい。溝の深さ（Ｂ１）は、肉薄部１１の厚さ（Ａ１）および平坦部の厚さ（Ｃ１）により決定される。このような溝状の平坦部の場合、平坦部の厚さ（Ｃ１）は、特に３０〜８０μｍであることが好ましい。溝の深さは、図２、３に示すように一定であることが好ましいが、部分的に溝の深さを変化させてもよい。溝の壁面にはテーパーを付してもよい。
【００１６】
略長円形の直線部の長さ（Ｌ１）は、０．５〜１０ｍｍであることが好ましいが、直線部は１０ｍｍより長くても良い。直線部が長いほど、平坦部の厚さを厚くすることができる。直線部の長さが短すぎると、ケースが膨らんで面方向への張力が生じたときに、張力によって平坦部が破断しにくくなる。直線部は、ケースが膨らんだときに平坦部１３が破断しやすいように、封口板の長手方向に対して平行もしくは、ほぼ平行であることが好ましい。また、直線部間の距離（Ｗ１）は、１．５〜８ｍｍであることが好ましい。この距離が短すぎると、安全弁が作動しても、破断部分による開口部が小さくなり、ガスを放出する能力が不十分になる。
【００１７】
封口板の大きさにもよるが、封口板の強度を保つ観点からは、肉薄部からなる安全弁の面積が小さい方が好ましい。一方、ガスを放出するという安全弁の機能を高める観点からは、安全弁の破断部分の面積が大きい方が好ましい。従って、より小さく、作動時においては複数の破断部分を生じる安全弁が最も好ましい。
本実施形態に係る安全弁は、以下に述べる実施形態２、３に係る安全弁に比べて、排気能力が優れており、高容量な電池の封口板に好適である。
【００１８】
参考形態１
本参考形態に係る封口板の上面図を図４に示す。また、図４に示す封口板のＶ−Ｖ線拡大断面図を図５に、VI−VI線拡大部分断面図を図６に示す。
本参考形態に係る封口板の安全弁は、図４に示すように、一対の平行な直線に沿う溝状の平坦部２０を有する。その他の構造については、実施形態１と同様である。溝幅は０．１ｍｍ以上であることが好ましく、１ｍｍ以下であることが好ましい。このような溝状の平坦部の場合、平坦部の厚さ（Ｃ２）は、特に３０〜５０μｍであることが好ましい。溝の深さ（Ｂ２）は、肉薄部２１の厚さ（Ａ２）および平坦部の厚さ（Ｃ２）により決定される。溝の深さは、図４に示すように一定であることが好ましいが、部分的に溝の深さを変化させてもよい。
【００１９】
直線部の長さ（Ｌ２）は、０．５〜１０ｍｍであることが好ましいが、直線部は１０ｍｍより長くても良い。直線部の長さが短すぎると、ケースが膨らんで面方向への張力が生じたときに、張力によって平坦部が破断しにくくなる。直線部は、ケースが膨らんだときに平坦部２０が破断しやすいように、封口板の長手方向に対して平行もしくは、ほぼ平行であることが好ましい。また、直線部間の距離（Ｗ２）は、１．５〜８ｍｍであることが好ましい。この距離が短すぎると、安全弁が作動しても、破断部分による開口部が小さくなり、ガスを放出する能力が不十分になる。。
【００２０】
参考形態２
本参考形態に係る封口板の上面図を図７に示す。また、図７に示す封口板のVIII−VIII線拡大断面図を図８に、IX−IX線拡大部分断面図を図９に示す。
本参考形態に係る封口板の安全弁も、図７に示すように、肉薄部３１に一対の平行な直線に沿う溝状の平坦部３０を有する。そして、一対の直線の対向する端部間を結ぶＲ状の輪郭に沿って、複数の小さな平坦部３２が間欠的に設けられていること以外は、参考形態１の封口板と同様の構造を有する。複数の小さな平坦部３２の厚さ（Ｃ３’）は、直線に沿う溝状の平坦部３０の厚さ（Ｃ３）よりも厚くしてもよい。
【００２１】
実施形態２
本実施形態に係る封口板の上面図を図１０に示す。また、図１０に示す封口板のXI−XI線拡大断面図を図１１に、XII−XII線拡大部分断面図を図１２に示す。
本実施形態に係る封口板の安全弁は、図１０〜１２に示すように、略長円形の輪郭で囲まれた凹部からなる平坦部４０を有する。その他の構造については、実施形態１と同様である。ここでも略長円形の輪郭は、一対の平行な直線部を有する。このような略長円形の他に、矩形の輪郭で囲まれた凹部からなる平坦部であってもよい。
【００２２】
略長円形の直線部の長さ（Ｌ４）は、０．５〜１０ｍｍであることが好ましいが、直線部は１０ｍｍより長くても良い。直線部の長さが短すぎると、ケースが膨らんで面方向への張力が生じたときに、張力によって平坦部が破断しにくくなる。直線部は、ケースが膨らんだときに平坦部４０が破断しやすいように、封口板の長手方向に対して平行もしくは、ほぼ平行であることが好ましい。
【００２３】
直線部間の距離（Ｗ４）は、１．５〜８ｍｍであることが好ましい。この距離が短すぎると、安全弁が作動しても、破断部分による開口部が小さくなり、ガスを放出する能力が不十分になる。凹部の深さ（Ｂ４）は、肉薄部の厚さ（Ａ４）および平坦部の厚さ（Ｃ４）により決定される。このような平坦部の場合、平坦部の厚さ（Ｃ４）は、特に３０〜８０μｍであることが好ましい。凹部の深さは、図１１、１２に示すように一定であることが好ましいが、部分的に深さを変化させてもよい。
【００２４】
上記のような封口板は、例えば、所定の凹凸形状を有するプレス金型を用いて、平坦な板状材料に、座押し加工（平坦な面を作るプレス加工）を施すことにより、得ることができる。座押し加工によれば、下面が平坦な肉薄部からなる安全弁を容易に得ることができる。板状材料に下面が平坦な肉薄部を形成する場合、製品のバラツキが少なくなり、加工条件の管理も容易である。そのような方法の一例について、実施形態１の封口板を例にとって、以下に具体的に説明する。
【００２５】
図１３は、実施形態１の封口板の製造工程を示すものであり、黒矢印は工程の流れを示す。先ず、加工し易い大きさの板状材料５０を準備する。ここでは、板状材料の短手方向における断面図をＡ１〜Ｄ１に示し、長手方向における断面図をＡ２〜Ｄ２に示す。
安全弁は、２段階のプレス加工により形成することができる。１段階目のプレス加工では、Ａ１、Ａ２に示すように上金型５１ａと下金型５１ｂにより、白抜矢印が示す方向に圧力をかけて、Ｂ１、Ｂ２に示すような肉薄部５２を形成する。
このとき、Ｂ２に示すように、肉薄部５２の形成と同時に端子孔５４と注液孔５５を形成してもよい。
【００２６】
次に、上金型５３および下金型５３ｂを用いて、２段階目のプレス加工（座押し加工）を行う。上金型５３の下面には、略長円形の輪郭に沿う頂部が平坦なリブ５３ａが形成されており、リブ５３ａに沿ってＣ１、Ｃ２に示すような平坦部５６が形成される。
最後に、所定形状の開口部を有する切断刃５７により、板状材料から所定形状の封口板を切り出せば、実施形態１に係る安全弁を有する封口板が得られる。次いで、得られた封口板から歪みを除去するために、切り出された封口板を焼鈍することが好ましい。焼鈍は、例えば１００〜３００℃で行えばよい。
【００２７】
次に、上記のような封口板と組み合わせる電池ケースの一例について説明する。
図１４に、密閉型電池に用いる角形電池ケース６０の一例の縦断面図を示す。ここでは、ケースと封口板の構造を理解し易いように、電池ケース６０の開口部を上述の実施形態１の封口板６１によって塞いだ図を示すが、電池の製造工程では、ケース内に、正極、負極およびセパレータを積層し、捲回してなる電極群とが収容されてからケースの開口部が閉じられる。封口板中央の端子孔には、絶縁材料６２を介して、電極端子６３が挿入されている。電極端子６３の両側には、安全弁６４と電解液の注液孔が設けられており、注液孔は封栓６５によって塞がれている。封口板の周縁部と電池ケースの開口端部、および注液孔と封栓は、それぞれレーザー溶接などにより接合される。
【００２８】
ケースの膨れやすさと電池ケースの寸法との間には、以下のような相関関係がある。電池ケースの厚さに対する横幅（Ｘ）の比、すなわち、封口板の短手方向の長さに対する長手方向の長さの比は３〜１７であることが好ましく、電池ケースの厚さに対する高さ（Ｙ）の比は、３〜３５であることが好ましい。また、ＸとＹとの比：Ｘ／Ｙは、０．３〜１．５であることが好ましい。
【００２９】
電池ケースの材質には、金属が好ましく用いられ、なかでもアルミニウム、鉄などが好ましく用いられる。電池ケースの広い方の側壁の厚さは、従来よりも薄くすることが安全弁の作動安定性を高める上で好ましく、例えば０．１〜０．３ｍｍであることが好ましい。前記側壁の厚さが厚すぎると、電池内圧の上昇時におけるケースの変形が妨げられて、安全弁が作動しにくくなる。一方、前記側壁の厚さが薄すぎると、電池ケースの強度を十分に確保することが困難になる。
【００３０】
電池ケース内にガスが発生し、電池ケースが厚さ方向に膨らむと、封口板には短手方向の張力が働く。そして、張力が一定値を超えると、安全弁の中で最も肉薄な平坦部が破断し、電池内部のガスが外部に放出される。
本発明は、非水電解液二次電池、アルカリ蓄電池および各種一次電池に適用することができるが、以下の実施例では、非水電解液二次電池を例にとって説明する。
【００３１】
【実施例】
《実施例１》
（イ）封口板の作製
板状材料として厚さ１ｍｍのアルミニウム板と、所定の凹凸形状を有するプレス金型を用いて、下記封口板Ａ、Ｂ、Ｃをそれぞれを作製した。なお、封口板Ｂは、参考例である。各封口板の寸法は、下記電池ケースの開口部の大きさに適合させて長さ３４ｍｍ、幅４．５ｍｍとした。
まず、所定形状のアルミニウム板に、座押し加工により、長径３．６ｍｍ、短径２．４ｍｍの略長円形の輪郭を有し、厚さ８０μｍの肉薄部を形成した。次に、肉薄部にさらなる座押し加工を施すことにより、所定の平坦部を形成した。平坦部の厚さは、いずれの封口板においても５０μｍとした。
【００３２】
封口板Ａの平坦部は、図１〜３に示すものと同様であり、一対の平行な直線部を有する略長円形の輪郭に沿う溝形状とした。溝幅（平坦部の幅）は０．１ｍｍとした。直線部の長さ（Ｌ１）は１．２ｍｍ、直線部間の距離（Ｗ１）は３．２ｍｍとした。
封口板Ｂの平坦部は、図４〜６に示すものと同様であり、一対の平行な直線に沿う溝形状とした。溝幅（平坦部の幅）は０．１ｍｍとした。直線部の長さ（Ｌ２）は１．２ｍｍ、直線部間の距離（Ｗ２）は３．２ｍｍとした。
封口板Ｃの平坦部は、図１０〜１２に示すものと同様であり、一対の平行な直線部を有する略長円形の輪郭で囲まれた凹部形状とした。直線部の長さ（Ｌ４）は１．２ｍｍ、直線部間の距離（Ｗ４）は３．２ｍｍとした。
【００３３】
（ロ）正極の作製
１００重量部の正極活物質（ＬｉＣｏＯ₂）に、導電材として３重量部のアセチレンブラックと、結着剤として７重量部のポリテトラフルオロエチレンと、カルボキシメチルセルロースを１重量％含む水溶液１００重量部とを加え、撹拌・混合し、ペースト状の正極合剤を得た。この正極合剤を、集電体となる厚さ２０μｍのアルミニウム箔の両面に塗布し、乾燥後、全体を圧延し、所定寸法に裁断して、正極を得た。
【００３４】
（ハ）負極の作製
平均粒子径が約２０μｍになるように粉砕・分級した１００重量部の鱗片状黒鉛に、結着剤としてスチレン／ブタジエンゴムを３重量部と、カルボキシメチルセルロースを１重量％含む水溶液１００重量部とを加え、撹拌・混合し、ペースト状の負極合剤を得た。この負極合剤を、集電体となる厚さ１５μｍの銅箔の両面に塗布し、乾燥後、全体を圧延し、所定寸法に裁断して、負極を得た。
【００３５】
（ニ）電池の組み立て
上記正極と負極を用い、所定の封口板とアルミニウム製の図１４に示した形状の角形電池ケース（アルミニウム材の厚さ０．３ｍｍ）を用いて、非水電解液二次電池（厚さ５ｍｍ、幅３４ｍｍ、高さ５０ｍｍ）を組み立てた。製造した電池の一部を切り欠いた部分斜視図を図１５に示す。
まず、正極と負極とを、厚さ２５μｍの微多孔性ポリエチレン樹脂製セパレータを介して捲回して、電極群７０を構成した。正極と負極には、それぞれアルミニウム製正極リード７１およびニッケル製負極リード７２を溶接した。電極群の上部にポリエチレン樹脂製の絶縁板７３を装着し、電池ケース７４内に収容した。正極リードの他端は、下記の所定の安全弁７７を有する封口板７８の下面にスポット溶接した。また、負極リードの他端は、封口板の中心部にある端子孔に絶縁材料７６を介して挿入されているニッケル製負極端子７５の下部と電気的に接続した。
【００３６】
電池ケースの開口端部と封口板の周縁部とをレーザ溶接してから、封口板に設けてある注入孔から所定量の非水電解液を注液した。最後に注入孔をアルミニウム製の封栓７９で塞ぎ、レーザー溶接で注液孔を密封して、電池を完成させた。
非水電解液には、エチレンカーボネートとエチルメチルカーボネートとの体積比１：３の混合溶媒に、１．０ｍｏｌ／Ｌの濃度でＬｉＰＦ₆を溶解したものを用いた。
なお、封口板Ａ〜Ｃを用いた電池は、それぞれ１０個作製した。
【００３７】
（ホ）電池の評価
環境温度２５℃で、各電池の電圧が４．２Ｖになるまで定電流充電を行い、電圧が４．２Ｖに到達してからは、合計充電時間が３時間になるように定電圧充電を行った。その後、各電池を２５０℃のホットプレートに乗せ、安全弁の開裂試験を行った。
上記試験の後、電池を観察したところ、それぞれ１０個中１０個の電池の安全弁が作動しており、電池の破裂・発火などは全く発生しなかった。このことから、本発明によれば、安全弁の破断部分の厚さが従来よりも厚く５０μｍであったにもかかわらず、安全弁が安定して作動することを確認することができた。
【００３８】
【発明の効果】
以上のように、本発明によれば、電池内圧上昇時のケースの変形により破断する安全弁を採用するため、安全弁の製造が比較的容易であり、しかも、安全弁の作動電圧が安定するため、密閉型電池の安全性を高めることができる。
【図面の簡単な説明】
【図１】実施形態１に係る封口板の上面図である。
【図２】図１に示す封口板のII−II線拡大断面図である。
【図３】図１に示す封口板のIII−III線拡大部分断面図である。
【図４】参考形態１に係る封口板の上面図である。
【図５】図４に示す封口板のＶ−Ｖ線拡大断面図である。
【図６】図４に示す封口板のVI−VI線拡大部分断面図である。
【図７】参考形態２に係る封口板の上面図である。
【図８】図７に示す封口板のVIII−VIII線拡大断面図である。
【図９】図７に示す封口板のIX−IX線拡大部分断面図である。
【図１０】実施形態２に係る封口板の上面図である。
【図１１】図１０に示す封口板のXI−XI線拡大断面図である。
【図１２】図１１に示す封口板のXII−XII線拡大部分断面図である。
【図１３】実施形態１に係る封口板の製造工程図である。
【図１４】密閉型電池に用いる角形電池ケースの一例の縦断面図である。
【図１５】本発明に係る非水電解液二次電池の一部を切り欠いた部分斜視図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery sealing plate that is broken by deformation of a case when the battery internal pressure increases, and a sealed battery using the same.
[0002]
[Prior art]
When the sealed battery is handled under abnormal conditions, gas may be generated inside the battery and the internal pressure may increase. Therefore, in such a case, a safety valve for preventing an excessive increase in the battery internal pressure has been developed. The safety valve is activated when the internal pressure of the battery reaches a predetermined value or more, and releases the gas inside the battery to the outside. For example, the following safety valves have been proposed.
[0003]
First, a safety valve has been developed in which a thin part having a predetermined contour is formed on a metal plate that seals the opening of a battery case, and the thin part is bulged to the surface side of the metal plate (for example, Patent Documents). 1 and 2). In addition, a safety valve that forms a thin portion along the outline excluding one long side of a rectangle or oval having a long side and a short side, and that is hinged toward the top as the internal pressure of the battery rises, It has been developed (see, for example, Patent Document 3).
[0004]
[Patent Document 1]
Japanese Patent No. 3322418 (Claim 1, FIG. 7)
[Patent Document 2]
JP 2001-325934 A (Claim 1, FIGS. 1 and 2)
[Patent Document 3]
JP 2002-8615 A (Claim 1, FIGS. 1 and 2)
[0005]
However, all of the safety valves are ruptured by the force that the gas inside the battery pushes up the valve body upward. These safety valves are operated by the gas pressure itself inside the battery. Therefore, the thin part is bulged or formed into a dome shape, and the part to be broken is designed to be easily subjected to upward pressure by gas. However, in such a safety valve, it is necessary to make the thin portion very thin, and it is difficult to maintain the uniformity of performance. Therefore, the operating pressure of the safety valve is not stable, and it is difficult to sufficiently prevent an excessive increase in the battery internal pressure.
[0006]
[Problems to be solved by the invention]
The present invention provides a safety valve that breaks due to deformation of the case when the battery internal pressure rises, and improves the drawbacks of the conventional safety valve as described above.
[0007]
[Means for Solving the Problems]
The present invention is a sealing plate made of a plate-like material that seals an opening of a battery case, the sealing plate having a safety valve, and the safety valve is a lower surface formed by pressing the plate-like material. Is formed of a flat thin portion, and the thin portion has a further thin flat portion formed by pressing, and the flat portion is a substantially oval shape having a rectangular outline or a pair of parallel straight portions. The present invention relates to a battery sealing plate that has a groove formed along an outline and is broken by a tension in a surface direction of the plate-like material due to deformation of the case when the battery internal pressure increases.
Further, the present invention is a sealing plate made of a plate-like material for sealing the opening of the battery case, the sealing plate has a safety valve, and the safety valve is formed by pressing the plate-like material. The lower surface is formed of a flat thin portion, and the thin portion has a thinner flat portion formed by countersink processing, and the flat portion has a substantially rectangular shape or a pair of parallel straight portions. The present invention relates to a battery sealing plate that is formed with a recess surrounded by a circular outline and that is broken by the tension in the surface direction of the plate-like material due to deformation of the case when the battery internal pressure rises.
[0008]
The flat part preferably has a thickness of 30 to 80 μm.
The width of the flat portion is preferably 0.1 mm or more.
[0009]
The present invention also includes an electrode group, an electrolytic solution, a rectangular battery case that accommodates the electrode group and the nonaqueous electrolytic solution, and a sealing plate made of a plate-like material that seals the opening of the case. The plate relates to a sealed battery having the safety valve.
The thickness of the wall material of the case is preferably 1 to 0.1 mm.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the sealing plate of the present invention and a sealed battery using the same will be described.
The sealing plate of the present invention is made of a plate-like material and has a safety valve. As the plate material, a metal plate is preferably used, and among them, a metal plate made of aluminum, iron, or the like is preferably used. The thickness of the plate material is preferably 0.6 to 2 mm. If the plate-like material is too thick, the tension in the surface direction applied to the thin part will be small, and if it is too thin, deformation at other parts than the thin part will become large, and stable operation of the safety valve may not be achieved.
[0011]
The safety valve is formed of a thin portion having a flat bottom surface formed by pressing a plate-like material. Further, the thin portion has a thinner flat portion (hereinafter referred to as a flat portion) formed by a pressing process. The thickness of the thin part other than the flat part is preferably 50 to 100 μm. If the thin part other than the flat part is too thick, it becomes difficult to process, and if it is too thin, the breakage part of the safety valve is not determined and stable operation may not be achieved.
[0012]
The flat portion is broken by the tension in the surface direction of the plate-like material due to the deformation of the case when the battery internal pressure increases. Such a tension in the surface direction can be relatively easily broken even if the flat portion is somewhat thick. Therefore, the flat part of the safety valve of the present invention can be made thicker than the conventional fractured part of the safety valve that is broken by an upward force. For example, in the case of a conventional safety valve that is broken by an upward force, the thickness of the broken portion needs to be 20 μm or less. On the other hand, the thickness of the flat part of the safety valve of the present invention can be 30 to 80 μm, more preferably 35 to 50 μm.
[0013]
In the safety valve of the present invention, the fracture portion can be made thicker than before, so even if there is some thickness variation, the effect of the variation on the operating pressure is small, and as a result, the operating pressure of the safety valve is stabilized. . Further, although depending on the size of the sealing plate, the width of the flat portion is preferably 0.1 mm or more, and more preferably 1 mm or more from the viewpoint of further stabilizing the operating pressure. To some extent, the wider the flat portion, the more stable the operating pressure.
[0014]
Hereinafter, the sealing board which has a preferable flat part is illustrated.
Embodiment 1
A top view of the sealing plate according to the present embodiment is shown in FIG. Moreover, the II-II line expanded sectional view of the sealing board shown in FIG. 1 is shown in FIG. 2, and the III-III line enlarged partial sectional view is shown in FIG.
As shown in FIGS. 1 to 3, the safety valve for a sealing plate according to the present embodiment includes a thin portion 11 having a flat bottom surface formed on a plate-like material 12 by a seating process. In FIG. 1, the thin portion 11 has a substantially oval contour 10, but the contour of the thin portion is not particularly limited. The thin portion 11 is formed with a groove-like flat portion 13 along a substantially oval outline having a pair of parallel straight portions. The groove-like flat portion 13 may have a shape along a rectangular outline in addition to such a substantially oval shape. A terminal hole 14a for inserting an electrode terminal is provided at the center of the sealing plate, and a recess 14b for fitting an insulating material for insulating the electrode terminal and the sealing plate is provided around the terminal hole 14a. It has been. The other end of the sealing plate without the safety valve is provided with a liquid injection hole 15a for injecting an electrolytic solution, and a recess 15b for fitting a sealing plug is provided around the hole. .
[0015]
As described above, the groove width is preferably 0.1 mm or more, and particularly preferably 1 mm or less. The depth (B1) of the groove is determined by the thickness (A1) of the thin portion 11 and the thickness (C1) of the flat portion. In the case of such a groove-like flat part, the thickness (C1) of the flat part is particularly preferably 30 to 80 μm. The depth of the groove is preferably constant as shown in FIGS. 2 and 3, but the depth of the groove may be partially changed. The wall surface of the groove may be tapered.
[0016]
The length (L1) of the substantially oval straight line portion is preferably 0.5 to 10 mm, but the straight line portion may be longer than 10 mm. The longer the straight part, the thicker the flat part can be made. If the length of the straight portion is too short, the flat portion is difficult to break due to tension when the case swells and tension in the surface direction occurs. The straight part is preferably parallel or substantially parallel to the longitudinal direction of the sealing plate so that the flat part 13 is easily broken when the case swells. Moreover, it is preferable that the distance (W1) between linear parts is 1.5-8 mm. If this distance is too short, even if the safety valve operates, the opening due to the broken portion becomes small, and the ability to release gas becomes insufficient.
[0017]
Although depending on the size of the sealing plate, from the viewpoint of maintaining the strength of the sealing plate, it is preferable that the area of the safety valve composed of the thin portion is small. On the other hand, from the viewpoint of enhancing the function of the safety valve for releasing gas, it is preferable that the area of the fractured portion of the safety valve is large. Therefore, a safety valve that is smaller and produces a plurality of fractured portions during operation is most preferred.
The safety valve according to the present embodiment is superior to the safety valve according to Embodiments 2 and 3 described below, and has an excellent exhaust capability, and is suitable for a sealing plate for a high capacity battery.
[0018]
Reference form 1
The top view of the sealing board which concerns on this reference form is shown in FIG. Moreover, the VV line expanded sectional view of the sealing board shown in FIG. 4 is shown in FIG. 5, and the VI-VI line expanded partial sectional view is shown in FIG.
A safety valve of the sealing plate according to this preferred embodiment, as shown in FIG. 4 has a groove-like flat portion 20 along a pair of parallel straight lines. Other structures are the same as those in the first embodiment. The groove width is preferably 0.1 mm or more, and preferably 1 mm or less. In the case of such a groove-like flat part, the thickness (C2) of the flat part is particularly preferably 30 to 50 μm. The depth (B2) of the groove is determined by the thickness (A2) of the thin portion 21 and the thickness (C2) of the flat portion. The depth of the groove is preferably constant as shown in FIG. 4, but the depth of the groove may be partially changed.
[0019]
The length (L2) of the straight portion is preferably 0.5 to 10 mm, but the straight portion may be longer than 10 mm. If the length of the straight portion is too short, the flat portion is difficult to break due to tension when the case swells and tension in the surface direction occurs. The straight portion is preferably parallel or substantially parallel to the longitudinal direction of the sealing plate so that the flat portion 20 is easily broken when the case swells. Moreover, it is preferable that the distance (W2) between linear parts is 1.5-8 mm. If this distance is too short, even if the safety valve operates, the opening due to the broken portion becomes small, and the ability to release gas becomes insufficient. .
[0020]
Reference form 2
The top view of the sealing board which concerns on this reference form is shown in FIG. Moreover, the VIII-VIII line expanded sectional view of the sealing board shown in FIG. 7 is shown in FIG. 8, and the IX-IX line enlarged partial sectional view is shown in FIG.
Also a safety valve of the sealing plate according to this preferred embodiment, as shown in FIG. 7 has a groove-like flat portion 30 along a pair of straight line parallel to the thin portion 31. And the structure similar to the sealing board of the reference form 1 is provided except that the several small flat part 32 is intermittently provided along the R-shaped outline which ties between the edge parts which a pair of straight line opposes. Have. The thickness (C3 ′) of the plurality of small flat portions 32 may be larger than the thickness (C3) of the groove-like flat portion 30 along the straight line.
[0021]
Embodiment 2
FIG. 10 shows a top view of the sealing plate according to the present embodiment. Moreover, the XI-XI line enlarged sectional view of the sealing board shown in FIG. 10 is shown in FIG. 11, and the XII-XII line enlarged partial sectional view is shown in FIG.
As shown in FIGS. 10 to 12, the safety valve of the sealing plate according to the present embodiment has a flat portion 40 formed of a concave portion surrounded by a substantially oval outline. Other structures are the same as those in the first embodiment. Again, the substantially oval contour has a pair of parallel straight portions. In addition to such a substantially oval shape, it may be a flat portion composed of a concave portion surrounded by a rectangular outline.
[0022]
The length (L4) of the substantially oval straight line portion is preferably 0.5 to 10 mm, but the straight line portion may be longer than 10 mm. If the length of the straight portion is too short, the flat portion is difficult to break due to tension when the case swells and tension in the surface direction occurs. The straight portion is preferably parallel or substantially parallel to the longitudinal direction of the sealing plate so that the flat portion 40 is easily broken when the case swells.
[0023]
The distance (W4) between the straight portions is preferably 1.5 to 8 mm. If this distance is too short, even if the safety valve operates, the opening due to the broken portion becomes small, and the ability to release gas becomes insufficient. The depth (B4) of the concave portion is determined by the thickness (A4) of the thin portion and the thickness (C4) of the flat portion. In the case of such a flat part, the thickness (C4) of the flat part is particularly preferably 30 to 80 μm. The depth of the recess is preferably constant as shown in FIGS. 11 and 12, but the depth may be partially changed.
[0024]
The sealing plate as described above can be obtained, for example, by subjecting a flat plate-like material to a press-pressing process (pressing process for creating a flat surface) using a press mold having a predetermined uneven shape. it can. According to the seating process, it is possible to easily obtain a safety valve composed of a thin portion with a flat bottom surface. When a thin portion having a flat bottom surface is formed on a plate-like material, product variations are reduced and processing conditions are easily managed. An example of such a method will be specifically described below by taking the sealing plate of Embodiment 1 as an example.
[0025]
FIG. 13 shows the manufacturing process of the sealing plate of Embodiment 1, and the black arrow shows the flow of the process. First, a plate-like material 50 having a size that can be easily processed is prepared. Here, sectional views in the short direction of the plate-like material are shown in A1 to D1, and sectional views in the longitudinal direction are shown in A2 to D2.
The safety valve can be formed by two-stage pressing. In the first stage press work, as shown in A1 and A2, the upper mold 51a and the lower mold 51b apply pressure in the direction indicated by the white arrow to form the thin portion 52 as shown in B1 and B2. To do.
At this time, as shown in B2, the terminal hole 54 and the liquid injection hole 55 may be formed simultaneously with the formation of the thin portion 52.
[0026]
Next, using the upper die 53 and the lower die 53b, the second stage press work (seat push process) is performed. On the lower surface of the upper mold 53, a rib 53a having a flat top portion along a substantially oval outline is formed, and a flat portion 56 as shown in C1 and C2 is formed along the rib 53a.
Finally, a sealing plate having the safety valve according to the first embodiment can be obtained by cutting a sealing plate having a predetermined shape from the plate-like material by the cutting blade 57 having an opening having a predetermined shape. Next, in order to remove distortion from the obtained sealing plate, it is preferable to anneal the cut sealing plate. Annealing may be performed at 100 to 300 ° C., for example.
[0027]
Next, an example of a battery case combined with the sealing plate as described above will be described.
FIG. 14 shows a longitudinal sectional view of an example of a rectangular battery case 60 used for a sealed battery. Here, in order to make it easier to understand the structure of the case and the sealing plate, a view in which the opening of the battery case 60 is closed by the sealing plate 61 of the above-described first embodiment is shown, but in the battery manufacturing process, After the positive electrode, the negative electrode, and the separator are stacked and the wound electrode group is accommodated, the opening of the case is closed. An electrode terminal 63 is inserted into the terminal hole at the center of the sealing plate via an insulating material 62. On both sides of the electrode terminal 63, a safety valve 64 and an electrolyte injection hole are provided, and the injection hole is closed by a sealing plug 65. The peripheral edge of the sealing plate and the opening end of the battery case, and the liquid injection hole and the plug are joined by laser welding or the like.
[0028]
There is the following correlation between the ease of swelling of the case and the dimensions of the battery case. The ratio of the width (X) to the thickness of the battery case, that is, the ratio of the length in the longitudinal direction to the length in the short direction of the sealing plate is preferably 3 to 17, and the height to the thickness of the battery case The ratio of (Y) is preferably 3 to 35. Further, the ratio of X and Y: X / Y is preferably 0.3 to 1.5.
[0029]
As the material of the battery case, metal is preferably used, and aluminum, iron, etc. are preferably used. In order to improve the operational stability of the safety valve, it is preferable to make the thickness of the wider side wall of the battery case thinner than before, for example, 0.1 to 0.3 mm. If the thickness of the side wall is too thick, deformation of the case at the time when the battery internal pressure rises is hindered, and the safety valve becomes difficult to operate. On the other hand, if the thickness of the side wall is too thin, it is difficult to ensure sufficient strength of the battery case.
[0030]
When gas is generated in the battery case and the battery case swells in the thickness direction, a tension in the short direction acts on the sealing plate. When the tension exceeds a certain value, the thinnest flat portion of the safety valve is broken, and the gas inside the battery is released to the outside.
The present invention can be applied to a non-aqueous electrolyte secondary battery, an alkaline storage battery, and various primary batteries. In the following examples, a non-aqueous electrolyte secondary battery will be described as an example.
[0031]
【Example】
Example 1
(A) Preparation of sealing plate The following sealing plates A, B, and C were prepared using a 1 mm thick aluminum plate as a plate-like material and a press mold having a predetermined uneven shape. The sealing plate B is a reference example. The dimensions of each sealing plate were 34 mm in length and 4.5 mm in width in accordance with the size of the opening of the battery case described below.
First, an aluminum plate having a predetermined shape was formed into a thin portion having a substantially elliptical shape with a major axis of 3.6 mm and a minor axis of 2.4 mm and having a thickness of 80 μm by countersitting. Next, a predetermined flat portion was formed by further pressing the thin portion. The thickness of the flat portion was 50 μm in any sealing plate.
[0032]
The flat portion of the sealing plate A is the same as that shown in FIGS. 1 to 3 and has a groove shape along a substantially oval outline having a pair of parallel straight portions. The groove width (width of the flat portion) was 0.1 mm. The length (L1) of the straight line portion was 1.2 mm, and the distance (W1) between the straight line portions was 3.2 mm.
The flat part of the sealing plate B is the same as that shown in FIGS. 4 to 6 and has a groove shape along a pair of parallel straight lines. The groove width (width of the flat portion) was 0.1 mm. The length (L2) of the straight line portion was 1.2 mm, and the distance (W2) between the straight line portions was 3.2 mm.
The flat portion of the sealing plate C is the same as that shown in FIGS. 10 to 12 and has a concave shape surrounded by a substantially oval outline having a pair of parallel straight portions. The length (L4) of the straight line portion was 1.2 mm, and the distance (W4) between the straight line portions was 3.2 mm.
[0033]
(B) Production of positive electrode 100 parts by weight of the positive electrode active material (LiCoO ₂ ), 3 parts by weight of acetylene black as a conductive material, 7 parts by weight of polytetrafluoroethylene as a binder, and 1% by weight of carboxymethyl cellulose 100 parts by weight of an aqueous solution containing the mixture was added and stirred and mixed to obtain a paste-like positive electrode mixture. This positive electrode mixture was applied to both surfaces of an aluminum foil having a thickness of 20 μm serving as a current collector, and after drying, the whole was rolled and cut into a predetermined size to obtain a positive electrode.
[0034]
(C) Production of negative electrode 100 parts by weight of flaky graphite ground and classified so that the average particle diameter is about 20 μm, 3 parts by weight of styrene / butadiene rubber as a binder, and 1% by weight of carboxymethyl cellulose 100 parts by weight of an aqueous solution was added, and the mixture was stirred and mixed to obtain a paste-like negative electrode mixture. This negative electrode mixture was applied to both surfaces of a 15 μm-thick copper foil serving as a current collector, and after drying, the whole was rolled and cut into predetermined dimensions to obtain a negative electrode.
[0035]
(D) Battery assembly Using the positive electrode and the negative electrode, a non-aqueous electrolyte solution 2 is prepared using a predetermined sealing plate and a rectangular battery case (aluminum thickness 0.3 mm) made of aluminum as shown in FIG. A secondary battery (thickness 5 mm, width 34 mm, height 50 mm) was assembled. FIG. 15 shows a partial perspective view in which a part of the manufactured battery is cut out.
First, the positive electrode and the negative electrode were wound through a separator made of a microporous polyethylene resin having a thickness of 25 μm to form an electrode group 70. An aluminum positive electrode lead 71 and a nickel negative electrode lead 72 were welded to the positive electrode and the negative electrode, respectively. An insulating plate 73 made of polyethylene resin was attached to the upper part of the electrode group and housed in the battery case 74. The other end of the positive electrode lead was spot welded to the lower surface of a sealing plate 78 having a predetermined safety valve 77 described below. The other end of the negative electrode lead was electrically connected to the lower portion of the nickel negative electrode terminal 75 inserted through the insulating material 76 into the terminal hole at the center of the sealing plate.
[0036]
After laser welding the opening end of the battery case and the peripheral edge of the sealing plate, a predetermined amount of nonaqueous electrolyte was injected from the injection hole provided in the sealing plate. Finally, the injection hole was closed with an aluminum plug 79, and the liquid injection hole was sealed by laser welding to complete the battery.
As the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ at a concentration of 1.0 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 3 was used.
In addition, ten batteries each using the sealing plates A to C were produced.
[0037]
(E) Battery evaluation At an environmental temperature of 25 ° C., constant current charging is performed until the voltage of each battery reaches 4.2 V, and after the voltage reaches 4.2 V, the total charging time is 3 hours. The battery was charged at a constant voltage. Thereafter, each battery was placed on a hot plate at 250 ° C., and a safety valve cleavage test was performed.
When the batteries were observed after the above test, 10 out of 10 battery safety valves were in operation, and no battery rupture or ignition occurred. Therefore, according to the present invention, it was possible to confirm that the safety valve operates stably despite the fact that the thickness of the fractured portion of the safety valve was 50 μm thicker than before.
[0038]
【The invention's effect】
As described above, according to the present invention, since the safety valve that is broken by deformation of the case when the battery internal pressure rises is adopted, the safety valve is relatively easy to manufacture, and the operating voltage of the safety valve is stabilized, so The safety of the battery can be increased.
[Brief description of the drawings]
FIG. 1 is a top view of a sealing plate according to Embodiment 1. FIG.
FIG. 2 is an enlarged cross-sectional view taken along line II-II of the sealing plate shown in FIG.
3 is an enlarged partial sectional view taken along line III-III of the sealing plate shown in FIG.
4 is a top view of a sealing plate according to Reference Embodiment 1. FIG.
FIG. 5 is an enlarged cross-sectional view taken along line VV of the sealing plate shown in FIG.
6 is an enlarged partial sectional view taken along line VI-VI of the sealing plate shown in FIG.
7 is a top view of a sealing plate according to Reference Embodiment 2. FIG.
8 is an enlarged sectional view taken along line VIII-VIII of the sealing plate shown in FIG.
9 is an enlarged partial sectional view taken along line IX-IX of the sealing plate shown in FIG.
10 is a top view of a sealing plate according to Embodiment 2. FIG.
11 is an enlarged sectional view taken along line XI-XI of the sealing plate shown in FIG.
12 is an enlarged partial sectional view taken along line XII-XII of the sealing plate shown in FIG.
13 is a manufacturing process diagram of a sealing plate according to Embodiment 1. FIG.
FIG. 14 is a longitudinal sectional view of an example of a rectangular battery case used for a sealed battery.
FIG. 15 is a partial perspective view in which a part of the non-aqueous electrolyte secondary battery according to the present invention is cut away.

Claims

A sealing plate made of a plate-like material that seals the opening of the battery case,
The sealing plate has a safety valve,
The safety valve consists of a thin part with a flat bottom surface formed by pressing the plate-like material,
The thin portion has a further thin flat portion formed by a counter-pressing process,
The flat part forms a groove along a rectangular outline or a substantially oval outline having a pair of parallel straight parts, and the surface of the plate-like material is formed by deformation of the case when the battery internal pressure rises. Battery sealing plate that breaks by tension in the direction.

A sealing plate made of a plate-like material that seals the opening of the battery case,
The sealing plate has a safety valve,
The safety valve consists of a thin part with a flat bottom surface formed by pressing the plate-like material,
The thin portion has a further thin flat portion formed by a pressing process,
The flat portion forms a concave portion surrounded by a rectangular contour or a substantially oval contour having a pair of parallel straight portions, and the plate-like material is deformed by deformation of the case when the battery internal pressure rises. A sealing plate for a battery that is broken by a tension in a surface direction.

The battery sealing plate according to claim 1 or 2, wherein the flat portion has a thickness of 30 to 80 µm.

The battery sealing plate according to any one of claims 1 to 3, wherein a width of the flat portion is 0.1 mm or more.

Electrode assembly, electrolyte, the electrode group before Symbol electrolytic solution and a prismatic battery case for housing, and consists of the sealing plate made of a sheet material for sealing the opening portion of the case,
The sealing plate has a safety valve, and the safety valve is formed of a thin portion with a flat bottom surface formed by pressing the plate-like material,
The thin portion has a further thin flat portion formed by a counter-pressing process,
The flat part forms a groove along a rectangular outline or a substantially oval outline having a pair of parallel straight parts, and the surface of the plate-like material is formed by deformation of the case when the battery internal pressure rises. Sealed battery that breaks by tension in the direction.

An electrode group, an electrolytic solution, a rectangular battery case containing the electrode group and the electrolytic solution, and a sealing plate made of a plate-like material that seals the opening of the case,
The sealing plate has a safety valve
The safety valve consists of a thin part with a flat bottom surface formed by pressing the plate-like material,
The thin portion has a further thin flat portion formed by a pressing process,
The flat portion forms a concave portion surrounded by a rectangular contour or a substantially oval contour having a pair of parallel straight portions, and the plate-like material is deformed by deformation of the case when the battery internal pressure rises. A sealed battery that is broken by the tension in the surface direction.

The sealed battery according to claim 5 or 6, wherein the flat portion has a thickness of 30 to 80 µm.

The thickness of the wall material of the said case is 1-0.1 mm, The sealed battery in any one of Claims 5-7 .

The sealed battery according to any one of claims 5 to 8 , wherein the flat portion has a width of 0.1 mm or more.